Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Arterial phase
hyperenhance
ment (APHE)
Enhancement in arterial
phase more than liver,
resulting in brightness
higher than liver.
Broad
CEUS, CT,
MRI
On MRI: assessment of APHE requires acquisiton of precontrast as
well as arterial phase (AP) images.
On CT: in absence of prior treatment ,APHE can usually be
assessed without precontrast images. The reason is that untreated
observations are rarely hyperattenuating on precontrast CT.
On CEUS: assessment of APHE requires continuous imaging during
the AP.
APHE can be seen in the entire observation or only in part(s) of the
observation. If any part of the observation has APHE, then APHE is
considered to be present.
Enhancement from hypo on precontrast to iso on arterial phase does
not qualify as APHE.
On CT and MRI:
• APHE has two main subtypes:
• Rim APHE
• Nonrim APHE
On CEUS:
• APHE has four main subtypes:
• Rim APHE
• Nonrim APHE
• Spokewheel, centrifugal APHE
• Peripheral discontinuous nodular APHE
• Spokewheel, centrifugal APHE is suggestive but not diagnostic of
FNH.
• Peripheral discontinuous nodular APHE is diagnostic of
hemangioma
Caveat:
Peripheral discontinuous nodular enhancement is a temporal
enhancement pattern that can be assessed on CT or MRI in addition
to CEUS. Unlike peripheral discontinuous nodular APHE, it is not
considered an APHE subtype because its assessment requires the
acquisition of at least one postarterial phase and it can be assessed
even if an arterial phase is not acquired. See peripheral
discontinuous nodular enhancement.
In the LI-RADS CT/MRI
diagnostic algorithms, the main APHE subtypes are classified as
follows:
• Rim APHE is a LR-M feature
• Nonrim APHE is a major feature of HCC
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn about
APHE and its subtypes.
In the LI-RADS CEUS
diagnostic algorithm, the main APHE subtypes are classified as
follows:
• Rim APHE is a LR-M feature
• Nonrim APHE is a major feature of HCC
• Peripheral discontinuous nodular APHE, diagnostic of
hemangioma
Arterial
hypervascularity, hyp
ervascularity in
arterial phase,
increased contrast
enhancement in
hepatic arterial
phase, increased
contrast
enhancement in late
hepatic arterial
phase,
hypervascularity, high
attenuation area in
arterial phase,
contrast uptake in
arterial phase, wash
in
5/2021
Arterial phase
(AP)
A postcontrast phase
when:
Broad
CEUS, CT,
MRI
On CEUS: the AP usually starts around 10-15 seconds after
injection, and lasts for 10- 20 seconds.
On CT and MRI: the AP is divided into two temporal subtypes:
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the early arterial phase.
Early phase,
angiographic phase
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Hepatic artery and
branches are fully
enhanced
AND
• Hepatic veins are not
enhanced more than
liver by antegrade flow.
• Early AP: Subtype of AP in which portal vein is not enhanced or is
enhanced less than liver
• Late AP: Subtype of AP in which portal vein is enhanced more
than liver
Blood pool
agents (BPAs)
Contrast agents that
distribute mainly in the
vascular space after
intravenous injection.
Broad
CEUS, MRI
Blood pool agents remain in the blood with little or no distribution in
the extravascular space.
Applies mainly to CEUS microbubble agents. Can also apply to iron-
based or protein-binding Gd-based MR agents with prolonged
vascular dwell times, such as gadofosveset trisodium and
ferumoxytol, respectively. Neither of these MR contrast agents is
approved for liver imaging in the United States.
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-
LI-RADS-2017-Core.pdf to learn more about BPAs.
Intravascular contrast
agents
5/2021
Blood products
in mass
Blood products in a mass,
in absence of biopsy,
trauma or intervention
LI-RADS
CT, MRI
Blood products
• Do not enhance
• Are typically heterogeneous
• Are often amorphous or geographic in shape
• Have imaging characteristics that depend on their acuity:
• CT
• Acute and subacute: hyperattenuating relative to liver
• Chronic: iso or hypoattenuating.
• MRI
• Acute (hours to days): T1 hypo or iso, T2 hypo
• Subacute (days to months): T1 hyper, T2 variable
• Chronic (months to years): T1 hypo, T2 hypo.
For subacute or chronic blood products: there may be signal loss on
2nd echo of dual-gradient-echo sequence or high R2* value on R2*
map (if obtained) or low T2* value on T2* map (if obtained).
In the context of the LI-RADS CT/MRI diagnostic algorithm, blood
products in mass
• Is an ancillary feature favoring malignancy in general.
• Should not be applied as an ancillary feature favoring malignancy if
there is history of biopsy, trauma or intervention
• Should not be applied as an ancillary feature favoring malignancy
in nonsolid lesions such as hemorrhagic cysts.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about blood products in mass and how it is used in LI-RADS.
Hematoma,
hemorrhage,
methemoglobin,
hemosiderin
5/2021
Capsule
Smooth, uniform, sharp
border on CT or MRI
around most or all of an
observation.
LI-RADS
CT, MRI
In the LI-RADS CT/MRI diagnostic algorithm, capsule has two
subtypes:
• Enhancing capsule, which is a major feature of HCC
• Nonenhancing capsule, which is an ancillary feature favoring HCC
in particular
Capsule appearance,
pseudocapsule,
tumor capsule, tumor
pseudocapsule,
fibrous capsule,
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
If the capsule is enhancing, the enhancement must be most
pronounced in a postarterial phase.
If a capsule is visible as both an enhancing rim AND as a
nonenhancing rim, it should be characterized as enhancing capsule,
NOT as nonenhancing capsule.
If the liver parenchyma visually consists of both nodules and fibrosis,
then the capsule must be thicker or more conspicuous than the
fibrotic tissue around background nodules.
The imaging feature, capsule, refers to the imaging appearance of a
capsule. Pathologically, it may represent a true tumor capsule or a
pseudocapsule. Thus, an imaging capsule does not imply that there
is a true capsule pathologically.
The imaging appearance of capsule may represent a true tumor
capsule or a pseudocapsule on pathology. The distinction between
true capsule and pseudocapsule can only be made at pathology.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about capsule and its subtypes.
fibrous
pseudocapsule
Continuous
imaging
Acquisition of images
without pause or
interruption.
Broad
US, CEUS
On US and CEUS, typically 10-20 frames/second.
CT and MRI can also acquire images without pause or interruption,
but this is not commonly performed with these modalities.
5/2021
Corona
enhancement
Periobservational
enhancement in late
arterial phase or early
portal venous phase.
The enhancement is
contiguous with and
surrounds all or part of the
observation.
Broad
CT, MRI
Usually lobulated and may vary in thickness.
Corona enhancement is thought to represent venous drainage from
arterialized tumor.
In the context of the LI-RADS CT/MRI diagnostic algorithm, corona
enhancement is an ancillary feature favoring malignancy in general.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about corona enhancement and how it is used in LI-RADS.
Corona, perilesional
staining
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Delayed
central
enhancement
Postarterial phase pattern
where inner part of
observation is more
enhanced than periphery.
Broad
CT, MRI
Delayed central enhancement is a subtype of targetoid morphology.
The area of delayed enhancement in an observation may be central,
eccentric, or heterogeneous, but not peripheral.
The adjective “central” refers to inner portions of the observation but
is not meant to imply that the delayed enhancement is literally in the
geometric center of the observation.
Delayed central enhancement:
• Does not apply to central scar with delayed enhancement
• Does not apply to observations that can be confidently diagnosed
as hemangioma based on other features
In the context of the LI-RADS CT/MRI diagnostic algorithm, delayed
central enhancement is an LR-M feature.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about delayed central enhancement.
Sustained central
enhancement,
concentric
progressive
enhancement,
centripetal
progressive
enhancement
5/2021
Delayed phase
(DP)
A postarterial phase
acquired at least 2 minutes
after injection of an
extracellular agent or
gadobenate when portal
and hepatic veins are
enhanced more than liver.
Broad
CT, MRI with
ECA, MRI
with
gadobenate
dimeguline
The DP is typically acquired 2 to 5 minutes after injection of an
extracellular agent or gadobenate.
The DP does not apply to MRI performed with gadoxetate (the term
“transitional phase” is used for images acquired 2 to 5 minutes after
injection).
The portal venous phase (PVP) and DP appear similar. They can be
distinguished by:
• Timing after injection
• If both phases are acquired: the liver, the portal veins, and the
hepatic veins are usually less enhanced in the DP than in the PVP.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the delayed phase.
Interstitial phase,
equilibrium phase,
late dynamic phase,
late venous phase
5/2021
Diffusion
restriction
Intensity higher than liver
on diffusion-weighted
images not caused only by
T2 shine-through.
Broad
MRI
Should be assessed on DW images acquired with at least moderate
diffusion weighting (b ≥ 400 s/mm
2
).
If an adequate ADC map is obtained or if ADC is calculated from
source images, ADC is lower than or similar to liver.
T2 shine-through can be seen in observations with moderate to high
signal intensity on T2-weighted images. To differentiate:
• Restricted diffusion: ADC (either calculated or based on the ADC
map) lower or similar to liver
In the context of the LI-RADS CT/MRI diagnostic algorithm, restricted
diffusion is:
• A nontargetoid LR-M feature, if marked in degree
• A targetoid LR-M feature, if targetoid morphology
• An ancillary feature favoring malignancy in general, otherwise
Impeded diffusion,
diffusion restriction,
high DWI signal
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• T2 shine-through: ADC (either calculated or based on the ADC
map) higher than liver
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about restricted diffusion.
Early arterial
phase (AP)
Subtype of AP on CT or
MRI when portal vein is not
enhanced or is enhanced
less than liver.
Broad
CT, MRI
In the early AP:
• There may be some enhancement of the portal vein. However, if
the portal vein is enhanced more than liver, the early AP has
passed.
• There should be no enhancement of the hepatic veins by
antegrade flow. If there is any enhancement of the hepatic veins by
antegrade flow, the early AP has passed.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the early arterial phase.
Early phase,
angiographic phase
5/2021
Early washout
Subtype of washout on
CEUS with early onset (<
60 s) after contrast
injection.
Broad
CEUS
Early washout is usually marked in degree.
Early washout usually happens earlier than 60 seconds, and late
washout much later.
In the context of the LI-RADS CEUS algorithm, onset must be less
than 60 seconds (< 60 s) after contrast injection. See
https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-LI-
RADS-2017-Core.pdf.
5/2021
Enhancing
capsule
Subtype of capsule visible
as an enhancing rim in
portal venous phase,
delayed phase, or
transitional phase.
LI-RADS
CT, MRI
In the LI-RADS CT/MRI algorithm, enhancing capsule is:
• One of two defined subtypes of capsule.
• A major feature of HCC
The enhancement of the capsule must be most pronounced in a
postarterial phase.
If there is a rim that enhances more in the arterial phase (AP) than
the postarterial phases, it should be characterized as rim arterial
phase hyperenhancement (APHE), not as enhancing capsule.
A border visible only as an enhancing rim in the hepatobiliary phase
(HBP) should not be characterized as an enhancing capsule.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about enhancing capsule.
Capsule, tumor
capsule,
pseudocapsule,
fibrous capsule,
capsular
enhancement,
delayed enhancing
rim
5/2021
Enhancing soft
tissue in vein
Presence of enhancing soft
tissue in vein, regardless of
visualization of
parenchymal mass.
Broad
CEUS, CT,
MRI
For terminology about vascular involvement in pediatric liver tumor
imaging, refer to PRETEXT
(https://www.pedrad.org/Portals/5/Subspecialties/Abdominal%20Im
aging/PRETEXT%202017.pdf)
In the context of the LI-RADS CEUS and CT/MRI diagnostic
algorithms, enhancing soft tissue in vein establishes the diagnosis of
tumor in vein and is categorized LR-TIV.
Tumor in vein and enhancing soft tissue in vein are related but not
identical terms:
• Tumor in vein is a LI-RADS category
• Enhancing soft tissue in vein is the LI-RADS imaging criterion for
tumor in vein
None
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Extracellular
agents (ECAs)
Contrast agents with
predominantly extracellular
distribution after
intravenous injection.
Broad
CT, MRI
For MRI, examples of FDA-approved agents (as of February, 2021,
nonexhaustive list) include: gadopentetate dimeglumine, gadoteridol,
gadodiamide, gadoversetamide, gadobutrol, gadoterate meglumine.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
ECAs.
Extracellular fluid
contrast agents
5/2021
Fade
Reduction in enhancement
relative to liver from
hyperehancement in an
earlier phase to
isoenhancement or
minimal
hyperenhancement in all
later phases.
This can have one of the
following patterns:
• hyper (arterial phase) →
iso/min hyper (all later
phases)
• hyper (portal venous
phase) → iso/min hyper
(all later phases)
Broad
CT, MRI,
CEUS
Fade can be assessed only if at least two contrast-enhanced phases
are obtained (e.g., arterial phase followed by one or more
postarterial phases) so that the reduction in enhancement over time
can be assessed.
Fade cannot be assessed if there is a single contrast-enhanced
phase.
If there is hypoenhancement relative to the liver on any postarterial
phase, do not characterize as fade.
While fade is similar to washout in that the area of interest appears
to de-enhance relative to liver, fade and washout are not the same.
See washout for detailed comparison.
In the LI-RADS CT/MRI diagnostic algorithm:
If any part of the observation has washout, then washout is
considered to be present, even if other or even most parts of the
observation show fade.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about fade.
5/2021
Fat in mass,
more than
adjacent liver
More fat in a mass than in
liver.
Broad
CT, MRI
Imaging criteria:
• Observation is a mass
AND
• As follows by imaging modality:
• CT:
• Mass or part of mass has attenuation < -10 HU
OR
• If unenhanced CT is available and liver is fatty, mass has
attenuation less than liver on unenhanced CT
• MRI: Mass or part of mass has any of following compared to liver:
• More signal loss on OP compared to IP
• Higher fat signal on fat-only images
• Higher fat fraction on fat-fraction maps
• More signal loss on fat-suppressed compared to non-fat-
suppressed images with similar or identical weighting
Use caution in applying this feature if OP has a longer TE than IP; in
this situation, signal loss on the longer echo may indicate either fat or
iron.
In the context of the LI-RADS CT/MRI diagnostic algorithm, fat in
mass, more than adjacent liver is an ancillary feature favoring HCC
in particular.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about fat in mass, more than adjacent liver and how it is used in LI-
RADS.
Steatotic nodule,
intralesional fat, fatty
lesion, fat deposition,
fatty metamorphosis,
and intralesional fatty
metaplasia
5/2021
Fat sparing in
solid mass
Less fat in a solid mass
than in fatty liver.
Broad
CT, MRI
Imaging criteria:
• Observation is solid mass
AND
• Liver is fatty
AND
In the context of the LI-RADS CT/MRI diagnostic algorithm:
• Fat sparing in solid mass is an ancillary feature favoring
malignancy in general
• Do not apply fat sparing as an ancillary feature favoring
malignancy in nonsolid lesions such as cysts or hemangiomas
Lesional fat sparing
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• As follows by imaging modality:
• CT: Mass has higher attenuation than liver on unenhanced CT
• MRI: Compared to liver, mass has any of following:
• Less signal loss on OP compared to IP
• Lower fat signal on fat-only images
• Lower fat fraction on fat-fraction maps
Less signal loss on fat-suppressed compared to non-fat-suppressed
images with similar or identical weighting.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about Iron sparing in solid mass and how it is used in LI-RADS.
Growth
Definite size increase of a
mass that cannot be
explained only by
technique differences,
artifact, measurement
error, or interval
hemorrhage.
Broad
US, CEUS,
CT, MRI
Measure on same phase, sequence, and plane on serial exams if
possible.
Do not characterize as growth if size increase can be explained by
technique differences, artifact, measurement error, or interval
hemorrhage.
There is insufficient evidence to define an absolute or percent
change in size as a cut-off for establishing the presence of growth.
Users should therefore use their judgement.
In the context of all LI-RADS diagnostic algorithms, if there is doubt
about the presence of growth:
• Do not characterize as growth
• Do not characterize as size stability
In the context of the LI-RADS CT/MRI diagnostic algorithm, growth:
• Applies only to masses; It does not apply to pseudolesions such as
perfusion alterations or nonmasslike lesion such as focal fat
deposition.
• Should be assessed only if there is a prior CT or MRI exam of
sufficient quality and appropriate technique to quantify the interval
growth.
• Should not be assessed by comparing to prior US or CEUS
exams.
• Has two subtypes:
• Threshold growth (a major feature of HCC)
• Subthreshold growth (an ancillary feature favoring malignancy in
general)
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about growth and its subtypes.
In the context of CEUS LI-RADS diagnostic algorithm, growth:
• Is an ancillary feature favoring malignancy in general
• Should not be assessed by comparing to prior CT or MRI exams
LI-RADS CEUS does not classify growth into subtypes.
Interval growth,
progression, size
increase, diameter
increase
5/2021
Hepatobiliary
agents (HBAs)
Contrast agents with
sufficient hepatobiliary
uptake and excretion to
allow hepatobiliary phase
(HBP) imaging.
Broad
MRI
Applies to gadoxetate and gadobenate.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf and
https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-13-HBA.pdf to learn more about HBAs.
Hepatocellular
agents, biphasic
agents
5/2021
Hepatobiliary
phase (HBP)
Postcontrast phase
acquired with a
hepatobiliary agent when
Broad
MRI with
gadoxetate
The HBP is typically acquired about 20 minutes after injection of
gadoxetate.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf and
Hepatocellular phase
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
liver parenchyma is
intended to be
hyperintense to hepatic
blood vessels.
or
gadobenate
If obtained with gadobenate, the HBP is acquired 1-3 hours after
injection.
Excretion of contrast into the biliary tree may or may not be present.
https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-13-HBA.pdf to learn more about HBP.
Hepatobiliary
phase (HBP)
hypointensity
Intensity in the
hepatobiliary phase lower
than liver.
Broad
MRI with
gadoxetate
or
gadobenate
HBP hypointensity does not qualify as washout appearance.
Compare to functional areas of parenchyma (i.e., do not compare to
vessels or to parts of liver that do not take up the agent).
In the context of the LI-RADS CT/MRI diagnostic algorithm:
• HBP hypointensity can be seen in the entire observation or only in
part(s) of the observation. If any part of the observation has HBP
hypointensity, then HBP hypointensity is considered to be present.
• Unless in a targetoid pattern, HBP hypointensity is an ancillary
feature favoring malignancy in general
• Targetoid HBP hypointensity is a subtype of HBP hypointensity.
This subtype is a targetoid LR-M feature and not an ancillary
feature favoring malignancy in general.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about HBP hypointensity and how it is used in LI-RADS.
Hepatobiliary phase
hypoenhancement,
hepatobiliary phase
“defect”
5/2021
Hepatobiliary
phase (HBP)
isointensity
Uniform intensity in
hepatobiliary phase
identical or nearly identical
to liver.
Broad
MRI with
gadoxetate
or
gadobenate
HBP isointensity applies only to observations that are homogeneous
in the HBP.
Compare to functional areas of parenchyma (i.e., do not compare to
vessels or to parts of liver that do not take up the agent).
In the context of the LI-RADS CT/MRI diagnostic algorithm, HBP
isointensity
• is an ancillary feature favoring benignity.
• should not be applied as an ancillary feature favoring benignity if
HBP enhancement of liver is suboptimal
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about HBP isointensity and how it is used in LI-RADS.
HBP
isoenhancement,
occult in HBP
5/2021
Hyperechoic
Echogenicity higher than a
reference tissue, organ, or
structure
Broad
US, CEUS
In the context of the LI-RADS US and CEUS algorithms, this
definition applies to observations, which should be compared to
background liver. See https://www.acr.org/-
/media/ACR/Files/RADS/LI-RADS/LI-RADS-US-Algorithm-Portrait-
2017.pdf to learn more about hyperechoic and how it is used in the
US algorithm.
Echogenic
5/2021
Hypoechoic
Echogenicity lower than a
reference tissue, organ, or
structure.
Broad
US, CEUS
In the context of the LI-RADS US and CEUS algorithms, this
definition applies to observations, which should be compared to
background liver. See https://www.acr.org/-
/media/ACR/Files/RADS/LI-RADS/LI-RADS-US-Algorithm-Portrait-
2017.pdf to learn more about hypoechoic and how it is used in the
US algorithm.
5/2021
Imaging phase
A time range after
intravenous contrast
injection with characteristic
changes in enhancement
of liver parenchyma,
Broad
CEUS, CT,
MRI
The time after contrast administration is divided into discrete phases
for simplicity and clinical utility.
Examples for liver imaging include:
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
imaging phases.
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
vessels, and for some
agents, bile ducts.
• Arterial phase
• Portal venous phase
• Delayed phase
• Late phase
• Transitional phase
• Hepatobiliary phase
The transitional phase and hepatobiliary phase are unique to
hepatobiliary agents.
The delayed phase is unique to extracellular agents.
The late phase is unique to blood pool agents such as those used in
CEUS.
The postarterial phase is a general term that refers to all phases
after the arterial phase.
The transition between the various phases is gradual, with exact
timing dependent on patient-related and technical factors.
Images might be acquired during a transition from one phase to the
next, in which case the images might have overlapping
characteristics of the two adjacent phases.
Intermittent
imaging
A series of brief CEUS
image acquisitions, each
lasting a few seconds and
repeated at intervals of
about 30 to 60 seconds
without any imaging in
between.
Broad
CEUS
5/2021
Iron in mass,
more than liver
More iron in a mass than in
liver.
Broad
CT, MRI
Imaging criteria (MRI):
• Observation is a mass
AND
• Mass contains iron, i.e., any of following:
• Lower signal intensity on second echo (longer TE) compared to
first echo (shorter TE) on dual-echo gradient-echo sequence
• Abnormally low signal intensity on T2W images
• Abnormally high R2* value on R2* maps (if obtained)
• Abnormally low T2* value on T2* maps (if obtained)
AND
• Compared to mass, liver has less iron i.e., any of following:
• Less signal loss on second echo (longer TE) compared to first
echo (shorter TE) on dual-echo gradient-echo sequence
• Higher signal intensity on T2W images
• Lower R2* value on R2* maps (if obtained)
• Higher T2* value on T2* maps (if obtained)
Use caution in applying this feature if OP has a longer TE than IP; in
this situation, signal loss on the longer echo may indicate either fat or
iron.
In the context of the LI-RADS CT/MRI diagnostic algorithm, iron in
mass, more than liver is an ancillary feature favoring benignity.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about iron in mass, more than liver and how it is used in LI-RADS
Siderotic nodule
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Iron sparing in
solid mass
Less iron in a solid mass
than in iron-overloaded
liver.
Broad
MRI
Imaging criteria (MRI):
• Observation is solid mass
AND
• Liver is iron-overloaded. Features suggesting iron overload
include:
• Lower signal intensity on second echo (longer TE) compared to
first echo (shorter TE) on dual-echo gradient-echo sequence
• Abnormally low signal intensity on T2W images
• Abnormally high R2* value on R2* maps (if obtained)
• Abnormally low T2* value on T2* maps (if obtained)
AND
• Compared to liver, mass has less iron, i.e., any of following:
• Less signal loss on second echo (longer TE) compared to first
echo (shorter TE) on dual-echo gradient-echo sequence
• Higher signal intensity on T2W images
• Lower R2* value on R2* maps (if obtained)
• Higher T2* value on T2* maps (if obtained)
This feature cannot be reliably characterized on US or CT.
In the context of the LI-RADS CT/MRI diagnostic algorithm:
• Iron sparing in solid mass is an ancillary feature favoring
malignancy in general.
• Do not apply iron sparing as an ancillary feature favoring
malignancy in nonsolid lesions such as cysts or hemangiomas
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about Iron sparing in solid mass and how it is used in LI-RADS.
Lesional iron sparing,
lesional iron
resistance
5/2021
Isoechoic
Echogenicity equal to a
reference tissue, organ, or
structure.
Broad
US, CEUS
In the context of the LI-RADS US and CEUS algorithms, this
definition applies to observations, which should be compared to
background liver. See https://www.acr.org/-
/media/ACR/Files/RADS/LI-RADS/LI-RADS-US-Algorithm-Portrait-
2017.pdf to learn more about isoechoic and how it is used in the US
algorithm.
5/2021
Late arterial
phase (AP)
Subtype of AP on CT or
MRI when portal vein is
enhanced more than liver.
Broad
CT, MRI
In late AP:
• Enhancement of the portal vein may or may not be homogeneous.
• There may be faint enhancement of the hepatic veins by antegrade
flow. However, if the hepatic veins are enhanced more than liver
by antegrade flow, the late AP has passed.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the late arterial phase.
5/2021
Late phase
(LP)
A postarterial phase on
CEUS images acquired
after the portal venous
phase when portal and
hepatic veins are
enhanced but less than in
portal venous phase.
Broad
CEUS
LP lasts from end of portal venous phase (PVP) until there is
clearance of microbubbles from the circulation at about 4-6 min.
Liver parenchyma is enhanced but usually less than in PVP.
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-
LI-RADS-2017-Core.pdf to learn about LP.
5/2021
Late washout
Subtype of washout on
CEUS with late onset (> 60
s) after contrast injection.
Broad
CEUS
In the context of the LI-RADS CEUS algorithm, onset of washout
must be 60 seconds or more (≥ 60 s) after contrast injection. See
https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-LI-
RADS-2017-Core.pdf.
5/2021
Lesion
An observation that
represents a pathologic
abnormality.
Broad
US, CEUS,
CT, MRI
May be a mass or a non-masslike lesion.
See mass for examples of mass.
Examples of nonmasslike lesions:
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about lesion.
FLL, focal liver lesion
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Nonmasslike fat deposition or sparing
• Nonmasslike iron deposition or sparing
The term “lesion” should not be used interchangeably with the term
“observation”. A lesion is a type of observation. Although all lesions
are observations, not all observations are lesions.
If there is uncertainty about whether an observation represents a
pathologic abnormality (i.e., a true lesion), the term “observation” is
preferred over the term “lesion”.
LI-RADS
ancillary
feature
Imaging feature used by
LI-RADS to adjust
category, increase
diagnostic confidence, or
detect observations difficult
to visualize on other
sequences
LI-RADS
CEUS, CT,
MRI
Ancillary features are divided into:
• Favoring malignancy
• Favoring benignity
Ancillary features favoring malignancy are subdivided into:
• Favoring malignancy in general
• Favoring HCC in particular
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about ancillary features and how they are is used in LI-RADS.
5/2021
LI-RADS
feature of TIV
Imaging feature used by
LI-RADS to assign or
suggest LR-TIV category.
LI-RADS
CEUS, CT,
MRI
In the context of the LI-RADS CT/MRI diagnostic algorithm, there are
two types of TIV features:
• Feature diagnostic of tumor in vein
• Feature suggestive of tumor in vein
Feature diagnostic of tumor in vein:
• In LI-RADS, there is one feature diagnostic of tumor in vein –
enhancing soft tissue in vein.
• This feature is necessary and sufficient to establish the presence
of tumor in vein and to categorize an observation as LR-TIV. Any
observation with this feature should be categorized LR-TIV,
regardless of the presence or absence or any other feature and
regardless of visualization of a parenchymal mass.
Features suggestive of tumor in vein:
• In LI-RADS, there are four features suggestive of TIV:
• Occluded vein with ill-defined walls
• Occluded vein with restricted diffusion
• Occluded or obscured vein in contiguity with malignant
parenchymal mass
• Heterogeneous vein appearance not attributable to artifact
• These features suggest but do not establish the presence of TIV
and cannot by themselves be used to categorize an observation as
LR-TIV. If present, such features should prompt the radiologist to
scrutinize the vein for enhancing soft tissue.
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about LI-RADS features of TIV and how they are used in LI-RADS.
In the context of LI-RADS CEUS diagnostic algorithm, tumor in vein
is defined as unequivocal enhancing soft tissue in vein, regardless of
visualization of a parenchymal mass.
Tumor in vein should be differentiated from partially
occlusive/recanalized bland thrombus. Arrival time of microbubble
contrast agent to the vein helps in this differentiation:
• Early arrival (~ same time as hepatic artery opacification): favors
tumor in vein
• Arrival several (~10) seconds after hepatic artery opacification:
favors portal flow in patent portion of non-occlusive/recanalized
bland thrombus
LI-RADS LR-M
features
Imaging features used by
LI-RADS to assign LR-M
category.
LI-RADS
CEUS, CT,
MRI
LR-M features indicate a high probability of malignancy but are not
specific for HCC.
In context of the LI-RADS CT/MRI diagnostic algorithm, LR-M
features are divided into:
• Targetoid LR-M features
• Nontargetoid LR-M features
Targetoid LR-M features include:
• Rim arterial phase hyperenhancement (APHE)
• Peripheral washout
• Delayed central enhancemenrt
• Targetoid diffusion restriction
• Targetoid transitional phase (TP) or hepatobiliary phase (HBP)
appearance
Nontargetoid LR-M features include:
• Infiltrative appearance
• Marked diffusion restriction
• Necrosis or severe ischemia
• Other feature that in radiologist’s judgment suggests non-HCC
malignancy
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about LR-M features and how they are used in LI-RADS.
In context of the LI-RADS CEUS diagnostic algorithm, LR-M features
include any one of the following:
• Rim APHE followed by any washout
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Early washout onset (< 1 min)
• Marked washout degree (if seen before 2 min)
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-
LI-RADS-2017-Core.pdf to learn more about LR-M features and how
they are used in the CEUS LI-RADS diagnostic algorithm.
LI-RADS major
feature
Imaging feature used by
LI-RADS in assigning LR-
3, LR-4, and LR-5
categories, reflecting the
relative probability that an
observation is HCC.
LI-RADS
CEUS, CT,
MRI
LI-RADS defines five major features on CT and MRI:
• Nonrim arterial phase hyperenhancement (APHE)
• Nonperipheral washout
• Enhancing capsule
• Size
• Threshold growth
LI-RADS defines three major features on CEUS:
• Nonrim APHE
• Late and mild washout
• Size
Locoregional
therapy
A therapy that targets a
specific lesion or part of
the liver without physically
removing it.
Broad
Examples include:
• Ablative therapy
• Transcatheter therapy
• External beam radiation
Surgical resection physically removes part of the liver and is not
considered locoregional therapy.
Systemic administration of chemotherapeutic or biologic agents is
also not considered locoregional therapy.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-9-Treatment-response.pdf learn more
about locoregional therapy.
5/2021
Marked T2
hyperintensity
Intensity on T2WI higher
than non-iron-overloaded
spleen and as high as or
almost as high as simple
fluid.
Broad
MRI
Characteristic imaging feature of cysts and some hemangiomas.
In the context of the LI-RADS CT/MRI diagnostic algorithm, marked
T2 hyperintensity is an ancillary feature favoring benignity.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about marked T2 hyperintensity and how it is used in LI-RADS.
T2 bright, high T2
signal intensity, fluid
signal, lightbulb T2
bright
5/2021
Marked
washout
Subtype of washout on
CEUS in which the
observation becomes black
or “punched out” while the
background liver is still
enhanced.
Broad
CEUS
In the context of the LI-RADS CEUS algorithm, the observation must
become black or “punched out” within 2 minutes from contrast
injection. See https://www.acr.org/-/media/ACR/Files/RADS/LI-
RADS/CEUS-LI-RADS-2017-Core.pdf.
5/2021
Mass
Space-occupying lesion
that distorts or destroys
parenchyma or other
anatomic structures.
Broad
US, CEUS,
CT, MRI
Examples include:
• Malignant neoplasms
• Benign neoplasms
• Hemangiomas
• Cysts
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about mass.
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Confluent fibrosis
• Treated lesions
May be of any size or shape:
• Round or oval
• Geographic
• Irregular
• Diffuse
• Confluent
• “Infiltrative” or “permeative”
If a mass is either oval or round in shape, it is considered a nodule.
For such observations, either the term “nodule” or “mass” may be
used, depending on context, user preference, and size.
If a mass is geographic or irregular in shape or has a diffuse,
confluent, or infiltrative appearance, the term “nodule” does not
apply.
Mild washout
Subtype of washout on
CEUS in which observation
becomes less enhanced
than liver, but not devoid of
enhancement (i.e., some
enhancement persists).
Broad
CEUS
Mild washout includes all washout appearing later than 2 minutes
after contrast injection. See https://www.acr.org/-
/media/ACR/Files/RADS/LI-RADS/CEUS-LI-RADS-2017-Core.pdf.
5/2021
Mild-moderate
T2
hyperintensity
Intensity on T2WI higher
than liver, similar to or
lower than non-iron-
overloaded spleen, and
lower than simple fluid
Broad
MRI
In patients without a spleen or with an iron-overloaded spleen,
intensity should be lower than simple fluid.
In the context of the LI-RADS CT/MRI diagnostic algorithm, mild-
moderate T2 hyperintensity is an ancillary feature favoring
malignancy in general.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about mild-moderate T2 hyperintensity and how it is used in LI-
RADS.
Slightly bright T2,
mild-moderate T2
signal
5/2021
Mosaic
appearance
Presence of any
combination of internal
nodules, compartments, or
septations, within a solid or
mostly solid mass.
Broad
CEUS, CT,
MRI
The internal nodules or compartments differ in imaging features from
each other.
If there is a single inner nodule within a mass, the term nodule-in-
nodule may be used.
Components of a mass with mosaic appearance may be necrotic or
cystic.
The term mosaic appearance does not apply to a septated cyst.
In the context of the LI-RADS CT/MRI diagnostic algorithm, mosaic
appearance is an ancillary feature favoring HCC in particular.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about mosaic appearance and how it is used in LI-RADS.
Mosaic pattern,
mosaic architecture
5/2021
Multiphase
imaging
Acquisition of images at
two or more different
phases after intravenous
contrast injection.
Broad
CEUS, CT,
MRI
Common examples of multiphase imaging on CT and MRI include
acquisition of:
• AP (arterial phase), PVP (portal venous phase)
• AP, PVP, and delayed phase (DP)
• AP, PVP, transitional phase (TP), and hepatobiliary phase (HBP)
For diagnosis and staging of patients at risk for HCC, LI-RADS
recommends acquisition of
• CEUS: AP, PVP, late phase
• CT: AP, PVP, and DP
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• MRI with extracellular agent or gadobenate: Precontrast, AP, PVP,
DP
• MRI with gadoxetate: Precontrast, AP, PVP, TP, and HBP
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
multiphase imaging and recommended LI-RADS technique
Nodule
Spherical or oval mass.
Broad
US, CEUS,
CT, MRI
A nodule is a type of mass that is either round or oval in shape, and
not a cyst or abscess. If a mass is geographic or irregular in shape or
has a diffuse, confluent, or infiltrative appearance, the term “nodule”
does not apply.
While there is no strict size cutoff, the term “nodule” is often reserved
for small masses, generally ≤ 2 cm.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about nodules.
5/2021
Nodule-in-
nodule
appearance
Presence of a smaller
inner nodule within a larger
outer nodule.
Broad
CEUS, CT,
MRI
The inner nodule differs in imaging features from the outer nodule or
mass.
It may be:
• Peripherally or centrally located within the outer nodule
• Small relative to the outer nodule or almost as large as the outer
nodule
• Round, oval, or lobulated in shape
Nodule-in-nodule appearance is a type of mosaic appearance.
The inner and outer nodules must be solid. The term nodule-in-
nodule appearance does not apply to a hemangioma.
In the context of the LI-RADS CT/MRI diagnostic algorithm, nodule-
in-nodule appearance is an ancillary feature favoring HCC in
particular.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about nodule-in-nodule appearance and how it is used in LI-RADS.
Nodule-in-nodule
pattern, nodule-in-
nodule architecture
5/2021
Nonenhancing
capsule
Subtype of capsule that
does not show
enhancement on any
image.
LI-RADS
CT, MRI
In the LI-RADS CT/MRI algorithm, nonenhancing capsule:
• Is one of two defined subtypes of capsule.
• Is an ancillary feature favoring HCC in particular.
• May be seen as follows:
• Precontrast CT: hypoattenuating
• Precontrast T1WI: hypointense
• T2WI: hypo- or hyperintense
• DWI: hyperintense
• Contrast-enhanced CT or T1WI: nonenhancing
• Transitional phase (TP): hypointense
• Hepatobiliary phase (HBP): hypointense
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about nonenhancing capsule.
Nonenhancing
distinctive rim
5/2021
Nonmasslike
(adjective)
Not having the properties
of a mass; without
distorting or destroying
parenchyma or other
anatomic structures.
Broad
US, CEUS,
CT, MRI
May apply to lesions or pseudolesions
Examples include:
• Nonmasslike fat deposition or sparing
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about mass, nonmasslike, and related terms.
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Nonmasslike iron deposition or sparing
• Nonmasslike arterial phase hyperenhancement (APHE)
• Nonmasslike heterogeneous enhancement
Nonperipheral
washout
Subtype of washout that is
NOT mainly in observation
periphery.
Broad
CT, MRI,
CEUS
Nonperipheral washout may be homogeneous or heterogeneous; if
heterogeneous, it may be focal, scattered (patchy, spotty), nodule-in-
nodule, or mosaic.
See washout for additional comments.
In the LI-RADS CT/MRI algorithm, nonperipheral washout is:
• One of two defined subtypes of washout
• A major feature of HCC
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about nonperipheral washout.
Washout;
venous/portal
venous/delayed/late
phase
hypoenhancement,
hypoattenuation, or
hypointensity;
deenhancement
5/2021
Nonrim arterial
hyperenhance
ment (nonrim
APHE)
Subtype of APHE that is
NOT mainly in observation
periphery.
Broad
CEUS, CT,
MRI
Nonrim APHE is a subtype of APHE.
Nonrim APHE may be homogeneous or heterogeneous.
See APHE for additional comments.
In the context of the LI-RADS CT/MRI diagnostic algorithm, nonrim
APHE is:
• One of two defined subtypes of APHE
• A major feature of HCC
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about APHE and its subtypes.
Arterial
hypervascularity,
hypervascularity in
arterial phase,
increased contrast
enhancement in
hepatic arterial
phase, increased
contrast
enhancement in late
hepatic arterial
phase,
hypervascularity, high
attenuation area in
arterial phase,
contrast uptake in
arterial phase, wash
in
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Observation
Area distinctive compared
to liver at imaging.
Broad
US, CEUS,
CT, MRI
Observation is a general term that includes lesion and pseudolesion.
May be a true lesion (if it corresponds to a pathologic abnormality) or
a pseudolesion (if it does not correspond to a pathologic
abnormality).
The LI-RADS decision tree and algorithm use the generic term
“observation” for simplicity. For clear communication in clinical
practice, radiologists may use the most specific term for which there
is certainty. For example, if a radiologist is certain that an
observation is a solid nodule, then the term “nodule” is acceptable.
On the other hand, if a radiologist is not certain if an observation is a
true lesion or a pseudolesion, the term “observation” is preferred, as
the terms “nodule” or “lesion” or “focal liver lesion” may be
misleading.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more observation, lesion, pseudolesion, and related terms.
Lesion or
pseudolesion
5/2021
Observation,
lesion,
pseudolesion,
mass, nodule
N/A
Broad
US, CEUS,
CT, MRI
Observation, lesion, pseudolesion, mass, and nodule are a group of
related but not identical terms.
The terms are related hierarchically.
Observation is a general term that encompasses all the other terms
in this group.
Lesion and pseudolesion are types of observations.
A mass is a type of lesion.
A nodule is a type of mass.
The most specific term can be used depending on context and user
preference. For example, if an observation is thought to be a true
lesion, then either the term “lesion” or the term “observation” may be
used. If there is uncertainty about whether an observation is a true
lesion or a pseudolesion, the term “observation” is preferable.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about observation, lesion, pseudolesion, mass, and nodule.
5/2021
Parallels blood
pool
enhancement
Temporal pattern in which
enhancement
approximates blood pool in
all phases.
Broad
CT, MRI
In general, the following blood vessels represent the blood pool in
each phase:
• Arterial phase (AP): aorta or hepatic artery
• Portal venous phase (PVP): portal vein
• Delayed (DP), transitional (TP), and hepatobiliary (HBP) phases:
portal vein or hepatic vein
This enhancement pattern is characteristic but in isolation is not
diagnostic of hemangiomas. Other features (i.e. marked T2-
hyperintensity and peripheral discontinuous nodular enhancement)
may be needed to confirm the diagnosis of hemangioma.
Note that with gadoxetate the blood pool usually becomes about
isointense to liver in transitional phase and hypointense to liver in
hepatobiliary phase (HBP). Therefore, care should be exercised
In the context of the LI-RADS CT/MRI diagnostic algorithm, parallels
blood pool enhancement is an ancillary feature favoring benignity.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about parallels blood pool enhancement and how it is used in LI-
RADS.
Following
signal/attenuation/brig
htness/enhancement
of blood pool on all
phases
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
when applying this feature with gadoxetate. See
https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about the application of this feature with gadoxetate.
Parenchymal
distortion
Parenchymal area seen on
ultrasound with one or
more of the following
characteristics:
• Ill-defined area of
heterogeneity
• Refractive shadow
• Loss of normal hepatic
architecture
Broad
US, CEUS
Loss of normal hepatic architecture includes loss of visualization of
normal portal triads or hepatic veins.
In the context of the LI-RADS US surveillance algorithm,
parenchymal distortion ≥ 10 mm in size is categorized US-3 Positive.
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/LI-
RADS-US-Algorithm-Portrait-2017.pdf.
5/2021
Perfusion
alteration
Nonmasslike change in
blood supply to an area of
the liver.
Broad
CT, MRI,
CEUS
Often seen as a nonmasslike area of hyperenhancement in the
arterial phase with isoenhancemeent on postarterial phases.
May be of any size.
Usually geographic, occasional round or oval in shape.
Often peripherally located.
May be caused by or be associated with a mass.
On CT and MRI, may be mistaken for a nodule, especially if round or
oval in shape, or for an infiltrative mass, especially if heterogeneous.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf and
https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-15-Benign-entities.pdf to learn more
about perfusion alterations.
THID, THAD, THED,
AP shunt, perfusional
abnormality,
perfusion anomaly,
vascular
pseudolesion
5/2021
Peripheral
discontinuous
nodular arterial
phase
hyperenhance
ment (APHE)
Areas of enhancement that
during the arterial phase
are initially round or
globular in shape and
distributed discontinuously
along the periphery of a
lesion and then rapidly
expand to fill the lesion in
its entirely or nearly in its
entirety.
Broad
CEUS
Peripheral discontinuous nodular APHE is a temporal subtype of
APHE assessable with continuous imaging during the arterial phase
(AP) on CEUS.
Diagnostic imaging feature of nonsclerosed hemangiomas on CEUS.
In the LI-RADS CEUS algorithm, peripheral discontinuous nodular
APHE is:
• A subtype of APHE
• Diagnostic of hemangioma
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-
LI-RADS-2017-Core.pdf to learn more about peripheral
discontinuous nodular APHE and how it is used in CEUS LI-RADS.
5/2021
Peripheral
discontinuous
nodular
enhancement
Areas of enhancement that
in the early postcontrast
phases are round or
globular in shape and
distributed discontinuously
along the periphery of a
lesion and that in
subsequent phases
expand and approximately
parallel the blood pool in
brightness.
Broad
CEUS, CT,
MRI
Peripheral discontinuous nodular enhancement is a temporal
enhancement pattern. Strict assessment of this feature requires
acquisition of two or more phases.
As the areas of enhancement expand they may coalesce to become
continuous, may fill the lesion in its entirely or nearly in its entirety,
and may no longer appear round or globular.
The enhancing areas approximately parallel the blood pool in
brightness. If a hepatobiliary agent is given, the enhancing areas
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about peripheral discontinuous nodular hyperenhancement
and how it is used in LI-RADS.
Peripheral
discontinuous
globular
enhancement,
peripheral
discontinuous
puddles of
enhancement,
peripheral
discontinuous
puddling
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
usually become iso- and then hypo-intense relative to liver in the
transitional and hepatobiliary phases.
Diagnostic imaging feature of nonsclerosed hemangiomas.
Although strict assessment of peripheral discontinuous nodular
enhancement requires acquisition of two or more phases, a
diagnosis of hemangioma can be made on a single postcontrast
phase if the imaging features are sufficiently characteristic. In such
cases, the temporal pattern is inferred.
Peripheral
washout
Subtype of washout that is
mainly in observation
periphery.
Broad
CT, MRI
Peripheral washout is
• a subtype of targetoid morphology and
• a subtype of washout.
See washout for additional comments.
In the context of the LI-RADS CT/MRI diagnostic algorithm, the
presence of peripheral washout suggests intrahepatic
cholangiocarcinoma (iCCA) or other non-HCC malignancy, but it
does not exclude HCC.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about peripheral washout and how it is used in LI-RADS.
Venous/portal
venous/delayed/late
phase peripheral
hypoenhancement,
peripheral
hypoattenuation, or
hypointensity;
peripheral
deenhancement
5/2021
Portal venous
phase (PVP)
A postarterial phase
acquired no more than 2
minutes after injection of a
contrast agent when portal
and hepatic veins are
enhanced more than liver.
Broad
CEUS, CT,
MRI
On CEUS: the PVP usually starts around 30-45 seconds after
injection, lasts for 90-100 seconds, and ends at around 2 minutes
after injection.
On CT and MRI: Typically PVP images are acquired around 60
seconds to 80 seconds after start of injection.
The PVP and delayed phase (DP) appear similar. They can be
distinguished by:
• Timing after injection
• If both phases are acquired: the liver, the portal veins, and the
hepatic veins are usually more enhanced in the PVP than in the
DP.
In some patients, the transitional phase may begin before 2 minutes
after injection of gadoxetate. If the liver is as enhanced or more
enhanced than veins after injection of gadoxetate, the PVP has
passed, even if the images are acquired within 2 minutes of injection.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the portal venous phase.
Early postarterial
phase, portal
dominant phase
5/2021
Postarterial
extracellular
phase (ECP)
A general term referring to:
• PVP and DP, if an
extracellular agent or
gadobenate is given
• PVP only, if gadoxetate
is given
Broad
CT, MRI
During the postarterial extracellular phase, enhancement of the liver
is mainly due to extracellular distribution of a contrast agent.
Does not apply to blood pool agents.
5/2021
Postarterial
phase
General term that refers to
imaging after the arterial
phase.
Broad
CEUS, CT,
MRI
On CEUS: the postarterial phase is divided into the portal venous
phase and the late phase.
On CT and MRI with extracellular contrast agents: the postarterial
Venous phase, late
phase
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
phase is divided into the portal venous phase and delayed phase.
On MRI with gadoxetate: the postarterial phase is divided into the
portal venous phase, transitional phase, and hepatobiliary phase.
On MRI with gadobenate: the postarterial phase is divided into the
portal venous phase, delayed phase, and hepatobiliary phase. A
transitional phase does occur but is rarely acquired.
Pseudolesion
An observation that may
simulate but does not
represent a pathologic
abnormality.
Broad
US, CEUS,
CT, MRI
May be mistaken for a true lesion.
Examples include:
• Round or oval perfusion alterations
• Some artifacts such as ghosting artifacts from aorta
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-7-The-LIRADS-observation.pdf to learn
more about pseudolesions.
5/2021
Refractive
shadowing
Linear shadows from the
lateral edges of an
observation. Observation
may be well-defined or ill-
defined.
Broad
US, CEUS
In some infiltrative tumors, refractive shadows may be the best
sonographic finding to indicate their presence.
See https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/LI-
RADS-US-Algorithm-Portrait-2017.pdf.
5/2021
Rim arterial
phase
hyperenhance
ment (rim
APHE)
Subtype of APHE that is
mainly in observation
periphery.
Broad
CEUS, CT,
MRI
Rim APHE is
• a subtype of targetoid morphology and
• a subtype of APHE.
Rim APHE can be smooth or irregular. It can vary in thickness.
Rim APHE should not be confused with peripheral discontinuous
nodular enhancement, which is characteristic of hemangioma.
See APHE for additional comments.
In the LI-RADS CEUS and CT/MRI algorithms, rim APHE is an LR-M
feature.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf and
https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-LI-
RADS-2017-Core.pdf to learn more about rim APHE.
Peripheral APHE, ring
APHE, targetoid
APHE, APHE in
target pattern, rim
enhancement
5/2021
Size
Largest outer-edge-to-
outer-edge dimension of
an observation.
Broad
US, CEUS,
CT, MRI
Pick phase, series, and plane in which margins are clearest.
In the context of the LI-RADS CT/MRI diagnostic algorithm:
• Include capsule in measurement.
• Do not measure in arterial phase or DWI if margins are clearly
visible on different series
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about size and how it is used in LI-RADS.
The definition of “size” in LI-RADS corresponds to the definition of
the “longest diameter” in RECIST. LI-RADS prefers “size” rather than
“diameter” as observations may not be spherical.
Diameter, dimension,
long axis
5/2021
Size reduction
Spontaneous decrease in
size over time, that cannot
be explained only by
technique differences,
artifact, or measurement
error.
Broad
CT, MRI,
US, CEUS
In the context of the LI-RADS CT/MRI diagnostic algorithm, size
reduction:
• Is an ancillary feature favoring benignity
• Should be measured on the same phase, sequence, and plane on
serial exams if possible
Decreased size,
shrinkage, regression
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
• Should be assessed only if there is a prior CT or MRI exam of
sufficient quality and appropriate technique to reliably measure
interval change in size, if any
• Should not be assessed by comparing to prior US or CEUS exams
• Should not be applied as an ancillary feature favoring benignity if
the size reduction is due to resorption of blood products. Rationale:
size reduction due to resorption of blood products can be seen in
malignant tumors
In the context of CEUS LI-RADS diagnostic algorithm, size reduction:
• Is an ancillary feature favoring favoring benignity
• Should not be assessed by comparing to prior CT or MRI exams
LI-RADS CEUS does not classify growth into subtypes.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about size reduction and how it is used in LI-RADS.
Size stability ≥
2 years
No change in observation
size measured on serial
exams ≥ 2 years apart.
LI-RADS
CT, MRI,
CEUS
In the context of the LI-RADS CT/MRI diagnostic algorithm, size
stability ≥ 2 years:
• Is an ancillary feature favoring benignity
• Should be measured on the same phase, sequence, and plane on
serial exams if possible
• Should be assessed only if there is a prior CT or MRI exam of
sufficient quality and appropriate technique to reliably measure
interval change in size, if any
• Should not be assessed by comparing to prior US or CEUS exams
• Should not be applied as an ancillary feature favoring benignity if
there is any doubt about size stability
In the context of CEUS LI-RADS diagnostic algorithm, size stability ≥
2 years:
• Is an ancillary feature favoring benignity
• Should not be assessed by comparing to prior CT or MRI exams
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about size stability ≥ 2 years and how it is used in LI-RADS.
Stable size,
unchanged size,
stable diameter,
unchanged diameter
5/2021
Spokewheel,
centrifugal
arterial phase
hyperenhance
ment (APHE)
Enhancement in a lesion
that during the arterial
phase begins as an
internal focus and then
rapidly expands outward in
a radial, spoke-wheel
pattern.
Broad
CEUS
Spokewheel, centrifugal APHE is a temporal subtype of APHE
assessable with continuous imaging during the arterial phase (AP)
on CEUS.
Imaging feature suggestive of FNH on CEUS.
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Subthreshold
growth
Size increase of a mass,
less than threshold growth.
Any of the following:
• Size increase < 50%
over any time period
• Any size increase over
time interval > 6 months
• A new mass of any size
LI-RADS
CT, MRI
In the context of the LI-RADS CT/MRI diagnostic algorithm,
subthreshold growth is a(n):
• Subtype of growth
• Ancillary feature favoring malignancy in general
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about subthreshold growth.
Subthreshold
diameter increase,
subthreshold size
increase, growth less
than threshold
5/2021
Targetoid
Target-like morphology on
CT or MRI. The center and
periphery of a mass have
different imaging
characteristics.
Broad
CT, MRI
In the context of the CT/MRI LI-RADS algorithm:
• Five subtypes of targetoid have been defined:
• Rim arterial phase hyperenhancement (APHE)
• Peripheral washout
• Delayed central enhancement
• Targetoid diffusion restriction
• Targetoid transitional phase (TP) or hepatobiliary phase (HBP)
appearance
• The presence of any of the targetoid subtypes suggests
intrahepatic cholangiocarcinoma (iCCA) or other non-HCC
malignancy, but it does not exclude HCC.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about targetoid features and how they are used in LI-RADS.
Target-like, target
appearance
5/2021
Targetoid
diffusion
restriction
Subtype of restricted
diffusion that is greatest in
observation periphery.
Broad
MRI
Targetoid diffusion restriction is
• A subtype of targetoid morphology and
• A subtype of diffusion restriction
In the context of the LI-RADS CT/MRI diagnostic algorithm, targetoid
diffusion restriction is an LR-M feature
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about targetoid diffusion restriction and how it is used in LI-RADS.
Peripheral restriction,
DWI target
sign/appearance,
targetoid diffusion
5/2021
Targetoid
transitional
phase (TP) or
hepatobiliary
phase (HBP)
appearance
Suptype TP or HBP
hypointensity where the
observation periphery is
more hypointense than the
center.
Broad
MRI with
HBA
Targetoid TP/HBP appearance is
• A subtype of targetoid morphology and
• A subtype of TP/HBP hypointensity
In the context of the LI-RADS CT/MRI diagnostic algorithm, targetoid
TP or HBP appearance is an LR-M feature.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about TP or HBP appearance and how it is used in LI-RADS.
HBP/TP cloud,
HBP/TP target
sign/appearance
5/2021
Threshold
growth
Size increase of a mass by
≥ 50% in ≤ 6 months.
LI-RADS
CT, MRI
In the context of the LI-RADS CT/MRI diagnostic algorithm, threshold
growth:
• Is one of two defined subtypes of growth.
• Is a major feature of HCC.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about threshold growth.
Growth by 50% or
more, size increase
by 50% or more
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Transitional
phase (TP)
Postarterial phase
acquired with an
intravenous hepatobiliary
contrast agent when liver
vessels and hepatic
parenchyma are of similar
signal intensity, which
occurs between the portal
venous and hepatobiliary
phase.
Broad
MRI with
gadoxetate.
(While the
TP does
occur with
gadobenate,
TP images
are usually
not acquired
with this
agent)
During the TP, enhancement of the liver is due to both extracellular
and intracellular distribution of a hepatobiliary contrast agent.
The TP is typically acquired 2 to 5 minutes after injection of
gadoxetate.
Although TP images are typically acquired 2 to 5 minutes after
injection of gadoxetate, the onset of the TP is variable. In some
patients, the onset may be before 2 minutes after injection; in other
patients, the onset may be later than 5 minutes after injecton.
This phase is acquired almost exclusively with gadoxetate. While TP
exists with gadobenate, it is rarely, if ever, acquired.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-12-Technique.pdf to learn more about
the TP.
Interstitial phase,
equilibrium phase,
late dynamic phase
are often misused to
indicate the
transitional phase but
they are not true
synonyms for the
transitional phase.
5/2021
Transitional
phase (TP)
hypointensity
Intensity in the transitional
phase lower than liver.
Broad
MRI with
gadoxetate
TP hypointensity does not qualify as washout.
Compare to functional areas of parenchyma (i.e., do not compare to
vessels or to parts of liver that do not take up the agent).
In the context of the LI-RADS CT/MRI diagnostic algorithm:
• TP hypointensity can be seen in the entire observation or only in
part(s) of the observation. If any part of the observation has TP
hypointensity, then TP. hypointensity is considered to be present.
• Unless in a targetoid pattern, TP hypointensity is an ancillary
feature favoring malignancy in general
• Targetoid TP hypointensity is a subtype of TP hypointensity. This
subtype is a targetoid LR-M feature and not an ancillary feature
favoring malignancy in general.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about TP hypointensity and how it is used in LI-RADS.
Transitional phase
hypoenhancement,
late dynamic phase
hypointensity, late
dynamic phase
hypoenhancement,
equilibrium phase
hypointensity,
interstitial phase
hypointensity
5/2021
Treated lesion
Lesion treated by any
therapy.
Broad
CEUS, CT,
MRI
Lesions can be treated by locoregional therapy, resection, systemic
therapy, or a combination.
LI-RADS provides guidance on assessing treatment response or
recurrence after locoregional therapy or resection. See
https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/LI-RADS-
2018-Core.pdf and https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-9-Treatment-response.pdf to learn more
about how to assess treatment response using LI-RADS.
LI-RADS does not yet provide guidance on assessing treatment
response after systemic therapy.
5/2021
Undistorted
vessels
Vessels traversing an
observation without
displacement, deformation,
or other alteration.
Broad
CT, MRI
Characteristic of perfusion alteration.
In the context of the LI-RADS CT/MRI diagnostic algorithm,
undistorted vessels is an ancillary feature favoring benignity.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about undistorted vessels.
Lack of mass effect
on vessels
5/2021
US visibility as
nodule
Unenhanced US visibility
as discrete nodule or mass
corresponding to CT- or
MRI-detected observation.
LI-RADS
CT, MRI
In the context of the LI-RADS CT/MRI diagnostic algorithm, US
visibility as nodule is an ancillary feature favoring malignancy in
general.
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf to learn more
about US visibility as nodule and how it is used in LI-RADS.
US detectability as
discrete nodule,
sonographic visibility
as discrete nodule,
sonographic visibility
as nodule
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
Washout
Reduction in enhancement
from earlier to later phase
resulting in
hypoenhancement relative
to liver.
This can have one of the
following patterns by
modality:
CT or MRI:
• Hyperenhancing to
hypoenhancing
• Isoenhancing to
hypoenhancing
If hepatobiliary agent is
given, must be assessed
before the transitional
phase.
CEUS:
• Hyperenhancing to
hypoenhancing
• Isoenhancing to
hypoenhancing
• Hypoenhancing to
unequivocally more
hypoenhancing
Broad
CT, MRI,
CEUS
Washout can be assessed only if at least two contrast-enhanced
phases are obtained (e.g., arterial phase followed by one or more
postarterial phases) so that the reduction in enhancement over time
can be assessed.
Washout cannot be assessed if there is a single contrast-enhanced
phase.
Washout must occur in an extracellular postarterial phase:
• For extracellular contrast agents and gadobenate:
hypoenhancement in portal venous phase (PVP), delayed phase
(DP), or both
• For gadoxetate: hypoenhancement in PVP only. Hypointensity in
transitional phase (TP) or hepatobiliary phase (HBP) does not
qualify as washout
Washout can be assessed qualitatively (i.e., visually) relative to liver
parenchyma. It does not require quantitative measurements.
Washout applies to observations with at least some enhancement. It
does not apply to nonenhancing observations.
Reduction in enhancement from arterial phase hyperenhancement
(APHE) to isoenhancement does not qualify as washout.
If APHE is present, the areas with APHE and washout do not need to
coincide.
If the liver parenchyma visually consists of both nodules and fibrosis,
then compare to composite liver tissue (i.e., a visual average of the
nodules and fibrosis).
Washout can be seen in the entire observation or only in part(s) of
the observation. If any part of the observation has washout, then
washout is considered to be present.
On CT or MRI:
• Washout has two subtypes based on morphology:
• Peripheral washout
• Nonperipheral washout
On CEUS:
• Washout is divided into subtypes based on time of onset and
degree:
• Time of onset:
• Early: < 60 seconds after contrast injection
• Late: ≥ 60 seconds after contrast injection
• Degree:
• Mild: less enhanced than liver, but not devoid of enhancement
(i.e., some enhancement persists). If mild washout becomes
In the LI-RADS CT/MRI diagnostic algorithm, the washout subtypes
are classified as follows:
• Peripheral washout is a LR-M feature
• Nonperipheral washout is a major feature of HCC
In the LI-RADS CEUS diagnostic algorithm, the washout subtypes
are classified as follows:
• Early or marked washout is a LR-M feature
• Late and mild washout is a major feature of HCC
See https://www.acr.org/-/media/ACR/Files/Clinical-
Resources/LIRADS/Chapter-16-Imaging-features.pdf and
https://www.acr.org/-/media/ACR/Files/RADS/LI-RADS/CEUS-LI-
RADS-2017-Core.pdf to learn more about washout and its subtypes.
venous/portal
venous/delayed/late
phase
hypoenhancement,
hypoattenuation, or
hypointensity;
deenhancement
5/2021
Term
Definition (2021)
Context of
Use (COU)
Applicable
modalities
General comments
LI-RADS specific comments
Synonyms (their
use is generally less
preferred)
Date
approved
marked > 2 minutes after contrast injection, it is still
characterized as mild.
• Marked: virtually devoid of enhancement (“punched-out”) by 2
min after contrast injection.
While washout is similar to fade in that the area of interest appears
to de-enhance relative to liver, washout and fade are not the same:
Washout:
• Follows isoenhancement or hyperenhancement in an earlier phase
(CT or MRI) or any degree of enhancement in an earlier phase
(CEUS)
• Results in hypoenhancement in a later phase relative to liver
• Examples (AP = arterial phase; PVP = portal venous phase; DP =
delayed phase; LP = late phase):
• CT/MRI/CEUS:
• Hyper (AP) → hypo (PVP or DP/LP or both)
• Hyper (PVP) → hypo (DP/LP)
• Iso (AP) → hypo (PVP or DP/LP or both)
• Iso (PVP) → hypo (DP/LP)
• CEUS only
• Hypo (AP) → more hypo (PVP or LP or both)
• Hypo (PVP) → more hypo (LP)
Fade:
• Follows hyperenhancement in an earlier phase
• Results in iso- or minimal hyperenhancement in all later phases
relative to liver
• Examples:
• CT/MRI/CEUS
• Hyper (AP) → iso/min hyper (all later phases)
• Hyper (PVP) → iso/min hyper (all later phases)
.