Interventional MRI of the Musculoskeletal System
(Montag, 16.50 Uhr, Schinkelsaal)
Magnetic resonance (MR)-guided interventions of the musculoskeletal system may be diagnostic or therapeutic and include selective perineural and intramuscular injections, sclerotherapy of vascular anomalies, percutaneous soft tissue and bone biopsy, as well as ablation and augmentation techniques. MR imaging guidance provides unparalleled soft-tissue detail for identification and targeting of neural structures, small muscles, vessels, joints, soft tissue masses and osseous targets; and avoids radiation exposure of patients, operators and staff. High spatial resolution MR imaging visualizes fine and deep anatomic targets, whereas MR Neurography techniques are used to target small nerves. Diffusion-weighted and contrast-enhanced MR imaging display specific tissue characteristics and enable differential tissue targeting. Metal artifact reduction techniques facilitate precise monitoring of instruments such as needles and drills. The combination of fat suppression techniques and fluid sensitive MR imaging sequences allow selective visualization of the distribution pattern of injectants.
The MR-guided procedures may be performed at 1.5 Tesla field strength clinical wide-bore MR imaging systems, which have increased the practicability and availability of interventional MR imaging. Specifically, the recent introduction of wide-bore 3-Tesla MR imaging systems now provide easier access to high-field MR-guided procedures. Modern surface coils and parallel imaging technology facilitate fast temporal image acquisition, higher spatial image resolution, and high image contrast, or combinations thereof. Device placement may be performed under real-time guidance inside the bore or with use of navigation systems outside the bore. Passive visualization of MR-conditional instruments is an easily achievable and reliable tracking method. The resulting artifacts are influenced by several factors such as the alloy composites, the strength of the static magnetic field, the sequence type, the spatial orientation as well as the echo time and may further be optimized during the intervention by operator modification of the last three factors. Injectants can be visualized based on their native T2 properties or based on the T1-shortening effects of added Gadolinium-based contrast agents. Fast acquisition techniques and image processing allow for continuous, near real-time MR fluoroscopic imaging and interactive needle navigation.
This presentation reviews the principles of interventional MR imaging as they are pertinent to procedures of the musculoskeletal system and illustrates a variety of MR-guided procedure including MR-guided pain management procedures such as perineural injections of the brachial and lumbosacral plexus, spinal injections, intramuscular Botox injections, diagnostic soft tissue and bone biopsies, as well as cryo-ablation and cement augmentation techniques.
M.D., Assistant Professor of Radiology, Attending Radiologist Musculoskeletal Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA