Experimental and simulation studies for the optimization of dedicated scintimammography cameras

Abstract

The main drawback of scintimammography with conventional gamma cameras is the large distance between detector and breast, which limits imaging performance and adds significant background noise from the heart and other organs. These limitations can be minimized by dedicated gamma cameras placed in tight contact with the breast. The purpose of this study was to determine the lowest Tumor-to-Background (T:B) ratio for detectable lesions and the smallest lesions that can be imaged with a dedicated system. The system is based on an R3292 position sensitive photomultiplier tube (PSPMT) from Hamamatsu, coupled to a 10 cm in diameter CsI(Tl) crystal and a general purpose collimator with hexagonal holes. Two crystals were assessed, with pixel size of 2 × 2 mm 2 and 3 × 3 mm 2 . The experimental setup consists of a cylindrical breast phantom, cylindrical tumor phantoms positioned inside the breast phantom at various depths, and a heart phantom. The same setup, as well as some additional tumor phantoms, were modeled with the GATE simulation toolkit, following the validation of the entire system. A 20% energy window and the Dual Energy Window Subtraction Method (DEWSM) for scatter correction were applied in experimental and simulation data. In all measurements 99m Tc was used. Signal to Noise Ratio (SNR) and contrast were measured in all experiments and used for quantification of results. Experimental and simulation results show that the lowest T:B ratio that can be detected is 2:1 with tumor phantom volume ≥ 0.25 ml at 1 cm depth. The smallest volume of a tumor phantom that can be detected is 0.04 ml with T:B ratio equal to 9:1 at 1 cm depth.

Effect of 176Lu intrinsic radioactivity on dual head PET system imaging and data acquisition, simulation, and experimental measurements

“…In order to properly sample the background counts, ROI 2 is the average value of two background ROIs. 22 The source that was used for the counting rate evaluation of the models was also utilized for the SNR of the models for activities less than 1 MBq. The simulated acquisition time was 60 s, to provide similar events with the experimental measurements, due to the fact that SNR depends strongly on the statistics.…”

¹⁷⁶Lu effect on the minimum detectable activity limits for a dual head, LSO: Ce based, PET system

“…ROI 1 is selected inside the imaging object while ROI 2 is selected at the background of the image. In order to properly sample the background counts, ROI 2 was the average value of two background ROIs [10]. The size of the ROIs was 149 pixels.…”

Development and evaluation of a small animal PET protype compatible with strong magnetic fields

“…where ROI 1 is selected inside the imaging object while ROI 2 is selected at the background of the image. In order to properly sample the background counts, ROI 2 is the average value of two background ROIs [137]. The size of the ROIs was 149 pixels.…”

“…On the other hand SPMM-3020, which has more cells, presents an approximately linear response [144][145][146][147]. Tc (c), 22 Na(511 keV) (d), 137 Cs (e) and 22 Na (1275 keV) (f).…”

“…Energy resolution Figure 5.11 shows the measured energy resolution for SPMM-3020 and SPMM-3035 as a function of V bias . BGO and LYSO:Ce scintillators were irradiated by 137 Cs and 22 Na. CsI:Tl was irradiated with 57 Co.…”