Sangwook Lim - Academia.edu (original) (raw)

Papers by Sangwook Lim

Kosin Medical Journal

Background: Radiotherapy improves overall survival in patients with abdominopelvic malignancies. ... more Background: Radiotherapy improves overall survival in patients with abdominopelvic malignancies. However, the toxic effects of radiation restrict the maximum dose that can be given, and there are no well-established preventive or therapeutic strategies. This study was conducted to evaluate whether rebamipide, sucralfate, and rifaximin have a suppressive effect on acute ionizing radiation (IR)-induced inflammation in the intestines of mice.Methods: Thirty-six ICR mice were divided into a vehicle-treated group with sham irradiation; a vehicle-treated group with irradiation; rebamipide, sucralfate, or rifaximin-treated groups with irradiation; and a rebamipide-treated group with sham irradiation. The expression of proinflammatory, anti-inflammatory, proapoptotic, and antiapoptotic factors was investigated.Results: The downregulated expression of nicotinamide phosphoribosyltransferase by IR was attenuated by all drugs (p<0.05). All drugs suppressed the IR-induced activation of NF-κB ...

Purpose: It is difficult to reproduce a brachytherapy measurement because of changes in the recta... more Purpose: It is difficult to reproduce a brachytherapy measurement because of changes in the rectal shape during inter-fraction. We constructed a multi-purpose brachytherapy phantom (MPBP) and reproduced the same conditions found in actual therapy. We further attempted to apply the measured optimal dose to reduce rectal complications. Methods: A measured dose was administered at rectal reference point R1 using a diode detector in four patients who used a tandem and ovoid in brachytherapy for carcinoma of the cervix. A total number of 20 rectal dose measurements were performed five times per patient. In addition, discrepancies in the set-up of the diode detector were analyzed with each repetitive measurement. After reproducing the same conditions as found in actual therapy using a multi-function applicator (MFA) in the multi-purpose brachytherapy phantom constructed for this study, the dose was measured at reference points in the rectum using a thermoluminescence dosimeter (TLD). Resu...

To introduce the four-dimensional computed tomography (4DCT, Light Speed RT, General Electric, US... more To introduce the four-dimensional computed tomography (4DCT, Light Speed RT, General Electric, USA) scanner newly installed in our department and evaluate its feasibility for gated radiotherapy. Respiratory signal measured by real-time position management (RPM ® , Varian Medical, USA) was recorded in synchronization with the 4DCT scanner. 4DCT data were acquired in axial cine mode and sorted retrospective image based on respiratory phase. PTVs delineated from helical CT and 4DCT images were compared. The PTV delineated from conventional helical CT images was 2 cc larger than that from 4DCT images. Dose in PTV of the plan from retrospective CT was 99.3% (minimum=72.0%, maximum=106.5%) and that of helical CT plan was 95.2% (minimum=24.1%, maximum=106.4%) of prescribed dose. Comparing with DVHs of both plan, the coverage for 4CDT plan was 3.7% improved. It is expected that 4DCT could improve tumor control and reduce radiation toxicity for liver cancer.

We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc.... more We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc., Palo Alto, CA, USA), with attention to the laser, the gantry, and operator performance. We let experienced technicians place the marker block on the couch using a lock bar system, with alignment to the isocenter of the laser, every morning. A pair of radiographic images of the marker block was acquired at 0 and 270 angles to the kV arm to correct the position using a 2D/2D matching technique. Once the desired match was achieved, the couch was moved remotely to correct the setup error and the parameters were saved. The average for the vertical and the longitudinal displacements were 0.65 mm and 0.66 mm, and 0.01 mm for the lateral displacement. The average for the vertical and longitudinal displacements were statistically significant at the 0.05 level (p value=0.000 for both), while the p value for the lateral direction was 0.829. These results show that the tendencies to displacement i...

Progress in Medical Physics, 2018

The purpose of this study is to build a database of patient information for efficient radiotherap... more The purpose of this study is to build a database of patient information for efficient radiotherapy management. Microsoft Office Access was used to build the database owing to its convenience and compatibility. The most important aspect when building the patient database is to make the input and management of patient information efficient at every step of radiotherapy process. The information input starts from the patient's first visit to the radiation therapy department and ends upon completion of the radiotherapy. The forms for each step of radiotherapy process include the patient information form, the radiotherapy schedule form, the radiotherapy information form, the simulation order form, and the patient history form. Every form is centrically connected to the radiation oncology department's patient information form. A test revealed that the database was found to be efficient in managing patient information at each step. An important benefit of this database is improved efficiency in radiotherapy management. Information on patients who received radiotherapy is stored in a database. This means that this clinical data can be found easily and used in future, which will be helpful in research studies on the radiation oncology department. Benefits such as these will potentially contribute to improved radiotherapy quality.

Radiation oncology journal, 2017

To see the gross tumor volume (GTV) dependency according to the phase selection and reconstructio... more To see the gross tumor volume (GTV) dependency according to the phase selection and reconstruction methods, we measured and analyzed the changes of tumor volume and motion at each phase in 20 cases with lung cancer patients who underwent image-guided radiotherapy. We retrospectively analyzed four-dimensional computed tomography (4D-CT) images in 20 cases of 19 patients who underwent image-guided radiotherapy. The 4D-CT images were reconstructed by the maximum intensity projection (MIP) and the minimum intensity projection (Min-IP) method after sorting phase as 40%-60%, 30%-70%, and 0%-90%. We analyzed the relationship between the range of motion and the change of GTV according to the reconstruction method. The motion ranges of GTVs are statistically significant only for the tumor motion in craniocaudal direction. The discrepancies of GTV volume and motion between MIP and Min-IP increased rapidly as the wider ranges of duty cycles are selected. As narrow as possible duty cycle such a...

Case Reports in Clinical Medicine, 2015

Sarcomas are relatively rare malignancies; however, their huge variety and shortage of the effect... more Sarcomas are relatively rare malignancies; however, their huge variety and shortage of the effective therapies make this disease face huge challenge for oncology. It is recently shown that hyperthermia could be successfully applied even in high-risk cases in combination with the available gold-standard regiments. Our aim is to present various advanced cases treated with a new hyperthermia method, oncothermia, showing its advantages and feasibility to successfully treat highly advanced sarcomas with curative intent.

Radiation Oncology Journal, 2015

Purpose: To compare audio-only biofeedback to conventional audiovisual biofeedback for regulating... more Purpose: To compare audio-only biofeedback to conventional audiovisual biofeedback for regulating patients' respiration during four-dimensional radiotherapy, limiting damage to healthy surrounding tissues caused by organ movement. Materials and Methods: Six healthy volunteers were assisted by audiovisual or audio-only biofeedback systems to regulate their respirations. Volunteers breathed through a mask developed for this study by following computer-generated guiding curves displayed on a screen, combined with instructional sounds. They then performed breathing following instructional sounds only. The guiding signals and the volunteers' respiratory signals were logged at 20 samples per second. Results: The standard deviations between the guiding and respiratory curves for the audiovisual and audio-only biofeedback systems were 21.55% and 23.19%, respectively; the average correlation coefficients were 0.9778 and 0.9756, respectively. The regularities between audiovisual and audio-only biofeedback for six volunteers' respirations were same statistically from the paired t-test. Conclusion: The difference between the audiovisual and audio-only biofeedback methods was not significant. Audio-only biofeedback has many advantages, as patients do not require a mask and can quickly adapt to this method in the clinic.

Progress in Medical Physics, 2013

Generally, to evaluate gated radiation therapy, moving phantoms are used to simulate organ motion... more Generally, to evaluate gated radiation therapy, moving phantoms are used to simulate organ motion. Since the target moves in every direction, we need to take into account motion in each direction. This study proposes methods to evaluate gated radiation therapy using gamma index analysis and to visualize adequate gating window sizes according to motion ranges. The moving phantom was fabricated to simulate motion in the craniocaudal direction. This phantom consisted of a moving platform, the I'm MatriXX, and solid water phantoms. A 6 MV photon filed with a field size of 4×4 cm 2 was delivered to the phantom using the gating system, while the phantom moved in the 1-, 2-, 3-, 4-, and 5-cm motion ranges. The gating windows were set at 40∼60%, 30∼40%, and 0∼90%, respectively. The I'm MatriXX acquired the dose distributions for each scenario and the dose distributions were compared with a 4×4 cm 2 static filed. The tolerance of the gamma index was set at 3%/3 mm. The greater the gating window, the lower the pass rate, and the greater the motion range, the lower the pass rate in this study. In case treatment without gated radiation therapy for the target with motion of 2 cm, the pass rate was less than 96%. But it was greater than 99% when gated radiation therapy was used. However gated radiation therapy was used for the target with motion greater than 4 cm, the pass rate could not be greater than 97% when gating window was set as 30∼70%. But when the gating window set as 40∼60%, the pass rate was greater than 99%.

Journal of the Korean Physical Society, 2015

The purpose of this study was to use various dosimetrical indices to determine the best IMRT moda... more The purpose of this study was to use various dosimetrical indices to determine the best IMRT modality technique for treating patients with prostate cancer. Ten patients with prostate cancer were included in this study. Intensity modulated radiation therapy plans were designed to include different modalities, including the linac step and shoot, Tomotherapy, RapidArc, and Proton systems. Various dosimetrical indices, like the prescription isodose to target volume (PITV) ratio, conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF) were determined to compare the different treatment plans. Biological indices such as the generalized equivalent uniform dose (gEUD), based tumor control probability (TCP), and normal tissue complication probability (NTCP) were also calculated and used to compare the treatment plans. The RapidArc plan attained better PTV coverage, as evidenced by its superior PITV, CI, TCI, MHI, and CN values. Regarding OARs, proton therapy exhibited superior dose sparing for the rectum and bowel in low dose volumes, whereas the Tomotherapy and RapidArc plans achieved better dose sparing in high dose volumes. The QF scores showed no significant difference among these plans (p=0.701). The average TCPs for prostate tumors in the RapidArc, Linac, and Proton plans were higher than the average TCP for Tomotherapy (98.79%, 98.76%, and 98.75% vs. 98.70%, respectively). Regarding the rectum NTCP, RapidArc showed the most favorable result (0.09%), whereas Linac resulted in the best bladder NTCP (0.08%).

Progress in Medical Physics, 2015

The purpose of this study is to see the usefulness of lead apron for critical organs near the bre... more The purpose of this study is to see the usefulness of lead apron for critical organs near the breast under examining. For clinical experiment, 30 female volunteers who agreed to their participation in the experiments, were chosen and divided into two groups, 15 in group A and 15 in group B respectively. group A is to see whether each side of breast under mammography affects to other side glandular on the critical organs is same, because it is not allowed to scan the both breast for same person or to scan repeatedly. Group B is to see the effectiveness of lead apron during the mammography of right breast. Glass dosimeters were placed on the thyroid, the contralateral breast, and lower abdomen where near the breast during examining. The average glandular doses on the surface in mammography of the thyroid gland, the contralateral breast, the lower abdomen were 0.0692 mGy, 0.6790 mGy, and 0.0122 mGy, respectively, which was an extremely low level of glandular dose. In group B, as to the thyroid gland, average dose was decreased from 0.0922 mGy to 0.0158 mGy. The average dose of contralateral breast was decreased from 0.8575 mGy to 0.0286 mGy. The average doses of lower abdomen was decrease 0.0150 mGy to 0.0173 mGy. As to the lower abdomen, dose decreased from 0.0150 mGy before the use of an apron down to 0.0173 mGy after the use. As p-value was under 0.05, statistically significant difference was observed between the two groups. Wearing an apron can have the protective effects on the thyroid gland up to 20 times lower than not wearing one. Besides, it is also necessary to protect the other breast during the examination by wearing one.

IFMBE Proceedings

Instructions for preparing papers for WC2006 Proceedings Series are presented. They are intended ... more Instructions for preparing papers for WC2006 Proceedings Series are presented. They are intended to guide the authors in preparing the electronic version of their paper. Only papers prepared according to these instructions will be published in the paper and online version of Proceedings. Provide an abstract of your paper no longer than 300 words.

IFMBE Proceedings

Targets inside lung or liver usually move significantly due to respiratory motion. A generous mar... more Targets inside lung or liver usually move significantly due to respiratory motion. A generous margin must be allowed and large volume of normal tissue is irradiated with intensive radiation. Several techniques have been suggested to minimize the PTV relating to ...

To track moving tumor in real time, CyberKnife system imports a technique of the synchrony respir... more To track moving tumor in real time, CyberKnife system imports a technique of the synchrony respiratory tracking system. The fiducial marker which are detectable in X-ray images were demand in CyberKnife Robotic radiosurgery system. It issued as reference markers to locate and track tumor location during patient alignment and treatment delivery. Fiducial marker implantation is an invasive surgical operation that carries a relatively high risk of pneumothorax. Most recently, it was developed a direct lung tumor registration method that does not require the use of fiducials. The purpose of this study is to measure the accuracy of target applying X-sight lung tracking using the Gafchromic film in dynamic moving thorax phantom. The X-sight Lung Tracking quality assurance motion phantom simulates simple respiratory motion of a lung tumor and provides Gafchromic dosimetry film-based test capability at locations inside the phantom corresponding to a typical lung tumor. The total average error for the X-sight Lung Tracking System with a moving target was 0.85±0.22 mm. The results were considered reliable and applicable for lung tumor treatment in CyberKnife radiosurgery system. Clinically, breathing patterns of patients may vary during radiation therapy. Therefore, additional studies with a set real patient data are necessary to evaluate the target accuracy for the X-sight Lung Tracking system.

Progress in Medical Physics, 2021

This study aimed to design a multipurpose dose verification phantom for external audits to secure... more This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy. Methods: In this study, we used International Atomic Energy Agency (IAEA) LiF powder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm 3). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm 3 ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements. Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour. Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.

Progress in Medical Physics, 2019

To manage radiation measurement equipment, a web-based management program has been developed in t... more To manage radiation measurement equipment, a web-based management program has been developed in this study. Materials and Methods: This program is based on a web service and Java Server Pages (JSP) and employs compatibility and accessibility. Results: The first step in the workflow has been designed to create accounts for each user or organization and to log in. The program consists of two parts: fields for listed instruments, and measurement information. The instruments for measuring radiation listed in this program are as follows: ionization chambers, survey meters, thermometers, barometers, electrometers, and phantoms. Instrument properties can be put in the recording fields and browsing for associated instruments can be performed. The main part of the program is the cross-calibration for each ion chamber. For instance, the ionization chamber to be used as a relative dosimeter can be registered by cross-calibration data with a reference chamber calibrated by an accredited laboratory. This program supports methods using the central axis transfer theory for cross-calibration for the ionization chambers. The reference and field ionization chambers were placed in a solid water phantom along the beam central axis at two different depths, and then the positions were switched. Each measured value was used for calculating the cross-calibration factor. Conclusions: Because many instruments are used and managed in radiation oncology departments, systematic, traceable recording is very important. The web-based program developed in this study is expected to be used effectively in the maintenance of radiation measurement instruments.

IFMBE Proceedings

The organ motion due to respiration necessitates adding adequate margins to the planning target v... more The organ motion due to respiration necessitates adding adequate margins to the planning target volume (PTV) to ensure adequate dose coverage in chest and abdomen. Several techniques have been suggested to minimize the PTV relating to respiratory motion. In this study, ten patients’ respiratory patterns were measured by thermocouple, spirometer, and skin motion simultaneously, to find the best method corresponding with respiratory target motion. Each respiration monitoring methods were compared with fluoroscopic target motion during simulation. Conventional spirometer and home made thermocouple were connected to a mouse piece to measure the patient’s respiration. A respiration acquisition program was developed, which acquire respiration signals and display its patterns. A fluoroscopic target tracking program was developed. Ten patients with lung or liver cancer participated in this study. Fluoroscopic movies were captured during acquisition of their respiration patterns. At the same time their skin motion was measured by using Real-time Position Management’ (RPM’, Varian, Palo Alto, CA) system. Respiratory patterns acquired from spirometer, thermocouple, and RPM’ system were compared with fluoroscopic target motion respectively. Its relationships were evaluated by correlation coefficient. Comparing each correlation coefficient for spirometer, thermocouple, and RPM®, skin motion detection is the most correspondent with fluoroscopic target motion. Respiration monitoring methods with spirometer or thermocouple, and skin motion detection are directly applicable to monitor the target motion for applying 4D radiotherapy.

Genes & Genomics, 2016

Unfortunately, there is a spelling error in the first name of the tenth author in the published a... more Unfortunately, there is a spelling error in the first name of the tenth author in the published article. The correct name is Taek Kyu Kwon, not Tae Kyu Kwon. The correction is now updated in the article and also shown in this erratum.

Progress in Medical Physics, 2016

Periodical calibrations of radiation detectors are important for accurate quality assurance of th... more Periodical calibrations of radiation detectors are important for accurate quality assurance of therapeutic linac. The measuring instruments such as ion-chamber, thermometer, barometer, and survey meter should be calibrated periodically. Period of calibration for these instruments is suggested 6 month to one year in Korea and two years in other countries nowadays. Therefore, the determination of reasonable period for calibration is needed. In this study, we plan to utilize the results of these survey; frequent in use, how to use and stability of instruments, to determine the optimized period of calibration for the instruments in the departments of radiation oncology in Korea based on the ILAC-G24. The SurveyMonkey web-based survey tool was used and the objects of survey were 18 department of radiation oncology in university hospitals, and 15 departments were answered. The 64 questionnaires which supposed to be answered in 50 minutes were classified as the information of candidates, the thermometer, the barometer, the surveymeter, and the ion-chamber. The thermometers and the barometers were not under periodical calibration for more than half of candidates. The periods of calibration of surveymeters were 6 month to 1 year. We expect that the calibration period can be determined based on these survey results.

Kosin Medical Journal

Background: Radiotherapy improves overall survival in patients with abdominopelvic malignancies. ... more Background: Radiotherapy improves overall survival in patients with abdominopelvic malignancies. However, the toxic effects of radiation restrict the maximum dose that can be given, and there are no well-established preventive or therapeutic strategies. This study was conducted to evaluate whether rebamipide, sucralfate, and rifaximin have a suppressive effect on acute ionizing radiation (IR)-induced inflammation in the intestines of mice.Methods: Thirty-six ICR mice were divided into a vehicle-treated group with sham irradiation; a vehicle-treated group with irradiation; rebamipide, sucralfate, or rifaximin-treated groups with irradiation; and a rebamipide-treated group with sham irradiation. The expression of proinflammatory, anti-inflammatory, proapoptotic, and antiapoptotic factors was investigated.Results: The downregulated expression of nicotinamide phosphoribosyltransferase by IR was attenuated by all drugs (p<0.05). All drugs suppressed the IR-induced activation of NF-κB ...

Purpose: It is difficult to reproduce a brachytherapy measurement because of changes in the recta... more Purpose: It is difficult to reproduce a brachytherapy measurement because of changes in the rectal shape during inter-fraction. We constructed a multi-purpose brachytherapy phantom (MPBP) and reproduced the same conditions found in actual therapy. We further attempted to apply the measured optimal dose to reduce rectal complications. Methods: A measured dose was administered at rectal reference point R1 using a diode detector in four patients who used a tandem and ovoid in brachytherapy for carcinoma of the cervix. A total number of 20 rectal dose measurements were performed five times per patient. In addition, discrepancies in the set-up of the diode detector were analyzed with each repetitive measurement. After reproducing the same conditions as found in actual therapy using a multi-function applicator (MFA) in the multi-purpose brachytherapy phantom constructed for this study, the dose was measured at reference points in the rectum using a thermoluminescence dosimeter (TLD). Resu...

To introduce the four-dimensional computed tomography (4DCT, Light Speed RT, General Electric, US... more To introduce the four-dimensional computed tomography (4DCT, Light Speed RT, General Electric, USA) scanner newly installed in our department and evaluate its feasibility for gated radiotherapy. Respiratory signal measured by real-time position management (RPM ® , Varian Medical, USA) was recorded in synchronization with the 4DCT scanner. 4DCT data were acquired in axial cine mode and sorted retrospective image based on respiratory phase. PTVs delineated from helical CT and 4DCT images were compared. The PTV delineated from conventional helical CT images was 2 cc larger than that from 4DCT images. Dose in PTV of the plan from retrospective CT was 99.3% (minimum=72.0%, maximum=106.5%) and that of helical CT plan was 95.2% (minimum=24.1%, maximum=106.4%) of prescribed dose. Comparing with DVHs of both plan, the coverage for 4CDT plan was 3.7% improved. It is expected that 4DCT could improve tumor control and reduce radiation toxicity for liver cancer.

We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc.... more We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc., Palo Alto, CA, USA), with attention to the laser, the gantry, and operator performance. We let experienced technicians place the marker block on the couch using a lock bar system, with alignment to the isocenter of the laser, every morning. A pair of radiographic images of the marker block was acquired at 0 and 270 angles to the kV arm to correct the position using a 2D/2D matching technique. Once the desired match was achieved, the couch was moved remotely to correct the setup error and the parameters were saved. The average for the vertical and the longitudinal displacements were 0.65 mm and 0.66 mm, and 0.01 mm for the lateral displacement. The average for the vertical and longitudinal displacements were statistically significant at the 0.05 level (p value=0.000 for both), while the p value for the lateral direction was 0.829. These results show that the tendencies to displacement i...

Progress in Medical Physics, 2018

The purpose of this study is to build a database of patient information for efficient radiotherap... more The purpose of this study is to build a database of patient information for efficient radiotherapy management. Microsoft Office Access was used to build the database owing to its convenience and compatibility. The most important aspect when building the patient database is to make the input and management of patient information efficient at every step of radiotherapy process. The information input starts from the patient's first visit to the radiation therapy department and ends upon completion of the radiotherapy. The forms for each step of radiotherapy process include the patient information form, the radiotherapy schedule form, the radiotherapy information form, the simulation order form, and the patient history form. Every form is centrically connected to the radiation oncology department's patient information form. A test revealed that the database was found to be efficient in managing patient information at each step. An important benefit of this database is improved efficiency in radiotherapy management. Information on patients who received radiotherapy is stored in a database. This means that this clinical data can be found easily and used in future, which will be helpful in research studies on the radiation oncology department. Benefits such as these will potentially contribute to improved radiotherapy quality.

Radiation oncology journal, 2017

To see the gross tumor volume (GTV) dependency according to the phase selection and reconstructio... more To see the gross tumor volume (GTV) dependency according to the phase selection and reconstruction methods, we measured and analyzed the changes of tumor volume and motion at each phase in 20 cases with lung cancer patients who underwent image-guided radiotherapy. We retrospectively analyzed four-dimensional computed tomography (4D-CT) images in 20 cases of 19 patients who underwent image-guided radiotherapy. The 4D-CT images were reconstructed by the maximum intensity projection (MIP) and the minimum intensity projection (Min-IP) method after sorting phase as 40%-60%, 30%-70%, and 0%-90%. We analyzed the relationship between the range of motion and the change of GTV according to the reconstruction method. The motion ranges of GTVs are statistically significant only for the tumor motion in craniocaudal direction. The discrepancies of GTV volume and motion between MIP and Min-IP increased rapidly as the wider ranges of duty cycles are selected. As narrow as possible duty cycle such a...

Case Reports in Clinical Medicine, 2015

Sarcomas are relatively rare malignancies; however, their huge variety and shortage of the effect... more Sarcomas are relatively rare malignancies; however, their huge variety and shortage of the effective therapies make this disease face huge challenge for oncology. It is recently shown that hyperthermia could be successfully applied even in high-risk cases in combination with the available gold-standard regiments. Our aim is to present various advanced cases treated with a new hyperthermia method, oncothermia, showing its advantages and feasibility to successfully treat highly advanced sarcomas with curative intent.

Radiation Oncology Journal, 2015

Purpose: To compare audio-only biofeedback to conventional audiovisual biofeedback for regulating... more Purpose: To compare audio-only biofeedback to conventional audiovisual biofeedback for regulating patients' respiration during four-dimensional radiotherapy, limiting damage to healthy surrounding tissues caused by organ movement. Materials and Methods: Six healthy volunteers were assisted by audiovisual or audio-only biofeedback systems to regulate their respirations. Volunteers breathed through a mask developed for this study by following computer-generated guiding curves displayed on a screen, combined with instructional sounds. They then performed breathing following instructional sounds only. The guiding signals and the volunteers' respiratory signals were logged at 20 samples per second. Results: The standard deviations between the guiding and respiratory curves for the audiovisual and audio-only biofeedback systems were 21.55% and 23.19%, respectively; the average correlation coefficients were 0.9778 and 0.9756, respectively. The regularities between audiovisual and audio-only biofeedback for six volunteers' respirations were same statistically from the paired t-test. Conclusion: The difference between the audiovisual and audio-only biofeedback methods was not significant. Audio-only biofeedback has many advantages, as patients do not require a mask and can quickly adapt to this method in the clinic.

Progress in Medical Physics, 2013

Generally, to evaluate gated radiation therapy, moving phantoms are used to simulate organ motion... more Generally, to evaluate gated radiation therapy, moving phantoms are used to simulate organ motion. Since the target moves in every direction, we need to take into account motion in each direction. This study proposes methods to evaluate gated radiation therapy using gamma index analysis and to visualize adequate gating window sizes according to motion ranges. The moving phantom was fabricated to simulate motion in the craniocaudal direction. This phantom consisted of a moving platform, the I'm MatriXX, and solid water phantoms. A 6 MV photon filed with a field size of 4×4 cm 2 was delivered to the phantom using the gating system, while the phantom moved in the 1-, 2-, 3-, 4-, and 5-cm motion ranges. The gating windows were set at 40∼60%, 30∼40%, and 0∼90%, respectively. The I'm MatriXX acquired the dose distributions for each scenario and the dose distributions were compared with a 4×4 cm 2 static filed. The tolerance of the gamma index was set at 3%/3 mm. The greater the gating window, the lower the pass rate, and the greater the motion range, the lower the pass rate in this study. In case treatment without gated radiation therapy for the target with motion of 2 cm, the pass rate was less than 96%. But it was greater than 99% when gated radiation therapy was used. However gated radiation therapy was used for the target with motion greater than 4 cm, the pass rate could not be greater than 97% when gating window was set as 30∼70%. But when the gating window set as 40∼60%, the pass rate was greater than 99%.

Journal of the Korean Physical Society, 2015

The purpose of this study was to use various dosimetrical indices to determine the best IMRT moda... more The purpose of this study was to use various dosimetrical indices to determine the best IMRT modality technique for treating patients with prostate cancer. Ten patients with prostate cancer were included in this study. Intensity modulated radiation therapy plans were designed to include different modalities, including the linac step and shoot, Tomotherapy, RapidArc, and Proton systems. Various dosimetrical indices, like the prescription isodose to target volume (PITV) ratio, conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF) were determined to compare the different treatment plans. Biological indices such as the generalized equivalent uniform dose (gEUD), based tumor control probability (TCP), and normal tissue complication probability (NTCP) were also calculated and used to compare the treatment plans. The RapidArc plan attained better PTV coverage, as evidenced by its superior PITV, CI, TCI, MHI, and CN values. Regarding OARs, proton therapy exhibited superior dose sparing for the rectum and bowel in low dose volumes, whereas the Tomotherapy and RapidArc plans achieved better dose sparing in high dose volumes. The QF scores showed no significant difference among these plans (p=0.701). The average TCPs for prostate tumors in the RapidArc, Linac, and Proton plans were higher than the average TCP for Tomotherapy (98.79%, 98.76%, and 98.75% vs. 98.70%, respectively). Regarding the rectum NTCP, RapidArc showed the most favorable result (0.09%), whereas Linac resulted in the best bladder NTCP (0.08%).

Progress in Medical Physics, 2015

The purpose of this study is to see the usefulness of lead apron for critical organs near the bre... more The purpose of this study is to see the usefulness of lead apron for critical organs near the breast under examining. For clinical experiment, 30 female volunteers who agreed to their participation in the experiments, were chosen and divided into two groups, 15 in group A and 15 in group B respectively. group A is to see whether each side of breast under mammography affects to other side glandular on the critical organs is same, because it is not allowed to scan the both breast for same person or to scan repeatedly. Group B is to see the effectiveness of lead apron during the mammography of right breast. Glass dosimeters were placed on the thyroid, the contralateral breast, and lower abdomen where near the breast during examining. The average glandular doses on the surface in mammography of the thyroid gland, the contralateral breast, the lower abdomen were 0.0692 mGy, 0.6790 mGy, and 0.0122 mGy, respectively, which was an extremely low level of glandular dose. In group B, as to the thyroid gland, average dose was decreased from 0.0922 mGy to 0.0158 mGy. The average dose of contralateral breast was decreased from 0.8575 mGy to 0.0286 mGy. The average doses of lower abdomen was decrease 0.0150 mGy to 0.0173 mGy. As to the lower abdomen, dose decreased from 0.0150 mGy before the use of an apron down to 0.0173 mGy after the use. As p-value was under 0.05, statistically significant difference was observed between the two groups. Wearing an apron can have the protective effects on the thyroid gland up to 20 times lower than not wearing one. Besides, it is also necessary to protect the other breast during the examination by wearing one.

IFMBE Proceedings

Instructions for preparing papers for WC2006 Proceedings Series are presented. They are intended ... more Instructions for preparing papers for WC2006 Proceedings Series are presented. They are intended to guide the authors in preparing the electronic version of their paper. Only papers prepared according to these instructions will be published in the paper and online version of Proceedings. Provide an abstract of your paper no longer than 300 words.

IFMBE Proceedings

Targets inside lung or liver usually move significantly due to respiratory motion. A generous mar... more Targets inside lung or liver usually move significantly due to respiratory motion. A generous margin must be allowed and large volume of normal tissue is irradiated with intensive radiation. Several techniques have been suggested to minimize the PTV relating to ...

To track moving tumor in real time, CyberKnife system imports a technique of the synchrony respir... more To track moving tumor in real time, CyberKnife system imports a technique of the synchrony respiratory tracking system. The fiducial marker which are detectable in X-ray images were demand in CyberKnife Robotic radiosurgery system. It issued as reference markers to locate and track tumor location during patient alignment and treatment delivery. Fiducial marker implantation is an invasive surgical operation that carries a relatively high risk of pneumothorax. Most recently, it was developed a direct lung tumor registration method that does not require the use of fiducials. The purpose of this study is to measure the accuracy of target applying X-sight lung tracking using the Gafchromic film in dynamic moving thorax phantom. The X-sight Lung Tracking quality assurance motion phantom simulates simple respiratory motion of a lung tumor and provides Gafchromic dosimetry film-based test capability at locations inside the phantom corresponding to a typical lung tumor. The total average error for the X-sight Lung Tracking System with a moving target was 0.85±0.22 mm. The results were considered reliable and applicable for lung tumor treatment in CyberKnife radiosurgery system. Clinically, breathing patterns of patients may vary during radiation therapy. Therefore, additional studies with a set real patient data are necessary to evaluate the target accuracy for the X-sight Lung Tracking system.

Progress in Medical Physics, 2021

This study aimed to design a multipurpose dose verification phantom for external audits to secure... more This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy. Methods: In this study, we used International Atomic Energy Agency (IAEA) LiF powder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm 3). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm 3 ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements. Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour. Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.

Progress in Medical Physics, 2019

To manage radiation measurement equipment, a web-based management program has been developed in t... more To manage radiation measurement equipment, a web-based management program has been developed in this study. Materials and Methods: This program is based on a web service and Java Server Pages (JSP) and employs compatibility and accessibility. Results: The first step in the workflow has been designed to create accounts for each user or organization and to log in. The program consists of two parts: fields for listed instruments, and measurement information. The instruments for measuring radiation listed in this program are as follows: ionization chambers, survey meters, thermometers, barometers, electrometers, and phantoms. Instrument properties can be put in the recording fields and browsing for associated instruments can be performed. The main part of the program is the cross-calibration for each ion chamber. For instance, the ionization chamber to be used as a relative dosimeter can be registered by cross-calibration data with a reference chamber calibrated by an accredited laboratory. This program supports methods using the central axis transfer theory for cross-calibration for the ionization chambers. The reference and field ionization chambers were placed in a solid water phantom along the beam central axis at two different depths, and then the positions were switched. Each measured value was used for calculating the cross-calibration factor. Conclusions: Because many instruments are used and managed in radiation oncology departments, systematic, traceable recording is very important. The web-based program developed in this study is expected to be used effectively in the maintenance of radiation measurement instruments.

IFMBE Proceedings

The organ motion due to respiration necessitates adding adequate margins to the planning target v... more The organ motion due to respiration necessitates adding adequate margins to the planning target volume (PTV) to ensure adequate dose coverage in chest and abdomen. Several techniques have been suggested to minimize the PTV relating to respiratory motion. In this study, ten patients’ respiratory patterns were measured by thermocouple, spirometer, and skin motion simultaneously, to find the best method corresponding with respiratory target motion. Each respiration monitoring methods were compared with fluoroscopic target motion during simulation. Conventional spirometer and home made thermocouple were connected to a mouse piece to measure the patient’s respiration. A respiration acquisition program was developed, which acquire respiration signals and display its patterns. A fluoroscopic target tracking program was developed. Ten patients with lung or liver cancer participated in this study. Fluoroscopic movies were captured during acquisition of their respiration patterns. At the same time their skin motion was measured by using Real-time Position Management’ (RPM’, Varian, Palo Alto, CA) system. Respiratory patterns acquired from spirometer, thermocouple, and RPM’ system were compared with fluoroscopic target motion respectively. Its relationships were evaluated by correlation coefficient. Comparing each correlation coefficient for spirometer, thermocouple, and RPM®, skin motion detection is the most correspondent with fluoroscopic target motion. Respiration monitoring methods with spirometer or thermocouple, and skin motion detection are directly applicable to monitor the target motion for applying 4D radiotherapy.

Genes & Genomics, 2016

Unfortunately, there is a spelling error in the first name of the tenth author in the published a... more Unfortunately, there is a spelling error in the first name of the tenth author in the published article. The correct name is Taek Kyu Kwon, not Tae Kyu Kwon. The correction is now updated in the article and also shown in this erratum.

Progress in Medical Physics, 2016

Periodical calibrations of radiation detectors are important for accurate quality assurance of th... more Periodical calibrations of radiation detectors are important for accurate quality assurance of therapeutic linac. The measuring instruments such as ion-chamber, thermometer, barometer, and survey meter should be calibrated periodically. Period of calibration for these instruments is suggested 6 month to one year in Korea and two years in other countries nowadays. Therefore, the determination of reasonable period for calibration is needed. In this study, we plan to utilize the results of these survey; frequent in use, how to use and stability of instruments, to determine the optimized period of calibration for the instruments in the departments of radiation oncology in Korea based on the ILAC-G24. The SurveyMonkey web-based survey tool was used and the objects of survey were 18 department of radiation oncology in university hospitals, and 15 departments were answered. The 64 questionnaires which supposed to be answered in 50 minutes were classified as the information of candidates, the thermometer, the barometer, the surveymeter, and the ion-chamber. The thermometers and the barometers were not under periodical calibration for more than half of candidates. The periods of calibration of surveymeters were 6 month to 1 year. We expect that the calibration period can be determined based on these survey results.