• Journal of Radiation Protection and Research
• /
• v.40 no.3
• /
• pp.147-154
• /
• 2015

The scatter photons and photoneutrons from high energy photon beams (more than 10 MV) will increase the undesired dose to the patient and the staff working in linear accelerator room. This undesired dose which is found at out-of-field area can increase the probability of secondary malignancy. The purpose of this study is to determine the equivalent dose of scatter photons and neutrons generated by 3 different treatment techniques: 3D-conformal, intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The measurement was performed using two types of the optically stimulation luminescence detectors (OSL and OSLN) in the Alderson Rando phantom that was irradiated by 3 different treatment techniques following the actual prostate cancer treatment plans. The scatter photon and neutron equivalent dose were compared among the 3 treatments techniques at the surface in the out-of-field area and the critical organs. Maximum equivalent dose of scatter photons and neutrons was found when using the IMRT technique. The scatter neutrons showed average equivalent doses of 0.26, 0.63 and $0.31mSv{\cdot}Gy^{-1}$ at abdominal surface region which was 20 cm from isocenter for 3D, IMRT and VMAT, respectively. The scattered photons equivalent doses were 6.94, 10.17 and $6.56mSv{\cdot}Gy^{-1}$ for 3D, IMRT and VMAT, respectively. For the 5 organ dose measurements, the scattered neutron and photon equivalent doses in out of field from the IMRT plan were highest. The result revealed that the scatter equivalent doses for neutron and photon were higher for IMRT. So the suitable treatment techniques should be selected to benefit the patient and the treatment room staff.

• The Journal of Korean Society for Radiation Therapy
• /
• v.32
• /
• pp.31-39
• /
• 2020

Purpose: The aims of this study were to compare the superficial dose with Optically Stimulated Luminescence Dosimeter(OSLD) measurement and Treatment Planning System(TPS) calculation for 6MV-Flattening Filter Free(FFF) energy using HalcyonTM and TrueBeamTM. Materials and methods: Phantom study was performed using the CT images of human phantom. In the treatment planning system, the Planning Target Volume(PTV) was contoured which is similar to Glottic cancer. Furthermore, Point(M), Point(R), and Point(L) were contoured at the iso-center of head and neck region and 5mm bolus was applied to the body contour. Each treatment plans using 6MV-FFF energy from HalcyonTM and TrueBeamTM with static Intensity Modulated Radiation Therapy(IMRT) and Volumetric Modulated Arc Therapy(VMAT) were established with eclipse. To reproduce the same position as the TPS, OSLDs were placed at the iso-center point and 5mm bolus was applied to compare the error rate after the dose delivery. Result: The results of the study using human phantom are as follows. In case of HalcyonTM, the mean absolute error rates of the point dose using the treatment planning system and the dose measured by OSLD were 1.7%±1.2% for VMAT and 4.0±2.8% for IMRT. Also TrueBeamTM was identified as 2.4±0.4% and 8.6±1.8% respectively for VMAT and IMRT. Conclusion: Through the results of this study, TrueBeamTM confirmed that the average error rate was 2.4 times higher for VMAT and 3.6 times higher for IMRT than HalcyonTM. Therefore, based on the results of this study, If we need a more accurate dose assessment for the superficial dose, It is expected that using HalcyonTM would be better than TrueBeamTM.

• The Journal of Korean Society for Radiation Therapy
• /
• v.22 no.2
• /
• pp.105-111
• /
• 2010

Purpose: There are various beam parameter in intensity modulated radiation therapy (IMRT). The aim of this study is to investigate how various dose rate affect the parotid in treatment plan of IMRT. Materials and Methods: The study was performed on 10 nasopharyngeal carcinoma patients who have undergone IMRT. CT images were scanned 3 mm of thickness in the same condition and the treatment plan was performed by Eclipse (Ver.7.1, Varian, Palo Alto, USA). The parameters for planning used 6 MV energy and 8 beams under the same dose volume constraint. The variation of dose rates were used 300, 400, 500 MU/min. The mean dose of both parotid was accessed from the calculated planning among the 10 patients. The mean dose of parotid was verificated by 2D diode array (Mapcheck from Sun Nuclear Corporation, Melbourne, Florida). Also, Total monitor unit (MU) and beam-on time was analysed. Results: According to the dose rate, the mean dose of parotid was increased by 0.8%, 2.0% each, when dose rate was changed from 300 MU/min to 400, 500 MU/min, moreover Total MU was increased by 5.4% and 10.6% each. There was also a dose upward trend in the dose measurement of parotid by 2D diode array. However, beam - on time difference of 1~2 minutes was no signigicant in the dose rate increases. Conclusion: From this study, when the dose rates increase, there was a signigicant increase of Total MU and the parotid dose accordingly, however the shortened treatment time was not significant. Hence, it is considered that there is a significant decrease of late side effect in parotid radiation therapy, if the precise dose rate in IMRT is used.

• Progress in Medical Physics
• /
• v.14 no.3
• /
• pp.196-202
• /
• 2003

In 3-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), many studies on reducing setup error have been conducted in order to focus the irradiation on the tumors while sparing normal tissues as much as possible. As one of these efforts, we developed an image enhancement and registration tool for simulators and portal images that analyze setup errors in a quantitative manner. For setup verification, we used simulator (films and EC-L films (Kodak, USA) as portal images. In addition, digital-captured images during simulation, and digitally-reconstructed radiographs (DRR) can be used as reference images in the software, which is coded using IDL5.4 (Research Systems Inc., USA). To improve the poor contrast of portal images, histogram-equalization, and adaptive histogram equalization, CLAHE (contrast limited adaptive histogram equalization) was implemented in the software. For image registration between simulator and portal images, contours drawn on the simulator image were transferred into the portal image, and then aligned onto the same anatomical structures on the portal image. In conclusion, applying CLAHE considerably improved the contrast of portal images and also enabled the analysis of setup errors in a quantitative manner.

• Nuclear Engineering and Technology
• /
• v.54 no.10
• /
• pp.3816-3823
• /
• 2022

This work analyzed the dosimetric difference between the intensity modulated radiotherapy (IMRT), partial/single/double-arc volumetric modulated arc therapy (PA/SA/DA-VMAT) techniques in treatment planning for treating more than one target of lung cancer at different isocenters. IMRT and VMAT plans at different isocenters were created systematically using a Harold heterogeneous lung phantom. The conformity index (CI), homogeneity index (HI), gradient index (GI), dose-volume histogram and mean and maximum dose of the PTV were calculated and analyzed. Furthermore, the dose-volume histogram and mean and maximum doses of the OARs such as right lung, contralateral lung and non GTV were determined from the plans. The IMRT plans showed the superior target dose coverage, higher mean and maximum values than other VMAT techniques. PA-VMAT technique shows more lung sparing and DA-VMAT increases the V_5/10/20 values of contralateral lung than other VMAT and IMRT techniques. The IMRT technique achieves highly conformal dose distribution to the target than other VMAT techniques. Comparing to the IMRT plans, the higher V_5/10/20 and mean lung dose were observed in the contralateral lung in the DA-VMAT.

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.281-287
• /
• 2014

Purpose : The purpose of this study is to compare the plan quality of volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of orbital lymphoma. IMRT, partial single arc(SA) and partial-double arc(DA) VMAT plans for four patients with orbital lymphoma treated at our institution were used for this study. Conformity Index(CI), Paddick's Conformity Index(PCI) and Homogeneity Index(HI) of planning target volume(PTV) were used to evaluate dosimetric quality of each plan. The Monitor Unit (MU), treatment time and dose of ipsilateral lens from each type of plan were measured for comparison. Materials and Methods : The CI of PTV for IMRT, SA and DA were measured as 0.88, 0.86, 0.92. The PCI of DA was the lowest as 1.33. Also HI of DA was the lowest in measured plans as 1.15. Mean dose of lens, lacrimal gland, optic chiasm, the opposite optic nerve and both orbit was analyzed with V30, V20, V10, V5. The result showed that the lowest dose in IMRT highest in SA in opposite lens, lacrimal gland, optic nerve, orbit. Results : Treatment time and average MU of IMRT was about three times higher than SA. Conclusion : Considering the superior plan quality as well as the delivery efficiency of VMAT compared with that of IMRT, VMAT may be the preferred modality for treating orbital lymphoma.

• The Journal of Korean Physical Therapy
• /
• v.26 no.6
• /
• pp.386-390
• /
• 2014

Purpose: We aimed to investigate whether visuomotor function would be modulated, when healthy subjects performed tracking task after tDCS application over the primary sensorimotor cortex (SM1) in the non-dominant hemisphere. Methods: Thirty four right-handed healthy participants were enrolled, who randomly and evenly divided into two groups, real tDCS group and sham control group. Direct current with intensity of 1 mA was delivered over SM1 for 15 minutes. After tDCS, tracking task was measured, and their performance was calculated by an accuracy index (AI). Results: No significant difference in AI at the baseline between the two groups was observed. The AI of the real tDCS group was significantly increased after electrical stimulation, compared to the sham control group. Two way ANOVA with repeated measurement showed a significant finding in a large main effects of time and group-by-repeated test interaction. Conclusion: This study indicated that application of the anodal tDCS over the SM1 could facilitate higher visuomotor coordination, compared to sham tDCS group. These findings suggest possibility that tDCS can be used as adjuvant brain modulator for improvement of motor accuracy in healthy individuals as well as patients with brain injury.

• The Journal of Korean Society for Radiation Therapy
• /
• v.25 no.1
• /
• pp.25-31
• /
• 2013

Purpose: The aim of this study is to evaluate the dosimetric properties of robust planning strategy for plain intensity-modulated proton therapy (IMPT) taking into account of the uncertainties of effective proton range and set up error as compared to photon intensity-modulated radiation therapy (photon-IMRT) in prostate cancer treatment. Materials and Methods: The photon-IMRT (7 beams, step & shoot), plain-IMPT (2, 4, and 7 portals), and robust- IMPT plans, which was recalculated the plain-IMPT based on the uncertainties of range error (${\pm}5%$) and set up error (0.5 cm), were evaluated for five prostate cancer patients prescribed by 70 Gy/35 fractions. To quantitatively evaluate the dose distributions, several parameters such as maximum dose, minimum dose, mean dose, conformity index (CI), and homogeneity index (HI) for PTV as well as dose-volume index of VxGy for OARs were calculated from dose-volume histograms. Results: Robust-IMPT showed superior dose distributios in the PTV and OARs as compared to plain-IMPT and photon-IMRT. Like plain-IMPT, robust-IMPT were resulted in dose fluctuation around OARs, while better homogeneity and conformity in PTVs and lower mean dose in OARs as compared to photon-IMRT. Conclusion: In consideration with the effective range correction and set up movement using robustness in IMPT plan, the dosimetric uncertainties from plain-IMPT could substantially reduce and suggest more effective solutions than photon-IMRT in prostate cancer treatment.

• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.1
• /
• pp.11-19
• /
• 2014

Purpose : To derive the most appropriate factors by considering the effects of the major factors when applied to the optimization algorithm, thereby aiding the effective designing of a ideal treatment plan. Materials and Methods : The eclipse treatment planning system(Eclipse 10.0, Varian, USA) was used in this study. The PBC (Pencil Beam Convolution) algorithm was used for dose calculation, and the DVO (Dose Volume Optimizer 10.0.28) Optimization algorithm was used for intensity modulated radiation therapy. The experimental group consists of patients receiving intensity modulated radiation therapy for the head and neck cancer and dose prescription to two planned target volume was 2.2 Gy and 2.0 Gy simultaneously. Treatment plan was done with inverse dose calculation methods utilizing 6 MV beam and 7 fields. The optimal algorithm parameter of the established plan was selected based on volume dose-priority(Constrain), dose fluence smooth value and the impact of the treatment plan was analyzed according to the variation of each factors. Volume dose-priority determines the reference conditions and the optimization process was carried out under the condition using same ratio, but different absolute values. We evaluated the surrounding normal organs of treatment volume according to the changing conditions of the absolute values of the volume dose-priority. Dose fluence smooth value was applied by simply changing the reference conditions (absolute value) and by changing the related volume dose-priority. The treatment plan was evaluated using Conformal Index, Paddick's Conformal Index, Homogeneity Index and the average dose of each organs. Results : When the volume dose-priority values were directly proportioned by changing the absolute values, the CI values were found to be different. However PCI was $1.299{\pm}0.006$ and HI was $1.095{\pm}0.004$ while D5%/D95% was $1.090{\pm}1.011$. The impact on the prescribed dose were similar. The average dose of parotid gland decreased to 67.4, 50.3, 51.2, 47.1 Gy when the absolute values of the volume dose-priority increased by 40,60,70,90. When the dose smooth strength from each treatment plan was increased, PCI value increased to $1.338{\pm}0.006$. Conclusion : The optimization algorithm was more influenced by the ratio of each condition than the absolute value of volume dose-priority. If the same ratio was maintained, similar treatment plan was established even if the absolute values were different. Volume dose-priority of the treatment volume should be more than 50% of the normal organ volume dose-priority in order to achieve a successful treatment plan. Dose fluence smooth value should increase or decrease proportional to the volume dose-priority. Volume dose-priority is not enough to satisfy the conditions when the absolute value are applied solely.

• The Journal of Korean Society for Radiation Therapy
• /
• v.27 no.1
• /
• pp.45-52
• /
• 2015

Purpose : The dose distribution of organ at risk (OAR) and normal tissue is affected by treatment technique in postoperative radiation therapy for prostate cancer. The aim of this study was to compare dose distribution characteristic and to evaluate treatment efficiency by devising VMAT plans according to applying differed number of arc and IMRT plan for postoperative patient of prostate cancer radiation therapy using a rectal balloon. Materials and Methods : Ten patients who received postoperative prostate radiation therapy in our hospital were compared. CT images of patients who inserted rectal balloon were acquired with 3 mm thickness and 10 MV energy of HD120MLC equipped Truebeam STx (Varian, Palo Alto, USA) was applied by using Eclipse (Version 11.0, Varian, Palo Alto, USA). 1 Arc, 2 Arc VMAT plans and 7-field IMRT plan were devised for each patient and same values were applied for dose volume constraint and plan normalization. To evaluate these plans, PTV coverage, conformity index (CI) and homogeneity index (HI) were compared and $R_{50%}$ was calculated to assess low dose spillage as per treatment plan. $D_{25%}$ of rectum and bladder Dmean were compared on OAR. And to evaluate the treatment efficiency, total monitor units(MU) and delivery time were considered. Each assessed result was analyzed by average value of 10 patients. Additionally, portal dosimetry was carried out for accuracy verification of beam delivery. Results : There was no significant difference on PTV coverage and HI among 3 plans. Especially CI and $R_{50%}$ on 7F-IMRT were the highest as 1.230, 3.991 respectively(p=0.00). Rectum $D_{25%}$ was similar between 1A-VMAT and 2A-VMAT. But approximately 7% higher value was observed on 7F-IMRT compare to the others(p=0.02) and bladder Dmean were similar among the all plan(P>0.05). Total MU were 494.7, 479.7, 757.9 respectively(P=0.00) for 1A-VMAT, 2A-VMAT, 7F-IMRT and at the most on 7F-IMRT. The delivery time were 65.2sec, 133.1sec, 145.5sec respectively(p=0.00). The obvious shortest time was observed on 1A-VMAT. All plans indicated over 99.5%(p=0.00) of gamma pass rate (2 mm, 2%) in portal dosimetry quality assurance. Conclusion : As a result of study, postoperative prostate cancer radiation therapy for patient using a rectal balloon, there was no significant difference of PTV coverage but 1A-VMAT and 2A-VMAT were more efficient for dose reduction of normal tissue and OARs. Between VMAT plans. $R_{50%}$ and MU were little lower in 2A-VMAT but 1A-VMAT has the shortest delivery time. So it is regarded to be an effective plan and it can reduce intra-fractional motion of patient also.