Ch 20: mammography

Breast cancer

• second most common cancer related death
• second most common cancer
• 1 in 8 women will develop breast cancer
• men’s chances of developing breast cancer are 1-2% of women’s chances
• best defense is regular mammograms
• mammograms can detect lesions as small as 2mm
• 2 year survival average if breast cancer has metastasized
• begin mammograms at age 40 unless risk factors suggest earlier

Mammography Quality Standards Act 1992

• enacted by federal government to standardize mammography care
• all facilities must be certified by DHHS, accredited, and inspected regularly to operate
• machinery and equipment is regulated

Anatomy of breast

• breast tissue in young women tends to be more glandular than older women
• average breast extends from rib 2 - rib 6/7 and from lateral border of sternum to axilla
• 15-20 lobes within breast covered by adipose tissue

Nipple

• 15-20 duct openings from secretory glands
• areola is darker area around nipple
• Montgomery glands: small oil glands that keep the nipple lubricated and protected, especially while nursing
• inframammary fold: junction of inferior breast with anterior chest wall
• axillary tail: band of tissue that wraps around pectoral muscle laterally
• mediolateral diameter: width of breast
• craniocaudal diameter: vertical measurement of breast

Methods of localization

• 4 quadrant system
• clock system

Anterior view anatomy

• 15-20 lobes arranged around nipple like spokes on a wheel
• clusters of alveoli are connected and drain through ducts, ducts enlarge into ampulla that serves as a reservoir for milk before the nipple surface
• cooper ligaments: provide support for breast between glands

Breast classifications

• fibroglandular
    * age 15-30 & childless women >30
    * pregnant & lactating women
    * very dense with little fat
• fibrofatty
    * age 30-50
    * young women with 3+ pregnancies
    * average density, 50% fat and 50% fibroglandular
• fatty
    * over 50 years
    * postmenopause
    * minimal density
    * breast tissue type of children and men

X-ray tube

• molybdenum and rhodium target
• .3mm and .1mm focal spots
• prominent heel effect due to short SID
• cathode is toward breast base and anode toward nipple
• AEC chambers are adjustable for up to 10 positions
    * for blind exams chamber under the chest wall should be selected

Compression

• controlled by tech
• usually 15-30 pounds of pressure but may go up to 40
• spot compression paddle may be used for a specific area of interest
• makes thickness more uniform, places structures closer to the IR, decreases dose and scatter, decreases motion and increases geometric sharpness, increases contrast, separates structures that may be superimposed

Magnification

• used to enlarge a specific area of interest
• .1mm focal spot used

dose is mainly controlled by good positioning

repeat rate should be no more than 5%, can use a waist and thyroid shield

Analog/film mammography

• standard in current imaging
• excellent image quality with low dose
• see fine details, good edge sharpness and soft tissue visualization

Digital mammography

• uses higher kVp which reduces dose
• resolution is slightly worse than analog

Contrast mammography

• uses iodinated contrast agent
• contrast will accumulate in lesions that are metabolically active
• very small doses needed, given IV

Computer aided detection system

• a second reader for mammography, does NOT replace physician viewing
• analyzes images for possible calcifications and distortions
• improves cancer detection by 5-15%

Alternative modalities

• sonography
• nuclear medicine
    * scintimammography
    * sentinel node studies
• PET mammography
• breast specific gamma imaging
• MRI
    * great way to evaluate cancers
    * great for imaging patients with implants
• digital breast tomosynthesis
    * 3D mammography
    * acquires images in multiple angles
    * images reconstructed into slices
    * increased lesion and margin visibility

Pathologies

• breast carcinoma: noninvasive & invasive
    * noninvasive is restricted to tissue and cannot spread through lymphatics or blood vessels
    * noninvasive cancers are 15-20% of all cancers
    * most invasive cancers are ductal carcinomas, 80% of all diagnoses
• cysts: fluid filled sacs that are benign and well circumscribed
• fibroadenoma: benign lumps, most common
• fibrocystic changes: common and benign condition, usually bilateral and in premenopausal women
• gynecomastia: benign overgrowth of breast tissue in males
• intraductal papilloma: small growth inside duct of breast near nipple
• paget disease of nipple: cancerous, causes crusty and discharge from nipple, may be invasive or noninvasive

Imaging views

• AT: axillary tail
• AX: axillary
• CC: craniocaudal
• CV: cleavage view
• FB: craniocaudal from below
• ID: implant displaced
• LM: lateromedial view
• LMO: lateromedial oblique
• ML: mediolateral
• MLO: mediolateral oblique
• RL: rolled lateral
• RM: rolled medial
• SIO: superolateral-inferomedial oblique
• TAN: tangential
• XXCL: exaggerated craniocaudal