Non-palpable breast cancers are more and more frequent. Their surgical management requires the excision of the tumor and sentinel lymph node (SLN) needing a technical preoperative organization combining preoperative identification of the tumor by wire guide and injection of a radioactive tracer for the identification of SLN. The implementation of this minimally invasive surgery is sometimes paradoxically complicated due to the presurgical organization requiring several medical teams. It is for this reason that hand-held gamma-cameras have been developed, used either preoperatively or during surgery to replace lymphoscintigraphy but also as a help to excision of the tumor after radioisotope injection. The objective of this study was to evaluate the interest of the main hand-held gamma-cameras used in breast cancer. (C) 2012 Elsevier Masson SAS. All rights reserved.

Designing the scintillation module of a mini gamma camera requests good understanding of how the scintillation light signal spreads within the crystal and how photons are finally collected on the PMT. For a given scintillation process, the key parameters are the geometry of the crystal, its optical coating and the interface between the crystal and the PMT. In order to optimize the design of our gamma camera TReCam, we studied the shape of the spatial distribution of the scintillation light for different values and combinations of these key parameters. Our approach was to produce computer simulations, for which the optical simulation transport software DETECT2000 was used. Three major parameters were investigated: optical coatings for the crystal (aluminum, Teflon, corner cube retro-reflectors), the thickness of the crystal (ranging from 1 mm up to 5 mm) and the interfaces (air, optical grease). In addition to the FWHM of the light spot distribution, specific figures of merit were implemented to further characterize photon spreading. In order to evaluate the influence of these parameters on the imaging performances of the TReCam, the whole scintillation module (including the PMT) was also simulated with GATE v4.0.0 based on GEANT 4.9.1.p02. It appears that the best configuration is a 5 mm thick LaBr3:Ce crystal plate covered on the top with Teflon optical coating coupled optically with a PMT.

Using the POCI camera, we recently demonstrated the clinical impact of per-operative imaging techniques thanks to a successful clinical trial. Taking advantage of both the POCI experience and the availability of new pixelated detectors, we are developing a new hand held gamma camera TReCam (tumor resection camera). The first prototype offers a 49 × 49 mm2 field of view. It combines a 15 mm thick parallel hole collimator (with an efficiency of 5.10-4 and a spatial resolution of 7.5 mm at 50 mm), a 5 mm thick LaBr3:Ce crystal optically coupled to a Hamamatsu H9500 flat panel multianode photomultiplier tube (MAPMT). The read-out of the MAPMT is ensured thanks to a new specific integrated circuit called HARDROC2 (hadronic Rpc detector readout chip). This chip was initially designed for the digital hadronic calorimeter (DHCAL) of the linear collider. The TReCam presents an intrinsic spatial resolution of 0.65 mm (FWHM) and an energetic resolution of 17.4% at 122 keV. The new read-out by the HARDROC2 chip is currently being implemented and using this new device energetic resolution is expected to be better.