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Huda_questions > Huda NucMed > Flashcards

Huda NucMed Flashcards

1
Q 
1. An ideal radiopharmaceutical would have all
the following except:
(A) Long half-life
(B) No particulate emissions
(C) Target specificity
(D) 150 to 250 keV photons
(E) Rapid biological distribution
A

1-A. The ideal radionuclide has a short half-life

to reduce the radiation dose to the patient.

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2
Q 
2. Which of the following is not a radiopharmaceutical
localization mechanism?
(A) Diffusion
(B) Phagocytosis.
(C) Capillary blockage
(D) Elution
(E) Cell sequestration
A 
2-D. Elution is a process whereby a radionuclide
is extracted (washed out) from a generator.
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3
Q
  1. What determines the residual activity of a 1-
    week-old 99Mo/99mTc generator?
    (A) Initial activity of molybdenum
    (B) Number of times the generator was milked
    (C) Half-life of 99mTc
    (D) Half-life of 99Tc
    (E) Thickness of PB shielding
A

3-A. The original activity of 99Mo and its halflife,
which determines the activity of molybdenum
(and thus of 99mTc) at the end of the week.

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4
Q 
4. 99mTc generators cannot be:
(A) Produced in a cyclotron
(B) Used to dispense more than 1 Ci
(C) Shipped by air
(D) Purchased by licensed users
(E) Used for more than 67 hours
A

4-A. 99Mo can be produced in a reactor or from
fission products, but it cannot be produced in a cyclotron
(99Mo is a beta emitter, requiring the addition
of neutrons, not protons).

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5
Q 
5. For 99mTc, which of the following cannot contribute
to the patient dose?
(A) Auger electrons
(B) Beta particles
(C) Internal conversion electrons
(D) Gamma rays
(E) Characteristic x-rays
A

5-B. There are no beta particles associated with 99mTc

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6
Q
  1. A long-lived radionuclide with a daughter
    (T1/2 = 10 hours) reaches equilibrium in:
    (A) About 3 hours
    (B) About 10 hours
    (C) About 40 hours
    (D) About 200 hours
    (E) More than 200 hours
A

6-C. It will take approximately four half-lives
(i.e.. 40 hours) for the daughter activity to be
equal or approximately equal to the parent activity

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7
Q
  1. A pulse height analyzer window width of 20%
    detects 99mTc gamma rays with energies of:
    (A) 140 keV only
    (B) Between 135 and 145 keV
    (C) Between 120 and 140 keV
    (D) Between 126 and 154 keV
    (E) Between 118 and 168 keV
A

7-D. If the window width is 20%. the PHA lower
energy level is 140% − 10% (126 keV). and the
upper energy level is 140 keV + 10% (156 keV).

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8
Q
  1. Gamma camera crystals:
    (A) Are made of cesium iodide
    (B) Convert about 95% of gamma ray energy to
    light
    (C) Are generally 100 μm thick
    (D) Have lead backing
    (E) Absorbs more than 90% of 140 keV photons
A

8-E. A typical NaI crystal (10 mm) will absorb
over 90% of 140 keV photons via the photoelectric
effect.

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9
Q
  1. NM images acquired using a computer will
    typically have all of the following except:
    (A) 500,000 to 1 million counts
    (B) Matrix sizes of 1282
    (C) 256 grayscale levels
    (D) Approximately 10 MB of data
    (E) Uniformity corrections
A

9-D. A typical NM image has about 10 kB of

data, not 10 MB.

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10
Q 
10. The pulse height analyzer in NM imaging increases:
(A) Detector efficiency
(B) Scattered photons
(C) Contrast-to-noise ratio
(D) Count rate
(E) Image distortion
A

10-C. The pulse height analyzer window is centered
around the pulses of the principal photon energy;
some signal (contrast) is lost, but a much
larger fraction of the noise is excluded.

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11
Q
  1. Which does not change as the distance from
    the face of a parallel-hole collimator is increased?
    (A) Resolution
    (B) Sensitivity
    (C) Energy resolution
    (D) Imaging time
    (E) Patient dose
A

11-E. Patient dose depends on administered activity.

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12
Q 
12. Imaging of the thyroid yields the highest resolution
with a:
(A) High-sensitivity collimator
(B) Diverging collimator
(C) High-energy collimator
(D) Low-energy all-purpose collimator
(E) Pinhole collimator
A

12-E. For pinhole collimators, the shorter the distance.
the larger the magnification; this characteristic
makes the pinhole collimator the most suitable
tool for high-resolution imaging of small
organs such as the thyroid.

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13
Q 
13. Gamma cameras are normally capable of resolving:
(A) 0.01 lp/mm
(B) 0.06 lp/mm
(C) 0.3 lp/mm
(D) 1.0 lp/mm
(E) More than 1.0 lp/mm
A

13-B. A typical FWHM value for a NM image of
a line source is about 8 mm; the maximum resolvable
frequency is thus [1/(2 X 8)] cycles/mm, or
0.06 lp/mm.

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14
Q
  1. SPECT requires all of the following except:
    (A) Gamma-emitting radioisotopes
    (B) Gamma camera rotation
    (C) Coincidence detection
    (D) Pulse height analysis
    (E) Filtered-back projection reconstruction algorithms
A

14-C. Annihilation radiation in PET, but not

in SPECT, is obtained using coincidence detection

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15
Q
  1. PET scanners detect:
    (A) Positrons of the same energy in coincidence
    (B) Positrons and electrons in coincidence
    (C) Photons of different energies in coincidence
    (D) Annihilation photons in coincidence
    (E) Annihilation photons in anticoincidence
A

15-D. PET detects and uses annihilation photons

(511 keV) detected in coincidence.

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16
Q
  1. PET scanners:
    (A) Need high-energy parallel-hole collimators
    (B) Cannot handle very high count rates
    (C) Suffer from significant attenuation losses
    (D) Detect 1.022 MeV photons
    (E) Have FWHM of 5 mm
A

16-D. The FWHM (resolution) of a PET scanner

is typically 5 mm.

17
Q 
17. The best radionuclide spatial resolution is normally
achieved using:
(A) SPECT
(B) Low-energy all-purpose collimator
(C) High-resolution collimator
(D) High-sensitivity collimator
(E) PET
A

17-E. The spatial resolution achieved using PET
is superior to that of any gamma camera or
SPECT.

18
Q
  1. Advantage of PET over gamma cameras include
    all of the following except:
    (A) More physiological tracer compounds
    (B) Better resolution
    (C) Less mottle
    (D) Rapid radiopharmaceutical decay
    (E) Availability of the positron radioisotopes
A

18-E. PET systems generally require a cyclotron,
which severely limits the availability of positronemitting
radionuclides.

19
Q 
19. Which of the following is not a quality control
test performed on a gamma camera?
(A) Field uniformity
(B) 99Mo breakthrough
(C) Extrinsic flood
(D) Spatial resolution
(E) Linearity
A

19-B. 99Mo breakthrough is a quality-control test

performed on a technetium generator.

20
Q 
20. The intrinsic (7?,) and collimator (Rc) resolution
are related to the system resolution R as:
(A) R = Ri+Rc
(B) R = (Ri+Rc)2
(C) R = (Ri+Rc)1/2
(D) R = Ri
2+Rc
2
(E) R = (Ri
2+Rc
2)1/2
A

20-E. The system resolution is the square root of
the sum of the squares of the resolutions of the individual
components.

21
Q 
21. The resolution of gamma camera does not depend
on:
( A) Photon energy
(B) Septal thickness
(C) NaI crystal thickness
(D) Counting time
(E) Distance from the collimator
A

21-D. The counting time has no direct relationship

with the gamma camera resolution.

22
Q 
22. The variance of a NM image pixel with a 100
count would be:
(A) 10
(B) 20
(C) 30
(D) 50
(E) 100
A

22-E. The variance is the standard deviation
squared (variance is σ2). For NM images that are
governed by Poisson statistics, cr = N1/2, where N
is the mean number of counts in a pixel.

23
Q 
23. A circular cold spot artifact in a gamma camera
image is most likely the result of:
(A) A cracked NaI crystal
(B) Using the incorrect collimator
(C) A defective PMT
(D) A faulty power supply
(E) Incorrectly administered activity
A

23-C. A defective PMT tube can give rise to a

cold spot artifact.

24
Q 
24. A radionuclide with a shorter half-life will
generally reduce the:
(A) Count rate
(B) Patient dose
(C) Biological clearance
(D) Scatter
(E) Photopeak energy
A

24-D. Patient doses should be lower for short

lived radionuclides.

25
Q
  1. For 99mTc decaying to 99Tc, which of the following
    is not true?
    (A) The half-life of 99mTc is 67 hours.
    (B) The half-life of 99Tc is 2.1 X 105 years.
    (C) Activity is N X λ, where N is the number of
    atoms, and λ is decay constant.
    (D) X = 0.693/T1/2, where T1/2 is the half-life.
    (E) The half-life of 99mTc is independent of its activity.
A

25-A. The half-life of 99mTc is 6 hours. The parent

of 99mTc, 99Mo, has a half-life of 67 hours.

26
Q
  1. The effective half-life is:
    (A) Longer than the physical half-life
    (B) Equal to the biological half-life
    (C) Dependent on the administered activity
    (D) Shorter or equal to the physical half-life
    (E) Independent of biological clearance
A

26-D. The effective half-life must be equal or
shorter than the physical half-life, depending on
the rate of biological clearance.

27
Q 
27. Cumulated activity in an organ does not depend
on:
(A) Administered activity
(B) Fractional uptake in organ
(C) Organ mass
(D) Physical half-life
(E) Biological clearance
A

27-C. The size of the organ has no effect on the

computed value of cumulated activity

28
Q 
28. The S factor does not depend on:
(A) Number of emission/transformation
(B) Emission energy
(C) Distance to target organ
(D) Target organ mass
(E) Organ activity
A

28-E. Organ activity is important for determination
of cumulated activity but does not affect the S
factor per se.

29
Q
  1. Which is not true for patient doses in SPECT
    imaging?
    (A) Effective doses are approximately 5 mSv
    (500 mrem).
    (B) Maximum organ doses are about 50 mGy (5
    rad).
    (C) Doses are much higher than chest x-rays.
    (D) Doses are similar to PET doses.
    (E) Dose is proportional to imaging time.
A

29-E. Patient dose is determined by the amount
of activity administered, and “imaging” time is irrelevant
to patient dose.

30
Q
  1. Following administration of 131I to a patient,
    the dose rate near the patient does not depend on:
    (A) Administered activity
    (B) Effective half-life
    (C) Patient size
    (D) Distance to patient
    (E) Patient age
A

30-E. Patient age has no direct bearing on the local

radiation level.

Huda_questions (3 decks)

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