SECONDARY NEUTRON DOSES IN A PROTON THERAPY CENTRE.

Area of Science:

• Medical Physics
• Radiation Protection
• Nuclear Instrumentation

Background:

• Proton therapy utilizes high-energy protons, but secondary neutron production raises radiation protection concerns for healthcare staff.
• Accurate assessment of neutron doses is crucial for ensuring safety in clinical environments.

Purpose of the Study:

• To intercompare the performance of various neutron detectors for assessing ambient dose equivalent (H*(10)) and personal dose equivalent (Hp(10)) in a proton therapy facility.
• To evaluate the accuracy of different detectors in measuring neutron doses relevant to staff exposure.

Main Methods:

• A joint intercomparative study was conducted at the Proton Therapy Centre, Essen, involving CERN, SCK•CEN, and IBA/IRISIB/ULB.
• Ambient dose equivalent (H*(10)) was measured using Berthold LB 6411, WENDI-2, tissue-equivalent proportional counter (TEPC), and Bonner spheres (BS).
• Personal dose equivalent (Hp(10)) was assessed using active personal dosemeters and bubble detectors, with reference values estimated from spectral and angular data.

Main Results:

• Staff exposure in a technical room indicated H*(10) doses ranging from 0.5 to 1 nSv/monitoring unit.
• The LB 6411 detector underestimated H*(10), whereas WENDI-2 and TEPC showed good agreement with Bonner sphere measurements.
• Active personal dosemeters significantly overestimated Hp(10), while bubble detectors exhibited only a slight overestimation.

Conclusions:

• WENDI-2 and TEPC are recommended for accurate H*(10) assessment in proton therapy settings.
• Bubble detectors provide a reasonable alternative for Hp(10) measurements, though active personal dosemeters require further investigation for accuracy.
• This study highlights the importance of detector selection for reliable radiation protection in proton therapy facilities.