Variance Reduction on Randoms from Delayed Coincidence Histograms for the HRRT

Byars, L.G.; Sibomana, M.; Burbar, Z.; Jones, J.P.; Panin, Vladimir; Barker, William; Liow, Jeih‐San; Carson, Richard E.; Michel, Christian

doi:10.1109/nssmic.2005.1596876

Cited by 50 publications

(47 citation statements)

References 10 publications

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“…The datasets were also binned (using span 9) and reconstructed using the OP-OSEM algorithm. The scatter sinograms were estimated using the single-scatter simulation method (22), and random sinograms were derived from smoothed delayed-coincidence window data (23).…”

Section: Noise and Contrast Recovery Characterizationmentioning

confidence: 99%

Impact of Image-Space Resolution Modeling for Studies with the High-Resolution Research Tomograph

Sureau¹,

Reader²,

Comtat³

et al. 2008

J Nucl Med

225

196

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Brain PET in small structures is challenged by low resolution inducing bias in the activity measurements. Improved spatial resolution may be obtained by using dedicated tomographs and more comprehensive modeling of the acquisition system during reconstruction. In this study, we assess the impact of resolution modeling (RM) during reconstruction on image quality and on the estimates of biologic parameters in a clinical study performed on a high-resolution research tomograph. Methods: An accelerated list-mode ordinary Poisson ordered-subset expectation maximization (OP-OSEM) algorithm, including sinogram-based corrections and an experimental stationary model of resolution, has been designed. Experimental phantom studies are used to assess contrast and noise characteristics of the reconstructed images. The binding potential of a selective tracer of the dopamine transporter is also assessed in anatomic volumes of interest in a 5-patient study. Results: In the phantom experiment, a slower convergence and a higher contrast recovery are observed for RM-OP-OSEM than for OP-OSEM for the same level of statistical noise. RM-OP-OSEM yields contrast recovery levels that could not be reached without RM as well as better visual recovery of the smallest spheres and better delineation of the structures in the reconstructed images. Statistical noise has lower variance at the voxel level with RM than without at matched resolution. In a uniform activity region, RM induces higher positive and lower negative correlations with neighboring voxels, leading to lower spatial variance. Clinical images reconstructed with RM demonstrate better delineation of cortical and subcortical structures in both time-averaged and parametric images. The binding potential in the striatum is also increased, a result similar to the one observed in the phantom study. Conclusion: In high-resolution PET, RM during reconstruction improves quantitative accuracy by reducing the partial-volume effects.

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Section: Noise and Contrast Recovery Characterizationmentioning

confidence: 99%

Impact of Image-Space Resolution Modeling for Studies with the High-Resolution Research Tomograph

Sureau¹,

Reader²,

Comtat³

et al. 2008

J Nucl Med

225

196

View full text Add to dashboard Cite

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“…3D-OSWLS showed accuracy in patient studies similar to that of 3D-FBP (21) but resulted in a much lower pixel variance. For all HRRT reconstructions, randoms were estimated by the variance reduction on randoms algorithm (23,25). All HRRT-reconstructed images were also postsmoothed with a 6-mm FWHM gaussian kernel to match image resolution with that of the HR1 scanner.…”

Section: Reconstructionsmentioning

confidence: 99%

HRRT Versus HR+ Human Brain PET Studies: An Interscanner Test–Retest Study

Velden¹,

Kloet²,

Berckel³

et al. 2009

J Nucl Med

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The high-resolution research tomograph (HRRT) is a dedicated human brain PET scanner. The purpose of this study was to compare the quantitative accuracy of the HRRT with that of the clinical HR1 PET scanner and to assess effects of differences in spatial resolution between both scanners (;2.7 mm and ;7.0 mm for HRRT and HR1, respectively). Methods: Paired 11 Cflumazenil scans of 7 healthy volunteers were assessed. For each volunteer, dynamic scans (including arterial sampling) were acquired on both scanners on the same day, thereby minimizing intersubject variability. Volume of distribution was generated using Logan plot analysis with plasma input. In addition, other plasma input, reference tissue (with pons as the reference tissue input), and parametric methods were included in the interscanner comparison. Results: Logan volume-of-distribution analysis of HRRT data showed higher values than that of HR1 data (slope with the intercept fixed at the origin of 1.14 6 0.10 to 1.19 6 0.10, depending on the HRRT reconstruction method used). Smoothing HRRT reconstructions with a 6-mm full width at half maximum gaussian kernel reduced this slope toward the line of identity (1.04 6 0.11 to 1.07 6 0.11), retaining good correlation between HR1 and HRRT data (r, ;0.98). Similar trends were observed for other plasma input, reference tissue, and parametric methods. However, after reference matching the reference tissue models showed lower HRRT kinetic parameter values than HR1 values (slope with fixed intercept, 0.90 6 0.10 to 0.94 6 0.13). Conclusion: Higher values of pharmacokinetic parameter values, obtained from HRRT versus HR1 PET studies, indicate improved HRRT PET quantification primarily due to a reduction in partial-volume effects. The availability of lutetium oxyorthosilicate/lutetiumyttrium oxyorthosilicate (LSO/LYSO) crystals has generated interest in new PET scanners that have higher spatial image resolution. The ECAT High-Resolution Research Tomograph (HRRT) (CTI/Siemens) is a dedicated human brain scanner with design features that enable high spatial image resolution combined with high sensitivity (1). The HRRT is the first commercially available PET scanner that uses a double layer of LSO/LYSO crystals to achieve photon detection with depth-of-interaction information.To date, only a limited number of human brain studies have been performed using the HRRT (2-7). Most human brain studies have been acquired with clinical (whole-body) PET scanners, such as the ECAT EXACT HR1 (CTI/Siemens). Therefore, it is worthwhile to compare the accuracy of quantitative human HRRT studies with that of HR1 studies. The HR1 scanner has a single layer of bismuth germinate crystals. Over the years, its quantitative accuracy has been studied extensively (8)(9)(10).A direct quantitative comparison between HRRT and HR1 has been performed in a limited way, using only phantoms (11). Recently, Leroy et al. (3) performed a comparative study between similar patient groups, matched in age, acquired on either an HR1 or an HRRT. Although this ...

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“…During emission scanning, continuous online arterial blood sampling was performed (26). At set times (5,10,15,20,30,40, and 60 min after injection), continuous blood sampling was interrupted to collect manual blood samples. These manual sample data were used for calibrating the (online) blood sampler, for measuring plasma or whole-blood ratios, and for determining metabolite fractions (27).…”

Section: Phantoms and Studiesmentioning

confidence: 99%

“…A 3-dimensional (3D) attenuation and normalization weighted ordered-subsets expectation maximization (ANW-OSEM) reconstruction method showed considerable bias for a homogeneous phantom (4). Therefore, a 3D ordinary Poisson OSEM (OP-OSEM) reconstruction method was implemented that showed considerably less bias, especially when randoms were estimated by the variance reduction on a randoms (VRR) algorithm (5). However, bias was still encountered for shortduration (5-60 s) frames (6,7).…”

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confidence: 99%

Accuracy of 3-Dimensional Reconstruction Algorithms for the High-Resolution Research Tomograph

et al. 2008

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The high-resolution research tomograph (HRRT) is a dedicated human brain PET scanner. At present, iterative reconstruction methods are preferred for reconstructing HRRT studies. However, these iterative reconstruction algorithms show bias in short-duration frames. New algorithms such as the shifted Poisson ordered-subsets expectation maximization (SP-OSEM) and ordered-subsets weighted least squares (OSWLS) showed promising results in bias reduction, compared with the recommended ordinary Poisson OSEM (OP-OSEM). The goal of this study was to evaluate quantitative accuracy of these iterative reconstruction algorithms, compared with 3-dimensional filtered backprojection (3D-FBP). Methods: The 3 above-mentioned 3D iterative reconstruction methods were implemented for the HRRT. To evaluate the various 3D iterative reconstruction techniques quantitatively, several phantom studies and a human brain study (n 5 5) were performed. Results: OSWLS showed a low and almost linearly increasing coefficient of variation (SD over average activity concentration), with decreasing noise-equivalent count rates. In decay studies, OSWLS showed good agreement with the 3D-FBP gray matter (GM)-to-white matter (WM) contrast ratio (,4%), and OP-OSEM and SP-OSEM showed agreement within 6% and 7%, respectively. For various frame durations, both SP-OSEM and OP-OSEM showed the fewest errors in GM-to-WM contrast ratios, varying 75% between different noise-equivalent count rates; this variability was much higher for other iterative methods (.92%). 3D-FBP showed the least variability (34%). Visually, OSWLS hardly showed any artifacts in parametric images and showed good agreement with 3D-FBP data for parametric images, especially in the case of reference-tissue kinetic methods (slope, 1.02; Pearson correlation coefficient, 0.99). Conclusion: OP-OSEM, SP-OSEM, and OSWLS showed good performance for phantom studies. In addition, OSWLS showed better results for parametric analysis of clinical studies and is therefore recommended for quantitative HRRT brain PET studies.

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Variance Reduction on Randoms from Delayed Coincidence Histograms for the HRRT

Cited by 50 publications

References 10 publications

Impact of Image-Space Resolution Modeling for Studies with the High-Resolution Research Tomograph

Impact of Image-Space Resolution Modeling for Studies with the High-Resolution Research Tomograph

HRRT Versus HR+ Human Brain PET Studies: An Interscanner Test–Retest Study

Accuracy of 3-Dimensional Reconstruction Algorithms for the High-Resolution Research Tomograph

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