A simulation of orientation dependent, global changes in camera sensitivity in ECT
ECT promises the abilities to: 1) observe radioisotope distributions in a patient without the summation of overlying activity to reduce contrast, and 2) measure quantitatively these distributions to further and more accurately assess organ function. Ideally, camera-based ECT systems should have a performance that is independent of camera orientation or gantry angle. This study is concerned with ECT quantitation errors that can arise from angle-dependent variations of camera sensitivity. Using simulated phantoms representative of heart and liver sections, the effects of sensitivity changes on reconstructed images were assessed both visually and quantitatively based on ROI sums. The sinogram for each test image was simulated with 128 linear digitization and 180 angular views. The global orientation-dependent sensitivity was modelled by applying an angular sensitivity dependence to the sinograms of the test images. Four sensitivity variations were studied. Amplitudes of 0% (as a reference), 5%, 10%, and 25% with a costheta dependence were studied as well as a cos2theta dependence with a 5% amplitude. Simulations were done with and without Poisson noise to: 1) determine trends in the quantitative effects as a function of the magnitude of the variation, and 2) to see how these effects are manifested in studies having statistics comparable to clinical cases. For the most realistic sensitivity variation (costheta, 5% ampl.), the ROIs chosen in the present work indicated changes of <0.5% in the noiseless case and <5% for the case with Poisson noise. The effects of statistics appear to dominate any effects due to global, sinusoidal, orientation-dependent sensitivity changes in the cases studied.
- Research Organization:
- Siemens Gammasonics, Inc., Des Plaines, IL
- OSTI ID:
- 6843573
- Report Number(s):
- CONF-840619-; TRN: 87-008871
- Journal Information:
- J. Nucl. Med.; (United States), Vol. 25:5; Conference: 31. annual meeting of the Society of Nuclear Medicine, Los Angeles, CA, USA, 5 Jun 1984
- Country of Publication:
- United States
- Language:
- English
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46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CAMERAS
SENSITIVITY ANALYSIS
EMISSION COMPUTED TOMOGRAPHY
HEART
LIVER
PHANTOMS
ACCURACY
AMPLITUDES
IMAGES
INCIDENCE ANGLE
NOISE
ORIENTATION
PATIENTS
QUANTITY RATIO
RADIOISOTOPES
SIMULATION
STATISTICS
BODY
CARDIOVASCULAR SYSTEM
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
DIGESTIVE SYSTEM
GLANDS
ISOTOPES
MATHEMATICS
MOCKUP
ORGANS
STRUCTURAL MODELS
TOMOGRAPHY
550602* - Medicine- External Radiation in Diagnostics- (1980-)
440101 - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments