title: Diffusion-weighted magnetic resonance imaging for assessment of lung lesions: repeatability of the apparent diffusion coefficient measurement.
abstract: OBJECTIVE
  To establish repeatability of apparent diffusion coefficients (ADCs) acquired from free-breathing diffusion-weighted magnetic resonance imaging (DW-MRI) in malignant lung lesions and investigate effects of lesion size, location and respiratory motion.
  
  
  METHODS
  Thirty-six malignant lung lesions (eight patients) were examined twice (1- to 5-h interval) using T1-weighted, T2-weighted and axial single-shot echo-planar DW-MRI (b = 100, 500, 800 s/mm(2)) during free-breathing. Regions of interest around target lesions on computed b = 800 s/mm(2) images by two independent observers yielded ADC values from maps (pixel-by-pixel fitting using all b values and a mono-exponential decay model). Intra- and inter-observer repeatability was assessed per lesion, per patient and by lesion size (> or <2 cm) or location.
  
  
  RESULTS
  ADCs were similar between observers (mean ± SD, 1.15 ± 0.28 × 10(-3) mm(2)/s, observer 1; 1.15 ± 0.29 × 10(-3) mm(2)/s, observer 2). Intra-observer coefficients of variation of the mean [median] ADC per lesion and per patient were 11% [11.4%], 5.7% [5.7%] for observer 1 and 9.2% [9.5%], 3.9% [4.7%] for observer 2 respectively; inter-observer values were 8.9% [9.3%] (per lesion) and 3.0% [3.7%] (per patient). Inter-observer coefficient of variation (CoV) was greater for lesions <2 cm (n = 20) compared with >2 cm (n = 16) (10.8% vs 6.5% ADCmean, 11.3% vs 6.7% ADCmedian) and for mid (n = 14) vs apical (n = 9) or lower zone (n = 13) lesions (13.9%, 2.7%, 3.8% respectively ADCmean; 14.2%, 2.8%, 4.7% respectively ADCmedian).
  
  
  CONCLUSIONS
  Free-breathing DW-MRI of whole lung achieves good intra- and inter-observer repeatability of ADC measurements in malignant lung tumours.
  
  
  CONCLUSIONS
  • Diffusion-weighted MRI of the lung can be satisfactorily acquired during free-breathing • DW-MRI demonstrates high contrast between primary and metastatic lesions and normal lung • Apparent diffusion coefficient (ADC) measurements in lung tumours are repeatable and reliable • ADC offers potential in assessing response in lung metastases in clinical trials.
authors.affiliation: CRUK and EPSRC Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Surrey, SM2 5PT, UK.
authors.forename: L
authors.initials: L
authors.lastname: Bernardin
authors.forename: N H M
authors.initials: NH
authors.lastname: Douglas
authors.forename: D J
authors.initials: DJ
authors.lastname: Collins
authors.forename: S L
authors.initials: SL
authors.lastname: Giles
authors.forename: E A M
authors.initials: EA
authors.lastname: O'Flynn
authors.forename: M
authors.initials: M
authors.lastname: Orton
authors.forename: N M
authors.initials: NM
authors.lastname: deSouza
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement; D008175:Lung Neoplasms / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D012119:Respiration