Cardiothoracic Ratio
A measurement on chest radiographs comparing the maximum cardiac width to the maximum thoracic width, used to assess cardiac enlargement.
Full Definition
The cardiothoracic ratio (CTR) is a radiographic measurement obtained from posteroanterior chest X-rays by dividing the maximum cardiac silhouette width by the maximum internal thoracic width at the level of the diaphragm. Normal values are typically less than 0.5 (50%) in adults and slightly higher in children and infants. In congenital heart disease, an elevated cardiothoracic ratio may indicate cardiac enlargement due to volume or pressure overload, helping guide clinical decision-making and monitoring disease progression. This measurement provides a quick assessment tool for cardiac size, though it has limitations in complex congenital anatomy. Editorial teams should note the compound nature requiring hyphenation.
Usage
Usage note: Hyphenate the compound term; CTR is acceptable abbreviation after first use.
In Context
- "The chest radiograph showed an elevated cardiothoracic ratio of 0.65, suggesting cardiac enlargement." — Radiology report
- "Serial cardiothoracic ratios demonstrated progressive improvement following surgery." — Follow-up imaging assessment