• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.101-108
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• 2021

The CT can accurately present the anatomical structure of an organ in the human body, and the resolution of the image is excellent. On Brain CT examination, the radiation sensitivity of the orbit is high and it is subject to many exposure effects. To reduce exposure dose of lens, this study compares change of exposure dose and shielding rate about non-shielding and shielding in a way of using two shielding materials, bismuth and tungsten. In this study, we used bismuth and tungsten filament as shielding materials made by 3D printing to measure the exposure dose according to the materials thickness and each of slices. To compare each shielding rate, 1 mm to 5 mm of two materials was measured with the head phantom fixed and the Magicmax universal dosimeter placed on the eye when the shielding material is not placed, and the shielding material is placed on it. In the 1 mm thick filament, the bismuth filament showed 26.8% and the tungsten filament showed 43.1% shielding rate. Therefore, tungsten presents much greater shielding effect than bismuth.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.3
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• pp.803-807
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• 2012

For patients with neck and upper thoracic esophageal carcinoma, it is difficult to control lymph node metastases with conventional dose therapy. In this study, we assessed the feasibility of simplified intensity-modulated radiotherapy (sIMRT) and concurrent chemotherapy for 44 patients and boosted high-dose to metastatic lymph nodes. Three radiation treatment volumes were defined: PGTVnd, with which 68.1Gy was delivered in high dose group (hsIMRT group), and 60Gy in the conventional dose group (csIMRT group); PTV1, featuring 63.9Gy in the hsIMRT group and 60Gy in the csIMRT group; PTV2, with 54Gy given to both groups. The sIMRT plan included 5 equi-angular coplanar beams. All patients received the cisplatin and 5-FU regimen concurrently with radiotherapy. The treatment was completed within six weeks and one case with grade three acute bronchitis was observed in hsIMRT group. For esophageal lesions, 80% complete response (CR) and 20% partial response (PR) rates were found in the hsIMRT group, and 79.2% CR, with 20.8% PR, in the csIMRT group; for lymph node lesions, 75% CR and 25% PR rates were observed in the hsIMRT group, with 45.8% and 37.5% respectively in the csIMRT group (P<0.05). The differences in 1-, 2- and 3-year relapse-free survival rates were all statistically significant (P<0.05). The major toxicity observed in both groups was Grade I~II leucopenia. sIMRT can generate a desirable dose distribution in treatment of neck and upper thoracic esophageal carcinoma with a better short-term efficacy. Boosted high dosing to metastatic lymph nodes can increase the relapse-free survival rate.

• The Korean Journal of Nuclear Medicine Technology
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• v.20 no.1
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• pp.32-36
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• 2016

Purpose In nuclear medicine examination, $^{131}I$ is widely used in nuclear medicine examination such as diagnosis, treatment, and others of thyroid cancer and other diseases. $^{131}I$ conducts examination and treatment through emission of ${\gamma}$ ray and ${\beta}^-$ ray. Since $^{131}I$ (364 keV) contains more energy compared to $^{99m}Tc$ (140 keV) although it displays high integrated rate and enables quick discharge through kidney, the objective of this study lies in comparing the difference in exposure dose of $^{131}I$ before and after wearing apron when handling $^{131}I$ with focus on 3 elements of external exposure protection that are distance, time, and shield in order to reduce the exposure to technicians in comparison with $^{99m}Tc$ during the handling and administration process. When wearing apron (in general, Pb 0.5 mm), $^{99m}Tc$ presents shield of over 90% but shielding effect of $^{131}I$ is relatively low as it is of high energy and there may be even more exposure due to influence of scattered ray (secondary) and bremsstrahlung in case of high dose. However, there is no special report or guideline for low dose (74 MBq) high energy thus quantitative analysis on exposure dose of technicians will be conducted based on apron wearing during the handling of $^{131}I$. Materials and Methods With patients who visited Department of Nuclear Medicine of our hospital for low dose $^{131}I$ administration for thyroid cancer and diagnosis for 7 months from Jun 2014 to Dec 2014 as its subject, total 6 pieces of TLD was attached to interior and exterior of apron placed on thyroid, chest, and testicle from preparation to administration. Then, radiation exposure dose from $^{131}I$ examination to administration was measured. Total procedure time was set as within 5 min per person including 3 min of explanation, 1 min of distribution, and 1 min of administration. In regards to TLD location selection, chest at which exposure dose is generally measured and thyroid and testicle with high sensitivity were selected. For preparation, 74 MBq of $^{131}I$ shall be distributed with the use of $2m{\ell}$ syringe and then it shall be distributed after making it into dose of $2m{\ell}$ though dilution with normal saline. When distributing $^{131}I$ and administering it to the patient, $100m{\ell}$ of water shall be put into a cup, distributed $^{131}I$ shall be diluted, and then oral administration to patients shall be conducted with the distance of 1m from the patient. The process of withdrawing $2m{\ell}$ syringe and cup used for oral administration was conducted while wearing apron and TLD. Apron and TLD were stored at storage room without influence of radiation exposure and the exposure dose was measured with request to Seoul Radiology Services. Results With the result of monthly accumulated exposure dose of TLD worn inside and outside of apron placed on thyroid, chest, and testicle during low dose $^{131}I$ examination during the research period divided by number of people, statistics processing was conducted with Wilcoxon Signed Rank Test using SPSS Version. 12.0K. As a result, it was revealed that there was no significant difference since all of thyroid (p = 0.345), chest (p = 0.686), and testicle (p = 0.715) were presented to be p > 0.05. Also, when converting the change in total exposure dose during research period into percentage, it was revealed to be -23.5%, -8.3%, and 19.0% for thyroid, chest, and testicle respectively. Conclusion As a result of conducting Wilcoxon Signed Rank Test, it was revealed that there is no statistically significant difference (p > 0.05). Also, in case of calculating shielding rate with accumulate exposure dose during 7 months, it was revealed that there is irregular change in exposure dose for inside and outside of apron. Although the degree of change seems to be high when it is expressed in percentage, it cannot be considered a big change since the unit of accumulated exposure dose is in decimal points. Therefore, regardless of wearing apron during high energy low dose $^{131}I$ administration, placing certain distance and terminating the administration as soon as possible would be of great assistance in reducing the exposure dose. Although this study restricted $^{131}I$ administration time to be within 5 min per person and distance for oral administration to be 1m, there was a shortcoming to acquire accurate result as there was insufficient number of N for statistics and it could be processed only through non-parametric method. Also, exposure dose per person during lose dose $^{131}I$ administration was measured with accumulated exposure dose using TLD rather than through direct-reading exposure dose thus more accurate result could be acquired when measurement is conducted using electronic dosimeter and pocket dosimeter.

• Journal of Radiation Protection and Research
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• v.33 no.4
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• pp.151-160
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• 2008

In Korean nuclear power plants (NPPs), two thermoluminescent dosimeters (TLD) were provided to workers who work in an inhomogeneous radiation field; one on the chest and the other on the head. In this way, the effective dose for radiation workers at NPPs was determined by the high deep dose between two radiation dose from these TLDs. This represented a conservative method of evaluating the degree of exposure to radiation. In this study, to prevent the overestimation of the effective dose, field application experiments were implemented using two-dosimeter algorithms developed by several international institutes for the selection of an optimal algorithm. The algorithms used by the Canadian Ontario Power Generation (OPG) and American ANSI HPS N13.41, NCRP (55/50), NCRP (70/30), EPRI (NRC), Lakslumanan, and Kim (Texas A&M University) were extensively analyzed as two-dosimeter algorithms. In particular, three additional TLDs were provided to radiation workers who wore them on the head, chest, and back during maintenance periods, and the measured value were analyzed. The results found no significant differences among the calculated effective doses, apart from Lakshmanan's algorithm. Thus, this paper recommends the NCRP(55/50) algorithm as an optimal two-dosimeter algorithm in consideration of the solid technical background of NCRP and the convenience of radiation works. In addition, it was determined that a two-dosimeter is provided to a single task which is expected to produce a dose rate of more than 1 mSv/hr, a difference of dose rates depending on specific parts of the body of more than 30%, and an exposure dose of more than 2 mSv.

• Progress in Medical Physics
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• v.22 no.1
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• pp.52-58
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• 2011

Our goal is to assess the suitability of a glass dosimeter on detection of high-energy electron beams for clinical use, especially for radiation therapy. We examined the dosimetric characteristics of glass dosimeters including dose linearity, reproducibility, angular dependence, dose rate dependence, and energy dependence of 5 different electron energy qualities. The GD was irradiated with high-energy electron beams from the medical linear accelerator andgamma rays from a cobalt-60 teletherapy unit. All irradiations were performed in a water phantom. The result of the dose linearity for high-energy electron beams showed well fitted regression line with the coefficient of determination; $R^2$ of 0.999 between 6 and 20 MeV. The reproducibility of GDs exposed to the nominal electron energies 6, 9, 12, 16, and 20 MeV was ${\pm}1.2%$. In terms of the angular dependence to electron beams,GD response differences to the electron beam were within 1.5% for angles ranging from $0^{\circ}$ to $90^{\circ}$ and GD's maximum response differencewas 14% lower at 180o. In the dose rate dependence, measured dose values were normalized to the value obtained from 500 MU/min. The uncertainties of dose rate were measured within ${\pm}1.5%$ except for the value from 100 MU/min. In the evaluation of the energy dependence of the GD at nominal electron energies between 6 and 20 MeV, we obtained lower responses between 1.1% and 4.5% based on cobalt-60 beam. Our results show that GDs have a considerable potentiality for measuring doses delivered by high-energy electron beams.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.219-226
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• 2010

In order to evaluate a removal characteristic of chloramphenicol, salicylic acid and ketoprofen according to dose of oxidants, $Cl_2$, $O_3$ and $O_3/H_2O_2$ are used as oxidants in this study. In case of that $Cl_2$ is used for oxidizing harmaceuticals, chloramphenicol, salicylic acid and ketoprofen is not removed entirely at $Cl_2$ dose rang of 0.5~5.0 mg/L for 60 min. However, removal tendency of salicylic acid is so obviously at $Cl_2$ dose higher than 1.0 mg/L. In addition, as $Cl_2$ dose and contact time increase, the removal rate of salicylic acid is enhanced. When $O_3$ is used as oxidant, chloramphenicol and ketoprofen is not eliminated at $O_3$ dose range of 0.2~2.0 mg/L. On the contrary, 30~70% of salicylic acid is removed at $O_3$ dose of 1.0~5.0 mg/L. Only 30% removal of salicylic acid is achieved at contact time of 5 min, however, the removal rate is enhanced remarkably at contact time over 10 min. In experiments using $O_3/H_2O_2$ as an oxidant, we can find that $O_3/H_2O_2$ is much more effective than $O_3$ only for removal of 3 pharmaceuticals, and the efficiency is raised according to increase of $H_2O_2$ dose. On reaction rate constant and half-life of 3 pharmaceuticals depending on $Cl_2$, $O_3$ and $O_3/H_2O_2$ dose, experiments using $O_3/H_2O_2$ show that oxidation of pharmaceuticals is less effective as the $H_2O_2/O_3$ ratio increases to above pproximately 1.0 related to reaction rate constant. An oxidation of salicylic acid by $Cl_2$ and $O_3$ particularly has a comparatively high reaction rate constant comparing $O_3/H_2O_2$, and thus salicylic acid is easily eliminated in oxidation processes.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.26 no.1
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• pp.46-50
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• 2024

Objective: Diagnostic cerebral angiograms (DCAs) are widely used in neurosurgery due to their high sensitivity and specificity to diagnose and characterize pathology using ionizing radiation. Eliminating unnecessary radiation is critical to reduce risk to patients, providers, and health care staff. We investigated if reducing pulse and frame rates during routine DCAs would decrease radiation burden without compromising image quality. Methods: We performed a retrospective review of prospectively acquired data after implementing a quality improvement protocol in which pulse rate and frame rate were reduced from 15 p/s to 7.5 p/s and 7.5 f/s to 4.0 f/s respectively. Radiation doses and exposures were calculated. Two endovascular neurosurgeons reviewed randomly selected angiograms of both doses and blindly assessed their quality. Results: A total of 40 consecutive angiograms were retrospectively analyzed, 20 prior to the protocol change and 20 after. After the intervention, radiation dose, radiation per run, total exposure, and exposure per run were all significantly decreased even after adjustment for BMI (all p<0.05). On multivariable analysis, we identified a 46% decrease in total radiation dose and 39% decrease in exposure without compromising image quality or procedure time. Conclusions: We demonstrated that for routine DCAs, pulse rate of 7.5 with a frame rate of 4.0 is sufficient to obtain diagnostic information without compromising image quality or elongating procedure time. In the interest of patient, provider, and health care staff safety, we strongly encourage all interventionalists to be cognizant of radiation usage to avoid unnecessary radiation exposure and consequential health risks.

• Tuberculosis and Respiratory Diseases
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• v.47 no.1
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• pp.77-89
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• 1999

Background: High-dose chemotherapy is increasingly employed in many refractory malignant diseases. This therapy has been reported to increase response rate and survival benefits but it is also associated with higher treatment-related morbidity and mortality. We evaluated clinical characteristics and course of the pulmonary toxicity following high-dose chemotherapy with peripheral blood stem cell transplantation. Methods: Ninety-seven patients who had received high-dose chemotherapy with peripheral blood stem cell transplantation were evaluated. Five patients who developed lung lesions which were not related to infection nor primary malignant disease underwent transbronchial lung biopsy. The patients' clinical characteristics, treatments, and prognosis were reviewed retrospectively. Results: Five patients(5.1%) developed idiopathic pneumonia syndrome. The high dose chemotherapy regimens employed were cyclophosphamide, BCNU, and cisplatin in 3 cases, one case of BCNU, etoposide, Ara-C, and cyclophosphamide combination, and a regimen consisting of BCNU, etoposide, Ara-C, and melphalan. The total dose of BCNU used was 300-400 mg/$m^2$ and that of cyclophosphsmide was 6,000 mg/$m^2$. All of 5 patients received radiation therapy before this treatment. After an average duration of 14 weeks (4-26 weeks) of high-dose chemotherapy, patients developed cough, dyspnea and fever. The chest X-rays showed bilateral diffuse infiltration in 3 cases and the focal infiltration in the other 2 cases. All the patients received corticosteroid therapy as a treatment for the lung lesions. Two of them progressed to acute respiratory distress syndrome and died. Three patients recovered without residual lung lesion but one of them died of dilated cardiomyopathy. Conclusion: High-dose chemotherapy with peripheral blood stem cell transplantation especially which containing BCNU regimen may develop idiopathic pneumonia syndrome related to pulmonary toxicity and corticosteroid therapy may be bel1eficial in some cases.

• Radiation Oncology Journal
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• v.16 no.4
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• pp.477-483
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• 1998

Purpose : Radiation proctitis and radiation cystitis are frequent and problematic late complications in patients treated with radiation for the uterine cervix cancer. Authors tried to find out the better patient's position in high dose rate intracavitary radiation to reduce the radiation dose of bladder and rectum. Materials and Methods : In 13 patients, Foley Catheters were inserted to patient's bladder and rectum and were ballooned with radioopaque dye. After insertion of a tandem and two ovoids, semi-orthogonal anteroposterior and lateral films were taken in both lithotomy and supine position. The rectal point and bladder point were defined according to the criteria recommended in the ICRU Report 38 with modification. Using these films, all patients' bladder and rectal dose were calculated in both positions (the radiation dose of A point was set to 400 cGy). And also, the distance of bladder and rectum from uterine cervical os was calculated in both positions. Results : The average radiation dose of rectum was 240.7 cGy in lithotomy position and 278.3 cGy in supine position, and the average radiation dose of bladder was 303.5 cGy in lithotomy position and 255.8 cGy in supine position. After the paired t-test, the radiation dose of rectum in lithotomy position was marginally significantly lower than that in supine position, while the radiation dose of bladder in lithotomy position was significantly higher than that in supine position. On the other hand, the average distance between rectum and cervical os was 35.2 mm in lithotomy position and 32.3 mm in supine position. and the average distance between bladder and cervical os was 30.4 mm in lithotomy position and 34.0 mm in supine position. After the paired t-test. the distance between rectum and cervical os in lithotomy position was significantly longer than that in supine position, while the distance between bladder and cervical os in lithotomy position was significantly shorter than that in supine position. Conclusion : The radiation dose of bladder can be reduced in supine position and the radiation dose of rectum can be reduced in lithotomy position, so we can choose appropriate position in each patient.

• Radiation Oncology Journal
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• v.24 no.3
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• pp.171-178
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• 2006

[ $\underline{Purpose}$ ]: To determine the efficacy and safety of concurrent chemotherapy and radiation therapy with high-dose-rate brachytherapy for cervical cancer. $\underline{Materials\;and\;Methods}$: From January 2001 to December 2002, 30 patients with cervical cancer were treated with concurrent chemotherapy (cisplatin and 5-FU) and definitive radiation therapy. The median age was 58 (range $34{\sim}74$) year old. The pathology of the biopsy sections was squamous cell carcinoma in 29 patients and one was adenocarcinoma. The distribution to FIGO staging system was as follows: stage IB, 7 (23%); IIA, 3 (10%); IIB, 12 (40%); IIIA, 3 (10%); IIIB, 5 (17%). All patients received pelvic external beam irradiation (EBRT) to a total dose of $45{\sim}50.4\;Gy$ (median: 50.4 Gy) over $5{\sim}5.5$ weeks. Ir-192 HDR intracavitary brachytherapy (ICBT) was given after a total dose of 41.4 Gy. HDR-ICBT was performed twice a week, with a fraction point A dose of 4 Gy and median dose to point A was 28 Gy (range: $16{\sim}32\;Gy$) in 7 fractions. The median cumulative biologic effective dose (BED) at point A (EBRT+ICBT) was $88\;Gy_{10}$ (range: $77{\sim}94\;Gy_{10}$). The median cumulative BED at ICRU 38 reference point (EBRT+ICBT) was $131\;Gy_3$ (range: $122{\sim}140\;Gy_3$) at point A, $109\;Gy_3$ (range: $88{\sim}125\;Gy_3$) at the rectum and $111\;Gy_3$ (range: $91{\sim}123\;Gy_3$) at the urinary bladder. Cisplatin ($60\;mg/m^2$) and 5-FU ($1,000\;mg/m^2$) was administered intravenously at 3 weeks interval from the first day of radiation for median 5 (range: $2{\sim}6$) cycles. The assessment was performed at 1 month after completion of radiation therapy by clinical examination and CT scan. The median follow-up time was 36 months (range: $8{\sim}50$ months). $\underline{: The complete response rate after concurrent chemoradiation therapy was 93.3%. The 3-yr actuarial pelvic control rate was 87% and 3-yr actuarial overall survival and disease-free survival rate was 93% and 87%, respectively. The local failure rate was 13% and distant metastatic rate was 3.3%. The crude rate of minor hematologic complications (RTOG grade 1-2) occurred in 3 patients (10%) and one patient had suffered from severe leukopenia (RTOG grade 4) during concurrent treatment. Acute minor enterocolitis (RTOG grade 1-2) occurred in 11 patients (37%) and one patient (3%) was suffered from colon perforation during radiation therapy. Late colitis of RTOG grade 1 occurred in 5 patients (15%). Acute cystitis of RTOG grade 1 occurred in 12 patients (40%) and late cystitis of RTOG grade 2 occurred in one patient (3%). No treatment related death was seen. $\underline{Conclusion}$: The results of this study suggest that the concurrent chemoradiation therapy with HDR brachytherapy could be accepted as an effective and safe treatment for cervical cancer.