Quantitative analysis of perfusion studies: strengths and pitfalls.
ABSTRACT Tools for automated quantification of myocardial perfusion are available to nuclear cardiology practitioners and researchers. These methods have demonstrated superior reproducibility with comparable diagnostic and prognostic performance, when compared with segmental visual scoring by expert observers. A particularly useful application of the quantitative analysis can be in the detection of subtle changes or in precise determination of ischemia. Some challenges remain in the routine application of perfusion quantification. Multiple quantitative parameters may need to be reconciled by the expert reader for the final diagnosis. Computer analysis may be sensitive to imaging artifacts, resulting in false positive scans. Perfusion quantification may require site specific normal limits and some degree of manual interaction. New software improvements have been proposed to address some of these challenges.
Article: Quantitative assessment of myocardial perfusion abnormality on SPECT myocardial perfusion imaging is more reproducible than expert visual analysis.[show abstract] [hide abstract]
ABSTRACT: Current guidelines of Food and Drug Administration for the evaluation of SPECT myocardial perfusion imaging (MPI) in clinical trials recommend independent visual interpretation by multiple experts. Few studies have addressed whether quantitative SPECT MPI assessment would be more reproducible for this application. We studied 31 patients (age 68 +/- 13, 25 male) with abnormal stress MPI who underwent repeat exercise (n = 11) or adenosine (n = 20) MPI within 9-22 months (mean 14.9 +/- 3.8 months) and had no interval revascularization or myocardial infarction and no change in symptoms, stress type, rest or stress ECG, or clinical response to stress on the second study. Visual interpretation per FDA Guidance used 17-segment, 5-point scoring by two independent expert readers with overread of discordance by a third expert, and percent myocardium abnormal was derived from normalized summed scores. The quantitative magnitude of perfusion abnormality was assessed by the total perfusion deficit (TPD), expressing stress, rest, and ischemic perfusion abnormality. High linear correlations were observed between visual and quantitative size of stress, rest, and ischemic defects (R = 0.94, 0.92, 0.84). Correlations of two tests were higher by quantitative than by visual methods for stress (R = 0.97 vs R = 0.91, P = 0.03) and rest defects (R = 0.94 vs R = 0.82, P = 0.03), respectively, and statistically similar for ischemic defects (R = 0.84 vs R = 0.70, P = ns). In stable patients having serial SPECT MPI, quantification is more reproducible than visual for magnitude of perfusion abnormality, suggesting its superiority for use in randomized clinical trials and monitoring the effects of therapy in an individual patient.Journal of Nuclear Cardiology 03/2009; 16(1):45-53. · 2.67 Impact Factor
Article: Automated quality control of emission-transmission misalignment for attenuation correction in myocardial perfusion imaging with SPECT-CT systems.[show abstract] [hide abstract]
ABSTRACT: Emission-transmission misalignment with single-photon emission computed tomography (SPECT)-computed tomography (CT) systems can impair attenuation correction (AC) in myocardial perfusion imaging. This study was performed to develop automated quality control (Auto-QC) to detect critical misalignment that can significantly impact AC. Auto-QC was developed to segment myocardium and mediastinum from emission and transmission reconstructions, respectively. Myocardium-mediastinum mismatch was used as the quality-control index (QCI). The QCI threshold for acceptable AC was determined with NCAT (NURBS [nonuniform rational B-spline]-based cardiac torso phantom) simulation and verified with 2 patients with minimal misalignment. Compromised data sets, generated by shifting the attenuation maps by 0.5, 1.0, 1.5, and 2.0 pixels along left-right, up-down, and head-foot directions, respectively, were qualitatively and quantitatively compared with the unshifted data sets. Auto-QC was tested with the 2 verification patients and 41 additional patients. Shifts by more than 1 pixel along any direction compromised AC. Auto-QC with the QCI threshold (3%) had highly concordant results with manual quality control in the detection of critical misalignment (sensitivity of 88% and 90% and specificity of 93% and 95% for the tests by use of the 2 verification patients and 41 additional patients, respectively). QCI quantitatively represented the severity of misalignment. Auto-QC can help clinicians be aware of critical misalignment and can assist in realignment of SPECT and CT images.Journal of Nuclear Cardiology 13(1):43-9. · 2.67 Impact Factor
Article: Quantitative assessment of motion artifacts and validation of a new motion-correction program for myocardial perfusion SPECT.[show abstract] [hide abstract]
ABSTRACT: Patient motion during myocardial perfusion SPECT can produce images that show artifactual perfusion defects. The relationship between the degree of motion and the extent of artifactual perfusion defects is not clear for either single- or double-head detectors. Using both single- and double-head detectors and quantitative perfusion SPECT (QPS) software, we studied the pattern and extent of defects induced by simulated motion and validated a new automatic motion-correction program for myocardial perfusion SPECT. Vertical motion was simulated by upward shifting of the raw projection datasets in a returning pattern (bounce) and in a nonreturning pattern at 3 different phases of the SPECT acquisition (early, middle, and late), whereas upward creep was simulated by uniform shifting throughout the acquisition. Lateral motion was similarly simulated by left shifting of the raw projection datasets in a returning pattern and in a nonreturning pattern. Simulations were performed using single- and double-head detectors, and simulated motion was applied to projection images from 8 patients who had normal 99mTc-sestamibi SPECT findings. Additionally, images from 130 patients with actual clinical motion were assessed before and after motion correction. The extent of perfusion defects was assessed by QPS, and a 20-segment, 5-point scoring system was used to assess the effect of motion on the presence and extent of perfusion defects. Of 12 bounce simulations, the bouncing motion failed to produce significant (>3%) perfusion defects with either the single- or the double-head detector. With the single-head detector, early shifting created the largest defect, whereas with the double-head detector, shifting during the middle of the acquisition created the largest defect. With regard to upward creep, defects were of larger extent with the double- than the single-head detector. With the single-head detector, 8 of 20 simulated motion patterns yielded significant perfusion defects of the left ventricle, 7 (88%) of which were significantly improved after motion correction. With the double-head detector, 12 of 20 patterns yielded significant defects, all of which improved significantly after correction. Of 2,600 segments in the 130 patients with actual clinical motion, only 1.3% (30/2,259) of segments that were considered normal (score = 0 or 1) changed to abnormal (score = 2-4) after motion correction, whereas 27% (92/341) of abnormal segments were reclassified as normal after motion correction. Artifactual perfusion defects created by simulated motion are a function of the time, degree, and type of motion and the number of camera detectors. Application of an automatic motion-correction algorithm effectively decreases motion artifacts on myocardial perfusion SPECT images.Journal of Nuclear Medicine 06/2001; 42(5):687-94. · 6.38 Impact Factor