Boris Radeleff

In vivo accuracy assessment of a needle-based navigation system for CT-guided radiofrequency ablation of the liver.

Computed tomography (CT)-guided percutaneous radiofrequency ablation (RFA) has become a commonly used procedure in the treatment of liver tumors. One of the main challenges related to the method is the exact placement of the instrument within the lesion. To address this issue, a system was developed for computer-assisted needle placement which uses a set of fiducial needles to compensate for organ motion in real time. The purpose of this study was to assess the accuracy of the system in vivo. Two medical experts with experience in CT-guided interventions and two nonexperts used the navigation system to perform 32 needle insertions into contrasted agar nodules injected into the livers of two ventilated swine. Skin-to-target path planning and real-time needle guidance were based on preinterventional 1 mm CT data slices. The lesions were hit in 97% of all trials with a mean user error of 2.4 +/- 2.1 mm, a mean target registration error (TRE) of 2.1 +/- 1.1 mm, and a mean overall targeting error of 3.7 +/- 2.3 mm. The nonexperts achieved significantly better results than the experts with an overall error of 2.8 +/- 1.4 mm (n=16) compared to 4.5 +/- 2.7 mm (n=16). The mean time for performing four needle insertions based on one preinterventional planning CT was 57 +/- 19 min with a mean setup time of 27 min, which includes the steps fiducial insertion (24 +/- 15 min), planning CT acquisition (1 +/- 0 min), and registration (2 +/- 1 min). The mean time for path planning and targeting was 5 +/- 4 and 2 +/- 1 min, respectively. Apart from the fiducial insertion step, experts and nonexperts performed comparably fast. It is concluded that the system allows for accurate needle placement into hepatic tumors based on one planning CT and could thus enable considerable improvement to the clinical treatment standard for RFA procedures and other CT-guided interventions in the liver. To support clinical application of the method, optimization of individual system modules to reduce intervention time is proposed.

Computer-assisted trajectory planning for percutaneous needle insertions

PURPOSE Computed tomography (CT) guided minimally invasive interventions such as biopsies or ablation therapies often involve insertion of a needle-shaped instrument into the target organ (e.g., the liver). Today, these interventions still require manual planning of a suitable trajectory to the target (e.g., the tumor) based on the slice data provided by the imaging modality. However, taking into account the critical structures and other parameters crucial to the success of the intervention--such as instrument shape and penetration angle--is challenging and requires a lot of experience. METHODS To overcome these problems, we present a system for the automatic or semiautomatic planning of optimal trajectories to a target, based on 3D reconstructions of all relevant structures. The system determines possible insertion zones based on so-called hard constraints and rates the quality of these zones by so-called soft constraints. The concept of pareto optimality is utilized to allow for a weight-independent proposal of insertion trajectories. In order to demonstrate the benefits of our method, automatic trajectory planning was applied retrospectively to n = 10 data sets from interventions in which complications occurred. RESULTS The efficient (graphics processing unit-based) implementation of the constraints results in a mean overall planning time of about 9 s. The examined trajectories, originally chosen by the physician, have been rated as follows: in six cases, the insertion point was labeled invalid by the planning system. For two cases, the system would have proposed points with a better rating according to the soft constraints. For the remaining two cases the system would have indicated poor rating with respect to one of the soft constraints. The paths proposed by our system were rated feasible and qualitatively good by experienced interventional radiologists. CONCLUSIONS The proposed computer-assisted trajectory planning system is able to detect unsafe and propose safe insertion trajectories and may especially be helpful for interventional radiologist at the beginning or during their interventional training.

Arterial Distribution Characteristics of Embozene Particles and Comparison with Other Spherical Embolic Agents in the Porcine Acute Embolization Model

PURPOSE To determine the arterial distribution pattern of the embolic agent Embozene within the porcine kidney and compare it with those of other spherical embolic agents. MATERIALS AND METHODS Embozene, Embosphere, Bead Block, and Contour SE in size classes of 100-300 microm, 500-700 microm, and 700-900 microm and Embozene and Embosphere in the size class of 40-120 microm were used for total arterial occlusion in minipig kidneys. Organs were evaluated microscopically regarding vascular distribution of the different embolic agents and particle sizes. RESULTS The following variations of arterial distribution were identified. In the 40-120-microm size class, Embosphere particles penetrated significantly deeper compared with Embozene (P = .04). In the 100-300-microm size class, Bead Block showed a significantly deeper distribution as microscopy identified particles in arteries much smaller than their nominal size. In the 500-700-microm size class, Embosphere and Contour SE showed a deeper distribution. The most uniform arterial distribution was observed in the 700-900 microm size class,. However, few Embosphere and Contour SE particles were found in arcuate arteries, also indicating a distal distribution. CONCLUSIONS Throughout the four most-used size classes, from very small (40-120 microm) to large (700-900 microm), the distribution characteristics of the four tested materials vary substantially. Particularly, small Embosphere particles and small Bead Block particles showed a more distal distribution, as did medium-sized Embosphere and Contour SE particles. In the largest investigated size class, the distribution was more uniform. In general, the Embozene particles are very uniform in size, and they seem to reach vessels closely corresponding to their nominal size.

Inflammation and Recanalization of Four Different Spherical Embolization Agents in the Porcine Kidney Model

PURPOSE To evaluate the pattern of recanalization and specific inflammatory reaction after superselective embolization with four commercially available spherical embolic agents of different sizes in the mini pig kidney model. MATERIALS AND METHODS In 40 mini pigs, the lower poles of both kidneys were superselectively embolized with Embozene, Embosphere, Bead Block, and Contour SE particles in sizes of 40-120 mircom (Embozene, Embosphere) and 100-300 microm, 500-700 microm, and 700-900 microm (Embozene, Embosphere, Bead Block, Contour SE). After a follow-up time of 4 or 12 weeks, recanalization was determined with angiography. Pathologic and histologic evaluation of the kidneys was performed, and the Banff 97 classification was used to evaluate the extent of vessel wall inflammation. Macroscopically visible ischemic changes were evaluated by using a specific ischemia score. RESULTS After embolization with Embozene microspheres, larger Embosphere particles, and Bead Block and Contour SE particles, the absence of inflammation or a low inflammation score was observed. Significantly elevated inflammation scores were evident with small Embosphere particles after 4 weeks (mean score, 1.21 +/- 1.0). Distinct recanalization occurred with Contour SE particles (100% recanalization with 100-300-microm particles at 12 weeks, 500-700-microm particles at 4 and 12 weeks, and 700-900-microm particles at 4 weeks). Ischemia scores were highest in the target area in all specimens. Mildly elevated ischemia scores in nontarget tissue areas were indicative of minor nontarget embolization. CONCLUSIONS Except for small Embosphere particles at 4 weeks, the absence of inflammatory reaction to the embolization procedure or only low inflammatory changes were observed with all embolic agents, particle sizes, and follow-up intervals. Recanalization was evident with all embolic agents; however, it was pronounced with Contour SE particles.

Expulsion of dominant submucosal fibroids after uterine artery embolization

PURPOSE Purpose of this study was to evaluate the frequency, probability, and factors associated with expulsion of submucosal fibroids after uterine artery embolization (UAE) in addition to the technical and clinical results at 1-year follow-up. MATERIALS AND METHODS We determined the preinterventional volume of each dominant submucosal fibroid using the commonly used ellipsoid formula and a 3D volumetry in the MRI to define a threshold value in milliliters that indicates the probability for a fibroid expulsion. Assessment of fibroid expulsion was done by MRI at 3-month intervals for a year. Assessment of clinical mid term success was achieved by applying questionnaires at 1-year follow-up. RESULTS Technical success was observed in all 20 patients (mean age of 41.4+/-5.6 years; range: 29.2-51.1 years). Two (10%) minor and one (5%) major complications occurred. 10/20 dominant submucosal fibroids were completely expelled during the follow-up. Using 3D MRI volumetry the preinterventional mean volume of the later expelled fibroids was 56.8+/-57.0 ml (range 2.3-198.0 ml) and the mean volume of non-expelled fibroids was 123.8+/-147.3 ml (range 24.0-531.8 ml). This difference was statistically significant, but weak (p=0.0494). Fibroids with a volume equal or less than the threshold value (66.0 ml) were 73% likely to be expelled and fibroids larger than 66.0 ml were 78% likely not to be expelled. All 20 patients demonstrated a significant reduction in the fibroid related symptoms. CONCLUSION In our study the complication rate was low despite increased rates of fibroid expulsion (50%); simultaneously the rate of treatment satisfaction was very high. Patients with a dominant submucosal fibroid under 66.0 ml should be informed about the probability of fibroid expulsion and the accompanying symptoms.

Branching patterns and drainage territories of the middle hepatic vein in computer-simulated right living-donor hepatectomies.

Full right hepatic grafts are most frequently used for adult‐to‐adult living donor liver transplantation (LDLT). One of the major problems is venous drainage of segments 5 and 8. Thus, this study was designed to provide information on venous drainage of right liver lobes for operation‐planning. Fifty‐six CT data sets from routine clinical imaging were evaluated retrospectively using a liver operation‐planning system. We defined and analyzed venous drainage segments and the impact of anatomic variations of the middle hepatic vein (MHV) on venous outflow from segments 5 and 8. MHV variations led to significant shifts of segment 5 drainage between the middle and right hepatic vein. In cases with the most frequent MHV branching pattern (n = 33), a virtual hepatectomy closely right to the MHV intersected drainage vessels that provided drainage for 30% of the potential graft, not taking into account potential veno‐venous shunts. In individuals with inferior MHV branches that extend far into segments 5 and 6 (n = 10), the overall graft volume at risk of impaired venous drainage increased by 5% (p < 0.001). If this is confirmed in clinical trials and correlated with intraoperative findings, the use of liver operation‐planning systems would be beneficial to improve overall outcome after right lobe LDLT.

Analysis of Nontarget Embolization Mechanisms During Embolization and Chemoembolization Procedures

Complications of embolization and chemoembolization remain a problem even with the development of low-profile catheter material and the introduction of new embolization agents. In recent years many new embolization materials have become available for clinical use, so the possibilities and limitations of these new materials must be understood to allow safe and effective embolization. Although up to now some scientific work has been published reporting the basic risk of embolization procedures, the underlying pathomechanism remains the object of speculation. Besides complications like drug toxicity, allergic reactions, and bleeding of the puncture site, the characteristics of embolization materials must be known to understand the potential complications of nontarget embolization and reflux of embolization material. This article gives an overview of established and new embolization materials, their potential risks, and the underlying pathophysiology.

The efficacy of nanoscale poly[bis(trifluoroethoxy) phosphazene] (PTFEP) coatings in reducing thrombogenicity and late in-stent stenosis in a porcine coronary artery model.

Objectives:Previous experimental studies have demonstrated that poly[bis(trifluoroethoxy)phosphazene] (PTFEP) nanocoated stents have antithrombotic characteristics, reduce in-stent stenosis, prevent wall inflammation, and do not hamper endothelialization. This study was designed to validate these findings in a porcine coronary artery model. Materials and Methods:PTFEP-coated (n = 15) and bare stents (n= 13) were implanted in coronary arteries of 18 mini-pigs (4- and 12-week follow-up). Primary study endpoints were thrombogenicity and in-stent stenosis, secondary study endpoints were inflammatory response and re-endothelialization evaluated by quantitative angiography and light microscopy. Results:No thrombus deposition occurred on any stent. At 4 weeks follow-up, the bare stents (n = 4) had a significantly smaller neointimal area (1.93 vs. 3.20 mm2, P = 0.009). At 12 weeks, PTFEP-coated stents (n = 11) had significantly superior results in almost all parameters: neointimal area (2.25 vs. 2.65 mm2, P = 0.034), neointimal height (204.46 vs. 299.41 &mgr;m, P = 0.048), percentage stenosis (38.25 vs. 50.42%, P = 0.019), and inflammation score (0.12 vs. 0.30, P = 0.029). Complete re-endothelialization was seen in both stent types at both intervals. Conclusion:At long-term follow-up, the superior results of PTFEP-coated stents were characterized by a noteworthy reduction of neointimal growth and inflammatory response.

Acute Pancreatitis after Embolization of Liver Tumors: Frequency and Associated Risk Factors

Introduction: Acute pancreatitis (AP) is a rare complication after liver embolization (LE) of primary and secondary liver tumors (approximately 1.7%), but it has a significant morbidity and mortality potential if associated with other complications. It usually develops early within 24 h after the LE procedure. Study Purpose: To calculate the frequency of AP after LE in our institution and to analyze the factors involved in this procedure (anatomical features, embolization materials, cytostatic drugs, technical factors). Materials and Methods: 118 LE (bland embolization and transarterial chemoembolization) were performed in our institution. The study group included 59 patients who met the following inclusion criteria: one or more LE events, with complete pre- and post-interventional laboratory studies including: serum Ca2+, creatinine, blood urea nitrogen, glucose, lactate dehydrogenase, aminotransferases, alkaline phosphatase, amylase, lipase, C-reactive protein, hematocrit and leukocytes. The diagnosis of AP was established according to the criteria of the Atlanta system of classification. For the statistical analysis the association between two response variables (e.g. AP after embolization and risk factor during the embolization, AP after embolization and volume of embolic material) was evaluated using Pearson’s χ2 test and Fisher’s exact test. Results: The calculated frequency of AP after LE in our series was 15.2%. Amylase and lipase were elevated up to 8.7 and 20.1 times, respectively, 24 h after LE. We observed a statistically significantly lower incidence of AP in those patients who received 2 ml or less of embospheres compared with those with an embolization volume of >2 ml (Pearson’s χ2 = 4.5000, Pr = 0.034, Fisher’s exact test = 0.040). Although carboplatin was administered to 7 of 9 of the patients who developed AP after the embolization procedure, there was no statistical significance (Fisher’s exact test = 0.197) for carboplatin as an AP risk factor when compared with all the patients who received this drug (n = 107). Conclusion: Although AP after LE seems to have a multifactorial etiology, both the toxicity of the antineoplastic drugs (carboplatin-related toxicity) as well as direct ischemic mechanisms (non-target embolization, reflux mechanisms) may be the most important causes of the inflammatory pancreatic reaction after LE. We suggest that systematic measurement of serum pancreatic enzymes should be performed in cases of abdominal pain following selective LE and transarterial chemoembolization in order to confirm acute pancreatitis after embolization, which can clinically mimic a postembolization syndrome.

Dual-energy computed-tomography cholangiography in potential donors for living-related liver transplantation: initial experience

Objectives:To report our initial experience with dual-energy computed-tomography (CT) cholangiography in potential donors for living-related liver transplantation. Materials and Methods:Seventeen potential donors for living-related liver transplantation (6 women and 11 men; average age 37.8 ± 10.4 years) underwent contrast-enhanced dual-energy CT cholangiography. A dual-energy CT scan of the liver was carried out with acquisition of 2 raw datasets at tube currents of 140 and 80 kV, respectively. A third weighted average dataset were obtained (weighting ratio: 70% 140 kV, 30% 80 kV). Pure iodine images (fourth dataset) and contrast-optimized images (fifth dataset) were reconstructed. Analysis of all datasets comprised determination of bile duct visualization scores (on a scale of 1 to 4: 1, not visualized; 2, faintly seen; 3, identified but the origin or portions of the duct are not visualized; and 4, excellent visualization from origin to branches), maximum bile duct diameters, bile duct attenuation, and liver parenchyma attenuation as well as image noise, signal-to-noise ratio, and contrast-to-noise ratio. Results:Highest maximum bile duct diameters were detected for optimized-contrast images and the 80 kV dataset, intermediate for pure iodine images and the weighted average dataset and lowest for the 140 kV dataset with significant differences. Highest bile duct attenuation was detected for optimized-contrast images (535.7 ± 148.3 HU) and the 80 kV dataset (533.7 ± 145.9 HU) with significant differences compared with pure iodine images (344.9 ± 106.5 HU) and the weighted average dataset (355.5 ± 87.6 HU) (P < 0.001). Highest image noise was detected for the 80 kV dataset (39.3 ± 5.4 HU) with significant differences compared with the optimized-contrast images (31.5 ± 4.0) (P < 0.001). Highest signal-to-noise ratio and contrast-to-noise ratio were detected for pure iodine images (18.3 ± 7.1 and 17.6 ± 7.0) and optimized-contrast images (17.3 ± 5.8 and 14.8 ± 5.5) with significant differences compared with the 80 kV dataset (14.0 ± 5.2 and 11.8 ± 4.8) and the weighted average dataset (15.1 ± 4.4 and 12.1 ± 4.1) (P < 0.001 and P < 0.01). Conclusions:Dual-energy CT cholangiography in potential donors for living-related liver transplantation is remarkable. Pure iodine images and contrast-optimized images allow precise analysis of the biliary system with increased image quality compared with conventional images. Contrast-optimized images should be used for detection and localization of the bile ducts and pure iodine images for quantitative description of the anatomic dimensions of the biliary segments.