Therapeutic Medical Physics. Stephen J. Amadon Jr., Ph.D., DABR

Transcription

1 Therapeutic Medical Physics Stephen J. Amadon Jr., Ph.D., DABR

2 Outline 1. Why physicists are needed in medicine 2. Branches of medical physics 3. Physics in Radiation Oncology 4. Treatment types and Treatment Planning 1. 3D conformal 2. IMRT (Intensity Modulated Radiation Therapy) 3. Brachytherapy 1. LDR 2. HDR 3. Xoft Electronic Brachytherapy

3 Worlds view of a physicist

4 Physicist in Medicine Safety and Accuracy Education Radiation Protection + Shielding New technologies New methodologies

5 Radiotherapy is the treatment of disease (usually cancer) using very high doses of X-ray or particle radiation. Radiotherapy

6 Nuclear Medicine In Nuclear Medicine, radioactive materials are used to obtain images of tissue function. Large radiation doses are also used to treat disease. Medical physicists are involved in: image processing assessing the performance and safety of imaging equipment working out radiation doses

7 Diagnostic Radiology (X-ray and CT) X-ray and CT images are made using X-ray radiation. Medical physicists are involved in: assessing the performance of imaging equipment working out X-ray radiation doses to patients and staff from scans improving image quality and safety

8 Magnetic Resonance Imaging (MRI) MRI uses a big strong magnet to image the water in the body (good soft tissue contrast) Medical physicists are involved in: all aspects of safety training-including checking patient implants carrying out quality assurance on equipment Analyzing patient data for reporting

9 Other Areas of Medical Physics Ultrasound Radiation Protection Physiological Measurement Biomedical Engineering

10 Physics of Radiation Oncology Ionizing Interactions can remove atomic orbital electrons Particulate: electron, positron, proton, neutron, alpha Non-Ionizing Ionizing c = ν λ E = hν E = hc/λ

11 X-Rays Interaction with Matter Directly ionization Electrons, Protons, positrons, heavy charged particles Indirectly ionization Photons and neutrons Interact via Coherent, Photoelectric, Compton, and pair production

12 X-Ray Production Electron Beam hits high density material. Typically Tungsten

13 X-Ray Production

14 Dose = de/dm Depth Dose Curves

15 Why X-rays for Cancer Treatment Radiobiology Damage DNA SF = e -(αd+βd2) BED = nd (1 + (D /(α/β)))

16 BiologicalModeling TCP pop = σ α 1 2π e ( α α ) 0 2 /2 2 σ α * N 0 i= 1 exp[ ρv i i exp( α D i βd 2 i )] dα NTCP OF = 1 2π t # = ofoars 1 TCP (1 i e x 2 / 2 Bio NTCP i ) dx wt f Dose(Gy) TCP NTCP

17 Medical physicists are involved in: CT System used for Planning Planning treatments Setting up and verifying Planning Systems Setting up and verifying Second Checks Maintaining treatment machines Calibrating treatment machines Developing new types of treatment Making sure radiation is used safely Checking the dose given by treatment machines is correct Review of Chart/Plan/Treatment

18 External Beam Therapy 3D - Photons and Electrons IMRT Rapid Arc Varian 21ex Treatment Machine

19 MLC

20 Breast Treatment Daily imaging -EPID - Checking chest Wall - Checking Flash

21 Prostate IMRT Daily Localization (imaging) - Ultrasound -Gold Seeds using EPID -Calypso -Cone beam CT or MVCT Dose Distribution DVH

22 Tomotherapy

23 Stereotactic Radio Surgery Cyberknife Treatment

24 BrachyTherapy LDR (Low Dose Rate) Prostate Seed Implants HDR (High dose Rate) Partial Breast Vaginal Cylinder Tandem and Ovoid Prostate

25 LDR: Prostate Seed Implant Iodine 125

26 HDR 10 curie iridium 192 sealed source 12 Gy per hour dose rate (1200 cgy/hr) 2 ft. Concrete vault walls Extensive QA and safety procedures

27 Vaginal Cylinder

28 Advanced Partial Breast Treatment

29 Xoft No radioisotope regulatory, handling and safety issues Lower shielding requirements brings HDR treatment out of the bunker Unique capabilities will permit dose sculpting Medical personnel can remain in treatment room Controller Balloon Applicators Vaginal Applicators

30 Xoft -Balloons Good visualization of balloons under CT and Fluoro, and ultrasound. NO CONTRAST NEEDED Standardized contrast concentration in balloon wall material minimizes radiation attenuation

31 Xoft Comparison 192 Ir HDR Xoft 50kV APBI Cylinder