Huda NucMed Flashcards
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
1-A. The ideal radionuclide has a short half-life
to reduce the radiation dose to the patient.
2. Which of the following is not a radiopharmaceutical localization mechanism? (A) Diffusion (B) Phagocytosis. (C) Capillary blockage (D) Elution (E) Cell sequestration
2-D. Elution is a process whereby a radionuclide is extracted (washed out) from a generator.
- 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
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.
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
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).
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
5-B. There are no beta particles associated with 99mTc
- 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
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
- 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
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).
- 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
8-E. A typical NaI crystal (10 mm) will absorb
over 90% of 140 keV photons via the photoelectric
effect.
- 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
9-D. A typical NM image has about 10 kB of
data, not 10 MB.
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
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.
- 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
11-E. Patient dose depends on administered activity.
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
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.
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
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.
- 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
14-C. Annihilation radiation in PET, but not
in SPECT, is obtained using coincidence detection
- 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
15-D. PET detects and uses annihilation photons
(511 keV) detected in coincidence.
- 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
16-D. The FWHM (resolution) of a PET scanner
is typically 5 mm.
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
17-E. The spatial resolution achieved using PET
is superior to that of any gamma camera or
SPECT.
- 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
18-E. PET systems generally require a cyclotron,
which severely limits the availability of positronemitting
radionuclides.
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
19-B. 99Mo breakthrough is a quality-control test
performed on a technetium generator.
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
20-E. The system resolution is the square root of
the sum of the squares of the resolutions of the individual
components.
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
21-D. The counting time has no direct relationship
with the gamma camera resolution.
22. The variance of a NM image pixel with a 100 count would be: (A) 10 (B) 20 (C) 30 (D) 50 (E) 100
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. 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
23-C. A defective PMT tube can give rise to a
cold spot artifact.
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
24-D. Patient doses should be lower for short
lived radionuclides.
- 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.
25-A. The half-life of 99mTc is 6 hours. The parent
of 99mTc, 99Mo, has a half-life of 67 hours.
- 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
26-D. The effective half-life must be equal or
shorter than the physical half-life, depending on
the rate of biological clearance.
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
27-C. The size of the organ has no effect on the
computed value of cumulated activity
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
28-E. Organ activity is important for determination
of cumulated activity but does not affect the S
factor per se.
- 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.
29-E. Patient dose is determined by the amount
of activity administered, and “imaging” time is irrelevant
to patient dose.
- 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
30-E. Patient age has no direct bearing on the local
radiation level.
