Integrated cardio-thoracic imaging with ECG-Gated 64-slice multidetector-row CT: initial findings in 133 patients

Rationale and design of the worldwide prospective multicenter registry on radiation dose estimates of cardiac CT angiography in daily practice in 2017 (PROTECTION VI)

BACKGROUND

Cardiac computed tomography angiography (cardiac CTA) is an increasingly used versatile imaging method to evaluate coronary and cardiac morphology. Owing to improvements in technology, image quality has continuously improved over the last 10-20 years. At the same time, numerous non-randomized and randomized studies have been performed to reduce the associated radiation exposure. Currently, it is unclear if the advances in technology and knowledge about radiation reduction translated into reduced levels of cardiac CTA radiation dose in daily clinical practice as well as a wide utilization of dose-saving strategies.

METHODS

The PROTECTION VI study is a multicenter, prospective, worldwide registry designed to evaluate radiation dose exposure, utilization of dose-saving strategies and diagnostic image quality during cardiac CTA in current daily practice. Assessment of image quality will be addressed by the evaluation of diagnostic image quality at the local study site and the calculation of quantitative image quality parameters in an imaging core laboratory. Above 4000 patients will be enrolled from approximately 70 sites in Europe, North America, South America, Asia and Australia. The study will analyze median radiation dose levels, image quality, frequency of use and efficacy of algorithms for dose reduction, and patient and study-related predictors associated with radiation dose.

CONCLUSIONS

The PROTECTION VI study is designed to provide a reliable estimate of current radiation dose for cardiac CTA and to assess the potential for additional dose reductions.

Comprehensive CT cardiothoracic imaging: a new challenge for chest imaging

In the past, thoracic and cardiac imaging were two distinct specialties of radiology. The technical evolution, however, has changed their boundaries with an important impact on CT imaging practices and has opened the new era of "cardiothoracic" imaging, due to the strong anatomic, mechanical, physiologic, physiopathologic, and therapeutic cardiopulmonary correlations. Modern thoracic radiologists can no longer avoid the assessment of heart and coronary arteries, as they used to do with earlier generations of CT scanner. The advent of ECG gating and state-of-art CT scanner faster rotation speed, high spatial and temporal resolution, high-pitch mode, shorter acquisition time, and dedicated cardiac reconstruction algorithms has opened new possibilities for chest imaging, integrating cardiac morphologic and even functional information within a diagnostic chest CT scan. The aim of this review is to briefly show and summarize the concept of integrated cardiothoracic imaging, which redefines the boundaries of chest CT imaging, opening the door to a new radiologic specialty.

Imaging of the right heart--CT and CMR

Right ventricular (RV) structure and function is of substantial importance in a broad variety of clinical conditions. Cardiac magnetic resonance (CMR) and computed tomography (CT) each provide three-dimensional RV imaging, high-resolution evaluation of RV structure/anatomy, and accurate functional assessment without geometric assumptions. This is of particular significance for the RV, where complex geometry compromises reliance on indices derived from two-dimensional (2D) imaging planes. CMR flow-based imaging can be applied to right-sided heart valves, enabling evaluation of hemodynamic and valvular dysfunction that may contribute to or result from RV dysfunction. Tissue characterization imaging by both CMR and CT provides valuable complementary assessment of the RV. Changes in myocardial tissue composition provide a mechanistic substrate for RV dysfunction and cardiac arrhythmias. This review provides an overview of RV imaging by both CMR and CT, with focus on assessment of RV structure/function, flow, and tissue characterization. Emerging evidence and established guidelines are discussed in the context of imaging contributions to diagnosis, prognostic risk stratification and disease management of clinical conditions that impact the right ventricle.

Noncardiac findings in clinical cardiac magnetic resonance: prevalence in 300 examinations after blind reassessment

PURPOSE

To assess the prevalence of noncardiac findings (NCFs) in a consecutive series of 300 cardiac magnetic resonance (CMR) studies.

METHODS

We retrospectively evaluated CMRs of 192 males and 108 females (42 ± 22 years), comparing findings included in reports to those detected after focused reassessment of CMR images. Noncardiac findings were classified as relevant if additional workup was required.

RESULTS

We found 19 NCFs, 14 (4.7%) tagged as nonrelevant and 5 (1.7%) as relevant. Images' reassessment presented 45 NCFs, 26 (8.7%) nonrelevant and 16 (5.3%) relevant (P < 0.003).

CONCLUSIONS

Cardiac magnetic resonance involves the study of areas larger than the heart alone, and NCFs are found in 1 of 7 patients; more than a half of them are not included in the initial CMR report. A small part is relevant, but detection can be unnecessarily stressful and harmful for patients and could increase costs. Risks of overdiagnosis or underreporting are to be taken into account.

Lung image quality with 320-row wide-volume CT scans: the effect of prospective ECG-gating and comparisons with 64-row helical CT scans

RATIONALES AND OBJECTIVES

To evaluate the image quality of 320-row wide-volume (WV) computed tomography (CT) scans in comparison with 64-row helical scans for the lung.

MATERIALS AND METHODS

The Institutional Review Board of each institution approved this prospective, multicenter study and informed consent was obtained. A total of 73 subjects underwent two types of chest CT, including 320-row WV scans and 64-row helical scans. Both scans used the same tube voltage, tube current, exposure time setting, and slice thickness. The helical scans were not electrocardiogram (ECG)-gated. For the WV scans, prospective ECG-gating was used for 38 subjects, whereas the other 35 subjects did not have ECG-gating. Using a 5-point scale from 1 (nondiagnostic) to 5 (excellent), three blinded observers independently evaluated image quality for five lobes and the lingula. The differences in the scores between WV scans and helical scans were compared using Wilcoxon's signed-rank test.

RESULTS

The WV scans with ECG-gating had significantly higher scores than 64-row helical scans for all lobes and lingula (right lower lobe, P < .01; other lobes and lingula, P < .0001, respectively). The 320-row WV scans without ECG-gating also had significantly higher scores than 64-row helical scans (P < .05), except for nonsignificant differences for the left upper lobe.

CONCLUSIONS

Lung image quality of ECG-gated WV scans, which do not require any additional radiation exposure, is better than that of non-ECG-gated 64-row helical scans. Non-ECG-gated 320-row WV scans are comparable or slightly superior to non-ECG-gated 64-row helical scans.

Imaging the heart-lung relationships during a chest computed tomography examination: is electrocardiographic gating the only option?

Before the advent of fast-scanning multidetector-row computed tomography (CT) technology, thoracic CT studies were exclusively used for the morphologic assessment of thoracic organs, as the concurrent examination of the heart was hampered by image degradation from cardiac motion artifacts. The introduction of fast rotation speed and dedicated cardiac reconstruction algorithms has opened new possibilities for chest imaging, starting with the possibility to integrate cardiac morphologic and functional information into a diagnostic CT scan of the chest. Initiated with 16-slice multidetector-row CT, this concept of integrating morphology and function has been further simplified with 64-slice CT scanners, thus allowing radiologists to provide vital information in the management of patients with a wide variety of acute or chronic respiratory disorders. Because this CT technology offers the possibility of generating high-resolution and motion-free images of the coronary arteries, evaluation of the coronary arteries during CT examinations of the chest should further widen the clinical applications of CT for respiratory patients, keeping in mind that cigarette smoking is a shared risk factor for both impaired lung function and cardiovascular events. The recent advent of high temporal resolution and high pitch modes with dual-source CT simplifies the concept of integrated cardiothoracic imaging, introducing non-electrocardiographic-gated coronary artery imaging. The purpose of this article is to review the successive approaches of these redefined borders of thoracic imaging.

[ECG-gated chest CT angiography: value for atypical chest pain evaluation]

PURPOSE

The aim of this study was to evaluate ECG-gated whole chest CTA as a routine triage tool for patients with acute chest pain.

MATERIAL AND METHODS

Whole chest CTA with retrospective ECG-gating was performed in 30 patients with acute atypical chest pain. The ten main segments of the coronary arteries, the pulmonary arteries, the aorta, and the myocardium (function, morphology) were independently analyzed by a resident and two senior radiologists. The inter-observer agreement between resident and senior radiologists was calculated. A final diagnosis was determined by consensus.

RESULTS

Thirty patients were included. The coronary artery segments, myocardium and pulmonary arteries were considered analyzable in 84%, 90% and 97% of cases respectively. A final diagnosis for the cause of pain was retained in 19 patients: significant coronary artery stenosis (5), pulmonary embolus (5), aortic dissection (1), hypokinetic cardiomyopathy (2), lung parenchymal abnormalities (5), and hiatus hernia (1). Inter-observer agreement ranged from 0.76 to 1 between senior radiologists and from 0.76 to 1 between resident and senior radiologists. The average time of image interpretation ranged from 14 to 15 minutes.

CONCLUSION

ECG-gated whole chest CT angiography appears as a promising tool for the evaluation of acute chest pain. Combined evaluation of appearance and function of the myocardium can reveal additional interesting information.

Triple rule-out CT in patients with suspicion of acute pulmonary embolism: findings and accuracy

RATIONALE AND OBJECTIVES

The aim of this study was to prospectively investigate the diagnostic value of triple rule-out computed tomography (CT) in patients suspected of having acute pulmonary embolism (PE).

MATERIALS AND METHODS

A total of 125 patients with suspicion of PE, of whom 14 patients had the additional clinical suspicion of acute aortic syndrome, underwent electrocardiogram-gated triple rule-out dual-source CT. The contrast media application protocol was adjusted to obtain a homogenous attenuation of the pulmonary arteries, thoracic aorta, and coronary arteries. The diagnostic performance of triple rule-out CT was assessed by using adjudicated discharge diagnoses as reference standards.

RESULTS

A total of 161 adjudicated cardiovascular discharge diagnoses were made in the 125 patients (including all true-positive and true-negative findings): acute PE was found in 26 (21%) and was excluded by CT in 99 (79%), coronary artery disease was found in 3 (3%) and was excluded by catheter angiography in 9 (6%), left ventricular systolic dysfunction was found in 2 (2%) and was excluded by echocardiography in 8 (6%), and acute aortic syndrome was found in 5 (4%) and was excluded by CT in 9 (7%) patients. Nonvascular chest disease was found in 34 (27%) and included pneumonia (n = 17), neoplasms (n = 5), fractures/osteolysis (n = 3), pericarditis (n = 2), and post-pneumonectomy syndrome (n = 1). Triple rule-out CT was normal in 53 (42%) patients. Overall sensitivity, specificity, and positive and negative predictive value of triple rule-out CT for cardiovascular disease were 100% (95% confidence interval [CI] 90-100%), 98% (95%CI 94-100%), 95% (95%CI 82-99%), and 100% (95%CI 97-100%, respectively).

CONCLUSIONS

Triple rule-out CT is feasible in patients with suspicion of PE, reveals a wide range of vascular and non-vascular chest disease, and offers an excellent overall diagnostic performance.

Influence of heart rate on diagnostic accuracy and image quality of 16-slice CT coronary angiography: comparison of multisegment and halfscan reconstruction approaches

The lower the heart rate the better image quality in multislice computed tomography (MSCT) coronary angiography. We prospectively assessed the influence of heart rate on per-patient diagnostic accuracy and image quality of MSCT coronary angiography and compared adaptive multisegment and standard halfscan reconstruction. A consecutive cohort of 126 patients scheduled to undergo conventional coronary angiography was examined with 16-slice CT. For all heart rate groups, per-patient diagnostic accuracy was significantly higher for multisegment than halfscan reconstruction with values of 95 vs. 79% (p < 0.05, <65 bpm, 38 patients), 85 vs. 66% (p < 0.05, 65-74 bpm, 47 patients), and 78% vs. 41% (p < 0.001, >74 bpm, 41 patients). Differences in diagnostic accuracy between adjacent heart rate groups were only significant for halfscan reconstruction for the comparison between the 65-74 and >74 bpm group (p < 0.05). The vessel lengths free of motion artifacts were significantly longer with multisegment reconstruction in all heart rate groups and for all coronary arteries (p < 0.005). For noninvasive MSCT coronary angiography, both per-patient diagnostic accuracy and image quality decline with increasing heart rate, and multisegment reconstruction at high heart rates yields similar results as standard halfscan reconstruction at low heart rates.

Non-cardiac findings on coronary computed tomography and magnetic resonance imaging

Both multislice computed tomography (CT) and magnetic resonance imaging (MRI) are emerging as methods to detect coronary artery stenoses and assess cardiac function and morphology. Non-cardiac structures are also amenable to assessment by these non-invasive tests. We investigated the rate of significant and insignificant non-cardiac findings using CT and MRI. A total of 108 consecutive patients suspected of having coronary artery disease and without contraindications to CT and MRI were included in this study. Significant non-cardiac findings were defined as findings that required additional clinical or radiological follow-up. CT and MR images were read independently in a blinded fashion. CT yielded five significant non-cardiac findings in five patients (5%). These included a pulmonary embolism, large pleural effusions, sarcoid, a large hiatal hernia, and a pulmonary nodule (>1.0 cm). Two of these significant non-cardiac findings were also seen on MRI (pleural effusions and sarcoid, 2%). Insignificant non-cardiac findings were more frequent than significant findings on both CT (n = 11, 10%) and MRI (n = 7, 6%). Incidental non-cardiac findings on CT and MRI of the coronary arteries are common, which is why images should be analyzed by radiologists to ensure that important findings are not missed and unnecessary follow-up examinations are avoided.

Coronary artery imaging during preoperative CT staging: preliminary experience with 64-slice multidetector CT in 99 consecutive patients

The purpose of this study was to evaluate the clinical feasibility of coronary artery imaging during routine preoperative 64-slice MDCT scans of the chest. Ninety-nine consecutive patients in sinus rhythm underwent a biphasic multidetector-row spiral CT examination of the chest without the administration of beta-blockers, including an ECG-gated acquisition over the cardiac cavities, followed by a non-gated examination of the upper third of the thorax. Data were reconstructed to evaluate coronary arteries and to obtain presurgical staging of the underlying disease. The percentage of assessable segments ranged from 65.4% (972/1,485) when considering all coronary artery segments to 88% (613/693) for the proximal and mid segments, reaching 98% (387/396) for proximal coronary artery segments. The 387 interpretable proximal segments included 97 (97%) LM, 99 (100%) LAD, 96 (97%) LCX and 95 (96%) RCA with a mean attenuation of 280.70+/-52.93 HU. The mean percentage of assessable segments was significantly higher in patients with a heart rate <or=80 bpm (n=48) than in patients with a heart rate greater than 80 bpm (n=35) (80+/-11% vs. 72+/-13%; P=0.0008). Diagnostic image quality was achieved in all patients for preoperative staging of the underlying disorder. The mean estimated effective dose was 12.06+/-3.25 mSv for ECG-gated scans and 13.88+/-3.49 mSv for complete chest examinations. Proximal and mid-coronary artery segments can be adequately evaluated during presurgical CT examinations of the chest obtained with 64-slice MDCT without the administration of beta-blockers.

Coronary imaging quality in routine ECG-gated multidetector CT examinations of the entire thorax: preliminary experience with a 64-slice CT system in 133 patients

To evaluate image quality in the assessment of the coronary arteries during routine ECG-gated multidetector CT (MDCT) of the chest. One hundred and thirty three patients in sinus rhythm underwent an ECG-gated CT angiographic examination of the entire chest without beta-blockers with a 64-slice CT system. In 127 patients (95%), it was possible to assess the coronary arteries partially or totally; coronary artery imaging failed in six patients (5%), leading to a detailed description of the coronary arteries in 127 patients. Considering ten coronary artery segments per patient, 75% of coronary segments were assessable (948/1270 segments). When the distal segments were excluded from the analysis (i.e., seven coronary segments evaluated per patient), the percentage of assessable segments was 86% (768/889 proximal and mid coronary segments) and reached 93% (474/508) when assessing proximal segments exclusively. The mean number of assessable segments was significantly higher in patients with a heart rate < or =80 bpm (n=95) than in patients with a heart rate >80 bpm (n=38) (p<0.002). Proximal and mid-coronary segments can be adequately assessed during a whole-chest ECG-gated CT angiographic examination without administration of beta-blockers in patients with a heart rate below 80 bpm.