Automated quantification of 99mTc sestamibi myocardial perfusion compared with visual analysis.
ABSTRACT The visual interpretation of 99mTc sestamibi single photon emission computed tomography (SPECT) myocardial perfusion images can be challenging due to the quantity of scan information generated, the large number of normal variants, attenuation artifacts and gender differences. The development of automated, computer derived, quantitative indices of perfusion can assist in this interpretation by providing an objective measure. It is important to verify that similar results can be obtained when the software is used in centres outside those where the algorithms were initially developed. Our objective was to assess the degree of concordance between the visual and automated diagnostic assessments of 99mTc sestamibi SPECT.
We studied 718 patients referred for 99mTc sestamibi SPECT myocardial perfusion imaging. The SPECT studies were initially interpreted visually without benefit of computer based analysis, and were then subjected to blinded reprocessing to extract quantitative indices of perfusion.
There was very good agreement between the visual and quantitative diagnostic classifications. When a visual abnormality was taken to be the reference standard, the automated summed stress score (SSS) showed agreement (SSS>3) in 80% (kappa 0.60, P<0.0001). The area under the receiver operating characteristic (ROC) curve was 0.89 (95% confidence interval (CI), 0.86-0.91). Concordance was greater in those with previous myocardial infarction or severe perfusion defects, but was not affected by age, prior revascularization, stress procedure or heart rate. Concordance over the presence or absence of visual reversibility and the summed difference score (SDS) in abnormal scans was slightly lower (overall agreement 73% (kappa 0.36, P<0.00001) and ROC area 0.84 (95% CI, 0.77-0.90)).
Automated quantification of 99mTc sestamibi SPECT myocardial perfusion with the SSS and SDS provides objective diagnostic information and concordance when compared with conventional visual image interpretation.
Article: Variation in heart rate influences the assessment of transient ischemic dilation in myocardial perfusion scintigraphy.[show abstract] [hide abstract]
ABSTRACT: Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice. Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238). In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04-0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio. Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans.BMC Nuclear Medicine 01/2007; 7:1.
Article: Prognostic utility of sestamibi lung uptake does not require adjustment for stress-related variables: a retrospective cohort study.[show abstract] [hide abstract]
ABSTRACT: Increased 99mTc-sestamibi stress lung-to-heart ratio (sLHR) has been shown to predict cardiac outcomes similar to pulmonary uptake of thallium. Peak heart rate and use of pharmacologic stress affect the interpretation of lung thallium uptake. The current study was performed to determine whether 99mTc-sestamibi sLHR measurements are affected by stress-related variables, and whether this in turn affects prognostic utility. sLHR was determined in 718 patients undergoing 99mTc-sestamibi SPECT stress imaging. sLHR was assessed in relation to demographics, hemodynamic variables and outcomes (mean follow up 5.6 +/- 1.1 years). Mean sLHR was slightly greater in males than in females (P < 0.01) and also showed a weak negative correlation with age (P < 0.01) and systolic blood pressure (P < 0.01), but was unrelated to stress method or heart rate at the time of injection. In patients undergoing treadmill exercise, sLHR was also positively correlated with peak workload (P < 0.05) but inversely with double product (P < 0.05). The combined explanatory effect of sex, age and hemodynamic variables on sLHR was less than 10%. The risk of acute myocardial infarction (AMI) or death increased by a factor of 1.7-1.8 for each SD increase in unadjusted sLHR, and was unaffected by adjustment for sex, age and hemodynamic variables (hazard ratios 1.6-1.7). The area under the ROC curve for the unadjusted sLHR was 0.65 (95% CI 0.59-0.71, P < 0.0001) and was unchanged for the adjusted sLHR (0.65, 95% CI 0.61-0.72, P < 0.0001). Stress-related variables have only a weak effect on measured sLHR. Unadjusted and adjusted sLHR provide equivalent prognostic information for prediction of AMI or death.BMC Nuclear Medicine 01/2006; 6:2.