Effects of adding local anesthetic and iodinated contrast agents to the paramagnetic contrast solution in direct MR arthrography Efeitos da adição do anestésico local e do contraste iodado na solução de contraste paramagnético utilizada na artrorressonância direta

The introduction of hardware and software innovations have resulted in a huge advance for diagnostic imaging in the last decades, especially the evolution of functional studies of human tissues which do not require the use of contrast medium (1–3) . Nevertheless, the use of contrast agents is still required in specific settings of the clinical practice to differentiate healthy from diseased tissues. The discussion about contrast agents’ techniques is therefore very important and has been valued in our community (4–7) . In this scenario, we can welcome the study developed by Pinheiro et al. (8) published in the present issue of Radiologia Brasileira. Such authors have carried out in vitro investigations of different concentrations of diluted gadolinium-saline solution combined with local anesthetic (lidocaine) and iodinated contrast agent. The results of this study have potential implications for the evaluation of internal joint derangements using magnetic resonance arthrography (MRA). Iodinated contrast agent is included by some radiologists in the composition of paramagnetic contrast-saline solution prepared for direct MRA. Other radiologists prefer to inject iodinated contrast into the joint prior the gadolinium injection. In both situations, the iodinated contrast agent is useful to confirm the intraarticular positioning of the needle in cases where fluoroscopy is utilized to guide the procedure. With both techniques, the end result is a mix of iodinated contrast agent and gadolinium in the intraarticular saline solution. Another advantage of using an end solution with iodinated contrast agent is the possibility of converting a MRA into a computed tomography arthrography (CTA), in cases where the patient shows claustrophobia or in case of unexpected technical problems with the MRI equipment during MRI acquisition. CTA represents an interesting alternative to investigate joint diseases when multislice CT equipment is available (9–11) and therefore it can be used if for any reason MRA cannot be performed. Local anesthetics may also be added to the MRA paramagnetic contrast saline solution, either to alleviate pain and discomfort (12) , potentially reducing motion artifacts in MRI acquisition, or to collect additional information in order to investigate the in