Optimising workflows of intracranial stereotactic radiosurgery quality assurance including single-isocentre multiple-target

The occurrence of brain metastases is one of the most common complications after primary cancer treatment. Recently published research reports incidence rates in cancer patients to be anywhere between 10 – 50%. There is a continuing trend of growing acceptance and referrals to intracranial stereotactic radiosurgery (SRS) for treatment with some of the driving factors being a lesser impact upon quality of life compared to the more traditional whole brain radiotherapy and an increased availability due to the use of conventional medical linear accelerators to deliver SRS treatment. This growth, along with the use of complex techniques, has seen the workload of the medical physicist increase making the efficiency of procedures an important consideration.

It is widely accepted that due to the ablative doses delivered in few fractions to small targets, SRS requires high precision and therefore high levels of quality assurance (QA). The use of complex techniques such as single-isocentre multiple-target (SIMT) SRS has increased the level of delivery accuracy required as targets may now be located at off-axis positions and hence be more susceptible to rotational uncertainties. It has been demonstrated previously that as departments’ confidence in accurate delivery grows through experience, the levels of QA being conducted may be reduced.

The aim of this thesis is to optimise workflows for SRS QA including SIMT, in order to reduce the workload of the medical physicist. The recommendations being developed will span many aspects of SRS treatment including machine QA, treatment planning and patient-specific QA (PSQA). This thesis will: examine overlap between routine QA and PSQA; identify planning factors which result in a greater plan robustness to uncertainties, potentially increasing confidence in delivery; and investigate an alternative to measurement-based PSQA techniques.