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https://www.readbyqxmd.com/read/28096372/helical-structure-stability-and-dynamics-in-human-apolipoprotein-e3-and-e4-by-hydrogen-exchange-and-mass-spectrometry
#1
Palaniappan S Chetty, Leland Mayne, Sissel Lund-Katz, S Walter Englander, Michael C Phillips
Apolipoprotein E (apoE) plays a critical role in cholesterol transport in both peripheral circulation and brain. Human apoE is a polymorphic 299-residue protein in which the less common E4 isoform differs from the major E3 isoform only by a C112R substitution. ApoE4 interacts with lipoprotein particles and with the amyloid-β peptide, and it is associated with increased incidence of cardiovascular and Alzheimer's disease. To understand the structural basis for the differences between apoE3 and E4 functionality, we used hydrogen-deuterium exchange coupled with a fragment separation method and mass spectrometric analysis to compare their secondary structures at near amino acid resolution...
January 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28072395/evaluation-of-adaptive-treatment-planning-for-patients-with-non-small-cell-lung-cancer
#2
Hualiang Zhong, Salim Siddiqui, Benjamin Movsas, Indrin Chetty
The purpose of this study was to develop metrics to evaluate uncertainties in deformable dose accumulation (DDA) for patients with non-small cell lung cancer (NSCLC). Initial treatment plans (primary) and cone-beam CT (CBCT) images were retrospectively processed for seven NSCLC patients, who showed significant tumor regression during the course of treatment. Each plan was developed with IMRT for 2 Gy��33 fractions. A B-spline-based DIR algorithm was used to register weekly CBCT images to a reference image acquired at fraction 21 and the resultant displacement vector fields (DVFs) were then modified using a finite element method (FEM)...
January 10, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28068232/analysis-of-the-factors-contributing-to-vertebral-compression-fractures-after-spine-stereotactic-radiosurgery
#3
David Boyce-Fappiano, Erinma Elibe, Lonni Schultz, Samuel Ryu, M Salim Siddiqui, Indrin Chetty, Ian Lee, Jack Rock, Benjamin Movsas, Farzan Siddiqui
PURPOSE: To determine our institutional vertebral compression fracture (VCF) rate after spine stereotactic radiosurgery (SRS) and determine contributory factors. METHODS AND MATERIALS: Retrospective analysis from 2001 to 2013 at a single institution was performed. With institutional review board approval, electronic medical records of 1905 vertebral bodies from 791 patients who were treated with SRS for the management of primary or metastatic spinal lesions were reviewed...
February 1, 2017: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/28048749/su-f-r-49-a-novel-kinetic-model-for-prediction-of-tumor-local-control-for-patients-with-lung-cancer
#4
H Zhong, S Siddiqui, B Zhao, H Li, K Barton, F Siddiqui, B Movsas, I Chetty
PURPOSE: Modeling tumor control probability (TCP) can help optimize treatment plans for better treatment outcomes. This study sought to quantify the radiobiological parameters of the TCP model for patients with lung cancer. METHODS: A two-compartment kinetic model was developed to model tumor regression for five NSCLC patients. The model has three parameters: cell survival fraction, dead-cell-resolving time and tumor doubling time. The last one was extended to a function of tumor volume...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048563/we-ab-207b-05-correlation-of-normal-lung-density-changes-with-dose-after-stereotactic-body-radiotherapy-sbrt-for-early-stage-lung-cancer
#5
Q Wu, S Devpura, K Feghali, C Liu, M Ajlouni, B Movsas, I Chetty
PURPOSE: To investigate correlation of normal lung CT density changes with dose accuracy and outcome after SBRT for patients with early stage lung cancer. METHODS: Dose distributions for patients originally planned and treated using a 1-D pencil beam-based (PB-1D) dose algorithm were retrospectively recomputed using algorithms: 3-D pencil beam (PB-3D), and model-based METHODS: AAA, Acuros XB (AXB), and Monte Carlo (MC). Prescription dose was 12 Gy × 4 fractions...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048506/we-ab-207b-12-prospective-study-of-the-relationship-between-dose-volume-clinical-toxicity-and-patient-reported-outcomes-in-lung-cancer-patients-treated-with-sbrt
#6
E Mayyas, S Vance, S Brown, J Liu, J Kim, S Zhen, S Devpura, M Ajlouni, S Salim, I Chetty, B Movsas
PURPOSE: To determine in a prospective study, the correlation between radiation dose/volume, clinical toxicities and patient-reported, quality of life (QOL) resulting from lung SBRT. METHODS: For 106 non-small cell lung cancer (NSCLC) patients receiving SBRT (12 Gy × 4), symptoms including cough, dyspnea, fatigue and pneumonitis were measured at baseline (before treatment), after treatment and 3, 6, and 12 months post-treatment. Toxicity was graded from zero to five...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048467/su-g-jep2-08-image-guided-radiation-therapy-using-synthetic-cts-in-brain-cancer
#7
R G Price, J Kim, W Zheng, I J Chetty, C Glide-Hurst
PURPOSE: Synthetic-CTs(synCTs) are essential for MR-only treatment planning. However, the performance of synCT for IGRT must be carefully assessed. This work evaluated the accuracy of synCT and synCT-generated DRRs and determined their performance for IGRT in brain cancer radiation therapy. METHODS: MR-SIM and CT-SIM images were acquired of a novel anthropomorphic phantom and a cohort of 12 patients. SynCTs were generated by combining an ultra-short echo time (UTE) sequence with other MRI datasets using voxel-based weighted summation...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048441/su-f-t-506-development-and-commissioning-of-the-effective-and-efficient-grid-therapy-using-high-dose-rate-flattening-filter-free-beam-and-multileaf-collimator
#8
M Liu, N Wen, C Beyer, F Siddiqui, I Chetty, B Zhao
PURPOSE: Treating bulky tumors with grid therapy (GT) has demonstrated high response rates. Long delivery time (∼15min), with consequent increased risk of intrafraction motion, is a major disadvantage of conventional MLC-based GT (MLC-GT). The goal of this study was to develop and commission a MLC-GT technique with similar dosimetric characteristics, but more efficient delivery. METHODS: Grid plan was designed with 10X-FFF (2400MU/min) beam and MLC in a commercial treatment planning system (TPS)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048385/su-g-brc-07-evaluation-of-aaa-focal-spot-size-for-srs-planning-using-end-to-end-dosimetric-data
#9
S Gardner, A Doemer, B Miller, N Wen, I Chetty
PURPOSE: To use end-to-end dosimetric measurements with Gafchromic film to evaluate the effects of focal spot size parameter for small-field dose calculations using AAA for SRS lesions. METHODS: A total of 13 plans, corresponding to 7 patients previously treated with cranial SRS, were analyzed in this study (target volume range:[0.67cc,13.9cc]). The plans included DCA delivery (4 plans total) and VMAT delivery (9 plans total). All plans were mapped to a solid water phantom (15 cm thickness; isocenter and film plane at 7...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048314/su-d-204-07-retrospective-correlation-of-dose-accuracy-with-regions-of-local-failure-for-early-stage-lung-cancer-patients-treated-with-stereotactic-body-radiotherapy
#10
S Devpura, H Li, C Liu, C Fraser, M Ajlouni, B Movsas, I Chetty
PURPOSE: To correlate dose distributions computed using six algorithms for recurrent early stage non-small cell lung cancer (NSCLC) patients treated with stereotactic body radiotherapy (SBRT), with outcome (local failure). METHODS: Of 270 NSCLC patients treated with 12Gyx4, 20 were found to have local recurrence prior to the 2-year time point. These patients were originally planned with 1-D pencil beam (1-D PB) algorithm. 4D imaging was performed to manage tumor motion...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048111/su-f-j-38-dose-rates-and-preliminary-evaluation-of-contouring-similarity-metrics-using-4d-cone-beam-ct
#11
A Santoso, K Song, Y Qin, S Gardner, C Liu, R Cattaneo, I Chetty, B Movsas, M Aljouni, N Wen
PURPOSE: 4D imaging modalities require detailed characterization for clinical optimization. The On-Board Imager mounted on the linear accelerator was used to investigate dose rates in a tissue mimicking phantom using 4D-CBCT and assess variability of contouring similarity metrics between 4D-CT and 4D-CBCT retrospective reconstructions. METHODS: A 125 kVp thoracic protocol was used. A phantom placed on a motion platform simulated a patient's breathing cycle. An ion chamber was affixed inside the phantom's tissue mimicking cavities (i...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047756/we-ab-207b-09-margin-reduction-for-planning-target-volume-ptv-in-patients-with-localized-prostate-cancer-impact-on-delivered-dose-and-quality-of-life
#12
A Kumarasiri, C Liu, S Brown, C Glide-Hurst, M Elshaikh, I Chetty, B Movsas
PURPOSE: To estimate the delivered (cumulative) dose to targets and organs at risk for localized prostate cancer patients treated with reduced PTV margins and to evaluate preliminary patient reported quality-of-life (QOL). METHODS: Under an IRB-approved protocol, 20 prostate cancer patients (including 11 control patients) were treated with reduced planning margins (5 mm uniform with 4 mm at prostate/rectum interface). Control patients had standard margin (10/6 mm)-based treatments...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047648/su-g-tep2-08-evaluation-of-plastic-scintillator-detector-for-small-field-stereotactic-patient-specific-quality-assurance
#13
Y Qin, S Gardner, Y Huang, J Kim, N Wen, I Chetty
PURPOSE: To evaluate the performance of a commercial plastic scintillator detector (PSD) for small-field stereotactic patient-specific quality assurance using flattening-filter-free (FFF) beams. METHODS: A total of ten spherical targets (volume range:[0.03cc-2cc]) were planned using Dynamic Conformal Arc(DCA-10 plans) and Volumetric Modulated Arc Therapy(VMAT-10 plans) techniques in Eclipse(AAA v.11, 1mm dose calculation grid size). Additionally, 15 previously-treated cranial and spine SRS plans were evaluated (6 DCA, 9 VMAT, volume range:[0...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047636/su-f-t-566-absolute-film-dosimetry-for-stereotactic-radiosurgery-and-stereotactic-body-radiotherapy-quality-assurance-using-gafchromic-ebt3-films
#14
N Wen, S Lu, Y Qin, Y Huang, B Zhao, C Liu, I Chetty
PURPOSE: To evaluate the dosimetric uncertainty associated with Gafchromic (EBT3) films and establish an absolute dosimetry protocol for Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT). METHODS: EBT3 films were irradiated at each of seven different dose levels between 1 and 15 Gy with open fields, and standard deviations of dose maps were calculated at each color channel for evaluation. A scanner non-uniform response correction map was built by registering and comparing film doses to the reference diode array-based dose map delivered with the same doses...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047603/su-f-t-555-accurate-stereotactic-cone-tmrs-converted-from-pdds-scanned-with-ray-trace
#15
H Li, H Zhong, Y Qin, K Snyder, I Chetty, N Wen
PURPOSE: To investigate whether the accuracy of TMRs for stereotactic cones converted from PDDs scanned with Ray Trace can be improved, when compared against the TMRs converted from the traditional PDDs. METHODS: Ray Trace measurement in Sun Nuclear 3D Scanner is for accurate scan of small field PDDs. The system detects the center of field at two depths, for example, at 3 and 20 cm in our study, and then performs scan along the line passing the two centers. With both Ray Trace and the traditional method, PDDs for conical cones of 4, 5, 7...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047440/su-f-j-68-deformable-dose-accumulation-for-voxel-based-dose-tracking-of-ptv-cold-spots-for-adaptive-radiotherapy-of-the-head-and-neck
#16
C Liu, I Chetty, W Mao, A Kumarasiri, H Zhong, S Brown, F Siddiqui
PURPOSE: To utilize deformable dose accumulation (DDA) to determine how cold spots within the PTV change over the course of fractionated head and neck (H&N) radiotherapy. METHODS: Voxel-based dose was tracked using a DDA platform. The DDA process consisted of B-spline-based deformable image registration (DIR) and dose accumulation between planning CT's and daily cone-beam CT's for 10 H&N cancer patients. Cold spots within the PTV (regions receiving less than the prescription, 70 Gy) were contoured on the cumulative dose distribution...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047401/tu-ab-202-07-a-novel-method-for-registration-of-mid-treatment-pet-ct-images-under-conditions-of-tumor-regression-for-patients-with-locally-advanced-lung-cancers
#17
Hoda Sharifi, Hong Zhang, Jian-Yyue Jin, Feng-Ming Kong, Indrin J Chetty, Hualiang Zhong
PURPOSE: In PET-guided adaptive radiotherapy (RT), changes in the metabolic activity at individual voxels cannot be derived until the duringtreatment CT images are appropriately registered to pre-treatment CT images. However, deformable image registration (DIR) usually does not preserve tumor volume. This may induce errors when comparing to the target. The aim of this study was to develop a DIR-integrated mechanical modeling technique to track radiation-induced metabolic changes on PET images...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047080/su-d-bra-03-analysis-of-systematic-errors-with-2d-3d-image-registration-for-target-localization-and-treatment-delivery-in-stereotactic-radiosurgery
#18
H Xu, I Chetty, N Wen
PURPOSE: Determine systematic deviations between 2D/3D and 3D/3D image registrations with six degrees of freedom (6DOF) for various imaging modalities and registration algorithms on the Varian Edge Linac. METHODS: The 6DOF systematic errors were assessed by comparing automated 2D/3D (kV/MV vs. CT) with 3D/3D (CBCT vs. CT) image registrations from different imaging pairs, CT slice thicknesses, couch angles, similarity measures, etc., using a Rando head and a pelvic phantom...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046928/su-f-r-38-impact-of-smoothing-and-noise-on-robustness-of-cbct-textural-features-for-prediction-of-response-to-radiotherapy-treatment-of-head-and-neck-cancers
#19
H Bagher-Ebadian, I Chetty, C Liu, B Movsas, F Siddiqui
PURPOSE: To examine the impact of image smoothing and noise on the robustness of textural information extracted from CBCT images for prediction of radiotherapy response for patients with head/neck (H/N) cancers. METHODS: CBCT image datasets for 14 patients with H/N cancer treated with radiation (70 Gy in 35 fractions) were investigated. A deformable registration algorithm was used to fuse planning CT's to CBCT's. Tumor volume was automatically segmented on each CBCT image dataset...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046890/su-f-j-177-a-novel-image-analysis-technique-center-pixel-method-to-quantify-end-to-end-tests
#20
N Wen, K Snyder, S Scheib, Y Qin, H Li, I Chetty
PURPOSE: To implement a novel image analysis technique, "center pixel method", to quantify end-to-end tests accuracy of a frameless, image guided stereotactic radiosurgery system. METHODS: The localization accuracy was determined by delivering radiation to an end-to-end prototype phantom. The phantom was scanned with 0.8 mm slice thickness. The treatment isocenter was placed at the center of the phantom. In the treatment room, CBCT images of the phantom (kVp=77, mAs=1022, slice thickness 1 mm) were acquired to register to the reference CT images...
June 2016: Medical Physics
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