Christie Medical Physics and Engineering Newsletter 70 May 2022

Upon further inspection by physics it was discovered that protection discountinuities were present in the framework holding the lead glass in place i.e. the non-glass part of the operator screen, as shown on a DR plate image below (black shows radiation getting through):

around CT scanners. Potential incidents arising from inadequate shielding in new facilities can be avodied through cooperation between employers (the organisation, the contractors and physics) to ensure communication and smooth handover of controlled areas. It is important that issues are identified immediately, before equipment is used during installation, critical exam/commissioning and long before it is used clinically. Multiple visits to new facilities may be required for thorough shielding measurements before the installers put equipment in and use radiation. On top of this, it is recommended that two days are scheduled into timelines for thorough completion of commissioning checks. Sufficient time should be factored into timelines to allow for physics to analyse data and issue a report before equipment is put into clinical use (a week in total from testing the unit to issuing a report would be a reasonable timeline but while the workforce is so reduced, this is aspirational). Furthermore, the possibility of potential issues occurring should be factored into timelines when considering new equipment. Physics often find problems. It should not be assumed that as soon as we leave the equipment will be ready to use on patients. The employer is required to decide if equipment can be put into clinical use. Physics data and the installer data contribute to this consideration but physics are not responsible for that decision. However, we can work as part of a multidisciplinary team drawing on all relevant expertise. Involve physics in your project development and timelines and keep us in the loop so you can start imaging patients, safely, sooner. Electrical Safety CMPE x-ray imaging physicists do not perform electrical safety testing. We require this to be performed and evidence provided before we undertake critical examinations and/or commissioning tests on imaging equipment. It is down to the equipment owner to ensure electrical safety is satisfactory when first installed and throughout its lifetime. Although there are no specific regulations related to medical electrical installations, there is a duty of care supported with standards and guidance (see below) that

The gap ran from the lead glass to the lower panel section, which could be a result of both sections not firmly assembled together or a missing lead strip, or both. CMPE also found shielding issues when assessing a mobile CT van. The structure of the van was tested using scattered radiation from a phantom on the CT bed and a dose rate meter providing Instantaneous Dose Rates (IDRs). Discountinuities were found where lights were fitted on the van, at joins between panels, around the base where the floor slides out to let patient beds into the van at the lift and around door frames. The IDRs were such that additional lead had to be put in place to reduce levels below acceptable dose constraints e.g. <0.3mSv per year when occupancy is taken into consideration. The lesson to others is that mobile imaging environments are a particular risk and require signiicant physics time to ensure the safety of staff, patients and members of the public. Don ’ t assume that the roof shielding is not a concern as, particularily for CT imaging, the scattered dose rates can reach staff in a second floor office if located beside these mobile imaging structures. A further example of inadequate shielding at installation of a facility came with our discovery of a CT control room window with normal glass with no radiation protection qualities. CT control rooms normally have at least 2 mm of lead equivalence due to the very high dose rates

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