Thoraco-abdominal high-pitch dual-source CT angiography: experimental evaluation of injection protocols with an anatomical human vascular phantom

Objective

To experimentally evaluate three different contrast injection protocols at thoraco-abdominal high-pitch dual-source computed tomography angiography (CTA), with regard to level and homogeneity of vascular enhancement at different cardiac outputs.

Materials and methods

A uniphasic, a biphasic as well as an individually tailored contrast protocol were tested using a human vascular phantom. Each protocol was scanned at 5 different cardiac outputs (3–5 L/min, steps of 0.5 L/min) using an extracorporeal cardiac pump. Vascular enhancement of the thoraco-abdominal aorta was measured every 5 cm. Overall mean enhancement of each protocol and mean enhancement for each cardiac output within each protocol were calculated. Enhancement homogeneity along the z-axis was evaluated for each cardiac output and protocol.

Results

Overall mean enhancement was significantly higher in the uniphasic than in the other two protocols (all p < .05), whereas the difference between the biphasic and tailored protocol was not significant (p = .76). Mean enhancement among each of the 5 cardiac outputs within each protocol was significantly different (all p < .05). Only within the tailored protocol mean enhancement differed not significantly at cardiac outputs of 3.5 L/min vs. 5 L/min (484 ± 25 HU vs. 476 ± 19 HU, p = .14) and 4 vs. 5 L/min (443 ± 49 HU vs. 476 ± 19 HU, p = .05). Both, uniphasic and tailored protocol yielded homogenous enhancement at all cardiac outputs, whereas the biphasic protocol failed to achieve homogenous enhancement.

Conclusion

This phantom study suggests that diagnostic and homogenous enhancement at thoraco-abdominal high-pitch dual-source CTA is feasible with either a uniphasic or an individually tailored contrast protocol.     

X-ray induced DNA double-strand breaks in coronary CT angiography: comparison of sequential, low-pitch helical and high-pitch helical data acquisition

Background

Aim of this study was to compare DNA double-strand breaks (DSBs) in blood lymphocytes of patients undergoing high-pitch helical, low-pitch helical and sequential coronary CT angiography.

Methods and results

66 patients were examined with various scan protocols and modes (low-pitch helical scan: 100–120 kV, 320–438 mAs/rot, pitch 0.18–0.39, with or without ECG-pulsing, n = 35; prospectively ECG-triggered high-pitch helical scan: 100–120 kV, 320–456 mAs/rotation, pitch 3.2–3.4, n = 19; prospectively ECG-triggered sequential scan: 100–120 kV, 150–300 mAs or 320–370 mAs/rotation, n = 12) either using a 64-slice or 128-slice dual-source CT or a 128-slice single source CT scanner. Blood samples were obtained before and 30 min after CT and DSBs were analyzed in isolated lymphocytes using γ-H2AX immunofluorescence microscopy.A significant increase of DSBs was measurable 30 min after CTA (range 0.01–0.71/cell). CT induced DSBs showed a significant correlation with the estimated effective dose (ρ = 0.90, p < 0.00001). Both prospectively ECG-triggered sequential (0.10 DSBs/cell, 176 mGy cm, p < 0.00001) and high-pitch helical scan protocols (0.03 DSBs/cell, 109 mGy cm, p < 0.00001) led to a significant reduction of median DLP and DSB levels compared to low-pitch helical scans (0.34 DSBs/cell, 828 mGy cm). A reduction of the tube voltage resulted in significantly lower whereas additional calcium scoring resulted in elevated DLP and DNA damages (p < 0.05 each).

Conclusion

In coronary CTA, data acquisition protocols have a significant influence on the X-ray induced DSB levels. Using γ-H2AX immunofluorescence microscopy different scan modes in different CT generations can be compared concerning their biological impact.     

Prospectively Electrocardiogram-Gated High-Pitch Spiral Acquisition Mode Dual-Source CT Coronary Angiography in Patients with High Heart Rates: Comparison with Retrospective Electrocardiogram-Gated Spiral Acquisition Mode

Objective

To assess the image quality and effective radiation dose of prospectively electrocardiogram (ECG)-gated high-pitch spiral acquisition mode (flash mode) of dual-source CT (DSCT) coronary angiography (CTCA) in patients with high heart rates (HRs) as compared with retrospectively ECG-gated spiral acquisition mode.

Materials and Methods

Two hundred and sixty-eight consecutive patients (132 female, mean age: 55 ± 11 years) with mean HR > 65 beats per minute (bpm) were prospectively included in this study. The patients were divided into two groups. Collection was performed in group A CTCA using flash mode setting at 20-30% of the R-R interval, and retrospectively ECG-gated spiral acquisition mode in group B. The image noise, contrast-to-noise ratio (CNR), image quality scores, effective radiation dose and influencing factors on image quality between the two groups were assessed.

Results

There were no significant differences in image quality scores and proportions of non-diagnostic coronary artery segments between two groups (image quality scores: 1.064 ± 0.306 [group A] vs. 1.084 ± 0.327 [group B], p = 0.063; proportion of non-diagnostic coronary artery segments: segment-based analysis 1.52% (group A) vs. 1.74% (group B), p = 0.345; patient-based analysis 7.5% (group A) vs. 6.7% (group B), p = 0.812). The estimated radiation dose was 1.0 ± 0.16 mSv in group A and 7.1 ± 1.05 mSv in group B (p = 0.001).

Conclusion

In conclusion, in patients with HRs > 65 bpm without cardiac arrhythmia, the prospectively high-pitch spiral-acquisition mode with image-acquired timing set at 20-30% of the R-R interval provides a similar image quality and low rate of non-diagnostic coronary segments to the retrospectively ECG-gated low-pitch spiral acquisition mode, with significant reduction of radiation exposure.     

Dose and image quality of high-pitch dual source computed tomography for the evaluation of cervical lymph node status – Comparison to regular 128-slice single source computed tomography

Purpose

A high-pitch dual-source CT (DSCT) was compared to a standard single-source CT protocol in terms of dose and image quality for malignant lymphoma staging.

Materials and methods

Data from 43 patients who underwent DSCT (group 1) of the neck for staging of malignant lymphoma and 40 patients who underwent regular single source CT (group 2) were investigated retrospectively. Volume CT dose index (CTDIvol), dose length product (DLP), background noise (BN), attenuation values, signal-to-noise-ratio (SNR), scan time, effective tube current-time product (eff. mAs), subjective diagnostic image quality and artifact burden were compared.

Results

CTDIvol (5.5 ± 0.8 mGy vs. 12.4 ± 1.4 mGy), DLP (172 ± 27 mGycm vs. 344 ± 60 mGycm, p < 0.0001), eff. mAs (98 ± 15 mAs vs. 183 ± 20 mAs, p < 0.0001) and scan time (0.64 ± 0.05 s vs. 8.21 ± 0.72 s) were lower for group 1. BN was higher (p < 0.001) for group 1 with a mean difference of 2.6 HU. SNR for sternocleidomastoid and pectoral muscle was lower (6.6–12.3 vs. 7.8–19.1) for group 1. Subjective image quality (1.55 ± 0.6 vs. 1.42 ± 0.5) and artifact burden (1.62 ± 1.0 vs. 1.57 ± 0.9) were not rated significantly different (p = 0.47 and p = 0.80) with a good inter-observer agreement (κ = 0.59–0.90).

Conclusion

High-pitch DSCT allows reduction of patient dose for cervical lymphoma staging while diagnostic image quality is preserved.     

Prospectively ECG-triggered high-pitch coronary CT angiography at 70 kVp with 30 mL contrast agent: An intraindividual comparison with sequential scanning at 120 kVp with 60 mL contrast agent

PurposeTo investigate image quality, radiation dose, and diagnostic efficiency of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) at 70 kVp with 30 mL contrast agent intra-individually compared with routine CCTA protocol.Materials and methodsOne hundred and thirty eight patients with suspected coronary artery disease, body mass index (BMI) ≤ 25 kg/m² and heart rate (HR) ≤ 70 beats per minute (bpm) underwent prospectively ECG-triggered high-pitch CCTA at 70 kVp and 30 mL contrast agent (protocol A) and prospectively ECG-triggered sequential scanning at 120 kVp and 60 mL contrast medium (protocol B). Objective and subjective image quality, radiation doses, and diagnostic accuracy were evaluated and compared between the two protocols.ResultsHigher CT attenuation, higher noise, lower signal-to-noise ratios (SNRs) and lower contrast-to-noise ratios (CNRs) were found in protocol A than in protocol B (P < 0.001). However, image quality of protocol A were diagnostic. In patients with BMI < 23 kg/m² or HR < 60 bpm, subjective image quality scores of some coronary arteries in protocol A were not significantly different from protocol B (P > 0.05). Effective dose in protocol A has reduced by 96.7% compared with protocol B (P < 0.001). No significant differences were found for diagnostic accuracy between the two protocols on a per-segment (P = 0.513), per-vessel (P = 0.317) and per-patient (P = 0.125) basis.ConclusionsProspectively ECG-triggered high-pitch CCTA at 70 kVp with 30 mL contrast agent can reduce radiation dose but maintain image quality and high diagnostic accuracy in a selected, non-obese population.     

Radiation doses from phantom measurements at high-pitch dual-source computed tomography coronary angiography

Objective

To compare radiation doses delivered at prospectively ECG-triggered sequential- (SEQ), retrospectively ECG-gated spiral- (RETRO) and prospectively ECG-triggered high-pitch spiral- (HP) computed tomography coronary angiography (CTCA) protocols, as well as catheter coronary angiography (CCA) using an anthropomorphic phantom.

Materials and methods

An anthropomorphic Alderson phantom equipped with 50 thermoluminescent dosimeters (TLDs) was scanned using different CTCA protocols and an uncomplicated diagnostic CCA examination was simulated. Absorbed doses were experimentally determined and effective doses calculated using the dose-length product (DLP) for CTCA and the dose-area product (DAP) for CCA, as well as according to International Commission on Radiation Protection (ICRP) publications 60 and 103.

Results

Effective organ doses were significantly lower for HP protocols (100 kV: 0.17 ± 0.26 mSv; 120 kV: 0.26 ± 0.39 mSv) compared to SEQ protocols (100 kV: 0.50 ± 0.79 mSv; 120 kV: 0.90 ± 1.41 mSv; each p < 0.05) and compared to RETRO protocols (100 kV: 1.59 ± 2.12 mSv; 120 kV: 2.75 ± 3.50 mSv; each p < 0.05). Effective organ doses at HP-CTCA tended to be lower than at CCA (0.37 ± 0.40 mSv), however this was not statistically significant (p = 0.13). Effective doses calculated according to ICRP guidelines could be estimated using the DLP and a conversion coefficient of k = 0.034 mSv/[mGy cm] (ICRP103) or k = 0.028 mSv/[mGy cm] (ICRP60), respectively. HP-CTCA led to a dose reduction of 89% compared to RETRO-CTCA, regardless of the calculation method used.

Conclusions

Radiation doses as determined by phantom measurements are significantly lower at HP-CTCA compared to SEQ-CTCA and RETRO-CTCA and comparable to uncomplicated diagnostic CCA.     

Image quality of ultra-low-dose dual-source CT angiography using high-pitch spiral acquisition and iterative reconstruction in young children with congenital heart disease

BackgroundObtaining diagnostic CT image quality with ultra-low radiation dose in young children with congenital heart disease remains challenging.ObjectiveWe evaluated the feasibility and image quality of prospectively electrocardiogram (ECG)-triggered high-pitch spiral acquisition with iterative reconstruction for pediatric cardiovascular CT angiography.MethodsSixty-two consecutive pediatric patients younger than 2 years with congenital heart disease underwent prospectively ECG-triggered high-pitch spiral dual-source CT acquisition. Patients were randomly assigned into 2 groups: full tube current (40–70 mAs) scans with filtered back projection reconstruction (group A) and half tube current (20–35 mAs) scans with sinogram-affirmed iterative reconstruction (group B). Attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were compared between the 2 groups. Effective radiation dose was also estimated for both groups.ResultsNo significant difference was found in the attenuation, image noise, SNR, and CNR between the 2 groups in the same evaluated anatomic regions, whereas the attenuation and image noise were slightly lower, and the SNR and CNR were slightly higher in group B. No significant difference was found in subjective image quality between the 2 groups (4.27 ± 0.73 vs. 4.34 ± 0.42; P = .813). Effective dose was 0.06 ± 0.03 mSv in group B and 0.13 ± 0.04 mSv in group A, reflecting dose savings of 53.8% by using iterative reconstruction.ConclusionsA combination of prospectively ECG-triggered high-pitch spiral acquisition, low tube current, and iterative reconstruction may offer diagnostic image quality in pediatric cardiovascular CT angiography with effective radiation dose < 0.1 mSv.     

Dual-source 128-slice MDCT neck: Radiation dose and image quality estimation of three different protocols

Purpose

To estimate the radiation dose and image quality of single-source (SSCT), high-pitch (HPCT), and dual-energy (DECT) protocols of a dual-source CT (DSCT) system for the examination of neck.

Materials and methods

180 patients were randomized to one of the three protocols: 60 patients (age: 55.4 ± 12 years; range: 44–84 years) were examined with a SSCT, other 60 (59.5 ± 16.4years; R: 40–85) with HPCT, and the last 60 (61.1 ± 14.9 years; R: 47–84) were examined with a DECT protocol. All examinations were performed using a DSCT system. The used protocols: Group-1 (SSCT: 120 kV; effective mAs: 185.4 ± 17.7), Group-2 (HPCT: 120 kV; eff. mAs: 97.7 ± 11.8), and Group-3 (DECT: 80 kV/140 kV with tin-filter; eff. mAs: 248.5 ± 25.7; 187 ± 21.2). A 100 ml iomeprol non-ionic contrast material was injected in to the patients during examination.

Results

Insignificant results were yielded regarding SNR and CNR between the groups (group-1 vs. 2: 0.3125, group-1 vs. 0.6W: 0.6875, group-2 vs. 0.6W: 0.3125), except DECT-80 (group-1 vs. 80 kV: 0.04289, group-2 vs. 80 kV: 0.025, group-0.6W vs.80 kV: 0.04567) and 140 kV data, moreover, qualitative analysis yielded the same results. Mean effective-dose was significantly lower (p < 0.05) in group-2 (1.06 ± 0.16 mSv) compared to group-1 (2.05 ± 0.22 mSv) or group-3 (1.76 ± 0.2 mSv). Single- and dual-energy comparison showed a significant difference (group-1 vs. 3: p = 0.00001 and group-2 vs. 3: p = 0.00001) for CTDIvol (percent difference: 16%, 64%) or DLP (PD: 15.5%, 50.5%).

Conclusion

Quantitative and qualitative analysis showed similar results for SSCT, HPCT, and DECT-0.6W datasets regarding quality. HPCT yielded lower dose compared to other groups, however, the DECT achieved a lower and significant dose difference from the SSCT protocol. HPCT and DECT can be used with similar image quality and lower radiation dose compared to SSCT for the scans and can be utilized to various clinical advantages.     

Accuracy of 128-slice dual-source CT using high-pitch spiral mode for the assessment of coronary stents: First in vivo experience

Objective

To investigate the accuracy of 128-slice dual-source CT using high-pitch spiral mode (HPS) for the assessment of coronary stents.

Methods

We conducted a prospective study on patients with previous stent implantation due to recurred suspicious symptoms of angina with positive findings at stress testing scheduled for coronary angiography (CA), while dual source computed tomography (DSCT) examinations were randomly done by one of the three different scan modes [HPS, sequential mode (SEQ), low-pitch spiral mode (LPS)] one week before CA examinations. The image quality, radiation dose and stent patency of DSCT were evaluated blinded to the results of CA.

Results

180 patients with total 256 stents were enrolled in this study. There was no significant difference on the image quality of DSCT by HPS (1.4 ± 0.5), SEQ (1.5 ± 0.5) and LPS (1.3 ± 0.6) (P > 0.05). The noise of images reconstructed with B26f kernel in HPS is significantly increased than in SEQ/LPS (P < 0.05), while no significant difference with images reconstructed with B46f kernel (P > 0.05). Heart rate (HR) variability had a slight impact on the image quality for HPS (P < 0.05), not for LPS/SEQ (P > 0.05). In the assessment of stent restenosis compared with CA on per-stent basis, there was no significant difference on sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of DSCT using HPS (100%, 97.1%, 83.3%, 100%), LPS (92.3%, 95.9%, 80%, 98.6%) and SEQ (93.3%, 97.3%, 87.5%, 98.6%) (P > 0.05). The effective dose of DSCT by HPS (1.0 ± 0.5 mSv) is significant less than that by SEQ (3.0 ± 1.4 mSv) or LPS (13.0 ± 5.4 mSv) (P < 0.01).

Conclusions

DSCT using HPS provides good diagnostic accuracy on coronary stent patency compared with CA, similar to that by SEQ/LPS, whereas with lower effective dose in patients with HR lower than 65 bpm.     

High-pitch coronary CT angiography in dual-source CT during free breathing vs. breath holding in patients with low heart rates

Background

Coronary CT angiography (CCTA) is usually performed during breath holding to reduce motion artifacts caused by respiration. However, some patients are not able to follow the breathing commands adequately due to deafness, hearing impairment, agitation or pulmonary diseases. The aim of this study was to evaluate the potential of high-pitch CCTA in free breathing patients when compared to breath holding patients.

Methods

In this study we evaluated 40 patients (20 free breathing and 20 breath holding patients) with a heart rate of 60 bpm or below referred for CCTA who were examined on a 2nd generation dual-source CT system. Image quality of each coronary artery segment was rated using a 4-point grading scale (1: non diagnostic–4: excellent).

Results

Mean heart rate during image acquisition was 52 ±5 bpm in both groups. There was no significant difference in mean image quality, slightly favoring image acquisition during breath holding (mean image quality score 3.76 ± 0.32 in breath holding patients vs. 3.61 ± 0.45 in free breathing patients; p = 0.411). Due to a smaller amount of injected contrast medium, there was a trend for signal intensity to be slightly lower in free breathing patients, but this was not statistically significant (435 ± 123 HU vs. 473 ± 117 HU; p = 0.648).

Conclusion

In patients with a low heart rate who are not able to hold their breath adequately, CCTA can also be acquired during free breathing without substantial loss of image quality when using a high pitch scan mode in 2nd generation dual-source CT.