The first clinical implementation of electromagnetic transponder-guided MLC tracking

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Accurate tumor targeting is crucial in radiotherapy.
• Real-time motion management systems are needed to address intra-fractional motion.
• Multileaf collimator (MLC) tracking offers potential for improved dose delivery accuracy.

Purpose of the Study:

• To report the clinical process, quality assurance, and results of the first clinical implementation of electromagnetic transponder-guided MLC tracking.
• To evaluate the geometric and dosimetric accuracy of this novel radiotherapy technique.

Main Methods:

• Modified an electromagnetic transponder system (Calypso) for real-time target positioning.
• Developed in-house MLC tracking code to adjust beam alignment with target position.
• Performed dose reconstruction to compare delivered dose with and without MLC tracking for a prostate cancer patient.

Main Results:

• The first clinical implementation involved a prostate cancer patient treated with VMAT.
• Total in-room time was 21 minutes with 2 minutes of beam delivery; no additional time or beam holds were required for MLC tracking.
• Dose reconstruction showed similar isodose distributions with MLC tracking compared to planned treatment, while uncompensated motion led to a significant increase in rectal V60.

Conclusions:

• Electromagnetic transponder-guided MLC tracking has been successfully translated to clinical practice.
• This real-time beam-target correction represents a significant advancement in radiotherapy.
• The technique enhances geometric and dosimetric accuracy, potentially improving treatment outcomes.