title: Semi-automated renal region of interest selection method using the double-threshold technique: inter-operator variability in quantitating 99mTc-MAG3 renal uptake.
abstract: In calculating the relative and absolute renal uptake of technetium-99m mercaptoacetyltriglycine (MAG3), inter-operator variability in the assignment of the renal region of interest (ROI) is a critical factor. Our goal was to develop a semi-automated method of assigning the renal ROI and then to compare the inter-operator variability in calculating the percent injected dose (%ID) in the kidney at 1-2 min, using semi-automated versus manual ROIs. The manual ROIs were drawn independently by three operators (A, B and C). Operator A had about 20 years, experience in nuclear medicine, while operators B and C respectively had 3 years and 1 year of experience. In the semi-automated renal ROI selection method using the double-threshold technique, the operators only click around the centre of each kidney. The same three operators processed the ROIs using this double-threshold method on 1-2 min images. The semi-automated method failed in three kidneys with very markedly reduced function owing to superimposition by liver or spleen. Inter-operator reproducibility in the remaining 59 kidneys was estimated using manual and semi-automated ROIs. With manual ROIs, the %ID (mean+/-standard error of mean) was 4.32+/-0.167 for A, 4. 14+/-0.165 for B and 3.28+/-0.139 for C. Although there was good correlation among them, these values were significantly different (P<0.0001). Using semi-automated ROIs, the %ID was 4.38+/-0.160 for three operators. No significant difference was observed. Complete reproducibility was shown in 58 of 59 kidneys; the %ID difference of the remaining kidney was only 1.2%. The lowest %ID of all the kidneys successfully detected using the semi-automated method was 0. 77%. The semi-automated renal ROI selection method using the double-threshold technique displays good detectability of the renal contour. The renal uptake calculated using this method is reproducible and acceptable in routine clinical practice.
authors.affiliation: Department of Nuclear Medicine, Gunma University School of Medicine, Gunma, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tomaru
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.forename: N
authors.initials: N
authors.lastname: Oriuchi
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Endo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015609:Organotechnetium Compounds; D011877:Radionuclide Imaging / Q000379:methods*; D019275:Radiopharmaceuticals; D012044:Regression Analysis; D015203:Reproducibility of Results
chemical_list: D000911:Antibodies, Monoclonal; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C104214:technetium-99m-MAG3-dsFV