• Progress in Medical Physics
• /
• v.19 no.4
• /
• pp.209-218
• /
• 2008

According to improved radiation therapy technology such as IMRT and proton therapy, the accuracy of patient alignment system is more emphasized and IGRT is dominated research field in radiation oncology. We proposed to study the feasibility of cone-beam CT system using simple x-ray imaging systems for image guided proton therapy at National Cancer Center. 180 projection views ($2,304{\times}3,200$, 14 bit with 127 ${\mu}m$ pixel pitch) for the geometrical calibration phantom and humanoid phantoms (skull, abdomen) were acquired with $2^{\circ}$ step angle using x-ray imaging system of proton therapy gantry room ($360^{\circ}$ for 1 rotation). The geometrical calibration was performed for misalignments between the x-ray source and the flat-panel detector, such as distances and slanted angle using available algorithm. With the geometrically calibrated projection view, Feldkamp cone-beam algorithm using Ram-Lak filter was implemented for CBCT reconstruction images for skull and abdomen phantom. The distance from x-ray source to the gantry isocenter, the distance from the flat panel to the isocenter were calculated as 1,517.5 mm, 591.12 mm and the rotated angle of flat panel detector around x-ray beam axis was considered as $0.25^{\circ}$. It was observed that the blurring artifacts, originated from the rotation of the detector, in the reconstructed toomographs were significantly reduced after the geometrical calibration. The demonstrated CBCT images for the skull and abdomen phantoms are very promising. We performed the geometrical calibration of the large gantry rotation system with simple x-ray imaging devices for CBCT reconstruction. The CBCT system for proton therapy will be used as a main patient alignment system for image guided proton therapy.

• The Journal of Korean Society for Radiation Therapy
• /
• v.31 no.1
• /
• pp.67-74
• /
• 2019

Purpose: The purpose is to correct for position errors caused by long treatment times. By correcting the target motion that can occur during lung SBRT using IntraFraction CBCT. Methods and materials: We analyzed retrospectively the IFM data of 14 patients with two treatment arc in the treatment plan for lung cancer with stereotactic radiotherapy. An IntraFraction Motion was applied to the Arccheck phantom to acquire the Gamma index data. Results : IntraFraction Motion during the first treatment arc is in the left-right(LR), superiorinferior(SI), anterior-posterior(AP) directions were $0.16{\pm}0.05cm$, 0.72 cm(max error), $0.2{\pm}0.14cm$, 1.26 cm, $0.24{\pm}0.08cm$, 0.82 cm and rotational directions was $0.84{\pm}0.23^{\circ}$, $2.8^{\circ}$(pitch), $0.72{\pm}0.23^{\circ}$, $2.5^{\circ}$(yaw), $0.7{\pm}0.19^{\circ}$, $2^{\circ}$(roll). IntraFraction Motion during the second treatment arc is in the LR, SI, AP directions were $0.1{\pm}0.04cm$, 0.37 cm, $0.14{\pm}0.17cm$, 2 cm, $0.12{\pm}0.04cm$, 0.5 cm and rotational directions was $0.45{\pm}0.12^{\circ}$, $1.3^{\circ}$, $0.37{\pm}0.1^{\circ}$, $1^{\circ}$, $0.35{\pm}0.1^{\circ}$, $1.2^{\circ}$. Gamma index pass rates were $82.64{\pm}10.51%$, 48.4 %. Conclusions : In this study, we examined the validity of IntraFraction Motion correction in lung SBRT and the efficiency of IntraFraction CBCT. Due to the nature of SBRT treatment, IFM may increase due to the increased treatment time. It is believed that the increase in IFM with the increase in treatment time can be improved with the use of FFF Beam and additional position correction using CBCT during treatment.

• The korean journal of orthodontics
• /
• v.33 no.2 s.97
• /
• pp.73-84
• /
• 2003

This study was performed to find out how much projection errors in the cephalometric measurements were made by vertical head rotation in taking posteroanterior cephalograms. 25 adults without any apparent facial asymmetry or severe sagittal skeletal discrepancy were selected and the posteroanterior cephalograms were taken with the head rotated $5^{\circ},\;10^{\circ}$ superior and inferior each to the reference $position(0^{\circ})$. The 7 height, 5 width and 6 angular measurements were taken at each 5 positions. Through the statistical analysis of all measurements taken at each rotated position, folowing results were obtained.1. The projection errors of height measurements were remarkably target than those of width or angular measure nents. f. Among the height measurements, the farther to the rotation axis the measurements were, the larger the projection errors were. 3. Among the width measurements, mandibular width and mandibular width of mandibular first molars showed significant differences between the values taken at each rotated position, while nasal width, maxillary width and intermolar width of maxillary first molars did not. 4. Among the angular measurements, the angle between horizontal reference line and the line that is connected to crista galli and antegonion or maxillare showed significant differences between the values taken at each rotated Position. The above results suggest that it is needed to the effort to keep constant head position for taking the useful posteroanterior cephalogra, because projection errors are caused by vertical head rotation.

• Journal of the Korean Society of Radiology
• /
• v.15 no.6
• /
• pp.861-867
• /
• 2021

Since SBRT takes up to 1 hour from 30 minutes to treatment fraction once or three to five times, there is a possibility of setup error during treatment. To reduce these set-up errors and give accurate doses, we intend to evaluate the usefulness of pre-treatment and post-treatment error values by imaging CBCT again to determine postural movement due to pre-treatment coordinate values using pre-treatment CBCT. On average, the range of systematic errors was 0.032 to 0.17 on the X and Y,Z axes, confirming that there was very little change in movement even after treatment. Tumor centripetal changes (±SD) due to respiratory tuning were 0.11 (±0.12) cm, 0.27 (±0.15) cm, and 0.21 cm (±0.31 cm) in the X, Y and Z directions. The tumor edges ±SD were 0.21 (±0.18) cm, 0.30 (±0.23) cm, and 0.19 cm (±0.26) cm in the X, Y and Z directions. The (±SD) of tumor-corrected displacements were 0.03 (±0.16) cm, 0.05 (±0.26) cm, and 0.02 (±0.23) cm in RL, AP, and SI directions, respectively. The range of the 3D vector value was 0.11 to 0-.18 cm on average when comparing pre-treatment and CBCT, and it was confirmed that the corrected set-up error was within 0.3 cm. Therefore, it was confirmed that there were some changes in values depending on some older patients, condition on the day of treatment, and body type, but they were within the significance range.

• Radiation Oncology Journal
• /
• v.20 no.4
• /
• pp.381-390
• /
• 2002

Purpose : To develop a dose calibration program for the IAEA TRS-277 and AAPM TG-21, based on the air kerma calibration factor (or the cavity-gas calibration factor), as well as for the IAEA TRS-398 and the AAPM TG-51, based on the absorbed dose to water calibration factor, so as to avoid the unwanted error associated with these calculation procedures. Materials and Methods : Currently, the most widely used dosimetry Protocols of high energy photon beams are the air kerma calibration factor based on the IAEA TRS-277 and the AAPM TG-21. However, this has somewhat complex formalism and limitations for the improvement of the accuracy due to uncertainties of the physical quantities. Recently, the IAEA and the AAPM published the absorbed dose to water calibration factor based, on the IAEA TRS-398 and the AAPM TG-51. The formalism and physical parameters were strictly applied to these four dose calibration programs. The tables and graphs of physical data and the information for ion chambers were numericalized for their incorporation into a database. These programs were developed user to be friendly, with the Visual $C^{++}$ language for their ease of use in a Windows environment according to the recommendation of each protocols. Results : The dose calibration programs for the high energy photon beams, developed for the four protocols, allow the input of informations about a dosimetry system, the characteristics of the beam quality, the measurement conditions and dosimetry results, to enable the minimization of any inter-user variations and errors, during the calculation procedure. Also, it was possible to compare the absorbed dose to water data of the four different protocols at a single reference points. Conclusion : Since this program expressed information in numerical and data-based forms for the physical parameter tables, graphs and of the ion chambers, the error associated with the procedures and different user could be solved. It was possible to analyze and compare the major difference for each dosimetry protocol, since the program was designed to be user friendly and to accurately calculate the correction factors and absorbed dose. It is expected that accurate dose calculations in high energy photon beams can be made by the users for selecting and performing the appropriate dosimetry protocol.

• Progress in Medical Physics
• /
• v.23 no.2
• /
• pp.114-122
• /
• 2012

For the determination of absorbed dose to water from a linear accelerator photon beams, it needs a exposure calibration factor $N_x$ or air kerma calibration factor $N_k$ of air ionization chamber. We used the exposure calibration factor $N_x$ to find the absorbed dose calibration factors of water in a reference source through the TG-21 and TRS-277 protocol. TG-21 used for determine the absorbed dose in accuracy, but it required complex calculations including the chamber dependent factors. The authors obtained the absorbed dose calibration factor $N_{dw}{^{Co-60}}$ for reduce the complex calculations with unknown $N_{dw}$ only with $N_x$ or $N_k$ calibration factor in a TM31010 (S/N 1055, 1057) ionization chambers. The results showed the uncertainty of calculated $N_{dw}$ of IC-15 which was known the $N_x$ and $N_{dw}$ is within -0.6% in TG-21, but 1.0% in TRS-277. and TM31010 was compared the $N_{dw}$ of SSDL to that of PSDL as shown the 0.4%, -2.8% uncertainty, respectively. The authors experimented with good agreement the calculated $N_{dw}$ is reliable for cross check the discrepancy of the calibration factor with unknown that of TM31010 and IC-15 chamber.

• Progress in Medical Physics
• /
• v.14 no.3
• /
• pp.175-183
• /
• 2003

Absorbed dose dosimetry protocols of high energy photon and electron beams, which are widely used and based on an air kerma (or exposure) calibration factors, have somewhat complex formalism and limitations for improving dosimetric accuracy due to the uncertainty of the physical parameters used. Recently, the IAEA and the AAPM published the absorbed dose to water-based dosimetry protocols(IAEA TRS-398 and AAPM TG-51). The dose calibration programs for these two protocols were developed. This program for high energy photon and electron beams was also developed for users to use in a window environment using the Visual C++ language. The formalism and physical parameters of these two protocols were strictly applied to the program. The tables and graphs of the physical data, and the information of ion chambers were numericalized for their incorporation into a database. This program can be useful in developing new dosimetry protocols in Korea.

• Journal of the Korea Society of Computer and Information
• /
• v.20 no.4
• /
• pp.57-67
• /
• 2015

The concept of detection and classification of objects based on infrared camera is widely applied to military applications. While the object detection technology using infrared images has long been researched and the latest one can detect the object in sub-pixel, the object classification technology still needs more research. In this paper, we present object classification method based on measured radiant intensity of objects such as target, artillery, and missile using infrared camera. The suggested classification method was verified by radiant intensity measuring experiment using black body. Also, possible measuring errors were compensated by modelling-based correction for accurate radiant intensity measure. After measuring radiation of object, the model of radiant intensity is standardized based on theoretical background. Based on this research, the standardized model can be applied to the object classification by comparing with the actual measured radiant intensity of target, artillery, and missile.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2C
• /
• pp.229-237
• /
• 2004

In this paper. we propose a new autocalibration algorithm. 3D-based image synthesis is roughly divided into two methods. One is using autocalibration method, and the other is using real 3D data like pattern information. The former is more progressive method. because there is no constraint or information about the scenes. Therefore autocalibration method has very difficult progress dealing with complicate non-lineal equations. Nowadays, constraints of camera intrinsic parameters are used in many researches. Therefore we solve the linear equations instead of complicate non-lineal equations. For example, to fix principal point of camera is a representative method.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.42 no.4 s.304
• /
• pp.13-20
• /
• 2005

In this paper, we propose new smoothing filters, i.e., occluding patterns that can accurately correct disparities of occluded areas in the estimated disparity map. An image is composed of several layers and each layer presents similar disparity. Furthermore, the distribution of the estimated disparities has a specific direction around the boundary of the occlusion, and this distribution presents the different direction with respect to the left- and the right-based disparity map. However, typical smoothing filters, such as mean filter and median filter, did not take into account those characteristic. So, they can decrease some error, but they cannot guarantee the accuracy of the corrected disparity. On the contrary, occluding patterns can accurately correct disparities of occluded areas because they consider both the characteristic that occlusion occurs and the characteristic that disparities of the occlusion are ranged, from estimated disparity maps with respect to the left and the right images. We made experiments on occluding patterns with some real stereo image set, and as a result, we can correct disparities of occluded areas more accurately than typical smoothing filters did.