Chasing the heart: new developments for cardiac CT

Deep learning reconstruction allows for usage of contrast agent of lower concentration for coronary CTA than filtered back projection and hybrid iterative reconstruction

BACKGROUND

The demand for homogeneous and higher vascular contrast enhancement is critical to provide an appropriate interpretation of abnormal vascular findings in coronary computed tomography angiography (CTA).

PURPOSE

To evaluate the effect of various contrast media concentrations (Iohexol-370, Iohexol-300, Iohexol-240) and image reconstructions (filtered back projection [FBP], hybrid iterative reconstruction [IR], and deep learning reconstruction [DLR]) on coronary CTA.

MATERIAL AND METHODS

A total of 63 patients referred for coronary CTA between July and October 2021 were enrolled in this prospective study, and they randomly received one of three contrast media. CTA images were reconstructed with FBP, hybrid IR, and DLR. The CT attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated for all three images. The images were subjectively evaluated by two radiologists in terms of overall image quality, artifacts, image noise, and vessel wall delineation on a 5-point Likert scale.

RESULTS

The application of DLR resulted in significantly lower image noise; higher CT attenuation, SNR, and CNR; and better subjective analysis among the three different concentrations of contrast media groups (P < 0.001). There was no significant difference in the CT attenuation of the left ventricle (P = 0.089) and coronary arteries (P = 0.072) between hybrid IR at Iohexol-300 and DLR at Iohexol-240. Furthermore, application of DLR to the Iohexol-240 significantly improved SNR and CNR; it achieved higher subjective scores compared with hybrid IR at Iohexol-300 (P < 0.001).

CONCLUSION

We suggest that using DLR with Iohexol-240 contrast media is preferable to hybrid IR with Iohexol-300 contrast media in coronary CTA.

Cardiovascular Imaging in China: Yesterday, Today, and Tomorrow

The high prevalence and mortality of cardiovascular diseases in China's large population has increased the use of cardiovascular imaging for the assessment of conditions in recent years. In this study, we review the past 20 years of cardiovascular imaging in China, the increasingly important role played by cardiovascular computed tomography in coronary artery disease and pulmonary embolism assessment, magnetic resonance imaging's use for cardiomyopathy assessment, the development and application of artificial intelligence in cardiovascular imaging, and the future of Chinese cardiovascular imaging.

Temporal changes of the diameter of the coronary sinus during the cardiac cycle

INTRODUCTION

Currently, there are no studies that analyse the changes in the cardiac venous system that are dependent on the phase (RR interval) of reconstruction. The aim of the study was to assess the size of the coronary sinus at two measurement sites depending on the phase of the heart cycle.

METHODS

Fifty patients were included. Cardiac computed tomography was performed in all of the patients due to a suspicion of coronary artery disease (typical indications) using a dual-source Siemens Somatom Force scanner. The "MM reading" presets were used to measure the coronary sinus ostium (measurement 1) and the coronary sinus trunk, which is close to the great cardiac vein (measurement 2) in millimetres. All of the calculations were performed on axial scans using 0%-100% and a 256 × 256 matrix.

RESULTS

The largest CS was found at the 30%, 40% and 50% RR interval-this phenomenon occurred in 37 of the 50 cases (74%). The CS was largest in the 30% phase (9/50 cases; 18%), in the 40% phase (17/50 cases; 34%) and in the 50% phase, and it was the largest in 11 of the 50 cases (22%). There were also no gender-related differences.

CONCLUSIONS

The size of the coronary sinus varies with the phase of the heart cycle. At the 40% phase, it is largest in most cases.

Cardiac computed tomography angiography in the paediatric population: Expert consensus from the Filiale de cardiologie pédiatrique et congénitale (FCPC) and the Société française d'imagerie cardiaque et vasculaire diagnostique et interventionnelle (SFICV)

This paper aims to provide a paediatric cardiac computed tomography angiography expert panel consensus based on the opinions of experts from the Société française d'imagerie cardiaque et vasculaire diagnostique et interventionnelle (SFICV) and the Filiale de cardiologie pédiatrique congénitale (FCPC). This expert panel consensus includes recommendations for indications, patient preparation, computed tomography angiography radiation dose reduction techniques and postprocessing techniques. We think that to realize its full potential and to avoid pitfalls, cardiac computed tomography angiography in children with congenital heart disease requires training and experience. Moreover, paediatric cardiac computed tomography angiography protocols should be standardized to acquire optimal images in this population with the lowest radiation dose possible, to prevent unnecessary radiation exposure. We also provide a suggested structured report and a list of acquisition protocols and technical parameters in relation to specific vendors.

Pediatric cardiac computed tomography angiography: Expert consensus from the Filiale de Cardiologie Pédiatrique et Congénitale (FCPC) and the Société Française d'Imagerie Cardiaque et Vasculaire diagnostique et interventionnelle (SFICV)

This article was designed to provide a pediatric cardiac computed tomography angiography (CCTA) expert panel consensus based on opinions of experts of the Société Française d'Imagerie Cardiaque et Vasculaire diagnostique et interventionnelle (SFICV) and of the Filiale de Cardiologie Pédiatrique Congénitale (FCPC). This expert panel consensus includes recommendations for indications, patient preparation, CTA radiation dose reduction techniques, and post-processing techniques. The consensus was based on data from available literature (original papers, reviews and guidelines) and on opinions of a group of specialists with extensive experience in the use of CT imaging in congenital heart disease. In order to reach high potential and avoid pitfalls, CCTA in children with congenital heart disease requires training and experience. Moreover, pediatric cardiac CCTA protocols should be standardized to acquire optimal images in this population with the lowest radiation dose possible to prevent unnecessary radiation exposure. We also provided a suggested structured report and a list of acquisition protocols and technical parameters in relation to specific vendors.

Noninvasive Derivation of Fractional Flow Reserve From Coronary Computed Tomographic Angiography: A Review

Coronary computed tomographic angiography (CCTA) has evolved as a rapid and highly sensitive method for the exclusion of obstructive coronary artery disease. Unfortunately, as it pertains to moderate and severe lesions, the ability to discriminate between those that are hemodynamically significant and those that are nonobstructive is lacking. Consequently, this deficiency can result in a significant number of unnecessary referrals for invasive angiography that yields nonobstructive results. Fractional flow reserve (FFR), which assesses the hemodynamic significance of a specific lesion, when performed during invasive angiography, results in improved patient outcomes compared with visual stenosis assessment alone. Through the application of computational analytic methods to CT-derived anatomic coronary models, noninvasive calculation of FFR has become possible. This allows for the improved ability to differentiate between nonobstructive coronary lesions and those that are truly hemodynamically significant. Currently, HeartFlow FFRCT is the only FDA-approved and commercially available CCTA-derived FFR (CT-FFR) platform. By reducing the number of invasive procedures performed for nonobstructive disease, CT-derived FFR has the ability to lower health care expenditures and become the true gatekeeper to invasive angiography.

Cardiothoracic Applications of 3-dimensional Printing

Medical 3-dimensional (3D) printing is emerging as a clinically relevant imaging tool in directing preoperative and intraoperative planning in many surgical specialties and will therefore likely lead to interdisciplinary collaboration between engineers, radiologists, and surgeons. Data from standard imaging modalities such as computed tomography, magnetic resonance imaging, echocardiography, and rotational angiography can be used to fabricate life-sized models of human anatomy and pathology, as well as patient-specific implants and surgical guides. Cardiovascular 3D-printed models can improve diagnosis and allow for advanced preoperative planning. The majority of applications reported involve congenital heart diseases and valvular and great vessels pathologies. Printed models are suitable for planning both surgical and minimally invasive procedures. Added value has been reported toward improving outcomes, minimizing perioperative risk, and developing new procedures such as transcatheter mitral valve replacements. Similarly, thoracic surgeons are using 3D printing to assess invasion of vital structures by tumors and to assist in diagnosis and treatment of upper and lower airway diseases. Anatomic models enable surgeons to assimilate information more quickly than image review, choose the optimal surgical approach, and achieve surgery in a shorter time. Patient-specific 3D-printed implants are beginning to appear and may have significant impact on cosmetic and life-saving procedures in the future. In summary, cardiothoracic 3D printing is rapidly evolving and may be a potential game-changer for surgeons. The imager who is equipped with the tools to apply this new imaging science to cardiothoracic care is thus ideally positioned to innovate in this new emerging imaging modality.

Cardiovascular Imaging: The Past and the Future, Perspectives in Computed Tomography and Magnetic Resonance Imaging

Today's noninvasive imaging of the cardiovascular system has revolutionized the approach to various diseases and has substantially affected prognostic information. Cardiovascular magnetic resonance (MR) and computed tomographic (CT) imaging are at center stage of these approaches, although 5 decades ago, these technologies were unheard of. Both modalities had their inception in the 1970s with a primary focus on noncardiovascular applications. The technical development of the various decades, however, substantially pushed the envelope for cardiovascular MR and CT applications. Within the past 10-15 years, MR and CT technologies have pushed each other in cardiac applications; and without the "rival" modality, neither one would likely not have reached its potential today. This view on the history of MR and CT in the field of cardiovascular applications provides insight into the story of success of applications that once have been ideas only but are at prime time today.

Image quality, radiation dose, and diagnostic accuracy of prospectively ECG-triggered high-pitch coronary CT angiography at 70 kVp in a clinical setting: comparison with invasive coronary angiography

PURPOSE

To investigate image quality, radiation dose, and diagnostic performance of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) at 70 kVp compared to invasive coronary angiography (ICA) as reference standard.

MATERIALS AND METHODS

Forty-three patients underwent prospectively ECG-triggered high-pitch CCTA at 70 kVp using 30 cc (11 g iodine) contrast medium and ICA. Subjective and objective image quality was evaluated for each CCTA study. CCTA performance for diagnosing ≥50% stenosis was assessed. Results were stratified according to heart rate (HR), body mass index (BMI), Agatston score, and image quality.

RESULTS

At CCTA, 94.3% (500/530) of coronary segments were of diagnostic quality. Using ICA as reference standard, sensitivity and accuracy were 100% and 93.0% on a per-patient basis. Per-vessel and per-segment performances were 92.2% and 89.5%; 79.5% and 88.3%, respectively. No differences were found in diagnostic accuracy between different HR, BMI, and calcification subgroups (all P > 0.05) on a per-patient basis. However, low image quality reduced diagnostic accuracy on a per-patient, per-vessel and per-segment basis (all P < 0.05). The mean effective radiation dose was 0.2 ± 0.0 mSv.

CONCLUSION

Our presented protocol results in an effective radiation dose of 0.2 mSv and high diagnostic accuracy for stenosis detection in a selected, non-obese population.

KEY POINTS

Prospectively ECG-triggered high-pitch CCTA at 70 kVp is feasible. This protocol has a high diagnostic accuracy for stenosis detection. The mean effective radiation dose was 0.2 ± 0.0 mSv. Only 30 cc of contrast material is used in this protocol. Low image quality reduced diagnostic accuracy of CCTA.

High-pitch coronary CT angiography at 70 kVp with low contrast medium volume: comparison of 80 and 100 kVp high-pitch protocols

The purpose of this article is to evaluate image quality and radiation dose of prospectively electrocardiogram (ECG)-triggered high-pitch coronary computed tomography angiography (CCTA) at 70 kVp and 30 mL contrast medium.One hundred fifty patients with a heart rate ≤70 beats per minute (bpm) underwent CCTA using a second-generation dual-source computed tomography (CT) scanner and were randomized into 3 groups according to tube voltage and contrast medium volume (370 mg/mL iodine concentration) (100 kVp group, 100 kVp/60 mL, n = 55; 80 kVp group, 80 kVp/60 mL, n = 44; 70 kVp group, 70 kVp/30 mL, n = 51). Objective and subjective image quality along with the effect of heart rate (HR) and body mass index (BMI) was evaluated and compared between the groups. Radiation dose was estimated for each patient.CT attenuation and image noise were higher in the 80 and 70 kVp groups than in the 100 kVp group (all P < 0.001). Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were lower in the 70 kVp group than in the 80 and 100 kVp groups (all P < 0.05). There was no difference for subjective image quality between the groups (P > 0.05). HR did not affect subjective image quality (all P > 0.05), while patients with BMI <23 kg/m had higher image quality than patients with BMI ≥23 kg/m (P < 0.05). Compared with the 100 kVp group, the radiation dose of the 70 kVp group was reduced by 75%.In conclusion, prospectively ECG-triggered high-pitch 70 kVp/30 mL CCTA can obtain diagnostic image quality with lower radiation dose in selected patients with BMI <23 kg/m compared with 80/100 kVp/60 mL CCTA.

Feasibility of prospectively ECG-triggered high-pitch coronary CT angiography with 30 mL iodinated contrast agent at 70 kVp: initial experience

OBJECTIVES

To evaluate the feasibility, image quality and radiation dose of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) with 30 mL contrast agent at 70 kVp.

METHODS

Fifty-eight patients with suspected coronary artery disease, a body mass index (BMI) of less than 25 kg/m(2), sinus rhythm and a heart rate (HR) of less than 70 beats per minute (bpm) were prospectively enrolled in this study. Thirty mL of 370 mg I/mL iodinated contrast agent was administrated at a flow rate of 5 mL/s. All patients underwent prospectively ECG-triggered high-pitch CCTA on a second-generation dual-source CT system at 70 kVp using automated tube current modulation.

RESULTS

Fifty-six patients (96.6%) had diagnostic CCTA images and two patients (3.4%) had one vessel with poor image quality each rated as non-diagnostic. No significant effects of HR, HR variability and BMI on CCTA image quality were observed (all P > 0.05). Effective dose was 0.17 ± 0.02 mSv and the size-specific dose estimate was 1.03 ± 0.13 mGy.

CONCLUSION

Prospectively ECG-triggered high-pitch CCTA at 70 kVp with 30 mL of contrast agent can provide diagnostic image quality at a radiation dose of less than 0.2 mSv in patients with a BMI of less than 25 kg/m(2) and an HR of less than 70 bpm.

KEY POINTS

• Prospectively ECG-triggered high-pitch CCTA at 70 kVp/30 mL contrast agent is feasible. • Diagnostic image quality can be obtained at a radiation dose of less than 0.2 mSv. • This protocol is suitable for normal-weight patients with slow heart rate.

Imaging techniques for cardiac strain and deformation: comparison of echocardiography, cardiac magnetic resonance and cardiac computed tomography

Myocardial function assessment is essential for determining the health of the myocardium. Global assessment of myocardial function is widely performed (by estimating the ejection fraction), but many common cardiac diseases initially affect the myocardium on a regional, rather than global basis. Regional myocardial wall motion can be quantified using myocardial strain analysis (a normalized measure of deformation). Myocardial strain can be measured in terms of three normal strains (longitudinal strain, radial strain and circumferential) and six shear strains. Cardiac MRI (cMRI) is usually considered the reference standard for measurement of myocardial strain. The most common cMRI method, termed tagged cMRI, allows full, 3D assessment of regional strain. However, due to its complexity and lengthy times for analysis, tagged cMRI is not usually used outside of academic centers. Tagged cMRI is also primarily used only in research studies. Echocardiography combined with tissue Doppler imaging or a speckle tracking technique is now widely available in the clinical setting. Myocardial strain measurement by echocardiography shows reasonable agreement with cMRI. Limited standardization and differences between vendors represent current limitations of the technique. Cardiac computed tomography (CCT) is the newest and most rapidly growing modality for noninvasive imaging of the heart. While CCT studies are most commonly applied to assess the coronary arteries, CCT is easily adapted to provide functional information for both the left and right ventricles. New methods for CCT assessment of regional myocardial function are being developed. This review outlines the current literature on imaging techniques related to cardiac strain analysis and discusses the strengths and weaknesses of various methods for myocardial strain analysis.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: image reconstruction and assessment of image quality

PURPOSE

To present the theory for image reconstruction of a high-pitch, high-temporal-resolution spiral scan mode for dual-source CT (DSCT) and evaluate its image quality and dose.

METHODS

With the use of two x-ray sources and two data acquisition systems, spiral CT exams having a nominal temporal resolution per image of up to one-quarter of the gantry rotation time can be acquired using pitch values up to 3.2. The scan field of view (SFOV) for this mode, however, is limited to the SFOV of the second detector as a maximum, depending on the pitch. Spatial and low contrast resolution, image uniformity and noise, CT number accuracy and linearity, and radiation dose were assessed using the ACR CT accreditation phantom, a 30 cm diameter cylindrical water phantom or a 32 cm diameter cylindrical PMMA CTDI phantom. Slice sensitivity profiles (SSPs) were measured for different nominal slice thicknesses, and an anthropomorphic phantom was used to assess image artifacts. Results were compared between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2. In addition, image quality and temporal resolution of an ECG-triggered version of the DSCT high-pitch spiral scan mode were evaluated with a moving coronary artery phantom, and radiation dose was assessed in comparison with other existing cardiac scan techniques.

RESULTS

No significant differences in quantitative measures of image quality were found between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2 for spatial and low contrast resolution, CT number accuracy and linearity, SSPs, image uniformity, and noise. The pitch value (1.6 pitch 3.2) had only a minor impact on radiation dose and image noise when the effective tube current time product (mA s/pitch) was kept constant. However, while not severe, artifacts were found to be more prevalent for the dual-source pitch = 3.2 scan mode when structures varied markedly along the z axis, particularly for head scans. Images of the moving coronary artery phantom acquired with the ECG-triggered high-pitch scan mode were visually free from motion artifacts at heart rates of 60 and 70 bpm. However, image quality started to deteriorate for higher heart rates. At equivalent image quality, the ECG-triggered high-pitch scan mode demonstrated lower radiation dose than other cardiac scan techniques on the same DSCT equipment (25% and 60% dose reduction compared to ECG-triggered sequential step-and-shoot and ECG-gated spiral with x-ray pulsing).

CONCLUSIONS

A high-pitch (up to pitch = 3.2), high-temporal-resolution (up to 75 ms) dual-source CT scan mode produced equivalent image quality relative to single-source scans using a more typical pitch value (pitch = 1.0). The resultant reduction in the overall acquisition time may offer clinical advantage for cardiovascular, trauma, and pediatric CT applications. In addition, ECG-triggered high-pitch scanning may be useful as an alternative to ECG-triggered sequential scanning for patients with low to moderate heart rates up to 70 bpm, with the potential to scan the heart within one heart beat at reduced radiation dose.

Emergency computed tomography for aortic valve vegetation mimicking disruption

A 47-year-old man presented with symptoms typical of infective endocarditis and history of streptococcal meningitis 8 months previously. Echocardiography showed a large aortic valve vegetation that was interpreted as disruption of the noncoronary cusp. This was ruled out by 64-slice cardiac computed tomography. Valve replacement was performed successfully.

Radiation dose reduction in computed tomography: techniques and future perspective

Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented.

Exact image reconstruction with triple-source saddle-curve cone-beam scanning

In this paper, we propose an exact shift-invariant filtered backprojection (FBP) algorithm for triple-source saddle-curve cone-beam CT. In this imaging geometry, the x-ray sources are symmetrically positioned along a circle, and the trajectory of each source is a saddle curve. Then, we extend Yang's formula from the single-source case to the triple-source case. The saddle curves can be divided into four parts to yield four datasets. Each of them contains three data segments associated with different saddle curves, respectively. Images can be reconstructed on the planes orthogonal to the z-axis. Each plane intersects the trajectories at six points (or three points at the two ends) which can be used to define the filtering directions. Then, we discuss the properties of these curves and study the case of 2N+1 sources (N>or=2). A necessary condition and a sufficient condition are given to find efficient curves. Finally, we perform numerical simulations to demonstrate the feasibility of our triple-source saddle-curve approach. The results show that the triple-source geometry is advantageous for high temporal resolution imaging, especially important for cardiac imaging and small animal imaging.

Exact image reconstruction with triple-source saddle-curve cone-beam scanning

In this paper, we propose an exact shift-invariant filtered backprojection (FBP) algorithm for triple-source saddle-curve cone-beam CT. In this imaging geometry, the x-ray sources are symmetrically positioned along a circle, and the trajectory of each source is a saddle curve. Then, we extend Yang's formula from the single-source case to the triple-source case. The saddle curves can be divided into four parts to yield four datasets. Each of them contains three data segments associated with different saddle curves, respectively. Images can be reconstructed on the planes orthogonal to the z-axis. Each plane intersects the trajectories at six points (or three points at the two ends) which can be used to define the filtering directions. Then, we discuss the properties of these curves and study the case of 2N+1 sources (N>or=2). A necessary condition and a sufficient condition are given to find efficient curves. Finally, we perform numerical simulations to demonstrate the feasibility of our triple-source saddle-curve approach. The results show that the triple-source geometry is advantageous for high temporal resolution imaging, especially important for cardiac imaging and small animal imaging.

Comparison of myocardial bridging by dual-source CT with conventional coronary angiography

BACKGROUND

The diagnosis of myocardial bridging (MB) is of clinical importance because of the association between MB and compromised coronary flow. The aim of this study was to compare the ability of dual-source computed tomography (DSCT) and conventional coronary angiography (CAG) to detect MB.

METHODS AND RESULTS

DSCT were performed in 53 patients and 4-dimensional (D) reconstruction was subsequently performed in 16 patients with MB for double-blinded comparison with the findings of CAG. The diameters at systole and diastole of the coronary segments proximal and distal to the MB and of the tunneled segment were measured. The relationship between the rate of stenosis of the tunneled artery and the "milking" effect on 4-D reconstruction was analyzed. Of the 53 patients, CAG and DSCT detected 4 MBs in 3 patients and 21 MBs in 16 patients, respectively (p<0.001). On a per-patient and per-MB basis, significant difference was found between both methods (p=0.001, p<0.001). The 4-D reconstruction showed the milking effect and abnormal blood flow, detecting more MBs than did CAG (p<0.001). The rate of stenosis of the tunneled artery was related to the milking effect on the 4-D reconstruction (r=0.640, p=0.006).

CONCLUSIONS

In the present study, DSCT detected more MBs than CAG, suggesting its clinical application for diagnosis of this condition.

Anatomical investigation of the sinus node artery using dual-source computed tomography

BACKGROUND

Few investigators have studied the anatomy of the sinus node artery (SNA) using noninvasive imaging modalities, so the objective of this study was to visualize the in-vivo 3-dimensional anatomical relations of the SNA using dual-source computed tomography (DSCT).

METHODS AND RESULTS

In the 101 patients included in this study, the visualization rate, anatomical type and diameter of the SNA, the distance between the orifice and coronary artery, and the terminal type of SNA were recorded. The visualization rate was 95.2% (96/101). Of 96 patients, 106 SNAs were detected among which 51 (48.1%, 51/106) originated from the right coronary artery, 52 (49.1%, 52/106) from the left circumflex artery, and 3 (2.7%, 3/106) from other branches. There were 3 types of SNA: right (n = 52), left (n = 45), and posterior (n = 9). The distance between the orifice of the right SNA and the right coronary sinus was 14.2+/-15.2 mm, for the left SNA it was 5.5+/-3.5 mm, and for the posterior SNA, 33.7+/-12.8 mm. The average diameter was 1.27+/-0.29 mm. The SNA approached the nodal tissue by 1 of 3 routes: retrocaval (51.5%), precaval (25.2%), or pericaval (22.3%).

CONCLUSION

The SNA can be visualized in vivo using DSCT, which is important for preoperative knowledge of its origin, course, termination, and anatomical type.

A technical solution to avoid partial scan artifacts in cardiac MDCT

Quantitative evaluation of cardiac image data obtained using multidetector row computed tomography (CT) is compromised by partial scan reconstructions, which improve the temporal resolution but significantly increase image-to-image CT number variations for a fixed region of interest compared to full reconstruction images. The feasibility of a new approach to solve this problem is assessed. An anthropomorphic cardiac phantom and an anesthetized pig were scanned on a dual-source CT scanner using both full and partial scan acquisition modes under different conditions. Additional scans were conducted with the electrocardiogram (ECG) signal being in synchrony with the gantry rotation. In the animal study, a simple x-ray detector was used to generate a signal once per gantry rotation. This signal was then used to pace the pig's heart. Phantom studies demonstrated that partial scan artifacts are strongly dependent on the rotational symmetry of angular projections, which is determined by the object shape and composition and its position with respect to the isocenter. The degree of partial scan artifacts also depends on the location of the region of interest with respect to highly attenuating materials (bones, iodine, etc.) within the object. Single-source partial scan images (165 ms temporal resolution) were significantly less affected by partial scan artifacts compared to dual-source partial scan images (82 ms temporal resolution). When the ECG signal was in synchrony with the gantry rotation, the same cardiac phase always corresponded to the same positions of the x-ray tube(s) and, hence, the same scattering and beam hardening geometry. As a result, the range of image-to-image CT number variations for partial scan reconstruction images acquired in synchronized mode was decreased to that achieved using full reconstruction image data. The success of the new approach, which synchronizes the ECG signal with the position of the x-ray tube(s), was demonstrated both in the phantom and animal experiments.

Esophagus imaging for radiofrequency ablation of atrial fibrillation using a dual-source computed tomography system: Preliminary observations

OBJECTIVE

The very recent introduction of dual-source computed tomography (DSCT) has significantly improved the temporal resolution of ECG-gated multidetector-row cardiac computed tomography (CT). The aim of the present study was to evaluate whether with a DSCT visualization of the esophagus is feasible without any use of contrast in the esophagus.

MATERIALS AND METHODS

A total of 20 patients were evaluated. Ten patients underwent examination with a DSCT scanner without a gastric tube. In another ten patients, which served as control group, a CT scan was performed with a radio-opaque gastric tube prior to circumferential pulmonary vein isolation (in seven patients with a 16-slice CT and in three patients with a DSCT).

RESULTS

In the control group the gastric tube and the left atrium were reconstructed and were well visualized in all ten patients in the electro-anatomic mapping system, independently whether 16-row CT or DSCT scan was used. In the study group integration of the esophagus into the electro-anatomic mapping system was not feasible, due to the lacking contrast counterpart the surrounding tissue.

CONCLUSIONS

Even with the newest generation of DSCT scanner it is not possible to integrate the esophagus image into the 3-D electroanatomic mapping system without contrast by whatever means. However placing a conventional gastric tube before performing the CT scan allowed visualization and integration of the esophagus into the 3-D electro-anatomical map in all patients.