Types of Scans for NETs
There are various types of scans that may or may not be suitable for your type of NETs. Here is a summary of some scans you might encounter.
Ultrasound imaging, also called ultrasound scanning or sonography, uses high-frequency sound waves to produce pictures of the inside of the body. Ultrasound exams do not use ionizing radiation (as used in x-rays) Because ultrasound images are captured in real-time, they can show the structure and movement of the body’s internal organs, as well as blood flowing through blood vessels. Ultrasounds might be used in the initial diagnosis by a GP but are no longer used to follow up people with NETs.
CT - Computerised Tomography
A computerised tomography (CT) scan provides a two dimensional picture of the inside of the body. Using a highly specialised xray machine and computers it creates multiple cross-sectional images of the body. A dye may be injected into a vein or swallowed to help organs or tissues show more clearly on he scan. It can be used to determine the position and size of NETs, and regular scans are useful to find out the rate of tumour growth.
MRI - Magnetic Resonance Imaging
This magnetic resonance imaging (MRI) scan uses radio waves- a powerful magnetic field- and computers to generate detailed images of the body. These scans are useful for contrasting different types of tissues like the liver and can help reveal where the tumours are positioned.
Positron Emission Tomography (PET)
Positron Emission Tomography (PET) is another type of scan that uses radioactive material and a special scanning device to detect neuroendocrine tumours.
FDG PET Scan
A small amount of FDG (fluorodeoxyglucose), a type of radioactive glucose (sugar), is injected into a vein. The PET scanner rotates around the body and makes a picture of where the body is using glucose. Cancer cells show up brighter in the picture because they are more active and take up more glucose than normal cells do. This type of ‘whole body’ scan picks up spots of very high cell growth. This type of scan is therefore not very useful if your NETs are low grade / or slow growing, but might be useful in detecting fast growing and poorly differentiated tumours.
GaTATE PET (OR Ga68 PET Scan OR Gallium 68 Scan)
This type of scan uses a radioactive tracer(Ga-68 dotatate) which binds to the neuroendocrine cells’ somatostatin receptors(SSRs) ie the tumour sites. The tracer is given intravenously and the PET scan images show clearly where NETs are in the body. It is particularly useful for slower growing, well differentiated neuroendocrine tumours.
Octreotide Scan or Tektrotyd Scan OR
This type of SRS is a useful diagnostic test that can help reveal the site of NET tumours. Some NETs have special receptors on their cell surfaces called somatostatin receptors(SSRs). Octreotide is a manufactured version of somatostatin, and can stick to these receptors. Octreotide is combined with a mildly radioactive agent is injected intravenously and travels through the bloodstream, and attaches to the tumour receptors which are visible to a special kind of scanner. A whole body scan is taken after a few hours, and doctors look at the scan to see the location(s) of the NETs. This type of scan is now slowly being used less in favour of a Gatate scan which produces much clearer imaging and detail. (add link to gatate scan info)
Somatostatin Receptor Scintigraphy (SRS)
Somatostatin Receptor Scintigraphy (SRS) is a type of radionuclide scan that uses a radioactive substance that can bind to a tumor’s somatostatin receptors and illuminate them. Not all neuroendocrine tumors have somatostatin receptors.
Patients who take somatostatin analogs should discuss with their doctor the best timing for their exam as treatment can interfere with the test. Talk to your doctor about how to adjust your somatostatin analog before testing.
SRS can also help predict response to somatostatin analogs therapy as well as peptide receptor radionuclide therapy (PRRT).
This is a similar scan to the Octreotide scan except a small amount of a radioactive substance called MIBG is injected into the bloodstream instead. Tumours with receptors for MIBG on their surface are highlighted in this scan. It is used to find certain neuroendocrine tumours such as phaeochromocytomas and paragangliomas.
A bone scan looks for abnormalities in bones that might be caused by cancer metastases. You will be given a small injection of radioactive tracer which over time will be absorbed into your skeleton. It takes about 3 hours for this to occur. Pictures of your skeleton are then taken using a special camera that detects the location of the tracer (called a gamma camera), and you will be asked to return for a second set of pictures 3 hours later. For this second set of pictures you will again be asked to lie or sit in front of the gamma camera. The scan will take around 30-45 minutes. These are not commonly used for NETs.
Cardiac Ultrasound Scan or Echocardiagram
This is an ultrasound scan of the heart. These are scans that doctors may request regularly for those with “functioning” or lower grade NETs that are known to have secretory hormones. Excessive hormone production is known to cause Carcinoid heart disease(link to what this is on website) so this scan is done to check the valves of the heart are working properly.
This is a way of examining your GI tract (digestive system) using a flexible fibre optic tube called an endoscope. The tube can be inserted down the back of the throat and down into the stomach, a procedure called a gastroscopy. Or it can be inserted into the colon via the anus (back passage), a procedure known as a colonoscopy. You will be offered sedation before either of the procedures, and the doctor may remove tiny biopsy samples of any suspicious areas for analysis. Sometimes a small ultrasound scanner is placed at the tip of the endoscope, so that pictures of a tumour can be taken from inside the body, very close to the cancer. This tool can also be used to take a biopsy sample.
This is a procedure to look inside the trachea and large airways in the lung for abnormal areas. A bronchoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue samples to be checked under a microscope for signs of cancer. It is inserted through the nose or mouth into the trachea and lungs.
Neuroendocrine Cancer NZ board member and radiologist, Dr Jane Reeve presents about radiology in neuroendocrine tumours.