Positioning reproducibility with and without rotational corrections for 2 head and neck immobilization systems

Area of Science:

• Radiation Oncology
• Medical Imaging
• Cancer Treatment

Background:

• Accurate patient positioning is critical for effective head and neck (H&N) cancer radiotherapy.
• Intrafraction motion can compromise treatment accuracy, necessitating robust immobilization techniques.
• The role of rotational corrections and custom immobilization devices in H&N cancer treatment requires further evaluation.

Purpose of the Study:

• To assess the impact of offline rotational corrections on patient positioning accuracy.
• To evaluate intrafraction motion in H&N cancer patients.
• To compare immobilization with and without a custom neck cushion.

Main Methods:

• Fifty H&N cancer patients underwent cone beam computed tomography (CBCT) imaging for each treatment fraction.
• CBCT registrations were performed offline, initially without and then with rotational corrections.
• Intrafraction motion was quantified by comparing pretreatment and posttreatment CBCTs; a custom neck cushion was used in half the patients.

Main Results:

• Offline rotational corrections significantly improved pretreatment patient positioning accuracy, reducing errors from 49% to 21% (3mm) and 15% to 4% (5mm).
• Patients with a custom neck cushion experienced significantly lower intrafraction motion (1.0 ± 0.5 mm) compared to those with a standard headrest (1.8 ± 1.6 mm).
• The custom neck cushion led to significantly improved posttreatment positioning accuracy compared to pretreatment imaging.

Conclusions:

• Offline rotational corrections are essential for enhancing pretreatment patient positioning in H&N cancer radiotherapy.
• The addition of a custom neck cushion significantly reduces intrafraction motion.
• Custom neck cushions improve overall treatment accuracy by increasing posttreatment positioning accuracy.