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J Radiat Res. 2013 Jul 1;54(4):762-8. doi: 10.1093/jrr/rrt001. Epub 2013 Feb 14.

Intrafractional setup errors in patients undergoing non-invasive fixation using an immobilization system during hypofractionated stereotactic radiotherapy for lung tumors.

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Department of Radiation Oncology, University of Yamanashi, 1110, Chuo-city, Yamanashi 409-3898, Japan.


Intrafractional setup errors during hypofractionated stereotactic radiotherapy (SRT) were investigated on the patient under voluntary breath-holding conditions with non-invasive immobilization on the CT-linac treatment table. A total of 30 patients with primary and metastatic lung tumors were treated with the hypofractionated SRT with a total dose of 48-60 Gy with four treatment fractions. The patient was placed supine and stabilized on the table with non-invasive patient fixation. Intrafractional setup errors in Right/Left (R.L.), Posterior/Anterior (P.A.), and Inferior/Superior (I.S.) dimensions were analyzed with pre- and post-irradiation CT images. The means and one standard deviation of the intrafractional errors were 0.9 ± 0.7mm (R.L.), 0.9 ± 0.7mm (P.A.) and 0.5 ± 1.0 mm (I.S.). Setup errors in each session of the treatment demonstrated no statistically significant difference in the mean value between any two sessions. The frequency within 3mm displacement was 98% in R.L., 98% in P.A. and 97% in I.S. directions. SRT under the non-invasive patient fixation immobilization system with a comparatively loose vacuum pillow demonstrated satisfactory reproducibility of minimal setup errors with voluntary breath-holding conditions that required a small internal margin.


hypofractionated stereotactic radiotherapy; intrafractional setup errors; lung cancers; non-invasive patient fixation immobilization

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