Gamma-Ray Imaging Techniques in Proton Therapy

Proton therapy exploits the sharply defined Bragg peak of proton dose deposition to deliver high doses to tumours while sparing surrounding tissue. However, uncertainties in proton range can compromise treatment precision. Gamma-ray imaging techniques seek to verify in real time the position of energy deposition by detecting γ rays emitted promptly during proton–nucleus interactions. These secondary emissions, arising within nanoseconds of proton arrival, carry spatial information that can be reconstructed into range maps. Approaches include collimated detection with coded apertures, uncollimated Compton cameras that infer source direction from photon scatter kinematics, and time-of-flight or prompt-timing methods that correlate γ-ray arrival times with proton transit times. Advanced reconstruction algorithms and detector developments aim to deliver millimetre-scale accuracy for clinical pencil-beam scanning. Together, these modalities promise adaptive monitoring of dose delivery, reduce safety margins, and enhance the therapeutic ratio by confirming that the Bragg peak coincides with the tumour volume.

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Gamma-Ray Imaging Techniques in Proton Therapy publication trend

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Technical terms

Bragg peak: The sharp maximum in energy deposition by protons at the end of their range in tissue.

Prompt gamma rays: Photons emitted within nanoseconds of proton–nucleus interactions during irradiation.

Compton camera: An uncollimated imaging system that reconstructs γ-ray source distributions by measuring successive Compton scatters.

Coded aperture: A patterned mask used to modulate incoming γ-rays, enabling image reconstruction by deconvolution of the detector signal.

Pencil-beam scanning: A delivery technique in proton therapy that steers a narrow proton beam spot by spot across the tumour volume.

References

1. Coded-aperture imaging systems: Past, present and future development – A review. Radiation Measurements (2016).
2. Range assessment in particle therapy based on prompt γ-ray timing measurements. Physics in Medicine and Biology (2014).
3. Range Verification Methods in Particle Therapy: Underlying Physics and Monte Carlo Modeling. Frontiers in Oncology (2015).
4. Processing of prompt gamma-ray timing data for proton range measurements at a clinical beam delivery. Physics in Medicine and Biology (2019).
5. Test of Compton camera components for prompt gamma imaging at the ELBE bremsstrahlung beam. Journal of Instrumentation (2014).