Liver Imaging Reporting and Data System Contrast-Enhanced US Nonradiation Treatment Response Assessment Version 2024.

The American College of Radiology Liver Imaging Reporting and Data System (LI-RADS) standardizes the imaging technique, reporting lexicon, disease categorization, and management for patients with or at risk for hepatocellular carcinoma (HCC). LI-RADS encompasses HCC surveillance with US; HCC diagnosis with CT, MRI, or contrast-enhanced US (CEUS); and treatment response assessment (TRA) with CT or MRI. LI-RADS was recently expanded to include CEUS TRA after nonradiation locoregional therapy or surgical resection. This report provides an overview of LI-RADS CEUS Nonradiation TRA v2024, including a lexicon of imaging findings, techniques, and imaging criteria for posttreatment tumor viability assessment. LI-RADS CEUS Nonradiation TRA v2024 takes into consideration differences in the CEUS appearance of viable tumor and posttreatment changes within and in close proximity to a treated lesion. Due to the high sensitivity of CEUS to vascular flow, posttreatment reactive changes commonly manifest as areas of abnormal perilesional enhancement without washout, especially in the first 3 months after treatment. To improve the accuracy of CEUS for nonradiation TRA, different diagnostic criteria are used to evaluate tumor viability within and outside of the treated lesion margin. Broader criteria for intralesional enhancement increase sensitivity for tumor viability detection. Stricter criteria for perilesional enhancement limit miscategorization of posttreatment reactive changes as viable tumor. Finally, the TRA algorithm reconciles intralesional and perilesional tumor viability assessment and assigns a single LI-RADS treatment response (LR-TR) category: LR-TR nonviable, LR-TR equivocal, or LR-TR viable.

Imaging Findings in Cirrhotic Liver: Pearls and Pitfalls for Diagnosis of Focal Benign and Malignant Lesions.

Cirrhosis is the end stage of chronic liver disease and causes architectural distortion and perfusional anomalies. It is a major risk factor for developing hepatocellular carcinoma (HCC). Common disease entities in noncirrhotic livers, such as hemangiomas, can be rare in cirrhotic livers, and benign entities such as confluent hepatic fibrosis and focal nodular hyperplasia-like lesions may mimic the appearance of malignancies,. HCC usually has typical imaging characteristics, such as the major features established by the Liver Imaging Reporting and Data System. However, HCC can also have a spectrum of atypical or uncommon appearances, such as cystic HCC, hypovascular HCC, or macroscopic fat-containing HCC. HCCs with certain genetic mutations such as CTNNB-1-mutated HCC can harbor unique imaging features not seen in other types of HCC. In addition, malignancies that are less common than HCC, such as cholangiocarcinoma and metastases, which can be difficult to differentiate, can still occur in cirrhotic livers. Atypical imaging features of benign and malignant lesions can be challenging to accurately diagnose. Therefore, familiarity with these features and an understanding of the prevalence of disease entities in cirrhotic livers are key in the daily practice of radiologists for evaluation of cirrhotic livers. The authors illustrate the typical and atypical features of benign and malignant lesions in cirrhosis and discuss the technical pitfalls and unique advantages associated with various imaging modalities in assessing cirrhotic livers, including noncontrast and contrast-enhanced US, CT, and MRI. Work of the U.S. Government published under an exclusive license with the RSNA. Quiz questions for this article are available in the supplemental material.

Contrast-enhanced US of the Liver and Kidney: A Problem-solving Modality.

Contrast-enhanced US (CEUS) has an important role as a supplement to CT or MRI in clinical practice. The main established utilizations are in the liver and the kidney. The primary advantages of CEUS compared with contrast-enhanced CT or MRI relate to its superior contrast resolution, real-time continuous scanning, pure intravascular nature, portability, and safety-especially in patients with renal impairment or CT or MRI contrast agent allergy. This article focuses on the use of CEUS in the liver and kidney.

The added value of contrast-enhanced ultrasound in evaluation of indeterminate small solid renal masses and risk stratification of cystic renal lesions.

OBJECTIVES: To investigate accuracy of contrast-enhanced ultrasound (CEUS) to characterize indeterminate small solid renal masses (sSRMs), excluding lipid-rich AMLs, and cystic renal masses (CRMs) according to the proposed Bosniak Classification 2019 MATERIALS AND METHODS: CEUS of pathology-proven CRMs and sSRMs (without definite enhancement or macroscopic fat on CT/MRI), and CRMs with ≥18 months follow-up were retrospectively reviewed. Two radiologists blindly categorized CRMs according to new Bosniak Classification on CT/MRI. On CEUS, two other radiologists evaluated arterial-phase enhancement of sSRMs relative to renal cortex and categorized CRMs following new Bosniak Classification. Fisher's exact/chi-squared test was used to compare categorical variables, and Cohen κ statistics for inter-observer agreement RESULTS: A total of 237 patients had 241 lesions: 161 pathology-proven sSRMs (122 malignant and 39 benign), 29 pathology-proven CRMs, 51 CRMs with adequate follow-up. Arterial-phase enhancement < renal cortex predicted malignancy with specificity of 97.4% (38/39) (CI 85.6-99.9%), and positive predictive value (PPV) of 98.2% (54/55) (CI 90.4-99.9%). Inter-observer kappa was 0.95. In pathology-proven CRMS, sensitivity of CEUS vs CT/MRI was 100% (15/15) (CI 79.6-100%) vs 60% (9/15) (CI 35.8-80.1%) (p value = .002) and negative predictive value (NPV) 100% (2/2) (CI 17.8-100%) vs 25% (2/8 ) (CI 4.4-59.1%) (p value < 0.0001), with similar specificity (50%) and PPV- 88.2% (15/17) (CI 65.7-97.9%) vs 81.8% (9/11) (CI 52.3-96.8%) ( p value = 0.586). Bosniak Classification inter-observer kappa was 0.92 for CEUS vs 0.68 for CT/MRI (p value = 0.009). CONCLUSION: In our cohort, CEUS had high specificity and PPV to diagnose RCC in sSRMs excluding lipid-rich AML. CEUS had significantly higher sensitivity/NPV to diagnose malignancy in CRMs as compared to CT/MRI. KEY POINTS: • Once lipid-rich AML is excluded by the other modalities, sSRM arterial phase hypo-enhancement relative to renal cortex on CEUS yielded high specificity (97.4%) and PPV (98.2%) to diagnose RCC. • When applying the proposed Bosniak Classification 2019, CEUS showed higher sensitivity compared to CT/MRI (100% vs 60%), p value=.0024, in the stratification of cystic renal masses to diagnose malignancy. • CEUS may reduce the number of CT/MRI Bosniak IIF lesions by assigning them to either II or III/IV categories.

Characterization of Indeterminate Liver Lesions on CT and MRI With Contrast-Enhanced Ultrasound: What Is the Evidence?

OBJECTIVE. CT or MRI is most commonly used for characterizing focal hepatic lesions. However, findings on CT and MRI are occasionally indeterminate. Contrast-enhanced ultrasound (CEUS), with its unique characteristics as a purely intravascular contrast agent and real-time evaluation of enhancement, is a useful next step. The purpose of this article is to review the evidence for performing CEUS in the assessment of indeterminate hepatic lesions seen on CT and MRI. CONCLUSION. CEUS is a useful problem-solving tool in the evaluation of liver lesions that are indeterminate on CT and MRI. Uses include detection of arterial phase hyperenhancement; differentiation between hepatocellular carcinoma and intrahepatic cholangiocarcinoma; determination of benign versus malignant tumor thrombus, benign versus neoplastic cystic hepatic lesions, and hepatocellular adenoma versus focal nodular hyperplasia; and monitoring for recurrence in postablative therapies. CEUS can help establish a confident diagnosis and determine the need for further invasive diagnosis or treatment.

Reproducibility of 2 Liver 2-Dimensional Shear Wave Elastographic Techniques in the Fasting and Postprandial States.

OBJECTIVES: The purpose of this study was to compare the reliability and agreement of 2 methods of 2-dimensional (2D) shear wave elastography (SWE) on liver stiffness in healthy volunteers. We also assessed effects of the prandial state and operator experience on measurements. METHODS: Two operators, 1 experienced and 1 novice, independently examined 20 healthy volunteers with 2D SWE on 2 ultrasound machines (Aixplorer [SuperSonic Imagine, Aix-en-Provence, France] and Aplio 500 [Canon Medical Systems Corporation, Otawara, Japan]). Volunteers were scanned 8 times by the operators using both machines in fasting and postprandial states. Agreement was evaluated by a Bland-Altman analysis, and the correlation was assessed by the Pearson correlation and intraclass correlation coefficients (ICCs). An analysis of variance was conducted to determine the contribution of the machine, prandial state, and operator experience to the variability. RESULTS: Agreement assessed by Bland-Altman plots showed no statistically significant difference in measured liver stiffness between the machines (mean difference, -0.8%; 95% confidence interval, -3.7%, 2.1%), with a critical difference of 1.36 kPa. The correlation was good to excellent for both the crude overall Pearson coefficient and the ICC, both measuring 0.88 (95% confidence interval, 0.82, 0.92). Subclass ICCs for the fasting state, postprandial state, novice operator, and experienced operator were 0.89, 0.88, 0.90, and 0.86, respectively. The 2-way mixed effect analysis of variance showed that the volunteers accounted for 86.3% of variation in median liver stiffness, with no statistically significant contribution from operator experience, the prandial state, or the machine (P = .108, .067, and .296, respectively). CONCLUSIONS: Our study showed that the 2D SWE techniques had a high degree of reliability and agreement in measurement of liver stiffness in a healthy population. Operator experience and the prandial state did not impart significant variability to stiffness measurements.

Successful Integration of Contrast-enhanced US into Routine Abdominal Imaging.

Contrast material-enhanced US is recognized increasingly as a useful tool in a wide variety of hepatic and nonhepatic applications. The modality recently was approved for limited use for liver indications in adult and pediatric patients in the United States. Contrast-enhanced US uses microbubbles of gas injected intravenously as a contrast agent to demonstrate blood flow and tissue perfusion. The growing worldwide application of contrast-enhanced US in multiple organ systems is due largely to its advantages, including high contrast resolution (sensitivity to the contrast agent), real-time imaging, lack of nephrotoxicity, the purely intravascular property of microbubble contrast agents that allows the use of disruption-replenishment techniques, and repeatability during the same examination. Through illustrative cases, common useful clinical scenarios are discussed, including characterization of liver and renal masses, especially indeterminate lesions at CT or MRI; differentiation of neoplastic cysts from nonneoplastic cysts in various organs; differentiation of tumor thrombus from bland thrombus; and assessment after a renal transplant or local ablative therapy. Common applications in the biliary system, pancreas, spleen, and vasculature also are introduced. Successful routine use of contrast-enhanced US requires an efficient setup and workflow and a thorough understanding of appropriate clinical indications and its advantages that provide added value after CT and MRI. This article familiarizes radiologists with common abdominal applications of contrast-enhanced US and guides them to implement contrast-enhanced US successfully in their clinical practice. Online supplemental material is available for this article. ©RSNA, 2018.

Integration of Contrast-enhanced US into a Multimodality Approach to Imaging of Nodules in a Cirrhotic Liver: How I Do It.

Accurate characterization of cirrhotic nodules and early diagnosis of hepatocellular carcinoma (HCC) are of vital importance. Currently, computed tomography (CT) and magnetic resonance (MR) imaging are standard modalities for the investigation of new nodules found at surveillance ultrasonography (US). This article describes the successful integration of contrast material-enhanced US into a multimodality approach for diagnosis of HCC and its benefits in this population. The application of contrast-enhanced US immediately following surveillance US allows for prompt dynamic contrast-enhanced evaluation, removing the need for further imaging of benign lesions. Contrast-enhanced US also provides dynamic real-time assessment of tumor vascularity so that contrast enhancement can be identified regardless of its timing or duration, allowing for detection of arterial hypervascularity and portal venous washout. The purely intravascular nature of US contrast agents is valuable as the rapid washout of nonhepatocyte malignancies is highly contributory to their differentiation from HCC. The authors believe contrast-enhanced US provides complementary information to CT and MR imaging in the characterization of nodules in high-risk patients. © RSNA, 2017 Online supplemental material is available for this article.

Contrast enhanced ultrasound (CEUS) in the prenatal evaluation of suspected invasive placenta percreta.

BACKGROUND: Morbidly adherent placentation now complicates approximately 1 in 500 pregnancies. Our group and others have demonstrated that antenatal diagnosis of invasive placentation and team-based delivery reduce severe morbidity. Ultrasound and magnetic resonance imaging (MRI) are both employed in the antenatal evaluation of pregnancies with suspected placenta increta/percreta. Accurate diagnosis in this context is essential to direct resources appropriately. Ultrasound methods, including colour and power Doppler, are the mainstays of screening at-risk women, whereas MRI is reserved for diagnostic purposes because of its cost and limited accessibility. In current practice, both methods are significantly limited by an inability to accurately define aberrant utero-placental blood flow, the definitive sign of deeply invasive placentation. We describe here an adjunctive method to define aberrant blood flow using ultrasound. CASE: We employed contrast-enhanced ultrasound (CEUS) in the antenatal evaluation of suspected extensive invasive placentation in a woman at 18 weeks' gestation. Invasive placentation was confirmed following hysterectomy. CONCLUSION: CEUS, a technique that has been established as safe and well tolerated in the non-pregnant setting, has the potential to be deployed as a powerful adjunct to ultrasound to enhance both the screening and diagnostic components of care for women with suspected invasive placentation.

Accuracy of Contrast-enhanced US for Differentiating Benign from Malignant Solid Small Renal Masses.

PURPOSE: To test the hypothesis that qualitative and quantitative features of contrast material-enhanced ultrasonography (US) can be used to differentiate benign from malignant small renal masses. MATERIALS AND METHODS: This is an institutional review board approved, HIPAA-compliant prospective study with written informed consent. Patients with histologically characterized solid small renal masses, excluding lipid-rich angiomyolipomas, underwent qualitative contrast-enhanced US with a combination of three different US machines. A subgroup of patients underwent quantitative contrast-enhanced US. Patients received a bolus injection of 0.2 mL of contrast material for qualitative and quantitative evaluations and were followed for 3 minutes. Two radiologists independently reviewed videotaped qualitative contrast-enhanced US examinations and were blinded to the final diagnoses. Features that were evaluated included lesion vascularity relative to the adjacent cortex in the arterial phase, the presence of a capsule, homogeneity, the pattern of vascularity, and washout. One radiologist separately reviewed a subset of contrast-enhanced US examinations that were performed with all three machines. Parameters of a first-pass time intensity curve were calculated for quantitative analysis. The Mann-Whitney test was used for quantitative parameters, the χ(2) or Fisher exact test was used for qualitative parameters, and κ statistics and Fleiss methodology were used to determine interobserver and intermachine agreement. RESULTS: The study population consisted of 91 patients (35 women and 56 men) with 94 lesions. The mean age was 62 years ± 14 (range, 21-91). Three patients had two lesions each, which were evaluated at two different sessions. There were 26 benign small renal masses (including 18 oncocytomas, seven lipid-poor angiomyolipomas, and one hemangioblastoma) and 68 malignant masses (including 41 clear cell, 20 papillary, and seven chromophobe renal cell carcinomas [RCCs[) that were 1.1-4.0 cm in diameter (mean, 2.7 cm ± 0.9). All patients underwent contrast-enhanced US on the same one machine, and 68 patients were imaged on all three machines. Vascularity was present in all lesions (n = 94) at contrast-enhanced US. Lesion hypovascularity relative to the adjacent cortex in the arterial phase was seen in only malignant lesions by both reviewers; reviewer 1 saw hypovascularity in 24 of 94 lesions (P = .0001), and reviewer 2 saw hypovascularity in 21 of 94 lesions (P = .0006), for a specificity of 100% (95% confidence interval [CI]: 84, 100). This feature had κ values of 0.91 (95%CI: 0.82, 1.00) between the two reviewers and 0.85 (95% CI: 0.72, 0.99) between the three machines. Eighteen of 20 papillary RCCs were hypovascular. Quantitative parameters of area under the receiver operating characteristics curve, peak intensity, wash-in slope of 10%-90% and 5%-45%, and washout slope of 100%-10% and 50%-10% were significantly higher in malignant renal masses (P = .018, P = .002, P = .036, P = .016, P = .001, and P = .005, respectively) than in benign lesions. CONCLUSION: Excluding lipid-rich angiomyolipoma, hypovascularity-which has high interobserver and intermachine agreement-of solid small renal masses relative to the cortex in the arterial phase has 100% specificity (95% CI: 84, 100) for detecting malignancy, most often papillary RCC.

Differentiating malignant from benign thrombosis in hepatocellular carcinoma: contrast-enhanced ultrasound.

BACKGROUND: To determine the accuracy of contrast-enhanced ultrasonography (CEUS) in differentiating malignant and benign venous thrombosis complicating hepatocellular carcinoma (HCC). METHODS: Fifty patients (M:F = 41:9; age range 46-83 years) with HCC and venous thrombosis [portal vein (PV) in 45 and hepatic vein (HV) in 5] detected on CT or MR scan were evaluated with CEUS. Reference standard of malignant and benign thrombosis was based on serial clinicoradiologic follow-up (n = 43) or pathology (n = 7). Two independent, blinded readers retrospectively recorded the enhancement features of the venous thrombosis and diagnosed as benign or malignant thrombosis with a five-point confidence scale. Receiver operating characteristic (ROC) curves were calculated to determine the diagnostic performance of CEUS in differentiating malignant from benign thrombosis. Confidence level ratings were also used to calculate the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the diagnosis of malignant thrombosis. Inter-reader agreement was calculated using κ statistics in each assessed finding. Gray scale and Doppler characteristics of primary tumor and thrombosis were also assessed. RESULTS: Of the 50 patients, 37 were malignant (33 with PV thrombosis and 4 with HV thrombosis) and 13 were benign (12 with PV thrombosis and 1 with HV thrombosis). In ROC curve analysis for differentiating malignant from benign thrombosis, Az was 0.947 (CI 0.841-0.991) for reader 1 and 0.958 (CI 0.861-0.995) for reader 2 with excellent inter-reader agreement (κ = 0.86). When the confidence level ratings of 1 or 2 were considered malignant thrombosis, the sensitivity, specificity, PPV, and NPV in differentiating malignant from benign thrombosis were 100%, 83%, 95%, and 100% for reader 1 and 100%, 92%, 97%, and 100% for reader 2. CONCLUSION: CEUS is useful to differentiate malignant and benign venous thrombosis associated with HCC with high diagnostic accuracy.

Iterative reconstruction algorithm for CT: can radiation dose be decreased while low-contrast detectability is preserved?

PURPOSE: To compare the low-contrast detectability and image quality of computed tomography (CT) at different radiation dose levels reconstructed with iterative reconstruction (IR) and filtered back projection (FBP). MATERIALS AND METHODS: A custom liver phantom with 12 simulated hypoattenuating tumors (diameters of 5, 10, 15, and 20 mm; tumor-to-liver contrast values of -10, -20, and -40 HU) was designed. The phantom was scanned with a standard abdominal CT protocol with a volume CT dose index of 21.6 mGy (equivalent 100% dose) and four low-dose protocols (20%, 40%, 60%, and 80% of the standard protocol dose). CT data sets were reconstructed with IR and FBP. Image noise was measured, and the tumors' contrast-to-noise ratios (CNRs) were calculated. Tumor detection was independently assessed by three radiologists who were blinded to the CT technique used. A total of 840 simulated tumors were presented to the radiologists. Statistical analyses included analysis of variance. RESULTS: IR yielded an image noise reduction of 43.9%-63.9% and a CNR increase of 74.1%-180% compared with FBP at the same dose level (P < .001). The overall sensitivity for tumor detection was 64.7%-85.3% for IR and 66.3%-85.7% for FBP at the 20%-100% doses, respectively. There was no significant difference in the sensitivity for tumor detection between IR and FBP at the same dose level (P = .99). The sensitivity of the protocol at the 20% dose with FBP and IR was significantly lower than that of the protocol at the 100% dose with FBP and IR (P = .019). CONCLUSION: As the radiation dose at CT decreases, the IR algorithm does not preserve the low-contrast detectability. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122349/-/DC1.

Characterization of 1-to 2-cm liver nodules detected on hcc surveillance ultrasound according to the criteria of the American Association for the Study of Liver Disease: is quadriphasic CT necessary?

OBJECTIVE: The purpose of this study was to identify the essential number of phases from multiphasic CT for 1- to 2-cm hepatocellular carcinoma (HCC) on surveillance ultrasound and to compare the results with the American Association for the Study of Liver Disease (AASLD) standard (arterial phase hypervascularity and portal venous phase [PVP] or delayed phase hypovascularity). MATERIALS AND METHODS: The study included 110 newly detected nodules (1-2 cm; 36 HCC, 74 benign) in 96 patients detected in an HCC surveillance program. Three radiologists prospectively evaluated the attenuation of each nodule relative to the liver on each phase of quadriphasic CT. Univariate and multivariate logistic regression analyses were used to identify parameters associated with HCC. Multiple combinations of phases were compared with the AASLD standard. RESULTS: Only arterial phase hypervascularity and delayed phase hypovascularity were significantly associated with HCC both on univariate (odds ratio, arterial phase 7.51 [95% CI, 2.79-20.20]; delayed phase, 2.80 [1.14-6.90]) and multivariate analyses (arterial phase, 11.30 [4.30-29.68]; delayed phase, 4.39 [1.20-16.13]). The combination of arterial phase and delayed phase yielded the highest specificity (99%) and sensitivity (57%). There was no significant difference between AASLD standard (sensitivity, 57%; specificity, 98%) versus biphasic (arterial phase hypervascularity and delayed phase hypovascularity: sensitivity, 57%; p = 1 and specificity, 99%; p = 0.32), triphasic (arterial phase hypervascularity and unenhanced or PVP hypovascularity: sensitivity, 53%; p = 0.325 and specificity, 97%; p = 0.32), or quadriphasic combination (arterial phase hypervascularity and unenhanced, PVP or delayed phase hypovascularity: sensitivity, 57%; specificity, 97%), whereas the sensitivity of biphasic arterial phase and PVP was significantly lower (39% vs 57%, p = 0.022). CONCLUSION: For diagnosing 1- to 2-cm HCC detected on surveillance ultrasound, arterial phase and delayed phase are two essential phases, providing higher sensitivity than the combination of arterial phase and PVP, and equal performance with triphasic and quadriphasic combinations. The biphasic combination of arterial phase and delayed phase may replace quadriphasic CT recommended by AASLD.

Indeterminate 1-2-cm nodules found on hepatocellular carcinoma surveillance: biopsy for all, some, or none?

UNLABELLED: In the latest hepatocellular carcinoma (HCC) management guidelines by the American Association for the Study of Liver Diseases, biopsy is advocated for all nodules deemed indeterminate after imaging work-up by contrast-enhanced scans. However, the latest guidelines' imaging work-up algorithm has been shown to improve sensitivity of characterization of HCC for 1-2-cm nodules, decreasing the proportion of HCCs that remain indeterminate after imaging work-up. We undertook a study of 1-2-cm indeterminate nodules to determine what proportions are malignant and which variables can be used to limit biopsy to a subset of nodules at higher risk of malignancy. Eighty consecutive patients with 93 indeterminate nodules were included. Final diagnosis was established in 85 nodules, with 13 malignant (9 by biopsy, 4 by growth) and 72 benign (stability of ≥18 months). Cause of liver disease, ethnicity, size, arterial hypervascularity, venous hypoenhancement, and presence of synchronous typical HCC were analyzed by univariate logistic analysis to determine significant predictors of malignancy. Rate of malignancy among indeterminate 1-2-cm nodules was found to be 14%-23%. Only arterial hypervascularity [odds ratio (OR), 3.7) and presence of synchronous HCC (OR, 7.1) were significant predictors of malignancy. A strategy of limiting biopsy to nodules that had either feature would result in 23 biopsies and potentially detect 8 of 13 malignant nodules, yielding a sensitivity of 62% and specificity of 79%. CONCLUSION: The prevalence of malignancy among 1-2-cm indeterminate nodules is low (14%-23%), and biopsy of all such nodules results in many negative results. Limiting biopsy to nodules with arterial hypervascularity or in the presence of a synchronous typical HCC would detect the majority of HCCs while substantially reducing the number of biopsies.

Perfusion and parenchymal changes related to vascular alterations of the liver.

Imaging plays a significant role in the diagnosis of vascular abnormalities of the liver and sometimes provides the only clue to the correct diagnosis. With advances of imaging techniques and multiphasic acquisition of liver imaging, various perfusion changes are frequently encountered. Correct imaging diagnosis of significant vascular diseases can prompt appropriate work-up and timely management. Accurate differentiation of clinically insignificant perfusion phenomena from clinically significant findings including neoplastic conditions and in the setting of post-transplantation is essential. This pictorial essay illustrates various perfusion and parenchymal changes associated with portal venous inflow, hepatic venous outflow, and non-portal venous third inflow and describes brief background pathophysiology and differential points.

Fading hepatic hemangiomas on multiphasic CT.

PURPOSE: To describe fading hemangiomas [substantially lower attenuation (>30 HU) than vascular pool in the portal venous phase (PVP)] and to determine their incidence and characteristics on multiphasic CT. METHODS: The study population composed of 168 hemangiomas (≥5 mm) in 114 consecutive patients which were imaged on multiphasic CT and also proved by diagnostic findings on MRI. The size of hemangiomas and CT attenuation number of the enhancing area within the hemangioma, liver parenchyma, and portal vein were measured on both arterial phase (AP) and PVP images. The rapidity of enhancement (slow, <50%; rapid, 50%-99%; flash-filler, 100% filling in the AP) and association with arterioportal shunting (APS) were also determined by two independent reviewers. Imaging features were compared between fading and non-fading hemangiomas using Kruskal-Wallis test. RESULTS: Of 168 hemangiomas, the enhancing area of 27 hemangiomas (16%, 27/168) showed substantially lower attenuation than that of PV (fading) in the PVP. When the attenuation difference was compared with the rapidity of enhancement, flash-fillers showed lower attenuation than PV in the PVP more frequently than both slow-fillers (P < 0.05) and rapid-fillers (P < 0.05). The proportion of fading hemangiomas was 52% (14/27) in flash-fillers, much more frequent than in rapid-fillers (4/27, 15%) as well as slow-fillers (9/27, 33.3%). The size of fading hemangiomas (17.9 ± 4.5 mm) was significantly smaller than that of non-fading (24.2 ± 3.6 mm) (P = 0.032). Although APS was more frequent in fading hemangiomas (55.6%, 15/27) than that of non-fading hemangiomas (37.6%, 53/141), there was no statistically significant difference (P = 0.086). CONCLUSIONS: Sixteen percentage (27/168) of the hemangiomas in our study showed substantially lower attenuation than the portal vein in the PVP CT and this was more frequent in flash-fillers (52%, 14/27). The knowledge that fading does not preclude the diagnosis of hemangioma as well as of its high incidence in flash-fillers is important, as flash-filling hemangiomas with fading may cause a diagnostic challenge in patients suspected to have hypervascular malignancy.