DIAGNOSTIC EQUIPMENT
Infrastructure implications of installing a Gamma Knife
Ian Paddick, a Consultant Physicist at specialist in radiation oncology, Amethyst Radiotherapy, discusses some of the challenges, practicalities, design considerations, and logistics, of installing a Gamma Knife radiosurgery machine into medical facilities, with a particular focus on the Queen Square Radiosurgery Centre within the University College Hospital in central London.
Gamma Knife has become a recognised treatment for small-medium-sized tumours and vascular disorders that develop in the brain and skull base, including secondary metastasised tumours and arteriovenous malformations (AVMs), for example. As a form of stereotactic radiosurgery, it presents a treatment option for complex cases where open surgery would carry significant risk. Gamma Knife uses 192 precisely focused beams of radiation, which converge to produce a high dosage of radiation to a highly focused target. This means that it is capable of treating complexly located lesions without damaging the surrounding healthy brain tissue.
10-year anniversary This year marks the 10-year anniversary of the Gamma Knife installation at the Queen Square Radiosurgery Centre (QSRC) within the University College Hospital (UCH) in central London – a centre of clinical excellence that operates within the National Hospital of Neuroscience and Neurology (NHNN). Providing stereotactic radiosurgery treatment options using Gamma Knife for complex lesions in the brain, this centre has been consistently listed as one of the world’s top three centres for neuroscience and neurology. However, the process of actually installing the Gamma Knife at QSRC was complex – and involved tonnes of equipment and live radioactive sources being fitted into the basement of UCH (where the QSRC is located), entailing the use of cranes, a prefabricated breakout wall, and temporarily moving a steel staircase. UK hospitals with medical ionising
radiation facilities such as X-rays, nuclear scans, and radiotherapy units, must meet the Care Quality Commission (CQC - NHS regulator group) regulations. These aim to minimise the risk of harm to patients and staff, and set out the responsibilities of duty-holders – to ensure that what is needed for sufficient radiation protection and the basic safety standards are met.
72 Health Estate Journal September 2023
Launched in 2015, the Leksell Gamma Knife Icon model introduced the ability to offer both frame treatments and mask-based treatments.
Unlike linear accelerators (LINACs) such as teletherapy and radiotherapy units, which produce radiation electronically – only active when turned on – Gamma Knife machines house live Cobalt sources. The sources are sourced from Canada,
and are made using Cobalt 59 in a nuclear reactor, which absorbs neutrons from the neutron flux in the reactor to become Cobalt 60. Each Gamma Knife unit contains 192 pellets of Cobalt, each measuring 1 mm x 1 mm, and is transported in a 9-tonne cask. After arriving on site, the
Other key players
Elekta used Flegg Projects as the logistics partner for the lifting and installation of equipment and components into the QSRC. The scheme was designed and project managed by specialist architect, CSM+ Architects, and the specialist builder on the project was DD Porter Construction.
sources are loaded into the Gamma Knife using a specifically designed machine – which itself weighs 3 tonnes – that removes the current pellets, as well as transferring the new ones into the Gamma Knife. As the casks and loading machine themselves weigh tonnes, cranes are often needed for loading and unloading the sources, which are returned to Canada after the five-year half-life for disposal/re-use.
Replacing the sources As the Cobalt 60 decays, it becomes weaker, and as the sources approach their five-year half-life, they have to be replaced. The sources must be delivered in a flask source container, weighing 2-3 tonnes, which then needs to have surface measurements taken on arrival to ensure that it is sealed. Although half as strong, the sources are still extremely strong after five years – up to 222 terabecquerels (1 TBq = 1 000 000 000 000 Bq – one becquerel being one unit of measurement of radioactivity). This means that there are 222 TBq radioactive disintegrations per second. Even so, after five years, treatment
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120
