Intraoperative US versus intraoperative MR imaging for guidance during intracranial neurosurgery

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.

Objective assessment of utility of intraoperative ultrasound in resection of central nervous system tumors: A cost-effective tool for intraoperative navigation in neurosurgery

Background:

Localization and delineation of extent of lesions is critical for safe maximal resection of brain and spinal cord tumors. Frame-based and frameless stereotaxy and intraoperative MRI are costly and not freely available especially in economically constrained nations. Intraoperative ultrasound has been around for a while but has been relegated to the background. Lack of objective evidence for its usefulness and the perceived “user unfriendliness” of US are probably responsible for this. We recount our experience with this “forgotten” tool and propose an objective assessment score of its utility in an attempt to revive this practice.

Materials and Methods:

Seventy seven intraoperative ultrasound (IOUS) studies were carried out in patients with brain and spinal cord tumors. Seven parameters were identified to measure the “utility” of the IOUS and a “utility score” was devised (minimum 0 and maximum 7). Individual parameter and overall scores were calculated for each case.

Results:

IOUS was found to be useful in many ways. The median overall score was 6 (mean score 5.65). There were no scores less than 4 with the majority demonstrating usefulness in 5 or more parameters (91%). The use of the IOUS significantly influenced the performance of the surgery in these cases without significantly prolonging surgery.

Conclusions:

The IOUS is a very useful tool in intraoperative localization and delineation of lesions and planning various stages of tumor resection. It is easy, convenient, reliable, widely available, and above all a cost-effective tool. It should be increasingly used by neurosurgeons in the developing world where costlier intraoperative localization and imaging is not available freely.

Role of intraoperative ultrasound in resection of pediatric brain tumors

PURPOSE

In neurosurgery, ultrasound is useful in determination of the tumor location, differentiation between solid tumors and cystic components, as well as definition of the shortest and safest access to the mass. This study aims to evaluate the role of the intraoperative ultrasound in resection of pediatric brain tumors.

METHODS

Intraoperative ultrasonography (conventional B-Mode) was performed in 25 pediatric patients with brain tumors pre-, during, and post-resection, in whom eight patients were supratentorial and 17 were infratentorial. Post-op Grayscale images of the brain tumors on conventional ultrasound were compared with the results of immediate postoperative magnetic resonance imaging.

RESULTS

The border of the tumor and post-resection residual tumor were more distinguishable from healthy brain on ultrasound during the operation. Improved definition of the tumor tissue from normal brain with ultrasound was demonstrated in all cases aiding in tumor resection.

CONCLUSION

Intraoperative ultrasound is suggested to be a useful imaging technique in defining the border between the tumor and healthy brain tissue pre-resection, in detecting residual tumor tissues after the resection of the mass, and in guiding to the shortest and safest access to the tumor during neurosurgery.

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.

Optically neuronavigated ultrasonography in an intraoperative magnetic resonance imaging environment

OBJECTIVE

To develop a clinically useful method that shows the corresponding planes of intraoperative two-dimensional ultrasonography and intraoperative magnetic resonance imaging (MRI) scans determined with an optical neuronavigator from an intraoperative three-dimensional MRI scan data set, and to determine the qualitative and the quantitative spatial correspondence between the ultrasonography and MRI scans.

METHODS

An ultrasound probe was interlinked with an ergonomic and MRI scan-compatible ultrasonography probe tracker to the optical neuronavigator used in a low-field intraoperative MRI scan environment for brain surgery. Spatial correspondence measurements were performed using a custom-made ultrasonography/MRI scan phantom. In this work, instruments to combine intraoperatively collected ultrasonography and MRI scan data with an optical localization method in a magnetic environment were developed. The ultrasonography transducer tracker played an important role. Furthermore, a phantom for ultrasonography and MRI scanning was produced. This is the first report, to our knowledge, regarding the possibility of combining the two most important intraoperative imaging modalities used in neurosurgery, ultrasonography and MRI scanning, to guide brain tumor surgery.

RESULTS

The method was feasible and, as shown in an illustrative surgical case, has direct clinical impact on image-guided brain surgery. The spatial deviation between the ultrasonography and the MRI scans was, on average, 1.90 +/- 1.30 mm at depths of 0 to 120 mm from the ultrasonography probe.

CONCLUSION

The overall result of this work is a unique method to guide the neurosurgical operation with neuronavigated ultrasonography imaging in an intraoperative MRI scanning environment. The relevance of the method is emphasized in minimally invasive neurosurgery.

Intraoperative Ultrasonography of the Brain and Spine

Intraoperative ultrasonography can play a particularly useful role in facilitating surgery or guiding biopsies in the brain and spinal canal. Given the limited access that is frequently afforded to the operating surgeon, coupled with lesions that may be located in deep or seemingly inaccessible locations, sonography performed through tiny burr holes is useful for confirming location of lesions, guiding biopsy, and confirming extent of resection. In the spine, sonography is most helpful for confirming the precise location of intradural or extradural masses and guiding biopsies. In this review, we describe the technical requirements necessary for scanning the brain and spinal cord and suggest scanning techniques. The spectrum of pathological entities are illustrated along with potential pitfalls that the inexperienced operator is likely to encounter.

Evaluation of intra-operative ultrasound imaging in brain tumor resection: a prospective study

AIMS

The purpose of our study was to evaluate intra-operative ultrasound (IOUS) as a tool of resection control after brain tumor surgery. In addition, we looked for tumor species suitable for ultrasound representation.

METHODS

Using a Siemens Omnia Sonoline Ultrasound, 36 tumors were examined, high-grade gliomas (62%), metastases (22%) and others (16%). We focused on tumor imaging by ultrasound with regard to its reliability of tumor expansion and margins. Evaluation of the images was carried out by correlating the ultrasound-based intra-operative measured tumor volume before and after resection with a pre- and post-operative (within 48 hours) measured volume by MRI. The IOUS measurements were performed by the neurosurgeon and the MRI measurements by the neuroradiologist. Thus, the measurement procedures were blinded. Corresponding to a deviation of the ultrasound volume by 10, 20 and > 20% from the MRI volume, the correlation was ranked good, moderate and poor. For assessing the agreement between these two methods of imaging, the statistical analysis was conducted using a method described by Bland and Altman.

RESULTS

High-grade gliomas mostly showed a moderate or poor correlation in comparing IOUS- and MRI-tumor volumetry resulting in incomplete resection. Metastases resulted in a good to moderate correlation with a satisfactory extent of resection. The other tumors had poor images with larger tumor residues. The MRI measured volumes tended to be larger on average; the deviation grew with tumor size .

CONCLUSION

The reliability of IOUS depends on tumor type. It is beneficial to use IOUS for the resection of metastases and a few high-grade gliomas. Concerning the volumetric accuracy, the value of IOUS is worse than its value of navigation and resection control.

Intraoperative ultrasound imaging: practical applicability as a real-time navigation system

Experience with the use of Intaoperative Ultrasound (US) imaging as real time navigation system in neurosurgery is presented and discussed. Since 1987 we have performed US routinely in a wide variety of intracerebral and intramedullar pathologies. In this analysis we define useful intraoperative applications. Accurate definition of deep-seated lesions and their delineation from surrounding anatomical structures is possible with an US frequency of 5 MHz. Small subcortically located lesions can clearly be visualized with a high frequency probe. Differentiation between solid tumor, cyst and necrosis can be delineated. Identification of residual tumor is difficult. Dural sinuses and eventual invading tumor can be visualized by a 10 MHz probe. US guidance can be helpful for puncturing with a catheter, needle or endoscope. Postoperative percutaneous US imaging through a burr hole did not prove to be useful. The intraoperative use of US imaging is a reliable method for determining the size, shape and localization of lesions. It can be used as a practicable, cost effective and timesaving real time navigation system.

Glioma surgery evaluated by intraoperative low-field magnetic resonance imaging

OBJECTIVE

To give an overview on intraoperative magnetic resonance (MR) imaging in glioma surgery.

MATERIAL AND METHODS

MR imaging was performed using a 0.2T scanner, located in a radiofrequency-shielded operating theatre. Two setups were used: surgery either in a neighbouring operating theatre, or directly at the 5G line. Additionally, in gliomas adjacent to eloquent brain areas microscope- or pointer-based neuronavigation with integrated functional data was applied. 106 gliomas were among the 330 patients investigated in the last 5 years.

RESULTS

We did not observe complications attributable to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumour resection in the majority of cases. Intraoperative imaging revealed remaining tumour in 63%. In a total of 26% patients further tumour could be removed due to the results of intraoperative imaging, increasing the rate of complete tumour removal especially in the low-grade tumours. The additional use of functional neuronavigation prevented an increased morbidity.

CONCLUSION

Intraoperative MR imaging offers the possibility of further tumour removal during the same surgical procedure in case of tumour remnants, increasing the rate of complete tumour removal. The effects of brain shift can be compensated for using intraoperative image data for updating.

Intraoperative ultrasound imaging: comparison of pathomorphological findings in US versus CT, MRI and intraoperative findings

Since 1987, Ultrasound (US) is performed routinely as real time navigation system in our neurosurgical practice. In 374 cases with different pathologies the preoperative CT and MRI images were compared with the intraoperative US images and the operative findings. In all instances, the lesion could be localized and described in detail. US findings correlated with the findings an CT/MRI, concerning size and shape of lesions. US allowed the differentiation of more structural details within tissue compartments. The demarcation of gliomas was not as well defined in US as compared to CT/MRI, which correlated with the intraoperative situation. As for CT/MRI imaging, a correlation between US findings and histopathology of the lesion was not possible. In our opinion. intraoperative US imaging is an excellent tool for localization of cerebral and medullar lesions and for detailed description of their interior. This indicates a widespread applicability of this method in neurosurgery as an anatomical link between preoperative imaging and the reality of the operative field.

Enhanced anatomic visualization with ultrasound-assisted intracranial image-guidance in neurosurgery

Anatomical comparisons between ultrasound images and magnetic resonance imaging (MRI)/computed tomography (CT) preoperative images were performed in four ultrasound-assisted image-guided intracranial surgeries. An ultrasound scanner connected to a surgical navigation system allowed the neurosurgeon to acquire useful views from that integration, offering an improved method for visualization. This surgical navigation device and associated ultrasound provides real-time brain shift correction. The accuracy of navigation depends on the identification of the anatomic structures. Despite some limitations of the ultrasound images, the ability to compare preoperative MRI and intraoperative ultrasound proved useful to the surgeon.

Intraoperative ultrasound arteriography with the "Coded Harmonic Angio" technique. Report of three cases

The result of combining the ultrasound Coded Excitation method and an ultrasound contrast agent (UCA), the Coded Harmonic Angio (CHA) technique provides arterial images with exceptional spatial, temporal, and contrast resolution that are comparable to those produced by conventional digital subtraction angiography. The authors report on their experience with intraoperative ultrasound arteriography performed using the transdural CHA technique in three patients: one harboring a meningioma, another with a middle cerebral artery aneurysm, and a third with an arteriovenous malformation. The present study demonstrates how intraoperative cerebral ultrasound arteriography can be applied to assess the adequacy of neurovascular procedures without the presence of an experienced operator.