Wide Beam Reconstruction Research Articles

Long-term prognostic value of low-dose normal stress-only myocardial perfusion imaging by wide beam reconstruction: A competing risk analysis

BackgroundA normal stress myocardial perfusion single-photon emission computed tomography (MPS) is associated with a good clinical outcome. New iterative algorithms, such as wide beam reconstruction (WBR), which improve image interpretation with half-dose or half-time acquisition, have been proposed for cardiac MPS. The aim of this study was to assess the long-term predictive value of a low-dose normal stress-only MPS with WBR using conventional Anger camera in patients with known or suspected coronary artery disease (CAD). Methods and ResultsA total of 2106 patients with known or suspected CAD and normal perfusion at half-dose stress-only MPS protocol were followed for a mean of 6.6 ± 2.7 years. MPS data were reconstructed with WBR iterative algorithm. End-point events were cardiac death or nonfatal myocardial infarction. Noncardiac death was considered the competing event. During follow-up, 149 cardiac events occurred with an annualized event rate of 1.2%. Independent predictors of cardiac events at Cox analysis were age, male gender, diabetes mellitus, previous myocardial infarction and the need for pharmacologic stress testing. At Fine-Gray analysis the cumulative incidence of cardiac events progressively increases with age and in the presence of diabetes for any combination of gender and stress type. Survival tree analysis confirmed that long-term prognosis considerably varies according of risk factors profile. ConclusionsLow-dose normal stress-only WBR MPS has a reliable long-term prognostic value in patients with suspected or known CAD. This finding supports the introduction of such a method into clinical practice with a consistent dose optimization in the interest of patients and exposed staff.

Regadenoson-induced coronary vasospasm resulting in severe reversible perfusion defects and transient ischemic dilation on SPECT stress myocardial perfusion imaging

A 58-year-old woman with hypertension and diabetes presented to the emergency department with exertional right-sided chest pain. Her cardiac biomarkers were negative and her electrocardiogram demonstrated no significant abnormalities. She subsequently underwent pharmacologic stress myocardial perfusion imaging using regadenoson. Her electrocardiogram demonstrated no significant ischemic changes and she only complained of dyspnea following regadenoson infusion. Perfusion images were acquired using the GE millennium MC scanner and processed using Xpress3 cardiac wide beam reconstruction software (UltraSPECT, Ltd.) at an xeleris functional imaging workstation. Review of the rotating raw data revealed breast attenuation artifact but no significant patient motion. Her perfusion imaging revealed a severe defect in the mid-to-distal inferolateral wall that was mostly reversible suggestive of significant ischemia. In addition, there was pronounced dilation of the left ventricle with stress (Figure 1). The patient underwent cardiac catheterization which demonstrated no obstructive coronary artery disease (Figures 2, 3). Upon further analysis of the patient’s history, she had apparently been diagnosed with Prinzmetal angina in the past and had undergone cardiac catheterization eight years prior for similar symptoms and this was normal as well. She was subsequently discharged on appropriate pharmacotherapy and was asymptomatic. Multiple reports have demonstrated coronary vasospasm after use of adenosine for stress testing. However, there is a limited data available in reference to regadenoson, which is a selective A2A adenosine receptor agonist. Recent emerging data demonstrate, however, that regadenoson may also lead to vasospasm as it has similar pharmacologic properties. Our case illustrates severely abnormal myocardial perfusion imaging with reversible regional ischemia and transient ischemic dilation with no obstructive coronary artery disease likely due to regadenoson-induced coronary vasospasm. Therefore, vasospastic heart disease is a potential confounding factor to consider in the interpretation of regadenoson stress MPI and may be clinically relevant in the management of patients with conflicting anatomic and perfusion findings.

Half-time Tc-99m sestamibi imaging with a direct conversion molecular breast imaging system.

BackgroundIn an effort to reduce necessary acquisition time to perform molecular breast imaging (MBI), we compared diagnostic performance of MBI performed with standard 10-min-per-view acquisitions and half-time 5-min-per-view acquisitions, with and without wide beam reconstruction (WBR) processing.MethodsEighty-two bilateral, two-view MBI studies were reviewed. Studies were performed with 300 MBq Tc-99 m sestamibi and a direct conversion molecular breast imaging (DC-MBI) system. Acquisitions were 10 min-per-view; the first half of each was extracted to create 5-min-per-view datasets, and WBR processing was applied.The 10-min-, 5-min-, and 5-min-per-view WBR studies were independently interpreted in a randomized, blinded fashion by two radiologists. Assessments of 1 to 5 were assigned; 4 and 5 were considered test positive. Background parenchymal uptake, lesion type, distribution of non-mass lesions, lesion intensity, and image quality were described.ResultsConsidering detection of all malignant and benign lesions, 5 min-per-view MBI had lower sensitivity (mean of 70% vs. 85% (p ≤ 0.04) for two readers) and lower area under curve (AUC) (mean of 92.7 vs. 99.6, p ≤ 0.01) but had similar specificity (p = 1.0). WBR processing did not alter sensitivity, specificity, or AUC obtained at 5 min-per-view.Overall agreement in final assessment between 5-min-per-view and 10-min-per-view acquisition types was near perfect (κ = 0.82 to 0.89); however, fair to moderate agreement was observed for assessment category 3 (probably benign) (κ = 0.24 to 0.48). Of 33 malignant lesions, 6 (18%) were changed from assessment of 4 or 5 with 10-min-per-view MBI to assessment of 3 with 5-min-per-view MBI. Image quality of 5-min-per-view studies was reduced compared to 10-min-per-view studies for both readers (3.24 vs. 3.98, p < 0.0001 and 3.60 vs. 3.91, p < 0.0001). WBR processing improved image quality for one reader (3.85 vs. 3.24, p < 0.0001).ConclusionsAlthough similar radiologic interpretations were obtained with 10-min- and 5-min-per-view DC-MBI, resulting in substantial agreement in final assessment, notable exceptions were found: (1) perceived image quality at 5 min-per-view was lower than that for 10-min-per-view studies and (2) in a number of cases, assessment was downgraded from a recommendation of biopsy to that of short interval follow-up.

Temporal evolution of administered activity in cardiac gated SPECT and patients’ effective dose: analysis of an historical series

Myocardial perfusion imaging contributes >20% of the average medical radiation exposure to the population in the USA. Imaging protocols able to achieve a radiation exposure ≤9mSv in 50% of the studies by 2014 have been recommended. The aim of this study was to analyse the temporal evolution of administered activities in patients scheduled for dual-day (99m)Tc tracer gated single photon emission computed tomography (SPECT) and to compare different dose administration protocols in terms of patients' effective dose. Patients evaluated from 1 July 2002 to 31 January 2012 were allocated according to the protocol adopted: group 1: fixed activity according to diagnostic reference level: 740MBq up to 80kg (adapted for weight <60kg); 900MBq 80-100kg, 1,110MBq >100kg, standard filtered back-projection (FBP) reconstruction; group 2: weight-adjusted activity: 8MBq/kg up to 1,110MBq, standard FBP reconstruction; and group 3: 4MBq/kg, UltraSPECT wide beam reconstruction (WBR) reconstruction. A dual-head Anger camera (GE Helix) was used. A total of 9,060 patients were allocated to different groups: 4,751 in group 1, 2,844 in group 2 and 1,465 in group 3. The stress + rest administered activity was 1,617 ± 180 in group 1, 1,136 ± 260 in group 2 and 682 ± 164MBq in group 3 (all p < 0.001). Patients' effective dose was 13.7 ± 3 in group 1, 9.5 ± 2.8 in group 2 and 5.7 ± 1.6mSv in group 3 (all p < 0.001). The 50th percentile was 12.6 in group 1, 9.1 in group 2 and 5.3mSv in group 3. The effective dose received by the dedicated cardiologists was 2.1, 1.5 and 1.0μSv/exam in group 1, group 2 and group 3 periods, respectively (all p < 0.001). A significant reduction over time in the administered activity for gated SPECT was achieved; accordingly, a significant reduction in patients' exposure was obtained. A simple weight-adjusted strategy with 8MBq/kg immediately fulfils the recommendations to limit exposure. In selected group 3 patients, a stress-only strategy allows for studies with <3mSv exposure. Thus, at least the adoption of a new reconstruction algorithm is strongly encouraged, and suggested tracer activities for cardiac gated SPECT are to be revised.

Very low-activity stress/high-activity rest, single-day myocardial perfusion SPECT with a conventional sodium iodide camera and wide beam reconstruction processing

BackgroundA stress (S)/rest (R) 1-day Tc-99m sestamibi protocol is logistically advantageous and facilitates stress-only imaging. However, with conventional 370 MBq (10 mCi) S activity and subsequent 1,110-1,295 MBq (30-35 mCi) R activity there is a risk of S-to-R “shine-through” and underestimation of defect reversibility. New software methods cope with lower counting statistics and should allow for both a reduced S activity and also less likelihood of S-to-R “shine-through.” Methods102 prospective patients [49 men, 53 women; mean weight 178 ± 41 lbs (range 98-265 lbs); chest 41.5″ ± 4.0″ (range 32″-52″)] received 192.4 + 18.5 MBq (5.2 ± 0.5 mCi) Tc-99m sestamibi S (25 exercise, 77 regadenoson) activity followed in 30-40 minutes by “full-time” (12 minutes) two-headed NaI camera S SPECT. Immediately thereafter, a 16-minute S SPECT acquisition was also performed in 37/102 patients. Then at 60-80 minute post-S all patients received 1328.3 + 129.5 MBq (35.9 ± 3.5 mCi) Tc-99m sestamibi, and “half-time” (7.5 minutes) R SPECT was acquired. All tomograms were processed with wide beam reconstruction (WBR, UltraSPECT Ltd.) software. A time-adjusted R/S myocardial count density ratio (MCDR) was calculated using automated software. S SPECT quality was visually graded (poor, fair, good, excellent) based upon myocardial definition, cavity contrast, RV visualization, and noise. For comparison, the S/R MCDR was calculated in 581 consecutive patients undergoing a conventional 370 MBq R/1110 MBq S (10 mCi R/30 mCi S) protocol. ResultsS SPECT was normal in 44 patients (43%). Image quality was good-excellent in 93 (91%) patients with 12-minute S SPECT. Also in 37 (98%) patients with 16-minute S SPECT, quality was good-excellent. In patients with >42″ chests 12-minute S SPECT quality worsened with increasing chest circumference, manifested by myocardial “blurring.” Image quality improved by ≥1 grade in the 12/37 patients (32%) also undergoing 16-minute S SPECT. The time- and decay-corrected 12-minute mean R/S MCDR was 5.78, a ratio adequate to minimize S-to-R shine-through, as verified in phantom experiments, and significantly better than a 3.79 S/R ratio achieved in the 581 patients undergoing a conventional R/S protocol. ConclusionsAn approximately 185 MBq (5 mCi S) Tc-99m SPECT processed with WBR provides adequate image quality. For larger patients prolonging image acquisition to 16 minutes is beneficial. For patients with normal S SPECT, a S-only protocol is feasible, affording them a very low (approximately 1.4 mSv) radiation dose. If subsequent R SPECT is necessary, it can be performed with approximately 1,332 MBq (36 mCi) with minimal S-R “shine-through.”

A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT

ObjectivesWide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity. MethodsIn 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate “half-time” acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received “half-dose” rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise. ResultsMean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for “full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for “half-time” WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for “half-dose” WBR. “Half-time” and “half-dose” WBR image quality were both superior to standard full-time OSEM (P’s < .001). There was no significant difference between the summed stress and rest scores for “full-time” OSEM vs “half-time” WBR in 82 patients with perfusion defects. ConclusionsBoth “half-time” and “half-dose” WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.

New Toys for Nuclear Cardiologists

Gordon Liljestrand is credited with establishing modern nuclear cardiology as a noninvasive imaging modality in 1939.1 Table summarizes major technological advancements in myocardial perfusion imaging over the past 70 years that have led to more accurate assessment of coronary artery disease (CAD). Most of these technical advances have involved radioisotopes and computer software. Camera hardware has undergone relatively little change since the introduction of the gamma camera, also commonly referred to as the scintillation camera, by Hal Anger in 1958.2 The gamma camera has performed admirably as the workhorse for myocardial perfusion imaging over the years but has several limitations. Sensitivity and resolution are modest. Imaging is inefficient as the heart occupies only a small portion of the field of view. Imaging places several demands on the patient, requiring relatively long imaging times (8 to 12 minutes) while lying motionless on a narrow, hard table with one or both arms fully abducted to minimize the distance between the patient's chest and the rotating detectors. The relatively long imaging times require administration of fairly high doses of radioisotopes with attendant higher radiation exposure, an issue of increasing medical and societal concern.3 View this table: Table. Developments in Nuclear Cardiology Article see p 51 In the past few years, there have been tremendous advances in gamma camera technology due to the replacement of the conventional sodium iodide (NaI)-based systems with solid-state detectors using cesium iodide coupled to photodiodes or novel semiconductor-based detectors using cadmium zinc telluride (CZT). The most promising of these new technologies is the CZT detector, which directly converts gamma radiation to an electronic pulse and thereby eliminates the need for a scintillating crystal and photomultiplier tubes. The CZT detector is substantially smaller than a NaI-based detector. In addition, the CZT detector offers substantially better energy resolution and spatial resolution than …

Wide-beam reconstruction half-time SPECT improves diagnostic certainty and preserves normalcy and accuracy: A quantitative perfusion analysis

BackgroundFiltered back-projection (FBP) has been a standard in SPECT imaging. Newer iterative reconstruction algorithms have been shown to improve image quality and shorten acquisition time by taking into account statistical nature of raw data and using resolution recovery (RR). Wide-beam reconstruction (WBR) is an iterative algorithm with RR and adaptive noise control. We prospectively investigated outcome of WBR half-time SPECT on diagnostic certainty, accuracy and normalcy by quantitative perfusion analysis in comparison to full-time FBP images. Methods434 patients underwent rest 201Tl/stress 99mTc-sestamibi full-time (20 s/stop, FBP) followed by a half-time (10 s/stop, WBR) SPECT. 34 patients underwent an angiogram within 90 days of SPECT. Diagnostic certainty was based on summed stress scores (SSS, 5-point/17 segments): normal if SSS ≤ 1, equivocal if SSS = 2-3, and abnormal if SSS ≥ 4. Perfusion defects were normalized to a percent of total myocardium, and expressed as %LV = defect SSS/maximal SSS × 100% with maximal SSS of 28 for left anterior descending (LAD), and of 20 for right coronary (RCA) and left circumflex (LCX). Change in %LV (Δ%LV = %LV FBP − %LV WBR) was evaluated for diagnostically discordant versus concordant scans. ResultsSSS and %LV demonstrated very good correlation. There were significantly fewer equivocal scans with WBR (38 vs 151 FBP, P < .0001). Most discordant scans were equivocal FBP SPECT becoming normal with WBR (123/151). Δ%LVLAD for discordant studies was greater for women (5.4% ± 4.2%, P < .001), while Δ%LVRCA,LCX (4.4% ± 5.1%, P < .001; 1.2% ± 5.0%, P = .04) were greater for men. Normalcy rate was 91.4% for FBP and WBR with more definitely normal WBR studies (84.5% vs 43.9% for FBP, P < .0001). There were no differences in sensitivity (FBP 84.2%, WBR 81.6%), specificity (FBP 54.6%, WBR 63.6%), and accuracy (FBP, WBR 77.6%). ConclusionQuantitative perfusion analysis suggests that adaptive noise control with WBR improves uniformity of myocardium comparing to FBP techniques, and results in improved diagnostic certainty while preserving normalcy and accuracy.

Wide beam reconstruction for half-dose or half-time cardiac gated SPECT acquisitions: optimization of resources and reduction in radiation exposure

A new iterative reconstruction algorithm (WBR™) has been recently proposed for cardiac single photon emission computed tomography (SPECT). The WBR™ technology is designed to reduce noise, improving lesion identification without affecting the image resolution, allowing SPECT studies with reduced count statistic. This allows for either half-time (HT) or half-dose (HD) cardiac SPECT, with image quality and quantitative data comparable to standard-time (ST) or standard-dose (SD) SPECT. Few data exist on the comparison between conventional filtered backprojection (FBP) and this new algorithm in a clinical setting. The aim of this study was to compare the performance of FBP and WBR™. Phantoms studies were performed to compare spatial resolution and contrast recovery with FBP, ordered subset expectation maximization (OSEM) and WBR™. A group of 92 patients, with different cardiac pathology, scheduled for a stress-rest SPECT were studied: 52 patients (group A) were injected with a SD of tracer and underwent both ST and HT SPECT; 40 patients (group B) were injected with a half dose of tracer and underwent ST SPECT and immediately after an additional SPECT at double time/projection (DT), to compensate for the low count statistic. A 2-day (99m)Tc-sestamibi protocol was used in all patients. SD/ST and HD/DT SPECT were reconstructed with a conventional FBP; SD/HT and HD/ST SPECT were reconstructed with WBR™. The summed stress score (SSS) and summed rest score (SRS) were calculated; the left ventricular ejection fraction (LVEF) was automatically derived. In group A (SD), no significant differences were observed between ST FBP SPECT and HT WBR™ in SSS (11.1 and 11.7, respectively) and SRS (9.4 and 10.3, respectively, NS). LVEF on rest acquisitions was also comparable (50% on ST SPECT and 49% on HT SPECT, NS); LVEF on post-stress studies in HT SPECT (46%) was lower than ST SPECT (50%), although not statistically significant. In group B (HD), SSS (6.2 in ST and 5.3 in DT) and SRS (4.0 in ST and 3.3 in DT) were also comparable. No differences were documented between ST and DT in rest (47 and 48%, respectively) and stress (48 and 50%, respectively) LVEF. WBR™ performance and image quality were comparable to those of conventional FBP, allowing for either HT or HD studies. The former allows for an increased patient throughput and optimization of resources. The latter modalities would allow for a significant reduction in both patients' and operators' exposure. Further studies are needed to validate the clinical use of this method.

Semiqualitative Visual and Quantitative Morphometric Evaluations of Reduced Scan Time and Wide-Beam Reconstruction in Rest-Gated Stress SPECT Myocardial Perfusion Imaging

SPECT myocardial perfusion imaging (MPI) now accounts for well over 90% of all MPI studies performed in the United States. A means of reducing the acquisition time while maintaining diagnostic-quality images would be beneficial for both patients and nuclear cardiology clinics. Wide-beam reconstruction (WBR) is a processing algorithm that attempts to address the challenge of obtaining diagnostic-quality images with shorter counting times. This study was designed to incorporate semiqualitative assessments (physician rankings of image parameters) into quantitative assessments (morphologic measurements), as other researchers have done, in an effort to compare filtered backprojection (FBP)-the gold standard-with WBR. Forty-seven MPI studies (from 34 men and 13 women) were masked to 3 physicians who qualitatively rated the images for image quality, myocardial normality, lesion reversibility, and treatment recommendation on a scale of 1-5, with 1 representing "good" and 5 representing "poor." Quantitative values for summed stress scores, summed rest scores, summed difference scores (SDS), end-diastolic volume, end-systolic volume, and the ejection fraction were calculated and reported. The semiqualitative analyses of image interpretation indicated that WBR yielded significant improvements over FBP in image quality and showed very good to moderate agreement with FBP among physicians for myocardial normality, lesion reversibility, and treatment recommendation. The quantitative analyses of the morphometric values representing myocardial perfusion, through SDS comparisons, were equivalent for the 2 reconstruction methods. Regression analysis indicated that WBR seemed to underestimate the gated stress-derived FBP ejection fraction by 9%-10%. Overall, the WBR method was equivalent or superior to the FBP reconstruction method for MPI with a rest-gated stress same-day protocol in terms of image quality, interpretation, and SDS. Additionally, the advantage of patient comfort derived from shorter imaging times should help reduce motion artifacts and repeat acquisitions as well as enhance patient care and throughput.

Wide beam reconstruction “quarter-time” gated myocardial perfusion SPECT functional imaging: a comparison to “full-time” ordered subset expectation maximum

BackgroundPreviously we reported that compared to iterative reconstruction with ordered subset expectation maximum (OSEM), wide beam reconstruction (WBR), which incorporates resolution recovery and controls noise during reconstruction without applying a post-processing filter, allows half-time SPECT acquisition with preserved diagnostic quality. We now postulate that with further Poisson noise treatment, quarter-time acquisition is possible. MethodsThe half-time WBR algorithm was optimized for quarter-time acquisition based upon anthropomorphic cardiac phantom data and a pilot group of 48 patients (pts). Then using the modified algorithm, 209 pts (91 men, 118 women, mean chest circumference = 40 in) were imaged at rest (R) and stress (S) (9/32 mCi 99mTc-sestamibi) full-time with OSEM, and again quarter-time with the modified WBR algorithm. The 180°, 64-stop, full-time single-day rest (R) (25 second-per-stop, sps) and 8-frame per cardiac cycle post-stress (S) (20 sps) gated SPECT, and then quarter-time R (6 sps) and post-S (4 sps) gated SPECT were acquired. Blinded observers graded scan quality (1 = poor to 5 = excellent) based on myocardial uniformity, endocardial/epicardial edge definition, and background noise. Perfusion defects were scored using a 17-segment model. Using three commercially available software methods, end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction (LVEF) were calculated. ResultsFor the 209 prospective pts, mean image quality for R full-time OSEM and quarter-time WBR were similar (3.5 ± 0.9 vs 3.6 ± 0.7, p NS). For S, quarter-time WBR quality was superior to full-time OSEM (4.3 ± 0.7 vs 3.9 ± 0.7) (P = 1.78 × 10−17). In 35 pts with chest circumferences >44 inches a longer, 10 sps WBR acquisition improved resting image quality. Of 48 pts with abnormal scans (SSSs > 2 by OSEM) mean summed stress scores, summed rest scores, and summed difference scores were not significantly different with quarter-time WBR vs full-time OSEM (11.2 vs 10.9), (9.1 vs 9.0), (2.0 vs 1.9) (P NS). For the three software methods, there was a good correlation of LVEF, EDV, and ESV determined by WBR vs OSEM (all r > 0.92). ESVs were generally higher with WBR, primarily due to better delineation of the valve plane at end-systole, whereas EDVs were similar. Thus, EFs were significantly lower with WBR. ConclusionsFor perfusion SPECT quarter-time WBR affords image quality, defect characterization, and functional assessment equivalent to full-time OSEM.

2.01: Quarter-time myocardial perfusion SPECT wide beam reconstruction

2.01: Quarter-time myocardial perfusion SPECT wide beam reconstruction

Ordered subset expectation maximization and wide beam reconstruction “half-time” gated myocardial perfusion SPECT functional imaging: A comparison to “full-time” filtered backprojection

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.

Clinical results of a novel wide beam reconstruction method for shortening scan time of Tc-99m cardiac SPECT perfusion studies

Newly developed reconstruction algorithms enable the acquisition of images at half of the scan time while maintaining image quality. The purpose of this investigation was to evaluate a novel wide beam reconstruction (WBR) method developed by UltraSPECT for decreasing scan times and to compare it with filtered backprojection (FBP), which is the technique routinely used. Phantom and clinical studies were performed. Hot and cold sphere and cardiac phantom acquisitions were reconstructed via WBR, FBP, and ordered-subsets expectation maximization. Fifty patients were prospectively studied by use of both a standard and a short protocol. The short protocol was performed first on 29 of 50 patients via 8-frame gated technetium 99m stress single photon emission computed tomography and low-energy high-resolution collimators. Stress Tc-99m studies (30-45 mCi) were scanned for 20 seconds per frame. For the short protocol, all parameters remained constant except for the time per frame, which was reduced by 50% on Tc-99m studies. All resting Tc-99m scans (36/50 patients) were processed with FBP for the standard full-scan time studies and with WBR for the short scan studies. The images were interpreted by use of a 17-segment model and 5-degree severity score, and the perfusion and functional variables were determined. Distributions including mean, median, and interquartile ranges were examined for all variables. The differences (FBP - WBR) were computed for all variables and were examined by use of nonparametric signed rank tests to determine whether the median difference was 0. The absolute value of the difference was also examined. Spearman rank-order correlation, a nonparametric measure of association, was used for the 2 methods to determine significant correlations between variables. The hot and cold sphere phantom studies demonstrated that WBR had improved contrast recovery and slightly better background uniformity than did the ordered-subsets expectation maximization. The cardiac phantom studies performed with attenuating medium and background activity showed that the half-scan time images processed with WBR had better contrast recovery and background uniformity than did the full-scan time FBP reconstruction. In the clinical studies, highly significant correlations were observed between WBR and FBP for functional as well as perfusion variables (P < .0001). The summed stress score, summed rest scores, and summed difference score were not statistically different for FBP and WBR (P > .05). Left ventricular volumes had a high correlation coefficient but were significantly larger with FBP than with WBR. Our study results suggest that cardiac single photon emission computed tomography perfusion studies may be performed with the WBR algorithm using half of the scan time without compromising qualitative or quantitative imaging results.

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34.20 Wide Beam Reconstruction method for shortening scan time of gated cardiac stress SPECT: Preliminary evaluation

34.20 Wide Beam Reconstruction method for shortening scan time of gated cardiac stress SPECT: Preliminary evaluation

Improved bone SPECT image quality with the Wide Beam Reconstruction technique

Improved bone SPECT image quality with the Wide Beam Reconstruction technique