Chest Radiographs -1

• The presentation is about chest radiographs and covers general radiology topics

Objectives

• Explain the indications for chest imaging
• Systematically interpret chest x-rays
• Identify lung anatomy of the chest

Indications for Chest X-Ray

• Acute respiratory or cardiac disease with no recent chest x-ray available
• Major chest trauma
• Hemoptysis
• Chronic dyspnea, suspected CHF, or interstitial lung disease
• Suspected PE, Pneumonia, CHF, pleural effusion, pneumothorax
• Positive TB skin test
• New respiratory symptoms in a febrile neutropenic immunosuppressed patient
• Persistent symptoms 6 weeks post community acquired pneumonia
• Post tube and line insertion, excluding pacemaker or tracheostomy
• Suspected mass, lymphadenopathy, or metastasis
• Suspected elevated diaphragm

Chest X-Ray - NOT normally considered indications

• Routine or regular orders: asymptomatic pre-admission or preoperative patients
• Daily routine intensive care portables with no clinical change
• Routine pre-employment screening
• Minor chest trauma
• Upper respiratory tract infection
• Uncomplicated acute exacerbation of asthma or COPD
• Acute on chronic chest pain
• Pneumonia without unusual clinical or radiographic features and improving symptoms, unless high risk for lung cancer: over 50, chronic lung disease, or smoker
• Routine stat portables immediately post pacemaker and tracheostomy procedure
• Thoracic aneurysm follow-up, CT scanning is the method of choice
• Screening for lung cancer in asymptomatic patients

Chest X-Ray Interpretation

• Name, DOB
• Film direction
• Technical quality - RIPE
• Cardiac shadow – size, shape, calcification
• Mediastinum – position, size, density, concave
• Hila
• Lungs – size, translucency, fissures, consolidation
• Plural space – effusion, soft tissue, masses, calcification, pneumothorax
• Bones - fractures, lytic or sclerotic lesions
• Soft tissue – diaphragm, masses, calcifications
• Mnemonic: To Care Means Healing Living People But Softly

Film Direction: Basic Views

• Posteroanterior (PA) view:
  • Best way to take a CXR, with patients front against the film
  • X-ray shot from the pt's back therefore called PA view
  • Heart minimally magnified and the heart borders are sharp
• Anteroposterior (AP) view:
  • Lower quality CXR
  • Taken if pt too sick to stand or sit for PA
  • X-ray is shot from front to back
  • Heart appears larger than it really is and borders are fuzzier
  • Scapula take up more lung field obliterating view of the parenchyma
• Lateral view:
  • Taken with the pt in profile
  • Taken routinely with PA view to localize lung lesions, which may be hidden behind the heart or diaphragm
• Structures visible in Lateral view:
  • 1. Trachea
  • 2. Ascending aorta
  • 3. Brachiocephalic vessels
  • 4. Pulmonary artery
  • 5. L ventricle
  • 6. Retrosternal space
  • 7. R hemidiaphragm
  • 8. L hemidiaphragm
• Decubitus view:
  • This is a PA view with the pt lying down on their side
  • Useful for identifying fluid in the pleural space
  • Often used for diagnosis of suspected pleural effusions
• Look at clavicles and scapula

Key things to spot

• If the "L" is on the opposite side of the heart, the x-ray was mislabeled, or the pt has dextrocardia

Technical Quality - RIPE

• Rotation: The distance between each medial end of the clavicles and the interposed spinous process should be equal if there is no rotation -If spinous process appears closer to the right clavicle and heart appears enlarged, then the patient is rotated left
  • If spinous process appears closer to the left, then it is right rotation and heart will be smaller than actual
• Inspiration: A deep inspiration is needed for a good image of the lungs
  • If the lung spans 9 posterior ribs or 5-7 anterior ribs, the inspiration is adequate
  • Expiratory view causes pulm vasculature to be more prominent.
• Position: Look for gastric air/fluid levels in upright pt.
• Exposure: -If the spine cannot be seen behind the heart, the film is too white (underexposed) -If the vessels cannot be seen in the vessels, the film is black (overexposed)

Cardiac Shadow

• Size - Cardiothoracic Ratio (CTR): Calculated by dividing the cardiac width by the thoracic width (should be <50% or 1:2 on PA view).
• Shape – right ventricle projecting anteriorly and inferiorly, and left ventricle and atrium forming posterior border.
• Calcification – look for increased densities along the heart's borders.

Mediastinum

• Position - centered and symmetrical
• Size - should be <1/3 the transthoracic distance
• Density - soft tissue
• Concave - created by the aerated medial left upper lobe against the mediastinal fat between the aortic arch and left pulmonary artery.

Hila

• Each hilum contains major bronchi and pulmonary vessels
• Hilar lymph nodes are not visible unless abnormal
• The left hilum is commonly higher than the right

Lungs

• Size - look for enlargement (hyperinflation) and reduced lung volume (atelectasis).
• Translucency – look for silhouette sign with loss of clearly visible borders.
• Fissures – locate to identify lobes affected by disease.
  • Major (oblique) fissure – thin linear shadow on lateral view
  • Minor (horizontal) fissure – thin line on PA view
• Infiltration – look for increased density in air spaces.

Pleural space

• Effusion – The costophrenic angles and hemidiaphragms should be well defined
• Soft tissue – look for breast tissue, fat planes, and irregular areas of black
• Masses – look for presence of space occupying densities either solitary or multiple.
• Calcification - dense areas of calcium deposits.
• Pneumothorax - lung marking should be visible.

Bones

• Rib fracture: often at lateral aspect of rib and may show a pneumothorax
  • Initial testing: Chest xray to diagnose rib fracture
  • Definitive dx: CT without contrast
  • Blunt chest trauma - СТА

Soft Tissue

• Diaphragm – Assess position sharpness, and contour
  • On a frontal cxr the right hemidiaphragm is higher than the left, due to the presence of the liver
• Masses - look at neck, thoracic wall, and breast areas
• Calcifications – look at location, size, shape, and densities
• On a lateral cxr the heart sits on the left hemidiaphragm

Key Anatomy

• Anterior rib
• Trachea
• Spinal process
• Clavicle
• Scapula
• Aortic knob
• Bronchial bifurcation
• Left bronchus
• Vascular hilum
• Posterior rib
• Right atrium
• Diaphragm
• Liver
• Hilum
• Descending aorta
• Breast soft tissue
• Gastric air bubble

Structures Seen On A PA CXR

• 1 = first rib
• 2-10 = post aspect of ribs 2-10
• AK = aortic knob
• APW = aortopulmonary window
• BS = breast shadow
• C = carina
• CA = colonic air
• CPA = costophrenic angle
• DA = descending aorta
• GA = gastric air
• LHB = left heart border
• LPA = left pulmonary artery
• RC = right clavicle
• RHB = right heart border
• RHD = right hemidiaphragm
• RPA = right pulmonary artery
• T = tracheal air column

Key Anatomy on Lateral Chest X-Ray

• A = aorta
• CPA = post costophrenic angle
• LHD = left hemidiaphragm
• PHB = posterior heart border
• RA = retrosternal airspace
• RHD = right hemidiaphragm
• RMF = right major fissure
• Scapula
• T = tracheal air column