• Radiation Oncology Journal
• /
• v.16 no.3
• /
• pp.251-258
• /
• 1998

Purpose : This study was performed to analyze the factors affecting local control in malignant tumors of the parotid gland treated with surgery and postoperative radiation. Materials and methods : Twenty-six patients were treated for malignant tumors of the parotid gland from 1986 to 1995 at Department of Therapeutic Radiology, Chonnam University Hospital. Age of the patients ranged from 14 to 72 years (median : 55 years). Histologically 10 patients of mucoepidermoid carcinoma, 7 of squamous cell carcinoma, 4 of acinic cell carcinoma, 4 of adenoid cystic carcinoma and 1 of adenocarcinoma were treated. Total parotidectomy was performd in 15 of 26 patients, superficial in 7, subtotal in 4. Facial nerve was sacrificed in 5 patients. Postoperatively 4 patients had residual disease, 4 had positive resection margin. Radiation was delivered through an ipsilateral wedged pair of photon in 11 patients. High energy electron beam was mixed with photon in 15 patients. Electron beam dose ranged from 900 cGy to 3800 cGy (median 1700 cGy). Total radiation dose ranged from 5000 cGy to 7560 cGy (median : 6020 cGy). Minimum follow-up period was 2 years. Local control and survival rate were calculated using Kaplan-Meier method. Generalized Wilcoxon test and Cox proportional hazard model were used to test factors affecting local control. Results : Five (19$\%$) of 26 patients had local recurrence. Five year local control rate was 77$\%$. Overall five year survival rate was 70$\%$. Sex, age, tumor size, surgical involvement of cervical lymph node, involvement of resection margin, surgical invasion of nerve, and total dose were analyzed as suggested factors affecting local control rate. Among them patients with tumor size less than 4 cm (p=0.002) and negative resection margin (p=0.011) were associated with better local control rates in univariate analysis. Multivariate analysis showed only tumor size factor is associated with local control rate (p=0.022). Conclusion : This study suggested that tumor size is important in local control of malignant tumors of parotid gland.

• Journal of the Korean Society of Radiology
• /
• v.15 no.7
• /
• pp.965-973
• /
• 2021

Since radiation therapy is irradiated with high-energy X-rays in a variety of at least 20 Gy to 80 Gy, a high dose is administered to the local area where the tumor is located, and various side effects of some normal tissues are expected. Currently, in clinical practice, lead, a representative material, is used as an effort to shield normal tissues, but lead is classified as a heavy metal harmful to the human body, and a large amount of skin contact can cause poisoning. Therefore, this study intends to manufacture a measurement sheet that can compensate for the limitations of lead using the materials Tungsten, Brass, and Copper of the 3D printer of the FDM (Fused Deposition Modeling) method and to investigate the penetration performance. Tungsten mixed filament transmission measurement sheet size was 70 × 70 mm and thickness 1, 2, 4 mm using a 3D printer, and a linear accelerator (TrueBeam STx, S/N: 1187) was measured by irradiating 100 MU at SSD 100 cm and 5 cm in water using a water phantom, an ion chamber (FC-65G), and an elcetrometer (PTW UNIDOSE), and the permeability was evaluated. As a result of increasing the measurement sheet of each material by 1 mm, in the case of Tungsten sheet at 3.8 to 3.9 cm in 6 MV, the thickness of the lead shielding body was thinner than 6.5 cm, and in case of Tungsten sheet at 4.5 to 4.6 cm in 15 MV. The sheet was thinner than the existing lead shielding body thickness of 7 cm, and equivalent performance was confirmed. Through this study, the transmittance measurement sheet produced using Tungsten alloy filaments confirmed the possibility of transmission shielding in the high energy region. It has been confirmed that the usability as a substitute is also excellent. It is thought that it can be provided as basic data for the production of shielding agents with 3D printing technology in the future.

• Radiation Oncology Journal
• /
• v.18 no.2
• /
• pp.79-84
• /
• 2000

Purpose : To evaluate the effectiveness and tolerance of postoperative e지ernai beam radiotherapy for patients with low grade glioma of the brain and define the optimal radiotherapeutic regimen. Materials and Methods : Between June, 1985 and May, 1998, 72 patients with low grade gliomas were treated with postoperative radiotherapy immediately following surgery. Median age was 37 years with range of 11 to 76 years. Forty one patients were male and 31 patients were female with male to female ratio of 1.3:1. Of those patients, 15 underwent biopsy alone and remaining 57 did subtotal resection. The distribution of the patients according to histologic type was as follows: astrocytomas-42 patients (58$\%$), mixed oligodendrogliomas-19 patients (27$\%$), oiigodendrogliomas-11 patients (15$\%$). Two patients were treated with whole brain irradiation followed by cone down boost and remaining 70 patients were treated with localized field with appropriate margin. Ail of the patients were treated with conventional once a day fractionation. Most of patients received total tumor dose of 5000 $\~$ 5500 cGy. Results : The overall 5 and 7 year survival rates for entire group of 72 patients were 61$\~$ and 50$\~$. Corresponding disease free survival rates for entire patients were 53$\~$ and 45$\~$, respectively. The 5 and 7 year overall survival rates for astrocytomas, mixed oligodendrogiiomas, and oligodendrogiiorras were 48$\%$ and 45$\%$, 76$\%$ and 56$\%$, and 80$\%$ and 52$\%$, respectively. Patients who underwent subtotal resection showed better survival rates than those who did biopsy alone. The overall 5 year survival rates for sub total resection patients and biopsy alone patients were 57$\%$ and 43$\%$, respectively. Forty six patients who were 40 years or younger survived batter than 26 patients who were 41 years or older (overall survival rate at 5 years, 69$\%$ vs 45$\%$). Although one patient was not able to complete the treatment because of neurological deterioration, there was no significant treatment related acute toxicities. Conclusion : Postoperative radiotherapy was safe and effective treatment for patients with low grade gliomas. However, we probably need prospective randomized trial to define optimal treatment timing and schedule for low grade gliomas and select patient group for different treatment philosophies.

• Nuclear Medicine and Molecular Imaging
• /
• v.40 no.4
• /
• pp.228-232
• /
• 2006

Purpose: electrophilic $^{18}F(T_{1/2}=110\;min)$ radionuclide in the form of $[^{18}F]F_2$ gas is of great significance for labeling radiopharmaceuticals for positron omission tomography (PET). However, its production In high yield and with high specific radioactivity is still a challenge to overcome several problems on targetry. The aim of the present study was to develop a method suitable for the routine production of $[^{18}F]F_2$ for the electrophilic substitution reaction. Materials and Methods: The target was designed water-cooled aluminum target chamber system with a conical bore shape. Production of the elemental fluorine was carried out via the $^{18}O(p,n)^{18}F$ reaction using a two-step irradiation protocol. In the first irradiation, the target filled with highly enriched $^{18}O_2$ was irradiated with protons for $^{18}F$ production, which were adsorbed on the inner surface of target body. In the second irradiation, the mixed gas ($1%[^{19}F]F_2/Ar$) was leaded into the target chamber, fellowing a short irradiation of proton for isotopic exchange between the carrier-fluorine and the radiofluorine absorbed in the target chamber. Optimization of production was performed as the function of irradiation time, the beam current and $^{18}O_2$ loading pressure. Results: Production runs was performed under the following optimum conditions: The 1st irradiation for the nuclear reaction (15.0 bar of 97% enriched $^{18}O_2$, 13.2 MeV protons, 30 ${\mu}A$, 60-90 min irradiation), the recovery of enriched oxygen via cryogenic pumping; The 2nd irradiation for the recovery of absorbed radiofluorine (12.0 bar of 1% $[^{19}F]fluorine/argon$ gas, 13.2 MeV protons, 30 ${\mu}A$, 20-30 min irradiation) the recovery of $[^{18}F]fluorine$ for synthesis. The yield of $[^{18}F]fluorine$ at EOB (end of bombardment) was achieved around $34{\pm}6.0$ GBq (n>10). Conclusion: The production of $^{18}F$ electrophilic agent via $^{18}O(p,n)^{18}F$ reaction was much under investigation. Especially, an aluminum gas target was very advantageous for routine production of $[^{18}F]fluorine$. These results suggest the possibility to use $[^{18}F]F_2$ gas as a electrophilic substitution agent.

• Korean Journal of Soil Science and Fertilizer
• /
• v.42 no.5
• /
• pp.399-407
• /
• 2009

Laser induced breakdown spectroscopy(LIBS) is an simple analysis method for directly quantifying many kinds of soil micro-elements on site using a small size of laser without pre-treatment at any property of materials(solid, liquid and gas). The purpose of this study were to find an optimum condition of the LIBS measurement including wavelengths for quantifying soil elements, to relate spectral properties to the concentration of soil elements using LIBS as a simultaneous un-breakdown quantitative analysis technology, which can be applied for the safety assessment of agricultural products and precision agriculture, and to compare the results with a standardized chemical analysis method. Soil samples classified as fine-silty, mixed, thermic Typic Hapludalf(Memphis series) from grassland and uplands in Tennessee, USA were collected, crushed, and prepared for further analysis or LIBS measurement. The samples were measured using LIBS ranged from 200 to 600 nm(0.03 nm interval) with a Nd:YAG laser at 532 nm, with a beam energy of 25 mJ per pulse, a pulse width of 5 ns, and a repetition rate of 10 Hz. The optimum wavelength(${\lambda}nm$) of LIBS for estimating soil and plant elements were 308.2 nm for Al, 428.3 nm for Ca, 247.8 nm for T-C, 438.3 nm for Fe, 766.5 nm for K, 85.2 nm for Mg, 330.2 nm for Na, 213.6 nm for P, 180.7 nm for S, 288.2 nm for Si, and 351.9 nm for Ti, respectively. Coefficients of determination($r^2$) of calibration curve using standard reference soil samples for each element from LIBS measurement were ranged from 0.863 to 0.977. In comparison with ICP-AES(Inductively coupled plasma atomic emission spectroscopy) measurement, measurement error in terms of relative standard error were calculated. Silicon dioxide(SiO2) concentration estimated from two methods showed good agreement with -3.5% of relative standard error. The relative standard errors for the other elements were high. It implies that the prediction accuracy is low which might be caused by matrix effect such as particle size and constituent of soils. It is necessary to enhance the measurement and prediction accuracy of LIBS by improving pretreatment process, standard reference soil samples, and measurement method for a reliable quantification method.