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A Comparison of Two Kinds of Patient Marking Methods Used With Vacuum Cushion Immobilization in the Radiotherapy for Various Treatment Sites

J Pan*, D Yu , G Han , Q Song , C Ruan , J Fu , B Wu , G Ma , L Wang , Renmin Hospital of Wuhan University, Wuhan, Hubei


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The two commonly used patient marking methods in mainland China are skin marking method (SMM) and bow-form-ruler marking method (BFRM). This study aims to evaluate SMM and BFRM by comparing the intra-fraction setup errors from using these two methods together with vacuum cushion immobilization in patients underwent radiotherapy for 3 treatment sites.

Methods: Patients with pelvic, abdominal and thoracic malignant tumors (n=18, with 6 patients per treatment site) were enrolled in this prospective randomized study. All the patients were immobilized with vacuum cushion. Each patient was marked by both SMM and BFRM before CT simulation.Target location was verified by cone beam CT (CBCT) with displacements assessed prior to each sampled treatment session. The localization errors in translational and three rotational directions were recorded and analyzed.

Results: Images from 108 fractions in 18 patients produced 324 translational and 324 rotational comparisons for SMM and BFRM. The setup errors of all treatment sites showed no difference in these two marking methods in any directions (p>0.05) as shown in Table 1. Table 1. The Mean ± standard deviation of intra-fraction setup errors for SMM and BFRM. Vertical(mm) Longitudinal(LNG)(mm)Lateral (mm) Pitch Roll Rotation(RTN)SMM 0.62±3.03 -0.98±3.14 -0.78±2.66 0.41±1.12° 0.22±0.60° 0.21±0.57°BFRM 0.70±2.35 -0.54±3.60 -1.13±1.90 0.38±1.11° 0.14±0.71° -0.37±0.62°In treatment site specific analysis, SMM significantly lessened the lateral and RTN setup errors compared to BFRM in the pelvic sites (0.39±1.85mm vs -1.28±1.13mm, p<0.01; -0.19±0.59° vs -0.61±0.59°, p<0.05). However, in the abdominal sites, BFRM was superior to SMM for reduced vertical errors (0.17±2.73mm vs 2.28±3.16mm, p<0.05).

Conclusion: This study shows no significant difference in patient setup errors for various treatment sites between SMM and BFRM. The SMM achieved less lateral and RTN setup errors in the pelvic tumor. The BFRM is recommended for the abdominal tumor sites nonetheless


Cone-beam CT, Image Guidance, Immobilization


IM- Cone Beam CT: 4DCBCT

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