Collimator-Detector Response Compensation in SPECT

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

doi:10.1007/0-387-25444-7_5

Cited by 48 publications

(40 citation statements)

References 39 publications

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“…As such one could conjecture that the NEQ, already enhanced by wider MTF due to better recovery of higher frequencies, will be further boosted, at higher frequencies, due to division by diminished NPS values. This was reported in a dissertation 110 in the case of collimator-detector response function (CDRF) compensation 111 in SPECT imaging, and recently 127 in the case of resolution modeling in PET: in fact complex NPS structures were observed, including increased mid-frequency components of the NPS and diminished high-frequency components, relative to no compensation, ultimately demonstrating limited NEQ improvements. Overall, the abovementioned framework, coupled with the complex nature of the NPS and thus NEQ, may hold a key to explaining why in the inclusion of resolution modeling, observer task performance may result in relatively less improvements compared to those observed in conventional resolution/contrast vs noise analysis.…”

Section: Aucmentioning

confidence: 93%

Resolution modeling in PET imaging: Theory, practice, benefits, and pitfalls

2013

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In this paper, the authors review the field of resolution modeling in positron emission tomography (PET) image reconstruction, also referred to as point-spread-function modeling. The review includes theoretical analysis of the resolution modeling framework as well as an overview of various approaches in the literature. It also discusses potential advantages gained via this approach, as discussed with reference to various metrics and tasks, including lesion detection observer studies. Furthermore, attention is paid to issues arising from this approach including the pervasive problem of edge artifacts, as well as explanation and potential remedies for this phenomenon. Furthermore, the authors emphasize limitations encountered in the context of quantitative PET imaging, wherein increased intervoxel correlations due to resolution modeling can lead to significant loss of precision (reproducibility) for small regions of interest, which can be a considerable pitfall depending on the task of interest.

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Section: Aucmentioning

confidence: 93%

Resolution modeling in PET imaging: Theory, practice, benefits, and pitfalls

2013

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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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“…The PSF can be integrated into reconstruction as part of an iterative algorithm. The PSF has 4 components: septal penetration, septal scatter, intrinsic detector response, and, most important, geometric response function (GRF) (6). The GRF component is defined as the normalized 2-dimensional Fourier transform of the point-source image formed in a plane behind the collimator by photons that are accepted geometrically through the collimator holes.…”

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confidence: 99%

Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction

Ali¹,

Ruddy²,

Almgrahi³

et al. 2009

J Nucl Med

103

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Reducing acquisition time may improve patient throughput, increase camera efficiency, and reduce costs; reducing acquisition time also increases image noise. Newly available software controls the effects of noise by maximum a posteriori reconstruction while maintaining resolution with resolution-recovery methods. This study compares half-time (HT) gated myocardial SPECT images processed with ordered-subset expectation maximization with resolution recovery (OSEM-RR) (with and without CT-based attenuation correction [AC]) with full-time (FT) images obtained with a standard clinical protocol and reconstructed with filtered backprojection (FBP) and OSEM (with and without AC). Methods: A total of 212 patients (mean age, 57 y; age range, 27-86 y) underwent 1-d rest/stress 99m Tc-tetrofosmin gated SPECT. FT (12.5 min, both rest and stress) and HT (rest, 7.5 min; stress, 6.0 min) images were acquired with low-dose CT for AC in 112 patients. HT acquisitions were processed with OSEM-RR (with and without AC) using software, and FT acquisitions were processed with FBP and OSEM (with and without AC). In another 100 patients, test-retest repeatability was assessed using 2 sets of FT images (FBP reconstruction) that were acquired one immediately after the other. Radiologists unaware of the acquisition and reconstruction protocols visually assessed all reconstructed images for summed stress, summed rest, and summed difference scores and regional wall motion using a 17-segment model. Automated analysis on gated SPECT was used to determine left ventricular volumes, ejection fraction, and dilation (end-diastolic volume, end-systolic volume, left ventricular ejection fraction, and transient ischemic dilation [TID]). A clinical diagnosis was also determined. Results: All measurements resulted in significant correlations (P , 0.01) between the HT and FT images. The only significant difference in mean values was for OSEM-RR plus AC; this method led to an increase in TID by 4% over FT imaging. The concordance in the clinical diagnosis for HT versus FT was 106 to 112 (k 5 0.88) for no AC and 102 to 106 (k 5 0.91) for AC, similar to the repeatability of FT versus FT (98/100, k 5 0.95). Conclusion: HT images processed with the new algorithm provided a clinical diagnosis in concordance with that from FT images in 95% (no AC) to 96% (AC) of cases. This concordance is similar to the test-retest repeatability of FT imaging.

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Collimator-Detector Response Compensation in SPECT

Cited by 48 publications

References 39 publications

Resolution modeling in PET imaging: Theory, practice, benefits, and pitfalls

Resolution modeling in PET imaging: Theory, practice, benefits, and pitfalls

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

Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction

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