• Asian Pacific Journal of Cancer Prevention
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• v.16 no.7
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• pp.2613-2617
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• 2015

Radiation induced lung injury has long been considered a treatment limiting factor for patients requiring thoracic radiation. This radiation induced lung injury happens early as well as late. Radiation induced lung injury can occur in two phases viz. early (< 6 months) when it is called radiation pneumonitis and late (>6 months) when it is called radiation induced lung fibrosis. There are multiple factors that can be patient, disease or treatment related that predict the incidence and severity of radiation pneumonitis. Radiation induced damage to the type I pneumocytes is the triggering factor to initiate such reactions. Over the years, radiation therapy has witnessed a paradigm shift in radiation planning and delivery and successfully reduced the incidence of lung injury. Radiation pneumonitis is usually a diagnosis of exclusion. Steroids, ACE inhibitors and pentoxyphylline constitute the cornerstone of therapy. Radiation induced lung fibrosis is another challenging aspect. The pathophysiology of radiation fibrosis includes continuing inflammation and microvascular changes due to pro-angiogenic and profibrogenic stimuli resembling those in adult bronchiectasis. General supportive management, mobilization of airway secretions, anti-inflammatory therapy and management of acute exacerbations remains the treatment option. Radiation induced lung injury is an inevitable accompaniment of thoracic radiation.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.11
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• pp.4717-4721
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• 2014

Background: Dosimetric comparison of two dimensional (2D) radiography and three-dimensional computed tomography (3D-CT) based dose distributions with high-dose-rate (HDR) intracavitry radiotherapy (ICRT) for carcinoma cervix, in terms of target coverage and doses to bladder and rectum. Materials and Methods: Sixty four sessions of HDR ICRT were performed in 22 patients. External beam radiotherapy to pelvis at a dose of 50 Gray in 27 fractions followed by HDR ICRT, 21 Grays to point A in 3 sessions, one week apart was planned. All patients underwent 2D-orthogonal and 3D-CT simulation for each session. Treatment plans were generated using 2D-orthogonal images and dose prescription was made at point A. 3D plans were generated using 3D-CT images after delineating target volume and organs at risk. Comparative evaluation of 2D and 3D treatment planning was made for each session in terms of target coverage (dose received by 90%, 95% and 100% of the target volume: D90, D95 and D100 respectively) and doses to bladder and rectum: ICRU-38 bladder and rectum point dose in 2D planning and dose to 0.1cc, 1cc, 2cc, 5cc, and 10cc of bladder and rectum in 3D planning. Results: Mean doses received by 100% and 90% of the target volume were $4.24{\pm}0.63$ and $4.9{\pm}0.56$ Gy respectively. Doses received by 0.1cc, 1cc and 2cc volume of bladder were $2.88{\pm}0.72$, $2.5{\pm}0.65$ and $2.2{\pm}0.57$ times more than the ICRU bladder reference point. Similarly, doses received by 0.1cc, 1cc and 2cc of rectum were $1.80{\pm}0.5$, $1.48{\pm}0.41$ and $1.35{\pm}0.37$ times higher than ICRU rectal reference point. Conclusions: Dosimetric comparative evaluation of 2D and 3D CT based treatment planning for the same brachytherapy session demonstrates underestimation of OAR doses and overestimation of target coverage in 2D treatment planning.

• Progress in Medical Physics
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• v.32 no.1
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• pp.18-24
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• 2021

Purpose: Kilovoltage computed tomography (kV-CT) is essential for radiation treatment planning. However, kV-CT images are significantly distorted by artifacts when a metallic prosthesis is present in the patient's body. Thus, the accuracies of target delineation and treatment dose calculation are inevitably lowered. We evaluated the accuracy of the calculated doses using an image restoration method with hybrid CT, which was introduced in our previous study. Methods: A cylindrical phantom containing four metals, namely, silver, copper, tin, and tungsten, was scanned using kV-CT and megavoltage CT to produce hybrid CT images. We created six verification plans for three head and neck patients on kV-CT and hybrid CT images of the phantom and calculated their doses. The actual doses were measured with film patches during beam delivery using tomotherapy. We used the gamma evaluation method to compare dose distribution between kV-CT and hybrid CT with three gamma criteria, namely, 3%/3 mm, 2%/2 mm, and 1%/1 mm. Results: The gamma pass rates decreased as the gamma criteria were strengthened, and the pass rate of hybrid CT was higher than that of kV-CT in all cases. When the 1%/1 mm criterion was used, the difference in gamma pass rates between them was up to 13%p. Conclusions: According to our findings, we expect that the use of hybrid CT can be a suitable approach to avoid the effect of severe metal artifacts on the accuracy of dose calculation and contouring.

• Radiation Oncology Journal
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• v.35 no.2
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• pp.180-184
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• 2017

Patients with locally advanced lung cancer and very limited pulmonary function (forced expiratory volume in 1 second $[FEV1]{\leq}1L$) have dismal prognosis and undergo palliative treatment or best supportive care. We describe two cases of locally advanced node-positive non-small cell lung cancer (NSCLC) patients with very limited lung function treated with induction chemotherapy and moderate hypofractionated image-guided radiotherapy (Hypo-IGRT). Hypo-IGRT was delivered to a total dose of 45 Gy to the primary tumor and involved lymph nodes. Planning was based on positron emission tomography-computed tomography (PET/CT) and four-dimensional computed tomography (4D-CT). Internal target volume (ITV) was defined as the overlap of gross tumor volume delineated on 10 phases of 4D-CT. ITV to planning target volume margin was 5 mm in all directions. Both patients showed good clinical and radiological response. No relevant toxicity was documented. Hypo-IGRT is feasible treatment option in locally advanced node-positive NSCLC patients with very limited lung function ($FEV1{\leq}1L$).

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.235-236
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• 2002

A Klystron powered dual photon energy electron linear accelerator 2300 C/D from Varian Associates has been installed in our center. From the radiological safety view as well as treatment planning, the output (contamination) of Bremsstrahlung Radiation with electron beam energy determined accurately. It has been found 0.5% to 4.7% with increasing the electron beam energy which is the clinically not much significant in the treatment of the malignant diseases with the treatment of electron beam.

• Journal of radiological science and technology
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• v.42 no.6
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• pp.413-422
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• 2019

Heavy ion particle, represented carbon ion, radiotherapy is currently most advanced radiation therapy technique. Conventional radiation therapy has made remarkable changes over a relatively short period of time and leading various developments such as intensity modulated radiation therapy, 4D radiation therapy, image guided radiation therapy, and high precisional therapy. However, the biological and physical superiority of particle radiation, represented by Bragg peak, can give the maximum dose to tumor and minimal dose to surrounding normal tissues in the treatment of cancers in various areas surrounded by radiation-sensitive normal tissues. However, despite these advantages, there are some limitations and factors to consider. First, there is not enough evidence, such as large-scale randomized, prospective phase III trials, for the clinical application. Secondly, additional studies are needed to establish a very limited number of treatment facilities, uncertainty about the demand for heavy particle treatment, parallel with convetional radiotherapy or indications. In addition, Bragg peak of the heavy particles can greatly reduce the dose to the normal tissues front and behind the tumor compared to the photon or protons. High precision and accuracy are needed for treatment planning and treatment, especially for lungs or livers with large respiratory movements. Currently, the introduction of the heavy particle therapy device is in progress, and therefore, it is expected that more research will be active.

• Radiation Oncology Journal
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• v.26 no.1
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• pp.35-44
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• 2008

Purpose: To evaluate the incidence and prognostic factors of treatment-related pneumonitis in non-small-cell lung cancer(NSCLC) patients treated with intensity modulated radiation therapy(IMRT). Materials and Methods: One-hundred-five patients with NSCLC treated with IMRT between 1 August 2004 and 30 November 2006 were analyzed retrospectively. The mean age of patients was 62.9 years, and squamous carcinomas were confirmed in 81 patients(77%). Sixty-six patients(62.9%) were classified as stage III, and 59 patients had lesions in the right lung. Twenty-seven patients were treated with a dose of 3,060 cGy preoperatively, and 10 patients were given a dose of 5,040 cGy postoperatively. Sixty-eight patients received a dose of 7,020 cGy for curative intent. Sixty-eight patients were treated with the use of the CORVUS planning system and 37 patients were treated with the use of the ECLIPSE planning system. Results: Of 105 patients, 21 patients(20%) had abnormal radiological findings, but only seven patients(6.7%) required treatment for radiation pneumonitis. Six of the seven patients had other serious lesions, including a bronchioesophageal fistula(one patient), recurrence in the treatment field(two patients), brain metastasis(one patient) and lung-to-lung metastasis(two patients); all of these patients died within 19 months after radiation treatment. Sixteen patients(23.5%) that received planning with the CORVUS system had abnormal lung findings. Five patients(13.5%) had abnormal lung findings with the use of the ECLIPSE planning system. Other prognostic factors such as perioperative radiation therapy, a volume over 10% of the V20 volume in the right lung, were also statistically significant. Conclusion: This retrospective analysis suggests that IMRT could be a beneficial treatment modality for the reduction of radiation pneumonitis in NSCLC patients. However, the higher incidence of abnormal radiological findings in perioperative patients treated with relatively lower doses($3,060{\sim}5,040$ cGy) suggest the need for judicious treatment planning in preoperative or postoperative treatment.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.302-304
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• 2002

In linac-based stereotactic radiosurgery, assuring the quality of the planning and delivery of external photon beam requires accurate evaluation of beam parameters, usually including output factors, tissue-phantom ratio and off-axis ratios, and measurement of actual dose distributions from simulated treatment. We're going to test the use of calibrated radio chromic film (Gafchromic film; type MD-55, Nuclear associate) using a Lumiscan 75 digitizer to measure absolute dose and relative dose distributions for linac-based radiosurgery unit Relative dose distribution of a human-style spherical acryl phantom were measured using radiochromic film and calculated by treatment planning system. The absolute dose at the sphere center was measured by radiochromic film and micro chamber (Exradin A-14, 0.009cc). What we want to demonstrate in this work, the 'well selected' radiochromic films when external photon beam are used in linac-based stereotactic radiosurgery are very accurate detector for dosimetry.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2006.08a
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• pp.99-99
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• 2006

• Progress in Medical Physics
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• v.11 no.1
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• pp.49-57
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• 2000

New method about the dose optimization problem in radiation treatment was researched. Since all conditions are more complex and there are more relevant variables, the solution of three-dimensional treatment planning is much more complicate than that of current two-dimensional one. There(ore, in this study, as a method to solve three-dimensional dose optimization problem, the considered variables was minized and researched by reducing the domain that solutions can exist and pre-determining the important beam parameters. First, the dangerous beam range that passes critical organ was found by coordinate transformation between linear accelerator coordinate and patient coordinate. And the beam size and rotation angle for rectangular collimator that conform tumor at arbitrary beam position was also determined. As a result, the available beam position could be reduced and the dependency on beam size and rotation angle, that is very important parameter in treatment planning, totally removed. Therefore, the resultant combinations of relevant variables could be greatly reduced and the dose optimization by objective function can be done with minimum variables. From the above results, the dose optimization problem was solved for the two-dimensional radiation treatment planning useful in clinic. The objective function was made by combination of dose gradient, critical organ dose and dose homogeniety. And the optimum variables were determined by applying step search method to objective function. From the dose distributions by optimum variables, the merit of new dose optimization method was verified and it can be implemented on commercial radiation treatment planning system with further research.