- Email: [email protected]
Evaluation of the Change in Respiration Motion using a Standard Elekta Cone Beam CT
Proceedings of the 51st Annual ASTRO Meeting Conclusions: Calypso electromagnetic alignments are accurate to within 1-2mm as compared with kV and CBCT alignments. Changes in transponder geometry seem to be related to prostate volume reduction and transponder implant location. Most patients fall within the default geometrical residual (2mm) and rotational alignment (10o) limits. Author Disclosure: L.D. Courlas, None; J.C. O’Daniel, None; Q.J. Wu, None; W. Lee, None; F. Yin, None.
2899
Evaluation of the Change in Respiration Motion using a Standard Elekta Cone Beam CT
1,2
C. Brink , K. L. Gottlieb1, C. R. Hansen1, O. Hansen3 1 Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark, 2Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark, 3Department of Oncology, Odense University Hospital, Odense, Denmark
Purpose/Objective(s): Using 4D-CT the respiration induced tumor motion can be measured and used in the treatment planning. However, the measured tumor motion might not be representative for the motion during the entire fractionated treatment course. If a standard Cone Beam CT (CBCT) scan, acquired before the treatment, could be time resolved, this could be used to verify the size of the intra-fractional motion during the treatment course. Sonke et al (IJROBP 2008-70,590) has demonstrated that it is possible to track a tumor without mediastinal infiltration using a slow gantry speed 4D-CBCT. The purpose of the current study is to test if it is possible to use a standard Elekta CBCT scan to measure intra-fractional tumor motion, rather than the slow scan which is not supported by the vendor. Materials/Methods: Analysis of the intra-fractional tumor motion has been performed for each patient on a 4D-CT scan as well as on 3 4D-CBCT (fractions 3, 10 and 20). The 4D-CBCTs were created as described by Sonke et al (MedPhys 200532,1176) although in the current study the standard gantry speed was used. The motion of the outlined GTV has been tracked in the planning 4D-CT using Pinnacle3Ô version 8.1w (research version). Registration of phase one from the 4D-CT and 4D-CBCT is used to transfer the GTV to the CBCT scans. Hence, tracking of the GTV was possible in the CBCT scans as well. The inter-fractional tumor movement (relative to the bony structure) can be obtained from the difference in tumor position between the mid-ventilation phase of the 4D-CT and the 3D-CBCT used to create the 4DCBCT. Results: Currently 15 patients have been included in this study. It has been possible to track the tumor in the 4D-CBCT scan based on a standard 3D-CBCT. A paired t-test shows that the respiration motion in the 4D-CBCT is not significantly different from the result found from the initial 4D-CT. Likewise, no differences in respiration motion was found between fractions 3, 10, and 20. The standard deviation of the respiration induced tumor motion based on all 4D-CT and 4D-CBCT scans was measured to be: Intra: 0.8 mm (LR) 1.3 mm (AP) 2.4 mm (CC) and Inter: 1.7 mm (LR) 1.5 mm (AP) 1.7 mm (CC). Conclusions: The study shows that standard CBCT scans can be used to create 4D-CBCT scans with an image quality which facilitates tracking of the tumor motion. No clinically relevant change in the intra-fractional tumor motion was observed during the fractionated treatment course. Thus, it has been shown that the tumor motion measured from the 4D-CT is representative of the tumor motion during the entire treatment. This study shows that it is possible to validate the 4D-CT respiration used for treatment planning based on standard 3D-CBCT data available in all institutions using Elekta CBCT. Author Disclosure: C. Brink, Research collaboration with Elekta, C. Other Research Support; K.L. Gottlieb, None; C.R. Hansen, None; O. Hansen, None.
2900
Real-time Lumpectomy Cavity Motion during External Beam Accelerated Partial Breast Irradiation
M. K. Afghan1, J. Ye1, T. P. Wong1, S. M. Eulau1, T. Mate1, T. Zeller2, D. M. Shepard1 1
Swedish Cancer Institute, Seattle, WA, 2Calypso Medical, Seattle, WA
Purpose/Objective(s): The Calypso 4D Localization SystemÔ uses non-ionizing AC electromagnetic radiation to localize and continuously track small wireless devices (called Beacon transponders) implanted in or near a patient’s tumor. Under an institution review board (IRB) approved protocol, we have investigated the use of the Calypso System in external beam accelerated partial breast irradiation (EB APBI). From this study, we report the characteristics of real-time three dimensional (3D) motion of the lumpectomy cavity during EB APBI as determined using the Calypso system. Materials/Methods: Fifteen patients receiving EB APBI were selected for this study and the Calypso System was used to track the lumpectomy motion for 93 fractions of radiation. Of the 15 patients, 13 were implanted with both gold markers and Beacon transponders and two were implanted with Beacon transponders alone. The Calypso System recorded and stored the three-dimensional coordinates of the transponders at a rate of 10 Hz. These coordinates were then used to determine the 3D motion of the treatment isocenter in real time. After the initial alignment of the patients, the Calypso System was used to continuously track the target motion, under normal respiration, during the treatment. For 10 patients, the target was tracked only at the default couch position of 180 degrees. For the five remaining patients, the target was also tracked at couch angles other than the default position. The collected data varied in duration from 50 to 1000 seconds. The range of motion of the isocenter in the lateral, anterior-posterior (AP) and superior-inferior (SI) directions were recorded and the distribution of the displacements between the treatment and planned isocenters were analyzed. Results: Initial data analysis has shown ranges of motion observed in the lateral, AP and SI directions were -3 to 5 mm, -3 mm to 5 mm, -3 mm to 4 mm, respectively. Negative values indicate displacements in the left, posterior, and inferior directions. Averaged over all patients the mean of the motion in all the three directions was 0.0 mm. Analysis is underway using the tracking data to determine the optimal dosimetric margin design in EB APBI. Conclusions: The Calypso System was able to track three dimensional motion of the lumpectomy cavity in real time during EB APBI. Results of the analysis to design optimized dosimetric margins to account for intrafraction motion will be presented. Author Disclosure: M.K. Afghan, None; J. Ye, None; T.P. Wong, None; S.M. Eulau, Calypso Medical, F. Consultant/Advisory Board; T. Mate, Calypso Medical, E. Ownership Interest; T. Zeller, Calypso Medical, A. Employment; D.M. Shepard, None.
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2899
Evaluation of the Change in Respiration Motion using a Standard Elekta Cone Beam CT
1,2
C. Brink , K. L. Gottlieb1, C. R. Hansen1, O. Hansen3 1 Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark, 2Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark, 3Department of Oncology, Odense University Hospital, Odense, Denmark
Purpose/Objective(s): Using 4D-CT the respiration induced tumor motion can be measured and used in the treatment planning. However, the measured tumor motion might not be representative for the motion during the entire fractionated treatment course. If a standard Cone Beam CT (CBCT) scan, acquired before the treatment, could be time resolved, this could be used to verify the size of the intra-fractional motion during the treatment course. Sonke et al (IJROBP 2008-70,590) has demonstrated that it is possible to track a tumor without mediastinal infiltration using a slow gantry speed 4D-CBCT. The purpose of the current study is to test if it is possible to use a standard Elekta CBCT scan to measure intra-fractional tumor motion, rather than the slow scan which is not supported by the vendor. Materials/Methods: Analysis of the intra-fractional tumor motion has been performed for each patient on a 4D-CT scan as well as on 3 4D-CBCT (fractions 3, 10 and 20). The 4D-CBCTs were created as described by Sonke et al (MedPhys 200532,1176) although in the current study the standard gantry speed was used. The motion of the outlined GTV has been tracked in the planning 4D-CT using Pinnacle3Ô version 8.1w (research version). Registration of phase one from the 4D-CT and 4D-CBCT is used to transfer the GTV to the CBCT scans. Hence, tracking of the GTV was possible in the CBCT scans as well. The inter-fractional tumor movement (relative to the bony structure) can be obtained from the difference in tumor position between the mid-ventilation phase of the 4D-CT and the 3D-CBCT used to create the 4DCBCT. Results: Currently 15 patients have been included in this study. It has been possible to track the tumor in the 4D-CBCT scan based on a standard 3D-CBCT. A paired t-test shows that the respiration motion in the 4D-CBCT is not significantly different from the result found from the initial 4D-CT. Likewise, no differences in respiration motion was found between fractions 3, 10, and 20. The standard deviation of the respiration induced tumor motion based on all 4D-CT and 4D-CBCT scans was measured to be: Intra: 0.8 mm (LR) 1.3 mm (AP) 2.4 mm (CC) and Inter: 1.7 mm (LR) 1.5 mm (AP) 1.7 mm (CC). Conclusions: The study shows that standard CBCT scans can be used to create 4D-CBCT scans with an image quality which facilitates tracking of the tumor motion. No clinically relevant change in the intra-fractional tumor motion was observed during the fractionated treatment course. Thus, it has been shown that the tumor motion measured from the 4D-CT is representative of the tumor motion during the entire treatment. This study shows that it is possible to validate the 4D-CT respiration used for treatment planning based on standard 3D-CBCT data available in all institutions using Elekta CBCT. Author Disclosure: C. Brink, Research collaboration with Elekta, C. Other Research Support; K.L. Gottlieb, None; C.R. Hansen, None; O. Hansen, None.
2900
Real-time Lumpectomy Cavity Motion during External Beam Accelerated Partial Breast Irradiation
M. K. Afghan1, J. Ye1, T. P. Wong1, S. M. Eulau1, T. Mate1, T. Zeller2, D. M. Shepard1 1
Swedish Cancer Institute, Seattle, WA, 2Calypso Medical, Seattle, WA
Purpose/Objective(s): The Calypso 4D Localization SystemÔ uses non-ionizing AC electromagnetic radiation to localize and continuously track small wireless devices (called Beacon transponders) implanted in or near a patient’s tumor. Under an institution review board (IRB) approved protocol, we have investigated the use of the Calypso System in external beam accelerated partial breast irradiation (EB APBI). From this study, we report the characteristics of real-time three dimensional (3D) motion of the lumpectomy cavity during EB APBI as determined using the Calypso system. Materials/Methods: Fifteen patients receiving EB APBI were selected for this study and the Calypso System was used to track the lumpectomy motion for 93 fractions of radiation. Of the 15 patients, 13 were implanted with both gold markers and Beacon transponders and two were implanted with Beacon transponders alone. The Calypso System recorded and stored the three-dimensional coordinates of the transponders at a rate of 10 Hz. These coordinates were then used to determine the 3D motion of the treatment isocenter in real time. After the initial alignment of the patients, the Calypso System was used to continuously track the target motion, under normal respiration, during the treatment. For 10 patients, the target was tracked only at the default couch position of 180 degrees. For the five remaining patients, the target was also tracked at couch angles other than the default position. The collected data varied in duration from 50 to 1000 seconds. The range of motion of the isocenter in the lateral, anterior-posterior (AP) and superior-inferior (SI) directions were recorded and the distribution of the displacements between the treatment and planned isocenters were analyzed. Results: Initial data analysis has shown ranges of motion observed in the lateral, AP and SI directions were -3 to 5 mm, -3 mm to 5 mm, -3 mm to 4 mm, respectively. Negative values indicate displacements in the left, posterior, and inferior directions. Averaged over all patients the mean of the motion in all the three directions was 0.0 mm. Analysis is underway using the tracking data to determine the optimal dosimetric margin design in EB APBI. Conclusions: The Calypso System was able to track three dimensional motion of the lumpectomy cavity in real time during EB APBI. Results of the analysis to design optimized dosimetric margins to account for intrafraction motion will be presented. Author Disclosure: M.K. Afghan, None; J. Ye, None; T.P. Wong, None; S.M. Eulau, Calypso Medical, F. Consultant/Advisory Board; T. Mate, Calypso Medical, E. Ownership Interest; T. Zeller, Calypso Medical, A. Employment; D.M. Shepard, None.
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