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TSOKOS READING ACTIVITY

OPTION I-2, Medical Imaging (5 Points)

1. IB Assessment Statements for Option I-2, Medical Imaging:

X-Rays

I.2.1. Define the terms attenuation coefficient and half-value thickness.

I.2.2. Derive the relation between attenuation coefficient and half-value thickness.

I.2.3. Solve problems using the equation [pic] .

I.2.4. Describe X-ray detection, recording and display techniques.

I.2.5. Explain standard X-ray imaging techniques used in medicine.

I.2.6. Outline the principles of computed tomography (CT).

Ultrasound

I.2.7. Describe the principles of the generation and the detection of ultrasound using piezoelectric crystals.

I.2.8. Define acoustic impedance as the product of the density of a substance and the speed of sound in that substance.

I.2.9. Solve problems involving acoustic impedance.

I.2.10. Outline the difference between A-scans and B-scans.

I.2.11. Identify factors that affect the choice of diagnostic frequency.

NMR and Lasers

I.2.12. Outline the basic principles of nuclear magnetic resonance (NMR) imaging.

I.2.13. Describe examples of the use of lasers in clinical diagnosis and therapy.

2. Objectives for Tsokos Option I-2, Medical Imaging:

a. State the properties of ionizing radiation.

b. State the meanings of the terms quality of X-rays, half-value thickness (HVT), and linear attenuation coefficient.

c. Perform calculations with X-ray intensity ([pic]) and HVT ([pic]).

d. Describe the main mechanisms by which X-rays lose energy in a medium.

e. State the meaning of fluoroscopy and moving film techniques.

f. Describe the basics of CT and PET scans.

g. Describe the principle of MRI.

h. State the uses of ultrasound in imaging.

i. State the main uses of radioactive sources in diagnostic medicine.

3. Read Option I-2 in your textbook.

4. Answer the following questions:

a. What are the two main classes of the use of radiation in medicine?

b. What is the formula for the intensity of radiation from a spherical emitter at a distance r from the source?

c. Regarding X-rays, what is meant by the quality of the radiation?

d. Give the equation used to determine how transmitted intensity decreases and the name for the variable μ in the equation.

e. What two factors are transmitted intensity dependent upon?

f. What is half-value thickness (HVT) and what is the equation for it?

g. Explain the two different ways X-ray photons are absorbed:

i. photoelectric effect

ii. Compton effect

iii. In both effects, what do the electrons do (naughty boys that they are) as they proceed along their merry way?

h. The photoelectric effect increases with atomic number. How does this affect the effect’s effects on bone versus soft tissue and how will it show up on photographic film?

i. What must be done to get an X-ray of soft tissue like the intestines?

j. What technique is used to allow you to watch your X-ray on TV? Explain.

k. Why is it not such a good idea to watch your X-ray on TV?

l. Give two reasons why CTs/CATs are better than traditional X-rays.

m. Give a simplified explanation of how CT/CAT scans work.

n. Give one advantage and one disadvantage of MRIs over CT/CAT scans.

o. Give a simplified explanation of how MRIs work.

p. Give a simplified explanation of how PET scans work.

q. What are PET scans used for?

r. Name two advantages and one disadvantage of ultrasound over X-rays?

s. Give a simplified explanation of how ultrasounds work.

t. What the heck is piezoelectricity?

u. Describe how radioactive sources can be used to provide information about organ function?

v. What is a radiopharmaceutical?

5. This assignment may be typed or neatly printed. Drawings may be freehand, but try to make use of the ‘Shapes’ or ‘Insert Clipart” functions of MS Word. If you submit this assignment electronically, the filename must be in the following format, “LastnameFirstinitialPerXReadActX-X”.

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IB Physics

Name: __________________________________

Period: ________ Date: ___________________

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