Preparation and incorporation of probe-labeled apoA-I for fluorescence resonance energy transfer studies of rHDL

Apolipoprotein A-I (apoA-I), the major constituent of HDL, plays an essential role in regulating cholesterol metabolism, acting as the physiological activator of lecithin: cholesterol acyltransferase, which converts cholesterol to cholesterol ester. Thiol-reactive fluorescent probes attached to cysteine-containing apoA-I mutants are currently being used to investigate the "LCAT active" conformation of lipid-bound apoA-I. Herein, we report new methodologies allowing rapid expression, fluorescent labeling, and recombinant HDL (rHDL) preparation for use in apoA-I in fluorescence resonance energy transfer (FRET) studies. Cysteine-containing mutant forms of human apoA-I were cloned into the pTYB12 vector containing a T7 promoter, a modified self-splicing protein element (intein), and a small affinity tag [chitin binding domain (CBD)]. The fusion proteins were expressed in Escherichia coli, isolated from cell lysates, and bound to a chitin-affinity column. Release of mature human apoA-I was initiated by the addition of DTT, which induced self-cleavage at the COOH terminus of the intein - CBD fusion protein. ApoA-I was further purified by Q-sepharose and then used for fluorescent probe labeling. Discoidal rHDL were then prepared with donor and/or acceptor labeled apoA-I and characterized with respect to their size, composition and ability to activate LCAT.

Linac radiosurgery for skull base meningiomas

INTRODUCTION

Skull base meningiomas present a difficult surgical challenge because of the high potential morbidity of radical surgical extirpation and their low potential for incapacitating symptomatology. The focal character of meningiomas makes stereotactic radiosurgery an attractive adjuvant treatment modality to resection. The purpose of this study was to evaluate the local control rates and complications in 56 patients with base of skull meningiomas undergoing radiosurgery.

METHODS

Patients underwent radiosurgery using the dedicated stereotactic linear accelerator at the Brigham and Women's Hospital. Minimal peripheral doses of radiosurgery ranged from 12 to 18.5 Gy (mean 15 Gy). Doses were designed to conform to the frequently irregular tumor volumes using the X-Knife treatment planning system. Multiple isocenters were used when required to increase conformality of dose. For 36 patients (64%), radiosurgery was used as an adjunct to surgery; for 20 patients (36%) it was the primary treatment.

RESULTS

Median followup was five years. Nineteen patients (34%) were improved clinically at follow-up; 32 (57%) were unchanged; and 5 patients (9%) developed new or worsened neurologic deficits. Serial imaging studies after radiosurgery showed a reduction in tumor volume in 23 patients (41%); 30 (54%) showed stable disease; 3 patients (5%) had tumors which increased in size (2 being outside the radiosurgery treatment site). The actuarial freedom from progression rate (defined as further tumor growth) was thus 95%, with a median imaging follow-up of 26 months (range, 6-66 months). Although further follow-up is necessary, the results of this series clearly demonstrate that these lesions are feasible for treatment by modern radiosurgical techniques. Linac radiosurgery can stabilize skull base meningiomas, with decreased or unchanged tumor volumes on radiologic follow-up in approximately 95% of patients. Radiosurgery is a low-morbidity, effective technique as adjunct and sometimes primary treatment of small to moderate-sized meningiomas of the skull base.

Optimizing brain tumor resection. Midfield interventional MR imaging

The development of the intraoperative MR imager represents an important example of creative vision and interdisciplinary teamwork. The result is a remarkable tool for neurosurgical applications. MRT allows surgical manipulation under direct visualization of the intracranial contents through the eye of the surgeon and through the volumetric images of the MR imaging system. This technology can be applied to cranial and spinal cases, and forseeably can encompass application to the entire gamut of neurosurgical efforts. The author's experience has been that this device is easy and comfortable for the surgeon to use. Image acquisition, giving views in the plane of choice, lasts no more than 2 to 60 seconds (depending on the imaging method), and does not increase the duration of a given procedure substantially. The author believes that the information received through intraoperative MR imaging scanning ultimately will contribute to decreasing the duration of surgery. Future possibilities include combining the intraoperative MR imager with other technologies, such as the endoscope, focused ultrasound, robotics, and the evaluation of brain function intraoperatively. The development of the intraoperative MR imager marks a significant advance in neurosurgery, an advance that will revolutionize intraoperative visualization as fully as the operating microscope. The combination of intraoperative visualization and precise surgical navigation is unparalleled, and its enhancement of surgical applications will be widespread. Considering the remarkable potential of the intraoperative MR imager for neurosurgical applications, optimal magnet design, image quality, and navigational methods are necessary to capitalize on the advantages of this revolutionary tool. The intraoperative MR imaging system that the author's team has developed and used has combined these features, and allows the performance of open surgical procedures without the need of patient or magnet repositioning. By using advanced navigational tools and computer technology, it represents an integration of frameless stereotactic methods with real-time interactive imaging. The midfield imager provides sufficient spatial and temporal resolution and image quality to assess anatomy and pathology adequately, to monitor a surgical procedure, and make image-based decisions. The intraoperative use of this unique system is not limited to biopsies or limited-access procedures. The entire range of neurosurgical procedures can be performed, if the requisite instrumentation is available. Much work remains to be done, however. The team did not develop this system only to enable the performance of current neurosurgical procedures. Forty years ago, the operating microscope enabled not only the performance of undreamt-of procedures but opened the door to entire new subspecialties. The entire landscape of neurosurgery will change at a fundamental level as the full ramifications of this exciting idea come to fruition. The holy grail of image-guided surgery is a seamless interface between the eye and hand in the purest sense (i.e., the mind's eye and hand). Ideally, this seamless interface represents effortless flow between the procedural goal compared with the present situation and the manipulation of the tools available to accomplish the task, whether they be the scalpel, drill, laser, ultrasonic aspirator, phased array focused ultrasound, microrobot, or high-dose irradiator. As in the realm of high-performance military jet fighters, the physical limits of the human being demarcate the confining boundary of the system. Those limits are much tighter around the domain of tool manipulation, where the surgeon will yield, early on, to the enhanced performance of robotics and other technical adjuncts. The era of large open magnet imaging systems for surgical procedures then will come to a close; however, the grander era of the surgeon's integration of precision-guided, multimodality therapeutics will just be beginning. The future will be very bright, indeed.

Clear cell pleomorphic xanthoastrocytoma: case report

Pleomorphic xanthoastrocytoma (PXA) is a well-described astrocytic neoplasm with distinctive clinical and pathological features. Although most patients with PXAs are cured by surgical excision, other patients experience malignant progression and tumor recurrence. We describe a 47-year-old woman with a left temporal lobe PXA that had classic histopathological characteristics as well as extensive clear cell and focal papillary changes, and some anaplastic findings. The patient has now suffered two recurrences after complete resection. The case illustrates a rare, previously undescribed histological variant of PXA, with a prominent clear cell and focal papillary morphology. The study of histologically similar cases is needed to determine whether this variant is always associated with a greater likelihood of recurrence.

[The efficacy of an individualized treatment schedule to maintain treatment adherence in an urban community mental health center]

OBJECTIVE

We present an observational study on the efficacy of an individualized treatment schedule, which is meant to support treatment adherence in an urban community mental health center (CMHC).

METHODS

The present investigation was carried out in the natural setting of a CMHC in Vienna. During a 3-month period we observed the compliance with the appointments and the actions taken by the team in response to missed appointments as well as the utilization of the CMHC during a follow-up period of 6 months.

RESULTS

During the observation period 393 (19,2 %) of 2049 scheduled visits were missed affecting more than half of the patients. Only a minority of patients with low-intensity treatment and a high rate of missed appointments had a high risk for discontinuing treatment.

CONCLUSIONS

Missed appointments in outpatient psychiatric care are a common phenomenon but they constitute no major threat to the continuity of care for the majority of the patients due to the graduated efforts of the team. The time required to make up for missed appointments is considerable but the results of the follow-up confirmed the beneficial effects on utilization of psychiatric care.

Radiosurgery in the management of pediatric brain tumors

OBJECTIVE

To describe the outcome of pediatric brain tumor patients following stereotactic radiosurgery (SRS), and factors associated with progression-free survival.

METHODS

We reviewed the outcome of 90 children treated with SRS for recurrent (n = 62) or residual (n = 28) brain tumors over a 10-year period. Median follow-up from SRS was 24 months for all patients and 55.5 months for the 34 patients currently alive.

RESULTS

The median progression-free survival (PFS) for all patients was 13 months. Median PFS according to tumor histology was medulloblastoma = 11 months, ependymoma = 8.5 months, glioblastoma and anaplastic astrocytoma = 12 months. Median PFS in patients treated to a single lesion was 15.4 months. No patient undergoing SRS to more than 1 lesion survived disease free beyond 2 years. After adjusting for histology and other clinical factors, SRS for tumor recurrence (RR = 2.49) and the presence of > 1 lesion (RR = 2.3) were associated with a significantly increased rate of progression (p < 0.05). Three-year actuarial local control (LC) was as follows: medulloblastoma = 57%, ependymoma = 29%, anaplastic astrocytoma/glioblastoma = 60%, other histologies = 56%. Nineteen patients with radionecrosis and progressive neurologic symptoms underwent reoperation after an interval of 0.6-62 months following SRS. Pathology revealed necrosis with no evidence of tumor in 9 of these cases.

CONCLUSION

SRS can be given safely to selected children with brain tumors. SRS appears to reduce the proportion of first failures occurring locally and is associated with better outcome when given as a part of initial management. Some patients with unresectable relapsed disease can be salvaged with SRS. SRS to multiple lesions does not appear to be curative. Serious neurologic symptoms requiring reoperation is infrequently caused by radionecrosis alone.

The case for radiosurgery

Brain metastases represent a significant health-care problem, with almost 200,000 patient in the Unite States annually suffering from symptomatic parenchymal lesions. Lung, breast, melanoma, renal, and gastrointestinal cancers contribute the majority of lesions that come to clinical attention. Although median survival once brain metastases are diagnosed is less than a year, timely therapy can restore neurological function and can often prevent further neurological complications of cancer for the duration of a patient's survival. Important prognostic features associated with improved survival include the absence of extracranial disease progression, young age, a high pretreatment neurological status, one to three versus more than three lesions, and a long interval from primary disease diagnosis to the development of brain metastases. The need to aggressively treat brain metastases effectively is becoming increasingly important, however, as advances in the treatment of systemic disease result in an increasing number of patients developing brain metastases in the setting of limited systemic disease. For many such patients, surgery provides the best therapy, but results are still not encouraging because even patients with the best prognostic indicators often die within 18 to 24 months. Until Superior treatment modalities are developed, the judicious use of available techniques for treatment of patients with limited systemic disease provides the best opportunities for palliation and extended survival. Perhaps the most significant development in the treatment of patients with brain metastases during the last decade is the increasing use of radiosurgery. For patients with a single lesion, local control and survival rates of radiosurgery compare well with those produced with surgical resection. Radiosurgery remains an important treatment modality and, when used promptly, can reverse neurological deficits, often for the remainder of a patients life. There is compelling evidence to suggest that aggressive local therapy (surgery or radiosurgery) for patients with a single brain metastasis produces superior survival and quality of life compared with treatment with whole brain radiotherapy alone. However, surgery should be restricted to the minority of patients for whom brain metastases represents the life-threatening site of their disease. For an asymptomatic or mildly symptomatic patient with a lesion smaller than 3 cm in diameter, radiosurgery is an excellent alternative to surgery. Although radiosurgery is a noninvasive procedure, the same selection criteria should be considered as for those patients undergoing surgical resection.

The present and future role of intraoperative MRI in neurosurgical procedures

OBJECTIVE

We have worked in conjunction with scientists from the General Electric Corporation over 6 years to develop an open-bore MR imaging system (0.5 T) enabling optimal vertical access of surgeon and assistant to the patient, and real-time imaging during major neurosurgical procedures.

METHODS

The intraoperative MR system (MRT) is located in a specially modified operative suite that combines the features of an MR-imaging suite with a fully functional operating room. An MR-compatible anesthesia machine and patient-monitoring device are located next to the magnet. The position of instruments, platforms and supports may be mapped in the operative field using 3 charge-coupled device video cameras mounted in the overhead support truncheon that follow various light-emitting diodes on the devices (Pixsys). The MR image plane can be defined as the axial, coronal or sagittal views through a point along the vector beneath the Pixsys tripod. A variety of surface coils were designed to take full advantage of full open patient access. The software, implemented by a technologist located outside the MR room, is now equivalent to that available on the commercial 0.5-tesla Signa Advantage system. Development of very robust 3-dimensional software in conjunction with the Surgical Planning Laboratory (SPL) at the Brigham & Women's Hospital is the subject of significant effort. The MRT system has been shown to possess imaging capabilities comparable, or even slightly superior (by 10%), to a conventional 0.5-tesla MR scanner. Two modified liquid-crystal display screens are mounted on the magnet housing for the surgeon to monitor the images during the procedures. Projection into larger screens or the operating microscope is under development.

RESULTS

We have performed 110 neurosurgical cases in MRT as of January 29, 1997, including 47 biopsies, 6 catheter placements, 4 cyst drainages, 47 craniotomies for resection, 3 spinal cases (1 syrinx drainage), and 3 laser tumor ablations.

CONCLUSIONS

MRT is especially useful in guiding biopsies and resections near cysts, ventricles and critical vascular structures where preoperative images with framed/frameless techniques would be inadequate to show anatomic changes during the procedure. Real-time images of a biopsy needle within the abnormal area are very useful in cases of subtle pathologic change. More complete resection of infiltrative tumor is readily accomplished. SPL image fusion of SPECT and neurofunctional data (e.g. from magnetic stimulation preoperatively) into the imaging space enables the surgeon to better visualize tumor invasion or neural function in real-time imaging during resection. Imaging of thermal gradients for cryoprobe or laser ablation, and combination with endoscopy and robotics will offer additional benefit in the performance of difficult neurosurgical procedures.

Disease concomitance in psoriasis: a clinical study of 61 cases

Sixty-one patients with psoriasis were studied for concomitant diseases and compared with 61 age and sex-matched controls. Concomitant cutaneous diseases most often seen with psoriasis were lichen simplex chronicus (16.3%), verruca vulgaris (9.8%) and me Iasina (4.9%). Of the systemic disorders, diabetes showed the highest frequency (13.1%) followed by hypertension (8.1%). Two patients had HIV infection (3.2%). Both the patients had severe and atypical lesions.

Spinal neurenteric cysts and their relation to more common aspects of occult spinal dysraphism

Object

Neurenteric cysts are infrequently reported congenital abnormalities believed to be derived from an abnormal connection between the primitive endoderm and ectoderm. The authors report a series of 13 patients treated over a 50-year period.

Methods

Of the 13 patients, seven were female and six were male. Their ages at presentation ranged widely from 5 weeks to 52 years of age. Children presented more commonly with cutaneous stigmata of occult spinal dysraphism (OSD) whereas adults presented primarily with pain. Neurological deficit as a presenting symptom was less common in our series, a finding that reflects the slow growth of these lesions. In all but one patient some form of vertebral anomaly was associated with the cystic lesions, including two patients with Klippel–Feil abnormalities. There was a high incidence of associated forms of OSD including split cord malformation, lipoma, dermal sinus tract, and tethered spinal cord. In previous reports the authors have suggested that neurenteric cysts are more common in the cervical region and in a position ventral to the cord. In the present series these cysts most commonly occurred as intradural, extramedullary masses in the thoracolumbar region, situated dorsal to the spinal cord. The median follow-up period was 7.5 years, and postoperative outcome reflected a patient's preoperative neurological status; in no patient was outcome worsened due to surgery.

Conclusions

Complete excision of the neurenteric cyst remains the treatment of choice, as subtotal excision is associated with recurrence.

Frameless stereotactic neurosurgery using intraoperative magnetic resonance imaging: stereotactic brain biopsy

OBJECTIVE

To assess the application accuracy of intraoperative magnetic resonance imaging for frameless stereotactic surgery, and to evaluate the performance of intraoperative magnetic resonance imaging for the brain biopsy, a standard stereotactic procedure.

METHODS

A series of spatial coordinate and phantom experiments were performed to analyze the application accuracy of the system. A prospective analysis of 68 consecutive patients undergoing stereotactic brain biopsy was then performed.

RESULTS

The spatial coordinate experiments revealed a mean overall error in acquisition of 0.2 mm. The phantom experiments demonstrated a 1:1 correlation between the magnetic resonance image of a stereotactically guided probe and its relationship to a target and the actual relationship of the probe and target. Sixty-eight brain biopsies were successfully performed in all intracranial compartments except the sella. The radiographic abnormality was localized successfully in all patients (100%). Sixty-six (97.1%) of the biopsies yielded diagnostic tissue. Two biopsies (2.9%) were complicated by intraparenchymal hemorrhage. One expanding temporal lobe hemorrhage was evacuated by immediate craniotomy in the magnet with no postoperative sequelae. A deep hemorrhage from a lymphoma was managed conservatively with interval resolution of symptoms. There were no infections. There was no perioperative mortality.

CONCLUSION

Intraoperative magnetic resonance imaging allows excellent target localization, provides true real-time imaging to account for anatomic changes during surgery, and permits intraoperative confirmation that the biopsy needle has reached the targeted lesion. Immediate postoperative imaging in the operating room allows assessment of adverse events and the potential for immediate management of hemorrhagic complications.

3131C--World War II neurosurgery

Preparation for surgical care of the wounded in a two-theater war was extensive and skillfully organized by Michael DeBakey, one of the prime advisors to the Surgeon General of the Army, and by his colleague, Eli Ginzberg, Ph.D. Some of the ways in which this organization was carried out are described. Although the number of neurosurgeons who can recall any involvement of neurosurgery in World War II is diminishing, there remain a significant number who do remember such involvement, many of whom have helped to provide information for this article.

World War II: a neurosurgeon in New Guinea

During World War II, many doctors joined the military after completing their medical training. Civilian careers were put on hold until after the war was over. In 1942, Eben Alexander, Jr., joined the Air Force, then the United States Army, and served 4 years, much of it overseas, as a "3131C" neurosurgeon.

Craniotomy for tumor treatment in an intraoperative magnetic resonance imaging unit

OBJECTIVE

The complex three-dimensional anatomic features of the brain and its vulnerability to surgical intervention make the surgical treatment of intracranial tumors challenging. We evaluated the surgical treatment of supratentorial tumors using intraoperative magnetic resonance imaging (MRI), which provides real-time guidance, allows localization of intracranial tumors and their margins, and facilitates continuous assessment of surgical progress.

METHODS

Sixty patients underwent craniotomies for tumor treatment in the General Electric intraoperative MRI unit at the Brigham and Women's Hospital (Boston, MA) during a 1-year period. The patients selected were those with intracranial tumors that were considered difficult to resect because of their locations or previous incomplete operations. Twenty-nine low-grade and 19 high-grade gliomas, 8 metastatic lesions, 2 meningiomas, 1 pineoblastoma, and 1 astroblastoma were resected.

RESULTS

Tumors were accurately localized and targeted, and the extent of resection, as well as any intraoperative complications, could be immediately assessed during surgery. Marked brain shifting occurred during the procedures, and repeated intraoperative imaging allowed surgical accommodation for this shifting. In more than one-third of the cases, intraoperative imaging showed residual tumor when resection appeared complete on the basis of surgical observation alone.

CONCLUSION

Intraoperative MRI is a revolutionary tool for the surgical treatment of brain tumors, providing observation of the procedure as it is being performed. With intraoperative MRI, tumor resection is safer, the extent of resection can be directly evaluated, and intraoperative complications can be noted if they occur. Outcomes after resection depend on minimizing injury to normal brain tissue and achieving maximal tumor resection. The use of intraoperative MRI directly affects these factors.

The viable-but-nonculturable condition is induced by copper in Agrobacterium tumefaciens and Rhizobium leguminosarum

Many bacteria respond to changes in environmental conditions by entering the viable-but-nonculturable state. We have determined that copper can induce nutrient-starved Agrobacterium tumefaciens and Rhizobium leguminosarum cells to become viable but nonculturable. This is the first report of a chemical inducer of this condition.

Mechanism of action of verbascoside on the isolated rat heart: increases in level of prostacyclin

The mechanism of the positive cardioactive effects induced by verbascoside in the Lagendorff rat heart has been investigated. Isolated rat hearts treated with alpha- or beta-adrenergic agents did not show significant reduction of the positive chronotropism, inotropism and increased coronary perfusion rate mediated by verbascoside. A significant increase in prostacyclin levels (142%) observed following the administration of verbascoside suggests that prostacyclin stimulates formation of cAMP which induces the cardioactivity associated with verbascoside.

Intraoperative MR imaging guidance for intracranial neurosurgery: experience with the first 200 cases

PURPOSE

To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures.

MATERIALS AND METHODS

A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed.

RESULTS

There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery.

CONCLUSION

Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.

The role of radiosurgery for glial neoplasms

Malignant gliomas are one of the most serious challenges in clinical neurosurgery. Despite advances in surgical and radiation techniques, chemotherapy, and other systemic antineoplastic regimens, such as gene therapy and immunotherapy, patients who suffer from malignant gliomas often succumb to their disease. Although some success has been made with forms of enhanced surgical guidance and localized radiotherapy, current techniques are unable to eradicate the infiltrative glioma cells.

Treatment of patients with primary glioblastoma multiforme with standard postoperative radiotherapy and radiosurgical boost: prognostic factors and long-term outcome

OBJECT

To assess the value of stereotactic radiosurgery (SRS) as adjunct therapy in patients suffering from glioblastoma multiforme (GBM), the authors analyzed their experience with 78 patients.

METHODS

Between June 1988 and January 1995, 78 patients underwent SRS as part of their initial treatment for GBM. All patients had undergone initial surgery or biopsy confirming the diagnosis of GBM and received conventional external beam radiotherapy. Stereotactic radiosurgery was performed using a dedicated 6-MV stereotactic linear accelerator. Thirteen patients were alive at the time of analysis with a median follow-up period of 40.8 months. The median length of actuarial survival for all patients was 19.9 months. Twelve- and 24-month survival rates were 88.5% and 35.9%, respectively. Patient age and Radiation Therapy Oncology Group (RTOG) class were significant prognostic indicators according to univariate analysis (p < 0.05). Twenty-three patients aged younger than 40 years had a median survival time of 48.6 months compared with 55 older patients who had 18.2 months (p < 0.001). Patients in this series fell into RTOG Classes III (27 patients), IV (29 patients), or V (22 patients). Class III patients had a median survival time of 29.5 months following diagnosis; this was significantly longer than median survival times for Classes IV and V, which were 19.2 and 18.2 months, respectively (p = 0.001). Only patient age (< 40 years) was a significant prognostic factor according to multivariate analysis. Acute complications were unusual and limited to exacerbation of existing symptoms. There were no new neuropathies secondary to SRS. Thirty-nine patients (50%) underwent reoperation for symptomatic necrosis or recurrent tumor. The rate of reoperation at 24 months following SRS was 54.8%.

CONCLUSIONS

The addition of a radiosurgery boost appears to confer a survival advantage to selected patients.

Initial clinical results of LINAC-based stereotactic radiosurgery and stereotactic radiotherapy for pituitary adenomas

PURPOSE

To retrospectively evaluate the initial clinical results of stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (SRT) for pituitary adenomas with regard to tumor and hormonal control and adverse effects of the treatment.

SUBJECTS AND METHODS

Forty-eight patients with pituitary adenoma who underwent SRS or SRT between September 1989 and September 1995 were analyzed. Of these, 18 received SRS and 30 received SRT. The median tumor volumes were 1.9 cm3 for SRS and 5.7 cm3 for SRT. Eleven of the SRS and 18 of the SRT patients were hormonally active at the time of the initial diagnosis. Four of the SRS and none of the SRT patients had a history of prior radiation therapy. Both SRS and SRT were performed using a dedicated stereotactic 6-MV linear accelerator (LINAC). The dose and normalization used for the SRS varied from 1000 cGy at 85% of the isodose line to 1500 cGy at 65% of the isodose line. For SRT patients, a total dose of 4500 cGy at 90% or 95% of the isodose line was delivered in 25 fractions of 180 cGy daily doses.

RESULTS

Disease control-The three year tumor control rate was 91.1% (100% for SRS and 85.3% for SRT). Normalization of the hormonal abnormality was achieved in 47% of the 48 patients (33% for SRS and 54% for SRT). The average time required for normalization was 8.5 months for SRS and 18 months for SRT. Adverse effects-The 3-year rate of freedom from central nervous system adverse effects was 89.7% (72.2% for SRS and 100% for SRT). Three patients who received SRS for a tumor in the cavernous sinus developed a ring enhancement in the temporal lobe as shown by follow-up magnetic resonance imaging. Two of these cases were irreversible and were considered to be radiation necrosis. None of the 48 patients developed new neurocognitive or visual disorders attributable to the irradiation. The incidence of endocrinological adverse effects were similar in the two groups, resulting in 3-year rates of freedom from newly initiated hormonal replacement of 78.4% (77.1% for SRS and 79.9% for SRT).

CONCLUSION

Considering the relatively high incidence of morbidity observed in the SRS group, we recommend SRT as the primary method of radiation therapy for pituitary tumors. When treating a lesion in the cavernous sinus with SRS, special attention should be paid to dose distribution in the adjacent brain parenchyma. Longer follow-up is necessary before drawing any conclusions about the advantages of these techniques over conventional external beam radiation therapy.

Intraoperative dynamic MRI: localization of sites of brain tumor recurrence after high-dose radiotherapy

In patients with malignant astrocytomas or metastatic brain disease treated with high-dose radiotherapy, conventional imaging methods may not adequately distinguish recurrent tumor from radiation change. We used a fast spoiled gradient refocusing technique in the open-configuration intraoperative MR system to assess the rate of regional enhancement of the treated tumor bed and to localize specific sites for pathologic sampling to determine whether gadolinium uptake correlated with histologic data. Twenty-four patients were studied. Fourteen of 15 patients with areas of early enhancement had recurrent tumor present in histologic samples, and 8 of the remaining 9 patients had only reactive changes. Dynamic MRI was predictive of recurrent tumor (P < .0005, Fisher exact test and P < .002, Student t test). We conclude that dynamic MRI in the open-bore magnet is a promising method for localizing potential sites of active tumor growth in patients treated for malignant astrocytomas and metastatic brain lesions.

Evaluation of intracranial cysts by intraoperative MR

Eleven patients with intracranial cystic collections were evaluated in the open-bore intraoperative MR system. In each case, the cystic collection or the surrounding cerebrospinal fluid (CSF) space was injected with .02 to .5 cc of .5 mol/l gadopentetate dimeglumine. Serial imaging was performed using T1-weighted imaging. In seven patients, free communication was demonstrated between the cystic collection and the surrounding CSF spaces. In four cases, the cyst did not communicate with the CSF; two of these were drained in the intraoperative MR system with reduction in symptoms. One patient developed an aseptic meningitis 10 days after the study, which was successfully treated with steroids; no other complications were noted. We conclude that the communication of intracranial cystic collections with the cisterns and ventricles can be safely and effectively elucidated with gadolinium injection in the intraoperative MR system.

Dual-isotope single-photon emission computerized tomography scanning in patients with glioblastoma multiforme: association with patient survival and histopathological characteristics of tumor after high-dose radiotherapy

OBJECT

The study was conducted to determine the association between dual-isotope single-photon emission computerized tomography (SPECT) scanning and histopathological findings of tumor recurrence and survival in patients treated with high-dose radiotherapy for glioblastoma multiforme.

METHODS

Studies in which SPECT with 201Tl and 99mTc-hexamethypropyleneamine oxime (HMPAO) were used were performed 1 day before reoperation in 47 patients with glioblastoma multiforme who had previously been treated by surgery and high-dose radiotherapy. Maximum uptake of 201Tl in the lesion was expressed as a ratio to that in the contralateral scalp, and uptake of 99mTc-HMPAO was expressed as a ratio to that in the cerebellar cortex. Patients were stratified into groups based on the maximum radioisotope uptake values in their tumor beds. The significance of differences in patient gender, histological characteristics of tissue at reoperation, and SPECT uptake group with respect to 1-year survival was elucidated by using the chi-square statistic. Comparisons of patient ages and time to tumor recurrence as functions of 1-year survival were made using the t-test. Survival data at 1 year were presented according to the Kaplan-Meier method, and the significance of potential differences was evaluated using the log-rank method. The effects of different variables (tumor type, time to recurrence, and SPECT grouping) on long-term survival were evaluated using Cox proportional models that controlled for age and gender. All patients in Group I (201Tl ratio < 2 and 99mTc-HMPAO ratio < 0.5) showed radiation changes in their biopsy specimens: they had an 83.3% 1-year survival rate. Group II patients (201Tl ratio < 2 and 99mTc-HMPAO ratio of > or = 0.5 or 201Tl ratio between 2 and 3.5 regardless of 99mTc-HMPAO ratio) had predominantly infiltrating tumor (66.6%); they had a 29.2% 1-year survival rate. Almost all of the patients in Group III (201Tl ratio > 3.5 and 99mTc-HMPAO ratio > or = 0.5) had solid tumor (88.2%) and they had a 6.7% 1-year survival rate. Histological data were associated with 1-year survival (p < 0.01): however, SPECT grouping was more closely associated with 1-year survival (p < 0.001) and was the only variable significantly associated with long-term survival (p < 0.005).

CONCLUSIONS

Dual-isotope SPECT data correlate with histopathological findings made at reoperation and with survival in patients with malignant gliomas after surgical and high-dose radiation therapy.

Visual hemifield mapping using transcranial magnetic stimulation coregistered with cortical surfaces derived from magnetic resonance images

The perception of a visual stimulus can be inhibited by occipital transcranial magnetic stimulation. This visual suppression effect has been attributed to disruption in the cortical gray matter of primary visual cortex or in the fiber tracts leading to V1 from the thalamus. However, others have suggested that the visual suppression effect is caused by disruption in secondary visual cortex. Here the authors used a figure-eight coil, which produces a focal magnetic field, and a Quadropulse stimulator to produce visual suppression contralateral to the stimulated hemisphere in five normal volunteer subjects. The authors coregistered the stimulation sites with magnetic resonance images in these same subjects using optical digitization. The stimulation sites were mapped onto the surface of the occipital lobes in three-dimensional reconstructions of the cortical surface to show the distribution of the visual suppression effect. The results were consistent with disruption of secondary visual cortical areas.

Experimentation with a transcranial magnetic stimulation system for functional brain mapping

We describe functional brain mapping experiments using a transcranial magnetic stimulation (TMS) device. This device, when placed on a subject's scalp, stimulates the underlying neurons by generating focused magnetic field pulses. A brain mapping is then generated by measuring responses of different motor and sensory functions to this stimulation. The key process in generating this mapping is the association of the 3-D positions and orientations of the TMS probe on the scalp to a 3-D brain reconstruction such as is feasible with a magnetic resonance image (MRI). We have developed a registration system which not only generates functional brain maps using such a device, but also provides real-time feedback to guide the technician in placing the probe at appropriate points on the head to achieve the desired map resolution. Functional areas we have mapped are the motor and visual cortex. Validation experiments focus on repeatability tests for mapping the same subjects several times. Applications of the technique include neuroanatomy research, surgical planning and guidance, treatment and disease monitoring, and therapeutic procedures.

Surgical treatment of low-grade gliomas in the intraoperative magnetic resonance imager

Radical resection of low-grade gliomas can decrease the incidence of recurrence, the time to tumor progression, and the incidence of malignant transformation. The authors present a series of 25 patients who underwent craniotomy and resection of low-grade tumor in an intraoperative magnetic resonance (MR) imager. This is an open configuration 0.5-tesla imager developed by The Brigham and Women's Hospital and General Electric, in which a patient can be placed to undergo surgery. Gross-total removal was accomplished under real-time image guidance. These intraoperative images allow definitive localization and targeting of the lesions and accommodate anatomical changes that may occur during surgery. The authors consistently found that the extent of abnormality seen on the intraoperatively obtained films of resection was larger than that apparent in the surgical field of view alone. Intraoperative imaging made accurate surgical identification of these abnormal areas and subsequent resection possible. Patients with tumors adjacent to or within motor or language cortex underwent resection while awake, with monitoring of neurological function. In these cases, an aggressive resection without increased neurological morbidity was accomplished using the image guidance in conjunction with serial testing. A 1-month postoperative MR image was obtained in all patients. These correlated with the final intraoperative images obtained after the resection was completed. Only one patient had a mild postoperative deficit that remained at the 1-month follow-up examination. As the long-term outcome in patients with low-grade gliomas has been shown to correspond to the degree of resection, surgical resection in which intraoperative MR imaging guidance is used can be an invaluable modality in the treatment of these tumors.