• Progress in Medical Physics
• /
• v.23 no.4
• /
• pp.292-302
• /
• 2012

The patient dose in advanced radiotherapy techniques is an important issue. These methods should be evaluated to reduce the dose in diagnostic imaging for radiotherapy. Especially, the Computed Tomography in radiotherapy has been used widely; hence the CT was evaluated for dose and image in this study. The evaluations for dose and image were done in equal condition due to compare the dose and image simultaneously. Furthermore, the possibility of dose and image evaluations by using the Monte Carlo simulation MCNPX was confirmed. We made the iterative reconstruction for low dose CT image to elevate image quality with Maximum Likelihood Expectation Maximization; MLEM. The system we developed is expected to be used not only to reduce the patient dose in radiotherapy, also to evaluate the overall factors of image modalities in industrial research.

• The Journal of the Korea Contents Association
• /
• v.13 no.9
• /
• pp.288-294
• /
• 2013

Chest digital tomosynthesis was the most advanced digital radiography technology, but it was higher patient dose than conventional chest radiography. Thus we tried to reduce a patient dose of chest digital tomosynthesis and evaluated its image quality. Result shows that radiation dose such as ESD, DAP and ED were 1.95 mGy, 17.66 $dGycm^2$ and 0.133 mSv respectively in default setting and 0.312 mGy, 2.27 $dGy.cm^2$ and 0.052 mSv in use additional filter, respectively. Doses were decrease 66.2%, 73.6% and 57.4% in ESD, DAP and ED, respectively. At the image quality assessment, overall sensitivities of use additional filter for nodule detection were not inferior to default mode for peripheral, central and peripheral micro nodules. However, sensitivity of low dose mode was significantly inferior to the default for central micro-nodules(p < .001).

• Progress in Medical Physics
• /
• v.12 no.2
• /
• pp.161-169
• /
• 2001

For the head and neck radiotherapy, the technique of half beam using independent collimator is very useful to avoid overlapping of fields particularly when the lateral neck fields are placed adjacent to anterior supraclavicular field. Also abutting photon field with electron field is frequently used for the irradiation of posterior neck when tolerable dose on spinal cord has been reached. Using 6 MV X-ray and 9 MeV electron beams of Clinac1800(Varian, USA) linear accelerator, we performed film dosimetry by the X-OMAT V film of Kodak in solid water phantom and the dose distribution at beam center of 2 half beams further examined according to depths(0 cm, 1.5 cm, 3 cm, 5 cm) for single anterior half beam and anterior/posterior half beam. The dose distribution to the junction line between photon and electron fields was also measured. For the single anterior half beam, the absorption doses at 0.3 cm, 0.5 cm and 1 cm distances from beam center were 88%, 93% and 95% of open beam, respectively. In the anterior/posterior half beams, the absorption doses at 0.3 cm, 0.5 cm and 1 cm distances from beam center were 92%, 93% and 95% of open beam, respectively At the junction line between photon and electron fields, hot spot was developed on the side of the photon field and a cold spot was developed on that of the electron field. The hot spot in the photon side was developed at depth 1.5 cm with 7 mm width. The maximum dose of hot spot was increased to 6% of reference doses in the photon field. The cold spot in the electron side was developed at all measured depths(0.5 cm-3 cm) with 1-12.5 mm widths. The decreased dose in the cold spot was 4.5-30% of reference dose in the electron field. With above results, we concluded that when using electron beam or independent jaw for head and neck radiotherapy, the hot and cold dose area should be considered as critical point.

• The Journal of Korean Society for Radiation Therapy
• /
• v.19 no.2
• /
• pp.77-82
• /
• 2007

Purpose: This study investigates peripheral dose from physical wedge and dynamic wedge system on a multileaf collimator (MLC) equipment linear accelerator. Materials and Methods: Measurments were performed using a 2D array ion chamber and solid water phantom for a 10$\times$10 cm, source-surface distance (SSD) 90 cm, 6 and 15 MV photon beam at depths of 0.5 cm, 5 cm through dmax. Measurments of peripheral dose at 0.5 cm and 5 cm depths were performed from 1 cm to 5 cm outside of fields for the dynamic wedge and physical wedge 15$^\circ$, 45$^\circ$. Dose profiles normalized to dose at the maximum depth. Results: At 6 MV photon beam, the average peripheral dose of dynamic wedge were lower by 1.4% and 0.1%. At 15 MV photon beam, the peripheral dose of dynamic wedge were lower by maximum 1.6%. Conclusion: This study showed that dynamic wedge can reduce scattered dose of clinical organ close to the field edge and reduced treatment time. The wedge systems produce significantly different peripheral dose that should be considered in properly choosing a wedge system for clinical use.

• Journal of radiological science and technology
• /
• v.32 no.2
• /
• pp.129-140
• /
• 2009

As CT has been increasingly used as an accurate screening tool for lung disease, radiation dose becomes an important issue for both radiographers and patients. Many researches have been done for a low-dose CT as a screening tool for early detection of asymptomatic lung diseases. From those studies, it has been reported that chest dose rate from the low-dose CT is considerably lower than from standard CT. The patient dose is determined by scanning parameters such as kVp, mAs, pitch, scan time and the radiation risk of lung in screening examination may not be negligible. Herein, we suggest that Low-dose CT is useful as a screening tool in routine clinical practice on the basis of published articles, but further study is necessary because Low-dose CT has poor sensitivity and specificity for screening early stage of lung cancer according to the results of the studies. This article is to provide a brief overview of the screening examinations by Low-dose CT.

• Journal of radiological science and technology
• /
• v.37 no.3
• /
• pp.195-201
• /
• 2014

The study examined the changes in the decreased facial exposure dose for radiological technologists depending on increased distance between the workers and the X-ray tube head during intraoral radiography. First, the facial phantom similar to the human tissues was manufactured. The shooting examination was configured to the maxillary molars for adults (60kVp, 10mA, 50msec) and for children (60kVp, 10mA, 20msec), and the chamber was fixed where the facial part of the radiation worker would be placed using the intraoral radiography equipment. The distances between the X-ray tube head and the phantom were set to 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, and 40cm. The phantom was radiated 20 times with each examination condition and the average scattered doses were examined. The rate at the distance of 40cm decreased by about 92.6% to 7.43% based on the scattered rays radiated at the distance of 10cm under the adult conditions. The rate at the distance of 40cm decreased by about 97.6% to 2.58% based on the scattered rays radiated at the distance of 10cm under the children conditions. Protection from the radiation exposure was required during the dental radiographic examination.

• Journal of Radiation Protection and Research
• /
• v.40 no.4
• /
• pp.244-251
• /
• 2015

The containment filtered venting system reduces the range of the contamination area around the nuclear power plant by strengthening the integrity of the containment building. In this study, the probabilistic assessment code MACCS2 was used to assess the effect of the CFVS to off-site. The accident source term was selected from a Probabilistic Safety Analysis report of SHINKORI 1&2 Nuclear Power Plant. The three source term categories from 19 STC were chosen to evaluate the effective dose and thyroid dose of residents around the power plant and the dose with CFVS and without CFVS were compared. The dose was calculated according to the distance from the nuclear power plant, so the damage scale based on the distance that exceeds the IAEA criteria for effective dose (100 mSv per 7 days) and thyroid dose (50 mSv per 7 days) were compared. The effective dose reduction rates of the STC-3, STC-4, STC-6 were about 95-99% in the whole range (0~35 km), 96-98% for the thyroid dose. There are similar results between effective dose and thyroid dose. After applying the CFVS, the damage scale that exceeds the effective dose criteria was about 1 km (mean). Especially, the STC-4 damage scale was decreased from 26 km (mean) to 1.2 km (mean) significantly. The damage scale that exceed the thyroid dose criteria was decreased to 2~3 km (mean). The STC-4 damage scale was also decreased significantly as compared to STC-3, STC-6 in terms of effective dose.

• Food Science and Preservation
• /
• v.8 no.1
• /
• pp.9-15
• /
• 2001

The effects of water soaking and gamma irradiation on the storage quality of chestnuts (Castanea crenata) were investigated. Chestnuts weirs soaked in water for 48 hrs at room temperature, irradiated at 0, 0.15, 0.25 and 0.35 kGy of $\^$60/Co gamma ray, and then stored at 0$\^{C}$ and 95$\pm$2% RH for 9 months. Spouting was observed at the end of storage only in chestnuts that were soaked and irradiated at below 0.25 kGy. Rotting was found from the early stage of storage in all pre-treatment conditions, but the rotting rate of soaked chestnuts was higher twice than unsoaked ones after 9 months of storage. Weight loss was lower in soaked than unseated samples regardless of irradiation dose. Loss of flesh firmness was appreciably retarded as irradiation dose increased. Total sugar content decreased slowly in irradiated samples at the later periods of storage. Gamma irradiation resulted in the decrease of vitamin C content immediately after treatment, but retarded its loss rate during storage. Soluble tannin content was not affected by gamma irradiation at scout inhibition doses.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
• /
• 2004.05a
• /
• pp.194-197
• /
• 2004

양념갈비의 품질 안정성 및 저장성 확보를 위한 일환으로 시판되는 양념갈비에 감마선 조사(0, 2.5, 5, 7.5 kGy)하여 포장 방법(함기 vs 진공) 및 저장 기간에 따른 양념갈비의 총균수, pH, 수분활성도, 전자공여능 및 지방산패도를 측정하였다. 감마선 조사한 양념갈비의 미생물 생육은 조사선량이 증가할수록 저하되었고 포장방법별로는 함기포장구보다 진공포장구가 미생물 생장억제에 더욱 효과적임을 확인하였다. pH는 함기포장구에서 저장 7일째 다소 감소하는 경향을 보였으나 포장방법과 조사선량에 따른 유의차가 나타나지 않았다. 감마선 조사한 양념갈비의 전자공여능은 저장기간에 따라 감소하는 경향을 보였으나 그 감소폭은 함기포장구가 진공포장구보다 크게 나타났다. TBARS값은 진공포장구의 경우 감마선 조사선량과 저장기간에 따라 유의적인 차이는 없었다. 그러나 함기포장구는 조사선량이 증가할수록 그리고 저장기간에 따라 유의적으로 증가하여 저장 7일째 진공포장구보다 2배의 높은 값을 나타내었다. 따라서 시판되는 양념갈비의 저장 중 유통 안전성을 확보하기 위한 감마선 조사의 사용에서 품질을 유지하기 위해서는 진공포장으로 유통하는 것이 바람직하다고 판단된다.

• Journal of the Korean Society of Radiology
• /
• v.11 no.1
• /
• pp.63-68
• /
• 2017

To reduce the exposure dose in head CT, the use of low tube voltage is required. However, increasing noise may cause errors in the second data processing. In this study, we proposed a method to reduce noise by using low tube voltage. Experimental results show that the noise level is high at 100kVp and lowest at 140 kVp. The dose was lower at 100 kVp and higher at 140 kVp. As a result of applying the wavelet according to the threshold value, the noise value in the wavelet Th30 decreased to 4.51. Using the parameter condition(100 kVp, rotation time 0.5 sec, dose: 40.64 mGy) and the wavelet Th 30, the dose reduction of 65.3% was possible. We believe that applying the proposed method to head CT images will help to patient safety and interpret accurate information.