Learn Chest X-Ray With Its Normal

Positioning & Radio-Anatomy

Dr. Santosh Atreya MD Resident (Phase- A) Radiology & Imaging BSMMU from Nepal

Before the procedure…

• Bring a signed form from your doctor when you visit the X-ray technician.

• Be aware that you may have to hold your breath for a few seconds during the X-ray, especially if the X-ray focuses on the stomach or chest areas.

What do I need to remove for the procedure?

• Any jewellery around the affected areas. unless otherwise advised by your doctor.

LUNGS

Introduction

• Radiographic examination of the lungs is performed for a wide variety of medical conditions, including primary lung disease and pulmonary effects of diseases in other organ systems. Such effects produce significant changes in the appearance of the lung parenchyma and may vary over time depending on the nature and extent of the disease.

Recommended projectionsExamination is performed by means of the following projections:• Basic Postero-anterior – erect• Alternative Antero-posterior – erect Antero-posterior – semi-erect Antero-posterior -supine• Supplementary Lateral Postero-anterior – expiration Apices Lateral – upper anterior region Decubitus with horizontal beam

Positioning• The choice of erect or decubitus technique is

governed primarily by the condition of the patient. • With the patient erect, positioning is simplified,

control of respiration is more satisfactory, the gravity effect on the abdominal organs allows for the disclosure of the maximum area of the lung tissue & fluid levels are defined more easily.

• Supplementary projections may be required for specific indications at the request of a clinician or radiologist.

Postero-anterior – erect

A 35 X 43-cm or 35 X 35-cm cassette is selected, depending on the size of the patient.

Position of patient and cassette

• The patient is positioned facing the cassette, with the chin extended and centered to the middle of the top of the cassette.• The median sagittal plane is adjusted at right-angles to the middle of the cassette. The shoulders are rotated forward and pressed downward in contact with the cassette.• This is achieved by placing the dorsal aspect of the hands behind and below the hips, with the elbows brought forward, or by allowing the arms to encircle the cassette.

….contdDirection and centering of the X-ray beam• The horizontal central beam is directed at right-angles to the cassette at the level of the eighth thoracic vertebrae (i.e. spinous process of T7), which is coincident with the lung midpoint• The surface marking of T7 spinous process can be assessed by using the inferior angle of the scapula before the shoulders are pushed forward.• Exposure is made in full normal arrested inspiration.These days automatic chest film changer devices is in use.

Essential image characteristics

• Full lung fields with the scapulae projected laterally away from the lung fields.

• The clavicles symmetrical & equidistant from the spinous processes & not obscuring the lung apices.

• The lungs well inflated.• The costophrenic angles & diaphragm

outlined clearly.• The mediastinum & heart central &

defined sharply.• The fine demarcation of the lung tissues

shown from the hilum to the periphery.

Penetration

• Adequate penetration of the patient is also required for a good film.

• On a good PA film, the thoracic spine disc spaces should be barely visible through the heart but bony details of the spine are not usually seen.

• On the other hand penetration is sufficient then bronchovascular structures can usually be seen through the heart.

•

Left, an example of a normal PA film that is underpenetrated. Right, an overpenetrated PA film.

Underpenetration: Likelihood of missing an abnormality overlying by another structure

Overpenetration: results in loss of visibility of low density lesion e.g. early consolidation

• Structures seen in a PA View

Trachea and Bronchi

• The tracheal lumen appears as a vertical radiolucent shadow. Around the aortic knuckle it deviates slightly to the right.

• Normal maximum coronal diameter: 25mm for males and 21mm for females.

• In proper erect posture trachea bifurcates at the level of lower border of 6th thoracic vertebra

……contd• The tracheal lumen is

bordered on the right by a water density stripe, called the right paratracheal stripe, it is seen in 60% of patients, normally measuring about less than 5mm.

• Lt paratracheal stripe is not visualized.

…….contd

• Rt bronchus is shorter,wider and steeper than left, which is longer, narrow and less oblique.

• .

The Heart• The central dense shadow seen on

the PA chest film-mediastinum, heart, spine and sternum.

• With good centering, 2/3rd of the cardiac shadow lies to the left of midline & 1/3rd to the right.

• The normal cardio-thoracic ratio < 50% in PA film in adult.in children however, the CTR is usually <60%.

• .

Right border of heart is formed by-

• Superior vena cava• The right atrium• Small part of inferior vena

cava

Left heart border is formed by-• aortic nuckle• The pulmonary bay• The auricle of left atrium• The left ventricle.

……Contd• In babies and young

children the normal thymus is a triangular sail-shaped structure with well-defined borders projecting from one or both sides of the mediastinum

Diaphragm

Diaphragm

• Dome shaped sheet of muscle • Contains right hemidiaphrgm,central tendon

and left hemidiaphragm• arches over abdominal contents• Seperating abdomen from chest

….contd• on inspiration the domes

are at the level of 6th rib anteriorly and at or below the 10th rib posteriorly

• In most patients the right hemidiaphragm is higher than the left.

Measurements of hyperinflation of the lungs

• The normal dome of each hemidiaphragm should rise at least 1.5cm above a line connecting the costophrenic angle posteriorly and sternophrenic angle anteriorly

OBLIQUE FISSURE OF LEFT LUNG

HORIZONTAL FISSURE

OBLIQUE FISSURE OF RIGHT LUNG

• The horizontal fissure of right lung may be seen ,on the PA film extending from right hilum to the region of the 6th rib in the axillary line.

On a PA radiograph the main lobes overlap, so the lung is divided into 3 zones separated by imaginary horizontal lines 1.upper zone 2.mid zone 3.lower zone.

• The central area on each side is referred to as the hilum of lung field. left hilum is higher than the right.

• Hilum is formed by pulmonary vessels,bronchus and bronchopulmonary lymph nodes .

• Of all the structures in the hilum only the pulmonary arteries and upper lobe veins contribute significantly to the hilar shadows.

• Normal bronchial walls are only seen end-on.

• The apex of each lung field projects above the medial third of clavicle.

• The infero-lateral corner of each lung field is called lateral costophrenic angle.

• The infero-medial corner of each lung field is called cardiophrenic angle.

Bones of chest wall1. Clavicles:• The radiograph shows almost entire length of

clavicle. The medial end of the clavicle lie equidistant from the midline of the spinous process of the 4th thoracic vertebra in proper position.

• Rotation Can be assessed by observing the clavicular heads and determining whether they are equal distance from the spinous process of the thoracic vertebral bodies.

2. Thoracic vertebrae The radiopaque bodies of thoracic vertebrae should be discernible within the cardiovascular shadow. 3. Ribs The radiograph shows the head and neck of most of the ribs and the bodies of the upper 8 to 10 ribs.4. Scapulae The scapula project lateral to the supero-lateral

regions of the lung field in proper positioning.

Soft tissues It is important to confirm the

presence or absence of breast shadows.The breast may partially obscure the lung bases.

Nipple shadows are nodular opacities that are consistent in shape, size and position

.

• oval or round– 5-15mm in diameter– between the 9th and 10th rib

posteriorly or the 5th and 6th rib anteriorly

• Care is necessary to avoid mis-interpretation as a neoplasm or vice versa

LATERAL VIEW

Lateral view

A supplementary lateral projection may be useful for localizing the position of a lesion, encysted pleural fluid and demonstrating anterior mediastinal masses not shown on the postero-anterior projection.

Position of patient and cassette• The patient is turned to bring the side under investigation in contact with the cassette.• The median sagittal plane is adjusted parallel to the cassette.• The arms are folded over the head or raised above the head to rest on a horizontal bar.• The mid-axillary line is coincident with the middle of the film, and the cassette is adjusted to include the apices and the lower lobes to the level of the first lumbar vertebra.

Direction and centering of the X-ray beam

• Direct the horizontal central ray at right-angles to the middle of the cassette at the mid-axillary line.

Postero-anterior and lateral radiographs of same patient showing a tumour in the right lower lobe

Structures seen in lateral view

The clear spaces

• There are two clear spaces;retrosternal and retrocardiac. these correspond to the sites where the lungs meet behind the sternum and the heart

• Loss of translucency of these areas indicates local pathology.

• Normally the retrosternal space is less than 3 cm deep maximum.

Normal lateral film. Note the retrosternal and retrocardiac clear spaces (open arrows) and the increased translucency of the lower vertebrae. The axillary folds (straight black arrows) and scapulae (curved black arrows) overlie the lungs. The tracheal translucency is well seen (small black arrows)

Trachea

• Tracheal lumen appears as an vertical radiolucent band which passes down slightly posterior direction to the T6/7 level of the spine.

• Tracheal lumen is bordered posteriorly by a water-density stripe that represents the posterior tracheal wall and collapsed esophagus together

• The right upper lobe bronchus is seen end-on as a circular structure overlying the lower trachea.

• Lying inferiorly is the left upper lobe bronchus seen end-on .

Mediastinal visceraThe chambers of the heart cast a

bulbous shadowThe anterior wall of the right

ventricle defines the lower half of the anterior border of the cardiac shadow

The posterior wall of left ventricle defines the lower third of the posterior border of the cardiac shadow

Posterior wall of left atrium defines the middle third of the posterior border of the cardiac shadow

The 3 segment of thoracic aorta cast a cane shaped shadow

The shadow of ascending aorta projects upward from the superior limit of the anterior border of the cardiac shadow

The shadow of aortic arch arches over the cardiac shadow and into the radiolucent space anterior to the bodies of the 3rd and 4th thoracic vertebra

The shadow of descending thoracic aorta parallels the curved stack of the bodies of the lower thoracic vertebrae

Diaphragm outline

• Both diaphragms are visible throughout their length, except the left anteriorly where it merges with the heart. A small segment of the right hemi diaphragm is effaced by the IVC.

• The posterior costophrenic angles are acute and small amounts of pleural fluid may be detected by blunting of these angles.

Lungs

• All fissures of lung are clearly seen on lateral film.

• The horizontal fissure runs anteriorly and often slightly downwards

• Both oblique fissures commence posteriorly at the level of T4 /T5,passing through the hilum. The left ends 5cm behind the anterior costophrenic angle and right ends just behind the angle.

Bones and soft tissues of chest wall

• The radiograph shows the manubrium sterni and body of sternum in profile.

• Shows the body of thoracic vertebrae, images of the paired pedicles of each vertebra are seen.

• The T4-T5 intervertebral disc lies at the level of manubrio-sternal joint.

• The bodies of thoracic vertebra appear progressively more radiolucent inferiorly.

• ANTERO POSTERIOR VIEW

Antero-posterior – erectThis projection is used as an alternative to the postero-anterior erect projection for elucidation of an opacity seen on a postero-anterior, or when the patient’s shape or medical condition makes it difficult or unsafe for the patient to stand or sit for the basic projection.

Position of patient and cassette• The patient may be standing or sitting with their back against the

cassette, which is supported vertically with the upper edge of the cassette above the lung apices.

• The median sagittal plane is adjusted at right-angles to the middle of the cassette.

• The shoulders are brought downward and forward, with the backs of the hands below the hips and the elbows well forward, which has the effect of projecting the scapulae clear of the lung fields.

• In the unwell patient, it may not be possible to perform this procedure, In this situation, it is preferable that the patient’s arms are rotated laterally and supported with the palms of the hands facing forward. In this position, the scapulae are superimposed on the lungs but the effect of absorption is less.

Direction and centering of the X-ray beam

• The horizontal ray is directed first at right-angles to the cassette and towards the sternal notch.• The central ray is then angled until it is coincident with the middle of the cassette. This has the effect of confining the radiation field to the film, thus avoiding unnecessary exposure of the eyes.• The exposure is taken on normal full inspiration.

Normal antero-posterior radiograph of thorax

• Antero-posterior - supine

Antero-posterior – supine

This projection is selected when patients are unable to either stand or sit for the projections described previously. The patient is usually lying supine on a trolley or bed.

Position of patient and cassette

• With assistance, a cassette is carefully positioned under the patient’s chest with the upper edge of the cassette above the lung apices.• The median sagittal plane is adjusted at right-angles to the middle of the cassette, and the patient’s pelvis is checked to ensure that it is not rotated.• The arms are rotated laterally and supported by the side of the trunk. The head is supported on a pillow, with the chin slightly raised.

Direction and centering of the X-ray beam

• The central ray is directed first at right-angles and towards the sternal notch.• The central ray is then angled until it is coincident with the middle of the film, thus avoiding unnecessary exposure to the eyes.

Normal supine radiograph of thorax

• ANTERO-POSTERIOR SEMI ERECT

Antero-posterior – semi-erect

This semi-recumbent position is adopted as an alternative to the antero-posterior erect projection when the patient is too ill to stand or sit erect without support.

Normal semi-erect radiograph of thorax. The chin is just superimposed on the upper thorax

DIFFERENCES OF PA & AP VIEW

S.N POSTERIOR ANTERIOR VIEW ANTEROPOSTERIOR VIEW1. Clavicles are more horizontal,donot project towards the

apicesProjects towards the apices

2. Scapula are away from the lung field Scapula are towards the lung field.

3. Reduces radiation dose to radiosensetive organs like eyes,thyroid and breasts.

Radiation exposure

4. Magnification of heart is reduced Heart size is exaggerated .

5. X-rays pass from the posterior to the anterior of the patient - hence Posterior-Anterior (PA) projection. The image is viewed as if looking at the patient face-to-face.

X-rays pass from the anterior to the posterior of the patient - hence Anterior-Posterior (AP) projection. The image is still viewed as if looking at the patient face-to-face.

6. Compression of breast tissue against the film cassette reduces the density of tissue around the cp bases therefore visualizing them more clearly

no any compressions.

•APICES

Apices

• Opacities obscured in the apical region by overlying ribs or clavicular shadows may be demonstrated by modification of the postero-anterior and antero-posterior projections.

Direction and centering of the X-ray beam

• With the patient in the position for the postero-anterior projection, the central ray is angled 30 degrees caudally towards the seventh cervical spinous process coincident with the sternal angle.

• With the patient in the position for the antero-posterior projection, the central ray is angled 30 degrees cephalad towards the sternal angle.

• With the patient reclining, and the coronal plane at 30 degrees to the cassette, to enable the nape of the neck to rest against the upper border of the cassette, the central ray is directed at right-angles to the film towards the sternal angle. Alternatively, if the patient is unable to recline 30 degrees, the technique is adapted, with the patient reclining 15 degrees and the tube angled 15 degrees cephalad.

Normal postero-anterior 30 degrees caudad

Antero-posterior 30 degrees cephalad, showing small tumour at the left apex

• LORDOTIC VIEW

Lordotic view

This technique may be used to demonstrate right middle-lobe collapse or an inter-lobar pleural effusion. The patient is positioned to bring the middle-lobe fissure horizontal.

Position of patient and cassette• The patient is placed for the postero-anterior projection.• Then clasping the sides of the vertical Bucky, the patient bends backwards at the waist.• The degree of dorsiflexion varies for each subject, but in general it is about 30–40 degrees.

Direction and centering of the X-ray beam

The horizontal ray is directed at right-angles to the cassette and towards the middle of the film.

Lordotic postero-anterior radiograph showing middle lobe collapse

• Decubitus: the patient is lying down. In the decubitus position,

• the patient may be lying in any of the following positions:• • Supine (dorsal decubitus): lying on the back.• • Prone (ventral decubitus): lying face-down.• • Lateral decubitus: lying on the side. Right lateral decubitus

–• lying on the right side. Left lateral decubitus – lying on the• left side.• • Semi-recumbent: reclining, part way between supine and

sitting

Heart and lungs – fluid level

Postero-anterior or antero-posterior (lateral decubitus)This projection is used to confirm the presence of fluid. Moving the patient into a different position causes movement of free fluid, so that loculation is also detected. It may also be used to demonstrate the lateral chest wall of the affected side clear of fluid, and to unmask any underlying lung pathology.

Position of patient and cassette• The patient is turned on to the lateral decubitus position and, if possible, raised on to a supporting foam pad.• A cassette is supported vertically against the anterior chest wall, and the median sagittal plane is adjusted at right-angles to the cassette.• The patient’s arms are raised and folded over the head to clear the chest wall.

.

• Direction and centring of the X-ray beam• • Centre to the level of the eighth thoracic

vertebra, with the central• ray horizontal and directed at right-angles to the

cassette.• Alternatively, an antero-posterior projection may

be taken, with• the cassette supported against the posterior aspect

of the patient

Postero-anterior radiograph in lateral decubitus position showing pleural effusion with pneumothorax

Patient positioned for postero-anterior chest (lateral decubitus) projection

Supine(dorsal decubitus)This projection will show as much as possible of the lung fields, clear of a fluid level, when the patient is unable to turn on their side.

Position of patient and cassette• The patient lies supine and, if possible, is raised off the bed on a supporting foam pad.• The arms are extended and supported above the head.• A cassette is supported vertically against the lateral aspect of the chest of the affected side and adjusted parallel to the median sagittal plane.

Direction and centring of the X-ray beam• Centre to the axilla, with the central ray horizontal and directed at right-angles to the cassette.

Patient positioned for lateral chest (dorsal decubitus) projection

Lateral radiograph in dorsal decubitus position showing pleural effusion with pneumothorax

Right anterior obliqueThis projection is used to separate the heart, aorta and vertebral column on a 35x 43-cm film. The projection will also demonstrate the diameter and the degree of unfolding of the aorta.

Position of patient and cassette• The patient is initially positioned facing the cassette, which is supported vertically in the cassette holder with the upper edge above the lung apices.• With the right side of the trunk kept in contact with the cassette, the patient is rotated to bring the left side away from the cassette, so that the coronal plane forms an angle of 60 degrees to the cassette.Direction and centring of the X-ray beam• Direct the horizontal central ray at right-angles to the middle of the cassette at the level of the sixth thoracic vertebrae, to show the heart, aortic arch and descending aorta.

Right anterior oblique radiographRight anterior oblique radiograph with barium outlining the oesophagus

LIMITATIONS OF THE PLAIN CHEST FILM

First,the radiologist may fail to spot a lesion.Felson reported that 20-30% of significant information on a chest film may be over-looked by a trained radiologist.

Second,a disease process may fail to appear as a visible abnormality on a plain film.examples includes miliary shadowing,metastasis,infective process such as tuberculosis,histoplasmosis,and pneumocystis,bronchiectasis and small pleural effusions.such lesions are demonstrated earlier using high resolution CT.