bluuebunny/crossref_metadata_2025 huggingface dataset:
TU‐G‐211‐01: Uptake Volume Histograms: A Novel Avenue towards Delineation of Biological Target Volumes (BTV) in Radiotherapy
Authors: Seuntjens J , Mohammed H , Devic S , Tomic N , Aldelaijan S , Deblois F , Seuntjens J , Lehnert S , Faria S
Published: November 2011

Purpose: To investigate the feasibility of decomposition of differential uptake volume histograms (UVH) derived from FDG‐PET and CT data for uncovering tumor sub‐volumes as a novel approach for defining biological target volumes (BTV) for use in radiotherapy treatment planning. Methods: For a cohort of 27 histopathologically proven non‐small cell lung carcinoma (NSCLC) patients, background uptake values were sampled within contra‐lateral healthy lung over PET slices containing tumor and then scaled by the ratio of tissue densities between healthy lung and tumor derived from CT data. Signal‐to‐background uptake values within volumes of interest encompassing the tumor were scored from which differential uptake volume histograms were constructed. These were subsequently decomposed into the minimum number of analytical functions that yielded acceptable net fits, as assessed by chî2 values. Results: Based on the assumption that each function used to decompose the UVH may correspond to a single sub‐volume comprising the volume of interest sampled, at least four sub‐volumes consistently evolved for our patient population. Furthermore, if crossing points between adjacent functions are interpreted as threshold values that differentiate sub‐volumes, average threshold values between the four sub‐volumes were found to be 0.80±0.21, 1.56±0.48, and 2.96±1.04 for adenocarcinomas, 0.89±0.48, 1.60±0.40, and 2.85±0.75 for large cell carcinomas, and 0.84±0.31, 1.70±0.58, and 3.72±1.68 for squamous cell carcinomas. Conclusions: Our study suggests that FDG‐based PET data could be used to identify biological sub‐volumes within tumor in NSCLC patients. Significant fluctuations in threshold values throughout the patient cohort can be explained as a consequence of large variability in physiological status of the tumor volume for each patient at the time of the PET/CT scan. This further suggests that BTV threshold values may be rather patient‐specific, and could be determined by creation and curve fitting of differential uptake volume histograms on a patient‐specific basis.
TU‐G‐211‐02: Design and Evaluation of Dual‐Ended Detectors for PET Mammography
Authors: Cuddy S , Taghibakhsh F , Rowlands J
Published: November 2011

Purpose: Positron emission mammography shows promise as a secondary breast screening technique to reduce the number of unnecessary biopsies. To reduce the dose to the patient, current PEM systems use depth of interaction (DOI) enabling detector modules. These detector designs however require a large number of channels per scintillator at high system cost and complexity. We propose a dual‐ended readout block detector module (DERBDM) design combining the high encoding ratio of Anger logic with the DOI measuring dual‐ended readout detector design to reduce the number of required channels while maintaining spatial resolution on the order of 2‐mm. Methods: A prototype DERBDM was constructed from 2 × 2 pixels with 3.4‐mm pitch from two SensL silicon photomultipliers arrays (SPMArray2‐A0), two 2‐mm thick glass light guides, and a 3 × 3 array of 2‐mm × 2‐mm × 20‐mm scintillators with 2.075‐mm pitch. The signal from the DERBDM was digitized using eight channels of a CAEN Systems 16‐channel 12‐bit 250‐MS/s waveform digitizer. The ability to identify crystal index, DOI resolution, and energy resolution were measured. Results: The DERBDM was found to resolve events in a flood field image and with energy‐based corrections clearly identifying the interacting scintillation crystals. After per‐crystal corrections were applied, DOI was resolved with 5‐mm FHWM resolution. Energy was corrected with crystal index‐ and DOI‐ dependant and found to discriminate the energy of events with a resolution of 20%. Conclusions: This work demonstrates the DERBDMˈs ability to increase encoding ratio at least 2‐fold from that of the dual‐ended readout design without sacrificing spatial resolution. It indicates that the DERBDM has the potential to meet the need for an affordable, high resolution, highly specific breast imaging system.
TU‐G‐301‐01: Practical Contouring: Prostate and H&N Anatomies
Authors: Wu J , Hsu I , Smith J
Published: November 2011

In the last decade IMRT and related treatment modes have become de facto, if not actual standards of care. These modes are heavily dependent on the anatomical modeling phase of treatment planning. It may in fact be argued that this is the most important step in the planning process, as the optimization and plan evaluation will be directly affected by a good or poor anatomical model. Physicists have increasingly been called upon to do much of this contouring, yet have traditionally had only a brief formal introduction to anatomy. This session will provide a brief overview and refresher on two anatomical regions that have come to be most often treated by IMRT and like modalities.

Dr. Jonn Wu will discuss the contouring of prominent normal structures and target volumes in the head and neck using multiple imaging modalities, and illuminate key concepts in identifying these structures. Dr. I‐Chow Hsu will discuss the structures in the pelvis relevant to prostatic treatments, including pelvic lymphatic chains, using CT and the Visible Human Project.

Learning Objectives:

1. To better understand how to identify structures in the head and neck

2. To better understand how to identify structures in the pelvis relevant to prostate treatments

3. To understand the impact and pitfalls of different imaging modalities in these anatomical locations.
WE‐A‐BRB‐10: Radiobiologically Based Treatment Plan Evaluation for Prostate Seed Implant
Authors: Knaup C , Mavroidis P , Esquivel C , Swanson G , Papanikolaou N
Published: November 2011

Purpose: Delivered dose distributions for prostate seed implant treatments are often considerably different from the planned distribution. This makes accurate treatment plan evaluation important for future patient care decisions. Presently, treatment plan evaluation is based on several dosimetric quantifiers for the tumor and organs at risk. However, these do not account for effects of varying dose‐rate, tumor repopulation and other biological effects. By including the biological response a more clinically relevant treatment plan evaluation may be obtained. Methods: Eleven patients were evaluated. Each patient received a 145 Gy implant. Iodine‐125 seeds were used and the treatment plans were created on the Prowess system. One month after the implant each patient received a CT scan. From these images the post‐implant plan was created. In the post‐plan, the primary tumor, urethra, bladder and rectum were contoured. The biologically effective dose (BED) was calculated for each voxel using the physical dose and the biological parameters of the appropriate organ. The BED was used to determine the tumor control probability and the normal tissue complication probabilities for the bladder, rectum and surrounding tissue. Results: By incorporating radiobiological measures into the evaluation the predicted clinical outcome is concisely given by response probabilities of each organ. The average tumor control probability and complication probabilities for the urethra, bladder, rectum and surrounding tissue were 99%, 39%, 0.2%, 12% and 4% respectively. These measures provide a simpler means for evaluation and since they include radiobiological factors, the response probabilities provide a more reliable estimate of the treatment outcome. Conclusions: The goal of this work was to create a more clinically relevant treatment evaluation by incorporating radiobiological measures that estimate the clinical results. This resulted in a simpler descriptor of treatment plan quality based on expected response probabilities rather than many endpoint doses for several organs.
WE‐A‐214‐01: Teaching Radiology Residents in the Era of the New ABR Exam
Authors: Nickoloff E , Mahesh M , Kanal K , Heintz P , Hendee W , Rzeszotarski M , Schueler B
Published: November 2011

Major changes in the ABR certification process have been implemented which would affect the physics teaching programs for radiology residents. Radiology residents entering residency programs after June 30, 2010 will take their first computer based ABR core examination in 2013 after completing three years of training. The final ABR certification examination is also computer based and will be administered 15 months after the completion of residency training. There will be no oral exam. Moreover, the organization and content of the physics portion of the core exam is scheduled to change. The emphasis of the questions will be directed toward image quality and safety and will have a clinical focus. This session is based upon an article published in the JACR in November 2010. The session is divided into several sections aimed at providing guidance for physicists who teach radiology residents. The first portion of the program will address the changes to the ABR examination process. The next portion will discuss several potential approaches for teaching residents in the era of the ABR changes. The following portions of the program will suggest several useful resources available to physicists to supplement their teaching programs. These resources include: the AAPM Diagnostic Radiology Physics Curriculum, the new AAPM / RSNA web‐based radiology teaching modules and the Radiographics AAPM / RSNA physics tutorial for residents articles. There are now 46 AAPM / RSNA web‐based modules and more than 25 Radiographics tutorial articles which all residents can access without any fees. This session will end with a discussion panel led by the speakers.
WE‐A‐220‐01: Current Status of HIFU Therapy for Treatment of Benign and Malignant Tumors of the Abdomen, Pelvis and Bone
Authors: Hwang J
Published: November 2011

High‐intensity focused ultrasound (HIFU) is a noninvasive method currently being investigated to treat certain primary solid tumors, metastatic disease, and enhance drug delivery. The field of medicine is evolving towards increasing use of noninvasive and minimally invasive therapies such as HIFU. The application of HIFU for tumor therapy has recently been gaining momentum due to advances in imaging technology such as magnetic resonance thermometry and advanced ultrasound imaging techniques that permit real‐time monitoring of HIFU treatment effects. Currently, several commercially available HIFU devices are manufactured worldwide for treatment of a wide variety of both benign and malignant tumors including uterine fibroids, prostate cancer, pancreatic cancer, liver tumors, thyroid tumors and other solid tumors that are accessible to ultrasound energy. Although HIFU technology has been used clinically since the 1950ˈs it remains a new therapeutic technology requiring further laboratory and clinical evaluation. This presentation provides an overview of the current status of clinical applications of HIFU for benign and malignant tumors within the abdomen and pelvis as well as treatment of bone metastasis.

Learning Objectives:

1. Understand the mechanisms that HIFU induces a biologic effect

2. Understand the current limitations of ultrasound and MR‐guided HIFU therapy

3. Understand the anatomic requisites and limitations for HIFU therapy
WE‐B‐BRA‐01: TG‐142: Quality Assurance for Medical Accelerators
Authors: Klein E
Published: November 2011

The task group (TG) for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicineˈs Science Council, under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The report was published in the Journal of Medical Physics in September of 2009. [http://aapm.org/pubs/reports/RPT_142.pdf] The task group (TG #142) had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG ▭ 40 Report on Quality Assurance, and second, to add recommendations for Asymmetric Jaws, Multileaf Collimation (MLC), and Dynamic/Virtual Wedges. The TG accomplished the update to TG▭40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies, but also for imaging devices that are part of the linear accelerator. The imaging devices include x▭ray imaging, photon portal imaging, and cone▭beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments, or intensity modulated radiotherapy (IMRT) require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. This is consistent with the philosophy of TG▭100, “Method for Evaluating QA Needs in Radiation Therapy.” The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report also gives specific implementation recommendations regarding setup of a QA program by the physicist, such as; building a QA team, establishing procedures, training of personnel, documentation, and end▭to▭end system checks. The tabulated items of this report have been considerably expanded as compared with the original TG 40 report and the recommended tolerances accommodate differences of the intended functionality (i.e., non▭IMRT, IMRT, or Stereotactic Delivery).

Learning Objectives:

1. To understand the updates to TG▭40 in the new TG▭142 report.

2. To understand the recommend QA tests for wedge, MLC, and imaging systems as they pertain to accelerator type and procedures performed (i.e. IMRT).

3. To understand the implementation plan and action level and response recommendations
WE‐B‐110‐01: Application of Medical Informatics to Patient Dose Management in Interventional Radiology
Authors: Pavlicek W
Published: November 2011

Tools for measurement and validation of radiation dose, including ALARA Policies for Fluoroscopically Guided Interventions (FGI) have been being developed using medical informatics. Informatics, primarily DICOM and Hl7 are rich content data sources that provide the potential for determination of peak skin dose, as well as a direct and immediate source of conventional metrics such as KAP, cumulative AK at the RP, and fluoroscopy duration. Newly purchased equipment may provide Radiation Dose Structured Reports which includes each radiation episode (fluoroscopy, DSA, Digitial Spots, or Cine) as separate records. For each of these data files, table position, exposure at the RP, collimation, etc. are available for use. A database has been created that uses DICOM exchange to capture dose related information for FGI. These data are used in conjunction with simulated C‐arm devices that more and mimic that which is encountered in a lab. When the desired physics parameters are included (backscatter factor, table attenuation, calibration of the vendors AK, etc) it is possible to re‐ create the exposure irradiations actually used, to compute and locate on a virtual patient the skin dose distribution and determine the Peak Skin Dose. This dose is saved to the data base for future QA uses.
WE‐B‐220‐02: Advances in MR for Guidance of US Therapy
Authors: Butts‐Pauly K , Kaye E , Holbrook A , Bitton R
Published: November 2011

Image guidance of focused ultrasound therapy is important for targeting the therapy, ensuring treatment and safety, and for assessing the therapy. This presentation will describe recent advances in these areas of the MR guidance of focused ultrasound.

Accurate focusing of the ultrasound beam to the target tissue can be done with a low temperature rise “test shot.” Alternatively, imaging the acoustic radiation force allows visualization of the focal spot without a temperature rise. MR imaging of the acoustic radiation force displacement (MR‐ARFI) relies on the application of the ultrasound during a portion of a series of gradient lobes. In areas where the tissue is displaced, the water spins experience a different magnetic field and accumulate phase, which is not fully refocused at the time of signal measurement. The visualization of the focal spot can thus be achieved without a temperature rise.

In addition to straightforward visualization of the focal spot, MR‐ARFI can provide a means for image feedback when correcting phase aberrations from the skull. An iterative method allows modification of transducer phases while maximizing the displacement at the focus. A non‐iterative method requires the MR‐ARFI measurements to be made, followed by a matrix inversion.

For tissue ablation, MR thermometry can be used to accurately monitor tissue temperature. MR thermometry can be very sensitive to motion, including motion of the treated tissue or even motion of tissue in the vicinity of the treated tissue (such as due to respiration). Temperature imaging methods must be robust to these types of motions and solutions include multibaseline, referenceless, and hybrid multibaseline/referenceless approaches. Another important task for MR guidance is in beam steering in moving organs, such as the liver and kidneys.This can be done based on imaging alone or on a combination of imaging and respiratory phase monitoring, such as can be done with the bellows.

Lastly, there are a number of methods under investigation for the visualization of ablated tissue. MR‐ARFI is a potential candidate. The acoustic radiation force displacement depends both on the ultrasound intensity and on the displacement of the tissue, which in the latter case ARFI relies on tissue displacement by the ultrasound beam, which is related to the tissue stiffness. Evaluating the change in tissue stiffness provides the spatial extent of the thermal ablation. Other evaluative imaging methods includes contrast enhanced MRI, which visualizes disruption of perfusion, and diffusion‐weighted MRI, which demonstrates a 36% decrease in ADC in the ablated tissue.

Learning Objectives

1. Understand the basis for acoustic radiation force imaging and its applications

2. Understand the current research in the image guidance of focused ultrasound
WE‐C‐224‐02: The Clinical Medical Physics Situation in Africa
Authors: Ige T , Nakatudde R , Seddik Aibn , Khaled M
Published: November 2011

Medical Physics in Africa has evolved over the last half a century from the Republic of South Africa in the southern tip of the continent to Ghana and Nigeria in the Western half and also Kenya, Uganda and United Republic of Tanzania in the Eastern sphere of the region and unto Algeria, Egypt, Morocco and Sudan in the Northern part.

There is a wide disparity in terms of educational infrastructure and availability of equipment across this very wide geographical landscape to provide the required medical physics services particularly in the health establishments as well as the other areas where the expertise of this cadre of professionals are needed. In terms of human resources capability, the continent can only boast of a slightly more than 300 personnel employed in and around her health facilities and about 60% of these staff are domiciled in just three countries — Egypt, Morocco and Republic of South Africa.

An attempt will be made in this paper to discuss the clinical medical physics issues both from the historical perspectives as well as the current state of affairs in the continent which culminated in the recent birth of the Federation of African Medical Physics Organisation (FAMPO) which has just been recently given a charter as the youngest regional body of the International Organisation of Medical Physics (IOMP).

Learning Objectives:

1. The Medical Physics infrastructure in terms of equipment and manpower.

2. The Status of Education and Training in Africa.

3. The gaps in the Medical Physics profession that FAMPO intends to address in the continent.
WE‐C‐224‐03: Medical Physics in Senegal: Status and Prospects
Authors: Gueye P , Ka O , Diagne M
Published: November 2011

Senegal is one of the leading economies in the western sub‐Saharan region. Still, first‐class radiological equipments are lacking in the country. Radiation treatments are still done with 60Co sources and only a few x‐ray machines with limited capabilities are available for diagnostic imaging. This situation is compounded by maintenance issues that are not always easily overcome, due to lack of adequate funds devoted to this aspect of the running of a medical infrastructure. On the other hand, specialized personnel are also needed, in particular medical physicists. The situation has a serious impact on the health care of patients in this country.

An ongoing effort to establish in Senegal an international interdisciplinary center is expected to contribute in solving the many issues existing in the field of medical physics. Indeed, the center will offer a strong medical physics component, with diagnosis and treatment tools as well as educational programs aimed at providing the basis for the improvement of health care.

This communication will present the current status of medical physics in Senegal together with the interdisciplinary center project and its impact in health care in this country and beyond, in particular in Western Africa.
WE‐C‐BRB‐03: Feasibility Study for Total Marrow Irradiation with RapidArc Volumetric Arc Therapy (VMAT‐TMI)
Authors: Surucu M , Yeginer M , Kavak G , Fan J , Aydogan B
Published: November 2011

Purpose: To investigate the dosimetric feasibility of VMAT‐TMI technique in terms of treatment planning and delivery efficiency and accuracy for a Rando phantom using Eclipse RapidArc technology. Methods: Total body irradiation (TBI) has been an integral part of pre‐conditioning regimens for the treatment of hematologic malignancies. Normal tissue toxicity is a common complication of TBI inclusive regimens especially at doses higher than 12 Gy due to inhomogeneous and excessive dose to organs at risk (OARs). Fixed gantry linear accelerator (linac) and Tomotherapy intensity modulated total bone marrow (IM‐TMI) techniques have been reported to reduce doses to OARs. However, the treatment time of more than one hour with both techniques may limit their clinical application. Volumetric modulated arc therapy (VMAT) may be able to increase the treatment delivery efficiency while increasing the target conformality and reducing the radiation dose to OARs. In order to treat all the bones in the Rando phantom, three sub‐plans with a total of nine arcs were used. A total of 100 thermoluminescent detectors (TLDs) were placed at 39 positions throughout the phantom. The measured TLD doses were compared to the calculated plan doses. Planar dose for each arc was verified using MapCheck and MapPhan. Results: Excellent target coverage with the prescription dose and dose reduction to the OARs were achieved similar to the fixed gantry linac IM‐TMI technique. The number of monitor units was decreased by 50%, while the delivery efficiency increased by more than 60%. TLD readings demonstrated accurate dose delivery, with a median dose difference of 0.5% from the calculated dose. Planar dose distributions of all arcs satisfied the 3% and 3 mm gamma criteria with an average pass rate of 97.8%. Conclusions: Results from this study suggest that RapidArc VMAT‐TMI technique is clinically feasible.

This study is supported by Varian Medical Systems
WE‐C‐BRB‐10: Dynamic Accelerated Partial Breast Arc Irradiation via Synchronized Trajectories of Couch and Gantry
Authors: Fahimian B , Xing L , Horst K , Hristov D
Published: November 2011

Purpose: Accelerated partial breast irradiation (APBI) and external beam boosts of the lumpectomy cavity are accessible non‐invasive alternatives to brachytherapy techniques. However, the utilization of IMRT, in a manner to adequately spare normal tissue beyond the chest wall, is limited due to angular and geometrical clearance restrictions in isocentric breast setups. To address this, a novel method is introduced in which synchronized motion of the gantry and couch, in conjunction with a prone breast setup, enables the placement of horizontal arcs around the ipsilateral breast and provides conformal coverage of complex targets with substantial sparing of normal tissue. Methods: Optimization algorithms were developed to determine non‐collisional gantry and couch trajectories that can concurrently maintain the target within beam apertures defined by a multi‐leaf collimator. The Varian TrueBeam STx, which in Developer Mode allows for customized programmable motion of the couch during beam‐on, was used to implement the method. Patient scans, simulated in the prone position on an in‐house immobilization board were used for treatment planning of non‐isocentric intensity modulated arcs. The dosimetric results were quantified against conventional limited angle IMRT for the clinical cases of APBI and lumpectomy boosts. Results: Relative to a typical 5 field IMRT APBI beam arrangement as suggested by RTOG‐0413, the proposed dynamic arc method resulted in 44% lower volume of normal tissue receiving 50% of the prescription (V50), and 40% lower volume of normal tissue receiving 100% of the prescription (V100). Conclusions: Recent reports have correlated the occurrence of unacceptable cosmesis in APBI to the volume of normal breast tissue receiving 50% and 100% of the prescription dose. From the results of this study, it is anticipated that the proposed method of synchronous treatment trajectories of the couch and gantry can allow for more clinically favorable APBI treatments.
WE‐C‐214‐01: Is Medical Radiation Safe? Can It Be Safer?
Authors: Hendee W
Published: November 2011

Recent media publicity about patients injured by mistakes in radiation therapy and other patients receiving excessive doses from computed tomography has emphasized the need for improved measures to keep patients safe during medical procedures employing ionizing radiation. In a list of technology health hazards compiled by the ECRI Institute for 2011, radiation therapy is listed as number 1 and computed tomography is listed as number 4. Missing from these analyses is recognition of the profound health benefits of computed tomography and radiation therapy. Still, safety and quality can be improved through a variety of measures being implemented by medical physicists. These measures help to allay concerns that medical physics is not doing enough to improve quality and safety in both medical imaging and radiation therapy.
WE‐C‐214‐06: Patient Safety Improvement through Incident Learning in Radiation Treatment ‐ Four Years Experience
Authors: Clark B , Brown R , Ploquin J , Kind A , Grimard L , Dunscombe P
Published: November 2011

Purpose: To describe results from our comprehensive incident learning system gained over 4 years. Methods: An incident learning system specifically tailored to a radiation treatment program and based on published principles was implemented in our large academic cancer centre in late 2006. In the adopted system, every incident, whether or not there is a resulting direct impact on a patient treatment, is recorded, investigated to determine basic causes and strategies developed to correct system weaknesses. Our centre operates 10 megavolt accelerators and treats nearly 4,000 patients per year. Incidents are categorized into one of 5 types and classified according to 4 levels of severity. Interventions introduced as part of the learning from these reports have included changes in staffing levels in more vulnerable areas and several human factor error reduction strategies. Results: Our data are derived from a total of 2,221 incidents reported during the four years of operation, with 98.1% classified as either minor or potential. Of the actual incidents reported, we have seen a significant decline from 117 in 2007 to 84, 62 and 52 in the subsequent three years (chi‐squared non‐parametric test). The actual incident rate at the point of treatment delivery has decreased from 0.095% in 2006 to 0.022% in 2010. During this period, the system provided rapid feedback to monitor several new initiatives including a new external beam treatment planning system, three different types of image guidance hardware and software and several new techniques such as stereotactic body radiosurgery and volumetric modulated arc therapy. Conclusions: We report a sustained significant increase in the safety of treatment through the use of root cause analysis. Our results indicate that an effective incident learning system implementation will strongly encourage the reporting of potential incidents as a proactive means of enhancing safety and quality.
WE‐C‐214‐08: Benefit of an Industrial Engineering Tool (Statistical Process Control) in Radiation Oncology: Clinical Experience
Authors: Palaniswaamy G , Rangaraj D , Yaddanapudi S , DeWees T , Brame S , Mutic S
Published: November 2011

Purpose:

1. Develop a tool for data collection, retrieval, visualization, real‐time feedback and advanced statistical analysis of IMRT QA process.

2. Evaluate the need for site‐specific tolerances for IMRT QA.

3. Timely identify systematic drifts in the IMRT QA measurements.

Methods: Statistical process control (SPC) is a statistical tool that can be used to study process variations and evaluate process capability. This tool is applicable to IMRT QA processes. There are two causes of variation present in a process — common cause, which is the reason for random variation in the process, and special (assignable) cause, which is the reason for identifiable variation in the process. Process capability and control charts (S chart for process variability and EWMA chart to study the process mean) are two of the several tools available to study the process of interest. We use SPC and paperless environment for collection and processing of clinical IMRT QA data to create a tool for improved management of IMRT QA. Results: Automatic data collection, data validation and visualization are facilitated with the help of the developed tool. Data visualization and control charts are used to study the process variation and identify drifts and outliers. Process capability studies identify systematic variations present in the process and evaluate the need for site‐specific tolerances. For instance, process capability studies of the QA results for treatment plans using 6 MV X‐rays revealed a 1.1% variation in calibration and 0.5% variation in beam model and MLC leaf model. Conclusion: We have built a tool that collects data, analyzes them, plots S chart for process variability and EWMA charts. Process capability studies show that using a global tolerance for all different sites is not sufficient. Hence, we propose the use of 2 standard deviations for a 95% confidence level in the IMRT QA measurements.
WE‐D‐220‐02: Relation of External Surface to Diaphragm Motion Based on Automatic Analysis of Ultrasound Images
Authors: Yan P , Burri R , Feng W , Chao K
Published: November 2011

Purpose: The accuracy of delivering gated‐radiation therapy to lung tumors using an external respiratory surrogate relies on the degree of correlation between the marker serving as a surrogate from breathing and motion of the anatomic structures. The irregular breathing during an imaging and treatment session and from one session to another may cause the dose distribution actually delivered to be different from the intended dose. The purpose of this work was to use the diaphragm images acquired from Ultrasound system and abdominal motion signal from Real‐time Position Management (RPM) system, to study the relation between diaphragm and external surface motion during uncontrolled breathing cycles. Methods: The ultrasound images of diaphragm were captured at the same time as RPM signal acquisition for three volunteers from our staffs. After capture, one point at the image of diaphragm was selected and tracked for the whole breathing cycles using a proposed automatic tracking method which combines moving average strategy with Gaussian filter. Then, the diaphragm motion was compared to the respiratory signal from RPM system. Results: On three normal volunteer data sets: (1) the phase shifts were measured between the RPM signal in the abdominal region and diaphragm motion. Three volunteers showed the diaphragm motion either leading or delay abdominal motion with the mean time around 0.2–0.4 second; (2) the phase shifts at difference breathing cycle for the same people were different; (3) there is no significant difference between the phases at the end of inhale and exhale. Conclusions: We conclude that the external monitor can be used to predict internal respiratory motion. However, it may be important to check with Ultrasound images or fluoroscopy of diaphragm for possible time delays. We found that the Ultrasound can be a more reliable non‐ionizing method than RPM system used for respiratory gating in radiation therapy.
WE‐D‐220‐04: Operator Uncertainties in a Soft Tissue 3D Ultrasound Image Guided Radiotherapy System
Authors: Meer S , Bloemen E , Hermans J , Voncken R , Heuvelmans D , Gubbels C , Berbee M , Seravalli E , Visser P , Lutgens L , Gils F , Verhaegen F
Published: November 2011

Purpose: Image Guided Radiotherapy (IGRT) is a necessity for accurate radiotherapy. Ultrasound (US) imaging is a frequently used diagnostic technique for qualitative imaging of soft tissues. Recently, a quantitative 3D US system was introduced (Clarity system, Resonant Medical, Canada) which can assess the position of soft tissue in absolute space. Before introducing the device into daily practice, user variability, during both image acquisition and matching procedures must be determined. In this study we determined the inter‐ and intra‐operator variability of 3D US matching in prostate cancer patients. Moreover, we studied the influence of the scan variability on patient setup corrections, and the influence of probe pressure on the prostate position while using a strict bladder filling protocol. Methods: For 12 prostate patients multiple US scans are acquired by one or two operators during treatment. The repeated scans are matched to the reference US‐scan by a single user (variability for scanning). The remaining scans are matched three times by different users, and for each patient one single scan is matched five times by the same user (variability for matching). Results: In all three directions the mean intra‐operator difference ranges from 1.5 to 2.4 mm, with a standard deviation of approximately 1.7 mm. The mean inter‐operator difference is of the same order, 1.7 to 2.3 ± 1.8 mm. The prostate displacement due to the probe pressure varies from patient to patient and is not limited to one direction. Only the superior/inferior displacement seemed significant for high pressure, which was not needed to obtain good image quality with our bladder filling protocol. The total uncertainty is conservatively estimated to be 4 mm. Conclusions: The uncertainty of the 3D US IGRT system is comparable to the uncertainty of the current standard IGRT for prostate: electronic portal imager in combination with fiducial markers.
WE‐E‐224‐04: Mental Preparation to Pass the ABR Board Certification in Radiological Physics
Authors: Stuller E
Published: November 2011

Passing the Board Certification in Radiological Physics by the American Board of Radiology presents unique challenges in all 3 phases. Recognizing ones individual learning and testing styles is critical to success in each phase. Although individual learning styles may vary, brain healthy preparation, handling test anxiety, and acquiring effective copping skills is essential to success. This talk is designed to inspire self‐confidence by acquiring specific oral and written test taking techniques, recognizing anticipatory and situational anxiety, and developing coping skills needed to pass all three phases of the Boards.

Learning Objectives:

1. Learn brain healthy strategies in preparation for the boards.

2. Recognize and develop coping skills for pre —test anxiety, anxiety during the exam and surviving posttest anxiety.

3. Build self‐confidence through adequate test preparation by acquiring skills in self‐care, sleep hygiene, strategies to cope with internal and external distractions, time management testing skills, and physical and sedentary exercises during preparation.

4. Learning to finish strong in all 3 phases of testing by learning and mastering the acquired skills of test taking in both the written and oral boards.
WE‐E‐BRB‐05: Characterization of a Novel DNA Dosimeter for Skin Dose Measurements
Authors: Wood T , Lewis BJ , Corcoran EC , Kerr A , Schreiner LJ
Published: November 2011

Purpose: To develop a novel DNA dosimeter for accurate dose measurements in a broad spectrum of therapeutics beams including contaminated x‐ray fields. Methods: Monte Carlo simulations were used to evaluate the DNA dosimeter for surface dose detection. The dose deposited to the detector while on the surface of a cylindrical tissue phantom was compared to the dose deposited to the first 1 mm of skin along the beamˈs central axis for electrons and photons with energies 100 keV to 20 MeV. These results were combined with a theoretical derivation of the dosimeterˈs response to a broad spectrum of electron‐photon fields and compared to experimental results. Results: Results from the Monte Carlo simulations and theoretical derivation concluded that the DNA detector is capable of measuring skin doses with a 4.2% relative uncertainty. The experimental uncertainty in absorbed dose measurements was found to be 9%. The DNA dosimeter showed a linear signal response with dose in the range of 10 cGy to 10 Gy and the responses were statistically equal in cobalt 60 and 6 MV beams. Conclusions: The DNA dosimeter is theoretically capable of accurate absorbed dose measurements in therapeutic beam including skin dose measurements from contaminated x‐ray beams. Further experimental testing is required to determine if the dosimeter is independent of energy in a broad energy range of electron and photon fields and lower the experimental uncertainty.

This work has been partially funded by the Chemical, Biological, Radiological‐Nuclear and Explosives Research and Technology Initiative (CRTI), project #06‐0186RD.
WE‐E‐BRB‐11: Radiation Hardness of the Storage Phosphor Europium Doped Potassium Chloride for Radiation Therapy Dosimetry
Authors: Driewer J , Chen H , Osvet A. , Sun B , Ice L , Low D , Li H
Published: November 2011

Purpose: An important property of a reusable dosimeter is its radiation hardness, that is, its ability to retain its dosimetric merits after irradiation. The radiation hardness of europium doped potassium chloride (KCl:Eu2+), a storage phosphor material recently proposed for radiation therapy dosimetry, is examined in this study. Methods: Pellet‐style KCl:Eu2+ dosimeters, 6 mm in diameter and 1 mm thick, were fabricated in‐house for this study. The pellets were exposed by a 6 MV photon beam or in a high dose‐rate 137Cs irradiator. Macroscopic properties, such as radiation sensitivity, dose response linearity, and signal stability, were studied with a laboratory photostimulated luminescence (PSL) readout system. Since phosphor performance is related to the state of the storage centers and the activator, Eu2+, in the host lattice, spectroscopic and temporal measurements were carried out in order to explore radiation‐induced changes at the microscopic level. Results: KCl:Eu2+ dosimeters retained 40% of their initial signal strength after a 5000 Gy dose history. Sensitivity recovered to nearly 90% via a high‐temperature annealing procedure. Dose response was initially supralinear over the dose range of 50–500 cGy but became more linear with dose history. Measured data fit a linear approximation to within an average of 2% after 200 Gy to 5000 Gy dose history. There were no significant changes in the PSL stimulation spectra, PSL emission spectra, photoluminescence spectra, or luminescent lifetime, indicating that the PSL signal process remains intact after irradiation but at a reduced efficiency due to recoverable radiation‐induced perturbations in the crystal lattice. Conclusions: Systematic studies of KCl:Eu2+ material are important for understanding how the material can be optimized for radiation therapy dosimetry purposes. The data presented here indicate that KCl:Eu2+ exhibits strong radiation hardness and lends support for further investigations of this novel material.

This work was supported in part by NIH Grant Nos. R21CA131690 and R01CA148853.
WE‐E‐BRC‐01: Impact of Tumor Size and 18F‐FDG Tracer Uptake Heterogeneity in Non‐Small Cell Lung Cancer Tumor Automatic Delineation on PET and CT Images for Gross Tumor Volumes Determination
Authors: Hatt M , Rest C Cheze‐Le , Pradier O , Visvikis D
Published: November 2011

Purpose: The objective of this study was to investigate the impact of tumor size and tracer uptake heterogeneity on the automatic delineation of 18F‐FDG PET and CT tumor volumes (TV) in NSCLC. Methods: 26 NSCLC patients with FDG PET/CT were considered. For 18 cases, the tumor maximum diameter was measured by macroscopic examination. Two observers performed manual delineation of the tumors on the CT images and of the PET uptakes using a fixed threshold (50% of the max), an adaptive threshold and the Fuzzy Locally Adaptive Bayesian (FLAB). Diameters of the delineated volumes were compared to the histopathology reference when available. Uptake heterogeneity was assessed using the coefficient of variation (std.dev/mean) within TV. Results: High consensus was reached regarding manual delineation of the CT TV (<10% variability). All diameters measured on the delineated images correlated with histopathology (r>0.84, p<0.0001). However, various levels of accuracy were reached depending on the method: manual delineation on CT resulted in large overevaluation (+30±40%), whereas all delineations on PET images resulted in underevaluation (from −16±17% for T50, to −5±10% for FLAB). CT‐based TV were significantly (p<0.05) larger than PET‐based ones. No correlation was found between CT TV and differences between CT‐based and PET‐based TV. On the other hand, a significant correlation (r=0.5, p<0.01) was found between CT TV and the PET uptake heterogeneity, as well as between this heterogeneity and differences between FLAB and threshold‐based delineations (r>0.7, p<0.0002). Conclusions: 18F‐FDG PET has the potential to provide specific tumor targeting for dose boosting/painting in NSCLC. However, threshold‐based techniques that have been suggested for the auto contouring of the PET uptake should not be used for tumors above 2–3cm in size, as they fail to address heterogeneous uptakes that tend to occur in these larger volumes. More advanced automatic delineation tools are required in such cases.
WE‐E‐211‐01: X‐Ray Phase Sensitive Imaging Methods
Authors: Chen G , Connor D , Liu H , Zambelli J
Published: November 2011

The basic principles of image formation and interpretation in x‐ray imaging, including x‐ray computed tomography (CT), have remained essentially unchanged since Roentgen first discovered x‐rays in 1895. As a result, absorption contrast is the sole contrast mechanism for x‐ray biomedical imaging, unlike some other imaging modalities such as magnetic resonance imaging (MRI) where multiple contrast mechanisms are available for use in clinical practice. In recent years, tremendous progress has been made in exploring other contrast mechanisms in x‐ray imaging by studying their wave nature. These methods have been classified as x‐ray phase sensitive imaging methods. To enable practical medical applications, the research of x‐ray phase sensitive imaging methods must overcome the limitations of the requirement of highly temporally and spatially coherent x‐rays. Recently, using laboratory x‐ray tubes, several x‐ray wave imaging methods have been successfully developed, including in‐line holography, diffraction enhanced imaging (DEI), and differential phase contract computed tomography (DPC‐CT).

The overall objective of this symposium is to present the AAPM community with an overview of x‐ray phase sensitive imaging methods including basic physics, basic implementation methods, pros and cons for each implementation method, and future research directions. The symposium consists of four lectures presented by invited speakers and a panel discussion with the audience at the end of the symposium.

Dr. Guang‐Hong Chen will be presenting an overview of basic x‐ray wave physics and other research directions not covered by the other three invited speakers.

Dr. Dean Connor will be presenting the basic principles and applications of diffraction enhanced imaging method (DEI). The most promising application is breast imaging, for which DEI has improved feature contrast relative to conventional mammography and could significantly reduce dose. Though DEI was first implemented only at synchrotron research facilities, Dr. Connor and his collaborators have developed an x‐ray tube‐based DEI system. He will discuss progress towards a clinical DEI mammography system.

Dr. Hong Liu and Dr. Xizeng Wu will be presenting the basic principles, newly developed prototype systems and results of experimental investigations on x‐ray in‐line phase contrast; as well as quantitative phase retrieval imaging methods.

Dr. Joseph Zambelli will be presenting basic principles and applications of differential phase contrast computed tomography imaging. Fundamentals of system design, measurements of performance on an experimental system, and comparisons this new imaging technique with conventional absorption imaging will be presented. Technical details such as of the fabrication of the specialized x‐ray phase and absorption gratings and unique system requirements imposed by the technique will also be discussed.
WE‐F‐110‐01: Radiation & Cataract: A New Challenge
Authors: Rehani M
Published: November 2011

We are passing through an era wherein it is certain that the currently accepted threshold for radiation cataract is no longer valid. Radiation cataract has, to date, been considered a deterministic effect with threshold. The International Commission on Radiological Protection (ICRP) has published threshold values for detectable opacities of 5 Gy for chronic and 0.5–2.0 Gy for acute exposures. A number of studies in staff involved in interventional procedures, in particular cardiology and other radiation exposed populations, including astronauts, atomic bomb survivors, X‐ray technologists and clean‐up workers in Chernobyl, have indicated that there is an increased incidence of lens opacities at doses below 1 Gy. The higher workload that is typical now in many cath labs, a lack of training in radiation protection and non‐availability or non‐use of radiation protection devices can result in doses to the eye lens that are high enough to cause lens injuries. International Atomic Energy Agency (IAEA) had launched a project to test the eyes of interventional cardiologists and support staff and results have been published in two papers in 2010. Further there have been publications in 2010 on the efficacy of various shielding strategies for protection of the operatorˈs eyes in the interventional suits. Leaded glasses, scatter‐shielding drapes and leaded shields were evaluated in various combinations and in different (characteristic) operator positions. It is reported that the use of leaded glasses alone reduced the lens dose rate by a factor of five to 10, while scatter‐shielding drapes alone reduced the dose rate by a factor of five to 25. Using both eye‐shielding implements together reduced the dose rate by a factor of 25 or more, and always proved more protective than either used alone.

The talk will review the basic information about radiation catactogenesis, epidemiological information and results of recent studies.

Learning Objectives:

1. To understand the basic information about radiation cataractogenesis

2. To understand the efficacy of protective tools

3. To become aware about the likely changes in current recommendation that may be brought up by international bodies such as the ICRP.