Radionuclide studies
General info about radionuclide studies
Involves the use of radioactive substances, combined with pharmaceuticals, to study various organ systems, or body cavities. Nuclear medicine studies are primarily studies of physiology, but also can give anatomical information. Results are mostly in the form of images，but can be represented by graphs , numerical values, or a combination of all three.
Patient Preparation
Nuclear medicine procedures usually involve no preparation. Exceptions to this are studies of the GIT, biliary system and cardiac studies. Prior to which, the patient must fast, and certain medications must be stopped.
Patient Safety
Nuclear medicine studies are considered amongst the safest diagnostic tests available. All studies involve administration of a small amount of radioactive tracer, bound to a pharmaceutical, which is usually injected intravenously, but may be swallowed or inhaled, depending on the particular procedure being performed.
Hypersensitivity reactions are extremely rare (less than 10 / year worldwide). Patients can be assured that the injection they receive will not cause any adverse reaction, nausea, dizziness or blurred vision.
After receiving their injection, patients pose no danger to other members of the community, including pregnant women and children. They need take no precautions, and can go about their daily tasks, or return to work as normal.
Radioactive isotopes should not be administered during pregnancy.
Most nuclear medicine procedures result in less radiation exposure than similar x-ray procedures. IMAGING
The time lapse between injection and imaging can vary from 0 for lung scans and cardiac scans, 20 minutes for thyroid scans, 3 hours for bone scans and 48 hours for Iodine 131 and gallium scans.
After the appropriate waiting period, the patient is scanned on a specially designed bed, similar to that of a CT scanner. The nuclear medicine "Gamma Camera" is a computer controlled device which is sensitive to the radiation emitted from the patient.
Heart:
MYOCARDIAL PERFUSION SCAN
(Other names(depending on radioisotope used): Myocardial perfusion scintigraphy, MIBI(2-methoxy isobutyl isonitrile) stress test,exercise radioisotope scan, thallium imaging, thallium scan, thallium, MIBI or tetrofosmin scintigraphy, and perfusion imaging)
What is it?
Myocardial perfusion scan is a radionuclide test which helps to evaluate how well your heart functions under stress or exercise.
Why is it done?
It is done to: 1) assess the amount of blood reaching the heart muscle, 2) identify areas of heart muscle lacking an adequate blood supply as a result of heart attack and 3) identify blocked coronary arteries and evaluate the effectiveness of coronary bypass grafts or angioplasty.
How is it done?
There are 2 phases in this test, the stress phase and the rest phase. (Not sure what phase we do first in Singapore)
Stress phase first,
An IV line will be set up in your forearm, blood pressure is measured, and ECG leads are attached to your chest, arm, and leg. You will then be asked to exercise at increasing levels on a treadmill before the radioisotope such as thallium, MIBI (Cardiolite), or tetrofosmin (Myoview) is injected into the IV line, and you resume exercising for another minute to allow the substance to travel through your body and concentrate in the heart muscle.
After you stop exercising, you are positioned on a narrow examination table directly under a special camera which picks up the radioactive signals (gamma scintillation camera). One or both arms are placed on a rest over your head, and the camera takes multiple pictures (about 30mins). In many instances, it rotates slowly around you, thereby producing three-dimensional images (SPECT or single-photon emission computed tomography). You will be then informed to return later (about 4hrs) to repeat the picture taking after you have rested. (If MIBI or tetrofosmin is used, a second injection at rest is necessary.) Between sessions, you should remain relatively quiet, even though you may be permitted to leave the testing center. You can drink water or other plain, noncaloric beverages, but you should not eat.
Preparation for the test
You should not consume or use alcohol, caffeine, or tobacco (or any other source of nicotine) for 24 hours before the test. Do not eat anything for at least three hours before the test. You may be instructed to stop certain medications (eg B-blockers and nitrates) before the test. Wear loose fitting clothings and running shoes for the stress phase.
Potential problems
Pain and discomfort: IV needle may be bothersome. Test may provoke angina, leg fatigue, and muscle aches. Remaining in position for imaging may be uncomfortable.
Radioactive isotopes should not be administered during pregnancy.
Lungs:
V/Q SCAN
What is it?
A pulmonary ventilation/perfusion scan is a pair of nuclear scan tests that use inhaled and injected radioactive material (radioisotopes) to measure breathing (ventilation) and circulation (perfusion) in all areas of the lungs.
Why is it done?
The ventilation scan is used to evaluate the ability of air to reach all portions of the lungs. The perfusion scan measures the supply of blood through the lungs.
V/Q scan is most often performed to detect a pulmonary embolus. Also used to evaluate lung function in people with advanced pulmonary disease such as COPD and to detect the presence of shunts (abnormal circulation) in the pulmonary blood vessels
How is it done?
An intravenous line will be placed within a vein in your arm. You will then be placed on a narrow bed within a nuclear medicine camera.
The ventilation portion of the exam will require that you wear a mask. You will then breathe in the radioactive gas (Xe-133= Xenon-133) while your lungs are scanned by the camera.
The perfusion scan is performed by injecting radioactive substance (Tc99m-MAA=technetium-99m microaggregated albumin) into a vein. The lungs are scanned to detect the location of the radioactive particles as blood flows through the lungs.
Preparation for the test
A chest x – ray should be performed prior to the test.
GI:
Helicobacter pylori Test/ Urea breath test
What is it?
The urea breath test (UBT) is a procedure for diagnosing the presence of a bacterium, Helicobacter pylori (H. pylori) that causes inflammation, ulcers, and atrophy of the stomach. The test also may be used to demonstrate that H.pylori has been eliminated by treatment with antibiotics.
How is this breath test done?
You will be asked to swallow a capsule containing a small amount of 14C-labeled urea. If the 14C-urea comes into contact with H. pylori (urease) in the stomach, it is hydrolyzed into 14C-carbon dioxide and ammonia. The carbon dioxide enters the bloodstream and is exhaled in your breath. Ten minutes after swallowing the capsule, a breath sample is collected and the isotopic carbon in the exhaled carbon dioxide is measured.
Preparation for the test
You should not be eating or drinking for 6hours prior to the test as food in the stomach may prevent the urease from H. pylori from contacting the 14C-urea in the test capsule.
The following medications should be discontinued at the listed intervals before the test is performed:
Antibiotics should be stopped 30 days before the test.
Bismuth medications containing bismuth, like Petpo Bismol, should be stopped 30 days prior to the test.
Sucralfate should be stopped 2 weeks prior to the test.
Proton-pump inhibitors should be stopped 2 weeks prior to the test.
Antacids should be stopped 6 hours prior to the test
Test should not be used on patients who have undergone resective gastric surgery.
The following medications do not interfere with the test:
H2-blockers
GASTRIC EMPTYING STUDIES
What is it?
A simple and non-invasive way to evaluate the emptying of ingested food from your stomach to your intestines.
How is it done?
Patient swallows a meal consisting of a Technetium labelled egg sandwich, and a glass of water, within 10mins and the stomach is imaged at regular intervals (15 minutes) over 2 hours.
Preparation for the test
You should not eat or drink after midnight. (Note: In patients currently on hyperalimentation or parenteral nutrition, feedings/TPN infusions should be stopped 4 hours prior to the examination).
Check to see which medications should be withheld and for how long before this study. Many medications can affect gastric emptying, and knowing which medications to withhold is very important.
G.I.T BLOOD LOSS STUDY
The patient's own red blood cells are labelled with Technetium, and re-injected. This study is very sensitive in detecting active bleeding sites - (0.5 ml / min ) . The patient can be imaged at intervals over 24 hours. The bleeding site can be localised to a section of small or large bowel, to guide further investigation such as angiography, or surgery.
PREPARATION - Nil, however the patient must be bleeding during the study for it to be positive
Renal:
Technetium labelled renal agents are an excellent way of studying the function of the kidneys, in both children and adult patients.
For all Nuclear Medicine renal scans, the patient should be well hydrated
DMSA RENAL SCAN
What is it?
This is an investigation in which pictures of the kidneys are taken with a special camera following the small injection of a radioactive material (DMSA=dimercaptosuccinic acid). Estimated time of test= 3-4hrs.
Why is it done?
It is a simple non-invasive way to evaluate whether there are any abnormalities with your kidneys (eg scarring) by showing how well your kidneys are perfused by the radioactive substance.
How is it done?
A small amount of radioactive substance (Technetium labelled DMSA) is injected into a vein in your arm. This material travels through the bloodstream to the kidneys. You should experience nothing as a result of this injection apart from the slight discomfort of the needle prick.
You will then have wait for 2 to 3 hours for the radioactive substance to accumulate in your kidneys before your pictures are taken. During this waiting period, you will be free to move around if you wish. After this waiting period, it will take approximately 30 minutes to take your pictures and complete the scan.
Additional pictures might be taken, such as SPECT or tomography of your kidneys if a more detailed study is deemed necessary. To take these pictures, you will be asked to lie still while an image is being taken. Then the camera will go around you for 20-30 minutes in a 360 degree orbit, after which you will be released by the technologist.
Preparation for the scan?
No special preparation is required before the scan. You may eat and drink normally beforehand. The injection will not impair your ability to drive a vehicle.
N.B. If you are pregnant or if there is any possibility that you may be pregnant please tell us before you receive your injection.
Should I take any precautions after having a DMSA renal scan?
Some of the radioactive material will remain in your body for approximately 12 hours after the scan. Since it emits a small amount of radiation you should take the following precautions during this period:
Drink plenty of fluids and empty your bladder as frequently as possible. When using the toilet you should avoid spills, flush the toilet twice and wash your hands thoroughly.
If possible avoid contact with infants and children.
If you are a nursing mother express and discard the first feed after your injection. You may resume normal breast feeding at the next feed.
D.T.P.A. Renal Scan
Technetium labelled DiethyleneTriaminePentaceticAcid is injected I.V. This agent is rapidly excreted via glomerular filtration by normal kidneys. This study allows assessment of renal perfusion, relative uptake, and excretion. Combined with a diuretic, (DTPA scan + Lasix), the renal collecting system and ureters can be imaged. Half clearance times can be measured, which can help in differentiating between a dilated collecting system and a functionally obstructed collecting system. Combined with an ACE inhibitor (usually captopril) - DTPA scan + Captopril - , the renal scan is sensitive for renal artery stenosis. A single, oral dose of ACE inhibitor is given (25 - 50mg), then after 1 hour, the renal scan proceeds.
CYSTOURETEROGRAM (Nuclear medicine MCU)
An excellent way to detect vesico-ureteric reflux in children. The test involves only about 2% to 5% of the radiation exposure involved in a radiological MCU. A small amount of Technetium 99m is introduced into the bladder via a catheter (usually a small feeding tube), and the bladder is filled with normal saline. Imaging is continuous, whereas the x-ray technique involves intermittent "snap-shots". The only limitation to this test is its lack of anatomical definition. If a urethral valve is to be excluded, a radiological M.C.U should be performed first, and the Nuclear Medicine study as a follow up.
Hepatobiliary:
COLLOID LIVER SCAN
(Other names: Liver Technetium Sulfur Colloid Scan, Liver-Spleen Radionuclide Scan, Nuclear Scan - Liver or Spleen, Nuclear Scan - Technetium, Technetium Scan)
What is it?
The liver-spleen scan is a safe, non-invasive way to evaluate the shape, size, and position or your liver and spleen, and a good screening method for detecting liver disease
Why is it done?
Investigation of space occupying lesions, such as hepatoma, metastases, and to differentiate between hepatic adenoma and focal nodular hyperplasia. Budd-Chiari syndrome, hepatic laceration/haematoma
Investigation of parenchymal liver diseases such as cirrhosis and alcoholic cirrhosis
Investigation of splenic size, position and function.
How is it done?
A radioisotope (Technetium labelled sulphur colloid) is injected into a vein. After the liver (reticuloendothelial cells in the bone marrow, spleen and liver) has had sufficient time to absorb the radioisotope, you will be asked to lie on a table where you will be positioned under the scanner.
The scanner is able to detect where the radioisotope material is located, and images are displayed on a computer. The technician operating the camera and computer can manipulate the equipment to get a clearer picture. You may be asked to remain still, hold your breath for short periods, or to change positions during the scan.
Preparation for test
No special preparations.
H.I.D.A (BILIARY) SCAN
Most sensitive and specific test for acute cholecystitis
Persistent right upper quadrant pain, in the presence of a normal ultrasound, can be investigated using H.I.D.A followed by I.V CCK to detect acalculous cholecystitis.
What is it?
A hydroxy iminodiacetic acid (HIDA) scan helps evaluate the function of the gallbladder and the bile ducts. Doctors may also refer to this procedure as cholescintigraphy Estimated time of test= 60-90 mins.
Why is it done?
A HIDA scan is used to diagnose:
Obstruction of the bile ducts (eg gallstones, biliary atresia, choledocal cyst or tumors)
Diseases of the gallbladder (eg acute cholecystitis)
Bile leaks
How is it done?
In this procedure, a radioactive tracer (technetium labelled H.I.D.A) is injected into your vein. The tracer travels to your liver and into the bile ducts and then concentrated within the gallbladder. A special scanner placed over your abdomen tracks the movement of the tracer through your biliary tract and makes images of the liver, gallbladder and bile ducts. This process takes about 1 hour.
In the event that we are evaluating for gallbladder ejection fraction, you will receive an intravenous injection of an enzyme (CCK= Cholecystokinin) after the first hour of imaging is completed and the gallbladder is visualized. Then, images of your abdomen will be taken for another 30 minutes.
Preparation
Refrain from eating anything four to six hours prior to the study. Do not take Demerol or morphine painkillers for 24 hours prior to the study. Be prepared to list all medications you are taking.
LIVER BLOOD POOL SCAN
The patient's red blood cells, labelled with technetium, are re-injected. The patient is then scanned after a 2 to 3 hour delay.
INDICATIONS - Investigation of cavernous haemangioma.
PREPARATION - Nil
Bone:
BONE SCAN
What is it?
A bone scan is a test that detects areas of increased or decreased bone metabolism (turnover).
Why is it done?
Detecting areas of abnormal bone metabolism is valuable in determining whether there is associated tumor, fracture, infection, or an underlying metabolic disorder.
Bone Tumour: Very sensitive for detecting both primary and secondary bone tumours. Also very sensitive for benign bone lesions such as osteoid osteoma and osteochondroma
Infection: OSTEOMYELITIS and SEPTIC ARTHRITIS
Arthritis
Avascular necrosis
Hip/knees prostheses: Helpful in differentiating between infected and loose prostheses.
Paget’s dx of the bone
Sports medicine: early periostitis in sports people and stress fractures, particularly of the tibia , and metatarsals
Fractures: Fractures in small children (Battered Baby Syndrome)- low dose of radiation compared with X-rays
Reflex sympathetic dystrophy
Metabolic bone dx: hyperparathyroidism, osteomalacia, renal osteodystrophy and hypertrophic pulmonary osteoarthropathy
Bone pain for invx: Useful in cases where there is persistent bone pain , and x-rays are normal.
How is it done?
This involves an injection of a Technetium labelled phosphate complex which adsorbs to bone tissue. Images may be taken at the time of injection (Dynamic and Blood Pool Images) in the case of suspected infection, fracture or inflammation, and in all cases after a 3 hour delay.
S.P.E.C.T imaging is often used for localising bone lesions, particularly in the spine and is critical for detecting stress fractures of the pars-interarticularis .
Preparation
Where the pelvis is the area of most interest, the patient is asked to drink plenty of fluids during the 3 hour gap, otherwise no special preparations needed.
Thyroid and parathyroid:
PARATHYROID SCANNING
This involves using Technetium 99m and Thallium 201. Thallium is a potassium analogue, and is taken up by Thyroid and Parathyroid tissue, whereas Technetium is predominantly taken up by the Thyroid gland. When the 2 scans are computer subtracted, hyperfunctioning parathyroid tissue can be identified - same day evaluation by Ultrasound is advisable for confirmation.
THYROID UPTAKE AND SCAN
(other names: Thyroid scan, Nuclear Scan - Thyroid, Radioactive Iodine Screening Test - Thyroid, RAUI, Scan – Thyroid)
What is it?
A Thyroid Scan shows the size, shape and location of your thyroid gland. The “uptake” is a measure of the thyroid function.
Why is it done?
When thyroid cancer and nodules are suspected and to assess hyperfunctioning gland.
How is it done?
You are given radioactive iodine to
drink (or in pill form) and then must wait until the iodine collects in the
thyroid. The first scan is usually 4 to 6 hours after the iodine has been
ingested, and another scan may be taken 24-hours later. After the radioactive
iodine has been absorbed by the thyroid, you lie on your back on a movable table
with your neck and chest positioned under the scanner. The scanner detects the
location and intensity of the gamma rays emitted. During this part of the
procedure, you must lie still to enable the scanner to get a clear image.
Next, the information is sent to a computer that displays images of the thyroid
and any possible nodules that have absorbed the iodine.
Preparations
You may need to discontinue thyroid supplement 6 weeks prior to the examination.
Antithyroid medications (eg PTU) may not be taken for at least three days.
No iodinated contrast material may have been given (IVP, CT with contrast, myelogram and angiogram) for at least six weeks.