Evaluation of the PETsys TOFPET2 ASIC in multi-channel coincidence experiments
Tóm tắt
Aiming to measure the difference in arrival times of two coincident γ-photons with an accuracy in the order of 200ps, time-of-flight positron emission tomography systems commonly employ silicon photomultipliers (SiPMs) and high-resolution digitization electronics, application specific integrated circuits (ASICs). This work evaluates the performance of the TOFPET2 ASIC, released by PETsys Electronics S.A. in 2017, dependent on its configuration parameters in multi-channel coincidence measurements. SiPM arrays fabricated by different vendors (KETEK, SensL, Hamamatsu, Broadcom) were tested in combination with the ASIC. Scintillator arrays featuring different reflector designs and different configurations of the TOFPET2 ASIC software parameters were evaluated. The benchtop setup used is provided with the TOFPET2 ASIC evaluation kit by PETsys Electronics S.A. Compared to existing studies featuring the TOFPET2 ASIC, multi-channel performance results dependent on a larger set of ASIC configuration parameters were obtained that have not been reported to this extend so far. The ASIC shows promising CRTs down to 219.9 ps in combination with two Hamamatsu S14161-3050-HS-08 SiPM arrays (128 channels read out, energy resolution 13.08%) and 216.1 ps in combination with two Broadcom AFBR-S4N44P643S SiPM arrays (32 channels read out, energy resolution 9.46%). The length of the trigger delay of the dark count suppression scheme has an impact on the ASIC performance and can be configured to further improve the coincidence resolution time. The integrator gain configuration has been investigated and allows an absolute improvement of the energy resolution by up to 1% at the cost of the linearity of the energy spectrum. Measuring up to the time-of-flight performance of state-of-the-art positron emission tomography (ToF-PET) systems while providing a uniform and stable readout for multiple channels at the same time, the TOFPET2 ASIC is treated as promising candidate for the integration in future ToF-PET systems.
Tài liệu tham khảo
Bailey DL, Townsend DW, Valk PE, Maisey MN. Positron Emission Tomography: Basic Sciences, 1st ed: Springer Science and Business Media; 2005. https://doi.org/10.1007/b136169.
Phelps ME. PET: Physics, Instrumentation, and Scanners, 1st ed: Springer; 2006. https://doi.org/10.1007/0-387-34946-4.
Vaquero JJ, Kinahan P. Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems. Annu Rev Biomed Eng. 2015; 17(1):385–414. https://doi.org/10.1146/annurev-bioeng-071114-040723.
Surti S, Karp JS. Advances in time-of-flight PET. Phys Med. 2016; 32(1):12–22. https://doi.org/10.1016/j.ejmp.2015.12.007.
Vandenberghe S, Mikhaylova E, D’hoe E, Mollet P, Karp J. Recent developments in time-of-flight PET. EJNMMI Phys. 2016; 3(1). https://doi.org/10.1186/s40658-016-0138-3.
Conti M. Focus on time-of-flight PET: the benefits of improved time resolution. Eur J Nucl Med Mol Imaging. 2011; 38(6):1147–57. https://doi.org/10.1007/s00259-010-1711-y.
Gundacker S, Knapitsch A, Auffray E, Jarron P, Meyer T, Lecoq P. Time resolution deterioration with increasing crystal length in a TOF-PET system. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2014; 737:92–100. https://doi.org/10.1016/j.nima.2013.11.025.
Surti S. Update on time-of-flight PET imaging. J Nucl Med. 2015; 56(1):98–105. https://doi.org/10.2967/jnumed.114.145029.
Spencer BA, Berg E, Schmall JP, Omidvari N, Leung EK, Abdelhafez YG, Tang S, Deng Z, Dong Y, Lv Y, Bao J, Liu W, Li H, Jones T, Badawi RD, Cherry SR. Performance evaluation of the uexplorer total-body pet/ct scanner based on nema nu 2-2018 with additional tests to characterize long axial field-of-view pet scanners. J Nucl Med. 2020. https://doi.org/10.2967/jnumed.120.250597.
UC Davis. Explorer Product Website; 2019. https://explorer.ucdavis.edu/about-explorer/. Accessed 16 Jan 2019.
Schug D, Wehner J, Dueppenbecker PM, Weissler B, Gebhardt P, Goldschmidt B, Salomon A, Kiessling F, Schulz V. PET performance and MRI compatibility evaluation of a digital, ToF-capable PET/MRI insert equipped with clinical scintillators. Phys Med Biol. 2015; 60(18):7045. https://doi.org/10.1088/0031-9155/60/18/7045.
Bugalho R, Di Francesco A, Ferramacho L, Leong C, Niknejad T, Oliveira L, Pacher L, Rolo M, Rivetti A, Silveira M, et al. Experimental results with TOFPET2 ASIC for time-of-flight applications. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2017. https://doi.org/10.1016/j.nima.2017.11.034.
Chen H, Briggl K, Fischer P, Gil A, Harion T, Munwes Y, Ritzert M, Schimansky D, Schultz-Coulon H-C, Shen W, et al.A dedicated readout ASIC for time-of-flight positron emission tomography using silicon photomultiplier (SiPM). In: Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014 IEEE. IEEE: 2014. p. 1–5. https://doi.org/10.1109/NSSMIC.2014.7431045.
Rolo MD, Bugalho R, Goncalves F, Rivetti A, Mazza G, Silva JC, Silva R, Varela J. A 64-channel ASIC for TOFPET applications. In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC). IEEE: 2012. p. 1460–4. https://doi.org/10.1109/NSSMIC.2012.6551353.
Nemallapudi MV, Gundacker S, Lecoq P, Auffray E, Ferri A, Gola A, Piemonte C. Sub-100 ps coincidence time resolution for positron emission tomography with LSO:Ce codoped with Ca. Phys Med Biol. 2015; 60(12):4635. https://doi.org/10.1088/0031-9155/60/12/4635.
Sarasola I, Nemallapudi MV, Gundacker S, Sánchez D, Gascón D, Rato P, Marín J, Auffray E. A comparative study of the time performance between NINO and FlexToT ASICs. J Instrum. 2017; 12:04016. https://doi.org/10.1088/1748-0221/12/04/P04016.
Gundacker S, Turtos RM, Auffray E, Paganoni M, Lecoq P. High-frequency SiPM readout advances measured coincidence time resolution limits in TOF-PET. Phys Med Biol. 2019; 64(5):055012. https://doi.org/10.1088/1361-6560/aafd52.
Lecoq P. Development of new scintillators for medical applications. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2016; 809:130–9. https://doi.org/10.1016/j.nima.2015.08.041.
Borghi G, Tabacchini V, Schaart DR. Towards monolithic scintillator based TOF-PET systems: practical methods for detector calibration and operation. Phys Med Biol. 2016; 61(13):4904–28. https://doi.org/10.1088/0031-9155/61/13/4904.
Müller F, Schug D, Hallen P, Grahe J, Schulz V. A novel DOI Positioning Algorithm for Monolithic Scintillator Crystals in PET based on Gradient Tree Boosting. IEEE Trans Radiat Plasma Med Sci. 2019; 3(4):465–74. https://doi.org/10.1109/TRPMS.2018.2884320.
Müller F, Schug D, Hallen P, Grahe J, Schulz V. Gradient Tree Boosting-Based Positioning Method for Monolithic Scintillator Crystals in Positron Emission Tomography. IEEE Trans Radiat Plasma Med Sci. 2018; 2(5):411–21. https://doi.org/10.1109/TRPMS.2018.2837738.
Peng P, Judenhofer MS, Cherry SR. Compton PET: a layered structure PET detector with high performance. Phys Med Biol. 2019. https://doi.org/10.1088/1361-6560/ab1ba0. http://iopscience.iop.org/10.1088/1361-6560/ab1ba0.
Gross-Weege N, Schug D, Hallen P, Schulz V. Maximum likelihood positioning algorithm for high-resolution pet scanners. Med Phys. 2016; 43:3049–61. https://doi.org/10.1118/1.4950719.
Schug D, Weissler B, Gebhardt P, Schulz V. Crystal Delay and Time Walk Correction Methods for Coincidence Resolving Time Improvements of a Digital-Silicon-Photomultiplier-Based PET/MRI Insert. IEEE Trans Radiat Plasma Med Sci. 2017; 1(2):178–90. https://doi.org/10.1109/TNS.2017.2654920.
Bisogni MG, Morrocchi M. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2016; 809:140–8. https://doi.org/10.1016/j.nima.2015.09.114.
Bisogni MG, Guerra AD, Belcari N. Medical applications of silicon photomultipliers. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2019; 926:118–28. https://doi.org/10.1016/j.nima.2018.10.175.
Weissler B, Gebhardt P, Lerche CW, Wehner J, Solf T, Goldschmidt B, Mackewn JE, Marsden PK, Kiessling F, Perkuhn M, Heberling D, Schulz V. MR compatibility aspects of a silicon photomultiplier-based PET/RF insert with integrated digitisation. Phys Med Biol. 2014; 59(17):5119–39. https://doi.org/10.1088/0031-9155/59/17/5119.
Weissler B, Gebhardt P, Dueppenbecker PM, Wehner J, Schug D, Lerche CW, Goldschmidt B, Salomon A, Verel I, Heijman E, Perkuhn M, Heberling D, Botnar RM, Kiessling F, Schulz V. A digital preclinical pet/mri insert and initial results. IEEE Trans Med Imaging. 2015; 34(11):2258–70. https://doi.org/10.1109/TMI.2015.2427993.
Frach T, Prescher G, Degenhardt C, de Gruyter R, Schmitz A, Ballizany R. The digital silicon photomultiplier — principle of operation and intrinsic detector performance. In: 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC): 2009. p. 1959–65. https://doi.org/10.1109/NSSMIC.2009.5402143.
Haemisch Y, Frach T, Degenhardt C, Thon A. Fully Digital Arrays of Silicon Photomultipliers (dSiPM) – a Scalable Alternative to Vacuum Photomultiplier Tubes (PMT). Phys Procedia. 2012; 37:1546–60. https://doi.org/10.1016/j.phpro.2012.03.749.
Schaart DR, Charbon E, Frach T, Schulz V. Advances in digital sipms and their application in biomedical imaging. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2015; 809:31–52. https://doi.org/10.1016/j.nima.2015.10.078.
Hallen P, Schug D, Weißler B, Gebhardt P, Salomon A, Kiessling F, Schulz V. PET performance evaluation of the small-animal Hyperion II PET/MRI insert based on the NEMA NU-4 standard. Biomed Phys Eng Express. 2018; 4. https://doi.org/10.1088/2057-1976/aae6c2.
Schug D, Lerche C, Weissler B, Gebhardt P, Goldschmidt B, Wehner J, Dueppenbecker PM, Salomon A, Hallen P, Kiessling F, Schulz V. Initial PET performance evaluation of a preclinical insert for PET/MRI with digital SiPM technology. Phys Med Biol. 2016; 61(7):2851. https://doi.org/10.1088/0031-9155/61/7/2851.
Omidvari N, Topping G, Cabello J, Paul S, Schwaiger M, Ziegler S. MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system. Phys Med Biol. 2018; 63(9). https://doi.org/10.1088/1361-6560/aab9d1.
Omidvari N, Cabello J, Topping G, Schneider FR, Paul S, Schwaiger M, Ziegler SI. PET performance evaluation of MADPET4: a small animal PET insert for a 7 T MRI scanner. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2017; 62(22):8671–92. https://doi.org/10.1016/j.nima.2017.11.097.
Ahmad S, Fleury J, de l Taille C, Seguin-Moreau N, Dulucq F, Martin-Chassard G, Callier S, Thienpont D, Raux L. Triroc: A Multi-Channel SiPM Read-Out ASIC for PET/PET-ToF Application. IEEE Trans Nucl Sci. 2015; 62(3):664–8. https://doi.org/10.1109/TNS.2015.2397973.
Ahmad S, de l Taille C, Fleury J, Seguin-Moreau N, Raux L, Callier S, Martin-Chassard G, Dulucq F, Thienpont D. Triroc, a Versatile 64-Channel SiPM Readout ASIC for Time-of-Flight PET. IEEE Nucl Sci Symp Med Imaging Conf Room-Temperature Semicond Detector Work (NSS/MIC/RTSD). 2016. https://doi.org/10.1109/NSSMIC.2016.8069882.
Sportelli G, Ahmad S, Belcari N, Bisogni MG, Camarlinghi N, Pasquale AD, Dussoni S, Fleury J, Morrochi M, Zaccaro E, Guerra AD. The TRIMAGE PET Data Acquisition System: Initial Results. IEEE Trans Radiat Plasma Med Sci. 2017; 1(2):168–77. https://doi.org/10,1109/TNS.2016.2633237.
Shen W, Briggl K, Chen H, Fischer P, Gil A, Harion T, Ritzert M, Schultz-Coulon HC. STiC – a Mixed Mode Chip for SiPM ToF Applications. 2012 IEEE Nucl Sci Symp Med Imag Conf Rec (NSS/MIC). 2012; N14-37:877–81.
Corsi F, Foresta M, Marzocca C, Matarrese G, Guerra AD. ASIC development for SiPM readout. J Instrum. 2009; 4. https://doi.org/10.1088/1748-0221/4/03/P03004.
Orita T, Koyama A, Yoshino M, Kamada K, Yoshikawa A, Shimazoe K, Sugawara H. The current mode Time-over-Threshold ASIC for a MPPC module in a TOF-PET system. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2017. https://doi.org/10.1016/j.nima.2017.11.097.
Fleury J. PETIROC2A : New measurement results on fast ToF SiPM read-out chip. Beijing: Talk at TIPP 2017; 2017.
Fischer P, Peric I, Ritzert M, Koniczek M. Fast Self Triggered Multi Channel Readout ASIC for Time- and Energy Measurement. IEEE Trans Nucl Sci. 2009; 53(3):1153–8. https://doi.org/10.1109/TNS.2008.2008807.
Fischer P, Peric I, Ritzert M, Solf T. Multi-Channel Readout ASIC for ToF-PET. In: 2006 IEEE Nuclear Science Symposium Conference Record, vol. 4: 2006. p. 2523–7. https://doi.org/10.1109/NSSMIC.2006.354423.
Piemonte C, Gola A, Tarolli A, Fisher P, Ritzert M, Schulz V, Solf T. Performance of FBK SiPMs coupled to PETA3 read-out ASIC for PET application. Elsevier Nucl Inst Methods Phys Res A. 2012; 718:345–6. https://doi.org/10.1016/j.nima.2012.10.012.
Sacco I, Fischer P, Ritzert M. PETA4: a multi-channel TDC/ADC ASIC for SiPM readout. J Instrum. 2013; 8. https://doi.org/10.1088/1748-0221/8/12/C12013.
Sacco I, Dohle R, Fischer P, Piemonte C, Ritzert M. A compact, high-density gamma-detection module for Time-of-Flight measurements in PET applications. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2015; 824. https://doi.org/10.1016/j.nima.2015.11.004.
Schug D, Gebhardt P, Weissler B, Gross-Weege N, Dey T, Schulz V. Measurements with a PET Coincidence Setup Based on the PETA5 ASIC and FBK RGB-HD SiPMs. In: 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC). IEEE: 2017. p. 1–3. https://doi.org/10.1109/NSSMIC.2017.8532761.
PETsys Electronics S.A.TOFPET 2 SiPM readout ASIC (rev.2). PETsys Electronics SA, Taguspark - Lisboa Science and Technology Park, Edificio Tecnologia I, 26, 2740-257 PORTO SALVO, Portugal. 2018. http://www.petsyselectronics.com/.
PETsys Electronics S.A.TOFPET ASIC v1 – Short Data Sheet (Rev. 1.2). PETsys Electronics SA, Taguspark - Lisboa Science and Technology Park, Edificio Tecnologia I, 26, 2740-257 PORTO SALVO, Portugal. 2014. http://www.petsyselectronics.com/.
PETsys Electronics S.A.Website; 2019. http://www.petsyselectronics.com/. Accessed 27 Feb 2019.
Schug D, Nadig V, Weissler B, Gebhardt P, Schulz V. Initial Measurements with the PETsys TOFPET2 ASIC Evaluation Kit and a Characterization of the ASIC TDC. IEEE Trans Radiat Plasma Med Sci. 2018:1–1. https://doi.org/10.1109/TRPMS.2018.2884564.
Bugalho R, Francesco AD, Ferramacho L, Leong C, Niknejad T, Oliveira L, Rolo M, Silva JC, Silva R, Silveira M, Tavernier S, Varela J. Experimental characterization of the TOFPET2 ASIC. J Instrum. 2019; 14(03):03029–03029. https://doi.org/10.1088/1748-0221/14/03/p03029.
Di Francesco A, Bugalho R, Oliveira L, Pacher L, Rivetti A, Rolo M, Silva J, Silva R, Varela J. TOFPET2: a high-performance ASIC for time and amplitude measurements of SiPM signals in time-of-flight applications. J Instrum. 2016; 11(03):03042. https://doi.org/10.1088/1748-0221/11/03/C03042.
Li M, Abbaszadeh S. Depth-of-interaction study of a dual-readout detector based on TOFPET2 application-specific integrated circuit. Phys Med Biol. 2019. https://doi.org/10.1088/1361-6560/ab3866.
Lamprou E, Gonzalez AJ, Sanchez F, Benlloch JM. Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs. Phys Med. 2020; 70:10–8. https://doi.org/10.1016/j.ejmp.2019.12.004.
Lamprou E, Gonzalez-Montoro A, Canizares G, Ilisie V, Barrio J, Sanchez F, Gonzalez AJ, Benlloch JM. Characterization of TOF-PET Detectors Based on Monolithic Blocks and ASIC-Readout. arXiv preprint arXiv:1806.08715. 2018.
PETsys Electronic S.A.PETsys TOF ASIC Evaluation Kit (Flyer), v15 ed. 2018. http://www.petsyselectronics.com/. Accessed Oct 2018.
Nadig V, Weissler B, Radermacher H, Schulz V, Schug D. Investigation of the Power Consumption of the PETsys TOFPET2 ASIC. IEEE TRPMS Spec Issue 2019. 2019. https://doi.org/10.1109/TRPMS.2019.2955032.
PETsys Electronics SA.TOFPET2 ASIC Evaluation Kit - Hardware User Guide (v1.2), v1.2 ed. 2018. http://www.petsyselectronics.com/. Accessed May 2018.
PETsys Electronics SA.TOFPET2 ASIC Evaluation Kit - Software User Guide V2018.04, v2018.04 ed. 2018. http://www.petsyselectronics.com/. Accessed Apr 2018.
PETsys Electronics S.A.Personal Communication. Emails, conferences. 2018.
Lecoq P. Pushing the limits in time-of-flight pet imaging. IEEE Trans Radiat Plasma Med Sci. 2017; 1(6):473–85. https://doi.org/10.1109/TRPMS.2017.2756674.
Burgess D, Tervo R. Background estimation for gamma-ray spectrometry. Nucl Inst Methods Phys Res. 1983; 214:431–4. https://doi.org/10.1016/0167-5087(83)90612-9.
Morháč M, Kliman J, Matoušek V, Veselský M, Turzo I. Background elimination methods for multidimensional coincidence γ-ray spectra. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 1997; 401(1):113–32. https://doi.org/10.1016/S0168-9002(97)01023-1.
Ryan CG, Clayton E, Griffin WL, Sie SH, Cousens DR. SNIP, a statistics-sensitive background treatment for the quantitative analysis of PIXE spectra in geoscience applications. NIM B. 1988; 34(3):396–402. https://doi.org/10.1016/0168-583X(88)90063-8.
Morháč M, Kliman J, Matoušek V, Veselský M, Turzo I. Identification of peaks in multidimensional coincidence γ-ray spectra. Nucl Inst Methods Phys Res A. 2000; 443:108–25. https://doi.org/10.1016/S0168-9002(99)01005-0.
PETsys Electronics SA.TOFPET2 ASIC Evaluation Kit - Software User Guide V2019.01, v2019.01 ed. 2019. http://www.petsyselectronics.com/. Accessed Jan 2019.
Huizenga J, Seifert S, Schreuder F, Dam HT, Dendooven P, Loehner H, Vinke R, Schaart D. A fast preamplifier concept for sipm-based time-of-flight pet detectors. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2012; 695:379–84. https://doi.org/10.1016/j.nima.2011.11.012.
Acerbi F, Gundacker S. Understanding and simulating sipms. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2019; 926:16–35. https://doi.org/10.1016/j.nima.2018.11.118.
Goertzen AL, Van Elburg D. Performance characterization of mppc modules for tof-pet applications. IEEE Trans Radiat Plasma Med Sci. 2019; 3(4):475–82. https://doi.org/10.1109/TRPMS.2018.2885439.
Belcari N, Bisogni MG, Camarlinghi N, Carra P, Cerello P, Morrocchi M, Patera A, Sportelli G, Del Guerra A. Design and detector performance of the pet component of the trimage pet/mr/eeg scanner. IEEE Trans Radiat Plasma Med Sci. 2019; 3(3):292–301. https://doi.org/10.1109/TRPMS.2019.2906407.
Siemens Healthcare. Biograph Vision Product Website. Siemens Healthcare GmbH, Henkestr. 127, 91052 Erlangen, Germany. https://www.siemens-healthineers.com/molecular-imaging/pet-ct/biograph-vision. Accessed 04 Sept 2019.
Siemens Healthineers - Biograph Vision. Website. 2019. https://www.siemens-healthineers.com/nl/molecular-imaging/pet-ct/biograph-vision. Accessed 12 Nov 2019.
Vandenberghe S, Marsden PK. PET-MRI: a review of challenges and solutions in the development of integrated multimodality imaging. Phys Med Biol. 2015; 60(4). https://doi.org/10.1088/0031-9155/60/4/R115.
Wehner J, Weissler B, Dueppenbecker PM, Gebhardt P, Goldschmidt B, Schug D, Kiessling F, Schulz V. MR-compatibility assessment of the first preclinical PET-MRI insert equipped with digital silicon photomultipliers. Phys Med Biol. 2015; 60(6):2231–55. https://doi.org/10.1088/0031-9155/60/6/2231.
Wehner J, Weissler B, Dueppenbecker P, Gebhardt P, Schug D, Ruetten W, Kiessling F, Schulz V. PET/MRI insert using digital SiPMs: Investigation of MR-compatibility. Nucl Inst Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip. 2014; 734:116–21. https://doi.org/10.1016/j.nima.2013.08.077.
KETEK GmbH. Product Data Sheet SiPM – Silicon Photomultiplier Array PA3325-WB-0808. 2017. https://www.ketek.net/. Accessed 10 Aug 2018.
SensL. J-Series - High PDE and Timing Resolution SiPM Sensors in a TSV Package. 2017. https://www.sensl.com/. Accessed 01 Aug 2018.
Hamamatsu. Product Flyer MPPC for scintillation S14160/S14161 series. 2017. https://www.hamamatsu.com/. Accessed 29 Oct 2018.
Broadcom. AFBR-S4N44P643 - 8x8 NUV-HD Silicon Photo Multiplier Array - Target Data Sheet. 2018. https://www.broadcom.com/. Accessed 29 Oct 2018.