PURPOSE: Point detectors are frequently used to measure patient's maximum skin dose (MSD) in fluoroscopically-guided interventional procedures (IP). However, their performance and ability to detect the actual MSD are rarely evaluated. The present study investigates the sampling uncertainty associated with the use of grids of point detectors to measure MSD in IP. METHOD: Chemoembolisation of the liver (CE), percutaneous coronary intervention (PCI) and neuroembolisation (NE) procedures were studied. Spatial dose distributions were measured with XR-RV3 Gafchromic(®) films for 176 procedures. These distributions were used to simulate measurements performed using grids of detectors such as thermoluminescence detectors, with detector spacing from 1.4 up to 10 cm. RESULTS: The sampling uncertainty was the highest in PCI and NE procedures. With 40 detectors covering the film area (36 cm × 44 cm), the maximum dose would be on average 86% and 63% of the MSD measured with Gafchromic(®) films in CE and PCI procedures, respectively. In NE procedures, with 27 detectors covering the film area (14 cm × 35 cm), the maximum dose measured would be on average 82% of the MSD obtained with the Gafchromic(®) films. CONCLUSION: Thermoluminescence detectors show good energy and dose response in clinical beam qualities. However the poor spatial resolution of such point-like dosimeters may far outweigh their good dosimetric properties. The uncertainty from the sampling procedure should be estimated when point detectors are used in IP because it may lead to strong underestimation of the MSD.

Belgian Nuclear Research Centre Boeretang 200 BE 2400 Mol Belgium

Centre Hospitalier Universitaire de Liège Zephyra scrl Avenue de l'Hôpital 4000 Liège Belgium

Institut de Radioprotection et de Sûreté Nucléaire BP17 92262 Fontenay aux Roses Cedex France

Institute of Nuclear Physics ul Radzikowskiego 152 PL 31 342 Kraków Poland

Istituto Superiore di Sanità Viale Regina Elena 299 00161 Rome Italy

Medical Physics Department Veneto Institute of Oncology IOV IRCCS Via Gattamelata 64 35128 Padova Italy

National Radiation Protection Institute Bartoškova 28 140 00 Prague 4 Czech Republic

Nofer Institute of Occupational Medicine 8 Sw Teresy Str 91 348 Łódź Poland

Radiation and Nuclear Safety Authority P O Box 14 00881 Helsinki Finland

Ruđer Bošković Institute Bijenička c 54 10000 Zagreb Croatia

Udine University Hospital pl S Maria della Misericordia 15 33100 Udine Italy

VINCA Institute of Nuclear Sciences University of Belgrade P O Box 522 11001 Belgrade Serbia

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