Sep 25, 2017 Last Updated 11:00 PM, Sep 10, 2017

Construction challenges for Linear Accelerators explained by Stantec

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Catherine Zeliotis, Senior Architect and Healthcare Leader at health sector architectural specialist, Stantec, discusses the considerations and construction challenges surrounding the installation of Linear Accelerators (Linacs) on the second floor of the new Cancer Centre at Guy’s Hospital; the first in Europe to provide this radiotherapy treatment above ground level.

Gallery

The £160m Cancer Centre at Guy’s Hospital for Guy’s and St Thomas’ NHS Foundation Trust is the first in Europe to locate Linear Accelerator (Linac) radiotherapy machines above ground level.

The need to locate the Linac machines on the second floor was made clear by the patient and clinical engagement process in the earliest stages of the design period. The ‘Patient Reference Group’ for the new Cancer Centre included both patients and cancer survivors. Their feedback was that being sent to a dark basement for radiotherapy treatment was both arduous and disheartening, regardless of any attempts to make the environment appear more homely.

The lack of natural light and the disconnection between the treatment suite and the consulting area in conventional treatment centres were key areas of concern for both patients and clinical teams. Both groups highlighted that patient wellbeing could be improved by locating the Linac treatment facilities more centrally within the treatment zone to create a more patient-centred care pathway.

Treatment village concept

This feedback dovetailed with the design concept for the Cancer Centre, which was led by globally-renowned architectural practice Rogers Stirk Harbour + Partners (RSH+P). The new building has been designed around distinct patient ‘journeys’ that reduce or remove the need for patients to find their way to unfamiliar areas or be relocated from floor to floor during their treatment.

This approach has led to a ‘treatment village’ concept, laid out across 14 storeys to maximise the accommodation despite the small footprint of the site, which is sandwiched between existing buildings. Placed one on top of another, these ‘villages’ are more manageable for patients and give the building a human scale. There are Radiotherapy, Outpatients and Chemotherapy treatment villages along with a 'Welcome Village' with communal spaces located on the ground floor.

Throughout the facility, the floors are organised into two zones. The high technology ‘Science of Treatment’ zones are at the rear, along the largest side of the triangular floorplate, and this is where six shielded bunkers have been placed within the Radiotherapy Village. The low technology ‘Art of Care’ zones are at the front apex of the triangular floorplate. This zone includes naturally-lit waiting areas and landscaped balconies, where radiotherapy patients can have some respite before they are taken through to the Linac treatment areas on the same floor.

The Stantec team developed the detailed planning and interior design for the villages. The Radiotherapy Village extends over three consecutive levels, each tailored to a particular aspect of care and treatment: the welcome reception is located on the second floor, leading to waiting areas, consulting rooms and the Linacs beyond. Staff areas, including treatment planning, are on the third floor and the imaging centre, where the patient has their individual treatment planned out prior to the treatment itself, is on the fourth floor. This area includes the latest technology, including a PET-CT suite.

Roman remains

Practical considerations relating to the size and position of the site were also instrumental in the decision to raise radiotherapy out of the basement.

The triangular footprint has one long and two short elevations, and it was only possible to fit all six shielded bunkers on the longer side of the building. This geometric constraint became the genesis of the ‘Science of Treatment’ and ‘Art of Care’ zones on opposing sides of each floor.

Below ground, on the longer side of the building, a Roman boat has been preserved in the London clay and this is protected as a Scheduled Ancient Monument. As the boat made excavation of 40-50% of the basement area impossible, the trust and the design team were faced with two options: either to excavate the boat or to build over it without damaging it.

The advice from the consulting archaeologist was that the boat could remain in the ground underneath the building as long as the building was constructed in such a way that it would cause no damage to the ancient artefact. A rainwater harvesting system has been put in place to release water into the ground should it be required, and a monitoring hatch is integrated in the ground floor design.

Shielding options

Locating the Linacs above ground not only presented load-bearing challenges, but actually increased the amount of weight involved in the construction. This is because the shielding must ensure that radiation cannot pass through any surrounding structure – walls, floor and ceiling. Whereas the floor does not require shielding in a ground-based solution.

It is conceivable that research will reduce and even remove the need for radiation therapy within the lifecycle of the building, so the trust was very keen to opt for a de-mountable shielding solution. Stantec specified a specialist shielding material fabricated from lead and other heavy metals which arrived on site as blocks that were stacked up in an interlocking manner to eliminate radiation leakage.

This system reduced overall wall thickness to around one metre, halving the space sacrifice required for the alternative concrete option. Furthermore, it offers the potential to remove some or all of the six bunkers in the future. The earliest stages of the design also involved careful consideration of how the machines would be brought into the building.

The Stantec team used manufacturer’s data on the size, weight and turning radii of the Linac components to model the access requirements and design an appropriately-sized aperture into the second floor facade. This was successfully used to lift the machines into position and can be used in future to remove the Linacs from the building when they need to be replaced or if they are no longer required.

New model

Whether the practice of locating radiotherapy suites above ground becomes more widespread remains to be seen. What this project proves, however, is that it is feasible, even on a site with very significant challenges.

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