Small Hypodense Lesions Research Articles

Dünn- und dickschichtige MSCT-Untersuchungen bei Niedrigkontrastobjekten (Leberläsionen): Vergleich der Bildqualität bei gleicher Dosis

To evaluate the image quality of thin-section MSCT examinations of low-contrast objects such as liver lesions, and to find out whether a thin slice technique requires an increase in radiation dose. MSCT examinations of the liver were performed in the portal venous phase on a Volume Zoom Scanner (Siemens, Erlangen) with a collimation of 4 x 2.5 mm, 120 kV, 125 mAs and table speed of 12.5 mm. Forty small hypodense liver lesions with a mean size of 3 mm (1 to 8 mm) were reconstructed using a slice thickness of 3, 5, 7, and 10 mm. All lesions were evaluated for each slice thickness by 3 independent radiologists using a 5-point scale (excellent to poor) for the following 7 criteria: contrast, demarcation and contour of the lesion, image noise and quality, demarcation of liver veins and liver contour. The mean values of the reviewers' scores were calculated. The correlation of the three observers in the evaluation of the criteria was determined using the Kendall's Tau coefficient. The 3-mm thin sections were excellent in the evaluation of lesion detection, lesion contrast and lesion contour with a mean score of 1.4 compared to 4.1 for 10-mm sections. Concerning the criteria image quality and liver contour, thin sections achieved the best results in our series. Image noise was pronounced in thin sections but did not affect negatively the image analysis. Interrater agreement was 0.53 for the criterium image noise. Thin sections in MSCT examinations of low contrast objects such as liver lesions do not require an increase in radiation dose because the increase in image noise is compensated by improved lesion contrast.

PSEUDOTUMOROUS RENAL INVOLVEMENT OF SARCOIDOSIS

Sarcoidosis, known mainly for pulmonary findings, can present with abdominal disease. Abdominal involvement most commonly affects the liver and spleen. Microscopic renal involvement is common but visible disease is unusual. Sarcoidosis of the kidney can cause nephrocalcinosis, nephrolithiasis, lesions or hydronephrosis. 1 Renal sarcoidosis is usually not visible on imaging and rarely presents as noncalcified renal masses. We report on a rare presentation of sarcoidosis with incidental bilateral noncalcified renal masses in the absence of renal dysfunction. CASE REPORT A 40-year-old black woman presented with right back and upper abdominal pain. She had a history of hypertension, cholelithiasis and a recent history of hematuria and urinary tract infection with suspected pyelonephritis. During the evaluation for source of infection, hilar adenopathy was discovered on a chest radiograph. Contrast enhanced abdominal computerized tomography (CT) revealed bilateral, multiple, wedge shaped renal masses from 2.0 to 4.6 cm. (fig. 1). The lesions were homogeneously hypodense and averaged 90 HU compared to adjacent parenchyma, which measured 205 HU. The lesions measured 29 HU on nonenhanced images and were well demarcated. There was no contour deformity of the renal margins. The kidneys were normal in size, and renal vasculature was unremarkable. Additional CT findings were retroperitoneal adenopathy, small hypodense hepatic lesions, gallstones and uterine leiomyomata. Both kidneys appeared normal on abdominal ultrasound for biopsy (fig. 2). No focal renal masses or contour deformities were identified. The cortical echo texture was homogeneous without focal areas of abnormality. After repeat contrast enhanced CT documented the persistence of the renal lesions, biopsy of the right renal lower pole, which had been the most severely affected region on CT, was performed. Pathological evaluation of the samples demonstrated noncaseating granulomas consistent with sarcoidosis. DISCUSSION

Increased cerebral blood flow in anemic patients on long-term hemodialytic treatment.

CBF was measured in 15 patients on chronic hemodialytic treatment. CBF was measured with xenon-133 inhalation using single photon emission tomography. In addition, computerized tomography (CT) and a neurological examination were done prior to hemodialysis. Mean CBF was 66.2 +/- 17.3 (SD) ml 100 g-1 min-1, which was significantly higher (t-test, p less than 0.05) than for an age-matched control group (54.7 +/- 10.2 ml 100 g-1 min-1). However, the hematocrit for the patients was considerably lower, 0.30 +/- 0.07, as compared to 0.43 +/- 0.03 in the controls. A significant negative correlation was observed between CBF and the hematocrit (y = -1.79x + 120.7, r = -0.71, p less than 0.01). Calculating CBF from this equation in the dialyzed patients using a hematocrit of 0.43 yielded a mean CBF value of 43.7 ml 100 g-1 min-1, i.e., 20% below the expected. Two patients showed a focal CBF decrease. CT showed central or cortical atrophy in five patients, and two had small hypodense lesions. The neurological examination revealed slight to moderate dementia in seven cases. Although mean CBF was found to be increased by 21% as compared to the control group, an even higher CBF level would have been expected to outweigh the decreased oxygen carrying capacity of the blood. The findings suggest a lowered metabolic demand of the brain tissue, probably due to subtle brain damage.

Ultrasonography and Computed Tomography in Diffuse Liver Disease with Cholestasis

Ultrasonography (US) and computed tomography (CT) were performed on respectively 67 and 42 (altogether 72) patients, for the assessment of intrahepatic cholestasis. The diagnostic ability to differentiate between malignant (17 patients) and benign (55 patients) liver disease was analyzed. Coarse echogenicity of the liver led to inconclusive results in differentiating between cirrhosis (2 out of 29 patients) and malignant infiltration (4 out of 15 patients) by US. Other benign liver diseases in 23 patients, including acute hepatitis, chronic active hepatitis, fatty liver, and liver congestion, were correctly interpreted as benign. CT correctly disclosed malignant liver disease in all cases. A false positive diagnosis of malignancy was encountered in 4 (out of 17) patients with decompensated hepatic cirrhosis because of non-homogeneous expansive areas on CT in 3 cases. The true cause was in 2 patients non-uniform fatty infiltration, and in one patient with acute hepatitis A, small hypodense lesions. Among cholestatic patients, decompensated cirrhosis and malignant liver infiltration could not always be differentiated on US or CT.

Appearing and disappearing CT scan abnormalities in epilepsy in India--an enigma.

In 230 consecutive cases of epilepsy, CT abnormalities were found in 51.7%. Out of these, 91 cases (39.5%) had non specific abnormalities consisting mostly of ring lesions, hyperdense disc lesions with surrounding oedema in enhanced scans and in a small percentage hypodense lesions, generalised brain oedema and calcifications. All these cases were treated with anticonvulsant drugs alone. A follow up scan was possible in 31 cases, 12 weeks or later, after the control of the seizures. Out of these 31 cases, 24 showed a complete or significant resolution and five remained unchanged. Two of these cases showed an increase in the lesions which resolved on treatment with antituberculous drugs. These lesions therefore may have an aetiology other than tuberculosis in the majority of cases and there is ample justification in treating them initially with anticonvulsant drugs only.

Fragments of lipoma ascending to the brain

A 37-year-old woman underwent microsurgical resection of a “lipodermoid” tumor of the conus medullaris. Pre-operative evaluation demonstrated an incidental finding of multiple small hypodense lesions in the cerebral ventricles and basal cisterns on cranial computed tomography. It is hypothesized that these lesions represent rostral subarachnoid embolization of flecks of fat from the conus lesion. Evidence supporting this hypothesis is presented.