PassFRCR Questions Flashcards
MTF curve improves as spatial frequency…
Decreases
Under IRMER, the DoH must be notified if there is overexposure due to…
Operator error
Venetian blinds MRI artefact is caused by…
Flowing blood
Quality control of a gamma camera system is carried out how often?
Daily
How many sources required to measure energy resolution in gamma camera QC?
At least 2
Quality control of a gamma camera includes a measurement of the…?
Speed of rotation of the camera head
How thick and wide are gamma camera collimators
25mm thick
400mm diameter
A technetium generator contains molybdenum 99 suspended in…
High grade aluminium beads
Cupping artefact in a ct image will show which part as brighter?
Peripheries
Image intensifier vertical resolution is determined by the number of…
Scan lines on the frame
A stationary mirror aids laser scanning in photo stimulable phosphor plates.
False- it rotates
Radiation badges should be worn under the lead apron
True
Radiation badge does not measure does less than 0.1mSv
True
Can vignetting artefact be controlled by strict quality control?
Yes
The AEC is usually placed between…
The patient and the image receptor
Inversion recovery sequences have a short or long Tr?
Long
Aliasing in MRI can be avoided by these 4 things:
- use a … field of view
- …. the field of view
- changeover…
- artefact …
Use a larger field of view
Remove signal outside of field of view
Artefact correcting software
Changeover phase encoding and frequency encoding gradients if problem only in 1 direction
What type of unsharpness is when there is a gradual change near the edge of a rounded sttructure?
Absorption unsharpness
The image intensifier is located opposite the X-ray tube
True
The larger the image intensifier, the higher the cost
Teue
The electrons in an image intensifier are focused by dynodes
It’s electrodes not dynodes
Pathological tissues are best shown on T1 MRI sequences
False - T2
Positron emitters are produced in cyclotrons
True
According to IRR17, who may not enter a controlled area?
Nobody
Everyone is allowed to enter
In gamma cameras, light from the scintillation event is shared between several PMTs
True
3rd gen CT scanners are based on parallel beam geometry
False
It’s fan beam geometry
Iodine 123 decays wholly by electron capture
True
Computed radiography exposure response is linear and wide exposure latitude
True
Doppler shift from arterial blood is maximally detected at twice the PRF
False
It’s half the PRF
Extrinsic contrast parameters in MRI are all…
Selected by the operator
MTF is a useful measure of true/effective resolution
True
Intensifying screens improve resolution and unsharpness
False
The receiver bandwidth is the range of….
Frequencies used to sample the MRI signal
The frequency range is called the receiver bandwidth
False
Transmitter bandwidth
Molybdenum 99 is prepared by fission of Uranium 235
True
Brightness gain comes from the inter related sources of minification gain and flux gain
False
The two are both related
Brightness gain reduces over time
True
Brightness gain conversion factor is usually equals to 1% of the brightness gain in value
Teue
ADC is an intrinsic contrast parameter of MRI
True
The DSA subtraction reduces noise
False
Beam steering in USS is optimal with an annular array
False
Stochastic effects may be somatic or genetic
True
Collimation has what effect on contrast, scatter and dose?
More contrast
Less scatter
Less dose
Alpha particles travel through matter quickly
False
They are big and slow
Alpha particles are useful in clinical radiology
False
Following radiation, chemical damage occurs how long after? This is unique to chemical damage
Immediately
Cornwall folks have 6x normal BG radiation
False
It’s 3x
TLDs are generally used in conjunction with filters
True
Film badges use a double sided emulsion film
True
Film badges are similarly sensitive to TLDs
True
Film badges are resistant to environment
False
Film badges require calibration
True
Film badges cost more than TLDs
False
Film badge sensitivity is 0.1-0.2mSv
False
The outer case of the Geiger muller counter is the cathode
True
Electronic dosimeters are more than a 100 times sensitive than TLDs
True
Geiger muller counters can detect all types of radiation
True
The effective focal spot size depends on anode angle
True
Anode heel effect occurs in a direction parallel to the anode cathode axis
True
Focused x ray grids increase side cut off
False
They decrease it
The CT number of a voxel increases with the attenuation of the X-ray beam
Yes
Technetium is produced from cyclotrons
False
It’s made in generators
Digital flat plate detectors have greater dynamic range than image intensifiers
True
USS waves refers to sound waves with frequencies above 200 kHz
False
It’s 20 kHz
Frequency encoding gradient just be changed every TR to fill K space
False
Phase encoding gradient should be changed
High resolution data is in the centre of k space
True
An artefact from a faulty CT detector would appear as a black line on the localiser image, parallel to the long axis of the patient
True
The spatial resolution of an image intensifier is in the 4-6lp/mm range
True
When magnification of an image intensifier doubles, the dose quadruples
True
The size of the input phosphor is fixed in image intensifier
False
List the 7 types of EM Spectrum radiation types in order from biggest to smallest wavelengths
Radio waves
Micro waves
Infra red
Visible light
UV light
X rays
Gamma rays
CT has better contrast than film screen radiography
True
Mammography needs anti scatter grids
True
The half life value for water is about 60mm in the diagnostic range of energies
False
It’s 30mm
For portal X-rays, the operator should clear a space of… metres
2 metres
Quality assurance is needed under the … guidelines
IRMER 2000
Dose limits can be relaxed for carers and comforters
True
A dose of 30mSv to an employer may be acceptable within a year
True but as long as it doesn’t exceed 100mSv over 5 years
A dose of 30mSv to an employer may be acceptable within a year
True but as long as it doesn’t exceed 100mSv over 5 years
Who is responsible for ensuring equipment is calibrated?
Radiation protection advisor
For chest radiography, film to focus distance should not be less than 30cm
False
Should not be less than 60cm though there are exceptions for mammo
CR: electrons jump from valence into conduction bands
True
In DR, high pass filtering is used for edge enhancement
True
In DR, low pass filtering leads to smoothing or blurring of features
True
In DR, fill factor falls as pixel sampling interval is increased
False
Falls as sampling interval is reduced
CR vs DR: which has more…
- resolution
- noise
- dose
- Direct
- Direct
- Direct
Aliasing will occur if the signal frequency is more than the Nyquist frequency
True
Nyquist frequency is equal to half the sampling frequency
True
Approx 100,000 light photons are emitted from the output screen for every xray photon detected
true
At 1m from the patient, the scatter is typically about 1% of the patient entrance dose rate
False it’s about 0.1%
Leakage from the tube housing is typically 5uGy per hour at 1m distance
True
Effective half life is always shorter than biological and physical
True
Solid state CT detectors have to be separated to prevent light crossover so their efficiency is compromised
True
Titanium causes fewer artefacts than other metals in ct
True
Aliasing in Ct occurs when the sampling frequency is less than 2x the nyquiat frequency
True
Beta decay is a spectrum or few characteristic energies?
Spectrum
A pinhole collimator produces minified and inverted images
True
Gamma camera crystals emit 5000 light photons when struck by a gamma photon
True
Nuclear medicine DRLs are provided by IRR
False
It’s ARSAC
Ultrasound is attenuated exponentially with depth
True
Photoelectric effect is most likely when X-rays hit contrast media
True because the density is so high
Air flight has an effective dose of approx… per hour
0.004mSv per hour
Does an employee getting an X-ray have to tell their employer to adjust their annual limit?
No
The effective dose for most imaging is usually higher for AP vs PA views
True
Radiosensitive organs at the front
Employees cannot be carers or comforters
True
For low dose exams the exposure of 10x is enough to be reportable
False
It’s 20x for low dose
TLDs may be used to monitor patient dose
True
Subtracting a high kv image from a low kv image will improve contrast of bony structures
True
Bismuth germanate is ideal for pet scintillators because if a long decay time and high detection efficiency
False
It has a short decay time, which is desirable
The length of the USS near field is proportional to…? (Equation)
Frequency X (beam diameter)^2
There is less near field divergence with an increasing transducer diameter
False
There is less far field divergence
Refraction is compensated for in ultrasound imaging
False
The lateral resolution is equal to the beam width at the depth of the objects
True
Slice selection is applied simultaneously with the initial RF excitation
True
The longer the TE the smaller the subsequent MRI Signal
True
Deoxygenated haemoglobin is paramagnetic - this is the foundation of functional MRI
True
Resistive electromagnets should be kept on ideally
False
Switch them off at the end of the day
What does a faraday cage do
Screens the scanner from external RF interference
Surface coils can be placed directly on the patient
True
Eg mri spine imaging
Plastic pacemakers are MRI Safe
False
It’s not about movement but about electrical interference with the pacemaker currents
Biggest risk from a joint replacement in mri is movement force in joints
False
It’s heating
The energy of K shell characteristic x rays is always just less than the K shell binding energy
True
The effective focal spot depends on the size of the cathode filament
True
Different filament sizes are used to make difference spot sizes
A photoconductor converts X-rays into light
False
that’s what a phosphor does
Spatial resolution of indirect FPDs is restricted by screen blur
True
That means the same as light spread in the phosphor
Spatial resolution is improved with increased beam filtration
False
No effect
X-rays Spatial resolution is improved with increased anti scatter grid ratio
False
Grids improve contrast not resolution
SPECT requires higher activity administration than planar imaging
True
Which has better sensitivity- PET or SPECT
PET cos it has no collimators
SUV equation?
SUV =
tissue concentration of FDG
/
injected activity/ patient mass
SUV is dependent on the type of scanner used
True
Paediatric nuclear medicine doses are usually half the adult dose
False
It’s calculated based on body weight
TE is the time between the initial 90 degree pulse and the refocusing pulse
False
It’s 2x that time
Holes or tears in the RF shielding of the room can result in truncation artefact
False
Zipper artefact could occur though
The DQE of detectors changes with kvp
True
Bow tie filters are made from copper
False
Usually aluminium
Interspace channels in grids can be filled with copper
False
Usually plastic or aluminium
In Fluoro, the dose rate at the input phosphor is 1 mgt/sec
False
It’s 1 micro Gray per second
The photoelectric effect is responsible for most of the radiation dose received by the patient
True
Permanent magnets are sensitive to ambient room temperature
True
