Forums SGRT – Best Practice Head and neck setup Reply To: Head and neck setup

Marko Laaksomaa

…to be continued. Head and neck groups evaluated further, 3- point open masks with AlignRT (A), 5 point closed masks with laser setup (L) with daily IGRT. Residual errors are evaluated after online match couch corrections, online matched location was near vertebrae c2-c3. I have offline matched both claviculas (only LNG direction, AP image), one at the time, at the location of 9 cm from mid-vertebrae laterally. Earlier reported results with 5- point mask: 528 claviculas (264 right, 264 left) matched (LNG), 23 % exceeded 6 mm, systematic error 3.4 mm, random error 3.8 mm, margin 1.1 cm. Now with 3 point masks, with the aid of postural video, with AlignRT: 440 claviculas (220×2) offline matched (LNG), 18 % exceeds 6 mm, systematic error 2.1 mm (p=0.06), random error 4.3 mm (p=0.13), margin 8.3 mm. With SGRT, systematic error is improved (as expected and which is a good thing), but there is still too much daily variation. On the other hand, neither errors are statistically different between the groups. Latest we have noticed that “surface deformation” workspace is a good and quick aid, in the cases when the shoulder positioning is challenging with video view only. I am waiting for the CBCT- studies, which compares the residual errors of the bony sub- regions around and inside PTV (posture/deformations) with SGRT setup and with laser setup. We have promising results with AlignRT.