ABC | Volume 113, Nº4, October 2019

Review Article Magalhães et al. Principles of MPCT Arq Bras Cardiol. 2019; 113(4):758-767 Table 1 – Evaluation of myocardial perfusion by computed tomography in the study of obstructive coronary artery disease and myocardial ischemia Study Year N Reference Sens. Spec. PPV NPV George et al. 43 2009 27 ICA and MPC 86 92 92 85 Rocha-Filho et al. 22 2010 35 ICA 96 100 100 91 George et al. 30 2012 50 MPC 72 91 81 85 Bettencourt et al. 44 2013 101 FFR 89 83 80 90 Rochitte et al. (CORE 320) 24 2014 381 ICA and MPC 80 74 65 86 Cury et al. 45 2015 110 MPC 90 84 36 99 Takx et al. 33 2015 2048 FFR 88 80 - - Sørgaard et al. 46 2016 1188 MPC, MRI, ICA, FFR 85* 81* - - Pontone et al. 47 2018 100 ICA and FFR 98 54 68 96 ICA: invasive coronary angiography; MPC: myocardial perfusion scintigraphy; Spec.: specificity; FFR: fractional flow reserve; MRI: Magnetic Resonance Imaging; Sens.: sensitivity; PPV: positive predictive value; NPV: negative predictive value. * Results of myocardial perfusion by computed tomography with MPC and MRI as reference. shown good diagnostic performance, with sensitivity and specificity ranging from 88 to 95%, and 74 to 90%, respectively. Although promising, the evaluation of this technique has been performed mainly through small sample unicentric studies, so the potential benefits of its use in relation to static Myocardial CTP need further investigation. Similarly, the use of dual energy in the evaluation of myocardial perfusion finds favorable ground for clinical research. Recent studies have shown promising data in the attempt to detect obstructive coronary artery disease (CAD) (86-94% sensitivity and 74-98% specificity), 40,41 however with data obtained in small samples. A prospective multicenter study to evaluate the use of this technique to identify flow‑limiting coronary stenosis using invasive FFR as a reference is underway. 42 Table 1 shows the results of selected studies evaluating Myocardial CTP performance in the search for myocardial ischemia and obstructive CAD. Equipment required Any 64-channel or more (4 cm z-axis coverage) CT scan is able to perform coronary angiography, and therefore synchronizes with the electrocardiogram (ECG) and appropriate settings, being also able to study pharmacological- stress myocardial perfusion. 43-47 For dynamic stress studies, with follow-up of the first pass of contrast through the myocardium (as opposed to a single acquisition at peak myocardial contrast – static perfusion), CT scans with at least 8 cm cover are required, either axially or in shuttle mode. Regarding image post-processing, it is recommended to use specific analysis software that allows segmenting the heart, coding the density of each area of the myocardium by color and displaying the result in a 3D map integrated with the coronary anatomy, or Bull's Eye representation form. Some newer tools allow correction of beam hardening hypo‑attenuation, which is common in the inferior/ inferolateral walls (from the aorta), septum (from contrast in the right ventricle) and anterior walls (from the ribs). This correction is highly recommended and can be done by probability algorithms 48 or by dual energy spectral acquisition with reconstruction of high energy monochrome images. 49 A contrast infusion pump, preferably with two heads, is required for dynamic injection of high flow contrast. There is no need for an infusion pump for dipyridamole, but its presence can help optimize and ensure protocol quality. Despite the safety of dipyridamole/adenosine demonstrated in past studies, emergency care supplies regularly present in radiological clinics should be readily available, as well as qualified personnel to use them. Since dipyridamole/adenosine may induce advanced atrioventricular blocks (especially in conjunction with beta-blockers), the presence of percutaneous pacemaker can be helpful. Aminophylline should be ready for infusion after dipyridamole/adenosine administration. Continuous monitoring by ECG of satisfactory quality is indispensable during infusion. Acquisition protocols – CT myocardial perfusion imaging Monitoring of coronary artery tomography images, as well as CTMP, should be conducted by a specialized professional. 50 CTMP imaging techniques vary according to manufacturer and equipment model used. Thus, we warn that for each manufacturer some adjustments should be made for protocol optimization. In addition, we emphasize that the description of patient preparation, techniques of acquisition and use of medications are suggestions based on previous studies and the authors’ experience, and may vary to meet the specific demands and workflows of each institution. – Pre-exam preparation As preparation for the exam, all patients should be fasting for at least four hours and not have caffeinated beverages in the last 24 hours. Patients should be punctured with 18-20 gauge Jelco intravenous catheter in the antecubital vein of the right arm for administration of iodinated contrast. Another IV line in the left arm should be made for infusion of the stressor agent (dipyridamole/adenosine/regadenoson) and aminophylline as dipyridamole antagonist when necessary. ECG, heart rate and blood pressure should be monitored by the attending physician throughout the examination. 760