Design and evaluation of an LSO PET detector for breast cancer imaging

Abstract

Functional imaging with positron emission tomography (PET) may be a promising technique in conjunction with x-ray mammography for breast cancer patient management. Conventional whole body PET scanners provide metabolic images of breast cancer patients with several shortcomings related to the general-purpose nature of these systems. In whole body scanners, the detectors are typically 20-30 cm away from the breast or axilla, reducing sensitivity, and these scanners have relatively large detector elements (> 4 mm), limiting spatial resolution. Dedicated PET systems for breast imaging aim to overcome these limitations and improve the overall diagnostic quality of the images by bringing the detectors closer to the area to be imaged, thereby improving sensitivity, and by using smaller detector elements to improve the spatial resolution. We have designed and developed a modular PET detector that is composed of a 9x9 array of 3x3x20 mm3 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to an optical fiber taper, which in turn is coupled to a Hamamatsu R5900-C8 position-sensitive photomultiplier tube. These detectors can be tiled together without gaps to construct large area detector arrays to form a dedicated PET breast cancer imaging system. Two complete detector modules have been built and tested. All detector elements are clearly visualized upon flood irradiation of the module. The intrinsic spatial resolution (full-width at half-maximum) was measured to be 2.26 mm (range 1.8-2.6 mm). The average energy resolution was 19.5% (range 17%-24%) at 511 keV. The coincidence time resolution was measured to be 2.4 ns. The detector efficiency for 511 keV gamma rays was 53% using a 350 keV energy threshold. These promising results support the feasibility of developing a high resolution, high sensitivity dedicated PET scanner for breast cancer applications.

Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast‐dedicated PET system

“…3,4 However, special considerations on detector design and system architecture need to be taken into account given the demands for high spatial resolution and high photon sensitivity in order to detect early stages of breast cancer, which cannot be satisfied with the current clinical tomograph designs. [5][6][7][8][9] Breast-dedicated PET systems have recently demonstrated their clinical relevance, 10 whereas specialized system designs may be used to improve system performance. 11 Our group is developing a 1 mm 3 resolution PET scanner dedicated to breast imaging.…”

Positron Emission Mammography Image Interpretation for Reduced Image Count Levels

“…Mot ivated by remaining challenges in diagnosis, staging, and management of breast cancer, small, high-resolution PET scanners dedicated to breast imaging have been investigated since the 1990s (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Dedicated breast PET systems (positron emission mammography [PEM]) have spatial resolutions better than whole-body (WB) PET scanners by factors of 2-4 and are much smaller than WB PET scanners, allowing placement of the detectors close to the breast, thus increasing geometric detection efficiency for annihilation photons relative to WB PET.…”

Comparison of rectangular and dual-planar positron emission mammography scanners

“…Another popular design that has been pursued by researchers is a parallel dual-planar geometry (Fig. 1b) [1], [5]. It is similar to using only the top and bottom detector banks in the rectangular PEM scanner.…”

“…Dedicated PET scanners, commonly referred to as positron emission mammography (PEM) cameras, are being developed to improve the cost effectiveness for detecting breast cancers [1][2][3][4][5]. These PEM scanners have special geometries that are different from the conventional circular design of whole body PET scanners.…”