bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐F‐P‐26: Study of Radiation Dose Evaluation for Organs at Risk Using MRI in Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma
Authors: Gong G , Guo Y , Yin Y 
Published: July 2016

Purpose:To study the contour and dosimetric feature of organs at risk (OARs) applying magnetic resonance imaging (MRI) images in intensity modulated radiation therapy (IMRT) of nasopharyngeal carcinoma (NPC) compared to computed tomography (CT) images.Methods:35 NPC patients was selected into this trail. CT simulation with non‐contrast and contrast enhanced scan, MRI simulation with non‐contrast and contrast enhanced T1, T2 and diffusion weighted imaging were achieved sequentially. And the OARs were contoured on the CT and MRI images after rigid registration respectively. 9 beams IMRT plan with equal division angle were designed for every patients, and the prescription dose for tumor target was set as 72Gy (2.4Gy/ fration). The boundary display, volume and dose‐volume indices of each organ were compared between on MRI and CT images.Results:Compared to CT, MRI showed clearer boundary of brainstem, spinal cord, the deep lobe of Parotid gland and the optical nerve in canal. MRI images increase the volume of lens, optical nerve, while reducing the volume of eye slightly, and the maximum dose of lens, the mean dose of eyes and optical raised in different percentage, while there was no statistical differences were found. The left and right parotid volume on MRI increased by 7.07%, 8.13%, and the mean dose raised by 14.95% (4.01Gy), 18.76% (4.95Gy) with statistical significant difference (p<0.05). The brainstem volume reduced by 9.33% (p<0.05), and the dose of 0.1cm3 volume (D0.1cm3) reduced by mean 8.46% (4.32Gy), and D0.1cm3 of spinal cord increased by 1.5Gy on MRI.Conclusion:It is credible to evaluate the radiation dose of lens, eye and the spinal cord, while it should be necessary to evaluate the dose of brainstem, parotid and the optical nerve applying MRI images sometime, it will be more meaningful for these organs with high risk of radiation injury.
SU‐F‐P‐36: Automation of Linear Accelerator Star Shot Measurement with Advanced XML Scripting and Electronic Portal Imaging Device
Authors: Nguyen N , Knutson N , Schmidt M , Price M 
Published: July 2016

Purpose:To verify a method used to automatically acquire jaw, MLC, collimator and couch star shots for a Varian TrueBeam linear accelerator utilizing Developer Mode and an Electronic Portal Imaging Device (EPID).Methods:An XML script was written to automate motion of the jaws, MLC, collimator and couch in TrueBeam Developer Mode (TBDM) to acquire star shot measurements. The XML script also dictates MV imaging parameters to facilitate automatic acquisition and recording of integrated EPID images. Since couch star shot measurements cannot be acquired using a combination of EPID and jaw/MLC collimation alone due to a fixed imager geometry, a method utilizing a 5mm wide steel ruler placed on the table and centered within a 15×15cm2 open field to produce a surrogate of the narrow field aperture was investigated. Four individual star shot measurements (X jaw, Y jaw, MLC and couch) were obtained using our proposed as well as traditional film‐based method. Integrated EPID images and scanned measurement films were analyzed and compared.Results:Star shot (X jaw, Y jaw, MLC and couch) measurements were obtained in a single 5 minute delivery using the TBDM XML script method compared to 60 minutes for equivalent traditional film measurements. Analysis of the images and films demonstrated comparable isocentricity results, agreeing within 0.3mm of each other.Conclusion:The presented automatic approach of acquiring star shot measurements using TBDM and EPID has proven to be more efficient than the traditional film approach with equivalent results.
SU‐F‐R‐51: Radiomics in CT Perfusion Maps of Head and Neck Cancer
Authors: Nesteruk M , Riesterer O , Bundschuh R , Veit‐Haibach P , Huellner M , Studer G , Stieb S , Glatz S , Pruschy M , Guckenberger M , Tanadini‐Lang S 
Published: July 2016

Purpose:The aim of this study was to test the predictive value of radiomics features of CT perfusion (CTP) for tumor control, based on a preselection of radiomics features in a robustness study.Methods:11 patients with head and neck cancer (HNC) and 11 patients with lung cancer were included in the robustness study to preselect stable radiomics parameters. Data from 36 HNC patients treated with definitive radiochemotherapy (median follow‐up 30 months) was used to build a predictive model based on these parameters. All patients underwent pre‐treatment CTP. 315 texture parameters were computed for three perfusion maps: blood volume, blood flow and mean transit time. The variability of texture parameters was tested with respect to non‐standardizable perfusion computation factors (noise level and artery contouring) using intraclass correlation coefficients (ICC). The parameter with the highest ICC in the correlated group of parameters (inter‐parameter Spearman correlations) was tested for its predictive value. The final model to predict tumor control was built using multivariate Cox regression analysis with backward selection of the variables. For comparison, a predictive model based on tumor volume was created.Results:Ten parameters were found to be stable in both HNC and lung cancer regarding potentially non‐standardizable factors after the correction for inter‐parameter correlations. In the multivariate backward selection of the variables, blood flow entropy showed a highly significant impact on tumor control (p=0.03) with concordance index (CI) of 0.76. Blood flow entropy was significantly lower in the patient group with controlled tumors at 18 months (p<0.1). The new model showed a higher concordance index compared to the tumor volume model (CI=0.68).Conclusion:The preselection of variables in the robustness study allowed building a predictive radiomics‐based model of tumor control in HNC despite a small patient cohort. This model was found to be superior to the volume‐based model.The project was supported by the KFSP Tumor Oxygenation of the University of Zurich, by a grant of the Center for Clinical Research, University and University Hospital Zurich and by a research grant from Merck (Schweiz) AG.
SU‐F‐R‐56: Early Assessment of Treatment Response During Radiation Therapy Delivery for Esophageal Cancer Using Quantitative CT
Authors: Li D , Chen X , Wu H , Wang J , Li X 
Published: July 2016

Purpose:To investigate the feasibility of assessing treatment response using CTs during delivery of radiation therapy (RT) for esophageal cancer.Methods:Daily CTs acquired using a CT‐on‐Rails during the routine CT‐guided RT for 20 patients with stage II to IV esophageal cancers were analyzed. All patients were treated with combined chemotherapy and IMRT of 45–50 Gy in 25 fractions, and were followed up for two years. Contours of GTV, spinal cord, and non‐specified tissue (NST) irradiated with low dose were generated on each daily CT. A series of CT‐texture metrics including Hounsfield Unit (HU) histogram, mean HU, standard derivation (STD), entropy, and energy were obtained in these contours on each daily CT. The changes of these metrics and GTV volume during RT delivery were calculated and correlated with treatment outcome.Results:Changes in CT texture (e.g., HU histogram) in GTV and spinal cord (but not in NST) were observed during RT delivery and were consistently increased with radiation dose. For the 20 cases studied, the mean HU in GTV was reduced on average by 4.0HU from the first to the last fractions, while 8 patients (responders) had larger reductions in GTV mean HU (average 7.8 HU) with an average GTV reduction of 51% and had increased consistently in GTV STD and entropy with radiation dose. The rest of 12 patients (non‐responders) had lower reductions in GTV mean HU (average 1.5HU) and almost no change in STD and entropy. For the 8 responders, 2 experienced complete response, 7 (88%) survived and 1 died. In contrast, for the 12 non‐responders, 4 (33%) survived and 8 died.Conclusion:Radiation can induce changes in CT texture in tumor (e.g., mean HU) during the delivery of RT for esophageal cancer. If validated with more data, such changes may be used for early prediction of RT response for esophageal cancer.
SU‐F‐I‐03: Correction of Intra‐Fractional Set‐Up Errors and Target Coverage Based On Cone‐Beam Computed Tomography for Cervical Cancer Patients
Authors: Zhang JY , Hong DL 
Published: July 2016

Purpose:The purpose of this study is to investigate the patient set‐up error and interfraction target coverage in cervical cancer using image‐guided adaptive radiotherapy (IGART) with cone‐beam computed tomography (CBCT).Methods:Twenty cervical cancer patients undergoing intensity modulated radiotherapy (IMRT) were randomly selected. All patients were matched to the isocenter using laser with the skin markers. Three dimensional CBCT projections were acquired by the Varian Truebeam treatment system. Set‐up errors were evaluated by radiation oncologists, after CBCT correction. The clinical target volume (CTV) was delineated on each CBCT, and the planning target volume (PTV) coverage of each CBCT‐CTVs was analyzed.Results:A total of 152 CBCT scans were acquired from twenty cervical cancer patients, the mean set‐up errors in the longitudinal, vertical, and lateral direction were 3.57, 2.74 and 2.5mm respectively, without CBCT corrections. After corrections, these were decreased to 1.83, 1.44 and 0.97mm. For the target coverage, CBCT‐CTV coverage without CBCT correction was 94% (143/152), and 98% (149/152) with correction.Conclusion:Use of CBCT verfication to measure patient setup errors could be applied to improve the treatment accuracy. In addition, the set‐up error corrections significantly improve the CTV coverage for cervical cancer patients.
SU‐F‐I‐04: Low Dose CT Lung Cancer Screening Protocol Evaluation
Authors: Nett E , Imai Y 
Published: July 2016

Purpose:The purpose of this study was to evaluate protocols for low dose CT (LDCT) for lung cancer screening on a Revolution CT (GE Healthcare; Waukesha, WI). Lung cancer the leading cause of cancer death for men and women, and more deaths are attributable to lung cancer than breast, colon and prostate cancers combined. Recently, the National Lung Screening Trial (NLST) showed LDCT screening resulted in a 20% reduction in lung cancer mortality and 6.7% in mortality from all causes [NEJM, 2011].Methods:The protocols for this study (Table 1) were designed based on the following criteria: (1) CTDIvol ≤ 3.0 mGy (for an “average” person), (2) dose variation based on patient size, (3) the ability to scan the entire lung in a single breath, (4) adequate image quality for LCS including the ability to detect nodules ≥ 5mm. A chest phantom (Chest Phantom N1, Kyoto Kagaku Co., Ltd, Kyoto Japan) was scanned with three fat plate configurations (small, average and large) and six artificial nodules: solid (+100 HU; 5, 8, and 10 mm) and non‐solid (‐630 HU; 5, 8, and 10 mm). The nodules were inserted into the lung structure along the vessels. Each scan was repeated 5 times. The contrast to noise ratio (CNR) was measured in the 5 mm nodules as the figure of merit for detectability (Figure 1). The sizes of all nodules were measured using a manual distance tool.Results:All phantom images showed sufficient image quality for lung nodule detection. CNR values were all more than sufficient for nodule detection of the kind and size related to lung cancer screening (Figure 2). Nodule size measurements all showed accuracy within 0.3 mm (Figure 3).Conclusion:This phantom study shows the presented low‐dose protocols should meet the needs for LDCT Lung Cancer Screening.All authors are employees of GE Healthcare.
SU‐F‐I‐19: MRI Positive Contrast Visualization of Prostate Brachytherapy Seeds Using An Integrated Laplacian‐Based Phase Processing
Authors: Soliman A , Nosrati R , Safigholi H , Owrangi A , Morton G , Song W 
Published: July 2016

Purpose:To propose a new method that provides a positive contrast visualization of the prostate brachytherapy seeds using the phase information from MR images. Additionally, the feasibility of using the processed phase information to distinguish seeds from calcifications is explored.Methods:A gel phantom was constructed using 2% agar dissolved in 1 L of distilled water. Contrast agents were added to adjust the relaxation times. Four iodine‐125 (Eckert & Ziegler SML86999) dummy seeds were placed at different orientations with respect to the main magnetic field (B0). Calcifications were obtained from a sheep femur cortical bone due to its close similarity to human bone tissue composition. Five samples of calcifications were shaped into different dimensions with lengths ranging between 1.2 – 6.1 mm.MR imaging was performed on a 3T Philips Achieva using an 8‐channel head coil. Eight images were acquired at eight echo‐times using a multi‐gradient echo sequence. Spatial resolution was 0.7 × 0.7 × 2 mm, TR/TE/dTE = 20.0/2.3/2.3 ms and BW = 541 Hz/pixel. Complex images were acquired and fed into a two‐step processing pipeline: the first includes phase unwrapping and background phase removal using Laplacian operator (Wei et al. 2013). The second step applies a specific phase mask on the resulting tissue phase from the first step to provide the desired positive contrast of the seeds and to, potentially, differentiate them from the calcifications.Results:The phase‐processing was performed in less than 30 seconds. The proposed method has successfully resulted in a positive contrast of the brachytherapy seeds. Additionally, the final processed phase image showed difference between the appearance of seeds and calcifications. However, the shape of the seeds was slightly distorted compared to the original dimensions.Conclusion:It is feasible to provide a positive contrast of the seeds from MR images using Laplacian operator‐based phase processing.
SU‐F‐I‐22: Development and Implementation of Task‐Specific Modular Phantom for MRI Quality Evaluation
Authors: Cho H , Hong C , Doh I , Ahn B 
Published: July 2016

Purpose:To investigate the potential of a newly developed modular phantom with image quality test structure for MRI quality control.Methods:The modular phantom consists of individual basic mapping (BM) modules, image quality control (QC) modules, and accessories to improve combination variability for multipurpose use. BM modules were designed based on the stud‐and‐tube coupling system with an internal hollow and an individual enclosed structure. The QC modules include signal‐to‐noise ratio, image intensity uniformity, geometric accuracy, high‐contrast spatial resolution, slice thickness accuracy, slice position accuracy and low‐contrast object detectability evaluation test structure. The scanner performance on various coils were evaluated by using image QC module which inserted into BM module. The MR data acquisition was performed using a 1.5 T MRI scanner (MAGNETOM ESSENZA, Siemens, Germany) with two coils, head and breast. The 2D SE T1 axial images of assembled QC modules, which are analogous to the ACR accreditation phantom were acquired in the head coil. We scanned BM modules and QC modules to evaluation off‐center impact on the image quality in the breast coil. Oil‐filled BM modules and QC modules designed to evaluate geometric accuracy and image intensity uniformity were used. The 2D TSE T2 weighted axial images and short‐tau inversion recovery (STIR) image of modules were acquired in the breast coil.Results:The evaluated MRI quality was acceptable according to the action criteria from the ACR. Due to non‐uniformity across the breast coil, the residual fat contents were shown on the STIR image. For the uniformity of image intensity, the PIU was calculated as 89% in the STIR image.Conclusion:The results showed the potential of the BM modules and image QC modules in a image quality control for MRI based on the ability of task‐specific construction with modular manner.This study was supported by the Medical Metrology Program at the Korea Research Institutes of Standards and Science (16011069).
SU‐F‐J‐11: Radiobiologically Optimized Patient Localization During Prostate External Beam Localization
Authors: Huang Y , Gardner S , Liu C , Zhao B , Wen N , Brown S , Chetty I 
Published: July 2016

Purpose:To present a novel positioning strategy which optimizes radiation delivery with radiobiological response knowledge, and to evaluate its application during prostate external beam radiotherapy.Methods:Ten patients with low or intermediate risk prostate cancer were evaluated retrospectively in this IRB‐approved study. For each patient, a VMAT plan was generated on the planning CT (PCT) to deliver 78 Gy in 39 fractions with PTV = prostate + 7 mm margin, except for 5mm in the posterior direction. Five representative pretreatment CBCT images were selected for each patient, and prostate, rectum, and bladder were delineated on all CBCT images. Each CBCT was auto‐registered to the corresponding PCT. Starting from this auto‐matched position (AM‐position), a search for optimal treatment position was performed utilizing a score function based on radiobiological and dosimetric indices (D98_DTV, NTCP_rectum, and NTCP_bladder) for the daily target volume (DTV), rectum, and bladder. DTV was defined as prostate + 4 mm margin to account for intra‐fraction motion as well as contouring variability on CBCT. We termed the optimal treatment position the radiobiologically optimized couch shift position (ROCS‐position).Results:The indices, averaged over the 10 patients’ treatment plans, were (mean±SD): 77.7±0.2 Gy (D98_PTV), 12.3±2.7% (NTCP_rectum), and 53.2±11.2% (NTCP_bladder). The corresponding values calculated on all 50 CBCT images at the AM‐positions were 72.9±11.3 Gy (D98_DTV), 15.8±6.4% (NTCP_rectum), and 53.0±21.1% (NTCP_bladder), respectively. In comparison, calculated on CBCT at the ROCS‐positions, the indices were 77.0±2.1 Gy (D98_DTV), 12.1±5.7% (NTCP_rectum), and 60.7±16.4% (NTCP_bladder). Compared to autoregistration, ROCS‐optimization recovered dose coverage to target volume and lowered the risk to rectum. Moreover, NTCPrectum for one patient remained high after ROCS‐optimization and therefore could potentially benefit from adaptive planning.Conclusion:These encouraging results illustrate the potential utility of applying radiobiologically optimized correction for online image‐guided radiotherapy of prostate patients.
SU‐F‐J‐25: Position Monitoring for Intracranial SRS Using BrainLAB ExacTrac Snap Verification
Authors: Jang S , McCaw T , Huq M 
Published: July 2016

Purpose:To determine the accuracy of position monitoring with BrainLAB ExacTrac snap verification following couch rotations during intracranial SRS.Methods:A CT scan of an anthropomorphic head phantom was acquired using 1.25mm slices. The isocenter was positioned near the centroid of the frontal lobe. The head phantom was initially aligned on the treatment couch using cone‐beam CT, then repositioned using ExacTrac x‐ray verification with residual errors less than 0.2mm and 0.2°. Snap verification was performed over the full range of couch angles in 15° increments with known positioning offsets of 0–3mm applied to the phantom along each axis. At each couch angle, the smallest tolerance was determined for which no positioning deviation was detected.Results:For couch angles 30°–60° from the center position, where the longitudinal axis of the phantom is approximately aligned with the beam axis of one x‐ray tube, snap verification consistently detected positioning errors exceeding the maximum 8mm tolerance. Defining localization error as the difference between the known offset and the minimum tolerance for which no deviation was detected, the RMS error is mostly less than 1mm outside of couch angles 30°–60° from the central couch position. Given separate measurements of patient position from the two imagers, whether to proceed with treatment can be determined by the criterion of a reading within tolerance from just one (OR criterion) or both (AND criterion) imagers. Using a positioning tolerance of 1.5mm, snap verification has sensitivity and specificity of 94% and 75%, respectively, with the AND criterion, and 67% and 93%, respectively, with the OR criterion. If readings exceeding maximum tolerance are excluded, the sensitivity and specificity are 88% and 86%, respectively, with the AND criterion.Conclusion:With a positioning tolerance of 1.5mm, ExacTrac snap verification can be used during intracranial SRS with sensitivity and specificity between 85% and 90%.
SU‐F‐J‐30: Application of Intra‐Fractional Imaging for Pretreatment CBCT of Breath‐Hold Lung SBRT
Authors: Cao D , Jermoumi M , Mehta V , Shepard D 
Published: July 2016

Purpose:Clinical implementation of gated lung SBRT requires tools to verify the accuracy of the target positioning on a daily basis. This is a particular challenge on Elekta linacs where the XVI imaging system does not interface directly to any commercial gating solution. In this study, we used the Elekta's intra‐fractional imaging functionality to perform the pretreatment CBCT verifications and evaluated both the image quality and gating accuracy.Methods:To use intrafraction imaging tools for pretreatment verifications, we planned a 360‐degree arc with 1mmx5mm MLC opening. This beam was designed to drive the gantry during the gated CBCT data collection. A Catphan phantom was used to evaluate the image quality for the intra‐fractional CBCT. A CIRS lung phantom with a 3cm sphereinsert and a moving chest plate were programmed with a simulated breathhold breathing pattern was used to check the gating accuracy. A C‐Rad CatalystHD surface mapping system was used to provide the gating signal.Results:The total delivery time of the arc was 90 seconds. The uniformity and low contrast resolution for the intra‐fractional CBCT was 1.5% and 3.6%, respectively. The values for the regular CBCT were 1.7% and 2.5%, respectively. The spatial resolution was 7 line‐pairs/cm and the 3D spatial integrity was less than 1mm for the intra‐fractional CBCT. The gated CBCT clearly demonstrated the accuracy of the gating image acquisition.Conclusion:The intra‐fraction CBCT capabilities on an Elekta linac can be used to acquire pre‐treatment gated images to verify the accuracy patient positioning. This imaging capability should provide for accurate patient alignments for the delivery of lung SBRT.This research was partially supported by Elekta