• 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.

• Progress in Medical Physics
• /
• v.16 no.1
• /
• pp.39-46
• /
• 2005

For the QA of IMRT treatment of head and neck cancer by using M3 (BrainLAB Inc. Germany), it is not easy to measure delivery dose exactly because the dose attenuation appears by the couch according to the position of table and gantry. In order to solve this problem, we fabricated head and neck phantom which would be implemented on the couch mount of Brain Lab Inc. We investigated dose attenuation by the couch and found the difference of dose distribution by the couch, in the applying this phantom to the clinic. After measurement, we found that point dose attenuation was 35% at maximum and dose difference was 5.4% for a point dose measurement of actual patient quality assurance plan.

• Progress in Medical Physics
• /
• v.24 no.3
• /
• pp.154-161
• /
• 2013

This study assessed compared photon and proton treatment techniques, such as intensity modulated radiation therapy (IMRT), uniform scanning proton therapy (USPT), and intensity modulated proton therapy (IMPT), for a total of 10 prostate cancers. All treatment plans delivered 70 Gy to 95% of the planned target volume in 28 fractions. IMRT plans had 7 fields for the step and shoot technique, while USPT and IMPT plans employed two equally weighted, parallel-opposed lateral fields to deliver the prescribed dose to the planned target. Inverse planning was then incorporated to optimize IMPT. The homogeneity index (HI) and conformity index (CI) for the target and the normal tissue complication probability (NTCP) for organ at risk (OAR) were calculated. Although the mean HI and CI for target were not significantly different for each treatment techniques, the NTCP of the rectum was 2.233, 3.326, and 1.707 for IMRT, USPT, and IMPT, respectively. The NTCP of the bladder was 0.008, 0.003, and 0.002 respectively. The NTCP values at the rectum and bladder were significantly lower using IMPT. Our study shows that using proton therapy, particularly IMPT, to treat prostate cancer could be beneficial compared to 7-field IMRT with similar target coverage. Given these results, radiotherapy using protons, particularly optimized IMPT, is a worthwhile treatment option for prostate cancer.

• Radiation Oncology Journal
• /
• v.31 no.1
• /
• pp.1-11
• /
• 2013

Purpose: Compared to conventional radiotherapy (RT), intensity-modulated radiotherapy (IMRT) significantly reduces the rate of treatment-induced late toxicities in head and neck cancer. However, a clear survival benefit of IMRT over conventional RT has not yet been shown. This study is among the first comparative study to compare the survival rates between conventional RT and helical tomotherapy in head and neck cancer. Materials and Methods: From January 2008 to November 2011, 37 patients received conventional RT and 30 patients received helical tomotherapy for management of head and neck cancer. We retrospectively compared the survival rates between patients treated with conventional RT and helical tomotherapy, and analyzed the prognostic factors for survival. Results: The 1- and 2-year locoregional recurrence-free survival rates were 61.2% and 58.1% for the conventional RT group, 89.3% and 80.3% for the helical tomotherapy group, respectively. The locoregional recurrence-free survival rates of the helical tomotherapy group were significantly higher than conventional RT group (p = 0.029). There were no significant differences in the overall and distant metastasis-free survival between the two groups. RT technique, tumor stage, and RT duration were significant prognostic factors for locoregional recurrence-free survival. Conclusion: This study showed the locoregional recurrence-free survival benefits of helical tomotherapy in the treatment of head and neck cancers.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.5
• /
• pp.2573-2577
• /
• 2016

Objective: The aim of this study was to determine a method of dose prescription that minimizes normal tissue irradiation outside the planning target volume (PTV) during stereotactic body radiotherapy (SBRT) for patients with non-small cell lung cancer. Methods: Previous research and patients with typical T1 lung tumors with peripheral lesions in the lung were selected for analysis. A PTV and several organs at risk (OARs) were constructed for the dose calculated; six treatment plans employing intensity modulated radiotherapy (IMRT) were produced, in which the dose was prescribed to encompass the PTV, with the prescription isodose level (PIL) set at 50, 60, 70, 80, 90 or 95% of the isocenter dose. Additionally, four OARs around the PTV were constructed to evaluate the dose received in adjacent tissues. Results: The use of higher PILs for SBRT resulted in improved sparing of OARs, with the exception of the volume of lung treated with a lower dose. Conclusions: The use of lower PILs is likely to create significant inhomogeneity of the dose delivered to the target, which may be beneficial for the control of tumors with poor conformity indices.

• Radiation Oncology Journal
• /
• v.35 no.4
• /
• pp.306-316
• /
• 2017

Purpose: To investigate the predictive role of maximum standardized uptake value ($SUV_{max}$) of 2-[$^{18}F$]fluoro-2-deoxy-D-glucose($^{18}F-FDG$) positron emission tomography/computed tomography (PET/CT) in nasopharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT). Materials and Methods: Between October 2006 and April 2016, 53 patients were treated with IMRT in two institutions and their PET/CT at the time of diagnosis was reviewed. The $SUV_{max}$ of their nasopharyngeal lesions and metastatic lymph nodes (LN) was recorded. IMRT was delivered using helical tomotherapy. All patients except for one were treated with concurrent chemoradiation therapy (CCRT). Correlations between $SUV_{max}$ and patients' survival and recurrence were analyzed. Results: At a median follow-up time of 31.5 months (range, 3.4 to 98.7 months), the 3-year overall survival (OS) and disease-free survival (DFS) rates were 83.2% and 77.5%, respectively. In univariate analysis, patients with a higher nodal pre-treatment $SUV_{max}$ (${\geq}13.4$) demonstrated significantly lower 3-year OS (93.1% vs. 55.5%; p = 0.003), DFS (92.7% vs. 38.5%; p < 0.001), locoregional recurrence-free survival (100% vs. 50.5%; p < 0.001), and distant metastasis-free survival (100% vs. 69.2%; p = 0.004), respectively. In multivariate analysis, high pre-treatment nodal $SUV_{max}$ (${\geq}13.4$) was a negative prognostic factor for OS (hazard ratio [HR], 7.799; 95% confidence interval [CI], 1.506-40.397; p = 0.014) and DFS (HR, 9.392; 95% CI, 1.989-44.339; p = 0.005). Conclusions: High pre-treatment nodal $SUV_{max}$ was an independent prognosticator of survival and disease progression in nasopharyngeal carcinoma patients treated with IMRT in our cohort. Therefore, nodal $SUV_{max}$ may provide important information for identifying patients who require more aggressive treatment.

• Progress in Medical Physics
• /
• v.27 no.2
• /
• pp.93-97
• /
• 2016

In this study, we evaluate the effect of respiration on the dose distribution in patient target volume (PTV) during intensity-modulated radiation therapy (IMRT) and research methods to reduce this impact. The dose distributions, homogeneity index (HI), coverage index (CVI), and conformity index of the PTV, which is calculated from the dose-volume histogram (DVH), are compared between the maximum intensity projection (MIP) image-based plan and other images at respiration phases of 30%, 60% and 90%. In addition, the reducing effect of complication caused by patient respiration is estimated in the case of a bolus and the expended PTV on the skin. The HI is increased by approximately twice, and the CVI is relatively decreased without the bolus at other respiration phases. With the bolus and expended PTV, the change in the dose distribution of the PTV is relatively small with patient respiration. Therefore, the usage of the bolus and expended PTV can be considered as one of the methods to improve the accuracy of IMRT in the treatment of breast cancer patients with respiratory motion.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.53-60
• /
• 2002

Motion of lung tumors from respiration has been reported in the literature to be as large as of 1-2 cm. This motion requires an additional margin between the Clinical Target Volume (CTV) and the Planning Target Volume (PTV). While such a margin is necessary, it may not be sufficient to ensure proper delivery of Intensity Modulated Radiotherapy (IMRT) to the CTV during the simultaneous movement of the DMLC. Gated treatment has been proposed to improve normal tissues sparing as well as to ensure accurate dose coverage of the tumor volume. The following questions have not been addressed in the literature: a) what is the dose error to a target volume without gated IMRT treatment\ulcorner b) what is an acceptable gating window for such treatment. In this study, we address these questions by proposing a novel technique for calculating the 3D dose error that would result if a lung IMRT plan were delivered without gating. The method is also generalized for gated treatment with an arbitrary triggering window. IMRT plans for three patients with lung tumor were studied. The treatment plans were generated with HELIOS for delivery with 6 MV on a CL2100 Varian linear accelerator with a 26 pair MLC. A CTV to PTV margin of 1 cm was used. An IMRT planning system searches for an optimized fluence map ${\Phi}$ (x,y) for each port, which is then converted into a dynamic MLC file (DMLC). The DMLC file contains information about MLC subfield shapes and the fractional Monitor Units (MUs) to be delivered for each subfield. With a lung tumor, a CTV that executes a quasi periodic motion z(t) does not receive ${\Phi}$ (x,y), but rather an Effective Incident Fluence EIF(x,y). We numerically evaluate the EIF(x,y) from a given DMLC file by a coordinate transformation to the Target's Eye View (TEV). In the TEV coordinate system, the CTV itself is stationary, and the MLC is seen to execute a motion -z(t) that is superimposed on the DMLC motion. The resulting EIF(x,y)is inputted back into the dose calculation engine to estimate the 3D dose to a moving CTV. In this study, we model respiratory motion as a sinusoidal function with an amplitude of 10 mm in the superior-inferior direction, a period of 5 seconds, and an initial phase of zero.

• Radiation Oncology Journal
• /
• v.31 no.4
• /
• pp.206-215
• /
• 2013

Purpose: Re-irradiation (re-RT) is considered a treatment option for inoperable locoregionally recurrent head and neck cancer (HNC) after prior radiotherapy. We evaluated the efficacy and safety of re-RT using Helical Tomotherapy as image-guided intensity-modulated radiotherapy in recurrent HNC. Materials and Methods: Patients diagnosed with recurrent HNC and received re-RT were retrospectively reviewed. Primary endpoint was overall survival (OS) and secondary endpoints were locoregional control and toxicities. Results: The median follow-up period of total 9 patients was 18.7 months (range, 4.1 to 76 months) and that of 3 alive patients was 49 months (range, 47 to 76 months). Median dose of first radiotherapy and re-RT was 64.8 and 47.5 $Gy_{10}$. Median cumulative dose of the two courses of radiotherapy was 116.3 $Gy_{10}$ (range, 91.8 to 128.9 $Gy_{10}$) while the median interval between the two courses of radiation was 25 months (range, 4 to 137 months). The response rate after re-RT of the evaluated 8 patients was 75% (complete response, 4; partial response, 2). Median locoregional relapse-free survival after re-RT was 11.9 months (range, 3.4 to 75.1 months) and 5 patients eventually presented with treatment failure (in-field failure, 2; in- and out-field failure, 2; out-field failure, 1). Median OS of the 8 patients was 20.3 months (range, 4.1 to 75.1 months). One- and two-year OS rates were 62.5% and 50%, respectively. Grade 3 leucopenia developed in one patient as acute toxicity, and grade 2 osteonecrosis and trismus as chronic toxicity in another patient. Conclusion: Re-RT using Helical Tomotherapy for previously irradiated patients with unresectable locoregionally recurrent HNC may be a feasible treatment option with long-term survival and acceptable toxicities.

• Progress in Medical Physics
• /
• v.17 no.1
• /
• pp.17-23
• /
• 2006

In Vivo dosimetry is a method to evaluate the radiotherapy; it is used to find the dosimetric and mechanical errors of radiotherapy unit. In this study, on-line In Vivo dosimetry was enabled by measuring the skin dose with MOSFET detectors attached to patient's skin during treatment. MOSFET dosimeters were found to be reproducible and independent on beam directions. MOSFET detectors were positioned on patient's skin underneath of the dose build-up material which was used to minimize dosimetric error. Delivered dose calculated by the plan verification function embedded in the radiotherapy treatment planning system (RTPs), was compared with measured data point by point. The dependency of MOSFET detector used in this study for energy and dose rate agrees with the specification provided by manufacturer within 2% error. Comparing the measured and the calculated point doses of each patient, discrepancy was within 5%. It was enabled to verify the IMRT by using MOSFET detector. However, skin dosimetry using conventional ion chamber and diode detector is limited to the simple radiotherapy.