Do Recent Advances in MR Technologies Contribute to Better Gamma Knife Radiosurgery Treatment Results for Brain Metastases?

2007 ◽  
Vol 20 (5) ◽  
pp. 481-490 ◽  
Author(s):  
M. Hayashi ◽  
M. Yamamoto ◽  
C. Nishimura ◽  
H Satoh
Keyword(s):  
Mr Imaging ◽  
Brain Metastases ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Lesion Size ◽  
Neurological Deficits ◽  
Consecutive Series ◽  
Slice Thickness ◽  
Treatment Results ◽  
Primary Tumors

The detection of intracerebral lesions has improved greatly with advancements in MR imaging, especially the greater sensitivity of the 1.5 Tesla unit versus the older 1.0 Tesla unit. We aimed to determine whether improvements in MR imaging have actually improved diagnostic capabilities and treatment outcomes in gamma knife radiosurgery (GKRS) for brain metastases (METs). Ours was a retrospective study of a consecutive series of 1179 patients (441 females, 738 males, mean age: 63 years, range: 19–92 years) with brain METs who underwent GKRS from 1998 to 2004. Our treatment policy was to irradiate all lesions visible on MR images during a single GKRS session. Mean and median tumor numbers were seven and three (range; 1–74). The 1179 patients were divided into two groups: a 1.0 T-group of 660 patients examined using a 1.0 Tesla MR unit before August, 2002, and a 1.5 T-group of 519 examined using a 1.5 Tesla MR unit after September 2002. In the 1.5 T-group, lesion volumes as small as 0.004 cc were detected with a 5 mm slice thickness. The corresponding lesion size was 0.013 cc in the 1.0 T-group. One or more lesions invisible on a 5 mm slice study were additionally detected on a 2 mm slice study in 47.8% of patients in the 1.0 T-group and 25.2% in the 1.5 T-group (p<.0001). The median survival time (MST) in the 1.5 T-group was significantly longer than that in the 1.0 T-group (8.4 vs. 6.3 months, p=.0004). Due to biases in patient numbers between the two groups, we analyzed subgroups with KPS of 80% or better, no neurological deficits, stable primary tumors, lung cancer, tumor numbers of four or less and tumor volumes of 10.0 cc or smaller. In every subgroup analysis, the MSTs of the 1.5-Tesla group were significantly longer than those of the 1.0-Tesla group. The prognosis of a cancer patient is undoubtedly influenced by multiple factors. Nevertheless, we conclude that application of the 1.5 Tesla MR unit has had a favorable impact on diagnosis and GKRS treatment results in patients with brain METs.

Gamma Knife surgery for metastatic brain tumors

2008 ◽  
Vol 109 (Supplement) ◽  
pp. 118-121 ◽  
Author(s):  
Toru Serizawa ◽  
Masaaki Yamamoto ◽  
Osamu Nagano ◽  
Yoshinori Higuchi ◽  
Shinji Matsuda ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Gamma Knife ◽  
Patient Selection ◽  
Selection Criterion ◽  
Gamma Knife Surgery ◽  
Treatment Result ◽  
Karnofsky Performance Scale ◽  
Consecutive Series ◽  
Primary Tumors ◽  
Patient Selection Criterion

Object The authors compared results of Gamma Knife surgery (GKS) for brain metastases obtained at 2 institutions in Japan. Methods They analyzed a consecutive series of 2390 patients with brain metastases who underwent GKS from 1998 through 2005 in 2 institutes (1181 patients in Chiba; 1209 in Mito). In the 2 facilities, 1 neurosurgeon each was responsible for diagnosis, patient selection, GKS procedures, and follow-up (T.S. in Chiba, M.Y. in Mito). Even if tumor numbers exceeded 4, all visible lesions were irradiated with a total skull integral dose (TSID) of ≤ 10–12 J. No prophylactic whole-brain radiotherapy (WBRT) was applied. If new distant lesions were detected, salvage GKS was appropriately performed. Results The distributions of patient and treatment factors did not differ between institutes. The most common primary tumors were lung cancer (1572 patients), followed by gastrointestinal tract (316), breast (211), kidney (113), and other cancers (159). The median survival periods were 7.7 months in Chiba and 7.0 months in Mito (p = 0.0635). The significant poor prognostic factors for overall survival were active extracranial disease status, male sex, and low initial Karnofsky Performance Scale score on multivariate analysis (all p < 0.0001). The neurological survival rates at 1 year were 86.6% in Chiba and 84.2% in Mito (p = 0.3310). Conclusions This 2-institute study demonstrated no significant institutional differences in any of the treatment result items. Gamma Knife surgery for brain metastases without prophylactic WBRT prevents neurological death and allows a patient to maintain good brain condition. However, there is 1 important patient selection criterion: regardless of how many tumors there are, all lesions can be irradiated with a TSID of ≤12 J.

scholarly journals Comparison of treatment results between 3- and 2-stage Gamma Knife radiosurgery for large brain metastases: a retrospective multi-institutional study

2019 ◽  
Vol 131 (1) ◽  
pp. 227-237 ◽  
Author(s):  
Toru Serizawa ◽  
Yoshinori Higuchi ◽  
Masaaki Yamamoto ◽  
Shigeo Matsunaga ◽  
Osamu Nagano ◽  
...  
Keyword(s):  
Overall Survival ◽  
Adverse Events ◽  
Brain Metastases ◽  
Tumor Progression ◽  
Gamma Knife ◽  
Tumor Volume ◽  
Gamma Knife Radiosurgery ◽  
Tumor Control ◽  
Treatment Results ◽  
Matched Study

OBJECTIVEIn order to obtain better local tumor control for large (i.e., > 3 cm in diameter or > 10 cm3 in volume) brain metastases (BMs), 3-stage and 2-stage Gamma Knife surgery (GKS) procedures, rather than a palliative dose of stereotactic radiosurgery, have been proposed. Here, authors conducted a retrospective multi-institutional study to compare treatment results between 3-stage and 2-stage GKS for large BMs.METHODSThis retrospective multi-institutional study involved 335 patients from 19 Gamma Knife facilities in Japan. Major inclusion criteria were 1) newly diagnosed BMs, 2) largest tumor volume of 10.0–33.5 cm3, 3) cumulative intracranial tumor volume ≤ 50 cm3, 4) no leptomeningeal dissemination, 5) no more than 10 tumors, and 6) Karnofsky Performance Status 70% or better. Prescription doses were restricted to between 9.0 and 11.0 Gy in 3-stage GKS and between 11.8 and 14.2 Gy in 2-stage GKS. The total treatment interval had to be within 6 weeks, with at least 12 days between procedures. There were 114 cases in the 3-stage group and 221 in the 2-stage group. Because of the disproportion in patient numbers and the pre-GKS clinical factors between these two GKS groups, a case-matched study was performed using the propensity score matching method. Ultimately, 212 patients (106 from each group) were selected for the case-matched study. Overall survival, tumor progression, neurological death, and radiation-related adverse events were analyzed.RESULTSIn the case-matched cohort, post-GKS median survival time tended to be longer in the 3-stage group (15.9 months) than in the 2-stage group (11.7 months), but the difference was not statistically significant (p = 0.65). The cumulative incidences of tumor progression (21.6% vs 16.7% at 1 year, p = 0.31), neurological death (5.1% vs 6.0% at 1 year, p = 0.58), or serious radiation-related adverse events (3.0% vs 4.0% at 1 year, p = 0.49) did not differ significantly.CONCLUSIONSThis retrospective multi-institutional study showed no differences between 3-stage and 2-stage GKS in terms of overall survival, tumor progression, neurological death, and radiation-related adverse events. Both 3-stage and 2-stage GKS performed according to the aforementioned protocols are good treatment options in selected patients with large BMs.

scholarly journals SURG-03. SPATIAL COORDINATES FROM GAMMA KNIFE RADIOSURGERY REVEAL PRIMARY CANCERS HAVE REGIONAL CNS TOPOGRAPHICAL DISTRIBUTION FOR BRAIN METASTASES

2019 ◽  
Vol 1 (Supplement_1) ◽  
pp. i31-i31
Author(s):  
Josh Neman ◽  
Meredith Franklin ◽  
Zachary Madaj ◽  
Tim Triche ◽  
Gal Sadlik ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Brain Metastases ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Additive Models ◽  
Cerebellar Hemisphere ◽  
Distribution Analysis ◽  
Primary Tumors ◽  
Topographical Distribution ◽  
The Brain

Abstract Brain metastases arise in the central nervous system (CNS) following spread of circulating mesenchymal-type cells from primary tumors. While accumulating evidence underlines the importance of the neural niche in the establishment and progression of metastases, there still remains ambiguity over CNS anatomical spatial distribution from primary cancers. We evaluated 973 patients with brain metastases (breast, colorectal, lung, melanoma, renal) totaling 2,106 lesions treated from 1994–2015 with gamma knife radiosurgery at the University of Southern California Keck Medical Center for topographical distribution analysis. MRI images of the brain were taken and used in conjunction with the frame to precisely localize tumors and measure their size. Each tumor was given an x, y, and z-coordinate derived from the head frame that corresponded to its volumetric center within a 3-dimensional Cartesian field. Topographical analyses were conducted using logistic and multinomial spatial generalized additive models (GAM). For each cancer origin type we compared the observed brain metastases to set of randomly generated spatial observations to determine whether there were statistically significant localization patterns. Spatial pattern results show: 1) melanoma has highest probability to metastasize to the right frontal (74.5%, 95% confidence interval [Cl] = 63.6%- 85.4%) and to occipital lobe (72.4%, 95% Cl = 65.8%-78.9%), 2) while breast cancers have highest proclivity to metastasize to left cerebellar hemisphere (25%, 95% Cl=16.0%-34.1%) and brainstem (16.6%, 95% Cl= 10.8%-22.4%), 3) with lung tumors metastasizing to the left (23.7%, 95% Cl= 16.0–31.3%) and right parietal (24.7%, 95% Cl=16.7–32.8%), left temporal lobe (25.2%, 95% Cl=21.4%-29.1%). Colon and renal metastases show weak spatial patterns across the CNS. We conclude there is evidence of non-uniform spatial distribution of metastasis in the brain. These tumor-specific CNS topography patterns may underlie the ability of cancer cells to adapt to the regional neural microenvironments in order to facilitate colonization and establishment of metastasis.

Gamma Knife surgery as sole treatment for multiple brain metastases: 2-center retrospective review of 1508 cases meeting the inclusion criteria of the JLGK0901 multi-institutional prospective study

2010 ◽  
Vol 113 (Special_Supplement) ◽  
pp. 48-52 ◽  
Author(s):  
Toru Serizawa ◽  
Masaaki Yamamoto ◽  
Yasunori Sato ◽  
Yoshinori Higuchi ◽  
Osamu Nagano ◽  
...  
Keyword(s):  
Brain Metastases ◽  
Gamma Knife ◽  
Class Ii ◽  
Hazard Ratio ◽  
Gamma Knife Surgery ◽  
Inclusion Criteria ◽  
Primary Tumors ◽  
Poor Prognostic Factor ◽  
Group A ◽  
Group B

Object The authors retrospectively reviewed the results of Gamma Knife surgery (GKS) used as the sole treatment for brain metastases in patients who met the eligibility criteria for the ongoing JLGK0901 multi-institutional prospective trial. They also discuss the anticipated results of the JLGK0901 study. Methods Data from 1508 consecutive cases were analyzed. All of the patients were treated at the Gamma Knife House of Chiba Cardiovascular Center or the Mito Gamma House of Katsuta Hospital between 1998 and 2007 and met the following JLGK0901 inclusion criteria: 1) newly diagnosed brain metastases, 2) 1–10 brain lesions, 3) less than 10 cm3 volume of the largest tumor, 4) no more than 15 cm3 total tumor volume, 5) no findings of CSF dissemination, and 6) no impairment of activities of daily living (Karnofsky Performance Scale score < 70) due to extracranial disease. At the initial treatment, all visible lesions were irradiated with GKS without upfront whole-brain radiation therapy. Thereafter, gadolinium-enhanced MR imaging was performed every 2–3 months, and new distant lesions were appropriately retreated with GKS. Patients were divided into groups according to numbers of tumors: Group A, single lesions (565 cases); Group B, 2–4 tumors (577 cases); and Group C, 5–10 tumors (366 cases). The differences in overall survival (OS) were compared between groups. Results The median age of the patients was 66 years (range 19–96 years). There were 963 men and 545 women. The primary tumors were in the lung in 1114 patients, gastrointestinal tract in 179, breast in 105, urinary tract in 66, and other sites in 44. The overall mean survival time was 0.78 years (0.99 years for Group A, 0.68 years for Group B, and 0.62 years for Group C). The differences between Groups A and B (p < 0.0001) and between Groups B and C (p = 0.0312) were statistically significant. Multivariate analysis revealed significant prognostic factors for OS to be sex (poor prognostic factor: male, p < 0.0001), recursive partitioning analysis class (Class I vs Class II and Class II vs III, both p < 0.0001), primary site (lung vs breast, p = 0.0047), and number of tumors (Group A vs Group B, p < 0.0001). However, no statistically difference was detected between Groups B and C (p = 0.1027, hazard ratio 1.124, 95% CI 0.999–1.265). Conclusions The results of this retrospective analysis revealed an upper CI of 1.265 for the hazard ratio, which was lower than the 1.3 initially set by the JLGK0901 study. The JLGK0901 study is anticipated to show noninferiority of GKS as sole treatment for patients with 5–10 brain metastases compared with those with 2–4 in terms of OS.

Gamma knife radiosurgery as a single treatment modality for large cerebral arteriovenous malformations

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 113-119 ◽  
Author(s):  
D. Hung-Chi Pan ◽  
Wan-Yuo Guo ◽  
Wen-Yuh Chung ◽  
Cheng-Ying Shiau ◽  
Yue-Cune Chang ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Arteriovenous Malformations ◽  
Radiation Treatment ◽  
Gamma Knife Radiosurgery ◽  
Consecutive Series ◽  
Content Type ◽  
Obliteration Rate ◽  
Complete Obliteration ◽  
Fine Print

Object. A consecutive series of 240 patients with arteriovenous malformations (AVMs) treated by gamma knife radiosurgery (GKS) between March 1993 and March 1999 was evaluated to assess the efficacy and safety of radiosurgery for cerebral AVMs larger than 10 cm3 in volume. Methods. Seventy-six patients (32%) had AVM nidus volumes of more than 10 cm3. During radiosurgery, targeting and delineation of AVM nidi were based on integrated stereotactic magnetic resonance (MR) imaging and x-ray angiography. The radiation treatment was performed using multiple small isocenters to improve conformity of the treatment volume. The mean dose inside the nidus was kept between 20 Gy and 24 Gy. The margin dose ranged between 15 to 18 Gy placed at the 55 to 60% isodose centers. Follow up ranged from 12 to 73 months. There was complete obliteration in 24 patients with an AVM volume of more than 10 cm3 and in 91 patients with an AVM volume of less than 10 cm3. The latency for complete obliteration in larger-volume AVMs was significantly longer. In Kaplan—Meier analysis, the complete obliteration rate in 40 months was 77% in AVMs with volumes between 10 to 15 cm3, as compared with 25% for AVMs with a volume of more than 15 cm3. In the latter, the obliteration rate had increased to 58% at 50 months. The follow-up MR images revealed that large-volume AVMs had higher incidences of postradiosurgical edema, petechiae, and hemorrhage. The bleeding rate before cure was 9.2% (seven of 76) for AVMs with a volume exceeding 10 cm3, and 1.8% (three of 164) for AVMs with a volume less than 10 cm3. Although focal edema was more frequently found in large AVMs, most of the cases were reversible. Permanent neurological complications were found in 3.9% (three of 76) of the patients with an AVM volume of more than 10 cm3, 3.8% (three of 80) of those with AVM volume of 3 to 10 cm3, and 2.4% (two of 84) of those with an AVM volume less than 3 cm3. These differences in complications rate were not significant. Conclusions. Recent improvement of radiosurgery in conjunction with stereotactic MR targeting and multiplanar dose planning has permitted the treatment of larger AVMs. It is suggested that gamma knife radiosurgery is effective for treating AVMs as large as 30 cm3 in volume with an acceptable risk.

Gamma knife radiosurgery in the management of cavernous sinus meningiomas

2000 ◽  
Vol 93 (supplement_3) ◽  
pp. 68-73 ◽  
Author(s):  
Pierre-Hugues Roche ◽  
Jean Régis ◽  
Henry Dufour ◽  
Henri-Dominique Fournier ◽  
Christine Delsanti ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Tumor Growth ◽  
Gamma Knife ◽  
Cavernous Sinus ◽  
Gamma Knife Radiosurgery ◽  
Surgical Removal ◽  
Content Type ◽  
Cavernous Sinus Meningioma ◽  
The Mean ◽  
Fine Print

Object. The authors sought to assess the functional tolerance and tumor control rate of cavernous sinus meningiomas treated by gamma knife radiosurgery (GKS). Methods. Between July 1992 and October 1998, 92 patients harboring benign cavernous sinus meningiomas underwent GKS. The present study is concerned with the first 80 consecutive patients (63 women and 17 men). Gamma knife radiosurgery was performed as an alternative to surgical removal in 50 cases and as an adjuvant to microsurgery in 30 cases. The mean patient age was 49 years (range 6–71 years). The mean tumor volume was 5.8 cm3 (range 0.9–18.6 cm3). On magnetic resonance (MR) imaging the tumor was confined in 66 cases and extensive in 14 cases. The mean prescription dose was 28 Gy (range 12–50 Gy), delivered with an average of eight isocenters (range two–18). The median peripheral isodose was 50% (range 30–70%). Patients were evaluated at 6 months, and at 1, 2, 3, 5, and 7 years after GKS. The median follow-up period was 30.5 months (range 12–79 months). Tumor stabilization after GKS was noted in 51 patients, tumor shrinkage in 25 patients, and enlargement in four patients requiring surgical removal in two cases. The 5-year actuarial progression-free survival was 92.8%. No new oculomotor deficit was observed. Among the 54 patients with oculomotor nerve deficits, 15 improved, eight recovered, and one worsened. Among the 13 patients with trigeminal neuralgia, one worsened (contemporary of tumor growing), five remained unchanged, four improved, and three recovered. In a patient with a remnant surrounding the optic nerve and preoperative low vision (3/10) the decision was to treat the lesion and deliberately sacrifice the residual visual acuity. Only one transient unexpected optic neuropathy has been observed. One case of delayed intracavernous carotid artery occlusion occurred 3 months after GKS, without permanent deficit. Another patient presented with partial complex seizures 18 months after GKS. All cases of tumor growth and neurological deficits observed after GKS occurred before the use of GammaPlan. Since the initiation of systematic use of stereotactic MR imaging and computer-assisted modern dose planning, no more side effects or cases of tumor growth have occurred. Conclusions. Gamma knife radiosurgery was found to be an effective low morbidity—related tool for the treatment of cavernous sinus meningioma. In a significant number of patients, oculomotor functional restoration was observed. The treatment appears to be an alternative to surgical removal of confined enclosed cavernous sinus meningioma and should be proposed as an adjuvant to surgery in case of extensive meningiomas.

Gamma knife radiosurgery for renal cell carcinoma brain metastases

2002 ◽  
Vol 97 ◽  
pp. 489-493 ◽  
Author(s):  
Laura Hernandez ◽  
Lucia Zamorano ◽  
Andrew Sloan ◽  
James Fontanesi ◽  
Simon Lo ◽  
...  
Keyword(s):  
Renal Cell Carcinoma ◽  
Brain Metastases ◽  
Cell Carcinoma ◽  
Gamma Knife ◽  
Median Survival ◽  
Renal Cell ◽  
Univariate Analysis ◽  
Gamma Knife Radiosurgery ◽  
Content Type ◽  
Fine Print

Object. The purpose of this study was to clarify the effectiveness of gamma knife radiosurgery (GKS) in achieving a partial or complete remission of so-called radioresistant metastases from renal cell carcinoma (RCC) and to propose guidelines for optimal treatment Methods. During a 5-year period, 29 patients (19 male and 10 female) with 92 brain metastases from RCC underwent GKS. The median tumor volume was 4.7 cm3 (range 0.5–14.5 cm3). Fourteen patients (48%) also underwent whole-brain radiotherapy (WBRT) before GKS, and two patients (6.8%) after GKS. The mean GKS dose delivered to the 50% isodose at the tumor margin was 16.8 Gy (range 13–30 Gy). All cases were categorized according to the Recursive Partitioning Analysis (RPA) classification for brain metastases. Univariate analysis was performed to determine significant prognostic factors and survival. The overall median survival was 7 months after GKS treatment. Age, sex, Karnofsky Performance Scale score, and controlled primary disease were not predictors of survival. Combined WBRT/GKS resulted in median survival of 18, 8.5, and 5.3 months for RPA Classes I, II, and III, respectively, compared with the median survival 7.1, 4.2, and 2.3 months for patients treated with WBRT alone. Conclusions. These results suggest that WBRT combined with GKS may improve survival in patients with brain metastases from RCC. Furthermore, this improvement in survival was seen in all RPA classes.

scholarly journals Ten-Year Survival of a Patient Treated with Stereotactic Gamma Knife Radiosurgery for Brain Metastases from Colon Cancer with Ovarian and Lymph Node Metastases: A Case Report

2016 ◽  
Vol 10 (1) ◽  
pp. 204-211 ◽  
Author(s):  
Nobuhiro Morinaga ◽  
Naritaka Tanaka ◽  
Yoshinori Shitara ◽  
Masatoshi Ishizaki ◽  
Takatomo Yoshida ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Lymph Node ◽  
Brain Metastasis ◽  
Brain Metastases ◽  
Sigmoid Colon ◽  
Gamma Knife ◽  
Gamma Knife Radiosurgery ◽  
Sigmoid Colon Cancer ◽  
Ovarian Lesion ◽  
Node Metastases

Brain metastasis from colorectal cancer is infrequent and carries a poor prognosis. Herein, we present a patient alive 10 years after the identification of a first brain metastasis from sigmoid colon cancer. A 39-year-old woman underwent sigmoidectomy for sigmoid colon cancer during an emergency operation for pelvic peritonitis. The pathological finding was moderately differentiated adenocarcinoma. Eleven months after the sigmoidectomy, a metastatic lesion was identified in the left ovary. Despite local radiotherapy followed by chemotherapy, the left ovarian lesion grew, so resection of the uterus and bilateral ovaries was performed. Adjuvant chemotherapy with tegafur-uracil (UFT)/calcium folinate (leucovorin, LV) was initiated. Seven months after resection of the ovarian lesion, brain metastases appeared in the bilateral frontal lobes and were treated with stereotactic Gamma Knife radiosurgery. Cervical and mediastinal lymph node metastases were also diagnosed, and irradiation of these lesions was performed. After radiotherapy, 10 courses of oxaliplatin and infused fluorouracil plus leucovorin (FOLFOX) were administered. During FOLFOX administration, recurrent left frontal lobe brain metastasis was diagnosed and treated with stereotactic Gamma Knife radiosurgery. In this case, the brain metastases were well treated with stereotactic Gamma Knife radiosurgery, and the systemic disease arising from sigmoid colon cancer has been kept under control with chemotherapies, surgical resection, and radiotherapy.

Gamma knife thalamotomy for movement disorders: evaluation of the thalamic lesion and clinical results

2005 ◽  
Vol 102 ◽  
pp. 234-240 ◽  
Author(s):  
Chihiro Ohye ◽  
Tohru Shibazaki ◽  
Sumito Sato
Keyword(s):  
Mr Imaging ◽  
Gamma Knife ◽  
Clinical Results ◽  
Lesion Size ◽  
Lesion Volume ◽  
Thalamic Lesion ◽  
Content Type ◽  
Before And After ◽  
Single Isocenter ◽  
Fine Print

Object.The authors studied the effects of gamma knife thalamotomy (GKT) on Parkinson disease-related tremor and essential tremor before and after reloading of radioactive cobalt.Methods.Based on experience in stereotactic thalamotomy aided by depth microrecording, the target was located at the lateral border of the thalamic ventralis intermedius nucleus (VIM). For more precise targeting, the percentage representation of the thalamic VIM in relation to the entire thalamic length is useful. The location of the target was determined on magnetic resonance (MR) imaging and computerized tomography scanning. A maximum dose of 130 Gy was delivered to the target by using a single isocenter with the 4-mm collimator. In more recent cases, a systematic follow-up examination was performed at 3, 6, 12, 18, and 24 months after GKT.Since 1993, the authors have treated 70 patients with PD. Throughout the series the same dosimetric technique has been used. The course after GKT was compared between the 25 cases with PD treated before reloading and the 35 cases treated after reloading. In the majority (80–85%) treated after reloading, tremor and rigidity were reduced around 6 months after GKT. In the cases treated before reloading this effect took approximately 1 year. The thalamic reaction on MR imaging showed the same two lesion types in both series: a restricted and a diffuse. After reloading the restricted lesion was more frequent and the lesion volume was smaller.Conclusions.The shorter delay in clinical improvement and smaller lesion size may be related to an increased radiation dose.

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