Detection Of Myocardial Perfusion Defects Research Articles

Beyond greyscale: improved detection of myocardial perfusion defects in spectral CT aortic angiography.

A 27-year-old female presented with acute-onset left-sided radiating chest pain, dizziness, and nausea triggered by recreational cycling and aggravated by exertion. Personal and family medical history was negative for heart disease. Nicotine and cannabis abuse stood out as the only cardiovascular risk factors. ECG showed T-wave inversions in V2 and V3 and cardiac biomarkers were elevated (peak hs-troponine I 17 900 ng/L, creatine kinase 1000 U/L). Thoracoabdominal ECG-gated CT angiography was performed on a second-generation spectral CT scanner (CT 7500, Philips Healthcare, the Netherlands) to rule out aortic dissection. While conventional images (A) appeared inconspicuous, the iodine density map (B) showed markedly reduced iodine uptake of the left anterolateral and inferolateral basal to midventricular myocardium (arrowhead). Emergency coronary angiography (C) confirmed type 2 spontaneous coronary dissection (SCAD) of the mid and distal left circumflex artery and hypokinesia of the lateral wall. SCAD was treated conservatively since coronary blood flow was preserved and the patient exhibited only mild symptoms at that time. In the absence of other risk factors for SCAD such as fibromuscular dysplasia or connective tissue disorders, cannabis use stands out as a possible provoking factor in our patient. This case illustrates the value of spectral CT as it allows for on-demand multi-energy analysis of routine scans without prior selection of a dedicated protocol and can improve the detection of perfusion-related pathologies. The area of reduced iodine uptake closely matched late gadolinium enhancement on follow-up cardiac MRI (D) performed 6 weeks later.

Contemporary Role of Cardiac Magnetic Resonance in the Management of Patients with Suspected or Known Coronary Artery Disease.

Cardiac magnetic resonance imaging (CMR) is a useful non-invasive radiation-free imaging modality for the management of patients with coronary artery disease (CAD). CMR cine imaging provides the “gold standard” assessment of ventricular function, late gadolinium enhancement (LGE) provides useful data for the diagnosis and extent of myocardial scar and viability, while stress imaging is an established technique for the detection of myocardial perfusion defects indicating ischemia. Beyond its role in the diagnosis of CAD, CMR allows accurate risk stratification of patients with established CAD. This review aims to summarize the data regarding the role of CMR in the contemporary management of patients with suspected or known coronary artery disease.

Improved myocardial perfusion PET imaging using artificial neural networks

Myocardial perfusion (MP) PET imaging plays a key role in risk assessment and stratification of patients with coronary artery disease. In this work, we proposed a patch-based artificial neural network (ANN) fusion approach that integrates information from the ML and the post-smoothed ML reconstruction to improve MP PET imaging. The proposed method was applied to images reconstructed from different noise levels to enhance quantification and task-based MP defect detection. Using the XCAT phantom, we simulated three MP PET imaging cases, one with normal perfusion and the other two with non-transmural and transmural regionally reduced perfusion of the left ventricular (LV) myocardium. The proposed ANN fusion technique was quantitatively evaluated in terms of the noise versus bias and noise versus contrast tradeoff, and compared with the post-smoothed ML reconstruction. Using the channelized Hotelling observer, we evaluated the detectability of the non-transmural and transmural defects through the receiver operating characteristic analysis. The quantitative results demonstrated that the ANN enhancement method reduced bias and improved contrast while reaching comparable noise to what the post-smoothed ML reconstruction achieved. Moreover, the ANN fusion technique significantly improved the defect detectability of both the non-transmural and transmural defects. In addition to the simulation study, we further evaluated the proposed method using patient data. Compared with the post-smoothed ML reconstruction, the ANN fusion improved the tradeoff between noise and the mean value on the LV myocardium, indicating its potential clinical application in MP PET imaging.

Task-Based Evaluation of Image Reconstruction Methods for Defect Detection and Radiation Dose Reduction in Myocardial Perfusion SPECT

We evaluated the ability of conventional and corrective image reconstruction methods to detect a myocardial perfusion defect in single-photon emission computed tomography (SPECT) images using the channelized hotelling observer (CHO). Using our previously developed 4-D extended cardiac-torso, we simulated realistic transmural and endocardial perfusion defects in various locations and sizes in the myocardium. Almost noise-free projection datasets were generated separately from the heart, blood pool, lungs, liver, kidneys, stomach, gall bladder, and the remaining body using Monte Carlo simulation techniques that included the effects of collimator detector response, photon attenuation, and scatter. The datasets were then scaled and combined to model 99mTc Sestamibi myocardial perfusion SPECT projection datasets from a typical patient with various reduced count levels, simulating reduced radiation doses. The final projection data were reconstructed using the 3-D filtered back-projection (FBP) without correction and a 3-D ordered-subset expectation-maximization (OS-EM) method with corrections of attenuation, collimator-detector response, and scatter (ADS), followed by smoothing filtering with several different cut-off frequencies. Task-based evaluations on the reconstructed images were performed by using the CHO followed by the receiver operating characteristics (ROC) methodology to evaluate the detectability of a myocardial perfusion defect by the two image reconstruction methods for various defect anatomies. Areas under the ROC curve (AUC) were computed to assess the changes in the detection of myocardial perfusion defects. The results showed that the 3-D OS-EM with ADS correction gave overall higher AUC values than FBP at several post smoothing levels, count levels, and myocardial perfusion defect sizes. The difference in AUC increased as image smoothness decreased, where the 3-D OS-EM with correction was able to provide similar AUC values with 20%–40% reduction in count levels compared to those of FBP. The AUC values for smaller myocardial perfusion defects were lower for both reconstruction methods with smaller differences. We concluded that the 3-D OS-EM with ADS correction provides higher performance in detecting myocardial perfusion defects. At the conventional count level, it allows for less counts or lower radiation doses without loss of defect detection in myocardial perfusion SPECT images compared to the conventional FBP method, especially regarding less smoothed images.

Evaluation of dual energy computed tomography iodine mapping within the myocardial blood pool for detection of acute myocardial infarction: correlation with histopathological findings in a porcine model

We assessed the diagnostic value of "one-step" dualenergy CT (DECT) in combination with coronary CT angiography and iodine mapping within the myocardial blood pool in detecting acute myocardial infarction (AMI). Five minipigs were subjected to transcatheter embolization of coronary artery with a gelatin sponge to induce AMI. Arterial-phase myocardial DECT imaging was carried out 1 h before and 24 h after embolism of the coronary. Color-coded iodine maps were used to evaluate myocardial blood pool deficits in the 17-segment model. Myocardial DECT imaging 24 h after MI induction was used for final comparison with post-mortem histology. We found a sensitivity of 95.55% and a specificity of 95%, respectively, for AMI detection by DECT-based iodine mapping within the myocardial blood pool. The dose-length product values were 219.4 ± 60.9 mGy.cm (172-321 mGy.cm) and the effective radiation dose was 5.7 ± 1.5 mSv (4.4-8.3 mSv). This experimental study demonstrated that DECT-based iodine mapping shows a high value for the detection of myocardial perfusion defects in the first-pass myocardial perfusion. Hybrid heart images obtained by coronary CTangiography and DECT-based iodine mapping may yield valuable data and help clinicians accurately identify cases requiring further treatment after AMI. Advances in knowledge: This study demonstrated that DECT-based iodine mapping is a promising new technique for the detection of myocardial perfusion defects in the first-pass myocardial perfusion.

MRI-assisted dual motion correction for myocardial perfusion defect detection in PET imaging.

Myocardial perfusion (MP) PET imaging is a powerful tool in risk assessment and stratification of patients with coronary artery disease. Involuntary organ motion degrades cardiac PET image resolution, while respiratory and/or cardiac gating to freeze the motion leads to noisier reconstructed images due to reduced counts in the gated frames. In this work, we propose an MRI-assisted dual motion correction method to compensate for respiratory and cardiac motion in MP PET data and study the impact of dual motion correction on MP defect detection using systematically designed experiments. The proposed dual motion correction method addresses the respiratory motion before correcting the cardiac motion among the respiratory motion corrected cardiac gates. The respiratory motion is estimated from the respiratory-gated only PET images and compensated within a 4D motion-incorporated image reconstruction algorithm. The cardiac motion is then corrected using the motion vector fields estimated from the corresponding cardiac-gated MR images. To evaluate the proposed method, we performed experiments using the standard XCAT phantom and two individual-specific volunteer XCAT phantoms. For each of the three phantoms, we simulated four dual-gated Rb-82 MP PET imaging datasets, one with normal perfusion and the other three with 50% nontransmural, 75% nontransmural, and transmural regionally reduced perfusion. The corresponding cardiac-gated MR images were simulated by the SIMRI simulator, with the sequence specified to be 3D T1-weighted as used in a protocol of a clinical PET/MRI scanner. We quantitatively evaluated the reconstructed images with no motion correction, only respiratory motion correction and dual motion correction, in terms of the myocardium to blood pool contrast and the trade-off between the noise and the normal to defect contrast. Using the channelized Hotelling observer, we performed receiver operating characteristic analysis for the task of detecting perfusion abnormalities with various myocardial coverages. Compared with no motion correction, the respiratory motion correction was demonstrated to improve the myocardium to blood pool contrast as well as the trade-off between the noise and the normal to defect contrast, on top of which the cardiac motion correction furthered the improvement. In the task of detecting regional perfusion defects, transmural or different levels of nontransmural, the respiratory motion correction significantly increased the defect detectability compared with no motion correction. Additionally, the respiratory and cardiac motion correction significantly improved the defect detection compared with the respiratory motion correction alone. Furthermore, the separability of the transmural and nontransmural defects was also improved by the proposed MRI assisted dual motion correction method. The proposed dual respiratory and cardiac motion correction technique improves the accuracy of PET quantification and MP defect detection and classification, which shows its promise for clinical applications especially in cardiac PET/MR imaging.

Direct comparison of stress- and rest-dual-energy computed tomography for detection of myocardial perfusion defect

We assessed the diagnostic performance of stress- and rest-dual-energy computed tomography (DECT) and their incremental value when used with coronary CT angiography (CCTA) compared with combined invasive coronary angiography (ICA)/cardiovascular magnetic resonance (CMR) for detecting hemodynamically significant stenosis causing a myocardial perfusion defect. Forty patients (30 men; mean age, 63.4 ± 8.8 years) with known or suspected coronary artery disease detected by CCTA underwent stress- and rest-DECT, CMR, and ICA. DECT iodine maps were compared with CMR on a per-segment and per-vessel basis. Diagnostic value of CCTA was assessed on a per-vessel basis before and after stress- and rest-DECT and compared to that of ICA/CMR. Compared to CMR, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of rest-DECT for detecting segment (vessel)-based perfusion defects were 29% (46%), 88% (79%), 56% (61%), and 70% (67%), respectively. Corresponding values using stress-DECT were 73% (94%), 83% (74%), 70% (72%), and 85% (95%), respectively. There was fair (κ = 0.39) agreement between rest- and stress-DECT iodine maps in identifying segments with perfusion defects. Compared with the ICA/CMR for identifying hemodynamically significant stenoses, per-vessel territory sensitivity, specificity, PPV, and NPV of CCTA were 91, 56, 55, and 91%, respectively; those using CCTA/rest-DECT were 42, 83, 59, and 70%, respectively; and those using CCTA/stress-DECT were 87, 79, 71, and 91%, respectively. The area under the receiver operating characteristic curve decreased from 0.74 to 0.62 (P = 0.06) using CCTA/rest-DECT but increased to 0.83 (P = 0.02) using CCTA/stress-DECT. Stress-DECT has incremental value when used with CCTA for detecting hemodynamically significant stenoses.

Dynamic Myocardial CT Perfusion Imaging for Evaluation of Myocardial Ischemia as Determined by MR Imaging

The aim of this study was to determine the feasibility of computed tomography (CT)-based dynamic myocardial perfusion imaging for the assessment of myocardial ischemia and infarction compared with cardiac magnetic resonance (CMR). Sequential myocardial CT perfusion imaging has emerged as a novel imaging technique for the assessment of myocardial hypoperfusion. We prospectively enrolled subjects with known coronary artery disease who underwent adenosine-mediated stress dynamic dual-source CT (100 kV, 320 mAs/rot) and CMR (3-T). Estimated myocardial blood flow (eMBF) and estimated myocardial blood volume (eMBV) were derived from CT images, using a model-based parametric deconvolution technique. The values were independently related to perfusion defects (ischemic and/or infarcted myocardial segments) as visually assessed during rest/stress and late gadolinium enhancement CMR. Conventional measures of diagnostic accuracy and differences in eMBF/eMBV were determined. Of 38 enrolled subjects, 31 (mean age 70.4 ± 9.3 years; 77% men) completed both CT and CMR protocols. The prevalence of ischemic and infarcted myocardial segments detected by CMR was moderate (11.6%, n= 56 and 12.6%, n= 61, respectively, of 484 analyzed segments, with 8.4% being transmural). The diagnostic accuracy of CT for the detection of any perfusion defect was good (eMBF threshold, 88 ml/mg/min; sensitivity, 77.8% [95% confidence interval (CI): 69% to 85%]; negative predictive value, 91.3% [95% CI: 86% to 94%]) with moderate positive predictive value (50.6% [95% CI: 43% to 58%] and specificity (75.41% [95% CI: 70% to 79%]). Higher diagnostic accuracy was observed for transmural perfusion defects (sensitivity 87.8%; 95% CI: 74% to 96%) and infarcted segments (sensitivity 85.3%; 95% CI: 74% to 93%). Although eMBF in high-quality examinations was lower but not different between ischemic and infarcted segments (72.3 ± 18.7 ml/100 ml/min vs. 73.1 ± 31.9 ml/100 ml/min, respectively, p> 0.05), eMBV was significantly lower in infarcted segments compared with ischemic segments (11.3 ± 3.3 ml/100 ml vs. 18.4 ± 2.8 ml/100 ml, respectively; p < 0.01). Compared with CMR, dynamic stress CT provides good diagnostic accuracy for the detection of myocardial perfusion defects and may differentiate ischemic and infarcted myocardium.

Dual-Energy CT Perfusion During Pharmacologic Stress for the Assessment of Myocardial Perfusion Defects Using a Second-Generation Dual-Source CT

This study aimed to assess the diagnostic performance of adenosine-stress dual-energy myocardial computed tomography perfusion (DECTP) imaging using 128-slice dual-source computed tomography (CT) for the detection of myocardial perfusion defects in comparison with stress-perfusion magnetic resonance imaging (MRI). This prospective study included 50 patients (mean age, 66 [9] years; 64% men) with suspected coronary artery disease who underwent adenosine-stress DECTP using 128-slice dual-source CT as well as adenosine-stress cardiac MRI using a 1.5-T scanner. Estimates of diagnostic accuracy in detecting myocardial perfusion defects were calculatedand compared with those of cardiac MRI. The estimates of diagnostic accuracy in detecting myocardial perfusion defects using DECTP were as follows: sensitivity, 77% (95% confidence interval [CI], 67%-87%); specificity, 94% (95% CI, 92%-95%); positive predictive value, 53% (95% CI, 44%-63%); and negative predictive value, 98% (95% CI, 97%-99%). The results of DECTP imaging were positively correlated with those of cardiac MRI (r = 0.602, P < 0.001). Mean effective radiation doses for stress DECTP imaging and rest coronary CTA were 6.5 (2.2) and 4.9 (1.7) mSv, respectively. Adenosine-stress DECTP imaging enables detection of myocardial ischemia. However, further technical developments are necessary to reduce artifacts and improve the sensitivity of DECTP.

Silent ischemic heart disease and pericardial fat volume in HIV-infected patients: a case-control myocardial perfusion scintigraphy study.

Objectivesto determine the prevalence of asymptomatic ischemic heart disease (IHD) in HIV patients by myocardial perfusion scintigraphy (MPS) and to determine the value of coronary artery calcium score (CACS), carotid intima-media thickness (cIMT) and pericardial fat volume as screening tools for detection of IHD in subjects with HIV.BackgroundPatients with HIV seem prone to early development of IHD.Methods105 consecutive HIV patients (mean age 47.4 years; mean duration of HIV 12.3 years; mean CD4+ cell count 636×106/L; all receiving antiretroviral therapy) and 105 controls matched for age, gender and smoking status, without history of IHD were recruited. MPS, CACS, cIMT, pericardial fat volume, and cardiovascular risk scores were measured.ResultsHIV patients demonstrated higher prevalence of perfusion defects than controls (18% vs. 0%; p<0.001) despite similar risk scores. Of HIV patients with perfusion defects, 42% had a CACS = 0. CACS and cIMT were similar in HIV patients and controls. HIV patients on average had 35% increased pericardial fat volume and increased concentration of biomarkers of atherosclerosis in the blood. HIV patients with myocardial perfusion defects had increased pericardial fat volume compared with HIV patients without perfusion defects (314±43 vs. 189±12 mL; p<0.001).ConclusionsHIV patients had an increased prevalence of silent IHD compared to controls as demonstrated by MPS. The finding was strongly associated with pericardial fat volume, whereas cardiovascular risk scores, cIMT and CACS seem less useful as screening tools for detection of myocardial perfusion defects in HIV patients.

Rest myocardial perfusion disturbance is related to inflammation but not to fibrosis inexperimental chronic chagas cardiomyopathy

Purpose: Myocardial perfusion disturbance is a common finding in human chronic Chagas cardiomyopathy (CC), but its underlying tissue changes and pathophysiologic mechanisms are unclear. We aimed at investigating the histologic changes related to the myocardial perfusion changes detected in an experimental model of CC in hamsters. Methods: Female Syrian hamsters (n=34) were infected with 35.000 or 100.000 trypomastigotes forms of T. cruzi Y-strain and were submitted to in vivo imaging 6 to 10 months afterwards. High-resolution rest Sestamibi-Tc-99m-SPECT imaging was used for detection of myocardial perfusion defects (MPD), defined as segments with uptake <50% of the maximum pixel uptake value on polar maps analysis. The segmental and global left ventricular (LV) function was assessed by using 2D-Echocardiogram. Ex vivo histologic analysis included quantitation of fibrosis (picrosirius red) and inflammatory infiltrate. A 13-segment model of LV segmentation was used for all imaging analyses and histologic topographic correlations. Results: MPD were found in 17 (50%) of the infected animals. No transmural scar was detected in segments with MPD. The subgroup of animals with MPD, in comparison to animals without MPD, showed: 1) reduced LV ejection fraction (65±21 and 81±9%, respectively, p<0.01); 2) larger inflammatory infiltrate (172.8±89 and 111.5±54 nuclei/mm2; p=0.04); 3) higher segmental wall motion score (1.44±0.5 and 1.04±0.05%; p=0.003); 4) but similar extent of fibrosis (8.4±3.9; 6.6±3.2%; p=0.06). There was a significant association between regional MPD and abnormal wall motion (p<0,001). The segments with MPD (n=57) as compared to the segments with normal perfusion (n=487) showed larger extent of inflammatory infiltrate (175.8±145.0 and 111.6±69.2 nuclei/mm2, respectively; p=0.001), higher segmental wall motion score (1.65±0.6 and 1.1±0.4; p<0.0001) and comparable extent of fibrosis (10.5±18.6 and 7.4±6.2%; p=0.37). Conclusions: Rest MPD in experimental CC is topographically correlated to inflammatory changes that are intense enough to be associated to wall motion impairment. The fact that these derangements are not due to fibrosis opens the possibility that therapeutic interventions aimed at reducing the degree of myocardial inflammation and/or hypoperfusion may favorably impact on the natural history of this model of experimental CC.

Detection of myocardial perfusion defect with 320-row volume CT myocardial perfusion imaging

Objective To evaluate the feasibility of 320-row volume CT myocardial perfusion imaging (CT-MPI) in detecting myocardial perfusion defect.Methods Fourteen patients with positive single-positron emission computed tomography myocardial perfusion imaging (SPECT-MPI) findings underwent both rest and adenosine stress 320-row volume CT-MPI.Rest and stress CT perfusion images were analyzed by employing dedicated software in 320-row CT workstation.Both SPECT-MPI and CT-MPI were evaluated for fixed and reversible perfusion defects using a 16-segment model (apex was excluded).The sensitivity,specificity of 320-row volume CT-MPI in detecting myocardial perfusion defect were evaluated by taking SPECT-MPI as a reference standard.Results Both rest and stress 320-row volume CT-MPI were successfully performed in all patients.Thirty nine segments with fixed or reversible perfusion defects in all patients were depicted by SPECT-MPI,while 34 perfusion defects in 12 patients were identified by CT-MPI.The sensitivity,specificity of 320-row volume CT-MPI for detection of perfusion defects were 87.2％(34/39),91.4％ ( 169/185 ),respectively.Conclusion 320-row volume CT-MPI has high sensitivity and specificity for detection of myocardial perfusion defects. Key words: Coronary disease; Tomography, X-ray computed; Myocardium; Perfusion

Adenosine Stress High-Pitch 128-Slice Dual-Source Myocardial Computed Tomography Perfusion for Imaging of Reversible Myocardial Ischemia

Background— Coronary computed tomography angiography (CTA) enables accurate anatomic evaluation of coronary artery stenosis but lacks information about hemodynamic significance. The aim of this study was to evaluate 128-slice myocardial CT perfusion (CTP) imaging with adenosine stress using a high-pitch mode, in comparison with cardiac MRI (CMR). Methods and Results— Thirty-nine patients with intermediate to high coronary risk profile underwent adenosine stress 128-slice dual source CTP (128×0.6 mm, 0.28 seconds). Among those, 30 patients (64±10 years, 6% women) also underwent adenosine stress CMR (1.5T). The 2-step CTP protocol consisted of (1) adenosine stress-CTP using a high-pitch factor (3.4) ECG-synchronized spiral mode and (2) rest-CTP/coronary-CTA using either high-pitch (heart rate &lt;63 bpm) or prospective ECG-triggering (heart rate &gt;63 bpm). Results were compared with CMR and with invasive angiography in 25 patients. The performance of stress-CTP for detection of myocardial perfusion defects compared with CMR was sensitivity, 96%; specificity, 88%; positive predictive value (PPV), 93%; negative predictive value (NPV), 94% (per vessel); and sensitivity, 78%; specificity, 87%; PPV, 83%; NPV, 84% (per segment). The accuracy of stress-CTP for imaging of reversible ischemia compared with CMR was sensitivity, 95%; specificity, 96%; PPV, 95%; and NPV, 96% (per vessel). In 25 patients who underwent invasive angiography, the accuracy of CTA for detection of stenosis &gt;70% was (per segment): sensitivity, 96%; specificity, 88%; PPV, 67%; and NPV, 98.9%. The accuracy improved from 84% to 95% after adding stress CTP to CTA. Radiation exposure of the entire stress/rest CT protocol was only 2.5 mSv. Conclusions— Adenosine-induced stress 128-slice dual-source high-pitch myocardial CTP allows for simultaneously assessment of reversible myocardial ischemia and coronary stenosis, with good diagnostic accuracy as compared with CMR and invasive angiography, at a very low radiation exposure.

Adenosine-stress dynamic real-time myocardial perfusion CT and adenosine-stress first-pass dual-energy myocardial perfusion CT for the assessment of acute chest pain: Initial results

PurposeRecent innovations in CT enable the evolution from mere morphologic imaging to dynamic and functional testing. We describe our initial experience performing myocardial stress perfusion CT in a clinical population with acute chest pain. Methods and materialsMyocardial stress perfusion CT was performed on twenty consecutive patients (15 men, 5 women; mean age 65±8 years) who presented with acute chest pain and were clinically referred for stress/rest SPECT and cardiac MRI. Prior to CT each patient was randomly assigned either to Group A or to Group B in a consecutive order (10 patients per group). Group A underwent adenosine-stress dynamic real-time myocardial perfusion CT using a novel “shuttle” mode on a 2nd generation dual-source CT. Group B underwent adenosine-stress first-pass dual-energy myocardial perfusion CT using the same CT scanner in dual-energy mode. Two experienced observers visually analyzed all CT perfusion studies. CT findings were compared with MRI and SPECT. ResultsIn Group A 149/170 myocardial segments (88%) could be evaluated. Real-time perfusion CT (versus SPECT) had 86% (84%) sensitivity, 98% (92%) specificity, 94% (88%) positive predictive value, and 96% (92%) negative predictive value in comparison with perfusion MRI for the detection of myocardial perfusion defects. In Group B all myocardial segments were available for analysis. Compared with MRI, dual-energy myocardial perfusion CT (versus SPECT) had 93% (94%) sensitivity, 99% (98%) specificity, 92% (88%) positive predictive value, and 96% (94%) negative predictive value for detecting hypoperfused myocardial segments. ConclusionOur results suggest the clinical feasibility of myocardial perfusion CT imaging in patients with acute chest pain. Compared to MRI and SPECT both, dynamic real-time perfusion CT and first-pass dual-energy perfusion CT showed good agreement for the detection of myocardial perfusion defects.

The Evaluation of Corrective Reconstruction Method For Reduced Acquisition Time and Various Anatomies of Perfusion Defect Using Channelized Hotelling Observer for Myocardial Perfusion SPECT.

We evaluated the effect of conventional and corrective image reconstruction methods on reduced acquisition time for detecting a myocardial perfusion (MP) defect in MP SPECT using the Channelized Hotelling Observer (CHO). Using the 4D Extended Cardiac-Torso (XCAT) phantom, we simulated realistic transmural and endocardial MP defects in various location and size. Realistic Tc-99m Sestamibi MP projection data were generated using an analytical projector that included the effects of attenuation (A), collimator-detector response (D) and scatter (S) for various count levels simulating different acquisition times. They were reconstructed using the 3D FBP without correction and a 3D OS-EM method with ADS correction followed by a smoothing filter with various cut-off frequencies. The CHO followed by receiver operating characteristics (ROC) methodology was applied to the reconstructed images to evaluate the detectability of a MP defect in each method for different defect anatomies and count levels. Areas under the ROC curve (AUC) were computed to assess the changes in the MP defect detection. The results showed that the 3D OS-EM with ADS corrections showed significantly less changes in AUC value and gave overall higher AUC values than FBP at all cut-off frequencies of the post smoothing filter, count levels and MP defect sizes. The difference in AUC increased towards less smoothed images where the 3D OS-EM with correction was able to provide similar AUC values with 20 - 40% reduction in acquisition time compared to FBP. The AUC values for smaller MP defects were lower for both reconstruction methods with smaller differences. We concluded that the 3D OS-EM with ADS corrections provides higher performance in the MP defect detection task. It allows increased reduction of acquisition time without loss of MP defect detection in MP SPECT compared to the conventional FBP method especially towards less smoothed images.

An investigation of the trade-off between the count level and image quality in myocardial perfusion SPECT using simulated images: the effects of statistical noise and object variability on defect detectability

Quantum noise as well as anatomic and uptake variability in patient populations limits observer performance on a defect detection task in myocardial perfusion SPECT (MPS). The goal of this study was to investigate the relative importance of these two effects by varying acquisition time, which determines the count level, and assessing the change in performance on a myocardial perfusion (MP) defect detection task using both mathematical and human observers. We generated ten sets of projections of a simulated patient population with count levels ranging from 1/128 to around 15 times a typical clinical count level to simulate different levels of quantum noise. For the simulated population we modeled variations in patient, heart and defect size, heart orientation and shape, defect location, organ uptake ratio, etc. The projection data were reconstructed using the OS-EM algorithm with no compensation or with attenuation, detector response and scatter compensation (ADS). The images were then post-filtered and reoriented to generate short-axis slices. A channelized Hotelling observer (CHO) was applied to the short-axis images, and the area under the receiver operating characteristics (ROC) curve (AUC) was computed. For each noise level and reconstruction method, we optimized the number of iterations and cutoff frequencies of the Butterworth filter to maximize the AUC. Using the images obtained with the optimal iteration and cutoff frequency and ADS compensation, we performed human observer studies for four count levels to validate the CHO results. Both CHO and human observer studies demonstrated that observer performance was dependent on the relative magnitude of the quantum noise and the patient variation. When the count level was high, the patient variation dominated, and the AUC increased very slowly with changes in the count level for the same level of anatomic variability. When the count level was low, however, quantum noise dominated, and changes in the count level resulted in large changes in the AUC. This behavior agreed with a theoretical expression for the AUC as a function of quantum and anatomical noise levels. The results of this study demonstrate the importance of the tradeoff between anatomical and quantum noise in determining observer performance. For myocardial perfusion imaging, it indicates that, at current clinical count levels, there is some room to reduce acquisition time or injected activity without substantially degrading performance on myocardial perfusion defect detection.

Adenosine-Stress Dynamic Myocardial CT Perfusion Imaging

To evaluate the feasibility of adenosine-stress dynamic myocardial volume perfusion imaging with second generation dual source computed tomography (CT) for the qualitative and quantitative assessment of myocardial blood flow (MBF) compared with stress perfusion and viability magnetic resonance imaging (MRI). Ten patients (8 male, 2 female, mean age 62.7 +/- 7.1 years) underwent stress/rest perfusion and delayed-enhancement MRI, and a cardiac CT protocol comprising prospectively electrocardiogram -triggered coronary CT angiography, dynamic adenosine-stress myocardial perfusion imaging using a "shuttle" mode, and delayed enhancement acquisitions. Two independent observers visually assessed myocardial perfusion defects. For semi-quantitative evaluation, CT- and MRI-derived myocardial-to-left ventricular upslope indices were compared. Additionally, absolute MBF was quantified based on dynamic perfusion CT and correlated with semi quantitative CT measurements. Myocardial perfusion analysis was performed on a segmental basis. Analysis used paired t tests, Wilcoxon signed-rank test, linear correlation, and Bland-Altman statistics. A total of 149 segments (93.1%) were suitable for analysis. Sensitivity, specificity, positive and negative predictive values for detection of myocardial perfusion defects at CT compared with MRI were 86.1%, 98.2%, 93.9%, and 95.7%, respectively. Semiquantitative analysis of CT data showed significant differences between ischemic and nonischemic myocardium with a signal intensity upslope that was comparable with MRI-derived values (CT: 5.2 +/- 2 SI/s, MRI: 4.8 +/- 2.3 SI/s, P > 0.05). Moderate correlation was observed between absolute CT quantification of MBF and semi-quantitative CT measurements. Mean total dose length product for the entire cardiac CT protocol was 1290.4 +/- 233.3 mGy cm. Adenosine-stress volumetric first pass CT perfusion imaging is feasible and may enable the evaluation of qualitative and semi quantitative parameters of myocardial perfusion in a comparable fashion as MRI.

Optimization of Rb-82 PET acquisition and reconstruction protocols for myocardial perfusion defect detection

The purpose of this study is to optimize the dynamic Rb-82 cardiac PET acquisition and reconstruction protocols for maximum myocardial perfusion defect detection using realistic simulation data and task-based evaluation. Time activity curves (TACs) of different organs under both rest and stress conditions were extracted from dynamic Rb-82 PET images of five normal patients. Combined SimSET-GATE Monte Carlo simulation was used to generate nearly noise-free cardiac PET data from a time series of 3D NCAT phantoms with organ activities modeling different pre-scan delay times (PDTs) and total acquisition times (TATs). Poisson noise was added to the nearly noise-free projections and the OS-EM algorithm was applied to generate noisy reconstructed images. The channelized Hotelling observer (CHO) with 32× 32 spatial templates corresponding to four octave-wide frequency channels was used to evaluate the images. The area under the ROC curve (AUC) was calculated from the CHO rating data as an index for image quality in terms of myocardial perfusion defect detection. The 0.5 cycle cm−1 Butterworth post-filtering on OS-EM (with 21 subsets) reconstructed images generates the highest AUC values while those from iteration numbers 1 to 4 do not show different AUC values. The optimized PDTs for both rest and stress conditions are found to be close to the cross points of the left ventricular chamber and myocardium TACs, which may promote an individualized PDT for patient data processing and image reconstruction. Shortening the TATs for <∼3 min from the clinically employed acquisition time does not affect the myocardial perfusion defect detection significantly for both rest and stress studies.

Auxílio à detecção de anormalidade perfusional miocárdica utilizando atlas de SPECT e registro de imagens: resultados preliminares

OBJETIVO: Criar um atlas de cintilografia de perfusão miocárdica e verificar sua aplicabilidade no auxílio computadorizado à detecção de defeitos perfusionais miocárdicos em pacientes portadores de cardiopatia isquêmica. MATERIAIS E MÉTODOS: O atlas foi criado com imagens de cintilografia de perfusão miocárdica, em condições de repouso e estresse, de 20 pacientes de ambos os gêneros com baixa probabilidade de doença arterial coronariana e julgadas normais por dois observadores experientes. Técnicas de registro de imagens e operações matemáticas sobre imagens foram utilizadas para obtenção de modelos de média e desvio-padrão da captação miocárdica percentual de cada gênero e condição fisiológica. RESULTADOS: Imagens de um paciente masculino e um feminino foram alinhadas com os atlas correspondentes, e os voxels apresentando valores de captação percentual dois desvios-padrão abaixo da média da respectiva região do atlas foram destacados nos cortes tomográficos e confirmados como defeitos de perfusão por dois observadores experientes. CONCLUSÃO: Demonstramos a criação de um atlas de cintilografia de perfusão miocárdica e obtivemos resultados promissores na sua utilização para auxílio à detecção de defeitos perfusionais. Entretanto, uma validação prospectiva com um número mais representativo de casos é necessária.

Integrated assessment of coronary anatomy and myocardial perfusion using a retractable SPECT camera combined with 64-slice CT: initial experience

We evaluated a prototype SPECT system integrated with multidetector row CT (MDCT) for obtaining complementary information on coronary anatomy and hemodynamic lesion significance. Twenty-five consecutive patients with known or suspected coronary artery disease (CAD) underwent routine SPECT myocardial perfusion imaging (MPI). All patients also underwent repeat MPI with a mobile SPECT unit which could be attached to a 64-slice MDCT system. Coronary CT angiography (cCTA) was performed without repositioning the patient. Investigational MPI was compared with routine MPI for detection of myocardial perfusion defects (PD). Two observers diagnosed presence or absence of CAD based on MPI alone, cCTA alone, and based on combined MPI and cCTA with fused image display. In 22/24 patients investigative MPI corresponded with routine MPI (r = 0.80). Stenosis >or= 50% at cCTA was detected in 6/24 patients. Six out of 24 patients had PD at regular MPI. Three of these six patients had no significant stenosis at cCTA. Three out of 19 patients with normal MPI studies had significant stenosis at cCTA. Our initial experience indicates that the integration of SPECT MPI with cCTA is technically feasible and enables the comprehensive evaluation of coronary artery anatomy and myocardial perfusion with a single instrumental setup.