# Computer Assisted Surgical Planning

CREATED: 200701010953 Author: Danny Chen ** Background

- intensity modulated radiation therapy
- delivered using linear accelerator with multi-leaf collimator *** Methods

# structure contouring (image segmentation)

** determine position of tumor

# beam angle selection

** select a set of angles to cover the whole tumor with sufficient radition without harming healthy tissue

# dose calculation and intensity maps

# leaf sequencing

** compute a set of apertures to deliver intensity map in minimum time

# delivery

** Step and shoot IMRT delivery

- NP hard in general
- special cases ** 2D SLS ** basic 3D SLS

** 2D SLS

- property of collimator, polygon monotone in y-axis
- assume intensitive either 0 or 1 (can be obtained by slcing the 3D problem)
- consider structures such as valley and peaks since they indicate different apertures, due to monotone property
- similar to matching valley and peaks but do not allow crossing
- solve as max flow on a planar graph

** 3D SLS

- restrict height of plateau to be 1
- if intensity less than 10 (usually), basic SLS ~ general SLS *** Method

# create delivery options

** may have exponential number of options ** actually only need to compute canonical option! => intervals are not contained