Multiple b value diffusion-weighted MRI of liver: A novel respiratory frequency-modulated continuous-wave radar-trigger technique and comparison with free-breathing technique.

OBJECTIVE

The aim of this study was to evaluate a novel respiratory frequency-modulated continuous-wave radar-trigger (FT) technique for multiple -b-value diffusion-weighted imaging (DWI) of liver and compare it with conventional free breathing (FB) DWI technique.

MATERIAL AND METHODS

39 patients with focal liver lesions underwent both frequency-modulated continuous-wave radar-trigger (FT) and conventional free-breathing (FB) multi-b-value diffusion-weighted imaging (DWI,b = 0,50,400,800 s/mm. Two abdominal radiologists independently assessed the quality of liver DWI images obtained using both techniques, measured and compared liver signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) at different b-values, as well as apparent diffusion coefficient (ADC) values calculated from all b-values.

RESULTS

In terms of image quality, the FT technique is superior to the conventional FB technique, with overall image quality scores (Reader 1, 3.56 ± 0.50 and Reader 2, 3.59 ± 0.55)vs (Reader 1, 2.90 ± 0.75 and Reader 2, 2.97 ± 0.71), respectively. The liver SNR (at b-values of 50,400,and 800 s/mm) obtained by FT was (138.5 ± 43.48, 96.67 ± 31.95, 71.54 ± 22.03), respectively, which was significantly higher than that obtained by conventional FB (110.90 ± 39.28, 80.86 ± 29.13, 60.43 ± 18.61, P < 0.05). The lesion CNR with FT was significantly higher than that with conventional FB (258.99 ± 151.38 vs 174.60 ± 99.90; 164.56 ± 87.25 vs 111.12 ± 42.43; 118.83 ± 68.76 vs 76.01 ± 35.48, P < 0.001). There was no significant difference in ADC values of liver and lesions between the two techniques: ADCliver-L and ADCliver-R: (FT 1479.3 ± 270.0 vs FB 1529.3 ± 275.5 and FT 1219.6 ± 127.4 vs FB 1248.7 ± 168.2, P > 0.05); ADC lesion:FT(969.0 ± 261.3) vs FB (1017.5 ± 240.4, P > 0.05).

CONCLUSION

For multi-b-value liver diffusion-weighted imaging, FT technique has higher image quality and better lesion visibility than conventional FB technique and there is no significant difference in ADC values of liver and lesions between the two techniques.