UNASSIGNED: The purpose of this study was to determine optimal sets of b-values in diffusion-weighted MRI (DW-MRI) for obtaining monoexponential apparent diffusion coefficient (ADC) close to perfusion-insensitive intravoxel incoherent motion (IVIM) model ADC (ADCIVIM) in @entity1149 . Ten subjects had 40 DW-MRI scans before and during radiotherapy in a 1.5 T MRI scanner. Respiratory triggering was applied to the echo-planar DW-MRI with [Formula: see text] ms, TE      =      74   ms, eight b-values of 0-1000  s  m(-2), pixel size      =      [Formula: see text] mm(2), slice thickness      =      6   mm, interslice gap      =      1.2   mm, 7 axial slices and total acquisition time    6   min. One or more DW-MRI scans together covered the whole @entity5 volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADCIVIM values using all eight b-values. Intra-scan coefficient of variation (CV) of active @entity5 volumes was computed to compare the relative noise in ADC maps. ADC values for one pre-treatment DW-MRI scan of each of the 10 subjects were computed using b-value pairs from DW-MRI images synthesized for b-values of 0-2000  s  m(-2) from the estimated IVIM parametric maps and corrupted by various Rician noise levels. The square root of mean of squared error percentage (RMSE) of the ADC value relative to the corresponding ADCIVIM for the @entity5 volume of the scan was computed. Monoexponential ADC values for the b-value sets of 250 and 1000; 250, 500 and 1000; 250, 650 and 1000; 250, 800 and 1000; and 250-1000  s  m(-2) were not significantly different from ADCIVIM values ([Formula: see text], paired t-test). Mean error in ADC values for these sets relative to ADCIVIM were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADCIVIM. The monoexponential ADC values for other sets-0-1000; 50-1000; 100-1000; 500-1000; and 250 and 800  s  m(-2) were significantly different from the ADCIVIM values. From Rician noise simulation using b-value pairs, there was a wide range of acceptable b-value pairs giving small RMSE of ADC values relative to ADCIVIM. The pairs for small RMSE had lower b-values as the noise level increased. ADC values of a two b-value set-250 and 1000  s  m(-2), and all three b-value sets with 250, 1000  s  m(-2) and an intermediate value approached ADCIVIM, with relative noise comparable to that of ADCIVIM. These sets may be @entity5 using comparatively short scan and post-processing times. Rician noise simulation suggested that the b-values in the vicinity of these experimental best b-values can be used with error within an acceptable limit. It also suggested that the optimal sets will have lower b-values as the noise level becomes higher.

Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in XXXX .

@entity5 :: ('MESH:D009369', 'Disease') :: ['used in lung tumours', 'tumour'] @entity1149 :: ('MESH:D002289', 'Disease') :: ['non-small cell lung cancer']
@entity1149 :: (MESH:D002289,Disease) :: ['non-small cell lung cancer']
