final exam

Question 1

dose limits

• to whole body
• to organs
• lens of eyes

Answer 1

• 5 mrem/yr
• 50 mrem/yr
• 15 rem/yr

Question 2

dose limits

• public (waiting room)
• minor workers (<18)
• declared pregnant woman

Answer 2

• 100 mrem/yr
• 10% of worker limits
• 500 mrem/term (recommended <50 mrem/month)

Question 3

typical dose currently received from a chest xray

Answer 3

8 mrem

Question 4

recommendations for pregnant workers

Answer 4

1. greater risk in first trimester
2. in first 2 weeks either no harm or total loss
3. weeks 2-12: congenital abnormalities and mental retardation
4. after 41 days there is a risk of cancer

Question 5

how many rem for pregnant workers

Answer 5

0.5 rem

Question 6

properties of a radionuclide that would make it good for diagnostic studies

Answer 6

1. Use a small amount (short half-life)
2. Carrier must be soluble but stable
3. Radionuclide that can be combined with many carriers
4. Should ideally emit only gammas
5. Gamma energy should be high enough to escape the body and low enough to be readily detectable (50 keV to 200 keV)
6. Effective half-life of radionuclide should be long enough for good imaging but not too long

Question 7

effective half life equation

Answer 7

effective half life = physical half-life + biological half life

Question 8

Tc-99m

• half-life
• energy
• metastable?
• type of chem

Answer 8

• 6 hours
• 140 keV
• yes
• good

Question 9

I-123

• used for what
• energy
• type of energy
• half-life
• type of chem

Answer 9

• thyroid
• 159 keV
• gamma
• 15 hrs
• limited

Question 10

I-131

• used for what
• energy
• what energy is too high
• half life

Answer 10

• therapy
• 364 keV
• gamma
• 8 days

Question 11

CT

• adv.
• disadv.

Answer 11

• 1. excellent contrast resolution
     
     2. good image of structure
     3. gives cross-sectional image
• 1. expensive compared to xray
     
     2. high dose to local area (800 mrem)
     3. heavy duty xray tube

Question 12

PET

• type of energy
• collimator?
• resolution
• 3 problems

Answer 12

• specific
• no
• 2-5 mm
• 1. expensive
     
     2. hard to produce nuclear med
     3. accelerator

Question 13

external beam

Answer 13

method for delivering high-energy x-ray beams to a patient’s tumor

Question 14

brachytherapy

Answer 14

sealed radiation source is placed inside or next to the area requiring treatment

Question 15

monoclonal antibodies

Answer 15

an antibody produced by a single clone of cells

-enlist natural immune system functions to fight cancer

Question 16

gamma knife

Answer 16

focuses low-dose gamma radiation from many sources on a precise target

Question 17

properties of a good radionuclide for therapy and how it differs from those used in diagnostic

Answer 17

1. Intentional high dose to tumor (fatal)
2. Side effects due to radiation acceptance (within limits)
3. Significant risks to patient and to you
4. Long course of treatment
5. Internally (Want short range emitters (alpha and beta))
6. Externally (Want high energy gammas and x-rays)