Performance Evaluation of a New Dedicated Breast PET Scanner Using NEMA NU4-2008 Standards

Abstract

The aim of this work was to evaluate the performance characteristics of a newly developed dedicated breast PET scanner, according to National Electrical Manufacturers Association (NEMA) NU 4-2008 standards. Methods: The dedicated breast PET scanner consists of 4 layers of a 32 · 32 lutetium oxyorthosilicate-based crystal array, a light guide, and a 64-channel position-sensitive photomultiplier tube. The size of a crystal element is 1.44 · 1.44 · 4.5 mm. The detector ring has a large solid angle with a 185-mm aperture and an axial coverage of 155.5 mm. The energy windows at depth of interaction for the first and second layers are 400-800 keV, and those at the third and fourth layers are 100-800 keV. A fixed timing window of 4.5 ns was used for all acquisitions. Spatial resolution, sensitivity, counting rate capabilities, and image quality were evaluated in accordance with NEMA NU 4-2008 standards. Human imaging was performed in addition to the evaluation. Results: Radial, tangential, and axial spatial resolution measured as minimal full width at half maximum approached 1.6, 1.7, and 2.0 mm, respectively, for filtered backprojection reconstruction and 0.8, 0.8, and 0.8 mm, respectively, for dynamic row-action maximum-likelihood algorithm reconstruction. The peak absolute sensitivity of the system was 11.2%. Scatter fraction at the same acquisition settings was 30.1% for the rat-sized phantom. Peak noise-equivalent counting rate and peak true rate for the ratlike phantom was 374 kcps at 25 MBq and 603 kcps at 31 MBq, respectively. In the image-quality phantom study, recovery coefficients and uniformity were 0.04-0.82 and 1.9%, respectively, for standard reconstruction mode and 0.09-0.97 and 4.5%, respectively, for enhanced-resolution mode. Human imaging provided highcontrast images with restricted background noise for standard reconstruction mode and high-resolution images for enhancedresolution mode. Conclusion: The dedicated breast PET scanner has excellent spatial resolution and high sensitivity. The performance of the dedicated breast PET scanner is considered to be reasonable enough to support its use in breast cancer imaging. Br east cancer is one of the leading causes of cancer death among women worldwide, accounting for 425,000 deaths in 187 countries in 2010 (1). A strategy for reducing breast cancer mortality is early detection for successful treatment. PET systems dedicated to the breast have been under development since 1994, when Thompson et al. reported the feasibility of the first of these systems (2). The dedicated PET systems are intended to have higher photon sensitivity and improved spatial resolution by bringing the detectors close to the breast and by using smaller detector elements than those for whole-body tomography. Most of the dedicated PET systems perform positron emission mammography with 2 planar or curved detector heads that can compress the breast mildly, providing planar and limited-angle tomography images (3-8). Fully tomographic dedicated PET systems have also been introduced. This...

Positron Emission Mammography Image Interpretation for Reduced Image Count Levels

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