CT scan

CT scanning is performed in spiral mode using a low dose protocol and without contrast injection. Extent of low-density areas relative to total lung volume is determined with a density mask method, using image eXplorer, and expressed as emphysema scores (ES)¹. Lung volume is calculated after segmenting both lungs with a fully automated region-growing  program. ES are calculated at -910 HU (for mild emphysema) and -950HU (for severe emphysema). ES of ≥10% at -910 HU and/or  ≥1% at -950 HU is considered abnormal and these subjects are labelled as ‘COPD’.

_{¹ Schilham AM, van Ginneken B, Gietema H, Prokop M. Local noise weighted filtering for emphysema scoring of low-dose CT images. IEEE Transactions on Medical Imaging 2006; 25: 451 – 63.}

More information about the other techniques used:

• Pulmonary function tests
• Genome wide screening