Imri

Brief summary: iMRI is an advanced MRI technology that allows imaging during surgery. It is used most often in neurosurgery and can support intraoperative decision-making with updated images. It is not necessary for every patient; suitability is individualized.

What is intraoperative MRI (iMRI)?

Intraoperative magnetic resonance imaging, or iMRI, is an advanced technology that allows MRI-based imaging while surgery is still in progress. It is used most often in brain and spine surgery because it can help the surgical team reassess the operative field with real-time or near-real-time information. Its key difference from standard MRI is timing: instead of providing information only before or after the operation, it can also provide important images during critical parts of surgery. This can be especially useful when the surgeon needs updated information about tumor boundaries, residual tissue, or the relationship of the operative site to delicate surrounding structures. ^[1][3][4]

iMRI is not needed in every operation. It is generally considered in selected neurosurgical procedures in which the aim is to maximize safe resection, in some epilepsy surgeries, and in other complex cases. One reason is that as surgery proceeds, brain tissue can shift, making preoperative images less accurate for navigation. Updated imaging during surgery may help recalibrate navigation systems and refine the next surgical step. In that sense, iMRI is not merely an imaging device but an intraoperative decision-support tool. ^[1][4][5][6]

When is it used?

iMRI is most commonly discussed in brain tumor surgery. The goal is to help balance maximal removal of abnormal tissue with preservation of critical functions such as speech, movement, vision, or major vascular structures. It may also be useful in selected pituitary, skull base, or epilepsy procedures. In some centers it can also play a role in certain spinal procedures or advanced thermal ablation techniques. However, use depends on the type of operation, the technical infrastructure of the center, and team experience. It is therefore not a standard step for every patient. ^[1][2][4][5]

In tumor surgery, for example, intraoperative imaging may reveal whether suspicious residual tissue remains. This may help the surgeon decide whether additional resection can be performed safely or whether stopping would be the safer choice. In that sense, the potential benefit of iMRI is not simply “removing more tissue,” but making surgery more precise and more informed. ^[2][4][5][7]

How is it applied during surgery?

Operations that use iMRI are planned somewhat differently from standard neurosurgical procedures. Before surgery, the team carefully reviews metal implants, pacemakers, clips, pumps, and other MRI-safety considerations. The operating room and imaging environment must be prepared accordingly, and equipment must be MRI-compatible. During surgery, the patient is under anesthesia, and at a selected stage the team may briefly pause to obtain updated images. The sterile field is protected, safety is rechecked, and the new images are acquired and interpreted. ^[1][3][6][7]

After imaging, the team may continue surgery, remove additional tissue, revise the approach, or end the procedure based on the new information. In some systems the patient is moved to the MRI scanner; in others, the surgical suite is integrated with imaging. From the patient’s point of view, iMRI itself is not consciously felt because it is performed during anesthesia. Recovery is usually shaped more by the underlying surgery than by the imaging technique itself. Still, iMRI can make the operative process more logistically complex and may lengthen the overall procedure. ^[1][2][5][7]

What are the advantages and limitations?

The main potential advantage of iMRI is that it provides updated anatomical information during the operation. This can improve navigation accuracy and help the surgeon judge resection margins more effectively. Some studies have associated iMRI use with higher rates of gross total resection in selected settings, but the size of this benefit is not the same for every disease or every center. Outcomes vary according to tumor type, location, concurrent technologies, and team experience. It would therefore be misleading to present iMRI as a guarantee of better outcomes in every patient. ^[4][5][6][7]

Limitations are also important. iMRI can extend operative time, increase cost, and require specialized infrastructure. MRI-safety rules also mean that not every implant or piece of equipment is suitable. In some situations, surgical materials or operative conditions can make image interpretation more difficult. The technology is most useful when applied in appropriately selected cases by experienced teams. ^[1][4][5][7]

Risks, preparation, and recovery

The most important issue specific to iMRI is MRI safety. Metal fragments, certain implanted devices, clips, or MRI-incompatible systems may prevent use or require special precautions. If contrast is planned, kidney function and allergy history are also reviewed. In practice, however, the patient’s postoperative recovery is usually determined mainly by the surgery itself rather than by iMRI. Headache, nausea, neurological symptoms, or wound-care issues after discharge are therefore usually assessed within the context of the underlying neurosurgical procedure. ^[1][3][6]

After discharge, worsening headache, new weakness, speech difficulty, seizures, confusion, high fever, wound drainage, or severe vomiting may require urgent evaluation. These warning signs are important regardless of whether iMRI was used. The most relevant recovery guidance comes from the operating team and depends on the reason for surgery and its extent. ^[1][2][3]

Which questions should be asked when deciding?

Patients and families should ask why iMRI is being used in their specific case. Is the goal to improve the safety of tumor removal, update resection boundaries, or protect critical structures more effectively? It is also reasonable to ask whether it may prolong surgery, whether there are MRI-safety concerns, and whether the imaging is likely to change the operative plan in a meaningful way. The most useful decision-making is goal-based rather than technology-based. ^[1][2][4][7]

Individual risk, suitability, and follow-up planning vary according to the procedure, coexisting medical conditions, and medications; the final decision should therefore be made with the relevant specialist team.