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


Marko Laaksomaa
Participant

Hi everyone

Here some of our new results:

Background: H&N setup using AlignRT with Orfit 3-point open face hybrid mask (Group A, patient n= 18, 445 kV- image pairs) and laser setup with Orfit 5- point closed masks (Group L, patient n=25, 437 kV-image pairs) were evaluated. During the mask formation, CT scanning and at the linac it was checked that patient mouth was closed and arms were relaxed on the side. In group A, SRS faceROI (head positioning) was used together with postural video (chest wall+shoulder positioning). When needed, after systematic patient posture errors were corrected, we captured new reference surfaces for the upcoming setups in Group A. Posture correction was done based on kV/kV- images, at the beginning or during the treatment course. Online match was performed based on our matching guidelines to the c3 vertebrae. In both groups translational and rotational errors were daily corrected with 0 AL in the online match. Pitch or roll corrections were not done based on IGRT. Realized, offline matched errors to the sub-regions after daily couch correction based on online match are given. Residual errors to the vertebrae c1, c5/7, mandible, occiput bone and left and right clavicle (from the measuring point of 9 cm from the vertebral midline laterally) were retrospectively evaluated. Re-setups in both groups were rare and have no significant effect on comparison. Systematic (S), random (R) errors and margins (M) are given in this order together with percentages of the residual errors exceeding 3 mm. Two-tailed F-test was applied for systematic errors (test for equality of variances). The Wilcoxon rank sum test was applied for random errors (test for equality of means). A p-value ≤ 0.05 was considered statistically significant. Results: (mm) C1: (Group L) (AP) 0.9 mm, 0.9 mm, 2.9 mm, (4%), (CC) 0.4 mm, 0.6 mm, 1.4 mm, (1%), (LAT) 0.8 mm, 1.1 mm, 2.6 mm, (7%), (Group A) (AP) 0.7 mm, 0.8 mm, 2.4 mm, (0%), (CC) 0.4 mm, 0.8 mm, 1.5 mm, 1%, (LAT) 0.4 mm, 0,8 mm, 1.6 mm, (1%). C5/7: (Group L) (AP) 1.0 mm, 1.0 mm, 3.2 mm, (5%), (CC) 0.7 mm, 0.9 mm, 2.4 mm, (3%), (LAT) 0.8 mm, 1.2 mm, 2.9 mm, (7%), (Group A) (AP) 0.8 mm, 0.9 mm, 2.6 mm, (1%), (CC) 0.5 mm, 1.1 mm, 1.9 mm, (1%), (LAT) 0.7 mm, 1.1 mm, 2.6 mm, (5%). Mandible: (Group L) (AP) 1.2 mm, 1.4 mm, 4.0 mm, 17%, (CC) 0.8 mm, 1.1 mm, 3.1 mm, 8%, (LAT) 0.5 mm, 1.2 mm, 1.6 mm, (5%), (Group A) (AP) 1.1 mm, 1.2 mm, 3.3 mm (7%), (CC) 0.9 mm, 1.1 mm, 3.1 mm, (4%), (LAT) 0.5 mm, 0.8 mm (p=0.02), 1.7 mm, (0%). Occiput bone: (Group L) (AP) 1.1 mm, 1.3 mm, 3.6 mm, (9%), (CC) 0.8 mm, 1.0 mm, 2.6 mm, (3%), (LAT) 0.8 mm, 1.4 mm, 3.1 mm, (9%), (Group A) (AP) 1.0 mm, 1.2 mm, 3.4 mm, (4%), (CC) 0.7 mm, 1.1 mm, 2.5 mm, (4%), (LAT) 0.6 mm, 1.0 mm (p=0.003), 2.1 mm, (1%). Clavicle (R&L) (Group L) (30 patients+1692 clavicle match) (CC) 2.9 mm, 3.4 mm, 9.8 mm, exceeding of 6 mm 18%, exceeding of 1 cm 5%. (Group A) (16 patients+ 864 clavicle match) (CC) 1.9 mm (p=0.01), 3.7 mm, 7.4 mm, exceeding of 6 mm 13%, exceeding of 1 cm 3%. Conclusion: Based on this preliminary study, sufficient realized posture accuracy was found in both groups around large PTV with well- planned workflows in the whole process. 3- point open masks with AlignRT and FaceROI led to excellent accuracy of the mandible. In the clavicles in CC direction, with AlignRT and postural setup, systematic residual errors were smaller (p=0.01), but the repeatability needs improvements in both groups. SGRT- results are promising, more patients (Group A) and CBCTs are needed to create more detailed analysis.

Larger 42″ monitor with AlignRT has been useful when using postural video for shoulder positioning inside treatment room.

Have a nice weekend.

Best regards Marko