Imaging of respiratory disease Flashcards
Basic lung anatomy
Anatomical position:
he lungs lie either side of the mediastinum, within the thoracic cavity. Each lung is surrounded by a pleural cavity, which is formed by the visceral and parietal pleura.
They are suspended from the mediastinum by the lung root – a collection of structures entering and leaving the lungs. The medial surfaces of both lungs lie in close proximity to several mediastinal structures:
Lung structure:
Each lung consists of:
Apex – The blunt superior end of the lung. It projects upwards, above the level of the 1st rib and into the floor of the neck.
Base – The inferior surface of the lung, which sits on the diaphragm.
Lobes (two or three) – These are separated by fissures within the lung.
Surfaces (three) – These correspond to the area of the thorax that they face. They are named costal, mediastinal and diaphragmatic.
Borders (three) – The edges of the lungs, named the anterior, inferior and posterior borders
Lobes:
The right and left lungs do not have an identical lobular structure.
The right lung has three lobes; superior, middle and inferior. The lobes are divided from each other by two fissures:
Oblique fissure – Runs from the inferior border of the lung in a superoposterior direction, until it meets the posterior lung border.
Horizontal fissure– Runs horizontally from the sternum, at the level of the 4th rib, to meet the oblique fissure.
The left lung contains superior and inferior lobes, which are separated by a similar oblique fissure.
Surfaces of the lungs:
There are three lung surfaces, each corresponding to an area of the thorax.
The mediastinal surface of the lung faces the lateral aspect of the middle mediastinum. The lung hilum (where structures enter and leave the lung) is located on this surface.
The base of the lung is formed by the diaphragmatic surface. It rests on the dome of the diaphragm, and has a concave shape. This concavity is deeper in the right lung, due to the higher position of the right dome overlying the liver.
The costal surface is smooth and convex. It faces the internal surface of the chest wall. It is related to the costal pleura, which separates it from the ribs and innermost intercostal muscles.
Techniques (projection) in PA axis
x rays are produced by x ray beam from the posterior to the anterior
so the heart is in the correct projection
detector of x rays in front of patient’s chest
pictures produced by x rays absorbed by dense material
bones are white because x rays are attenuated
lungs are black because x rays aren’t attenuated as much so attenuation is blackened
Lung zones
apical zone: above the clavicles
upper zone: below the clavicles and above the cardiac sillhouette
mid zone: the level of the hilar structures
lower zone: the bases
Left upper lobe and lingula:
in pneumonia chest infection- area of lung that is affected willl decrease in amount of air and therefore becomes lighter
pathology increases the density
Left lower lobe/right lower lobe/middle lobe/middle lobe ( shown by random white area)
sometimes infections don’t fill the entire lung and they cause rounded densities
Child with cough and fever
sometimes infections don’t fill the entire lung and they cause rounded densities
you can see a rounded lesion in this young patient
this is usually of no concern
Observation: round area of consolidation in the mid to upper zone of the right lung.
Interpretation: round pneumonia. This is seen in the early consolidative phase of pneumococcal pneumonia and is the most common cause of an apparent mass lesion in the paediatric chest.
Adult with cough and haemoptysis (CA lung or misplaced ET tube in bronchus)
central lung cancer mass
blocking entire lung
no lung enters entire lung
however, not necessarily does complete opacification of the chest mean that there is cancer
there are many other reasons why air entry to left lung can be blocked
eg this patient is in ITU- you can see the central line going down the jugular to give fluids
ET tube- endo tracheal tube is used for oxygenating the patient
opacification is the light area
Observations: 1- central mediastinal oval-shaped radiopacity 2- heart size normal, lungs clear.
Interpretation: suspicious mass
(C.T. scan with contrast will allow further assessment).
trachea slightly off
shows a mas projecting behind the heart
shows some patholgoy in this region
chest x ray no longer helps further
so now we need a CT to show strucutres behind the mediastinum
Pneumothorax
A pneumothorax is when air gets into the space between the outside of your lung and the inside of your chest wall, your ribcage.
here you can see outline of lung
you can see air between chest wall and lung itself
the lung is collapsed- a pneumothorax. The lung is not attached to the chest wall so if if air gets in between the lung and the chest wall, so air can get trapped in between
tension pneumothroax
nasogastric tube used for feeding the patient act in a similar way
increased pressure in the right lung in a pneumothorax can actually move the mediastinum and move towards the left lung.
medical emergency- needs chest drain
air can also be under the diaghragm- usually there should be no air at all
if there is air- this is indicative or a perforation or abdominal viscous (gastric ulcer of perforaiton of bowel)
this is a surgical emergency
gas bubbles on the left side are not as significant because you can have stomach gas bubbles project into this area
but on the right it is significant because this area is usually taken up by the liver so no gas should be seen in this region
How CT scanner works
CT can image the internal portion of organs and separate overlapping structures precisely
Computed tomography or CT, shows organs of interest at selected levels of the body with each scan being a single slice
x ray source moves around the patient
detector detects each individual slice
reconstructs the image of that slice
algorithim shows slice at that level
The scans are produced by having the source of the x-ray beam encircle or rotate around the patient. X-rays passing through the body are detected by an array of sensors. Information from the sensors is computer processed and then displayed as an image on a video screen.
you can analyse a pulmonary thrombus or embolism
part coming out of pulmonary artery shows filling defect with a clot
this is called a saddle thrombus because it is directly on the bifurcation and can extend into the periphery
V/Q scanning
sometimes patients can’t do ct scan
VQ scan done w gamma camera
Gamma camera
detects the source of the radiation to build a picture
multihole collimator -Sodium Iodide - Thallium activated scintillation crystal - light guide for optical coupling array of photo-multiplier tubes - lead shield to minimize background radiation
radioactive source injected into patient
emitted gamma rays channeled through collimator make sure they are coming through the patient and not through the side
hit a scintillation crystal
gives off light impulses
apparatus shielding from outside to avoid gamma rays coming from outside
reconstructed image
Investigation lung perfusion and ventilation with gamma camera
Perfusion
Tc Microaggregated Albumin (MAA)
Ventilation Krypton Xenon Tc DTPA Technegas (nanoparticles)
in a blood clot the ventilation and perfusion are reduced
perfusion: to find this we use technetium attached to albumin (MAA)
areas where the albumin does not pass through will be radioluscent- radiosotope doesn’t get to the area
whereas in an area of normal blood flow we will get signal from that area
ventiliated: area with clot will be less ventilated
we can use technetium attached to either nanoparticles or DTP. Patient breathes this in. Areas that are ventilated will show up on the scan
dark areas are where perfusion is reduced
correlate this with ventilation scan
if areas are dark for both perfusion and ventilations scan that can suggest different pathology
pulmonary embolism
ventilation will be normal, perfusion will be reduced
abnormal perfusion means high chance of PE
Condition for adult with mild cough and imaging
sarcoid and pulmonary fibrosis
Sarcoid
inflamed cells clump together to make small lumps called granulomas. These granulomas can develop in any part of your body. They are most commonly found in the lungs and the lymph glands which drain the lungs.
lots of spotty changes
this is a granulomatous disease called sarcoid
interstitial changes and calcification can be seen
OR
Pulmonary Fibrosis calcified asbestos plaques
similar changes seen in diseases that cause pulmonary fibrosis
this patient has been exposed to abestos
shows calcification of the pleura
better way of diagnosing these diseases rather than using x rays is CT
high resolution CTs show the details in high resolution
notice heavily calcified pleural plaque along chest wall
lungs are still dark and featureless but that’s fine because you can change the window settings
window settings mean it is possible to highlight things the human eye might miss out on
for example you can tell the CT computer that you’re interested in the soft tissue and that will produce the left image (the soft image)
when you change it back to bone setting you can’t distinguish the soft tissue changes as much anymore but on the right we are more interested in the overall lung structures
In pulmonary fibrosis, we can see changes called ‘honeycombing’-clustered cystic ari spaces
these are fibrotic chages (do not confuse with alveoli), these do not exchange oxygen
these are much bigger and are dead spaces within the lungs surrounded by thick fibrotic scar tissue
emphysema imaging
Observations: 1-hyperinflated lungs 2-flattened diaphragms 3-bullae (air filled space in lung parenchyma). If the bulla is ruptured more likely to be pneumothorax 4-small cardiac shadow. Interpretation: emphysema
CT:on the CT scan of emphysema you can see these dead spaces with no oxygenation of the blood, so these patients are short of breath
asthma imaging
Observations: hyperlucent lungs implying air trapping.
Interpretation: intrinsic airway obstruction
Diagnosis: Asthma .
hyperlucent lungs is often a sign of airway obstruction
muscles of bronchial walls are thickened and contracted
patient breathes in but there is significant resistance to breathing out
thickened bronchi and air trapping
when the patient breathes out the greyness of the lung increases
but where the air is trapped it remains consistently dark
Chronic chest infections: bronchiestasis
Bronchiectasis is a long-term condition where the airways of the lungs become abnormally widened, leading to a build-up of excess mucus that can make the lungs more vulnerable to infection.
The most common symptoms of bronchiectasis include:
a persistent cough that usually brings up phlegm (sputum)
breathlessness
whilst you get pathological constriction of the lungs,
you can get pathological dilatation of the bronchi
this patient has irregular shallowing throughout the lungs
prone to recurrent chronic chest infections
airways get dilated
in bronchiectasis, these dilated airways mean that mucous and bacteria are more likely to grow as well
respiration is reduced and gas exchage is limited, leading to fluid and mucus collecting in lumen and chronic lung infections
this patient has irregular shadowing throughout lungs
central line called port of cath shows this patient is going through treatment to avoid having recurrent infections- antibiotics get injected through this
Child with chronic cough and shortness of breath (CF imaging)
Observation: irregular shadowing throughout the lungs, central line “Port-a-Cath” suggesting longterm therapy.
Interpretation: consolidations and interstitial changes
Diagnosis: Cystic Fibrosis.
Respiratory infections underlie morbidity and mortality in most CF patients.
respiratory infections cause significant mrobidity in patients
ion channel CTFR mutation
2 membrane spanning domains and binding sites and a regulatory domain
exchanges chloride ions
