• Journal of Radiation Protection and Research
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• v.48 no.1
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• pp.15-19
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• 2023

Background: Cone beam computed tomography (CBCT) is a specialized medical equipment and plays a significant role in the diagnosis of oral and maxillofacial diseases and abnormalities; however, it is attributed to risk of exposure of ionizing radiation. The aim of the study was to estimate and determine the amount of scattered radiation dose to the thyroid gland in dental CBCT during maxilla and mandible scan. Materials and Methods: The average scattered radiation dose for i-CAT 17-19 Platinum CBCT (Imaging Sciences International) was measured using a Multi-O-Meter (Unfors Instruments), placed at the patient's neck on the skin surface of the thyroid cartilage, with an exposure parameter of 120 kVp and 37.07 mAs. The surface entrance dose was noted using the Multi-O-Meter, which was placed at the time of the scan at the level of the thyroid gland on the anterior surface of the neck. Results and Discussion: The surface entrance dose to the thyroid from both jaws scans was 191.491±78.486 µGy for 0.25 mm voxel and 26.9 seconds, and 153.670±74.041 µGy from the mandible scan, whereas from the maxilla scan the surface entrance dose was 5.259±10.691 µGy. Conclusion: The surface entrance doses to the thyroid gland from imaging of both the jaws, and also from imaging of the maxilla and mandible alone were within the threshold limit. The surface entrance dose and effective dose in CBCT were dependent on the exposure parameters (kVp and mAs), scan length, and field of view. To further reduce the radiation dose, care should be taken in selecting an appropriate protocol as well as the provision of providing shielding to the thyroid gland.

• Journal of the Korean Society of Radiology
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• v.13 no.6
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• pp.889-894
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• 2019

Upper gastrointestinal series is an examination that uses X-rays. It is important to defend against exposure to radiation during upper gastrointestinal examination because the organs, such as thyroid gland, lens, breasts, and gonads, with relatively high biological sensitivity to radiation are distributed on the examination area. We have made a whole body phantom that can change the depth of organs. radiation dose of eye, thyroid gland, breast and gonads were measured by the same procedure as the actual upper gastrointestinal examination. When performed only fluoroscopy the mean dose reduction of lens, thyroid gland, breast and gonads was 62.2%. The mean dose reduction of lens, thyroid gland, breast and gonads was 59.0% when both fluoroscopy and spot shoot were performed. Therefore, when performed upper gastrointestinal examination it was confirmed that shielding of the lens, thyroid gland, breast and gonads was effective in decreasing the exposure dose. The manufactured human phantom can be used in measuring radiation dose for deep organ because it can adjust the height corresponding to the organs located in the human body.

• The Korean Journal of Zoology
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• v.3 no.1
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• pp.19-23
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• 1960

A method for determination of thyroid secretion rate in rabbit by means of radioactive iodine presented. After injection of radioactive iodine, in vivo determination so f radioactivity in thyroid gland were made during a 19 day-experimental period. In the same period blood samples were drawn and analyzed for protein-bound iodine (PBI) and for protein-bound radioactive iodine(PBI181). A rate constant for secretion of thyroid hormone was calculated from the disappearance rate of radioactive iodine in thyroid gland. The secretion rate of radioactive hormone iodine was calculated by multiplying this rate constant by the amount of radioactive iodine present in thyroid gland. Assuming that the specific radioactiveness of the circulating thyroid hormone and of the hormone just secreted were identical , thyroid secretion rate was calculated by the equation. {{{{ { Secreted hormone-iodine , gamma /hr} over { Secreted hormone-I^131, % dose/hr }= { PBI, ${\gamma}$/ml.Serum} over { PBI^131 , % dose/ml . Serum } }} The method presented consisted of measurements for series of independent criteria on thyroid function, and the resulting thyroid secretion rate was calculated by combination of those.

• Imaging Science in Dentistry
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• v.30 no.1
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• pp.11-15
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• 2000

Purpose: The primary objective of this study was to estimate the radiation absorbed doses in certain critical organs in the head and neck region with an Orthopos plus, a Panelipse, and a Panex-E machines. The second objective was to compare the absorbed doses between 5 inch by 12 inch and 6 inch by 12 inch image field for the Orthopos plus. Materials and Methods: Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses were measured at the thyroid gland, the submandibular gland, the parotid gland, the mouth floor, the maxillary sinus, the brain, the mandibular body, the mandibular ramus, the 2nd cervical spine and the skin over TMJ area. Results: The highest absorbed dose value was recorded at the mandibular ramus for the Orthopos plus with narrow image field. Higher absorbed dose values were recorded at the parotid gland, the mouth floor, the submandibular gland, and the 2nd cervical spine. The doses in the parotid gland were 597 μGy and 529 μGy with Orthopos plus, 638 μGy with Panelipse, and 1094μGy with Panex-E. Corresponding figures for the mandibular ramus were 2363 Gy and 1220 μGy, 248 μGy, and 118 μGy. The absorbed doses to the thyroid gland, the maxillary sinus, the brain, and the skin over TMJ were very low. Conclusion: Higher exposure values were recorded for the Orthopos plus than Panelipse and Panex-E. There was no significant differences of the absorbed doses according to the image field size.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.1
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• pp.255-260
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• 1999

Purpose: The objective of this study was to evaluate the possibility of substitution of the zonography for the full-mouth periapical radiography in aspect of radiation protection. Materials and Methods: Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses at brain, skin above the TMJ. parotid gland. bone marrow in the mandibular body. and thyroid gland during the full-mouth periapical radiography. panoramic radiography. and zonography were measured. Resul ts: From the zonography. the absorbed doses to the brain. the skin over the TMJ. and the parotid gland were relatively high. but the absorbed doses to the bone marrow in the mandibular body and. especially. the thyroid gland were very low. Conclusion: The zonography can be an alternative to the full-mouth periapical radiography in aspect of radiation protection.

• The Journal of the Korean dental association
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• v.53 no.8
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• pp.558-568
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• 2015

Objective: The objectives of this study were to measure pediatric organ and effective doses of cone-beam computed tomography (CBCT) for orthodontic analysis and to compare them to those of panoramic and lateral cephalometric radiography, the conventional radiography for orthodontic analysis. Materials and Methods: Alphard VEGA for CBCT, Planmeca Proline XC for panoramic radiography and Orthophos CD for cephalometric radiography were used for this study. Thermoluminescent dosimeter (TLD) chips were located at 24 anatomic sites of 10-year-old anthropomorphic phantom and exposed during CBCT (C-mode; $200{\times}179mm$ FOV), panoramic and lateral cephalometric radiographic procedures at the clinical exposure settings for 10-year-old patient. Pediatric organ and effective doses were measured and calculated using ICRP 2007 tissue weighting factors. Results: Effective doses of CBCT, panoramic radiography and lateral cephlometric radiography in pediatric clinical exposure settings were $292.5{\mu}Sv$, $19.3{\mu}Sv$, and $4.4{\mu}Sv$ respectively. The thyroid gland contributed most significantly to the effective dose in all the radiographic procedures. Conclusion: Effective dose of CBCT was about 12 times to conventional radiographic procedures for orthodontic analysis in pediatric patient. The use of CBCT for orthodontic analysis should be fully justified over conventional radiography and dose optimization to decrease thyroid dose is needed in pediatric patients.

• Journal of Radiation Protection and Research
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• v.48 no.3
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• pp.131-143
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• 2023

Background: This study examined the detection limit of thyroid screening monitoring conducted at the time of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 using a Monte Carlo simulation. Materials and Methods: We calculated the detection limit of a NaI(Tl) survey meter to measure ¹³¹I accumulation in the thyroid gland of children. Mathematical phantoms of 1- and 5-year-old children were developed in the simulation of the Particle and Heavy Ion Transport code System code. Contamination of the body surface with eight radionuclides found after the FDNPP accident was assumed to have been deposited on the neck and shoulder area. Results and Discussion: The detection limit was calculated as a function of ambient dose rate. In the case of 40 Bq/cm² contamination on the body surface of the neck, the present simulations showed that residual thyroid radioactivity corresponding to thyroid dose of 100 mSv can be detected within 21 days after intake at the ambient dose rate of 0.2 µSv/hr and within 11 days in the case of 2.0 µSv/hr. When a time constant of 10 seconds was used at the dose rate of 0.2 µSv/hr, the estimated survey meter output error was 5%. Evaluation of the effect of individual differences in the location of the thyroid gland confirmed that the measured value would decrease by approximately 6% for a height difference of ±1 cm and increase by approximately 65% for a depth of 1 cm. Conclusion: In the event of a nuclear disaster, simple measurements carried out using a NaI(Tl) scintillation survey meter remain effective for assessing ¹³¹I intake. However, it should be noted that the presence of short-half-life radioactive materials on the body surface affects the detection limit.

• Journal of radiological science and technology
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• v.44 no.5
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• pp.435-441
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• 2021

The purpose of this study was to evaluate the quality of images and to quantitatively measure and analyze the dose of scattered ray to the organs, which were highly sensitive to radiation according to the use of cylinder cone in mastoid process radiography. When the cylinder cone was not used, the SID was 100cm and the field size was 24 × 36 cm(864 cm²). When using the cylinder cone which was a circle, the SID was 70 cm, the radius was 10.5 cm and field size was 86.59 cm². As a result of the study, SNR of the image quality evaluation was measured to be 2.58 for Law method and 3.90 for Stenver's method when not using cylinder cone, and 2.87 for Law method and 14.67 for Stenver's method when using cylinder cone. CNR was measured to be 0.03 for Law method and 0.04 for Stenver's method when cylinder cone was not used, and 0.04 for Law method and 0.05 for Stenver's method when using cylinder cone. When the cylinder cone was not used, the scattered ray dose was measured to be 0.10 mGy in the right eyeball, 0.30 mGy in the left eyeball, 2.02 mGy in the parotid gland, and 0.29 mGy in the thyroid gland for Law method and to be 0.03 mGy in the right eyeball, 0.12 mGy in the left eyeball, 1.43 mGy in the parotid gland, and 0.09 mGy in the thyroid gland for Stenver's method. When the cylinder cone was used, the scattered ray dose was measured to be 0.05 mGy in the right eyeball, 0.03 mGy in the left eyeball and the parotid and thyroid gland were below the measurable values for Law method and all areas were below the measurable values for Stenver's method. This was found to be statistically significant(p<0.000).

• Imaging Science in Dentistry
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• v.40 no.1
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• pp.9-14
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• 2010

Purpose : We evaluated the absorbed doses to the organs and calculated the effective doses when using the digital panoramic radiography. Materials and Methods : The absorbed dose averages in major organs of oral and maxillofacial region were measured using the Dental head phantom (CIRS Co., USA), $^nLi_2B_4O_7$ TLD chip and UD-716AGL dosimeter (Matsushita Electric Industrial Co., JPN) when performing indirect and direct digital panoramic radiography. Effective doses were calculated from correspond to ICRP 2007 recommendations for two panoramic radiography. Results : The absorbed dose average on indirect and direct digital panoramic radiography was highest in parotid glands as measured 1259.6 mGy and 680.7 mGy respectively. Absorbed dose average in another organs were high in order of esophagus, submandibular gland, tongue and thyroid gland on both types of digital panoramic radiography. The absorbed dose average was higher on indirect type than direct one (p<0.05). The effective dose was higher on indirect type than direct one as measured 13.28 mSv and 8.70 mSv respectively. Conclusion : The absorbed doses in salivary gland and oral mucosa were high. However, thyroid gland also demands the attention on radiography due to high tissue weighting factor in spite of the low absorbed dose.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.309-318
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• 1995

In head and neck region, the critical organ and tissue doses were determined, and the risks were estimated from lateral, posteroanterial and basilar cephalometric radiography. For each cephalometric radiography, 31 TLDs were placed in selected sites(18 internal and 13 external sites) in a tissue-equivalent phantom and exposed, then read-out in the TLD reader. The results were as follows: 1. From lateral cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland(3.6pSv) and the next highest dose was that received by the bone marrow(3pSv). 2. From posteroanterial cephalometric radiography, the highest effective dose recorded was that delivered to the salivary gland(2pSv) and the next highest dose was that received by the bone marrow(1.8pSv). 3. From basilar cephalometric radiography, the highest effective dose recorded was that delivered to the thyroid gland(31A p Sv) and the next highest dose was that received by the salivary gland(13.3 p Sv). 4. The probabilities of stochastic effect from lateral, posteroanterial and basilar cephalometric radiography were $0.72{\times}10^{-6}$, $0.49{\times}10^{-6}$ and $3.51{\times}10^{-6}$, respectively