LROC analysis of detector-response compensation in SPECT

Gifford, Howard C.; King, Michael A.; Wells, R. Glenn; Hawkins, William G.; Narayanan, Manoj; Pretorius, P. Hendrik

doi:10.1109/42.870256

Cited by 72 publications

(30 citation statements)

References 34 publications

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“…With the above projection data as input, the actual attenuation map was generated using the BITAB reconstruction algorithm [12]. The Gaussian diffusion method for detector response correction was chosen because of the feasibility and enhanced performance of this approach in single activity detection tasks [13]. The two-energy window (TEW) method was selected for scatter correction [14].…”

Section: Methodsmentioning

confidence: 99%

Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging

Smyczynski

Gifford

Lehovich

et al. 2007

2007 IEEE Nuclear Science Symposium Conference Record

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The objective of this investigation is to determine the impact of respiratory motion on the detection of small solitary pulmonary nodules (SPN) in single photon emission computed tomographic (SPECT) imaging. We have previously modeled the respiratory motion of SPN based on the change of location of anatomic structures within the lungs identified on breath-held CT images of volunteers acquired at two different stages of respiration. This information on respiratory motion within the lungs was combined with the end-expiration and time-averaged NCAT phantoms to allow the creation of source and attenuation maps for the normal background distribution of Tc-99m NeoTect. With the source and attenuation distribution thus defined, the SIMIND Monte Carlo program was used to produce SPECT projection data for the normal background and separately for each of 150 end-expiration and time-averaged simulated 1.0 cm tumors. Normal and tumor SPECT projection sets each containing one lesion were combined with a clinically realistic noise level and counts. These were reconstructed with RBI-EM using 1) no correction (NC), 2) attenuation correction (AC), 3) detector response correction (RC), and 4) attenuation correction, detector response correction, and scatter correction (AC_RC_SC). The post-reconstruction parameters of number of iterations and 3-D Gaussian filtering were optimized by human-observer studies. Comparison of lesion detection by human-observer LROC studies reveals that respiratory motion degrades tumor detection for all four reconstruction strategies, and that the magnitude of this effect is greatest for NC and RC, and least for AC_RC_SC. Additionally, the AC_RC_SC strategy results in the best detection of lesions.

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Section: Methodsmentioning

confidence: 99%

Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging

Smyczynski

Gifford

Lehovich

et al. 2007

2007 IEEE Nuclear Science Symposium Conference Record

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“…The resolution of gcamera images decreases as the source increases its distance from the collimator surface. By modeling the point-spread function (PSF) and other sources of image blurring inside the image-creation process, it is possible to compensate for these effects and improve the image quality (5). The PSF can be integrated into reconstruction as part of an iterative algorithm.…”

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confidence: 99%

Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction

Ali¹,

Ruddy²,

Almgrahi³

et al. 2009

J Nucl Med

104

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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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“…That noted, spatial resolution modeling is worth evaluating in a future study, since it has potential to improve localization. 33 Because localization is better in regions proximal to the detector trajectory and since tumor location is known approximately, on-board SPECT trajectories could be optimized for imaging specific tumor sites.…”

Section: Discussionmentioning

confidence: 99%

On‐board SPECT for localizing functional targets: A simulation study

2009

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Single photon emission computed tomography ͑SPECT͒ was investigated for imaging on-board radiation therapy machines in order to localize functional and molecular targets. A computersimulated female NCAT phantom was positioned supine on a flat-top treatment couch. Twenty tumor locations were defined in the upper torso. The eight lung tumors were subject to the effects of respiratory motion. Tumor diameters of 10.8, 14.4, and 21.6 mm were simulated for tumor-tobackground ratios of 3:1 and 6:1 that are characteristic of the radiotracer 99m Tc-sestamibi. Projection images representing scan times of 4, 8, and 20 min were simulated for an anterior, half-circular trajectory. Images were reconstructed with attenuation correction by ordered-subsets expectation maximization ͑OSEM͒ using six subsets and five iterations. Contrast-to-noise ratios ͑CNRs͒ were calculated from ensembles of 25 images. Cross correlation with a noise-free tumor template was used to select the most suspicious tumor location within a 14.4-mm-radius search volume surrounding each tumor, with only that one tumor in each search volume. Localization accuracy was assessed by calculating average distances between measured and true tumor locations. Localization accuracy and CNRs were strongly affected by tumor location relative to the detector trajectory. For example, CNR values near the chest wall were greater by a factor of 3.5 than for tumors near the spine and posterior ribs, a much greater effect than the factor of 1.6 difference in CNR between 6:1 and 3:1 tumor uptakes. Typically, tumors of 6:1 uptake were localized as accurately with 4 min of scan time as tumors of 3:1 uptake that had been imaged for 20 min. Using 4 min scans, 14.4 and 21.6 mm anterior tumors of 6:1 uptake were localized within 2 mm. These results suggest that SPECT, on-board radiation therapy machines, may be a viable modality for localizing certain functional and molecular targets using relatively short scan times.

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LROC analysis of detector-response compensation in SPECT

Cited by 72 publications

References 34 publications

Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging

Impact of respiratory motion on the detection of small pulmonary nodules in SPECT imaging

Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction

On‐board SPECT for localizing functional targets: A simulation study

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