Quantification of urinary stone volume: attenuation threshold-based CT method--a technical note.

Area of Science:

• Radiology
• Medical Imaging
• Nephrology

Background:

• Accurate quantification of urinary stone volume is crucial for patient management.
• Computed tomography (CT) is a common imaging modality for urinary stones.
• Threshold-based CT methods offer potential for automated stone volume quantification.

Purpose of the Study:

• To compare two threshold-based CT methods for urinary stone volume quantification.
• To assess the accuracy and precision of these methods under varying CT parameters.
• To evaluate interobserver agreement in a clinical setting.

Main Methods:

• Calcium oxalate stones were scanned in a phantom using fixed and variable threshold CT methods.
• Variable threshold method utilized stone-specific attenuation and varying section thicknesses (0.6-3 mm).
• Accuracy and precision were compared to fluid displacement; interobserver agreement assessed in 17 patients.

Main Results:

• The variable threshold method demonstrated superior accuracy and precision compared to the fixed threshold method (P < .0001).
• Thinner CT sections (0.6-1 mm) yielded more accurate and precise measurements.
• No significant differences in accuracy/precision were observed with varying tube currents or voltages; high interobserver agreement (r > 0.97).

Conclusions:

• CT-based threshold methods can accurately quantify urinary stone volume, even at reduced radiation doses.
• The optimal method employs variable attenuation thresholds tailored to each stone and thin imaging sections.
• This approach enhances precision and accuracy in urinary stone volume assessment.