***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Qualitative interpretation of myocardial contrast echocardiography ( MCE ) improves the accuracy of wall-motion analysis for assessment of coronary artery disease ( CAD ) . We examined the feasibility and accuracy of quantitative MCE for diagnosis of CAD . METHODS Dipyridamole/exercise stress MCE ( destruction-replenishment protocol with real-time imaging ) was performed in 90 patients undergoing quantitative coronary angiography , 48 of whom had significant ( > 50 % ) stenoses .  MCE was repeated with exercise alone in 18 patients .  Myocardial blood flow ( A*beta ) was obtained from blood volume ( A ) and time to refill ( beta ) . RESULTS Quantification of flow reserve was feasible in 88 % . The mean A*beta reserve in the anterior wall was significantly impaired for patients with left anterior descending coronary artery disease ( n = 28 ) compared with those with no disease ( 1.6 + /- 1.2 vs 4.0 + /- 2.5 , P < or = .001 ) . This reflected impaired beta reserve , with no difference in the A reserve . Applying a receiver operating characteristic curve derived cutoff of 2.0 for A*beta reserve , quantitative MCE was 76 % sensitive and 71 % specific for the diagnosis of significant left anterior descending coronary artery stenosis . Posterior circulation results were similar , with 78 % sensitivity and 59 % specificity for detection of posterior CAD . Overall , quantitative MCE was similarly sensitive to qualitative approach for diagnosis of CAD ( 88 % vs 93 % ) , but with lower specificity ( 52 % vs 65 % , P = .07 ) . In 18 patients restudied with pure exercise stress , the mean myocardial blood flow reserve was less than after combined stress ( 2.1 + /- 1.6 vs 3.7 + /- 1.9 , P = .01 ) . CONCLUSION Quantitative MCE is feasible for the diagnosis of CAD with dipyridamole/exercise stress . Dipyridamole prolongs postexercise hyperemia , augmenting the degree of hyperemia at the time of imaging Myocardial contrast echocardiography ( MCE ) is a new technique for assessing myocardial perfusion that uses intracoronary injections of microbubbles of air . Because these microbubbles have a mean diameter of 4.3 + /- 0.3 microns and an intravascular rheology similar to that of red blood cells ( RBCs ) , we hypothesized that their mean myocardial transit rates recorded on echocardiography would provide an estimation of regional myocardial blood flow in the in vivo beating heart . Accordingly , blood flow to the left anterior descending coronary artery ( LAD ) of 12 open-chest anesthetized dogs ( group I ) was adjusted to 4 to 6 flows ( total of 60 flows ) , and microbubbles and radiolabeled RBCs were injected into the LAD in a r and om order at each stage . The mean myocardial RBC transit rates were measured by fitting a gamma-variate function to time-activity plots generated by placing a miniature CsI2 probe over the anterior surface of the heart , and the mean myocardial microbubble transit rates were measured from time-intensity plots derived from off-line analysis of MCE images obtained during the injection of microbubbles . An excellent correlation was noted between flow ( measured with an extracorporeal electromagnetic flow probe ) and mean myocardial RBC transit rate ( y = 2.83 x 10(-3)x + 0.01 , r = .96 , SEE = 0.02 , P < .001 ) . A close correlation was also noted between mean RBC and microbubble myocardial transit rates ( y = 1.01x + 0.01 , r = .89 , SEE = 0.02 , P < .001 ) . Despite its theoretical advantages , a lagged normal density function did not provide a better fit to the MCE data than the gamma-variate function . ( ABSTRACT TRUNCATED AT 250 WORDS OBJECTIVES The purpose of this study was to compare the assessment of myocardial perfusion by myocardial parametric quantification ( MPQ ) with technetium-99 m sestamibi single-photon emission computed tomographic ( SPECT ) imaging in humans . BACKGROUND Accurate visual interpretation of myocardial contrast echocardiographic ( MCE ) images is qualitative and requires considerable experience . Current computer-assisted quantitative perfusion protocol s are tedious and lack spatial resolution . Myocardial parametric quantification is a novel method that quantifies , color encodes , and displays perfusion data as a set of myocardial parametric images according to the relative degree of perfusion . METHODS Forty-six consecutive patients underwent prospect i ve stress/rest technetium-99 m sestamibi gated-SPECT imaging and MCE using intravenous Optison or Definity . Apical two- and four-chamber cine loops at rest and after dipyridamole ( 0.56 mg/kg ) stress were acquired . For each patient , the following assessment s of myocardial perfusion were performed : 1 ) . visual cine-loop assessment ( VIS ) ; 2 ) . MPQ assessment ; and 3 ) . combined VIS + MPQ assessment . RESULTS The segmental rates of agreement for myocardial perfusion with SPECT were 83 % , 89 % , and 92 % ( kappa = 0.46 , 0.58 , and 0.68 ) for VIS , MPQ , and VIS + MPQ , respectively . Similar trends were seen for the classification of the presence or absence of a moderate to severe perfusion defect , with the agreement for VIS , MPQ , and VIS + MPQ being 92 % , 97 % , and 97 % , respectively . CONCLUSIONS Myocardial parametric quantification demonstrates good agreement with SPECT and incremental agreement with VIS . Analysis strategies that incorporate MPQ demonstrate better agreement with SPECT than visual analysis alone AIMS Parametric imaging of myocardial perfusion provides useful visual information for the diagnosis of coronary artery disease ( CAD ) . We developed a technique for automated detection of perfusion defects based on quantitative analysis of parametric perfusion images and vali date d it against coronary angiography . METHODS AND RESULTS Contrast-enhanced , apical 2- , 3- and 4-chamber images were obtained at rest and with dipyridamole in 34 patients with suspected CAD . Images were analyzed to generate parametric perfusion images of the st and ard contrast-replenishment model parameters A , beta and A.beta . Each parametric image was divided into six segments , and mean parameter value ( MPV ) was calculated for each segment . Segmental MPV ratio between stress and rest was defined as a flow reserve index ( FRI ) . Receiver operating characteristics ( ROC ) analysis was used in a Study group ( N=17 ) to optimize FRI threshold and the minimal number of abnormal segments per vascular territory ( LAD and non-LAD ) , required for automated detection of stress-induced perfusion defects . The optimized detection algorithm was then tested prospect ively in the remaining 17 patients ( Test group ) . LAD and non-LAD stenosis > 70 % was found in 19 and 17 patients , respectively . In the Study group , FRI threshold was : LAD=0.95 and non-LAD=0.68 , minimal number of abnormal segments was four and two , correspondingly . Sensitivity , specificity and accuracy in the Test group were : 75 % , 67 % and 71 % in the LAD , and 75 % , 75 % and 75 % in the non-LAD territories . CONCLUSION Automated quantitative analysis of contrast echocardiographic parametric perfusion images is feasible and may aid in the objective detection of CAD 
    Output:
    
Evidence supports the use of quantitative MCE as a non-invasive test for detection of CAD .