Marcelo Andrade da Costa Vieira PhD, Presenter: Nothing to Disclose

Maurício Cunha Escarpinati PhD, Abstract Co-Author: Nothing to Disclose

Homero Schiabel PHD, Abstract Co-Author: Nothing to Disclose

Paulo Domingues Oliveira MSc, Abstract Co-Author: Nothing to Disclose

Alex Okajima Watanabe, Abstract Co-Author: Nothing to Disclose

Measurement of focal spot size for mammography can be achieved by using a CCD intraoral sensor for image acquisition and an electronic test stand for automatic alignment. Results have shown that the proposed method is fast, accurate and less time-consuming than the NEMA standard. 

The focal spot size of an x-ray tube has a direct effect on image quality of a radiographic imaging system. For clinical mammographic systems, measurement of focal spot size is necessary during acceptance testing and is occasionally performed during image quality evaluation. This measurement requires precise alignment and direct-exposure film, which is difficult and time-consuming. The purpose of this work is to present an easier methodology for the measurement of focal spot size of mammography x-ray tubes. It was built an electronic test stand coupled to a CCD intraoral sensor to automatically locate the x-ray central beam by a computational analysis of a test pattern image. A mechanical system of two moving directions, electronically controlled by a microcontroller under USB communication, makes the alignment to the central beam. When properly aligned, focal spot size is automatic determined by acquiring a digital image of the focal spot projections using the slit camera technique.

Results have shown a good agreement between the proposed method and the NEMA standard for the measurement of focal spot size of the mammographic units. However, considering the proposed methodology, the alignment process and the focal spot measurement are fully automatic, fast and accurate, which allow a considerable time saving for acceptance tests and image quality evaluations for mammography.

The proposed method was used for evaluation of five mammographic units. The test stand was placed at different locations along the field and the system moved automatically to align to the central beam. The alignment was confirmed by using a commercial alignment test tool. Focal spot size was measured for each mammographic unit considering the proposed method and also the standard procedure provided by the National Electrical Manufacturers Association (NEMA).

Vieira, M, Escarpinati, M, Schiabel, H, Oliveira, P, Watanabe, A, Measurement of Focal Spot Size of Mammography X-ray Tubes with a CCD Intraoral Sensor and an Electronic Self-alignment Test Stand.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12029045.html