• Radiation Oncology Journal
• /
• v.3 no.1
• /
• pp.69-73
• /
• 1985

• Radiation Oncology Journal
• /
• v.12 no.1
• /
• pp.9-16
• /
• 1994

Hypothesis that hypoxic tumors should be more responsive to the addition of preferential hypoxic cell cytotoxin SR 4233 (tirapazamine) to fractionated irradiation was tested in the mouse SCCVll carcinoma and RIF-1 sarcoma, Model of hypoxic tumor was established using the tumor bed effect: tumors growing in the preirradiated tissue (preirradiated tumors) were more hypoxic than tumors growing in the unirradiated tissue (unirradiated tumors). When the tumors reached a mean volume of 100 $mm^{3}$, both unirradiated and preirradiated tumors were treated with a fractionated course of 6${\times}$2 Gy in 3 days or 8${\times}$2.5 Gy in 4 days with SR 4233 (0.08 mmol/kg/injection) given 30 minutes before each irradiation or without SR 4233. Compared to the unirradiated tumors, hypoxic preirradiated tumors were approximately 5 times more resistant to fractionated irradiation alone but were approximately 5 times more responsive to SR 4233. Addition of SR 4233 Potentiated the effect of fractionated irradiation in both unirradiated and preirradiated tumors. Potentiation in the preirradiated tumors was morequal to or greater than that in the unirradiated tumors and seemed to be higher for more fractionated treatment. We confirm the hypothesis in a transplantable mouse tumor. Present results suggest that radioresistance of some hypoxic tumors can be overcome with hypoxic cytotoxin.

• Radiation Oncology Journal
• /
• v.1 no.1
• /
• pp.79-83
• /
• 1983

• 대한두경부종양학회:학술대회논문집
• /
• 1994.11a
• /
• pp.17.1-17.1
• /
• 1994

• Radiation Oncology Journal
• /
• v.8 no.2
• /
• pp.169-176
• /
• 1990

Radiotherapy result was analyzed in 23 children with retinoblastoma treated in Seoul National University Hospital from 1980 to 1987. Three ($17\%$) had bilateral tumor at diagnosis. Among 20 children with unilateral retinoblastoma 13 children got radiotherapy after enucleation, 2 were treated with radiotherapy alone, and 5 were delivered with radiotherapy after relapse. Of 15 non-recurrent unilateral tumors, there were 5 stage II children, 8 stage III, and 2 stage IV by staging system proposed by St. Jude Children's Research Hospital. Chemotherapy was combined when resection margin of the optic nerve was positive or when malignant cell was found in CSF. Of 12 children who completed radiotherapy, local or distant failure was not found but 2 cases of relapse at the contralateral retina were observed. Their 5 year survival rate was $82.2\%$. Another case of contralateral relapse was detected in children who was treated with radiotherapy alone. Thus overall frequency of the bilateral disease was $33\%$. Prognosis of recurrent tumors were so poor that no cases of CR was obtained and that 3 year survival rate was $20\%$. Two of 3 bilateral cases at diagnosis were in NED status. Complication were sunken orbit only. Result of radiotherapy was so good in early stage or small bulk tumor that treatment delay after diagnosis must not be allowed.

• The Journal of Korean Society for Radiation Therapy
• /
• v.33
• /
• pp.9-14
• /
• 2021

This study examined dose change depending on the reposition error of the junction at the time of treatment with multi-isocenter volumetric modulated arc therapy. This study selected a random treatment region in the Arccheck Phantom and established the treatment plan for multi-isocenter volumetric modulated arc therapy. Then, after setting the error of the junction at 0 ~ 4 mm in the X (left), Y (upper), and Z (inner and outer) directions, the area was irradiated using a linear accelerator; the point doses and gamma indexes obtained through the Phantom were subsequently analyzed. It was found that when errors of 2 and 4 mm took place in the X and Y directions, the gamma pass rates (point doses) were 99.3% (2.085) and 98% (2.079 Gy) in the former direction and 98.5% (2.088) and 95.5% (2.093 Gy) in the latter direction, respectively. In addition, when errors of 1, 2, and 4 mm occurred in the inner and outer parts of the Z direction, the gamma pass rates (point doses) were found to be 94.8% (2.131), 82.6% (2.164), and 72.8% (2.22 Gy) in the former part and 93.4% (2.069), 90.6% (2.047), and 79.7% (1.962 Gy) in the latter part, respectively. In the X and Y directions, errors up to 4 mm were tolerable; however, in the Z direction, error values exceeding 1 mm were beyond the tolerance level. This suggests that for high and low dose areas, errors in the direction same as the progress direction in the treatment region have a more sensitive dose distribution. If the guidelines for set-up errors are established at the institutional level through continuous research in the future, it will be possible to provide good quality treatment using junctions.

• Radiation Oncology Journal
• /
• v.18 no.2
• /
• pp.120-126
• /
• 2000

Purpose : Tumor hypoxia can be overcome with hypoxic cytotoxin. In mouse tumor, tirapazamine's efficacy of the potentiating radiation effect was tested by the tumor oxygenation status combined with hype facti on ated rad iotherapy .:The control and hypoxic mouse tumors we established by inoculation of RIF-1 tumor cells into the normal or previously irradiated back and thigh of C3H mice. When the tumors reached a proper size, both the control and hypoxic tumors were given hypefractionated treatments (8fractions/4 days) with saline (0.02 ml/g), tirapazamin (0.08 mM/0.02 ml/kg), irradiation (2.5 Gy), irradiation combined with tirapazamine given 30 minutes prior to each irradiation. The response was evaluated by the growth delay assay by measuring tumor size from day 0 (12 hrs prior to the first fractionation) to the day when the volume had 4-fold increase or cross sectional area had 2-fold increase. Results : Overall growth pattern showed that tirapazamine Potentiated radiation effect in back and thigh tumors grew in the normal and preirradiated tumor bed. With growth delay assay using reference point of initial tumor volume or cross sectional area, tirapazamine potentiated radiation effect 1.9 times for the control and 2.4 times for the hypoxic tumors in back, and 1.85 times for the control and 1.6 times for the hypoxic tumors. With reference of 4-fold increase of the initial volume or 2-fold increase of the cross sectional area, tirapazamine potentiated radiation effect 1.48 times for the control and 2.02 times for the hypxic tumors in back, and 1.85 times for the control and 1.6 times for the hypoxic tumors. Conclusions : Present result indicated that radiation response of hypoxic tumors was potentiated by tirapazamine in the back or thigh tumors grew in the control or preirradiated tumor bed, and potentiation of the hypoxic tumors was eDual to or greater than that of the control tumors in the back or thigh.

• Journal of radiological science and technology
• /
• v.45 no.6
• /
• pp.553-560
• /
• 2022

The purpose of this study is to evaluate the clinical risk according to the applicator heterogeneity, mislocation, and tissue heterogeneity correction through a dose verification program during brachytherapy of cervical cancer. We performed image processing with MATLAB on images acquired with CT simulator. The source was modeled and stochiometric calibration and Monte-Carlo algorithm were applied based on dwell time and location to calculate the dose, and the secondary cancer risk was evaluated in the dose verification program. The result calculated by correcting for applicator and tissue heterogeneity showed a maximum dose of about 25% higher. In the bladder, the difference in excess absolute risk according to the heterogeneity correction was not significant. In the rectum, the difference in excess absolute risk was lower than that calculated by correcting applicator and tissue heterogeneity compared to the water-based calculation. In the femur, the water-based calculation result was the lowest, and the result calculated by correcting the applicator and tissue heterogeneity was 10% higher. A maximum of 14% dose difference occurred when the applicator mislocation was 20 mm in the Z-axis. In a future study, it is expected that a system that can independently verify the treatment plan can be developed by automating the interface between the treatment planning system and the dose verification program.

• Radiation Oncology Journal
• /
• v.20 no.2
• /
• pp.100-107
• /
• 2002

Purpose : The aim of this retrospective study was to assess the treatment results of 30 patients with pineal region tumors who were underwent radiation therapy under the diagnosis by either CT or MRI. There was no histological verification. We analyzed the prognostic factors that have a significant effect on the overall survival (OS) and disease free survival (DFS) rates. Materials and Methods : A total 30 patients with pineal region tumors were treated between March 1983 and August 1995. After a trial radiation therapy of $20\~30\;Gy/2\~3$ weeks, the patients were evaluated for their clinical response and radiological response by either CT or MRI and the final treatment direction was then decided. According to their response to the trial radiation therapy and the involved site, radiation treatment was given in various fields i.e., local, ventricle, whole brain and craniospinal field. The radiation dose ranged from 40.8 to 59.4 Gy (Median 50.4 Gy). The median follow up was 36.5 months $(4\~172\;months)$. Results : An improvement or stability in the clinical symptoms was observed in 28 patients $(93.3\%)$ after the trial RT. Nineteen patients $(63.3\%)$ showed a partial or complete response by CT or MRI. The two-year and five-year survival rates of the patients were $66.7\%$ and $55.1\%$, respectively. No significant difference in the survival rates according to the degree of the radiological response was abserved after the trial RT. The results of univariate analysis showed that age, the primary site, the performance status $(KPS\geq70)$, the degree of response after completing RT and the RT field were significant prognostic factors affecting the survival and disease free survival rates (p<0.05). Conclusion : The clinical and histological characteristics of pineal region tumors are quite complex and diverse. Therefore, it is difficult to predict the histological diagnosis and the possibility of radiocurability only with the initial response to RT. We think that the development of less invasive histological diagnostic techniques and tailored treatment to the histological type of each tumor are needed.

• 대한두경부종양학회:학술대회논문집
• /
• 1992.11a
• /
• pp.136.3-137
• /
• 1992