The present report was the first application case of LAARP using intraoperative open MRI system for a pediatric patient with ARM. We successfully performed LAARP for ARM, with intraoperative confirmation of the precision of the rectal pull-through procedure. The essential goal of LAARP for ARM is the precise placement of the rectum through the muscle complex and external sphincters, which prevents division and injury of these muscles, which play an important role in the postoperative anorectal function . Inaccurate pull-through would lead to a poor bowel function, including soiling and fecal incontinence. Thus far, confirmation of the pull-through procedure was performed in the postoperative period . If the pulled-through rectum is found to be located in an inappropriate position after the operation, revision is difficult due to adhesion and perirectal scarring, and is also associated with a risk of injury of the pelvic nerve and muscle complex . However, this open MRI operating theater allows pediatric surgeons to evaluate the quality of an operation intraoperatively.
MRI operating theater systems have some advantages over other imaging modalities. First, MRI provides multiple images without an increased risk of radiation exposure to the patient . A low magnetic field does not any affect the human body, even in small infants. Second, regarding the above advantage, repeatable scanning during a short period is feasible. Third, MRI is superior to CT in terms of imaging of the soft tissue, including muscles. Above all of these advantages, in an operating theater equipped with open MRI, preoperative, intraoperative and immediate postoperative scanning are all possible for the real-time evaluation of an operative procedure, including the quality and results. In the neurosurgery field, prior to the introduction of intraoperative imaging modalities, the evaluation of the completion of brain tumor resection depended on the surgeon’s subjective impression. The same traditional decision and subjective evaluation processes were recognized in anorectoplasty for AMR. However, LAARP using a high-resolution image can allow us to confirm and grossly observe the muscle complex, as was demonstrated in this case. The combination of an open MRI operating theater and LAARP could provide an absolutely objective evaluation of the pull-through procedure for ARM. If MRI revealed inaccurate pull-through during the operation, revision surgery could be immediately performed to achieve for accurate pull-through.
Open MRI have some advantage compared with conventional “closed” MRI. Thomas et al.  reported the guiding technique for placing the neorectum through the entire sphincter complex with the conventional MRI in operating theater. They moved patients to the operation room from the MRI room after scanning. Open MRI can be established in same room because of lower magnetic field than conventional MRI. We could perform LAARP and scan with open MRI in the same room. In addition, conventional MRI require expensive cost for installation because of reinforcing the operation room.
In this case, we successfully performed accurate pull-through without residual fistula on the first attempt in an open MRI operating theater. The precise placement of the rectum would potentially facilitate the acquisition of a satisfactory postoperative bowel function; however, long-term follow-up is required to evaluate the outcome of the operative procedure. Bjørsum-Meyer et al.  mentioned that the presence and thickness of interposed fat between the sphincter complex and the bowel was positively correlated to the postoperative continence score with statistically significance at late follow-up of PSARP operation. We will follow the patient and evaluate his bowel function over the long term to validate the open MRI findings.
An open MRI operating theater is associated with some disadvantages and problems. An MRI scan generally takes longer to perform in comparison to computed tomography (CT) scan or radiography; however, it took approximately 3 min for each open MRI scan in the present case. It is a feasible and useful intraoperative modality for pediatric patients. In addition to the characteristics of MRI systems, we had several technical problems that should be solved before the operation. This is the first case in which the abdomen of a child was scanned with the QD head coil; thus, we scanned the patient using an open MRI system in the operation room to adjust the scanning condition of the pediatric abdomen on the operation day. To set the system, radiology engineers and the neurosurgeon performed several scans to acquire proficiency in open MRI scanning. On the operation day, we scanned the patient under general anesthesia. In our institution, all neurosurgery patients were adults and were scanned during awake craniotomy. A long respiratory tube between the anesthetic instrument and the gantry was needed for general anesthesia (Fig. 3). The dead space of the long tube might cause failure of effective mechanical ventilation because of the small body size of the patient. The anesthesiologist prepared a flow-inflating bag that could be used in the gantry. Fortunately, the anesthetic instruments provided good ventilation during scanning.
Despite the above stated disadvantages and problems, an open MRI operating theater offers promising possibilities for pediatric surgery. We are planning real-time navigation for ARM as a next challenge. Intraoperative MR cholangiopancreatography for choledochal cyst and MR urography for urinary tract disease may be other good indications for the use of an open MRI operating theater. Real-time evaluation would improve the operative quality and postoperative functional outcome in pediatric patients.