bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐E‐T‐383: Using a Force Gauge to Detect the Treatable Length of a HDR Catheter
Authors: Liu L , Li W 
Published: November 2011

Purpose: Complex interstitial implant using flexible catheters often introduces tight curvatures or kinks in the catheters. The purpose of this study is to utilize a force gauge to determine potential blockage in HDR catheters, thus helping to create optimal deliverable treatment plans and to avoid potential treatment emergencies. Method and Materials: A VariSource iX HDR machine was used in this study. A compact digital force gauge from Wagner Instruments (Greenwich, CT) was used to measure the friction encountered in the catheters. A stainless steel telescoping‐type tube, about 5 cm long when retracted, was used to guide the check wire while it is being pushed into the catheter.A flexible catheter wrapped around a cylinder was used to find out the maximum push force of the VariSource HDR machine. The farthest position that the HDR machineˈs check cable advanced before reporting a blockage was marked, and the force gauge was then used to push a check wire to the same position and the gaugeˈs reading was recorded. Results: The maximum push force of the VariSource HDR machine as measured using the catheter‐around‐cylinder method was found to be about 1.4 lb. For a patient implant, once the problematic catheter(s) were identified during CT simulation, a treatment plan was developed using only unblocked catheters and reachable dwell positions. Conclusions: By using a force gauge to identify potential blockage in catheters a prior, optimal HDR treatment plan is developed using only unblocked catheters and treatable dwell positions. This avoids the need for modifying the plan at the time of treatment and reduces potential treatment emergencies.
SU‐E‐T‐390: Real‐Time Measurement of Urethral Dose and Position Using a RADPOS Array during Permanent Seed Implantation for Prostate Brachytherapy
Authors: Cherpak A , Cygler J , E C , Perry G 
Published: November 2011

Purpose: The new in vivo dosimetry tool, RADPOS, combines MOSFET dosimetry with an electromagnetic positioning sensor. It has recently been modified to include a MOSFET array rather than a single MOSFET for dose monitoring at five points along the detector axis. The detector is in use as part of a clinical trial which is the first to measure both urethral dose and internal motion concurrently during permanent seed implantation for prostate brachytherapy using a single probe. Methods: The RADPOS detector was secured inside a Foley catheter inside the patientˈs urethra. Spatial coordinates of the RADPOS detector were read every 0.5 s and the timing of events such as needle insertion was noted. MOSFET readings were taken over two ten minute periods once all seeds had been implanted both before and after the TRUS probe was removed. Results: Locations of the dosimeters could be inferred using a marker located at the end of the detector wire which is visible on fluoroscopy images. Although detector position varied slightly between patients, on average one dose point was inside the bladder, two/three dose points were within the prostatic urethra, and one/two dose points were at or inferior to the apex of the prostate. Maximum integral dose in the prostatic urethral ranged from 110–195 Gy, and it was found that the dose can change up to 63 cGy depending on whether the rectal probe is in place. The average change in displacement from the beginning of the procedure to the end for all patients was &#916;r=(5.5 ± 2.2) mm, with changes in individual coordinates of &#916;x (right/left) = (0.1–2.6) mm, &#916;y (superior/inferior) = (0.3–8.7) mm, and &#916;z (anterior/posterior) = (1.2–5.0) mm. Conclusions: The modified RADPOS is a powerful tool that can provide accurate real time dose and position information for use during prostate brachytherapy.This project has been supported by grants from The Health Technology Exchange, Ontario Research Funds RE‐04‐026, The Ottawa Hospital Cancer Centre Foundation and by financial and technical support from Best Medical Canada and Ascension Technology Corporation.
SU‐E‐T‐399: CT Image Artifacts from Brachytherapy Seed Implants: The Impact of Seed Size and Motion
Authors: Wells D , Basran P , Robertson A 
Published: November 2011

Purpose: To determine the impact of seed thickness on post‐operative CT image quality, seed detection and dosimetry, with and without breathing motion. Methods: An acrylic prostate phantom mounted to a computer controlled motion platform was created for both standard (5 × 1 mm)‐ and small (5 × 0.5 mm)‐diameter non‐radioactive I‐125 seeds (Oncura Inc., Arlington Heights, IL). Seed arrangement within the phantom was based on a patient brachytherapy plan. Ten low‐contrast inserts, 2, 5, and 10 mm in diameter with contrast differences of 2, 12 and 29 HU, respectively, were embedded in the phantom. Volumetric CT scans were performed while the phantom exhibited vertical, longitudinal and elliptical motion cycles of amplitudes 0, 2, and 5mm. Streak artifacts were quantified by sampling the standard deviation (SD) of pixel values over regions of interest (ROI) within the phantom volume. Soft tissue contrast was quantified by calculating the contrast to noise ratio (CNR) for each low‐contrast insert. Seed localization and dosimetry were assessed using VariSeed v8.0 (Varian Medical Systems, Palo Alto, CA) with prostate, rectal and urethral volumes copied from the patient plan onto the phantom. Results: Image noise was reduced with the small seeds for no motion cases (SD 49 vs. 32HU) and for 5mm amplitude cases (SD 60 vs. 37HU). CNR with the small seeds was higher by a median value of 55% for the low‐contrast ROIs. Although VariSeed identified more erroneous seed positions for the small seeds, there were no clinically significant dosimetric differences to the prostate, rectal or urethral volumes. Conclusions: The use of smaller seeds for prostate brachytherapy results in improved image quality of post‐operative CT scans, without hindering the ability in localizing the seeds or affecting the dose to the prostate, rectum or urethra, irrespective of motion parameters.Seeds used in this study were donated by GE Healthcare.
SU‐E‐T‐400: Evaluation of a Pencil Beam Algorithm and Pencil Beam Redefinition Algorithm for Bolus Electron Conformal Therapy
Authors: Kavanaugh J , Carver R , Chu C , Mancuso G , Hogstrom K 
Published: November 2011

Purpose: To evaluate the accuracy of the pencil beam algorithmˈs (PBA) and pencil beam redefinition algorithmˈs (PBRA) calculated electron conformal therapy (ECT) dose distributions by comparing with phantom measured dose distributions. Method: The planning target volumes (PTV) from a parotid and a chest wall patient were modified to fit the CT image set of a cylindrical polystyrene phantom. A bolus ECT plan for both PTV sets was developed using .decimal p.d software to design a custom bolus, with the distal bolus surface fitting to the phantom and the proximal bolus surface conforming the 90% isodose surface to the distal PTV edge. PBA and PBRA dose distributions were calculated using the Pinnacle treatment planning system and in‐house software, respectively. In‐phantom film measurements were taken for each plan in five transverse slices and one sagittal slice. Accuracy of both the PBA and PBRA calculations was tested by comparing the measured 2D film data to corresponding planar dose files from both the PBA and PBRA treatment plans, respectively. Passing criteria of 5% dose difference or 2mm distance to agreement were applied to each pixel (0.5mm pixel size) to quantify the accuracy of each dose calculation. Results: Comparison between measured and PBA calculated pixels for the post‐mastectomy chest wall and parotid cases for all 6 measured planes resulted in 93.3% and 95.3% pass rates, respectively. Using the same criteria, the PBRA had pass rates of 96.6% and 95.6%, respectively. In a phantom with no heterogeneities, the PBA and PBRA are both expected to have excellent agreement. Conclusions: The PBA and PBRA produced highly accurate calculations for bolus ECT dose distributions. As expected, the PBRA is slightly more accurate than the PBA, however this difference may not have any clinical significance unless significant heterogeneities are present, currently under study.Support: This work was supported in part by a research grant from .decimal, Inc.
SU‐E‐T‐410: Clinical Application of Dose Reconstruction Based on Full‐Scope Monte Carlo Calculations
Authors: Yeo I , Xu Q , Chen Y , Jung J , Kim J 
Published: November 2011

Purpose: To reconstruct dose delivered to a deformable phantom from images acquired by an electronic portal imaging device (EPID) using a full‐scope Monte Carlo based non‐iterative reconstruction method we have developed and to evaluate the delivered dose to the deformed organs using the resulting reconstructed dose. Methods: A deformable prostate phantom was embedded into a 20cm‐deep and 40cm‐wide water phantom. The phantom was CT scanned and the anatomical models of prostate, seminal vesicles, and rectum were contoured. A coplanar 4‐field IMRT plan was used for this study. The XVMC Monte Carlo code, XVMC, was used for verification of planned dose in phantom and calculation of dose response by EPID. Organ deformation was simulated by inserting a “transrectal” balloon containing 20ml of water and air. A new CT scan was obtained and the deformed structures were contoured. The IMRT plan was delivered to the two phantoms and integrated EPID images were respectively acquired. Dose reconstruction was performed using these images with calculated EPID responses. The deformed phantom was registered to the original phantom using an in‐house developed software based on the Demons algorithm. The transfer matrix for each voxel was obtained and used to correlate the two sets of the reconstructed dose to generate a cumulative reconstructed dose on the original phantom. Results: Forwardly calculated planning dose in the original phantom was compared to the cumulative reconstructed dose from EPID in the original phantom. The prescribed 200 cGy isodose lines showed little difference with respect to the “prostate” and “seminal vesicles”, but appreciable difference (3%) was observed at 210cGy dose level. Conclusions: The results validate our dose reconstruction method for EPID dosimetry. Organ deformation resulted small but observable dose changes in the target and critical structure.This study was in part supported by Varian Medical Systems, Inc.
SU‐E‐T‐684: Simple Integrated Tissue‐Air Ratio (SITAR)
Authors: Firpo M. A. , Chell E. 
Published: November 2011

Purpose: Performing direct depth‐dose measurements on the IRay ophthalmological SRS device (designed to treat wet age‐related macular degeneration), with its narrow (4mm), low energy (100kVp) photon beam is not feasible using currently available equipment. The constant SAD indicates use of Tissue‐Air Ratio (TAR). The imperfect water‐equivalency of available tissue‐equivalent plastics at these energies and the absence of small water‐proof, energy‐independent detectors make it impossible to measure TAR directly. The Simple Integrated Tissue‐Air Ratio (SITAR) is a novel method of determining depth‐dose for this novel device. SITAR is Simple in that it is measured simply using a tissue‐equivalent plastic, and applied simply as if to water. It is Integrated because it integrates all appreciable effects: inverse R‐squared divergence, attenuation in water and in tissue‐equivalent plastic, and scatter. SITAR is used to characterize the depth dose of individual IRay devices. Methods: The attenuation properties of three tissue‐equivalent plastics are compared to those of water by direct measurement. The scatter properties of these plastics are compared to scatter in water using Monte‐Carlo simulation. The most water‐like plastic in attenuation and scatter is selected for use in SITAR. Comparing the properties of plastic to water, determinations are made of the SITAR Correction: values that correct measurements taken through the plastic to measurements in water. The SITAR Correction enables a simple series of measurements through plastic to be corrected to a TAR in water. Results: Plastic Water LR (CIRS, Norfolk, VA) is found to be the most water‐like plastic for the IRay treatment beam. Kerma measurements made through varying thicknesses of Plastic Water LR and converted with the SITAR Correction yield a very good estimate of measurements in water. Conclusions: SITAR allows each IRay device to be characterized for depth dose in water simply by taking measurements through plastic.Research sponsored by Oraya Therapeutics.This work is funded by Oraya Therapeutics Inc., Newark, CA
SU‐E‐T‐775: Toward Web‐Based Real‐Time VMAT and IMRT Inverse Planning Using Cloud Computing
Authors: Na Y , Suh T , Xing L 
Published: November 2011

Purpose: To provide an efficient cloud computing infrastructure for VMAT and IMRT inverse planning. Methods: Amazon Elastic Compute Cloud (EC2) with a master node (17.1 GB memory, 2 virtual cores, 420 GB instance storage, 64‐bit platform) is used as the backbone of cloud computing for VMAT and IMRT dose optimization. The master node is scalable on an “on‐demand” basis. It can lunch more workers if the CPU usage exceeds the upper limit for given time (e.g., over 90% usage for 2 minutes), or terminate the workers if there are finished tasks. A quadratic objective function with volumetric constraints is expressed as a function of the aperture shapes and weights of the incident beams. A Monte Carlo simulation is employed to generate accurate dose kernel by parallel tasks. The number of parallel tasks is approximately the same as or less than the total number of beamlets in iterative simulation for all beams. The cloud optimization is implemented for a Varian TrueBeam STX linac beams with and without flattening filters available. The filed output from EC2 is sent down to the Simple Storage Service (S3). Three clinical cases have been studied for the purpose of evaluating the performance of the new planning platform. Results: A cloud computing environment leads to speedups of 150–300 times for the cases considered in this study. The speedup scales approximately linearly with the number of nodes used for computing. The resultant plans from the cloud computing are found almost identical to that obtained using a desktop PC, indicating the reliability of the cloud computing platform. Conclusions: A cloud computing infrastructure has been established for VMAT and IMRT inverse planning with different beam characteristics. The cloud computing environment substantially improves the speed of inverse planning and makes future on‐treatment adaptive replanning possible.This work was supported by grants from the National Research Foundation of Korea (NRFK) of the Korea Government (MEST) (Grant No. K20901000001‐09E0100‐ 00110)
SU‐E‐T‐811: A Comparative Study of Replanning at the Midcourse and the Latter Course during Intensity‐Modulated Radiotherapy for Patients with Nasopharyngeal Carcinoma
Authors: Yang H , Wang W , Yu C , Shan G , Hu W 
Published: November 2011

Purpose: The aim of replanning at the midcourse and the latter course was to illustrate the superior timing of replanning during intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) patients. Methods: Twenty‐three NPC patients received IMRT in 33 fractions were enrolled. Each patient with two repeated CT scans before the 16 fraction and before the 25 fraction, respectively. The anatomic changes were determined in the three CT scans. The differences of the dose distribution were compared in inital plan vs. phantom plan 1 and replanning 1vs. phantom plan 2. Results: The mean decrements of the transverse diameter of nasopharyngeal level (d1) and the transverse diameter of the neck level (d2) were 4.66mm, 2.63mm and 7.94mm, 5.78mm before the 16th and 25th fraction. The target volume reduced mainly in the first half. The mean decrements of volume GTVnx and GTVnd were 12.20cc, 8.91cc and 18.25cc, 13.71cc before the 16th and 25th fraction. While the volume of the parotid glands reduced mainly in the second half. The mean decrements of the left and right parotid glands volume were 1.40cc, 1.98cc and 6.31cc, 6.08cc before the 16th and 25th fraction. But the dose changes of bilateral parotids were more prominent in the first half than in the second half. There was a statistically significant increase in the mean dose and V30 to the bilateral parotid only in the first half (P < 0.05). Based on dose constraint criterion in the RTOG0225 protocol, the dose of the normal critical structures for 39.13% (9/23) were out of limit comparing to in the first half than 17.39(4/23) in the second half. Conclusions: Replanning at the midcourse may reach more benefits both in the coverage of the targets and sparing of normal structures for NPC patients.This study was supported by Zhejiang Provincial Medical and Health science Foundation of China (2008B198).
SU‐E‐T‐815: Deformable Registration and Cumulative Dose Records as Applied to Patients with Cervical Carcinoma
Authors: Hooker C , Scanderbeg D , Yashar C , Cerviño L 
Published: November 2011

Purpose: Use daily patient imaging to calculate cumulative dose to target and organs at risk during the course of radiation treatment for cervical cancer patients and compare with the planned dose.Methods: Daily cone beam CT (CBCT) scans were taken for 10 patients during their cervical cancer radiation therapy treatment course. Dose from the treatment plan was calculated on each of the CBCTs. Deformable registration was performed on each of the daily CBCTs in order to map the patientˈs daily anatomy and dose onto the planning CT (reference). The cumulative dose was then calculated and the Dose Volume Histogram (DVH) of the cumulative dose was compared to the DVH of the original planned dose. Results: The DVH for the calculated cumulative dose deviated from the DVH of the actual dose due to changes in the patientsˈ daily anatomy. The planning target volume (PTV) showed similar coverage; however, the dose received by the organs at risk (OARs) differed from the original plan. Conclusions: Since patient anatomy varies on a daily basis, daily imaging combined with deformable registration and cumulative dose calculations yields an accurate dose to target and organs at risk. This dose information can then be used by the clinician to guide additional radiation therapy to boost target dose and spare OARs.This work was supported by Varian Medical Systems, Inc.
SU‐E‐T‐854: Key Anatomical Factors Influencing OAR Dose‐Volume Distribution in Prostate IMRT Plans
Authors: Yuan L , Ge Y , Li T , Zhu X , Yin F , Wu Q 
Published: November 2011

Purpose: To identify the key factors of patient anatomy that influence the optimal dose volume histograms (DVHs) for the organs‐at‐risk (OARs) and to explore the tradeoffs between different OAR sparing goals. Methods: 88 prostate IMRT plans were studied retrospectively. The PTV‐OAR (bladder and rectum) geometry was described by the distance‐to‐target histogram (DTH) with a variable distance model to reflect the co‐planar beam configuration. Principal Component (PC) analysis was applied to DVH and DTH distributions in the patient pool to extract their salient features. The PCs were interpreted in terms of the patient anatomy and dose‐volume distribution metrics. The correlation coefficients between the PCs and these metrics were calculated. Finally, a stepwise multiple regression method was used to quantify the influence of these key anatomy parameters on the quality of corresponding DVHs. Results: The first PCs of DTH and DVH characterize the means of the histograms; the second PCs characterize the gradients of the histograms within a range. The most significant factor contributing to the first PC score (PC1) of DVH is the PC1 of DTH. It represents the correlation between the mean distance and the mean dose. The DVH PC2 is correlated with the DTH PC2, indicating the influence of DTH gradient on the gradient of DVH. Another significant factor affecting DVH PC2 is the fraction of OAR volume outside treatment fields with co‐planar beam setting. These factors combined account for significant majority of the cross patient DVH variation in the OARs: with the determination coefficients R, 2</sup>=0.88 and R, 2</sup>=0.85 for PC1 and PC2 of bladder, respectively, and R, 2</sup>=0.68 and R, 2</sup>=0.69 for PC1 and PC2 of rectum, respectively. Conclusions: Key factors representing the influence of patientˈs anatomy on the corresponding DVHs are extracted and quantified. This knowledge can be used to predict patient specific DVHs in IMRT planning.Duke Univesity has a master research agreement with VARIAN Systems, Inc..
MO‐D‐220‐10: Automatic Quality Control Processing for Detection of Elements Dropout in Ultrasound Transducers
Authors: Padilla F , Carson P , Hooi F , Goodsitt M , van der Spek S , Larson S , Hanes C 
Published: November 2011

Purpose: To develop a simple and reliable method of detection of lost or reduced sensitivity elements in diagnostic ultrasound arrays through analysis of the systematic features evident in appropriately acquired cineloops Methods: An algorithm was developed to detect the systematic features produced by element/channel signal loss evident in a cineloop acquired with a random background signal: A temporal median of the cineloop is produced followed by construction of a profile defined as the mean over depth [column‐wise mean] within a horizontal strip of the median image. A modified anisotropic diffusion filter is applied to the profile to isolate outlying features from characteristic noise, and simple statistical methods are then used to identify regions of the profile which exhibit characteristics of reduced sensitivity elements such as well‐defined, symmetric troughs. With an element occluded by fishing line to simulate dropout, cineloops were acquired with a GE‐Logiq 9 scanner either by rapidly scanning a transducer over a tissue mimicking phantom or by placing the transducer in a liquid phantom composed of an agitated cornstarch and water suspension. Results: Analysis with the algorithm clearly revealed the occluded section of the array as well as previously unnoticed reduced‐sensitivity elements. The efficacy of a simple and inexpensive method of detecting lost or reduced sensitivity elements of diagnostic ultrasound arrays was demonstrated in a confined dataset. The algorithm has been developed into an ImageJ plugin which presently handles uncompressed DICOM data containing rectangular scan regions; this should soon be made available for use by the medical ultrasound community after testing by Ultrasound Subcommittee members.Supported in part by the Ultrasound Subcommittee of the AAPM Science Council andNIH Grant CA91713