The default algorithm of Plastimatch DRR

[kiyoshi yoda]

Hello,

I would like to know the default algorithm of Plastimatch drr.

"http://plastimatch.org/drr.html" tells that:

   -i algorithm Choose algorithm {exact,uniform}.

Can I assume the default is exact which means trilinear interpolation, whereas unifirm means nearest neighbor approximation?

Currently, I am still using Plastimatch 1.6.4. I am assuming that the drr performance is the same between 1.6.4 and 1.9.4.

Please let me know if my understandings are all correct.

Thanks,

Kiyoshi

[Sharp, Gregory C.]

Hi Kiyoshi,

 

You are correct, there is no difference between 1.6.4 and 1.9.3.

 

Exact means that the intersection between a ray and each voxel boundary is computed, and the attenuation is accumulated based on the exact length the ray transverses within the voxel.

 

Uniform means the ray is sampled at a fixed step size.

 

Neither method uses trilinear interpolation.

 

Greg

 

 

From: plast...@googlegroups.com <plast...@googlegroups.com> On Behalf Of kiyoshi yoda
Sent: Wednesday, August 09, 2023 2:58 AM
To: Plastimatch <plast...@googlegroups.com>
Subject: [Plastimatch] The default algorithm of Plastimatch DRR

 

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[kiyoshi yoda]

Dear Greg,

Thanks for your reply.

Can I assume exact if I do not add -i option on the DRR command line?

Do you think trilinear interpolation would increase the accuracy of the DRR calculation when it is compared with a portal imaging result?

Lastly, are you aware of any open source that employs trilinear interpolation for the DRR calculation?

Thanks a lot for yiour further support,

Kiyoshi

2023年8月9日水曜日 22:39:27 UTC+9 Sharp, Gregory C.:

[kiyoshi yoda]

Dear Greg,

I have tried the drr with no -i option, -i exact and -i uniform.

Major differences were that the uniform option required 8 times more CPU time, compared to no option and exact option that led to very similar CPU times.

I did not see any major image quality differences among the three. So my guesses are: 1) default setting is -i exact, and 2) the calculation step size for the uniform option was intentionally reduced  to approximately 1/8 of that for the exact option in order to provide similar image quality. 

Please let me know if you are on board.

Kiyoshi

2023年8月9日水曜日 22:56:34 UTC+9 kiyoshi yoda: