Observation: Distinctive area with imaging features that differ from those of adjacent liver parenchyma; may be nodule or pseudolesion
Nodule: Discrete mass of rounded or irregular shape
On CEUS, with exception of focal fatty infiltration and sparing, most liver observations are true nodules
CT and MR literature often uses term "observation" to describe focal signal abnormality since many findings detected on CT and MR may not be true nodules but rather contrast enhancement abnormalities
CEUS exam characterized as adequate when entire observation or nodule can be unequivocally visualized for entirety of exam
Observations or nodules that cannot be categorized due to image degradation or omission reported as "not categorizable"
Location: Liver observation or nodule location using Couinaud liver segment classification
Size: Largest dimensions of liver observation or nodule
No universally accepted guidelines for US measurements
Measurements preferably performed on precontrast B-mode imaging
If margins indistinct on B-mode imaging, measurements on arterial-phase CEUS could be performed instead
CEUS measurements might be affected by contrast blooming artifact or inclusion of hyperenhancing surrounding liver parenchyma in observation or nodule size measurement
Unequivocal diameter increase: Increase in maximal diameter of observation or nodule, measured on exams performed on different dates, which is not attributable to artifact, differences in technique or modality between exams, or measurement error
Often used as ancillary feature to suggest malignancy
Unequivocal diameter decrease: Decrease in maximal visualized diameter of observation or nodule, measured on exams performed on different dates, which is not attributable to artifact, differences in technique or modality between exams, or measurement error
Often used as ancillary feature to suggest benign process
Diameter stability: No significant change in maximal diameter of observation or nodule, measured on exams performed on different dates over ≥ 2 years, and in absence of treatment
Often used as ancillary feature to suggest benign process
Judgment of US examiner to determine if changes in size unequivocal and not attributable to artifact, differences in technique or modality between exams, or measurement error
IMAGING
Enhancement Phases
Arterial-Phase Enhancement
Arterial-Phase Hyperenhancement
Washout
Tumor-in-Vein
Mosaic Architecture
Selected References
Dietrich CF et al: How to perform contrast-enhanced ultrasound (CEUS). Ultrasound Int Open. 4(1):E2-E15, 2018
Lyshchik A et al: Contrast-enhanced ultrasound of the liver: technical and lexicon recommendations from the ACR CEUS LI-RADS working group. Abdom Radiol (NY). 43(4):861-879, 2018
Wilson SR et al: CEUS LI-RADS: algorithm, implementation, and key differences from CT/MRI. Abdom Radiol (NY). 43(1):127-142, 2018
Related Anatomy
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Related Differential Diagnoses
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References
Tables
Tables
KEY FACTS
CEUS EXAMINATION
TERMINOLOGY
Liver CEUS Lexicon
Observation: Distinctive area with imaging features that differ from those of adjacent liver parenchyma; may be nodule or pseudolesion
Nodule: Discrete mass of rounded or irregular shape
On CEUS, with exception of focal fatty infiltration and sparing, most liver observations are true nodules
CT and MR literature often uses term "observation" to describe focal signal abnormality since many findings detected on CT and MR may not be true nodules but rather contrast enhancement abnormalities
CEUS exam characterized as adequate when entire observation or nodule can be unequivocally visualized for entirety of exam
Observations or nodules that cannot be categorized due to image degradation or omission reported as "not categorizable"
Location: Liver observation or nodule location using Couinaud liver segment classification
Size: Largest dimensions of liver observation or nodule
No universally accepted guidelines for US measurements
Measurements preferably performed on precontrast B-mode imaging
If margins indistinct on B-mode imaging, measurements on arterial-phase CEUS could be performed instead
CEUS measurements might be affected by contrast blooming artifact or inclusion of hyperenhancing surrounding liver parenchyma in observation or nodule size measurement
Unequivocal diameter increase: Increase in maximal diameter of observation or nodule, measured on exams performed on different dates, which is not attributable to artifact, differences in technique or modality between exams, or measurement error
Often used as ancillary feature to suggest malignancy
Unequivocal diameter decrease: Decrease in maximal visualized diameter of observation or nodule, measured on exams performed on different dates, which is not attributable to artifact, differences in technique or modality between exams, or measurement error
Often used as ancillary feature to suggest benign process
Diameter stability: No significant change in maximal diameter of observation or nodule, measured on exams performed on different dates over ≥ 2 years, and in absence of treatment
Often used as ancillary feature to suggest benign process
Judgment of US examiner to determine if changes in size unequivocal and not attributable to artifact, differences in technique or modality between exams, or measurement error
IMAGING
Enhancement Phases
Arterial-Phase Enhancement
Arterial-Phase Hyperenhancement
Washout
Tumor-in-Vein
Mosaic Architecture
Selected References
Dietrich CF et al: How to perform contrast-enhanced ultrasound (CEUS). Ultrasound Int Open. 4(1):E2-E15, 2018
Lyshchik A et al: Contrast-enhanced ultrasound of the liver: technical and lexicon recommendations from the ACR CEUS LI-RADS working group. Abdom Radiol (NY). 43(4):861-879, 2018
Wilson SR et al: CEUS LI-RADS: algorithm, implementation, and key differences from CT/MRI. Abdom Radiol (NY). 43(1):127-142, 2018
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