OPTIma: a tracking solution for proton computed tomography in high proton flux environments

Abstract

Currently there is a large discrepancy between the currents that are used for treatments in proton beam therapy facilities and the ultra low beam currents required for many proton CT imaging systems. Here we provide details of the OPTIma silicon strip based tracking system, which has been designed for performing proton CT imaging in conditions closer to the high proton flux environments of modern spot scanning treatment facilities. Details on the physical design, sensor testing, modelling, and track reconstruction are provided along with Monte-Carlo simulation studies of the expected performance for proton beam currents of up to 50 pA at the nozzle when using a σ = ∼10 mm spot scanning cyclotron system. Using a detailed simulation of the proposed OPTIma system, a discrepancy of less than 1% on the Relative Stopping Power is found for various tissues when embedded within a 150 mm diameter Perspex sphere. It is found that by accepting up to 7 protons per bunch it is possible to operate at cyclotron beam currents up to 5 times higher than would be possible with a single proton based readout, significantly reducing the total beam time required to produce an image, while also reducing the discrepancy between the beam currents required for treatment and those used for proton CT.

OPTIma: simplifying calorimetry for proton computed tomography in high proton flux environments

“…The resulting performance in terms of RSP discrepancy as a function of beam current is shown in figure 11. As was seen in earlier studies using a resolving calorimeter (Winter et al 2023), the overall trends are that the RSP discrepancy gets larger with (i) beam current and (ii) as the contrast with the surrounding material gets larger. This is largely due to failures in the track reconstruction, where as the number of hits in the system increases, so too does the chance of incorrectly matching hits across modules.…”

“…A detailed description of the OPTIma tracking system has already been presented (Winter et al 2023), and it has been shown that with a suitable calorimeter, the tracking system could facilitate a discrepancy of less than 1% on the measured RSP of various tissues for beam currents up to 50 pA at the nozzle at the Christie research line.…”

“…Discrete silicon strip detectors were modelled in detail in order to match the real detector design (Winter et al 2023). Effects such as dead space, alignment tolerances, charge sharing, noise and thresholds were all included to ensure a realistic response.…”

Meeting the detector challenges for pre-clinical proton and ion computed tomography

“…Similarly, the tracker lateral dimensions are only about 10 cm, so the prototype is limited to making CT images of phantoms much smaller than, for example, a human head. It does nevertheless illustrate the technological principle, and the collaboration is currently working on building an advanced, well funded, full-scale system named OPTIma (Winter et al 2023).…”

“…The Bergen collaboration is working on an instrument that could be the ultimate pCT scanner in terms of speed and RSP resolution and is inherently capable of measuring many simultaneous particles. The PRaVDA/OPTIma project is funded and well underway, with tracking based on silicon strip sensors and a segmented energy detector that is not yet well defined but may be based on scintillating bars (Winter et al 2023). It is aiming for advanced performance that would be useful in a clinical setting, in particular a capability to handle high rates in a scanned pencil beam, with up to seven charged-particle tracks measured simultaneously.…”