Safety and Feasibility Assessment of the O-Arm as an Intraoperative Angiography Device in Aneurysm Surgery

Intraoperative Stereotactic Arteriography in Complex Cervical Spine Surgery

Intra-operative navigation has revolutionized spinal instrumentation. The O-arm (a mobile X-ray system; Medtronic, Minneapolis, MN) is uniquely capable of enabling visualization of the spine in axial planes. The application of this technology is wide yet underutilized in terms of its capacity to image spinal vascular anatomy. We completed a retrospective chart review of the following case studies. A 24-year-old neurologically intact female presented with a Jefferson fracture without vertebral artery dissection after a motor vehicle accident. After the failure of conservative management due to pseudoarthrosis, the patient opted for fusion. Prior to the procedure, bilateral 5 French femoral sheaths were placed. After exposure, intraarterial (IA) contrast was injected prior to the O-arm spin to visualize both vertebral arteries, which were stretched and adjacent to a mobile boney segment. In the second case, a 71-year-old male presented with right shoulder pain and a flaccid left deltoid secondary to a large enhancing epidural lesion spanning C4-C7. Further work-up confirmed a diagnosis of metastatic intrahepatic cholangiocarcinoma. Prior to resection with cervical spinal stabilization, a right radial artery 4 French Glidesheath was placed. Prior to the O-arm spin, the right vertebral artery was selected, and intravenous contrast was injected to permit visualization of the vertebral artery, which was encased within the tumor and at significant risk for iatrogenic injury. Both patients tolerated the endovascular and spinal procedures well without vertebral artery injury. This is the first series to report the effective use of the O-arm for improved visualization of vascular anatomy during surgery for cervical spinal trauma and oncology.

Validation of SART 3.5D algorithm for cerebrovascular dynamics and artery versus vein classification in presurgical 3D digital subtraction angiographies

Classification of arteries and veins in cerebral angiograms can increase the safety of neurosurgical procedures, such as StereoElectroEncephaloGraphy, and aid the diagnosis of vascular pathologies, as arterovenous malformations. We propose a new method for vessel classification using the contrast medium dynamics in rotational digital subtraction angiography (DSA). After 3D DSA and angiogram segmentation, contrast enhanced projections are processed to suppress soft tissue and bone structures attenuation effect and further enhance the CM flow. For each voxel labelled as vessel, a time intensity curve (TIC) is obtained as a linear combination of temporal basis functions whose weights are addressed by simultaneous algebraic reconstruction technique (SART 3.5D), expanded to include dynamics. Each TIC is classified by comparing the areas under the curve in the arterial and venous phases. Clustering is applied to optimize the classification thresholds. On a dataset of 60 patients, a median value of sensitivity (90%), specificity (91%), and accuracy (92%) were obtained with respect to annotated arterial and venous voxels up to branching order 4–5. Qualitative results are also presented about CM arrival time mapping and its distribution in arteries and veins respectively. In conclusion, this study shows a valuable impact, at no protocol extra-cost or invasiveness, concerning surgical planning related to the enhancement of arteries as major organs at risk. Also, it opens a new scope on the pathophysiology of cerebrovascular dynamics and its anatomical relationships.

A New Classification of Anterior Choroidal Artery Aneurysms and Its Clinical Application

Background and Purpose: The aim of this study was to compare the different subtypes of anterior choroidal artery (AChoA) aneurysm based on a new classification and to analyze the risk factors according to individual endovascular treatment (EVT).

Methods: In the new classification, AChoA aneurysms are classified into independent type (I type) and dependent type (II type) based on the relationship between the AChoA and the aneurysm. II type aneurysms have three subtypes, IIa (neck), IIb (body), and IIc (direct). We retrospectively analyzed 52 cases of AChoA aneurysm treated in our center between 2015 to 2019. There were 13 (25.0%) I type aneurysms, 24 (46.2%) IIa aneurysms, 15 (28.8%) IIb aneurysms, and no IIc type; 28 cases had a subarachnoid hemorrhage. According to our preoperative EVT plan for the different subtypes: II type should achieve Raymond-Roy Occlusion Class 1 (RROC 1) where possible. To protect the AChoA, it is best to preserve the neck of the IIa type aneurysms (RROC 2), and RROC 3 is enough for IIb type.

Results: Ten asymptomatic cases with minimal aneurysms were treated conservatively. Of the other cases, 42 were treated with individualized EVT (26 with a simple coil, 6 with balloon-assisted coiling, 7 with stent-assisted coiling, and 3 by flow diverter. Different subtypes had different RROC (Z = 14.026, P = 0.001). IIb type aneurysms (χ² = 7.54, P = 0.023) were one of the factors related to temporary or permanent AChoA injury during surgery. Overall, two patients (IIa = 1, IIb = 1) developed contralateral hemiparesis.

Conclusions: The new classification diagram clearly shows the features of all types of AChoA aneurysm and makes EVT planning more explicit. The II type (particularly IIb) was a potential risk factor for AChoA injury.

Comparison of Intra- and Postoperative 3-Dimensional Digital Subtraction Angiography in Evaluation of the Surgical Result After Intracranial Aneurysm Treatment

BACKGROUND

Postoperative three-dimensional digital subtraction angiography (3D-DSA) is the gold standard in evaluating intracranial aneurysm (IA) remnants after clipping. Should intraoperative 3D-DSA image quality be equally good as postoperative 3D-DSA, it could supplant the latter as standard of care for follow-up of clipped IA.

OBJECTIVE

To directly compare the quality of assessment of clipped IA by intraoperative and postoperative 3D-DSA.

METHODS

From a prospective cohort of 221 consecutive patients who underwent craniotomy for IA treatment in a hybrid operating room, we retrospectively studied 26 patients who had both intraoperative and postoperative 3D-DSA imaging of their clipped aneurysm. Comparison of intraoperative and postoperative 3D-DSA images (blinded for review) included parameters that affected image quality and differences between the 2 periods.

RESULTS

In the 26 patients with 32 clipped IAs, the mean interval was 11 ± 7 mo between intraoperative and postoperative imaging 3D-DSA examinations. Reconstruction with multiple clips was used in 14 (44%) cases. Of 15 remnants, 9 (60%) were small (<2 mm). In comparing intraoperative and postoperative 3D-DSA, no discordance or discrepancy in assessment of the surgical result was noted for any clipped IA, and overall imaging quality was excellent for both modalities. Factors affecting minor differences in image quality were not identified.

CONCLUSION

Compared with postoperative 3D-DSA, intraoperative 3D-DSA images achieved equally high quality and effective, immediate interpretation of the surgical clipping result. With comparable imaging quality and no discordant findings, intraoperative 3D-DSA could replace postoperative 3D-DSA to become the standard of care in IA surgery.

The accuracy of 3D fluoroscopy (XT) vs computed tomography (CT) registration in deep brain stimulation (DBS) surgery

BACKGROUND

Stereotactic registration is the most critical step ensuring accuracy in deep brain stimulation (DBS) surgery. 3D fluoroscopy (XT) is emerging as an alternative to CT. XT has been shown to be safe and effective for intraoperative confirmation of lead position following implantation. However, there is a lack of studies evaluating the suitability of XT to be used for the more crucial step of registration and its capability of being merged to a preoperative MRI. This is the first study comparing accuracy, efficiency, and radiation exposure of XT- vs CT-based stereotactic registration and XT/MRI merging in deep brain stimulation.

METHODS

Mean absolute differences and Euclidean distance between planned (adjusted for intraoperative testing) and actual lead trajectories were calculated for accuracy of implantation. The radiation dose from each scan was recorded as the dose length product (DLP). Efficiency was measured as the time between the patient entering the operating room and the initial skin incision. A one-way ANOVA compared these parameters between patients that had either CT- or XT-based registration.

RESULTS

Forty-one patients underwent DBS surgery-25 in the CT group and 16 in the XT group. The mean absolute difference between CT and XT was not statistically significant in the x (p = 0.331), y (p = 0.951), or z (p = 0.807) directions. The Euclidean distance between patient groups did not differ significantly (p = 0.874). The average radiation exposure with XT (220.0 ± 0.1 mGy*cm) was significantly lower than CT (1269.3 ± 112.9 mGy*cm) (p < 0.001). There was no significant difference in registration time between CT (107.8 ± 23.1 min) and XT (106.0 ± 18.2 min) (p = 0.518).

CONCLUSION

XT-based frame registration was shown to result in similar implantation accuracy and significantly less radiation exposure compared with CT. Our results surprisingly showed no significant difference in registration time, but this may be due to a learning curve effect.