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Purpose: The texture analysis method is useful to estimate structural features of images as color, size, and shape. The study aims to determine a dose-response curve by texture analysis of Gafchromic EBT3 film images using scanning electron microscopy (SEM). Methods: The uncoated Gafchromic EBT3 films were prepared to directly scan over the active surface layer of EBT3 film using SEM. The EBT3 films were exposed at a dose range of 0 to 10 Gy using a 6 MV photon beam. The exposed film samples were SEM-scanned at 100X, 1000X, and 3000X magnifications. The four texture features (Homogeneity, Correlation, Contrast, and Energy) were calculated based on the gray level co-occurrence matrix (GLCM) derived from the SEM images at each dose. To validate a correlation between delivered doses and texture features, an R-squared value in linear regression was tested. Results: The results showed that the Correlation index was more suitable as dose indices than the other three texture features due to higher linearity and sensitivity of the dose response curves. Further the Correlation index of 3000X magnified SEM images with 9 pixel offsets had an R-squared value of 0.964. The differences between the delivered doses and the doses measured by this method were 0.9, 1.2, 0.2, and 0.2 Gy at 5, 10, 15, and 20 Gy, respectively. Conclusion: It seems to be feasible to convert micro-scale structural features of χtχχχhe EBT3 films to absorbed doses using the texture analysis method.

Purpose: The deconvolution method to compensate the movement of the object during PET scanning was investigated. The motion artifact should be removed for exact staging of the patient. Method and Materials: The PETimages for movable object with FDG using Biograph(Siemens, USA) were obtained. The FDG drugged small object with 1mm diameter and 5 cm long was installed at the end of the cam of the moving phantom. The profiles for Z‐direction, movement direction, including the maximum intensity point, were extracted from the images. The 1‐D movement of the phantom was calculated from the physical distance of the moving phantom. The iterative deconvolution method was implemented on the profile obtained from the moving phantom to compensate the movement of the object. Results: The profile from convolution between profile for stationary case and 1‐dimensional movement of the scanning object was calculated. The maximum intensity of the stationary case (543,915 bq/ml) was 158% higher than the movable case(343,803 bq/ml). The calculated profile (319,685 Bq/ml) was well agreed with the movable one within 7%. Conclusion: Due to the movement during the PET scanning, the scanning signals are reduced and affect on the maximum SUV, derived from the maximum intensity in the interested region. The movement of the organ should be monitored by given solution such as RPM. The suggested iterative deconvolution method could be implemented on the most movable direction, and it could successfully remove at least 1‐dimentional motion artifact.

To examine the dosimetric stability against geometrical variations in the treatment plan of spine radiosurgery, the positioning data of CBCTimage guidance for 28 patients were used to make a comparison between the treatment plans before and after image guidance. The dose distribution in treatment plans were recalculated with the same IMRT fluence map and the CTimage shifted by the correction values. Some dosimetric parameters were employed to verify the tumor coverage and the spinal cord dose in the treatment plans. The Target volume which receive more than 95% of prescription dose(D95) for tumors and the equivalent uniform dose (EUD )for spinal cord were calculated to fish out the dosimetric variations. The relation between the tumor coverage and the geometric variations presents to be quadratic in all directions, while the EUD of spinal cord are linearly increased by geometrical variations in anterior‐posterior direction in which tumors are located in the view of spinal cord. Since there is no margin at the interface of tumor and spinal cord in most cases, the dosimetric effect of geometrical variation for spinal cord is significant. The tolerance dose of spinal cord in radiosurgery have to be considered very carefully with this dosimetric stability and the geometrical uncertainties.

Purpose: Scatter radiation can degrade the quality of a kilovoltage cone‐beam CT (KV CBCT)image due to the use of a larger flat‐panel detector. Especially, if KV CBCT is employed for seed localization, the effect of streak metal artifacts of the seeds can be magnified in CBCTimages. In this study, we describe the preliminary application of MV cone‐beam reconstruction (CBR) image from EPID projections and deformable registration for metal artifact reduction in a test phantom. Method and Materials: To perform the CBR and deformable registration based technique, the following three steps were used. (1) Extract a seeds only image and an image of seeds with bright metal streak regions by using a user‐defined threshold value in the CBR image and KV CBCTimages. (2) A derived intensity based 3D ‘demon’ deformable registration algorithm was applied to both seeds images, and the use of the algorithm generated the deformation field. (3) Resample the original CTimage according to the deformation field. Results: The intensities of the metal artifact region were decreased with the use of the deformation grid, as the seeds in KV CBCTimages were deformed as compared to the original seeds in CBR images. Although image quality was not dramatically enhanced, the metal artifact removed volume which causes the dose calculation error was 2.795 mm3 over 61 CT slices of the test phantom. Conclusion: Preliminary results with a test phantom demonstrated a bright streak metal artifact reduction effect. We believe that if dose calculation associated with KV CBCT yields reliable results, our study could provide an efficient method for post‐implant dosimetry. Conflict of Interest: This research sponsored by the Seoul R&BD Program (10550) and the Mid‐ and Long‐Term Nuclear R&D Program of the Ministry of Science and Technology (M20706000007‐07M0600‐00710).

Purpose: Accurate delivery of the most‐up‐to‐date treatment techniques, such as intensity‐modulated radiation therapy(IMRT), is essential. An anthropomorphic phantom was designed and constructed for a remote‐audit program that allows evaluation of an institution's accuracy for deliveringIMRT. The dosimetric characteristics in the phantom were investigated. Method and Materials: The phantom has the shape of a cylinder with one target and three organ‐at‐risks (OARs) inside. The target and OARs were shaped analogous to those of nasopharynx cancer patients. TLD holders were inserted inside the target and the OARs for absolute dose measurements. The phantom allows measurements with ion chamber (IC) at the TLD locations, so that inter‐comparison between two dosimeters was possible. For the measurement of relative dose distribution, two film slots were orthogonally placed near the center of the phantom, which also enables inserting inhomogeneities near the target. Measurements with TLDs and ICs were done for four cases. The first was an anterior one‐port 6MV X‐ray (Primus, Siemens, USA) delivery; the second used the same beam geometrically, but with inhomogeneities inserted, and in the third case three ports of beams were distributed in equi‐gantry angle, and the fourth was an IMRT without inhomogeneities. For case 1–3, theoretical predictions were computed by using Monte Carlo code. Results: For anterior one port X‐ray delivery to a homogeneous/ inhomogeneous phantom, the deviation between the IC and TLD measurements, ranged from 1.7% to 2.3%. For three‐port beam delivery, the range was also similar. For IMRTdelivery, the differences were 0.1–2.8%. The differences between the TLD measurements and MC predictions ranged from −0.14–1.8%. Conclusion: The TLD measurements in the developed phantom agreed with IC and MC results within acceptable differences. The developed phantom with TLDdosimeters are feasible to be used for remote monitoring of IMRT. Supported by KFDA Grant No 05102eui BangPum and 06112eui BangAn300.

Purpose: A patient‐specific treatment planning system for BoronNeutron Capture Therapy (BNCT) based on dose calculation using MCNP, called BTPS, was developed at Hanyang University, Korea. To facilitate treatment planning for BNCT, overall procedures of the BTPS were designed based on a graphical user interface (GUI) and matched to clinical treatments of BNCT. Appropriate tools automatically associated with MCNP were built‐in. To provide optimized irradiation time in treatment by re‐calculating absorbed doses with measured boron concentrations and irradiatingneutron flux, various tools, which can decrease computation time, were employed into the BTPS. Method and Materials: The GUI based BTPS was built with a C++ Builder, and works on Windows. The BTPS reconstructs a 3D voxel phantom from patient's images, and simulates treatment environments including the delineated target, irradiation field, and boron concentrations in tumor/normal tissues with easy manipulations through the GUI. MCNP input with the treatment environments are automatically generated for calculating the absorbed dose or neutron fluxes in the voxel phantom. Results: Computation time for calculating the absorbed dose and neutron fluxes in a voxel phantom (17×18×23 cm of 1 cm3 voxels, boron concentration of 10 ppm in each voxel, and histories of 10 millions) was about 5 minutes by using accelerated tallying techniques in MCNP and a parallel computing system (Pentium IV, 48 nodes). The results from the MCNP run are automatically imported. Total absorbed dose or neutron fluxes are calculated with irradiatingneutron flux and treatment time, and displayed as an isodose contour or dose volume histogram. Conclusion: Since the BTPS facilitates patient‐specific treatment planning for BNCT with efficient computation time, it is expected that the BTPS is applicable to clinical treatments of BNCT. Conflict of Interest: Research sponsored by the SRC/ERC program (R11‐2000‐067‐01001‐0) and the long‐term research and development program (M20505050003‐05A0905‐00310) of MOST/KOSEF.

Purpose: In order to spare the normal tissues as much as possible during stereotactic radiosurgey (SRS) of lungcancer by limiting the tumor motion within 5 mm, 4D CT was implemented and its usefulness was evaluated. By comparing CT during the simulation with CT during the treatment, the interfractioanl positioning errors were assessed and image guided radiotherapy was performed using the images from ExacTrac x‐ray system (BrainLab, Germany) in the treatment room. Method and Materials: For 11 lungcancer patients positioned in the SRS frame, 4D CT was acquired and treatment was planned based on 4D CT. For the patients whose tumor motion was larger, the motion was controlled to be less than 5 mm using the real‐time positioning management (RPM, Varian, USA) system. To verify the interfractional patient positioning errors, CT was acquired twice during the course of treatment and ExacTrac x‐ray system was used to reproduce the patients' setup. Results: From the 4D CT, mean GTV and PTV were 15.9±9.6 cc and 40.7±16.6 cc, respectively. Tumor motions were 2.9±1.4 mm, 3.4±3.2 mm, and 12.1±5.0 mm in lateral, vertical, and longitudinal direction, respectively, for the full respiratory phases, which were reduced to 3.7±1.1 mm during 30 ∼ 70 % phases selected for the gated radiotherapy. Discrepancy between planning CT and two CT during treatment was 1.2±1.0 mm, 1.4±1.2 mm, and 2.3±1.5 mm, and setup errors from ExacTrac system were 1.0±1.8 mm, −0.3±2.2 mm, and −0.6±3.2 mm in lateral, vertical, and longitudinal direction, respectively. Conclusion: The use of 4D CT, the repeated CT scans during treatment, and image‐guided technique using x‐ray imaging system in treatment room for setup correction was effectively implemented for SRS of lungcancer, which assured the tumor motion and positioning errors within 5 mm during treatment.

Purpose: To find the best method corresponding with respiratory target motion, ten patients' respiratory patterns were measured by various methods simultaneously. Respective respiration monitoring methods were compared with fluoroscopic target motion during simulation. Method and Materials: A respiration monitoring system using thermocouple was developed to measure patient's respiration. Conventional spirometer and home made thermocouple were connected to a mouse piece to measure the patient's respiration simultaneously. A respiration acquisition program was built by using Labview 7.0 (National Instruments, Austin, TX), which acquire respiration signals and display its patterns. A fluoroscopic target tracking program was built by using IDL 6.1 (Research Systems, Inc, Boulder, CO). Ten patients with lung or livercancer 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 from spirometer, thermocouple, and RPM® system were compared with fluoroscopic target motion respectively. Its relationships were evaluated as correlation coefficient. Results: Comparing each correlation coefficient for spirometer, thermocouple, and RPM®, skin motion detection is the most correspondent with fluoroscopic target motion. However, respiration monitoring methods with spirometer or thermocouple also correlate well (more than 0.9). Conclusion: Respiratory pattern depends on a patient and his/her conditions. The relationship between thermocouple and fluoroscopic target motion could be enhanced by correlating respiratory signal with target motion. Respiration monitoring methods with spirometer or thermocouple, and skin motion detection are feasible to monitor the target motion for applying 4D radiotherapy.

Purpose: A system to non‐invasively fix and monitor eye by a head mounted display (HMD) with a CCDcamera for stereotactic radiotherapy(SRS) of uveal melanoma has been developed and implemented clinically. Method and Materials: The eye fixing and monitoring system consists of a HMD showing patient a screen for fixing eyeball, a CCDcamera monitoring patient's eyeball, and an immobilization mask. At first, patient's head was immobilized with a mask. Then, patient was instructed to wear HMD, to which CCDcamera was attached, on the mask and see the given reference point on its screen. While patient stared at the given point in order to fix eyeball, the camera monitored its motion. Four volunteers and one patient of uveal melanoma for SRS came into this study. For the volunteers, setup errors and the motion of eyeball were analyzed. For the patient, CT scans were performed, with patient's wearing HMD and fixing the eye to the given point. To treat patient under the same condition, daily CT scans were also performed before every treatment and the motion of lens was compared to the planning CT.Results: Setup errors for four volunteers were within 1 mm and the motion of eyeball was fixed within the clinically acceptable ranges. For the patient with uveal melanoma, the motion of lens was fixed within 2 mm from daily CT scans.Conclusion: An eye fixing and monitoring system allowed immobilizing patient as well as monitoring eyeball and was successfully implemented in the treatment of uveal melanoma for SRS.