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Tumor Tracking for Adaptive Radiation Therapy System by Multiresolution Wavelet Deformable Registration Framework
Poster Viewing Abstracts S727
Volume 84 Number 3S Supplement 2012 Materials/Methods: The VGRPM-Tomo consisted of three components: an image acquisition device consisting of two PC-cams, a main control computer with a radiation signal controller and warning system, and patient motion analysis software, which was developed in house. The system was designed for synchronization with a beam on/off trigger signal to limit operation during treatment time only and to enable system automation. In order to detect the patient motion while the couch is moving into the gantry, a reference image, which continuously updated its background by exponential weighting filter (EWF), is compared with subsequent live images using the real-time frame difference-based analysis software. When the error range exceeds the set criteria (d_movement) due to patient movement, a warning message is generated in the form of light and sound. The described procedure repeats automatically for each patient. A motion phantom, which operates by moving a distance of 0.1, 0.2, 0.5, and 1.0 cm for 1 and 2 sec, respectively, was used to evaluate the system performance at maximum couch speed (0.196 cm/sec) in Helical Tomotherapy. We measured the optimal EWF factor (a) and d_movement, which is the minimum distance that can be detected with this system, and the response time of the whole system. Results: The optimal a for clinical use ranged from 0.85 to 0.9. The system was able to detect phantom motion as small as 0.2 cm with tight d_movement, 0.1% total number of pixels in the reference image. The measured response time of the whole system was 0.1 sec. Conclusion: The VGRPM-tomo can contribute to reduction of treatment error caused by the motion of patients and increase the accuracy of treatment dose delivery in HD. Author Disclosure: S. Ju: None. C. Hong: None. D. Yim: None. M. Kim: None. J. Kim: None. Y. Han: None. J. Shin: None. E. Shin: None. S. Ahn: None. D. Choi: None.
3356 Tumor Tracking for Adaptive Radiation Therapy System by Multiresolution Wavelet Deformable Registration Framework D. Li1 and Y. Yin2; 1College of Physics and Electronics, Shandong Normal University, Jinan, China, 2Department of Radiation Oncology, Shandong Cancer Hospital, Jinan, China Purpose/Objective(s): This study was to achieve tumor tracking by deformable registration algorithm. Both of PCT-CBCT (Planning CT to daily cone beam CT) and CBCT series are registered using a multi-resolution wavelet deformable registration framework (WR) for efficiency. Material/Methods: Data were collected from 30 patients who are treated under CBCT Systems, including rectum, prostate, lung, H&N and breast cancer cases. Before treatment planning, each patient underwent intravenous contrast PCT imaging. At each treatment fraction, CBCT scans were obtained for patients during normal breathing. GTV (gross tumor volume) were delineated on every section of the planning CT scans by the radiation oncologists. First, PCT is registered to the daily CBCT, and then daily CBCT images during the breathing process are registered with each other for tumor tracking. The deformation fields are estimated using wavelet representation. The wavelet coefficients in low resolution can describe the global deformation, while coefficients in higher resolution with the finest details describe the local deformation. Furthermore, the deformation energy function is built by internal and external forces. The internal force is designed by Navier partial differential equation, and the external force is derived from the mutual information. Semi-orthogonal wavelet (spline wavelet of order 3) is used for simplify the expression and computation process. Three known deformations are used for quantitative assessment of the method, and both artificially deformed and real clinical images are performed in experiments. Finally, GTV contours on daily CBCT images are delineated automatically by the deformation fields by proposed algorithm for tumor tracking. Results: The experiment shows that the deformation differences (DDs) gained by proposed WR method are always smaller than the traditional Bspline based registration method. It found that WR can accelerate the registration process by an average 10%-15% for CBCT-CBCT and 20%25% for PCT-CBCT when keeping both WR and B-spline based methods
in same accuracy. WR method is more efficient for lung cases with larger deformation, which is benefit from the global to local deformation estimation. H&N case is not obvious, because rigid transformation always exists in this case. After gaining the deformation maps, deformable automatic re-contouring for adaptive tumor tracking were implemented, the GTV contours are transferred on the daily CBCT volumes from PCT automatically using the deformation maps of PCT-CBCT and CBCTCBCT. The overlap between the automatically generated contours and the contours delineated by the oncologist using the planning system are on an average 85%-95%. Conclusion: Wavelet based registration method can recover the deformation fields, and achieve tumor tracking efficiently. Author Disclosure: D. Li: None. Y. Yin: None.
3357 A Patient Alignment Solution for Lung SBRT Setups Based on a Deformable Registration Technique B. Lu, K. Mittauer, S. Samant, D. Kahler, R. Dagan, P. Okunieff, J.G. Li, and C. Liu; University of Florida, Gainesville, FL Purpose/Objective(s): In this work, we propose a novel registration strategy for translational-only correction scenarios of lung SBRT setups, which can not only achieve optimal dose coverage for tumors but can also preserve the consistency of registrations with minimum human interference. Materials/Methods: The proposed solution (centroid-to-centroid CTC) involves using the average 4-dimensional CT (A4DCT) as the reference CT, and deforming with cone-beam CT (CBCT) to acquire a new centroid of Internal Tumor Volume (ITV) in the CBCT, then simply aligning the centroids of the ITVs between the A4DCT and the CBCT to accomplish the registration. Sixteen cases with 13 patients (each case is associated with separate isocenters) have been investigated with the CTC method, the grey value (G) mode registration method and the bone (B) mode registration method. Statistical data of comparison among the three methods have been presented and analyzed. Deformable registration results have also been validated. Results: The registration results demonstrate the superiority of the CTC method compared with the other two methods. The difference between the D99 and D95 dose coverage of the ITV using the CTC method versus the original plan is small (within 5%) for all of the cases except for one for which the tumor presented significant growth during the period between the CT scan and the treatment. Meanwhile, the dose coverage differences between the original plan and the registration results using either the B or G method are significant as tumor positions varied dramatically from their positions on the original CT, relative to the rib cage. The largest difference between the D99 and D95 dose coverage of the ITV using the B or G methods versus the original plan are as high as 50%. The D20 differences between any of the methods versus the original plan are all less than 2%. Conclusion: The CTC method can generate optimal dose coverage to tumors with much better consistency compared with the G and B methods, and it is especially useful as the tumor position varies greatly from its position on the original CT, relative to the rib cage. Author Disclosure: B. Lu: None. K. Mittauer: None. S. Samant: None. D. Kahler: None. R. Dagan: None. P. Okunieff: None. J.G. Li: None. C. Liu: None.
3358 Dosimetric and Deformation Effects of Image Guided Interventions During Stereotactic Body Radiation Therapy of the Prostate Using an Endorectal Balloon B. Jones,1 G. Gan,1 Q. Diot,1 B. Kavanagh,1 R.D. Timmerman,2 and M.M. Miften1; 1University of Colorado School of Medicine, Aurora, CO, 2University of Texas Southwestern Medical Center, Dallas, TX Purpose/Objective(s): During Stereotactic Body Radiation Therapy (SBRT) for the treatment of prostate cancer, an inflatable endorectal
Volume 84 Number 3S Supplement 2012 Materials/Methods: The VGRPM-Tomo consisted of three components: an image acquisition device consisting of two PC-cams, a main control computer with a radiation signal controller and warning system, and patient motion analysis software, which was developed in house. The system was designed for synchronization with a beam on/off trigger signal to limit operation during treatment time only and to enable system automation. In order to detect the patient motion while the couch is moving into the gantry, a reference image, which continuously updated its background by exponential weighting filter (EWF), is compared with subsequent live images using the real-time frame difference-based analysis software. When the error range exceeds the set criteria (d_movement) due to patient movement, a warning message is generated in the form of light and sound. The described procedure repeats automatically for each patient. A motion phantom, which operates by moving a distance of 0.1, 0.2, 0.5, and 1.0 cm for 1 and 2 sec, respectively, was used to evaluate the system performance at maximum couch speed (0.196 cm/sec) in Helical Tomotherapy. We measured the optimal EWF factor (a) and d_movement, which is the minimum distance that can be detected with this system, and the response time of the whole system. Results: The optimal a for clinical use ranged from 0.85 to 0.9. The system was able to detect phantom motion as small as 0.2 cm with tight d_movement, 0.1% total number of pixels in the reference image. The measured response time of the whole system was 0.1 sec. Conclusion: The VGRPM-tomo can contribute to reduction of treatment error caused by the motion of patients and increase the accuracy of treatment dose delivery in HD. Author Disclosure: S. Ju: None. C. Hong: None. D. Yim: None. M. Kim: None. J. Kim: None. Y. Han: None. J. Shin: None. E. Shin: None. S. Ahn: None. D. Choi: None.
3356 Tumor Tracking for Adaptive Radiation Therapy System by Multiresolution Wavelet Deformable Registration Framework D. Li1 and Y. Yin2; 1College of Physics and Electronics, Shandong Normal University, Jinan, China, 2Department of Radiation Oncology, Shandong Cancer Hospital, Jinan, China Purpose/Objective(s): This study was to achieve tumor tracking by deformable registration algorithm. Both of PCT-CBCT (Planning CT to daily cone beam CT) and CBCT series are registered using a multi-resolution wavelet deformable registration framework (WR) for efficiency. Material/Methods: Data were collected from 30 patients who are treated under CBCT Systems, including rectum, prostate, lung, H&N and breast cancer cases. Before treatment planning, each patient underwent intravenous contrast PCT imaging. At each treatment fraction, CBCT scans were obtained for patients during normal breathing. GTV (gross tumor volume) were delineated on every section of the planning CT scans by the radiation oncologists. First, PCT is registered to the daily CBCT, and then daily CBCT images during the breathing process are registered with each other for tumor tracking. The deformation fields are estimated using wavelet representation. The wavelet coefficients in low resolution can describe the global deformation, while coefficients in higher resolution with the finest details describe the local deformation. Furthermore, the deformation energy function is built by internal and external forces. The internal force is designed by Navier partial differential equation, and the external force is derived from the mutual information. Semi-orthogonal wavelet (spline wavelet of order 3) is used for simplify the expression and computation process. Three known deformations are used for quantitative assessment of the method, and both artificially deformed and real clinical images are performed in experiments. Finally, GTV contours on daily CBCT images are delineated automatically by the deformation fields by proposed algorithm for tumor tracking. Results: The experiment shows that the deformation differences (DDs) gained by proposed WR method are always smaller than the traditional Bspline based registration method. It found that WR can accelerate the registration process by an average 10%-15% for CBCT-CBCT and 20%25% for PCT-CBCT when keeping both WR and B-spline based methods
in same accuracy. WR method is more efficient for lung cases with larger deformation, which is benefit from the global to local deformation estimation. H&N case is not obvious, because rigid transformation always exists in this case. After gaining the deformation maps, deformable automatic re-contouring for adaptive tumor tracking were implemented, the GTV contours are transferred on the daily CBCT volumes from PCT automatically using the deformation maps of PCT-CBCT and CBCTCBCT. The overlap between the automatically generated contours and the contours delineated by the oncologist using the planning system are on an average 85%-95%. Conclusion: Wavelet based registration method can recover the deformation fields, and achieve tumor tracking efficiently. Author Disclosure: D. Li: None. Y. Yin: None.
3357 A Patient Alignment Solution for Lung SBRT Setups Based on a Deformable Registration Technique B. Lu, K. Mittauer, S. Samant, D. Kahler, R. Dagan, P. Okunieff, J.G. Li, and C. Liu; University of Florida, Gainesville, FL Purpose/Objective(s): In this work, we propose a novel registration strategy for translational-only correction scenarios of lung SBRT setups, which can not only achieve optimal dose coverage for tumors but can also preserve the consistency of registrations with minimum human interference. Materials/Methods: The proposed solution (centroid-to-centroid CTC) involves using the average 4-dimensional CT (A4DCT) as the reference CT, and deforming with cone-beam CT (CBCT) to acquire a new centroid of Internal Tumor Volume (ITV) in the CBCT, then simply aligning the centroids of the ITVs between the A4DCT and the CBCT to accomplish the registration. Sixteen cases with 13 patients (each case is associated with separate isocenters) have been investigated with the CTC method, the grey value (G) mode registration method and the bone (B) mode registration method. Statistical data of comparison among the three methods have been presented and analyzed. Deformable registration results have also been validated. Results: The registration results demonstrate the superiority of the CTC method compared with the other two methods. The difference between the D99 and D95 dose coverage of the ITV using the CTC method versus the original plan is small (within 5%) for all of the cases except for one for which the tumor presented significant growth during the period between the CT scan and the treatment. Meanwhile, the dose coverage differences between the original plan and the registration results using either the B or G method are significant as tumor positions varied dramatically from their positions on the original CT, relative to the rib cage. The largest difference between the D99 and D95 dose coverage of the ITV using the B or G methods versus the original plan are as high as 50%. The D20 differences between any of the methods versus the original plan are all less than 2%. Conclusion: The CTC method can generate optimal dose coverage to tumors with much better consistency compared with the G and B methods, and it is especially useful as the tumor position varies greatly from its position on the original CT, relative to the rib cage. Author Disclosure: B. Lu: None. K. Mittauer: None. S. Samant: None. D. Kahler: None. R. Dagan: None. P. Okunieff: None. J.G. Li: None. C. Liu: None.
3358 Dosimetric and Deformation Effects of Image Guided Interventions During Stereotactic Body Radiation Therapy of the Prostate Using an Endorectal Balloon B. Jones,1 G. Gan,1 Q. Diot,1 B. Kavanagh,1 R.D. Timmerman,2 and M.M. Miften1; 1University of Colorado School of Medicine, Aurora, CO, 2University of Texas Southwestern Medical Center, Dallas, TX Purpose/Objective(s): During Stereotactic Body Radiation Therapy (SBRT) for the treatment of prostate cancer, an inflatable endorectal