The Clatterbridge high-energy neutron therapy facility: specification and performance

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• The Medical Research Council initiated clinical trials for fast neutron therapy.
• Previous neutron therapy equipment faced criticisms regarding design and performance.
• A new facility was required to advance these clinical trials.

Purpose of the Study:

• To install and commission a new high-energy neutron therapy facility at the Douglas Cyclotron Centre.
• To characterize the performance of the new neutron beam.
• To assess radiation safety aspects of the new facility.

Main Methods:

• A new neutron beam was generated by bombarding a beryllium target with 62 MeV protons.
• The facility features an isocentric target mount with 360-degree rotation and a variable collimator for diverse field sizes (5x5 cm to 30x30 cm).
• Key beam parameters including output, field flatness, penumbra, and depth-dose data were measured. Radiation shielding and neutron-induced radioactivity were also assessed.

Main Results:

• For a 10x10 cm field, the 50% depth dose was measured at 16.2 cm in water.
• The neutron beam output was 1.63 cGy μA⁻¹ min⁻¹ at the depth of maximum dose.
• Target shielding was effective, and neutron-induced radioactivity was within acceptable limits. Radiation levels throughout the center were low, posing no significant hazard.

Conclusions:

• The new high-energy neutron therapy equipment meets its design specifications.
• The facility successfully addresses criticisms of earlier neutron therapy equipment.
• The new installation provides a safe and effective platform for advancing fast neutron therapy clinical trials.