Comparison of intraoperative MR imaging and 3D-navigated ultrasonography in the detection and resection control of lesions

Fluorescence and Intraoperative Ultrasound as Surgical Adjuncts for Brain Metastases Resection: What Do We Know? A Systematic Review of the Literature

(1) Background: brain metastases (BMs) are the most common neoplasm of the central nervous system; despite the high incidence of this type of tumour, to date there is no universal consensus on the most effective treatment in patients with BMs, even if surgery still plays a primary role. Despite this, the adjunct systems that help to reach the GTR, which are well structured for other tumour forms such as ultrasound and fluorescence systems, are not yet well employed and standardised in surgical practice. The aim of this review is to provide a picture of the current state-of-art of the roles of iOUS and intraoperative fluorescence to better understand their potential roles as surgical tools. (2) Methods: to reach this goal, the PubMed database was searched using the following string as the keyword: (((Brain cerebral metastasis [MeSH Major Topic])OR (brain metastasis, [MeSH Major Topic])) AND ((5-ala, [MeSH Terms]) OR (Aminolevulinicacid [All fields]) OR (fluorescein, [MeSH Terms]) OR (contrast enhanced ultrasound [MeSH Terms])OR ((intraoperative ultrasound. [MeSH Terms]))) AND (english [Filter]) AND ((english [Filter]) AND (2010:2022 [pdat])) AND (english [Filter]). (3) Results: from our research, a total of 661 articles emerged; of these, 57 were selected. 21 of these included BMs generically as a secondary class for comparisons with gliomas, without going deeply into specific details. Therefore, for our purposes, 36 articles were considered. (4) Conclusions: with regard to BMs treatment and their surgical adjuncts, there is still much to be explored. This is mainly related to the heterogeneity of patients, the primary tumour histology and the extent of systemic disease; regardless, surgery plays a paramount role in obtaining a local disease control, and more standardised surgical protocols need to be made, with the aim of optimizing the use of the available surgical adjuncts and in order to increase the rate of GTR.

Is intraoperative ultrasound more efficient than magnetic resonance in neurosurgical oncology? An exploratory cost-effectiveness analysis

Objective

Intraoperative imaging is a chief asset in neurosurgical oncology, it improves the extent of resection and postoperative outcomes. Imaging devices have evolved considerably, in particular ultrasound (iUS) and magnetic resonance (iMR). Although iUS is regarded as a more economically convenient and yet effective asset, no formal comparison between the efficiency of iUS and iMR in neurosurgical oncology has been performed.

Methods

A cost-effectiveness analysis comparing two single-center prospectively collected surgical cohorts, classified according to the intraoperative imaging used. iMR (2013-2016) and iUS (2021-2022) groups comprised low- and high-grade gliomas, with a maximal safe resection intention. Units of health gain were gross total resection and equal or increased Karnofsky performance status. Surgical and health costs were considered for analysis. The incremental cost-effectiveness ratio (ICER) was calculated for the two intervention alternatives. The cost-utility graphic and the evolution of surgical duration with the gained experience were also analyzed.

Results

50 patients followed an iMR-assisted operation, while 17 underwent an iUS-guided surgery. Gross total resection was achieved in 70% with iMR and in 60% with iUS. Median postoperative Karnofsky was similar in both group (KPS 90). Health costs were € 3,220 higher with iMR, and so were surgical-related costs (€ 1,976 higher). The ICER was € 322 per complete resection obtained with iMR, and € 644 per KPS gained or maintained with iMR. When only surgical-related costs were analyzed, ICER was € 198 per complete resection with iMR and € 395 per KPS gained or maintained.

Conclusion

This is an unprecedented but preliminary cost-effectiveness analysis of the two most common intraoperative imaging devices in neurosurgical oncology. iMR, although being costlier and time-consuming, seems cost-effective in terms of complete resection rates and postoperative performance status. However, the differences between both techniques are small. Possibly, iMR and iUS are complementary aids during the resection: iUS real-time images assist while advancing towards the tumor limits, informing about the distance to relevant landmarks and correcting neuronavigation inaccuracy due to brain shift. Yet, at the end of resection, it is the iMR that reliably corroborates whether residual tumor remains.

Evaluation of a Navigated 3D Ultrasound Integration for Brain Tumor Surgery: First Results of an Ongoing Prospective Study

The aim of the study was to assess the quality, accuracy and benefit of navigated 2D and 3D ultrasound for intra-axial tumor surgery in a prospective study. Patients intended for gross total resection were consecutively enrolled. Intraoperatively, a 2D and 3D iUS-based resection was performed. During surgery, the image quality, clinical benefit and navigation accuracy were recorded based on a standardized protocol using Likert’s scales. A total of 16 consecutive patients were included. Mean ratings of image quality in 2D iUS were significantly higher than in 3D iUS (p < 0.001). There was no relevant decrease in rating during the surgery in 2D and 3D iUS (p > 0.46). The benefit was rated 2.2 in 2D iUS and 2.6 in 3D iUS (p = 0.08). The benefit remained stable in 2D, while there was a slight decrease in the benefit in 3D after complete tumor resection (p = 0.09). The accuracy was similar in both (mean 2.2 p = 0.88). Seven patients had a small tumor remnant in intraoperative MRT (mean 0.98 cm3) that was not appreciated with iUS. Crucially, 3D iUS allows for an accurate intraoperative update of imaging with slightly lower image quality than 2D iUS. Our preliminary data suggest that the benefit and accuracy of 2D and 3D iUS navigation do not undergo significant variations during tumor resection.

Navigated Intraoperative 3D Ultrasound in Glioblastoma Surgery: Analysis of Imaging Features and Impact on Extent of Resection

Background

Neuronavigation is routinely used in glioblastoma surgery, but its accuracy decreases during the operative procedure due to brain shift, which can be addressed utilizing intraoperative imaging. Intraoperative ultrasound (iUS) is widely available, offers excellent live imaging, and can be fully integrated into modern navigational systems. Here, we analyze the imaging features of navigated i3D US and its impact on the extent of resection (EOR) in glioblastoma surgery.

Methods

Datasets of 31 glioblastoma resection procedures were evaluated. Patient registration was established using intraoperative computed tomography (iCT). Pre-operative MRI (pre-MRI) and pre-resectional ultrasound (pre-US) datasets were compared regarding segmented tumor volume, spatial overlap (Dice coefficient), the Euclidean distance of the geometric center of gravity (CoG), and the Hausdorff distance. Post-resectional ultrasound (post-US) and post-operative MRI (post-MRI) tumor volumes were analyzed and categorized into subtotal resection (STR) or gross total resection (GTR) cases.

Results

The mean patient age was 59.3 ± 11.9 years. There was no significant difference in pre-resectional segmented tumor volumes (pre-MRI: 24.2 ± 22.3 cm³; pre-US: 24.0 ± 21.8 cm³). The Dice coefficient was 0.71 ± 0.21, the Euclidean distance of the CoG was 3.9 ± 3.0 mm, and the Hausdorff distance was 12.2 ± 6.9 mm. A total of 18 cases were categorized as GTR, 10 cases were concordantly classified as STR on MRI and ultrasound, and 3 cases had to be excluded from post-resectional analysis. In four cases, i3D US triggered further resection.

Conclusion

Navigated i3D US is reliably adjunct in a multimodal navigational setup for glioblastoma resection. Tumor segmentations revealed similar results in i3D US and MRI, demonstrating the capability of i3D US to delineate tumor boundaries. Additionally, i3D US has a positive influence on the EOR, allows live imaging, and depicts brain shift.

Surgical advances in the management of brain metastases

As the epidemiological and clinical burden of brain metastases continues to grow, advances in neurosurgical care are imperative. From standard magnetic resonance imaging (MRI) sequences to functional neuroimaging, preoperative workups for metastatic disease allow high-resolution detection of lesions and at-risk structures, facilitating safe and effective surgical planning. Minimally invasive neurosurgical approaches, including keyhole craniotomies and tubular retractors, optimize the preservation of normal parenchyma without compromising extent of resection. Supramarginal surgery has pushed the boundaries of achieving complete removal of metastases without recurrence, especially in eloquent regions when paired with intraoperative neuromonitoring. Brachytherapy has highlighted the potential of locally delivering therapeutic agents to the resection cavity with high rates of local control. Neuronavigation has become a cornerstone of operative workflow, while intraoperative ultrasound (iUS) and intraoperative brain mapping generate real-time renderings of the brain unaffected by brain shift. Endoscopes, exoscopes, and fluorescent-guided surgery enable increasingly high-definition visualizations of metastatic lesions that were previously difficult to achieve. Pushed forward by these multidisciplinary innovations, neurosurgery has never been a safer, more effective treatment for patients with brain metastases.

Utilizing Intraoperative Navigated 3D Color Doppler Ultrasound in Glioma Surgery

Background

In glioma surgery, the patient’s outcome is dramatically influenced by the extent of resection and residual tumor volume. To facilitate safe resection, neuronavigational systems are routinely used. However, due to brain shift, accuracy decreases with the course of the surgery. Intraoperative ultrasound has proved to provide excellent live imaging, which may be integrated into the navigational procedure. Here we describe the visualization of vascular landmarks and their shift during tumor resection using intraoperative navigated 3D color Doppler ultrasound (3D iUS color Doppler).

Methods

Six patients suffering from glial tumors located in the temporal lobe were included in this study. Intraoperative computed tomography was used for registration. Datasets of 3D iUS color Doppler were generated before dural opening and after tumor resection, and the vascular tree was segmented manually. In each dataset, one to four landmarks were identified, compared to the preoperative MRI, and the Euclidean distance was calculated.

Results

Pre-resectional mean Euclidean distance of the marked points was 4.1 ± 1.3 mm (mean ± SD), ranging from 2.6 to 6.0 mm. Post-resectional mean Euclidean distance was 4.7. ± 1.0 mm, ranging from 2.9 to 6.0 mm.

Conclusion

3D iUS color Doppler allows estimation of brain shift intraoperatively, thus increasing patient safety. Future implementation of the reconstructed vessel tree into the navigational setup might allow navigational updating with further consecutive increasement of accuracy.

Intraoperative Imaging for High-Grade Glioma Surgery

This article discusses intraoperative imaging techniques used during high-grade glioma surgery. Gliomas can be difficult to differentiate from surrounding tissue during surgery. Intraoperative imaging helps to alleviate problems encountered during glioma surgery, such as brain shift and residual tumor. There are a variety of modalities available all of which aim to give the surgeon more information, address brain shift, identify residual tumor, and increase the extent of surgical resection. The article starts with a brief introduction followed by a review of with the latest advances in intraoperative ultrasound, intraoperative MRI, and intraoperative computed tomography.

Navigated 3D Ultrasound in Brain Metastasis Surgery: Analyzing the Differences in Object Appearances in Ultrasound and Magnetic Resonance Imaging

Background: Implementation of intraoperative 3D ultrasound (i3D US) into modern neuronavigational systems offers the possibility of live imaging and subsequent imaging updates. However, different modalities, image acquisition strategies, and timing of imaging influence object appearances. We analyzed the differences in object appearances in ultrasound (US) and magnetic resonance imaging (MRI) in 35 cases of brain metastasis, which were operated in a multimodal navigational setup after intraoperative computed tomography based (iCT) registration. Method: Registration accuracy was determined using the target registration error (TRE). Lesions segmented in preoperative magnetic resonance imaging (preMRI) and i3D US were compared focusing on object size, location, and similarity. Results: The mean and standard deviation (SD) of the TRE was 0.84 ± 0.36 mm. Objects were similar in size (mean ± SD in preMRI: 13.6 ± 16.0 cm3 vs. i3D US: 13.5 ± 16.0 cm3). The Dice coefficient was 0.68 ± 0.22 (mean ± SD), the Hausdorff distance 8.1 ± 2.9 mm (mean ± SD), and the Euclidean distance of the centers of gravity 3.7 ± 2.5 mm (mean ± SD). Conclusion: i3D US clearly delineates tumor boundaries and allows live updating of imaging for compensation of brain shift, which can already be identified to a significant amount before dural opening.

Segmentation-based registration of ultrasound volumes for glioma resection in image-guided neurosurgery

PURPOSE

In image-guided surgery for glioma removal, neurosurgeons usually plan the resection on images acquired before surgery and use them for guidance during the subsequent intervention. However, after the surgical procedure has begun, the preplanning images become unreliable due to the brain shift phenomenon, caused by modifications of anatomical structures and imprecisions in the neuronavigation system. To obtain an updated view of the resection cavity, a solution is to collect intraoperative data, which can be additionally acquired at different stages of the procedure in order to provide a better understanding of the resection. A spatial mapping between structures identified in subsequent acquisitions would be beneficial. We propose here a fully automated segmentation-based registration method to register ultrasound (US) volumes acquired at multiple stages of neurosurgery.

METHODS

We chose to segment sulci and falx cerebri in US volumes, which remain visible during resection. To automatically segment these elements, first we trained a convolutional neural network on manually annotated structures in volumes acquired before the opening of the dura mater and then we applied it to segment corresponding structures in different surgical phases. Finally, the obtained masks are used to register US volumes acquired at multiple resection stages.

RESULTS

Our method reduces the mean target registration error (mTRE) between volumes acquired before the opening of the dura mater and during resection from 3.49 mm (± 1.55 mm) to 1.36 mm (± 0.61 mm). Moreover, the mTRE between volumes acquired before opening the dura mater and at the end of the resection is reduced from 3.54 mm (± 1.75 mm) to 2.05 mm (± 1.12 mm).

CONCLUSION

The segmented structures demonstrated to be good candidates to register US volumes acquired at different neurosurgical phases. Therefore, our solution can compensate brain shift in neurosurgical procedures involving intraoperative US data.

The real-time ultrasonography for fusion image in glioma neurosugery

OBJECTIVES

The aim of study is to evaluate the general performance and efficiency of the using real time intraoperative ultrasound system with Volume Navigation system technology in glioma. Compare glioma intraoperative ultrasound and contrast agent ultrasound images to obtained preoperative MRI with fusion image in a real-time.

PATIENTS AND METHODS

Fifteen patients had been performed fusion imaging involved intraoperative real-time ultrasound and contrast agent ultrasound with preoperative MR imaging including preoperative gadolinium-enhanced MRI from March 2017 to December 2017. The number of tumor was counted online fusion imaging in real time ultrasound with and without preoperative MR. We analyzed ultrasound coplanar MR modalities in real time including tumor location, margin (obscure or defined). In addition, intraoperative ultrasound enhancement pattern was analyzed compare it to preoperative reconstruction gadolinium-enhanced T1-weighted MRI. Two radiologists who made planning ultrasound assessment for the focus lesion based on a 4 scoring system according to the degree of confidence.

RESULTS

Thirteen of fifteen patients whose automatically registration successful intraoperative neurosurgery accepted preoperative MR examination. Seven of fifteen fine-tuning registration phase were performed and satisfactory with fusion image substantially. Intraoperatively, 73.3% (11/15) glioma nodules were definite on conventional B-mode US by a radiologist who doesn't know the MR result before fusion US with MRI. However, 100% tumors were detected on fusion B-mode ultrasound imaging with MRI. Two radiologists evaluated the score between fusion B-mode ultrasound and CEUS with coplanar MRI and had a result that score was upgraded in 69.2% (9/13) and 84.6% (11/13) patients. Inter-observer agreement was significant (kappa value = 1.0, p < 0.001) in B-mode ultrasound fusion image with MRI. Inter-observer agreement was moderate (kappa value = 0. 0.618, p < 0.001) in CEUS fusion image with MRI.

CONCLUSION

Fusion imaging is very useful to detect poor sonographic visibility tumor on fusion B-mode US imaging with MR images. Fusion image may demonstrate multiplane images including same standard and nonstandard MRI and US images to help localize tumor. The additional real time fusion CEUS mode image with MR is a safe method for neurosurgery and the use of CEUS should be considered when fusion B-mode ultrasound imaging alone is not satisfactory for margin.

Ultrasound-guided brain surgery: echographic visibility of different pathologies and surgical applications in neurosurgical routine

BACKGROUND

The use of intraoperative ultrasound (iUS) has increased in the last 15 years becoming a standard tool in many neurosurgical centers. Our aim was to assess the utility of routine use of iUS during various types of intracranial surgery. We reviewed our series to assess ultrasound visibility of different pathologies and iUS applications during the course of surgery.

MATERIALS AND METHODS

This is a retrospective review of 162 patients who underwent intracranial surgery with assistance of the iUS guidance system (SonoWand). Pathologic categories were neoplastic (135), vascular (20), infectious (2), and CSF related (5). Ultrasound visibility was assessed using the Mair classification, a four-tiered grading system that considers the echogenicity of the lesion and its border visibility (from 0 to 3; grade 0, pathology not visible; grade 3, visible with clear border with normal tissue). iUS applications included lesion localization, approach planning to deep-seated lesions, and lesion removal.

RESULTS

All pathologies were visible on iUS except one aneurysm. On average, extra-axial tumors were identified more easily and had clearer limits compared to intra-axial tumors (extra-axial 17% grade 2, 83% grade 3; intra-axial 5.5% grade 1, 46.5% grade 2, 48% grade 3). iUS provided precise and safe transcortical trajectories to deep-seated lesions (71 patients; tumors, hemangiomas, ICHs); iUS was judged to be less useful to approach skull base tumors and aneurysms. iUS was used to judge extent of resection in 152 cases; surgical artifacts reduced sonographic visibility in 25 cases: extent of resection was correctly checked in 127 patients (53 gliomas, 15 metastases, 39 meningiomas, 4 schwannomas, 4 sellar region tumors, 6 hemangiomas, 3 AVMs, 2 abscesses).

CONCLUSIONS

iUS was highly sensitive in detecting all types of pathology, was safe and precise in planning trajectories to intraparenchymal lesions (including minimally mini-invasive approaches), and was accurate in checking extent of resection in more than 80% of cases. iUS is a versatile and feasible tool; it could improve safety and its use may be considered in routine intracranial surgery.

Technical accuracy of the integration of an external ultrasonography system into a navigation platform: effects of ultrasonography probe registration and target detection

BACKGROUND

Intraoperative navigated ultrasonography has reached clinical acceptance, while published data for the accuracy of some systems are missing. We technically quantified and optimised the accuracy of the integration of an external ultrasonography system into a BrainLab navigation system.

METHODS

A high-end ultrasonography system (Elegra; Siemens, Erlangen, Germany) was linked to a navigation system (Vector Vision; BrainLab, Munich, Germany). In vitro accuracy and precision was calculated from differences between a real world target (high-precision crosshair phantom) and the ultrasonography image of this target in the navigation coordinate system. The influence of the intrinsic component of the calibration phantom (for ultrasonography probe registration), type of target definition (manual versus automatic) and orientation of the ultrasound probe in relation to the navigation tracking device on accuracy and precision were analysed in different settings (100 measurements for each setting) resembling clinically relevant scenarios in the neurosurgical operating theatre.

RESULTS

Line-of-sight angles of 45°, 62° and 90° for the optical tracking of the navigated ultrasonography probe and a distance of 1.8 m revealed best accuracy and precision. Technical accuracy of the integration of ultrasonography into a standard navigation system is high [Euclidean error: median, 0.79 mm; mean, 0.89 ± 0.42 mm for 62° angle; median range: 1.16-1.46 mm; mean range (±SD): 1.22 ± 0.32 mm to 1.46 ± 0.55 mm for grouped analysis of all angles tested]. Software-based automatic target definition improved precision significantly (p < 0.001).

CONCLUSIONS

Integration of an external ultrasonography system into the BrainLab navigation is accurate and precise. By modifying registration (and measurement conditions) via software modification, the in vitro accuracy and precision is improved and requirements for a clinical application are fully met.

Neurosurgical tools to extend tumor resection in hemispheric low-grade gliomas: conventional and contrast enhanced ultrasonography

PURPOSE

Pediatric low-grade gliomas (LGGs) are the most frequent solid tumor in childhood. Based on an increasing number of literature reports, maximal safe resection is recommended as the first line of treatment whenever possible. However, distinguishing tumor tissue from the surrounding normal brain is often challenging with infiltrating neoplasms, even with the assistance of intraoperative, microscopic and conventional neuronavigation systems. Therefore, any technique that enhances the detection and visualization of LGGs intraoperatively is certainly desirable.

METHODS

In this paper, we reviewed the role of intraoperative conventional ultrasound and contrast-enhanced ultrasound (CEUS) as a tool for extending tumor resection in LGGs. Moreover, our experience with this technology is reported and discussed.

RESULTS

Both B-mode and CEUS are helpful in highlighting LGGs, detecting tumor margins and providing additional information such as vascularization, thus improving the safety of a more radical resection.

CONCLUSIONS

Although the full potentialities of the method are yet to be explored, intraoperative ultrasound is a promising tool in oncologic surgery and LGG surgery.

Applications of Ultrasound in the Resection of Brain Tumors

Neurosurgery makes use of preoperative imaging to visualize pathology, inform surgical planning, and evaluate the safety of selected approaches. The utility of preoperative imaging for neuronavigation, however, is diminished by the well-characterized phenomenon of brain shift, in which the brain deforms intraoperatively as a result of craniotomy, swelling, gravity, tumor resection, cerebrospinal fluid (CSF) drainage, and many other factors. As such, there is a need for updated intraoperative information that accurately reflects intraoperative conditions. Since 1982, intraoperative ultrasound has allowed neurosurgeons to craft and update operative plans without ionizing radiation exposure or major workflow interruption. Continued evolution of ultrasound technology since its introduction has resulted in superior imaging quality, smaller probes, and more seamless integration with neuronavigation systems. Furthermore, the introduction of related imaging modalities, such as 3-dimensional ultrasound, contrast-enhanced ultrasound, high-frequency ultrasound, and ultrasound elastography, has dramatically expanded the options available to the neurosurgeon intraoperatively. In the context of these advances, we review the current state, potential, and challenges of intraoperative ultrasound for brain tumor resection. We begin by evaluating these ultrasound technologies and their relative advantages and disadvantages. We then review three specific applications of these ultrasound technologies to brain tumor resection: (1) intraoperative navigation, (2) assessment of extent of resection, and (3) brain shift monitoring and compensation. We conclude by identifying opportunities for future directions in the development of ultrasound technologies.

The value of intraoperative ultrasonography during the resection of relapsed irradiated malignant gliomas in the brain

Purpose

The aim of this study was to investigate whether intraoperative ultrasonography (IOUS) helped the surgeon navigate towards the tumor as seen in preoperative magnetic resonance imaging and whether IOUS was able to distinguish between tumor margins and the surrounding tissue.

Methods

Twenty-five patients suffering from high-grade gliomas who were previously treated by surgery and radiotherapy were included. Intraoperatively, two histopathologic samples were obtained a sample of unequivocal tumor tissue (according to anatomical landmarks and the surgeon’s visual and tactile impressions) and a small tissue sample obtained using a navigated needle when the surgeon decided to stop the resection. This specimen was considered to be a boundary specimen, where no tumor tissue was apparent. The decision to take the second sample was not influenced by IOUS. The effect of IOUS was analyzed semi-quantitatively.

Results

All 25 samples of unequivocal tumor tissue were histopathologically classified as tumor tissue and were hyperechoic on IOUS. Of the boundary specimens, eight were hypoechoic. Only one harbored tumor tissue (P=0.150). Seventeen boundaries were moderately hyperechoic, and these samples contained all possible histological results (i.e., tumor, infiltration, or no tumor).

Conclusion

During surgery performed on relapsed, irradiated, high-grade gliomas, IOUS provided a reliable method of navigating towards the core of the tumor. At borders, it did not reliably distinguish between remnants or tumor-free tissue, but hypoechoic areas seldom contained tumor tissue.

Intraoperative Ultrasound-Guided Resection of Gliomas: A Meta-Analysis and Review of the Literature

BACKGROUND

Image-guided surgery has become standard practice during surgical resection, using preoperative magnetic resonance imaging. Intraoperative ultrasound (IoUS) has attracted interest because of its perceived safety, portability, and real-time imaging. This report is a meta-analysis of intraoperative ultrasound in gliomas.

METHODS

Critical literature review and meta-analyses, using the MEDLINE/PubMed service. The list of references in each article was double-checked for any missing references. We included all studies that reported the use of ultrasound to guide glioma-surgery. The meta-analyses were conducted according to statistical heterogeneity between the studies using Open MetaAnalyst Software. If there was no heterogeneity, fixed effects model was used for meta-analysis; otherwise, a random effect model was used. Statistical heterogeneity was explored by χ(2) and inconsistency (I(2)) statistics; an I(2) value of 50% or more represented substantial heterogeneity.

RESULTS

A wide search yielded 19,109 studies that might be relevant, of which 4819 were ultrasound in neurosurgery; 756 studies used ultrasound in cranial surgery, of which 24 studies used intraoperative ultrasound to guide surgical resection and 74 studies used it to guide biopsy. Fifteen studies fulfilled our stringent inclusion criteria, giving a total of 739 patients. The estimated average gross total resection rate was 77%. Furthermore, the relationship between extent of surgical resection and study population was not linear. Gross total resection was more likely under IoUS when the lesion was solitary and subcortical, with no history of surgery or radiotherapy. IoUS image quality, sensitivity, specificity, and positive and negative predictive values deteriorated as surgical resection proceeded.

CONCLUSION

IoUS-guided surgical resection of gliomas is a useful tool for guiding the resection and for improving the extent of resection. IoUS can be used in conjunction with other complementary technologies that can improve anatomic orientation during surgery. Real-time imaging, improved image quality, small probe sizes, repeatability, portability, and relatively low cost make IoUS a realistic, cost-effective tool that complements any existing tools in any neurosurgical operating environment.

The Art of Intraoperative Glioma Identification

A major dilemma in brain-tumor surgery is the identification of tumor boundaries to maximize tumor excision and minimize postoperative neurological damage. Gliomas, especially low-grade tumors, and normal brain have a similar color and texture, which poses a challenge to the neurosurgeon. Advances in glioma resection techniques combine the experience of the neurosurgeon and various advanced technologies. Intraoperative methods to delineate gliomas from normal tissue consist of (1) image-based navigation, (2) intraoperative sampling, (3) electrophysiological monitoring, and (4) enhanced visual tumor demarcation. The advantages and disadvantages of each technique are discussed. A combination of these methods is becoming widely accepted in routine glioma surgery. Gross total resection in conjunction with radiation, chemotherapy, or immune/gene therapy may increase the rates of cure in this devastating disease.

Intraoperative stereotactic injection of Indigo Carmine dye to mark ill-defined tumor margins: a prospective phase I-II study

OBJECT

A critical goal in neurosurgical oncology is maximizing the extent of tumor resection while minimizing the risk to normal white matter tracts. Frameless stereotaxy and white matter mapping are indispensable tools in this effort, but deep tumor margins may not be accurately defined because of the "brain shift" at the end of the operation. The authors investigated the safety and efficacy of a technique for marking the deep margins of intraaxial tumors with stereotactic injection of Indigo Carmine dye.

METHODS

Investigational New Drug study approval for a prospective study in adult patients with gliomas was obtained from the FDA (Investigational New Drug no. 112680). At surgery, 1-3 stereotactic injections of 0.01 ml of Indigo Carmine dye were performed through the initial bur holes into the deep tumor margins before elevation of the bone flap. White light microscopic resection was conducted in standard fashion by using frameless stereotactic navigation until the injected margins were identified. The resection of the injected tumor margins and the extent of resection of the whole tumor volume were determined by using postoperative volumetric MRI.

RESULTS

In total 17 injections were performed in 10 enrolled patients (6 male, 4 female), whose mean age was 49 years. For all patients, the injection points were identified intraoperatively and tumor was resected at these points. The staining pattern was reproducible; it was a sphere of stained tissue approximately 5 mm in diameter. A halo of stained tissue and a backflow of dye through the needle tract were also noted, but these were clearly distinct from the staining pattern of the injection point, which was vividly colored and demarcated. Postoperative MR images verified the resection of all injection points. The mean extent of resection of the tumor as a whole was 97.1%. For 1 patient, a brain abscess developed on postoperative Day 16 and needed additional surgical treatment.

CONCLUSIONS

Stereotactic injection of Indigo Carmine dye can be used to demarcate multiple deep tumor margins, which can be readily identified intraoperatively by using standard white light microscopy. This technique may enhance the accuracy of frameless stereotactic navigation and increase the extent of resection of intraaxial tumors.

The value of intraoperative sonography in low grade glioma surgery

OBJECTIVE

There is a number of different methods to localize a glioma intraoperatively. Neuronavigation, intraoperative MRI, 5-aminolevulinic acid, as well as intraoperative sonography. Every method has its advantages and disadvantages. Low grade gliomas do not show a specific signal with 5-aminolevulinic acid and are difficult to distinguish macroscopically from normal tissue. In the present study we stress out the importance of intraoperative diagnostic ultrasound for localization of low grade gliomas.

METHODS

We retrospectively evaluated the charts and MRIs of 34 patients with low grade gliomas operated in our department from 2011 until December 2014. The efficacy of ultrasound as an intraoperative navigational tool was assessed. In 15 patients ultrasound was used and in 19 not. Only histologically proven low grades gliomas (astrocytomas grade II) were evaluated.

RESULTS

In none of the patients where ultrasound (combined with neuronavigation) was used (N=15) to find the tumors, the target was missed, whereas the exclusive use of neuronavigation missed the target in 5 of 19 cases of small subcortical low grade gliomas.

CONCLUSIONS

Intraoperative ultrasound is an excellent tool in localizing low grade gliomas intraoperatively. It is an inexpensive, real time neuronavigational tool, which overcomes brain shift. Even when identifying the tumors with ultrasound is very reliable, the extend of resection and the decision to remove any residual tumor with the help of ultrasound is at the moment unreliable.

Neck tumor dissection improved with 3-dimensional ultrasound image guidance: technical case report

BACKGROUND AND IMPORTANCE

Three-dimensional ultrasound navigation has been performed to assist in resection of cranial and spinal tumors, but to the best of our knowledge, no one has described the use of real-time 3-dimensional ultrasound navigation in the resection of neck tumors beyond biopsy.

CLINICAL PRESENTATION

This case report describes the use of 3-dimensional ultrasonic navigation in assisting with resection of a large neck paraganglioma. The 3-dimensional ultrasonic navigation improved real-time visualization of the carotid arteries, the trachea, and other vital structures.

CONCLUSION

The use of 3-dimensional ultrasound navigation should be considered in aiding resection of large neck tumors because it can allow more efficient and safer tumor resection.

Intraoperative ultrasonography for presumed brain metastases: a case series study

Brain metastases (BM) are one of the most common intracranial tumors and surgical treatment can improve both the functional outcomes and patient survival, particularly when systemic disease is controlled. Image-guided BM resection using intraoperative exams, such as intraoperative ultrasound (IOUS), can lead to better surgical results.

METHODS

To evaluate the use of IOUS for BM resection, 20 consecutive patients were operated using IOUS to locate tumors, identify their anatomical relationships and surgical cavity after resection. Technical difficulties, complications, recurrence and survival rates were noted.

RESULTS

IOUS proved effective for locating, determining borders and defining the anatomical relationships of BM, as well as to identify incomplete tumor resection. No complications related to IOUS were seen.

CONCLUSION

IOUS is a practical supporting method for the resection of BM, but further studies comparing this method with other intraoperative exams are needed to evaluate its actual contribution and reliability.

Intraoperative magnetic resonance spectroscopy for identification of residual tumor during low-grade glioma surgery: clinical article

OBJECT

The authors had previously shown that 3-T intraoperative MRI (ioMRI) detects residual tumor tissue during low-grade glioma and that it helps to increase the extent of resection. In a proportion of their cases, however, the ioMRI disclosed T2-hyperintense areas at the tumor resection border after the initial resection attempt and prompted a differential diagnosis between residual tumor and nontumoral changes. To guide this differential diagnosis the authors used intraoperative long-TE single-voxel proton MR spectroscopy (ioMRS) and tested the correlation of these findings with findings from pathological examination of resected tissue.

METHODS

Patients who were undergoing surgery for hemispheric or insular WHO Grade II gliomas and were found to have T2 changes around the resection cavity at the initial ioMRI were prospectively examined with ioMRS and biopsies were taken from corresponding localizations. In 14 consecutive patients, the ioMRS diagnosis in 20 voxels of interest was tested against the histopathological diagnosis. Intraoperative diffusion-weighted imaging (ioDWI) was also performed, as a part of the routine imaging, to rule out surgically induced changes, which could also appear as T2 hyperintensity.

RESULTS

Presence of tumor was documented in 14 (70%) of the 20 T2-hyperintense areas by histopathological examination. The sensitivity of ioMRS for identifying residual tumor was 85.7%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 75%. The specificity of ioDWI for surgically induced changes was high (100%), but the sensitivity was only 60%.

CONCLUSIONS

This is the first clinical series to indicate that ioMRS can be used to differentiate residual tumor from nontumoral changes around the resection cavity, with high sensitivity and specificity.

Effect of sonographically guided cerebral glioma surgery on survival time

OBJECTIVES

We investigated the value of intraoperative sonography in improving the prevalence of total tumor resection and the survival time of patients who underwent resection of cerebral gliomas.

METHODS

One hundred thirty-seven patients who underwent sonographically guided surgery were followed for 6 to 60 months. In addition, 60 randomly selected patients (30 with low-grade gliomas and 30 with high-grade gliomas) who had surgery in our hospital without sonographic guidance served as the control group. Follow-up included the survival time, and the difference in the survival time between the study and control groups was statistically analyzed.

RESULTS

Total removal of the lesion was achieved in 77 cases (69%), and partial removal was achieved in 35 (31%). In the control low-grade glioma group, 6-month survival was 96.7%; 1-year survival was 73.3%; and 2-year survival was 53.3%. In the study low-grade glioma group, survival rates at 6 months, 1 year, and 2 years were 98.0%, 96.1%, and 88.2%, respectively. In the control and study high-grade glioma groups, survival rates at 6 months, 1 year, and 2 years were 83.3% and 93.4%, 43.3% and 59.2%, and 13.3% and 32.8%. When comparing survival at 6 months, 1 year, and 2 years between the control and study groups, there was no significant difference at 6 months (P > .05), but survival at 1 and 2 years was significantly different (P < .05).

CONCLUSIONS

Sonographically guided resection of cerebral gliomas helps the surgeon understand the relationship between the lesion and the surrounding structures. It is of value in improving the prevalence of total tumor resection and the patient's survival time.

Resection of pediatric intracerebral tumors with the aid of intraoperative real-time 3-D ultrasound

PURPOSE

Intraoperative ultrasound (IOUS) has become a useful tool employed daily in neurosurgical procedures. In pediatric patients, IOUS offers a radiation-free and safe imaging method. This study aimed to evaluate the use of a new real-time 3-D IOUS technique (RT-3-D IOUS) in our pediatric patient cohort.

MATERIAL AND METHODS

Over 24 months, RT-3-D IOUS was performed in 22 pediatric patients (8 girls and 14 boys) with various brain tumors. These lesions were localized by a standard navigation system followed by analyses before, intermittently during, and after neurosurgical resection using the iU22 ultrasound system (Philips, Bothell, USA) connected to the RT-3-D probe (X7-2).

RESULTS

In all 22 patients, real-time 3-D ultrasound images of the lesions could be obtained during neurosurgical resection. Based on this imaging method, rapid orientation in the surgical field and the approach for the resection could be planned for all patients. In 18 patients (82%), RT-3-D IOUS revealed a gross total resection with a favorable neurological outcome.

CONCLUSION

RT-3-D IOUS provides the surgeon with advanced orientation at the tumor site via immediate live two-plane imaging. However, navigation systems have yet to be combined with RT-3-D IOUS. This combination would further improve intraoperative localization.

Advanced imaging in brain tumor surgery

The advanced imaging techniques outlined in this article are only slowly establishing their place in surgical practice. Even a low risk of false information is unacceptable in neurosurgery, thus decision-making is necessarily conservative. As more validation studies and greater experience accrue, surgeons are becoming more comfortable weighing the quality of information from functional imaging studies. Advanced imaging information is highly complementary to established surgical "good practice" such as anatomic planning, awake craniotomy, and electrocortical stimulation; its greatest impact is perhaps on how neurosurgery is planned and discussed before the patient is ever brought to the operating room. Access to functional magnetic resonance (MR) imaging, diffusion tractography, and intraoperative MR imaging can influence neurosurgical decisions before, during, and after surgery. However, the widespread adoption of these techniques in neurosurgical practice remains limited by the lack of standardized methods, the need for validation across institutions, and the unclear cost-effectiveness particularly for intraoperative MR imaging. Before advanced imaging results can be used therapeutically, it is incumbent on the neurosurgeon and neuroradiologist to develop a working understanding of each technique's strengths and weaknesses, positive and negative predictive values, and modes of failure. This content presents several imaging methods that are increasingly used in neurosurgical planning. As these techniques are progressively applied to surgery, radiologists, medical physicists, neuroscientists, and engineers will be necessary partners with the treating neurosurgeon to bridge the gap between the experimental and the therapeutic.

Ultrasound-guided operations in unselected high-grade gliomas--overall results, impact of image quality and patient selection

BACKGROUND

A number of tools, including intraoperative ultrasound, are reported to facilitate surgical resection of high-grade gliomas. However, results from selected surgical series do not necessarily reflect the effectiveness in common neurosurgical practice. Delineation of seemingly similar brain tumours vary in different ultrasound-guided operations, perhaps limiting usefulness in certain patients.

METHODS

We explore and describe the results associated with use of the SonoWand system with intraoperative ultrasound in a population-based, unselected, high-grade glioma series. Surgeons filled out questionnaires about presumed extent of resection, use of ultrasound and ultrasound image quality just after surgery. We evaluate the impact of ultrasound image quality. We also explore the importance of patient selection for surgical results.

RESULTS

Of 156 consecutive malignant glioma operations, 142 (91%) were resections whilst 14 (9%) were only biopsies. We achieved gross total resection (GTR) in 37% of all high-grade glioma resections, whilst worsening of functional status was seen in 13%. The risk of getting worse was significantly higher in reoperations, resections in eloquent locations, resections in cases with poor ultrasound image quality, resection when surgeons' resection grade estimates were inaccurate and in cases with surgery-related complications. Aiming for GTR, unifocality of lesion, non-eloquent location and medium or good ultrasound image quality were identified as independent factors associated with achieving GTR.

CONCLUSION

We report good overall results, both in terms of resection grades and functional outcome in consecutive malignant glioma resections, in which intraoperative ultrasound was used in 95%. We observed a seeming dose-response relationship between ultrasound image quality and clinical and radiological results. This may suggest that better ultrasound facilitates better surgery. The study also clearly demonstrates that, in terms of surgical results, the selection of patients seems to be much more important than the selection of surgical tools.

New prototype neuronavigation system based on preoperative imaging and intraoperative freehand ultrasound: system description and validation

PURPOSE

The aim of this report is to present IBIS (Interactive Brain Imaging System) NeuroNav, a new prototype neuronavigation system that has been developed in our research laboratory over the past decade that uses tracked intraoperative ultrasound to address surgical navigation issues related to brain shift. The unique feature of the system is its ability, when needed, to improve the initial patient-to-preoperative image alignment based on the intraoperative ultrasound data. Parts of IBIS Neuronav source code are now publicly available on-line.

METHODS

Four aspects of the system are characterized in this paper: the ultrasound probe calibration, the temporal calibration, the patient-to-image registration and the MRI-ultrasound registration. In order to characterize its real clinical precision and accuracy, the system was tested in a series of adult brain tumor cases.

RESULTS

Three metrics were computed to evaluate the precision and accuracy of the ultrasound calibration. 1) Reproducibility: 1.77 mm and 1.65 mm for the bottom corners of the ultrasound image, 2) point reconstruction precision 0.62-0.90 mm: and 3) point reconstruction accuracy: 0.49-0.74 mm. The temporal calibration error was estimated to be 0.82 ms. The mean fiducial registration error (FRE) of the homologous-point-based patient-to-MRI registration for our clinical data is 4.9 ± 1.1 mm. After the skin landmark-based registration, the mean misalignment between the ultrasound and MR images in the tumor region is 6.1 ± 3.4 mm.

CONCLUSIONS

The components and functionality of a new prototype system are described and its precision and accuracy evaluated. It was found to have an accuracy similar to other comparable systems in the literature.

Adaptive spatial calibration of a 3D ultrasound system

PURPOSE

The authors present a method devised to calibrate the spatial relationship between a 3D ultrasound scanhead and its tracker completely automatically and reliably. The user interaction is limited to collecting ultrasound data on which the calibration is based.

METHODS

The method of calibration is based on images of a fixed plane of unknown location with respect to the 3D tracking system. This approach has, for advantage, to eliminate the measurement of the plane location as a source of error. The devised method is sufficiently general and adaptable to calibrate scanheads for 2D images and 3D volume sets using the same approach. The basic algorithm for both types of scanheads is the same and can be run unattended fully automatically once the data are collected. The approach was devised by seeking the simplest and most robust solutions for each of the steps required. These are the identification of the plane intersection within the images or volumes and the optimization method used to compute a calibration transformation matrix. The authors use adaptive algorithms in these two steps to eliminate data that would otherwise prevent the convergence of the procedure, which contributes to the robustness of the method.

RESULTS

The authors have run tests amounting to 57 runs of the calibration on two a scanhead that produce 3D imaging volumes, at all the available scales. The authors evaluated the system on two criteria: Robustness and accuracy. The program converged to useful values unattended for every one of the tests (100%). Its accuracy, based on the measured location of a reference plane, was estimated to be 0.7 +/- 0.6 mm for all tests combined.

CONCLUSIONS

The system presented is robust and allows unattended computations of the calibration parameters required for freehand tracked ultrasound based on either 2D or 3D imaging systems.

Image guidance and neuromonitoring in neurosurgery

INTRODUCTION

The localization of tumors and epileptogenic foci within the somatosensory or language cortex of the brain of a child poses unique neurosurgical challenges. In the past, lesions in these regions were not treated aggressively for fear of inducing neurological deficits. As a result, while function may have been preserved, the underlying disease may not have been optimally treated, and repeat neurosurgical procedures were frequently required. Today, with the advent of preoperative brain mapping, image guidance or neuronavigation, and intraoperative monitoring, peri-Rolandic and language cortex lesions can be approached directly and definitively with a high degree of confidence that neurosurgical function will be maintained.

METHODS AND RESULTS

The preoperative brain maps can now be achieved with magnetic resonance imaging (MRI), functional MRI, magnetoencephalography, and diffusion tensor imaging. Image guidance systems have improved significantly and include the use of the intraoperative MRI. Somatosensory, motor, and brainstem auditory-evoked potentials are used as standard neuromonitoring techniques in many centers around the world. Added to this now is the use of continuous train-of-five monitoring of the integrity of the corticospinal tract while operating in the peri-Rolandic region.

CONCLUSION

We are in an era where continued advancements can be expected in mapping additional pathways such as visual, memory, and hearing pathways. With these new advances, neurosurgeons can expect to significantly improve their surgical outcomes further.

Reliability of intraoperative high-resolution 2D ultrasound as an alternative to high–field strength MR imaging for tumor resection control: a prospective comparative study

Object

Ultrasound may be a reliable but simpler alternative to intraoperative MR imaging (iMR imaging) for tumor resection control. However, its reliability in the detection of tumor remnants has not been definitely proven. The aim of the study was to compare high-field iMR imaging (1.5 T) and high-resolution 2D ultrasound in terms of tumor resection control.

Methods

A prospective comparative study of 26 consecutive patients was performed. The following parameters were compared: the existence of tumor remnants after presumed radical removal and the quality of the images. Tumor remnants were categorized as: detectable with both imaging modalities or visible only with 1 modality.

Results

Tumor remnants were detected in 21 cases (80.8%) with iMR imaging. All large remnants were demonstrated with both modalities, and their image quality was good. Two-dimensional ultrasound was not as effective in detecting remnants < 1 cm. Two remnants detected with iMR imaging were missed by ultrasound. In 2 cases suspicious signals visible only on ultrasound images were misinterpreted as remnants but turned out to be a blood clot and peritumoral parenchyma. The average time for acquisition of an ultrasound image was 2 minutes, whereas that for an iMR image was ~ 10 minutes. Neither modality resulted in any procedure-related complications or morbidity.

Conclusions

Intraoperative MR imaging is more precise in detecting small tumor remnants than 2D ultrasound. Nevertheless, the latter may be used as a less expensive and less time-consuming alternative that provides almost real-time feedback information. Its accuracy is highest in case of more confined, deeply located remnants. In cases of more superficially located remnants, its role is more limited.

Usefulness of Intraoperative Ultra Low-field Magnetic Resonance Imaging in Glioma Surgery

Objective:

The aim of this study was to demonstrate the usefulness of a mobile, intraoperative 0.15-T magnetic resonance imaging (MRI) scanner in glioma surgery.

Methods:

We analyzed our prospectively collected database of patients with glial tumors who underwent tumor resection with the use of an intraoperative ultra low-field MRI scanner (PoleStar N-20; Odin Medical Technologies, Yokneam, Israel/Medtronic, Louisville, CO). Sixty-three patients with World Health Organization Grade II to IV tumors were included in the study. All patients were subjected to postoperative 1.5-T imaging to confirm the extent of resection.

Results:

Intraoperative image quality was sufficient for navigation and resection control in both high-and low-grade tumors. Primarily enhancing tumors were best detected on T1-weighted imaging, whereas fluid-attenuated inversion recovery sequences proved best for nonenhancing tumors. Intraoperative resection control led to further tumor resection in 12 (28.6%) of 42 patients with contrast-enhancing tumors and in 10(47.6%) of 21 patients with noncontrast-enhancing tumors. In contrast-enhancing tumors, further resection led to an increased rate of complete tumor resection (71.2 versus 52.4%), and the surgical goal of gross total removal or subtotal resection was achieved in all cases (100.0%). In patients with noncontrast-enhancing tumors, the surgical goal was achieved in 19 (90.5%) of 21 cases, as intraoperative MRI findings were inconsistent with postoperative high-field imaging in 2 cases.

Conclusion:

The use of the PoleStar N-20 intraoperative ultra low-field MRI scanner helps to evaluate the extent of resection in glioma surgery. Further tumor resection after intraoperative scanning leads to an increased rate of complete tumor resection, especially in patients with contrast-enhancing tumors. However, in noncontrast-enhancing tumors, the intraoperative visualization of a complete resection seems less specific, when compared with postoperative 1.5-T MRI.

A comparative analysis of coregistered ultrasound and magnetic resonance imaging in neurosurgery

OBJECTIVE

This work presents qualitative and quantitative side-by-side comparisons of oblique coregistered magnetic resonance imaging (MRI) scans and ultrasound images obtained during 35 neurosurgical procedures.

METHODS

Spatially registered series of ultrasound images were recorded for subsequent off-line evaluation and comparison with corresponding preoperative MRI studies. The degree of misalignment was reduced by reregistering the target volume directly with segmented features.

RESULTS

The initial apparent spatial misalignment of the target volume after craniotomy ranged from 0.11 to 8.73 mm (mean, 4.01 mm). After reregistration, the mutual information in overlapping segmented features was increased, presumably evidence of a better alignment locally. Additionally, the degree of feature congruence, which was assessed quantitatively through a convex hull approximation, demonstrated that the ultrasound volume was consistently smaller than its MRI counterpart.

CONCLUSION

Although intraoperative ultrasound tends to be difficult to interpret by itself, when accurately coregistered with preoperative MRI scans, its potential utility as a navigational guide is enhanced.

SURGERY OF INTRINSIC CEREBRAL TUMORS

TUMORS AND OTHER structural lesions located with and adjacent to the cerebral cortex present certain challenges in terms of the overall management and design of surgical strategies. This comprehensive analysis attempts to define the current understanding of cerebral localization and function and includes the latest advances in functional imaging, as well as surgical technique, including localization of tumors and neurophysiological mapping to maximize extent of resection while minimizing morbidity. Finally, it remains to be seen whether or not stimulation mapping will be the most useful way to identify function within the cortex in the future. Another potential paradigm would be to actually record baseline oscillatory rhythms within the cortex and, following presentation of a given task, determine if those rhythms are disturbed enough to identify eloquent cortex as a means of functional localization. This would be a paradigm shift away from stimulation mapping, which currently deactivates the cortex, as opposed to identifying an activation function which identifies functional cortex.

A neurosurgical navigation system based on intraoperative tumour remnant estimation

This paper proposes a method to intra-operatively visualize the process of tumour resection until complete resection is accomplished. A fuzzy connectedness method that is robust against image noises was used to identify the tumour position and volume. Based on the tumour segmentation results, the removed area and the residual tumour tissues were examined with reference to the electrocautery trace log. Unique processes that are specific to glioma resection were introduced in the method to improve the accuracy of estimation. Invalid data in the trace log were excluded, and the tumour region surrounded by valid log points was included in the removed area. The proposed system also produces an alarm to indicate whether the electrocautery is being accurately performed within the tumour area. Thus, this surgical navigation system can assist surgeons in intuitively monitoring the tumour resection process and properly removing tumour remnants. Preliminary experiments and a clinical pilot study showed the feasible application of this method.