Yee Liang Thian MBBS, FRCR, Presenter: Nothing to Disclose

Yonghan Ting MBBS, Abstract Co-Author: Nothing to Disclose

Andrew Tan Eh MBBS, FRCR, Abstract Co-Author: Nothing to Disclose

Cher Heng Tan MBBS, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to assess the diagnostic performance of normalized apparent diffusion coefficient (ADC) values for differentiation of malignant and benign focal hepatic lesions when varied diffusion weighted imaging (DWI ) techniques were used.

Abdominal MRI studies of 32 consecutive patients with 50 hepatic lesions larger than 1 cm were retrospectively reviewed. Lesions were classified as malignant or benign based on histopathological diagnosis or classic imaging findings. ADC maps were generated with one of 3 techniques : (1) 1.5 T with b values of 0,500 (2) 1.5 T with b values of 0,1000 and (3) 3.0 T with b values of 0,50,500,1000. Absolute ADC values of focal hepatic lesions were calculated by region of interest analysis. Normalization was performed by dividing absolute ADC values with the absolute ADC of the spleen. Diagnostic performances were evaluated by receiver operating characteristic (ROC) curve analysis .

There were 19 malignant lesions (9 metastases, 10 hepatocellular carcinomas) and 31 benign lesions (12 hemangiomas, 12 cysts, 6 focal nodular hyperplasia and 1 abscess). ADC maps for 11 lesions were obtained using technique #1, 19 lesions using technique #2 and 20 lesions with technique #3. Significant difference (p<0.01) was found between mean normalized ADCs of benign (2.34±0.94) and malignant (1.27±0.27) lesions. Malignancy and normalized ADC values were significantly correlated (point-biserial correlation coefficient = -0.51, p<0.01). The area under the ROC curve of normalized ADC values (0.890) was significantly higher than that of absolute ADC (0.783) for detection of malignancy (p=0.008). Using a normalized ADC value cutoff of 1.6, overall sensitivity, specificity and accuracy for malignant lesions was 89% (17/19), 84% (26/31), and 86% (43/50) respectively, with diagnostic odds ratio 44.2 (95% CI 33.2-121.5). Individual accuracy rates for techniques 1, 2 and 3 were 82% (9/11), 89% (17/19) and 85% (17/20) respectively.

Normalized ADC values allow reliable differentiation between benign and malignant hepatic lesions despite differences in DWI technique. Normalization of ADC values with the spleen may allow comparison of ADC values across imaging platforms.

Normalization of hepatic ADC values with the spleen may allow inter-imager comparison of ADC values for characterisation of hepatic lesions.

Thian, Y, Ting, Y, Tan Eh, A, Tan, C, Utility of Normalized Apparent Diffusion Coefficient Values in Characterization of Focal Hepatic Lesions Across Imaging Platforms.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9003446.html