• The Journal of Korean Society for Radiation Therapy
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• v.30 no.1_2
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• pp.35-40
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• 2018

Purpose : The range of force differs from the size of proton energy used in our hospital. The compensator enables to change energy size based on distal thickness which also makes changes in dose rate. Therefore, the purpose of this study is to evaluate the effect of changing the thickness of compensator distal on dose range and beam on time. Subject and Methodology : Five low energy patients who have received proton therapy were selected as subjects for this study. Beam on was checked for the selected patients during the existing therapy. After then, the thickness of distal of compensator was increased by 2 cm up to 14 cm through proton therapy plan system(TPS) for comparative analysis. For the evaluation of dose range, the value of the target's conformity index(CI) and the maximum dose of rear side target's organ at risk(OAR) were compared. Furthermore, to evaluate the effect of therapy time, beam on time was compared by making compensator distal in each thickness. Result : The result of homogeneity index and conformity index of the increased compensator distal showed the same level in all patients. The comparison results of OAR of target rear side showed 7 cGy at spine cord of abdomen at maximum, 88 cGy at eyeball's RT lens, 391 cGy at RT lens of nasal cavity 51 cGy at trachea of the mediastinum, and 661 cGy at a small bowl of the pelvis. The comparison results of the beam on time showed a reduction from 126 seconds to 62 seconds for the abdomen, from 105 seconds to 37 seconds for the eyeball, from 187 seconds to 134 seconds for nasal cavity, from 100 seconds to 40 seconds for mediastinum, from 440 seconds to 118 seconds for the pelvis. Conclusion : The research result showed that as the distal thickness of compensator increased, the size of energy increased. In addition, beam on decreased due to the increase of dose rate. It is expected that the result would help reduce the treatment time and increase the convenience of patients if it is applied to liver patients who need respiratorygated therapy and pediatric patients. However, distal penumbra increased as the size energy increased. Therefore, in treating cases where OAR is in the vicinity of the target rear side, the influence of penumbra should be taken into account in adjusting thickness level of the compensator in proton therapy plan.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.1
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• pp.57-64
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• 2016

Purpose : To evaluate the results of absorbed and effective doses using CBCT and 4D-CBCT settings for lung cancer. Materials and Methods : This experimental study. Measurements were performed using a Anderson rando phantom with OSLD(optically stimulated luminescent dosimeters). It was performed computed tomography(Lightspeed GE, USA) in order to express the major organs of the human body. Measurements were obtained a mean value is repeated three times each. Evaluations of effective dose and absorbed dose were performed the CL-IX-Thorax mode and Truebeam-Thorax mode CBCT. Additionally, compared Truebeam-Thorax mode CBCT with Truebeam-Thorax mode 4D-CBCT(Four-dimensional Cone Beam Computed Tomography) Results : Average absorbed dose in the CBCT of CL-IX was measured in lung 2.505cGy, heart 2.595cGy, liver 2.145cGy, stomach 1.934cGy, skin 2.233cGy, in case of Truebeam, It was measured lung 1.725cGy, heart 2.034cGy, liver 1.616cGy, stomach 1.470cGy, skin 1.445cGy. In case of 4D-CBCT, It was measured lung 3.849cGy, heart 4.578cGy, liver 3.497cGy, stomach 3.179cGy, skin 3.319cGy Average effective dose, considered tissue weighting and radiation weighting, in the CBCT of CL-IX was measured lung 2.164mSv, heart 2.241mSVv, liver 0.136mSv, stomach 1.668mSv, skin 0.009mSv, in case of Turebeam, it was measured lung 1.725mSv, heart 1.757mSv, liver 0.102mSv, stomach 1.270mSv, skin 0.005mSv, In case of 4D-CBCT, It was measured lung 3.326mSv, heart 3.952mSv, liver 0.223mSv, stomach 2.747mSv, skin 0.013mSv Conclusion : As a result, absorbed dose and effective Dose in the CL-IX than Truebeam was higher about 1.3 times and in the 4D-CBCT Truebeam than CBCT of Truebeam was higher about 2.2times However, a large movement of the patient and respiratory gated radiotherapy may be more accurate treatment in 4D-CBCT. Therefore, it will be appropriate to selectively used.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.123-130
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• 2016

Purpose : The aim of this study was to compare the differences between the volumes acquired with four-dimensional computed tomography (4DCT)images with a reconstruction image-filtering algorithm and cone-beam computed tomography (CBCT) images with dynamic phantom. Materials and Methods : The 4DCT images were obtained from the computerized imaging reference systems (CIRS) phantom using a computed tomography (CT) simulator. We analyzed the volumes for maximum intensity projection (MIP), minimum intensity projection (MinIP) and average intensity projection (AVG) of the images obtained with the 4DCT scanner against those acquired from CBCT images with CT ranger tools. Results : Difference in volume for node of 1, 2 and 3 cm between CBCT and 4DCT was 0.54~2.33, 5.16~8.06, 9.03~20.11 ml in MIP, respectively, 0.00~1.48, 0.00~8.47, 1.42~24.85 ml in MinIP, respectively and 0.00~1.17, 0.00~2.19, 0.04~3.35 ml in AVG, respectively. Conclusion : After a comparative analysis of the volumes for each nodal size, it was apparent that the CBCT images were similar to the AVG images acquired using 4DCT.