A small field of view camera for hybrid gamma and optical imaging

Abstract

The development of compact low profile gamma-ray detectors has allowed the production of small field of view, hand held imaging devices for use at the patient bedside and in operating theatres. The combination of an optical and a gamma camera, in a co-aligned configuration, offers high spatial resolution multi-modal imaging giving a superimposed scintigraphic and optical image. This innovative introduction of hybrid imaging offers new possibilities for assisting surgeons in localising the site of uptake in procedures such as sentinel node detection. Recent improvements to the camera system along with results of phantom and clinical imaging are reported.

A Multimodality Hybrid Gamma-Optical Camera for Intraoperative Imaging

“…At present, the HGC uses a Hamamatsu CsI(Tl) columnar scintillator (Hamamatsu Photonics UK Ltd., Welwyn Garden City, UK) (1500 µm thick) directly coupled to a charge-coupled device (CCD) (e2v CCD97 BI, E2V Technologies Ltd., Chelmsford, UK) and a tungsten pinhole collimator. This thickness of scintillator has an absorption ranging from ~100% to 38% over the energy range of interest [12]. A simple, single pinhole collimator was chosen, partly to simplify the construction but also to extend the imaging field of view (FOV)—the field of view, when using a pinhole collimator, increases with the distance of the camera to the object.…”

“…Gamma photons interact with the scintillator and generate optical photons, the number being related to the incident photon energy. The position and the energy of the incident photon are recorded by the hybrid system [12]. …”

“…A thin (1 mm thick) first surface mirror at 45° to the collimator is positioned directly in front of the pinhole and reflects optical photons to an optical camera outside the direct line of sight of the pinhole [12]. Gamma photons from a source will pass through the mirror with minimal absorption (<1%) whereas optical photons will be reflected by the mirror towards the optical camera.…”

“…( A ) Photograph of the Hybrid Gamma Camera (HGC); ( B ) schematic of the HGC showing the internal layout (for more details see Lees et al [12]).…”

“…Many research groups around the world have been developing a range of hand-held or portable systems for medical gamma imaging [1,2,3,4,5,6,7,8,9,10,11,12]. To date, these smaller systems have all concentrated on a single imaging modality.…”