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’


The measurement of the size of lung nodules using dimensions from 3D scans to assess their growth rate.3 See also ‘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

  3. Devaraj A, van Ginneken B, Nair A, et al. 2017. Use of Volumetry for Lung Nodule Management: Theory and Practice. Radiology 284(3): 630-44