In recent years, breast imaging using radiolabelled molecules has attracted significant interest. Our group has proposed a multi-pinhole molecular breast tomosynthesis (MP-MBT) scanner to obtain 3D functional molecular breast images at high resolutions. After conducting extensive optimisation studies using simulations, we here present a first prototype of MP-MBT and evaluate its performance using physical phantoms. The MP-MBT design is based on two opposing gamma cameras that can image a lightly compressed pendant breast. Each gamma camera consists of a 250 × 150 mm² detector equipped with a collimator with multiple pinholes focusing on a line. The NaI(Tl) gamma detector is a customised design with 3.5 mm intrinsic spatial resolution and high spatial linearity near the edges due to a novel light-guide geometry and the use of square PMTs. A volume-of-interest is scanned by translating the collimator and gamma detector together in a sequence that optimises count yield from the scan region. Derenzo phantom images showed that the system can reach 3.5 mm resolution for a clinically realistic ^99mTc activity concentration in an 11-minute scan, while in breast phantoms the smallest spheres visible were 6 mm in diameter for the same scan time. To conclude, the experimental results of the novel MP-MBT scanner showed that the setup had sub-centimetre breast tumour detection capability which might facilitate 3D molecular breast cancer imaging in the future.

Anger cameras based on monolithic NaI scintillators read out by an array of PMTs are predominant in planar gamma imaging and SPECT. However, position estimation of gamma interactions is usually severely degraded near the edges of the scintillator which can be extremely undesirable for applications like breast imaging. Here we propose a relatively cost-effective solution based on the use of scintillators with absorptive edges with an unconventional light-guide-PMT layout employing a maximum likelihood positioning algorithm. The basic design on which we aim to improve consists of a monolithic NaI(Tl) scintillator read out by 3 × 5 square PMTs (conventional layout, CL) that could be suitable for molecular breast imaging. To better detect gamma interactions near the crystal's critical edge, we tried different set-ups: we replaced the 5 large PMTs near the edge by 11 smaller PMTs (small-sensor layout, SSL); we emulated rectangular PMTs along the critical edge by inserting a row of 5 rectangular light-guides that direct the light toward square PMTs placed behind (shifted layout, SL); we inserted rectangular light-guides alternatingly, such that the PMTs are in an interlocking pattern (alternating shifted layout, ASL). The performance of our designs was tested with Monte Carlo simulations. Results showed that SSL, SL, and ASL gave better spatial resolution near the critical edge than CL (3.4, 3.6, and 4.1 mm near the edge compared with 5.3 mm for CL), and thus resulted in a larger usable detector area. To conclude, for applications where small dead edges are crucial, our designs may be cost-effective solutions.