a) Describe what is meant by the terms "good geometry" or “narrow beam geometry" and how it affects the measurement of Half Value Layer (HVL) in mammographic x-ray systems. With

reference to this geometry, describe in detail your testing methodology for the measurement of HVL include details of the following: equipment used, setup (can be diagram(s)), measurement,calculation method, and performance limits. Note: If your HVL calculation method is performed by a modern dose meter, you must describe the conditions under which these measurements are made, the uncertainty in this measurement,and any limitation of this method. b) For dosimetry purposes the output in air is measured with a dosimeter in contact with the underside of the compression paddle. Why is it important to include the compression paddle in the beam and why is this the best measurement position?