Radial Sensitivity
Criteria
The sensitivity distribution is evaluated equidistant to the frontal radiation entrance window dependant on the polar angle. The full width at half maximum (FWHM) of the distribution function is a good quality criterion for the detectability of lymph nodes in presence of non target radiation (injection depot, background). With a broad measurement cone the background signal can exceed the target signal of the lymph node, which then cannot be detected. A small cone mainly reduces background maintaining a constant target signal. Therefore with increased background in the target area a smaller FWHM of radial sensitivity distribution is desired.

Crystal Probe's Performance
The Crystal Probe’s measured far field FOV is <40° FWHM, exactly in the appropriate parameters for optimal radial sensitivity distribution. Radial sensitivity is essential in pinpointing the exact lymph node (the sentinel lymph node, SLN). A larger FOV may include two nodes which is unnecessary and a smaller FOV makes is difficult to find the SLN, which wastes time.
Crystal Probe Radial Sensitivity
<40° FWHM (Far Field)