Radiation and Cancer Physics

SS 42 - Physics 13 - Treatment Delivery Techniques

308 - Quantifying the Impact of Optical Surface Guidance in the Treatment of Cancers of the Head and Neck

Wednesday, October 24
3:45 PM - 3:55 PM
Location: Room 303

Quantifying the Impact of Optical Surface Guidance in the Treatment of Cancers of the Head and Neck
W. Wei, P. J. Ioannides, V. Sehgal, and P. Daroui; University of California, Irvine, Orange, CA

Purpose/Objective(s): Surface guided radiation therapy (SGRT) is increasingly being adopted for use in radiation treatment delivery for Head and Neck (H&N) cancer patients. This study investigated the improvement of patient setup accuracy and reduction of setup time of SGRT compared to the conventional non-SGRT setup.

Materials/Methods: Sixteen H&N cancer patients who underwent either definitive or post-operative radiation therapy were included in this retrospective study. Patients were divided into two groups (8 treated with SGRT, 8 without SGRT). All patients were immobilized with S frame masks. SGRT patients were first set up to surface markings and subsequently with optical image guidance to the reference area created at the mask opening. The non-SGRT patients were setup to marks placed during CT simulation. Positioning was confirmed by daily kV imaging. Post matching of kV-kV images, six-dimensional robotic couch shifts were applied. Translational couch shifts and patient setup time of the SGRT and non-SGRT patients were recorded and compared. The couch rotational shifts were not included in the analyses since the therapists corrected for these manually rather than using automated couch shifts. Both systematic and random errors were calculated for the couch shifts. The couch shifts related to different tumor sites were also compared.

Results: Compared to non-SGRT patients, SGRT showed a trend to reduced mean shift values in vertical (-1.7 mm for non-SGRT vs. 0.1 mm for SGRT, p = 0.01), longitudinal (0.8 vs. 0.3 mm, p = 0.36), and lateral (-0.2 vs. 0.3 mm, p = 0.15) directions. The SGRT group also had lower systematic errors compared to the non-SGRT group (1.4 mm non-SGRT vs. 0.9 mm SGRT, 1.3 vs. 0.6 mm, and 0.7 vs. 0.6 mm). The random error difference was minimal in all directions between both groups (2.6 vs. 2.6, 1.9 vs. 2.1, and 2.2 vs. 2.7 mm). Setup time was similar for the both SGRT patients (285 ± 141 sec) and the non-SGRT patients (255 ± 113 sec). 8 patients were treated definitively and 8 patients were treated post-operatively. Tumor subtypes treated included oral cavity (4), nasopharynx/sinonasal (4), oropharynx (4) and hypopharynx (4). Setup time was lower for SGRT in both definitive and post-operative nasopharynx/sinonasal groups. For example, for definitive cases receiving non-SGRT treatments, the mean treatment time was 496 sec vs. 248 sec for SGRT treatments. For postoperative cases receiving non-SGRT treatments, the mean treatment time was 325 sec vs. 258 sec for SGRT treatments.

Conclusion: Our results suggest that use of SGRT decreases the magnitude and systematic errors of couch shifts during the patient setup. Thus, it potentially improves setup accuracy by decreasing couch positioning uncertainty. Although the overall setup times for H&N patients were similar for SGRT and non-SGRT patients, definite time reduction was observed for nasopharynx/sinonasal and hypopharynx cancer patients.

Author Disclosure: W. Wei: None. P.J. Ioannides: None. V. Sehgal: None.

Pericles Ioannides, MD

Disclosure:
No relationships to disclose.

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Send Email for Pericles Ioannides


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