MRI Findings of Miliary Tuberculosis of the Brain

PURPOSE: To evaluate MRI(Magnetic Resonance Imaging) findings of miliary tuberculosis of the brain. MATERIALS AND METHODS: Six patients with miliary tuberculosis of the brain diagnosed by characteristic clinical or laboratory findings were studied with spin echo MRI before and after contrast enhancement. We retrospectively evaluated MRI findings acording to the appearance, distribution, location, and enhancement pattern of the granulomas as well as associated other abnormalities. RESULTS: In six patients, contrast-enhanced MRI of thebrain showed numerous punctate, contrast enhancing lesions scattered throughout the brain. Unenhanced MRI failed to demonstrate small granulomas except a few small foci of high signal intensity on T2-weighted images. The shapes of enhancing granulomas were homogeneous nodular enhancement in 86% of cases and small ring enhancement in 14%.98% of granulomas were smaller than 3-mm and 2% were larger. Although several lesions were located in the basalganglia, thalamus, and brain stem, the majority were located in the subpial and subarachnoid space. There was no significant difference in distribution of granulomas between the supratentorial and the infratentorial areas. Other associated abnormalities were focal meningitis in five cases and focal cerebritis in one. On chest radiograph, all patients had miliary tuberculosis in the lungs. CONCLUSION: Contrast-enhanced T1-weighted MRimaging showed numerous round, very small enhancing lesions scattered throughout the brain. The majority of lesions were located in the subpial and subarachnoid space. Contrast-enhanced T1-weighted images are helpful inthe detection and diagnosis of miliary disseminated tuberculous granulomas and meningitis.

Value of Axial 3-D Fourier Transformation GRASS MR Images in Diagnosis of Meniscal Tears of the Knee

PURPOSE: The purpose of this study is to compare the sensitivity and specificity of axial 3-D imaging with those of conventional 2-D imaging in the diagnosis of meniscal injuries. MATERIALS AND METHODS: Twenty-nine kneesof 27 patients with clinically suspected meniscal tears were imaged at a 1.5 T MR system. Conventional 2-D imagesand axial 3-D GRASS images were obtained in all cases. Arthroscopic or surgical confirmation was available in allcases and was used as the gold standard. RESULTS: Among the 29 knee-joints evaluated, 21 of 23 meniscal tears and 33 of 35 normal menisci were correctly identified with axial 3-D imaging, yielding a sensitivity of 91.3% and specificity of 94.3%. Conversely, the sensitivity was 82.6% and the specificity was 97.1% for the conventional 2-Dtechnique. A combination of both techniques yielded 95.7% sensitivity and 100% specificity in the diagnosis of meniscal tears. Of the 23 meniscal tears proven at arthroscopy or surgery, there were four discrepancies between the two techniques ; three of the four represented false-negative 2-D images and one was a false-negative axial3-D image. Of 35 normal menisci, two false-positives occurred with axial 3-D imaging and one with 2-D imaging. CONCLUSION: Despite the lack of a statistically significant difference between the efficacy of the two techniques, these results suggest that the sensitivity in the diagnosis of meniscal tears can be improved by adding thin-sliced axial 3-D GRASS imaging to conventional 2-D imaging in the limited cases with clinically suspected meniscal tears.

Detection of Liver Metastases: Usefulness of Dynamic Spiral CT during the Portal Phase with a Higher IV Injection Rate of Contrast Material

PURPOSE: To evaluate the usefulness of dynamic spiral computed tomography(CT) during the portal phase with ahigher IV injection rate of contrast material in detecting hepatic metastases. MATERIALS AND METHODS: We reviewed two-phase dynamic spiral CT in 44 patients with hepatic metastases of pathologically proven primary malignancy. One hundred and fifty ml. of non-ionic contrast material was administered with a power injector at a rate of 5ml/sec., and two-phase images at 55-80 sec.(portal phase) and 2-5 min.(equilibrium phase) were obtained after thestart of bolus injection. Two phase images were compared for detectability of hepatic metastases according tosize, number and enhancement pattern. RESULTS: In cases of metastases less than 1cm, 113 lesions(100%) that showed clearly defined hypodense lesions were detected in the portal phase of dynamic CT. However, the equilibriumphase images showed hypodense lesions in 58 cases(51%) and isodense lesions in 55cases(49%). In cases of metastases 1-2cm in size, the portal phase images detected 70 hypodense lesions(92%) and six hyperdense lesions(8%). In the equilibrium phase, however, the lesions were hypodense in 54 cases(71%), hyperdense infour(5%), and isodense in 18(24%). In cases of metastases larger than 2 cm, portal phase images showed 29 hypodense lesions(97%) and one hyperdense lesion(3%). In the equilibrium phase, however, the lesions were hypodense in 25 cases(83%), hyperdense in two(7%), and mixed in three(10%). As compared with the portal phase, most metastatic lesions were detected as poorly defined hypodense or isodense lesions in the equilibrium phase and decrease in size due to peripheral enhancement. CONCLUSION: Dynamic spiral CT during the portal phase with a higher IV injection rate(5 ml/sec) of contrast material is a useful method for detecting hepatic metastases, especially small lesions less than 1cm.

Spiral CT of Hepatocellular Carcinoma: Value of Dynamic Fast Infusion of Contrast Material

PURPOSE: To assess the value of dynamic fast infusion of contrast material in the detection and diagnosis of hepatocellular carcinoma(HCC) with spiral CT. MATERIALS AND METHODS: Two-phase dynamic spiral CT was performed in 59 patients with 104 HCCs. 150ml of nonionic contrast material was injected with an automatic injector at the rateof 5 ml/sec. Two-phase images were obtained at 20-45 sec(arterial dominant phase) and 2-5 min(equilibrium phase)after the initiation of bolus injection of contrast material. The tumors were divided into three groups(5cm) according to the size and the enhancement patterns on two-phase images were compared. RESULTS: Inthe arterial phase, HCCs showed total or partial hyperattenuation in 79% of cases(82/104), isoattenuation in 12%,and hypoattenuation in 9%. In the equilibrium phase, HCCs showed hypoattenuation in 86%(89/104) and isoattenuationin 14%. The most common and characteristic enhancement patterns of HCCs were hyperattenuation in the arterialphase and hypoattenuataion in the equilibrium phase ; in the latter, capsules were demonstrated in 45% of cases. Invasions of the portal and/or hepatic vein were demonstrated in 34% of cases. CONCLUSION: Dynamic fastinfusion(5ml/sec) of contrast material(150ml) is useful in the detection and diagnosis of HCCs with spiral CT.