Imaging of the Lung I & II Flashcards Preview

CVPR: Pulmonary > Imaging of the Lung I & II > Flashcards

Flashcards in Imaging of the Lung I & II Deck (14)
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Primary imaging modalities for chest evaluation

  • CXR
  • CT (computed tomography)
  • nuclear scintigraphy
  • MRI (magnetic resonance imaging)
  • Echocardiography
  • ultrasound


CXR technique

  • x-rays from a focal point ==> radiographic detector
  • pt casts shadow on detector = x-ray image
  • shadows depend on: size, distance from light source to object, distance of light source to wall
  • ideal positioning of the patient for standard two-view chest radiographs places their anterior chest against the detector for the frontal view and the left chest against detector for the lateral view.   


CT technique

  • image produced by passing patient between rotating xray beams and detectors
  • produces volumetric data ==> anatomic planar images (usually axial)


Advantages of CT

  • mroe accurate depication of anatomic objects 
  • includes density of objects
  • grey-scale can differentiate densisties of air, fat, fluid, soft tissue, bone/calcium, and metal
    • caused by various levels of x-ray attenuation (measure in Hounsfield units (HU))
    • water = 0 HU
    • air (-1000 HU) < fat < water < soft tissue < calcium/bone < bone < metal (>2000 HU)


HRCT and indications

  • High resolution Chest CT = axial slices < 3mm thick + images acquired @ supine inspiration, supine expiration and prone inspiration (vs. only supine inspiration in standard CT)
  • Allows evaluation of: "air trapping" and subtle pulmonary fibrosis
    • order if DDx includes: diseases of small airways (bronchioles) or pulmonary fibrosis


Imagining of vasculature technique

  • CT w/IV contrast
  • contrast into peripheral vein and time CT imaging with target vasculature (e.g. pulmonary arteries vs. coronary arteries/aorta)


Nuclear Scintigraphy characteristics

  • pt administered a radioactive substance (radiotracer) ==> emits gamma radiation ==> absorbed by detector ==> image
  • used in pulmonary VQ scans
  • common radionuclide = technetium 99m


VQ scan technique

  • nuclear scintigraphy technique used
  • upright pt inhales aerosolized technetium or xenon 133 with the gamma camera positioned next to the chest ==> single posterior projection or multiple projections

  • perfusion measured via administered IV macro-aggregated albumin (MAA) with technetium the collects in the patient’s pulmonary capillaries and reflects the distribution of pulmonary perfusion


MRI technique

  • Hydrogen atoms (plentiful within the water in body) create a magnetic field
  • Place body within strong magnetic field ==> protons aligh ==> radiofrequency passed trhough and detected ==> image


Value of portable chest radiograph

  • detect correct/incorrectly positioned central catheters
  • study supports of regular ICU portable chest radiographs to guide pt care


Imaging used to dx pulmonary embolism

  • CT pulmonary angiogram 
  • easy/fast availability
  • binary diagnosis of pulmonary embolism
  • demonstrates alternative diagnoses
  • provides prognostic information 


Major radiographic findings of cardiogenic pulmonary edema

  • cardiomegaly
  • vascular redistribution
  • interstitial opacities (Kerley B lines)
  • consolidation
  • pleural effusions


Classic imaging finding in pneumonia

  • silhouette sign: in the setting of community-acquired pneumonia
  • The silhouette sign is a fundamental concept in radiography where objects of equal density lose their differentiating borders when placed in contact with each other
  • The term “Consolidation” will also be discussed to include the major substances that can fill the alveoli in the setting of consolidation.