Requirements for a Compton camera forin vivorange verification of proton therapy

Abstract

To ensure the optimal outcome of proton therapy, in vivo range verification is highly desired. Prompt γ-ray imaging (PGI) is a possible approach for in vivo range monitoring. For PGI, dedicated detection systems, e.g. Compton cameras, are currently under investigation. The presented paper deals with substantial requirements regarding hardware and software that a Compton camera used in clinical routine has to meet. By means of GEANT4 simulations, we investigate the load on the detectors and the percentage of background expected in a realistic irradiation and we simulate γ-ray detections subsequently used as input data for the reconstruction. By reconstructing events from simulated sources of well-defined geometry, we show that large-area detectors are favourable. We investigate reconstruction results in dependence of the number of events. Finally, an end-to-end test for a realistic patient scenario is presented: starting with a treatment plan, the γ-ray emissions are calculated, the detector response is modelled, and the image reconstruction is performed. By this, the complexity of the system is shown, and requirements and limitations regarding precision and costs are determined.

On the Role of Single Particle Irradiation and Fast Timing for Efficient Online-Control in Particle Therapy

“…Compton imaging may yield to higher detection efficiency than collimated devices. However, at clinical beam intensity, the coincidence rate between the two detection stages is dominated by fortuitous coincidence events induced by quasi-simultaneous projectiles [10,18,19]. A significant reduction of the incident flux is needed in order to minimize this background source [10], at the level of one incident proton within the duration of the time-coincidence window, unless efficient filtering strategies are used, which has not been demonstrated so far.…”

Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: A Theoretical Study

“…The literature about the cost of PGI prototypes is scarce due to early stage of research development and the several years remaining until a final product is actually commercialized. Some rough estimates state an overall material cost of at least 200 k$ [29] and up to 1 M$ [84], not accounting for development, commissioning and maintenance. Furthermore, these costs do not include the potential integration in the rotating gantry structure, for covering several beam incidence angles.…”

3-D Reconstruction Benchmark of a Compton Camera Against a Parallel-Hole Gamma Camera on Ideal Data

“…Although Compton cameras should have superior efficiency ( [13], [14], [15], [16], [17], [18], [19]), imaging of γ sources in nuclear medicine is still carried out with collimator-based gamma cameras. Compton cameras have recently regained interest as they may allow ion-range monitoring in proton and hadron-therapy using prompt-γ emission generated by nuclear interactions of the ions with tissue ( [20], [21], [22], [23], [24], [25], [26], [27], [28]). The energies of the promptγ rays are too large to cope with parallel hole acquisition and requires hard collimation ( [29], [30]).…”

“…The geometry of acquisition as well as data selection and pre-processing strategies have a major impact on the resulting Compton camera images (see e.g., [49], [14], [22], [50], [51], [27]). The spatial resolution of reconstruction can be improved by more accurate modeling of the physical effects ( [52], [53] [54], [55]) and by deconvolution methods in data space for energy spectrum ( [56]) or in spatial domain ( [57], [58]).…”