• Radiation Oncology Journal
• /
• v.23 no.4
• /
• pp.217-222
• /
• 2005

Purpose: To develop the respiration simulating phantom with thermocouple for evaluating 4D radiotherapy such as gated radiotherapy breathing control radiotherapy and dynamic tumor tracking radiotherapy. Materials and Methods: The respiration monitoring mask(ReMM) with thermocouple was developed to monitor the patient's irregular respiration. The signal from ReMM controls the simulating phantom as organ motion of patients in real-time. The organ and the phantom motion were compared with its respiratory curves to evaluate the simulating phantom. ReMM was used to measure patients' respiration, and the movement of simulating phantom was measured by using $RPM^{(R)}$. The fluoroscope was used to monitor the patient's diaphragm motion. relative to the organ motion, respectively. The standard deviation of discrepancy between the respiratory curve and the organ motion was 8.52% of motion range. Conclusion: Patients felt comfortable with ReMM. The relationship between the signal from ReMM and the organ motion shows strong correlation. The phantom simulates the organ motion in real-time according to the respiratory signal from the ReMM. It is expected that the simulating phantom with ReMM could be used to verify the 4D radiotherapy.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2004.11a
• /
• pp.119-121
• /
• 2004

• Progress in Medical Physics
• /
• v.16 no.2
• /
• pp.89-96
• /
• 2005

In this study, we investigated the effect of time gating threshold on the delivered dose at a organ with internal motion by respiration. Generally, the internal organs have minimum motion at exhalation during normal breathing. Therefore to compare the dose distribution time gating threshold, in this paper, was determined as the moving region of target during 1 sec at the initial position of exhalation. The irradiated fields were then delivered under three conditions; 1) non-moving target 2) existence of the moving target in the region of threshold (1sec), 3) existence of the moving target region out of threshold (1.4 sec, 2 sec). And each of conditions was described by the moving phantom system. It was compared with the dose distributions of three conditions using film dosimetry. Although the treatment time increased when the dose distributions was obtained by the internal motion to consider the TGT, it could be obtained more exact dose distribution than in the treatment field that didn't consider the internal motion. And it could be reduced the unnecessary dose at the penumbra region. When we set up 1.4 sec of threshold, to reduce the treatment time, it could not be obtained less effective dose distribution than 1 sec of threshold. Namely, although the treatment time reduce, the much dose was distributed out of the treatment region. Actually when it is treated the moving organ, it would rather measure internal motion and external motion of the moving organ than mathematical method. If it could be analyzed the correlation of the internal and external motion, the treatment scores would be improved.

• Progress in Medical Physics
• /
• v.23 no.3
• /
• pp.145-153
• /
• 2012

In this study, we quantify the residual motion artifact in 4D-CT scan using the dynamic lung phantom which could simulate respiratory target motion and suggest a simple one-dimension theoretical model to explain and characterize the source of motion artifacts in 4DCT scanning. We set-up regular 1D sine motion and adjusted three level of amplitude (10, 20, 30 mm) with fixed period (4s). The 4DCT scans are acquired in helical mode and phase information provided by the belt type respiratory monitoring system. The images were sorted into ten phase bins ranging from 0% to 90%. The reconstructed images were subsequently imported into the Treatment Planning System (CorePLAN, SC&J) for target delineation using a fixed contour window and dimensions of the three targets are measured along the direction of motion. Target dimension of each phase image have same changing trend. The error is minimum at 50% phase in all case (10, 20, 30 mm) and we found that ${\Delta}S$ (target dimension change) of 10, 20 and 30 mm amplitude were 0 (0%), 0.1 (5%), 0.1 (5%) cm respectively compare to the static image of target diameter (2 cm). while the error is maximum at 30% and 80% phase ${\Delta}S$ of 10, 20 and 30 mm amplitude were 0.2 (10%), 0.7 (35%), 0.9 (45%) cm respectively. Based on these result, we try to analysis the residual motion artifact in 4D-CT scan using a simple one-dimension theoretical model and also we developed a simulation program. Our results explain the effect of residual motion on each phase target displacement and also shown that residual motion artifact was affected that the target velocity at each phase. In this study, we focus on provides a more intuitive understanding about the residual motion artifact and try to explain the relationship motion parameters of the scanner, treatment couch and tumor. In conclusion, our results could help to decide the appropriate reconstruction phase and CT parameters which reduce the residual motion artifact in 4DCT.