Diagnostic performance of combined noninvasive coronary angiography and myocardial perfusion imaging using 320-MDCT: the CT angiography and perfusion methods of the CORE320 multicenter multinational diagnostic study

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.

Comprehensive assessment of radiation dose estimates for the CORE320 study

OBJECTIVE. The purpose of this study was to comprehensively study estimated radiation doses for subjects included in the main analysis of the Combined Non-invasive Coronary Angiography and Myocardial Perfusion Imaging Using 320 Detector Computed Tomography (CORE320) study ( ClinicalTrials.gov identifier NCT00934037), a clinical trial comparing combined CT angiography (CTA) and perfusion CT with the reference standard catheter angiography plus myocardial perfusion SPECT. SUBJECTS AND METHODS. Prospectively acquired data on 381 CORE320 subjects were analyzed in four groups of testing related to radiation exposure. Radiation dose estimates were compared between modalities for combined CTA and perfusion CT with respect to covariates known to influence radiation exposure and for the main clinical outcomes defined by the trial. The final analysis assessed variations in radiation dose with respect to several factors inherent to the trial. RESULTS. The mean radiation dose estimate for the combined CTA and perfusion CT protocol (8.63 mSv) was significantly (p < 0.0001 for both) less than the average dose delivered from SPECT (10.48 mSv) and the average dose from diagnostic catheter angiography (11.63 mSv). There was no significant difference in estimated CTA-perfusion CT radiation dose for subjects who had false-positive or false-negative results in the CORE320 main analyses in a comparison with subjects for whom the CTA-perfusion CT findings were in accordance with the reference standard SPECT plus catheter angiographic findings. CONCLUSION. Radiation dose estimates from CORE320 support clinical implementation of a combined CT protocol for assessing coronary anatomy and myocardial perfusion.

Functional relevance of coronary artery disease by cardiac magnetic resonance and cardiac computed tomography: myocardial perfusion and fractional flow reserve

Coronary artery disease (CAD) is one of the leading causes of morbidity and mortality and it is responsible for an increasing resource burden. The identification of patients at high risk for adverse events is crucial to select those who will receive the greatest benefit from revascularization. To this aim, several non-invasive functional imaging modalities are usually used as gatekeeper to invasive coronary angiography, but the diagnostic yield of elective invasive coronary angiography remains unfortunately low. Stress myocardial perfusion imaging by cardiac magnetic resonance (stress-CMR) has emerged as an accurate technique for diagnosis and prognostic stratification of the patients with known or suspected CAD thanks to high spatial and temporal resolution, absence of ionizing radiation, and the multiparametric value including the assessment of cardiac anatomy, function, and viability. On the other side, cardiac computed tomography (CCT) has emerged as unique technique providing coronary arteries anatomy and more recently, due to the introduction of stress-CCT and noninvasive fractional flow reserve (FFR-CT), functional relevance of CAD in a single shot scan. The current review evaluates the technical aspects and clinical experience of stress-CMR and CCT in the evaluation of functional relevance of CAD discussing the strength and weakness of each approach.

Noninvasive physiologic assessment of coronary stenoses using cardiac CT

Coronary CT angiography (CCTA) has become an important noninvasive imaging modality in the diagnosis of coronary artery disease (CAD). CCTA enables accurate evaluation of coronary artery stenosis. However, CCTA provides limited information on the physiological significance of stenotic lesions. A noninvasive "one-stop-shop" diagnostic test that can provide both anatomical significance and functional significance of stenotic lesions would be beneficial in the diagnosis and management of CAD. Recently, with the introduction of novel techniques, such as myocardial CT perfusion, CT-derived fractional flow reserve (FFRCT), and transluminal attenuation gradient (TAG), CCTA has emerged as a noninvasive method for the assessment of both anatomy of coronary lesions and its physiological consequences during a single study. This review provides an overview of the current status of new CT techniques for the physiologic assessments of CAD.

Myocardial blood flow quantification for evaluation of coronary artery disease by positron emission tomography, cardiac magnetic resonance imaging, and computed tomography

The noninvasive detection of the presence and functional significance of coronary artery stenosis is important in the diagnosis, risk assessment, and management of patients with known or suspected coronary artery disease. Quantitative assessment of myocardial perfusion can provide an objective and reproducible estimate of myocardial ischemia and risk prediction. Positron emission tomography, cardiac magnetic resonance, and cardiac computed tomography perfusion are modalities capable of measuring myocardial blood flow and coronary flow reserve. In this review, we will discuss the technical aspects of quantitative myocardial perfusion imaging with positron emission tomography, cardiac magnetic resonance imaging, and computed tomography, and its emerging clinical applications.

Relationship of left ventricular mass to coronary atherosclerosis and myocardial ischaemia: the CORE320 multicenter study

AIMS

The aim of this study was to investigate the association of left ventricular mass (LVM) with coronary atherosclerosis and myocardial infarction (MI).

METHODS AND RESULTS

Patients (n = 338) underwent 320 × 0.5 mm detector row coronary computed tomography (CT) angiography, invasive coronary angiography (ICA), and single-photon emission CT (SPECT) myocardial perfusion imaging. Quantitative coronary atheroma volume was obtained from the CT images for the entire coronary tree (19-segment model) with an arterial contour detection algorithm. Normalized total atheroma volume (NormTAV) was analysed to reflect quantitative total atheroma volume. LVM was measured on myocardial CT images and indexed to height to the power of 2.7 (LVMi). Patients with obstructive coronary artery disease (CAD) were defined as those with ≥50% diameter stenosis by quantitative ICA. Abnormal perfusion defect was defined as ≥1 abnormal myocardial segment by SPECT. The association of LVMi with coronary atherosclerosis and myocardial perfusion defect on SPECT at the patient level was determined with uni- and multivariable linear and logistic regression analyses. Obstructive CAD was present in 60.0% of enrolled patients. LVMi was independently associated with abnormal summed rest score [SRS; odds ratio (OR), 1.07; 95% confidence interval (CI), 1.03-1.09] and summed stress score (OR, 1.04; 95% CI, 1.01-1.07). An increase in LVMi was also independently associated with that in NormTAV (coefficient, 10.44; 95% CI, 1.50-19.39) and SRS ≥1 (OR, 1.05; 95% CI, 1.01-1.10), even after adjusting for cardiovascular risk factors in patients without previous MI.

CONCLUSIONS

LVM was independently associated with the presence of coronary artery atherosclerosis and MI.

Patterns of Opacification in Coronary CT Angiography: Contrast Differences and Gradients

Iodinated contrast delivery is a key component of coronary CT angiography. However, the purpose of contrast delivery has been limited to morphology alone. Specifically, iodine opacification of the coronary lumen has been used to separate it from the coronary artery wall and lesions within the coronary arteries. Because contrast is delivered to the coronary arteries according to the coronary blood flow, there is flow information encoded within the contrast opacification which, depending on CT hardware and acquisition protocol, can be recognized in coronary CT angiography. In addition, metrics related to flow have been identified and studied. They include coronary contrast opacification differences and contrast opacification gradients.

Physiologic evaluation of ischemia using cardiac CT: current status of CT myocardial perfusion and CT fractional flow reserve

Cardiac CT, specifically coronary CT angiography (CTA), is an established technology which detects anatomically significant coronary artery disease with a high sensitivity and negative predictive value compared with invasive coronary angiography. However, the limited ability of CTA to determine the physiologic significance of intermediate coronary stenoses remains a shortcoming compared with other noninvasive methods such as single-photon emission CT, stress echocardiography, and stress cardiac magnetic resonance. Two methods have been investigated recently: (1) myocardial CT perfusion and (2) fractional flow reserve (FFR) computed from CT (FFRCT). Improving diagnostic accuracy by combining the anatomic aspects of coronary CTA with a physiologic assessment via CT perfusion or FFRCT may reduce the need for additional testing to evaluate for ischemia, reduce downstream costs and risks associated with an invasive procedure, and lead to improved patient outcomes. Given a rapidly expanding body of research in this field, this comparative review summarizes the present literature while contrasting the benefits, limitations, and future directions in myocardial CT perfusion and FFRCT imaging.

Myocardial CT perfusion imaging and SPECT for the diagnosis of coronary artery disease: a head-to-head comparison from the CORE320 multicenter diagnostic performance study

PURPOSE

To compare the diagnostic performance of myocardial computed tomographic (CT) perfusion imaging and single photon emission computed tomography (SPECT) perfusion imaging in the diagnosis of anatomically significant coronary artery disease (CAD) as depicted at invasive coronary angiography.

MATERIALS AND METHODS

This study was approved by the institutional review board. Written informed consent was obtained from all patients. Sixteen centers enrolled 381 patients from November 2009 to July 2011. Patients underwent rest and adenosine stress CT perfusion imaging and rest and either exercise or pharmacologic stress SPECT before and within 60 days of coronary angiography. Images from CT perfusion imaging, SPECT, and coronary angiography were interpreted at blinded, independent core laboratories. The primary diagnostic parameter was the area under the receiver operating characteristic curve (Az). Sensitivity and specificity were calculated with use of prespecified cutoffs. The reference standard was a stenosis of at least 50% at coronary angiography as determined with quantitative methods.

RESULTS

CAD was diagnosed in 229 of the 381 patients (60%). The per-patient sensitivity and specificity for the diagnosis of CAD (stenosis ≥50%) were 88% (202 of 229 patients) and 55% (83 of 152 patients), respectively, for CT perfusion imaging and 62% (143 of 229 patients) and 67% (102 of 152 patients) for SPECT, with Az values of 0.78 (95% confidence interval: 0.74, 0.82) and 0.69 (95% confidence interval: 0.64, 0.74) (P = .001). The sensitivity of CT perfusion imaging for single- and multivessel CAD was higher than that of SPECT, with sensitivities for left main, three-vessel, two-vessel, and one-vessel disease of 92%, 92%, 89%, and 83%, respectively, for CT perfusion imaging and 75%, 79%, 68%, and 41%, respectively, for SPECT.

CONCLUSION

The overall performance of myocardial CT perfusion imaging in the diagnosis of anatomic CAD (stenosis ≥50%), as demonstrated with the Az, was higher than that of SPECT and was driven in part by the higher sensitivity for left main and multivessel disease.

Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study

AIMS

To evaluate the diagnostic power of integrating the results of computed tomography angiography (CTA) and CT myocardial perfusion (CTP) to identify coronary artery disease (CAD) defined as a flow limiting coronary artery stenosis causing a perfusion defect by single photon emission computed tomography (SPECT).

METHODS AND RESULTS

We conducted a multicentre study to evaluate the accuracy of integrated CTA-CTP for the identification of patients with flow-limiting CAD defined by ≥50% stenosis by invasive coronary angiography (ICA) with a corresponding perfusion deficit on stress single photon emission computed tomography (SPECT/MPI). Sixteen centres enroled 381 patients who underwent combined CTA-CTP and SPECT/MPI prior to conventional coronary angiography. All four image modalities were analysed in blinded independent core laboratories. The prevalence of obstructive CAD defined by combined ICA-SPECT/MPI and ICA alone was 38 and 59%, respectively. The patient-based diagnostic accuracy defined by the area under the receiver operating characteristic curve (AUC) of integrated CTA-CTP for detecting or excluding flow-limiting CAD was 0.87 [95% confidence interval (CI): 0.84-0.91]. In patients without prior myocardial infarction, the AUC was 0.90 (95% CI: 0.87-0.94) and in patients without prior CAD the AUC for combined CTA-CTP was 0.93 (95% CI: 0.89-0.97). For the combination of a CTA stenosis ≥50% stenosis and a CTP perfusion deficit, the sensitivity, specificity, positive predictive, and negative predicative values (95% CI) were 80% (72-86), 74% (68-80), 65% (58-72), and 86% (80-90), respectively. For flow-limiting disease defined by ICA-SPECT/MPI, the accuracy of CTA was significantly increased by the addition of CTP at both the patient and vessel levels.

CONCLUSIONS

The combination of CTA and perfusion correctly identifies patients with flow limiting CAD defined as ≥50 stenosis by ICA causing a perfusion defect by SPECT/MPI.

Diagnostic performance of dual-source CT coronary angiography with and without heart rate control: systematic review and meta-analysis

AIM

To investigate the diagnostic accuracy of dual-source computed tomography (DSCT) coronary angiography with and without the application of a β-blocker.

MATERIALS AND METHODS

An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize diagnostic test data.

RESULTS

The pooled sensitivity at the patient level was 0.98 [95% confidence intervals (CI): 0.97-0.99], and specificity 0.88 (95% CI: 0.84-0.91). The results showed that without heart rate control, the sensitivity and specificity at the patient level did not decrease (p = 0.27 and 0.56, respectively). At the artery level, no significant differences in sensitivity and specificity for studies with and without heart rate control were detected (p = 0.04 and 0.05, respectively). At the segment level, the specificity decreased without heart rate control (p = 0.03), whereas the sensitivity was not influenced (p = 0.63). The median radiation exposure was 2.6 mSv, with 1.6 mSv and 8 mSv for heart rate-controlled studies and uncontrolled studies, respectively.

CONCLUSIONS

DSCT coronary angiography without heart rate control has a similar excellent diagnostic performance at the patient level as that of heart rate control groups. However, controlling for heart rate to decrease radiation and to provide effective information for selecting the therapeutic strategy and risk stratification is recommended.

Myocardial perfusion imaging with cardiac computed tomography: state of the art

Cardiac computed tomography (CCT) has become an important tool for the anatomic assessment of patients with suspected coronary disease. Its diagnostic accuracy for detecting the presence of underlying coronary artery disease and ability to risk stratify patients are well documented. However, the role of CCT for the physiologic assessment of myocardial perfusion during resting and stress conditions is only now emerging. With the addition of myocardial perfusion imaging to coronary imaging, CCT has the potential to assess both coronary anatomy and its functional significance with a single non-invasive test. In this review, we discuss the current state of CCT myocardial perfusion imaging for the detection of myocardial ischemia and myocardial infarction and examine its complementary role to CCT coronary imaging.

Personalized assessment of radiation risks from the one-stop-shop myocardial 256-slice CT examination

BACKGROUND

This study provides data on the cumulative life attributable risk (LAR) of radiation-induced cancer from the combination of coronary CT angiography (CCTA), dynamic CT perfusion (CTP) and delayed enhancement (DE) CT scans, required for reliable risk-benefit analysis of the one-stop-shop CCTA + CTP + DECT cardiac examination.

METHODS

Monte Carlo simulation of the dynamic CTP and DECT exposures on 62 adult individuals was employed to determine radiation absorbed dose to exposed radiosensitive organs. Corresponding data for CCTA were derived using patient chest circumference and previously published data. Individual-specific LARs of cancer were estimated using organ/tissue-specific radiogenic cancer risk factors. Total LAR from CCTA + CTP + DECT scans' sequence were estimated and compared to nominal intrinsic risk of cancer.

RESULTS

The main contribution, up to 80%, to cumulative radiation burden from CCTA + CTP + DECT scan-sequence was found to originate from the CTP scan. The total LAR from CCTA + CTP + DECT for females was found 4-6 times higher, compared to males. The mean cumulative risk of radiogenic cancer associated with the complete CCTA + CTP + DECT scan sequence was found to marginally increase the intrinsic risk for cancer induction by less than 0.6% and 0.1% for females and males, respectively.

CONCLUSIONS

The radiation risk from the 256-slice CCTA + CTP + DECT scan sequence may be considered low and should not constitute an obstacle for the clinical endorsement of the one-stop-shop cardiac CT examination, given that its clinical value has been well verified. Nevertheless, every effort should be made towards optimization of the dynamic CTP component which is the main contributor to patient radiation burden.

An en bloc approach to CT perfusion for the evaluation of limb ischemia

We examine volumetric CT perfusion in soft tissues of the entire foot with an en bloc technique to provide a meaningful measure of differentiation between mild and major vascular impairment. With Institutional Review Board approval, 22 healthy male subjects between the ages of 21 and 50 (mean 37) were enrolled. Volumetric computed tomography using an en bloc technique was conducted on 14 subjects for validation while unilateral vascular obstruction was simulated in the calves of the remaining 8 subjects. Perfusion estimates were made using in-house software and differences in perfusion estimates between feet were evaluated with Student's t-test at 95% confidence. Subjects with simulated major vascular obstruction (calf blood pressure cuff inflated to 200 mmHg) showed significantly higher ratios of perfusion estimates between the unobstructed and obstructed foot compared to subjects with simulated mild vascular obstruction (cuff inflated to 120 mmHg), mean 4.6, SD 2.6 vs. mean 1.3, SD 0.2; P = 0.05. CT perfusion using an en bloc technique shows promise for the future evaluation of patients with critical limb ischemia and particularly for re-characterization post medical, surgical or endovascular intervention.

Current status of cardiac CT for the detection of myocardial ischemia

Stress and rest myocardial perfusion imaging using computed tomography (CT) can be accurately and safely performed. CT angiography allows for the anatomic visualization of coronary lesions and the components of atherosclerotic plaque, whereas according to currently available data, CT perfusion imaging improves the diagnostic accuracy for detecting ischemic lesions. However, the radiation exposure and contrast load that are involved cannot be neglected. Owing to the limited number of trials that have been published so far, and the fact that they used a wide variety of image acquisition and stress protocols, a standard acquisition protocol for CT perfusion imaging still needs to be found and evaluated in larger multicenter trials. Therefore, CT perfusion imaging, as opposed to other modalities such as magnetic resonance perfusion, SPECT, or positron emission tomography, cannot yet be regarded as clinical routine, but may be considered in patients with contraindications for other imaging modalities.

CT imaging of myocardial perfusion: possibilities and perspectives

Functional imaging in patients with suspected or known coronary artery disease (CAD) is crucial for the identification of patients who could benefit from coronary revascularization. Several studies demonstrated the high diagnostic accuracy of Single-photon-emission computed tomography myocardial perfusion imaging, stress perfusion magnetic resonance imaging, and of invasive FFR measurements for the detection of hemodynamic relevant stenosis. Cardiac computed tomography (CT) used to be limited to coronary angiography (CTA); current guidelines recommend CTA only for the exclusion of CAD. Technological advances now offer the possibility to assess myocardial perfusion by computed tomography (CT-MPI). Though different acquisition protocols and post-processing algorithms still have to be evaluated, initial clinical studies could already show a diagnostic accuracy comparable to the established imaging modalities. Thus, cardiac CT may offer a combined approach of anatomical and functional imaging. Beside the need for further studies, especially on the prognostic value of CT-MPI to stratify future cardiovascular events, the comparatively high radiation exposure and additional administration of contrast agent has to be taken in account.

Four-dimensional image processing of myocardial CT perfusion for improved image quality and noise reduction

BACKGROUND

Image noise and multiple sources of artifact may affect the accurate interpretation of myocardial CT perfusion (CTP) studies. Although artifact within the image is often time dependent, tissue characteristics remain unchanged irrespective of cardiac phase.

OBJECTIVE

We assessed a new technique of 4-dimensional, spatiotemporal analysis, using redundant time domain information within additional phase acquisitions to reduce CTP image noise.

METHODS

Four-dimensional analysis was assessed in a static phantom and in 10 CTP studies with invasive fractional flow reserve (FFR) correlation. For each voxel within the CTP study the distribution of local Hounsfield values was measured in both time and space with the use of a customized program within MATLAB software. These values were filtered to eliminate those likely to represent noise or rapidly changing beam hardening artifact. All CTP images were acquired within a single heartbeat with 320 detector-row CT. Image noise was quantified as the SD of voxel values within myocardial segments. Contrast was measured between normal and abnormal vascular territories as assessed by FFR.

RESULTS

The mean image noise within the unprocessed CTP images was 30 HU (range, 23-42 HU). After 4-dimensional filtering the mean image noise was 22 HU (range, 15-29 HU). The mean reduction in image noise was 28% (P < 0.001). The mean contrast between normally perfused and ischemic segments was not significantly changed. The mean increase in contrast-to-noise ratio between ischemic territories and the myocardial average was 52% (P < 0.001).

CONCLUSION

Four-dimensional analysis of CTP significantly reduces image noise and may assist in the assessment of myocardial perfusion studies.

Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.

Submillisievert median radiation dose for coronary angiography with a second-generation 320-detector row CT scanner in 107 consecutive patients

PURPOSE

To (a) use a new second-generation wide-volume 320-detector row computed tomographic (CT) scanner to explore optimization of radiation exposure in coronary CT angiography in an unselected and consecutive cohort of patients referred for clinical purposes and (b) compare estimated radiation exposure and image quality with that from a cohort of similar patients who underwent imaging with a previous first-generation CT system.

MATERIALS AND METHODS

The study was approved by the institutional review board, and all subjects provided written consent. Coronary CT angiography was performed in 107 consecutive patients with a new second-generation 320-detector row unit. Estimated radiation exposure and image quality were compared with those from 100 consecutive patients who underwent imaging with a previous first-generation scanner. Effective radiation dose was estimated by multiplying the dose-length product by an effective dose conversion factor of 0.014 mSv/mGy ⋅ cm and reported with size-specific dose estimates (SSDEs). Image quality was evaluated by two independent readers.

RESULTS

The mean age of the 107 patients was 55.4 years ± 12.0 (standard deviation); 57 patients (53.3%) were men. The median body mass index was 27.3 kg/m(2) (range, 18.1-47.2 kg/m(2)); however, 71 patients (66.4%) were overweight, obese, or morbidly obese. A tube potential of 100 kV was used in 97 patients (90.6%), single-volume acquisition was used in 104 (97.2%), and prospective electrocardiographic gating was used in 106 (99.1%). The mean heart rate was 57.1 beats per minute ± 11.2 (range, 34-96 beats per minute), which enabled single-heartbeat scans in 100 patients (93.4%). The median radiation dose was 0.93 mSv (interquartile range [IQR], 0.58-1.74 mSv) with the second-generation unit and 2.67 mSv (IQR, 1.68-4.00 mSv) with the first-generation unit (P < .0001). The median SSDE was 6.0 mGy (IQR, 4.1-10.0 mGy) with the second-generation unit and 13.2 mGy (IQR, 10.2-18.6 mGy) with the first-generation unit (P < .0001). Overall, the radiation dose was less than 0.5 mSv for 23 of the 107 CT angiography examinations (21.5%), less than 1 mSv for 58 (54.2%), and less than 4 mSv for 103 (96.3%). All studies were of diagnostic quality, with most having excellent image quality. Three of four image quality indexes were significantly better with the second-generation unit compared with the first-generation unit.

CONCLUSION

The combination of a gantry rotation time of 275 msec, wide volume coverage, iterative reconstruction, automated exposure control, and larger x-ray power generator of the second-generation CT scanner provides excellent image quality over a wide range of body sizes and heart rates at low radiation doses.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13122621/-/DC1.

Time efficiency and diagnostic accuracy of new automated myocardial perfusion analysis software in 320-row CT cardiac imaging

Objective

We aimed to evaluate the time efficiency and diagnostic accuracy of automated myocardial computed tomography perfusion (CTP) image analysis software.

Materials and Methods

320-row CTP was performed in 30 patients, and analyses were conducted independently by three different blinded readers by the use of two recent software releases (version 4.6 and novel version 4.71GR001, Toshiba, Tokyo, Japan). Analysis times were compared, and automated epi- and endocardial contour detection was subjectively rated in five categories (excellent, good, fair, poor and very poor). As semi-quantitative perfusion parameters, myocardial attenuation and transmural perfusion ratio (TPR) were calculated for each myocardial segment and agreement was tested by using the intraclass correlation coefficient (ICC). Conventional coronary angiography served as reference standard.

Results

The analysis time was significantly reduced with the novel automated software version as compared with the former release (Reader 1: 43:08 ± 11:39 min vs. 09:47 ± 04:51 min, Reader 2: 42:07 ± 06:44 min vs. 09:42 ± 02:50 min and Reader 3: 21:38 ± 3:44 min vs. 07:34 ± 02:12 min; p < 0.001 for all). Epi- and endocardial contour detection for the novel software was rated to be significantly better (p < 0.001) than with the former software. ICCs demonstrated strong agreement (≥ 0.75) for myocardial attenuation in 93% and for TPR in 82%. Diagnostic accuracy for the two software versions was not significantly different (p = 0.169) as compared with conventional coronary angiography.

Conclusion

The novel automated CTP analysis software offers enhanced time efficiency with an improvement by a factor of about four, while maintaining diagnostic accuracy.

Coronary pressure-derived fractional flow reserve in the assessment of coronary artery stenoses

OBJECTIVES

Catheter-based angiography is the reference-standard to establish coronary anatomy. While routinely employed clinically, lumen assessment correlates poorly with physiological measures of ischaemia. Moreover, functional studies to identify and localise ischaemia before elective angiography are often not available. This article reviews fractional flow reserve (FFR) and its role in guiding patient management for patients with a potentially haemodynamic significant coronary lesion.

METHODS

This review discusses the theory, evidence, indications, and limitations of FFR. Also included are emerging non-invasive imaging FFR surrogates currently under evaluation for accuracy with respect to standard FFR.

RESULTS

Coronary pressure-derived fractional flow reserve (FFR) rapidly assesses the haemodynamic significance of individual coronary artery lesions and can readily be performed in the catheterisation laboratory. The use of FFR has been shown to effectively guide coronary revascularization procedures leading to improved patient outcomes.

CONCLUSIONS

FFR is an invaluable modality in guiding coronary disease treatment decisions. It is safe, cost-effective and leads to improved patient outcomes. Non-invasive imaging modalities to assess the physiologic significance of CAD are currently being  developed and evaluated.

Aligning coronary anatomy and myocardial perfusion territories: an algorithm for the CORE320 multicenter study

BACKGROUND

Appropriate clinical decisions concerning diagnosis and treatment of coronary artery disease rely on correct integration of data on coronary anatomy and myocardial perfusion. The purpose of this article is to introduce a new left ventricular segmentation model for improved alignment of coronary arterial segments and myocardial perfusion territories, designed for the CORE320 study.

METHODS AND RESULTS

CORE320 is a prospective, multicenter study with a primary objective to evaluate the diagnostic accuracy of 320-row detector computed tomography (CT) to detect coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected coronary artery disease compared with the gold standard of conventional coronary angiography and single-photon emission CT myocardial perfusion imaging. We describe a 19-coronary segment and 13-myocardial territory alignment model, its application in both standard and CT image data sets, and the adjudication process of the initial cohort of patients recruited for the CORE320 study. Adjudication committees reviewed the images of the first 101 gold standard and 107 CT data sets. On the basis of the presented model and rules, all cases for adjudication were correctly identified. During image review, 6 (5.9%) gold standard and 9 (8.4%) CT data sets needed further realignment not triggered by the algorithm.

CONCLUSIONS

We present a vascular territory distribution model developed for the CORE320 multicenter study, which accounts for variability in coronary anatomy and potential myocardial perfusion territory overlap.

Stress CT perfusion: coupling coronary anatomy with physiology

While multiple different imaging tests can be used to evaluate patients with known or suspected coronary artery disease (CAD), each of them is designed to evaluate either coronary anatomy or physiology. Recently, it has been recognized that cardiac CT can be used to evaluate stress and rest myocardial perfusion in addition to its capabilities to image the coronary arteries, thus allowing for the simultaneous evaluation of the anatomical burden and physiological significance of CAD in a single exam. In this review, the strengths and the limitations of imaging coronary anatomy and myocardial perfusion will be discussed. Next, key technical aspects of how to perform and interpret CT perfusion imaging will be summarized while providing an update of the most recent data in this emerging field. Finally, future directions and opportunities for further research will be discussed.

Computed tomography myocardial perfusion imaging with 320-row detector computed tomography accurately detects myocardial ischemia in patients with obstructive coronary artery disease

BACKGROUND

Computed tomography coronary angiography (CTA) has been shown to be accurate in detecting anatomic coronary arterial obstruction, but is limited for the detection of myocardial ischemia. The primary aim of this study was to assess the accuracy of 320-row computed tomography perfusion imaging (CTP) to detect atherosclerosis causing myocardial ischemia.

METHODS AND RESULTS

Fifty symptomatic patients with recent single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) underwent a comprehensive cardiac computed tomography (CT) protocol that included 320-CTA, followed by adenosine stress CTP. CTP images were analyzed quantitatively for the presence of subendocardial perfusion deficits. All analyses were blinded to imaging and clinical results. CTA alone was a limited predictor of myocardial ischemia compared with SPECT, with a sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of 56%, 75%, 56%, and 75%, and the area under the receiver operator characteristic curve (AUC) was 0.65 (95% CI, 0.51-0.78, P=0.07). CTP was a better predictor of myocardial ischemia, with a sensitivity, specificity, PPV, and NPV of 72%, 91%, 81%, and 85%, with an AUC of 0.81 (95% CI, 0.68-0.91, P<0.001), and was an excellent predictor of myocardial ischemia on SPECT-MPI in the presence of stenosis (≥50% on CTA), with a sensitivity, specificity, PPV, and NPV of 100%, 81%, 50%, and 100%, with an AUC of 0.92 (95% CI, 0.80-0.97, P<0.001). The radiation dose for the comprehensive cardiac CT protocol and SPECT were 13.8±2.9 and 13.1±1.7; respectively (P=0.15).

CONCLUSIONS

Computed tomography perfusion imaging with rest and adenosine stress 320-row CT is accurate in detecting obstructive atherosclerosis causing myocardial ischemia.

Coronary enhancement for prospective ECG-gated single R-R axial 320-MDCT angiography: comparison of 60- and 80-mL iopamidol 370 injection

OBJECTIVE

The objective of our study was to evaluate the difference in coronary enhancement provided by 60 versus 80 mL of contrast medium (370 mg I/mL) for prospectively ECG-gated single-heartbeat axial 320-MDCT.

MATERIALS AND METHODS

We retrospectively evaluated 108 consecutive 320-MDCT angiography studies. Group 1 (n = 36) received 60 mL of an iodinated contrast medium and group 2 (n = 72), 80 mL. All patients were imaged with a standardized protocol: iopamidol 370 followed by 40 mL of saline, both administered at a rate of 6 mL/s. Two imagers subjectively assessed image quality throughout the coronary arteries. Region-of-interest attenuation (HU) measurements were performed in the aorta plus the proximal and distal coronary arteries.

RESULTS

Subjective analysis of all coronary segments showed slightly better image quality for group 2. Patients in group 1 had significantly (p < 0.05) lower mean attenuation values for the individual coronary vessels. Nevertheless, 96.7% of all coronary segments in the group 1 patients had an attenuation of greater than 300 HU; when analysis was limited to group 1 patients with a body mass index of greater than 30, 92.8% of the segments were more than 300 HU, and all segments measured more than 250 HU.

CONCLUSION

An injection protocol based on 60 mL of iopamidol (370 mg I/mL) for prospectively ECG-gated wide-area detector single-heartbeat coronary CT angiography (CTA) has less coronary enhancement than a protocol based on 80 mL. However, using 60 mL, more than 96% of coronary segments had sufficient enhancement (i.e., > 300 HU), supporting the general use of 60-mL protocols for clinical wide-area detector coronary CTA.

Diagnostic performance of combined noninvasive coronary angiography and myocardial perfusion imaging using 320 row detector computed tomography: design and implementation of the CORE320 multicenter, multinational diagnostic study

Multidetector coronary computed tomography angiography (CTA) is a promising modality for widespread clinical application because of its noninvasive nature and high diagnostic accuracy as found in previous studies using 64 to 320 simultaneous detector rows. It is, however, limited in its ability to detect myocardial ischemia. In this article, we describe the design of the CORE320 study ("Combined coronary atherosclerosis and myocardial perfusion evaluation using 320 detector row computed tomography"). This prospective, multicenter, multinational study is unique in that it is designed to assess the diagnostic performance of combined 320-row CTA and myocardial CT perfusion imaging (CTP) in comparison with the combination of invasive coronary angiography and single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). The trial is being performed at 16 medical centers located in 8 countries worldwide. CT has the potential to assess both anatomy and physiology in a single imaging session. The co-primary aim of the CORE320 study is to define the per-patient diagnostic accuracy of the combination of coronary CTA and myocardial CTP to detect physiologically significant coronary artery disease compared with (1) the combination of conventional coronary angiography and SPECT-MPI and (2) conventional coronary angiography alone. If successful, the technology could revolutionize the management of patients with symptomatic CAD.

A stepwise approach to the visual interpretation of CT-based myocardial perfusion

Cardiovascular anatomic and functional testing have been longstanding and key components of cardiac risk assessment. As part of that strategy, CT-based imaging has made steady progress, with coronary computed tomography angiography (CTA) now established as the most sensitive noninvasive strategy for assessment of significant coronary artery disease. Myocardial CT perfusion imaging (CTP), as the functional equivalent of coronary CTA, is being tested in currently ongoing multicenter trials and is proposed to enhance the accuracy of coronary CTA alone. However, unlike coronary CTA that has published guidelines for interpretation and is rapidly gaining applicability in the noninvasive risk assessment paradigms, myocardial CTP is rapidly evolving, and guidance on a standard approach to its interpretation is lacking. In this article we describe a practical stepwise approach for interpretation of myocardial CTP that should add to the clinical applicability of this modality. These steps include (1) coronary CTA interpretation for potentially obstructive atherosclerosis, (2) reconstruction and preprocessing of myocardial CTP images, (3) image quality assessment and the identification of potentially confounding artifacts, (4) rest and stress image interpretation for enhancement patterns and areas of hypoattenuation, and (5) correlation of coronary anatomy and myocardial perfusion deficits. This systematic review uses already published methods from multiple clinical studies and is intended for general usage, independent of the platform used for image acquisition.