• Journal of radiological science and technology
• /
• v.44 no.3
• /
• pp.183-187
• /
• 2021

The field size of the lumbar spine X-ray examination, which belongs to the most frequent examination in general radiography, is 5 times wider than the width of the lumbar spine. Exposure index (EI) as per International Electrotechnical Commission has a proportional relationship with the dose incident on the image receptor for clinical protocols in addition to RQA5, which is a calibration beam quality. In this study, the effectiveness of the set field size was evaluated through the change of EI according to the size of field during lumbar spine X-ray examinations. Lumbar anterior-posterior and lateral examinations was performed using a whole-body phantom, and the national average exposure conditions of Korea investigated in 2017 were introduced for the X-ray exposure. As a result of comparing the EI displayed on the console of digital radiography system for the three field size in ① 18 × 36 cm2 ② 25 × 36 cm2 ③ 36 × 36 cm2, the EI values showed a tendency to increase as the field size increased. Since the patient dose, such as organ dose around the lumbar spine, increases as the field size becomes larger, thus, if the EI obtained from the field size at a level that does not interfere with diagnosis is set as a reference, the effectiveness of the field size can be evaluated through the EI displayed on the console when the lumbar spine X-ray examination is conducted.

• Journal of the Korean Society of Radiology
• /
• v.9 no.5
• /
• pp.323-329
• /
• 2015

This study is aimed at assessing whether dynamic wedge filters are appropriate to be used instead of physical wedge filters. The X-ray energy generated from linear accelerator is commercialize 6 MV and 10 MV. $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ of physical wedge filter was irradiated by dose rate 100, 200, 300, 400, 500, and 600 MU/min for each angle and for comparison with a dynamic wedge filter, irradiate 96 times under the same conditions. The measurement conditions are as 100 cm source-film distance and $10{\times}10cm$ irradiated surface. A developed film was scanned and analyzed after a calibration through a dose analysis program and the dose rate was compared after calculating the standard deviation. Dynamic wedge filters make dose, scattered rays and treatment time reduced and very useful due to less irradiated doses to patients. The errors at each dose rate under the same conditions were irrelevant. Thus, treatment based on a high dose rate depending on the patient is expected to be feasible.

• Journal of Radiation Protection and Research
• /
• v.23 no.4
• /
• pp.267-271
• /
• 1998

It is required to measure air density correction factor at the time of absorbed dose calibration or measurement. In general, thermometer and barometer are widely used for air density correction. However, this can be done using the radioactive check device with better accuracy. The measurements of air density correction were performed by using the radioactive check device, Unidos electrometer, and 0.6 cc Farmer-type ion chamber of PTW under the different environmental conditions. Above experiments were repeated with thermometer and barometer. By comparing the two methods, they were within the difference of 0.2 %. The overall uncertainty for the dose found in thermometer and barometer was 1.2 - 1.6 %, depending upon either one step or two, whereas the overall uncertainty for the radioactive check device was 1.02 %. This method may reduce the possible error which could occur when thermometer and barometer are not calibrated at regular basis.

• Journal of Radiation Protection and Research
• /
• v.18 no.2
• /
• pp.71-79
• /
• 1993

Form the pure Maxwellian distribution(kT= 1.42MeV), the effects upon calibration factors of encapsulating a $^{252}Cf$ spontaneous fission neutron source were investigated to establish a standard neutron field in the Secondary Standard Dosimetry Laboratory at Korea Atomic Energy Research Institute(KAERI). A Monte Carlo code MCNP was used in simulating the encapsulation SR-Cf-100 and SR-Cf-1273 to be real conditions. The anisotropy(FI) and fluence-to-dose equivalents conversion factors$(H/{\Phi})$ were evaluated and compared with other results. As the results, the FI was determined to be 1.061 at ${\theta}=90^{\circ}$ with ${\pm}0.2%$ statistical error and the $(H/{\Phi})$ was evaluated to be $333.9 [pSv\;cm^2]\;with\;{\pm}0.5%$ statistical error, which is lower by 1.8% than that recommended by the ISO 8529. This means physically that the neutron spectrum of the unmoderated $^{252}Cf$ source in KAERI is a little more softened than that by the ISO.

• Journal of Biomedical Engineering Research
• /
• v.16 no.2
• /
• pp.129-138
• /
• 1995

High-energy and high-dose X-ray and electron beam have been used in radiation therapy after developing particle accelerators. It is recommended to irradiate patients exect real dose for improving therapy effectiveness by International Committee on Radiation Units and Measurement. The radiation detector for daily beam checks of medical accelerators is described. Using thirteen silicon diodes, we have designed the diode detector providing information about calibration, beam symmetry, flatness, stability variation according to radiation damage, time and general quality assurance for both photon and eletron beams. we also compared these measurement values with those of using ionization chamber, film and semiconductor dosimeter.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.1
• /
• pp.80-86
• /
• 1997

High energy particles in the earth's radiation belts cause transient and long term effects on electronic materials, devices, and integrated circuits on board the satellites. Hence, it is very important to have the information on the space radiation environment and the damage on the electronics caused by the se high energy particles. One of the radiation monitor devices frequently used in space is RADFET, a specially designed MOSFET with a thick gate oxide region. The present study focuses on the calibration of RADFET TOT500 using the $Co^{60}{\gamma}-ray$ source. The result shows that the response of RADFET is very sensitive to the change of temperature. The peculiar behavior observed in the TDE (Total Dose Experiment) on board the KITSAT-1 is identified as the thermal effect due to the change in the eclipse rate of the satellite.

• Progress in Medical Physics
• /
• v.16 no.4
• /
• pp.161-165
• /
• 2005

The CT number corresponds to electron density and its influence on dose calculation was studied. Five kinds of CT scanners were used to obtain Images of electron density calibration phantom (Gammex RMI 467), Then the differences between CT numbers for each scanners were ${\pm}2\%$ In homogeneous medium and $9.5\%$ in high density medium. In order to Investigate the influence of CT number to dose calculation, patients' thoracic CT images were analyzed. The maximum dose difference was $0.48\%$ for each organ. It acquired the phantom Images inserted high density material in the water phantom. Comparing the doses calculated with CT Images from each CT scanner, the maximum dose difference was $2.1\%$ in 20 cm in depth. The exact density to CT number conversion according to CT scanner is required to minimize the uncertainty of dose depends on CT number Especially the each hospital with various CT scanners has to discriminate CT numbers for each CT scanner. Moreover a periodic quality assurance is required for reproducibility of CT number.

• Progress in Medical Physics
• /
• v.10 no.3
• /
• pp.151-157
• /
• 1999

The GafChromic film was used for the dosimetry of a balloon angio catheter filled with the radioisotope HO-166 for endovascular irradiation. The balloon angio catheter was 2 cm long and 3 mm in diameter when inflated. The isotope, Ho-166, was produced by the neutron bombardment using the research reactor in Korea Atomic Energy Research Insititute. Co-60 teletherapy beam was used for making H-D curve for the Gaf-Chromic film. The film dosimetry was measured with a videodensitometer. The radial dose distribution indicated that the absorbed dose dropped to about 20% of the surface dose at the 1 mm away from the balloon surface and at 5 mm position the dose decreased to below 1% of the surface dose. The result also shows that with the specific activity of Ho-l66, 250 mCi/ml it takes 230 seconds to deliver 1200 cGy to the region where is 1mm away from the balloon surface. The concentric isodose curves were also presented. The Ho-166 is an another alternative for endovascualr irradiation to prevent restenosis after PTCA (Percutaneous Trans Coronary Angioplasty)

• Journal of Pharmaceutical Investigation
• /
• v.39 no.3
• /
• pp.177-183
• /
• 2009

A rapid and sensitive reversed-phase high performance liquid chromatography (HPLC) method was developed for the determination of piroxicam in the rabbit plasma. After a treatment of plasma sample by liquid-liquid extraction, the drug was analyzed on an HPLC system with ultraviolet detection at 330 nm. HPLC was carried out using reversed-phase isocratic elution with a C18 column, a mobile phase of a mixture of acetonitril, doubly deionized water and acetic acid 43.74:56.00:0.26 v/v%) at a flow rate of 1.1 mL/min. The chromatograms showed good resolution and sensitivity and no interference of plasma. The calibration curve for the drug in plasma sample was linear over the concentration range of 0.01-2.0 ${\mu}$g/mL. The intra- and inter-day assay accuracies of this method ranged from 86.82% to 108.33% of normal values and the precision did not exceed 13% of relative standard deviation. The plasma concentration of piroxicam decreased to below the quantifiable limit at 12 hr after the i.v. bolus administration to rabbits following dose of 0.375 mg/kg yielding a apparen t plasma half life of 1.38 hr. The transdermal route prolongs plasma levels of piroxicam. The bioavailability, calculated from the dose-adjusted ratio of the $AUC_{transdermal}$ to the $AUC_{i.v.}$, was 7.44%. The plasma concentration of piroxicam was detected by 48 hr after the transdermal administration of patch at a dose of 32 mg/kg. This method was suitable for cutaneous absorption studies of piroxicam in the rabbit after transdermal administration of different types of dosages of the drug.

• Progress in Medical Physics
• /
• v.30 no.4
• /
• pp.128-138
• /
• 2019

Purpose: Segmental analysis of volumetric modulated arc therapy (VMAT) is not clinically used for compositional error source evaluation. Instead, dose verification is routinely used for plan-specific quality assurance (QA). While this approach identifies the resultant error, it does not specify which machine parameter was responsible for the error. In this research study, we adopted an approach for the segmental analysis of VMAT as a part of machine QA of linear accelerator (LINAC). Methods: Two portal dose QA plans were generated for VMAT QA: a) for full arc and b) for the arc, which was segmented in 12 subsegments. We investigated the multileaf collimator (MLC) position and dosimetric accuracy in the full and segmented arc delivery schemes. A MATLAB program was used to calculate the MLC position error from the data in the dynalog file. The Gamma passing rate (GPR) and the measured to planned dose difference (DD) in each pixel of the electronic portal imaging device was the measurement for dosimetric accuracy. The eclipse treatment planning system and a MATLAB program were used to calculate the dosimetric accuracy. Results: The maximum root-mean-square error of the MLC positions were <1 mm. The GPR was within the range of 98%-99.7% and was similar in both types of VMAT delivery. In general, the DD was <5 calibration units in both full arcs. A similar DD distribution was found for continuous arc and segmented arcs sums. Exceedingly high DD were not observed in any of the arc segment delivery schemes. The LINAC performance was acceptable regarding the execution of the VMAT QA plan. Conclusions: The segmental analysis proposed in this study is expected to be useful for the prediction of the delivery of the VMAT in relation to the gantry angle. We thus recommend the use of segmental analysis of VMAT as part of the regular QA.