BOLD MRI与~（99）Tc-DTPA肾动态显像在CKD肾功能评价中的相关性研究
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摘要
研究背景及意义
近年来慢性肾脏病(chronic kidney disease, CKD)的发病率和患病率呈逐年上升趋势,目前国内外报道在成年人群的患病率达11%,已成为危害人类的公共健康问题。CKD病人肾功能下降是一个逐渐加重的过程,最终的发展趋势都是肾功能衰竭。大量资料显示慢性肾脏病早期进行相应的治疗和干预,可明显延缓肾功能衰竭的进程。多数CKD病人早期临床症状不明显,很难被发现,出现临床症状就诊时肾功能已显著降低。目前临床常用的肾功能检查方法多为有创性或放射性检查,无法作为常规性检查。99Tc-DTPA'肾动态显像是目前临床测定肾功能最常用的方法之一,同时也是唯一测定分肾功能的检测手段,滤过标志物为核素99Tc-DTPA,检查过程中病人需接触一定的放射剂量。磁共振成像(magnetic resonanceimage, MRI)技术具有无创伤性、无辐射性、高空间分辨率、可重复操作等优点,并可以观察肾脏及周围组织的形态结构,随着MR软件技术的发展,血氧水平依赖磁共振成像(blood oxygen level dependent magnetic resonanceimage, BOLD MRI)技术在临床得到了应用,此项技术研究组织功能水平和氧利用度之间的关系,是一种分子水平的功能影像学检查方法,目前在脑功能成像的应用已较成熟,在肾脏的应用尚处于初步研究阶段。
研究目的
通过BOLD MRI技术和99Tc-DTPA'肾动态显像在CKD肾功能评价的相关性分析,探讨BOLD MRI技术在肾功能评价中的应用价值。
材料与方法
1病例选择
选择2010年6月至2011年1月于珠江医院进行肾动态显像检查的患者。男性14例,女性12例,年龄22-68岁,平均年龄43.56±8.91岁。所有病人均符合2002年美国肾脏病基金会发布的肾脏病指南中慢性肾脏病要求,且排除肾脏肿瘤、肾结石、尿路感染等肾源性疾病和心血管疾病、糖尿病、凝血功能异常、肝功异常等疾病患者。全部病人两项检查均在24小时之内完成。
2 BOLD MRI检查方法
2.1 BOLD MRI检查设备及参数
全部病例使用Phihips Archieva 3.0T超导磁共振扫描仪。定位像：横断、冠状位和矢状位；常规MRI序列：T2WI横断位和冠状位,T1WI横断位,快速旋转回波(fast spin echo, FSE)序列；BOLD成像序列：冠状位和横断位,序列为多次梯度回波(multilple gradient recalled echo,mGRE)序列。扫描过程中使用SENSE Cardiac线圈+呼吸门控技术。BOLD序列扫描过程病人需闭气10s。
全部扫描时间约10-12min。
2.2图像质量分析
由2位有经验的MR诊断医师对每组BOLD功能图像质量进行评价,主要的评价指标包括图像信噪比、分辨率、解剖定位分辨能力等。分优、中、差三个等级对图像质量进行评价。
2.3 BOLD MRI功能图R2*值的测算
病人每个肾共得到5幅冠状位和5幅轴位BOLD MRI图像,冠状位对肾锥体和肾皮质分界显示清楚,多数测量工作在冠状肾功能图像上进行,部分病人冠状位图像分辨困难时,结合横断位进行测量。5幅冠状位肾功能图像中,挑选2幅定位清楚的图像作为测量对象。每幅肾图在肾髓质上各取7个感兴趣区(region of interest, ROI),分别去除两个极值进行原始数据记录。ROI大小在2-3mm2之间。每个肾髓质得到一个平均T2*值,根据公式R2*=1/T2*转化为R2*值进行记录。每个病人两个肾脏各得到一个R2*值。
3 99Tc-DTPA'肾动态显像检查方法
全部病例均使用美国GE公司生产的Infinavc Hawkeye双探头单光子发射计算机断层仪(single photon emission computed tomography apparatus, SPECT),试剂由中国原子科学研究院同位素研究所生产的核素锝-99二乙三胺五乙酸(99Tc-DTPA),纯度>99%。
被检查者取俯卧位,探头中心对准肾脏水平的脊柱中线,探头视野应完全包括双肾、输尿管和膀胱区。前臂右肘静脉“弹丸”式注入99Tc-DTPA核素混合液约1ml,放射剂量约5mCi,即刻开始扫描。血流灌注相3s/帧,采集60s。血流灌注相采集完毕后利用计算机软件自动对这一段时间内的肾图进行叠加,肾轮廓大致显现,用人工的方法在肉眼可辨的区域勾画出双肾轮廓、本底、膀胱等感兴趣区。然后开始采集功能相,60s/帧,采集20帧,时间20min。全部检查过程需约21分钟。
使用GE公司提供的配套计算机软件对图像进行后处理生成肾图,根据身高、体重等信息将数据标准化,计算机自动分析出双肾总GFR、分肾GFR、滤过峰值和双侧肾小球滤过率变化曲线等信息。采用Gates法,根据左右肾净计数率分别于双肾计数率之和的比值,计算机自动算出分肾GFR。
4实验分组
参考目前临床上广泛使用的美国肾脏病基金会2002年指定的CKD分组标准,按照其规定的双肾总GFR值的1/2进行单个肾脏分组：第一组：单个肾脏GFR≥45ml/min* 1.73m3;第二组：单个肾脏GFR 30-40ml/min* 1.73m3;第三组：单个肾脏GFR 15-30 ml/min* 1.73m3;第四组：单个肾脏GFR7.5-15ml/min* 1.73m3;第五组：单个肾脏GFR<7.5ml/min* 1.73m3。
5统计学分析
使用SPSS13.0软件对五组52个肾脏信息进行统计学分析,计数资料描述均数±标准差,显著性水平α=0.05。两组间均数比较使用配对t检验,各组间均数两两比较使用LSD法多重比较。方差齐性检验使用单因素方差分析(one-way ANOVA),如果数据符合正态分布,使用Pearson相关性分析；如果数据不符合正态分布,选用Spearman相关分析法进行统计学分析。
结果
1图像质量分析
本课题共搜集到26例CKD病人,52个肾脏的信息。按照GFR值水平分为五个组,每组8-12个肾脏。第一组至第三组功能轻中度下降的肾脏BOLDMRI图像质量多数为优,信噪比较高,测量定位准确。第四、五图像信噪比低,伪影较多,。肾脏髓质萎缩变形,定位测量时辨别皮髓质困难。99Tc-DTPA肾动态显像重度功能下降的肾脏在核素注射60s后显影很淡,肾轮廓显示不清,肾脏ROI勾画范围欠准确,会导致一定的误差产生。
2 CKD BOLD MRI和99Tc-DTPA'肾动态显像及两者的对比分析
2.1第一组至第五组肾脏,BOLD MRI图像质量呈下降趋势。前三组图像肾锥体形态完整,皮髓质分界清,ROI定位准确,测量时定位准确,结果可靠性高；第四、五组部分肾脏伴有萎缩、囊肿等改变,皮髓质分界不清,部分肾脏测量时根据解剖学定位确定ROI区域,误差较大；
2.2第一组至第三组为轻中度功能下降的肾脏,注射核素99Tc-DTPA 60s后肾脏轮廓显示多较清晰,ROI及本底勾画准确。第四、五组重度功能下降的肾脏,开始扫描60s后肾轮廓仍模糊,呈云雾状,ROI勾画准确性差。
2.3从第一组至第五组,随着肾脏GFR值逐渐下降趋势。对应各组肾脏R2*值逐渐下降,但其下降程度小于GFR。提示随着肾脏功能的降低,肾脏髓质耗氧量呈逐渐降低的趋势,肾脏R2*值下降；
2.4 BOLD MRI与99Tc-DTPA'肾动态显像测得的反映肾功能水平的数据中,第一组至第三组Spearman相关系数rs分别为0.804、0.817和0.745,两种技术测得的结果相关程度较高,提示BOLD MRI技术在轻中度肾功能降低的肾脏功能评价中价值很大；第四、五组肾脏Spearman相关系数rs值为0.406、0.476,均小于0.5,两组结果相关程度较低,BOLD MRI技术在重度肾功能降低的肾脏功能评价中价值不大。
结论
99Tc-DTPA(?)肾动态显像法是一种成熟、可靠的肾功能评测技术,是目前应用于临床唯一可测定单肾功能的技术,是本实验最合适的参照方法。BOLD MRI与99Tc-DTPA'肾动态显像的对比研究发现,BOLD MRI技术在重度功能下降时评价肾功能效果差,在轻中度功能下降的肾脏功能评价中应用价值很大。
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.
Objective
To compare BOLD MRI with 99Tc-DTPA renal dynamic imaging in CKD, and explore the value of BOLD MRI in evaluation of renal function
Materials and methods
1 Case selection
26 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 methods
2.1 BOLD MRI inspection equipment and sequences
MRI 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 analysis
Images 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 MRI
Each 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 examination
All 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 subjects
Refer 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.
Results
1 BOLD MRI image quality analysis
This 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 sutdy
2.1 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.
Conclusion
Tc-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.
近年来慢性肾脏病(chronic kidney disease, CKD)的发病率和患病率呈逐年上升趋势,目前国内外报道在成年人群的患病率达11%,已成为危害人类的公共健康问题。CKD病人肾功能下降是一个逐渐加重的过程,最终的发展趋势都是肾功能衰竭。大量资料显示慢性肾脏病早期进行相应的治疗和干预,可明显延缓肾功能衰竭的进程。多数CKD病人早期临床症状不明显,很难被发现,出现临床症状就诊时肾功能已显著降低。目前临床常用的肾功能检查方法多为有创性或放射性检查,无法作为常规性检查。99Tc-DTPA'肾动态显像是目前临床测定肾功能最常用的方法之一,同时也是唯一测定分肾功能的检测手段,滤过标志物为核素99Tc-DTPA,检查过程中病人需接触一定的放射剂量。磁共振成像(magnetic resonanceimage, MRI)技术具有无创伤性、无辐射性、高空间分辨率、可重复操作等优点,并可以观察肾脏及周围组织的形态结构,随着MR软件技术的发展,血氧水平依赖磁共振成像(blood oxygen level dependent magnetic resonanceimage, BOLD MRI)技术在临床得到了应用,此项技术研究组织功能水平和氧利用度之间的关系,是一种分子水平的功能影像学检查方法,目前在脑功能成像的应用已较成熟,在肾脏的应用尚处于初步研究阶段。
研究目的
通过BOLD MRI技术和99Tc-DTPA'肾动态显像在CKD肾功能评价的相关性分析,探讨BOLD MRI技术在肾功能评价中的应用价值。
材料与方法
1病例选择
选择2010年6月至2011年1月于珠江医院进行肾动态显像检查的患者。男性14例,女性12例,年龄22-68岁,平均年龄43.56±8.91岁。所有病人均符合2002年美国肾脏病基金会发布的肾脏病指南中慢性肾脏病要求,且排除肾脏肿瘤、肾结石、尿路感染等肾源性疾病和心血管疾病、糖尿病、凝血功能异常、肝功异常等疾病患者。全部病人两项检查均在24小时之内完成。
2 BOLD MRI检查方法
2.1 BOLD MRI检查设备及参数
全部病例使用Phihips Archieva 3.0T超导磁共振扫描仪。定位像：横断、冠状位和矢状位；常规MRI序列：T2WI横断位和冠状位,T1WI横断位,快速旋转回波(fast spin echo, FSE)序列；BOLD成像序列：冠状位和横断位,序列为多次梯度回波(multilple gradient recalled echo,mGRE)序列。扫描过程中使用SENSE Cardiac线圈+呼吸门控技术。BOLD序列扫描过程病人需闭气10s。
全部扫描时间约10-12min。
2.2图像质量分析
由2位有经验的MR诊断医师对每组BOLD功能图像质量进行评价,主要的评价指标包括图像信噪比、分辨率、解剖定位分辨能力等。分优、中、差三个等级对图像质量进行评价。
2.3 BOLD MRI功能图R2*值的测算
病人每个肾共得到5幅冠状位和5幅轴位BOLD MRI图像,冠状位对肾锥体和肾皮质分界显示清楚,多数测量工作在冠状肾功能图像上进行,部分病人冠状位图像分辨困难时,结合横断位进行测量。5幅冠状位肾功能图像中,挑选2幅定位清楚的图像作为测量对象。每幅肾图在肾髓质上各取7个感兴趣区(region of interest, ROI),分别去除两个极值进行原始数据记录。ROI大小在2-3mm2之间。每个肾髓质得到一个平均T2*值,根据公式R2*=1/T2*转化为R2*值进行记录。每个病人两个肾脏各得到一个R2*值。
3 99Tc-DTPA'肾动态显像检查方法
全部病例均使用美国GE公司生产的Infinavc Hawkeye双探头单光子发射计算机断层仪(single photon emission computed tomography apparatus, SPECT),试剂由中国原子科学研究院同位素研究所生产的核素锝-99二乙三胺五乙酸(99Tc-DTPA),纯度>99%。
被检查者取俯卧位,探头中心对准肾脏水平的脊柱中线,探头视野应完全包括双肾、输尿管和膀胱区。前臂右肘静脉“弹丸”式注入99Tc-DTPA核素混合液约1ml,放射剂量约5mCi,即刻开始扫描。血流灌注相3s/帧,采集60s。血流灌注相采集完毕后利用计算机软件自动对这一段时间内的肾图进行叠加,肾轮廓大致显现,用人工的方法在肉眼可辨的区域勾画出双肾轮廓、本底、膀胱等感兴趣区。然后开始采集功能相,60s/帧,采集20帧,时间20min。全部检查过程需约21分钟。
使用GE公司提供的配套计算机软件对图像进行后处理生成肾图,根据身高、体重等信息将数据标准化,计算机自动分析出双肾总GFR、分肾GFR、滤过峰值和双侧肾小球滤过率变化曲线等信息。采用Gates法,根据左右肾净计数率分别于双肾计数率之和的比值,计算机自动算出分肾GFR。
4实验分组
参考目前临床上广泛使用的美国肾脏病基金会2002年指定的CKD分组标准,按照其规定的双肾总GFR值的1/2进行单个肾脏分组：第一组：单个肾脏GFR≥45ml/min* 1.73m3;第二组：单个肾脏GFR 30-40ml/min* 1.73m3;第三组：单个肾脏GFR 15-30 ml/min* 1.73m3;第四组：单个肾脏GFR7.5-15ml/min* 1.73m3;第五组：单个肾脏GFR<7.5ml/min* 1.73m3。
5统计学分析
使用SPSS13.0软件对五组52个肾脏信息进行统计学分析,计数资料描述均数±标准差,显著性水平α=0.05。两组间均数比较使用配对t检验,各组间均数两两比较使用LSD法多重比较。方差齐性检验使用单因素方差分析(one-way ANOVA),如果数据符合正态分布,使用Pearson相关性分析；如果数据不符合正态分布,选用Spearman相关分析法进行统计学分析。
结果
1图像质量分析
本课题共搜集到26例CKD病人,52个肾脏的信息。按照GFR值水平分为五个组,每组8-12个肾脏。第一组至第三组功能轻中度下降的肾脏BOLDMRI图像质量多数为优,信噪比较高,测量定位准确。第四、五图像信噪比低,伪影较多,。肾脏髓质萎缩变形,定位测量时辨别皮髓质困难。99Tc-DTPA肾动态显像重度功能下降的肾脏在核素注射60s后显影很淡,肾轮廓显示不清,肾脏ROI勾画范围欠准确,会导致一定的误差产生。
2 CKD BOLD MRI和99Tc-DTPA'肾动态显像及两者的对比分析
2.1第一组至第五组肾脏,BOLD MRI图像质量呈下降趋势。前三组图像肾锥体形态完整,皮髓质分界清,ROI定位准确,测量时定位准确,结果可靠性高；第四、五组部分肾脏伴有萎缩、囊肿等改变,皮髓质分界不清,部分肾脏测量时根据解剖学定位确定ROI区域,误差较大；
2.2第一组至第三组为轻中度功能下降的肾脏,注射核素99Tc-DTPA 60s后肾脏轮廓显示多较清晰,ROI及本底勾画准确。第四、五组重度功能下降的肾脏,开始扫描60s后肾轮廓仍模糊,呈云雾状,ROI勾画准确性差。
2.3从第一组至第五组,随着肾脏GFR值逐渐下降趋势。对应各组肾脏R2*值逐渐下降,但其下降程度小于GFR。提示随着肾脏功能的降低,肾脏髓质耗氧量呈逐渐降低的趋势,肾脏R2*值下降；
2.4 BOLD MRI与99Tc-DTPA'肾动态显像测得的反映肾功能水平的数据中,第一组至第三组Spearman相关系数rs分别为0.804、0.817和0.745,两种技术测得的结果相关程度较高,提示BOLD MRI技术在轻中度肾功能降低的肾脏功能评价中价值很大；第四、五组肾脏Spearman相关系数rs值为0.406、0.476,均小于0.5,两组结果相关程度较低,BOLD MRI技术在重度肾功能降低的肾脏功能评价中价值不大。
结论
99Tc-DTPA(?)肾动态显像法是一种成熟、可靠的肾功能评测技术,是目前应用于临床唯一可测定单肾功能的技术,是本实验最合适的参照方法。BOLD MRI与99Tc-DTPA'肾动态显像的对比研究发现,BOLD MRI技术在重度功能下降时评价肾功能效果差,在轻中度功能下降的肾脏功能评价中应用价值很大。
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.
Objective
To compare BOLD MRI with 99Tc-DTPA renal dynamic imaging in CKD, and explore the value of BOLD MRI in evaluation of renal function
Materials and methods
1 Case selection
26 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 methods
2.1 BOLD MRI inspection equipment and sequences
MRI 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 analysis
Images 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 MRI
Each 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 examination
All 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 subjects
Refer 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.
Results
1 BOLD MRI image quality analysis
This 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 sutdy
2.1 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.
Conclusion
Tc-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.
引文
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[2]陈葳,王辉,董秀清等,广州市城区普通人群中慢性肾脏病流行病学研究[J].中华肾脏病杂志,2007,23(3)：147-151.
[3]Samuel N,Heyman Mogher Khamaisi,Seymour Rosen,et al.Renal Parenchymal Hypoxia,Hypoxia Response and the Progression of Chronic Kidney Disease[J].Nephrology,2008,28:998-1006.
[4]Marckmann P,Skov L,Rossen K,et al.Nephrogenic systemic fibrosis:suspected causative role of gadodiamide used for contrastenhanced magnetic resonance imaging.J Am Soc Nephrol 2006(17):2359-2362.
[5]Fleming JS,Wilkinson J,Oliver RM,et,al.Comparison of radionuclide estimation of glomerular filtration rate using technetium 99m diethylene triamine pentaacccetic acid and chromium51 ethyl ene diaminete tra-acetic acid.Eur J Nucl Med.1991,18:391.395
[6]Thoeny HC, Zumstein D, Simon-Zoula S,et al.Functional evaluation of transplanted kidneys with diffusion-weighted and BOLD MR imaging:initial experience.Radiology,2006(241)812-829.
[7]Hofmann L,Simon Zoula S,Nowak A,et al:BOLD MRI for the assessment of renal oxygenation in humans:acute effect of nephrotoxic xenobiotics.Kidney Int,2006(70)144-153.
[8]Elizabeth A,Sadowski,Arjang Djamali,et al.Blood oxygen level dependent and perfusion magnetic resonance imaging:detecting differences in oxygen bioavailability and blood flow in transplanted kidneys[J]:Magnetic Resonance Imaging,2010(28):56-64
[9]Thulborn KR,Waterton JC,Matthews PM,et al.Oxygenation dependence of the transverse relaxation time of water protons in whole blood at high field [J].Biochim Biophys Acta,1982,714(2):265-270.
[10]Epstein FH.Oxygen and renal metabolism. Kidney Int 1997;51:381-385.
[11]Brezis M,Heyman SN,Epstein FH.Determinants of intrarenal oxygenation. II.Hemodynamic effects.Am J Physiol 1994;267:F1063-F1068.
[12]Nangaku M,Eckardt KU.Hypoxia and the HIF system in kidney disease. J Mol Med 2007;85:1325-1330.
[13]Pedersen M,Dissing TH,Morkenborg J,et al.Validation of quantitative BOLD MRI measurements in kidney:application to unilateral ureteral obstruction.Kidney Int 2005;67:2305-2312.
[14]Thoeny HC,Zumstein D,Simon-Zoula S,et al.Functional evaluation of transplanted kidneys with diffusion-weighted and BOLD MR imaging:initial experience.Radiology 2006;241:812-821.
[15]Li LP,Storey P,Pierchala L,et al.Evaluation of the reproducibility of intrarenal R2* and Delta R2* measurements following administration of furosemide and during waterload.J Magn Reson Imaging 2004;19:610-616.
[16]Prasad PV,Chen Q,Goldfarb JW,et al.Breath-hold R2* mapping with a multiple gradient recalled echo sequence:application to the evaluation of intrarenal oxygenation.J Magn Reson Imaging 1997;7:1163-1165.
[17]Li LP,Vu AT,Li BS,et al.Evaluation of intrarenal oxygenation by BOLD MRI at 3.0 T[J].Magn Reson Imaging,2004,20(5):901-914.
[18]Li LP,Storey P,Pierchala L,et al.Evaluation of the reproducibility of intrarenal R2* and Delta R2* measurements following administration of furosemide and during water load[J].J Magn Reson Imaging,2004,19(5):610-616.
[19]P.Malvezzi,I.Bricault,N.Terrier,et,al.Evaluation of Intrarenal Oxygenation by Blood Oxygen Level-Dependent Magnetic Resonance Imaging in Living Kidney Donors and Their Recipients:Preliminary Results[J]:Transplantation Proceedings,2009(41):641-644.
[20]Zuo CS,Rofsky NM,Mahallati H,et al.Visualization and quantification of renal R2R changes during water diuresis[J].J Magn Reson Imaging,2003,17(6):676-682.
[21]Xuedong Yang,Ju Cao,Xiaoying Wang,et al.Evaluation of Renal Oxygenation in Rat by Using R2* at 3-T Magnetic Resonance:Initial Observation[J]:Medicina Intensiva,2007,31:521-525.
[22]Schachinger H,Klarhofer M,Linder L,et al.Angiotensin II decreases the renal MRI blood oxygenation level-dependent signal.Hypertension 2006;47:1062-1066.
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