Diffusion-weighted MR Imaging of Hypoxic-Ischemic Encephalopathy

PURPOSE: The purpose of this study was to determine the characteristics of hypoxic-ischemic encephalopathy (HIE) on diffusion-weighted imaging (DWI) and the role of DWI for the diagnosis of HIE. MATERIALS AND METHODS: Six patients with HIE underwent MRI including DWI. MR examinations were performed within 4 - 32 days (mean, 11.8 days) after hypoxic brain insult. We assessed the distribution of the lesions and compared the DWI and T2, FLAIR images for the subjective conspicuity of the lesions. RESULTS: In all patients, symmetrical hyperintense lesions were demonstrated in the bilateral basal ganglia on T2, FLAIR, and DWI. On ADC map image, the lesions were hypointense in four of six patients and isointense in other two patients. Lesion conspicuity on DWI was higher than on T2 and FLAIR images in four of six patients and similar in other two patients. For the involvement of the cortex and subcortical white matter, in five of six patients, bilateral symmetric hyperintense lesions were seen on T2, FLAIR, and DWI. Lesion conspicuity on DWI was higher than on T2 and FLAIR images in three of them and similar in other two patients. On ADC map image, the lesions showed hypointensity in three of five patients and isointensity in other two patients. For the involvement of the deep cerebral white matter, T2, FLAIR, and DWI showed bilateral symmetric hyperintense lesions in four of six patients. Among them, Lesion conspicuity on DWI was higher than on T2 and FLAIR images in only one patient. CONCLUSION: HIE is characterized by symmetrical hyperintense lesions in the bilateral basal ganglia, cerebral cortex, and white matter on DWI and the lesions are more conspicuously demonstrated on DWI than on T2 and FLAIR images.

In Vivo and In Vitro Studies of the Steady State Free Precession-Diffusion-Weighted MR Imagings on Low b-value: Validation and Application to Bone Marrow Pathology / 영남의대학술지

PURPOSE: The purpose of this study was a phantom study to measure the diffusion properties of water molecules by steady-state free precession diffusion-weighted imaging (SSFP-DWI) with a low b-value and to determine if this sequence might be useful for application to the evaluation of bone marrow pathology. MATERIALS AND METHODS: 1. The phantom study: A phantom study using two diffusion weighted sequences for the evaluation of the diffusion coefficient was performed. Three water-containing cylinders at different temperatures were designed: phantom A was 3degrees C, B was 23degrees C and C was 63degrees C. Both SSFP and echo planar imaging (EPI) sequences (b-value: 1000 s/mm2) were performed for comparison of the diffusion properties. The Signal to noise ratios (SNR) and apparent diffusion coefficient (ADC) values of the three phantoms using each diffusion-weighted sequence were assessed. 2. The Clinical study: SSFP-DWI was performed in 28 patients [sacral insufficiency fractures (10), osteoporotic lumbar compression fractures (10), malignant compression fractures (8)]. To measure the ADC maps, a diffusion-weighted single shot stimulated echo-acquisition mode sequence (650s/ mm2) was obtained using the same 1.5-T MR imager RESULTS: For the phantom study, the signal intensity on the SSFP as well as the classic EPI-based DWI was decreased as the temperature increased in phantom A to C. The ADC values of the phantoms on EPI-DWI were 0.13x10(-3) mm2/s in phantom A, 0.22x10(-3) mm2/s in B and 0.37x10(-3) mm2/s. in C. The SSFP can be regarded as a DWI sequence in view of the series of signal decreases. CONCLUSION: Bone marrow pathologies with different diffusion coefficients were evaluated by SSFP-DWI. All benign fractures were hypointense compared to the adjacent normal bone marrow where as the malignant fractures were hyperintense compared to the adjacent normal bone marrow.

Diffusion-weighted Imaging of MRI in Acute Cerebral Stroke / 中国医师杂志

Objective To analyze the diffusion properties of acute cerebral stroke to understand the effects of infarct and hematoma on diffusion-weighted MR images of patients with acute cerebral stroke. Methods 25 acute cerebral infarcts, 22 intracranial hematomas and 5 hemorrhagic infarctions were studied with CT, conventional and diffusion MR imaging. The DWI and ADC parameters of acute cerebral stroke were analyzed. Results The DWI images of 25 acute cerebral infarcts, 1 hyperacute hematoma, 2 acute hematomas and 3 subacute hematomas were hyperintensity, and that of 8 early subacute hematomas were hypointensity. The DWI images of early stage of 4 chronic hematomas were hyperintensity at center and hypointensity at periphery, and that of late stage were hypointensity. The DWI images of acute hemorrhagic infarctions had both the hyperintensity and hypointensity. Meanwhile, the ADC images of majority of the lesions were hypointensity. Conclusion DWI could reflect the diffusion properties of different types of cerebral strokes and play an important role in evaluating the strokes.