The Main Factors Affecting The Accuracy Of GFR Determined By SPECT And Correlation Analysis

Backgrounds and Objective:Glomerular filtration rate （GFR） refers to theultrafiltrate volume per unit time ofdouble kidney generation. It is an important index to reflect the renal function, whichcan be used as a judgment of the severity of the disease, curative effect observation andjudgment of renal function after renal transplantation objective index. For a long time,pollen removal rate is regarded as the gold standard for determination of GFR in kidney.This method requires constant perfusion, bladder catheterization, repeat collect urine,expensive and spend a lot of time, it not only difficult for clinical application, but alsowill be difficult for scientific research.^99mTc-DTPA was injected in vivo, within hoursof repeated acquisition plasma sample, through the method of counting of radioactivitymeasurement of plasma samples change with time to calculate GFR called plasmamethod. Multiple plasma method needs some time interval of collecting a plasmasample, the whole process lasted four hours, because the longer time checking also notwidely used in the clinic, this method has high accuracy, often as reference standard forthe determination of renal GFR.^99mTc-DTPA renal dynamic imaging is an ideal methodfor determination of GFR, also known as the Gates method. This method is a simplemethod, need less time, noninvasive, repeatability characteristics, has been widelyapplied in clinic. But this method is affected by many factors, such as region of interest（ROI） size and shape of the kidney and the background, radioactive decay coefficient,net injection dose, pellet injection quality, kidney depth and SPECT hardwareequipment. In this study, the dual plasma sample method as the reference standard,analyzing the main factors affecting the accuracy of GFR SPECT determination, inorder to improve the reliability and accuracy of GFR by SPECT. The research from thefollowing five aspects: First,evaluation of the influence of kidney depth in themeasurement of the glomerular filtration rate with SPECT; Second,evaluation of The influence of the time window position of SPECT counting on determination ofglomerular filtration rate; Third, establishment of the GFR forecast equation based onthe modified Gates method for health people; Fourth, determination of glomerularfiltration rate in geometric mean method; Fifth, estimate the accuracy of SPECTdetermination glomerular filtration rate in different age of healthy people.Methods:1.232cases Community Health residents of Beijing area were selected as theresearch object, using two-sample method and^99mTc-DTPA dynamic renal imagingmethod for the determination of GFR (GFR_dtand GFR_Gates) respectively. Six estimationformulas obtained six GFR_Gates. Analyze and compare the correlation and consistency ofGFR_dtwith six GFR_Gates.2.231cases Community Health residents of Beijing area were selected as theresearch object, using two-sample method and^99mTc-DTPA dynamic renal imagingmethod for the determination of GFR (GFR_dtand GFR_Gates) respectively. There was atime-count rate curve whose new time origin was blood perfusion phase peak. Movedtime window and extracted twenty-five counts on25time points, then got twenty-fiveGFR_Gates. According to thecumulative phase peak time,231cases were divided intothree groups. Analysis and comparison of three groups of GFR_Gatesand the changes ofcorrelation between GFR_Gatesand GFR_dt.3.232cases Community Health residents of Beijing area were selected as theresearch object, using two-sample method and^99mTc-DTPA dynamic renal imagingmethod for the determination of GFR (GFR_dtand GFR_Gates) respectively. By using themethod of stepwise regression analysis GFR_dtwith GFR_Gates, gender, age, height, weight,weight/height and height/weight.4.77cases Community Health residents of Beijing area were selected as theresearch object, using two-sample method and^99mTc-DTPA dynamic renal imagingmethod （post single detector） and geometric mean method （double detector） for thedetermination of GFR (GFR_dt，GFR_POSTand GFRGM) respectively. GFR_dtas thereference, analysis and compare the accuracy of GFR_POSTand GFRGM. 5. Totally232Beijing community health residents were selected as the researchsubjects. Two-sample method and^99mTc–DTPA dynamic renal imaging were used fordetermination of GFR (GFR_dtand GFR_Gates, respectively). GFR_dtas the referencestandard, compare the accuracy of six different age groups GFR_Gateswhich get bySPECT.Results1.①Formula1and5derived kidney depths are significantly lower than that ofother four formulas, the largest difference between formula1and4up to1.38cm.②The correlation between GFR_Gateswhich were derived by formula3and6and GFR_dtarethe best （r=0.81）, the correlation between GFR_Gateswhich was derived by formula2andGFR_dtis the worst.③The consistency between GFR_Gateswhich were derived byformula1and5and GFR_dtare the worst, the difference of mean between GFR_GatesandGFR_dtare-23.62±18.60and-20.66±18.00respectively; The consistency betweenGFR_Gateswhich were derived by formula3and4and GFR_dtare the best, the differenceof mean between GFR_Gatesand GFR_dtare-5.80±16.76and-3.81±17.87respectively.2.①Left and right renal blood perfusion phase peak time were nearly normaldistribution, the mean were19.69±5.20s and20.29±5.19s respectively.②Renalfiltration accumulation phase peak time showed a skewed distribution, the frequencypeak was132s; the mean was166.19±50.22s.③When the time window waspositioned on the cumulative phase peak area, GFR_Gateswas Maximum. In both sides ofthe peak value, GFR_Gateswere decreased.④When time window in the accumulationphase peak rises on the left area, the correlation coefficient between GFR_Gatesand GFR_dtwas increasing with time window after the shift; When moved to the time windowwhich contains some peak section, the correlation coefficient is slowing; With theincrease of time window and peak overlapping segments, the correlation coefficientreached inflection point, then began to decrease.3. The study found that GFR_Gates, age and weight are statistical significance toGFR_dt.The GFR forecast equation is: GFRforecast（ml/min）=0.895×GFR_Gates-0.44×age+0.857×weight-1.001（r=0.86）. The correlation coefficent between GFR_Gates and GFRforecastwith GFR_dtare0.78and0.86respectively. The difference of meanbetween GFR_Gatesand GFRforecastwith GFR_dtare-23.6±18.6and-0.2±14.5respectively.4.①GFR_POSTand GFRGMare paired by t test, the results are: t=-26.128, P<0.001.②The correlation coefficient between GFR_dtand GFR_POSTis0.80. The correlationcoefficient between GFR_dtand GFRGMis0.72.③The difference of the meanbetween GFR_dtand GFR_POSTis-10.72±12.77. The difference of the mean betweenGFR_dtand GFR_POSTis45.21±18.66.5.①There are significant differences between GFR_dtand GFR_Gateson six differentage groups. Six different age groups GFR_Gatesare significantly lower than those ofGFR_dt.②The difference between GFR_dtand GFR_Gatesin the group of30-39years is themaximum, the mean difference is-34.26±20.79ml/min. The difference between GFR_dtand GFR_Gatesin the group of≥70years is the minimum, the mean difference is-23.62±18.60ml/min.③The correlation coefficient between GFR_dtand GFR_Gatesin thegroup of30-39years is the worst （r=0.42）. The correlation coefficient between GFR_dtand GFR_Gatesin the group of≥70years is the best （r=0.81）.Conclusions1. The accuracy of kidney depth estimation formula1、2、5are poor, other formulasresult difference are lesser. Other formulas can be used in clinical. But relativelyspeaking, formula3and formula4are better.2. We can achieve GFR which impact smaller by time, when we extract of86-145stime window count on a time-count rate curve whose new time origin was bloodperfusion phase peak.3. The GFR forecast equation for healthy people based on Gates method is betterthan Gates method.4. Geometric mean method overestimated renal function, the accuracy is poor. Itneed to be improved before it can be used in clinical.5. The accuracy of GFR which got by SPECT is poor in20-49years health people,it is better in≥50years health people, while it is the best in≥70years health people.