**2.5 The utility of MRI in the postoperative follow up of the patients with rectal cancer**

Local recurrence occurs in approximately 30% of patients operated for rectal cancer. Early identification of local recurrence in these patients is of particular importance both for the therapeutic management of these patients as well as for their long-term prognosis [89]. Local recurrence is characterized by the appearance of a tumor formation at the level of the anastomosis, at the level of the operating bed or at the level of the pelvic lymph nodes. At the time of local recurrence, only about 20% of these patients are still suitable for surgical treatment [90].

Although currently the most used imaging method in postoperative follow-up of patients with operated rectal cancer is abdomino-pelvic CT scan, recently there are more and more studies in the literature that recommend performing abdominalpelvic MRI in these patients. Those who promote this method are based on the fact that in the detection of pelvic neoplasms, the specificity and sensitivity of pelvic MRI in differentiating areas of fibrosis from tumor recurrence is much higher than pelvic CT scan [91, 92]. At the same time, it has been shown that, in the case of small liver metastases, abdominal MRI has a better detection rate compared to abdominal CT. Also, another argument for the utility of pelvic MRI in these cases is given by the fact that, compared to the pelvic CT, MRI offers a much better spatial resolution, and can also provide functional information (tissue diffusion, local vascularization) [93]. Recent studies have shown that when using diffusionweighted MRI (DWI-MRI) there is the possibility of identifying tumor recurrence, in these cases, faster than when using conventional MRI techniques or when using abdominal CT [94, 95].
