• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.199-206
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• 2014

Purpose : According to the rapid increase recently in image-guided radiation therapy, It is necessary to control of the image guidance system completely. In particular for the main subject to the accuracy of image guided radiation therapy device to be done essentially the quality assurance. We made efficient phantom in AMC for the management of the accurate and efficient. Materials and Methods : By setting up of five very important as a quality assurance inventory of the Image guidance system, we made (AMC G-Box) phantom for quality assurance efficient and accurate. Quality assurance list were the Iso-center align, the real measurement, the center align of four direction, the accuracy of table movement and the reproducibility of Hounsfield Unit. The rectangular phantom; acrylic with a thickness of 1 cm to $10cm{\time}10cm{\time}10cm$ was inserted the three materials with different densities respectively for measure the CBCT HU. The phantom was to perform a check of consistency centered by creating a marker that indicates the position of the center fixed. By performing the quality assurance using the phantom of existing, comparing the resulting value to the different resulting value using the AMC G-Box, experiment was analyzed time and problems. Therapy equipment was used Varian device. It was measured twice at 1-week intervals. Results : When implemented quality assurance of an image guidance system using AMC G-Box and a phantom existing has been completed, the quality assurance result is similar in $0.2mm{\pm}0.1$. In the case of the conventional method, it was 45 minutes at 30 minutes. When using AMC G-Box, it takes 20 minutes 15 minutes, and declined to 50% of the time. Conclusion : The consistency and accurate of image guidance system tend to decline using device. Therefore, We need to perform thoroughly on the quality assurance related. It needs to be checked daily to consistency check especially. When using the AMC G-Box, It is possible to enhance the accuracy of the patient care and equipment efficiently performing accurate quality assurance.

• The Journal of the Korea Contents Association
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• v.14 no.9
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• pp.362-370
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• 2014

This study measured and analyzed the correlation coefficient between movements of thoracoabdominal tumors and external respiration in a free-breathing state, using cyberknife image guided radiotherapy(IGRT). This study subjects included a total of 30 patients with lung tumors(n=10), liver tumors(n=10) and pancreatic tumor(n=10) who underwent radiotherapy, and the movements of tumors were analyzed using converted log data of the tumor motion tracking system(MTS). In a free-breathing state, In relation to Peason's correlation coefficient between external respiration and lung tumors in the entire treatment process, the correlation coefficient was 0.646(p<0.05) in the cranio-caudal direction, 0.365(p<0.088) in the left and right direction and 0.196(p<0.115) in the antero-posterior direction. The correlation coefficient of liver tumors was 0.841(p<0.000) in the cranio-caudal direction, 0.346 (p<0.179) in the left and right direction and 0.691(p<0.001) in the antero-posterior direction. The correlation coefficient of Pancreatic tumors was 0.683(p<0.000) in the cranio-caudal direction, 0.397(p<0.006) in the left and right direction and 0.268(p<0.127) in the antero-posterior direction. In conclusion, the measurement findings of thoracoabdominal tumor movement using IGRT would be helpful in determining an accurate target volume. Moreover, the analysis of correlation between external respiration and movements of internal tumors would provide important information to correct movements of tumors for diverse radiotherapy techniques.

• Journal of KIISE
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• v.43 no.3
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• pp.353-361
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• 2016

During image-guided radiation treatment of lung cancer patients, it is necessary to track the tumor motion because it can change during treatment as a consequence of respiratory motion and cardiac motion. In this paper, we propose a method for tracking the motion of the lung tumors based on the three-dimensional image information from planning 4D MDCT and treatment 4D CBCT images. First, to effectively track the tumor motion during treatment, the global motion of the tumor is estimated based on a tumor-specific motion model obtained from planning 4D MDCT images. Second, to increase the accuracy of the tumor motion tracking, the local motion of the tumor is estimated based on the structural information of the tumor from 4D CBCT images. To evaluate the performance of the proposed method, we estimated the tracking results of proposed method using digital phantom. The results show that the tumor localization error of local motion estimation is reduced by 45% as compared with that of global motion estimation.

• Radiation Oncology Journal
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• v.27 no.1
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• pp.42-48
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• 2009

Purpose: The introduction of image guided radiation therapy/four-dimensional radiation therapy (IGRT/4DRT) potentially increases the accumulated dose to patients from imaging and verification processes as compared to conventional practice. It is therefore essential to investigate the level of the imaging dose to patients when IGRT/4DRT devices are installed. The imaging dose level was monitored and was compared with the use of pre-IGRT practice. Materials and Methods: A four-dimensional CT (4DCT) unit (GE, Ultra Light Speed 16), a simulator (Varian Acuity) and Varian IX unit with an on-board imager (OBI) and cone beam CT (CBCT) were installed. The surface doses to a RANDO phantom (The Phantom Laboratory, Salem, NY USA) were measured with the newly installed devices and with pre-existing devices including a single slice CT scanner (GE, Light Speed), a simulator (Varian Ximatron) and L-gram linear accelerator (Varian, 2100C Linac). The surface doses were measured using thermo luminescent dosimeters (TLDs) at eight sites-the brain, eye, thyroid, chest, abdomen, ovary, prostate and pelvis. Results: Compared to imaging with the use of single slice non-gated CT, the use of 4DCT imaging increased the dose to the chest and abdomen approximately ten-fold ($1.74{\pm}0.34$ cGy versus $23.23{\pm}3.67$cGy). Imaging doses with the use of the Acuity simulator were smaller than doses with the use of the Ximatron simulator, which were $0.91{\pm}0.89$ cGy versus $6.77{\pm}3.56$ cGy, respectively. The dose with the use of the electronic portal imaging device (EPID; Varian IX unit) was approximately 50% of the dose with the use of the L-gram linear accelerator ($1.83{\pm}0.36$ cGy versus $3.80{\pm}1.67$ cGy). The dose from the OBI for fluoroscopy and low-dose mode CBCT were $0.97{\pm}0.34$ cGy and $2.3{\pm}0.67$ cGy, respectively. Conclusion: The use of 4DCT is the major source of an increase of the radiation (imaging) dose to patients. OBI and CBCT doses were small, but the accumulated dose associated with everyday verification need to be considered.

• The Journal of Korean Society for Radiation Therapy
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• v.24 no.2
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• pp.175-181
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• 2012

Purpose: This study aimed to analyze the influence of aquaplastic mask which is used for the radiotherapy for patients with head and neck cancer on patient positioning by analyzing the results of 2D/2D matching with the use of Exactrac 6D couch system. Materials and Methods: 2D/2D matching-based Image guidance was performed with the use of Exactrac 6D couch system on a total of 14 patients with head and neck cancer who received radiotherapy at this hospital in a period from June 2010 to June 2011. The adjusted 6D values obtained after the image guidance were classified into values related with patients and values not related with patients as to the correlation between the results. Results: In the analysis of the relation of each adjusted value to patients, the coefficient of determination ($R^2$) of longitudinal and pitch direction was 0.76, of longitudinal and yaw direction was 0.48, and of pitch and yaw direction was 0.42 although the coefficient of determination for above factors was 0.03 or less when the dependency of patients was excluded. Conclusion: It was demonstrated that intrinsic factors of aquaplastic mask had influence on the immobilization of patients by aquaplastic mask although various factors related with patients had influence on the immobilization of patients. It is believed that if these factors are adjusted, the treatment of patients with head and neck cancer can be more accurate.

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

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.195-195
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• 2017

• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.65-71
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• 2018

Purpose : Standardized pillow may not support patient's individual cervical spine thoroughly when head and neck radiation therapy with $Tomotherapy^{(R)}$. Therefore, the purpose of this study was to make a comparative analysis for the difference of using standardized pillow only and using customized cervical spine immobilizer with standardized pillow. Materials and Methos : The head and neck cancer patients who are treated image-guided radiation therapy(IGRT) with $Tomotherapy^{(R)}$ were divided into two groups, 20 patients using standardized pillow only, and 20 patients using customized cervical spine immobilizer with standardized pillow. We achieved 20 mega-voltage computed tomography(MVCT) image per patient, compared curvature of the cervical spine in MVCT with curvature of the cervical spine in CT-simulation. Results : Results of comparative analysis were curvature consistency 95.9 %, maximum error of distance 41.9 mm, average distance error per fractionation 19.4 mm, average standard deviation 1.34 mm in case of using standardized pillow only, curvature consistency 98.9 %, maximum error of distance 12.9 mm, average distance error per fractionation 5.8 mm, average standard deviation 0.59 mm in case of using customized cervical spine immobilizer with standardized pillow. Conclusion : Using customized cervical spine immobilizer shows higher reproducibility and low distance error, therefore customized cervical spine immobilizer could be useful for head and neck cancer patients who need radiation therapy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6932-6939
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• 2015

The respiration is one of important factor in the radiation therapy. The existing commercial method of cone-beam computed tomography on LINAC does not consider respiratory motion of patient hence the images are both distorted and inaccurate. In this study, the cone-beam computed tomography images have been reconstructed from back projection radiography of specific phase on breathing cycle which concerned about respiratory movement in radiation therapy. This study investigated how different between cone-beam CT images with and without gating respiratory movement, and this paper provides that guide and implementation of gated cone-beam CT on radiation therapeutic equipment.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.289-295
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• 2014

Purpose : Cone Beam Computed Tomography(CBCT) in Image Guided Radiation Therapy(IGRT), Set-up error can be reduced but exposure dose of the patient due to CBCT will increase. Through this study, we are to evaluate by making a scenario with the implementation period of CBCT as every other day. Materials and Methods : Of prostate cancer patients, 9 patients who got a Intensity Modulated Radiation Therapy(IMRT) with CBCT in IGRT were analyzed. Based on values corrected by analyzing set-up error by using CBCT every day during actual treatment, we created a scenario that conducts CBCT every other day. After applying set-up error values of the day not performing CBCT in the scenario to the treatment planning system(Pinnacle 9.2, Philips, USA) by moving them from the treatment iso-center during actual treatment, we established re-treatment plan under the same conditions as actual treatment. Based on this, the dose distribution of normal organs and Planning Target Volume(PTV) was compared and analyzed. Results : In the scenario that performs CBCT every other day based on set-up error values when conducting CBCT every day, average X-axis : $0.2{\pm}0.73mm$, Y-axis : $0.1{\pm}0.58mm$, Z-axis : $-1.3{\pm}1.17mm$ difference was shown. This was applied to the treatment planning to establish re-treatment plan and dose distribution was evaluated and as a result, Dmean : -0.17 Gy, D99% : -0.71 Gy of PTV difference was shown in comparison with the result obtained when carrying out CBCT every day. As for normal organs, V66 : 1.55% of rectal wall, V66 : -0.76% of bladder difference was shown. Conclusion : In case of a CBCT perform every other day could reduce exposure dose and additional treatment time. And it is thought to be able to consider the application depending on the condition of the patient because the difference in the dose distribution of normal organs, PTV is not large.