Renal stone detection using a low kilo-voltage paediatric CT protocol - a porcine phantom study

Area of Science:

• Radiology
• Medical Imaging
• Pediatric Imaging

Background:

• Computed tomography (CT) dose reduction is crucial, especially in pediatric patients.
• Lowering tube voltage (kV) is a key dose-saving technique.
• The impact of low-voltage CT (70 kV) on visualizing renal stones in children was previously unclear due to potential noise increases.

Purpose of the Study:

• To evaluate the detectability of renal stones using low-voltage (70 kV) non-contrast CT in a pediatric phantom.
• To assess the inter-observer agreement among radiologists in identifying nephrolithiasis at different kV settings.

Main Methods:

• A pediatric phantom containing porcine kidneys with 42 renal stones of varying sizes and compositions was used.
• Scans were performed at 120 kV and 70 kV.
• Three radiologists assessed stone detectability, and agreement was analyzed using absolute agreement and Fleiss' kappa.

Main Results:

• Stone sizes ranged from 1 to 11 mm, with a mean diameter of 4.24 mm.
• Sensitivity for stone detection was high at both 70 kV (93-98%) and 120 kV (95-98%).
• Specificity was 100% for all observers and kV levels, with strong inter-observer agreement (kappa = 0.86 at 70 kV, 0.96 at 120 kV).

Conclusions:

• Reducing CT tube voltage to 70 kV does not compromise the detection rate of renal stones.
• Low-voltage CT is a viable and effective strategy for dose reduction in the assessment of pediatric nephrolithiasis.