Normal lung tissue complication probability in MR-Linac and conventional radiotherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Technology

Background:

• Conventional radiotherapy (RT) poses risks of normal lung tissue (NLT) complications.
• Advancements in RT technology aim to minimize these risks.
• Magnetic resonance (MR) image-guidance offers potential for improved treatment precision.

Purpose of the Study:

• To compare normal lung tissue (NLT) complications between MR image-guided linac and conventional RT techniques.
• To evaluate the impact of MR-linac on key dosimetry parameters related to lung toxicity.
• To assess the potential of MR-linac to reduce radiation-induced lung damage.

Main Methods:

• Simulations using the Geant4 toolkit for a 6 MV photon beam.
• Application of a 1.5 Tesla homogenous magnetic field in parallel and perpendicular orientations.
• Analysis of normal lung tissue complication probability (NTCP), mean lung dose (MLD), and V20 using 4D-XCAT phantom CT images.

Main Results:

• MR-linac RT demonstrated lower mean lung dose (MLD) and V20 compared to conventional RT.
• The largest observed reductions in MLD and V20 for MR-linac were 5 Gy and 29.3%, respectively.
• These findings suggest improved dose distribution to the lungs with MR-linac.

Conclusions:

• MR-linac radiotherapy may lead to reduced normal lung tissue complications.
• The dosimetry advantages observed with MR-linac support its potential for safer lung SBRT.
• Further clinical studies are warranted to confirm these findings.