| Rsaearch background and significance:The incidence rate of chronic kidney disease(CKD) is increasing year by year, and in recent it has become a public health problem to humanity. The reduce in renal function is a long time pathological process in most patients with chronic kidney disease and the final trend is renal failure. Large amounts of data show that if the detection of disease is early, and some treatment measures were took, the process of renal failure can significantly delay. Most patients with chronic kidney disease were hard to be find early because clinical symptoms were not obviously. Now renal function examination methods in clinic are invasive and harmful, not fit to some patients.Magnetic Resonance Imaging (MRI) is a new technology with many advantages, such as non-invasive, no radiation, high spatial resolution and others. With the further development of MRI software, blood oxygen level dependent magnetic resonance imaging (BOLD MRI) technique is a new functional imaging, its main research is the relationship between physiology and oxygen utilization of tissues. Recently this technology are using in brain function. The purpose in our study is to compare with 99Tc-DTPA renal dynamic imaging technique and discuss the value of BOLD MRI in assessment of renal function.ObjectiveTo compare BOLD MRI with 99Tc-DTPA renal dynamic imaging in CKD, and explore the value of BOLD MRI in evaluation of renal functionMaterials and methods1 Case selection26 patients with chronic kidney disease who accepted renal dynamic scintigraphy from June 2010 to January 2011 in the ZhuJiang hospital were selected. The 26 patients consisted of 14 men and 12 women with a mean age of 43.56±8.91 years(range 22-68 years).All patients were comformed to requirements of chronic kidney disease which published by United States of America Kidney Foundation in 2002, get rid of the patients who with kidney cancer, kidney stones, urinary tract infection, cardiovascular disease, diabetes, coagulopathy, abnormal liver function and other related diseases. All patients took two tests within 24 hours.2 BOLD MRI examination methods2.1 BOLD MRI inspection equipment and sequencesMRI Scanner:Phihips Archieva 3.0T superconduct magnetic resonance scanner, SENSE cardiac coil and respiratory gating technology. Scout view:transverse, coronal and sagittal section; Routine MRI sequence:fast spin echo (FSE) sequence,T2WI transverse and coronal section,T1WI transverse section. BOLD imaging sequences:multiple gradient echo sequence (mGRE),coronal and transverse section. Inspection process need suffocating for 10s in BOLD MRI. Full scans took about 10-12 mins.2.2 Image quality analysisImages quality was evaluated and scorred by two experienced radiologists of MRI diagnosis. Key evaluation indicators included image signal to noise ratio(SNR), resolution, capability of anatomical location. Finally all images were divided into three levels. 2.3 The measurements of R2* value in BOLD MRIEach kidney get 5 coronal images and five transverse images. The imagings with a clear view in cortex images to distinguish renal cortex and medulla was choosed.Three images from five coronal images as the measurement objects were slected. Each image took seven areas as region of interest (ROI), the maximum and minimum values were removed. ROI size between the 2-3mm2. Each patient received single R2* values of the right and left kidneys respectively.3 Method of renal dynamic imaging examinationAll patients received examination of Infinavc Hawkeye single photon emission computed tomography (SPECT) made by U.S. company GE. Radioactive drugs were Tc-DTPA,which made by the China Institute of Atomic Research Institute.Patients were obtained by prone position, probe should be fully included renal perspective, ureter and bladder areas. Radioactive drugs were injected about lml from the right elbow vein by the way of "pellet" type, the radiation dose about 5mCi/ml. The scansion was started immediately after injection. Blood perfusion phase was first scan,3s/frame, collecting 60s. using computer software to stack images of blood perfusion phase, the renal profile was clear, draw the areas of outlined renal profile, background and regions of interest of bladder. Then started collect function photograph,60s/frame and capture 20 frames, all the program needed time about 20mins. All these inspections process took about 21mins.The tasks of deal with post-processing images used computer software provided by GE, according to the information such as the height and weight of the data standardization, the computer automaticly analysed the total renal GFR, single renal GFR and other informations. According to two renal counting rate and ratio of bilateral renal count, the computer could automaticly calculate the singal renal GFR by means of the method of Gates.4 Grouping subjectsRefer to the standard specified published in 2002 by Foundation of United States kidney disease group, grouping principle is 1/2 of total kidney GFR of the rule. The first group:single kidney GFR≥45ml/min* 1.73m3; The second group:single kidney GFR 30-40ml/min*1.73m3; The third group:single kidney GFR 15-30 ml/min* 1.73m3; The fourth group:single kidney GFR 7.5-15ml/min* 1.73m3; The fifth group:single kidney GFR<7.5ml/min* 1.73m3.5 Statistical methods:The five groups of 52 kidneys were analysed by statistical analysis soft of SPSS 13.0, counting materials were described by mean differences±standard deviation, there was be significant differtence with P<0.05. The means between every two groups were compared with t test, multiple comparisons used the LSD method. one-way ANOVA was used in the test of homogeneity of variance. If datas were fit normal distribution, use the correlation analysis of Pearson, if not, use the correlation analysis of Spearman.Results1 BOLD MRI image quality analysisThis subject gathered 26 patients with CKD,52 renal informations. All kidneys were divided into five groups accorded by GFR value. The quality of BOLD MRI images in the former three groups with the mild-to-moderate decline in renal functions was better, with high SNR and accurate location. The image quality in the last two groups with lower SNR and more artifact was poorer.2 BOLD MRI,99Tc-DTPA renal dynamic imaging and comparative sutdy2.1 With decline of renal function, BOLD MRI image quality was lowered. High quality images were easy to resolute renal cortical and medulla, measurement results were accurate.2.2 With decline of renal GFR value, the R2* value was fall gradually. As renal function was lower, the oxygen consumption was gradually reduced too, the renal R2* value was lower.2.3 When renal function was slightly lower, after radioactive drugs injection for 60 seconds,kidney contour showd clear, The ROI and background was accurate. But when renal function was serious lower, kidney contour was not clear after injection for 60 seconds. The selection of ROI and background could caused much error.2.4 In the comparative study of BOLD MRI wtih 99Tc-DTPA renal dynamic imaging, the correlation coefficients in first three groups was high, they were 0.804,0.817 and 0.745,and the correlation coefficients in last two groups were lower, they were 0.406 and 0.476. It suggested that when renal function with mild-to-moderate decline, BOLD MRI evaluative effection was good, but when renal function with serious decline, it had a bad evaluative effection.ConclusionTc-DTPA renal dynamic imaging technology is a mature and reliable renal evaluation mathod, It is the only method to determine single renal function technology in clinic. Through the comparative study between BOLD MRI and 99Tc-DTPA renal dynamic imaging technology in renal function, we can learn that in patients with severe decline in renal function, BOLD MEI has a small value, but in the patients with mild-to-moderate decline in renal function, it has a great value. |
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