Physics Flashcards
EM radiation velocity?
3 * 10^8 m/s
What is the K shell binding energy of tungsten?
-69.5 keV
Relationship between Z and K shell binding energy
K shell binding energy is proportional to Z^2
Relationship between xray production and mA
linear increase
Relationship between xray production and kVp
Increasing kVp by 15% will double intensity of spectrum
What do you give to detect extrahepatic biliary atresia and how much
phenobarbitol
5 mg/kg/day
2 divided doses
3-5 days
Half life of gallium
78hours
Iso-osmolality iodinated contrast media
300 mOsm/kg
low-osmolality iodinated contrast media
600 mOsm/kg
high-osmolality iodinated contrast media
1200 mOsm/kg
human plasma
295 mOsm/kg
CTDIw
1/3 CTDI central + 2/3 CTDI peripheral
CTDIvol
CTDIw/Pitch
Window levels for Brain
W 80, L +40
Window levels for Lung
W 1500, L -400
Window levels for Abdomen
W 440, L +50
Window levels for Bone
W 1600, L +500
Adult Head Avg Dose CTDI
58 mGy, effective dose (1-2 mSv)
Adult Abd CTDI
18 mGy, effective dose (8-11 mSv)
Peds Abd CTDI
15 mGy
ACR “reference” dose, for which if they are above should be investigated:
CTDIvol for Head
75 mGy
ACR “reference” dose, for which if they are above should be investigated
CTDIvol for Adult Abd
25 mGy
ACR “reference” dose, for which if they are above should be investigated
CTDIvol for Peds
20 mGy
Embryo Dose in CT A/P
30 mGy
Individual dose monitoring mandated if occupational dose is greater than ___ of annual dose limit ____.
10%, 500 mrem
CT Head CTDIvol
CTDIvol of 60 mGy.
CT Head CTDIvol
CTDIvol of 60 mGy.
diagnostic workstation avg monitor brightnes
500 cd/m2
diagnostic workstation avg monitor brightnes
500 cd/m2
The instantaneous RF power (W) of a body coil in MR operated at 1.5 T is typically ____. However, remember that this RF is only switched on for the duration of a typical pulse (ms or so), so the energy consumption is not going to be large.
10000 W
The instantaneous RF power (W) of a body coil in MR operated at 1.5 T is typically ____. However, remember that this RF is only switched on for the duration of a typical pulse (ms or so), so the energy consumption is not going to be large.
10000 W
ultrasound mode A
echo intensity as a function of time or depth is A (Amplitude) display mode
ultrasound mode A
echo intensity as a function of time or depth is A (Amplitude) display mode
Which does not affect spatial resolution? Detector “size”, focal spot, and patient motion, radiation intensity?
radiation intensity ALWAYS affect spatial resolution performance, and nothing else dose (directly). Radiation intensity (number of photons), as such, is essentially irrelevant for resolution performance which means image blurriness, but will affect lesion visibility by impacting on mottle.
Which does not affect spatial resolution? Detector “size”, focal spot, and patient motion, radiation intensity?
radiation intensity ALWAYS affect spatial resolution performance, and nothing else dose (directly). Radiation intensity (number of photons), as such, is essentially irrelevant for resolution performance which means image blurriness, but will affect lesion visibility by impacting on mottle.
The maximum patient eye lens dose (mGy) after 5 minutes of fluoroscopy in interventional neuroradiology is likely___ Gy?
150 mGy
Which does not affect spatial resolution? Detector “size”, focal spot, and patient motion, radiation intensity?
ALWAYS affect spatial resolution performance, and nothing else dose (directly). Radiation intensity (number of photons), as such, is essentially irrelevant for resolution performance which means image blurriness, but will affect lesion visibility by impacting on mottle.
max patient eye dose after 5 min of fluro
150 mgy
max patient eye dose after 5 min of fluro
150 mgy
In cardiac ultrasound imaging, the pulse repetition period is most likely (ms):
0.25 ms, which corresponds to a Pulse Repetition Frequency of 4 kHz
listening period of cardiac ultrasound corresponds to penetration depth of
20 cm
listening period of cardiac ultrasound corresponds to penetration depth of
20 cm
frequency encoding gradient of single 128 x 196 Spin Echo MR image
128
frequency encoding gradient of single 128 x 196 Spin Echo MR image
128
sampling echo of single 128 x 196 Spin Echo MR image
196
sampling echo of single 128 x 196 Spin Echo MR image
196
The ideal fluoroscopic x-ray tube voltage in cardiac imaging is about ___ kV since this results in an average energy of ~35 keV that matches the k-edge energy of iodine contrast
he ideal fluoroscopic x-ray tube voltage in cardiac imaging is about 75 kV since this results in an average energy of ~35 keV that matches the k-edge energy of iodine contrast (Z = 53; k-edge 33 keV) that is ALWAYS administered to the patient to visualize the cardiac vasculature.
effective dose of chest CT
5 mSv
effective dose of CXR (1 ct = 100 CXR)
.05 mSv
effective dose of CXR (1 ct = 100 CXR)
.05 mSv
In chest CT, increasing the x-ray beam filtration would likely result in a lesion contrast that is
decreased
In chest CT, increasing the x-ray beam filtration would likely result in a lesion contrast that is
decreased
At the same techniques, increasing the patient size in chest CT from 70 kg to 100 kg will likely change the patient dose by (%):
decrease by 30%
At the same techniques, increasing the patient size in chest CT from 70 kg to 100 kg will likely change the patient dose by (%):
decrease by 30%
Which type of electronic (digital) correction is least likely to be applied to a gamma camera image?
a. Energy Incorrect
b. Sensitivity
c. Linearity
d. Septal penetration
septal penetration
Which type of electronic (digital) correction is least likely to be applied to a gamma camera image?
a. Energy Incorrect
b. Sensitivity
c. Linearity
d. Septal penetration
septal penetration
In chest MRI, doubling the duration of an RF pulse would likely cause the longitudinal Magnetization “flip angle” to be:
doubled
In chest MRI, doubling the duration of an RF pulse would likely cause the longitudinal Magnetization “flip angle” to be:
doubled
MP for clinical review station, MR/CT, general workstation, viewing mammogram
1 MP workstations are used in a clinician review station, 2 MP are used for MR/CT, 3 MP is a general purpose radiologists workstation (chest x-rays), and 5 MP is required for viewing mammogram
MP for clinical review station, MR/CT, general workstation, viewing mammogram
1 MP workstations are used in a clinician review station, 2 MP are used for MR/CT, 3 MP is a general purpose radiologists workstation (chest x-rays), and 5 MP is required for viewing mammogram
M mode imaging
echo intensities as a function of time
has intensities about four times higher than in B mode imaging
M mode imaging
echo intensities as a function of time
has intensities about four times higher than in B mode imaging
The average compressed breast thickness (mm) in the US is about ___ mm, which is much more that the ___ thick phantom that physicists currently use to measure mammography doses.
60 mm for avg breast
42 mm for breast phantom
The average compressed breast thickness (mm) in the US is about ___ mm, which is much more that the ___ thick phantom that physicists currently use to measure mammography doses.
60 mm for avg breast
42 mm for breast phantom
Energy deposited (joules) in the anode in an abdominal radiograph (100 kW; 0.1 s exposure) is most likely:
10,000 joules
Energy deposited (joules) in the anode in an abdominal radiograph (100 kW; 0.1 s exposure) is most likely:
10,000 joules
Increased bandwidth causes S:N to go up or down
makes S:N worse
Increased bandwidth causes S:N to go up or down
makes S:N worse
for every primary photon emerging from patient, there are _scatter photons
5
for every primary photon emerging from patient, there are _scatter photons
5
Coils:
Gradient
Shielding
Shim
Gradient - spatial information
Shielding - reduce magnitude of fringe magnetic field from main magnet
Shim - improve homogeneity
halving FOV of collimation does what to spatial resolution
nothing
halving FOV of collimation does what to spatial resolution
Collimation generally does not change spatial resolution, or the Entrance Air Kerma
halving FOV of collimation does what to spatial resolution
Collimation generally does not change spatial resolution, or the Entrance Air Kerma
The minimum Focus to Skin Distance (cm) on a mobile fluoroscopy unit is ___ to make sure that the patient’s skin can’t get too close to the x-ray source.
30 cm
For fixed fluoroscopy units, this distance is 38 cm (FDA rules).
The minimum Focus to Skin Distance (cm) on a mobile fluoroscopy unit is ___ to make sure that the patient’s skin can’t get too close to the x-ray source.
30 cm
For fixed fluoroscopy units, this distance is 38 cm (FDA rules).
In extremity ultrasound, increasing the Pulse Repetition Frequency is unlikely to permit an increased:
imaging depth
In extremity ultrasound, increasing the Pulse Repetition Frequency is unlikely to permit an increased:
imaging depth
projection is all the ___ at a given rotational angle of the xray tube
rays
projection is all the ___ at a given rotational angle of the xray tube
rays
Which one does not reduce motion blur? increased: exposure time tube voltage tube current matrix size
exposure time everything else (voltage, current, matrix size) decreases blur
Which one does not reduce motion blur? increased: exposure time tube voltage tube current matrix size
exposure time everything else (voltage, current, matrix size) decreases blur
reducing image slice thickness has the biggest impact on what
thin slices will be NOISIER
reducing image slice thickness has the biggest impact on what
thin slices will be NOISIER
thin slices will not affect in plane resolution, only long axis resolution
reducing image slice thickness has the biggest impact on what
thin slices will be NOISIER
thin slices will not affect image contrast, in plane resolution, only long axis resolution
reducing image slice thickness has the biggest impact on what
thin slices will be NOISIER
thin slices will not affect image contrast, in plane resolution, only long axis resolution
replacing plastic apron (Z = 8) with lead equivalent apron (z=80) will increase abrosption of xrays by
1000 (bc mainly photoelectric interaction, Z^3)
replacing plastic apron (Z = 8) with lead equivalent apron (z=80) will increase abrosption of xrays by
1000 (bc mainly photoelectric interaction, Z^3)
CTDIvol is___ to scan length
indepdent
CTDIvol is INDEPENDENT of scan length. CTDIvol tells you about the quality of an individual CT slice; the total amount of radiation that you use to perform the CT examination is the Dose Length Product (CTDIvol x Scan Length).
The correct answer is: Independent of
CTDIvol is___ to scan length
indepdent
CTDIvol is INDEPENDENT of scan length. CTDIvol tells you about the quality of an individual CT slice; the total amount of radiation that you use to perform the CT examination is the Dose Length Product (CTDIvol x Scan Length).
The correct answer is: Independent of
fission products are most likely to emit
beta - emitters
fission products are most likely to emit
beta - emitters
antiscatter grid most likely seen at
bedside
antiscatter grid most likely seen at
bedside
S distortion in Image Intensifier fluoroscopic imaging is a result of extraneous:
mag field
S distortion in Image Intensifier fluoroscopic imaging is a result of extraneous:
mag field
The current US regulatory eye lens dose limit in interventional radiology (mSv/year) is
150 mSv
The current US regulatory eye lens dose limit in interventional radiology (mSv/year) is
150 mSv
Diagnostic workstation brightness is measured in
cd/m2, which is sometimes referred to as nits. A typical diagnostic workstation has a working brightness value of a few hundred cd/m2.
Diagnostic workstation brightness is measured in
cd/m2, which is sometimes referred to as nits. A typical diagnostic workstation has a working brightness value of a few hundred cd/m2.
In gamma cameras, the detected pulse height is ____ to the energy deposited in a gamma camera crystal (NaI).
In gamma cameras, the detected pulse height is directly proportional to the energy deposited in a gamma camera crystal (NaI). This is the basis of all Pulse Height Analysis.
In gamma cameras, the detected pulse height is ____ to the energy deposited in a gamma camera crystal (NaI).
In gamma cameras, the detected pulse height is directly proportional to the energy deposited in a gamma camera crystal (NaI). This is the basis of all Pulse Height Analysis.
SPECT and PET image reconstruction makes use of _____algorithm
SPECT and PET image reconstruction makes use of Iterative Reconstruction algorithm
SPECT and PET image reconstruction makes use of _____algorithm
SPECT and PET image reconstruction makes use of Iterative Reconstruction algorithm
Total Cardiac SPECT imaging time (minutes) is most likely:
15 min
Total Cardiac SPECT imaging time (minutes) is most likely:
15 min
Gamma cameras usually have ___PMTs
37
Gamma cameras usually have ___PMTs
37
nuclear isotopes have same number of__
protons
nuclear isotopes have same number of__
protons
If the parent is long lived, it is called +++; if the parent is short lived, it is called _____. The parent in the 99Mo/99mTc generator has a half-life of only 67 hours, so is called ____.
If the parent is long lived, it is called secular; if the parent is short lived, it is called transient. The parent in the 99Mo/99mTc generator has a half-life of only 67 hours, so is called transient. Note that equilibrium is established after 24 hours, which is four daughter half-lives.
If the parent is long lived, it is called +++; if the parent is short lived, it is called _____. The parent in the 99Mo/99mTc generator has a half-life of only 67 hours, so is called ____.
If the parent is long lived, it is called secular; if the parent is short lived, it is called transient. The parent in the 99Mo/99mTc generator has a half-life of only 67 hours, so is called transient. Note that equilibrium is established after 24 hours, which is four daughter half-lives.
Use of non-circular orbits in body SPECT imaging is most likely to result in images with improved:
resolution
Use of non-circular orbits in body SPECT imaging is most likely to result in images with improved:
resolution
Low energy collimators are made of __, whereas medium energy collimators are “_____” because these are much thicker. We do/do not collimators to image annihilation photons anywhere, but get positional information by detecting these photons in coincidence in PET cameras.
Low energy collimators are made of foil, whereas medium energy collimators are “cast” because these are much thicker. We don’t use collimators to image annihilation photons anywhere, but get positional information by detecting these photons in coincidence in PET cameras.
K shell binding energy of oxygen
0.5 keV
K shell binding energy of Lead
88 kev
K shell binding energy of Lead
88 kev
k shell beinding energy of iodine and barium
33 and 36 keV
