Normal values of myocardial blood flow measured with dynamic myocardial computed tomography perfusion.

AIMS: Dynamic myocardial computed tomography (CT) perfusion (DM-CTP) can, in combination with coronary CT angiography (CCTA), provide anatomical and functional evaluation of coronary artery disease (CAD). However, normal values of myocardial blood flow (MBF) are needed to identify impaired myocardial blood supply in patients with suspected CAD. We aimed to establish normal values for MBF measured using DM-CTP, to assess the effects of age and sex, and to assess regional distribution of MBF. METHODS AND RESULTS: A total of 82 healthy individuals (46 women) aged 45-78 years with normal coronary arteries by CCTA underwent either rest and adenosine stress DM-CTP (n = 30) or adenosine-induced stress DM-CTP only (n = 52). Global and segmental MBF were assessed. Global MBF at rest and during stress were 0.93 ± 0.42 and 3.58 ± 1.14 mL/min/g, respectively. MBF was not different between the sexes (P = 0.88 at rest and P = 0.61 during stress), and no correlation was observed between MBF and age (P = 0.08 at rest and P = 0.82 during stress). Among the 16 myocardial segments, significant intersegmental differences were found (P < 0.01), which was not related to age, sex, or coronary dominance. CONCLUSION: MBF assessed by DM-CTP in healthy individuals with normal coronary arteries displays significant intersegmental heterogeneity which does not seem to be affected by age, sex, or coronary dominance. Normal values of MBF may be helpful in the clinical evaluation of suspected myocardial ischaemia using DM-CTP.

Quantification of myocardial blood flow using dynamic myocardial CT perfusion compared with 82Rb PET.

PURPOSE: Absolute measures of myocardial blood flow (MBF) obtained with dynamic myocardial CT perfusion (DM-CTP) are underestimated when compared with reference standards. This is to some extent explained by incomplete extraction of iodinated contrast agent (iCA) to the myocardial tissue. We aimed to establish an extraction function for iCA, use the function to calculate MBFCT and to compare this with MBF measured with 82Rb positron emission tomography (PET). MATERIALS AND METHODS: Healthy individuals without coronary artery disease (CAD) were examined with 82Rb PET and DM-CTP. The factors a and ß of the generalized Renkin-Crone model were estimated using a non-linear least squares model. The factors providing the best fit for the data were subsequently used to calculate MBFCT. RESULTS: Of consecutive 91 individuals examined, 79 were eligible for analysis. The factors a and ß providing the best fit of the nonlinear least-squares model to the data were a â€‹= â€‹0.614 and ߠ​= â€‹0.218 (R-squared â€‹= â€‹0.81). Conversion of the CT inflow parameter (K1) values using the derived extraction function resulted in a significant correlation between MBF measured during stress using CT and PET (P â€‹= â€‹0.039). CONCLUSION: In healthy individuals, flow estimates obtained with dynamic myocardial CT perfusion during stress were, after conversion to MBF using the extraction of iodinated CT contrast agent, correlated with absolute MBF quantified with 82Rb PET.

Pre-procedural planning of coronary revascularization by cardiac computed tomography: An expert consensus document of the Society of Cardiovascular Computed Tomography.

Coronary CT angiography (CCTA) demonstrated high diagnostic accuracy for detecting coronary artery disease (CAD) and a key role in the management of patients with low-to-intermediate pretest likelihood of CAD. However, the clinical information provided by this noninvasive method is still regarded insufficient in patients with diffuse and complex CAD and for planning percutaneous coronary intervention (PCI) and surgical revascularization procedures. On the other hand, technology advancements have recently shown to improve CCTA diagnostic accuracy in patients with diffuse and calcific stenoses. Moreover, stress CT myocardial perfusion imaging (CT-MPI) and fractional flow reserve derived from CCTA (CT-FFR) have been introduced in clinical practice as new tools for evaluating the functional relevance of coronary stenoses, with the possibility to overcome the main CCTA drawback, i.e. anatomical assessment only. The potential value of CCTA to plan and guide interventional procedures lies in the wide range of information it can provide: a) detailed evaluation of plaque extension, volume and composition; b) prediction of procedural success of CTO PCI using scores derived from CCTA; c) identification of coronary lesions requiring additional techniques (e.g., atherectomy and lithotripsy) to improve stent implantation success by assessing calcium score and calcific plaque distribution; d) assessment of CCTA-derived Syntax Score and Syntax Score II, which allows to select the mode of revascularization (PCI or CABG) in patients with complex and multivessel CAD. The aim of this Consensus Document is to review and discuss the available data supporting the role of CCTA, CT-FFR and stress CT-MPI in the preprocedural and possibly intraprocedural planning and guidance of myocardial revascularization interventions.

Diagnostic performance of deep learning algorithm for analysis of computed tomography myocardial perfusion.

PURPOSE: To evaluate the diagnostic accuracy of a deep learning (DL) algorithm predicting hemodynamically significant coronary artery disease (CAD) by using a rest dataset of myocardial computed tomography perfusion (CTP) as compared to invasive evaluation. METHODS: One hundred and twelve consecutive symptomatic patients scheduled for clinically indicated invasive coronary angiography (ICA) underwent CCTA plus static stress CTP and ICA with invasive fractional flow reserve (FFR) for stenoses ranging between 30 and 80%. Subsequently, a DL algorithm for the prediction of significant CAD by using the rest dataset (CTP-DLrest) and stress dataset (CTP-DLstress) was developed. The diagnostic accuracy for identification of significant CAD using CCTA, CCTA + CTP stress, CCTA + CTP-DLrest, and CCTA + CTP-DLstress was measured and compared. The time of analysis for CTP stress, CTP-DLrest, and CTP-DLStress was recorded. RESULTS: Patient-specific sensitivity, specificity, NPV, PPV, accuracy, and area under the curve (AUC) of CCTA alone and CCTA + CTPStress were 100%, 33%, 100%, 54%, 63%, 67% and 86%, 89%, 89%, 86%, 88%, 87%, respectively. Patient-specific sensitivity, specificity, NPV, PPV, accuracy, and AUC of CCTA + DLrest and CCTA + DLstress were 100%, 72%, 100%, 74%, 84%, 96% and 93%, 83%, 94%, 81%, 88%, 98%, respectively. All CCTA + CTP stress, CCTA + CTP-DLRest, and CCTA + CTP-DLStress significantly improved detection of hemodynamically significant CAD compared to CCTA alone (p < 0.01). Time of CTP-DL was significantly lower as compared to human analysis (39.2 ± 3.2 vs. 379.6 ± 68.0 s, p < 0.001). CONCLUSION: Evaluation of myocardial ischemia using a DL approach on rest CTP datasets is feasible and accurate. This approach may be a useful gatekeeper prior to CTP stress..

Clinical utility of two-phase computed tomography angiography for the detection of myocardial perfusion defects related to acute coronary syndrome in patients with acute chest pain: a case series.

BACKGROUND: Evaluation of acute chest pain (ACP) in the emergency department is a major health issue and differential diagnosis remains challenging for the physician, particularly in patients with atypical symptoms and inconclusive changes in electrocardiogram (ECG) or biomarkers levels. CASE SUMMARY: We present the potential value of the two-phase computed tomography angiography (TP-CTA) imaging protocol done in six different patients evaluated with ACP and underwent non-gated or gated computed tomography angiography (CTA) to exclude pulmonary embolism (PE), acute aortic syndrome (AAS), or acute coronary syndrome (ACS). All patients had new-onset chest pain and atypical clinical presentation with non-diagnostic ECG and initially negative or near-normal cardiac biomarkers. DISCUSSION: The evaluation of myocardial computed tomography perfusion (MCTP) using TP-CTA imaging protocol might open a new diagnostic approach to evaluate MCTP in patients with ACP related to PE, AAS, or ACS.

Optimization of image sampling rate to lower the radiation dose of dynamic myocardial CT perfusion.

BACKGROUND: Dynamic myocardial CT perfusion (CTP) has emerged as a potential strategy to combine anatomical and functional evaluation in a single modality. However, this method results in a high radiation dose. METHODS: Dynamic CTP was performed in 56 patients with suspected or known ischemic heart disease of whom 48 had complete CT-data. Datasets with reduced sampling rate of 2- and 3 RR-intervals (2RR and 3RR) were constructed post hoc. Myocardial blood flow (MBF) estimates from the 2RR and 3RR datasets were compared with estimates based on the full dataset (1RR) using the two one-sided test of equivalence for paired samples. RESULTS: Significant equivalence was found for rest MBFLV (p â€‹< â€‹0.001), stress MBFLV (p â€‹< â€‹0.001) and for the CFRLV (p â€‹= â€‹0.005) when comparing 2RR blood flow estimates with the results based on the 1RR dataset. The 2RR reconstruction protocol led to an estimated reduction in radiation dose of 35.4 â€‹± â€‹3.8%. CONCLUSION: MBF can be quantitated with dynamic CTP using a sampling strategy of one volume for every second heartbeat. This strategy could lead to a significant reduction in radiation dose.

[Update on coronary CT-more than just anatomical imaging? : Current guidelines and functional CT techniques for the quantification of stenoses]. / Update Kardio-CT ­ mehr als nur anatomische Bildgebung? : Aktuelle Leitlinien und funktionelle CT-Techniken zur Stenosequantifizierung.

BACKGROUND: Coronary CT angiography (cCTA) has a high negative predictive value for ruling out significant coronary stenoses. However, it is limited in determining hemodynamic significance of a stenosis and hence to prove the indication for therapy. OBJECTIVES: When and how is cCTA used according to current guidelines? Which functional CT techniques are available to test for hemodynamic significance of coronary stenoses? MATERIALS AND METHODS: The value of cCTA is explained on the basis of current guidelines by the European Society of Cardiology (ESC) for the diagnosis of chronic coronary syndromes. Functional CT techniques which test for hemodynamic significance of coronary stenoses are myocardial CT-perfusion (CT­P) and CT-based fractional flow reserve (CT-FFR). RESULTS: The new ESC guidelines classify cCTA as a class 1 recommendation for diagnosing coronary artery disease in symptomatic patients with low clinical likelihood. If clinical likelihood is high or an at least moderate stenosis is detected with cCTA, noninvasive functional (stress) imaging is preferred. There is a large body of evidence for CT­P and CT-FFR as functional tests. CONCLUSION: In the current guidelines, cCTA is highly recommended for the diagnosis of coronary artery disease. The functional CT techniques CT­P and CT-FFR have shown high diagnostic accuracy for myocardial ischemia of coronary stenoses in many clinical studies. However, these methods are not part of current guidelines yet and clinical adoption is still low.

Evaluation of computed tomography myocardial perfusion in women with angina and no obstructive coronary artery disease.

Women with angina and no obstructive coronary artery disease (CAD) have worse cardiovascular prognosis than asymptomatic women. Limitation in myocardial perfusion caused by coronary microvascular dysfunction (CMD) is one of the proposed mechanisms contributing to the adverse prognosis. The aim of this study was to assess myocardial perfusion in symptomatic women with no obstructive CAD suspected for CMD compared with asymptomatic sex-matched controls using static CT perfusion (CTP). We performed a semi-quantitative assessment of the left ventricular myocardial perfusion and myocardial perfusion reserve (MPR), using static CTP with adenosine provocation, in 105 female patients with angina and no obstructive CAD (< 50% stenosis) and 33 sex-matched controls without a history of angina or ischemic heart disease.  Patients were on average 4 years older (p = 0.04) and had a higher burden of cardiovascular risk factors. While global perfusion during rest was comparable between the groups (age-adjusted p = 0.12), global perfusion during hyperemia was significantly reduced in patients compared with controls (163 ± 23 HU vs. 171 ± 25 HU; age-adjusted p = 0.023). The ability to increase myocardial perfusion during adenosine-induced vasodilation was significantly diminished in patients (MPR 148% vs. 158%; age-adjusted p < 0.001). This remained unchanged after adjustment for cardiovascular risk factors (p = 0.008). Women with angina and no obstructive CAD have reduced hyperemic myocardial perfusion and MPR compared with sex-matched controls. Impaired myocardial perfusion may be related to the presence of CMD in some of these women.

FFRCT and CT perfusion: A review on the evaluation of functional impact of coronary artery stenosis by cardiac CT.

Coronary computed tomography angiography (CCTA) is at the frontline of the diagnostic strategies to detect coronary artery disease (CAD). Anatomical information have proven to be insufficient to detect hemodynamic significant epicardial stenosis. In the present invited review we discuss on FFRCT and stress CTP, emerging technologies for an accurate and comprehensive evaluation of patients with suspected CAD, offering both anatomical (i.e. luminal and plaque) and functional assessment in one single technique.

Single-phase coronary artery CT angiography extracted from stress dynamic myocardial CT perfusion on third-generation dual-source CT: Validation by coronary angiography.

BACKGROUND: CT advances allow coronary arterial tree to be entirely covered during one CTP scan. Our aim was to investigate the potential value of single-phase coronary CT angiography (SP-CCTA) extracted from stress dynamic myocardial CT perfusion (CTP) for coronary artery stenosis assessment. METHODS: Consecutive symptomatic patients were prospectively recruited and scanned with an ATP-stress dynamic myocardial CTP and routine CCTA protocol using third-generation DSCT. Noise reduction was applied to optimize image quality (IQ), the CTP phase with the best enhancement of the coronary arteries was selected as the SP-CCTA. IQ was assessed qualitatively. Using coronary angiography (CAG) as the reference standard, the diagnostic performance for stenosis detection was compared for SP-CCTA and routine CCTA. RESULTS: 56 patients underwent the CTP and CCTA examination, among which 39 patients underwent CAG. The qualitative IQ scores of SP-CCTA were similar to that of routine CCTA (p > 0.05). On a per-segment basis, the sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy and area under the receiver-operating-characteristic curve results of SP-CCTA and routine CCTA for diagnosis of stenosis ≥50% exhibited no significant difference (SP-CCTA: 78.1%, 94.9%, 77.4%, 95.1%, 91.6% and 0.935 vs. routine CCTA: 74.7%, 95.3%, 78.0%, 95.3%, 91.6% and 0.937; all p > 0.05). The mean effective radiation dose of CTP and routine CCTA plus CTP were 3.92 ±â€¯1.72 mSv and 5.98 ±â€¯2.01 mSv (p < 0.05), respectively. CONCLUSIONS: The IQ and diagnostic value of SP-CCTA was equivalent to routine CCTA on third-generation DSCT. SP-CCTA images from CTP may potentially replace a separate routine CCTA, allowing the possibility of "one-stop" cardiac examination for high-risk CAD patients who need myocardial ischemia assessment.

Geographic and demographic variabilities of quantitative parameters in stress myocardial computed tomography perfusion.

BACKGROUND/AIMS: To evaluate the geographic and demographic variabilities of the quantitative parameters of computed tomography perfusion (CTP) of the left ventricular (LV) myocardium in patients with normal coronary artery on computed tomography angiography (CTA). METHODS: From a multicenter CTP registry of stress and static computed tomography, we retrospectively recruited 113 patients (mean age, 60 years; 57 men) without perfusion defect on visual assessment and minimal (< 20% of diameter stenosis) or no coronary artery disease on CTA. Using semiautomatic analysis software, quantitative parameters of the LV myocardium, including the myocardial attenuation in stress and rest phases, transmural perfusion ratio (TPR), and myocardial perfusion reserve index (MPRI), were evaluated in 16 myocardial segments. RESULTS: In the lateral wall of the LV myocardium, all quantitative parameters except for MPRI were significantly higher compared with those in the other walls. The MPRI showed consistent values in all myocardial walls (anterior to lateral wall: range, 25% to 27%; p = 0.401). At the basal level of the myocardium, all quantitative parameters were significantly lower than those at the mid- and apical levels. Compared with men, women had significantly higher values of myocardial attenuation and TPR. Age, body mass index, and Framingham risk score were significantly associated with the difference in myocardial attenuation. CONCLUSIONS: Geographic and demographic variabilities of quantitative parameters in stress myocardial CTP exist in healthy subjects without significant coronary artery disease. This information may be helpful when assessing myocardial perfusion defects in CTP.

Relation between quantitative coronary CTA and myocardial ischemia by adenosine stress myocardial CT perfusion.

BACKGROUND: Coronary-computed tomography angiography (CTA) has limited accuracy to predict myocardial ischemia. Besides luminal area stenosis, other coronary plaque morphology and composition parameters may help to assess ischemia. With the integration of coronary CTA and adenosine stress CT myocardial perfusion (CTP), reliable information regarding coronary anatomy and function can be derived in one procedure. This analysis aimed to investigate the association between coronary stenosis severity, plaque composition and morphology and the presence of ischemia measured with adenosine stress myocardial CTP. METHODS AND RESULTS: 84 patients (age, 62 ± 10 years; 48% men) who underwent sequential coronary CTA and adenosine stress myocardial CT perfusion were analyzed. Automated quantification was performed in all coronary lesions (quantitative CTA). Downstream myocardial ischemia was assessed by visual analysis of the rest and stress CTP images and defined as a summed difference score of ≥1. One or more coronary plaques were present in 146 coronary arteries of which 31 (21%) were ischemia-related. Of the lesions with a stenosis percentage <50%, 50%-70%, and >70%, respectively, 9% (6/67), 18% (9/51), and 57% (16/28) demonstrated downstream ischemia. Furthermore, mean plaque burden, plaque volume, lesion length, maximal plaque thickness, and dense calcium volume were significantly higher in ischemia-related lesions, but only stenosis severity (%) (OR 1.06; 95% CI 1.02-1.10; P = .006) and lesion length (mm) (OR 1.26; 95% CI 1.02-1.55; P = .029) were independent correlates. CONCLUSIONS: Increasing stenosis percentage by quantitative CTA is positively correlated to myocardial ischemia measured with adenosine stress myocardial CTP. However, stenosis percentage remains a moderate determinant. Lumen area stenosis and lesion length were independently associated with ischemia, adjusted for coronary plaque volume, mean plaque burden, maximal lesion thickness, and dense calcium volume.

Prediction of clinical outcome by myocardial CT perfusion in patients with low-risk unstable angina pectoris.

The prognostic implications of myocardial computed tomography perfusion (CTP) analyses are unknown. In this sub-study to the CATCH-trial we evaluate the ability of adenosine stress CTP findings to predict mid-term major adverse cardiac events (MACE). In 240 patients with acute-onset chest pain, yet normal electrocardiograms and troponins, a clinically blinded adenosine stress CTP scan was performed in addition to conventional diagnostic evaluation. A reversible perfusion defect (PD) was found in 38 patients (16 %) and during a median follow-up of 19 months (range 12-22 months) 25 patients (10 %) suffered a MACE (cardiac death, non-fatal myocardial infarction and revascularizations). Accuracy for the prediction of MACE expressed as the area under curve (AUC) on receiver-operating characteristic curves was 0.88 (0.83-0.92) for visual assessment of a PD and 0.80 (0.73-0.85) for stress TPR (transmural perfusion ratio). After adjustment for the pretest probability of obstructive coronary artery disease, both detection of a PD and stress TPR were significantly associated with MACE with an adjusted hazard ratio of 39 (95 % confidence interval 11-134), p < 0.0001, for visual interpretation and 0.99 (0.98-0.99) for stress TPR, p < 0.0001. Patients with a PD volume covering >10 % of the LV myocardium had a worse prognosis compared to patients with a PD covering <10 % of the LV myocardium, p = 0.0002. The optimal cut-off value of the myocardial PD extent to predict MACE was 5.3 % of the left ventricle [sensitivity 84 % (64-96), specificity 95 % (91-97)]. Myocardial CT perfusion parameters predict mid-term clinical outcome in patients with recent acute-onset chest pain.

Geographic and demographic variabilities of quantitative parameters in stress myocardial computed tomography perfusion

BACKGROUND/AIMS: To evaluate the geographic and demographic variabilities of the quantitative parameters of computed tomography perfusion (CTP) of the left ventricular (LV) myocardium in patients with normal coronary artery on computed tomography angiography (CTA). METHODS: From a multicenter CTP registry of stress and static computed tomography, we retrospectively recruited 113 patients (mean age, 60 years; 57 men) without perfusion defect on visual assessment and minimal (< 20% of diameter stenosis) or no coronary artery disease on CTA. Using semiautomatic analysis software, quantitative parameters of the LV myocardium, including the myocardial attenuation in stress and rest phases, transmural perfusion ratio (TPR), and myocardial perfusion reserve index (MPRI), were evaluated in 16 myocardial segments. RESULTS: In the lateral wall of the LV myocardium, all quantitative parameters except for MPRI were significantly higher compared with those in the other walls. The MPRI showed consistent values in all myocardial walls (anterior to lateral wall: range, 25% to 27%; p = 0.401). At the basal level of the myocardium, all quantitative parameters were significantly lower than those at the mid- and apical levels. Compared with men, women had significantly higher values of myocardial attenuation and TPR. Age, body mass index, and Framingham risk score were significantly associated with the difference in myocardial attenuation. CONCLUSIONS: Geographic and demographic variabilities of quantitative parameters in stress myocardial CTP exist in healthy subjects without significant coronary artery disease. This information may be helpful when assessing myocardial perfusion defects in CTP.

Effect of Beam Hardening on Transmural Myocardial Perfusion Quantification in Myocardial CT Imaging.

The detection of subendocardial ischemia exhibiting an abnormal transmural perfusion gradient (TPG) may help identify ischemic conditions due to micro-vascular dysfunction. We evaluated the effect of beam hardening (BH) artifacts on TPG quantification using myocardial CT perfusion (CTP). We used a prototype spectral detector CT scanner (Philips Healthcare) to acquire dynamic myocardial CTP scans in a porcine ischemia model with partial occlusion of the left anterior descending (LAD) coronary artery guided by pressure wire-derived fractional flow reserve (FFR) measurements. Conventional 120 kVp and 70 keV projection-based mono-energetic images were reconstructed from the same projection data and used to compute myocardial blood flow (MBF) using the Johnson-Wilson model. Under moderate LAD occlusion (FFR~0.7), we used three 5 mm short axis slices and divided the myocardium into three LAD segments and three remote segments. For each slice and each segment, we characterized TPG as the mean "endo-to-epi" transmural flow ratio (TFR). BH-induced hypoenhancement on the ischemic anterior wall at 120 kVp resulted in significantly lower mean TFR value as compared to the 70 keV TFR value (0.29±0.01 vs. 0.55±0.01; p<1e-05). No significant difference was measured between 120 kVp and 70 keV mean TFR values on segments moderately affected or unaffected by BH. In the entire ischemic LAD territory, 120 kVp mean endocardial flow was significantly reduced as compared to mean epicardial flow (15.80±10.98 vs. 40.85±23.44 ml/min/100g; p<1e-04). At 70 keV, BH was effectively minimized resulting in mean endocardial MBF of 40.85±15.3407 ml/min/100g vs. 74.09±5.07 ml/min/100g (p=0.0054) in the epicardium. We also found that BH artifact in the conventional 120 kVp images resulted in falsely reduced MBF measurements even under non-ischemic conditions.

Simultaneous achievement of accurate CT number and image quality improvement for myocardial perfusion CT at 320-MDCT volume scanning.

PURPOSE: To investigate differences in image-to-image variations between full- and half-scan reconstruction on myocardial CT perfusion (CTP) study. METHODS: Using a cardiac phantom we performed ECG-gated myocardial CTP on a second-generation 320-multidetector CT volume scanner. The heart rate was set at 60 bpm; once per second for a total of 24 s were performed. CT images were acquired at 80- and 120 kVp and subjected to full- and half-scan reconstruction. On images acquired at the same slice level we then measured image-to-image variations, coefficients of variance (CV), and image noise. RESULTS: The image-to-image variations with full- and half-scan reconstruction were 1.3 HU vs. 27.2 HU at 80 kVp (p < 0.001) and 0.70 HU vs. 9.3 HU at 120 kVp (p < 0.001) even though the mean HU value was almost the same for both reconstruction methods. The CV of 80- and 120-kVp images of the left ventricular cavity decreased by 0.16% and 0.17%, respectively, with full-scan reconstruction; with half-scan reconstruction it decreased by 3.34% and 2.30%, respectively. Compared with half-scan reconstruction, the image noise was reduced by 27.2% at 80 kVp and by 28.0% at 120 kVp with full-scan reconstruction. CONCLUSION: Myocardial CTP with full-scan reconstruction substantially decreased image-to-image variations and provided accurate CT attenuation.

Combined coronary angiography and myocardial perfusion by computed tomography in the identification of flow-limiting stenosis - The CORE320 study: An integrated analysis of CT coronary angiography and myocardial perfusion.

BACKGROUND: The combination of coronary CT angiography (CTA) and myocardial CT perfusion (CTP) is gaining increasing acceptance, but a standardized approach to be implemented in the clinical setting is necessary. OBJECTIVES: To investigate the accuracy of a combined coronary CTA and myocardial CTP comprehensive protocol compared to coronary CTA alone, using a combination of invasive coronary angiography and single photon emission CT as reference. METHODS: Three hundred eighty-one patients included in the CORE320 trial were analyzed in this study. Flow-limiting stenosis was defined as the presence of ≥50% stenosis by invasive coronary angiography with a related perfusion defect by single photon emission CT. The combined CTA + CTP definition of disease was the presence of a ≥50% stenosis with a related perfusion defect. All data sets were analyzed by 2 experienced readers, aligning anatomic findings by CTA with perfusion defects by CTP. RESULTS: Mean patient age was 62 ± 6 years (66% male), 27% with prior history of myocardial infarction. In a per-patient analysis, sensitivity for CTA alone was 93%, specificity was 54%, positive predictive value was 55%, negative predictive value was 93%, and overall accuracy was 69%. After combining CTA and CTP, sensitivity was 78%, specificity was 73%, negative predictive value was 64%, positive predictive value was 0.85%, and overall accuracy was 75%. In a per-vessel analysis, overall accuracy of CTA alone was 73% compared to 79% for the combination of CTA and CTP (P < .0001 for difference). CONCLUSIONS: Combining coronary CTA and myocardial CTP findings through a comprehensive protocol is feasible. Although sensitivity is lower, specificity and overall accuracy are higher than assessment by coronary CTA when compared against a reference standard of stenosis with an associated perfusion defect.

Myocardial CT perfusion for the prediction of obstructive coronary artery disease, valuable or not?

Adenosine stress myocardial computed tomography perfusion (CTP) is a relatively new myocardial perfusion imaging technique. Together with coronary CT angiography (CTA) it provides anatomic and functional information of coronary artery disease (CAD). In previous studies, the combination of these techniques demonstrated to be valuable for identifying hemodynamically significant stenoses. George et al., performed a secondary analysis on the CORE320 study and compared the diagnostic performance of CTP to single positron emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to diagnose obstructive CAD (defined as ≥50% luminal stenosis). In this editorial the results and limitations of the study are discussed, as well as opportunities that this new perfusion technique brings with it.

Dynamic Myocardial Perfusion in a Porcine Balloon-induced Ischemia Model using a Prototype Spectral Detector CT.

Myocardial CT perfusion (CTP) imaging is an application that should greatly benefit from spectral CT through the significant reduction of beam hardening (BH) artifacts using mono-energetic (monoE) image reconstructions. We used a prototype spectral detector CT (SDCT) scanner (Philips Healthcare) and developed advanced processing tools (registration, segmentation, and deconvolution-based flow estimation) for quantitative myocardial CTP in a porcine ischemia model with different degrees of coronary occlusion using a balloon catheter. The occlusion severity was adjusted with fractional flow reserve (FFR) measurements. The SDCT scanner is a single source, dual-layer detector system, which allows simultaneous acquisitions of low and high energy projections, hence enabling accurate projection-based material decomposition and effective reduction of BH-artifacts. In addition, the SDCT scanner eliminates partial scan artifacts with fast (0.27s), full gantry rotation acquisitions. We acquired CTP data under different hemodynamic conditions and reconstructed conventional 120kVp images and projection-based monoenergetic (monoE) images for energies ranging from 55keV-to-120keV. We computed and compared myocardial blood flow (MBF) between different reconstructions. With balloon completely deflated (FFR=1), we compared the mean attenuation in a myocardial region of interest before iodine arrival and at peak iodine enhancement in the left ventricle (LV), and we found that monoE images at 70keV effectively minimized the difference in attenuation, due to BH, to less than 1 HU compared to 14 HU with conventional 120kVp images. Flow maps under baseline condition (FFR=1) were more uniform throughout the myocardial wall at 70keV, whereas with 120kVp data about 12% reduction in blood flow was noticed on BH-hypoattenuated areas compared to other myocardial regions. We compared MBF maps at different keVs under an ischemic condition (FFR < 0.7), and we found that flow-contrast-to-noise-ratio (CNR f ) between LAD ischemic and remote healthy territories attains its maximum (2.87 ± 0.7) at 70keV. As energies diverge from 70keV, we noticed a steady decrease in CNRf and an overestimation of mean-MBF. Flow overestimation was also noticed for conventional 120kVp images in different myocardial regions.