Implementation of simultaneous attenuation and detector response correction in SPECT

Tsui, B.M.W.; Hu, Haifeng; Gilland, D.R.; Gullberg, Grant T.

doi:10.1109/23.12831

Cited by 219 publications

(81 citation statements)

References 13 publications

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“…The probability of a g-ray's having been emitted from coordinates (x, y, z) relative to the detector is modeled, creating a probability map used by the reconstruction algorithm. The characteristics of the collimator are included in the probability map estimation (16)(17)(18)(19)(20), but attenuation and scatter are not included.…”

Section: Image Reconstructionmentioning

confidence: 99%

A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

Gambhir¹,

Berman²,

Ziffer³

et al. 2009

J Nucl Med

244

173

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This study described and validated a new solid-state singlephoton g-camera and compared it with a conventional-SPECT Anger camera. The compact new camera uses a unique method for localizing g-photon information with a bank of 9 solid-state detector columns with tungsten collimators that rotate independently. Methods: Several phantom studies were performed comparing the new technology with conventional-SPECT technology. These included measurements of line sources and single-and dual-radionuclide studies of a torso phantom. Simulations were also performed using a cardiothoracic phantom. Furthermore, 18 patients were scanned with both the new camera and a conventional-SPECT camera. Results: The new camera had a count sensitivity that was 10 times higher than that of the conventional camera and a compensated spatial resolution that was moderately better. Dual-radionuclide studies using a phantom show the further potential of the new camera for a 2-tracer simultaneous acquisition. Two-minute clinical studies with the new camera and 11-min studies with the conventional camera qualitatively showed good-to-excellent image quality and improved myocardial edge definition for the new camera. Conclusion: These initial performance characteristics of a new solid-state single-photon g-camera offer great promise for clinical dynamic SPECT protocols, with important implications for applications in nuclear cardiology and molecular imaging. Nucl ear medicine has evolved as a clinical and research discipline for the noninvasive assessment of physiologic and molecular function in normal and diseased tissues. Principally performed with nanomolar quantities of administered radiopharmaceuticals and an external scintillation camera, nuclear medicine imaging uses 2 types of modalities: singlephoton imaging (including planar imaging and SPECT) and PET, with the former comprising nearly three fourths of all clinical procedures. With SPECT, myocardial perfusion studies predominate; these studies were performed in approximately 7,000,000 patients in the United States in 2004 and provided images of relative myocardial perfusion at rest and under stress. By assessing the extent of ischemic and infarcted myocardium, SPECT provides noninvasive information that has become central in clinical decision making, determining the need for invasive cardiac catheterization and myocardial revascularization in many patients (1,2).SPECT is typically performed using an Anger scintillation camera, named after its inventor, Hal Anger (3). Most myocardial SPECT is performed with 2 scintillation cameras oriented at 90°and mounted on a gantry that rotates around the patient. Typically, each scintillation camera is equipped with parallel-hole high-resolution collimators. Since collimation is necessary to acquire the projection views, only 0.02% of the photons emitted from the heart are collected. As a result, acquisition times of 10-20 min are required for myocardial SPECT studies. Although new detector technologies using solid-state materials have been explored (...

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Section: Image Reconstructionmentioning

confidence: 99%

A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

Gambhir¹,

Berman²,

Ziffer³

et al. 2009

J Nucl Med

244

173

View full text Add to dashboard Cite

show abstract

“…The quantitative image reconstruction method consists of a 3-dimensional (3D) iterative ordered-subset expectation-maximization algorithm (5 iterations with 10 subsets) and a projector and back-projector pair that models image degradation factors including nonuniform attenuation 26 and scatter 27 of photons within the animal and the full collimator-detector response 28 with the medium energy collimator for their accurate compensation 29,30 to obtain higher image resolution and less noise compared with the conventional filtered back-projection reconstruction method. The registered CT images were used for nonuniform attenuation distribution within the animal's body.…”

Section: Spect/ct Image Reconstruction and Analysismentioning

confidence: 99%

Dynamic Imaging of Allogeneic Mesenchymal Stem Cells Trafficking to Myocardial Infarction

et al. 2005

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Background— Recent results from animal studies suggest that stem cells may be able to home to sites of myocardial injury to assist in tissue regeneration. However, the histological interpretation of postmortem tissue, on which many of these studies are based, has recently been widely debated. Methods and Results— With the use of the high sensitivity of a combined single-photon emission CT (SPECT)/CT scanner, the in vivo trafficking of allogeneic mesenchymal stem cells (MSCs) colabeled with a radiotracer and MR contrast agent to acute myocardial infarction was dynamically determined. Redistribution of the labeled MSCs after intravenous injection from initial localization in the lungs to nontarget organs such as the liver, kidney, and spleen was observed within 24 to 48 hours after injection. Focal and diffuse uptake of MSCs in the infarcted myocardium was already visible in SPECT/CT images in the first 24 hours after injection and persisted until 7 days after injection and was validated by tissue counts of radioactivity. In contrast, MRI was unable to demonstrate targeted cardiac localization of MSCs in part because of the lower sensitivity of MRI. Conclusions— Noninvasive radionuclide imaging is well suited to dynamically track the biodistribution and trafficking of mesenchymal stem cells to both target and nontarget organs.

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“…There has been a great deal of effort to model attenuation, 8,16,17 the collimator-detector response, [18][19][20][21] and scatter in the patient. [22][23][24][25][26] However, 131 I presents a set of unique challenges compared to other radionuclides used for TRT treatment planning such as 111 In.…”

Section: Introductionmentioning

confidence: 99%

Development and evaluation of a model-based downscatter compensation method for quantitative I-131 SPECT

Song

et al. 2011

Med. Phys.

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Purpose: The radionuclide 131 I has found widespread use in targeted radionuclide therapy (TRT), partly due to the fact that it emits photons that can be imaged to perform treatment planning or posttherapy dose verification as well as beta rays that are suitable for therapy. In both the treatment planning and dose verification applications, it is necessary to estimate the activity distribution in organs or tumors at several time points. In vivo estimates of the 131 I activity distribution at each time point can be obtained from quantitative single-photon emission computed tomography (QSPECT) images and organ activity estimates can be obtained either from QSPECT images or quantification of planar projection data. However, in addition to the photon used for imaging, 131 I decay results in emission of a number of other higher-energy photons with significant abundances. These higher-energy photons can scatter in the body, collimator, or detector and be counted in the 364 keV photopeak energy window, resulting in reduced image contrast and degraded quantitative accuracy; these photons are referred to as downscatter. The goal of this study was to develop and evaluate a model-based downscatter compensation method specifically designed for the compensation of high-energy photons emitted by 131 I and detected in the imaging energy window. Methods: In the evaluation study, we used a Monte Carlo simulation (MCS) code that had previously been validated for other radionuclides. Thus, in preparation for the evaluation study, we first validated the code for 131 I imaging simulation by comparison with experimental data. Next, we assessed the accuracy of the downscatter model by comparing downscatter estimates with MCS results. Finally, we combined the downscatter model with iterative reconstruction-based compensation for attenuation (A) and scatter (S) and the full (D) collimator-detector response of the 364 keV photons to form a comprehensive compensation method. We evaluated this combined method in terms of quantitative accuracy using the realistic 3D NCAT phantom and an activity distribution obtained from patient studies. We compared the accuracy of organ activity estimates in images reconstructed with and without addition of downscatter compensation from projections with and without downscatter contamination. Results: We observed that the proposed method provided substantial improvements in accuracy compared to no downscatter compensation and had accuracies comparable to reconstructions from projections without downscatter contamination.Conclusions: The results demonstrate that the proposed model-based downscatter compensation method is effective and may have a role in quantitative 131 I imaging.

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Implementation of simultaneous attenuation and detector response correction in SPECT

Cited by 219 publications

References 13 publications

A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

Dynamic Imaging of Allogeneic Mesenchymal Stem Cells Trafficking to Myocardial Infarction

Development and evaluation of a model-based downscatter compensation method for quantitative I-131 SPECT

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