Transient hepatic attenuation difference (THAD) following transcatheter arterial chemoembolization for hepatic malignancy: changes on serial CT examinations

A multi-institutional study designed by members of Tokyo Guidelines (TG) Core Meeting to elucidate the clinical characteristics and pathogenesis of acute cholangitis after bilioenteric anastomosis and biliary stent insertion with a focus on biliary obstruction: Role of transient hepatic attenuation difference (THAD) and pneumobilia in improving TG diagnostic performance

BACKGROUND/PURPOSE

The aim of this study was to clarify the clinical characteristics of acute cholangitis (AC) after bilioenteric anastomosis and stent-related AC in a multi-institutional retrospective study, and validate the TG18 diagnostic performance for various type of cholangitis.

METHODS

We retrospectively reviewed 1079 AC patients during 2020, at 16 Tokyo Guidelines 18 (TG 18) Core Meeting institutions. Of these, the post-biliary reconstruction associated AC (PBR-AC), stent-associated AC (S-AC) and common AC (C-AC) were 228, 307, and 544, respectively. The characteristics of each AC were compared, and the TG18 diagnostic performance of each was evaluated.

RESULTS

The PBR-AC group showed significantly milder biliary stasis compared to the C-AC group. Using TG18 criteria, definitive diagnosis rate in the PBR-AC group was significantly lower than that in the C-AC group (59.6% vs. 79.6%, p < .001) because of significantly lower prevalence of TG 18 imaging findings and milder bile stasis. In the S-AC group, the bile stasis was also milder, but definitive-diagnostic rate was significantly higher (95.1%) compared to the C-AC group. The incidence of transient hepatic attenuation difference (THAD) and pneumobilia were more frequent in PBR-AC than that in C-AC. The definitive-diagnostic rate of PBR-AC (59.6%-78.1%) and total cohort (79.6%-85.3%) were significantly improved when newly adding these items to TG18 diagnostic imaging findings.

CONCLUSIONS

The diagnostic rate of PBR-AC using TG18 is low, but adding THAD and pneumobilia to TG imaging criteria may improve TG diagnostic performance.

Quantification of Liver Fat Content after Radiofrequency Ablation for Liver Cancer: Correlation with Hepatic Perfusion Disorders

PURPOSE

To quantitatively investigate the correlation between liver fat content and hepatic perfusion disorders (HPD) after radiofrequency ablation (RFA) for liver cancer using magnetic resonance imaging (MRI)-determined proton density fat fraction (PDFF).

MATERIALS AND METHODS

A total of 150 liver cancer patients underwent liver MRI examination within one month after RFA and at four months after RFA. According to the liver fat content, they were divided into non-, mild, moderate, and severe fatty liver groups. The liver fat content and hepatic perfusion disorders were determined using PDFF images and dynamic contrast-enhanced MRI images. The relationship between the liver fat content and HPD was investigated.

RESULTS

At the first postoperative MRI examination, the proportion of patients in the nonfatty liver group with hyperperfused foci (11.11%) was significantly lower than that in the mild (30.00%), moderate (42.86%), and severe fatty liver (56.67%) groups (p < 0.05), whereas the proportions of patients with hypoperfused foci (6.67%, 7.5%, 5.71%, and 6.67%, respectively) were not significantly different among the four groups (p > 0.05). In the nonfatty liver group, the liver fat content was not correlated with hyperperfusion abnormalities or hypoperfusion abnormalities. By contrast, in the three fatty liver groups, the liver fat content was correlated with hyperperfusion abnormalities but was not correlated with hypoperfusion abnormalities. At the second postoperative MRI examination, six patients in the nonfatty liver group were diagnosed with fatty liver, including two patients with newly developed hyperperfusion abnormalities and one patient whose hypoperfusion abnormality remained the same as it was in the first postoperative MRI examination.

CONCLUSION

There was a high correlation between the liver fat content and hyperperfusion abnormalities after RFA for liver cancer. The higher the liver fat content was, the higher the was risk of hyperperfusion abnormalities. However, there was little correlation between liver fat content and hypoperfusion abnormalities, and the increase in postoperative liver fat content did not induce or alter the presence of hypoperfused foci.

Multislice Computed Tomographic Manifestation of Transient Hepatic Attenuation Difference in the Left Lobe of the Liver: A Retrospective Study

INTRODUCTION

Transient hepatic attenuation differences (THAD) are areas of high parenchymal enhancement observed during the hepatic arterial phase on computed tomography (CT). THAD in the left lobe of the liver can lead to surgical complications.

METHODS

A retrospective study was conducted on patients who underwent multislice computed tomography (MSCT) examination of the upper abdomen to understand the morphology, distribution, and causes of THAD and their correlation with hepatic artery variation.

RESULTS

Among 179 cases, 65 and 114 belonged to diseased and normal groups, respectively. THAD as observed in MSCT demonstrated various shapes: lobe/segment (127 cases; 70.9%), irregular sheet (31; 17.3%), strip shape (9; 5.02%), arc/semicircle (7; 3.9%), and segment + flaky (5; 2.79%). THAD were found to be caused by liver tumor (32.3%), hepatic inflammatory lesions (6.15%), biliary tract diseases (13.8%), perihepatic disease compression (9.23%), portal vein obstructive disease (1.53%), and lesion in left hepatic lobe with hepatic artery variation (29.2%). THAD exhibited variation in distribution in the left lobe of the liver. Among 114 cases, THAD in 18 (15.7%) cases were observed in the S2 segment, six (5.26%) in the S3 segment, and 90 (78.9%) in multiple segments of the liver, that is, 50 cases in S2 and S3 segments and 40 cases in S2, S3, and S4 segments. The hepatic artery of 179 cases was of various types based on Hiatt classification: 57 cases of Hiatt I (31%), 65 cases of Hiatt II (37%), 11 cases of Hiatt III (6%), 17 cases of Hiatt IV (10%), 7 cases of Hiatt V (4%), 12 cases of large left hepatic artery (7%), 6 cases of right hepatic artery originating from the celiac trunk (3%), and 4 cases (2%) of superior mesenteric artery originating from the celiac trunk.

CONCLUSION

THAD can occur as a result of specific pathological causes and hence should be considered as a diagnostic sign in liver pathologies.

Utility of diffusion weighted imaging with the quantitative apparent diffusion coefficient in diagnosing residual or recurrent hepatocellular carcinoma after transarterial chemoembolization: a meta-analysis

Background

Accurate and early diagnosis of residual tumors or intrahepatic recurrences after TACE is critically needed for determining the success of treatments and for guiding subsequent therapeutic planning. This meta-analysis was performed to assess the efficacy of diffusion weighted imaging (DWI) with the quantitative apparent diffusion coefficient (ADC) value in diagnosing residual or recurrent hepatocellular carcinoma after transarterial chemoembolization (TACE).

Materials and methods

A comprehensive literature search of PubMed, Embase, Web of Science, Scopus and the Cochrane Library database, from inception to July 2019, was conducted to select original studies on diagnosing residual or recurrent HCCs after TACE using DWI sequence with its ADC value. Two researchers independently chose study, extracted data, conducted meta-analysis, and evaluated methodological quality according to Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool.

Results

Twelve studies comprising 624 patients and 712 tumors were finally included. The pooled sensitivity, specificity and AUC value of DWI in diagnosing residual or recurrent HCCs after TACE were 85% (95%CI: 74–92%), 83% (95%CI: 75–88%) and 0.90 (95%CI: 0.87–0.92), respectively. Residual or recurrent HCCs have significantly lower ADC value than necrotic tumors (MD = -0.48, 95%CI: − 0.69~ − 0.27, P < 0.01).

Conclusion

This study demonstrated that DWI performed better in diagnosing residual or recurrent HCCs after TACE, and ADC value may serve as alternatives for further evaluation of residual or recurrent leisions in HCC patients after TACE.

Gadoxetic acid-enhanced MRI of transient hepatic enhancement differences: Another cause of hypointense observation on hepatobiliary phase

PURPOSE

To retrospectively determine the frequency, natural history and factors associated with the presence of transient hepatic enhancement difference showing hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced MRI.

MATERIALS AND METHODS

Gadoxetic acid-enhanced MRI of 125 patients (91 men; 34 women) with transient hepatic enhancement difference were retrospectively reviewed. Three readers qualitatively and quantitatively evaluated MR imaging features and evolution at follow up. The Chi-square test, Fisher's exact test and Kruskall-Wallis rank test were used for statistical analysis.

RESULTS

Transient hepatic enhancement difference were hypointense on hepatobiliary phase images in 20 of 125 cases (16%). At univariate analysis there was association with wedge-shape morphology (p < 0.001), size ≥21 mm (p < 0.001), hyperintensity on T2-weighted imaging (p < 0.001), restricted diffusion (p < 0.001) and previous treatment (p < 0.005). At multivariate analysis, the following factors were associated: previous treatment (p < 0.05), hyperintensity on T2-weighted imaging (p < 0.001) and size ≥21 mm (p < 0.001). Of 12 patients with hypointense transient hepatic enhancement difference on hepatobiliary phase images who had follow-up MRI, nine showed reduction in size.

CONCLUSION

Transient hepatic enhancement difference observations showing hypointensity on hepatobiliary phase images of gadoxetic acid-enhanced MRI are not infrequent and may shrink at follow-up. They are more likely associated with size ≥21 mm, hyperintensity on T2-weighted images and previous treatment of adjacent tumor.

Prognostication and response assessment in liver and pancreatic tumors: The new imaging

Diffusion-weighted imaging (DWI), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and perfusion computed tomography (CT) are technical improvements of morphologic imaging that can evaluate functional properties of hepato-bilio-pancreatic tumors during conventional MRI or CT examinations. Nevertheless, the term “functional imaging” is commonly used to describe molecular imaging techniques, as positron emission tomography (PET) CT/MRI, which still represent the most widely used methods for the evaluation of functional properties of solid neoplasms; unlike PET or single photon emission computed tomography, functional imaging techniques applied to conventional MRI/CT examinations do not require the administration of radiolabeled drugs or specific equipments. Moreover, DWI and DCE-MRI can be performed during the same session, thus providing a comprehensive “one-step” morphological and functional evaluation of hepato-bilio-pancreatic tumors. Literature data reveal that functional imaging techniques could be proposed for the evaluation of these tumors before treatment, given that they may improve staging and predict prognosis or clinical outcome. Microscopic changes within neoplastic tissues induced by treatments can be detected and quantified with functional imaging, therefore these techniques could be used also for post-treatment assessment, even at an early stage. The aim of this editorial is to describe possible applications of new functional imaging techniques apart from molecular imaging to hepatic and pancreatic tumors through a review of up-to-date literature data, with a particular emphasis on pathological correlations, prognostic stratification and post-treatment monitoring.

Diffusion-weighted MRI of hepatocellular carcinoma in cirrhosis

The internationally accepted diagnostic criteria for hepatocellular carcinoma (HCC) in cirrhosis are highly accurate for large tumours, but offer relatively low sensitivity for small (<2 cm) tumours. Diffusion-weighted imaging (DWI) is a functional magnetic resonance imaging (MRI) technique that has been studied extensively as an aid to visualize various abdominal malignancies, including HCC in cirrhosis. DWI maps water diffusivity, which in HCC may be restricted as a result of changes ensuing from hepatocarcinogenesis. The present review is based on up-to-date evidence and describes the strengths and weaknesses of DWI, both as a standalone technique and as an adjunct sequence to conventional protocols, in the diagnosis, staging, prognostication, and assessment of treatment response of HCC in cirrhosis.

Added value of diffusion-weighted imaging in the MRI assessment of perilesional tumor recurrence after chemoembolization of hepatocellular carcinomas

PURPOSE

To investigate the additional value of diffusion-weighted imaging (DWI) in the MRI assessment of perilesionally recurrent hepatocellular carcinomas (HCCs) after transcatheter arterial chemoembolization (TACE).

MATERIALS AND METHODS

For gadopentetate dimeglumine-enhanced multiphasic dynamic images with precontrast T1- and T2-weighted images of 23 patients treated with TACE, two radiologists independently sorted the confidence levels for the presence of a viable tumor in the vicinity of the treated lesions into five grades. In another session, images from DWI (b factor = 50, 400, and 800 s/mm(2)) were added to the previously reviewed images and the same radiologists sorted the confidence levels.

RESULTS

A total of 26 lesions (0.7-3.5 cm) from 16 patients were confirmed to be perilesional recurrences of HCC. The area under the receiver operating characteristic curve (A(z)) for the second interpretation session (0.826) was not significantly different (P = 0.299) from that of the first session (0.859). The overall sensitivity was increased from 85% to 92%, but the specificity decreased from 65% to 50% after adding DWI.

CONCLUSION

The addition of DWI has the potential to improve sensitivity, but not the overall diagnostic accuracy, in the assessment of perilesional recurrence of HCCs after chemoembolization.

Nontumorous arterioportal shunts in the liver: CT and MRI findings considering mechanisms and fate

The intrahepatic non-tumorous arterioportal shunt (APS) is one of the important causes of transient hepatic enhancement differences (THED) on dynamic CT or MRI. Most small APSs are located in the peripheral portion of the liver. Because of the parenchymal distortion in the advanced cirrhotic liver, many small APSs tend to show an amorphous or nodular appearance, making them difficult to distinguish from hypervascular tumors. In addition to the use of dynamic CT or MRI, iso-attenuation densities or iso-intensities on pre-contrast and equilibrium phases, MRI using a liver-specific contrast agent can be useful to characterize the hypervascular pseudolesions. Because there is no difference in water diffusion in the hepatic parenchyma in the region of the APS, diffusion-weighted MRI also has great potential to distinguish non-tumorous shunts from true focal lesions. Larger (>2 cm) APSs of direct arterio-portal venous fistulas from extrinsic insults show typical subcapsular wedge-like THEDs that are only temporarily depicted several months after the traumatic event; most of these THEDs gradually decrease in size or vanish completely. By understanding the nature of non-tumorous APSs, radiologists will be able to provide a more accurate assessment of many THEDs during daily interpretations of CT or MR images of the liver.