PT - JOURNAL ARTICLE AU - Yoko Satoh TI - Comparison of image quality between different positions in the ring-shaped detector for dedicated breast PET DP - 2019 May 01 TA - Journal of Nuclear Medicine PG - 385--385 VI - 60 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/60/supplement_1/385.short 4100 - http://jnm.snmjournals.org/content/60/supplement_1/385.full SO - J Nucl Med2019 May 01; 60 AB - 385Objectives: High-resolution dedicated breast positron emission tomography (dbPET) scanners equipped with ring-shaped detectors have been developed to identify early-stage breast cancers that may not be visible on whole-body PET/computed tomography (PET/CT) [1]. Standard performance parameters for the dbPET scanner, including its spatial resolution, sensitivity, scatter fraction, recovery coefficients, and uniformity according to NEMA NU4-2008 standards, have been reported previously [2]. We also reported the results of physical assessment of a breast phantom using a dbPET scanner at the last annual meeting [3]. In our previous study, a breast phantom was placed at the center of both a ring-shaped dbPET detector and whole-body PET/CT, and scanned for physical assessment. However, many Japanese women have small breasts, and their mammary glands are often located near the chest wall above the center of the detector, even when they are in the prone position. This tendency is particularly common in young women who are less likely to have breast ptosis than older women. Therefore, it is necessary to evaluate the consequences of a shift in the position of the breast phantom in the detector, away from the center. The purpose of this study was to evaluate image quality obtained by placing a breast phantom at different positions in relation to the detector during dbPET scans. Methods: A cylindrical breast phantom with four spheres of different diameters (16, 10, 7.5, and 5 mm) was filled with an 18F-fluorodeoxyglucose (FDG) solution. The four spheres were aligned on the same axial plane. The sphere-to-background ratio (SBR) was simulated as 8:1, with a background radioactivity level of 2.46 kBq/mL The breast phantom was positioned so that the spheres were precisely located at 8 mm, 13 mm, 39 mm (depth of 1/8), 19.5 mm (depth of 1/4), and 78 mm (depth of 1/2, the center of the detector) below the top edge of the detector. Images were acquired for 5 minutes in each position (Figure 1). The reconstructed images were visually evaluated and the % background variability (%N5mm), % contrast (%QH,5mm), contrast-to-noise ratio (QH,5mm/N5mm), and coefficient variation of the background (CVbackground) were calculated. We also evaluated the correlation between the breast position in the detector and image quality in human images. Results: The %N5mm, %QH,5mm, QH,5mm/N5mm, and CVbackground at the center of the detector were 6.41, 10.02, 1.56, and 5.91, respectively. The %N5mm and CVbackground were higher, and %QH,5mm and QH,5mm/N5mm lower, when the phantom was placed closer to the edges of the detector (Table 1). The disadvantages of this placement were visually confirmed by a nuclear medicine physician and two nuclear medicine technologists who examined the phantom images (Figure 2). In addition, the human images showed that background noise could be difficult to distinguish from small lesions when the breasts were closer to the edge of the detector (Figure 3). Conclusions: Although lesion detectability is equal at from the center of the ring-shaped detector to the depth of 1/8, it decreases when it is closer to the edge. References: 1. Kalynyak JE, Berg WA, Schilling K, et al. Breast cancer detection using high-resolution breast PET compared to whole-body PET or PET/CT. Eur J Nucl Med Mol Imaging 2014; 41: 260-275. 2. Miyake KK, Matsumoto K, Inoue M, et al. Performance evaluation of a new dedicated breast PET scanner using NEMA NU4-2008 standards. J Nucl Med 2014; 55: 1198-1203.