Takashi Kokubo

Avascular necrosis of the femoral head. Natural history and magnetic resonance imaging

We studied the prognostic value of MRI in 32 radiographically normal, asymptomatic hips in 25 patients at risk of osteonecrosis from glucocorticoids or alcoholism. The early findings were band-like hypointense zones on spin-echo images. No operations were performed. Life-table survival curves showed that femoral heads in which the hypointense zone traversed the middle portion of the head were most at risk of subsequent segmental collapse.

Case report: Enormous intrahepatic communication between the portal vein and the hepatic vein

A case of enormous intrahepatic shunt between the portal vein and the hepatic vein is described. The lesion was successfully treated by embolisation using stainless steel coils on two occasions, after demonstration by percutaneous transhepatic portography (PTP).

Transient hepatic attenuation differences on dynamic computed tomography.

Transient hepatic attenuation differences (THAD) are occasionally noted on dynamic CT in patients with portal vein obstruction, arterioportal shunt, liver tumor, and liver abscess. We report four additional cases of THAD with unreported and/or unexplained etiology.

Transient osteoporosis of the hip. Magnetic resonance imaging.

Magnetic resonance (MR) images of seven hips were reviewed in six patients with transient osteoporosis of the hip. The MR images of the affected joint showed increased joint fluid and diffuse signal abnormalities in the marrow of the femoral head, corresponding to a decreased signal intensity on T1-weighted images and an increased signal intensity on T2-weighted images. The MR images at the time of clinical improvement showed regression of the abnormalities. These MR abnormalities reflect the pathophysiology of this condition.

CT and MR imaging of fatty tumors of the liver.

The presence of fat in hepatic masses narrows the range of differential diagnoses down to hepatic angiomyolipoma, lipoma, adenoma, hepatoma, metastatic fatty tumors of the liver, focal fatty infiltration of the liver, and extrahepatic fatty masses such as intraperitoneal implants from malignant teratomas, and packed omentum. We report six hepatic tumors containing fat (lipoma, hepatocellular carcinoma, and calcified mass with fat–fluid level) with CT and magnetic resonance (MR) imaging. The distribution of fat was diffuse in the lipomas and some hepatocellular carcinomas and localized in other hepatocellular carcinomas and fat-fluid masses. The density ranged from – 100 to 0 HU. High intensity areas on both T1− and T2-weighted MR images corresponded to the hypodense areas on CT.

Magnetic resonance imaging and histopathology in femoral head necrosis

We correlated preoperative magnetic resonance (MR) images and histopathology of eight femoral heads from patients with osteonecrosis. The signal intensity of the MR image was low in the area where fibrovascular tissue, disintegrated fibrovascular tissue, or amorphous necrotic material occupied the medullary space. On the other hand, the necrotic marrow without revascularization showed high signal intensity. Osteonecrosis can be detected by MR imaging as soon as a certain amount of bone marrow is replaced by fibrovascular tissue.

Magnetic resonance imaging and scintigraphy of avascular necrosis of the femoral head. Prediction of subsequent segmental collapse.

For the purpose of an effective management of patients at high risk for nontraumatic avascular necrosis of the femoral head (ANFH), it is expedient to examine the femoral heads of patients most likely to undergo subsequent segmental collapse. The purpose of this study was to evaluate the ability of magnetic resonance imaging (MRI) and radionuclide bone scanning (RS) to predict segmental collapse of the femoral head at the roentgenographically normal stage. Fifty-five hips in 37 patients at risk for ANFH and having normal roentgenograms were included in this study. Magnetic resonance imaging was performed in all hips and RS in 29 hips. The patients were observed during a period of more than two years without any invasive intervention, and nine femoral heads manifested collapse during this period. Predictive values for subsequent segmental collapse of a positive test of MRI and RS were 31% and 13%, respectively, whereas those indicative of a negative test were 100% and 76%, respectively. Magnetic resonance imaging was more useful than RS in detecting patients in need of intensive follow-up examination. In particular, a bandlike area of low intensity that traversed the femoral head in midcoronal slices on MR images seemed to be a significant indicator of subsequent collapse.

MR demonstration of intraosseous beta-2-microglobulin amyloidosis

We present a case of intraosseous beta-2-microglobulin amyloidosis of a patient receiving long-term hemodialysis. Magnetic resonance imaging clearly demonstrated intraosseous amyloid deposits as hypointense masses in the femoral head.

CT and MR imaging of postnecrotic liver scars.

Four cases of postnecrotic liver scar were examined by dynamic CT or MR imaging or both. Postnecrotic scars appeared as low-density areas on plain CT, showed marked and prolonged enhancement on single level dynamic CT, and became isodense on postcontrast sca. On T2-weighted images, postnecrotic scar were as hyperintense as the spleen. Postnecrotic liver scar is an example of localized attenuation or intensity difference not corresponding to mass lesion. It should be distinguished from mass lesions associated with lobar or segmental attenuation (or intensity) difference of the liver as well as nonmass lesions such as irregular fatty infiltration, radiation hepatitis, and hepatic infarction.

MR imaging of hepatoma treated by embolization

The magnetic resonance findings of two hepatomas treated by embolization are presented. The T2-weighted spin echo images showed an increase in signal intensity in the tumor after embolization. This phenomenon corresponded to a decrease in tumor density on CT and to necrosis observed histologically. Magnetic resonance also demonstrated gas bubbles as low signal foci within the embolized tumor.