Coronary CT angiography radiation dose trends: A 10-year analysis to develop institutional diagnostic reference levels

Establishment of local diagnostic reference levels for abdomen and chest radiographies in the region of Algarve, Portugal

PURPOSE

To assess doses variabilities in the same abdomen and chest RX exams for adults, to check the need for dose harmonization. To calculate Diagnostic Reference Levels (DRL), mandatory in the European Union, for the Algarve district in Portugal. Our results can be a valuable reference for the Portuguese official determination of DRLs, still in progress.

METHOD

We considered 4,936 abdomen and 41,320 chest radiographs of adults, covering 7 health centres and 35 radiographers in Algarve. Entrance skin dose (ESD) was calculated for each radiograph and the corresponding uncertainty estimated. Mean doses per centre and per technician, and their uncertainties, were calculated to access dose variabilities. DRLs, set at the 3rd quartile of the total ESD distribution, were determined for a standard patient and for intervals of body mass index (BMI) to study their correlation with patient anatomical variations. Standard quartile errors were estimated.

RESULTS

Our results suggest significant dispersion in applied ESDs among different centres and radiographers. Estimates of DRLs also show small fluctuations across years and an important dependence on BMI intervals. For a standard patient, they are 8.7 ± 0.1 (abdomen) and 0.44 ± 0.01 (chest), while the European DRLs are, respectively, 5.1 and 0.2 (all in mGy).

CONCLUSIONS

Results suggest that there is room for dose optimization and harmonization with European DRLs, urging a national dose survey and the establishment of official national DRLs. Official DRLs in intervals of BMI would be quite beneficial, to avoid unnecessary dose exposures.

High-Sensitivity Troponins and Subclinical Coronary Atherosclerosis Evaluated by Coronary Calcium Score Among Older Asians Living With Well-Controlled Human Immunodeficiency Virus

Background

Elevated levels of high-sensitivity cardiac troponin (hs-cTn) are suggestive of myocardial cell injury and coronary artery disease. We explored the association between hs-cTn and subclinical arteriosclerosis using coronary artery calcification (CAC) scoring among 337 virally suppressed patients with human immunodeficiency virus (HIV) who were ≥50 years old and without evidence of known coronary artery disease.

Methods

Noncontrast cardiac computed tomography and blood sampling for hs-cTn, both subunit I (hs-cTnI) and subunit T (hs-cTnT), were performed. The relationship between CAC (Agatston score) and serum hs-cTn levels was analyzed using Spearman correlation and logistic regression models.

Results

The patients, of whom 62% were male, had a median age of 54 years and had been on antiretroviral therapy for a median of 16 years; the CAC score was >0 in 50% of patients and ≥100 in 16%. Both hs-cTn concentrations were positively correlated with the Agatston score, with correlation coefficients of 0.28 and 0.27 (P < .001) for hs-cTnI and hs-cTnT, respectively. hs-cTnI and hs-cTnT concentrations of ≥4 and ≥5.3 pg/mL, respectively, provided the best performance for discriminating patients with Agatston scores ≥100, with a sensitivity and specificity of 76% and 60%, respectively, for hs-cTnI and 70% and 50% for hs-cTnT. In multivariable logistic regression analysis, each log unit increase in hs-cTnI level was independently associated with increased odds of having an Agatston score ≥100 (odds ratio, 2.83 [95% confidence interval, 1.69-4.75]; P <.001). Although not an independent predictor, hs-cTnT was also associated with an increased odds of having an Agatston score ≥100 (odds ratio, 1.58 [95% confidence interval, .92-2.73]; P = .10).

Conclusions

Among Asians aged ≥50 years with well-controlled HIV infection and without established cardiovascular disease, 50% had subclinical arteriosclerosis. Increasing hs-cTnI and hs-cTnT concentrations were associated with an increased risk of severe subclinical arteriosclerosis, and hs-cTn may be a potential biomarker to detect severe subclinical arteriosclerosis.

Radiation Doses in Cardiovascular Computed Tomography

We discussed the contemporary views on the effects of ionising radiation on living organisms and the process of estimating radiation doses in CT examinations and the definitions of the CTDI, CTDIvol, DLP, SSDE, ED. We reviewed the reports from large analyses on the radiation doses in CT examinations of the coronary arteries prior to TAVI procedures, including the CRESCENT, PROTECTION, German Cardiac CT Registry studies. These studies were carried out over the last 10 years and can help confront the daily practice of performing cardiovascular CT examinations in most centres. The reference dose levels for these examinations were also collected. The methods to optimise the radiation dose included tube voltage reduction, ECG-monitored tube current modulation, iterative and deep learning reconstruction techniques, a reduction in the scan range, prospective study protocols, automatic exposure control, heart rate control, rational use of the calcium score, multi-slices and dual-source and wide-field tomography. We also present the studies that indicated the need to raise the organ conversion factor for cardiovascular studies from the 0.014-0.017 mSv/mGy*cm used for chest studies to date to a value of 0.0264-0.03 mSv/mGy*cm.

Comparison of two different GSI scanning protocols in head and neck CT angiography: Image quality and radiation dose

OBJECTIVES

To compare image quality and radiation dose of computed tomography angiography (CTA) of the head and neck in patients using two Gemstone Spectral Imaging (GSI) scanning protocols.

METHODS

A total of 100 patients who underwent head-neck CTA were divided into two groups (A and B) according to the scanning protocols, with 50 patients in each group. The patients in group A underwent GSI scanning protocol 1 (GSI profile: head and neck CTA), while those in group B underwent GSI scanning protocol 2 (GSI profile: chest 80 mm). All images were reconstructed using 40% and 70% pre- and post-adaptive level statistical iterative reconstruction V (pre-ASiR-V and post-ASiR-V) algorithms, respectively. The CT dose index (CTDIvol) and dose-length (DLP) product were recorded and the mean value was calculated and converted to the effective dose. CT values, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of all images were calculated. Additionally, subjective image evaluation was conducted by two independent radiologists using a five-point scoring method. All data were statistically analyzed.

RESULTS

There were no significant differences in the CT values, SNR, CNR, and subjective score between groups A and B (p > 0.05); however, the mean effective dose (1.2±0.1 mSv) in group B was 45.5% lower than that in group A (2.2±0.2 mSv) (p < 0.05).

CONCLUSIONS

GSI scanning protocol 2 could more effectively reduce the radiation dose in head-neck CT angiography while maintaining image quality compared to GSI scanning protocol 1.

Coronary Evaluation Before Heart Valvular Surgery by Using Coronary Computed Tomographic Angiography Versus Invasive Coronary Angiography

Background

Coronary computed tomography angiography (CCTA) is a noninvasive, less expensive, low‐radiation alternative to invasive coronary angiography (ICA). ICA is recommended for coronary evaluation before heart valvular surgery, and the supporting evidence for CCTA is insufficient. Our study is a single‐center, prospective cohort study designed to evaluate the feasibility of CCTA instead of ICA in detection of coronary artery disease before surgery.

Methods and Results

Heart valvular surgery candidates were consecutively enrolled between April 2017 and December 2018. Nine hundred fifty‐eight patients in the CCTA group underwent CCTA primarily, and those with ≥50% coronary stenosis or uncertain diagnosis underwent subsequent ICA. One thousand five hundred twenty‐five patients in the ICA group underwent ICA directly before surgery. Coronary artery bypass grafting decision was made by surgeons according to CCTA or ICA results. Most of the patients (78.8%) in the CCTA group avoided invasive angiography. Thirty‐day mortality (0.7% versus 0.9%, P=0.821), myocardial infarction (6.4% versus 6.9%, P=0.680 ), and low cardiac output syndrome (4.2% versus 2.8%, P=0.085) were similar in the CCTA and ICA groups. Median duration of follow‐up was 19.3 months (interquartile range, 14.2–30.0 months), cumulative rates of mortality (2.6% versus 2.6%, P=0.882) and major adverse cardiac events (9.6% versus 9.0%, P=0.607) showed no difference between the 2 groups. Coronary evaluation expense was lower in the CCTA group ($149.6 versus $636.0, P<0.001).

Conclusions

The strategy of using CCTA as a doorkeeper in coronary evaluation before heart valvular surgery showed noninferiority in identification of candidates for coronary artery bypass grafting and postoperative safety.

Comparison of the image quality and radiation dose of different scanning modes in head-neck CT angiography

OBJECTIVES

To analyze and compare the radiation dose and image quality of different CT scanning modes on head-neck CT angiography.

METHODS

A total of 180 patients were divided into Group A and Group B. The groups were further subdivided according to different scanning modes: subgroups A1, A2, A3, B1, B2, and B3. Subgroups A1 and B1 used conventional CT protocol, subgroups A2 and B2 used the kV-Assist scan mode, and subgroups A3 and B3 used the dual-energy gemstone spectral imaging protocol. The CT dose index and dose-length product were recorded. The objective image quality and subjective image evaluation was conducted by two independent radiologists.

RESULTS

The signal-to-noise ratios, contrast-to-noise ratios, and subjective scores of subgroups A3 and B3 were higher than the other subgroups. In subgroups B1 and B2, the subjective scores of 9 patients and 12 patients were lower than 3, respectively. The subjective scores of subgroups B1 and B2 were lower than the other subgroups. There was no statistically significant difference in signal-to-noise ratios, contrast-to-noise ratios, and subjective scores between subgroups A1 and A2. The effective dose of subgroup A2 was 41.7 and 36.4% lower than that in subgroups A1 and A3, respectively (p < 0.05). In Group B, there were no statistically significant differences in CT dose indexvol, dose-length product, and ED among the subgroups (p > 0.05).

CONCLUSION

In the head-neck CT angiography, the kV-Assist scan mode is recommended for patients with body mass index between 18.5 and 34.9 kg m^-2; gemstone spectral imaging scanning mode is recommended for patients with body mass index ≥34.9 kg m^-2.

Comparison of image quality and radiation dose using different pre-ASiR-V and post-ASiR-V levels in coronary computed tomography angiography

OBJECTIVE

To determine the optimal pre-adaptive and post-adaptive level statistical iterative reconstruction V (ASiR-V) for improving image quality and reducing radiation dose in coronary computed tomography angiography (CCTA).

METHODS

The study was divided into two parts. In part I, 150 patients for CCTA were prospectively enrolled and randomly divided into 5 groups (A, B, C, D, and E) with progressive scanning from 40% to 80% pre-ASiR-V with 10% intervals and reconstructing with 70% post-ASiR-V. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Subjective image quality was assessed using a 5-point scale. The CT dose index volume (CTDIvol) and dose-length product (DLP) of each patient were recorded and the effective radiation dose (ED) was calculated after statistical analysis by optimizing for the best pre-ASiR-V value with the lowest radiation dose while maintaining overall image quality. In part II, the images were reconstructed with the recommended optimal pre-ASiR-V values in part I (D group) and 40%-90% of post-ASiR-V. The reconstruction group (D group) was divided into 6 subgroups (interval 10%, D0:40% post-ASiR-V, D1:50% post - ASiR-V, D2:60% post-ASiR-V, D3:70% post-ASiR-V, D4:80% post-ASiR-V, and D5:90% post-ASiR-V).The SNR and CNR of D0-D5 subgroups were calculated and analyzed using one-way analysis of variance, and the consistency of the subjective scores used the k test.

RESULTS

There was no significant difference in the SNRs, CNRs, and image quality scores among A, B, C, and D groups (P > 0.05). The SNR, CNR, and image quality scores of the E group were lower than those of the A, B, C, and D groups (P < 0.05). The mean EDs in the B, C, and D groups were reduced by 7.01%, 13.37%, and 18.87%, respectively, when compared with that of the A group. The SNR and CNR of the D4-D5 subgroups were higher than the D0-D3 subgroups, and the image quality scores of the D4 subgroups were higher than the other subgroups (P < 0.05).

CONCLUSION

The wide-detector combined with 70% pre-ASiR-V and 80% post-ASiR-V significantly reduces the radiation dose of CCTA while maintaining overall image quality as compared with the manufacture's recommendation of 40% pre-ASiR-V.

Role of Coronary CT Angiography in Spontaneous Coronary Artery Dissection

Spontaneous coronary artery dissection (SCAD) is more common than previously thought and is present in up to 4% of patients presenting with acute coronary syndrome. SCAD predominantly occurs in relatively young women and is an important cause of myocardial infarction in young patients without traditional risk factors of atherosclerotic coronary artery disease. There have been substantial improvements in spatial and temporal resolution and reduction in ionizing radiation dose with new generation scanners. The risk of dissection propagation with an invasive coronary angiogram, improved CT scanner parameters, and predominantly conservative management of SCAD make coronary CT angiography a useful noninvasive imaging modality for the assessment of SCAD. © RSNA, 2020.

Network Medicine: A Clinical Approach for Precision Medicine and Personalized Therapy in Coronary Heart Disease

Early identification of coronary atherosclerotic pathogenic mechanisms is useful for predicting the risk of coronary heart disease (CHD) and future cardiac events. Epigenome changes may clarify a significant fraction of this "missing hereditability", thus offering novel potential biomarkers for prevention and care of CHD. The rapidly growing disciplines of systems biology and network science are now poised to meet the fields of precision medicine and personalized therapy. Network medicine integrates standard clinical recording and non-invasive, advanced cardiac imaging tools with epigenetics into deep learning for in-depth CHD molecular phenotyping. This approach could potentially explore developing novel drugs from natural compounds (i.e. polyphenols, folic acid) and repurposing current drugs, such as statins and metformin. Several clinical trials have exploited epigenetic tags and epigenetic sensitive drugs both in primary and secondary prevention. Due to their stability in plasma and easiness of detection, many ongoing clinical trials are focused on the evaluation of circulating miRNAs (e.g. miR-8059 and miR-320a) in blood, in association with imaging parameters such as coronary calcifications and stenosis degree detected by coronary computed tomography angiography (CCTA), or functional parameters provided by FFR/CT and PET/CT. Although epigenetic modifications have also been prioritized through network based approaches, the whole set of molecular interactions (interactome) in CHD is still under investigation for primary prevention strategies.