A normal chest ratio, referring to the cardiothoracic ratio (CTR) on a chest X-ray, typically falls between 0.42 and 0.50.
Understanding the Cardiothoracic Ratio (CTR)
The cardiothoracic ratio (CTR) is a measurement used on chest X-rays to assess heart size. It compares the maximum width of the heart to the maximum width of the chest. This ratio helps determine if the heart is enlarged (cardiomegaly), which can indicate various underlying heart conditions.
How is the CTR Measured?
The CTR is calculated by:
- Measuring the widest horizontal diameter of the heart on a PA (posteroanterior) chest X-ray.
- Measuring the widest internal diameter of the chest at the level of the diaphragm.
- Dividing the heart's width by the chest's width.
Interpreting the CTR
| CTR Measurement | Interpretation |
|---|---|
| Less than 0.42 | Usually considered pathological. |
| 0.42 - 0.50 | Normal range. |
| Greater than 0.50 | Usually considered abnormal; some radiologists consider up to 0.55 "borderline". |
It's important to remember that the interpretation of CTR should always be done in conjunction with a clinical evaluation and other relevant investigations.
