Quantitative /sup 131/I SPECT with triple energy window Compton scatter correction

Dewaraja, Yuni K.; Li, Jia; Koral, Kenneth F.

doi:10.1109/23.737672

Cited by 34 publications

(18 citation statements)

References 12 publications

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“…Here is defined as the ratio of the background activity concentration in the cylindrical phantom over the activity concentration in the target. In contrast, in previous phantom measurements, we observed that the total count for a fixed-size spherical target changed when the level of the background activity changed [4]. Our images were reconstructed by a regularized algorithm (SAGE) without detector response [5], [6] and a fixed-size VoI determined from computed tomography (CT) was employed.…”

Section: Introductionmentioning

confidence: 90%

“…For the calibration phantom with SAGE reconstruction, this transformation was final. It is the same procedure that was employed for a previous camera calibration with a high-energy collimator [4] and for processing patient data [10].…”

Section: F Ct-to-spect Registration and Voi Determinationmentioning

confidence: 99%

“…Our images were reconstructed by a regularized algorithm (SAGE) without detector response [5], [6] and a fixed-size VoI determined from computed tomography (CT) was employed. To account for the dependence of total count on background level, we used a phantom-based conversion factor that varied with the background level [4], [7]. Others have used a count-threshold percent that varied with the background level to choose the size of their VoI [8], [9].…”

Section: Introductionmentioning

confidence: 99%

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Determining total I-131 activity within a VoI using SPECT, a UHE collimator, OSEM, and a constant conversion factor

Koral

Yendiki

Lin

et al. 2004

IEEE Trans. Nucl. Sci.

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Accurate determination of activity within a volume of interest is needed during radiopharmaceutical therapies. Single-photon emission computed tomography(SPECT) is employed but requires a method to convert counts to activity. We use a phantom-based conversion; that is, we image an elliptical cylinder containing a sphere that has a known amount of 131-I activity inside. The regularized space alternating generalized expectation (SAGE) algorithm employing a strip-integral detector-response model was employed for reconstruction in previous patient evaluations. With that algorithm and a high-energy collimator, the estimates for sphere activity varied with changes in: 1) the level of uniform background activity in the cylinder; 2) the image resolution due to different values of the radius of rotation ; and 3) the volume of the sphere. When one used those to convert reconstructed counts within a patient tumor into an activity estimate, the resultant value may have been in error because of patient-phantom mismatch. As a potential remedy, in this paper, we use an ordered subsets expectation maximization (OSEM) algorithm with a 3-D depth-dependent detector-response model and an ultra-high-energy collimator. Results after 100 OSEM iterations and using a maximum counts registration show the estimates for sphere activity: 1) have a dependence on the level of background activity with a slope whose absolute magnitude is typically only 0.37 times that with SAGE; 2) are independent of ; and 3) are independent of sphere volume down to and including a sphere volume of 20 cm 3. We conclude that using a global-average conversion factor to relate counts to activity and no volume-based correction might be reasonable with OSEM. For a test of that conclusion, target activity is estimated for an anthropomorphic phantom containing a 100 cm 3 spherical tumor centrally located inferior to the lungs. With OSEM-based quantification, using: 1) a global-average conversion factor and 2) no volume-based correction, mean bias in the simulated-tumor activity estimate over 20 realizations is 7 37% (relative standard deviation = 5 93%). With SAGE-based quantification using: 1) the conversion factor corresponding to the experimental estimate of background and 2) volume-based correction, the mean bias is 10 7% (relative standard deviation = 2 37%). The mean bias

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Section: Introductionmentioning

confidence: 90%

Section: F Ct-to-spect Registration and Voi Determinationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determining total I-131 activity within a VoI using SPECT, a UHE collimator, OSEM, and a constant conversion factor

Koral

Yendiki

Lin

et al. 2004

IEEE Trans. Nucl. Sci.

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“…Sinograms were corrected for scatter using standard triple energy window ͑TEW͒ correction. 26 After scatter subtraction, the data were reconstructed into 128ϫ 128 pixel images ͑3.67 mm pixel size͒ using standard MLEM ͑64 iterations͒ with attenuation correction as in Ref. 27.…”

Section: Iie2 Thorax Phantommentioning

confidence: 99%

Physics process level discrimination of detections for GATE: Assessment of contamination in SPECT and spurious activity in PET

et al. 2009

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The GEANT4 application for tomographic emission (GATE) is one of the most detailed Monte Carlo simulation tools for SPECT and PET. It allows for realistic phantoms, complex decay schemes, and a large variety of detector geometries. However, only a fraction of the information in each particle history is available for postprocessing. In order to extend the analysis capabilities of GATE, a flexible framework was developed. This framework allows all detected events to be subdivided according to their type: In PET, true coincidences from others, and in SPECT, geometrically collimated photons from others. The framework of the authors can be applied to any isotope, phantom, and detector geometry available in GATE. It is designed to enhance the usability of GATE for the study of contamination and for the investigation of the properties of current and future prototype detectors. The authors apply the framework to a case study of Bexxar, first assuming labeling with 124I, then with 131I. It is shown that with 124I PET, results with an optimized window improve upon those with the standard window but achieve less than half of the ideal improvement. Nevertheless, 124I PET shows improved resolution compared to 131I SPECT with triple-energy-window scatter correction.

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“…The effective hole-length parameter Those planar images were later added together. Planar images were acquired with a 20%-width window around the 364 keV photopeak, and adjacent 10%-width windows for scatter correction using the triple-energy window (TEW) method [7], [8]. The estimated scatter events in the photopeak window calculated by TEW were about 5% of the total number of events in the photopeak window.…”

Section: B Crystal Efjiciency Calibrationmentioning

confidence: 99%

Absolute quantitation of I-131 activity distributions using a high-resolution rotating collimator: a phantom study

Trotter

Bowsher²,

Jaszczak³

1999 IEEE Nuclear Science Symposium. Conference Record. 1999 Nuclear Science Symposium and Medical Imaging Conference (Cat. No.

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We acquired SPECT data using a high-resolution rotating parallel-hole collimator especially designed for imaging of medium-energy radionuclides. We reconstructed images of 1-131 activity distributions for a sphere inside a water-filled cylinder. Reconstructions were performed using FBP and iterative MAP/ICD methods. The MAP/ICD reconstructions with an edge-preserving convex prior provided the more accurate absolute activity distributions with better resolution (FWHM of 0.5 cm). The sphere's activity and activity density were reproduced to within 5% of their known values.

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Quantitative /sup 131/I SPECT with triple energy window Compton scatter correction

Cited by 34 publications

References 12 publications

Determining total I-131 activity within a VoI using SPECT, a UHE collimator, OSEM, and a constant conversion factor

Determining total I-131 activity within a VoI using SPECT, a UHE collimator, OSEM, and a constant conversion factor

Physics process level discrimination of detections for GATE: Assessment of contamination in SPECT and spurious activity in PET

Absolute quantitation of I-131 activity distributions using a high-resolution rotating collimator: a phantom study

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