Dosimetric evaluation of a computed tomography treatment system

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Treatment Planning

Background:

• Accurate dose calculation is crucial in radiation therapy.
• Tissue inhomogeneities, like lung, pose challenges for treatment planning systems.
• Conventional systems may lack precision in handling complex density variations.

Purpose of the Study:

• To evaluate a novel pixel-by-pixel correction method for tissue inhomogeneities in radiotherapy.
• To assess the accuracy of CT-interfaced treatment planning systems using physical density conversion.
• To compare the performance of this advanced system against conventional methods.

Main Methods:

• Implemented pixel-by-pixel correction using a CT-interfaced treatment planning system.
• Converted CT numbers to physical density for each pixel.
• Validated dose calculations against measurements in a RANDO phantom.

Main Results:

• The pixel calculation method showed a dose overestimation of 5-7% near lung tissue.
• This overestimation is attributed to the algorithm not accounting for scatter loss.
• The system demonstrated advantages compared to conventional treatment planning systems.

Conclusions:

• Pixel-by-pixel correction offers potential improvements in radiotherapy dose calculation accuracy.
• Further refinement is needed to address scatter effects, particularly around low-density tissues like the lung.
• The developed system presents a viable alternative with specific benefits for complex treatment scenarios.