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Background: Portable gamma cameras are being developed for nuclear medicine procedures such as thyroid scintigraphy. This article introduces Seracam® – a new technology that combines small field of view gamma imaging with optical imaging – and reports its performance and suitability for small organ imaging. Methods: The count rate capability, uniformity, spatial resolution, and sensitivity for 99mTc are reported for four integrated pinhole collimators of nominal sizes of 1 mm, 2 mm, 3 mm and 5 mm. Characterisation methodology is based on NEMA guidelines, with some adjustments necessitated by camera design. Two diagnostic scenarios – thyroid scintigraphy and gastric emptying – are simulated using clinically relevant activities and geometries to investigate application-specific performance. A qualitative assessment of the potential benefits and disadvantages of Seracam is also provided. Results: Seracam's performance across the measured characteristics is appropriate for small field of view applications in nuclear medicine. At an imaging distance of 50 mm, corresponding to a field of view of 77.6 mm × 77.6 mm, spatial resolution ranged from 4.6 mm to 26 mm and sensitivity from 3.6 cps/MBq to 52.2 cps/MBq, depending on the collimator chosen. Results from the clinical simulations were particularly promising despite the challenging scenarios investigated. The optimal collimator choice was strongly application dependent, with gastric emptying relying on the higher sensitivity of the 5 mm pinhole whereas thyroid imaging benefitted from the enhanced spatial resolution of the 1 mm pinhole. Signal to noise ratio in images was improved by pixel binning. Seracam has lower measured sensitivity when compared to a traditional large field of view gamma camera, for the simulated applications this is balanced by advantages such as high spatial resolution, portability, ease of use and real time gamma-optical image fusion and display. Conclusion: The results show that Seracam has appropriate performance for small organ 99mTc imaging. The results also show that the performance of small field of view systems must be considered holistically and in clinically appropriate scenarios. [ABSTRACT FROM AUTHOR]

Portable gamma cameras suitable for intraoperative imaging are in active development and testing. These cameras utilise a range of collimation, detection, and readout architectures, each of which can have significant and interacting impacts on the performance of the system as a whole. In this review, we provide an analysis of intraoperative gamma camera development over the past decade. The designs and performance of 17 imaging systems are compared in depth. We discuss where recent technological developments have had the greatest impact, identify emerging technological and scientific requirements, and predict future research directions. This is a comprehensive review of the current and emerging state-of-the-art as more devices enter clinical practice. [ABSTRACT FROM AUTHOR]

A custom Python-based Monte Carlo Simulation Tool (PMST) has been developed to assist in the development of portable gamma cameras or the generation of simulated gamma image datasets, e.g. for deep learning. The simulation tool has been validated by comparison between theoretical and experimental results. PMST includes common attenuation interactions such as the photoelectric effect and Compton and Rayleigh scattering and fluorescence and non-radiative secondary effects. It allows users to simulate and visualise a gamma imaging system with multiple absorbers, flexible geometry, and different materials. [ABSTRACT FROM AUTHOR]

To examine the imaging capability of a novel small field of view hybrid gamma camera (HGC) using 125I seeds prior to surgical use. The imaging performance of the camera system was assessed quantitatively and qualitatively at different source depths, source to collimator distances (SCD), activity levels, acquisition times and source separations, utilising bespoke phantoms. The system sensitivity and spatial resolution of the HGC for 125I were 0.41 cps/MBq (at SCD 48 mm) and 1.53 ± 0.23 mm (at SCD 10 mm) respectively. The camera was able to detect the 125I seed at a SCD of 63 mm (with no scattering material in place) in images recorded within a 1-min acquisition time. The detection of the seeds beneath scattering material (simulating deep-seated tumours) was limited to depths of less than 20 mm beneath the skin surface with a SCD of 63 mm and seed activity of 2.43 MBq. Subjective assessments of the hybrid images acquired showed the capability of the HGC for localising the 125I seeds. This preliminary ex vivo study demonstrates that the HGC is capable of detecting 125I seeds and could be a useful tool in radioactive seed localisation with the added benefit of providing hybrid optical γ images for guiding breast conserving surgery. The SFOV HGC could provide high resolution fused optical-gamma images of 125I radioactive seeds indicating the potential use in intraoperative surgical procedure such as RSL. [ABSTRACT FROM AUTHOR]