• The Journal of Korean Society for Radiation Therapy
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• v.26 no.1
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• pp.21-28
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• 2014

Purpose : For non-small cell lung cancer, if the treatment volume is large or the total lung volume is small, and the tumor is located in midline of patient's body, total lung dose tends to increase due to tolerance dose of spinal cord. The purpose of this study is to compare and evaluate the total lung dose of three dimensional conformal radiotherapy(3D CRT), intensity modulated radiotherapy(IMRT) and volumetric modulated arc therapy(VMAT) using restricted angle for non-small cell lung cancer patients. Materials and Methods : The treatment plans for four patients, being treated on TrueBeam STx($Varian^{TM}$, USA) with 10 MV and prescribed dose of 60 Gy in 30 fractions, 3D CRT, restricted angle IMRT and VAMT radiotherapy plans were established. Planning target volume(PTV), dose to total lung and spinal cord were evaluated using the dose volume histogram(DVH). Conformity index(CI), homogeneity index(HI), Paddick's index(PCI) for the PTV, $V_{30}$, $V_{20}$, $V_{10}$, $V_5$, mean dose for total lung and maximum dose for spinal cord was assessed. Results : Average value of CI, HI and PCI for PTV was $0.944{\pm}0.009$, $1.106{\pm}0.027$, $1.084{\pm}0.016$ respectively. $V_{20}$ values from 3D CRT, IMRT and VMAT plans were 30.7%, 20.2% and 21.2% for the first patient, 33.0%, 29.2% and 31.5% for second patient, 51.3%, 34.3% and 36.9% for third patient, finally 56.9%, 33.7% and 40.0% for the last patient. It was noticed that the $V_{20}$ was lowest in the IMRT plan using restricted angle. Maximum dose for spinal cord was evaluated to lower than the tolerance dose. Conclusion : For non-small cell lung cancer, IMRT with restricted angle or VMAT could minimize the lung dose and lower the dose to spinal cord below the tolerance level. Considering PTV coverage and tolerance dose to spinal cord, it was possible to obtain IMRT plan with smaller angle and this could result in lower dose to lung when compared to VMAT.

• Radiation Oncology Journal
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• v.35 no.1
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• pp.32-38
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• 2017

Purpose: Several accelerated partial breast radiation (APBR) techniques have been investigated in patients with early-stage breast cancer (BC); however, the optimal treatment delivery techniques remain unclear. We evaluated the feasibility and toxicity of APBR delivered using intensity-modulated radiation therapy (IMRT) in elderly patients with stage I BC, using a novel fractionation schedule. Materials and Methods: Forty-two patients aged ${\geq}65$ years, with stage I BC who underwent breast conserving surgery were enrolled in a phase I/II study evaluating APBR using IMRT. Forty eligible patients received 40 Gy in 4 Gy daily fractions. Patients were assessed for treatment related toxicities, and cosmesis, before APBR, during, and after completion of the treatment. Results: The median age was 73 years, median tumor size 0.8 cm and the median follow-up was 54 months. The 5-year locoregional control was 97.5% and overall survival 90%. Erythema and skin pigmentation was the most common acute adverse event, reported by 27 patients (69%). Twenty-six patients (65%) reported mild pain, rated 1-4/10. This improved at last follow-up to only 2 (15%). Overall the patient and physician reported worst late toxicities were lower than the baseline and at last follow-up, patients and physicians rated cosmesis as excellent/good in 93% and 86 %, respectively. Conclusion: In this prospective trial, we observed an excellent rate of tumor control with daily APBR. The acceptable toxicity profile and cosmetic results of this study support the use of IMRT planned APBR with daily schedule in elderly patients with early stage BC.

• Radiation Oncology Journal
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• v.29 no.2
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• pp.99-106
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• 2011

Purpose: To analyze our quality assurance (QA) data for intensity modulated radiation therapy (IMRT) according to treatment site and to possibly improve QA for IMRT in Hospital. Materials and Methods: We performed QA on 50 patients (head and neck, 28 patients; Breast, 14 patients; Pelvis, 8 patients) for IMRT. The calculated dose from RTP was compared with the measured value film, gamma index, and ionization chamber for dose measurement in each case. Results: The point dose measurement results in 45 of 50 patients showed good agreement with the calculation dose (${\pm}3%$). The largest error measured thus far has been 3.60%, with a mean of only -0.17% (SD, 2.25%). Each treatment site showed an error rate of -0.13% (SD, 1.93%) for head and neck cases, -0.26% (SD, 2.79%) for breast cases, and 0.24% (SD, 2.44%) for pelvis cases. The gamma index verified with the error rate of head and neck cases (6%), breast (10%), and pelvis (6%), which corresponded to a tolerance of 3 mm (3% for the head and neck, 2%, for the breast 1% for the pelvis, and 0% in the region where the isodose curve was greater than 90%. Conclusion: We recognize the cause of errors for each treatment site of IMRT QA and so we maximize our efforts to reduce error and increase accuracy.

• Journal of Chest Surgery
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• v.53 no.4
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• pp.184-190
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• 2020

Radiation therapy (RT) has improved patient outcomes, but treatment-related complication rates remain high. In the conventional 2-dimensional and 3-dimensional conformal RT (3D-CRT) era, there was little room for toxicity reduction because of the need to balance the estimated toxicity to organs at risk (OARs), derived from dose-volume histogram data for organs including the lung, heart, spinal cord, and liver, with the planning target volume (PTV) dose. Intensity-modulated RT (IMRT) is an advanced form of conformal RT that utilizes computer-controlled linear accelerators to deliver precise radiation doses to the PTV. The dosimetric advantages of IMRT enable better sparing of normal tissues and OARs than is possible with 3D-CRT. A major breakthrough in the treatment of esophageal cancer (EC), whether early or locally advanced, is the use of proton beam therapy (PBT). Protons deposit their highest dose of radiation at the tumor, while leaving none behind; the resulting effective dose reduction to healthy tissues and OARs considerably reduces acute and delayed RT-related toxicity. In recent studies, PBT has been found to alleviate severe lymphopenia resulting from combined chemo-radiation, opening up the possibility of reducing immune suppression, which might be associated with a poor prognosis in cases of locally advanced EC.

• Journal of Radiation Protection and Research
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• v.46 no.2
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• pp.48-57
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• 2021

Background: In this study, the complexities of step-and-shoot intensity-modulated radiation therapy (IMRT) plans in magnetic resonance-guided radiation therapy systems were evaluated. Materials and Methods: Overall, 194 verification plans from the abdomen, prostate, and breast sites were collected using a ⁶⁰Co-based ViewRay radiotherapy system (ViewRay Inc., Cleveland, OH, USA). Various plan complexity metrics (PCMs) were calculated for each verification plan, including the modulation complexity score (MCS), plan-averaged beam area (PA), plan-averaged beam irregularity, plan-averaged edge (PE), plan-averaged beam modulation, number of segments, average area among all segments (AA/Seg), and total beam-on time (TBT). The plan deliverability was quantified in terms of gamma passing rates (GPRs) with a 1 mm/2% criterion, and the Pearson correlation coefficients between GPRs and various PCMs were analyzed. Results and Discussion: For the abdomen, prostate, and breast groups, the average GPRs with the 1 mm/2% criterion were 77.8 ± 6.0%, 79.8 ± 4.9%, and 84.7 ± 7.3%; PCMs were 0.263, 0.271, and 0.386; PAs were 15.001, 18.779, and 35.683; PEs were 1.575, 1.444, and 1.028; AA/Segs were 15.37, 19.89, and 36.64; and TBTs were 18.86, 19.33, and 5.91 minutes, respectively. The various PCMs, i.e., MCS, PA, PE, AA/Seg, and TBT, showed statistically significant Pearson correlation coefficients of 0.416, 0.627, -0.541, 0.635, and -0.397, respectively, with GPRs. Conclusion: The area-related metrics exhibited strong correlations with GPRs. Moreover, the AA/Seg metric can be used to estimate the IMRT plan accuracy without beam delivery in the ⁶⁰Co-based ViewRay radiotherapy system.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.1
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• pp.85-92
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• 2017

purpose: Image Guide System offers therapy precise, especially Intensity Modulated Radiation Therapy. However, organs at pelvis have variation and uncertainties each therapy. it brings IG system for verifying patient's position. In this study, analysis the variation at pelvis during rectal cancer radiation therapy. Moreover design the patient re-setup technique and apply to patients. Material and Method: 40 rectal cancer patient who have radiation therapy. The 530 image which acquired from IG system are analyzed. The bone structure, bladder, gas in the rectum, small bowel, soft tissue, weigh loss are evaluated by the criterion. The criterion are classified by best, good, bad and figure out the ratio with count. The re-setup proceed in case of one or over the two get the bad criterion and figure out the ratio of re-setup results: The ideal of therapy ratio is 19.2 % each criterion. And the good for therapy ratio is 54.9 %, the cases of bad for therapy is 25.8 %. The bad cases are have therapy after re-setup with post process. conclusion: Each pre-treatment image that acquired IG system has different results despite of same patients. The 25.8 % need to re-setup in order to unsuitable therapy. It is implies that the IG system is necessary establishing precise treatment plan like IMRT especially rectal cancer.

• Progress in Medical Physics
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• v.27 no.4
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• pp.196-202
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• 2016

We aim to develop the breast bolus by using a 3D printer to minimize the air-gap, and compare it to commercial bolus used for patients undergoing reconstruction in breast cancer. The bolus-shaped region of interests (ROIs) were contoured at the surface of the intensity-modulated radiation therapy (IMRT) thorax phantom with 5 mm thickness, after which the digital imaging and communications in mdicine (DICOM)-RT structure file was acquired. The intensity-modulated radiation therapy (Tomo-IMRT) and direct mode (Tomo-Direct) using the Tomotherapy were established. The 13 point doses were measured by optically stimulated luminescence (OSLD) dosimetry. The measurement data was analyzed to quantitatively evaluate the applicability of 3D bolus. The percentage change of mean measured dose between the commercial bolus and 3D-bolus was 2.3% and 0.7% for the Tomo-direct and Tomo-IMRT, respectively. For air-gap, range of the commercial bolus was from 0.8 cm to 1.5 cm at the periphery of the right breast. In contrast, the 3D-bolus have occurred the air-gap (i.e., 0 cm). The 3D-bolus for radiation therapy reduces the air-gap on irregular body surface that believed to help in accurate and precise radiation therapy due to better property of adhesion.

• Progress in Medical Physics
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• v.27 no.3
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• pp.169-174
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• 2016

The aim of this study is to investigate the delivery accuracy of intensity-modulated radiation therapy (IMRT) plans in the two-headed mode of the ViewRay$^{TM}$ system in comparison with that of the normal operation treatment plan of the machine. For this study, a total of eight IMRT plans and corresponding verification plans were generated (four head and neck, two liver, and two prostate IMRT plans). The delivered dose distributions were measured using ArcCHECK$^{TM}$ with the insertion of an ionization chamber. We measured the delivered dose distributions in three-headed mode (normal operation of the machine), two-headed mode with head 1 disabled, two-headed mode with head 2 disabled, and two-headed mode with head 3 disabled. Therefore, a total of four measurements were performed for each IMRT plan. The global gamma passing rates (3%/3 mm) in three-headed mode, head 1 disabled, head 2 disabled, and head 3 disabled were $99.9{\pm}0.1%$, $99.8{\pm}0.3%$, $99.6{\pm}0.7%$, and $99.7{\pm}0.4%$, respectively. The difference in the gamma passing rates of the three- and two-headed modes was insignificant. With 2%/2 mm, the rates were $96.6{\pm}3.6%$, $97.2{\pm}3.5%$, $95.7{\pm}6.2%$, and $95.5{\pm}4.3%$, respectively. Between three-headed mode and head 3 disabled, a statistically significant difference was observed with a p-value of 0.02; however, the difference was minimal (1.1%). The chamber readings showed differences of approximately 1% between three- and two-headed modes, which were minimal. Therefore, the treatment plan delivery in the two-headed mode of the ViewRay$^{TM}$ system seems accurate and robust.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.1
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• pp.33-41
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• 2019

Purpose : To evaluate the effectiveness of Jaw-tracking(JT) technique in Intensity-modulated radiation therapy(IMRT) and Volumetric-modulated arc therapy(VMAT) for radiation therapy of esophageal cancer by analyzing volume dose of perimetrical normal organs along with the low-dose volume regions. Materials and Method: A total of 27 patients were selected who received radiation therapy for esophageal cancer with using $VitalBeam^{TM}$(Varian Medical System, U.S.A) in our hospital. Using Eclipse system(Ver. 13.6 Varian, U.S.A), radiation treatment planning was set up with Jaw-tracking technique(JT) and Non-Jaw-tracking technique(NJT), and was conducted for the patients with T-shaped Planning target volume(PTV), including Supraclavicular lymph nodes(SCL). PTV was classified into whether celiac area was included or not to identify the influence on the radiation field. To compare the treatment plans, Organ at risk(OAR) was defined to bilateral lung, heart, and spinal cord and evaluated for Conformity index(CI) and Homogeneity index(HI). Portal dosimetry was performed to verify a clinical application using Electronic portal imaging device(EPID) and Gamma analysis was performed with establishing thresholds of radiation field as a parameter, with various range of 0 %, 5 %, and 10 %. Results: All treatment plans were established on gamma pass rates of 95 % with 3 mm/3 % criteria. For a threshold of 10 %, both JT and NJT passed with rate of more than 95 % and both gamma passing rate decreased more than 1 % in IMRT as the low dose threshold decreased to 5 % and 0 %. For the case of JT in IMRT on PTV without celiac area, $V_5$ and $V_{10}$ of both lung showed a decrease by respectively 8.5 % and 5.3 % in average and up to 14.7 %. A $D_{mean}$ decreased by $72.3{\pm}51cGy$, while there was an increase in radiation dose reduction in PTV including celiac area. A $D_{mean}$ of heart decreased by $68.9{\pm}38.5cGy$ and that of spinal cord decreased by $39.7{\pm}30cGy$. For the case of JT in VMAT, $V_5$ decreased by 2.5 % in average in lungs, and also a little amount in heart and spinal cord. Radiation dose reduction of JT showed an increase when PTV includes celiac area in VMAT. Conclusion: In the radiation treatment planning for esophageal cancer, IMRT showed a significant decrease in $V_5$, and $V_{10}$ of both lungs when applying JT, and dose reduction was greater when the irradiated area in low-dose field is larger. Therefore, IMRT is more advantageous in applying JT than VMAT for radiation therapy of esophageal cancer and can protect the normal organs from MLC leakage and transmitted doses in low-dose field.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.83-85
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• 2002

Yonsei Cancer Center introduced an IMRT System at the beginning of February, 2002. The system consists of CORVUS(NOMOS) inverse planning machine, LANTIS(SIEMENS), PRIMEVIEW and PRIMART Linac(SIEMENS). The optimization of CORVUS planning system with PRIMART is an important work to get an efficient treatment plan. So, we studied two Finite Size Pencil Beams, 1.0 x 1.0 cm$^2$ and 0.5 x 1.0 cm$^2$, and four leaf transmission sets, 5%, 10%, 20%, 33%. We compared the dose distribution of target volume and delivery efficiency of the plan results.