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Normal and Transplanted Rat Kidneys: Diffusion MR Imaging at 7 T¹

¹ From the Department of Biological Sciences, Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, 4400 Fifth Ave, Pittsburgh, PA 15213. From the 2002 RSNA scientific assembly. Received November 27, 2002; revision requested January 30, 2003; final revision received October 7; accepted October 20. Supported by contract grants P41EB-001977 and R01EB/AI-00318 from the National Institutes of Health. Address correspondence to C.H. (e-mail: chienho@andrew.cmu.edu).

View larger version (41K): [in a new window]   Figure 1. T1-weighted fast spin-echo MR image (400/20) and ADC maps obtained with spin-echo sequence with the diffusion gradient oriented cephalocaudally (ADCc), mediolaterally (ADCm), or anteroposteriorly (ADCa) in normal Brown Norway rat. Bright areas on upper poles of kidneys in T1-weighted image are chemical shift artifacts caused by fat.

View larger version (36K): [in a new window]   Figure 2. Graphs show, A, mean arterial blood pressure (in one representative animal), and, B, ADCm values (averaged over all six animals) as measured during renal blood flow modulation with angiotensin II. ADC values were measured on images obtained at the following five time points (each data point represents mean value ± SD): 1st, before angiotensin II infusion; 2nd, 17 minutes after the start of infusion; 3rd, immediately after infusion; 4th, 30 minutes after stopping the infusion; and 5th, 60 minutes after stopping the infusion.

View larger version (85K): [in a new window]   Figure 3. MR images show time response of renal ADC values in one representative rat in the angiotensin II infusion group. T1-weighted image (400/20) and ADC maps obtained before angiotensin II infusion (1st), 17 minutes after the start of infusion (2nd), immediately after infusion (3rd), 30 minutes after stopping the infusion (4th), and 60 minutes after stopping the infusion (5th). A water phantom used to provide standard-of-reference measurements appears in the top right corner of each image. Angiotensin II infusion caused more than a 35% decrease in ADCm values in the cortex and the medulla. ADCm values returned to normal 30 minutes after angiotensin II infusion was stopped.

View larger version (29K): [in a new window]   Figure 4. Graph shows variation in ADCm over an 8-hour period in the cortex and medulla of six native kidneys and six allografts on day 4 after surgery. Error bars represent 1 SD of each ADC value. A significant decrease in ADCm values was observed in allografts starting from postoperative day 4 (P < .01). (For better visualization, error bars are shown only on one side of the symbols.)

View larger version (76K): [in a new window]   Figure 5. A, Gradient-echo MR images (100/7.3), and, B, ADC maps obtained in an allograft over an 8-hour period on day 4 after surgery. The allograft kidneys show graft enlargement on gradient-echo images, but no significant difference in signal intensity was observed between transplanted and native kidneys, and no significant signal intensity change was observed over a period of 8 hours. A significant decrease in ADCm values was observed in allografts on postoperative day 4. 4d = postoperative day 4, 4d2hr = 2nd hour of postoperative day 4, 4d4hr = 4th hour of postoperative day 4, 4d6hr = 6th hour of postoperative day 4, 4d8hr = 8th hour of postoperative day 4.

View larger version (27K): [in a new window]   Figure 6. Graph shows variation in ADCm over an 8-hour period in the cortex and medulla of three native kidneys and three isografts. Error bars represent 1 SD of each ADC value. No difference in ADC values was found between native kidneys and isografts. (For better visualization, error bars are shown only on one side of the symbols.)

View larger version (65K): [in a new window]   Figure 7. A, Gradient-echo MR images (100/7.3), and, B, ADCm maps obtained in an isograft over an 8-hour period on day 4 after surgery. No substantial difference in ADC values was observed between native kidneys and isografts. 4d = postoperative day 4, 4d2hr = 2nd hour of postoperative day 4, 4d4hr = 4th hour of postoperative day 4, 4d6hr = 6th hour of postoperative day 4, 4d8hr = 8th hour of postoperative day 4.