CT scan — Detailed cross-sectional body imaging

A CT scan, also referred to as a CAT scan, employs a rotating gantry equipped with an X-ray tube and digital detectors. As the patient passes through the circular scanner bore, the machine captures numerous attenuation measurements across a specific anatomical region. Computer algorithms process these raw datasets to generate thin, cross-sectional slices—often less than a millimetre thick—which can be formatted into high-resolution three-dimensional representations of the body.

To improve tissue contrast, CT imaging regularly incorporates radiopaque contrast agents administered intravenously, orally, or rectally. Intravenous iodinated contrast highlights the vasculature and reveals abnormal enhancement patterns characteristic of malignant lesions, which often exhibit irregular angiogenesis. CT scans provide vital anatomical information, delineating tumour dimensions, depth of invasion into adjacent structures, involvement of regional lymph nodes, and presence of distant organ metastases.

CT scans are central to cancer care pathways. They reveal whether a lump is present, show if cancer has spread, and provide precise coordinates for biopsies and radiotherapy planning. Tracking tumour size across periodic scans allows doctors to judge whether a treatment is working or needs adjustment, giving patients and clinical teams objective data to make informed choices.

CT scans do not test for cellular biomarkers directly, but they measure physical tumour burden, such as RECIST criteria. They are often combined with blood tests (like serum creatinine to check kidney safety before iodinated contrast) and functional scans like PET (in PET-CT) to link anatomical changes with metabolic tumour activity.

CT scans are used across almost all solid malignancies, including lung, colorectal, pancreatic, kidney, ovarian, and stomach cancers. They are also standard tools for staging lymphomas and detecting secondary metastatic spread to the liver, lungs, brain, or retroperitoneal lymph nodes.

The imaging findings dictate whether a patient's cancer is resectable by surgery, requires initial chemotherapy, or is best managed with radiotherapy. During radiation treatment, dedicated CT simulation scans are used to map target fields, ensuring high radiation doses hit the tumour while avoiding healthy organs.