Geometry and surface treatment dependence of the light collection from LSO crystals

Huber, J.; Moses, W.W.; Andreaco, M.; Loope, M.; Melcher, Charles L.; Nutt, R.

doi:10.1016/s0168-9002(99)00766-4

Cited by 67 publications

(41 citation statements)

References 10 publications

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“…The crystals were chemically etched according to standard processes, 44 separated with an ESR reflector (3M, MN) and had polished surfaces at the readout faces (Agile Technologies, TN). The crystals and reflectors were glued to each other using an optical adhesive (OP-20, Dymax, Torrington, CT) without an air gap.…”

Section: B Detector Setupmentioning

confidence: 99%

Development of a novel depth of interaction PET detector using highly multiplexed G‐APD cross‐strip encoding

Kolb¹,

Parl²,

Mantlik³

et al. 2014

Medical Physics

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Purpose: The aim of this study was to develop a prototype PET detector module for a combined small animal positron emission tomography and magnetic resonance imaging (PET/MRI) system. The most important factor for small animal imaging applications is the detection sensitivity of the PET camera, which can be optimized by utilizing longer scintillation crystals. At the same time, small animal PET systems must yield a high spatial resolution. The measured object is very close to the PET detector because the bore diameter of a high field animal MR scanner is limited. When used in combination with long scintillation crystals, these small-bore PET systems generate parallax errors that ultimately lead to a decreased spatial resolution. Thus, we developed a depth of interaction (DoI) encoding PET detector module that has a uniform spatial resolution across the whole field of view (FOV), high detection sensitivity, compactness, and insensitivity to magnetic fields. Methods: The approach was based on Geiger mode avalanche photodiode (G-APD) detectors with cross-strip encoding. The number of readout channels was reduced by a factor of 36 for the chosen block elements. Two 12 × 2 G-APD strip arrays (25 μm cells) were placed perpendicular on each face of a 12 × 12 lutetium oxyorthosilicate crystal block with a crystal size of 1.55 × 1.55 × 20 mm. The strip arrays were multiplexed into two channels and used to calculate the x, y coordinates for each array and the deposited energy. The DoI was measured in step sizes of 1.8 mm by a collimated 18 F source. The coincident resolved time (CRT) was analyzed at all DoI positions by acquiring the waveform for each event and applying a digital leading edge discriminator. Results: All 144 crystals were well resolved in the crystal flood map. The average full width half maximum (FWHM) energy resolution of the detector was 12.8% ± 1.5% with a FWHM CRT of 1.14 ± 0.02 ns. The average FWHM DoI resolution over 12 crystals was 2.90 ± 0.15 mm. Conclusions: The novel DoI PET detector, which is based on strip G-APD arrays, yielded a DoI resolution of 2.9 mm and excellent timing and energy resolution. Its high multiplexing factor reduces the number of electronic channels. Thus, this cross-strip approach enables low-cost, high-performance PET detectors for dedicated small animal PET and PET/MRI and potentially clinical PET/MRI systems.

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Section: B Detector Setupmentioning

confidence: 99%

Development of a novel depth of interaction PET detector using highly multiplexed G‐APD cross‐strip encoding

Kolb¹,

Parl²,

Mantlik³

et al. 2014

Medical Physics

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“…Chemical etches have been similarly developed for BGO [12] and GSO [13] scintillators. We etch the LSO crystals in a 200˚C pyrophosphoric acid bath, followed by a cleaning process consisting of a 5 minute bath in boiling water, a 5 minute bath in concentrated HCl, a water rinse, and an ethanol cleaning [14,15]. The pyrophosphoric acid is prepared by heating concentrated phosphoric acid (85% in water) in an uncovered vessel until the water is driven off and its volume is reduced by at least 15%.…”

Section: A Surface Finishmentioning

confidence: 99%

“…We test the light collection of single LSO crystals using the experimental method previously described for studying light collection efficiency and pulse-height resolution (i.e., a mechanically collimated beam of 511 keV photons exciting a specific depth) [14]. Single crystals and multiple-crystal arrays are also tested using the experimental set-up shown in Fig.…”

Section: B Light Collection Characterizationmentioning

confidence: 99%

An LSO scintillator array for a PET detector module with depth of interaction measurement

Huber

Moses

Andreaco

et al. 2001

IEEE Trans. Nucl. Sci.

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Abstract--We present construction methods and performance results for a production scintillator array of 6 4 optically isolated, 3 mm x 3 mm x 30 mm sized LSO crystals. This scintillator array has been developed for a PET detector module consisting of the 8x8 LSO array coupled on one end to a single photomultiplier tube (PMT) and on the opposite end to a 64 pixel array of silicon photodiodes (PD). The PMT provides an accurate timing pulse and initial energy discrimination, the PD identifies the crystal of interaction, the sum provides a total energy signal, and the PD/(PD+PMT) ratio determines the depth of interaction (DOI). Unlike the previous LSO array prototypes, we now glue Lumirror reflector material directly onto 4 sides of each crystal to obtain an easily manufactured, mechanically rugged array with our desired depth dependence. With 511 keV excitation, we obtain a total energy signal of 3600 electrons, pulse-height resolution of 25% fwhm, and 6-15 mm fwhm DOI resolution.

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“…In collaboration with CTI, we developed a chemical etch procedure for our LSO crystals which produced similar light collection properties to the mechanical polish [4]. Since the PEM camera uses 2700 crystals, this saved us both time and money in production.…”

Section: Submitted To Physica Medica Lbnl 56612mentioning

confidence: 99%

“…It was more difficult than expected to produce similar light collection properties using a technique that could reasonably be used for production [4]. We ultimately settled on using 180 µm thick Lumirror glued on to the LSO using Epotek 301-2 epoxy (see Fig.…”

Section: Submitted To Physica Medica Lbnl 56612mentioning

confidence: 99%

A retrospective on the LBNL PEM project

et al. 2006

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We present a retrospective on the LBNL Positron Emission Mammography (PEM) project, looking back on our design and experiences. The LBNL PEM camera utilizes detector modules that are capable of measuring depth of interaction (DOI) and places them into 4 detector banks in a rectangular geometry. In order to build this camera, we had to develop the DOI detector module, LSO etching, Lumirror-epoxy reflector for the LSO array (to achieve optimal DOI), photodiode array, custom IC, rigid-flex readout board, packaging, DOI calibration and reconstruction algorithms for the rectangular camera geometry. We will discuss the highlights (good and bad) of these developments. I.) DESIGN AND DEVELOPMENT A.) Rectangular GeometryWe proposed a rectangular geometry (see Fig. 1) for our PEM camera assuming it would give a better efficiency to resolution tradeoff compared with a planar camera without depth of interaction. The rectangular geometry has a 3D solid angle coverage of 14% (when averaged over a 3″ x 3″ x 4″ imaging volume), which is higher than the 6% 3D solid angle coverage if the same number of detectors are configured (with the same image volume) in a planar geometry and higher than the 2% coverage of a typical 2D whole body PET camera. The rectangular geometry also has more complete angular sampling and more uniform coverage. The main difficulty with rectangular geometry is the penetration artifacts that degrade the spatial resolution if the interaction position

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Geometry and surface treatment dependence of the light collection from LSO crystals

Cited by 67 publications

References 10 publications

Development of a novel depth of interaction PET detector using highly multiplexed G‐APD cross‐strip encoding

Development of a novel depth of interaction PET detector using highly multiplexed G‐APD cross‐strip encoding

An LSO scintillator array for a PET detector module with depth of interaction measurement

A retrospective on the LBNL PEM project

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