In order to study the image characteristics of motion artifacts and todetermine the relations of motion artifacts with varied motion types, and the inag-ing timings, frames, distances and directions during SPECT acqui...In order to study the image characteristics of motion artifacts and todetermine the relations of motion artifacts with varied motion types, and the inag-ing timings, frames, distances and directions during SPECT acquisition, a myocardialphantom filled with pertechnetate solution was used to simulate the patient motion.In nonreturning pattern, the simulation motion was timed at the 0°, -45° and -90°positions during the rotation of the detector over a 180° arc from +45° right antcrioroblique to -135° left posterior oblique. Simulation motion was performed by movingthe phantom +5mm, ±-10mm and +20mm along X- (from left to right), Y- (fromhead to caudal) and Z-axis (from back to ventral) respectively. In returning patternthe acquired 30 projections were divided into three equal parts. The simulation motionwas timed at the middle 1-7 projections of each part and performed by moving thephantom +5, ±10, ±15, ±20, ±25, ±30 and ±50 mm along X-, Y- and Z-axis respec-tively. Each image was compared with normal image and assessed by three experiencedobservers without knowledge of the phantom motion. Logistic regression analysis wasused to determine the relationship of motion artifacts with the affecting factors. Nosignificant artifacts can be found when the phantom was moved slightly, no matterwhich motion pattern, direction and timing were taken. The characteristics of motionartifacts showed a radioactive marker dot in inferior wall firstly when the phantomwas moved along X-axis. Septal and lateral wall became "hot" symmetrically whenthe phantom was moved along Y-axis. And nodular hot could be found in anteriorwall when the phantom was moved along Z-axis. At last the "lumpy" and "defect"areas existed alternately and formed a triangle respectively. The presence of motionartifacts was related to motion directions, distance and affected frames, but was in-dependent of motion timing. The characteristics of motion artifacts could be foundwhen the phantom was moved along different axis. Motion distance contributed moreto the appearance of motion artifacts than other related factors, this was especiallyclear when motion was along Y-axis.展开更多
The radiation dosimetry in medical practice requires special phantom to simulate the organs and tissues of a human body. To achieve the same elemental composition as that of the human lung by weight percent, we constr...The radiation dosimetry in medical practice requires special phantom to simulate the organs and tissues of a human body. To achieve the same elemental composition as that of the human lung by weight percent, we constructed lung equivalent phantom (LEP) using cork with absorbed water in order for it to uniformly absorb the water. Then, we presented the physical properties and dosimetric characteristics of other commercial phantoms and the LEP. We found that the physical properties and dosimetric characteristics of the LEP were approximately the same as those of human lung tissue. LEP constitutes a new dosimetry tool because it can provide the dose distributions and point doses similar to those for the body with respiratory motion of lung.展开更多
Objective:To investigate the influences of motion artifacts on three-dimensional (3D) reconstruction volume and conformal radiotherapy planning. Methods:A phantom which can mimic the clip motion of lung tumor along th...Objective:To investigate the influences of motion artifacts on three-dimensional (3D) reconstruction volume and conformal radiotherapy planning. Methods:A phantom which can mimic the clip motion of lung tumor along the cranial-caudal direction is constructed by step motor, small ball of polyethylene and potato. Ten different scan protocols were set and CT data of the phantom were acquired by using a commercial GE LightSpeed16 CT scanner. The 3D reconstruction of the CT data was implemented by adopting volume-rendering technology of GE AdvantageSim 6.0 system. The reconstructed volumes of each target in different scan protocols were measured through 3D measuring tools. Thus, relative deviations of the reconstruction volumes between moving targets and static ones were determined. The three-dimensional conformal radiation therapy (3D-CRT) plans and conformal fields were created and compared for a static/moving target with the WiMRT treatment planning system (TPS). Results:For a static target, there was no obvious difference among the 3D reconstruction volumes when the CT data were acquired with different pitches and slices. The appearance of 3D reconstruction volume and 3D conformal field of a moving target was quite different from that of static one. The maximum relative deviation is nearly 90% for a moving target scanned with different scan protocols. The relative deviations are variable among the different targets, about from -39.8% to 89.5% for a smaller target and from -18.4% to 20.5% for a larger one. Conclusion:The motion artifacts have great effects on 3D-CRT planning and reconstruction volume, which will greatly induce distorted conformal radiation fields and false DVHs for a moving target.展开更多
Purpose: To develop and test an integrated simulation system based on the digital Extended Cardio Torso (XCAT) phantom for 4-dimensional (4D) radiation therapy of lung cancer. Methods: A computer program was developed...Purpose: To develop and test an integrated simulation system based on the digital Extended Cardio Torso (XCAT) phantom for 4-dimensional (4D) radiation therapy of lung cancer. Methods: A computer program was developed to facilitate the characterization and implementation of the XCAT phantom for 4D radiation therapy applications. To verify that patient-specific motion trajectories are reproducible with the XCAT phantom, motion trajectories of the diaphragm and chest were extracted from previously acquired MRI scans of five subjects and were imported into the XCAT phantom. The input versus the measured trajectories was compared. Simulation methods of 4D-CT and 4D-cone-beam CT (CBCT) based on the XCAT phantom were developed and tested for regular and irregular respiratory patterns. Simulation of 4D dose delivery was illustrated in a simulated lung stereotactic-body radiation therapy (SBRT) case based on the XCAT phantom. Dosimetric comparison was performed between the planned dose and simulated delivered dose. Result: The overall mean (±standard deviation) difference in motion amplitude between the input and measured trajectories was 1.19 (±0.79) mm for the XCAT phantoms with voxel size of 2 mm. 4D-CT and 4D-CBCT images simulated based on the XCAT phantom were validated using regular respiratory patterns and tested for irregular respiratory patterns. Comparison between simulated 4D dose delivery and planned dose for the lung SBRT case showed comparable results in all dosimetric matrices: the relative differences were 0.3%, 4.0%, 0%, and 2.8%, respectively, for max cord dose, max esophagus dose, mean heart dose, and V20Gy of the lungs. 97.5% of planning target volume (PTV) received prescription dose in the simulated 4D delivery, as compared to 95% of PTV received prescription dose in the plan. Conclusion: We developed an integrated simulation system based on the XCAT digital phantom and illustrated its utility in 4D radiation therapy of lung cancer. This simulation system is potentially a useful tool for quality control and development of imaging and treatment techniques for 4D radiation therapy of lung cancer.展开更多
The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stere...The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stereotactic body radiation therapy (SBRT) and other motion-managed therapies. However, it is known that 4DCT and 4DCBCT differ in aspects of image acquisition and reconstruction that may lead to discrepancies between the two modalities. To evaluate quantitative differences between 4DCT and 4DCBCT imaging under respiratory motion, we performed a phantom study in the ground truth setting. A programmable respiratory motion phantom was used to simulate the 1D S-I position of a known-size lesion. Ten sinusoidal and twenty patient-specific breathing waveforms were applied to drive lesion motion during the 4DCT and 4DCBCT acquisitions. The difference in lesion volume acquired between the two imaging modalities was as high as 34.4% and 18.4% for sinusoidal and patient-specific breathing motions, respectively. When compared to the true volume, 4DCT measurement often underestimated the lesion size whereas 4DCBCT overestimated the lesion volume in most of the cases. 4DCBCT gave more accurate recovery of the volume than 4DCT for most settings tested in this study. These findings may be helpful for improving the definition of internal target and planning target volume margins, and extracting quantitative information from on-board treatment verification imaging.展开更多
文摘In order to study the image characteristics of motion artifacts and todetermine the relations of motion artifacts with varied motion types, and the inag-ing timings, frames, distances and directions during SPECT acquisition, a myocardialphantom filled with pertechnetate solution was used to simulate the patient motion.In nonreturning pattern, the simulation motion was timed at the 0°, -45° and -90°positions during the rotation of the detector over a 180° arc from +45° right antcrioroblique to -135° left posterior oblique. Simulation motion was performed by movingthe phantom +5mm, ±-10mm and +20mm along X- (from left to right), Y- (fromhead to caudal) and Z-axis (from back to ventral) respectively. In returning patternthe acquired 30 projections were divided into three equal parts. The simulation motionwas timed at the middle 1-7 projections of each part and performed by moving thephantom +5, ±10, ±15, ±20, ±25, ±30 and ±50 mm along X-, Y- and Z-axis respec-tively. Each image was compared with normal image and assessed by three experiencedobservers without knowledge of the phantom motion. Logistic regression analysis wasused to determine the relationship of motion artifacts with the affecting factors. Nosignificant artifacts can be found when the phantom was moved slightly, no matterwhich motion pattern, direction and timing were taken. The characteristics of motionartifacts showed a radioactive marker dot in inferior wall firstly when the phantomwas moved along X-axis. Septal and lateral wall became "hot" symmetrically whenthe phantom was moved along Y-axis. And nodular hot could be found in anteriorwall when the phantom was moved along Z-axis. At last the "lumpy" and "defect"areas existed alternately and formed a triangle respectively. The presence of motionartifacts was related to motion directions, distance and affected frames, but was in-dependent of motion timing. The characteristics of motion artifacts could be foundwhen the phantom was moved along different axis. Motion distance contributed moreto the appearance of motion artifacts than other related factors, this was especiallyclear when motion was along Y-axis.
文摘The radiation dosimetry in medical practice requires special phantom to simulate the organs and tissues of a human body. To achieve the same elemental composition as that of the human lung by weight percent, we constructed lung equivalent phantom (LEP) using cork with absorbed water in order for it to uniformly absorb the water. Then, we presented the physical properties and dosimetric characteristics of other commercial phantoms and the LEP. We found that the physical properties and dosimetric characteristics of the LEP were approximately the same as those of human lung tissue. LEP constitutes a new dosimetry tool because it can provide the dose distributions and point doses similar to those for the body with respiratory motion of lung.
基金Grant sponsor:Guangzhou Municipal Medicin &Health ProgramGrant number:2006-YB-177
文摘Objective:To investigate the influences of motion artifacts on three-dimensional (3D) reconstruction volume and conformal radiotherapy planning. Methods:A phantom which can mimic the clip motion of lung tumor along the cranial-caudal direction is constructed by step motor, small ball of polyethylene and potato. Ten different scan protocols were set and CT data of the phantom were acquired by using a commercial GE LightSpeed16 CT scanner. The 3D reconstruction of the CT data was implemented by adopting volume-rendering technology of GE AdvantageSim 6.0 system. The reconstructed volumes of each target in different scan protocols were measured through 3D measuring tools. Thus, relative deviations of the reconstruction volumes between moving targets and static ones were determined. The three-dimensional conformal radiation therapy (3D-CRT) plans and conformal fields were created and compared for a static/moving target with the WiMRT treatment planning system (TPS). Results:For a static target, there was no obvious difference among the 3D reconstruction volumes when the CT data were acquired with different pitches and slices. The appearance of 3D reconstruction volume and 3D conformal field of a moving target was quite different from that of static one. The maximum relative deviation is nearly 90% for a moving target scanned with different scan protocols. The relative deviations are variable among the different targets, about from -39.8% to 89.5% for a smaller target and from -18.4% to 20.5% for a larger one. Conclusion:The motion artifacts have great effects on 3D-CRT planning and reconstruction volume, which will greatly induce distorted conformal radiation fields and false DVHs for a moving target.
文摘Purpose: To develop and test an integrated simulation system based on the digital Extended Cardio Torso (XCAT) phantom for 4-dimensional (4D) radiation therapy of lung cancer. Methods: A computer program was developed to facilitate the characterization and implementation of the XCAT phantom for 4D radiation therapy applications. To verify that patient-specific motion trajectories are reproducible with the XCAT phantom, motion trajectories of the diaphragm and chest were extracted from previously acquired MRI scans of five subjects and were imported into the XCAT phantom. The input versus the measured trajectories was compared. Simulation methods of 4D-CT and 4D-cone-beam CT (CBCT) based on the XCAT phantom were developed and tested for regular and irregular respiratory patterns. Simulation of 4D dose delivery was illustrated in a simulated lung stereotactic-body radiation therapy (SBRT) case based on the XCAT phantom. Dosimetric comparison was performed between the planned dose and simulated delivered dose. Result: The overall mean (±standard deviation) difference in motion amplitude between the input and measured trajectories was 1.19 (±0.79) mm for the XCAT phantoms with voxel size of 2 mm. 4D-CT and 4D-CBCT images simulated based on the XCAT phantom were validated using regular respiratory patterns and tested for irregular respiratory patterns. Comparison between simulated 4D dose delivery and planned dose for the lung SBRT case showed comparable results in all dosimetric matrices: the relative differences were 0.3%, 4.0%, 0%, and 2.8%, respectively, for max cord dose, max esophagus dose, mean heart dose, and V20Gy of the lungs. 97.5% of planning target volume (PTV) received prescription dose in the simulated 4D delivery, as compared to 95% of PTV received prescription dose in the plan. Conclusion: We developed an integrated simulation system based on the XCAT digital phantom and illustrated its utility in 4D radiation therapy of lung cancer. This simulation system is potentially a useful tool for quality control and development of imaging and treatment techniques for 4D radiation therapy of lung cancer.
文摘The ability of respiratory-correlated fan beam CT (4DCT) and respiratory-correlated cone beam CT (4DCBCT) to accurately estimate tumor volume is critical to accurate dosimetry and treatment verification for lung stereotactic body radiation therapy (SBRT) and other motion-managed therapies. However, it is known that 4DCT and 4DCBCT differ in aspects of image acquisition and reconstruction that may lead to discrepancies between the two modalities. To evaluate quantitative differences between 4DCT and 4DCBCT imaging under respiratory motion, we performed a phantom study in the ground truth setting. A programmable respiratory motion phantom was used to simulate the 1D S-I position of a known-size lesion. Ten sinusoidal and twenty patient-specific breathing waveforms were applied to drive lesion motion during the 4DCT and 4DCBCT acquisitions. The difference in lesion volume acquired between the two imaging modalities was as high as 34.4% and 18.4% for sinusoidal and patient-specific breathing motions, respectively. When compared to the true volume, 4DCT measurement often underestimated the lesion size whereas 4DCBCT overestimated the lesion volume in most of the cases. 4DCBCT gave more accurate recovery of the volume than 4DCT for most settings tested in this study. These findings may be helpful for improving the definition of internal target and planning target volume margins, and extracting quantitative information from on-board treatment verification imaging.
