The Role of Ultrasound and Magnetic Resonance Imaging in the Evaluation of Colon Cancer

Abstract

Considering the increasing incidence of colorectal cancer (CRC) worldwide, diagnostic imaging has come to play an important complementary role to colonoscopy in the management of colorectal pathology. With ongoing refinement of surgical techniques and oncologic therapies, the need for and importance of highly accurate and reproducible imaging has grown exponentially. Advancements in the fields of ultrasonography, computerised tomography (CT) and magnetic resonance imaging (MRI) have reinforced the role of diagnostic imaging. Abdominal ultrasound is used to identify metastatic involvement of the solid abdominal viscera but cannot evaluate the primary lesion. MR colonography (MRC) depicts all segments of the colon and can identify visceral and nodal metastases. However, staging of the primary lesion, particularly of early tumours, is limited by the resolution of MRC. Transrectal ultrasound and MRI of the rectum provide high-definition imaging of the local spread of rectal tumours, but only assess a limited portion of the colon and do not detect distant metastatic spread. Imaging also plays a crucial role in the management of patients after surgical and oncologic therapy, providing information on the response of the tumour and guiding oncologic treatment, as well as for future surveillance. The ongoing development of three-dimensional (3D) imaging as well as advanced algorithms to further refine image quality will in future add to the role of diagnostic imaging. The assistance of artificial imaging (AI) in diagnostic imaging is also being explored and has shown promise in aiding tumour characterisation, staging, and prognostication.