Michael Galanski

Radiation exposure in multi-slice versus single-slice spiral CT: results of a nationwide survey.

Multi-slice (MS) technology increases the efficacy of CT procedures and offers new promising applications. The expanding use of MSCT, however, may result in an increase in both frequency of procedures and levels of patient exposure. It was, therefore, the aim of this study to gain an overview of MSCT examinations conducted in Germany in 2001. All MSCT facilities were requested to provide information about 14 standard examinations with respect to scan parameters and frequency. Based on this data, dosimetric quantities were estimated using an experimentally validated formalism. Results are compared with those of a previous survey for single-slice (SS) spiral CT scanners. According to the data provided for 39 dual- and 73 quad-slice systems, the average annual number of patients examined at MSCT is markedly higher than that examined at SSCT scanners (5500 vs 3500). The average effective dose to patients was changed from 7.4xa0mSv at single-slice to 5.5xa0mSv and 8.1xa0mSv at dual- and quad-slice scanners, respectively. There is a considerable potential for dose reduction at quad-slice systems by an optimisation of scan protocols and better education of the personnel. To avoid an increase in the collective effective dose from CT procedures, a clear medical justification is required in each case.

Correlation of MRI and CT findings with histopathology in hepatic angiomyolipoma

Abstract. Hepatic angiomyolipomas are rare and often mimic other liver tumors. The aim of our study was to describe the CT and MRI findings and to correlate imaging features with histopathology. The CT and/or MR images were available for retrospective analysis in seven patients. Patients had non-enhanced as well as enhanced CT (n=6) or MRI (n=4) before and after administration of Gd-DTPA (n=2) or MnDPDP, a liver specific contrast agent, (n=3). In three patients CT and MRI did not detect fat, and in two patients the angiomyolipomas were also histopathologically devoid of fat. Vascularity ranged from hypervascular (n=4) with arteriovenous shunts (n=1) to equal (n=1) or less (n=2) post-contrast enhancement compared with the normal liver parenchyma. No uptake of the liver specific contrast agent, MnDPDP, was observed (n=3). Predominantly, CT and MRI did not include angiomyolipoma in the differential diagnosis, and the initial histopathological evaluation was inconclusive in more than half the cases. Hepatic angiomyolipomas frequently manifest as solitary well-circumscribed heterogeneous masses in patients with no underlying liver disease or elevation of serum tumor markers. If present, the demonstration of intratumoral fat is helpful in the diagnosis of angiomyolipoma. The final diagnosis can be obtained by immunohistochemistry.

Hybrid Endograft for One-Step Treatment of Multisegment Disease of the Thoracic Aorta

PURPOSEnAt present, a two-step surgical approach is necessary to treat patients with coexistent pathologic conditions involving the proximal and descending thoracic aorta. A hybrid endograft is described here that enables such treatment during a single operation.nnnMATERIALS AND METHODSnThe Chavan-Haverich endograft consists of a Dacron vascular prosthesis with stainless-steel stents affixed at its distal end. After approval by the institutional review board, the endograft was prospectively implanted in 22 patients with multisegment thoracic aortic disease (13 men, nine women; median age, 64 years). Eleven patients had type A dissections (one acute, 10 chronic), four had a chronic type B dissection, and seven had atherosclerotic aneurysms of the ascending aorta or aortic arch as well as of the descending aorta. Of these patients, 11 additionally required aortic valve replacement or coronary artery bypass grafting. Via median sternotomy, the aortic arch was opened in circulatory arrest. After antegrade deployment of the stent-containing portion in the descending aorta, the proximal non-stent-containing endograft was used to reconstruct the aortic arch. Median follow-up was 14 months.nnnRESULTSnEndograft implantation was successful in all but one patient. Complications included neurologic deficits that were transient in one case and lasting in two, two cases of vocal cord paralysis, and one death. In all patients with atherosclerotic aneurysms who received the endograft (six of seven), aneurysm thrombosis was noted at follow-up. In aortic dissections, partial or complete false-lumen thrombosis to the level of the stents occurred in all patients. None of the patients showed a progressive widening of the descending aorta.nnnCONCLUSIONnThe Chavan-Haverich endograft enables one-step treatment of multisegment pathologic conditions affecting the thoracic aorta that otherwise would require two or more operations.

Matched-pair analysis of conventional versus endoluminal AAA treatment outcomes during the initial phase of an aortic endografting program.

Purpose: To investigate whether endovascular stent-grafts implanted during the early phase of an aortic endografting program have advantages over conventional surgical procedures for treatment of infrarenal aortic aneurysm (AAA). Methods: In the first months of an endografting program, 37 patients (36 men; mean age 67.9 ± 7.1 years, range 55 to 86) underwent AAA repair with endovascular implantation of a Vanguard (n = 17) or Talent (n = 20) bifurcated stent-graft. Data collected during the perioperative period and in follow-up were compared retrospectively to a matched group of 37 elective surgical patients. Results: All endograft implantations were completed. Two type I and 6 type II endoleaks (21.6%) were seen postoperatively. Five type II sealed without intervention; 1 type I endoleak was corrected with an additional stent, but 1 type I and 1 type II endoleaks persisted despite attempts with coil embolization. Two (5.4%) endograft patients died during the perioperative period; however, this was not significantly different (p = 0.15) from the control group. In the mean follow-up of 12 ± 6 months for both groups, 1 (2.7%) late conversion was necessary at 2 years for aneurysm expansion in an endograft patient with an unsealed type I endoleak. Conclusions: In our learning curve experience with aortic endografting, postoperative morbidity and mortality were higher in endograft patients compared to conventionally treated controls. Only in the endograft group was reoperation required during follow-up. Careful monitoring with periodic imaging studies is mandatory after endoluminal AAA treatment.

Endoluminal treatment of aortic dissection

Aortic dissection is most often a catastrophic medical emergency which, if untreated, can be potentially fatal. The intention of therapy in patients with aortic dissection is to prevent aortic rupture or aneurysm formation as well as to relieve branch vessel ischaemia. Patients with aortic dissection are often poor candidates for anaesthesia and surgery and the surgical procedure itself is challenging requiring thoracotomy, aortic cross clamping, blood transfusion as well as prolonged hospital stay in some cases. Operative mortality is especially high in patients with critical mesenteric or renal ischaemia. The past decade has experienced the emergence of a number of interventional radiological or minimally invasive techniques which have significantly improved the management of patients with aortic dissection. These include stent grafting for entry site closure to prevent aneurysmatic widening of the false lumen as well as percutaneous techniques such as balloon fenestration of the intimal flap and aortic true lumen stenting to alleviate branch vessel ischaemia. False lumen thrombosis following entry closure with stent grafts has been observed in 86–100% of patients, whereas percutaneous interventions are able to effectively relieve organ ischaemia in approximately 90% of the cases. In the years to come, it is to be expected that these endoluminal techniques will become the method of choice for treating most type-B dissections and will assist in significantly reducing the number of open surgical procedures required for type-A dissections. The intention of this article is to provide an overview of the current status of these endoluminal techniques based on our own experience as well as on a review of the relevant literature.

Role of the intra-arterial calcium stimulation test in the preoperative localization of insulinomas.

Abstract. The aim of this study was determination of the significance of the arterial stimulation test with venous sampling (ASVS) in the preoperative localization of insulinoma. Eleven patients with endogenous hyperinsulinism underwent preoperative transabdominal US, spiral computer tomography (spiral CT), MRI, endoscopic ultrasound (EUS) as well as angiography (DSA) combined with ASVS. The results were compared with intraoperative findings, intraoperative ultrasound (IOUS) and histopathology. There were no complications related to the ASVS test. In 11 patients the tumor could be localized with the various modalities as follows: US 1 of 11 (9 %), MRI 3 of 10 (30 %), spiral CT 4 of 11 (36 %), EUS 5 of 10 (50 %), DSA 8 of 11 (73 %), and ASVS 10 of 11 (91 %). In 2 patients the tumors were intraoperatively neither palpable nor detectable by IOUS, and consequently the intraoperative management was governed by information provided by DSA combined with the ASVS test. Ten patients had solitary benign insulinomas and 1 patient with multiple endocrine neoplasia I had two tumors adjacent to each other in the pancreatic tail. Arterial stimulation test with venous sampling was the most sensitive preoperative test for regionalizing the insulinoma in our set of patients. It can be performed safely in the course of a regular DSA examination and may affect intra-operative management in patients in whom the tumors are not detectable by palpation or IOUS.

In vitro model of the human liver parenchyma to study hepatotoxic side effects by Dy-EOB-DTPA.

RATIONALE AND OBJECTIVESnIn vivo studies have shown species-specific toxicity after application of the liver-specific contrast agent Dy-ethoxybenzyl (EOB)-DTPA. To predict species differences in the laboratory, an in vitro model of the liver was used to examine the divergent results.nnnMETHODSnRat, canine, porcine, and human hepatocytes were isolated and embedded between layers of collagen. During and after 48 hours of incubation with different concentrations of Dy-EOB-DTPA (maximum concentration 50 mmol/L), morphological changes and enzyme leakage were determined.nnnRESULTSnThe response to the contrast agent varied for hepatocytes from different species. For canine cells, morphological changes and cell death were evident with as little as 5 mmol/L Dy-EOB-DTPA. Rat hepatocytes tolerated up to 50 mmol/L Dy-EOB-DTPA, and enzyme leakage was transient. Only after incubation with 50 mmol/L Dy-EOB-DTPA was the formation of intracellular vacuoles evident. In contrast, even the highest concentration of Dy-EOB-DTPA did not cause an enzyme leakage of porcine or human hepatocytes, although similar vacuoles were seen.nnnCONCLUSIONSnThese data demonstrate a species-dependent toxicity for Dy-EOB-DTPA in vitro, with similar responses in porcine and human hepatocytes.

Endoluminal grafting of abdominal aortic aneurysms: experience with the Talent endoluminal stent graft

Abstract. The aim of this study was to evaluate the Talent endoluminal stent graft (TESG) in treating abdominal aortic aneurysms (AAA). The TESG is a polyester-covered nitinol endograft (proximal diameters 20–38 mm and iliac limb diameters 8–22 mm). Twenty-two men were treated with the TESG via bilateral femoral arteriotomies. Pre-implantation, coil embolization of various vessels arising from the aneurysm was performed in 6 patients. Plain radiographs and spiral CT angiograms (CTA) were carried out at 7 days, 3, 6, and 12 months following TESG implantation or re-intervention. Median aortic and iliac diameters were 27 mm (range 20–34 mm) and 14 mm (range 10–19 mm). The corresponding graft diameters were 30 mm (range 24–38 mm) and 14 mm (range 12–20 mm). No patient was rejected purely on the basis of too large aortic or iliac diameters. Eight patients required custom-made grafts. Graft implantation was successful in all patients. There were no blood transfusions, distal embolic episodes, or conversions to open surgery. Re-intervention was necessary in 1 patient. Complications included one fatal myocardial infarction, one inguinal hematoma, and two superficial wound infections. The aneurysm thrombosed completely following implantation in 14 patients and at 3 or 6 months in 4 other patients. One patient with endoleak is awaiting his 3-month control and 2 patients show tiny endoleaks but reduction of aneurysm size. The mean aneurysm size decreased significantly from 58 ± 10 to 53 ± 13 mm (p < 0.0005). Due to the large sizes available and the option of custom-made grafts, the TESG helps widen the spectrum of patients who can be treated with endoluminal grafting. The treatment is associated with a significant reduction in aneurysm size.

Precise determination of aortic length in patients with aortic stent grafts: in vivo evaluation of a thinning algorithm applied to CT angiography data

Abstract The aim of this study was to develop a technique for precise determination of the aortic length using volumetric CT data for potential use prior to endovascular stent-graft placement. The study population consisted of 20 patients (38 measurements) with already performed endoluminal grafting. This allowed for in vivo evaluation of our technique. Its length according to the graft specifications served as a gold standard for our own measurements. The implemented graft length varied between 120 and 195 mm. Computed tomography angiography was performed with 3-mm slice collimation, 5-mm table feed and a reconstruction interval of 2 mm. Following semi-automatic segmentation of the aorta and its large side branches, the median centerline (skeleton) of the vessels was determined employing a modified three-dimensional thinning algorithm. The algorithm was validated by comparing the calculated length of the resulting skeleton with the specifications of the grafts. The calculated length was sufficiently precise despite the limiting reconstruction interval of 2 mm of our CT data which only permitted an assessment of stent length in 2-mm steps. The differences in the measured length and graft length were in the range between 0 and 8 mm ( < 5 %) with a mean fractional error of 2.46 ± 2.37 mm. The use of an intelligent region growing algorithm capable of coping with variable arterial enhancement significantly reduced operator post-processing time. The average time necessary for segmentation was 7 min (range 3–10 min). Our algorithm provides a non-invasive method for objective and precise measurement of aortic length apparently even in tortuous vessels. It has the potential to replace angiography for aortic and iliac length measurements with calibrated catheters prior to endovascular intervention.

Simultaneous treatment of thoracic and infrarenal aortic aneurysm using a combination of conventional surgery and endoluminal stent grafting.

Abstractu2002 Introduction: Patients with multiple aortic aneurysms represent a small subgroup with the need for extensive surgical treatment at considerable risk. Endovascular treatment in combination with conventional operation is possible. We demonstrate a case with simultaneous exclusion of aneurysms of the descending thoracic and the infrarenal aorta to outline the technical obligations. Conclusion: Simultaneous exclusion of a thoracic and an abdominal aneurysm can be performed successfully by conventional infrarenal aortic replacement with bifurcated dacron prosthesis and endovascular implantation of a thoracic stent-graft within one operation.