Teste | Abstract: 83-1 | ||||
Abstract:The technological evolution within radiology aims to increase the effectiveness of safe diagnostics and radiological protection for patients and workers. Technological changes bring challenges to ensuring image quality and radiological protection. The methodologies and instruments necessary to evaluate these systems need to be constantly reviewed in order to obtain a real assessment of mammography systems. Digital breast tomosynthesis (DBT) was recently introduced to the market, being approved for commercial use only in 2011 by the FDA (Food and Drug Administration) [1]. This technique consists of performing low-dose projections that are used for volumetric breast reconstruction. The greatest advantage of DBT compared to 2D mammography is the elimination of tissue overlap. The Collegiate Board Resolution No. 611, which addresses health requirements for the operation of diagnostic and interventional radiology in Brazil, does not provide specific quality control criteria for DBT [2]. 2D mammography has some negative points, such as its low sensitivity (36-70%) depending on breast density and high recall rates [3]. Tissue overlap is one of the main causes of recall since overlapped healthy tissue can both appear as non-existent lesions or hide existing lesions. In DBT, the formation of a pseudo-three-dimensional image allows the breast to be viewed in sections, thus there are no overlapping tissues that could hinder the examination diagnosis. In the DBT examination, the X-ray tube moves around a point performing low-dose exposures. The movement of the X-ray tube can be continuous while making the exposure or performing stops between each exposure [4]. The Quality Control Protocol for Breast Tomosynthesis Systems by the Spanish Society of Medical Physics presents parameters that need to be evaluated in mammography equipment, some of which are common to both 2D mammography and DBT, and others specific to only one type of acquisition [5]. Due to the new exposure geometry of DBT, simulators specifically developed for this type of examination need to be used. This study aims to develop a protocol for evaluating the image quality and radiation dose in DBT equipment using criteria from the Quality Control Protocol for Breast Tomosynthesis Systems. The evaluation of image quality will be carried out with the Tomophan simulator, which was specifically developed for quality control in DBT. Thermoluminescent dosimeters (TL) cards will be used to measure the mean glandular dose (MGD). The image quality parameters to be evaluated are: geometric distortion, loss of thoracic wall tissue, slice thickness, low contrast resolution, local and global uniformity, contrast-to-noise ratio, modulation transfer function, and slice increment. To obtain the MGD, a dosimetric system composed of 4 TL detectors (LiF,Ti) will be used. The dosimetric card reading will be performed at Thermoluminescent Dosimetry Laboratory (LDTL), located at the Centre for the Development of Nuclear Technology (CDTN). Test images were obtained with the Tomophan simulator to familiarize with image acquisition and quality assessment. Calibration curves of the dosimetric system were constructed, which is necessary to correctly measure the MGD. The application of the protocol will be carried out in mammography services in the city of Belo Horizonte/MG that have DBT equipment. Keywords: Digital Breast Tomosynthesis, Mammography, Tomophan, Image quality |