Archive for August, 2008

Homodyne

August 19, 2008

Today I was reading the homodyne technique in Berstein book , its very nicely described.

At first I thought it is just simple Hermitian Property of the FFT that is used.

But the Phase Correction need to be done so that we account for the assymetry and also for the assumption that Image is real.

Now I understood why we need those Extra K-space lines and for 256 Y Res we need to acquire little moree than 128 lines … i.e around 160 linjes 🙂

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P File Details

August 11, 2008

Data Elements = No. of Data Elements need to be read for 1 Slice.  ( da_xres *2* (da_yres-1)  )

The Multiplication with 2 is because of the Real and Imaginary Portion

FrameSize = Size of One View ( da_xres *2*point_size )

here Point_size is if each element is a captured as 32 bit or 16 bit , related to Extended Dynamic Range

Echo_Size = Size of Data for a single Echo ( FrameSize * da_yres)

slice_size = Size of Data for a single Slice (n_echos * Echo_Size)

mSlice_size = Size of the data in one acquisition ( N-Slices_in_1_pass * slice_size)

Way a P FIle has Data

Acq1

      rec1 :  Slice1 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                 Slice2 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                  Slice 3: Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

      rec2 :  Slice1 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                 Slice2 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                  Slice 3: Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

    rec3 :  Slice1 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                 Slice2 :Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….

                  Slice 3: Echo 1 (All Views) :Echo2(All Views) : Echo 3 (All Views) ……….