• Journal of radiological science and technology
• /
• v.45 no.5
• /
• pp.439-448
• /
• 2022

The purpose of this study was to analyze the results from statistical process control (SPC) to recommend upper and lower control limits for planning parameters based on delivery quality assurance (DQA) results and establish our institutional guidelines regarding planning parameters for helical tomotherapy (HT). A total of 53 brain, 41 head and neck (H & N), and 51 pelvis cases who had passing or failing DQA measurements were selected. The absolute point dose difference (DD) and the global gamma passing rate (GPR) for all patients were analyzed. Control charts were used to evaluate upper and lower control limits (UCL and LCL) for all assessed treatment planning parameters. Treatment planning parameters were analyzed to provide its range for DQA pass cases. We confirmed that the probability of DQA failure was higher when the proportion of leaf open time (LOT) below 100 ms was greater than 30%. LOT and gantry period (GP) were significant predictor for DQA failure using the SPC method. We investigated the availability of the SPC statistic method to establish the local planning guideline based on DQA results for HT system. The guideline of each planning parameter in HT may assist in the prediction of DQA failure using the SPC statistic method in the future.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.41 no.6
• /
• pp.61-66
• /
• 2004

To make a guide line of property control of angiography equipments, we made standard evaluation sheet forms of facility and management of angiography suite, physical properties of angiography equipments, and image quality of film and then surveyed them at 29 hospital nationwide. Survey and development of standard evaluation sheet form of physical properties of angiography equipments. By using resolution & radiation dose, physical properties of angiography equipments of 49 in number nationwide were evaluated. Most of them (91%) had good performance.

• Progress in Medical Physics
• /
• v.21 no.1
• /
• pp.99-112
• /
• 2010

In Republic of Korea, there are many Quality Assurance protocol for general radiation treatment machine such as linac. However, Quality Assurance protocol for radiosurgery treatment system is not ready perfectly. One of the radiation treatment machine for radiosurgery, novalis system needs to suitable Quality Assurance protocol for using it right way during radiation treatment and maintaining suitable accuracy for daily, weekly, monthly and annually periods. Therefore, in this article, we develop Quality Assurance protocol for novalis system. We collected and analysed domestic and foreign novalis Quality Assurance protocol. After that, we selected essential QA items and each tolerance range for developing proper QA protocol, and we made anatomical phantom for execution of selected QA items and evaluation of overall state of QA, and then, we use this measured value as a reference. Quality Assurance items are consisted of Mechanical accuracy QA part and Radiation delivery QA part. Mechanical accuracy QA part is comprised of radiation generation machine part, assistive devices part and multi-leaf collimator part. Radiation delivery QA part is divided into radiation isocenter accuracy and dosimetric evaluation. After that, developed novalis QA tables are made by using these QA items. These novalis QA tables would be used to good standard in order to maintain apt accuracy for radiosurgery in daily, weekly, monthly and annually periods.

• Journal of Radiation Protection and Research
• /
• v.38 no.1
• /
• pp.29-36
• /
• 2013

The aim of this study was to determine the correlation between exposure index (EI) and dose factors related to radiation dose optimization in digital radiography (DR) system. Two phantoms with built-in regional test object for quantitative assessment of images were used to produce image signals that acquired in chest radiography background. EI and entrane surface dose (ESD) increased proportionally with rise of radiation dose (kVp, mAs) in both DR and CR systems. Especially, DR detector was effective to form good contrast and hence, reached easily to improvement of image quality with minimal dose changes. It made operators possible to expect the accuracy of EI values deeply related to absorbed dose of the detector. The evaluation of images was obtained specially employed calculation of noise to signal ratio (NSR) and contrast to noise ratio (CNR). These measurements were performed for how exposure factors affect image quality. NSR was inversely proportional to kVp and mAs and low NSR represented high signal detection efficiency. Consequently, EI values was the measure of the amount of exposure received by the image receptor and it was proportional to exposure factors. Therefore the EI in a recommended range from manufacturer can offer optimal image quality. Also, continuous monitoring of EI values in the digital radiography can reduce the unnecessary patient dose and help the quality control of the system.

• Korean Journal of Food Science and Technology
• /
• v.36 no.5
• /
• pp.711-716
• /
• 2004

Gamma irradiation was applied to dried pollack to improve its microbiological quality and evaluate quality stability of irradiated samples. Thermoluminescence (TL) properties of minerals separated from irradiated samples were measured for possible use in identifying irradiation treatment. Dried pollack was packaged in commercial unit (PVC film, 0.06 mm thickness) and stored at $15{\pm}1^{\circ}C$ for 6 months. Samples showed over $10^4\;CFU/g$ in total aerobic bacteria or yeasts&molds, which increased during storage, reaching $10^6-10^7\;CFU/g$ at 3rd month of storage. Irradiation at 3 kGy was effective for improving hygienic quality for 6 months, keeping microbial population under 20 CFU/g. Gamma irradiation at 3 kGy or less did not significantly influence physicochemical quality attributes, such as browning, TBA value, volatile basic nitrogen, trimethylamine, and sensory properties, whereas storage time remarkably induced quality changes of dried pollack. TL analysis was proved suitable for identifying irradiated from non-irradiated samples over 6 months of storage.

• Progress in Medical Physics
• /
• v.26 no.4
• /
• pp.241-249
• /
• 2015

As radiation therapy is one of three major cancer treatment methods, many cancer patients get radiation therapy. To exposure as much radiation to cancer while normal tissues near tumor get little radiation, medical physicists make a radiotherapy plan treatment and perform quality assurance before patient treatment. Despite these efforts, unintended medical accidents can occur by some errors. In order to solve the problem, patient internal dose reconstruction methods by measuring transit dose are suggested. As feasibility study for development of patient dose verification system, inverse square law, percentage depth dose and scatter factor are used to calculate dose in the water-equivalent homogeneous phantom. As a calibration results of ionization chamber and glass dosimeter to transit radiation, signals of glass dosimeter are 0.824 times at 6 MV and 0.736 times at 10 MV compared to dose measured by ionization chamber. Average scatter factor is 1.4 and Mayneord F factor was used to apply percentage depth dose data. When we verified the algorithm using the water-equivalent homogeneous phantom, maximum error was 1.65%.

• The Journal of Korean Society for Radiation Therapy
• /
• v.20 no.1
• /
• pp.17-23
• /
• 2008

Purpose: Cone-beam CT using linear accelerator attached to on-board imager is a image guided therapy equipment. Because it is to check the patient's set-up error, correction, organ and target movement. but imaging dose should be cause of the secondary cancer when taking a image. The aim of this study is investigation of appropriate cone beam CT scan mode to compare and estimate the image quality and skin dose. Materials and Methods: Measurement by Thermoluminescence dosimeter (TLD-100, Harshaw) with using the Rando phantom are placed on each eight sites in seperately H&N, thoracic, abdominal section. each 4 methods of scan modes of are measured the for skin dose in three time. Subsequently, obtained average value. Following image quality QA protocol of equipment manufacturers using the catphan 504 phantom, image quality of each scan mode is compared and analyzed. Results: The results of the measured skin dose are described in here. The skin dose of Head & Neck are measured mode A: 8.96 cGy, mode B: 4.59 cGy, mode C: 3.46 cGy mode D: 1.76 cGy and thoracic mode A: 9.42 cGy, mode B: 4.58 cGy, mode C: 3.65 cGy, mode D: 1.85 cGy, and abdominal mode A: 9.97 cGy, mode B: 5.12 cGy, mode C: 4.03 cGy, mode D: 2.21 cGy. Approximately, dose of mode B are reduced 50%, mode C are reduced 60%, mode D are reduced 80% a point of reference dose of mode A. the results of analyzed HU reproducibility, low contrast resolution, spatial resolution (high contrast resolution), HU uniformity in evaluation item of image quality are within the tolerance value by recommended equipment manufacturer in all scan mode. Conclusion: Maintaining the image quality as well as reducing the image dose are very important in cone beam CT. In the result of this study, we are considered when to take mode A when interested in soft tissue. And we are considered to take mode D when interested in bone scan and we are considered to take mode B, C when standard scan. Increasing secondary cancer risk due to cone beam CT scan should be reduced by low mAs technique.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.2
• /
• pp.247-254
• /
• 2016

This study evaluated the effects of low-dose X-ray irradiation treatment on quality characteristics and sensory evaluation of imported navel oranges during storage at $3^{\circ}C$ for 45 days. The samples were irradiated at doses of 0.2, 0.4, 0.6, 0.8, and 1.0 kGy, and changes in their color value, hardness, Brix/acid ratio, total sugar content, reducing sugar content, vitamin C contents, and sensory evaluation were investigated. There was no significant increase or decrease in Brix/acid ratio, total sugar content, reducing sugar content, or vitamin C content between the non-irradiated and irradiated samples. Color value of orange peels decreased with increasing levels of irradiation treatment. Color b value of orange pulp increased with an increase in irradiation dose. Difference in hardness between the non-irradiated and irradiated samples decreased at the end of storage. For the sensory evaluation after 30 days, sweetness and overall acceptability of irradiated samples at more than 0.6 kGy were low. These results suggest that X-ray irradiation under 0.6 kGy does not affect quality characteristics and sensory evaluation.

• Radiation Oncology Journal
• /
• v.25 no.4
• /
• pp.249-260
• /
• 2007

Purpose: In order to enhance the quality of IMRT as employed in Korea, we developed a remote monitoring system. The feasibility of the system was evaluated by conducting a pilot study. Materials and Methods: The remote monitoring system consisted of a head and neck phantom and a user manual. The phantom contains a target and three OARs (organs at risk) that can be detected on CT images. TLD capsules were inserted at the center of the target and at the OARs. Two film slits for GafchromicEBT film were located on the axial and saggital planes. The user manual contained an IMRT planning guide and instructions for IMRT planning and the delivery process. After the manual and phantom were sent to four institutions, IMRT was planed and delivered. Predicted doses were compared with measured doses. Dose distribution along the two straight lines that intersected at the center of the axial film was measured and compared with the profiles predicted by the plan. Results: The measurements at the target agreed with the predicted dose within a 3% deviation. Doses at the OARs that represented the thyroid glands showed larger deviations (minimum 3.3% and maximum 19.8%). The deviation at OARs that represented the spiral cord was $0.7{\sim}1.4%$. The percentage of dose distributions that showed more than a 5% of deviation on the lines was $7{\sim}27%$ and $7{\sim}14%$ along the horizontal and vertical lines, respectively. Conculsion: Remote monitoring of IMRT using the developed system was feasible. With remote monitoring, the deviation at the target is expected to be small while the deviation at the OARs can be very large. Therefore, a method that is able to investigate the cause of a large deviation needs to be developed. In addition, a more clinically relevant measure for the two-dimensional dose comparison and pass/fail criteria need to be further developed.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2004.11a
• /
• pp.33-35
• /
• 2004

방사선치료를 위한 고에너지 광자선의 품질관리를 위해 사용하는 TLD의 광자선 선질에 대한 에너지 의존도를 몬테카를로 모사법을 사용하여 평가하였다. IAEA 선량보증사업에 이용되는 LiF TLD 및 홀더를 EGS4기반의 사용자 코드인 DOSIMETER 와 MCNP4C 몬테카를로 코드를 사용하여 기하학구조를 구성하고, Co, 4, 6,10 밑 15 MV 광자선을 시뮬레이션하였다. DOSIMETER계산 결과를 통해 TLD의 에너지 보정인자가 실험 데이터와 일치함을 확인할 수 있었으며, 이와 별도로 캡슐에 의한 교란량도 무시할 수 없음을 발견하였다.