### Abstract

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 (ADC_{IVIM}) in non-small cell lung cancer. 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 ms, TE = 74 ms, eight b-values of 0-1000 μs μm^{-2}, pixel size = 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 tumour volume. Monoexponential model ADC values using various b-value sets were compared to reference-standard ADC_{IVIM} values using all eight b-values. Intra-scan coefficient of variation (CV) of active tumour 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 μs μm^{-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 ADC_{IVIM} for the tumour 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 μs μm^{-2} were not significantly different from ADC_{IVIM} values (, paired t-test). Mean error in ADC values for these sets relative to ADC_{IVIM} were within 3.5%. Intra-scan CVs for these sets were comparable to that for ADC_{IVIM}. The monoexponential ADC values for other sets - 0-1000; 50-1000; 100-1000; 500-1000; and 250 and 800 μs μm^{-2} were significantly different from the ADC_{IVIM} 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 ADC_{IVIM}. 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 μs μm^{-2}, and all three b-value sets with 250, 1000 μs μm^{-2} and an intermediate value approached ADC_{IVIM}, with relative noise comparable to that of ADC_{IVIM}. These sets may be used in lung tumours 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.

Original language | English (US) |
---|---|

Pages (from-to) | 7877-7891 |

Number of pages | 15 |

Journal | Physics in Medicine and Biology |

Volume | 60 |

Issue number | 20 |

DOIs | |

State | Published - Sep 25 2015 |

### Fingerprint

### Keywords

- ADC
- diffusion
- DW-MRI
- IVIM model
- lung cancer
- Rician noise

### ASJC Scopus subject areas

- Radiology Nuclear Medicine and imaging
- Radiological and Ultrasound Technology

### Cite this

*Physics in Medicine and Biology*,

*60*(20), 7877-7891. https://doi.org/10.1088/0031-9155/60/20/7877

**Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer.** / Karki, Kishor; Hugo, Geoffrey D.; Ford, John; Olsen, Kathryn M.; Saraiya, Siddharth; Groves, Robert; Weiss, Elisabeth.

Research output: Contribution to journal › Article

*Physics in Medicine and Biology*, vol. 60, no. 20, pp. 7877-7891. https://doi.org/10.1088/0031-9155/60/20/7877

}

TY - JOUR

T1 - Estimation of optimal b-value sets for obtaining apparent diffusion coefficient free from perfusion in non-small cell lung cancer

AU - Karki, Kishor

AU - Hugo, Geoffrey D.

AU - Ford, John

AU - Olsen, Kathryn M.

AU - Saraiya, Siddharth

AU - Groves, Robert

AU - Weiss, Elisabeth

PY - 2015/9/25

Y1 - 2015/9/25

N2 - 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 non-small cell lung cancer. 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 ms, TE = 74 ms, eight b-values of 0-1000 μs μm-2, pixel size = mm2, 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 tumour 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 tumour 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 μs μm-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 tumour 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 μs μm-2 were not significantly different from ADCIVIM values (, 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 μs μm-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 μs μm-2, and all three b-value sets with 250, 1000 μs μm-2 and an intermediate value approached ADCIVIM, with relative noise comparable to that of ADCIVIM. These sets may be used in lung tumours 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.

AB - 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 non-small cell lung cancer. 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 ms, TE = 74 ms, eight b-values of 0-1000 μs μm-2, pixel size = mm2, 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 tumour 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 tumour 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 μs μm-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 tumour 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 μs μm-2 were not significantly different from ADCIVIM values (, 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 μs μm-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 μs μm-2, and all three b-value sets with 250, 1000 μs μm-2 and an intermediate value approached ADCIVIM, with relative noise comparable to that of ADCIVIM. These sets may be used in lung tumours 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.

KW - ADC

KW - diffusion

KW - DW-MRI

KW - IVIM model

KW - lung cancer

KW - Rician noise

UR - http://www.scopus.com/inward/record.url?scp=84946073444&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84946073444&partnerID=8YFLogxK

U2 - 10.1088/0031-9155/60/20/7877

DO - 10.1088/0031-9155/60/20/7877

M3 - Article

VL - 60

SP - 7877

EP - 7891

JO - Physics in Medicine and Biology

JF - Physics in Medicine and Biology

SN - 0031-9155

IS - 20

ER -