Combined gamma radiation source detector and ultrasound imaging system: Proof of concept and first results

The examination of lymphogenic metastasis is the basis for the treatment of tumors. It primarily targets the sentinel lymph nodes (SLN). Common imaging techniques to identify SLNs expose patients to high doses of radiation. Ultrasound imaging supported by radiation detectors is a more patient-friendly alternative that can be used intraoperatively. This work aims to develop a gamma source detector which can localize the source and can be combined with a commercial ultrasound system to a dual-modality system.

The problem is modeled, and a localization algorithm is developed that robustly determines position estimates from noisy sensor readings. An accuracy optimized arrangement of sensors is determined. The concept is verified by using a test setup based on infrared radiation. Furthermore first tests with gamma radiation are performed.

An infrared radiation source with unknown radiant flux is localized with a spatial deviation of 3.64 ± 1.66 mm (2σ) on average within a wide measurement range of 40 × 20 × 60 mm³. A visualization setup to combine and display data from the developed sensor system and an ultrasound system is shown, that achieves a display rate of 3 frames/s. Tests with gamma radiation show that two gamma source positions can be distinguished.

The system presented allows 3D localization of a gamma radiation source with reduced radiation exposure to patients. The measurements are combined registration-free with ultrasound imaging to a dual-modality system and provide an enriched database for SLN identification. To reduce measurement times, more efficient sensors must be used.