Lab6 X-Ray Beam updated

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Toronto Metropolitan University *

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704

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Mechanical Engineering

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Jan 9, 2024

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BME704 | Radiation Therapy Devices Lab 6 Department of Electrical, Computer, and Biomedical Engineering Program: Biomedical Engineering BME704: Radiation Therapy Devices Lab 6: Image Quality and Dose, Diagnostic X-Ray Beam Parameters NAME: Nourhan Chalhoub, Tori Butler ID: 500982281, 500920088 1
BME704 | Radiation Therapy Devices Lab 6 Objectives - Understand why the following statements are true: o “kV should be the lowest that will penetrate the area of interest” o ”mA should be as high as practical” o “mAs should be as low as practical” (acceptable noise level; ALARA; dose) - Understand how filtration affects the x-ray beam. - To understand how the factors that control the x-ray beam production (voltage and current) affect the image quality. Instructions: During the lab, the answers to the questions have to be directly filled into this instruction document. Extra time will be given, where the student must hand in their completed solutions at the beginning of the next scheduled laboratory time. *Note this is an individual lab assignment, and a department cover page must be included. References The following sections from the “X-Ray Imaging Physics for Nuclear Medicine Technologists. Part 2: X-Ray Interactions and Image Formation” article. - Review sections of article on “X-rays and Interaction with Matter” and “Attenuation Coefficients” found on pages 3 to 7. - Focus on section on “X-Ray Beam Attenuation” on pages 7-9 (stop at “Transmitted X-Ray Beam and Subject Contrast”) The following sections from the “Part 4: Principles of Patient Radiation Protection & ALARA” continuing education session found at: http://www.ceessentials.net/article5.html - Introduction - Section 4.1: Beam Filtration - Section 4.2: Achieve ALARA through technique selection Safety Code 35 http://www.hc-sc.gc.ca/ewh-semt/pubs/radiation/safety-code_35-securite/section-a3-eng. php#a353 2
BME704 | Radiation Therapy Devices Lab 6 X-Ray Beam Attenuation 1. Why is there x-ray beam filtration built into x-ray imaging systems? (1 point) There is an x-ray beam filtration built into x-ray imaging systems to absorb lower-energy x-ray photons emitted by the tube. This results in a less noisy image due to the increased scattering of lower-energy photons. 2. What is this analogous to in analog filters (i.e. low pass, high pass, or band pass)? (1 point) In analog filters, this process is similar to high pass filters, as it involves the removal of lower-energy photons, comparable to filtering out signals with low frequency. 3. Is there a reason to limit the amount of filtration you put in the x-ray beam? (2 points) Reducing the level of filtration may be warranted for specific applications, such as when examining small body parts or pediatric cases, as these scenarios require less X-ray penetration compared to adult examinations. 3
BME704 | Radiation Therapy Devices Lab 6 X-ray Technique The amount of current that is applied to an x-ray tube to produce x-rays is measured in milliamperes (mA). This current is applied for a time period that is measured in seconds. Theses two characteristics are combined together in the “mAs”, or seconds of amperage that are applied to an x-ray tube. 4) Which curve (Upper or lower) in the above graph was produced with a higher mAs? (1 point) A higher mAs was produced in generating the upper curve in the provided graph. 5) What is the impact of increasing the mAs on dose? (1 point) The impact of increasing the mAs on dose results in the increase of electron production, consequently leading to an increased dose. 6) What is the relationship between mAs and dose? (1 point) The relationship between mAs and dose is that as mAs increases, so does the dose, indicating a proportional relationship between the two. 7) What happens to an x-ray image when the mAs is too low? (1 point) When the mAs is insufficiently low, the x-ray photons lack the necessary energy to interact effectively with the crystals, leading to the occurrence of quantum mottling in the x-ray image. 4
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