http://imagej.273.s1.nabble.com/Hyperstack-with-nz-1-problem-tp5019980p5020064.html
> Good day Fred,
>
> no problem with your statements. They are compatible with signal theory
> (see my answer to Kenneth).
>
> Mathematical fact is that samples are numbers (or in RGB number triplets)
> that have no spatial or temporal extension.
>
> If you consider the physical process of sampling, the question may arise
> of how an extended little area, or in your tomographic case, an extended
> little volume eventually leads to a number. The answer is easy:
>
> By spatial integration.
>
> Consequently, it is not the little integration area or the little
> integration volume that is later (after pictorial or tomographic
> reconstruction) displayed as little area or little volume. It is the number
> (gray value) that resulted from integration during signal acquisition that
> is smeared out or interpolated in some fashion on a display or by a
> projector and presented as a light intensity.
>
> Of course the integration area or volume during signal acquisition may be
> much larger than the sampling distance. In tomography (CT and MRI) this is
> not only the case regarding the z-direction but also, usually not as
> pronounced, in the xy-directions. The classic example however, is the
> flying spot scanner in which the spot represents the integration area and
> the sampling distance may be chosen independently from the spot size.
>
> Hopefully I could clarify the topic a bit.
>
> Regards
>
> Herbie
>
> ::::::::::::::::::::::::::::::::::::::::
> Am 10.02.18 um 02:54 schrieb Fred Damen:
>
> Greetings,
>>
>> Beauty is in the eyes of the beholder... and my beauty is MRI.
>>
>> In MRI a slice is a 3D entity with length, width and depth -- which we
>> call
>> slice thickness. A voxel, i.e., volume element, represents a single
>> value for
>> a location in 3D space. Voxels are contiguous within the slice and
>> depending
>> on how data was collected may be contiguous in z also -- you can have
>> what we
>> call an interslice gap. In MRI there is no way to acquire a slice with
>> infinitesimally thin slice thickness. Usually the slice thickness is more
>> than twice that of the in-slice voxel size.
>>
>> Thanks for the info,
>>
>> Fred
>>
>> On Fri, February 9, 2018 11:03 am, Herbie wrote:
>>
>>> Good day!
>>>
>>> "[...] so that ImageJ treats a single slice as a volume?"
>>>
>>> A slice is an image!
>>>
>>> A slice has no extension orthogonal to itself.
>>> A pixel also has no extension in any direction because it is a
>>> mathematical
>>> point in 2D, i.e. a number or sample value.
>>> A voxel also has no extension in any direction because it is a
>>> mathematical
>>> point in 3D, i.e. a number or sample value.
>>>
>>> Pixels, i.e. values at points in 2D, are arranged in a 2D grid and the
>>> sometimes equidistant *spacing* of the grid points is often confused with
>>> the pixel size, that actually doesn't exist.
>>> (A pixel doesn't have a size.)
>>>
>>> Voxels, i.e. values at points in 3D, are arranged in a 3D grid and the
>>> sometimes equidistant *spacing* of the grid points is often confused with
>>> the voxel size, that actually doesn't exist.
>>> (A voxel doesn't have a size.)
>>>
>>> In short:
>>> A slice has no neighbors orthogonal to itself, i.e. there is no (defined)
>>> spacing in the third dimension.
>>>
>>> That said, you may indeed use dummy slices to define the missing spacing!
>>>
>>> HTH
>>>
>>> Herbie
>>>
>>>
>>>
>>> --
>>> Sent from:
http://imagej.1557.x6.nabble.com/>>>
>>> --
>>> ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>>>
>>>
>> --
>> ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>>
>>
> --
> ImageJ mailing list:
http://imagej.nih.gov/ij/list.html>