Hi, I have multidimensional data that I want to mask. I can do this by using a mask of ones, and then selectively taking elements that I want to ignore and making those in the mask 0. I then multiply my data with this mask, like so:

`% Masking - Factor 2`

MASK_ODD_ECHOS = ones(size(kspace));MASK_ODD_ECHOS(:,1:2:end,:,:,:,:,1:2:end,:) = 0;MASK_EVEN_ECHOS = ones(size(kspace));MASK_EVEN_ECHOS(:,2:2:end,:,:,:,:,2:2:end,:) = 0;

However, I also want to always take the central 10% of this array on the (2nd dimension), which extends from 1 to 320. Thus I want to take 32 data points (ie: 10 % of 320) from the centre of a length 320 array, which means taking 16 on points on the left of datapoint 160, and 16 points to the right, giving me a central region index of 144:176. But I can't easily set this to 1 as some would have already been zero'd out by then.

I have a hacky solution to this which is to have 2 sets of mask. Start from the beginning, mask until centre. Skip centre, then mask again after centre.

`% Masking - Factor 2MASK_ODD_ECHOS_1 = ones(size(kspace));MASK_ODD_ECHOS_2 = ones(size(kspace));MASK_ODD_ECHOS_1(:,1:2:143,:,:,:,:,1:2:end,:) = 0;MASK_ODD_ECHOS_2(:,177:2:end,:,:,:,:,1:2:end,:) = 0;% Undersample even echos (2:2:end), skip every 2nd PE line with shift of one (2:2:end)`

MASK_EVEN_ECHOS_1 = ones(size(kspace));MASK_EVEN_ECHOS_2 = ones(size(kspace));MASK_EVEN_ECHOS_1(:,2:2:142,:,:,:,:,2:2:end,:) = 0;MASK_EVEN_ECHOS_2(:,178:2:end,:,:,:,:,2:2:end,:) = 0;% Applying Masks:

kspace_CAIPI = kspace .* MASK_ODD_ECHOS_1;kspace_CAIPI = kspace_CAIPI .* MASK_ODD_ECHOS_2;kspace_CAIPI = kspace_CAIPI .* MASK_EVEN_ECHOS_1;kspace_CAIPI = kspace_CAIPI .* MASK_EVEN_ECHOS_2;

This is inelegant and I feel this could be done in the opposite way: Start with a mask of zero, and set to 1 all points.

`MASK_ODD_ECHOS = zeros(size(kspace));MASK_ODD_ECHOS(:,1:2:end,:,:,:,:,1:2:end,:) = 1;`

But this would mean losing all other data points. Is there a way to access those points in a more elegant way without making everything 0?

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