Cardiac Computed Tomography for Atrial Fibrillation Patients Undergoing Ablation: Implications for the Prediction of Early Recurrence.

OBJECTIVE: The objective of this study was to correlate early recurrence of atrial fibrillation (AF) after ablation with noninvasive imaging using cardiac computed tomography (CT). METHODS: CT image data of 260 patients who had undergone wide area circumferential ablation (WACA) between October 2005 and August 2010 as well as from 30 subjects in sinus rhythm without a history of AF (control group) were retrospectively analyzed. To evaluate early outcome of AF ablation, all AF patients underwent follow-up with a 30-day event monitor 3 to 4 months after ablation. In addition, a cardiac CT was also performed 3 to 4 months after ablation to exclude pulmonary vein (PV) stenosis. The presence of early AF was correlated with anatomic and functional PV and left atrial parameters, as assessed by cardiac CT. RESULTS: A total of 70 patients (26.9%) were found to have early recurrence of AF. However, we found no association between PV or left atrial anatomic or functional parameters derived from cardiac imaging with early AF recurrence. Furthermore, no correlation (P>0.05) between AF recurrence and coronary artery stenosis, anatomic origin of the sinoatrial, or atrioventricular nodal arteries was observed. Finally, PV contraction did not predict AF recurrence. However, when comparing PV contraction in WACA patients with the control group, a significant (P<0.05) reduction in left superior PV and right superior PV contractility was found in patients after radiofreqency ablation. CONCLUSIONS: In our relatively large cohort, cardiac CT did not yield any anatomic or functional markers for the prediction of early AF recurrence after undergoing WACA. However, our data may provide insights into functional changes that occur following ablation procedures.

Segmentations of the cartilaginous skeletons of chondrichthyan fishes by the use of state-of-the-art computed tomography.

AIM: To apply dual-source multidetector computed tomography (DSCT) scanning technology in conjunction with computationally assisted segmentation in order to explore and document skeletal variation that has occurred over the course of evolution. METHODS: We examined 4 divergent species of elasmobranchs with high-resolution 3rd generation DSCT. The formalin prepared species examined were: Aptychotrema vincentiana, Mitsukurina owstoni, Negaprion brevirostris and Dactylobatus armatus. RESULTS: All three structures of the hyoid arch (hyomandibular, ceratohyal, and basihyal) were clearly visible whereas in the two batoids, the hyomandibular was the prominent feature, the ceratohyal was not visible and the basihyal was more reduced and closer to the gill arches. The general shape of the puboischiadic bar, or pelvic girdle, illustrated a closer relationship between the two sharks and the two batoids than between the two groups. CONCLUSION: In exquisite detail, DSCT imaging revealed important morphological variations in various common structures in the four elasmobranch specimens studied, providing insights into their evolutionary diversification.

Low contrast medium-volume third-generation dual-source computed tomography angiography for transcatheter aortic valve replacement planning.

PURPOSE: To investigate feasibility, image quality and safety of low-tube-voltage, low-contrast-volume comprehensive cardiac and aortoiliac CT angiography (CTA) for planning transcatheter aortic valve replacement (TAVR). MATERIALS AND METHODS: Forty consecutive TAVR candidates prospectively underwent combined CTA of the aortic root and vascular access route (270 mgI/ml iodixanol). Patients were assigned to group A (second-generation dual-source CT [DSCT], 100 kV, 60 ml contrast, 4.0 ml/s flow rate) or group B (third-generation DSCT, 70 kV, 40 ml contrast, 2.5 ml/s flow rate). Vascular attenuation, noise, signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were compared. Subjective image quality was assessed by two observers. Estimated glomerular filtration (eGFR) at CTA and follow-up were measured. RESULTS: Besides a higher body-mass-index in group B (24.8±3.8 kg/m2 vs. 28.1±5.4 kg/m2, P=0.0339), patient characteristics between groups were similar (P≥0.0922). Aortoiliac SNR (P=0.0003) was higher in group B. Cardiac SNR (P=0.0003) and CNR (P=0.0181) were higher in group A. Subjective image quality was similar (P≥0.213) except for aortoiliac image noise (4.42 vs. 4.12, P=0.0374). TAVR-planning measurements were successfully obtained in all patients. There were no significant changes in eGFR among and between groups during follow-up (P≥0.302). CONCLUSION: TAVR candidates can be safely and effectively evaluated by a comprehensive CTA protocol with low contrast volume using low-tube-voltage acquisition. KEY POINTS: • Third-generation dual-source CT facilitates low-tube-voltage acquisition. • TAVR planning can be performed with reduced contrast volume and radiation dose. • TAVR-planning CT did not result in changes in creatinine levels at follow-up. • TAVR candidates can be safely evaluated by comprehensive low-tube-voltage CT angiography.

Semiautomated Global Quantification of Left Ventricular Myocardial Perfusion at Stress Dynamic CT:: Diagnostic Accuracy for Detection of Territorial Myocardial Perfusion Deficits Compared to Visual Assessment.

RATIONALE AND OBJECTIVES: To evaluate the diagnostic accuracy of semiautomated global quantification of left ventricular myocardial perfusion derived from stress dynamic computed tomography myocardial perfusion imaging (CTMPI) for detection of territorial perfusion deficits (PD). MATERIALS AND METHODS: Dynamic CTMPI datasets of 71 patients were analyzed using semiautomated volume-based software to calculate global myocardial blood flow (MBF), myocardial blood volume, and volume transfer constant. Optimal cutoff values to assess the diagnostic accuracy of these parameters for detection of one- to three-vessel territories with PD in comparison to visual analysis were calculated. RESULTS: Nonsignificant differences (P = 0.694) were found for average global MBF in patients without PD and single-territorial PD. Significant differences were found for mean global MBF in patients with PD in two (P < 0.0058) and three territories (P < 0.0003). Calculated optimal thresholds for global MBF and myocardial blood volume resulted in a sensitivity, specificity, and negative predictive value of 100% for detection of three-vessel territory PD. For detection of ≥2 territories with PD, global MBF was superior to other parameters (sensitivity 81.3%, specificity 90.9%, and negative predictive value 94.3%). CONCLUSIONS: Semiautomated global quantification of left ventricular MBF during stress dynamic CTMPI shows high diagnostic accuracy for detection of ≥2 vessel territories with PD, facilitating identification of patients with multi-territorial myocardial PD.

Approaches to ultra-low radiation dose coronary artery calcium scoring based on 3rd generation dual-source CT: A phantom study.

OBJECTIVES: To investigate to what extent 3rd generation dual-source computed tomography (DSCT) can reduce radiation dose in coronary artery calcium scoring. METHODS: Image acquisition was performed using a stationary calcification phantom. Prospectively electrocardiogram (ECG)-triggered 120 kV sequential, and 120 and Sn100 kV ultra-high pitch (UHP) acquisitions were performed with different tube currents (80, 60, 40, 20 mA). Images were reconstructed using filtered back projection (FBP) and 3rd generation iterative reconstruction (IR). Contrast-to-noise ratio (CNR), Agatston score, calcium volume, and radiation dose were assessed. For statistical analysis Friedman tests and Wilcoxon rank sum tests were used. RESULTS: Even at reduced tube currents, the three acquisition techniques did not show significant differences in Agatston score (p=0.4) or calcium volume (p=0.08) with FBP reconstruction. Calcium volumes were significantly lower for 3rd generation IR compared to FBP reconstructions (p<0.01). CTDIvol for the 120 kV sequential, 120 and Sn100 kV UHP acquisitions at 80 and 20 mA were 1.2-0.37, 0.48-0.17, and 0.07-0.02 mGy, respectively. CONCLUSION: 3rd generation DSCT enabled a reduction of tube current in both the sequential and UHP acquisitions without significantly affecting coronary calcium scoring. Tin filtered 100 kV scanning may allow accurate quantification of calcium score without correction of the HU threshold.

Quantitative evaluation of beam-hardening artefact correction in dual-energy CT myocardial perfusion imaging.

OBJECTIVES: To assess quantitatively the impact of a novel reconstruction algorithm ("kernel") with beam-hardening correction (BHC) on beam-hardening artefacts of the myocardium at dual-energy CT myocardial perfusion imaging (DE-CTMPI). METHODS: Rest-series of DE-CTMPI examinations from 14 patients were retrospectively analyzed. Six image series were reconstructed for each patient: a) 100 kV, b) 140 kV, and c) linearly blended MIX0.5, each with BHC (D33f kernel) and without (D30f kernel). Seven hundred and fifty-six myocardial regions were assessed. Seven equal regions of interest divided the myocardium in the axial section. Three subdivisions were created within these regions in areas prone to BHA. Reports of SPECT studies performed within 30 days of CT examination were used to confirm the presence and location of true perfusion defects. Paired student t-test was used for statistical evaluation. RESULTS: Overall mean myocardial attenuation was lower using BHC (D30f: 87.3 ± 24.1 HU; D33f: 85.5 ± 21.5 HU; p = 0.009). Overall relative difference from average myocardial attenuation (RDMA) was more homogeneous using BHC (D30f: -0.3 ± 11.4 %; D33f: 0.1 ± 10.1 %; p < 0.001). Changes in RDMA were greatest in the posterobasal myocardium (D30f: -16.2 ± 10.0 %; D33f: 3.4 ± 10.7 %; p < 0.001). CONCLUSIONS: A dedicated reconstruction algorithm with BHC can significantly reduce beam-hardening artefacts in DE-CTMPI. KEY POINTS: • Beam-hardening artefacts (BHA) cause interference with attenuation-based CT myocardial perfusion assessment (CTMPI). • BHA occur mostly in the posterobasal left ventricular wall. • Beam-hardening correction homogenized and decreased mean myocardial attenuation. • BHC can help avoid false-positive findings and increase specificity of static CTMPI.

Prospectively ECG-triggered high-pitch 80 kVp coronary computed tomography angiography with 30 mL of 270 mg I/mL contrast material and iterative reconstruction.

BACKGROUND: The smallest diagnostically appropriate amount of contrast medium should be used in coronary computed tomography angiography (CCTA). PURPOSE: To investigate the feasibility of prospectively ECG-triggered high-pitch CCTA using 30 mL of 270 mg I/mL contrast material, 80 kVp, and iterative reconstruction (IR). MATERIAL AND METHODS: Eighty-two consecutive patients underwent CCTA with a prospectively ECG-triggered high-pitch protocol. Forty-three patients were examined at 100 kVp with filtered back projection after 60 mL of 370 mg I/mL contrast material was administered. Another 39 patients were examined at 80 kVp with IR after 30 mL of 270 mg I/mL contrast material was administered. Subjective and objective image quality was evaluated for each patient. Radiation doses were estimated and compared. RESULTS: Mean attenuation, noise and signal-to-noise ratio in 80 kVp group were significantly lower than in 100 kVp group (all P < 0.05), while there was no significant difference in contrast-to-noise ratio (CNR), although a trend towards a lower CNR in 80 kVp group was observed (P = 0.099). The subjective image quality between the two groups was not significantly different (P = 0.905). The effective dose and iodine load in 80 kVp group were reduced by 54% and 64%, respectively, when compared with 100 kVp group. CONCLUSION: Prospectively ECG-triggered high-pitch CCTA at 80 kVp with 30 mL of 270 mg I/mL contrast material and IR is feasible for patients with BMI less than 25 kg/m(2) and reduces radiation dose and iodine load when compared with the standard CCTA protocol.

Effect of reduced x-ray tube voltage, low iodine concentration contrast medium, and sinogram-affirmed iterative reconstruction on image quality and radiation dose at coronary CT angiography: results of the prospective multicenter REALISE trial.

BACKGROUND: Both low tube voltage and sinogram-affirmed iterative reconstruction (IR) techniques hold promise to decrease radiation dose at coronary CT angiography (CCTA). The increased iodine contrast at low tube voltage allows for minimizing iodine load. OBJECTIVE: To assess the effect of reduced x-ray tube voltage, low iodine concentration contrast medium and IR on image quality and radiation dose at CCTA. METHODS: Two hundred thirty-one consecutive patients with suspected coronary artery disease were enrolled in this prospective, multicenter trial and randomized to 1 of 2 dual-source CCTA protocols: 120-kVp with 370 mgI/mL iopromide or iopamidol (n = 116; 44 women; 55.3 ± 9.8 years) or 100 kVp with 270 mgI/mL iodixanol (n = 115; 48 women; 54.2 ± 10.4 years). Reconstruction was performed with filtered back projection and IR. Attenuation, image noise, signal-to-noise ratio, and contrast-to-noise ratio were measured and image quality scored. Size-specific dose estimates and effective doses were calculated. RESULTS: There were no significant differences in mean arterial attenuation (406.6 ± 76.7 vs 409.7 ± 65.2 Hounsfield units; P = .739), image noise (18.7 ± 3.8 vs 17.9 ± 3.4 Hounsfield units; P = .138), signal-to-noise ratio (22.5 ± 5.4 vs 23.7 ± 6.1; P = .126), contrast-to-noise ratio (17.5 ± 5.5 vs 18.3 ± 6.1; P = .286), or image quality scores (4.1 ± 0.9 vs 4.0 ± 0.9; P > .05) between 120-kVp filtered back projection-reconstructed and 100-kVp IR-reconstructed series. Mean iodine dose was 26.5% lower (18.3 ± 0.5 vs 24.9 ± 0.9 g; P < .0001), mean size-specific dose estimate was 35.1% lower (17.9 ± 6.6 vs 27.5 ± 8.2 mGy; P < .0001), and effective dose was 34.9% lower (2.3 ± 1.0 vs 3.5 ± 1.1 mSv; P < .0001) with the 100 kVp compared with the 120-kVp protocol, respectively. CONCLUSION: Using low x-ray tube voltage and IR allows for decreasing the iodine load and effective radiation dose at CCTA while maintaining image quality.

Computed tomography of acute pulmonary embolism: state-of-the-art.

Multidetector computed tomography (CT) plays an important role in the detection, risk stratification and prognosis evaluation of acute pulmonary embolism. This review will discuss the technical improvements for imaging peripheral pulmonary arteries, the methods of assessing pulmonary embolism severity based on CT findings, a multidetector CT technique for pulmonary embolism detection, and lastly, how to avoid overutilization of CT pulmonary angiography and overdiagnosis of pulmonary embolism. Key Points • We describe clinical prediction rules and D-dimers for pulmonary embolism evaluation. • Overutilization of CT pulmonary angiography and overdiagnosis of pulmonary embolism should be avoided. • We discuss technical improvements for imaging peripheral pulmonary arteries. • Pulmonary embolism severity can be assessed based on CT findings. • We discuss multidetector CT techniques for pulmonary embolism detection.

Coronary In-Stent Restenosis: Assessment with Corrected Coronary Opacification Difference across Coronary Stents Measured with CT Angiography.

PURPOSE: To determine whether changes in coronary opacification normalized to the aorta (corrected coronary opacification [CCO]) across stents can help identify in-stent restenosis (ISR) severity with use of invasive coronary angiography as the standard of reference. MATERIALS AND METHODS: This study was approved by the institutional review board, and the requirement to obtain informed consent was waived. The authors retrospectively analyzed 106 patients (88 men, 18 women; mean age, 59.6 years ± 10.4; age range, 36-84 years) who had previously undergone stent implantation within 3 months of coronary computed tomographic (CT) angiography. Attenuation values in the coronary lumen were measured proximal and distal to the stents and normalized to the descending aorta. The CCO difference across the stent was compared with the severity of ISR. One-way analysis of variance least significant difference was used for comparison. RESULTS: A total of 141 stents were assessed. Seventy-six stents were normally patent, 18 had ISR of less than 50%, 28 had ISR of 50%-99%, and 19 were fully occluded. The median CCO differences in the four groups were 0.078, 0.163, 0.346, and 0.606, respectively. There was no significant difference between stents with an ISR of at least 50% and those with total occlusion (P = .056), although the other groups had significant differences at pairwise comparison (P < .01 for all). For stents smaller than 3 mm in diameter, the median CCO differences in the four groups were 0.086, 0.136, 0.390, and 0.471, respectively. The CCO differences across normal stents and stents with ISR of less than 50% were significantly less than those across stents with an ISR of at least 50% and those with total occlusion (P < .01 for all). There were no significant differences between stents with no ISR and those with an ISR of less than 50% (P = .821) and between stents with an ISR of at least 50% and those with an ISR of 100% (P = .836). CONCLUSION: The CCO difference across coronary stents is related to ISR severity in obstructive ISR in stents smaller than 3 mm in diameter.

Delayed adverse reactions to the parenteral administration of iodinated contrast media.

OBJECTIVE: This article presents an overview of delayed adverse reactions (DARs) to parenteral iodinated contrast media and discusses the clinical nature, risk factors, mechanisms, and potential economic implications of these DARs. CONCLUSION: DARs to contrast media are not rare but are often not recognized as being linked to contrast administration and may be falsely ascribed to other drugs. These side effects are problematic because the patient is usually without medical supervision.

High-pitch computed tomography pulmonary angiography with iterative reconstruction at 80 kVp and 20 mL contrast agent volume.

OBJECTIVES: To evaluate the image quality, radiation dose and diagnostic accuracy of 80kVp, high-pitch CT pulmonary angiography (CTPA) with iterative reconstruction using 20 ml of contrast agent. METHODS: One hundred patients with suspected pulmonary embolism (PE) were randomly divided into two groups (n = 50 each; group A, 100 kVp, 1.2 pitch, 60 ml of contrast medium and filtered back projection algorithm; group B, 80 kVp, 2.2 pitch, 20 ml of contrast medium and sinogram affirmed iterative reconstruction). Image quality, diagnostic accuracy and radiation dose were evaluated and compared. RESULTS: Mean CT numbers of pulmonary arteries in group B were higher than those in group A (all P < 0.001). Contrast-to-noise ratio and signal-to-noise ratio of group B were higher than those of group A (both P < 0.001). There was no significant difference in subjective image quality scores between two groups (P = 0.807). The interobserver agreement was excellent (k = 0.836). There was no significant difference in diagnostic accuracy between the two groups (P > 0.05). Compared with group A, radiation dose of group B was reduced by 50.3% (P < 0.001). CONCLUSIONS: High-pitch CTPA at 80 kVp can obtain sufficient image quality in normal-weight individuals with 20 ml of contrast agent and half the radiation dose of a conventional CTPA protocol. KEY POINTS: CTPA is feasible at 80 kVp using only 20 ml of contrast agent. High-pitch CTPA at 80 kVp has an effective dose under 1 mSv. This CTPA protocol can obtain sufficient image quality in normal-weight individuals.

Is contrast medium osmolality a causal factor for contrast-induced nephropathy?

The exact pathophysiology of contrast-induced nephropathy (CIN) is not fully clarified, yet the osmotic characteristics of contrast media (CM) have been a significant focus in many investigations of CIN. Osmotic effects of CM specific to the kidney include transient decreases in blood flow, filtration fraction, and glomerular filtration rate. Potentially significant secondary effects include an osmotically induced diuresis with a concomitant dehydrating effect. Clinical experiences that have compared the occurrence of CIN between the various classes of CM based on osmolality have suggested a much less than anticipated advantage, if any, with a lower osmolality. Recent animal experiments actually suggest that induction of a mild osmotic diuresis in association with iso-osmolar agents tends to offset potentially deleterious renal effects of high viscosity-mediated intratubular CM stagnation.

Low tube voltage and low contrast material volume cerebral CT angiography.

OBJECTIVES: To evaluate the image quality, radiation dose and diagnostic accuracy of low kVp and low contrast material volume cerebral CT angiography (CTA) in intracranial aneurysm detection. METHODS: One hundred twenty patients were randomly divided into three groups (n = 40 for each): Group A, 70 ml iodinated contrast agent/120 kVp; group B, 30 ml/100 kVp; group C, 30 ml/80 kVp. The CT numbers, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in the internal carotid artery (ICA) and middle cerebral artery (MCA). Subjective image quality was evaluated. For patients undergoing DSA, diagnostic accuracy of CTA was calculated with DSA as reference standard and compared. RESULTS: CT numbers of ICA and MCA were higher in groups B and C than in group A (P < 0.01). SNR and CNR in groups A and B were higher than in group C (both P < 0.05). There was no difference in subjective image quality among the three groups (P = 0.939). Diagnostic accuracy for aneurysm detection among these groups had no statistical difference (P = 1.00). Compared with group A, the radiation dose of groups B and C was decreased by 45% and 74%. CONCLUSION: Cerebral CTA at 100 or 80 kVp using 30 ml contrast agent can obtain diagnostic image quality with a low radiation dose while maintaining the same diagnostic accuracy for aneurysm detection. KEY POINTS: • Cerebral CTA is feasible using 100/80 kVp and 30 ml contrast agent. • This approach obtains diagnostic image quality with 45-74% radiation dose reduction. • Diagnostic accuracy for intracranial aneurysm detection seems not to be compromised.

Dynamic CT myocardial perfusion imaging: performance of 3D semi-automated evaluation software.

OBJECTIVES: To evaluate the performance of three-dimensional semi-automated evaluation software for the assessment of myocardial blood flow (MBF) and blood volume (MBV) at dynamic myocardial perfusion computed tomography (CT). METHODS: Volume-based software relying on marginal space learning and probabilistic boosting tree-based contour fitting was applied to CT myocardial perfusion imaging data of 37 subjects. In addition, all image data were analysed manually and both approaches were compared with SPECT findings. Study endpoints included time of analysis and conventional measures of diagnostic accuracy. RESULTS: Of 592 analysable segments, 42 showed perfusion defects on SPECT. Average analysis times for the manual and software-based approaches were 49.1 ± 11.2 and 16.5 ± 3.7 min respectively (P < 0.01). There was strong agreement between the two measures of interest (MBF, ICC = 0.91, and MBV, ICC = 0.88, both P < 0.01) and no significant difference in MBF/MBV with respect to diagnostic accuracy between the two approaches for both MBF and MBV for manual versus software-based approach; respectively; all comparisons P > 0.05. CONCLUSIONS: Three-dimensional semi-automated evaluation of dynamic myocardial perfusion CT data provides similar measures and diagnostic accuracy to manual evaluation, albeit with substantially reduced analysis times. This capability may aid the integration of this test into clinical workflows. KEY POINTS: • Myocardial perfusion CT is attractive for comprehensive coronary heart disease assessment. • Traditional image analysis methods are cumbersome and time-consuming. • Automated 3D perfusion software shortens analysis times. • Automated 3D perfusion software increases standardisation of myocardial perfusion CT. • Automated, standardised analysis fosters myocardial perfusion CT integration into clinical practice.

Comparison of epicardial fat volume by computed tomography in black versus white patients with acute chest pain.

Disparities in the risk of coronary artery disease (CAD) between races may be influenced by differences in the thoracic adipose tissue. We compared computed tomography (CT)-derived volumes of epicardial adipose tissue (EAT), mediastinal adipose tissue (MAT), and pericoronary fat thickness (PFT) and correlations with CAD between black and white patients. This institutional review board-approved Health Insurance Portability and Accountability Act-compliant study included 372 age- and gender-matched black versus white patients (186 black, 54 ± 11 years, 50% men; 186 white, 54 ± 11 years, 50% men) who underwent CT for chest pain evaluation. EAT, MAT, and PFT were measured. The amount of coronary calcium was quantified as calcium score. CAD was defined as ≥50% coronary artery narrowing. EAT and MAT volumes were significantly lower in black than white patients (59 [twenty-fifth to seventy-fifth percentile 39 to 84] vs 97 [67 to 132] cm(3) and 44 [27 to 77] vs 87 [52 to 157] cm(3), for both p <0.001). Mean PFT in black patients was slightly lower than white patients (17.2 ± 3.2 vs 18.1 ± 3.4 mm, p <0.01). The relation between race and extent of adipose tissue remained significant after adjustment for cardiovascular risk factors. Significant correlations were observed between EAT and MAT volumes and calcium score in black and white patients (r = 0.19 to 0.26, p <0.01). For both races, the level of thoracic fat measurements was higher in present versus absent coronary calcification. A greater amount of thoracic fat was found with obstructive CAD only in white patients. In conclusion, CT-derived measurements of thoracic fat differ between symptomatic black and white patients, suggesting a differential relation between thoracic adipose tissue and CAD pathophysiology by race.