Mammography System

Overview

A mammography system is an X-ray unit built specifically for imaging breast tissue, where the diagnostic targets, microcalcifications a few hundred microns across and subtle soft-tissue densities, demand far higher spatial resolution and softer X-ray spectra than general radiography. It produces a low-energy beam, compresses the breast to a uniform thickness, and records a high-resolution digital image while keeping dose low enough for routine screening.

The breast is positioned on the Compression Assembly assembly and flattened against the support plate by a motorized paddle, which spreads the tissue and holds it still. Above it the Mammographic Tube Head emits the beam through the Collimator & Filter Wheel, whose filter wheel selects the target/filter combination for the spectrum. The HV Generator supplies the precise low kilovoltage, and the Automatic Exposure Control watches the transmitted dose and ends the exposure once enough signal has reached the Flat-Panel Detector. The whole imaging chain rides on the C-Arm Gantry, which rotates to acquire the standard craniocaudal and oblique projections, and the technologist drives everything from the Acquisition Workstation.

How it works

Image quality starts with the spectrum. Breast tissue has low intrinsic contrast, so the Mammographic Tube Head uses a beryllium exit window and molybdenum or rhodium focal tracks that emit characteristic X-rays in a narrow low-energy band, and the Collimator & Filter Wheel filter wheel matches a filter to that band so contrast is maximized for the breast thickness. Compression is not just for stillness: by reducing thickness the Compression Assembly paddle lowers scatter, evens out density, and cuts the dose needed, with its Pressure Sensor limiting force to a safe value.

During exposure the Automatic Exposure Control sensor integrates the dose passing through the densest region and signals the HV Generator to cut off once the detector has the signal-to-noise it needs, so a dense breast and a fatty one both yield a well-exposed image. The Flat-Panel Detector converts X-rays to charge in an amorphous-selenium or scintillator layer read out by a fine-pitch TFT array, resolving the microcalcifications that are the earliest sign of disease. To capture the standard views, the C-Arm Gantry rotates the tube and detector together about the breast, while the System Control Board enforces the interlocks that keep the beam off until compression, positioning, and AEC are all ready.