MPHY214 Hofstra University Radiological Physics & Radiation Midterm Exam

User Generated

Ehnn

Science

MPHY214

Description

I attached my midterm's Qs to be solve in 6 to 9 hours. They are 6 Qs in the Nuclear medicine.

Unformatted Attachment Preview

Hofstra 2019 Fall MPHY 214 Midterm Exam Rules of the exam A. There are six questions in this exam. B. The full marks of this exam are 100 points. It is worth 20% of your final grade. C. The exam begins on 8:00 am, 11/3/2019 and ends on 12:00 noon, 11/6/2018. D. You are NOT allowed to discuss your work with other people. E. Please type your answers in a MS Word document and email me the final document by the deadline. F. You need to show all steps to earn full credit. Just putting the answer on the paper is not enough. G. If you don’t want to type, please write your anwers neatly. You might lose points if I can not read your writings. 1. Two x-rays detectors were used to measure the intensity of an x-ray souce at the same location. Each dectior was used to measure the intensity 100 times and the averaged intensity was the same (1000) for both detectors. However, the standard deviation was 50 for the first dector and 35 for the second detector. Can you explanation what might cause such discrepancy? (10 points) 2. A -ray h1, is emitted by a radioactive atom in V. The photon undergoes triplet production, giving kinetic energy T1 and T2 to the electrons and T3 to the positron. Illustrate the events in the following questions using a circle diagram similar to that 𝑛𝑒𝑡 used in the text book, and calculate 𝜖𝑡𝑟 , 𝜀𝑡𝑟 , 𝜀, K, Kc, and D. (10 points) a. Both electrons leave V with kinetic energy T’1 and T’2. The positron runs its course in V and still has kinetic energy T’3 when it is annihilated inside V. The resulting two photons escaped from V b. Electron 1 stops within the volume and electron2 leaves V with kinetic energy T’2. The positron also leaves V with kinetic energy T’3 and still has kinetic energy T’’3 when it is annihilated outside V. 3. In radioactive decay from an initially pure parent, the parent’s and daughter’s half-lives are respectively 𝜏1⁄2,𝑃 and 𝜏1⁄2,𝐷 . Let 𝑡𝑁,𝑒𝑞 be the time when the daughter’s population is equel to the parent’s population: (20 points) a. What is the general form for 𝑡𝑁,𝑒𝑞 ? What are the assumptions for your answers? b. What is 𝑡𝑁,𝑒𝑞 if 𝜏1⁄2,𝑃 = 𝜏1⁄2,𝐷 ? c. Plot the populations of parent and daughter as a function of time for 𝜏1⁄2,𝑃 and 𝜏1⁄2,𝐷 of you choice when the assumptions in (a) hold true. d. Plot the populations of parent and daughter as a function of time for 𝜏1⁄2,𝑃 and 𝜏1⁄2,𝐷 of you choice when the assumptions in (a) are violated. 4. What is the average dose (Gy) in an tin foil of thickness 1.2 g/cm2, from being irradiated perpendicularly by 1012 e/cm2 of energy T0 = 10 MeV. (20 points) 5. Appendix A is the TMR table of the 15X beam of a linear accelerator measures with 𝑆𝐷𝐷 = 100 cm from the source. Solve the following questions for the 10×10 cm2 field size using the Greening’s approximation. Note: there are some typos on the slide for “Relation between TPR or PDD” for “Andreo CHAPTER 7. X-ray Production and Quality.” Please check the textbook for the correct formulas. (20 points) 𝑆𝐷𝐷 𝑆𝑆𝐷 𝑆𝑆𝐷 a. What are 𝜇𝑒𝑓𝑓,𝑝 , 𝜇𝑒𝑓𝑓,𝑝 , 𝜇𝑒𝑓𝑓,𝑒 and 𝑧max ? b. Plot the PDD curve and compare it with the measured PDD in Appendix B. 6. Design an experiment for measuring 𝜇𝑡𝑟 . (20 points)
Purchase answer to see full attachment
User generated content is uploaded by users for the purposes of learning and should be used following Studypool's honor code & terms of service.

Explanation & Answer

Attached.

Hofstra 2019 Fall MPHY 214

Midterm Exam

1. Two x-rays detectors were used to measure the intensity of an x-ray source at the same
location. Each detector was used to measure the intensity 100 times and the averaged
intensity was the same (1000) for both detectors. However, the standard deviation was 50
for the first detector and 35 for the second detector. Can you explanation what might
cause such discrepancy? (10 points)
The x-ray source is assumed to have a strictly random occurrence in terms of the time
interval taken for x-ray to impinge on the detector and an a given point per unit area. The
distribution of the detection is assumed to be Poisson. The mean represents the average
intensity detected which is a is affected by the energy of the source and its distance to the
detector. For same source and distance, the average intensity would same. However, the
standard deviation is a square root of the ratio expected value of the number of rays
detected to the number of measurements. Since the detector counts every incident ray, the
standard deviation is entirely stochastic in nature.

2. A

-ray hv1, is emitted by a radioactive atom in V. The photon undergoes triplet

production, giving kinetic energy T1 and T2 to the electrons and T3 to the positron.
𝑡𝑟

Illustrate the events in the following questions using a circle diagram similar to that
used in the text book, and calculate 𝜖𝑡𝑟, 𝜀𝑛𝑒𝑡, 𝜀, K, Kc, and D. (10 points)
a. Both electrons leave V with kinetic energy T’1 and T’2. The positron runs its
course in V and still has kinetic energy T’3 when it is annihi...


Anonymous
Just what I needed…Fantastic!

Studypool
4.7
Trustpilot
4.5
Sitejabber
4.4

Related Tags