bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐FF‐J‐16: A Tool for Off‐Line Review of 3D Target Verification and Localization with Cone‐Beam Computed Tomography
Authors: Wu Q , Yan H , Yin F , Yoo S , Das S , Willett C 
Published: July 2006

Purpose: To implement a clinical tool for off‐line review of Cone‐Beam Computed Tomography (CBCT) based 3D target verification and localization. Methods and Materials: An in‐house 3D target localization and verification tool is being developed to allow physicians and physicists to review daily treatment target off‐line. The system provides quick initial target verification via user selected landmark points. An automatic gray‐scale registration technique provides fine‐tuning of the 3D target localization. It also allows the preference of soft‐tissue weighted vs. bony landmark weighted registration. A rigid body 3D‐image registration method, using a combination of correlation coefficient and mutual information measurements, has been developed. The registration algorithm uses a downhill simplex optimization technique to search for the best match of the two image sets. This study evaluates the efficacy and accuracy of the system. First, each CBCT and CT pair is manually registered by a human expert. Then these CBCT are input to the software to be registered with the planning CT. The comparison of the computer calculated 3D correction against the manual alignment evaluates the accuracy of the system. Results: 5 CBCT sets of prostate cancer patients are tested. The registration is bone weighted to simulate actual treatment target position. For all cases, the bone structures are well superimposed on the fused images. However, part of the prostate and rectum shown certain degree of mismatch due to different rectal fillings between CBCTs and CTs. Overall registration accuracy is as accurate as 1 mm and 1 degree for bone structures. Conclusion: An off‐line 3D target localization review tool was implemented. For prostate cases, its accuracy is acceptable for clinical use. Further implementation of the tool to other disease sites and evaluation of soft tissue vs. bone based target localization is underway.Partially supported by a Varian research grant.
SU‐FF‐J‐85: Inter‐Observer Variation In The Planning Of Head/Neck Radiotherapy
Authors: Lu L , Cuttino L , Barani I , Song S , Fatyga M , Murphy M , Keall P , Siebers J , Williamson J 
Published: July 2006

Purpose: Understanding inter‐observer variation is not only important for evaluating deformable image registration (DIR) which can be used to automatically transform the manual contours of a treatment plan into daily contours facilitating offline or online adaptive radiotherapy, but also helps physicians set reasonable margins on the regions of interest (ROI) when they make treatment plans. The purpose of this study is to determine the observer variation for Head/Neck patients using the implemented radial‐difference approach and the common‐area method to study the observer‐drawn contour pairs. Method and Materials: Two sets of images for each of seven head and neck patients were taken several weeks apart, and the original image sets were used for treatment plans. For each image set, the ROIs: Primary GTV, Nodal GTV, Cord, left Parotid, and right Parotid were contoured by three experienced physicians. The difference of two contours drawn by different physicians was measured using: (1) the radial difference of the paired contours where the center‐mass of a contour is used as the origin of the polar coordinate system, and (2) the ratio of the common area of two contours over the total area of those contours, R=2[C1∩C2/(C1∪C2)]. Results for all the ROI are plotted in histograms to quantify the observer variation.Results: The radial differences for primary GTV, nodal GTV, cord, left parotid, and right parotid are 2.7 ± 2.0 mm, 2.4 ± 1.9 mm, 1.8 ± 0.8 mm, 2.6 ± 2.1 mm, and 2.5 ± 1.9 mm, respectively, and the values of R are 0.75 ± 0.14, 0.82 ± 0.11, 0.82 ± 0.07, 0.80 ± 0.10, and 0.80 ± 0.12, respectively. Conclusion: The inter‐observer variations in the planning of Head/Neck patients are about 3 mm for Cord and 5 mm for the others. These values place an upper limit on the accuracy of DIR algorithm.
SU‐FF‐T‐413: The Deviation of Leaf Position in DIMRT
Authors: Lo C , Huang Y , Huang H , Hong J 
Published: July 2006

Purpose: To analysis the deviation of leaf position on fraction size and on dose rate in dynamic IMRT (DIMRT). Methods and materials: The shape of target, which is similar to 60° wedge profile, was drawn at 11.5cm depth in phantom on the Eclipse system. The field size is set as 11.3*16.0 cm2 and energy used is 6 MV. The constraint of optimization of target is kept the same, using single portal, for different fraction sizes which varied from 500cGy/fx to 5cGy/fx. The treatment file is transferred to LINAC for beam‐on at Varian 21EX. The MLC log file is analyzed using MLC dynalogfile viewer 6.2.0. We varied the dose rate during beam‐on for the same treatment file to take the leaf deviation data. Results: Dose rate 300MU/min is using in clinical treatment. It is the least error for dynamic leaf for the biggest fraction size with single portal. The quantity, field width multiplied dose rate then divided by MU, is used to evaluate the average speed of dynamic leaf. The evaluated average speed is 89.2 (cm/min) and 121.1 (cm/min) for 10cGy/fx and 5cGy/fx respectively and the larger speed caused the large average deviation around 0.4mm and 0.6mm respectively. The maximum deviation is 1.0mm and has 37.7% in deviation histogram for the smallest fraction size, 5cGy/fx.For the same fraction size, 5cGy/fx, the dose rate affected the leaf deviation too. A larger dose rate has larger average leaf speed and a large deviation too. Our data showed the average speed is 242.2 (cm/min) and the average deviation is 0.9mm for dose rate 600MU/min. With this dose rate, the maximum deviation is 2.5mm and has 14.3% in deviation histogram. Conclusion: The positions accuracy is better for lower dose rate even with a large dose fraction.
SU‐FF‐T‐414: The Dose Area Product in Radiation Therapy‐ a New Concept for the Parameterisation of Small Fields
Authors: Poppe B , Djouguela A , Rubach A , Harder D , Willborn K 
Published: July 2006

Purpose: To establish a new parameterisation of small fields.Material and Methods: The traditional parameterisation of a narrow photon field via the central axis dose and the relative transversal dose profile has met considerable methodical complications. These difficulties are to find a sufficiently small detector, to adjust the detector accurately on the axis of the narrow beam and to find a detector material not responding to lateral changes of the electron spectrum within the small field. These obstacles can be avoided by reconsidering the parameterisation of the narrow‐field dose distribution. The new parameter recommended for characterising the absolute dose values in a plane perpendicular to the beam axis is the dose‐area product DAP (the area integral of the dose in this plane). It can be measured with a flat ionisation chamber of large cross section of the sensitive volume. Results and Conclusions: The radial adjustment of the large area chamber is by no means critical. The dose‐area product provides a simple normalisation of the relative transversal dose distribution which can be measured with radiochromic film. We have investigated the abilities of a large‐area flat ionisation chamber of PTW Freiburg (PTW TM 34070‐2,5) of 8,1 cm diameter and 2 mm thickness of the sensitive volume to measure the DAP of narrow photon beams with side lengths up to 5 cm. A modified output factor has been defined as the quotient of the DAP, measured at 5 cm phantom depth for SSD 100 cm distance of the phantom, and the monitor reading. Besides the useful feature of the DAP is its direct measurability during patient treatment by means of the DAVID chamber, an on‐line monitor arranged in the accessory holder, so that non‐negligible deviations of the actual from the chosen field size of narrow photon fields can be immediately detected.
SU‐FF‐T‐421: The Influence of Field Length, Pitch, and Modulation Factor On the Quality of Helical Tomotherapy Plans
Authors: Bhavin C , Langen K , Meeks S , Zeidan O , Jeswani S 
Published: July 2006

Purpose: The planning process for helical tomotherapy plans is governed by three basic planning parameters: field length, pitch ratio, and modulation factor. The purpose of this work is to evaluate the influence of each parameter on the achievable plan. Method and Materials: Using commercial treatment planning software (TomoTherapy, Inc.) the same head and neck case was re‐planned by the same person using different planning parameters. The standard settings (field length of 25 mm, pitch of 0.287 and modulation factor of 2.5) were used to generate a baseline plan. Using the standard settings for two parameters the third parameter was varied for different plans. Three field lengths (10, 25, 50 mm), four pitch ratios (0.2, 0.287, 0.5, 1) and seven modulation factors were used (1.5, 2, 2.5, 4, 6, 8, 10). The plans were evaluated in terms of treatment time, target coverage, conformity, and sensitive structure sparing. Results: Increasing the pitch ratio leads to an increase in the volume of unspecified tissues that receives prescription dose (less conformal plans) and an increase in the dose to sensitive structures. The treatment time did not significantly reduce with increasing pitch (there are fewer gantry rotation but the gantry rotation period increases).Similarly, an increased modulation reduces the dose to unspecified tissue and sensitive structures. However the cost is an increased treatment time. Using a larger field length increases the dose to unspecified tissue and sensitive structures while reducing the treatment time. All plans achieved acceptable target coverage and homogeneity. Conclusions: Changing the planning parameters mainly affects plan conformity. It appears that with respect to our standard settings a slight reduction of the pitch or a slight increase in the modulation factor should improve plan quality with a modest increase in treatment time. Conflict of Interest: One co‐author is employed by TomoTherapy, Inc.
SU‐FF‐T‐432: Time‐Delay Measurement of a Varian Real‐Time Position Management System
Authors: Hanna G , Wang Z , Yin F 
Published: July 2006

Purpose: Respiratory gating systems have been developed to reduce treatment uncertainty caused by organ motions related to respiration. The time‐delay between when the gating signal is triggered and when the beam is turned on may affect the actual radiation dose delivered. In this study, we investigated the time delay for a Varian real‐time position management (RPM) respiratory gating system. Method and Materials: A motion phantom with infrared markers was used to simulate a respiration signal. A small metal target ball was also attached to the phantom. An infrared camera was used to observe the motion of the phantom and to plot out a true motion curve. A narrow 2% phase gating window was set at various phases of 0%, 10%, 20%… and 90%. Electronic Portal Vision images were taken with a Varian Linear Accelerator at various phases of the simulated breathing cycle, and the location of the target ball was then plotted verses time to give a measured motion curve. The shift in time between the RPM gating signal and motion curve from portal imager was then measured to determine the time delay in the gating system. Results: The time‐delay in Varian's gating system was found to be 0.0173 seconds. Conclusion: This work shows that there was a short time delay between the gating signal and the time when the radiation beam is turned on. The effect of time‐delay on patient dosimetry needs to be further investigated.Partially supported by Varian research grant.
SU‐FF‐T‐448: Validation of a New Photon Dose Calculation Model—Analytical Anisotropic Algorithm
Authors: Rong Y , Mubata C , Chisela W , Jaradat H , Tewatia D , Paliwal B 
Published: July 2006

Purpose: To validate a new photon dose calculation model Analytical Anisotropic Algorithm (AAA) on Eclipse™ treatment planning system (TPS). Comparison of AAA dose calculation was performed with measurements and other two conventional algorithms, Pencil Beam Convolution (PBC) algorithm on Eclipse™ and Collapsed Cone Convolution/Superposition (CCC) algorithm on Pinnacle3.0 TPS.Method and Materials: Four phantoms were CT scanned and the image set was imported into both TPS for dose computation and analysis. The four phantoms were: 1) homogenous tissue equivalent phantom, 2) tissue equivalent phantom with infinite lung heterogeneity, 3) tissue equivalent phantom with finite lung, 4) IMRT dose verification phantom. Measurements were made by exposing the phantom using Varian Linac. Point measurement and film measurements were compared with calculated results from the three algorithms. Dose responses for high and low energy photon beams were investigated for several different depths and PDD curves were compared in the phantom for various field sizes. The IMRT plans were generated by both TPS and were performed on the IMRT phantom to compare fluence maps. Results: AAA dose prediction fits the film measurements well except that there is up to ±6% discrepancy for dose profile perpendicular to the interface of tissue and lung. Point measurements support the AAA algorithm calculations. AAA also accurately predicts the decrease in PDD curves due to the lung inhomogeneity for 6MV energy. For the high energy photon beam and very small field size (2cm*2cm) in lung region, AAA prediction is up to 8% lower than the measurements. Conclusion: AAA algorithm accounts for attenuation corrections and electron transport, and models the deposited dose in the lung with greater accuracy than PBC. It is also faster than CCC algorithm. AAA algorithm can not accurately model the lateral scattering in tissue heterogeneity, but it can still give a reasonably close (within ±6%) prediction.
SU‐FF‐T‐449: Validation of a Plan‐Based Calibration Method for Relative Dosimetry of IMRT
Authors: Olch A 
Published: July 2006

Purpose: Validation of a new “plan‐based” image calibration method for IMRT relative dosimetry comparisons. Method and Materials: Radiological Imaging Technology image analysis software (version 4.2) contains a new calibration routine called plan‐based calibration (patent pending). After registration of a 2‐D dose image from the planning system with a measured but uncalibrated dose image, the routine then maps the planning system doses to each film or CR image pixel value and constructs a calibration curve. This calibration curve is then applied throughout measurement image to convert all pixels to dose. Because it does not use an independent dose vs. pixel calibration, it can be used for relative dosimetry only. Ten IMRT cases were studied for which both conventional dose calibration using parallel irradiation of film and the plan‐based calibration were used. The Gamma value was used as a measure of agreement where 3% dose and 3 mm distance to agreement were set as tolerances. For these same cases, a 5 mm registration error was introduced and the comparison repeated. Results: In all properly registered cases, the plan‐based calibration had fewer pixels with Gamma >1 than did the conventional calibration. Overall, the plan‐based method gave 50% fewer pixels with Gamma > 1 than did the film‐based calibration. This may be due to additional errors of the film calibration process convolving with intrinsic planning system, phantom setup, and film processing and scanning errors. The plan‐based calibration was equally able to detect the registration error by giving a similarly large increase in percentage of pixels with Gamma >1.Conclusion: These data suggest that the plan‐based calibration method provides a more accurate comparison of the measured vs. calculated dose distribution than conventional calibration methods using less time and materials. Conflict of Interest: This research was supported by Radiological Imaging Technology.
SU‐FF‐T‐452: Verification of Cell Irradiation Dose Deposition Using Radiochromic Film
Authors: Tomic N , Gosselin M , Wan J , Saragovi U , Evans M , Podgorsak E , Devic S 
Published: July 2006

Purpose: A standard technique for cell survival curve determination is based on the cell culture technique. Survival curve is reconstructed by plotting the fraction of surviving cells as a function of delivered dose. We describe a technique that irradiates all cells at once by using two wedges (static and dynamic wedge concurrently) on a linear accelerator whereby we irradiate the multi‐compartmental dish to a desired dose range from 1 – 5 Gy. We also employed EBT model GAFCHROMIC™ film to verify the dose delivered in each of the compartments within the dish. Our technique overcomes the problem of possible contamination during the re‐plating after irradiation and all cells are kept under the same conditions.Method and Materials: Cells, plated within a multi‐compartmental (8 × 12) dish were irradiated using a 6 MV photon beam employing a combination of 60° physical (“static”) wedge and 60° Enhanced Dynamic Wedge. A 10 cm by 12.5 cm piece of EBT film was positioned below cells. Spatial dosimetry was performed using the AGFA Arcus II document scanner. The change in optical density of the unexposed film piece was subtracted from the exposed film piece to obtain the final netOD that was converted to dose using previously determined calibration curve for the reference type dosimetry. Results: Technique described delivers a dose gradient ranging from 1 Gy within the first compartment to 5 Gy within the last compartment. Maximum relative uncertainty of 2% was observed at 5 Gy. Conclusions: In this work, we describe a technique using a combination of static and dynamic wedge to obtain doses necessary to reliably perform MTT Assay in a dose range from 1 Gy to 5 Gy within a multi compartmental dish. We have also described a method to verify the dose delivered using the EBT model radiochromic film.
SU‐FF‐T‐465: Relating Changes in Pulmonary Functin Tests (PFTs) to Changes in Radiation‐Induced Regional Lung Perfusion
Authors: Mao J , Zhang J , Zhou S , Folz R , Wong T , Marks L 
Published: July 2006

Purpose: To further assess if RT‐induced changes in pulmonary function tests (PFTs) can be prospectively predicted based on the sum of predicted RT‐induced changes in regional lung perfusion. Method and Materials: Between 1991 and 2005, 123 evaluable patients with lung cancer underwent pre‐ and post‐RT PFTs (forced volume capacity [FVC], forced expiratory volume in one second [FEV1] and diffusion capacity for carbon monoxide [DLCO]) as part of a prospective trial. Patients with recurrence or death within 6‐month post‐RT were excluded. The maximal declines in PFTs were noted. The anticipated decline in PFTs was computed by summing the predicted reductions in regional perfusion, throughout the lung, based on a previously‐defined population dose‐response model [DRC] and the patient's pre‐RT SPECT (single photon emission computed tomography) lung perfusion scan. This “integrated response” is also termed the overall response parameter (ORP):
urn:x-wiley:0094-2405:media:mp1379:mp1379-math-0001 where Vd is the percentage volume of lung irradiated to dose d, and Rd is the predicted reduction in regional perfusion at dose d based on a population DRC. Correlations between predicted and measured changes in PFTs were evaluated using 2‐tailed Pearson test. Results: There was a statistically‐significant association between the reduction in PFTs (i.e. FVC and DLCO) and ORP, p<0.01; however, correlation coefficients were low (range: 0.24–0.35). Correlations were better in the subgroup of patients without large central tumors (i.e. those often with associated hypoperfusion of adjacent lung on the pre‐RT SPECT) and with more than 2 follow‐up PFTs post‐RT (range: 0.41–0.62). Conclusion: The sum of predicted RT‐induced changes in regional perfusion is related to RT‐induced changes in PFTs, however, correlations are relatively weak. These findings are consistent with our prior analysis involving fewer patients and continue to illustrate that predicting changes in PFTs is extremely challenging.Supported partly, by NIH grant R01‐CA69579. Thanks to UNC for PLUNC planning software.
MO‐A‐ValA‐01: The Role of the Physicist in the Planning and Design of Digital Image Management Systems (PACS)
Authors: Langer S 
Published: July 2006

The classically trained medical physicist strives to yield maximum diagnostic information from an exam with minimal impact on patient health (i.e. by minimizing dose). This simple objective means that in practice the physicist must: become expert on following the latest technological developments across modalities to assist in equipment purchases, monitor and oversee the imaging protocols used at an institution, and monitor the equipment performance over its lifetime.As the department transitions to filmless radiology, the mission remains the same, but the scope of implementation increases. The DICOM services that an imager supports are analogous to the filming options supported of yesteryear. The H&D curve of film days maps to the DQE and JND of today's detectors and displays. Quality Control encompasses not only median film density of a laser camera and MTF of a CT, but how those image properties propagate from acquisition to final display device. The key point to realize is the medical physicist is uniquely empowered to have a holistic systems view of the imagers, PACS, RIS and the needs to QC the entire chain.In this lecture, we will discuss the value add that the medical physicist provides due to the unique collection of training and skills we possess.Educational Objectives:1. Compare and contrast the classic role of a medical physicist in the film based department verses the filmless radiology department.2. Identify the areas of technology and practice where the Medical Physicist adds value.3. Case studies of cost savings made possible by the practice knowledge that a medical physicist brings to the table that IT staff may not have.
MO‐A‐230A‐01: Monte Carlo I: Source Modeling and Beam Commissioning for Treatment Planning
Authors: Ma C 
Published: July 2006

In this presentation, we will discuss source modeling and beam commissioning for Monte Carlo treatment planning. We will review the current status of Monte Carlo simulations of clinical photon and electron beams and the theories and methodologies used in particle phase space representation and reconstruction for Monte Carlo dose calculation. We will discuss the sensitivity of beam characterization to simulation details, such as beam energy, angle, intensity, and details of the treatment head design. We will review different source models for photon and electron beam characterization and discuss the accuracy and efficiency tradeoffs between full phase space and simplified source models. We will describe the methods and software that have been developed for source modeling and beam commissioning for the clinical implementation of the Monte Carlo method for treatment planning and beam delivery verification. We will present different methods for source parameterization based on simulated phase space data and a standard set of measured beam data including in‐air and in‐phantom output factors and in‐phantom dose distributions.Educational Objectives:1. Describe the Monte Carlo method for clinical photon and electron beam simulations.2. Review theories and methodologies for phase space representation and reconstruction.3. Present different source models for Monte Carlo dose calculation.4. Describe different methods for source parameterization and beam commissioning.