Diffusion weighted imaging combined with dynamic contrast enhanced magnetic resonance imaging in diagnosis of Hepatocellular carcinoma.

Abstract

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy of adults. It is the fifth most common cancer in the world and the third most common cause of death attributed to cancer

Triphasic CT together with high alpha fetoprotein, was believed to be the standard in diagnosis of HCC. Unfortunately, not all cases with HCC have high alpha fetoprotein and not all cases having typical imaging criteria of HCC and also, not all lesions detected by US are seen in the dynamic CT study.

Because of its high contrast resolution, MRI, using fast imaging technique, non-specific and liver-specific contrast agents, is a very powerful modality for the detection and characterization of hepatic focal lesions.

For hepatic focal lesions detection and characterization, conventional MRI relies on T1-weighted, T2-weighted, and dynamic gadolinium-enhanced T1-weighted imaging.

DW MR imaging is an attractive technique for multiple reasons: it can potentially add useful qualitative and quantitative information to conventional imaging sequences; it is quick (performed within a breath hold) and can be easily incorporated to existing protocols; and it is a non-enhanced technique (performed without the use of gadolinium-based contrast media), thus easy to repeat, and useful in patients with severe renal dysfunction at risk for nephrogenic systemic fibrosis. The ADC maps provide quantitative measurements of tissue water diffusivity, which can be used not only for disease assessment, but also for the evaluation of disease response to treatment.

The ideal MRI protocol for diagnosing HCC in cirrhosis should include gadoxetic acid enhanced dynamic and hepatobiliary phases, and DWI. Dynamic images detect neovascularity, GA-HP images confirm the absence of hepatocytes, and DWI depicts hypercellularity; the three biological hallmarks of HCC over benign cirrhotic nodules. This protocol has been reported to improve the diagnostic accuracy of either gadoxetic acid-enhanced or DWI sequences alone.

The internationally accepted morphological criteria of HCC are early arterial enhancement followed by a rapid wash-out during the porto-venous and late phases(rapid wash-in and wash-out) together with hyperintensity on DWI(restricted diffusion) ,The ADC value of HCC is low.