| Name of projection | Chest - Anterior Oblique (preferred over Posterior Obliques) |
| Area Covered | Lung fields, apices, costophrenic angles, cardiac shadow and mediastinal structures, trachea |
| Pathology shown | Pathologies involving the lung fields, abnormal cardiac shadows and mediastinal structures |
| Radiographic Anatomy | Chest Radiographic Anatomy |
| IR Size & Orientation | 35 x 43 cm
Portrait
D.R. may cover 43 x 43 cm |
| Film / Screen Combination | Regular
(CR and DR as recommended by manufacturer) |
| Bucky / Grid | Moving or Stationary Grid |
| Filter | No |
| Exposure | 100 kVp
5 mAs |
| FFD / SID | 180 cm |
| Central Ray | Directed to the level of T7 (for Anterior Obliques)
Directed 10 cm inferior to the jugular notch (for Posterior Obliques)
Perpendicular to the IR |
| Collimation | Centre: T7 (the level of the inferior border of the scapula)
Shutter A: Open to approximately 5 cm above the shoulder to include the upper airway
Shutter B: Open to include soft tissue borders laterally |
| Markers | Superior and Lateral
Marker orientation for Anterior Obliques - PA, for Posterior Obliques - AP |
| Shielding | Gonadal (check your department's policy guidelines) |
| Respiration | On suspended deep inspiration |
| Positioning | Anterior Oblique
- Patient erect, standing or seated, facing the bucky
- From this PA position, rotate the patient 45°, the shoulder maintaining contact with the bucky (the side of interest is further from the bucky)
- Centre the chest to the IR
- Remove the arms from the area of interest by
- placing the hand on the side closest to the bucky on the patient's hip
- Raise the arm on the side away from the bucky to shoulder level and rest their hand on the top of the bucky for support
- Ensure shoulders are in the same horizontal plane
Posterior Oblique
- Patient erect, standing or seated, with their back to the bucky
- From this AP position, rotate the patient 45°, the shoulder maintaining contact with the bucky (the side of interest is closer to the bucky)
- Centre the chest to the IR
- Remove the arms from the area of interest by
- Raising the arm on the side closest to the bucky to shoulder level
- placing the hand on the side further from the film on the patient's hip
- Ensure shoulders are in the same horizontal plane
|
Critique
| Positioning
- The patient's chest is obliqued 45°, evidenced by
- The sternoclavicular joints do not superimpose the thoracic spine
- The thoracic spine is shown so that the lungs/ribs on one side occupies twice as much space as on the other side
- on an RAO, the cardiac shadow is shown without spinal superimposition (an LAO requires 60° obliquity to achieve this)
- on an LPO, the cardiac shadow is shown without spinal superimposition (an RPO requires 60° obliquity to achieve this)
- The 10th posterior ribs will be visualised above the diaphragm on full inspiration
Area Covered
- Lungs fields, apices, costophrenic angles, heart
Collimation
- Centre: At the level of the T7 Thoracic vertebra, and centred to the chest cavity as visualised on the image
- Shutter A: Open to show the lung apices superiorly and the costophrenic angles inferiorly
- Shutter B: Open to show the lung fields laterally
Exposure
- There should be adequate exposure so that
- the ribs are seen faintly through the heart
- the thoracic vertebrae are visualised
- vascular lungs markings are shown
- the cardiac shadow and mediastinal structures are visualised
|
| Special Notes | Anterior Obliques
Keep in mind that the side shown is the side further from the IR, that is,
Right Anterior Oblique (RAO) shows the left lung field
Left Anterior Oblique (LAO) shows the right lung field
Posterior Obliques
Keep in mind that the side shown is the side closer to the IR, that is,
Right Posterior Obliques (RPO) shows the right lung field
Left Posterior Obliques (LPO) shows the left lung field
Anterior Obliques vs Posterior Obliques
Posterior Obliques - |