| BackgroundsThe glomerular filtration rate (GFR) is an important index of renal function. The measured method is through introduction of a substance without tubular secretion, and then the renal clearance of such material as glomerular filtration rate is calculated. The commonly methods in Nuclear Medicine are the Gates'method with renal dynamic imaging and the two-sample method. The principle of renal dynamic imaging method is to determine the rate of kidney uptake through the measuring ratio of renal count rate to total injiected radioactive dose at the peak time of renal uptake and then the GFR is calculated through the formula in SPECT workstation. The advantages of this method is simple, no blood, etc. However, there are more factors in determination of GFR by Gates'method, included the factors of drug itself, the equipment,measuring the accuracy of the injecting drug and mapping of regions of interest, etc. All may lead to the error of GFR measurement. In addition, the Gates'equation is a empirical equation, which includes the experience of a number of parameters, parameters of these experiences obtained in a group of bodys are not necessarily suitable for all individuals, especially for a special body, such as obese patients, skinny patients and children, the deviation value of the GFR obtained in these individuals may be increase, so the accuracy assessment of Gates'method is more necessary. An accurate determination of GFR is the multiple blood sampling method in Plasma clearance methods. Namely, that is the acquisition of multiple-phase blood samples to measure plasma radioactivity counts and through a multi-compartment model to obtain GFR。Relatively easy way are three-phase blood sampling method, two-phase blood sampling method (referred to as two-sample method) and single-phase blood sampling method. Studies have shown that the two-sample method and multiple blood sampling method has a good correlation. Taking into account the clinical application of operability, we used two-sample method as the reference standard for GFR。The subject uses the two-sample method as an accurate determination of GFR as a reference standard, evaluates the relevance and sensitivity differences of GFR measured with Gates method in different chronic kidney disease (CKD) of renal function stages referenced the method that NKF-K/DOQI recommended, to assess the reliability of gates determination of GFR。ObjectivesTo compare the estimation of glomerular filtration rate (GFR) by renal dynamic imaging with that estimated by two-sample method, and evaluate the reliability of measurement of GFR by renal dynamic imaging.Methods42 cases were selected from the Nuclear Medicine in GuangDong TCM to check the chronic kidney disease (CKD) patients, in line with the United States NKF-K/DOQI on diagnostic criteria for chronic kidney disease and the exclusion of this study was to develop standards (According to the staging of chronic kidney disease, there are six cases in stage one, eleven cases in stage two, twelve cases in stage there, eight cases in stagefour and five cases in stage five). The patients were intravenously bolus injected with 185 MBq/1 mL of Tc-99m-DTPA after drinking 300mL-500ml of water. Imaging before the first measurement of needle syringe full of radioactive count rate, that is, before the Tc-99m-DTPA intravenous injection of radioactive total counts. Method is to probe y the camera facing up, and intravenous injection of Tc-99m-DTPA before the probe placed in the Central High 30cm Department to obtain the total number of one minute. Imaging can be done when the seat or lying position, get the best supine, the probe close to the nose, pay attention to kidneys and bladder all included in the probe field of vision, "shot" immediately after injection of contrast media for dynamic acquisition, the time is about 15min, collected by the above methods after air tube count rate measured syringe (syringe residual count rate). Renal dynamic imaging was performed and the image was processed according to standard procedure (Gates' method) to obtain GFR.3mL of blood was withdrawn 2h and 4h postinjection, respectively, and radioactivity of 1mL plasma was measured. GFR was calculated by the formula of two-sample method. The correlation of GFRs measured by renal dynamic imaging and by two-sample method was analyzed using regression analysis.ResultsGates'method and two-sample method has a good correlation in 1-2 period of chronic kidney disease. Gates'measured GFR had slightly lower than the two-sample method measured GFR. In the 3-5 period of Chronic kidney disease, the error factors in the Gates'method are significantly increased. Gates' measured GFR was significantly higher than two-sample method measured GFR. The relevance of Gates'method and two-sample method and the stability of measurements are obvious effectted. Although Gates'method still has a certain correlation with the two-sample method, the value deviation is larger. With the progress of renal impairment, the instability of Gates'measurement is also increased. Differences between the two method are larger in the period of renal failure, and statistically significant difference is also obvious. GFRs measured by the two methods showed a good agreement for most of patients except three patients who were too thin or too fat.ConclusionsThe correlation of the GFR value with Gates'measurement and the real value in patients with chronic kidney disease 1-2 is better with high reliability. but the accuracy of Gates'method is decreased along with the progress of impaired renal function, The great erorr may be obtained with specific individuals, such as too thin or too fat subjects. |
