Coronary computed tomography angiography with model-based iterative reconstruction using a radiation exposure similar to chest X-ray examination

Cross-sectional study on the impact of adverse childhood experiences on coronary flow reserve in male physicians with and without occupational burnout

OBJECTIVE

Physicians face documented challenges to their mental and physical well-being, particularly in the forms of occupational burnout and cardiovascular disease. This study examined the previously under-researched intersection of early life stressors, prolonged occupational stress, and cardiovascular health in physicians.

METHODS

Participants were 60 practicing male physicians, 30 with clinical burnout, defined by the Maslach Burnout Inventory, and 30 non-burnout controls. They completed the Adverse Childhood Experiences (ACE) Questionnaire asking about abuse, neglect and household dysfunctions before the age of 18, and the Perceived Stress Scale to rate thoughts and feelings about stress in the past month. Endothelium-independent (adenosine challenge) coronary flow reserve (CFR) and endothelium-dependent CFR (cold pressor test) were assessed by positron emission tomography-computed tomography. The segment stenosis score was determined by coronary computed tomography angiography.

RESULTS

Twenty-six (43%) participants reported at least one ACE and five (8%) reported ≥4 ACEs. A higher ACEs sum score was associated with lower endothelium-independent CFR (r partial (rp) = -0.347, p = .01) and endothelium-dependent CFR (rp = -0.278, p = .04), adjusting for age, body mass index, perceived stress and segment stenosis score. In exploratory analyses, participants with ≥4 ACEs had lower endothelium-independent CFR (rp = -0.419, p = .001) and endothelium-dependent CFR (rp = -0.278, p = .04), than those with <4 ACEs. Endothelium-dependent CFR was higher in physicians with burnout than in controls (rp = 0.277, p = .04). No significant interaction emerged between burnout and ACEs for CFR.

CONCLUSION

The findings suggest an independent association between ACEs and CFR in male physicians and emphasize the nuanced relationship between early life stressors, professional stress, and cardiovascular health.

Risk stratification using coronary artery calcium scoring based on low tube voltage computed tomography

To determine if coronary artery calcium (CAC) scoring using computed tomography at 80 kilovolt-peak (kVp) and 70-kVp and tube voltage-adapted scoring-thresholds allow for accurate risk stratification as compared to the standard 120-kVp protocol. We prospectively included 170 patients who underwent standard CAC scanning at 120-kVp and 200 milliamperes and additional scans with 80-kVp and 70-kVp tube voltage with adapted tube current to normalize image noise across scans. Novel kVp-adapted thresholds were applied to calculate CAC scores from the low-kVp scans and were compared to those from standard 120-kVp scans by assessing risk reclassification rates and agreement using Kendall's rank correlation coefficients (Τb) for risk categories bounded by 0, 1, 100, and 400. Interreader reclassification rates for the 120-kVp scans were assessed. Agreement for risk classification obtained from 80-kVp and 70-kVp scans as compared to 120-kVp was good (Τb = 0.967 and 0.915, respectively; both p < 0.001) with reclassification rates of 7.1% and 17.2%, respectively, mostly towards a lower risk category. By comparison, the interreader reclassification rate was 4.1% (Τb = 0.980, p < 0.001). Reclassification rates were dependent on body mass index (BMI) with 7.1% and 13.6% reclassifications for the 80-kVp and 70-kVp scans, respectively, in patients with a BMI < 30 kg/m2 (n = 140), and 2.9% and 7.4%, respectively, in patients with a BMI < 25 kg/m2 (n = 68). Mean effective radiation dose from the 120-kVp, the 80-kVp, and 70-kVp scans was 0.54 ± 0.03, 0.42 ± 0.02, and 0.26 ± 0.02 millisieverts. CAC scoring with reduced tube voltage allows for accurate risk stratification if kVp-adapted thresholds for calculation of CAC scores are applied.ClinicalTrials.gov NCT03637231.

Coronary Angiography Print: An Automated Accurate Hidden Biometric Method Based on Filtered Local Binary Pattern Using Coronary Angiography Images

Background and purpose: Biometrics is a commonly studied research issue for both biomedical engineering and forensics sciences. Besides, the purpose of hidden biometrics is to discover hidden biometrics features. This work aims to demonstrate the biometric identification ability of coronary angiography images. Material and method: A new coronary angiography images database was collected to develop an automatic identification model. The used database was collected from 51 subjects and contains 2156 images. The developed model has to preprocess; feature generation using local binary pattern; feature selection with neighborhood component analysis; and classification phases. In the preprocessing phase; image rotations; median filter; Gaussian filter; and speckle noise addition functions have been used to generate filtered images. A multileveled extractor is presented using local binary pattern and maximum pooling together. The generated features are fed to neighborhood component analysis and the selected features are classified using k nearest neighbor classifier. Results: The presented angiography image identification method attained 99.86% classification accuracy on the collected database. Conclusions: The obtained findings demonstrate that the angiography images can be utilized as biometric identification. Moreover, we discover a new hidden biometric feature using coronary angiography images and name of this hidden biometric is coronary angiography print.

Coronary Artery Anomalies

Coronary artery anomalies (CAAs) are a group of congenital conditions characterized by abnormal origin or course of any of the 3 main epicardial coronary arteries. Although CAAs have been identified as a common underlying condition in young athletes with sudden cardiac death, the widespread use of invasive and noninvasive coronary imaging has led to increased recognition of CAAs among adults. CAAS are often discovered as an incidental finding during the diagnostic workup for ischemic heart disease. The clinical correlates and prognostic implication of CAAs remain poorly understood in this context, and guideline-recommended therapeutic choices are supported by a low level of scientific evidence. Several studies have examined whether assessment of CAA-related myocardial ischemia can improve risk stratification in these patients, suggesting that multimodality imaging and functional tests may be key in the management of CAAs. The aim of this review is to outline definitions, classification, and epidemiology of the most relevant CAAs, highlighting recent advances and the potential impact of multimodality evaluation, and to discuss current therapeutic opportunities.

A Hidden Threat: Anomalous Aortic Origins of the Coronary Arteries in Athletes

Purpose of Review

Anomalous aortic origins of the coronary arteries (AAOCA) are a primary cause of sudden cardiac death in athletes. This review will detail the epidemiology, pathophysiology, and risk stratification of AAOCA, while also highlighting return-to-play considerations for athletes.

Recent Findings

Sport pre-participation cardiovascular screening methods lack sensitivity and specificity in the identification of AAOCA. For the symptomatic athlete, clinicians must maintain a heightened clinical suspicion for AAOCA in order to proceed with appropriate cardiac imaging and functional assessments. Anomalous origin of the left coronary artery with an interarterial course is considered high-risk and requires sport restriction until surgical correction. In contrast, risks associated with anomalous origin of the right coronary artery are controversial, thus management and sports eligibility decisions may incorporate principles of shared-decision making.

Summary

Management options for athletes with AAOCA are complex, requiring a comprehensive clinical evaluation. While advances in multimodality cardiovascular imaging and physiologic functional assessments have improved AAOCA risk stratification, best practice treatment strategies for some AAOCA subtypes remain uncertain. As such, clinical management and sport eligibility decisions require an individualized approach. Future prospective data will guide optimization of treatment strategies for athletes with AAOCA.

Independent role of low-density lipoprotein cholesterol in subclinical coronary atherosclerosis in the absence of traditional cardiovascular risk factors

AIMS

Individuals without traditional cardiovascular risk factors (CVRFs) still experience adverse events in clinical practice. This study evaluated the predictors of subclinical coronary atherosclerosis in individuals without traditional CVRFs.

METHODS AND RESULTS

A total of 1250 (52.8 ± 6.5 years, 46.9% male) asymptomatic individuals without CVRFs who underwent coronary computed tomographic angiography for a general health examination were analysed. The following were considered as traditional CVRFs: systolic/diastolic blood pressure ≥140/90 mmHg; fasting glucose ≥126 mg/dL; total cholesterol ≥240 mg/dL; low-density lipoprotein cholesterol (LDL-C) ≥160 mg/dL; high-density lipoprotein cholesterol <40 mg/dL; body mass index ≥25.0 kg/m2; current smoking status; and previous medical history of hypertension, diabetes, and dyslipidaemia. Subclinical atherosclerosis, defined as the presence of any coronary plaque, was present in 20.6% cases; the incidences of non-calcified, calcified, and mixed plaque were 9.6%, 12.6%, and 2.6%, respectively. Multivariate regression analysis showed that LDL-C level [odds ratio (OR): 1.008; 95% confidence interval (CI): 1.001-1.015], together with age (OR: 1.101; 95% CI: 1.075-1.128) and male sex (OR: 5.574; 95% CI: 3.310-9.388), was associated with the presence of subclinical atherosclerosis (All P < 0.05). LDL-C level was significantly associated with an increased risk of calcified plaques rather than non-calcified or mixed plaques.

CONCLUSION

LDL-C, even at levels currently considered within normal range, is independently associated with the presence of subclinical coronary atherosclerosis in individuals without traditional CVRFs. Our results suggest that a stricter control of LDL-C levels may be necessary for primary prevention in individuals who are conventionally considered healthy.

Should computed tomography and bronchoscopy be routine examinations for chronic cough?

Chronic cough is a common symptom of many diseases. Guidelines on cough from different countries recommend chest X-ray as the first-line examination. However, as compared to computerized tomography (CT), chest X-ray is insensitive in the diagnosis of many diseases. We speculate that CT is more helpful in excluding the causes of long-term cough, such as bronchial tumors and pulmonary interstitial diseases, which prevents patients from receiving unnecessary examinations and diagnostic treatments for chronic cough. In addition, a single chest CT is safe and affordable in some regions. Therefore, chest CT may be recommended as a first-line examination for patients with chronic cough. In addition, although bronchoscopy is employed as a further examination for chronic cough, it plays an important role in the diagnosis of chronic cough, especially in rare bronchial diseases such as amyloidosis and foreign body inhalation. Induced sputum cytology was not accepted as a necessary examination for chronic cough, but it becomes a first-line examination until physicians recognize that non-asthmatic eosinophilic bronchitis is a common cause of chronic cough. Therefore, we speculate that the roles of chest CT and bronchoscopy in the identification of causes of chronic cough are increasingly important; in some regions, or for patients suspicious for uncommon causes of chronic cough, CT and bronchoscopy are recommended as first-line examinations.

Diagnostic criteria for left ventricular non-compaction in cardiac computed tomography

Purpose

Left ventricular non-compaction (LVNC) is characterized by a 2-layered myocardium composed of a noncompacted (NC) and a compacted (C) layer. The echocardiographic NC:C ratio is difficult to assess in many patients. The aim of the study was to assess the value of cardiac computed tomography (CCT) for the diagnosis of LVNC.

Methods

In this prospective controlled study, segmental analysis of transthoracic echocardiography (TTE) and prospective ECG-triggered CCT was performed in 17 patients with LVNC and 19 healthy controls. In TTE maximal NC and C thickness was measured at enddiastole and endsystole in the segment with most prominent trabeculation in short axis views. In CCT, maximal segmental NC and C thickness was measured during diastole, and NC:C ratio was determined. Spearman’s correlation coefficient and receiver operating characteristic curves were calculated.

Results

The median [IQR] radiation dose was 1.3[1.2–1.5]mSv. The CCT thickness of the C layer was significantly lower in patients with LVNC as compared to controls in the inferolateral, midventricular, lateral-, inferior-, and septal-apical segments. The CCT NC:C ratio differed significantly between LVNC and controls in the inferior-midventricular and all the apical segments. NC:C ratio correlated significantly between TTE and CCT at enddiastole (σ = 0.8) and endsystole (σ = 0.9). Using a CCT NC:C ratio ≥1.8, all LVNC patients could be identified.

Conclusion

LVNC can be diagnosed with ECG-triggered low-dose CCT and discriminated from normal individuals using a NC:C ratio of ≥1.8 in diastole. There is a very good correlation of NC:C ratio in TTE and CCT.

Clinical utility of early postoperative cardiac multidetector computed tomography after coronary artery bypass grafting

We evaluated the clinical utility of early postoperative cardiac computed tomography (CT) for evaluating left ventricular (LV) function and predicting prognosis in patients who had undergone coronary artery bypass grafting (CABG). Of the 205 patients who underwent CABG from March 2011 to December 2014, 136 underwent early postoperative cardiac CT (within 30 days after CABG) and were enrolled as the study population. The baseline and postoperative follow-up echocardiographic findings, major adverse cardiac events (MACE), and death were recorded for a follow-up period (mean, 5.9 ± 1.1 years). Functional cardiac CT parameters were compared to echocardiographic measurements. The associations between cardiac CT findings and functional recovery and prognosis were evaluated by logistic regression analyses. The LVEF measured via cardiac CT was significantly higher (56.2 ± 11.5% vs. 61.9 ± 12.9%; p = 0.0002) compared to those via early postoperative echocardiography, but the wall motion score index (WMSI) was not significantly different (1.23 ± 0.33 vs. 1.21 ± 0.28, p = 0.5041) between the two methods. During the follow-up period, 17 patients (12.5%) died and 40 (29.4%) developed MACE. Both the LVEF and WMSI measured with early postoperative echocardiography (p = 0.0202 and odds ratio [OR] = 5.0171, p = 0.0039, respectively), and cardiac CT (OR = 0.9625, p = 0.0091 and OR = 14.3605, p = 0.0001, respectively) predicted MACE OR = 0.9630, but only the WMSI, measured using cardiac CT, predicted all-cause death (OR = 10.6017, p = 0.0035). In CABG patients, LVEF and the WMSI measured with early postoperative cardiac CT were comparable with echocardiography and predicted the development of MACE and all-cause death.

Homocysteine is not a risk factor for subclinical coronary atherosclerosis in asymptomatic individuals

BACKGROUND

Homocysteine has been known as a risk factor for cardiovascular disease. This study sought to evaluate the influence of homocysteine on the risk of subclinical coronary atherosclerosis in asymptomatic individuals.

METHODS

We reviewed 3,186 asymptomatic individuals (mean age 53.8 ± 8.0 years, 2,202 men [69.1%]) with no prior history of coronary artery disease who voluntarily underwent coronary computed tomographic angiography (CCTA) and laboratory tests as part of a general health examination. The subjects were stratified into tertiles according to their homocysteine levels. The degree and extent of subclinical coronary atherosclerosis were assessed by CCTA. Logistic regression analysis was used to determine the association between homocysteine levels and subclinical coronary atherosclerosis.

RESULTS

The prevalence of significant coronary artery stenosis, any atherosclerotic, calcified, mixed, and non-calcified plaques increased with homocysteine tertiles (all p < 0.05). However, after adjustment for cardiovascular risk factors, there were no statistically significant differences in the adjusted odds ratios (ORs) for any atherosclerotic plaque (OR 1.06; 95% CI [confidence interval] 0.85-1.32; p = 0.610), calcified plaques (OR 1.17; 95% CI 0.92-1.48; p = 0.199), non-calcified plaques (OR 0.80; 95% CI 0.61-1.04; p = 0.089), and mixed plaques (OR 1.42; 95% CI 0.96-2.11; p = 0.077) between the third and first homocysteine tertiles. In addition, the adjusted OR for significant coronary artery stenosis (OR 0.92; 95% CI 0.63-1.36; p = 0.687) did not differ between the first and third tertiles.

CONCLUSIONS

In asymptomatic individuals, homocysteine is not associated with an increased risk of subclinical coronary atherosclerosis.

Triglyceride glucose index is a useful marker for predicting subclinical coronary artery disease in the absence of traditional risk factors

BACKGROUND

Atherosclerotic cardiovascular (CV) events commonly occur in individuals with a low CV risk burden. This study evaluated the ability of the triglyceride glucose (TyG) index to predict subclinical coronary artery disease (CAD) in asymptomatic subjects without traditional CV risk factors (CVRFs).

METHODS

This retrospective, cross-sectional, and observational study evaluated the association of TyG index with CAD in 1250 (52.8 ± 6.5 years, 46.9% male) asymptomatic individuals without traditional CVRFs (defined as systolic/diastolic blood pressure ≥ 140/90 mmHg; fasting glucose ≥126 mg/dL; total cholesterol ≥240 mg/dL; low-density lipoprotein cholesterol ≥160 mg/dL; high-density lipoprotein cholesterol < 40 mg/dL; body mass index ≥25.0 kg/m²; current smoking; and previous medical history of hypertension, diabetes, or dyslipidemia). CAD was defined as the presence of any coronary plaque on coronary computed tomographic angiography. The participants were divided into three groups based on TyG index tertiles.

RESULTS

The prevalence of CAD increased with elevating TyG index tertiles (group I: 14.8% vs. group II: 19.3% vs. group III: 27.6%; P < 0.001). Multivariate logistic regression models showed that TyG index was associated with an increased risk of CAD (odds ratio [OR] 1.473, 95% confidence interval [CI] 1.026-2.166); especially non-calcified (OR 1.581, 95% CI 1.002-2.493) and mixed plaques (OR 2.419, 95% CI 1.051-5.569) (all P < 0.05). The optimal TyG index cut-off for predicting CAD was 8.44 (sensitivity 47.9%; specificity 68.5%; area under the curve 0.600; P < 0.001). The predictive value of this cut-off improved after considering the non-modifiable factors of old age and male sex.

CONCLUSIONS

TyG index is an independent marker for predicting subclinical CAD in individuals conventionally considered healthy.

Coronary computed tomography angiography using model-based iterative reconstruction algorithms in the detection of significant coronary stenosis: how the plaque type influences the diagnostic performance

Purpose

To evaluate the ability of coronary computed tomography angiography (CCTA) with model-based iterative reconstruction (MBIR) algorithm in detecting significant coronary artery stenosis compared with invasive coronary angiography (ICA).

Material and methods

We retrospectively identified 55 patients who underwent CCTA using the MBIR algorithm with evidence of at least one significant stenosis (≥ 50%) and an ICA within three months. Patients were stratified based on calcium score; stenoses were classified by type and by coronary segment involved. Dose-length-product was compared with the literature data obtained with previous reconstruction algorithms. Coronary artery stenosis was estimated on ICAs based on a qualitative method.

Results

CCTA data were confirmed by ICA in 89% of subjects, and in 73% and 94% of patients with CS < 400 and ≥ 400, respectively. ICA confirmed 81% of calcific stenoses, 91% of mixed, and 67% of soft plaques. Both the dose exposure of patients with prospective acquisition (34) and the exposure of the whole population were significantly lower than the standard of reference (p < 0.001 and p = 0.007).

Conclusions

CCTA with MBIR is valuable in detecting significant coronary artery stenosis with a solid reduction of radiation dose. Diagnostic performance was influenced by plaque composition, being lower compared with ICA for patients with lower CAC score and soft plaques; the visualisation of an intraluminal hypodensity could cause false positives, particularly in D1 and MO segments.

High HDL-C levels reduce the risk of obstructive coronary artery disease in asymptomatic diabetics who achieved optimal glycemic control

The benefit of a high level of high-density lipoprotein cholesterol (HDL-C) against coronary atherosclerosis risk after achieving optimal glycemic control (OGC) in diabetics remains uncertain. We aimed to evaluate the association between HDL-C and obstructive coronary artery disease (CAD) according to OGC status in diabetics. We analyzed 1,114 asymptomatic diabetics who underwent coronary computed tomographic angiography in a health examination. OGC was defined as hemoglobin A1C <7.0%. Obstructive CAD was defined as the presence of plaques with ≥50% stenosis. Patients with a high HDL-C level (≥40 mg/dL and ≥50 mg/dL in males and females, respectively) showed a lower prevalence of obstructive CAD than those with a low HDL-C level in the OGC group (8.9% vs. 14.4%; p = 0.046), but not in the non-OGC group (22.3% vs. 23.2%, p = 0.850). Multiple logistic regression models showed that the risk for obstructive CAD was lower in patients with a high HDL-C level than in those with a low HDL-C level in the OGC group (odds ratio: 0.584, 95% confidence interval: 0.343-0.995; p = 0.048), but not in the non-OGC group. In conclusion, it may be necessary to maintain a high HDL-C level to reduce the risk of obstructive CAD in asymptomatic diabetics after OGC is achieved.

Ultra-low-dose coronary artery calcium scoring using novel scoring thresholds for low tube voltage protocols-a pilot study

Aims

To determine if tube-adapted thresholds for coronary artery calcium (CAC) scoring by computed tomography at 80 kilovolt-peak (kVp) tube voltage and 70-kVp yield comparable results to the standard 120-kVp protocol.

Methods and results

We prospectively included 103 patients who underwent standard scanning with 120-kVp tube voltage and additional scans with 80 kVp and 70 kVp. Mean body mass index (BMI) was 27.9 ± 5.1 kg/m2. For the lowered tube voltages, we applied novel kVp-adapted thresholds for calculation of CAC scores and compared them with standard 120-kVp scans using intraclass correlation and Bland-Altman (BA) analysis. Furthermore, risk-class (CAC score 0/1-10/11-100/101-400/>400) changes were assessed. Median CAC score from 120-kVp scans was 212 (interquartile range 25-901). Thirteen (12.6%) patients had zero CAC. Using the novel kVp-adapted thresholds, CAC scores derived from 80-kVp scans showed excellent correlation (r = 0.994, P < 0.001) with standard 120-kVp scans with BA limits of agreement of -235 (-39.5%) to 172 (28.9%). Similarly, for 70-kVp scans, correlation was excellent (r = 0.972, P < 0.001) but with broader limits of agreement of -476 (-85.0%) to 270 (48.2%). Only 2 (2.8%) reclassifications were observed for the 80-kVp scans in patients with a BMI <30 kg/m2 (n = 71), and 2 (6.1%) for the 70-kVp scans in patients with a BMI <25 kg/m2 (n = 33). Mean effective radiation dose was 0.60 ± 0.07 millisieverts (mSv), 0.19 ± 0.02 mSv, and 0.12 ± 0.01 mSv for the 120-kVp, 80-kVp, and 70-kVp scans, respectively.

Conclusion

The present study suggests that CAC scoring with reduced peak tube voltage is accurate if kVp-adapted thresholds for calculation of CAC scores are applied while offering a substantial further radiation dose reduction.

High-density lipoprotein cholesterol and the risk of obstructive coronary artery disease beyond low-density lipoprotein cholesterol in non-diabetic individuals

AIMS

The relationship between high-density lipoprotein cholesterol and the severity of coronary artery disease beyond low-density lipoprotein cholesterol, the primary target of cholesterol-lowering therapy, remains uncertain. We evaluated the association between high-density lipoprotein cholesterol and obstructive coronary artery disease using parameters of any obstructive plaque, obstructive plaque in the left main coronary artery or proximal left anterior descending artery, and obstructive plaque in multi-vessels, according to low-density lipoprotein cholesterol levels.

METHODS AND RESULTS

We analyzed 5130 asymptomatic non-diabetics who underwent coronary computed tomography angiography for general health examination. Obstructive plaque was defined as a plaque with ≥50% luminal diameter stenosis. The participants were divided into three groups based on low-density lipoprotein cholesterol levels of ≤129, 130-159, and ≥160 mg/dl. The prevalence of any obstructive plaque (5.9% vs 6.4% vs 10.6%) and obstructive plaque in the left main coronary artery or proximal left anterior descending artery (2.1% vs 2.1% vs 4.3%) significantly increased with low-density lipoprotein cholesterol category (all p < 0.05). Compared with subjects with high-density lipoprotein cholesterol level ≥40 mg/dl, those with high-density lipoprotein cholesterol level <40 mg/dl had a significantly higher prevalence of any obstructive plaque (10.4% vs 5.1%), obstructive plaque in the left main coronary artery or proximal left anterior descending artery (3.6% vs 1.8%), and obstructive plaque in multi-vessels (4.3% vs 1.1%), only in the group with low-density lipoprotein cholesterol level ≤129 mg/dl (all p < 0.05). Multiple regression analysis showed that increased high-density lipoprotein cholesterol levels were associated with a reduced risk of all obstructive coronary artery disease parameters only in the group with low-density lipoprotein cholesterol level ≤129 mg/dl (all p < 0.05).

CONCLUSION

Increased high-density lipoprotein cholesterol levels were independently associated with a lower risk of obstructive coronary artery disease in asymptomatic non-diabetics with low low-density lipoprotein cholesterol levels.

Image reconstruction in cardiovascular CT: Part 2 - Iterative reconstruction; potential and pitfalls

The use of IR in CT previously has been prohibitively complicated and time consuming, however improvements in computer processing power now make it possible on almost all CT scanners. Due to its potential to allow scanning at lower doses, IR has received a lot of attention in the medical literature and has become a successful commercial product. Its use in cardiovascular CT has been driven in part due to concerns about radiation dose and image quality. This manuscript discusses the various vendor permutations of iterative reconstruction (IR) in detail and critically appraises the current clinical research available on the various IR techniques used in cardiovascular CT.

Computed tomography coronary angiography vs. standard diagnostic procedure for the diagnosis of angina due to coronary heart disease: A cross-sectional study

Patients with episodes of angina are likely to experience future cardiac events and benefit from a revascularization procedure. Conventional invasive coronary angiography is a well-established and reliable method for the detection of angina, but it has a risk of complications and false-negative diagnosis. The objective of the present study was to assess the utility of computed tomography coronary angiography (CTCA) in the diagnosis of angina due to coronary heart disease. A total of 2,426 patients with chest pain referred to the rapid access chest pain clinic of Beijing Anzhen Hospital, Capital Medical University (Beijing, P.R. China) between 18 January 2016 and 1 December 2017 were included in the present cross-sectional study. All patients were subjected to evaluation of symptoms, blood tests, 12-lead electrocardiogram (ECG), exercise ECG, coronary artery calcium scoring and CTCA. The cost of the diagnosis of angina was determined for each individual method. In total, 776 (32%) and 1,420 (58%) of patients were identified to be abnormal on clinical assessment and CTCA, respectively. Exercise ECG results were not correlated with the interpretation of CTCA (r=0.8511). The working area of the angina due to coronary heart disease detected at one time by the different diagnostic procedures was in the order of ECG <clinical assessment <exercise ECG <coronary artery calcium scoring <CTCA. The cost of the 'standard diagnostic procedure (clinical assessments, ECG, exercise ECG)' was 15,452±806 ¥/patient and that of CTCA was 12,546±612 ¥/patient. CTCA had a higher sensitivity for the diagnosis of angina due to coronary heart disease and the cost was lower than that of the 'standard diagnostic procedure' (level of evidence: 3). The current study was registered at the Research Registry on 11th January 2016 (trial no. researchregistry4232).

Head-to-head comparison of adaptive statistical and model-based iterative reconstruction algorithms for submillisievert coronary CT angiography

Aims

Iterative reconstruction (IR) algorithms allow for a significant reduction in radiation dose of coronary computed tomography angiography (CCTA). We performed a head-to-head comparison of adaptive statistical IR (ASiR) and model-based IR (MBIR) algorithms to assess their impact on quantitative image parameters and diagnostic accuracy for submillisievert CCTA.

Methods and results

CCTA datasets of 91 patients were reconstructed using filtered back projection (FBP), increasing contributions of ASiR (20, 40, 60, 80, and 100%), and MBIR. Signal and noise were measured in the aortic root to calculate signal-to-noise ratio (SNR). In a subgroup of 36 patients, diagnostic accuracy of ASiR 40%, ASiR 100%, and MBIR for diagnosis of coronary artery disease (CAD) was compared with invasive coronary angiography. Median radiation dose was 0.21 mSv for CCTA. While increasing levels of ASiR gradually reduced image noise compared with FBP (up to - 48%, P < 0.001), MBIR provided largest noise reduction (-79% compared with FBP) outperforming ASiR (-59% compared with ASiR 100%; P < 0.001). Increased noise and lower SNR with ASiR 40% and ASiR 100% resulted in substantially lower diagnostic accuracy to detect CAD as diagnosed by invasive coronary angiography compared with MBIR: sensitivity and specificity were 100 and 37%, 100 and 57%, and 100 and 74% for ASiR 40%, ASiR 100%, and MBIR, respectively.

Conclusion

MBIR offers substantial noise reduction with increased SNR, paving the way for implementation of submillisievert CCTA protocols in clinical routine. In contrast, inferior noise reduction by ASiR negatively affects diagnostic accuracy of submillisievert CCTA for CAD detection.

Non-inferior low-dose coronary computed tomography angiography image quality with knowledge-based iterative model reconstruction for overweight patients

We investigated the feasibility of low-dose coronary computed tomography angiography (CCTA), using a prospective electrocardiogram (ECG)-triggered axial scan protocol, knowledge-based iterative model reconstruction (IMR), and fixed tube current, in overweight subjects. Forty non-overweight (group A; body-mass index [BMI] < 25 kg/m²) and 40 overweight individuals (group B; BMI = 25–30 kg/m²), who underwent CCTA for coronary artery disease screening, were retrospectively and consecutively enrolled. A 64-slice CT scanner was used at 100-kVp tube voltage and 150-mA tube current, and images were reconstructed using IMR techniques. Image noise, attenuation at the aorta, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) at the proximal right and left main coronary arteries (pRCA and LMCA) were calculated. CCTA images were qualitatively evaluated using a four-point scale (1, poor; 4, excellent) and analyzed using a non-inferiority test with a pre-defined non-inferiority margin of -0.2. The mean CCTA radiation dose (Group A: 1.33 ± 0.02 mSv; Group B: 1.35 ± 0.10 mSv; p = 0.151) and mean aortic root CT attenuation values (Group A: 447.9 ± 81.6 HU; Group B: 439.5 ± 63.6 HU; p = 0.571) did not differ significantly between the two groups. The mean noise in groups A and B was 26.0 ± 4.8 HU and 29.2 ± 4.4 HU, respectively (p = 0.005). The noise reduction ratio in the groups, compared to filtered back projection, was 65.0% and 68.1%, respectively. The mean grade of image quality did not differ significantly (3.75 ± 0.04 vs. 3.71 ± 0.04, p = 0.478). Group B CCTA image quality was non-inferior (mean difference = -0.043, 95% CI = -0.162–0.077) to that of Group A. We concluded that low-dose CCTA with prospective ECG-triggering and IMR might be applied to overweight subjects, as well as to normal-weight subjects, by using a fixed tube current without an increase in tube current based on the patient’s body size.

Development of an organ-specific insert phantom generated using a 3D printer for investigations of cardiac computed tomography protocols

INTRODUCTION

An ideal organ-specific insert phantom should be able to simulate the anatomical features with appropriate appearances in the resultant computed tomography (CT) images. This study investigated a 3D printing technology to develop a novel and cost-effective cardiac insert phantom derived from volumetric CT image datasets of anthropomorphic chest phantom.

METHODS

Cardiac insert volumes were segmented from CT image datasets, derived from an anthropomorphic chest phantom of Lungman N-01 (Kyoto Kagaku, Japan). These segmented datasets were converted to a virtual 3D-isosurface of heart-shaped shell, while two other removable inserts were included using computer-aided design (CAD) software program. This newly designed cardiac insert phantom was later printed by using a fused deposition modelling (FDM) process via a Creatbot DM Plus 3D printer. Then, several selected filling materials, such as contrast media, oil, water and jelly, were loaded into designated spaces in the 3D-printed phantom. The 3D-printed cardiac insert phantom was positioned within the anthropomorphic chest phantom and 30 repeated CT acquisitions performed using a multi-detector scanner at 120-kVp tube potential. Attenuation (Hounsfield Unit, HU) values were measured and compared to the image datasets of real-patient and Catphan® 500 phantom.

RESULTS

The output of the 3D-printed cardiac insert phantom was a solid acrylic plastic material, which was strong, light in weight and cost-effective. HU values of the filling materials were comparable to the image datasets of real-patient and Catphan® 500 phantom.

CONCLUSIONS

A novel and cost-effective cardiac insert phantom for anthropomorphic chest phantom was developed using volumetric CT image datasets with a 3D printer. Hence, this suggested the printing methodology could be applied to generate other phantoms for CT imaging studies.

Cardiac CT: Technological Advances in Hardware, Software, and Machine Learning Applications

Purpose of Review

Multidetector row computed tomography (CT) allows noninvasive imaging of the heart and coronary arteries. The purpose of this review is to briefly summarize recent advances in CT hardware and software technology, and machine learning applications for cardiovascular imaging.

Recent Findings

In the last decades, there have been significant improvements in CT hardware focusing on faster gantry rotation resulting in improved temporal resolution. Concurrent hardware improvements include improved spatial resolution and higher coverage of the patient, enabling faster acquisition. Advances in cardiac CT software include methods for measurement of noninvasive FFR, coronary plaque characterization, and adipose tissue characteristics around the heart. Machine learning approaches using cardiac CT have been shown to improve both risk of prognosis and lesion-specific ischemia.

Summary

Recent advances in CT hardware and software have expanded the clinical utility of CT for cardiovascular imaging. In the next decades, continued advances can be anticipated in these areas, and in machine learning applications in cardiac CT, as they are incorporated into clinical routine for image acquisition, image analysis, and prediction of patient outcomes.

The feasibility of low-concentration contrast and low tube voltage in computed tomography perfusion imaging: an animal study

Aim: To investigate the feasibility of low-concentration contrast (270 mg/ml) together with low tube voltage (80 kV) and adaptive iterative dose reduction (AIDR)-3D reconstruction in liver computed tomography (CT) perfusion imaging.

Method: A total of 15 healthy New Zealand rabbits received two CT scans each. The first scan (control) was acquired at 100 kV and 100 mA with iopromide (370 mg/ml), while the second scan (experimental) was acquired at 80 kV and 100 mA with iodixanol (270 mg/ml) 24 h after the first scan. The obtained images were reconstructed with filtered back projection (FBP) and AIDR-3D in the control and experimental groups respectively. The perfusion parameters (hepatic artery perfusion [HAP], portal vein perfusion [PVP], hepatic perfusion index [HPI], and total liver perfusion [TLP]) and image quality (image quality score, average CT value of abdomen aorta, signal-to-noise ratio [SNR], contrast-to-noise ratio [CNR], and figure of merit [FOM]) were compared using a paired t-test or Mann–Whitney U test between the two groups, when appropriate. The effective radiation dose and iodine intake were also recorded and compared.

Results: With the exception of the FOM criteria, the image quality and perfusion parameters were not significantly different between the two groups. The effective radiation dose and iodine intake were 38.79% and 27.03% lower respectively, in the experimental group.

Conclusion: Low-concentration contrast (iodixanol, 270 mg/ml) together with low tube voltage (80 kV) and AIDR-3D reconstruction help to reduce radiation dose and iodine intake without compromising perfusion parameters and image quality in liver CT perfusion imaging.

The role of advanced reconstruction algorithms in cardiac CT

Non-linear iterative reconstruction (IR) algorithms have been increasingly incorporated into clinical cardiac CT protocols at institutions around the world. Multiple IR algorithms are available commercially from various vendors. IR algorithms decrease image noise and are primarily used to enable lower radiation dose protocols. IR can also be used to improve image quality for imaging of obese patients, coronary atherosclerotic plaques, coronary stents, and myocardial perfusion. In this article, we will review the various applications of IR algorithms in cardiac imaging and evaluate how they have changed practice.

Recent advances in cardiac computed tomography dose reduction strategies: a review of scientific evidence and technical developments

Cardiac imagers worldwide are bracing for increased utilization of cardiac computed tomography (CT) in clinical practice. This expanding opportunity brings along a responsibility to produce diagnostic quality images with optimized radiation dose. The following review aims to address the dose reduction strategies in cardiac CT in light of recent scientific evidence and technical developments.

Cardiac SPECT/CCTA hybrid imaging : One answer to two questions?

Noninvasive cardiac imaging has witnessed tremendous advances in the recent past, particularly with regard to coronary computed tomography angiography (CCTA) where substantial improvements in image quality have been achieved while at the same time patients' radiation dose exposure has been reduced to the sub-millisievert range. Similarly, for single-photon emission computed tomography (SPECT) the introduction of novel cadmium-zinc-telluride-based semiconductor detectors has significantly improved system sensitivity and image quality, enabling fast image acquisition within less than 2-3 min or reduction of radiation dose exposure to less than 5 mSv. However, neither imaging modality alone is able to fully cover the two aspects of coronary artery disease (CAD), that is, morphology and function. Both modalities have distinct advantages and shortcomings: While CCTA may prove a superb modality for excluding CAD through its excellent negative predictive value, it does not allow for assessment of hemodynamic relevance if obstructive coronary lesions are detected. Conversely, SPECT myocardial perfusion imaging cannot provide any information on the presence or absence of subclinical coronary atherosclerosis. This article aims to highlight the great potential of cardiac hybrid imaging that allows for a comprehensive evaluation of CAD through combination of both morphological and functional information by fusing SPECT with CCTA.

Long-term prognostic performance of low-dose coronary computed tomography angiography with prospective electrocardiogram triggering

OBJECTIVES

To assess long-term prognosis after low-dose 64-slice coronary computed tomography angiography (CCTA) using prospective electrocardiogram-triggering.

METHODS

We included 434 consecutive patients with suspected or known coronary artery disease referred for low-dose CCTA. Patients were classified as normal, with non-obstructive or obstructive lesions, or previously revascularized. Coronary artery calcium score (CACS) was assessed in 223 patients. Follow-up was obtained regarding major adverse cardiac events (MACE): cardiac death, myocardial infarction and elective revascularization. We performed Kaplan-Meier analysis and Cox regressions.

RESULTS

Mean effective radiation dose was 1.7 ± 0.6 mSv. At baseline, 38% of patients had normal arteries, 21% non-obstructive lesions, 32% obstructive stenosis and 8% were revascularized. Twenty-nine patients (7%) were lost to follow-up. After a median follow-up of 6.1 ± 0.6 years, MACE occurred in 0% of patients with normal arteries, 6% with non-obstructive lesions, 30% with obstructive stenosis and 39% of those revascularized. MACE occurrence increased with increasing CACS (P < 0.001), but 4% of patients with CACS = 0 experienced MACE. Multivariate Cox regression identified obstructive stenosis, lesion burden in CCTA and CACS as independent MACE predictors (P ≤ 0.001).

CONCLUSION

Low-dose CCTA with prospective electrocardiogram-triggering has an excellent long-term prognostic performance with a warranty period >6 years for patients with normal coronary arteries.

KEY POINTS

• Coronary CT angiography (CCTA) has an excellent long-term prognostic performance. • CCTA can accurately stratify cardiac risk according to coronary lesion severity. • A normal CCTA predicts freedom from cardiac events for >6 years. • Patients with a coronary calcium score of 0 may experience cardiac events. • CCTA allows for reclassification of cardiac risk compared with ESC SCORE.

Reduction of metal artifacts due to dental hardware in computed tomography angiography: assessment of the utility of model-based iterative reconstruction

PURPOSE

The aim of this study is to assess the value of adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) for reduction of metal artifacts due to dental hardware in carotid CT angiography (CTA).

METHODS

Thirty-seven patients with dental hardware who underwent carotid CTA were included. CTA was performed with a GE Discovery CT750 HD scanner and reconstructed with filtered back projection (FBP), ASIR, and MBIR. We measured the standard deviation at the cervical segment of the internal carotid artery that was affected most by dental metal artifacts (SD₁) and the standard deviation at the common carotid artery that was not affected by the artifact (SD₂). We calculated the artifact index (AI) as follows: AI = [(SD₁)2 - (SD₂)2]1/2 and compared each AI for FBP, ASIR, and MBIR. Visual assessment of the internal carotid artery was also performed by two neuroradiologists using a five-point scale for each axial and reconstructed sagittal image. The inter-observer agreement was analyzed using weighted kappa analysis.

RESULTS

MBIR significantly improved AI compared with FBP and ASIR (p < 0.001, each). We found no significant difference in AI between FBP and ASIR (p = 0.502). The visual score of MBIR was significantly better than those of FBP and ASIR (p < 0.001, each), whereas the scores of ASIR were the same as those of FBP. Kappa values indicated good inter-observer agreements in all reconstructed images (0.747-0.778).

CONCLUSIONS

MBIR resulted in a significant reduction in artifact from dental hardware in carotid CTA.

Variability of radiation doses of cardiac diagnostic imaging tests: the RADIO-EVINCI study (RADIationdOse subproject of the EVINCI study)

BACKGROUND

Patients with coronary artery disease can accumulate significant radiation dose through repeated exposures to coronary computed tomographic angiography, myocardial perfusion imaging with single photon emission computed tomography or positron emission tomography, and to invasive coronary angiography. Aim of the study was to audit radiation doses of coronary computed tomographic angiography, single photon emission computed tomography, positron emission tomography and invasive coronary angiography in patients enrolled in the prospective, randomized, multi-centre European study-EVINCI (Evaluation of Integrated Cardiac Imaging for the Detection and Characterization of Ischemic Heart Disease).

METHODS

We reviewed 1070 tests (476 coronary computed tomographic angiographies, 85 positron emission tomographies, 310 single photon emission computed tomographies, 199 invasive coronary angiographies) performed in 476 patients (mean age 60 ± 9 years, 60% males) enrolled in 12 centers of the EVINCI. The effective doses were calculated in milli-Sievert (mSv) as median, interquartile range (IQR) and coefficient of variation of the mean.

RESULTS

Coronary computed tomographic angiography (476 exams in 12 centers) median effective dose was 9.6 mSv (IQR = 13.2 mSv); single photon emission computed tomography (310 exams in 9 centers) effective dose was 9.3 (IQR = 2.8); positron emission tomography (85 in 3 centers) effective dose 1.8 (IQR = 1.6) and invasive coronary angiography (199 in 9 centers) effective dose 7.4 (IQR = 7.3). Inter-institutional variability was highest for invasive coronary angiography (100%) and coronary computed tomographic angiography (54%) and lowest for single photon emission computed tomography (20%). Intra-institutional variability was highest for invasive coronary angiography (121%) and coronary computed tomographic angiography (115%) and lowest for single photon emission computed tomography (14%).

CONCLUSION

Coronary computed tomographic angiography and invasive coronary angiography doses vary substantially between and within centers. The variability in nuclear medicine procedures is substantially lower. The findings highlight the need to audit doses, to track cumulative exposures and to standardize doses for imaging techniques.

TRIAL REGISTRATION

The study protocol is available at https://www.clinicaltrials.gov/ (ClinicalTrials.gov Identifier: NCT00979199 ). Information provided on September 16, 2009.

Adaptive Statistical Iterative Reconstruction-V: Impact on Image Quality in Ultralow-Dose Coronary Computed Tomography Angiography

OBJECTIVE

The clinical utility of a latest generation iterative reconstruction algorithm (adaptive statistical iterative reconstruction [ASiR-V]) has yet to be elucidated for coronary computed tomography angiography (CCTA). This study evaluates the impact of ASiR-V on signal, noise and image quality in CCTA.

METHODS

Sixty-five patients underwent clinically indicated CCTA on a 256-slice CT scanner using an ultralow-dose protocol. Data sets from each patient were reconstructed at 6 different levels of ASiR-V. Signal intensity was measured by placing a region of interest in the aortic root, LMA, and RCA. Similarly, noise was measured in the aortic root. Image quality was visually assessed by 2 readers.

RESULTS

Median radiation dose was 0.49 mSv. Image noise decreased with increasing levels of ASiR-V resulting in a significant increase in signal-to-noise ratio in the RCA and LMA (P < 0.001). Correspondingly, image quality significantly increased with higher levels of ASiR-V (P < 0.001).

CONCLUSIONS

ASiR-V yields substantial noise reduction and improved image quality enabling introduction of ultralow-dose CCTA.

Iterative model reconstruction reduces calcified plaque volume in coronary CT angiography

OBJECTIVE

To assess the impact of iterative model reconstruction (IMR) on calcified plaque quantification as compared to filtered back projection reconstruction (FBP) and hybrid iterative reconstruction (HIR) in coronary computed tomography angiography (CTA).

METHODS

Raw image data of 52 patients who underwent 256-slice CTA were reconstructed with IMR, HIR and FBP. We evaluated qualitative, quantitative image quality parameters and quantified calcified and partially calcified plaque volumes using automated software.

RESULTS

Overall qualitative image quality significantly improved with HIR as compared to FBP, and further improved with IMR (p<0.01 all). Contrast-to-noise ratios were improved with IMR, compared to HIR and FBP (51.0 [43.5-59.9], 20.3 [16.2-25.9] and 14.0 [11.2-17.7], respectively, all p<0.01) Overall plaque volumes were lowest with IMR and highest with FBP (121.7 [79.3-168.4], 138.7 [90.6-191.7], 147.0 [100.7-183.6]). Similarly, calcified volumes (>130 HU) were decreased with IMR as compared to HIR and FBP (105.9 [62.1-144.6], 110.2 [63.8-166.6], 115.9 [81.7-164.2], respectively, p<0.05 all). High-attenuation non-calcified volumes (90-129 HU) yielded similar values with FBP and HIR (p=0.81), however it was lower with IMR (p < 0.05 both). Intermediate- (30-89 HU) and low-attenuation (<30 HU) non-calcified volumes showed no significant difference (p=0.22 and p=0.67, respectively).

CONCLUSIONS

IMR improves image quality of coronary CTA and decreases calcified plaque volumes.

Coronary Computed Tomographic Angiography at 80 kVp and Knowledge-Based Iterative Model Reconstruction Is Non-Inferior to that at 100 kVp with Iterative Reconstruction

The aims of this study were to compare the image noise and quality of coronary computed tomographic angiography (CCTA) at 80 kVp with knowledge-based iterative model reconstruction (IMR) to those of CCTA at 100 kVp with hybrid iterative reconstruction (IR), and to evaluate the feasibility of a low-dose radiation protocol with IMR. Thirty subjects who underwent prospective electrocardiogram-gating CCTA at 80 kVp, 150 mAs, and IMR (Group A), and 30 subjects with 100 kVp, 150 mAs, and hybrid IR (Group B) were retrospectively enrolled after sample-size calculation. A BMI of less than 25 kg/m² was required for inclusion. The attenuation value and image noise of CCTA were measured and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated at the proximal right coronary artery and left main coronary artery. The image noise was analyzed using a non-inferiority test. The CCTA images were qualitatively evaluated using a four-point scale. The radiation dose was significantly lower in Group A than Group B (0.69 ± 0.08 mSv vs. 1.39 ± 0.15 mSv, p < 0.001). The attenuation values were higher in Group A than Group B (p < 0.001). The SNR and CNR in Group A were higher than those of Group B. The image noise of Group A was non-inferior to that of Group B. Qualitative image quality of Group A was better than that of Group B (3.6 vs. 3.4, p = 0.017). CCTA at 80 kVp with IMR could reduce the radiation dose by about 50%, with non-inferior image noise and image quality than those of CCTA at 100 kVp with hybrid IR.

First experiences with model based iterative reconstructions influence on quantitative plaque volume and intensity measurements in coronary computed tomography angiography

PURPOSE

Investigate the influence of adaptive statistical iterative reconstruction (ASIR) and the model-based IR (Veo) reconstruction algorithm in coronary computed tomography angiography (CCTA) images on quantitative measurements in coronary arteries for plaque volumes and intensities.

METHODS

Three patients had three independent dose reduced CCTA performed and reconstructed with 30% ASIR (CTDI_vol at 6.7 mGy), 60% ASIR (CTDI_vol 4.3 mGy) and Veo (CTDI_vol at 1.9 mGy). Coronary plaque analysis was performed for each measured CCTA volumes, plaque burden and intensities.

RESULTS

Plaque volume and plaque burden show a decreasing tendency from ASIR to Veo as median volume for ASIR is 314 mm³ and 337 mm³-252 mm³ for Veo and plaque burden is 42% and 44% for ASIR to 39% for Veo. The lumen and vessel volume decrease slightly from 30% ASIR to 60% ASIR with 498 mm³-391 mm³ for lumen volume and vessel volume from 939 mm³ to 830 mm³. The intensities did not change overall between the different reconstructions for either lumen or plaque.

CONCLUSION

We found a tendency of decreasing plaque volumes and plaque burden but no change in intensities with the use of low dose Veo CCTA (1.9 mGy) compared to dose reduced ASIR CCTA (6.7 mGy & 4.3 mGy), although more studies are warranted.

Minimized Radiation and Contrast Agent Exposure for Coronary Computed Tomography Angiography: First Clinical Experience on a Latest Generation 256-slice Scanner

RATIONALE AND OBJECTIVES

The aim of the study was to evaluate the impact of the latest coronary computed tomography angiography (CCTA) techniques allowing a radiation- and contrast-sparing protocol on image quality in unselected patients referred for exclusion of suspected coronary artery disease (CAD).

MATERIALS AND METHODS

This prospective study was approved by the local ethics committee, and all patients provided written informed consent. Between March and June 2015, 89 consecutive patients (61% male; mean age 55 ± 11 years) referred for exclusion of CAD by 256-slice CCTA using prospective electrocardiogram triggering were included. Tube voltage (80-120 kVp), tube current (180-310 mA) as well contrast agent volume (25-45 mL) and flow rate (3.5-5 mL/s) were adapted to body mass index. Signal intensity was measured by placing a region of interest in the aortic root, the left main artery, and the proximal right coronary artery. Image noise was measured in the aortic root. Two independent blinded readers semi-quantitatively assessed the image quality regarding motion, noise, and contrast on a 4-point scale.

RESULTS

Median contrast agent volume and median effective radiation dose were 35 mL (interquartile range, 30-40 mL) and 0.5 mSv (interquartile range, 0.4-0.6 mSv), respectively. Mean attenuation in the aortic root was 412 ± 89 Hounsfield units. Diagnostic image quality was obtained in 1050 of 1067 (98.4%) coronary segments and, on an intention-to-diagnosis basis, in 85 of 89 (95.5%) patients. Below a cut-off heart rate of 67 beats/min, only 1 of 974 (0.1%) coronary segments was nondiagnostic.

CONCLUSION

A radiation- and contrast-sparing protocol for CCTA on a latest generation 256-slice computed tomography scanner yields diagnostic image quality in patients referred for CAD exclusion in daily clinical routine.

Comparison of the diagnostic accuracy of FBP, ASiR, and MBIR reconstruction during CT angiography in the evaluation of a vessel phantom with calcified stenosis in a distal superficial femoral artery in a cadaver extremity

PURPOSE

To investigate whether adaptive statistical iterative reconstruction (ASiR) or model-based iterative reconstruction (MBIR) improves the diagnostic performance of computed tomography angiography (CTA) for small-vessel calcified lesions relative to filtered back projection (FBP) using cadaver extremities and a calcified stenosis phantom.

METHODS

A cadaver was used in accordance with our institutional regulations, and a calcified stenosis phantom simulating 4 grades of stenosis was prepared. The phantom was inserted within the distal superficial femoral artery of the cadaver leg. Ten CT images per reconstruction type and stenosis grade were acquired using a 64-slice multidetector-row CTA.As an objective measurement, the first and second derivatives of the CT value function profiles were calculated. As a subjective measurement, 2 blinded reviewers measured the stenosis ratio using a quantitative scale. The Wilcoxon rank-sum test was used to evaluate the data.

RESULTS

Objective measurements of both 25% and 50% stenosis differed significantly (P < 0.01) between MBIR (25/50%: 25.80/50.30 ± 3.88/3.86%) and FBP (25/50%: 35.60/83.80 ± 3.44/26.10%), whereas significant differences were not observed between ASiR and FBP.Reviewer 2's subjective measurements of 25% stenosis differed significantly (P < 0.01) between MBIR (35.13 ± 3.25%) and ASiR (40.89 ± 3.14%), and the measurements of 50% stenosis differed significantly (P < 0.01) between MBIR (reviewers 1/2, 62.36/54.78 ± 2.78/4.96%) and FBP (reviewers 1/2, 62.36/74.84 ± 2.78/18.10%). Significant differences in the subjective measurements were not observed between ASiR and FBP.

CONCLUSION

MBIR improves the diagnostic performance of CTA for small-vessel calcified lesions relative to FBP.

Feasibility of Free-breathing CCTA using 256-MDCT

Usually, coronary computed tomography angiography (CCTA) is performed during breath-holding to reduce artifact caused by respiration. The objective of this study was to evaluate the feasibility of free-breathing CCTA compared to breath-holding using CT scanner with wide detector. To evaluate the feasibility of CCTA during free-breathing using a 256-MDCT. In 80 patients who underwent CCTA, 40 were performed during breath-holding (group A), and the remaining 40 during free-breathing (group B). The quality scores for coronary arteries were analyzed and defined as: 3 (excellent), 2 (good), and 1 (poor). The image noise, signal-to-noise ratio and effective radiation dose as well as the heart rate variation were compared. The noise, signal-to-noise ratio, and effective radiation dose were not significantly different between the 2 groups. The mean heart rate variation between planning and scanning for group A was 7 ± 7.6 bpm, and larger than 3 ± 2.6 bpm for group B (P = 0.012). Quality scores of the free-breathing group were better than those of the breath-holding group (group A: 2.55 ± 0.64, group B: 2.85 ± 0.36, P = 0.018). Free-breathing CCTA is feasible on wide detector CT scanner to provide acceptable image quality with reduced heart rate variation and better images for certain patients.