title: Diffusion-weighted (DW) MRI in lung cancers: ADC test-retest repeatability.
abstract: OBJECTIVE
  To determine the test-retest repeatability of Apparent Diffusion Coefficient (ADC) measurements across institutions and MRI vendors, plus investigate the effect of post-processing methodology on measurement precision.
  
  
  METHODS
  Thirty malignant lung lesions >2 cm in size (23 patients) were scanned on two occasions, using echo-planar-Diffusion-Weighted (DW)-MRI to derive whole-tumour ADC (b = 100, 500 and 800smm-2). Scanning was performed at 4 institutions (3 MRI vendors). Whole-tumour volumes-of-interest were copied from first visit onto second visit images and from one post-processing platform to an open-source platform, to assess ADC repeatability and cross-platform reproducibility.
  
  
  RESULTS
  Whole-tumour ADC values ranged from 0.66-1.94x10-3mm2s-1(mean = 1.14). Within-patient coefficient-of-variation (wCV) was 7.1% (95% CI 5.7-9.6%), limits-of-agreement (LoA) -18.0 to 21.9%. Lesions >3 cm had improved repeatability: wCV 3.9% (95% CI 2.9-5.9%); and LoA -10.2 to 11.4%. Variability for lesions <3 cm was 2.46 times higher. ADC reproducibility across different post-processing platforms was excellent: Pearson's R2= 0.99; CoV 2.8% (95% CI 2.3-3.4%); and LoA -7.4 to 8.0%.
  
  
  CONCLUSIONS
  A free-breathing DW-MRI protocol for imaging malignant lung tumours achieved satisfactory within-patient repeatability and was robust to changes in post-processing software, justifying its use in multi-centre trials. For response evaluation in individual patients, a change in ADC >21.9% will reflect treatment-related change.
  
  
  CONCLUSIONS
  • In lung cancer, free-breathing DWI-MRI produces acceptable images with evaluable ADC measurement. • ADC repeatability coefficient-of-variation is 7.1% for lung tumours >2 cm. • ADC repeatability coefficient-of-variation is 3.9% for lung tumours >3 cm. • ADC measurement precision is unaffected by the post-processing software used. • In multicentre trials, 22% increase in ADC indicates positive treatment response.
authors.affiliation: CRUK Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, SM2 5PT, UK. alex.weller@icr.ac.uk.
authors.forename: Alex
authors.identifier: http://orcid.org/0000-0003-0506-5236
authors.initials: A
authors.lastname: Weller
authors.affiliation: CRUK Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, SM2 5PT, UK.
authors.forename: Marianthi Vasiliki
authors.initials: MV
authors.lastname: Papoutsaki
authors.affiliation: University of Manchester, Manchester, UK.
authors.forename: John C
authors.initials: JC
authors.lastname: Waterton
authors.affiliation: Humanitas University, Milan, Italy.
authors.forename: Arturo
authors.initials: A
authors.lastname: Chiti
authors.affiliation: Universiteit Antwerpen, Antwerpen, Belgium.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Stroobants
authors.affiliation: Vrije Universiteit Medisch Centrum, Amsterdam, The Netherlands.
authors.forename: Joost
authors.initials: J
authors.lastname: Kuijer
authors.affiliation: CRUK Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, SM2 5PT, UK.
authors.forename: Matthew
authors.initials: M
authors.lastname: Blackledge
authors.affiliation: Department of Medicine, Royal Marsden NHS Foundation Trust, London, UK.
authors.forename: Veronica
authors.initials: V
authors.lastname: Morgan
authors.affiliation: CRUK Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, SM2 5PT, UK.
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D047368:Tumor Burden
keywords: Apparent Diffusion Coefficient (ADC); Diffusion-weighted MRI; Lung Cancer; Repeatability; Reproducibility