Hand-held gamma-ray imaging device for localization of sentinel lymph nodes

A hand-held scintillation camera has been developed for localizing Sentinel Lymph Nodes (SLN) during or prior to surgery. Use of gamma proves has increased in recent years to identify SLNs as these are increasingly implicated in the spread of cancerous cells. The functionality of this new imaging probe will go beyond that of current non-imaging devices by displaying activity distributions in addition to counting rates. Using different collimators changes the spatial resolution, sensitivity and field of view (FOV) of the camera. In addition, the camera produces audible tones proportional to the count rate. The tone is modulated in real time to indicate the presence of complex distributions of activity within the FOV. The modulated tone alerts the user to localized concentrations of activity that may be nodes. The 22 mm FOV camera has 1 mm intrinsic spatial resolution. System FWHM in air is 2.1 mm and 2.6 mm at 0 cm and 1 cm from a high-resolution parallel hole collimator, respectively. FWHM of 3.8 mm is measured 2 cm from a 3 mm pinhole. Pinhole sensitivity is 600 cps/MBq above a 125 cps/MBq background for a 1 cm lesion 1 cm below a water surface. Nodes are identified in images even when overall count rate is not above background.