Implementing reconstruction with hand-held gamma cameras

Minimally invasive surgery has spurred development of portable nuclear medicine nonimaging detection products. Although these probes function well in simple anatomic regions (e.g., extremities), more complicated regions (e.g., head and neck, axilla) can present surgeons with difficulties due to the presence of overlapping tissue activity. Conventional gamma cameras, with large camera heads, are not ideal for intraoperative applications. Due to the bulky camera size, SPECT is difficult to implement in OR settings. Although small gamma cameras may be helpful when a lesion is already identified, surveillance of larger areas (e.g., for peritoneal evaluation) can be difficult due to limited field-of-view. Ideally, the information from a small hand-held gamma camera would be integrated from multiple views taken at arbitrary positions and angles. The authors present a method of creating an image with 3D information from a portable hand-held gamma camera held in arbitrary positions and angles near a radioactive source (patent pending). The method takes advantage of recent developments in iterative reconstruction algorithms, computer speed, and position sensing devices. Corrections were implemented for inhomogeneous sampling in time and space. Experimentally, the method appeared to improve contrast of small hot spots by reducing the effect of overlapping activity. This new method, like ectomography, may be helpful in tight quarters (e.g., intraoperative and ICU settings).