Patient dose versus image quality in digital mammography at Instituto Português de Oncologia de Coimbra (IPOC) - Portugal

Abstract

In the scope of the optimization of patient protection process (ALARA concept), the assessment of the patient radiation dose is not enough; image quality must be taken into consideration. The aim of this work is double: 1- to assess the image quality in clinical practice using the subjective rating scales of the European Guidelines on Quality Criteria for Diagnostic Radiographic Images, and 2- to estimate patient doses for the digital mammography exams carried out in the Instituto Português de Oncologia de Coimbra (IPOC) for auditing compliance with the European Diagnostic Reference Levels (DRL). The study sample was constituted by 81 patients randomly chosen, providing a total of 264 images, i.e. 134 images for the cranio-caudal (CC) projection and 130 images for the medium lateral oblique (MLO) projection. 25 images have been selected of each projection with compressed breast thickness between 4 and 6 cm and with four images per case (CC and MLO), for which the image quality was assessed by two radiologists. 8 exposures in the CC incidence and 11 exposures in the MLO incidence, representing respectively 32% and 44% of the evaluated images for each projection presented a good diagnostic image, i.e. accomplished at least 70% of all the analyzed criteria. The local patient doses were determined for 69 CC and 55 MLO incidences with compressed breast thicknesses between 4 and 6 cm. The mean entrance surface dose values are below the European DRL of 10 mGy and the mean average glandular dose values are below the suggested European limit dose value of 2.5 mGy. © 2009 Springer-Verlag.