The broncho-arterial (BA) ratio is a descriptive parameter used in thoracic CT imaging. It is defined as the diameter of the bronchial lumen divided by the diameter of its accompanying artery 1. It is usually measured in the segmental to subsegmental artery level.
In healthy humans, the broncho-arterial ratio is usually taken as being around 1:1.
It can increase or decrease in various situations.
Increased broncho-arterial ratio
Some authors term an increased broncho-arterial ratio of >1.5 as bronchiectasis although several non-pathological conditions can slightly increase the ratio. These include
- ageing 2
- high altitude 3
Pathological conditions that can increase the bronchoarterial ratio includes
Conditions that can reduce pulmonary arterial calibres
Decreased broncho-arterial ratio
Decreased broncho-arterial ratios have been described with
- normal individual - ratios down to 0.65 have been described as acceptable within normal limits 5
- conditions that cause bronchoconstriction
- asthma 4
- 1. Kim SJ, Im JG, Kim IO et-al. Normal bronchial and pulmonary arterial diameters measured by thin section CT. J Comput Assist Tomogr. 1995;19 (3): 365-9. Pubmed citation
- 2. Matsuoka S, Uchiyama K, Shima H et-al. Bronchoarterial ratio and bronchial wall thickness on high-resolution CT in asymptomatic subjects: correlation with age and smoking. AJR Am J Roentgenol. 2003;180 (2): 513-8. doi:10.2214/ajr.180.2.1800513 - Pubmed citation
- 3. Kim JS, Müller NL, Park CS et-al. Bronchoarterial ratio on thin section CT: comparison between high altitude and sea level. J Comput Assist Tomogr. 1997;21 (2): 306-11. Pubmed citation
- 4. Park CS, MüLler NL, Worthy SA et-al. Airway obstruction in asthmatic and healthy individuals: inspiratory and expiratory thin-section CT findings. Radiology. 1997;203 (2): 361-7. Radiology (abstract) - Pubmed citation
- 5. Naidich DP, Srichai MB, Krinsky GA. Computed tomography and magnetic resonance of the thorax. Lippincott Williams & Wilkins. (2007) ISBN:0781757657. Read it at Google Books - Find it at Amazon
- 6. Diaz AA, Young TP, Maselli DJ, Martinez CH, Maclean ES, Yen A, Dass C, Simpson SA, Lynch DA, Kinney GL, Hokanson JE, Washko GR, San José Estépar R. Bronchoarterial ratio in never-smokers adults: Implications for bronchial dilation definition. (2017) Respirology (Carlton, Vic.). 22 (1): 108-113. doi:10.1111/resp.12875 - Pubmed