A method to correct for spectral artifacts in optical-CT dosimetry.

Area of Science:

• Medical Physics
• Radiological Physics
• Optical Imaging

Background:

• Radiochromic dosimeters enable fast 3D dosimetry via optical computed tomography (optical-CT).
• Broad-beam optical-CT scanners using light-emitting diodes (LEDs) can suffer from spectral artifacts.
• These artifacts arise from polychromatic LED light interacting with spectrally selective dosimeter absorption, leading to dose measurement errors.

Purpose of the Study:

• To develop and validate an analytic method for correcting spectral artifacts in optical-CT dosimetry.
• To assess the impact of spectral artifacts on dose reconstruction accuracy.
• To provide a correction method applicable when physical filters are not feasible.

Main Methods:

• An analytic correction method was developed, requiring knowledge of light source, dosimeter, and detector spectral characteristics.
• The method was implemented for PRESAGE® dosimeters using the DLOS telecentric scanner.
• Spectrometer and spectrophotometer measurements characterized emission and absorption profiles.

Main Results:

• Simulations indicated potential errors of up to 8% due to spectral changes in moderately attenuating samples.
• The spectral artifact correction improved reconstructed coefficients from ~7.5% to ~1.5% for normalized dose distributions.
• Evaluation used a PRESAGE® phantom with a stepped dose distribution to assess correction accuracy.

Conclusions:

• The developed analytic method effectively corrects spectral artifacts in optical-CT dosimetry.
• This correction is valuable when physical filtering is impractical due to potential introduction of Schlieren bands.
• The method enhances the accuracy of dose measurements in radiochromic dosimetry systems.