This issue of Journal of Medical Radiation Sciences includes two papers presenting different uses of magnetic resonance (MR) in radiation therapy (RT). With the advancement of MR‐simulators and Magnetic resonance linear accelerators (MRL), in addition to the use of diagnostic MR becoming more common place in the radiotherapy setting, there are a number of challenges to be considered. In this article, we present the perspectives of radiation therapists and medical physicists involved in the commissioning of an MRL in our centre. Image shows in‐house 3D printed supports mounted on the vendor‐supplied QA platform. The supports locate an array so that it is centred in the radiation field.
Psoriasis is an inflammatory autoimmune disease of the skin and nails, causing debilitating pain and having an adverse effect on the patients' life. Typical treatment regimens involve topical and systemic therapies in combination with phototherapy. However, patients with extensive, chronic disease may encounter treatment resistance, with limited or no success of these therapies. Radiation therapy (RT) has been shown to be an effective treatment for benign skin lesions; however, recommended dose, fractionation and long-term follow-up is not well established within the literature making clinical implementation challenging. Furthermore, RT may induce the Koebner Phenomenon, exacerbating the disease. This case study presents a patient with chronic hyperkeratotic palmoplantar psoriasis who was offered RT as a last resort. A total dose of 6Gy was delivered using photons and superficial energies. Significant reduction in extent of disease was seen as a result, with the patient no longer wheelchair-bound and able to mobilise with minimal discomfort. This case is a single example of RT as a successful treatment for chronic palmoplantar psoriasis; however, a larger sample size and clinical trial is needed to ascertain dose and fractionation for optimal long-term control. Implementation of such treatments within departments invites clinicians to further develop RT practices and provide much needed relief to a new cohort of patients with non-malignant conditions.
MR-guided radiotherapy technology is relatively new and commissioning publications, QA protocols and commercial products are limited. This work provides guidance for implementation measurements that may be performed on the Elekta Unity MR-Linac (Elekta, Stockholm, Sweden). Adaptions of vendor supplied phantoms facilitated determination of gantry angle accuracy and MV isocentre, whereas in-house developed phantoms were used for End-to-End (E2E) testing and anterior coil attenuation measurements. Third-party devices were used for measuring beam quality, reference dosimetry and during IMRT commissioning; however, due to several challenges, variations on standard techniques were required. Gantry angle accuracy was within 0.1°, confirmed with pixel intensity profiles, and MV isocentre diameter was < 0.5 mm. Anterior coil attenuation was < 0.6 %. Beam quality as determined by TPR20,10 was 0.704 ± 0.002, in agreement with treatment planning system (TPS) calculations, and gamma comparison against the TPS for a 22.0 × 22.0 cm2 field was above 95.0 % (2.0 %, 2.0 mm). G90 output was 1.000 ± 0.002 Gy per 100 MU, depth 5.0 cm. During IMRT commissioning, sub-standard results indicated issues with machine behaviour. Once rectified, gamma comparisons were above 95.0 % (2.0 %, 2.0 mm). Centres which may not have access to specialized equipment can use in-house developed phantoms, or adapt those supplied by the vendor, to perform commissioning work and confirm operation of the MRL within published tolerances. The IMRT QA devices and techniques used in this work highlight issues with machine behaviour when appropriate gamma criteria are set.
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