Preliminary experiences with "real-time" intraoperative ultrasonography associated to the laser and the ultrasonic aspirator in neurosurgery

Ultrasound-based real-time neuronavigated fluorescence-guided surgery for high-grade gliomas: technical note and preliminary experience

BACKGROUND

The extent of resection (EOR) plays a fundamental role in the prognosis of patients with high-grade gliomas (HGG). One of the main challenges in achieving a complete resection is the distinction between tumor and normal brain. Nowadays, several technologies are employed to obtain a higher tumor removal rate and respect the normal tissue in glioma surgery and in the last decades, fluorescein sodium (FS) and intraoperative ultrasound (IOUS) have been widely used. The aim of our technical note is to demonstrate how combining these two tools offers an ultrasound-based real-time neuronavigated fluorescence-guided surgery in order to optimize HGG removal.

METHODS

Five patients (3 males, 2 females; mean age 55.2 years, range 36-68 years) undergoing craniotomies for removal of intraaxial lesions suggestive of high-grade gliomas on preoperative MRI were included in the study. Intraoperative navigated B-mode and CEUS associated with sodium fluorescein were used in all cases; white light appearance, IOUS, and fluorescence findings were recorded immediately after each surgery. Also, extent of resection was evaluated on postoperative Gd-enhanced MRI performed within 72 h.

RESULTS

All tumors effectively stained yellow with fluorescein sodium during the surgical procedure and four were well delineated by IOUS. IOUS was repeated frequently (average 2.6 time) to obtain an orientation of the gross residual tumor with respect to anatomical landmarks as the surgery proceeded. Tumor removal was completed under Yellow 560 filter.

CONCLUSIONS

In our technical report, we demonstrate that combining intraoperatively fluorescein sodium and IOUS improves the information and facilitates making decisions during the HGG surgery. Further experience gained in larger studies will help confirm these findings.

Use of ultrasonic aspiration for dural opening in cranial reoperations: technical note

OBJECTIVE

Dural detachment from the brain in cranial reoperations has been accomplished previously by selective coagulation and the cutting of brain-dural adhesions. The results of ultrasonic aspiration during tumor surgery or brain cutting procedures led the authors to speculate that the detachment of the dura mater from brain tumors by applying the Cavitron ultrasonic surgical aspirator (Valleylab, Boulder, CO [formerly Cavitron, Inc., Stamford, CT]) to the brain-dura mater interface could be used to reduce bleeding and facilitate dural opening during cranial reoperations.

METHODS

Ten patients underwent a second craniotomy for epilepsy surgery (five cases of extended temporal lobectomy and five cases of extended extratemporal lesionectomy). The use of ultrasonic aspiration and its effects on brain separation from the dura mater were examined.

RESULTS

Intraoperative use of the Cavitron ultrasonic surgical aspirator during dural opening produced immediate blanching of the dura mater and enhanced visualization of the cortical surface without distortion of the brain anatomy.

CONCLUSION

Incremental dural opening and brain visualization is achieved by careful application of ultrasonic aspiration directly into the brain-dura limit, producing immediate regional dural devascularization. Use of this technique reduces cortical and dural bleeding and enhances the ease and effectiveness of brain visualization.

Volume CT with a flat-panel detector on a mobile, isocentric C-arm: Pre-clinical investigation in guidance of minimally invasive surgery

A mobile isocentric C-arm (Siemens PowerMobil) has been modified in our laboratory to include a large area flat-panel detector (in place of the x-ray image intensifier), providing multi-mode fluoroscopy and cone-beam computed tomography (CT) imaging capability. This platform represents a promising technology for minimally invasive, image-guided surgical procedures where precision in the placement of interventional tools with respect to bony and soft-tissue structures is critical. The image quality and performance in surgical guidance was investigated in pre-clinical evaluation in image-guided spinal surgery. The control, acquisition, and reconstruction system are described. The reproducibility of geometric calibration, essential to achieving high three-dimensional (3D) image quality, is tested over extended time scales (7 months) and across a broad range in C-arm angulation (up to 45 degrees), quantifying the effect of improper calibration on spatial resolution, soft-tissue visibility, and image artifacts. Phantom studies were performed to investigate the precision of 3D localization (viz., fiber optic probes within a vertebral body) and effect of lateral projection truncation (limited field of view) on soft-tissue detectability in image reconstructions. Pre-clinical investigation was undertaken in a specific spinal procedure (photodynamic therapy of spinal metastases) in five animal subjects (pigs). In each procedure, placement of fiber optic catheters in two vertebrae (L1 and L2) was guided by fluoroscopy and cone-beam CT. Experience across five procedures is reported, focusing on 3D image quality, the effects of respiratory motion, limited field of view, reconstruction filter, and imaging dose. Overall, the intraoperative cone-beam CT images were sufficient for guidance of needles and catheters with respect to bony anatomy and improved surgical performance and confidence through 3D visualization and verification of transpedicular trajectories and tool placement. Future investigation includes improvement in image quality, particularly regarding x-ray scatter, motion artifacts and field of view, and integration with optical tracking and navigation systems.

History of intraoperative ultrasound

Intraoperative ultrasound (IOUS) using A-mode or non-real-time B-mode imaging started in the 1960s; however, it was not widely accepted mainly because of difficulty in image interpretation. In the late 1970s, IOUS became one of the topics in the surgical communities upon the introduction of high-frequency real-time B-mode ultrasound. Special probes for operative use were developed. In the 1980s, all over the world the use of IOUS spread to a variety of surgical fields, such as hepatobiliary pancreatic surgery, neurosurgery, and cardiovascular surgery. IOUS changed hepatic surgery dramatically because IOUS was the only modality that was capable of delineating and examining the interior of the liver during surgery. After 1990, color Doppler imaging and laparoscopic ultrasound were incorporated into IOUS. Currently, IOUS is considered an indispensable operative procedure for intraoperative decision-making and guidance of surgical procedures. For better surgical practice, education of surgeons in the use of ultrasound is the most important issue.

Brain tumor resection guided by intraoperative computed tomography

Intraoperative computed tomography (CT) with a dedicated, therapeutic scanner facilitated resection of intracranial tumors in nine patients. Major benefits of intraoperative CT included exact, multiplanar lesion localization, maximal surgical resection and immediate recognition of potential intraoperative complications such as intracranial hemorrhage. Three cases are presented in detail to demonstrate the surgical technique. No complications related to the use of intraoperative imaging occurred. Although total resection of malignant brain neoplasms remained an unrealized goal, intraoperative CT increased the surgical accessibility of malignant and benign lesions located in critical areas of the brain.