bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐GG‐I‐29: Comparison of Spatial Resolution Properties for Three Cone‐Beam CT Systems Using An Aluminum Wire Phantom
Authors: Shen Y , Liu X , Chen L , Lai C , Han T , Wang T , Shaw C 
Published: July 2008

Purpose: To evaluate and compare the spatial resolution properties of three different cone beam CT systems using an aluminum wire phantom. Method and Materials: A wire phantom was constructed to evaluate and compare different cone‐beam CT systems for their spatial resolution. The phantom contains 12 aluminum wires of various sizes (51, 76, 102, 127, 152, 178, 203, 229, 254, 279, 305, and 356 μm in diameter) suspended in air in the axial direction and positioned along a 7.2 cm diameter circle around the rotating axis. The wire phantom was imaged with cone‐beam CT systems using three different detectors: an aSi/aSe flat panel detector (Anrad FPD14), an aSi/CsI flat panel detector (Varian PaxScan 4030CB) and a CCD/CsI detector (Hamamatsu C4742). Images were acquired in both continuous and pulsed x‐ray modes and in various binning modes (1×1, 2×2, 3×3 and 4×4). 300 projection images were acquired over 360° for each scan. Feldkamp's filtered backprojection algorithm with a pure ramp filter was used for 3D reconstruction. Results: Careful examination of the reconstructed images shows that wires as small as 100 μm were resolved with Anrad and Varian detectors. However, despite the smaller pixel size of the Anrad detector, images obtained with the Varian detector showed slightly better quality. It was found that binning did not affect the visibility but degraded quality was observed with increased binning size. Due to motion blur, images obtained with continuous x‐rays showed lower spatial resolution. Conclusion: It was found that the spatial resolution of cone‐beam CT system does not solely depend on detector's resolution. Using pulse mode X‐ray shows a better performance in cone‐beam CT system than continuous mode.This work was supported in part by grants CA104759 and CA124585 from NIH‐NCI, a grant EB00117 from NIH‐NIBIB, and a subcontract from NIST‐ATP.
SU‐GG‐I‐67: Assessment of Gamma Dose Rate in City of Kermanshah
Authors: Hosseinabad M Tavakoli , Kodamoradi E 
Published: July 2008

Purpose: Environmental natural radiation measurement is of great importance and interest especially for human health. The induction of genetic disorder and cancer appears to be the most important in an exposed population. Method and Materials: Measurements of background gamma rays were performed using a mini‐rad environmental survey meter at 25 different locations around the city of Kermanshah (a city in the west of Iran). The measurements were also performed at two different time of day one in the morning and the other in the afternoon. At each location and time measurement were repeated for five times and the mean was considered as the background dose at that location. Results and Conclusion: Comparison between the measured results in the morning and afternoon have not shown any significant difference (P>0.95). The maximum and minimum obtained results were 2.63 mSv/y and 1.49 mSv/y respectively. From the total measurement at 25 sites mean and SD background radiation dose to the population is 2.24±0.25 mSv. It is about 2.5 times of the world average total external exposure cosmic rays and terrestrial gamma rays dose reported by UNSCEAR.Keywords: Background radiation, Ionizing radiation, low level radiation, Environment radiation.
SU‐GG‐J‐90: Ex Post Facto Addition of Headframes to DICOM Image Sets for Radiosurgery Treatment Planning
Authors: Wiant D , Rossmeisl J , Robertson J , Bourland J 
Published: July 2008

Purpose: To facilitate Gamma Knife™ stereotactic radiosurgery (GK‐SRS) headframe placement and pre‐planning using pre‐existing DICOM images, for a canine radiosurgery clinical trial. Method and Materials: Software has been developed and tested for virtual GK‐SRS headframe placement using pre‐existing images obtained for diagnostic or other purposes. The Matlab‐based software allows for user‐interactive graphical positioning of the headframe or manual entry of headframe position relative to the clinical image coordinate system. Six degrees of freedom (translations and rotations) are enabled. The process was tested by matching the graphically added (virtual) fiducial markers to the true fiducial markers obtained from headframe image sets having known translations and rotations. Results: GK‐SRS fiducials can be virtually positioned either graphically or manually and then written to a new combined set of DICOM images for export to the GK‐SRS planning system. Frame placement accuracy is estimated at 1mm (∼ 1 voxel), dependent on the base image pixel resolution. GK‐SRS treatment plans can be developed prior to the treatment day to optimize both frame placement (e.g. ideal location) and treatment (e.g. dose location). Conclusion: Adding GK‐SRS fiducials to a DICOM image set allows possible headframe positions to be evaluated and enables transfer of the modified image set to the GK‐SRS planning system for definition of potential stereotactic coordinate systems. Viability of GK‐SRS can then be assessed with an initial treatment plan, without the patient present, to demonstrate treatment feasibility and increase efficiency on the treatment day. These tools, with slight modifications, serve a similar purpose for human GK‐SRS patients, allowing off‐site cases to be initially evaluated and pre‐planned, to aid in both treatment optimization as well as treatment day efficiency.Supported in part by the Wake Forest University TRADONC program NCI T‐32 CA113267 and by the Wake Forest University Translational Science Institute.
SU‐GG‐J‐163: Radiotherapy Response Assessment Using Deformed Serial 18F‐FDG PET/CT
Authors: Cannon B , Zhang L , Mawlawi O , Schwartz D , Moeller B , Dong L 
Published: July 2008

Purpose: To assess the ability of SUV measured on serial PET/CT to differentiate radiotherapy (RT) responders from non‐responders. Method and Materials: Between November 2005 and August 2007, 88 eligible patients with AJCC stage III‐IVb HNSCC were enrolled in an IRB approved protocol to receive serial PET/CT imaging studies prior to and following RT. Analysis of similar anatomic volumes on temporally separated images was facilitated with a deformable image registration technique to map pre‐ and post‐RT CT images to a reference image set, namely the RT planning CT images. The resulting deformable transformations were applied to the pre‐ and post‐RT PET images, thereby aligning both PET data sets to the RT planning CT images. SUV reduction factors were created from pre‐ and post‐RT SUV ratios and calculated for RT contours and fixed thresholds of the maximum signal intensity on PET images. Variations in pre‐ and post‐RT PET/CT scanner model and uptake duration were controlled to eliminate possible confounding factors for intrapatient analysis. Results: Cross correlation of patients whose serial PET/CT images were collected with the same scanner model and with uptake duration differences ⩽ 15 min reduced the useable number of patients drastically from 88 to 10. For the controlled patient cohort, the average SUV reduction factor for responders (N = 7) vs. non‐responders (N = 3) calculated for the GTV contour was (1.4 ± 1.6) and (1.0 ± 1.7), respectively. For all contours (N = 4), nonparametric testing revealed [P > 0.05]. Conclusion: The average SUV reduction factor was not able to significantly differentiate responders and non‐responders in all contours studied. The large reduction in useable patients following strict data set control may be an important cautionary note for future studies investigating serial PET/CT for treatment response monitoring.Research sponsored by Varian Medical Systems.
SU‐GG‐T‐545: Dosimetric Verification of RapidArc Treatment Delivery Using the Delta4 Phantom
Authors: Korreman S , Medin J , Wiberg I , Bocanek J , Archambault Y , Cozzi L 
Published: July 2008

Purpose: Recently, Varian Medical Systems have introduced a new treatment technique, in which dose is delivered over one gantry rotation with variable MLC positions, dose rate and gantry speed, RapidArc. A preclinical RapidArc installation was carried out on a Varian Clinac at our institution. We report dosimetric verification of reproducibility and consistency of RapidArc delivery using the Delta4 phantom (Scandidos, SE). Method and materials: 9 treatment plans generated in the Eclipse preclinical version of the RapidArc optimizer (H&N, prostate and lung) were delivered using a Clinac equipped with RadidArc delivery capability. The delivered dose was measured using the Scandidos Delta4 phantom. The measured dose distributions were compared with doses calculated in Eclipse. All plans were delivered three times consecutively, and the first run was used as reference for constancy checks. The temporal resolution of the delivery was analysed by investigating the arc segments between control points separately (177 control points per rotation). Gamma analysis (3%/3mmDTA) was used to quantify correspondence between dose distributions. Results: Overall, good agreement was observed between measured and calculated doses, generally with gamma values <1 in >95% of measured points. Comparison of the accumulated doses for two consecutive runs of a plan showed gamma values <1 in all measured points. The segment‐by‐segment analysis showed discrepancies between two consecutive runs, with >90% gamma values <1 in around 50–60% of the segments (gamma dose criterium 3%; <1–2 mGy for single segments). Segments with large dose deviations were typically counter‐balanced by following segments with large deviations of the opposite sign. The segment discrepancies cancelled out in the accumulated dose. Conclusion: The delivery of RapidArc beam delivery corresponded well with calculated dose distributions for different cases. The delivery was reproducible, and was carried out with high stability of the accelerator performance.Research sponsored by Varian Medical Systems, Inc.
MO‐B‐AUD C‐01: Proton Therapy
Authors: Smith A , Paganetti H 
Published: July 2008

The clinical advantages of proton beams have become widely recognized and there has recently been a significant increase in interest for building additional proton therapy facilities. There are currently over 25 institutions worldwide treating patients with proton beams and over 55,000 patients have been treated. There are at least 25 new facilities in various stages of planning and building. However, the fraction of patients treated with protons each year remains extremely small compared to the total number of cancer patients treated with external beam photons and electrons. The advantage of proton beams lies primarily in their excellent dose localization as compared to that which can be achieved using photon beams. Due to the Bragg peak characteristic in the depth dose of proton beams, the integral dose from proton therapy is, in general, about two times less that that for photon treatments. This allows higher doses to be delivered to target volumes, resulting in increased probabilities of local control, and lower doses delivered to critical normal tissues, resulting in decreased probabilities of treatment‐related morbidity. There are many challenges associated with increasing the accessibility of proton therapy not the least of which is the very limited number of clinical staff with knowledge of and training in proton therapy. The aim of the present Continuing Education Course is to provide a basic understanding of the rationale for proton therapy, physics of proton beams, technology of proton beam acceleration and transport, delivery of proton treatments, proton treatment planning and clinical results of proton therapy.Educational Objectives:1. Understanding of the physical characteristics of proton beams and interactions in tissues.2. Understanding of the beam production and treatment delivery technology for proton beams.3. Understanding of the clinical commissioning of proton therapy beams.4. Understanding of the basic principles of proton treatment planning.5. Understanding of the clinical results for proton therapy.
MO‐E‐332‐04: Comparison of Dose‐Area‐Product (DAP) and Fluoroscopy Time Between a Mobile and a Fixed C‐Arm Unit for Electrophysiology (EP) Procedures
Authors: Dohatcu A , Bednarek D , Rudin S 
Published: July 2008

Purpose: To determine if there is a difference in dose‐area‐product (DAP) or fluoroscopy time between electrophysiology (EP) procedures performed using a mobile and a fixed C‐arm fluoroscopic unit. Method and Materials: DAP and fluoroscopy‐time data was logged for 800 EP procedures performed using a mobile C‐arm unit from 2003 to 2005. In early 2006, a fixed C‐arm unit was installed and the same data logged for over 200 procedures. The procedures were sorted into five categories: 1. electrophysiology studies, 2. radiofrequency ablations, 3. pacemaker and implantable‐cardiac‐defibrillator implants, 4. biventricular interventions, and 5. lead changes. For each category, the distributions of DAP and time were compared and the average, median and range of values determined. Results: The median fluoroscopy time more than doubled for all procedure categories when using the fixed unit. Median DAP increased significantly for procedures 3 and 4, but remained nearly the same for procedures 1, 2 and 5. In all cases, the procedures were successfully completed without evidence of compromising patient care for either unit. However, the cardiologists were much more conservative in their use of fluoroscopy for the mobile unit due to its heat loading limitations and, also, they worked quicker because of their impression that the older mobile C‐arm gave more radiation dose to themselves and the patient. In addition, fluoroscopy at 15 frames per second was used on the fixed unit versus 7 frames per second on the mobile unit. Conclusion: Although the DAP and fluoroscopy time generally was higher for the fixed installation, it should not be concluded that the mobile unit is to be preferred. Rather, these results point out the importance of physician training and dose monitoring, not only to track patient radiation risk, but also to provide physician feedback.(*Support: NIH Grant R01‐NS43924).
TU‐A‐350‐01: Electron Monte Carlo: Clinical Impact
Authors: Ma C 
Published: July 2008

This presentation will facilitate participants with the clinical application of Monte Carlo dose calculation algorithms in radiotherapy treatment planning and dosimetry verification. Following a brief introduction to the clinical implementation and commissioning of the Monte Carlo dose calculation software detailed discussions will be given on the actual and potential impact of Monte Carlo dose calculation algorithms on conventional electron beam therapy and advanced mixed beam treatments.Comparisons of patient treatment plans generated using conventional dose calculation algorithms and Monte Carlo methods will be made with an emphasis on the causes of the dose discrepancies. Further discussions will be conducted on the use of Monte Carlo dose calculation as a radiotherapy treatment QA tool to validate individual patient plans and as an investigation tool to improve target dose conformity and normal tissue sparing using novel treatment techniques.Educational Objectives:1. To describe clinical implement and commissioning of Monte Carlo dose calculation algorithms for radiotherapy treatment planning.2. To discuss the impact of Monte Carlo dose calculation in electron therapy and advanced mixed beam therapy treatment planning.3. To describe the applications of Monte Carlo dose calculation in treatment planning and beam delivery QA for advanced radiotherapy treatments.
TU‐A‐350‐02: Monte Carlo Dose Calculation for Clinical IMRT Treatment Planning
Authors: Siebers J 
Published: July 2008

Monte Carlo (MC) dose calculation algorithms are now available in some commercial treatment planning systems for applications in photon beam IMRT planning. This course will examine the various stages of a MC IMRT dose calculation, including methods for particle sourcing, fluence modulation, and patient dose computation dose. The use MC as a QA tool to validate commercial IMRT dose calculation algorithms and its use as a QA tool to validate 3D dose distributions for individual IMRT plans will be reviewed. To this end, large‐scale comparison of clinical IMRT plans created with a commercial planning system with MC dose re‐calculation will be presented. Advantages of using MC algorithms directly in the IMRT optimization loop to circumvent optimization convergence errors and strategies to reduce MC dose calculation time when used within an optimization framework will be discussed.Educational Objectives:1. To understand the stages of a Monte Carlo dose calculation when applied to clinical IMRT treatment planning.2. To illustrate the role of Monte Carlo for IMRT treatment planning quality assurance.3. To evaluate the dose accuracy of a commercial non‐Monte Carlo IMRT dose calculation algorithms with respect to Monte Carlo dose computations.4. To demonstrate methods for Monte Carlo‐based clinical IMRT dose optimization.The author is supported in part by NCI Grant P01 CA116602, by Philips Medical Systems and by Varian Medical Systems.
TU‐A‐AUD A‐01: LINAC and MLC QA for IMRT
Authors: LoSasso T , Xia P 
Published: July 2008

Intensity‐modulated radiotherapy (IMRT) is now common in many therapy centers. Quality assurance (QA) procedures for a linear accelerator (linac) and multi‐leaf collimator (MLC) designed for conventional static fields do not address the unique dosimetric issues pertinent to IMRT planning and delivery. IMRT portals are composed of many irregular, small, off‐center, and abutting field segments throughout the target volume, each delivering only a few MU. In these regards, emphasis should be placed on beam stability for small MU and leaf position accuracy with gantry rotation. At the same time, the target volume, shielded by the MLC for much of the treatment, sees a larger transmitted dose, especially for MLC with rounded leaf ends, The impact of delivery technique, segmented (step and shoot) or dynamic (sliding window), on the required leaf position tolerance is not fully appreciated and will be addressed. While the mechanics and software of the various linacs and MLC distinguish them, there are many aspects of QA in common. This course will discuss: (1) the specific QA related to the MLC design; (2) additional QA for linear accelerators pertinent to the small MU and small field sizes used in IMRT; (3) tools and procedures often used to perform these QA tasks; (4) specific QA issues for different IMRT delivery methods.Educational Objectives:1. Understand different IMRT delivery methods and their specific QA issues.2. Understand effect of QA on the IMRT delivery accuracy.3. Understand the importance of proper commissioning of the planning system to avoid confusion with dose delivery issues.
TU‐B‐352‐02: Assessing Tumor Response to Therapy Over Time
Authors: Bullitt E 
Published: July 2008

Monitoring the efficacy of brain tumor therapy is a clinical dilemma. Results of biopsy provide the most reliable indicator but biopsy is too invasive for frequent use. The clinical standard of practice is to perform serial magnetic resonance scans and to assess changes to tumor “size” as seen on gadolinium enhanced images, with “size” measured in one, two, or three dimensions. This review discusses the advantages and disadvantages of the three measurement methods as well as some of the effects of voxel size on the calculation. Problems inherent to the use of gadolinium enhanced images include the effect of steroids and the confounding appearance of radiation necrosis. New treatment methods, such as administration of anti‐VEGF agents, may even cause disappearance of gadolinium enhancement while the tumor continues to grow. The limitations of the “tumor size” approach have led multiple groups to explore alternative methods of assessing tumor activity. We briefly explore some of these alternative methods to assessing tumor growth and treatment response.Educational Objectives:1. Understand the clinical standard of practice of monitoring brain tumor therapy from T1 gadolinium enhanced images.2. Understand the different common approaches to assessing tumor activity and their strengths/limitations.3. Understand the limitations inherent to various approaches.
TU‐C‐350‐02: Professional Services: What Can the AAPM Do to Support Your Practice?
Authors: Sherouse G 
Published: July 2008

The Professional Services Committee (PROFS) is a relatively new node in the AAPM's Committee Tree, created by gathering together some previously free‐floating entities that all have in common that they represent services to the membership in nominal support of professional practice. These include the newsletter, insurance, the Placement Service, and the Professional (salary) Survey. In addition, PROFS also serves as a home for some critical infrastructure including subcommittees charged with gathering workforce statistics and with validating the results of the Professional Survey.PROFS is the right platform for addition of new member‐directed services to the membership in support of professional practice. The last three bullets in the current Rules describing the charge of PROFS are.• Create and operate a career services booth at the Association annual meeting.• Educate the membership on issues related to practice development and business management support.• Offer programs and services of value to the membership that support the careers of medical physicists, such as malpractice insurance, legal and contractual guidance, business education, employment counseling, marketing techniques and compensation negotiation.We're currently underachieving at most of this, and both Vice Chair Mark Davidson and I are anxious to try to fill some of the void with your help. In this presentation I'll briefly review the structure of PROFS and the work of the current subcommittees. But I'll move pretty quickly to the question of what PROFS can be and what our priorities ought to be in the coming year, and will solicit audience feedback about that.It should be no surprise that an overarching theme of my presentation will be that if you want help from the AAPM, you've got to volunteer to be part of the effort. Requests from members for new services from subcommittees or task groups in PROFS are always welcome, and the potential for funding of new projects is high, but a suggestion is way more likely to be implemented if the request is accompanied by a draft charge and a list of 6 willing and enthusiastic volunteer members.