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Half-Time SPECT Myocardial Perfusion Imaging with Attenuation Correction
Abstract and Figures
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).
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.
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 (kappa = 0.88) for no AC and 102 to 106 (kappa = 0.91) for AC, similar to the repeatability of FT versus FT (98/100, kappa = 0.95).
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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... In the 2000s, the invention of cadmium zinc telluride (CZT) detector further improved imaging efficiency [1]. Iftikhar Ali et al. [2] adopted ordered-subset expectation maximization with resolution recovery (OSEM-RR) algorithm to keep the image quality for half-time SPECT myocardial perfusion imaging. Aju P. Pazhenkottil [3] proposed a dose-saving algorithm to depress the radiation in SPECT/CT examination. ...
... In this work, we collect anonymous clinical SPECT/CT image pairs, enhance the fast acquired image using deep neural network and evaluate the quality of augmented image quantitatively. Compared to previous work, the innovation of this work lies in: (1) we use clinical SPECT image rather than simulated data used in other works; (2) we combine the SPECT image and corresponding CT images which bear richer anatomical information; and (3) we investigate deep learning performance on ultra-high-speed SPECT (1/7 scan time of normal examination), and the noise level is below the standard for making valid clinical diagnosis. ...
... The fast SPECT imaging technique ameliorates patient experience and reduces motion artifacts. Methods have been proposed to speed up SPECT imaging [1,2,12,13]. However, traditional methods like using advanced detectors or using iterative algorithms could only increase the imaging efficiency by a factor of two, and our methods could apply to ultra-low-dose SPECT imaging with only 1/7 scan time. ...
Background
To generate high-quality bone scan SPECT images from only 1/7 scan time SPECT images using deep learning-based enhancement method.
Materials and methods
Normal-dose (925–1110 MBq) clinical technetium 99 m-methyl diphosphonate (99mTc-MDP) SPECT/CT images and corresponding SPECT/CT images with 1/7 scan time from 20 adult patients with bone disease and a phantom were collected to develop a lesion-attention weighted U ² -Net (Qin et al. in Pattern Recognit 106:107404, 2020), which produces high-quality SPECT images from fast SPECT/CT images. The quality of synthesized SPECT images from different deep learning models was compared using PSNR and SSIM. Clinic evaluation on 5-point Likert scale (5 = excellent) was performed by two experienced nuclear physicians. Average score and Wilcoxon test were constructed to assess the image quality of 1/7 SPECT, DL-enhanced SPECT and the standard SPECT. SUVmax, SUVmean, SSIM and PSNR from each detectable sphere filled with imaging agent were measured and compared for different images.
Results
U ² -Net-based model reached the best PSNR (40.8) and SSIM (0.788) performance compared with other advanced deep learning methods. The clinic evaluation showed the quality of the synthesized SPECT images is much higher than that of fast SPECT images ( P < 0.05). Compared to the standard SPECT images, enhanced images exhibited the same general image quality ( P > 0.999), similar detail of 99mTc-MDP ( P = 0.125) and the same diagnostic confidence ( P = 0.1875). 4, 5 and 6 spheres could be distinguished on 1/7 SPECT, DL-enhanced SPECT and the standard SPECT, respectively. The DL-enhanced phantom image outperformed 1/7 SPECT in SUVmax, SUVmean, SSIM and PSNR in quantitative assessment.
Conclusions
Our proposed method can yield significant image quality improvement in the noise level, details of anatomical structure and SUV accuracy, which enabled applications of ultra fast SPECT bone imaging in real clinic settings.
... Velden et al introduced a efficient radioembolization procedues with acquisition protocols using nonuniform duration of the projection (van der Velden et al 2019). Ali et al introduced ordered-subset expectation maximization with resolution recovery (OSEM-RR) algorithm to enable half-time SPECT myocardial perfusion imaging (Ali et al 2009). However, the physics limitations of these techniques prevent them from being used with older SPECT systems or could not achieve much faster imaging without sacrifice image quality. ...
Objectives To evaluate the clinical performance of deep learning-enhanced ultrafast single photon emission computed tomography/computed tomography (SPECT/CT) bone scans in patients with suspected malignancy.
Approach In this prospective study, 102 patients with potential malignancy were enrolled and underwent a 20 min SPECT/CT and a 3 min SPECT scan. A deep learning model was applied to generate algorithm-enhanced images (3 min-DL SPECT), and the reference modality was the 20 min SPECT/CT scan. Two reviewers independently evaluated general image quality, Tc-99m MDP distribution, artifacts, and diagnostic confidence of 20 min SPECT/CT, 3 min SPECT/CT, and 3 min-DL SPECT/CT images. The sensitivity, specificity, accuracy, and interobserver agreement were calculated. The lesion maximum standard uptake value (SUVmax) of the 3 min-DL and 20 min SPECT/CT images was analyzed. The peak signal-to-noise ratio (PSNR) and structure similarity index measure (SSIM) were evaluated.
Main results The 3 min-DL SPECT/CT images showed significantly superior general image quality, Tc-99m MDP distribution, artifacts, and diagnostic confidence than the 20 min SPECT/CT images (P < 0.0001). The diagnostic performance of the 20 min and 3 min-DL SPECT/CT images was similar for reviewer 1 (paired X2 = 0.333, P = 0.564) and reviewer 2 (paired X2 = 0.05, P = 0.823). The diagnosis results for the 20 min (kappa = 0.822) and 3 min-DL (kappa = 0.732) SPECT/CT images showed high interobserver agreement. The 3 min-DL SPECT/CT images had significantly higher PSNR and SSIM than the 3 min SPECT/CT images (51.44 vs. 38.44, P<0.0001; 0.863 vs. 0.752, P < 0.0001). The SUVmax of the 3 min-DL and 20 min SPECT/CT images showed a strong linear relationship (r = 0.991; P < 0.0001).
Significance Ultrafast SPECT/CT with a 1/7 scan time can be enhanced by deep learning to achieve comparable image quality and diagnostic value to standard acquisition.
... Reduce acquisition time has been investigated in the specific application of myocardial perfusion imaging using SPECT in various studies. [16][17][18] Ali et al. 19 investigated the used of half -time and full-time myocardial perfusion images reconstructed with resolution recovery (RR) on 112 patients. They reported that there was no difference in terms of image quality between full-time and half -time gated images as well as no significant differences in quantitative analysis of left ventricle volume and function. ...
Purpose
Investigate the impact of acquisition time and reconstruction parameters on single‐photon emission computed tomography/computed tomography (SPECT/CT) image quality with the ultimate aim of finding the shortest possible acquisition time for clinical whole‐body SPECT/CT (WB‐SPECT/CT) while maintaining image quality
Methods
The National Electrical Manufacturers Association (NEMA) image quality measurements were performed on a SPECT/CT imaging system using a NEMA International Electrotechnical Commission (IEC) phantom with spherical inserts of varying diameter (10–37 mm), filled with 99mTc in activity sphere‐to‐background concentration ratio of 8.5:1. A gated acquisition was acquired and binned data were summed to simulate acquisitions of 15, 8, and 3 s per projection angle. Images were reconstructed on a Hermes (HERMES Medical Solutions AB, Stockholm, Sweden) workstation using eight subsets and between 4 and 24 iterations of the three‐dimensional (3D) ordered subset expectation maximization (OSEM) algorithm. Reconstructed images were post‐smoothed with 3D Gaussian filter ranging from 0 to 12 mm full‐width at half maximum (FWHM). Contrast recovery, background variability, and contrast‐to‐noise ratio were evaluated
Results
As expected, the spheres were more clearly defined as acquisition time and count statistics improved. The optimal iteration number and Gaussian filter were determined from the contrast recovery convergence and level of noise. Convergence of contrast recovery was observed at eight iterations while 12 iterations yielded stabilized values at all acquisition times. In addition, it was observed that applying 3D Gaussian filter of 8–12 mm FWHM suppressed the noise and mitigated Gibbs artifacts. Background variability was larger for small spheres than larger spheres and the noise decreased when acquisition time became longer. A contrast‐to‐noise ratio >5 was reached for the two smallest spheres of 10 and 13 mm at acquisition times of 8 s
Conclusion
Optimized reconstruction parameters preserved image quality with reduce acquisition time in present study. This study suggests an optimal protocol for clinical 99mTc SPECT/CT can be reached at 8 s per projection angle, with data reconstructed using 12 iterations and eight subset of the 3D OSEM algorithm and 8 mm Gaussian post‐filter.
... Moreover, time reducing also produces image noise. 21 Half time image reconstruction algorithm can generate reconstructed images with enhanced spatial resolution and reduced noise level developed newly available. 22 In previous analysis of gated SPECT MPI, data were reconstructed by FBP and newly iterative produced basically showed similar results. ...
Objective: Myocardial perfusion imaging (MPI) with superior quality of imagesin least acquisition time is imperative for diagnostic purpose. The objective of this study wasto compare the Filter Back Projection (FBP) and half time Astonish reconstruction techniquesin diagnosis of coronary artery disease using cardiac catheterization as gold standard. Placeand period of study: Study was conducted in nuclear cardiology department, at Faisalabadinstitute of cardiology, Faisalabad from November 2014 to July2015. Material & Methods:A total of 60patients (56 + 19years) underwent gated MPI with Tc-99m Sestamibi and 30patients of these underwent cardiac catheterization as well. Images were reconstructed withhalf time Astonish and FBP algorithms. CAD detection, LVEF, perfusion defect comparisonusing polar maps and diagnostic performance were calculated. Results: Perfusion defectscalculated through Astonish and FBP techniques were compared and correlated with coronaryangiogram. The sensitivity, specificity and accuracy for detection of CAD in vascular territories(LAD, LCX & RCA) of the patients were 72%, 41% and 57% with FBP and 86%, 54% and 71%with Astonish. The calculated LVEF showed good correlation (r = 0.8773) between Astonishand cardiac catheterization. Conclusion: There were no significant changes in image quality ofHalf-time Astonish compared to full-time FBP. Astonish reconstruction showed equal resolution,reduced background noise and radiation dose. Reduced scanning time will improve patientscan quality due to less chance of attenuation.
The clinical presentation of coronary artery disease (CAD) has changed during the last 20 years with less ischemia on stress testing and more nonobstructive CAD on coronary angiography. Single-photon emission computed tomography (SPECT) myocardial perfusion imaging should include the measurement of myocardial flow reserve and assessment of coronary calcium for the diagnosis of nonobstructive CAD and coronary microvascular disease. SPECT/CT systems provide reliable attenuation correction for better specificity and low-dose CT for coronary calcium evaluation. SPECT MFR measurement is accurate, well validated, and repeatable.
Myocardial perfusion imaging is a non-invasive procedure that plays an integral role in the diagnosis and management of coronary artery disease. With the routine use of computerised tomography attenuation correction (CTAC) in myocardial perfusion imaging still under debate, the aim of this review was to determine the impact of CTAC on image quality in myocardial perfusion imaging. Medline, Embase and CINAHL were searched from the earliest available time until August 2019. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies version 2. Details pertaining to image quality and diagnostic accuracy were analysed, and results summarised descriptively. Three studies with 'unclear' risk of bias and low applicability concerns (1002 participants) from a yield of 2725 articles were identified. Two studies demonstrated an increase in image quality, and one study found no difference in image quality when using CTAC compared to no attenuation correction. Benefits of CTAC for improving image quality remain unclear. Given the potential exposure risk with the addition of CTAC, patient and clinician factors should inform decision making for use of CTAC in myocardial perfusion imaging for coronary artery disease.
Shortening scan time and/or reducing radiation dose at maintained image quality are the main issues of the current research in radionuclide myocardial perfusion imaging (MPI). We aimed to validate a new iterative reconstruction (IR) algorithm for SPECT MPI allowing shortened acquisition time (HALF time) while maintaining image quality vs. standard full time acquisition (FULL time).
In this study, 50 patients, referred for evaluation of known or suspected coronary artery disease by SPECT MPI using 99mTc-Tetrofosmin, underwent 1-day adenosine stress 300 MBq/rest 900 MBq protocol with standard (stress 15 min/rest 15 min FULL time) immediately followed by short emission scan (stress 9 min/rest 7 min HALF time) on a Ventri SPECT camera (GE Healthcare). FULL time scans were processed with IR, short scans were additionally processed with a recently developed software algorithm for HALF time emission scans. All reconstructions were subsequently analyzed using commercially available software (QPS/QGS, Cedars Medical Sinai) with/without X-ray based attenuation correction (AC). Uptake values (percent of maximum) were compared by regression and Bland-Altman (BA) analysis in a 20-segment model.
HALF scans yielded a 96% readout and 100% clinical diagnosis concordance compared to FULL. Correlation for uptake in each segment (n = 1,000) was r = 0.87at stress (p < 0.001) and r = 0.89 at rest (p < 0.001) with respective BA limits of agreement of -11% to 10% and -12% to 11%. After AC similar correlation (r = 0.82, rest; r = 0.80, stress, both p < 0.001) and BA limits were found (-12% to 10%; -13% to 12%).
With the new IR algorithm, SPECT MPI can be acquired at half of the scan time without compromising image quality, resulting in an excellent agreement with FULL time scans regarding to uptake and clinical conclusion.
The aim of the present study was to investigate a new type of Bayesian one-step late reconstruction method which utilizes a median root prior (MRP). The method favours images which have locally monotonous radioactivity concentrations. The new reconstruction algorithm was applied to ideal simulated data, phantom data and some patient examinations with PET. The same projection data were reconstructed with filtered back-projection (FBP) and maximum likelihood-expectation maximization (ML-EM) methods for comparison. The MRP method provided good-quality images with a similar resolution to the FBP method with a ramp filter, and at the same time the noise properties were as good as with Hann-filtered FBP images. The typical artefacts seen in FBP reconstructed images outside of the object were completely removed, as was the grainy noise inside the object. Quantitatively, the resulting average regional radioactivity concentrations in a large region of interest in images produced by the MRP method corresponded to the FBP and ML-EM results but at the pixel by pixel level the MRP method proved to be the most accurate of the tested methods. In contrast to other iterative reconstruction methods, e.g. ML-EM, the MRP method was not sensitive to the number of iterations nor to the adjustment of reconstruction parameters. Only the Bayesian parameter had to be set. The proposed MRP method is much more simple to calculate than the methods described previously, both with regard to the parameter settings and in terms of general use. The new MRP reconstruction method was shown to produce high-quality quantitative emission images with only one parameter setting in addition to the number of iterations.
Compared to filtered back projection (FBP), OSEM with resolution recovery (OSEM-RR) and wide beam reconstruction (WBR)(UltraSPECT Ltd.), which resolve resolution and suppress noise simultaneously during reconstruction, have been shown to maintain/improve myocardial perfusion SPECT quality, even with low count density half-time acquisitions. We postulated that their characteristics would be advantageous for gated SPECT, where each frame is only 1/8th the count density of the summed perfusion images.
An 9 mCi rest/32 mCi (333/1184 MBq) stress Tc(99m) sestamibi protocol was used. 15-min FBP, and additional 7-min OSEM-RR and WBR post-stress 8-frame/cardiac cycle SPECT scans were acquired with 90 degrees -angled dual-headed detectors equipped with high resolution collimators in 156 patients. In 82 patients (48F, 34M) (123-252 lbs) with perfusion defects gated image quality was graded visually: 1 (poor)-5 (excellent) Regional LV wall motion (WM) was scored: 0 (normal)-4 (dyskinesis) in a total of 50 vascular territories with defects. Using Myometrix software (GE Healthcare), post-stress EDV, ESV, and EF were calculated for each method. Additionally, for purposes of comparison, the FBP gated tomograms were processed with other commercially available packages, Emory Toolbox and Cedars QGS.
Despite half-time acquisitions, compared to FBP, image quality increased marginally with OSEM-RR (P = .09) but very significantly with WBR (P = 1.9 x 10(-21)). The WM score was greater only for WBR (P = 4.8 x 10(-8)). Although quantitative parameters correlated well with those determined by FBP (all EF r's > 0.85; all volume r's > 0.93), EFs were significantly lower (P = .0001 for OSEM-RR, 3.4 x 10(-14) for WBR), primarily due to a decrease in EDV with OSEM-RR (P = 7.3 x 10(-13)) and an increase in ESV with WBR (P = 9.2 x 10(-5)). However, inter-method differences in these parameters were of similar magnitude to differences encountered among the commercially available software methods.
Half-time OSEM-RR and particularly WBR improve gated SPECT diagnostic quality compared to full-time FBP due to increased resolution and reduced noise. However, these attributes, which affect endocardial edge detection, result in a systematic offset in EDV, ESV, and EF.