Interscan reproducibility of quantitative coronary plaque volume and composition from CT coronary angiography using an automated method

Objectives

Quantitative measurements of coronary plaque volume may play a role in serial studies to determine disease progression or regression. Our aim was to evaluate the interscan reproducibility of quantitative measurements of coronary plaque volumes using a standardized automated method.

Methods

Coronary dual source computed tomography angiography (CTA) was performed twice in 20 consecutive patients with known coronary artery disease within a maximum time difference of 100 days. The total plaque volume (TP), the volume of non-calcified plaque (NCP) and calcified plaque (CP) as well as the maximal remodelling index (RI) were determined using automated software.

Results

Mean TP volume was 382.3?±?236.9 mm³ for the first and 399.0?±?247.3 mm³ for the second examination (p?=?0.47). There were also no significant differences for NCP volumes, CP volumes or RI. Interscan correlation of the plaque volumes was very good (Pearson’s correlation coefficients: r?=?0.92, r?=?0.90 and r?=?0.96 for TP, NCP and CP volumes, respectively).

Conclusions

Automated software is a time-saving method that allows accurate assessment of coronary atherosclerotic plaque volumes in coronary CTA with high reproducibility. With this approach, serial studies appear to be possible.

Key Points

? Reproducibility of coronary atherosclerotic plaque volume in coronary CTA is high. ? Using automated software facilitates quantitative measurements. ? Serial studies to determine progression or regression of coronary plaque are possible.     

Variability and accuracy of coronary CT angiography including use of iterative reconstruction algorithms for plaque burden assessment as compared with intravascular ultrasound—an ex vivo study

Objectives

To systematically assess inter-technique and inter-/intra-reader variability of coronary CT angiography (CTA) to measure plaque burden compared with intravascular ultrasound (IVUS) and to determine whether iterative reconstruction algorithms affect variability.

Methods

IVUS and CTA data were acquired from nine human coronary arteries ex vivo. CT images were reconstructed using filtered back projection (FBPR) and iterative reconstruction algorithms: adaptive-statistical (ASIR) and model-based (MBIR). After co-registration of 284 cross-sections between IVUS and CTA, two readers manually delineated the cross-sectional plaque area in all images presented in random order.

Results

Average plaque burden by IVUS was 63.7?±?10.7% and correlated significantly with all CTA measurements (r?=?0.45–0.52; P?P?>?0.05). Increased overestimation was associated with smaller plaques, eccentricity and calcification (P?P?P?>?0.05).

Conclusion

In ex vivo coronary arteries, plaque burden by coronary CTA had extremely low inter-/intra-reader variability and correlated significantly with IVUS measurements. Accuracy as well as reader reliability were independent of CT image reconstruction algorithm.

Key Points

? IVUS is deemed the gold standard in-vivo coronary plaque assessment ? But coronary CT angiography findings correlate strongly with IVUS results ? Coronary CT angiography now allows plaque quantification close to IVUS ? Iterative image reconstruction algorithms do not alter accuracy or reproducibility ? Plaque quantification is more challenging in smaller eccentric calcified lesions     

Quantitative assessment of stenosis severity and atherosclerotic plaque composition using 256-slice computed tomography

Objective

To quantitatively estimate lumen narrowing and to assess the volume and composition of atherosclerotic plaque with 256-slice computed tomography angiography (CTA), using conventional quantitative coronary angiography (QCA) as the gold standard.

Methods

Twenty-seven consecutive patients with suspected coronary artery disease (CAD) underwent 256-slice CTA and subsequent coronary angiography within 4 weeks. Quantification of lumen narrowing was performed on curved multiplanar reformatted CTA images, in identical projections to those used for QCA. Atherosclerotic plaque volume and composition were assessed by using commercially available software.

Results

The overall correlation between the stenosis severity by QCA compared with CTA was high (r ²?=?0.79, p?<?0.001). For the detection of ≥50% and ≥75% diameter lesions, CTA yielded high sensitivity, specificity and accuracy (86%, 95% and 90%; and 89%, 100% and 96%, respectively), using QCA as the standard reference. Furthermore, assessment of atherosclerotic plaque yielded highly reproducible results (inter-observer and intra-variability of 13% and 9%, respectively, for the assessment of plaque volume, and high agreement between observers (κ?=?0.86) for the differentiation between non-calcified, mixed and calcified plaque).

Conclusions

Clinically indicated 256-slice CT angiography in symptomatic patients can aid both quantification of lumen narrowing and evaluation of atherosclerotic plaque, with high reproducibility.     

Automated quantitative coronary computed tomography correlates of myocardial ischaemia on gated myocardial perfusion SPECT

Purpose

Automated software tools have permitted more comprehensive, robust and reproducible quantification of coronary stenosis, plaque burden and plaque location of coronary computed tomography angiography (CTA) data. The association between these quantitative CTA (QCT) parameters and the presence of myocardial ischaemia has not been explored. The aim of the present investigation was to evaluate the association between QCT parameters of coronary artery lesions and the presence of myocardial ischaemia on gated myocardial perfusion single-photon emission CT (SPECT).

Methods

Included in the study were 40 patients (mean age 58.2?±?10.9 years, 27 men) with known or suspected coronary artery disease (CAD) who had undergone multidetector row CTA and gated myocardial perfusion SPECT within 6 months. From the CTA datasets, vessel-based and lesion-based visual analyses were performed. Consecutively, lesion-based QCT was performed to assess plaque length, plaque burden, percentage lumen area stenosis and remodelling index. Subsequently, the presence of myocardial ischaemia was assessed using the summed difference score (SDS ≥2) on gated myocardial perfusion SPECT.

Results

Myocardial ischaemia was seen in 25 patients (62.5 %) in 37 vascular territories. Quantitatively assessed significant stenosis and quantitatively assessed lesion length were independently associated with myocardial ischaemia (OR 7.72, 95 % CI 2.41–24.7, p?<?0.001, and OR 1.07, 95 % CI 1.00–1.45, p?=?0.032, respectively) after correcting for clinical variables and visually assessed significant stenosis. The addition of quantitatively assessed significant stenosis (χ ²?=?20.7) and lesion length (χ ²?=?26.0) to the clinical variables and the visual assessment (χ ²?=?5.9) had incremental value in the association with myocardial ischaemia.

Conclusion

Coronary lesion length and quantitatively assessed significant stenosis were independently associated with myocardial ischaemia. Both quantitative parameters have incremental value over baseline variables and visually assessed significant stenosis. Potentially, QCT can refine assessment of CAD, which may be of potential use for identification of patients with myocardial ischaemia.     

Reproducibility of quantitative plaque measurement in advanced coronary artery disease

BackgroundThe ability to characterize and to quantify the extent of coronary artery disease has the potential to improve the prognostic capability of coronary computed tomography angiography. Although reproducible techniques have been described in those with mild coronary disease, this has yet to be assessed in patients with advanced disease.MethodsTwenty patients with known multivessel disease underwent repeated computed tomography coronary angiography, 2 weeks apart. Coronary artery segments were analysed using semi-automated software by two trained observers to determine intraobserver, interobserver and interscan reproducibility.ResultsOverall, 149 coronary arterial segments were analysed. There was excellent intraobserver and interobserver agreement for all plaque volume measurements (Lin’s coefficient 0.95 to 1.0). There were no substantial interscan differences (P ?> ?0.05 for all) for total (2063 ?± ?1246 ?mm³, mean of differences ?35.6 ?mm³), non-calcified (1795 ?± ?910 ?mm³, mean of differences ?4.3 ?mm³), calcified (298 ?± ?425 ?mm³, mean of differences ?31.3 ?mm³) and low-attenuation (13 ?± ?13 ?mm³, mean of differences ?2.6 ?mm³) plaque volumes. Interscan agreement was highest for total and noncalcified plaque volumes. Calcified and low-attenuation plaque (?236.6 to 174 ?mm³ and -15.8 to 10.5 ?mm³ respectively) had relatively wider 95% limits of agreement reflecting the lower absolute plaque volumes.ConclusionIn the presence of advanced coronary disease, semi-automated plaque quantification provides excellent reproducibility, particularly for total and non-calcified plaque volumes. This approach has major potential to assess change in disease over time and optimize risk stratification in patients with established coronary artery disease.     

Contrast agent bolus tracking with a fixed threshold or a manual fast start for coronary CT angiography

Objectives

Comparison of bolus tracking with a fixed threshold versus a manual fast start for coronary CT angiography.

Methods

We retrospectively analysed 320-row coronary CT angiography of 50 patients with suspected or known coronary artery disease. Twenty-five examinations were initiated by a bolus tracking method (group 1), 25 examinations with a manual fast surestart (group 2).

Results

Mean attenuation values in the ascending aorta were 519?±?111 Hounsfield units (HU) in group 1 and 476?±?65 HU in group 2 (p?=?0.10). Assessable vessel lengths were 171?±?44 mm vs 172?±?29 mm for the right coronary artery (p?=?0.91), 11?±?4 mm vs 12?±?4 mm for the left main (p?=?0.9), 163?±?28 mm vs 151?±?26 mm for the left anterior descending coronary artery (p?=?0.11) and 125?±?41 mm vs 110?±?37 mm for the left circumflex coronary artery (p?=?0.18). Image quality for all coronary arteries was not significantly different between the groups (p?>?0.41). The attenuation ratio between the left and right ventricle was 2.8?±?0.7 vs 3.6?±?1.0 (p?=?0.003). Significantly less contrast agent was used in group 2 (64?±?6 ml vs 80?±?0 ml; p?<?0.001).

Conclusions

Bolus tracking with a fixed threshold and with a manual fast start are both suitable methods; the fast start allowed a reduction of contrast agent volumes.

Key Points

? Fixed threshold bolus tracking is suitable for coronary 320-row CT angiography ? Manual fast start bolus tracking can reduce contrast agent volumes ? Manual fast start and fixed threshold initiation achieve good image quality ? Fixed threshold bolus tracking achieves a more reliable contrast bolus position     

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

Background

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.

Methods

150 patients with low heart rates and less than 100?kg body weight were randomised and examined by contrast-enhanced dual-source CT coronary angiography (100?kV, 320?mAs). 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.

Results

Mean effective dose was 1.4?±?0.2?mSv for axial, 0.8?±?0.07?mSv for high-pitch spiral, and 5.3?±?2.6?mSV for standard spiral acquisition (P?P?Conclusion Low-dose coronary CT angiography permits the detection of coronary atherosclerotic plaque with good interobserver agreement.

Key Points

? 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.     

Assessment of coronary artery disease and calcified coronary plaque burden by computed tomography in patients with and without diabetes mellitus

Purpose

To compare the coronary atherosclerotic burden in patients with and without type-2 diabetes using CT Coronary Angiography (CTCA).

Methods and Materials

147 diabetic (mean age: 65?±?10?years; male: 89) and 979 nondiabetic patients (mean age: 61?±?13?years; male: 567) without a history of coronary artery disease (CAD) underwent CTCA. The per-patient number of diseased coronary segments was determined and each diseased segment was classified as showing obstructive lesion (luminal narrowing >50%) or not. Coronary calcium scoring (CCS) was assessed too.

Results

Diabetics showed a higher number of diseased segments (4.1?±?4.2 vs. 2.1?±?3.0; p??400 (p?p?p?p?=?0.003) and obstructive CAD (12.5% vs. 3.8%, p?=?0.01). Among patients with CCS????10 all diabetics with obstructive CAD had a zero CCS and one patient was asymptomatic.

Conclusions

Diabetes was associated with higher coronary plaque burden. The present study demonstrates that the absence of coronary calcification does not exclude obstructive CAD especially in diabetics.     

Computed tomography angiography of carotid and coronary artery via a single-bolus injection protocol: a feasibility study using 320-row multidetector CT

Objectives

To investigate the feasibility of using a single-dose injection protocol in CT angiography (CTA) of the carotid and coronary artery with 320-row multidetector CT.

Methods

A total of 82 consecutive patients with suspected carotid artery disease underwent an original CTA protocol aiming at capturing the extra-cranial carotid arteries and coronary arteries simultaneously using 320-row MDCT. The image quality, attenuation, and CNRs of the carotid and coronary arteries were assessed. The lag time (between two separated volumetric acquisitions) was compared between patients with and without cardiac venous opacification (CVO). The contrast medium volume and radiation dose were recorded.

Results

The image quality was 99.4 % diagnostic in carotid and 86.9 % in coronary artery segments. The mean attenuation of carotid and coronary arteries ranged from 462.2 Hu to 533.7 Hu, 415.9 Hu to 454.7 Hu respectively. The mean CNR of the carotid and coronary artery ranged from 15.8 to 18.9 and 17.7 to 20.4 respectively. The lag time in patients with and without CVO was 5.75?±?1.64 s vs. 4.21?±?1.14 s (p?<?0.05). The mean radiation dose was 6.6?±?4.1 mSv.The mean contrast media volume was 71.9?±?9.1 ml.

Conclusions

The carotid and coronary artery can be imaged simultaneously via our original single-dose injection CTA protocol using 320-row CT with adequate image quality.

Key Points

? Carotid and coronary 320-row CTA can be achieved in a single-dose injection. ? Longer coverage was achieved with two or more volumes using 320-row CT. ? The single-dose protocol allows a reduced contrast agent dose of about 72 ml.     

Detection of coronary plaques using MR coronary vessel wall imaging: validation of findings with intravascular ultrasound

Objectives

Compared with X-ray coronary angiography (CAG), magnetic resonance imaging of the coronary vessel wall (MR-CVW) may provide more information about plaque burden and coronary remodelling. We compared MR-CVW with intravascular ultrasound (IVUS), the standard of reference for coronary vessel wall imaging, with regard to plaque detection and wall thickness measurements.

Methods

In this study 17 patients with chest pain, who had been referred for CAG, were included. Patients underwent IVUS and MR-CVW imaging of the right coronary artery (RCA). Subsequently, the coronary vessel wall was analysed for the presence and location of coronary plaques.

Results

Fifty-two matching RCA regions of interest were available for comparison. There was good agreement between IVUS and MR-CVW for qualitative assessment of presence of disease, with a sensitivity of 94% and specificity of 76%. Wall thickness measurements demonstrated a significant difference between mean wall thickness on IVUS and MR-CVW (0.48 vs 1.24?mm, P?<?0.001), but great heterogeneity between wall thickness measurements, resulting in a low correlation between IVUS and MR-CVW.

Conclusions

MR-CVW has high sensitivity for the detection of coronary vessel wall thickening in the RCA compared with IVUS. However, the use of MRI for accurate absolute wall thickness measurements is not supported when a longitudinal acquisition orientation is used.

Key Points

? Both MRI and IVUS can assess coronary vessels ? Both MRI and IVUS can identify coronary vessel wall thickening. ? MRI provides more information about the coronary plaque burden than conventional angiography. ? However, MRI overestimates absolute coronary wall thickness when compared with IVUS.     

Diagnostic accuracy of combined coronary angiography and adenosine stress myocardial perfusion imaging using 320-detector computed tomography: pilot study

Objectives

To determine the diagnostic accuracy of combined 320-detector row computed tomography coronary angiography (CTA) and adenosine stress CT myocardial perfusion imaging (CTP) in detecting perfusion abnormalities caused by obstructive coronary artery disease (CAD).

Methods

Twenty patients with suspected CAD who underwent initial investigation with single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI) were recruited and underwent prospectively-gated 320-detector CTA/CTP and invasive angiography. Two blinded cardiologists evaluated invasive angiography images quantitatively (QCA). A blinded nuclear physician analysed SPECT-MPI images for fixed and reversible perfusion defects. Two blinded cardiologists assessed CTA/CTP studies qualitatively. Vessels/territories with both >50 % stenosis on QCA and corresponding perfusion defect on SPECT-MPI were defined as ischaemic and formed the reference standard.

Results

All patients completed the CTA/CTP protocol with diagnostic image quality. Of 60 vessels/territories, 17 (28 %) were ischaemic according to QCA/SPECT-MPI criteria. Sensitivity, specificity, PPV, NPV and area under the ROC curve for CTA/CTP was 94 %, 98 %, 94 %, 98 % and 0.96 (P?<?0.001) on a per-vessel/territory basis. Mean CTA/CTP radiation dose was 9.2?±?7.4 mSv compared with 13.2?±?2.2 mSv for SPECT-MPI (P?<?0.001).

Conclusions

Combined 320-detector CTA/CTP is accurate in identifying obstructive CAD causing perfusion abnormalities compared with combined QCA/SPECT-MPI, achieved with lower radiation dose than SPECT-MPI.

Key Points

? Advances in CT technology provides comprehensive anatomical and functional cardiac information. ? Combined 320-detector CTA/adenosine-stress CTP is feasible with excellent image quality. ? Combined CTA/CTP is accurate in identifying myocardial ischaemia compared with QCA/SPECT-MPI. ? Combined CTA/CTP results in lower patient radiation exposure than SPECT-MPI. ? CTA/CTP may become an established imaging technique for suspected CAD.     

MRI assessment of experimental gliomas using 17.6 T

Introduction

Using ultra-high-field contrast-enhanced magnetic resonance imaging (MRI), an increase of field strength is associated with a decrease of T ₁ relaxivity. Yet, the impact of this effect on signal characteristics and contrast-enhanced pathology remains unclear. Hence, we evaluated the potential of a 17.6-T MRI to assess contrast-enhancing parts of experimentally induced rat gliomas compared to 3 T.

Methods

A total of eight tumor-bearing rats were used for MRI assessments either at 17.6 T (four rats) or at 3 T (four rats) at 11 days after stereotactic implantation of F98 glioma cells into the right frontal lobe. T ₁-weighted sequences were used to investigate signal-to-noise-ratios, contrast-to-noise-ratios, and relative contrast enhancement up to 16 min after double-dose contrast application. In addition, tumor volumes were calculated and compared to histology.

Results

The 17.6-T-derived contrast-enhancing volumes were 31.5?±?15.4 mm³ at 4 min, 38.8?±?12.7 mm³ at 8 min, 51.1?±?12.6 mm³ at 12 min, and 61.5?±?10.8 mm³ at 16 min after gadobutrol injection. Corresponding histology-derived volumes were clearly higher (138.8?±?8.4 mm³; P?<?0.01). At 3 T, contrast-enhancing volumes were 85.2?±?11.7 mm³ at 4 min, 107.3?±?11.0 mm³ at 8 min, 117.0?±?10.5 mm³ at 12 min, and 129.1?±?10.0 mm³ at 16 min after contrast agent application. Averaged histology-derived volumes (139.1?±?13.4 mm³) in this group were comparable to the 16-min volume (P _{?16 min}?=?0.38). Compared to ultra-high-field MRI, all 3-T-derived volumes were significantly higher (P?<?0.02).

Conclusion

Compared to 3-T-derived images and histology, tumor volumes were underestimated by approximately 50 % at 17.6 T. Hence, contrast-enhanced 17.6-T MRI provided no further benefits in tumor measurement compared to 3 T.     

Diagnostic accuracy of low-dose 256-slice multi-detector coronary CT angiography using iterative reconstruction in patients with suspected coronary artery disease

Objectives

To evaluate the accuracy of low-dose coronary CTA with iterative reconstruction (IR) in the diagnosis of coronary artery disease (CAD) in patients with suspected CAD.

Methods

Ninety-six patients with suspected CAD underwent low-dose prospective electrocardiogram-gated coronary CTA, with images reconstructed using IR. Image quality (IQ) of coronary segments were graded on a 4-point scale (4, excellent; 1, non-diagnostic). With invasive coronary angiography (ICA) considered the “gold standard”, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of coronary CTA were calculated on segment-, vessel- and patient-based levels. The patient data were divided into two groups (Agatston scores of ≥ 400 and <400). The differences in diagnostic performance between the two groups were tested.

Results

Diagnostic image quality was found in 98.1 % (1,232/1,256) of segments. The sensitivity, specificity, PPV, NPV and accuracy were 90.8 %, 95.3 %, 81.8 %, 97.8 % and 94.3 % (segment-based) and 97.2 %, 83.3 %, 94.6 %, 90.9 % and 93.8 % (patient-based). Significant differences between the two groups were seen in specificity, PPV and accuracy (92.1 % vs. 97.9 %, 76.0 % vs. 86.7 %, 91.7 % vs. 96.6 %, P?<?0.05; segment-based). The average effective dose was 1.30?±?0.15 mSv.

Conclusion

Low-dose prospective coronary CTA with IR can acquire satisfactory image quality and show high diagnostic accuracy in patients with suspected CAD; however, blooming continues to pose a challenge in severely calcified segments.

Key Points

? Coronary artery disease (CAD) is increasingly investigated using coronary CTA. ? The iterative reconstruction (IR) algorithm is promising in decreasing radiation doses. ? Low-dose prospective coronary CTA with IR can acquire satisfactory image quality. ? Low-dose prospective coronary CTA with IR can show high diagnostic accuracy.     

Intravoxel incoherent motion MR imaging: comparison of diffusion and perfusion characteristics between nasopharyngeal carcinoma and post-chemoradiation fibrosis

Objectives

To compare the intravoxel incoherent motion (IVIM) diffusion and perfusion characteristics of nasopharyngeal carcinoma (NPC) and post-chemoradiation fibrosis to aid in their differentiation.

Methods

Fifty-three (64 %) patients with newly diagnosed NPC and 30 (36 %) patients with biopsy-proven post-chemoradiation fibrosis were recruited into tumour and fibrosis groups respectively. Diffusion-weighted magnetic resonance (MR) imaging was performed using 13 b values (0–1,000 s/mm²). Their respective IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were obtained.

Results

D and f were significantly lower in NPC (D?=?0.752?±?0.194?×?10^-3 mm²/s, P <0.001; f?=?0.122?±?0.095, P <0.001) than in fibrosis (D?=?1.423?±?0.364?×?10^-3 mm²/s; f?=?0.190?±?0.120); while D* was significantly higher in NPC (111.366?±?65.528?×?10^-3 mm²/s, P <0.001) than in fibrosis (77.468?±?62.168?×?10^-3 mm²/s). Respective cut-off values with sensitivity, specificity and accuracy were: D?=?1.062?×?10^-3 mm²/s (100 %, 100 %, 100 %); f?=?0.132 (66.0 %, 100 %, 78.3 %); D*?=?85.283?×?10^-3 mm²/s (100 %, 90.7 %, 96.4 %).

Conclusion

NPC and post-chemoradiation fibrosis have distinctive IVIM parameters. IVIM MR imaging is potentially useful in discrimination between NPC and fibrosis.

Key Points

? New MRI techniques offer greater help in the assessment of nasopharyngeal carcinoma. ? Tumour and post-chemoradiation fibrosis have distinctive intravoxel incoherent motion diffusion/perfusion parameters. ? Non-invasive IVIM MRI may help differentiate between tumour and fibrosis. ? Pure diffusion is a robust independent discriminating factor which improves diagnostic confidence.     

Clinical evaluation of automatic tube voltage selection in chest CT angiography

Objective

To evaluate the clinical impact of automatic tube voltage selection on chest CT angiography (CTA).

Methods

Ninety-three patients were prospectively evaluated with a CT protocol aimed at comparing two successive CTAs acquired under similar technical conditions except for the kV selection: (1) the initial CTA was systematically obtained at 120 kVp and 90 ref mAs; (2) the follow-up CTA was obtained with an automatic selection of the kilovoltage (Care KV; Siemens Healthcare) for optimised CTA.

Results

At follow-up, 90 patients (97 %) underwent CTA with reduced tube voltage, 100 kV (n?=?26; 28 %) and 80 kV (n?=?64; 69 %), resulting in a significant dose-length-product reduction (follow-up: 87.27; initial: 141.88 mGy.cm; P?<?0.0001; mean dose reduction: 38.5 %) and a significant increase in the CNR at follow-up (follow-up: 11.5?±?3.5 HU; initial: 10.9?±?3.7 HU; P?=?0.03). The increase in objective image noise at follow-up (follow-up: 23.2?±?6.7 HU vs. 17.8?±?5.1 HU; P?<?0.0001) did not alter the diagnostic value of images.

Conclusion

Automatic tube voltage selection reduced the radiation dose delivered during chest CT angiograms by 38.5 % while improving the contrast-to-noise ratio of the examinations.

Key Points

? As low a dose as possible must be used for CT angiography. ? Automatic tube voltage selection permits reduced patient exposure. ? Lowering the kVp enables increased intravascular attenuation. ? Automatic tube voltage selection does not compromise the overall image quality.     

Comprehensive assessment of spotty calcifications on computed tomography angiography: Comparison to plaque characteristics on intravascular ultrasound with radiofrequency backscatter analysis

Background

The purpose of the study was to systematically compare calcification patterns in plaques on computed tomography angiography (CTA) with plaque characteristics on intravascular ultrasound with radiofrequency backscatter analysis (IVUS-VH).

Methods and Results

In total, 108 patients underwent CTA and IVUS-VH. On CTA, calcification patterns in plaques were classified as non-calcified, spotty or dense calcifications. Plaques with spotty calcifications were differentiated into small spotty (<1 mm), intermediate spotty (1-3 mm) and large spotty calcifications (≥3 mm). Plaque characteristics deemed more high-risk on IVUS-VH were defined by % necrotic core (NC) and presence of thin cap fibroatheroma (TCFA). Overall, 300 plaques were identified both on CTA and IVUS-VH. % NC core was significantly higher in plaques with small spotty calcifications as compared to non-calcified plaques (20% vs 13%, P = .006). In addition, there was a trend for a higher % NC in plaques with small spotty calcifications than in plaques with intermediate spotty calcifications (20% vs 14%, P = .053). Plaques with small spotty calcifications had the highest % TCFA as compared to large spotty and dense calcifications (31% vs 9% and 31% vs 6%, P < .05).

Conclusion

Plaques with small spotty calcifications on CTA were related to plaque characteristics deemed more high-risk on IVUS-VH. Therefore, CTA may be valuable in the assessment of the vulnerable plaque.     

Characterization and therapy monitoring of head and neck carcinomas using diffusion-imaging-based intravoxel incoherent motion parameters—preliminary results

Introduction

Using the intravoxel incoherent motion (IVIM) model, diffusion-related coefficient (D) and perfusion-related parameter (f) can be measured. Here, we used IVIM imaging to characterize squamous cell carcinomas of head and neck (HNSCC) and evaluated its application in follow-up after nonsurgical organ preserving therapy.

Methods

Twenty-two patients with locally advanced HNSCC (clinical stage III to IVb) were examined before treatment using eight different b values (b?=?0, 50, 100, 150, 200, 250, 700, 800 s/mm²). All patients were followed for at least 7.5 months after conclusion of therapy. In 16 of these patients, follow-up MRI was available. Using the IVIM approach, f and D were extracted using a bi-exponential fit. For comparison, ADC maps were calculated.

Results

The initial values of f before therapy were located between 5.9 % and 12.9 % (mean: 9.4?±?2.4 %) except for two outliers (f?=?17.9 % and 18.2 %). These two patients exclusively displayed poor initial treatment response. Overall, high initial f (13.1?±?4.1 % vs. 9.1?±?2.4 %) and ADC (1.17?±?0.08?×?10^?3?mm²/s vs. 0.98?±?0.19?×?10^?3?mm²/s) were associated with poor short term outcome (n?=?6) after 7.5 months follow-up. D values before treatment were 0.98?×?10^?3?±?0.18 mm²/s and ADC values were 1.03?×?10^?3?±?0.18 mm²/s. At follow-up, in all primary responders, D (69?±?52 %), f (65?±?46 %), and ADC (68?±?49%) increased.

Conclusions

Our preliminary evaluation indicates that an initial high f may predict poor prognosis in HNSCC. In responders, a significant increase of all IVIM parameters after therapy was demonstrated.     

Diagnostic accuracy of dual-source CT coronary angiography with prospective ECG-triggering on different heart rate patients

Objective

To evaluate the diagnostic accuracy of dual-source CT (DSCT) prospective ECG-triggering coronary angiography in patients with different heart rate (HR).

Methods

103 patients with suspected coronary artery disease underwent DSCT prospective ECG-triggered coronary angiography and invasive coronary angiography (ICA). The patients were grouped by HR during CT scans: low HR (??60?bpm, n?=?34); medium HR (60?n?=?36) and high HR (>70?bpm, n?=?33). The sensitivity and specificity of DSCT in detecting ??50% stenosis were compared among subgroups where ICA was the gold standard. Image quality was scored using a 4-point scale.

Results

A total of 1,580 (95.9%) coronary artery segments were evaluable. Sensitivity and specificity were 82.8% and 98.4%, 88.3% and 98.7%, and 80.3% and 98.6% for different subgroups (all p?>?0.05). The overall area under the curve of the receiver-operating characteristic analysis was 0.94. The image quality scores were 3.1?±?0.3, 3.1?±?0.3 and 3.0?±?0.4 for subgroups (p?>?0.05). The overall average effective radiation dose was 3.60?±?1.60?mSv.

Conclusion

DSCT coronary angiography with prospective ECG-triggering could be just as accurate in patients with medium to high HR compared to those with low HR.     

Quantitative coronary CT angiography: absolute lumen sizing rather than %stenosis predicts hemodynamically relevant stenosis

Objective

To identify the most accurate quantitative coronary stenosis parameter by CTA for prediction of functional significant coronary stenosis resulting in coronary revascularization.

Methods

160 consecutive patients were prospectively examined with CTA. Proximal coronary stenosis was quantified by minimal lumen area (MLA) and minimal lumen diameter (MLD), %area and %diameter stenosis. Lesion length (LL) was measured. The reference standard was invasive coronary angiography (ICA) (>70 % stenosis, FFR <0.8).

Results

210 coronary segments were included (59 % positive). MLA of ≤1.8 mm² was identified as the optimal cut-off (c?=?0.97, p?<?0.001; 95 % CI 0.94–0.99) (sensitivity 90.9 %, specificity 89.3 %) for prediction of functional-relevant stenosis (for MLA >2.1 mm² sensitivity was 100 %). The optimal cut-off for MLD was 1.2 mm (c?=?0.92; p?<?0.001; 95 % CI 0.88–95) (sensitivity 90.9, specificity 85.2) while %area and %diameter stenosis were less accurate (c?=?0.89; 95 % CI 0.84–93, c?=?0.87; 95 % CI 0.82–92, respectively, with thresholds at 73 % and 61 % stenosis). Accuracy for LL was c?=?0.74 (95 % CI 0.67–81), and for LL/MLA and LL/MLD ratio c?=?0.90 and c?=?0.84.

Conclusions

MLA ≤1.8 mm² and MLD ≤1.2 mm are the most accurate cut-offs for prediction of haemodynamically significant stenosis by ICA, with a higher accuracy than relative % stenosis.

Key Points

? Quantitative coronary CT-angiography is accurate for prediction of functional relevant stenosis. ? Absolute lumen area and diameter rather than %stenosis predict functional relevance. ? Lumen area <1.8 mm ² and diameter <1.2 mm are the most accurate cut-offs. ? Quantitative parameters are helpful for decision-making in terms of patient management.

     

Association of inflammation of the left anterior descending coronary artery with cardiovascular risk factors, plaque burden and pericardial fat volume: a PET/CT study

Purpose

Measurements of [¹⁸F]fluorodeoxyglucose (FDG) uptake as a potential marker of the inflammatory activity of the vessel wall could be useful to identify vulnerable atherosclerotic plaques. The purpose of this study was to correlate the FDG uptake in the left anterior descending coronary artery (LAD) with cardiovascular risk factors, pericardial fat volume (PFV) and calcified plaque burden (CPB).

Methods

A total of 292 consecutive tumour patients were examined by whole-body FDG PET and contrast-enhanced CT. The blood pool-corrected standardized uptake value (target to background ratio, TBR) was measured in the LAD, and the contrast-enhanced CT images were used to measure the PFV and the CPB. The Spearman correlation coefficient and the unpaired t test were used for statistical comparison between image-based results and cardiovascular risk factors.

Results

Vascular FDG uptake could be measured for 161 of 292 (55%) patients without myocardial uptake, but the vessel uptake could not be distinguished in the other patients, due to pervasive myocardial uptake. The TBR of the LAD showed significant correlations with hypertension (R?=?0.18; p?<?0.05), coronary heart disease (R?=?0.19; p?<?0.05), body mass index (BMI) (R?=?0.19; p?<?0.05), CPB (R?=?0.36; p?<?0.001) and PFV (R?=?0.20; p?<?0.05), but not with other risk factors. Patients with a TBR in the upper tertile had a larger CPB and a higher PFV than patients with a TBR in the lower tertile (9.1 vs 3.5; p?<?0.001 for CPB and 92.2 vs 71.5 mm³; p?<?0.05 for PVF).

Conclusion

FDG uptake measurement in the LAD correlates with hypertension, coronary heart disease, BMI, PFV and CPB. However, due to myocardial FDG uptake these measurements are only feasible in one half of the patients.