Fluke Biomedical 07-611 - Manual (Page 5)

Introduction
Introduction
1
1-1
Section 1
Introduction
1.1 Introduction
This manual is to be used for the following models:
07-624, 07-624-1000, 07-624-2222 - Slit Cameras
07-622 - Multipurpose Focal Spot/HVL Test Stand
07-623 - Mammography Focal Spot Measurement Test Stand
07-503, 07-509, 07-510, 07-542, 07-543, 07-550 - Star X-Ray Test Patterns for Measuring Focal Spot
Size
07-611, 07-613, 07-617 and 07-633 - X-Ray Pinhole Assemblies
Focal spot size and intensity distribution play a significant role in mammographic image quality. It is
particularly important to verify the size of the focal spot during acceptance testing of new mammographic
equipment or when a new x-ray tube is installed.
The National Electrical Manufacturers Association (NEMA) has developed a standard of describing a
technique for measuring the focal spot size. Some of the aspects of the standard are difficult, if not
impossible, to meet in the clinical setting. This manual follows as closely as possible, the present NEMA
standard.
Additional information regarding focal spot measurement techniques is available in the references cited
on page 2-12. Data is available that indicates that detail screen-film systems can be used in place of
direct x-ray exposure film, with a considerable reduction in x-ray tube loading
1 . Studies also indicate that
the slit measurement technique, the recommended NEMA technique, is a repeatable method for
acceptance testing, but that the star measurement technique can also be used as a repeatable method
for obtaining quality control measurements
1 .
The American College of Radiology has published a document regarding quality control in
mammography. This document, which has separate sections for the radiologist, medical physicist, and
technologist, describes tests that will help assure quality mammographic imaging. The Mammography
Focal Spot Test Stand (Figure 1-1) can be used as one of the tools in the ACR Mammographic Quality
Control Program.
Figure 1-1. Mammography Focal Spot Test Stand (Model 07-623)