Background: Folate, a water-soluble B vitamin and one of the major micronutrients in vegetables, is known as an essential factor for the de novo biosynthesis of purines and thymidylate, and it plays an important role in DNA synthesis and replication. Thus, folate deficiency results in ineffective DNA synthesis, and has been shown to induce the initiation and progression of colorectal cancer (CRC). Recently, the incidence of CRC in Korea has increased markedly in both men and women; this trend may be related to the adoption of a more 'westernized' lifestyle, including dietary habits. Objective: A hospital-based case-control study was conducted to examine the relationship between folate intake and the risk of CRC within a Korean population. Methods: A total of 596 cases and 509 controls, aged 30À79 years, were recruited from two university hospitals. Site-and sexspecific odds ratios (ORs) were estimated using logistic regression models. Results: Cases were more frequently found to have a family history of CRC among first-degree relatives, to consume more alcohol, to be more likely current smokers and less likely to participate in vigorous physical activity than the controls. In the overall data for men and women combined, multivariate ORs (95% confidence interval (CI), P for trend) comparing the highest vs the lowest quartile of dietary folate intake were: 0.47 (0.32-0.69, o0.001) for CRC, 0.42 (0.26-0.69, o0.001) for colon cancer and 0.48 (0.28-0.81, 0.007) for rectal cancer. An inverse association was also found in women with dietary folate intake: 0.36 (0.20-0.64, o0.001) for CRC, 0.34 (0.16-0.70, 0.001) for colon cancer and 0.30 (0.12-0.74, 0.026) for rectal cancer, but not in men. In addition, the total folate intake of women was strongly associated with a reduced risk of rectal cancer (OR, 0.38; 95% CI, 0.17-0.88; P for trend ¼ 0.04). Conclusion: We found a statistically significant relationship between higher dietary folate intake and reduced risk of CRC, colon cancer and rectal cancer in women. A significant association is indicated between higher total folate intake and reduced risk of rectal cancer in women.

Purpose: The aim of this study was to investigate the gantry angle dependency of the multileaf collimator (MLC) leaf position error. Methods: An automatic MLC quality assurance system (AutoMLCQA) was developed to evaluate the gantry angle dependency of the MLC leaf position error using an electronic portal imaging device (EPID). To eliminate the EPID position error due to gantry rotation, we designed a reference maker (RM) that could be inserted into the wedge mount. After setting up the EPID, a reference image was taken of the RM using an open field. Next, an EPID‐based picket‐fence test (PFT) was performed without the RM. These procedures were repeated at every 45° intervals of the gantry angle. A total of eight reference images and PFT image sets were analyzed using in‐house software. The average MLC leaf position error was calculated at five pickets (‐10, ‐5, 0, 5, and 10 cm) in accordance with general PFT guidelines using in‐house software. This test was carried out for four linear accelerators. Results: The average MLC leaf position errors were within the set criterion of <1 mm (actual errors ranged from ‐0.7 to 0.8 mm) for all gantry angles, but significant gantry angle dependency was observed in all machines. The error was smaller at a gantry angle of 0° but increased toward the positive direction with gantry angle increments in the clockwise direction. The error reached a maximum value at a gantry angle of 90° and then gradually decreased until 180°. In the counter‐clockwise rotation of the gantry, the same pattern of error was observed but the error increased in the negative direction. Conclusion: The AutoMLCQA system was useful to evaluate the MLC leaf position error for various gantry angles without the EPID position error. The Gantry angle dependency should be considered during MLC leaf position error analysis.

Purpose: The recent integration of kilo‐voltage cone beam computed tomography (kV‐CBCT) imaging systems into linear accelerators makes it possible to image and treat a patient on a single machine. The goal of this study is to investigate the feasibility and usefulness of acquiring kV‐CBCT for adaptive radiotherapy for patients with lung and phantom study with significant target position. Method and Materials: A self made brain phantom and quality assurance phantom were used to compare the dosimetric and geometric accuracy between planning CT and kV‐CBCT with bow‐tie filter added. The quality of the kV‐CBCT volume images acquired using phantom was evaluated by measuring the spatial accuracy, contrast, hounsfield units (HU), and converting HU to electron density. The kV‐CBCT was registered to the CT image using normalized mutual information. Results: In both phantom studies, the DVH based on kV‐CBCT images were in excellent agreement with DVH based on planning CT images. CBCT images were dependent on image uniformity, linearity and it needed verify the difference the mean HU value of the center ROI and peripheral ROI using histogram. The difference (<1%) is found in the calculated dose to the target for a complex inhomogeneous phantom between using kV‐CBCT images and planning CT images. These results indicate that kV‐CBCT images can be used to calculate dosimetric parameter accurately in radiotherapy treatment planning. In a patient study, doses for targets volume plans calculated on kV‐CBCT images agreed within 5% with those calculated on planning CT. Conclusion: We have investigated the feasibility and usefulness of acquiring on‐board kV‐CBCT images for adaptive radiotherapy treatment planning and tested the accuracy. It is feasible to use kV‐CBCT to determine dosimetric consequences resulting from tumor volume changes. The kV‐CBCT has potential to become a very useful tool for adaptive radiotherapy treatment planning.

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 liver cancer 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.