SPECT imaging (140-364 keV): Influence of photon scattering and penetration on backprojected noise within tomographic plane

Conference · Sun Jan 01 04:00:00 EST 1984 · J. Nucl. Med.; (United States)

OSTI ID:7087998

Saw, C B; Clarke, L P; Hourani, M; Leong, L; Gentili, A; Sfakianakis, G; Serafini, A

In functional imaging with SPECT, differential uptake measurements within the tomographic plane are important. In many investigations, a distributed source or multiple sources within this plane are imaged. Backprojected noise may be significant, influencing differential uptake. Noise factors, apart from backprojection algorithms include photon scattering and collimator photon penetration. The influence of noise on differential uptake within the transverse plane was empirically evaluated for Tc-99m (140 keV), Ga-67, 993,184 keV) and I-131 (364 keV). A Picker International SPECT system, equipped with LEC and thick septa MEC and Iodine collimators (theoretical leakage for both<3%), was employed, to minimize photon penetration. A dual concentric ring (contrast) phantom was scanned and results of higher photon emitters compared to Tc-99m data. The activity in the outer/inner ring was 3:1, to critically evaluate noise within the transverse plane. Acquired counts were large (>20 x 10/sup 6/) to minimize statistical (unstructed) noise. For given acquisition and filter parameters, the noise level for Ga-67 was approximately three times greater than the Tc-99m, the latter attributed to scatter contribution to the lower energy window. This noise was non-uniform and degraded differential uptake measurements. The noise level for I-131 was approximately twice that for Tc-99m and was more uniform than Ga-67. The noise was attributed, in part, to photon penetration. Despite difference in collimation, data suggest that provided collimator sensitivity can be reduced, the limiting noise factor is photon scattering where multiple peaks are involved.

• Research Organization: Univ. of Miami, Miami, FL
• OSTI ID: 7087998
• Report Number(s): CONF-840619-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

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550602* -- Medicine-- External Radiation in Diagnostics-- (1980-)
62 RADIOLOGY AND NUCLEAR MEDICINE
ALGORITHMS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
COLLIMATORS
COMPUTERIZED TOMOGRAPHY
DATA ACQUISITION
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DIGITAL FILTERS
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTARY PARTICLES
EMISSION COMPUTED TOMOGRAPHY
ENERGY RANGE
GALLIUM 67
GALLIUM ISOTOPES
HOURS LIVING RADIOISOTOPES
IMAGE PROCESSING
INTERMEDIATE MASS NUCLEI
IODINE 131
IODINE ISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KEV RANGE
KEV RANGE 100-1000
MASSLESS PARTICLES
MATHEMATICAL LOGIC
MATHEMATICS
MOCKUP
NOISE
NUCLEI
ODD-EVEN NUCLEI
PHANTOMS
PHOTONS
PROCESSING
RADIOISOTOPES
SCATTERING
SENSITIVITY
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY
STATISTICS
STRUCTURAL MODELS
TECHNETIUM 99
TECHNETIUM ISOTOPES
TOMOGRAPHY
UPTAKE
YEARS LIVING RADIOISOTOPES