Glomerular filtration rate measured by 99mTc-DTPA Gates method is not significantly affected by the premature or delayed initiation of image acquisition

Background

This study was performed to examine the effect of non-synchronization of the radiotracer injection and image acquisition on estimates of the glomerular filtration rate (GFR) by the Gates' method.

Methods

A total of 218 volunteers were selected as the research subjects. Two-sample method (GFR_dt) and ^99mTc-DTPA dynamic renal imaging (GFR_Gates) were used for determination of the GFR. We took GFR_dt as the reference method, and then took the peak time of blood perfusion phase as the new time origin to ensure that all patients were unified on the time-radioactivity count rate curve. We moved the radioactivity curve on 9 time points to simulate premature (+20/+15/+10/+5 seconds), synchronous (0 seconds), and delayed (-20/-15/-10/-5 seconds) image acquisition in relation to the completion of tracer injection; we then acquired 9 GFR_Gates. The correlation and consistency of GFR_Gates and GFR_dt were analyzed. Variance analysis compared the differences between different GFR_Gates.

Results

All 9 GFR_Gates had good correlation with GFR_dt. GFR_dt and GFR_Gates derived from -5, -10 and -15 s had the best correlation (r=0.827, P<0.01). The consistency between GFR_Gates derived from +20 s and GFR_dt was the worst, and GFR_Gates derived from -15 s and GFR_dt was the best. There were no significant differences between the 9 GFR_Gates.

Conclusions

Non-synchronization of the radiotracer injection and image acquisition has no significant effect on the estimates of the GFR_Gates if the premature or delayed time between image acquisition and tracer injection is not more than 20 seconds.

Establish new formulas for the calculation of renal and isthmus depth in horseshoe kidney

This study was performed to develop a new formula to estimate the renal and isthmus depth in horseshoe kidney, and to compare the new formula with previously published formulas.Renal depth, isthmus depth, vertebral thickness, and total thickness (T, cm) of the body at the level of the kidneys were measured by CT in 124 adults. Their sex, age, height (H, cm), and weight (W, kg) were recorded. Multiple stepwise linear regression analysis was conducted. The 124 cases were divided into 2 random groups, of which the first group was used to derive a regressive formula and the second group was used to verify the formula and compare the formula with previously published formulas.Multiple stepwise linear regression analysis showed that the important variables in estimating the depth of each kidney were the body weight (W, kg) and the total thickness (T, cm) of the body at the level of the kidneys. The important variables in estimating the depth of isthmus soft tissue and vertebral thickness were W, T, and age, W. The new formula was the following: right renal depth (cm) = 0.273 × T + 0.043 × W + 1.086 (r = 0.82, P < .05; standardized regressive coefficient: T = 0.500, W = 0.367), left renal depth (cm) = 0.245 × T + 0.041 × W + 0.676 (r = 0.83, P < .05; standardized regressive coefficient: T = 0.520, W = 0.353); isthmus depth (cm) = soft tissue depth + vertebral thickness, soft tissue depth (cm) = 0.144 × T + 0.044 × W + 0.536 (r = 0.58, P < .05; standardized regressive coefficient: T = 0.272, W = 0.335), vertebral thickness (cm) = 0.012 × age + 0.018 × W + 3.683 (r = 0.53, P < .05; standardized regressive coefficient: age = 0.326, W = 0.438). It is much better than the literatures.The new renal depth estimation formula in horseshoe kidney that we derived by using multiple stepwise linear regression has greatly outperformed other 6 previously published formulas. Isthmus depth estimation formula can also get accurate results. Our new formula provides a more reliable and accurate renal and isthmus depth estimation and contributes to improving the methods used to estimate renal function from radionuclide renography in horseshoe kidney.

THE ROLE OF RADIOACTIVE METHODS IN THE DIAGNOSTIC TYPE OF HYDRONEPHROSIS IN CLEAN-UP WORKERS OF CHORNOBYL ACCIDENT

RATIONALE

Since the introduction of radionuclide research methods into clinical practice, they occupy an importantplace in the diagnosis of hydronephrosis and, at the same time, sufficiently objective, sensitive and atraumaticmethods of investigation.

OBJECTIVE

On the basis of retrospective data, to investigate the diagnostic role of radionuclide renography (RRG)and the method of indirect radionuclide renangiography (IRAG) in clean-up workers of Chornobyl accident withhydronephrosis.

MATERIALS AND METHODS

A total of 257 patients with hydronephrosis (140 women and 117 men) aged 15 to 77 yearswere examined by the RRG and the IRAG. The RRG technique consists of intravenous administration of a solution of131I-hypurane (2.5 kBq/kg) and continuous registration for 20 minutes of the level of radioactivity above the kid-neys with the help of sensors of the renograph UR 1-1. The IRAG was conducted for 30-45 seconds with exposure1 frame per second after intravenous administration of a solution of 99mTc-pentatech (2 MBq/kg).

RESULTS

The results of the radionuclide study of the hemodynamics of patients with different stages ofhydronephrosis made it possible to draw a conclusion regarding the expediency of taking into account the condi-tion of the cup-pelvic system in the preoperative period, as well as the parameters of the arterial and venous circu-lation.

CONCLUSIONS

Combined use of X-ray and radionuclide methods allows establishing the cause and consequences ofhydronephrosis, to develop a rational treatment plan. RRG and IRAG are reliable methods of dynamic control in post-operative observation of clean-up workers of Chornobyl accident with hydronephrosis.

Evaluation of the accuracy of renal depth estimation formulas in horseshoe kidney

Estimation formulas are usually used to calculate renal depth when glomerular filtration rate (GFR) is measured by the Gates method. Horseshoe kidney (HSK) anatomical structure is different from the normal form of the kidney. The existing formulas are based on the normal form. It is unknown whether the existing formulas are valid in HSK patients. This study was performed to estimate the accuracy of the existing 6 renal depth estimation formulas in HSK.Renal depth and total thickness (T, cm) of the body at the level of the kidneys were measured by CT in 94 HSK patients. Their sex, age, height (H, cm), and weight (W, kg) were recorded. The existing 6 estimation formulas were used to obtain estimated renal depth. Correlation coefficients, Bland-Altman analysis, and paired t test were performed between estimated and the CT measured renal depth.Estimated renal depths were all lower than the CT measured renal depths and there was significant difference between estimated and CT measured renal depth. The CT measured renal depth and estimated renal depth derived from Ma GY formula correlated best (right: r = 0.80, P < .01; left: r = 0.77, P < .01). The renal depth derived from Tonnesen formula was significantly lower than the CT measured renal depth. The agreement between the estimated renal depth derived from Tonnesen formula and the CT measured renal depth was the worst, with the mean difference of (right: -3.11 ± 1.13 cm; left: -2.79 ± 1.07 cm). The agreement between the estimated renal depth derived from Li Q formula and Ma GY formula and the CT measured renal depth was the best, with the mean difference of right: -1.68 ± 1.09 cm; left: -1.32 ± 1.06 cm and right: -1.59 ± 1.01 cm; left: -1.59 ± 0.99 cm, respectively. But the greatest error of the difference between Li Q formula and Ma GY formula estimated depth and the CT measured depth was up to -4.83 cm, and the estimated deviation is unacceptable.All the existing formulas do not fully apply to HSK. To provide reliable and accurate estimates of renal depth, we should develop a new formula to estimate the renal depth in HSK patients.