Measurement of the coincidence response of very thin BGO crystals

Conference · Mon Aug 01 00:00:00 EDT 1994 · IEEE Transactions on Nuclear Science (Institute of Electrical and Electronics Engineers); (United States)

OSTI ID:6838657

Murthy, K; Thompson, C J ^[1]; Weinberg, I N ^[2]; Mako, F M ^[3]

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1. McGill Univ., Montreal, Quebec (Canada). Montreal Neurological Inst.
2. F M Technologies Inc., Fairfax, VA (United States) Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Radiology
3. F M Technologies Inc., Fairfax, VA (United States)

More then half the 511 keV photons in BGO crystals undergo Compton scattering at least once prior to photo-electric interaction within the detector. In a PET scanner, this can result in mis-positioning of annihilation events. As crystal dimensions are made smaller, the fraction of mispositioned events increases. The authors have studied the coincidence aperture function (CAF) of 25 mm [times] 10 mm BGO crystals with thicknesses varying from 1 mm to 3 mm in steps of 0.5 mm. By sandwiching the active crystal between two other BGO crystals not in contact with the photomultiplier, the authors have studied the effect of Compton scatter upon CAF. By allowing the annihilation photons to be incident along the 25 mm axis and the 10 mm axis, the authors have studied the effect of detector depth upon the CAF, with and without Compton Scatter. The CAF increases linearly with crystal width, ranging from 1.3 mm for the 1 mm wide crystal to 2.15 for 3 mm crystal. The lines joining the FWHM of the CAFs as a function of crystal width appear to converge indicating that no further improvement in resolution can be achieved by reducing crystal width. The CAFs for 10 mm and 25 mm long crystals without Compton scatter is essentially the same. The presence of neighboring crystals results in an increase in the CAF which is greater for long crystals compared with short ones of the same width. Using 1 mm wide and 10 mm long crystals sandwiched between two uncoupled BGO crystals, the authors have achieved spatial resolution of 1.64 mm FWHM for a PMT separation of 34 cm. Recent experiments with PMT separation of 11.5 cm have yielded 1.23 mm FWHM CAF in the same setup.

• OSTI ID: 6838657
• Report Number(s): CONF-931051-; CODEN: IETNAE
• Journal Information: IEEE Transactions on Nuclear Science (Institute of Electrical and Electronics Engineers); (United States), Vol. 41:4PT1; Conference: NSS-MIC '93: nuclear science symposium and medical imaging conference, San Francisco, CA (United States), 30 Oct - 6 Nov 1993; ISSN 0018-9499
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BGO DETECTORS
PERFORMANCE
POSITRON CAMERAS
POSITRON COMPUTED TOMOGRAPHY
SPATIAL RESOLUTION
IMAGE PROCESSING
OPTIMIZATION
CAMERAS
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
EMISSION COMPUTED TOMOGRAPHY
GAMMA CAMERAS
MEASURING INSTRUMENTS
PROCESSING
RADIATION DETECTORS
RESOLUTION
SCINTILLATION COUNTERS
SOLID SCINTILLATION DETECTORS
TOMOGRAPHY
550601* - Medicine- Unsealed Radionuclides in Diagnostics