bluuebunny/crossref_metadata_2025 huggingface dataset:
SU‐D‐BRCD‐05: Evaluation of New Exit Detector Based Transit Dosimetry Software for TomoTherapy Treatments
Authors: Levinson L , Ding K , Chen Q , Renner W , Benedict S , Read P
Published: June 2012

Purpose: The prospect of 3D transit dosimetry to verify treatment delivery is a novel and emerging technology in TomoTherapy. Math Resolutions, LLC, has expanded their Dosimetry Check (DC) quality control software to include transit dosimetry calculations for TomoTherapy treatments. The data recorded by the MVCT detectors during patient treatment is used in conjunction with the planning CT to calculate the delivered dose to the patient from each fraction. This study presents a summation of our experiences at the University of Virginia in collaboration with Math Resolutions in verifying and implementing the transit‐dose calculation aspects of this new TomoTherapy specific product. Methods: Low and high modulation cheese phantom plans and clinical plans (prostate, GYN, pituitary, and thoracic vertebra) were used to evaluate the DC transit dosimetry software. The TomoTherapy planning CT, structure set, plan, and dose for each plan were imported into the DC software. The fluence maps were reconstructed from the exit detector data by correcting for patient attenuation and used to compute the delivered dose. The resulting dose distribution is compared with the TPS planned dose using isodose line comparison and gamma index. Results: The percent difference between the planned and DC calculated doses ranged between 0.63% for a low modulation cheese phantom plan to 5.94% for a prostate plan. Using criteria of 3%, 3mm, the gamma index passing rate for the tested plans ranged from 94.7% to 99.1% <1 for the overall patient area and from 88% to 96.4% for the treatment area receiving at least 80% of the prescribed dose. Conclusions: The results from our evaluation of Math Resolutions' DC look promising and generally within an acceptable range for portal dosimetry programs. Further investigations will include developments to improve the DC algorithm and determine how it can best be implemented in a typical TomoTherapy clinical workflow. Research Grant from Math Resolutions LLC 01/12/2012‐01/11/2013 Math Resolutions™ Dosimetry Checksoftware was given to UVa to assist with evaluating the precision of the product in reconstructing dose from the TomoTherapy exit detector data.
SU‐D‐BRCD‐06: Measurement of Elekta Electron Energy Spectra Using a Small Magnetic Spectrometer
Authors: Hogstrom K , McLaughlin D , Gibbons J , Shikhaliev P , Clarke T , Henderson A , Taylor D , Shagin P , Liang E
Published: June 2012

Purpose: To demonstrate how a small magnetic spectrometer can measure the energy spectra of seven electron beams on an Elekta Infinity tuned to match beams on a previously commissioned machine. Methods: Energyspectra were determined from measurements of intensity profiles on 6″‐long computed radiographic (CR) strips after deflecting a narrow incident beam using a small (28 lbs.), permanent magnetic spectrometer. CR plateexposures (<1cGy) required special beam reduction techniques and bremsstrahlung shielding. Curves of CR intensity (corrected for non‐ linearity and background) versus position were transformed into energy spectra using the transformation from position (x) on the CR plate to energy (E) based on the Lorentz force law. The effective magnetic field and its effective edge, parameters in the transformation, were obtained by fitting a plot of most probable incident energy (determined from practical range) to the peak position. Results: The calibration curve (E vs. x) fit gave 0.423 Tesla for the effective magnetic field. Most resulting energy spectra were characterized by a single, asymmetric peak with peak position and FWHM increasing monotonically with beam energy. Only the 9‐MeV spectrum was atypical, possibly indicating suboptimal beam tuning. These results compared well with energy spectra independently determined by adjusting each spectrum until the EGSnrc Monte Carlo calculated percent depth‐dose curve agreed well with the corresponding measured curve. Conclusions: Results indicate that this spectrometer and methodology could be useful for measuring energy spectra of clinical electron beams at isocenter. Future work will (1) remove the small effect of the detector response function (due to pinhole size and incident angular spread) from the energy spectra, (2) extract the energy spectra exiting the accelerator from current results, (3) use the spectrometer to compare energy spectra of matched beams among our clinical sites, and (4) modify the spectrometer to utilize radiochromic film.
SU‐D‐BRB‐05: Small Animal Lung Compliance Imaging: Assessment System for Tissue Sensitivity to Radiation Induced Lung Injury
Authors: Ding K , Deng J , Du K , Cao K , Christensen G , Reinhardt J , Sheng K , Libby B , Benedict S , Lamer J , Chen Q
Published: June 2012

Purpose: Recent clinical trials and animal studies have indicated that the tissue sensitivity to radiation induced lung injury (RILI) may be region‐ specific. In this study, we propose a new 4D cone beam CT (CBCT) basedcompliance imaging method to measure regional pulmonary function change in precisely irradiated small animal under CBCT guidance on small animal radiation research platform (SARRP) to facilitate our understanding of region‐specific tissue sensitivity to RILI. Methods: Four Sprague‐Dawley rats underwent prospective pressure gated 4D CBCT on SARRP. Three animals were selected as control group which underwent a second 4D CBCT scan. The fourth animal was irradiated in the central lung (24 Gy) using 3 × 3 mm collimating cone 2 months prior to the scan. The specific compliance (Csp) was calculated via the real time pressure measurement from the ventilator and displacement field from 3D B‐spline image registration between the end of inhale and end of exhale phases from the 4D CBCT scan. The 3D Csp maps from the control animal group were mapped to the irradiated animal as a Csp functional atlas for statistical analysis. We alsoevaluated the repeatability of the Csp measurement on a voxel‐by‐voxel basis. Results: No significant Csp difference is found after two month of radiation between the irradiated rat (0.22±0.05) and the functional atlas (0.21±0.07). The observation is consistent with previous publications. The averaged linear correlation coefficient between the voxel‐by‐voxel Csp measurements from initial and repeat scans in control group is 0.98.Conclusions: We proposed a method that uses 4D CBCT based compliance imaging to measure region‐specific tissue sensitivity of RILI. We compared the irradiated animal two months after radiation with the control group. Our study shows an excellent robustness of the proposed method for regional lung tissue specific compliance measurement. This work was supported in part by UVa George Amorino Pilot Grant
SU‐D‐BRA‐01: Accurate Real‐Time Tumor Motion Estimation from Respiratory Surrogates via Memory‐Based Learning
Authors: Li R , Xing L
Published: June 2012

Purpose: Respiratory tumor motion is a major challenge in radiation therapy. Effective beam gating or tracking approaches necessitate an accurate knowledge of the real‐time tumor motion. Fluoroscopic tracking with implanted fiducial markers is invasive and exposes the patient to additional imaging dose. Respiratory surrogate signal measured by external noninvasive and non‐ionizing devices provides an attractive approach, in which estimating the tumor motion from respiratory surrogates is crucial. Methods: We utilize a powerful memory‐based learning approach to find the complex relations between tumor motion and respiratory surrogates. The learning method uses locally weighted functions to interpolate between and extrapolate from training data. Due to the local nature of the learning functions, it is inherently robust to outliers. Moreover, both training and adapting to new data is highly efficient and almost free, making it suitable for dynamically following possibly variable internal/external relations. We evaluated the method using respiratory motion data (3D tumor motion plus 1D surrogate) from six patients (three lung and three pancreas patients). Results: Given only 5‐sec (roughly one breath) pretreatment training data, the method achieved an average 3D error of 0.37 mm (range: 0.10 mm – 1.06 mm) and 95th percentile error of 0.86 mm (range: 0.24 mm – 2.47 mm) on 120‐sec unseen test data. These errors are well below the average peak‐ to‐peak amplitude (—10 mm). The errors decrease monotonically with an increasing amount of training data. Compared with the best linear model, the learning approach achieved a 21% reduction in error for an average patient (range: 10% – 42%). Conclusions: The memory‐based learning technique is able to accurately capture the highly nonlinear and complex relations between tumor and surrogate motion in an efficient manner (∼1 ms per prediction). These desirable properties make it an ideal candidate for accurate and robust tumor gating/tracking using respiratory surrogates.
SU‐D‐BRA‐04: Improvement of Diaphragm Motion Reproducibility in MRI Using Audiovisual Biofeedback for Lung Cancer Radiotherapy
Authors: Kim Taeho
Published: June 2012

Purpose: Previous studies have investigated the effect of AV biofeedback on the external respiratory signal reproducibility. This is the first study investigating the effect of AV biofeedback to improve the motion reproducibility of the internal anatomy. The aim of the project is to test the hypothesis that AV biofeedback improves the diaphragm motion reproducibility. Methods: An AV biofeedback system has been employed with MRI acquisitions. The AV biofeedback system utilized (1) the external marker position on the abdomen using an RPM system (Real‐time Position Management, Varian) to audio‐visually guide a human subject for regular breathing and (2) a fast Gradient‐Recalled‐Echo (fGRE) MR pulse sequence of 3 Tesla GE MRI (GE Healthcare) to monitor the diaphragm motion (200ms). The improvement in the diaphragm motion reproducibility using the AV biofeedback system combined with MRI has been assessed in 26 studies with 13 healthy human subjects. Each subject underwent two studies for assessment of the diaphragm motion reproducibility both with AV biofeedback and without (free breathing). The second study features a reversed order of breathing conditions. The total MRI acquisitions across the 26 studies are 202 measurements including sagittal and coronal planes. Results: Average RMSE (root mean square error) of diaphragm displacement obtained from MRI analysis has been reduced from 2.7mm of free breathing to 1.6mm of AV biofeedback breathing (p‐value < 0.05). Additionally, the average RMSE of diaphragm motion period was reduced from 1.84s with free breathing to 0.34s with AV biofeedback breathing (p‐ value < 0.05). 22% of average displacement error was reduced using AV biofeedback in the first study, and 47% reduction in the second study. Conclusions: The study demonstrated the improvement in the diaphragm motion reproducibility using AV biofeedback. This system can provide clinically applicable motion management of the internal anatomy in MRI and for Image Guided Radiotherapy (IGRT).
SU‐D‐BRA‐06: Investigation of Prostate Intrafractional Motion during External Beam Radiotherapy for a Large Patient Population
Authors: Tong X , Chen X , Li J , Lin M , Chen L , Xu Q , Ma C
Published: June 2012

Purpose: To analyze and report prostate intrafractional motion recorded online during external beam radiotherapy and to provide guidance for advanced prostate IMRT. Methods: Prostate intrafractional motion during IMRT and RapidARC treatments was tracked and recorded using a Calypso 4D‐localization system. Data for 8600 treatment fractions of 230 prostate patients was analyzed. The percentage of treatment fractions, the fractional treatment time, and the fractional time of any individual minute were analyzed separately for prostate movements greater than the thresholds (2, 3, 5 and 7mm). Results: The percentages of fractions in which prostate shifted more than the thresholds for a duration >10 seconds are 66.2%, 34.9%, 8.9% and 2.6% (57.9%, 27.9%, 5.2% and 0.8% for >30 seconds duration), respectively. For 10 patients who exhibited the largest motion, the percentages are 95.2%, 76.0%, 43.2% and 14.7% (91.3%, 72.4%, 36.3% and 6.0% for >30 seconds duration). The fractional time for motion larger than the thresholds is 27.8%, 10.7%, 1.6% and 0.3% (56.2%, 33.7%, 11.2% and 2.1% for these patients). The posterior‐direction motion is significantly higher than those in other directions. The fractional time of an individual minute with shift >3mm is higher at the 10th minute than at the 5th minute (20% vs. 10%) after the initial setup. For treatments completed within 5 minutes, the average fractional time with motion >3mm was lower than those within 10 minutes (4% vs. 12%). Irregular movements were observed most likely in the first minute after patient's setup, which were 12% and 7% among all fractions with movements >2mm and >3mm, respectively. Conclusions: The prostate intrafractional motion was within 3mm for most treatment fractions. However, larger movements were observed for some patients, who require real‐time corrections or larger treatment margins. The results indicate that it is beneficial if the treatment can be completed within 5 minutes.
SU‐D‐213CD‐02: The Accuracy of AlignRT Guided Set‐Up for Whole Breast and Chestwall Irradiation
Authors: Wiant D , Pursley J , Sintay B
Published: June 2012

Purpose: To evaluate the ability of AlignRT (VisionRT Ltd., London, UK) to accurately position patients receiving whole breast or chestwall irradiation and the impact of AlignRT on portal image dose. Methods and Materials: Twenty whole breast or chestwall cases set‐up using AlignRT at our site were compared to a series of 20 similar patients set‐up without the use of AlignRT over the same time span. All patients were set‐up head first supine, on a Quest Breastboard (Qfix, Avondale,PA). The AlignRT patients were positioned with an AlignRT region of interest that encompassed the ipsa‐lateral chest minus the breast tissue drawn on a surface created from the patient contour generated in treatment planning. Non‐AlignRT patients were positioned using skin marks added in simulation. Positional accuracy was verified by qualitative evaluation of portal imaging on the first treatment day, then once weekly. Results: The percentage of port images that were deemed unacceptable by therapists or radiation oncologists (> 3 mm deviation from simulation position) was 7.5 +/− 8.1% for the AlignRT group (with a range of 0 – 15%). In 14 of the 20 cases, one or fewer port images were unacceptable over the entire treatment. For the non‐AlignRT group 20 +/− 14% (0–45%) of the images were unacceptable. In only 6 of the 20 cases one or fewer port images were found to be unacceptable over the course of treatment. Conclusion: As judged by port images, AlignRT is able to provide a more accurate positioning of whole breast and chestwall patients, with a reduction in port dose and in set‐up time, compared to the use of lasers and skin marks. The reduced number of rejected port images strongly suggests that AlignRT gives a more consistent, reproducible set‐up on non‐ port days than skin marks alone.
SU‐D‐213CD‐03: Live Video‐Guided Volumetric Tracking of Respiration Motion
Authors: Li S , Haiti B , Serratore D , Neicu T , Chan P , Valakh V , Bizhan M , Miyamoto C , Geng J
Published: June 2012

Purpose: To introduce video surface imaging guidance in synchronization with 4D cone‐beam CT (CBCT) scans, and in combination with respiration‐ gated or target‐tracked dose delivery to treat mobile tumors, without collaterally damaging nearby critical structures. Methods: The approach uses the concept that the integral of balanced forces over the moving surfaces is directly proportional to the lung volume changes. The respiratory motions, representing the lung volume variations, were measured with the dynamic volume under the moving surfaces of the thorax and abdomen. Sequential surface images on several patients and volunteers were acquired for the feasibility study. Respiratory motions were repeatedly measured on volunteers undertaking a quiet (normal) or a forced (deep) breath. The dynamic volume under the moving surfaces were robustly fitted with a linear trend and a trigonometric wave function that was compared with the fitted curves for target moving trajectories derived from forty 4D‐CBCT scans. Results: A large chest wall superior‐outward movement was the unique characteristic of a forced breath that had doubled the volume variations and elongated the respiration period from quiet breath of ∼4 seconds to >6 seconds. Under a quiet breath, target motion trajectories could be easily described by single sine functions that were consistent with dynamic surface volume modeling except for having different motion amplitudes. The accuracy in synchronization of the real‐time surface motion with respiration motion was within the measurement uncertainty of ∼2 mm. Conclusions: The analytical results with a hypothetical single sine platform allow us to accurately predict internal target motion with use of real‐time video images. Synchronization of dynamic volume with respiratory motion appears applicable for association of 4D medical imaging with 4D videoimaging.
SU‐D‐213CD‐04: Dosimetric Evaluation of HexaPOD as a Tool for Patient Setup Verification Accuracy
Authors: Ahmad S (Chaudhari) , Spencer K , Brahmavar S , Hyder J , Saleeby J , Bornstein L
Published: June 2012

Purpose: To quantify the dosimetric accuracy of 6 degrees vs. 3 degrees of motion for patient positioning for cone‐beam CT and HexaPOD Evo RT system (Elekta, Inc.) using the ArcCHECK (Sun Nuclear Corporation, software v.6.0) QA phantom. Methods: The average absolute values of our daily reported patient hexapod shift data were recorded and averaged for 18 patients. Using the CT scans of ArcCHECK, a QA plan was created in the Pinnacle (v.9.0) treatment planning system. By setting up ArcCHECK according to the QA plan and measuring the dose on Elekta Synergy, the baseline data was established. Next, an artificial shift was introduced in our phantom setup. A cone‐beam CT scan of the phantom was obtained and images adjusted. The resulting translational and rotational shifts were recorded. The table was then moved according to the translational shifts only, and another measurement was taken. Next, using hexapod translational and rotational shifts, the table was moved in 6 degrees of motion, and the dose was re‐measured. Results: For 18 IMRT patients, the average translational shifts were: x= 0.53 cm, y=0.38 cm and z= 0.516 cm, and average rotational shifts were pitch=0.979°, roll=0.8° and yaw= 0.67°. The ArcCHECK phantom measured results were quantified using 3%, 3mm distance to agreement gamma analysis criteria when comparing measured to planned dose. Our measurements showed that an average 97.3% of the points agreed in plans with no shift. After the artificial shift was introduced, and cone‐beam CT translational shifts were applied, 76.3% of points agreed. When both rotational and translational shifts were applied using Hexapod, an average of 93.4% of points agreed. Conclusions: Using hexapod for imaging and patient positioning results in a significantly more accurate dose delivery as compared to using only CBCT, as shown by our ArcCHECK QA phantom results.
SU‐D‐217BCD‐01: Corrupted DICOM Image Recovering: A Clinical Experience
Authors: Chen L , Walz‐Flannigan A , Langer S
Published: June 2012

Purpose: Colored DICOM secondary capture images generated from CT perfusion studies were corrupted if they were sent directly from a Siemens acquisition workstation to a GE viewing workstation. However, those images were properly displayed in the GE viewing workstation if they were transferred through a GE PACS first. The purpose of this work is to investigate the cause of image corruption and determine why passing through PACS corrected it. Methods: DICOM headers of corrupted and non‐corrupted (sent through the PACS) images were compared with a free DICOM software tool (http://DVTK.org); the differences were highlighted. Certain header tags were found in non‐corrupted images, but not in corrupted images. These tags were sequentially removed until the non‐ corrupted image became corrupted. Once a candidate tag was found, fresh corrupt images were modified by adding a ‘repair’ tag and tested. Results: It was found that the absence of Planar Configuration (0028, 0006) is the cause of image corruption. This attribute is used in the DICOM color image to specify whether the color pixel data are sent color‐by‐plane or color‐by‐ pixel and should be present if the Sample per Pixel (0028, 0002) tag has a value greater than 1. In our DICOM color images, the values of (0028, 0002) and Photometric Interpretation (0028, 0004) are 3 and RGB, respectively. Thus (0028, 0006) should equal 0 (color‐by‐pixel), which is used for uncompressed or lossless compressed transfer syntaxes. Adding this tag and setting the value to zero manually repaired corrupt images. Conclusions: Using open source DICOM tools and following the described process can be a valuable ally in the search for causes of image corruption. Comparing the headers and finding the handful of different tags rapidly led to an explanation that could be used by the vendor for a permanent fix.
SU‐D‐217A‐06: Impact of Anterior‐Posterior (AP) and Posterior‐Anterior (PA) Scout Scans on the CT Radiation Dose in the Whole Body PET/CT Scan
Authors: Luo D , Pan T
Published: June 2012

Purpose: CT can contribute over 50% of radiation dose in the whole body (WB) PET/CT scan. Tube current modulation (TCM) is a standard technique for reducing CT radiation dose to the patient by changing the tube current with the patient size, and is controlled by a very low‐dose scoutscan, which assumes the patient is positioned at the center of the CT gantry opening. However, most patients are not positioned at the center due to practicality or to avoid claustrophobic or to reduce time of radiation exposure from the patient to the technologist. We study the impact of the AP and PA scout scans to the patient radiation exposure from CT. Methods: Ina retrospective study of 200 patients, each received two WB PET/CT scans: one with AP, and the other one with PA. The helical CT with TCM and PET acquisitions were identical in both scans. Separation of the two scans was about 10 months in average. The scans were performed on four GE PET/CT scanners: three 16‐ and one 64‐slice with the same TCM settings. The 200patients were selected for the same scan coverage and similar body weight (difference = 3 kg). The tube current in each slice and average exposure tothe patient were recorded and compared. Results: The AP scout caused lower radiation dose on 94% of the patients. Both the tube current, and radiation exposure were reduced by 46±30 mA and 1.6±1.0 mGy, respectively. The effective radiation dose is reduced by 1.7±1.2 mSv. These results were statistically significant (p<0.00001). Conclusions: The AP scout caused significantly less radiation dose than the PA scout in the CT scan of the whole‐body PET/CT scan. Care should be taken to select theorientation of the scout scan to achieve appropriate radiation exposure to the patient when TCM is applied.
SU‐D‐218‐05: Material Quantification in Spectral X‐Ray Imaging: Optimization and Validation
Authors: Nik S J , Thing R S , Watts R , Meyer J
Published: June 2012

Purpose: To develop and validate a multivariate statistical method to optimize scanning parameters for material quantification in spectral x‐rayimaging. Methods: An optimization metric was constructed by extensively sampling the thickness space for the expected number of counts for m (two or three) materials. This resulted in an m‐dimensional confidence region ofmaterial quantities, e.g. thicknesses. Minimization of the ellipsoidal confidence region leads to the optimization of energy bins. For the given spectrum, the minimum counts required for effective material separation can be determined by predicting the signal‐to‐noise ratio (SNR) of the quantification. A Monte Carlo (MC) simulation framework using BEAM was developed to validate the metric. Projection data of the m‐materials was generated and material decomposition was performed for combinations of iodine, calcium and water by minimizing the z‐score between the expected spectrum and binned measurements. The mean square error (MSE) and variance were calculated to measure the accuracy and precision of this approach, respectively. The minimum MSE corresponds to the optimal energy bins in the BEAM simulations. In the optimization metric, this is equivalent to the smallest confidence region. The SNR of the simulated images was also compared to the predictions from the metric. Results: TheMSE was dominated by the variance for the given material combinations,which demonstrates accurate material quantifications. The BEAMsimulations revealed that the optimization of energy bins was accurate to within 1keV. The SNRs predicted by the optimization metric yielded satisfactory agreement but were expectedly higher for the BEAM simulations due to the inclusion of scattered radiation. Conclusions: The validation showed that the multivariate statistical method provides accurate material quantification, correct location of optimal energy bins and adequateprediction of image SNR. The BEAM code system is suitable for generating spectral x‐ ray imaging simulations.
SU‐E‐E‐01: Commissiong of Linear Accelerator and Beam Modeling in Treatment Planning Systems
Authors: Pella S , Chilukuri M , Smith C , Bacala A , Dumitru N
Published: June 2012

Purpose: Sooner or later every medical physicist is involved with commissioning and beam modeling of a new linear accelerator (linac) and a new treatment planning system (TPS). In spite of all instructions and training offered by the vendors, at the time a new linac is being purchased and added to the present ones the outside help is not so complete. The physicist who has to perform the commissioning job may not even be the one who was trained for that. What we are missing is a good comprehensive set of information and instructions on how to do's. From shielding calculation verifications, surveys, to collecting the beam data, modeling, entering the data into the TPS, and verifications of the goodness of the data we need a lot of support and we don't have it. I will provide a step by step description of the required work with the results we are looking for. Methods: Presentation of the shielding calculations, survey required, tools needed to perform them. Detailed beam data collections, scanning system needed, machine set of specs needed, applicator details needed. Importing beam data from the scanning system and beam calculations. Algorithms used in dose calculation, IMRT optimization, heterogeneity corrections presented to be understood before modeling the beam data. Results: At the completion of this course the medical physicist will be able to commission a linear accelerator and a treatment planning system with confidence and very little help from the outside. Conclusions: This compendium of detailed instructions on commissioning a linear accelerator will provide good uidance to every physicist who will be involved with the installation and bringing into safe use for treatment of a new linear accelerator.
SU‐E‐E‐02: The Use of Social Media in a Medical Physics Classroom
Authors: Starkschall G
Published: June 2012

Purpose: The purpose of this presentation is to provide an example of how Facebook has been used in a medical physics classroom. Methods: Facebook was used in an introductory course in radiation interactions taken by graduate students in a CAMPEP‐accredited medical physics program. Facebook served two major functions in the class, as a means for communicating announcements to students, and as a forum for discussion of unclear points in the course. At the end of every class, students were prompted to fill out a questionnaire asking them to identify points that were not clear. After class, all questions were posted by the instructor (so students maintained anonymity and did not have to be embarrassed by lack of knowledge). Students had 24 hr to post responses to their peers' questions. Students who responded correctly to peers' questions received additional in‐ class credit for their response, thus encouraging them to respond. After 24 hr, the instructor or a teaching assistant posted a response to the question. Results: 12/16 students participated in discussions. The students who did not respond were all postdoctoral fellows (3/4 foreign) auditing the course. From 3 to 9 students typically responded to questions. Students responding to questions received credit for their responses (0.4 points per response up to a maximum of 5 points added to an in‐class grade that counted for 10% of their final grade). Student evaluations of the use of Facebook were generally positive. Furthermore, use of Facebook for this application extended the time students were interacting with each other in medical physics. Conclusions: The use of social media in a medical physics classroom appears to be an effective tool to incorporate into a teaching methodology.
SU‐E‐E‐03: Ethics and Professionalism Education in Medical Physics: A Needs Assessment Study
Authors: Ozturk N , Armato S , Giger M L , Serago C , Ross L F
Published: June 2012

Purpose: To perform a needs assessment survey of ethics/professionalism education in medical physics and ethical/professional challenges in clinical,research and educational settings with the intent of supplementing and customizing TG159 recommended ethics curriculum for medical physics trainees. Methods: A web‐based survey was conducted among AAPM members to assess current practices, attitudes and perceptions pertaining to ethics/professionalism education and ethical/professional misconduct or questionable behavior and practices in the field. Results: The survey was distributed by AAPM to 7708 members via email; 1362 (17.7%) responded. Seventy‐five percent of the respondents were male. Sixty percent (805/1345) stated they received no education in ethics/professionalism. Eighty‐one percent (126/155) of current trainees received instruction in ethics/professionalism, as opposed to 35% (392/1130) of those who are post‐training. There was strong support (>90%) for continuing education in ethics/professionalism; seventy‐five percent (1019/1354) supported sessions on ethics and professionalism at national meetings. Most preferred method of ethics instruction was periodic discussion sessions involving faculty and trainees, with the least interest expressed for a separate course. Many reported direct personal knowledge of one or more instances of a variety of professional/ethical misconduct or questionable behavior. Thirty eight percent (458/1192) reported poor mentorship, with women reporting this concern more often than men (129/281,46% versus 316/877, 36%, p<.05). Over one‐fourth of respondents reported being asked to perform low educational value tasks and expressed concerns about fairness. A significant minority also reported questionable behavior with respect to authorship assignment (346/920, 38%), data fabrication (107/924, 12%), data falsification (94/919, 10%); concerns about research subject privacy and confidentiality were lower (64/887, 7%). Conclusions: Data gathered through the survey is guiding our efforts to develop a case‐based ethics curriculum and instructional materials for medical physics trainees at our institution. This effort may be useful to other medical physics programs which offer ethics training/education. This work has been funded in part by a grant from the National Institutes of Health, T32 EB002103‐22S1.
SU‐E‐E‐05: An Educational Physical Environment Concept with Close Research and Clinical Collaborations
Authors: Rudin S , Bednarek D
Published: June 2012

Purpose: To create a physical environment where imaging medical physicists can be educated in a real‐work, clinical and research setting in close collaboration with professionals such as physicians, biomédical engineers, and other medical personnel. Methods: A single building structure has been designed where medical physics students can be immersed in a collaborative clinical and research educational environment. Results: A Clinical Translational Research Center has been constructed on the top four floors over a new Global Vascular Institute (GVI) which is connected to the main university hospital complex and adjacent to radiation therapy facilities. The research and educational component including offices, labs, and conference rooms for the Medical Physics Program is on the top floor and dedicated research imaging suites (fluoroscopic interventional systems, CT, PET/CT, and MRI) along with complete animal facilities and additional research labs for cardiac and vascular investigators are on the two top floors. An atrium and numerous meeting spaces are in place to encourage informal communication among students and science and clinical investigators. The clinical GVI, which occupies the lower four floors, has a full upper floor containing 15 vascular imaging suites for cardiac, neuro, and peripheral vascular imaging and interventions while the floors below have short‐term hotel‐like patient and family rooms favoring ambulatory patients having minimally invasive procedures. Medical physics didactic education is designed to take place in modern meeting rooms; however, because of the close proximity to research labs and clinical suites, students are expected to get a unique perspective on how research is done and how it is translated into clinical practice. Conclusions: A new physical structure has been built which enables medical physics education to be an integral part of a highly collaborative clinical translational research environment. Research funds provided by NIH grants and equipment grants from Toshiba Medical Systems Corp.
SU‐E‐l‐01: Investigating the Dependence of 2D and 3D Scatter‐To‐Primary Ratios on Breast Density in Clinical Breast CT
Authors: Shah J , Mann S , Tornai M
Published: June 2012

Purpose: To characterize 2D and 3D scatter‐to‐primary ratios (SPR) and investigate the dependence of SPR on breast density based on clinicalpatient imaging on our dedicated SPECT‐CT mammotomography system. Methods: As a part of an on‐going IRB approved protocol, 7 consented women underwent a breast imaging study with our SPECT‐CT system. Using a quasi‐monochromatic x‐ray cone beam and flat panel detector, 240 projections were obtained. 6 beam stop array (BSA) projections were also obtained over 40 degree intervals. The CT data were scatter corrected using a phantom‐validated algorithm based on the BSA technique. For each projection, 2D scatter fluence was determined behind each beam stop shadow through the patient's breast, and cubic spline interpolated throughout the thresholded breast region. 2D SPRs were calculated as the average of 6 measured ratios of scatter projections to scatter corrected (primary) projections. Angular cubic spline interpolation was performed to obtain the remaining 234 azimuthal BSA projections for reconstruction correction. Corrected and uncorrected projection images were individually reconstructed and 3D SPRs calculated as the ratio of difference between primary and un‐corrected volumes to primary volumes. Histograms of the reconstructed patient data‐sets yielded distinct peaks representing linear attenuation coefficients of glandular+skin and fatty tissue. Percentage glandular and fatty tissue was estimated by fitting a double Gaussian to the histogram and integrating area under the curve. Results: Only 4 CT data sets devoid of motion and truncation artifacts were suitable for scatter correction. Preliminary results show that 2D SPR values peak at the center of breast volumes and were greatest (∼50%) for the most glandular breast, whereas 3D SPR values remained fairly constant throughout the breast and did not obviously correlate with density, consistent with prior phantom results. Conclusions: 2D SPR values are greater in breasts with higher glandular tissue composition, whereas 3D SPR values appear independent of breast composition. This work is funded by the National Cancer Institute of the National Institutes of Health grant RO1‐CA096821, with partial support (JHP) from NIH T32‐EB001040. MPT is the inventor of this CT technology, and is named as an inventor on the patent for this technology awarded to Duke University. If this technology becomes commercially successful, MPT and Duke could benefit financially.
SU‐E‐I‐02: Size‐Dependent Computed Tomography Histogram Analysis: Towards Breast Tissue Segmentation
Authors: Mann SD , Shah JP , Tornai MP
Published: June 2012

Purpose: To examine the effects of object size on scatter‐corrected CT histograms to be used in threshold‐based tissue segmentation. Methods: A polyethylene cone filled with various concentrations of water and methanol mixtures, simulating glandular and adipose tissues, were imaged with our quasi‐monochromatic dedicated breast CT, and scatter corrected using beam‐stop array measurements. Images were reconstructed using iterative OSC, and individual coronal slices along the central axis of the cone were analyzed, with radii ranging from 3.25–6.25cm. Histograms from each slice were fit with two Gaussians (fluid filling and cone material) using nonlinear least squares methods, and the corresponding standard deviation and peak centroid of each filled material were evaluated as a function of object radius. Identical methods were applied to dedicated breast CT images of four patients for clinical comparison. Results: Analysis of phantoms and breast data indicates low correlation between the standard deviation and object diameter. The centroids of the Gaussian peaks demonstrate an inverse linear relationship with increasing object size, independent of object material. The clinical datasets show a similar linear relationship between centroids and breast radius. Conclusions: Data indicate that using a linear combination of Gaussian distribution functions to segment breast tissue in scatter corrected, quasi‐monochromatic cone beam dedicated breast CT is possible. An object size‐independent variation of attenuation values may allow for consistent restraints on initial fit parameters, resulting in improved confidence using Gaussian curve fitting. Appropriate scaling of the size‐dependent volume slices, or independent slice analysis, is necessary to minimize binning variability for accurate tissue segmentation using Gaussian curve fitting. This work is supported by National Institutes of Health (R01‐CA096821) and NIH Training Grant (T32‐EB007185). MPT is the inventor of this hybrid breast imaging technology, and is named as an inventor on the patent for this technology assigned to Duke (US Pat. #7,609,808). If this technology becomes commercially successful, MPT and Duke could benefit financially.
SU‐E‐I‐07: Proposal for a Novel Algorithm of Effective Dose Evaluation for Medical Radiation Exposure
Authors: Wang C , Dewhirst M , Jiang X , Qian Z , Boon S , Yoshizumi T
Published: June 2012

Purpose: The validity of effective dose (ED) in medical applications, which mostly involving partial‐organ irradiation, has long been argued. We now propose a new algorithm of effective dose evaluation for medical radiation exposure. The new algorithm will include new Relative Volume Factors, or RVFs, to account for the relative irradiated volume of the partially‐irradiated organs, such as skin and bone marrow. Methods: To validate the proposed algorithm, three ED evaluation methods were applied to five neuro‐imaging protocols of a C‐arm cone‐beam CT: 1) MOSFET‐anthropomorphic‐ phantom measurement for organ doses, ED evaluated with the original ICRP algorithm; 2) using the same MOSFET‐measured organ doses, ED evaluated with the new algorithm; and 3) Monte Carlo (PCXMC, developed by STUK) dose estimation as gold standard. Results: For all five imaging protocols, the ED evaluations by the new algorithm agreed very well with the Monte Carlo simulation results (within 10% difference), whereas the original ICRP algorithm overestimated EDs by approximately a factor of 2. Conclusions: The proposed algorithm provides a more accurate estimation of ED in medical exposures than the original ICRP algorithm. It potentially establishes the ED as a more reasonable index for cross‐protocol dose comparison.
SU‐E‐I‐09: Patient Organ Doses from KV‐CBCT Acquisitions as Function of Patient Size and Scan Protocols
Authors: Nelson A , Ding G
Published: June 2012

Purpose: To investigate the organ dose dependence on patient size and position resulting from an image guidance procedures. Depending upon the degree of variability between patients, the feasibility tabulating the organ dose based upon patient size and imaging acquisition procedure. Such tables could be useful in estimating and accounting for organ dose resulting from imaging procedures. Methods: Monte‐Carlo methods were used to calculate radiation dose to the patient resulting from a kV CBCT imaging scan based upon CT image data. A Python program was created to generate DVHs using the calculated 3D dose matrix and the DICOM‐RT Structure Set for the patient. A number of head and pelvic CT scans were used in the study, and the resulting DVHs were analyzed to determine the variation of organ dose as a function of patient size. Results: For the head scans in supine position, the average of the mean doses for some organs, along with the standard deviation in those mean doses, are as follows:Brainstem: 0.25cGy +/− 0.02cGyBrain: 0.26cGy +/− 0.01cGyOptic Chiasm: 0.22 +/− 0.03cGyBone: 0.55 +/− 0.04cGyAnterior Skin: 0.13 +/− 0.05cGyPosterior Skin: 0.23 +/− 0.06cGyEye: 0.11cGy +/− 0.05cGyFor Pelvic scans, dose to organs such as rectum, have likewise been shown to have some variation between patients of different sizes. Conclusions: The results show that it is possible to express organ dose as a function of imaging procedure, imaging device, scan location, body size, and orientation. For example, using a standard head scan on an OBI 1.4 system, the dose to the eye ranged from 0.05–0.20cGy, depending upon the patient size. Considering the amount of imaging dose compared to the therapeutic dose, this study indicates that organ dose could be estimated by using tabulated values based upon the scan procedure and patient size.
SU‐E‐I‐14: Evaluation of Image Quality Parameters of Small and Full Field of View Cone Beam Computed Tomography Dental Imaging Systems
Authors: Hoffmann E , Silva A Marques da , Azevedo D , Borges J
Published: June 2012

Purpose: CBCT systems are being used in dental preoperative planning, which rely on 3D surface model representations of the jaw, using a segmentation algorithm for extracting the bony tissues. However, CBCT systems have differences of imaging parameters, which affect the image quality and segmentation process, influencing the accuracy of the 3D surface models used in preoperative implant planning. The purpose of this study was to evaluate image quality parameters of different types of CBCT systems, showing their potentialities and limitations for preoperative planning. Methods: Images were acquired using the systems: i‐CAT (Imaging Sciences International Inc., USA); ProMax 3Ds (Planmeca Oy, Finland); Kodak 9500 Cone Beam 3D and Kodak 9000C Cone Beam 3D (Kodak Dental Systems, USA). CBCT systems were divided into categories, related to their field of view size: Small Field of View (SFOV) and Full Field of View (FFOV) systems. Image quality parameters evaluated were: CT number accuracy, uniformity, noise level, and artifacts. Measurements were performed in slices around the center of the phantom. Results: CT numbers are highly affected by the amount of mass outside the reconstructed volume, confirming the relation between density variability and imaging volume. The mean CT number shows little correspondence to that of the traditional CT protocols. The variability is especially high in the case for SFOV systems. Uniformity artifacts occur at the top or bottom of the FOV, and Result in voxel values that are unsuitable for CT number accuracy analysis. SFOV systems showed a higher noise level (11,9%) comparing to FFOV systems (4.4%). Conclusion: The experiments showed that the size and position of the FOV affect the image quality for all CBCT systems. The study was limited to the CBCT systems that were accessible when this study was conducted. Whether new CBCT systems models would perform differently remains to be investigated.
SU‐E‐I‐15: Comparison of State‐Of‐The‐Art Interpolation‐Based Metal Artifact Reduction (MAR) Algorithms for Cone‐Beam Computed Tomography (CBCT)
Authors: Seghers D , Berkus T , Oelhafen M , Munro P , Star‐Lack J
Published: June 2012

Purpose: To compare four metal‐artifact‐reduction (MAR) algorithms in their ability to correct the typical streaking artifacts that appear in cone‐ beam computed tomography (CBCT) images. Methods: The goal was to compare the strengths and weaknesses of four MAR algorithms, Basic; Wei; Mazin and Meyer, using typical clinical situations where metal is present. Three clinical situations were evaluated: fiducial markers in the abdomen; hip implants and multiple dental fillings. The algorithms take original CBCT projections as input and produce a corrected image. The location of the metal is identified in the CBCT images and a forward projection identifies which pixels in the projections need to be replaced by interpolation of neighboring pixels. The three advanced algorithms extend the Basic technique with more sophisticated interpolation schemes. Wei and Meyer identify the high contrast structures using image segmentation in order to reduce their appearance in the projections before interpolation. Mazin corrects the original projections using a forward projection of the Basic correction. Results: All the algorithms reduced the streak artifacts typical of metal structures. Nevertheless, depending upon the clinical task, the algorithms also added shading and streaks which reduced the overall visual impression. Images containing fiducial markers in the abdomen showed obvious improvements; images containing hip implants were improved but also showed distracting shading artifacts; and, images with multiple dental fillings all appeared visually worse than the uncorrected images. In almost all cases, Mazin outperformed the other approaches and introduced the fewest additional streaks and shading artifacts. Conclusions: This work indicates that the Mazin algorithm is best suited for clinical usage of MAR. Furthermore the algorithm is fairly simple and can be computational very efficient making it well suited for clinical use. Nevertheless, the overall improvement is highly dependent on the individual characteristics of the original image. For dental implants no correction is recommended.