الفهرس 
Anatomy of the liverOnly 14 pages are availabe for public view
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Abstract
Hepatic focal lesions may be benign or malignant. Therapy requires an accurate diagnosis, which in turn relies primarily on appropriate imaging and image-guided biopsy.
Triphasic CT was believed to be the standard in evaluating the hepatic focal lesions and together with alpha fetoprotein, the lesions were decided either non conclusive and needing biopsy or conclusive. According to number and distribution of the lesions (if proved malignant); surgery, radiofrequency ablation, alcohol injection or chemo-embolization was decided. Unfortunately, not all cases with HCC having 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.
MRI having many sequences, markedly helps in the detection of small lesions and in reaching the diagnosis easily even without contrast injection or the need for biopsy as in cysts and hemangiomas.
For hepatic focal lesions detection and characterization, conventional MRI relies on T1-weighted, T2-weighted, and dynamic gadolinium-enhanced T1-weighted imaging.
DW MRI in the liver is a relative new and increasingly used imaging technique. It has the advantage that it can be obtained during a single breath-hold, there is no need to use contrast media and it provides unique information that reflects tissue cellularity and organization. The ADC maps can also 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.
In our work we concluded that diffusion-weighted MRI sequence with quantitative ADC measurements can be useful in the differentiation of benign and malignant liver lesions.
Both qualitative evaluation of high b-value DW-MR images and quantitative evaluation of ADC maps are employed for lesion characterization. The ADC values of benign lesions are significantly higher than those of malignant lesions, with variable degrees of overlap between the pathological entities.
DWI proved to be helpful in the characterization of focal liver lesions, but should always be used in conjunction with traditional MRI since there is great overlap between ADC values of benign and malignant lesions. It seems reasonable to use DWI in conjunction to conventional imaging.
In our opinion, DWI is a useful adjunct to routine liver imaging (i.e. used as an additional sequence to the standard protocol study and not as a unique imaging series); it is fast, requires no intravenous contrast and is non-invasive. The radiologist has to be aware of the potential pitfalls and limitations of the technique. In patients who cannot receive gadolinium-based contrast agents, DW MR imaging has the potential to be a reasonable alternative technique to contrast-enhanced imaging.
In any case, all these sequences are not mutually exclusive techniques and a maximum efficiency in diagnosis is achieved by combining diffusion-weighted sequences with conventional sequences, including T2-weighted sequences and sequences following contrast administration.