Imaging of the thorax

Question 1

What is the mediastinum?

Answer 1

A cavity between the lungs containing the heart, trachea, oesophagus, major vessels and lymph nodes

Question 2

What is the hilum? And what does it consist of?

Answer 2

The root of the lung, it consists of the major bronchi, pulmonary veins and arteries.

Question 3

What are some criteria that need to met on a chest x-ray?

Answer 3

-patient name, DOB
-anatomical marker
-clavicles horizontal
-scapula clear of lung fields
-spine to T4 clear
-Apices shown

Question 4

What is the cardio-thoracic ratio?

Answer 4

it is a way of measuring heart size. CTR- the cardiac diameter should be 50% or less than the width of the chest.

Question 5

Outline the process of respiration/ breathing.

Answer 5

o Air is drawn in and moistened/filtered via nasal passages/mouth
o Drawn then into the trachea (windpipe)-then the 2 main bronchi (left/right)
o Travels to bronchioles-finally ending at the alveoli
o Gas exchange takes place-02 passes into the bloodstream from the warmed air and CO2 passes out of the blood into the air filled alveoli

Question 6

what happens to the intercostal muscles on inspiration?

Answer 6

intercostal muscles contract, thorax expands, diaphragm also contracts, lung volume increases, lung pressure drops & air is drawn into the lungs

Question 7

what happens to the intercostal muscles on expiration?

Answer 7

intercostal muscles relax, thoracic cage reduces in volume, diaphragm relaxes and moves upwards-this reduces lung volume; pressure then increases and air is expelled

Question 8

What is the diaphragm divided into?

Answer 8

it is divided into 2, the left and right hemi-diaphragm.

Question 9

outline key points on patient preparation

Answer 9

Remove patient’s clothing/objects down to the waist – patients will require a radiolucent hospital gown.
-Investigate if the patient has any individual communication needs
-Explain clearly the procedure to the patient – this aids the examination performance and helps put the patient at ease.
-Inform patient of breathing technique required and rehearse, if necessary, prior to exposure being taken
Move/ remove any monitor lines or dressings if necessary

Question 10

What are the main chest x-ray projections? Give reasons as to why they may be used.

Answer 10

-Erect PA (golden standard)
-Lateral- secondary view to locate structures better.
-Erect AP- if the patient is too unsteady to stand.
-Supine AP- if it is unsafe or inappropriate to sit up.

Question 11

Outline the Erect PA projection

Answer 11

-Patient should always be positioned in the erect postero-anterior position.
-Exposure should be made at the end of deep arrested inspiration.

Question 11

Why do we take the radiograph on arrested inspiration?

Answer 11

To open up the lungs to get a better/wider view.

Question 11

Outline Erect PA positioning

Answer 11

1. patient stands facing image receptor (wall stand).
2. patients arms should be: Rotated medially with the dorsal aspects of the hands resting on the back of the hips
   or
   Rotated from the shoulder joint with the hands and forearms against the sides of the wall stand or encircling the IR.
   3.Must be positioned without rotation.
   4.chin is extended & on IR support.

Question 12

What should the distance be between the x-ray source and image receptor?

Answer 12

180cm

Question 13

Why do we need to ensure a sufficient distance?

Answer 13

Reduction of magnification

Question 14

Outline the centering points of an Erect PA.

Answer 14

-Central ray - horizontal & 90 degrees to the IR in the patients’ midline at the level of T8
-This is best found by finding the inferior angle of scapula
-T7 spinous process is palpable and lies on same level as thoracic vertebra 8.

Question 15

What are some benefits of the erect PA.

Answer 15

-standardised.
-gravity effect.
-fluid levels.
-Easier for patients to breathe in.
-Reduces magnification of the heart
-Scapula are cleared from the lung field.

Question 16

Outline AP Erect patient positioning

Answer 16

-Patient sits upright, back against IR.
-Chin raised so its out of image field.
-Hands placed by patients side.
-Shoulders relaxed so clavicles don’t obscure apices.

Question 17

Centring and angulation of AP erect.

Answer 17

-Level of 8th vertebra.
-central ray angles to be perpendicular to long axis of patients sternum and IR.
-Some degree of caudal angulation

Question 18

What is the portable/mobile chest examination

Answer 18

Portable/Mobile examinations are those which are undertaken outside the confines of an x-ray room. This will usually be on a ward such as Intensive Care, Resuscitation Room or an Operating Theatre

Question 19

What is the centring of lateral projection

Answer 19

-Normally left lateral is taken- places heart nearer to film reducing magnification.
-If known pathology is present, affected side should be positioned against IR.
-Used to localise and demonstrate the extent of a lesion

Question 20

What is the positioning of a lateral chestprojection?

Answer 20

-patients MS plane is parallel to IR.
-Centre through the axilla at T8 midway.
-deep arrested inspiration.
-ensure the chin is raised.

Question 21

What is the image criteria of Lateral projection?

Answer 21

Left-hemi diaphragm disappears at border.
-Look for diff densities.
-look for evidence of mass.

Question 22

What is lordosis?

Answer 22

The patient is leaning too far backwards/ insufficient caudal angulation.

Question 23

How can you correct lordosis?

Answer 23

*Apply more caudal angulation
*Sit patient more upright if possible.

Question 24

What is kyphosis?

Answer 24

*Patient is leaning too far forwards or there is too much caudal angulation (Horizontal beam is NOT perpendicular to the long axis sternum)

Question 25

How can you correct a kyphotic image.

Answer 25

*You can attempt to sit patient more upright (by leaning back) and ask them to lift their chin high.
*You can reduce caudal angle of the beam- sometimes requires either straight tube or even cranial angulation of horizontal beam to achieve a diagnostic image.

Question 26

what may cause axial rotation?

Answer 26

*Patients with comorbidities may struggle to support themselves in upright, straight position
*Stroke patients/paraplegic patients/muscular dystrophy/dementia/general weakness

Question 27

Some points on patient aftercare

Answer 27

-Allow the patient to dress
-Ensure the patient has clear instructions of how to obtain results i.e. back to a clinic or GP
-Replace any dressings, lines etc removed prior to examination
-As with any examination do not discuss with the patient what you have seen on the radiograph!

Question 28

Summarise an Erect PA- what is it used for?

Answer 28

Its a routine view for fit and able bodied patients

Question 29

What is a lateral view used for?

Answer 29

To locate opacities & demonstrate their extent.

Question 30

What is an Erect AP used for?

Answer 30

Used for infirm patients or when taking most mobile radiographs.

Question 31

What is a supine AP used for?

Answer 31

For very ill or multiple injury patients.

Question 32

What is axial rotation, give examples?

Answer 32

-When medial ends of clavicles are not equidistant from spinous processes.
-Lung bases are unequal in size and shape.
-Half of the heart shadow is on the right half of the thoracic cavity.