Does two-segment image reconstruction at 64-section CT coronary angiography improve image quality and diagnostic accuracy?

Myocardial CT perfusion imaging for the detection of obstructive coronary artery disease: multisegment reconstruction does not improve diagnostic performance

BACKGROUND

Multisegment reconstruction (MSR) was introduced to shorten the temporal reconstruction window of computed tomography (CT) and thereby reduce motion artefacts. We investigated whether MSR of myocardial CT perfusion (CTP) can improve diagnostic performance in detecting obstructive coronary artery disease (CAD) compared with halfscan reconstruction (HSR).

METHODS

A total of 134 patients (median age 65.7 years) with clinical indication for invasive coronary angiography and without cardiac surgery prospectively underwent static CTP. In 93 patients with multisegment acquisition, we retrospectively performed both MSR and HSR and searched both reconstructions for perfusion defects. Subgroups with known (n = 68) or suspected CAD (n = 25) and high heart rate (n = 30) were analysed. The area under the curve (AUC) was compared applying DeLong approach using ≥ 50% stenosis on invasive coronary angiography as reference standard.

RESULTS

Per-patient analysis revealed the overall AUC of MSR (0.65 [95% confidence interval 0.53, 0.78]) to be inferior to that of HSR (0.79 [0.69, 0.88]; p = 0.011). AUCs of MSR and HSR were similar in all subgroups analysed (known CAD 0.62 [0.45, 0.79] versus 0.72 [0.57, 0.86]; p = 0.157; suspected CAD 0.80 [0.63, 0.97] versus 0.89 [0.77, 1.00]; p = 0.243; high heart rate 0.46 [0.19, 0.73] versus 0.55 [0.33, 0.77]; p = 0.389). Median stress radiation dose was higher for MSR than for HSR (6.67 mSv versus 3.64 mSv, p < 0.001).

CONCLUSIONS

MSR did not improve diagnostic performance of myocardial CTP imaging while increasing radiation dose compared with HSR.

TRIAL REGISTRATION

CORE320: clinicaltrials.gov NCT00934037, CARS-320: NCT00967876.

Restricting motion effects in CT coronary angiography

OBJECTIVE

Evaluation of coronary CT image blur using multi segment reconstruction algorithm.

METHODS

Cardiac motion was simulated in a Catphan. CT coronary angiography was performed using 320 × 0.5 mm detector array and 275 ms gantry rotation. 1, 2 and 3 segment reconstruction algorithm, three heart rates (60, 80 and 100bpm), two peak displacements (4, 8 mm) and three cardiac phases (55, 35, 75%) were used. Wilcoxon test compared image blur from the different reconstruction algorithms.

RESULTS

Image blur for 1, 2 and 3 segments in: 60 bpm, 75% R-R interval and 8 mm peak displacement: 0.714, 0.588, 0.571 mm (1.18, 0.6, 0.4 mm displacement) 80 bpm, 35% R-R interval and 8 mm peak displacement: 0.869, 0.606, 0.606 mm (1.57, 0.79,0.52 mm displacement) 100 bpm, 35% R-R interval and 4 mm peak displacement: 0.645, 0.588, 0.571 mm (0.98, 0.49, 0.33 mm displacement). The median image blur overall for 1 and 2 segments was 0.714 mm and 0.588 mm respectively (p < 0.0001).

CONCLUSION

Two-segment reconstruction significantly reduces image blur.

ADVANCES IN KNOWLEDGE

Multisegment reconstruction algorithms during CT coronary angiography are a useful method to reduce image blur, improve visualization of the coronary artery wall and help the early detection of the plaque.

Frequency-Selective Computed Tomography: Applications During Periodic Thoracic Motion

We seek to use computed tomography (CT) to characterize regional lung parenchymal deformation during high-frequency and multi-frequency oscillatory ventilation. Periodic motion of thoracic structures results in artifacts of CT images obtained by standard reconstruction algorithms, especially for frequencies exceeding that of the X-ray source rotation. In this paper, we propose an acquisition and reconstruction technique for high-resolution imaging of the thorax during periodic motion. Our technique relies on phase-binning projections according to the frequency of subject motion relative to the scanner rotation, prior to volumetric reconstruction. The mathematical theory and limitations of the proposed technique are presented, and then validated in a simulated phantom as well as a living porcine subject during oscillatory ventilation. The 4-D image sequences obtained using this frequency-selective reconstruction technique yielded high-spatio-temporal resolution of the thorax during periodic motion. We conclude that the frequency-based selection of CT projections is ideal for characterizing dynamic deformations of thoracic structures that are ordinarily obscured by motion artifact using conventional reconstruction techniques.

Optimized heart rate for 320-row cardiac CT can be feasibly predicted from prescan parameters

To evaluate the degree of heart rate (HR) changes at rest (HRrest), during breath hold (HRtest), and during cardiac CT examinations (HRscan) in a large group of patients , and to derive and asses the feasibility of a predictive formula for HRscan. HRrest, HRtest, and HRscan were retrospectively compared in a total of 563 consecutive patients who underwent 320-row cardiac CT. Multiple regression analysis was performed to derive predictive formulae for HRscan in the entire study population and, in each group of patients with decreased (Dec) or increased (Inc) HR during breath hold. The predictive formula was evaluated as accurate when less than 5 % of the actual HRscan exceeded the predicted HRscan by ±5 beats per minute (bpm). The average values of the HRtest (65.3 ± 12.0 bpm) and HRscan (63.7 ± 11.9 bpm) significantly decreased from those of the HRrest (68.4 ± 11.9 bpm) (p < 0.0001). The predictive formula (HRscan = 3.601 + 0.113HRrest + 0.8HRtest) was determined to be accurate only in Group Dec. The HRtest significantly decreased from the HRrest, and the HRscan significantly decreased from the HRtest. An accurate predictive formula for HRscan could be built only for Group Dec.

Organ and effective dose evaluation in coronary angiography by using a 320 MDCT based on in-phantom dose measurements with TLDs

The purpose of this study is to estimate the organ and effective dose (E) from computed tomography coronary angiography (CTCA) on a 320-MDCT scanner. Radiation dose was estimated for the prospectively ECG-gated CTCA in a male phantom. A total of 451 chips of thermoluminescent dosimeter were implanted in the phantom for measuring the organ doses. The effective doses were calculated using measured organ doses and the tissue-weighting factors. The dose length product (DLP) values were recorded and used to develop the conversion coefficient k = 0.017 mSv•(mGy•cm)(-1) (E/DLP). In a 3-beat acquisition, the organ doses ranged from 0.24 to 71.55 mGy, and the doses in breast, bone surface, oesophagus, and lung were higher than 20 mGy. The effective doses in 2-beat and 3-beat acquisition were estimated to be 14.3 and 24.3 mSv. More beats of acquisition led to higher radiation dose. The reported k values for chest CT scan can be used to roughly estimate the E value from CTCA for 320 MDCT.

Impact of an intra-cycle motion correction algorithm on overall evaluability and diagnostic accuracy of computed tomography coronary angiography

OBJECTIVES

The aim of this study was to evaluate the impact of a novel intra-cycle motion correction algorithm (MCA) on overall evaluability and diagnostic accuracy of cardiac computed tomography coronary angiography (CCT).

METHODS

From a cohort of 900 consecutive patients referred for CCT for suspected coronary artery disease (CAD), we enrolled 160 (18 %) patients (mean age 65.3 ± 11.7 years, 101 male) with at least one coronary segment classified as non-evaluable for motion artefacts. The CCT data sets were evaluated using a standard reconstruction algorithm (SRA) and MCA and compared in terms of subjective image quality, evaluability and diagnostic accuracy.

RESULTS

The mean heart rate during the examination was 68.3 ± 9.4 bpm. The MCA showed a higher Likert score (3.1 ± 0.9 vs. 2.5 ± 1.1, p < 0.001) and evaluability (94%vs.79 %, p < 0.001) than the SRA. In a 45-patient subgroup studied by clinically indicated invasive coronary angiography, specificity, positive predictive value and accuracy were higher in MCA vs. SRA in segment-based and vessel-based models, respectively (87%vs.73 %, 50%vs.34 %, 85%vs.73 %, p < 0.001 and 62%vs.28 %, 66%vs.51 % and 75%vs.57 %, p < 0.001). In a patient-based model, MCA showed higher accuracy vs. SCA (93%vs.76 %, p < 0.05).

CONCLUSIONS

MCA can significantly improve subjective image quality, overall evaluability and diagnostic accuracy of CCT.

KEY POINTS

Cardiac computed tomographic coronary angiography (CCT) allows non-invasive evaluation of coronary arteries. Intra-cycle motion correction algorithm (MCA) allows for compensation of coronary motion. An MCA improves image quality, CCT evaluability and diagnostic accuracy.

The diagnostic performance of coronary artery angiography with 64-MSCT and post 64-MSCT: systematic review and meta-analysis

PURPOSE

To comprehensively investigate the diagnostic performance of coronary artery angiography with 64-MDCT and post 64-MDCT.

MATERIALS AND METHODS

PubMed was searched for all published studies that evaluated coronary arteries with 64-MDCT and post 64-MDCT. The clinical diagnostic role was evaluated by applying the likelihood ratios (LRs) to calculate the post-test probability based on Bayes' theorem.

RESULTS

91 studies that met our inclusion criteria were ultimately included in the analysis. The pooled positive and negative LRs at patient level were 8.91 (95% CI, 7.53, 10.54) and 0.02 (CI, 0.01, 0.03), respectively. For studies that did not claim that non-evaluable segments were included, the pooled positive and negative LRs were 11.16 (CI, 8.90, 14.00) and 0.01 (CI, 0.01, 0.03), respectively. For studies including uninterruptable results, the diagnostic performance decreased, with the pooled positive LR 7.40 (CI, 6.00, 9.13) and negative LR 0.02 (CI, 0.01, 0.03). The areas under the summary ROC curve were 0.98 (CI, 0.97 to 0.99) for 64-MDCT and 0.96 (CI, 0.94 to 0.98) for post 64-MDCT, respectively. For references explicitly stating that the non-assessable segments were included during analysis, a post-test probability of negative results >95% and a positive post-test probability <95% could be obtained for patients with a pre-test probability of <73% for coronary artery disease (CAD). On the other hand, when the pre-test probability of CAD was >73%, the diagnostic role was reversed, with a positive post-test probability of CAD >95% and a negative post-test probability of CAD <95%.

CONCLUSION

The diagnostic performance of post 64-MDCT does not increase as compared with 64-MDCT. CTA, overall, is a test of exclusion for patients with a pre-test probability of CAD<73%, while for patients with a pre-test probability of CAD>73%, CTA is a test used to confirm the presence of CAD.

Methodological quality of diagnostic accuracy studies on non-invasive coronary CT angiography: influence of QUADAS (Quality Assessment of Diagnostic Accuracy Studies included in systematic reviews) items on sensitivity and specificity

OBJECTIVES

To evaluate the methodological quality of diagnostic accuracy studies on coronary computed tomography (CT) angiography using the QUADAS (Quality Assessment of Diagnostic Accuracy Studies included in systematic reviews) tool.

METHODS

Each QUADAS item was individually defined to adapt it to the special requirements of studies on coronary CT angiography. Two independent investigators analysed 118 studies using 12 QUADAS items. Meta-regression and pooled analyses were performed to identify possible effects of methodological quality items on estimates of diagnostic accuracy.

RESULTS

The overall methodological quality of coronary CT studies was merely moderate. They fulfilled a median of 7.5 out of 12 items. Only 9 of the 118 studies fulfilled more than 75 % of possible QUADAS items. One QUADAS item ("Uninterpretable Results") showed a significant influence (P = 0.02) on estimates of diagnostic accuracy with "no fulfilment" increasing specificity from 86 to 90 %. Furthermore, pooled analysis revealed that each QUADAS item that is not fulfilled has the potential to change estimates of diagnostic accuracy.

CONCLUSIONS

The methodological quality of studies investigating the diagnostic accuracy of non-invasive coronary CT is only moderate and was found to affect the sensitivity and specificity. An improvement is highly desirable because good methodology is crucial for adequately assessing imaging technologies.

KEY POINTS

• Good methodological quality is a basic requirement in diagnostic accuracy studies. • Most coronary CT angiography studies have only been of moderate design quality. • Weak methodological quality will affect the sensitivity and specificity. • No improvement in methodological quality was observed over time. • Authors should consider the QUADAS checklist when undertaking accuracy studies.

Use of 3x2 tables with an intention to diagnose approach to assess clinical performance of diagnostic tests: meta-analytical evaluation of coronary CT angiography studies

OBJECTIVE

To determine whether a 3 × 2 table, using an intention to diagnose approach, is better than the "classic" 2 × 2 table at handling transparent reporting and non-evaluable results, when assessing the accuracy of a diagnostic test.

DESIGN

Based on a systematic search for diagnostic accuracy studies of coronary computed tomography (CT) angiography, full texts of relevant studies were evaluated to determine whether they could calculate an alternative 3 × 2 table. To quantify an overall effect, we pooled diagnostic accuracy values according to a meta-analytical approach.

DATA SOURCES

Medline (via PubMed), Embase (via Ovid), and ISI Web of Science electronic databases.

ELIGIBILITY CRITERIA

Prospective English or German language studies comparing coronary CT with conventional coronary angiography in all patients and providing sufficient data for a patient level analysis.

RESULTS

120 studies (10,287 patients) were eligible. Studies varied greatly in their approaches to handling non-evaluable findings. We found 26 studies (including 2298 patients) that allowed us to calculate both 2 × 2 tables and 3 × 2 tables. Using a bivariate random effects model, we compared the 2 × 2 table with the 3 × 2 table, and found significant differences for pooled sensitivity (98.2 (95% confidence interval 96.7 to 99.1) v 92.7 (88.5 to 95.3)), area under the curve (0.99 (0.98 to 1.00) v 0.93 (0.91 to 0.95)), positive likelihood ratio (9.1 (6.2 to 13.3) v 4.4 (3.3 to 6.0)), and negative likelihood ratio (0.02 (0.01 to 0.04) v 0.09 (0.06 to 0.15); (P<0.05)).

CONCLUSION

Parameters for diagnostic performance significantly decrease if non-evaluable results are included by a 3 × 2 table for analysis (intention to diagnose approach). This approach provides a more realistic picture of the clinical potential of diagnostic tests.

Coronary CT angiography: current status and continuing challenges

Coronary CT angiography has been increasingly used in the diagnosis of coronary artery disease owing to rapid technological developments, which are reflected in the improved spatial and temporal resolution of the images. High diagnostic accuracy has been achieved with multislice CT scanners (64 slice and higher), and in selected patients coronary CT angiography is regarded as a reliable alternative to invasive coronary angiography. With high-quality coronary CT imaging increasingly being performed, patients can benefit from an imaging modality that provides a rapid and accurate diagnosis while avoiding an invasive procedure. Despite the tremendous contributions of coronary CT angiography to cardiac imaging, study results reported in the literature should be interpreted with caution as there are some limitations existing within the study design or related to patient risk factors. In addition, some attention must be given to the potential health risks associated with the ionising radiation received during cardiac CT examinations. Radiation dose associated with coronary CT angiography has raised serious concerns in the literature, as the risk of developing malignancy is not negligible. Various dose-saving strategies have been implemented, with some of the strategies resulting in significant dose reduction. The aim of this review is to present an overview of the role of coronary CT angiography on cardiac imaging, with focus on coronary artery disease in terms of the diagnostic and prognostic value of coronary CT angiography. Various approaches for dose reduction commonly recommended in the literature are discussed. Limitations of coronary CT angiography are identified. Finally, future directions and challenges with the use of coronary CT angiography are highlighted.

Influence of coronary artery disease prevalence on predictive values of coronary CT angiography: a meta-regression analysis

OBJECTIVE

To evaluate the impact of coronary artery disease (CAD) prevalence on the predictive values of coronary CT angiography.

METHODS

We performed a meta-regression based on a generalised linear mixed model using the binomial distribution and a logit link to analyse the influence of the prevalence of CAD in published studies on the per-patient negative and positive predictive values of CT in comparison to conventional coronary angiography as the reference standard. A prevalence range in which the negative predictive value was higher than 90%, while at the same time the positive predictive value was higher than 70% was considered appropriate.

RESULTS

The summary negative and positive predictive values of coronary CT angiography were 93.7% (95% confidence interval [CI] 92.8-94.5%) and 87.5% (95% CI, 86.5-88.5%), respectively. With 95% confidence, negative and positive predictive values higher than 90% and 70% were available with CT for a CAD prevalence of 18-63%. CT systems with >16 detector rows met these requirements for the positive (P < 0.01) and negative (P < 0.05) predictive values in a significantly broader range than systems with ≤16 detector rows.

CONCLUSION

It is reasonable to perform coronary CT angiography as a rule-out test in patients with a low-to-intermediate likelihood of disease.

Limited clinical utility of CT coronary angiography in a district hospital setting

BACKGROUND

Studies have demonstrated considerable accuracy of multi-slice CT coronary angiography (MSCT-CA) in comparison to invasive coronary angiography (I-CA) for evaluating coronary artery disease (CAD). The extent to which published MSCT-CA accuracy parameters are transferable to routine practice beyond high-volume tertiary centres is unknown.

AIM

To determine the accuracy of MSCT-CA for the detection of CAD in a Scottish district general hospital.

DESIGN

Prospective study of diagnostic accuracy.

METHOD

One hundred patients with suspected CAD recruited from two Glasgow hospitals underwent both MSCT-CA (Philips Brilliance 40 × 0.625 collimation, 50-200 ms temporal resolution) and I-CA. Studies were reported by independent, blinded radiologists and cardiologists and compared using the AHA 15-segment model.

RESULTS

Of 100 patients [55 male, 45 female, mean (SD) age 58.0 (10.7) years], 59 and 41% had low-intermediate and high pre-test probabilities of significant CAD, respectively. Mean (SD) heart rate during MSCT-CA was 68.8 (9.0) bpm. Fifty-seven per cent of patients had coronary artery calcification and 35% were obese. Patient prevalence of CAD was 38%. Per-patient sensitivity, specificity, positive and negative (NPV) predictive values for MSCT-CA were 92.1, 47.5, 52.2 and 90.6%, respectively. NPV was reduced to 75.0% in the high pre-test probability group. Specificity was compromised in patients with sub-optimally controlled heart rates, calcified arteries and elevated BMI.

CONCLUSION

Forty-Slice MSCT-CA has a high NPV for ruling out significant CAD when performed in a district hospital setting in patients with low-intermediate pre-test probability and minimal arterial calcification. Specificity is compromised by clinically appropriate strategies for dealing with unevaluable studies. Effective heart rate control during MSCT-CA is imperative. National guidelines should be utilized to govern patient selection and direct MSCT-CA reporter training to ensure quality control.

Diagnostic performance of 320-detector CT coronary angiography in patients with atrial fibrillation: preliminary results

OBJECTIVE

To evaluate the feasibility, diagnostic accuracy, and radiation dose of CT coronary angiography (CTCA) in patients with atrial fibrillation (AF) using 320-detector CT.

METHODS

Thirty-seven patients with persistent AF and suspected coronary artery disease (CAD) were enrolled. All patients underwent both 320-detector CTCA and conventional coronary angiography (CCA). CT image quality and the presence of significant (≥ 50%) stenosis were evaluated by two radiologists blinded to the results of CCA. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated using CCA as the reference standard. Differences in detection of coronary artery stenosis between 320-detector CTCA and CCA were evaluated with McNemar's test. Patient radiation dose was calculated by multiplying dose length product by conversion coefficient of 0.017.

RESULTS

In total 474 evaluated coronary segments, 459 (96.8%) segments were diagnostically evaluable. On per-segment analysis, sensitivity, specificity, PPV and NPV were 90.0% (18 of 20), 99.3% (436 of 439), 85.7% (18 of 21) and 99.5% (436 of 438). No significant difference was found between 320-detector CTCA and CCA on the detection of significant stenosis (P = 1.000). Effective doses of 320-detector CTCA was 13.0 ± 4.7 mSv.

CONCLUSION

320-detector CTCA is feasible and accurate in excluding CAD in patients with AF.

Abolition of Respiratory-Motion Artifact in Computed Tomography Coronary Angiography with Ultrafast Examinations: A Comparison between 64-row and 320-row Multidetector Scanners

Purpose

To compare the incidence of respiratory artifact in computed tomography (CT) coronary angiography performed with 64-row and 320-row multidetector scanners and to assess its effect on coronary evaluability.

Methods

A retrospective review of consecutive coronary angiograms performed on a 64-row multidetector CT from March to April 2007 (group 1: 115 patients, 63 men; mean age [standard deviation] 59.6 ± 12.8 years) and on a 320-row multidetector CT from March to April 2008 (group 2: 169 patients, 89 men; mean [SD] age 57.9 ± 11.6 years). Two cardiac radiologists assessed the occurrence of respiratory artifact and coronary evaluability in studies with respiratory artifacts. Unevaluable coronary segments because of motion at the same anatomical level of the respiratory artifact were considered unevaluable because of this artifact. The association between the occurrence of respiratory artifact and patient biometrics, medication, and scan parameters was examined.

Results

Respiratory artifacts were detected in 9 of the 115 patients from group 1 (7.8%) and in none of the 169 patients from group 2 ( P < .001). Group 1 had longer scan times (median, 9.3 seconds; range, 7.5−14.4 seconds) compared with group 2 (median, 1.5 seconds; range, 1.1−3.5 seconds; P < .001). In group 1, 4 patients (3.5%) showed unevaluable coronary segments because of respiratory artifacts, and the CT coronary angiography was repeated in 1 patient (0.9%).

Conclusions

Respiratory artifacts are important in CT coronary angiography performed with 64-row multidetector scanners and impair the diagnostic utility of the examination in up to 3.5% of the studies. These artifacts can be virtually eliminated with a faster scan time provided by 320-row multidetector CT.

CT of coronary artery disease

Technical innovation is rapidly improving the clinical utility of cardiac computed tomography (CT) and will increasingly address current technical limitations, especially the association of this test with relatively high levels of radiation. Guidelines for appropriate indications are in place and are evolving, with an increasing evidence base to ensure the appropriate use of this modality. New technologies and new applications, such as myocardial perfusion imaging and dual-energy CT, are being explored and are widening the scope of coronary CT angiography from mere coronary artery assessment to the integrative analysis of cardiac morphology, function, perfusion, and viability. The scientific evaluation of coronary CT angiography has left the stage of feasibility testing and increasingly, evidence-based data are accumulating on outcomes, prognosis, and cost-effectiveness. In this review, these developments will be discussed in the context of current pivotal transitions in cardiovascular disease management and their potential influence on the current role and future fate of coronary CT angiography will be examined.

Influence of pixel size on quantification of airway wall thickness in computed tomography

OBJECTIVES

The purpose of this study was to determine the point where a further decrease in voxel size does not result in better automatic quantification of the bronchial wall thickness by using 2 different assessment techniques.

MATERIALS AND METHODS

The results from the commonly used full-width-at-half-maximum (FWHM) principle and a new technique (integral-based method [IBM]) were compared for thin-section multidetector computed tomography (MDCT) data sets from an airway phantom containing 10 different tubular airway phantoms and in a human subsegmental bronchus in vivo. Correlation with the actual wall thickness and comparison of the wall thicknesses assessed for different voxel sizes were performed, and the image resolutions were also compared subjectively.

RESULTS

The relative error ranged from 0% (biggest phantom) to 330% (smallest phantom, biggest field of view, smaller matrix, and FWHM). Using IBM, the maximum relative error was 10% in the same setting. For FWHM, the improvement was marginal for most settings with a pixel spacing less than 0.195 x 0.195 x 0.8 mm; however, it still decreases the relative error from 290% to 273.6% for a wall thickness of 0.3 mm and a pixel spacing of 0.076 x 0.076 x 0.8 mm.

CONCLUSIONS

(1) Using a special technique such as IBM to account for computed tomography's blurring effect in assessing airway wall thickness had the greatest impact on correct quantification. (2) The visual impression and the automatic quantification using the FWHM technique improved marginally by decreasing the voxel size to less than 0.195 x 0.195 x 0.8 mm. (3) The FWHM technique as a model for visual quantification is not reliable for airway wall thicknesses less than 1.5 mm.

What are the basic concepts of temporal, contrast, and spatial resolution in cardiac CT?

An imaging instrument can be characterized by its spatial resolution, contrast resolution, and temporal resolution. The capabilities of computed tomography (CT) relative to other cardiac imaging modalities can be understood in these terms. The purpose of this review is to characterize the spatial, contrast, and temporal resolutions of cardiac CT in practical terms.

Randomized comparison of 64-slice single- and dual-source computed tomography coronary angiography for the detection of coronary artery disease

OBJECTIVES

The purpose of this study was to analyze the influence of a systematic approach to lower heart rate for coronary computed tomography (CT) angiography on diagnostic accuracy of 64-slice single- and dual-source CT.

BACKGROUND

Coronary CT angiography is often impaired by motion artifacts, so that routine lowering of heart rate is usually recommended. This is often conceived as a major limitation of the technique. It is expected that higher temporal resolution, such as with dual-source 64-slice CT, would allow diagnostic imaging even without systematic pre-treatment for lowering the heart rate.

METHODS

Two hundred patients with suspected coronary artery disease were first randomized to either 64-slice single-source CT (n = 100) or dual-source CT (n = 100) for contrast-enhanced coronary artery evaluation. In each group, patients were further randomized to either receive systematic heart rate control (oral and intravenous beta-blockade for a target heart rate < or =60 beats/min) or receive no premedication. Evaluability of datasets and diagnostic accuracy were compared between groups against the results obtained from invasive angiography.

RESULTS

Systematic pre-treatment lowered heart rate during CT coronary angiography by 10 beats/min. Heart rate control significantly improved evaluability in single-source CT (93% vs. 69% on a per-patient basis, p = 0.005), whereas it did not in dual-source CT (96% vs. 98%). In evaluable patients, sensitivity to detect the presence of at least 1 coronary stenosis by single-source CT was 86% and 79%, respectively, with and without heart rate control (p = NS). For dual-source CT, it was 100% and 95%, respectively (p = NS). The rate of correctly classified patients, defined as evaluable and correct classification as to the presence or absence of at least 1 coronary artery stenosis, was significantly improved by heart rate control in single-source CT (78% vs. 57%, p = 0.04), whereas there was no such influence in dual-source CT (87% vs. 93%).

CONCLUSIONS

Systematic heart rate control significantly improves image quality for coronary visualization by 64-slice single-source CT, whereas image quality and diagnostic accuracy remain unaffected in dual-source CT angiography. Improved temporal resolution obviates the need for heart rate control.

The influence of reconstruction algorithm and heart rate on coronary artery image quality and stenosis detection at 64-detector cardiac CT

Objective

We wanted to evaluate the impact of two reconstruction algorithms (halfscan and multisector) on the image quality and the accuracy of measuring the severity of coronary stenoses by using a pulsating cardiac phantom with different heart rates (HRs).

Materials and Methods

Simulated coronary arteries with different stenotic severities (25, 50, 75%) and different luminal diameters (3, 4, 5 mm) were scanned with a fixed pitch of 0.16 and a 0.35 second gantry rotation time on a 64-slice multidetector CT. Both reconstruction algorithms (halfscan and multisector) were applied to HRs of 40-120 beats per minute (bpm) at 10 bpm intervals. Three experienced radiologists visually assessed the image quality and they manually measured the stenotic severity.

Results

Fewer measurement errors occurred with multisector reconstruction (p = 0.05), a slower HR (p < 0.001) and a larger luminal diameter (p = 0.014); measurement errors were not related with the observers or the stenotic severity. There was no significant difference in measurements as for the reconstruction algorithms below an HR of 70 bpm. More nonassessable segments were visualized with halfscan reconstruction (p = 0.004) and higher HRs (p < 0.001). Halfscan reconstruction had better quality scores when the HR was below 60 bpm, while multisector reconstruction had better quality scores when the HR was above 90 bpm. For the HRs between 60 and 90 bpm, both reconstruction modes had similar quality scores. With excluding the nonassessable segments, both reconstruction algorithms achieved a similar mean measured stenotic severity and similar standard deviations.

Conclusion

At a higher HR (above 90 bpm), multisector reconstruction had better temporal resolution, fewer nonassessable segments, better quality scores and better accuracy of measuring the stenotic severity in this phantom study.

Predictors of image quality of coronary computed tomography in the acute care setting of patients with chest pain

OBJECTIVE

We aimed to determine predictors of image quality in consecutive patients who underwent coronary computed tomography (CT) for the evaluation of acute chest pain.

METHOD AND MATERIALS

We prospectively enrolled patients who presented with chest pain to the emergency department. All subjects underwent contrast-enhanced 64-slice coronary multi-detector CT. Two experienced readers determined overall image quality on a per-patient basis and the prevalence and characteristics of non-evaluable coronary segments on a per-segment basis.

RESULTS

Among 378 subjects (143 women, age: 52.9+/-11.8 years), 345 (91%) had acceptable overall image quality, while 33 (9%) had poor image quality or were unreadable. In adjusted analysis, patients with diabetes, hypertension and a higher heart rate during the scan were more likely to have exams graded as poor or unreadable (odds ratio [OR]: 2.94, p=0.02; OR: 2.62, p=0.03; OR: 1.43, p=0.02; respectively). Of 6253 coronary segments, 257 (4%) were non-evaluable, most due to severe calcification in combination with motion (35%). The presence of non-evaluable coronary segments was associated with age (OR: 1.08 annually, 95%-confidence interval [CI]: 1.05-1.12, p<0.001), baseline heart rate (OR: 1.35 per 10 beats/min, 95%-CI: 1.11-1.67, p=0.003), diabetes, hypertension, and history of coronary artery disease (OR: 4.43, 95%-CI: 1.93-10.17, p<0.001; OR: 2.27, 95-CI: 1.01-4.73, p=0.03; OR: 5.12, 95%-CI: 2.0-13.06, p<0.001; respectively).

CONCLUSION

Coronary CT permits acceptable image quality in more than 90% of patients with chest pain. Patients with multiple risk factors are more likely to have impaired image quality or non-evaluable coronary segments. These patients may require careful patient preparation and optimization of CT scanning protocols.

Meta-analysis of 40- and 64-MDCT angiography for assessing coronary artery stenosis

OBJECTIVE

The purpose of our study was to assess the diagnostic performance of thin-slice (< or = 0.625 mm) MDCT coronary angiography compared with invasive coronary angiography for the detection of significant (> or = 50%) stenosis.

MATERIALS AND METHODS

Twenty-two articles on 40- and 64-MDCT coronary angiography were included. Sensitivity and specificity were calculated on a per-patient and per-segment basis; in addition, proximal versus distal segments were evaluated. The effect of nonevaluable patients, nonevaluable segments, and disease prevalence on diagnostic performance was assessed.

RESULTS

Pooled sensitivity on a patient level was 97.7% ([95% CI] 96.2-98.7%) and specificity 91.0% (88.5-93.1%). Pooled sensitivity on a segmental level was 90.8% (89.0-92.4%) and specificity 95.7% (95.2-96.1%); for proximal segments, respectively, 94.2% (92.3-95.7%) and 94.1% (93.4-94.8%), and for distal segments 84.8% (81.1-88.0%) and 96.9% (96.4-97.4%). If nonevaluable MDCT investigations were included, the per-patient specificity was reduced from 91.0% to 89.1% (p > 0.05) when allocating excluded patients as having significant coronary artery stenosis, and the sensitivity was reduced from 97.7% to 96.2% (p > 0.05) when allocating excluded patients as not having significant stenosis. The per-patient prevalence of coronary artery stenosis had no significant influence on the sensitivity for detecting significant stenosis.

CONCLUSION

Forty- and 64-MDCT provide good-to-excellent performance in detecting or ruling out significant coronary artery stenosis, with better results for proximal than for distal coronary artery segments.

Dual-source CT for visualization of the coronary arteries in heart transplant patients with high heart rates

OBJECTIVE

The purpose of this study was to evaluate the quality of dual-source CT images of the coronary arteries in heart transplant recipients with high heart rates.

SUBJECTS AND METHODS

Contrast-enhanced dual-source CT coronary angiography was performed on 23 heart transplant recipients (20 men, three women; mean age, 61.1 +/- 12.8 years). Data sets were reconstructed in 5% steps from 30% to 80% of the R-R interval. Two blinded independent readers using a 5-point scale (0, not evaluative; 4, excellent quality) assessed the quality of images of coronary segments.

RESULTS

The mean heart rate during scanning was 89.2 +/- 10.4 beats/min. Interobserver agreement on the quality of images of the whole coronary tree was a kappa value of 0.78 and for selection of the optimal reconstruction interval was a kappa value of 0.82. The optimal reconstruction interval was systole in 17 (74%) of the 23 of heart transplant recipients. At the best reconstruction interval, diagnostic image quality (score >or= 2) was obtained in 92.1% (303 of 329) of the coronary artery segments. The mean image quality score for the whole coronary tree was 3.1 +/- 1.01. No significant correlation between mean heart rate (rho = 0.31) or heart rate variability (rho = 0.23) and overall image quality score was observed (p = not significant).

CONCLUSION

Dual-source CT acquisition yields coronary angiograms of diagnostic quality in heart transplant recipients. Mean heart rate and heart rate variability during scanning do not have a negative effect on the overall quality of images of the coronary arteries.

Volumetric measurement of pericardial adipose tissue from contrast-enhanced coronary computed tomography angiography: a reproducibility study

PURPOSE

Pericardial adipose tissue may exert unique metabolic and cardiovascular risks in patients. The use of cardiac multidetector computed tomography (MDCT) imaging may enable the accurate localization and quantification of pericardial and intrathoracic adipose tissue. The reproducibility of electrocardiogram-gated high-resolution cardiac MDCT-based volumetric quantification of pericardial and intrathoracic adipose tissue has not been reported.

METHODS

We included 100 consecutive patients (age 54.5 +/- 12.0 yr, 60% men) who underwent a standard contrast-enhanced coronary CT for the evaluation of coronary artery plaque and stenosis (64-slice MDCT, temporal resolution: 210 ms, spatial resolution: 0.6 mm, 850 mAs, 120, kvp) after a presentation of acute chest pain. Two independent observers measured intrathoracic (IAT) and pericardial adipose tissue (PAT) by using a semiautomatic segmentation algorithm based on three-dimensional analysis.

RESULTS

Inter-reader reproducibility was excellent (relative difference: 7.35 +/- 7.22% for PAT and 6.23 +/- 4.91% for IAT, intraclass correlation 0.98 each). Similar results were obtained for intra-observer reproducibility (relative difference: 5.18 +/- 5.19% for PAT and 4.34 +/- 4.12% for IAT, intraclass correlation 0.99 each).

CONCLUSION

This study demonstrates that MDCT-based 3D semiautomatic segmentation for volumetric quantification of PAT and IAT is highly reproducible. Further research is warranted to assess whether volumetric measurements may substantially improve the predictive value of obesity measures for insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases.

Initial evaluation of coronary images from 320-detector row computed tomography

PURPOSE

To evaluate image quality and contrast opacification from coronary images acquired from 320-detector row computed tomography (CT). Patient dose is estimated for prospective and retrospective ECG-gating; initial correlation between 320-slice CT and coronary catheterization is illustrated.

METHODS

Retrospective image evaluation from forty consecutive patients included subjective assessment of image quality and contrast opacification (80 ml iopamidol 370 mg I/ml followed by 40 ml saline). Region of interest opacification measurements at the ostium and at 2.5 mm diameter were used to determine the gradient of contrast opacification (defined as the proximal minus distal HU measurements) in coronary arteries imaged in a single heartbeat. Estimated effective dose was compared for prospective versus retrospective ECG-gating, two body mass index categories (30 kg/m(2) cutoff), and single versus two heartbeat acquisition. When available, CT findings were correlated with those from coronary catheterization.

RESULTS

Over 89% of arterial segments (15 segment model) had excellent image quality. The most common reason for image degradation was cardiac motion. One segment in one patient was considered unevaluable. Contrast opacification was almost universally considered excellent. The mean Hounsfield units (HU) was greater than 350; the coronary contrast opacification gradient was 30-50 HU. Patient doses were greater for retrospective ECG-gating, larger patients, and those imaged with two heartbeats. For the most common (n=25) protocol (120 kV, 400 mA, prospective ECG-gating, 60-100% phase window, 16 cm craniocaudal coverage, single heartbeat), the mean dose was 6.8+/-1.4 mSv. All CT findings were confirmed in the four patients who underwent coronary catheterization.

CONCLUSION

Initial 320-detector row coronary CT images have consistently excellent quality and iodinated contrast opacification. These patients were scanned with conservative protocols with respect to iodine load, prospective ECG-gating phase window, and craniocaudal coverage. Future work will focus on lowering contrast and radiation dose while maintaining image quality.

Dual-source CT: effect of heart rate, heart rate variability, and calcification on image quality and diagnostic accuracy

PURPOSE

To prospectively evaluate the effect of heart rate, heart rate variability, and calcification on dual-source computed tomography (CT) image quality and to prospectively assess diagnostic accuracy of dual-source CT for coronary artery stenosis, by using invasive coronary angiography as the reference standard.

MATERIALS AND METHODS

This study had local Ethics Committee approval; all patients gave informed consent. Patients who underwent bypass surgery were excluded; patients with coronary artery stent-grafts were included. One hundred patients (20 women, 80 men; mean age, 62 years +/- 10 [standard deviation]) known to have or suspected of having coronary artery disease underwent dual-source CT and invasive coronary angiography. Image quality was assessed. Accuracy of dual-source CT in depiction or exclusion of significant stenosis (>or=50%) was evaluated on a per-segment and per-patient basis. Effects of heart rate, heart rate variability, and calcification on image quality and accuracy were analyzed by using multivariate regression and were analyzed between subgroups of predictor variables. Simple regression was performed to calculate thresholds for adequate image quality.

RESULTS

Mean heart rate was 64.9 beats per minute +/- 13.2, mean variability was 23.6 beats per CT examination +/- 36.2, and mean Agatston score was 786.5 +/- 965.9. Diagnostic image quality was obtained in 90.2% of segments. Sensitivity, specificity, and positive and negative predictive values for the presence of significant stenosis were, respectively, 91.1%, 92.0%, 75.4%, and 97.5% by segment and 100%, 81.5%, 93.6%, and 100% by patient. Image quality was significantly related to heart rate variability (P = .015) and calcification (P < .001); the number of nondiagnostic segments was significantly affected by calcification only. Calcification was the single factor with significant impact on diagnostic accuracy (P = .001).

CONCLUSION

While dual-source CT resulted in heart-rate independent image quality, image quality remained prone to heart rate variability and calcification.

Clinical utility of cardiac computed tomography

Technological advances have made cardiac computed tomography (CT) an important player in cardiac imaging. Cardiac CT has become a powerful tool in the armamentarium of cardiac risk stratification assessment of intermediate-risk patients, bypass grafts, stents, and anomalous coronary arteries. With advancement in accuracy and reliability, cardiac CT is becoming mainstream in everyday clinical cardiology. It is up to the clinician to use the technology effectively and appropriately. It is certain that cardiac CT technology will continue to improve.

Coronary CT Angiography

Owing to ongoing technical refinements and intense scientific and clinical evaluations, computed tomography (CT) of the heart has left the research realm and matured into a clinical application that is about to fulfill its promise to replace invasive cardiac catheterization in selected patient populations. CT coronary angiography is technically more challenging than other CT applications owing to the nature of its target, the continuously moving heart. Rapid technical developments in this field require constant adaptation of acquisition protocols. These challenges, however, are in no way insurmountable for users with knowledge of the general CT technique. The intent of this communication is to provide those interested in and involved with coronary CT angiography with a step-by-step "manual" describing the authors' approach to performing coronary CT angiography. Included are considerations regarding appropriate patient selection, patient medication, radiation protection, contrast enhancement, acquisition and reconstruction parameters, image display and analysis techniques, and the radiology report. The recommendations are based on the authors' experience, which spans the evolution of multi-detector row CT for cardiac applications, from its beginning to the advent of the most current generations of 64-section and dual-source CT technologies, which they believe herald the entrance of this examination into routine clinical practice.