Register and Overlay Model

Create a plain text-file containing the coordinates of the prostate phantom fiducials, in the same order and format as data/PelvisPhantom/CT_Fiduicial_Markers.txt. These markers have been labeled on the phantom. You must measure the points using the tracked pointer, in the same order. You should end up with a file, of the same format as CT.txt, containing the corresponding world coordinates, lets call it world.txt.

Compute the registration of CT points in CT_Fiduicial_Markers.txt to your world points, run this;

python bardProcrustes.py -f world.txt -m data/PelvisPhantom/CT_Fiduicial_Markers.txt

So here -f stands for “fixed” points, also called “target” points in the literature, and -m stands for “moving” points, also called “source” points in the literature. This will output a rotation, a translation, and Fiducial Registration Error. Cut and paste the rotation and translation into a CT_to_world.txt file as

R11 R12 R13 T1
R21 R22 R23 T2
R31 R31 R33 T3
0   0   0   1

and edit config/reference_with_model.json to use this file instead of data/id.txt.

Rerun BARD using this configuration file, using:

python sksurgerybard.py --config config/reference_with_model.json

and see what happens.

• Is it a good registration?
• What happens when you move the camera?
• What could you do to make it better?
• How could you measure the accuracy?

Repeat this process a few times. Is there any correlation between the Fiducial Registration Error and the apparent accuracy? Make some videos and discuss. Here’s a couple we made earlier.