LEC 20: Introduction to Radiographic Anatomy Thoracic Imagining Flashcards
Plain radiograph
x-rays pass through tissues, based on density, and are detected on other side (image)
- (radiation!)
- 2-D project of 3-D object
- orthogonal projects can help localize objects and identify pathology
Fluoroscopy
moving/continuous x-rays often with contrast agent (radiation!)
CT (computed tomography)
similar to radiographs but the x-rays pass through the body in “all” directions (360 degrees) from a rotating source and are detected, used to generate slices through the tissues
- radiation!
- imagine walking into patient’s room and viewing slices from the foot of bed to the head
When are x-ray, fluoroscopy, and CT ill-advisded
pregnancy
- developing structures in first trimester are at increased risk of mutogenesis
- at end of pregnancy, fetuses that get irradiated have increased risk of childhood cancer (leukemia)
CT coronary angiography (CTA)
a computerized tomography (CT) coronary angiogram is an imaging test that looks at the arteries that supply your heart with blood
- radiation!
- less invasive than traditional coronary angiogram
MRI (magnetic resonance imaging)
uses body’s intrinsic magnetic properties to create images; spinning water hydrogen proton is a mini magnet in a larger magnet
- energy (RF pulse) sent in and signal comes out to produce image
- no radiation!
- no metal, not good for people with claustrophobia
Ultrasound
uses high frequency sound waves; different tissues reflect back more or less sound waves, detected by a hand held transducer to generate images
- portable, “real time” information
- no radiation!
Density principle
- bone/metal = white
- soft tissue = light gray
- fat = darker gray
- air = black
How is the anatomy of the thoracic cavity divided
- Pleural cavities
- Mediastinum
Contents of the pleural cavities
- pleura = made up of flat layer of mesothelial cells and supporting tissues
- lungs = respiratory organs
Pleura
2 layers:
- parietal layer = lines inner surface of chest cavity
- visceral layer = covers surfaces of the lungs
Parietal and visceral layers merge at the Hila of the lungs where vessels and airways pass in/out
Hila of the lungs
Where parietal and visceral layers of pleura merge; Hila is where vessels and airways pass in/out
Costodiaphragmatic recesses
area of pleural space where there is NO visceral pleura (or lung) between 2 parietal layers
- fluid accumulates here first
- many recesses in pleura
- costodiaphragmatic recess is the largest
- potential space
What is the motion of diaphragm when breathing in
Diaphragm moves down; creates negative interthoracic pressure so air will be sucked in
Pleural effusion
excess fluid builds up around the lung in pleural space (between visceral and parietal layers)
- hydrothorax (serous fluid)
- hemothorax (blood)
- chylothorax (chyle)
- pneumothorax (air)
- pyothorax (pus)
mesothelioma
pleural plaques due to asbestos exposure
lungs
- organs of respiration (gas exchange)
- fill the pleural cavities surounded by visceral (lung facing) and parietal (body wall facing) pleura
- straddle mediastinum
- divided into lobes
- lobes divided into bronchopulmonary segments
- areas of the lung supplied by segmental bronchus and pulmonary artery branches
left lung
- one fissure (oblique/major): divides lung into 2 lobes (upper and lower)
- left mainstream bronchus enters lung and then branches into upper and lower lobe branches
right lung
- two fissures (oblique and horizontal) divide it into 3 lobes (upper/middle/lower)
- right mainstem bronchus branches outside the lung into upper lobe branch and then branches inside lung
Lungs have dual blood supply
- pulmonary arteries
- R atrium–>R ventricle–>main pulmonary artery–>R/L pulmonary arteries (deoxygenated blood)
- bronchial arteries
- blood comes from aorta or its branches (oxygenated blood)
Divisions of Mediastinum
- can be divided into inferior mediastinum and superior mediastinum
- inferior mediastinum
- anterior
- posterior
- middle
- origins of great vessels
- heart
- pericardium
Contents of Mediastinum
- thymus (immune system, site of T-cell maturation)
- heart in pericardial sac
- major vessels
- trachea
- esophagus
- nerves and lymphatics
Position of heart in chest
- NOT straight up and down in chest
- apex points down, forward, to left
- base sits over diaphragm with right more forward than left
- major vessels enter/exit posteriorly at base
Right pump of the heart
carries deoxygenated blood from body to lungs
SVC/IVC–>R atrium–>R ventricle–>pulmonary arteries
–>lungs
Left pump of the heart
carries oxygenated blood from lungs
lungs–>pulmonary veins–>L atrium–>L ventricle–>aorta
–>body
dextrocardia
congenital birth defect where heart is pointed toward right side of chest (instead of normally pointing to the left)
What heart margins are visible in chest x-ray (right side)
- SVC
- R atrium
- IVC
- NOT R ventricle; heart is rotated
What heart margins are visible in chest x-ray (left side)
- Aortic arch
- pulmonary trunk
- L atrium
- L ventricle
Superior mediastinum
- R/L brachiocephalic veins
- thoracic aorta and major branches
- SVC
- Trachea
- Esophagus
- Thymus
- Phrenic and vagus nerves
- Left recurrent laryngeal nerve (passes under arch)
SVC syndrome
group of symptoms caused by obstruction of the superior vena cava (a short, wide vessel carrying circulating blood into the heart)
- 90% of SVC syndrome caused by cancer
