Dosimetry of mono-isocenter irradiation technique in radiotherapy for nasopharyngeal carcinoma / 中华放射肿瘤学杂志

ABSTRACT

Objective To study the dosimetry of mono isocenter irradiation technique in radiotherapy for nasopharyngeal carcinoma. Methods Conventional and mono isocenter irradiation techniques were used to simulate irradiation of the phantom and nasopharyngeal carcinoma patients with Siemens primus linear accelerator equipped with asymmetric collimators. Dose uniformity?isodose distribution and field overlap were measured at the plane of junction with TLD and film dosimeter on the phantom. The reproducibility of the set up was tested on patients with verification films. Results For an applied dose of 1?Gy, TLD dosimetry showed that the mean dose at the junction of fields were 1.01 ?Gy for the mono isocenter technique as compared to 1.09 1.13?Gy for the conventional technique. An ideal isodose distribution at the junction with mono isocenter technique was found by film dosimetry. The reproducibility of the set up was obviously better for the mono isocenter technique, with less field overlap (1mm) and set up deviation (0.5?mm) than those (6 14?mm and 3?mm) of the conventional technique. Conclusions This investigation of junction dosimetry confirms the potential advantage of the mono isocentric technique. Not only does it lead to superior dosimetry in the plane of junction but also associates with a better reproducibility of the set up.