A fast projector-backprojector pair modeling the asymmetric, spatially varying scatter response function for scatter compensation in SPECT imaging

Frey, Eric; Ju, Zhenyu; Tsui, B.M.W.

doi:10.1109/23.256735

Cited by 96 publications

(65 citation statements)

References 9 publications

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“…For instance, the effective scatter source estimation (ESSE) method, developed by Frey et al (49,50), uses precalculated kernels obtained from Monte Carlo simulations to estimate self-scatter in the photopeak window, whereas the analytic photon distribution interpolative (APDI) method (51,52) uses the KleinNishina cross-section for Compton scattering to analytically calculate scatter distribution in projections. Reconstructions included compensations for attenuation, scatter, and collimator response.…”

Section: Compton Scattermentioning

confidence: 99%

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

et al. 2015

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The accuracy of absorbed dose calculations in personalized internal radionuclide therapy is directly related to the accuracy of the activity (or activity concentration) estimates obtained at each of the imaging time points. MIRD Pamphlet no. 23 presented a general overview of methods that are required for quantitative SPECT imaging. The present document is next in a series of isotope-specific guidelines and recommendations that follow the general information that was provided in MIRD 23. This paper focuses on 177 Lu (lutetium) and its application in radiopharmaceutical therapy. Theradi onuclide 177 Lu (lutetium) has been proven useful in several targeted radionuclide therapies because of its favorable decay characteristics and the possibility of reliable labeling of biomolecules used for tumor targeting. Initially, 177 Lu was used in a colloidal form for interstitial injections for sterilization of peritumoral lymph nodes (1). A second important clinical application of 177 Lu has been for peptide receptor radionuclide therapy (PRRT) with 177 Lu-DOTATATE and other structurally related peptides. The PRRT use in treatment of neuroendocrine tumors (NETs) is motivated by the fact that the carrier peptide, octreotate, shows highaffinity binding to somatostatin receptors, which are overexpressed on the cell surface of many NETs (2-6). Furthermore, 177 Lu has been used in radioimmunotherapy clinical trials to label different kinds of monoclonal antibodies (7-15).There is a growing body of evidence that radionuclide therapy should follow patient-specific planning protocols, similar to those that are being routinely used in external-beam radiation therapy. Recent literature reviews show correlations between absorbed dose and tumor response as well as normal-tissue toxicity (16). Such correlations indicate that treatments should be based on personalized dosimetry, aiming to deliver therapeutically effective absorbed doses to tumors, while keeping doses to organs at risk below the threshold levels for deterministic adverse effects. In clinical PRRT studies, the primary adverse effects have been mainly renal and hematologic toxicities (2,6).Although several studies have reported estimates of absorbed doses (4,7-9,12) for 177 Lu-DOTATATE PRRT and 177 Lu radioimmunotherapy, most of these estimates have been based on planar imaging and conjugate-view activity quantification. Planar imaging, however, is known to have inherent limitations regarding the accuracy of activity quantification (17). As a result, an increasing number of clinical dosimetry protocols currently include 177 Lu SPECT/CT imaging studies (15,(17)(18)(19) because of their superior accuracy. Comparisons of renal dose estimates in 177 Lu-DOTATATE PRRT based on planar imaging and SPECT/CT, for example, have been reported (17,20) and are summarized in Cremonesi et al. (21).This document presents a set of guidelines outlining data acquisition protocols and image reconstruction techniques that are recommended for quantitative 177 Lu SPECT imaging. The guidelines are...

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Section: Compton Scattermentioning

confidence: 99%

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

et al. 2015

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“…For each energy window investigated, model-estimated basis projections were generated for each of the six basis objects using a forward projection code [28][29][30][31] implementing a modeling method developed previously for quantitative 90 Y bremsstrahlung SPECT imaging. 5 We modeled all the image degrading effects including attenuation, object scatter and the full collimator-detector response (CDR) including geometric response, lead characteristic x-ray, septal penetration and scatter, partial deposition in the crystal, intrinsic resolution, and backscatter from structures behind the crystal.…”

Section: Iib2b Generation Of Model-estimated Basis Projectionsmentioning

confidence: 99%

Optimization of energy window for ⁹⁰Y bremsstrahlung SPECT imaging for detection tasks using the ideal observer with model‐mismatch

2013

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Purpose: In yttrium-90 ( 90 Y) microsphere brachytherapy (radioembolization) of unresectable liver cancer, posttherapy 90 Y bremsstrahlung single photon emission computed tomography (SPECT) has been used to document the distribution of microspheres in the patient and to help predict potential side effects. The energy window used during projection acquisition can have a significant effect on image quality. Thus, using an optimal energy window is desirable. However, there has been great variability in the choice of energy window due to the continuous and broad energy distribution of 90 Y bremsstrahlung photons. The area under the receiver operating characteristic curve (AUC) for the ideal observer (IO) is a widely used figure of merit (FOM) for optimizing the imaging system for detection tasks. The IO implicitly assumes a perfect model of the image formation process. However, for 90 Y bremsstrahlung SPECT there can be substantial model-mismatch (i.e., difference between the actual image formation process and the model of it assumed in reconstruction), and the amount of the model-mismatch depends on the energy window. It is thus important to account for the degradation of the observer performance due to model-mismatch in the optimization of the energy window. The purpose of this paper is to optimize the energy window for 90 Y bremsstrahlung SPECT for a detection task while taking into account the effects of the model-mismatch. Methods: An observer, termed the ideal observer with model-mismatch (IO-MM), has been proposed previously to account for the effects of the model-mismatch on IO performance. In this work, the AUC for the IO-MM was used as the FOM for the optimization. To provide a clinically realistic object model and imaging simulation, the authors used a background-known-statistically and signalknown-statistically task. The background was modeled as multiple compartments in the liver with activity parameters independently following a Gaussian distribution; the signal was modeled as a tumor with a Gaussian-distributed activity parameter located randomly with equal probability at one of three positions. The IO test statistics (i.e., likelihood ratios) were estimated using Markov-chain Monte Carlo methods. The authors realistically modeled human anatomy using a digital phantom code, and realistically simulated 90 Y bremsstrahlung SPECT imaging with a clinical SPECT system and typical imaging parameters using a previously validated Monte Carlo bremsstrahlung simulation method. Model-mismatch was included by modeling image formation process in the calculation of IO test statistics using an analytic modeling method previously developed for quantitative 90 Y bremsstrahlung SPECT. To demonstrate the effects of the model-mismatch on the detection task, the authors optimized the energy window both with and without model-mismatch included in the IO. Results: For all the energy windows, the AUC values for the IO-MM were smaller than that for the IO. The optimal windows for the IO-MM and the IO were 80-180 and 60-400 k...

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“…Iterative reconstruction-based scatter compensation has received considerable attention during the last decade. Earlier studies [14,37] indicated that when scatter is modelled in iterative reconstruction, higher contrast and lower noise can be obtained than when the technique of scatter subtraction is used. In addition, model-based iterative reconstruction does not require patient-dependent parameterisation.…”

Section: Discussionmentioning

confidence: 99%

Comparative evaluation of scatter correction techniques in 3D positron emission tomography

Zaidi

2000

Eur J Nucl Med

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Abstract. Much research and development has been concentrated on the scatter compensation required for quantitative 3D positron emission tomography (PET). Increasingly sophisticated scatter correction procedures are under investigation, particularly those based on accurate scatter models and iterative reconstruction-based scatter compensation approaches. The main difference among the correction methods is the way in which the scatter component in the selected energy window is estimated. Monte Carlo methods provide further insight and might in themselves offer a possible correction procedure. Five scatter correction methods were compared in this study where applicable: the dual-energy window (DEW) technique, the convolution-subtraction (CVS) method, two variants of the Monte Carlo-based scatter correction technique (MCBSC1 and MCBSC2) and our newly developed statistical reconstruction-based scatter correction (SRBSC) method. These scatter correction techniques were evaluated using Monte Carlo simulation studies, experimental phantom measurements and clinical studies. Accurate Monte Carlo modelling is still the gold standard since it allows the separation of scattered and unscattered events and comparison of the estimated and true unscattered component. In this study, our modified version of Monte Carlo-based scatter correction (MCBSC2) provided a good contrast recovery on the simulated Utah phantom, while the DEW method was found to be clearly superior for the experimental phantom studies in terms of quantitative accuracy at the expense of a significant deterioration in the signal-to-noise ratio. On the other hand, the immunity to noise in emission data of statistical reconstruction-based scatter correction methods makes them particularly applicable to low-count emission studies. All scatter correction methods gave very good activity recovery values for the simulated 3D Hoffman brain phantom, which averaged within 3%. The CVS and MCBSC1 techniques tended to overcorrect while SRBSC undercorrected for scatter in most regions of this phantom. It was concluded that all correction methods significantly improve the image quality and contrast compared to the case where no correction is applied. Generally, it was shown that the differences in the estimated scatter distributions did not have a significant impact on the final quantitative results. The DEW method showed the best compromise between ease of implementation and quantitative accuracy, but entailed a significant deterioration in the signal-to-noise ratio.

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A fast projector-backprojector pair modeling the asymmetric, spatially varying scatter response function for scatter compensation in SPECT imaging

Cited by 96 publications

References 9 publications

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

Optimization of energy window for ⁹⁰Y bremsstrahlung SPECT imaging for detection tasks using the ideal observer with model‐mismatch

Comparative evaluation of scatter correction techniques in 3D positron emission tomography

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A fast projector-backprojector pair modeling the asymmetric, spatially varying scatter response function for scatter compensation in SPECT imaging

Cited by 96 publications

References 9 publications

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative 177Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative 177Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

Optimization of energy window for 90Y bremsstrahlung SPECT imaging for detection tasks using the ideal observer with model‐mismatch

Comparative evaluation of scatter correction techniques in 3D positron emission tomography

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MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative ¹⁷⁷Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy

Optimization of energy window for ⁹⁰Y bremsstrahlung SPECT imaging for detection tasks using the ideal observer with model‐mismatch