Technical modifications required to treat cervical chemodactomas with stereotactic radiosurgery

This report describes the radiosurgical treatment of a high neck lesion in a patient with familial multifocal bilateral chemodactoma. The necessary modifications to standard radiosurgery are described. The advantages of this treatment modality for patients with familial chemodactoma are discussed.

Evolution of the Journal of Neurosurgery

The Journal of Neurosurgery, begun in 1944, has successfully fulfilled the purposes of its founders. During the 50 years of its existence it has remained pre-eminent in its field, while evolving in presentation, size, and content in response to the needs of succeeding generations of neurosurgeons and allied specialists. This article draws from the memories of many people, from the minutes of meetings of the Editorial Board, and from reports of successive editors, and touches on some of the knotty problems faced by those dedicated individuals.

Image fusion for stereotactic radiotherapy and radiosurgery treatment planning

PURPOSE

We describe an image fusion application that addresses two basic problems that previously limited the use of magnetic resonance imaging (MRI) for geometric localization in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The first limitation is imposed by the use of a relocatable, MRI-incompatible, stereotactic frame for stereotactic radiotherapy. The second limitation is an inherent lack of geometric fidelity in current MRI scanners that invalidates the use of MRI for stereotactic localization.

METHODS AND MATERIALS

We recently developed and implemented a novel automated method for fusing computerized tomography (CT) and MRI volumetric image studies. The method is based on a chamfer matching algorithm, and provides a quality assurance procedure to verify the accuracy of the fused image set. The image fusion protocol removes the need for stereotactic fixation of the patient for the MRI study.

RESULTS

The image fusion protocol significantly improves on the spatial accuracy of the MRI study. We demonstrate the effect of distortion and the effectiveness of the fusion with a phantom study. We present two case studies, an acoustic neurinoma treated with SRS, and a pilocytic astrocytoma treated with SRT.

CONCLUSION

The image fusion protocol significantly improves our logistical management of treating patients with radiosurgery and makes conformal therapy practical for treating patients with SRT. The image fusion protocol demonstrates both the superior diagnostic quality and the poor geometric fidelity of MRI. MRI is a required imaging modality in stereotactic therapy. Image fusion combines the superior MRI diagnostic quality with the superior CT geometric definition, and makes the use of MRI in stereotactic therapy possible and practical.

Compensation equity between men and women in academic medicine: methods and implications

BACKGROUND

Compensation inequity by gender is a problem across occupations in the United States. Most compensation-monitoring efforts in academic medicine have been informal. The authors developed an analytic method for formal, ongoing evaluation of compensation equity in academic medicine.

METHOD

A historical cohort study was conducted at Michigan State University College of Medicine using data from 1990, 1991, and 1992 to (1) evaluate methods for monitoring compensation equity, (2) test the feasibility of compensation-equity monitoring as part of administrative information systems, and (3) determine whether compensation inequity existed in a case study of faculty salaries. Internal market adjustments for specialty, clinical or basic science "type," and calendar- or academic-year appointments were made before establishing a male cohort for each female faculty member.

RESULTS

The method developed appears feasible for routine administrative monitoring of compensation equity. When the compensations of women of each type and rank were compared with the compensations of their male cohorts, inequities appeared to exist for basic scientists, but not clinicians, based on a criterion of the groups' compensations being 4% or more below those of their cohorts for two successive years.

CONCLUSION

The authors suggest that formal monitoring of compensation equity is an important and feasible administrative undertaking to correct historical inequities. This is an area in which leadership by U.S. medical colleges is needed.

Video registration virtual reality for nonlinkage stereotactic surgery

We have combined three-dimensional (3D) computer-reconstructed neuroimages with a novel video registration technique for virtual reality-based, image-guided surgery of the brain and spine. This technique allows the surgeon to localize cerebral and spinal lesions by superimposing a 3D-reconstructed MR or CT scan on a live video image of the patient. Once the patient's scan has been segmented into the relevant components (e.g., tumor, edema, ventricles, arteries, brain and skin), the surgeon studies the 3D anatomy to determine the optimal surgical approach. The proposed intraoperative surgeon's perspective is displayed in the operating room at the time of surgery using a portable workstation. The patient is then brought to the operating room and positioned according to the planned approach. A video camera is trained on the patient from the proposed intraoperative surgeon's perspective. A video mixer merges the images from the video camera and the 3D computer reconstruction. This video mixer can vary the output intensity of the two input images between 100% of either and 50% of both. This visually superimposes the two images, not unlike a photographic double exposure. The patient's position and the 3D reconstruction are then adjusted until the images on the video mixer's output monitor are identical in terms of scale, position and rotation. This superimposition is facilitated by aligning various surface landmarks such as the external auditory canal, lateral canthus, and nasion. In some cases, such as with spinal tumors, capsules placed on the skin prior to scanning serve as fiducials.(ABSTRACT TRUNCATED AT 250 WORDS)

Autocrine regulation of the production of the gaseous messenger nitric oxide in a glioblastoma cell line

We used a glioblastoma multiform (GBM) cell line to study the mechanism of cellular regulation of nitric oxide (NO) production. Our experiments indicate a confluent monolayer of GBM cells to release NO as measured through its oxidized NO2 form which gradually accumulates and reaches a peak by 7 to 10 days of culture. the addition of the L-arginine analogs L-NG-monomethyl-L-arginine and L-N omega-nitro-L-arginine and dexamethasone to the GBM cultures caused a substantial inhibition of NO production. The addition of monoclonal antibodies against IL-1 and TNF alpha to the cultures resulted in an inhibition of NO production, whereas the addition of anti-TGF beta monoclonal antibodies resulted in an increase in NO production. These findings suggest the presence of an autocrine regulatory mechanism for NO production in some tumor cell lines.

Stereotactic radiotherapy: a technique for dose optimization and escalation for intracranial tumors

Stereotactic radiosurgery offers the ability to treat relatively small volume intracranial lesions with single fraction, high dose radiotherapy while sparing surrounding tissue due to rapid fall off of dose outside of the treatment volume. Conventional radiotherapy takes advantage of the sparing effects of dose fractionation, but includes relatively large amounts of normal brain in the treatment volume the tolerance of which is dose-limiting. For some intracranial lesions it may not be optimal to treat with large single fractions due to tumor location or size. Conventional fractionated radiotherapy may not be optimum in all cases due to the necessary inclusion of normal structures. Through the development of relocatable head frames, the precision of stereotactic techniques and the biologic advantages of fractionation may be combined in stereotactic radiotherapy (SRT). We report on the treatment of 68 patients with intracranial lesions using a dedicated stereotactic linear accelerator to deliver SRT between June 1992 and June 1993. SRT was used either in order to optimize dose distribution and spare normal tissues in patients with excellent prognosis or in order to increase the dose to tumor while keeping doses to normal tissues below tolerance levels in patients with poorer prognosis (dose escalation). Histologies treated included meningioma, low grade astrocytoma, pituitary adenoma and acoustic neuroma. The most common treatment sites were the parasellar region and cavernous sinuses. Most patients (79%) had surgical debulking prior to SRT. 10-12 patients were treated daily. Patient positioning using relocatable stereotactic frames was highly precise. Acute and subacute side effects were minimal and radiographic responses have been similar to those expected with conventional radiotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Tolerance of cranial nerves of the cavernous sinus to radiosurgery

PURPOSE

Stereotactic radiosurgery is becoming a more accepted treatment option for benign, deep seated intracranial lesions. However, little is known about the effects of large single fractions of radiation on cranial nerves. This study was undertaken to assess the effect of radiosurgery on the cranial nerves of the cavernous sinus.

METHODS AND MATERIALS

We examined the tolerance of cranial nerves (II-VI) following radiosurgery for 62 patients (42/62 with meningiomas) treated for lesions within or near the cavernous sinus. Twenty-nine patients were treated with a modified 6 MV linear accelerator (Joint Center for Radiation Therapy) and 33 were treated with the Gamma Knife (University of Pittsburgh). Three-dimensional treatment plans were retrospectively reviewed and maximum doses were calculated for the cavernous sinus and the optic nerve and chiasm.

RESULTS

Median follow-up was 19 months (range 3-49). New cranial neuropathies developed in 12 patients from 3-41 months following radiosurgery. Four of these complications involved injury to the optic system and 8 (3/8 transient) were the result of injury to the sensory or motor nerves of the cavernous sinus. There was no clear relationship between the maximum dose to the cavernous sinus and the development of complications for cranial nerves III-VI over the dose range used (1000-4000 cGy). For the optic apparatus, there was a significantly increased incidence of complications with dose. Four of 17 patients (24%) receiving greater than 800 cGy to any part of the optic apparatus developed visual complications compared with 0/35 who received less than 800 cGy (p = 0.009).

CONCLUSION

Radiosurgery using tumor-controlling doses of up to 4000 cGy appears to be a relatively safe technique in treating lesions within or near the sensory and motor nerves (III-VI) of the cavernous sinus. The dose to the optic apparatus should be limited to under 800 cGy.

Thallium-201 technetium-99m HMPAO single-photon emission computed tomography (SPECT) imaging for guiding stereotactic craniotomies in heavily irradiated malignant glioma patients

SPECT scanning with Tl-201 and Tc-99m offers a unique, inexpensive functional imaging modality to combine with CT stereotactic craniotomy for guiding resection of necrosis and/or tumour in patients treated with escalated doses of radiation (> 6000 cGy) by either brachytherapy or radiosurgery. Thirty-two cases were analyzed, with a detailed description of the imaging and operative techniques.

Stereotactic techniques in managing pediatric brain tumors

Stereotactic techniques available for managing pediatric brain tumors include not only stereotactic biopsy but also stereotactic craniotomy, brachytherapy, and stereotactic radiosurgery. This paper illustrates the use of these techniques in brain tumors in children over a 2-year period at Children's Hospital, Boston. Stereotactic biopsy was used in six cases of deep-seated tumor, with successful tissue diagnosis in all six. Stereotactic craniotomy, in which excision of a mass was done in the stereotactic frame with computed tomography-guided localization and control, was employed in three children. Interstitial radiation using implanted 125I seeds was carried out in two children with malignant astrocytomas: in both it provided good local control but there was later distant recurrence. Stereotactic radiosurgery with a modified linear accelerator was used in eight children as adjunctive therapy for local control. These cases illustrate the versatility of stereotactic techniques involved in a comprehensive approach to pediatric brain tumors.

Dose-volume histogram computations for small intracranial volumes

A sampling formalism is presented to accurately compute the absolute volumes and integral dose-volume histograms of small volumes treated in stereotactic radiosurgery. The presence of small volumes and sharp dose gradients places special constraints on the computational formalism and the accuracy required to compute the dose-volume relationships. We use a spatially nonuniform random sampling method to allow an efficient and accurate computation of the dose-volume histograms for an arbitrary number of volumes. The computation of absolute volume vs dose allows intercomparison of dose delivered to target and dose-critical volumes and allows a quantitative trade-off analysis often critical to an optimal treatment of the lesion.

Dynamic field shaping for stereotactic radiosurgery: a modeling study

PURPOSE

This work assesses the relative field shaping advantages of dynamic field shaping devices for stereotactic radiosurgery using a linear accelerator.

METHODS AND MATERIALS

We selected 43 intracranial tumors (2.0-4.2 cm maximum dimension, 1.5-25.5 cc tumor volume) out of the first 64 intracranial tumors treated with radiosurgery at the Joint Center for Radiation Therapy. We modeled five field shaping devices, each including a fixed auxiliary circular collimator: (a) fixed circular collimator alone; (b) two independent parallel jaws; (c) four independent rectangular jaws; (d) four independent rotatable jaws; and (e) "ideal" multileaf collimator. We adjusted the model parameters until the minimum target isodose was 80% of the dose delivered to isocenter. We defined the treatment volume ratio as the target volume divided by the treatment volume (volume receiving at least the minimum target dose). We used the treatment volume ratio to compare the five models and the actual patient treatments.

RESULTS

For 34 tumors originally treated with one isocenter, the median Treatment Volume Ratio was higher for all of the device models except the fixed circular collimator compared to the actual patient treatments. For the nine tumors originally treated with multiple isocenters, the median Treatment Volume Ratio for the actual multiple isocenter treatments was similar to that for two parallel jaws, four rectangular jaws and four rotatable jaws. Only the median "ideal" collimator treatment volume ratio was higher for these nine tumors.

CONCLUSION

Simple field shaping devices have approximately 50% of the conformal advantage of an "ideal" multileaf collimator. Approximately 50% of typical radiosurgical tumors between 2 and 4 cm have field shaping advantages which exceed the geometrical uncertainties inherent in linear accelerator radiosurgery treatments. The three models, two parallel, four rectangular, or four rotatable independent jaws would improve current linear accelerator technology by providing homogeneous doses with equivalent field shaping for most tumors originally treated with inhomogeneous multiple isocenter plans (6/9 tumors in the current series).

Detection of recurrent gliomas with quantitative thallium-201/technetium-99m HMPAO single-photon emission computerized tomography

Deteriorating clinical status after high-dose radiation therapy for high-grade gliomas may be due to radiation changes or may signal recurrent or residual tumor mass. The two conditions cannot be distinguished reliably by computerized tomography (CT) or magnetic resonance (MR) imaging. The authors assessed the ability of sequential thallium-201 chloride (201Tl) and technetium-99m hexamethylpropylene amine oxime (99mTc HMPAO) single-photon emission CT (SPECT) to distinguish tumor recurrence from radiation changes after high-dose (greater than or equal to 600 cGy) radiation therapy for malignant gliomas. Preoperative tumor/nontumor uptake ratios were analyzed in 32 patients and correlated with the presence of gross tumor at the time of reoperation. In 12 of 13 patients with 201Tl tumor/scalp ratios of 3.5 or greater, recurrent tumor was present. The authors found 99mTc HMPAO SPECT to be useful for identifying the absence of solid tumor recurrence in patients with low to moderate 201Tl uptake (ratio 1.1 to 3.4) and low perfusion to that site. In 11 of 12 patients with 99mTc HMPAO tumor/cerebellum ratios of 0.50 or less, no recurrent tumor mass was present. Three of seven patients with 201Tl ratios of 3.4 or less and 99mTc HMPAO ratios of 0.51 or more had recurrent tumor found at surgery; thus the test was not predictive in this group. It is concluded that the use of sequential 201Tl and 99mTc HMPAO SPECT accurately identifies the presence of tumor recurrence versus radiation changes in most patients with high-grade astrocytomas who have undergone tumor resection and high-dose radiation therapy.

Radiosurgery as part of the initial management of patients with malignant gliomas

PURPOSE

Between May 1988 and May 1991, 41 patients with malignant gliomas were enrolled onto a prospective study designed to evaluate the role of radiosurgery as a component of initial management.

PATIENTS AND METHODS

Thirty-seven patients underwent radiosurgery according to the protocol and were assessable for survival and complications of treatment. Diagnoses included glioblastoma multiforme (GBM) in 23 (62%) cases and anaplastic astrocytoma in 14 (38%) cases. In 20 (54%) cases, surgical resection was attempted initially, whereas 17 (46%) patients underwent biopsy only. Patients in the study group received external-beam radiotherapy that consisted of 5,940 cGy given in 33 fractions to partial brain fields that encompassed the primary tumor with a 3 to 4 cm margin. Radiosurgery, used as a technique for boosting the dose to any residual contrast-enhancing mass lesion, was given 2 to 4 weeks after the completion of conventional radiotherapy. Minimum radiosurgical doses ranged from 1,000 to 2,000 cGy (median, 1,200 cGy), whereas maximum doses ranged from 1,250 to 2,500 cGy (median, 1,500 cGy). The median tumor volume at the time of radiosurgery was 4.8 cm3 (range, 1.2 to 72 cm3). Adjuvant chemotherapy was not given.

RESULTS

After a median follow-up of 19 months, only nine of 37 (24%) patients have died. Six patients (all glioblastoma multiforme) died of recurrent tumor, whereas death was attributable to complications of treatment in two cases and intercurrent disease in one case. Four patients with recurrent tumor failed at the margins of the radiosurgical treatment volume, whereas two patients progressed locally. One patient is alive with local and marginal failure. Seven (19%) patients underwent reoperation at a median time of 5 months (range, 1 to 14 months) after radiosurgery.

CONCLUSION

We conclude that radiosurgery is a useful adjunct to other modalities in the initial management of patients with small, radiographically well-defined malignant gliomas.

Central nervous system disease in Sjögren's syndrome. New insights into immunopathogenesis

Although peripheral nervous system disease is a well-established complication of primary Sjögren's syndrome (SS), until relatively recently little attention has been focused on the central nervous system (CNS) complications of this disorder. The observations discussed in this article pertain to patients with primary SS in whom the presence of a second connective tissue disorder and other etiologies for neurologic disease have been rigorously excluded. In this article, the growing clinical spectrum of CNS manifestations, neurodiagnostic techniques, serologic analyses, and immunogenetic markers associated with this disorder are reviewed.

Anti-Ro/SS-A antibodies in the pathophysiology of congenital heart block in neonatal lupus syndrome, an experimental model. In vitro electrophysiologic and immunocytochemical studies

OBJECTIVE

To determine whether anti-Ro/SS-A antibodies selectively bind to neonatal cardiac cells and alter membrane repolarization.

METHODS

An in vitro electrophysiologic and immunocytochemical experimental model contrasting neonatal and rabbit cardiac tissue was employed.

RESULTS

Sera and IgG-enriched fractions from anti-Ro/SS-A antibody-positive mothers of infants with neonatal lupus erythematosus and congenital heart block bind to neonatal, rather than adult, rabbit cardiac tissue and alter the transmembrane action potential (i.e., inhibit repolarization). The additional presence of anti-La/SS-B antibodies was not additive or synergistic for these immunocytochemical and electrophysiologic features. Sera containing other antibody specificities (i.e., anti-native DNA, cardiolipin, Sm, and nuclear RNP) failed to stain the neonatal cardiac tissue or produced alterations in membrane repolarization.

CONCLUSION

Anti-Ro/SS-A antibodies may play a pathophysiologic role in the development of congenital heart block in neonatal lupus.

Distribution of etanidazole into human brain tumors: implications for treating high grade gliomas

Etanidazole was developed as an oxygen-mimetic radiosensitizer less lipophilic than misonidazole. Sensitization depends on an adequate concentration of drug in the tumor at the time of irradiation. Therefore, due to the presence of the blood-brain barrier, brain tumors may theoretically be difficult to radiosensitize due to the hydrophilic characteristics of etanidazole. Based on previous reports of loss of BBB integrity in brain tumors, we investigated the ability of etanidazole to penetrate into malignant gliomas of patients receiving etanidazole as part of a Phase I continuous infusion protocol. The patients had completed previous external beam irradiation. Twenty-two patients were studied and their etanidazole plasma and biopsy data were compared to the 2-compartment model derived from a second group of 19 patients with bolus etanidazole. Etanidazole concentration in brain tumor biopsies varied widely and appeared to be clustered into a higher and a lower pharmacokinetic group having mean tumor to well-perfused second compartment ratios of 1 and 0.25, respectively. Both high and low etanidazole concentrations were evident in different biopsies obtained from the same patient. Correlations between histology and tissue concentrations suggested that the higher level correspond to malignant tissue. These data indicate that the blood brain barrier is disrupted to varying degrees by the brain tumor and/or prior irradiation and that etanidazole penetrates into brain tumors.

Final report of the phase I trial of continuous infusion etanidazole (SR 2508): a Radiation Therapy Oncology Group study

Seventy-eight patients have been treated on a Phase I trial using continuous infusion etanidazole while undergoing brachytherapy for locally advanced tumors. There were two sequential schemata, the first treated 63 patients with doses ranging from 8-23 g/m2 over 48 hr and the second treated 15 patients with doses ranging from 20-23 g/m2 over 96 hr. The tumor sites were: brain (n = 42), cervix (n = 22), and breast (n = 14). Patients received a loading dose of etanidazole of 2 g/m2 followed by a continuous infusion for a total of 48 or 96 hr while radioactive implants were in place. Of the 63 patients in the 48-hr study, 52 were entered at doses of less than or equal to 21 g/m2 and there were no definite neuropathies but two patients with the cramping/arthralgia syndrome. Of the 11 patients entered at 22-23 g/m2, 1 patient had symptoms of peripheral neuropathy (Grade II) and 6 had the cramping/arthralgia syndrome. This is a new syndrome, distinct from the peripheral neuropathy, characterized by transient alterations in sensations consisting of cramping, arthralgias, or tingling that resolved completely at intervals varying from a few hours to about 1 week post-treatment. The cramping/arthralgia syndrome limited dose escalation; therefore, the maximum tolerated dose over 48 hr was determined to be 20-21 g/m2. The 96-hr infusion was limited to patients with recurrent gliomas undergoing stereotactic implantation. To date, 15 patients have been treated with doses of 20-23 g/m2. No toxicity was encountered at doses less than or equal to 22 g/m2. At 23 g/m2, one patient developed Grade III neuropathy and three patients had mild cramping/arthralgia syndrome, for whom the drug was discontinued. Therefore, it appears the maximum tolerated dose at 96 hr will be approximately 23 g/m2, which is 10-15% higher than for the 48-hr infusion.

Radiosurgery using a modified linear accelerator

Stereotactic radiosurgery using modified LINACs is a powerful new technique that offers a versatile method for administering high-dose radiation in a single session. Treatment-planning techniques currently in use enable individual isocenter field shaping, three-dimensional optimization of isocenter placement (including the use of multiple isocenters), and real-time analysis of isodose distribution in three dimensions relative to specifically defined anatomic structures from MR imaging or CT data. Modified linear accelerators offer successful control of both arteriovenous malformations and benign tumors (acoustic neuromas, craniopharyngiomas, and meningiomas), with results equal to the best series reported by users of the gamma knife or heavy-particle systems. More recent work indicates that radiosurgery may play an important role in controlling recurrent pediatric malignant tumors, metastatic cerebral lesions, and even malignant astrocytomas in some patients. Improved correlation of isodose distributions with imaging data allows for sophisticated analysis of results and specific complications, ultimately enabling improved patient care using this exciting new technique.

Quality assurance in stereotactic radiosurgery using a standard linear accelerator

Methods have recently been developed for using standard linear accelerators to perform stereotactic radiosurgery. The accuracy necessary to perform this procedure requires an intensive quality assurance program to encompass all aspects of dose calibration and mechanical integrity of the treatment unit, the treatment planning process, and treatment delivery. The programs developed at the Joint Center for Radiation Therapy (JCRT) include testing of the linear accelerator and the stereotactic system, cross checking of the treatment planning process, and a quality assurance check list of the treatment delivery procedure. This report outlines in detail the quality assurance program currently in use at the JCRT.

Variables associated with the development of complications from radiosurgery of intracranial tumors

Between 5/21/86 and 11/1/89, we treated 64 recurrent or inoperable intracranial tumors in 60 patients (40 primary, 24 metastatic) with stereotactic radiosurgery using a modified 6 MeV linear accelerator at the Joint Center for Radiation Therapy. Patients were followed until death or 1/1/90. The median follow-up was 8 months (2-43 months). Fourteen patients experienced complications from 12 hours to 7 months (median 3 months, but only two patients more than 4 months) following radiosurgery. To determine variables related to complication, we calculated integral dose-volume histograms for 61/64 lesions and the surrounding CT-defined normal tissue. We excluded 16 lesions in 15 patients for follow-up less than 4 months (12 patients) or insufficient treatment information (3 patients). The variables for which higher values were associated with significantly more toxicity in a univariate score test were: a) tumor dose inhomogeneity (p less than 0.00001), b) maximum tumor dose (p = 0.00002), c) number of isocenters (p = 0.00002), d) maximum normal tissue dose (p = 0.00005) and e) tumor volume (p = 0.0001). These variables were all highly correlated with tumor dose inhomogeneity (coefficients of rank correlation 0.75-0.81). Tumor dose inhomogeneity had a much higher loglikelihood in a logistic model than any other single variable and a higher loglikelihood than any other two variables combined. None of the 21 patients with metastatic lesions experienced a complication. When we excluded the metastatic lesions, the above five variables remained significant in univariate tests. The mean tumor dose, number of treatment arcs, total degrees of arc, tumor location, previous radiotherapy, tumor geometry, pretreatment performance status, collimator size, and age were not significantly associated with toxicity. We conclude that radiosurgery of intracranial tumors is associated with a low risk of complications for lesions less than 10cc treated with a single isocenter to maximum tumor doses less than 25 Gy with tumor dose inhomogeneity less than 10 Gy, but that treatment of larger lesions will require new treatment strategies which reduce the tumor dose inhomogeneity associated with multiple isocenter treatments.

Treatment planning for stereotactic radiosurgery of intra-cranial lesions

Stereotactic radiosurgery of intra-cranial lesions is a treatment modality where a well defined target volume receives a high radiation dose in a single treatment. Our technique delivers this dose using a set of non-coplanar arcs and small circular collimators. We use a standard linear accelerator in our treatments, and the adjustable treatment parameters are: isocenter location, gantry arc rotation interval, couch angle, collimator field size, and dose. The treatment planning phase of the treatment determines these parameters such that the target volume is sufficiently irradiated, and dose to surrounding healthy tissue and critical, dose-limiting structures is minimized. The attachment of a BRW localizing frame to the patient's cranium combined with CT imaging (and optionally MRI or angiography) provides the required accuracy for localizing individual structures in the treatment volume. The treatment is fundamentally 3-dimensional and requires a volumetric assessment of the treatment plan. The selection of treatment arcs relies primarily on geometric constraints and the beam's eye view concept to avoid irradiating critical structures. The assessment of a treatment plan involves isodose distributions throughout the volume and integral dose-volume histograms. We present the essential concepts of our treatment planning approach, and illustrate these in three clinical cases.

Cerebral vasculopathy associated with collateralization resembling moya moya phenomenon and with anti-Ro/SS-A and anti-La/SS-B antibodies

We describe a 48-year-old, previously healthy, anti-Ro/SS-A and anti-La/SS-B antibody positive black woman with negative risk factors for atherosclerosis, who developed mental status and personality changes over a 6-12-month period, and progressive cortical blindness over a 2-week period. Angiographic and computed axial tomographic studies of the brain demonstrated multiple large areas of infarction correlating with stenosis and occlusions of the internal carotid and posterior cerebral arteries. Moya moya-like findings were prominent radiographically. Results of angiographic, computed tomographic, and magnetic resonance imaging studies were interpreted as being compatible with large, medium, and small vessel disease, most likely a vasculitis.

Computer-assisted superimposition of magnetic resonance and high-resolution technetium-99m-HMPAO and thallium-201 SPECT images of the brain

A method for registering three-dimensional CT, MR, and PET data sets that require no special patient immobilization or other precise positioning measures was adapted to high-resolution SPECT and MRI and was applied in 14 subjects (five normal volunteers, four patients with dementia (Alzheimer's disease), two patients with recurrent glioblastoma, and three patients with focal lesions (stroke, arachnoid cyst and head trauma]. T2-weighted axial magnetic resonance images and transaxial 99mTc-HMPAO and 201Tl images acquired with an annular gamma camera were merged using an objective registration (translation, rotation and rescaling) program. In the normal subjects and patients with dementia and focal lesions, focal areas of high uptake corresponded to gray matter structures. Focal lesions observed on MRI corresponded to perfusion defects on SPECT. In the patients who had undergone surgical resection of glioblastoma followed by interstitial brachytherapy, increased 201Tl corresponding to recurrent tumor could be localized from the superimposed images. The method was evaluated by measuring the residuals in all subjects and translational errors due to superimposition of deep structures in the 12 subjects with normal thalamic anatomy and 99mTc-HMPAO uptake. This method for superimposing magnetic resonance and high-resolution SPECT images of the brain is a useful technique for correlating regional function with brain anatomy.

L-arginine normalizes endothelial function in cerebral vessels from hypercholesterolemic rabbits

We hypothesized that normal vascular reactivity could be restored in vessels from hypercholesterolemic animals by exposing them to L-arginine, the precursor of endothelium-derived relaxing factor (EDRF). Basilar arteries were harvested from New Zealand white rabbits fed normal chow or that supplemented with 2% cholesterol for 10 wk. Vessels were cannulated for perfusion at physiologic pressure. Changes in vessel diameter were monitored by videomicroscopy. In comparison to normal vessels, those from hypercholesterolemic animals vasoconstricted more to KCl, endothelin (E), and 5-hydroxytryptamine (5-HT). Conversely, vasodilation to acetylcholine (ACh) (but not that to verapamil) was significantly impaired in the hypercholesterolemic animals. In vitro administration of L-arginine (3 mM) for 45 min normalized vasodilation to ACh and vasoconstriction to E, 5-HT, and KCl in the isolated vessels from hypercholesterolemic animals. This effect was stereospecific, since D-arginine had no effect. To conclude, these data confirm that hypercholesterolemia attenuates endothelium-derived relaxation, and enhances the sensitivity of these vessels to vasoconstrictors. In vitro administration of L-arginine normalized vascular reactivity of isolated vessels from hypercholesterolemic animals. Thus, hypercholesterolemia induces a reversible endothelial dysfunction that may be corrected by supplying the precursor of EDRF, L-arginine.

Extracranial metastatic glioblastoma: appearance on thallium-201-chloride/technetium-99m-HMPAO SPECT images

Sequential thallium-201-chloride and technetium-99m-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) images were obtained in a patient with extracranial metastatic glioblastoma multiforme. Thallium-201 uptake was high (three times the scalp background) in all pathologically confirmed extracranial metastases and moderate (1.6 times scalp background) intracranially, where most biopsy specimens showed gliosis with scattered atypical astrocytes. Technetium-99m-HMPAO uptake was decreased intracranially in the right frontal and parietal lobes which had been irradiated. It was also decreased in one well-encapsulated scalp lesion and high in another scalp mass with less defined borders. Possible mechanisms of tumor uptake of these agents are reviewed.

Subacute cutaneous lupus erythematosus-immunogenetic associations

Thirty-two patients who fulfilled criteria for subacute cutaneous lupus erythematosus (SCLE) were examined for their immunogenetic associations. Our results confirm the previously reported association of HLA-DR3 (15/31 48% P less than 0.01) and also demonstrate an increase in HLA-DR2 (14/31, 45%, P = less than 0.05). These findings indicate there are two distinct immunogenetic (HLA) populations of Ro(SS-A) antibody-positive SCLE patients. The increased frequency of HLA-DR2 and DR3 appears to be associated with expression of the Ro(SS-A) antibody, since no HLA associations were seen in Ro(SS-A)-negative SCLE patients when compared with normal population controls. Furthermore, these data indicate that the distinctive cutaneous lesions of SCLE are not associated with one specific HLA allele, as previously suspected. These findings contrast with the relatively homogeneous immunogenetic background seen in other lupus erythematosus subsets with a high frequency of Ro(SS-A) antibody, i.e., neonatal lupus erythematosus and Sjögren's syndrome/lupus erythematosus overlap (increased frequency of HLA-DR3, DQw2 and DRW52).

Radiation necrosis vs high-grade recurrent glioma: differentiation by using dual-isotope SPECT with 201TI and 99mTc-HMPAO

Conventional imaging techniques are often unreliable in distinguishing between radiation necrosis and recurrent glioma in patients who are symptomatic after high-dose radiotherapy. We performed dual-isotope single-photon emission computed tomography (SPECT) with the use of thallium-201 (201TI) and the perfusion agent 99mTc-hexamethyl-propyleneamine oxime (HMPAO) to aid in this differentiation in 15 patients with glioma prior to biopsy. We found that dual-isotope SPECT scanning correlated with the pathologic findings in 14 of the 15 cases. All patients with high 201TI uptake in their treated tumor beds had local tumor recurrence, and all patients with low 201TI uptake showed only radiation changes without evidence of solid tumor. In patients with an intermediate level of 201TI concentration in their tumor bed, 99mTc-HMPAO uptake differentiated those patients with active tumor from those without; three of four patients with preserved or increased perfusion had pathologic evidence of solid tumor, whereas none of the four patients with decreased perfusion to the tumor bed had evidence of local recurrence. We believe that dual-isotope SPECT with 201TI and 99mTc-HMPAO may be useful in differentiating sites of likely tumor growth from nonspecific radiation changes in patients treated for malignant glioma.