# Application of Image Fusion in Diagnosis and Treatment of Liver Cancer
## 5 Clinical Applications of Image Fusion in Liver Cancer Diagnosis and Treatment
### Ultrasonography/MRI, Ultrasonography/CT and Ultrasonography/PET-CT
#### 5.1.1 Utility of CEUS/MRI in Diagnosis and Treatment of Small Liver Cancer  
The natural course of subclinical stage liver cancer is at least two years. Through the study of subclinical stage liver cancer, the 5-year survival rate of small liver cancer is markedly higher than that of advanced large liver cancer.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Fusion Methods** & **Diagnostic Modality** & **References** \\ \hline Arithmetic combination & US, MRI, PET, CT & [8, 63, 72, 162, 163, 164, 165, 166, 167] \\ \hline IHS & MRI/PET & [31, 32, 33, 34, 35] \\ \hline PCA & US-PET/CT, MRI/CT & [41, 42, 43] \\ \hline Pyramid based methods & MRI, CT, PET, SPECT & [57, 58, 59] \\ \hline Wavelet transformation-based methods & CT, PET, MRI, SPECT, Ultrasonography, Multiparametric & [7, 8, 9, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 82, 83, 85, 86, 117, 168, 169] \\ \hline Pulse-coupled Neural network methods & CT, PET, MRI, SPRECT, Ultrasonography, Multiparametric MR & [84, 94, 111, 112, 113, 114] \\ \hline Fuzzy logic-based methods & CT, PET, MRI, MRA, fMRI, SPECT, Ultrasonography & [121, 122, 123, 124, 125] \\ \hline Sparse representation and compressive sensing-based methods & PET, CT, MRI, Multiparametric MR & [138, 139, 140, 141] \\ \hline Edge-preserving based methods & CT/MRI & [142, 143] \\ \hline Deep Learning & PET-CT, MRI-CT, MRI-SPECT & [12, 13, 145, 146, 147, 148, 149, 150, 151, 152, 153] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Major medical image fusion methods.  
However, the clinical diagnosis rate of small liver cancer is a big problem for clinicians. In addition to screening for AFP indicators in blood samples, effective imaging examination methods urgently require application to optimize clinical practice.  
Contrast-enhanced ultrasound has a high diagnostic efficacy for liver lesions, especially small lesions less than 1 cm [162]. However, Ultrasonography presents inherent limitations. First, researchers with significant clinical experience are essential for effective implementation. Second, Ultrasonography lacks high resolution, and is unable to provide information on spatial hierarchical relationships. As mentioned above, MRI images are characterized by high soft tissue resolution and multiple signals, especially for intrahepatic vessel imaging. At the same time, micro-cancerous nodules, precancerous nodules and vascular cancer thrombus display different signals on MRI sequences. Introduction of the liver-specific contrast agent, Gd-EOB-DTPA (i.e., Gadoxetate Disodium-ethoxybenzyl-diethylenetriamine pentaacetic acid), has greatly improved the image quality of enhanced MRI scans, clearly revealing the boundaries of liver cancer and micro-lesions [172].  
Multistage image fusion technology of contrast-enhanced ultrasound and MRI is reported to improve the accuracy of the diagnosis of small liver cancer. Originally, conventional ultrasound and MRI were used to conduct an image fusion of the axial profile of the liver. Furthermore, upon combination of contrast-enhanced ultrasonography to observe the blood flow direction of liver lesions, data from the fusion image of contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) allowed the determination of the three-dimensional parameter index of tumor lesions in liver (size, spatial location, blood supply arteries, drainage area), resulting in increased detection rates of suspicious small liver cancer. Moreover, the main blood supply source of liver cancer, portal vein tumor thrombus and the specific hepatic arterioportal fistulas caused by tumor pathological factors were clearly displayed.