[MINC-users] Another bug in dcm2mnc -> x/y step switch?

[Alex Zijdenbos]

Hello all,

I have been trying to solve another dicom-to-minc conversion problem,
and that is that I have some data that are anisotropic in-plane
(128x256), with step sizes 0.19 and 0.39 mm (the FoV is square).
However, when converting this with dcm2mnc, the x- and y-step sizes
are inverted, such that the resulting minc volume is, well rather
squashed. In the DICOM data, I have:

(0028, 0010) US      2: Rows                              = 128
(0028, 0011) US      2: Columns                           = 256
(0028, 0030) DS     18: PixelSpacing                      = 0.390625\0.1953125

However, converting that with dcm2mnc, I get:

    dimension name         length         step        start
    --------------         ------         ----        -----
    zspace                     29            1        -13.3
    yspace                    128    -0.195312           25
    xspace                    256    -0.390625           25

Clearly the x-and y-steps are reversed.

On lines 1417/18 of dicom_read.c:

    steps[VCOLUMN] = psize[0];
    steps[VROW] = psize[1];     /* anisotropic resolution? */

I *think* that this is wrong, that the indices into psize should in
fact be reversed. And sure enough, if I do that and reconvert my data,
everything looks good...

However, I was wondering if somebody more familiar than I am with
dicom-to-minc conversions could verify this. Anybody else seen this?
Most commonly people acquire data which is isotropic, or close to
isotropic, in-plane, so it would not surprise me if it hasn't been
noticed before - but there could also be something specific about the
data that I have. If this is indeed a bug I'm happy to check the fix
into cvs, but I'd rather be sure that it is a general problem.

Thanks,

-- Alex