title: Radiation protection for an intra-operative X-ray device.
abstract: OBJECTIVE
  Therapeutic partial breast irradiation can be delivered intra-operatively using the Intrabeam 50 kVp compact X-ray device. Spherical applicators are added to the source to give an isotropic radiation dose. The low energy of this unit leads to rapid attenuation with distance, but dose rates are much greater than for diagnostic procedures.
  
  
  METHODS
  To investigate the shielding requirements for this unit, attenuation measurements were carried out with manufacturer-provided tungsten-rubber sheets, lead, plasterboard and bricks. A prospective environmental dose rate survey was also conducted in the designated theatre.
  
  
  RESULTS
  As a result of isotropic geometry, the scattered dose around shielding can be 1% of primary and thus often dominates measured dose rates compared with transmission. The absorbed dose rate of the unshielded source at 1 m was 11.6 mGy h(-1) but this was reduced by 95% with the shielding sheets. Measured values for the common shielding materials were similar to reference data for the attenuation of a 50 kVp diagnostic X-ray beam. Two lead screens were constructed to shield operators remaining in the theatre and an air vent into a service corridor. A lead apron would also provide suitable attenuation, although a screen allows greater flexibility for treatment operators. With these measures, staff doses were reduced to negligible quantities. Survey measurements taken during patient treatments confirmed no additional measures were required, but the theatre should be a controlled area and access restricted.
  
  
  CONCLUSIONS
  Results from this study and reference data can be used for planning other facilities.
authors.affiliation: Radiotherapy Physics, Royal Free Hospital, London, UK. davideaton@nhs.net
authors.forename: D J
authors.initials: DJ
authors.lastname: Eaton
authors.forename: R
authors.initials: R
authors.lastname: Gonzalez
authors.forename: S
authors.initials: S
authors.lastname: Duck
authors.forename: M
authors.initials: M
authors.lastname: Keshtgar
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D011446:Prospective Studies; D011482:Protective Devices; D011835:Radiation Protection / Q000295:instrumentation / Q000379:methods; D011878:Radiotherapy / Q000295:instrumentation; D011879:Radiotherapy Dosage