Dear All,

I am interested in doing slice timing correction for sparse acquisitions on a Philips Ingenia CX scanner. The experiment has a TR of 4 seconds, acquiring 40 slices in this period. The temporal spacing between the slices is set to minimal at the scanner console.

As far as I know, Philips does not save slice timing information in the DICOM header. However, we do have the "Exam card" from the scanner which is a text file containing all the acquisition parameters. One of the values in this file is "min. TR" which is equal to 2053 ms. This looks like the time the scanner took to acquire these 40 slices and the rest of the TR becomes the silent period. The slices are acquired foot to head linearly without any slice gap.

I have two questions:

1. How do I go about computing slice timing information? Simply specifying the TR and slice order would be incorrect since the slices were not spread out over the TR. Since we know that the per volume acquisition took 2053 ms, would the actual slice timings be = 0:(2.053/40):2.053 (the first 40 values)? I would also have to re-order this vector so that the last entry corresponds to the first slice which was acquired (bottom-most).

2. Let's say that I specify the timing for the 20th slice (middle slice) as the reference slice. During the first level specification, the microtime resolution would be equal to 40 (number of slices); would it be correct to specify the microtime onset as 20 as it requires an integer rather than actual timing?

Thank you for your help

Regards