Joerg Neuerburg

Real-time MR fluoroscopy for MR-guided iliac artery stent placement

The purpose of this study was to test the feasibility of real‐time magnetic resonance (MR) guidance of iliac artery stent placement. Radial scanning together with the sliding window reconstruction technique was implemented on a 1.5 T magnet, yielding a frame rate of 20 images per second. Seven prototype nitinol ZA stents were deployed in iliac arteries of living pigs under MR control. All stents were well visualized on the radial MR images, allowing depiction of the mounted stents as well as stent deployment without anatomy‐obscuring artifacts. Stent placement was sucessful in all cases and took 6 minutes on average. The position of the stents was correctly visualized by real‐time radial MR scanning, as proved by digital subtraction X‐ray angiography. Combined radial scanning and the sliding window reconstruction technique allow real‐time MR‐guided stent placement in iliac arteries. J. Magn. Reson. Imaging 2000;12:616–622.

Real-time MR Guidance for Inferior Vena Cava Filter Placement in an Animal Model

It was the aim of this study to examine the feasibility of real-time magnetic resonance (MR) imaging for MR-guided placement of inferior vena cava (IVC) filters, which were placed in five pigs via a femoral approach. The introducer sheath and dilator were marked with Dysprosium rings. The procedures were performed under MR guidance with use of a 1.5-T ACS-NT imager. Radial filling of k-space in conjunction with the sliding window reconstruction technique achieved real-time MR imaging with a frame rate of 20 images/sec. Simultaneous real-time visualization of the vascular anatomy and interventional instruments was achieved under real-time conditions and allowed correct placement of IVC filters in all five cases as confirmed by radiographic angiography.

Iliocaval stenosis and iliac venous thrombosis in retroperitoneal fibrosis : percutaneous treatment by use of hydrodynamic thrombectomy and stenting

A case of bilateral iliac stenosis and caval stenosis due to retroperitoneal fibrosis was treated by caval stenting and iliac balloon angioplasty, but was complicated by subsequent iliac thrombosis. Venous thrombectomy was successfully achieved by hydrodynamic thrombectomy, and iliac patency was stabilized by bilateral stent insertion.

Effects of lithotripsy on rat kidney: evaluation with MR imaging, histology, and electron microscopy

Magnetic resonance (MR) imaging at 1.5 T was used to evaluate the effects of extracorporeal shock wave lithotripsy (ESWL) in 30 rats and the findings on T1– and T2-weighted (spin echo 600/22, 1,600–2,000/90) images were compared with histology and scanning microscopy. The observed pathologic changes increased in severity with the number of shock waves given (500–5,000 15 kV). Post-ESWL MR findings in 54 kidneys included perirenal and subcapsular fluid (n = 30), diffuse loss of corticomedullary junction definition (n = 28), intrarenal foci of increased (n = 7) or decreased (n = 6) signal intensity, focal indentation of the renal contour (n = 5), and loss of distinction between the renal, splenic, or hepatic contour (n = 7). The subcapsular and intrarenal findings corresponded pathologically to areas of hemorrhage and hematoma formation—the contour changes to foci of renal scarring or perirenal adhesions. Electron microscopy demonstrated marked alterations of the renal tubules and vasculature. The study shows the feasibility of assessing the nature and chronology of renal damage post-ESWL in a rat model by MR.

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

Abstract 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.

Circular spirit level guidance system for CT- and MR-guided punctures.

A circular spirit level guidance system was tested for control of CT- and MR-guided punctures. The device consists of a needle holder fixed to a ground plate and two protractors. This allows adjustment of the fixed needle according to the angulation of the supposed puncture path as measured on tomographic images. A circular spirit level is fixed to the needle and leveled. Now the needle can be removed from the needle holder; by leveling the circular spirit level during the puncture, the formerly adjusted angulation is achieved. The system was tested in vitro and in vivo (22 patients) under CT and MR guidance. The average needle deviation was measured to be 1.96 degrees in vitro and 2.51 degrees in vivo. This simple device allows accurate puncture under CT and MR guidance.

In Vitro Evaluation of a Rheolytic Thrombectomy System for Clot Removal from Five Different Temporary Vena Cava Filters

AbstractPurpose: To evaluate the feasibility of thrombus removal from temporary vena cava filters using a rheolytic thrombectomy device and to assess the embolization rate of this procedure. Methods: Five temporary vena cava filters together with porcine thrombi were placed in a vena cava flow model (semitranslucent silicone tube of 23 mm diameter, pulsatile flow at a mean flow rate of 4 L/min). A rheolytic thrombectomy system (Hydrolyser) was used with a 9 Fr guiding catheter to remove the clots. The effluent was passed through filters of different size and the amount of embolized particles as well as the remaining thrombus were measured. Results: Thrombus removal rates ranged from 85% to 100%. Embolization rates between 47% and 60% were calculated for the different filters. Conclusion: The Hydrolyser is able to remove sufficiently high amounts of thrombus from temporary vena cava filters. However, the amount of embolized particles makes it impossible to utilize this method without special precautions against embolization.

Long-term retrieval of modified Günther Tulip vena cava Filters: an animal study.

We modified the Günther Tulip Filter to allow long-term retrieval and tested this modified filter design in an animal experiment. Fourteen modified Günther Tulip Filters (Celect filter) were inserted percutaneously into the inferior venae cavae of 7 domestic adult sheep (2 filters per animal). Before removal, 3 months after filter placement, cavography was performed and the filters were removed. Subsequently, cavography was obtained to check for any signs of bleeding. All venae cavae were prepared, removed, and macroscopically examined for bleeding. Filter placement was easy and successfully performed in all cases. No thrombi were detected inside the filters. All cases showed some narrowing of the vena cava at the level, where the filter legs were connected with the vessel wall. Neither cavograms after filter removal nor macroscopic examinations of the perivascular vena cava tissue showed any significant bleeding. The modified Günther Tulip Filter allowed for successful and uncomplicated filter removal up to 3 months after placement.