Detection and evaluation of localization errors in patient radiation therapy

Abstract

Inability to irradiate the entire diseased area consistently and accurately can result in local failure or improper control of disease. Since 1969, a film technique developed for imaging of the complete patient radiation exposure has been applied to evaluate localization errors. Upon evaluation of the film, localization errors were noted if a portion of the diseased area was not properly included in the treatment field, or if an excessive region of normal tissue was improperly shielded. In an initial investigation with an average of 1-2 films taken per patient per week, localization errors were found in 27% of the 173 cases. Examples from this study were shown in which errors were attributed to the physician, technician or patient. In a further investigation, verification films were taken for every treatment in four selected cases, including three patients treated with extended mantle fields and one treated with a pelvic field. 55 out of 146 treatments showed localization errors. The potential relevance of localization errors to the recurrence of disease was discussed.