Nitinol Guidewire Research Articles

Positive contrast spiral imaging of a nitinol guidewire

Background The clinical translation of MRI-guided cardiovascular catheterization has been limited by the unavailability of devices that are both visible and safe under MRI. In particular, rigid metallic guidewires are essential for most catheterization procedures and are at risk of heating during MR imaging [1]. Here we present an MRI method that simultaneously improves the visualization of commercially available nitinol guidewires and minimizes RF induced heating.

Two channel passive visualization of a nitinol guidewire with iron markers

Background MRI-guidance for cardiovascular catheterization is appealing to reduce ionizing radiation exposure and to enable novel procedures. “Active” guidewire-antennas for MRI-guided procedures are often designed such that the tip and shaft have distinct signals [1] to improve navigation and to make it obvious when the tip moves out of plane. Here we present a method to isolate the signal from iron markers, and produce a two channel color overlay for visualizing the shaft and tip of a nitinol guidewire.

MP62-05 MAGNETIC RESONANCE IMAGING (MRI)-GUIDED TRANSURETHRAL ULTRASOUND ABLATION OF PROSTATE CANCER: PRELIMINARY OUTCOMES OF A PHASE I CLINICAL TRIAL

You have accessJournal of UrologyProstate Cancer: Localized VII1 Apr 2014MP62-05 MAGNETIC RESONANCE IMAGING (MRI)-GUIDED TRANSURETHRAL ULTRASOUND ABLATION OF PROSTATE CANCER: PRELIMINARY OUTCOMES OF A PHASE I CLINICAL TRIAL Michele Billia, Mathieu Burtnyk, Timur Kuru, Sascha Pahernik, Matthias Roethke, Heinz-Peter Schlemmer, Cesare Romagnoli, and Joseph Chin Michele BilliaMichele Billia More articles by this author , Mathieu BurtnykMathieu Burtnyk More articles by this author , Timur KuruTimur Kuru More articles by this author , Sascha PahernikSascha Pahernik More articles by this author , Matthias RoethkeMatthias Roethke More articles by this author , Heinz-Peter SchlemmerHeinz-Peter Schlemmer More articles by this author , Cesare RomagnoliCesare Romagnoli More articles by this author , and Joseph ChinJoseph Chin More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.1962AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES MRI-guided transurethral ultrasound ablation (TULSA) is a new minimally-invasive technology for treatment of localized prostate cancer (PCa), aiming to provide good local disease control with a low side-effect profile. This modality consists of a transurethral device emitting planar ultrasound and generating a continuous and precise volume of thermal coagulation shaped to conform to the prostate, using real-time MRI monitoring and active temperature feedback control. A prospective, multi-center phase I clinical trial was initiated in March 2013 with the aim to determine safety and feasibility of MRI-guided TULSA, and to assess initial efficacy for localized PCa treatment. METHODS Patients with low-risk PCa: cT1c-T2a, N0, M0; PSA≤10ng/ml; GS≤6 are enrolled. Under general anesthesia, suprapubic catheter (SPC) is inserted and left in for 2 weeks. The TULSA device (PAD-105, Profound Medical Inc.) is inserted manually over a Nitinol guidewire and positioned precisely in the prostatic urethra with MRI guidance (3-Tesla unit). Treatment planning is performed under MRI prostate visualization, with therapeutic intent of conservative whole-gland ablation. Treatment is delivered under continuous MR thermometry feedback control, and patients recover with an outpatient protocol. Primary study endpoints are safety and feasibility, with follow-up to 12 months. Complete clinical monitoring is 5 years, including serial PSA, TRUS biopsy and QoL questionnaires (IPSS, IIEF, bowel domain of UCLA-PCI-SF). RESULTS To-date, 17 patients have been treated with no intraoperative complications. Median treatment time was 29 (24 – 61) min and prostate volume 45 (34 – 95) cc. Spatial control of thermal ablation was within ±1.5 mm and contrast-enhanced MRI confirmed the resulting non-perfused volume. Clavien II complications included urinary tract infections (4), and epididymitis (1). Clavien I complications included hematuria (3), and acute urinary retention after SPC removal (2) resolving after SPC re-insertion. At 1 month, median PSA reduced by 87% (60 – 99%) to 0.7 ng/ml (0.1 – 3.3 ng/ml), with the nadir expected by 6 months. Normal micturition returned after SPC removal, with no significant change in QoL at 3 months. CONCLUSIONS MRI-guidance enables accurate planning and real-time dosimetry and control of the thermal ablation volume. Initial results indicate that MRI-guided TULSA is safe and clinically feasible with a well-tolerated, low side effect profile. © 2014FiguresReferencesRelatedDetailsCited byBurtnyk M, Hill T, Cadieux-Pitre H and Welch I (2018) Magnetic Resonance Image Guided Transurethral Ultrasound Prostate Ablation: A Preclinical Safety and Feasibility Study with 28-Day FollowupJournal of Urology, VOL. 193, NO. 5, (1669-1675), Online publication date: 1-May-2015. Volume 191Issue 4SApril 2014Page: e718-e719 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Michele Billia More articles by this author Mathieu Burtnyk More articles by this author Timur Kuru More articles by this author Sascha Pahernik More articles by this author Matthias Roethke More articles by this author Heinz-Peter Schlemmer More articles by this author Cesare Romagnoli More articles by this author Joseph Chin More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Dual echo bSSFP for real-time positive contrast of passive nitinol guidewires in MRI-guided cardiovascular interventions

Background MRI-guidance of cardiovascular catheterization procedures potentially offers an ionizing radiation-free alternative to X-Ray guidance. Imaging methods allowing visualization of commercially available passive guidewires would facilitate MRI-guided interventions. Previous work has demonstrated that positive contrast of paramagnetic materials, such as nitinol, can be generated with dephased echo sequences [1,2]. Here, we demonstrate a dual echo bSSFP sequence producing a wire image and an anatomical reference image in one TR, with variable flip angle for reduced SAR.

Heating and safety of a new MR-compatible guidewire prototype versus a standard nitinol guidewire

Our purpose in this study was to examine heating of nitinol and polyetheretherketone (PEEK) guidewires during near-real-time MR imaging in an artificial vascular model an "aorta phantom". The first 100cm of the nitinol- and PEEK-based guidewires both 145×0.08cm were immersed in a saline-filled aorta phantom. The probes of a fiber-optic thermometer were positioned at the tips of both wires. Balanced steady-state free precession (bSSFP) [TE 1.6ms; TR 3.5ms; flip angle (FA) 60°; field of view (FOV) 40cm; matrix 256×256; specific absorption rate (SAR); 1.15 Watt (W)/kg] and spoiled gradient-echo (SPGR) (TE 1.8ms; TR 60ms; FA 60°; FOV 40cm; matrix 256×256; SAR 1.15W/kg) pulse sequences were acquired in a 1.5-T MR scanner with use of an 8-channel array coil. Temperatures were recorded while the phantom was placed centrally in the bore of a MR scanner and in an off-center position (x=24cm, y=-5cm, z=-10/10cm). The temperature of the nitinol guidewire increased by 0.3°C (center) and 1.1°C (off-center position) with use of the bSSFP and by 9.6 and 13°C (off-center position) with use of the SPGR sequence. Only minor temperature changes up to a maximum of 0.4°C were observed with the MR-compatible PEEK guidewire when any position or sequence was applied. The PEEK guidewire showed substantially lower heating as compared to the nitinol guidewire in near-real-time imaging sequences in a phantom.

The use of a novel nitinol guidewire to facilitate transseptal puncture and left atrial catheterization for catheter ablation procedures

An increasing number of transseptal punctures (TSPs) are performed worldwide for atrial ablations. Transseptal punctures can be complex and can be associated with potentially life threatening complications. The purpose of the study was to evaluate the safety and efficacy of a novel transseptal guidewire (TSGW) designed to facilitate TSPs. Transseptal punctures were performed using a SafeSept TSGW passed through a standard TSP apparatus. Transseptal punctures were performed by standard technique with additional use of a TSGW allowing probing of the interatrial septum without needle exposure and penetration of the fossa into the left atrium (LA). Transseptal puncture using the TSGW was performed in 210 patients. Left atrial access was achieved successfully in 205 of 210 patients (97.6%) and in 96.3% of patients undergoing repeat TSP. Left atrial access was achieved with the first pass in 81.2% (mean 1.4 ± 0.9 passes, range 1-6) using the TSGW. No serious complications were attributable to the use of the TSGW, even in cases of failed TSP. The TSGW is associated with a high success rate for TSP and may be a useful alternative to transoesophageal or intracardiac echocardiogram-guided TSP.

Use of a novel needle wire in patients undergoing transseptal puncture associated with severe septal tenting

An increasing number of patients undergo left atrial ablation procedures, since several approaches have proven efficacy in the treatment of atrial fibrillation. Although transseptal catheterization was generally shown be a safe technique, it harbors the principal risk of cardiac injury. Therefore, there is a need for a safe and effective tool to enable transseptal puncture in difficult cases as well. In 158 consecutive patients, a transseptal puncture was intended for mapping and ablation of left atrial tachycardias. In seven patients of this series transseptal puncture using different sheaths and needle designs, the operators failed to cross the interatrial septum as a result of severe tenting. Three patients were known to have a septal aneurysm; a redo procedure was performed in two patients. In the remaining patients, there was no obvious explanation for the difficulty in crossing the interatrial septum conventionally. In all seven patients, a 120-cm-long nitinol guidewire ("needle wire") with a 0.014-inch diameter was used to cross the atrial septum with the following idea: after tenting the fossa ovalis with the transseptal dilator and the Brockenbrough needle positioned just inside the tip, effortless advancement of the needle wire perforates the membranous fossa. Unsupported by the needle and dilator, the tip of the wire immediately assumes a "J" shape, rendering it incapable of further tissue penetration after its entry into the left atrium. In all seven patients, the needle wire could be placed into a left pulmonary vein. In five patients, a single attempt was sufficient to reach the left atrium with the wire, two patients needed two and three attempts, respectively. No complications occurred. Additional use of a needle wire to perform transseptal puncture in a subset of patients at higher risk for complications appears safe and effective.

Preclinical Evaluation of a Novel Fiber Compound MR Guidewire In Vivo

Interventional magnetic resonance imaging requires dedicated and MR-compatible devices. The guidewire is a key item for intravascular interventions. Mechanical stability, good visibility during real-time imaging, and RF safety are essential. A novel fiber-compound MR guidewire (GW) was evaluated in different MR-guided interventional scenarios. The GW (diameter 0.032") consists of a fiber-compound produced using a micropultrusion technique doped with iron particles and a 10-cm Nitinol tip. Several iron splints are additionally attached at regular distances to visualize GW-movement. A protective polymer jacket with hydrophilic coating covers the core material. As approved by the government committee on animal investigations, the GW was evaluated in 5 pigs. Under complete MR-guidance, catheterization of the carotid and renal arteries, segmental arteries of the kidneys, the contralateral inguinal artery, and the left ventricle was performed using real-time gradient echo sequences in a 1.5 Tesla scanner. Different interventional applications including balloon dilatation, stent deployment, and embolization of small vessels were investigated. The time to probe the vessels under magnetic resonance imaging guidance and visibility of the GW are assessed. Handling and visibility under fluoroscopy were compared with a standard Nitinol guidewire as a benchmark. On real-time magnetic resonance imaging, the iron-induced artifacts enabled a distinct visualization of the GW shaft and of its markings with a mean size of 2.6 mm and 5.4 mm, respectively. This facilitated fast navigation to the target vessels (averages: renal arteries 16 seconds, carotid artery 5 seconds, and contralateral inguinal artery 42 seconds.) with an exact depiction of the respective vessel. All interventional procedures were performed successfully. No GW-related side effects as kinking or breakage of the wire or GW induced blood-clotting were observed. All interventionalists assessed handling of the GW to be nearly equal in terms of stiffness, flexibility, and guidance compared with a standard Nitinol guidewire. X-ray visibility was less distinct but still diagnostically good. With the aid of the GW, different fully real-time MR-guided endovascular interventions become feasible.

Percutaneous Therapy for Anastomotic Bile Leak in Liver-Transplant Patients with Nondilated Bile Ducts

Bile leaks remain a significant cause of postoperativemorbidity in 4.9% to 26.6% of liver transplant recipients[1–4] and can be managed surgically or nonsurgically.Most leaks can be treated with interventional radiologictechniques. However, in cases with bile ducts that aredecompressed because of massive leakage (mostly anas-tomotic), percutaneous access into a peripheral bile duct isusually difficult. In the cases presented here, we performedretrograde catheterization of a peripheral bile duct to makethe percutaneous procedure easier to perform and lesstraumatic for the patient.Case ReportsCase 1Forty-nine days after orthotopic liver transplantation, a 59-year-oldman presented withabdominalpainandtenderness.A large perihepatic fluid collection, or biloma, was found onultrasound examination. After bile-stained fluid aspiration,percutaneous drainage of the perihepatic biloma was per-formed under ultrasonographic guidance. Following thisprocedure, output through the drainage catheter was high(>200 ml per 24 h). Two weeks later, drip-infusion pouch-ography obtained via the drainage catheter showed a com-munication between the biloma and the biliary system at thesite of the surgical anastomosis. Endoscopic managementwas our first treatment option, but it failed in crossing theanastomosis. We decided to perform percutaneous transhe-patic biliary drainage. Because the leak had caused decom-pressionofbileducts,wedecidedtouseourbilomaaccesstomake the percutaneous bile duct puncture easier.The procedure was performed after antibiotic prophy-laxis. After initiation of intravenous (IV) sedation and localanesthesia, the drainage catheter was exchanged for a 6-Fintroducer sheath (Arrow International, Inc., Reading, PA,USA) positioned over a guide wire. A 5-F catheter (SOSOMNI; AngioDynamics, Queensbury, NY, USA) was in-serted from the biloma pouch and passed through the dis-rupted anastomosis. Then a microcatheter (fast tracker;Boston Scientific, Natick, MA, USA) was coaxially in-serted into a peripheral bile duct available for percutaneousaccess (Fig. 1), and contrast material was injected throughthe microcatheter to opacify and distend this duct. Underfluoroscopy and using a 21-gauge needle (AccuStickIntroducer System; Boston Scientific), a percutaneouspuncture was made in the same duct.After the percutaneous needle puncture was made in theduct, a coaxial dilator (AccuStick Introducer System;Boston Scientific) was placed over an 0.018-in. Nitinolguide wire, then a 0.035-in. glide wire (Terumo, Tokyo)was advanced through the dilator, and a 6-F introducer(Terumo) was inserted into the duct over the wire. A 5-Fcatheter (Terumo) with a guide wire was used to cross theleak site. Then, over a stiff guide wire (Amplatz Super StiffGuide Wire; Boston Scientific), a 10-F biliary drainagecatheter (Flexima; Boston Scientific) with multiple sideholes positioned on both sides of the anastomosis wasplaced to divert bile away from the defect. The leak haddisappeared after 57 days of percutaneous biliary drainage.

Delivery and assessment of endovascular stents to repair aortic coarctation using MR and X‐ray imaging

To investigate the utility of MR and X-ray imaging for characterizing aortic coarctation and flow, and guiding the endovascular catheter to place a stent to repair the coarctation. The descending aorta in eight dogs was looped with elastic band and tightened distal to the subclavian artery. Balanced fast field echo (bFFE) and velocity-encoded cine (VEC) MRI sequences were used for device tracking and measuring aortic flow. A T1-weighted fast-field echo sequence (T1-FFE) was used to visualize the coarctation and roadmap the aorta. Nitinol stents were guided by a nitinol guidewire and placed under MR guidance. Aortic coarctation was visible on MR and X-ray imaging. The procedure success rate was 88%. VEC MRI measured the changes in aortic flow (baseline = 1.3 +/- 0.2, coarctation = 0.2 +/- 0.02, and stent placement = 0.8 +/- 0.1 liters/minute). A significant reduction in iliac blood pressure was measured after coarctation, but it was reversed by stent placement. The stent lumen was visible on X-ray fluoroscopy, but not on MRI. Stent deployment to repair aortic coarctation is feasible under MR guidance. The combined use of MR and X-ray imaging is effective for anatomic and functional evaluation of aortic coarctation dilation, which may be crucial for optimal therapy.

High maneuverability guidewire with functionally graded properties using new superelastic alloys

Nitinol shape memory alloys (SMAs) are attracting considerable attention as core materials for medical guidewires because of their excellent flexibility and shape retention. However, since Nitinol guidewires possess low rigidity, the pushability and torquability of the guidewires are insufficient. On the other hand, although guidewires made of stainless steel have high pushability, plastic deformation occurs easily. We have developed a new class of superelastic guidewires with functionally graded properties from the tip to the end by using new SMA core materials such as Cu‐Al‐Mn‐based or Ni‐free Ti‐Mo‐Sn SMAs. The tip portion of the guidewire shows excellent superelasticity (SE), while the body portion possesses high rigidity. These functionally graded characteristics can be realized by microstructural control. These guidewires with functionally graded properties show excellent pushability and torquability and are considerably easier to handle than conventional guidewires with Nitinol or stainless steel cores. Moreover, a metallic catheter using a Ni‐free Ti‐based SMA with high biocompatibility is introduced.

Continuous Access Technique for Dilation, Evaluation, and Stent Palliation of Malignant Luminal Digestive Tract Strictures

Introduction: Endoluminal stent placement is an effective means of palliating malignant stenoses. Malignant stenoses in which there is complete obstruction, fistula, and/or inability to pass the endoscope present challenges to endoluminal stent therapy. It is advantageous to advance the endoscope through these malignant stenoses to precisely appreciate their localization, length, and configuration. These factors impact on stent selection and deployment. We define, and describe our experience with, a technique to establish and maintain continuous access to facilitate evaluation and stent placement in challenging malignant stenoses. Methods: The continuous access technique employs advancement of an 0.035″ Teflon coated coiled steel or hydrophilic coated nitinol guidewire under endoscopic and fluoroscopic guidance through the stenosis. A guidewire-compatible graded radial diameter through-the-scope balloon dilator is then advanced into the stenosis. Incremental balloon dilation is performed to 1-mm above the outside diameter of the endoscope. Then, with the inflated dilator snug to the tip of the endoscope, using the balloon dilator as an obturator tip, this assembly is advanced over the guidewire through the stenosis. The dilation catheter is then removed; the distal margin of the tumor marked; and stent placement performed. This Continuous Access (CA) technique was defined and detailed in the records of stent placement beginning in February 1999. We reviewed the records for techniques of all stent placements by two clinicians from Feb 1999 through Aug 2004. Results: There were 126 attempted stent placements for malignant strictures (96 Esophageal/EG junction, 22 Gastroduodenal, 8 Colorectal). In 75 (60%) the endoscope traversed the stricture with no dilation. In 13 (10%) the scope traversed after standard dilation was performed. In 8 (6%) stents were placed after only a guidewire was advanced across the stricture under fluoroscopic guidance. In 30 (24%), inability to advance the scope with or without standard dilation prompted use of the CA technique. CA technique was successful in traversing the stricture in 29 (1 failure,esophageal). A stent was successfully placed in all but one patient. There were no procedure related complications. Conclusion: The continuous access technique safely and effectively facilitates scope passage through strictures thereby enhancing precision in stent selection and deployment for palliation of challenging malignant stenoses. Introduction: Endoluminal stent placement is an effective means of palliating malignant stenoses. Malignant stenoses in which there is complete obstruction, fistula, and/or inability to pass the endoscope present challenges to endoluminal stent therapy. It is advantageous to advance the endoscope through these malignant stenoses to precisely appreciate their localization, length, and configuration. These factors impact on stent selection and deployment. We define, and describe our experience with, a technique to establish and maintain continuous access to facilitate evaluation and stent placement in challenging malignant stenoses. Methods: The continuous access technique employs advancement of an 0.035″ Teflon coated coiled steel or hydrophilic coated nitinol guidewire under endoscopic and fluoroscopic guidance through the stenosis. A guidewire-compatible graded radial diameter through-the-scope balloon dilator is then advanced into the stenosis. Incremental balloon dilation is performed to 1-mm above the outside diameter of the endoscope. Then, with the inflated dilator snug to the tip of the endoscope, using the balloon dilator as an obturator tip, this assembly is advanced over the guidewire through the stenosis. The dilation catheter is then removed; the distal margin of the tumor marked; and stent placement performed. This Continuous Access (CA) technique was defined and detailed in the records of stent placement beginning in February 1999. We reviewed the records for techniques of all stent placements by two clinicians from Feb 1999 through Aug 2004. Results: There were 126 attempted stent placements for malignant strictures (96 Esophageal/EG junction, 22 Gastroduodenal, 8 Colorectal). In 75 (60%) the endoscope traversed the stricture with no dilation. In 13 (10%) the scope traversed after standard dilation was performed. In 8 (6%) stents were placed after only a guidewire was advanced across the stricture under fluoroscopic guidance. In 30 (24%), inability to advance the scope with or without standard dilation prompted use of the CA technique. CA technique was successful in traversing the stricture in 29 (1 failure,esophageal). A stent was successfully placed in all but one patient. There were no procedure related complications. Conclusion: The continuous access technique safely and effectively facilitates scope passage through strictures thereby enhancing precision in stent selection and deployment for palliation of challenging malignant stenoses.

Magnetic resonance--guided coronary artery stent placement in a swine model.

Magnetic resonance (MR)--guided coronary artery stent placement is a challenging vascular intervention because of the small size of the coronary arteries combined with incessant motion during the respiratory and cardiac cycles. These obstacles necessitate higher temporal and higher spatial resolution real-time MR imaging techniques when compared with interventional peripheral MR angiography. A new, ultrafast, real-time MR imaging technique that combines steady-state free precession (SSFP) for high signal-to-noise ratio and radial k-space sampling (rSSFP) for motion artifact suppression was implemented on a 1.5-T clinical whole-body interventional MR scanner. The sliding window reconstruction technique yielded a frame rate of 15/s allowing for data acquisition during free breathing and without cardiac triggering. Eleven balloon-expandable stainless steel coronary stents were placed in both coronary arteries of 7 pigs (40 to 70 kg body weight) using a nitinol guidewire and passive device visualization. Position of the coronary stents was controlled by a navigator-gated free-breathing ECG-triggered three-dimensional SSFP coronary MRA sequence and confirmed visually on the ex vivo heart. The presented real-time MR imaging sequence reliably allowed for high-quality coronary MR fluoroscopy without motion artifacts in all pigs. Ten of 11 coronary stents were correctly placed under MR guidance. One stent dislodged proximally from the left main coronary artery because of too-small balloon size. Stent dislocation was correctly predicted during real-time MR imaging. The presented approach allows for real-time MR-guided coronary artery stent placement in a swine model.

Truly Hybrid Interventional MR/X-Ray System: Investigation of in Vivo Applications

Rationale and Objectives The purpose of this study was to provide in vivo demonstrations of the functionality of a truly hybrid interventional x-ray/magnetic resonance (MR) system. Materials and Methods A digital flat-panel x-ray system (1,024 2 array of 200 μm pixels, 30 frames per second) was integrated into an interventional 0.5-T magnet. The hybrid system is capable of MR and x-ray imaging of the same field of view without patient movement. Two intravascular procedures were performed in a 22-kg porcine model: placement of a transjugular intrahepatic portosystemic shunt (TIPS) (x-ray–guided catheterization of the hepatic vein, MR fluoroscopy–guided portal puncture, and x-ray–guided stent placement) and mock chemoembolization (x-ray–guided subselective catheterization of a renal artery branch and MR evaluation of perfused volume). Results The resolution and frame rate of the x-ray fluoroscopy images were sufficient to visualize and place devices, including nitinol guidewires (0.016–0.035-inch diameter) and stents and a 2.3-F catheter. Fifth-order branches of the renal artery could be seen. The quality of both real-time (3.5 frames per second) and standard MR images was not affected by the x-ray system. During MR-guided TIPS placement, the trocar and the portal vein could be easily visualized, allowing successful puncture from hepatic to portal vein. Conclusion Switching back and forth between x-ray and MR imaging modalities without requiring movement of the patient was demonstrated. The integrated nature of the system could be especially beneficial when x-ray and MR image guidance are used iteratively.

MR-guided percutaneous drainage of abdominal fluid collections in combination with X-ray fluoroscopy: initial clinical experience.

The aim of this study was to examine the feasibility of a hybrid interventional MR system, which combines a closed bore magnet with a C-arm fluoroscopy unit for percutaneous drainage of abdominal fluid collections. During the past 2 years, we have performed four drainage procedures in four patients (mean age 47 years). Three patients had abscesses (psoas muscle, kidney, subphrenic location) and the fourth patient had a recurrent splenic cyst. All procedures were performed on an interventional MR system consisting of a 1.5-T ACS-NT scanner combined with a specially shielded C-arm. The drainages were guided by T1-weighted fast gradient-echo images, T2-weighted single-shot turbo spin-echo images or both. A standard 18 G (1.2 mm) nonferromagnetic stainless steel needle with a Teflon sheath was used for the punctures following which a 0.89 mm nitinol guidewire was inserted into the fluid collection. Thereafter, the patient was positioned in the immediate adjacent fluoroscopy unit and a drainage catheter was placed under fluoroscopic control. All drainage catheters were successfully placed into the fluid collections, as proven by fluid aspiration and resolution of the collection. The mean time needed for the entire drainage procedure (MR and fluoroscopy) was 110 min. No procedure-related complications occurred. It is feasible to perform drainage procedures on a closed-bore MR scanner. The multiplanar imaging capabilities of MR are particularly helpful for fluid collections in the subphrenic location.

MR-guided balloon angioplasty of stenosed aorta: in vivo evaluation using near-standard instruments and a passive tracking technique.

The purpose of this study was to assess the feasibility of magnetic resonance (MR)-guided balloon angioplasty of a stenosed aorta on an open low-field magnet using a passive tracking technique. Visualization of vessels and position of instruments were realized by using a fast low-angle shot (FLASH) sequence. Catheters and guidewire were prepared for susceptibility-based MR visualization. Standard balloon catheters were inflated with diluted gadolinium, and nitinol guidewires were modified by incorporation of iron oxide markers into their walls. After validation on a flow phantom, balloon angioplasty was performed on an in vivo model of arterial stenosis. Creation of abdominal aorta stenosis was realized in five piglets. MR-guided balloon angioplasty of the aorta was performed with success in all but one. In one of them, stent implantation was achieved in the descending aorta. Balloon angioplasty using a passive tracking technique is a simple concept that can be realized with near-standard instruments and any MR imaging system. This represents an advance toward MR-guided vascular interventions in the future.

Recanalization of chronic coronary occlusions using a new hydrophilic guidewire.

Chronic total occlusion remains a relative contraindication and the main cause of failure of coronary angioplasty. Previously available hydrophilic guidewires had numerous limitations. The Crosswire is a new 0.014" hydrophilic nitinol guidewire which can be accommodated by very-low-profile balloon catheters and has a shapeable and highly radiopaque platinum-iridium coiled tip. This guidewire was used in 55 patients with 56 chronic coronary occlusions in which recanalization by conventional guidewires had failed. Clinical success was 79%. Coronary perforation occurred in two cases, one of them requiring pericardiocentesis for tamponade. These results illustrate the usefulness of this new guidewire in the treatment of chronic total occlusions.

Invasive or noninvasive angiography? The role of "classical" catheter angiography

Within the last decade, diagnostic and interventional angiography have been developed to a high degree of performance, due to the widespread use od DSA, the miniaturisation of the puncture trauma and the introduction sets (catheters, sheaths), the development of high-tech materials (e.g., Nitinol guidewires) and the application of non-ionic, low osmolal contrast media. The specific risks of the procedure, thereby, have been significantly reduced, but could not be totally eliminated. To evaluate vascular diseases non-invasively, special attention was attributed to the progress of colour coded duplex, (spiral) CT-angiography and (CE) MR-angiography, based on the established imaging with US, CT and MRT. The matter is question is whether or not they can substitute the role of conventional angiography as the "gold standard" of vessel imaging. Clinical validity and economic efficiency both determine the indication for the use of invasive or non-invasive methods. In diagnostic procedures, there is a growing tendency for the use of non-invasive techniques, like in imaging of the abdominal and thoracic aorta, the renal, pulmonary and extra- and intra-cranial arteries. Conventional angiography is still reserved for the evaluation of small vessels of the upper and lower extremities, and vessel status in preoperative conditions (carotid, celiac trunk, mesenteric and renal arteries and aneurysms of the cerebral vasculature). Fluoroscopic guiding of catheters and contrast enhancement in interventional procedures, however, cannot be substituted by alternative techniques in the foreseeable future.