Evaluation of administered dose using portal images in craniospinal irradiation of pediatric patients

Abstract

This study aimed to assess the administered dose based on portal imaging in craniospinal pediatric irradiation by evaluating cases in which portal images did or did not account for the total administered dose. We also intended to calculate the mean increase in total administered dose. Data were collected from General University Hospital Gregorio Marañón; we evaluated the total dose administered, total dose planned, number of portal images per treatment and corresponding monitor units of two different groups: one in which the dose from portal images is deducted from the total administered dose (D), and another in which it was not (N). We used descriptive statistics to analyze the collected data, including the mean and respective standard deviation. We used the Shapiro-Wilk and Spearman rank correlation coefficient tests and estimated the linear regression coefficients. Patients in group D received a mean dose of 29.00 ± 10.28 cGy based on the verification portal images, a quantity that was deducted from the planned dose to match the total administered dose. Patients in group N received a mean dose of 41.50 ± 30.53 cGy, which was not deducted from the planned dose, evidencing a mean increase of 41.50 ± 30.55 cGy over the total administered dose. The acquisition of the set-up verification portal images, without their inclusion in the total administered dose, reflects an average increase in total dose for craniospinal irradiation of pediatric patients. Subtraction of the monitor units used to acquire the verification images is recommended.