Computed Tomography (CT)

What is Computed Tomography?

Computed tomography (CT), also known as computed axial tomography (CAT), is a non-invasive technique used to observe various human organs and tissue through a machine that uses radiation.

One of the particularities of these images is the fact that they are divided and show transversal and, in newer machines, other sections of the body (i.e., as if the body was cut into slices).

The aim of the scan is to diagnose diseases that cause visible changes in the organs, identify the extent of primary tumours and confirm the existence, or absence, of any metastases.

Importance of CT Scans

Through a CT scan, the specialist can detect the underlying causes and certain symptoms, often excluding the need for other diagnostic tests.

In practical terms, for prostate diseases, it is essentially useful for diagnosing adenopathies (enlarged lymph nodes) or metastases in other organs or soft tissue (formation of new tumours that have spread from the prostate). It is not a good exam for assessing the prostate.

For other purposes, it is non-invasive and useful in studying different pathologies of the brain, lungs, heart, liver, pancreas, kidneys, bladder, bones and soft tissue, etc.

What is the Procedure for Taking a CT Scan?

It can take 15–30 minutes depending on the type of scan.

The scan is done in a machine called a tomographer. This consists of a movable stretcher that slides into a circular aperture (around 80 cm in diameter) which emits X-rays.

In some cases, an intravenous iodinated contrast is injected in the aim of improving the definition of the blood vessels or lesions on the organs, dilation of structures, etc.

The machine revolves around the patient (who lies still on the stretcher) as it emits X-rays. On average, 950 images are obtained per second, as it has 256 channels, making the CT a very fast exam.

As a result of technological development, the scanners have newer software to help doctors make a more accurate diagnosis.

Preparation for the CT Scan

The patient must not eat for at least 4 hours beforehand and if they have diabetes, the medication must be stopped on the day of the scan and for 24–48 hours afterwards, under medical supervision.

This is important when an iodinated contrast is used, as it can interfere with the diabetes and its medication.

Risks of CT Scans

The procedure uses more ionising radiation than normal exams using conventional X-rays.

Pregnant women and people with asthma or allergies are advised against taking a CT scan (if iodinated contrast is used).

After a CT scan, women must wait at least 8 hours before breastfeeding.

Children should only undergo this exam when strictly necessary, as they are more sensitive to radiation and the dosages used can cause problems that may remain as they grow.

Dr. José Santos Dias

Clinical Director of the Instituto da Próstata

  • Bacherlor's Degree from the Faculty of Medicine at the University of Lisbon
  • Specialist in Urology
  • Fellow of the European Board of Urology
  • Autor dos livros "Tudo o que sempre quis saber Sobre Próstata", "Urologia fundamental na Prática Clínica", "Urologia em 10 minutos","Casos Clínicos de Urologia" e "Protocolos de Urgência em Urologia"

FAQs about CT Scans

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