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Intro to Medical Physics

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Presentation on theme: "Intro to Medical Physics"— Presentation transcript:

1 Intro to Medical Physics
William Y. Song, PhD Associate Professor Medical Physics, Radiation Oncology Virginia Commonwealth University Slides courtesy of: Dr. Laura Padilla, PhD

2 What is Medical Physics?
Application of the concepts and methods of physics to the diagnosis and treatment of human disease Medical Physicist Physics Medicine Slide adapted from AAPM Medical Physics Education Presentation

3 General Areas of Responsibility for Medical Physicist
Clinical Research Education Regulatory Compliance

4 Medical Physics Disciplines
Therapeutic Medical Physics Diagnostic Medical Physics Nuclear Medical Physics Medical Health Physics Radiation Oncology Radiology Radiation Safety

5 Therapeutic Medical Physics

6 Diagnostic Medical Physics

7 Nuclear Medical Physics
Brain perfusion neurotransmission

8 Medical Health Physics
Radiation Protection Radiation Safety Officer

9 Therapeutic Medical Physics

10 Radiation Therapy Process
Diagnosis, staging, consultation Simulation Decide patient position Take images Planning Design the treatment Treatment Delivery Implement your plan Response Assessment

11 Radiation Therapy Process
Diagnosis, staging, consultation Simulation Decide patient position Take images Planning Design the treatment Treatment Delivery Implement your plan Response Assessment

12 Safe and Efficient Treatment Delivery
Simulation Simulation Planning Treatment Process Immobilization for patient positioning and reproducibility Localization establish a fixed coordinate system in relation to a reference point (Isocenter) Modeling 2D or 3D model of patient constructed through imaging Physicist: CT scanner quality assurance HU vs electron density table Immobilization device assessment

13 Safe and Efficient Treatment Delivery
Planning Simulation Planning Treatment Process Define target / critical structures Prescribe dose / dose limits Establish field portals Calculate dose Physicist: Machine modeling Dose algorithm Image registration Feasibility of treatment

14 Safe and Efficient Treatment Delivery
Simulation Planning Treatment Process Setup patient Localization External beam: Set the reference point in patient to the linac isocenter Delivery Safety checks (right patient, site, plan etc.) Equipment functionality (interlocks) Clearance Physicist: Machine quality assurance and calibration Fidelity of treatment process Implementation of new technologies Workflow efficiency

15 Treatment Assessment Kong et al, JCO, 2008

16 What possible issues do you see?
Safe and Efficient Treatment Delivery Diagnosis Simulation Planning Treatment Treatment Assessment What possible issues do you see? anatomical changes visibility of disease radiosensitivity/radioresistance patient comfort setup uncertainty validity of assumptions during dose calcs reliable response assessment treatment speed image registration errors normal tissue toxicity multimodality treatments

17 What possible issues do you see?
Safe and Efficient Treatment Delivery Diagnosis Simulation Planning Treatment Treatment Assessment What possible issues do you see? Research opportunities!

18 VCU Medical Physics Research
MRI (Taeho Kim) Collision detection/avoidance, surface imaging (Laura Padilla) CT physics / image reconstruction (Jeff Williamson) Brachytherapy, radiation transport (Jeff Williamson) Motion management, deformable image registration / image processing (Geoff Hugo, Mihaela Rosu, Martin Murphy) Adaptive radiotherapy (Geoff Hugo, Jeff Williamson) Clinical physics and engineering, immobilization (Siyong Kim) Outcomes research, remote practice improvement tools, IMRT (Jatinder Palta)

19 Combined CRT for Cervix Cancer
Problem: Treatment planning for EBRT and BT are done separately BT done with standard applicators potentially resulting in underdose to tumor EBRT BT Hypothesis: Cumulative (EBRT + BT) dose distribution will enable IMRT-based EBRT to correct for underdosed tumor and improve sparing of sensitive tissue via IMRT Weiss, Williamson, Hugo, Christensen, S. Oh

20 Combined CRT for Cervix Cancer
Challenges: Large position and volume changes between days Large changes, applicator presence/absence between EBRT, BT Multimodality imaging (MR / CT) Conventional deformable image registration not suitable EBT early EBT week 5 BT 1 BT 4 ? Weiss, Williamson, Hugo, Christensen, S. Oh

21 Combined CRT for Cervix Cancer
Day 1 HRCTV & Corpus Day 3 HRCTV & Corpus Day 2 HRCTV & Corpus V1(i), D1(i) V2(i), D2(i) V3(i), D3(i) Solution: Contour-assisted biophysical image registration to align organ boundaries and estimate correspondence within and between organs Weiss, Williamson, Hugo, Christensen, S. Oh

22 Changes During Treatment
Dial et al., AAPM 2012

23 Adaptive Radiation Therapy
Assessment (Imaging) Imaging Planning Treatment Assessment (Imaging) Quantify geometric variability Correct what we can at time of treatment Adapt the treatment plan to changes during therapy

24 Mid-Tx Change in Locally-Advanced Lung Cancer Patients
Problem: Tumor regression, breathing, multiple targets (nodes/primary) contribute to large margins Tumor Collapsed Lung Week 1 Week 6 Solution: Characterize these changes, develop adaptive strategies to compensate Subclinical Target Tumor Planning Week 5 Hugo, Weiss, Guy, Riblett, Glide-Hurst, Christensen, et al.

25 Anatomical vs Functional ART
Problem: Would like to adapt to shrinking tumor. But, residual, regressed tumor on CT is mostly non-viable tissue. How to identify pockets of viable, residual radioresistive tissue early in RT? FDG-PET may have challenges due to inflammation of lung (specificity), resolution CT Solution: Diffusion-weighted MRI to identify highly cellular regions and necrotic pockets Commonly measured by Apparent Diffusion Coefficient (ADC) PET/CT DW-MRI Weiss, Hugo, Ford, Karki, Mahon, Olsen, et al.

26 Diffusion Weighted MRI
Measures average water diffusion length over time in a region, which is highly dependent on tissue microstructure Restricted by ‘cellularity’, cell density, cell membrane integrity, cell structure Commonly measured by Apparent Diffusion Coefficient (ADC) In clinical studies, cancerous tissue has lower apparent diffusion than similar density normal tissue CT PET/CT DW-MRI (ADC)

27 Professional Training
Academic Training MS or PhD in medical physics, or MS or PhD in physics or related discipline with post-graduate academic training in medical physics - Graduate Certificate Professional Doctorate in Medical Physics Clinical Training (Required for board certification) Residency in clinical medical physics Slide adapted from AAPM Medical Physics Education Presentation

28 Professional Salary, 2016

29 VCU Medical Physics Division Leadership
Division Chair: Jatinder Palta, PhD Clinical Director / Residency Director: Siyong Kim, PhD Graduate Program Director: William Song, PhD 14 faculty physicists, 3 physics residents, 2 medical physics student workers

30 VCU Medical Physics Education
Graduate Program Joint program between Radiation Oncology and Radiology CAMPEP accredited (ABR board eligible graduates) PhD, MS, and post-graduate certificate programs 12 students Full component of medical physics coursework (12 courses / 35 credit hours) Residency Program 3 medical physics residents (CAMPEP accredited) CAMPEP = Commission on Accreditation of Medical Physics Education Programs ABR = American Board of Radiology

31

32 More Information… American Association of Physicists in Medicine ( Commission on Accreditation of Medical Physics Education Programs ( International Organization for Medical Physics ( International Atomic Energy Agency ( American Society for Therapeutic Radiology and Oncology ( American Brachytherapy Society ( European Society for Radiotherapy & Oncology (

33 Questions?


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