Intra-arterial chemotherapy for retinoblastoma: the dosimetric impact

Purposes are (1) to measure main radiation parameters and (2) to propose a method to estimate the absorbed doses of internal organs starting from DAP values. Measuring the exposition of internal organs by repeated irradiations on an anthropomorphic phantom with the same settings used in vivo, we could establish correlations between (1) DAP and the dose recorded by a dosimeter placed along the X-ray beam entrance pathway; (2) the dose recorded by the same dosimeter and the absorbed dose in internal organs.

Forty-four consecutive patients (16 males, 28 females) (mean age 35.4 months) treated at our institution with IAC (216 procedures: 196 via the ICA and 20 into branches of the ECA) were included in this prospective study. IAC was divided into 5 phases. Fluoroscopic time, DAP, and ESD were measured.

The mean DAP was 595 ± 445 cGy cm² and the mean fluoroscopic time was 540 ± 403 s. ESD was on average 9.59 mGy (range 0.8-165 mGy). The absorbed dose was lower than 12.1 mGy in the left retina (the more exposed organ) in 75% of single treatments and lower than 25 mGy in 95% of treatments. In the cases of 3 and 6 sessions, the left retina of 75% of patients absorbed respectively less than 36.3 and 72.7 mGy, whereas the left retina of 95% of patients received less than 75.2 and 150.4 mGy. Other organs were less exposed.

This paper describes a method of absorbed dose estimation providing ranges used clinically in a single practice and the basis for further prospective studies.