Visuel and semiquantitative analysis of Tc-99m dmsa scintigraphy in children with pyelonephritis

Abstract

Aim: The aim of the study is to evaluate a quantitative method in comparison with a visual method based on 99mTc-DMSA renal planar scintigraphy performed during pyelonephritis (PN). Material and Method: A total of 21 children (6,6 +/- 3,2 y old (mean +/- SD)) were examined by 99mTc-DMSA scintigraphy during (DMSA1) and 12,4 +/- 6,8 month (mean +/- SD) after (DMSA2) PN. Two levels of interpretation were performed independently: first, a visual analysis to classify the kidneys by considering the evolution between DMSA1 and DMSA2, and second, a semiquantitative analysis of DMSA1 and DMSA2. A visual method of kidney evaluation, 9-point visual analysis of each kidney was performed. A kidney was considered normal when the score was >= 7. Renal scarring was defined as a score of < 7 on DMSA1 and DMSA2, and 2 groups were obtained normal(N) and defective(DF). Semiquantitative analysis of kidney evolution; was performed to an automatic threshold (% 20-80) for the kidney and then calculating ratios of the count density and number of pixels (nC%=C in a given isocount/C in a 20% isocount, nS%=S in a given isocount/S in a 20% isocount). Results: For the semiquantitative analysis, the nC70 ve nS70 ratio was considered the best index to classify the kidneys by considering the evolution between DMSA1 (to determine which kidneys N or DF group) (table1). When this nC70 ratio was used a cutoff value of 0,34, it was able to differentiate between N and DF groups with a sensitivity of % 55, a specificity of % 100. According to the semiquantitative analysis of DMSA-2, when the cutoff value of C70% (0.36) was taken into consideration, 12 of 15 kidneys were in the N group, and 14 of 27 were in the DF group. As a result, a group change occurred in 16/42 (% 38) kidneys. Discussion: We concluded that the assessment of DMSA scintigraphy might show significant interobserver variation and that there was a need for quantitative parameters to make more objective evaluations.