Comparison of MRI, 64-slice MDCT and DSCT in assessing functional cardiac parameters of a moving heart phantom

Scoping review of magnetic resonance motion imaging phantoms

To review and analyze the currently available MRI motion phantoms. Publications were collected from the Toronto Metropolitan University Library, PubMed, and IEEE Xplore. Phantoms were categorized based on the motions they generated: linear/cartesian, cardiac-dilative, lung-dilative, rotational, deformation or rolling. Metrics were extracted from each publication to assess the motion mechanisms, construction methods, as well as phantom validation. A total of 60 publications were reviewed, identifying 48 unique motion phantoms. Translational movement was the most common movement (used in 38% of phantoms), followed by cardiac-dilative (27%) movement and rotational movement (23%). The average degrees of freedom for all phantoms were determined to be 1.42. Motion phantom publications lack quantification of their impact on signal-to-noise ratio through standardized testing. At present, there is a lack of phantoms that are designed for multi-role as many currently have few degrees of freedom.

[Using CT to Evaluate Cardiac Function]

A comprehensive evaluation of cardiac function includes information in relation to cardiac output and systemic venous return. The heart is composed of four chambers: two atria and two ventricles, each with its own unique mechanical function. These four cardiac chambers, their valves, and the pulmonary circulation system are inter-related as they preload or afterload on each other. Cardiac dysfunction is a failure of global cardiac function, resulting in typical clinical manifestations. To investigate the underlying cause of cardiac dysfunction, a step-by-step evaluation of cardiac blood flow tracks is necessary. In this context, imaging markers showing details of the cardiac structures have an important role in assessing cardiac function. An image-based evaluation allows for investigation of function in terms of individual cardiac components. Evaluation of cardiac function using cardiac CT has recently been validated. This review aimed to discuss cardiac CT-based imaging markers for comprehensive and detailed cardiac function assessment.

Cardiovascular CT for evaluation of single-ventricle heart disease: risks and accuracy compared with interventional findings

OBJECTIVE

We sought to evaluate the risk and image quality from cardiovascular CT in patients across all stages of single-ventricle palliation, and to define accuracy by comparing findings with intervention and surgery.

METHODS

Consecutive CT scans performed in patients with single-ventricle heart disease were retrospectively reviewed at a single institution. Diagnosis, sedation needs, estimated radiation dose, and adverse events were recorded. Anatomical findings, image quality (1-4, 1=optimal), and discrepancy compared with interventional findings were determined. Results are described as medians with their 25th and 75th percentiles.

RESULTS

From January, 2010 to August, 2015, 132 CT scans were performed in single-ventricle patients of whom 20 were neonates, 52 were post-Norwood, 15 were post-Glenn, and 45 were post-Fontan. No sedation was used in 76 patients, 47 were under minimal or moderate sedation, and nine were under general anaesthesia. The median image quality score was 1.2. The procedural dose-length product was 24 mGy-cm, and unadjusted and adjusted radiation doses were 0.34 (0.2, 1.8) and 0.82 (0.55, 1.88) mSv, respectively. There was one adverse event. No major and two minor discrepancies were noted at the time of 79 surgical and 10 catheter-based interventions.

CONCLUSIONS

Cardiovascular CT can be performed with a low radiation exposure in patients with single-ventricle heart disease. Its accuracy compared with that of interventional findings is excellent. CT is an effective advanced imaging modality when a non-invasive pathway is desired, particularly if cardiac MRI poses a high risk or is contraindicated.

Feasibility of low radiation dose retrospectively-gated cardiac CT for functional analysis in adult congenital heart disease

Background:

The use of cardiac computed tomography (CT) in the evaluation of adult congenital heart disease patients is limited due to concerns of high radiation doses. The purpose of this study was to prospectively assess whether low radiation dose cardiac CT is feasible to evaluate ventricular systolic function in adults with congenital heart disease.

Methods:

The study group included 30 consecutive patients with significant congenital heart disease who underwent a total of 35 ECG-gated cardiac CT scans utilizing a 320-detector row CT scanner. Each study included a non-contrast scan and subsequent contrast-enhanced retrospectively-gated acquisition. Effective radiation dose was estimated by multiplying the dose length product by a k-factor of 0.014 mSv/mGy cm.

Results:

The mean age of the patients was 34.4 ± 8.9 years, 60% were men, and mean body mass index was 24.2 ± 4.3 kg/m². A majority of patients (n = 28, 93.3%) had contraindications to cardiac MRI. A tube potential of 80 kV was used in 27 (77.1%) of the contrast-enhanced scans. The mean signal-to-noise and contrast-to-noise ratios were 11.5 ± 3.9 and 10.3 ± 3.7, respectively. The median radiation dose for non-contrast and contrast-enhanced images were 0.1 mSv (0.07–0.2 mSv) and 0.94 mSv (0.5–2.1 mSv), respectively. All 35 CT scans were successfully analyzed for ventricular systolic function.

Conclusions:

A low radiation contrast-enhanced, retrospectively-gated cardiac CT with a median radiation dose of less than 1 mSv was successful in evaluating ventricular systolic function in 30 consecutive adult congenital heart disease patients who underwent a total of 35 scans.

Conventional Medical Education and the History of Simulation in Radiology

Simulation is a promising method for improving clinician performance, enhancing team training, increasing patient safety, and preventing errors. Training scenarios to enrich medical student and resident education, and apply toward competency assessment, recertification, and credentialing are important applications of simulation in radiology. This review will describe simulation training for procedural skills, interpretive and noninterpretive skills, team-based training and crisis management, professionalism and communication skills, as well as hybrid and in situ applications of simulation training. A brief overview of current simulation equipment and software and the barriers and strategies for implementation are described. Finally, methods of measuring competency and assessment are described, so that the interested reader can successfully implement simulation training into their practice.

Dual-source computed tomography for evaluating coronary stenosis and left ventricular function

This study aimed to evaluate the correlation between coronary stenosis and left ventricular function using dual-source computed tomography (DSCT). DSCT coronary angiography (CAG) was performed on 66 patients with coronary disease and 36 healthy volunteers. The degree of coronary stenosis, end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were measured for the left ventricle. These values were compared with the results obtained by echocardiography (ECHO) and selective CAG, which were both adopted as controls. The diagnoses of coronary stenosis based on DSCT CAG and those based on selective CAG were not significantly different (P>0.05). Similarly, the values of EDV, ESV, SV or EV measured by DSCT CAG were not significantly different from thoses obtained by ECHO (P>0.05). However, significant differences were observed in the ESV, EF and SV of the severe stenosis group compared with the moderate and mild stenosis groups (both P<0.05). The values of EDV and MM significantly varied between the mild, moderate and severe stenosis groups (P<0.05). DSCT CAG is a highly accurate and highly reproducible method for evaluating the preliminary changes in cardiac function based on the variations of coronary stenosis. Significant changes were detected in the EDV and MM of the moderate stenosis group and in all parameters of the severe stenosis group.

The optimal use of cardiac imaging in the quantification of carcinoid heart disease

Carcinoid heart disease is a rare cause of right-sided valvular dysfunction, primarily mediated by serotonin. It is an important complication in patients with carcinoid syndrome and occurs in 20-50% of such patients. Echocardiography is the main technique used for the assessment of carcinoid heart disease, but other imaging modalities are also important, particularly in the quantification of the severity of the disease. We sought to review the role of cardiac imaging in the assessment of carcinoid heart disease.

Development and characterization of rodent cardiac phantoms: comparison with in vivo cardiac imaging

The increasing availability of rodent models of human cardiovascular disease has led to a need to translate noninvasive imaging techniques such as magnetic resonance imaging (MRI) from the clinic to the animal laboratory. The aim of this study was to develop phantoms simulating the short-axis view of left ventricular motion of rats and mice, thus reducing the need for live animals in the development of MRI.

Cylindrical phantoms were moulded from polyvinyl alcohol (PVA) Cryogel and attached via stiff water-filled tubing to a gear pump. Pulsatile distension of the phantoms was effected by suitable programming of the pump. Cine MRI scanning was carried out at 7 T and compared with in vivo rodent cardiac imaging.

Suitable pulsatile performance was achieved with phantoms for which the PVA material had been subjected to two freeze–thaw cycles, resulting in T1 and T2 relaxation time constants of 1656±124 ms and 55±10 ms, respectively. For the rat phantom operating at 240 beats per min (bpm), the dynamic range of the outer diameter was from 10.3 to 12.4 mm with the wall thickness varying between 1.9 and 1.2 mm. Corresponding figures for the mouse phantom at 480 bpm were outer diameter range from 5.4 to 6.4 mm and wall thickness from 1.5 to 1.2 mm.

Dynamic cardiac phantoms simulating rodent left ventricular motion in the short-axis view were successfully developed and compared with in vivo imaging. The phantoms can be used for future development work with reduced need of live animals.