X-rays

Summary

Introduction

X-rays are transmitted through different parts of the body with varying intensity. The number of X-rays that are transmitted through a material depends on the atomic number and the density of that material. For example, bone has a higher atomic number and a greater density than air; fewer X-rays penetrate bone than the air-filled lungs. The plain radiograph is obtained when the emergent X-rays interact with a photosensitive plate.

Gas, fat, soft tissue/fluid, bone/calcification and non-organic radio-opaque materials/contrast can be differentiated on a plain radiograph.

Indications

‘Making the Best Use of a Department of Clinical Radiology: Guidelines for Doctors’ is a very useful reference. If in doubt, discuss the case with a radiologist.

Preoperative chest X-ray: not routinely performed. Consider if the patient is known to have cardiorespiratory disease, >60 years.

Preoperative cervical spine: not routinely performed. Consider in patients who are at risk of atlanto-axial instability, who may be at risk of subluxation at the time of intubation e.g. rheumatoid arthritis, Down's syndrome.

Post-procedure chest X-ray: to check the satisfactory position of tubes and lines:

1. ▪ Nasogastric tube: tip should be seen within the stomach i.e. below the diaphragm; this should be confirmed before use.

2. ▪ Endotracheal tube (ETT): flexion and extension of the neck can cause the tip of ETT to move by up to 5 cm; therefore the tip should be placed 5 cm above the carina. If seen within 2 cm of the carina then the likelihood of it passing into the right main bronchus is increased and the tube should be withdrawn.

3. ▪ Tracheostomy tube: the tip should be seen centrally within the trachea at the level of T3.

4. […]