Optimal uniformity index selection and acquisition counts for daily gamma camera quality control

Introduction: The purpose of this study was to investigate the optimized use of common uniformity indices [National Electrical Manufacturers’ Association (NEMA) indices (differential and integral), Cox–Diffey and the coefficient of variation (CoV)]. Methods: The indices were calculated for induced [localized two-dimensional (2D) Gaussian and gradient] artefacts added to three image sets (5, 10 and 15 million counts), each containing 25 extrinsic images, using Matlab. The intensity of the induced artefacts was varied between a 1 and 10% drop in pixel counts. The induced artefacts simulated photomultiplier tube [10 cm full width at half maximum (FWHM)], smaller focused artefacts (2.5 cm FWHM) and gradients artefacts. Results: For five million count acquisitions, the Cox–Diffey, CoV and NEMA integral indices detected the 6% 2D Gaussian artefacts [10 cm full-width at half-maximum (FWHM)], whereas the NEMA differential index performed relatively poorly. NEMA differential and integral indices performed equally well at detecting smaller 2D Guassian (2.5 cm FWHM) artefacts. The 10% artefact was the minimum artefact detected by both indices for five million count acquisitions. The Cox–Diffey and CoV indices did not detect any artefacts for five million acquired counts. The CoV index performed best at detecting gradient artefacts at five million acquired counts. Conclusion: This work provides evidence that daily quality control can be acquired with as few as five million counts while maintaining the same ability to detect both chronic and acute nonuniformities compared with higher count acquisitions. A combination of the NEMA integral and the CoV indices gives the optimal selection of uniformity indices for detecting a range of artefact forms and intensities

Measuring glomerular filtration rate using chromium-51 EDTA: body surface area normalization before or after Brochner-Mortensen correction?

We read with interest the article by Pottel et al. [1] 'Measuring glomerular filtration rate using 51Cr-EDTA: body surface area normalization before or after Bröchner-Mortensen correction?' The authors question the basis for the recommendation in the British Nuclear Medicine Society (BNMS) guidelines[2] that glomerular filtration rate (GFR) measurements using the slope-intercept (SI) method be corrected for body surface area (BSA) before applying the Bröchner-Mortensen (BM) correction for the missing area under the curve (AUC)

Extracellular fluid volume and glomerular filtration rate in 1,878 healthy potential renal transplant donors. Effects of age, gender, obesity and scaling.

Aim. The aim of this study was to investigate the influence of age, gender, obesity and scaling on glomerular filtration rate (GFR) and extracellular fluid volume (ECV) in healthy subjects. Methods. This is a retrospective multi-centre study of 1878 healthy prospective kidney transplant donors (819 men) from 15 centres. Age and body mass index (BMI) were not significantly different between men and women. Slope-intercept GFR was measured (using Cr-51-EDTA in 14 centres; Tc-99m-DTPA in one) and scaled to body surface area (BSA) and lean body mass (LBM), both estimated from height and weight. GFR was also expressed as the slope rate constant, with one-compartment correction (GFR/ECV). ECV was measured as the ratio, GFR to GFR/ECV. Results. ECV was age independent but GFR declined with age, at a significantly faster rate in women than men. GFR/BSA was higher in men but GFR/ECV and GFR/LBM were higher in women. Young women (65 years). There was no difference in GFR between obese (BMI > 30 kg/m2) and non-obese men. Obese women, however, had lower GFR than non-obese women and negative correlations were observed between GFR and both BMI and %fat. The decline in GFR with age was no faster in obese versus non-obese subjects. ECV/BSA was higher in men but ECV/LBM was higher in women. ECV/weight was almost gender independent, suggesting that fat-free mass in women contains more extracellular water. BSA is therefore a misleading scaling variable. Conclusion. There are several significant differences in GFR and ECV between healthy men and women

The reliability of glomerular filtration rate measured from plasma clearance: a multi-centre study of 1,878 healthy potential renal transplant donors

PURPOSE The objective of the study was to undertake a clinical audit of departmental performance in the measurement of glomerular filtration rate (GFR) using the coefficient of variation (CV) of extracellular fluid volume (ECFV) as the benchmark. ECFV is held within narrow limits in healthy subjects, narrower than GFR, and should therefore have a low CV. METHODS Fifteen departments participated in this retrospective study of healthy renal transplant donors. Data were analysed separately for men (n ranged from 28 to 115 per centre; total = 819) and women (n = 28-146; 1,059). All centres used the slope-intercept method with blood sample numbers ranging from two to five. Subjects did not fast prior to GFR measurement. GFR was scaled to body surface area (BSA) and corrected for the single compartment assumption. GFR scaled to ECFV was calculated as the terminal slope rate constant and corrected for the single compartment assumption. ECFV/BSA was calculated as the ratio of GFR/BSA to GFR/ECFV. RESULTS The departmental CVs of ECFV/BSA and GFR/BSA ranged from 8.3 to 25.8% and 12.8 to 21.9%, respectively, in men, and from 9.6 to 21.1% and 14.8 to 23.7%, respectively, in women. Both CVs correlated strongly between men and women from the same centre, suggesting department-specific systematic errors. GFR/BSA was higher in men in 14 of 15 centres, whereas GFR/ECFV was higher in women in 14 of 15 centres. Both correlated strongly between men and women, suggesting regional variation in GFR. CONCLUSION The CV of ECFV/BSA in normal subjects is a useful indicator of the technical robustness with which GFR is measured and, in this study, indicated a wide variation in departmental performance