Intra- and interoperator variations in region-of-interest drawing and their effect on the measurement of glomerular filtration rates.

PURPOSE: Quantitative results are often obtained from images after drawing regions of interest (ROIs) about the organ or area being evaluated. The accuracy and reproducibility of ROIs is an important aspect of quality-control protocols. Attempts to increase ROI accuracy and precision by generating them automatically must be compared with manually processed images to evaluate the success of the automatic methods. Operators' abilities to reproduce ROIs and the effect this has on the reproducibility of estimating glomerular filtration rate from renograms were assessed. METHODS: Estimation of the glomerular filtration rate using Sampson's method requires a) exclusion ROIs around both kidneys for background subtraction, b) whole-kidney ROIs, and c) exclusion ROIs for the collecting system. Two nuclear medicine professionals were asked to produce glomerular filtration rate estimates for 20 patients with diverse renal function. This was repeated 1 month later. The intra- and interoperator variations were calculated for the glomerular filtration rate results and on a pixel basis for the ROIs. RESULTS: THE percentage of common pixels, on average, for a) intraoperator repeats and b) interoperator comparisons were a) 95%, 94%, 85%, and b) 94%, 93%, and 81% for region types 1, 2, and, 3, respectively. Analysis of variance for the glomerular filtration rate estimates showed significant variations in estimates for left kidneys (P < 0.025) but none (P > 0.1) for right kidneys. CONCLUSION: Spatial reproducibility in ROI drawing does not necessarily relate directly to the associated quantitative reproducibility.

CA549 and TPS patterns in the diagnosis and staging of patients with breast carcinoma.

This study compares the clinical value of the breast cancer tumour makers CA549 and TPS, and their tandem use when one or both markers indicate abnormality. For 144 patients presenting with active disease, 33 were classified as Stage I, 37 as Stage II, 40 as Stage III and 34 as Stage IV. For these patients the sensitivity of CA549 using a cut-off of 10 U/ml was 27%, 32%, 42% and 79%, respectively. The sensitivity of TPS for each stage using a cut-off of 100 U/l was 12%, 22%, 28% and 73%, respectively. At these cut-off levels, 36%, 46%, 63% and 91% of patients, respectively, have either CA549 or TPS or both markers raised. For 161 patients with diagnosed benign breast disease, the specificity of marker levels was 96% for CA549, 88% for TPS and 84% for tandem use. CA549 is shown to be superior to TPS and this was confirmed by Receiver Operating Characteristic (ROC) analysis using variable threshold levels, with the areas under the curves for all stages combined being 0.74 +/- 0.03 (ISD) and 0.66 +/- 0.03, respectively. The corresponding area under the curve for tandem use (0.75 +/- 0.03) is marginally greater than for either individual marker, although the difference with respect to CA549 is statistically insignificant.