CXR Normal Anatomy

A. Almasi MDIran University of Medical Science

Department of Radiology

PA CXR

• Quality Control• Trachea• Mediastinum& Heart• Diaphragms• Pleural space including fissures• Lungs• Hidden Areas of the Lungs• Hila• Below Diaphragm• Bones

PA view

Quality Control

• Inspiration:• Ant. end of 5th - 6th or post. end of 10th rib above the

diaphragm

• Centering: • Medial end of the clavicles equidistant from T4-5

spinous process

• Exposure:• Vertebral bodies and disc spaces behind the heart must

be barely visible and bronchovascular marking should be visible through the heart

PA view

Rotation Effect• Anterior structures (e.g. heart) shift to the side farther from the film• The lung farther from the film appears more lucent and the ipsilateral

hemithorax appears wider• In this rotated film skin folds can be mistaken for a tension

pneumothorax (blue arrows)

Expiratory Film• Increased heart size• More prominent bronchovascular markings• Basal opacities• Tracheal deviation to the right

Expiratory Film• Increased heart size• More prominent bronchovascular markings• Basal opacities• Tracheal deviation to the right

inspiration expiration

Respiration and Rotation Effect

Inspiration Expiration& Leftwards Rotation

Improper ExposureUnderexposed Overexposed

Trachea

• Exact midline in the upper part& deviating to the right around the aortic knob

• Even diameter up to M:25mm F:21mm• Right paratracheal stripe <4-5mm• Azygos vein at the anlge between the RMB&

trachea (less than 10mm in diameter)• Carina at T6-7 angle: 60-75°

Trachea in Superior Mediastinum• Left side of the trachea is not border forming on

CXR it is not surrounded by aerated lung

Normal PA Viewright paratracheal stripe

SVC

right brachiocephalic artery

carina

Right Paratracheal Stripe

Normal after Radiotherapy

Hodjkin’s Disease

Wide Carinain Mitral Malady

left atrial appendage

cephalization

left atrium

The Heart

• 1/3(1/5-1/2) to the right& 2/3 to the left of midline

• CT ratio 50% on PA and 60% on AP view• Diameter up to F:14.5cm M:15.5cm• 1-1.5cm increase on two consecutive films

is significant• Enlarges in expiration& when diaphragm is

high

Cardiothoracic (CT) Ratio

Normal PA View

Mediastinal BordersRight Superior

Brachiocephalic A&VSVCTortuous or dilated

ascending aorta may contribute

InferiorRt atriumIVC (probable)

LeftSubclavian AAortic knobPulmonary ALt atrial appendageLt ventricle

1.1MediastinalBorders

1.1.BraciocephalicA&V1.SVC2.RA3.SubclavianA4.Aortic Knob5.Descending Aorta6.Pulmonary Trunk7.LA Auricle8.LV

Normal PA View

ProminentPulmonaryTrunk

Is normal in young women& children

Tortuous Aorta& Prominent LtCardiophrenicAngle Fat Pad

Ascending A

Fat Pad

CardiophrenicAngle Fat Pad on LateralCXR

Tortuous Aorta& Brachiocephalic Aneurysm

PA CXR• Quality Control• Trachea• Mediastinum& Heart• Diaphragms• Pleural space including fissures• Lungs• Hidden Areas of the Lungs• Hila• Below Diaphragm• Bones

Diaphragm

• Right hemidiaphragm is usually higher• More than 3cm difference between heights

of the hemidiaphragms may be abnormal• Dome of the hemidiaphragms is usually

posteriorly located but on the right it may be anterior 40% of the times

• Contour should be sharp except where heart lies on the diaphragm

PA view

Anterior right diaphragm dome

High Hemidiaphragm DDx

• Normal esp. when there is much gas in the bowel, normal motion on fluoroscopy or sonography

• Diaphragmatic Paralysis esp. after thoracic surgery, paradoxical motion of the diaphragm

• Eventration usu.paradoxical motion on fluoroscopy

High Hemidiaphragm

DiaphragmaticScalloping

DiaphragmaticSlipping in flatdiaphragms

• Athletes• Emphysema

Hump of Diaphragm

Hump

Sonography rules outsubdiaphragmatic mass

Pleural Space

• Lateral Costophrenic Angles should be acute, blunting indicate effusion (250ml at least), flattening or thickening

• Posterior Costophrenic Angles can become blunted by as little as 75ml fluid on lateral view

• Fissures are double layered pleura separating lobes

Fissures

• Oblique (major) visible only on lateral view

From T4-5 to just posterior to costophrenic angel on the right and 5cm posterior on the left

• Horizontal (minor) visible on both PA& lateral views

From right hilum to the 6th rib at axillary line

Fissures

Fluid-filled fissures• The patient below has a pleural effusion extending into the fissure.  Which fissure is

which?  • What is the bright loop near the center of the films?

Segmental Lung Anatomy

•Lung lobes are separated by fissures which are composed of two adjacent layers of parietal pleura•A lung segment is the lung parenchyma surrounding a segmental bronchus

Lobar& Segmental Anatomy of the Lungs

Lobar& segmental anatomy

Minor FissureFrom right hilum to the 6th rib at axillaryline

MinorFissure

Major FissuresFrom T4-5 crossing the hilum and terminating behind costophrenic angel on the right and 5cm more posteriorly on the left

Fissuresminor

left major

right major

The Lungs

• Opacity• Symmetry in marking& lucency• Vasculature

– Inferior vessels are more prominent– No vessel>3mm in diameter in the 1st anterior intercostal space– Concave lateral border of Rt descending pulmonary A

• Hidden Areas– Apex– Posterior Recess– Areas superimposed by mediastinum, hila& bones

Normal PA View

Lung Hila• Left hilum higher 97%• Symmetric in size and density• Concave lateral border• Contour made up of superior pulmonary vein&

descending branch of main pulmonary artery • Descending branch of main pulmonary artery on

the Rt has concave lateral contour and measures less than 16mm in diameter

• Normal LNs not visible

Hilar Anatomy

Hila on PA View

Hila on Lateral View

Hila on Lateral

View

* Lt Sup Bronchus

* Rt Sup Bronchus

Rt MainPul. A

Lt Main Pul. A

Hilar Adenopathy

HilarAdenopathy

ProminentHila-Vascular(Pulmonary Venous HTN)

ProminentHilaPulmonary ArterialHTN

ProminentHilaPulmonary ArterialHTN

Hilar Enlargement Vascular vs Adenopathy

Below diaplragm, Soft tissue& Bones

• Gas shadows (stomach, bowel, surgical emphysema, etc.)

• Symmetric axillary lines, Mastectomy• Bone lesions

Normal PA View

Normal PA

Prominent skin fold vs pneumothorax

Calcified Costal Cartilage

Hypertrophied 1st Costochondral Junction

Hypertrophied 1st Costochondral Junction

Lateral CXR

• Clear Spaces• Vretebral

Translucency• Diaphragm Outline• The fissures• The lung Hila• The Trachea& Upper

Lobe Bronchi• The Sternum

Clear Spaces& Vertebral Translucency

• Ant. Clear Space– Ant. medistinal masses, LNs& aortic aneurysm

may fill this space– In emphysema it widens (>3cm)

• Post. Clear Space– Vertebral translucency increases progressively

downward in this space

CXR Lateral View

PE on lateral view(effect on vertebral translucency)

PE

Fissuresminor

left major

right major

Hila on Lateral

View

* Rt Sup Bronchus

* Lt Sup Bronchus

Rt MainPul. A

Lt Main Pul. A

HilarAdenopathy

LLL Consolidation

Lateral Decubitus Films

• To differentiate pleural effusion from thickening in case of a blunt costophrenic angle

• To assess the volume of pleural effusion• Demonstrates whether a pleural effusion is mobile or loculated• Detection of a pneumothorax in the nondependent hemithorax in a patient

who could not be examined erect• The dependant lung should increase in density due to atelectasis from the

weight of the mediastinum putting pressure on it.  Failure to do so indicates air trapping

PA versus AP CXR

PA versus AP CXR

Recommended order of reading a CXR

•It is recommended to start from the regions of least radiologic interest to decrease the likelihood of missing details. 1- Abdomen

2- Thorax (soft tissues and bones)

3- Mediastinum

4- Lung-unilateral

5- Lungs-bilateral

This order can be memorized by the breviation ATMLL

Abdomen

• The recommended path is shown, beginning at the right lower corner.

Thorax (soft tissues and bones)

• The path again starts from the right lower corner of the x-ray

Mediastinum• Mediastinum can be assessed in two consecutive runs

one for the trachea And bronchi and the other for the soft-tissue structures and pulmonary hila

Lung

• It is recommended to look at the lungs one by one at first and then a look that compares the two lungs

Lateral Film• The same order that was mentioned (ATMLL) is

applicable to lateral films too

Proposed reading order for a CXR

• Turn off stray lights, optimize room lighting, view images in order• Patient Data (name history #, age, sex, old films)• Routine Technique: AP/PA, exposure, rotation, supine or erect• Trachea: midline or deviated, caliber, mass• Lungs: abnormal shadowing or lucency• Pulmonary vessels: artery or vein enlargement• Hila: masses, lymphadenopathy• Heart: thorax: heart width > 2:1 ? Cardiac configuration?• Mediastinal contour: width? mass?• Pleura: effusion, thickening, calcification• Bones: lesions or fractures• Soft tissues: don’t miss a mastectomy• ICU Films: identify tubes first and look for pneumothorax

Atelectasis vs Lobar Pneumonia

Atelectasis•        

Volume Loss Associated Ipsilateral Shift 

• Linear, Wedge-Shaped• Apex at Hilum  

Pneumonia• Normal or Increased Volume

No Shift, or if Present Contralateral

• Consolidation, Air Space Process

• Not Centered at Hilum