European Radiology: Application of DTI in the identification of benign and malignant liver lesions

At this stage, liver tumors are one of the tumors with high incidence, and early detection and risk stratification are essential
for accurate management and patient prognosis.
Liver lesions (HFLs) are classified as benign and malignant
.
Hemangiomas are the most common benign tumors, while hepatocellular carcinoma (HCC) is the most common primary liver malignancy
.
In addition, liver metastases are more common
than primary liver tumors.

Current technological improvements in contrast-enhanced ultrasound (CEUS), computed tomography (CT) and magnetic resonance imaging (MRI) have facilitated the differential diagnosis of benign and malignant HFLs.

Among them, dynamic enhancement of MR is a key to
show the characteristics of liver lesions.
According to the latest Liver Imaging Reporting and Data Systems (LI-RADs), the accurate diagnosis of HCC depends on five main features
such as enhancement pattern and size.

Diffusion-weighted imaging (DWI) is a plain scan technique that has been progressively used to characterize
HFLs.
DWI can be analyzed qualitatively and quantitatively by apparent diffusion coefficient (ADC) plots, reflecting histopathological tissue features, but not describing diffusion characteristics
in anisotropic environments.
Although previous studies have revealed the utility of ADCs in liver lesion characteristics, ADC values for benign and malignant liver lesions have shown considerable overlap.

Diffusion tensor imaging (DTI) is an advanced and newly introduced MR technology
developed on the basis of DWI.
Unlike DWI in one or three orthogonal directions, DTI visually characterizes the microstructure of biological tissues by using six or more diffusion-sensitive gradients in different directions to measure the diffusivity of water molecules, allowing assessment of the properties
of their anisotropy.
The calculated DTI parameters are mean diffusivity (MD) and anisotropic fraction (FA), which reflect the size and shape
of the diffusion ellipse, respectively.

A study published in the journal European Radiology evaluated the role and value of DTI in the classification of HFLs and compared
it with DWI.

A prospective analysis of 49 patients (23 men and 26 women) with a total of 74 HFLs was performed, and each patient received Dynamic MRI, DWI and DTI scans
.
The apparent diffusion coefficient (ADC) value, anisotropy (FA) value, and mean diffusivity (MD) value of DTI of DWI were measured
by two independent radiologists.
HFLs are classified as benign and malignant HFLs; The latter is subdivided into HCC and non-HCC lesions
.
Binary logistic regression was performed to analyze the association
between DTI parameters and the difference between malignant lesions.

The critical values for ADC, MD, and FA are ≤1.
17×10-3 mm2/s, ≤1.
71×^{10-3 mm2, respectively} /s and >0.
29 are important differentiating indicators between malignant and benign HFLs.

The average ADC and MD values for hemangiomas were significantly higher than those for HCC and non-HCC malignant lesions
.
In contrast, the average FA value of hemangiomas was significantly lower than that of non-HCC malignant lesions and HCCs
.
The ADC and MD are >1.
03×10-3 ^mm2/s and >1.
12×^10-3 mm, respectively ²/s is a very good identification indicator
.
At a cut-off of 0.
38 >, FA is a good differentiator between HCC and non-HCC malignancies.

Of the three parameters, only an FA value > 0.
38 was a statistically significant, independent predictor
of HCC versus non-HCC lesions.
There is good agreement between observers, ICC> 0.
9
.
 

Figure A 58-year-old man with HCC: T2 The fat suppression image (A) shows focal lesions of the liver with moderate T2 signal intensity
.
Axial dynamic arterial and delayed images (B, C) show typical nonperipheral arterial enhancement with delayed clearance
.
The axial ADC image (D) shows a limited diffusion with ADC values of 1.
07 ×^10-3 mm 2/s
.
In the MD and FA plots (E, F), the MD values of HCC are 1.
21 × ^10-3mm2/s and 0.
47, respectively

This study shows that MD and FA derived from diffusion tensor imaging are two non-invasive, reliable, and reproducible imaging indicators, and are superior to ADCs measured by conventional DWI, and can be used for the differential diagnosis
of benign liver focal lesions.

Original source:

Gehad A Saleh,Ali H Elmokadem,Ahmed Abdel Razek,et al.
Utility of diffusion tensor imaging in differentiating benign from malignant hepatic focal lesions.
DOI:10.
1007/s00330-022-09091-w