Intraoperative MRI - Guided Neurosurgery - Indications and Benefits.

Introduction

Bloch and Purcell, who shared the 1952 Nobel Prize in Physics, first experimentally documented the nuclear magnetic resonance (NMR) phenomena in 1946. A powerful magnet and radio waves are used to create images of the body in magnetic resonance imaging (MRI), which is based on the magnetic resonance phenomenon.

The first intraoperative MRI was created in 1991 due to improved soft tissue details, the requirement for intraoperative guiding to achieve precision and accuracy, and technological advancements. Intraoperative MRI is more accurate and provides near-real-time picture guidance than earlier navigational methods. When microscopic visualization is inadequate, it can evaluate the integrity and dynamic changes in the lesion and surrounding tissues. Specific operating rooms must be used for intraoperative MRI, and MRI-compatible monitoring equipment must be used.

The capability of MRI to generate high-quality pictures with greater soft-tissue contrast without ionizing radiation is a significant benefit. Based on the distinct magnetic properties of the tissues, which are influenced by the spin characteristics of hydrogen molecules, the magnet produces images.

What Are the Functions of MRI?

1. Using MRI to image the central nervous system is generally beneficial. To assess for acute and subacute infarcts, headaches, and seizure evaluation, as well as to track a neoplastic process, it is a lovely complement to non-contrast CT.
2. A non-contrast-enhanced brain MRI is recommended for patients after a non-contrast CT of the head or brain to assess for ischemic stroke due to the time-sensitive nature of stroke evaluation. Hyperacute ischemia can be seen in some parts of an image sequence based on the water diffusion coefficient in the brain parenchyma.
3. Due to the use of a particular breast coil, a wide field of view, and standardized sequences, breast MR is only suggested in a minimal number of circumstances. Letting the patient know that the exam will be carried out with the arms raised overhead. Dynamic contrast-enhanced breast MRI is an essential technique for assessing the severity of breast disease, the effectiveness of treatment, and the surveillance of persistent or recurrent disease.
4. Cardiac MRI offers structural as well as functional data. The patient must be able to endure imaging for up to 45 minutes and follow instructions to hold their breath. However, modern cardiac MR methods frequently use intravenous contrast agents; patterns of late gadolinium enhancement are crucial for recognizing scarred tissue. Non-contrast techniques are becoming more common.
5. Multiphase, post-contrast sequences help identify lesions and masses of the abdomen and pelvis and track treatment outcomes. MR typically comes after less expensive and more accessible first imaging, such as ultrasound or CT.
6. The diagnosis of soft-tissue masses, occult fractures, bone marrow edema, infiltrative processes of the marrow space, and internal derangements of the support systems of the joints can all be made using magnetic resonance imaging. The musculoskeletal structures are best imaged by radiographs, contributing significantly to MRI interpretation.

What Is Intraoperative Magnetic Resonance Imaging (iMRI)?

Using intraoperative magnetic resonance imaging (iMRI), neurosurgeons can more precisely operate on the brain's most delicate regions, a breakthrough for doctors and their patients. The iMRI (the IMRIS Surgical Theatre) is connected to a track system that hangs from the ceiling and, when necessary, transports the MRI right to the child in the operating room. The high-resolution magnetic resonance scans give surgeons a real-time view of the afflicted area so they may decide if the targeted area is wholly treated or whether they need to make any last-minute adjustments to their surgical plans.

• The iMRI can be utilized for MRI treatments for hospital inpatients needing post-anesthesia monitoring when it is not in use and is housed in a separate imaging room. The operating room's Brainlab Cranial neuro-navigation application from the hospital is coupled with the iMRI. This device offers "GPS-like guidance" to surgeons inside the brain.

• iMRI technology is used by neurosurgeons to treat:

  1. Tumors (both benign and malignant, primary and metastatic, affecting both the base of the skull and the brain itself).

  2. Congenital illnesses.

  3. Epilepsy.

  4. Illnesses like abscesses.

  5. Diseases like Parkinson's and Huntington's that cause movement difficulties.

  6. Vessel abnormalities.

This method of stereotactic intracranial lesion biopsy, craniotomy for the removal of intracranial space-occupying lesions and arteriovenous malformations, drainage of the intracranial cyst, cervical spine surgeries, and interstitial hyperthermia for tumor ablation has been used successfully.

The complete range of applications for intraoperative MRI has increased due to improvements in imaging, neurosurgical, and anesthetic technologies, as well as increased awareness of its benefits.

Pediatric neurosurgery, endoscopic transsphenoidal pituitary surgery, epilepsy surgery, transoral resection of cervical spine pathologies, and electrode implantation in deep brain stimulation patients have all been completed using intraoperative MRI-guided neurosurgery.

What Are the Benefits of Intraoperative Magnetic Resonance Imaging (iMRI) In Neurosurgery?

The hospital's neurosurgeons can maximize the removal of aberrant brain tissue with the aid of the iMRI. Studies show that using an iMRI enhances surgical safety and efficacy, providing the finest neurosurgical outcomes for a skilled surgical team.

• Increased tumor detection.

• Enhanced brain shift detection.

• Increased resection intensity.

• Enhanced safety.

• Shorter stays in the hospital.

• Improved quality of life and recovery.

What Are the Limitations of Intraoperative Magnetic Resonance Imaging (iMRI) In Neurosurgery?

Despite giving the surgeon in-the-moment assistance, intraoperative MRI has drawbacks. The older MRI systems produced average-quality images and needed MRI-compatible surgical equipment. The recent high-field MRI systems provide outstanding image quality without needing MRI-compatible surgical tools. Both systems need anesthetic machines, patient monitoring equipment, and MRI-compatible infusion pumps. Before scanning, MRI-unsafe monitoring equipment must be transferred beyond the 5G line, including patient warming devices, needle electrodes for evoked potential monitoring, and temperature probes. Compared to low and mid-field MRI systems, access to the patient in high-field MRI systems is particularly challenging. Before scanning the patient, the ventilatory circuit connections and anesthesia connections need to be double-checked. To maintain anesthesia, long ventilatory tubes, and intravenous infusion lines are needed, which could cause the administration of anesthetics to the patient to be delayed. Patients, particularly youngsters, may experience hypothermia as the MRI setting needs a cool environment to maximize the magnetic field, which could delay anesthetic recovery. Due to direct skin contact with the operating table or MRI coils, morbidly obese patients and patients with procedures requiring non-supine positions are more likely to develop pressure ulcers and compression-induced peripheral nerve damage. By choosing patients carefully and making sure there is enough padding, this can be prevented.

Investment is needed to set up an intraoperative MRI facility. Preparing the patient for the scan and executing the scan are included in intraoperative MRI, and both impact how long the surgery will last and how much it will ultimately cost. Contrast media are employed to enhance the imaging quality. They do have some negative side effects. These adverse consequences could manifest either right away or later. There are a variety of immediate adverse effects, ranging from minor (allergic urticaria, cutaneous edema, physiologic hypertension, tachycardia, nausea, and vomiting) to severe (allergic laryngospasm, bronchospasm, physiologic hypertensive emergencies, arrhythmias, seizures). The effect of injected contrast media on the kidneys (contrast-induced nephropathy, nephrogenic systemic fibrosis) is the cause of delayed side effects. Preoperative queries about prior contrast media exposure, allergic responses, kidney problems, diabetes mellitus, and hypertension should be given to patients receiving intraoperative MRI.

Conclusion

The care of neurosurgical patients now includes a new dimension thanks to intraoperative MRI. It has led to improved patient outcomes through increased surgical precision and accuracy. Still, it has also presented new problems to anesthesiologists regarding patient safety, monitoring, and equipment needs. To achieve patient and staff safety with positive outcomes, proper preoperative planning, personnel training on issues specific to intraoperative MRI, efficient communication, teamwork, and strict adherence to the preprocedural checklist will be helpful.