Investigating the brain with scans

Cells and control · The brain · note 2 of 3

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Investigating the brain with scansSpec 2.11B

In short

CT and PET scans let doctors investigate the brain without surgery. A CT scan uses X-rays taken from many angles to build up images of the brain's structure, so it can reveal damage or a tumour. A PET scan uses a radioactive tracer, which active areas of the brain use more of, so it shows brain function.

The brain is inside the skull and is very delicate. It is difficult and risky to get at brain tissue to find out how it works or what is wrong. Scanning allows doctors to investigate the brain without surgery.

CT and PET scans
Scan	How it helps
CT scan	Uses X-rays taken from many angles to build up images of the brain. It shows the structure, so it can reveal damage or a tumour.
PET scan	A radioactive tracer is put into the body. Active areas of the brain use more of it, so the scan shows which areas are active. It shows brain function.

Both methods let scientists and doctors link areas of the brain to their functions and find the cause of problems, without opening the skull.

Exam tip:

CT shows structure and PET shows function. Say what each one shows, and that the benefit is not having to access the brain by surgery.

Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026

Frequently asked questions

What are the main parts of the brain and their functions?

The main parts of the brain are the cerebral hemispheres, cerebellum and medulla oblongata. The cerebral hemispheres are involved in conscious thought, intelligence, memory and language. The cerebellum coordinates movement and helps to control balance. The medulla oblongata controls unconscious activities, such as heart rate and breathing rate.

What is the difference between a CT scan and a PET scan?

Higher tier A CT scan uses X-rays taken from many angles to build up images of the brain's structure, so it can reveal damage or a tumour. A PET scan uses a radioactive tracer, which active areas of the brain use more of, so it shows brain function. Both investigate the brain without surgery.

Why is it difficult to treat damage to the nervous system?

Higher tier It is difficult because the brain is complex and delicate, and hard to reach inside the skull, so surgery risks damaging healthy tissue. Neurones in the central nervous system do not easily repair themselves, so damage is often permanent. A spinal injury can cause paralysis, and some brain tumours cannot be removed safely.