bluuebunny/crossref_metadata_2025 huggingface dataset:
WE‐G‐BRC‐03: Medical Physics Beyond Borders: IAEA Educational Resources Relevant to Both the Developed and Developing World
Authors: Van Dyk J , Meghzifene A
Published: November 2011

Purpose: To summarize the medical physics educational and training materials freely available through the website of the International Atomic Energy Agency (IAEA). Methods: The IAEA works for the safe, secure and peaceful uses of nuclear science and technology. Much this work relates to human health, including the worldwide cancer problem. The medical physicist fulfils an essential role in the safe and effective use of radiation in medicine, most commonly in cancer treatment, x‐ray diagnostic imaging and nuclear medicine. The IAEA produces a large amount of educational and training materials much of which is relevant to the medical physics community worldwide. Resource materials range from setting up a radiation therapy program, to dosimetry calibration protocols, quality assurance guidance documents, basic medical physics education textbooks, along with thousands of ready‐made PowerPoint slides downloadable and ready to use by students and instructors. Furthermore, a detailed residency training program is now available for radiation oncology physics and similar material for diagnostic radiology and nuclear medicine physicists is in print. Results: These resource materials are available through the IAEA website, http://www.iaea.org and subcomponents of this website including the newly developed website called “IAEA Human Health Campus”, http://humanhealth.iaea.org. Furthermore, there are significant patient safety resources available through the “Radiation Protection of the Patient” website, http://rpop.iaea.org/, also including multiple PowerPoint presentations. New teaching/learning resources are being developed for advancing to more sophisticated image‐based radiation therapy, ranging from 2‐D to intensity‐modulated and image‐guided radiation therapy. Conclusions: The IAEA has developed a wealth of educational resources now readily and freely available through its new “Human Health Campus” website. These resource materials and website contents are continuously evolving to meet the increasing needs of the IAEA member states. The emphasis is on advancing radiation medicine safely and effectively. Many of these resources are useful to the medical physics community worldwide.
WE‐G‐214‐01: Investigation of Magnetic Shielding for a 6MV In‐Line Linac for a Parallel Linac‐MR Configuration
Authors: Santos D M , Aubin J St. , Fallone B , Steciw S
Published: November 2011

Purpose: To achieve real‐time tumor tracking, our group is integrating a 6 MV in‐line linac with an MR imager, where the linac is placed on the MR magnetˈs central axis to create a linac‐MR system. Because of the linacˈs location, it experiences large fringe magnetic fields parallel to the electron trajectories in the waveguide. To minimize the adverse affects of these fields on the linac, both passive and active magnetic shielding was investigated. Methods: COMSOL was used to model 3D fringe magnetic fields from a 0.5T PARAmed openMRTM magnet with and without magnetic shielding in place. These fields were added to our electron gun model (created previously using OPERA/SCALA‐3D), and to our waveguide model (created previously using COMSOL and PARMELA) to optimize both passive and active shielding. Results: The unshielded linac electron gun experiences up to a 0.011 T longitudinal field. The injection electron beamˈs rms‐emittance increases from 0.299pi mm‐mrad at 0 T to 2.834pi mm‐mrad at 0.011 T. This non‐laminar beam results in a decreased target current to 84% of nominal. A 5 mm thick and 141.5 mm long passive steel shield reduces the beamˈs rms‐emittance to 0.450pi mm‐mrad. In this configuration, >99% of the target current is recovered. With an optimized active shield (two current rings) in place, the rms‐emittance was reduced to 0.308pi mm‐mrad and the target current was recovered to 100.2% of nominal. Homogenous fringe magnetic field strengths up to 0.2 T were also modeled to test the passive shielding under larger‐field conditions. A 5 mm thick passive shield is sufficient to magnetically shield the linac at 0.04 T at which the target current decreased to only 97.6%. Conclusions: Both passive and active magnetic shielding can be used in our linac‐MR system to recover any beam loss resulting from MR fringe magnetic fields.
WE‐G‐214‐02: Utility of 18F‐FDOPA PET for Radiotherapy Target Delineation in Glioma Patients
Authors: Pafundi D , Brinkmann D , Laack N , Sarkaria J , Yan E , Kemp B , Lowe V
Published: November 2011

Purpose: To evaluate the impact of adding 18F‐FDOPA‐PET, an amino acid tracer, to standard of care MRI for radiotherapy target volume delineation for gliomas. Methods: 6 patients with newly diagnosed brain tumors were given 5.0 mCi +/− 10% of 3,4‐dihydroxy‐6‐[18F]‐fluoro‐L‐phenylalanine (18F‐FDOPA), and underwent a 10‐minute PET/CT acquisition. Overall pathology confirmed WHO grade 3 astrocytoma (n=3), grade 3 oligoastrocytoma (n=1), and glioblastoma (n=2). T1‐weighted post gadolinium (T1‐gad) and T2‐weighted/FLAIR MRI sequences were rigidly aligned to the 18F‐FDOPA‐PET/CT. Three experienced radiation oncologists contoured the T2/FLAIR abnormality, T1‐gad enhancement, and areas of 18F‐FDOPA uptake separately. An experienced nuclear medicine physician contoured 18F‐FDOPA uptake, which was considered as the gold standard for positive disease on PET imaging. Intersection, union, and exclusion boolean operators were performed to determine discordance and concordance between MRI and 18F‐FDOPA‐PET, along with interobserver variability defining 18F‐FDOPA‐PET volume. In addition, uniform expansions of the T1‐gad contours were performed in increments of 0.5 cm until 100% of the 18F‐FDOPA‐PET volume was covered. Results: 18F‐FDOPA‐PET uptake was observed in all patients, with interobserver delineation variability between radiation oncologists (RadOnc1‐RadOnc3) and the gold standard ranging from 47% less to 191% more volume. On average 9.5% (0.3%–29.1%) of the 18F‐FDOPA‐PET gold standard volume extended beyond the RadOnc T2/FLAIR volumes. Half of the cases had no enhancement, and of the remainder on average 77.8% (61.3%–93.1%) of the 18F‐FDOPA‐PET volume extended outside the T1‐gad enhancement. An average expansion of 2.0cm (1.0cm–5.0cm) beyond the T1‐gad contours was necessary to cover 100% of the 18F‐FDOPA‐PET volume. Conclusions: This work introduces the potential utilization of 18F‐FDOPA‐PET for identifying positive disease not visible with conventional MRI and the potential to customize radiotherapy target volumes to the active disease. Future studies will correlate pathology with concordant and discordant regions, and compare biopsy confirmed results with automatic segmentation techniques for 18F‐FDOPA‐PET.

Funding has been provided by Brains Together for a Cure
WE‐G‐214‐06: Pulmonary Ventilation and Perfusion Imaging Using 4DCT
Authors: Mistry N , Hou J , Ballard R , Feigenberg S , DˈSouza W
Published: November 2011

Purpose: To develop a functional imaging technique that can simultaneously detect changes in lung ventilation and lung perfusion using 4D‐CT. This high‐resolution functional information can be incorporated in a treatment planning to minimize the dose to highly functional areas of the lung, and can also be used to assess the efficacy of treatment post radiation therapy. Methods: Recently, a technique was presented to estimate lung ventilation using 4DCT by detecting the changes in CT characteristics of the pulmonary parenchyma. We go a step further and develop the theory to extract not only regional fractional changes in ventilation but also fractional changes in mass that may be indicative of blood flow. Changes in lung ventilation are estimated by applying a mass correction that is estimated using the ratio of the global inhale‐mass and end‐exhale mass. Changes in lung perfusion are indicated by changes in “apparent mass”. Changes in “apparent mass” are estimated by applying a volume correction that is estimated using the ratio of global inhale volume and end‐exhale volume. In both the cases a subtraction of the corrected images is performed by spatially matching the images at each phase of the respiratory cycle. Spatial matching is carried out using a deformable image registration algorithm. Results: Preliminary studies indicate a linear relationship between the mass‐corrected fractional changes in volume and global measurement of tidal volume changes (slope = 1.01, R‐square = 0.97). A similar slightly linear relationship is observed between the volume‐corrected fractional changes in “apparent mass” and global measurement of mass (slope = 1.21, R‐square = 0.75). Conclusions: The technique presented above can extract both changes in ventilation and “apparent mass” that maybe indicative of perfusion simultaneously from a single set of 4DCT images. It however remains to the shown that these changes correspond to perfusion (future studies).
WE‐G‐110‐01: Task‐Based Modeling and Optimization of a Dedicated Cone‐Beam CT Scanner for Musculoskeletal Imaging
Authors: Prakash P , Gang G , Zbijewski W , Yorkston J , Machado A , Carrino J , Siewerdsen J
Published: November 2011

Purpose: Cascaded systems analysis (CSA) offers a quantitative basis to optimize design and operation of novel imaging systems. Considering a CBCT scanner under development for musculoskeletal imaging, we employed CSA for design and technique optimization in relation to specific imaging tasks. Methods and Materials: A comprehensive system model combined spatial‐frequency‐dependent noise transfer characteristics, “system” parameters such as focal spot size and x‐ray scatter, and “generalized” parameters of anatomical clutter — each in relation to task‐based detectability. System performance was computed as a function of system geometry (magnification, detector pixel size, focal spot size, etc.), anatomical site (upper and lower extremities), imaging technique (kVp and dose), and reconstruction technique (voxel size and reconstruction filter). The vast parameter space was investigated in multivariate analysis for tasks ranging from low‐contrast, low‐frequency, soft‐tissue discrimination to higher‐contrast, high‐frequency detectability. Theoretical predictions were validated versus measurements on an imaging bench, and qualitative verification was obtained in cadaver images. Results: The analysis identified distinct optima and key tradeoffs among factors of contrast, noise, resolution, and dose. System geometry was a critical parameter in terms of focal spot blur, dose, and scatter, and a multivariate optimum was identified at magnification ∼1.3. Other optima included: kVp (90 kVp + 0.3 mm Cu); pixel size (0.15–0.19 mm); binning (2×2 binning for soft‐tissue discrimination); and filter (Hann versus ramp for soft‐tissue and bone tasks). Results were qualitatively confirmed in cadaver images and guided the selection of components and physical design of the extremity scanner. Conclusions: A CSA model providing a comprehensive treatment of quantum noise with “system” and “generalized” parameters provided a powerful basis for design and optimization. The work identified distinct optima in system geometry and operation without costly experimental trial and error and guided the development of a prototype CBCT scanner for musculoskeletal imaging now in translation.

Work supported by the National Institutes of Health grant R01‐CA‐112163 and research collaboration with Carestream Health Inc. (Rochester NY).
WE‐G‐110‐08: Dose Reporting and Analysis Tool for Interventional X‐Ray Imaging Systems
Authors: Esposito J , Desponds L , Bourdeaux G , Remenyi J
Published: November 2011

Purpose: Interventional procedures are growing in complexity and length. There is increased regulatory focus on medical radiation exposure. Medical physicists need data and advanced analytical tools that can help identify patient exams with high dose and can highlight practice patterns and trends that can lead to high dose exams. Methods and Materials: A machine data monitoring tool (Innova Dose Reports) was developed for GE Innova fluoroscopy systems. The tool captures near real time detailed exam data including dose (air kerma), acquisition mode, protocol, duration, source to image distance, field of view, angulation, table height, and equivalent patient thickness. The tool provides monthly summaries and exam level detail. The data can be used to 1) monitor and manage dose, 2) quickly spot and correct undesirable trends, 3) benchmark with all other Innova systems in the GE installed base and 4) utilize dose more efficiently. For exams exceeding the threshold, an alert is sent following the exam, with details that can help estimate potential deterministic effects for the patient. Results: Innova Dose Reports facilitated reduction of dose in a variety of clinical settings. We were able to achieve overall reductions in dose of up to 40% in one electrophysiology lab and 29% and 50% in two cardiac catheterization labs. In one of the cardiac labs, the number of cases exceeding 5Gy went from 14 to 3 while exam volume remained the same. In the other, average patient dose went from 1.6Gy to 1 Gy. These reductions were the result of protocol adjustments, increased utilization of dose reduction features and clinical practice changes. There were no complaints of diminished image quality. Conclusions: Innova Dose Reports help monitor and minimize patient dose. The detailed information provided (in conjunction with clinical information, dose reduction features and training) can pinpoint areas of opportunity for improvement.
WE‐G‐211‐01: Breast Microwave Radar Image Reconstruction Using Circular Holography: Initial Results on Preclinical Datasets
Authors: Tapia D Flores , Pistorius S
Published: November 2011

Purpose: To evaluate the performance of circular holography techniques to reconstruct Breast Microwave Radar (BMR) images using preclinical datasets recorded from synthetic phantoms. Unlike the majority of the previous BMR studies, the materials used in this work mimic the dielectric properties of healthy and malignant breast tissues to emulate the propagation losses and the reflections from dense tissue regions. Methods: A custom data acquisition system was assembled to record the experimental datasets. This system was formed by a plexiglass tank, a vector network analyzer and a Vivaldi antenna. The bandwidth of this system was 6GHz. Two phantoms, one formed mostly by synthetic fatty tissue and one containing a fibroglandular tissue structure were constructed. A spherical 8 mm synthetic tumor was inserted in both phantoms. The phantoms were radiated using a stepped frequency continuous waveform with 551 equidistant frequency values, along a circular geometry with 72 scan locations and a radius of 18.5 cm. The performance of the reconstruction approach was evaluated by calculating the signal to noise ratio and spatial accuracy of the reconstructed images. Results: The images formed using the circular holography technique exhibited an average signal to noise ratio of 8.1 dB and a spatial error of 1.5mm. In all the reconstructed datasets the synthetic tumor response can be clearly visualized. No artifacts were observed in any of the reconstructed images. Conclusions: This work shows that images formed using circular holography presented similar spatial accuracy and a signal to noise ratio three times larger than datasets formed using current BMR reconstruction methods. In all the reconstructed datasets the tumor responses was clearly identifiable and consistent with its location in the experimental setups, suggesting that this approach can generate accurate and specific images in a realistic setting.
WE‐G‐211‐04: Experimental Demonstration of Cone‐Beam Polychromatic X‐Ray Fluorescence Computed Tomography (XFCT) Imaging of Gold Nanoparticle‐Loaded Regions within Small Animal‐Sized Phantoms
Authors: Jones B , Manohar N , Cho S
Published: November 2011

Purpose: To demonstrate the feasibility of determining the location and gold concentration of gold nanoparticle (GNP)‐loaded regions within polymethyl methacrylate (PMMA) phantoms using cone‐beam polychromatic x‐ray fluorescence computed tomography (XFCT) technique. Methods: Tubes containing water and GNPs at 2%, 1%, and 0.5% by weight were inserted into two 5 cm‐long cylindrical PMMA phantoms with 3 cm and 5 cm in diameter, respectively. The phantoms were irradiated by a cone‐beam of polychromatic 110 kVp x‐rays filtered by 1.0 mm of lead. Energy‐sensitive cadmium telluride detectors behind a 2.5 mm diameter lead pinhole collimator collected the spectrum of emitted gold K‐shell fluorescence and Compton scattered photons at an angle of 90° relative to the beam central axis as the phantom was rotated to a series of 60 projection angles in 6° steps. Sinograms of gold fluorescence photon signals were constructed by extracting the gold fluorescence peak height from the Compton background, and the image of GNP location and concentration was reconstructed using a maximum likelihood iterative reconstruction algorithm. Results: Using the measured sinograms, images of GNP location were successfully reconstructed for both the 3 cm and 5 cm phantoms. Additionally, the signal intensity was linearly related to gold concentration. The x‐ray dose delivered during the XFCT scanning was measured using the TG‐61 protocol, and it was determined that, using an array detector, it would be possible to acquire these images with roughly 30 cGy of x‐ray dose delivered. Conclusions: This study demonstrates, for the first time to our knowledge, the feasibility of imaging GNP location and concentration within small animal‐sized objects using an ordinary cone‐beam polychromatic x‐ray source under realistic constraints on dose and scan time. This investigation strongly suggests a bench‐top XFCT system will ultimately become a viable option for in‐vivo molecular imaging with conjugated or unconjugated GNPs.
WE‐G‐211‐06: Multiplexed Radio Luminescence Imaging for Radiation Therapy
Authors: Carpenter CM , Pratx G , Sun C , Liu H , Xing L
Published: November 2011

Purpose: Radio Luminescence Imaging is being investigated for its potential to provide biological feedback during radiation treatment. We are investigating the use of biologically‐targeted phosphor nanoparticles to enable high‐resolution molecular imaging with standard therapeutic systems. This work demonstrates the ability of this technique to image multiple molecular markers in a small‐animal model. We investigate their potential in resolving markers pertinent to treatment monitoring. Method and Materials: Images were acquired with a custom‐built imaging system incorporating a Princeton Instruments Pro‐EM camera CCD with 512×512 pixels) and a 50mm lens. Tb‐ and Eu‐doped BaYF4 nanoparticles of linearly varying amounts (0mg/ml:10mg/ml; 2.5mg/ml:7.5 mg/ml; 7.5mg/ml:2.5mg/ml; and 10mg/ml:0mg/ml) were mixed into cuvettes and imaged under irradiation with an 80keV X‐ray source (Pantak Therapax). BaYF4 nanoparticles were also placed in the right foreleg and right and left flanks of a nude mouse. In another experiment, phosphor nanoparticles were placed in a cylindrical plug‐shaped phantom and irradiated with a 9MeV electron beam produced by a Varian Trilogy linear accelerator. All images were processed with custom spectral unmixing software, which enabled the visualization of each phosphor. Results: Concentrations less than 0.1 mg/ml were resolved. Spectral unmixing showed excellent separation of the phosphor nanoparticles (r = −0.98), demonstrating the multiplexing ability of the technique. In addition, phosphor concentrations showed excellent linearity (R>0.99), with excellent separation of the phosphor nanoparticles. Images of the phosphor nanoparticles implanted in the fore and hindquarters demonstrated the ability to spectrally separate in small‐animal model. Conclusion: The ability of radio luminescent imaging was demonstrated in phantom and small‐animal models, for both X‐rays and electron beams. Enabling simultaneous imaging of multiple molecular imaging markers is possible in Radiation Therapy applications. This technique has potential for introducing the monitoring of biological markers during treatment.

The Department of Defense Breast Cancer Research Program, the National Institutes of Health ICMIC P50CA114747, the Center for Biomedical Imaging at Stanford, and the Friends for Early Breast Cancer Detection.
WE‐G‐301‐01: Airport Security Imaging Systems: Design, Dose, Risks, and Quality
Authors: Moulder J , Kassiday D , Segraves J , Gray J
Published: November 2011

Imaging at ports of entry into the United States has become ubiquitous— cargo scanners at seaports; CT luggage scanners, x‐ray backscatter whole‐ body scanners, and millimeter wave imaging systems at airports. The use of x‐ray backscatter scanners has become quite controversial in that hundreds millions to over a billion of people will be exposed to very low levels of radiation, perhaps many times each year, in the U.S. alone.

This special symposium has been developed for the medical physics community in order to provide technical information about these scanners and the risk of exposing large numbers of airline staff and passengers, including pregnant women and children, to ionizing or electromagnetic radiation. Since the primary purpose of these systems is to provide a security tool, one must also consider the quality of the images produced and the ability to detect contraband material.
WE‐G‐220‐04: Enhanced Uptake of Doxorubicin in Prostate Tumor Using Pulsed Focused Ultrasound — An in Vivo Study
Authors: Chen X , Cvetkovic D , Ma C‐M , Chen L
Published: November 2011

Purpose: To investigate the effect of pulsed focused ultrasound (pFUS) on the uptake of doxorubicin (DOX) in prostate tumor in vivo. Methods: A mouse prostate tumor model was used in this study by implanting and growing LNCaP tumor cells in male nude mice prostate. An InSightec ExAblate 2000 system with a 1.5T GE MR scanner was used for MRI‐ guided pFUS treatment. Non‐thermal sonications were delivered by keeping the local body temperature below 42°C as measured in real‐time by MR thermometry. Tumor‐bearing mice were exposed to pFUS (1MHz; 25W acoustic power; 10% duty cycle with 0.1 sec on and 0.9 sec off) for 60 sec in each sonication. A total of 4–8 sonication spots, depending on the tumor size, were used to cover the whole tumor. Immediately after pFUS exposure, DOX (10mg/kg) was injected via tail vein. Mice were euthanized after two hours and the DOX concentration in tumor (microgram of DOX per gram of tumor weight) was measured using the fluorescence technique. Mice were randomly assigned to two groups (n=8 for each group). One group received DOX injection only (group: DOX). The other received both pFUS exposure and DOX injection (group: FUS+DOX). Results: The DOX concentration in the FUS+DOX group was 14.9+/−2.5 ug/g compared to 9.5+/−1.6 ug/g of the DOX group (p=0.051). There was an about 60% increase of the DOX uptake in the prostate tumor exposed to pFUS. Conclusion: Results show that pFUS exposures significantly enhanced the uptake of DOX in prostate tumors. This result is consistent with our previous study of enhanced [3H]‐docetaxel uptake in prostate tumors. Further studies are being conducted to investigate the optimal pFUS parameters to maximize the uptake enhancement and its clinical benefits for cancer therapy (Study supported by a grant from Focused Ultrasound Surgery Foundation and partially by DOD PC073127).
TH‐A‐214‐01: Patient‐Specific Dosimetry for Pediatric X‐Ray Computed Tomography
Authors: Clark J , Stabin M , Pickens D , Price R
Published: November 2011

Purpose: CT radiation dose estimates are commonly reported as CTDI (mGy) values derived from measurements made with standard phantoms for a specific technique (kVp, mAs, collimation and pitch). Estimates of effective dose (mSv) are generally calculated from the dose‐length‐product (mGy‐cm) and a weighting factor that is derived from a standardized model. These dose estimates are not patient specific and do not include dose estimates for specific organs. There is general agreement of the need for more accurate dose estimates for x‐ray computed tomography examinations in pediatric patients. The purpose of our research is to investigate methods that can lead to more patient‐specific dosimetry. Methods: We used Monte Carlo particle transport methods in the GEANT4 toolkit to investigate radiation dose estimates in previously acquired pediatric CT scans of the chest, abdomen, and pelvis (CAP) for which several abdominal organs were semi‐automatically segmented. Resulting voxel data were used as input to our existing GEANT4 code. Results: Monte Carlo dose calculations were made using pediatric CT CAP scans of patients with a wide range of age and body weight. The GEANT4 results were compared to scanner‐reported dose estimates of CTDIvol values. Organ dose estimates were obtained with the ImPACT CT Patient Dosimetry spreadsheet(St. Georgeˈs Healthcare NHS Trust, London, UK). Conclusions: We found that the dose estimate to a specific organ may be either underestimated or overestimated by as much as a factor of two relative to ImPACT values. CTDIvol values appear to significantly overestimate doses. One of the major variables impacting dose estimates was the large range of organ volume and masses and how they can differ from phantom values. Because of these findings, we conclude that CTDIvol values do not appear toprovide particularly good estimates of organ doses. NIH Grant: R25‐CA092043
TH‐A‐214‐05: Creation of Patient Size Dependent Methods of Estimating Organ Doses in Tube‐Current Modulated MDCT Exams
Authors: Fisher R , Hintenlang D , Arreola M
Published: November 2011

Purpose: To assess the feasibility of developing patient‐size specific methods of estimating organ doses in tube‐current modulated MDCT exams. Methods: A previously developed tissue‐equivalent anthropomorphic phantom and an accompanying adipose equivalent add‐on were used with a fiber optic dosimetry system to collect specific organ doses for tube‐current modulated chest, abdomen, and pelvic MDCT exams on both a Siemens and Toshiba scanner. The adipose add‐on allowed for measurements in both a 50th and 90th percentile by weight male, with the same image quality setting being used for imaging both phantoms. Plots of tube current response of each system to the phantoms were collected along with average doses to organs of interest. Organ doses from each phantom were then compared and plotted versus phantom circumference in order to develop scanner and organ specific equations to adjust organ dose for patient size in tube‐current modulated exams. Results: Organ doses were seen to increase in the larger phantom for nearly all organs and exams across both scanners, with average increases on the order of 25%. The nature of the increases differed between the scanners, which showed markedly differing tube‐current responses to the two phantoms, indicating that any attempts to account for TCM and patient size in organ doses must be scanner specific. A circumference based, patient size dependent organ dose calculator was developed for both scanners using the collected dose measurements, though much more data is required for the calculator to be useful. Collected physical measurements for breast and lung dose on a Siemens chest scan matched well with the limited published simulation data. Conclusions: The creation of patient size specific, organ dose estimators for TCM MDCT scans appears feasible, though a larger sample of organ dose data is required, which is something more easily achieved through simulation, rather than physical measurement. A portion of the authorˈs graduate assistantship during the course of this research was funded by Toshiba.
TH‐A‐214‐10: Comparison of Bismuth Shielding and Globally Reducing Tube Current in Head and Thoracic CT
Authors: Wang J , Duan X , Christner J , Leng S , Yu L , McCollough C
Published: November 2011

Purpose: To compare the dose reduction and image quality achieved using bismuth shielding or global decreasing of the tube current in head and thoracic CT. Methods: An anthropomorphic head phantom and four sizes of thorax phantoms were used for dose measurement and image quality assessment. Three scans were performed on each phantom with a 128‐slice clinical CT scanner: 1) reference (relevant clinical protocol); 2) reference plus bismuth shield; 3) reference with a global reduction in tube current chosen to match the dose reduction from bismuth shielding. Dose to the eye was measured with OSL dosimeters. Dose to the breast was measured with an ion chamber on the surface of the phantom. Image quality was evaluated by measuring the mean and standard deviation of CT numbers within the brain region for head CT and the lung and heart regions for thoracic CT. Results: Compared to reference scan, dose to the eye was reduced by 26.4% with bismuth shielding; dose to the breast region was decreased by 21% for the 15‐cm phantom with a pediatric (2‐ply) shield and by 37% for the 30, 35 and 40‐cm phantoms with adult (4‐ply) shields. The dose reduction achieved with bismuth shielding was limited to the anterior surface. Globally decreasing tube current reduced dose by similar amounts, but for all projection angles. Image noise was increased in the brain, lung and heart regions by similar amounts with both techniques. However, streak artifacts and an increase in CT numbers were observed for using bismuth shields, but not for global tube current reduction. Conclusions: Globally decreasing tube current can produce the same dose reduction, but for all projections, as bismuth shielding reduces dose to the anterior surface (eye and breast), with a similar noise increase, yet without the streak artifacts and CT number errors caused by bismuth shields.
TH‐A‐214‐11: Dose to Implantable Cardiac Devices from Cone Beam CT
Authors: Wronski M , Pang G
Published: November 2011

Purpose: To quantify the cumulative dose contribution to implantable cardiac rhythm management devices (ICRMDs) from cone beam CT (CBCT) for patients undergoing radiotherapy and to investigate dose reduction strategies. Methods: An implantable pacemaker (IP) and implantable cardioverter‐defibrillator (ICD) with internal MOSFET dosimeters were used to measure the cumulative CBCT dose to the IP and ICD. Specifically, the MOSFET threshold voltage shifts resulting from standard clinical CBCT imaging protocols were recorded and compared to shifts caused by peripheral megavoltage dose associated with 6 MV IMRT treatment delivery. The dose assessments were performed on an anthropomorphic phantom with the IP or ICD placed in the left clavicular area both inside and outside of the CBCT field of view (FOV). Two dose reduction strategies were evaluated: the use of a 2 mm copper plate to shield the device during imaging and the use of partial‐angle scanning. Results: The average internal IP and ICD doses due to standard clinical CBCT imaging protocols with the device inside the FOV were in the 2.2 – 4.3 cGy and 0.8 – 1.9 cGy range, respectively, but could reach as high as 11.2 cGy per scan. Five centimeters outside the FOV, the dose can reach up to 10% of the in‐field dose in the cranio‐caudal direction and up to 70% in the medio‐ lateral direction. Copper shielding resulted in a 3‐fold reduction in total CBCT dose and a posterior 180 degree scan reduced the dose by a factor of 8 in comparison to a full 360 degree scan. Conclusions: The CBCT imaging dose to ICRMDs can be substantial and needs to be accounted for. Use of a MOSFET dosimeter during the first treatment fraction is an effective way of obtaining a reasonable upper limit of the average cumulative ICRMD dose. Partial posterior scans can greatly reduce this dose.
TH‐A‐220‐04: MVCT Noise Reduction and Feature Enhancement for Target Delineation
Authors: Chen Q , Gering D , Martin S , Yartsev S
Published: November 2011

Purpose: To investigate the denoising and feature enhancement of the TomoTherapy® MVCT image. The improvement on the target delineation was evaluated by the contrast to noise ratio (CNR) and by comparison of contouring on original and enhanced images. Methods: A texture enhancing anisotropic diffusion approach different from conventional method was implemented. Parameters may be tweaked to achieve the best performance. Over 300 daily MVCT images from 7 head and neck patients were used for the CNR improvement evaluation. The images were segmented into air, fat, muscle, bone and the contrast between muscle and fat was used for CNR calculation. Five physicians contoured the gross tumour volume (GTV) for three head and neck cancer patients on 34 original and enhanced MVCT images. Variation between the targets outlined using original and enhance MVCT studies was quantified by DICE coefficient and the coefficient of variance. Results: The CNR improved almost three times (from 3.5–5.5 to 10–17) while the sharp muscle‐fat boundary was preserved. Based on volume of agreement between physicians, higher correlation was observed in GTV delineation for enhanced MVCT for patients 1, 2 and 3 by 15%, 3%, and 7%, respectively, while delineation variance among physicians wasreduced using enhanced MVCT for 12 of 17 weekly image studies. Conclusions: The texture enhancing anisotropic diffusion performs well inreducing MVCT noise while enhancing image features. The improvement of the TomoTherapy® MVCT image CNR helps in target delineation.
TH‐A‐220‐07: Semi‐Automatic Multi‐Modality Image Segmentation for Normal Organ Delineation in Head & Neck Radiation Treatment Planning
Authors: Hu Y , Grossberg M , Mageras G
Published: November 2011

Purpose: With increasing availability of MR simulators and their ability to provide better soft tissue contrast, we propose a semi‐automatic multi‐modality segmentation method to improve medical expertsˈ productivity and consistency in delineating normal radiation‐dose‐limiting tissues in head‐and‐neck cases with co‐registered CT and MR. Methods: Based on our previous graph based semi‐automatic segmentation method for single modality, we minimize a global energy function defined by local probabilistic regional and boundary terms: p(yi | xi) and p(yi, yj | xi not equal to xj),where yi is the image feature (intensity) at voxel i, xi is the classification (target organ or background) and voxels i and j are neighbors. To accommodate information from multiple image modalities, e.g. CT and MR, we use a multi‐value vector for image feature, by defining yi = (yi_CT, yi MR). CT and MR are registered using rigid mutual information registration to obtain image features from both modalities. Probabilities are estimated from samples collected locally from expertsˈ input by using an intuitive paint brush tool to roughly specify the voxels inside and outside the target organ. Side‐by‐side manual segmentation on the registered CT and MR is used as ground truth for comparison. Results: A preliminary study of brainstem segmentation in 4 patient cases, the dice similarity coefficient is 89.8±0.8% and the surface distance to the ground truth is 0.7±1.5mm. Conclusions: The novelty of our approach is the use of a multi‐value feature vector to exploit image formation from multiple modalities and use these features in a statistical energy minimization scheme for segmentation without removing expert oversight. Our initial results are encouraging and the semi‐automatic method has the potential to reduce user fatigue and improve productivity in treatment planning.
TH‐A‐220‐10: Ventilation Imaging of the Lung: Comparison of 4DCT with Hyperpolarized Helium‐3 MR
Authors: Ding K , Cao K , Miller W , Christensen G , Reinhardt J , Benedict S , Libby B , Sheng K
Published: November 2011

Purpose: Radiation induced pulmonary diseases can change the tissue material properties of lung parenchyma and the regional ventilation. 4DCT can be used to measure regional ventilation when combined with non‐linear 3D image registration. The purpose of this study is to analyze the effects of the B‐Spline grid spacing and the weighting of linear elasticity in 4DCT and image registration based measurement of ventilation by comparing the result to hyperpolarized helium‐3 MR (HP He‐3 MR). Methods: 4DCT data set and HP He‐3 MR before RT were acquired from one patient. The regularized tissue volume and vesselness preserving image registration algorithm was applied to register the maximum inhalation image to the maximum exhalation image for the measurement of regional ventilation. The HP He‐3 MR ventilation map was rigidly registered to the maximum exhalation image for direct comparison to the 4DCT derived ventilation map. Relative overlap (RO) was used to quantify the similarity between the two measurements. Ventilation maps derived from different B‐Spline grid spacing and Laplacian weighting in the image registration were compared. Results: The similarity between the two measurements increases as the increase of the B‐Spline grid spacing and Laplacian weighting which result a smoother ventilation map. In this study, the best similarity with the RO value 0.75 is found with Laplacian weighting of 0.5 and B‐Spline grid spacing of 32 mm. The Laplacian weighting of 0.01 with B‐Spline grid spacing of 8 mm shows the lowest OR value of 0.68. Visual inspection indicates the two measurements have similar anterior/posterior and superior/inferior gradients. Conclusions: We have compared the 4DCT based ventilation measurement with the results from hyperpolarized helium‐3 MR. This result will be valuable for improving the lung CT image registration algorithm toward accuracy not only in the measure of landmark error but also the underlying physiological changes.

This work is is supported in part by NIH 1R21CA144063.
TH‐B‐BRA‐01: Educational Course Therapy
Authors: Howell R , Newhauser W
Published: November 2011

Long‐term survivors of radiation therapy have an increased risk of developing second cancers, cardiovascular disease, and many other late effects. Population‐based epidemiological studies have established risk models to quantify the relationship between excess risk and radiation dose. The quantification of radiation‐related late effects and the use of modern delivery techniques to reduce such effects is an important and growing area of research in medical physics.

Currently, in the United States there are more than ten million cancer survivors and this number is rapidly increasing due to improved treatments, more frequent screening, and greater life expectancy. As the population of survivors increases so too does the need to minimize the likelihood of cancer therapy related late effects and specifically those related to radiation therapy. This continuing education session will focus on the two most commonly reported late effects from radiation therapy, second cancers and cardiac toxicity.

This session will provide an overview of the dosimetric techniques currently used in late effects studies, dose response models, and how data in the literature can be translated into clinical practice (now and in the future). The specific learning objectives for this session include:

1. To provide a general overview of the methods used in epidemiological studies of radiation‐related late effects.

2. To present an overview of the current knowledge on radiation‐related cardiac toxicity.

3. To present an overview of the current knowledge on radiation‐related second cancers.

4. To improve understanding of the results of late effects studies and their effect on the future practice of medical physics.
TH‐B‐BRB‐01: HDR Brachytherapy Commissioning and Quality Assurance for HDR Remote Afterloader, Source Exchange, Applicators
Authors: Pella S , McKee M , Chilukuri M
Published: November 2011

Brachytherapy is the first conformal radiation therapy. A sealed source is placed in or in contact with the tumor providing dose to the tumor with small volumes of normal tissue irradiated. It became more sophisticated with the usage of remote afterloader. With this, our responsibility as physicists increased and became critical in ensuring an accurate and precise treatment planning and delivery. The ability to deliver a correct treatment is conditioned by the precision of the source placement at the dwell point/points predicted by the treatment planning system (TPS). The introducing of the CT based planning gave the possibility of reconstructing not only the correct shape of a treated volume but the correct reconstruction of the applicators, the catheters, and localizing the first dwell position (the stopping point) of the radioactive source that will deliver the treatment.

The first condition of delivering a good and accurate treatment is correct catheter and applicators reconstruction, correct distance evaluation to each dwell position, and extremely good and well organized quality control program before the applicators and connectors are used and before the treatment plan is sent to the treatment console.

This lecture will provide an introduction into the understanding of High Dose Radiation Therapy QA and commissioning of the applicators. It will provide detailed descriptions of the remote afterloader, applicators, and all the quality assurance tools necessary for organizing and running a safe and secure High dose radiation therapy program (HDR) in a cancer center. Learning Objective:

1. Understanding the HDR process: technical and practical

2. Understanding the importance of a well implemented quality assurance program

3. Understanding the different aspects of commissioning and calibrating of the radioactive source and the applicators used in HDR.

4. Challenges and solutions of running a HDR program in a cancer center
TH‐B‐BRB‐02: HDR Brachytherapy Commissioning and Quality Assurance for HDR Remote Afterloader, Source Exchange, Applicators
Authors: McKee M
Published: November 2011

Brachytherapy is the first conformal radiation therapy. A sealed source is placed in or in contact with the tumor providing dose to the tumor with small volumes of normal tissue irradiated. It became more sophisticated with the usage of remote afterloader. With this, our responsibility as physicists increased and became critical in ensuring an accurate and precise treatment planning and delivery. The ability to deliver a correct treatment is conditioned by the precision of the source placement at the dwell point/points predicted by the treatment planning system (TPS). The introducing of the CT based planning gave the possibility of reconstructing not only the correct shape of a treated volume but the correct reconstruction of the applicators, the catheters, and localizing the first dwell position (the stopping point) of the radioactive source that will deliver the treatment.

The first condition of delivering a good and accurate treatment is correct catheter and applicators reconstruction, correct distance evaluation to each dwell position, and extremely good and well organized quality control program before the applicators and connectors are used and before the treatment plan is sent to the treatment console.

This lecture will provide an introduction into the understanding of High Dose Radiation Therapy QA and commissioning of the applicators. It will provide detailed descriptions of the remote afterloader, applicators, and all the quality assurance tools necessary for organizing and running a safe and secure High dose radiation therapy program (HDR) in a cancer center.

Learning Objective:

1. Understanding the HDR process: technical and practical

2. Understanding the importance of a well implemented quality assurance program

3. Understanding the different aspects of commissioning and calibrating of the radioactive source and the applicators used in HDR.

4. Challenges and solutions of running a HDR program in a cancer center
TH‐B‐110‐01: Informatics in Radiation Oncology
Authors: Siochi R
Published: November 2011

Informatics covers not only the information technology (IT) and infrastructure required to support data collection and management but also the computer science concepts that turn data into knowledge. In radiation oncology, medical physicists need to be familiar with the basic IT infrastructure that makes it possible to transfer and transform data through clinical processes that ultimately control radiation treatment delivery. The application of informatics continues with patient outcomes. Typically, this happens through participation in national protocols (e.g. RTOG). While they provide a framework for evidence‐based medicine, the data are often limited to parameters that were designed to test a pre‐defined hypothesis. As the ability to acquire and distribute data increases, we may be able to adopt data mining approaches to discover knowledge, even without asking specific questions. While simple database queries can efficiently provide statistical information (e.g. the NCI Surveillance, Epidemiology and End Results, SEER), data mining seeks hidden patterns through clustering, classification, regression and association. These principles can be applied to large volumes of concisely described data sets, similar to what can be found in clinical trials. Researchers in radiation oncology informatics are developing the infrastructure to acquire large data sets. The Radiation Oncology Data Alliance (RODA) initiative aims to provide online aggregate de‐identified data from participating users of the MOSAIQ EMR. Borrowing from the field of astronomy, researchers from Johns Hopkins used the SkyServer framework to build the OncoSpace project. The NCI caBIG (Cancer Bioinformatics Grid) also provides infrastructure support. Data analytics have also been developing in parallel, with researchers structuring the data collection phases to answer questions in Comparative Effectiveness Research (CER). While a majority of researchers look for links between treatment and outcome, others have used informatics to improve not only the efficiency and business of providing care but also its quality and safety, which ultimately affects outcome.

Learning Objectives:

1. Review the information technology and infrastructure required to deliver radiation therapy.

2. Understand the use of informatics in radiotherapy clinical trials.

3. Learn the basics of data mining and its applicability to radiation oncology.

4. Become familiar with the information technology that can be leveraged to improve clinical operations.
TH‐C‐224‐02: Economic Focus: Practical Aspects
Authors: White G
Published: November 2011

The Continuing Medical Physics Consultation CPT© code (77336) is one of only two codes that explicitly recognize the work effort of the Medical Physicist in the title and text. It provides the foundation for the reimbursement of clinical medical physics services in radiation oncology departments. As the complexity of the work done by the Medical Physicist increases, the valuation of this code has been decreasing. In this presentation, we will review the components of the work process that give rise to the code, the process by which the code is assigned a relative value, the recent changes to the valuation in both the Hospital Outpatient Payment system and the Medicare Fee Schedule, and strategies for returning the value of the code to an appropriate level.

Learning Objectives:

1. Understand the components of the work effort associated with the Continuing Medical Physics Consultation CPT© code (77336)

2. Understand how the code is valued and priced by Medicare

3. Offer opinions and comments on strategies to properly value the CPT© code 77336

4. Implement procedures in the clinic that properly reflect the description of the code provided by AAPM and ASTRO