Half-life is the time it takes for fifty percent of the sample to decay. Both D and E are true, since they are related by a λ, the decay constant.
The radioactivity (how many radioactive atoms are undergoing decay every second) in a given sample decreases with time as an inverse exponential.
Half-life is fifty percent of the time it takes for all of the sample to decay.
All are true.
The number of radioactive atoms remaining in a given sample decreases with time as an inverse exponential.
Its statistics is governed by the Poisson distribution.
That’s how it works
Is designed to be extremely sensitive to light photons
Used in an Anger camera to produce an electrical signal whose pulse height is related to the number of light photons generated by a gamma event.
Uses a series of dynodes at successively more positive voltage within the tube to create increasing numbers of cascading electrons from an initial few electrons.
Uses a photocathode to generate electrons from incoming photons
Gamma photons a, b, and c do not reach the detector, so do not increase the signal. Photon d does reach the detector, but at the wrong location (assuming it makes it through the collimator), and so it constitutes noise, not signal.
‘b’ in the diagram.
‘c’ in the diagram
‘d’ in the diagram.
‘e’ in the diagram.
‘a’ in the diagram.
: Collimator resolution degrades as |z| increases. No collimator can actually let more gamma photons through than initially hit it. Sensitivity stays constant with |z|, as is seen in the equation given, and understood by the fact that with greater |z| a l
There is a trade-off between resolution and sensitivity.
Collimator resolution degrades as |z| decreases.
All are incorrect.
The collimator can actually increase the number of gamma photons hitting the scintillation crystal.
Sensitivity decreases with greater |z|
Thicker crystals detect more radiation than thinner crystals, but they have poorer resolution. The number of electrons at the output of a photomultiplier tube is much larger than the number of light photons at the input. Using the largest amplitude only g
Both PET and SPECT require a collimator to allow only the specific photons traveling in an appropriate direction.
The number of electrons at the output of a photomultiplier tube is the same as the number of light photons at the input.
Thicker crystals detect more radiation than thinner crystals, and they have better resolution.
The advantage of dynamic frame mode acquisition is that it applies the temporal succession of frame mode images and needs less storage space compared with static frame mode acquisition.
The accurate position (X, Y ) of the event is equal to the location of photomultiplier tube having the largest amplitude.
Scintillation within the body, if it were to occur at all, would be very bad for the patient and not produce other useful high-energy patients.
Unlike fluorescence, the higher energy photon causes ionization and many lower energy photons are formed from a single higher energy photon.
They are generally the first step within a detector in using high-energy photons (X-ray or gamma) to create an image.
Like fluorescence, lower energy photons are created from higher energy photons.
All of the others are true.
It occurs within the body providing a natural amplification of the number of useful high-energy photons reaching the detector
The matrix translates a 2D location in the form of a homogeneous vector (which is scaled to keep its last element equal to 1) by +2 in the x direction and +3 in the y direction.
It operates in homogeneous coordinates.
It transforms coordinates for 2-dimensional locations.
It performs pure translation (no rotation or scaling).
It performs a geometric (rigid body) transformation.
Photomultiplier tubes are designed to detect light photons. To detect gamma or x-ray photons, a photomultiplier tube requires a scintillation crystal or other device to produce light photons.
Uses a photocathode to generate electrons from incoming photons.
. Is designed to be extremely sensitive to high energy photons, including gamma and x-ray photons
III is false. The pulse height generally results from summing the signals generated from a group of photomultiplier tubes.
I and III
I and II
II and III
I, II, and III
PET is not based on a projection modality, though SPECT is. Only PET involves the annihilation of matter and antimatter
I and II
II and III.
I, II, and III.
Bremsstrahlung is only used in x-ray and CT. High-energy photons are due to nuclear events in nuclear medicine
crystals are used to convert high energy photons into light photons.
electromagnetic radiation, not particulate radiation, is used to image.
Bremsstrahlung is not used to produce high-energy photons.
signal can be increased by increasing the radiation dose.
causing cancer is not a risk.
Beta decay is not often used, although it is occasionally, as in I-131. Alpha decay is never used, because an alpha particle (2 protons + 2 neutrons) is extremely destructive
All are used.
The average binding energy per nucleon varies and accounts for the relative stability of atoms.
For a given nuclide it is dictated by the difference between the sum of the masses of protons, neutrons, and electrons and an atom’s actual mass (the mass defect).
It is equivalent to electron binding energy, but for the particles within the nucleus.
The average binding energy per nucleon is identical for all stable elements.
For protons, it accounts for the fact that they can overcome the electrostatic repulsion within the nucleus.
: All are true, see text.
They have too few neutrons, and so “want” to turn a proton into a neutron but giving off a positron
They tend to be isotopes with too many neutrons
Their decay leads to the creation of antimatter.
Their decay leads to the creation of two 511 keV gamma photons.
. They are particularly useful in imaging brain function.
They include atoms found in normal organic molecules.
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