Hyon-Chol Jang

Dynamic Response Topology Optimization in the Time Domain using Equivalent Static Loads

Most topology optimization techniques find the optimal layout of a structure under static loads. Some studies are focused on dynamic response topology optimization because the dynamic forces act in the real world. Dynamic response topology optimization is solved in the time or frequency domain. A method for dynamic response topology optimization in the time domain is proposed using equivalent static loads. Equivalent static loads are static loads that generate the same displacement field as dynamic loads at each time step. The equivalent static loads are made by multiplying the linear stiffness matrix and the displacement field from dynamic analysis and used as multiple loading conditions for linear static topology optimization. The results of topology optimization are utilized in dynamic analysis again and a cyclic process is utilized until the convergence criterion is satisfied. The paradigm of the method was originally developed for size and shape optimizations. A new objective function is defined to minimize the peaks of the compliance in the time domain and a convergence criterion is newly defined considering that there are many design variables in topology optimization. The developed method is verified by solving some examples and the results are discussed.

Factor Analysis of Biochemical Markers Associated with Bone Mineral Density in Adults

[Purpose] The aim of this study was to find biochemical markers related to low bone mineral density in Korean adults. [Subjects and Methods] From August 1 to September 15, 2013, subjects receiving medical checkups were classified as lumbar spine bone normal, osteopenic, or osteoporotic using a bone mineral densitometer. Next, age, body mass index, and biochemical parameter differences were compared among the three groups. [Results] The results revealed that, the relevant factors were maximum blood pressure, minimum blood pressure, bone mineral density, total bilirubin, alkaline phosphatase (ALP), fasting blood glucose, iron, neutrophils, monocytes, and eosinophils. The bone mineral density of patients with osteoporosis was 0.763 times lower than that of normal subjects. The total bilirubin level of patients with osteoporosis was 0.45 times lower than that of normal subjects. The alkaline phosphatase level of patients with osteopenia was 1.059 times higher than that of normal subjects, and that in patients with osteoporosis was 1.088 times higher than that in normal subjects. The fasting blood glucose level of patients with osteoporosis was 0.963 times lower than that of normal subjects. The iron level of patients with osteoporosis was 0.986 times lower than that of normal subjects. [Conclusion] In conclusion, osteoporosis is a representative disease in elderly women due to aging and menopause, and more active interest should be taken for prevention and treatment.

Study on the Validation of the Gated Cone-Beam Computed Tomography on Radiation Therapeutic Linear Accelerator

The respiration is one of important factor in the radiation therapy. The existing commercial method of cone-beam computed tomography on LINAC does not consider respiratory motion of patient hence the images are both distorted and inaccurate. In this study, the cone-beam computed tomography images have been reconstructed from back projection radiography of specific phase on breathing cycle which concerned about respiratory movement in radiation therapy. This study investigated how different between cone-beam CT images with and without gating respiratory movement, and this paper provides that guide and implementation of gated cone-beam CT on radiation therapeutic equipment.

SU-E-T-594: Preliminary Active Scanning Results of KHIMA

PURPOSE To verify the design criteria on heavy ion beam irradiation, developing a proto type active scanning system was purposed. The active scanning system consists of scanning magnet, power supplies, beam monitors, energy modulation system, and irradiation control system. METHODS Each components of the active scanning system was designed for carbon beam first. For the fast ramping a laminated yoke was purposed. To measure incoming dose and profile, a plate and strip type of ion chambers were designed. Also, ridge filter and range shifter was manufactured. And, the scanning system was modified to adopt 45 MeV of proton beam because of the absence of carbon ion beam in Korea. The system was installed in a beam line at MC-50, KIRAMS. Also, the irradiation control system and planning software was provided. RESULTS The scanning experiment was performed by drawing KHIMA logo on GaF film. The logo was scanned by 237 scanning points through time normalized intensity modulation. Also, a grid points scanning was performed to measure the scanning resolution and intensity resolution. CONCLUSION A prototype active scanning system was successfully designed and manufactured. Also, an initial experiment to print out a drawing on GaF film through the scanning system was completed. More experiments would be required to specify the system performance.

Analysis of Attenuation Differences According to Radiolucent and Radiopague Materials : Based on DECT (Dual Energy Computed Tomography)

This study analyzed CT values of radiolucent and radiopaque materials by energy region after selecting radiolucent and radiopaque materials at random using GE`s DECT((Dual Energy Com-puted Tomography) at S University Hospital located in Gyeonggi-province from July through August in 2013. Besides, it drew out the most analogous energy region to the value of 120kVp CT, which is applied to existing SECT(Single Energy Computed Tomography), by utilizing the analysis method of CT values and tried to find out the most useful and appropriate materials when contrast was applied within visible area in clinical application. As a result, there was little decrease of CT value after 90KeV in the case of materials with low density and high moisture content such as normal saline, methyl-cellulose and gels used in ultra-sonic waves test; energy does not influence much on materials with extremely low or high density such as air and contrast medium; methyl-cellulose and gels used in ultra-sonic waves test are considered to be the most useful materials for clinical applications.

SU-E-T-318: A Simulation Study for Active Scanning Nozzle Design Using Beam Optic Parameters

PURPOSE The beam conditions at the end of HEBT (High Energy Beam Transport) line affect on active scanning nozzle design and scanning parameters. In this study, the different initial conditions at HEBT were applied to determine an appropriate active scanning nozzle dimension. Using determined beam conditions, the dose distribution at the Io-center was calculated to provide a spot spacing at active scanning scanning. METHODS In this study, the initial geometry dimension was set to about 9 m from the end of HEBT to Iso-center. The beam line was considered an vacuum space until 7.3 m from HEBT. Two different initial beam conditions were applied. The first was a simple gaussian distribution for simple divergence beam case. And, the second was a focused beam based on Twiss parameters. The beam line was produced by Geant4 simulation tool kit. For the drifted beam, the position and momentum distribution were considered as 3 mm and 0.6 mradian as sigma. For the focused beam, the given emittance was 10 pi mm mradian. Twiss parameter were derived by drift length to create 3 mm of sigma, as waist point, at the iso-center. The required inner diamater for HEBT and scanning magnet were predicted by the size of the beam, which was obtained by above calculations. Also, the dose distribution near the iso-center was obtained to get optimized scan spacing. RESULTS Based on the size of the transported beam, the minimum inner diameter of HEBT and Scanning Magnet should be larger then 21mm of sigma. Also, the sigma difference of dose distribution at water phantom shows about 20 % at given beam conditions. CONCLUSION Depending on the initial beam condition at the end of HEBT, the beam nozzle dimension and scan spacing should be determined. Through this simulation study, more precise data could be given.

SU‐E‐T‐175: A Study on Design and Fabrication of 25 * 25 cm2 Beam Monitor for Scanning Carbon Beam

PURPOSE The KHIMA is developing a superconducting cyclotron of 430 MeV/u for carbon therapy. In order to verify the irradiated beam dose and position, detectors have been developed. The detector has a considered in the active area of 25*25cm2 to cover the entire beam scanning area. To minimize the loss of data during beam irradiation, a fast data acquisition system was required. METHODS A PPIC type was adopted. To measure the beam position and profile, the electrode of PPIC was designed to have a strip pattern. The PCB technique was applied to large area with thin FR-4 plate of electrodes. The chamber has a strip interval of 1.7mm. He was used as the filling gas in order to reduce the ion collection time. Output signal from the detector connected to the two charge integrators was transferred every 10us. The signal can be stored temporarily in memory of FPGA through one of 2 integrators. RESULTS The fabricated large electrode plates did not show any deformation on their shape. Depending on the beam position, the amount of dose from the ion chamber will be measured. For fast data acquisition, the DAQ board was fabricated by using 2 charge integrators and the FPGA. The obtained data from the ion chamber was displaced on the PC screen every 10us. The fluence map of a single layer will be shown on the PC screen at the end of beam irradiation on the layer. The output data from the profile monitor will be compared with Gafchromic Film results. CONCLUSIONS PCB method for active area of thin electrodes was used in the strip pattern. To reduce the loss of data during irradiation, 2 charge integrators are used alternately. The response of the readout data was set 1 0us. The beam tests will be performed with the MC-50 Cyclotron.

SU‐E‐T‐282: Preliminary Simulation Study for 3 Dimensional Dose Delivery in Carbon Beam Active Scanning System of KHIMA

PURPOSE KHIMA (Korea Heavy Ion Medical Accelerator) project has a plan to develop and construct a research beam line for carbon beam active scanning system. The carbon beam line consists with scanning magnet, beam-monitoring system, energy modulation system. In this study, the significant components, scanning magnets and ridge filter, were designed for the carbon beam active scanning beam line. METHODS The designed scanning magnet and ridge filter were used for 3 dimensional active beam dose delivery simulation by Geant4 Monte Carlo code. The target volume of the active scanning was 10 × 10 × 5 cm2 on the water phantom with 400 MeV/u of carbon beam. The transvers plane on the target was scanned by 3mm of step size. And, the optimized weighting factors of transverse scanning were obtained by MINUIT fitting package of ROOT. An aluminum ridge filter was designed to generate 5 cm of physical SOBP through step shape, which was optimized through in-house iteration method and the MINUIT package.The simulation was performed with Geant4 through applying the transverse scanning with the obtained weighting factor and the designed ridge filter. RESULTS The uniformity on the transverse plan will be expected below 4% when it considered scattered beam. Also, the uniformity for longitudinal plane will be expected lower then 5%. CONCLUSIONS This preliminary computational study was shown a possibility of using ridge filter for acceptable 3 dimensional uniformity on active beam delivery system in carbon beam therapy line. The optimization process to reach an acceptable uniformity on clinical use should be followed. In addition, it would be used for the design of treatment planning system software for KIHMA project.

A Comparative Quantitative Analysis of IDEAL (Iterative Decomposition of Water and Fat with Echo Asymmetry and Least Squares Estimation) and CHESS (Chemical Shift Selection Suppression) Technique in 3.0T Musculoskeletal MRI

Patients who underwent hip arthroplasty using the conventional fat suppression technique (CHESS) and a new technique (IDEAL) were compared quantitatively to assess the effectiveness and usefulness of the IDEAL technique. In 20 patients who underwent hip arthroplasty from March 2009 to December 2010, fat suppression T2 and T1 weighted images were obtained on a 3.0T MR scanner using the CHESS and IDEAL techniques. The level of distortion in the area of interest, the level of the development of susceptibility artifacts, and homogeneous fat suppression were analyzed from the acquired images. Quantitative analysis revealed the IDEAL technique to produce a lower level of image distortion caused by the development of susceptibility artifacts due to metal on the acquired images compared to the CHESS technique. Qualitative analysis of the anterior area revealed the IDEAL technique to generate fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the middle area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique but with homogeneous fat suppression. In the posterior area, the IDEAL technique generated fewer susceptibility artifacts than the CHESS technique. Fat suppression was not statistically different, and the two techniques achieved homogeneous fat suppression. In conclusion, the IDEAL technique generated fewer susceptibility artifacts caused by metals and less image distortion than the CHESS technique. In addition, homogeneous fat suppression was feasible. In conclusion, the IDEAL technique generates high quality images, and can provide good information for diagnosis.