This is a report of our experience with percutaneous, MRI‐guided biopsies in 25 patients with skeletal lesions using a 1.5‐T MR hybrid system. Twenty‐five consecutive patients with skeletal lesions were referred for MRI‐guided biopsy. Biopsies were performed with a 1.5‐T Philips Gyroscan (Philips Medical Systems, Best, The Netherlands) combined with a c‐arm fluoroscopy. Specimens were obtained percutaneously either with a 14‐ or 18‐gauge “side‐slit” type of biopsy needle (n = 10 skeletal lesions that had penetrated through the cortex), or using a prototype coaxial drill system powered either by hand or an optional motor (n = 15 skeletal lesions still covered with cortical bone). All but two biopsies could be completed within the MR unit. For one patient, who required a transpedicular approach to a lumbar vertebra, and for one child, who required general anesthesia, we decided to switch to CT guidance. In 19 of the 25 cases (17 of the 23 cases performed in MR), the sample was sufficient and the histopathologic diagnosis was confirmed. Three patients had an inadequate sample, and three others had adequate samples but inaccurate results. No procedural complications occurred. Percutaneous biopsy of skeletal lesions performed under MRI‐guidance was found to be safe and reasonably accurate. There were no procedural complications in our small series. MRI may be used as an alternative to CT, but its role vis‐à‐vis CT has yet to be ascertained.

Purpose: To test the feasibility of real-time MR controlled guidance of field-inhomogeneity catheters in vitro and in vivo as a first step to MR-guided angiographic interventions. Methods: Applying a combination of radial scanning with the sliding window reconstruction technique, a frame rate of 23 low resolution images per second was achieved. Field inhomogeneity catheters were steered through a flow phantom and into the renal arteries of a pig. Results: It was possible to visualize flow or, respectively, vessels and to depict catheter movements. This enabled real-time MR-guidance of the catheter into the renal arteries of the flow phantom and into those of the pig. Conclusions: The new technique yields a sufficiently high temporal resolution for MR-guidance of catheters through vessels.

PURPOSE:To test the feasibility of real-time MR controlled guidance of field-inhomogeneity catheters in vitro and in vivo as a first step to MR-guided angiographic interventions.METHODS:Applying a combination of radial scanning with the sliding window reconstruction technique, a frame rate of 23 low resolution images per second was achieved. Field inhomogeneity catheters were steered through a flow phantom and into the renal arteries of a pig.RESULTS:It was possible to visualize flow or, respectively, vessels and to depict catheter movements. This enabled real-time MR-guidance of the catheter into the renal arteries of the flow phantom and into those of the pig.CONCLUSIONS:The new technique yields a sufficiently high temporal resolution for MR-guidance of catheters through vessels.

Ziel: Überprüfung von Technik und Durchführbarkeit einer MR-tomographisch gesteuerten perkutanen Nephrostomie (MR-PNS) im Tierexperiment. Methoden: Bei drei Hausschweinen wurde eine einseitige perkutane Nephrostomie des nicht dilatierten Hohlraumsystems ausschließlich unter MR-tomographischer Kontrolle mit einem geschlossenen 1,5-T-System durchgeführt. Die Kontrastierung des oberen Harntraktes erfolgte durch eine intravenöse Injektion von Gd-DTPA und niedrigdosiertem Furosemid. Die einzelnen Interventionsschritte wurden mit einer T1-gewichteten „Doppel-Schichtstapel” 2 D-TFE Sequenz in zwei orthogonalen Schichtebenen kontrolliert. Ergebnisse: Bei allen drei Versuchstieren ließ sich die Punktionsnadel unter MR-tomographischer Steuerung sicher zum festgelegten Zielkelch vorführen. Auch leichte Abweichungen der Nadelspitze waren mit beiden MR-tomographischen Kontrollebenen problemlos nachzuweisen und konnten direkt korrigiert werden. Die erfolgreiche Punktion des Hohlsystems gelang jeweils bereits im ersten Versuch. Über einen Nitinol-Führungsdraht wurde ein 5 F-Katheter eingeführt, dessen mit Dysprosium markierte Spitze innerhalb des kontrastangehobenen Nierenbeckens gut abzugrenzen war. Schlußfolgerungen: Die perkutane Nephrostomie unter MR-Kontrolle ist bei nicht dilatiertem Harntrakt gut möglich und bietet Vorteile gegenüber den bisherigen Standardverfahren.