A Study on MR Signal Intensity of Calcifications According to Calcium Concentration and Compound

PURPOSE: The signal of intracranial calcification on magnetic resonance (MR) imaging has been known to bevariable. The purpose of this study was to evaluate the MR signal of calcifications according to calciumconcentration and compound. MATERIALS AND METHODS: T1-weighted, proton density and T2-weighted images were obtained in phantoms with various conposition of calcium carbonate and calcium phosphate. The signal intensities and T1/T2 relaxation times were measured and analyzed according to calcium concentration and compound. The configurations of calcium particles were evaluated by scanning electron microscopy. RESULTS: The signal intensity of calcium carbonate on T1-weighted images gradually decreased as the concentration increased, while that ofcalcium phosphate showed a biphasic curve with a peak intensity at 0.2 g/ml. The signal intensity of both calcium compounds on T2-weighted images decreased as the concentration increased. The T1 relaxation time of calcium carbonate remained constant with increasing calcium concentration, however, that of calcium phosphate decreased upto 0.2g/ml and then remained constant. The T2 relaxation time of both calcium compounds decreased in a similar fashion with increasing concentration. Calcium phosphate showed larger surface area on scanning electron microscope. CONCLUSION: Calcifications show variable MR signal due to difference of T1 and T2 relaxation times according to calcium concentration and compound. Large surface area of calcium particle might cause shortening of T1 relaxation time leading to high signal on T1-weighted image. Understanding of these findings will help interpretation of MR images more precisely.

Histopathologic Study on Liver Tissue Damage after Injection of Various Contrast Materials into the Liver Parenchyma of Rat

PURPOSE: To evaluate the severity of tissue necrosis of liver according to various kinds of contrast materials used in percutaneous transhepatic procedure. MATERIALS AND METHODS: Four kinds of commercially available contrast material were used in the this study :meglumine ioxithalamate (ionic monomer, Telebrix 30, Guerbet, France), meglumine ioglicinate (ionic dimer, Rayvist 300, Schering, Germany), iopromide (nonionic monomer, Ultravist 300, Schering, Germany), and iotrolan (nonionic dimer, Isovist 300, Schering, Germany). The same amount(0.1 ml) of each contrast material was directly injected into the liver of Sprongue-Dawley rats. After two days and four weeks, the histopathologic findings of resected liver were assessed and analysed with special emphasis on the difference in the area of tissue necrosis between each group. RESULTS: In the liver resected 48 hours later, the area of necrosis was related to the osmolality and ionicity of contrast material used :the higher the osmolality, the wider the area of necrosis and ionic contrast material exhibited wider area of necrosis than nonionic contrast material. In the liver resected four weeks later, almost complete recovery was seen at the site of necrosis in all groups. CONCLUSION: Nonionic contrast materials caused less tissue necrosis than ionic contrast materials in percutaneous transhepatic procedure because of their lower osmolality.

Functional Imaging of Cerebral Cortex Activation with a 1.5-T IVIR Imaging System

PURPOSE: Most of recent MR imagings of cerebral cortex activation have been performed by using high field magnet above 2-T or echo-planar imaging technique. We report our experience on imaging of cerebral cortex activation with a widely available standard 1.5-T MR. MATERIALS AND METHODS: Series of gradient-echo images (TR/TE/flip angle :80/60/40 degrees64 x 128 matrix) were acquired alternatively during the periods of rest and task in five normal volunteers. Finger movement (n=10 ;5 right, 5 left) and flashing photic stimulation (n=l) were used as a motor task and a visual task to activate the motor cortex and visual cortex, respectively. Activation images were obtained by subtracting sum of rest images from that of task images. Changes of signal intensity were analyzed over the periods of rest and task. RESULTS: Activation images were obtained in all cases. Changes of signal intensity between rest and task periods were 6.5-14.6%(mean, 10.5%) in the motor cortex and 4.2% in the visual cortex. CONCLUSION: Functional imaging of cerebral cortex activation could be performed with a widely available 1.5-T MR. Widespread applications of this technique to basic and clinical neuroscience are expected.

Percutaneous Catheter Drainage of Liver Abscess: Clinical Outcome

PURPOSE: We studied to evaluate the effect of percutaneous catheter drainage (PCD) in liver abscess. MATERIALS AND METHODS: We retrospectively analyzed clinical data (presence of fever, WBC count), radiological findings (computed tomography, ultrasonography and abscessogram) and correlated them with treatment period. Percutaneous drainage of liver abscess were performed in 19 patients under fluoroscopy guide during recent three years. RESULTS: Eighteen patients (95%) were cured, and one patient underwent surgery because of peritonitis caused by PCD procedure. Average treatment period was 17 days. CONCLUSION: In the treatment of liver abscess, PCD is thought to be safe and effective.

Epithelioid Hemangioendothelioma of the Liver: A Case Report

Hepatic epithelioid hemangioendothelioma is a rare tumor of vascular origin having a intermediate clinical course between benign cavernous hemangioma and malignant anglosarcoma. Patients present nonspecific clinical signs and symptomas. We experienced a case of surgically proven hepatic epithelioid hemangioen-dothelioma. Computed tomography showed multiple nodules with internal calcifications, chiefly in peripheral portion of both lobes of the liver. Ultrasonography showed hypoechoic nodules and tiny calcific foci in peripheral portion. Open biopsy of the liver and the omenrum confirmed epithelioid hemangioendotheliomas.