what are the different diagnostic imaging modalities based on?
sound, radiation, nuclear medicine and magnetics
how are diagnostic images produced?
by the interaction of energy with matter (tissue) densities
what is imaging modality selection based on?
- suspected pathology
- sensitivity and specificity
what is the primary question when it comes to radiology?
will the results change the way you manage your patient?
How are imaging studies used in making a diagnosis or tracking patient provement from treatment?
they are used to reduce the level of uncertainty
why is high sensitivity and high specificity important? What are some other factors to consider?
- we want a test to find what you're looking for and doesn't give false reports
- other factors to consider are: patient safety, medical history, availability, and timeliness
the probability that a test will be positive in a patient with the condition refers to what?
the probability that a test will be negative in a patient without a condition refers to what?
what is the sensitivity and specificity for a test based on?
a reference sample of patients in whom the diagnosis is known as determined by the gold standard
the probability that a given patient with a positive test has the condition refers to what?
Positive predictive value
the probability that a given patient with a negative test is free of the condition refers to what?
Negative predictive value
how are screening tests and specific tests used?
Initially you want a very sensitive test to detect all possible disease, then follow up with a highly specific test to eliminate false positives
what are the terms used for white when looking at conventional radio graphs?
Increased density or opaque.
what are the terms used for black when looking at conventional radiographs?
decreased density or lucent
what are the terms used for white when looking at computed tomography?
- Increased attenuation
what are the terms used for black when looking at computed tomography?
- Decreased attenuation
what are the chances used for white when looking at magnetic resonance imaging?
increased signal intensity
what are the terms used for black when looking at magnetic resonance imaging?
Decreased signal intensity
what are the terms used for white when looking ultrasounds?
- Increased echogenicity
what are the terms used for black when looking at an ultrasound?
- decreased echogenicity
what are the terms used for white when looking at nuclear medicine images?
Increased tracer uptake
what are the terms used for black when looking at a nuclear medicine image?
- Decreased tracer uptake
what are the terms used for white when looking at barium studies?
what are the terms used for black when looking at barium studies?
Which imaging study is best used for soft tissue, fluid, and blood flow?
ultrasound (ie, trans-esophophageal echocardiography; valves, ejection fraction)
Which imaging modality is best used when studying ribs, masses, fluid and air collections?
- Xray (CXR)
- ie, pneumonia, pneumo-/hemothoraces, CHF, pulmonary edema
Which imaging study provides a great resolution than CXR and is used to assess trauma, masses, and pulmonary perfusion?
- Computed tomography (CT)
- **Is the standard level of care in lvl I EDs**
Which imaging study is best used to assess physiologic function with tumors, cardiac function and metastases?
Nuclear medicine scans
Which imaging study is best used to examine exquisite soft tissue detail such as the spinal cord, and masses?
Magnetic resonance imaging (MRI)
What are the basic concepts and procedure to ultrasound imaging?
- Sound wave is created by a transducer
- Operator uses it to direct wave at region of interest
- Reflected sound returns to transducer
- Signal processor converts sound energy into an image
- Image is displayed on a screen
What term describes the progressive weakening of the U/S sound wave that occurs in several different ways?
What U/S term describes the tissue's ability to redirect sound waves back to the source?
What U/S term describes redirection of part of the sound wave as it crosses the boundaries of different mediums (tissues)?
What U/S term describes redirection of the sound wave away from the transducer when an irregular shape is encountered?
What U/S term describes sound waves absorbed in tissues, converted from acoustic energy to thermal energy?
What U/S term describes resistance of tissue to sound waves directly related to tissue density?
What U/S artifact can be caused by metal, bone, or calculi blocking the sound wave?
What U/S artifact is described as tapering bright echoes, caused by air bubbles, cholesterol crystals, or motion?
What is the image of an ultrasound based on?
- Strength of echo
- Time for echo to return to transducer
How is echo strength in an U/S determined?
A weaker echo or signal in U/S will produce what kind of image?
A stronger echo or signal in U/S will produce what kind of image?
What is U/S image depth based on?
How long it takes to "hear" the echo.
How are gases on an ultrasound interpreted?
- Low density
- Poor transmission
How are fluid filled structures on U/S interpreted?
- Anechoic, black
- Defined by walls
- Cysts, blood vessels
How are solid organs on U/S interpreted?
- Uniform transmission through tissue
- Speckled appearance due to lack of homogeneity
How is fat on U/S interpreted?
- Hyper-echoic relative to solid organ
- Outlines structures
What are some pathological changes that show up on U/S and what do they look like?
- Inflammation: increased thickness, reduces compressibility
- Mass effect distorts structures
What appears like a snow storm on ultrasound?
What tissue looks black on ultrasound?
What tissue gives an appearance of shades of grey on ultrasound?
What tissue looks white on ultrasound?
What are the uses for ultrasound in clinical evaluations?
- Cystic structures/abscesses
- Free fluid (ascites)
- Soft tissue studies
- Guiding biopsies
- Inflammatory changes
- Cardiac evaluations
What are the uses for ultrasound in emergencies?
- Ectopic pregnancy
- Ovarian torsion
- Testicular torsion
- Deep vein thrombosis
- Blunt abdominal trauma
- Focused assessment sonography in trauma (FAST)
What are the four views of a FAST exam?
- Cardiac views (substernal/parasternal): valuates for pericardial effusion
- Right Upper Quadrant (RUQ): free fluid (blood in abdomen), Morrison's pouch-most common site for free blood in abdomen
- Left Upper Quadrant (LUQ): free fluid around renal splenic flexure
- Pelvis: fluid around the bladder, Pouch of Douglas (females-recto uterine pouch)
What does the extended FAST exam look and evaluate for?
- Looks for pneumothorax: US has better specificity and sensitivity than chest X-rays, almost equivalent to CT
- Evaluates for fluid in chest cavity: hemothorax
What are the advantages of using ultrasound?
- Excellent for soft tissue studies: abdominal, OBGYN, inflammation, masses, fluid collections (blood)
- Blood flow: electrocardiography, DVT
- Rapid results and widely available: trauma
- Safe: no ionizing radiation (peds, OB), non invasive
What are disadvantages to using ultrasound?
- Operator dependent
- Obesity (increased attenuation)
- Bowel gas (prevents imaging deep structures)
- Bone density (limited musculoskeletal eval)
What studies are included in radiography?
What imaging studies utilize x-rays?
- Electromagnetic wave
- Conventional X-rays and CT imaging
- Ionizing radiation
What imaging studies utilize gamma rays?
- Nuclear imaging
- Ionizing radiation
Bone attenuates ____ radiation than soft tissue.
Why do denser tissues produce lighter images?
more attenuation=less x-rays reaching the film
As an object moves away from the x-ray photoreceptor, what happens to it's shadow?
It becomes larger
How many imaging views are needed to localize an object?
Two (orthogonal views)
What provides uniform technique for all countries that allows comparison of studies over time by standardizing magnification and distortion?
How is an upright PA and lateral routine chest x-ray taken as directed by the international standard?
- 72 inches from source to "bucky"
- Lateral with left side against "bucky"
What are the patient positioning standard views?
- Upright PA and Lateral (routine films): lungs at full inspiratory effort
- AP and Supine (portable films): lungs appear hypo-inflated, heart appears enlarged
- Lateral decubitus film: aids in identifying free fluid/air
What is an example of patient positioning or non-standard views?
- Positioning can be adjusted to enhance study
- Expiratory film is used to assess airway obstruction (asthma/foreign body in airway)Lordotic exposure to assess lung apices
What are the advantages of using x-ray?
- Widely available
- Sensitive and specific for bony lesions
What are the disadvantages of x-ray?
- Low resolution
- Poor soft-tissue visualization (contrast)
- Radiation exposure
What imaging study utilizes advanced x-ray technology, taking images in "slices" 1mm wide?
Computer tomography (CT)
What does the computer allow for as far as imaging while performing a CT? Which settings govern sensitivity for tissue?
- Multi-planar imaging
- "Window" settings adjust energy level of radiation beam depending on tissue (important to specify objective in consult)
What are the indications for using computerized tomography (CT)?
- Evaluation of internal organs, trauma, and masses
- Required for level I trauma center designation
What are the advantages of computed tomography (CT)?
- Higher sensitivity and specificity than plain film
- Greater resolution than plain-film
- Widely available
What are the disadvantages of computed tomography (CT)?
- More expensive than plain films
- Increased radiation exposure
Which soft tissues limits the usefulness of imaging studies because of their radiolucency?
- Urinary tract
What are contrast agents used to enhance visualization in imagining studies generally composed of?
Metallic substances (barium, gadolinium)
What are contrast agent reactions related to?
- Osmolarity of agent
What body systems can contrast agents affect?
How are reactions to contrast agents categorized?
- Mild: nausea, vomiting, temperature sensations, urticaria, sneezing, bradycardia/tachycardia, arm pain
- Intermediate: extensive urticaria, angioedema, bronchospasm, HOTN
- Severe (anaphylaxis): cardiopulmonary collapse, pulmonary edema, refractory bronchospasm, HOTN (fatality rate= 1:40,000-1:75,000)
What contrast agent side effect occurs when the agent interacts with Glucophage? How is this treated?
- Lactic acidosis
- D/C Glucophage for at least 48 hrs after IV push
What side effect can occur with the use of gadolinium contrast used in MR studies?
Nephrogenic systemic fibrosis
What side effect can occur with the use of iodinated agents injected IV with (rapid) renal clearance?
When are iodinated contrast agents contraindicated?
In the setting of compromised renal function or myeloma.
A dose of radiation is the _______ of the radiation multiplied by the _______ of the exposure.
What are the biological effects of ionizing radiation?
- Intra-cellular free radical formation (peroxidases): may react with and damage DNA
- Cellular damage correlates with dose: repair mechanisms are overwhelmed leading to permanent damage or death, genetically damaged cells may produce abnormal cells that can become cancerous
What are the things that influence the risk of developing biological effects from ionizing radiation?
- Probability of interaction
- Probability of repair
- Probability of mutation
- Probability of inadequate immune response
What are the diagnostic modalities used in nuclear medicine?
- Scintigraphy: bone scans
- Positron emission tomography (PET): metabolic activity-tumor, myocardial viability, and brain metabolism
- Single photon emission computed tomography (SPECT): for evaluating bone disorders
- Co-Registration: PET or SPECT in conjunction with MRI or CT
What are some examples of information on physiologic function provided by nuclear medicine diagnostic imaging studies?
- Coronary artery perfusion and cardiac function
- Lung scans for respiratory and blood flow problems
- Inflammation and infection
- Orthopedic fractures, infection, arthritis and tumors
- Cancer detection, localization, and staging
Which nuclear medicine diagnostic modality indicates increased metabolic activity by showing "hot spots" where uptake is high, uses low radiation exposure and has extensive application in many specialties such as orthopedics, cardiology, endocrinology, etc?
Scintigraphy (molecular imaging)
Which nuclear medicine diagnostic modality uses radioactively labeled glucose to identify tumors and staging in lung nodules and mediastinal lymph nodes? What are the advantages to using this method?
- Positron emission tomography (PET)
- Decreases need for invasive procedures, and can detect occult metastatic disease in normal sized lymph nodes and extra thoracic sites
What are the radiation exposure risks to nuclear medicine studies?
- Low energy gamma and positron radiations
- Low exposure (dose): comparable to x-rays/natural background radiation
- Low risk: rapidly metabolized and excreted in healthy pts
How does magnetic resonance imaging produce an image?
- Radiofrequency field is rapidly cycled (pulsed)
- Pulsing creates magnetic field
- Magnetic field aligns proton spin
- Continued pulsing increases magnetic field strength
- Field intensity increases resulting in greater alignment of proton spin
- RF field is turned off
- Protons return to randomized orientation (spin decays) with RF emission
- Computer converts received RF signal into image
What are some contraindications for MRI?
- Retained metal objects: orthopedic hardware, shrapnel, etc
- Pacemaker: electromagnetic field can disrupt operation
- Claustrophobia: cramped and loud
What are the indications for using MRI?
- Neurology/CNS eval
- Head trauma (TBI, cognitive function, mapping)
- Pediatric studies (concerns about radiation)
- Normal CT in setting of positive physical exam findings
- Soft tissue studies
What are the advantages to using MRI?
- No ionizing radiation
- Cross sectional, multi planar imaging
- Non-invasive vascular imaging (flow imaging)
- High sensitivity and specificity for soft tissue
- High contrast resolution
What are the limitations to using MRI?
- Lengthy exam
- Noisy environment
How are posterior ribs differentiated from anterior ribs on an x-ray?
- Appear more prominent on frontal CXR
- Oriented more or less horizontally
- Attach to a thoracic vertebral body
How are anterior ribs differentiated from posterior ribs on an x-ray?
- Less prominent than posterior ribs
- Oriented toward the feet (45° angle)
- Attach to sternum or each other with cartilage typically not visible until later in life when cartilage may calcify
What are the "blind spots" when looking at an x-ray that shows a lateral view of the thoracic cavity?
- Retro-sternal space
- Retro-cardiac space
- Hilar regions
Which lung fissure separates the right lower lobe from the middle and upper lobes?
Right Major Fissure
Which lung fissure separates the right upper lobe from the middle lobe?
Right Minor Fissure
Definition: bounded anteriorly by the sternum; posteriorly by the pericardium, aorta, and brachiocephalic vessels; superiorly by the thoracic inlet; and inferiorly by the diaphragm.
Anterior Mediastinum (Felson Method)
Definition: bounded anteriorly by the pericardium, posteriorly by the pericardium and posterior tracheal wall, superiorly by the thoracic inlet, and inferiorly by the diaphragm.
Middle Mediastinum (Felson Method)
Definition: bounded anteriorly by the posterior trachea and pericardium, anteroinferiorly by the diaphragm, posteriorly by the vertebral column, and superiorly by the thoracic inlet.
Posterior Mediastinum (Felson Method)
What are the contents of the anterior mediastinum according to the Felson Method?
- Lymph nodes
- Adipose tissue
- Internal mammary vessels
- Thyroid (if it extends into the mediastinum)
What are the contents of the middle mediastinum according to the Felson Method?
- Ascending and transverse aorta
- Superior vena cava (SVC) and inferior vena cava (IVC)
- Brachiocephalic vessels
- Pulmonary vessels
- Trachea and main bronchi
- Lymph nodes
- Phrenic, vagus, and left recurrent laryngeal nerves
What are the contents of the posterior mediastinum according to the Felson Method?
- Descending aorta
- Azygos and hemiazygos veins
- Thoracic duct
- Vagus and splanchnic nerves
- Lymph nodes
What are some pathologies that occur in the anterior mediastinum?
- thyroid mass
What are some pathologies that occur in the middle mediastinum?
- neoplasia (benign/malignant)
- ascending aortic aneurysm/dissection
What are some pathologies that occur in the posterior mediastinum?
- descending aortic aneurysm/dissection
- lymph nodes
- neurogenic tumors
What defines a technically adequate chest radiograph?
- Penetration: overexposure/underexposure (should see spine through heart)
- Inspiratory effort: visualize at least eight to nine posterior ribs
- Rotation: medial ends of clavicles equidistant to spinous process
- Magnification: AP (portable) will magnify heart slightly
- Angulation: clavicle normally has an "S" shape and superimposes on the third or fourth rib
What allows viewers to adjust image exposure quality, review old images for comparison, and helps to reduce duplicate imaging (decreasing ionizing radiation exposure)?
Picture Archiving and Communications Systems (PACS)
What causes false enlargement of the heart and difficulty in evaluating lung fields when looking at a chest x-ray?
If spinous processes are closer to the right clavicle, which direction is the patient rotated?
Toward their Left
If spinous processes are closer to the left clavicle, which direction is the patient rotated?
Toward their Right
X-ray beams angled towards the head (pt is semi-recumbent) is called what?
Apical lordotic view
What differences in structures do apical lordotic films project? What were they previously used for?
- Unusually shaped heart, and absent border between the heart and left hemidiaphragm.
- Were used to get views of lung apices without interference of clavicles (rarely used now due to CT).
What structures in the thoracic cavity become distorted on x-rays as a result of a slight rotation?
- Anatomic appearance of the heart
- Great vessels
What are the characteristics of now the lungs and heart appear on routine films (PA upright and lateral)?
- Lungs at full volume show diaphragm at 10th rib
- Cardiac shadow is less than half the chest width
What are the characteristics of how the lungs and heart appear on an AP, supine, and portable film?
- Lungs appear hypo-inflated
- Heart appears enlarged
What does a lateral decubitus film particularly aid in identifying?
Describe the general systematic approach to evaluating a CXR.
- Verify patient ID (correct patient)
- Verify date of study (correct date)
- Inspect the technical adequacy of the film (penetration, inspiration, rotation, magnification, angulation, full fields of lungs)
What does the acronym RIP ABCDEfGH stand for as far as evaluating a CXR?
- Rotation: look at the clavicles
- Inspiration: should see 9 ribs on each side
- Penetration: should faintly see thoracic spine through heart shadow
- Airway: lucency from neck down to the carine, should be midline, should see bronchi split from it
- Bones: look at shoulder joint and each rib contour for fractures/other abnormalities
- Cardiac silhouette: check the right and left heart borders
- Diaphragms: should be well defined, no obscuration of margins
- Empty fields (lungs): look at lungs bilaterally and compare
- Gastric bubble: lucency in left upper abdominal quadrant
- Hardware: make sure placement of any lines/other hardware is appropriate
What does the acronym CRIPS ABCDEfGH stand for as far as evaluating a CXR?
- Costophrenic angles: ensure full lung field
- Soft tissue: check tissues outside of bony framework & breast shadows
- Cardiac silhouette
- Empty fields
- Gastric bubble
What are the characteristics of thoracic structures on an expiratory film? When are they typically requested?
- High diaphragms, widened cardiac silhouette, crowding of normal lung markings.
- Requested for foreign body obstruction.
X-ray penetration: causes a dark image, can be useful in emphasizing dense structures and retro-cardiac areas.
X-ray penetration: causes a white image.
X-ray penetration: pulmonary vasculature (blood filled) seen to peripheral one-third of image, thoracic vertebrae and hemidiaphragms visible behind the cardiac silhouette.
Normal (proper) exposure
What are the characteristics of seeing breast shadows on a chest x-ray?
- Usually involves females, but men can have them too
- May cause density effects (apparent consolidation)
- Mastectomy (loss of density, increased lucency, loss of bilateral symmetry, check for masses)
- Nipple shadows may appear as nodules
What are the things you HAVE to look at when viewing a chest x-ray?
- Soft tissues
- Bony framework
- Mediastinum & heart
- Pleura & diaphragm
- Hila & lung fields
- Pulmonary vasculature
- "Blind spots" (retrocardiac, hemi-diaphragms, costophrenic angles, lung apices, scapulae)
When looking at a chest x-ray what things should you pay attention to when doing a mediastinal evaluation?
- mediastinum position: mid-line/shifted
- hila: left should be higher than right
- pulmonary vasculature: increased, normal, or decreased
- lymph nodes: should not be seen in hilar region or mediastinum
- lateral film: compartments and "blind spots"
Which chest x-ray is valuable for localizing a lesion seen on frontal CXR, clarifying lobar collapse/consolidation, evaluating a retrosternal or retrocardiac shadow, and confirming the presence of encysted fluid (loculated) in the oblique fissure?
Lateral chest x-ray
What are the "blind spots" on a lateral view CXR?
- Hilar regions
- Posterior hemi-diaphragms
- Costo-phrenic angles (small effusions)
- "Spine Sign"
What is especially useful for differentiating aggressive from benign lesions, and evaluating changes in preexisting disease in a CXR?
Compare current film to old films
What are evidence of pathologies when looking at a CXR?
- Deviation from anatomical norms
- Loss of expected symmetry
- Displacement of structures
- Disruption of normal contours
- Fluid collections
What can a pulmonary inflammatory response lead to?
- Abscess formation: thick walled cavity w/fluid inclusion
- Granuloma formation: solid mass
- Fibrotic changes: thickened tissue w/ reduced compliance (elasticity)
What are examples of airway pathology?
- Obstruction: partial/complete, mass effects, foreign body aspiration, mucous plugging, edema, may lead to atelectasis
- Inflammation: acute- asthma, infection, chemical irritation/ chronic- bronchitis, emphysema
- Structural change: blebs and bulae
- Genetic: cystic fibrosis
What are some pathologic changes that can occur in the airway?
- Obstruction: restrict air movement, may lead to lung hypo inflation, collapse of lung (atelectasis)
- Inflammation: fluid accumulation, white appearance, hypertrophy or scarring ("thickening") of structures
- Genetic: high viscosity secretions
What are some things that can cause an airway obstruction?
- Lung tumors, mucous, foreign body, edema
- Inadequate inspiratory effort
- Partial or complete obstruction
- Resorption of air
Definition: collapse or incomplete expansion of the lung or part of the lung (single lobe/part of a lobe).
How does atelectasis appear on x-ray?
- Opaque (decreased air/increased density)
- Linear (discoid), lobar/round
- Round atelectasis gives appearance of tumor on plain x-ray (best eval by CT)
- **almost always linear with increased density on the x-ray with the apex at the HILUM**
What side do structures get displaced in atelectasis?
Toward affected lobe/segment
In which patients is atelectasis very common?
What are indications for further eval of atelectasis with bronchoscopy or CT?
- Entire lung atelectasis
- Atelectasis of a lob of more than 2 days
- Atelectasis of a segment of more than 2 weeks
- Round atelectasis
- Other findings on CXR (lymphadenopathy, tumors, etc)
When would a CXR be indicated for asthma/reactive airway disease?
- Suspicion of infectious process or aspiration of a foreign body
- Chronic/long standing asthma (may show interstitial pattern caused by scarring/mild bronchiectasis)
Definition: localized irreversible dilatation of part of the bronchial tree, thickening of bronchial walls ("tram tracking"-parallel line opacities), cartilage damage from chronic inflammation, reduced bronchial compliance, and best evaluated by CT.
How is emphysema diagnosed? What does a CXR look like in early stages of disease?
What are the indications for doing a CXR for suspected emphysema?
- Exacerbation of symptoms
- Weight loss
- Suspected pneumonia
What are indications on a CXR of hyperinflation seen in advanced stages of emphysema?
- Hyper lucent (dark) lung fields
- Increased retrosternal space
- Vertical heart
- Flattening of hemidiaphragms with blunting of costophrenic angles best viewed on lateral x-ray
- Increased AP diameter of chest of lateral view
- Presence of bullae or large air cavities
What is the appearance of blebs or bullae on CXR?
- Parenchyma without alveoli
- Distinction based on size (bullae >1 cm, blebs <1 cm)
- Thin walled (suggests non-inflammatory, difficult to see on CXR, CT more sensitive)
What are some lung parenchymal pathologies?
- Inflammation (infection, chemical irritation)
- Cardiogenic (pulmonary edema)
- Cavitation and abscesses (gram neg bacteria)
- Pulmonary nodules/masses (granulomas, tumors)
When evaluating lung parenchymal pathologies what are you looking for?
- Location: interstitial/alveolar, lobar involvement
- Cavitation/abscess: wall thickness, air-fluid levels
- Masses/nodules: check if margins are smooth or irregular (comparison films helpful!)
What makes the gray outline or shape of the lung on an x-ray? What are the white lines that are visible on a lung x-ray, mostly in healthy lung tissue?
- Combination of the thin-walled alveoli and bronchi and blood vessels
- White lines are the blood vessels (branch and taper starting in the hila and extend peripherally)
How is airspace disease differentiated from interstitial disease in the lungs on x-ray?
- Appearance described as wispy, fluffy, cloudy or hazy
- Opacities merge into one another
- Margins are indistinct
- Air bronchograms may be present
- Creates silhouette sign
How is interstitial disease differentiated from airspace disease in the lungs on x-ray?
- Discrete reticular, nodular, or reticulonodular pattern
- "Packets" of disease separate and discrete from normal tissue
- May be focal or diffuse
- Air brochograms usually NOT present
Definition: fluid, soft tissue swelling or inflammation replaces the air around bronchus, which then causes the air filled bronchus to show up as a series of black, branching tubular structures on x-ray.
Definition: common in airspace disease, occurs when 2 objects of the same radio density touch each other causing the margin between them to disappear on x-ray (useful in localizing abnormalities).
Definition: opacification of vertebral bodies in the lower thoracic spine on lateral view x-ray.
What causes a spine sign to show on an x-ray?
- Vertebrae normally become darker caudally
- Accumulation of fluid or mass increases vertebral density which results in opacification of the vertebral column
What are some lung airspace pathologies?
- Community-acquired pneumonia
- Aspiration pneumonitis
- Pulmonary edema
- Acute Respiratory Distress Syndrome (ARDS)
How are x-rays used for confirmation and follow-up on pneumonia?
- PA and Lat are used for accurate localization
- Presence of alveolar, interstitial, round or mixed patterns of inflammation
When evaluating an x-ray for confirmation of pneumonia, what does the x-ray NOT indicate?
What is the location of a lobar (segmental) pattern of inflammation of a chest x-ray suggestive of? What about a diffuse pattern?
- Suggestive of etiologic agent but is not diagnostic
- Diffuse pattern may indicate immunocompromised condition
What kind of pathogen commonly causes upper lobe pneumonia?
What are the typical pathogens that cause segmental pneumonia?
- Staphylococcus aureus
Which type of pneumonia is more common in children than adults and can simulate a mass lesion such as a neoplasm?
What are the common pathogens that cause round pneumonia?
- Haemophilus influenza
What fungal pathogen causes pneumonia in immunocompromised hosts?
What is the progression of disease in an immunocompromised patient with pneumonia?
- Uncontrolled dissemination of pathogens
- Rapid evolution from interstitial to alveolar pattern
- Adenopathy and pleural effusions are uncommon
What initially appears as an alveolar infiltrate caused by inhalation of gastric contents (near drowning, etc) which has a radiographic appearance that develops over several hours (initial CXR normal, repeat in 12 hrs), and may progress to pulmonary interstitial edema?
Aspiration pneumonitis (keep pt under observation!)
What appearance does fluid in the alveolar space have in a CXR?
White shadows ("patchy", "cloud-like", "cluster of grapes")
How do the discrete "particles" of disease appear on CXR in a patient with interstitial lung disease?
- Reticular: network of lines
- Nodular: assortment of dots
- Reticulonodular: both lines and dots
- Tend to be heterogenous: separated from normal areas of lung with sharp margins
- Usually show NO air bronchogram
What are the pitfalls of interstitial lung disease evaluation with CXR?
- Several overlapping "packets" of interstitial lung disease creates the appearance of airspace disease.
- Blood vessels viewed on-end may mimic small pulmonary nodules.
What are the solutions to the pitfalls of CXR evaluation of interstitial lung disease?
- Look at the periphery of the overlapping packets to find discrete lines or dots of interstitial lung disease.
- Vessels will have "lines" leading up to the dots and will not appear in the orthogonal views.
- Other vessels in the region will be approx the same save, where nodules will be disproportional to the vessels.
What are the causes of interstitial lung disease based on the patterns of infiltrate on CXR?
- Reticular patterns: pulmonary fibrosis, rheumatoid lung, pulmonary interstitial edema
- Nodular patterns: bronchogenic carcinoma, metastatic lung disease
- Reticulonodular patterns: sarcoidosis
What are the CXR findings in a patient with idiopathic pulmonary fibrosis? How is it best evaluated and in which pt population does it usually occur?
- Fine to course reticular pattern
- Best evaluated by CT
- Usually occurs in older males (SOB & cough)
What pattern on interstitial infiltrate appears in CXR in a pt with rheumatoid lung disease?
Predominantly reticular pattern in the lung bases.
How does rheumatoid lung disease manifest?
- Pleural effusions
- Interstitial lung disease
- Nodules called necrobiotic nodules
- Pleural effusions are usually unilateral and remain unchanged for long periods of time
What are the causes for pulmonary interstitial edema?
- Increase capillary pressure (CHF)
- Increased capillary permeability (allergic reactions)
- Decreased fluid absorption (lymphatic drainage blocked by metastatic tumor)
What is pulmonary interstitial edema aa precursor to?
Alveolar edema (airway disease)
What are the four key ways in which pulmonary interstitial edema appear on CXR?
- Fluid in fissures (both major and minor)
- Peribronchial cuffing
- Pleural effusions
- Kerley B lines
Definition: fluid in thickened interlobular septa.
Kerley A and B lines
What are the four major cell types of bronchogenic carcinoma?
- Squamous cell
- Small cell
- Large cell
Adenocarcinomas in the lungs can present as ______ nodule that usually appears more sharply ______, and is best evaluated by ______.
- CT scan
What are the 3 categories that metastases to the lung are divided into? What appearance does each generally give?
- Hematogenous: produces "cannonball" appearance
- Lymphatic: resembles pulmonary interstitial edema, but more localized
- Direct spread/extension: least common, have local pleural based mass with adjacent rib destruction
What are the two types of primary tumors that metastasize to the lung, and what cancers do they metastasize from?
- Nodular metastatic tumors: breast, colorectal, renal cell, bladder, testicular, malignant melanoma and soft tissue sarcomas
- Lymphatic metastatic tumors: breast, lung, stomach, pancreatic and prostate
What lung infection is seen as bilateral hilar and paratracheal adenopathy (on the right), often with interstitial lung appearance, and progresses to interstitial disease? What is the prognosis for most patients with this condition?
- Most pts have complete resolution
What are some pleural pathologies?
- Subcutaneous emphysema
- Pleural effusions
- Pleural calcifications and masses
What is the radiographic appearance of a pneumothorax?
- Thin white line (MUST BE PRESENT!)
- Area of no vascularity perpheral to costal margin (edge of ribs)
- Deep sulcus sign (supine AP CXR)
What are the general causes for pneumothorax?
- traumatic cause
What can appear as a pneumothorax on CXR?
Is the absence of peripheral vascular markings on CXR sufficient to diagnose pneumothorax? If not, what is?
- Visceral white line is definitive!
What are other lesions or artifacts that may mimic a pneumothorax on CXR?
- Bullous emphysema
- Skin folds
To what side do mediastinal structures shift in a pt with a pneumothorax?
The unaffected side
Definition: fluid in the pleural space.
What is the appears of a pleural effusion on CXR?
Increased radiodensity from normal parenchyma.
What are the pathologies that can cause pleural effusion?
What are the causes of hemothorax?
- Blunt/penetrating trauma
- Neoplasia, bleeding dyscrasias
What is the primary diagnostic study performed for evaluation of a hemothorax? What are other imaging studies used for further evaluation?
- upright CXR
- U/S (FAST scan), CT (later in course of evaluating trauma)
Definition: pus in the pleural space caused by infection, post-surgical or post-traumatic injury, often appears elliptical on radiographic scans, and may be loculated (encapsulated).
Empyema (CT scan indicated to guide therapy)
Definition: difficult to differentiate, dx based on history and clinical exam, typiciallly require higher level imaging (CT, MRI, etc).
What type scan is indicated for work-up of suspicious mediastinum lesions?
CT scan/MRI with contrast
What is the most common primary tumor of the anterior mediastinum in adults? Where is it normally seen on lateral view x-ray? What are some other lesions of the anterior mediastinum?
- Retrosternal space
- Thyroid lesions, teratoma, t-cell lymphoma, lymphadenopathy
What is the most common middle mediastinal lesion? What are some other causes of middle mediastinal lesions?
- Thoracic aortic aneurysm, hematoma, neoplasm, esophageal lesion (hiatal hernias), and diaphragmatic hernia
What scans are always indicated for further evaluation of mediastinal lesions?
CT scan/MRI with contrast
What are the most common posterior mediastinal lesions (90%)? What are some other lesions that occur in the posterior mediastinum?
- Neurogenic lesions
- Descending aortic aneurysm, neoplasms, hematomas
What is the preferred imaging modality to further evaluate posterior mediastinal lesions?
What are two general things to keep in mind when trying to differentiate mediastinal from lung tissue masses on CXR?
- Margins of mediastinal masses are sharper
- Mediastinal masses frequently compress or displace mediastinal structures
What are pathological changes that occur in the lungs due to nodules?
- Alveolar infiltrate
- Calcified lymph nodes
- Parenchymal calcification
What may be the only manifestation of primary TB, especially in children?
Unilateral hilar adenopathy
If pneumonia is present along with a primary TB infection, how does it appear on CXR?
Ill-defined localized "atypical" pneumonia
Definition: inflammatory response to TB bacilli, fibrosis and calcification results in an opaque spheroidal lesion on x-ray.
Definition: pulmonar granuloma + lymph granuloma seen with TB on x-ray.
Cavitary upper lobe pneumonia is presumptively ___ until prove otherwise.
What kind of TB infection affects apical/posterior segments of upper lobes OR superior aspects of lower lobes?
Postprimary TB (reactivation)
What are the findings on x-ray typically associated with primary tuberculosis?
- Affects upper lobes slightly more than lower lobes
- Cavitary pneumonia is rare (thin walled, smooth inner surface)
- Ghon focus
- Ghon complex
- Caseous necrosis
What are the findings on x-ray typically associated with reactivation TB?
- Cavitation common (thin walled, smooth inner margin)
- Bilateral upper lobe disease very common
- Trans-bronchial spread (TB from upper lobe to opposite lower lobe or to another lobe)
- Ghon complex (calcification of healed site of infection)
- Disseminated spread (miliary TB)
What type of TB appears as diffuse bilateral nodular infiltrates in a late phase of TB? What are other etiologies that have a similar appearance?
- Miliary TB
- Histoplasmosis, varicella pneumonia, metastatic thyroid cancer, and melanoma
Definition: multisystem inflammatory disease of unknown etiology that predominantely affects the lungs and intrathoracic lymph nodes?
How is the prognosis for a pt with sarcoidosis determined? What makes the prognosis worse?
- Radiographic findings
- More parenchymal "airspace" disease
What condition presents with radiographic findings of adenopathy that is usually very symmetric, shows interstitial disease more pronounced in upper lungs and shows air space disease?
Definition: group of pulmonary diseases caused by inhalation of inorganic dusts such as coal dust, asbestos, or silica.
What are the characteristics of pneumoconiosis, what infection does it increase the risk of getting, and what may obscure radiographic appearance of silicosis?
- Neoplastic granulomatous nodular and fibrotic changes on imaging studies
- Increases risk (3 fold) of mycobacterial infections
- TB may obscure appearance of silicosis
What makes up 80% of solitary pulmonary nodules?
Cancer or granuloma
What is the 3rd most common cause of a solitary pulmonary nodule? What are some other etiologies?
- Other etiologies: septic embolus (from R heart), AV malformation
What is the presentation in a patient who is a good candidate for lung cancer?
- Typically asymptomatic for cancer (variable)
- May have symptoms of hemoptysis, cough, chest pain, SOB
- Usually an incidental finding in work-up for another pathology
- **LOOK AT THE WHOLE IMAGE!**
What is the best imaging study to use when evaluating and staging lung cancers?
CT scan with IV contrast
How are lung cancers classified?
- Small cell lung cancer (SCLC): aka "oat cell" cancer
- Non small cell lung cancer (NSCLC): adenocarcinoma, squamous cell, and large cell carcinomas
What non small cell lung cancer is unlikely to cavitate, is peripheral and most common in non-smokers?
What non small cell lung cancer appears as a cavitary lesion in a proximal bronchus on imaging?
What is the most worrisome radiographic appearance of lung nodules on imaging studies?
Irregular or spiculated
What are the rules of thumb for location of lung nodules on imaging films?
- Peripheral: adenocarcinoma
- Central: squamous cell carcinoma (bronchial cancer), small cell (including oat cell) cancer
- Peripheral or central: large cell carcinomas
What are the radiographic characteristics of benign lung nodules?
- Size <4 mm (>3 cm mass)
- Smooth, well defined margins
- Cnetral caclification within nodule (usually determined on CT)
- Growth rate slow or absent (use prior studies for comparison)
- CT or biopsy for further eval
What are the radiographic characteristics of malignant lung nodules?
- Rapid growth rate (doubling 1-18 months, use comparison studies)
- Size 8-10 mm or larger warrants eval
- Irregular, spiculated margins
- Invasion of surrounding tissue
- Evaluation (CT, scintigraphy, MRI, PET/SPECT)
What are the indications to perform a CT scan for lung masses?
- Rapid growth rate
- Size 8-10 mm
- Calcifications absent or eccentric
- Hilar enlargement/lymphadenopathy
Definition: localized suppuration with destruction of lung parenchyma, round thick-walled cavity in areas of destroyed lung, typically irregular wall, irregular luminal margin and exterior surfaces.
How are lung abscesses usually treated?
By prolonged antibiotics and postural drainage.
Definition: pus in the pleural cavity, "split pleural" sign (separation of uniformly thickened visceral pleura from parietal pleura), compression of uninvolved lung, usually requires early tube drainage.
How are lung abscesses and empyema differentiated from each other?
- Most specific signs: "split pleura" is a sign of empyema as well as compression of adjacent uninvolved lung
- Helpful signs: at least one wall of empyema is thin, uniform and smooth on both luminal margin and exterior surface
What are the imagining modalities used for cardiovascular imaging?
- Plain film: CXR
- Echocardiography: U/S
- Duplex U/S of large vessels
- Nuclear medicine scan (MUGA)
- CT and MRI (not initial evaluation)
The cardiac silhouette is normally less than ____ the width of the thoracic cavity when viewed on a PA upright film.
The cardiac borders should be _____ and with normal _____ contours.
What are causes for misdiagnosing cardiomegaly on CXR?
- AP view CXR (most common!)
- Pt not taking full inspiration (obesity, pregnancy, ascites)
- Chest wall abnormalities (kyphosis, pectus excavatum)
- Fluid collection
What are some pathological causes for cardiomegaly?
- Valvular disease
- Congenital heart disease
- Mass lesions
How is cardiomegaly evaluated on the lateral CXR? From what view is cardiomegaly best evaluated?
- NORMAL cardiac silhouette does not extend posteriorly over spine, also look at the level of the diaphragm.
- Best evaluated from PA view
Can a pt with a normal cardiac silhouette on CXR still have an abnormal heart? What will radiologists assess to identify potential problems without overt cardiomegaly?
- YES (hypertrophy does not produce recognizable cardiomegaly at first)
- Cardiac contours (R side- ascending aorta, Lt & Rt atrium; L side- aortic knob, pulm artery, Lt & Rt ventricle)
What is the most common cause of left atrial hypertrophy? What are some other causes?
- Mitral stenosis
- Obesity, HTN, lung disease
How is left atrial hypertrophy identified on CXR?
- "double density" on right overlap the Rt atrium
- "straightening" of L cardiac border, loss of concavity more common than double density
One cannot identify which ventricle is enlarged on CXR without looking at what?
The outflow tracts (pulm artery, aorta)
Cardiomegaly with pulmonary artery enlargement shows what?
Rt ventricular enlargement (at least partly)
Cardiomegaly with a prominent aorta (ascending/descending, or aortic knob) shows what?
Lt ventricular enlargement
What are the etiologies of left ventricular hypertrophy?
- Coronary artery disease
- Aortic stenosis
- Ventricular aneurysm
How is left ventricular hypertrophy best evaluated?
What is a common finding on CXRs in infants to 3 yo that can also be seen in children up to 8 yo?
What are indicators to a prominent thymus on CXR? How is this differentiated from cardiomegaly?
- Sail sign, notch sign, wave sign
- A normal cardiac silhouette indicates a prominent thymus, not cardiomegaly
What are some conditions that cause an enlarged aorta (or widened mediastinum)?
- Aneurysm/dissection of the aorta
- Aortic valve disease (stenosis and regurgitation)
- Congenital & genetic (marfan's syndrome, coractation of the aorta)
What is the most common cause of aortic aneurysms?
What are normal aorta x-ray findings?
- Should not project farther to the right than R atrial heart border
- Aortic knob should be less than 35 mm from the left tracheal border (PA view)
- Descending aorta should parallel and almost disappear with T-spine
What is the test of choice for evaluation of an aortic aneurysm?
CT scan with contrast
Widening of the aorta greater than ____ is at risk for rupture (aortic aneurysm).
What causes dilation of thoracic or abdominal aorta with or without dissection?
What are the risk factors for developing an aortic dissection?
- Age (45-70)
- Male > Female
- Marfan's syndrome
What are the clinical signs and symptoms of an aortic dissection?
- Sudden onset of severe chest/upper back pain (tearing, ripping, shearing) that radiates to the neck or down the back
- Sudden difficulty speaking, loss of vision, weakness, paralysis of one side of body (like a stroke)
- Weak pulse in ONE arm compared to other
- Loss of consciousness (fainting)
What are the possible CXR findings of an aortic dissection?
- dilated aorta
- widened mediastinum
- double contour of aortic arch
How is the pulmonary artery measured on CXR?
By drawing a line from the aortic knob to the apex of the Lt ventricle
The pulmonary artery should _____ project laterally past the line from the aortic knob to the apex of the left ventricle.
- (ALWAYS abnormal if its past that line)
Definition: blood flow to lung apex becomes equal or greater to flow in the lung base due to pulmonary venous hypertension, comparison of base to apex has similar density on CXR.
In pulmonary venous hypertension with cephalization, the Rt main pulmonary artery by be ______ or ______.
Definition: 2cm to 6cm unbranching lines coursing diagonally from the hila out to the periphery of the lungs on CXR, caused by distention of anastomotic channels between peripheral and central lymphatics of the lungs.
Kerley A lines (less common than Kerley B)
Definition: short horizontal white lines seen in CXR caused by distended interlobular septa about 1-2 cm long due to fluid accumulation between the secondary lobules of the lungs in pulm edema, seen close to the pleura and perpendicular to it usually at the lung bases near the costophrenic angles.
Kerley B lines (individual lines are parallel to each other)
Kerley A and Kerley B lines are indicators of what condition?
Which type of pulmonary hypertension causes blood flow to be redistributed from centrally to peripherally, shows no cephalization, and causes the loss of gradual tapering of vessels from central to peripheral ("pruning")?
Pulmonary arterial hypertension
Definition: acute marked enlargement of the heart with a "water bag appearance" or delta shape (pendulous with a wide base).
What imaging modalities are used to evaluate pericardial effusion?
- CXR (must be >250 ml to be seen this way)
What are the symptoms of a pulmonary embolism?
- Pleuritic chest pain
What is the imaging study of choice for a suspected pulmonary embolism? What is the "gold standard"?
- Spiral CT with IV contrast
- Pulmonary angiography
Why is CXR not the preferred study for pulmonary embolism? What is evidence on CXR that may indicate the need for further evaluation of a pulmonary embolism?
- It is non-specific
- Pt may have small pleural effusion, atelectasis, infiltrate or elevated hemidiaphragm