Patient-specific Effective Dose Estimation from Dose-Length Product in Lung Computed Tomography Using Monte Carlo...

Area of Science:

• Medical Physics
• Radiological Dosimetry
• Computational Imaging

Background:

• Computed tomography (CT) contributes significantly to patient radiation dose in medical imaging.
• Accurate estimation of radiation risk in CT is crucial for patient safety.
• Existing dose metrics may not fully account for patient-specific factors.

Purpose of the Study:

• To introduce a method for determining patient-specific effective dose in lung CT scans.
• To utilize Monte Carlo (MC) simulation for calculating radiation dose based on the dose-length product (DLP) index.
• To investigate the influence of body habitus on radiation dose and effective dose conversion factors.

Main Methods:

• Simulated a CT scanner using EGSnrc/BEAMnrc MC code.
• Modeled voxelized male and female phantoms of varying body habits (slim, standard, fat).
• Calculated organ doses and effective doses using DOSxyznrc simulation, correlating DLP and CTDIvol with effective dose.

Main Results:

• Lung radiation doses varied with body habitus, with slim patients exhibiting higher doses per mAs.
• The DLP to effective dose conversion factor (k-factor) was found to be higher in slimmer patients, particularly women.
• Calculated lung radiation doses for men: slim (0.164 mGy/mAs), standard (0.103 mGy/mAs), fat (0.078 mGy/mAs).
• Calculated lung radiation doses for women: slim (0.164 mGy/mAs), standard (0.105 mGy/mAs), fat (0.079 mGy/mAs).

Conclusions:

• CT scan dose indices may underestimate radiation exposure in slimmer patients.
• Patient body habitus significantly influences effective dose calculations.
• CT dose reporting should be adjusted for patient body habitus to ensure accurate radiation risk assessment.