What is Diagnostic Nuclear Medicine?
In diagnostic nuclear medicine, the unique characteristics of chemicals called radio-pharmaceuticals* are used for diagnosis. Typically, a small amount of a radiopharmaceutical is introduced into the body by injection, ingestion, or inhalation. The radiopharmaceutical is attracted to particular organs, bones, or other tissues. The radioisotope releases small amounts of energy (radiation) that can be detected outside the body by special “cameras.” These cameras record the movement and localization of radiopharmaceuticals in the body. The resulting 2- and 3-dimensional images document the function (metabolic, physiologic, and pathologic) of the tissue or organ of interest. Physicians examine these images to evaluate and diagnose a large number of diseases.
Some procedures in nuclear medicine do not involve imaging. These tests involve the injection of a small amount of radiopharmaceutical usually followed by the taking of blood samples for analysis.
* Radiopharmaceuticals are molecules or chemicals that are attached to a small amount of radioactive isotope that once administered to the patient are able to specifically localize within organs and/or organ systems in health and disease.
Some common procedures.
Nuclear medicine images can assist your doctor in diagnosing diseases
or planning and monitoring your treatment. Tumours, infection and other
disorders can be detected by evaluating organ function.
Nuclear medicine imaging procedures can be used to:
- Analyze kidney function
- Image blood flow and function of the heart
- Scan lungs for respiratory and blood-flow problems
- Evaluate bones for fracture, infection, arthritis or tumour
- Determine the presence or spread of cancer
- Locate the presence of infection
- Measure thyroid function to detect an overactive or underactive thyroid
Non-imaging procedures can be used to:
- Analyze kidney function
- Measure blood and plasma volume
- Evaluate problems with vitamin B12 uptake
- Measure thyroid function to detect an overactive or underactive thyroid
The most common procedures carried out are:
- Bone Scan
- Lung scan
- Myocardial perfusion scan (MPS scan)
- Multi gated cardiac scan (MUGA scan)
- Renal static scan (DMSA scan)
- Renal dynamic scan (MAG3 or DTPA scan)
- Sentinel lymph node scan (SLN scan)
- Iodine whole body scan
- Glumerular filtration rate measurement (GFR)
- Red cell mass and plasma volume measurement
- B12 absorption measurement (Schilling test)
- Thyroid uptake measurement
- Other scans
How should I prepare for the procedure?
Usually no special preparation is needed for a nuclear medicine procedure. However, if the procedure involves evaluation of the heart, you may have to skip a meal before the test and avoid caffeinated products such as coffee and tea. You will always be given information about how to prepare for a certain procedure.
What does the equipment look like?
For imaging procedures we use a gamma camera. This is a piece of equipment
which can detect radiation and from where it is coming. During most nuclear
medicine examinations, you will lie down on a scanning table. The gamma
camera will take pictures of the parts of your body in which the doctors
are interested. Some procedures involve scanning your whole body.
The images are stored on a computer for processing.
What is involved?
For imaging procedures a small amount of radioactive
tracer is injected into a vein, usually in your arm. The injection is no
more painful than a blood test.
You may then have pictures taken immediately or after a delay, depending
on the type of scan you are having. For the scan you will be asked to lie
on a bed or sit in a chair whilst the gamma camera obtains the images.
You do not normally have to undress but we will ask you to remove any metal
objects such as jewellery.
For non-imaging procedures a small amount of radioactive
tracer is injected into a vein, usually in your arm. The injection is no
more painful than a blood test. Sometimes the radioactive material is swallowed
rather than injected.
Following this administration we may need to take one or more blood samples
from another vein, usually in your arm. You may instead have to come back
for a measurement or you may be required to collect your urine for 24 hours.
How is an imaging procedure performed?
Depending on the type of scan, it may take several seconds to several
days for the substance to travel through the body and accumulate in the
organ to be studied, thus there is a wide range in scanning times.
While the images are being obtained, you must remain as still as possible.
This is especially true when a series of images is obtained to show how
an organ functions over time or when a tomographic* procedure is taking
place.
After the procedure, the radiographer will check that the quality of the
images are optimal for processing and diagnosis.
When this is done you will be able to leave.
The images will then be processed to enable a doctor with specialised training
in nuclear medicine to report on the findings and let your doctor know
within a few days.
* A tomographic image is created by letting the gamma camera rotate around your body.
What will I experience during the procedure?
Some minor discomfort during a nuclear medicine procedure may arise from the intravenous injection, usually done with a small needle. Lying still on the examining table may be uncomfortable for some patients. The amount of radiopharmaceutical we use is very small and you would normally not feel anything from this. During the scan you should be as still as possible to enable us to collect good images at the first attempt.
For cardiac procedures we will sometimes need to get your heart to beat
faster than normal and we will use a special drug to achieve this. Patients
normally experience some minor symptoms from this drug, but they will quickly
go away once we stop giving this drug. You will be monitored by highly
qualified staff while this is taking place.
If you are having a non-imaging test you can leave between the injection
and the blood sampling if you so wish. Just make sure you return for the
blood sampling at the correct time.
Who will interpret the results and how do I get them?
Most patients undergo a nuclear medicine examination because their primary care doctor has recommended it. A physician who has specialised training in nuclear medicine will interpret the images or test results and forward a report to your doctor. It usually takes a few days to interpret, report and deliver the results.
What are the benefits versus risks?
Benefits:
- The functional information provided by nuclear medicine examinations is unique and can not be obtained by using other procedures. For many diseases, nuclear medicine studies will give the most useful information needed to make a diagnosis and to determine appropriate treatment, if any.
- Nuclear medicine is much less traumatic than exploratory surgery, and allergic reaction to the radiopharmaceutical material is extremely rare.
Risks:
- Because the doses of radiopharmaceutical administered are very small, nuclear medicine procedures result in exposure to a small dose of radiation. Nuclear medicine has been used for more than five decades, and there are no known long-term adverse effects from such low-dose studies. The dose you will receive is similar to an X-ray examination and can be compared to the dose you receive from natural background radiation* over a few days to a couple of years, dependent on the type of procedure you have.
- As with all radiologic procedures, be sure to inform your physician if you are pregnant. In general, exposure to radiation during pregnancy should be kept to a minimum.
- Allergic reactions to the radiopharmaceutical can occur, but are extremely rare.
*Everybody is exposed to what is called natural background radiation coming from space, building material the ground, e.g. radon gas and from radioactivity inside our body. This natural radiation gives us a radiation dose equivalent to many hundred chest X-rays a year.
What are the limitations of General Nuclear Medicine?
Nuclear medicine procedures are time-consuming. They involve administration of a radiopharmaceutical, acquisition of images or analysis of blood or urine samples and interpretation of the results. It can take hours to days for the radiopharmaceutical to accumulate in the part of the body under study. Imaging and some non-imaging procedures can take up to three hours to perform.
More advice is available on the internet. Good information is available on:
References
This information has been produced by:
Head of Nuclear Medicine Lars Jansson
Senior Medical Physicist K. Dixon
Date Produced: February 2007
Review Date: February 2008
Responsible Clinician: Dr NK Robson, Consultant Radiologist
