Low-dose CT Coronary Angiography Research Articles

Higher Iodine Concentration Enables Radiation Dose Reduction in Coronary CT Angiography

To test whether higher iodine concentration together with higher noise level could lead to a further dose reduction in an already low dose coronary CT angiography (CCTA) protocol without comprising image quality. One hundred eighty patients with suspected coronary artery disease (CAD) were randomly assigned into three groups: (a) conventional dose (CD) group, 100 kV with a noise index (NI) of 25 and iohexol (350 mg I/ml); (b) low dose (LD) group, 80 kV with a NI of 25 and iohexol (350 mg I/ml); (c) further low dose (FLD) group, 80 kV with a NI of 30 and iomeprol (400 mg I/ml). The volume and injection rate of contrast medium were fixed at 60 ml and 5 ml/s. The radiation dose (volume CT dose index [CTDIvol], dose length product [DLP], and effective dose [ED]) were recorded. For image quality, both quantitative (enhancement, noise, signal-to-noise ratio [SNR], and contrast-to-noise ratio [CNR]) and qualitative indices were assessed. Compared to the CD group, ED was reduced by 16% and 42% in the LD and FLD groups, respectively (p < 0.05). Qualitative analysis showed no significant difference among the 3 groups (p > 0.05), while quantitative analysis revealed significantly higher attenuation in the LD and FLD groups. Signal-to-noise ratios and CNRs of the LD and FLD groups were significantly higher except for the CNR at the left circumflex branch of the FLD group (p < 0.05). Increasing iodine concentration and noise level may further reduce the radiation dose by 26% on top of a 16% reduction from 100 kV to 80 kV without image quality compromise.

Impact of Deep Learning-based Optimization Algorithm on Image Quality of Low-dose Coronary CT Angiography with Noise Reduction: A Prospective Study

To evaluate deep learning (DL)-based optimization algorithm for low-dose coronary CT angiography (CCTA) image noise reduction and image quality (IQ) improvement. A postprocessing platform for the CCTA image was built using a DL-based algorithm. Seventy subjects referred for CCTA were randomly divided into two groups (study group A with 80 kVp and control group B with 100 kVp). Group C was obtained by DL optimization of group A. Subjective IQ was blindly graded by two experienced radiologists on a four-point scale (4-excellent,1-poor). The image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated to evaluate IQ objectively. The difference between the time consumed of iterative reconstruction and DL algorithm was also recorded. The subjective IQ score of group C using the DL algorithm was significantly better than that of group A (p = 0.005). The noise of group C was significantly decreased, while SNR and CNR were significantly increased compared to group A (p < 0.001). The subjective IQ scores were lower in group A compared to group B (p = 0.037), whereas subjective IQ scores in group C were not significantly different (p = 0.874). For objective IQ, the noise of group A was significantly higher, while SNR and CNR were significantly lower than that of group B (p < 0.05). There was no significant difference in noise and SNR between group C and group B (p > 0.05), but CNR in group C was significantly higher than that in group B (p < 0.05). The DL algorithm processes the image twice as fast as the iterative reconstruction speed. The DL-based optimization algorithm could effectively improve the IQ of low-dose CCTA by noise reduction.

Low-Dose Coronary CT Angiography in Patients with Atrial Fibrillation: Comparison of Image Quality and Radiation Exposure with Two Different Approaches

To evaluate image quality, coronary interpretability and radiation exposure of coronary CT angiography (CCTA) performed in patients with atrial fibrillation (AF) with the latest scanner generation, comparing two different technical approaches. A new scanner that combines a 0.23mm spatial resolution, a new generation of iterative reconstruction, fast gantry rotation time and the intracycle motion-correction algorithm to improve the temporal resolution was recently introduced in the clinical field. We enrolled 105 consecutive patients with chronic AF who performed CCTA with a whole-heart coverage high-definition CT scanner (16-cm z-axis coverage with 256 detector rows, 0.28s gantry rotation time). Five of them were excluded for impaired renal function. Patients were randomized between a double acquisition protocol (50 patients, group 1) or a single acquisition protocol (50 patients, group 2). The image quality, coronary segment interpretability and effective dose (ED) of CCTA were assessed. The mean HR during the scan was 85.6±21bpm in group 1vs. 83.7±23bpm in Group 2, respectively (p<ns). In group 2, overall image quality was high and comparable with that of group 1 (Likert scale=3.2±1.4vs. 3.3±1.2, p=ns, in group 1 and 2, respectively). Coronary interpretability was high and similar between the two groups (97.5% and 97.1% in group 1 and 2, p =ns, respectively). Mean ED was significantly higher in group 1 than in group 2 (5.3±1.8mSv vs. 2.7±0.7mSv, p<0.001). The novel whole-heart coverage CT scanner allows to perform CCTA with a single-acquisition protocol with high image quality and low radiation exposure in AF patients.

P1789Implementation of low dose coronary CT angiography in the workflow for the assessment of new onset chest pain in clinical practice

P1789Implementation of low dose coronary CT angiography in the workflow for the assessment of new onset chest pain in clinical practice

3-D Neural denoising for low-dose Coronary CT Angiography (CCTA)

CCTA has become an important tool for coronary arteries assessment in low and medium risk patients. However, it exposes the patient to significant radiation doses, resulting from high image quality requirements and acquisitions at multiple cardiac phases. For widespread use of CCTA for coronary assessment, significant reduction of radiation exposure with minimal image quality loss is still needed. A neural denoising scheme, relying on a fully convolutional neural network (FCNN) architecture, is developed and applied to noisy CCTA. In contrast to previously published methods, the proposed FCNN is trained directly on 3-D CT data patches (blocks), implementing 3-D convolutions. Considering that anatomy is inherently tridimensional, the proposed 3-D approach may better capture and enforce inter-slice continuity of tiny structures. While training is performed on individual blocks, whole input scans can be fed and denoised in one piece, thus leveraging the fully convolutional architecture to maximize processing speed. The proposed method is compared to state-of-the-art denoising algorithms on a dataset of 45 CCTA scans. Low-dose scans are simulated by synthetic Poisson noise applied to the sinogram corresponding to a 90% reduction in radiation dose. The average feature similarity score (0.864) and the peak signal-to-noise ratio (41.47) obtained for the proposed algorithm outperformed the compared methods while requiring significantly shorter processing time. A set of 2-D FCNNs, structurally similar to the proposed 3-D network, are also implemented to demonstrate contribution of the additional dimension to the improved denoising. For further validation of the method coronary reconstruction using the Intellispace cardiac tool (Philips, Holland) is performed both on a real noisy CCTA scan and on the denoised scan using the proposed method. It is shown that the cardiac tool succeeds in reconstructing more coronaries using the scan denoised by the proposed method. The obtained results suggest the proposed method provides an efficient and powerful approach to low-dose CCTA denoising.

Coronary CT angiography in patients with atrial fibrillation: Standard-dose and low-dose imaging with a high-resolution whole-heart CT scanner.

To compare image quality, observer confidence, radiation exposure in the standard-dose (SD-CCTA) and low-dose (LD-CCTA) protocols of coronary CT angiography (CCTA) in patients with atrial fibrillation (AF). CCTA was performed in 303 patients using a CT scanner with 16-cm coverage (111 scans during sinus rhythm (SR); 192 during AF). LD-CCTA was used in 218 patients; SD-CCTA in 85 patients suspected of having coronary artery disease (CAD). Image quality and observer confidence were evaluated on 5-point scales. Radiation doses were recorded. Image quality was superior in the SD-CCTA compared to the LD-CCTA (SR 1.45±0.40; AF 1.72±0.46; vs. SR 1.83±0.48; AF 1.92±0.50; p < 0.001). Observers were more confident with SD-CCTA than with LD-CCTA (SR 1.38±0.33; AF 1.61±0.43; vs. SR 1.70±0.45; AF 1.82±0.50; p < 0.001). Radiation doses in AF were significantly higher than in the SR (LD-CCTA, 1.68±0.71 mSv; SD-CCTA, 3.72±1.95 mSv; vs. LD-CCTA, 1.3 ±0.52 mSv; SD-CCTA, 2.67±1.47 mSv; p < 0.001). Using a low-dose protocol in AF, radiation exposure can be decreased by 50 % at the expense of 20 % impaired image quality. A low-dose CCTA protocol can be considered in young patients, whereas the standard-dose protocol is recommended for older patients and those suspected of having CAD. • Whole-heart CT allows visualization of the coronary arteries in atrial fibrillation. • Low-dose CT decreases radiation exposure by 50%, image quality by 20%. • Standard-dose CT seems advantageous when concomitant coronary artery disease is suspected.

Rapid Fire Abstract session: usefulness of CT and radionuclide imaging in different clinical scenarios378Improving the cost-effectiveness of chest pain investigations using single photon emission computed tomography379Is autonomic nervous dysfunction severity associated to less benefit from cardiac resynchronization therapy?380Validation of stress Thallium-201/Rest Technetium-99m sequential dual isotope high-speed myocardial perfusion imaging against fractional flow reserve for the detection of the extent of

Rapid Fire Abstract session: usefulness of CT and radionuclide imaging in different clinical scenarios378Improving the cost-effectiveness of chest pain investigations using single photon emission computed tomography379Is autonomic nervous dysfunction severity associated to less benefit from cardiac resynchronization therapy?380Validation of stress Thallium-201/Rest Technetium-99m sequential dual isotope high-speed myocardial perfusion imaging against fractional flow reserve for the detection of the extent of

Preliminary study of low-dose CT coronary angiography by using low concentration isotonic contrast agent

Objective To compare the iodine intake,image quality and radiation dose of dual-source CT coronary artery angiography between the low concentration isotonic contrast agent with iterative reconstruction technique of sinogram affirmed iterative rEconstruction (SAFIRE) and common concentration contrast agent with filtered back projection (FBP).Methods One hundred patients [58 men,42 women; age:(62± 11)y] were enrolled in this study.Fifty consecutive patients (Group A) were scanned with FBP and common concentration contrast agent and another 50 consecutive patients (Group B) were scanned with low concentration isotonic contrast agent and iterative reconstruction technique.The image quality were assessed by two experienced radiologists with a double blinded fashion in a five score scale.The attenuation of coronary artery,scan time,imaging noise,signal-to-noise ratio (SNR),contrast-to-noise ratio (CNR),radiation dose and iodine intake between these two groups were compared using two sample t test.The observer agreement for image quality was calculated using Kappa statistics.Results All examinations were completed successfully.There was no statistical difference (P＞0.05) between two groups in clinical characteristics and scan parameters.There was no statistical difference for the mean subjective image quality of group A (4.4±0.7) and group B (4.3±0.8) (t=0.924,P＞0.05).The Kappa value between two radiologists was 0.887 (P＜0.01)on image quality.The mean attenuation of coronary artery segments was higher than 300 HU,especially in group A (386.1±51.5) HU,which was slightly higher than the group B (384.1±77.1) HU,but there was no statistical difference (t=0.157,P＞0.05).The SNR and CNR in two groups did not have significant differences (P＞0.05).The total iodine and iodine injection rates were 21.0 g,17.5 g/s in Group A and 16.2 g,13.5 g/s in Group B,respectively.The iodine intake was decreased by 22.9％ in Group B.The effective radiation dose in Group B (1.09±0.19) mSv was significantly (t=20.260,P＜0.01) lower than that in Group A (2.85±0.59) mSv,with the radiation dose reduced by 61.8％.Conclusion Low concentration isotonic contrast agent and iterative reconstruction technique can significantly reduce the radiation dose and iodine intake in CT coronary artery angiography and achieve the same image quality using common concentration contrast agent with FBP. Key words: Contrast media; Tomography, X-ray computed; Radiation dosage; Comparative study

Impact of a New Motion-Correction Algorithm on Image Quality of Low-Dose Coronary CT Angiography in Patients with Insufficient Heart Rate Control

Prospective electrocardiogram (ECG) triggering allows coronary computed tomography angiography (CCTA) scanning with low radiation dose but requires heart rates below 63 beats/min. We assessed the impact of a novel vendor-specific motion-correction algorithm on image quality and interpretability of low-dose CCTA acquired despite insufficient heart rate control. In 40 patients undergoing CCTA for the assessment of known or suspected coronary artery disease who did not reach the target heart rate below 63 beats/min despite β-blockade before prospective low-dose scanning, the temporal acquisition window was increased (80 ms additional padding). The new algorithm detects and integrates vessel path and velocity from adjacent cardiac phases for motion correction. Two blinded observers assessed image quality on a 4-point Likert scale (1, nonevaluative; 2, reduced but evaluative; 3, good; and 4, excellent) and the fraction of interpretable segments (score 2 or more) using motion correction versus standard reconstruction. Image reconstruction with motion correction resulted in an increased median coronary artery image quality score (excellent interobserver agreement, κ = 0.85) compared to standard reconstruction (3.4 vs. 3.0, P < .001). Consequently, motion-corrected reconstruction significantly improved the overall interpretability of coronary arteries (from 78% to 88%, P < .001). Estimated mean effective radiation dose was 2.3 ± 0.8 mSv. A novel, vendor-specific, motion-corrected, reconstruction algorithm improves image quality and interpretability of prospectively ECG-triggered low-dose CCTA despite insufficient heart rate control.

Stent evaluation in low-dose coronary CT angiography: Effect of different iterative reconstruction settings

BackgroundDifferent iterative reconstruction (IR) techniques compensate increased noise from lower tube current-time product settings, yet the differences between IR settings remain unclear. ObjectiveAim of this study was to test whether different IR settings have a clinically relevant influence on image quality and on the diagnostic accuracy of low-dose CT angiography in patients with a stent. MethodsForty-two patients with 73 coronary stents were prospectively enrolled. Data were acquired with dual-source CT, and images were reconstructed with standard filtered back projection (FBP) and raw data-based IR with different settings (I3, I4, I5). Quantitative parameters, including CT-attenuation, noise, signal-to-noise ratio, contrast-to-noise ratio, as well as the presence of in-stent stenosis > 50% were determined. All patients had invasive angiography as reference standard. ResultsMean effective dose was 0.32 ± 0.02 mSv. Image noise decreased significantly compared with FBP (I3 = 29%; I4 = 38% and I5 = 45%), whereas signal-to-noise and contrast-to-noise ratios increased significantly (all IR settings P < .01). Subjective image quality was superior with all IR settings (P < .01). FBP sensitivity, specificity, positive predictive value, and negative predictive value were 83%, 71%, 36%, and 96% per stent compared with 100%, 76%, 44%, and 100%, respectively, in IR reconstructions independent of the IR setting applied. ConclusionIn low-dose coronary CT angiography, higher IR settings significantly improved subjective and objective image quality but had no effect on accuracy.

Low-dose coronary-CT angiography using step and shoot at any heart rate: comparison of image quality at systole for high heart rate and diastole for low heart rate with a 128-slice dual-source machine

To compare image quality of coronary CT angiography in step-and-shoot mode at the diastolic phase at low heart rates (<70 bpm) and systolic phase at high heart rates (≥70 bpm). We prospectively included 96 consecutive patients then excluded 5 patients with arrhythmia. Coronary CT-angiography was performed using a dual-source 128-slice CT machine, at the diastolic phase in the 55 patients with heart rates <70 bpm (group D) and at the systolic phase in the 36 patients with heart rates ≥70 (group S). Image quality was scored on a 5 point-scale (1, not interpretable; 2, insufficient for diagnosis; 3, fair, sufficient for diagnosis; 4, good; 5, excellent). In addition, we compared the number of stair-step artifacts in the two groups. Mean image quality score was 4 (0.78) in group D and 4.1 (0.34) in group S (NS), with an unequal distribution (p = 0.01). Step artifacts were seen in 44 % of group D and 18 % of group S patients (p = 0.02). In 3 group D patients and no group S patients, the image score was <3 due to artifacts, requiring repeat CT-angiography. When performing dual-source 128-slice CT-angiography, step-and-shoot acquisition provides comparable mean image quality in systole, with less variability and fewer stair-step artifacts, compared to diastole. This method may be feasible at any heart rate in most patients in sinus rhythm, allowing low-dose prospective acquisition without beta-blocker premedication.

Image quality and radiation dose of low dose coronary CT angiography in obese patients: Sinogram affirmed iterative reconstruction versus filtered back projection

PurposeTo investigate the image quality and radiation dose of low radiation dose CT coronary angiography (CTCA) using sinogram affirmed iterative reconstruction (SAFIRE) compared with standard dose CTCA using filtered back-projection (FBP) in obese patients. Materials and methodsSeventy-eight consecutive obese patients were randomized into two groups and scanned using a prospectively ECG-triggered step-and-shot (SAS) CTCA protocol on a dual-source CT scanner. Thirty-nine patients (protocol A) were examined using a routine radiation dose protocol at 120kV and images were reconstructed with FBP (protocol A). Thirty-nine patients (protocol B) were examined using a low dose protocol at 100kV and images were reconstructed with SAFIRE. Two blinded observers independently assessed the image quality of each coronary segment using a 4-point scale (1=non-diagnostic, 4=excellent) and measured the objective parameters image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Radiation dose was calculated. ResultsThe coronary artery image quality scores, image noise, SNR and CNR were not significantly different between protocols A and B (all p>0.05), with image quality scores of 3.51±0.70 versus 3.55±0.47, respectively. The effective radiation dose was significantly lower in protocol B (4.41±0.83mSv) than that in protocol A (8.83±1.74mSv, p<0.01). ConclusionCompared with standard dose CTCA using FBP, low dose CTCA using SAFIRE can maintain diagnostic image quality with 50% reduction of radiation dose.

Interobserver agreement for the detection of atherosclerotic plaque in coronary CT angiography: comparison of two low-dose image acquisition protocols with standard retrospectively ECG-gated reconstruction

We compared the interobserver variability concerning the detection of calcified and non-calcified plaque in two different low-dose and standard retrospectively gated protocols for coronary CTA. 150 patients with low heart rates and less than 100kg body weight were randomised and examined by contrast-enhanced dual-source CT coronary angiography (100kV, 320mAs). 50 patients were examined with prospectively ECG-triggered axial acquisition, 50 patients with prospectively ECG-triggered high pitch spiral acquisition, and 50 patients using spiral acquisition with retrospective ECG gating. Two investigators independently analysed the datasets concerning the presence of calcified and non-calcified plaque on a per-segment level. Mean effective dose was 1.4 ± 0.2mSv for axial, 0.8 ± 0.07mSv for high-pitch spiral, and 5.3 ± 2.6mSV for standard spiral acquisition (P < 0.0001). In axial acquisition, interobserver agreement concerning the presence of atherosclerotic plaque was achieved in 650/749 coronary segments (86.8%). In high-pitch spiral acquisition, agreement was achieved in 664/748 segments (88.8%, n.s.). In standard spiral acquisition, agreement was achieved in 672/738 segments (91.0%, P < 0.0001). Interobserver agreement was significantly higher for calcified than for non-calcified plaque in all data acquisition modes. Low-dose coronary CT angiography permits the detection of coronary atherosclerotic plaque with good interobserver agreement. • Low-dose CT protocols permit coronary plaque detection with good interobserver agreement. • Image noise is a major predictor of interobserver variability. • Interobserver agreement is significantly higher for calcified than for non-calcified plaque.

Image quality and radiation dose comparison of prospectively triggered low-dose CCTA: 128-slice dual-source high-pitch spiral versus 64-slice single-source sequential acquisition

Currently 64-multislice computed tomography (MSCT) scanners are the most widely used devices allowing low radiation dose coronary CT angiography (CCTA) with prospective ECG triggering. Latest 128-slice dual-source CT (DSCT) scanners offer prospective high-pitch spiral acquisition covering the heart during one single beat. We compared radiation dose and image quality from prospective 64-MSCT versus high-pitch spiral 128-slice DSCT scanning, as such data is lacking. CCTA of 50 consecutive patients undergoing 128-DSCT (2 × 64 × 0.6 mm collimation, 0.28 s rotation time, 3.4 pitch, 100-120 kV tube voltage and 320 mAs tube current-time product) were compared to CCTA of 50 heart rate (HR) and BMI matched patients undergoing 64-MSCT (64 × 0.625 mm collimation, 0.35 s rotation time, 100-120 kV tube voltage and 400-650 mA tube current). Image quality was rated on a 4-point scale by two independent cardiac imaging physicians (1 = excellent to 4 = non-diagnostic). Of 710 coronary segments assessed on 128-DSCT, 216 (30.4%) achieved an image quality score 1 excellent, 400 (56.3%) score 2, 76 (10.7%) score 3 and 18 (2.6%) score 4 (non-diagnostic). Of 737 coronary segments evaluated on 64-MSCT 271 (36.8%) had an image quality score of 1, 327 (44.4%) 2, 110 (14.9%) score 3, and 29 (3.9%) segments score 4. Average image quality score for both scanners was similar (P = 0.641). The mean heart rate during scanning was 58.7 ± 5.6 bpm on 128-DSCT and 59.0 ± 5.6 bpm on 64-MSCT, respectively. Mean effective radiation dose was 1.0 ± 0.2 mSv for 128-DSCT and 1.7 ± 0.6 mSv for 64-MSCT (P < 0.001). 128-DSCT with high-pitch spiral mode allows CCTA acquisition with reduced radiation dose at maintained image quality compared to 64-MSCT.

Prognostic performance of low-dose coronary CT angiography with prospective ECG triggering

ObjectiveTo assess the prognostic value of low-dose 64-slice coronary CT angiography (CCTA) using prospective ECG triggering in a patient population with known or suspected coronary artery disease (CAD).DesignLongitudinal follow-up study.SettingTertiary...

Low-dose, 128-slice, dual-source CT coronary angiography: accuracy and radiation dose of the high-pitch and the step-and-shoot mode

ObjectiveTo compare the diagnostic accuracy and radiation doses of two low-dose protocols for coronary artery imaging with second-generation, dual-source CT in comparison with catheter angiography (CA).Design, setting and patientsProspective, single-centre...

Adapting the contrast material protocol to the body surface area for an optimized low-dose CT coronary angiography with prospective ECG-triggering: a new evolving concept?

Adapting the contrast material protocol to the body surface area for an optimized low-dose CT coronary angiography with prospective ECG-triggering: a new evolving concept?

Validation of a new contrast material protocol adapted to body surface area for optimized low-dose CT coronary angiography with prospective ECG-triggering

In patients with large total blood volume contrast material (CM) dilution decreases coronary attenuation in CT coronary angiography (CTCA). As increased blood volume is well paralleled by body surface area (BSA) we assessed a BSA-adapted CM protocol to compensate for dilution effects. Low-dose CTCA with prospective ECG-triggering was performed in 80 patients with a BSA-adapted CM bolus ranging 40-105 ml and injection rate ranging 3.5-5.0 ml/s for a BSA of <1.70 to >or=2.5 m(2). Eighty control patients matched for BSA who had previously undergone routine CTCA with a fixed CM protocol of 80 ml at 5 ml/s served as reference group. The average vessel attenuation from the proximal right (RCA) and the left main coronary artery (LMA) was assessed. Correlation of BSA with vessel attenuation was assessed in both groups. BSA-matching of all patients was successful (BSA-adapted group 1.98 +/- 0.15 m(2), range 1.66-2.39 m(2) versus reference group 1.98 +/- 0.17 m(2), range 1.59-2.38 m(2); P = 0.74). Mean CM bolus was significantly smaller in the BSA-adapted versus the reference group (70.9 +/- 14.1 vs. 80.0 +/- 0 ml, P < 0.001). There was no correlation in the BSA-adapted group (r = -0.07, P = 0.53, SEE = 0.15), while coronary attenuation was inversely related to BSA in the reference group (r = -0.59, P < 0.001, SEE = 0.14). We have successfully validated a BSA-adapted contrast material protocol which results in a comparable coronary contrast enhancement independent of individual BSA. This was achieved despite a significant reduction in the overall contrast material amount.

Image Quality and Radiation Exposure in Coronary CT Angiography According to Tube Voltage and Body Mass Index

Purpose: To investigate the image quality and radiation dose of a coronary CT angiography (CCTA) according to tube voltage and body mass index (BMI). Materials and Methods: This study included 139 patients who underwent CCTA using a retrospective electrocardiography-gating technique. A total of 48 patients (BMI 25, group B) with 120 kVp, and 46 patients (BMI 85 HU; group B, 437 46 HU; group C, 469 62 HU, p 5 HU versus 22 6 HU, p=0.427), but significantly higher in group A compared to group C (23 5 HU versus 17 4 HU, p 6; group B, 19 3; group C, 27 5: p 5 versus group B 14 3, p 4, p=0.127). The percentage of coronary segments with diagnostic image quality was 97.9% in group A, 96.0% in group B, and 99.0% in group C. The mean image quality score was 4.5 0.5 in group A, 4.1 0.4 in group B, and 4.2 0,4 in group C (p 0.8 mSv in group A, 14.3 1.3 mSv in group B, and 14.9 1.3 mSv in group C. A 42% reduction in mean effective radiation dose in group A was observed compared with groups B and C. Conclusion: In patients with BMI less than 25 and a low-dose CCTA with 100 kVp leads to a significant reduction in radiation exposure without degradation of image quality.

Usefulness of Additional Coronary Calcium Scoring in Low-dose CT Coronary Angiography with Prospective ECG-Triggering: Impact on Total Effective Radiation Dose and Diagnostic Accuracy

To determine the impact of additional coronary calcium scoring on total effective radiation dose and diagnostic accuracy of low-dose computed tomography coronary angiography (CTCA) with prospective electrocardiogram (ECG) triggering. Sixty-one consecutive patients underwent 64-slice CTCA using prospective ECG triggering, calcium scoring, and invasive quantitative coronary angiography, the latter served as standard of reference. Diagnostic accuracy was calculated for CTCA, calcium scoring, and for the combination of both. Receiver operator characteristic analyses were performed to determine cutoffs for prediction of significant coronary artery stenoses. Mean effective radiation dose was 2.1 + or - 0.7 mSv (range, 1.0-3.3 mSv) for CTCA and 1.1 + or - 0.1 mSv (range, 0.9-1.4 mSv) for calcium scoring. Per-patient sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 85.7%, 89.2%, and 100% for CTCA, and 72.7%, 82.1%, 82.8%, and 71.9% for calcium scoring. Adding calcium-scoring with a cutoff at 133 in patients aged >50.7 years with nondiagnostic CTCA improved the respective values of diagnostic accuracy of the entire study population to 100%, 96.4%, 97.1%, and 100%; the added value of calcium scoring was confined to only three patients (5%), who were reclassified from false positive to true negative. Specificity and PPV of low-dose CTCA may be further improved by combining it with coronary calcium scoring. However, only a fraction of patient may benefit, whereas exposing the entire population to more than 50% increase in effective radiation dose.