Size-specific dose estimates: Localizer or transverse abdominal computed tomography images?

Area of Science:

• Radiological Physics
• Medical Imaging
• Radiation Dosimetry

Background:

• Accurate radiation dose assessment in computed tomography (CT) is crucial for patient safety.
• Size Specific Dose Estimate (SSDE) aims to provide a more personalized dose metric than CT Dose Index Volume (CTDIvol).
• Body dimensions are key inputs for calculating SSDE.

Purpose of the Study:

• To evaluate the impact of body dimensions derived from localizer radiographs and transverse abdominal CT images on Size Specific Dose Estimate (SSDE).
• To compare the accuracy of patient size measurements from different imaging modalities for dose estimation.

Main Methods:

• Fifty patients undergoing abdominal CT were included.
• Anterior-posterior (AP) and lateral (Lat) diameters were measured from localizer radiographs and transverse CT images.
• Conversion factors were used to calculate SSDE from CTDIvol, considering various diameter measurements and patient centering.

Main Results:

• In 11% of measurements, accurate diameter measurements were not possible due to incomplete body coverage.
• Forty-one patients were off-centered from the gantry iso-center.
• SSDE values showed significant variation compared to CTDIvol, ranging from 32% lower to 74% higher.

Conclusions:

• Localizer radiographs tend to overestimate patient size, leading to an underestimation of SSDE.
• There is a notable discrepancy between SSDE and CTDIvol, highlighting the need for precise body dimension measurements.
• This study underscores the importance of accurate patient sizing for reliable dose estimation in CT.