Nuclear Medicine

NUCLEAR MEDICINE

 

INTRODUCTION

Nuclear Medicine is the use of radioactive molecules (radionuclides) for the diagnosis, staging, therapy and monitoring of the response of a disease process. A nuclear medicine test which may be used in the diagnosis and staging of pancreatic cancer is Positron Emission Tomography (PET). A sugar molecule tagged with a radionuclide is used to build a picture of which organs are using the most sugar. Tumours are one of the most sugar avid tissues and a PET scan can show the extent of the tumour & whether it has spread locally or more distantly.

PET SCAN

 

PET stands for “positron emission tomography”. It is a nuclear medicine imaging test in which a small amount of liquid radioactive material is injected into your body and is used to diagnose a variety of diseases, including many types of cancers, heart disease and other diseases. The radioactive substance most commonly used in PET scanning is a simple sugar (like glucose) called FDG, which stands for “fluorodeoxyglucose”. It is injected into your bloodstream and accumulates in your body where it gives off energy in the form of gamma rays. These are detected by the PET scanner and a computer converts the signals into detailed pictures or images showing how tissue and organs are working. If you are having an FDG PET, your sugar metabolism (how sugar is used by your body) is imaged. This is commonly used for cancer imaging as tumours need sugar to grow.

 

PET

 

PET scanners are now commonly combined with computed tomography (CT) scanners, called PET-CT scanners. CT imaging uses X-ray equipment to create detailed images of slices of the inside of your body. The PET-CT combination allows any abnormality on the PET scan to be precisely located within the body, allowing for more accurate diagnosis of any problems. The PET or PET-CT scanner looks like a large box with a circular hole in the middle.
You will usually be in the PET imaging department for between two to three hours. The time on the PET scanner is typically 30 minutes but time is also needed for preparation.
When the scan is completed you will be asked to wait while the images are checked to make sure they are clear. Occasionally, there is a need to obtain more images following this check.
PET scanning is a powerful diagnostic test that is having a major impact on the diagnosis and treatment of disease. It provides unique information which may assist in making a diagnosis, in determining treatment or providing a prognosis, that is, the likely outcome of any disease.
Nuclear medicine tests, including PET scanning, can provide information on how tissue or organs are working, which cannot be obtained from other imaging techniques. PET scans may detect disease earlier than other types of scanning by identifying early changes to tissue and organs.

 

PET2

 

PREPARING FOR THE SCAN 

You will receive specific instructions based on the type of PET scan you are undergoing. If you are unsure about any aspect of preparation you should contact the centre where your PET scan is going to be performed.
It is important that you let staff at the hospital or radiology practice where you are having the scan done know if you are (or think you could be) pregnant or are breast feeding.
This study may not be suitable for pregnant women because of the radiation dose to the growing foetus. Please discuss this with your doctor.
Women who are breastfeeding and people who are the primary or sole carer for small children may need to make special preparations for after the test, to stop breastfeeding for a short time, and to avoid close contact with young children. This is due to the small amount of radioactivity your body may release for a while after the test. Talk to your referring doctor or the nuclear medicine practice where you will have the test for details. The Australian Radiation Protection and Nuclear Safety Agency has recommendations about breastfeeding and close contact with children after nuclear medicine tests.
Bring with you to your appointment any previous X-ray or radiology images you have, as comparison with these by the nuclear medicine physician (a specialist doctor), who looks at and interprets your PET scan, can be very helpful.
Generally, you will be asked not to eat or drink anything for several hours before the PET scan because this may alter your sugar metabolism and may affect the quality of the images or pictures. Drinking water is usually acceptable. If you are diabetic, you will be provided with specific instructions and may need to stop taking some diabetic medications before having the scan.
You need to wear comfortable, loose clothing and will generally be changed into a hospital gown. It is important that you are not wearing metal, including jewellery, watches, zips and bra hooks as these can affect the quality of the images produced.

WHAT HAPPENS DURING THE SCAN 

After you arrive at the hospital or radiology practice, a nurse or nuclear medicine technologist will explain the procedure and prepare you for the PET scan. You will be asked to change into a gown. A small needle will be inserted into a vein, usually in your arm or the back of your hand, to fit an intravenous line (a thin plastic tube) through which the liquid radioactive material is injected. A brief medical history will be taken to ensure the optimal (or best) scanning method is used and to also help with subsequent image interpretation. Your blood sugar level will be checked, as high or low blood sugar levels can alter the appearance of the scan. The radioactive substance is then injected into your vein through the intravenous line.
If you are having an FDG PET scan, you will be asked to rest quietly in a bed or arm chair, avoiding movement or talking for 90 minutes. During this time you will be alone as there is limited room for visitors, and it will prevent your friends or relatives from receiving unnecessary radiation exposure. You may be asked to drink some contrast material that moves through your stomach and bowel and helps to improve the interpretation of the scan. Occasionally, depending on the medical indication (symptom or condition), a catheter (a thin flexible tube) may be placed into your bladder to help improve image quality.
You will then be moved to the scanning room and positioned on the PET scanning bed. It is important to remain as still as possible during the scan as movement can result in reduced image quality and the images may be blurry. Therefore, if you are uncomfortable after being positioned on the bed please tell the nurse or technologist.
If you are having a PET-CT, the CT scan is performed first and takes less than 2 minutes. The PET scan takes approximately 30 minutes but the time will vary depending on the regions of your body being scanned.
The intravenous line will be removed before you leave.

GALLIUM DOTATATE SCAN

 

Nuclear medicine uses radioactive materials to diagnose or treat diseases. An octreotide scan is one that uses radioactive material to detect certain types of cancers arising from the neuro-endocrine systems (this means cancers that relate to the interaction between the nervous system and hormones from the endocrine system – glands that produce hormones in the body). It shows where the cancer started (the primary site) and any places it has spread to (called metastases).
Liquid radioactive octreotide (gallium dotatate) is injected into a vein, travels through the bloodstream and attaches to any cancer cells in the body. A radiation detecting device, a gamma camera, detects the radioactive octreotide and makes pictures showing where the cancer cells are.

octreo

PREPARING FOR THE SCAN 

It is important that you let staff at the hospital know if you are (or think you could be) pregnant or are breast feedingThis study may not be suitable for pregnant women because of the radiation dose to the growing foetus. Please discuss this with your doctor.
Women who are breastfeeding and people who are the primary or sole carer for small children may need to make special preparations for after the test, to stop breastfeeding for a short time, and to avoid close contact with young children. This is due to the small amount of radioactivity your body may release for a while after the test. Talk to your referring doctor or the nuclear medicine practice where you will have the test for details. The Australian Radiation Protection and Nuclear Safety Agency has recommendations about breastfeeding and close contact with children after nuclear medicine tests.
Sometimes you are required to stop taking certain medicines such as somatostatin or octreotide therapy prior to having the procedure. Please ask your doctor to explain what this entails in your situation and for specific instructions.
Drink plenty of fluids prior to and throughout this procedure and up to one day after having the procedure. This encourages the excretion of the radioactive tracer that is not absorbed and is also useful in obtaining better pictures.

WHAT HAPPENS DURING THE SCAN 

The procedure begins with an injection of a small amount of radioactive material into a vein in your arm. You will be asked to return in four hours for a scan of your whole body.
Upon your return, you will lie on a special table that allows pictures to be taken of your whole body. A camera will be positioned above and below your body which can take pictures at the same time.
The camera, which can detect radioactivity, will travel from your head to your toes, recording pictures as it goes. None of the equipment touches your body. This process takes about 40 minutes. It is very important that you stay still during the scan.
Next, a special set of pictures called a SPECT scan, a three dimensional image, is taken. For this set of pictures, the camera will be set up to travel in a circle around your whole body. Sometimes a separate set of SPECT scans is made for the chest and the abdomen (stomach) area.
Later, after you have left the hospital or radiology practice, the technologist will work with the pictures to create three dimensional images.
The scan takes place over 3 sessions:
  • The first session on the first morning can take up to 1 hour.
    • A nuclear medicine technologist will prepare the radioactive material when you arrive. This takes just over 30 minutes. The technologist and nuclear medicine consultant will discuss the scanning procedure with you.
    • You will have a small plastic needle inserted into your arm so the radioactive octreotide can be injected into your blood stream and be absorbed into your body.
  • You are required to return to the nuclear medicine department 4 hours later for the second session to take the first images/pictures of your whole body. This can take from 1 to 2½ hours, depending on the number of images that are required.
  • The third session occurs the following day. You will be given a time to return the next morning for the same images of your whole body as well as more SPECT, three dimensional, image(s) of your body. This session will also take from 1 to 2½ hours to complete but you do not have another injection.

RADIATION THERAPY

Radiation therapy aims to kill cancer cells but avoid damage to the structure and function of nearby healthy tissue.
Radiation therapy is a safe, effective way to treat cancer. It is a well established treatment. Radiation therapy offers clear benefits to patients. It allows organ preservation, preserves quality of life, reduces pain and improves survival. 

COMPUTER GUIDED 

Technological advances mean that radiation oncologists can see 3D images of tumours. This means they can direct radiation beams very precisely so less normal tissue is affected. Intensity Modulated Radiation Therapy (IMRT) and Image-guided Radiation Therapy (IGRT) allow radiation oncologists to better see and target tumours.
The radiation dose can be closely fitted to the tumour. This reduces radiation dose to important structures like the spinal cord or parts of the brain.
Radiation therapy  is a vital part of curing about 40% of all cured cancers.