mammography

Learning Outcomes

• Demonstrate Critical Understanding and Application of Theoretical Principles:
    - Grasp key concepts underlying mammography.
• Analyse Technical Performance and Fitness for Role:
    - Assess mammography equipment effectiveness.
• Appreciate Radiation Doses:
    - Understand the radiation exposure of mammography and strategies to minimize it.
• Impact of Radiographer on Quality Assurance and Service Provision:
    - Recognize the critical role of radiographers in maintaining quality and efficient healthcare delivery.

Normal Mammograms

• Types of mammogram views: RMO (Radial Medial Oblique), LMO (Lateral Medial Oblique).

The Mammography Challenge

• Requirements of effective mammography:
    - Visualization of Pathologies:
      - High-density macro- and microcalcifications.
      - Low contrast areas.
    - Radiation Dose Management:
      - Doses must be kept "As low as reasonably practicable (ALARP)."

Having a Mammogram

• Video Resource: "Do The Test - GO FOR IT!" on Vimeo (4:45 mins).
• Imaging Requirements:
    - Two views required:
      - CC: Cranio-caudal view.
      - MLO: Medio-lateral oblique view.
    - Additional views may be needed, and must facilitate biopsy guidance.

Equipment Requirements

• Essential components of mammography units:
    - High-quality imaging detector.
    - Automatic exposure device.
    - Compression plates and paddles.
    - Flexible positioning capabilities.
    - Motorized controls for adjustments.
    - High-resolution monitors.
    - Compatibility with biopsy devices for image-guided biopsies.

Safety Features

• Critical safety components:
    - Emergency cut-out buttons.
    - Interlocks and brakes.
    - Lead glass screen to protect the operator.
    - Grip handles for the exposure button behind the screen.
    - Compact design (small footprint) and ease of cleaning.
    - Earthed for electrical safety.
    - Regular quality assurance checks must be performed.

Equipment Design

• Brand Example: Hologic
    - Specific dimensions and design considerations.

Control Panel Design

• Features:
    - Fingerprint recognition for identifying the mammographer and setting imaging order.
    - Touch screen interface for ease of use.
    - Bilateral grip handles for exposure.

Positioning Features

• Adjustability and support elements:
    - Motorized controls for height and angulation.
    - Handles for patient positioning and support.
    - Perspex face plate to prevent overlap and stabilize the patient.
    - Compression paddles to reduce breast thickness.
    - Manual compression knob for fine adjustments.
    - Space for wheelchairs or biopsy chairs underneath the equipment.

Difficulties in Imaging Breast Tissue

• Challenges with breast imaging include:
    - Difficulty in patient positioning.
    - Challenges in immobilizing the breast.
    - Variations in breast size and density.
    - Soft tissue with low inherent contrast.
    - Radiosensitive glandular tissue requiring high-resolution imaging.
    - Need for quick procedures in a non-threatening environment.

Design Solutions to Imaging Difficulties

• Positioning Improvements:
    - Dedicated equipment with isocentric movement.
    - Ergonomic design for both patients and staff.
    - Smooth edges and corners for patient comfort.
    - Compression paddles and adjustable height features for optimal positioning.
• Immobilization Techniques:
    - Utilization of handles and grips, compression paddles, and techniques like breath-holding.

Importance of Compression

• Essential for Image Quality:
    - Improves image quality by:
      - Reducing breast thickness.
      - Maintaining position for clear imaging.
• Benefits of Compression:
    - Enhances spatial resolution, reduces blur and motion artifacts, improves contrast, and decreases exposure time leading to better images.

Image Quality Considerations

• Compression Effects:
     - Reduces breast thickness and maintains breast position, allowing maximum tissue capture within the imaging field.
     - Avoids loss of tissue from the detector, allowing symmetrical image production.

Preventing Image Blur

• Motion Artifact Prevention:
    - Compression prevents blur caused by heart and lung movement behind the breast.
• Importance of Adequate Compression:
    - Stops patient movement, leading to clearer images.

Improving Spatial Resolution

• Impacts of Detector Distance:
    - Reducing the geometric distance to the detector improves spatial resolution.
    - The penumbra effect:
      - Increased distance leads to unsharpness.
      - Compression minimizes this distance for better clarity.

Improving Image Contrast and Reducing Scatter

• Compression and Photon Pathways:
    - Direct paths for photons enhance contrast by ensuring accurate representation of breast tissue without scatter contributing to noise.

Reducing Radiation Dose

• Principle of Compression:
    - Compression lowers x-ray attenuation in the breast, which allows for reduced x-ray exposure and patient dose.

Localized Spot Compression Projections

• Usage of Spot Compression:
    - Provides better visualization of suspicious areas and distinguishes between lesions and tissue overlaps.
    - Enhances visibility of microcalcifications and abnormal structures.
• Methodology:
    - Conducted by radiographers marking areas from original mammograms.
    - Small paddles are utilized; often employing tomosynthesis when available.

Magnification Projections

• Purpose:
    - Evaluate microcalcifications and assess suspicious tissue borders.
• Technique:
    - Use of magnification devices to enhance detail; requires small focal spots and specific positioning away from the detector.

Variation in Size and Density

• Equipment considerations include:
    - Digital detectors and Automatic Exposure Control (AEC).
    - Various sized compression paddles and sensitive compression controls.

Low Inherent Contrast in Breast Tissue

• Challenge of Density Differences:
    - Limited density variations necessitate high contrast.
• Optimal Exposure Settings:
    - Requires lower kVp for greater subject contrast; must balance energy levels to avoid excessive radiation while maintaining image quality.

Linear Attenuation Coefficient

• Understanding the absorption characteristics of different breast tissue types at various photon energies.

Maximizing Image Contrast

• Recommendations for achieving enhanced contrast while minimizing doses:
    - Utilize proper filtration materials (Rhodium/Silver/Copper) with tailored target materials (such as tungsten).
    - Use direct digital capture technology with post-processing enhancements.

Radiation Protection: Filtration Strategies

• Importance of Filtration in Mammography:
    - Enhances patient safety by removing low-energy photons and minimizing skin dose.
    - Effective materials used: Rhodium, Silver, and Copper.

Anode Heel Effect

• Overview:
    - Due to absorption in anode material, intensity differs across the x-ray beam.
• Photonic Distribution:
    - More intensity on cathode side; important for positioning breast tissue over the cathode to balance exposure.

Optimizing for the Anode Heel Effect in Imaging

• Maintain proper orientation of breast tissue to utilize the anode heel effect effectively during mammography imaging.

National Diagnostic Reference Levels (NDRLs)

• NDRLs for Screening Mammography:
    - Average Mean Glandular Dose (MGD) for standard mammography (2022): 2.5 mGy.
  - This value is suggested for mediolateral oblique views for typical breast thicknesses and frameworks.

Mammography QA Procedures

• Quality Assurance Reports and Protocols:
    - IPEM Report 89 details commissioning and performance testing schedules for mammographic systems.
    - NHSBSP Equipment Report outlines systematic checks for digital mammography suitability.

Regular Testing Frequencies for Equipment

• Daily, Weekly, Monthly Checks:
    - Examples of routine tests involve checks on acquisition/reporting monitors, contrast-to-noise ratios, and artefact uniformity assessments.
    - Specific remedial measures for failures need to be documented.

Monitor Checks

• Proper monitoring practices involve visual inspections and performance checks under prescribed conditions to ensure reliable imaging outputs.

System Checks Using Perspex Blocks

• Techniques for Performance Assessment:
    - Utilize mAs, dose, SNR, and CNR checks to monitor X-ray set performance and detect any irregularities.

TOR(MAM) Testing

• Utility of the TOR(MAM) Test Tool:
    - Provides ongoing quality assessments of mammographic imaging systems to identify any trends in performance decline.
• Structure of Testing:
    - Comprehensive evaluations of both low-contrast and structural simulation for realistic assessment standards.

Further Developments in Imaging

• Breast Tomosynthesis Technology:
    - Involves low-dose exposures processed into multiple slices for detailed imaging. Enhances clarity and pathology differentiation in 3D formats.

Benefits of Breast Tomosynthesis

• Advantages Over 2D Imaging:
    - Improved specificity and sensitivity, enhanced delineation of tissue margins, and better detection rates with fewer false positives.

Imaging with Implants

• Adjustments for Patients with Implants:
    - Routine and enhanced views are necessary to ensure accurate diagnosis without compromising the integrity of the breast tissue.

The Eklund Technique for Mammography

• Method for Patients with Implants:
    - Ensures careful imaging alongside routine screenings for a comprehensive assessment of breast health.