• Radiation Oncology Journal
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• v.31 no.4
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• pp.191-198
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• 2013

Purpose: To observe long-term clinical outcomes for patients with early-stage breast cancer treated with forward intensity-modulated radiation therapy (IMRT), including local control and clinical toxicities. Materials and Methods: We retrospectively analyzed a total of 214 patients with stage I-II breast cancer who were treated with breast conserving surgery followed by adjuvant breast radiation therapy between 2001 and 2008. All patients were treated using forward IMRT. The whole breast was irradiated to a dose of 50 to 50.4 Gy followed by an 8 to 12 Gy electron boost to the surgical bed. Results: The median age was 46 years (range, 21 to 82 years) and the medial follow-up time was 7.3 years (range, 2.4 to 11.7 years). Stage T1 was 139 (65%) and T2 was 75 (35%), respectively. Ipsilateral breast recurrence was observed in 3 patients. The 5- and 10-year local control rates were 99.1% and 97.8%, respectively. The cosmetic outcome was evaluated according to the Harvard scale and 89.4% of patients were scored as excellent or good. Conclusion: The whole breast radiation therapy as an adjuvant treatment using a forward IMRT technique showed excellent long-term local control as well as favorable outcomes of toxicity and cosmesis.

• Progress in Medical Physics
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• v.33 no.3
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• pp.25-35
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• 2022

Purpose: Planning for radiotherapy relies on implicit estimation of the probability of tumor control and the probability of complications in adjacent normal tissues for a given dose distribution. Methods: The aim of this pilot study was to reconstruct dose-volume histograms (DVHs) from text files generated by the Eclipse treatment planning system developed by Varian Medical Systems and to verify the integrity and accuracy of the dose statistics. Results: We further compared dose statistics for intensity-modulated radiotherapy of the head and neck between the Eclipse software and software developed in-house. The dose statistics data obtained from the Python software were consistent, with deviations from the Eclipse treatment planning system found to be within acceptable limits. Conclusions: The in-house software was able to provide indices of hotness and coldness for treatment planning and store statistical data generated by the software in Oracle databases. We believe the findings of this pilot study may lead to more accurate evaluations in planning for radiotherapy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.743-744
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.652-657
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• 2003

This paper proposes a method to generate virtual intensity field in space. The sound field of a zone enclosing the listener position is controlled to have maximum acoustic intensity to the desired direction. In order to control acoustic intensity of a zone, space-averaged active intensity is introduced. The ratio of space-averaged active intensity and control effort is defined as a cost function and expressed as a function of source control signals. It is shown that the cost function represents radiation efficiency of multiple sources. The control signals maximizing the cost function is found through eigenvalue analysis. The proposed method is verified by numerical simulations performed in free field condition, and the results provide a relation between wavelength and the size of controllable intensity field.

• 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.35 no.1
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• pp.1-15
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• 2017

Locoregional failure is the most frequent pattern of failure in locally advanced head and neck cancer patients and it leads to death in most of the patients. Second primary tumors occurring in the other head and neck region reach up to almost 40% of long-term survivors. Recommended and preferred retreatment option in operable patients is salvage surgical resection, reporting a 5-year overall survival of up to 40%. However, because of tumor location, extent, and underlying comorbidities, salvage surgery is often limited and compromised by incomplete resection. Reirradiation with or without combined chemotherapy is an appropriate option for unresectable recurrence. Reirradiation is carefully considered with a case-by-case basis. Reirradiation protocol enrollment is highly encouraged prior to committing patient to an aggressive therapy. Radiation doses greater than 60 Gy are usually recommended for successful salvage. Despite recent technical improvement in intensity-modulated radiotherapy (IMRT), the use of concurrent chemotherapy, and the emergence of molecularly targeted agents, careful patient selection remain as the most paramount factor in reirradiation. Tumors that recur or persist despite aggressive prior chemoradiation therapy imply the presence of chemoradio-resistant clonogens. Treatment protocols that combine novel targeted radiosensitizing agents with conformal high precision radiation are required to overcome the resistance while minimizing toxicity. Recent large number of data showed that IMRT may provide better locoregional control with acceptable acute or chronic morbidities. However, additional prospective studies are required before a definitive conclusion can be drawn on safety and effectiveness of IMRT.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.796-803
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• 2003

The discrete ordinates interpolation method (DOIM) has shown good accuracy and versatile applicability for the radiation $problems^{(1,2)}$. The DOIM is a nonconservative method in that the intensity and temperature are computed only at grid points without considering control volumes. However, when the DOIM is used together with a finite volume algorithm such as $SIMPLER^{(3)}$, intensities at the control surfaces need to be calculated. For this reason, a 'quadratic' and a 'decoration' schemes are proposed and examined. They are applied to two kinds of radiation problem in one-dimensional geometries. In one problem, the intensity and temperature are calculated while the radiative heat source is given, and in the other, the intensity and the radiative heat source are computed with a given temperature field. The quadratic and the decoration schemes show very successful results. The quadratic scheme gives especially accurate results so that further decoration may not be needed. It is recommended that the quadratic and the decoration schemes may be used together, or, one of them may be applied for control volume radiative energy balance.

• Korean Journal of Head & Neck Oncology
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• v.19 no.1
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• pp.9-15
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• 2003

Purpose: To introduce our early experience with intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma. Methods and Materials: Eight patients who underwent IMRT for no disseminated nasopharyngeal carcinoma at the Asan Medical Center between September 2001 and November 2002 were evaluate by prospective analysis. According to the 1997 American Joint Committee on Cancer staging classification, 5 had Stage III, and 3 had Stage IVB disease. The IMRT plans were designed to be delivered as a 'Simultaneous Modulated Accelerated Radiation Therapy' (SMART) using the 'step and shoot' technique with a MLC (multileaf collimator). Daily fractions of 2.2-2.5Gy and 1.9-2Gy were prescribed and delivered to the GTV and CTV and clinically negative neck node, respectively. The prescribed dose was 70A-79.0Gy to the gross tumor volume (GTV), 60Gy to the clinical target volume (CTV) and metastatic nodal station, and 46Gy to the clinically negative neck. All patients also received weekly cisplatin during radiotherapy. Acute and late normal tissue effects were graded according to the Radiation Therapy Oncology Group (RTOG) radiation morbidity scoring criteria. Results: Follow-up period was ranging from 5 to 18 months. All patients showed complete response and loco-regional control rate was 100% but one patient died of malnutrition due to treatment related toxicity. There were no Grade 3 or 4 xerostomia and all patients had experienced improvement of salivary gland function. Conclusion: 'Simultaneous Modulated Accelerated Radiation Therapy' (SMART) boost intensity-modulated radiotherapy technique allows parotid sparing as evidenced both clinically and by dosimetry. Initial tumor response and loco-regional control was promising. It is clinically feasible. A larger population of patients and a long-term follow-up are needed to evaluate ultimate tumor control and late toxicity.

• Radiation Oncology Journal
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• v.20 no.1
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• pp.68-72
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• 2002

This study was done to implement intensity-modulated radiation therapy (IMRT) for the treatment of primary prostate cancer and to compare this technique with conventional treatment methods. A 72-year-old male patient with prostate cancer stage T2a was treated with IMRT delivered with dynamic multi-leaf collimation. Treatment was designed using an inverse planning algorithm, which accepts dose and dose-volume constraints for targets and normal structures. The IMRT plan was compared with a three-dimensional (3D) plan using the same 6 fields technique. Lower normal tissue doses and improved target coverage were achieved using IMRT at current dose levels, and facilitate dose escalation to further enhance locoregional control and organ movement during radiotherapy is an important issue of IMRT in prostate cancer.

• Radiation Oncology Journal
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• v.35 no.4
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• pp.325-331
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• 2017

Purpose: There is controversy regarding the cosmetic outcome after accelerated partial breast radiation (APBR). We report the cosmetic outcome from a single-arm prospective clinical trial of APBR delivered using intensity-modulated radiation therapy (IMRT) in elderly patients with stage I breast cancer (BC), using a novel fractionation schedule. Materials and Methods: Forty-two patients aged ${\geq}65$, with Stage I BC who underwent breast-conserving surgery were enrolled in a phase I/II study evaluating a 2-week course of APBR. Thirty eligible patients received 40 Gy in 4 Gy daily fractions. Cosmetic outcome was assessed subjectively by physician/patient and objectively by using a computer program (BCCT.core) before APBR, during, and after completion of the treatment. Results: The median age was 72 years, the median tumor size was 0.8 cm, and the median follow-up was 50.5 months. The 5-year locoregional control in this cohort was 97% and overall survival 87%. At the last follow-up, patients and physicians rated cosmesis as 'excellent' or 'good' in 100% and 91 %, respectively. The BCCT.core program scored the cosmesis as 'excellent' or 'good' in 87% of the patients at baseline and 81% at the last follow-up. The median $V_{50}$ (20 Gy) of the whole breast volume (WBV) was 37.2%, with the median WBV $V_{100}$ (40 Gy) of 10.9%. Conclusion: An excellent rate of tumor control was observed in this prospective trial. By using multiple assessment techniques, we are showing acceptable cosmesis, supporting the use of IMRT planned APBR with daily schedule in elderly patients with early stage BC.