Mammography, MMed Anatomy, Chest
Breast Anatomy
v Embryology
Ø Ectodermal origin. Skin Glands
Ø Develop from mammary ridges which begin as ventral streaks from the axilla to the thigh in the 5th week of gestation
Ø Ridges extend from the axilla to the groin
Ø The middle portion of the upper 1/3 persists to form the breast bud, the remainder disappear.
§ Accessory breast tissue is due to failure of the ridges to envolute and may occur anywhere along the milk line.
Ø A number of epithelial cords penetrate the underlying mesenchyme, giving rise to 15 to 20 specialised outbuddings. Ducts open to a surface pit, which undergoes mesenchymal proliferation at birth to become the nipple.
Ø At birth the focal breast has a network of branching ducts (no lobules until adolescence). Secretion may occur under hormonal stimulation. Expect a large breast at birth for both males and females.
Ø At puberty the buds enlarge (augmented). Increase adipose tissue and connective tissue, ductal elements proliferate as does growth of the lobules. (under influence of pituitary, ovarian and other hormones).
v Anatomy. (Pansky 264, Grant , Moore p632, Butler p173)
Ø 15-20 lobes, lobules, 10 to 100 acini)
Ø Each lobule is drained by a lactiferous duct, each opens onto the nipple. Under the areola each duct has a dilated portion, proximal to its termination, the lactiferous sinus.
Ø Lies vertically between the 2nd and 6th Costal cartilage (RIBS)
Ø Lies laterally from the sternum to the mid Axillary line
Ø Overlies 3 muscles. Pectoralis major, External Oblique and Serratus anterior muscles.
Ø Is incompletely encapsulated by fascia. Superficial pectoral fascia
Ø Contains 15 to 20 radiating lobes
Ø Each lobe contains a variable number of lobules with 10 to 100 acini (blind ending secs)
§ These are lined by a single layer of cuboidal epithelial cells and a flattened layer of myoepithelial cells, the ducts being lined by columnar epithelial cells.
Ø The breast ducts form a branching structure and the ducts are described on the basis of their location as:
§ Interlobular
§ Intralobular
§ Interlobar
§ Intralobar
Ø The terminal duct lobular unit (TDLU). Terminal Dutal Lobular Unit consists of a margin of the lobule and the extralobular terminal unit.
Ø Breast tissue consists of
§ Parenchymia. Glandular and ductal tissue
§ Stroma. Fatty and fibrotic tissue.
Ø Breast tissue is contained in a sac formed by the superficial pectoral fascia splitting into
§ Anterior (superficial layer). Form Coopers ligaments that bind the glands to the overlying skin, suspensory ligaments.
· Dimpling of the skin: Shortening of the suspensory ligaments results from the Ca breast. Subareolar Cancers may cause inversion of the nipple.
§ Posterior (deep layer)
Ø The Axillary tail of Spencer. Edge of axilla
§ Number of lobules and acini vary according to age, parity, individual factors
§ Puberty / adolescence – lactiferous ducts undergo branching and thereafter progressive enlargement of the breast occurs. Increase fat
§ Pregnancy – increase acini. Formation of new glandular tissue.
§ Elderly – involution, increase fatty and decrease glandular tissue
Ø Nipple and areola contain erectile smooth muscle, subcutaneous glands. The glands may contain calcium – this is a diagnostic problem on mammography.
v Blood supply
Ø Internal thoracic Artery.
§ Perforating branches. Intercostal spaces 2 to 4.
Ø Lateral Thoracic Artery. Lateral mammary branches.
Ø Lateral and anterior branches of Intercostal Arteries (3,4 and 5). Posterior Thoracic
v The chief venous drainage is towards the axilla. Venous drainage via the Axillary, internal thoracic, lateral thoracic and intercostal veins. Also subclavian and Azygos veins. There are connections between the intercostal veins and the vertebral venous plexus. This connection allows metastasis to the bones (spinal column) and brain.
v Lymphatic Drainage of the breast
Ø Via 2 plexus
§ Subareolar plexus - axillary
§ Submammary (on Pectoralis Major) – axial (deep) L/N, Diaphragmatic, Parasternal, Across midline to other breast
§ Most of the lymphatic drainage of the breast is to the pectoral group Axillary lymph nodes. Some lymph vessels pass to the apical and subscapular groups of Axillary lymph nodes. Some pass to the
· Infraclavicular lymph nodes
· Opposite breast
· Parasternal lymph nodes and
· Abdominal lymph nodes
v Carcinoma Breast: Ca breast spreads to the Axillary Lymph Nodes (75% of total lymphatic drainage.
Ø Axillary lymph nodes are the most common site for metastasis of Ca Breast. Cancerous nodes are usually hard and non-tender.
§ Axillary nodes May also enlarge because of lymphangitis (injured thumb). These are tender.
Ø Free communication between lymph nodes exists between superior and inferior clavicular lymph nodes, and Axillary and Cervial lymph nodes. Metastasis may develop in the supraclavicular lymph nodes, the opposite breast or in the abdomen.
v
v Developmental and Normal Variants
Ø Polythelia – extra nipple along milk line. Duplication of the nipple on the on the areolar may occur.
Ø Polymastia – extra breast. Look for it in the axilla.
§ An Axillary breast. The outline of an Axillary breast can be made out with central thickening from fibroglandular tissue.
§ Accessory glandular tissue, can be seen lying high in the breast towards the axilla. This is a normal variant and may be a cause for much pain and discomfort and occasionally a lump. Look for Axillary lymph node.
Ø Amastia
Ø Supranumerary breast consists of a nipple or areola only and may be mistaken for a mole or nevus
Ø Hypoplasia. Underdevelopment of the breast tissue, may occasionally be related to under-development of the chest wall or the forearm (Poland’s syndrome)
Ø Asymmetry of the breast: normal 3% of women
Ø Multiple sebaceous gland calcifications. These are rounded, dense and are either punctuate or have a very fine lucent centre. The can be seen as skin associated if tangentially projected. This is NOT PATHALOGICAL INTRAMAMMARY CALCIFICATIONS.
Ø Skin papilloma or wart. May appear as an intramammary mass. Usually a low density, extremely well-circumscribed masses, with a thin lucent rim representing a halo caused by air trapped between the skin and the compression plate.
Ø Vascular calcifications: Calcification in the arterial walls is a normal finding and showing a typical tubular and occasionally a segmental morphology.
v Neural Supply
Ø Anterior and lateral branches of the 2nd to 6th thoracic intercostal nerves
Ø Cervical plexus supply the upper breast
Pathophysiological Changes
v Cyclical changes
Ø Estrogens – in the proliferative stage cause proliferation of breast tissue
Ø Progesterone – causes ductal dilatation and differentiation
v Pregnancy
Ø Marked proliferation of the terminal ductal lobular units (TDLU) and a decrease in fat and connective tissue
v Prolactin, insulin and growth hormone
Ø Induce the ductules to form secretary acini
v Lactation
Ø Proliferation of acini and ducts
v Menopause
Ø Regression of fibroglandular tissue and fatty replacement
Ø Hormone replacement therapy arrest these changes
Breast Imaging
v Mammography
Ø US
Ø Indications
§ Screening
§ Diagnostic procedure
§ Follow up
§ Localisation FNA / Core
§ Workup of metastatic disease of unknown origin
§ Other
· Contralateral mastectomy
· Family of 1st degree relative Ca Breast premenopausally
· Imaging of post prosthesis breast
v Essential parameters that justify the dose risk
Ø Dedicated
§ Technical quality
§ Experience
Ø Correction of history and examination
Ø Confirmation – histological confirmation
v Direct film mammography
v Screeen film mammography
v Equipment
Ø Constant potential generator
Ø 360 degree
Ø Focal spot – Mo
Ø Cathode
Ø Shielded tube – Be
Ø Added filtration
Ø Compression cones
Ø FSD >50cm
Ø Screen. Simple
Ø Close Film screen contract
Ø Grid (optional)
Ø Processing
Ø Projections
§ Craniocaudal
§ Lateral Oblique
v Benefits of compression
Ø Decrease motion unsharpness
Ø Decrease geometric unsharpness
Ø Decrease dose
Ø Increase contrast
Ø More uniform image density
Ø Less superimposition
v Magnification views
v Comparative views
v Nipples in profile
v Support arm, pertoralis relaxed
v Posterior breast and axillary tail
Exposure factors
v kV 25 to 30 (30 for glandular breast)
v mAs as short as possible
Viewing
v mirror image viewing in ~ Light
v Advantages
Ø Decrease kV
Ø Good contrast
Ø Decrease skin dose
Ø Decrease mean breast dose
v Disadvantages
Ø Greater compression required
Ø Lateral oblique
Ø Decrease efficiency in imaging microcalcifications and soft tissue abnormalities
Xeromammography
v Replaced by current methods
v Required a high dose of ionising radiation
v Advantages
Ø Wide latitude capable of demonstrating lungs, ribs and breast tissue on a single image
Non-palpable breast lesions biopsy
Ductography
v Ductogram or Galactogram. Cannulation of the duct orifice. Inject contrast.
v Rather use a high frequency Ultrasound
US:
v 7.5 MHz transducer
v Adipose tissue: hypoecohic
v Septa: Ecogenic usually encompass the adipose tissue
CT. Iodide contrast. Breast cancer cells have an unusual affinity for iodide and so become recognisable.
MRI
v Limited indications
Ø Surface coils with fat suppression and use of contrast material
Thermography
Isotopes
Mammography anatomy
v Contrast between fat and soft tissue is optimised using low energy x-ray spectra from dedicated units,
v Characteristic peaks of Molybdenum anode 17,4 to 19,6 keV
v Small focal spot, compression and a sensitive film screen
Ø maximise resolution
Ø Reduce scatter, and
Ø Minimise dose of ionising radiation
v 45Θ Mediolateral oblique view is the Standard projection –
Ø Use bright light to visualise the skin and subcutaneous tissue to best effect
Ø Coopers suspensory ligaments, fine shadow curvilinear structures
Ø Intramammary lymph node can be seen on the upper outer quadrant. Presence of a small fatty Hilum confirms their origin.
v Wolfe grading of amount and distribution fibroglandular tissue in the breast. Not used for everyday reporting, valuable for descriptive and comparative purposes
Ø N1. Normal largely adipose tissue
Ø P1. The breast is still adipose but there is parenchymal thickening with ductal prominence anteriorly, usually in the retroareolar region but occupying less than one quarter of the breast volume.
Ø P2. A much more prominent ductal and fibroglandular pattern involving greater than one quarter of the breast volume.
Ø DY. Generalised increase density of the fibroglandular pattern, without a recognisable ductal or nodular appearance.
§ Such dense tissue may obscure small masses. Consider an ultrasound, if a discrete clinical abnormality is present.
Ø There is an increase risk of malignancy with a P2 and DY pattern, largely related to the increased glandular tissue and the epithelial components present.
v Craniocaudal examination
Ø The pectoralis major muscle will not be visualised posteriorly
Ø Better compression, better resolution
v Male breast
Ø To Differentiate carcinoma from gynecomastia
Ø A normal male breast with no discernable fibroglandular structure. The breast is small and fatty with tiny vessels just visible.
Focal Spot Size and Geometry
v Focal spot size decrease
v Resolution depends on
v Decrease geometric unshapeness
v Shape of focal spot
Focal spot composition
v Soft Radiation. To enhance the tissue contrast in breast
v Molybdenum. Photons and energies less than 20 keV
Ø Molybdenum Anode tube
Ø Molybdenum Target
Ø Molybdenum Filter
v Reducing keV enhances contrast separation of breast structures, BUT limited by the thickness of the breast and its ‘radiographic density’
Ø Large, dense breast filter beam as it passes through. Beam Harding, therefore decreased overall contrast.
Ø Need increased keV to penetrate, therefore decrease contrast
v Of Tungsten tubes can be used but need beryllium windows to permit passage of low keV photons
Scatter. Degrade image quality. Decrease contrast, decrease sharpness and contribute to film blackening.
Ø Increased Scatter:
§ Increase scatter with thick, larger breast.
§ Increased diameter of filed imaged
Ø Decrease Scatter with
§ Vigorous breast compression (decreased amount of tissue traversed by beam)
§ Collimators (exposes smaller volumes of breast tissue)
§ Air gap between breast and detector (decrease the effect of scatter be spreading it over a larger area)
§ Scatter reduction grid (specially breast greater than 6cm after compressed)
Dose Measurement
v Average glandular dose. Several methods of measurement, indirect measurement
v Important factors:
Ø Strength of the x-ray beam and its half value layer
Ø Thickness of the tissue through which the beam passes (compression thickness)
Ø Composition of the tissue (fat or glandular)
v By measuring the dose where the beam enters the breast (skin entrance dose
Dose Reduction
`eroradiography
v Wide exposure latitude
v Thin front to the thick proximal end of breast- that cant be significantly compressed
v Conventional tungsten overhead tube – 45 to 55 kvp
Ø Source image distance >75cm
Ø Focal spots of 1-2mm
v Process
Ø Aluminium plate coated with selenium = semiconductor
Film Screen Mammography
v Require dedicated mammography equipment
v Mammographic positioning and technique
v High contrast film and narrow exposure latitude
Ø Rigorous compression required to even anterior thickness
v Advantages
Ø Decrease dose to the reduced thickness of the tissue
Ø Decrease dose because of decreased exposure times
Ø Overlapping structures are separated
Ø Breast structures are pressed closer to the detector with better geometry and better resolution
Ø Decreased motion related blurring
v Edge compression plate – straight or curved (not spoon shapped)
v Mo target and filter systems
Ø Tungsten anode and beryllium windows to permit passage of low keV photons. Must produce low keV spectrum
Ø Produced preferred high contrast
v Small focal spot 0.6mm
Ø Lesions 5 cm from detector
Ø Focal spot object distance >45cm
v Scatter reduction grids (stationary devices, focus grids, oscillating grids)
Ø Aid in diagnosis of breast (male and female)
§ >50% dense tissue
§ >6 cm compression thickness
v Magnification
Xerox vs Film/Screen
v Exposure latitude
v Dose
v Dedicated equipment
v Preference
v Economics
Clinical (Moore p632)
v Klinefelter Syndrome, the breast begin to enlarge at or soon after the onset of puberty. The breast usually slowly increase in size over a period of several years and then remain stationary.
v Gynecomastia: breast in males, consider XXY sex chromosome complex.
Ø Temporary gynecomastia may occur in response to pubertal hormonal stimulation
v Damage of the long thoracic nerve during radical mastectomy
Ø Winged scapula and inability to elevating the arm superior to the head.
v 1% Breast Ca in males
An average department talking part in the UK Breast Screening Program can expect to perform 10000 to 15000 screenings per year and upto 5000 symptomatic examinations per year.
Tidak ada komentar:
Posting Komentar