• Radiation Oncology Journal
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• v.9 no.1
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• pp.47-52
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• 1991

From April,1983 through April,1989, we have treated histologically proven 21 patients with oligodendroglioma using 6 MV linear accelerator at the Division of Radiation Therapy, Kangnam 51. Mary's Hospital Catholic University Medical College. These are 8% of the irradiated 246 primary brain tumors during the same period. To investigate influencing factors on the survival of irradiated U patients with oligodendroglioma, we analyzed the cerebral location of the involvements, initial symptoms, CT findings and survival rates, retrospectively. One case was lost to follow up and excluded from survival data. Of the 28 patients, thirteen were male and 8 female. Ages ranged from 5 to 68 years with a median age of 38 years. Radiation doses varied from 3900 cGy to 0480 cGy and were given for 5 to 8 weeks. All but one were supratentorial. The involvement of the frontal and parietal lobes were 10 (48%) patients in each and temporal lobe in 8 (38.1%). Histological diagnosis was made by stereotactic biopsy in 3 and postoperatively in 18. The type of surgery was divided into partial, subtotal and total resection in 7,9 and 2 cases respectively. In 6 cases, chemotherapy was also tried during or after radiation therapy. Major presenting symptoms were headache, cerebral motor, nausea & vomiting and epilepsy in 18,12, 7 and 5 respectively in decreasing order. In CT analysis, low density (02%), cystic mass (33%), calcifiestion (66%) and positive contrast enhancement (42.8%) were observed as the highest frequency. Mean survival duration after radiation therapy was 38 months (K-M methods). We could not achieve statistically significant factors influencing on the survival rate after radiation therapy for oligodendrogliomas by one or two tail test.

• Journal of Radiation Protection and Research
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• v.26 no.2
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• pp.59-66
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• 2001

It is a hot issue to determine the spatial location and shape of tumor boundary in fractionated stereotactic radiotherapy (FSRT). We could get consecutive transaxial plane images from the phantom (paraffin) and 4 patients with brain tumor using helical computed tomography(HCT). K-means classification algorithm was adjusted to change raw data pixel value in CT images into classified average pixel value. The classified images consists of 5 regions that ate tumor region (TR), normal region (NR), combination region (CR), uncommitted region (UR) and artifact region (AR). The major concern was how to separate the normal region from tumor region in the combination area. Relative average deviation analysis was adjusted to alter average pixel values of 5 regions into 2 regions of normal and tumor region to define maximum point among average deviation pixel values. And then we drawn gross tumor volume (GTV) boundary by connecting maximum points in images using semi-automatic contour method by IDL(Interactive Data Language) program. The error limit of the ROI boundary in homogeneous phantom is estimated within ${\pm}1%$. In case of 4 patients, we could confirm that the tumor lesions described by physician and the lesions described automatically by the K-mean classification algorithm and relative average deviation analyses were similar. These methods can make uncertain boundary between normal and tumor region into clear boundary. Therefore it will be useful in the CT images-based treatment planning especially to use above procedure apply prescribed method when CT images intermittently fail to visualize tumor volume comparing to MRI images.

• Progress in Medical Physics
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• v.21 no.3
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• pp.291-297
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• 2010

This study examined the dosimetric influence of implanted gold markers in proton therapy and the effects of their positions in the spread-out Bragg peak (SOBP) proton beam. The implanted cylindrical gold markers were 3 mm long and 1.2 mm in diameter. The dosimetric influence of the gold markers was determined with markers at various locations in a proton-beam field. Spatial dose distributions were measured using a three-dimensional moving water phantom and a stereotactic diode detector with an effective diameter of 0.5 mm. Also, a film dosimetry was performed using Gafchromic External Beam Treatment (EBT) film. The GEANT4 simulation toolkit was used for Monte-Carlo simulations to confirm the measurements and to construct the dose-volume histogram with implanting markers. Motion data were obtained from the portal images of 10 patients to investigate the effect of organ motions on the dosimetric influence of markers in the presence of a rectal balloon. The underdosed volume due to a single gold marker, in which the dose was less than 95% of a prescribed amount, was 0.15 cc. The underdosed volume due to the presence of a gold marker is much smaller than the target volume. However, the underdosed volume is inside the gross tumor volume and is not smeared out due to translational prostate motions. The positions of gold markers and the conditions of the proton-beam field give different impacts on the dose distribution of a target with implanted gold markers, and should be considered in all clinical proton-based therapies.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.13-19
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• 2011

Purpose: It's essential to minimize the tumor motion and identify the exact location of the lesions to achieve the improvement in radiation therapy efficiency during SBRT. In this study, we made the established compression belt to reduce respiratory motion and evaluated the usefulness of clinical application in SBRT. Materials and Methods: We analyzed the merits and demerits of the established compression belt to reduce the respiratory motion and improved the reproducibility and precision in use. To evaluate the usefulness of improved compression belt for respiratory motion reduction in SBRT, firstly, we reviewed the spiral CT images acquired in inspiration and expiration states of 8 lung cancer cases, respectively, and analyzed the three dimensional tumor motion related to respiration. To evaluate isodose distribution, secondly, we also made the special phantom using EBT2 film (Gafchronic, ISP, USA) and we prepared the robot (Cartesian Robot-2 Axis, FARARCM4H, Samsung Mechatronics, Korea) to reproduce three dimensional tumor motion. And analysis was made for isodose curves and two dimensional isodose profiles with reproducibility of respiratory motion on the basis of CT images. Results: A respiratory motion reduction compression belt (Velcro type) that has convenient use and good reproducibility was developed. The moving differences of three dimensional tumor motion of lung cancer cases analyzed by CT images were mean 3.2 mm, 4.3 mm and 13 mm each in LR, AP and CC directions. The result of characteristic change in dose distribution using the phantom and rectangular coordinates robot showed that the distortion of isodose has great differences, mean length was 4.2 mm; the differences were 8.0% and 16.8% each for cranio-caudal and 8.1% and 10.9% each for left-right directions in underdose below the prescribed dose. Conclusion: In this study, we could develop the convenient and efficient compression belt that can make the organs' motion minimize. With this compression belt, we confirmed that underdose due to respiration can be coped with when CTV-PTV margins of mean 6 mm would be used. And we conclude that the respiratory motion reduction compression belt we developed can be used for clinical effective aids along with the gating system.

• Radiation Oncology Journal
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• v.21 no.4
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• pp.269-275
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• 2003

Purpose: To evaluate the results of radiation management on recurrence, survival and prognostic factors of patients with nasopharyngeal cancer Materials and Methods: Forty-nine patients, treated for nasopharyngeal cancer by radiotherapy between January 1984 and June 2000, were retrospectively studied. All patients were followed up for at least 2.5 years. Their median age was 52 years (range 17$\~$78). The histological types were 21 squamous cell carcinoma, 25 undifferentiated carcinoma, and 3 adenoid cystic carcinoma. The tumor stages were as follows: T1 in 14 patients, T2 in 24, T3 in 3, and T4 in 8, and N0 in 17 patients, Nl in 15, N2 in 4 and N3 in 13. Stages I, IIa, IIb ,III, IV and IVb were 4, 7, 12, 5, 8, and 13 patients respectively. Radiation doses of 58$\~$70 Gy (median 68.7 Gy) were given to the nasopahryngeal and involved lymphatic areas and of 46 $\~$ 50 Gy to the uninvolved neck areas. Results: The overall 5 and 10-year actuarial and disease free survival rates were 54.53$\%$ and 47$\%$ and 55.7$\%$ and 45.3$\%$, respectively The overall five-year survival rates were 100$\%$ in stage I , 80$\%$ in stage IIa, 59.5$\%$ in stage IIIb, 40$\%$ in stage III, and 42.2$\%$ in stage IV tumors. Twenty-three patients fatted either loco-regionally or distantly. Incidences of local failure, regional failure and distant metastasis for the first failure were 20.4$\%$, 8.2$\%$ and 20.4$\%$, respectively. Local recurrences were 4.3$\%$ in T1, 12.5$\%$ in T2, 0$\%$ in T3, and 62.5$\%$ in T4 lesions. Distant metastasis was seen in 41.2$\%$ of N2-3 lesions. Fifty percent of local recurrence appeared within 2 years of treatment at the primary lesion, whereas 70$\%$ of distant metastasis appeared within 2 years following treatment. Young age, female, early T stage, N0 stage; and poorly differentiated carcinoma were all related with good survival. However only stage showed statistically significance. Conclusionn: Based on the results of this study, radiation therapy to nasopharyngeal cancer showed high local recurrence in T4 and increased metastasis in N2-3 lesions. To improve local failure, further radiation doses, such as stereotactic radiation or IMRT radiation, are necessary especially in T4 lesions. The high incidence of distant metastasis in positive lymph node patients, indicates that combined radiation and effective chemotherapeutic agents with appropriated schedule are necessary.

• Progress in Medical Physics
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• v.21 no.2
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• pp.192-200
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• 2010

Cyberknife with small field size is more difficult and complex for dosimetry compared with conventional radiotherapy due to electronic disequilibrium, steep dose gradients and spectrum change of photons and electrons. The purpose of this study demonstrate the usefulness of Geant4 as verification tool of measurement dose for delivering accurate dose by comparing measurement data using the diode detector with results by Geant4 simulation. The development of Monte Carlo Model for Cyberknife was done through the two-step process. In the first step, the treatment head was simulated and Bremsstrahlung spectrum was calculated. Secondly, percent depth dose (PDD) was calculated for six cones with different size, i.e., 5 mm, 10 mm, 20 mm, 30 mm, 50 mm and 60 mm in the model of water phantom. The relative output factor was calculated about 12 fields from 5 mm to 60 mm and then it compared with measurement data by the diode detector. The beam profiles and depth profiles were calculated about different six cones and about each depth of 1.5 cm, 10 cm and 20 cm, respectively. The results about PDD were shown the error the less than 2% which means acceptable in clinical setting. For comparison of relative output factors, the difference was less than 3% in the cones lager than 7.5 mm. However, there was the difference of 6.91% in the 5 mm cone. Although beam profiles were shown the difference less than 2% in the cones larger than 20 mm, there was the error less than 3.5% in the cones smaller than 20 mm. From results, we could demonstrate the usefulness of Geant4 as dose verification tool.

• Radiation Oncology Journal
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• v.18 no.2
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• pp.101-106
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• 2000

Purpose : This study was peformed to evaluate the effectiveness and tolerance of craniospinal irradiation for patients with modulloblastoma and to define the optimal radiotherapeutic regimen. Materials and Methods : We retrospectively analyzed the records of 43 patients with modulloblastoma who were treated with external beam craniospinal radiotherapy at our institution between May, 1984 and April, 1998. Median follow up period was 47 months with range of 18 to U months. Twenty seven patients were male and sixteen patients were female, a male to female ratio of 1.7:1. Surgery consisted of biopsy alone in 5 patients, subtotal excision in 24 patients, and gross total excision in 14 patients. All of the patients were treated with craniospinal irradiation. All of the patients except four received at least 5,000 cGy to the posterior fossa and forty patients received more than 3,000 cGy to the spinal cord. Results : The overall survival rates at 5 and 7 years for entire group of patients were 57$\%$ and 56$\%$, respectively. Corresponding disease free survival rates were 60$\%$ and 51$\%$, respectively, The rates of disease control in the posterior fossa were 77$\%$ and 67$\%$ at 5 and 7 years. Gross total excision and subtotal excision resulted in 5 year overall survival rates of 76$\%$ and 66$\%$, respectively, In contrast, those patients who had biopsy alone had a 5 year survival rate of only 40$\%$. Posterior fossa was a component of failure in 11 of the 18 recurrences. Seven recurrences were isolated to the posterior fossa. Four patients had neuraxis recurrences, three had distant metastasis alone and four had multiple sites of failure, all involving the primary site. Conclusion : Craniospinal irradiation for patients with moduiloblastoma is an effective adjuvant treatment without significant treatment related toxicitles. There is room for Improvement in terms of posterior fossa control, especially in biopsy alone patients. The advances in radiotherapy including hypefractionation, stereotactic radiosurgery and 3D conformal radiotherapy would be evolved to improve the tumor control rate at primary site.

• Radiation Oncology Journal
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• v.28 no.4
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• pp.238-248
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• 2010

Purpose: To compare the dose distributions between three-dimensional (3D) and four-dimensional (4D) radiation treatment plans calculated by Ray-tracing or the Monte Carlo algorithm, and to highlight the difference of dose calculation between two algorithms for lung heterogeneity correction in lung cancers. Materials and Methods: Prospectively gated 4D CTs in seven patients were obtained with a Brilliance CT64-Channel scanner along with a respiratory bellows gating device. After 4D treatment planning with the Ray Tracing algorithm in Multiplan 3.5.1, a CyberKnife stereotactic radiotherapy planning system, 3D Ray Tracing, 3D and 4D Monte Carlo dose calculations were performed under the same beam conditions (same number, directions, monitor units of beams). The 3D plan was performed in a primary CT image setting corresponding to middle phase expiration (50%). Relative dose coverage, D95 of gross tumor volume and planning target volume, maximum doses of tumor, and the spinal cord were compared for each plan, taking into consideration the tumor location. Results: According to the Monte Carlo calculations, mean tumor volume coverage of the 4D plans was 4.4% higher than the 3D plans when tumors were located in the lower lobes of the lung, but were 4.6% lower when tumors were located in the upper lobes of the lung. Similarly, the D95 of 4D plans was 4.8% higher than 3D plans when tumors were located in the lower lobes of lung, but was 1.7% lower when tumors were located in the upper lobes of lung. This tendency was also observed at the maximum dose of the spinal cord. Lastly, a 30% reduction in the PTV volume coverage was observed for the Monte Carlo calculation compared with the Ray-tracing calculation. Conclusion: 3D and 4D robotic radiotherapy treatment plans for lung cancers were compared according to a dosimetric viewpoint for a tumor and the spinal cord. The difference of tumor dose distributions between 3D and 4D treatment plans was only significant when large tumor movement and deformation was suspected. Therefore, 4D treatment planning is only necessary for large tumor motion and deformation. However, a Monte Carlo calculation is always necessary, independent of tumor motion in the lung.

• Radiation Oncology Journal
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• v.15 no.1
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• pp.1-10
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• 1997

Purpose : To evaluate the role of radiotherapy in the management of incompletely resected supratentorial low grade astrocytoma with the analysis of the survival, the Pattern of failure, and the prognostic variables affecting survival. Material and methods : Between January 1990 and December 1995, fifty-one patients with supratentorial low grade astrocytoma received radiotherapy after subtotal resection(16 patients) or stereotactic biopsy(35 patients) at Asan Medical Center, External radiotherapy was done by conventional fractionation with the total dose of 4820cGy to 6000cGy(median 5580cGy) and partial brain volume. The follow-up was done from 6 to 79 months(median 48 months) Result : Overall actuarial survival rate at 2 and 5 years were $83.4\%\;and\;54.8\%$, respectively. Progression free survival at 2 and 5 years were $67.4\%\;and\;48.7\%$, respectively The significant prognostic factors affecting overall survival rate were the performance status, 1 stage, histologic subtype, radiation field and radiation response. The major pattern of failure was local failure, such as Progressive disease and primary site recurrence in 23 patients $(45.1\%)$. Progression free survivors excluding 2 patients were physically and intellectually intact without major neurologic deficit. Conclusion : Although the follow-up period of this study was relatively short, overall actuarial and progression free survival rate were encouraging. Patients with good performance status, lower T stage, pilocytic subtype, patients treated with small radiation field and radiation responder showed better survival. As the local failure was the major pattern of failure, the various efforts to decrease the local failure is necessary.

• Radiation Oncology Journal
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• v.14 no.3
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• pp.181-189
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• 1996

Purpose : To find the more effective treatment methods that improving the survival of patients with glioblastoma multiforme(GBM), we analyze the prognostic factors and the outcome of therapy in patients with GBM. Materials and Methods : One hundred twently-one patients with a diagnosis of GBM treated at Severance Hospital between 1973 and 1993 were analyzed for survival with respect to patients characteristics, that is, duration of symptom, age, and Karnofsky performance status, as well as treatment related variables such as extent of surgery and radiotherapy. Results : The median survival time(MST) and 2-year overall survival rate (OSR) of the patients with GBM were 13 months and $20.8\%$, respectively. Duration of symptom, age, Karnofsky performance status(KPS), radiotherapy, and extent of surgical resection were associated with improved survial in a univariate analysis. Patients whose duration of symptom was longer than 3 months, had the 2-year OSR of $47.2\%$(p=0.0082), who were younger than age 50, $32.9\%$(p=0.0003) In patients with a KPS of 80 or higher, the 2-rear OSR was $36.9\%$(p=0.0422). Patients undergoing radiotherapy had the 2-year OSR of $22.9\%$(p=0.0030), and surgical resection of $23.3\%$ (p<0.000). A Cox regression model confirmed a significant correlation of duration of symptom, age, radiotherapy, and extent of surgical resection with survival, excluding KPS(P=0.8823). The 2-year OSR were $22.3\%$ and $19.4\%$, combined with chemotherapy or without, respectively(p=0.6028). The duration of symptom of 3 months or shorter, 50 years of age or older, and undergoing stereotactic biopsy only were considered as risk factors, then patients without any risk factors had the MST of 29 months and 2-year OSR of $53.9\%$ compared to 4 months and $0\%$ for Patients who had all 3 risk factors. Most of all treatment failures occurred in the primary tumor site($80.4\%$). Conclusion : The duration of symptom, age, radiotherapy, and extent of surgical resection were a prognostically significant indeuendent variables. To get a better survival, it seems to be reasonable that the study design which improves the local control rates is warranted.