A Clinical Interactive Technique for MR-CT Image Registration for Target Delineation of Intracranial Tumors

Replacement of current CT-based, three-dimensional (3D) treatment planning systems by newer versions capable of automated multi-modality image registration may be economically prohibitive for most radiation oncology clinics. We present a low-cost technique for MR-CT image registration on a “first generation” CT-based, 3D treatment planning system for intracranial tumors. The technique begins with fabrication of a standard treatment mask. A second truncated mask, the “minimask,” is then made, using the standard mask as a mold. Two orthogonal leveling vials glued onto the minimask detect angular deviations in pitch and roll. Preservation of yaw is verified by referencing a line marked according to the CT laser on the craniocaudal axis. The treatment mask immobilizes the patient's head for CT. The minimask reproduces this CT-based angular treatment position, which is then maintained by taping the appropriately positioned head to the MR head coil for MR scanning. All CT and MR images, in DICOM 3.0 format, are entered into the treatment planning system via a computer network. Interactive registration of MR to CT images is controlled by real-time visual feedback on the computer monitor. Translational misalignments at the target are eliminated or minimized by iterative use of qualitative visual inspection. In this study, rotational errors were measured in a retrospective series of 20 consecutive patients who had undergone CT-MR image registration using this technique. Anatomic structures defined the three CT orthogonal axes from which angular errors on MR image were measured. Translational errors at the target isocenter were within pixel size, as judged by visual inspection. Clinical setup using the minimask resulted in overall average angular deviation of 3°±2° (mean ± SD) and translational deviation within the edges of the target volume of typically less than 2 mm. The accuracy of this registration technique for target delineation of intracranial tumors is compatible with practice guidelines. This method, then, provides a cost-effective means to register MR and CT images for target delineation of intracranial tumors.

Dosimetry techniques for narrow proton beam radiosurgery

Characterization of narrow beams used in proton stereotactic radiosurgery (PSRS) requires special efforts, since the use of finite size detectors can lead to distortion of the measured dose distributions. Central axis depth doses, lateral profiles and field size dependence factors are the most important beam characteristics to be determined prior to dosimetry calculations and beam modelling for PSRS. In this paper we report recommendations for practical dosimetry techniques which were developed from a comparison of beam characteristics determined with a variety of radiation detectors for 126 and 155 MeV narrow proton beams shaped with 2-30 mm circular brass collimators. These detectors included small-volume ionization chambers, a diamond detector, an Hi-p Si diode, TLD cubes, radiographic and radiochromic films. We found that both types of film are suitable for profile measurements in narrow beams. Good agreement between depth dose distributions measured with ionization chambers, diamond and diode detectors was demonstrated in beams with diameters of 20-30 mm. The diode detector can be used in smaller beams, down to 5 mm diameter. For beams with diameters less than 5 mm, reliable depth dose data may be obtained only with radiochromic film. The tested ionization chambers are appropriate for calibration of beams with diameters of 20-30 mm. TLD cubes and diamond detectors are useful to determine relative dose in beams with diameters of 10-20 mm. Field size factors for smaller beams should be obtained with diode and radiochromic film. We conclude that dosimetry characterization of proton beams down to several millimetres in diameter can be performed using the described procedures.

Microsurgical resection of incompletely obliterated intracranial arteriovenous malformations following stereotactic radiosurgery

Radiosurgery is effective in obliterating small arteriovenous malformations (AVMs), but less successful in thrombosing larger AVMs. This study reviewed patients who underwent surgical resection of their large AVMs following failed radiosurgical obliteration. AVMs from 36 patients (aged 7 to 64 years, mean 29.9) were surgically resected 1 to 11 years after radiosurgery. Initial AVM volumes were 0.7 to 117 cm3 (mean 21.6 cm3), and radiosurgical doses ranged from 4.6 to 45 Gray equivalent (GyE) (mean 21.1 GyE). Thirty AVMs (83%) were located in eloquent tissue. Venous drainage was deep (14), superficial (13), or both (9). Spetzler grades were II (2), III (12), IV (18), and V (4). Nine patients suffered rehemorrhage after radiosurgery but prior to surgery, while three patients developed radiation necrosis. Twenty-seven patients underwent endovascular embolization prior to surgery. During microsurgical resection, the AVMs were found to be significantly less vascular and more easily resected, compared to AVMs in patients who had not received radiosurgery. Histology showed endothelial proliferation with hyaline and mineralization in vessel walls. Partial or complete thrombosis of some AVM vessels, and evidence of vessel and brain necrosis were noted in many cases. Clinical outcome was excellent or good in 34 cases, with two patients dying of rebleeding from residual AVM. Five patients were neurologically worse following microsurgical resection. Final outcome was largely related to the pretreatment grade. Radiosurgery several years prior to surgical resection appears useful in treating unusually large and complex AVMs.

Stereotactic radiosurgery--the role of charged particles

Stereotactic radiosurgery using charged-particle beams has been the subject of biomedical research and clinical development for more than 50 years. Charged particles of proton mass or greater manifest unique physical properties that can be used to place a high dose of radiation preferentially within the boundaries of a deeply located intracranial target volume. Since 1954, nearly 10000 patients have been treated using this technique. Treated disorders include pituitary tumors, vascular malformations, primary and metastatic brain tumors, and subfoveal neovascularization. Charged-particle radiosurgery is particularly advantageous for the conformal treatment of large and/or irregularly shaped lesions, or for the treatment of lesions located in front of or adjacent to sensitive brain structures.

Stereotactic radiosurgery of angiographically occult vascular malformations: 14-year experience

OBJECTIVE

Radiosurgery is generally effective in obliterating true arteriovenous malformations, but less is known about its effects on angiographically occult vascular malformations (AOVMs). Since July 1983, 57 patients with surgically inaccessible AOVMs of the brain were treated using helium ion (47 patients) or linear accelerator (10 patients) radiosurgery. This study retrospectively evaluates the response of these AOVMs to treatment.

METHODS

All patients presented with previous hemorrhage. The mean patient age was 35.6 years (range, 13-71 yr). The mean AOVM volume was 2.25 cm3 (range, 0.080-15.2 cm3), treated with a mean of 18.0 Gy equivalent (physical dose x relative biological effectiveness, which is 1.3 for helium ion Bragg peak) (range, 7.0-40 Gy equivalent). The Drake scale scores before treatment were as follows: excellent (25 patients), good (26 patients), and poor (6 patients). The mean follow-up period was 7.5 years (range, 9 mo-13.8 yr).

RESULTS

Eighteen patients (32%) bled symptomatically (20 hemorrhages) after radiosurgery. Sixteen hemorrhages occurred within 36 months after radiosurgery (9.4% annual bleed rate; 16 hemorrhages/171 patient yr); 4 hemorrhages occurred more than 36 months after treatment (1.6% annual bleed rate; 4 hemorrhages/257 patient yr) (P < 0.001). Complications included symptomatic radiation edema (four patients, 7%), necrosis (one patient, 2%), and increased seizure frequency (one patient, 2%). Eight patients underwent surgical resection of their AOVMs 8 to 59 months after radiosurgery because of subsequent hemorrhage. The Drake scale scores after treatment were as follows: excellent (25 patients), good (24 patients), poor (3 patients), and dead (5 patients, 3 of whom died as a result of causes unrelated to the AOVMs or radiosurgery).

CONCLUSION

Radiosurgery may be useful for AOVMs located in surgically inaccessible regions of the brain. A significant decrease in bleed rate exists more than 3 years after treatment compared with the bleed rate within 3 years of treatment. Because current neuroradiological techniques are not able to image obliterative response in these slow-flow vascular lesions, longer term clinical follow-up is required.

The management of patients with arteriovenous malformations and associated intracranial aneurysms

OBJECTIVE

Few published studies have focused specifically on the unique management issues encountered in treating patients with arteriovenous malformations (AVMs) and associated intracranial aneurysms. The primary objective of this study was to retrospectively review the clinical and radiographic features of these patients.

METHODS

Medical records of all patients seen at Stanford University Hospital between 1988 and 1996 with a diagnosis of AVMs were retrospectively reviewed. Aneurysms were identified by conventional angiography and characterized by size, number, and location relative to the AVMs. AVMs were graded according to the Spetzler-Martin scale. Odds ratios were calculated for the risk of intracranial hemorrhage. Variables included age, sex, number of aneurysms, and AVM grade.

RESULTS

Forty-five of 600 patients (7.5%) were identified as having coexisting intracranial aneurysms. All 45 patients had high-flow malformations, and 58% had AVMs of Spetzler-Martin Grade IV or higher. A majority of patients had multiple aneurysms. There was a statistically significant increase in AVM hemorrhage in female patients (odds ratio, 8.53 [1.87-38.98]; P < 0.005). There was no statistically significant correlation between the development of hemorrhage and either age, AVM grade, or the number of aneurysms. Twenty-three patients (51%) presented with intracranial hemorrhage: bleeding occurred from the AVMs in 15 and from ruptured aneurysms in 5, and the source of the bleeding could not be determined in 3. Overall, nine patients (20%) bled from ruptured aneurysms: five at presentation, two during or within 3 weeks of AVM treatment, and two from new aneurysms. Two of these nine patients died as a direct result of aneurysmal subarachnoid hemorrhage. Five patients (11%) developed new aneurysms.

CONCLUSION

Aneurysms associated with AVMs are at risk for rupture before, during, and immediately after treatment of the AVMs. New aneurysms may arise in patients with high-flow AVMs. The risk of intracranial hemorrhage from either source is higher in female patients. To reduce the complications of intracranial hemorrhage in these patients, we recommend a management protocol designed to treat the aneurysms by surgical or endovascular means before administering definitive therapy for the AVMs. Meticulous intraoperative blood pressure control and fluid management during aneurysm surgery is critical to avoid hemorrhage from the AVMs.

Pathological changes in surgically resected angiographically occult vascular malformations after radiation

OBJECTIVE

The goal of this study was to evaluate the pathological changes associated with radiation treatment (stereotactic radiosurgery or conventional irradiation) of angiographically occult vascular malformations (AOVMs).

METHODS

Eleven patients underwent surgical resection of an AOVM in the mesial temporal lobe, brain stem, thalamus, or basal ganglia after previous radiation treatment. The indications for surgery were recurrent symptomatic bleeding from the lesion in 10 patients and recurrent intractable seizures in 1 patient. Radiation was used as the initial therapy because the risk of surgical resection was deemed too high. Three patients received conventional radiation therapy of 3000 to 5400 rads at an outside institution. One patient received radiosurgery with the gamma knife at another institution using a dose of 15 Gy to the margin. The remaining 7 patients received stereotactic radiosurgery with a helium-ion particle beam. The dose range was from 18 to 26 Gy equivalents. The interval from radiation to surgical resection ranged from 1 to 10 years, with a mean of 3.5 years. These lesions were compared with 10 nonirradiated cavernous malformations.

RESULTS

One irradiated lesion was identified pathologically as a true arteriovenous malformation despite being angiographically occult. This lesion did not demonstrate significant changes in the vasculature but did have radiation necrosis of the surrounding brain 5 years after 25 Gy equivalents of helium-ion radiosurgery. Two other specimens were too small to identify the type of vascular malformation adequately. Of the remaining eight malformations identified as cavernous malformations, six showed a combination of marked fibrosis of the vascular channels, fibrinoid necrosis, and ferrugination. However, the fibrinoid necrosis was the only finding unique to the irradiated lesions compared with nonirradiated controls. All the irradiated lesions still had patent vascular channels; none were completely thrombosed.

CONCLUSION

Radiosurgery or conventional radiation therapy did not cause histologic vascular obliteration in intracranial AOVMs evaluated 1 to 10 years (mean 3.5 yr) after radiation delivery. It should be recognized that these patients are irradiation failures who may not be representative of all irradiated patients. However, recurrent bleeding from AOVMs may relate to poor radiation response in some patients.

Amphiphilic networks. X. Diffusion of glucose and insulin (and nondiffusion of albumin) through amphiphilic membranes

Select semipermeable amphiphilic membranes have been prepared and their diffusional characteristics for glucose, insulin, and albumin investigated. The membranes were prepared by cast copolymerization of a hydrophilic monomer (i.e., N,N-dimethyl acrylamide, or N,N-dimethylaminoethyl methacrylate) with the hydrophobic crosslinker methacrylate-ditelechelic polyisobutylene. The products have sufficient mechanical properties for the fabrication of swollen membranes, sheets, tubes, etc. Membranes have been identified which allowed the rapid simultaneous countercurrent diffusion of glucose (Mn = 180 Da) and insulin (Mn = 5733 Da) but did not allow albumin (Mn approximately 60,000 Da) to pass. Evidently, the effective molecular weight cutoff point of these membranes is in the 6-60-KDa range.

Stereotactic radiosurgery of arteriovenous malformations: pathologic changes in resected tissue

Both stereotactic radiosurgery and microsurgery are treatment modalities for arteriovenous malformations (AVM), and more recently, multimodality treatment using these approaches has been utilized. We surgically resected AVMs from 33 patients (ages 7-64 years old, mean age 30.4) 1-11 years after radiosurgery. AVM volumes were 0.8-117 cm3 (mean 21.6 cm3), and doses ranged from 4.6-45 GyE (mean 21.2 GyE). AVMs resected were submitted for pathologic review. Each AVM was evaluated for the following radiation changes, and the number of AVMs demonstrating these changes were noted: endothelial proliferation (27), hyaline (18) and calcium (10) in AVM vessel walls, partial (9) or complete (24) thrombosis of some AVM vessels, and necrosis of vessels (15) and adjacent brain tissue (11). A semiquantitative scale (mild, moderate, severe) incorporating the aforementioned changes present in each case classified the extent of radiation-induced change. There was a significant correlation (r = 0.624, p < 0.01) between extent of radiation change and dose of radiation received. There was no absolute radiation dose threshold below which radiation-induced changes were absent. However, all but one patient receiving greater than 20 GyE developed moderate to severe radiation vascular changes and the 3 patients treated with greater than 30 GyE all had severe radiation-induced changes. Radiation changes in AVMs following stereotactic radiosurgery appear to be dose-related. The correlation of dose to extent of radiation change may allow the determination of the optimal dose of radiation to treat AVMs.

Surgical resection of large incompletely treated intracranial arteriovenous malformations following stereotactic radiosurgery

Although radiosurgery is effective in obliterating small arteriovenous malformations (AVMs), it has a lower success rate for thrombosing larger AVMs. The authors surgically resected AVMs from 33 patients ranging in age from 7 to 64 years (mean 30.4 years) 1 to 11 years after radiosurgery. Initial AVM volumes were 0.8 to 117 cm3 (mean 21.6 cm3), and doses ranged from 4.6 to 45 GyE (mean 21.2 GyE). Of 27 AVMs in eloquent or critical areas, 10 were located in language, motor, sensory, or visual cortex, 11 in the basal ganglia/thalamus, one each in the brainstem, hypothalamus, and cerebellum, and three in the corpus callosum. Venous drainage was deep in 13, superficial in 12, or both in eight lesions. Spetzler-Martin grades were II in one, III in 12, IV in 16, and V in four patients. Eight patients experienced rebleeding after radiosurgery but prior to surgery. Three patients developed radiation necrosis and 25 underwent endovascular embolization prior to surgery. At surgery the AVMs were found to be markedly less vascular, partially thrombosed, and more easily resected, compared to those seen in patients who had not undergone radiosurgery. Pathological investigation showed endothelial proliferation with hyaline and calcium in vessel walls. There was partial or complete thrombosis of some AVM vessels and evidence of vessel and brain necrosis in many cases. Complete resection was achieved in 28 patients and partial resection in five. Clinical outcome was excellent or good in 31 cases, and two patients died of rebleeding from residual AVM. Four patients' conditions worsened following microsurgical resection. Final clinical outcome was largely related to the pretreatment grade. Radiosurgery several years prior to open microsurgery may prove to be a useful adjunct in treating unusually large and complex AVMs.

Computed tomography slice-by-slice target-volume delineation for stereotactic proton irradiation of large intracranial arteriovenous malformations: an iterative approach using angiography, computed tomography, and magnetic resonance imaging

PURPOSE

Target-volume delineation for stereotactic irradiation is problematic for large and irregularly shaped arteriovenous malformations (AVMs). The purpose of this report is to quantify modifications in the target volume that result from iterative treatment planning that incorporates multimodality imaging data.

METHODS AND MATERIALS

Stereotactic neuroimaging procedures were performed for 20 consecutive patients with AVM volumes > 10 cm3. Angiographically defined extrema were transformed into computed tomography (CT) space. The resulting target contours were then modified by a multidisciplinary treatment planning team after iterative review of angiographic, CT, and magnetic resonance imaging (MRI) data. Volumes of interest and dose-volume histograms for proton irradiation were calculated before and after iterative target delineation.

RESULTS

Initial (angiographically defined) target volumes ranged from 15.3 to 96.1 cm3 (mean, 43.6 cm3). Final (iteratively defined) target volumes ranged from 10.7 to 114.0 cm3 (mean, 38.4 cm3). The volume of presumed normal tissue excluded by iterative planning ranged from 2.6 to 47.0 cm3 (mean, 15.5 cm3). Initially untargeted AVM, most commonly obscured by embolization material, was identified in all cases (range, 0.3 to 57.8 cm3; mean, 10.3 cm3). Corresponding dose-volume histograms demonstrated marked differences regarding lesion coverage and sparing of normal tissue structures.

CONCLUSIONS

Iterative target-volume delineation resulted in significant modifications from initial, angiographically defined target volumes. Substantial amounts of apparently normal tissue were excluded from the final target, and additional abnormal vascular structures were identified for incorporation. We conclude that an iterative multimodality approach to target-volume delineation may improve the overall results for stereotactic irradiation of large and complex AVMs.

Endovascular treatment of cerebral arteriovenous malformations following radiosurgery

PURPOSE

Previous reports of embolization of cerebral arteriovenous malformations (AVMs) have evaluated the technique as adjunctive therapy prior to surgery or radiosurgery; our aim is to assess the role of embolization following radiosurgery.

PATIENTS

Six patients previously treated with radiosurgery and showing no response as judged by cerebral angiography were embolized 24 to 55 months (mean 34.3 months) after initial radiosurgery.

RESULTS

In five of six, a significant volume reduction was achieved ranging from 60%-100% (mean 74%). One patient was treated with embolization alone and the AVM has remained fully thrombosed 2 years after treatment. Three patients underwent surgical resection for cure after embolization, and two patients had repeat radiosurgery to a significantly smaller AVM volume. One patient had an asymptomatic carotid dissection at embolization; however, no clinically apparent complications occurred in the treatment group.

CONCLUSION

Embolization can be used after radiosurgery to assist in the management of those AVMs that have not responded to initial treatment.

Hemophilus influenza infection of an implantable insulin-pump pocket

OBJECTIVE

To increase awareness of adverse events associated with the use of implantable insulin pumps.

RESEARCH DESIGN AND METHODS

A descriptive case report of a pump implant infection.

RESULTS

This is a case report of one implanted insulin pump-pocket infection among a series of 15 patients. After exposure to a child with a respiratory infection on PID 30, V.L.C. (the patient) developed a fulminant pump-pocket infection. H. influenza was recovered from it. Despite aggressive antibiotic therapy, the infection could not be controlled. Insulin delivery ceased, and the pump was explanted. The pump-pocket infection rapidly resolved with pump removal, permitting later reimplantation.

CONCLUSIONS

We have adopted the American Heart Association indications and antimicrobial prophylaxis regimens recommended for prevention of endocarditis in patients with prosthetic values for patients with implanted insulin pumps.

Radiation physics for particle beam radiosurgery

For the particles and energies considered suitable for radiosurgery, with increasing particle charge, the Bragg peak height reaches a maximum with helium and then decreases, the Bragg peak width narrows, the distal fall-off steepens, and the exit dose increases (Table 1). The helium-ion beam is superior to a proton beam because of the higher peak-plateau ratio, more rapid dose fall-off, and smaller beam deflection, and it suffers only in the modest exit dose. Comparison of the therapeutically useful parameters of these beams is complicated by the change in beam quality (LET) with depth. Considerations of RBE values, which change with the ion species and with depth of penetration, may alter the relative rankings based on one or more of these beam characterization values. For all these beams, the RBE increases with increasing LET. The effect for protons is small and occurs just at the end of range of the particles. Effective isodose distributions based on modeled beams have been reported for helium, carbon, and neon ions. These distributions include the effects of a varying RBE with changes in the beam quality (as measured by a dose-weighted LET) and the change in dose fraction size with depth (the dose per fraction is a function of the depth of penetration). These calculations suggest that the optimal charged-particle beam for radiosurgery might be carbon. Heavy charged-particle beams can produce dose distributions superior to those obtainable with photon or electron beams. In clinical trials, these dose distributions have proved to be useful for the treatment of human diseases, including neoplasia and life-threatening intracranial disorders.(ABSTRACT TRUNCATED AT 250 WORDS)

Charged-particle radiosurgery for intracranial vascular malformations

Heavy charged-particle radiation has unique physical characteristics that offer several advantages over photons and protons for stereotactic radiosurgery of intracranial AVMs. These include improved dose distributions with depth in tissue, small angle of lateral scattering, and sharp distal fall-off of dose in the Bragg ionization peak. Under multi-institutionally approved clinical trials, we have used stereotactic helium-ion Bragg peak radiosurgery to treat approximately 400 patients with symptomatic, surgically inaccessible vascular malformations at the UCB-LBL 184-in synchrocyclotron and bevatron. Treatment planning for stereotactic heavy charged-particle radiosurgery for intracranial vascular disorders integrates anatomic and physical information from the stereotactic cerebral angiogram and stereotactic CT and MR imaging scans for each patient, using computerized treatment-planning calculations for optimal isodose contour distribution. The shape of an intracranial AVM is associated strongly with its treatability and potential clinical outcome. In this respect, heavy charged-particle radiosurgery has distinct advantages over other radiosurgical methods; the unique physical properties allow the shaping of individual beams to encompass the contours of large and complexly shaped AVMs, while sparing important adjacent neural structures. We have had a long-term dose-searching clinical protocol in collaboration with SUMC and UCSF and have followed up over 300 patients for more than 2 years. Initially, treatment doses ranged from 45 GyE to 35 GyE. Currently, total doses up to 25 GyE are delivered to treatment volumes ranging from 0.1 cm3 to 70 cm3. This represents a relatively homogeneous dose distribution, with the 90% isodose surface contoured to the periphery of the lesion; there is considerable protection of normal adjacent brain tissues, and most of the brain receives no radiation exposure. Dose selection depends on the volume, shape, and location of the AVM and several other factors, including the volume of normal brain that must be traversed by the plateau portion of the charged-particle beam. The first 230 patients have been evaluated clinically to the end of 1989. Using the clinical grading of Drake, about 90% of the patients had an excellent or good neurologic grade, about 5% had a poor grade, and about 5% had progression of disease and died, or died as a result of unrelated intercurrent illness. Neuroradiologic follow-up to the end of 1989 indicated the following rates of complete angiographic obliteration 3 years after treatment: 90% to 95% for AVM treatment volumes less than 4 cm3, 90% to 95% for volumes 4 to 14 cm3, and 60% to 70% for volumes greater than 14 cm3.(ABSTRACT TRUNCATED AT 400 WORDS)

Image correlation of MRI and CT in treatment planning for radiosurgery of intracranial vascular malformations

Magnetic resonance imaging (MRI) has been incorporated with stereotactic cerebral angiography and computed tomography (CT) in the treatment planning process of heavy ion radiosurgery of intracranial arteriovenous malformations (AVM's). Correlation of the images of the AVM and normal tissue on each of these neuroradiological imaging modalities is achieved by means of fiducial markers. The computerized transfer of angiographic information to the CT images regarding the size, shape, and location of the abnormal vasculature has been described in an earlier report. A separate computer program calculates a fit between individual fiducial markers on the CT and MR images that enables the transfer of contours between the two imaging modalities. The MR images aid in the determination of the 3-dimensional shape of the AVM, adding to the information derived from the two angiographic projections. Currently, MRI cannot replace cerebral angiography in delineating the entire arterial phase of the AVM. Magnetic resonance imaging is invaluable in the treatment planning of angiographically-occult AVM's, determining the location, size, and shape of the volume to be treated. Correlation of the CT and MRI images allows for the transfer of CT-calculated isodose contours to the MRI images to aid in the determination of optimal treatment plans.

Stereotactic helium ion Bragg peak radiosurgery for intracranial arteriovenous malformations. Detailed clinical and neuroradiologic outcome

89 patients with angiographically documented arteriovenous malformations were treated with helium ion Bragg peak radiation. The rate of complete angiographic obliteration 2 years after radiation was 94% in those lesions smaller than 4 cm3 (2.0 cm in diameter), 75% for those 4-25 cm3 and 39% for those larger than 25 cm3 (3.7 cm in diameter); at 3 years after radiation, the corresponding obliteration rates were 100, 95 and 70%. Major clinical complications occurred in 10 patients (8 permanent, 2 transient) between 3 and 21 months after treatment; all were in the initial stage of the protocol (higher radiation doses). 10 patients bled from residual malformation between 4 and 34 months after treatment. Seizures were improved in 63% and headaches in 68% of patients. Excellent or good clinical outcome was achieved in 94% of patients. Compared to the natural history and risks of surgery for these difficult malformations, we consider these results encouraging. Heavy-charged-particle radiation is a valuable therapy for surgically inaccessible symptomatic cerebral arteriovenous malformations. The current procedure has two disadvantages: the prolonged latent period before complete obliteration and the small risk of serious neurological complications.

Heavy-charged-particle radiosurgery for intracranial arteriovenous malformations

We have treated over 400 patients with symptomatic inoperable intracranial arteriovenous malformations (AVMs) with stereotactic heavy-charged-particle Bragg peak radiosurgery at the University of California at Berkeley in a collaborative program with Stanford University Medical Center and the University of California Medical Center, San Francisco. A long-term dose-searching clinical trial protocol has been developed and we have followed more than 250 patients for more than 2 years. Initially, radiation doses ranged from 45 to 35 GyE, and now doses of 25, 20, 15 and, under special circumstances, 10 GyE, depending on a number of factors, are being evaluated. The characteristics of charged-particle beams provide a relatively homogeneous dose distribution with the 90% isodose contour to the periphery of the lesion. When the entire arterial phase of the AVM core is included in the treatment field, the rates for complete obliteration 3 years after treatment are: 90-95% for volumes less than or equal to 4 cm3; 90-95% for volumes greater than 4 and less than or equal to 14 cm3; and 60-70% for volumes greater than 14 cm3. The total obliteration rate for all volumes up to 70 cm3 is approximately 80-85%. For complete radiation-induced obliteration there is a relationship of dose and volume primarily, and location secondarily. Results on relationships between dose, AVM obliteration, and complications and sequelae of the radiosurgical procedure are presented and discussed.

Stereotactic helium ion Bragg peak radiosurgery for angiographically occult intracranial vascular malformations

Between July 1983 and July 1989, we treated 35 patients with surgically inaccessible, symptomatic angiographically occult vascular malformations (AOVMs) using stereotactic heavy-charged-particle radiosurgery. AOVMs were located in the brainstem (19), thalamus or internal capsule (9), basal ganglia (3), deep cerebral hemisphere and motor area (3), or cerebellopontine angle (1). All patients presented with clinical and radiological evidence of previous hemorrhage, usually with multiple episodes of hemorrhage. Treatment volumes ranged from 80 to 15,200 mm3 and treatment doses from 7.7 to 34.6 Gy. Mean follow-up was 40 months, with 31 patients followed for at least 2 years. Clinical outcome was excellent in 46%, good in 34% and poor in 14%; 6% died. Twenty-seven patients in excellent and good condition prior to treatment remained stable or improved neurologically. Two patients initially in poor condition, who had previously received conventional radiotherapy, died at 9 and 14 months after treatment, respectively. Six patients experienced recurrent hemorrhage 2-60 months following treatment. Three of these patients made a complete recovery. Although a larger number of treated patients must be followed over longer periods of time, stereotactic heavy-particle radiotherapy may be a valuable treatment modality for surgically inaccessible intracranial AOVMs.

Heavy-charged-particle radiosurgery of the pituitary gland: clinical results of 840 patients

Since 1954, 840 patients have been treated at Lawrence Berkeley Laboratory with stereotactic charged-particle radiosurgery of the pituitary gland. The initial 30 patients were treated with proton beams; the subsequent 810 patients were treated with helium ion beams. In the great majority of the 475 patients treated for pituitary tumors, marked and sustained biochemical and clinical improvement was observed. Variable degrees of hypopituitarism developed in about one-third of patients treated solely with radiosurgery. In the earlier years of the program, 365 patients underwent radiosurgery to treat selected systemic diseases by inducing hypopituitarism. Focal temporal lobe necrosis and cranial nerve injury occurred in about 1% of patients who were treated with doses less than 230 Gy.

Charged-particle radiosurgery of the brain

Charged-particle beams (e.g., protons and helium, carbon and neon ions) manifest unique physical properties which offer advantages for neurosurgery and neuroscience research. The beams have Bragg ionization peaks at depth in tissues, and finite range and are readily collimated to any desired cross-sectional size and shape by metal apertures. Since 1954 nearly 6000 neurosurgical patients worldwide have been treated with stereotactic charged-particle radiosurgery of the brain for various localized and systemic malignant and nonmalignant disorders. Experimental studies with charged-particle beams have been carried out in laboratory animals to characterize anatomic and physiologic correlates of various behavioral and functional properties in the brain. Highly focused charged-particle beams have been used to induce sharply delineated laminar lesions or discrete focal ablation of deep-seated brain structures for the study of the functional anatomy of selected intracranial sites. Charged-particle beam irradiation for stereotactic radiosurgery and radiation oncology of intracranial disorders has achieved increasing importance internationally. More than 30 biomedical accelerator facilities on four continents are currently fully operational, under construction, or in an active planning stage; this last group consists primarily of dedicated biomedical hospital-based facilities. Therapeutic efficacy has been demonstrated clearly for the treatment of selected intracranial sites, e.g., pituitary adenomas and intracranial arteriovenous malformations. Heavier charged particles (e.g., carbon and neon ions) have been found to manifest a number of valuable radiobiologic properties and appear to be of potential advantage in the radiosurgical treatment of those primary or metastatic brain tumors that are radioresistant. The optimal dose and choice of charged-particle species must be determined for the treatment of the different intracranial disorders to improve the cure rate and to minimize potential adverse sequelae of the reaction of the brain to radiation injury.

Stereotactic heavy-charged-particle Bragg-peak radiation for intracranial arteriovenous malformations

BACKGROUND

Heavy-charged-particle radiation has several advantages over protons and photons for the treatment of intracranial lesions; it has an improved physical distribution of the dose deep in tissue, a small angle of lateral scattering, and a sharp distal falloff of the dose.

METHODS

We present detailed clinical and radiologic follow-up in 86 patients with symptomatic but surgically inaccessible cerebral arteriovenous malformations that were treated with stereotactic helium-ion Bragg-peak radiation. The doses ranged from 8.8 to 34.6 Gy delivered to volumes of tissue of 0.3 to 70 cm3.

RESULTS

Two years after radiation treatment, the rate of complete obliteration of the lesions, as detected angiographically, was 94 percent for lesions smaller than 4 cm3, 75 percent for those of 4 to 25 cm3, and 39 percent for those larger than 25 cm3. After three years, the rates of obliteration were 100, 95, and 70 percent, respectively. Major neurologic complications occurred in 10 patients (12 percent), of whom 8 had permanent deficits. All these complications occurred in the initial stage of the protocol, before the maximal dose of radiation was reduced to 19.2 Gy. In addition, hemorrhage occurred in 10 patients from residual malformations between 4 and 34 months after treatment. Seizures and headaches were less severe in 63 percent of the 35 and 68 percent of the 40 patients, respectively, who had them initially.

CONCLUSIONS

Given the natural history of these inaccessible lesions and the high risks of surgery, we conclude that heavy-charged-particle radiation is an effective therapy for symptomatic, surgically inaccessible intracranial arteriovenous malformations. The current procedure has two disadvantages: a prolonged latency period before complete obliteration of the vascular lesion and a small risk of serious neurologic complications.

Heavy charged-particle stereotactic radiosurgery: cerebral angiography and CT in the treatment of intracranial vascular malformations

A method is described for stereotactic localization of intracranial arteriovenous malformations (AVM) and for calculating treatment plans for heavy charged-particle Bragg peak radiosurgery. A stereotactic frame and head immobilization system is used to correlate the images of multivessel cerebral angiography and computed tomography. The AVM is imaged by angiography, and the frame provides the stereotactic coordinates for transfer of this target to CT images for the calculation of treatment plans. The CT data are used to calculate the residual ranges and compensation for the charged-particle beam required for each treatment port. Three-dimensional coordinates for the patient positioner are calculated, and stereotactic radiosurgery is performed. Verification of the accuracy of the stereotactic positioning is obtained with computer-generated overlays of the vascular malformation, stereotactic fiducial markers, and bony landmarks on orthogonal radiographs immediately prior to treatment. Using these procedures, the accuracy of the repositioning of the patient at each of a series of imaging and treatment procedures is typically within 1 mm in each of three orthogonal planes.

Stereotactic heavy-charged-particle Bragg peak radiosurgery for the treatment of intracranial arteriovenous malformations in childhood and adolescence

Forty patients aged 6 to 18 years have now been treated for inoperable intracranial arteriovenous malformations (AVMs) using stereotactic heavy-charged-particle Bragg peak radiosurgery at the Lawrence Berkeley Laboratory 184-inch Synchrocyclotron at the University of California, Berkeley. This paper describes the procedures for selection of patients, the treatment protocol, and the neurological and neuroradiological responses to stereotactic radiosurgery in this age group. The volumes of the treated AVMs ranged from 265 mm3 to 60,000 mm3. The results are favorable: thus far, 20 of 25 patients have experienced greater than or equal to 50% obliteration of their AVMs within 1 year after treatment, and 14 of 18 patients have experienced total obliteration of the AVM by 2 years after treatment. Two patients hemorrhaged from radiosurgically treated AVMs within 12 months after treatment, but none thereafter. Complications include vasogenic edema and arterial occlusion; three patients have had neurological worsening as definite or possible sequelae of treatment. The strengths and limitations of the method are discussed.

Intracranial vascular malformations: imaging of charged-particle radiosurgery. Part I. Results of therapy

Twenty-four patients with intracranial vascular malformations were examined before and after helium ion radiosurgical treatment with angiography, computed tomography (CT), and magnetic resonance (MR) imaging. Twenty patients had high-flow arteriovenous malformations (AVMs). After treatment 18 of 20 AVMs (90%) showed a significant reduction in size on angiograms or MR images. Eleven of 20 (55%) had complete resolution on angiograms or MR images, 35% had partial resolution, and 10% showed no size change. Before treatment, the size range of the AVMs was 0.86-383 cm3 (median, 21.7 cm3). Smaller AVMs (less than 8 cm3) were more likely to resolve completely than medium-sized AVMs (8-64 cm3) or larger AVMs (greater than 64 cm3). Four additional patients had slow-flow vascular malformations: One had a venous angioma; one, a probable cavernous hemangioma; and two, malformations that were not seen on angiograms. CT proved inaccurate in demonstrating the boundaries of the AVM after treatment because it showed persistent contrast enhancement even when the AVM was completely obliterated on angiograms. MR imaging and angiography were complementary in the evaluation of therapeutic results and should be the primary modalities in the examination of patients with AVMs.

Intracranial vascular malformations: imaging of charged-particle radiosurgery. Part II. Complications

Seven of 24 patients with intracranial vascular malformations who were treated with helium-ion Bragg-peak radiosurgery had complications of therapy. New symptoms and corresponding radiologic abnormalities developed 4-28 months after therapy. Five patients had similar patterns of white matter changes and mass effect on computed tomographic scans and magnetic resonance images. The abnormalities were centered in the radiation field. Gray matter changes and abnormal enhancement in the thalamus and hypothalamus outside the radiation field developed in one patient. This patient also had vasculopathic changes on angiograms. Rapidly progressive large vessel vasculopathy developed in another patient and caused occlusion of major vessels. Thus, different mechanisms may be involved in the complications of heavy-ion radiosurgery.

Potential pitfalls in the use of Glucoscan and Glucoscan II meters for self-monitoring of blood glucose

We discovered that skilled nurses only casually trained in the use of a fingertip blood glucose reflectance meter (Glucoscan, Lifescan, Mountainview, California) had a 36% incidence of unacceptable results (greater than 15% from reference). A controlled study was undertaken and showed that with Glucoscan I (GI) 4 of 27 readings were unacceptable and with Glucoscan II (GII) 3 of 27 readings were unacceptable, a statistically nonsignificant difference. Minor deviations from the manufacturer's recommended technique had a significant effect on the results with GI. In contrast, GII was much less sensitive to variations in recommended technique. GI underestimated the reference glucose concentration by 11.7%, and GII overestimated by 6.5%, a statistically significant difference. We conclude that the health professional must be aware of interdevice and intradevice variability in self-monitoring of blood glucose (SMBG). Patients need careful training in the method of SMBG. The results of any single value should be interpreted with caution.

X.25 implementation the untold story

CCITT Recommendation X.25 specifies an access protocol for the interface between Data Terminal Equipment and Data Circuit-Terminating Equipment for terminals operating in the packet mode on public data networks. The recommendation is written from the Data Circuit-Terminating Equipment's point of view. All of the internal implementation is left up to the designer.

This paper describes some of the packet level issues that were encountered during the design and implementation of a packet switch; some solutions are given. Although some of these issues are general and pertain to other protocols, some are specific to Recommendation X.25. Issues covered are: what are the network actions when buffers are depleted; how is a permanent virtual circuit set up; what is done when the remote side of a permanent virtual circuit goes out of order; and what strategy should be taken for internal coupling of the network endpoints.

Serum thyroid hormone abnormalities in psychiatric disease

Psychiatric illness is a cause of "euthyroid sick syndrome" (ESS), defined as abnormal concentrations of circulating iodothyronines in euthyroid subjects with nonthyroidal illness (NTI). We describe a prospective study of 150 consecutive psychiatric admissions studied by endocrine and psychologic techniques. Based on 150 admission blood samples, we found a 7% incidence of ESS and with serial samples (74 patients) the incidence was 27%, demonstrating that ESS can develop after hospital admission. Of the 20 patients with ESS, 11 had elevation of both serum total T4 concentrations (T4) and free thyroxine index (FTI) while their serum total T3 concentrations (T3) remained normal; 5 had elevation of FTI without elevation of T4 or T3; and 4 had low T4 and low FTI and normal TSH. In 2 of the 4 patients in the last category, the T3 was also low. The free T3 index (FT3I) was normal in all but 1 patient who had low FT3I and FTI, low T4 and T3, and normal TSH. The serum thyroid hormone abnormalities were transient in the ESS patients during the 10 day period with 2 exceptions; 1 patient had persistently elevated T4 and FTI with normal T3 and FT3I values while another patient had persistently depressed T4 and FTI without abnormality of FT3I or TSH. Multivariate statistical analysis demonstrated a difference (P less than .06) in the psychologic attributes of somatic and autonomic symptoms in ESS patients compared to controls. We conclude that ESS is as common amongst psychiatric admissions as in general hospital patients previously studied and that blood thyroid function tests should be interpreted cautiously in all hospitalized patients.

The myth of goiter in pregnancy

A common belief is that pregnancy causes goiter. Forty-nine matched pairs each consisting of a pregnant and a nonpregnant woman were examined by means of a blind, multiple-observer design. In 22 pairs the pregnant woman had the larger thyroid, whereas in 20 pairs the opposite was true. In six pairs the thyroid glands were not palpable, and in one pair the thyroid glands were of equal size. Five pregnant and three nonpregnant women had clinically significant goiters. None of the differences was statistically significant. No significance appeared when the data were controlled for race, age, body weight, or family history of thyroid disease. Therefore, goiter in pregnancy should be considered to be a pathologic condition in an iodine-replete population.

Occult adrenal insufficiency in surgical patients

Eight patients admitted to a University hospital with acute surgical problems and related adrenal insufficiency were reviewed and three are presented in detail. Surgical stress and continued sepsis played major roles in the lack of responsiveness to usual modes of therapy until the adrenal insufficiency was corrected. The patients fell into three major clinical categories of adrenal insufficiency. Chronic illness and sepsis are shown to affect steroid production and metabolism, as well as adrenal responsiveness to ACTH. Pharmacologic amounts of steroids are often needed in patients with shock, gram negative sepsis and prolonged illnesses, even if normal or elevated serum cortisols are present. Therapeutic trials of cortisol administration are shown to be confusing when not accompanied by easily performed diagnostic tests of adrenal function. It is emphasized that a pretreatment serum cortisol should be obtained whenever possible. The evaluation of adrenal function is of lifelong importance to the patient.