Anjali Chelliah

Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography

OBJECTIVES This study sought to determine updated conversion factors (k-factors) that would enable accurate estimation of radiation effective dose (ED) for coronary computed tomography angiography (CTA) and calcium scoring performed on 12 contemporary scanner models and current clinical cardiac protocols and to compare these methods to the standard chest k-factor of 0.014 mSv·mGy-1cm-1. BACKGROUND Accurate estimation of ED from cardiac CT scans is essential to meaningfully compare the benefits and risks of different cardiac imaging strategies and optimize test and protocol selection. Presently, ED from cardiac CT is generally estimated by multiplying a scanner-reported parameter, the dose-length product, by a k-factor which was determined for noncardiac chest CT, using single-slice scanners and a superseded definition of ED. METHODS Metal-oxide-semiconductor field-effect transistor radiation detectors were positioned in organs of anthropomorphic phantoms, which were scanned using all cardiac protocols, 120 clinical protocols in total, on 12 CT scanners representing the spectrum of scanners from 5 manufacturers (GE, Hitachi, Philips, Siemens, Toshiba). Organ doses were determined for each protocol, and ED was calculated as defined in International Commission on Radiological Protection Publication 103. Effective doses and scanner-reported dose-length products were used to determine k-factors for each scanner model and protocol. RESULTS k-Factors averaged 0.026 mSv·mGy-1cm-1 (95% confidence interval: 0.0258 to 0.0266) and ranged between 0.020 and 0.035 mSv·mGy-1cm-1. The standard chest k-factor underestimates ED by an average of 46%, ranging from 30% to 60%, depending on scanner, mode, and tube potential. Factors were higher for prospective axial versus retrospective helical scan modes, calcium scoring versus coronary CTA, and higher (100 to 120 kV) versus lower (80 kV) tube potential and varied among scanner models (range of average k-factors: 0.0229 to 0.0277 mSv·mGy-1cm-1). CONCLUSIONS Cardiac k-factors for all scanners and protocols are considerably higher than the k-factor currently used to estimate ED of cardiac CT studies, suggesting that radiation doses from cardiac CT have been significantly and systematically underestimated. Using cardiac-specific factors can more accurately inform the benefit-risk calculus of cardiac-imaging strategies.

Estimating Effective Dose of Radiation From Pediatric Cardiac CT Angiography Using a 64-MDCT Scanner: New Conversion Factors Relating Dose-Length Product to Effective Dose

OBJECTIVE The purpose of this study is to determine the conversion factors that enable accurate estimation of the effective dose (ED) used for cardiac 64-MDCT angiography performed for children. MATERIALS AND METHODS Anthropomorphic phantoms representative of 1- and 10-year-old children, with 50 metal oxide semiconductor field-effect transistor dosimeters placed in organs, underwent scanning performed using a 64-MDCT scanner with different routine clinical cardiac scan modes and x-ray tube potentials. Organ doses were used to calculate the ED on the basis of weighting factors published in 1991 in International Commission on Radiological Protection (ICRP) publication 60 and in 2007 in ICRP publication 103. The EDs and the scanner-reported dose-length products were used to determine conversion factors for each scan mode. The effect of infant heart rate on the ED and the conversion factors was also assessed. RESULTS The mean conversion factors calculated using the current definition of ED that appeared in ICRP publication 103 were as follows: 0.099 mSv · mGy-1 · cm-1, for the 1-year-old phantom, and 0.049 mSv · mGy-1 · cm-1, for the 10-year-old phantom. These conversion factors were a mean of 37% higher than the corresponding conversion factors calculated using the older definition of ED that appeared in ICRP publication 60. Varying the heart rate did not influence the ED or the conversion factors. CONCLUSION Conversion factors determined using the definition of ED in ICRP publication 103 and cardiac, rather than chest, scan coverage suggest that the radiation doses that children receive from cardiac CT performed using a contemporary 64-MDCT scanner are higher than the radiation doses previously reported when older chest conversion factors were used. Additional up-to-date pediatric cardiac CT conversion factors are required for use with other contemporary CT scanners and patients of different age ranges.

USE OF A 3D PRINTED HEART MODEL TO PLAN SURGICAL REPAIR OF COMPLEX CONGENITAL HEART DISEASE

Complex congenital heart disease, particularly defects that are corrected by creating intracardiac tunnels or baffles, can be difficult to visualize by conventional cardiac imaging. Three-dimensional (3D) printed heart models based on imaging data can delineate complex anatomy and guide surgical

Patients with anomalous aortic origin of the coronary artery remain at risk after surgical repair

Objectives: Anomalous aortic origin of a coronary artery (AAOCA) from the opposite sinus of Valsalva is a rare cardiac anomaly associated with sudden cardiac death (SCD). Single‐center studies describe surgical repair as safe, although medium‐ and long‐term effects on symptoms and risk of SCD remain unknown. We sought to describe outcomes of surgical repair of AAOCA. Methods: We reviewed institutional records for patients who underwent AAOCA repair, from 2001 to 2016, at 2 affiliated institutions. Patients with associated heart disease were excluded. Results: In total, 60 patients underwent AAOCA repair. Half of the patients (n = 30) had an anomalous left coronary artery arising from the right sinus of Valsalva and half had an anomalous right. Median age at surgery was 15.4 years (interquartile range, 11.9–17.9 years; range, 4 months to 68 years). The most common presenting symptoms were chest pain (n = 38; 63%) and shortness of breath (n = 17; 28%); aborted SCD was the presenting symptom in 4 patients (7%). Follow‐up data were available for 54 patients (90%) over a median of 1.6 years. Of 53 patients with symptoms at presentation, 34 (64%) had complete resolution postoperatively. Postoperative mild or greater aortic insufficiency was present in 8 patients (17%) and moderate supravalvar aortic stenosis in 1 (2%). One patient required aortic valve replacement for aortic insufficiency. Two patients required reoperation for coronary stenosis at 3 months and 6 years postoperatively. Conclusions: Surgical repair of AAOCA is generally safe and adverse events are rare. Restenosis, and even sudden cardiac events, can occur and long‐term surveillance is critical. Multi‐institutional collaboration is vital to identify at‐risk subpopulations and refine current recommendations for long‐term management.

Radiation dose management for pediatric cardiac computed tomography: a report from the Image Gently ‘Have-A-Heart’ campaign

Children with congenital or acquired heart disease can be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical imaging procedures including radiography, fluoroscopic procedures including diagnostic and interventional cardiac catheterizations, electrophysiology examinations, cardiac computed tomography (CT) studies, and nuclear cardiology examinations. Despite the clinical necessity of these imaging studies, the related ionizing radiation exposure could pose an increased lifetime attributable cancer risk. The Image Gently “Have-A-Heart” campaign is promoting the appropriate use of medical imaging studies in children with congenital or acquired heart disease while minimizing radiation exposure. The focus of this manuscript is to provide a comprehensive review of radiation dose management and CT performance in children with congenital or acquired heart disease.

Fetal Myocardial Strain Abnormalities in Pulmonary Atresia with Intact Ventricular Septum

Global and regional myocardial deformation have not been well described in fetuses with pulmonary atresia and intact ventricular septum (PA/IVS). Speckle‐tracking echocardiography (STE), an angle‐independent technique for assessing global and regional strain, may be a more sensitive way of determining ventricular systolic dysfunction compared with traditional 2D echocardiography. The aim of this study was to assess myocardial deformation in fetuses with PA/IVS compared with control fetuses and to determine if, in fetuses with PA/IVS, strain differs between those with and those without right ventricle‐dependent coronary circulation (RVDCC).

Imaging Considerations and Challenges in Pediatrics

Cardiovascular MRI, CT, and 3D echocardiography may all be used to acquire source datasets for 3D printing. In pediatric patients with cardiac disease, each of these imaging modalities poses unique challenges that must be considered when choosing and performing an optimal study that extracts maximal clinical information with minimal risk. Use of each modality to create 3D cardiac datasets in children, including practical considerations, benefits, and limitations of each modality, is reviewed in detail, with an emphasis on maximizing patient safety.

Myocardial strain can be measured from first trimester fetal echocardiography using velocity vector imaging.

Alterations in myocardial strain can identify cardiac dysfunction and can be measured in the mid‐gestation fetus. This study evaluates feasibility of strain measurements in early fetuses and establishes normal early fetal strain values.

BETTER ESTIMATING RADIATION EFFECTIVE DOSE FROM CARDIAC COMPUTED TOMOGRAPHY (CT): A COMPREHENSIVE EXAMINATION OF THE RELATIONSHIP BETWEEN EFFECTIVE DOSE AND DOSE-LENGTH PRODUCT

Radiation from CT is commonly quantified in term of effective dose (ED), estimated by multiplying the scanner reported dose-length product (DLP) by a conversion factor, referred to as the k factor. Current guidelines suggest a k factor of 0.014 mSv·mGy-1cm-1 for chest CT. While this value is

Multimodality Cardiac Imaging in a Patient with Kawasaki Disease and Giant Aneurysms

Kawasaki disease is a well-known cause of acquired cardiac disease in the pediatric and adult population, most prevalent in Japan but also seen commonly in the United States. In the era of intravenous immunoglobulin (IVIG) treatment, the morbidity associated with this disease has decreased, but it remains a serious illness. Here we present the case of an adolescent, initially diagnosed with Kawasaki disease as an infant, that progressed to giant aneurysm formation and calcification of the coronary arteries. We review his case and the literature, focusing on the integral role of multimodality imaging in managing Kawasaki disease.