Pixelated CdTe detectors to overcome intrinsic limitations of crystal based positron emission mammographs

Abstract

A positron emission mammograph (PEM) is an organ dedicated positron emission tomography (PET) scanner for breast cancer detection. State-of-the-art PEMs employing scintillating crystals as detection medium can provide metabolic images of the breast with significantly higher sensitivity and specificity with respect to standard whole body PET scanners. Over the past few years, crystal PEMs have dramatically increased their importance in the diagnosis and treatment of early stage breast cancer. Nevertheless, designs based on scintillators are characterized by an intrinsic deficiency of the depth of interaction (DOI) information from relatively thick crystals constraining the size of the smallest detectable tumor. This work shows how to overcome such intrinsic limitation by substituting scintillating crystals with pixelated CdTe detectors. The proposed novel design is developed within the Voxel Imaging PET (VIP) Pathfinder project and evaluated via Monte Carlo simulation. The volumetric spatial resolution of the VIP-PEM is expected to be up to 6 times better than standard commercial devices with a point spread function of 1 mm full width at half maximum (FWHM) in all directions. Pixelated CdTe detectors can also provide an energy resolution as low as 1.5% FWHM at 511 keV for a virtually pure signal with negligible contribution from scattered events.

Simulation of the Expected Performance of a Seamless Scanner for Brain PET Based on Highly Pixelated CdTe Detectors

“…The use of semiconductor detectors, such as CdTe or CdZnTe (CZT), for photon detection in PET applications is described in [2]–[5]. The VIP modular design allows us to package the detector in different shapes and for different functionalities: e.g., a whole-body (WB) PET, a small-animal PET, a positron emission mammography (PEM) scanner [6], a Compton camera [7]. Since the clinical applications related to brain pathologies are among the challenging screenings, we present and evaluate the VIP as a human brain dedicated PET.…”

Simulation and evaluation of a high resolution VIP PEM system with a dedicated LM-OSEM algorithm

“…PSF is measured at each position. Simulation results indicate a spatial resolution around 1 mm FWHM regardless of the three spatial directions [9] (8 times better volumetric resolution with respect to conventional scanner [4]).…”

“…The VIP PEM scanner has already been tested with the most well-known analytic algorithm Filtered Background (FBP) [14]. This method works very fast, but the main problem with FBP is that it requires a detector with an angular coverage of at least 180 degrees and thus can not be used for the VIP PEM scanner without producing artifacts in the final image [9].…”

“…All these intrinsic limitations affect the detector sensitivity, and the image quality, and limit the minimum detectable tumor size and the correct assessment of the malignancy of small lesions [7]. In the framework of the VIP pathfinder project [8], we propose a high resolution PEM design [9] based on finely segmented room temperature CdTe detectors to overcome the intrinsic limitations of state-of-the-art commercial PEMs based on scintillating crystals. In this study, the high resolution VIP-PEM design is simulated and evaluated in terms of detector performance, and imaging performance according to the NEMA NU-4 2008 protocol [10] and by using the LM-OSEM algorithm [11] for image reconstruction.…”

Evaluation of Origin Ensemble algorithm for image reconstruction for pixelated solid-state detectors with large number of channels

“…The VIP PEM scanner [7] consists of two scanning paddles, each with two heads (figure 3) of 80 VIP unit modules each. The heads are moved with 160 steps of 1.5 mm along the z-axis.…”