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TU-AB-204-00: Advances in Cone-Beam CT and Emerging Applications

This symposium highlights advanced cone-beam CT (CBCT) technologies in four areas of emerging application in diagnostic imaging and image-guided interventions. Each area includes research that extends the spatial, temporal, and/or contrast resolution characteristics of CBCT beyond conventional limits through advances in scanner technology, acquisition protocols, and 3D image reconstruction techniques. Dr. G. Chen (University of Wisconsin) will present on the topic: Advances in C-arm CBCT for Brain Perfusion Imaging. Stroke is a leading cause of death and disability, and a fraction of people having an acute ischemic stroke are suitable candidates for endovascular therapy. Critical factors that affect both the likelihood of successful revascularization and good clinical outcome are: 1) the time between stroke onset and revascularization; and 2) the ability to distinguish patients who have a small volume of irreversibly injured brain (ischemic core) and a large volume of ischemic but salvageable brain (penumbra) from patients with a large ischemic core and little or no penumbra. Therefore, “time is brain” in the care of the stroke patients. C-arm CBCT systems widely available in angiography suites have the potential to generate non-contrast-enhanced CBCT images to exclude the presence of hemorrhage, time-resolved CBCT angiography to evaluate the site of occlusion and collaterals, and CBCT perfusion parametric images to assess the extent of the ischemic core and penumbra, thereby fulfilling the imaging requirements of a “one-stop-shop” in the angiography suite to reduce the time between onset and revascularization therapy. The challenges and opportunities to advance CBCT technology to fully enable the one-stop-shop C-arm CBCT platform for brain imaging will be discussed. Dr. R. Fahrig (Stanford University) will present on the topic: Advances in C-arm CBCT for Cardiac Interventions. With the goal of providing functional information during cardiac interventions, significant effort has been expended to improve the quantitative accuracy of C-arm CBCT reconstructions. The challenge is to improve image quality while providing very short turnaround between data acquisition and volume data visualization. Corrections for x-ray scatter, view aliasing and patient motion that require no more than 2 iterations keep processing time short while reducing artifact. Fast, multi-sweep acquisitions can be used to permit assessment of left ventricular function, and visualization of radiofrequency lesions created to treat arrhythmias. Workflows for each imaging goal have been developed and validated against gold standard clinical CT or histology. The challenges, opportunities, and limitations of the new functional C-arm CBCT imaging techniques will be discussed. Dr. W. Zbijewski (Johns Hopkins University) will present on the topic: Advances in CBCT for Orthopaedics and Bone Health Imaging. Cone-beam CT is particularly well suited for imaging of musculoskeletal extremities. Owing to the high spatial resolution of flat-panel detectors, CBCT can surpass conventional CT in imaging tasks involving bone visualization, quantitative analysis of subchondral trabecular structure, and visualization and monitoring of subtle fractures that are common in orthopedic radiology. A dedicated CBCT platform has been developed that offers flexibility in system design and provides not only a compact configuration with improved logistics for extremities imaging but also enables novel diagnostic capabilities such as imaging of weight-bearing lower extremities in a natural stance. The design, development and clinical performance of dedicated extremities CBCT systems will be presented. Advanced capabilities for quantitative volumetric assessment of joint space morphology, dual-energy image-based quantification of bone composition, and in-vivo analysis of bone microarchitecture will be discussed, along with emerging applications in the diagnosis of arthritis and osteoporosis and assessment of novel therapies. Finally, Dr. J. Boone (UC Davis) will present on the topic: Advances in CBCT for Breast Imaging. Breast CT has been studied as an imaging tool for diagnostic breast evaluation and for potential breast cancer screening. The breast CT application lends itself to CBCT because of the small dimensions of the breast, the tapered shape of the breast towards higher cone angle, and the fact that there are no bones in the breast. The performance of various generations of breast CT scanners developed in recent years will be discussed, focusing on advances in spatial resolution and image noise characteristics. The results will also demonstrate the results of clinical trials using both computer and human observers. Learning Objectives: Understand the challenges, key technological advances, and emerging opportunities of CBCT in: Brain perfusion imaging, including assessment of ischemic stroke Cardiac imaging for functional assessment in cardiac interventions Orthopedics imaging for evaluation of musculoskeletal trauma, arthritis, and osteoporosis Breast imaging for screening and diagnosis of breast cancer. Work presented in this symposium includes research support by: Siemens Healthcare (Dr. Chen); NIH and Siemens Healthcare (Dr. Fahrig); NIH and Carestream Health (Dr. Zbijewski); and NIH (Dr. Boone)

60 APPLIED LIFE SCIENCES↗

TU-AB-204-01: Advances in C-Arm CBCT for Brain Perfusion Imaging

This symposium highlights advanced cone-beam CT (CBCT) technologies in four areas of emerging application in diagnostic imaging and image-guided interventions. Each area includes research that extends the spatial, temporal, and/or contrast resolution characteristics of CBCT beyond conventional limits through advances in scanner technology, acquisition protocols, and 3D image reconstruction techniques. Dr. G. Chen (University of Wisconsin) will present on the topic: Advances in C-arm CBCT for Brain Perfusion Imaging. Stroke is a leading cause of death and disability, and a fraction of people having an acute ischemic stroke are suitable candidates for endovascular therapy. Critical factors that affect both the likelihood of successful revascularization and good clinical outcome are: 1) the time between stroke onset and revascularization; and 2) the ability to distinguish patients who have a small volume of irreversibly injured brain (ischemic core) and a large volume of ischemic but salvageable brain (penumbra) from patients with a large ischemic core and little or no penumbra. Therefore, “time is brain” in the care of the stroke patients. C-arm CBCT systems widely available in angiography suites have the potential to generate non-contrast-enhanced CBCT images to exclude the presence of hemorrhage, time-resolved CBCT angiography to evaluate the site of occlusion and collaterals, and CBCT perfusion parametric images to assess the extent of the ischemic core and penumbra, thereby fulfilling the imaging requirements of a “one-stop-shop” in the angiography suite to reduce the time between onset and revascularization therapy. The challenges and opportunities to advance CBCT technology to fully enable the one-stop-shop C-arm CBCT platform for brain imaging will be discussed. Dr. R. Fahrig (Stanford University) will present on the topic: Advances in C-arm CBCT for Cardiac Interventions. With the goal of providing functional information during cardiac interventions, significant effort has been expended to improve the quantitative accuracy of C-arm CBCT reconstructions. The challenge is to improve image quality while providing very short turnaround between data acquisition and volume data visualization. Corrections for x-ray scatter, view aliasing and patient motion that require no more than 2 iterations keep processing time short while reducing artifact. Fast, multi-sweep acquisitions can be used to permit assessment of left ventricular function, and visualization of radiofrequency lesions created to treat arrhythmias. Workflows for each imaging goal have been developed and validated against gold standard clinical CT or histology. The challenges, opportunities, and limitations of the new functional C-arm CBCT imaging techniques will be discussed. Dr. W. Zbijewski (Johns Hopkins University) will present on the topic: Advances in CBCT for Orthopaedics and Bone Health Imaging. Cone-beam CT is particularly well suited for imaging of musculoskeletal extremities. Owing to the high spatial resolution of flat-panel detectors, CBCT can surpass conventional CT in imaging tasks involving bone visualization, quantitative analysis of subchondral trabecular structure, and visualization and monitoring of subtle fractures that are common in orthopedic radiology. A dedicated CBCT platform has been developed that offers flexibility in system design and provides not only a compact configuration with improved logistics for extremities imaging but also enables novel diagnostic capabilities such as imaging of weight-bearing lower extremities in a natural stance. The design, development and clinical performance of dedicated extremities CBCT systems will be presented. Advanced capabilities for quantitative volumetric assessment of joint space morphology, dual-energy image-based quantification of bone composition, and in-vivo analysis of bone microarchitecture will be discussed, along with emerging applications in the diagnosis of arthritis and osteoporosis and assessment of novel therapies. Finally, Dr. J. Boone (UC Davis) will present on the topic: Advances in CBCT for Breast Imaging. Breast CT has been studied as an imaging tool for diagnostic breast evaluation and for potential breast cancer screening. The breast CT application lends itself to CBCT because of the small dimensions of the breast, the tapered shape of the breast towards higher cone angle, and the fact that there are no bones in the breast. The performance of various generations of breast CT scanners developed in recent years will be discussed, focusing on advances in spatial resolution and image noise characteristics. The results will also demonstrate the results of clinical trials using both computer and human observers. Learning Objectives: Understand the challenges, key technological advances, and emerging opportunities of CBCT in: Brain perfusion imaging, including assessment of ischemic stroke Cardiac imaging for functional assessment in cardiac interventions Orthopedics imaging for evaluation of musculoskeletal trauma, arthritis, and osteoporosis Breast imaging for screening and diagnosis of breast cancer. Work presented in this symposium includes research support by: Siemens Healthcare (Dr. Chen); NIH and Siemens Healthcare (Dr. Fahrig); NIH and Carestream Health (Dr. Zbijewski); and NIH (Dr. Boone)

60 APPLIED LIFE SCIENCES↗

TU-AB-204-02: Advances in C-Arm CBCT for Cardiac Interventions

This symposium highlights advanced cone-beam CT (CBCT) technologies in four areas of emerging application in diagnostic imaging and image-guided interventions. Each area includes research that extends the spatial, temporal, and/or contrast resolution characteristics of CBCT beyond conventional limits through advances in scanner technology, acquisition protocols, and 3D image reconstruction techniques. Dr. G. Chen (University of Wisconsin) will present on the topic: Advances in C-arm CBCT for Brain Perfusion Imaging. Stroke is a leading cause of death and disability, and a fraction of people having an acute ischemic stroke are suitable candidates for endovascular therapy. Critical factors that affect both the likelihood of successful revascularization and good clinical outcome are: 1) the time between stroke onset and revascularization; and 2) the ability to distinguish patients who have a small volume of irreversibly injured brain (ischemic core) and a large volume of ischemic but salvageable brain (penumbra) from patients with a large ischemic core and little or no penumbra. Therefore, “time is brain” in the care of the stroke patients. C-arm CBCT systems widely available in angiography suites have the potential to generate non-contrast-enhanced CBCT images to exclude the presence of hemorrhage, time-resolved CBCT angiography to evaluate the site of occlusion and collaterals, and CBCT perfusion parametric images to assess the extent of the ischemic core and penumbra, thereby fulfilling the imaging requirements of a “one-stop-shop” in the angiography suite to reduce the time between onset and revascularization therapy. The challenges and opportunities to advance CBCT technology to fully enable the one-stop-shop C-arm CBCT platform for brain imaging will be discussed. Dr. R. Fahrig (Stanford University) will present on the topic: Advances in C-arm CBCT for Cardiac Interventions. With the goal of providing functional information during cardiac interventions, significant effort has been expended to improve the quantitative accuracy of C-arm CBCT reconstructions. The challenge is to improve image quality while providing very short turnaround between data acquisition and volume data visualization. Corrections for x-ray scatter, view aliasing and patient motion that require no more than 2 iterations keep processing time short while reducing artifact. Fast, multi-sweep acquisitions can be used to permit assessment of left ventricular function, and visualization of radiofrequency lesions created to treat arrhythmias. Workflows for each imaging goal have been developed and validated against gold standard clinical CT or histology. The challenges, opportunities, and limitations of the new functional C-arm CBCT imaging techniques will be discussed. Dr. W. Zbijewski (Johns Hopkins University) will present on the topic: Advances in CBCT for Orthopaedics and Bone Health Imaging. Cone-beam CT is particularly well suited for imaging of musculoskeletal extremities. Owing to the high spatial resolution of flat-panel detectors, CBCT can surpass conventional CT in imaging tasks involving bone visualization, quantitative analysis of subchondral trabecular structure, and visualization and monitoring of subtle fractures that are common in orthopedic radiology. A dedicated CBCT platform has been developed that offers flexibility in system design and provides not only a compact configuration with improved logistics for extremities imaging but also enables novel diagnostic capabilities such as imaging of weight-bearing lower extremities in a natural stance. The design, development and clinical performance of dedicated extremities CBCT systems will be presented. Advanced capabilities for quantitative volumetric assessment of joint space morphology, dual-energy image-based quantification of bone composition, and in-vivo analysis of bone microarchitecture will be discussed, along with emerging applications in the diagnosis of arthritis and osteoporosis and assessment of novel therapies. Finally, Dr. J. Boone (UC Davis) will present on the topic: Advances in CBCT for Breast Imaging. Breast CT has been studied as an imaging tool for diagnostic breast evaluation and for potential breast cancer screening. The breast CT application lends itself to CBCT because of the small dimensions of the breast, the tapered shape of the breast towards higher cone angle, and the fact that there are no bones in the breast. The performance of various generations of breast CT scanners developed in recent years will be discussed, focusing on advances in spatial resolution and image noise characteristics. The results will also demonstrate the results of clinical trials using both computer and human observers. Learning Objectives: Understand the challenges, key technological advances, and emerging opportunities of CBCT in: Brain perfusion imaging, including assessment of ischemic stroke Cardiac imaging for functional assessment in cardiac interventions Orthopedics imaging for evaluation of musculoskeletal trauma, arthritis, and osteoporosis Breast imaging for screening and diagnosis of breast cancer. Work presented in this symposium includes research support by: Siemens Healthcare (Dr. Chen); NIH and Siemens Healthcare (Dr. Fahrig); NIH and Carestream Health (Dr. Zbijewski); and NIH (Dr. Boone)

60 APPLIED LIFE SCIENCES↗

TU-AB-204-03: Advances in CBCT for Orhtopaedics and Bone Health Imaging

This symposium highlights advanced cone-beam CT (CBCT) technologies in four areas of emerging application in diagnostic imaging and image-guided interventions. Each area includes research that extends the spatial, temporal, and/or contrast resolution characteristics of CBCT beyond conventional limits through advances in scanner technology, acquisition protocols, and 3D image reconstruction techniques. Dr. G. Chen (University of Wisconsin) will present on the topic: Advances in C-arm CBCT for Brain Perfusion Imaging. Stroke is a leading cause of death and disability, and a fraction of people having an acute ischemic stroke are suitable candidates for endovascular therapy. Critical factors that affect both the likelihood of successful revascularization and good clinical outcome are: 1) the time between stroke onset and revascularization; and 2) the ability to distinguish patients who have a small volume of irreversibly injured brain (ischemic core) and a large volume of ischemic but salvageable brain (penumbra) from patients with a large ischemic core and little or no penumbra. Therefore, “time is brain” in the care of the stroke patients. C-arm CBCT systems widely available in angiography suites have the potential to generate non-contrast-enhanced CBCT images to exclude the presence of hemorrhage, time-resolved CBCT angiography to evaluate the site of occlusion and collaterals, and CBCT perfusion parametric images to assess the extent of the ischemic core and penumbra, thereby fulfilling the imaging requirements of a “one-stop-shop” in the angiography suite to reduce the time between onset and revascularization therapy. The challenges and opportunities to advance CBCT technology to fully enable the one-stop-shop C-arm CBCT platform for brain imaging will be discussed. Dr. R. Fahrig (Stanford University) will present on the topic: Advances in C-arm CBCT for Cardiac Interventions. With the goal of providing functional information during cardiac interventions, significant effort has been expended to improve the quantitative accuracy of C-arm CBCT reconstructions. The challenge is to improve image quality while providing very short turnaround between data acquisition and volume data visualization. Corrections for x-ray scatter, view aliasing and patient motion that require no more than 2 iterations keep processing time short while reducing artifact. Fast, multi-sweep acquisitions can be used to permit assessment of left ventricular function, and visualization of radiofrequency lesions created to treat arrhythmias. Workflows for each imaging goal have been developed and validated against gold standard clinical CT or histology. The challenges, opportunities, and limitations of the new functional C-arm CBCT imaging techniques will be discussed. Dr. W. Zbijewski (Johns Hopkins University) will present on the topic: Advances in CBCT for Orthopaedics and Bone Health Imaging. Cone-beam CT is particularly well suited for imaging of musculoskeletal extremities. Owing to the high spatial resolution of flat-panel detectors, CBCT can surpass conventional CT in imaging tasks involving bone visualization, quantitative analysis of subchondral trabecular structure, and visualization and monitoring of subtle fractures that are common in orthopedic radiology. A dedicated CBCT platform has been developed that offers flexibility in system design and provides not only a compact configuration with improved logistics for extremities imaging but also enables novel diagnostic capabilities such as imaging of weight-bearing lower extremities in a natural stance. The design, development and clinical performance of dedicated extremities CBCT systems will be presented. Advanced capabilities for quantitative volumetric assessment of joint space morphology, dual-energy image-based quantification of bone composition, and in-vivo analysis of bone microarchitecture will be discussed, along with emerging applications in the diagnosis of arthritis and osteoporosis and assessment of novel therapies. Finally, Dr. J. Boone (UC Davis) will present on the topic: Advances in CBCT for Breast Imaging. Breast CT has been studied as an imaging tool for diagnostic breast evaluation and for potential breast cancer screening. The breast CT application lends itself to CBCT because of the small dimensions of the breast, the tapered shape of the breast towards higher cone angle, and the fact that there are no bones in the breast. The performance of various generations of breast CT scanners developed in recent years will be discussed, focusing on advances in spatial resolution and image noise characteristics. The results will also demonstrate the results of clinical trials using both computer and human observers. Learning Objectives: Understand the challenges, key technological advances, and emerging opportunities of CBCT in: Brain perfusion imaging, including assessment of ischemic stroke Cardiac imaging for functional assessment in cardiac interventions Orthopedics imaging for evaluation of musculoskeletal trauma, arthritis, and osteoporosis Breast imaging for screening and diagnosis of breast cancer. Work presented in this symposium includes research support by: Siemens Healthcare (Dr. Chen); NIH and Siemens Healthcare (Dr. Fahrig); NIH and Carestream Health (Dr. Zbijewski); and NIH (Dr. Boone)

60 APPLIED LIFE SCIENCES↗

TU-AB-204-04: Advances in CBCT for Breast Imaging

This symposium highlights advanced cone-beam CT (CBCT) technologies in four areas of emerging application in diagnostic imaging and image-guided interventions. Each area includes research that extends the spatial, temporal, and/or contrast resolution characteristics of CBCT beyond conventional limits through advances in scanner technology, acquisition protocols, and 3D image reconstruction techniques. Dr. G. Chen (University of Wisconsin) will present on the topic: Advances in C-arm CBCT for Brain Perfusion Imaging. Stroke is a leading cause of death and disability, and a fraction of people having an acute ischemic stroke are suitable candidates for endovascular therapy. Critical factors that affect both the likelihood of successful revascularization and good clinical outcome are: 1) the time between stroke onset and revascularization; and 2) the ability to distinguish patients who have a small volume of irreversibly injured brain (ischemic core) and a large volume of ischemic but salvageable brain (penumbra) from patients with a large ischemic core and little or no penumbra. Therefore, “time is brain” in the care of the stroke patients. C-arm CBCT systems widely available in angiography suites have the potential to generate non-contrast-enhanced CBCT images to exclude the presence of hemorrhage, time-resolved CBCT angiography to evaluate the site of occlusion and collaterals, and CBCT perfusion parametric images to assess the extent of the ischemic core and penumbra, thereby fulfilling the imaging requirements of a “one-stop-shop” in the angiography suite to reduce the time between onset and revascularization therapy. The challenges and opportunities to advance CBCT technology to fully enable the one-stop-shop C-arm CBCT platform for brain imaging will be discussed. Dr. R. Fahrig (Stanford University) will present on the topic: Advances in C-arm CBCT for Cardiac Interventions. With the goal of providing functional information during cardiac interventions, significant effort has been expended to improve the quantitative accuracy of C-arm CBCT reconstructions. The challenge is to improve image quality while providing very short turnaround between data acquisition and volume data visualization. Corrections for x-ray scatter, view aliasing and patient motion that require no more than 2 iterations keep processing time short while reducing artifact. Fast, multi-sweep acquisitions can be used to permit assessment of left ventricular function, and visualization of radiofrequency lesions created to treat arrhythmias. Workflows for each imaging goal have been developed and validated against gold standard clinical CT or histology. The challenges, opportunities, and limitations of the new functional C-arm CBCT imaging techniques will be discussed. Dr. W. Zbijewski (Johns Hopkins University) will present on the topic: Advances in CBCT for Orthopaedics and Bone Health Imaging. Cone-beam CT is particularly well suited for imaging of musculoskeletal extremities. Owing to the high spatial resolution of flat-panel detectors, CBCT can surpass conventional CT in imaging tasks involving bone visualization, quantitative analysis of subchondral trabecular structure, and visualization and monitoring of subtle fractures that are common in orthopedic radiology. A dedicated CBCT platform has been developed that offers flexibility in system design and provides not only a compact configuration with improved logistics for extremities imaging but also enables novel diagnostic capabilities such as imaging of weight-bearing lower extremities in a natural stance. The design, development and clinical performance of dedicated extremities CBCT systems will be presented. Advanced capabilities for quantitative volumetric assessment of joint space morphology, dual-energy image-based quantification of bone composition, and in-vivo analysis of bone microarchitecture will be discussed, along with emerging applications in the diagnosis of arthritis and osteoporosis and assessment of novel therapies. Finally, Dr. J. Boone (UC Davis) will present on the topic: Advances in CBCT for Breast Imaging. Breast CT has been studied as an imaging tool for diagnostic breast evaluation and for potential breast cancer screening. The breast CT application lends itself to CBCT because of the small dimensions of the breast, the tapered shape of the breast towards higher cone angle, and the fact that there are no bones in the breast. The performance of various generations of breast CT scanners developed in recent years will be discussed, focusing on advances in spatial resolution and image noise characteristics. The results will also demonstrate the results of clinical trials using both computer and human observers. Learning Objectives: Understand the challenges, key technological advances, and emerging opportunities of CBCT in: Brain perfusion imaging, including assessment of ischemic stroke Cardiac imaging for functional assessment in cardiac interventions Orthopedics imaging for evaluation of musculoskeletal trauma, arthritis, and osteoporosis Breast imaging for screening and diagnosis of breast cancer. Work presented in this symposium includes research support by: Siemens Healthcare (Dr. Chen); NIH and Siemens Healthcare (Dr. Fahrig); NIH and Carestream Health (Dr. Zbijewski); and NIH (Dr. Boone)

60 APPLIED LIFE SCIENCES↗

MRI screening for breast cancer in women at high risk; is the Australian breast MRI screening access program addressing the needs of women at high risk of breast cancer?

Breast magnetic resonance imaging (MRI) screening of women under 50 years old at high familial risk of breast cancer was given interim funding by Medicare in 2009 on the basis that a review would be undertaken. An updated literature review has been undertaken by the Medical Services Advisory Committee but there has been no assessment of the quality of the screening or other screening outcomes. This review examines the evidence basis of breast MRI screening and how this fits within an Australian context with the purpose of informing future modifications to the provision of Medicare-funded breast MRI screening in Australia. Issues discussed will include selection of high-risk women, the options for MRI screening frequency and measuring the outcomes of screening.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Overview of the forthcoming AAPM TG-158 Report, 'Measurements and calculations of doses outside the treatment volume from External Beam Radiation Therapy' - Paper 85

The evolution of techniques and technology in radiotherapy has greatly improved our ability to deliver higher tumor doses while minimizing the dose to the adjacent organs at risk. However, this improved conformality has not removed the problem of doses to normal tissues outside the target volume. Whether these out-of-field doses arise from photons, electrons, protons or neutrons, there are unique challenges that many medical physicists may have limited knowledge about or experience with. With modern treatment planning systems, high dose regions and areas within the primary beam path are typically well described. However, their accuracy beyond a few centimeters outside the treatment field edge are usually poor. In these cases, alternate methods are required to assess the out-of-field dose. Such assessments require additional care to avoid potentially large errors associated with a variety of unique complications in performing dosimetry outside the treatment field. Furthermore, physicists will not always have an a priori estimate of the expected dose, and, as a result, large dosimetric errors are more easily missed. Low radiation doses outside the treatment volume are a concern because they can cause deleterious effects to the patient. The risk of late effects from the secondary radiation may be more evident today because of the success of cancer screening and modern therapies that have increased the number of cancer patients who survive and live long enough for the adverse radiation effects on healthy tissues to manifest. Simultaneously, radiotherapy procedures have become more complex, making the estimation of low out-of-field doses even more challenging. Over the past 30 years, numerous studies have been published detailing non-target doses from various radiotherapy treatments (for a detailed review see Xu et al. However, dosimetry data were obtained using a variety of measurement or computational techniques. An overview of dosimetry techniques for measuring low-level non-target doses is not available. Improved, or at least valid, dosimetry is important for several reasons. In clinical care (e.g. fetal dose estimates), large dose errors can lead to inappropriate or unnecessary treatment decisions, with potentially serious consequences to the patient. In a broader sense of somatic effects, more accurate dosimetry will improve patient risk assessment, understanding of dose responses, treatment planning, and design of the radiation delivery machines. Once reliable dosimetry data are available, it is then the clinician's responsibility to assess the risk vs. benefit of the radiotherapy treatment to make a sound and informed assessment of all possible treatment outcomes. (author)

61 RADIATION PROTECTION AND DOSIMETRY↗

Lung cancer mortality among construction workers: implications for early detection

Objectives This study examined predictors of lung cancer mortality, beyond age and smoking, among construction workers employed at US Department of Energy (DOE) sites to better define eligibility for low-dose CT (LDCT) lung cancer screening. Methods Predictive models were based on 17 069 workers and 352 lung cancer deaths. Risk factors included age, gender, race/ethnicity, cigarette smoking, years of trade or DOE work, body mass index (BMI), chest X-ray results, spirometry results, respiratory symptoms, beryllium sensitisation and personal history of cancer. Competing risk Cox models were used to obtain HRs and to predict 5-year risks. Results Factors beyond age and smoking included in the final predictive model were chest X-ray changes, abnormal lung function, chronic obstructive pulmonary disease (COPD), respiratory symptoms, BMI, personal history of cancer and having worked 5 or more years at a DOE site or in construction. Risk-based LDCT eligibility demonstrated improved sensitivity, specificity and positive predictive value compared with current US Preventive Services Task Force guidelines. The risk of lung cancer death from 5 years of work in the construction industry or at a DOE site was comparable with the risk from a personal cancer history, a family history of cancer or a diagnosis of COPD. LDCT eligibility criteria used for DOE construction workers, which includes factors beyond age and smoking, identified 86% of participants who eventually would die from lung cancer compared with 51% based on age and smoking alone. Conclusions Results support inclusion of risk from occupational exposures and non-malignant respiratory clinical findings in LDCT clinical guidelines.

Public, Environmental & Occupational Health↗

WE-A-16A-01: International Medical Physics Symposium: Increasing Access to Medical Physics Education/Training and Research Excellence

In response to a world in which cancer is a growing global health challenge, there is now a greater need for US Medical Physicists and other Radiation Oncology professionals across institutions to work together and be more globally engaged in the fight against cancer. There are currently many opportunities for Medical Physicists to contribute to alleviating this pressing need, especially in helping enhance access to Medical Physics Education/training and Research Excellence across international boundaries, particularly for low and middle-income countries (LMIC), which suffer from a drastic shortage of accessible knowledge and quality training programs in radiotherapy. Many Medical Physicists are not aware of the range of opportunities that even with small effort could have a high impact. Faculty at the two CAMPEP-accredited Medical Physics Programs in New England: the University of Massachusetts Lowell and Harvard Medical School have developed a growing alliance to increase Access to Medical Physics Education/training and Research Excellence (AMPERE), and facilitate greater active involvement of U.S. Medical Physicists in helping the global fight against cancer and cancer disparities. In this symposium, AMPERE Alliance members and partners from Europe and Africa will present and discuss the growing global cancer challenge, the dearth of knowledge, research, and other barriers to providing life-saving radiotherapy in LMIC, mechanisms for meeting these challenges, the different opportunities for participation by Medical Physicists, including students and residents, and how participation can be facilitated to increase AMPERE for global health. Learning Objectives: To learn about the growing global cancer challenge, areas of greatest need and limitations to accessing knowledge and quality radiotherapy training programs, especially in LMIC; To learn about the range of opportunities for Medical Physicists, including students and residents, to work together in global health to help increase AMPERE and alleviate the growing global burden of cancer; To present and discuss a new model for harmonizing Medical Physics Training across countries and how this model (UMass and Heidelberg) could be extended to LMIC in collaboration with the IAEA; To highlight a new platform and program for facilitating contributions by Medical Physicists to increase AMPERE towards the elimination of global cancer disparities. Challenges in Cancer Control in Africa Twalib A. Ngoma, MD, Professor, Executive Director, Ocean Road Cancer Institute, Dar Es Salaam, Tanzania Cancer care in Africa is beset by lack of attention, political will, cancer registries, cancer plans, human resources, financial resources and treatment facilities.. As a result of this, cancer patients in Africa are far more likely to die of their disease than those in developed countries. According to data from the WHO 750,000 new cancer cases occur in Africa every year and this number is predicted to rise by 70% by 2020. To make matters worse, an estimated 75% of cancer patients in Africa have advanced or incurable cancers at diagnosis making palliative care the most realistic approach to their management. Furthermore, Cancer prevention is nearly nonexistent, cancer detection is rare and treatment usually comes too late and is inefficient. The overall mortality-to-incidence ratio for men with cancer in the Africa is 0.75 compared with 0.54 in the developed world while the ratios for women in Africa, is 0.65 compared with 0.45 for women in the developed world. There is also limited access to radiotherapy. According to the International Atomic Energy Agency (IAEA), whilst developed countries usually have one radiotherapy machine per 250,000 people, most African nations have only one machine per ten million people. The above numbers are alarming and speak for themselves. The only solution to improve this alarming situation is to address the major challenges which African countries face in provision of cancer services which include but not limited to lack of cancer registries, lack of funding, lack of human resources, lack of radiotherapy machines, lack of cancer drugs and lack of accessible and affordable cancer screening, early diagnosis, treatment or palliative care services. Since there are considerable differences among African countries, in my presentation I will share with the audience how we address cancer control challenges in Tanzania in general and specifically in radiation oncology. The African continent cancer plan 2013 2017 Folakemi Odedina, PhD, Professor and Director of Health Disparities, UF Health Cancer Center, University of Florida The burden of cancer is rising in Africa, in addition to current heavy burden of communicable, and other non-cancer related non—communicable diseases. Conquering cancer in Africa will require a comprehensive collaborative approach with cancer clinicians, scientists, patients, advocates, policy makers and community leaders working hand-in-hand at the local, state, national, and continent levels with the primary mission: To reduce the number of deaths from cancer and improve the quality of life of cancer patients, survivors and caregivers. Unfortunately, less than 40% of African countries have a credible cancer control policy and program. The African Organization for Research and Training in Cancer (AORTIC) decided to create an African Cancer Plan to provide cost-effective strategies that can be employed throughout the continent to fight cancer. Based on the African proverb that “It takes a village to raise a child”, the Cancer Plan provides specific strategies that can be used by individuals, employers, organizations and policy-makers to fight cancer. In addition, we have provided overarching strategies to address cancer in Africa and targeted 5-year plan for prostate, breast, cervix, lung and liver cancers. In developing this Cancer Plan, our primary goal is to decrease cancer incidence and mortality in Africa. This goal can only be achieved by stakeholders and dedicated individuals to lead and implement the strategies outlined in this plan. If you are interested in partnering with AORTIC to reduce the burden of cancer in Africa, please send an email to info@aortic-africa.org. Synergies in research and clinical care through international collaboration Thomas Bortfeld and David Gierga, Massachusetts General Hospital, Harvard Medical School, MA Medical Physics relies on high technology that is not distributed equally. The whole spectrum of Medical Physics technologies is not available at every hospital or research institute, and not even in every high income country. One example is heavy ion therapy equipment which is currently only available in Japan, Germany and Italy. There is also a large global variation in terms of research infrastructure and focus. A student of Medical physics cannot gain broad experience, certainly not hands-on experience, by staying at one place only. While it is debatable what a good trade-off between breadth and depth in Medical Physics education is, it is generally agreed upon that some breadth is necessary. Researchers in Medical Physics have to cross borders if they need specific technologies for their projects. Therefore it is self-evident that international programs in Medical Physics education and research make sense. Yet, very few programs of this type exist. In this presentation we will report on our own experience of pursuing an international career in Medical Physics, with international student programs, and with the international exchange of researchers. We will present new or planned opportunities such as the medical beamline at CERN in Geneva. We will also report on the synergies in clinical care through international collaborations between partners in high and low income countries. One example is the partnership of the MGH/Harvard Medical School community with the oncology community and government of Botswana to form the BOTSOGO (BOTSwana Oncology Global Outreach) initiative. This collaborative effort in oncology care was spurred by existing relationships in HIV/AIDS research and care delivery developed within the Botswana-Harvard AIDS Institute Partnership (BHP). The initial efforts of the BOTSOGO initiative have been organized as follows: 1) on-site visits to share expertise in clinical cancer care for capacity building purposes (e.g. cervical brachytherapy), 2) developing a forum for multi-disciplinary case discussions and education and 3) relationship building with local stakeholders for long-term sustainability and growth. An international system for the certification of medical physicists Raymond K. Wu, Chairman, IOMP Professional Relations Committee; Chairman, AAPM Exchange Scientist Program Subcommittee An international system for the certification of medical physicists is an important issue. The International Organization for Medical Physicists (IOMP) has in collaboration with a number of member countries established the International Medical Physics Certification Board (IMPCB) to address this issue, and to provide a mechanism to mark the milestone for the professional development of clinical medical physicists. Raymond Wu, PhD, is the CEO of IMPCB and the Chairman of the IOMP Professional Relations Committee. He is the invited speaker recommended by IOMP to give a talk on this important subject. He will give the latest update of the work of IMPCB, its near term goals, and pathways to the goals. He will also discuss the importance of such an International System of certification in the training/education of next generation Medical Physicists, including those in low and middle income countries (LMIC) where such training is crucial in the fight against cancer. Learning Objectives: Understand the certification program as described in the IOMP Policy Statements. Understand the plan of the IMPCB to establish the accreditation process of national certification programs. Understand the goals of this international collaborative effort and the potential impacts to the quality of clinical medical physics practice. Medical Physics Education Across Continents: The UMass Lowell and Heidelberg University Joint Coordination Effort Erno Sajo, Director of Medical Physics, University of Massachusetts at Lowell Medical Physics education has unique flavors across institutions within the US and shows significant differences across continents. In the latter, even the definition of Medical Physics may differ. Not only is there a difference in topical coverage, but often what is considered a cohesive topic in one institution, and taught as a single course, is fragmented among several other courses in the other institution due to a different philosophy. Because of the regulatory and certification requirements, these differences impact the mobility of medical physicists across continents. As a result, physicists who wish to practice in the US or Canada but have completed their education elsewhere often find that they have to take remedial courses or even obtain a new degree in Medical Physics despite the fact that they already have one. Outreach to developing countries, therefore, is even more difficult. The University of Massachusetts Lowell and Heidelberg University recently completed a joint coordination effort, in which they identified topics that are common versus complementary in their medical physics curricula. A student exchange program was developed that permits students to take any of the common topics at the other institution while taking complementary courses as electives, which count towards their degree requirements at their home institution. Thesis research is also mutually accepted. When properly documented, in this way CAMPEP recommendations can be met across the institutions. Therefore, students participating in this program satisfy both the American Board of Radiology (ABR) requirements and the European regulatory requirements. The framework on which this collaboration rests and the cross-comparison methods developed therein may be implemented in other exchange programs and thus a similar approach can be adopted in outreach programs with developing countries. IAEA PACT Program and opportunities for support and collaboration Susan Morgan, Program Coordinator, International Atomic Energy Agency, Vienna, Austria In response to the developing world's cancer crisis, the International Atomic Energy Agency (IAEA) established the Program of Action for Cancer Therapy (PACT) in 2004 to fully realize the public health impact obtained through global partnerships in cancer control and technology transfer in radiation medicine. PACT's vision strives for global partnerships to confront the cancer crisis in developing countries, notably with our sister United Nations agency, the World Health Organization (WHO), and our Joint Programme on Cancer Control established in 2009. The IAEA, through PACT, the WHO, the International Agency for Research on Cancer (IARC) and other cancer-related organizations work together to make a coordinated global response in supporting low and middle income (LMI) IAEA Member States in the implementation of comprehensive national cancer control programmes. PACT's goals are: To build global partnerships of cancer-related organizations committed to addressing the challenge of cancer in LMI Member States in all its aspects; To mobilize resources from charitable trusts, foundations, and others in public and private sectors sources to assist LMI Member States to develop and implement their radiation medicine capacities within a national cancer control programme (NCCP); and, To ensure the effective and sustainable transfer of radiation medicine technologies or knowledge to all LMI Member States where unmet needs exist. PACT work focuses on: imPACT: Assessing Cancer Burden PMDS: Developing Global Partnerships VUCCnet: Promoting Cancer Control Training AGaRT: Making Radiotherapy Accessible Facilitating increased participation and professional development of Medical Physicists and other Radiation Oncology professionals in global health Wilfred Ngwa, Harvard Medical School, University of Massachusetts Lowell, MA The 2014 World Health Organization (WHO) Cancer report highlights an alarming increase in the global burden of cancer. It also highlights what it terms “the cancer divide”, or disparities, evinced by a substantially higher cancer burden in low and middle income countries (LMIC) in Asia, Central/South America and Africa. The WHO even predicts a potential African cancer epidemic by 2020 if significant progress is not made in global cancer control efforts. Evidence that collaborative global health approaches have led to major progress in controlling infectious diseases including in LMIC suggests that similar approaches will be useful for non-communicable diseases like cancer. In consonance with this, leaders in cancer policy from the USA and 14 economically diverse countries recently concluded that successful campaigns to control cancers with existing methods and to improve current strategies will increasingly depend onconcerted multinational collaborations (Sci Transl Med 5, p. 175, 2013). Hence there is growing urgency for increasing collaborative global cancer Care Research and Education (CaRE), as well as support for greater effectiveness of already existing initiatives involving partners from different nations, diverse economic and cultural backgrounds. The good news is that there is a growing awareness of the importance of global health and growing interest including amongst Medical Physicists and other Radiation oncology (RadOnc) professionals to participate in global health. However, many are unaware of currently existing opportunities for participation that even with small effort could have a high impact. Over 50% of cancer patients in the developed world depend on RadOnc professionals for their treatment, and hence participation of RadOnc professionals in global health efforts in the global fight against cancer is crucial. It is also important that the next generation of RadOnc professionals (students, and residents) be trained with a global perspective, to be global health leaders in cancer CaRE. This presentation will highlight a novel platform for enhancing participation and professional development of Medical Physicists and other RadOnc professionals in global health. Ways in which this platform can facilitate contributions by Medical Physicists and other RadOnc Professionals, students and residents in global health towards the elimination of global cancer disparities will be discussed. This will be followed by a panel discussion by some of the pioneers/leaders in collaborative global cancer CaRE on the growing cancer burden, challenges and opportunities for greater active involvement and professional development.

60 APPLIED LIFE SCIENCES↗

A 3D detailed breast model for dose estimation in mammography - Paper 14

The risk of radiation-induced breast cancer in mammography should be paid more attention for the number of women choosing mammography for breast cancer screening is increasing, and the recommended tissue weighting factors for breast tissue of ICRP changed from 0.05 in 1990 to 0.12 in 2007. The average dose to the glandular tissue is regarded as the most reasonable dose descriptor related to the risk of breast cancer induced by ionizing radiation. The IAEA protocol for breast dosimetry in mammography at present is based on the calculations of Dance which were based on very simple models of the breast. Therefore it is necessary to construct a more detailed breast model in order to estimate the dose more precisely. A 3D detailed breast model is constructed and Monte Carlo stimulation of mammography is performed based on this model in this paper. A series of glandular tissue dose conversion coefficients for mammography based on the 3D detailed breast model were calculated, which provide available data for the mammographic dosimetry assessment. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗

TH-A-18A-01: Innovation in Clinical Breast Imaging

Several novel modalities have been or are on the verge of being introduced into the breast imaging clinic. These include tomosynthesis imaging, dedicated breast CT, contrast-enhanced digital mammography, and automated breast ultrasound, all of which are covered in this course. Tomosynthesis and dedicated breast CT address the problem of tissue superimposition that limits mammography screening performance, by improved or full resolution of the 3D breast morphology. Contrast-enhanced digital mammography provides functional information that allows for visualization of tumor angiogenesis. 3D breast ultrasound has high sensitivity for tumor detection in dense breasts, but the imaging exam was traditionally performed by radiologists. In automated breast ultrasound, the scan is performed in an automated fashion, making for a more practical imaging tool, that is now used as an adjunct to digital mammography in breast cancer screening. This course will provide medical physicists with an in-depth understanding of the imaging physics of each of these four novel imaging techniques, as well as the rationale and implementation of QC procedures. Further, basic clinical applications and work flow issues will be discussed. Learning Objectives: To be able to describe the underlying physical and physiological principles of each imaging technique, and to understand the corresponding imaging acquisition process. To be able to describe the critical system components and their performance requirements. To understand the rationale and implementation of quality control procedures, as well as regulatory requirements for systems with FDA approval. To learn about clinical applications and understand risks and benefits/strength and weakness of each modality in terms of clinical breast imaging.

60 APPLIED LIFE SCIENCES↗

Radio-guided occult lesion localisation using iodine 125 Seeds “ROLLIS” to guide surgical removal of an impalpable posterior chest wall melanoma metastasis

Cancer screening and surveillance programmes and the use of sophisticated imaging tools such as positron emission tomography-computed tomography (PET-CT) have increased the detection of impalpable lesions requiring imaging guidance for excision. A new technique involves intra-lesional insertion of a low-activity iodine-125 ({sup 125}I) seed and detection of the radioactive signal in theatre using a hand-held gamma probe to guide surgery. Whilst several studies describe using this method to guide the removal of impalpable breast lesions, only a handful of publications report its use to guide excision of lesions outside the breast. We describe a case in which radio-guided occult lesion localisation using an iodine 125 seed was used to guide excision of an impalpable posterior chest wall metastasis detected on PET-CT.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Feature‐shared adaptive‐boost deep learning for invasiveness classification of pulmonary subsolid nodules in CT images

Purpose In clinical practice, invasiveness is an important reference indicator for differentiating the malignant degree of subsolid pulmonary nodules. These nodules can be classified as atypical adenomatous hyperplasia (AAH), adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA), or invasive adenocarcinoma (IAC). The automatic determination of a nodule's invasiveness based on chest CT scans can guide treatment planning. However, it is challenging, owing to the insufficiency of training data and their interclass similarity and intraclass variation. To address these challenges, we propose a two‐stage deep learning strategy for this task: prior‐feature learning followed by adaptive‐boost deep learning. Methods The adaptive‐boost deep learning is proposed to train a strong classifier for invasiveness classification of subsolid nodules in chest CT images, using multiple 3D convolutional neural network (CNN)‐based weak classifiers. Because ensembles of multiple deep 3D CNN models have a huge number of parameters and require large computing resources along with more training and testing time, the prior‐feature learning is proposed to reduce the computations by sharing the CNN layers between all weak classifiers. Using this strategy, all weak classifiers can be integrated into a single network. Results Tenfold cross validation of binary classification was conducted on a total of 1357 nodules, including 765 noninvasive (AAH and AIS) and 592 invasive nodules (MIA and IAC). Ablation experimental results indicated that the proposed binary classifier achieved an accuracy of with an AUC of 81.3 . These results are superior compared to those achieved by three experienced chest imaging specialists who achieved an accuracy of , , and , respectively. About 200 additional nodules were also collected. These nodules covered 50 cases for each category (AAH, AIS, MIA, and IAC, respectively). Both binary and multiple classifications were performed on these data and the results demonstrated that the proposed method definitely achieves better performance than the performance achieved by nonensemble deep learning methods. Conclusions It can be concluded that the proposed adaptive‐boost deep learning can significantly improve the performance of invasiveness classification of pulmonary subsolid nodules in CT images, while the prior‐feature learning can significantly reduce the total size of deep models. The promising results on clinical data show that the trained models can be used as an effective lung cancer screening tool in hospitals. Moreover, the proposed strategy can be easily extended to other similar classification tasks in 3D medical images.

Wang, Jun↗

Enhanced Laser-Induced Graphene Microfluidic Integrated Sensors (LIGMIS) for On-Site Biomedical and Environmental Monitoring

The convergence of microfluidic and electrochemical biosensor technologies offers significant potential for rapid, in-field diagnostics in biomedical and environmental applications. Traditional systems face challenges in cost, scalability, and operational complexity, especially in remote settings. Addressing these issues, laser-induced graphene microfluidic integrated sensors (LIGMIS) are presented as an innovative platform that integrates microfluidics and electrochemical sensors both comprised of laser-induced graphene. This study advances the LIGMIS concept by resolving issues of uneven fluid transport, increased hydrophobicity during storage, and sensor biofunctionalization challenges. Key innovations include Y-shaped reservoirs for consistent fluid flow, hydrophilic polyethyleneimine coatings to maintain wettability, and separable microfluidic and electrochemical components enabling isolated electrode nanoparticle metallization and biofunctionalization. Multiplexed electrochemical detection of the neonicotinoid imidacloprid and nitrate ions in environmental water samples yields detection limits of 707 nm and 10 -5.4 m with wide sensing ranges of 5–100 µm and 10 -5 –10 -1 m, respectively. Similarly, uric acid and calcium ions are detected in saliva, demonstrating detection limits of 217 nm and 10 -5.3 m with sensing ranges of 10–50 µm, and 10 -5 –10 -2.5 m, respectively. Overall, this biosensing demonstrates the capability of the LIGMIS platform for multiplexed detection in biologically complex solutions, with applications in environmental water quality monitoring and oral cancer screening.

environmental monitoring↗

Understanding Clinical Mammographic Breast Density Assessment: a Deep Learning Perspective

Mammographic breast density has been established as an independent risk marker for developing breast cancer. Breast density assessment is a routine clinical need in breast cancer screening and current standard is using the Breast Imaging and Reporting Data System (BI-RADS) criteria including four qualitative categories (i.e., fatty, scattered density, heterogeneously dense, or extremely dense). In each mammogram examination, a breast is typically imaged with two different views, i.e., the mediolateral oblique (MLO) view and cranial caudal (CC) view. The BI-RADS-based breast density assessment is a qualitative process made by visual observation of both the MLO and CC views by radiologists, where there is a notable inter- and intra-reader variability. In order to maintain consistency and accuracy in BI-RADS-based breast density assessment, gaining understanding on radiologists’ reading behaviors will be educational. In this study, we proposed to leverage the newly emerged deep learning approach to investigate how the MLO and CC view images of a mammogram examination may have been clinically used by radiologists in coming up with a BI-RADS density category. We implemented a convolutional neural network (CNN)-based deep learning model, aimed at distinguishing the breast density categories using a large (15,415 images) set of real-world clinical mammogram images. Our results showed that the classification of density categories (in terms of area under the receiver operating characteristic curve) using MLO view images is significantly higher than that using the CC view. This indicates that most likely it is the MLO view that the radiologists have predominately used to determine the breast density BI-RADS categories. Our study holds a potential to further interpret radiologists’ reading characteristics, enhance personalized clinical training to radiologists, and ultimately reduce reader variations in breast density assessment.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Hyperpigmentation and higher incidence of cutaneous malignancies in moderate-high PCB- and dioxin exposed individuals

Highlights: • Elevated blood levels of PCBs and dioxins were found in workers of a transformer recycling company. • Higher incidence of acne and malignancies of the skin in PCB- and dioxin exposed workers. • A correlation between hyperpigmentation on the skin and exposure levels in the workers. Polychlorinated biphenyls (PCB) are well known persistent and toxic environmental pollutants. Our aim was to identify effects of moderate-high exposure to dioxin-like (dl) and non-dioxin-like (ndl)-PCBs on the skin in order to provide more insight in the pathophysiological effects of these compounds. We performed a dermatological examination on 92 former workers from a transformer recycling company with known elevated serum PCB and/or dioxin (polychlorinated dibenzo-p-dioxin/polychlorinated dibenzo-p-furan (PCDD/F)) levels. In addition, we performed a skin cancer screening over a period of seven years (2010–2016) on resp. 268, 271, 210, 149, 92, 129 and 79 participants. We found a higher incidence of acne and malignancies of the skin (malignant melanoma, basal cell carcinoma and mycosis fungoides) in the workers compared to normal population. The probability of having hyperpigmentation on the skin was statistically significantly higher in workers with higher sumPCBs- (OR:1.09(1.12–2.17)), dioxin-like (dl)-PCBs- (OR:1.56(1.12–2.17)) and dioxin (PCDD/Fs) (OR:1.09(1.02–1.16)) levels. Age was a confounding factor in this model. Formation of hyperpigmentation could be an indicator for (moderate-high) exposure to toxic compounds like PCBs. The higher incidence of cutaneous malignancies found in the workers might be associated with PCB- and dioxin exposure, warranting further investigation on larger cohorts.

54 ENVIRONMENTAL SCIENCES↗

Thyroid Malignancies in Survivors of Hodgkin Lymphoma

Purpose: To quantify the incidence of thyroid cancer after Hodgkin lymphoma (HL) and determine disease characteristics, risk factors, and treatment outcomes. Methods and Materials: Thyroid cancer cases were retrospectively identified from a multi-institutional database of 1981 HL patients treated between 1969 and 2008. Thyroid cancer risk factors were evaluated by a Poisson regression model. Results: With a median follow-up duration of 14.3 years (range, 0-41.2 years), 28 patients (1.4%) developed a thyroid malignancy. The overall incidence rate (expressed as the number of cases per 10,000 person-years) and 10-year cumulative incidence of thyroid cancer were 9.6 and 0.26%, respectively. There were no observed cases of thyroid malignancy in patients who received neck irradiation for HL after age 35 years. Age <20 years at HL diagnosis and female sex were significantly associated with thyroid cancer. The incidence rates of females aged <20 at HL diagnosis in the first 10 years, ≥10 years, ≥15 years, and ≥20 years after treatment were 5, 31, 61, and 75 cases per 10,000 person-years of follow-up, respectively. At a median follow-up of 3.5 years after the thyroid cancer diagnosis, 26 patients (93%) were alive without disease, 1 (4%) was alive with metastatic disease, and 1 (4%) died of metastatic disease, at 6 and 3.6 years after the thyroid cancer diagnosis, respectively. Conclusions: Although HL survivors have an increased risk for thyroid cancer, the overall incidence is low. Routine thyroid cancer screening may benefit females treated at a young age and ≥10 years from HL treatment owing to their higher risk, which increases over time.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

Compensator models for fluence field modulated computed tomography

Purpose: Fluence field modulated computed tomography (FFMCT) presents a novel approach for acquiring CT images, whereby a patient model guides dynamically changing fluence patterns in an attempt to achieve task-based, user-prescribed, regional variations in image quality, while also controlling dose to the patient. This work aims to compare the relative effectiveness of FFMCT applied to different thoracic imaging tasks (routine diagnostic CT, lung cancer screening, and cardiac CT) when the modulator is subject to limiting constraints, such as might be present in realistic implementations.Methods: An image quality plan was defined for a simulated anthropomorphic chest slice, including regions of high and low image quality, for each of the thoracic imaging tasks. Modulated fluence patterns were generated using a simulated annealing optimization script, which attempts to achieve the image quality plan under a global dosimetric constraint. Optimization was repeated under different types of modulation constraints (e.g., fixed or gantry angle dependent patterns, continuous or comprised of discrete apertures) with the most limiting case being a fixed conventional bowtie filter. For each thoracic imaging task, an image quality map (IQM{sub sd}) representing the regionally varying standard deviation is predicted for each modulation method and compared to the prescribed image quality plan as well as against results from uniform fluence fields. Relative integral dose measures were also compared.Results: Each IQM{sub sd} resulting from FFMCT showed improved agreement with planned objectives compared to those from uniform fluence fields for all cases. Dynamically changing modulation patterns yielded better uniformity, improved image quality, and lower dose compared to fixed filter patterns with optimized tube current. For the latter fixed filter cases, the optimal choice of tube current modulation was found to depend heavily on the task. Average integral dose reduction compared to a uniform fluence field ranged from 10% using a bowtie filter to 40% or greater using an idealized modulator.Conclusions: The results support that FFMCT may achieve regionally varying image quality distributions in good agreement with user-prescribed values, while limiting dose. The imposition of constraints inhibits dose reduction capacity and agreement with image quality plans but still yields significant improvement over what is afforded by conventional dose minimization techniques. These results suggest that FFMCT can be implemented effectively even when the modulator has limited modulation capabilities.

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