• Progress in Medical Physics
• /
• v.24 no.2
• /
• pp.85-91
• /
• 2013

At present, megavoltage computed tomography (MVCT) is the only method used to correct the position of tomotherapy patients. MVCT produces extra radiation, in addition to the radiation used for treatment, and repositioning also takes up much of the total treatment time. To address these issues, we suggest the use of a video image-guided setup (VIGS) system for correcting the position of tomotherapy patients. We developed an in-house program to correct the exact position of patients using two orthogonal images obtained from two video cameras installed at $90^{\circ}$ and fastened inside the tomotherapy gantry. The system is programmed to make automatic registration possible with the use of edge detection of the user-defined region of interest (ROI). A head-and-neck patient is then simulated using a humanoid phantom. After taking the computed tomography (CT) image, tomotherapy planning is performed. To mimic a clinical treatment course, we used an immobilization device to position the phantom on the tomotherapy couch and, using MVCT, corrected its position to match the one captured when the treatment was planned. Video images of the corrected position were used as reference images for the VIGS system. First, the position was repeatedly corrected 10 times using MVCT, and based on the saved reference video image, the patient position was then corrected 10 times using the VIGS method. Thereafter, the results of the two correction methods were compared. The results demonstrated that patient positioning using a video-imaging method ($41.7{\pm}11.2$ seconds) significantly reduces the overall time of the MVCT method ($420{\pm}6$ seconds) (p<0.05). However, there was no meaningful difference in accuracy between the two methods (x=0.11 mm, y=0.27 mm, z=0.58 mm, p>0.05). Because VIGS provides a more accurate result and reduces the required time, compared with the MVCT method, it is expected to manage the overall tomotherapy treatment process more efficiently.

• Progress in Medical Physics
• /
• v.18 no.3
• /
• pp.118-125
• /
• 2007

In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of $315^{\circ}$) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.

• The Journal of Korean Society for Radiation Therapy
• /
• v.24 no.2
• /
• pp.115-121
• /
• 2012

Purpose: The process of the proton treatment is done by comparing the DRR and DIPS anatomic structure to find the correction factor and use the PPS to use this factor in the treatment. For the accuracy of the patient set up, the PPS uses a 6 axis system to move. Therefore, there needs to be an evaluation for the accuracy between the PPS moving materialization and DIPS correction factor. In order to do this, we will use a self made PPS QA Phantom to measure the accuracy of the PPS. Materials and Methods: We set up a PPS QA Phantom at the center to which a lead marker is attached, which will act instead of the patient anatomic structure. We will use random values to create the 6 axis motions and move the PPS QA Phantom. Then we attain a DIPS image and compare with the DRR image in order to evaluate the accuracy of the correction factor. Results: The average correction factor, after moving the PPS QA Phantom's X, Y, Z axis coordinates together from 1~5 cm, 1 cm at a time, and coming back to the center, are 0.04 cm, 0.026 cm, 0.022 cm, $0.22^{\circ}$, $0.24^{\circ}$, $0^{\circ}$ on the PPS 6 axis. The average correction rate when moving the 6way movement coordinates all from 1 to 2 were 0.06 cm, 0.01 cm, 0.02 cm, $0.1^{\circ}$, $0.3^{\circ}$, $0^{\circ}$ when moved 1 and 0.02 cm, 0.04 cm, 0.01 cm, $0.3^{\circ}$, $0.5^{\circ}$, $0^{\circ}$ when moved 2. Conclusion: After evaluating the correction rates when they come back to the center, we could tell that the Lateral, Longitudinal, Vertical were all in the acceptable scope of 0.5 cm and Rotation, Pitch, Roll were all in the acceptable scope of $1^{\circ}$. Still, for a more accurate proton therapy treatment, we must try to further enhance the image of the DIPS matching system, and exercise regular QA on the equipment to reduce the current rate of mechanical errors.

• Radiation Oncology Journal
• /
• v.26 no.2
• /
• pp.118-125
• /
• 2008

Purpose: On-line image guided radiation therapy(on-line IGRT) and(kV X-ray images or cone beam CT images) were obtained by an on-board imager(OBI) and cone beam CT(CBCT), respectively. The images were then compared with simulated images to evaluate the patient's setup and correct for deviations. The setup deviations between the simulated images(kV or CBCT images), were computed from 2D/2D match or 3D/3D match programs, respectively. We then investigated the correctness of the calculated deviations. Materials and Methods: After the simulation and treatment planning for the RANDO phantom, the phantom was positioned on the treatment table. The phantom setup process was performed with side wall lasers which standardized treatment setup of the phantom with the simulated images, after the establishment of tolerance limits for laser line thickness. After a known translation or rotation angle was applied to the phantom, the kV X-ray images and CBCT images were obtained. Next, 2D/2D match and 3D/3D match with simulation CT images were taken. Lastly, the results were analyzed for accuracy of positional correction. Results: In the case of the 2D/2D match using kV X-ray and simulation images, a setup correction within $0.06^{\circ}$ for rotation only, 1.8 mm for translation only, and 2.1 mm and $0.3^{\circ}$ for both rotation and translation, respectively, was possible. As for the 3D/3D match using CBCT images, a correction within $0.03^{\circ}$ for rotation only, 0.16 mm for translation only, and 1.5 mm for translation and $0.0^{\circ}$ for rotation, respectively, was possible. Conclusion: The use of OBI or CBCT for the on-line IGRT provides the ability to exactly reproduce the simulated images in the setup of a patient in the treatment room. The fast detection and correction of a patient's positional error is possible in two dimensions via kV X-ray images from OBI and in three dimensions via CBCT with a higher accuracy. Consequently, the on-line IGRT represents a promising and reliable treatment procedure.

• Progress in Medical Physics
• /
• v.19 no.1
• /
• pp.9-13
• /
• 2008

The purpose of this study was to measure the skin dose using the glass dosimeter and diode and to compare those measurements to the planned skin dose from the treatment planning system. For the reproducibility of the glass dosimeter (ASAHI TECHNO GLASS CIRPORATION, Japan), the same dose was irradiated to 40 glass dosimeters three times, among which 28 with the reproducibility within 3% were selected for the use of this study. For each of 27 breast cancer patients, the glass dosimeters and diodes were attached to 4 different locations on the skin to measure the dose during treatment. All the patients received one fraction of 180 cGy each. The maximum difference of measurements between the glass dosimeter and diode at the same location was 3.2%. Comparing with the planned skin dose from the treatment planning system (Eclipse v6.5, Varian, USA), the dose measured by the glass dosimeter and the diodeshowed on an average 3.4% and 2.3% difference, respectively. The measured doses were always less than the planned skin dose. This may be due to the specific errors of both detectors. Also, the difference may be caused by the fact that since the skin where the detectors were attached is pretty moveable, it was not fix the detectors on the skin.

• Journal of radiological science and technology
• /
• v.40 no.1
• /
• pp.57-62
• /
• 2017

The purpose of this study is to reconstruct the treatment plan by applying CBCT and DIR to dose changes according to the change of the patient's motion and breast shape in the large breast cancer patients and to compare the doses using TWF, FIF and IMRT. CT and CBCT were performed with MIM6 to create DIRCT and each treatment plan was made. The patient underwent computed tomography simulation in both prone and supine position. The homogeneity index (HI), conformity index (CI), coverage index (CVI) to the left breast as planning target volume (PTV) were determined and the doses to the lung, heart, and right breast as organ at risk (OAR) were compared by using dose-volume histogram and the unique property of each organ. The value of HI of the PTV breast increased in all treatment planning methods using DIRCT, and CVI and CI were decreased in the treatment planning methods using DIRCT.

• Journal of Aerospace System Engineering
• /
• v.16 no.1
• /
• pp.97-103
• /
• 2022

An aircraft component can only be mounted on an aircraft if it has been certified to have a structural robustness under flight load conditions. Among the major components of the aircraft, a pylon is a structure that connects external equipment such as an engine, and external attachments with the main wing of an aircraft and transmits the loads acting on it to the main structure of the aircraft. In civil aircraft, when there is an incident of fire in the engine area, the pylon prevents the fire from spreading to the wings. This study presents the results of structural static tests performed to verify the structural robustness of a fuel pylon used to mount external fuel tank in an aircraft. In the main text, we present the test set-up diagram consisting of test fixture, hydraulic pressure unit, load control system, and data acquisition equipment used in the structure static test of the fuel pylon. In addition, we introduce the software that controls the load actuator, and provide a test profile for each test load condition. As a result of the structural static test, it was found that the load actuator was properly controlled within the allowable error range in each test, and the reliability of the numerical analysis was verified by comparing the numerical analysis results and the strain obtained from the structural test at the main positions of the test specimen. In conclusion, it was proved that the fuel pylon covered in this study has sufficient structural strength for the required load conditions through structural static tests.

• The Journal of Korean Society for Radiation Therapy
• /
• v.24 no.2
• /
• pp.189-196
• /
• 2012

Purpose: The sufficiency of skin dose and the reemergence of patient set-up position to the success of skin cancer radiation treatment is a very important element. But the conventional methods to increase the skin dose were used to vacuum cushion, bolus and water tank have several weak points. For this reason, we producted Foxtail Millet Vacuum Cushion and evaluated the efficiency of the Foxtail Millet Vacuum Cushion in skin cancer Radiation treatment. Materials and Methods: We measured absolute dose for 3 materials (Foxtail Millet Vacuum Cushion, bolus and solid water phantom) and compared each dose distribution. We irradiated 6 MV 100 MU photon radiation to every material of 1 cm, 2 cm, 3 cm thickness at three times. We measured absolute dose and compared dose distribution. Finally we inspected the CT simulation and radiation therapy planing using the Foxtail Millet Vacuum Cushion. Results: Absolute dose of Foxtail Millet Vacuum Cushion was similar to absolute dose of bolus and solid water phantom's result in each thickness. it Showed only the difference of 0.1~0.2% between each material. Also the same result in dose distribution comparison. About 97% of the dose distribution was within the margin of error in the prescribed ranges ($100{\pm}3%$), and achieved the enough skin dose (Gross Tumor Volume dose : $100{\pm}5%$) in radiation therapy planing. Conclusion: We evaluated important fact that Foxtail Millet Vacuum Cushion is no shortage of time to replace the soft tissue equivalent material and normal vacuum cushion at the low energy radiation transmittance. Foxtail Millet Vacuum Cushion can simultaneously achieve the enough skin dose in radiation therapy planing with maintaining normal vacuum cushion' function. Therefore as above We think that Foxtail Millet Vacuum Cushion is very useful in skin cancer radiation treatment.

• 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.

• The Journal of Korean Society for Radiation Therapy
• /
• v.25 no.1
• /
• pp.57-67
• /
• 2013

Purpose: Replacing the film which used to be used for checking the set-up of the patient and dosimetry during radiation therapy, more and more EPID equipped devices are in use at present. Accordingly, this article tried to evaluated the accuracy of the position check-up and the usefulness of dosimetry during the use of an electronic portal imaging device. Materials and Methods: On 50 materials acquired with the search of Korea Society Radiotherapeutic Technology, The Korean Society for Radiation Oncology, and Pubmed using "EPID", "Portal dosimetry", "Portal image", "Dose verification", "Quality control", "Cine mode", "Quality - assurance", and "In vivo dosimetry" as indexes, the usefulness of EPID was analyzed by classifying them as history of EPID and dosimetry, set-up verification and characteristics of EPID. Results: EPID is developed from the first generation of Liquid-filled ionization chamber, through the second generation of Camera-based fluoroscopy, and to the third generation of Amorphous-silicon EPID imaging modes can be divided into EPID mode, Cine mode and Integrated mode. When evaluating absolute dose accuracy of films and EPID, it was found that EPID showed within 1% and EDR2 film showed within 3% errors. It was confirmed that EPID is better in error measurement accuracy than film. When gamma analyzing the dose distribution of the base exposure plane which was calculated from therapy planning system, and planes calculated by EDR2 film and EPID, both film and EPID showed less than 2% of pixels which exceeded 1 at gamma values (r%>1) with in the thresholds such as 3%/3 mm and 2%/2 mm respectively. For the time needed for full course QA in IMRT to compare loads, EDR2 film recorded approximately 110 minutes, and EPID recorded approximately 55 minutes. Conclusion: EPID could easily replace conventional complicated and troublesome film and ionization chamber which used to be used for dosimetry and set-up verification, and it was proved to be very efficient and accurate dosimetry device in quality assurance of IMRT (intensity modulated radiation therapy). As cine mode imaging using EPID allows locating tumors in real-time without additional dose in lung and liver which are mobile according to movements of diaphragm and in rectal cancer patients who have unstable position, it may help to implement the most optimal radiotherapy for patients.