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CONSTRUCTION ProtonBeamTherapyvs.conventionalradiationtreatment

When cancer tumours are treated using conventional X-ray radiation, the radiation beam is fairly large, and travels through the body, damaging healthy tissue around the tumour. The proton beam is much smaller (about the size of a pencil), and only travels to the depth of the tumour. The protons release their energy at a predefined depth in the body, known as the ‘Bragg peak’. This means that during treatment very little healthy tissue is damaged in front of the tumour, and none behind it. This is why proton beam therapy is generally preferred for young cancer patients, as the risk of serious and long-lasting side effects is significantly reduced.

Proton beam therapy has been around for decades, but legacy systems are traditionally extremely expensive and require a large, new-build site. Lee Forrest said: “Conventional systems, such as the ones featured in the 2019 BBC Horizon documentary ‘The £250 m Cancer Cure’, begin with a 90-tonne circular accelerator. This accelerates the particles to the required energy level, and this is then delivered via the beam line into the treatment rooms. The beam passes through a series of electromagnets before reaching a degrader, which ‘dumps’ excess energy before it reaches the patient. Such facilities require concrete walls up to four metres thick to slow down these particles. “In contrast, Advanced Oncotherapy’s LIGHT accelerator

Excavation and construction David Wright continues: “Excavation works for the project started in March 2017. The construction period was always going to be longer than a conventional refurbishment, owing to the extensive excavations required, and the fact that the buildings involved were listed. However, the project duration still compares favourably to building times associated with the construction of multi-

benefits from a linear accelerator with high efficiency, and therefore low stray radiation, creating significantly lower shielding requirements. The accelerator also comes in modules, with no part heavier than 1.5 tonnes, and each module can be installed through a lift. A rotating robotic couch and minimal beam size allow for more accurate targeting of cancerous tumours, and obviate the need for a rotating gantry.

“This,” Lee Forrest continued, “will allow our facility in Harley Street to provide two treatment rooms sat side by side in the sub-basement. Initially the north treatment room will be used for preparation and pre-treatment scanning, with patients then taken through to the south room for treatment immediately afterwards. Following the recent partnership with The London Clinic, both rooms should become full treatment rooms.”

Lee Forrest added that the conventional proton beam therapy units described above use 58-tonne gantries to rotate the beam around the patient. In contrast, the facility at Harley Street will not need anywhere near as much space for treatment. Instead, the patient is positioned in a robotic chair which moves them between a vertical sliding CT scanner and the beam nozzle – rotating them as necessary to gain the best access to the tumour, and reducing the number of healthy cells affected during treatment.

room proton beam facilities using legacy technologies traditionally built in out-of- town locations. These take, on average, three to four years to complete. The £10 m building refurbishment was completed in August 2019, and the project moved into the fit-out phase. This meant that Advanced Oncotherapy could now focus on the installation of the LIGHT system – the modular nature of which lends itself to the quicker and more

convenient installation of these easily handled modules, rather than large volumes of heavy equipment, ensuring minimal disruption, and no requirement for cranes on site.

Each LIGHT module will be transported directly into the accelerator hall through a 2.7 m deep, 1.8 m wide, and 2.4 m high lift. The fact that the accelerator hall is located in the basement of the Harley Street site, which is only 156 m2


demonstrates the small footprint required for the technology. Dry-packed high- density modular concrete blocks with overlapping joints will prevent protons and neutrons passing through, and will be installed during the fit-out stage.

The project team on site. 88 Health Estate Journal September 2020

Soft and hard concrete piling Due to the depth of the dig, soft and hard concrete piles were used, as opposed to underpinning the existing building fabric. Working with the piling sub-contractor and main contractor allowed the structural engineer to provide efficiencies in the final design of the sub-structure, reducing both the piles’ diameter and depth. The piling rigs used on this job were designed specifically for confined spaces and inner-city groundworks projects. Localised underpinning was also required for the party wall between 29 and 30 Devonshire Mews West, as the party walls were not aligned with 139 and 141 Harley Street, and piling in this area would have prevented Advanced Oncotherapy’s beam line from aligning within the space. As such, the pile cap drops down to lower basement level in this location. Temporary ring beams and

©Andy Catterall Photography and Motion

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