[Locoregional and local ablative treatment options for liver tumors]. / Lokoregionäre und lokal ablative Therapien von Lebertumoren.

Interventional radiology offers a large variety of locoregional and local ablative treatment options for liver tumors. These can be applied as stand-alone minimally invasive procedures or in combination with other treatment options and with curative as well as palliative intent depending on the respective tumor stage. This review article presents the various locoregional and local ablative treatment techniques and describes the clinical value in the treatment of hepatocellular carcinoma and intrahepatic cholangiocarcinoma.

High-resolution flat panel CT versus 3-T MR arthrography of the wrist: initial results in vivo.

OBJECTIVES: The objective of this study was to compare the diagnostic performance of direct C-arm flat panel computed tomography arthrography (FPCT-A) with direct magnetic resonance arthrography (MR-A) of the wrist in patients with clinically suspected pathologies. METHODS: Forty-nine patients underwent tri-compartmental wrist arthrography. FPCT-A was acquired using a high-resolution acquisition mode, followed by a 3-T MR exam using a dedicated wrist coil. Image quality and artifacts of FPCT-A and MR-A were evaluated with regard to the depictability of anatomical structures. The time stamps for the different image acquisitions were recorded for workflow assessment. RESULTS: Image quality was rated significantly superior for all structures for FPCT-A (p < 0.001) as compared to MR-A including intrinsic ligaments, TFCC, cartilage, subchondral bone, and trabeculae. The differences in image quality were highest for cartilage (2.0) and lowest for TFCC (0.9). The artifacts were rated lower in MR-A than in FPCT-A (p < 0.001). The procedure was more time-efficient in FPCT-A than in MR-A. CONCLUSIONS: FPCT-A of the wrist provides superior image quality and optimized workflow as compared to MR-A. Therefore, FPCT-A should be considered in patients scheduled for dedicated imaging of the intrinsic structures of the wrist. KEY POINTS: • FPCT arthrography allows high-resolution imaging of the intrinsic wrist structures. • The image quality is superior as compared to MR arthrography. • The procedure is more time-efficient than MR arthrography.

Evaluation of a newly developed 2D parametric parenchymal blood flow technique with an automated vessel suppression algorithm in patients with chronic thromboembolic pulmonary hypertension undergoing balloon pulmonary angioplasty.

AIM: To evaluate the feasibility of two-dimensional parametric parenchymal blood flow (2D-PPBF) to quantify perfusion changes in the lung parenchyma following balloon pulmonary angioplasty (BPA) for treatment of chronic thromboembolic pulmonary hypertension. MATERIALS AND METHODS: Overall, 35 consecutive interventions in 18 patients with 98 treated pulmonary arteries were included. To quantify changes in pulmonary blood flow using 2D-PPBF, the acquired digital subtraction angiography (DSA) series were post-processed using dedicated software. A reference region of interest (ROI; arterial inflow) in the treated pulmonary artery and a distal target ROI, including the whole lung parenchyma distal to the targeted stenosis, were placed in corresponding areas on DSA pre- and post-BPA. Half-peak density (HPD), wash-in rate (WIR), arrival to peak (AP), area under the curve (AUC), and mean transit time (MTT) were assessed. The ratios of the reference ROI to the target ROI (HPDparenchyma/HPDinflow, WIRparenchyma/WIRinflow; APparenchyma/APinflow, AUCparenchyma/AUCinflow, MTTparenchyma/MTTinflow) were calculated. The relative differences of the 2D-PPBF parameters were correlated to changes in the pulmonary flow grade score. RESULTS: The pulmonary flow grade score improved significantly after BPA (1 versus 3; p<0.0001). Likewise, the mean HPDparenchyma/HPDinflow (-10.2%; p<0.0001), APparenchyma/APinflow (-24.4%; p=0.0007), and MTTparenchyma/MTTinflow (-3.5%; p=0.0449) decreased significantly, whereas WIRparenchyma/WIRinflow (+82.4%) and AUCparenchyma/AUCinflow (+58.6%) showed a significant increase (p<0.0001). Furthermore, a significant correlation between changes of the pulmonary flow grade score and changes of HPDparenchyma/HPDinflow (ρ=-0.21, p=0.04), WIRparenchyma/WIRinflow (ρ=0.43, p<0.0001), APparenchyma/APinflow (ρ=-0.22, p=0.03), AUCparenchyma/AUCinflow (ρ=0.48, p<0.0001), and MTTparenchyma/MTTinflow (ρ=-0.39, p<0.0001) could be observed. CONCLUSION: The 2D-PPBF technique is feasible for the quantification of perfusion changes following BPA and has the potential to improve monitoring of BPA.

Optimal table feed in run-off CT angiography in patients with abdominal aortic aneurysms.

OBJECTIVES: To assess the influence of different table feeds (TFs) on vascular enhancement and image quality in patients with an abdominal aortic aneurysm (AAA) undergoing computed tomography (CT) angiography of the lower extremities (run-off CTA). METHODS: Seventy-nine patients (71 ± 8 years) with an AAA (>30 mm) who underwent run-off CTA between January 2004 and August 2011 were included in this retrospective institutional review board-approved study. Run-off CTA was conducted using 16- and 64-row CT. The range of TFs was 30-86 mm/s and was categorised in quartiles TF1 (32.6 ± 1.9 mm/s), TF2 (38.9 ± 0.9 mm/s), TF3 (43.9 ± 3.1 mm/s) and TF4 (57.4 ± 10.5 mm/s). Image quality was rated independently by two radiologists and vessel enhancement was assessed. RESULTS: Image quality was diagnostic at all aortic, pelvic and almost all thigh levels. Below the knee, the number of diagnostic levels was highest for TF1 and decreased to TF4. Arterial enhancement between the aorta and fibular trunk was not different in all TF groups, P > 0.05. At the calf and foot strongest arterial enhancement was noted for TF1 and TF2 and decreased to TF4, P < 0.01. CONCLUSION: Results indicate that the highest image quality of run-off CTA in patients with an AAA may be obtained using table feeds measuring 30-35 mm/s. KEY POINTS: • CTA has become a key investigation for peripheral vascular disease. • Run-off CTA is more complex in patients with an abdominal aortic aneurysm. • Run-off CTA is feasible with a short bolus of intravenous contrast medium. • A constant 30-35 mm/s table feed provides the highest likelihood of diagnostic images.

Percutaneous Transsplenic Balloon-Assisted Transjugular Intrahepatic Portosystemic Shunt Placement in Patients with Portal Vein Obliteration for Portal Vein Recanalization: Feasibility, Safety and Effectiveness.

PURPOSE: To assess the feasibility, safety and effectiveness of portal vein recanalization (PVR)-transjugular portosystemic shunt (TIPS) placement via splenic access using a balloon puncture technique. MATERIALS AND METHODS: In a single-center retrospective study from March 2017 to February 2021, 14 consecutive patients with portal hypertension, chronic liver disease and portal vein occlusion or near-complete (> 95%) occlusion were referred for PVR-TIPS placement. Feasibility, safety and effectiveness including procedural characteristics such as technical success, complication profile and splenic access time (SAT), balloon positioning time (BPT), conventional portal vein entry time (CPVET), overall procedure time (OPT), fluoroscopy time (FT), dose-area product (DAP) and air kerma (AK) were evaluated. RESULTS: Transsplenic PVR-TIPS using balloon puncture technique was technically feasible in 12 of 14 patients (8 men, 49 ± 13 years). In two patients without detectable intrahepatic portal vein branches, TIPS placement was not feasible and both patients were referred for further treatment with nonselective beta blockers and endoscopic variceal ligation. No complications grade > 3 of the Cardiovascular and Interventional Radiological Society of Europe classification system occurred. The SAT was 25 ± 21 min, CPVET was 33 ± 26 min, the OPT was 158 ± 54 min, the FT was 42 ± 22 min, the DAP was 167.84 ± 129.23 Gy*cm2 and the AK was 1150.70 ± 910.73 mGy. CONCLUSIONS: Transsplenic PVR-TIPS using a balloon puncture technique is feasible and appears to be safe in our series of patients with obliteration of the portal vein. It expands the interventional options in patients with chronic PVT.

Predictive Parameters in Patients Undergoing Percutaneous Hepatic Perfusion with Melphalan for Unresectable Liver Metastases from Uveal Melanoma: A Retrospective Pooled Analysis.

PURPOSE: The aim of this study was to identify positive predictors for survival in uveal melanoma (UM) patients treated with percutaneous hepatic perfusion with melphalan (M-PHP), by retrospectively pooling data from three centers. MATERIALS AND METHODS: Retrospective analysis including patients ([Formula: see text] 18 years) treated with M-PHP between February 2014 and December 2019 for unresectable liver-dominant or liver-only metastases from UM. Predictors for OS were assessed using uni- and multivariate analyses. Other study outcome measures were response rate, progression-free survival (PFS), liver progression-free survival (LPFS), overall survival (OS) and complications according to CTCAEv5.0. RESULTS: In total, 101 patients (47.5% males; median age 59.0 years) completed a minimum of one M-PHP. At a median follow-up time of 15.0 months, complete response (CR), partial response (PR), stable disease (SD) and progressive disease were seen in five (5.0%), 55 (54.5%), 30 (29.7%) and 11 (10.9%) patients, respectively, leading to a 89.1% disease control rate. Median PFS, LPFS and OS were 9.0, 11.0 and 20.0 months, respectively. Survival analyses stratified for radiological response demonstrated significant improved survival in patients with CR or PR and SD category. Treatment of the primary tumor with radiotherapy, ≥ 2 M-PHP and lactate dehydrogenase (LDH) < 248 U/L were correlated with improved OS. Thirty-day mortality was 1.1% (n = 2). Most common complication was hematological toxicity (self-limiting in most cases). CONCLUSION: M-PHP is safe and effective in patients with UM liver metastases. Achieving CR, PR or SD is associated with improved survival. Primary tumor treatment with radiotherapy, normal baseline LDH and > 1 M-PHP cycles are associated with improved OS.

Percutaneous isolated hepatic perfusion (chemosaturation) with melphalan following right hemihepatectomy in patients with cholangiocarcinoma and metastatic uveal melanoma: peri- and post-interventional adverse events and therapy response compared to a matched group without prior liver surgery.

To evaluate feasibility, frequency and severity of peri-procedural complications and post-procedural adverse events (AEs) in patients with advanced cholangiocarcinoma or liver metastasis of uveal melanoma and prior hemihepatectomy undergoing chemosaturation percutaneous hepatic perfusion (CS-PHP) and to analyze therapy response and overall survival compared to a matched group without prior surgery. CS-PHP performed between 10/2014 and 02/2018 were retrospectively assessed. To determine peri-procedural safety and post-procedural adverse events, hospital records and hematological, hepatic and biliary function were categorized using Common Terminology Criteria for Adverse Events (CTCAE) v5.0 (1-5; mild-death). Significance was tested using Wilcoxon signed-rank and Mann-Whitney U test. Kaplan-Meier estimation and log-rank test assessed survival. Overall 21 CS-PHP in seven patients (4/7 males; 52 ± 10 years) with hemihepatectomy (grouphemihep) and 22 CS-PHP in seven patients (3/7 males; 63 ± 12 years) without prior surgery (groupnoresection) were included. No complications occurred during the CS-PHP procedures. Transient changes (CTCAE grade 1-2) of liver enzymes and blood cells followed all procedures. In comparison, grouphemihep presented slightly more AEs grade 3-4 (e.g. thrombocytopenia in 57% (12/21) vs. 41% (9/22; p = 0.37)) 5-7 days after CS-PHP. These AEs were self-limiting or responsive to treatment (insignificant difference of pre-interventional to 21-45 days post-interventional values (p > 0.05)). One patient in grouphemihep with high tumor burden died eight days following CS-PHP. No deaths occurred in groupnoresection. In comparison, overall survival after first diagnosis was insignificantly shorter in groupnoresection (44.7(32-56.1) months) than in grouphemihep (48.3(34.6-72.8) months; p = 0.48). The severity of adverse events following CS-PHP in patients after hemihepatectomy was comparable to a matched group without prior liver surgery. Thus, the performance of CS-PHP is not substantially compromised by a prior hemihepatectomy.

The value of combined soft-tissue and vessel visualisation before transarterial chemoembolisation of the liver using C-arm computed tomography.

The purpose of the study was to prospectively evaluate intrahepatic vessel depiction on C-arm CT (CACT) and the influence of the additional combined tissue and three-dimensional vessel visualisation on the positioning of the TACE catheter in comparison to DSA alone. Thirty consecutive patients scheduled for their first transarterial chemoembolisation underwent biphasic CACT and DSA of the liver. After assessing the DSA images for procedure planning, the CACT images were reviewed. The number and origin of the tumour-feeding arteries and the ideal position of the catheter for TACE on both DSA and CACT were assessed and correlated. The number of vessels identified as tumour feeders in each patient was significantly higher using additional CACT than on DSA alone (CACT: 4.0 +/- 1.7; DSA: 3.3 +/- 1.4; P = 0.003, t-test). After considering CACT, in 50% of the patients the catheter position was changed for TACE. Segmental portal vein thrombosis was seen in three patients on CACT, but in only one on DSA. As CACT depicts soft tissue and small vessels with high spatial resolution, tumour vessel allocation is facilitated, and ideal catheter position for TACE can be more accurately identified. The high impact of CACT on the TACE procedure suggests the benefits of its routine use for all patients undergoing their first TACE.

Magnetic resonance imaging-guided renal artery stent placement in a Swine model: comparison of two tracking techniques.

BACKGROUND: Magnetic resonance (MR)-guided interventions have evolved from a pure research application to a preclinical method over the last decade. Among the device-tracking techniques, susceptibility artifact-based tracking relies on the contrast between the surrounding blood and the device, and radiofrequency coil-based tracking relies on the local gradient field amplification in a resonating circuit attached to the interventional device. PURPOSE: To evaluate the feasibility and precision of susceptibility artifact-based and microcoil-based MR guidance methods for renal artery stent placement in a swine model. MATERIAL AND METHODS: MR imaging-guided renal artery stent placements were performed in six fully anesthetized pigs using a 1.5T short-bore MR scanner. Susceptibility artifact-based tracking with manual scan-plane adjustments and microcoil tracking with automatic scan-plane adjustments were used for renal artery stent placements in three pigs in each group. With both methods, near real-time steady-state free-precession (SSFP) imaging was used. Differences between the two tracking approaches on stenting time, total procedure time, and stent position were measured. RESULTS: The microcoil-based approach yielded a shorter mean procedure time (17 vs. 23 min). There was no relevant difference for the mean stenting time (12 vs. 13 min). The mean stent deviation from the aortic wall with the susceptibility approach was larger than with the microcoil approach (10 vs. 4.0 mm). CONCLUSION: For MRI-guided renal artery stent placement, the microcoil-based technique had a shorter procedure time and a higher stent placement precision than the susceptibility artifact-based approach.

[Flat-detector CT-based electromagnetic navigation]. / Auf Flachdetektor-CT basierende elektromagnetische Navigation.

Flat-detector CT coupled to an angiography device provides an imaging technique for interventions which can be used for electromagnetically navigated percutaneous punctures. This report explains the functionality of an electromagnetic navigation system and describes the course of an electromagnetically navigated puncture and the capabilities of such a system in the clinical routine.

[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.

[Use of C-arm CT for improving the hit rate for selective blood sampling from adrenal veins]. / Einsatz der C-Arm-CT zur Verbesserung der Trefferquote bei selektiver Nebennierenvenen-Blutentnahme.

Primary hyperaldosteronism is the most common curable cause of hypertension with a prevalence of up to 12% among patients with hypertension. Selective blood sampling from adrenal veins is considered the diagnostic gold standard. However, it is underutilized due to the high technical failure rate. The use of C-arm CT during the sampling procedure can reduce or even eliminate this failure rate. If adrenal vein sampling is augmented by native C-arm CT to check for the correct catheter position, the technical success rate increases substantially. General use of this technique will result in correct diagnosis and treatment for patients with primary hyperaldosteronism.

Retrieval of vascular foreign bodies using a self-made wire snare.

BACKGROUND: Foreign bodies in the vascular system have a high potential to cause embolization, perforation, and infection. Therefore, numerous commercially available percutaneous retrieval devices have been developed. PURPOSE: To evaluate the feasibility and efficacy of a self-made wire snare for the retrieval of foreign bodies in the vascular system. MATERIAL AND METHODS: 16 consecutive patients, who underwent percutaneous foreign-body retrieval between 1997 and 2007, were included in this retrospective analysis. Percutaneous extraction was performed using an adjustable wire snare that was fabricated using a 5F diagnostic Headhunter or Multipurpose catheter and a 4-m-long 0.018-g/inch standard heavy-duty wire that was bent in the middle to create an eccentric loop. RESULTS: Percutaneous foreign-body retrieval was successful in all 16 cases. Intraluminal materials including partially fractured venous catheters, guidewires, a stent, and a vena cava filter were removed from various locations. In six cases, mobilization of the intraluminal material via a pigtail catheter was necessary before using the wire snare for removal. Successful retrieval was investigator independent. In no cases were surgical procedures required, and no relevant complications were encountered. CONCLUSION: This snare technique is an effective, feasible, and cost-effective method to retrieve intraluminal material. It is an alternative to commercially available retrieval devices.

Virtual single source CT using dual source acquisition: Clinical applicability in run-off CT-angiography for intra-individual comparison of different scan protocols.

PURPOSE: Virtual single source computed tomography (VSS-CT) acquisition on a dual source CT (DSCT) has been demonstrated to allow for dose-neutral intra-individual comparison of three acquisition protocols at different radiation dose levels (RDL) within one acquisition in a phantom. The purpose of this study was twofold: first to evaluate the applicability of VSS-CT in patients and second to optimize the task-dependent trade-off between radiation dose and image quality of lower extremity CT angiography (run-off CTA). MATERIAL AND METHODS: In this IRB-approved prospective study 52 patients underwent run-off CTA between 06/2012 and 06/2013. VSS-CT acquisition was conducted using a first generation DSCT applying equal X-ray tube settings (120 kVp), collimation (2 × 32 × 0.6 mm), and slice thickness (1.0 mm) but different effective tube current-time products (tube A: 80 mAs, tube B: 40 mAs). Three different image datasets representing three different radiation dose levels (RDL40, RDL80, RDL120) were reconstructed using a soft kernel from the raw data of tube B, tube A or both tubes combined. Dose length products (DLP) of each raw data set were documented. Quantitative image quality (IQ) was assessed for five anatomical levels using image noise and contrast-to-noise ratio (CNR). To investigate dose efficiency of each acquisition, the dose-weighted CNR (CNRD) was determined. Qualitative IQ was evaluated by two blinded readers in consensus using a 5-point Likert scale and compared with a Friedman- and posthoc Wilcoxon test. RESULTS: Mean DLP was 200 ±â€¯40, 400 ±â€¯90 and 600 ±â€¯130 mGy·cm for the RDL40, RDL80 and RDL120, respectively. Image noise and CNR were best for RDL120 and decreased significantly for RDL80 and RDL40, independent of the anatomic level (p < 0.001). CNRD showed no significant differences at the abdominal and pelvic level between the investigated radiation dose levels. However, for thigh to foot level a significant increase of CNRD was noted between RDL120, RDL80 and RDL40. Significant differences of qualitative IQ were observed between RDL120 and RDL40 from the abdominal to the foot level, whereas no difference was seen for the other dose levels. CONCLUSION: Radiation dose splitting with VSS-CT can be applied to run-off CTA facilitating intra-individual comparison of different acquisition protocols without additional radiation exposure. Furthermore, a radiation dose reduction potential for run-off CTA of approximately 1/3 as compared to the acquisition protocol recommended by the manufacturer could be identified in this study.

[Magnetic resonance imaging-guided endovascular interventions]. / Magnetresonanztomografie-gestützte endovaskuläre Interventionen.

Historically, the combination of relatively long imaging times and restricted patient access has made MRI-guided intervention an impractical technique. Recent developments in MR hardware, pulse sequence improvements that have allowed the development of rapid imaging, and the availability of instruments that can be used under MR guidance have helped to overcome many of the disadvantages of MRI. Parallel to the development of MRI, image-guided percutaneous and endovascular interventions are becoming increasingly complex and require progressively more sophisticated imaging techniques to guide and control such interventions. These initially parallel trends have converged in the last couple of years. The ability of MRI to provide both unprecedented morphology and functional information has created a growing interest in both percutaneous and endovascular MRI-guided interventions. The goal of this review is to describe the technical prerequisites for MR-guided endovascular interventions, to discuss experimental and clinical applications, and to explain safety aspects of this technique.

[Alternate hemodialysis catheterization access in patients with occluded peripheral venous access sites]. / Alternative Zugangswege für Hämodialysekatheter bei Patienten mit verschlossenen peripheren venösen Zugangswegen.

PURPOSE: The goal of this study was to evaluate translumbar and transhepatic placement of hemodialysis (HD) catheters for patients with occlusion of the veins that are commonly used for hemodialysis access. METHOD: Over a 12-month period three translumbar and one transhepatic hemodialysis catheters were placed in 4 patients suffering from end-stage renal disease, who had thrombosis of the upper and lower extremity veins as well as the jugular veins. The percutaneous access was performed under fluoroscopic guidance. After successful passage of a guidewire into the right atrium and creation of a subcutaneous tunnel at the skin entry site, all patients received a 14 F double-lumen catheter that was placed with its tip in the right atrium. RESULTS: Percutaneous translumbar and transhepatic placement of the HD catheters was successful in all patients. No intervention-associated complications were observed. Hemodialysis could be started 1 to 20 hours after initial catheter placement in all patients. During an observation period of 3 to 7 months, 3 patients underwent hemodialysis without any complications. In one patient, an occlusion of an translumbar HD catheter was observed after 5 months. This catheter could be temporarily recanalized using rTPA injection and was then exchanged after 6 months. CONCLUSION: Transhepatic and translumbar placement of HD catheters is a safe and viable alternative for patients who have exhausted conventional venous access sites.

Integrative teaching in radiology - a survey.

PURPOSE: To survey integrative teaching in radiology at German universities. MATERIALS AND METHODS: A questionnaire about radiological education was sent electronically to all 37 chairpersons of university radiology departments in Germany. The questions included the course type, teaching methods, concept, perception, and advantages and disadvantages of integrative teaching. Statistical analysis was performed with nonparametric statistics and chi-square test. RESULTS: The survey was considered representative with a return rate of 68 %. Integrative teaching is established at 4/5 of all departments. Integrative teaching is well accepted with an acceptance rate that is significantly higher in so-called "Modellstudiengängen" [model courses of study] (100 %) compared to conventional courses of study (72 %). The advantages of integrative teaching include linking of content (92 %) and preparation for interdisciplinary work (76 %). The disadvantages include high effort (75 %) and time (67 %) for organization. Furthermore, there is a risk that basic radiological facts and knowledge cannot be conveyed and that the visibility of radiology as an independent discipline is lost. Conventional radiological teaching has a similarly high acceptance (84 %) compared to integrative courses (76 %). CONCLUSION: Integrative teaching has a high acceptance among chairpersons in radiology in Germany despite the greater effort. A good interdisciplinary collaboration is essential for integrative teaching and at the same time this can be conveyed to the students. However, the visibility of radiology as a discipline and the possibility to cover basic radiological content must be ensured. Therefore, both conventional courses and integrative teaching seems reasonable, especially in cross-disciplinary subjects such as radiology. KEY POINTS: Both integrative teaching and conventional radiological teaching are highly accepted. The advantages include the linking of multidisciplinary content and the preparation for interdisciplinary cooperation. The disadvantages include more time and effort for organization and reduced visibility of cross-disciplinary subjects.

Visualization, tracking, and navigation of instruments for magnetic resonance imaging-guided endovascular procedures.

Interventional procedures using magnetic resonance imaging (MRI) guidance have increased in interest during the last few years. Central to the success and safety of MRI-guided procedures is the accurate visualization of the interventional instruments relative to the surrounding anatomy. A variety of methodologies for visualizing and automatically tracking instruments, including needles, radiofrequency and laser ablation devices, endoscopes, catheters, and guidewires have been developed and introduced to help the interventionalist to safely guide the device toward the target region. This article describes and compares characteristics of the four most commonly used localization and tracking systems used for MRI-guided interventional procedures: those based on the susceptibility artifact of the device, those that intentionally create field inhomogeneity along the device, those that rely on an optical tracking system, and active tracking systems using micro receive coils.

MR imaging-guided biliary drainage in an open low-field system: first clinical experiences.

PURPOSE: To test the feasibility of MR imaging (MRI)-guided percutaneous biliary drainages in patients using an open MR-system. METHODS: 6 patients with mechanical cholestasis underwent MRI-guided puncture and catheterization of the biliary system following intervention planning with magnetic resonance cholangiography (MRC) in an open low-field MR system. Data on the number of punctures required, success in establishing external and internal drainage, and total procedure time were compared to those of 6 patients who underwent biliary drainage with fluoroscopic guidance. RESULTS: MRC facilitated intervention planning in all patients. Near-real-time MR imaging enabled interactive positioning of the devices. The bile ducts were punctured under MRI control in three patients in the first, in two in the second, and in one in the third attempt. MRI-guided puncture was faster than the fluoroscopic procedure. Catheterization for external drainage was successful in all patients. Passing the obstructions was not possible under MRI guidance. The procedure time for MRI-guided catheterization was longer than in the conventional technique. CONCLUSION: MRI-guidance allows reliable placement of an external biliary drainage in an open low-field MR system.

[A head-mounted display system for augmented reality: initial evaluation for interventional MRI]. / Augmentierte Realität mit einem brillenähnlichen Monitor: Erste Erfahrungen in Kombination mit interventioneller MRT.

PURPOSE: To discuss the technical details of a head mounted display with an augmented reality (AR) system and to describe a first pre-clinical evaluation in interventional MRI. METHOD: The AR system consists of a video-see-through head mounted display (HMD), mounted with a mini video camera for tracking and a stereo pair of mini cameras that capture live images of the scene. The live video view of the phantom/patient is augmented with graphical representations of anatomical structures from MRI image data and is displayed on the HMD. The application of the AR system with interventional MRI was tested using a MRI data set of the head and a head phantom. RESULTS: The HMD enables the user to move around and observe the scene dynamically from various viewpoints. Within a short time the natural hand-eye coordination can easily be adapted to the slightly different view. The 3D perception is based on stereo and kinetic depth cues. A circular target with a diameter of 0.5 square centimeter was hit in 19 of 20 attempts. In a first evaluation the MRI image data augmented reality scene of a head phantom allowed good planning and precise simulation of a puncture. CONCLUSION: The HMD in combination with AR provides a direct, intuitive guidance for interventional MR procedures.