Comparison of User-Directed and Automatic Mapping of the Planned Isocenter to Treatment Space for Prostate IGRT

Table 1

Isocenter Mapping Methods.

	Clinical mapping	Automatic mapping
1	CT simulate. Align patient with laser beams intersecting at simulated isocenter. Tattoo skin at centers of lateral and anterior laser beams.	Import pCT, structure sets, and isocenter to MxAnatomy. Fit models to planning contours.
2	Plan. Place crosshairs at planned isocenter in axial slice. Mark skin contour at lateral and anterior intersections with crosshairs.	Acquire tCT using standard procedures.
3	Prepare patient for treatment imaging. Tape BBs to anterior and lateral skin tattoos. Acquire tCT with laser beams centered on BBs.	Import tCT. Rigidly register pCT with pCT using automatic multiscale procedure.
4	Import tCT to PLanUNC. Autoregister imaged BBs in tCT with skin marks in pCT from Step 2.	Autosegment prostate in tCT.
5	Inspect registration by comparing prostate contours in pCT with intensity patterns in the tCT. Manually edit registration to get best match between contours and tCT intensities.	Determine correspondences between pCT and tCT prostate models.
6	Convert manual 𝑥, 𝑦, 𝑧 edits from Step 5 to table shifts relative to laser beams. Apply shifts >3 mm and treat.	Map isocenter label from pCT to tCT via correspondence from Step 5 (2).