Application of heavy-ion CT.

Area of Science:

• Medical Physics
• Radiotherapy
• Biomedical Imaging

Background:

• Hadron therapy treatment planning relies on accurate relative stopping power data.
• Current methods use x-ray CT (CT) with a polybinary tissue model for conversion, but its accuracy in animal tissues is unverified.
• Precise heavy ion irradiation in radiotherapy necessitates evaluating this model's accuracy in diverse biological tissues.

Purpose of the Study:

• To evaluate the accuracy of the polybinary tissue calibration model for relative stopping power in animal tissues.
• To compare relative stopping power data derived from polybinary-tissue-model CT (PTCT) with direct measurements from heavy-ion CT (HICT).

Main Methods:

• Animal tissue samples were scanned using both x-ray CT and heavy-ion CT (HICT).
• X-ray CT images were converted to relative stopping power images using the polybinary tissue calibration (PTCT).
• HICT directly provided a two-dimensional distribution of relative stopping power for comparison.

Main Results:

• A direct comparison between PTCT and HICT images was performed to verify the calibration table's accuracy.
• The study found good agreement between the relative stopping powers calculated by PTCT and measured by HICT.
• The agreement was within 1.6% for fat, muscle, and bone tissues.

Conclusions:

• The polybinary tissue model demonstrates sufficient accuracy for converting x-ray CT numbers to relative stopping powers in animal tissues.
• This verification supports the reliable use of the polybinary tissue model in hadron therapy treatment planning, enhancing precision in heavy ion radiotherapy.
• The findings validate the existing conversion table for clinical application in radiotherapy.