Chulalongkorn Medical Journal


Background : Attenuation correction is one of important steps in calculation of renalfunction, either glomerular filtration rate (GFR) or effective renal plasmaflow (ERPF), from nuclear medicine procedure. To do this correctly, depthof the kidney must be known. Generally, depth of the kidney can becalculated by some equation pre-installed in the machine’s computer usingpatient’s weight and height information. This technique will only result inestimated kidney depth values of the patients with the same equationderivedpopulation and will not be valid in patients from other populationsuch as kidney transplanted patients.Objective : To evaluate a more generalized and practical technique in calculation ofkidney depth using attenuation-related technique.Methods : By using anterior and posterior images of the body phantom with knownwidth, the kidney depth is calculated using attenuation-related techniqueand compared with the actual value. The intra- and inter-operator variationsare determined. The technique is applied in 98 patients of age 32.75 ±23.20 (average ± SD) years old, including 30 children and 68 adults.The results on kidney depth are compared with other technique usinglateral view images measurements and equation-derived kidney depth values.Results : The phantom studies showed no significant intra-operator variations(deviation < 5%, P ≥ 0.99) and inter-operator variations (P = 0.9995).The relationship of calculated kidney phantom depth and the actual valueis close to the ideal straight line (r > 0.99). The studies in patients showgood correlation with other techniques (r2 > 0.8099) and no significantdifferent values of the kidney depth calculated by this technique ascompared to lateral view technique (P = 0.4414). However, when comparedto equation-derived values, there is no significant difference in the adultpatients only, but significant difference in pediatric patients.Conclusion : The kidney depth calculation using attenuation related technique isaccurate, practical and can be used in most patient groups.



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