Applications of Accelerators and Detectors to Cancer Treatment

Abstract:

Following on from the 2015 Lancet Oncology Commission on expanding global access to radiotherapy, Radiotherapy and theranostics: a Lancet Oncology Commission was created to assess the access and availability of radiotherapy to date and to address the important issue of access to the promising field of theranostics at a global level. A marked disparity in the availability of radiotherapy machines between high-income countries and low-income and middle-income countries (LMICs) has been identified previously and remains a major problem. The availability of a suitably trained and credentialled workforce has also been highlighted as a major limiting factor to effective implementation of radiotherapy, particularly in LMICs. We investigated initiatives that could mitigate these issues in radiotherapy, such as extended treatment hours, hypofractionation protocols, and new technologies. The broad implementation of hypofractionation techniques compared with conventional radiotherapy in prostate cancer and breast cancer was projected to provide radiotherapy for an additional 2·2 million patients (0·8 million patients with prostate cancer and 1·4 million patients with breast cancer) with existing resources, highlighting the importance of implementing new technologies in LMICs. A global survey undertaken for this Commission revealed that use of radiopharmaceutical therapy-other than ¹³¹I-was highly variable in high-income countries and LMICs, with supply chains, workforces, and regulatory issues affecting access and availability. The capacity for radioisotope production was highlighted as a key issue, and training and credentialling of health professionals involved in theranostics is required to ensure equitable access and availability for patient treatment. New initiatives-such as the International Atomic Energy Agency's Rays of Hope programme-and interest by international development banks in investing in radiotherapy should be supported by health-care systems and governments, and extended to accelerate the momentum generated by recognising global disparities in access to radiotherapy. In this Commission, we propose actions and investments that could enhance access to radiotherapy and theranostics worldwide, particularly in LMICs, to realise health and economic benefits and reduce the burden of cancer by accessing these treatments.

Abstract:

The discovery of the FLASH effect has revealed a high potential for treating cancer more efficiently by sparing healthy tissue. The surge in related medical research activities over the last couple of years has triggered a demand for technology with the capability of generating and measuring ionizing radiation at ultra-high dose-rates (UHDR). A reliable dosimetry system is an integral part of a radiotherapy machine. Because existing active dosimetry methods are unable to handle the dose-rates required for FLASH, UHDR dosimetry has emerged as an important area of research. In this paper we present an active dosimetry method based on a scintillating screen and an integrating current transformer. This method provides a simultaneous measurement of the absolute dose delivery as well as the 2D dose distribution. The measurements have been correlated with corresponding readings from radiochromic films (RCFs), and a procedure for image processing has been established. Moreover, different methods of calibrating the active dosimetry system against RCFs have been introduced and evaluated. Lastly, we present results which demonstrate that an agreement with RCFs of better than 5% can be realistically expected if camera parameters are carefully optimized.