High throughput detection chain for time domain optical mammography

Abstract

A novel detection chain, based on 8 Silicon Photomultipliers (forming a wide-area custom-made detection probe) and on a time-to-digital converter, was developed to improve the signal level in multi-wavelength (635-1060 nm) time domain optical mammography. The performances of individual components and of the overall chain were assessed using established protocols (BIP and MEDPHOT). The photon detection efficiency was improved by up to 3 orders of magnitude, and the maximum count rate level was increased by a factor of 10 when compared to the previous system, based on photomultiplier tubes and conventional time-correlated single-photon counting boards. In the estimate of optical parameters, the novel detection chain provides performances comparable to the previous system, widely validated in clinics, but with higher signal level, higher robustness, and at a lower price per channel, thus targeting important requirements for clinical applications.

Keywords: (030.5260) Photon counting; (040.6070) Solid state detectors; (170.3830) Mammography; (170.5280) Photon migration; (170.6510) Spectroscopy, tissue diagnostics; (170.6920) Time-resolved imaging.

Conflict of interest statement

The authors declare no conflicts of interest related to this article.

Figures

Fig. 1

Layout of the pre-existing instrument (top) and of the new detection chain (bottom). The red dashed line contours the set of components interested by the renewal process. The blue dashed line surrounds the detection elements and the green one the acquisition system.

Fig. 2

The 8-channel SiPM probe (left) with the black shield that covers the probe during operation (center), and the detail of the PCB (right).

Fig. 3

Layout diagram of the 8-channel SiPM probe. The dotted line delimits the active area, and the dashed line the package.

Fig. 4

Diffuse responsivity of the previous detection chain (red circles) and new detection chain (blue triangles) vs wavelength.

Fig. 5

a) Recorded DNL expressed in LSB. b) DNL effect on a DTOF raw curve (red) and the same curve processed with the proposed corrections A (blue) and B (yellow). The three curves are arbitrarily offset from one another for clarity.

Fig. 6

Overlapping of the IRFs at 3 different wavelengths at 10 MHz laser repetition rate. The dashed black line (slightly shifted upward for clarity) is the sum of the 3 IRFs.

Fig. 7

Stability test on the IRF integral number of counts Ntot (left) and first moment m1 (right). Ntot0 is the average integral after the end of the warm up period (5-9 hr). The dashed lines indicate the ranges of ± 0.5% (left) and ± 5 ps (right).

Fig. 8

Relative error vs relative count rate on the estimate of a) μa and b) μs′ using the TCSPC board (red circles) and the TDC (blue squares). The laser repetition rate was 10 MHz.

Fig. 9

Linearity plots reflecting the system linearity in a) absorption and b) scattering measurement; and coupling of c) scattering to absorption and d) absorption to scattering.