The glossary explains some of the words used across this website and covers some key cancer and research terms, which primarily focus on lung cancer.

Volume doubling time (VDT)

A measure of the number of days in which a nodule that is visible on a scan is calculated to double in size (volume). In lung cancer screening, VDT may be used to understand how fast a nodule, whether a benign or suspected lung cancer tumour, may be growing between scans.1 2 See also ‘Benign tumour’ and ‘Nodule’


  1. Spratt JS, Spratt JA. 1976. The prognostic value of measuring the gross linear radial growth of pulmonary metastases and primary pulmonary cancers. J Thorac Cardiovasc Surg 71(2): 274-8

  2. Kanashiki M, Tomizawa T, Yamaguchi I, et al. 2012. Volume doubling time of lung cancers detected in a chest radiograph mass screening program: Comparison with CT screening. Oncol Lett 4(3): 513-16