KICKSTART PHYSICS MEDICAL PHYSICS 1. RADIOACTIVE HALF-LIFE DECAY 2. ULTRASOUND 3. NUCLEAR MAGNETIC RESONANCE 4. OPTICAL CT SCAN

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1 KICKSTART PHYSICS MEDICAL PHYSICS 1. RADIOACTIVE HALF-LIFE DECAY 2. ULTRASOUND 3. NUCLEAR MAGNETIC RESONANCE 4. OPTICAL CT SCAN 5. PENETRATION OF RADIOACTIVE EMISSION Kickstart would like to acknowledge and pay respect to the traditional owners of the land the Gadigal people of the Eora Nation. It is upon their ancestral lands that the University of Sydney is built. As we share our knowledge, teaching, learning, and research practices within this University may we also pay respect to the knowledge embedded forever within the Aboriginal Custodianship of Country. For more information head to

2 What s the Diagnosis? Risk Analysis Conduct a risk analysis by filling out the following table. List 3 risks to do with this investigation in the 2 nd year lab. Also, list 3 risks in an industry where physics is used. What are the consequences of those risks? Use the risk matrix below to make your judgment. What precautions would you take to stop those risks from coming about? What steps would you take to mitigate those risks? Risk Consequence Precaution/Mitigation Kickstart Physics Industry What sort of careers do you think you could get if you studied this topic at the University of Sydney? 1

3 Radioactive Half-Life Decay Radioactive Dice This experiment is a model of radioactive decay; that is, how quickly certain radioactive materials change from one element to another. Count Iteration Use your data from your experiment to draw a graph of exponential half-life decay. Title: A graph can help us make predictions. What predictions or conclusions can you make from your graph? How long until half of the nuclei have decayed? 2

4 Ultrasound You are in the middle of your ultrasound diagnosis and you have run out of the special ultrasound gel! All you have nearby is Water, Honey and Olive Oil. Which material should you use? Make a qualitative judgment and justify your answer: Make a quantitative judgment and show your working. You will need some data! Z!"#$ = ! kg/m 2 The physical properties of Water, Honey and Olive Oil relevant to the problem are listed in this table: Density (kg/m 2 ) Velocity of Sound (m/s) Water (at 20 C) Honey Olive Oil The relevant equations are: Z = ρv I! = [Z! Z! ]! I! [Z! + Z! ]! where Z is the acoustic impedance, ρ is the density of the material, v is the speed of sound through the material; and I is the intensity of the incident (I! ) and reflected (I! ) sound. This is a process called impedance matching! 3

5 Nuclear Magnetic Resonance (NMR) In this experiment, you ll see the difference between different materials that model different tissues in the body. To do this experiment: 1. Place Material 1 inside the Helmholtz coils and turn the power on. 2. Introduce the bar magnet to change the magnetic field. 3. Take the bar magnet away and observe how long it takes for the needles to stop wiggling. This is a model for T1 relaxation! Fill in the table with the times and comparisons of relaxation times for different materials in the body: Time Comparison in the Body Material 1 (Air) Material 2 (Light Oil) Material 3 (Medium Oil Material 4 (Glycerine) With all models, there are limitations and inaccuracies. Sometimes, the use of a model can actually have a negative effect on the intended purposes of the model. In the following table, list some accuracies, limitations and inaccuracies to the model. Advantages Limitations 4

6 Optical CT Scan In the following table, compare how typical X-Ray CT scans and this Optical CT scan produce an image: Similarities Differences Dosimetry is the measurement of radioactive doses and its purpose is to assure quality control of radioactive treatments. 3D dosimetry, although not widely used in hospitals yet, is much more accurate and developing quickly. Medical Physicists will use an optical CT scanner (amongst other pieces of equipment) to plan the treatment. I have prepared 3 treatments for a patient who has been diagnosed with cancer. The oncologist recommends that we treat for a small cancer in the spleen. 5

7 Penetration of Radioactivity Through Solids Put your source in the second slot in the lead castle and measure the counts in 15 seconds: counts. Next, place various solids between your source and the detector and fill in the following table: Name of Source: Type of Emission: Material Counts in 15 seconds For a spot of collaboration, compare with the results from your colleagues. Which particle has the highest penetration power? First, identify the control in this experiment: Identify the experimental variables in this experiment: 1. Dependent 2. Independent 6