Richard T George

Johns Hopkins University, Baltimore, Maryland, United States

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Publications (65)275.34 Total impact

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    ABSTRACT: The aim of this study was to investigate the association of left ventricular mass (LVM) with coronary atherosclerosis and myocardial infarction (MI).
    European Heart Journal – Cardiovascular Imaging 11/2014; · 3.67 Impact Factor
  • The Journal of infectious diseases. 10/2014;
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    ABSTRACT: Purpose To compare the diagnostic performance of myocardial computed tomographic (CT) perfusion imaging and single photon emission computed tomography (SPECT) perfusion imaging in the diagnosis of anatomically significant coronary artery disease (CAD) as depicted at invasive coronary angiography. Materials and Methods This study was approved by the institutional review board. Written informed consent was obtained from all patients. Sixteen centers enrolled 381 patients from November 2009 to July 2011. Patients underwent rest and adenosine stress CT perfusion imaging and rest and either exercise or pharmacologic stress SPECT before and within 60 days of coronary angiography. Images from CT perfusion imaging, SPECT, and coronary angiography were interpreted at blinded, independent core laboratories. The primary diagnostic parameter was the area under the receiver operating characteristic curve (Az). Sensitivity and specificity were calculated with use of prespecified cutoffs. The reference standard was a stenosis of at least 50% at coronary angiography as determined with quantitative methods. Results CAD was diagnosed in 229 of the 381 patients (60%). The per-patient sensitivity and specificity for the diagnosis of CAD (stenosis ≥50%) were 88% (202 of 229 patients) and 55% (83 of 152 patients), respectively, for CT perfusion imaging and 62% (143 of 229 patients) and 67% (102 of 152 patients) for SPECT, with Az values of 0.78 (95% confidence interval: 0.74, 0.82) and 0.69 (95% confidence interval: 0.64, 0.74) (P = .001). The sensitivity of CT perfusion imaging for single- and multivessel CAD was higher than that of SPECT, with sensitivities for left main, three-vessel, two-vessel, and one-vessel disease of 92%, 92%, 89%, and 83%, respectively, for CT perfusion imaging and 75%, 79%, 68%, and 41%, respectively, for SPECT. Conclusion The overall performance of myocardial CT perfusion imaging in the diagnosis of anatomic CAD (stenosis ≥50%), as demonstrated with the Az, was higher than that of SPECT and was driven in part by the higher sensitivity for left main and multivessel disease. © RSNA, 2014.
    Radiology 05/2014; · 6.34 Impact Factor
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    ABSTRACT: Cytokines released by epicardial fat are implicated in the pathogenesis of atherosclerosis. HIV infection and antiretroviral therapy have been associated with changes in body fat distribution and coronary artery disease. We sought to determine whether HIV infection is associated with greater epicardial fat and whether epicardial fat is associated with subclinical coronary atherosclerosis. We studied 579 HIV-infected and 353 HIV-uninfected men aged 40-70 years with noncontrast computed tomography to measure epicardial adipose tissue (EAT) volume and coronary artery calcium (CAC). Total Plaque Score (TPS) and plaque subtypes (noncalcified, calcified, and mixed) were measured by coronary computed tomography angiography in 706 men. We evaluated the association between EAT and HIV serostatus, and the association of EAT with subclinical atherosclerosis, adjusting for age, race, and serostatus and with additional cardiovascular risk factors and tested for modifying effects of HIV serostatus. HIV-infected men had greater EAT than HIV-uninfected men (P = 0.001). EAT was positively associated with duration of antiretroviral therapy (P = 0.02), specifically azidothymidine (P < 0.05). EAT was associated with presence of any coronary artery plaque (P = 0.006) and noncalcified plaque (P = 0.001), adjusting for age, race, serostatus, and cardiovascular risk factors. Among men with CAC, EAT was associated with CAC extent (P = 0.006). HIV serostatus did not modify associations between EAT and either CAC extent or presence of plaque. Greater epicardial fat volume in HIV-infected men and its association with coronary plaque and antiretroviral therapy duration suggest potential mechanisms that might lead to increased risk for cardiovascular disease in HIV.
    AIDS (London, England) 05/2014; · 4.91 Impact Factor
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    ABSTRACT: Coronary artery disease (CAD) has been associated with HIV infection, but data are not consistent. To determine whether HIV-infected men have more coronary atherosclerosis than uninfected men. Cross-sectional study. Multicenter AIDS Cohort Study. HIV-infected (n = 618) and uninfected (n = 383) men who have sex with men who were aged 40 to 70 years, weighed less than 136 kg (200 lb), and had no history of coronary revascularization. Presence and extent of coronary artery calcium (CAC) on noncontrast cardiac computed tomography (CT) and of any plaque; noncalcified, mixed, or calcified plaque; or stenosis on coronary CT angiography. 1001 men had noncontrast CT, of whom 759 had coronary CT angiography. After adjustment for age, race, CT scanning center, and cohort, HIV-infected men had a greater prevalence of CAC (prevalence ratio [PR], 1.21 [95% CI, 1.08 to 1.35]; P = 0.001) and any plaque (PR, 1.14 [CI, 1.05 to 1.24]; P = 0.001), including noncalcified (PR, 1.28 [CI, 1.13 to 1.45]; P < 0.001) and mixed (PR, 1.35 [CI, 1.10 to 1.65]; P = 0.004) plaque, than uninfected men. Associations between HIV infection and any plaque or noncalcified plaque remained significant (P < 0.005) after CAD risk factor adjustment. HIV-infected men had a greater extent of noncalcified plaque after CAD risk factor adjustment (P = 0.026). They also had a greater prevalence of coronary artery stenosis greater than 50% (PR, 1.48 [CI, 1.06 to 2.07]; P = 0.020), but not after CAD risk factor adjustment. Longer duration of highly active antiretroviral therapy (PR, 1.09 [CI, 1.02 to 1.17]; P = 0.007) and lower nadir CD4+ T-cell count (PR, 0.80 [CI, 0.69 to 0.94]; P = 0.005) were associated with coronary stenosis greater than 50%. Cross-sectional observational study design and inclusion of only men. Coronary artery plaque, especially noncalcified plaque, is more prevalent and extensive in HIV-infected men, independent of CAD risk factors. National Heart, Lung, and Blood Institute and National Institute of Allergy and Infectious Diseases.
    Annals of internal medicine 04/2014; 160(7):458-67. · 13.98 Impact Factor
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    ABSTRACT: Transendocardial Stem Cell Injection (TESI) with mesenchymal stem cells improves remodeling in chronic ischemic cardiomyopathy, but the impact of the injection site remains unknown. To address whether TESI exerts its effects at the site of injection only or also in remote areas, we hypothesized that segmental myocardial scar and segmental ejection fraction improve to a greater extent in injected than in non-injected segments. Biplane ventriculographic and endocardial tracings were recorded. TESI was guided to 10 sites in infarct-border zones. Sites were mapped according to the 17-myocardial segment model. As a result, 510 segments were analyzed in 30 patients before and 13-months after TESI. Segmental early enhancement defect (SEED, a measure of scar size) was reduced by TESI in both injected (-43.7±4.4%, n=95, p<0.01) and non-injected segments (-25.1±7.8%, n=148, p<0.001; between group comparison p<0.05). Conversely, segmental ejection fraction (SEF, a measure of contractility) improved in injected scar segments (19.9±3.3 to 26.3±3.5%, p=0.003) but not in non-injected scar segments (21.3±2.6 to 23.5±3.2%, p=0.20, between group comparison p<0.05). In the subgroup of scar segments with baseline SEF<20%, the SEF improvement was even greater in injected segments (12.1±1.2% to 19.9±2.7%, n=18, p=0.003) vs. non-injected segments (13.3±1.3% to 16.1±2.1%, n=15, p=0.05; between group comparison p<0.05). These findings illustrate a dichotomy in regional responses to TESI. Although scar reduction was evident at the site of TESI and remotely, ventricular functional responses occurred preferentially at the sites of TESI. Furthermore, improvement was greatest when segmental left ventricular dysfunction was severe.
    Circulation Research 01/2014; · 11.86 Impact Factor
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    ABSTRACT: PURPOSE The conventional form of non-invasive testing by stress single photon emission computed tomography (SPECT) perfusion imaging is known to be less reliable in the presence of clinical situations associated with balanced ischemia. The international, multicenter CORE320 trial was designed to test a non invasive risk stratification approach using combined computed tomography angiography (CTA) and adenosine stress CT perfusion (CTP) imaging compared to the reference standards of combined stress SPECT perfusion imaging and invasive coronary angiography (ICA). This design allows for the head-to-head comparison of the two forms of stress perfusion imaging (CTP and SPECT) vs. the reference standard of ICA in a post-hoc manner. The purpose of this analysis was to examine the non-concordance of CTP and SPECT perfusion imaging among participants of the CORE320 trial and compare to percent stenosis by ICA. METHOD AND MATERIALS The international, multicenter CORE320 study enrolled 381 symptomatic patients referred for ICA. Prior to ICA, patients underwent rest CTA and adenosine stress CTP as well as SPECT perfusion imaging. CTA, CTP, ICA, and SPECT were all analyzed using parallel methods in blinded independent laboratories. As part of this post-hoc analysis, when SPECT and CTP showed discordant results, we compared these results to the reference standard ICA. ICA was defined as abnormal at the ≥ 50% diameter stenosis threshold. RESULTS A positive CTP with a negative SPECT study occurred in 113 of the 381 enrolled subjects. Compared to ICA, 62% (70 of 113) of these had single vessel disease or greater and 33% (36 of 113) had multi-vessel (≥ 2 vessels) or left main disease. Conversely, a negative CTP with a positive SPECT study occurred in 33 subjects Only 27% (9/33) of these had single vessel disease or greater and 15% (7/33) had multi-vessel disease (P=0.004). CONCLUSION These data suggest that in patients with discordant findings in CTP and SPECT, CTP imaging is more sensitive than SPECT imaging for the detection of anatomic coronary stenosis. The majority of positive CTP studies without concordant SPECT defects do, in fact, demonstrate single, multi-vessel or left main coronary artery disease. CLINICAL RELEVANCE/APPLICATION CT perfusion imaging is more accurate than SPECT perfusion in predicting significant coronary stenosis, by ICA.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting; 12/2013
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    ABSTRACT: To evaluate the diagnostic power of integrating the results of computed tomography angiography (CTA) and CT myocardial perfusion (CTP) to identify coronary artery disease (CAD) defined as a flow limiting coronary artery stenosis causing a perfusion defect by single photon emission computed tomography (SPECT). We conducted a multicentre study to evaluate the accuracy of integrated CTA-CTP for the identification of patients with flow-limiting CAD defined by ≥50% stenosis by invasive coronary angiography (ICA) with a corresponding perfusion deficit on stress single photon emission computed tomography (SPECT/MPI). Sixteen centres enroled 381 patients who underwent combined CTA-CTP and SPECT/MPI prior to conventional coronary angiography. All four image modalities were analysed in blinded independent core laboratories. The prevalence of obstructive CAD defined by combined ICA-SPECT/MPI and ICA alone was 38 and 59%, respectively. The patient-based diagnostic accuracy defined by the area under the receiver operating characteristic curve (AUC) of integrated CTA-CTP for detecting or excluding flow-limiting CAD was 0.87 [95% confidence interval (CI): 0.84-0.91]. In patients without prior myocardial infarction, the AUC was 0.90 (95% CI: 0.87-0.94) and in patients without prior CAD the AUC for combined CTA-CTP was 0.93 (95% CI: 0.89-0.97). For the combination of a CTA stenosis ≥50% stenosis and a CTP perfusion deficit, the sensitivity, specificity, positive predictive, and negative predicative values (95% CI) were 80% (72-86), 74% (68-80), 65% (58-72), and 86% (80-90), respectively. For flow-limiting disease defined by ICA-SPECT/MPI, the accuracy of CTA was significantly increased by the addition of CTP at both the patient and vessel levels. The combination of CTA and perfusion correctly identifies patients with flow limiting CAD defined as ≥50 stenosis by ICA causing a perfusion defect by SPECT/MPI.
    European Heart Journal 11/2013; · 14.72 Impact Factor
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    ABSTRACT: Pharmacologic stress myocardial CT perfusion (CTP) has been reported to be a viable imaging modality for detection of myocardial ischemia compared with single-photon emission CT (SPECT) in several single-center studies. However, regadenoson-stress CTP has not previously been compared with SPECT in a multicenter, multivendor study. The rationale and design of a phase 2, randomized, cross-over study of regadenoson-stress myocardial perfusion imaging by CTP compared with SPECT are described herein. The study will be conducted at approximately 25 sites by using 6 different CT scanner models, including 64-, 128-, 256-, and 320-slice systems. Subjects with known/suspected coronary artery disease will be randomly assigned to 1 of 2 imaging procedure sequences; rest and regadenoson-stress SPECT on day 1, then regadenoson-stress CTP and rest CTP/coronary CT angiography (same acquisition) on day 2; or regadenoson-stress CTP and rest CTP/CT angiography on day 1, then rest and regadenoson-stress SPECT on day 2. The prespecified primary analysis examines the agreement rate between CTP and SPECT for detecting or excluding ischemia (≥2 or 0-1 reversible defects, respectively), as assessed by 3 independent blinded readers for each modality. Non-inferiority will be indicated if the lower boundary of the 95% CI for the agreement rate is within 0.15 of 0.78 (the observed agreement rate in the regadenoson pivotal trials). The protocol described herein will support the first evaluation of regadenoson-stress CTP by using multiple scanner types compared with SPECT.
    Journal of cardiovascular computed tomography 10/2013; · 2.55 Impact Factor
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    ABSTRACT: The purpose of this study was to develop a novel theory and method for generating regional myocardial perfusion images using fluoroscopy in the coronary angiography lab. We modified the Kety model to introduce the Patlak plot method for two-dimensional fluoroperfusion (FP) imaging. For evaluation, seven porcine models of myocardial ischemia with stenosis in the left coronary artery were prepared. Rest and stress FP imaging were performed using cardiovascular X-ray imaging equipment during the injection of iopamidol via the left main coronary artery. Images were acquired and retrospectively ECG gated at 80 % of the R-R interval. FP myocardial blood flow (MBF) was obtained using the Patlak plot method applied to time-intensity curve data of the proximal artery and myocardium. The results were compared to microsphere MBF measurements. Time-intensity curves were also used to generate color-coded FP maps. There was a moderate linear correlation between the calculated FP MBF and the microsphere MBF (y = 0.9758x + 0.5368, R(2) = 0.61). The color-coded FP maps were moderately correlated with the regional distribution of flow. This novel method of first-pass contrast-enhanced two-dimensional fluoroscopic imaging can quantify MBF and provide color coded FP maps representing regional myocardial perfusion.
    The international journal of cardiovascular imaging 10/2013; · 2.15 Impact Factor
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    ABSTRACT: Cell- and molecule-based therapeutic strategies to support wound healing and regeneration after myocardial infarction (MI) are under development. These emerging therapies aim at sustained preservation of ventricular function by enhancing tissue repair after myocardial ischaemia and reperfusion. Such therapies will benefit from guidance with regard to timing, regional targeting, suitable candidate selection, and effectiveness monitoring. Such guidance is effectively obtained by non-invasive tomographic imaging. Infarct size, tissue characteristics, muscle mass, and chamber geometry can be determined by magnetic resonance imaging and computed tomography. Radionuclide imaging can be used for the tracking of therapeutic agents and for the interrogation of molecular mechanisms such as inflammation, angiogenesis, and extracellular matrix activation. This review article portrays the hypothesis that an integrated approach with an early implementation of structural and molecular tomographic imaging in the development of novel therapies will provide a framework for achieving the goal of improved tissue repair after MI.
    European heart journal cardiovascular Imaging. 05/2013;
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    ABSTRACT: Objective: The methodology for use of cardiac CT angiography (CTA) in low risk populations is not well defined. In order to present a reference for future studies, we present CTA methodology that is being used in an epidemiology study- the Multicenter AIDS Cohort Study (MACS). Methods: The Multicenter AIDS Cohort Study (MACS) is an on-going multicenter prospective, observational cohort study. The MACS Cardiovascular Disease substudy plans to enroll 800 men (n= 575 HIV seropositive and n=225 HIV seronegative) age 40-70 years for coronary atherosclerosis imaging using cardiac CTA. The protocol includes heart rate (HR) optimization with beta blockers; use of proper field of view; scan length limitation; prospective ECG-gating using the lowest beam voltage possible. All scans are evaluated for presence, extent, and composition of coronary atherosclerosis, left atrial volumes, left ventricular volume and mass and non-coronary cardiac pathology. Results: The first 498 participants had an average radiation dose of 2.5±1.6 milliSieverts (mSv) for the cardiac CTA study. Overall quality of scans was fair to excellent in 98.6% of studies. There were three significant adverse events-two allergic reactions to contrast and one subcutaneous contrast extravasation. Conclusion: Cardiac CTA was safe and afforded a low effective radiation exposure to these asymptomatic research participants and provides valuable cardiovascular endpoints for scientific analysis. The cardiac CTA methodology described here may serve as a reference for use in future epidemiology studies aiming to assess coronary atherosclerosis and cardiac anatomy in low risk populations while minimizing radiation exposure.
    Anadolu kardiyoloji dergisi: AKD = the Anatolian journal of cardiology 01/2013; · 0.72 Impact Factor
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    ABSTRACT: PURPOSE Volumetric CT has the potential for accurate, noninvasive assessment of CAD and corresponding myocardial perfusion defects. CORE320 is a multicenter, multinational trial whose primary objective is to evaluate diagnostic accuracy of 320-row detector CT angiography (CTA) and perfusion (CTP) in patients with suspected CAD, compared to reference standard conventional diagnostic coronary angiography (CCA) and SPECT. This substudy analyzes estimated radiation dose, not diagnostic accuracy, on a per modality basis and tests the hypothesis that the cumulative dose from CTA and CTP (a) are not significantly different from individual CCA or SPECT doses, and (b) are significantly less than the total dose from the reference standard (CCA plus SPECT). METHOD AND MATERIALS Dose data from 428 subjects were available from independent core labs for each imaging modality. Doses were estimated for CT calcium score (CACS), rest cardiac CTA, and stress CTP (all CT was prospective ECG gated 240-320 x 0.5 mm detector row), diagnostic CCA (excluding any intervention), and SPECT. CT and CCA doses were estimated from reported DLP and DAP values, respectively. SPECT doses were estimated from injected activity, according to ICRP-80. Total diagnostic doses were compared between each modality and between the sum of all CT exams (test modality) vs the total dose from reference standard imaging (SPECT plus CCA). Diagnostic accuracy was not analyzed for this report. RESULTS The median (IQR) for CACS, CTA, CTP, and total CT was 0.9(0.2) mSv, 3.2(0.8) mSv, 5.3(2.3) mSv, and 10.9(3.1) mSv, respectively. Preliminary analyses suggest a slightly higher radiation dose for the complete CT assessment when compared to SPECT alone and a slightly lower radiation dose when compared to CCA alone. Preliminary analysis suggests that the total CT dose was lower than the total dose from reference standard imaging. Final analysis will be reported at the time of presentation. CONCLUSION To our knowledge, these data are the first to comprehensively evaluate the complete radiation dose from CACS, CTA, and CTP compared to the effective doses from CCA and SPECT. CLINICAL RELEVANCE/APPLICATION Preliminary estimated radiation dose from CTA and CTP appear comparable to other modalities.
    Radiological Society of North America 2012 Scientific Assembly and Annual Meeting; 11/2012
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    ABSTRACT: Background- Appropriate clinical decisions concerning diagnosis and treatment of coronary artery disease rely on correct integration of data on coronary anatomy and myocardial perfusion. The purpose of this article is to introduce a new left ventricular segmentation model for improved alignment of coronary arterial segments and myocardial perfusion territories, designed for the CORE320 study. Methods and Results- CORE320 is a prospective, multicenter study with a primary objective to evaluate the diagnostic accuracy of 320-row detector computed tomography (CT) to detect coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected coronary artery disease compared with the gold standard of conventional coronary angiography and single-photon emission CT myocardial perfusion imaging. We describe a 19-coronary segment and 13-myocardial territory alignment model, its application in both standard and CT image data sets, and the adjudication process of the initial cohort of patients recruited for the CORE320 study. Adjudication committees reviewed the images of the first 101 gold standard and 107 CT data sets. On the basis of the presented model and rules, all cases for adjudication were correctly identified. During image review, 6 (5.9%) gold standard and 9 (8.4%) CT data sets needed further realignment not triggered by the algorithm. Conclusions- We present a vascular territory distribution model developed for the CORE320 multicenter study, which accounts for variability in coronary anatomy and potential myocardial perfusion territory overlap. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00934037.
    Circulation Cardiovascular Imaging 08/2012; 5(5):587-95. · 5.80 Impact Factor
  • Alan Cheng, Richard T George
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    ABSTRACT: We present a case that demonstrates mitral valve annuloplasty ring dehiscence discovered on a cardiac computed tomography imaging study performed prior to radiofrequency ablation for atrial fibrillation. We describe the relevant imaging findings and the clinical implications this finding has on catheter selection and patient safety during a radiofrequency ablation procedure.
    Journal of cardiovascular computed tomography 07/2012; 6(4):287-8. · 2.55 Impact Factor
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    ABSTRACT: The objective of this study was to investigate the impact of image acquisition settings and patients' characteristics on image quality and radiation dose for coronary angiography by 320-row computed tomography (CT). CORE320 is a prospective study to investigate the diagnostic performance of 320-detector CT for detecting coronary artery disease and associated myocardial ischemia. A run-in phase in 65 subjects was conducted to test the adequacy of the computed tomography angiography (CTA) acquisition protocol. Tube current, exposure window, and number of cardiac beats per acquisition were adjusted according to subjects' gender, heart rate, and body mass index (BMI). Main outcome measures were image quality, assessed by contrast/noise measurements and qualitatively on a 4-point scale, and radiation dose, estimated by the dose-length-product. Average heart rate at image acquisition was 55.0±7.3 bpm. Median Agatston calcium score was 27.0 (interquartile range 1-330). All scans were prospectively triggered. Single heart beat image acquisition was obtained in 61 of 65 studies (94%). Sixty-one studies (94%) and 437 of 455 arterial segments (96%) were of diagnostic image quality. Estimated radiation dose was significantly greater in obese (5.3±0.4 mSv) than normal weight (4.6±0.3 mSv) or overweight (4.7±0.3 mSv) subjects (P<0.001). BMI was the strongest factor influencing image quality (odds ratio=1.457, P=0.005). The CORE320 CTA image acquisition protocol achieved a good balance between image quality and radiation dose for a 320-detector CT system. However, image quality in obese subjects was reduced compared to normal weight subjects, possibly due to tube voltage/current restrictions mandated by the study protocol.
    Heart International 06/2012; 7(2):e11.
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    Richard T George
    Journal of the American College of Cardiology 04/2012; 59(17):1549-50. · 14.09 Impact Factor
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    ABSTRACT: Multidetector row computed tomography (CT) allows noninvasive anatomic and functional imaging of the heart, great vessels, and coronary arteries. In recent years, there have been several advances in CT hardware, which have expanded the clinical utility of CT for cardiovascular imaging; such advances are ongoing. This review article from the Society of Cardiovascular Computed Tomography Basic and Emerging Sciences and Technology Working Group summarizes the technical aspects of current state-of-the-art CT hardware and describes the scan modes this hardware supports for cardiovascular CT imaging.
    Journal of cardiovascular computed tomography 04/2012; 6(3):154-63. · 2.55 Impact Factor

Publication Stats

1k Citations
275.34 Total Impact Points

Institutions

  • 2006–2014
    • Johns Hopkins University
      • Department of Medicine
      Baltimore, Maryland, United States
  • 2013
    • Toshiba Corporation
      Edo, Tōkyō, Japan
    • West Kendall Baptist Hospital
      Kendall, Florida, United States
  • 2010–2013
    • Johns Hopkins Medicine
      • • Department of Medicine
      • • Division of Cardiology
      Baltimore, Maryland, United States
  • 2009–2011
    • Fujita Health University
      • • Faculty of Radiological Technology
      • • School of Health Sciences
      Nagoya, Aichi, Japan
    • Johns Hopkins Bloomberg School of Public Health
      Baltimore, Maryland, United States
    • Mie University
      Tu, Mie, Japan