A feasibility study of photosensor charge signal transmission to preamplifier using long cable for development of hybrid PET-MRI
Several approaches for designing hybrid MR compatible PET. (a) Approach 1: Scintillation light transmission from crystal to photosensor. (b) Approach 2: Voltage signal transmission from amplifier to subsequent electronics. (c) Approach 3: Charge signal transmission from photosensor to preamplifier.
Images of the PET detector components: (a) LYSO crystal, (b) GAPD array, and (c) PET detector shielded from light.
Experimental setup to examine the effect of the cable length on both PET and MRI. (a) PET detector performance measurement outside MRI. A pair of PET detector modules was exposed by Na-22 point source and PET charge signals were transmitted to the preamplifier using FFC of 300 cm. (b) PET performance measurement inside the MRI. The PET detector modules were inserted into the MR bore between the RF coil and gradient coil (not displayed), while the preamplifier is located outside the MR bore ( line, away from the magnet isocenter).
Schematic diagram of the two types of PET detector modules to examine the temperature stability. (a) The LYSO, GAPD, and preamplifiers were located in the integrated housing box similar to approach 2 [Fig. 1(b)]. (b) PET detectors and preamplifiers were positioned in a separated housing box simulating approach 3 [Fig. 1(c)].
Representative output waveform of the preamplifier. The rise time obtained using the 300 cm cable (▲) was noticeably slower than the one obtained using the 10 cm cable (◻).
PET detector performance as a function of the cable length. (a) The changes in amplitude (◻) and area under the pulse (▲) obtained as a function of the cable length, 10–300 cm. (b) The changes in the rise time (◻) and fall time (▲) obtained as a function of the cable length, 10–300 cm.
(a) Representative energy and (b) time spectra of the PET detector acquired with a 10 cm (−) and 300 cm cable (◻)
PET detector performance as a function of the cable length. (a) The changes in the photopeak channel (◻) and energy resolution (▲) measured with different cable lengths, 10–300 cm. (b) The changes in time resolution (◻) measured with different cable lengths, 10–300 cm.
The changes in PET detector performance as a function of the cable length measured inside the MRI. (a) The energy and (b) time information of the PET detector with seven different cable lengths were acquired using no sequence (◼), GE (●), SE.T1 (▲), and SE.T2 MR imaging sequences.
Acquired MR phantom images and line profiles (a) without and (b) with the PET detector in the GE sequence .
(a) The energy and (b) time spectra of the PET module fabricated in the integrated housing box. The temperature of the housing box was increased from 26 up to after 1 h.
(a) The energy and (b) time spectra of the PET module fabricated in the separated housing box. The temperature of the housing box with the PET detector was unchanged.
Change in performance of the PET detector modules fabricated in the (a) integrated housing box and (b) separated housing box as a function of the elapsed time. Each data point was obtained at 10 min intervals for 1 h for each configuration.
Specifications of the three-sided buttable GAPD arrays used in this study.
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