title: Evaluation of set-up deviations during the irradiation of patients suffering from breast cancer treated with two different techniques.
abstract: OBJECTIVE
  To compare reproducibility of set-up for two different treatment techniques for external irradiation of the breast.
  
  
  METHODS
  In total, the analysis comprised 56 pairs of portal and simulator films for 14 consecutive patients treated following breast conserving therapy and 98 pairs of portal and simulator films for 20 consecutive patients treated after mastectomy. For the first group the tangential field technique (TF technique) was used, for the second the inverse hockey stick technique (IHS technique). Evaluation of the treatment reproducibility was performed in terms of systematic and random error calculated for the whole groups, comparison of set-up accuracy by means of comparison of cumulative distribution of the length of the displacement vector.
  
  
  RESULTS
  In the IHS and TF techniques for medial and lateral fields, displacement larger than 5 mm occurred in 28.3, 15.8 and 25.4%, respectively. For the IHS technique, the systematic errors for lateral and cranial-caudal direction were 1.9 and 1.7 mm, respectively (1 SD), the random errors for lateral and cranial-caudal direction were 2.0 and 2.5 mm. For the TF technique, the systematic errors for ventral-dorsal and cranial-caudal direction were 2.6 and 1.3 mm for medial field and 3.7 and 0.7 mm for lateral fields, respectively, the random errors for lateral and cranial-caudal direction were 2.2 and 1.0 mm for medial field and 2.9 and 1.1 for lateral field, respectively. Rotations were negligible in the IHS technique. For the TF technique the systematic and random components amounted to about 2.0 degrees (1 SD).
  
  
  CONCLUSIONS
  Both the inverse hockey stick and standard tangential techniques showed good reproducibility of patients' set-up with respect to cranial-caudal direction. For the TF technique, the accuracy should be improved for the medial field with respect to the ventral-dorsal direction.
authors.affiliation: Medical Physics Department, Holycross Cancer Centre, 25-734 Kielce, Poland. pawelku@onkol.kielce.pl
authors.forename: Pawel Franciszek
authors.initials: PF
authors.lastname: Kukołowicz
authors.forename: Andrzej
authors.initials: A
authors.lastname: Debrowski
authors.forename: Piotr
authors.initials: P
authors.lastname: Gut
authors.forename: Leszek
authors.initials: L
authors.lastname: Chmielewski
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wieczorek
authors.forename: Piotr
authors.initials: P
authors.lastname: Kedzierawski
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D010347:Patient Care Planning; D011874:Radiometry; D018714:Radiotherapy, Adjuvant; D015203:Reproducibility of Results