Dose verification of helical tomotherapy intensity modulated radiation therapy planning using 2D-array ion chambers

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• Helical Tomotherapy is an advanced radiotherapy technique requiring precise dose verification.
• Current methods for dose verification may not fully capture the complexities of rotational delivery.
• Accurate dosimetry is critical for patient safety and treatment efficacy in Intensity-Modulated Radiation Therapy (IMRT).

Purpose of the Study:

• To assess the clinical utility of 2D-array ion chambers for verifying Helical Tomotherapy dose plans.
• To establish an efficient and accurate method for validating patient doses during treatment.
• To investigate the performance of the IMRT MatriXX™ and Multicube™ system for rotational radiotherapy QA.

Main Methods:

• Utilized the IMRT MatriXX™ and Multicube™ phantom for dose distribution measurements in coronal and sagittal planes.
• Verified treatment positions using pre-treatment Tomotherapy MVCT images.
• Compared measured dose distributions with planning system calculations using absolute/relative doses and Gamma (γ) analysis.

Main Results:

• Measured dose distributions closely agreed with Tomotherapy planning system calculations.
• Discrepancies between measured and predicted doses at selected points were within ±3%.
• Mean passing rates using the 3 mm/3% Gamma (γ) function criteria exceeded 96% in both coronal and sagittal planes.

Conclusions:

• The MatriXX system with Multicube is a reliable tool for rotational delivery quality assurance (QA).
• This system enables simultaneous measurement of absolute and relative dose distributions.
• It provides an efficient and accurate dosimetry validation method for Helical Tomotherapy IMRT.