Assessment of detector sensitivity and uniformity during SPECT rotation
The purpose of this research was to: a) evaluate variations in sensitivity and uniformity of SPECT detectors during 360/sup 0/ rotation, b) explore the causes of the variations and c) to discuss a correction procedure. A flood source consisting of a lucite disc 47.7 cm in diameter containing 3 microcuries of Co-57 was constructed. This source can be firmly attached to the uncollimated detector guaranteeing no detector-source geometry change during rotation. Four different SPECT cameras were tested. Measurements were obtained at 45/sup 0/ intervals throughout a 360/sup 0/ rotation, and repeated in 3 different orientations with respect to the earth's magnetic field. In one camera the effects of the direction and strength of induced magnetic fields were studied. All detectors showed cyclic rotational variations in sensitivity; in three cameras 6%, in one 3%. The amplitude and phase of the sensitivity variation curves and the variations in uniformity were unique for each camera. The detector's degree of variation did not change with regard to the earth's magnetic field orientation, but did change with regard to direction and strength of B fields. By measuring the gain of each PM tube at different detector positions, with and without B field influence, it was found that the gains shift were the cause of rotational changes in sensitivity and uniformity. By recording the variations of the detector during rotation at the clinical setting, a correction factor (either using software or hardware) can be applied to each angular image to improve SPECT resolution.
- Research Organization:
- UCSF - Saint Agnes Medical Center, Fresno, CA
- OSTI ID:
- 6931364
- Report Number(s):
- CONF-840619-
- Journal Information:
- J. Nucl. Med.; (United States), Journal Name: J. Nucl. Med.; (United States) Vol. 25:5; ISSN JNMEA
- Country of Publication:
- United States
- Language:
- English
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46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
550602* -- Medicine-- External Radiation in Diagnostics-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
AMPLITUDES
BETA DECAY RADIOISOTOPES
CAMERAS
COBALT 57
COBALT ISOTOPES
COMPUTER CODES
COMPUTERIZED TOMOGRAPHY
CORRECTIONS
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
ELECTRON CAPTURE RADIOISOTOPES
EMISSION COMPUTED TOMOGRAPHY
ESTERS
GEOMAGNETIC FIELD
INTERMEDIATE MASS NUCLEI
ISOTOPES
LUCITE
MAGNETIC FIELDS
MATERIALS
MEASURING INSTRUMENTS
MOTION
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC POLYMERS
ORIENTATION
PERFORMANCE TESTING
PETROCHEMICALS
PETROLEUM PRODUCTS
PLASTICS
POLYACRYLATES
POLYMERS
POLYVINYLS
RADIATION DETECTORS
RADIOISOTOPES
RESEARCH PROGRAMS
ROTATION
SENSITIVITY ANALYSIS
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
SYNTHETIC MATERIALS
TESTING
TOMOGRAPHY