A dose distribution overlay technique for image guidance during prostate radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Adaptive radiotherapy (ART) necessitates accurate dose distribution assessment to account for anatomical changes during treatment.
• Current methods often require full dose recalculation, which can be time-consuming and computationally intensive.
• Image-guided radiotherapy (IGRT) relies on precise verification imaging to ensure treatment accuracy.

Purpose of the Study:

• To propose and validate a novel workflow for assessing dose coverage in adaptive radiotherapy using a planned dose distribution overlay technique.
• To evaluate the accuracy and clinical acceptability of this overlay technique compared to traditional dose recalculation.
• To determine the suitability of the proposed method for routine implementation in prostate cancer treatment.

Main Methods:

• A pilot study involving 10 prostate cancer patients with 7-10 on-treatment CT studies each.
• Quantification of geometric differences between the planned 95% isodose and recalculated 95% isodose from verification CT data.
• Assessment of dosimetric coverage of the verification clinical target volume (vCTV) using both the overlay technique and recalculated dose distribution.

Main Results:

• Differences in the geometric shape of the 95% isodose were found to be insignificant for typical anatomical variations.
• Decisions on the adequacy of vCTV coverage were consistent between the overlay technique and recalculated dose in 80 out of 87 cases.
• Discrepancies were minimal, affecting a maximum of three slices per study within a small range (0.5-4.5 mm).

Conclusions:

• The proposed dosimetric overlay technique is a validated and acceptable method for assessing dose coverage in image-guided radiotherapy for prostate cancer.
• This technique provides a viable alternative to full dose recalculation, potentially streamlining clinical workflows.
• The method is suitable for effective implementation in radiation oncology treatment clinics.