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Peter A Balter - One of the best experts on this subject based on the ideXlab platform.
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SU-E-T-715: Evaluation of Off-Target Isocenter Placement On TArget Coverage and Critical Structure Dose
Medical Physics, 2013Co-Authors: R. Sadagopan, Peter A BalterAbstract:Purpose: To evaluate the effect of placing the isocenter away from the PTV (so that collision is avoided during VMAT treatment) on tumor coverage or Critical Structure doses in SBRT. Method: CT images of lung SBRT patients were acquired for pre‐treatment alignment using CT‐on‐rails and imported back in to the planning system. The daily images were registered with the original simulation CT using the GTV as the alignment Structure. We re planned the patient (on original CT) using 2 additional scenarios 1) isocenter at the midline of the patient at the AP and Sup‐Inf level of the GTV and 2) The isocenters at the center of the vertebral body at the Sup‐Inf level of the GTV. In both cases, the plans were normalized so that PTV coverage is similar to the original clinical plan. The treatment plans were recomputed on the daily CTs using original isocenter and the two off target isocenters and doses to target and serial Critical Structure cord were tabulated. The MU units remained the same between the plans on original CT and daily CT. Result: The target doses were observed to be not affected by the off target placement of isocenter. On average, the dose to 99% GTV and 95% PTV differed from planned value by 0.25 and 0.35 Gy respectively. The 0.1 and 1cc cord doses differed by .23 and .85 Gy respectively. Conclusions: Off center placement of isocenter does not affect target coverage and serial Critical Structure dose such as cord. However, care should be exercised not to beam penumbra adjacent to Critical Structure.
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Evaluation of dose variation to normal and Critical Structures for lung hypofractionated stereotactic body radiation therapy
Practical radiation oncology, 2012Co-Authors: H Chung, Laurence E. Court, Steven H. Lin, Dhananjay Kulkarni, Peter A BalterAbstract:Abstract Purpose To quantify the dose received by normal and Critical Structures during lung stereotactic body radiation therapy (SBRT) when registered to tumor or bone. Methods and Materials Sixteen patients with lung cancer receiving a total dose of 50 Gy in 4fractions for lung SBRT were retrospectively studied. Cone-beam computed tomography (CT) was performed for all fractions, and the images obtained were registered with planning CT with respect tosoft tissue for target localization. Isocenter shifts were determined for each fraction from differences between the bony and tumor alignments; doses were then recalculated based on the new isocenters and summed over all 4 fractions to compare against the planned normal and Critical tissue dose. The normal and Critical Structures evaluated were total and ipsilateral lung, spinal cord, and esophagus. The first data collected were isocenter coordinate shifts in all 3 Cartesian coordinates for both tumor andbony alignments. The second were the dose differences to the normal and Critical Structures fromthe planned and recalculated doses for alignment based on the tumor. Results The study showed that while the maximum isocenter coordinate shifts in any direction couldbe as much as 1.60 cm, the normal and Critical Structure dose variations between the original plans and the simulated plans showed almost no change. The mean volume of total lung that receivedat least 20Gy difference for total lung and ipsilateral lung were 0.01% and −0.04%, respectively. For the esophagus, spinal cord, and heart the maximum and mean dose differences were 0.25 Gy and −0.04 Gy, −0.08 Gy and −0.02 Gy, and 0.02 Gy and 0.05 Gy, respectively. Conclusions Target localization using daily cone-beam CT with soft tissue registration was appropriate for minimizing the dose to the normal and Critical Structures without the need to re-plan due to the changes in the tumor position. For tumors located close to a Critical Structure, daily cone-beam CT is recommended to determine the appropriate isocenter shifts.
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MO‐D‐BRB‐09: Evaluation of Dose to Normal/Critical Structures from Lung Hypo‐Fractionated Stereotactic Body Radiation Therapy
Medical Physics, 2011Co-Authors: H Chung, S. Lim, Laurence E. Court, L. Dong, Peter A BalterAbstract:Purpose: The purpose of this work was to quantify the dose received by the normal/Critical Structures during lung stereotactic body radiation therapy(SBRT) when registered with respect to the tumor. Methods: For this retrospective work, 16 lungSBRT patients were treated with total dose of 50 Gy in 4 fractions. Cone‐beam CT was done for all fractions and registered with planning CT for target localization. Isocenter shifts were determined from the differences between the boney and tumor alignments. Once the isocenter shifts were determined for each fraction, doses were recalculated based on the new isocenter and summed over all four fractions to compare against the planned normal/Critical tissuedose. The normal/Critical Structures evaluated were total and ipsilateral lung, spinal cord, and esophagus. Two data sets were collected from this work. The first data set was the collection of isocenter coordinate shifts in all three Cartesian coordinates. The second data set was the doses to the normal/Critical Structures from the planned and recalculated doses. Results: The study showed that while the maximum isocenter coordinate shifts in any direction could be as much as 1.60 cm, the normal/Critical Structure dose variations between the original plans and the simulated plans showed almost no change. The average V20 difference for total lung, ipsilateral lung, and esophagus were 0.01%, −0.03%, and −0.35%, respectively. For spinal cord, the maximum and mean dose differences were −0.08 Gy and −0.02 Gy, respectively. Conclusions: Target localization using daily CBCT with soft tissue registration was appropriate for minimizing the dose to the normal/Critical Structures without the need to re‐plan due to the changes in the tumor position. For tumors located close to a Critical Structure, it is advised that a daily CBCT is used to determine appropriate isocenter shifts.
Benjamin J. Dixon - One of the best experts on this subject based on the ideXlab platform.
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augmented real time navigation with Critical Structure proximity alerts for endoscopic skull base surgery
Laryngoscope, 2014Co-Authors: Benjamin J. Dixon, Michael J. Daly, Harley Chan, Allan Vescan, Ian J. Witterick, Jonathan C. IrishAbstract:Objectives/Hypothesis Image-guided surgery (IGS) systems are frequently utilized during cranial base surgery to aid in orientation and facilitate targeted surgery. We wished to assess the performance of our recently developed localized intraoperative virtual endoscopy (LIVE)-IGS prototype in a preclinical setting prior to deployment in the operating room. This system combines real-time ablative instrument tracking, Critical Structure proximity alerts, three-dimensional virtual endoscopic views, and intraoperative cone-beam computed tomographic image updates. Study Design Randomized-controlled trial plus qualitative analysis. Methods Skull base procedures were performed on 14 cadaver specimens by seven fellowship-trained skull base surgeons. Each subject performed two endoscopic transclival approaches; one with LIVE-IGS and one using a conventional IGS system in random order. National Aeronautics and Space Administration Task Load Index (NASA-TLX) scores were documented for each dissection, and a semiStructured interview was recorded for qualitative assessment. Results The NASA-TLX scores for mental demand, effort, and frustration were significantly reduced with the LIVE-IGS system in comparison to conventional navigation (P < .05). The system interface was judged to be intuitive and most useful when there was a combination of high spatial demand, reduced or absent surface landmarks, and proximity to Critical Structures. The development of auditory icons for proximity alerts during the trial better informed the surgeon while limiting distraction. Conclusions The LIVE-IGS system provided accurate, intuitive, and dynamic feedback to the operating surgeon. Further refinements to proximity alerts and visualization settings will enhance orientation while limiting distraction. The system is currently being deployed in a prospective clinical trial in skull base surgery. Laryngoscope, 124:853–859, 2014
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Augmented Real-Time Navigation with Critical Structure Proximity Alerts for Endoscopic Skull Base Surgery
Journal of Neurological Surgery Part B: Skull Base, 2012Co-Authors: Benjamin J. Dixon, Michael J. Daly, Harley Chan, Allan Vescan, Ian J. Witterick, Jonathan C. IrishAbstract:Objectives/Hypothesis Image-guided surgery (IGS) systems are frequently utilized during cranial base surgery to aid in orientation and facilitate targeted surgery. We wished to assess the performance of our recently developed localized intraoperative virtual endoscopy (LIVE)-IGS prototype in a preclinical setting prior to deployment in the operating room. This system combines real-time ablative instrument tracking, Critical Structure proximity alerts, three-dimensional virtual endoscopic views, and intraoperative cone-beam computed tomographic image updates. Study Design Randomized-controlled trial plus qualitative analysis. Methods Skull base procedures were performed on 14 cadaver specimens by seven fellowship-trained skull base surgeons. Each subject performed two endoscopic transclival approaches; one with LIVE-IGS and one using a conventional IGS system in random order. National Aeronautics and Space Administration Task Load Index (NASA-TLX) scores were documented for each dissection, and a semiStructured interview was recorded for qualitative assessment. Results The NASA-TLX scores for mental demand, effort, and frustration were significantly reduced with the LIVE-IGS system in comparison to conventional navigation (P
H Chung - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of dose variation to normal and Critical Structures for lung hypofractionated stereotactic body radiation therapy
Practical radiation oncology, 2012Co-Authors: H Chung, Laurence E. Court, Steven H. Lin, Dhananjay Kulkarni, Peter A BalterAbstract:Abstract Purpose To quantify the dose received by normal and Critical Structures during lung stereotactic body radiation therapy (SBRT) when registered to tumor or bone. Methods and Materials Sixteen patients with lung cancer receiving a total dose of 50 Gy in 4fractions for lung SBRT were retrospectively studied. Cone-beam computed tomography (CT) was performed for all fractions, and the images obtained were registered with planning CT with respect tosoft tissue for target localization. Isocenter shifts were determined for each fraction from differences between the bony and tumor alignments; doses were then recalculated based on the new isocenters and summed over all 4 fractions to compare against the planned normal and Critical tissue dose. The normal and Critical Structures evaluated were total and ipsilateral lung, spinal cord, and esophagus. The first data collected were isocenter coordinate shifts in all 3 Cartesian coordinates for both tumor andbony alignments. The second were the dose differences to the normal and Critical Structures fromthe planned and recalculated doses for alignment based on the tumor. Results The study showed that while the maximum isocenter coordinate shifts in any direction couldbe as much as 1.60 cm, the normal and Critical Structure dose variations between the original plans and the simulated plans showed almost no change. The mean volume of total lung that receivedat least 20Gy difference for total lung and ipsilateral lung were 0.01% and −0.04%, respectively. For the esophagus, spinal cord, and heart the maximum and mean dose differences were 0.25 Gy and −0.04 Gy, −0.08 Gy and −0.02 Gy, and 0.02 Gy and 0.05 Gy, respectively. Conclusions Target localization using daily cone-beam CT with soft tissue registration was appropriate for minimizing the dose to the normal and Critical Structures without the need to re-plan due to the changes in the tumor position. For tumors located close to a Critical Structure, daily cone-beam CT is recommended to determine the appropriate isocenter shifts.
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MO‐D‐BRB‐09: Evaluation of Dose to Normal/Critical Structures from Lung Hypo‐Fractionated Stereotactic Body Radiation Therapy
Medical Physics, 2011Co-Authors: H Chung, S. Lim, Laurence E. Court, L. Dong, Peter A BalterAbstract:Purpose: The purpose of this work was to quantify the dose received by the normal/Critical Structures during lung stereotactic body radiation therapy(SBRT) when registered with respect to the tumor. Methods: For this retrospective work, 16 lungSBRT patients were treated with total dose of 50 Gy in 4 fractions. Cone‐beam CT was done for all fractions and registered with planning CT for target localization. Isocenter shifts were determined from the differences between the boney and tumor alignments. Once the isocenter shifts were determined for each fraction, doses were recalculated based on the new isocenter and summed over all four fractions to compare against the planned normal/Critical tissuedose. The normal/Critical Structures evaluated were total and ipsilateral lung, spinal cord, and esophagus. Two data sets were collected from this work. The first data set was the collection of isocenter coordinate shifts in all three Cartesian coordinates. The second data set was the doses to the normal/Critical Structures from the planned and recalculated doses. Results: The study showed that while the maximum isocenter coordinate shifts in any direction could be as much as 1.60 cm, the normal/Critical Structure dose variations between the original plans and the simulated plans showed almost no change. The average V20 difference for total lung, ipsilateral lung, and esophagus were 0.01%, −0.03%, and −0.35%, respectively. For spinal cord, the maximum and mean dose differences were −0.08 Gy and −0.02 Gy, respectively. Conclusions: Target localization using daily CBCT with soft tissue registration was appropriate for minimizing the dose to the normal/Critical Structures without the need to re‐plan due to the changes in the tumor position. For tumors located close to a Critical Structure, it is advised that a daily CBCT is used to determine appropriate isocenter shifts.
Andrea T. Ricolfi - One of the best experts on this subject based on the ideXlab platform.
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Virtual classes and virtual motives of Quot schemes on threefolds
Advances in Mathematics, 2020Co-Authors: Andrea T. RicolfiAbstract:Abstract For a simple, rigid vector bundle F on a Calabi–Yau 3-fold Y, we construct a symmetric obstruction theory on the Quot scheme Quot Y ( F , n ) , and we solve the associated enumerative theory. We discuss the case of other 3-folds. Exploiting the Critical Structure on the local model Quot A 3 ( O ⊕ r , n ) , we construct a virtual motive (in the sense of Behrend–Bryan–Szendrői) for Quot Y ( F , n ) for an arbitrary vector bundle F on a smooth 3-fold Y. We compute the associated motivic partition function. We obtain new examples of higher rank (motivic) Donaldson–Thomas invariants.
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Virtual classes and virtual motives of Quot schemes on threefolds
arXiv: Algebraic Geometry, 2019Co-Authors: Andrea T. RicolfiAbstract:For a simple, rigid vector bundle $F$ on a Calabi-Yau $3$-fold $Y$, we construct a symmetric obstruction theory on the Quot scheme $\textrm{Quot}_Y(F,n)$, and we solve the associated enumerative theory. We discuss the case of other $3$-folds. Exploiting the Critical Structure on $\textrm{Quot}_{\mathbb A^3}(\mathscr O^r,n)$, we construct a virtual motive (in the sense of Behrend-Bryan-Szendrői) for $\textrm{Quot}_Y(F,n)$ for an arbitrary vector bundle $F$ on a smooth $3$-fold $Y$. We compute the associated motivic partition function. We obtain new examples of higher rank (motivic) Donaldson-Thomas invariants.
Jonathan C. Irish - One of the best experts on this subject based on the ideXlab platform.
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augmented real time navigation with Critical Structure proximity alerts for endoscopic skull base surgery
Laryngoscope, 2014Co-Authors: Benjamin J. Dixon, Michael J. Daly, Harley Chan, Allan Vescan, Ian J. Witterick, Jonathan C. IrishAbstract:Objectives/Hypothesis Image-guided surgery (IGS) systems are frequently utilized during cranial base surgery to aid in orientation and facilitate targeted surgery. We wished to assess the performance of our recently developed localized intraoperative virtual endoscopy (LIVE)-IGS prototype in a preclinical setting prior to deployment in the operating room. This system combines real-time ablative instrument tracking, Critical Structure proximity alerts, three-dimensional virtual endoscopic views, and intraoperative cone-beam computed tomographic image updates. Study Design Randomized-controlled trial plus qualitative analysis. Methods Skull base procedures were performed on 14 cadaver specimens by seven fellowship-trained skull base surgeons. Each subject performed two endoscopic transclival approaches; one with LIVE-IGS and one using a conventional IGS system in random order. National Aeronautics and Space Administration Task Load Index (NASA-TLX) scores were documented for each dissection, and a semiStructured interview was recorded for qualitative assessment. Results The NASA-TLX scores for mental demand, effort, and frustration were significantly reduced with the LIVE-IGS system in comparison to conventional navigation (P < .05). The system interface was judged to be intuitive and most useful when there was a combination of high spatial demand, reduced or absent surface landmarks, and proximity to Critical Structures. The development of auditory icons for proximity alerts during the trial better informed the surgeon while limiting distraction. Conclusions The LIVE-IGS system provided accurate, intuitive, and dynamic feedback to the operating surgeon. Further refinements to proximity alerts and visualization settings will enhance orientation while limiting distraction. The system is currently being deployed in a prospective clinical trial in skull base surgery. Laryngoscope, 124:853–859, 2014
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Augmented Real-Time Navigation with Critical Structure Proximity Alerts for Endoscopic Skull Base Surgery
Journal of Neurological Surgery Part B: Skull Base, 2012Co-Authors: Benjamin J. Dixon, Michael J. Daly, Harley Chan, Allan Vescan, Ian J. Witterick, Jonathan C. IrishAbstract:Objectives/Hypothesis Image-guided surgery (IGS) systems are frequently utilized during cranial base surgery to aid in orientation and facilitate targeted surgery. We wished to assess the performance of our recently developed localized intraoperative virtual endoscopy (LIVE)-IGS prototype in a preclinical setting prior to deployment in the operating room. This system combines real-time ablative instrument tracking, Critical Structure proximity alerts, three-dimensional virtual endoscopic views, and intraoperative cone-beam computed tomographic image updates. Study Design Randomized-controlled trial plus qualitative analysis. Methods Skull base procedures were performed on 14 cadaver specimens by seven fellowship-trained skull base surgeons. Each subject performed two endoscopic transclival approaches; one with LIVE-IGS and one using a conventional IGS system in random order. National Aeronautics and Space Administration Task Load Index (NASA-TLX) scores were documented for each dissection, and a semiStructured interview was recorded for qualitative assessment. Results The NASA-TLX scores for mental demand, effort, and frustration were significantly reduced with the LIVE-IGS system in comparison to conventional navigation (P