Customized irradiation sites for medical isotope production

A new medical isotope device based on holmium-166 (t= = 27 h) has shown great promise for treating liver metastases, which are associated with many common cancers. The device is prepared by bombarding polylactic acid microspheres containing natural holmium with thermal neutrons in a nuclear research reactor. The objective of this work was to design and validate an appropriate neutron irradiation site for producing this medical device at the McMaster Nuclear Reactor (MNR). Initial neutron irradiations resulted in massive damage to the microspheres. Further experiments indicated that this damage was due to gamma heating within the sample, not site temperature or radiolysis. Passive cooling and gamma shielding were introduced to improve the outcomes of the holmium activation. MNR is now an approved supplier of this medical device for clinical trials in Europe, and will begin supplying this material for North American clinical trials when they launch later in 2018.