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Diagnosis, staging and monitoring are different tasks
Imaging can locate an abnormality, help plan a biopsy, assess the extent of a confirmed cancer or measure changes during treatment. The same scan can serve different purposes at different points in care.
Stage describes the extent of disease and helps guide treatment. For many solid tumours, staging considers the original tumour, nearby lymph nodes and distant spread. Some cancers use different systems. A stage is based on all relevant findings, not just one phrase in a scan report.
CT: detailed cross-sectional X-ray images
CT is commonly used to examine areas such as the chest, abdomen and pelvis. It can show the size and position of abnormalities and help assess lymph nodes and organs. Some examinations use injected or oral contrast to make structures clearer.
Tell the team about previous contrast reactions, kidney problems and possible pregnancy. Blood tests or tailored preparation may be needed. CT uses ionising radiation; the team balances its diagnostic benefit with exposure and avoids unnecessary duplication.
MRI: detailed soft-tissue assessment
MRI uses a strong magnet and radio waves rather than ionising radiation. It can be particularly useful for questions involving the brain, spine, liver, pelvis or other soft tissues. Sometimes contrast is given.
The scanner is noisy and you need to remain still. Tell staff about implanted devices, metal fragments, kidney disease, pregnancy or claustrophobia before the appointment. Many implants can be scanned under specific conditions, but they must be checked individually.
PET-CT: tracer activity alongside anatomy
PET-CT combines a radioactive tracer study with CT. The commonly used FDG tracer highlights glucose uptake; other tracers answer different questions in selected cancers. PET-CT can help stage certain cancers, assess treatment response or identify an area for further investigation.
Not every cancer needs PET-CT, and not every bright area is cancer: inflammation and infection can also show uptake. Some tumours and very small deposits may not be detected. A PET result must be interpreted with other findings and does not routinely replace a biopsy.
Follow the centre’s instructions about food, exercise and medicines. Diabetes requires specific preparation; do not independently omit insulin or other treatment. Tell the team about pregnancy or breastfeeding so the appropriate advice can be given.
Ultrasound: a focused, real-time examination
Ultrasound uses sound waves without ionising radiation. It can assess selected lumps and organs, distinguish some fluid-filled from solid abnormalities and guide a needle biopsy. It is useful for many breast, neck and abdominal questions.
Preparation may include fasting or a full bladder, depending on the area examined. Ultrasound cannot answer every staging question; air, bone and depth can limit what is visible.
Mammography and assessment of a breast symptom
Mammography uses low-dose X-rays to examine breast tissue, including tiny calcifications that may not be felt as a lump. Screening mammography is performed in people without symptoms; diagnostic mammography investigates a symptom or an abnormal screening result, sometimes using additional views.
The breast is compressed briefly to improve image quality. Ultrasound or, in selected situations, MRI may add useful information. Dense breast tissue can make mammograms harder to interpret. Neither a normal mammogram nor a normal ultrasound should end the assessment of a persistent concerning symptom without clinical review. An abnormal image may need a biopsy; it does not by itself prove cancer.
Other imaging and the limits of a scan
An ordinary X-ray or a bone scan may answer a specific question. Your team chooses tests according to the suspected cancer and the information needed, rather than ordering every available scan.
Scans can miss microscopic disease or show findings whose significance is unclear. Words such as “indeterminate” or “suspicious” indicate a level of uncertainty, not necessarily a final diagnosis. Comparison with previous images, an interval scan or a biopsy may resolve the question.
Preparing and discussing results
- Bring your previous scan images, preferably on a CD (DICOM format with viewing software), or via a web link or as films, together with the written scan reports, so changes can be compared.
- Confirm preparation for your specific examination; instructions for one scan may not apply to another.
- Tell staff about pregnancy, breastfeeding, implants, allergies, diabetes and kidney disease as relevant.
- Ask how the result will change the plan and whether further tests are needed.
- Arrange a results discussion. Do not change or stop treatment because of a scan report without speaking to the treating team.
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Arranging investigations through CTI
Contact CTI to coordinate the appropriate investigation with the hospital team. Confirm the procedure, preparation and location before travelling; specialised tests may involve another department or a referral laboratory.
