CT dose reduction using prospectively triggered or fast-pitch spiral technique employed in cardiothoracic imaging (the CT dose study).

OBJECTIVES: To establish current radiation dose levels with contemporary scanners capable of prospectively triggered or high-pitch spiral scan modes to previous generation scanners among patients evaluated for coronary artery disease, pulmonary embolism, aortic disease, and "triple rule out" in a large population of patients at multiple centers. BACKGROUND: Previous small-scale studies with carefully controlled scan protocols report that CT scanners that facilitate prospectively triggered scanning and provide high-pitch spiral CT scan modes drastically lower radiation doses. However, diagnostic reference levels should be selected by medical bodies on the basis of large surveys of representative sites and reviewed at appropriate time intervals. METHODS: Scan data including dose and image quality parameters were collected retrospectively from 64 slice scanners (control) and prospectively after sites installed 128-slice dual-source scanners with high-pitch capability (study). Protocol selection was purposely not specified to survey "real world" results. Blinded quantitative image analysis was performed on every fifth scan. RESULTS: From April 2011 to March 2012, 2085 patients at 9 sites completed the study: 1051 coronary artery disease (509 control, 542 study), 528 pulmonary embolism (267 control, 261 study), 419 aortic disease (268 control, 151 study), and 87 triple rule out (53 control, 34 study). There was a significant reduction in median dose-length product (DLP) from 669 mGy ∙ cm (interquartile range [IQR]: 419-1026 mGy ∙ cm) in the control group to 260 mGy ∙ cm (IQR: 159-441 mGy ∙ cm) in the study group, a reduction by 61% (P < .0001) and was lower in all categories. No significant differences were noted in image quality. CONCLUSION: Use of advanced scanners facilitating prospectively triggered or high-pitch spiral scan modes results in marked dose reduction across a variety of cardiovascular studies, with no compromise in image quality. These findings may contribute to new target dose recommendations in societal guidelines.

Progressive radiation dose reduction from coronary computed tomography angiography in a statewide collaborative quality improvement program: results from the Advanced Cardiovascular Imaging Consortium.

BACKGROUND: A best-practice intervention previously demonstrated significant dose reduction over a period of one year. We sought to evaluate whether this reduction would be incremental and sustained by promoting new scanner technology in the context of an ongoing quality improvement program during a 3-year period in a statewide registry of coronary computed tomography angiography. METHODS AND RESULTS: In this prospective, controlled, nonrandomized study involving 11 901 patients at 15 Michigan centers participating in the Advanced Cardiovascular Imaging Consortium, radiation doses and image quality were compared between the following periods: control (May to June 2008) versus follow-up I (July 2008 to June 2009) and follow-up I versus follow-up II (July 2009 to April 2011). Intervention during these study periods included continuous education, feedback, and mandatory participation in this initiative. The median radiation dose remained unchanged from control to follow-up I: dose-length product of 697 (interquartile range, 407-1163) to 675 (interquartile range, 418-1146) mGy·cm (P=0.93). With the introduction of newer technology in follow-up I period, there was incremental 31% decrease during follow-up II to median dose-length product of 468 (interquartile range, 292-811) mGy·cm (P<0.0001). No significant change was noted in the percentage of diagnostic quality scans from follow-up I (92%) to follow-up II (92.7%). CONCLUSIONS: Although ongoing application of a best-practice algorithm was associated with sustaining previously achieved targets, the use of newer scanner technology resulted in incremental radiation dose reduction in a statewide coronary computed tomography angiography registry without image quality degradation. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00640068.

State-of-the-art in CT hardware and scan modes for cardiovascular CT.

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.

SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT.

Over the last few years, computed tomography (CT) has developed into a standard clinical test for a variety of cardiovascular conditions. The emergence of cardiovascular CT during a period of dramatic increase in radiation exposure to the population from medical procedures and heightened concern about the subsequent potential cancer risk has led to intense scrutiny of the radiation burden of this new technique. This has hastened the development and implementation of dose reduction tools and prompted closer monitoring of patient dose. In an effort to aid the cardiovascular CT community in incorporating patient-centered radiation dose optimization and monitoring strategies into standard practice, the Society of Cardiovascular Computed Tomography has produced a guideline document to review available data and provide recommendations regarding interpretation of radiation dose indices and predictors of risk, appropriate use of scanner acquisition modes and settings, development of algorithms for dose optimization, and establishment of procedures for dose monitoring.

Cardiac magnetic resonance imaging assessment of regional and global left atrial function before and after catheter ablation for atrial fibrillation.

BACKGROUND: Ablation of the left atrium and pulmonary veins antrum (PVAI) can be an effective treatment of atrial fibrillation (AF). However, there is discrepancy in the literature regarding the effect extensive ablation has on left atrial (LA) function. We sought to evaluate the effect that AF ablation procedures has on global and regional wall motion as assessed by cardiovascular magnetic resonance imaging (MRI). METHODS: Consecutive patients undergoing PVAI had cardiac MRI performed preablation and 3 months post ablation. Patients included paroxysmal (n = 16) and persistent/permanent (n = 13). In addition, 12 volunteers underwent cardiac MRI to provide a control population. LA transport function was assessed by obtaining cyclical change indices, total percent emptying, LA stroke volume indices, and LA active percent emptying. Using chordal segment analysis and radial motion of the left atrium, regional motion was assessed throughout the LA emptying cycle. RESULTS: All four PVs were isolated for all patients. Imaging revealed a significant reduction in LA volumes in AF patients post-PVAI. In the subset of patients with persistent AF, post-PVAI improvements were seen in global (p < 0.01) and regional LA functions (p = 0.01). In the paroxysmal AF patients, post-PVAI measurements revealed decreases in LA transport function (p = 0.02) as well as diminished regional function in the LA lateral wall (p = 0.02). The paroxysmal AF patients had global and regional LA functions comparable to the normal volunteers prior to ablation; however, these were significantly diminished post ablation. CONCLUSION: Extensive ablation during PVAI causes mild deterioration in LA function. However, in patients with a high burden of AF, it appears that the positive remodeling that occurs with rhythm restoration outweighs any negative effects of ablation.

Radiation dose from cardiac computed tomography before and after implementation of radiation dose-reduction techniques.

CONTEXT: Cardiac computed tomography angiography (CCTA) can accurately diagnose coronary artery disease, but radiation dose from this procedure is of concern. OBJECTIVES: To determine whether a collaborative radiation dose-reduction program would be associated with reduced radiation dose in patients undergoing CCTA in a statewide registry over a 1-year period and to define its effect on image quality. DESIGN, SETTING, AND PATIENTS: A prospective, controlled, nonrandomized study conducted during a control period (July-August 2007), an intervention period (September 2007-April 2008), and a follow-up period (May-June 2008) at 15 hospital imaging centers participating in the Advanced Cardiovascular Imaging Consortium in Michigan, which included small community hospitals and large academic medical centers. A total of 4995 sequential patients undergoing CCTA for suspected coronary artery disease were enrolled; 4862 patients (97.3%) had complete radiation data for analysis. INTERVENTION: A best-practice CCTA scan model was used, which included minimized scan range, heart rate reduction, electrocardiographic-gated tube current modulation, and reduced tube voltage in suitable patients. MAIN OUTCOME MEASURES: Primary outcomes included dose-length product and effective radiation dose from all phases of the CCTA scan. Secondary outcomes were image quality assessed by a 4-point scale (1 indicated excellent; 2, good; 3, adequate; and 4, nondiagnostic) and frequency of diagnostic-quality scans. RESULTS: Compared with the control period, patients' estimated median radiation dose in the follow-up period was reduced by 53.3% (dose-length product decreased from 1493 mGy x cm [interquartile range {IQR}, 855-1823 mGy x cm] to 697 mGy x cm [IQR, 407-1163 mGy x cm]; P < .001) and effective dose from 21 mSv (IQR, 12-26 mSv) to 10 mSv (IQR, 6-16 mSv) (P < .001). The greatest reduction in dose occurred at low-volume sites. There were no significant changes in median image quality assessment during the control period compared with the follow-up period (median image quality of 2 [images rated as good] vs median image quality of 2; P = .13) or frequency of diagnostic-quality scans (554/620 patients [89%] vs 769/835 patients [92%]; P = .07). CONCLUSION: Consistent application of currently available dose-reduction techniques was associated with a marked reduction in estimated radiation doses in a statewide CCTA registry, without impairment of image quality. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00640068.

Vascular endothelial growth factor-165 gene therapy promotes cardiomyogenesis in reperfused myocardial infarction.

BACKGROUND: Vascular endothelial growth factor (VEGF)-165 promotes cardiomyogenesis in chronic myocardial ischemia and nonreperfused myocardial infarction (MI). It is unknown whether this effect is present in reperfused MI. We sought to investigate the effect of VEGF-165 gene therapy on cardiomyogenesis after reperfused MI. METHODS AND RESULTS: Twenty-four Yucatan minipigs underwent thoracotomy and a vascular clamp was placed in the left circumflex artery. Reperfusion was reestablished after 90 minutes, and VEGF-165 gene therapy or placebo was administered. A replication-deficient recombinant human adenovirus serotype 5 was used for gene transfer (Ad5-VEGF165). The same viral vector devoid of VEGF gene (Ad5-beta-galactosidase) was used as placebo. Two administration routes were tested, intramyocardial (IM) injection and circumflex intracoronary (IC) infusion. The pigs were assigned to one of the following groups: IM Ad5-VEGF165 (n = 6), IM Ad5-betaGal (n = 6), IC Ad5-VEGF165 (n = 6), and IC Ad5-betaGal (n = 6). All pigs received 5-bromo-2'-deoxyuridine (BrdU) 250 mg IV twice a week to label cells undergoing DNA replication. The hearts were explanted at 4 weeks. BrdU-labeled cardiomyocytes in the peri-infarct area were counted by a pathologist blinded to group assignment. The number of BrdU-labeled cardiomyocytes per million cells was 4-fold higher in the group receiving IM VEGF-165 (64 +/- 11.4) vs. IM placebo (16 +/- 10.6), P = 0.034. No difference in infarct size or ventricular function was observed between the groups. CONCLUSIONS: IM VEGF-165 gene therapy promotes cardiomyogenesis in reperfused MI. However, no benefit in infarct size or cardiac function was observed at 4 weeks. The origin of these cells remains unknown and needs to be determined.

Microvascular obstruction and myocardial function after acute myocardial infarction: assessment by using contrast-enhanced cine MR imaging.

UNLABELLED: This study was approved by the Human Investigation Committee of William Beaumont Hospital, and all patients gave informed consent. The purpose of this study was to prospectively compare contrast material-enhanced cine magnetic resonance (MR) imaging with more-standard MR imaging for the evaluation of microvascular obstruction and myocardial function in 80 patients (56 men, 24 women; mean age, 57 years; range, 29-80 years) with acute myocardial infarction after reperfusion therapy. Findings at contrast-enhanced cine MR imaging agreed with the global and transmural extent of microvascular obstruction at first-pass perfusion (intraclass correlation coefficient [IC] of 0.96 [P < .001] and 0.88 [P < .001], respectively) and inversion-recovery gradient-echo (IC of 0.90 [P < .001] and 0.93 [P < .001], respectively) MR imaging. There was no significant difference between myocardial function parameters before and after contrast material enhancement. Contrast-enhanced cine MR imaging reduced imaging time by 34% (11 of 32 minutes) and improved spatial resolution. SUPPLEMENTAL MATERIAL: radiology.rsnajnls.org/cgi/content/full/240/2/529/DC1

MRI-based volumetric assessment of cardiac anatomy and dose reduction via active breathing control during irradiation for left-sided breast cancer.

PURPOSE: Heart dose-volume analysis using computed tomography (CT) is limited because of motion artifact and poor delineation between myocardium and ventricular space. We used dedicated cardiac magnetic resonance imaging (MRI) to quantify exclusion of left ventricular (LV) myocardium via active breathing control (ABC) during left breast irradiation and to determine the correlation between irradiated whole heart and LV volumes. METHODS AND MATERIALS: Fifteen patients who completed adjuvant irradiation for early-stage left breast cancer participated. Treatment consisted of 45 Gy to the entire breast using ABC followed by a 16-Gy electron boost to the lumpectomy cavity. Patients underwent planning CT scans in free breathing (FB) and moderate deep inspiration breath hold (mDIBH). Electrocardiogram-gated cardiac MRI was performed in the treatment position using alpha-cradle immobilization. MRI scans were acquired in late diastole (LD), mid-diastole (MD), and systole (S) for both FB and mDIBH. After image fusion with the patients' radiation therapy planning CT scan, MRI LV volumes were defined for the three examined phases of the cardiac cycle, and comparative dose-volume analysis was performed. RESULTS: Cardiac volume definition was found to differ significantly because of combinations of respiratory and intrinsic heart motion. The fraction of LV myocardium receiving 50% (22.5 Gy) of the prescribed whole breast dose (V(22.5)) was reduced by 85.3%, 91.8%, and 94.6% via ABC for LD, MD, and S, respectively. Linear regression revealed strong correlation between MRI-defined whole heart and LV V(22.5) reduction via ABC, suggesting that LV myocardium accounts for up to approximately 50% of the excluded heart volume through this technique. Significant but weaker correlations were noted between CT-defined whole heart and LV V(22.5) reductions with marked variability in the measurements of patients with larger amounts of heart in the treatment field. CONCLUSIONS: Cardiac MRI demonstrated a significant reduction in LV myocardium irradiated with the use of ABC. The correlation between reduction in V(22.5) values for LV wall and CT-defined whole heart suggests that CT is adequate for determining which patients are likely to benefit from ABC treatment, but inaccuracies inherent to standard CT dictate that more detailed imaging studies such as MRI are required for accurate cardiotoxicity assessment.