Components of the simulated energy spectrum for CZT (with 3.8% energy resolution) for an MBI acquisition using standard energy window and wide energy window.
System spatial resolution of the LumaGem detector [shown in (a)] and the Discovery NM 750b detector [shown in (b)] with their respective standard and optimal collimators. A 95% confidence interval of uncertainty of the linear fit is indicated. Vertical lines indicated bmin, the distance below which spatial resolution plateaus to equal collimator hole size.
Schematic of tumor placement within the breast phantom. Tumor diameter given in millimeter.
Images of breast phantom acquired on the LumaGem and Discovery NM 750b CZT detectors using their respective standard collimators and a standard 126–154 keV energy window (top row) and respective optimized collimators and wide (110–154 keV energy window (bottom row). Activity concentration ratio in tumors versus background was ∼20:1. Images from the LumaGem are shown in (a) with tumors were placed at a depth of 1 cm and in (b) depth was 3 cm from the collimator face. Images from Discovery NM 750b are shown in (c) with tumors at 1 cm depth and in (d) with tumors at 3 cm depth. The highest simulated count density with standard settings of 800 counts/cm2 was chosen to match that observed in patient studies performed with injection of 740 MBq Tc-99m sestamibi. A proportionally decreased dose was calculated to correspond with phantom images of decreased count densities.
Lesion CNR as a function of lesion size measured on breast phantom images with respective count densities representing a 148 MBq dose of Tc-99m sestamibi. Images were acquired on LumaGem at lesion depths of 1 and 3 cm from the collimator face [shown in (a) and (b)] and Discovery NM 750b also at lesion depths of 1 and 3 cm [shown in (c) and (d)] with each combination of standard and optimized collimators and standard and wide energy windows. Total simulated breast thickness was 6 cm. Error bars represent the standard error of the CNR measurements. Lesions were considered detectable at a CNR greater than 1, as indicated by the dotted line. Significantly improved CNR relative to that obtained with standard collimator and standard energy window is noted with “*.”
Breast phantom images acquired on the LumaGem system performed using (a) wide energy window (110–154 keV), (b) standard energy window (126–154 keV), and (c) their difference.
Specifications of standard collimators and optimized low-dose collimators for each CZT detector.
Count sensitivity measurements for standard and low-dose collimation and energy window settings on each CZT detector.
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