Mapping Iterative Medical Imaging Algorithm on Cell Accelerator

Algorithm 2

Parallel OS-SART on SPE.

Require: receive related environment variables from PPE, 𝑝 is the total number of SPEs used, 𝑄 is the total number of projections,

𝑇 is the total number of subsets,

(1) 𝑛𝑢𝑂𝑓𝐶ℎ𝑢𝑛𝑘𝑠=𝑛/rowsPerDMA   {n is the one dimension size of the image, rowsPerDMA is the number of rows of the image

for each DMA transfer.}

(2) while (𝑟<𝑅) do

(3)  for 𝑙=0 to 𝑇  do

(4)    wait for and receive messages from PPE to start new subset 𝑙;

(5)    {go through forward projection, correction, backprojection step for assigned projections in the subset 𝑙}

(6)   for 𝑗=0 to 𝑄/(𝑇×𝑝)  do

(7)    {forward projection}

(8)     locate the projection index 𝑞 for the current SPE and 𝑗;

(9)     rotate the current image clockwise by the corresponding angle for projection 𝑞;

(10)    for 𝑘=0 to 𝑛𝑢𝑂𝑓𝐶ℎ𝑢𝑛𝑘𝑠  do

(11)      DMAin related data from the main memory, including the base weighting factors matrix, the current image;

(12)      calculate and accumulate the raysums for the forward projection step in SIMD way;

(13)    end for

(14)     {corrections}

(15)     calculate and accumulate the raysum corrections;

(16)     {bacprojection}

(17)    for 𝑘=0 to 𝑛𝑢𝑂𝑓𝐶ℎ𝑢𝑛𝑘𝑠  do

(18)      DMAin related data, including the weighting factors;

(19)      calculate and accumulate backprojection for each pixel in SIMD way;

(20)      DMAout the backprojection data;

(21)    end for

(22)     rotate the image counter clockwise by the corresponding angles for the projectin 𝑞;

(23)   end for

(24)   end for

(25) end while