Haijo Jung

Trends for the Past 10 Years and International Comparisons of the Structure of Korean Radiation Oncology

OBJECTIVE Study aims include determination of nationwide structural characteristics of radiation oncology facilities, types of radiation therapy equipment, availability of human resources and trends and comparisons with previous surveys. METHODS An annual nationwide survey was conducted to collect the statistics of infrastructure since 1997. All requested questionnaires have been identical for 10 years. The questionnaires included status on basic radiation therapy facilities, human resources and radiation therapy equipment. Journal and statistical data reviews were performed to evaluate the structure of other countries. RESULTS Radiation oncology facilities have steadily increased for 10 years and reached 60 sites in 2006. Also a steady increase of 1.5 times for linear accelerators, 5.8 times for computed tomography simulators and 3.0 times for radiation treatment planning systems was noted. Meanwhile, cobalt-60 teletherapy units and hyperthermia equipment had steadily deceased for 10 years. The number of human resources has steadily increased for the past 10 years, especially for radiation therapy technologists. However, radiation therapy equipment and human resources per population are relatively low compared with advanced countries. CONCLUSIONS This study will assist preparation of the administrative planning policy of radiation oncology and should be useful to indicate the direction of future development and educational training programs in Korea and possibly in other countries.

Clinical characteristics of radiation oncology in Korea during past 10 years.

To understand trends in the clinical characteristics of radiation oncology over the last 10 yr in Korea, annual survey questionnaires were sent to all of Korean radiation oncology facilities since 1990. Questionnaires addressed basic radiation therapy facilities and the clinical information. Responses were obtained from all facilities, and data collected from 1997 to 2006 was analyzed. The numbers of new patients that have undergone radiation therapy and the numbers of hospitals with a department of radiation oncology have steadily increased over the past 10 yr, and totaled 37,215 patients and 60 hospitals, respectively, in 2006. However, the proportion of patients irradiated among total cancer patients has remained below 30% over the last 10 yr. The numbers of prostate cancer, breast cancer, and hepatoma have increased by more than 3 fold over the past 10 yr. Moreover, the percentage of irradiated patients treated by brachytherapy was 10.3% in 1997, but this gradually fell to only 4.2% in 2006. The information collected described the role played by radiation oncology in Korea. Continuous surveys are required to enable trends to be detected.

ASSESSMENT OF DIAGNOSTIC MULTILEAF COLLIMATOR FOR CEPHALOMETRIC EXPOSURE REDUCTION USING OPTICALLY STIMULATED LUMINESCENT DOSEMETERS

A diagnostic multileaf collimator (MLC) was developed for diagnostic radiography dose reduction. Optically stimulated luminescent dosemeters (OSLDs) were used to evaluate the efficacy of this device for dental radiography cephalometric exposure reduction. The OSLD dosimetric characteristics for 80 kVp cephalometric exposure were first obtained. The batch homogeneity and reproducibility were 1.67 % and 0.18-1.58, respectively. Good linearity was obtained between the OSLD dose and response, and the angular dependence was within ±4 %. The equivalent organ doses for the left eye, right eye and thyroid were 41.20±6.58, 178.86±1.71 and 171.12±8.78 μSv and 36.80±0.33, 156.63±0.22 and 22.04±0.13 μSv for the open and MLC fields, respectively. The MLC-induced dose reductions for the left and right eyes of in field were 10.67±16.78 and 12.42±8.84 %, respectively, and that of the thyroid gland of out of field was 87±8.82 %, considering combined uncertainty. Therefore, use of diagnostic MLC for dose reduction during dental radiography cephalometric exposure is both feasible and effective.

Trends of the effective dose distribution of occupational exposures in medical and research departments for KIRAMS in Republic of Korea

This work proposes the basic reference data of occupational dose management and statistical dose distribution with the classification of radiation work groups though analysis of occupational dose distribution. Data on occupational radiation exposure from medical and scientific usage of radiation in Korea Institute of Radiological and Medical Sciences for the years 2002-11 are presented and evaluated with the characteristic tendency of radiation working groups. The results of occupational radiation exposure were measured by personal dosemeters. The monitored occupational exposure dose data were evaluated according to the average effective dose and collective dose. The most annual average effective dose for all occupational radiation workers was under 1 mSv. Considering the dose distribution of each department, most overexposure workers worked in radiopharmaceutical product facilities, nuclear medicine department and radiation oncology department. In addition, no monitored workers were found to have received an occupational exposure over 50 mSv in single year or 100 mSv in this period. Although the trend of occupational exposure was controlled <1 mSv after 2007 and the radiation protection status was sufficient, it was consistently necessary to optimise and reduce the occupational radiation exposure.

SU-FF-I-51: Interoperability Validation of DICOM Portable Data for Imaging in Nuclear Medicine

Purpose: In PACS (Picture Archiving and Communications System) environment, the export of DICOM portable data for imaging (PDI) has been increased in accordance with the demands of patents referring to other hospitals. The DICOM PDI currently stored in a CD (Compact Disk) causes the problems of retrieve and archive occasionally in PACS environment of destination hospital although it was created under obeying DICOM standards. Method and Materials: DICOM validation toolkit was developed for verifying the DICOM data sets complying with the DICOM standard PS 3.3 to improve compatibility between the DICOM PDI and multi-vendor PACSs. The interoperability of problematic PDI in nuclear medicine imported to Yonsei University Medical Center in Seoul, Korea was evaluated through validation of DICOM CD data using the DICOM data validation toolkit. The evaluated PDIs were 5 NM (Nuclear Medicine) series and 10 PT (Positron Emission Tomography) series. Results: The main factors of the problematic NM PDI are that series number, content data, and content time presented null value and detector vector had no tag. As for the problematic PT PDI, series number presented null value, pixel aspect ratio had no tag, and both of image orientation and image position had no any values for VM=3 and VM=6 defined by DICOM standards. Conclusion: The DICOM data validation toolkit is expected to play an important role in validation of problematic PDI for patients and hospitals. Evaluation of problematic PDI will enable to bring the feedback of incompatibility to PACS vendors and PACS operating team in hospitals to improve interoperability of PDI.

SU-E-T-299: Dosimetric Characterization of Small Field in Small Animal Irradiator with Radiochromic Films

Purpose: The small animal irradiator has been used with small animals to optimize new radiation therapy as preclinical studies. The small animal was irradiated by whole- or partial-body exposure. In this study, the dosimetric characterizations of small animal irradiator were carried out in small field using Radiochromic films Material & Methods: The study was performed in commercial animal irradiator (XRAD-320, Precision x-ray Inc, North Brantford) with Radiochromic films (EBT2, Ashland Inc, Covington). The calibration curve was generated between delivery dose and optical density (red channel) and the films were scanned by and Epson 1000XL scanner (Epson America Inc., Long Beach, CA).We evaluated dosimetric characterization of irradiator using various filter supported by manufacturer in 260 kV. The various filters were F1 (2.0mm Aluminum (HVL = about 1.0mm Cu) and F2 (0.75mm Tin + 0.25mm Copper + 1.5mm Aluminum (HVL = about 3.7mm Cu). According to collimator size (3, 5, 7, 10 mm, we calculated percentage depth dose (PDD) and the surface –source distance(SSD) was 17.3 cm considering dose rate. Results: The films were irradiated in 260 kV, 10mA and we increased exposure time 5sec. intervals from 5sec. to 120sec. The calibration curve of films was fitted with cubic function. The correlation between optical density and dose was Y=0.1405 X3−2.916 X2+25.566 x+2.238 (R2=0.994). Based on the calibration curve, we calculated PDD in various filters depending on collimator size. When compared PDD of specific depth (3mm) considering animal size, the difference by collimator size was 4.50% in free filter and F1 was 1.53% and F2 was within 2.17%. Conclusion: We calculated PDD curve in small animal irradiator depending on the collimator size and the kind of filter using the radiochromic films. The various PDD curve was acquired and it was possible to irradiate various dose using these curve.

SU-E-T-315: The Change of Optically Stimulated Luminescent Dosimeters (OSLDs) Sensitivity by Accumulated Dose and High Dose

PURPOSE The objective of this study is to evaluate radiation sensitivity of optical stimulated luminance dosimeters (OSLDs) by accumulated dose and high dose. METHODS This study was carried out in Co-60 unit (Theratron 780, AECL, and Canada) and used InLight MicroStar reader (Landauer, Inc., Glenwood, IL) for reading. We annealed for 30 min using optical annealing system which contained fluorescent lamps (Osram lumilux, 24 W, 280 ∼780 nm). To evaluate change of OSLDs sensitivity by repeated irradiation, the dosimeters were repeatedly irradiated with 1 Gy. And whenever a repeated irradiation, we evaluated OSLDs sensitivity. To evaluate OSLDs sensitivity after accumulated dose with 5 Gy, We irradiated dose accumulatively (from 1 Gy to 5 Gy) without annealing. And OSLDs was also irradiated with 15, 20, 30 Gy to certify change of OSLDs sensitivity after high dose irradiation. After annealing them, they were irradiated with 1Gy, repeatedly. RESULTS The OSLDs sensitivity increased up to 3% during irradiating seven times and decreased continuously above 8 times. That dropped by about 0.35 Gy per an irradiation. Finally, after 30 times irradiation, OSLDs sensitivity decreased by about 7%. For accumulated dose from 1 Gy to 5 Gy, OSLDs sensitivity about 1 Gy increased until 4.4% after second times accumulated dose compared with before that. OSLDs sensitivity about 1 Gy decreased by 1.6% in five times irradiation. When OSLDs were irradiated ten times with 1Gy after irradiating high dose (10, 15, 20 Gy), OSLDs sensitivity decreased until 6%, 9%, 12% compared with it before high dose irradiation, respectively. CONCLUSION This study certified OSLDs sensitivity by accumulated dose and high dose. When irradiated with 1Gy, repeatedly, OSLDs sensitivity decreased linearly and the reduction rate of OSLDs sensitivity after high dose irradiation had dependence on irradiated dose.

Brachytherapy source reconstruction for estimating the dose distribution and source position with SPECT system: Monte Carlo method

Brachytherapy is term used to describe the short distance treatments of cancer with encapsulated radioactive source. Currently, high dose rate brachytherapy with Iridium-192 is mainly used in radiation treatment. In conventional brachytherapy, C-arm and ultrasound imaging device is used to simply confirm the location of source. However, the dose distribution of radiation source in human body and location of source is necessary to be measured accurately in brachytherapy. In this study, we investigate the feasibility of applying the SPECT (Single Photon Emission Computed Tomography) system for estimating the dose distribution of after-loading brachytherapy source. The three-dimensional dose distribution of brachy-therapy source detected by SPECT system was simulated using a detection system with planar detector provided two-dimensional projection of three-dimensional configuration around the phantom. Scintillation detectors which were consisted of 0.5 × 0.5 × 5 mm3 BGO pixels with 3mm parallel lead collimator were arrayed. To construct three-dimensional image in SPECT system configuration images were taken around 360 degree. The two-dimensional projection represented the dose distribution and the location of source. However two-dimensional projection limited to confirm the location of source. Therefore, projection images were reconstructed by using filtered back-projection method. The three-dimensional reconstruction image during the brachy-therapy treatment was well matched the location of source in phantom. In addition, the dose distribution in phantom was able to be acquired through the SPECT system.

SU‐E‐T‐268: The Evaluation of Dosimetric Characteristic of Radiophotoluminescent Glass Dosimeter According to Reading Methods of Reader

Purpose: Statistical checks of system parameters and follow up of readers behavior will give a broader understanding into the operational characteristics of the reader and may help for proper maintenance of the system. The purpose of this study is to suggest effective use of reading methods for reducing the uncertainty in dose measurements through the investigation of characteristics of GD‐based reader system. Methods: To evaluate the characteristics of readers, we performed measurement such as reproducibility of repeated reading, readout variation according to the number of GD loading on readout magazine, and deviation depending on each magazine position. To evaluate dose reproducibility we made a try to do repeated reading up to 200 times for each 15 GDs. Also, to evaluate readout variation characteristic, 80 GDs are irradiated one by one under the same irradiation conditions. Reading process was measured with 4 different cases. Lastly, to measure the deviation magazine position, we examine the readout values according to each loading position.Results: According to measurement result, reproducibility shows 1.3% lower measurement from total 200 times. Readout sensitivity of GD on magazine values is normalized to 1st position response. 1 to 5th position measured 1.015, also 1 to 10th position examined 1.022, and 1 to 20th position presented 1.035. Lastly, at all position except for 20th position of magazine, response is tend to increase gradually. It was overestimated on 2.0% of average rather than response at reference position (first position). Conclusions: According to the result, we should put each GD in consecutive order from 1st space of magazine to get accuracy value of dose and it is recommended that reading process should be performed the only first position of magazine with regard to absolute dosimetry. This work was supported by Nuclear Research & Development Program of the National Research Foundation of Korea(NRF) grant funded by the Korean government(MEST).

Quantitative Evaluation of Gating Radiotherapy System and Dynamic Tumor Tracking Radiotherapy System Developed at KIRAMS

To quantitatively assess of Gating Radiotherapy (GRT) system and Dynamic Tumor Tracking Radiotherapy (DTTRT) system using MLC developed at KIRAMS (Korea Institute of Radiological & Medical Sciences) and evaluate effectiveness and efficiency of beam delivery for the both RT system. DTTRT system resulted to same treatment effect compared with the GRT system controlled with the gating rate of 20%. However, when treat by applying lower gating rate for the GRT system, longer treatment time give inconvenience to patients and cause obstacle to effective utilization of the equipment. On the one hand, DTTRT system presents advantage to reduce treatment time and to achieve effective dose delivery.