Usefulness of Fluid Attenuated Inve rsion Re c overy(FLAIR) Image

PURPOSE: To determine the usefulness of fluid attenuated inversion recovery(FLAIR) imaging for the in detection of high signal intensity of hippocampus or amygdala in mesial temporal sclerosis (MTS), compared with that of turbo spin-echo T2-weighted imaging. MATERIALS AND METHODS: Two neuroradiologists independently analyzed randomly mixed MR images of 20 lesions of 17 patients in whom MTS had been diagnosed, and ten normal controls. All subjects underwent both who performed both FLAIR and turbo spin-echo T2-weighted imaging, in a blind fashion. In order to determine hippocampal morphology, oblique coronal images perpendicular to the long axis of the hippocampus were obtained. The detection rate of high signal intensity in hippocampus or amygdala, the radiologists 'preferred imaging sequence, and intersubject consistency of detection were evaluated. Signal intensity in hippocampus or amygdala was considered high if substantially higher than signal intensity in the cortex of adjacent temporo-parietal lobe. RESULTS: In all normal controls, FLAIR and spin-echo T2-weighted images showed normal signal intensity in hippocampus or amygdala. In MTS, the mean detection rate of high signal intensity in hippocampus or amyg-dala, as seen on FLAIR images was 93%, compared with 43% on spin-echo T2-weighted images. In all cases in which signal intensity on FLAIR images was normal, signal intensity on spin-echo T2-weighted images was also normal. The radiologists preferred the contrast properties of FLAIR to those of spin-echo T2-weighted images. CONCLUSION: In the diagnosis of MTS using MRI, FLAIR images are more useful for the detection of high signal intensity of hippocampus or amygdala than are spin-echo T2-weighted images. In the diagnosis of MTS, FLAIR imaging is therefore a suitable alternative to spin-echo T2-weighted imaging.

Contrast Enhanced Two-Phase Spiral CT of Urinary Bladder

PURPOSE: To determine optimal scan time for the early phase of two-phase spiral CT and to evaluate its usefulness in the detection and assessment of extension of urinary bladder lesions. MATERIALS AND METHODS: In four normal adults, we performed dynamic scanning and obtained time-density curves for internal and external iliac arteries and veins, and the wall of the urinary bladder. Sixty patients with 68 lesions of the urinary bladder or prostate underwent precontrast and two-phase spiral CT scanning. After injection of 100ml of noninonic contrast material, images for the early and delayed phases were obtained at 60 seconds and 5 minutes, respectively. We measured CT H.U. of the wall, the lesion, and lumen of urinary bladder as seen on axial scanning, in each image in which the lesion was best shown. For the detection of bladder lesions and assessment of their extension, precontrast, early-, and delayed phase images were compared. RESULTS: Dynamic study of normal adults showed maximum enhancement of bladder wall between 60 and 100 seconds. The difference of CT H.U. between bladder wall and the lesion was greatest in the early phase. The best detection rate (98.5%) was seen during this phase, and for the detection of bladder lesion, this same phase was superior or equal (66/68,97.1%) to the delayed phase. The precontrast image was also superior or equal (31/68,45.6%) to that of the delayed phase. For the assessment of extension of bladder lesion, the early phase was superior (36/68,52.9%) to the delayed phase, and precontrast image was superior (1/68, 1.5%) to that of the delayed phase. For determining the stage of bladder cancer, the early phase was most accurate if the stages was below B2 or D, while for stage C, the delayed phase was most accurate. CONCLUSION: In two-phase spiral CT scanning, we consider the optimal time for the early phase to be between 60 and 100 seconds after injection of contrast material. For the detection and assessment of extension of urinary bladder lesion, the early phase was superior to the late phase, and for evaluation of the ureter, the delayed phase was useful. The precontrast image was inferior to that of the delayed phase. We suggest that for the detection and assessment of extension of urinary bladder lesion without scanning of the precontrast image, two-phase spiral CT is reliable.

Mercuric Chloride-Induced Acute Tubular Necrosis in the Rabbits: Gd-DTPA Enhanced Dynamic IVIR Imaging

PURPOSE: To evaluate potential usefulness of dynamic Gd-DTPA enhanced MRI in the diagnosis of HgCI2 induced acute tubular necrosis of rabbits. MATERIALS AND METHODS: Sixteen rabbits were used as control group, and 14 rabbits and 12 rabbits were used as acute tubular necrosis groups of 24 hours and 48 hours after HgCI2 injection, respectively. Sequential dynamic MR imagings were acquired using Gd-DTPA(0.25mmol/kg), and time-signal intensity curves were obtained from cortex, outer medulla and inner medulla. RESULTS: In control group, a dark band, which reflects concentrated Gd-DTPA, migrated from cortex to inner medulla of the kidney, and the ratio of the signal intensity of post Gd-DTPA injection to the signal intensity of pre Gd-DTPA injection(RSI) decreased below 1 at 13sec and 26sec (mean:17 +/- 6.2sec) in cortex, at 52sec (mean :52sec) in outer medulla, and after 117sec(mean :112 +/- 33.9sec) in inner medulla of the kidney. In acute tubular necrosis group of 24 hours after HgCI2 injection, the dark band did not appear and signal intensity in cortex and medulla increased diffusely, and RSI increased above 1 in all locations. In acute tubular necrosis group of 48 hours after HgCI2 injection, the dark band appeared only in the cortex and no sign of migration was observed, and RSI is little changed except in cortex at 13sec(0.76 +/- 0.05) and 26sec(0.86 +/- 0.06). There were statistically significant differences in the time-RSI curves among cortex, outer medulla, and inner medulla in study groups, respectively (p<0.0001). CONCLUSION: Dynamic Gd-DTPA enhanced MRI of the kidney could be utilized to evaluate both renal structure and functional changes.

Measurement of Normal Corpus Callosum with MRI in Korean Adults and Morphological Change of Corpus Callosum by Grade of Hydrocephalus

PURPOSE: To measure the size of normal corpus callosum in each portion using objective and reproducible method with MRI and evaluation of morphological change of corpus callosum by grade of hydrocephalus. MATERIALS AND METHODS: Midsagittal Tl-weighted MR imaging of the corpus callosum was investigated in 41 volunteers of normal Korean adults and 19 patients with hydrocephalus. Corpus callosum was measured for the anteroposterior length(A), height(B), and the thickness of genu(C), body (D), splenium(E), and the narrowest portion of body(F). And the analysis of morphology and signal intensity of the corpus callosum were also evaluated. Hydrocephalus was graded as mild, moderate, and severe, and comparision of thickness with normal corpus callosum in each portion was done. RESULTS: The mean length and height were 72.3mm, 28.6mm in male, and 70.7ram, 28.9mm in female. And the mean dimention for C, D, E, and F were 13.1 ram, 8ram, 13.2mm, 5.2ram in male, and 12.8mm, 7.5ram, 12.3 ram, 5mm in female. The morphology of normal corpus callosum was "hook" shaped on midline sagittal Tl-weighted image. Narrowing at posterior third portion of body were present on 30 cases(73.2%) and even in thickness of the body in 11 cases(26.8%). The signal intensity of the corpus callosum on midsagittal Tl-weighted spin echo image of normal cases was homogeneous hyperintense as compared with cerebral gray matter. In hydrocephalus, A and B were increased and other portions were decreased in thickhess. Genu and the narrowest portion of body showed significant difference of thickness according to the grade of hydrocephalus. CONCLUSION: The mean dimention of all portion of corpus callosum were larger in male than female except for callosal height but not significant statistically with the exception of splenium. Hydrocephalus lead to morphological change of the corpus callosum. Among the portion of corpus callosum, genu and the narrowest portion of the body were thought to be the most sensitive indicators of degree in hydrocephalus.

MR Findings of Cerebral Palsy

PURPOSE: To evaluate the MR findings of brain damage in cerebral palised patients and to correlate it with gestational age and the time of damage. MATERIALS AND METHOD: A retrospective analysis was performed in 40 patients who underwent MR scanning for evaluation of brain lesion in clinically diagnosed cerebral palsy. Authors classified the patients into two groups as premature and full-term and compared MR findings of the two groups. RESULTS: Abnormal MR findings were noted in 28 cases (70%). Five out of 6 patients who had been born prematurely showed isolate periventricular white matter lesions. Twenty-three out of 34 patients who had been born at full-term showed abnormal MR findings. Of these 23 patients, migration anomalies in 7 patients, isolate periventricular white matter lesions in 3 patients, and other combined periventricular subcortical white matter and deep gray matter lesions in 14 patients were seen. At least, 10 patients(43%) of full term group showed abnormal MRI findings reflecting intrauterine brain damage and all 5 patients of premature group showed isolate periventricular white matter lesions suggesting immaturity of brain. CONCLUSION: MRI is thought to be very useful in the assessment of brain damage for the patients with cerebral palsy by recognizing the location of the lesion and estimating the time of damage.