Radiology ch 9

Ionization

Gain or loss of an electron

Can cause biological effects

Sources of ionizing radiation

1. Natural (earth/sun/stars)

2. Manmade (humans)

Largest portion of human made radiation exposure

Medical and dental X-ray examinations

X-ray production requirements

-source of electrons

-method to accelerate electrons to great speed

-method to stop electrons

- X-ray tube with vacuum inside

X-ray beam is…

Heterogeneous (different energies produced)

Characteristic X-rays

Incoming electron ejects inner shell electron, outer shell fills vacancy, creating X-ray photon

Occurs in X-ray tube 80% of time

Happens bc of ionization

Bremsstrahlung Radiation

“breaking radiation”

produced when high-speed electrons are decelerated upon striking tungsten target

occurs in the X-ray tube 20%

Photoelectric Absorption

process where incoming X-ray photon is absorbed by inner-shell electron, outer shell electrons fill vacancies creating an ion pair. Excess energy will hit body creating “characteristics radiation”

• Largest contributor to patient exposure

Compton Scatter

occurs when incoming photon collides w/ outer-shell electron, causing the photon to lose energy and change directions creating “recoil electron” and ion pair

• Techs get exposure from Compton

• Degrades images

Pair production

When high energy photon interacts w/ nucleus creating negation/positron pair. Same energy that goes in comes out.

• used in radiation therapy

Cultural Competency

1. Value/diversity

2. Possessing capacity for cultural self assessment

3. consciousness of dynamics of cross cultural interactions

4. Institutionalizing cultural knowledge

5. Developing adaptation of service delivery that reflect understanding multicultural environment

Human rights law

1. Autonomy

2. Dignity

3. Equality

4. Solidarity

Diagnostic efficiency

Accuracy of diagnostic info on a medical image

Human diversity characteristics

1. Age

2. Race

3. Sexual Orientation and gender

4. Ethnicity and nationality

Largest growing population is

Geriatric (65+)

Globalization

People cross board to other countries for school/work/ etc.

Assimilation vs. Biculturalism

Assimilation = blending in

Biculturalism = bi-racial

Diagnostic yield

Clinically useful information on a diagnostic image

Photodisintegration

When incoming photon is captured by nucleus, then will release “fragment” of the nucleus due to amount of energy used

• also used in radiation therapy

General population whole body dose

5 mSv (0.5 rem)

Radioactivity (Bq)

Used in radiation therapy and nuclear medicine

Bq/Cu = units used to measure

Effective dose

Occupational exposure

• measured in Sv

QF of x-ray is 1

X-ray tube design

Annual effective dose

50 mSv/ 5 rem

Max cumulative whole body dose

10 mSv x age

Cellular response to radiation

-cellular death

-delayed mitosis

-altered mitotic rate

Cellular irradiation damage theories

1. Direct

2. Indirect

Attenuation

Loss of radiation energy as it passes thru absorbing matter (human)

ALARA

As Low As Reasonably Achievable

• minimize radiation exposure.

Radiation Monitoring Dosimeters

Optically stimulated luminescence dosimeter (OSL)

• most commonly used

Total Body response

acute radiation syndrome

Stages

-padromal (vomit, diarrhea)

-Latent (cool off)

-manifest (get better or die)

No dose = safe dose

No dose is considered totally risk free

Exposure

Measures exposure in AIR

• Measured in R/ Gya

Absorbed dose

Measures amount of radiation absorbed in tissue

• assured in (gray) Gyt/Rad

Cardinal Rules of Protection

Time -least time possible

Distance- inv. Sq. Law (far from x-ray beam)

Shielding - always shield

Inside X-ray tube

- BREMS 20%

-CHARACTERISTIC 80%

-HEAT

3 general interactions btwn x-ray photons and matter

1. No interaction

2. Complete absorption

3. Partial absorption w/ scatter

What patient interactions ate important

-Compton scatter

-photoelectric absorption

5 patient interactions

1. Classic coherent scatter

2. Compton scatter

3. Photoelectric absorption

4. Pair production

5. Photodisintegration

Classic coherent scatter

Incoming photon hits atom and is absorbed, atom releases excess energy creating another X-ray photon in a different direction aka scattering

(<10 kVp)

Radiation syndromes

-bone marrow syndrome

- gastrointestinal syndrome (GI)

-central nervous syndrome (CNS)

Dose limit for full term pregnancy is..

5 mSv

Geiger meter

occupational workers use to measure presence and exposure in real time