Description and validation of a scoring system for tomosynthesis in pulmonary cystic fibrosis.

OBJECTIVES:
To design and validate a scoring system for tomosynthesis (digital tomography) in pulmonary cystic fibrosis.

METHODS:
A scoring system dedicated to tomosynthesis in pulmonary cystic fibrosis was designed. Three radiologists independently scored 88 pairs of radiographs and tomosynthesis examinations of the chest in 60 patients with cystic fibrosis and 7 oncology patients. Radiographs were scored according to the Brasfield scoring system and tomosynthesis examinations were scored using the new scoring system.

RESULTS:
Observer agreements for the tomosynthesis score were almost perfect for the total score with square-weighted kappa >0.90, and generally substantial to almost perfect for subscores. Correlation between the tomosynthesis score and the Brasfield score was good for the three observers (Kendall's rank correlation tau 0.68, 0.77 and 0.78). Tomosynthesis was generally scored higher as a percentage of the maximum score. Observer agreements for the total score for Brasfield score were almost perfect (square-weighted kappa 0.80, 0.81 and 0.85).

CONCLUSIONS:
The tomosynthesis scoring system seems robust and correlates well with the Brasfield score. Compared with radiography, tomosynthesis is more sensitive to cystic fibrosis changes, especially bronchiectasis and mucus plugging, and the new tomosynthesis scoring system offers the possibility of more detailed and accurate scoring of disease severity.

KEY POINTS :
• Tomosynthesis is more sensitive than conventional radiography for pulmonary cystic fibrosis changes. • The radiation dose from chest tomosynthesis is low compared with computed tomography. • Tomosynthesis may become useful in the regular follow-up of patients with cystic fibrosis.