DocumentCode :
1181840
Title :
Collimator optimization for detection and quantitation tasks: application to gallium-67 imaging
Author :
Moore, Stephen C. ; Kijewski, Marie Foley ; Fakhri, G.E.
Author_Institution :
Dept. of Radiol., Brigham & Women´´s Hosp. & Harvard Med. Sch., Boston, MA, USA
Volume :
24
Issue :
10
fYear :
2005
Firstpage :
1347
Lastpage :
1356
Abstract :
We describe a new approach to the problem of collimator optimization in nuclear medicine; our methodology is illustrated for the challenging case of gallium-67 imaging. Collimator-design methods based on empirical rules, such as specification of an allowable level of single-septal penetration (SSP) at a fixed energy, are especially inappropriate for radionuclides characterized by an abundance of high-energy contaminant photons that scatter in the patient, collimator, and/or detector before detection within one of a few photopeak energy windows. Lead X-rays produced in the collimator are an additional source of contamination. We designed optimal collimation for 67Ga based on relevant clinical imaging tasks and a realistic simulation of photon transport in a phantom, collimator, and detector. Collimator designs were compared on the basis of performance in lesion detection, as predicted by a three-channel Hotelling observer (CHO), as well as in tumor and background activity estimation (EST), quantified by task-specific signal-to-noise ratios (SNRs). The optimal values of collimator lead content were 22.0 and 23.8 g/cm2, respectively, for CHO and EST, while the optimal geometric resolution values were 1.8 and 1.6 cm full-width at half-maximum (FWHM), respectively, at a distance of 23.5 cm. The resolution of a commercially available medium-energy low-penetration collimator (MELP) is 1.9 cm FWHM at this distance. The optimal values for SSP at 300 keV were 7.3% and 5.8% based on CHO and EST, respectively, compared to 5.2% for the MELP collimator. Compared with the commercial MELP collimator, the 67Ga collimator optimized for tumor detection or activity estimation tasks provided improved geometric spatial resolution with reduced geometric efficiency and, surprisingly, allowed an increased level of single-septal penetration.
Keywords :
collimators; optimisation; phantoms; radioisotope imaging; tumours; 23.5 cm; 300 keV; background activity estimation; collimator optimization; gallium-67 imaging; high-energy contaminant photons; lesion detection; nuclear medicine; phantom; radionuclides; single-septal penetration; three-channel Hotelling observer; tumor; Contamination; Detectors; Electromagnetic scattering; Imaging phantoms; Nuclear medicine; Optical collimators; Optical imaging; Optimization methods; Particle scattering; X-ray scattering; Collimator; Ga-67; SPECT; detection; estimation; scintigraphy; Citrates; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Gallium; Humans; Image Enhancement; Image Interpretation, Computer-Assisted; Models, Biological; Neoplasms; Phantoms, Imaging; Positron-Emission Tomography; Radiopharmaceuticals; Reproducibility of Results; Sensitivity and Specificity;
fLanguage :
English
Journal_Title :
Medical Imaging, IEEE Transactions on
Publisher :
ieee
ISSN :
0278-0062
Type :
jour
DOI :
10.1109/TMI.2005.857211
Filename :
1514553
Link To Document :
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