Tae Yeon Jeon

Assessment of triple-phase CT findings for the differentiation of fat-deficient hepatic angiomyolipoma from hepatocellular carcinoma in non-cirrhotic liver.

BACKGROUND To evaluate the triple-phase CT findings for the differentiation of fat-deficient angiomyolipoma from hepatocellular carcinoma in non-cirrhotic liver. METHODS We retrospectively reviewed contrast-enhanced triple-phase CT images of 10 patients with fat-deficient hepatic angiomyolipoma and 28 patients with 29 hepatocellular carcinomas in non-cirrhotic liver proved on histologic examination. The CT findings for the two types of tumors were compared using Fishers exact test. RESULTS Early draining vein depicted on arterial or portal phases was seen in eight (80%) angiomyolipomas and two hepatocellular carcinomas (7%) (p<0.001), in which the early draining vein was connected with tumoral vessels. The tumoral vessels in the angiomyolipoma were more prominent and ectatic, were distributed both centrally and peripherally, and were seen in smaller tumors than in the hepatocellular carcinoma. Tumor capsule enhancement was absent in all angiomyolipomas as compared with two (7%) hepatocellular carcinomas with no tumor capsule (p<0.001). The other CT findings were not significantly different for the two different types of tumors. CONCLUSIONS The presence of early draining vein connecting with prominent tumoral vessels and absent tumor capsule were useful CT findings for the differentiation of fat-deficient angiomyolipoma from hepatocellular carcinoma in non-cirrhotic liver.

Diffusion and Perfusion Characteristics of MELAS (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episode) in Thirteen Patients

Objective We analyzed the diffusion and perfusion characteristics of acute MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode) lesions in a large series to investigate the controversial changes of the apparent diffusion coefficient (ADC) that were reported in prior studies. Materials and Methods We analyzed 44 newly appearing lesions during 28 stroke-like episodes in 13 patients with MELAS. We performed a visual assessment of the MR images including the ADC and perfusion maps, comparison of the ADC between the normal and abnormal areas, comparison of % ADC between the 44 MELAS lesions and the 30 acute ischemic infarcts. In addition, the patterns of evolution on follow-up MR images were analyzed. Results Decreased, increased, and normal ADCs were noted in 16 (36%), 16 (36%), and 12 (27%) lesions, respectively. The mean % ADC was 102 ± 40.9% in the MELAS and 64 ± 17.8% in the acute vascular infarcts (p < 0.001), while perfusion imaging demonstrated hyper-perfusion in six acute MELAS lesions. On follow-up images, resolution, progression, and tissue loss were noted in 10, 4, and 17 lesions, respectively. Conclusion The cytotoxic edema gradually evolves following an acute stroke-like episode in patients with MELAS, and this may overlap with hyper-perfusion and vasogenic edema. The edematous swelling may be reversible or it may evolve to encephalomalacia, suggesting irreversible damage.

Prevalence of Unruptured Intracranial Aneurysm on MR Angiography

Objective To evaluate the prevalence of incidentally found unruptured intracranial aneurysms (UIAs) on the brain MR angiography (MRA) from a community-based general hospital. Materials and Methods This was a prospectively collected retrospective study, carried out from January 2004 to December 2004. The subjects included 3049 persons from a community-based hospital in whom MRA was performed according to a standardized protocol in an outpatient setting. Age- and sex-specific prevalence of UIAs was calculated. The results by MRA were compared with intra-arterial digital subtraction angiography (DSA) findings. Results Unruptured intracranial aneurysms were found in 137 (5%) of the 3049 patients (M:F = 43:94; mean age, 60.2 years). The prevalence of UIAs was 5% (n = 94) in women and 4% (n = 43) in men, respectively (p = 0.2046) and showed no age-related increase. The most common site of aneurysm was at the distal internal carotid artery (n = 64, 39%), followed by the middle cerebral artery (n = 40, 24%). In total, 99% of aneurysms measured less than 12 mm, and 93% of aneurysms measured less than 7 mm. Direct comparisons between MRA and DSA were available in 70 patients with 83 UIAs; the results revealed two false positive and two false negative results. Conclusion This community-hospital based study suggested a higher prevalence of UIAs observed by MRA than previously reported. These findings should be anticipated in the design and use of neuroimaging in clinical practice.

Fontan-associated liver disease: Spectrum of US findings.

PURPOSE To describe ultrasonography (US) findings of Fontan-associated liver disease (FALD) and to determine whether screening US examinations can identify FALD before biochemical hepatic dysfunction. METHODS This retrospective study included 55 patients who underwent Fontan procedure over a 20-year period. Hepatobiliary US findings (n=55), CT or MRI findings (n=19), biochemical hepatic function tests (n=49), and histopathological results (n=4) were analyzed. Images were reviewed focusing on the hepatic parenchymal changes, presence of focal lesions, and signs of portal hypertension. RESULTS Hepatic parenchymal changes (either heterogeneous echotexture or surface nodularity) evident on US were present in 67% (37/55) and showed positive correlation with the Fontan duration. Hyper-echoic lesions were noted in 35% (19/55) and showed a predilection for multiplicity, small size, right lobe location, and irregular margin on high-frequency transducer. These lesions were not demonstrated by CT or MRI or by low-frequency transducer. Histopathological results of targeted biopsy for hyper-echoic lesions revealed lesser degree of patchy sinusoidal and portal fibrosis than seen in cases with surface nodularity. Abnormal parenchymal enhancement was commonly seen with CT or MRI in 63% (12/19) and hypervascular nodules in 21% (4/19). Most patients (82%, 40/49) showed normal biochemical hepatic function tests, despite the presence of hepatic parenchymal changes on imaging. CONCLUSION The common US findings of FALD included heterogeneous parenchymal echotexture, surface nodularity, and hyper-echoic lesions. We suggest that hyper-echoic lesions without surface nodularity detected by high-frequency transducer may represent the early stage of fibrosis. US examination may be useful for identifying the progression of FALD before biochemical hepatic dysfunction.

The degree of tumor volume reduction during the early phase of induction chemotherapy is an independent prognostic factor in patients with high-risk neuroblastoma.

In patients with high‐risk neuroblastoma, the reduction in primary tumor volume was measured during the early phase of induction chemotherapy as an indicator of early tumor response, and the authors investigated whether the degree of tumor volume reduction could predict outcome in these patients.

Hypointense Hepatic Lesions Depicted on Gadobenate Dimeglumine-Enhanced Three-Hour Delayed Hepatobiliary-Phase MR Imaging: Differentiation between Benignancy and Malignancy

Gadobenate dimeglumine-enhanced magnetic resonance (MR) imaging simultaneously provides both morphological and functional information by the acquisition of dynamic and hepatobiliary-phase imaging. Focal lesions with no functioning hepatocytes, where hepatobiliary metabolism is blocked or inhibited, are generally unable to uptake and excrete gadobenate dimeglumine into the bile. Such lesions are typically malignant and usually appear hypointense as compared to the normal liver parenchyma as seen on hepatobiliary-phase imaging. However, various benign hepatic lesions may also be hypointense due to (a) the presence of no functioning hepatocytes, (b) damage to the functioning hepatocytes or (c) impairment of biliary function as depicted on hepatobiliary-phase imaging. All of these imaging features may result in recognition of the benign hepatic lesions as hepatic malignancies. As depicted on three-hour delayed hepatobiliary-phase imaging, peripheral iso/hyperintensity due to fibrotic tissue compared to the hypointense center with a fuzzy margin may be a clue for the presence of a benign hepatic lesion. In contrast, peripheral hypointensity due to rich tumoral cellularity compared to the center with a clear margin may favor an indication of the presence of a malignant hepatic lesion.

Can preoperative MR imaging predict optic nerve invasion of retinoblastoma

PURPOSE To evaluate the accuracy of pre-operative MRI for the detection of optic nerve invasion in retinoblastoma. MATERIALS AND METHODS Institutional review board approval and informed consent were waived for this retrospective study. A total of 41 patients were included. Inclusion criteria were histologically proven retinoblastoma, availability of diagnostic-quality preoperative MR images acquired during the 4 weeks before surgery, unilateral retinoblastoma, and normal-sized optic nerve. Two radiologists retrospectively reviewed the MR images independently. Five imaging findings (diffuse mild optic nerve enhancement, focal strong optic nerve enhancement, optic sheath enhancement, tumor location, and tumor size) were evaluated against optic nerve invasion of retinoblastoma. The predictive performance of all MR imaging findings for optic nerve invasion was also evaluated by the receiver operating characteristic curve analysis. RESULTS Optic nerve invasion was histopathologically confirmed in 24% of study population (10/41). The differences in diffuse mild enhancement, focal strong enhancement, optic sheath enhancement, and tumor location between patients with optic nerve invasion and patients without optic nerve invasion were not significant. Tumor sizes were 16.1mm (SD: 2.2mm) and 14.9 mm (SD: 3.6mm) in patients with and without optic nerve involvement, respectively (P=0.444). P-Values from binary logistic regression indicated that all five imaging findings were not significant predictors of tumor invasion of optic nerve. The AUC values of all MR imaging findings for the prediction of optic nerve invasion were 0.689 (95% confidence interval: 0.499-0.879) and 0.653 (95% confidence interval: 0.445-0.861) for observer 1 and observer 2, respectively. CONCLUSION Findings of MRI in patients with normal-sized optic nerves have limited usefulness in preoperatively predicting the presence of optic nerve invasion in retinoblastoma.

Posttransplantation Lymphoproliferative Disorder in Children: Manifestations in Hematopoietic Cell Recipients in Comparison with Liver Recipients

PURPOSE To compare the clinical and imaging features of posttransplantation lymphoproliferative disorder (PTLD) in pediatric patients who underwent hematopoietic cell transplantation with those in pediatric patients who underwent liver transplantation. MATERIALS AND METHODS This study was approved by the institutional review board, and the requirement to obtain informed consent was waived. The authors retrospectively reviewed the medical records and images of 552 hematopoietic cell transplant recipients and 195 liver transplant recipients. PTLD was histopathologically confirmed in 17 of the patients who underwent hematopoietic cell transplantation and 27 of the patients who underwent liver transplantation. The overall frequency, clinical course, histopathologic type, and imaging findings of PTLD were compared between the two patient groups by using the Fisher exact test. RESULTS The overall frequency of PTLD was 3% (17 of 552 patients) after hematopoietic cell transplantation (12% [nine of 75 patients] after umbilical cord blood transplantation) and 14% (27 of 194 patients) after liver transplantation. PTLD occurred within 6 months of transplantation in 14 of the 17 hematopoietic cell recipients (82%) and 11 of the 27 liver recipients (41%) (P = .012). Histopathologic examination revealed monomorphic disease in 11 of the 17 hematopoietic cell recipients (65%) and eight of the 27 liver recipients (30%) (P = .031). The abdomen was the most common site of involvement in both groups. Extraabdominal PTLD developed in 12 of the 17 hematopoietic cell recipients (71%) and five of the 27 liver recipients (19%) (P = .002). Although 15 of the 17 patients with hematopoietic cell transplantation-related PTLD (88%) exhibited responses after treatment, the overall mortality rate was 35% (six of 17 patients). All 27 patients with PTLD after liver transplantation improved after treatment and remain alive. CONCLUSION PTLD after umbilical cord blood transplantation occurred as frequently as liver transplantation-related PTLD. Compared with liver transplantation-related PTLD, PTLD after hematopoietic cell transplantation is characterized by an earlier onset, a higher proportion of malignant monomorphic disease, and a worse outcome.

Dynamic MRI Findings and Clinical Features of Benign Hypervascular Hepatic Nodules in Childhood-Cancer Survivors

OBJECTIVE The purpose of this study is to investigate the dynamic MRI findings and clinical features of benign hypervascular hepatic nodules in childhood-cancer survivors. MATERIALS AND METHODS We reviewed dynamic MRI findings and clinical features in 15 patients who had been treated for childhood malignant solid tumors and in whom hypervascular hepatic nodules were later found on surveillance imaging by either CT or ultrasound (or both). The benign nature of the lesion was based on histologic examination or clinical and radiologic follow-up (or both). RESULTS Time between initial diagnosis of malignancy and detection of the hepatic nodule ranged from 4.5 to 13.5 years with the majority of the malignancies being neuroblastoma treated by high-dose chemotherapy and hematopoietic stem cell transplantation. A total of 43 nodules were detected, often multiple and small. Most of the lesions were isointense or slightly hyperintense on T2-weighted imaging and isointense or slightly hypointense on T1-weighted imaging. All nodules had intense enhancement on the arterial phase and were isointense or slightly hyperintense on the delayed phase. A central scar was seen in four. Additionally, hepatic hemosiderosis was noted in four patients, in whom all the lesions were hyperintense on both T1- and T2-weighted imaging. CONCLUSION Benign hypervascular hepatic nodules in survivors of childhood malignancy occur years after high-dose chemotherapy and hematopoietic stem cell transplantation. Dynamic MRI findings including intense arterial enhancement and absence of washout in the delayed phase are of great value in the differential diagnosis of these hepatic nodules.

Clinical and Imaging Features of Focal Nodular Hyperplasia in Children

OBJECTIVE The purpose of this article is to review the clinical and imaging features of focal nodular hyperplasia (FNH) developed in children. MATERIALS AND METHODS At a single institution, pediatric patients who underwent imaging studies and who had pathologically proven FNH were studied. Clinical characteristics, including presenting symptoms and signs and the presence of underlying disease, were reviewed from the medical records. Imaging features of FNHs, including the number, size, ultrasound echogenicity and vascularity, CT attenuation, MRI signal intensity and enhancement pattern, and the presence of a central scar, were evaluated. RESULTS Twenty-five patients (11 boys and 14 girls; median age, 8.6 years) were found to have a solitary (n = 23) or multiple (n = 2) FNH lesions with a mean size of 4.9 cm (range, 1-10 cm). Multiple lesions were associated with small size of the lesions and history of malignancy treated by chemotherapy. Most patients were asymptomatic (n = 22). Biliary atresia was the most common underlying disease (n = 5). On ultrasound, FNHs most commonly appeared to be isoechoic and hypervascular. On dynamic CT and MRI, strong enhancement on the arterial phase and becoming isoattenuated or of isointense signal intensity on the portal or delayed phase was common. A central scar was usually noted in large lesions in about half the cases. CONCLUSION Pediatric FNH is uncommon and usually is found incidentally in otherwise healthy children. However, it may occur in children who have underlying diseases, including biliary atresia. In addition, it can be encountered during surveillance of childhood cancer survivors with less common imaging features, including lack of a central scar and multiplicity.