Nuclear Imaging

Physicians use radionuclide imaging procedures to visualize the structure and function of an organ, tissue, bone or system within the body. In adults, nuclear medicine is used to:

Heart

• visualize heart blood flow and function (such as a myocardial perfusion scan)

• detect coronary artery diseaseand the extent of coronary stenosis

• assess damage to the heart following a heart attack

• evaluate treatment options such as bypass heart surgery and angioplasty

• evaluate the results of revascularization procedures

• detect heart transplant rejection

• evaluate heart function before and after chemotherapy (MUGA)

Lungs

• scan lungs for respiratory and blood flow problems

• assess differential lung function for lung reduction or transplant surgery

• detect lung transplant rejection

Bones

• evaluate bones for fractures, infection and arthritis

• evaluate for metastatic bone disease

• evaluate painful prosthetic joints

• evaluate bone tumors

• identify sites for biopsy

Brain

• investigate abnormalities in the brain, such as seizures, memory loss and abnormalities in the blood flow

• detect the early onset of neurological disorders such as Alzheimer disease

• plan surgery and localize seizure foci

• evaluate for abnormalities in the brain involved in controlling movement in patients with suspected Parkinson’s disease

• evaluation of brain tumor recurrence, surgical or radiation planning or localization for biopsy

Other Systems

• identify inflammation or abnormal function of the gallbladder

• identify bleeding into the bowel

• assess post-operative complications of gallbladder surgery

• evaluate lymphedema

• evaluate fever of unknown origin

• locate the presence of infection

• measure thyroid function to detect an overactive or underactive thyroid

• help diagnose hyperthyroidism and blood cell disorders

• evaluate for hyperparathyroidism

• evaluate stomach emptying

• evaluate spinal fluid flow and potential spinal fluid leaks

Cancer

• stage cancer by determining the presence or spread of cancer in various parts of the body

• localize sentinel lymph nodes before surgery in patients with breast cancer or skin and soft tissue tumors

• plan treatment

• evaluate response to therapy

• detect the recurrence of cancer

• detect rare tumors of the pancreas and adrenal glands

Renal

• analyze native and transplant kidney function

• detect urinary tract obstruction

• evaluate for hypertension related to the kidney arteries

• evaluate kidneys for infection versus scar

• detect and follow-up urinary reflux

You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing.

Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding.

You should inform your physician and the technologist performing your exam of any medications you are taking, including vitamins and herbal supplements. You should also inform them if you have any allergies and about recent illnesses or other medical conditions.

Jewelry and other metallic accessories should be left at home if possible, or removed prior to the exam because they may interfere with the procedure.

You will receive specific instructions based on the type of the scan you are undergoing. In some instances, certain medications or procedures may interfere with the examination ordered. Please refer to a specific Nuclear Imaging test overview for a detailed preparation guide.

Special camera used in nuclear imaging include the gamma camera and single-photon emission-computed tomography (SPECT).

The gamma camera, also called a scintillation camera, detects radioactive energy that is emitted from the patient’s body and converts it into an image. The gamma camera does not emit any radiation. The gamma camera is composed of radiation detectors, called gamma camera heads, which are encased in metal and plastic and most often shaped like a box, attached to a round circular donut shaped gantry. The patient lies on the examination table which slides in between the parallel gamma camera heads which are suspended over the examination table and located beneath the examination table. Sometimes, the gamma camera heads are oriented at a 90 degree angle and placed over the patient’s body.

SPECT involves the rotation of the gamma camera heads around the patient’s body to produce more detailed, three-dimensional images.

A probe is a small hand-held device resembling a microphone that can detect and measure the amount of the radiotracer in a small area of your body. Probes are used for thyroid uptakes scans.

With ordinary x-ray examinations, an image is made by passing x-rays through the patient’s body. In contrast, nuclear imaging procedures use a radioactive material, called a radiopharmaceutical or radiotracer, which is injected into the bloodstream, swallowed or inhaled as a gas. This radioactive material accumulates in the organ or area of your body being examined, where it gives off a small amount of energy in the form of gamma rays. Special cameras detect this energy, and with the help of a computer, create pictures offering details on both the structure and function of organs and tissues in your body.

Unlike other imaging techniques, nuclear imaging exams focus on depicting physiologic processes within the body, instead of showing anatomy and structure. Areas of greater intensity, called “hot spots,” indicate where large amounts of the radiotracer have accumulated and where there is a high level of chemical or metabolic activity. Less intense areas, or “cold spots,” indicate a smaller concentration of radiotracer and less chemical activity.

You will be positioned on an examination table. If necessary, a nurse or technologist will insert an intravenous (IV) catheter into a vein in your hand or arm.

Depending on the type of nuclear medicine exam you are undergoing, the dose of radiotracer is then injected intravenously, swallowed or inhaled as a gas.

It can take anywhere from several seconds to several days for the radiotracer to travel through your body and accumulate in the organ or area being studied. As a result, imaging may be done immediately, a few hours later, or even several days after you have received the radioactive material.

When it is time for the imaging to begin, the camera or scanner will take a series of images. The camera may rotate around you or it may stay in one position and you will be asked to change positions in between images. While the camera is taking pictures, you will need to remain still for brief periods of time. In some cases, the camera may move very close to your body. This is necessary to obtain the best quality images. If you are claustrophobic, you should inform the technologist before your exam begins.

If a probe is used, this small hand-held device will be passed over the area of the body being studied to measure levels of radioactivity. Other nuclear imaging tests measure radioactivity levels in blood, urine or breath.

The length of time for nuclear imaging procedures varies greatly, depending on the type of exam. Actual scanning time for nuclear imaging exams can take from 20 minutes to several hours and may be conducted over several days.

When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed. Occasionally, more images are obtained for clarification or better visualization of certain areas or structures. The need for additional images does not necessarily mean there was a problem with the exam or that something abnormal was found, and should not be a cause of concern for you.

If you had an intravenous line inserted for the procedure, it will usually be removed unless you are scheduled for an additional procedure that same day that requires an intravenous line.

Except for intravenous injections, most nuclear medicine procedures are painless and are rarely associated with significant discomfort or side effects.

When the radiotracer is given intravenously, you will feel a slight pin prick when the needle is inserted into your vein for the intravenous line. When the radioactive material is injected into your arm, you may feel a cold sensation moving up your arm, but there are generally no other side effects.

When swallowed, the radiotracer has little or no taste. When inhaled, you should feel no differently than when breathing room air or holding your breath.

It is important that you remain still while the images are being recorded. Though nuclear imaging itself causes no pain, there may be some discomfort from having to remain still or to stay in one particular position during imaging.

Unless your physician tells you otherwise, you may resume your normal activities after your nuclear medicine scan. If any special instructions are necessary, you will be informed by a technologist, nurse or physician before you leave the nuclear medicine department.

Through the natural process of radioactive decay, the small amount of radiotracer in your body will lose its radioactivity over time. It may also pass out of your body through your urine or stool during the first few hours or days following the test. You should also drink plenty of water to help flush the radioactive material out of your body as instructed by the nuclear medicine personnel.

You will be informed as to how often and when you will need to return to the nuclear medicine department for further procedures.

A radiologist or other physician who has specialized training in nuclear medicine will interpret the images and forward a report to your referring physician.

Benefits

• Nuclear medicine examinations provide unique information—including details on both function and anatomic structure of the body that is often unattainable using other imaging procedures.

• For many diseases, nuclear medicine scans yield the most useful information needed to make a diagnosis or to determine appropriate treatment, if any.

• Nuclear imaging offers the potential to identify disease in its earliest stage, often before symptoms occur or abnormalities can be detected with other diagnostic tests.

• Because the doses of radiotracer administered are small, diagnostic nuclear medicine procedures result in relatively low radiation exposure to the patient, acceptable for diagnostic exams. Thus, the radiation risk is very low compared with the potential benefits.

Risks

• Nuclear diagnostic procedures have been used for more than five decades, and there are no known long-term adverse effects from such low-dose exposure.

• Allergic reactions to radiopharmaceuticals may occur but are extremely rare and are usually mild. Nevertheless, you should inform the nuclear medicine personnel of any allergies you may have or other problems that may have occurred during a previous nuclear medicine exam.

• Injection of the radiotracer may cause slight pain and redness which should rapidly resolve.

• Women should always inform their physician or radiology technologist if there is any possibility that they are pregnant or if they are breastfeeding.

Nuclear medicine procedures can be time consuming. It can take several hours to days for the radiotracer to accumulate in the body part of interest and imaging may take up to several hours to perform, though in some cases, newer equipment is available that can substantially shorten the procedure time.

The resolution of structures of the body with nuclear medicine may not be as high as with other imaging techniques, such as CT or MRI. However, nuclear medicine scans are more sensitive than other techniques for a variety of indications, and the functional information gained from nuclear medicine exams is often unobtainable by other imaging techniques.

For abdominal scintigraphy, indications are specific to a particular screening.

Liver/spleen

This study is performed to determine the size and shape of the liver and spleen as well as for detecting functional abnormalities of the reticuloendothelial cells of these organs. Occasionally, the study is performed for:

· Suspected focal nodular hyperplasia of the liver.These lesions often have normal or increased uptake on sulphur colloid imaging.

· Assessments of reticuloendothelial system (RES) function in patients with suspected liver disease. The decision to perform a liver biopsy or to continue treatment with a hepatotoxic agent may be influenced by the severity of the liver disease that is seen on liver-spleen imaging as a complement to blood tests.

· Detecting functional splenic tissue.

· Adults with recurrent thrombocytopenia previously treated by splenoctomy.

· Characterization of an incidentally noted mass as functional splenic tissue.

· Evaluation of abdominal trauma with suspected splenic rupture.

· Viability assessment of splenic grafts.

Hepatobiliary scintigraphy 

The study evaluates hepatocellular function and patency of the biliary system by tracing the production and flow of bile from the liver through the biliary into the small intestine. Sequential images of the liver, biliary tree and intestinal tract are obtained. Computer acquisitions and analysis as well as pharmaceutical interventions are frequently employed. Clinical indication include but are not limited to the following:

· Functional assessment of the hepatobiliary system.

· Evaluation of integrity of the hepatobiliary tree.

· Investigation of: suspected acute cholecystitis, chronic biliary tract disorders, common bile duct obstruction, bile extravasation, atresia of the biliary tree (differential diagnosis in neonatal jaundice), patency of bilio-enteric surgical anastomosis, enterogastric reflux.

Gastrointestinal bleeding

Gastrointestinal bleeding can be upper, originating above the ligament of Treitz, or lower, distal to the ligament of Treitz. Frequent causes of upper gastrointestinal bleeding include esophageal varices, gastric and duodenal ulcers, gastritis, esophagitis, Mallory-Weiss tears or neoplasms. Causes of lower gastrointestinal haemorrhage include angiodysplasia, diverticula, neoplasms and inflammation. The goals of gastrointestinal bleeding scintigraphy are to locate the bleeding site and to determine which patients require aggressive treatment as opposed to those who can be medically managed.

Meckel’s diverticulum scintigraphy 

A Meckel diverticulum is a vestigial remnant of the omphalomesenteric duct located in the ileum, about 50-80 cm from the ileocecal valve. About half of Meckel diverticuli contain gastric mucosa. Bleeding may result from ileal mucosal ulceration from acid secretion. ^99mTc pertechnetate avidly accumulates in gastric mucosa and is the study of choice for identifying ectopic gastric mucosa in Meckel diverticulum.

Oesophageal studies

By using radionuclide techniques, the function of the oesophagus and the gastro-oesophagus junction, and the presence and severity of gastro-oesophageal reflux can be studied. The main advantages of the procedure. Oesophageal motility disorders usually present with dysphagia or chest pain (often mimicking ischaemic cardiac disease). The following symptoms and conditions often occur in combination:

· Reflux oesophagitis

· Hiatus hernia

· Oropharyngeal dysfunction

· Primary and secondary achalasia

· Diffuse oesophageal spasm

· Oesophageal atresia and structure

· Connective tissue disorders

· Other systemic, neurological and myopathic disorders.

Liver/spleen imaging: No special preparation is required.

Hepatobiliary scan: To permit gall bladder visualization, the patient must have fasted for a minimum of two and preferably four hours prior to administration of the radiopharmaceutical. If the patient has fasted for longer than 24 hours or is on total parental nutrition, a false positive study for cholecystitis may occur. Please inform the technologist if this is case.

Gastrointestinal bleeding: Upon arrival to the clinic, the blood pressure and heart rate will be checked to confirm that the patient is haemodynamically stable. Intravenous catheter might be in place so that hypotension can be rapidly treated. No other preparation is needed.

Meckel’s diverticulum scintigraphy: Two days before the procedure you will be asked to start taking a medicine that would allow a better scanning procedure.

Oesophageal studies: Patients are usually studied in fasting state.

• Detection, localization, staging and follow-up of the following:

· Pheochromocytomas

· Neuroblastomas

· Ganglioneuroblastomas

· Ganglioneuromas

· Paragangliomas

· Carcinoid tumours

· Multiple endocrine neoplasia type 2 (MEN2) syndromes

• Assessment of uptake and residence time for treatment planning

• Evaluation of tumour response therapy

• Determination if high-dose 131-I-MIBG therapy may be beneficial

• Confirmation of suspected tumours arising from neuroendocrine tissue

• Evaluation of function of the adrenal medulla (hyperplasia)

• Pregnant/breast-feeding • Interfering medications:

· Amphetamines

· Tricyclic antidepressants · Bretylium

· Calcium Channel blocking agents (e.g. Norvasc, Plendil, Cardene, Procardia etc.)

· Cocaine

· Guanethidine

· Haloperidol (Haldol)

· Labetalol (Trandate)

· Loxapine (Loxapac, Loxatine)

· Metaraminol (Aramine, Metaramin, Pressonex)

· Phenothiazines (Thorazine, Compazine)

· Reserpine (Serpalan)

· Sympathomimetics ( Ephedra, Ritalin)

· Thiothixene (Navane)

• Known hypersensitivity to iodine (low risk)

• Recent nuclear medicine study

• It is an absolute requirement that drugs which may interfere with the hypothalamic–pituitary–adrenal axis (e.g. glucocorticoids) or on the renin–angiotensin–aldosterone axis (e.g. spironolactone, most diuretics, sympathetic inhibitors, oestrogens) be discontinued to avoid distortion of the biodistribution and misinterpretation of the scintigraphic imaging. Please refer to the list of medications interfering medications listed above.

• You can eat and take medications as necessary (other than mentioned above).

• Please bring the list of your current medications for your appointment.

Diagnostic investigations are carried out for any of the following purposes:

• To detect the existence, location, extent and distribution of brain lesions (tumour, infarct, inflammation, haemorrhage or trauma) or intracranial lesions,

• To assess the integrity of the BBB in systemic disorders such as infection, intoxication or connective tissue diseases,

• To detect the patency and morphology of major intracranial vessels,

• To diagnose brain death.

The purposes for which an investigation is needed include:

• Detection and evaluation of cerebrovascular disease:

· Differentiation of cerebral infarction

· Prediction of the outcome of patients with cerebrovascular accident (CVA)

· Work-up of patients with transient ischaemic attack (TIA)

• Evaluation of patients with suspected dementia

• Presurgical localization of epileptic foci

• Evaluation of symptomatic traumatic brain injury, especially in the absence of CT and/or MRI findings

• Diagnosis of encephalitis

• Monitoring and assessment of subarachnoid haemorrhage

• Verification of brain death

• Assistance in planning and monitoring treatment for intracranial or brain disorders.

Other indications include neuropsychiatric disorders such as depression, obsessive-compulsive disorder, chronic fatigue syndrome, neural degenerative diseases, for example Huntington’s chorea, and functional disorders, for example schizophrenia, where the findings of SPECT brain perfusion imaging have not been fully characterized. In HIV-positive encephalopathy, CO₂ intoxication and connective tissue diseases, SPECT brain perfusion can detect organic changes in the brain and point to appropriate treatment and monitoring.

Patients will be instructed to stop taking caffeine, alcohol or other drugs known to affect cerebral blood flow (CBF) at least 1-3 days before the study. They will also be instructed to avoid smoking for at least the day of the test. Other medications should be discussed with a family physician.

You will be asked to sign a written consent for performing the procedure.

You will be asked to change into the clinic gown and void right before the procedure.

During the procedure you will be asked to keep your eyes closed or open, depending on the indication for the test and chosen protocol.

If the patients are unable to cooperate, (e.g. mental deficiency), sedation will be needed.

A gallium scan is done to:

• Detect the source of an infection that is causing a fever (called a fever of unknown origin).

• Detect an abscess or certain infections, especially in the bones.

• Monitor the response to antibiotic treatment.

• Diagnose inflammatory conditions such as pulmonary fibrosis or sarcoidosis (Sarcoidosis is a disease involving abnormal collections of inflammatory cells that can form as nodules in multiple organs).

• Detect certain types of cancer (such as lymphoma). A gallium scan also may be done to see if cancer has spread (metastasized) to other areas of the body, or to watch how well a cancer treatment is working.

Before the gallium scan, tell your doctor if:

• You are or might be pregnant.

• You are breast-feeding. If you will no longer be breast-feeding after the test, you will be asked to stop breast-feeding 2 weeks before the test so that the radioactive tracer will not build up in your breast tissue. If you will continue to breast-feed after the test, it is recommended that you not use your breast milk for 4 weeks after a gallium scan because the tracer can be passed to your baby. Some doctors may advise you to stop breast-feeding completely after this scan.

• Within the 4 days before the gallium scan, you have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine (such as Pepto-Bismol) that contains bismuth. Barium and bismuth can interfere with test results.

• Gallium builds up in the large intestine (colon) before it is eliminated in the stool. You may need to take a laxative the night before the scan and have an enema 1 to 2 hours before the scan to prevent the gallium in your colon from interfering with pictures of the area being studied.

A gallium scan is usually done by a nuclear medicine technologist. The scan pictures are usually interpreted by a radiologist or nuclear medicine specialist.

The technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected. You will need to return for the diagnostic scans. Gallium scans are usually done 24 hours (1 day), 48 hours (2 days), and 72 hours (3 days) after the tracer is injected. It is absolutely necessary for you to come on a specific time for repeated scan.

When you come in for the scan, you will need to remove any jewellery that might interfere with the scan. You may need to take off all or most of your clothes, a gown will be given to use during the test.

You will lie on your back on a table, and a large scanning camera will be positioned closely above you. The camera does not produce any radiation, so you are not exposed to any additional radiation while the scan is being done.

Each scan may take about 60 to 90 minutes.

There is always a slight risk of damage to cells or tissue from being exposed to any radiation, including the low level of radiation released by the radioactive tracer used for this test.

Allergic reactions to the radioactive tracer are rare. Most of the tracer will be eliminated from your body (through your urine or stool) within 4 days. The amount of radiation is so small that it is not a risk for people to come in contact with you following the test.

Normal: The collection and activity of gallium in the bones, liver, spleen, and large intestine (colon) is normal. No areas of unusual gallium accumulation are seen.

Abnormal: An abnormally high gallium accumulation (hot spot) is present in one or more areas of the body, possibly meaning inflammation, infection, or a tumour.

A gallium scan is used for specific types of cancers, mainly of the lymph nodes, bones, or bone marrow. A normal scan does not exclude the possibility of cancer, because some types of cancer do not show up on a gallium scan. A gallium scan also cannot determine whether a tumour is cancerous (malignant) or noncancerous (benign).

The results of a gallium scan should be interpreted along with the results of other tests, such as a physical exam, blood tests, and X-rays.

• To detect sites of infection/inflammation in patients with granulocytosis and fever of unknown origin.

• To localize an unknown source of sepsis and to detect additional site(s) of infection in patients with persistent or recurrent fever and a known infection site.

• To survey for site(s) of abscess or infection in a febrile post-op patient without localizing signs or symptoms. Fluid collections, ileus, bowel gas and/or fluid, and healing wounds reduce the specificity of CT and ultrasound.

• To detect site(s) and extent of inflammatory bowel disease.

• To detect and follow-up osteomyelitis primarily when there is existing bone pathology such as infected joint prostheses, non-united fractures or sites of metallic hardware from prior bone surgery.

• To detect osteomyelitis in diabetic patients when degenerative or traumatic changes, neuropathic osteoarthropathy or prior osteomyelitis have caused increased bone remodeling.

• To detect osteomyelitis involving the skull in postoperative patients and for follow-up of therapy.

• To detect mycotic aneurysms, vascular graft and shunt infections.

Patients must be able to cooperate for whole body or regional scanning which may require 30–60 min for completion. No other special preparation for the test is needed.

In In-111 leukocyte scan, the white blood cells (mostly neutrophils) are removed from the patient, tagged with the radioisotope Indium-111, and then injected intravenously into the patient. The tagged leukocytes subsequently localize to areas of relatively new infection. The study is particularly helpful in differentiating conditions such as osteomyelitis from decubitus ulcers for assessment of route and duration of antibiotic therapy.

In imaging of infections, the gallium scan has a sensitivity advantage over the indium white blood cell scan in imaging osteomyelitis (bone infection) of the spine, lung infections and inflammation, and in detecting chronic infections. In part, this is because gallium binds to neutrophil membranes, even after neutrophil death, whereas localization of neutrophils labeled with indium requires them to be in relatively good functional order. However, indium leukocyte imaging is better at localizing acute (i.e., new) infections, where live neutrophils are still rapidly and actively localizing to the infection, for imaging for osteomyelitis that does not involve the spine, and for locating abdominal and pelvic infections.

Both the gallium scan and indium-111 white blood cell imaging may be used to image fever of unknown origin (elevated temperature without an explanation). However, the indium leukocyte scan will localize only to the approximately 25% of such cases which are caused by acute infections, while gallium is more broadly sensitive, localizing to other sources of fever, such as chronic infections and tumours. Gallium may be a better choice for spleen study because gallium does not normally accumulate in the spleen.

A lung scan is done to:

• Find a blood clot that is preventing normal blood flow (perfusion) to part of a lung (pulmonary embolism).

• Check the flow of blood (perfusion) or air (ventilation) through the lungs.

• See which parts of the lungs are working and which are damaged. This is often done before lung surgery to remove parts of the lung.

Before your lung scan, tell your doctor if:

• You are or might be pregnant.

• You are breast-feeding. The radioactive tracer used in this test can get into your breast milk. Do not breast-feed your baby for 1 or 2 days after this test. During this time, you can give your baby breast milk you stored before the test, or you can give formula. Discard the breast milk you pump for the 1 or 2 days after the test.

• A chest X-ray is usually done the same day either before or after the lung scan.

You may be asked to sign a consent form.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form.

A lung scan is usually done by a nuclear medicine technologist. The scan pictures are usually interpreted by a radiologist or nuclear medicine specialist.

You will need to remove any jewellery that might interfere with the scan. You will be asked to change into the clinic patient gown.

During the scan, you will either lie on your back with the scanning camera positioned over or under your chest, or you will sit with the camera positioned next to your chest. The camera does not produce any radiation, so you are not exposed to any more radiation while the scan is being done.

Ventilation scan

For the ventilation scan, a mask will be placed over your mouth and nose. Or you may have a nose clip on your nose and a tube in your mouth that you use for breathing. You will inhale the tracer gas or mist through the mask or tube by taking a deep breath and then holding it. The camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. You may be asked to breathe the gas in and out through your mouth for several minutes. You may then be asked to hold your breath for short periods (about 10 seconds) and to change positions so your lungs can be viewed from other angles. The camera may move to take pictures from different angles. You need to remain very still during the scans to avoid blurring the pictures.

Afterward, the radioactive gas or mist will clear from your lungs as you breathe.

The ventilation scan takes about 15 to 30 minutes.

Perfusion scan

For the perfusion scan, the technologist cleans the site on your arm where the radioactive tracer will be injected. A small amount of the radioactive tracer is then injected.

After the radioactive tracer is administered, the camera will scan for radiation released by the tracer and produce pictures as the tracer moves through your lungs. The camera may be repositioned around your chest to get different views. You need to remain very still during the scans to avoid blurring the pictures.

The perfusion scan takes about 5 to 10 minutes.

Normal

The radioactive tracer is evenly distributed throughout the lungs during ventilation and perfusion.

Abnormal

The ventilation scan is abnormal but the perfusion scan is normal. This may mean abnormal airways in all or parts of the lung. Chronic obstructive pulmonary disease (COPD) or asthma may be present.

The perfusion scan is abnormal but the ventilation scan is normal. Depending on the difference between the two scans, a pulmonary embolism may be present.

Both the ventilation and perfusion scans are abnormal. This can be caused by certain types of lung disease, such as pneumonia, COPD, or a pulmonary embolism.

The thyroid scan is used to determine the size, shape and position of the thyroid gland. The thyroid uptake is performed to evaluate the function of the gland. A whole-body thyroid scan is typically performed on people who have or had thyroid cancer.

A physician may request these imaging tests to:

• determine if the gland is working properly

• help diagnose problems with the thyroid gland, such as an overactive thyroid gland, a condition called hyperthyroidism, cancer or other growths processes

• assess the nature of a nodule discovered in the gland

• detect areas of abnormality, such as lumps (nodules) or inflammation

• determine whether thyroid cancer has spread beyond the thyroid gland

• evaluate changes in the gland following medication use, surgery, radiotherapy or chemotherapy

You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing.

Women should always inform their physician or technologist if there is any possibility that they are pregnant or if they are breastfeeding.

You should inform your physician and the technologist performing your exam of any medications you are taking, including vitamins and herbal supplements. You should also inform them if you have any allergies and about recent illnesses or other medical conditions.

You should tell your physician if you:

• have had any tests, such as an x-ray or CT scan, surgeries or treatments using iodinated contrast material within the last two months.

• are taking medications or ingesting other substances that contain iodine, including kelp, seaweed, cough syrups, multivitamins or heart medications.

• have any allergies to iodine, medications and anesthetics.

• are breastfeeding.

In the days prior to your examination, blood tests may be performed to measure the level of thyroid hormones in your blood. You may be told not to eat for several hours before your exam because eating can affect the accuracy of the uptake measurement.

Jewelry and other metallic accessories should be left at home if possible, or removed prior to the exam because they may interfere with the procedure.

You will receive specific instructions based on the type of scan you are undergoing.

Thyroid Scan

You will be positioned on an examination table. If necessary, a nurse or technologist will insert an intravenous (IV) catheter into a vein in your hand or arm.

When radiotracer is taken by mouth, in either liquid or capsule form, it is typically swallowed up to 24 hours before the scan. The radiotracer given by intravenous injection is usually given up to 30 minutes prior to the test.

When it is time for the imaging to begin, you will lie down on a moveable examination table with your head tipped backward and neck extended. The gamma camera will then take a series of images, capturing images of the thyroid gland from three different angles. You will need to remain still for brief periods of time while the camera is taking pictures.

When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed. Occasionally, more images are obtained for clarification or better visualization of certain areas or structures. The need for additional images does not necessarily mean there was a problem with the exam or that something abnormal was found, and should not be a cause of concern for you.

If you had an intravenous line inserted for the procedure, it will usually be removed unless you are scheduled for an additional procedure that same day that requires an intravenous line.

Actual scanning time for a thyroid scan is 30 minutes or less.

Thyroid Uptake

You will be given radioactive iodine (I-123 or I-131) in liquid or capsule form to swallow. The thyroid uptake will begin several hours to 24 hours later. Often, two separate uptake measurements are obtained at different times. For example, you may have uptake measurements at four to six hours and 24 hours.

When it is time for the imaging to begin, you will sit in a chair facing a stationary probe positioned over the thyroid gland in the neck.

When the examination is completed, you may be asked to wait until the technologist checks the images in case additional images are needed. Occasionally, more images are obtained for clarification or better visualization of certain areas or structures. The need for additional images does not necessarily mean there was a problem with the exam or that something abnormal was found, and should not be a cause of concern for you.

Actual scanning time for each thyroid uptake is five minutes or less.

The thyroid scan and thyroid uptake are not performed on patients who are pregnant because of the risk of exposing the fetus to radiation. These tests are also not recommended for breastfeeding women.

Nuclear imaging procedures can be time consuming. It can take several hours to days for the radiotracer to accumulate in the body part of interest and imaging may take up to several hours to perform.

The resolution of structures of the body with nuclear medicine may not be as high as with other imaging techniques, such as CT or MRI. However, nuclear medicine scans are more sensitive than other techniques for a variety of indications, and the functional information gained from nuclear medicine exams is often unobtainable by other imaging techniques.