A step and shoot intensity modulated technique for total body irradiation

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Total body irradiation (TBI) is a critical component of conditioning regimens for bone marrow transplantation.
• Conventional TBI techniques may pose challenges in dose delivery and organ-at-risk sparing.

Purpose of the Study:

• To introduce and evaluate a step and shoot intensity-modulated radiation therapy (SS IMRT) technique for TBI.
• To assess the feasibility and dosimetric accuracy of SS IMRT for TBI in clinical practice.

Main Methods:

• Patients underwent CT scanning with 5 mm slices for treatment planning.
• Multiple multi-leaf collimator (MLC) defined fields were employed in the SS IMRT technique.
• In-vivo dosimetry was conducted on 113 patients, and calculated doses for 22 patients were analyzed.

Main Results:

• In-vivo dosimetry at Royal Marsden showed a mean TLD measured dose difference of -1.9% (SD 4.5%).
• SS IMRT plans for Rigshospitalet patients achieved mean doses of 11.1-11.8 Gy to the brain, lungs, and kidneys.
• Organ-at-risk sparing was demonstrated, with V(12 Gy) below 5% for the brain, 2% for the lungs, and 0% for the kidneys.

Conclusions:

• Step and shoot IMRT is a feasible technique for delivering total body irradiation.
• SS IMRT enables precise dose delivery to target volumes while sparing organs at risk.
• This technique can be implemented using standard external beam radiation equipment.