[Feasibility of using Statistical tests in evaluation of non-uniformity]

Non-uniformity test is essentially the only required daily QC procedure in nuclear medicine practice. Noise creates statistical variation or random error in a flood image. Non-uniformity on the other hand does not have statistical nature and may be regarded as systemic error. The present methods of non-uniformity calculation do not distinguish between these two types of error. The Jarque-Bera and Kolmogorov-Smirnov tests were examined as alternative methods in calculation of non-uniformity in flood test images. Using the Monte carol method, uniform and non-uniform flood images of different matrix sizes and count density were generated. The uniformity of the images was calculated using the present and proposed methods. The results were also tested using 1300 planar images of 128x128 matrix size. The proposed methods were more accurate and sensitive to non-uniformity at low count density. However, their precisions were less than the conventional methods. There were no significant differences between these procedures at high count density. The integral and differential uniformity do not distinguish between noise always present in the data or in occasional non-uniformity. In a uniform intact flood image, the difference between maximum and minimum pixel count [the value of integral uniformity] is much more than recommended values for non-uniformity. After filtration of image this difference decreases but still remains high. The proposed methods are more sensitive to non-uniformity at low count density and may be used as alternative methods in daily uniformity test

Assessent of deconvolution technique for diagnosis of hydrone-phrosis in infants [under 6 months]

Hydronephrosis is one of the major causes of referring infants for nuclear medicine investigation. Renal dynamic study is the most reliable investigation for such children. However direct evaluation of renogram leads to generation of parameters that have no physiological interpretation. The configuration of renogram is very much dependent upon the rate at which radiopharmaceutical enters the kidney. In order to decrease such effect, the radiopharmaceutical has to be injected in a small volume and very fast into the vein, which is not always possible, especially in the infants. Deconvolution is a method in which the injection quality does not have any effect upon renogram decreasing the diagnostic errors. The renal retention function [RRF] is independent of input function and derived parameters have physiological significance and clinical values. In this study 54 patients data were evaluated. All the patients were under 6 month of age, suspicious for hydronephrosis referred to our imaging center for 99mTc-DTPA renal dynamic studies. All data were transformed into interfile format. Full renal package software was developed in visual basic 6 to read and process the data. Deconvolution was performed using matrix algorithm. Background subtraction was performed using conventional and Ruthland-Patlack method. All transit time parameters were calculated in 6 different filtering conditions. Our results show that deconvolution is useful for evaluation of infant hydronephrosis. Mean transit time is the most useful parameter for estimation of renal function in infants