Ideal flood field images for SPECT uniformity correction
Since as little as 2.5% camera non-uniformity can cause disturbing artifacts in SPECT imaging, the ideal flood field images for uniformity correction would be made with the collimator in place using a perfectly uniform sheet source. While such a source is not realizable the equivalent images can be generated by mapping the activity distribution of a Co-57 sheet source and correcting subsequent images of the source with this mapping. Mapping is accomplished by analyzing equal-time images of the source made in multiple precisely determined positions. The ratio of counts detected in the same region of two images is a measure of the ratio of the activities of the two portions of the source imaged in that region. The activity distribution in the sheet source is determined from a set of such ratios. The more source positions imaged in a given time, the more accurate the source mapping, according to results of a computer simulation. A 1.9 mCi Co-57 sheet source was shifted by 12 mm increments along the horizontal and vertical axis of the camera face to 9 positions on each axis. The source was imaged for 20 min in each position and 214 million total counts were accumulated. The activity distribution of the source, relative to the center pixel, was determined for a 31 x 31 array. The integral uniformity was found to be 2.8%. The RMS error for such a mapping was determined by computer simulation to be 0.46%. The activity distribution was used to correct a high count flood field image for non-uniformities attributable to the Co-57 source. Such a corrected image represents camera plus collimator response to an almost perfectly uniform sheet source.
- Research Organization:
- Indiana Univ. School of Medicine, Indianapolis, IN
- OSTI ID:
- 6861693
- 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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62 RADIOLOGY AND NUCLEAR MEDICINE
BETA DECAY RADIOISOTOPES
CAMERAS
CAT SCANNING
COBALT 57
COBALT ISOTOPES
COLLIMATORS
COMPUTERIZED TOMOGRAPHY
DATA COVARIANCES
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
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ELECTRON CAPTURE RADIOISOTOPES
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GAMMA CAMERAS
IMAGE PROCESSING
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INTERMEDIATE MASS NUCLEI
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MASSLESS PARTICLES
NUCLEI
ODD-EVEN NUCLEI
OPTIMIZATION
PHOTONS
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SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
TOMOGRAPHY