• Radiation Oncology Journal
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• v.36 no.4
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• pp.295-303
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• 2018

Purpose: We evaluated prognostic value of the 8th edition of the American Joint Committee on Cancer/International Union for Cancer Control (AJCC/UICC) staging system for nasopharyngeal cancer and investigated whether tumor volume/metabolic information refined prognostication of anatomy based staging system. Materials and Methods: One hundred thirty-three patients with nasopharyngeal cancer who were staged with magnetic resonance imaging (MRI) and treated with intensity-modulated radiotherapy (IMRT) between 2004 and 2013 were reviewed. Multivariate analyses were performed to evaluate prognostic value of the 8th edition of the AJCC/UICC staging system and other factors including gross tumor volume and maximum standardized uptake value of primary tumor (GTV-T and SUV-T). Results: Median follow-up period was 63 months. In multivariate analysis for overall survival (OS), stage group (stage I-II vs. III-IVA) was the only significant prognostic factor. However, 5-year OS rates were not significantly different between stage I and II (100% vs. 96.2%), and between stage III and IVA (80.1% vs. 71.7%). Although SUV-T and GTV-T were not significant prognostic factors in multivariate analysis, those improved prognostication of stage group. The 5-year OS rates were significantly different between stage I-II, III-IV (SUV-T ≤ 16), and III-IV (SUV-T > 16) (97.2% vs. 78% vs. 53.8%), and between stage I, II-IV (GTV-T ≤ 33 mL), and II-IV (GTV-T > 33 mL) (100% vs. 87.3% vs. 66.7%). Conclusion: Current anatomy based staging system has limitations on prognostication for nasopharyngeal cancer despite the most accurate assessment of tumor extent by MRI. Tumor volume/metabolic information seem to improve prognostication of current anatomy based staging system, and further studies are needed to confirm its clinical significance.

• Radiation Oncology Journal
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• v.34 no.1
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• pp.10-17
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• 2016

Purpose: To evaluate the patterns of nodal failure after radiotherapy (RT) with the reduced volume approach for elective neck nodal irradiation (ENI) in nasopharyngeal carcinoma (NPC). Materials and Methods: Fifty-six NPC patients who underwent definitive chemoradiotherapy with the reduced volume approach for ENI were reviewed. The ENI included retropharyngeal and level II lymph nodes, and only encompassed the echelon inferior to the involved level to eliminate the entire neck irradiation. Patients received either moderate hypofractionated intensity-modulated RT for a total of 72.6 Gy (49.5 Gy to elective nodal areas) or a conventional fractionated three-dimensional conformal RT for a total of 68.4-72 Gy (39.6-45 Gy to elective nodal areas). Patterns of failure, locoregional control, and survival were analyzed. Results: The median follow-up was 38 months (range, 3 to 80 months). The out-of-field nodal failure when omitting ENI was none. Three patients developed neck recurrences (one in-field recurrence in the 72.6 Gy irradiated nodal area and two in the elective irradiated region of 39.6 Gy). Overall disease failure at any site developed in 11 patients (19.6%). Among these, there were six local failures (10.7%), three regional failures (5.4%), and five distant metastases (8.9%). The 3-year locoregional control rate was 87.1%, and the distant failure-free rate was 90.4%; disease-free survival and overall survival at 3 years was 80% and 86.8%, respectively. Conclusion: No patient developed nodal failure in the omitted ENI site. Our investigation has demonstrated that the reduced volume approach for ENI appears to be a safe treatment approach in NPC.

• Radiation Oncology Journal
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• v.22 no.2
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• pp.106-114
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• 2004

Purpose : This study was done to evaluate xerostomia fellowing intensity modulated radiotherapy for patients with head and neck cancer, and to analyze the correlation between the dosimetric parameters and xerostomia parameters. Materials and Methods : From February till October 2003, 13 patients with 3 months of follow-up were evaluated for xerostomia after being treated for head and neck cancer with IMRT. Their median age was 57 years(range: 43$\~$77). Xerostomia were assessed with a 4-question xerostomia questionnaire score (XQS) and a test for salivary flow rates (unstimulated and stimulated). The patients were also given a validated LENT SOMA scale (LSC) questionnaire. The evaluations were completed before radiation therapy (pre-RT) and at 1 and, 3 months after radiation therapy (RT). We evaluated xerostomia at pre-RT, 1 and, 3 months after RT. The association between the xerostomia parameters (XQS and LSC) and salivary flow rates (unstimulated and stimulated: USFR and SSFR) was assessed at 1 and 3 months after RT. Resrlts : All 13 patients showed no significant changes in XQS, LSC and Salivary Flow rates. As a result, we couldn't find out about xerostomia development. Based on the total mean parotid dose, 3,500 cGy, we divided these patients into two groups. The 8 patients (<3,500 cGy) showed no significant changes in XQS, LSC and Salivary Flow rates However, in 5 Patients ($\geq$3,500 cOGy), there was a significant increase in USFR and, SSFR at 3 months after RT, and for the XQS and, LSC at 1 and 3 months after RT. The correlation between XQS and, LSC, and USFR and, SSFR in ail patients (13) was significant at 3 months after RT. The correlation had a tendency to the decrease for USFR and, SSFR in proportion to the increase of XQS and, LSC. Conclusion : Based on the results of this study, IMRT seem to be an effective treatment to significantly decrease the xerostomia. XQS and, LSC seem to be a effective tool for predicting the xerostomia. A total parotid gland mean dose of <3,500 cGy should be a planning goal if substantial sparing of the gland function is desired. Furthermore, patients should be enrolled in a study to define a more accurate threshold dose for the parotid gland.

• Journal of the Korean Society of Radiology
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• v.14 no.2
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• pp.105-109
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• 2020

Intensity-modulated radiotherapy(IMRT) has disadvantages such as increasing the low doses of irradiation to normal tissues and accumulated dose for the whole volume by leakage and transmission of the Multi Leaf Collimator (MLC). The accumulated dose and low dose may increase the occurrence of secondary malignant neoplasms. For this reasons, the jaw tracking function of the TrueBeam (Varian Medical Systems, Palo Alto, CA) was developed to reduce the leakage and transmission dose of the MLC with existing linear accelerators. But quantitative analysis of the dose reduction has not been verified. Therefore, in the present study, we intended to verify the clinical possibility of utilizing the jaw tracking function in brain tumor with comparison of treatment plans. To accomplish this, 3 types of original treatment plans were made using Eclipse11 (Varian Medical Systems, Palo Alto, CA): 1) beyond 2 cm distance from the Organs At Risk (OARs); 2) within 2 cm distance from the OARs; and 3) intersecting with the OARs. Jaw tracking treatment plans were also made with copies of the original treatment planning using Smart LMC Version 11.0.31 (Varian Medical Systems, Palo Alto, CA). A comparison between the 2 types of treatment planning methods was performed using the difference of the mean dose and maximum dose to the OARs in cumulative Dose Volume Histogram (DVH). In the DVH comparison, the maximum difference of 0.5 % was observed between the planning methods in the case of over 2 cm distance, and the maximum of 0.6 % was obtained for within the 2 cm distance. For the case intersecting with the OAR, the maximum difference of 2 % was achieved. According to these results, it could be realized that the differences of mean dose and maximum dose to the OARs was larger when the OARs and PTV were closer. Therefore, treatment plans with the jaw tracking function consistently affected the dose reduction and the clinical possibility could be verified.

• Progress in Medical Physics
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• v.24 no.2
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• pp.127-132
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• 2013

The position of the internal organs can change continually and periodically inside the body due to the respiration. To reduce the respiration induced uncertainty of dose localization, one can use a respiratory gated radiotherapy where a radiation beam is exposed during the specific time of period. The main disadvantage of this method is that it usually requests a long treatment time, the massive effort during the treatment and the limitation of the patient selection. In this sense, the combination of the real-time position management (RPM) system and the volumetric intensity modulated radiotherapy (RapidArc) is promising since it provides a short treatment time compared with the conventional respiratory gated treatments. In this study, we evaluated the accuracy of the respiratory gated RapidArc treatment. Total sic patient cases were used for this study and each case was planned by RapidArc technique using varian ECLIPSE v8.6 planning machine. For the Quality Assurance (QA), a MatriXX detector and I'mRT software were used. The results show that more than 97% of area gives the gamma value less than one with 3% dose and 3 mm distance to agreement condition, which indicates the measured dose is well matched with the treatment plan's dose distribution for the gated RapidArc treatment cases.

• The Journal of Korean Society for Radiation Therapy
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• v.19 no.1
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• pp.7-17
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• 2007

Purpose: As increasing complexity of modern radiotherapy technique, more developing dosimetry is required. Polymer gel dosimeters offer a wide range of potential applications with high resolution and assured quality in the thee-dimensional verification of complex dose distribution such as intensity-modulated radiotherapy (IMRT). The purpose of this study is to find the most sensitive and suitable gel as a dosimeter by varying its composition ratio and its condition such as temperature during manufacturing. Materials and Methods: Each polymer gel with various ratio of composition was irradiated with the same amount of photon beam accordingly. Various polymer gels were analyzed and compared using a dedicated software written in visual C++ which converts TE images to R2 map images. Their sensitivities to the photon beam depending on their composition ratio were investigated. Results: There is no dependence on beam energy nor dose rate, and calibration curve is linear. Conclusion: The polymer gel dosimeter developed by using anti-oxidant in this study proved to be suitable for dosimetry.

• Radiation Oncology Journal
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• v.22 no.3
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• pp.165-176
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• 2004

Purpose: Firstly, to analyze facto in terms of radiation treatment that might potentially cause subfrontal relapse in two patients who had been treated by craniospinal irradiation (CSI) for medulloblastoma, Secondly, to explore an effective salvage treatment for these relapses. Materials and Methods: Two patients who had high-risk disease (T3bMl, T3bM3) were treated with combined chemoradiotherapy CT-simulation based radiation-treatment planning (RTP) was peformed. One patient who experienced relapse at 16 months after CSI was treated with salvage surgery followed by a 30.6 Gy IMRT (intensity modulated radiotherapy). The other patient whose tumor relapsed at 12 months after CSI was treated by surgery alone for the recurrence. To investigate factors that might potentially cause subfrontal relapse, we evaluated thoroughly the charts and treatment planning process including portal films, and tried to find out a method to give help for placing blocks appropriately between subfrotal-cribrifrom plate region and both eyes. To salvage subfrontal relapse in a patient, re-irradiation was planned after subtotal tumor removal. We have decided to treat this patient with IMRT because of the proximity of critical normal tissues and large burden of re-irradiation. With seven beam directions, the prescribed mean dose to PTV was 30.6 Gy (1.8 Gy fraction) and the doses to the optic nerves and eyes were limited to 25 Gy and 10 Gy, respectively. Results: Review of radiotherapy Portals clearly indicated that the subfrontal-cribriform plate region was excluded from the therapy beam by eye blocks in both cases, resulting in cold spot within the target volume, When the whole brain was rendered in 3-D after organ drawing in each slice, it was easier to judge appropriateness of the blocks in port film. IMRT planning showed excellent dose distributions (Mean doses to PTV, right and left optic nerves, right and left eyes: 31.1 Gy, 14.7 Gy, 13.9 Gy, 6.9 Gy, and 5.5 Gy, respectively. Maximum dose to PTV: 36 Gy). The patient who received IMRT is still alive with no evidence of recurrence and any neurologic complications for 1 year. Conclusion: To prevent recurrence of medulloblastoma in subfrontal-cribriform plate region, we need to pay close attention to the placement of eye blocks during the treatment. Once subfrontal recurrence has happened, IMRT may be a good choice for re-irradiation as a salvage treatment to maximize the differences of dose distributions between the normal tissues and target volume.

• Progress in Medical Physics
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• v.25 no.3
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• pp.167-175
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• 2014

The purpose of this study is to evaluate the variation of the dose which is delivered to the patients with glottis cancer under IMRT (intensity modulated radiation therapy) by using the 3D registration with CBCT (cone beam CT) images and the DIR (deformable image registration) techniques. The CBCT images which were obtained at a one-week interval were reconstructed by using B-spline algorithm in DIR system, and doses were recalculated based on the newly obtained CBCT images. The dose distributions to the tumor and the critical organs were compared with reference. For the change of volume depending on weight at 3 to 5 weeks, there was increased of 1.38~2.04 kg on average. For the body surface depending on weight, there was decreased of 2.1 mm. The dose with transmitted to the carotid since three weeks was increased compared be more than 8.76% planned, and the thyroid gland was decreased to 26.4%. For the physical evaluation factors of the tumor, PITV, TCI, rDHI, mDHI, and CN were decreased to 4.32%, 5.78%, 44.54%, 12.32%, and 7.11%, respectively. Moreover, $D_{max}$, $D_{mean}$, $V_{67.50}$, and $D_{95}$ for PTV were increased or decreased to 2.99%, 1.52%, 5.78%, and 11.94%, respectively. Although there was no change of volume depending on weight, the change of body types occurred, and IMRT with the narrow composure margin sensitively responded to such a changing. For the glottis IMRT, the patient's weight changes should be observed and recorded to evaluate the actual dose distribution by using the DIR techniques, and more the adaptive treatment planning during the treatment course is needed to deliver the accurate dose to the patients.

• Journal of the Korean Society of Radiology
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• v.6 no.5
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• pp.343-349
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• 2012

Intensity Modulated Radiotherapy (IMRT) is increasing its use recently due to its benefits of minimizing the dose on surrounding normal organs and being able to target a high dose specifically to the tumor. The study aims to measure and evaluate the dose distribution according to its dynamic changes in Mapcheck. In order to verify the dose distribution by EDW angle($10^{\circ}$,$15^{\circ}$,$20^{\circ}$,$25^{\circ}$,$30^{\circ}$,$45^{\circ}$,$60^{\circ}$), field size (asymmetric field) and depth changes (1.5 cm, 5.0 cm) using IMRT in Clinac ix, a solid phantom was placed on the Mapcheck and 100MU was exposed by 6 MV, 10MV X-ray. Using a 6MV, 10MV energy, the percentage depth dose according to a dynamic changes at a maximum dose depth (1.5 cm) and at 5.0 cm depth showed the value difference of maximum 0.6%, less than 1%, which was calculated by a treatment program device considering the maximum dose depth at the center as 100%, the percentage depth dose was in the range between 2.4% and 7.2%. Also, the maximum value difference of a percentage depth dose was 4.1% in Y2-OUT direction, and 1.7% in Y1-IN direction. When treating a patient using a wedge, it is considered that using an enhanced dynamic wedge is effective to reduce the scattered dose which induces unnecessary dose to the surroundings. In particular, when treating a patient at clinic, a treatment must be performed considering that the wedge dose in a toe direction is higher than the dose in a heel direction.

• Radiation Oncology Journal
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• v.28 no.3
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• pp.166-176
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• 2010

Purpose: To determine the appropriate prostate planning target volume (PTV) margins for 3-dimensitional (3D) conformal radiotherapy (CRT) and intensity-modulated radiation therapy (IMRT) patients treated with an endorectal balloon (ERB) under our institutional treatment condition. Materials and Methods: Patients were treated in the supine position. An ERB was inserted into the rectum with 70 cc air prior to planning a CT scan and then each treatment fraction. Electronic portal images (EPIs) and digital reconstructed radiographs (DRR) of planning CT images were used to evaluate inter-fractional patient's setup and ERB errors. To register both image sets, we developed an in-house program written in visual $C^{++}$. A new method to determine prostate PTV margins with an ERB was developed by using the common method. Results: The mean value of patient setup errors was within 1 mm in all directions. The ERB inter-fractional errors in the superior-inferior (SI) and anterior-posterior (AP) directions were larger than in the left-right (LR) direction. The calculated 1D symmetric PTV margins were 3.0 mm, 8.2 mm, and 8.5 mm for 3D CRT and 4.1 mm, 7.9 mm, and 10.3 mm for IMRT in LR, SI, and AP, respectively according to the new method including ERB random errors. Conclusion: The ERB random error contributes to the deformation of the prostate, which affects the original treatment planning. Thus, a new PTV margin method includes dose blurring effects of ERB. The correction of ERB systematic error is a prerequisite since the new method only accounts for ERB random error.