Liver Metastases: Correlation between Imaging Features and Pathomolecular Environments.

A wide range of imaging manifestations of liver metastases can be encountered, as various primary cancers preferably metastasize to the liver (organ-specific metastases), with the imaging characteristics largely depending on various primary tumor-specific factors such as histopathologic category, degree of tumor differentiation, histologic behavior, and intratumor alterations. Characteristic imaging features potentially can help provide a more precise diagnosis in some clinical settings. These settings include those of (a) primary cancers of hollow organs such as gastrointestinal organs, the lungs, and the bladder, owing to the appearance of metastases that cannot be applied to the liver, which is a parenchymal organ; (b) unknown primary tumors; (c) more than one primary tumor; (d) another emergent malignancy; and (e) transformation to a different histopathologic tumor subtype. The characteristic features include the target sign on T2-weighted MR images or during the hepatobiliary phase of hypovascular metastasis, the peripheral rim washout sign on delayed phase images, peritumor hyperintensity during the hepatobiliary phase, hypervascular metastasis, a cystic appearance with marked hyperintensity on T2-weighted images, marked hyperintensity on T1-weighted images, calcification, capsular retraction, absence of the vessel-penetrating sign, distribution of liver metastases, and rare intraductal forms of metastases. In addition to various factors associated with the primary cancer, desmoplastic reactions around the tumor-which can be observed in adenocarcinomas with peripheral and peritumor enhancement, distinct arterioportal shunts with metastases from pancreatic ductal carcinoma, and pseudocirrhosis-also can affect these findings. The authors review the characteristic imaging findings of liver metastases from various primary cancers, with a focus on the mechanisms that underlie organ-specific liver metastases. Online supplemental material is available for this article. ©RSNA, 2022.

Magnetic resonance imaging of an endometrial stromal nodule.

Endometrial stromal nodules are rare benign tumors that appear as well-circumscribed globular masses in the myometrium. In this report, a myometrial mass exhibited heterogeneous hyperintensity without hypointense bands on T2-weighted images and homogeneous isointensity on T1-weighted images. A dynamic contrast study revealed the same degree of uterine myometrial enhancement only in the marginal area. The structures were pathologically confirmed to correspond with proliferating endometrial stromal cells. Herein, we report this rare tumor and the correlation between magnetic resonance imaging and pathological findings.

[A Case of Malignant Lymphoma of the Spleen Infiltrating the Diaphragm Treated with Splenectomy].

A 67-year-old man was treated for diabetes mellitus by his family doctor. A splenic tumor was suspected based on his pain in the left side of the abdomen. He was admitted to our hospital for close inspection and medical treatment. Abdominal CT and MRI scans showed a tumor, 10 cm in diameter, in the spleen. An opaque boundary with the diaphragm was also observed. On PET-CT, accumulations of FDG were observed in the left supraclavicular fossa and the left axilla. The serum levels of LDH and sIL-2R were elevated, and therefore a diagnosis of malignant lymphoma was suspected. Due to the risk of splenic rupture, a splenectomy was performed. After pathological examination, the patient was diagnosed with diffuse large B-cell malignant lymphoma. He is currently being treated with chemotherapy at another medical institute. Splenic rupture occurs in some cases of splenic malignant lymphoma, although the number of reported cases is low. In some of the cases, splenic rupture occurred during treatment of the malignant lymphoma. There is no specific way to measure the risk of splenic rupture; however, performing a prophylactic splenectomy is one option in cases where tumor cells have extended to the capsula lienis, similar to that in our patient.

Right ventricular reverse remodelling after balloon pulmonary angioplasty.

Balloon pulmonary angioplasty (BPA) has been reported to improve haemodynamics and functional capacity, with an acceptable risk, in patients with chronic thromboembolic pulmonary hypertension (CTEPH) who are not candidates for pulmonary endarterectomy. However, right ventricular (RV) function, an important predictor in CTEPH, remains to be elucidated. We aimed to examine the impact of BPA on RV remodelling and dysfunction relative to haemodynamic improvements in patients with inoperable CTEPH. 20 consecutive patients with inoperable CTEPH who underwent BPA with cardiovascular magnetic resonance before and after BPA were retrospectively studied. BPA led to significant amelioration of the mean pulmonary arterial pressure, cardiac index and pulmonary vascular resistance (PVR), without death or major complications. Furthermore, BPA significantly ameliorated right-sided heart failure symptoms and signs, and exercise capacity. Cardiovascular magnetic resonance revealed a marked improvement in RV end-diastolic and end-systolic volume index, with concomitant improvements in RV ejection fraction, mass and interventricular septal bowing after BPA. Changes in RV volumes strongly correlated with changes in cardiac index and PVR. BPA induced RV reverse remodelling and improved systolic dysfunction safely by ameliorating haemodynamics in patients with inoperable CTEPH. Evaluating RV function with cardiovascular magnetic resonance may be effective for noninvasively monitoring BPA efficacy.

Improved vascular depiction and image quality through deep learning reconstruction of CT hepatic arteriography during transcatheter arterial chemoembolization.

PURPOSE: To evaluate the effect of deep learning reconstruction (DLR) on vascular depiction, tumor enhancement, and image quality of computed tomography hepatic arteriography (CTHA) images acquired during transcatheter arterial chemoembolization (TACE). METHODS: Institutional review board approval was obtained. Twenty-seven patients (18 men and 9 women, mean age, 75.7 years) who underwent CTHA immediately before TACE were enrolled. All images were reconstructed using three reconstruction algorithms: hybrid-iterative reconstruction (hybrid-IR), DLR with mild strength (DLR-M), and DLR with strong strength (DLR-S). Vascular depiction, tumor enhancement, feeder visualization, and image quality of CTHA were quantitatively and qualitatively assessed by two radiologists and compared between the three reconstruction algorithms. RESULTS: The mean signal-to-noise ratios (SNR) of sub-segmental arteries and sub-sub-segmental arteries, and the contrast-to-noise ratio (CNR) of tumors, were significantly higher on DLR-S than on DLR-M and hybrid-IR (P < 0.001). The mean qualitative score for sharpness of sub-segmental and sub-sub-segmental arteries was significantly better on DLR-S than on DLR-M and hybrid-IR (P < 0.001). There was no significant difference in the feeder artery detection rate of automated feeder artery detection software among three reconstruction algorithms (P = 0.102). The contrast, continuity, and confidence level of feeder artery detection was significantly better on DLR-S than on DLR-M (P = 0.013, 0.005, and 0.001) and hybrid-IR (P < 0.001, P = 0.002, and P < 0.001). The weighted kappa values between two readers for qualitative scores of feeder artery visualization were 0.807-0.874. The mean qualitative scores for sharpness, granulation, and diagnostic acceptability of CTHA were better on DLR-S than on DLR-M and hybrid-IR (P < 0.001). CONCLUSIONS: DLR significantly improved the SNR of small hepatic arteries, the CNR of tumor, and feeder artery visualization on CTHA images. DLR-S seems to be better suited to routine CTHA in TACE than does hybrid-IR.

[Usefulness of Electron Density Calculated from Dual Energy CT in Differential Diagnosis between Hepatocellular Carcinoma and Hepatic Hemangioma].

PURPOSE: The aim of this study were to compare electron density (ED), obtained by dual energy computed tomography (DECT), between hepatocellular carcinoma (HCC) and hemangioma, and to assess the differential diagnostic performance of ED between HCC and hemangioma. METHODS: A total of 46 patients (27 men and 19 women; mean age, 65.7±14.0 years) diagnosed with HCC or hemangioma who underwent upper abdominal DECT between October 2021 and December 2022 were included. ED of each lesion was measured. Relative ED (rED), which is normalized by the ED of background liver parenchyma, was calculated. ED and rED of HCC and hemangioma were statistically analyzed. RESULTS: The HCC group showed significantly higher ED (48.1±5.2) and rED (80.0±7.3) than the hemangioma group (43.7±4.1, 69.7±7.2, respectively) (p<0.01). The area under the curve of rED was greater than that of ED, but no significant difference was found (p=0.153). CONCLUSION: ED may help in the differential diagnosis between HCC and hemangioma.

[Usefulness of Breath-hold DWI Focused on the Hepatic Dome in EOB-MRI].

PURPOSE: Respiratory-triggered-diffusion-weighted imaging (R-DWI) of the liver often results in poor image quality under the diaphragmatic dome on the cephalic side of the liver (hepatic dome) secondary to magnetic field inhomogeneity in liver magnetic resonance imaging (MRI). Hence, the usefulness of additional breath-hold-DWI (B-DWI) focusing on the hepatic dome was investigated. METHODS: A total of 22 patients (14 men and 8 women; mean age 69.0±11.7 years) who underwent ethoxybenzyl (EOB)-MRI at our hospital between July and August, 2022 using a 3.0 T MRI system were included. One radiologist and three radiology technologists visually assessed the visibility of R-DWI and B-DWI in the hepatic dome on a 4-point scale (1 to 4). Additionally, the apparent diffusion coefficient (ADC) values of the hepatic parenchyma on each DWI were compared. RESULTS: B-DWI improved visibility in the hepatic dome compared to R-DWI (2.67±0.71 vs. 3.25±0.43, p<0.05). No significant difference was found in the ADC values for each DWI. CONCLUSION: B-DWI has excellent visibility in the hepatic dome and is expected to complement R-DWI. Therefore, B-DWI is very useful as an additional imaging in EOB-MRI.

A case of focal nodular hyperplasia-like lesion presenting unusual signal intensity on the hepatobiliary phase of gadoxetic acid-enhanced magnetic resonance image.

Focal nodular hyperplasia (FNH) or FNH-like lesions of the liver are benign lesions that can be mostly diagnosed by hepatobiliary phase gadoxetic acid-enhanced magnetic resonance imaging (MRI). Accurate imaging diagnosis is based on the fact that most FNHs or FNH-like lesions show characteristic hyper- or isointensity on hepatobiliary phase images. We report a case of an FNH-like lesion in a 73-year-old woman that mimicked a malignant tumor. Dynamic contrast-enhanced computed tomography (CT) and MRI using gadoxetic-acid revealed an ill-defined nodule showing early enhancement in the arterial phase and gradual and prolonged enhancement in the portal and equilibrium/transitional phases. Hepatobiliary phase imaging revealed inhomogeneous hypointensity, accompanied by a slightly isointense area compared to the background liver. Angiography-assisted CT showed a portal perfusion defect of the nodule, inhomogeneous arterial blood supply in the early phase, and less internal enhancement in the late phase, accompanied by irregularly shaped peritumoral enhancement. No central stellate scar was identified in any of the images. Imaging findings could not exclude the possibility of hepatocellular carcinoma, but the nodule was pathologically diagnosed as an FNH-like lesion by partial hepatectomy. In the present case, an unusual inhomogeneous hypointensity on hepatobiliary phase imaging made it difficult to diagnose the FNH-like lesions.

Extracellular volume fraction obtained by dual-energy CT depicting the etiological differences of liver fibrosis.

PURPOSE: To assess etiological differences in extracellular volume fraction (ECV) and evaluate its influence on staging performance. METHODS: A total of 166 patients with normal liver (n = 14) and chronic liver disease related to viral hepatitis (n = 71), alcohol (n = 44), and nonalcoholic steatohepatitis (NASH) (n = 37) underwent dual-energy CT (DECT) of the liver (5-min equilibrium-phase images) between January 2020 and July 2022. The iodine densities of the parenchyma and aorta were measured and ECV was calculated. Comparisons of ECV between each etiology and METAVIR fibrosis stage were statistically analyzed (p < 0.05). RESULTS: ECV in each etiology and all patients significantly increased with higher fibrosis stage (p < 0.001) and showed a strong or moderate correlation with fibrosis stage (Spearman's ρ; all patients, 0.701; viral hepatitis, 0.638; alcoholic, 0.885; NASH, 0.791). In stages F2-F4, ECV in alcoholic liver disease was significantly larger than those for viral hepatitis and NASH (p < 0.05); however, no significant difference in stage F1 was found among the three etiologies. The cutoff values and areas under the receiver operating characteristic curve (AUC-ROCs) for discriminating fibrosis stage (≥ F1- ≥ F4) were higher for alcohol (cutoff values and AUC-ROC; 20.1% and 0.708 for ≥ F1, 23.8% and 0.990 for ≥ F2, 24.3% and 0.968 for ≥ F3, and 26.6% and 0.961 for ≥ F4, respectively) compared with those for the others. CONCLUSION: ECV in alcoholic liver disease is higher than that in other etiologies in the advanced stages of fibrosis, and etiological differences in ECV affect the staging performance of fibrosis.

Liver fibrosis estimated using extracellular volume fraction obtained from dual-energy CT as a risk factor for hepatocellular carcinoma after sustained virologic response: A preliminary case-control study.

PURPOSE: To assess hepatocellular carcinoma (HCC) risk after sustained virologic response (SVR) through clinical data analyses, including evaluation of liver fibrosis using the extracellular volume fraction (ECV) obtained from dual-energy computed tomography (DECT). METHODS: Ninety-two patients (52 men and 40 women; mean age, 69.9 years) with hepatitis C virus infection after SVR underwent DECT of the liver (3-minute equilibrium-phase images) between January 2020 and March 2022. The ECV was calculated by measuring iodine density; fibrous markers, including ECV, fibrosis-4 index, aspartate aminotransferase to platelet ratio index, and platelet count, were statistically analyzed (p < 0.05). The risk factors associated with HCC were analyzed using univariate and multivariate logistic regression analyses. RESULTS: The ECV (26.1 ± 4.6 %) in patients with HCC (n,21) was significantly larger than the ECV (20.7 ± 3.3 %) in patients without HCC (n = 71) (p < 0.001). The cutoff value for the ECV was 24.3 %. The area under the operating characteristic curve of the ECV was 0.857, which was higher than that of the serum fibrosis markers. Older age, SVR achieved with interferon, alpha-fetoprotein level (>5 ng/mL), advanced fibrosis before treatment (>F3), and ECV were associated with HCC according to the univariate analysis. Multivariate analyses showed that ECV was the only factor independently associated with HCC (odds ratio 0.619, 95 % confidence interval 0.482-0.795, p < 0.001). CONCLUSION: Liver fibrosis estimated using ECV can be a predictive marker in patients with HCC after SVR.

Diagnostic performance of abbreviated gadoxetic acid-enhanced magnetic resonance protocols with contrast-enhanced computed tomography for detection of colorectal liver metastases.

BACKGROUND: Although contrast-enhanced magnetic resonance imaging (MRI) using gadoxetic acid has been shown to have higher accuracy, sensitivity, and specificity for the detection and characterization of hepatic metastases compared with other modalities, the long examination time would limit the broad indication. Several abbreviated enhanced MRI (Ab-MRI) protocols without dynamic phases have been proposed to achieve equivalent diagnostic performance for the detection of colorectal liver metastases. However, an optimal protocol has not been established, and no studies have assessed the diagnostic performance of Ab-MRI combined with contrast-enhanced computed tomography (CE-CT), which is the preoperative imaging of colorectal cancer staging in clinical settings, to determine the best therapeutic strategy. AIM: To compare the diagnostic performance of two kinds of Ab-MRI protocol with the standard MRI protocol and a combination of the Ab-MRI protocol and CE-CT for the detection of colorectal liver metastases. METHODS: Study participants comprised 87 patients (51 males, 36 females; mean age, 67.2 ± 10.8 years) who had undergone gadoxetic acid-enhanced MRI and CE-CT during the initial work-up for colorectal cancer from 2010 to 2021. Each exam was independently reviewed by two readers in three reading sessions: (1) Only single-shot fast spin echo (FSE) T2-weighted or fat-suppressed-FSE-T2-weighted, diffusion-weighted, and hepatobiliary-phase images (Ab-MRI protocol 1 or 2); (2) all acquired MRI sequences (standard protocol); and (3) a combination of an Ab-MRI protocol (1 or 2) and CE-CT. Diagnostic performance was then statistically analyzed. RESULTS: A total of 380 Lesions were analyzed, including 195 metastases (51.4%). Results from the two Ab-MRI protocols were similar. The sensitivity, specificity, and positive and negative predictive values from Ab-MRI were non-inferior to those from standard MRI (P > 0.05), while those from the combination of Ab-MRI protocol and CE-CT tended to be higher than those from Ab-MRI alone, although the difference was not significant (P > 0.05), and were quite similar to those from standard MRI (P > 0.05). CONCLUSION: The diagnostic performances of two Ab-MRI protocols were non-inferior to that of the standard protocol. Combining Ab-MRI with CE-CT provided better diagnostic performance than Ab-MRI alone.

Assessing the progression of segmental fibrosis in chronic liver disease using extracellular volume fractions.

PURPOSE: To assess the segmental difference of liver fibrosis during the progression of chronic liver disease (CLD) using hepatic extracellular volume fractions (fECVs) obtained by dual-energy CT. METHODS: A total of 218 patients (92 men and 126 women; mean age, 67.8 ± 11.7 years) with CLD and 85 patients (44 men and 41 women; mean age, 62.8 ± 13.7 years) without CLD as a control underwent dual-energy computed tomography (CT) of the liver (5-min equilibrium phase images). The iodine densities of the lateral, medial, anterior, and posterior segments and the aorta were measured, and fECVs were calculated. Comparisons of the fECV of each segment and for each albumin-bilirubin (ALBI) grade were then statistically analyzed. RESULTS: In the control group and ALBI grades 1 and 3, no significant difference in fECV was found between each segment, whereas in ALBI grade 2, the fECVs were significantly larger in the medial and anterior than in the other segments (p < 0.001). The fECVs of the lateral and posterior segments significantly increased with higher ALBI grade (p < 0.001). The fECVs of the medial and anterior segments were significantly increased with higher ALBI grade, up to grade 2 (p < 0.001), but no significant difference was found between ALBI grades 2 and 3. CONCLUSION: During the progression of CLD, fibrosis antecedently progressed in the medial and anterior segments, followed by the other liver segments.

Pearls and pitfalls of imaging features of pancreatic cystic lesions: a case-based approach with imaging-pathologic correlation.

A variety of neoplastic and non-neoplastic lesions of the pancreas can present with a predominantly cystic architecture. These lesions are increasingly being detected as incidental findings on routine cross-sectional imaging following technological advances in these techniques and their widespread use. The different histopathological behaviors show various common and uncommon imaging findings, and some cases show similar appearance in spite of different histopathology. Each lesion requires specific management because of the differing risk of progression to malignancy, and an accurate imaging diagnosis is crucial. The typical imaging characteristics that differentiate pancreatic cystic lesions have been well described and fully summarized. However, in addition to a small percentage of cases that shows uncommon imaging findings, a substantial percentage of cystic lesions shows overlapping imaging findings that can lead to radiological misdiagnosis. For appropriate diagnosis and optimal treatment strategy, it is important to know the uncommon and overlapping imaging findings of these lesions, in addition to familiarity with the typical aspects. In this article, we reconfirm the well-known characteristic imaging features of pancreatic cystic lesions and present several diagnostically challenging cases, focusing on the uncommon and overlapping imaging findings.

Selective atrophy of the middle hepatic venous drainage area in hepatitis C-related cirrhotic liver: morphometric study by using multidetector CT.

PURPOSE: To retrospectively analyze the morphologic changes of hepatitis C-related cirrhosis, which commonly show macronodular cirrhosis, in relation to the portal venous supply and hepatic venous drainage, by using multidetector computed tomographic volumetry. MATERIALS AND METHODS: Institutional ethics committee approval and informed consent were obtained. The volume of the entire liver, each portal segment, and hepatic venous drainage area with the respective proportion relative to the entire liver and the volume of hepatic area with the respective proportion relative to the anterior segment of the right lobe were measured in 74 patients without cirrhosis and with normal liver function and in 64 patients with cirrhosis classified as Child-Pugh class A and in 68 with that classified as Child-Pugh class B. The diameter and length of each hepatic vein were measured in normal liver. All measurements were statistically analyzed by using the Kruskal-Wallis test, and multiple comparisons were made by using a Bonferroni correction (P < .05). RESULTS: The entire liver volume was significantly smaller in patients with Child-Pugh class B cirrhosis (P = .002), whereas there was no significant difference in volume between the normal liver and the liver with Child-Pugh class A cirrhosis (P > .99). Middle hepatic venous (MHV) drainage area revealed significant atrophy in cirrhosis (P < .0001), more markedly in Child-Pugh class B. The right hepatic venous (RHV) and left hepatic venous drainage areas showed significant hypertrophy in cirrhosis (P < .0001). The anterior and medial segments showed significant atrophy (P < .0001), and the lateral and posterior segments and caudate lobe showed significant hypertrophy in cirrhosis (P < .05). In the anterior segment, the MHV drainage area showed significant atrophy (P < .0001), and the RHV drainage area demonstrated relative hypertrophy in cirrhosis, more definitely in Child-Pugh class B. The diameter of MHV was significantly the smallest (P < .0001), and the length of MHV was relatively longer in normal livers. CONCLUSION: The morphologic changes in hepatitis C-related cirrhosis (mainly macronodular cirrhosis) were attributed to a selective volume reduction of the MHV drainage area and relative enlargement of the other areas.

Severe intestinal bleeding due to sinistral portal hypertension after pylorus-preserving pancreatoduodenectomy.

A rare case of severe intestinal bleeding caused by sinistral portal hypertension after pylorus-preserving pancreatoduodenectomy is reported. Examinations revealed that the developed collateral vessels adjacent to the pancreas and elevated jejunum in the right upper abdomen were the source of the intestinal bleeding, and typical gastric varices were not identified. The present case showed atypical development of collateral vessels due to the postoperative state, which made diagnosis difficult.

A case of focal confluent hepatic fibrosis in the patient with hepatitis C virus-related liver cirrhosis: a mimic of cholangiolocellular carcinoma.

During routine ultrasound examination, a hyperechoic mass was detected in the anterior segment of the liver in an 80-year-old woman with hepatitis C virus-related cirrhosis. Computed tomography and magnetic resonance imaging findings suggested a malignant tumor with abundant fibrous stroma, similar to cholangiolocellular carcinoma. However, subsequent partial hepatectomy revealed a mass characterized by abundant fibrosis without tumor cells, dilated blood vessels, and marginal ductular reaction. Accordingly, focal confluent fibrosis was diagnosed. Generally, the diagnosis of focal confluent fibrosis is straightforward because of its well-established imaging characteristics. However, its differentiation from a malignant tumor can occasionally be difficult because of variation in presentation depending on the amount of fibrous stroma and the degree of inflammatory cell infiltration. In the present case, diagnosis was difficult because the lesion was more localized than usual, presenting a mass-like shape, and there was obvious hyperintensity on T2-weighted imaging and ring-shaped hyperintensity on diffusion-weighted imaging. Moreover, hepatic capsular retraction was indistinct, which can be one of the key findings of focal confluent fibrosis. When a hepatic mass is associated with a fibrous lesion, focal confluent fibrosis should be considered in the differential diagnosis, even though the lesion is associated with several atypical findings.

Morphometric changes and imaging findings of diffuse liver disease in relation to intrahepatic hemodynamics.

Diffuse hepatic diseases have a variety of etiologies, with each showing characteristic morphometric changes. These changes are closely related to micro- and macro-level intrahepatic hemodynamics, in addition to the specific underlying pathophysiology. Short-term disorders in intrahepatic hemodynamics caused by each pathophysiological condition are compensated for by the balance of blood perfusion systems using potential trans-sinusoidal, transversal, and transplexal routes of communication (micro-hemodynamics), while long-term alterations to the intrahepatic hemodynamics result in an increase in total hepatic vascular resistance. Blood flow disorders induced by this increased vascular resistance elicit hepatic cellular necrosis and fibrosis. These changes should be uniformly widespread throughout the whole liver. However, morphometric changes do not occur uniformly, with shrinkage or enlargement not occurring homogeneously. Against this background, several macro-intrahepatic hemodynamic effects arise, such as asymmetrical and complicating morphometric structures of the liver, intricate anatomy of portal venous flow and hepatic venous drainage, and zonal differentiation between central and peripheral zones. These hemodynamic factors and pathophysiological changes are related to characteristic morphometric changes in a complicated manner, based on the combination of selective atrophy and compensatory hypertrophy (atrophy-hypertrophy complex). These changes can be clearly depicted on CT and MR imaging.

FDG-PET/CT imaging findings of hepatic tumors and tumor-like lesions based on molecular background.

The usefulness of whole-body 18-fluoro-2-deoxyglucose (FDG)-fluorodeoxyglucose positron emission (PET)/computed tomography (CT) is established for assessment of disease staging, detection of early disease recurrence, therapeutic evaluation, and predicting prognosis in various malignancies; and for evaluating the spread of inflammation. However, the role of FDG-PET/CT for the liver is limited because CT and magnetic resonance imaging (MRI) can provide an accurate diagnosis of most tumors. In addition, in other potentially useful roles there are several pitfalls in the interpretation of FDG uptake in PET/CT imaging. Accurate evaluation demands knowledge of the FDG uptake of each lesion, including potential negative and positive uptakes, and requires an understanding of the underlying background of the molecular mechanisms. The degree of FDG uptake is dependent on cellular metabolic rate and the expression of glucose transporter, hexokinase, and glucose-6-phosphatase, which in turn are closely affected by biological characteristics such as pathological category (e.g., adenocarcinoma, squamous cell carcinoma, small cell cancer, transitional cell cancer, neuroendocrine tumor, sarcoma, lymphoma), tumor differentiation, histological behavior (e.g., solid, cystic, mucinous), and intratumoral alterations (e.g., necrosis, degeneration, hemorrhage). Correlation with the CT and MRI findings, which also precisely depict the pathological findings, is important to avoid misdiagnosis.

Primary hepatic diffuse large B-cell lymphoma presenting unusual imaging features.

Primary hepatic lymphomas are frequently misdiagnosed, due to their rarity and non-specific clinical manifestations. As these tumors can be successfully treated with chemotherapy and/or radiotherapy, early recognition on imaging is essential to avoid unnecessary surgery. We report a case of primary hepatic lymphoma in a 73-year-old woman presenting with a 1-week history of persistent fever and elevated hepatobiliary enzymes. Ultrasound showed a hypoechoic hepatic mass in the anterior segment. Dynamic contrast-enhanced computed tomography (CT) revealed an ill-defined solitary mass showing peripherally dominant slight-to-moderate enhancement contrasting with a hypovascular central area. On magnetic resonance imaging, the mass showed moderate hyperintensity on T2-weighted imaging, hypointensity on T1-weighted imaging, doughnut-like hyperintensity on diffusion-weighted imaging, and an obviously low apparent diffusion coefficient (ADC). The pattern of enhancement resembled that of CT. Neither calcification nor any fat component was observed. Doughnut-like accumulation was seen on 18F-fluorodeoxyglucose (FDG)-positron emission tomography/CT without other FDG-avid lesions. Imaging findings suggested the possibility of cholangiocellular carcinoma, but the low ADC and extremely high FDG accumulation were suggestive of malignant lymphoma, and diffuse large B-cell lymphoma was pathologically confirmed from percutaneous biopsy. The mass disappeared after radiochemotherapy, and no recurrence has been observed for 3 years.

Renal involvement of polyarteritis nodosa: CT and MR findings.

BACKGROUND: To evaluate the imaging findings in patients with renal involvement of Polyarteritis nodosa (PN) to diagnose as early as possible. MATERIALS AND METHODS: Four patients diagnosed as having PN participated in the present study. Two patients underwent abdominal dynamic CT, one underwent only pre- and post-contrast CT, and the remaining patient underwent only noncontrast CT and MR imaging, including dynamic contrast study. RESULTS: The common findings of CT and MR imaging were diffuse enlargement, multiple small wedge-shaped less-enhanced areas on dynamic contrast study, and indistinctness of the margin between the cortex and medulla on equilibrium-phase CT. Renal arteriogram showed multiple microaneurysms on arterial phase image in all four cases, and PN was diagnosed. The common CT and MR findings of renal involvement of PN mimicked those of pyelonephritis, when microaneurysms were not demonstrated. CONCLUSION: The differentiation between PN and pyelonephritis on CT and MR imaging is difficult. Therefore, the radiologist should be familiar with the imaging findings of renal involvement of PN. When PN is suspected, angiography should be performed as early as possible to make a definite diagnosis.