bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐P‐24: Simplified EDW Profile Measurements Using Two Commonly Available Detector Arrays
Authors: Reynolds T , Arentsen L , Watanabe Y , Alaei P 
Published: June 2015

Purpose:Enhanced dynamic wedge (EDW) profiles are needed as part of the commissioning of a treatment planning system. This work compares the acquisition of EDW profiles using a linear diode array (LDA) with two commonly used detector arrays available in the clinics, with the goal of identifying the simplest approach for these measurements.Methods:The measurements of EDW profiles were performed on a Varian TrueBeam linear accelerator for 6, 10, and 18 MV photon beams for all seven wedge angles at four depths. The measurements were done using the LDA 99 in Blue Phantom2 (IBA Dosimetry), and IC Profiler and MapCHECK2 (Sun Nuclear) in solid water phantoms. The water phantom was set up at 100 cm SSD, whereas the two other devices were set up at 75 cm due to the size limitations of the devices. The largest possible field size was used. The average and maximum percentage differences were examined within the central 90% of the field and in the penumbra.Results:Dose profiles measured with IC Profiler were in a good agreement with LDA 99 data. The average percentage difference within the field did not exceed 0.5% for all energies. MapCHECK2 measurements matched well with LDA 99 for 10 and 18 MV (within 0.3%) with discrepancies of up to 1.4% observed for the 6 MV beam. The maximum percentage differences for both devices in the penumbra exhibited larger variations than LDA 99 results due to differences in detector spacing and high dose gradient, as expected.Conclusion:Common linac QA devices such as IC Profiler or MapCHECK2 provide EDW beam profile data of reasonable accuracy as compared to measurements performed using a linear diode array in a water phantom, saving the expense and time involved in acquiring and setting up a LDA.
SU‐E‐P‐25: Evaluation of Motion in Pancreas SBRT Treatment Deliveries
Authors: Xiong L , Halvorsen P 
Published: June 2015

Purpose:Stereotactic Body Radiation Therapy (SBRT) procedures for pancreatic cancer present a challenge in motion management because the target is directly adjacent to critical structures and the target is subject to significant respiratory motion. Gated treatment is usually planned with a tight (few mm) PTV margin. The positioning and setup relies on on‐board‐imaging (OBI) of internal fiducials. This study evaluates the corrections for inter‐ and intra‐fractional target motion as evidenced by the OBI.Methods:20 patients with gated pancreas SBRT treatment were setup with KV imaging guidance before and during each treatment. The couch position was fine‐tuned to align with the internal fiducials for each patient. The data for 148 intra‐ and 111 inter‐fractional couch movements were captured and analyzed.Results:The mean ± standard deviation of couch shifts for the initial daily setup is 4.9±4.1 mm for couch vertical, 5.3±4.6 mm for couch longitudinal, and 3.7±4.0 mm for couch lateral. The mean ± standard deviation of intra‐treatment adjustments are 1.1±1.6, 2.5±3.8, and 1.1±1.8 mm for couch vertical, longitudinal and lateral. The probability of intra‐fractional motion in the three orthogonal directions with magnitude no more than 2 mm, 3 mm and 5 mm is 55%, 68% and 84% respectively.Conclusion:The intra‐treatment target motion for pancreas SBRT patients indicates that a PTV margin of 5mm may be necessary.
SU‐E‐P‐32: Adapting An MMLC to a Conventional Linac to Perform Stereotactic Applications
Authors: Emam I , Hosini M 
Published: June 2015

Purpose:Micro‐MLCs minimizes beam scalloping effects caused by conventional‐MLCs and facilitates conformal dynamic treatment delivery. But their effect on dosimetric parameters require careful investigations. Physical and dosimetric parameters and Linac mechanical stability with mMLC (net weight 30 Kg) attached to the gantry are to be investigated. Moreover, output study along with recommended jaws offsets are studied. Adaptation of an mMLC to our 16‐years old conventional Linac is investigated in this workMethods:BrainLab mMLC (m3) mounted in a detachable chassis to the Philips SL‐15 Linac (30kg). Gantry and collimator spoke shots measurements are made using a calibrated film in a solid phantom and compared with pin‐point measurements. Leaf penumbra, transmission, leakage between the leaves, percentage depth dose (PDD) are measured using IBA pin‐point ion chamber at 6 and 10 MV. For output measurements (using brass build‐up cap), jaws are modified continuously regarding to m3‐fields while output factor are compared with fixed jaws situation, while the mMLC leaf configuration is modified for different m3‐fieldsResults:Mean transmission through leaves is 1.9±0.1% and mean leakage between leaves is 2.8±0.15%. Between opposing leaves abutting along the central beam‐axis mean transmission is 15±3%, but it is reduced to 4.5±0.6% by moving the abutment position 4.5cm off‐axis. The penumbra was sharper for m3 ‐fields than jaws‐fields (maximum difference is 1.51±0.2%). m3‐fields PDD show ∼3% variation from those of jaws‐fields. m3‐fields output factors show large variations (<4%) from Jaws defined fields. Output for m3‐rectangular fields show slight variation in case of leaf‐end&leaf‐side as well as X‐jaw&Y‐jaw exchange. Circular m3‐fields output factors shows close agreement with their corresponding square jaws‐defined fields using 2mm Jaws offsets, If jaws are retracted to m3 limits, differences become <5%.Conclusion:BrainLab m3 is successfully adapted to our 16 old Philips‐SL‐15 Linac. Dosimetric properties should be taken into account for treatment planning considerations.
SU‐E‐P‐44: The Characteristics and Clinical Application of the ArcCHECK for VMAT Verification
Authors: Chengqiang L 
Published: June 2015

Purpose:To evaluate the characteristics and clinical suitability of the ArcCHECK QA system for VMAT verification.Methods:The intrinsic sensitivity,short and long term reproducibility,dose and dose rate dependence,dose per pulsed dependence,field sizes dependence and directional response of the diodes were measured.The results of the diodes were compared with the measurement results of an ionization chamber and calculated results of TPS. Gamma index (3mm distance to agreement and 3% percentage difference ) was used to analyze the dose difference between the calculation and measurement for random selected 211 verified VMAT plans.Results:The ArcCHECK diodes performed well for all tests except directional dependence, which varies from a minimum of −3.9% (seen only when the beam is incident on the diode at 180°) to a maximum of 7.7% (approximately at 255°). Average gamma analysis passing rates with 3mm/3% for 113 NPC,48 cervical cancer and 50 rectal cancer VMAT plans are 93.5%,95.7% and 97.5%, statistical significance has been found between either two of the groups(t=−12.69∼−4.88,all P<0.01).Conclusion:With proposed calibration method,the ArcCHECK QA system is very suitable for VMAT pretreatment verification,the complexity of VMAT plan is the main factor affecting the passing rate.
SU‐E‐P‐52: Dose‐Volume Toxicity Analysis of Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma
Authors: Bergamo A , Kauweloa K , Daniels J , Crownover R , Mavroidis P , Papanikolaou N , Gutierrez A 
Published: June 2015

Purpose:To investigate the relationship between physical and biological effective dose (BED) to liver toxicity for SBRT fractionations.Methods:A total of 16 patients (13–10×3Gy, 2–5×10Gy and 1–3×15Gy were selected. Physical dose distributions were converted to voxel based BED values using the linear‐quadratic (LQ) and linear‐quadratic linear (LQ‐L) models for doses per fraction larger than 6Gy. Patients were graded for effective toxicity (post‐treatment minus pre‐treatment grades) using the RTOG Late Radiation Morbidity Scoring Schema associated with Radiation Induced Liver Disease (RILD). Evaluated physical dose‐volume levels consisted of V10Gy, V15Gy, V20Gy, V25Gy and V30Gy which were then converted to BED values corresponding to V16.7Gy3, V30Gy3, V46.7Gy3, V66.7Gy3 and V90Gy3, respectively. All levels were normalized to their respective patient normal liver volumes (NLV) and evaluated for correlation to RILD. Results were measured quantitatively using R‐squared regression analysis.Results:Mean Dose Tolerable to Normal Liver (MDTNL) against RILD grade resulted in an R‐squared value of 0.0104. NLV‐normalized physical dose linear regression fit of V10Gy, V15Gy, V20Gy, V25Gy and V30Gy against RILD yielded R‐squared values of 0.1041, 0.0895, 0.0698, 0.0398 and 0.0009 while BED levels of V16.7Gy3, V30Gy3, V46.7Gy3, V66.7Gy3 and V90Gy3 resulted in values of 0.0002, 0.0153, 0.0533, 0.0427 and 0.0072, respectively. The average NLV‐normalized V10Gy, V15Gy, V20Gy, V25Gy and V30Gy per grade plotted against RILD grade yielded R‐squared correlations of 0.8092, 0.6362, 0.5899, 0.5846 and 0.0224 while the BED levels of V16.7Gy3, V30Gy3, V46.7Gy3, V66.7Gy3 and V90Gy3 resulted in R‐squared correlations of 0.0003, 0.3831, 0.8476, 0.678 and 0.076, respectively.Conclusion:Regression analysis between physical dose, BED and RILD showed strong correlation for the V30Gy and V46.7Gy3 dose‐levels. Average BED and physical dose per grade both exhibit strong correlations to RILD however, a lack of statistical significance exists due to small patient sample size.
SU‐E‐P‐55: The Reaserch of Cervical Cancer Delivered with Constant Dose Rate and Gantry Speed Arc Therapy(CDR‐CAS‐IMAT) On Conventional Linac
Authors: Zhang R , Bai W , Gao Y , Chi Z , Gao C , Xiaomei F 
Published: June 2015

Purpose:Postoperative cervical cancer patients with large target volume and the target shape is concave, treatmented with static intensity‐modulated radiotherapy (IMRT) is time consuming. The purpose of this study is to investigate using constant dose rate and gantry speed arc therapy(CDR‐CAS‐IMAT) on conventional linear accelrator, by comparing with the IMRT technology to evaluate the performance of CDR‐CAS‐IMAT on postoperative cervical cancer patients.Methods:18 cervical cancer patients treated with IMRT on Varian 23IX were replanted using CDR‐CAS‐IMAT. The plans were generated on Oncentra v4.1 planning system, PTV was prescribed to 50.4 Gy in 28 fractions. Plans were evaluated based on the ability to meet the dose volume histogram. The homogeneity index (HI), conformity index (CI) of target volume, the dose of organs at risk, radiation delivery time and monitor units were also compared. SPSS 19.0 software paired T‐test analysis was carried out on the two sets of data.Results:Compared with the IMRT plans PTV's CI (t= 3.85, P =0.001), CTV's CI, HI, D90, D95, D98, V95, V98, V100 (t=4.21, −3.18, 2.13, 4.65, 7.79, 2.29, 6.00, 2.13, p=0.001, 0.005, 0.049, 0.000, 0.000, 0.035, 0.000, 0.049), and cord D2 and rectum V40 (t=−2.65, −2.47, p= P =0.017, 0.025), and treatment time and MU (t=−36.0, −6.26, P =0.000, 0.000) were better than that of IMRT group. But the IMRT plans in terms of decreasing bladder V50, bowel V30 (t=2.14, 3.00, P =0.048, 0.008) and low dose irradiation volume were superior to that of CDR‐CAS‐IMAT plans. There were no significant differences in other statistical index.Conclusion:Cervical cancer patients with CDR‐CAS‐IMAT on Varian Clinical 23IX can get equivalent or superior dose distribution compared with the IMRT technology. IMAT have much less treatment time and MU can reduce the uncertainty factor and patient discomfort in treatment.This work was supported by the Medical Science Foundation of the health department of Hebei Province (No. 20130253)
SU‐E‐P‐56: Dosimetric Comparison of Three Post Modified Radical Mastectomy Radiotherapy Techniques for Locally Advanced Left‐Sided Breast Cancer and Beyond
Authors: Ma C , Zhang W , Lu J , Wu L , Wu F , Huang B , Li D 
Published: June 2015

Purpose:To compare the dosimetry of post modified radical mastectomy radiotherapy (PMRMRT) for left‐sided breast cancer using 3‐dimensional conformal radiotherapy (3DCRT), intensity‐modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT).Methods:We created ten sets of PMRMRT plans for ten consecutive patients and utilized two tangential and one or two supraclavicular beams in 3DCRT, a total of 5 beams in IMRT and two optimized partial arcs in VMAT. The difference in results between any two of the three new plans, between new and previous 3DCRT plans were compared and analyzed by ANOVA (α =0.05) and paired‐sample t‐test respectively. P values less than 0.05 were considered statistically significant.Results:Both IMRT and VMAT plans had similar PTV coverage, hotspot area and conformity (all p>0.05), and significantly higher PTV coverage compared with new 3DCRT (both p<0.001). IMRT plans had significantly less heart and left lung radiation exposure compared with VMAT (all p<0.05). The 3DCRT plans with larger estimated CTV displacement had better target coverage but worse OARs sparing compared to those with smaller one.Conclusion:IMRT has dosimetrical advantages over the other two techniques in PMRMRT for left‐sided breast cancer. Individually quantifying and minimizing CTV displacement can significantly improve dosage distribution.This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)
SU‐E‐U‐04: Evaluation of Normal Tissue Toxicity of Drug‐Loaded Nanodroplets Used for Treating Prostate Cancer with MR‐Guided Focused‐Ultrasound
Authors: Gupta R , Cvetkovic D , Wang B , Ma C , Chen L 
Published: June 2015

Purpose:Our prior studies have showed significant prostate tumor growth‐delay when pulsed focused ultrasound (pFUS) is applied under MR‐guidance in combination with docetaxel‐encapsulated nanodroplets (DTX‐ND). The purpose of the present work was to investigate normal tissue toxicity of DTX‐ND in order to study true efficacy of a novel prostate cancer treatment approach combining DTX‐ND injections and pFUS exposures under MR guidance.Methods:Poly {ethylene oxide}‐co‐poly {D, L‐lactide} (PDLA) nanodroplets loaded with docetaxel were synthesized in our lab using solid dispersion technique with 0.5% docetaxel, 2% perfluorocarbon and 2% PDLA. The mean diameter of the nanodroplets was 220 ± 30nm. Human prostate cancer, LNCaP cells were implanted orthotopically in prostates of male nude mice. Tumor growth was monitored using MRI. Tumor–bearing mice were randomly divided into 5 groups. Group 1 animals were treated with DTX‐ND and pFUS. Ultrasound treatment parameters were 1MHz, 25W acoustic power, 10% duty cycle and 60 seconds for each sonication. Group 2 mice were treated with pFUS. Group 3 mice were injected with DTX‐ND. Group 4 received free docetaxel and Group 5 mice were used as control (no treatment). Mice weights were monitored for toxicity.Results:Docetaxel‐loaded nanodroplets showed no normal tissue toxicity as average mice weights (27.12 ±0.75 g) from group 1 were statistically, no different when compared with average mice weights (24.39 ±0.62 g) from control group (p >0.05). Also, average mice weights from group2 (24.95 ±1.2 g), group3 (26.16 ± 0.66 g) and group4 (27.10 ±0.65 g) showed no significant difference in weights when compared to control group (p >0.05).Conclusion:This study demonstrates that our formulation of DTX‐ND shows no normal tissue toxicity in mice. These findings help us in evaluating the true efficacy of our hypothesized prostate cancer treatment strategy using focused‐ultrasound activated drug‐delivery under MR guidance without incurring additional toxicity.
SU‐E‐I‐09: The Impact of X‐Ray Scattering On Image Noise for Dedicated Breast CT
Authors: Yang K , Gazi P , Boone J 
Published: June 2015

Purpose:To quantify the impact of detected x‐ray scatter on image noise in flat panel based dedicated breast CT systems and to determine the optimal scanning geometry given practical trade‐offs between radiation dose and scatter reduction.Methods:Four different uniform polyethylene cylinders (104, 131, 156, and 184 mm in diameter) were scanned as the phantoms on a dedicated breast CT scanner developed in our laboratory. Both stationary projection imaging and rotational cone‐beam CT imaging was performed. For each acquisition type, three different x‐ray beam collimations were used (12, 24, and 109 mm measured at isocenter). The aim was to quantify image noise properties (pixel variance, SNR, and image NPS) under different levels of x‐ray scatter, in order to optimize the scanning geometry. For both projection images and reconstructed CT images, individual pixel variance and NPS were determined and compared. Noise measurement from the CT images were also performed with different detector binning modes and reconstruction matrix sizes. Noise propagation was also tracked throughout the intermediate steps of cone‐beam CT reconstruction, including the inverse‐logarithmic process, Fourier‐filtering before backprojection.Results:Image noise was lower in the presence of higher scatter levels. For the 184 mm polyethylene phantom, the image noise (measured in pixel variance) was ∼30% lower with full cone‐beam acquisition compared to a narrow (12 mm) fan‐beam acquisition. This trend is consistent across all phantom sizes and throughout all steps of CT image reconstruction.Conclusion:From purely a noise perspective, the cone‐beam geometry (i.e. the full cone‐angle acquisition) produces lower image noise compared to the lower‐scatter fan‐beam acquisition for breast CT. While these results are relevant in homogeneous phantoms, the full impact of scatter on noise in bCT should involve contrast‐to‐noise‐ratio measurements in heterogeneous phantoms if the goal is to optimize the scanning geometry for dedicated breast CT.This work was supported by a grant from the National Institute for Biomedical Imaging and Bioengineering (R01 EB002138).
SU‐E‐I‐12: Flexible Geometry Computed Tomography
Authors: Shaw R 
Published: June 2015

Purpose:The concept separates the mechanical connection between the radiation source and detector. This design allows the trajectory and orientation of the radiation source/detector to be customized to the object that is being imaged. This is in contrast to the formulaic rotation‐translation image acquisition of conventional computed tomography(CT).Background/significance:CT devices that image a full range of: anatomy, patient populations, and imaging procedures are large. The root cause of the expanding size of comprehensive CT is due to the commitment to helical geometry that is hardwired into the image reconstruction. FGCT extends the application of alternative reconstruction techniques, i.e. tomosynthesis, by separating the two main components— radiation source and detector— and allow for 6 degrees of freedom motion for radiation source, detector, or both. The image acquisition geometry is then tailored to how the patient/object is positioned. This provides greater flexibility on the position and location that the patient/object is being imaged. Additionally, removing the need of a rotating gantry reduces the footprint so that CT is more mobile and more available to move to where the patient/object is at, instead of the other way around.Methods:As proof‐of‐principle, a reconstruction algorithm is designed to produce FGCT images. Using simulated detector data, voxels intersecting a line drawn between the radiation source and an individual detector are traced and modified using the detector signal. The detector signal is modified to compensate for changes in the source to detector distance. Adjacent voxels are modified in proportion to the detector signal, providing a simple image filter.Results:Image‐quality from the proposed FGCT reconstruction technique is proving to be a challenge, producing hardily recognizable images from limited projections angles.Conclusion:Preliminary assessment of the reconstruction technique demonstrates the inevitable tradeoff of producing meaningful image‐quality verses the practicality of how to obtain sufficient image data.
SU‐E‐I‐13: Evaluation of Metal Artifact Reduction (MAR) Software On Computed Tomography (CT) Images
Authors: Huang V , Kohli K 
Published: June 2015

Purpose:A new commercially available metal artifact reduction (MAR) software in computed tomography (CT) imaging was evaluated with phantoms in the presence of metals. The goal was to assess the ability of the software to restore the CT number in the vicinity of the metals without impacting the image quality.Methods:A Catphan 504 was scanned with a GE Optima RT 580 CT scanner (GE Healthcare, Milwaukee, WI) and the images were reconstructed with and without the MAR software. Both datasets were analyzed with Image Owl QA software (Image Owl Inc, Greenwich, NY). CT number sensitometry, MTF, low contrast, uniformity, noise and spatial accuracy were compared for scans with and without MAR software. In addition, an in‐house made phantom was scanned with and without a stainless steel insert at three different locations. The accuracy of the CT number and metal insert dimension were investigated as well.Results:Comparisons between scans with and without MAR algorithm on the Catphan phantom demonstrate similar results for image quality. However, noise was slightly higher for the MAR algorithm. Evaluation of the CT number at various locations of the in‐house made phantom was also performed. The baseline HU, obtained from the scan without metal insert, was compared to scans with the stainless steel insert at 3 different locations. The HU difference between the baseline scan versus metal scan was improved when the MAR algorithm was applied. In addition, the physical diameter of the stainless steel rod was over‐estimated by the MAR algorithm by 0.9 mm.Conclusion:This work indicates with the presence of metal in CT scans, the MAR algorithm is capable of providing a more accurate CT number without compromising the overall image quality. Future work will include the dosimetric impact on the MAR algorithm.
SU‐E‐I‐19: Optimization of Low Contrast Detectability Across Two CT Manufacturers
Authors: Mahmood U , Dauer L , Erdi Y 
Published: June 2015

Purpose:Our goal was to evaluate low contrast detectability (LCD) for abdominal CT protocols across two CT scanner manufacturers, while producing a similar noise texture and CTDIvol for acquired images.Methods:A CIRS tissue equivalent LCD phantom containing three columns of 7 spherical targets, ranging from 10 mm to 2.4 mm, that are 5, 10, and 20 HU below the background matrix (HUBB) was scanned using two a GE HD750 64 slice scanner and a Siemens Somatom Definition AS 64 slice scanner. Protocols were designed to deliver a CTDIvol of 12.26 mGy and images were reconstructed with FBP, ASIR and Sapphire. Comparisons were made with those algorithms that had matching noise power spectrum peaks (NPS). NPS information was extracted from a previously published article that matched NPS peak frequencies across manufacturers by calculating the NPS from uniform phantom images reconstructed with several IR algorithms.Results:The minimum detectable lesion size in the 20 HUBB and 10 HUBB column was 6.3 mm, and 10 mm in the 5 HUBB column for the GE HD 750 scanner. The minimum detectable lesion size in the 20 HUBB column was 4.8 mm, in the 10 HUBB column, 9.5 mm, and the 5 HUBB column, 10 mm for the Siemens Somatom Definition AS.Conclusion:Reducing radiation dose while improving or maintaining LCD is possible with application of IR. However, there are several different IR algorithms, with each generating a different resolution and noise texture. In multi‐manufacturer settings, matching only the CTDIvol between manufacturers may Result in a loss of clinically relevant information.