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Interinstitutional Dosimetric Comparison Between Stereotactic Radiosurgery and Volumetric Modulated Arc Therapy Radiosurgery for Difficult Intracranial Cases
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Volume 96 Number 2S Supplement 2016
3698 Clinical Accuracy of Linear AcceleratoreBased Frameless Stereotactic Radiosurgery for Trigeminal Neuralgia S. Mayekar, Y. Chen, J. Plonsker, A. Templeton, Y. Liao, S. Sani, R. Byrne, J.V. Turian, and A.Z. Diaz; Rush University Medical Center, Chicago, IL Purpose/Objective(s): Stereotactic radiosurgery (SRS) is a treatment option for patients with refractory trigeminal neuralgia. We investigated the clinical accuracy of a linear accelerator (Linac)-based noninvasive frameless SRS system in the treatment of trigeminal neuralgia. Materials/Methods: We retrospectively reviewed all patients treated in our institution with SRS for refractory trigeminal neuralgia using Linac-based SRS. Twenty-seven consecutive patients received SRS between August 2011 and November 2015. Twenty-three had at least one postprocedure MRI available. Patients treated prior to December 2012 were treated with a head frame. All patients treated after December 2012 were treated with a noninvasive frameless system. Preprocedure MRI (MRI1) was fused with a simulation CT as part of the treatment planning. The trigeminal nerve was contoured on the preprocedural CT/MRI1 fusion. The postprocedure MRI (MRI2) was fused with the planning CT and MRI1. We contoured the trigeminal nerve as well as the postprocedure enhancing area, if present on MRI2. Using the enhancing area as an in vivo marker for high dose region, we calculated the distance between the planning isocenter and the center of the enhancement. Results: Eight patients were treated with a head frame, and 19 patients were treated with a frameless system. The median follow-up for all patients was 10 months (32.4 months for the patients treated with a head frame, and 13.2 months for the patients treated with a frameless system). Twenty-three patients (85.2%) had at least a temporary or partial response to SRS (8/8 patients treated with a head frame, 15/19 patients treated with a frameless system). Fourteen patients (60.9% with available postprocedure MRI) developed contrast enhancement on postprocedure MRI (71.4% patients treated with a head frame, 50% patients treated with a frameless system). The distance between the planning isocenter and the center of the enhancement was 1.30.5 mm (1.90.4 mm for the head frame system, and 1.10.3 mm for the frameless system). The enhancing area received a mean dose of 75.7 Gy. Conclusion: Linac based frameless SRS system can provide safe and effective treatment for patients with trigeminal neuralgia. Author Disclosure: S. Mayekar: None. Y. Chen: None. J. Plonsker: None. A. Templeton: None. Y. Liao: None. S. Sani: None. R. Byrne: None. J.V. Turian: None. A.Z. Diaz: None.
3699 Validation of an External Motion Surrogate Using Markerless Motion Tracking With Single and Dual Energy Fluoroscopy in Lung Stereotactic Body Radiation Therapy A.M. Block,1 R. Patel,2 M.M. Harkenrider,1 M. Surucu,1 and J.C. Roeske1; 1 Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 2 Loyola University Medical Center, Maywood, IL Purpose/Objective(s): The use of external markers as surrogates for respiratory motion relies on the assumption that there is a correlation between the surrogate and internal tumor position. Previously, the feasibility of markerless motion tracking (MMT) for lung tumors treated with image guided stereotactic body radiation therapy (SBRT) using dual energy (DE) fluoroscopy and a novel tracking algorithm was reported. The purpose of the present clinical study is to validate external respiratory position management software by correlating external signal coordinates with MMT coordinates using DE and single energy (SE) fluoroscopy. Materials/Methods: Patients with stage IA-IV lung cancer treated with SBRT were considered in this IRB-approved clinical study. At the time of treatment, sequential 60 kVp and 120 kVp fluoroscopic sequences were acquired, exported offline, and aligned based on respiratory signal coordinates obtained from external markers. Frame-by-frame weighted logarithmic subtraction was performed resulting in DE fluoroscopic sequences. A template-based MMT algorithm using a template that was
derived from the contoured gross tumor volume (GTV) on the simulation CT scan was used to track tumor motion throughout the DE and SE fluoroscopy sequences. Subsequently, for each patient, the MMT coordinates on the DE and SE fluoroscopy images were correlated with the coordinates of the external surrogate. A Pearson correlation coefficient (PCC) between MMT and external coordinates of 0.85 or greater was considered a successful correlate. Results: A total of 229 fluoroscopy frames from 8 different patients were analyzed. Fluoroscopy sequences were obtained both anterior-posterior (AP) (43% of cases) and at oblique angles (57% of cases). MMT with DE fluoroscopy correlated with external surrogates (with a PCC 0.85) in 61% of cases, compared to 52% when using MMT with SE fluoroscopy. However, considering fluoroscopy sequences in which either SE or DE MMT correlated with external markers, a successful correlate occurred in 83% of the cases. Conclusion: This study suggests that having the ability to perform DE and SE fluoroscopy in combination with an MMT algorithm results in a strong correlation between MMT and external surrogate position. Future studies involve optimizing imaging technique (SE or DE fluoroscopy) versus tumor size and imaging angle to maximize the correlation between MMT and external surrogates. Author Disclosure: A.M. Block: None. R. Patel: None. M.M. Harkenrider: None. M. Surucu: Research Grant; Varian Medical Systems. J.C. Roeske: Research Grant; Varian Medical Systems.
3700 Interinstitutional Dosimetric Comparison Between Stereotactic Radiosurgery and Volumetric Modulated Arc Therapy Radiosurgery for Difficult Intracranial Cases E.M. Thomas,1 S.T. Chao,2 J.M. Markert,1 G. Neyman,3 R.A. Popple,1 G.H. Barnett,3 and J.B. Fiveash1; 1University of Alabama at Birmingham, Birmingham, AL, 2Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH, 3Cleveland Clinic, Cleveland, OH Purpose/Objective(s): In this work, we present an interinstitutional collaborative dosimetric comparison of stereotactic radiosurgery (SRS) treatment platforms for 6 cases commonly encountered in neuroradiation oncology. It has previously been shown that equivalent plan quality between the older 201-source SRS platform and single-isocenter volumetric modulated arc therapy (VMAT) is possible for complex SRS cases. In 6 challenging cases, we test the hypothesis that single-isocenter VMAT can also deliver similarly high-quality SRS treatments as the more modern 192-source SRS platform. Materials/Methods: Six different intracranial cases that were treated with SRS at one institution were replanned with single-isocenter VMAT (10 MV FFF) with 2.5 mm MLC at another institution. The cases were pituitary adenoma, meningioma (x2), acoustic neuroma, solitary metastasis, metastases (x3), and metastases (x9) with multiple prescriptions. Plan quality was compared via conformality, V12Gy, KARE index, V4.5Gy, and mean dose to healthy tissue. Results: For each case treated with SRS, a clinically equivalent single-isocenter VMAT plan was generated. Mean conformity was similar between the 2 sets of plans (CISRSZ1.40, CIVMATZ1.12), as were mean dose (MeanSRSZ100 cGy, VMAT MeanVMAT Z110.9 cGy), 12 gray isodose volume (VSRS 12GyZ32.3cc, V12Gy SRS VMAT Z25.3 mL), low dose spill (V4.5GyZ163.1 cGy, V4.5Gy Z206.2 cGy), and KARE index (KARESRSZ2.75, KAREVMATZ1.61). Conclusion: For these 6 representative intracranial SRS cases, the high plan quality of modern 192-source SRS can be replicated with singleisocenter VMAT. For most cases, well-planned VMAT deliveries can be expected to exhibit equivalent or improved conformity and equivalent moderate/low isodose spill when compared to SRS. However, in cases with very high numbers of targets, SRS may retain an advantage in low isodose spill. VMAT treatments in 10-MV FFF can be delivered substantially more quickly than with SRS platforms. Author Disclosure: E.M. Thomas: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems. S.T. Chao: Honoraria; Varian Medical Systems. J.M. Markert: None. G. Neyman: None. R.A. Popple: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems. G.H. Barnett: None. J.B. Fiveash: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems.
Volume 96 Number 2S Supplement 2016
3698 Clinical Accuracy of Linear AcceleratoreBased Frameless Stereotactic Radiosurgery for Trigeminal Neuralgia S. Mayekar, Y. Chen, J. Plonsker, A. Templeton, Y. Liao, S. Sani, R. Byrne, J.V. Turian, and A.Z. Diaz; Rush University Medical Center, Chicago, IL Purpose/Objective(s): Stereotactic radiosurgery (SRS) is a treatment option for patients with refractory trigeminal neuralgia. We investigated the clinical accuracy of a linear accelerator (Linac)-based noninvasive frameless SRS system in the treatment of trigeminal neuralgia. Materials/Methods: We retrospectively reviewed all patients treated in our institution with SRS for refractory trigeminal neuralgia using Linac-based SRS. Twenty-seven consecutive patients received SRS between August 2011 and November 2015. Twenty-three had at least one postprocedure MRI available. Patients treated prior to December 2012 were treated with a head frame. All patients treated after December 2012 were treated with a noninvasive frameless system. Preprocedure MRI (MRI1) was fused with a simulation CT as part of the treatment planning. The trigeminal nerve was contoured on the preprocedural CT/MRI1 fusion. The postprocedure MRI (MRI2) was fused with the planning CT and MRI1. We contoured the trigeminal nerve as well as the postprocedure enhancing area, if present on MRI2. Using the enhancing area as an in vivo marker for high dose region, we calculated the distance between the planning isocenter and the center of the enhancement. Results: Eight patients were treated with a head frame, and 19 patients were treated with a frameless system. The median follow-up for all patients was 10 months (32.4 months for the patients treated with a head frame, and 13.2 months for the patients treated with a frameless system). Twenty-three patients (85.2%) had at least a temporary or partial response to SRS (8/8 patients treated with a head frame, 15/19 patients treated with a frameless system). Fourteen patients (60.9% with available postprocedure MRI) developed contrast enhancement on postprocedure MRI (71.4% patients treated with a head frame, 50% patients treated with a frameless system). The distance between the planning isocenter and the center of the enhancement was 1.30.5 mm (1.90.4 mm for the head frame system, and 1.10.3 mm for the frameless system). The enhancing area received a mean dose of 75.7 Gy. Conclusion: Linac based frameless SRS system can provide safe and effective treatment for patients with trigeminal neuralgia. Author Disclosure: S. Mayekar: None. Y. Chen: None. J. Plonsker: None. A. Templeton: None. Y. Liao: None. S. Sani: None. R. Byrne: None. J.V. Turian: None. A.Z. Diaz: None.
3699 Validation of an External Motion Surrogate Using Markerless Motion Tracking With Single and Dual Energy Fluoroscopy in Lung Stereotactic Body Radiation Therapy A.M. Block,1 R. Patel,2 M.M. Harkenrider,1 M. Surucu,1 and J.C. Roeske1; 1 Stritch School of Medicine, Loyola University Chicago, Maywood, IL, 2 Loyola University Medical Center, Maywood, IL Purpose/Objective(s): The use of external markers as surrogates for respiratory motion relies on the assumption that there is a correlation between the surrogate and internal tumor position. Previously, the feasibility of markerless motion tracking (MMT) for lung tumors treated with image guided stereotactic body radiation therapy (SBRT) using dual energy (DE) fluoroscopy and a novel tracking algorithm was reported. The purpose of the present clinical study is to validate external respiratory position management software by correlating external signal coordinates with MMT coordinates using DE and single energy (SE) fluoroscopy. Materials/Methods: Patients with stage IA-IV lung cancer treated with SBRT were considered in this IRB-approved clinical study. At the time of treatment, sequential 60 kVp and 120 kVp fluoroscopic sequences were acquired, exported offline, and aligned based on respiratory signal coordinates obtained from external markers. Frame-by-frame weighted logarithmic subtraction was performed resulting in DE fluoroscopic sequences. A template-based MMT algorithm using a template that was
derived from the contoured gross tumor volume (GTV) on the simulation CT scan was used to track tumor motion throughout the DE and SE fluoroscopy sequences. Subsequently, for each patient, the MMT coordinates on the DE and SE fluoroscopy images were correlated with the coordinates of the external surrogate. A Pearson correlation coefficient (PCC) between MMT and external coordinates of 0.85 or greater was considered a successful correlate. Results: A total of 229 fluoroscopy frames from 8 different patients were analyzed. Fluoroscopy sequences were obtained both anterior-posterior (AP) (43% of cases) and at oblique angles (57% of cases). MMT with DE fluoroscopy correlated with external surrogates (with a PCC 0.85) in 61% of cases, compared to 52% when using MMT with SE fluoroscopy. However, considering fluoroscopy sequences in which either SE or DE MMT correlated with external markers, a successful correlate occurred in 83% of the cases. Conclusion: This study suggests that having the ability to perform DE and SE fluoroscopy in combination with an MMT algorithm results in a strong correlation between MMT and external surrogate position. Future studies involve optimizing imaging technique (SE or DE fluoroscopy) versus tumor size and imaging angle to maximize the correlation between MMT and external surrogates. Author Disclosure: A.M. Block: None. R. Patel: None. M.M. Harkenrider: None. M. Surucu: Research Grant; Varian Medical Systems. J.C. Roeske: Research Grant; Varian Medical Systems.
3700 Interinstitutional Dosimetric Comparison Between Stereotactic Radiosurgery and Volumetric Modulated Arc Therapy Radiosurgery for Difficult Intracranial Cases E.M. Thomas,1 S.T. Chao,2 J.M. Markert,1 G. Neyman,3 R.A. Popple,1 G.H. Barnett,3 and J.B. Fiveash1; 1University of Alabama at Birmingham, Birmingham, AL, 2Department of Radiation Oncology, Cleveland Clinic, Cleveland, OH, 3Cleveland Clinic, Cleveland, OH Purpose/Objective(s): In this work, we present an interinstitutional collaborative dosimetric comparison of stereotactic radiosurgery (SRS) treatment platforms for 6 cases commonly encountered in neuroradiation oncology. It has previously been shown that equivalent plan quality between the older 201-source SRS platform and single-isocenter volumetric modulated arc therapy (VMAT) is possible for complex SRS cases. In 6 challenging cases, we test the hypothesis that single-isocenter VMAT can also deliver similarly high-quality SRS treatments as the more modern 192-source SRS platform. Materials/Methods: Six different intracranial cases that were treated with SRS at one institution were replanned with single-isocenter VMAT (10 MV FFF) with 2.5 mm MLC at another institution. The cases were pituitary adenoma, meningioma (x2), acoustic neuroma, solitary metastasis, metastases (x3), and metastases (x9) with multiple prescriptions. Plan quality was compared via conformality, V12Gy, KARE index, V4.5Gy, and mean dose to healthy tissue. Results: For each case treated with SRS, a clinically equivalent single-isocenter VMAT plan was generated. Mean conformity was similar between the 2 sets of plans (CISRSZ1.40, CIVMATZ1.12), as were mean dose (MeanSRSZ100 cGy, VMAT MeanVMAT Z110.9 cGy), 12 gray isodose volume (VSRS 12GyZ32.3cc, V12Gy SRS VMAT Z25.3 mL), low dose spill (V4.5GyZ163.1 cGy, V4.5Gy Z206.2 cGy), and KARE index (KARESRSZ2.75, KAREVMATZ1.61). Conclusion: For these 6 representative intracranial SRS cases, the high plan quality of modern 192-source SRS can be replicated with singleisocenter VMAT. For most cases, well-planned VMAT deliveries can be expected to exhibit equivalent or improved conformity and equivalent moderate/low isodose spill when compared to SRS. However, in cases with very high numbers of targets, SRS may retain an advantage in low isodose spill. VMAT treatments in 10-MV FFF can be delivered substantially more quickly than with SRS platforms. Author Disclosure: E.M. Thomas: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems. S.T. Chao: Honoraria; Varian Medical Systems. J.M. Markert: None. G. Neyman: None. R.A. Popple: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems. G.H. Barnett: None. J.B. Fiveash: Research Grant; Varian Medical Systems. Honoraria; Varian Medical Systems.