1
Q
electric charge of protons
A
▪ (1.6 x10 -19 C)
2
Q
Radioactive nuclides with a very high atomic numbers greater than? or atomic mass of ? most frequently undergo Alpha emission According to condition of nuclear instability Alpha particle emission has an excess number of protons and neutrons or nucleons
A
82
150
3
Q
⚫ ⚫ ⚫
⚫ ⚫
It emits 2 protons and 2 neutrons Atomic mass decreased by 4 while the atomic number decreased by 2
A
ALPHA PARTICLE DECAY
4
Q
Alpha particle emitters has an energy range from ? to ? MeV
It is not use in medical imaging because it ranges to approximately ?cm/MeV in air and less than ? micrometer in tissue
A
5 to 10 MeV
1cm/MeV
1 micrometer
5
Q
Process of radioactive decay which is accompanied by the ejection of a positive or a negative electron from the nucleus
A
BETA PARTICLE DECAY
6
Q
when The mass number remains constant so described as
A
isobaric transition
7
Q
Radionuclides with a deficient number of neutrons or low neutron-to-proton ratio It is described as neutron poor or proton rich radionuclide 1 proton will be transformed into neutron to reach the stability state
A
POSITRON EMISSION
8
Q
positron emission is the emission of
A
positron and neutrino
9
Q
negatron is accompanied by the emission of
A
negatron and antineutrino
10
Q
ELECTRON CAPTURE Alternative process to the ?
It is also known as ?
A
Positron Decay
K electron capture
11
Q
Increase of Positive charge of the nucleus
Proton + electron will transform into neutron
Ionization occurs thus giving off characteristic radiation
A
ELECTRON CAPTURE
12
Q
The process of emitting excess energy in the form of gamma ray of unstable nuclide and is passed on to one of the orbital electrons which is then ejected from the atom thus rather emitting characteristic radiation
A
INTERNAL CONVERSION
13
Q
Radionuclides may be produced in a nuclear reactor by adding ? to a stable nuclide.
A
neutrons
14
Q
Reactor-produced radionuclides generally decay by a ? process
A
beta minus process.
15
Q
Radionuclides may be produced in cyclotrons were ? are added to stable nuclides.
A
charged particles (e.g., protons or deuterons)
16
Q
Cyclotron-produced radionuclides can decay by a ?
may also decay by ?
A
beta plus process.
electron capture.
17
Q
123I is produced in ? and decays via ?
A
cyclotrons
electron capture.
18
Q
99mTc is obtained from ? and emits ? ( ? decay)
A
99Mo
gamma rays (isomeric transition),
19
Q
82Rb is obtained from ? and is a ?
A
82Sr
positron emitter.
20
Q
is the number of transformations per unit time.
A
Activity
21
Q
SI unit of activity is the ?
A
becquerel (Bq).
22
Q
One curie is ? transformations per second.
A
3.7 × 10^10
23
Q
1 mCi is equivalent to ? MBq.
A
37 MBq.
24
Q
is the time required for a half of the radionuclide present to decay.
A
Physical half-life (T1/2)
25
Activity =
N × λ, where N is the number of atoms in the sample.
26
Technetium (99mTc) is readily available from a generator used in ∼ ?% of all nuclear medicine examinations.
80
27
T 1/2=
0.693/λ.
28
99mTc has a gamma ray energy of ? keV that is ideal for imaging and a halflife of ?hours that is convenient.
140
6 hours
29
is produced directly from 99 Mo using a saline eluant.
Pertechnetate (99mTcO4)
30
99mTc decays by ? where?% of nuclear transformations result in emission of a ?keV gamma ray.
• Energy is also emitted in the form of ? (3)
isomeric transition
88
140
internal conversion electrons, characteristic x-rays, and Auger electrons.
31
99Mo decays to 99mTc, and ? is added to the generator when 99m Tc is needed.
• it passes through the column to elute (wash off) the 99m Tc in the form of ?
• The 99 Mo is not soluble in it and remains in the column.
saline
sodium pertechnetate.
32
The half-life of 99Mo is ? which allows the generator to remain useful for approximately ? (? half-lives).
66 hours,
1 week
(∼2.5 half-lives).
33
Moly generators (sometimes called " ?") are usually delivered ? and eluted each ?, allowing for maximal in-growth of the daughter.
cows
weekly
morning
34
Two types of moly generators are commercially available.
wet & dry generator"
35
has a large reservoir of saline connected by tubing to one end of the column; an evacuated vial draws the saline through the column, thus keeping the column wet.
wet generator"
36
requires a small vial containing normal saline to be attached to one end of a dry column and a vacuum extraction vial to the other.
dry generator"
37
Sterility is achieved by a ?r connected to the end of the column, by the use of a ? in the eluant, or by ? of the loaded column by the manufacturer.
• When the saline solution is passed through the column, the chloride ions easily exchange with the Tc0 4 - (but not the Mo04 - ) ions, producing sodium pertechnetate,
Na + (99m TcO4 - )
millipore filter
bacteriostatic agent
autoclave sterilization
38
Moly generators are typically delivered with approximately ? to ? GBq (? to ? Ci) of Mo-99,
37 to 111 GBq (1 to 3 Ci)
39
The activity of the daughter at the time of elution depends on the following
1. The activity of the parent (like a big factory)
• 2. The rate of formation of the daughter, which is equal to the rate of decay of the parent (The faster Mo-99 decays, the faster Tc-99m is produced)
• 3. The decay rate of the daughter (faucet filling a cup with Tc-99m (water)
• 4. The time since the last elution (The longer you wait (usually 24 hours), the more Tc-99m accumulates)
• 5. The elution efficiency (typically 80% to 90%) (Not all Tc-99m can be removed from the generator)
40
–A typical generator initially starts with ∼ ? of 99Mo.
37 GBq (1 Ci)
41
–It takes approximately ? daughter half-lives to reach equilibrium.
• –A 99 Mo generator thus takes approximately ? hours to reach equilibrium.
–In equilibrium, the activity of 99mTc is ∼ ?% of the 99 Mo activity.
four
24
90
42
After approximately 23 hours the Tc-99m activity reaches a maximum, at which time the production rate and the decay rate are equal, and the parent and daughter are said to be
Transient equilibrium
43
Transient equilibrium occurs when the half-life of the parent is greater than that of the daughter by a factor of approximately .
10
44
When the half-life of the parent is much longer than that of the daughter (more than about? longer), secular equilibrium occurs after approximately ? to ?halflives of the daughter.
1OOx
five to six
45
in ?, the activity of the parent and the daughter are the same if all the parent atoms decay directly to the daughter.
secular equilibrium
46
radiopharmaceutical should Produce ? gamma rays with energies between ? and ? keV
monochromatic
100 and 300 keV
47
The ability to detect and evaluate lesions depends largely on the ? of the radiopharmaceutical in the organ or lesion of interest
concentration
48
• Refers to the introduction of the radiopharmaceutical into a well-defined anatomic compartment.
COMPARTMENTAL LOCALIZATION AND LEAKAGE
49
Heart failure (especially ? failure),
left ventricular
50
is used to identify an abnormal opening in an otherwise closed compartment, as when labeled RBCs are used to detect gastrointestinal bleeding.
Compartmental leakage
51
the spleen’s ability to recognize and remove () the damaged RBCs is evaluated. This procedure allows for the evaluation of both splenic morphology and
CELL SEQUESTRATION
52
CELL SEQUESTRATION
• RBCs are withdrawn from the patient, labeled with Tc-99m, and slightly damaged by in ? in a boiling water bath for approximately ?
vitro heating
30 minutes.
53
The cells reticuloendothelial system are distributed in the ? (?%), ? (?%), and ?(?%).
liver (85%), spleen (10%), and bone marrow (5%).
54
These cells recognize small foreign substances in the blood and remove them by.
In a liver scan, for example, the Tc-99m labeled sulfur colloid particles (?) are recognized, being substantially smaller than circulating cellular elements and are rapidly removed from circulation.
phagocytosis
100 nm
55
is simply the free movement of a substance from a region of high concentration to one of lower concentration.
Anatomic and physiologic mechanism exist in the brain tissue and surrounding vasculature that allow essential nutrients, metabolites, and lipid-soluble compounds to pass freely between the plasma and brain tissue while many water-soluble
Passive diffusion
56
substances (including most radiopharmaceutical) are prevented from entering healthy brain tissue.
• This system is called the ?, protects and regulates access to the brain.
blood-brain barrier
57
Bone scanning with ?
• is chemically similar to phosphate, one of the components of bone mineral.
• When Tc-99m ? circulates in the bloodstream, it binds to calcium in areas where new bone is forming or repairing.
pyrophosphates.
58
involves cellular metabolic processes that expend energy to concentrate the radiopharmaceutical into tissue against a concentration gradient above plasma levels.
it uses energy) and against a concentration gradient (it moves from low to high concentration).
Active transport
59
is a glucose analogue: its increased uptake correlates with increased glucose metabolism.
•, is used in approximately 85% of all clinical PET applications.
• crosses the blood-brain barrier, where it is metabolized by brain cells.
• enters cells via carrier-mediated diffusion (as does glucose) and is then phosphorylated and trapped in brain tissue for several hours as FDG-6-phosphate.
(FDG) fluorodeoxyglucose
60
FDG is fluorodeoxyglucose, is used in approximately?% of all clinical PET applications.
• FDG enters cells via carrier-mediated diffusion (as does glucose) and is then ? and trapped in brain tissue for several hours as ?
85
phosphorylated
FDG-6-phosphate.
61
• When particles slightly larger than RBCs are injected intravenously, they become trapped in the narrow capillary beds.
• A common example in NM study is the assessment of pulmonary perfusion by the injection of Tc-99m MAA, which is trapped
CAPILLARY BLOCKADE
62
describes the movement of a cell such as a leukocyte in response to a chemical stimulus. 111 Inlabeled leukocytes respond to products formed in immunologic reactions by migrating and accumulating at the site of the reaction as part of an overall inflammatory response.
Chemotaxis
63
is a biomolecule (typically a protein) that is capable of inducing the production of, and binding to, an antibody in the body. has a strong and specific affinity for the antibody.
antigen
64
Antigen-antibody complexation is also used in diagnostic imaging with such agents as ? -labeled antibodies for the detection of colorectal carcinoma.
• In addition, a variety of radio labeled (typically ? labeled) monoclonal antibodies directed toward tumors are being used in an attempt to deliver tumoricidal radiation doses.
In-111
I-131
65
• For example, the uptake of In-111-octreotide, used for the localization of neuroendocrine and other tumors, is based on the binding of a somatostatin analog to receptor sites in tumors.
receptor binding
66
example is Methylenediphosphonate (MDP) localization occurs primarily by adsorption in the mineral phase of the bone.
Physiochemical Adsorption
67
MDP concentrations are significantly higher in ? than in mature hydroxyapatite crystalline structures, which helps to explain its concentration in areas of increased ? activity.
amorphous calcium
osteogenic
68
Perfusion is also an important diagnostic element in examinations such as ?(3)
renograms and cerebral and hepatic blood flow studies.
69
phase of a threephase bone scan helps to distinguish between an acute process (e.g., osteomyelitis) and remote fracture.
Perfusion
70
produce projection images of the distribution of radioactivity in patients.
Scintillation cameras /gamma cameras / Anger cameras.
71
are essential for providing spatial information in planar NM imaging.
Collimators
72
Approximately?% of the absorbed gamma ray energy is converted to light.
10
73
Light output from the NaI scintillator is detected by an array of ?) and converted to an electrical sign
Scintillation cameras typically use of these
photomultiplier tubes (PMTs
55
74
?refers to the registration of a single gamma ray by the detector, and -? are acquired for a typical scintillation camera image.
Count
∼500,000 counts
75
The lead strips between the holes are called ?. in the collimator
septa
76
?collimators project the same object size onto the camera, and the field of view (FOV) does not change with distance.
The most used collimator i
General-purpose imaging.
Parallel-hole
77
The holes may be ? however, most state-of-the-art collimators have ? holes.
round, square, or triangular;
hexagonal ( 6 sides )
78
has many holes, all aimed at a focal point in front of the camera and produce a magnified image, and FOV decreases with distance.
The magnification increases as the object is moved away from the collimator Imaging small organs that need enlargement
Converging collimators
79
?collimators project an image size that is smaller than the object size, and FOV increases with distance.
collimator has many holes aimed at a focal point behind the camera.
It produces a minified image in which the amount of minification increases as the object is moved away from the camera.
Diverging
80
A diverging collimator may be used to image a large portion of a patient on a small ( ?-cm diameter) or standard (?-cm diameter) field-of-view (FOV) camera
25
30
81
?collimators are cone shaped with a single hole at the apex.
–Images generated are normally magnified and inverted.
Pinhole
82
a? mix ? & ? collimator, called a fan-beam collimator, is used in single photon emission computed tomography (SPECT).
Hybrid
parallel-hole and converging
83
is the fraction of gamma rays reaching it from all directions that pass through the holes.
Collimator Sensitivity
84
? -sensitivity collimators have larger holes and lower resolution.
High
85
86
Resolution is? with increasing distance from the collimator.
degraded
87
Low-energy collimators used with? and ?have thin septa.
99mTc
201 TI
88
?collimators are most frequently used.
Low-energy high-resolution (LEHR)
89
Medium-energy collimators used with ? & ? have thicker septa and therefore fewer holes and lower sensitivity.
67Ga and 111In
90
High-energy collimators are required for ? imaging and have the thickest septa.
131 I
91
NaI scintillators detect gamma rays emerging from patients and are generally ?.
For gamma ray imaging, NaI scintillators are ∼ ?thick.
rectangular
10 mm
92
is when an incident gamma ray is completely absorbed (photoelectric effect).
photopeak
93
is the percentage of incident gamma rays absorbed in the scintillator
Detection Efficiency
94
INCREASING PHOTON ENERGY = DETECTION EFFICIENCY?
DECREASE
95
is an electronic device used to determine which portion of the detected spectrum is used to create images.
– can be set to allow only selected energies to be counted and reduce the number of Compton scatter photons in the image.
–analysis maximizes the number of photopeak events while minimizing the detected photons that would degrade image quality (i.e., Compton scatter)
Pulse Height Analyzer (PHA)
96
provides computed tomographic views of the three-dimensional distribution of radioisotopes in the body.
– ? collimators are commonly used for this imaging.
–Scintillation cameras rotate 180 or 360 degrees around the patient.
–Projection images are obtained at selected angles, typically every 3 or 6 degrees.
Single photon emission computed tomography (SPECT)
Parallel-hole
97
Scintillation cameras rotate ? lr ? degrees around the patient.
–Projection images are obtained at selected angles, typically every ? or ? degrees.
180 or 360
3 or 6 degrees.
98
SPECT physics
–Each projection takes ∼ ? with a total scan time of ∼?
–Cardiac SPECT images make use of a ? matrix size.
–Noncardiac SPECT imaging likely uses a ? matrix size
30s
15 minutes.
64 × 64
128 × 128
99
?were originally used as inputs for filtered-back projection reconstruction algorithms to compute tomographic images, but it causes ? artifacts; less accurate
Scan projections
streaks
100
? reconstruction is more accurate, minimizes artifacts and better quality.
algorithms that is now used.
Iterative
Nucmed
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