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

• Journal of radiological science and technology
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• v.33 no.2
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• pp.127-132
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• 2010

The purpose of this study is to measure scattered ray which is occurred except for Z-axis range of the detector in MDCT's iso-center and present the basic data about the standard for reduction of scattered ray. The development of MDCT brings out the enlargement of beam thickness to the patient's Z-axis, which distributes to the increase in exposure dose according to the rise of scattered ray. Also MDCT brings out the increase of scattered ray about 4times more than SDCT. To evaluate scattered ray according to the change of beam thickness on MDCT, we measured scattered ray of MDCT's Z-axis beam thickness by using one 16-slice CTs and two 64-slice CTs. We used the ionization chamber 60ml 2026C as the equipment of measurement. In our results, we found out that the change of scattered ray according to the beam thickness in the same kVp has increase of scattered ray. Secondly we found out the increase of scattered ray according to the increase of kVp. Lastly we found out the decrease of scattered ray according to the increase of the distance from the ionization chamber.

• Journal of Radiation Protection and Research
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• v.35 no.1
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• pp.34-42
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• 2010

With the expanded use of radiation in modern medical practices, the most important issue in regards to efforts to reduce individual exposure dose is quality assurance. Therefore in order to study the present condition of quality assurance, the Gwangju Metropolitan City area was divided into five districts each containing ten hospitals. Four experiments were conducted: a reproducibility experiment for kVp, mA, and examination time (sec) intensity of illumination; half-value layer (HVL) measurement; and beam perpendicularity test matching experiment. The tube voltage reproducibility experiment for all fifty hospitals resulted in a 95.33% passing rate and mA and examination time both resulted in a 77.0% passing rate. The passing rate for intensity of illumination was 86.0% and 52.0% for HVL, which was the lowest passing rate of all four factors. For the beam perpendicularity test matching experiment, generally the central flux is matched to within $1.5^{\circ}$. Of all fifty hospitals 30.0% were beyond $3^{\circ}$. The results of the survey showed that 58% responded that they knew about quality assurance cycle. All fifty respondents stated that they have not received any training in regards to quality assurance at their current place of employment. Although quality assurance is making relative progress, the most urgent issue is awareness of the importance of quality assurance. Therefore, the implementation of professional training focusing on safety management and accurate quality assurance of radiation will reduce the exposure to radiation for radiologists and patients and higher quality imaging using less dosage will also be possible.

• Journal of Chest Surgery
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• v.38 no.6 s.251
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• pp.410-414
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• 2005

There are several options for choosing a graft in CABG, we routinely chose LIMA for LAD and great saphenous vein for other target vessels. To evaluate the posoperative graft patency, we have studied the results using a 16 slices multi-detector computed tomography. Material and Method: From 1995 to 2003, 80 CABG patients who did not complain any event of MACE have been examined by 16-MDCT, mostly in an out patient clinic. Result: There were 61 men and 19 women. MDCT was used as early as 7 days to 9 years post-operatively with a median follow-up period of 6.5 years, and mean follow-up peiod of $31.5\pm25.4$ months. Mean age was $58.4\pm12.6$ years old in men and $61.5\pm17.2$ years old in women. 72180 patients received LIMA to LAD, and all other patients received vein grafts for bypass. The target vessel of vein grafts were 8 in LAD, 47 in RCA, 60 in diagonals, and 61 in obtuse marginals. Among them 42 sequential anastomoses were performed. The mean graft number was $3.1\pm1.8$ grafts. 5 year graft patency rate of each grafts was as followings; $93.1\%$ in LIMA to LAD, $94.9\%$ in vein to diagonals, $92.1\%$ in vein to obtuse marginals, and $79.2\%$ in vein to RCA. Sequential grafting showed better graft patency than the isolated grafting $(95.2\%\;vs\;78.7\~95.0\%)$. Conclusion: In this study, CABG with LIMA and saphenous veins showed satisfactory longterm results. 16-MDCT provided good images for follow-up study after CABG. Additionally, as radiologic tools (64-MDCT, MRI) improve more in the future, they can be used for diagnosing preoperative anatomical coronary disease as well as cardiac functions.

• Journal of the Korean Society of Radiology
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• v.7 no.4
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• pp.285-291
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• 2013

In this study, compare and analyze the dose distribution and availability of radiation therapy when using a different devices to TNI(Total Lymphnodal Irradiation). Test subjects(patients) are 15 people(Male 7, Female 8). Acquire CT Simulation images of the 15 people using Somatom Sansation Open 16 channel and then acquired images was transferred to each treatment planning system Pinnacle Ver 8.0 and Tomotherapy Planning System and separate the tumor tissue and normal tissues(whole lung, spinal cord, Rt kidney, Lt kidney). Tumor prescription dose was set to 750 cGy. and then Compare the Dose Compatibility, Normal Tissue's Absorbed Dose, Dose Distribution and DVH. Statistical analysis was performed SPSS Ver. 18.0 by paired sample Assay. The absorbed dose in the tumor tissue was $751.0{\pm}4.7cGy$ in tomotherapy planning, $746.9{\pm}14.1cGy$ in linac. Tomotherapy's absorbed dose in the tumor was more appropriate than linac. and These values are not statistically significant(p>0.05). Tomotherapy plan's absorbed dose in the normal tissues were less than linac's plan. This value was statistically significant(p<0.05) excepted of whole lung. In DVH, appropriated on tumor and normal tissues in tomotherapy and linac but tomotherapy's TER was better than linac. Namely, a result of Absorbed dose in tumor and normal tissue, Dose distribution pattern, DVH, Both radiation therapy devices were appropriated in radiation therapy on TER. The Linac has a short treatment time(about 15-20 min) and open space on treatment time. It cause infant and pediatric patients to receiving uncomfortable treatment. So, In this case, it will be fine that Linac based therapy was restricted use. and if the patient was cooperative, it will be show a better prognosis that Tomotherapy using Radiation Therapy.

• Journal of radiological science and technology
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• v.33 no.2
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• pp.109-120
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• 2010

The purpose of this study was first to analyze the utilization of dental examination through questionnaire to develop a diagnostic reference level of patient doses for dental radiography in korea. 77 dental institutions were classified into three groups: A group for the dental hospitals of the college of dentistry (11 institutions), B group for dental hospitals (30 institutions) and C group for dental clinics (36 institutions). The results were as follows : The mean numbers of unit chairs and medical staffs were 140.2, 15.3 and 5.8 sets, 112.6, 7.3 and 1.7 dentists, 3.1, 0.5 and no one radiologic technologists, and 19.7, 12.5 and 3.3 dental hygienists in A, B and C groups, respectively. The mean numbers of dental X-ray equipments were 14.64, 3.21 and 2.19 in A, B and C groups, respectively. Intraoral dental X-ray unit was used the most, the following equipments were panoramic, cephalometric, and cone-beam CT units. The most used X-ray imaging system was also digital system (above 50%) in all three groups. Insight dental film (Kodak, USA) having high sensitivity was routinely used for periapical radiography. The automatic processor was not used in many dental institutions, but the film-holding device was used in many dental institutions. The utilization rates of PACS in A, B and C groups were 90.9%, 83.3% and 16.7% respectively, and the PACS software program was used the most PiView STAR (Infinitt, Korea). The annual mean number of radiographic cases in one dental institution in 2008 for A group was 6.8 times and 21.2 times more than those for B and C groups, and periapical and panoramic radiographs were taken mostly. Tube voltage (kVp) and tube current (mA) for periapical radiography were similar in all three groups, but exposure time in C group was 12.0 times and 3.5 times longer than those in B and C groups. The amount of radiation exposure in C group, in which dental hygienists take dental radiographs, was more than those in other groups. The exposure parameters for panoramic radiography were similar in all three groups. In conclusion, the exposure parameters in dental radiography should be determined with reference level, not past experiences. Use of automatic processor and film-holding devices reduces the radiation exposure in film system. The quality assurance of dental equipments are necessary for the reduction of the patient dose and the improvement of X-ray image quality.