Intraprocedural assessment of ablation margins using computed tomography co-registration in hepatocellular carcinoma treatment with percutaneous ablation: IAMCOMPLETE study.

PURPOSE: The primary objective of this study was to determine the feasibility of ablation margin quantification using a standardized scanning protocol during thermal ablation (TA) of hepatocellular carcinoma (HCC), and a rigid registration algorithm. Secondary objectives were to determine the inter- and intra-observer variability of tumor segmentation and quantification of the minimal ablation margin (MAM). MATERIALS AND METHODS: Twenty patients who underwent thermal ablation for HCC were included. There were thirteen men and seven women with a mean age of 67.1 ± 10.8 (standard deviation [SD]) years (age range: 49.1-81.1 years). All patients underwent contrast-enhanced computed tomography examination under general anesthesia directly before and after TA, with preoxygenated breath hold. Contrast-enhanced computed tomography examinations were analyzed by radiologists using rigid registration software. Registration was deemed feasible when accurate rigid co-registration could be obtained. Inter- and intra-observer rates of tumor segmentation and MAM quantification were calculated. MAM values were correlated with local tumor progression (LTP) after one year of follow-up. RESULTS: Co-registration of pre- and post-ablation images was feasible in 16 out of 20 patients (80%) and 26 out of 31 tumors (84%). Mean Dice similarity coefficient for inter- and intra-observer variability of tumor segmentation were 0.815 and 0.830, respectively. Mean MAM was 0.63 ± 3.589 (SD) mm (range: -6.26-6.65 mm). LTP occurred in four out of 20 patients (20%). The mean MAM value for patients who developed LTP was -4.00 mm, as compared to 0.727 mm for patients who did not develop LTP. CONCLUSION: Ablation margin quantification is feasible using a standardized contrast-enhanced computed tomography protocol. Interpretation of MAM was hampered by the occurrence of tissue shrinkage during TA. Further validation in a larger cohort should lead to meaningful cut-off values for technical success of TA.

Preprocedural physiological assessment of coronary disease patterns to predict haemodynamic outcomes post-PCI.

BACKGROUND: Even with intracoronary imaging-guided stent optimisation, suboptimal haemodynamic outcomes post-percutaneous coronary intervention (PCI) can be related to residual lesions in non-stented segments. Preprocedural assessment of pathophysiological coronary artery disease (CAD) patterns could help predict the physiological response to PCI. AIMS: The aim of this study was to assess the relationship between preprocedural pathophysiological haemodynamic patterns and intracoronary imaging findings, as well as their association with physiological outcomes immediately post-PCI. METHODS: Data from 206 patients with chronic coronary syndrome enrolled in the ASET-JAPAN study were analysed. Pathophysiological CAD patterns were characterised using Murray law-based quantitative flow ratio (µQFR)-derived indices acquired from pre-PCI angiograms. The diffuseness of CAD was defined by the pullback pressure gradient (PPG) index. Intracoronary imaging in stented segments after stent optimisation was also analysed. RESULTS: In the multivariable analysis, diffuse disease - defined by the pre-PCI µQFR-PPG index - was an independent factor for predicting a post-PCI µQFR <0.91 (per 0.1 decrease of PPG index, odds ratio 1.57, 95% confidence interval: 1.07-2.34; p=0.022), whereas the stent expansion index (EI) was not associated with a suboptimal post-PCI µQFR. Among vessels with an EI ≥80% and post-PCI µQFR <0.91, 84.0% of those vessels had a diffuse pattern preprocedure. There was no significant difference in EI between vessels with diffuse disease and those with focal disease. The average plaque burden in the stented segment was significantly larger in vessels with a preprocedural diffuse CAD pattern. CONCLUSIONS: A physiological diffuse pattern preprocedure was an independent factor in predicting unfavourable immediate haemodynamic outcomes post-PCI, even after stent optimisation using intracoronary imaging. Preprocedural assessment of CAD patterns could identify patients who are likely to exhibit superior immediate haemodynamic outcomes following PCI.

Three-dimensional quantitative margin assessment in patients with colorectal liver metastases treated with percutaneous thermal ablation using semi-automatic rigid MRI/CECT-CECT co-registration.

PURPOSE: To assess the quantitative minimal ablation margin (MAM) in patients with colorectal liver metastases (CRLM) treated with percutaneous thermal ablation (TA) and correlate the quantitative MAM with local tumour recurrence (LTR). METHOD: Thirty-nine of 143 patients with solitary or multiple CRLM who underwent a first percutaneous TA procedure between January 2011 and May 2020 were considered eligible for study enrolment. Image fusion of pre- and post-ablation scans and 3D quantitative MAM assessment was performed using the in-house developed semi-automatic rigid MRI/CECT-CECT co-registration software deLIVERed. The quantitative MAM was analysed and correlated with LTR. RESULTS: Eighteen (46 %) patients were additionally excluded from further analyses due to suboptimal co-registration (quality co-registration score ≤ 3). The quality of co-registration was considered sufficient in 21 (54 %) patients with a total of 29 CRLM. LTR was found in 5 of 29 (17 %) TA-treated CRLM. In total, 12 (41 %) negative MAMs were measured (mean MAM -4.7 ± 2.7 mm). Negative MAMs were significantly more frequently seen in patients who developed LTR (100 %) compared to those without LTR (29 %; p = 0.003). The median MAM of patients who developed LTR (-6.6 mm (IQR -9.5 to -4.6)) was significantly smaller compared to the median MAM of patients without LTR (0.5 mm (IQR -1.8 to 3.0); p < 0.001). The ROC curve showed high accuracy in predicting LTR for the quantitative MAM (area under the curve of 0.975 ± 0.029). CONCLUSION: This study demonstrated the feasibility of 3D quantitative MAM assessment, using deLIVERed co-registration software, to assess technical success of TA in patients with CRLM and to predict LTR.

Discordance in the diagnostic assessment of vulnerable plaques between radiofrequency intravascular ultrasound versus optical coherence tomography among patients with acute myocardial infarction: insights from the IBIS-4 study.

We aimed to evaluate the diagnostic agreement between radiofrequency (RF) intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for thin-cap fibroatheroma (TCFA) in non-infarct-related coronary arteries (non-IRA) in patients with ST-segment elevation myocardial infarction (STEMI). In the Integrated Biomarker Imaging Study (IBIS-4), 103 STEMI patients underwent OCT and RF-IVUS imaging of non-IRA after successful primary percutaneous coronary intervention and at 13-month follow-up. A coronary lesion was defined as a segment with ≥ 3 consecutive frames (≈1.2 mm) with plaque burden ≥ 40% as assessed by grayscale IVUS. RF-IVUS-derived TCFA was defined as a lesion with > 10% confluent necrotic core abutting to the lumen in > 10% of the circumference. OCT-TCFA was defined by a minimum cap thickness < 65 µm. The two modalities were matched based on anatomical landmarks using a dedicated matching software. Using grayscale IVUS, we identified 276 lesions at baseline (N = 146) and follow-up (N = 130). Using RF-IVUS, 208 lesions (75.4%) were classified as TCFA. Among them, OCT identified 14 (6.7%) TCFA, 60 (28.8%) thick-cap fibroatheroma (ThCFA), and 134 (64.4%) non-fibroatheroma. All OCT-TCFA (n = 14) were confirmed as RF-TCFA. The concordance rate between RF-IVUS and OCT for TCFA diagnosis was 29.7%. The reasons for discordance were: OCT-ThCFA (25.8%); OCT-fibrous plaque (34.0%); attenuation due to calcium (23.2%); attenuation due to macrophage (10.3%); no significant attenuation (6.7%). There was a notable discordance in the diagnostic assessment of TCFA between RF-IVUS and OCT. The majority of RF-derived TCFA were not categorized as fibroatheroma using OCT, while all OCT-TCFA were classified as TCFA by RF-IVUS.ClinicalTrials.gov Identifier NCT00962416.

Preclinical evaluation of a thin-strut bioresorbable scaffold (ArterioSorb): acute-phase invasive imaging assessment and hemodynamic implication.

AIMS: The aim of this study was to assess the acute performance of the 95 µm ArterioSorb oriented poly L-lactic acid (PLLA) scaffold in comparison with the XIENCE metallic drug-eluting stent (DES) in porcine coronary arteries. METHODS AND RESULTS: In 15 non-atherosclerotic Yucatan mini pigs, the ArterioSorb (3.0/14 mm) and XIENCE (3.0/15 mm) were implanted in 25 and 15 vessels, respectively. Acute performance was evaluated by using quantitative coronary angiography (QCA) and optical coherence tomography (OCT). Following three-dimensional reconstruction of the coronary arteries, endothelial shear stress (ESS) was quantified using non-Newtonian steady-flow simulation. Acute recoil measured by QCA was comparable in the two arms. Post-procedural flow and scaffold/stent area by OCT did not differ between the two devices. ESS post procedure was comparable between ArterioSorb and XIENCE (2.21±1.97 vs 2.25±1.71 Pa, p=0.314). CONCLUSIONS: Acute recoil, luminal dimensions and ESS in the ArterioSorb oriented PLLA scaffold with thin struts of 95 µm were comparable to those in the XIENCE metallic DES.

Assessment of Vascular Patency and Inflammation with Intravascular Optical Coherence Tomography in Patients with Superficial Femoral Artery Disease Treated with Zilver PTX Stents.

PURPOSE: Zilver PTX nitinol self-expanding drug-eluting stent with paclitaxel coating is effective for treatment of superficial femoral artery (SFA) disease. However, as with any stent, it induces a measure of vascular inflammatory response. The current clinical trial (NCT02734836) aimed to assess vascular patency, remodeling, and inflammatory markers with intravascular optical coherence tomography (OCT) in patients with SFA disease treated with Zilver PTX stents. METHODS: Serial OCT examinations were performed in 13 patients at baseline and 12-month follow-up. Variables evaluated included neointimal area, luminal narrowing, thrombus area, stent expansion as well as measures of inflammation including, peri-strut low-intensity area (PLIA), macrophage arc, neovascularization, stent strut apposition and coverage. RESULTS: Percentage of malapposed struts decreased from 10.3 ±â€¯7.9% post-intervention to 1.1 ±â€¯2.2% at 12-month follow-up, but one patient showed late-acquired stent malapposition (LASM). The percent of uncovered struts at follow-up was 3.0 ±â€¯4.5%. Average expansion of stent cross-sectional area from baseline to follow-up was 35 ±â€¯19%. The average neointimal area was 7.8 ±â€¯3.8 mm2. Maximal luminal narrowing was 61.1 ±â€¯25.0%, and average luminal narrowing was 35.4 ±â€¯18.2%. Average peri-strut low-intensity area (PLIA) per strut was 0.017 ±â€¯0.018 mm2. Average number of neovessels per mm of stent was 0.138 ±â€¯0.181. Average macrophage angle per frame at follow-up was 7 ±â€¯11°. Average thrombus area at follow-up was 0.0093 ±â€¯0.0184 mm2. CONCLUSION: At 12-month follow-up, OCT analysis of Zilver PTX stent shows outward remodeling and minimal neointimal growth, but evidence of inflammation including PLIA, neovessels, thrombus and macrophages. SUMMARY: Thirteen patients with PAD had paclitaxel-coated stents implanted in their SFAs and were then imaged with OCT at baseline and 12-month follow-up. OCT proxy metrics of inflammation were quantified.

Comparison of visual assessment and computer image analysis of intracoronary thrombus type by optical coherence tomography.

BACKGROUND: Analysis of intracoronary thrombus type by optical coherence tomography (OCT) imaging is highly subjective. We aimed to compare a newly developed image analysis method to subjective visual classification of thrombus type identified by OCT. METHODS: Thirty patients with acute ST elevation myocardial infarction were included. Thrombus type visually classified by two independent readers was compared with analysis using QCU-CMS software. RESULTS: Repeatability of the computer-based measurements was good. By using a ROC, area under curve values for discrimination of white and red thrombi were 0.92 (95% confidence intervals (CI) 0.83-1.00) for median attenuation, 0.96 (95% CI 0.89-1.00) for mean backscatter and 0.96 (95% CI 0.89-1.00) for mean grayscale intensity. Median attenuation of 0.57 mm-1 (sensitivity 100%, specificity 71%), mean backscatter of 5.35 (sensitivity 92%, specificity 94%) and mean grayscale intensity of 120.1 (sensitivity 85%, specificity 100%) were identified as the best cut-off values to differentiate between red and white thrombi. CONCLUSIONS: Attenuation, backscatter and grayscale intensity of thrombi in OCT images differentiated red and white thrombi with high sensitivity and specificity. Measurement of these continuous parameters can be used as a less user-dependent method to characterize in vivo thrombi. The clinical significance of these findings needs to be tested in further studies.

Repeatability Assessment of Intravascular Polarimetry in Patients.

Intravascular polarimetry with polarization sensitive optical frequency domain imaging (PS-OFDI) measures polarization properties of the vessel wall and offers characterization of coronary atherosclerotic lesions beyond the cross-sectional image of arterial microstructure available to conventional OFDI. A previous study of intravascular polarimetry in cadaveric human coronary arteries found that tissue birefringence and depolarization provide valuable insight into key features of atherosclerotic plaques. In addition to various tissue components, catheter and sample motion can also influence the polarization of near infrared light as used by PS-OFDI. This paper aimed to evaluate the robustness and repeatability of imaging tissue birefringence and depolarization in a clinical setting. 30 patients scheduled for percutaneous coronary intervention at the Erasmus Medical Center underwent repeated PS-OFDI pullback imaging, using commercial imaging catheters in combination with a custom-built PS-OFDI console. We identified 274 matching cross sections among the repeat pullbacks to evaluate the reproducibility of the conventional backscatter intensity, the birefringence, and the depolarization signals at each spatial location across the vessel wall. Bland-Altman analysis revealed best agreement for the birefringence measurements, followed by backscatter intensity, and depolarization, when limiting the analysis to areas of meaningful birefringence. Pearson correlation analysis confirmed highest correlation for birefringence (0.86), preceding backscatter intensity (0.83), and depolarization (0.78). Our results demonstrate that intravascular polarimetry generates robust maps of tissue birefringence and depolarization in a clinical setting. This outcome motivates the use of intravascular polarimetry for future clinical studies that investigate polarization properties of arterial atherosclerosis.

Serial volumetric assessment of coronary fibroatheroma by optical frequency domain imaging: insights from the TROFI trial.

Aims: Coronary lesions precursors of acute events remain elusive, since they undergo continuous changes and their temporal changes are not very well-characterized. In natural history studies, optical frequency domain imaging (OFDI) has been used only to assess fibroatheromas as a 2D structure and sometimes in a single frame fashion. We aim at describing the serial volumetric modifications of the fibrous cap (FC) of the fibroatheromas as determined by OFDI over a 6-month follow-up period. Methods and results: In 49 patients, OFDI investigation was performed following treatment of culprit lesion and at 6-month follow-up in patients with ST-segment elevation myocardial infarction (STEMI). A fully automatic volumetric quantification of FC was done in all lipid-containing frames of non-culprit lesions in the infarct related artery. These lesions were matched at baseline and 6-month follow-up. A total of 58 non-culprit lipid rich lesions (34 TCFAs and 24 thick-cap fibroatheroma [ThCFA]) were found in 34 patients at baseline. Overall, there was a FC volume decrease of 1.57 (Inter-quartile Range [IQR] -4.13 to 0.54) mm3 at 6-months. 27% of the lesions changed their phenotype over time (TCFA or ThCFA). TCFAs that became ThCFAs at follow-up had smaller mean and maximal FC as compared with lesions that remained TCFAs (P = 0.01 for both). Conclusions: Non-culprit fibroatheromas located in the infarct related artery of patients with STEMI had a volumetric reduction of the FC after 6-month follow-up. Quantitative FC assessment was able to differentiate high-risk lesions that became ThCFAs. There was a considerable change of plaque phenotype (TCFAs or ThCFAs) over time.

Fate of post-procedural malapposition of everolimus-eluting polymeric bioresorbable scaffold and everolimus-eluting cobalt chromium metallic stent in human coronary arteries: sequential assessment with optical coherence tomography in ABSORB Japan trial.

Aims: The natural course of post-procedural incomplete strut apposition (ISA) after the implantation of bioresorbable scaffolds (BVS) remains unknown. The purpose of the present study was to evaluate the fate of post-procedural ISA after everolimus-eluting Absorb BVS in comparison with the second-generation everolimus-eluting cobalt chromium stent (CoCr-EES). Methods and results: Fate of post-procedural ISA was evaluated by serial optical coherence tomography (OCT) in the ABSORB Japan randomized trial [OCT-1 subgroup: 110 paired lesions of post-procedure and 2-year follow-up (BVS 73 lesions vs. CoCr-EES 37 lesions)] with respect to ISA distance. Post-procedure ISA struts were categorized into either 'resolved' or 'persistent' by matched OCT imaging at 2-year follow-up. Post-procedure %malapposed strut and ISA area were smaller in BVS than in CoCr-EES (%malapposed strut: 4.8 ± 6.9% vs. 9.9 ± 9.8%, P = 0.002; ISA area 0.10 ± 0.18 mm2 vs. 0.23 ± 0.26 mm2, P = 0.003). At 2-year follow-up, the difference diminished, and majority of the ISA struts spontaneously resolved in both arms (%malapposed strut: 0.10 ± 0.46% vs. 0.24 ± 0.65%, P = 0.183). Receiver operating characteristic curve analysis (BVS 661 struts vs. CoCr-EES 807 struts) demonstrated that the best cut-off value of endoluminal ISA distance post-procedure for predicting persistent-ISA at 2-year follow-up was 396 µm for BVS (sensitivity 0.875; specificity 0.851) and 359 µm for CoCr-EES (sensitivity 0.778; specificity 0.881). Conclusion: BVS as compared with CoCr-EES allows larger ISA distance at post-procedure, although we should make every effort to minimize post-procedure ISA. The reported cut-off value of OCT-estimated ISA distance at post-stenting for predicting persistent-ISA would be helpful to optimize PCI with BVS and CoCr-EES.

Serial Assessment of Tissue Precursors and Progression of Coronary Calcification Analyzed by Fusion of IVUS and OCT: 5-Year Follow-Up of Scaffolded and Nonscaffolded Arteries.

OBJECTIVES: The aim of this study was to assess calcium growth with fused grayscale intravascular ultrasound (IVUS), IVUS-virtual histology, and optical coherence tomography (OCT) from baseline to 5-year follow-up in patients treated with bioresorbable vascular scaffolds. BACKGROUND: IVUS and OCT have individual strengths in assessing plaque composition and volume. Fusion of images obtained using these methods could potentially aid in coronary plaque assessment. METHODS: Anatomic landmarks and endoluminal radiopaque markers were used to fuse OCT and IVUS images and match baseline and follow-up. RESULTS: Seventy-two IVUS-virtual histology and OCT paired matched cross-sectional in- and out-scaffold segments were fused at baseline and follow-up. In total, 46 calcified plaques at follow-up were detected using the fusion method (33 in-scaffold, 13 out-scaffold), showing either calcium progression (52.2%) or de novo calcifications (47.8%). On OCT, calcification volume increased from baseline to follow-up by 2.3 ± 2.4 mm3 (p = 0.001). The baseline virtual histologic tissue precursors of dense calcium at follow-up were necrotic core in 73.9% and fibrous or fibrofatty plaque in 10.9%. In 15.2%, calcium was already present at baseline. Precursors on OCT were lipid pool in 71.2%, fibrous plaque in 4.3%, and fibrocalcific plaque in 23.9%. CONCLUSIONS: The use of OCT and IVUS fusion imaging shows similar calcium growth in- and out-scaffold segments. Necrotic core is the most frequent precursor of calcification. The scaffold resorption process creates a tissue layer that re-caps the calcified plaques. (Absorb Clinical Investigation, Cohort B [ABSORB B]; NCT00856856).

Variability in the measurement of minimum fibrous cap thickness and reproducibility of fibroatheroma classification by optical coherence tomography using manual versus semi-automatic assessment.

AIMS: The minimum fibrous cap thickness (FCT) is considered a major criterion of coronary plaque vulnerability according to autopsy studies. We aimed to assess the reproducibility in the measurement of the optical coherence tomography (OCT)-detected minimum FCT and the agreement in the classification of thin-cap fibroatheroma (TCFA), by a software-based semi-automatic method compared with the manual method. METHODS AND RESULTS: A total of 50 frames with fibroatheromas (FA) were randomly selected from the Integrated Biomarker Imaging Study-4 (IBIS-4). Two experienced OCT analysts independently measured the minimum FCT at two different time points, manually and by three different semi-automatic software-based algorithms, based on the assessment of light intensity along the axial scan line. A TCFA was defined as an FA with minimum FCT <65 µm. The inter- and intra-observer reproducibility of the manual measurement of the minimum FCT was moderate with an intra-class correlation coefficient (ICC) of 0.71 and 0.79, respectively. The corresponding ICCs by either one of the three semi-automatic algorithms were 0.99. When categorising FA according to the minimum FCT based on the manual assessment, the inter- and intra-observer agreement was poor (κ=0.23) and moderate (κ=0.50), respectively. In contrast, the semi-automatic assessment showed perfect agreement for both inter- and intra-observer assessments (κ=0.90-1.00 and 1.00, respectively). CONCLUSIONS: While semi-automatic assessment of FCT and TCFA classification was associated with excellent reproducibility and agreement, manual measurements were associated with a moderate reproducibility and agreement in the quantification of FCT and classification of TCFA.

Quantitative assessment of the stent/scaffold strut embedment analysis by optical coherence tomography.

The degree of stent/scaffold embedment could be a surrogate parameter of the vessel wall-stent/scaffold interaction and could have biological implications in the vascular response. We have developed a new specific software for the quantitative evaluation of embedment of struts by optical coherence tomography (OCT). In the present study, we described the algorithm of the embedment analysis and its reproducibility. The degree of embedment was evaluated as the ratio of the embedded part versus the whole strut height and subdivided into quartiles. The agreement and the inter- and intra-observer reproducibility were evaluated using the kappa and the interclass correlation coefficient (ICC). A total of 4 pullbacks of OCT images in 4 randomly selected coronary lesions with 3.0 × 18 mm devices [2 lesions with Absorb BVS and 2 lesions with XIENCE (both from Abbott Vascular, Santa Clara, CA, USA)] from Absorb Japan trial were evaluated by two investigators with QCU-CMS software version 4.69 (Leiden University Medical Center, Leiden, The Netherlands). Finally, 1481 polymeric struts in 174 cross-sections and 1415 metallic struts in 161 cross-sections were analyzed. Inter- and intra-observer reproducibility of quantitative measurements of embedment ratio and categorical assessment of embedment in Absorb BVS and XIENCE had excellent agreement with ICC ranging from 0.958 to 0.999 and kappa ranging from 0.850 to 0.980. The newly developed embedment software showed excellent reproducibility. Computer-assisted embedment analysis could be a feasible tool to assess the strut penetration into the vessel wall that could be a surrogate of acute injury caused by implantation of devices.

OCT assessment of the long-term vascular healing response 5 years after everolimus-eluting bioresorbable vascular scaffold.

BACKGROUND: Although recent observations suggest a favorable initial healing process of the everolimus-eluting bioresorbable vascular scaffold (BVS), little is known regarding long-term healing response. OBJECTIVES: This study assessed the in vivo vascular healing response using optical coherence tomography (OCT) 5 years after elective first-in-man BVS implantation. METHODS: Of the 14 living patients enrolled in the Thoraxcenter Rotterdam cohort of the ABSORB A study, 8 patients underwent invasive follow-up, including OCT, 5 years after implantation. Advanced OCT image analysis included luminal morphometry, assessment of the adluminal signal-rich layer separating the lumen from other plaque components, visual and quantitative tissue characterization, and assessment of side-branch ostia "jailed" at baseline. RESULTS: In all patients, BVS struts were integrated in the vessel and were not discernible. Both minimum and mean luminal area increased from 2 to 5 years, whereas lumen eccentricity decreased over time. In most patients, plaques were covered by a signal-rich, low-attenuating layer. Minimum cap thickness over necrotic core was 155 ± 90 µm. One patient showed plaque progression and discontinuity of this layer. Side-branch ostia were preserved with tissue bridge thinning that had developed in the place of side-branch struts, creating a neo-carina. CONCLUSIONS: At long-term BVS follow-up, we observed a favorable tissue response, with late luminal enlargement, side-branch patency, and development of a signal-rich, low-attenuating tissue layer that covered thrombogenic plaque components. The small size of the study and the observation of a different tissue response in 1 patient warrant judicious interpretation of our results and confirmation in larger studies.

3D assessment of stent cell size and side branch access in intravascular optical coherence tomographic pullback runs.

We present a semi-automatic approach to assess the maximum circular unsupported surface area (MCUSA) of selected stent cells and the side branch access through stent cells in intravascular optical coherence tomography (IVOCT) pullback runs. Such 3D information may influence coronary interventions, stent design, blood flow analysis or prognostic evaluation. First, the stent struts are detected automatically and stent cells are reconstructed with users' assistance. Using cylinder fitting, a 2D approximation of the stent cell is generated for MCUSA detection and measurement. Next, a stent surface is reconstructed and stent-covered side branches are detected. Both the stent cell contours and side branch lumen contours are projected onto the stent surface to indicate their areas, and the overlapping regions are measured as the side branch access through these stent cells. The method was evaluated on phantom data sets and the accuracy of the MCUSA and side branch access was found to be 95% and 91%, respectively. The usability of this approach for clinical research was proved on 12 in vivo IVOCT pullback runs.

In vivo assessment of the relationship between shear stress and necrotic core in early and advanced coronary artery disease.

AIMS: Atherosclerotic plaques develop at low shear stress locations in the arterial tree. However, at a certain moment, plaques encroach into the lumen causing local wall shear stress (WSS) increase. Minimal information is available on the relationship between WSS and plaque composition. We investigated in human coronary arteries in vivo the frequency with which the necrotic core and necrotic core in contact with the lumen are located at either low or high WSS regions in early and advanced plaques. METHODS AND RESULTS: We combined a 3-D reconstruction technique of coronary arteries based on angiography and intravascular ultrasound with IVUS-virtual histology (IVUS-VH) data. With IVUS-VH the necrotic core was determined. The lumen of these 3-D reconstructions served as input for the computational fluid dynamics. Per cross-section the WSS at the regions with major necrotic core and necrotic core in contact with the lumen were compared to the median WSS in the cross-section. Ten human coronary arteries were studied. Only cross-sections with average wall thickness >0.5 mm were included in the analysis. In early plaques (plaque burden <40%), the necrotic core was most frequently located at WSS smaller than the median (61%) contrasting the advanced plaques (plaque burden >40%), being located at WSS higher than the median (60%, p<0.05 Mann-Whitney U test). Necrotic core in contact with the lumen was most often exposed to high WSS, being most pronounced in advanced disease (61%, p<0.05). CONCLUSIONS: With the advancement of disease, necrotic core is less often located at low WSS regions, but exposed to high WSS, which is probably the result of lumen narrowing. Necrotic core in contact with the lumen was most frequently exposed to high WSS.

Towards quantitative analysis of coronary CTA.

The current high spatial and temporal resolution, multi-slice imaging capability, and ECG-gated reconstruction of multi-slice computed tomography (MSCT) allows the non-invasive 3D imaging of opacified coronary arteries. MSCT coronary angiography studies are currently carried out by the visual inspection of the degree of stenosis and it has been shown that the assessment with sensitivities and specificities of 90% and higher can be achieved. To increase the reproducibility of the analysis, we present a method that performs the quantitative analysis of coronary artery diseases with limited user interaction: only the positioning of one or two seed points is required. The method allows the segmentation of the entire left or right coronary tree by the positioning of a single seed point, and an extensive evaluation of a particular vessel segment by placing a proximal and distal seed point. The presented method consists of: (1) the segmentation of the coronary vessels, (2) the extraction of the vessel centerline, (3) the reformatting of the image volume, (4) a combination of longitudinal and transversal contour detection, and (5) the quantification of vessel morphological parameters. The method is illustrated in this paper by the segmentation of the left and right coronary trees and by the analysis of a coronary artery segment. The sensitivity of the positioning of the seed points is studied by varying the position of the proximal and distal seed points with a standard deviation of 6 and 8 mm (along the vessel's course) respectively. It is shown that only close to the individual seed points the vessel centerlines deviate and that for more than 80% of the centerlines the paths coincide. Since the quantification depends on the determination of the centerline, no user variability is expected as long as the seed points are positioned reasonably far away from the vessel lesion. The major bottleneck of MSCT imaging of the coronary arteries is the potential lack of image quality due to limitations in the spatial and temporal resolution, irregular or high heart beat, respiratory effects, and variations of the distribution of the contrast agent: the number of rejected vessel segments in diagnostic studies is currently still too high for implementation in routine clinical practice. Also for the automated quantitative analysis of the coronary arteries high image quality is required. However, based upon the trend in technological development of MSCT scanners, there is no doubt that the quantitative analysis of MSCT coronary angiography will benefit from these technological advances in the near future.