[C-arm CT for planning and guidance of extrahepatic embolizations]. / C-Arm-CT zur Planung und Steuerung extrahepatischer Embolisationen.

Interventional radiological vascular embolizations are complex procedures that require exact imaging of the target region to facilitate safe and effective treatment. The purpose of this paper is to present the technique and feasibility of flat detector C-arm computed tomography (C-arm CT) for control and guidance of extrahepatic abdominal embolization procedures. C-arm CT images can provide important information on both vascular and cross-sectional anatomy of the target region, help in determining therapy endpoints and provide follow-up during and immediately after the abdominal interventions.The cases presented demonstrate that C-arm CT images are beneficial for abdominal embolization procedures and facilitate precise treatment.

[C-arm CT for chemo-embolization of liver tumors]. / C-Arm-CT bei der Chemoembolisation von Lebertumoren.

Local efficacy of transarterial chemo-embolization (TACE) is enhanced if selective treatment is performed. Selectivity of TACE mainly depends on vascular anatomy but also on the identification and catheterization of tumor feeding arteries. Correlation of vascular territories and target tumor volume in angiographic projection images is more difficult if tumors are not hypervascularized and contrast of liver parenchyma is inhomogeneous.C-arm CT offers the option of selective perfusion imaging via tumor-feeding arteries. This allows the comparison of perfusion images and baseline cross-sectional imaging to evaluate if tumors are covered completely by local treatment and to change the catheter position if necessary. Furthermore the uptake of embolization material, such as lipiodol can be checked by C-arm CT.In a prospective study of 75 TACE of liver tumors and liver metastases we evaluated the appropriateness of 85 catheter positions ready for delivery by perfusion C-arm CT and compared the diagnostic confidence of angiography and perfusion C-arm CT in terms of judgment of correct catheter position for the planned treatment. Diagnostic confidence was improved by perfusion C-arm CT in 55% of cases and in 11 cases (13%) catheter positions were inappropriate and had to be corrected. The reasons for catheter repositioning were incomplete coverage of the target tumor by perfusion volume (mismatch) in 6 cases, inappropriate perfusion of adjacent liver parenchyma in 2 cases and non-selective tumor perfusion via collateral arteries in 3 cases. C-arm CT allowed sufficient visualization of uptake of lipiodol in all cases evaluated.The diagnostic benefit of C-arm CT increases if tumors are treated more selectively, are not strongly hypervascular, are located centrally and if the enhancement of liver parenchyma is inhomogeneous. C-arm CT causes additional working time and contrast load, which is relatively low compared to angiography. Radiation exposure of 151 microGy per C-arm series necessitates careful and therapy-oriented assessment of indications.

[Intravascular optical coherence tomography: differentiation of atherosclerotic plaques and quantification of vessel dimensions in crural arterial specimens]. / Intravaskuläre optische Kohärenztomographie: Unterscheidung verschiedener Plaquetypen und Vermessung von Gefässdimensionen in atherosklerotischen Unterschenkelarterien.

PURPOSE: Intravascular optical coherence tomography (OCT) is a new technique based on infrared light that visualizes the arteries with a resolution of 10-20 microm. Intravascular ultrasound (IVUS) is the current in vivo reference standard and provides a resolution of 100-150 microm. This study compared OCT to IVUS and histopathology with respect to the ability to differentiate atherosclerotic plaques and quantify vascular dimensions in peripheral crural arteries ex vivo. MATERIALS AND METHODS: 50 segments of atherosclerotic arteries derived from five amputated human lower extremities were examined. The different plaque types (fibrous, high-lipid content, calcified) were assigned by two independent examiners, and the sensitivity and specificity of OCT in comparison with histopathology as well as intra- and interobserver consensus were calculated. A comparison of OCT with IVUS addressed the parameters: luminal area (LA), vascular wall area (VA) and plaque area (PA). RESULTS: When comparing OCT and histopathology with respect to the differentiation of various plaque types, sensitivities of 81 % and specificities of 89 % for fibrous plaques, of 100 % and 93 % for lipid-rich plaques and of 80 % and 89 % for calcified plaques were achieved (overall correlation 83 %). Intra- and interobserver consensus was very high (kappa = 0.86 and kappa = 0.89, p < 0.001, respectively). There was also a high correlation between quantitative measurements (Bland-Altman plot [LA]: mean bias, 0.1 mm(2) accuracy +/- 1.8 mm(2), r = 0.95 [p < 0.001] Bland-Altman plot [VA]: mean bias, 0.3 mm(2) accuracy +/- 2.3 mm(2), r = 0.94 [p < 0.001] Bland-Altman plot [PA]: mean bias, 0.4 mm(2) accuracy +/- 2.3 mm(2), r = 0.80 [p < 0.01]. CONCLUSION: OCT allows the differentiation of atherosclerotic plaque types in crural arteries with high accuracy compared to histopathology. Quantitative measurements show a high correlation with IVUS, the current reference standard.

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.

Investigation on radiofrequency and laser (980 nm) effects after endoluminal treatment of saphenous vein insufficiency in an ex-vivo model.

OBJECTIVES: An ex-vivo model for the experimental evaluation of endoluminal thermal procedures for occlusion of saphenous veins was developed. Radiofrequency obliteration (RFO) and endovenous laser therapy (ELT) were compared using this model. DESIGN: Experimental ex-vivo treatment study. MATERIALS AND METHODS: The model consists of the subcutaneous foot veins from freshly slaughtered cows which were reperfused in situ with heparinised bovine blood. The veins were treated with either radiofrequency (RFO n=5) or with endoluminal 980 nm laser light (ELT n=5) using a continuous pull-back for RFO and a stepwise illumination and pull-back protocol for ELT. Immediately after treatment perivenous tissue and veins were examined macroscopically. In a second study the same treatment parameters were used in four further vein segments with RFO (n=2) and ELT (n=2). These vein segments were examined microscopically in HE-stained histological sections. RESULTS: Induration of the vessel wall and contraction of the vessel lumen were observed after RFO. Laser treatment produced carbonised lesions of the vein wall. After 12-24 laser exposures these lesions often became transmural, causing complete perforation of the vessel wall. Histological evaluation after radiofrequency treatment demonstrated homogenous circular thermal tissue alteration with disintegration of intima and media structures. Histological evaluation after endovenous laser treatment showed large variations of thermal tissue effects. Tissue effects ranged from major tissue ablation and vessel wall disruption to minor effects located between laser exposures and on the opposite vessel wall. CONCLUSIONS: Our model is suitable for systematic scientific evaluation of endovenous thermal occlusion procedures. Our first results and theoretical considerations indicate that endovenous laser treatment should be modified in order to ensure controlled homogenous circular thermal damage, avoiding vessel wall perforation and damage to perivascular structures.