Exam style Questions Flashcards
Radionuclides decay exponentially
True
Radionuclides do not occur naturally
False
Concerning DR, the receptor dose indicator gives a record of patient dose
True
In automatic mode fluoroscopy, the patient ESD rate usually increases with image intensifier field size
False
In automatic mode fluoroscopy the patient ESD should ideally be under 50mGy/min
True
IRR- overall responsibility for keeping dose ALARP tests with practitioner
False (employer)
IRR- the practitioner is the only person that can authorise exposures
False (skilled operators)
For MRI Signal to noise ratio to be increased, what are the few things that will have to decrease?
- TE
- Receiver bandwidth
Typical wavelength of ultrasound in abdominal scanning (in soft tissue) is 0.5mm
True
CT SNR increases when kvs is decreased
False
KV and SNR are proportional
Gadolinium should be avoided during the first trimester
True
Avoid in all stages of gestation
K space is a table of spatial frequencies
True
Each horizontal line of K space represents data from each frequency encoded gradient applied
False
It’s each phase encoding Gradient applied
Information from the edge of K space corresponds to contrast of the image
False
Fine detail at the edges
Noise is related to the square root of the number of photons
True
Contrast is usually T1 weighted
True
The larger the anode angle the larger the focal spot size and the less heat loading there is
True
I’m CT scanners the anode-cathode axis is placed along the xy plane
False
Z plane
Photomultiplier tubes take light produced by scintillation layers, from X-rays or gamma rays, and convert them into electric signal
True
The gamma camera PMT tube is filled with inert halogen gas
False
The effective dose is usually lower than the absorbed dose
True
Compton scatter is the predominant mode of interaction in the input screen of the image intensifier
False
Photoelectric dominates due to high atomic number of CSI
Compton scatter is the dominant mode of interaction on soft tissue with nuclear medicine studies
True
Average kv is high
Increasing kVP from 40 to 60 will require mA to be reduced by approx a half to deliver the same dose?
True
60^2 / 40^2 = 2.25, so mA must decrease by factor of about 2.
The spatial resolution of indirect FPDs is restricted by screen blur
True
Spatial resolution in DR increases with pixel depth
False, decreases with pixel size
Pixel depth determines number of X-rays that can be recorded
I’m fluoroscopy, magnification mode improves both contrast and spatial resolution
True, at expense of increased dose
Xray image contrast is improved by reducing the area of the X-ray beam
True
Using an anti scatter grid with a higher grid ratio improves Xray spatial resolution
False
Improves contrast not resolution
Spatial resolution of Xray images is improved by decreasing patient to image receptor distance
True
Reduced geometric unsharpness penumbra
Spatial resolution of Xray images is improved by increasing the amount of added filtration on the beam
False
This affects contrast and dose, not SR
DRLs should be reviewed annually
True
Dose rate from scattered radiation at 1m from patient is approx 0.1% of the dose rate incident on the patient
True
Leakage radiation from Xray tubes must not exceed 1mGy/hr at 1m from the focal spot
True
Spatial resolution in CT can be improved by reducing scan time
True
Less motion artefact
Noise from a CT study will increase with increasing matrix size
True
Smaller pixels so decreased SNR
The main role of the collimator of a gamma camera is to reject scatter
False
True for X-rays but not for gamma.
Scatter rejection is performed by PHA window. The collimator is for spatial localisation.
TC99m emits energy rays of 140keV
True
Contrast in planar nuclear medicine is dependent on the type of collimator used in the gamma camera
False
SPECT scans are acquired using high resolution collimator
True
They are needed to make up for the shitty resolution
An uptake time of 30mins is used to prevent excessive decay of FDG
False it’s 60mins
Tissue concentration of fDG is proportional to injected dose and inversely proportional to body weight
True
Radiation dose from a radio pharmaceutical May be measured by a gamma camera
False
The camera only visualises activity distribution, not doze
On average around 0.4mSv per year of irradiation is due to medical exposures
True
USS waves have a wavelength of 1-5mm in soft tissue
False
It’s 0.3-1mm
Muscle has a higher acoustic impedance than fat
True
Increased operating frequency will result in improved axial resolution (USS)
True
Improves both axial and lateral resolution
An increased operating frequency will result in no change in the speed of USS wave propagation
True
Speed depends on medium
An increased operating frequency will give reduced incidence of aliasing in Doppler
False
Results in more Doppler shift so more chance of aliasing
MRI spin echo- the spin echo signal appears at time TE after the 90 degree pulse
True
Gradient recalled echo sequences are affected by main field inhomogeneities
True
Chemical shift artefact occurs along the frequency encoding axis gradient
True
The anode angle is generally 7-20 degrees
True
If the anode angle is reduced, the tube rating is…?
Increased
The anode angle determines the size of field covered by the cray beam at a given…
Focus film distance
