Evaluation Of Intra-renal Oxygenation Of Kidneys In Normal Subjects And Patients With Renal Transplant By BOLD MRI

Objective: To prospectively assess the intra-renal oxygenation of kidneys in normal subjects and patients with renal transplants by blood oxygen level dependent (BOLD) MR imaging and to detect acute rejection of the transplants in early stage.Methods: 15 healthy volunteers , and 50 patients who had recently received renal transplants were included in this study , 34 renal-transplant patients had clincally normal function transplants, 16 had biopsy-proved acute rejection. BOLD MR imaging was performed with 16 gradient-recalled-echoe at a gap of 1mm and a 5-mm section thickness in the coronal plane. The parameters were as follows: TE:2.5—90 and TR:100msec; flip angle:35° ; bandwidth:31kHz; matrix:192 ×128.Region of intrusting (ROIs) were placed in the medulla and cortex on both gray-scale imaging and color maps . R2~*(1/sec) values for the cortex and medulla of the kidneys were obtained respectively. Statistical analysis was performed by using Student t tests. Threshold R2~* values were identified to discriminate between transplanted kidneys with acute rejection and those with normal function.Results: In normal subjects, R2~* values were significantly higher in the medulla 19.812±1.86/sec) than in the cortex (11.722±0.49/sec)(P < 0.05). In normalfunction transplants, R2~* values of the medulla (15.224 ± 3.810/sec) were also higher than that of the cortex (10.335 ± 0.2 /sec) (P < 0.05). The differences of the R2~* values of the medulla and cortex between the normal subjects and renal transplants were significant. Furthermore, R2~* values for the medulla were significantly lower in the acute rejection patients (11.606±1.623/sec) than that in the normal function grafts (18.224± 0.70/sec) (P <0. 0001). Acute rejection could be differentiated from normal function transplant kidney in all cases by using a threshold R2~* value of 13.00/sec.Conclusion: BOLD MR imaging proved to be a repid, noninvasive method for assessing renal oxygen state in transplanted kidneys and detectingting acute rejetion. R2~*measurements in the medullary of transplanted kidneys with acute rejection were significanlly lower than those in normally functioning transplants. Acute rejection could be differentiated from normally functioning transplants cases by using a threshold R2~* value 13/sec.