Clinical Radiology - PowerPoint by qLu36Hx

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Views for standard chest
• The patient's chest is placed against the film
• The x-rays enter the patient posteriorly and
  exit ventrally.
• The PA view minimizes cardiac
  magnification which can be a complication
  of other views.
            LATERAL VIEW
• A lateral view is ordered in conjuction with a PA
• By convention, the left side of chest is placed
  against the film cassette.
• Since the right side of the body is closer to the
  source of the x-rays, the right side is magnified
  greater than the left side. This will help separate
  structures. For example, the right costophrenic
  margin appears larger than the left costophrenic
  margin in this image.
• It is similar to a PA view except the x-ray
  beam is angled cranially.
• It is performed to evaluate upper lobe
• This view removes the clavicular shadows
  seen in the PA view.
• It is performed on patients who are unable to stand
  for the PA exam.
• AP radiographs are performed at bedside. The film
  cassette is placed under the patients back and a
  portable x-ray machine is positioned over the
  patients chest.
• Difficult to interpret due to many potential
  technical problems.
• May cause cardiac magnification as demonstrated
  in this comparison.
  *Chest x-rays are designed
 specifically for heart and lung
anatomy. Do not order chest x-
rays to examine rib or vertebral
     – Right major fissure
       separates the right
       upper lobe, and right
       middle lobe from the
       right lower lobe.
     – Right minor
       (horizontal) fissure
       separates the right
       upper lobe from the
       right middle lobe.
– Left major fissure
  separates the left
  upper lobe from the
  left lower lobe
– Also note that the
  lower lobes extend
  behind the outline
  of the diaphragm on
  a PA view.
• Right upper lobe
  – Segments: apical,
    posterior, anterior
• Right middle lobe
  – Segments: lateral,
• Right lower lobe
  – Segments: medial
    basal, anterior basal,
    lateral basal, posterior
    basal and superior.
• Left upper lobe
  – Segments:
    anterior, superior
    lingular, inferior
• Left lower lobe
  – Segments: superior,
    anteromedial basal,
    lateral basal, posterior
• The right cardiac border is formed by the
  right atrium
• the left cardiac border is formed by the left
• The right ventricle and left atrium are
  superimposed structures and are not border
• The Superior vena cava: forms a right
  paramedian border.
          • On the lateral
            projection, the anterior
            cardiac border is the
            right ventricle while
            the posterior cardiac
            border is composed of
            both the LV and LA.
          • The right atrium is not
            a border-forming
          • The inferior vena cava
            is seen best on lateral
          • The posterior border is
            evident in contrast to
            the air-filled lungs.
            Hilar Anatomy

• The "hilum" is composed of the pulmonary
  artery and its branches, and adjacent airway
  and pulmonary veins.
• Since airways do not produce a significant
  shadow on plain film radiography, the
  majority of the detectable "hilar" structures
  are vascular.
       • On the left side, the
         left pulmonary artery
         is directed
         toward the left scapula
         and goes over the left
         main stem bronchus.
         The left pulmonary
         artery is therefore
         located higher than the
         right pulmonary

      • On the lateral
        projection, the left
        pulmonary artery is
        posterior to a line
        drawn down the
        tracheal air column.
      • The right pulmonary
        artery (RPA) courses
        underneath the left main
        stem bronchus.
      • The right hilar shadow is
        inferior to the left on the
        PA projection ( 70%).
        Hilar shadows are equal
        in height (30%).
      • The right hilum is never
        superior to the left hilum.
      • On the lateral projection,
        the right hilum is
        anterior to a line drawn
        through the tracheal air
      • The right pulmonary
        artery is approximately 3
        times larger than the
        LPA, due to the more
        horizontal course of the
Tracheobronchial Anatomy
   • The trachea appears as
     an air-shadow
     coursing down the
     midline of the chest
     and terminating at the
     carina. The left and
     right mainstem
     bronchus may be
     evident as well as the
     lobar bronchi.
        • Pulmonary veins course
          more horizontally than
          pulmonary arteries, are
          ultimately directed
          toward the left atrium
          and best seen on a lateral
        • Pulmonary venous
          anatomy should not to be
          confused with a
          retrocardiac infiltrate.
• Borders include the sternum anteriorly, and
  the ventral cardiac surface posteriorly.
• Includes fat, ascending aorta, lymph nodes,
  internal mammary artery and vein, adjacent
  osseous structures (ribs and sternum),
  thymus. Knowledge of the mediastinal
  contents can aid in your differential
• This thymoma has spread throughout the
  Anterior Mediastinal compartment.
• Borders composed of the anterior
  mediastinal compartment ventrally, and the
  anterior surface of the spine, posteriorly.
• Structures include the esophagus, vagus
  nerve, recurrent laryngeal nerve, heart,
  proximal pulmonary arteries and veins
  (hilar), trachea and root of the bronchial
  tree, and superior and inferior vena cava
• Borders: Anterior surface of the spine
  posteriorly to the ribs.
• Structures include the descending aorta,
  adjacent osseous structures (the spine and
  ribs) and nerves, roots, spinal cord, and the
  azygous and hemiazygous veins.
• It is located above a horizontal line drawn
  from the angle of Louis posteriorly to the
• Structures include the thyroid gland, aortic
  arch and great vessels, proximal portions of
  the vagus and recurrent laryngeal nerves,
  esophagus and trachea.
• A "space" located underneath the aortic arch
  and above the left pulmonary artery.
• Contains fat.
• On the PA projection, it appears as a
  concave shadow. If adenopathy is present,
  it manifests as a convex shadow.
• The left and right diaphragm appear as
  sharply marginated domes.
• The peripheral margins of the diaphragm
  define the costophrenic sulci.
• The right diaphragm is higher than left due
  to the position of the liver. Will appear
  larger on a lateral chest film
   •   Ribs
   •   Anterior and posterior ribs.
   •   Spine
   •   Pedicles
   •   Transverse processes
   •   Spinous Processes
   •   Sternum
              X-ray densities
• Density is related to the structures ability to block
  photons. Air, for example, allows a greater
  number of photons to pass through and
  subsequently exposes more film generating a
  black image. More dense structures, such as bone
  or metal, reflect or absorb photons. Therefore, the
  film absorbs less photons and appears white.
• Five different densities are represented on plain
  films: air, fat, soft tissue (fluid), bone & metal
  (contrast material)
   Sensitivity and specificity of
            plain films.
• Plain films are not very sensitive.
• A great deal of pathology is missed on plain
• They are also not very specific since the
  majority of possible pathology falls under
  the catagory of fluid or soft tissue density
  making it difficult to differentiate.
Detection rates of abnormality.
• Plain films are poor screening exams.
• Studies looked at patients with
  documented lung disease
  approximately 10% of the patients had
  normal looking plain films.
Basic Pulmonary Pathology

• Concept of the silhouette sign
  – able to distinguish anatomical margins
    when two structures of different density
    abut one another. When two structures of
    similar density abut one another, their
    margins are lost.
• Right upper lobe: up and in
• Right middle lobe: like a fan.
• Right lower lobe : inferior and posteriorly

• Left upper lobe: medial and anterior
• Left lower lobe :inferior and posteriorly
          Pleural effusions

• Pleural efusions may be caused by a number
  of possible etiologies. Some of the most
  common causes are congestive heart failure,
  trauma, or blood.
• One cannot determine the nature of the
  pleural fluid based solely on the plain film
  (blood, pus, transudate, or exudate, etc).
           Pleural effusions
• The pleural fluid collects first in the
  posterior gutters. As the amount of fluid
  increases, plain films will reveal a blunting
  of the posterior and lateral gutters
• The build up of fluid will apply pressure to
  the lung causing a decrease in air intake.
• Treament - drain pleural fluid.
• The fissures are in continuity with the
  pleural space.
• Fluid can fill the fissures.
• This phenomenon is often refered to as
  pseudotumor due to its strong resemblance
  to a tumor.
Fluid has filled the minor fissure creating a density
          that resembles a tumor (arrow).
• It is often difficult to determine the size of a
  pleural effusion based on a plain film.
• The patient lies on their affected side and
  gravity causes the pleural fluid to coalesce
  in the lateral margin.
• A Decubitus chest film can detect as little as
  5 cc's of fluid.
• Pneumonia causes pus (bacterial, viral,
  fungal) to accumulate in the lungs causing
  increased density of the lung.
• It is possibly confused with blood, water or
  even tumor.
• Clinical history is necessary to help
  differentiate pneumonia from other possible
• Radiographic
  appearance predicated
  on infiltrate location,
  i.e. broncho-
  pneumonia vs. lobar
• Radiographic appearance predicated on
  infiltrate location, i.e. broncho-pneumonia
  vs. lobar pneumonia.

• The infection causing the pneumonia may
  lead to cavitation or destruction of the lung
  tissue, forming abscesses.
• The three most common organisms that
  cause pulmonary abcesses are staph aureus,
  strep pyogenes, and Klebsciella.
• Gram negatives are also very common
  causes of abscesses.
           Pulmonary Nodules
  Can be benign, malignant primary or metastatic
• Carcinoma can resemble other pathology such as
• Criteria for malignancy: presence of calcification,
  size, margins-not defined, growth, patient age/sex,
  and smoking history.
• Metastatic disease is hematogenously
  disseminated from another primary source such as
  colon or ovary which usually present as multiple
• If the nodule is
  highly calcified, it
  is a benign process
  and is not life-
  threatening and
  typically is a
     What should you do if you
       discover a nodule?
• The first step is to review the patient's old
  chest films.
   – No change over a two-year period then the
     nodule is more than likely benign.
   – If there are no old chest films, then a CT should
     be ordered. If the nodule is enlarging over time,
     then the nodule should be worked up.
         Cardiac Pathology

• A buldge on left cardiac boarder is
  indicative of possible Mitral Valve Stenosis.
  Left Ventricle Enlargement is evident on a
  PA view by distension of the lower left
  cardiac boarder.
               Rigler's rule
• A line is drawn from the point where the
  inferior vena cava meets the heart border up
  2 cm and then a second line is drawn
  posteriorly from this point 2 cm. If the
  cardiac boarder is beyond this point than the
  posterior cardiac boarder is enlarged.
     Congestive Heart Failure
• Cardiomegaly.
  – determined by comparing the width of the
    heart to the width of the thoracic cavity
    on a PA film. If the heart is greater than
    50% of the width of the thoracic cavity,
    then the heart is enlarged.
      Congestive Heart Failure
• The upper lobe vessels become more
  prominent due to vascular congestion or
  interstitial edema - results from transudation
  of fluid through the capillary walls into the
  interstitium around the vessels which can
  render normally indistinct vessels distinct,
  and creates a shaggy appearance around the
  heart border on a chest film.
       Congestive Heart Failure
• The increased transudate burdening the lymphatic
  system results in interstitial edema , evident on
  chest films by the appearance of Kerley lines,
  which represent thickening of the interlobular
  septa which carry the lymphatics.
• As hydrostatic pressure continues to increase,
  fluid begins to accumulate in the pleural space
  resulting in pleural effusions. With continued
  pressure, transudate infiltrates the alveolar spaces
  causing pulmonary edema.

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