Flashcards in Dx testing and Pulmonary imaging Deck (76):
What are the dx tests used for dx pulmonary diseases?
- Chest CT
- Chest MRI
- V/Q scan
What is a bronchoscopy?
- direct visualization of trachea, bronchi, and segmental airways out to the 3rd generation of branching
- can be used to sample and tx lesions or abnormalities such as FBs, bleeding, tumors or inflammation in those airways
- can also be used as part of pre op evals
- may be rigid flexible or virtual
- may cause tachycardia, bronchospasm, or hypoxemia
- contraindicated in pts with cardiac problems or severe hypoxemia
What are the dx indications for bronchoscopy?
- atelectasis/ accumulated secretions
- unresolved pneumonia
- positive cytology
- bx of suspicious tissue
- abnormal CXR
- bronchial obstruction
- diffuse lung disease
- pre/post intubation
What are the therapeutic considerationf for use of bronchoscopy?
- accumulated secretions
- lung abscess
- control of bleeding
What are the advantages of a rigid bronchoscopy? disadvantages?
- advantages: better control of the airway, easier to deal with large lesions, foreign bodies
- disadvantages: requires general anesthesia, higher rate of tissue damage/complications
What are CIs to rigid bronchoscopy?
- absolute CIs: inability to adequately oxygenate the pt during procedure
- coagulopathy or bleeding diathesis that can't be corrected
- rigid bronchoscopy: aneurysm, marked kyphosis
- recent MI or unstable angina
- respiratory failure requiring mechanical ventilation
What are the components of the ventilating bronchoscope?
- light source and telescope
- prismatic light detector and attachment to light source
- telescope bridge
- aspiration and instrumentation channel
- connector to anesthesia
What are the complications of a ventilating bronchoscope?
- injury to teeth
- hemorrhage from the bx site
- hypoxia and cardiac arrest
- laryngeal edema
Use of the flexible bronchoscopy (pros and cons)?
- doesn't require general anesthesia
- mainly for dx purposes
- limited intervention (sunctioning)
- can be used for intubation
- limited airway control
- can do bx, minor cautery
- very few complications in healthy pts
Use of flexible optic bronchoscopy?
- provides magnification and better illumination
- smaller size: permits examination of subsegmental bronchi
- easy to use in pts with neck or jaw abnormalities
- can be performed under topical anesthesia and useful for bedside exam of critically ill pts
- sunctioning of bx channel helps to remove secretions, inspissated mucus plug and small FBs
- can be easily passed through endotracheal tube or in tracheostomy opening
- limited use in children because of problem of adequate ventilations
Use of the virtual bronchoscopy?
- computer generated pictures of the endobronchial tree, which are constructed from computed tomography (CT) images of the thorax
- non-invasive, fine detail, and also provides info about structures outside of the airways
- cant be used for bx or tx
Limitations of the CXR?
- 2 dimensional image of 3 dimensional structure
- x-ray findings may lag behind other clinical features
- normal x-ray doesn't rule out pathology
- dependent on good quality image
- ** not really helpful in PE dx
Hierarchy of relative densities from least dense (dark) to most dense (light)?
- gas (air)
- fat (fat layer in soft tissue)
- water (same density as heart and blood vessels)
- bone (the most dense of tissue)
- metal (fbs)
What 3 main factors determine the technical quality of the radiograph?
- inspiration: CXR should be obtained with the pt in full inspiration to help assess intrapulmonary abnormalities, at full inspiration the diaphragm should be observed at about the level of the 8th to 10th rib posteriorly, or 5th to 6th rib anteriorly
- penetration: the lower thoracic vertebrae should be visible through the heart, bronchovascular structures behind the heart (trachea, aortic arch, pulmonary arteries) should be seen
- rotation: can be assessed by observing the clavicular heads and determining whether they are equal distance from spinous processes of the thoracic vertebral bodies
Problems with underexposure and overexposure (penetration) of CXR?
- in underexposed CXR: cardiac shasow is opaque, with little or no visibility of the thoracic vertebrae
- the lungs may appear much denser and whiter, much as they might appear with infiltrates present
- overexposure: heart becomes radiolucent and lungs become proportionately darker, in an overexposed CXR: air filled lung periphery becomes extremely radiolucent and often gives the appearance of lackng lung tissue, as would be seen in condition such as emohysema
What are the 4 major positions that are utilized for producing a CXR?
- lateral decubitus
- std position for obtaining routine adult CXR
- pt stands upright with anterior chest placed against front of film
- shoulders are rotated forward enough to touch the film, ensuring that the scapulae don't obscure a portion of the lung fields
- usually taken with pt in full inspiration
- PA film is viewed as if pt is standing in front of you with his/her right side on your left
- pt stands upright with left side of chest against the film and arms raised over the head
- allows the viewer to see behind the heart and diaphragmatic dome
- is typically used in conjunction with a PA view of the same chest to help determine the 3D position of organs or abnormal densities
- ordered as PA and lateral views
- used when pt is debilitated, immobilized or unable to cooperate with PA procedure
- film is placed behind the pts back with pt in supine position
- because the heart is a greater distance from the film, it will appear more magnified than in a PA
- the scapulae are usually visible in the lung fields because they are not rotated out of the view as they are in a PA
The lateral decubitus position?
- pt lies on either right or left side rather than in a standing position as with a regular lateral xr
- XR is labeled according to side it is placed on
- often used in revealing a pleural effusion that can't be easily observed in an upright view, since effusion will collect in dependent position
What are the anatomical structures in the chest?
- lung fields
- diaphragmatic domes
- pleural surfaces
- soft tissues
Location of mediastinum?
- trachea should be centrally located or slightly to the right
- the aortic arch is the first convexity on the L side of the mediastinum
- pulmonary artery: next convexity on the left, the branches should be traceable as it fans out through the lungs
- the lateral margin of superior vena cava lies above the R heart border
Location of the heart on a CXR?
- 2/3 of heart should lie on L side of chest, 1/3 on R
- heart should take up less than half of thoracic cavity
- left atrium and left ventricle create the left heart border
- R heart border is created entirely by the R atrium (R ventricle lies anteriorly and therefore doesn't have border on PA)
Location of the hilum on CXR?
- Hila consist of primarily major bronchi and pulmonary veins and arteries
- the hila are not symmetrical but contain the same basic structures on each side
- the hila may be at same level but the left hilum is usually higher than the R
- both hila should be of similar size and density
Location of lungs on CXR?
- visible markings throughout lungs due to pulmonary arteries and veins, continuing all way to chest wall
- both lungs should be scanned starting at apices and working downward comparing the L and R lung fields at the same level (as done with ausculatation)
- on a PA: minor fissure can often be seen as faint horizontal line dividing RML from RUL
- major fissures arent usually seen on PA view
Location of the diaphragm on a CXR?
- left dome is normally slightly lower than R due to elevation of the liver, located under the R hemidiaphragm
- cosophrenic recesses are formed by diaphragms and chest wall
- on the PA: costophrenic recess is seen only on each side where an angle is formed by the lateral chest wall and the dome of each diaphragm (costophrenic angle)
- pleura and pleural spaces will only be visible when there is abnromality present
- common abnormalities seen with pleura include pleural thickening or fluid or air in pleural space
Soft tissue on CXR?
- thick soft tissue may obscure underlying structures:
thick soft tissue due to obesity may obscure some underlying structures such as lung markings
- breast tissue may obscure the costophrenic angles
- lucencies within soft tissue may represent gas
What bones will be visible in the CXR?
- proximal humeri
- the bones are useful as markers to assess pt rotation, adequacy of inspiration, and x ray penetration
Should you make a dx from an abnormal finding on a CXR?
- no only should describe what you see rather than a dx (a CXR alone isn't dx but is only one piece of descriptive info used to formulate a dx)
- descriptive words such as shadows, density, or patchiness, should be used
What is a silhouette sign?
- loss of lung/soft tissue interface due to presence of fluid in normally air filled lung
- if an intrathoracic opacity is in anatomic contact with a border then the opacity will obscure that border
What is an air bronchogram? seen in what conditions?
- a tubular outline of an airway made visible due to the filling of the surrounding alveoli by fluid or inflammatory exudates
- conditions such as:
non-obstructive pulmonary atelectasis
When will you see consolidation?
- lung is consolidated when the alveoli and small airways are filled with dense material
- dense material may consist of:
fluid (pulmonary edema)
blood (pulmonary hemorrhage)
What is atelectasis?
- almost always associated with a linear increased density due to volume loss
- indirect indications of volume loss include vascular crowding or mediastinal shift toward the collapse
- possible observance of hilar elevation with an upper lobe collapse or hilar depression with a lower lobe collapse
What will you see on a CXR of pneumonia?
- airspace opacity
- lobar consolidation
- interstitial opacities
What will a pleural effusion look like on a CXR?
- on upright film: effusion will cause blunting on the lateral costophrenic sulcus and if large enough on posterior costophrenic sulcus
- approx 200 ml of fluid are needed to detect effusion on PA film and 75 ml on lateral view
- in AP film: effusion will appear as a graded haze that is denser at the base
- a lateral decubitas film is helpful because fluid will collect on the dependent side
Pneumothorax on CXR?
- appears as air without lung markings
- in PA film: seen in apices since air rises to least dependent part of chest
- air is typically found peripheral to the white line of the visceral pleura
- best demonstrated by expiration film
Pulmonary edema on CXR?
- 2 basic types of pulmonary edema:
cadiogenic pulmonary edema: caused by increased hydrostatic pulmonary capillary pressure
- noncardiogenic pulmonary edema: caused by either altered capillary membrane permeability or decreased plasma oncotic pressure
What does CHF look like on a CXR?
- common features:
cardiomegaly: cardiothoracic ratio is greater than 50%
cephalization of pulmonary veins: raised
appearance of Kerley B lines
alveolar edema often present in a classis perihilar bat wing pattern of density
What does emphysema look like on CXR?
- hyperinflation with flattening of diaphragms
- increased retrosternal space, bullae, enlargement of PA/RV (cor pulmonale)
How will a lung mass appear on a CXR?
- typically present as a lesion with sharp margins and a homogenous appearance, in contrast to the diffuse appearance of an infiltrate
What can be scanned in CT?
performed with or w/o contrast
- IV contrast is used to obtain vascular and tissue enhancement for some CT scans
- any body part can be scanned (most helpful eval the brain, lung, mediastinum, retroperitoneal)
- measurements called hounsfield units are used to difff cysts, lipomas, hemochromatosis, vascular and avascular lesions (bone is +1000, water is 0, fat is -1000)
Usefulness of a chest CT?
- depicts more nodules than plain CXR
- useful in differentiating hilar adenopathy from vascular structures seen on plain CXR especially when contrast enhanced images are obtained
- high resolution images are useful for characterizing interstitial lung disease
- PE protocol scans are obtained with contrast enhancement on spiral scanner, frequently includes CT venography of lower pelvis and legs
What are the diff CT types?
- High resolution (HRCT)
- low dose
- CT angio
Indications for standard CT?
- slice thickness: 3-10 mm
- scans a large volume, very quickly
- covers full lung, can have +/- contrast
- indications: CXR abnormalitiy, pleural and mediastinal abnormalities, lung cancer staging, F/U metastases, empyema vs abscess
Indications of HRCT?
- narrow x ray beam collimation, 1-1.3 mm vs 3-10 mm
- cross sections further apart
- high def images of lung parenchyma: vessels, airspaces, airway and interstitial
- no contrast
-diffusely abnorm CXR
-normal CXR with abnorm PFTs
-baseline for pts with diffuse lung disease
-solitary pulm nodules
-reversible vs non-reversible (fibrotic) lung disease
-lung bx guide
-F/U known lung disease
-assess tx response
When is low dose CT used?
- wont reduce dx functionality of scan but detail is decreased
- uses: screening: smokers,or former smokers, ongoing trials
post lung transplant
When is angiography (CTA) used?
- contrast injected into peripheral vein
- injection timing/rate controlled automatically
- dye is where you want it during scan
- replaced conventional cath angiogram
iodinated contrast - allergic/nephrotoxic
Use of spiral CT?
- can be used with any type of CT
- tube spins around pt while table moves
- minimizes motion artifact and allows capture of a bolus of contrast material at peak levels in region being scanned
- useful in dx of PE, eval of flank pain, kidney stones and rapid eval of trauma
WHat are some common pathologic featurs on a chest cT?
- air bronchograms
- septal thickening
- ground glass opacity
- filling defect
air bronchograms on CT?DDX?
- bronchi become more visible due to increased attenuation of surrounding lung
- implies proximal bronchi patency
- excludes pleural or mediastinal lesion
Bronchiectasis on CT? DDx?
- 3 types: cylindrical, cystic and varicose
- dilation of medium sized bronchi (greater than 2 mm): leads to impaired clearance which leads to recurrent infection and bronchial damage
- HRCT is dx tool of choice
primary ciliary dyskinesia
alpha 1 antitrypsin deficiency
RA and Sjogren
Septal thickening on CT? most common causes?
- abnormalities of interlobular septa or peripheral alveoli
- thickening and outlining of secondary pulmonary lobules is best seen on HRCT
- often well depicted in apices
- most common causes: pulmonary edema, pulmonary hemorrhage, and lymphangitic cancer spread
Ground glass opacities on CT? DDx?
- common nonspecific finding
- decreased air content without totally obliterating the alveoli
- increased lung opacity not sufficient to obscure pulmonary vessles
-alveolitis or interstitial pneumonitis: HP, IPF, sarcoidosis
Emphysema on CT? DDx?
- perm enlargement of air spaces distal to terminal bronchioles
- destruction of the walls without obvious fibrosis
connective tissue disorders
What are the 3 types of emphysema?
- centriacinar/lobular: resp bronchioles - to periphery, upper half of lungs, from smoking
- panacinar: destroys entire alveolus uniformly, lower half of lungs, homozygous AAT deficiency
- distal acinar/paraseptal: distal airway, alveolar ducts, around lung septae or pleura, apical bullae may spont. pneumothorax
Nodules on a CT? diff b/t benign and malignant?
- CT can detect nodules 3-4 mm
benign: small, unchanged over 2 years, less than 15-20 HU, fat within, halo sign: ground glass surrounding nodule indicates infection
- malignant: enhancement of greater than 20 HU, caution: active granulomas/infectious lesions, spiculated, multiple
- circumscribed nodules: suspect metastatic disease, septated nodules, suspect primary lung malignancy
Filling defects on CT? DDx?
- PE is a well defined hypodensity in pulmonary artery
- CTA sensitive for PE (90%)
- can't eval arteries below 4th segmental level
anatomical landmarks and variants: intersegmental nodes, vascular tumor invasion, technical pseudo filling defects (flow artifact)
How does a MRI work?
- measurements of the magnetic movements of atomic nuclei are used to delineate tissues
- defined sequence of magnetic pulses and interval pauses produces measured changes in the magnetic vectors of tissue
- inherent tissue differences gives visual contrast in images seen on MRI
- MRI contrast: gadolinium is ionic contrast agent - enhances vessels and lesions of abnormal vascularity
What are the advantages of an MRI?
- no ionizing radiation
- display of vascular anatomy without contrast
- visualization of linear structures
- visualization of hard to see CT areas
- gives a clearer set of images than CAT scans
- slice images can be taken on many planes
Disadvantages of MRI?
- claustrophobia due to confining magnet - open MRI scanners, and sedation help
- pt size
- longer scanning time resulting in motion artifacts
- people with pacemakers cant have scan
- unable to scan critically ill pts requiring life support
- metallic fbs: pacemakers, shrapnel, CNS vascular clips, metallic eye fragments, cochlear implants are CIs
How is the MRI image made?
- pts are often injected with contrast dye during the scan: gadolinium
- the dye will reach diff tissues at diff rates
- image being sent back to computer will have diff strengths depending on level of contrast dye in the tissues
Indications for MRI?
- dx: MS, strokes, infections of brain/spine/CNS, tendonitis
- visualizing: injuries, torn ligaments
- eval: masses in soft tissues, cysts, bone tumors or disc problems
MRI specific for thorax imaging?
- mediastinal masses
- vascular abnormalities
- congenital abnormalities
- diff nodes from vessels
- tumor staging
- aortic dissection or aneurysm
- cardiac diseases
What is a VQ scan?
- type of imaging using scintigraphy to eval the circulation of air and blood within a pts lungs
- ventilation part: looks at ability of air to reach all parts of lungs
- perfusion: evals how well blood circulates within lungs
- relatively noninvasive
- remains initial test of choice in some places for PE
- preferred test in pregnant pts (50 mrem vs 800 mrem)
Indications of V/Q scan?
-most common: rule out or dx blood clot or abnormal blood flow inside lungs
- post lobectomy
Virchows triad for PE?
- hypercoagulability: malignancy, pregnancy, postpartum (less than 4 weeks), estrogen/OCPs
- stasis to flow: bed rest for more than 24 hours, recent cast or external fixture, long distance travel
- vessel injury: surgery or trauma (lower extremities, and pelvis)
Presentation of PE?
- pleuritic chest pain
- low grade fever
Radiographic eval of PE?
- V/Q scan
- spiral CT with contrast
- angiogram (gold std)
CXR of PE?
- initial CXR usually normal but may progress to show:
pleural effusion and elevated hemidiaphragm
(myth: you have to do a CXR to find hamptons hump or westermarck sign)
- most xrays in pts with PEs are nonspecific and insensitive
- westermarcks sign: dilation of pulmonary vessels proximal to embolism along with collapse of distal vessels sometimes with a sharp cutoff
- hamptons hump: triangular or rounded pleural based infiltrate or consolidation with apex towards hilum
V/Q scan procedure?
- gaseous radionucleotide such as krypton or xenon in an aerosol form is inhaled by the pt through a mask
- perfusion phase involves I/V injection of radioactive technetium macro aggregated albumin
- a gamma camera acquires the images for both phases of study
- V and Q phases of scan are performed together along with CXR for comparison or to look for other causes of lung disease
- normal: no perfusion defects or perfusion exactly outlines shape of lungs seen on CXR
Results of V/Q scan?
- normal perfusion scan: means the pt is very unlikely to have acute PE
- low prob V/Q scan: means pt has less than 20% prob
- high: means pt has greater than 80% prob
- intermediate: pt has b/t 20 and 80% prob of having acute PE
- artifacts may result from clumping of inhaled particles with severe airway disease or where errors occurred in prep or admin of particles
CI of V/Q scan?
- no absolute CI
- relative CI: pulm HTn or R to L shunts (VSD)
Advantages and disadvantages of spiral chest CT and PE?
- advantages: rapid and alt dx (lung mass, or atypical pneumonia)
- disadvantage: costly, risk to pts with borderline renal fxn, hard to detect subsegmental PE
Pulmonary angiogram use for PE dx?
- was the gold std but is invasive
- + angiogram = 100% certainity that an obstruction exists in pulm. artery
- negative angiogram provides greater than 90% certainity in exclusion of PE