26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Filmless real-time end-to-end verification of dose placement for IGRT with MagicPlate-976 detector

Not scheduled

1h 30m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral COMMAD - Optoelectronic and Microelectronic Materials and Devices Parallel sessions

Description

Purpose

End-to-end (E2E) verification in image guided radiotherapy (IGRT) ensures the delivered radiation dose corresponds to the intended target throughout the treatment workflow. Conventional E2E methods rely on radiochromic film, requiring time-consuming processing and preventing rapid feedback. This study investigates the feasibility of using the high-spatial- and high-temporal-resolution MagicPlate-976 (MP976) semiconductor detector for film-free E2E verification. Two phantom configurations with different imaging contrast and a hidden target were evaluated, together with the detector's ability to detect positional shifts during static and arc-based dose delivery.

Methods

The MP976 is a monolithic pixelated semiconductor detector comprising 976 square diodes with a 1 mm pitch in the central region. It was incorporated into two custom phantoms: a low-contrast Perspex phantom and a lung-equivalent phantom, each containing a hidden 10 mm spherical solid water target. The E2E workflow included planning CT, treatment planning, image guidance, and LINAC delivery with and without intentional 1 mm translational shifts. Static beam deliveries at 0°, 45°, and 225° assessed target localisation and detector response. Arc delivery feasibility was also investigated. Anterior-posterior localisation was determined by summing the 45° and 225° beam responses for static delivery and by full width at half maximum analysis for arc delivery.

Results

The 3D-printed phantom demonstrated satisfactory manufacturing accuracy and sufficient CT contrast. Imaging contrast did not significantly affect phantom positioning. The MP976 detected 1 mm positioning errors in all three translational axes during static delivery, with measured shifts of approximately 0.8 to 1.3 mm. The measured detector dose of approximately 3 Gy agreed with the treatment planning system.

Conclusion

The MP976 enables rapid, film-free E2E verification with near real-time positional and dosimetric information. The detector accurately identified millimetre-scale positioning errors, although anterior-posterior localisation required additional analysis, demonstrating its potential for efficient verification of complex IGRT treatments.