Vol 62, No 4 (2012)
Research paper (original)
Published online: 2012-09-01
Where is a single dosimeter best placed to demonstrate that classification levels are not exceeded during fluoroscopy and ALARP is achieved for unclassified radiation workers? Inside or outside the protective apron: an opinion?
Nowotwory. Journal of Oncology 2012;62(4):263-268.
Abstract
Under United Kingdom legislation, employers must demonstrate that no unclassified radiation worker exceeds
3/10ths of any dose limit and all doses are as low as reasonably practicable (ALARP). If no substantial radiation dose
is envisaged, compliance is conveniently monitored using a single personal dosimeter. Historically this dosimeter
has been worn under the protective apron, on grounds that this reflects whole-body dose. Over the years however,
radiological practices, protective apron design and dose limits have changed. This study compares the capability of
dosimeters both inside and outside the apron to meet legislative requirements. Evaluation entailed reconstructing
a typical fluoroscopic layout. Single dosimeters may be attached to a lanyard to hang midline just above waist level.
With a front-fastened apron this coincides with an overlapping protective layer and in many procedures the scattered
radiation passes obliquely through the double layer. In this study an irradiated Perspex phantom represented the
radiation worker and the surface dose was measured above and below one and two layers of 0.35 mm and 0.25 mm
lead-equivalence. Incident measurements were up to three orders of magnitude higher than the doses underneath
the double layer and thus substantial eye doses can arise before any dose is registered inside the apron. Organs of the
trunk adjacent to the overlap can, moreover, receive 20 times the dose beneath the overlap, making ALARP difficult
to demonstrate. A dosimeter outside the apron measures no organ dose in itself, but when combined with other
data can be used retrospectively to estimate dose to critical organs. It alerts to rising doses and provides an evidence
base for issuing multiple dosimeters and for selecting optimal shielding.
3/10ths of any dose limit and all doses are as low as reasonably practicable (ALARP). If no substantial radiation dose
is envisaged, compliance is conveniently monitored using a single personal dosimeter. Historically this dosimeter
has been worn under the protective apron, on grounds that this reflects whole-body dose. Over the years however,
radiological practices, protective apron design and dose limits have changed. This study compares the capability of
dosimeters both inside and outside the apron to meet legislative requirements. Evaluation entailed reconstructing
a typical fluoroscopic layout. Single dosimeters may be attached to a lanyard to hang midline just above waist level.
With a front-fastened apron this coincides with an overlapping protective layer and in many procedures the scattered
radiation passes obliquely through the double layer. In this study an irradiated Perspex phantom represented the
radiation worker and the surface dose was measured above and below one and two layers of 0.35 mm and 0.25 mm
lead-equivalence. Incident measurements were up to three orders of magnitude higher than the doses underneath
the double layer and thus substantial eye doses can arise before any dose is registered inside the apron. Organs of the
trunk adjacent to the overlap can, moreover, receive 20 times the dose beneath the overlap, making ALARP difficult
to demonstrate. A dosimeter outside the apron measures no organ dose in itself, but when combined with other
data can be used retrospectively to estimate dose to critical organs. It alerts to rising doses and provides an evidence
base for issuing multiple dosimeters and for selecting optimal shielding.