Biomedical subjects

Pottumarthi Prasad

Publications and source records attributed to Pottumarthi Prasad.

4 recordsLinked to original sources

PubMed2006

Three-dimensional T1 mapping for dGEMRIC at 3.0 T using the Look Locker method.

OBJECTIVE: The objective of this study was to implement a three-dimensional (3-D) T1 mapping sequence (3DLL) at 3.0 T for dGEMRIC based on the Look Locker scheme. MATERIALS AND METHODS: Because all current reports on dGEMRIC are at 1.5 T and mostly using 2-D IR fast spin echo (FSE), data were acquired at 1.5 T and 3.0 T with both 3DLL and 2-D IR-FSE sequence. Phantoms with different concentrations of Gd(DTPA) were used and seven subjects (three asymptomatic, four symptomatic) were scanned using the dGEMRIC technique. RESULTS: The T1 measurements obtained on the phantom with 3DLL show very good agreement with those acquired with 2-D IR-FSE. Using a two-tailed paired t test, the T1 (Gd) measurements in two sections obtained in all subjects with both sequences were found to be statistically indistinguishable at either field strength (P = 0.07 at 1.5 T and P = 0.07 at 3.0 T). CONCLUSIONS: The preliminary data presented here suggest that the 3DLL sequence provides accurate T1 values with sufficient in-plane resolution and allows full joint coverage in less than 10 minutes.

Adult↗

PubMed2005

Effect of free radical scavenger (tempol) on intrarenal oxygenation in hypertensive rats as evaluated by BOLD MRI.

PURPOSE: To demonstrate a differential response following administration of a free radical scavenger, tempol, in kidneys of hypertensive compared to normotensive rats. MATERIAL AND METHODS: Data were obtained in spontaneously hypertensive rats (SHR, N = 5). Wistar-Kyoto rats (WKY, N = 6) were used as normotensive controls. RESULTS: Consistent with prior reports, SHRs show a significant response to tempol (R(2)*decreased from 40.56 +/- 0.66 second(-1) to 28.58 +/- 0.6 second(-1) in medulla, P < 0.05), while WKY rats exhibit a minimal change (R(2)* measuring 22.36 +/- 4.38 second(-1) pre-tempol and 21.57 +/- 4.78 second(-1) post-tempol, in medulla). The post-tempol R(2)* in SHR was found to be comparable to pre-tempol values in WKY rats, suggesting an improved medullary oxygenation in SHRs. CONCLUSION: Based on both baseline R(2)* values and the differential effect of the free radical scavenger on renal medullary oxygenation, BOLD MRI can distinguish hypertensive from normal kidney in rats.

Animals↗

PubMed2004

Evaluation of the reproducibility of intrarenal R2* and DeltaR2* measurements following administration of furosemide and during waterload.

PURPOSE: To estimate the reproducibility of BOLD MRI measurements in the evaluation of intrarenal oxygenation levels. MATERIALS AND METHODS: In this study, the reproducibility of semiquantitative BOLD MRI measurements performed on a 1.5 T scanner with a multiple gradient-echo sequence in the renal medulla and cortex, and their response to furosemide and waterload, were assessed in eight healthy young subjects (25.6 +/- 4.1 years). Each subject underwent an identical experimental procedure on two separate days. RESULTS: Renal R2* measurements were shown to be reproducible within approximately 12% from day to day based on a coefficient of variance (CV) analysis. The changes in R2* (DeltaR2*) following administration of furosemide were statistically significant, as shown by ANOVA and a paired Student's t-test, and were deemed reliable based on the reliable change index (RCI). However, DeltaR2* values following waterload were not statistically significant, and were not deemed reliable. CONCLUSION: R2* measurements were reproducible over 270 days within 12%. Furosemide produced a significant and reliable change (approximately 30%), and the magnitude of change (5.7 s(-1)) was reproducible and consistent with our previous data. The response to waterload, however, did not reach statistical significance, and the magnitude did not reach the level that we had previously reported.

Adult↗

PubMed2003

Kidneys in hypertensive rats show reduced response to nitric oxide synthase inhibition as evaluated by BOLD MRI.

PURPOSE: To examine whether the noninvasive technique of blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) can detect changes in renal medullary oxygenation following administration of a nitric oxide (NO) synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME). Hypertension is associated with endothelial dysfunction and is characterized by a lack of response to endothelial-dependent vasoactive substances, including nitric oxide synthase inhibitors. We hypothesized that the magnitude of the change would be reduced in the kidneys of hypertensive subjects relative to normal controls. MATERIALS AND METHODS: To test this hypothesis, data were obtained in spontaneously hypertensive rats (SHR, n = 6). Wistar-Kyoto rats (WKY, n = 7) were used as normotensive controls. RESULTS: As expected, WKY rats showed a significant response to L-NAME (R(2)* increasing from 23.6+/-1.5 Hz to 32.5+/-2.2 Hz, P < 0.05), while SHR exhibited a minimal change in medullary oxygenation (R(2)* measuring 31.9+/-2.8 Hz pre- and 35.5+/-2.2 Hz post-L-NAME). The baseline R(2)* in SHR is found to be comparable to post-L-NAME values in WKY rats, suggesting a basal deficiency of nitric oxide in SHR. CONCLUSION: Based on the differential effect of NO synthase inhibition on medullary oxygenation, BOLD MRI can distinguish hypertensive from normal kidney. Our results are consistent with previously reported observations using invasive methods.

Animals↗