Chest X-ray Dose Equivalent Low-dose CT with Tin Filtration: Potential Role for the Assessment of Pectus Excavatum.

RATIONALE AND OBJECTIVES: To determine the value of chest CT with tin filtration applying a dose equivalent to chest x-ray for the assessment of the Haller index for evaluation of pectus excavatum. MATERIALS AND METHODS: Two hundred seventy-two patients from a prospective single center study were included and underwent a clinical standard dose chest CT (effective dose 1.8 ± 0.7 mSv) followed by a low-dose CT (0.13 ± 0.01 mSv) in the same session. Two blinded readers independently evaluated all data sets. Image quality for bony chest wall assessment was noted. Radiologists further assessed (a) transverse thoracic diameter, (b) anteroposterior thoracic diameter, and calculated (c) Haller index by dividing transverse diameter by anteroposterior diameter. The agreement of both readers in standard dose and low-dose CT was assessed using Lin's concordance correlation coefficient (pc). RESULTS: Subjective image quality was lower for low dose compared to standard dose CT images by both readers (p < 0.001). In total, 99% (n = 540) of low-dose CT scans were rated as diagnostic for bony chest wall assessment by both readers. There was a high agreement for assessment of transverse diameter, anteroposterior diameter and Haller index comparing both readers in standard dose and low-dose CT with pc values indicating substantial agreement (i.e., 0.95> and ≤0.99) in 12/18 (67%) and almost perfect agreement (i.e., >0.99) in 6/18 (33%). CONCLUSION: Our study suggests that low-dose CT with tin filtration applying a radiation dose equivalent to a plain chest X-ray is excellent for assessing the Haller index.

Coronary risk assessment at X-ray dose equivalent ungated chest CT: Results of a multi-reader study.

OBJECTIVES: To determine the value of ultra-low dose chest CT with tin filtration for ordinal coronary artery calcium (CAC) risk scoring. METHODS: 50 patients were prospectively included and underwent clinical standard dose chest CT (1.8±0.7mSv) and ultra-low dose CT (0.13±0.01mSv). Four radiologists estimated presence and extent of CAC. RESULTS: Weighted kappa values for CAC were 0.76-0.97 in standard dose and 0.75-0.95 in ultra-low dose CT (p<0.001). Good to excellent agreement was observed for CAC ordinal risk assessment, with readers reporting identical risk in 81% of cases. CONCLUSION: CAC risk can be qualitatively assessed from X-ray dose equivalent ungated chest CT.

Diagnostic accuracy of chest X-ray dose-equivalent CT for assessing calcified atherosclerotic burden of the thoracic aorta.

OBJECTIVE: To determine the value of ultralow-dose chest CT for estimating the calcified atherosclerotic burden of the thoracic aorta using tin-filter CT and compare its diagnostic accuracy with chest direct radiography. METHODS: A total of 106 patients from a prospective, IRB-approved single-centre study were included and underwent standard dose chest CT (1.7 ± 0.7 mSv) by clinical indication followed by ultralow-dose CT with 100 kV and spectral shaping by a tin filter (0.13 ± 0.01 mSv) to achieve chest X-ray equivalent dose in the same session. Two independent radiologists reviewed the CT images, rated image quality and estimated presence and extent of calcification of aortic valve, ascending aorta and aortic arch. Conventional radiographs were also reviewed for presence of aortic calcifications. RESULTS: The sensitivity of ultralow-dose CT for the detection of calcifications of the aortic valve, ascending aorta and aortic arch was 93.5, 96.2 and 96.2%, respectively, compared with standard dose CT. The sensitivity for the detection of thoracic aortic calcification was significantly lower on chest X-ray (52.3%) compared with ultralow-dose CT (p < 0.001). CONCLUSION: A reliable estimation of calcified atherosclerotic burden of the thoracic aorta can be achieved with modern tin-filter CT at dose values comparable to chest direct radiography. Advances in knowledge: Our findings suggest that ultralow-dose CT is an excellent tool for assessing the calcified atherosclerotic burden of the thoracic aorta with higher diagnostic accuracy than conventional chest radiography and importantly without the additional cost of increased radiation dose.

Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial.

OBJECTIVES: To demonstrate non-inferiority of iobitridol 350 for coronary CT angiography (CTA) compared to higher iodine content contrast media regarding rate of patients evaluable for the presence of coronary artery stenoses. METHODS: In this multicentre trial, 452 patients were randomized to receive iobitridol 350, iopromide 370 or iomeprol 400 and underwent coronary CTA using CT systems with 64-detector rows or more. Two core lab readers assessed 18 coronary segments per patient regarding image quality (score 0 = non diagnostic to 4 = excellent quality), vascular attenuation, signal and contrast to noise ratio (SNR, CNR). Patients were considered evaluable if no segment had a score of 0. RESULTS: Per-patient, the rate of fully evaluable CT scans was 92.1, 95.4 and 94.6 % for iobitridol, iopromide and iomeprol, respectively. Non-inferiority of iobitridol over the best comparator was demonstrated with a 95 % CI of the difference of [-8.8 to 2.1], with a pre-specified non-inferiority margin of -10 %. Although average attenuation increased with higher iodine concentrations, average SNR and CNR did not differ between groups. CONCLUSIONS: With current CT technology, iobitridol 350 mg iodine/ml is not inferior to contrast media with higher iodine concentrations in terms of image quality for coronary stenosis assessment. KEY POINTS: • Iodine concentration is an important parameter for image quality in coronary CTA. • Contrast enhancement must be balanced against the amount of iodine injected. • Iobitridol 350 is non-inferior compared to CM with higher iodine concentrations. • Higher attenuation with higher iodine concentrations, but no SNR or CNR differences.

Individual patient data meta-analysis for the clinical assessment of coronary computed tomography angiography: protocol of the Collaborative Meta-Analysis of Cardiac CT (CoMe-CCT).

BACKGROUND: Coronary computed tomography angiography has become the foremost noninvasive imaging modality of the coronary arteries and is used as an alternative to the reference standard, conventional coronary angiography, for direct visualization and detection of coronary artery stenoses in patients with suspected coronary artery disease. Nevertheless, there is considerable debate regarding the optimal target population to maximize clinical performance and patient benefit. The most obvious indication for noninvasive coronary computed tomography angiography in patients with suspected coronary artery disease would be to reliably exclude significant stenosis and, thus, avoid unnecessary invasive conventional coronary angiography. To do this, a test should have, at clinically appropriate pretest likelihoods, minimal false-negative outcomes resulting in a high negative predictive value. However, little is known about the influence of patient characteristics on the clinical predictive values of coronary computed tomography angiography. Previous regular systematic reviews and meta-analyses had to rely on limited summary patient cohort data offered by primary studies. Performing an individual patient data meta-analysis will enable a much more detailed and powerful analysis and thus increase representativeness and generalizability of the results. The individual patient data meta-analysis is registered with the PROSPERO database (CoMe-CCT, CRD42012002780). METHODS/DESIGN: The analysis will include individual patient data from published and unpublished prospective diagnostic accuracy studies comparing coronary computed tomography angiography with conventional coronary angiography. These studies will be identified performing a systematic search in several electronic databases. Corresponding authors will be contacted and asked to provide obligatory and additional data. Risk factors, previous test results and symptoms of individual patients will be used to estimate the pretest likelihood of coronary artery disease. A bivariate random-effects model will be used to calculate pooled mean negative and positive predictive values as well as sensitivity and specificity. The primary outcome of interest will be positive and negative predictive values of coronary computed tomography angiography for the presence of coronary artery disease as a function of pretest likelihood of coronary artery disease, analyzed by meta-regression. As a secondary endpoint, factors that may influence the diagnostic performance and clinical value of computed tomography, such as heart rate and body mass index of patients, number of detector rows, and administration of beta blockade and nitroglycerin, will be investigated by integrating them as further covariates into the bivariate random-effects model. DISCUSSION: This collaborative individual patient data meta-analysis should provide answers to the pivotal question of which patients benefit most from noninvasive coronary computed tomography angiography and thus help to adequately select the right patients for this test.

Combining cardiac magnetic resonance and computed tomography coronary calcium scoring: added value for the assessment of morphological coronary disease?

To investigate prospectively, in patients with suspicion of coronary artery disease (CAD), the added value of coronary calcium scoring (CS) as adjunct to cardiac magnetic resonance (CMR) for the diagnosis of morphological coronary stenosis in comparison to catheter angiography (CA). Sixty consecutive patients (8 women; 64 ± 10 years) referred to CA underwent CMR (1.5 T) including perfusion and late gadolinium-enhancement imaging as well as CS with computed tomography. Diagnostic performance was evaluated for CMR and CS separately, and for both methods combined, with CA as reference standard. Best CS threshold combined with a specificity >90% to predict significant stenosis in patients without abnormalities on CMR was determined from receiver operator characteristics (ROC) analysis. Abnormal CMR results were considered to indicate significant stenosis regardless of CS; CS above threshold reclassified patients to have CAD regardless of CMR. CA identified 104/960 (11%) coronary segments with coronary artery stenosis >50% in 36/60 (60%) patients. ROC revealed an area-under-the-curve of 0.83 (95%CI: 0.68-0.99) with the best CS threshold of 495 Agatston score (sensitivity 50%). CMR depicted 128/960 (13%) myocardial segments with abnormalities in 31/60 (52%) patients. Sensitivity, specificity, negative (NPV) and positive predictive value (PPV) of CMR were 78, 88, 72 and 90%. When adding CS to CMR, sensitivity and NPV increased to 89 and 83%, while specificity and PPV slightly decreased to 83 and 89%. Accuracy of the combined approach (87%) was significantly (P < 0.05) higher than that of CMR (82%) alone. Adding CS to CMR improves the accuracy for the detection of morphological CAD.

High-pitch 128-slice dual-source CT for the assessment of coronary stents in a phantom model.

RATIONALE AND OBJECTIVES: To evaluate the quality of stent lumen delineation using dual-source computed tomography (DSCT) in the standard-pitch mode (SP) as compared to the high-pitch mode (HP) in a phantom study. MATERIALS AND METHODS: Forty different coronary stents placed in plastic tubes filled with contrast agent were imaged with a second generation DSCT system in a SP (pitch 0.23) and HP (pitch 3.4) mode in orientations of 0°, 45°, and 90° relative to the z-axis. Two observers independently measured the in-stent lumen and the attenuation values in the center of the stents. The artificial lumen narrowing (ALN) was calculated using the measured in-stent lumen and the nominal diameter of the plastic tube. RESULTS: Interobserver correlation was excellent for in-stent lumen (0.86) and attenuation measurements (0.91). There was no significant difference neither for ALN (SP: 54.7-62.8%; HP: 55.8-64.0%) nor attenuation (SP: 356-395 Hounsfield units [HU]; HP: 352-384 HU) between SP and HP mode. For both modes, the orientation of the stent relative to the z-axis significantly affected ALN and attenuation (each P < .001). CT volume dose index was significantly lower using HP mode as compared to SP mode (P < .001). CONCLUSION: The HP mode in DSCT provides visualization of the coronary in-stent lumen comparable to that measured in SP mode while reducing applied radiation dose in a stationary phantom model.

High-pitch dual-source CT angiography of the thoracic and abdominal aorta: is simultaneous coronary artery assessment possible?

OBJECTIVE: The purpose of this study was to prospectively evaluate the average heart rate and heart rate variability required for diagnostic imaging of the coronary arteries with high-pitch dual-source CT angiography of the thoracic and thoracoabdominal aorta. SUBJECTS AND METHODS: One hundred consecutively registered patients (82 men, 18 women; mean age, 68 +/- 13 years) underwent clinically indicated CT angiography of the thoracic (n = 33) and thoracoabdominal (n = 67) aorta with a dual-source 128-MDCT scanner in ECG-synchronized high-pitch (pitch, 3.2) data acquisition mode. No beta-blockers were administered. The image quality of the coronary arteries was graded on a 3-point scale by two independent blinded readers. The average heart rate and heart rate variability before data acquisition were noted. Effective radiation doses were calculated. RESULTS: Interobserver agreement on grade of image quality for the 1,414 coronary segments evaluated by both observers was good (kappa = 0.68). Diagnostic image quality was found for 1,375 of the 1,414 segments (97.2%) in 83 of 100 patients (83%). In 17% of the patients, image quality was nondiagnostic for at least one coronary artery segment. Average heart rate and heart rate variability (each p < 0.05) were significantly higher in patients with at least one nondiagnostic coronary segment compared with those without. All patients with an average heart rate less than 63 beats/min and heart rate variability less than 1.2 beats/min had diagnostic image quality in all coronary segments. Effective radiation doses were 2.3 +/- 0.3 mSv for thoracic and 4.4 +/- 0.5 mSv for thoracoabdominal CT angiography. The average scan times were 0.88 +/- 0.06 second for thoracic and 1.67 +/- 0.15 seconds for thoracoabdominal CT angiography. CONCLUSION: For patients with an average heart rate less than 63 beats/min and heart rate variability less than 1.2 beats/min, dual-source CT angiography of the thoracoabdominal aorta at a high pitch of 3.2 delivers diagnostic depiction of the coronary arteries at a low radiation dose.

Coronary artery disease in patients with cardiac tumors: preoperative assessment by computed tomography coronary angiography.

We studied the diagnostic accuracy of computed tomography coronary angiography (CTCA) for the diagnosis of significant coronary artery disease (CAD) compared to conventional coronary angiography (CCA) in patients with primary cardiac tumors. Thirty-eight consecutive patients with primary cardiac tumors (27 females, 11 males; mean age 56+/-6 years, range 32-86 years) underwent dual-source CTCA and CCA. Significant stenosis was defined as diameter reduction >50%. CCA served as the standard of reference. The prevalence of significant CAD in the study population was 8% (3/38 patients). Five of 544 segments (0.9%) in 1/38 patients (2.6%) was considered of non-diagnostic image quality on CTCA because of motion artifacts. In a segment-based analysis taking not-evaluative segments as false-positive, sensitivity, specificity, positive and negative predictive value of CT was 100%, 99%, 70%, and 100%, respectively. Preoperative CCA could have been avoided in 95% (36/38) of the patients and CCA would have confirmed the CTCA diagnosis in 5% (2/38) of the patients. Our results indicate that CTCA provides a high diagnostic performance for diagnosing significant CAD in patients with primary cardiac tumors. CTCA may thus be used as a filter test prior to surgery.

Diagnostic accuracy of high-pitch dual-source CT for the assessment of coronary stenoses: first experience.

OBJECTIVES: The objective was to prospectively investigate the diagnostic accuracy of high-pitch (HP) dual-source computed tomography coronary angiography (CTCA) compared with catheter coronary angiography (CCA) for the diagnosis of significant coronary stenoses. METHODS: Thirty-five patients (seven women; mean age 62 ± 8 years) underwent both CTCA and CCA. CTCA was performed with a second-generation dual-source CT system permitting data acquisition at an HP of 3.4. Patients with heart rates >60 bpm were excluded from study enrolment. All coronary segments were evaluated by two blinded and independent observers with regard to image quality on a four-point scale (1: excellent to 4: non-diagnostic) and for the presence of significant coronary stenoses (defined as diameter narrowing exceeding 50%). CCA served as the standard of reference. Radiation dose values were calculated using the dose-length product. RESULTS: Diagnostic image quality was found in 99% of all segments (455/459). Non-diagnostic image quality occurred in a single patient with a sudden increase in heart rate immediately before and during CTCA. Taking segments with non-evaluative image quality as positive for disease, the sensitivity, specificity and positive and negative predictive values were 94, 96, 80 and 99% per segment and 100, 91, 88 and 100% per patient. The effective radiation dose was on average 0.9 ± 0.1 mSv. CONCLUSION: In patients with heart rates ≤60 bpm, CTCA using the HP mode of the dual-source CT system is associated with high diagnostic accuracy for the assessment of coronary artery stenoses at sub-milli-Sievert doses.

Aortic regurgitation: assessment with 64-section CT.

PURPOSE: To prospectively evaluate diagnostic accuracy of 64-section computed tomography (CT) for evaluation of aortic regurgitation (AR), with transthoracic echocardiography (TTE) as reference. MATERIALS AND METHODS: The institutional review board approved this study; written informed consent was obtained. Thirty patients (23 men, seven women; mean age, 56.6 years) with AR underwent TTE and retrospective electrocardiographically gated 64-section CT. CT data sets were reconstructed in 5% steps from 40% to 90% of R-R interval for analysis. Maximum regurgitant orifice area (ROA) in diastole was planimetrically measured with CT, and measurements were compared with semiquantitative classification with TTE (Spearman rank order correlation coefficients). Receiver operating characteristic (ROC) curves were calculated for differentiation between degrees of AR with ROA measurements. Dimensions of the aortic root and left ventricular parameters were compared (Pearson correlation analysis). RESULTS: A significant correlation was observed between CT planimetric size of ROA (mean, 62 mm2+/-63 [standard deviation]; range, 6-224 mm2) and TTE classification of mild, moderate, and severe AR (r=0.84, P<.001). With ROC analysis, discrimination between degrees of AR with CT was highly accurate when cutoff ROAs (25 mm2 and 75 mm2) were used. A significant correlation was observed between methods in dimensions of aortic annulus (mean, 29.0 mm+/-4.6), sinus of Valsalva (mean, 38.3 mm+/-8.6), and ascending aorta (mean, 37.2 mm+/-8.0); mean values were 27.4 mm+/-4.9 (r=0.76, P<.001), 37.7 mm+/-8.6 (r=0.94, P<.001), and 38.2 mm+/-7.9 (r=0.96, P<.001), respectively. Mean end-systolic volume (67 mL+/-38), end-diastolic volume (149 mL+/-48), and ejection fraction (57%+/-13) at CT correlated well with mean results at TTE (65 mL+/-36 [r=0.96, P<.001], 140 mL+/-48 [r=0.91, P<.001], 56%+/-13 [r=0.98, P<.001], respectively). CONCLUSION: Results of assessment of AR with 64-section CT are similar to those with TTE.

Image quality of the aortic and mitral valve with CT: relative versus absolute delay reconstruction.

RATIONALE AND OBJECTIVE: The purpose of this study was to compare image quality and artifacts of 16-detector row CT imaging of the aortic and mitral valve when performing ECG-gated synchronization using relative and absolute reconstructions. MATERIALS AND METHODS: Cardiac CT was performed in 22 consecutive patients; 20 data sets per RR interval were reconstructed with relative and absolute reconstructions. Mean and variability of heart rate during data acquisition were noted. Two readers assessed contrast media-related artifacts, calcification-related artifacts, ECG gating-related artifacts, and image quality in parallel and perpendicular planes. RESULTS: Contrast media-related and calcification-related artifacts similarly occurred with both reconstruction techniques. ECG gating-related artifacts occurred in both valves more often with relative reconstructions than with absolute reconstructions (p = .001). Image quality was significantly better for absolute reconstructions for the open aortic cusp surface (p = .014) and edge (p = .008) in both planes, and of the closed mitral valve leaflets (p = .003) and apposition zone (p = .003) in perpendicular planes. Occurrence of ECG gating-related artifacts in both valves significantly correlated (p = .01) with heart rate variability for relative reconstructions, whereas no correlation was found using the absolute technique. CONCLUSION: Absolute reconstructions allow CT imaging of the aortic and mitral valve with fewer artifacts and are less sensitive to heart rate variability as compared to relative reconstructions.

Thick maximum intensity projections for the assessment of left ventricular function with 64-slice computed tomography.

OBJECTIVE: The objective of this study was to assess the accuracy of thick maximum intensity projections (MIP) from computed tomography (CT) data sets mimicking projection images from biplane ventriculography for evaluation of left ventricular (LV) parameters. MATERIALS AND METHODS: Fifty-eight patients underwent 64-slice CT. Multiphase images were reconstructed in 10% steps of the RR interval. MIP images (70-mm thickness) of the contrast-enhanced LV in fixed 30 degrees right anterior oblique (RAO)/60 degrees left anterior oblique (LAO) and in adapted short-/long-axis planes were reconstructed. LV parameters were calculated using the area-length method formula. Three-dimensional assessment with semiautomated software served as reference standard. RESULTS: Use of thick MIP reconstructions had a high intermethod reliability (86-94%) compared with the 3-dimensional approach. Smaller measurement errors were found for thick MIP reconstructions in adapted short-/long-axis planes. A significant projection error (3.0%, P < 0.001) of thick MIP reconstructions was found using fixed 30 degrees RAO/60 degrees LAO compared with adapted short-/long-axis reconstructions. CONCLUSION: Thick MIP reconstructions with adapted short-/long-axis planes allow an accurate assessment of LV parameters compared with the established 3-dimensional method.