Design and imaging performance of BPET-DBT - a dedicated scanner for breast imaging.

BACKGROUND: A dedicated breast PET (BPET) scanner integrated with digital breast tomosynthesis (DBT) enables three-dimensional functional imaging with quantitative information co-registered to high-resolution anatomical images. With the availability of breast cancer specific PET radiotracers, such a scanner has the potential to improve treatment planning in breast cancer. We recently developed a BPET-DBT scanner utilizing an integrated gantry design to generate intrinsically co-registered BPET-DBT images. PURPOSE: This paper presents the scanner design, characterizes its imaging performance, and reports on our initial human imaging experience to demonstrate scanner's clinical readiness. METHODS: The PET component is comprised of two detector heads, providing a 20 × 10 × 10 cm3 scanner field-of-view. The detector provides time-of-flight (TOF) measurement and is comprised of 32×32 LYSO arrays of 1.5 × 1.5 × 15 mm3 crystals coupled to multi-anode PMTs. Custom waveform-sampling electronics ensures high spatial and timing resolution with minimal deadtime. The DBT component is a state-of-the-art system which employs 2D x-ray tube and detector motion for improved contrast and resolution. Phantoms appropriate for breast imaging were imaged to assess spatial resolution, image quantitation, count-rate capability, and co-registration accuracy. First human imaging was performed in volunteers with estrogen-receptor-positive (ER+) breast cancer. A five-minute BPET-DBT scan using 18F-fluoroestradiol was acquired and compared with a whole-body PET scan. RESULTS: System timing resolution of 425 ps and energy resolution of 16% were measured. Spatial resolution measurements showed an in-plane (parallel to the detector) resolution of 2 mm and demonstrates the ability to resolve 1.6 mm rods in the micro-deluxe hot rod phantom. TOF reconstruction combined with image-based resolution modeling mitigates artifacts typical in scanners with incomplete angular coverage and enables good out-of-plane (orthogonal to detector) discrimination of the 2.4 mm rods. Count-rate measurements confirm low scanner dead-time, with sufficient count-rate capability for clinical use. CONCLUSIONS: We successfully constructed and tested a BPET scanner and integrated it with DBT. BPET scanner performance was characterized, and imaging capabilities relevant for clinical imaging have been highlighted. Images from a patient with ER+ breast cancer show clear tumor delineation and visualization of heterogeneous uptake, as also seen with WB-PET. This approach offers a promising strategy for improved treatment planning and outcomes in breast cancer care.