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PubMed1990

Estimation of complications for linear accelerator radiosurgery with the integrated logistic formula.

Radiosurgery techniques permit high doses of single fraction irradiation to be administered to small volumes of tumor with relative sparing of surrounding brain tissue. The tolerance of surrounding normal brain tissue to dose distributions from linear accelerator radiosurgery with different collimator sizes is an important factor that must be estimated by anyone using these treatment techniques. The exponential and linear quadratic versions of the integrated logistic formula were used to estimate the probability of brain necrosis at different doses for radiosurgical dose distributions administered by a 6 MV linear accelerator with a 5 arc technique for collimator sizes from 12.5 to 30 mm in diameter. Dose-volume isoeffect curves for a 3% risk of brain necrosis from linear accelerator radiosurgery were then calculated. These curves approximate those calculated for gamma knife radiosurgery and a published 1% dose-volume isoeffect line predicted for proton beam irradiation. Similar dose-volume isoeffect curves were calculated for single fraction radiosurgery boosts administered after 30 Gy of whole brain irradiation in 12 fractions. The integrated logistic formula appears to be a useful tool for estimating tolerance and providing guidelines for prescribing radiation doses for linear accelerator radiosurgery.

Brain Diseases↗
PubMed1991

Radiosurgery for solitary brain metastases using the cobalt-60 gamma unit: methods and results in 24 patients.

To define the role of stereotactic radiosurgery in the treatment of metastatic brain tumors we treated 24 consecutive patients (20 men, 4 women) with the 201-source 60Co gamma unit between May 1988 and March 1990. The primary tumors included malignant melanoma (n = 10), non-small cell lung carcinoma (n = 6), renal cell carcinoma (n = 3), colorectal carcinoma (n = 1), oropharyngeal carcinoma (n = 1), and adenocarcinoma of unknown origin (n = 3). All tumors were less than or equal to 3.0 cm in greatest diameter. Twenty patients received a planned combination of 30-40 Gy whole brain fractionated irradiation and a radiosurgical "boost" of 16-20 Gy to the tumor margins; one patient refused conventional fractionated irradiation. Three patients with recurrent, persistent, or new non-small cell lung carcinomas had radiosurgical treatment 12-20 months after receiving 30-42.5 Gy whole-brain external beam irradiation. Stereotactic computed tomographic imaging was used for target coordinate determination and imaging-integrated dose planning. All tumors were enclosed by the 50-90% isodose shell using one (n = 22), two (n = 1), or three (n = 1) irradiation isocenters. During this 23-month period (median follow-up of 7 months) no patient died from progression of a radiosurgically-treated brain metastasis. Ten patients died of systemic disease (n = 8) or remote central nervous system metastasis (n = 2) between 1 week and 10 months after radiosurgery. One patient had tumor progression and underwent craniotomy and tumor excision 5 months after radiosurgery. To date, median survival after radiosurgery has been 10 months; 1-year survival was 33.3%. Stereotactic radiosurgery eliminated the surgical and anesthetic risks associated with craniotomy and resection of solitary brain metastases. Radiosurgery also effectively controlled the growth of tumors considered "resistant" to conventional irradiation.

Adult↗
PubMed2002

Stereotactic radiosurgery for patients with ACTH-producing pituitary adenomas after prior adrenalectomy.

PURPOSE: To review the results of stereotactic radiosurgery for patients with adrenocorticotropic hormone (ACTH)-producing pituitary adenomas after bilateral adrenalectomy. METHODS AND MATERIALS: Eleven patients with ACTH-producing pituitary adenomas after bilateral adrenalectomy underwent radiosurgery between 1990 and 1999. Nine patients had documented tumor growth, hyperpigmentation, and elevated ACTH levels (median 920 ng/mL) at the time of radiosurgery. Five of these patients had tumor enlargement despite prior fractionated radiotherapy (median dose 50 Gy). Two patients were treated prophylactically within 1 month of their adrenalectomies to prevent future tumor growth. The median follow-up was 37 months (range 22-74). RESULTS: Tumor growth control was achieved in 9 patients (82%); 2 patients had had continued tumor growth after radiosurgery. The ACTH levels decreased a median of 66% (range -99% to +27%); 4 patients had normal ACTH levels. Three patients had radiation-related complications, including diplopia (n = 2), ipsilateral blindness (n = 1), testosterone/growth hormone deficiency (n = 1), and asymptomatic temporal lobe radiation necrosis (n = 1): all had received prior radiotherapy. One patient who had undergone three prior resections and radiotherapy died 59 months after radiosurgery despite two additional attempts at tumor resection. CONCLUSION: Although our experience is limited, it appears that radiosurgery provides tumor control for most patients with ACTH-producing pituitary adenomas who have undergone bilateral adrenalectomy.

Adenoma↗
PubMed1995

Linear Accelerator Configurations for Radiosurgery.

The dramatic proliferation of radiosurgery in the 1980s and 1990s has resulted in the development of a plethora of hardware systems and an exponential increase in clinical use. This article summarizes the initial, now mostly historical, developments and emphasizes that most linear accelerator radiosurgery systems are based on three early prototypical systems from Buenos Aires, Heidelberg, and Montréal. These systems have more recently been tailored to permit fractionated radiosurgery, blurring the distinction between radiosurgery and radiotherapy. The commonly used fractionated systems are described. Clinical outcome data for arteriovenous are described. Clinical outcome data for arteriovenous malformations, acoustic neuroma, and meningioma, are mostly preliminary but substantial data are available for the radiosurgical management of metastases. With the recent emphasis on cost containment, cost-effectiveness issues have become significant and at least for metastases some preliminary data suggest a potential "cost benefit" with radiosurgery. The recent publication of data from a prospective randomized trial has established the superiority of boost therapy for malignant glioma and in this article, we present preliminary evidence supporting the use of radiosurgery. Finally, some of the new and exciting developments such as the robot-mounted linear accelerator, the use of shaped fields, and tomotherapy are described.

Journal Article↗
PubMed1995

Neurotoxicity of Radiosurgery.

Radiosurgery is a technique to deliver (in most cases) a single fraction of ionizing radiation, usually in the range of 10 to 25 Gy, to a precisely localized intracranial volume of pathological tissue. The radiobiological principles that govern the practice of single-fraction radiosurgery differ from those of conventional fractionated external beam radiation therapy. Rather, the results are primarily a consequence of either vascular effects or antiproliferative effects. The neurotoxicity of radiosurgery can be described according to its time course (immediate, acute, or chronic) and severity (mild, moderate, severe, life-threatening, or fatal( based on existing definitions established by the Radiation Therapy Oncology Group. Current indications for radiosurgery include arteriovenous malformations, acoustic neuromas, brain metastases, high-grade and other gliomas, meningiomas, and pituitary adenomas. The efficacy of radiosurgery and the time course and severity of radiosurgical neurotoxicity are dependent both on the nature of the lesion being treated and the normal tissue milieu which the lesion resides. This article describes the spectrum of neurotoxicity reported in the medical literature pertaining to the current variety of space-occupying lesions, benign tumors, and malignant neoplasms for which radiosurgery currently is being used.

Journal Article↗
PubMed1996

Neuro-otological findings after radiosurgery for acoustic neurinomas.

OBJECTIVE: To evaluate the neuro-otological complications in patients after radiosurgery for acoustic neurinomas. DESIGN: Inception cohort, retrospective study. SETTING: University hospital. PATIENTS: A consecutive sample of 46 patients with acoustic neurinomas who underwent unilateral gamma knife radiosurgery at the University of Tokyo, Japan, between June 1990 and June 1994 were followed up by otolaryngologists for more than 3 months. INTERVENTION: Gamma knife stereotactic radiosurgery. MAIN OUTCOME MEASURES: Neuro-otological examinations including pure tone audiometry, auditory brain stem response, and caloric test. RESULTS: Tumor growth occurred in 2 patients (4.3%). Seven (18%) of the 38 patients with preserved hearing of any extent became deaf within 1 year. In cases of gradual hearing loss, the average deterioration rate was approximately 8 dB per year. Abnormalities of auditory brain stem response preceded deafness in 2 patients. Caloric response, preserved before treatment in 13 patients, disappeared 4 to 13 months after treatment (median, 8 months) in 9 (69%) of them, whereas their hearing was preserved. Delayed facial palsy and persistent trigeminal neuropathy occurred in 10 (22%) and 7 (15%) of the 46 patients, respectively. Severe facial palsy tended to persist. CONCLUSIONS: The rates of neuro-otological complications of radiosurgery are almost comparable with those previously reported from other institutions. The deafness within 1 year after treatment might be attributed to a lesion in the cochlear nerve. Hearing loss did not parallel vestibular function loss. The persistent severe facial palsy contrasts with previously reported findings. Considering the serious facial nerve complications that occurred in some of our patients, further study to disclose the risk factors for neurological dysfunction would be needed for radiosurgery to become a true, safe alternative to microsurgery.

Adolescent↗
PubMed1997

Stereotactic radiosurgery for patients with nonsmall cell lung carcinoma metastatic to the brain.

BACKGROUND: A retrospective study of patients undergoing stereotactic radiosurgery for one to four brain metastases from nonsmall lung cell carcinoma (NSCLC) was performed to document outcomes and risks. METHODS: Seventy-seven patients underwent radiosurgery during a 7-year interval; 71 also underwent whole brain radiation therapy. Univariate and multivariate analyses were used to determine significant prognostic factors affecting survival. RESULTS: The overall median survival was 10 months after radiosurgery, and 15 months from the diagnosis of brain metastases. Five factors significantly affected survival: extent of systemic disease, presence of a neurologic deficit, size of the intracranial tumor, initial imaging appearance of intratumoral necrosis, and initial resection of the primary tumor of the chest. Median survival time was 26 months in a subgroup of patients with no extracranial metastases, no neurologic deficits, and a small tumor without necrosis. The authors evaluated 91 tumors with imaging. Local tumor control was achieved in 77 lesions (85%) and tumoral radiation necrosis developed in 4 lesions (4.4%). Nineteen new metastatic tumors developed during the observation interval. CONCLUSIONS: Stereotactic radiosurgery for NSCLC brain metastases is effective and is associated with few complications. The early detection of brain metastases and treatment with radiosurgery combined with radiation therapy provide the opportunity for extended high quality survival.

Aged↗
PubMed1995

Single-stage stereotactic diagnosis and radiosurgery: feasibility and cost implications.

We compared the efficacy and the hospital charges of either single-stage or two-stage stereotactic diagnosis and radiosurgery procedures. Twelve patients underwent either one-stage or two-stage diagnosis and management of their brain tumors. Both techniques utilize high-resolution intraoperative stereotactic image-guided technology and rapid touch preparation (imprint) cytopathological techniques to confirm the presence of neoplasm. Following this pathologic diagnosis, six patients immediately underwent stereotactic radiosurgery employing the same frame application and dose planning based on preoperative and intraoperative images. Six patients underwent two-stage procedures, i.e., discharge from the hospital after histopathological diagnosis followed by readmission, reapplication of the stereotactic head frame, and repeat neuroradiological imaging prior to radiosurgery. Requirements for success of the single-stage procedure include intraoperative stereotactic high-resolution imaging, a hospital-wide ethernet system for transferring neurodiagnostic images, and expertise in rapid touch-preparation histopathological technique for accurate diagnosis. Intraoperative computed tomography imaging after biopsy confirmed the target accuracy and lack of movement of the target after brain biopsy. The advantages of the single-stage approach include reduced length of overall hospital stay, simultaneous histopathological diagnosis and therapy in a single hospital admission, and reduced total hospital charges. For patients highly suspected of having brain tumors and for whom stereotactic radiosurgery will be utilized in the treatment, single-stage stereotactic diagnosis immediately followed by radiosurgery is an accurate, effective, and potentially less costly management strategy than a two-stage approach.

Adult↗
PubMed2005

Single-fraction radiosurgery for the treatment of spinal breast metastases.

BACKGROUND: The spine is the most common site of bony metastases in patients with osseous breast carcinoma metastases. Spine metastases are the source of significant pain and occasionally neurologic deficit in this patient population. Conventional external beam radiotherapy lacks the precision to allow delivery of large single-fraction doses of radiation and simultaneously limit the dose to radiosensitive structures such as the spinal cord. This study evaluated the clinical efficacy of the treatment of spinal breast carcinoma metastases with a single-fraction radiosurgical technique. METHODS: In this prospective cohort evaluation, 68 breast carcinoma metastases to the spine in 50 patients were treated with a single-fraction radiosurgery technique with a follow-up period of 6-48 months, median 16 months. The most common indication for radiosurgery treatment was pain in 57 lesions, as a primary treatment modality in 8 patients, and for radiographic tumor progression, as a postsurgical boost, and for a progressive neurologic deficit in 1 patient each. RESULTS: Tumor volume ranged from 0.8-197 cm3 (mean, 27.7 cm3). Maximum tumor dose was maintained at 15-22.5 Gy (mean, 19 Gy). No radiation-induced toxicity occurred during the follow-up period (6-48 mo). Long-term axial and radicular pain improvement occurred in 55 of 57 (96%) patients who were treated primarily for pain. Long-term radiographic tumor control was seen in all patients who underwent radiosurgery as their primary treatment modality, for radiographic tumor progression, or as a postsurgical treatment. CONCLUSIONS: Spinal radiosurgery was found to be feasible, safe, and clinically effective for the treatment of spinal metastases from breast carcinoma. The results indicate the potential of radiosurgery in the treatment of patients with spinal breast metastases, especially those with solitary sites of spine involvement, to improve long-term palliation.

Adult↗
PubMed2002

Radiosurgery for paraganglioma of the temporal bone.

PURPOSE: To report the outcome of patients with paraganglioma of the temporal bone treated with stereotactic radiosurgery at the University of Florida. METHODS AND MATERIALS: Between January 1997 and June 1999, five patients with paraganglioma of the temporal bone were treated with Linac-based stereotactic radiosurgery at the University of Florida. The ages of the three female and two male patients were between 40 and 88 years (median, 49 years). Four patients were treated at initial presentation, and one had recurrent disease. Treatment volumes ranged from 4.9 cm3 to 18.4 cm3, with a mean of 10.84 cm3. The dose applied to the margin of the tumor varied from 12.5 to 15 Gy (median, 15 Gy). The treatment dose was specified to the 80% isodose shell in two cases and to the 70% isodose shell in three cases. The median follow-up time was 27 months, ranging from 14 to 50 months. RESULTS: One of four previously untreated patients had a relapse at the primary tumor site. Treatment failure occurred at the field margin 6 months after radiosurgery; the patient was subsequently treated with fractionated stereotactic radiotherapy and at the time of analysis had no evidence of disease, 21 months after initiation of salvage therapy. The patient treated at the time of recurrence after conventional radiotherapy had a local recurrence 40 months after radiosurgery. At the time of this recurrence, the patient had biopsy-proven metastatic disease in two cervical lymph nodes, and no salvage therapy was performed. All patients were alive at the time of the analysis, one with disease present. Presenting symptoms improved in two patients and stabilized in one. The two patients who had local recurrence develop had worsening of their symptoms. One patient had a cranial nerve V palsy develop 6 months after treatment, which resolved after a few months. CONCLUSIONS: In this series, the results with stereotactic radiosurgery are discouraging compared with our results with conventional fractionated radiotherapy in patients with paraganglioma of the temporal bone.

Adult↗
PubMed2002

Stereotactic radiosurgery for locally recurrent nasopharyngeal carcinoma.

BACKGROUND: Stereotactic radiosurgery has been used to treat intracranial tumors. Recently, it has also been used for the treatment of head and neck tumors involving the base of skull, including recurrent NPC. METHODS: From October 1994 to April 1999, 36 patients with recurrent NPC, were retreated by stereotactic radiosurgery. These patients received radiosurgery as a boost treatment after reirradiation for recurrence. The external RT dose ranged from 20 to 60 Gy. The tumor volume ranged from 3.58 to 24.6 cc. The target surface dose ranged from 8 to 20 Gy. The median follow-up was 22.1 months. RESULTS: The 3-year local control rate was 56%. The 5-year overall survival was 49%. Persistence after radiosurgery had a worse survival than those who had secondary recurrence. Age and gender were marginally significant. No patient had new severe complications after retreatment. Four patients (11%) had nasopharyngeal necrosis after radiosurgery, none had nasal bleeding or headache, but a foul odor was present in one patient. CONCLUSIONS: Conformal radiotherapy and stereotactic radiotherapy provide good local control and survival without severe complications for patients with recurrent NPC.

Adult↗
PubMed2004

Modern multimodal neuroimaging for radiosurgery: the example of PET scan integration.

Radiosurgery relies critically on medical imaging modalities. Leksell Gamma Knife (LGK) radiosurgery presents the highest requirements in terms of imaging accuracy as the treatment is applied in a single high-dose session with no other spatial control than medical imaging. The advent of new imaging modalities opens challenges for LGK planning strategies. The integration of stereotactic PET in LGK represents an example of such application of modern multimodality imaging in radiosurgery. Our experience consists of 80 patients treated with the combination of MR/CT and PET guidance. In order to analyze the specific contribution of PET findings, we developed a classification reflecting the strategy used to define the target volume. When combining PET and MR information, 102 target volumes were defined, because some patients presented with multiple lesions or multifocal tumor areas. Abnormal PET uptake was found in 86% of the lesions, and this information altered significantly the MR-defined tumor in 73%. In conclusion, integration of PET in radiosurgery provides additional information opening new perspectives for the treatment of brain tumors. The use of a standardized classification allows to assess the relative role of PET. A similar approach could be useful and may serve as a template for the evaluation of the integration of other new imaging modalities in radiosurgery.

Adenoma↗
PubMed2004

Results of outpatient gamma knife radiosurgery for primary therapy of acoustic neuromas.

Stereotactic radiosurgery (SRS) has been recognized as a non-invasive alternative to surgery for the treatment of acoustic neuromas. Purpose of the current study was to define the impact of outpatient gamma knife radiosurgery (GKS) for patients with unilateral sporadic acoustic neuromas treated within ten years. Follow-up images were analyzed using tumor volume measurements. 219 patients with sporadic acoustic neuromas were treated by GKS as primary therapy. Patients with NF-2 tumors were excluded. Patients were eligible for GKS up to a size limit of 12.5 cm3. The median follow up time was 6 years after radiosurgery. The local tumor control rate was high (97%). Cranial nerve morbidities were comparably low. 10% of the patients developed hearing loss after radiosurgery and one patient experienced a transient facial neuropathy (0.5%). Transient trigeminal neuropathy developed in 12 patients (5%) and was found to be dependent on the tumor size before treatment. Outpatient gamma knife radiosurgery is a safe and effective treatment method for selected patients with sporadic vestibular schwannomas.

Ambulatory Surgical Procedures↗
PubMed2004

Gamma knife radiosurgery for patients with multiple cerebral metastases.

Although efficacy of gamma knife radiosurgery has been demonstrated in numerous studies, the policies in patients with multiple metastases seem to be unequivocal. The maintained quality of life, the possibility of short hospitalization and the continuation of a systemic chemotherapy are increasingly important arguments in favor of a minimally invasive radiosurgical approach. These factors are particularly emphasized in patients with a dismal prognosis. The current retrospective analysis was undertaken to summarize the clinical results of radiosurgery in patients with multiple cerebral metastases of various primary cancer. Fractionated whole brain radiotherapy (WBRT) was omitted as prophylactic treatment and applied only in cases with general tumor spread. Clinical data of all consecutive patients (n = 215) who received gamma knife radiosurgery for cerebral metastases between January 2001 and January 2003 at the gamma knife Centers of the Karolinska Hospital and H.M. Queen Sophia Hospital (Sophiahemmet) Stockholm were analyzed retrospectively. 172 patients were treated for multiple metastases (198 treatments). The median prescription dose was 22 Gy (range 14-34 Gy). The Kaplan Meier plot shows a median survival (MST) of 7.8 months for patients with multiple cerebral metastases and 13.7 months for patients with single metastases. There was no relation between survival and number of metastases in patients with multiple metastases. Within this group 11.6% (20/172 patients) developed adverse radiation reactions. Tumor recurrences were documented by FDG-PET in 7 patients (out of 172 patients: 4.1%) after a median latency of 10 months after radiosurgery. In summary, gamma knife radiosurgery provides a highly effective and minimally invasive method to treat patients with multiple cerebral metastases even without prophylactic WBRT. Local control and patient survival in the present series of patients is in accordance with other retrospective series of patients with single and multiple metastases.

Adult↗
PubMed2003

Interstitial stereotactic radiosurgery.

Stereotactic radiosurgery by means of interstitial application of either radionuclides or radiation devices has been used extensively in primary and secondary brain tumors. A few centers have gained sufficient expertise and clinical data to scientifically evaluate this treatment modality. Interstitial stereotactic radiosurgery is limited to circumscribed lesions with a diameter of 3.5 cm or less. The radiobiology of interstitial radiosurgery is quite well elaborated as to doses, dose rates and effects on vascular physiology. Efficacy in low grade gliomas is well documented by several European centers using 125-J sources. Different modes of implantation have been used and evaluated including single fraction treatment using a miniature linear accelerator (Photoelectron). In malignant gliomas interstitial radiosurgery has been investigated in a prospective, randomised, controlled trial and not shown to be effective. Steretactic interstitial radiosurgery is a powerful treatment option in circumscribed CNS tumors like some low grade gliomas and metastasis but does play no major role in the treatment of malignant glioma.

Animals↗
PubMed1994

Stereotactic radiosurgery for pituitary adenomas: imaging, visual and endocrine results.

To determine the endocrine, ophthalmologic, and tumor growth control responses after stereotactic radiosurgery using the gamma unit, we reviewed our experience in 35 patients with pituitary adenomas. Twenty-four females and 11 males (mean age 47 years, range 9-81 years) had radiosurgery with average follow-up of 26 months (range 6-60 months). Most patients were refractory to surgical removal. Fifteen patients had Cushing's disease. Prior transsphenoidal resection was performed in 14 patients (6 had two prior operations), fractionated radiotherapy in 3, and adrenalectomy in 2. In 11 evaluable patients, the hormone response was normalized in 8, decreased in 2 and increased in 1. Five patients remained on cortisol suppression. Of 12 patients with imaging follow-up, 4 had decreased tumor size, 6 had no change, and 2 had an increase; these 2 patients underwent subsequent surgery. Ten patients had acromegaly, and 6 had undergone prior surgery. Of 8 evaluable patients, growth hormone secretion has normalized in 3, decreased in 3, and increased in 2. Six tumors decreased in size, and 2 were unchanged. One patient had repeat resection 21 months after radiosurgery and one patient underwent repeat radiosurgery. Ten patients had non-secreting adenomas; all 10 had prior operations (1-4 operations, 6 underwent frontal craniotomy) and 5 had undergone fractionated radiotherapy. Eight patients had panhypopituitarism prior to radiosurgery. Four tumors decreased in size and 6 were without change.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed2004

Methodology of continuous extracranial radiosurgery for lung cancer using EXOMIO 3-D CT simulation.

BACKGROUND: It is well known that precision can be achieved using radiosurgery for brain tumors. This method can be extended to treat localized lung tumors and lung metastases. MATERIAL AND METHODS: The conventional procedure of extracranial radiosurgery is contained in the following steps: adaptation of the vacuum mattress, planning CT, three-dimensional (3-D) treatment planning, CT repositioning, and irradiation. In the new procedure of continuous extracranial radiosurgery, a short treatment planning is often used for simple target shapes (spherical, rotation-symmetrical), and the irradiation follows directly after the planning procedure. During continuous extracranial radiosurgery, the patient has to lie still in the body frame from the planning CT to irradiation. Fast treatment planning is performed by using multileafs and EXOMIO (Medintec, Bochum, Germany), a software for CT simulation. The high quality of the digitally reconstructed radiographs (DRRs) of each field enables a high precision in dose application by the comparison with the verification radiograph and the DRR (Elekta iView, Hamburg, Germany). RESULTS: In five lung cancer patients the average time for the complete procedure from planning CT to irradiation was 107 min (range: 91-124 min). The mean positioning accuracy of the patient in the vacuum bed (total shift) was 3.3 mm (range: 2.9-4.7 mm). CONCLUSION: Continuous extracranial radiosurgery can be performed for small peripheral lung tumors or metastases and is optimizing the conventional procedure. It is of special interest to clinics with restricted CT capacity.

Equipment Design↗
PubMed2005

Radiation exposure of extracranial organs at risk during stereotactic linac radiosurgery.

BACKGROUND AND PURPOSE: Stereotactic radiosurgery of intracranial tumors and vascular malformations can be performed by either a linear accelerator (Linac) or gamma knife. The aim of this first study on patients was to determine the radiation exposure of organs at risk and assess the risk for late effects including secondary tumors and/or hereditary disorders after stereotactic Linac radiosurgery. MATERIAL AND METHODS: Thermoluminescent dosimetry (TLD) measurements were done on 21 consecutively admitted patients with various intracranial lesions scheduled for Linac radiosurgery. The TLD chips were placed on the eyelid, thyroid, breast and the regions of the ovary or testes. RESULTS: The mean doses in organs at risk were 276 +/- 200 mGy (eye lens), 155 +/- 83 mGy (thyroid), 47 +/- 22 mGy (breast), 20 +/- 12 mGy (ovary), and 9 +/- 3 mGy (testes). The doses decreased significantly with a larger distance from the isocenter. CONCLUSION: The absorbed doses to the extracranial organs at risk in patients undergoing Linac radiosurgery were very low, ranging from 0.025% (testes) to 0.76% (eye lens) of the mean maximum target dose (36 Gy). Nevertheless, while the majority of radiosurgery patients have benign tumors or arteriovenous malformations and their life expectancy is long, all doses should be kept as low as reasonably achievable. This could be accomplished by the use of modern irradiation techniques including conformal beams with micro-multileaf collimator and avoiding beams directed to the trunk.

Adult↗