Comparison of four depth-encoding PET detector modules with wavelength shifting (WLS) and optical fiber read-out

Abstract

We propose detectors for a laboratory positron emission tomography scanner specific for mouse imaging that utilizes fewer detectors and channels of electronics compared with existing designs. The detectors are based on lutetium oxyorthosilicate arrays, read out by orthogonal optical fibers placed on the top and bottom of the arrays. Depth of interaction (DOI) information is obtained from the ratio of the signals at either end of the array. Four different detector modules were evaluated, using different reflector materials and two types of optical fibers (wavelength shifting (WLS) fibers and clear optical fibers). The modules were compared in terms of flood histograms, energy resolution, DOI resolution and timing resolution. Energy resolution for single crystals at one irradiation depth was around 65% full-width half-maximum (FWHM). A DOI resolution of approximately 6 mm was obtained for the modules. Timing resolution was in the range of 5.1-7.8 ns. An array assembled in the laboratory and coupled with WLS fibers had the best DOI resolution; the same array with clear fibers had the best timing resolution and a commercially manufactured array and coupled with WLS fibers had the best energy resolution.

Development of a low cost planar detector for positron emission tomography

“…Good performances have been achieved reading out pixelated crystals with WLS bars [7]. Keeping the same WLS bar geometry means that the optimum pixel pitch is 1.5 Â 1.5 mm 2 .…”

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

“…There have been several efforts to address parallax errors in pinhole SPECT, including algorithm-based DOI modeling and correction, and the use of a curved fiber bundle to collimate light from a curved scintillator [5, 6]. In PET, various methods are used to correct DOI-related errors, including use of an avalanche photodiode at the front surface of a scintillator crystal to detect the entry point an annihilation photon [7], measuring the ratio of the signals of detectors placed at opposite ends of a scintillator crystal [8], and the use of a 3D scintillator crystal array [9]. …”

Optimizing PET DOI Resolution With Crystal Coating and Length

“…Dual-ended readout of crystal is required when the light sharing method is used to retrieve the DOI information [12]- [15]. Although a continuous sampling of the DOI is obtained, the price paid is an increase in the number of photodetector channels which can be reduced using optical fibers as proposed by [16].…”