Comparison of longitudinal geometric measurement in human coronary arteries between frequency-domain optical coherence tomography and intravascular ultrasound

Previous studies have demonstrated the higher accuracy of frequency-domain optical coherence tomography (FD-OCT) for quantitative measurements in comparison with intravascular ultrasound (IVUS). However, those analyses were based on the cross-sectional images. The aim of this study was to assess the accuracy of FD-OCT for longitudinal geometric measurements of coronary arteries in comparison with IVUS. Between October 2011 and March 2012, we performed prospective FD-OCT and IVUS examinations in consecutive 77 patients who underwent percutaneous coronary intervention with single stent. Regression analysis and Bland–Altman analysis revealed an excellent correlation between the FD-OCT-measured stent lengths and IVUS-measured stent lengths (r = 0.986, p < 0.001; mean difference = ?0.51 mm). There was an excellent agreement between the actual stent lengths and the FD-OCT-measured stent lengths (r = 0.993, p < 0.001) as well as between the actual stent lengths and the IVUS-measured stent lengths (r = 0.981, p < 0.001). The difference between the actual stent lengths and the FD-OCT-measured stent lengths was significantly smaller than that between the actual stent lengths and the IVUS-measured stent lengths (0.15 ± 0.68 vs. 0.70 ± 1.15 mm, p < 0.001). Both FD-OCT (mean difference = ?0.04 and ?0.04 mm, respectively) and IVUS (mean difference = ?0.06 and ?0.06 mm, respectively) showed an excellent intra-observer and inter-observer reproducibility for the stent length measurements. In conclusion, FD-OCT provides accurate longitudinal measurement with excellent intra-observer and inter-observer reproducibility. FD-OCT might be a reliable technique for longitudinal geometric measurement in human coronary arteries.     

Interstudy reproducibility of the second generation, Fourier domain optical coherence tomography in patients with coronary artery disease and comparison with intravascular ultrasound: a study applying automated contour detection

Recently, Fourier domain OCT (FD-OCT) has been introduced for clinical use. This approach allows in vivo, high resolution (15 micron) imaging with very fast data acquisition, however, it requires brief flushing of the lumen during imaging. The reproducibility of such fast data acquisition under intracoronary flush application is poorly understood. To assess the inter-study variability of FD-OCT and to compare lumen morphometry to the established invasive imaging method, IVUS. 18 consecutive patients with coronary artery disease scheduled for PCI were included. In each target vessel a FD-OCT pullback (MGH system, light source 1,310 nm, 105 fps, pullback speed 20 mm/s) was acquired during brief (3 s) injection of X-ray contrast (flow 3 ml/s) through the guiding catheter. A second pullback was repeated under the same conditions after re-introduction of the FD OCT catheter into the coronary artery. IVUS and OCT imaging was performed in random order. FD-OCT and IVUS pullback data were analyzed using a recently developed software employing semi automated lumen contour and stent strut detection algorithms. Corresponding ROI were matched based on anatomical landmarks such as side branches and/or stent edges. Inter-study variability is presented as the absolute difference between the two pullbacks. FD-OCT showed remarkably good reproducibility. Inter-study variability in native vessels (cohort A) was very low for mean and minimal luminal area (0.10 ± 0.38, 0.19 ± 0.57 mm², respectively). Likewise inter-study variability was very low in stented coronary segments (cohort B) for mean lumen, mean stent, minimal luminal and minimal stent area (0.06 ± 0.08, 0.07 ± 0.10, 0.04 ± 0.09, 0.04 ± 0.10 mm², respectively). Comparison to IVUS morphometry revealed no significant differences. The differences between both imaging methods, OCT and IVUS, were very low for mean lumen, mean stent, minimal luminal and minimal stent area (0.10 ± 0.45, 0.10 ± 0.36, 0.26 ± 0.54, 0.05 ± 0.47 mm², respectively). FD-OCT shows excellent reproducibility and very low inter-study variability in both, native and stented coronary segments. No significant differences in quantitative lumen morphometry were observed between FD-OCT and IVUS. Evaluating these results suggest that FD-OCT is a reliable imaging tool to apply in longitudinal coronary artery disease studies.     

In-stent area stenosis on 64-slice multi-detector computed tomography coronary angiography: optimal cutoff value for minimum lumen cross-sectional area of coronary stents compared with intravascular ultrasound

We aimed to prospectively assess the optimal cutoff value for a minimum lumen cross-sectional area (CSA) on a 64-slice multidetector computed tomography (MDCT) compared with an intravascular ultrasound (IVUS). In 39 patients with 43 stents, the minimum lumen diameter, stent diameter, diameter stenosis, minimum lumen CSA, stent CSA, and area stenosis at the narrowest point were measured independently on 64-slice MDCT and IVUS images. For the assessment of diameter and CSA, 64-slice MDCT showed good correlations with IVUS (r = 0.82 for minimum lumen diameter, r = 0.66 for stent diameter, r = 0.79 for minimum lumen CSA, and r = 0.75 for stent CSA, respectively, P < 0.0001). For the assessment of diameter and area stenoses, a 64-slice MDCT showed good correlations with IVUS (r = 0.89 and 0.91, respectively, P < 0.0001). The overall sensitivity, specificity, positive predictive value, and negative predictive value to detect in-stent area restenosis (≥50 % area stenosis) of a 64-slice MDCT were 77, 100, 100, and 91 %, respectively. The cutoff value of a 64-slice MDCT, determined by receiver operator characteristic (ROC) analysis, was 5.0 mm² with 76.5 % sensitivity and 92.3 % specificity for significant in-stent area restenosis; the area under the ROC curve was 0.902 (P < 0.0001). A good correlation was found between a 64-slice MDCT and the IVUS, regarding the assessment of diameter and area stenoses of coronary stents in selected patients implanted with stents of more than 3 mm in diameter. Optimal cutoff value for the minimum lumen CSA of coronary stents on the 64-slice MDCT is 5 mm² to predict a CSA of 4 mm² on IVUS.     

Comparative analysis of lumen enlargement mechanisms achieved with the bifurcation dedicated BiOSS® stent versus classical coronary stent implantations by means of provisional side branch stenting strategy: an intravascular ultrasound study

The aim of this study was to analyze the mechanisms of lumen enlargement in bifurcation lesions, as assessed by intravascular ultrasound (IVUS), after percutaneous treatment with classic provisional “T” stenting with conventional drug-eluting stents (DES) versus bifurcation dedicated BiOSS^® (Balton, Warsaw, Poland) stent. In this prospective study between Jan and Dec/11, 32 patients with single de novo coronary bifurcation lesions suitable for treatment with BiOSS stents were randomized (1:1). IVUS method included pre- and post-procedure analysis in the parent vessel. Vessel, lumen and plaque cross-sectional areas were determined at the target lesion [minimum lumen area (MLA) site], proximal limb, distal limb, and “window”—defined as the segment between the carina (flow divider) and the vessel wall at the level of the side branch inflow. All lesions were treated with provisional approach and only 1 case in BiOSS group had a stent implanted in the side branch. Angiographic and IVUS results including MLA at the target site and proximal/distal references were similar. However, mean window length—largest diameter within the window, was similar at baseline, but BiOSS measured significantly longer at postprocedure (2.21 ± 0.37 vs. 1.76 ± 0.52 mm, p = 0.01). In addition, the magnitude of changes in vessel (27 ± 24 % vs. 9 ± 10 %, p = 0.01) and plaque (2 ± 26 % vs. ?2 ± 26 %, p = 0.02) areas at the window were significantly different for DES versus BiOSS groups, respectively. The contribution of vessel extension for lumen enlargement represented 54 versus 43 %, 130 versus 46 %, 98 versus 80 % and 51 versus 19 % of the result achieved at the proximal limb, window, distal limb and MLA sites for DES versus BiOSS, respectively; as for plaque re-distribution, results were 36 versus 57 %, ?30 versus 54 %, 2 versus 20 %, and 49 versus 81 %, at the proximal limb, window, distal limb and MLA sites, respectively. These results suggest different mechanisms of lumen enlargement comparing conventional DES versus BiOSS dedicated bifurcation stent, which can impact side branch compromise during procedure.     

Optical coherence tomography guided in-stent thrombus removal in patients with acute coronary syndromes

The persistence of thrombus inside stent struts is a frequent event in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI), and this phenomenon might be associated with an increased risk of stent thrombosis. We sought to quantify by means of optical coherence tomography (OCT) the presence of in-stent thrombus after achievement of an optimal angiographic result in patients with ACS undergoing PCI. In addition, we evaluated the feasibility and safety of an OCT-guided strategy of in-stent thrombus removal. Eighty consecutive patients with ACS undergoing PCI were treated with two different strategies equally divided into two groups: angio-guided PCI, and OCT-guided PCI, in which additional OCT-driven in-stent balloon dilatation was adopted to reduce thrombus encroachment of the lumen. Overall in-stent thrombus area was 4.3 % with a maximal thrombus encroachment of 16.7 %. In the OCT-guided group, use of high pressure intra-stent dilatation led to a significant increase in stented area (9.6 ± 2.4 vs. 9.1 ± 2.49 mm², p = 0.002) and lumen area (9.2 ± 2.4 vs. 8.7 ± 2.3 mm², p < 0.001) and also significantly decreased in-stent thrombus area in absolute (0.35 ± 0.29 vs. 0.42 ± 0.30 mm², p = 0.001) and relative terms (3.58 ± 3.25 vs. 4.53 ± 3.01 %, p = 0.001). Values of TIMI flow, frame count and blush grade, as well as clinical outcomes were not detrimentally affected by such additional dilatations. The use of additional OCT-driven in-stent balloon dilatations is feasible, safe and might be effective in the treatment of in-stent thrombus for patients with ACS.     

First in vivo head-to-head comparison of high-definition versus standard-definition stent imaging with 64-slice computed tomography

The aim of this study was to compare image quality characteristics from 64-slice high definition (HDCT) versus 64-slice standard definition CT (SDCT) for coronary stent imaging. In twenty-five stents of 14 patients, undergoing contrast-enhanced CCTA both on 64-slice SDCT (LightSpeedVCT, GE Healthcare) and HDCT (Discovery HD750, GE Healthcare), radiation dose, contrast, noise and stent characteristics were assessed. Two blinded observers graded stent image quality (score 1 = no, 2 = mild, 3 = moderate, and 4 = severe artefacts). All scans were reconstructed with increasing contributions of adaptive statistical iterative reconstruction (ASIR) blending (0, 20, 40, 60, 80 and 100 %). Image quality was significantly superior in HDCT versus SDCT (score 1.7 ± 0.5 vs. 2.7 ± 0.7; p < 0.05). Image noise was significantly higher in HDCT compared to SDCT irrespective of ASIR contributions (p < 0.05). Addition of 40 % ASIR or more reduced image noise significantly in both HDCT and SDCT. In HDCT in-stent luminal attenuation was significantly lower and mean measured in-stent luminal diameter was significantly larger (1.2 ± 0.4 mm vs. 0.8 ± 0.4 mm; p < 0.05) compared to SDCT. Radiation dose from HDCT was comparable to SDCT (1.8 ± 0.7 mSv vs. 1.7 ± 0.7 mSv; p = ns). Use of HDCT for coronary stent imaging reduces partial volume artefacts from stents yielding improved image quality versus SDCT at a comparable radiation dose.     

Comparison of neointimal hyperplasia and peri-stent vascular remodeling after implantation of everolimus-eluting versus sirolimus-eluting stents: intravascular ultrasound results from the EXCELLENT study

This study was designed to compare neointimal hyperplasia and peri-stent arterial remodeling after implantation of everolimus-eluting stent (EES) versus sirolimus-eluting stent (SES) using intravascular ultrasound (IVUS). The study population was a subgroup of 278 patients from the EXCELLENT trial, a randomized study comparing EES to SES in de novo coronary artery lesions (total n = 1,443, 3:1 randomization) who underwent post-PCI and 9-month follow-up IVUS evaluation. There were 209 patients in the EES group and 69 in the SES group. Baseline clinical and angiographic characteristics were similar between the two groups except for age and target lesion locations. At 9 months, percent neointimal volume obstruction did not differ between EES and SES (2.6 ± 4.0 % vs. 2.5 ± 4.8 %, p = 0.814). However, the relative change in the vessel (4.3 ± 13.7 % vs. 8.8 ± 18.6 %, p = 0.030) and plaque volume index (4.2 ± 17.4 % vs. 10.5 ± 22.3 %, p = 0.016) of the stented segment from post-intervention to follow-up was significantly less with EES than with SES. In addition, positive peri-stent vascular remodeling defined as an increase in vessel volume index >10 % (27.8 vs. 42.0 %, p = 0.027) and late acquired stent malapposition (LASM, 1.9 vs. 15.9 %, p < 0.001) were observed less frequently with EES than SES. EES and SES were similarly effective in reducing neointimal hyperplasia. However, positive peri-stent vascular remodeling and LASM occurred less frequently with EES than SES.     

Accuracy of Stent Measurements Using ECG-Gated Greyscale Intravascular Ultrasound Images: A Validation Study

Greyscale intravascular ultrasound (IVUS) is an accurate tool for measuring stent dimensions and residual disease at the stent edge. Electrocardiographically (ECG)-gated IVUS is used in evolving second-generation IVUS systems, but this modality provides fewer greyscale cross-sectional images, and its accuracy to measure stent dimensions has not been assessed. This study was designed to validate the use of ECG-gated greyscale IVUS in measuring minimum stent area (MSA), stent length and reference dimensions compared to standard greyscale IVUS data. IVUS imaging was performed after drug-eluting stent implantation in 53 target lesions in 48 patients with acute coronary syndrome. The IVUS catheter was mechanically withdrawn at 0.5 mm/s, standard greyscale images were collected at 10 frames/s, and ECG-gated greyscale images were constructed from R-wave gated images. The MSA measured 6.20 ± 1.75 mm²vs. 5.98 ± 1.55 mm² on standard greyscale and ECG-gated greyscale IVUS, respectively (R² = 0.91, p = 0.005). The MSA position (R² = 0.66, p = 0.179) and stent length (R² = 0.99, p = 0.435) measurements were similar between modalities. Proximal reference vessel area was larger by ECG-gated IVUS, but proximal reference lumen and distal reference measurements were similar. Bland-Altman plots demonstrated good agreement between modalities. In conclusion, ECG-gated greyscale IVUS provides accurate and reliable measurements of stent length, area and reference segment plaque burden after stent implantation and is not inferior to standard greyscale IVUS. (E-mail: gsm18439@aol.com or gmintz@crf.org).     

Serial changes of minimal stent malapposition not detected by intravascular ultrasound: follow-up optical coherence tomography study

Morphologic changes of small-sized post-stent malapposition have not been sufficiently evaluated. We investigated serial changes of minimal post-stent malapposition with a follow-up optical coherence tomography (OCT) study. Post-stent OCT and intravascular ultrasound (IVUS) and follow-up OCT were performed in 26 patients with minimal post-stent malapposition. Serial changes of number and percent of malapposition struts, and mean extra-stent malapposition area were measured in OCT analysis. Zotarolimus-eluting stent (ZES), sirolimus-eluting stent (SES), and paclitaxel-eluting stent (PES) were deployed in 17, 7 and 2 patients, respectively. Mean durations of the follow-up OCT study were 5.7 ± 3.0 months. The minimal post-stent malapposition cannot be detected by the IVUS, but be visualized with an OCT examination. According to different drug-eluting stents, malapposed stent struts were defined as the struts with detachment from the vessel wall ≥160 μm for SES, ≥130 μm for PES, and ≥110 μm for ZES. The percent of malapposition struts significantly decreased from 12.2 ± 11.0% post-stent to 1.0 ± 2.2% follow-up (P < 0.001). There was a significant decrease in the mean extra-stent malapposition area from 0.35 ± 0.16 mm² post-stent to 0.04 ± 0.11 mm² follow-up (P < 0.001). Complete disappearance of stent malapposition was also observed in 22 (85%) patients. In conclusion, minimal stent malapposition which is not detectable by IVUS may disappear or decrease in follow-up OCT evaluation.     

Improvement of coronary morphology and blood flow after stenting

Intravascular ultrasound (IVUS) and intracoronary Doppler (ICD) were performed in eight patients (54.3±6.5 years, 6 male) immediately after PTCA and after stenting. ICD was also performed before PTCA. After PTCA, IVUS has demonstrated intimal rupture in all patients. After stenting, IVUS revealed wall wrapping of the intimal flap with a free lumen in all patients. The lumen diameter was 2.42±0.55 mm after PTCA and was 2.74±0.49 mm after stenting (p<0.001). The cross-sectional area increased from 4.70±1.99 mm² post-PTCA to 6.40±2.15 mm² post-stent (p<0.005). Coronary flow velocity reserve, calculated by the ratio of mean flow velocity at rest and after intracoronary papaverine administration, increased from 2.05±1.01 to 2.99±1.14 after PTCA (p = 0.015); and increased to 4.51±1.33 after stenting (p<0.001). The morphological data derived from IVUS correlated with the functional information obtained with ICD. In addition to its established role in bail out situations, stent implantation may be considered when a suboptimal morphological and functional result has been demonstrated.     

Unrestricted utilization of frequency domain optical coherence tomography in coronary interventions

Frequency domain optical coherence tomography (FD-OCT) has shown promise to evaluate coronary devices in clinical trials, however, little is known about its application in clinical practice. This prospective, single center initiative planned for 100 % FD-OCT utilization in all patients undergoing coronary interventions during a 60-day period. Operators pre-specified the planned intervention based on angiography alone. FD-OCT success was defined as acquisition of good quality images enabling adequate quantification of vessel dimensions and lesion/percutaneous coronary intervention (PCI) assessment. Impact on management occurred when angiography-based planning was altered based on FD-OCT data. There were 297 FD-OCT acquisitions performed in 155 vessels from 150 patients. There were no FD-OCT procedural related cardiac adverse events and success was obtained in 85.7 % of all target vessels (pre-PCI = 76.8 % vs. post-PCI = 90.1 %, p = 0.004). Success on the first pullback occurred in 80.3 % overall (61.9 % in the initial operator experience and 85.5 % after the third procedure). FD-OCT impact on management was 81.8 % pre-PCI and 54.8 % post-PCI. Stent malapposition was detected in 39.2 % (89.4 % underwent further intervention) and edge dissection in 32.5 % (21.1 % treated with stent). FD-OCT success and management impact were similar in ACS and non-ACS patients (82.1 vs. 81.1 %, p = 1.000, and 62.5 vs. 65.1 %, p = 0.854, respectively). FD-OCT is safe, can successfully be incorporated into routine practice, and alters procedural strategy in a high proportion of patients undergoing PCI.     

MR image overlay guidance: system evaluation for preclinical use

Purpose

A clinical augmented reality guidance system was developed for MRI-guided musculoskeletal interventions Magnetic Resonance Image Overlay System (MR-IOS). The purpose of this study was to assess MRI compatibility, system accuracy, technical efficacy, and operator performance of the MR-IOS.

Methods and materials

The impact of the MR-IOS on the MR environment was assessed by measuring image quality with signal-to-noise ratio (SNR) and signal intensity uniformity with the system in various on/off states. The system accuracy was assessed with an in-room preclinical experiment by performing 62 needle insertions on a spine phantom by an expert operator measuring entry, depth, angle, and target errors. Technical efficacy and operator performance were tested in laboratory by running an experiment with 40 novice operators (20 using freehand technique versus 20 MR-IOS-guided) with each operator inserting 10 needles into a geometric phantom. Technical efficacy was measured by comparing the success rates of needle insertions between the two operator groups. Operator performance was assessed by comparing total procedure times, total needle path distance, presumed tissue damage, and speed of individual insertions between the two operator groups.

Results

The MR-IOS maximally altered SNR by 2% with no perceptible change in image quality or uniformity. Accuracy assessment showed mean entry error of 1.6 ± 0.6 mm, depth error of 0.7 ± 0.5 mm, angle error of 1.5 ± 1.1°, and target error of 1.9 ± 0.8 mm. Technical efficacy showed a statistically significant difference (p = 0.031) between success rates (freehand 35.0% vs. MR-IOS 80.95%). Operator performance showed: mean total procedure time of 40.3 ± 4.4 (s) for freehand and 37.0 ± 3.7 (s) for MR-IOS (p = 0.584), needle path distances of 152.6 ± 15.0 mm for freehand and 116.9 ± 8.7 mm for MR-IOS (p = 0.074), presumed tissue damage of 7,417.2 ± 955.6 mm² for freehand and 6062.2 ± 678.5 mm² for MR-IOS (p = 0.347), and speed of insertion 5.9 ± 0.4 mm/s for freehand and 4.3 ± 0.3 mm/s for MR-IOS (p = 0.003).

Conclusion

The MR-IOS is compatible within a clinical MR imaging environment, accurate for needle placement, technically efficacious, and improves operator performance over the unassisted insertion technique. The MR-IOS was found to be suitable for further testing in a clinical setting.     

Intravascular ultrasound assessment of the effects of rotational atherectomy in calcified coronary artery lesions

We sought to clarify intravascular ultrasound (IVUS) features of rotational atherectomy (RA) of calcified lesions. IVUS was performed post-RA and post-stent in 38 lesions and analyzed every 1 mm. Pre-intervention IVUS was performed when the IVUS catheter crossed the lesion (n?=?11). Calcium Index was average calcium angle multiplied by calcium length. We compared lowest (n?=?13), middle (n?=?13), and highest (n?=?12) Calcium Index tertiles. Reverberations (multiple reflections from calcium) with a concave-shaped lumen in the post-RA IVUS were considered to represent RA-related calcium modification. Newly visible perivascular tissue through a previously solid arc of calcium in the post-stent IVUS was also evaluated. Comparing the pre and post-RA IVUS, maximum reverberation angle, and length increased significantly after RA (angle, from 45° [31, 67] to 96° [50, 148], p?=?0.003; length, from 4.0 mm [2.0, 6.0] to 8.0 mm [4.0, 14.0], p?=?0.005). In the post-RA IVUS, reverberations had a larger angle in the middle and highest Calcium Index tertiles (lowest, 91° [64, 133]; middle, 135° [107, 201]; highest, 150° [93, 208], p?=?0.03). Post-stent newly visible perivascular tissue was more frequent in the middle and highest Calcium Index tertiles (lowest, 30.8%; middle, 69.2%; highest, 75.0%, p?=?0.049). Minimum stent area was similar after calcium modification by RA irrespective of the severity of the Calcium Index (lowest, 6.7 mm² [5.7, 8.9]; middle, 5.6 mm² [4.9, 6.8]; highest, 6.7 mm² [5.9, 8.2], p?=?0.2). Greater calcium modification by RA occurs in severely calcified lesions with smaller lumen diameters to mitigate against stent underexpansion.     

Stent implant follow-up in intravascular optical coherence tomography images

The objectives of this article are (i) to utilize computer methods in detection of stent struts imaged in vivo by optical coherence tomography (OCT) during percutaneous coronary interventions (PCI); (ii) to provide measurements for the assessment and monitoring of in-stent restenosis by OCT post PCI. Thirty-nine OCT cross-sections from seven pullbacks from seven patients presenting varying degrees of neointimal hyperplasia (NIH) are selected, and stent struts are detected. Stent and lumen boundaries are reconstructed and one experienced observer analyzed the strut detection, the lumen and stent area measurements, as well as the NIH thickness in comparison to manual tracing using the reviewing software provided by the OCT manufacturer (LightLab Imaging, MA, USA). Very good agreements were found between the computer methods and the expert evaluations for lumen cross-section area (mean difference = 0.11 ± 0.70 mm²; r ² = 0.98, P < 0.0001) and the stent cross-section area (mean difference = 0.10 ± 1.28 mm²; r ² = 0.85, P value <  0.0001). The average number of detected struts was 10.4 ± 2.9 per cross-section when the expert identified 10.5 ± 2.8 (r ² = 0.78, P value < 0.0001). For the given patient dataset: lumen cross-sectional area was on the average (6.05 ± 1.87 mm²), stent cross-sectional area was (6.26 ± 1.63 mm²), maximum angle between struts was on the average (85.96 ± 54.23°), maximum, average, and minimum distance between the stent and the lumen were (0.18 ± 0.13 mm), (0.08 ± 0.06 mm), and (0.01 ± 0.02 mm), respectively, and stent eccentricity was (0.80 ± 0.08). Low variability between the expert and automatic method was observed in the computations of the most important parameters assessing the degree of neointimal tissue growth in stents imaged by OCT pullbacks. After further extensive validation, the presented methods might offer a robust automated tool that will improve the evaluation and follow-up monitoring of in-stent restenosis in patients.     

Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.     

Automatic quantification and characterization of coronary atherosclerosis with computed tomography coronary angiography: cross-correlation with intravascular ultrasound virtual histology

Plaque constitution on computed tomography coronary angiography (CTA) is associated with prognosis. At present only visual assessment of plaque constitution is possible. An accurate automatic, quantitative approach for CTA plaque constitution assessment would improve reproducibility and allows higher accuracy. The present study assessed the feasibility of a fully automatic and quantitative analysis of atherosclerosis on CTA. Clinically derived CTA and intravascular ultrasound virtual histology (IVUS VH) datasets were used to investigate the correlation between quantitatively automatically derived CTA parameters and IVUS VH. A total of 57 patients underwent CTA prior to IVUS VH. First, quantitative CTA quantitative computed tomography (QCT) was performed. Per lesion stenosis parameters and plaque volumes were assessed. Using predefined HU thresholds, CTA plaque volume was differentiated in 4 different plaque types necrotic core (NC), dense calcium (DC), fibrotic (FI) and fibro-fatty tissue (FF). At the identical level of the coronary, the same parameters were derived from IVUS VH. Bland–Altman analyses were performed to assess the agreement between QCT and IVUS VH. Assessment of plaque volume using QCT in 108 lesions showed excellent correlation with IVUS VH (r = 0.928, p < 0.001) (Fig. 1). The correlation of both FF and FI volume on IVUS VH and QCT was good (r = 0.714, p < 0.001 and r = 0.695, p < 0.001 respectively) with corresponding bias and 95 % limits of agreement of 24 mm³ (?42; 90) and 7.7 mm³ (?54; 70). Furthermore, NC and DC were well-correlated in both modalities (r = 0.523, p < 0.001) and (r = 0.736, p < 0.001). Automatic, quantitative CTA tissue characterization is feasible using a dedicated software tool.

Ability and efficiency of an automatic analysis software to measure microvascular parameters

Analysis of the microcirculation is currently performed offline, is time consuming and operator dependent. The aim of this study was to assess the ability and efficiency of the automatic analysis software CytoCamTools 1.7.12 (CC) to measure microvascular parameters in comparison with Automated Vascular Analysis (AVA) software 3.2. 22 patients admitted to the cardiothoracic intensive care unit following cardiac surgery were prospectively enrolled. Sublingual microcirculatory videos were analysed using AVA and CC software. The total vessel density (TVD) for small vessels, perfused vessel density (PVD) and proportion of perfused vessels (PPV) were calculated. Blood flow was assessed using the microvascular flow index (MFI) for AVA software and the averaged perfused speed indicator (APSI) for the CC software. The duration of the analysis was also recorded. Eighty-four videos from 22 patients were analysed. The bias between TVD-CC and TVD-AVA was 2.20 mm/mm² (95 % CI 1.37–3.03) with limits of agreement (LOA) of ?4.39 (95 % CI ?5.66 to ?3.16) and 8.79 (95 % CI 7.50–10.01) mm/mm². The percentage error (PE) for TVD was ±32.2 %. TVD was positively correlated between CC and AVA (r = 0.74, p < 0.001). The bias between PVD-CC and PVD-AVA was 6.54 mm/mm² (95 % CI 5.60–7.48) with LOA of ?4.25 (95 % CI ?8.48 to ?0.02) and 17.34 (95 % CI 13.11–21.57) mm/mm². The PE for PVD was ±61.2 %. PVD was positively correlated between CC and AVA (r = 0.66, p < 0.001). The median PPV-AVA was significantly higher than the median PPV-CC [97.39 % (95.25, 100 %) vs. 81.65 % (61.97, 88.99), p < 0.0001]. MFI categories cannot estimate or predict APSI values (p = 0.45). The time required for the analysis was shorter with CC than with AVA system [2′42″ (2′12″, 3′31″) vs. 16′12″ (13′38″, 17′57″), p < 0.001]. TVD is comparable between the two softwares, although faster with CC software. The values for PVD and PPV are not interchangeable given the different approach to assess microcirculatory flow.     

Subclinical left ventricular systolic impairment in steady state young adult patients with sickle-cell anemia

Chronic volume overload in sickle-cell anemia (SCA) is associated with left ventricular (LV) enlargement and hypertrophy. The effect of the disease on LV systolic function remains debated. The aim of our study was to investigate LV systolic function in SCA patients using 2D speckle-tracking imaging. We compared 30 steady state asymptomatic adult SCA patients (17 women, mean age 24.7 ± 5.1 years) with 30 age and sex-matched healthy subjects (17 women, mean age 25.0 ± 4.9 years). In addition to conventional echocardiographic parameters including LV ejection fraction (LVEF) and LV mass index (LVMi), global longitudinal strain (GLS) and strain rate (GLSR) were measured. GLS (?17.9 ± 2.0 vs. ?19.7 ± 2.5 %, p = 0.004) and GLSR (?0.92 ± 0.09 vs. ?1.07 ± 0.17 s^?1, p < 0.0001) values were lower in SCA patients while LVEF values (60.1 ± 3.8 vs. 61.7 ± 4.7 %, p = 0.30) were not different. LVMi was increased in SCA patients (100.7 ± 23.5 vs. 72.4 ± 15.2 g/m², p = 0.0001) and GLSR was significantly lower in the subgroup of patients with LV hypertrophy (?0.88 ± 0.09 vs. ?0.96 ± 0.08 s^?1, p = 0.02). In SCA patients LVMi was correlated to GLS (r = 0.58, p = 0.001) and GLSR (r = 0.45, p = 0.015) pleading in favor of a pathological LV remodeling. Asymptomatic SCA patients exhibited a subclinical alteration of LV systolic function. Myocardial dysfunction appears to be linked to the degree of LV hypertrophy. 2D speckle-tracking imaging might be useful for long-term follow-up and to study the natural course of LV dysfunction in SCA patients.     

In vivo Variability in Quantitative Coronary Ultrasound and Tissue Characterization Measurements with Mechanical and Phased-array Catheters

Background: Both mechanical and phased-array catheters are used in clinical trials to assess quantitative parameters. Only limited evaluation of the in vivo agreement of volumetrical measurements between such systems has been performed, despite the fact that such information is essential for the conduction of atherosclerosis regression trials. Methods and results: We prospectively evaluated the agreement in morphometric measurements and intravascular ultrasound (IVUS)-based plaque characterization between a 40 MHz rotating transducer (3.2 F Atlantis, Boston Scientific Corp.) and a 20 MHz phased-array catheter (2.9 F Eagle Eye, Volcano Therapeutics, Rancho Cordova, California) in 16 patients. Lumen (7.3 ± 2.0 mm² vs. 6.7 ± 1.8 mm², p = 0.001) and vessel (11.8 ± 3.3 mm² vs. 11.0 ± 2.9 mm², p = 0.02) cross-sectional areas (CSA) were significantly greater with the 20 MHz system. Plaque CSA measurements showed no significant difference between systems (4.4 ± 2.3 mm² vs. 4.4 ± 2.1). The relative differences were less than 10% for the three variables. On IVUS-based tissue characterization (13 patients), calculated percentage hypoechogenic volume was significantly higher for the 20 MHz system (96.7 ± 2.38 vs. 88.4 ± 5.53, p < 0.0001). Conclusions: Quantitative IVUS analyses display significant catheter type-dependent variability. It is unclear whether the variability reflects overestimation of measurements with the phased-array or underestimation with the mechanical system. Although plaque burden measurements did not differ significantly between systems, it appears prudent to recommend the use of a single system for progression/regression studies.     

Bypass to the left coronary artery system may accelerate left main coronary artery negative remodeling and calcification

Aims

This study aimed to use intravascular ultrasound (IVUS) data to reveal the mechanism of lesion progression in the native coronary circulation proximal to bypass grafts after coronary artery bypass grafting (CABG).

Methods and results

We reviewed IVUS images in 86 patients with an angiographically significant left main coronary artery (LMCA) stenosis. Overall, 41 patients underwent CABG more than 6 months (mean 8.2 ± 6.1 years) previously and had at least one patent graft to the left coronary artery system. The number of patent grafts to the left coronary artery was 1.4 ± 0.7. Comparing patent graft vs. non-CABG groups, external elastic membrane and lumen areas and remodeling index at the minimum lumen area (MLA) site trended smaller with no difference in the plaque & media area. In addition, patients in the patent graft group had more LMCA calcium whether defined by cross-sectional (arc at the MLA site of 141 ± 109° vs. 88 ± 108°, P = 0.025) or longitudinal measurements (calcium length index, calculated as LMCA calcium length divided by total LMCA length, 0.69 ± 0.38 vs. 0.50 ± 0.42, P = 0.035).

Conclusions

Negative remodeling may be the main mechanism of lesion progression proximal to a patent bypass graft, and more calcium was found in LMCA after CABG compared with non-CABG patients.