Strategies for reduction of radiation dose in cardiac multislice CT

Radiation dose and diagnostic accuracy of multidetector computed tomography for the detection of significant coronary artery stenoses: a meta-analysis

We conducted a meta-analysis evaluating the critical ratio between effective radiation dose (ED), feasibility (Fe) and diagnostic accuracy (Ac) of multidetector computed tomography (MDCT) for the detection of significant coronary artery disease. By using our predetermined criteria, we selected human studies published in English in which the ED and raw data of Ac vs. invasive coronary angiography in a segment based model were specified. Data from 31 studies including 3661 patients (mean age 61.9 ± 4.5 years, heart rate 62.5 ± 6.7 bpm) and 50,236 coronary artery segments were analysed and are reported. Overall, Fe, sensitivity, specificity, negative predictive value, positive predictive value, Ac and ED were 95%, 90%, 96%, 99%, 69%, 95% and 10.4 ± 5.4 mSv, respectively. Multivariate analysis showed that prospective ECG-gating (-8.8 mSv CI95% -13.4 to -4.3 mSv, p=0.001), dual-source (-3.7 mSv CI95% -7.9 to 0 mSv, p=0.05) and BMI-adapted scanning protocols (-4.5 mSv CI95% -8.7 to -2.7 mSv, p=0.03) were independent predictors of ED reduction. In patients with low heart rate, the best compromise between ED, Fe and Ac (2.5 mSv, 97% and 98%, respectively) was obtained combining prospective ECG-gating and BMI-adapted scanning protocols, while in patients with high heart rate the strategy associated with the best results (10 mSv, 98% and 97%, respectively) was the use of dual-source MDCT with retrospective ECG gating and modulation dose. In conclusion, careful selection of CT scanning protocols according to the patient's characteristics is critical for keeping the radiation exposure "as low as reasonably achievable" (ALARA) without impairing Fe and Ac.

Step-and-shoot prospectively ECG-gated vs. retrospectively ECG-gated with tube current modulation coronary CT angiography using 128-slice MDCT patients with chest pain: diagnostic performance and radiation dose

BACKGROUND

With increasing awareness for radiation exposure, the study of diagnostic accuracy of coronary CT angiography (CCTA) with low radiation dose techniques is mandatory to both radiologist and clinician.

PURPOSE

To compare diagnostic performance and effective radiation dose between step-and-shoot prospectively ECG-gated and retrospectively ECG-gated with tube current modulation (TCM) CCTA using 128-slice multidetector computed tomography (MDCT).

MATERIAL AND METHODS

We retrospectively evaluated 60 patients who underwent CCTA with either of two different low-dose techniques using 128-slice MDCT (23 patients for step-and shoot-prospectively ECG-gated and 37 patients for retrospectively ECG-gated with TCM CCTA) followed by conventional coronary angiography. All coronary arteries and all segments thereof, except anatomical variants or small size (< 1.5 mm) ones, were included in analysis.

RESULTS

In per-segment analysis, sensitivity, specificity, positive predictive value, and negative predictive value were 91/96%, 95/94%, 75/73%, and 98/99% for step-and-shoot prospectively ECG-gated and retrospectively ECG gated with TCM CCTA, respectively, relative to conventional coronary angiography. Effective radiation dose were 1.75 ± 0.83 mSv, 4.91 ± 1.71 mSv in the step-and-shoot prospectively ECG-gated and retrospectively ECG-gated with TCM CCTA groups, respectively.

CONCLUSION

The two low-radiation dose CCTA techniques using 128-slice MDCT yields comparable diagnostic performance for coronary artery disease in symptomatic patients with low heart rates.

Coronary computed tomography angiography in coronary artery disease

AIM

To investigate the research directions of coronary computed tomography (CT) angiography in the diagnosis of coronary artery disease (CAD) based on a systematic review of the literature.

METHODS

A search of articles on coronary CT angiography in the diagnosis of CAD was performed during a 6-year-period between 2005 and 2010 from five main radiology journals namely, Radiology, American Journal of Roentgenology, European Radiology, European Journal of Radiology and British Journal of Radiology. Analysis of the references was focused on the research directions of coronary CT angiography with regard to the type of studies in terms of diagnostic value, application of dose-reduction strategies and resultant effective radiation doses with use of these techniques.

RESULTS

One hundred and forty two studies were identified which met the selection criteria and were included in the analysis. 64-slice CT (single source and dual-source CT) dominated 78% of the coronary CT angiography studies. Prior to 2007, research was focused on the diagnostic value of coronary CT angiography, but since 2008 more attention has been paid to radiation dose reduction. Radiation dose was reported in 64 studies, representing 45% of total studies published in the five radiology journals. Various dose-saving strategies have been implemented and prospective electrocardiography-triggering and high pitch techniques were found to be the most effective approaches for radiation dose reduction, with the corresponding mean effective dose being 3.5 ± 1.9 mSv and 1.7 ± 0.6 mSv, respectively.

CONCLUSION

This review shows that the current research in coronary CT angiography has shifted from the previous focus on diagnostic accuracy in CAD to more emphasis on radiation dose reduction.

Paediatric cardiac CT examinations: impact of the iterative reconstruction method ASIR on image quality--preliminary findings

BACKGROUND

Radiation dose exposure is of particular concern in children due to the possible harmful effects of ionizing radiation. The adaptive statistical iterative reconstruction (ASIR) method is a promising new technique that reduces image noise and produces better overall image quality compared with routine-dose contrast-enhanced methods.

OBJECTIVE

To assess the benefits of ASIR on the diagnostic image quality in paediatric cardiac CT examinations.

MATERIALS AND METHODS

Four paediatric radiologists based at two major hospitals evaluated ten low-dose paediatric cardiac examinations (80 kVp, CTDI(vol) 4.8-7.9 mGy, DLP 37.1-178.9 mGy·cm). The average age of the cohort studied was 2.6 years (range 1 day to 7 years). Acquisitions were performed on a 64-MDCT scanner. All images were reconstructed at various ASIR percentages (0-100%). For each examination, radiologists scored 19 anatomical structures using the relative visual grading analysis method. To estimate the potential for dose reduction, acquisitions were also performed on a Catphan phantom and a paediatric phantom.

RESULTS

The best image quality for all clinical images was obtained with 20% and 40% ASIR (p < 0.001) whereas with ASIR above 50%, image quality significantly decreased (p < 0.001). With 100% ASIR, a strong noise-free appearance of the structures reduced image conspicuity. A potential for dose reduction of about 36% is predicted for a 2- to 3-year-old child when using 40% ASIR rather than the standard filtered back-projection method.

CONCLUSION

Reconstruction including 20% to 40% ASIR slightly improved the conspicuity of various paediatric cardiac structures in newborns and children with respect to conventional reconstruction (filtered back-projection) alone.

Detection of coronary artery stenoses by low-dose, prospectively ECG-triggered, high-pitch spiral coronary CT angiography

OBJECTIVES

We sought to evaluate the diagnostic accuracy of a new prospectively electrocardiogram (ECG)-triggered high-pitch scan mode for coronary computed tomography angiography (CTA), which allows an effective dose of less than 1 mSv.

BACKGROUND

Coronary CTA provides increasingly reliable image quality, but the associated radiation exposure can be high.

METHODS

Seventy-five patients with suspected coronary artery disease and in sinus rhythm were screened for participation. After exclusion of 25 patients for body weight >100 kg or failure to lower heart rate to ≤ 60 beats/min, 50 patients were studied by prospectively ECG-triggered high-pitch spiral computed tomography (CT). Coronary CTA was performed using a dual-source CT system with 2 × 128 × 0.6-mm collimation, 0.28-s rotation time, a pitch of 3.4, 100-kVp tube voltage, and current of 320 mA. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within 1 cardiac cycle. Diagnostic accuracy for detection of coronary artery stenoses ≥ 50% diameter stenosis was determined by comparison to invasive coronary angiography. Per-patient diagnostic performance was the primary form of analysis.

RESULTS

In all 50 patients (34 males, 59 ± 12 years of age), imaging was successful. For the detection of 16 patients with at least 1 coronary artery stenosis, CT demonstrated a sensitivity of 100% (95% confidence interval [CI]: 79% to 100%) and specificity of 82% (95% CI: 65% to 93%). The positive predictive value was 72% (95% CI: 49% to 89%) and the negative predictive value was 100% (95% CI: 87% to 100%). Sensitivity was 100% (95% CI: 88% to 100%) and specificity was 94% (95% CI: 89% to 97%) on a per-vessel basis. Per-segment sensitivity was 92% (95% CI: 80% to 97%), and specificity was 98% (95% CI: 96% to 98%). Mean dose-length product for coronary CTA was 54 ± 6 mGy · cm, the effective dose was 0.76 ± 0.08 mSv (0.64 to 0.95 mSv).

CONCLUSIONS

In nonobese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides high diagnostic accuracy for the detection of coronary artery stenoses.

Dose modulated retrospective ECG-gated versus non-gated 64-row CT angiography of the aorta at the same radiation dose: comparison of motion artifacts, diagnostic confidence and signal-to-noise-ratios

PURPOSE

To compare ECG-gated and non-gated CT angiography of the aorta at the same radiation dose, with regard to motion artifacts (MA), diagnostic confidence (DC) and signal-to-noise-ratios (SNRs).

MATERIALS AND METHODS

Sixty consecutive patients prospectively randomized into two groups underwent 64-row CT angiography, with or without dose-modulated ECG-gating, of the entire aorta, due to several pathologies of the ascending aorta. MA and DC were both assessed using a four-point scale. SNRs were calculated by dividing the mean enhancement by the standard deviation. The dose-length-product (DLP) of each examination was recorded and the effective dose was estimated.

RESULTS

Dose-modulated ECG-gating showed statistically significant advantages over non-gated CT angiography, with regard to MA (p<0.001) and DC (p<0.001), at the aortic valve, at the origin of the coronary arteries, and at the dissection membrane, with a significant correlation (p<0.001) between MA and DC. At the aortic wall, however, ECG-gated CT angiography showed statistically significant fewer MA (p<0.001), but not a statistically significant higher DC (p=0.137) compared to non-gated CT angiography. At the supra-aortic vessels and the descending aorta, the ECG-triggering showed no statistically significant differences with regard to MA (p=0.861 and 0.526, respectively) and DC (p=1.88 and 0.728, respectively). The effective dose of ECG-gated CT angiography (23.24mSv; range, 18.43-25.94mSv) did not differ significantly (p=0.051) from that of non-gated CT angiography (24.28mSv; range, 19.37-29.27mSv).

CONCLUSION

ECG-gated CT angiography of the entire aorta reduces MA and results in a higher DC with the same SNR, compared to non-gated CT angiography at the same radiation dose.

Radiation exposure to patients in a multicenter coronary angiography trial (CORE 64)

OBJECTIVE

The objective of this study was to assess the exposure of patients to radiation for the cardiac CT acquisition protocol of the multicenter Coronary Artery Evaluation Using 64-Row Multidetector Computed Tomography Angiography (CORE 64) trial.

MATERIALS AND METHODS

An algorithm for patient dose assessment with Monte Carlo dosimetry was developed for the Aquilion 64-MDCT scanner. During the CORE 64 study, different acquisition protocols were used depending on patient size and sex; therefore, six patient models were constructed representing three men and three women in the categories of small, normal size, and obese. Organ dose and effective dose resulting from the cardiac CT protocol were assessed for these six patient models.

RESULTS

The average effective dose for coronary CT angiography (CTA) calculated according to Report 103 of the International Commission on Radiological Protection (ICRP) is 19 mSv (range, 16-26 mSv). The average effective dose for the whole cardiac CT protocol including CT scanograms, bolus tracking, and calcium scoring is slightly higher-22 mSv (range, 18-30 mSv). An average conversion factor for the calculation of effective dose from dose-length product of 0.030 mSv/mGy · cm was derived for coronary CTA.

CONCLUSION

The current methods of assessing patient dose are not well suited for cardiac CT acquisitions, and published effective dose values tend to underestimate effective dose. The effective dose of cardiac CT is approximately 25% higher when assessed according to the preferred ICRP Report 103 compared with ICRP Report 60. Underestimation of effective dose by 43% or 53% occurs in coronary CTA according to ICRP Report 103 when a conversion factor (E / DLP, where E is effective dose and DLP is dose-length product) for general chest CT of 0.017 or 0.014 mSv/mGy · cm, respectively, is used instead of 0.030 mSv/mGy · cm.

Radiation dose threshold for coronary artery calcium score with MDCT: how low can you go?

OBJECTIVES

To evaluate the lowest radiation exposure threshold at which coronary calcium scoring (CCS) remains accurate.

METHODS

A prospective study of 43 consecutive eligible patients referred for CCS underwent imaging in accordance with the manufacturer's recommended protocol. Dedicated software was used to generate 8 series of images simulating tube currents ranging from 20 to 300 mA. These images were randomised and read in blinded fashion to determine the lowest tube current at which the CCS remained accurate. The minimum mA was correlated with 6 different patients' biometric parameters: bodyweight, body mass index, AP and lateral thoracic diameters, average thoracic diameter and the scout attenuation coefficient (SAC). The 95% confidence interval for each parameter was used to calculate tube current threshold levels and hence stratified CCS protocols were derived.

RESULTS

Spearman's correlation coefficients of the minimum tube current for the 6 parameters were: 0.66, 0.63, 0.65, 0.74, 0.77 and 0.86 respectively (p < 0.001). SAC offered the largest potential reduction in mean effective dose from 1.86 mSv to 0.88 mSv.

CONCLUSION

CCS with at least 50% reduction in radiation exposure and below 1 mSv is feasible if CT scout projections are utilised effectively.

Optimal systolic and diastolic reconstruction windows for coronary CT angiography using 320-detector rows dynamic volume CT

AIM

To investigate the optimal pattern of systolic and diastolic reconstruction windows for coronary computed tomography (CT) angiography using 320-detector rows dynamic volume CT (DVCT).

MATERIAL AND METHODS

A prospective analysis was performed on the data from 77 patients who were admitted between December 2008 and July 2009 for DVCT. The images were reconstructed in 10% steps throughout the 10-100% of R-R interval. Data sets for the three major coronary arteries [right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX)] were evaluated by two independent readers. The quality of the images from each examined artery was graded from 1 (no motion artefacts) to 4 (severe motion artefacts over the entire vessel). The optimal systolic and diastolic reconstruction windows and the relationship between image quality and heart rate (HR) were analysed. The HR at which the optimal reconstruction window shifted from diastole to systole was predicted.

RESULTS

The average HR during imaging was 69.5±12.8 beats/min (range 46-102beats/min). HR was positively correlated with the proportion of systole (r=0.78, p<0.001). As HR increased, the optimal reconstruction windows shifted to later phases in both systole and diastole. Image quality for optimal systolic and diastolic reconstructions both deteriorated significantly with higher HRs (r=0.38, p<0.001; r=0.82, p<0.001). However, image quality in systolic reconstructions did not deteriorate as much as in diastolic reconstructions. The cut-off HRs at which optimal reconstruction intervals turned from diastole to systole was 90.8beats/min.

CONCLUSIONS

In patients with a low HR, the optimal coronary reconstruction window is in mid-late diastole. As the HR increases, systolic reconstruction often yields superior image quality compared with diastolic reconstruction.

Heart transplant patient outcomes: 5-year mean follow-up by coronary computed tomography angiography

BACKGROUNDS

We evaluate the feasibility and safety of coronary computed tomography angiography (CCTA) as the first-line investigation in heart transplant patients and the rate of coronary allograft vasculopathy detected using CCTA.

METHODS

From September 2003 to June 2009, we prospectively included 65 heart transplant recipients, retaining 62 who underwent yearly CCTA for coronary allograft vasculopathy detection (261 CCTAs). We used 16-slice, 64-slice, and 2×64-slice CT machines. Patients with coronary artery stenosis by CCTA had a confirmation and a further follow-up exclusively by conventional coronary angiography (CCA).

RESULTS

No major coronary events occurred during the study. Of the 62 baseline CCTAs, 37 (60%) were normal, 18 (29%) showed wall thickening, and 7 (11%) known significant stenosis, confirmed by CCA. The mean follow-up duration was 5 years. At the last follow-up, 26 (70%) patients with normal baseline findings remained normal, 9 (24%) had wall thickening, and 2 (6%) significant stenoses. Time to stenosis was consistently greater than 3 years. Of the 18 patients with initially wall thickening, 14 (78%) had wall thickening and 4 (22%) significant stenosis at last follow-up. The mean interval without any coronary lesion was 9.46±3.98 years. The mean interval without de novo significant stenosis was 10.31±4 years.

CONCLUSIONS

CCTA seems to be a safe noninvasive tool for monitoring heart transplant patients, and thus obviating the need for CCA. In patients with normal baseline CCTA, a 2-year interval between CCTAs may be safe.

Radiation dose for thoracic and coronary step-and-shoot CT using a 128-slice dual-source machine in infants and small children with congenital heart disease

BACKGROUND

For coronary artery visualization, retrospective ECG-gated acquisition by dual-source computed tomography (DSCT) was superior to spiral non-ECG-gated acquisition in a paediatric population of congenital heart disease (CHD) patients. However, retrospective cardiac CT is associated with substantial radiation doses to the patient. Recently, DSCT with end-systolic reconstruction was found to be robust for imaging the coronary arteries in patients with high heart rates.

OBJECTIVE

To evaluate step-and-shoot DSCT with end-systolic reconstruction for evaluating the heart, coronary arteries and other thoracic structures in young children with CHD.

MATERIALS AND METHODS

All neonates and children younger than 6 years of age who were referred to our institution for CHD evaluation between September and October 2009 were included in the study. ECG-gated DSCT was performed in sequential prospective mode centred on the systolic phase identified by ECG analysis. To assess the radiation dose, we recorded the dose-length product (DLP) in mGy·cm and the effective dose in mSv estimated from the DLP. Overall image quality was evaluated using a 5-grade scoring system and was assessed by looking at cardiac and vascular structures. The image quality for the proximal and middle segments of the right and left coronary arteries was also evaluated using a 5-grade scale.

RESULTS

Images of diagnostic quality (grade ≥ 3) were obtained in all 30 children with a mean image quality grade of 4.7 ± 0.6 (range, 3-5). Mean DLP was 5.7 ± 4.8 mGy*cm (range, 1-22 mGy cm) and mean effective radiation dose was 0.26 ± 0.16 mSv (range, 0.05-0.8 mSv).

CONCLUSION

Prospective ECG-gated thoracic DSCT at end-systole usually provides adequate thoracic and coronary artery image quality in neonates, infants and young children with CHD, independent of heart rate. This new method is associated with lower radiation doses compared to previous literature (mean effective dose, 0.26 mSv).

Computed tomography angiography successfully used to diagnose postoperative systemic-pulmonary artery shunt narrowing

In recent years, there has been a marked reduction in surgical mortality for many complex forms of congenital heart disease. Treatment or palliative strategies vary but may include systemic-pulmonary central or Blalock-Taussig shunt. These shunts can be complicated by overcirculation, infection, thrombosis, and thromboembolism. Many diagnostic modalities are available to aide in diagnosis of postoperative shunt complications including echocardiography and cardiac catheterization but these may be invasive, inconclusive, or difficult to obtain adequate images. Computed tomography angiography (CTA) has many attributes that make it potentially useful in the evaluation of congenital heart disease and postoperative shunt complications. We report one patient where CTA guided the post-operative algorithm and appropriately identified a shunt narrowing despite repeated echocardiograms showing a patent shunt. These findings along with clinical suspicion appropriately guided us toward cardiac catheterization. To our knowledge, this is the first paper where CTA appropriately suspected a shunt narrowing in the absence of echocardiographic confirmation.

Individualized assessment of radiation dose in patients undergoing coronary computed tomographic angiography with 256-slice scanning

BACKGROUND

Available data on the radiation burden from coronary computed tomography (CT) angiography (CCTA) are mostly limited to effective dose estimates. This study provides individualized estimates of doses and associated life attributable risks of radiation-induced cancer in a clinical patient population undergoing 256-slice CCTA.

METHODS AND RESULTS

Typical retrospectively and prospectively ECG-gated CCTA exposures in a 256-slice CT scanner were simulated on 52 patient-specific voxelized phantoms. Dose images depicting the dose deposition on the exposed region were generated, and normalized organ doses for all primarily irradiated radiosensitive organs were derived and correlated to patient body habitus. Lung, breast, and esophagus absorbed doses were then determined in 136 consecutive patients subjected to CCTA. Projected life attributable risks of radiation-induced cancer were estimated through the use of appropriate sex-, age- and organ-specific cancer risk factors and compared with corresponding nominal cancer risks. The total projected life attributable risk of radiogenic cancer after CCTA decreases steeply with age at exposure, and lung cancer constitutes the most probable detriment for both sexes. The relative risks of lung cancer associated with prospectively ECG-gated CCTA were 1.0032 and 1.0008 for women and men, respectively. The mean total projected life attributable risks were estimated to be 24.9±7.4 and 71.5±30.0 per 100,000 women undergoing prospectively and retrospectively ECG-gated CCTA, respectively. The corresponding values for men were 7.3±1.3 and 31.4±5.0 per 100 000 patients.

CONCLUSIONS

The mean projected life attributable risks of radiation-induced cancer in a typical clinical patient cohort undergoing standard prospectively ECG-gated CCTA with a 256-slice scanner were found to inconsequentially increase the natural cancer incidence rates.

[Dose reduction during CT coronary angiography]

Dose delivery during CT coronary angiography with retrospective ECG gating is high especially due to the important slice overlapping. Optimization of the acquisition parameters is necessary to reduce patient exposure. First, the height of the scan field should be limited to the heart. Both kV and mA should be adjusted based on patient morphology. ECG gated exposure modulation with mA reduction during systole, a technique most applicable for patients with slow and regular heart rate, can result in a dose reduction up to 50%. The use of prospective ECG gating can also reduce patient dose. This technique also requires patients with slow and regular heart rate.

Radiation dose of cardiac computed tomography - what has been achieved and what needs to be done

This review highlights the recently introduced techniques by manufacturers and various research workers to reduce radiation dose in coronary CT. It discusses in detail the development of ECG-based tube current modulation, the application of low tube voltage protocols and prospective ECG-gating. It also briefly discusses two further methods of dose reduction, namely minimisation of the x-y anatomical coverage and adaptive statistical iterative reconstruction.

Multislice CT in congenital bronchopulmonary malformations in children

Congenital bronchopulmonary malformations encompass a wide spectrum of pathologies involving the lungs, trachea and bronchi, pulmonary vessels, and oesophagus. These developmental lesions are often isolated, but the association of two or more anomalies is not infrequent. Contrast-enhanced multidetector computed tomography (MDCT), thanks to multiplanar and 3D reconstructions, allows for detailed studies of these malformations, achieving better accuracy compared with conventional techniques such as chest X-ray, fluoroscopy, ventilation and perfusion scintigraphy and ultrasonography. MDCT is characterised by fast data acquisition and does not require sedation in the majority of cases. The main drawbacks of MDCT are the use of ionising radiation and - in many cases -contrast media. Recently, improved CT scanners and optimised CT protocols have made available to children all the benefits of MDCT, thanks to a significant reduction in radiation dose and an improved risk-benefit ratio. The aim of our paper was to evaluate MDCT in children with bronchopulmonary malformations by reporting our experience (about 2,400 studies in 30 months with a 64-slice MDCT scanner) and comparing it with the available literature.

Is it possible to predict heart rate and range during enhanced cardiac CT scan from previous non-enhanced cardiac CT?

The effect of heart rate and variation during cardiac computed tomography (CT) on the examination quality. The purpose of this study is to investigate whether it is possible to predict heart rate and range during enhanced cardiac computed CT scan from previous non-enhanced cardiac CT scan. Electrocardiograph (ECG) files from 112 patients on three types of cardiac 64-slice CT (non-enhanced, prospective ECG-triggered and retrospective ECG-gated enhanced scans) were recorded. The mean heart rate, range (defined as difference between maximal and minimal heart rates) and the range ratio (defined as maximal heart rate divided by minimal heart rate) during the scans were compared. Scan time was 4.8, 4.6, and 7.3 s on non-enhanced, prospective ECG-triggered and retrospective ECG-gated scans, respectively (p < 0.0001). The heart rates were not significantly different (60 ± 9 beats per minute (bpm), 60 ± 9 and 61 ± 10 bpm; p = 0.64). Heart rate on the enhanced scan markedly correlated with that of the non-enhanced scan (r = 0.78 and 0.74). In contrast, the ranges of heart rate were 2 ± 5, 4 ± 8, and 8 ± 21 bpm, with different range ratios (1.04, 1.07, and 1.14; p < 0.0001). Correlation of heart rate ranges between non-enhanced scan versus prospective ECG-triggered scan was low (r = 0.27) and that between non-enhanced scan versus retrospective ECG-gated scan negligible (r = -0.027).Heart rate on enhanced cardiac CT, in most cases, can be predicted from a non-enhanced scan. Heart rate range on enhanced cardiac CT, however, is hard to predict from the non-enhanced scan.

Use of 100 kV versus 120 kV in cardiac dual source computed tomography: effect on radiation dose and image quality

To evaluate the effective radiation dose and image quality resulting from use of 100 vs. 120 kV among patients referred for cardiac dual source CT exam (DSCT). Prospective data was collected on 294 consecutive patients referred for DSCT. For each scan, a physician specializing in cardiac CT chose all parameters including tube current and voltage, axial versus helical acquisition, and use of tube current modulation. Lower tube voltage was selected for thinner patients or when lower radiation was desired for younger patients, particularly females. For each study, image quality (IQ) was rated on a subjective IQ score and contrast (CNR) and signal-to-noise (SNR) ratios were calculated. Tube voltage of 100 kV was used for 77 (26%) exams while 120 kV was used for 217 (74%) exams. Use of 100 kV was more common in thinner patients (weight 166 lbs vs. 199 lbs, P < .001). The effective radiation dose for the 100 and 120 kV scans was 8.5 and 15.4 mSv respectively. Among scans utilizing 100 and 120 kV, there was no difference in exam indication, use of beta blockers, heart rate, scan length and use of radiation saving techniques such as prospective ECG triggering and tube current modulation. The IQ score was significantly higher for 100 kV scans. While 100 kV scans were found to have higher image noise then those utilizing 120 kV, the contrast-to-noise and signal-to-noise were significantly higher (SNR: 9.4 vs. 8.3, P = .02; CNR: 6.9 vs. 6.0, P = .02). In selected non-obese patients, use of low kV results in a substantial reduction of radiation dose and may result in improved image quality. These results suggest that low kV should be used more frequently in non-obese patients.

Effect of CT scan protocols on x-ray-induced DNA double-strand breaks in blood lymphocytes of patients undergoing coronary CT angiography

AIMS

To compare in vivo DNA lesions induced during helical and sequential coronary computed tomography angiography (CTA) and to evaluate the effect of CT parameters on double-strand break (DSB) levels.

METHODS

Thirty-six patients were examined with various CT protocols and modes (helical scan, n = 27; sequential scan, n = 9) either using a 64-slice dual-source or a 128-slice CT system. Blood samples were obtained before and 30 min after CT. Lymphocytes were isolated, stained against the phosphorylated histone variant γ-H2AX, and DSBs were visualised by using fluorescence microscopy.

RESULTS

DSB yields 30 min after CTA ranged from 0.04 to 0.71 per cell and showed a significant correlation to DLP (ρ = 0.81, p < 0.00001). Median DSB yield and median DLP were significantly lower after sequential compared to helical CT examinations (0.11 vs. 0.37 DSBs/cell and 249 vs. 958 mGy cm, p < 0.00001). Additional calcium scoring led to an increase in DLP (p = 0.15) and DSB levels (p = 0.04). DSB levels normalised to the DLP showed a significant correlation to the attenuation of the blood (ρ = 0.53, p = 0.01) and a negative correlation to the body mass index of the patients (ρ = -0.37, p = 0.06).

CONCLUSION

γ-H2AX immunofluorescence microscopy allows one to determine dose-related effects on x-ray-induced DSB levels and to consider individual factors which cannot be monitored by physical dose measurements.

Reduction of X-ray induced DNA double-strand breaks in blood lymphocytes during coronary CT angiography using high-pitch spiral data acquisition with prospective ECG-triggering

OBJECTIVES

Purpose of this study was to compare the effect of high-pitch spiral data acquisition with prospective electrocardiography (ECG)-triggering on the x-ray induced DNA damages to blood lymphocytes with commonly used low-pitch spiral scans.

MATERIALS AND METHODS

Thirty four patients underwent coronary computed tomography angiography either using high-pitch spiral data acquisition (n = 15; dual-source computed tomography (CT) scanner, 38.4 mm collimation, 100-120 kV, 320-456 mAs/rotation, pitch value 3.2-3.4) or using a low-pitch protocol (n = 19; dual-source CT scanner, 19.2 mm collimation, 120 kV, 330-438 mAs/rotation, pitch 0.2-0.39, ECG-based tube current modulation). Blood samples were obtained before and 30 minutes after CT. Lymphocytes were isolated, stained against the phosphorylated histone variant gammaH2AX, and DNA double-strand breaks (DSBs) were visualized using fluorescence microscopy. Radiation dose to the blood was estimated by relating in vivo DSB levels to values of in vitro irradiated blood samples (50 mGy). Dose length product was registered as provided by the patient protocol.

RESULTS

Total dose length product ranged from 101 to 237 (median 112) mGy cm in high-pitch and from 524 to 1283 (median 1025) mGy cm in low-pitch scans (P < 0.0001). The median CT induced DSB level 30 minutes after exposure was significantly lower after high-pitch (0.04 DSBs/cell, range 0.02-0.10 DSBs/cell) compared with low-pitch scans (0.39 DSBs/cell, 0.22-0.71 DSBs/cell, P < 0.0001). Both DSB levels and radiation dose to the blood showed a significant correlation to the dose length product (r = 0.82, P < 0.0001). The radiation dose to the blood was significantly reduced in the high-pitch (median 3.1, range 2.0-8.1 mGy) compared with the low-pitch group (median 26.9; range 14.2-44.9 mGy, P < 0.0001).

CONCLUSIONS

Prospectively ECG-triggered high-pitch spiral data acquisition can considerably reduce the radiation dose to the blood in coronary CT angiography as compared with low pitch protocols.

Multidetector CT for congenital heart patients: what a paediatric radiologist should know

Multidetector CT (MDCT) is increasingly used for imaging congenital heart disease (CHD) patients in addition to echocardiography, due to its ability to provide high quality three-dimensional images, giving a comprehensive evaluation of complex heart malformations. Using 4-slice or 16-slice CT, diagnostic information in CHD patients is limited to extra-cardiac anatomy, mainly the pulmonary arteries, aorta and venous connections. Due to high heart rates in babies however, coronary evaluation and intra-cardiac analysis were not reliable with the first generations of MDCT. Larger detector size with 64-slice CT and faster acquisition time, up to 75 ms for one slice, has progressively improved coronary and intra-cardiac visualization. Because radiation dose is the main concern, especially in children, every attempt to minimize dose whilst preserving image quality is important: the ALARA concept should always be applied in this population. The 80 kVp setting is now well accepted as a standard for more and more radiological teams involved in CT of children. Different acquisition strategies are now possible for childhood coronary imaging, using retrospective or even prospective gating. Using the latest technology, sub-mSv acquisitions are now attainable for scanning a whole thorax, providing a complete analysis of any 3-D cardiac malformation, including coronary artery course visualisation. This review will describe how technological developments have improved image quality with continuous reduction of radiation dose.

Radiation dose optimisation in dynamic volume CT of the heart: tube current adaptation based on anterior-posterior chest diameter

To compare tube current adaptation based on 3 body mass index (BMI) categories versus anterior-posterior chest diameter (APD) for radiation dose optimisation in patients undergoing dynamic volume cardiac CT. Two cardiac imaging centres participated in the study. 20 patients underwent a prospectively triggered 320-slice single beat cardiac CT using the X-ray tube current [mA] manually adjusted to the patient's BMI (group I). In 20 subsequent patients, the tube current was adapted according to the patient's APD (group II). All other parameters were kept constant. Image noise was defined as the standard deviation of attenuation values and measured using a ROI in the descending aorta. Variation in image noise was statistically compared between both patient groups. Average and standard deviation of pixel noise were 29.1 HU and 14.8 HU in group I and 28.0 HU and 4.2 HU in group II. Inter-individual variation of pixel noise was significantly lower in group II compared to group I (p < 0.0001). Tube current adaptation based on APD is superior to stepwise adaptation based on BMI for optimising radiation dose in dynamic volume cardiac CT and therefore limits unnecessary radiation dose while ensuring diagnostic image quality in patients with diverse body habitus.

Computed tomographic attenuation value of coronary atherosclerotic plaques with different tube voltage: an ex vivo study

OBJECTIVES

To compare the diagnostic performance of computed tomographic (CT) attenuation and CT attenuation ratio at different tube voltages for ex vivo plaque characterization.

MATERIALS AND METHODS

Human coronary arteries were obtained at the time of autopsy in 15 subjects. The coronary arteries were serially cut into 5-mm-long segments and scanned ex vivo using 4 sets of tube voltages and tube currents (80 kV, 660 mA; 100 kV, 500 mA; 120 kV, 400 mA; and 140 kV, 340 mA). The CT attenuation value at the center of each plaque was obtained, and the ratio of the CT attenuation value at the 80-kV setting divided by that at the 140-kV setting (Hounsfield ratio [HR], 80:140) was calculated. Separate receiver operating characteristic (ROC) analyses were used to assess the usefulness of the CT attenuation value and the 80:140 HR for the differential diagnosis of lipid-rich plaques from other types of plaques.

RESULTS

A total of 93 coronary plaques were detected macroscopically. Histological examination revealed 39 lipid-rich, 24 calcified, and 30 fibrotic plaques. At all the tube voltages, the CT attenuation values of the lipid-rich plaques were lower than those of the calcified plaques, whereas the CT attenuation values of the lipid-rich and fibrotic plaques overlapped. An ROC analysis showed that the area under the curve (AUC) for the differential diagnosis of lipid-rich plaques from fibrotic plaques was 0.813 at 80 kV, 0.772 at 100 kV, 0.682 at 120 kV, or 0.651 at 140 kV. Regarding the 80:140 HR, the AUC was 0.952 (0.029). The AUC was significantly larger at 80 and 100 kV and 80:140 HR compared with the AUC at 120 kV.

CONCLUSIONS

The diagnostic performance of CT analysis for ex vivo plaque characterization was superior at lower energy settings and using the dual-energy method.

Reducing radiation dose to selected organs by selecting the tube start angle in MDCT helical scans: a Monte Carlo based study

PURPOSE

Previous work has demonstrated that there are significant dose variations with a sinusoidal pattern on the peripheral of a CTDI 32 cm phantom or on the surface of an anthropomorphic phantom when helical CT scanning is performed, resulting in the creation of "hot" spots or "cold" spots. The purpose of this work was to perform preliminary investigations into the feasibility of exploiting these variations to reduce dose to selected radiosensitive organs solely by varying the tube start angle in CT scans.

METHODS

Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, and eye lenses) resulting from MDCT scans were estimated using Monte Carlo simulation methods on voxelized patient models, including GSF's Baby, Child, and Irene. Dose to fetus was also estimated using four pregnant female models based on CT images of the pregnant patients. Whole-body scans were simulated using 120 kVp, 300 mAs, both 28.8 and 40 mm nominal collimations, and pitch values of 1.5, 1.0, and 0.75 under a wide range of start angles (0 degree-340 degrees in 20 degrees increments). The relationship between tube start angle and organ dose was examined for each organ, and the potential dose reduction was calculated.

RESULTS

Some organs exhibit a strong dose variation, depending on the tube start angle. For small peripheral organs (e.g., the eye lenses of the Baby phantom at pitch 1.5 with 40 mm collimation), the minimum dose can be 41% lower than the maximum dose, depending on the tube start angle. In general, larger dose reductions occur for smaller peripheral organs in smaller patients when wider collimation is used. Pitch 1.5 and pitch 0.75 have different mechanisms of dose reduction. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x-ray tube is posterior to the patient when it passes the longitudinal location of the organ. For pitch 0.75 scans, the dose is lowest when the tube start angle is such that the x-ray tube is anterior to the patient when it passes the longitudinal location of the organ.

CONCLUSIONS

Helical MDCT scanning at pitch 1.5 and pitch 0.75 results in "cold spots" and "hot spots" that are created both at surface and in-depth locations within patients. For organs that have a relatively small longitudinal extent, dose can vary considerably with different start angles. While current MDCT systems do not provide the user with the ability to control the tube start angle, these results indicate that in these specific situations (pitch 1.5 or pitch 0.75, small organs and especially small patients), there could be significant dose savings to organs if that functionality would be provided.

Prospectively ECG-triggered high-pitch spiral acquisition for coronary CT angiography using dual source CT: technique and initial experience

OBJECTIVE

We evaluated radiation exposure and image quality of a new coronary CT angiography protocol, high-pitch spiral acquisition, using dual source CT (DSCT).

MATERIAL AND METHODS

Coronary CTAwas performed in 25 consecutive patients with a stable heart rate of 60 bpm or less after premedication, using 2 x 128 0.6-mm sections, 38.4-mm collimation width and 0.28-s rotation time. Tube settings were 100 kV/320 mAs and 120 kV/400 mAs for patients below and above 100-kg weight, respectively. Data acquisition was prospectively ECG-triggered at 60% of the R-R interval using a pitch of 3.2 (3.4 for the last 10 patients). Images were reconstructed with 75-ms temporal resolution, 0.6-mm slice thickness and 0.3-mm increment. Image quality was evaluated using a four-point scale (1 = excellent, 4 = unevaluable).

RESULTS

Mean range of data acquisition was 113 +/- 22 mm, mean duration was 268 +/- 23 ms. Of 363 coronary artery segments, 327 had an image quality score of 1, and only 2 segments were rated as "unevaluable". Mean dose-length product (DLP) was 71 +/- 23 mGy cm, mean effective dose was 1.0 +/- 0.3 mSv (range 0.78-2.1 mSv). For 21 patients with a body weight below 100 kg, mean DLP was 63 +/- 5 mGy cm (0.88 +/- 0.07 mSv; range 0.78-0.97 mSv).

CONCLUSION

Prospectively ECGtriggered high-pitch spiral CT acquisition provides high and stable image quality at very low radiation dose.

Radiation dose and safety in cardiac computed tomography

As a result of the changes in use of imaging procedures that rely on ionizing radiation, the collective dose has increased by over 700%, and the annual per-capita dose by almost 600% in recent years. It is possible that this growing use may have significant effects on public health. Although uncertainties exist related to the accuracy of estimated radiation exposure and biologic risk, there are measures that can be taken by the referring and the performing health care provider to reduce the potential risks while maintaining diagnostic accuracy. This article reviews the existing data regarding biologic hazards of radiation exposure associated with medical diagnostic testing, the methodologies used to estimate radiation exposure and dose, and the measures that can be taken to effectively reduce that exposure.

Assessment of left ventricular ejection fraction and regional wall motion with 64-slice multidetector CT: a comparison with two-dimensional transthoracic echocardiography

The aim of this study was to compare the measurement of left ventricular ejection fraction (LVEF) and regional wall motion using 64-slice multidetector CT (MDCT) with that using two-dimensional transthoracic echocardiography (2D-TTE) in a heterogeneous patient population. In 126 patients with angina pectoris, acute myocardial infarction, chronic myocardial infarction, atypical chest pain without coronary artery disease or valvular heart disease, 64-slice MDCT was performed using retrospective electrocardiography gating without dose modulation. 20 phases of the cardiac cycle were analysed to identify the end-diastolic and end-systolic phases and to assess regional LV wall motion. For these measurements, 2D-TTE served as the reference standard. MDCT and 2D-TTE were performed within 10 days of each other. An excellent correlation between MDCT and 2D-TTE was shown for the evaluation of LVEF (59.2+/-11% vs 57.9+/-10%, respectively; r = 0.87). LVEF was slightly overestimated by MDCT, when compared with 2D-TTE, by an average of 1.4+/-5.6%. Good agreement was obtained between the use of the two techniques, with 94% of the segments scored identically on both modalities (kappa = 0.70). MDCT had a sensitivity of 97% and a specificity of 82% when compared with 2D-TTE as the reference standard. In conclusion, the use of 64-slice MDCT can provide comparable results to those using 2D-TTE for LVEF and regional wall motion assessment in a heterogeneous population.

X-ray computed tomography of the heart

INTRODUCTION

Cardiac imaging is an emerging application of multidetector computed tomography (MDCT). This review summarizes the current capabilities, possible applications, limitations and developments of cardiac CT.

SOURCES OF DATA

Relevant publications in peer reviewed literature and national and international guidelines are used to discuss important issues in cardiac CT imaging.

AREAS OF AGREEMENT AND CONTROVERSY

There is broad consensus that coronary CT angiography is indicated in patients with an intermediate pre-test probability of coronary artery disease (CAD) when other non-invasive tests have been equivocal. In this context, CT can reliably exclude significant CAD. Cardiac CT also has an established role in the evaluation of bypass grafts and suspected coronary anomalies. Radiation exposure from CT procedures remains a concern, although techniques are now available to reduce the X-ray dosage without significantly compromising the image quality. However, with the current level of knowledge, the cardiac CT examinations are not justified to screen for CAD in asymptomatic individuals. Neither is it considered appropriate in patients with a high pre-test probability of CAD, for whom invasive catheter coronary angiography is usually of more benefit.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

The ability to reconstruct the volumetric cardiac CT data set opens up avenues for advanced physiological analyses of the heart. For example, if CT myocardial perfusion assessment becomes a reality, there is potential to revolutionize the practice of MDCT imaging. Research is also ongoing to investigate whether cardiac CT has a role in the appropriate triage of patients with chest pain in the emergency department.

Low-dose multidetector-row CT-angiography of abdominal aortic aneurysm after endovascular repair

PURPOSE

To investigate the possibility of reducing radiation dose exposure while maintaining image quality using multidetector computed tomography angiography (MDCTA) with high-concentration contrast media in patients undergoing follow-up after endovascular aortic repair (EVAR) to treat abdominal aortic aneurysm.

MATERIALS AND METHODS

In this prospective, single center, intra-individual study, patients underwent two consecutive MDCTA scans 6 months apart, one with a standard acquisition protocol (130 mAs/120 kV) and 120 mL of iomeprol 300, and one using a low dose protocol (100 mAs/80 kV) and 90 mL of iomeprol 400. Images acquired during the arterial phase of contrast enhancement were evaluated both qualitatively and quantitatively for image noise and intraluminal contrast enhancement.

RESULTS

Thirty adult patients were prospectively enrolled. Statistically significantly higher attenuation values were measured in the low-dose acquisition protocol compared to the standard protocol, from the suprarenal abdominal aorta to the common femoral artery (p<0.0001; all vascular segments). Qualitatively, image quality was judged significantly (p=0.0002) better with the standard protocol than with the low-dose protocol. However, no significant differences were found between the two protocols in terms of contrast-to-noise ratio (CNR) (13.63±6.97 vs. 11.48±8.13; p=0.1058). An overall dose reduction of up to 74% was observed for the low-dose protocol compared with the standard protocol.

CONCLUSION

In repeat follow-up examinations of patients undergoing EVAR for abdominal aortic aneurysm, a low-dose radiation exposure acquisition protocol provides substantially reduced radiation exposure while maintaining a constant CNR and good image quality.

Coronary computed tomography angiography with a consistent dose below 1 mSv using prospectively electrocardiogram-triggered high-pitch spiral acquisition

AIMS

We evaluated the feasibility and image quality of a new scan mode for coronary computed tomography angiography (CTA) with an effective dose of less than 1 mSv.

METHODS AND RESULTS

In 50 consecutive patients (body weight <or= 100 kg, sinus rhythm <or=60 b.p.m. after pre-medication, coronary CTA was performed using a dual-source CT system with 2 x 128 x 0.6 mm collimation, 0.28 s rotation time, a pitch of 3.2 or 3.4, 100 kV tube voltage and current of 320 mA s. Data acquisition was prospectively triggered at 60% of the R-R interval and completed within one cardiac cycle. Image quality was evaluated using a four-point scale (1 = absence of any artefacts to 4 = uninterpretable). In all 50 patients, imaging was successful. Mean duration of data acquisition was 258 +/- 20 ms. Mean dose-length product was 62 +/- 5 mGy cm, the effective dose was 0.87 +/- 0.07 mSv (0.78-0.99 mSv). Of the 742 coronary artery segments, 94% had an image quality score of 1, 5.0% a score of 2, 0.9% a score of 3, and 4 segments (0.5%) were 'uninterpretable'.

CONCLUSION

In non-obese patients with a low and stable heart rate, prospectively ECG-triggered high-pitch spiral coronary CTA provides excellent image quality at a consistent dose below 1.0 mSv.

Demonstration of dose and scatter reductions for interior computed tomography

With continuing developments in computed tomography (CT) technology and its increasing use of CT imaging, the ionizing radiation dose from CT is becoming a major public concern particularly for high-dose applications such as cardiac imaging. We recently proposed a novel interior tomography approach for x-ray dose reduction that is very different from all the previously proposed methods. Our method only uses the projection data for the rays passing through the desired region of interest. This method not only reduces x-ray dose but scatter as well. In this paper, we quantify the reduction in the amount of x-ray dose and scattered radiation that could be achieved using this method. Results indicate that interior tomography may reduce the x-ray dose by 18% to 58% and scatter to the detectors by 19% to 59% as the FOV is reduced from 50 to 8.6 cm.

Choice strategy of different dose-saving protocols in 64-slice MDCT coronary angiography

PURPOSE

Multidetector-row computed tomography coronary angiography (MDCT-CA) produces high-level radiation dose because of submillimetre slice thickness and short scan time. As a result, manufacturers have produced different dose-saving protocols that may, however, reduce image quality and thus diagnostic accuracy. The aim of our study was to assess the diagnostic quality of MDCT-CA using different dose-saving protocols.

MATERIALS AND METHODS

Between April and August 2008, we examined 65 patients with 64-slice MDCT-CA: 6/65 using the step-and-shoot dose-saving protocol, 45/65 the cardiac dose right protocol and 14/65 using a standard protocol. Image quality was evaluated on a per-patient and per-segment basis, and the effective dose of each protocol was recorded.

RESULTS

In the per-patient analysis, image quality was excellent in 100% of the step-and-shoot protocols, in 91.1% of the cardiac dose right protocols and in 85.8% of the standard protocols. Effective dose to the patient considering the whole study (i.e. scout, calcium score, triggering and MDCT-CA) was 20.49 mSv in the standard protocol, 14.8 mSv in the cardiac dose right protocol and 6.63 mSv in the step-and-shoot protocol.

CONCLUSIONS

The radiologist should apply the appropriate protocol in relation to the clinical indications, type of patient and information required in order to spare as much dose as possible while maintaining high image quality.

Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease

BACKGROUND

There are only a few reports on the diagnostic accuracy, and the technical and clinical feasibility, of multidetector CT (MDCT) in infants with congenital heart disease (CHD).

OBJECTIVE

To evaluate the image quality and radiation dose of DSCT in babies with CHD.

MATERIALS AND METHODS

From November 2006 to November 2007, 110 consecutive infants with CHD referred for pre- or postoperative CT evaluation were included. All these infants had a spiral angiothoracic DSCT scan after injection of 300 mg/ml iopromide at 0.5-1 ml/s with a power injector using a low-dose protocol (80 kVp and 10 mAs/kg). Of these infants, 34 also underwent an ECG-gated coronary CT scan for evaluation of the course of the coronary arteries.

RESULTS

No serious adverse events were recorded. The mean dose-length product was 8+/-6 mGy x cm (effective dose 0.5+/-0.2 mSv) and 21+/-9 mGy x cm (effective dose 1.3+/-0.6 mSv) during the non-ECG-gated spiral acquisition and ECG-gated acquisition, respectively. Diagnostic quality images were achieved with the spiral acquisition in 89% of cases. Compared to the spiral mode, ECG-gated acquisition significantly improved the visualization of the coronary arteries, with a diagnostic rate of 91% and 84% for the left and right coronary arteries, respectively.

CONCLUSION

DSCT together with iopromide at 300 mg/ml is a valuable tool for the routine clinical evaluation of infants with CHD. ECG-gated acquisition provides reliable visualization of the course of the coronary arteries.

Cardiac computed tomography radiation dose reduction using interior reconstruction algorithm with the aorta and vertebra as known information

High x-ray radiation dose is a major public concern with the increasing use of multidetector computed tomography (CT) for diagnosis of cardiovascular diseases. This issue must be effectively addressed by dose-reduction techniques. Recently, our group proved that an internal region of interest (ROI) can be exactly reconstructed solely from localized projections if a small subregion within the ROI is known. In this article, we propose to use attenuation values of the blood in aorta and vertebral bone to serve as the known information for localized cardiac CT. First, we describe a novel interior tomography approach that backprojects differential fan-beam or parallel-beam projections to obtain the Hilbert transform and then reconstructs the original image in an ROI using the iterative projection onto convex sets algorithm. Then, we develop a numerical phantom based on clinical cardiac CT images for simulations. Our results demonstrate that it is feasible to use practical prior information and exactly reconstruct cardiovascular structures only from projection data along x-ray paths through the ROI.

Technical advances in cardiovascular imaging

Cardiovascular imaging technology is continuously evolving and provides an increasing array of tests to evaluate cardiovascular morphology and function. A basic understanding of imaging technology is helpful to select the best modality to answer a specific clinical question. This article provides a brief overview of recent technical developments in computed tomography (CT), magnetic resonance (MR), and echocardiography, which have increased our diagnostic understanding and may modulate treatment planning of patients with cardiovascular diseases: electrocardiographically (ECG)-gated CT, 4D-flow magnetic resonance imaging (MRI), and three-dimensional (3D) echocardiography.