how to calculate the volume of objects in milimeter cube

i have two methods for calculating volume of objects in millimeter cube, please tell me which of them is correct or any other method for volume calculation.

thanks

Answer 1

[Image Analyst]

We have no idea what voxel_count or voxel_size are. Neither one looks like it would sum up the volume of individual objects/regions in the "cube" - it looks like it just computes the volume of the entire cube regardless of any segmented regions inside it.

[Muhammad Shoaib]

sir i guess that the voxel_size and voxel_count will be clear with demo code, or please guide me with a demo code for volume calculation in 3d (dicom images )

voxel_size = [info.PixelSpacing;info.SliceThickness]';
mriAdjust = mri;
lev = graythresh(double(mri)/min_level) * max_level;
bw = (mri>=lev);
nhood = ones([3 3 1]);
bw = imopen(bw,nhood);
bw = bwareaopen(bw,1000);
L = bwlabeln(bw);
stats = regionprops(L,'Area','Centroid');
A = [stats.Area]
voxel_count = sum(sum(sum(bw==1)))%is the area of blob

[Image Analyst]

Then your line

mmm = voxel_count*(xx*yy*zz);

does not make any sense since you're multiplying the volume of total of all the blobs by the volume of the entire image block. It's like if the volume of your entire image was 5 cubic meters, and the sum of all objects in the image was 0.3 cubic meters, then you're multiplying 5 by 0.3. That does not make any sense at all - none whatsoever. Your second method is equally nonsensical.

To get the area of the objects in the cube/volume, simply sum A

volumeOfAllObjects = sum(A); % Get volume in voxels.

If you want it in real world units, such as mm, then multiply by your spatial calibration factor cubed

volumeInMm = volumeOfAllObjects * mmPerPixel^3;

To get mmPerPixel you divide the real world field of view by the number of pixels across it. It's possible that the slice separation in the z direction could be different than in the x and y directions so be aware of that and use two or three different spatial calibration factors if you need to.

volumeInMm = volumeOfAllObjects * mmPerPixelX * mmPerPixelY * mmPerPixelZ;

[Muhammad Shoaib]

After masking with bwareaopen i have just one blob left with area 18301, can you please guide me how to get mmPerPixel,i have mmPerPixelX=0.7188 , mmPerPixely=0.7188 and mmPerPixelZ=5.0000

    volumeInMm = 18301 * mmPerPixelX * mmPerPixelY * mmPerPixelZ;
    %am i right?

[Image Analyst]

Yes. If the volume is 18301 voxels, and those are the spatial calibration factors in the 3 dimensions, then that will give you the volume in cubic mm.