mammo 2

• Mammography

  The goal of mammography is the early detection of breast cancer, typically through detection of characteristic masses or microcalcifications
• Risk factors

  • Age
  • Hormonal History
  • Family History
  • Genetics presence of BRCA1 or, BRCA2 gene
  • Breast architecture (density)
  • Menstruation (before 12yr)
  • Menopause (after 55 yr)
  • Late age of birth of first child or no children
  • Never breast fed
• Mammography equipment

  • High contrast sensitivity
  • High resolution
  • Low dose
• Components of dedicated mammography equipment


  • Generator
  • Support system
  • X-ray tube
  • Collimator / cone
  • Breast compressor
  • Anti scatter grids
  • Cassette holder
  • Automatic exposure control
  • Photo timers
  • Detector systems
• Generator

  • 20-40 kvp of x ray energy is required for good contrast
  • Max mA-200mA
  • For homogenous x-ray beam, HFG is required
  • 3 - 10 kw tube rating
  • 3-5 lakh HU-heat loading capacity
• Patient support

  • Breast support table
  • Lead apron
  • Seating table
  • Holding support
  • Screen / Face shield
  • Space
• Anode

  • Target material: Molybdenum, Rhodium, Tungsten
  • Characteristic radiation produced by Mo & Rmh are effective for breast imaging
  • Molybdenum is the most common anode target material used in mammography x-ray tubes
  • With digital detectors, W is becoming the target of choice

  
• Cathode

  • Serves as the source of electrons necessary for generating X-rays
  • The mammography x-ray tube is configured with dual filaments in the focusing cup to produce 0.3- and 0.1-mm focal spot sizes
• 1. ray tube

  • Mammographic x ray tubes have rotating anode
  • Anode angle: 0 to 16 degrees
  • Tube tilt: 6 -24 degree
  • Source-to-image receptor distance is about 65-70 cm
  • Effective anode angle: (the actual anode angle plus the physical tube tilt) is at least 22-24 degrees for coverage of the 24 × 30-cm field area
  • Be(beryllium) window: is used as it has low atomic no. (4) and lower absorption of less than 5 kVp x-rays
  • Heel effect: Positioning the cathode over the chest wall of the patient and the anode over the anterior portion (nipple) achieves better uniformity of the transmitted x-rays through the breast
• Focal spot size


  • 0.3 to 0.4 mm for contact mammography (breast compressed against the grid and image receptor)
  • 0.10 to 0.15 mm for magnification imaging
  • It reduce geometric blurring so that micro calcifications can be resolved
• CR mammography target and filter combination

  • Mo target with 0.03mm(30µm) Mo filter
  • Rh target with 0.025mm (25µm)Rh filter
  • W target with 0.05mm (50µm) Rh filter
• CR mammography target and filter combination

  • Molybdenum target with molybdenum filter combinations are appropriate for breasts less than 5 cm thick
  • Molybdenum target with rhodium filters or rhodium target with rhodium filters may be appropriate for breasts greater than 5 cm thick

  
• Collimator / cones

  • Fixed aperture
  • A set of interchangeable cones for various sizes of breast
  • An internal set of collimating blades
  • For magnification and spot compression studies, manually adjusted shutters allow the x-ray field to be more closely matched to the volume being imaged
• Anti scatter grid

  • Moving grid
  • High transmission cellular grid
• Moving grid

  • Carbon fiber
  • Focused grid, with a grid ratio of 3:1 or 5:1
  • Grid frequencies of 30-40 lines/cm
  • Increase the patient dose
• High transmission cellular grid

  • Honeycomb-shaped structure
  • Reduce the scattered radiation in two direction
  • Composed of copper as grid strip material and air for interspaced material
  • 4:1 or 5:1 grid ratio
  • Improves contrast significantly
  • Spatial resolution improves
• Compression and compression devices

  • Advantages
  • Disadvantages
• Advantages of compression

  • Radiographic sharpness
  • Motion Unsharpness
  • Geometric Unsharpness
  • Contrast
  • Separates the superimposed areas of glandular tissue
  • Dose
  • Uniform film density
  • Useful assessment of the apparent density of masses
• Disadvantage of compression

  • Patient comfort
• Compression paddle design

  • Thin Plastic Composition
  • Straight Chest Wall Edge
  • Height and Angulation of Chest Wall Edge
  • Squared-Off Chest Wall Edge
  • Parallel Alignment with Image Receptor
  • Vertical Alignment with Image Receptor
  • Initial and Final Compression
• Spot compression device

  • Round spot compression device: 2 inches
  • Rectangular spot compression device: 4 inches
  • Advantages
  • Disadvantages
• Advantages of spot compression device

  • Adequate to use with patients who have a nonpalpable area in a small breast
  • They can be used on any breast size that has a palpable lesion

  
• Disadvantages of spot compression device

  • Little value in attempting to obtain an extra view of a nonpalpable lesion in a large breast
• Image receptor: screen-film


  • Holds a screen-film cassette in a carbon-fiber support with a moving antiscatter grid in front of the cassette and an AEC detector behind it
  • Single-coated film-screen combination is commonly used today (Gadolinium Oxysulphite)
  • 18 × 24 cm and 24 × 30 cm in size
  • Cassette: inherent spatial resolution of 18 to 21 lp/mm
  • Limitations: Restricted latitude and display contrast, Low quantum detection efficiency (56% at 20 KeV), Inefficient scatter rejection scheme (Bucky-Potter grid)
• Image receptor: digital detector

  • The transmitted x-ray pattern is recorded by a digital detector at discrete spatial intervals (pixels) and intensities are represented by digital values
  • No film or chemical processing is used
  • Thalium activated cesium iodide used as phosphor
  • Can be grown as parallel needle like light pipes for improved spatial resolution (5 lp/mm)

  
• Digital vs screen-film

  • Linear response (film: restricted latitude; over-exposure; under- exposure)
  • High dynamic range
  • Digital image processing
  • High spatial resolution
  • Efficient absorption of X-rays
  • No film treatment (Tdevelop minutes)
  • Field-of-view mammography:18x24 cm²
• Digital mammography

  • Single exposure digital radiography: Area detectors
  • Multi-exposure digital radiography: Scanning slot detectors
  • Multi-exposure digital radiography: Mosaic detectors
• Automatic exposure control

  • Phototimers are desingn not only to measure x-ray intensity at image receptor but also for x-ray quality
  • Phototimers are also called AEC device
  • X-rays transmitted through the breast, antiscatter grid, and the image receptor generate a signal in the detector
  • Consist of a single ionization chamber or an array of three or more semiconductor diodes
  • The signal is accumulated (integrated), and when the accumulated signal reaches a present value, the exposure is terminated
  • The present value corresponds to a specified signal-to-noise ratio (SNR) in a digital mammography unit or an acceptable optical density (OD) if a film-screen system is used

  
• Digital mammography

  • CR mammography
  • DR mammography
• CR mammography

  • Used with existing film mammography unit
  • Film cassettes are replaced with CR imaging plates with photo-stimulable (BaFBr:Eu2)
  • Image reader or ADC
  • Image processor or the computer system for post-processing
• DR mammography

  • Also called "full-field digital mammography" (FFMDM)
  • The x-ray film is replaced by solid-state detectors (aSi or a selenium) that convert x-rays into electrical signals
  • The electrical signals are used to produce images, can be seen on a computer or printed on special film
• Digital mammography detectors

  • Direct conversion: Amorphous selenium (direct conversion) using (TFT) flat panel technology
  • Indirect conversion: Scintillating phosphor (CsI columns) on an array of amorphous silicon photodiodes using thin-film transistor (TFT) flat panel technology
  • Computed radiography
  • Slot scanning CCD
• Advantages of digital mammography

  • Pixel size decreases: Spacial resolution improves, Noise increase, Signal-to-noise decreases
  • Post acquisition manipulation possible
  • Enhance detection of anomalies
  • Selectively increases magnification
  • Distinguishes between malignant and benign lesions
  • High contrast resolution
• Advancements in digital mammography

  • Tomosynthesis
  • Photon counting
  • Computer aided detection
• Digital breast tomosynthesis

  3D imaging technology that acquires series of low-dose projection images of the compressed or uncompressed breast at different angles

  
• Benefits of digital breast tomosynthesis

  • Minimal pressure needed
  • Lower dose of radiation required
  • Cost of DTS is cheaper
  • Easier differentiation between benign and malignant lesions
  • Early detection of small breast cancers
  • Greater accuracy in pinpointing abnormalities

  
• Photon counting

  • One of the newer forms of X-ray based mammography technology
  • Employ a slot-scanning design
  • The main principle is that smaller the detector used, lower the risk that a scattered photon will interact and increase image quality
  • The detector system consists of large number of crystalline silicon strip detectors
  • Silicon has excellent electronic properties
  • Sufficient absorption length is created
  • The X-ray beam is collimated to a fan beam matching the pre-collimator
  • Beneath the breast support is a detector box
  • Si-strip detectors matching the line beams exiting the breast
• Computer aided detection

  • Radiologist misdiagnose 10-30% of the Malignant cases
  • Of the cases sent for surgical biopsy, only 10-20% are actually Malignant
  • The CAD Technology basically works as a second pair of eye reviewing a patient's mammogram
  • Can detect stage 1 Cancers
  • Marks cluster of calcification with small triangle masses with a star
  • 100% Sensitivity
  • Decrease false negative readings
  • Requires digital output
  • Highlights suspicious area
• Limitations of mammography

  • Not always certain between benign and malignant tumors
  • Interpretations of mammograms can be difficult because a normal breast ca appear differently for each women
  • Appearance of an image may be compromise if there is a powder or cream on the breast or post operative cases
  • Not all types of Cancers of the breast can be seen in Mammogram

  
• Other modalities

  • USG
  • Dedicated breast CT
  • Breast MRI