• Bachir Taouli, Alison Sandberg, Alto Stemmer, Tejas Parikh, Samson Wong, Jian Xu, and Vivian S Lee.
• NYU Medical Center, Department of Radiology, New York, NY, USA. btaouli@yahoo.com
• J Magn Reson Imaging. 2009 Sep 1; 30 (3): 561-8.

PurposeTo compare a free breathing navigator triggered single shot echoplanar imaging (SS EPI) diffusion-weighted imaging (DWI) sequence with prospective acquisition correction (PACE) with a breathhold (BH) DWI sequence for liver imaging.Materials And MethodsThirty-four patients were evaluated with PACE-DWI and BH DWI of the liver using b-values of 0, 50, and 500 s/mm(2). There were 29 focal liver lesions in 18 patients. Qualitative evaluation was performed on a 3-point scale (1-3) by two independent observers (maximum score 9). Quantitative evaluation included estimated SNR (signal to noise ratio), lesion-to-liver contrast ratio, liver and lesion apparent diffusion coefficients (ADCs), and coefficient of variation (CV) of ADC in liver parenchyma and focal liver lesions (estimate of noise contamination in ADC).ResultsPACE-DWI showed significantly better image quality, higher SNR and lesion-to-liver contrast ratio when compared with BH DWI. ADCs of liver and focal lesions with both sequences were significantly correlated (r = 0.838 for liver parenchyma, and 0.904 for lesions, P < 0.0001), but lower with the BH sequence (P < 0.02). There was higher noise contamination in ADC measurement obtained with BH DWI (with a significantly higher SD and CV of ADC).ConclusionThe use of a navigator echo to trigger SS EPI DWI improves image quality and liver to lesion contrast, and enables a more precise ADC quantification compared with BH DWI acquisition.

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