Physics Flashcards

Question

System resolution

Answer 1

**R_s²=R_c² + R_i²** R_c (collimator) ~ 8 mm R_i (instrinsic) ~ 3 mm R_s (system) ~ 8.5 mm

Answer 2

Degrades *_resolution_* but not *_sensitivity_*

Answer 3

How many projections | (recommended # is 64)

Answer 4

Mathematical filter to remove star artifact (RAMP FILTER)

Answer 5

low frequency = gross objects mid frequency = detail + noise high frequency = noise + detail

Answer 6

- can create lesions - cut-off frequency set too high

Answer 7

- can mask a lesion - cut-off frequency set too low

Answer 8

isob**a**r -- equal "a" nucleons ⁹⁹₄₃Tc and ⁹⁹₄₂Mo

Answer 9

Isoto**p**es - Equal **P**rotons (z)

Answer 10

Isoto**n**es - Equal **n**eutrons (a - z)

Answer 11

Isom**e**rs -- same radionuclide, but different **e**nergy state ^99mTc (metastable) and ⁹⁹Tc

Answer 12

\<0.15 uCi/1 mCi Tc (at time of dose administration)

Answer 13

1/effective half-life = 1/biologic half-life + 1/radioactive or physical half-life.

Answer 14

Physical t ½ = 0.693/x (decay constant)

Answer 15

**Production:** Reactor → Generator (parent ⁹⁹Mo) **Decays:** Gamma decay

Answer 16

**Production:** Cylcotron (parent ²⁰¹Pb) **Decays:** Electron capture (decays to ²⁰¹Hg)

Answer 17

**Production:** Cyclotron **Decays:** Beta + decay (Positron)

Answer 18

**Stochastic** (probabilistic) *The probability, not severity, of occurrence increases with dose* * Severity is not related to magnitude of dose * No threshold dose * Any dose is assumed to carry some risk

Answer 19

Non-stochastic (**deterministic**) *Severity of ailment increases with dose* * Known threshold dose of disease induction * Severity increases above that threshold * Examples: Skin injury, cataract formation

Answer 20

~360 mRem/year (1 mRem/day) ~300 from natural ~60 from artificial sources

Answer 21

RADIATION WORKERS: 5 Rem/year

Answer 22

- hydralazine - prazosin - heparin - digoxin

Answer 23

LVEF = Background corrected end diastolic counts – Background corrected end systolic counts/ Background corrected end diastolic counts ## Footnote

Answer 24

1:10,000 (0.01% )

Answer 25

Thirty-two to sixty-four planar projections are acquired 180 degrees around the patient perpendicular to the long axis of the body, and the initial reconstruction is into the transaxial plane. From these transaxial images, the long axis of the heart is defined, and subsequently the conventional vertical and horizontal long-axis and the short-axis images are reconstructed for analysis.

Answer 26

In a cardiac SPECT study, typically 64 projections are obtained over 180 degrees at 3- degree increments, and each projection usually takes about 20 seconds.

Answer 27

amount of energy deposited per **length** of absorber (keV/um) electomagnetic and beta- have low LET alpha- have high LET

Answer 28

Reduces number of false positives

Answer 29

Rubidium-82 is the daughter of strontium-82 (half-life = 25 days) and is eluted from a strontium-82/ rubidium-82 generator. The other PET agents are produced in medical cyclotrons.

Answer 30

NRC regulation states that when an individual could receive a dose \> 500 rads per hour at 1 m from the source, area should have the "Caution: High Radiation Area sign posted".

Answer 31

Exposure measurement at 1 m from the surface of the package.

Answer 32

A well counter is a device used for measuring radioactivity in small samples. It usually employs a sodium iodide crystal detector. It was invented in 1951 by Hal Anger, who is also well known for inventing the scintillation camera.

Answer 33

LVH may improve count statistics, which results in better-quality images with the risk of hiding small areas of ischemia.

Answer 34

Prone imaging (patient lies on abdomen) provides greater separation between the heart and the diaphragm, so there is less inferior wall attenuation in comparison to a supine image (patient lays on back).

Answer 35

A1 - AV node A2A - target A2B/A3 - bronchial

Answer 36

Dipyridamole is primarily metabolized in the liver and should be used cautiously in patients with hepatic dysfunction. The biologic half-life of dipyridamole is 30 to 45 minutes. Adenosine but not dipyridamole is rapidly taken up by red blood cells and endothelial cells, and this explains the short biologic half-life of adenosine. The longer half-life makes it a good agent for PET imaging as it does not need to be given.

Answer 37

The patients usually undergo a low-level exercise without achieving target heart rate in order to minimize side effects of vasodilators and facilitate the clearance of tracer activity from the liver and gut

Answer 38

DTS = exercise time (in minutes) – [5 × (amount of ST-segment deviation in mm) – 4 × exercise angina index

Answer 39

hypertensive heart disease

Answer 40

once a week

Answer 41

once a month

Answer 42

once a year

Answer 43

four-bar phantom is placed between the cobalt-57 sheet and the collimator

Answer 44

remove collimator, test with single ^99mTc point source

Answer 45

planar sheet of 10-15 mCi of Co-57 is placed ON TOP OF COLLIMATOR

Answer 46

Technetium is eluted in the form of sodium pertechnetate via ion exchange with chlorine in the alumina column. In sodium pertechnetate, the oxidation state of technetium is +7, its most stable oxidation state. It is reduced to +5 and +4 before labeling.

Answer 47

99mTc-labelled macroaggregated albumin localizes predominately in the lungs and is used for lung perfusion.

Answer 48

hydrolyzed reduced 99mTc as TcO2 or 99mTc-stannous colloid localize mainly in the liver

Answer 49

123I is used in the MIBG scan for patients with heart failure and has prognostic value. The cardiac sympathetic nervous system can be imaged noninvasively using 123I-MIBG tracer. The reduced heart-to-mediastinum (H/M) ratio uptake of123I-MIBG has been associated with worse cardiovascular outcomes, including ventricular arrhythmia and death.

Answer 50

Administering the wrong radiopharmaceutical to a person, by a route other than the route prescribed by the authorized physician, to a part of the body other than the part of the body specified by the authorized physician, a diagnostic dose of more than 50 mSv effective dose equivalent, and a therapeutic dose of more than 20% are all examples of misadministration.

Answer 51

The NRC, not the FDA, should be informed about the misadministration of a radioactive tracer. The NRC must be notified by the next calendar day by telephone after the misadministration, and a written report must be submitted no later than 15 days after the event.

Answer 52

LVEF decreased by 10% and is lower than 50%

Answer 53

Gated blood pool SPECT but NOT First-pass ventriculography

Answer 54

A minimum of 200 counts/ pixel using technetium-99m and 100 counts/ pixel using thallium-201 in the myocardium on an anterior projection is recommended.

Answer 55

tidal breathing

Answer 56

about the same as water

Answer 57

A sinogram is a single row of pixels, repeated for each planar projection. Each sinogram is used to reconstruct a single transaxial slice.

Answer 58

Colorimetric test

Answer 59

740 and 780 Kev

Answer 60

AND \>50 mSev total body **_OR_** \> 0.5 Sev organ

Answer 61

11C-hydroxyephedrine is used to depict sympathetic innervation of the myocardium.

Answer 62

11C-acetate is a marker of myocardial oxidative substrate metabolism. Because 11C-acetate has a high first-pass myocardial extraction fraction, images obtained early following tracer injection can also be used to measure regional tissue blood flow,

Physics Flashcards

(117 cards)