Attenuation correction for single photon emission computed tomography myocardial perfusion imaging.
ABSTRACT The specificity of cardiac single photon emission computed tomography (SPECT) perfusion imaging is significantly affected by internal photon absorption. Commonly referred to as anterior wall breast and inferior wall diaphragm attenuation artifacts, even when following characteristic patterns in women and men, the reduced activity produced can be difficult to differentiate from real perfusion defects. Unfortunately, wide variations in body habitus result in unpredictable variations in tissue attenuation and the specificity of uncorrected SPECT is unacceptably low in many laboratories. This manuscript reviews recent developments in attenuation correction methods for cardiac SPECT. Several commercial methods are now available, and although the initial success using these methods varied widely, as these methods have been improved successful clinical reports are appearing with increasing frequency. Recent developments have yielded more robust validated methods and significant clinical advantages have been achieved in the diagnostic evaluation of coronary heart disease (sensitivity as well as specificity) and myocardial viability. As these methods continue to mature, further advances should be anticipated.
Article: Cardiac cameras.[show abstract] [hide abstract]
ABSTRACT: Cardiac imaging with radiotracers plays an important role in patient evaluation, and the development of suitable imaging instruments has been crucial. While initially performed with the rectilinear scanner that slowly transmitted, in a row-by-row fashion, cardiac count distributions onto various printing media, the Anger scintillation camera allowed electronic determination of tracer energies and of the distribution of radioactive counts in 2D space. Increased sophistication of cardiac cameras and development of powerful computers to analyze, display, and quantify data has been essential to making radionuclide cardiac imaging a key component of the cardiac work-up. Newer processing algorithms and solid state cameras, fundamentally different from the Anger camera, show promise to provide higher counting efficiency and resolution, leading to better image quality, more patient comfort and potentially lower radiation exposure. While the focus has been on myocardial perfusion imaging with single-photon emission computed tomography, increased use of positron emission tomography is broadening the field to include molecular imaging of the myocardium and of the coronary vasculature. Further advances may require integrating cardiac nuclear cameras with other imaging devices, ie, hybrid imaging cameras. The goal is to image the heart and its physiological processes as accurately as possible, to prevent and cure disease processes.Seminars in nuclear medicine 05/2011; 41(3):182-201. · 3.96 Impact Factor
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ABSTRACT: Attenuation correction (AC) has been shown to improve the accuracy of myocardial perfusion single photon emission computed tomography (SPECT) for the detection and evaluation of patients with coronary artery disease. Attenuation artifacts, because of diaphragmatic attenuation, frequently affect the evaluation of the inferior wall, especially in male patients. The aim of this study was to evaluate the value of AC for the assessment of infarct size in coronary artery disease patients after inferior myocardial infarction. Gated-SPECT with Tc-labeled compounds with AC by hybrid SPECT/computed tomography (CT) was performed in 56 male patients with documented previous inferior myocardial infarction. Both corrected and uncorrected SPECT images were processed after motion and scatter correction by ordered-subset expectation maximization iterative reconstruction. When needed, a manual realignment between SPECT and computed tomography (CT) sections was performed. Uncorrected and corrected SPECT images were analyzed for perfusion using a 5-point segmental scoring scale from 0 (normal) to 4 (absent). Summed stress score (SSS), summed rest score (SRS), and summed difference score (SDS) of the inferior left ventricle wall (inferoseptal, inferior, infero-apical and infero-lateral segments) were determined and compared with the regional wall motion score as determined by uncorrected gated-SPECT. The SSS, SRS, SDS for attenuation-uncorrected and attenuation-corrected studies were 14.02 ± 7.9, 9.51 ± 7, 4.5 ± 3.2 and 9.39 ± 7.1, 5.6 ± 6.1, 3.8 ± 2.8, respectively. Differences were statistically significant (P<0.0001) for SSS and SRS but not for SDS. The regional summed rest score of the inferior wall (SRS of inferior segments) showed a better correlation with the regional summed wall motion score of the same segments: R²=0.50 in comparison to uncorrected SRS, R²=0.46. The combination of diaphragmatic attenuation and inferior myocardial infarction determines an artifactual overestimation of infarct size of inferior infarcts. The AC regional perfusion score (SRS) correlates with the regional wall motion score of the inferior wall. AC does not affect the detection and size of residual ischemia (SDS).Nuclear Medicine Communications 09/2011; 32(11):1026-32. · 1.38 Impact Factor
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ABSTRACT: This study aimed to determine whether attenuation correction using the Hybrid SPECT/CT reduced attenuation artifacts. Ninety-nine patients (55 men and 44 women) underwent coronary angiography and electrocardiography gated stress/rest myocardial perfusion imaging using Tc-99m sestamibi (MIBI) with CT-attenuation correction (CT-AC) for stress scans. Visual semi-quantitative analysis of the CT-AC and noncorrected perfusion images was performed. In this study, there was 39.3% moderate or severe misregistration. The overall specificity, sensitivity, and accuracy for noncorrected versus CT-AC were 62.9% versus 79.0% (P = 0.041), 94.6% versus 91.9% (P = NS), and 74.7% versus 83.8% (P = 0.035), respectively. CT-AC increased specificity in the right coronary artery region, from 77.9% to 98.7% (P = 0.000), accompanied by a decrease in specificity in the left anterior descending region, from 94.1% to 82.4% (P = 0.008). CT-AC significantly reduced defect scores in the inferior wall. This was more obvious in men than in women (P = 0.027). In the anterior wall, although a tendency for defect scores to increase with CT-AC was observed only in men, no significant difference was found between the gender (P = 0.049). Attenuation correction using Hybrid SPECT/CT improved specificity in the right coronary artery, but decreased specificity in the left anterior descending. This technique is likely to be more useful in men than in women.Clinical nuclear medicine 05/2011; 36(5):344-9. · 3.92 Impact Factor