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Jan Gralla, Raphael Guzman, Caspar Brekenfeld, Luca Remonda and Claus Kiefer

Object. Conventional imaging for neuronavigation is performed using high-resolution computerized tomography (CT) scanning or a T1-weighted isovoxel magnetic resonance (MR) sequence. The extension of some lesions, however, is depicted much better on T2-weighted MR images. A possible fusion process used to match low-resolution T2-weighted MR image set with a referenced CT or T1-weighted data set leads to poor resolution in the three-dimensional (3D) reconstruction and decreases accuracy, which is unacceptable for neuronavigation. The object of this work was to develop a 3D T2-weighted isovoxel sequence (3D turbo—spin echo [TSE]) for image-guided neuronavigation of the whole brain and to evaluate its clinical application.

Methods. The authors performed a phantom study and a clinical trial on a newly developed T2-weighted isovoxel sequence, 3D TSE, for image-guided neuronavigation using a common 1.5-tesla MR imager (Siemens Sonata whole-body imager). The accuracy study and intraoperative image guidance were performed with the aid of the pointer-based Medtronic Stealth Station Treon.

The 3D TSE data set was easily applied to the navigational setup and demonstrated a high registration accuracy during the experimental trial and during an initial prospective clinical trial in 25 patients. The sequence displayed common disposable skin fiducial markers and provided convincing delineation of lesions that appear hyperintense on T2-weighted images such as low-grade gliomas and cavernomas in its clinical application.

Conclusions. Three-dimensional TSE imaging broadens the spectrum of navigational and intraoperative data sets, especially for lesions that appear hyperintense on T2-weighted images. The accuracy of its registration is very reliable and it enables high-resolution reconstruction in any orientation, maintaining the advantages of image-guided surgery.

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Serge Marbacher, Itai Mendelowitsch, Basil Erwin Grüter, Michael Diepers, Luca Remonda and Javier Fandino

OBJECTIVE

During the last decade, improvements in real-time, high-resolution imaging of surgically exposed cerebral vasculature have been realized with the successful introduction of intraoperative indocyanine green video angiography (ICGVA) and technical advances in intraoperative digital subtraction angiography (DSA). With the availability of 3D intraoperative DSA (3D-iDSA) in hybrid operating rooms, the present study offers a contemporary comparison for rates of accuracy and discordance.

METHODS

In this retrospective study of prospectively collected data, 140 consecutive patients underwent microsurgical treatment of intracranial aneurysms (IAs) in a hybrid operating room. Variables analyzed included patient demographics, aneurysm-specific characteristics, intraoperative ICGVA and 3D-iDSA findings, and the need for intraoperative clip readjustment. The authors defined the discordance rate of the two modalities as a false-negative finding that necessitated clip repositioning after 3D-iDSA.

RESULTS

In 120 patients, ICGVA and 3D-iDSA were used to evaluate 134 IA obliterations. Of 215 clips used, 29 (14%) were repositioned intraoperatively, improving the surgical result in all 29 patients (24%). Repositioning was prompted by visual inspection and microvascular Doppler ultrasonography in 8 (28%), ICGVA in 13 (45%), and 3D-iDSA in 7 (24%) patients. Clip repositioning was needed in 7 patients (6%) based on 3D-iDSA, yielding an ICGVA accuracy rate of 94%. Five (71%) of the ICGVA–3D-iDSA discordances that prompted clip repositioning occurred at the anterior communicating artery complex.

CONCLUSIONS

A combination of vascular monitoring techniques most often achieved correct intraoperative interpretation of complete IA occlusion and parent artery integrity. Compared with 3D-iDSA imaging, ICGVA demonstrated high accuracy. Despite the relatively low discordance rate, iDSA was confirmed to be the gold standard. Improved imaging quality, including 3D-iDSA, supports its routine use in IA surgery, obviating the need for postoperative DSA.

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Sven Berkmann, Javier Fandino, Sascha Zosso, Hanspeter E. Killer, Luca Remonda and Hans Landolt

Object

Sellar lesions with suprasellar extension may cause loss of visual acuity and visual field damage due to compression of the optic chiasm. Using intraoperative MR (iMR) imaging to detect symptomatic lesion remnants adjacent to the optic chiasm (that may be resected in the same procedure) may positively affect the functional outcome of patients with these lesions. The aim of this study was to evaluate the correlation between visual improvement and optic nerve decompression detected by iMR imaging in patients undergoing transsphenoidal resection of pituitary lesions.

Methods

A total of 32 patients (23 men and 9 women) who underwent transsphenoidal resection of sellar lesions causing visual impairment were included in this study. Tumor volume ranged from 0.9 cm3 to 55.7 cm3 (mean 9.8 ± 11.7 cm3). Preoperative assessment showed visual field damage in 31 patients (97%) and loss of visual acuity in 28 patients (88%). The latency period between the appearance of symptoms and transsphenoidal decompression was 14.9 ± 19.5 weeks.

Results

Intraoperative MR imaging was performed after the resection was believed to be complete, or if further tumor removal was not safely possible due to changed conditions in the surgical field. Complete resection was detected on these initial scans in 17 patients (53%). Partial resection was achieved in 9 patients (28%) and tumor debulking in 6 (19%). Additional resection was possible in 8 (53%) of these 15 patients. Four (50%) of these 8 cases had suprasellar remnants and the optic chiasm was subsequently decompressed. In 5 cases optimal decompression of the optic chiasm was not possible. On early follow-up within 1 month after surgery, overall improvement of visual field damage was observed in 27 patients (87%). In 23 patients (74%), the Goldmann perimetry demonstrated complete recovery. Improvement of visual acuity was noted in 24 patients (86%). Eighteen patients (64%) regained full visual acuity. Identification of a decompressed optic chiasm on iMR imaging was significantly correlated with visual field improvement (p = 0.0007; positive predictive value 0.96, 95% CI 0.81–0.99) and relief of visual acuity deficits (p = 0.0002; positive predictive value 0.96, 95% CI 0.79–0.99). Two patients needed transcranial procedures for symptomatic tumor remnants detected on iMR imaging.

Conclusions

Intraoperative MR imaging findings correlate with prognosis of visual deficits after transsphenoidal decompression of the anterior optic pathways. The use of iMR imaging may prevent revision surgery for unexpected symptomatic remnants.

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Alexander Spiessberger, Fabio Strange, Basil Erwin Gruter, Stefan Wanderer, Daniela Casoni, Philipp Gruber, Michael Diepers, Luca Remonda, Javier Fandino, Javier Añon and Serge Marbacher

OBJECTIVE

Temporary parent vessel occlusion performed to establish a high-flow interpositional bypass carries the risk of infarcts. The authors investigated the feasibility of a novel technique to establish a high-flow bypass without temporary parent vessel occlusion in order to lower the risk of ischemic complications.

METHODS

In 10 New Zealand white rabbits, a carotid artery side-to-end anastomosis was performed under parent artery patency with a novel endovascular balloon device. Intraoperative angiography, postoperative neurological assessments, and postoperative MRI/MRA were performed to evaluate the feasibility and safety of the novel technique.

RESULTS

A patent anastomosis was established in 10 of 10 animals; 3 procedure-related complications occurred. No postoperative focal neurological deficits were observed. The MRI/MRA findings include no infarcts and bypass patency in 50% of the animals.

CONCLUSIONS

The authors demonstrated the feasibility of an endovascular assisted, nonocclusive high-flow bypass. Future refinement of the device and technique in an animal model is necessary to lower the complication rate and increase patency rates.