Intraoperative liver deformation and organ motion caused by ventilation, laparotomy, and pneumoperitoneum in a porcine model for image-guided liver surgery.

BACKGROUND: Image-guidance promises to make complex situations in liver interventions safer. Clinical success is limited by intraoperative organ motion due to ventilation and surgical manipulation. The aim was to assess influence of different ventilatory and operative states on liver motion in an experimental model. METHODS: Liver motion due to ventilation (expiration, middle, and full inspiration) and operative state (native, laparotomy, and pneumoperitoneum) was assessed in a live porcine model (n = 10). Computed tomography (CT)-scans were taken for each pig for each possible combination of factors. Liver motion was measured by the vectors between predefined landmarks along the hepatic vein tree between CT scans after image segmentation. RESULTS: Liver position changed significantly with ventilation. Peripheral regions of the liver showed significantly higher motion (maximal Euclidean motion 17.9 ± 2.7 mm) than central regions (maximal Euclidean motion 12.6 ± 2.1 mm, p < 0.001) across all operative states. The total average motion measured 11.6 ± 0.7 mm (p < 0.001). Between the operative states, the position of the liver changed the most from native state to pneumoperitoneum (14.6 ± 0.9 mm, p < 0.001). From native state to laparotomy comparatively, the displacement averaged 9.8 ± 1.2 mm (p < 0.001). With pneumoperitoneum, the breath-dependent liver motion was significantly reduced when compared to other modalities. Liver motion due to ventilation was 7.7 ± 0.6 mm during pneumoperitoneum, 13.9 ± 1.1 mm with laparotomy, and 13.5 ± 1.4 mm in the native state (p < 0.001 in all cases). CONCLUSIONS: Ventilation and application of pneumoperitoneum caused significant changes in liver position. Liver motion was reduced but clearly measurable during pneumoperitoneum. Intraoperative guidance/navigation systems should therefore account for ventilation and intraoperative changes of liver position and peripheral deformation.

Effects of laparoscopy, laparotomy, and respiratory phase on liver volume in a live porcine model for liver resection.

BACKGROUND: Hepatectomy, living donor liver transplantations and other major hepatic interventions rely on precise calculation of the total, remnant and graft liver volume. However, liver volume might differ between the pre- and intraoperative situation. To model liver volume changes and develop and validate such pre- and intraoperative assistance systems, exact information about the influence of lung ventilation and intraoperative surgical state on liver volume is essential. METHODS: This study assessed the effects of respiratory phase, pneumoperitoneum for laparoscopy, and laparotomy on liver volume in a live porcine model. Nine CT scans were conducted per pig (N = 10), each for all possible combinations of the three operative (native, pneumoperitoneum and laparotomy) and respiratory states (expiration, middle inspiration and deep inspiration). Manual segmentations of the liver were generated and converted to a mesh model, and the corresponding liver volumes were calculated. RESULTS: With pneumoperitoneum the liver volume decreased on average by 13.2% (112.7 ml ± 63.8 ml, p < 0.0001) and after laparotomy by 7.3% (62.0 ml ± 65.7 ml, p = 0.0001) compared to native state. From expiration to middle inspiration the liver volume increased on average by 4.1% (31.1 ml ± 55.8 ml, p = 0.166) and from expiration to deep inspiration by 7.2% (54.7 ml ± 51.8 ml, p = 0.007). CONCLUSIONS: Considerable changes in liver volume change were caused by pneumoperitoneum, laparotomy and respiration. These findings provide knowledge for the refinement of available preoperative simulation and operation planning and help to adjust preoperative imaging parameters to best suit the intraoperative situation.

Mobile, real-time, and point-of-care augmented reality is robust, accurate, and feasible: a prospective pilot study.

BACKGROUND: Augmented reality (AR) systems are currently being explored by a broad spectrum of industries, mainly for improving point-of-care access to data and images. Especially in surgery and especially for timely decisions in emergency cases, a fast and comprehensive access to images at the patient bedside is mandatory. Currently, imaging data are accessed at a distance from the patient both in time and space, i.e., at a specific workstation. Mobile technology and 3-dimensional (3D) visualization of radiological imaging data promise to overcome these restrictions by making bedside AR feasible. METHODS: In this project, AR was realized in a surgical setting by fusing a 3D-representation of structures of interest with live camera images on a tablet computer using marker-based registration. The intent of this study was to focus on a thorough evaluation of AR. Feasibility, robustness, and accuracy were thus evaluated consecutively in a phantom model and a porcine model. Additionally feasibility was evaluated in one male volunteer. RESULTS: In the phantom model (n = 10), AR visualization was feasible in 84% of the visualization space with high accuracy (mean reprojection error ± standard deviation (SD): 2.8 ± 2.7 mm; 95th percentile = 6.7 mm). In a porcine model (n = 5), AR visualization was feasible in 79% with high accuracy (mean reprojection error ± SD: 3.5 ± 3.0 mm; 95th percentile = 9.5 mm). Furthermore, AR was successfully used and proved feasible within a male volunteer. CONCLUSIONS: Mobile, real-time, and point-of-care AR for clinical purposes proved feasible, robust, and accurate in the phantom, animal, and single-trial human model shown in this study. Consequently, AR following similar implementation proved robust and accurate enough to be evaluated in clinical trials assessing accuracy, robustness in clinical reality, as well as integration into the clinical workflow. If these further studies prove successful, AR might revolutionize data access at patient bedside.

Towards markerless navigation for percutaneous needle insertions.

PURPOSE: Percutaneous needle insertions are increasingly used for diagnosis and treatment of abdominal lesions. The challenging part of computed tomography (CT)-guided punctures is the transfer of the insertion trajectory planned in the CT image to the patient. Conventionally, this often results in several needle repositionings and control CT scans. To address this issue, several navigation systems for percutaneous needle insertions have been presented; however, none of them has thus far become widely accepted in clinical routine. Their benefit for the patient could not exceed the additional higher costs and the increased complexity in terms of bulky tracking systems and specialized markers for registration and tracking. METHODS: We present the first markerless and trackerless navigation concept for real-time patient localization and instrument guidance. It has specifically been designed to be integrated smoothly into the clinical workflow and does not require markers or an external tracking system. The main idea is the utilization of a range imaging device that allows for contactless and radiation-free acquisition of both range and color information used for patient localization and instrument guidance. RESULTS: A first feasibility study in phantom and porcine models yielded a median targeting accuracy of 6.9 and 19.4 mm, respectively. CONCLUSIONS: Although system performance remains to be improved for clinical use, expected advances in camera technology as well as consideration of respiratory motion and automation of the individual steps will make this approach an interesting alternative for guiding percutaneous needle insertions.

Retrospective study in 23 patients of the self-expanding sinus-XL stent for treatment of malignant superior vena cava obstruction caused by non-small cell lung cancer.

PURPOSE: To evaluate retrospectively the self-expanding nitinol Sinus-XL stent (OptiMed, Ettlingen, Germany) for the treatment of superior vena cava (SVC) obstruction caused by non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Between October 2009 and December 2012, 23 patients (7 women and 16 men; age, 62.5 y ± 8.5) with stage IIIA (1 patient), IIIB (4 patients) or IV (18 patients) NSCLC and acute SVC obstruction were scheduled for urgent stent implantation. The primary study endpoints were technical success (defined as accurate stent placement with complete coverage of the obstructed SVC), residual stenosis < 30%, and clinical efficacy. Complications were assessed as a secondary study endpoint. RESULTS: There were 26 stents implanted in 23 patients. The technical success was 100%. Stent dilation was performed after deployment in 18 cases (78%). Stent migration into the right atrium occurred immediately after deployment in one patient; however, this stent was successfully repositioned and stabilized by a second stent. The clinical symptoms improved at least one category according to the International Consensus Committee on Chronic Venous Disease after stent implantation in all but one patient. The mean clinical follow-up was 66 days ± 83 (range, 1-305 d). Three minor complications (13%) and one major complication (4%) occurred. CONCLUSIONS: Implantation of the self-expanding Sinus-XL stent for treatment of SVC obstruction caused by NSCLC is a safe and effective urgent treatment in this palliative setting.

Evaluation of the plasmatic and parenchymal elution kinetics of two different irinotecan-loaded drug-eluting embolics in a pig model.

PURPOSE: To evaluate and compare irinotecan elution kinetics of two drug-eluting embolic agents in a porcine model. MATERIALS AND METHODS: Embolization of the left liver lobe was performed in 16 domestic pigs, with groups of two receiving 1 mL of DC Bead M1 (70-150 µm) or Embozene TANDEM (75 µm) loaded with 50 mg irinotecan. Irinotecan plasma levels were measured at 0, 10, 20, 30, 60, 120, 180, and 240 minutes after completed embolization and at the time of euthanasia (24 h, 48 h, 72 h, or 7 d). Liver tissue samples were taken to measure irinotecan tissue concentrations. RESULTS: The highest irinotecan plasma concentrations of both embolic agents were measured 10 and 20 minutes after embolization, and concentrations were significantly higher for DC Bead M1 versus Embozene TANDEM (P = .0019 and P = .0379, respectively). At 48 hours and later follow-up, no irinotecan was measurable in the plasma. For both embolic agents, the highest irinotecan tissue concentration was found after 24 hours and decreased in a time-dependent manner at later follow-up intervals. Additionally, SN-38 tissue levels for both agents were therapeutic at 24 hours, with therapeutic levels of SN-38 at 48 hours in one liver embolized with TANDEM particles. Histopathologic analysis revealed ischemic, inflammatory, and fibrotic tissue reactions. CONCLUSIONS: Irinotecan is measurable in plasma and hepatic tissue after liver embolization with both types of irinotecan-eluting embolic agents. DC Bead M1 shows early burst elution kinetics, whereas Embozene TANDEM has a lower and slower release profile. The initial burst is significantly greater after embolization with DC Bead M1 than with Embozene TANDEM.

Accuracy of estimation of graft size for living-related liver transplantation: first results of a semi-automated interactive software for CT-volumetry.

OBJECTIVES: To evaluate accuracy of estimated graft size for living-related liver transplantation using a semi-automated interactive software for CT-volumetry. MATERIALS AND METHODS: Sixteen donors for living-related liver transplantation (11 male; mean age: 38.2±9.6 years) underwent contrast-enhanced CT prior to graft removal. CT-volumetry was performed using a semi-automated interactive software (P), and compared with a manual commercial software (TR). For P, liver volumes were provided either with or without vessels. For TR, liver volumes were provided always with vessels. Intraoperative weight served as reference standard. Major study goals included analyses of volumes using absolute numbers, linear regression analyses and inter-observer agreements. Minor study goals included the description of the software workflow: degree of manual correction, speed for completion, and overall intuitiveness using five-point Likert scales: 1--markedly lower/faster/higher for P compared with TR, 2--slightly lower/faster/higher for P compared with TR, 3--identical for P and TR, 4--slightly lower/faster/higher for TR compared with P, and 5--markedly lower/faster/higher for TR compared with P. RESULTS: Liver segments II/III, II-IV and V-VIII served in 6, 3, and 7 donors as transplanted liver segments. Volumes were 642.9±368.8 ml for TR with vessels, 623.8±349.1 ml for P with vessels, and 605.2±345.8 ml for P without vessels (P<0.01). Regression equations between intraoperative weights and volumes were y = 0.94x+30.1 (R2 = 0.92; P<0.001) for TR with vessels, y = 1.00x+12.0 (R2 = 0.92; P<0.001) for P with vessels, and y = 1.01x+28.0 (R2 = 0.92; P<0.001) for P without vessels. Inter-observer agreement showed a bias of 1.8 ml for TR with vessels, 5.4 ml for P with vessels, and 4.6 ml for P without vessels. For the degree of manual correction, speed for completion and overall intuitiveness, scale values were 2.6±0.8, 2.4±0.5 and 2. CONCLUSIONS: CT-volumetry performed with P can predict accurately graft size for living-related liver transplantation while improving workflow compared with TR.

Hepatic artery stent-grafts for the emergency treatment of acute bleeding.

PURPOSE: We evaluated the technical success and clinical efficacy of stent-graft implantation for the emergency management of acute hepatic artery bleeding. METHODS: Between January 2010 and July 2013, 24 patients with hemorrhage from the hepatic artery were scheduled for emergency implantation of balloon expandable stent-grafts. The primary study endpoints were technical and clinical success, which were defined as successful stent-graft implantation with sealing of the bleeding site at the end of the procedure, and cessation of clinical signs of hemorrhage. The secondary study endpoints were complications during the procedure or at follow-up and 30-day mortality rate. RESULTS: In 23 patients, hemorrhage occurred after surgery, and in one patient hemorrhage occurred after trauma. Eight patients had sentinel bleeding. In most patients (n=16), one stent-graft was implanted. In six patients, two overlapping stent-grafts were implanted. The stent-grafts had a target diameter between 4mm and 7 mm. Overall technical success was 88%. The bleeding ceased after stent-graft implantation in 21 patients (88%). The mean follow-up was 137 ± 383 days. In two patients, re-bleeding from the hepatic artery occurred during follow-up after 4 and 29 days, respectively, which could be successfully treated by endovascular therapy. The complication rate was 21% (minor complication rate 4%, major complication rate 17%). The 30-day mortality rate was 21%. CONCLUSIONS: Implantation of stent-grafts in the hepatic artery is an effective emergency therapy and has a good technical success rate for patients with acute arterial hemorrhage.

Emergency embolization for the treatment of acute hemorrhage from intercostal arteries.

To evaluate embolotherapy for the emergency management of acute bleeding from intercostal arteries. Between October 2003 and August 2012, 19 consecutive patients with hemorrhage from intercostal arteries were scheduled for emergency embolization. The primary study endpoints were technical and clinical success, which were defined as angiographic cessation of bleeding, and cessation of clinical signs of hemorrhage. The secondary study endpoints were periprocedural complications and 30-day mortality rate. In most patients (74 %), hemorrhage was caused by iatrogenic procedures with subsequent intercostal artery laceration. One of the patients was treated twice for recurrent hemothorax caused by a new intercostal artery pseudoaneurysm 7.5 years after the initial procedure. Thus, 20 procedures were performed in these 19 patients. Overall technical success was 85 %. In six patients, no embolization of the "backdoor" was feasible, and in two of these patients additional embolization of other intercostal arteries was necessary to prevent hemorrhage via collateral vessels. Clinical signs of hemorrhage ceased after embolotherapy in 16 of 20 procedures (clinical success 80 %). The mean follow-up was 358.7 ± 637.1 days. One minor procedure-related complication occurred. The 30-day mortality rate was 21 %, however, this was unrelated to intercostal artery hemorrhage. Embolotherapy is an effective emergency therapy for patients with acute hemorrhage from intercostal arteries. Especially if embolization of the backdoor is not feasible, collateral supply via other intercostal arteries should be either ruled out or embolized to prevent ongoing hemorrhage. Despite successful embolotherapy, a majority of patients underwent surgery during follow-up to remove the symptomatic hematoma.

Specific CT 3D rendering of the treatment zone after Irreversible Electroporation (IRE) in a pig liver model: the "Chebyshev Center Concept" to define the maximum treatable tumor size.

BACKGROUND: Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the "Chebyshev Center Concept" was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin. METHODS: In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the "Chebyshev Center Concept" implemented (the "Chebyshev Center" is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position. RESULTS: For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 ± 13.1 mm versus 53.8 ± 1.1 mm and 39.0 ± 8.4 mm versus 53.8 ± 1.1 mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B. CONCLUSIONS: Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the "Chebyshev Center Concept" implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the "Chebyshev Center Concept" could be used for a more objective acute treatment control.

Therapeutic lymphangiography and CT-guided sclerotherapy for the treatment of refractory lymphatic leakage.

PURPOSE: To evaluate therapeutic lymphangiography and computed tomography (CT)-guided sclerotherapy for the treatment of refractory inguinal, pelvic, abdominal, and thoracic lymphatic leakage. MATERIALS AND METHODS: Between January 2008 and April 2011, 18 patients with refractory lymphatic leakage were treated with therapeutic lymphangiography. Additionally, 10 of these 18 patients underwent CT-guided sclerotherapy with injection of ethanol at the site of the leakage. In the delayed sclerotherapy group (n = 5), the sclerotherapy procedure was performed when the leak persisted after therapeutic lymphangiography. In the immediate sclerotherapy group (n = 5), sclerotherapy was performed on the same day as lymphangiography. The sites of the lymphatic leakage were as follows: inguinal leakage in 8 patients, pelvic leakage in 4 patients, abdominal leakage in 2 patients, and thoracic leakage in 4 patients. Data collected included technical success, clinical success, and procedural complications. RESULTS: Lymphangiography was technically successful in all patients. In eight patients undergoing therapeutic lymphangiography alone, the clinical success rate was 75%, and the drainage catheter could be removed in six patients after the treatment. Lymphangiography followed by immediate sclerotherapy was clinically successful in four of five patients. Lymphangiography combined with delayed sclerotherapy was clinically successful in three of five patients. Overall, the clinical success rate was 72% (13 of 18 patients). One minor complication occurred. CONCLUSIONS: Therapeutic lymphangiography alone or in combination with CT-guided sclerotherapy is a promising treatment option for the management of refractory lymphatic leakage.

Irreversible electroporation of the pig kidney with involvement of the renal pelvis: technical aspects, clinical outcome, and three-dimensional CT rendering for assessment of the treatment zone.

PURPOSE: To analyze irreversible electroporation (IRE) of the pig kidney with involvement of the renal pelvis. MATERIALS AND METHODS: IRE of renal tissue including the pelvis was performed in 10 kidneys in five pigs. Three study groups were defined: group I (two applicators with parallel configuration; n = 11), group II (three applicators with triangular configuration; n = 2), and group III (six applicators with complex configuration; n = 3). After IRE and before euthanasia, pigs underwent contrast-enhanced computed tomography (CT). Technical aspects (radial distance of applicators, resulting mean current), clinical outcome (complications, blood samples), and three-dimensional CT rendering for assessment of the treatment zone (short axis, circularity) were assessed. RESULTS: Radial distances of applicators were 14.3 mm ± 2.8 in group I, 12.3 mm ± 1.9 in group II, and 16.4 mm ± 3.5 in group III. Resulting mean currents were 25.7 A ± 6.5 in group I, 27.0 A ± 7.1 in group II, and 39.4 A ± 8.9 in group III. In group III, two perirenal hematomas were identified. There was no damage to the renal pelvis. During IRE, clinical blood parameters and cardiovascular markers did not change significantly. Short axis measurements were 20.6 mm ± 3.6 in group I, 31.9 mm ± 8.2 in group II, and 39.3 mm ± 2.4 in group III (P < .01 between groups). Circularity scores were 0.8 ± 0.2 in group I, 0.7 ± 0.1 in group II, and 0.7 ± 0.1 in group III, with a score of 1 indicating perfect roundness (P value not significant). CONCLUSIONS: IRE of the pig kidney with involvement of the renal pelvis is feasible and safe. Size but not shape of the treatment zone is significantly affected by applicator configuration.

Optimisation of the coagulation zone for thermal ablation procedures: a theoretical approach with considerations for practical use.

PURPOSE: This paper outlines a theoretical approach for optimisation of the coagulation zone for thermal ablation procedures and considerations for its practical application. METHODS: The theoretical approach is outlined in the Cartesian coordinate system. Considerations for practical application are implemented. The optimised coagulation zone is defined as the bare coverage of tumour mass plus a safety margin. The eccentricity of coagulation centre (ECC) is defined as the distance between the coagulation centre and the tumour centre. The direction of the applicator shaft is determined based on the x-axis direction. The tumour centre and coagulation centre are defined within the x/y-plane. The distance between coagulation margin (applicator tip) and tumour margin is called parallel offset (PAO). RESULTS: For spherical coagulation shapes, a linear relationship exists between optimised coagulation diameter and ECC. An exponential relationship exists between optimised coagulation volume and ECC. A complex relationship was found between PAO and determinants of ECC, which are ex and ey. PAO is an extremely important parameter, which allows for determination of the optimal applicator tip position in relation to the tumour margin. It can be calculated in such a manner that the optimised coagulation zone is minimised by neutralising dislocation of the coagulation centre in applicator shaft direction. The latter can be realised by withdrawing or further inserting the applicator shaft. CONCLUSIONS: The presented concept can be used to optimise the extent of the coagulation zone for thermal ablation procedures after positioning of the applicator. Its inherent advantage is the simple adjustment of the applicator shaft, which obviates the need for a repuncture.

Quantification of tissue shrinkage and dehydration caused by microwave ablation: experimental study in kidneys for the estimation of effective coagulation volume.

PURPOSE: To quantify the extent of tissue shrinkage and dehydration caused by microwave (MW) ablation in kidneys for estimation of effective coagulation volume. MATERIALS AND METHODS: MW ablations were carried out in ex vivo porcine kidneys. Six study groups were defined: groups 1A, 2A, and 3A for MW ablation (90 W for 5 min, 7.5 min, or 10 min), and groups 1B, 2B, and 3B for control (without MW ablation). Pre- and postinterventional volume analyses were performed. Effective coagulation volumes (original tissue included in coagulation) were determined. Postinterventional dehydration analyses were performed with calculation of mean mass fractions of water. RESULTS: Mean deployed energies were 21.6 kJ ± 1.1 for group 1A, 29.9 kJ ± 1.0 for group 2A, and 42.1 kJ ± 0.5 kJ for group 3A, and were significantly different (P < .0001). Differences between pre- and postinterventional volumes were -3.8% ± 0.6 for group 1A, -5.6% ± 0.9 for group 2A, and -7.2% ± 0.4 for group 3A, and -1.1% ± 0.3 for group 1B, -1.8% ± 0.4 for group 2B, and -1.1% ± 0.4 for group 3B. Postinterventional volumes were significantly smaller than preinterventional volumes for all groups (P < .01). Underestimations of effective coagulation volume from visualized coagulation volume were 26.1% ± 3.5 for group 1A, 35.2% ± 11.2 for group 2A, and 42.1% ± 4.9 for group 3A, which were significantly different (P < .01). Mean mass fractions of water were 64.2% ± 1.4 for group 1A, 63.2% ± 1.7 for group 2A, and 62.6% ± 1.8% for group 3A, with significant differences versus corresponding control groups (P < .01). CONCLUSIONS: For MW ablation in kidneys, underestimation of effective coagulation volume based on visualized coagulation volume is significantly greater with greater deployed energy. Therefore, local dehydration with tissue shrinkage is a potential contributor.

Multimodal visibility (radiography, computed tomography, and magnetic resonance imaging) of microspheres for transarterial embolization tested in porcine kidneys.

OBJECTIVE: The objective of this study was to test multimodal visibility (radiography, computed tomography [CT], and magnetic resonance imaging [MRI]) of microspheres for transarterial embolization in porcine kidneys. MATERIALS AND METHODS: Currently available embolization particles (microspheres) were modified. A dense x-ray material (barium sulfate) was added to create visibility for radiography and CT. A magnetic substance (iron oxide) was additionally added to create visibility for MRI. This chemical modification was performed for particles with sizes of 100 ± 25 and 700 ± 50 µm. Three different prototypes per size class (samples A, B, and C) resulted, each with a different degree of barium sulfate but with the same degree of iron oxide. The currently available embolization particles with sizes of 100 ± 25 and 700 ± 50 µm were used as controls (sample control). Eight renal arteries of 4 pigs were embolized. Study end points were size distribution evaluated in vitro as well as qualitative and quantitative particle visibility evaluated in vivo. RESULTS: The size distribution of the particles with a size of 100 ± 25 µm was between 96 ± 11 µm for sample A and 102 ± 13 µm for the sample control without significant differences (n.s.). The size distribution of the particles with a size of 700 ± 50 µm was between 691 ± 20 µm for sample A and 716 ± 34 µm for sample C without significant differences (n.s.). For radiography, the particles with sizes of 100 ± 25 and 700 ± 50 µm for samples A, B, and C were definitely visible during the embolization. The sample control was definitely not visible. For CT and MRI (T1-weighted [T1w] and T2-weighted [T2w]), the particles with sizes of 100 ± 25 and 700 ± 50 µm for samples A, B, and C were definitely visible after the embolization. The sample control was definitely not visible. For CT, the signal-to-noise ratio for samples A, B, and C increased significantly after the embolization (eg, sample A, particles with a size of 100 ± 25 µm: 66.5% ± 23.7%, P < 0.05). The signal-to-noise ratio for the sample control did not change after the embolization (eg, sample control, particles with a size of 700 ± 25 µm: -0.2% ± 15.2%, n.s.). For MRI (T1w and T2w), the signal-to-noise ratio for samples A, B, and C decreased significantly after the embolization (eg, sample B, particles with a size of 700 ± 50 µm, T1w: -72.9% ± 6.6%; P < 0.05). The signal-to-noise ratio for the sample control did not change after the embolization (eg, sample control, particles with a size of 100 ± 25 µm, T2w: 6.2% ± 16.1%, n.s.). CONCLUSIONS: In this study, the chemical modification of the currently available microspheres for transarterial embolization resulted in a size distribution comparable with the currently available microspheres and created multimodal visibility for radiography, CT, and MRI.

Bipolar versus multipolar radiofrequency (RF) ablation for the treatment of renal cell carcinoma: differences in technical and clinical parameters.

PURPOSE: This study aimed to compare retrospectively bipolar RF ablation with multipolar RF ablation for the treatment of renal cell carcinoma. MATERIALS AND METHODS: Between March 2009 and June 2012, 12 tumours (nine patients) treated with bipolar RF ablation (one applicator) and 14 tumours (11 patients) treated with multipolar RF ablation (two applicators) were compared systematically. Selection between bipolar RF ablation and multipolar RF ablation was operator choice considering tumour size. Study goals included differences in tumour and coagulation extent, and technical parameters (total RF energy delivery and RF ablation time per coagulation volume). RESULTS: Tumour maximum diameter was significantly larger for multipolar RF ablation compared with bipolar RF ablation (27.0 mm versus 19.4 mm; p < 0.01). This difference is partially dependent on operator choice. Coagulation length, width and volume were significantly larger for multipolar RF ablation compared with bipolar RF ablation (35.0 mm versus 26.5 mm, 27.5 mm versus 23.0 mm and 14.3 cm(3) versus 8.1 cm(3); p < 0.01, p < 0.05 and p < 0.05, respectively). Coagulation circularity was not significantly different between both study groups (0.8 versus 0.8; not significant). Total RF energy delivery was significantly higher and RF ablation time per coagulation volume was significantly shorter for multipolar RF ablation compared with bipolar RF ablation (52.0 kJ versus 28.6 kJ and 2.4 min/cm(3) versus 4.1 min/cm(3); p < 0.05 and p < 0.05, respectively). CONCLUSIONS: Multipolar RF ablation creates a significantly larger coagulation width, but identical coagulation shape, compared with bipolar RF ablation. Additionally, multipolar RF ablation coagulates faster according to the shorter RF ablation time per coagulation volume.

Microwave ablation in porcine livers applying 5-minute protocols: influence of deployed energy on extent and shape of coagulation.

PURPOSE: To evaluate the influence of deployed energy on extent and shape of microwave (MW)-induced coagulation in porcine livers applying 5-minute protocols. MATERIALS AND METHODS: MW ablations (n = 25) were performed in ex vivo porcine livers (n = 8). Ablation time was 5 minutes. Five study groups were defined, each with different power output: I, 20 W (n = 5); II, 40 W (n = 5); III, 60 W (n = 5); IV, 80 W (n = 5); and V, 105 W (n = 5). Extent and shape of white coagulation was evaluated macroscopically, including short diameter, volume, front margin, coagulation center (distance between center of short diameter of coagulation and applicator tip), and ellipticity index (short diameter/long diameter). Deployed energy was also analyzed. RESULTS: Short diameter and volume were significantly different (P<.001 and P<.001) between the groups: I, 23.0 mm and 11.1 cm(3); II, 12.4 mm and 12.4 cm(3); III, 27.0 mm and 17.6 cm(3); IV, 31.0 mm and 29.2 cm(3); and V, 35.0 mm and 42.3 cm(3). Front margin and coagulation center were also significantly different (P<.05 and P<.001): I, 6.0 mm and 13.0 mm; II, 8.0 mm and 11.0 mm; III, 8.0 mm and 14.0 mm; IV, 8.0 mm and 18.0 mm; and V, 10.0 mm and 19.0 mm. Ellipticity index was not significantly different. Deployed energy was significantly different (P<.001): I, 5.7 kJ; II, 11.0 kJ; III, 15.5 kJ; IV, 21.6 kJ; and V, 26.6 kJ. CONCLUSIONS: Extent, but not shape, of MW-induced coagulation depends on the deployed energy. Applying the protocols described in this study, significantly different coagulation volumes can be created with an ablation time of 5 minutes but different power output.

Multimodal visibility of a modified polyzene-F-coated spherical embolic agent for liver embolization: feasibility study in a porcine model.

PURPOSE: To evaluate multimodal visibility of modified currently available microspheres on radiography, magnetic resonance (MR) imaging, and computed tomography (CT) in a porcine liver model. MATERIALS AND METHODS: Livers of four pigs were embolized with two sizes (100 µm ± 25 and 700 µm ± 50) of modified Embozene Microspheres embedded with different densities of barium sulfate and iodine as radiopaque materials (intensity groups A-C, with increasing intensity from A to C for 100 µm and intensities A and C for 700 µm) and iron oxide as magnetic substance for MR imaging visibility. Pigs embolized with currently available Embozene Microspheres served as control groups. Pre- and postinterventional MR imaging (T1- and T2-weighted) and CT were performed. Qualitative and quantitative (ie, determination of signal-to-noise ratio [SNR]) particle visibility was evaluated on radiography, MR imaging, and CT. RESULTS: Modified particles of both sizes were visible on radiography, MR imaging, and CT. Particles in the control group were not visible. For modified particles of both sizes, SNRs measured on MR imaging decreased significantly after embolization (eg, cluster analysis of group A, 100 µm ± 50 particles, T1-weighted, -74.6% ± 3.4; P = .03). For modified particles of both sizes, SNR measured on CT increased significantly after embolization (eg, cluster analysis of group A, 700 µm ± 25 particles, +54.3% ± 13.5; P = .03). CONCLUSIONS: Modification of currently available Embozene Microspheres was successful, with multimodal visibility on radiography, MR imaging, and CT in porcine liver. In the future, this might improve procedure accuracy and allow monitoring, control, and improvement of embolotherapy during and after the procedure.

Portal vein embolization using a Histoacryl/Lipiodol mixture before right liver resection.

PURPOSE: The purpose of this retrospective study was to evaluate the efficacy and safety of percutaneous transhepatic portal vein embolization (PVE) of the right liver lobe using Histoacryl/Lipiodol mixture to induce contralateral liver hypertrophy before right-sided (or extended right-sided) hepatectomy in patients with primarily unresectable liver tumors. METHODS: Twenty-one patients (9 females and 12 males) underwent PVE due to an insufficient future liver remnant; 17 showed liver metastases and 4 suffered from biliary cancer. Imaging was performed prior to and 4 weeks after PVE. Surgery was scheduled for 1 week after a CT or MRI control. The primary study end point was technical success, defined as complete angiographical occlusion of the portal vein. The secondary study end point was evaluation of liver hypertrophy by CT and MRI volumetry and transfer to operability. RESULTS: In all the patients, PVE could be performed with a Histoacryl/Lipiodol mixture (n = 20) or a Histoacryl/Lipiodol mixture with microcoils (n = 1). No procedure-related complications occurred. The volume of the left liver lobe increased significantly (p < 0.0001) by 28% from a mean of 549 ml to 709 ml. Eighteen of twenty-one patients (85.7%) could be transferred to surgery, and the intended resection could be performed as planned in 13/18 (72.3%) patients. CONCLUSION: Preoperative right-sided PVE using a Histoacryl/Lipiodol mixture is a safe technique and achieves a sufficient hypertrophy of the future liver remnant in the left liver lobe.

Superselective embolization for the management of postpancreatectomy hemorrhage: a single-center experience in 25 patients.

PURPOSE: To evaluate the efficacy of superselective embolization in patients with late postpancreatectomy hemorrhage (PPH). MATERIALS AND METHODS: Between January 2002 and July 2010, 25 patients (19 men) with suspected late PPH (> 24 hours after the operation) were evaluated. The primary study endpoint was technical success, defined as complete angiographic occlusion of the site of hemorrhage. Secondary study endpoints were multidetector computed tomography (CT) and angiographic findings regarding accurate detection of the site of hemorrhage, persistence of hemorrhage, or occurrence of rebleeding during clinical follow-up. RESULTS: Multidetector CT was performed before the intervention in 17 (68%) patients with detection of hemorrhage in 15 (88%) patients. The site of hemorrhage was detected in 23 (92%) of 25 patients by angiography. Four (17%) patients required a superselective catheter position. Embolization was attempted in all 23 patients with angiographically visible hemorrhage. In three (13%) patients, embolization could not be performed because a superselective catheter position was not achievable. Technical success was 83% (19 patients). In one patient, hemostasis was not achieved by embolization. Minor complications occurred in three (13%) patients. No major complications occurred. Three patients with technically successful embolization (16%) had a second episode of bleeding during follow-up and required repeat embolization 5-23 days after the procedure. The 30-day mortality rate was 20%. CONCLUSIONS: Superselective embolization is a technically and clinically effective procedure in patients with late PPH. Diagnostic angiography should be performed with a superselective microcatheter position to detect the bleeding site effectively.