A Comparison of Two Imaging Protocols for Patient's Receiving a Radical Course of Radiotherapy to the Brain.

Abstract

Background Accurate patient positioning is vital in radiotherapy to deliver precise targets to defined areas. Image guided radiotherapy (IGRT) can help to increase this accuracy. In a large regional radiotherapy department patients receiving a course of radical radiotherapy to the brain undergo daily image guidance prior to delivery of treatment. A 3-mm tolerance of movement is in place for these patients. This service evaluation examined whether it is essential to perform this type of imaging on a daily basis or whether a less frequent imaging protocol would be more clinically relevant. Method This retrospective small scale service evaluation was based on quantitative research. A quasi-experimental design was used. IGRT data was collected from 25 patients who had previously undergone daily image radiotherapy to the brain. Retrospectively couch movements in anterior/posterior, left /right and superior/inferior directions for all the patients for a total of 704 fractions. Data was divided into two groups. Group 1 (daily image group), this group consisted of data from all 25 patients for each daily image recorded throughout their treatment. Group 2 (weekly image group) consisted of data from all patients on the first three days then once weekly. Results A one-sided one-sample t-test was performed to confirm that the mean movement was less than 3-mm. The p-value was p=0.000, the null hypothesis was rejected. Hence μ (the true mean of the movement data) is less than 3-mm. A two sample unpaired t-test (two sided) was carried out to show that the mean movement for the daily group data was not significantly different to the mean movement for the weekly data group. The p-value was above 0.05, the null hypothesis was not rejected. Hence μ_D (the true mean of the daily data) is equal to μ_W (the true mean of the weekly data). Conclusion There was no statistical difference when both imaging schedules were compared. Therefore weekly image guidance would be a more suitable type of imaging schedule. Weekly imaging would also reduce radiographer workload and any potential contaminant dose to the patient.