Optimal Cobfiguration of low dose dual-head breast-specific gamma camera based on semiconductor CdZnTe pixelated detectors

Breast cancers is one of the most frequent tumour in women, the introduction of screening programmes during the ́90s has reduced this mortality up to 50%, allowing the detection of cancer before the touchable stage. Therefore, about half of the women between 30 and 50 years present dense breast parenchyma and decrease to 30% between 50 to 80 years; in these women mammography has a sensitivity around 30% and small tumour are covered by the dense parenchyma and missed in the mammogram. Breast-specific gamma-cameras based on semiconductor CZT detectors have shown to be of great interest in early diagnosis due to the high energy and saptial resolution and high sensitivity of CZT; Breast SPECT has shown to have a sensitivity of about 90% indipendently to the breast parenchyma. The aim of this project is to determine the optimal combination of pixel size, hole shape and material for the collimator in a low dose dual head breast-specific gamma-camera based on a CdZnTe pixelated detector at 140 keV in order to achieve high count rate and the best possible image spatial resolution. The optimal combination has been studied with a Monte Carlo modelling in GATE (Geant4 Application for Emission Tomography) of the system, were considered: six different pixel sizes from 0.85 mm to 1.6 mm, two different collimator materials, Lead (ρ = 11.4 g/cm 3 ) and Tungsten (ρ = 19.4 g/cm 3 ), and two hole shapes, hexagonal and square. The system shown a better counts rate and a better signal-to-noise ratio when equipped with square hole and bigger pixels; however at these configuration the spatial resolution were worse than in smaller pixel sizes, remaining in any case under 3.6 mm.