Cirrhotic nodules: association between MR imaging signal intensity and intranodular blood supply

Large (>or=2 cm) non-hypervascular nodules depicted on MRI in the cirrhotic liver: fate and implications

AIM

To determine the fate and clinical implication of large (>or=2 cm), non-hypervascular nodules depicted on magnetic resonance imaging (MRI) in the cirrhotic liver.

MATERIALS AND METHODS

In 21 patients with cirrhosis (14 hepatitis B, two ethanol abuse, four cryptogenic, one Wilson's disease), 25 large (>or=2 cm in the longest dimension) non-hypervascular nodules were identified on dynamic MRI. The implications for diagnosis of the initial size, contour, and signal characteristics on MRI in addition to patients' age and cause of cirrhosis were assessed in our analysis.

RESULTS

Twelve (75%) out of 16 lesions were malignant or potentially-malignant from 14 hepatitis B patients, while seven (78%) of the nine lesions from other patients were benign (p=0.016). The mean age of the patients who had malignant or potentially malignant lesions (57 years) was older than that for the other patients (47 years; p=0.039). The ratio of the short-to-long diameter was higher in malignant or potentially malignant lesions (mean 0.86) than in benign lesions (mean 0.69; p=0.008). There was no discriminative signal intensity characteristic (p>0.2 for all factors) that indicated the malignant potential for each non-hypervascular nodule. For all 10 lesions in the hepatitis B patients who were older than 52 years with a short-to-long diameter ratio of more than 0.75, the positive predictive value for malignant potential based on these three combined factors was 100%.

CONCLUSION

In older patients with cirrhosis from hepatitis B, large (>or=2 cm), non-hypervascular nodules with a spherical contour have a high malignant potential.

Radiofrequency ablation of hepatocellular carcinoma: value of virtual CT sonography with magnetic navigation

OBJECTIVE

Virtual CT sonography with magnetic navigation yields cross-sectional images of CT volume data that correspond to the angle of the transducer in the magnetic field in real time. The purpose of this study was to evaluate the efficiency and feasibility of virtual CT sonography for radiofrequency ablation of hypervascular hepatocellular carcinoma poorly defined on B-mode sonography.

MATERIALS AND METHODS

One hundred one patients enrolled in the study were separated into two groups. Fifty-one patients with 65 hepatocellular carcinomas underwent prospective virtual CT sonography as guidance for radiofrequency ablation. Fifty patients with 63 hepatocellular carcinomas managed with B-mode sonographic guidance were retrospectively selected under the same conditions as the virtual CT sonography group to act as a historical control group.

RESULTS

In the virtual CT sonography group, technically successful ablation was achieved in a single session in 92% (47/51) of the patients and in two sessions in 8% (4/51). In the B-mode sonography group, technical success was achieved in a single session in 72% (36/50) of the patients, in two sessions in 24% (12/50), and in three sessions in 4% (2/50). Treatment analysis showed that the technical success rate after a single treatment session was significantly (p = 0.017) higher for the virtual CT sonography group. The number of treatment sessions was significantly (p = 0.021) lower for the virtual CT sonography group (mean, 1.1 +/- 0.1 vs 1.3 +/- 0.3 sessions).

CONCLUSION

Virtual CT sonographically assisted radiofrequency ablation is an efficient treatment of patients with hepatocellular carcinoma that is poorly defined on B-mode sonography.

MR Imaging of hepatocellular carcinoma in the cirrhotic liver: challenges and controversies

The incidence of hepatocellular carcinoma (HCC) is expected to increase in the next 2 decades, largely due to hepatitis C infection and secondary cirrhosis. HCC is being detected at an earlier stage owing to the implementation of screening programs. Biopsy is no longer required prior to treatment, and diagnosis of HCC is heavily dependent on imaging characteristics. The most recent recommendations by the American Association for the Study of Liver Diseases (AASLD) state that a diagnosis of HCC can be made if a mass larger than 2 cm shows typical features of HCC (hypervascularity in the arterial phase and washout in the venous phase) at contrast material-enhanced computed tomography or magnetic resonance (MR) imaging or if a mass measuring 1-2 cm shows these features at both modalities. There is an ever-increasing demand on radiologists to detect smaller tumors, when curative therapies are most effective. However, the major difficulty in imaging cirrhosis is the characterization of hypervascular nodules smaller than 2 cm, which often have nonspecific imaging characteristics. The authors present a review of the MR imaging and pathologic features of regenerative nodules and dysplastic nodules and focus on HCC in the cirrhotic liver, with particular reference to small tumors and lesions that may mimic HCC. The authors also review the sensitivity of MR imaging for the detection of these tumors and discuss the staging of HCC and the treatment options in the context of the guidelines of the AASLD and the imaging criteria required by the United Network for Organ Sharing for transplantation. MR findings following ablation and chemoembolization are also reviewed.

MR imaging of hepatocellular carcinoma: relationship between lesion size and imaging findings, including signal intensity and dynamic enhancement patterns

PURPOSE

To assess the relationship between lesion size and MR imaging findings of pathologically-proven hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

In a retrospective, single-center study, 37 consecutive patients were identified between 1999 and 2005 that underwent preoperative MRI and surgical resection of HCC. A total of 47 lesions (mean size = 6.85 cm, range = 1-25 cm) were assessed for signal intensity (SI), enhancement patterns, and secondary morphologic features. Interobserver rating, percentage enhancement, and contrast-to-noise-ratio (CNR) were determined. Lesions were assessed for combinations of typical MRI features. Regression analysis was used to assess relations between MRI findings and tumor size.

RESULTS

On fat-suppressed T2-weighted (T2w) fast-spin-echo, smaller lesions had lower SI compared to larger lesions (P < 0.05). In the arterial phase, smaller lesions showed significantly higher percentage enhancement compared to larger lesions (P < 0.05). In the delayed phase, smaller lesions showed less pronounced washout (P < 0.05). Heterogeneity of the lesions, including fatty infiltration, internal nodules, or mosaic pattern, was observed significantly more frequently in larger lesions (P < 0.001). The classic combination of high T2w signal, strong arterial enhancement, and delayed phase washout was present in 23 of 44 lesions (52%).

CONCLUSION

Smaller HCC often showed lower SI on T2w, more intense arterial enhancement, and less pronounced delayed washout compared to larger HCC.

Enhancement patterns and signal-intensity characteristics of small hepatocellular carcinoma in cirrhosis: pathologic basis and diagnostic challenges

Recent pathologic studies of hepatic resection and transplantation specimens have elucidated the morphologic features of the precancerous lesions and small hepatocellular carcinomas (HCCs) arising in cirrhotic livers. Small HCCs measuring less than 2 cm in diameter are of two types: vaguely nodular, well-differentiated tumors, also known as "early" HCCs, and distinctly nodular tumors, with histologic features of "classic" HCC. The precancerous lesions include dysplastic foci and dysplastic nodules. "Classic" small HCCs are supplied by nontriadal arteries, whereas early HCCs and dysplastic nodules may receive blood supply from both portal tracts and nontriadal arteries. The similarities in blood supply of these three types of nodular lesions result in significant overlap of findings on dynamic imaging. Nevertheless, small HCCs sometimes display characteristic radiologic features, such as "nodule-in-nodule" configuration and "corona enhancement" pattern. Moreover, various histologic features of these nodular lesions may also be related to a variety of signal intensities and attenuation coefficients, while the presence of cirrhosis is known to limit the sensitivity and specificity of any imaging modality, due to liver inhomogeneity. Because of these reasons, imaging findings of nodular lesions in cirrhotic livers are often inconclusive, emphasizing the need for a better understanding of these imaging features.

Imaging of multistep human hepatocarcinogenesis

In Japan, there are approximately 32 000 deaths ( approximately 30 deaths per 100 000) per year due to hepatocellular carcinoma (HCC), and it is the third most common cancer in men and fifth in women. Approximately 90% of them are associated with chronic liver diseases due to hepatitis C or B virus infection. Therefore, it has become possible to detect small early stage HCC by the periodic screening in these high-risk patients group. During the screening imaging diagnosis of HCC, various kinds of hepatocellular nodules are also frequentlydetected. To characterize them is very important for the early diagnosis and treatment of HCC. For this purpose, it is necessary to understand the concept of multistep hepatocarcinogenesis and the sequential changes of imaging findings.

Ultraselective Transcatheter Arterial Chemoembolization with a 2-F Tip Microcatheter for Small Hepatocellular Carcinomas: Relationship Between Local Tumor Recurrence and Visualization of the Portal Vein with Iodized Oil

PURPOSE

To retrospectively evaluate the relationship between local tumor recurrence and iodized oil deposition in the portal vein by using ultraselective transcatheter arterial chemoembolization (TACE) for small hepatocellular carcinoma.

MATERIALS AND METHODS

One-hundred twenty-three tumors smaller than 5 cm in diameter (mean diameter, 1.9 cm; median diameter, 1.6 cm) were treated with TACE by using a 2-F tip microcatheter at a distal portion of the subsegmental artery of the liver. Portal vein visualization at spot radiography during TACE was divided into three grades, as follows: 0 = not visualized, 1 = limited near the tumor, and 2 = whole or extended to the embolized area. Local recurrence rates of each grade group were compared. The recurrent pattern was divided into intratumoral and peritumoral recurrence. Complications were also analyzed.

RESULTS

Of the 123 tumors, 53 (43.1%) were classified as grade 2, 52 (42.3%) were classified as grade 1, and 18 (14.6%) tumors were classified as grade 0. Overall local recurrence rates at 12, 24, and 36 months were 25.6%, 34.7%, and 34.7%, respectively. The local recurrence rates for the grades 2, 1, and 0 groups were 7.9%, 24.8%, and 85.7%, respectively, at 12 months and 17.7%, 38.9%, and 85.7% at 24 months. Recurrence rates in the grade 2 group were significantly lower than those in the grades 1 and 0 groups (P = .0485 and P < .0001, respectively). Intratumoral recurrence was observed in 21 tumors, most of which were in the grade 0 group. Peritumoral recurrence was noted in 16 tumors, most of which were in the grade 2 group. There were no major complications.

CONCLUSION

Ultraselective TACE was safe and effective in a significant number of tumors. In particular, local recurrence was significantly lower when a greater degree of portal vein visualization was demonstrated during TACE.

Stepwise carcinogenesis of hepatocellular carcinoma in the cirrhotic liver: demonstration on serial MR imaging

PURPOSE

To demonstrate imaging findings of stepwise carcinogenesis of hepatocellular carcinoma (HCC) in cirrhosis at serial state-of-the-art MR imaging exams.

MATERIALS AND METHODS

In a retrospective search of the hospital archives, three patients were identified in which developing HCC was observed in serial MR examinations, with histopathology or alpha-fetoprotein (AFP) correlation. Image findings were assessed for signal intensity of the lesions at multiple sequences, including dynamic gadolinium-enhanced imaging.

RESULTS

Initial findings in patient A showed a small nodule with fatty infiltration that developed in HCC in follow-up MRI, comprised of low-grade dysplastic nodule (DN; DN I), high-grade DN (DN II), and eventually classic HCC. In patient B, increased signal intensity on T2-weighted images in a single DN among numerous regenerative nodules was the only initial sign. Follow up MRI showed further increase in signal intensity and increased neovascularity, which suggested focal HCC in a DN II. Patient C demonstrated gradually increasing neovascularity as only initial sign, with development of classic HCC over time.

CONCLUSION

MR imaging provides insight in various pathways of stepwise carcinogenesis of developing HCC in cirrhosis. This may further explain the genetic heterogeneity, and may facilitate early detection and better selection of patients for follow-up.

Multidetector helical CT plus superparamagnetic iron oxide-enhanced MR imaging for focal hepatic lesions in cirrhotic liver: a comparison with multi-phase CT during hepatic arteriography

The aim of this study was to evaluate multidetector helical computed tomography (MDCT), superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging, and CT arterial portography (CTAP) and CT during hepatic arteriography (CTHA) for the detection and diagnosis of hepatocellular carcinomas (HCC). This included visual correlations of MDCT and SPIO-MR imaging in the detection of HCC using receiver operating characteristic (ROC) analysis. Twenty-five patients with 57 nodular HCCs were retrospectively analyzed. A total of 200 segments, including 49 segments with 57 HCCs, were reviewed independently by three observers. Each observer read four sets of images (set 1, MDCT; set 2, unenhanced and SPIO-enhanced MR images; set 3, combined MDCT and SPIO-enhanced MR images; set 4, combined CTAP and CTHA). The mean Az values representing the diagnostic accuracy for HCCs of sets 1, 2, 3, and 4 were 0.777, 0.814, 0.849, and 0.911, respectively, and there was no significant difference between sets 3 and 4. The sensitivity of set 4 was significantly higher than those of set 3 for all the lesions and for lesions 10 mm or smaller (p<0.05); however, for lesions larger than 10mm, the sensitivities of the two sets were similar. No significant difference in positive predictive value and specificity was observed between set 3 and set 4. Combined MDCT and SPIO-enhanced MR imaging may obviate the need for more invasive CTAP and CTHA for the pre-therapeutic evaluation of patients with HCC more than 10mm.