Olof Henrikson

Ethylene vinyl alcohol copolymer (Onyx) to seal type 1 endoleak. A new technique

The aim of this study was to investigate whether the liquid embolic agent Onyx, an ethylene vinyl alcohol copolymer, can be used to seal type 1 endoleaks during endovascular aortic repair (EVAR). Six patients with large aortic aneurysms and remaining type 1 endoleaks during or after EVAR were treated with Onyx embolization through a microcatheter placed in the proximal neck in five cases and in the distal neck in one case. Four of the patients were treated using the chimney technique. The type 1 endoleak was primarily sealed by Onyx in all six patients. There was no distal embolization. Two patients had complications during follow-up. One patient had occlusions of chimney grafts to the renal arteries and to one leg extension. These occlusions were not anatomically related to Onyx embolization. One patient had late stentgraft migration of the Onyx-treated distal neck with aneurysm rupture 18 months after treatment. Early experience of Onyx embolization as a bailout solution of type 1 endoleaks after complicated EVAR is promising. However, effective seal with Onyx does not prevent late stentgraft migration. More reported patients and longer follow-up are necessary to evaluate this new technique.

EVAR Guided by 3D Image Fusion and CO2 DSA: A New Imaging Combination for Patients With Renal Insufficiency.

Purpose: To present a new combination of imaging techniques that helps reduce the use of iodinated contrast during endovascular aneurysm repair (EVAR) procedures in patients with renal insufficiency. Technique: Relevant anatomical structures are marked in the preprocedure computed tomography (CT) angiogram. A 3D-3D image fusion between the preprocedure CT and an intraprocedure cone-beam CT is performed in order to overlay anatomical information on live fluoroscopy. Verification of the correct overlay matching (or adjustment if necessary) is based on carbon dioxide (CO2) digital subtraction angiograms (DSA) instead of iodine DSA. The stent-graft is placed and deployed based on the overlaid information. Correct device placement is finally verified with conventional contrast angiography. Conclusion: The combination of 3D image fusion of a preoperative CT with live fluoroscopy and CO2 DSA verification is feasible and sufficient for guidance of abdominal EVAR. This method minimizes the use of iodinated contrast media, protecting residual function in the setting of preexisting renal insufficiency.

Heterogeneity of microsphere distribution in resected liver and tumour tissue following selective intrahepatic radiotherapy.

BackgroundSelective arterial radioembolisation of liver tumours has increased, because of encouraging efficacy reports; however, therapeutic parameters used in external beam therapy are not applicable for understanding and predicting potential toxicity and efficacy, necessitating further studies of the physical and biological characteristics of radioembolisation. The aim was to characterise heterogeneity in the distribution of microspheres on a therapeutically relevant geometric scale considering the range of yttrium-90 (90Y) β-particles.MethodsTwo patients with intrahepatic cholangiocarcinoma, marginally resectable, were treated by selective arterial embolisation with 90Y resin microspheres (SIRTEX®), followed 9 days post-infusion by resection, including macroscopic tumour tissue and surrounding normal liver parenchyma. Formalin-fixed, sectioned resected tissues were exposed to autoradiographic films, or tissue biopsies of various dimensions were punched out for activity measurements and microscopy.ResultsAutoradiography and activity measurements revealed a higher activity in tumour tissue compared to normal liver parenchyma. Heterogeneity in activity distribution was evident in both normal liver and tumour tissue. Activity measurements were analysed in relation to the sample mass (5 to 422 mg), and heterogeneities were detected by statistical means; the larger the tissue biopsies, the smaller was the coefficient of variation. The skewness of the activity distributions increased with decreasing biopsy mass.ConclusionsThe tissue activity distributions in normal tissue were heterogeneous on a relevant geometric scale considering the range of the ionising electrons. Given the similar and repetitive structure of the liver parenchyma, this finding could partly explain the tolerance of a relatively high mean absorbed dose to the liver parenchyma from β-particles.

Increased absorbed liver dose in Selective Internal Radiation Therapy (SIRT) correlates with increased sphere-cluster frequency and absorbed dose inhomogeneity

BackgroundThe higher tolerated mean absorbed dose for selective internal radiation therapy (SIRT) with intra-arterially infused 90Y microspheres compared to external beam therapy is speculated to be caused by absorbed dose inhomogeneity, which allows for liver regeneration. However, the complex liver microanatomy and rheology makes modelling less valuable if the tolerance doses are not based on the actual microsphere distribution. The present study demonstrates the sphere distribution and small-scale absorbed dose inhomogeneity and its correlation with the mean absorbed dose in liver tissue resected after SIRT.MethodsA patient with marginally resectable cholangiocarcinoma underwent SIRT 9 days prior to resection including adjacent normal liver tissue. The resected specimen was formalin-fixed and sliced into 1 to 2-mm sections. Forty-one normal liver biopsies 6-8 mm in diameter were punched from these sections and the radioactivity measured. Sixteen biopsies were further processed for detailed analyses by consecutive serial sectioning of 15 30-μm sections per biopsy, mounted and stained with haematoxylin-eosin. All sections were scrutinised for isolated or conglomerate spheres. Small-scale dose distributions were obtained by applying a 90Y-dose point kernel to the microsphere distributions.ResultsA total of 3888 spheres were found in the 240 sections. Clusters were frequently found as strings in the arterioles and as conglomerates in small arteries, with the largest cluster comprising 453 spheres. An increased mean absorbed dose in the punch biopsies correlated with large clusters and a greater coefficient of variation. In simulations the absorbed dose was 5–1240 Gy; 90% were 10-97 Gy and 45% were <30 Gy, the assumed tolerance in external beam therapy.ConclusionsSphere clusters were located in both arterioles and small arteries and increased in size with increasing sphere concentration, resulting in increased absorbed dose inhomogeneity, which contradicts earlier modelling studies.

Endovascular Closure of Chronic Dissection Entries in the Aortic Arch Using the Amplatzer Vascular Plug II as a Sealing Button

Purpose: To present a new endovascular technique to avoid open surgical arch reconstruction in selected patients with aneurysmal dilatation due to small chronic dissection entries in the aortic arch. Technique: The true and the false lumen of the aortic arch are catheterized from the femoral arteries. An Amplatzer Vascular Plug II (AVP II) is advanced through the proximal entry from the false lumen side and deployed as a sealing button in the entry hole, with 1 disc in the true lumen and the remaining 2 discs in the false lumen. This technique was used in 4 patients with chronic dissection involving the aortic arch, three of whom had had previous surgery for acute type A aortic dissection. In 3 patients, the false lumen of the thoracic aorta was successfully obliterated, with thrombosis and aortic diameter reduction during follow-up. In 1 patient, false lumen flow persisted, and he was subsequently treated with a total arch reconstruction and frozen elephant trunk. Conclusion: Endovascular closure of small proximal dissection entries in the aortic arch with an AVP II used as a sealing button is feasible and may be an alternative to open surgical arch reconstruction in selected patients with chronic aortic dissection and secondary aneurysm expansion.

Autoradiography and biopsy measurements of a resected hepatocellular carcinoma treated with 90 yttrium radioembolization demonstrate large absorbed dose heterogeneities

Purpose Radioembolization is an alternative palliative treatment for hepatocellular carcinoma. Here, we examine the uptake differences between tumor tissue phenotypes and present a cross-section of the absorbed dose throughout a liver tissue specimen. Methods and materials A patient with hepatocellular carcinoma was treated with 90Y radioembolization followed by liver tissue resection. Gamma camera images and autoradiographs were collected and biopsy tissue samples were analyzed using a gamma well counter and light microscopy. Results An analysis of 25 punched biopsy tissue samples identified 4 tissue regions: Normal tissue, viable tumor tissue with and without infarcted areas, and tumor areas with postnecrotic scar tissue. Autoradiography and biopsy tissue sample measurements showed large dose differences between viable and postnecrotic tumor tissue (159 Gy vs 23 Gy). Conclusions Radioembolization of 90 yttrium with resin microspheres produces heterogeneous-absorbed dose distributions in the treatment of unifocal hepatic malignancies that could not be accurately determined with current gamma camera imaging techniques.