Ashley M. Lee

Coronary computed tomography angiography during arrhythmia: Radiation dose reduction with prospectively ECG-triggered axial and retrospectively ECG-gated helical 128-slice dual-source CT

BACKGROUND Arrhythmia during coronary computed tomography angiography (coronary CTA) acquisition increases the risk of nondiagnostic segments and high radiation exposure. An advanced arrhythmia rejection algorithm for prospectively electrocardiogram (ECG)-triggered axial scans using dual-source CT (DSCT) examinations has recently been reported. OBJECTIVE We compared image quality and effective dose at DSCT examinations using prospectively ECG-triggered axial scanning with advanced arrhythmia rejection software (PT-AAR) versus retrospectively ECG-gated helical scanning with tube-current modulation (RG-TCM) during arrhythmia. METHODS This was a retrospective case-control study of 90 patients (43 PT-AAR, 47 RG-TCM) with arrhythmia (defined as heart rate variability [HRV] > 10 beats/min during data acquisition) referred for physician-supervised coronary CTA between April 2010 and September 2011. A subset of 22 cases matched for body mass index, HR, HRV, and other scan parameters was identified. Subjective image quality (4-point scale) and effective dose (dose length product method) were compared. RESULTS PT-AAR was associated with lower effective dose than RG-TCM (4.1 vs 12.6 mSv entire cohort and 4.3 vs 9.1 mSv matched controls; both P < 0.01). Image quality scores were excellent in both groups (3.9 PT-AAR vs 3.6 RG-TCM) and nondiagnostic segment rates were low (0.1% vs 0.6%). Significantly higher image quality scores were found with PT-AAR in the entire cohort (P < 0.05), and in matched controls with high HRV > 28 beats/min (P < 0.05). CONCLUSIONS In patients with variable heart rates, prospectively ECG-triggered axial DSCT with arrhythmia rejection algorithm is feasible and can decrease radiation exposure by ∼50% versus retrospectively ECG-gated helical DSCT, with preserved image quality.

Defining left ventricular noncompaction using cardiac computed tomography.

Purpose: Left ventricular noncompaction (LVNC) is a cardiomyopathy characterized by a distinctive 2-layered appearance of the myocardium because of increased trabeculation and deep intertrabecular recesses. Echocardiography serves as the initial noninvasive diagnostic test. Currently, magnetic resonance imaging (MRI) is increasingly being used to diagnose LVNC because of its improved temporal and spatial resolution. So far, no criteria have been proposed to define pathologic LVNC with the use of computed tomography (CT). Materials and Methods: We analyzed CT images using an American Heart Association 17-segment model in 8 patients previously diagnosed with LVNC by clinical diagnosis, echocardiography, and/or MRI, as well as in 11 patients with nonischemic dilated cardiomyopathy, 11 patients with hypertrophic cardiomyopathy, 10 patients with severe aortic stenosis, 9 patients with severe aortic regurgitation, 10 patients with left ventricular hypertrophy due to essential hypertension, and, additionally, in a control group of 20 patients who had normal CT scans without a history of cardiovascular disease. The distribution of LVNC was assessed by qualitative analysis of 17 myocardial segments for the presence or absence of any degree of noncompaction. Each segment was analyzed in each of the 3 end-diastolic long-axis views for the presence or absence of noncompaction, and the most prominent trabeculation was chosen for measurement. The left ventricular apex was excluded. Thickness of noncompacted and compacted myocardium was measured perpendicular to the compacted myocardium. The ratio of noncompacted to compacted (NC:C) myocardium was calculated for each segment. Receiver operating characteristics were used to generate cutoff values with sensitivity and specificity to distinguish the LVNC group from other groups. Results: An end-diastolic NC:C ratio >2.3 distinguished pathologic LVNC with 88% sensitivity and 97% specificity; positive and negative predictive values were 78% and 99%, respectively. Conclusions: CT using the standard MRI NC:C ratio cutoff >2.3 accurately characterizes pathologic LVNC.

Effect of the 2010 task force criteria on reclassification of cardiovascular magnetic resonance criteria for arrhythmogenic right ventricular cardiomyopathy

BackgroundWe sought to evaluate the effect of application of the revised 2010 Task Force Criteria (TFC) on the prevalence of major and minor Cardiovascular Magnetic Resonance (CMR) criteria for Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) versus application of the original 1994 TFC. We also assessed the utility of MRI to identify alternative diagnoses for patients referred for ARVC evaluation.Methods968 consecutive patients referred to our institution for CMR with clinical suspicion of ARVC from 1995 to 2010, were evaluated for the presence of major and minor CMR criteria per the 1994 and 2010 ARVC TFC. CMR criteria included right ventricle (RV) dilatation, reduced RV ejection fraction, RV aneurysm, or regional RV wall motion abnormalities. When quantitative measures of RV size and function were not available, and in whom abnormal size or function was reported, a repeat quantitative analysis by 2 qualified CMR physicians in consensus.ResultsOf 968 patients, 220 (22.7%) fulfilled either a major or a minor 1994 TFC, and 25 (2.6%) fulfilled any of the 2010 TFC criterion. Among patients meeting any 1994 criteria, only 25 (11.4%) met at least one 2010 criterion. All patients who fulfilled a 2010 criteria also satisfied at least one 1994 criterion. Per the 2010 TFC, 21 (2.2%) patients met major criteria and 4 (0.4%) patients fulfilled at least one minor criterion. Eight patients meeting 1994 minor criteria were reclassified as satisfying 2010 major criteria, while 4 patients fulfilling 1994 major criteria were reclassified to only minor or no criteria under the 2010 TFC.Eighty-nine (9.2%) patients had alternative cardiac diagnoses, including 43 (4.4%) with clinically significant potential ARVC mimics. These included cardiac sarcoidosis, RV volume overload conditions, and other cardiomyopathies.ConclusionsApplication of the 2010 TFC resulted in reduction of total patients meeting any diagnostic CMR criteria for ARVC from 22.7% to 2.6% versus the 1994 TFC. CMR identified alternative cardiac diagnoses in 9.2% of patients, and 4.4% of the diagnoses were potential mimics of ARVC.

Early Resting Myocardial Computed Tomography Perfusion for the Detection of Acute Coronary Syndrome in Patients With Coronary Artery Disease

Background—Acute rest single-photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has high predictive value for acute coronary syndrome (ACS) in emergency department patients. Prior studies have shown excellent agreement between rest/stress computed tomography perfusion (CTP) and SPECT-MPI, but the value of resting CTP (rCTP) in acute chest pain triage remains unclear. We sought to determine the diagnostic accuracy of early rCTP, incremental value beyond obstructive coronary artery disease (CAD; ≥50% stenosis), and compared early rCTP to late stress SPECT-MPI in patients with CAD presenting with suspicion of ACS to the emergency department. Methods and Results—In this prespecified subanalysis of 183 patients (58.1±10.2 years; 33% women), we included patients with any CAD by coronary computed tomography angiography (CCTA) from Rule Out Myocardial Infarction Using Computer-Assisted Tomography I. rCTP was assessed semiquantitatively, blinded to CAD interpretation. Overall, 31 had ACS and 48 had abnormal rCTP. Sensitivity and specificity of rCTP for ACS were 48% (95% confidence interval [CI], 30%–67%) and 78% (95% CI, 71%–85%), respectively. rCTP predicted ACS (adjusted odds ratio, 3.40 [95% CI, 1.37–8.42]; P=0.008) independently of obstructive CAD, and sensitivity for ACS increased from 77% (95% CI, 59%–90%) for obstructive CAD to 90% (95% CI, 74%–98%) with addition of rCTP (P=0.05). In a subgroup undergoing late rest/stress SPECT-MPI (n=81), CCTA/rCTP had noninferior discriminatory value to CCTA/SPECT-MPI (area under the curve, 0.88 versus 0.90; P=0.64) using a noninferiority margin of 10%. Conclusions—Early rCTP provides incremental value beyond obstructive CAD to detect ACS. CCTA/rCTP is noninferior to CCTA/SPECT-MPI to discriminate ACS and presents an attractive alternative to triage patients presenting with acute chest pain. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00990262.

Weekly Dose Reports: The Effects of a Continuous Quality Improvement Initiative on Coronary Computed Tomography Angiography Radiation Doses at a Tertiary Medical Center

RATIONALE AND OBJECTIVES Numerous protocols have been developed to reduce cardiac computed tomography angiography (cCTA) radiation dose while maintaining image quality. However, cCTA practice is highly dependent on physician and technologist experience and education. In this study, we sought to evaluate the incremental value of real-time feedback via weekly dose reports on a busy cCTA service. MATERIALS AND METHODS This time series analysis consisted of 450 consecutive patients whom underwent physician-supervised cCTA for clinically indicated native coronary evaluation between April 2011 and January 2013, with 150 patients before the initiation of weekly dose report (preintervention period: April-September 2011) and 150 patients after the initiation (postintervention period: September 2011-February 2012). To assess whether overall dose reductions were maintained over time, results were compared to a late control group consisting of 150 consecutive cCTA exams, which were performed after the study (September 2012-January 2013). Patient characteristics and effective radiation were recorded and compared. RESULTS Total radiation dose was significantly lower in the postintervention period (3.4 mSv [1.7-5.7] and in the late control group (3.3 mSv [2.0-5.3] versus the preintervention period (4.1 mSv [2.1-6.6] (P = .005). The proportion of high-dose outliers was also decreased in the postintervention period and late control period (exams <10 mSv were 88.0% preintervention vs. 97.3% postintervention vs. 95.3% late control; exams <15 mSv were 98.0% preintervention vs. 100.0% postintervention vs. 98.7% late control; exams <20.0 mSv were 98.7% preintervention vs. 100.0% postintervention vs. 100.0% late control). CONCLUSION Weekly dose report feedback of site radiation doses to patients undergoing physician-supervised cCTA resulted in significant overall dose reduction and reduction of high-dose outliers. Overall dose reductions were maintained beyond the initial study period.

Ultra-Low Dose Cardiac CT Angiography at 80 kV using Second Generation Dual-Source CT: Assessment of Radiation Dose and Image Quality

Objectives: We sought to determine the feasibility of using 80 kV in clinical cardiac CTA, by comparing radiation doses and image quality versus standardized 100 kV protocols. Methods: In this retrospective study, a tube potential of 80 kV was used in 40 consecutive patients (BMI 22.6 ± 2.8). 40 matched patients (BMI 23.1 ± 2.8) were scanned with a tube potential of 100 kV and served as the control group. Qualitative and quantitative image quality parameters were determined in the proximal and distal segments of the coronary arteries. Results: Similar subjective image quality scores were seen between the two protocols. The mean CNR and SNR were at 100 kV vs 80 kV (CNR 19.9 ± 6.0 vs 15.7 ± 5.5; p<0.01 and SNR 17.7 ± 5.5 vs 14.4 ± 4.9). The median radiation dose for the 80 kV protocol was significantly lower compared to the 100 kV protocol (83.0 mGy x cm [58.0- 134.0] vs 193.0 mGy x cm [108.5-225.0]; p<0.01) Conclusion: A tube potential of 80 kV is feasible and results in a radiation dose reduction of 57% compared to 100 kV protocols while preserving subjective image quality.

Feasibility of a radiation dose conserving CT protocol for myocardial function assessment

OBJECTIVE Assessment of myocardial function can be performed at higher noise levels than necessary for coronary arterial evaluation. We evaluated image quality and radiation exposure of a dose-conserving function-only acquisition vs retrospectively electrocardiogram(ECG)-gated coronary CTA with automatic tube current modulation. METHODS Of 26 patients who underwent clinically indicated coronary CTA for coronary and function evaluation, 13 (Group I) underwent prospectively ECG-triggered coronary CTA, followed by low-dose retrospectively ECG-gated scan for function (128-slice dual-source, 80 kVp; reference tube current, 100 mA; 8-mm-thick multiplanar reformatted reconstructions) performed either immediately (n = 6) or after 5- to 10-min delay for infarct assessment (n = 7). 13 corresponding controls (Group II) underwent retrospectively ECG-gated protocols (automatic tube potential selection with CARE kV/CARE Dose 4D; Siemens Healthcare, Forchheim, Germany) with aggressive dose modulation. Image quality assessment was performed on the six Group I subjects who underwent early post-contrast dedicated function scan and corresponding controls. Radiation exposure was based on dose-length product. RESULTS Contrast-to-noise ratio (CNR) was preserved throughout the cardiac cycle in Group I and varied according to dose modulation in Group II. Visual image quality indices were similar during end systole but were better in Group II at end diastole. Although the total radiation exposure was equivalent in Group I and Group II (284 vs 280 mGy cm), the median radiation exposure associated with only the dedicated function scan was 138 mGy cm (interquartile range, 116-203 mGy cm). CONCLUSION A low-dose retrospective ECG-gated protocol permits assessment of myocardial function at a median radiation exposure of 138 mGy cm and offers more consistent multiphase CNR vs traditional ECG-modulation protocols. This is useful for pure functional evaluation or as an adjunct to single-phase scan modes. ADVANCES IN KNOWLEDGE Radiation exposure can be limited with a tailored myocardial function CT protocol while maintaining preserved images.

Coronary computed tomography angiography at 140 kV versus 120 kV: assessment of image quality and radiation exposure in overweight and moderately obese patients

Background Although a tube potential of 140 kV is available on most computed tomography (CT) scanners, its incremental diagnostic value versus 120 kV has been controversial. Purpose To retrospectively evaluate the image quality and radiation exposure of cardiac computed tomography angiography (CCTA) performed at 140 kV in comparison to CCTA at 120 kV in overweight and moderately obese patients. Material and Methods Eighty-eight patients who were referred for CCTA between January 2010 and May 2012 were included. Forty-four patients who were overweight or moderately obese (body mass index [BMI], 25–35 kg/m2) underwent CCTA with dual-source CT (DSCT) scanner at 140 kV. Forty-four match controls who underwent CCTA with DSCT at 120 kV were identified per BMI, average heart rate, scan indication, and scan acquisition mode. All scans were performed per routine protocols with direct physician supervision. Quantitative image metrics (CT attenuation, image noise, contrast-to-noise ratio [CNR], and signal-to-noise ratio [SNR] of left main [LM] and proximal right coronary artery [RCA]) were assessed. Effective radiation dose was compared between the two groups. Results Overall, all scans were diagnostic without any non-evaluable coronary segment per clinical report. 140 kV had a lower attenuation and image noise versus 120 kV (P < 0.01). Both SNR and CNR of proximal coronary arteries were similar between 140 kV and 120 kV (SNR, LM P = 0.93, RCA P = 0.62; CNR, LM P = 0.57, RCA P = 0.77). 140 kV was associated with a 35.3% increase in effective radiation dose as compared with 120 kV (5.1 [3.6–8.2] vs. 3.3 [2.0–5.1] mSv, respectively; P < 0.01). Conclusion 140 kV CCTA resulted in similar image quality but a higher effective radiation dose in comparison to 120 kV CCTA. Therefore, in overweight and moderately obese patients, a tube potential of 120 kV may be sufficient for CCTA with diagnostic image quality.

Leveraging Imperfect Data Sets to Draw New Conclusions: Radiogenomics' True Value?

When Reporting Adverse Events, Less 1⁄4 More In the September 2015 JACR “Speaking of Language” column, titled “Inadvertent s Accidental,” Dr Samson Munn urges radiologists to use the word unintended, accidental, or unintentional instead of inadvertent when reporting adverse events because, as he argues, inadvertent implies carelessness, while the other terms do not connote fault [1]. I have a better suggestion. When describing adverse events, do just that, without adjectives or adverbs of any kind. Consider: Dr Munn would say, “During balloon angioplasty the arterial wall was accidentally perforated” (instead of “inadvertently perforated”). One should say, “During balloon angioplasty the arterial wall was perforated.” First, the word accidental, no matter how nuanced the interpretation, invites suspicion that the standard of care was violated. Second, words such as accidental and unintended are superfluous in this context unless there are instances of balloon angioplasty in which the vessel wall is intentionally perforated, which in fact is never the case. Moreover, adverse events in medical practice are never intentional unless the operator means the patient harm, which, one would hope, is never the case. Any adverse event is, ipso facto, unintentional. The message from the column should not be that accidental, unintended, or unintentional is preferable to inadvertent but that such words have no place in the radiology lexicon.

A review of adherence to the guidelines for coronary CT angiography quantitative stenosis grading thresholds in published research.

Abstract Background: The degree of coronary stenosis of potential hemodynamic significance is central to the interpretation of coronary computed tomography angiography (CCTA), but has been variably defined in the literature. Societal guidelines have attempted to address this issue via recommended thresholds. Objectives: We surveyed the various thresholds for defining significant coronary stenosis reported in research published since the introduction of the Society for Cardiovascular Computed Tomography guidelines regarding the interpretation and reporting of CCTA. Methods: We systematically reviewed the results of bibliographic searches of all original research articles on CCTA, focusing on studies reporting > 25 subjects, to assess the definitions of severity of coronary lesions as found on CCTA. To enable comparisons, we stratified the methods of reporting lesion severity into ≥ 50%, 50% to 69%, and “others” (including infrequent reporting methods). Results: Fifty-nine11 published studies were identified and met inclusion criteria. Eighteen studies reported the severity of coronary stenosis using a definition of 50% to 69% as moderate stenosis; 35 studies defined ≥ 50% coronary stenosis as “stenosis,” “significant stenosis,” or “obstructive lesion” without distinguishing a threshold for moderate versus severe stenosis. Six studies utilized other thresholds, such as 20% to 75%, 40% to 69%, 40% to 70%, 40% to 79%, and 50% to 75% to define moderate coronary stenosis. Conclusions: Fifty-three of 59 studies were graded in accordance with the recommended threshold of ≥ 50% defining potentially significant stenosis, with 18 studies reporting precisely in accordance with the guidelines-recommended thresholds of ≥ 50% narrowing as defining moderate stenosis and ≥ 70% narrowing as defining severe stenosis. Six studies were reported using alternative thresholds for significant stenosis. However, a majority of research studies published since 2009 do not follow the societal guidelines for stenosis grading, since these studies do not clearly describe the degree of coronary stenosis.