Ultra-fast imaging for the safe delivery of electron FLASH radiation therapy - Abstract
Radiation therapy is a supplementary curative treatment used adjuvant with most surgery and chemotherapy,
being delivered to nearly 1 out of every 4 people in their lifetime. While image guidance and conformal planning
reduced the dose to healthy tissue, there is still a substantial risk of tissue damage that sets the upper limit of
dose deposited to the tumor. A recent radical approach to minimize healthy tissue damage was demonstrated
with ultra-high dose rate irradiation, and is known as the FLASH effect. This treatment operates at dose rates
1000x higher than in conventional mode, and by delivering an entire treatment course in 100 millisecond, it
promises a reduction of radiation-induced toxicities by 10-50%. Several clinical centers, including Dartmouth
Hitchcock Clinic, demonstrated that an existing clinical linac can be reversibly converted into an ultra-high dose
rate electron source. This modification shows enormous translational potential to deliver electron FLASH
(eFLASH) in any radiotherapy center using existing systems. However, while most research in the field is focused
on elucidating the radiobiological mechanisms of FLASH, work towards mitigating the risks of FLASH is largely
untouched, yet will be pivotal for wide clinical implementation. New techniques for detection monitoring radiation
need to be developed due to the millisecond timescales at which FLASH operates which make traditional
methods unsuitable. In this project, we exploit the uniqueness of DoseOptics BeamSiteTM system, a recently
510(k) cleared single photon capable camera designed to monitor conventional radiotherapy providing the first
direct videos of the radiation dose delivery. BeamSite images are used by radiation therapists to monitor radiation
delivery real-time. Clinical use has shown that routine monitoring of radiotherapy can reveal sub-optimal delivery
which can be addressed by the therapists as needed. More importantly, it offers an automatic detection of beam
and patient misalignments and delivery errors, and therefore it is very scalable even to the ultra-fast FLASH
application. In this Phase I project we propose to develop an ultra-fast version of the BeamSite camera capable
of tracking the beam on patients at kiloframe/s frame rate, which is required to keep up with the standard 360
Hz beam pulse rate in order to provide critically needed beam location and a linear and scalable dosimetry at
these ultra-high dose rates. Once the camera is developed, these methods will be studied on DHMC’s existing
clinical dual-purpose FLASH linac. The current proposal provides resources for the goals of: (i) developing a
hardware prototype of an ultra-fast Cherenkov camera equipped with optimized, firmware-based algorithms, and
(ii) demonstrating its capabilities for detecting beam deviations and dose on an existing eFLASH linac. The work
includes hardware and software support and development, and eFLASH resources at Dartmouth Hitchcock to
be leveraged towards these goals.
