ACCURACY OF SIZE-SPECIFIC DOSE ESTIMATE CALCULATION FROM CENTER SLICE IN COMPUTED TOMOGRAPHY

Area of Science:

• Medical Physics
• Radiological Sciences

Background:

• Accurate dose assessment in CT is crucial for patient safety.
• Size-specific dose estimate (SSDE) aims to personalize dose metrics.
• Current methods for SSDE calculation require evaluation for accuracy.

Purpose of the Study:

• To assess the accuracy of SSDE calculated from the center slice compared to a volume-based reference standard.
• To investigate the influence of patient size (weight, height, BMI) on SSDE calculation accuracy.

Main Methods:

• Retrospective analysis of 1812 CT exams (adult and pediatric).
• Automatic calculation of water-equivalent diameter (Dw) and effective diameter (Deff) for all slices.
• Comparison of SSDE calculated from the center slice versus the average of all slices.

Main Results:

• The center slice SSDE method introduced a mean difference of 2.0-5.0% compared to the reference standard.
• Accuracy correlated with patient size (BMI and weight), leading to overestimation in smaller and underestimation in larger patients.
• Observed errors ranged from 0% to 17.2% depending on the patient group and size.

Conclusions:

• Using the center slice for SSDE calculation introduces clinically relevant errors, particularly for non-average sized patients.
• Patient size significantly impacts the accuracy of the center slice SSDE method.
• Refined SSDE calculation methods accounting for patient size variations are warranted.