Put the “Q” *in* quality imaging
PET radioactivity is given in these SI units
Becquerel
This is the HU value of water.
0 (this is by definition/calibration)
To reduce heating of the anode, one of these parameters can be reduced
These are the major components, in order, in an X-ray tube
System is in a vacuum and surrounded by oil to help dissipate heat. Heated cathode filament emits electrons. Electric field accelerates them to anode (strength of field governs the kVp of the photons). Tungsten (high Z, high melting point) anode spins to dissipate heat from electron beam while ~1% of electrons produce bremsstrahlung photons (and a few characteristic X-rays). X-rays exit through a barium window and go through a filter to remove remaining lower energy photons.
FOV and ROI
Field of View and Region of Interest
If the mAs is doubled, this is how much the SNR in an x-ray image improves
Square root of 2
This is the typical range of kVp for clinical diagnostic CT scanners
80 – 140 kVp
Smaller anode angle and smaller filament (focal spot size f = F sin(θ))
These are the major components, in order, in PET imaging
Radioactive drug (injected, ingested, inhaled), patient, detector crystals (e.g., LYSO), Photomultiplier tube (PMT), electronics, reconstruction computer
ADC
Analog to digital converter
This term describes the set of RF pulses and gradient fields used to generate an MRI image
Sequence
42.58 MHz/T is what quantity?
Gyromagnetic ratio of a proton
Mean over standard deviation within an ROI is one way how we calculate this image quality metric
Signal to noise ratio (SNR)
These are the major components in Computed Tomography
X-ray tube (has higher heat capacity than planar x-ray), filter, collimator (usually limited to 2-3 options), patient on moving bed, anti-scatter grid, detectors (thin and curved to match curve of bore), reconstruction computer
AEC
Automatic Exposure Control
Multiplying the magnetic field B0 by the gyromagnetic ratio provides this quantity used in MRI
Larmor Frequency
An image with this many grayscale levels has a bit depth of 8
256
Ghosting, distortion, motion and aliasing are artifacts in what imaging modality?
MRI
These are the major components in Ultrasound imaging
Transducer with piezoelectric crystal, coupling gel, patient, coupling gel, transducer, processing electronics and monitor
(signals are sent out from the transducer, echo back and are detected by the same transducer)
DR and CR and TFT
Digital Radiography (directly digitized, read out with Thin-Film Transistor) and Computed Radiography (detector cassette + reader to digitize)
Tube arcing and ring artifacts are this type/category of CT artifact
Equipment
This is the rest mass energy of an electron or positron
511 keV (this is thus the energy of each of the resulting photons used in PET from positron-electron annihilation)
These are the two main reasons for collimation in x-ray imaging
Reduce dose and scatter (scatter reduces contrast)
These are the major components, in order, in MR imaging
B0 field (from main solenoid electromagnet), patient (protons align on average with the B0 field), RF pulse to excite a single slice (selected with gradient field and matched frequency), phase altering gradient field (orthogonal), frequency altering gradient field (orthogonal), coil receives RF signal
CTDI and DLP
Computed Tomography Dose Index (usually weighted based on central and peripheral measurements, adjusted for pitch in helical scans) and Dose Length Product (CTDIvol * Length), proportional to effective dose - need a k-factor to *estimate* patient dose