Helical tomotherapy versus single-arc intensity-modulated arc therapy: a collaborative dosimetric comparison between...

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT) are advanced radiation delivery techniques.
• Both modalities utilize rotational beams with multileaf collimators for precise radiation delivery.

Purpose of the Study:

• To compare the dosimetric aspects of helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT).
• To evaluate target dose homogeneity, conformation, and doses to critical organs for both techniques.

Main Methods:

• A dual-institution study involving 16 patients across brain, head and neck, lung, and prostate cancer sites.
• Single-arc IMAT (Varian RapidArc) and HT plans were generated using identical contours and prescriptions.
• Dosimetric indices, beam-on time, monitor units, and leakage dose were analyzed.

Main Results:

• Helical tomotherapy (HT) demonstrated superior target dose homogeneity (4.2% vs. 7.6%) and lower maximum doses (105% vs. 110%) compared to Varian RapidArc (RA).
• Varian RapidArc (RA) had significantly shorter average beam-on times (1.4 min vs. 4.8 min) and lower monitor units.
• Doses to normal tissues were comparable, with HT showing advantages for critical structures; dose conformation was similar, favoring RA slightly.

Conclusions:

• Both HT and single-arc IMAT (RA) produce highly conformal radiation plans meeting treatment goals.
• HT excels in target dose uniformity, whereas RA offers efficiency through reduced delivery time and monitor units.
• Post-comparison replanning improved dose distributions and delivery times for both techniques.