title: Image guidance based on MRI for spinal interstitial laser thermotherapy: technical aspects and accuracy.
abstract: OBJECTIVE Image guidance for spinal procedures is based on 3D-fluoroscopy or CT, which provide poor visualization of soft tissues, including the spinal cord. To overcome this limitation, the authors developed a method to register intraoperative MRI (iMRI) of the spine into a neuronavigation system, allowing excellent visualization of the spinal cord. This novel technique improved the accuracy in the deployment of laser interstitial thermal therapy probes for the treatment of metastatic spinal cord compression. METHODS Patients were positioned prone on the MRI table under general anesthesia. Fiducial markers were applied on the skin of the back, and a plastic cradle was used to support the MRI coil. T2-weighted MRI sequences of the region of interest were exported to a standard navigation system. A reference array was sutured to the skin, and surface matching of the fiducial markers was performed. A navigated Jamshidi needle was advanced until contact was made with the dorsal elements; its position was confirmed with intraoperative fluoroscopy prior to advancement into a target in the epidural space. A screenshot of its final position was saved, and then the Jamshidi needle was exchanged for an MRI-compatible access cannula. MRI of the exact axial plane of each access cannula was obtained and compared with the corresponding screenshot saved during positioning. The discrepancy in millimeters between the trajectories was measured to evaluate accuracy of the image guidance RESULTS Thirteen individuals underwent implantation of 47 laser probes. The median absolute value of the discrepancy between the location predicted by the navigation system and the actual position of the access cannulas was 0.7 mm (range 0-3.2 mm). No injury or adverse event occurred during the procedures. CONCLUSIONS This study demonstrates the feasibility of image guidance based on MRI to perform laser interstitial thermotherapy of spinal metastasis. The authors' method permits excellent visualization of the spinal cord, improving safety and workflow during laser ablations in the epidural space. The results can be extrapolated to other indications, including biopsies or drainage of fluid collections near the spinal cord.
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Claudio E
authors.initials: CE
authors.lastname: Tatsui
authors.affiliation: Department of Neurosurgery, University of São Paulo, São Paulo, Brazil.
authors.forename: Clarissa N G
authors.initials: CNG
authors.lastname: Nascimento
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Dima
authors.initials: D
authors.lastname: Suki
authors.affiliation: Diagnostic Radiology.
authors.forename: Behrang
authors.initials: B
authors.lastname: Amini
authors.affiliation: Radiation Oncology.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Radiation Oncology.
authors.forename: Amol J
authors.initials: AJ
authors.lastname: Ghia
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Thomas
authors.affiliation: Imaging Physics, and.
authors.forename: R Jason
authors.initials: RJ
authors.lastname: Stafford
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Rhines
authors.affiliation: Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston; and.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Cata
authors.affiliation: Diagnostic Radiology.
authors.forename: Ashok J
authors.initials: AJ
authors.lastname: Kumar
authors.affiliation: Departments of 1 Neurosurgery.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Rao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000768:Anesthesia, General; D005240:Feasibility Studies; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods*; D053685:Laser Therapy / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation / Q000295:instrumentation / Q000379:methods*; D056888:Patient Positioning; D012189:Retrospective Studies; D013117:Spinal Cord Compression / Q000000981:diagnostic imaging / Q000209:etiology / Q000628:therapy*; D013125:Spinal Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000556:secondary / Q000628:therapy*
keywords: AP = anteroposterior; ESCC = epidural spinal cord compression; KPS = Karnofsky Performance Status; SINS = Spinal Neoplastic Instability Score; SSRS = spinal stereotactic radiosurgery; cEBRT = conventional external beam radiotherapy; iMRI = intraoperative MRI; image guidance; magnetic resonance images; oncology; sLITT = spinal laser interstitial thermotherapy; spinal laser interstitial thermotherapy