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Patient InteractionsPatient Interactions

2010 2010

FINALFINAL

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Patient Interactions

1. ______________

2. ______________

3. ______________

4. ______________

5. ______________

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Interaction in the body begin at the atomic

level

1. _______________

2. _______________

3. _______________

4. _______________

5. _______________

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X-ray photons can change cells

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Some radiations are energetic enough to rearrange atoms in materials through which

they pass, and can therefore he hazardous to living tissue.

1913

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EM Interactions with Matter

General interactions with matter include:1. ______________

– With or without partial absorption

2. ______________ – Full attenuation

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Interactions of X-rays with matter

1. ________________: X-ray passes completely and get to film

2. ________________: no x-rays get to film

3. ________________________________

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Photoelectric effect

1. Low energy (low kVp) x-ray photon ejects inner shell electron (energy absorbed)

2. Leaving an orbital vacancy. As vacancy is filled a photon is produced

3. More likely to occur in absorbers of high atomic number (eg, bone, positive contrast media)

4. Contributes significantly to patient dose,

5. As all the photon energy is absorbed by the patient (and for the latter reason, is responsible for the production of short-scale contrast).

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FIG. 9–3 Photoelectric absorption interaction.

(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: http://www.thomsonrights.com.

Fax 800-730-2215.)

11CASCADE

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Photoelectric – Absorption

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PHOTOELECTRIC ABSORBTION

IN THE PATIENT

(CASCADE OF ELECTRONS)

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• PHOTOELECTRIC

ABSORBTION

IS WHAT GIVES US

THE CONTRAST

ON THE FILM

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8 p+ + 8e- = neutral atom

1. Incoming photons form tube

2. Pass by the electrons in the patient

3. Do not interact with e–

4. Causes them to vibrate- releasing smnall amounts of heat

CLASSICAL SCATTER IN PATIENT

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Classical (Coherent) ScatteringClassical (Coherent) Scattering

1. Excitation of the total complement of atomic electrons occurs as a result of interaction with the incident photon

2. No ionization takes place

3. Electrons in shells “vibrate”

4. Small heat is released

5. The photon is scattered in different directions

6. Energies below 10K keV

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Coherent / Classical Scatter

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Classic Coherent Scatter

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FIG. 9–2 Classic coherent scatter interaction.

(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: http://www.thomsonrights.com.

Fax 800-730-2215.)

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Compton scatter1. High energy (high kVp) x-ray photon ejects an

outer shell electron. 2. Energy is divided between scattered photon

and the compton electron (ejected e-)3. Scattered photon has sufficient energy to exit

body. 4. Since the scattered photon exits the body, it

does not pose a radiation hazard to the patient.

5. Can increase film fog (reduces contrast)6. Radiation hazard to personnel

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FIG. 9–4 Compton scatter interaction.

(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: http://www.thomsonrights.com.

Fax 800-730-2215.)

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Compton Scatter

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COMPTON SCATTERING

1. ______ shell electron in body

2. Interacts with x-ray photon from the _________

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(WAVY LINE IN = ________ MUST BE INTERACTION IN THE BODY)

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During Fluoro – the patient is the largest scattering object

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XXXXX

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Differential Absorbtion

• Results from the differences between xrays being abosorbed and those transmitted to the image receptor

1. ____________________________

2. ____________________________

3. ____________________________

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Compton and Differential Absorbtion

1. Provides ____ useful info to the image

2. Produces image ________• dulling of the image • NOT representing ___________ information

3. At ____________ energies

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Photoelectric and Differential Absorbtion

1. Provides _________________ information

2. X-rays do not reach film because they are __________________

3. ______ energies (more differential absorbtion)

4. Gives us the ______________ on our image

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No interactions with Image Receptor and Differential

Absorbtion

1. No interaction

2. Usually ____________ kVp

3. Goes ______________ body

4. Hits ____________ ________________

5. Usually represents areas of __________• _____atomic numbers

6. Results in __________ areas on the film

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1. The probability of radiation interaction is a function of tissue electron density, tissue thickness, and X-ray energy (kVp).

2. Dense material like bone and contrast dye attenuates more X-rays from the beam than less dense material (muscle, fat, air).

3. The differential rate of attenuation provides the contrast necessary to form an image.

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Pair Production

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FIG. 9–5 Pair production interaction.

(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: http://www.thomsonrights.com.

Fax 800-730-2215.)

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Photodisintegration

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FIG. 9–6 Photodisintegration interaction.

(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: http://www.thomsonrights.com.

Fax 800-730-2215.)

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Remember….When reviewing diagrams

What is coming in (e or photon?

Where is it occurring (the tube or body?)

Keep practicing – you will get it