CC	Cross Correlation
CCGIP	Normalized Correlation Coefficient summed with the Gradient Internal Products
CR	Correlation Index
dB	Decibels
DC	Coefficient of Dice
EMAF	Enhanced Multiple Acquisition Frames
EMT	Extrinsic Motion Tracking systems
FWHM	Full Width Half Maximum
GRAD	Sum of degraded internal products
HD	Hellinger distance
IMP	Precision Coincidence of Intensities
JE	Joint Entropy
JHCT	Jensen–Havrda–Charvat–Tsallis divergence
JRD	Jensen–Renyi divergence
LOR	Line of Response
MAF	Multiple Acquisition Frames
MFDT	Minimal Frame Duration Threshold
MI	Mutual Information
MLEM-OS	Maximum Likelihood Expectation Maximisation with Ordered Subsets
MSD	Mean Square Difference
NCC	Normalized Correlation
NMI	Standardized Mutual Information
PET	Positron Emission Tomography
PSE	Point Set Expectation
PSNR	Peak Signal-to-Noise Ratio
PVE	Partial Volume Effect
RIU	Image Uniformity Ratio
RMSE	Root Mean Square Error
SAD	Sum of Absolute Differences
SADG	Sum of Absolute Differences plus sum of the Gradient internal products
SLS	Scaled Least Squares difference image
SNR	Signal-to-Noise Ratio
SSD	Sum of Squared Differences
VAMPIRE	Variational Algorithm for Mass-Preserving Image REgistration