Development of a computed tomography calcium scoring technique for assessing calcinosis distribution, pattern and burden in dermatomyositis

OBJECTIVES

To utilize whole-body CT imaging and calcium scoring techniques as tools for calcinosis assessment in a prospective cohort of patients with adult and juvenile dermatomyositis (DM and JDM, respectively).

METHODS

Thirty-one patients (14 DM and 17 JDM) who fulfilled Bohan and Peter Classification criteria as probable or definite DM, the EULAR-ACR criteria for definite DM, and with calcinosis identified by physical examination or prior imaging studies were included. Non-contrast whole-body CT scans were obtained using low-dose radiation procedures. Scans were read qualitatively and quantitated. We calculated the sensitivity and specificity of calcinosis detection of physician physical exam against CT. We quantified calcinosis burden using the Agatston scoring technique.

RESULTS

We identified five distinct calcinosis patterns: Clustered, Disjoint, Interfascial, Confluent and Fluid-filled. Novel locations of calcinosis were observed, including the cardiac tissue, pelvic and shoulder bursa, and the spermatic cord. Quantitative measures using Agatston scoring for calcinosis were used in regional distributions across the body. Physician physical exams had a sensitivity of 59% and a specificity of 90% compared with CT detection. A higher calcium score correlated with higher Physician Global Damage, Calcinosis Severity scores, and disease duration.

CONCLUSION

Whole-body CT scans and the Agatston scoring metric define distinct calcinosis patterns and provide novel insights relating to calcinosis in DM and JDM patients. Physicians' physical examinations underrepresented the presence of calcium. Calcium scoring of CT scans correlated with clinical measures, which suggests that this method may be used to assess calcinosis and follow its progression.

Coronary Artery Calcium Scoring in Asymptomatic Patients

Coronary artery calcium (CAC) scoring is an important prognostic tool for personalized cardiovascular preventive care and has recently been incorporated into American College of Cardiology/American Heart Association guidelines. CAC provides direct visualization and quantification of CAC burden for risk stratification and primary prevention of cardiovascular events in an asymptomatic population. CAC scoring is recommended for individuals with intermediate 10-year atherosclerotic cardiovascular disease (ASCVD) risk and selective populations with borderline ASCVD risk. In this review, we outline the interpretation of CAC scores for predicting the risk of cardiovascular events, and we highlight the guidelines for starting statin and potentially starting aspirin therapy. A CAC score of 0 is the strongest negative predictive factor for cardiovascular disease (CVD), and a 0 score can successfully de-risk a patient. On the contrary, higher CAC scores correlate with worse cardiovascular prognostic outcomes. The CAC scan is a widely available and reproducible means for an early look at the atherosclerotic burden, and it can help strategize early interventions. The CAC interpretation and the decision to start treatment need to be personalized based on individual risk factors. We believe the emerging literature supports our contention that the CAC score can be used more broadly to improve the prophylaxis and treatment of a wider range of apparently healthy patients.

Integrated intensity-based technique for coronary artery calcium mass measurement: A phantom study

BACKGROUND

Agatston scoring, the traditional method for measuring coronary artery calcium, is limited in its ability to accurately quantify low-density calcifications, among other things. The inaccuracy of Agatston scoring is likely due partly to the arbitrary thresholding requirement of Agatston scoring.

PURPOSE

A calcium quantification technique that removes the need for arbitrary thresholding and is more accurate, sensitive, reproducible, and robust is needed. Improvements to calcium scoring will likely improve patient risk stratification and outcome.

METHODS

The integrated Hounsfield technique was adapted for calcium scoring (integrated calcium mass). Integrated calcium mass requires no thresholding and includes all calcium information within an image. This study utilized phantom images acquired by G van Praagh et al., with calcium hydroxyapatite (HA) densities in the range of 200-800 mgHAcm-3 to measure calcium according to integrated calcium mass and Agatston scoring. The calcium mass was known, which allowed for accuracy, reproducibility, sensitivity, and robustness comparisons between integrated calcium mass and Agatston scoring. Multiple CT vendors (Canon, GE, Philips, Siemens) were used during the image acquisition phase, which provided a more robust comparison between the two calcium scoring techniques. Three calcification inserts of different diameters (1, 3, and 5 mm) and different HA densities (200, 400, and 800 mgHAcm-3 ) were placed within the phantom. The effect of motion was also analyzed using a dynamic phantom. All dynamic phantom calcium inserts were 5.0 ± 0.1 mm in diameter with a length of 10.0 ± 0.1 mm. The four different densities were 196 ± 3, 380 ± 2, 408 ± 2, and 800 ± 2 mgHAcm-3 .

RESULTS

Integrated calcium mass was more accurate than Agatston scoring for stationary scans (R M S E I n t e g r a t e d = 2.87 $RMS{E}_{Integrated} = 2.87$ ,R M S E A g a t s o n = 4.07 $RMS{E}_{Agatson} = 4.07$ ) and motion affected scans (R M S E I n t e g r a t e d = 9.70 $RMS{E}_{Integrated} = 9.70$ ,R M S E A g a t s o n = 19.98 $RMS{E}_{Agatson} = 19.98$ ). On average, integrated calcium mass was more reproducible than Agatston scoring for two of the CT vendors. The percentage of false-negative and false-positive calcium scores were lower for integrated calcium mass (15.00%, 0.00%) than Agatston scoring (28.33%, 6.67%). Integrated calcium mass was more robust to changes in scan parameters than Agatston scoring.

CONCLUSIONS

The results of this study indicate that integrated calcium mass is more accurate, reproducible, and sensitive than Agatston scoring on a variety of different CT vendors. The substantial reduction in false-negative scores for integrated calcium mass is likely to improve risk-stratification for patients undergoing calcium scoring and their potential outcome.

Coronary artery calcium mass measurement based on integrated intensity and volume fraction techniques

Purpose

Agatston scoring does not detect all the calcium present in computed tomography scans of the heart. A technique that removes the need for thresholding and quantifies calcium mass more accurately and reproducibly is needed.

Approach

Integrated intensity and volume fraction techniques were evaluated for accurate quantification of calcium mass. Integrated intensity calcium mass, volume fraction calcium mass, Agatston scoring, and spatially weighted calcium scoring were compared with known calcium mass in simulated and physical phantoms. The simulation was created to match a 320-slice CT scanner. Fat rings were added to the simulated phantoms, which resulted in small (30×20  cm2), medium (35×25  cm2), and large (40×30  cm2) phantoms. Three calcification inserts of different diameters and hydroxyapatite densities were placed within the phantoms. All the calcium mass measurements were repeated across different beam energies, patient sizes, insert sizes, and densities. Physical phantom images from a previously reported study were then used to evaluate the accuracy and reproducibility of the techniques.

Results

Both integrated intensity calcium mass and volume fraction calcium mass yielded lower root mean squared error (RMSE) and deviation (RMSD) values than Agatston scoring in all the measurements in the simulated phantoms. Specifically, integrated calcium mass (RMSE: 0.49 mg, RMSD: 0.49 mg) and volume fraction calcium mass (RMSE: 0.58 mg, RMSD: 0.57 mg) were more accurate for the low-density stationary calcium measurements than Agatston scoring (RMSE: 3.70 mg, RMSD: 2.30 mg). Similarly, integrated calcium mass (15.74%) and volume fraction calcium mass (20.37%) had fewer false-negative (CAC = 0) measurements than Agatston scoring (75.00%) and spatially weighted calcium scoring (26.85%), on the low-density stationary calcium measurements.

Conclusion

The integrated calcium mass and volume fraction calcium mass techniques can potentially improve risk stratification for patients undergoing calcium scoring and further improve risk assessment compared with Agatston scoring.

Enhancing Radiation Dose Efficiency in Prospective ECG-Triggered Coronary CT Angiography Using Calcium-Scoring CT

BACKGROUND

This study investigates whether the scan length adjustment of prospectively ECG-triggered coronary CT angiography (CCTA) using calcium-scoring CT (CAS-CT) images can reduce overall radiation doses.

METHODS

A retrospective analysis was conducted on 182 patients who underwent CAS-CT and prospectively ECG-triggered CCTA using a second-generation Dual-Source CT scanner. CCTA planning was based on CAS-CT images, for which simulated scout view planning was performed for comparison. Effective doses were compared between two scenarios: Scenario 1-CAS-CT-derived CCTA + CAS-CT and Scenario 2-scout-view-derived CCTA without CAS-CT. Dose differences were further analyzed with respect to scan mode and body mass index.

RESULTS

Planning CCTA using CAS-CT led to a shorter scan length than planning via scout view (114.3 ± 9.7 mm vs. 133.7 ± 13.2 mm, p < 0.001). The whole-examination effective dose was slightly lower for Scenario 1 (3.2 [1.8-5.3] mSv vs. 3.4 [1.5-5.9] mSv; p < 0.001, n = 182). Notably, Scenario 1 resulted in a significantly lower radiation dose for sequential scans and obese patients. Only high-pitch spiral CCTA showed dose reduction in Scenario 2.

CONCLUSIONS

Using CAS-CT for planning prospectively ECG-triggered CCTA reduced the overall radiation dose administered compared to scout view planning without CAS-CT, except for high-pitch spiral CCTA, where a slightly opposite effect was observed.

Radiation Dose Reduction for Coronary Artery Calcium Scoring Using a Virtual Noniodine Algorithm on Photon-Counting Detector Computed-Tomography Phantom Data

Background: On the basis of the hypothesis that virtual noniodine (VNI)-based coronary artery calcium scoring (CACS) is feasible at reduced radiation doses, this study assesses the impact of radiation dose reduction on the accuracy of this VNI algorithm on a photon-counting detector (PCD)-CT. Methods: In a systematic in vitro setting, a phantom for CACS simulating three chest sizes was scanned on a clinical PCD-CT. The standard radiation dose was chosen at volumetric CT dose indices (CTDI_Vol) of 1.5, 3.3, 7.0 mGy for small, medium-sized, and large phantoms, and was gradually reduced by adjusting the tube current resulting in 100, 75, 50, and 25%, respectively. VNI images were reconstructed at 55 keV, quantum iterative reconstruction (QIR)1, and at 60 keV/QIR4, and evaluated regarding image quality (image noise (IN), contrast-to-noise ratio (CNR)), and CACS. All VNI results were compared to true noncontrast (TNC)-based CACS at 70 keV and standard radiation dose (reference). Results: IN_TNC was significantly higher than IN_VNI, and IN_VNI at 55 keV/QIR1 higher than at 60 keV/QIR4 (100% dose: 16.7 ± 1.9 vs. 12.8 ± 1.7 vs. 7.7 ± 0.9; p < 0.001 for every radiation dose). CNR_TNC was higher than CNR_VNI, but it was better to use 60 keV/QIR4 (p < 0.001). CACS_VNI showed strong correlation and agreement at every radiation dose (p < 0.001, r > 0.9, intraclass correlation coefficient > 0.9). The coefficients of the variation in root-mean squared error were less than 10% and thus clinically nonrelevant for the CACS_VNI of every radiation dose. Conclusion: This phantom study suggests that CACS_VNI is feasible on PCD-CT, even at reduced radiation dose while maintaining image quality and CACS accuracy.

Online Calibration of a Linear Micro Tomosynthesis Scanner

In a linear tomosynthesis scanner designed for imaging histologic samples of several centimeters size at 10 µm resolution, the mechanical instability of the scanning stage (±10 µm) exceeded the resolution of the image system, making it necessary to determine the trajectory of the stage for each scan to avoid blurring and artifacts in the images that would arise from the errors in the geometric information used in 3D reconstruction. We present a method for online calibration by attaching a layer of randomly dispersed micro glass beads or calcium particles to the bottom of the sample stage. The method was based on a parametric representation of the rigid body motion of the sample stage-marker layer assembly. The marker layer was easy to produce and proven effective in the calibration procedure.

Generative models for reproducible coronary calcium scoring

Purpose: Coronary artery calcium (CAC) score, i.e., the amount of CAC quantified in CT, is a strong and independent predictor of coronary heart disease (CHD) events. However, CAC scoring suffers from limited interscan reproducibility, which is mainly due to the clinical definition requiring application of a fixed intensity level threshold for segmentation of calcifications. This limitation is especially pronounced in non-electrocardiogram-synchronized computed tomography (CT) where lesions are more impacted by cardiac motion and partial volume effects. Therefore, we propose a CAC quantification method that does not require a threshold for segmentation of CAC. Approach: Our method utilizes a generative adversarial network (GAN) where a CT with CAC is decomposed into an image without CAC and an image showing only CAC. The method, using a cycle-consistent GAN, was trained using 626 low-dose chest CTs and 514 radiotherapy treatment planning (RTP) CTs. Interscan reproducibility was compared to clinical calcium scoring in RTP CTs of 1662 patients, each having two scans. Results: A lower relative interscan difference in CAC mass was achieved by the proposed method: 47% compared to 89% manual clinical calcium scoring. The intraclass correlation coefficient of Agatston scores was 0.96 for the proposed method compared to 0.91 for automatic clinical calcium scoring. Conclusions: The increased interscan reproducibility achieved by our method may lead to increased reliability of CHD risk categorization and improved accuracy of CHD event prediction.

A Pilot Study Comparing Aortic Sonography, Flow Cytometry, and Coronary CT

PURPOSE

To improve cardiovascular disease (CVD) risk prediction by combining screening techniques and to determine whether the combination of sonographic aortic calcification quantification, measurement of aortic intimal thickness, and monocyte laboratory values provides improved diagnostic detection compared with computed tomography (CT) calcium scoring.

METHODS

A pre-experimental design was used to collect imaging, demographic, and biometric data. Data were collected from a convenience sample of 11 volunteers aged 40 to 60 years, including 6 men and 5 women. Collected data included anthropometric measures, laboratory values, flow cytometry, coronary artery calcium scores, atherosclerotic cardiovascular disease (ASCVD) 10-year risk scores, and aortic intimal-medial thickness (IMT).

RESULTS

Aortic IMT in the distal portion of the aorta or region 1 was related significantly to mass (r = 0.725, P = .012), body mass index (r = 0.668, P = .025), and ASCVD 10-year risk score (r = 0.747, P = .033). The aortic IMT in mid portion of the aorta or region 2 was related significantly to mass (r = 0.651, P = .030), antihypertensive medications (r = 0.682, P = .021), ASCVD 10-year risk score (r = 0.753, P = .031), and total coronary artery calcification (CAC) (r = 0.626, P = .039). In addition, the proportions of circulating CD14⁺CD16- (traditional) and CD14⁺CD16⁺ (inflammatory) monocytes, and the monocyte surface expression of the adhesion molecules CD11a and CD11c, were correlated with the number of calcifications in regions 1 and 2.

DISCUSSION

The use of a modified grading system for sonography provided a nonionizing, noninvasive option to easily assess patients' risks of CVD in an office environment. Although CAC has been used widely as a screening mechanism for CVD, ionizing radiation use might not be justified for those who are asymptomatic. The combination of sonography with flow cytometry demonstrated a promising alternative for assessing CVD risk.

CONCLUSION

tBetter quantification of inflammatory markers and atherosclerotic plaques is needed. The combination of noninvasive imaging and advanced laboratory analysis holds promise for assessing and managing CVD risk. This study provides further evidence of the need for continued research with larger sample sizes and diversified populations to improve the quality of CVD risk assessment.

Virtual monochromatic imaging reduces beam hardening artefacts in cardiac interior photon counting computed tomography: a phantom study with cadaveric specimens

In interior cardiac computed tomography (CT) imaging, the x-ray beam is collimated to a limited field-of-view covering the heart volume, which decreases the radiation exposure to surrounding tissues. Spectral CT enables the creation of virtual monochromatic images (VMIs) through a computational material decomposition process. This study investigates the utility of VMIs for beam hardening (BH) reduction in interior cardiac CT, and further, the suitability of VMIs for coronary artery calcium (CAC) scoring and volume assessment is studied using spectral photon counting detector CT (PCD-CT).Ex vivocoronary artery samples (N = 18) were inserted in an epoxy rod phantom. The rod was scanned in the conventional CT geometry, and subsequently, the rod was positioned in a torso phantom and re-measured in the interior PCD-CT geometry. The total energy (TE) 10-100 keV reconstructions from PCD-CT were used as a reference. The low energy 10-60 keV and high energy 60-100 keV data were used to perform projection domain material decomposition to polymethyl methacrylate and calcium hydroxylapatite basis. The truncated basis-material sinograms were extended using the adaptive detruncation method. VMIs from 30-180 keV range were computed from the detruncated virtual monochromatic sinograms using filtered back projection. Detrending was applied as a post-processing method prior to CAC scoring. The results showed that BH artefacts from the exterior structures can be suppressed with high (≥100 keV) VMIs. With appropriate selection of the monoenergy (46 keV), the underestimation trend of CAC scores and volumes shown in Bland-Altman (BA) plots for TE interior PCD-CT was mitigated, as the BA slope values were -0.02 for the 46 keV VMI compared to -0.21 the conventional TE image. To conclude, spectral PCD-CT imaging using VMIs could be applied to reduce BH artefacts interior CT geometry, and further, optimal selection of VMI may improve the accuracy of CAC scoring assessment in interior PCD-CT.

De-risking primary prevention: role of imaging

Atherosclerotic cardiovascular disease (ASCVD) is a common disease among the general population, and includes four major areas: (1) coronary heart disease (CHD), manifested by stable angina, unstable angina, myocardial infarction (MI), heart failure, and coronary death; (2) cerebrovascular disease, manifested by transient ischemia attack and stroke; (3) peripheral vascular disease, manifested by claudication and critical limb ischemia; and (4) aortic atherosclerosis and aortic aneurysm (thoracic and abdominal). CHD remains the leading cause of death for both men and women in the United States. So, it is imperative to identify people at risk of CHD and provide appropriate medical treatment or intervention to prevent serious complications and outcomes including sudden cardiac death. Coronary artery calcification (CAC) is a marker of subclinical coronary artery disease. Therefore, coronary artery calcium score is an important screening method for Coronary artery disease (CAD). In this article, we performed a comprehensive review of current literatures and studies assessing the prognostic value of CAC for future cardiovascular disease (CVD) events. We searched PubMed, MEDLINE, Google Scholar, and Cochrane library. We also reviewed the 2018 American College of Cardiology (ACC)/American Heart Association (AHA) guideline on the assessment of CVD risk. A CAC score of zero corresponds to very low CVD event rates (∼1% per year) and hence a potent negative risk marker. This has been referred to as the ‘power of zero’ and affords the lowest risk of any method of risk calculation. It is now indicated in the 2018 ACC/AHA Cholesterol guidelines to be used to avoid statins for 5–10 years after a score of zero, and then re-assess the patient.

Prediction of cardiovascular events in patients with chronic myeloid leukaemia using baseline risk factors and coronary artery calcium scoring

A standardised method for cardiovascular risk stratification in chronic myeloid leukaemia patients treated with tyrosine kinase inhibitors is lacking. We report an algorithm for risk stratification applicable to all patients commencing tyrosine kinase inhibitor therapy based on age, prior cardiovascular disease and Framingham Risk Score, incorporating coronary artery calcium scoring in patients at intermediate Framingham Risk Score risk. Of 88 patients retrospectively studied, major adverse cardiovascular event rates in our study-defined low-, intermediate- and high-risk categories were 0%, 10% and 19% respectively. Of nine patients down-classified from intermediate to low risk on the basis of coronary artery calcium scoring, none went on to experience a major adverse cardiovascular event.

Mitral annular calcification and valvular dysfunction: multimodality imaging evaluation, grading, and management

Mitral annular calcification (MAC) refers to calcium deposition in the fibrous skeleton of the mitral valve. It has many cardiovascular associations, including mitral valve dysfunction, elevated cardiovascular risk, arrhythmias, and endocarditis. Echocardiography conventionally is the first-line imaging modality for anatomic assessment, and evaluation of mitral valve function. Cardiac computed tomography (CT) has demonstrated importance as an imaging modality for the evaluation and planning of related procedures. It also holds promise in quantitative grading of MAC. Currently, there is no universally accepted definition or classification system of MAC severity. We review the multimodality imaging evaluation of MAC and associated valvular dysfunction and propose a novel classification system based on qualitative and quantitative measurements derived from echocardiography and cardiac CT.

Surgical management of misdeployed transcatheter aortic valve due to eccentric leaflet calcification

A serious complication of transcatheter valves is the mechanistic failure of the deployment system and prosthesis migration. We report the case of a transcatheter aortic valve implantation which failed during implantation resulting in dislodgement of the prosthesis. Emergency surgery to retrieve the deployment system and surgically replace the native valve was the only option to salvage the patient.

Measurement of Aortic Atherosclerotic Disease Severity: A Novel Tool for Simplified, Objective Disease Scoring Using CT Angiography

Introduction

Vascular calcification is a recognized indicator of cardiovascular morbidity and mortality. Calcium scoring is a widely used tool to measure coronary artery calcification, however has limitations for use elsewhere in the body. There is currently no gold standard for quantifying abdominal aortic calcification (AAC).

We propose a simple and reproducible method to assess the severity of AAC using multiplanar reconstruction (MPR) in CT angiograms (CTA).

Methods

A retrospective analysis of CTAs from 75 patients over two years was performed. Using a novel six-point scoring system, three radiologists independently scored the severity of AAC in the distal abdominal aorta. Interclass correlation (ICC) was used to assess the degree of agreement between the three raters.

Calcium scoring of the same region was also calculated for each patient. We used Spearman's rank correlation coefficient to compare the CT calcium score with the corresponding average rater's atheroma score.

Results

There was significant agreement between raters’ scores, with an ICC value = 0.972, 95% (CI 0.959-0.981, p < 0.0001). There was also a strong correlation between an average rater's atheroma score with the corresponding CT calcium score, rho = 0.85 (p < 0.0001).

Conclusion

The results show excellent reproducibility of scores between radiologists, as well as a strong correlation between this novel scoring tool and calcium scores, indicating that it is a reliable method for the grading of AAC. 

We propose that this simple semi-quantitative method could form a widely used system for AAC disease stratification.

coronary artery calcium scoring

Background

In a primary prevention screening program of asymptomatic middle-aged subjects, we sought to assess the degree of risk-reclassification provided by traditional risk assessment vs. coronary artery calcification scoring (CACS).

Methods

A total of 1,806 consecutive asymptomatic subjects (age 55 years, 76% men), who underwent comprehensive screening in a primary prevention clinic between 3/2016 and 9/2017 were included. Standard risk factors, C-reactive protein (CRP) and CAC scoring were performed. % 10-year coronary heart disease (CHD) risk was calculated using Reynolds Risk Score (RRS), atherosclerotic cardiovascular disease (ASCVD) score and multiethnic study on subclinical atherosclerosis (MESA) CACS were calculated. % 10-year CHD risk for all scores was categorized as follows: <1%, 1-5%, 6-10% and >10%.

Results

Mean CRP, RRS, ASCVD and MESA-CACS were 2.1±4.2, 3.7±4, 4.9±6, 4.9±5; 54% had CAC of 0, while 21% had CAC >75th percentile. There was a significant, but modest correlation between MESA-CAC score and (I) RRS (r=0.62) and (II) ASCVD scores (r=0.65, both P<0.001). Compared to MESA-CAC, for RRS, (I) 188 (10%) patients had a downgrade in risk and (II) 538 (30%) patients had an upgrade in risk (40% reclassification of risk). Similarly, compared to MESA-CAC, for ASCVD score, (I) 412 (23%) patients had a downgrade in risk and (II) 329 (18%) patients had a downgrade in risk (41% reclassification of risk).

Conclusions

In a primary prevention screening program of asymptomatic middle-aged patients, RRS overestimates and ASCVHD underestimates 10-year CHD risk vs. MESA-CACS. Addition of CACS results in significant risk reclassification.

Impact of automatically detected motion artifacts on coronary calcium scoring in chest computed tomography

The amount of coronary artery calcification (CAC) quantified in computed tomography (CT) scans enables prediction of cardiovascular disease (CVD) risk. However, interscan variability of CAC quantification is high, especially in scans made without ECG synchronization. We propose a method for automatic detection of CACs that are severely affected by cardiac motion. Subsequently, we evaluate the impact of such CACs on CAC quantification and CVD risk determination. This study includes 1000 baseline and 585 one-year follow-up low-dose chest CTs from the National Lung Screening Trial. About 415 baseline scans are used to train and evaluate a convolutional neural network that identifies observer determined CACs affected by severe motion artifacts. Therefore, 585 paired scans acquired at baseline and follow-up were used to evaluate the impact of severe motion artifacts on CAC quantification and risk categorization. Based on the CAC amount, the scans were categorized into four standard CVD risk categories. The method identified CACs affected by severe motion artifacts with 85.2% accuracy. Moreover, reproducibility of CAC scores in scan pairs is higher in scans containing mostly CACs not affected by severe cardiac motion. Hence, the proposed method enables identification of scans affected by severe cardiac motion, where CAC quantification may not be reproducible.

Detection and quantification of coronary calcium from dual energy chest x-rays: Phantom feasibility study

PURPOSE

We have demonstrated the ability to identify coronary calcium, a reliable biomarker of coronary artery disease, using nongated, 2-shot, dual energy (DE) chest x-ray imaging. Here we will use digital simulations, backed up by measurements, to characterize DE calcium signals and the role of potential confounds such as beam hardening, x-ray scatter, cardiac motion, and pulmonary artery pulsation. For the DE calcium signal, we will consider quantification, as compared to CT calcium score, and visualization.

METHODS

We created stylized and anatomical digital 3D phantoms including heart, lung, coronary calcium, spine, ribs, pulmonary artery, and adipose. We simulated high and low kVp x-ray acquisitions with x-ray spectra, energy dependent attenuation, scatter, ideal detector, and automatic exposure control (AEC). Phantoms allowed us to vary adipose thickness, cardiac motion, etc. We used specialized dual energy coronary calcium (DECC) processing that includes corrections for scatter and beam hardening.

RESULTS

Beam hardening over a wide range of adipose thickness (0-30 cm) reduced the change in intensity of a coronary artery calcification (ΔI_CAC ) by < 3% in DECC images. Scatter correction errors of ±50% affected the calcium signal (ΔI_CAC ) in DECC images ±9%. If a simulated pulmonary artery fills with blood between exposures, it can give rise to a residual signal in DECC images, explaining pulmonary artery visibility in some clinical images. Residual misregistration can be mostly compensated by integrating signals in an enlarged region encompassing registration artifacts. DECC calcium score compared favorably to CT mass and volume scores over a number of phantom perturbations.

CONCLUSION

Simulations indicate that proper DECC processing can faithfully recover coronary calcium signals. Beam hardening, errors in scatter estimation, cardiac motion, calcium residual misregistration etc., are all manageable. Simulations are valuable as we continue to optimize DE coronary calcium image processing and quantitative analysis.

The prognostic value of CT coronary angiography in patients attending hospital with troponin-negative acute chest pain and inconclusive exercise treadmill tests

AIMS

Once acute coronary syndrome (ACS) is excluded in patients presenting to hospital with acute chest pain, usual practice is to stratify future risk of adverse cardiovascular events. Commonly this is performed by pre-discharge exercise treadmill testing (ETT). Often however, patients are unable to perform the test for various reasons, or the final result is inconclusive. This potentially could lead to uncertainty and to unnecessary invasive coronary angiography. We wished to evaluate the potential prognostic significance of CT coronary angiography (CTCA) in patients with prior inconclusive ETTs.

METHODS AND RESULTS

Two hundred and thirty-two consecutive patients underwent CTCA and calcium scoring following hospital attendance with acute chest pain and following exclusion of ACS. All patients were followed up for a combined primary outcome of death, non-fatal myocardial infarction, and late revascularization. The mean follow-up period was 2.5 ± 0.9 years. The combined primary outcome occurred in 26 patients (11.2%). Calcium score (HR 1.16; 95% CI 1.02-1.31, P = 0.023 per 100 Agatston unit increase), the presence of coronary artery disease (CAD) on CTCA (non-obstructive CAD, HR 4.52; 95% CI 1.30-15.73, P = 0.018; obstructive CAD, HR 17.00; 95% CI 4.60-62.85, P < 0.001), and ≥3 segments with non-calcified plaque (HR 3.30; 95% CI 1.24-8.76, P = 0.017) were significant univariable predictors of the primary outcome. CTCA was the only significant multivariable predictor of adverse outcome.

CONCLUSIONS

The presence of CAD assessed by CTCA is a strong predictor of adverse events in patients with troponin-negative acute chest pain and could potentially be used as an alternative, non-invasive risk stratifier in patients with inconclusive exercise tests.

Relationship between breast arterial calcification on mammography with CT Calcium scoring and coronary CT angiography results

Background:

Mammography as a non invasive method has been suggested to be helpful in predicting coronary artery disease. This study aimed to investigate whether presence and severity of breast artery calcification (BAC) on mammograms is associated with computed tomography coronary angiography (CTCA) finding such as coronary artery calcium (CAC) score and the severity of coronary artery stenosis.

Materials and Methods:

This cross-sectional study was performed on 150 women aged >40 years who were referred for CTCA. Women who had undergone screening mammography during the first year after CTCA entered the study. CAC score was determined and the severity of coronary artery stenosis was classified into normal, non-significant stenosis, or significant stenosis. Based on the severity of BAC, patients were also grouped into normal, mild, moderate, or severe groups. Then, the correlation between BAC severity and CAC score was determined. Patients with different BAC severity were also compared regarding the relative frequency of different grades of coronary artery stenosis.

Results:

Mean age of subjects with BAC (n: 35) was significantly higher than patients without BAC (n: 115) (68.03 ± 6.16 versus 54.36 ± 7.63 years, P < 0.0001). Although the relative frequency of different grades of coronary artery stenosis was significantly higher in women with BAC (P < 0.0001), after controlling for age, there was no significant difference between patients with different severity of BAC in the mean of CAC score (P: 0.09). In addition, the correlation between BAC severity and CAC score was not statistically significant (R: 0.09, P: 0.26).

Conclusion:

We concluded that presence and severity of BAC have no significant correlation with CAC score on CTCA.

Coronary computed tomographic angiography (CCTA) in community hospitals: "current and emerging role"

Coronary computed tomographic angiography (CCTA) is a rapidly evolving test for diagnosis of coronary artery disease. Although invasive coronary angiography is the gold standard for coronary artery disease (CAD), CCTA is an excellent noninvasive tool for evaluation of chest pain. There is ample evidence to support the cost-effective use of CCTA in the early triage process of patients presenting with chest pain in the emergency room. CCTA plays a critical role in the diagnosis of chest pain etiology as one of potentially fatal conditions, aortic dissection, pulmonary embolism, and myocardial infarction. This 'triple rule out' protocol is becoming an increasingly practicable and popular diagnostic tool in ERs across the country. In addition to a quick triage of chest pain patients, it may improve quality of care, decrease cost, and prevent medico-legal risk for missing potentially lethal conditions presenting as chest pain. CCTA is also helpful in the detection of subclinical and vulnerable coronary plaques. The major limitations for wide spread acceptance of this test include radiation exposure, motion artifacts, and its suboptimal imaging with increased body mass index.