Ultrasound-guided biopsy for deep-seated brain tumors

Intraoperative ultrasonography in microsurgical resection of vestibular schwannomas via retrosigmoid approach: surgical technique and proof-of-concept illustrative case series

PURPOSE

Intraoperative ultrasonography (ioUS) is an established tool for the real-time intraoperative orientation and resection control in intra-axial oncological neurosurgery. Conversely, reports about its implementation in the resection of vestibular schwannomas (VS) are scarce. The aim of this study is to describe the role of ioUS in microsurgical resection of VS.

METHODS

ioUS (Craniotomy Transducer N13C5, BK5000, B Freq 8 MHz, BK Medical, Burlington, MA, USA) is integrated into the surgical workflow according to a 4-step protocol (transdural preresection, intradural debulking control, intradural resection control, transdural postclosure). Illustrative cases of patients undergoing VS resection through a retrosigmoid approach with the use of ioUS are showed to illustrate advantages and pitfalls of the technique.

RESULTS

ioUS allows clear transdural identification of the VS and its relationships with surgically relevant structures of the posterior fossa and of the cerebellopontine cistern prior to dural opening. Intradural ioUS reliably estimates the extent of tumor debulking, thereby helping in the choice of the right moment to start peripheral preparation and in the optimization of the extent of resection in those cases where subtotal resection is the ultimate goal of surgery. Transdural postclosure ioUS accurately depicts surgical situs.

CONCLUSION

ioUS is a cost-effective, safe, and easy-to-use intraoperative adjunctive tool that can provide a significant assistance during VS surgery. It can potentially improve patient safety and reduce complication rates. Its efficacy on clinical outcomes, operative time, and complication rate should be validated in further studies.

Cottonoid-guided intraoperative ultrasonography in neurosurgery: a proof-of-concept single surgeon case series

Ultrasonography was introduced into neurosurgery in the 1950s, but its successful utilization as an intraoperative tool dates from the early 1980s. However, it was not used widely because of limited technology, a lack of specific training, and, most importantly, the concurrent evolution of computerized tomography and magnetic resonance imaging. The intraoperative use of cottonoid patties as acoustical markers was first described in 1984, but the practice did not gain acceptance, and no articles have been published since. Herein, we reconsider the echogenic properties of the surgical cottonoid patty and demonstrate its usefulness with intraoperative ultrasonography (ioUS) in neurosurgical practice as a truly real-time neuronavigation tool. We also discuss its advantages and compare it with other intraoperative image guidance tools. The echogenic properties of the handmade cottonoid patties in various sizes used with ioUS are described. Details of our cottonoid-guided ioUS technique and its advantages with illustrated cases are also described. As an echogenic marker, cottonoid patties can be easily recognized with ioUS. Their usage with ultrasonography provides truly real-time anatomical orientation throughout the surgery, allowing easy access to intraparenchymal pathologies, and precise and safer resection. Cottonoid-guided ioUS helps not only to localize intraparenchymal pathologies but also to delineate the exact surgical trajectory for each type of lesion. Furthermore, it is not affected by brain shift and distortion. Thus, it is a truly real-time, dynamic, cost-effective, and easy-to-use image guidance tool. This technique can be used safely for every intraparenchymal pathology and increases the accuracy and safety of the surgeries.

Comparison of Stereotactic and Ultrasound-guided Biopsy of Solid Supratentorial Tumor: A Preliminary Report

Introduction:

The computed tomography (CT) guided stereotactic biopsy (STB) is considered as method of choice for biopsy of intracranial mass lesions. However, it's disadvantages are frame fixation, time requirement for transportation between CT scan suit to the operation theater with added much higher equipment cost in the relatively resource scarred developing country. Ultrasound-guided biopsy (USGB) is relatively simpler, economical, less time consuming, and real-time procedure.

Clinical Materials and Methods:

Thirty-seven consecutively admitted patients with supratentorial brain tumors, who underwent biopsy of the lesion using CT compatible stereotactic and ultrasound-guided (USGB) procedure formed cohort of the study. Based on location and size of the lesions, the cases were divided into two groups, superficial and deep. Twenty-two patients underwent ultrasound-guided biopsy and 15 with STB.

Results:

The diagnostic yield of STB was 93% and 91% for ultrasound-guided biopsy. The mean operation time of STB group was 149.00 min and 94 min for USGB, which was statistically significant. Two cases in each group developed hematoma; however, one case in USGB group needed surgical evacuation. The real-time monitoring detected two hematoma intraoperatively, which were further also confirmed on postoperative CT scan head.

Conclusions:

The ultrasound-guided biopsy procedure (USGB) was simple, relatively shorter time-consuming procedure and equally efficacious and utilizing economical equipment and can act as a safer alternative to CT STB process for biopsy of the intracranial mass lesion. Furthermore, USGB also provided intra-operative real-time monitoring, which provided clue for close monitoring in the postoperative period after completion of biopsy to look for development of fresh hematoma development not only at the biopsy site but also along the biopsy track and adjoining area. Perhaps, a longer period of ultrasonic monitoring following the procedure would be of greater help to detect hematoma formation, which is one of the most common complications of the biopsy procedure.

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.

Intraoperative Color Doppler Sonography in the Surgical Treatment of Perimedullary Arteriovenous Fistula-Case Report-

A 36-year-old female was treated for a perimedullary arteriovenous fistula (AVF) using intraoperative color Doppler sonography monitoring. Color Doppler sonography before interruption of the fistulous point clearly demonstrated an abnormal hyperechoic lesion. After interruption of the shunting point, the lesion had disappeared. Intraoperative angiography confirmed the disappearance of the perimedullary AVF. Intraoperative color Doppler sonography is a noninvasive, reliable, and cost-effective method for monitoring the effect of interruption on perimedullary AVF.

Ultrasound-based navigation during intracranial burr hole procedures: experience in a series of 100 cases

BACKGROUND

To establish a rational basis for intraoperative ultrasound guidance in neurosurgical procedures via a single burr hole approach based on the experience of one hundred cases.

METHODS

The single burr hole approach is carried out using a bayonet-shaped ultrasound transducer with a tip dimension of 8 x 8 mm. The ultrasound probe with a mounted puncture adapter fits a standard burr hole and allows real-time imaging of the ongoing surgical steps.

RESULTS

One hundred cases with five indications have been operated on so far: tapping of the ventricular system (46 patients), tapping of intracranial cysts (23 patients), biopsy of intracranial tumors (15 patients), evacuation of intracranial abscesses (9 patients), and evacuation of intracerebral hematomas (7 patients). Depending on their size, the ventricles could be clearly visualized in 34 of 46 patients. In the remaining patients the free margin of the falx served as orientation. Two ventricles could neither be visualized nor entered. Visualization and puncture of intracranial cysts were easy to achieve throughout, as was the case with abscesses. Tumor biopsy was unsuccessful in two patients harboring lymphomas at distances of more than 50 mm from probe to target. Intracerebral hematomas were easily visualized but, due to the presence of clots, aspiration was impossible in two patients. One patient with a giant glioblastoma died the day after the uneventful biopsy due to increased cerebral edema. No other complications occurred.

CONCLUSIONS

The presented method of ultrasound-based neuronavigation is an easy-to-use, fast, and safe technique of real-time imaging for free-hand single burr hole procedures.

Intraoperative brain shift and deformation: a quantitative analysis of cortical displacement in 28 cases

OBJECTIVE

A quantitative analysis of intraoperative cortical shift and deformation was performed to gain a better understanding of the nature and extent of this problem and the resultant loss of spatial accuracy in surgical procedures coregistered to preoperative imaging studies.

METHODS

Three-dimensional feature tracking and two-dimensional image analysis of the cortical surface were used to quantify the observed motion. Data acquisition was facilitated by a ceiling-mounted robotic platform, which provided a number of precision tracking capabilities. The patient's head position and the size and orientation of the craniotomy were recorded at the start of surgery. Error analysis demonstrated that the surface displacement measuring methodology was accurate to 1 to 2 mm. Statistical tests were performed to examine correlations between the amount of displacement and the type of surgery, the nature of the cranial opening, the region of the brain involved, the duration of surgery, and the degree of invasiveness.

RESULTS

The results showed that a displacement of an average of 1 cm occurred, with the dominant directional component being associated with gravity. The mean displacement was determined to be independent of the size and orientation of the cranial opening.

CONCLUSION

These data suggest that loss of spatial registration with preoperative images is gravity-dominated and of sufficient extent that attention to errors resulting from misregistration during the course of surgery is warranted.

Color Doppler ultrasound imaging in the emergency management of an intracerebral hematoma caused by cerebral arteriovenous malformations: technical case report

OBJECTIVE AND IMPORTANCE

Ruptured arteriovenous malformations (AVMs) are important causes of spontaneous intracerebral hemorrhages. This is a report of emergency hematoma removal, avoiding damage to the nidus of the AVM, using intraoperative color Doppler imaging.

CLINICAL PRESENTATION

A 38-year-old woman suddenly presented with coma. The patient underwent emergency surgery immediately after admission, without preoperative angiographic examination, because of progressive neurological deterioration caused by a massive hematoma in the right basal ganglia, as diagnosed with computed tomographic scanning.

INTERVENTION

A right frontotemporoparietal craniotomy was performed. Intraoperative ultrasound imaging with a color Doppler system (EUP-NS32, 5 MHz; Hitachi Medical, Tokyo, Japan) clearly demonstrated a nidus complex in the hematoma. Based on the imaging, effective decompression of the hematoma was performed without damage to the AVM complex.

CONCLUSION

Color Doppler imaging (with real-time availability) of an atypical hematoma provided significant information on the vascular lesion causing the hematoma and could reduce the surgical risks during emergency evacuation of large intracerebral hemorrhages resulting from ruptured AVMs.

Correlation of intra-operative ultrasound with histopathologic findings after tumour resection in supratentorial gliomas. A method to improve gross total tumour resection

The aim of this study was to evaluate whether intra-operative ultrasound (= IOUS) is a suitable tool to detect residual tumour tissue after gross total resection in supratentorial gliomas. During a period of 18 months 45 patients with supratentorial gliomas (38 high-grade and 9 low-grade, according to the WHO-grading system [42]) were operated on. A series of 78 biopsies was taken from the resection cavity under continuous sonographic control at the end of surgery. Gross total tumour resection was intended in 34 patients (= 76%). The biopsy specimens were matched with the sonographic features at each biopsy site. The sonographic appearance of the resection margins were classified into 2 groups: (1) Irregular hyperechoic areas extending from the cavity into the iso-echogenic brain tissue and (2) a dense small (< or = 3 mm in diameter) rather regular hyperechoic rim surrounding the resection cavity. 47 out of 53 biopsies taken from hyperechoic areas (group I) (36 high-grade/11 low-grade) revealed solid tumour tissue (= 89%). 34 (= 72%) of these 47 areas were microscopically assessed as inconspicuous by the surgeon. 6 samples (4 high-grade/2 low-grade) contained tumour infiltration zone. 25 biopsies (23 high-grade/2 low-grade) taken from the hyperechoic rim [group 2] were diagnosed as follows: Normal brain tissue in 11, tumour infiltration zone in 8 and solid tumour tissue in 6 cases. Of 34 cases with "gross total removal" according to the surgeon's assessment 25 showed sonographic signs of residual tumour tissue, which was confirmed histologically as solid tumour tissue in 22 of these cases. It is concluded, that IOUS following resection of supratentorial gliomas can detect residual tumour tissue with high specificity and thus improve gross total resection. However, a thin hyperechoic rim surrounding the resection cavity (less than 3 mm in diameter) is a non-specific finding, which can mask thin residual tumour layers and therefore needs further evaluation of its nature.

Ultrasound stereotaxic endoscopy in neurosurgery

Stereotaxic endoscopy assisted by laser- and video technique can be used in a circumscribed number of intracerebral lesions. In the present series of patients, ultrasound imaging has been used as a stereotaxic method to guide the tip of the endoscope to a target area in the depth of the brain via a burr hole in the cranial vault. Initial experience has been obtained in the evacuation of various intracerebral and ventricular as well as cerebellar haematomas; moreover, ventricular tumours can be laser-coagulated and resected. In cases of cystic hemispheric tumours biopsies can be taken under visual control and the inner surface coagulated with laser. The method is less traumatic compared to conventional neurosurgery.

Application of superfine fiberscope for endovasculoscopy, ventriculoscopy, and myeloscopy

In the past three years, we have used a superfine fiberscope for endovasculoscopy, ventriculoscopy, and myeloscopy. Flexible superfine fiberscope, 0.75 mm in outer diameter, could visualize various intravascular findings. In in-vivo canine experiment, sequential changes of thrombus produced by endothelial abrasion by needle or balloon in the canine carotid artery can be clearly seen. And thrombolysis by focal arterial injection of tissue plasminogen activator was sequentially observed. In the clinical study, we could evaluate the stenotic lesions of the subclavian and vertebral arteries before and after balloon angioplasty. During ventriculoscopy, a 2 mm of mini-caliber fiberscope was introduced under ultrasound monitoring, and provided clear visualization of intraventricular tumours. In myeloscopy, draining veins of arteriovenous malformations and nerve roots of the cauda equina could be clearly seen by flexible fiberscope. From these results, it can be said that the superfine fiberscope provides clear and useful visualizations of the interior of vessels, ventricles, and the intrathecal area of the spinal canal. The new applications of this superfine fiberscope for minimally invasive neurosurgery may bring about a marked improvement of therapeutic results.

A comparison of computerized tomography-guided stereotactic and ultrasound-guided techniques for brain biopsy

Forty-one patients with brain lesions underwent brain biopsy using either a computerized tomography (CT)-guided stereotactic approach or an ultrasound-guided technique. The cases were selected according to location and size of the mass lesion. Lesions 15 mm or less in diameter and those in the posterior fossa were biopsied by a CT-guided stereotactic technique (18 patients). Supratentorial lesions with a diameter larger than 15 mm were approached using ultrasound guidance (23 patients). These criteria for procedure selection provided a diagnostic yield of 94% for the CT-guided procedures and 91% for those guided by ultrasound. Safety for the two procedures was similar. The ultrasound procedure was more rapid, simpler, and less costly to perform. It is concluded that, with the protocol described, CT-guided stereotactic procedures could be reserved for cases in which absolute accuracy is mandatory.

Intraoperative ultrasound-guided biopsy of intracranial lesions: comparison with freehand biopsy

Achieving the required accuracy during such relatively straightforward procedures as tumour biopsy or abscess aspiration remains a challenge especially for the more junior neurosurgeon. A study comparing freehand biopsy with ultrasound-guided biopsy is presented. The use of intraoperative ultrasound increases the accuracy at the expense of a slightly longer operating time. Diagnostic tissue was always obtained using this technique.

The value of intraoperative ultrasound in neurosurgery

Intraoperative ultrasound is not a technique which has been widely accepted by neurosurgeons in this country, not least because bulky probes and machines become more of a hindrance than an asset in theatre. The development of new smaller probes, including ones small enough to visualize the brain through a conventional burr-hole has rekindled interest in this subject. Its use for guidance in tumour biopsy, cyst aspiration and catheter placement, as well as volume estimations and determining the completeness of tumour resection, are outlined. The ability to recognize peri-operative haemorrhage is demonstrated.

Intraoperative ultrasound (US) imaging. Comparison of pathomorphological findings in US and CT

Experience with the use of intraoperative ultrasound (US) imaging in over 300 patients are presented in this paper and discussed with special reference to various pathomorphologies as well as their identifiability within the brain/intracranium. In 201 of these patients, the pathomorphological peculiarities in US could be compared with preoperative CT findings. As a general result, all investigated lesions could be identified during intraoperative US investigations with the exception of small aneurysms. Most of the lesions gave at least partly higher echosignals than normal brain tissue, except arachnoid cysts. Size and shape of lesions were comparable in US and CT with the exception of some gliomas; in the latter group, the diffuse image in US was more akin to the situation likely to be found by the surgeon during operation, whereas CT used to give a misleading picture of a more or less clearly delineated tumour. US allowed more accurate differentiation between intratumoural necrosis and cysts than CT: the latter was misleading in many instances. At the present state of development, real time US imaging does not allow a histopathological diagnosis. The ease of handling and the high quality of morphological imaging, however, warrant a number of practical applications in daily neurosurgical practice.

Intraoperative ultrasound imaging of the entire brain through unilateral exploratory burr holes after severe head injury: technical note

A portable ultrasound unit with a 3.5-MHz probe allows accurate imaging of both cerebral hemispheres and partial imaging of the posterior fossa through unilateral exploratory burr holes or a craniotomy. In patients with clinical signs of transtentorial herniation after severe head injury, this unilateral technique can detect extraaxial and intraparenchymal mass lesions more accurately than is possible with bilateral exploratory burr holes.

Practical application of intraoperative ultrasound imaging

Intraoperative real-time ultrasound imaging (US) was used in over 500 patients to investigate which of the previously considered applications are of practical use in everyday neurosurgery. During all intraoperative applications for a wide variety of pathological conditions, small deep-seated as well as subcortically located lesions were detected with accuracy; in many instances they could be approached through smaller surgical exposures. US guidance was accurate in 209 cases for the stereotactic introduction of needles or endoscopes into various lesions: thus burrhole evacuation was performed on 148 intracerebral haematomas; in 16 patients endoscopic biopsy and resection of ventricular tumours was performed as well as biopsies of 39 hemispheric brain tumours and aspiration of a brain abscess in 6 instances. Seventy six gliomas were investigated by US imaging; the frequently unclear boundary between tumour and surrounding oedema was not better visualized than with CT or MRI. Moreover, US imaging for the detection of residual tumour towards the end of operation was unreliable. Postoperative imaging through burrholes or other cranial defects was mostly of unacceptably low quality for therapeutic decision making.

Correlation of intraoperative ultrasound tumor volumes and margins with preoperative computerized tomography scans. An intraoperative method to enhance tumor resection

Twenty-two patients with primary or metastatic brain tumors were evaluated with computerized tomography (CT) and intraoperative ultrasound. Tumor volume was estimated using a geometric formula based on CT and intraoperative ultrasound measurements. In most cases, tumor margins were marked with indigo carmine injected by ventricular cannula or with Silastic ventricular catheters placed under ultrasonographic control. Nine tumors had previously been operated on and irradiated (Group A). In this group, intraoperative ultrasound tended to overestimate the tumor volume compared to CT (intraoperative ultrasound findings 141.39% +/- 37.73% of CT findings (mean +/- standard deviation]. Sixteen patients were operated on for the first time (Group B), and in this group the volume estimates were comparable (intraoperative ultrasound findings 101.69% +/- 24.65% of CT findings). The difference between the means was statistically significant (p less than 0.01). Ultrasonography improved intraoperative delineation of tumor margins, as depicted by CT, thus maximizing the extent of resection; however, with recurrent tumors, intraoperative ultrasound tended to overestimate the tumor volume. Gliosis may account for this difference.

A new ultrasound-guided brain biopsy technique through a burr hole. Technical note

There is a disadvantage in brain biopsy by ultrasonic guidance comparing it with the CT guided approach. It is the fact that the ultrasonic method requires a small craniotomy or multiple trephinations because the size of the transducer exceeds the diameter of the burr hole and the echographic information from the trocar which houses the biopsy forceps, becomes poor when the sound beams run nearly parallel with the site of its insertion. The authors devised a brain biopsy technique through only one burr hole under real time monitoring, using a small foot-print transducer, 12 mm in diameter, and a special trocar with engraved scales on its surface. We believe that this new biopsy technique surpasses the traditional CT directed and ultrasound-guided methods in many respects. A representation case biopsied by this technique is presented.

Correlation of neuropathologic findings, computerized tomographic and high-resolution ultrasound scans of canine avian sarcoma virus-induced brain tumors

The location, size, geometry and neuropathological findings of anaplastic astrocytomas (AA), gliosarcomas and sarcomas induced by the avian sarcoma virus (ASV) in dogs were compared with images generated using computerized tomography (CT) and real time high-resolution ultrasound (HRUS). Seven AA showed a wide range of findings on CT. Pre-contrast CT scans showed that the tumors could be hyper, hypo, or isodense. Three of seven AA had no contrast enhancement; two of these tumors were also isodense which resulted in a false-negative CT exam. Partial enhancement was seen in one tumor. This resulted in a sensitivity of detection of 72%. Real time HRUS was able to define tumor location, size and geometry of the AA missed or incompletely imaged by CT. All tumors were hyperechoic. Inhomogeneity of the echo pattern was due to hemorrhage, cyst formation, and necrosis within the tumors. Such secondary tumor characteristics were more accurately defined by HRUS compared to CT. Vasogenic edema in the brain surrounding tumors was of low density on CT and hypoechoic or indistinguishable from normal brain on US. Similar findings were seen in six gliosarcomas, two of which were not visualized by either pre- or post-contrast enhanced CT scans (sensitivity of 66%). Sarcomas differed in that they were either hyper or isodense; none were hypodense. The area of increased density matched the tumor geometry and correlated with dense cellularity and reticulin deposition. All 13 sarcomas showed contrast enhancement (100% sensitivity), but in two tumors, contrast enhanced CT underestimated the size of the tumor. Because of the large size and multiplicity of the sarcomas, HRUS imaging was not able to resolve the entire tumor volume because of limited imaging access. Intravenously injected horseradish peroxidase (HRP) crossed the tumor blood-brain barrier (BBB) only in those tumors in which contrast enhancement was seen. These studies suggest that intraoperative HRUS imaging may be useful in detecting and delineating human AA incompletely visualized by CT.

Tumors and cysts

"Congenital" tumors that cause hydrocephalus early in life are large masses and can easily be detected by ultrasound. CT is better for differentiating among the diverse types of mass lesions and is performed after screening by ultrasound. In our experience, ultrasound has proved successful for visualizing all of the intracranial cysts except those in the temporal fossa. Most patients with temporal fossa cysts, however, have other symptoms and signs, such as asymmetric head and seizures that lead to further investigation and correct diagnosis despite the failure to identify the temporal cysts by ultrasound. With newer and better ultrasound equipment, the detection of temporal fossa arachnoid cysts will be improved. We believe that neurosonography should be the initial tool for investigating infants and neonates who present with large heads or abnormally rapid increase in head size.

Ultrasound-guided stereotaxic biopsy using a new apparatus

A skull-mounted apparatus is described for use with ultrasound probes 16 mm in diameter (5.0-MHz probes for near-field and 7.5-MHz probes for far-field lesions). The system permits ultrasound-guided stereotaxic biopsy of intracranial lesions through a burr hole in awake or anesthetized patients. This apparatus has been used in 19 patients for biopsy of central nervous system lesions 1.5 to cm in diameter and for drainage of abscess cavities and cysts. The time required to obtain a tissue sample after incision of the skin ranged from 25 to 40 minutes. The only complication was a delayed hemorrhage in a patient with acquired immunodeficiency syndrome. The advantages of this method over those guided by computerized tomography (CT) include less time required for the entire procedure, immediate confirmation of the biopsied target by imaging the echogenic needle track, assessment of cyst or abscess drainage, and detection of hemorrhage within minutes after biopsy. The apparatus may be especially useful in pediatric patients because it obviates the need for general anesthesia during transport to and from the CT scanner. This ultrasound-guided system does not require a craniotomy, craniectomy, or two separate burr holes.

New technique for removable implantation of radionuclides in central nervous system neoplasm by ultrasonic guidance

Introduced here is a new technique for the insertion of removable tubes into a brain tumor guided by a real-time ultrasonic B-mode scanner as a preliminary stage for interstitial brachytherapy of malignant brain tumors. Because tube insertion is conducted while watching in real time the tumor echo displayed on the cathode ray tube, the tube-positioning locations for insertion into the tumor can be freely selected with this technique. Additionally, the length of the tube that remains within the tumor bulk can be easily measured and recorded during the operation. Moreover, in that all these procedures can be carried out in the operating room, the operation will be performed under aseptic conditions and in a shorter time. These are the major advantages of this technique.

Intraoperative ultrasonography through a burr-hole

Intraoperative ultrasound diagnosis through a burr-hole was performed in 22 cases using a 5 MHz electronic sector-scanning transducer. The pathology along with the landmarks, such as ventricles and the interhemispheric fissure, were visualized. In two cases, a second burr-hole was placed nearby, and aspiration of the fluid was accomplished under real-time ultrasonic monitoring using the first hole as an acoustic window. Our results suggest a possibility of ultrasound-guided stereotactic surgery of the brain through twin burr-holes.

Intraoperative localization of intracranial lesions with real time ultrasound

High resolution ultrasound has been used intraoperatively on forty-five patients with various intracranial lesions. The technique is quickly and easily carried out under sterile conditions in the operating room. Successful localization of both primary and metastatic tumors of various sizes, depths and consistencies have been made prior to extirpation or biopsy. Several of the biopsies were done through small burr holes. Arteriovenous malformations, abscesses, bone fragments from trauma, gliotic epileptic foci and ventricles for shunt placement have been readily found. No significant complications have been encountered. A new technique for localizing superficial lesions is described. An overall reduction in operating time and unnecessary trauma to the patient has resulted from more accurate intraoperative localization of intracranial lesions with real time ultrasound.

Colloid cysts with and without ventriculomegaly: role of intraoperative real-time ultrasound

Intraoperative real-time ultrasound was used to assist localization and surgical removal of colloid cysts in patients without ventriculomegaly. In the most commonly used surgical approach for removal of colloid cysts, dilated lateral ventricles can expedite the localization of lesions because, once entered surgically, a dilated ventricle offers more space near the foramen of Monro in which to work. Additionally, the enlargement of the foramen of Monro, seen with hydrocephalus, provides greater accessibility to the colloid cyst. In patients with symptoms related to the colloid cyst. In patients with symptoms related to intermittent obstruction of cerebral fluid flow but with normal-sized ventricles, the precise localization of the foramen of Monro and colloid cyst is more difficult and may result in unnecessary exploration/resection of brain. Using intraoperative ultrasound, the colloid cyst and adjacent anatomic structures can be clearly visualized regardless of ventricular size. Intraoperative ultrasonography has a unique role in the operative treatment of patients with colloid cysts and nondilated ventricles.

Intraoperative Doppler and real time sonography in neurosurgery

Ultrasound Doppler sonography with miniaturized probes and high resolution offers new possibilities of intraoperative control of neurovascular procedures. Patency, flow direction stenoses and changes in resistance can be investigated atraumatically, repeatedly and without additional preparation. In bypass and aneurysm surgery, about 10% of the cases were shown by Doppler examinations to be unsatisfactory, with stenoses and occlusions. These could be immediately corrected without loss of time. In normal cases, the information on the local haemodynamics enlarges the knowledge as to the effects of the operation and make it safer. Real time ultrasonography, which can be easily adapted to neurosurgery, is a new atraumatic tool for localizing, in two dimensions, subcortical intrinsic processes, haematomas, ventricles ect. It is useful for guided biopsies and punctures and for the centering of the dura and brain incision over the middle of the lesion, especially in microsurgical procedures.

Cottonoid as an acoustical marker for intraoperative ultrasound scanning. Technical note

The authors demonstrate the use of cottonoid as a marker for ultrasound localization of a subcortical tumor.

Intraoperative and outpatient echoencephalography through a burr hole

Ultrasound images of the brain were obtained intraoperatively and on an outpatient basis through a burr hole. The patient's tumor was well visualized, prior to biopsy, after biopsy, and during radiation therapy treatment. The ultrasound images correlated closely to the CT scan findings.

A cannula for use in ultrasonically guided biopsies of the brain. Technical note

The authors describe a cannula that has been modified to improve its visibility during ultrasonically guided biopsies of the brain. To enhance the echogenicity of the tip of the cannula, six parallel rings, 0.25 to 0.30 mm deep and 0.40 to 0.50 mm apart, were etched into the tip of the cannula. The cannula was also lengthened to approximately 19 cm to permit its unencumbered passage through any biopsy guidance device that may be employed. Detailing the precise location of the tip of the biopsy cannula is most important. The tip of this modified probe is much more echogenic and hence more easily seen ultrasonically than it would be otherwise, both in vivo and in vitro. This modified cannula is useful in any ultrasonically guided intracranial biopsy procedure.