Making renal stones change size-impact of CT image post processing and reader variability

Area of Science:

• Radiology
• Medical Imaging
• Nephrology

Background:

• Accurate renal stone size measurement is critical for diagnosis and treatment planning.
• Computed Tomography (CT) is a primary imaging modality for renal stones.
• Image post-processing parameters can influence quantitative measurements.

Purpose of the Study:

• To quantify the effect of image post-processing parameters on apparent renal stone size.
• To assess intra- and inter-reader variability in renal stone size estimation using CT.
• To highlight the need for standardized CT measurement protocols.

Main Methods:

• Retrospective analysis of 50 CT datasets with renal or ureteral stones.
• Systematic variation of post-processing parameters: slice thickness, slice increment, and window settings.
• Intra-reader (n=1) and inter-reader (n=11) variability assessment of stone size measurements.

Main Results:

• Apparent renal stone size varied significantly with post-processing parameters, notably window settings (mean difference 1.5 mm) and slice thickness (mean difference 0.8 mm).
• Parameter changes introduced bias and pseudo-random variability in measurements.
• Inter-reader variability was substantially greater than intra-reader variability.

Conclusions:

• Image post-processing parameters significantly affect renal stone size measurements on CT.
• Substantial inter-reader variability exists in renal stone size estimation.
• Standardization of CT image acquisition and post-processing is necessary for consistent and reliable renal stone measurements.