Characterization of focal liver lesions by ADC measurements using a respiratory triggered diffusion-weighted single-shot echo-planar MR imaging technique

Abstract

The aim of this study was to determine apparent diffusion coefficients (ADCs) of focal liver lesions on the basis of a respiratory triggered diffusion-weighted single-shot echo-planar MR imaging sequence (DW-SS-EPI) and to evaluate whether ADC measurements can be used to characterize lesions. One hundred and two patients with focal liver lesions [11 hepatocellular carcinomas (HCC), 82 metastases, 4 focal nodular hyperplasias (FNH), 56 hemangiomas and 51 cysts; mean size, 16.6 mm; range 5-92 mm] were examined on a 1.5-T system using respiratory triggered DW-SS-EPI (b-values: 50, 300, 600 s/mm2). Results were correlated with histopathologic data and follow-up imaging. The ADCs of different lesion types were compared, and lesion discrimination using optimal thresholds for ADCs was evaluated. Mean ADCs (x10(-3)mm2/s) were 1.24 and 1.04 for normal and cirrhotic liver parenchyma and 1.05, 1.22, 1.40, 1.92 and 3.02 for HCCs, metastases, FNHs, hemangiomas and cysts, respectively. Mean ADCs differed significantly for all lesion types except for comparison of metastases with HCCs and FNHs. Overall, 88% of lesions were correctly classified as benign or malignant using a threshold value of 1.63 x 10(-3)mm2/s. Measurements of the ADCs of focal liver lesions on the basis of a respiratory triggered DW-SS-EPI sequence may constitute a useful supplementary method for lesion characterization.

Diffusion‐weighted imaging of the liver: Comparison of navigator triggered and breathhold acquisitions

“…There are several recent reports on the use of respiratory triggered acquisitions for liver DWI (15,16,[28][29][30][31]. However, only two studies have specifically compared different diffusion acquisition schemes for liver imaging (28,30).…”

“…Few recent studies have reported the use of respiratory triggered liver DWI without (28 -30) or with a navigator echo (15,16). Gourtsoyianni et al (29) assessed the accuracy of ADC obtained with non navigator echo respiratory triggered SS EPI DWI sequence (n ϭ 38) for characterization of liver lesions, and found sensitivity and specificity of 100% for diagnosis of malignancy using lesion ADC Ͻ 1.26 ϫ 10 Ϫ3 mm 2 /s, similar to our reported sensitivity and specificity.…”

“…Gourtsoyianni et al (29) assessed the accuracy of ADC obtained with non navigator echo respiratory triggered SS EPI DWI sequence (n ϭ 38) for characterization of liver lesions, and found sensitivity and specificity of 100% for diagnosis of malignancy using lesion ADC Ͻ 1.26 ϫ 10 Ϫ3 mm 2 /s, similar to our reported sensitivity and specificity. Bruegel et al (15,16) used the same MR system used in our study and a similar PACE DWI sequence to detect and characterize liver lesions. They observed better performance of DWI Figure 3.…”

“…SS EPI sequences are very fast, however, suffer from limited image quality, mostly related to limited signal to noise ratio (SNR) especially at higher b-values, and limited spatial resolution, which constitute an obstacle for its widespread use in clinical practice. Techniques such as parallel imaging (25,26) and pulse triggering (27) have been proposed to improve SS EPI image quality and precision of ADC measurement.There are several recent reports on the use of respiratory triggered acquisitions for liver DWI (15,16,[28][29][30][31]. However, only two studies have specifically compared different diffusion acquisition schemes for liver imaging (28,30).…”

“…THERE IS A GROWING interest in using liver diffusionweighted imaging (DWI) for lesion detection and characterization, prediction of treatment response and assessment of chronic liver disease, by means of apparent diffusion coefficient (ADC) measurement (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). The interest in DWI is motivated by the recently described risk of nephrogenic systemic fibrosis (21)(22)(23)(24), which makes DWI an attractive alternate method to Gadolinium-enhanced sequences.…”