Performance of the mediPROBE compact gamma camera for coded aperture imaging

The aim of this work is to assess the performance of a prototype compact gamma camera (MediPROBE) based on a CdTe semiconductor hybrid pixel detector for coded aperture imaging. This probe can be adopted for various tasks in nuclear medicine such as preoperative sentinel lymph node localization, breast imaging with
^99m
Tc-sestamibi and thyroid imaging with iodinated radioisotopes. The hybrid detector is an assembly of a 1mm thick CdTe semiconductor detector (sensitive area 14.08×14.08 mm
²
) bump-bonded to a photon-counting CMOS readout circuit of the Medipix2 series (256×256 square pixels, 55-μm pitch) or with a photon counting, energy-sensitive Timepix detector (128×128 square pixels, 110-μm pixel pitch). MediPROBE is equipped with a set of three interchangeable knife-edge pinhole collimators (hole aperture of 0.78 mm, 1 mm, or 1.9 mm) and a set of two coded aperture masks with 0.070-mm or 0.080-mm round holes. We performed measurements of field of view (FOV), system spatial resolution, and signal-difference-to-noise ratio (SDNR) by using a point-like gamma-emitting
²⁴¹
Am source (60 keV). The detector is operated at a single low-energy threshold of about 5 keV. At 60 keV the sensitivity is 0.0085 cps/kBq (w/0.78 mm pinhole). The system spatial resolution was 2.57 mm FWHM (w/ 0.78 mm pinhole) at a source-collimator distance of 45 mm, and 0.560 mm FWHM (w/ coded aperture 0.080 mm) at a source-collimator distance of 50 mm. We observed greater values of SDNR with the use of the coded aperture and the Timepix detector. A clinical trial is ongoing to evaluate the performance of MediPROBE for gamma-ray nuclear imaging.