• The Journal of Korean Society for Radiation Therapy
• /
• v.26 no.2
• /
• pp.289-295
• /
• 2014

Purpose : Cone Beam Computed Tomography(CBCT) in Image Guided Radiation Therapy(IGRT), Set-up error can be reduced but exposure dose of the patient due to CBCT will increase. Through this study, we are to evaluate by making a scenario with the implementation period of CBCT as every other day. Materials and Methods : Of prostate cancer patients, 9 patients who got a Intensity Modulated Radiation Therapy(IMRT) with CBCT in IGRT were analyzed. Based on values corrected by analyzing set-up error by using CBCT every day during actual treatment, we created a scenario that conducts CBCT every other day. After applying set-up error values of the day not performing CBCT in the scenario to the treatment planning system(Pinnacle 9.2, Philips, USA) by moving them from the treatment iso-center during actual treatment, we established re-treatment plan under the same conditions as actual treatment. Based on this, the dose distribution of normal organs and Planning Target Volume(PTV) was compared and analyzed. Results : In the scenario that performs CBCT every other day based on set-up error values when conducting CBCT every day, average X-axis : $0.2{\pm}0.73mm$, Y-axis : $0.1{\pm}0.58mm$, Z-axis : $-1.3{\pm}1.17mm$ difference was shown. This was applied to the treatment planning to establish re-treatment plan and dose distribution was evaluated and as a result, Dmean : -0.17 Gy, D99% : -0.71 Gy of PTV difference was shown in comparison with the result obtained when carrying out CBCT every day. As for normal organs, V66 : 1.55% of rectal wall, V66 : -0.76% of bladder difference was shown. Conclusion : In case of a CBCT perform every other day could reduce exposure dose and additional treatment time. And it is thought to be able to consider the application depending on the condition of the patient because the difference in the dose distribution of normal organs, PTV is not large.

• Progress in Medical Physics
• /
• v.27 no.1
• /
• pp.8-13
• /
• 2016

Dual energy cone-beam CT can distinguish two materials with different atomic compositions. The principle of dual energy cone-beam CT based on modulation layer is that higher energy spectrum can be acquired at blocked x-ray window. To evaluate the possibility of modulation layer based dual energy cone-beam CT, we analyzed x-ray spectrum for various thicknesses of modulation layers by Monte Carlo simulation. To compare with the results of simulation, the experiment was performed on prototype cone-beam CT for 50~100 kVp with CdTe XR-100T detector. As the result of comparing, the mean energy of energy spectrum for 80 kVp are well matched with that of simulation. The mean energy of energy spectrum for 80 and 120 kVp were increased as 1.67 and 1.52 times by 2.0 mm modulation layer, respectively. We realized that the virtual dual energy x-ray source can be generated by modulation layer.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.39 no.3
• /
• pp.273-279
• /
• 2012

Purpose : This study was aimed to calculate effective dose from cone beam CT and compare effective dose from periapical and panoramic radiography for mesiodens. Materials and Methods : Upper anteiror periapical, panoramic radiography and cone-beam CT were taken for diagnosis of mesiodens. The effective dose were calculated by using an anthropomorphic phantom loaded with thermoluminescent dosimeters at the 23 sites related to sensitive organs. Results : The highest absorbed doses were received by the mandibular body, parotid gland and cheek from periapical, panoramic and cone-beam CT, respectively. The effective doses for periapical, panoramic radiography and cone-beam CT measured 2, 18 and 48 ${\mu}Sv$. Conclusion : Cone-beam CT, although providing additional diagnostic benefits, exposes patients to higher levels of radiation than conventional periapical and panoramic radiography.

• 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.

• 전기의세계
• /
• v.64 no.7
• /
• pp.26-34
• /
• 2015

• 대한방사선방어학회:학술대회논문집
• /
• 2010.04a
• /
• pp.144-145
• /
• 2010

• Proceedings of the Korea Information Processing Society Conference
• /
• 2022.05a
• /
• pp.312-315
• /
• 2022

CT의 반복재구성방법은 투영과 역투역을 번갈아가며 최적의 단면영상을 얻을 때까지 반복한다. 영상재구성 시간을 단축하기 위하여 시간이 많이 소요되는 투영을 빠르게 수행할 수 있는 알고리즘이 필요하다. 본 논문은 Siddon 알고리즘을 개선한 Jacobs 버전보다 대략 10% 빠른 알고리즘을 제안한다. 평행빔의 경우에 대해 조사되었지만 향후 부채살빔 및 콘빔의 경우로 확장이 가능하다.

• Progress in Medical Physics
• /
• v.27 no.1
• /
• pp.31-36
• /
• 2016

The paper discusses radiation dose of dual energy CT on which copper modulation layer, is mounted in order to improve diagnostic performance of the dual energy CT. The radiation dose is estimated using MCNPX and its results are compared with that of the conventional dual energy CT system. CT X-ray spectra of 80 and 120 kVp, which are usually used for thorax, abdominal, head, and neck CT scans, were generated by the SPEC78 code and were used for the source specification 'SDEF' card for MCNPX dose modeling. The copper modulation layer was located 20 cm away from a source covering half of the X-ray window. The radiation dose was measured as changing its thickness from 0.5 to 2.0 mm at intervals of 0.5 mm. Since the MCNPX tally provides only normalized values to a single particle, the dose conversion coefficients of F6 tally for the modulation layer-based dual energy CBCT should be calculated for matching the modeling results into the actual dose. The dose conversion coefficient is $7.2*10^4cGy/output$ that is obtained from dose calibration curve between F6 tally and experimental results in which GAFCHORMIC EBT3 films were exposed by an already known source. Consequently, the dose of the modulation layer-based dual energy cone beam CT is 33~40% less than that of the single energy CT system. On the basis of the results, it is considered that scattered dose produced by the copper modulation layer is very small. It shows that the modulation layer-based dual energy CBCT system can effectively reduce radiation dose, which is the major disadvantage of established dual energy CT.

• Progress in Medical Physics
• /
• v.19 no.3
• /
• pp.186-190
• /
• 2008

In this study, we describe the preliminary application for the delineation of a metal object using cone-beam reconstruction (CBR) based on limited electronic portal imaging device (EPID) projections. A typical Feldkamp, Davis and Kress (FDK) reconstruction algorithm accompanying the edge preserving smoothing filter was used as only a few projections are acquired for reconstruction. In a correlation study of the projection numbers, we found that the size of the seeds and their location depicted by these CBR images were almost identical. Limited views were used for CBR, and our method is inexpensive and competitive for use in clinical applications.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2015.05a
• /
• pp.72-73
• /
• 2015