Bone analogue phantoms: redefining standards in patient specific MRT dosimetry

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Molecular Radiotherapy (MRT) is a relatively common procedure in counties with developed healthcare systems. In thisprocedure, a labelled radioisotope is administered to the body in order to irradiate and kill tumour cells whilst sparing thesurrounding healthy organ tissue. In the UK alone, there are some 200 departments performing over 11000 MRTs annuallyand ~200,000 therapies in some 28 EU countries.In a recent development towards personalised healthcare, a new EU directive 2013/59 was introduced which requires thatall Member states performing any form of radiotherapeutics (including MRT) must provide dosimetry treatment planning foreach patient by 6th February 2018. Although this may sound like an obvious situation, MRT has in fact been used clinicallyfor around 75 years with no fully established dosimetry practice for calculating the absorbed dose delivered to tumourtargets or to organs at risk. Even though the general steps have been agreed, there still exists a wide variation in thecurrent acquisition, quality and treatment of images used to determine dose. As a result, treatment protocols have oftenevolved locally, based on experience with a relatively small numbers of patients. Although such patients would all havereceived similar administered activities, the actual dose received to particular organs could have large variations.As a consequence of the complexities involved, the application of radionuclide dosimetry has been restricted to thoseacademic groups with the facilities to develop in-house techniques. Very few therapy centres currently can validate dosecalculations to a known level of accuracy and only a few academic therapy centres can perform MRT Monte Carlo (MC)calculations. Our group, established between The University of Manchester and The Christie, has developed the ability todeliver this within a very large MRT practice. We were recently selected to lead the EU work on validating dose calculations from simulated patient phantoms and physical 3D printed phantoms in the EMPIR MRTDosimetry project (2016-19). Theproject will provide a standardised European framework for clinical implementation of MRT dose planning. In our approach,developed with an STFC Mini-IPS grant, 3D-printed patient analogues (phantoms) are constructed based on patient CTimages. This novel technique has clear potential to provide the foundation of a clinical service to provide a basis forimproved activity quantification to all clinical centres and MRT patients in the UK.We are uniquely positioned to deliver this work, having access to a large data base of MRT patient data at The Christie.Working with these data, we can provide the foundation for establishing a future national clinical service. The Christie hasthe experience in both MRT dosimetry research and in providing training and support for a national clinical service(PET/CT) required to provide a MRT dosimetry service. In addition our collaboration has strong links with industry, inparticular Hermes Medical Solutions Ltd, a leading provider of nuclear medicine workstation software. By developing acomprehensive validation methodology for clinical dosimetry systems, and thereby demonstrating that the HERMESdosimetry system meets this standard, our collaboration will be able to provide a de-facto validation standard for clinicaldosimetry systems and a market leading package. These links provide a pathway to distribute the techniques to the widerEU and international nuclear medicine market. In turn, this improves patient outcomes by allowing modification of therapybased on disease response and also benefits the healthcare provider by maximising outcome for the same or reducedresource.