Mammographs and Mammography Systems

Operating principles, detector types, radiation parameters, and modern imaging technologies

A mammograph is a specialized X‑ray system optimized for imaging the soft tissues of the breast with high contrast resolution and minimal radiation exposure. Technical evolution has led to digital solutions that enable image processing and tomosynthesis. We invite you to explore the technical aspects of mammography systems: component design, physical parameters, standards, and operational characteristics.

1. Architecture and main components

Any mammograph consists of an X‑ray tube with a metal or glass envelope, a high‑voltage generator, a collimation system, a compression device (compression paddle), an anti‑scatter grid, and an image receptor. In analog systems, the receptor is a cassette with a screen‑film system; in digital systems, it is a flat‑panel detector (DR) or a photostimulable plate (CR).

X‑ray tube

The anode is molybdenum (Mo) or rhodium (Rh), rarely tungsten (W), with a beryllium window. Typical values for anode voltage are 20–40 kV, optimal for glandular tissue.

Generator and filtration

A typical solution is the use of a high‑frequency generator. Several manufacturers implement automatic filtration: Mo/Mo, Mo/Rh, Rh/Rh, Rh/Al — depending on breast thickness and density. An additional Be filter reduces the low‑energy component.

Detectors (DR / CR)

The detector/cassette size is usually from 18×24 cm to 30×24 cm.

2. Key technical parameters

Parameter	Value / Range	Note
Anode voltage (kV)	20 – 40 kV (0.5–1 kV step)	Most modern devices allow automatic exposure control (AEC)
Anode current (mA)	20 – 400 mA	Pulsed mode, duration up to 5 s
Spatial resolution	DR: 6–20 lp/mm; CR: 5–12 lp/mm; film: 12–15 lp/mm	Depends on pixel size
Compression force	Automatic control from 5 to 100 N	Compression reduces scatter and dose
Average glandular dose (AGD)	0.8–3.0 mGy for a standard breast (4.5 cm)	MQSA / EU requirements ≤ 3 mGy

3. Automatic exposure control (AEC)

AEC sensors (ionization chamber) are located behind or in front of the image receptor. The transmitted radiation in the central zone is analyzed. Modern digital systems use a low‑dose pre‑shot to calculate the optimal exposure parameters. The criterion is to achieve the target exposure index (EI) as normalized by the DICOM protocol. Density reproducibility accuracy is ±0.1 OD.

4. Tomosynthesis (DBT): technical features

Digital Breast Tomosynthesis (DBT) reconstructs a series of thin slices. The tube moves along an arc (15–50 degrees) in steps of 1–5°, acquiring 9–60 projections. Technical parameters:

Scan angle: 15°–50° (high angle) — improved z‑resolution.
Scan time: 3–10 seconds depending on the number of exposures.
Tomosynthesis dose: 1.5–2 times higher than 2D mammography, but remains within acceptable limits (≤ 4.5 mGy).

Integration of a synthesized 2D image from the tomosynthesis dataset eliminates the need for an additional 2D exposure (e.g., combo mode).

5. Anti‑scatter grid and focal distance

A grid is used in modern mammography systems. The grid reduces the proportion of scattered radiation from 60% to 10–15%, increasing contrast. Some digital systems employ software‑based scatter suppression (virtual grid).

6. Interfaces and DICOM standards

All modern digital mammographs support DICOM 3.0 for mammography (DICOM MG) and tomosynthesis (DICOM DBT). Key SOP classes: Mammography Image Storage, Breast Tomosynthesis Image Storage, Mammography CAD SR.

7. Safety classes and radiation protection

Mammographs are classified as medical devices class 2b (MDD 93/42/EEC) or class IIb (MDR). Requirements for leakage radiation at 1 m from the housing ≤ 0.02 mGy/h. The tube housing and additional shielding protect personnel. Automatic dose control includes an exposure termination system in case of AEC failure. Permissible voltage reproducibility error ±2%, current ±5%.

8. Recent trends: artificial intelligence and 4D

Modern mammography systems employ neural network algorithms for segmentation, detection of microcalcifications and asymmetries. Technical implementation: GPU modules inside the workstation or cloud computing with a DICOM gateway. Metrics: AUC for cancer detection > 0.90. The concept of 4D mammography is based on time series (multi‑year comparisons) with deformable registration, allowing the detection of dynamic changes in breast density.

Additionally, dual‑energy spectral mammography for contrast‑enhanced visualization (CESM) is being introduced. Technical characteristics: two exposures at low and high kV (e.g., 26 and 45 kV) followed by subtraction, spatial resolution 200 μm.

Summary

A modern mammograph is a high‑tech X‑ray system with optimized geometry, digital detectors, and advanced reconstruction algorithms. Understanding the technical parameters enables proper equipment operation and high diagnostic accuracy.