Person: Winey, Brian
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Winey
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Brian
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Winey, Brian
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Publication Immobilization precision of a modified GTC frame(John Wiley and Sons Inc., 2012) Winey, Brian; Daartz, Juliane; Dankers, Frank; Bussiere, MarcThe purpose of this study was to evaluate and quantify the interfraction reproducibility and intrafraction immobilization precision of a modified GTC frame. The error of the patient alignment and imaging systems were measured using a cranial skull phantom, with simulated, predetermined shifts. The kV setup images were acquired with a room‐mounted set of kV sources and panels. Calculated translations and rotations provided by the computer alignment software relying upon three implanted fiducials were compared to the known shifts, and the accuracy of the imaging and positioning systems was calculated. Orthogonal kV setup images for 45 proton SRT patients and 1002 fractions (average 22.3 fractions/patient) were analyzed for interfraction and intrafraction immobilization precision using a modified GTC frame. The modified frame employs a radiotransparent carbon cup and molded pillow to allow for more treatment angles from posterior directions for cranial lesions. Patients and the phantom were aligned with three 1.5 mm stainless steel fiducials implanted into the skull. The accuracy and variance of the patient positioning and imaging systems were measured to be 0.10±0.06 mm, with the maximum uncertainty of rotation being ±0.07°.957 pairs of interfraction image sets and 974 intrafraction image sets were analyzed. 3D translations and rotations were recorded. The 3D vector interfraction setup reproducibility was 0.13 mm ±1.8 mm for translations and the largest uncertainty of ±1.07° for rotations. The intrafraction immobilization efficacy was 0.19 mm ±0.66 mm for translations and the largest uncertainty of ±0.50° for rotations. The modified GTC frame provides reproducible setup and effective intrafraction immobilization, while allowing for the complete range of entrance angles from the posterior direction. PACS number: 87.53.Ly, 87.55.QrPublication Evaluation of permanent alopecia in pediatric medulloblastoma patients treated with proton radiation(BioMed Central, 2014) Min, Chul Hee; Paganetti, Harald; Winey, Brian; Adams, Judith; MacDonald, Shannon; Tarbell, Nancy; Yock, TorunnBackground: To precisely calculate skin dose and thus to evaluate the relationship between the skin dose and permanent alopecia for pediatric medulloblastoma patients treated with proton beams. Methods: The dosimetry and alopecia outcomes of 12 children with medulloblastoma (ages 4-15 years) comprise the study cohort. Permanent alopecia was assessed and graded after completion of the entire therapy. Skin threshold doses of permanent alopecia were calculated based on the skin dose from the craniospinal irradiation (CSI) plan using the concept of generalized equivalent uniform dose (gEUD) and accounting for chemotherapy intensity. Monte Carlo simulations were employed to accurately assess uncertainties due to beam range prediction and secondary particles. Results: Increasing the dose of the CSI field or the dose given by the boost field to the posterior fossa increased total skin dose delivered in that region. It was found that permanent alopecia could be correlated with CSI dose with a threshold of about 21 Gy (relative biological effectiveness, RBE) with high dose chemotherapy and 30 Gy (RBE) with conventional chemotherapy. Conclusions: Our results based on 12 patients provide a relationship between the skin dose and permanent alopecia for pediatric medulloblastoma patients treated with protons. The alopecia risk as assessed with gEUD could be predicted based on the treatment plan information.Publication Geometric and dosimetric uncertainties in intracranial stereotatctic treatments for multiple nonisocentric lesions(John Wiley and Sons Inc., 2014) Winey, Brian; Bussiere, MarcThe purpose of this study was to determine the effects of geometric uncertainties of patient position on treatments of multiple nonisocentric intracranial lesions. The average distance between lesions in patients with multiple targets was determined by a retrospective survey of patients with multiple lesions. Retrospective patient imaging data from fractionated stereotactic patients were used to calculate interfractional and intrafractional patient position uncertainty. Three different immobilization devices were included in the positioning study. The interfractional and intrafractional patient positioning error data were used to calculate the geometric offset of a lesion located at varying distances from the mechanical isocenter for treatments of multiple lesions with a single arc, assuming that no intrafractional position correction is employed during an arc rotation. Dosimetric effects were studied using two representative lesions of two sizes, 6 mm and 13 mm maximum dimensions, and prescribed to 20 Gy and 18 Gy, respectively. Distances between lesions ranged from < 10 mm to 150 mm, which would correspond to a range of isocenter to lesion separations of < 10 mm to 75 mm, assuming an isocenter located at the geometric mean. In the presence of a full six degree of freedom patient correction system, the effects of the intrafractional patient positioning uncertainties were less than 1.8 mm (3.6 mm) for 1σ (2σ) deviations for lesion spacing up to 75 mm assuming a quadratic summation of 1σ and 2σ. Without the benefit of a six DOF correction device, only correcting for three translations, the effects of the intrafractional patient positioning uncertainties were within 3.1 mm (7.2 mm) for 1σ (2σ) deviations for distances up to 75 mm. 1σ and 2σ deviations along all six axes were observed in 3.6% and 0.3%, respectively, of 974 fractions analyzed. Dosimetric effects for 2 mm and 4 mm offsets were most significant for the small lesion with minimum dose (Dmin) decreasing from 20 Gy to 13.6 Gy and 5.7 Gy and volume receiving the prescription (V20Gy) reducing from 100% to 57% and 16%, respectively. The dosimetric effects on the larger lesion were less pronounced with Dmin reducing from 18 Gy to 17.5 Gy and 14.2 Gy, and V18Gy reducing from 100% to 98.3% and 85.4%, for 2 mm and 4 mm offsets, respectively. In the 1σ scenario (3.6% of patients) angular uncertainties in patient positioning can introduce 1.0 mm shifts in the location of the lesion position at distances of 75 mm, compared to an isocentric treatment even with a full six DOF correction. Without the ability to correct angular positioning errors, a lesion positioned 75 mm away from the mechanical isocenter can be located in 3.6% of patients > 3.0 mm distant from the planned position. Dosimetric results depend upon the distance from isocenter and the size of the target. Single isocenter treatments for multiple lesions should be considered only when full six DOF corrections can be applied, the intrafractional immobilization precision is well quantified, and a PTV expansion is included for more distant lesions to account for unavoidable residual patient positioning uncertainties. PACS number: 87.55.Qr, 87.53.Ly, 87.55.D‐