A computed tomography (CT) scan, or, in other words, a computed axial tomography (CAT) scan and a spiral or helical CT.

• A CT scan is nothing but an X-ray examination that employs a computer to generate 3D cross-sectional images of the body.
• The CT scanner produces detailed images of internal organs, bones, and soft tissues. It differs from a medical X-ray image because it employs a doughnut-shaped machine to emit X-ray beams at various angles.
• To obtain clearer images, some CT scans require the injection of contrast or dye. 
• Your doctor will definitely order a CT scan with contrast in this case.

Can a CT scan detect cancer?

Like any other imaging tool, a CT scan cannot detect cancer, but it can help identify a mass while determining its location and size. It may also provide helpful information, such as the mass's shape and makeup (e.g., solid vs. liquid), indicating that the mass is cancerous. However, only a pathology review of tissue under a microscope following a biopsy can definitively determine it is a cancer diagnosis.

What does a CT scan show?

A CT scan can identify whether you have a tumour and, if so, where it is located and how large it is. CT scans can also reveal the blood vessels that supply the tumour. Your medical team may use these images to determine whether cancer has spread to other body parts, for example, the lungs or the liver. The photographs are in black and white.

However, CT scan may miss some cancers. Also, the experts might even miss lesions due to a variety of factors, including location and human error. Nonetheless, CT is more sensitive than an X-ray.

A CT scan can detect lesions as small as 2-3 mm in size. However, the tumor's location may influence how large it must grow before it becomes visible.

CT scans, as opposed to traditional X-rays, can provide more information about the size of suspicious nodules and their potential for harm. When combined with contrast injection, they can be especially beneficial. Contrast is used to highlight specific tissues. Cancer cells absorb contrast, making them appear white on the scan. As a result, your radiologist can better interpret the images, which is critical when diagnosing. The person will also be able to see tissues surrounding a potentially cancerous lesion more clearly, including nearby organs.

With contrast, a CT scan may also be used to aid in treatment planning. For example, using contrast can help determine whether cancer can be removed surgically.

Types of CT scans

3D CT

3D CT pinpoints tumour locations, determines whether cancer has spread to other body parts, and evaluates treatment effects.

Benefits may include:

• Images that are more detailed than those obtained from magnetic resonance imaging (MRI) or ultrasounds
• Most 3D scans are completed in less than 10 minutes.

3D CT angiography

CT angiography (CTA) identifies tumour blood vessels and other abnormal blood vessels that may pose a health risk.

Benefits may include:

• Blood vessel evaluation that is less invasive than catheter angiography
• Obtaining 3D images of nearly every blood vessel in the body, as well as the brain, heart, lungs, pelvis, abdomen, and extremities.
• While it takes around 20 minutes for the scans, the entire procedure may take several hours.

Large bore CT scanner or radiation therapy (RT) with simulation

This medical device generates detailed images of internal organs to plan radiation therapy. It plans and delivers radiation using simulation, fluoroscopy, and respiratory gating.

Benefits may include:

• Detecting anomalies and directing precision radiation therapy
• Treatment options are planned based on a patient's breathing patterns.
• Adapting to different patient sizes and positioning
• Spending 15 to 30 minutes on the session, including time to position yourself and set up the equipment.

Multi-detector CT scanner

This scanner can display multiple image slices in a single rotation, allowing radiologists to view high-quality images in micro-level detail and at a faster rate. The vast scanning space of the CT machine makes it a more comfortable experience for the patient. This scan can take 10 to 30 minutes, depending on the body part. It may take longer to set up if you require contrast before your scan.

PET/CT scan

This nuclear imaging technique employs both positron emission tomography (PET) and computerised tomography (CT) to provide detailed information about the structure and also the function of the body's cells and tissues. The patient is given a glucose injection laced with a trace of radiation as a contrast agent. However, the radiation dose is absorbed by the organs or tissues under examination, allowing them to be seen in medical imaging. This procedure exposes you to very little radiation.

Benefits may include:

• Identifying damaged or cancerous cells where glucose is being absorbed abnormally (cancer cells often use more glucose than normal cells)
• Determining therapy response by measuring the rate at which the tumour consumes glucose
• Providing a more detailed and more precise image of cancerous tissues than either test alone can provide
• Including both types of diagnostic imaging in a single scan
• Spending approximately 20 minutes

How is a CT scan performed?

At first, the professional places a patient on a table that slides into the CT scanner, which rotates an X-ray tube around the patient. For more detailed CT images, a technologist may inject a contrast material, usually an iodine contrast dye, into a vein in the arm. Many abdominal and pelvic exams also necessitate liquid consumption to obstruct the GI tract. This non-invasive outpatient procedure usually takes around 10 minutes.

Why do professionals use a CT scan for cancer?

CT scans serve numerous functions in the diagnosis and treatment of cancer.

• Screening: CT scans are sometimes used to screen for cancers such as lung cancer and also colorectal cancer.
• Diagnosis: Your medical professional may order a CT scan to locate the size of the suspected tumors. It may also aid in determining whether a tumour has returned.
• Planning and treatment: A CT scan may assist your doctor in identifying and locating the tissue that requires biopsies. Experts can also use it to guide various treatments like cryotherapy, microwave ablation, and radioactive seed implantation, as well as to plan surgery or external-beam radiation.
• Treatment response: Doctors may order a scan to determine whether or not a tumour is responding to treatment.
• Monitoring tool for other diseases: CT scans may be required to rule out other conditions that possibly may or may not be related to cancer, such as:

1. Abnormal brain function
2. Coronary artery disease (CAD)
3. Aneurysms of blood vessels
4. Clots in the blood
5. Fractures of the bones
6. Pneumonia or emphysema
7. Stones in the kidneys and bladder
8. Inflammatory diseases.
9. Head injuries or internal organ damage

The frequency of CT scans will depend on your treatment and the type of cancer. For example, it is recommended that patients undergoing colorectal cancer surgery have two CT scans within the first three years. Supposedly, you're between the ages of 55 and 74 and have smoked an average of a pack a day for the past 30 years (even if you quit in the last 15 years), the American Cancer Society recommends a low-dose CT scan every year to screen for lung cancer.