MR arthrogram solution
An MR arthrogram solution is a dilute solution of gadolinium that is used in MR arthrography for injection into the joint prior to imaging. The joint injection is performed under fluoroscopic guidance.
In vitro studies suggest that the ideal gadolinium concentration is ~2 to 2.5 mmol/L, however, most commercial preparations have a concentration of 0.5 mol/L (500 mmol/L). Therefore, a large volume of normal saline is required to dilute the gadolinium down about 200 times 4.
As is the case with many such procedures, many recipes are described and many heated arguments arise between various factions. A simple approach to preparing 20 mL of solution is as follows:
- 10 mL normal saline
- 0.1 mL gadolinium (use a tuberculum syringe to measure this)
- 10 mL non-ionic iodinated contrast
Adding local anesthetic to the mixture can be done to relieve joint pain due to capsular distension, although even then pain may remain for 24 to 48 hours after injection.
The amount of this mixture actually injected used will, obviously, depend on the size of the joint.
Other preparations include:
- 5 mL solution made up of 0.1 mL gadolinium, 3.5 mL non-ionic iodinated contrast, and 1.5 mL local anesthetic
- 2.5 mL solution of 0.1 mL gadolinium and 2.5 mL non-ionic iodinated contrast for wrist, elbow and ankle injections
Alternatively, intra-articular location can be confirmed with iodinated contrast injected immediately after needle placement, from a separate syringe. The advantage of this approach is that if you are not in the joint, then you won't have contaminated T1 weighted scans with extra-articular gadolinium. The downside is that in small joints, care should be taken not to fill the joint with iodinated contrast, impairing subsequent installation of gadolinium containing contrast.
Regardless of mixture and number of syringes, it is important to ensure the solution contains no gas bubbles as these may be confused with intra-articular loose bodies.
Choice of local anesthetic
Many local anesthetics have been shown to be chondrotoxic at typical therapeutic doses and are thus best avoided (e.g. lidocaine) or used at low concentrations 5,6. Of all routinely available anesthetics, ropivacaine at concentrations of 0.5% appears safest 5.
- 1. Chew FS, Bui-Mansfield LT, Kline MJ. Musculoskeletal imaging. Lippincott Williams & Wilkins. (2003) ISBN:0781737974. Read it at Google Books - Find it at Amazon
- 2. Maeurer J. Imaging strategies for the shoulder. Thieme Medical Publishers. (2004) ISBN:1588902501. Read it at Google Books - Find it at Amazon
- 3. Kreuz PC, Steinwachs M, Angele P. Knee Surg Sports Traumatol Arthrosc. 2018 Mar;26(3):819-830. Single-dose local anesthetics exhibit a type-, dose-, and time-dependent chondrotoxic effect on chondrocytes and cartilage: a systematic review of the current literature.
- 4. Rastogi AK, Davis KW, Ross A, Rosas HG. Fundamentals of Joint Injection. (2016) AJR. American journal of roentgenology. 207 (3): 484-94. doi:10.2214/AJR.16.16243 - Pubmed
- 5. Jayaram P, Kennedy DJ, Yeh P, Dragoo J. Chondrotoxic Effects of Local Anesthetics on Human Knee Articular Cartilage: A Systematic Review. (2019) PM & R : the journal of injury, function, and rehabilitation. 11 (4): 379-400. doi:10.1002/pmrj.12007 - Pubmed
- 6. Kreuz PC, Steinwachs M, Angele P. Single-dose local anesthetics exhibit a type-, dose-, and time-dependent chondrotoxic effect on chondrocytes and cartilage: a systematic review of the current literature. (2018) Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 26 (3): 819-830. doi:10.1007/s00167-017-4470-5 - Pubmed