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Interfile Keys
Standard Keys
"!INTERFILE" Used to signal that a
file is an Interfile header.
"!imaging
modality" or "image modality"
This key must have value NUCMED.
"!version
of keys" Assumed to be 3.3.
"!conversion
program", "!program author",
"!program version"
and "!program date"
When writing out Interfiles these keys will be adjusted.
"data
description" If this key contains the word sinogram in its value the data
image read in will be transposed. When writing out Interfiles this keys value
will be emptied.
"!data
starting block" or "!data
offset in bytes" Used to locate the start of binary data
within data
file (below). Blocks used by data
starting block are 2048 bytes long. Only one of these keys is
required. If neither is present, 0 offset will be assumed. If both are present,
!data
offset in bytes value will be used.
"!name
of data file" Name of the file containing the binary image data.
"data
compression" and "data
encode" Above keys assumed to be none in value.
"comment" Introduces a comment.
Comments are preserved and ignored.
"!type
of data" Value must be tomographic (tomo is adequate).
"!total
number of images" Equivalent to number of slices in case of reconstruction
image.
"imagedata
byte order" Assumed to be bigendian.
"!number
of energy windows" Assumed to be 1 or 2.
"number
of detector heads" Assumed to be 1. May be expanded later to handle multiple headed
cameras.
"number
of images/energy window" Assumed to be equal to total number of images.
"!process
status" Value of acquired for sinograms. Value of reconstructed for reconstructions. Value of phantom for research
phantoms.
"!matrix
size [1]" and "!matrix size [2]"
For reconstruction these are equal to each other and give the dimension of the
reconstruction grid. For sinogram, matrix 1 is number of projection bins in
projection slice and matrix 2 is the number of slices.
"!number
format" Value must be one of ASCII, short float, signed integer or unsigned integer.
"!number
of bytes per pixel" Value must be 1 or 2 for integer types, 4 or 8 for float
types, ignored for ASCII type.
"!scaling
factor (mm/pixel) [1]" and "!scaling
factor (mm/pixel) [2]" Scaling factor for matrix 1 and matrix
2. Assumed matrix 2 equals matrix 1 for reconstructions.
"!number
of projections" Number of projections in sinogram or number of
projections that were used in reconstruction.
"!extent
of rotation" Angle in degrees that camera covered during data
collection.
"!maximum
pixel count" Is set to correct value when any image is saved. Note: Two
byte unsigned binary images, will have a range of 8 to 32000. Two byte signed
binary images, will have a range of -32768 to 32000. One byte unsigned images
have a range of 8 to 255. One byte signed images have a range of -128 to 127.
Values outside that range are scaled using !RPAH Scale. So, true maximum is
this value divided by !RPAH Scale.
"patient
orientation" Value must be one of feet in or head in. head in is assumed.
"patient
rotation" Value must be one of prone or supine. supine is assumed.
"!SPECT
STUDY (acquired data)" Key is present for sinogram (acquired) data.
"!direction
of rotation" Value must be CW or CCW, standing for clockwise and counter-clockwise
respectively. Clockwise is assumed.
In absence of attenuation correction, reconstruction will be the same, only
reflect in the X axis. In case of attenuation correction, must be correctly set
to prevent strange artefacts appearing in reconstruction.
"start
angle" Angle in degrees at which camera began its coverage.
"centre
of rotation|center of rotation" Value must be one of corrected or single value. If single value is specified the keys
"x_offset" and "y_offset" are used to
translate the camera position for all angles. There is currently no way in
Interfile headers to specify projection by projection corrections. Corrected is assumed.
"!SPECT
STUDY (reconstructed data)" Key is present for non-sinogram (reconstructed,
phantom) data.
"method
of reconstruction" Should be filled in by R. I'll look into it soon. (Mail me)
"!number
of slices" Number of slices in the reconstruction.
"attenuation
correction coefficient/cm", "method
of attenuation correction", "scatter
corrected" and "method
of scatter correction" Should be filled in by R. I'll look into it soon. (Mail me)
"!end
of interfile" If present will cause R
to ignore any further lines/data in the header file.
Recently Added
Keys
"radius
of rotation" Radius of rotation in mm.
"crystal
to focus" Effective focal point of collimator in mm from crystal. This key is written by R but not read. See -FBFmm for how to set this value.
Macquarie
University Extensions
"[mqu]
image scale factor" or "RPAH
Scale" Image will be divided
by this amount after being read in.
"[mqu]
phantom description" Not used by R.
Must have value listed in P
help. e.g. RD1, HIL, GRY, RD1ATT, PNT, etc. Produces a
phantom lambda image, according to phantom name and scaling parameters provided
after name. Complete format is [mqu] phantom description :=
NAME,Xs,Ys,Zs,Xo,Yo,Zo
e.g. [mqu] phantom description := RD1,0.8,0.8,0.8,0.1,0.1,0.0
This would produce the RD1 phantom scaled in all axes by 80offset (.1,.1,0)
within a unit cube. The unit cube is mapped to the grid and slice dimensions
after phantom scaling and translation. The Zs and Zo are not currently useful
as all the phantoms are two dimensional. Add your own, its not too hard if you
have the source!
"[mqu]
average count per pixel" Sets the average pixel count for phantom lambda images.
Average for a emission study may be 100 or so. For an attenuation map you might
use 0.09 give or take.
