• Journal of Korean Neurosurgical Society
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• v.61 no.5
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• pp.592-599
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• 2018

Objective : Metastatic brain tumors (MBTs) often present with intracerebral hemorrhage. Although Gamma Knife surgery (GKS) is a valid treatment option for hemorrhagic MBTs, its efficacy is unclear. To achieve oncologic control and reduce radiation toxicity, we used a radiosurgical targeting technique that confines the tumor core within the hematoma when performing GKS in patients with such tumors. We reviewed our experience in this endeavor, focusing on local tumor control and treatment-associated morbidities. Methods : From 2007 to 2014, 13 patients with hemorrhagic MBTs were treated via GKS using our targeting technique. The median marginal dose prescribed was 23 Gy (range, 20-25). GKS was performed approximately 2 weeks after tumor bleeding to allow the patient's condition to stabilize. Results : The primary sites of the MBTs included the liver (n=7), lung (n=2), kidney (n=1), and stomach (n=1); in two cases, the primary tumor was a melanoma. The mean tumor volume was $4.00cm^3$ (range, 0.74-11.0). The mean overall survival duration after GKS was 12.5 months (range, 3-29), and three patients are still alive at the time of the review. The local tumor control rate was 92% (tumor disappearance 23%, tumor regression 46%, and stable disease 23%). There was one (8%) instance of local recurrence, which occurred 11 months after GKS in the solid portion of the tumor. No GKS-related complications were observed. Conclusion : Our experience shows that GKS performed in conjunction with our targeting technique safely and effectively treats hemorrhagic MBTs. The success of this technique may reflect the presence of scattered metastatic tumor cells in the hematoma that do not proliferate owing to the inadequate microenvironment of the hematoma. We suggest that GKS can be a useful treatment option for patients with hemorrhagic MBTs that are not amenable to surgery.

• Journal of the Korean Society of Radiology
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• v.11 no.1
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• pp.9-17
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• 2017

A high degree of precision and accuracy in Gamma Knife Radiosurgery(GKRS) is a fundamental requirement for therapeutical success. Elaborate radiation delivery and dose gradients with the steep fall-off of radiation are clinically applied thus necessitating a dedicated Quality Assurance(QA) program in order to guarantee dosimetric and geometric accuracy and reduce all the risk factors that can occur in GKRS. In this study, as a part of QA we verified the accuracy of single-shot dose profiles used in the algorithm of Gamma Knife Perfexion(PFX) treatment planning system employing Variable Ellipsoid Modeling Technique(VEMT). We evaluated the dose distributions of single-shots in a spherical ABC phantom with diameter 160 mm on Gamma Knife PFX. The single-shots were directed to the center of ABC phantom. Collimating configurations of 4, 8, and 16 mm sizes along x, y, and z axes were studied. Gamma Knife PFX treatment planning system being used in GKRS is called Leksell GammaPlan(LGP) ver 10.1.1. From the verification like this, the accuracy of GKRS will be doubled. Then the clinical application must be finally performed based on precision and accuracy of GKRS. Specifically the width at the 50% isodose level, that is, Full-Width-of-Half-Maximum(FWHM) was verified under such conditions that a patient's head is simulated as a sphere with diameter 160mm. All the data about dose profiles along x, y, and z axes predicted through VEMT were excellently consistent with dose profiles from LGP within specifications(${\leq}1mm$ at 50% isodose level) except for a little difference of FWHM and PENUMBRA(isodose level: 20%~80%) along z axis for 4 mm and 8mm collimating configurations. The maximum discrepancy of FWHM was less than 2.3% at all collimating configurations. The maximum discrepancy of PENUMBRA was given for the 8 mm collimator along z axis. The difference of FWHM and PENUMBRA in the dose distributions obtained with VEMT and LGP is too small to give the clinical significance in GKRS. The results of this study are considered as a reference for medical physicists involved in GKRS in the whole world. Therefore we can work to confirm the validity of dose distributions for all collimating configurations determined through the regular preventative maintenance program using the independent verification method VEMT for the results of LGP and clinically assure the perfect treatment for patients of GKRS. Thus the use of VEMT is expected that it will be a part of QA that can verify and operate the system safely.

• Journal of Korean Neurosurgical Society
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• v.46 no.2
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• pp.116-122
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• 2009

Objective: Intracranial arteriovenous malformation (AVM) associated with aneurysm has been infrequently encountered and the treatment for this malady is challenging. We report here on our clinical experience with AVMs associated with arterial aneurysms that were managed by multimodality treatments, including clipping of the aneurysm, microsurgery, Gamma-knife radiosurgery (GKS) and Guglielmi detachable coil (GDC) embolization. Methods: We reviewed the treatment plans, radiological findings and clinical courses of 21 patients who were treated with GKS for AVM associated with aneurysm. Results: Twenty-seven aneurysms in 21 patients with AVMs were enrolled in this study. Hemorrhage was the most frequent presenting symptom (17 patients: 80.9%). Bleeding was caused by an AVM nidus in 11 cases, aneurysm rupture in 5 and an undetermined origin in 1. Five patients were treated for associated aneurysm with clipping followed by GKS for the AVM and 11 patients were treated with GDC embolization combined with GKS for an AVM. Although 11 associated aneurysms remained untreated after GKS, none of them ruptured and 4 aneurysms regressed during the follow up period. Two aneurysms increased in size despite the disappearance of the AVM nidus after GKS and then these aneurysms were treated with GDC embolization. Conclusion: If combined treatment using microsurgery, GKS and endovascular treatment can be adequately used for these patients, a better prognosis can be obtained. In particular, GKS and GDC embolization are considered to have significant roles to minimize neurologic injury.

• Progress in Medical Physics
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• v.16 no.1
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• pp.24-31
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• 2005

The stereotactic radiosurgery (SRS) describes a method of delivering a high dose of radiation to a small tar-get volume in the brain, generally in a single fraction, while the dose delivered to the surrounding normal tissue should be minimized. To perform automatic plan of the SRS, a new method of multi-isocenter/shot linear accelerator (linac) and gamma knife (GK) radiosurgery treatment plan was developed, based on a physical lattice structure in target. The optimal radiosurgical plan had been constructed by many beam parameters in a linear accelerator or gamma knife-based radiation therapy. In this work, an isocenter/shot was modeled as a sphere, which is equal to the circular collimator/helmet hole size because the dimension of the 50% isodose level in the dose profile is similar to its size. In a computer-aided system, it accomplished first an automatic arrangement of multi-isocenter/shot considering two parameters such as positions and collimator/helmet sizes for each isocenter/shot. Simultaneously, an irregularly shaped target was approximated by cubic structures through computation of voxel units. The treatment planning method by the technique was evaluated as a dose distribution by dose volume histograms, dose conformity, and dose homogeneity to targets. For irregularly shaped targets, the new method performed optimal multi-isocenter packing, and it only took a few seconds in a computer-aided system. The targets were included in a more than 50% isodose curve. The dose conformity was ordinarily acceptable levels and the dose homogeneity was always less than 2.0, satisfying for various targets referred to Radiation Therapy Oncology Group (RTOG) SRS criteria. In conclusion, this approach by physical lattice structure could be a useful radiosurgical plan without restrictions in the various tumor shapes and the different modality techniques such as linac and GK for SRS.

• Journal of Korean Neurosurgical Society
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• v.58 no.5
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• pp.471-475
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• 2015

Intracerebral hemorrhage (ICH) is common among various types of storkes; however, it is rare in young patients and patients who do not have any risk factors. In such cases, ICH is generally caused by vascular malformations, tumors, vasculitis, or drug abuse. Basal ganglia ICH is rarely related with distal lenticulostriate artery (LSA) aneurysm. Since the 1960s, a total of 29 distal LSA aneurysm cases causing ICH have been reported in the English literature. Despite of the small number of cases, various treatment methods have been attempted : surgical clipping, endovascular treatment, conservative treatment, superficial temporal artery-middle cerebral artery anastomosis, and gamma-knife radiosurgery. Here, we report two additional cases and review the literature. Thereupon, we discerned that young patients with deep ICH are in need of conventional cerebral angiography. Moreover, initial conservative treatment with follow-up cerebral angiography might be a good treatment option except for cases with a large amount of hematoma that necessitates emergency evacuation. If the LSA aneurysm still persists or enlarges on follow-up angiography, it should be treated surgically or endovascularly.

• Journal of Korean Neurosurgical Society
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• v.52 no.2
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• pp.148-151
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• 2012

Intracranial squamous cell carcinoma is extremely rare, with most of the cases arising from malignant transformation of an epidermoid or a dermoid cyst. The patient presented with facial weakness. Initial magnetic resonance imaging revealed a mass in the right cerebellopontine angle. A subtotal resection was performed via right retrosigmoid suboccipital approach. Histopathological findings were consistent with an epidermoid tumor. Five months later, the patient underwent gamma knife radiosurgery due to highly probable recurrent epidermoid tumor. Two years after, the patient's neurological deficit had been newly developed, and follow-up magnetic resonance imaging demonstrated a large contrast-enhancing tumor in the left cerebellopontine angle, which compressed the brainstem. After resection of the tumor, histopathological examinations revealed a squamous cell carcinoma probably arising from an underlying epidermoid cyst. We report a case of an epidermoid tumor in the cerebellopontine angle that transformed into a squamous cell carcinoma.

• Journal of Korean Neurosurgical Society
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• v.59 no.4
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• pp.405-409
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• 2016

Meningiomas are typically diagnosed by their characteristic appearance on conventional magnetic resonance imaging (MRI). However, detailed image findings regarding peri- and intra-tumoral anatomical structures, tumor consistency and vascularity are very important in pre-surgical planning and surgical outcomes. At the 7.0 T MRI achieving ultra-high resolution, it could be possible to obtain more useful information in surgical strategy. Four patients who were radiologically diagnosed with intracranial meningioma in 1.5 T MRI underwent a 7.0 T MRI. Three of them underwent surgery afterwards, and one received gamma knife radiosurgery. In our study, the advantages of 7.0 T MRI over 1.5 T MRI were a more detailed depiction of the peri- and intra-tumoral vasculature and a clear delineation of tumor-brain interface. In the safety issues, all patients received 7.0 T MRI without any adverse event. One disadvantage of 7.0 T MRI was the reduced image quality of skull base lesions. 7.0 T MRI in patients with meningiomas could provide useful information in surgical strategy, such as the peri-tumoral vasculature and the tumor-brain interface.

• Investigative Magnetic Resonance Imaging
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• v.19 no.2
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• pp.117-121
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• 2015

Chordoid glioma is a rare, low-grade brain neoplasm typically located in the third ventricle. Herein, we report an unusual case of histologically confirmed chordoid glioma located in the pituitary fossa and suprasellar region, not attached to the third ventricle. A 57-year-old woman presented with a 2-month history of headache and visual disturbance. Magnetic resonance imaging revealed an ovoid mass in the pituitary fossa and suprasellar region, compressing the optic chiasm without involvement of the third ventricle. The tumor showed low signal intensity on T1-weighted images and iso- to high signal intensity on T2-weighted images, with strong and homogenous contrast enhancement. Subtotal resection was performed via the transcranial approach, and the patient subsequently received adjuvant gamma knife radiosurgery. However, the residual mass showed disease progression 5 months after the initial surgery.

• Journal of the Korean Society of Radiology
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• v.11 no.4
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• pp.235-240
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• 2017

The purpose of this study is to confirm the safety of the clinical application of image co - registration in steteotactic radiosurgery by evaluating the 3D positioning of magnetic resonance imaging using image co-registration. We performed a retrospective study using three-dimensional coordinate measurement of 32 patients who underwent stereotactic radiosurgery and performed magnetic resonance imaging follow-up using image co-registration. The 3 dimensional coordinate errors were $1.0443{\pm}0.5724mm$ (0.10 ~ 1.89) in anterior commissure and $1.0348{\pm}0.5473mm$ (0.36 ~ 2.24) in posterior commissure. The mean error of MR1 (3.0 T) was lower than that of MR2 (1.5 T). It is necessary to minimize the error of magnetic resonance imaging in the treatment planning using the image co - registration technique and to confirm it.

• Journal of Korean Neurosurgical Society
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• v.64 no.6
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• pp.983-994
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• 2021

Objective : The effectiveness of gamma knife radiosurgery (GKR) in the treatment of brain metastases is well established. The aim of this study was to evaluate the efficacy and safety of maximizing the radiation dose in GKR and the factors influencing tumor control in cases of small and medium-sized brain metastases from non-small cell lung cancer (NSCLC). Methods : We analyzed 230 metastatic brain tumors less than 5 mL in volume in 146 patients with NSCLC who underwent GKR. The patients had no previous radiation therapy for brain metastases. The pathologies of the tumors were adenocarcinoma (n=207), squamous cell carcinoma (n=18), and others (n=5). The radiation doses were classified as 18, 20, 22, and 24 Gy, and based on the tumor volume, the tumors were categorized as follows : small-sized (less than 1 mL) and medium-sized (1-3 and 3-5 mL). The progression-free survival (PFS) of the individual 230 tumors and 146 brain metastases was evaluated after GKR depending on the pathology, Eastern Cooperative Oncology Group (ECOG) performance score (PS), tumor volume, radiation dose, and anti-cancer regimens. The radiotoxicity after GKR was also evaluated. Results : After GKR, the restricted mean PFS of individual 230 tumors at 24 months was 15.6 months (14.0-17.1). In small-sized tumors, as the dose of radiation increased, the tumor control rates tended to increase (p=0.072). In medium-sized tumors, there was no statistically difference in PFS with an increase of radiation dose (p=0.783). On univariate analyses, a statistically significant increase in PFS was associated with adenocarcinomas (p=0.001), tumors with ECOG PS 0 (p=0.005), small-sized tumors (p=0.003), radiation dose of 24 Gy (p=0.014), synchronous lesions (p=0.002), and targeted therapy (p=0.004). On multivariate analyses, an improved PFS was seen with targeted therapy (hazard ratio, 0.356; 95% confidence interval, 0.150-0.842; p=0.019). After GKR, the restricted mean PFS of brain at 24 months was 9.8 months (8.5-11.1) in 146 patients, and the pattern of recurrence was mostly distant within the brain (66.4%). The small and medium-sized tumors treated with GKR showed radiotoxicitiy in five out of 230 tumors (2.2%), which were controlled with medical treatment. Conclusion : The small-sized tumors were effectively controlled without symptomatic radiation necrosis as the radiation dose was increased up to 24 Gy. The medium-sized tumors showed potential for symptomatic radiation necrosis without signifcant tumor control rate, when greater than 18 Gy. GKR combined targeted therapy improved the tumor control of GKR-treated tumors.