[MINC-users] mincconcat: 3D->4D or 4D-4D ?

[Christopher Bailey]

Dear MINC-users,

I am trying to concatenate 3D volumes (frames of a dynamic PET scan) into 
a 4D one. Below is the call to mincconcat; I give the frame start times 
and widths with -coordlist and -widhtlist. As you can see, the sampling is 
irregular.

>>>
mincconcat -clobber -concat_dimension time -coordlist 
"0,15,30,45,60,90,120,180,240,300,450,600,900,1200,1500,1800,2400,3000,3600,4200,4800" 
-widthlist 
"15,15,15,15,30,30,60,60,60,150,150,300,300,300,300,600,600,600,600,600,599" 
/tmp/frame1.mnc /tmp/frame2.mnc /tmp/frame3.mnc /tmp/frame4.mnc 
/tmp/frame5.mnc /tmp/frame6.mnc /tmp/frame7.mnc /tmp/frame8.mnc 
/tmp/frame9.mnc /tmp/frame10.mnc /tmp/frame11.mnc /tmp/frame12.mnc 
/tmp/frame13.mnc /tmp/frame14.mnc /tmp/frame15.mnc /tmp/frame16.mnc 
/tmp/frame17.mnc /tmp/frame18.mnc /tmp/frame19.mnc /tmp/frame20.mnc 
output.mnc
<<<

Doing a mincinfo on output.mnc, I get 

image dimensions: time zspace yspace xspace
    dimension name         length         step        start
    --------------         ------         ----        -----
    time                       21          240            0
    zspace                     63      0.12115            0
    yspace                    128    0.0845247            0
    xspace                    128    0.0845247            0

Why is there a step and a start for the time dimension? All the original 
frames were 3D, the starts and widths were given as lists. A mincheader on 
the same files has the following:
<<<
        double time(time) ;
                time:varid = "MINC standard variable" ;
                time:vartype = "dimension____" ;
                time:version = "MINC Version    1.0" ;
                time:spacing = "irregular" ;
                time:alignment = "start_" ;
                time:start = 0. ;
                time:step = 240. ;
        double time-width(time) ;
                time-width:varid = "MINC standard variable" ;
                time-width:vartype = "dim-width____" ;
                time-width:version = "MINC Version    1.0" ;
                time-width:spacing = "irregular" ;
                time-width:filtertype = "square____" ;
>>>


So it realises the spacings are irregular and yet insists on having the
time:start and
time:step 
fields! Later in the header the "real" starts and widths appear (as 
"globals"?):

<<<
data:
 
 time = 0, 15, 30, 45, 60, 90, 120, 180, 240, 300, 450, 600, 900, 1200, 
1500,1800, 2400, 3000, 3600, 4200, 4800 ;
 
 time-width = 15, 15, 15, 15, 30, 30, 60, 60, 60, 150, 150, 300, 300, 300,
    300, 600, 600, 600, 600, 600, 599 ;
>>>

Now I'm not sure this will ever cause me problems, but it is a peculiar 
"feature", no? Can I be sure none of the MINC tools get confused about 
this matter, screwing up the timing info?

Best,

Chris Bailey
Center for Functionally Integrative Neuroscience
Aarhus General Hospital, Denmark