Oliver Meissner

Diagnostic accuracy of optical coherence tomography and intravascular ultrasound for the detection and characterization of atherosclerotic plaque composition in ex-vivo coronary specimens: A comparison with histology

BackgroundBoth intravascular ultrasound and optical coherence tomography have been purported to accurately detect and characterize coronary atherosclerotic plaque composition. The aim of our study was to directly compare the reproducibility and diagnostic accuracy of optical coherence tomography and intravascular ultrasound for the detection and characterization of coronary plaque composition ex vivo as compared with histology. Methods and resultsIntravascular ultrasound (20 MHz) and optical coherence tomography imaging was performed in eight heart specimens using motorized pullback. Standard histology using hematoxylin–eosin and van Gieson staining was performed on 4 μm thick slices. Each slice was divided into quadrants and accurately matched cross-sections were analyzed for the presence of fibrous, lipid-rich, and calcified coronary plaque using standard definitions for both intravascular ultrasound and optical coherence tomography and correlated with histology. After exclusion of 145/468 quadrants, we analyzed the remaining 323 quadrants with excellent image quality in each procedure. Optical coherence tomography demonstrated a sensitivity and specificity of 91/88% for normal wall, 64/88% for fibrous plaque, 77/94% for lipid-rich plaque, and 67/97% for calcified plaque as compared with histology. Intravascular ultrasound demonstrated a sensitivity and specificity of 55/79% for normal wall, 63/59% for fibrous plaque, 10/96% for lipid-rich plaque, and 76/98% for calcified plaque. Both intravascular ultrasound and optical coherence tomography demonstrated excellent intraobserver and interobserver agreement (optical coherence tomography: κ=0.90, κ=0.82; intravascular ultrasound: κ=0.87, κ=0.86). ConclusionOptical coherence tomography is superior to intravascular ultrasound for the detection and characterization of coronary atherosclerotic plaque composition, specifically for the differentiation of noncalcified, lipid-rich, or fibrous plaque.

3D Imaging with Flat-Detector C-Arm Systems

Three-dimensional (3D) C-arm computed tomography is a new and innovative imaging technique. It uses two-dimensional (2D) X-ray projections acquired with a flat-panel detector C-arm angiography system to generate CT-like images. To this end, the C-arm system performs a sweep around the patient, acquiring up to several hundred 2D views. They serve as input for 3D cone-beam reconstruction. Resulting voxel data sets can be visualized either as cross-sectional images or as 3D data sets using different volume rendering techniques. Initially targeted at 3D high-contrast neurovascular applications, 3D C-arm imaging has been continuously improved over the years and is now capable of providing CT-like soft-tissue image quality. In combination with 2D fluoroscopic or radiographic imaging, information provided by 3D C-arm imaging can be valuable for therapy planning, guidance, and outcome assessment all in the interventional suite.

High-resolution MR Imaging of Human Atherosclerotic Femoral Arteries In Vivo: Validation with Intravascular Ultrasound

PURPOSE To establish a magnetic resonance (MR) imaging protocol for noninvasive in-vivo analysis of atherosclerotic femoral artery segments in humans and to compare the results to those of intravascular ultrasonography (IVUS). MATERIALS AND METHODS In seven patients with peripheral arterial occlusive disease, 20 femoral arterial segments per person were examined by high-resolution (HR) MR imaging and IVUS. Comparison was possible in 123 of 140 segments. MR imaging was performed at 1.5 T with use of a three-dimensional (3D) time-of-flight sequence with an in-plane resolution of 0.78 x 0.49 mm(2). 3D contrast-enhanced MR angiography was used for exact positioning of the HR MR imaging slices. IVUS (3.5 F, 40 MHz) was performed with use of a motorized pullback system. Parameters analyzed included cross-sectional lumen area (LA), vessel area (VA), and extent of vessel wall calcification. RESULTS Agreement between IVUS and HR MR imaging was analyzed with use of the Bland-Altman method. The paired LA measurements were in close agreement: the Bland-Altman mean bias in LA was -0.4 mm with a precision of +/-5.1 mm (P =.062). As a result of dorsal echo extinction in IVUS, VA measurements were feasible in only 74 of 140 segments. VA measurements were moderately correlated (r = 0.74; P <.0001), and a 25% overestimation by HR MR imaging compared to IVUS was observed. Intra- and interobserver comparisons for LA and VA measured with HR MR imaging did not show significant differences. Vessel wall calcifications were classified with a sensitivity of 91%, a specificity of 93%, and an accuracy of 93%. CONCLUSIONS The MR imaging protocol introduced in the present study permits precise assessment of LA and extent of calcification in peripheral arterial occlusive disease in vivo. HR MR imaging shows high concordance with IVUS and may have the potential for noninvasive therapy monitoring.

Intravascular optical coherence tomography: comparison with histopathology in atherosclerotic peripheral artery specimens.

PURPOSE Intravascular optical coherence tomography (OCT) is a new imaging modality that provides microstructural information on atherosclerotic plaques and has an axial resolution of 10-20 microm. OCT of coronary arteries characterizes different atherosclerotic plaque components by their distinctive signal patterns. Peripheral human arteries were examined ex vivo by means of OCT, and attempts to distinguish among fibrous, lipid-rich, and calcified atherosclerotic plaques were made based on imaging criteria previously established for coronary arteries. MATERIALS AND METHODS One hundred fifty-one atherosclerotic arterial segments were obtained from 15 below-knee amputations. OCT imaging criteria for different plaque types (fibrous, lipid-rich, calcified) were established in a subset of 30 arterial segments. The remaining 121 OCT images were analyzed by two independent readers. Each segment was divided into four quadrants. Agreement between histopathology and OCT was quantified by the kappa test of concordance, as were interobserver, intraobserver, and inter-method variability. RESULTS Four hundred sixty-nine of 484 quadrants (97%) were available for comparison. Sensitivity and specificity for OCT criteria (consensus readers 1 and 2) were 86% and 86% for fibrous plaques, 78% and 93% for lipid-rich plaques, and 84% and 95% for calcified plaques, respectively (overall agreement, 84%). The interobserver and intraobserver reliabilities of OCT assessment were high (kappa values of 0.84 and 0.87, respectively). The inter-method agreement was 0.74 for consensus OCT versus consensus histology. CONCLUSIONS OCT of peripheral human arteries ex vivo characterized different atherosclerotic plaque types with a high degree of agreement with histopathologic findings. Findings were comparable to those reported for coronary arteries. OCT promises to improve understanding of the progression or regression of peripheral atherosclerosis in vivo.

Magnetic Resonance Angiography in the Follow-up of Distal Lower-Extremity Bypass Surgery: Comparison with Duplex Ultrasound and Digital Subtraction Angiography

PURPOSE The danger of limb loss as a consequence of acute occlusion of infrapopliteal bypasses underscores the requirement for careful patient follow-up. The objective of this study was to determine the agreement and accuracy of contrast material-enhanced moving-table magnetic resonance (MR) angiography and duplex ultrasonography (US) in the assessment of failing bypass grafts. In cases of discrepancy, digital subtraction angiography (DSA) served as the reference standard. MATERIALS AND METHODS MR angiography was performed in 24 consecutive patients with 26 femorotibial or femoropedal bypass grafts. Each revascularized limb was divided into five segments--(i) native arteries proximal to the graft; (ii) proximal anastomosis; (iii) graft course; (iv) distal anastomosis; and (v) native arteries distal to the graft-resulting in 130 vascular segments. Three readers evaluated all MR angiograms for image quality and the presence of failing grafts. The degree of stenosis was compared to the findings of duplex US, and in case of discrepancy, to DSA findings. Two separate analyses were performed with use of DSA only and a combined diagnostic endpoint as the reference standard. RESULTS Image quality was rated excellent or intermediate in 119 of 130 vascular segments (92%). Venous overlay was encountered in 26 of 130 segments (20%). In only two segments was evaluation of the outflow region not feasible. One hundred seventeen of 130 vascular segments were available for quantitative analysis. In 109 of 117 segments (93%), MR angiography and duplex US showed concordant findings. In the eight discordant segments in seven patients, duplex US overlooked four high-grade stenoses that were correctly identified by MR angiography and confirmed by DSA. Percutaneous transluminal angioplasty was performed in these cases. In no case did MR angiography miss an area of stenosis of sufficient severity to require treatment. Total accuracy for duplex US ranged from 0.90 to 0.97 depending on the reference standard used, whereas MR angiography was completely accurate (1.00) regardless of the standard definition. CONCLUSION Our data strongly suggest that the accuracy of MR angiography for identifying failing grafts in the infrapopliteal circulation is equal to that of duplex US and superior to that of duplex US in cases of complex revascularization. MR angiography should be included in routine follow-up of patients undergoing infrapopliteal bypass surgery.

Catheter-based Intraluminal Optical Coherence Tomography Versus Endoluminal Ultrasonography of Porcine Ureter Ex Vivo

OBJECTIVES To compare the distinction of tissue layers of porcine ureters ex vivo between optical coherence tomography (OCT) and endoluminal ultrasonography (ELUS). Catheter-guided OCT is a new method of intraluminal microstructural imaging, with a spatial resolution of 10-20 mum. METHODS Porcine ureters and kidneys were obtained fresh from the municipal slaughtery, cannulated with a 7F catheter sheath, flushed with normal saline solution, and marked on the outside with surgical suture. Between the marked positions, images were obtained from within the ureter lumen using OCT (M1, Lightlab, Westport, MA) and ELUS at 40 MHz. The distinction of the urothelium, lamina propria, and inner and outer muscle layers was rated as possible (1) or impossible (0) by 2 independent observers (O1, O2). The rates of distinction were compared between OCT and ELUS image quadrants using the chi(2) test. RESULTS Of the 224 OCT image quadrants and 144 ELUS image quadrants, OCT was superior to ELUS in the distinction of any wall layers (O1, chi(2)P = 68.1051, P < .001; O2, chi(2)P = 66.1630, P < .001), urothelium and lamina propria (O1, chi(2)P = 200.0750, P < .001; O2, chi(2)P = 240.0024, P < .001), and lamina propria and muscle layer (O1, chi(2)P = 38.8411, P < .001; O2, chi(2)P = 24.7536, P < .001) but was inconclusive for the inner and outer muscle layer (O1, chi(2)P = 260.3004, P < .001; O2, chi(2)P = 0.4992, P > .25). CONCLUSIONS OCT was able to distinguish significantly better than ELUS between different wall layers of porcine ureter ex vivo. The feasibility of OCT in vivo and in the presence of pathologic wall thickening of the ureter remains to be demonstrated.

Primary Endovascular Stent Placement for Focal Infrarenal Aortic Stenosis: Initial and Midterm Results

The objectives of this retrospective study were to determine the technical success, safety, and midterm results of primary stent placement of infrarenal aortic stenosis. Eight stenoses and one occlusion were treated with stent placement after balloon pre-dilation. Primary technical success was achieved in all patients. Five patients showed reperfusion or restored normal direction of flow of the inferior mesenteric artery. No complications occurred. There was a mean follow-up of 12 months (range, 3-20 months). Primary clinical and hemodynamic patency rates were 100% on follow-up examinations. Stent placement after balloon pre-dilation in properly selected patients with isolated infrarenal aortic stenosis is a promising durable treatment.

Endoluminal repair of peripheral arterial aneurysms: 4-year experience with the cragg endopro system I.

PURPOSE To assess the efficiency and long-term patency of the Cragg EndoPro System I in patients with peripheral arterial aneurysms. MATERIALS AND METHODS In 10 patients, 13 stent-grafts were used to treat 15 arterial aneurysms. Aneurysms were located in the common iliac (n = 4), superficial femoral (n = 4), popliteal (n = 3), and subclavian arteries (n = 2), and in a femoropopliteal bypass-graft (n = 2). Follow-up ranged between 2 and 46 months (mean, 36 months). Examination included clinical status, color-coded duplex sonography, computed tomography angiography, and intra-arterial digital subtraction angiography (DSA). RESULTS Technical success was achieved in all patients. Primary patency was four of four in iliac vessels and three of nine in non-iliac vessels; secondary patency in noniliac vessels was four of nine. Repairs included one local lysis, four percutaneous transluminal angioplasties, one surgical thrombectomy, and one bypass surgery. Stent wire disintegration was detected in one of four iliac stent-grafts and in seven of nine noniliac stent-grafts. In noniliac grafts, significant stenoses occurred in three of nine; occlusion occurred in five of nine. One complication at the iliac level was a vessel wall penetration at the proximal stent edge, with development of a new aneurysmal formation. No late endoleaks were found. CONCLUSION Exclusion of peripheral arterial aneurysms with stent-grafts is feasible. Long-term results are excellent in iliac vessels. Mechanical weakness of the stent assembly and frequent re-stenoses or occlusions are significant drawbacks in noniliac vessels with low patency rates.

C-Arm Computed Tomography Compared With Positron Emission Tomography/Computed Tomography for Treatment Planning Before Radioembolization

The purpose of this study was to determine whether rotational C-arm computed tomography (CT) allows visualization of liver metastases and adds relevant information for radioembolization (RE) treatment planning. Technetium angiography, together with C-arm CT, was performed in 47 patients to determine the feasibility for RE. C-arm CT images were compared with positron emission tomography (PET)/CT images for the detection of liver tumors. The images were also rated according one of the following three categories: (1) images that provide no additional information compared with DSA alone; (2) images that do provide additional information compared with DSA; and (2) images that had an impact on eligibility determination for and planning of the RE procedure. In all patients, 283 FDG-positive liver lesions were detected by PET. In venous contrast-phase CT, 221 (78.1%) and 15 (5.3%) of these lesions were either hypodense or hyperdense, respectively. In C-arm CT, 103 (36.4%) liver lesions were not detectable because they were outside of either the field of view or the contrast-enhanced liver segment. Another 25 (8.8%) and 98 (34.6%) of the liver lesions were either hyperdense or presented primarily as hypodense lesions with a rim enhancement, respectively. With PET/CT as the standard of reference, venous CT and C-arm CT failed to detect 47 (16.6%) and 57 (20.1%) of all liver lesions, respectively. For RE planning, C-arm CT provided no further information, provide some additional information, or had an impact on the procedure in 20 (42.5%), 15 (31.9%) and 12 (25.6%) of patients, respectively. We conclude that C-arm CT may add decisive information in patients scheduled for RE.

[C-arm CT-guided 3D navigation of percutaneous interventions].

So far C-arm CT images were predominantly used for a precise guidance of an endovascular or intra-arterial therapy. A novel combined 3D-navigation C-arm system now also allows cross-sectional and fluoroscopy controlled interventions. Studies have reported about successful CT-image guided navigation with C-arm systems in vertebroplasty. Insertion of the radiofrequency ablation probe is also conceivable for lung and liver tumors that had been labelled with lipiodol. In the future C-arm CT based navigation systems will probably allow simplified and safer complex interventions and simultaneously reduce radiation exposure.