# Application of Image Fusion in Diagnosis and Treatment of Liver Cancer
## 5 Clinical Applications of Image Fusion in Liver Cancer Diagnosis and Treatment
### PET/CT & PET/MRI  
PET/CT is the most widely used fusion imaging technique in clinical diagnosis. However, due to its imaging principles, PET/CT is less effective in locating tumor lesions in spatial resolution, and can only show a specific standard uptake value (SUV) range, which fails to accurately evaluate liver tumor position and its adjacent relationship in anatomical space. PET/MRI fusion technology has greater advantages in the assessment of tumor morphology, function and metabolic imaging than PET/CT [165; 166]. Firstly, based on the advantages of diffusion-weighted imaging (DWI), perfusion imaging PWI and MR spectrum, MRI is far superior to CT in the functional imaging of human soft tissue organs. Secondly, the PET/MRI imaging system does not impose an ionizing radiation burden on the patient or operator. Thirdly, on CT images, signals of some abdominal and pelvic lesions may be disrupted by peristaltic bowel, poor bladder filling or uterine translocation. This type of interference is often unavoidable in the imaging process and affects the observation of diseased organs, which can be effectively overcome by the hybrid technology conditions of PET/MRI [167]. Clinical findings suggest that PET/MRI has an advantage in regular postoperative follow-up for patients at high risk of liver metastases from colorectal cancer with regard to the monitoring of tumor recurrence, especially in distinguishing inflammatory tissue around the surgical area of rectal cancer lesions, distant liver metastasis and the clinical TNM stage. With regard to adjacent tissue, taking into consideration both the metabolism of \({}^{18}\)F-FDG in postoperative inflammatory tissues of rectal cancer and DWI images in enhanced MRI, morphologic and functional imaging can effectively discriminate whether the newly formed mass in the rectal cancer area is an inflammatory scar or recurrent tumor tissue [181]. In terms of N-staging, \({}^{18}\)F-FDG activity is not specific to cancer, since it has been observed in macrophages involved in inflammatory and infectious diseases. Cancer patients with acute inflammatory or infectious diseases also display high SUV signals on PET/CT images, which makes it impossible to determine whether lymph nodes with high metabolic signals  
Figure 4: A 59-year-old man with hepatocellular carcinoma (HCC) following radical resection, who was treated with percutaneous cryoablation. (**a**) A single tumor measuring 0.8 cm is noted in segment 5 on the portal phase of contrast-enhanced magnetic resonance image (MRI) before cryoablation. (**b**) The intraoperative CT image at the end of cryoablation shows a clear ablation zone. (**c**) The fusion image is created after automatic rigid registration combined with manual correction. The medication-assisted manipulation (MAM) is categorized as group II: MAM 0e5 mm. (**d**) Contrast-enhanced MRI image obtained 4 months after cryoablation shows Local Tumor Progression (LTP) [180]. present an inflammatory lesion or neoplastic metastasis that affects the N stage of correctly diagnosed cancer patients. Owing to the significant benefits of the MRI in soft tissue imaging of lymph nodes, PET/MRI is obviously superior to PET/CT in distinguishing internal lymph node structures. Taking the morphological, functional and metabolic features of suspected lymph nodes into consideration, PET/MRI can effectively distinguish tissue structures, such as fat hilum, margin and necrotic area within lymph nodes, which allows determination of the tumor metabolism of lymph node tissue with high suspicion of metastasis, and thus the differentiation of malignant from benign lymph nodes. With regard to M-staging, PET/MRI, which can distinguish metastatic lesions less than 1 cm, is of greater diagnostic value in patients with suspected liver metastasis of rectal cancer. [PERSON] reported a higher diagnostic rate of PET/MRI relative to enhanced CT/PET fusion [182].