Thoracic positioning

By Dr Kushagra V

Garg

Most common radiological investigation

Standard component of a pulmonary examination

Systematic review is vital in interpretation of chest x-rays

Chest radiographs are one of the most difficult X Rays to interpret because of subject to subject variation.

2 dimensional image of a 3 dimensional structure

X-ray findings may lag behind other clinical features

Normal x-ray does not rule out pathology Dependent on good quality image

1: Name 2: Date 3: Old films 4: What type of view(s) 5: Penetration 6: Inspiration 7: Rotation 8: Angulation 9: Soft tissues / bony structures 10: Mediastinum 11: Diaphragms 12: Lung Fields

Quality Control

Findings

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Pre-read}

1. Check the name 2. Check the date/Side 3. Obtain old films if available

4. Which view(s) do you have? PA / AP, lateral, decubitus, AP lordotic

5. Penetration

Should see ribs through the heart

Barely see the spine through the heart

Should see pulmonary vessels nearly to the edges of the lungs

Overpenetrated Film

• Lung fields darker than normal—may obscure subtle pathologies

• See spine well beyond the diaphragms

• Inadequate lung detail

Underpenetrated Film•Hemidiaphragms are obscured

•Pulmonary markings more prominent than they actually are

Should be kept minimum to decrease/minimize motion unsharpness

For faster cassette we have to compromise on the kV and penetration but exposure time is minimized

6. Inspiration

Should be able to count 9-10 posterior ribs

Heart shadow should not be hidden by the diaphragm

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9-10 posterior ribs are showing

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About 8 posterior ribs are showing

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With better inspiration, the

“disease process” at the lung bases has

cleared

7. Rotation

Medial ends of bilateral clavicles are equidistant from the midline or vertebral bodies

If spinous process appears closer to the right clavicle (red arrow), the patient is rotated toward their own left side

If spinous process appears closer to the left clavicle (red arrow),

the patient is rotated toward their own right side

8. Angulation

Clavicle should lay over 3rd rib

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Pitfall Due to AngulationPitfall Due to Angulation

A film which is apical lordotic (beam is angled up A film which is apical lordotic (beam is angled up toward head) will have an unusually shaped heart toward head) will have an unusually shaped heart

and the usually sharp border of the left and the usually sharp border of the left hemidiaphragm will be absenthemidiaphragm will be absent

Apical lordotic Same patient, not lordotic

9. Soft tissue and bony structures Check for

Symmetry Deformities Fractures Masses Calcifications Lytic lesions

10. Mediastinum Check for

Cardiomegaly Mediastinal

and Hilar contours for hilar masses

11. Diaphragms

Check sharpness of borders

Right is normally higher than left

Check for free air, gastric bubble, pleural effusions

Posteroanterior – PA(erect) Anteroposterior – AP(mostly supine) Lateral Decubitus Lordotic Thoracic Inlet View

Standard, radiology dept X-rays posterior to anterior Standing position Cassette in the front FFD of 180 cms Centring inferior angle of scapula(T7) kV,mAs and cassette selection depends

on the patient

Intervertebral disc spaces upto T4 should be ideally visualised

Chest PA Expiration study Expiratory view demonstrates air trapping and diaphragm movement Exp : pneumothorax, interstitial shadowing,

obstructive emphysema(foreign body)

Cassette placed behind patient X-rays anterior to posterior Sitting in chair, semi-erect in bed, supine AP marked on film Heart enlarged, poor inspiration Collimation

Cassette above lung apices.

MSP perpendicular to cassette

Shoulder brought downwards, hand behind the back and elbows way forward

The central ray is then angled until it is coincident with the

middle of the film

Normal AP

upper edge of cassette just above the lung apices

arms laterally rotated

Central beam is directed towards sternal notch

FFD of 120cms.

Level of diaphragm is

on a higher level

Cassette should be parallel to the coronal plane

Central ray is angled till it is coincidental with middle of the cassette

Centring is at sternal notch

Used to visualize ribs Used for non ambulatory patients Used for pediatric age group

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.

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

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 cephalad head towards the sternal angle

The patient is placed for the postero-anterior projection.

he clasps 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.

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

The patient lies supine, with the median sagittal plane adjusted to coincide with the central long axis of the imaging couch.

The chin is raised to bring the radiographic baseline to an angle of 20 degrees from the vertical.

The cassette is centred at the level of the sternal notch.

Central beam is directed at the midline at the level of the sternal notch.

Exposure is made on forced expiration.

Antero-posterior radiograph of trachea showing paratracheal lymph node mass.

The patient stands or sits with either shoulder against a vertical Bucky.

The median sagittal plane of the trunk and head are parallel to the cassette.

The cassette should be large enough to include from the

lower pharynx to the lower end of the trachea at the level of the sternal angle.

The shoulders are pulled well backwards to enable the visualization of the trachea.

This position is aided by the patient clasping their hands

behind the back and pulling their arms backwards.

The cassette is centred at the

level of the sternal notch.

Patient lie semi prone on the affected side. Arms over the head Upper edge of the cassette is placed just above the lung

apices Centering is at the middle of the cassette or at the level of

T7. AP setup should be made. Knee flexed and should be on top of one another The affected side should be supported by some radiolucent

material so that the affected side completely comes in the xray.

Marker Decubitus - useful for differentiating pleural effusions from

consolidation (e.g. pneumonia) ; Loculated effusions from free fluid in the pleura. Abscess

Radiographic positioning by clarks Wikipedia Radiographic positioning and procedures

by Greathouse Valuble inputs by Dr Kirti and Dr Gandhi

Thank You for the long and ?? Boring Thank You for the long and ?? Boring presentationpresentation

CT Hrct MRI Angiography

But due to limitation of time and topic these modalities will be covered in subsequent presentations