Original ArticlesCombined corrections for attenuation, depth-dependent blur, and motion in cardiac SPECT: A multicenter trial☆
Abstract
Background. The diagnostic accuracy of cardiac single photon emission computed tomography (SPECT) is limited by image-degrading factors, such as heart or subject motion, depth-dependent blurring caused by the collimator, and photon scatter and attenuation. We developed correction approaches for motion, depth-dependent blur, and attenuation and performed a multicenter validation. Methods and Results. Motion was corrected both transversely and axially with a cross-correlation technique. Depth-dependent blurring was corrected by first back-projecting each projection and then applying a depth-dependent Wiener filter row by row. Attenuation was corrected with an iterative, nonuniform Chang algorithm, based on a transmission scan-generated attenuation map. We validated these approaches in 112 subjects, including 36 women (20 healthy volunteers, 8 angiographically normal patients, and 8 patients with coronary artery disease [CAD] found by means of angiography) and 76 men (23 healthy volunteers, 10 angiographically normal patients, and 43 patients with CAD found by means of angiography). Either technetium 99m or thallium 201 was used for emission; either gadolinium 153 or Tc-99m was used for transmission. Images were reconstructed and blindly interpreted with a 5-point scale for receiver operating characteristic analysis in 2 ways: motion correction plus a Butterworth filter, and combined motion and blur and attenuation corrections. The interpretation by means of consensus was for the overall presence of CAD and vascular territory. The receiver operating characteristic curves for overall presence and each of the 3 main coronary arteries were all shifted upward and to the left and had larger areas under the curve, for combined corrections compared with motion correction and Butterworth. Sensitivity/specificity for motion correction and Butterworth were 84/69, 64/71, 32/94, and 71/81 overall for the left anterior descending, the right coronary artery, and circumflex territories, respectively, compared with 88/92, 77/93, 50/97, and 74/95, respectively, for the combined corrections. Conclusions. The proposed combined corrections for motion, depth-dependent blur, and attenuation significantly improve diagnostic accuracy, when compared with motion correction alone. (J Nucl Cardiol 2000;7:414-25.)
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Myocardial perfusion imaging with retrospective gating and integrated correction of attenuation, scatter, respiration, motion, and arrhythmia
2023, Journal of Nuclear CardiologyAbsolute quantitative myocardial perfusion SPECT requires addressing of aleatory and epistemic uncertainties in conjunction with providing image quality sufficient for lesion detection and characterization. Iterative reconstruction methods enable the mitigation of the root causes of image degradation. This study aimed to determine the feasibility of a new SPECT/CT method with integrated corrections attempting to enable absolute quantitative cardiac imaging (xSPECT Cardiac; xSC).
We compared images of prototype xSC and conventional SPECT (Flash3DTM) acquired at rest from 56 patients aged 71 ± 12 y with suspected coronary heart disease. The xSC prototype comprised list-mode acquisitions with continuous rotation and subsequent iterative reconstructions with retrospective electrocardiography (ECG) gating. Besides accurate image formation modeling, patient-specific CT-based attenuation and energy window-based scatter correction, additionally we applied mitigation for patient and organ motion between views (inter-view), and within views (intra-view) for both the gated and ungated reconstruction. We then assessed image quality, semiquantitative regional values, and left ventricular function in the images.
The quality of all xSC images was acceptable for clinical purposes. A polar map showed more uniform distribution for xSC compared with Flash3D, while lower apical count and higher defect contrast of myocardial infarction (p = 0.0004) were observed on xSC images. Wall motion, 16-gate volume curve, and ejection fraction were at least acceptable, with indication of improvements. The clinical prospectively gated method rejected beats ≥20% in 6 patients, whereas retrospective gating used an average of 98% beats, excluding 2% of beats. We used the list-mode data to create a product equivalent prospectively gated dataset. The dataset showed that the xSC method generated 18% higher count data and images with less noise, with comparable functional variables of volume and LVEF (p = ns).
Quantitative myocardial perfusion imaging with the list-mode-based prototype xSPECT Cardiac is feasible, resulting in images of at least acceptable image quality.
Comparison of non-attenuation corrected and attenuation corrected myocardial perfusion SPECT
2016, Egyptian Journal of Radiology and Nuclear MedicineCitation Excerpt :Our study also showed considerable improvement in normalcy rate after attenuation correction i.e. from 19% to 74% (Fig. 2). There are other studies that also showed similar results (4,18,26–35). In patients with low likelihood of CAD the normalcy rate can be obtained as high as 98% (15).
To assess the significance of attenuation correction on sensitivity, specificity and diagnostic accuracy of myocardial perfusion SPECT.
102 patients referred for myocardial perfusion imaging (MPI) were divided into two groups: 42 patients (mean age: 54.6 ± 12.6) were enrolled in the group A, who had undergone coronary artery angiography, within six months of the scan. 60 patients (mean age: 49.79 ± 11.3) were placed in the group B who had a <15% pretest likelihood of CAD. Both non-corrected (NC) and attenuation corrected (AC) images were visually analyzed according to 17-segment model of the left ventricular cavity. Visual assessment derived sensitivity, specificity, diagnostic accuracy and normalcy rate of NC and AC sets of images were compared using McNemar test.
Sensitivity, specificity and diagnostic accuracy for detection of coronary artery disease were found to be 100%, 11% and 79% respectively for NC images and 66%, 78% and 68% for AC images. The p value was found to be significant in only the RCA territory. Normalcy rates in the group B population were 19% for NC image set and 74% for the AC image set. No significant difference on basis of BMI was observed in attenuation corrected scans. The technique appears to be more valuable in men.
This study demonstrates that CT based attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging significantly improved the specificity of the RCA territory compared with non-attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging in both genders irrespective of BMI.
Risk stratification using line source attenuation correction with rest/stress Tc-99m sestamibi SPECT myocardial perfusion imaging
2014, Journal of Nuclear CardiologyAlthough line source attenuation correction (AC) in SPECT MPI studies improves diagnostic accuracy, its prognostic value is less understood.
Consecutive patients (n = 6,513) who underwent rest/stress AC ECG-gated SPECT MPI were followed for cardiac death or non-fatal myocardial infarction (MI). A 17-segment model and AC summed stress score (SSS) were used to classify images.
Of the 6,513 patients, cardiac death or non-fatal MI occurred in 267 (4.1%), over 2.0 ± 1.4 years. The AC-SSS in patients with a cardiac event (5.6 ± 7.8) was significantly higher than in those without (1.9 ± 4.6, P < .001). The annualized cardiac event rate in patients with an AC-SSS 1-3 (3.6%) was significantly higher than in those with an AC-SSS = 0 (1.1%, P < .001) but similar to that in those with an AC-SSS 4-8 (2.9%, P = .4). Accordingly, patients were classified to AC-SSS = 0, 1-8, and >8 with annualized cardiac event rates of 1.1%, 3.2%, and 8.5%, respectively (P < .0001). In multivariate analysis, an AC-SSS 1-8 and >8 emerged as independent predictors of cardiac events (P < .02 and P < .0001, respectively).
Rest/stress ECG-gated SPECT MPI with line source AC provides highly effective and incremental risk stratification for future cardiac events.
Does rubidium-82 PET have superior accuracy to SPECT perfusion imaging for the diagnosis of obstructive coronary disease?: A systematic review and meta-analysis
2012, Journal of the American College of CardiologyCitation Excerpt :From these 10 full-text articles were obtained, of which 3 met inclusion criteria (10,13,14). From the previous systematic review we extracted citations for 12 full-text articles that were examined, of which 4 (12,27–29) were included. Examination of reference lists yielded 1 further study for inclusion (11) (Fig. 1).
The purpose of this study was to evaluate the accuracy of rubidium (Rb)-82 positron emission tomography (PET) for the diagnosis of obstructive coronary artery disease (CAD) in comparison to single-photon emission tomography (SPECT).
Myocardial perfusion imaging is widely used in the assessment of patients with known or suspected CAD. PET using Rb-82 has potential advantages over SPECT that may make it more accurate and that reduce radiation exposure compared with SPECT but has increased costs. Comparisons of these technologies are highly relevant for policy makers and practice guidelines. However, studies directly comparing Rb-82 PET with contemporary SPECT have been limited.
The authors therefore undertook a systematic review of studies where either Rb-82 PET or technetium-99m SPECT with both attenuation correction and electrocardiography-gating were used as a diagnostic test for obstructive CAD with invasive coronary angiogram as a reference standard. These technologies were then compared.
Fifteen PET and 8 SPECT studies (1,344 and 1,755 patients, respectively) met inclusion criteria and pooled accuracy using weighted averages according to the size of the patient population was determined for PET and SPECT with sensitivities of 90% (confidence interval [CI]: 0.88 to 0.92) and 85% (CI: 0.82 to 0.87) and specificities of 88% (CI: 0.85 to 0.91) and 85% (CI: 0.82 to 0.87), respectively. Summary receiver-operating characteristic curves were computed: area under the curve was 0.95 and 0.90 for PET and SPECT, respectively (p < 0.0001). There was heterogeneity among study populations and some studies were limited by referral bias.
Rb-82 PET is accurate for the detection of obstructive CAD and, despite advances in SPECT technology, remains superior. More widespread use of Rb-82 PET may be beneficial to improve CAD detection.
Impact of attenuation correction in myocardial perfusion scintigraphy
2012, Medecine NucleaireLa tomoscintigraphie myocardique de perfusion est un examen de routine pour l’évaluation de patients atteints de cardiopathie ischémique. Cependant, des artefacts d’atténuation peuvent entraîner une diminution de la spécificité. Ils peuvent être corrigés avec une correction d’atténuation. Nous avons inclus de manière prospective 70 patients ayant bénéficié d’une tomoscintigraphie myocardique de perfusion avec et sans correction d’atténuation à l’aide d’une imagerie de transmission tomodensitométrique intégrée dans le système d’acquisition d’émission chez des patients à faible prévalence de cardiopathie ischémique. Une analyse quantitative automatique constituant des scores sommés de stress (SSS) et de repos (SRS) et un score sommé de différences (SDS) a été utilisée comme critères d’interprétation. Les résultats ont montré une spécificité de 80 % pour les images avec correction d’atténuation (IRAC) et 56 % pour les images sans correction d’atténuation (IRNC), une valeur prédictive positive de 40 % pour les IRAC et 23 % pour les IRNC, sans modification significative de la sensibilité. Un test de Student non apparié n’a pas mis en évidence de différence significative entre la population globale et celle où un artefact a été corrigé pour la fréquence cardiaque et respiratoire, l’index de masse corporelle (IMC), le périmètre abdominal, thoracique et le rapport de ces deux derniers. La correction d’atténuation améliore nettement la spécificité de la scintigraphie myocardique sans différence significative de la sensibilité. La majorité des corrections ont concerné des artefacts de la paroi inférieure chez des hommes. Il n’y a pas de corrélation entre les paramètres anthropomorphiques et physiologiques et la survenue d’un artefact d’atténuation corrigé par les données de tomodensitométrie.
Myocardial perfusion SPECT is a routine for the assessment of patients with coronary artery disease (CAD). However, attenuation artifacts may decrease the specificity of the test. These artifacts can be corrected with an attenuation correction. We prospectively included 70 patients who underwent myocardial perfusion SPECT with (IRAC) and without (IRNC) attenuation correction using transmission CT imaging integrated in the acquisition system in patients with low prevalence of CAD. Automatic quantitative analysis with summed stress score (SSS) and rest (SRS) and summed difference score (SDS) was used as interpretation criteria. The results showed a specificity of 80% for IRAC and 56% for IRNC, a positive predictive value of 40% for IRAC and 23% for IRNC, without any significant change in sensitivity. An unpaired t-test showed no significant difference between the overall population and one where an artifact was corrected for heart rate and breath rate during the acquisition effort, the body mass index, chest and abdomen circumferences, and the ratio of these two parameters. Attenuation correction significantly improves the specificity of myocardial scintigraphy with no significant difference in sensitivity. The majority of corrections were for artifacts from the inferior wall in men. There is no correlation between the anthropomorphic and physiological parameters and the occurrence of an artifact of attenuation corrected with CT data.
Accuracy and precision of radioactivity quantification in nuclear medicine images
2012, Seminars in Nuclear MedicineThe ability to reliably quantify activity in nuclear medicine has a number of increasingly important applications. Dosimetry for targeted therapy treatment planning or for approval of new imaging agents requires accurate estimation of the activity in organs, tumors, or voxels at several imaging time points. Another important application is the use of quantitative metrics derived from images, such as the standard uptake value commonly used in positron emission tomography (PET), to diagnose and follow treatment of tumors. These measures require quantification of organ or tumor activities in nuclear medicine images. However, there are a number of physical, patient, and technical factors that limit the quantitative reliability of nuclear medicine images. There have been a large number of improvements in instrumentation, including the development of hybrid single-photon emission computed tomography/computed tomography and PET/computed tomography systems, and reconstruction methods, including the use of statistical iterative reconstruction methods, which have substantially improved the ability to obtain reliable quantitative information from planar, single-photon emission computed tomography, and PET images.
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Supported in part by an unrestricted gift from SMV America.