This scan looks at and identifies sentinel lymph nodes, which are responsible for draining fluid (lymph) from the breast.

The lymphatic system is a network of vessels that drain fluid (lymph) into small glands called lymph nodes. These nodes act as filters and trap bacteria, viruses and other foreign substances.

How the scan works

A sentinel node scan identifies sentinel lymph nodes, which receive material drained from the breast in the underarm area. These nodes are responsible for filtering the area of the breast where the lump or abnormality is.

We will do this scan in preparation for a sentinel lymph node biopsy later in the day, or on the following day. The scan will identify the nodes that your surgeon may want to perform a biopsy on, and later remove if needed.

When you have the scan, we will ask you to remove any clothing covering your chest. An experienced and usually female technologist will give you a small injection. This injection has a small amount of radioactive material called a "tracer", which helps to with images showing up on the scan. The technologist will give you the injection just beneath the skin in the breast.

You will then lie on the scanner couch with your arms raised above your head. The technologist will take three images with the scanner. We use a felt-tip skin-marking pen to place a dot in the axilla (underarm) over any sentinel lymph node identified.

You will receive a copy of the images to give to the surgeon when you attend your operation. They will also be available on the in-hospital electronic system.

The whole procedure may take up to an hour.

How to prepare for the scan

There is no specific preparation for this scan. You can eat and drink as you would before the test and continue to take all your usual medication.

If you are unable to raise your arms above your head, you should still come for the scan. You can speak to the technologist and find a way to take the pictures without causing you discomfort.

After the scan

Once the scan has finished the doctor will check the quality of your scan while you wait, and the technologist will then let you go home. The radiation dose from this procedure is very small and there is no need to make any change to your routine.

There are no side effects from the injection so it will not make you feel sleepy or affect your ability to drive. 

There are currently no related conditions associated with this test.


Level 3
Chelsea Wing
Sydney Street


Monday to Friday, 9am to 5pm

Tel: 020 7351 8666 / 9
Fax: 020 7351 8668

Patient advice line: 020 7351 8667

If you have any questions or concerns about the scan please call our patient advice line.

It is an answerphone service – leave a message and we will call you back within 24 hours.

Department head

Kshama Wechalekar