Publications (35) View all
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Article: TU-G-BRA-05: Intra-Fraction Motion Management for Prostate SBRT: Clinical Experience and Imaging Frequency Analysis.
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ABSTRACT: Purpose: To clinically evaluate the intra-fraction motion management performance of an IGRT protocol established for hypo-fractionated SBRT prospective Phase IIa trial for the treatment of localized prostate cancer. Specifically, to analyze patient data to determine the adequacy of imaging frequency. Methods: Novalis Tx equipped with Exactrac was used for stereoscopic imaging and localization based on three implanted fiducial markers. For intra-fraction motion management, two nearly 360-degree RapidArcs were split to four half-arcs. Following initial Exactrac positioning, CBCT is obtained for volumetric evaluation of bladder and rectal filling and position confirmation. The patient is then stereoscopically imaged prior to the delivery of each half-arc and repositioned when 2 mm tolerance is exceeded. Data from 66 patients with 330 fractions and 2597 image pairs has been analyzed. Results: Following the initial Exactrac and CBCT, mean treatment time from first arc to treatment end was 6.7 mins. ver the course of 66 treatments, patients were repositioned on 257 occasions. On average patients were repositioned 11.9% of the time (SD 10.0%, range 0-40.5%). The mean distance these patients were repositioned was 3.5 mm (SD 1.7 mm, range 2.0-8.5 mm). Of all repositions, 53.5% (SD 29.2%, range 0-100%) occurred before delivery of first arc; in addition, patient repositioning frequency following any half-arc was 9.1% (SD 9.9%, range 0-45%) over the treatment course. Nine patients did not require repositioning throughout the treatment course while nine patients required repositioning more than 25% of the time. Conclusions: Current imaging protocol for intra-fraction motion management fits the clinical workflow. Frequency analysis indicates that the intra-fraction imaging is not excessive. Due to the time spent on performing and analyzing the additional CBCT after initial Exactrac localization, 53.5% of repositions occur preceding first arc. Future analysis will include quantitative dosimetric consequences and tolerances utilized for repositioning patients in this study. Member of Brainlab Academy Speakers Bureau Varian Industry Grant - Rapid Arc: Radisurgical and SBRT Applications, May 2009- May 2011.Medical Physics 06/2012; 39(6):3922. · 2.83 Impact Factor -
Article: SU‐GG‐T‐573: Total Scalp Irradiation: Comparison between Volumetric Modulated Arc Therapy, Helical Tomotherapy and Conventional Electron and Photon Field Combination
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ABSTRACT: Purpose: Homogeneous irradiation of the scalp is challenging due to relatively complex and superficial treatment volume. Conventional treatment approach of combining matched electron and photon fields produces dose heterogeneity, especially at matched lines. Fixed gantry IMRT techniques have not been able to provide clinically acceptable plans but helical tomotherapy has been demonstrated to be an alternative option. We have implemented total scalp treatment with volumetric modulated arc therapy (VMAT) and compared the dosimetric characteristics to tomotherapy and conventional method. Materials and Methods: Two patients have been planned for total scalp irradiation using RapidArc VMAT, helical tomotherapy and conventional electron and photon field combination. The same anatomy and structure sets have been used for the planning purposes. After each operator achieved clinically acceptable results for the particular method, the dose distributions and dose volume histograms were compared. Results: VMAT and tomotherapy provide significantly more homogeneous dose distribution and target coverage. Maximum PTV dose with VMAT and tomotherapy were 20% and 30% less than the conventional method respectively. Although, the conventional method provided 2/3 less dose to brain at D50% and D75%, tomotherapy and VMAT gave lower dose to the brain in high‐dose regions. Brainstem was best spared by conventional method with 1/4 of the maximum dose delivered with tomotherapy and VMAT. Tomotherapy provided more homogeneous dose distribution than VMAT but the brain and brainstem sparing were comparable. Conclusions: VMAT for total scalp irradiation is a clinically acceptable and comparable to tomotherapy. VMAT provides significantly more homogeneous distribution than conventional method. VMAT and Tomotherapy give lower dose to the brain in high‐dose regions than conventional method. Moreover, VMAT and tomotherapy plans can be delivered more reproducibly and reliably than conventional treatments. Average beam on time for VMAT and tomotherapy were 2.5 mins and 7.7 mins respectively. Research sponsored by Varian Medical Systems.Medical Physics 05/2010; 37(6):3319-3319. · 2.83 Impact Factor -
Chapter: Monoscopic Imaging for Intra-fraction Motion Management
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ABSTRACT: Purpose: Image-guidance allows for accurate positioning of spinal radiosurgery patients; however, due to long treatment times an accurate and efficient intra-fraction motion management is necessary. An analysis tool, Snap Verification (SV, BrainLAB AG, Feldkirchen, Germany) has been implemented to monitor intra-fraction motion based on single oblique digital radiographs. We investigate the feasibility of the method in a clinical setting and its performance in detecting spinal radiosurgery patient movements in 3D space. Materials and Methods: Intra-fraction motion for initial group of patients was monitored using stereoscopic kV X-ray images obtained before each treatment beam or arc. The reference intra-fraction translations and rotations were quantified based on 6D fusion using 2D-3D registration algorithm. Then, 2D-2D analysis tool was applied to fuse individual 2D images to the corresponding DRRs, each time assuming the complementary image was not obtained. The results of 2D-3D (stereoscopic) and 2D-2D (monoscopic) methods were compared. For this initial investigation, the analysis was applied to 82 X-ray images. Results: The differences between monoscopic and stereoscopic estimates of translations were less than 1.0mm. To further assess the performance of SV, contingency tables were analyzed. For detecting 1.5mm movement, single image analysis with 1.2mm threshold maximizes Youden Index. Furthermore, when monoscopic threshold is set to 1.2mm with the goal of detecting 1.5mm or larger 3D movements, the following results are observed – sensitivity 89%, specificity 79%, positive predictive value 59% and negative predictive value 95%. Conclusions: Monoscopic imaging is suitable for intra-fraction motion detection. Appropriate thresholds should be utilized for acceptable rate of false positive and false negative predictions. For 1.5mm 3D movement detection 1.2mm 2D analysis threshold results to greater than 95% negative predictive value. Large scale study has been initiated for better understanding the performance of the method to detect intra-fraction patient motion. KeywordsIGRT-monoscopic-stereoscopic-imaging12/2009: pages 1057-1059; -
Article: Radiosurgery from the brain to the spine: 20 years experience.
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ABSTRACT: Radiosurgery evolved from brain to spine. Mechanical and computer advances in linear accelerator (LINAC) radiosurgery apply precise single/fractional stereotactic radiation to multiple pathologies. During a 10-year span the senior author used proton-beam radiosurgery in over 300 lesions, followed by gamma-knife, adapted and dedicated LINACS, including cyber-knife, in another 700 patients. The last 10 years, experience was accumulated with the Novalis in over 3,000 patients. Novalis uses a beam-shaper in a high-speed delivery LINAC. It operates using conventional circular arc, conformal static beam, dynamic conformal or intensity modulated modes. Patients treated with Novalis at the UCLA since 1997 were evaluated regarding effectiveness, complications and failure. These results were compared with previous 1997 data. Over 4,000 patients with trigeminal neuralgia/intractable pain, arteriovenous malformations/angiomas, metastases, ependymomas, gliomas, meningiomas hemangiopericytomas, schwannomas, adenomas, hemangioblastomas, and chordoma were treated. Spinal lesions were treated with frameless stereotaxis and on-line precision checks. Treatment was expeditious, comfortable and with reduced complications. Success is similar or superior to published data. Reduced treatment time of complex lesions and highly homogeneous dose compares favorably to other radiosurgery. The senior author's experience validates the novel shaped-beam approach. Long-term follow-up supports safety and effectiveness and capability to treat brain and spine.Acta neurochirurgica. Supplement 01/2008; 101:163-8. -
Chapter: Radiosurgery from the brain to the spine: 20 years experience
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ABSTRACT: IntroductionRadiosurgery evolved from brain to spine. Mechanical and computer advances in linear accelerator (LINAC) radiosurgery apply precise single/fractional stereotactic radiation to multiple pathologies. MethodsDuring a 10-year span the senior author used proton-beam radiosurgery in over 300 lesions, followed by gamma-knife, adapted and dedicated LINACS, including cyber-knife, in another 700 patients. The last 10 years, experience was accumulated with the Novalis in over 3,000 patients. Novalis uses a beam-shaper in a high-speed delivery LINAC. It operates using conventional circular arc, conformai static beam, dynamic conformai or intensity modulated modes. Patients treated with Novalis at the UCLA since 1997 were evaluated regarding effectiveness, complications and failure. These results were compared with previous 1997 data. ResultsOver 4,000 patients with trigeminal neuralgia/intractable pain, arteriovenous malformations/angiomas, métastases, ependymomas, gliomas, meningiomas hemangiopericytomas, schwannomas, adenomas, hemangioblastomas, and chordoma were treated. Spinal lesions were treated with frameless stereotaxis and on-line precision checks. Treatment was expeditious, comfortable and with reduced complications. Success is similar or superior to published data. Reduced treatment time of complex lesions and highly homogeneous dose compares favorably to other radiosurgery. ConclusionsThe senior author’s experience validates the novel shaped-beam approach. Long-term follow-up supports safety and effectiveness and capability to treat brain and spine.12/2007: pages 163-168;
