Iterative Reconstruction in Image Space (IRIS) in Cardiac Computed Tomography: Inital Experience

OBJECTIVES: Improvements in image quality in cardiac computed tomography may be achieved through iterative image reconstruction techniques. We evaluated the ability of “Iterative Reconstruction in Image Space” (IRIS) reconstruction to reduce image noise and improve subjective image quality.

METHODS: 55 consecutive patients undergoing coronary CT angiography to rule out coronary artery stenosis were included. A dual source CT system and standard protocols were used. Images were reconstructed using standard filtered back projection and IRIS. Image noise, attenuation within the coronary arteries, contrast, signal to noise and contrast to noise parameters as well as subjective classification of image quality (using a scale with four categories) were evaluated and compared between the two image reconstruction protocols.

RESULTS: Subjective image quality (2.8 ± 0.4 in filtered back projection and 2.8 ± 0.4 in iterative reconstruction) and the number of “evaluable” segments per patient 14.0 ± 1.2 in filtered back projection and 14.1 ± 1.1 in iterative reconstruction) were not significant different between the two methods. However iterative reconstruction had a lower image noise (22.6 ± 4.5 HU vs. 28.6 ± 5.1 HU) and higher signal to noise and image to noise ratios in the proximal coronary arteries.

CONCLUSIONS: IRIS reduces image noise and contrast-to-noise ratio in coronary CT angiography, thus providing potential for reducing radiation exposure.

PMID: 21120612

Gate-Keeper to Coronary Angiography: Comparison of Exercise Testing, Myocardial Perfusion SPECT and Individually Tailored Approach For Risk Stratification

OBJECTIVES: We aimed to evaluate the differences between exercise testing (ET), myocardial perfusion SPECT (MPS) and a combination of ET and MPS based risk assessment as outlined by the guidelines with respect to their “gate-keeper” role to coronary angiography (cath) and the associated diagnostic procedural costs if prognostic considerations, as those proposed by the current guidelines and the recent literature, were taken into account.

METHODS: The Duke-score and the summed difference score (SDS; extent of ischemia) were assessed in 955 consecutive patients referred for MPS combined with ET. According to the guidelines and the available literature, three different algorithms for risk stratification were retrospectively applied: (1) ET based risk stratification and cath if intermediate or high risk Duke-score; (2) MPS based risk stratification and cath if SDS ≥ 8; (3) combined approach with ET as first step and MPS in case of intermediate risk Duke-score. A cath would have been suggested in every patient with either high risk Duke-score or SDS ≥ 8 in patients with intermediate risk Duke-score.

RESULTS: The referral rate to cath was 27% according to the ET alone, 13% using MPS, and finally 12% applying the combined risk stratification. The cost of the diagnostic work-up including cath were: 615<euro>, 1’299<euro>, and 598<euro> per patient, respectively. The coronary angiography referral rate widely depends on the diagnostic modality used for risk stratification and according to the referral criteria provided by the guidelines.

CONCLUSIONS: In the present study, the use of a stress imaging modality (MPS) and published prognostic data was associated with a lower referral rate to cath as compared to exercise testing alone and thus underlines the advantage of a risk based approach applying stress imaging in patients with intermediate risk Duke-score.

PMID: 20411429

Four-Dimensional Computed Tomography: A Method of Assessing Right Ventricular Outflow Tract and Pulmonary Artery Deformations Throughout the Cardiac Cycle

OBJECTIVES: To characterise 3D deformations of the right ventricular outflow tract (RVOT)/ pulmonary arteries (PAs) during the cardiac cycle and estimate the errors of conventional 2D assessments.

METHODS: Contrast-enhanced, ECG-gated cardiovascular computed tomography (CT) findings were retrospectively analysed from 12 patients. The acquisition of 3D images over 10 phases of the cardiac cycle created a four-dimensional CT (4DCT) dataset. The datasets were reconstructed and deformation measured at various levels of the RVOT/PAs in both space and time. Section planes were either static or dynamic relative to the motion of the structures.

RESULTS: 4DCT enabled measurement and characterisation of in vivo 3D changes of patients’ RVOT/PA during the cardiac cycle. The studied patient population showed a wide range of RVOT/PA morphologies, sizes and dynamics that develop late after surgical repair of congenital heart disease. There were also significant differences in the measured cross-sectional areas of the structures between static and dynamic section planes (up to 150%, p < 0.05) secondary to large 3D displacements and rotations.

CONCLUSIONS: 4DCT imaging data suggest high variability in RVOT/PA dynamics and significant errors in deformation measurements if 3D analysis is not carried out. These findings play an important role for the development of novel percutaneous approaches to pulmonary valve intervention.

PMID: 20680286

Assessment of the Aortic Root Using Real-Time 3D Transesophageal Echocardiography

OBJECTIVES: Precise evaluation of the aortic root geometry prior to transcatheter aortic valve implantation is important for procedural success in patients with aortic stenosis (AS). To determine the potential for 3-dimensional transesophageal echocardiography (3DTEE), the aims of the present study were: (1) to assess the accuracy of 3DTEE measurements of the aortic root using multidetector computed tomography (MDCT) as a reference, and (2) to examine whether aortic root geometry differs between patients with and without AS.

METHODS: 3DTEE and contrast-enhanced MDCT were performed in 35 patients. Multiplanar reconstruction was used to measure the left ventricular outflow tract (LVOT) and aortic annulus diameter/area, aortic valve area (AVA), and distances between the annulus and coronary artery ostium. The same 3DTEE measurements were performed in patients with (n=71) and without AS (n=80).

RESULTS: Aortic annular and LVOT areas measured by 3DTEE were slightly but significantly smaller compared with values obtained with MDCT. Both methods revealed that the aortic annulus and LVOT have an oval shape. Aortic annular and LVOT area, AVA and the distances between the aortic annulus and the coronary ostia correlated well between the 2 modalities. Only minor differences in aortic root geometry were observed between patients with AS and those without.

CONCLUSIONS: The geometry of the aortic annulus can be reliably evaluated using 3DTEE as an alternative to MDCT for the assessment of aortic root.

PMID: 21084759

Does Carotid Intima-Media Thickness Regression Predict Reduction of Cardiovascular Events?: A Meta-Analysis of 41 Randomized Trials

OBJECTIVES: The purpose of this study was to verify whether intima-media thickness (IMT) regression is associated with reduced incidence of cardiovascular events. Carotid IMT increase is associated with a raised risk of coronary heart disease (CHD) and cerebrovascular (CBV) events. However, it is undetermined whether favorable changes of IMT reflectprognostic benefits.

METHODS: The MEDLINE database and the Cochrane Database were searched for articles published until August 2009. All randomized trials assessing carotid IMT at baseline, at end of follow-up, andreporting clinical end points were included. A weighted random-effects meta-regression analysis was performed to test the relationship between mean and maximum IMT changes and outcomes. The influence of baseline patients’ characteristics, cardiovascular risk profile, IMT at baseline, follow-up, and quality of the trials was also explored. Overall estimates of effect were calculated with a fixed-effects model, random-effects model, or Peto method.

RESULTS: Forty-one trials enrolling 18,307 participants were included. Despite significant reduction in CHD, CBV events, and all-cause death induced by active treatments (for CHD events, odds ratio [OR]: 0.82, 95% confidence interval [CI]: 0.69 to 0.96, p = 0.02; for CBV events, OR: 0.71, 95% CI: 0.51 to 1.00, p = 0.05; and for all-cause death, OR: 0.71, 95% CI: 0.53 to 0.96, p = 0.03), there was no significant relationship between IMT regression and CHD events (Tau 0.91, p = 0.37), CBV events (Tau –0.32, p = 0.75), and all-cause death (Tau –0.41, p = 0.69). In addition, subjects’ baseline characteristics, cardiovascular risk profile, IMT at baseline, follow-up, and quality of the trials did not significantly influence the association between IMT changes and clinical outcomes.

CONCLUSIONS Regression or slowed progression of carotid IMT, induced by cardiovascular drug therapies, do not reflect reduction in cardiovascular events.

PMID:

Individualized Assessment of Radiation Dose in Patients Undergoing Coronary Computed Tomographic Angiography With 256-Slice Scanning

OBJECTIVES: Available data on the radiation burden from coronary computed tomography (CT) angiography (CCTA) are mostly limited to effective dose estimates. This study provides individualized estimates of doses and associated life attributable risks of radiation-induced cancer in a clinical patient population undergoing 256-slice CCTA.

 METHODS: Typical retrospectively and prospectively ECG-gated CCTA exposures in a 256-slice CT scanner were simulated on 52 patient-specific voxelized phantoms. Dose images depicting the dose deposition on the exposed region were generated, and normalized organ doses for all primarily irradiated radiosensitive organs were derived and correlated to patient body habitus. Lung, breast, and esophagus absorbed doses were then determined in 136 consecutive patients subjected to CCTA. Projected life attributable risks of radiation-induced cancer were estimated through the use of appropriate sex-, age- and organ-specific cancer risk factors and compared with corresponding nominal cancer risks. The total projected life attributable risk of radiogenic cancer after CCTA decreases steeply with age at exposure, and lung cancer constitutes the most probable detriment for both sexes.

RESULTS: The relative risks of lung cancer associated with prospectively ECG-gated CCTA were 1.0032 and 1.0008 for women and men, respectively. The mean total projected life attributable risks were estimated to be 24.9±7.4 and 71.5±30.0 per 100 000 women undergoing prospectively and retrospectively ECG-gated CCTA, respectively. The corresponding values for men were 7.3±1.3 and 31.4±5.0 per 100 000 patients.

CONCLUSIONS: The mean projected life attributable risks of radiation-induced cancer in a typical clinical patient cohort undergoing standard prospectively ECG-gated CCTA with a 256-slice scanner were found to inconsequentially increase the natural cancer incidence rates.

PMID: 21098451

A Heart With 67 Stents

PMID: 21029877

The Ability of Optical Coherence Tomography to Monitor Percutaneous Coronary Intervention: Detailed Comparison With Intravascular Ultrasound

PMID: 21041851

Ruling Out Coronary Artery Disease With Noninvasive Coronary Multidetector CT Angiography before Noncoronary Cardiovascular Surgery

OBJECTIVES: To assess the usefulness of preoperative coronary computed tomographic (CT) angiography in the detection of coronary artery disease (CAD) in nonselected patients scheduled to undergo noncoronary cardiovascular surgery to avoid unnecessary invasive coronary angiography (ICA).

METHODS: The institutional review board approved the study protocol; informed consent was given. This prospective study involved 161 consecutive patients who underwent coronary calcium scoring and coronary CT angiography before undergoing noncoronary cardiovascular surgery. Seven patients were excluded because of contraindications to CT angiography. The major indication of noncoronary cardiovascular surgery was valvular heart disease (121 patients). Follow-up was performed at a median of 20 months to define ischemic events described as acute coronary syndrome or death secondary to acute coronary syndrome, arrhythmias, or cardiac failure. Multivariate analysis was performed to determine predictors of nondiagnostic coronary CT angiography. Kaplan-Meier analysis was performed to evaluate outcome at follow-up.

RESULTS: Twenty-one patients did not undergo surgery, which left 133 patients as the study group. Atrial fibrillation was present in 45 of 133 patients. The interquartile range of the Agatston coronary calcium score was 0-471. Coronary CT angiography was diagnostic in 108 of 133 patients. Of these, 93 of 108 had no significant CAD (≤50% stenosis), and noncoronary cardiovascular surgery was performed in them without preoperative ICA. No patients in this group had postoperative ischemic events at follow-up. Coronary CT angiography was nondiagnostic in 25 of 133 patients who were referred for preoperative ICA. Multivariate analysis showed Agatston score to be the only independent predictor of nondiagnostic coronary CT angiography (odds ratio = 1.002; 95% confidence interval: 1.001, 1.003; P = .001). The best Agatston score cutoff for diagnostic coronary CT angiography was 579.

CONCLUSIONS: In nonselected patients scheduled to undergo noncoronary cardiovascular surgery, preoperative coronary CT angiography was diagnostic in 81% of cases. Preoperative ICA could be safely avoided in patients without significant CAD by using coronary CT angiography. The Agatston score, but not the presence of atrial fibrillation, was an independent predictor of nondiagnostic coronary CT angiography.

PMID: 21079198

Bisphosphonate Use and Prevalence of Valvular and Vascular Calcification in Women MESA (The Multi-Ethnic Study of Atherosclerosis)

OBJECTIVES: The aim of this study was to determine whether nitrogen-containing bisphosphonate (NCBP) therapy is associated with the prevalence of cardiovascular calcification. Cardiovascular calcification correlates with atherosclerotic disease burden. Experimental data suggest that NCBP might limit cardiovascular calcification, which has implications for disease prevention.

METHODS: The relationship of NCBP use to the prevalence of aortic valve, aortic valve ring, mitral annulus, thoracic aorta, and coronary artery calcification (AVC, AVRC, MAC, TAC, and CAC, respectively) detected by computed tomography was assessed in 3,710 women within the MESA (Multi-Ethnic Study of Atherosclerosis) with regression modeling.

RESULTS: Analyses were age-stratified, because of a significant interaction between age and NCBP use (interaction p values: AVC p < 0.0001; AVRC p < 0.0001; MAC p = 0.002; TAC p < 0.0001; CAC p = 0.046). After adjusting for age; body mass index; demographic data; diabetes; smoking; blood pressure; cholesterol levels; and statin, hormone replacement, and renin-angiotensin inhibitor therapy, NCBP use was associated with a lower prevalence of cardiovascular calcification in women ≥65 years of age (prevalence ratio: AVC 0.68 [95% confidence interval (CI): 0.41 to 1.13]; AVRC 0.65 [95% CI: 0.51 to 0.84]; MAC 0.54 [95% CI: 0.33 to 0.93]; TAC 0.69 [95% CI: 0.54 to 0.88]; CAC 0.89 [95% CI: 0.78 to 1.02]), whereas calcification was more prevalent in NCBP users among the 2,181 women <65 years of age (AVC 4.00 [95% CI: 2.33 to 6.89]; AVRC 1.92 [95% CI: 1.42 to 2.61]; MAC 2.35 [95% CI: 1.12 to 4.84]; TAC 2.17 [95% CI: 1.49 to 3.15]; CAC 1.23 [95% CI: 0.97 to 1.57]).

CONCLUSIONS: Among women in the diverse MESA cohort, NCBPs were associated with decreased prevalence of cardiovascular calcification in older subjects but more prevalent cardiovascular calcification in younger ones. Further study is warranted to clarify these age-dependent NCBP effects.

PMID: 21070928

Image Quality and Radiation Exposure With a Low Tube Voltage Protocol for Coronary CT Angiography Results of the PROTECTION II Trial

OBJECTIVES: The purpose of this study was to evaluate image quality and radiation dose using a 100 kVp tube voltage scan protocol compared with standard 120 kVp for coronary computed tomography angiography (CTA). Concerns have been raised about radiation exposure during coronary CTA. The use of a 100 kVp tube voltage scan protocol effectively lowers coronary CTA radiation dose compared with standard 120 kVp, but it is unknown whether image quality is maintained.

METHODS: We enrolled 400 nonobese patients who underwent coronary CTA: 202 patients were randomly assigned to a 100 kVp protocol and 198 patients to a 120 kVp protocol. The primary end point was to demonstrate noninferiority in image quality with the 100 kVp protocol, which was assessed by a 4-point grading score (1 = nondiagnostic, 4 = excellent image quality). For the noninferiority analysis, a margin of -0.2 image quality score points for the difference between both scan protocols was pre-defined. Secondary end points included radiation dose and need for additional diagnostic tests during follow-up.

RESULTS: The mean image quality scores in patients scanned with 100 kVp and 120 kVp were 3.30 ± 0.67 and 3.28 ± 0.68, respectively (p = 0.742); image quality of the 100 kVp protocol was not inferior, as demonstrated by the 97.5% confidence interval of the difference, which did not cross the pre-defined noninferiority margin of -0.2. The 100 kVp protocol was associated with a 31% relative reduction in radiation exposure (dose-length product: 868 ± 317 mGy × cm with 120 kVp vs. 599 ± 255 mGy × cm with 100 kVp; p < 0.0001). At 30-day follow-up, the need for additional diagnostic studies did not differ (13.4% vs. 19.2% for 100 kVp vs. 120 kVp, respectively; p = 0.114).

CONCLUSIONS: A coronary CTA protocol using 100 kVp tube voltage maintained image quality, but reduced radiation exposure by 31% as compared with the standard 120 kVp protocol. Thus, 100 kVp scan protocols should be considered for nonobese patients to keep radiation exposure as low as reasonably achievable. (Prospective Randomized Trial on Radiation Dose Estimates of Cardiac CT Angiography in Patients Scanned With a 100 kVp Protocol

PMID: 21070998

Magnetic Resonance Imaging of Carotid Atherosclerotic Plaque in Clinically Suspected Acute Transient Ischemic Attack and Acute Ischemic Stroke

OBJECTIVES: Carotid atherosclerotic plaque rupture is thought to cause transient ischemic attack (TIA) and ischemic stroke (IS). Pathological hallmarks of these plaques have been identified through observational studies. Although generally accepted, the relationship between cerebral thromboembolism and in situ atherosclerotic plaque morphology has never been directly observed noninvasively in the acute setting.

METHODS: Consecutive acutely symptomatic patients referred for stroke protocol magnetic resonance imaging/angiography underwent additional T1- and T2-weighted carotid bifurcation imaging with the use of a 3-dimensional technique with blood signal suppression. Two blinded reviewers performed plaque gradings according to the American Heart Association classification system. Discharge outcomes and brain magnetic resonance imaging results were obtained.

RESULTS: Image quality for plaque characterization was adequate in 86 of 106 patients (81%). Eight TIA/IS patients with noncarotid pathogenesis were excluded, yielding 78 study patients (38 men and 40 women with a mean age of 64.3 years, SD 14.7) with 156 paired watershed vessel/cerebral hemisphere observations. Thirty-seven patients had 40 TIA/IS events. There was a significant association between type VI plaque (demonstrating cap rupture, hemorrhage, and/or thrombosis) and ipsilateral TIA/IS (P<0.001). A multiple logistic regression model including standard Framingham risk factors and type VI plaque was constructed. Type VI plaque was the dominant outcome-associated observation achieving significance (P<0.0001; odds ratio, 11.66; 95% confidence interval, 5.31 to 25.60).

CONCLUSIONS: In situ type VI carotid bifurcation region plaque identified by magnetic resonance imaging is associated with ipsilateral acute TIA/IS as an independent identifier of events, thereby supporting the dominant disease pathophysiology.

PMID: 21041694

Three-Dimensional Imaging in the Context of Minimally Invasive and Transcatheter Cardiovascular Interventions using Multi-Detector Computed Tomography: From Pre-Operative Planning to Intra-Operative Guidance

PMID: 20797981

Cardiac Magnetic Resonance Imaging Characteristics of Isolated Left Ventricular Noncompaction in a Chinese Adult Han Population

PMID: 21046254

Frontline Diagnostic Evaluation of Patients Suspected of Angina by Coronary Computed Tomography Reduces Downstream Resource Utilization when Compared to Conventional Ischemia Testing

OBJECTIVES: It has been proposed that the increasing use of coronary computed tomographic angiography (CTA) may introduce additional unnecessary diagnostic procedures. However, no previous study has assessed the impact on downstream test utilization of conventional diagnostic testing relative to CTA in patients suspected of angina. The purpose of this study was to investigate the consequences of frontline exercise-stress testing (Ex-test) versus CTA on downstream test utilization in clinical practice.

METHODS: In two collaborating departments using either Ex-test (n = 247) or CTA (n = 251) as the frontline diagnostic test in patients suspected of angina, comparable cohorts of consecutive patients were retrospectively identified (Jan. 2007-Feb. 2008). Downstream test utilization (invasive coronary angiography, ICA; myocardial perfusion scintigraphy, and CTA) during 12 months after the index diagnostic test was recorded.

RESULTS: Mean age was 56 years (51% men), and 96% of the total study cohort were at low-intermediate pretest risk of significant coronary disease. Overall, downstream test utilization was more frequent in the Ex-test group than in the CTA group, 32% versus 21% (P = 0.003). Subsequent myocardial scintigraphy was more frequent used (9% versus 4%, P = 0.03), whereas ICA tended to be more frequent applied in the Ex-test versus CTA group (23% vs. 18%, P = 0.15).

CONCLUSIONS: A frontline diagnostic use in symptomatic patients of Ex-test in comparison to CTA leads to more downstream diagnostic test utilization. Future prospective trials are needed in order to define the most cost-effective diagnostic use of CTA relative to conventional ischemia testing.

PMID: 21042860