Effects of Tissue Temperature and Injury on ADC during Therapeutic Hypothermia in Newborn Hypoxic-Ischemic Encephalopathy.

BACKGROUND AND PURPOSE: ADC changes are useful in detecting ischemic brain injury, but mechanisms other than tissue pathology may affect the kinetic movement and diffusion of water molecules. We aimed to determine the effects of brain temperature on the corresponding ADC in infants undergoing therapeutic hypothermia. MATERIALS AND METHODS: Brain temperature and ADC values in the basal ganglia, thalamus, cortical GM, and WM were analyzed during and after therapeutic hypothermia. The study cohort was categorized as having no-injury or injury. Among infants without injury, the correlation between ADC values and temperature was analyzed using the Pearson correlation. Intrasubject comparison of ADC changes during and after therapeutic hypothermia were analyzed, excluding patients who had an MR image interval of >5 days to minimize the effects of injury evolution. RESULTS: Thirty-nine infants with hypoxic-ischemic encephalopathy were enrolled (23 no-injury; 16 injury). The median ADC was significantly lower during therapeutic hypothermia (837; interquartile range, 771-928, versus 906; interquartile range, 844-1032 ×10-6mm2/s; P < .001). There was no difference in the ADC between the no-injury and injury groups during therapeutic hypothermia (823; interquartile range, 782-868, versus 842; interquartile range, 770-1008 ×10-6mm2/s; P = .4). In the no-injury group, in which ADC is presumed least affected by the evolution of injury, the median ADC was significantly lower during therapeutic hypothermia (826; interquartile range, 771-866, versus 897; interquartile range, 846-936 ×10-6mm2/s; P < .001). There was a moderate correlation between temperature and ADC in the no-injury group (during therapeutic hypothermia: Spearman ρ, 0.48; P < .001; after therapeutic hypothermia: ρ, 0.4; P < .001). CONCLUSIONS: Aside from brain injury, reduced tissue temperature may also contribute to diffusion restriction on MR imaging in infants undergoing therapeutic hypothermia.

Differentiation between classic and atypical meningiomas with use of diffusion tensor imaging.

BACKGROUND AND PURPOSE: The differentiation between classic and atypical meningiomas may have implications in preoperative planning but may not be possible on the basis of conventional MR imaging. Our hypothesis was that classic and atypical meningiomas have different patterns of intratumoral water diffusion that will allow for differentiation between them. MATERIALS AND METHODS: Preoperative diffusion tensor imaging (DTI) was performed in 12 classic and 12 atypical meningiomas. Signal intensity of solid-enhancing tumor regions on diffusion-weighted trace images and apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps was assessed. Regions of interest (ROIs) were placed in solid-enhancing regions, peritumoral edema, and contralateral normal-appearing white matter (NAWM) to measure tensor metrics including major (lambda(1)), intermediate (lambda(2)) and minor eigenvalues (lambda(3)) and FA and ADC values. Distribution of tensor shapes within enhancing tumors was calculated for all tumors. Differences between classic and atypical meningiomas in tumor signal intensity, intratumoral and peritumoral tensor metrics, as well as tensor shapes distribution were statistically analyzed. RESULTS: A significantly greater proportion of atypical meningiomas were isointense and hypointense on ADC maps (P = .007). Classic meningiomas had significantly lower FA (P = .012), higher ADC (P = .011), greater lambda(2) (P = .020) and lambda(3) (P = .003). There was significantly more spherical diffusion in classic than in atypical meningiomas (P = .020). All diffusion tensor metrics for peritumoral edema of the 2 tumor groups did not differ. CONCLUSION: DTI showed that intratumoral microscopic water motion is less organized in classic than in atypical meningiomas. This feature may allow for noninvasive differentiation between classic and atypical meningiomas.

Primary cerebral lymphoma and glioblastoma multiforme: differences in diffusion characteristics evaluated with diffusion tensor imaging.

BACKGROUND AND PURPOSE: Differentiating between primary cerebral lymphoma and glioblastoma multiforme (GBM) based on conventional MR imaging sequences may be impossible. Our hypothesis was that there are significant differences in fractional anisotropy (FA) and apparent diffusion coefficient (ADC) between lymphoma and GBM, which will allow for differentiation between them. MATERIALS AND METHODS: Preoperative diffusion tensor imaging (DTI) was performed in 10 patients with lymphoma and 10 patients with GBM. Regions of interest were placed in only solid-enhancing tumor areas and the contralateral normal-appearing white matter (NAWM) to measure the FA and ADC values. The differences in FA and ADC between lymphoma and GBM, as well as between solid-enhancing areas of each tumor type and contralateral NAWM, were analyzed statistically. Cutoff values of FA, FA ratio, ADC, and ADC ratio for distinguishing lymphomas from GBMs were determined by receiver operating characteristic curve analysis. RESULTS: FA and ADC values of lymphoma were significantly decreased compared with NAWM. Mean FA, FA ratio, ADC (x10(-3) mm(2)/s), and ADC ratios were 0.140 +/- 0.024, 0.25 +/- 0.04, 0.630 +/- 0.155, and 0.83 +/- 0.14 for lymphoma, respectively, and 0.229 +/- 0.069, 0.40 +/- 0.12, 0.963 +/- 0.119, and 1.26 +/- 0.13 for GBM, respectively. All of the values were significantly different between lymphomas and GBM. Cutoff values to differentiate lymphomas from GBM were 0.192 for FA, 0.33 for FA ratio, 0.818 for ADC, and 1.06 for ADC ratio. CONCLUSIONS: The FA and ADC of primary cerebral lymphoma were significantly lower than those of GBM. DTI is able to differentiate lymphomas from GBM.

A case of colonic tuberculosis mimicking Crohn's disease.

A 26-year-old Thai woman who has lived in Hong Kong for the past 3 years presented with a 2-month history of feverishness, intermittent epigastric discomfort, anorexia, and weight loss. She had had per rectal bleeding for 10 days. Colonoscopy on two separate occasions revealed multiple ulcerations involving the entire colon, with rectal sparing. Histological examination of the two sets of colonic biopsies that were obtained during colonoscopy suggested Crohn's disease. There was no response to mesalazine and metronidazole, but the patient responded promptly to a therapeutic trial of antituberculous drugs. Cultures from the first set of colonic biopsies were negative for acid-fast bacilli, but 8 weeks after the second colonoscopy, cultures from the second set of biopsies yielded Mycobacterium tuberculosis. This case illustrates that the diagnosis of colonic tuberculosis requires a high index of suspicion. In cases where the information available does not reveal a definite differentiation between colonic tuberculosis and Crohn's disease, corticosteroids should be withheld. The administration of corticosteroids to a patient with colonic tuberculosis may have disastrous results, and a therapeutic trial of antituberculous drugs should be considered instead.