The radiobiology of human acoustic schwannoma xenografts after stereotactic radiosurgery evaluated in the subrenal capsule of athymic mice

1993 ◽  
Vol 78 (4) ◽  
pp. 645-653 ◽  
Author(s):  
Mark E. Linskey ◽  
A. Julio Martinez ◽  
Douglas Kondziolka ◽  
John C. Flickinger ◽  
Ann H. Maitz ◽  
...  
Keyword(s):  
Stereotactic Radiosurgery ◽  
Nude Mice ◽  
Time Course ◽  
Tumor Volume ◽  
Tumor Diameter ◽  
Vascular Effects ◽  
Content Type ◽  
Subrenal Capsule ◽  
Fine Print

✓ An experimental model with xenograft transplantation into the subrenal capsule of athymic (nude) mice was used to evaluate the early response of human acoustic schwannomas to stereotactic radiosurgery. After xenograft placement, 45 mice underwent radiosurgery with single doses of 10, 20, or 40 Gy using a 201-source 60Co gamma unit (4-mm collimator, single isocenter, 80% isodose line). The 45 radiosurgery-treated xenografts were compared with 15 untreated xenografts and 15 xenografts in mice that underwent “sham radiosurgery.” All five study groups were matched for the following pretreatment variables: patient of origin, animal weight, average xenograft diameter, and percentage of xenograft surface vascularity. Immediately prior to sacrifice of the mice all xenografts were evaluated in situ to determine the average tumor diameter, tumor volume, and percentage of surface vascularity. Mice were sacrificed 2 weeks, 1 month, or 3 months after radiosurgery. Blinded histological review was performed by an independent neuropathologist. Tumor volume was reduced 33.6% after 2 weeks (p = 0.023) and 45% after 3 months (p = 0.018) in the 40-Gy radiosurgery group. Tumor volume was reduced by 46.2% after 1 month (p = 0.0002) and 35.2% after 3 months (p = 0.032) in the 20-Gy radiosurgery group. An average volume reduction of 16.4% was observed after 3 months (p = 0.17) in the 10-Gy radiosurgery group. At 3 months after surgery, tumor surface vascularity was reduced by an average of 19.7% (p = 0.043) in the 40-Gy radiosurgery group and 5.8% (p = 0.12) in the 20-Gy radiosurgery group and was unchanged in the 10-Gy radiosurgery group and both control groups. Histological examination demonstrated a higher incidence of hemosiderin deposits (p = 0.026) and vascular mural hyalinization (p = 0.032) in radiosurgery xenografts versus control. The subrenal capsule xenograft in nude mice was an excellent model for studying the in vivo radiobiology of acoustic schwannomas after radiosurgery. Both cellular and vascular effects could be assessed serially in situ and the model was stable even 4 months after transplantation. Additional studies investigating radiobiology over periods better approximating the time course of clinical neuroimaging changes (6 to 12 months) are warranted.

Stereotactic radiosurgery for residual neurocytoma

2001 ◽  
Vol 95 (5) ◽  
pp. 879-882 ◽  
Author(s):  
Elizabeth Tyler-Kabara ◽  
Douglas Kondziolka ◽  
John C. Flickinger ◽  
L. Dade Lunsford
Keyword(s):  
Stereotactic Radiosurgery ◽  
Tumor Volume ◽  
Neurological Deficits ◽  
Response To Treatment ◽  
Imaging Studies ◽  
Content Type ◽  
Adjacent Structures ◽  
Initial Resection ◽  
Fine Print

✓ The purpose of this report was to review the results of stereotactic radiosurgery in the management of patients with residual neurocytomas after initial resection or biopsy procedures. Four patients underwent stereotactic radiosurgery for histologically proven neurocytoma. Clinical and imaging studies were performed to evaluate the response to treatment. Radiosurgery was performed to deliver doses to the tumor margin of 14, 15, 16, and 20 Gy, depending on tumor volume and proximity to critical adjacent structures. More than 3 years later, imaging studies revealed significant reductions in tumor size. No new neurological deficits were identified at 53, 50, 42, and 38 months of follow up. The authors' initial experience shows that stereotactic radiosurgery appears to be an effective treatment for neurocytoma.

Antifibrinolytic therapy of experimentally grown malignant brain tumors

1986 ◽  
Vol 64 (2) ◽  
pp. 263-268 ◽  
Author(s):  
Raymond Sawaya ◽  
Thaddeus Mandybur ◽  
Illona Ormsby ◽  
John M. Tew
Keyword(s):  
Tumor Growth ◽  
Nude Mice ◽  
Tumor Volume ◽  
Malignant Gliomas ◽  
Fibrinolytic System ◽  
Survival Times ◽  
Content Type ◽  
Antifibrinolytic Therapy ◽  
Group A ◽  
Fine Print

✓ This study was designed to evaluate the effect of an inhibitor of plasminogen activation on the growth of a human glioblastoma line grown in nude mice up to the seventh passage. The tumors produced plasminogen activators and showed histological characteristics similar to those of the original tumor. Three groups of mice were studied. Group A received 5% epsilon aminocaproic acid (EACA); Group B received 2.5% EACA; and Group C served as a control. There was no statistical difference among the three groups with regard to: 1) age at time of tumor transplantation; 2) the interval between implant and treatment; or 3) tumor volume at time of treatment. Blood measurements of EACA, performed in a limited number of animals, have shown that the drug at 5% concentration had reached toxic levels. Statistically significant differences between the three groups were noted in the following categories: 1) rate of tumor growth; 2) tumor volume at time of death, where Group A had smaller tumors than Group C; and 3) mean survival times of Groups A and B as compared to Group C. A statistically significant negative correlation was found between the rate of tumor growth and the length of survival of animals in Group C, while no correlation could be found for either Group A or B, indicating that the antifibrinolytic therapy modified this important biological variable. This study supports the hypothesis that the fibrinolytic system plays a role in the growth and development of malignant gliomas and that interference with the fibrinolytic system may retard the growth of these tumors grown in nude mice.

Stereotactic radiosurgery for pilocytic astrocytomas when multimodality therapy is necessary

2002 ◽  
Vol 97 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Constantinos G. Hadjipanayis ◽  
Douglas Kondziolka ◽  
Paul Gardner ◽  
Ajay Niranjan ◽  
Shekhar Dagam ◽  
...  
Keyword(s):  
Tumor Progression ◽  
Stereotactic Radiosurgery ◽  
Multimodal Treatment ◽  
Tumor Volume ◽  
Parietal Lobe ◽  
Optic Tract ◽  
Content Type ◽  
Pilocytic Astrocytomas ◽  
Fine Print

Object. The goal of this study was to examine the role of stereotactic radiosurgery in the treatment of patients with recurrent or unresectable pilocytic astrocytomas. Methods. During a 13-year interval, 37 patients (median age 14 years) required multimodal treatment of recurrent or unresectable pilocytic astrocytomas. Tumors involved the brainstem in 18 patients, cerebellum in three, thalamus in five, temporal lobe in four, and parietal lobe in two, as well as the hypothalamus, optic tract, corpus callosum, insular cortex, and third ventricle in one patient each. Diagnosis was confirmed with the aid of stereotactic biopsy in 12 patients, open biopsy in five, partial resection in eight, and near-total resection in 12. Multimodal treatment included fractionated radiation therapy in 10 patients, stereotactic intracavitary irradiation of tumor in four, chemotherapy in two, cyst drainage in six, ventriculoperitoneal shunt placement in three, and additional cytoreductive surgery in four. Tumor volumes varied from 0.42 to 25 cm3. The median radiosurgical dose to the tumor margin was 15 Gy (range 9.6–22.5 Gy). After radiosurgery, serial imaging demonstrated complete tumor resolution in 10 patients, reduced tumor volume in eight, stable tumor volume in seven, and delayed tumor progression in 12. No procedure-related death was encountered. Thirty-three (89%) of 37 patients are alive at a median follow-up period of 28 months after radiosurgery and 59 months after diagnosis. Eight patients participated in follow-up review for more than 60 months. Three patients died of local tumor progression. Conclusions. Stereotactic radiosurgery is a valuable adjunctive strategy in the management of recurrent or unresectable pilocytic astrocytomas. Despite the favorable histological characteristics and prognosis usually associated with this neoplasm, an adverse location, recurrence, or progression of this disease requires alternative therapeutic approaches such as radiosurgery.

Stereotactic radiosurgery providing long-term tumor control of cavernous sinus meningiomas

2002 ◽  
Vol 97 (1) ◽  
pp. 65-72 ◽  
Author(s):  
John Y. K. Lee ◽  
Ajay Niranjan ◽  
James McInerney ◽  
Douglas Kondziolka ◽  
John C. Flickinger ◽  
...  
Keyword(s):  
Stereotactic Radiosurgery ◽  
Cavernous Sinus ◽  
External Beam Radiation ◽  
Tumor Control ◽  
Tumor Diameter ◽  
Beam Radiation ◽  
Content Type ◽  
Tumor Control Rate ◽  
Fine Print

Object. To evaluate long-term outcomes of patients who have undergone stereotactic radiosurgery for cavernous sinus meningiomas, the authors retrospectively reviewed their 14-year experience with these cases. Methods. One hundred seventy-six patients harbored meningiomas centered within the cavernous sinus. Seventeen patients were lost to follow-up review, leaving 159 analyzable patients, in whom 164 procedures were performed. Seventy-six patients (48%) underwent adjuvant radiosurgery after one or more attempts at surgical resection. Eighty-three patients (52%) underwent primary radiosurgery. Two patients (1%) had previously received fractionated external-beam radiation therapy. Four patients (2%) harbored histologically verified atypical or malignant meningiomas. Conformal multiple isocenter gamma knife surgery was performed. The median dose applied to the tumor margin was 13 Gy. Neurological status improved in 46 patients (29%), remained stable in 99 (62%), and eventually worsened in 14 (9%). Adverse effects of radiation occurred after 11 procedures (6.7%). Tumor volumes decreased in 54 patients (34%), remained stable in 96 (60%), and increased in nine (6%). The actuarial tumor control rate for patients with typical meningiomas was 93.1 ± 3.3% at both 5 and 10 years. For the 83 patients who underwent radiosurgery as their sole treatment, the actuarial tumor control rate at 5 years was 96.9 ± 3%. Conclusions. Stereotactic radiosurgery provided safe and effective management of cavernous sinus meningiomas. We believe it is the preferred management strategy for tumors of suitable volume (average tumor diameter ≤ 3 cm or volume ≤ 15 cm3).

Efficacy of direct intratumoral therapy with targeted protein toxins for solid human gliomas in nude mice

1994 ◽  
Vol 80 (3) ◽  
pp. 520-526 ◽  
Author(s):  
Douglas W. Laske ◽  
Orhan Ilercil ◽  
Aytac Akbasak ◽  
Richard J. Youle ◽  
Edward H. Oldfield
Keyword(s):  
Tumor Growth ◽  
Nude Mice ◽  
Dose Response ◽  
Tumor Volume ◽  
Human Gliomas ◽  
Content Type ◽  
Protein Toxins ◽  
Fine Print ◽  
Intratumoral Injections

✓ Targeted protein toxins are a new class of reagents with the potential for great tumor selectivity and cytotoxic potency. Two such compounds were studied: 1) Tf-CRM107, a conjugate of human transferrin (Tf) and diphtheria toxin with a point mutation (CRM107); and 2) 454A12-rRA, a conjugate of a monoclonal antibody (454A12) to the human Tf receptor and recombinant ricin A chain (rRA). Both compounds are potent and specific in killing human glioblastoma cell lines in vitro. The authors investigated the activity of these reagents administered intratumorally against solid U251 MG human gliomas in vivo. Nude mice with established U251 MG flank tumors (0.5 to 1.0 cm in diameter) were randomly assigned to be treated with 100-µl intratumoral injections of Tf-CRM107 (10 µg) or 454A12-rRA (10 µg), equimolar doses of CRM107 (4.3 µg), 454A12 antibody (7.5 µg), or rRA (1.5 µg), or phosphate-buffered saline (PBS) every 2 days for a total of four doses. Tumor volume and animal weight were assessed by a blinded observer before each treatment and biweekly for 30 days after initiating therapy. With Tf-CRM107 administration, tumor regression of greater than 95% occurred by Day 14 (p < 0.01) and tumors did not recur by Day 30. Treatment with 454A12-rRA caused a 30% decrease in tumor volume by Day 14 (p < 0.01). Treatment with equimolar doses of the unconjugated targeted protein toxin components CRM107, 454A12, or rRA caused significant U251 MG tumor growth inhibition, but the effects were less potent than the antitumor effects of the conjugates. This study also characterized the dose-response effect of Tf-CRM107 on tumor growth and tumor weight on Day 30. Nude mice with established U251 MG flank tumors (0.5 to 1.0 cm in diameter) were treated with 100-µl intratumoral injections of 10, 1.0, or 0.1 µg of Tf-CRM107 or PBS every 2 days for a total of four doses. All three doses of Tf-CRM107 significantly inhibited tumor growth by Day 14 (p < 0.01) and at Day 30 (p < 0.05), with a significant dose-response relationship. This study demonstrated in vivo efficacy of the targeted toxins Tf-CRM107 and 454A12-rRA against a human glioma. With intratumoral administration, the effect of Tf-CRM107 was tumor-specific and in some animals curative. Regional therapy with these potent tumor-specific agents using direct intratumoral infusion should limit systemic toxicity and may be efficacious against brain tumors.

Gamma knife radiosurgery for craniopharyngiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 47-56 ◽  
Author(s):  
Wen-Yuh Chung ◽  
David Hung-Chi Pan ◽  
Cheng-Ying Shiau ◽  
Wan-Yuo Guo ◽  
Ling-Wei Wang
Keyword(s):  
Clinical Outcome ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Tumor Control ◽  
Content Type ◽  
Stereotactic Aspiration ◽  
Cystic Component ◽  
The Mean ◽  
Fine Print

Object. The goal of this study was to elucidate the role of gamma knife radiosurgery (GKS) and adjuvant stereotactic procedures by assessing the outcome of 31 consecutive patients harboring craniopharyngiomas treated between March 1993 and December 1999. Methods. There were 31 consecutive patients with craniopharyngiomas: 18 were men and 13 were women. The mean age was 32 years (range 3–69 years). The mean tumor volume was 9 cm3 (range 0.3–28 cm3). The prescription dose to the tumor margin varied from 9.5 to 16 Gy. The visual pathways received 8 Gy or less. Three patients underwent stereotactic aspiration to decompress the cystic component before GKS. The tumor response was classified by percentage reduction of tumor volume as calculated based on magnetic resonance imaging studies. Clinical outcome was evaluated according to improvement and dependence on replacement therapy. An initial postoperative volume increase with enlargement of a cystic component was found in three patients. They were treated by adjuvant stereotactic aspiration and/or Ommaya reservoir implantation. Tumor control was achieved in 87% of patients and 84% had fair to excellent clinical outcome in an average follow-up period of 36 months. Treatment failure due to uncontrolled tumor progression was seen in four patients at 26, 33, 49, and 55 months, respectively, after GKS. Only one patient was found to have a mildly restricted visual field; no additional endocrinological impairment or neurological deterioration could be attributed to the treatment. There was no treatment-related mortality. Conclusions. Multimodality management of patients with craniopharyngiomas seemed to provide a better quality of patient survival and greater long-term tumor control. It is suggested that GKS accompanied by adjuvant stereotactic procedures should be used as an alternative in treating recurrent or residual craniopharyngiomas if further microsurgical excision cannot promise a cure.

Safety and efficacy of stereotactic radiosurgery for tumors of the spine

2004 ◽  
pp. 413-418 ◽  
Author(s):  
Deborah L. Benzil ◽  
Mehran Saboori ◽  
Alon Y. Mogilner ◽  
Ronald Rocchio ◽  
Chitti R. Moorthy
Keyword(s):  
Spinal Cord ◽  
Single Dose ◽  
Pain Relief ◽  
Total Dose ◽  
Stereotactic Radiosurgery ◽  
Medical Center ◽  
Primary Tumors ◽  
Content Type ◽  
Increased Risk ◽  
Fine Print

Object. The extension of stereotactic radiosurgery treatment of tumors of the spine has the potential to benefit many patients. As in the early days of cranial stereotactic radiosurgery, however, dose-related efficacy and toxicity are not well understood. The authors report their initial experience with stereotactic radiosurgery of the spine with attention to dose, efficacy, and toxicity. Methods. All patients who underwent stereotactic radiosurgery of the spine were treated using the Novalis unit at Westchester Medical Center between December 2001 and January 2004 are included in a database consisting of demographics on disease, dose, outcome, and complications. A total of 31 patients (12 men, 19 women; mean age 61 years, median age 63 years) received treatment for 35 tumors. Tumor types included 26 metastases (12 lung, nine breast, five other) and nine primary tumors (four intradural, five extradural). Thoracic tumors were most common (17 metastases and four primary) followed by lumbar tumors (four metastases and four primary). Lesions were treated to the 85 to 90% isodose line with spinal cord doses being less than 50%. The dose per fraction and total dose were selected on the basis of previous treatment (particularly radiation exposure), size of lesion, and proximity to critical structures. Conclusions. Rapid and significant pain relief was achieved after stereotactic radiosurgery in 32 of 34 treated tumors. In patients treated for metastases, pain was relieved within 72 hours and remained reduced 3 months later. Pain relief was achieved with a single dose as low as 500 cGy. Spinal cord isodoses were less than 50% in all patients except those with intradural tumors (mean single dose to spinal cord 268 cGy and mean total dose to spinal cord 689 cGy). Two patients experienced transient radiculitis (both with a biological equivalent dose (BED) > 60 Gy). One patient who suffered multiple recurrences of a conus ependymoma had permanent neurological deterioration after initial improvement. Pathological evaluation of this lesion at surgery revealed radiation necrosis with some residual/recurrent tumor. No patient experienced other organ toxicity. Stereotactic radiosurgery of the spine is safe at the doses used and provides effective pain relief. In this study, BEDs greater than 60 Gy were associated with an increased risk of radiculitis.

Functional stereotactic radiosurgery involving a dedicated linear accelerator and gamma unit: a comparison study

2004 ◽  
pp. 373-380 ◽  
Author(s):  
Timothy D. Solberg ◽  
Steven J. Goetsch ◽  
Michael T. Selch ◽  
William Melega ◽  
Goran Lacan ◽  
...  
Keyword(s):  
Stereotactic Radiosurgery ◽  
Linear Accelerator ◽  
Treatment Plan ◽  
Single Shot ◽  
Submillimeter Range ◽  
Primate Model ◽  
Content Type ◽  
Stereotactic Frame ◽  
Targeting Ability ◽  
Fine Print

Object. The purpose of this work was to investigate the targeting and dosimetric characteristics of a linear accelerator (LINAC) system dedicated for stereotactic radiosurgery compared with those of a commercial gamma knife (GK) unit. Methods. A phantom was rigidly affixed within a Leksell stereotactic frame and axial computerized tomography scans were obtained using an appropriate stereotactic localization device. Treatment plans were performed, film was inserted into a recessed area, and the phantom was positioned and treated according to each treatment plan. In the case of the LINAC system, four 140° arcs, spanning ± 60° of couch rotation, were used. In the case of the GK unit, all 201 sources were left unplugged. Radiation was delivered using 3- and 8-mm LINAC collimators and 4- and 8-mm collimators of the GK unit. Targeting ability was investigated independently on the dedicated LINAC by using a primate model. Measured 50% spot widths for multisource, single-shot radiation exceeded nominal values in all cases by 38 to 70% for the GK unit and 11 to 33% for the LINAC system. Measured offsets were indicative of submillimeter targeting precision on both devices. In primate studies, the appearance of an magnetic resonance imaging—enhancing lesion coincided with the intended target. Conclusions. Radiosurgery performed using the 3-mm collimator of the dedicated LINAC exhibited characteristics that compared favorably with those of a dedicated GK unit. Overall targeting accuracy in the submillimeter range can be achieved, and dose distributions with sharp falloff can be expected for both devices.

Gamma knife surgery for vestibular schwannoma: 10-year experience of 195 cases

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 87-97 ◽  
Author(s):  
Wen-Yuh Chung ◽  
Kang-Du Liu ◽  
Cheng-Ying Shiau ◽  
Hsiu-Mei Wu ◽  
Ling-Wei Wang ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Gamma Knife ◽  
Vestibular Schwannoma ◽  
Tumor Volume ◽  
Radiation Effect ◽  
Gamma Knife Surgery ◽  
Homogeneous Distribution ◽  
Content Type ◽  
Fine Print

Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation. Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm3 (range 0.04–23.1 cm3). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months. A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor. Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.

Geometrical accuracy of the Novalis stereotactic radiosurgery system for trigeminal neuralgia

2004 ◽  
Vol 101 (Supplement3) ◽  
pp. 351-355 ◽  
Author(s):  
Javad Rahimian ◽  
Joseph C. Chen ◽  
Ajay A. Rao ◽  
Michael R. Girvigian ◽  
Michael J. Miller ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Trigeminal Neuralgia ◽  
Image Fusion ◽  
Stereotactic Radiosurgery ◽  
Ct Images ◽  
Radiochromic Film ◽  
Quality Assurance Program ◽  
Content Type ◽  
Geometrical Accuracy ◽  
Fine Print

Object. Stringent geometrical accuracy and precision are required in the stereotactic radiosurgical treatment of patients. Accurate targeting is especially important when treating a patient in a single fraction of a very high radiation dose (90 Gy) to a small target such as that used in the treatment of trigeminal neuralgia (3 to 4—mm diameter). The purpose of this study was to determine the inaccuracies in each step of the procedure including imaging, fusion, treatment planning, and finally the treatment. The authors implemented a detailed quality-assurance program. Methods. Overall geometrical accuracy of the Novalis stereotactic system was evaluated using a Radionics Geometric Phantom Chamber. The phantom has several magnetic resonance (MR) and computerized tomography (CT) imaging—friendly objects of various shapes and sizes. Axial 1-mm-thick MR and CT images of the phantom were acquired using a T1-weighted three-dimensional spoiled gradient recalled pulse sequence and the CT scanning protocols used clinically in patients. The absolute errors due to MR image distortion, CT scan resolution, and the image fusion inaccuracies were measured knowing the exact physical dimensions of the objects in the phantom. The isocentric accuracy of the Novalis gantry and the patient support system was measured using the Winston—Lutz test. Because inaccuracies are cumulative, to calculate the system's overall spatial accuracy, the root mean square (RMS) of all the errors was calculated. To validate the accuracy of the technique, a 1.5-mm-diameter spherical marker taped on top of a radiochromic film was fixed parallel to the x–z plane of the stereotactic coordinate system inside the phantom. The marker was defined as a target on the CT images, and seven noncoplanar circular arcs were used to treat the target on the film. The calculated system RMS value was then correlated with the position of the target and the highest density on the radiochromic film. The mean spatial errors due to image fusion and MR imaging were 0.41 ± 0.3 and 0.22 ± 0.1 mm, respectively. Gantry and couch isocentricities were 0.3 ± 0.1 and 0.6 ± 0.15 mm, respectively. The system overall RMS values were 0.9 and 0.6 mm with and without the couch errors included, respectively (isocenter variations due to couch rotation are microadjusted between couch positions). The positional verification of the marker was within 0.7 ± 0.1 mm of the highest optical density on the radiochromic film, correlating well with the system's overall RMS value. The overall mean system deviation was 0.32 ± 0.42 mm. Conclusions. The highest spatial errors were caused by image fusion and gantry rotation. A comprehensive quality-assurance program was developed for the authors' stereotactic radiosurgery program that includes medical imaging, linear accelerator mechanical isocentricity, and treatment delivery. For a successful treatment of trigeminal neuralgia with a 4-mm cone, the overall RMS value of equal to or less than 1 mm must be guaranteed.

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