Single photon-emission computed tomography (SPECT) is a test that uses a special type of camera and a tracer (a radioactive substance in liquid form) to look at organs or bones in the body. During the test, the tracer is put into a vein (intravenous, or IV) in your arm. Sometimes it's taken by mouth or inhaled through the nose.
The tracer moves through your body, where it may collect in the specific organ or tissue. The tracer gives off tiny bits of radiation called gamma rays. The camera records the gamma rays. Then a computer turns the recording into 3-dimensional pictures. SPECT scan pictures show how organs are working.
Other types of scans, such as computed tomography (CT) scans or magnetic resonance imaging (MRI) show more details of the organs themselves. The SPECT picture may be matched with those from a CT scan to get more detailed information about where the tracer is located.
A SPECT scan is often used to evaluate brain, head, and neck problems; to look at blood flow to the heart; to examine bones; and to diagnose problems in other organs such as the gall bladder, liver, spleen, and kidneys.
Why It Is Done
A SPECT scan is done to:
Check to see how well treatments are working.
Examine bones for signs of cancer and sometimes for fractures or degenerative bone diseases such as osteoporosis.
Evaluate brain conditions such as Alzheimer's disease and other types of dementia, Parkinson's, transient ischemic attack (TIA), and stroke.
Help diagnose some psychological conditions, including schizophrenia.
Help determine brain death.
Find out what's causing seizures, including for epilepsy.
Find poor blood flow to the heart, which may mean coronary artery disease or other heart conditions.
Assess heart attack risk or find damaged heart tissue after a heart attack.
Diagnose gall bladder disease.
Evaluate the extent of some cancers, especially lymphomas and lung cancer.
Help a doctor choose the best treatment for cancer or find out how well cancer treatment is working.
Check the liver, kidney, and spleen for cancers.
Find tumors in the endocrine system.
Find areas of inflammation or infection.
How To Prepare
Before you have a SPECT scan, tell your doctor if you:
Have diabetes. If you take medicine to control diabetes, you may need to take less than your normal dose. Talk with your doctor about how much medicine you should take.
Have had other nuclear scans.
Have any allergies, especially to iodine.
Take any medicines, supplements, or herbal remedies. You may need to stop taking some medicines or change your dose before this test.
Are or might be pregnant.
Are breastfeeding. The radioactive tracer used in this test can get into your breast milk. Do not breastfeed your baby for 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. Don't use the breast milk you pump for 2 days after the test. Get rid of it.
Have a fear of enclosed spaces.
You may not be able to eat or drink for at least 6 hours before some SPECT scans. Ask your doctor when or if you need to fast before the test.
Your doctor will also let you know if you should avoid smoking or drinking caffeine or alcohol for 24 hours before this test.
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 mean.
How It Is Done
A single photon-emission computed tomography (SPECT) scan is done in a hospital nuclear medicine department or at a special radiology center by a radiologist or nuclear medicine specialist and a technologist. You will lie on a table that is hooked to a large scanner, cameras, and a computer.
During the test
The radioactive tracer is usually given in a vein (IV). You may need to wait as long as an hour for the tracer to move through your body. During this time, you may need to avoid moving and talking.
The SPECT scanner is a large machine that scans your body. It has two cameras that rotate slowly around your body. They will be very close to your body but should not touch you. The scanned pictures are sent to a computer screen so your doctor can see them. Many scans are done to make a series of pictures.
It's very important to lie still while each scan is being done. At some medical centers, a CT scan will be done at the same time.
For a SPECT scan of the brain, you will lie on a bed. You may be asked to read, name letters, or tell a story, depending on whether speech, reasoning, or memory is being tested. During the scan, you may be given earplugs and a blindfold (if you don't need to read during the test) to wear for your comfort.
If you are having a SPECT scan of your heart, electrodes for an electrocardiogram (EKG, ECG) will be put on your body. During the test, you will be alone in the scanner room. The technologist will watch you through a window. You will be able talk to him or her at all times through a two-way intercom.
The test takes 1 to 3 hours. You may need to return for follow-up scans.
After the test
After the test, drink lots of fluids for the next 24 hours to help flush the tracer out of your body.
Be careful with body fluids. Flush toilets and wash hands well right after you use the bathroom. Avoid using a urinal.
There is always a slight chance of damage to cells or tissue from radiation, including the low levels of radiation used for this test. But the chance of damage is usually very low compared with the benefits of the test.
Most of the tracer will be flushed from your body within 6 to 24 hours. Allergic reactions to the tracer are very rare.
In rare cases, you may have some soreness or swelling at the IV site where the radioactive tracer was put in. If so, apply a moist, warm compress to your arm.
What are serologic tests?
Serologic tests are blood tests that look for antibodies in your blood. They can involve a number of laboratory techniques. Different types of serologic tests are used to diagnose various disease conditions.
Serologic tests have one thing in common. They all focus on proteins made by your immune system. This vital body system helps keep you healthy by destroying foreign invaders that can make you ill. The process for having the test is the same regardless of which technique the laboratory uses during serologic testing.
Why do I need a serologic test?
It’s helpful to know a little about the immune system and why we get sick to understand serologic tests and why they’re useful.
Antigens are substances that provoke a response from the immune system. They’re usually too small to see with the naked eye. They can enter the human body through the mouth, through broken skin, or through the nasal passages. Antigens that commonly affect people include the following:
The immune system defends against antigens by producing antibodies. These antibodies are particles that attach to the antigens and deactivate them. When your doctor tests your blood, they can identify the type of antibodies and antigens that are in your blood sample, and identify the type of infection you have.
Sometimes the body mistakes its own healthy tissue for outside invaders and produces unnecessary antibodies. This is known as an autoimmune disorder. Serologic testing can detect these antibodies and help your doctor diagnose an autoimmune disorder.
What happens during a serologic test?
A blood sample is all that the laboratory needs to conduct serologic testing.
The test will occur in your doctor’s office. Your doctor will insert a needle into your vein and collect blood for a sample. The doctor may simply pierce the skin with a lancet if conducting serologic testing on a young child.
The testing procedure is quick. The pain level for most people isn’t severe. Excessive bleeding and infection may occur, but the risk of either of these is low.
What are the types of serologic tests?
Antibodies are diverse. So, there are various tests for detecting the presence of different types of antibodies. These include:
An agglutination assay shows whether antibodies exposed to certain antigens will cause particle clumping.
A precipitation test shows whether the antigens are similar by measuring for the presence of antibody in body fluids.
The Western blot test identifies the presence of antimicrobial antibodies in your blood by their reaction with target antigens.
What do the results mean?
Normal test results
Your body produces antibodies in response to antigens. If testing shows no antibodies, it indicates you don’t have an infection. Results that show there are no antibodies in the blood sample are normal.
Abnormal test results
Antibodies in the blood sample often mean you’ve had an immune system response to an antigen from either current or past exposure to a disease or foreign protein.
Testing may also help your doctor diagnose an autoimmune disorder by finding out if antibodies to normal or non-foreign proteins or antigens are present in the blood.
The presence of certain types of antibodies can also mean that you’re immune to one or more antigen. This means that future exposure to the antigen or antigens won’t result in illness.
Serologic testing can diagnose multiple illnesses, including:
brucellosis, which is caused by bacteria
amebiasis, which is caused by a parasite
measles, which is caused by a virus
rubella, which is caused by a virus
What happens after serologic testing?
The care and treatment provided after serologic testing can vary. It often depends on whether antibodies were found. It may also depend on the nature of your immune response and its severity.
An antibiotic or another type of medication may help your body fight the infection. Even if your results were normal, your doctor might order an additional test if they still think you might have an infection.
The bacteria, virus, parasite, or fungus in your body will multiply over time. In response, your immune system will produce more antibodies. This makes the antibodies easier to detect as the infection gets worse.
The test results may also show the presence of antibodies related to chronic conditions, such autoimmune disorders.
Your doctor will explain your test results and your next steps.
Psychological testing is the administration of psychological tests, which are designed to be "an objective and standardized measure of a sample of behavior". The term sample of behavior refers to an individual's performance on tasks that have usually been prescribed beforehand. The samples of behavior that make up a paper-and-pencil test, the most common type of test, are a series of items. Performance on these items produce a test score. A score on a well-constructed test is believed to reflect a psychological construct such as achievement in a school subject, cognitive ability, aptitude, emotional functioning, personality, etc. Differences in test scores are thought to reflect individual differences in the construct the test is supposed to measure. The science behind psychological testing is psychometrics.
A psychological test is an instrument designed to measure unobserved constructs, also known as latent variables. Psychological tests are typically, but not necessarily, a series of tasks or problems that the respondent has to solve. Psychological tests can strongly resemble questionnaires, which are also designed to measure unobserved constructs, but differ in that psychological tests ask for a respondent's maximum performance whereas a questionnaire asks for the respondent's typical performance. A useful psychological test must be both valid (i.e., there is evidence to support the specified interpretation of the test results) and reliable (i.e., internally consistent or give consistent results over time, across raters, etc.).
It is important that people who are equal on the measured construct also have an equal probability of answering the test items accurately . For example, an item on a mathematics test could be "In a soccer match two players get a red card; how many players are left in the end?"; however, this item also requires knowledge of soccer to be answered correctly, not just mathematical ability. Group membership can also influence the chance of correctly answering items (differential item functioning). Often tests are constructed for a specific population, and this should be taken into account when administering tests. If a test is invariant to some group difference (e.g. gender) in one population (e.g. England) it does not automatically mean that it is also invariant in another population (e.g. Japan).
Psychological assessment is similar to psychological testing but usually involves a more comprehensive assessment of the individual. Psychological assessment is a process that involves checking the integration of information from multiple sources, such as tests of normal and abnormal personality, tests of ability or intelligence, tests of interests or attitudes, as well as information from personal interviews. Collateral information is also collected about personal, occupational, or medical history, such as from records or from interviews with parents, spouses, teachers, or previous therapists or physicians. A psychological test is one of the sources of data used within the process of assessment; usually more than one test is used. Many psychologists do some level of assessment when providing services to clients or patients, and may use for example, simple checklists to osis for treatment settings; to assess a particular area of functioning or disability often for school settings; to help select type of treatment or to assess treatment outcomes; to help courts decide issues such as child custody or competency to stand trial; or to help assess job applicants or employees and provide career development counseling or training.
There are several broad categories of psychological tests:
IQ tests purport to be measures of intelligence, while achievement tests are measures of the use and level of development of use of the ability. IQ (or cognitive) tests and achievement tests are common norm-referenced tests. In these types of tests, a series of tasks is presented to the person being evaluated, and the person's responses are graded according to carefully prescribed guidelines. After the test is completed, the results can be compiled and compared to the responses of a norm group, usually composed of people at the same age or grade level as the person being evaluated. IQ tests which contain a series of tasks typically divide the tasks into verbal (relying on the use of language) and performance, or non-verbal (relying on eye–hand types of tasks, or use of symbols or objects). Examples of verbal IQ test tasks are vocabulary and information (answering general knowledge questions). Non-verbal examples are timed completion of puzzles (object assembly) and identifying images which fit a pattern (matrix reasoning).
IQ tests (e.g., WAIS-IV, WISC-V, Cattell Culture Fair III, Woodcock-Johnson Tests of Cognitive Abilities-IV, Stanford-Binet Intelligence Scales V) and academic achievement tests (e.g. WIAT, WRAT, Woodcock-Johnson Tests of Achievement-III) are designed to be administered to either an individual (by a trained evaluator) or to a group of people (paper and pencil tests). The individually administered tests tend to be more comprehensive, more reliable, more valid and generally to have better psychometric characteristics than group-administered tests. However, individually administered tests are more expensive to administer because of the need for a trained administrator (psychologist, school psychologist, or psychometrician).
Public safety employment tests
Vocations within the public safety field (i.e., fire service, law enforcement, corrections, emergency medical services) often require Industrial and Organizational Psychology tests for initial employment and advancement throughout the ranks. The National Firefighter Selection Inventory - NFSI, the National Criminal Justice Officer Selection Inventory - NCJOSI, and the Integrity Inventory are prominent examples of these tests.
Attitude test assess an individual's feelings about an event, person, or object. Attitude scales are used in marketing to determine individual (and group) preferences for brands, or items. Typically attitude tests use either a Thurstone scale, or Likert Scale to measure specific items.
These tests consist of specifically designed tasks used to measure a psychological function known to be linked to a particular brain structure or pathway. Neuropsychological tests can be used in a clinical context to assess impairment after an injury or illness known to affect neurocognitive functioning. When used in research, these tests can be used to contrast neuropsychological abilities across experimental groups.
Psychological measures of personality are often described as either objective tests or projective tests. The terms "objective test" and "projective test" have recently come under criticism in the Journal of Personality Assessment. The more descriptive "rating scale or self-report measures" and "free response measures" are suggested, rather than the terms "objective tests" and "projective tests," respectively.
The number of tests specifically meant for the field of sexology is quite limited. The field of sexology provides different psychological evaluation devices in order to examine the various aspects of the discomfort, problem or dysfunction, regardless of whether they are individual or relational ones.
Psychological tests to assess a person’s interests and preferences. These tests are used primarily for career counseling. Interest tests include items about daily activities from among which applicants select their preferences. The rationale is that if a person exhibits the same pattern of interests and preferences as people who are successful in a given occupation, then the chances are high that the person taking the test will find satisfaction in that occupation. A widely used interest test is the Strong Interest Inventory, which is used in career assessment, career counseling, and educational guidance.
Psychological tests measure specific abilities, such as clerical, perceptual, numerical, or spatial aptitude. Sometimes these tests must be specially designed for a particular job, but there are also tests available that measure general clerical and mechanical aptitudes, or even general learning ability. An example of an occupational aptitude test is the Minnesota Clerical Test, which measures the perceptual speed and accuracy required to perform various clerical duties. Other widely used aptitude tests include Careerscope, the Differential Aptitude Tests (DAT), which assess verbal reasoning, numerical ability, abstract Reasoning, clerical speed and accuracy, mechanical reasoning, space relations, spelling and language usage. Another widely used test of aptitudes is the Wonderlic Test. These aptitudes are believed to be related to specific occupations and are used for career guidance as well as selection and recruitment.
A prolactin (PRL) test measures how much of a hormone called prolactin you have in your blood. The hormone is made in your pituitary gland, which is located just below your brain.
When women are pregnant or have just given birth, their prolactin levels increase so they can make breast milk. But it’s possible to have high prolactin levels if you’re not pregnant, and even if you’re a man.
Your doctor may order a prolactin test when you report having the following symptoms:
Irregular or no periods
Breast milk discharge when you’re not pregnant or nursing
Tenderness in your breast
Menopausal symptoms such as hot flashes and vaginal dryness
Decreased sex drive
Difficulty in getting an erection
Breast tenderness or enlargement
Breast milk production (very rare)
Causes of Abnormal Prolactin Levels
Normally, men and nonpregnant women have just small traces of prolactin in their blood. When you have high levels, this could be caused by:
Prolactinoma (a benign tumor in your pituitary gland that produces too much prolactin)
Hypothyroidism (your thyroid gland isn’t producing enough hormones)
Diseases affecting the hypothalamus(the part of the brain that controls the pituitary gland)
Anorexia (an eating disorder)
Drugs that are used to treat depression, psychosis, and high blood pressure
Chest injury or irritation (for example, scars, shingles, or even a bra that’s too tight)
Also, kidney disease, liver failure, and polycystic ovarian syndrome (a hormone imbalance that affects ovaries) all can affect the body’s ability to remove prolactin.
How the Test Is Done
You don’t need to make any special preparations for a prolactin test. You will get a blood sample taken at a lab or a hospital. A lab worker will insert a needle into a vein in your arm to take out a small amount of blood.
Some people feel just a little sting. Others might feel moderate pain and see slight bruising afterwards.
After a few days, you’ll get the results of your prolactin test in the form of a number.
The normal range for prolactin in your blood are:
Males: 2 to 18 nanograms per milliliter (ng/mL)
Nonpregnant females: 2 to 29 ng/mL
Pregnant females: 10 to 209 ng/mL
If Your Prolactin Levels Are High
If your value falls outside the normal range, this doesn’t automatically mean you have a problem. Sometimes the levels can be higher if you’ve eaten or were under a lot of stress when you got your blood test.
Also, what’s considered a normal range may be different depending on which lab your doctor uses.
If your levels are very high -- up to 1,000 times the upper limit of what’s considered normal -- this could be a sign that you have prolactinoma. This tumor is not cancer, and it can be treated with medicine. In this case, your doctor may want you to get an MRI.
You’ll lie inside a magnetic tube as the MRI device uses radio waves to put together a detailed image of your brain. It will show whether there’s a mass near your pituitary gland and, if so, how big it is.
If Your Levels Are Low
If your prolactin levels are below the normal range, this could mean your pituitary gland isn’t working at full steam. That’s known as hypopituitarism. Lower levels of prolactin usually do not need medical treatment.
Certain drugs can cause low levels of prolactin. They include:
Dopamine (Intropine), which is given to people in shock
Levodopa (for Parkinson’s disease)
Ergot alkaloid derivatives (for severe headaches)
Not all cases of high prolactin levels need to be treated.
Your treatment will depend on the diagnosis. If it turns out to be a small prolactinoma or a cause can’t be found, your doctor may recommend no treatment at all.
In some cases, your doctor may prescribe medicine to lower prolactin levels. If you have a prolactinoma, the goal is to use medicine to reduce the size of the tumor and lower the amount of prolactin.
Photorefractive keratectomy (PRK) is a type of refractive surgery. This kind of surgery uses a laser to treat vision problems caused by refractive errors. You have a refractive error when your eye does not refract (bend) light properly.
With PRK, your ophthalmologist uses a laser to change the shape of your cornea. This improves the way light rays are focused on the retina. PRK is used to treat myopia (nearsightedness), hyperopia (farsightedness) and astigmatism.
The goal of photorefractive keratectomy is to correct your refractive error to improve your vision. PRK may reduce your need for eyeglasses or contact lenses. In some cases, it may even allow you to do without them completely.
Should I Get PRK?
If you have dry eyes or thin corneas and want to have refractive surgery, PRK may be a good choice for you. This is because some other types of refractive surgery, such as LASIK, are not recommended if you have these conditions.
Also, if you have a very active lifestyle or job, PRK may be a better option for you than LASIK or similar procedures. This is because PRK does not involve cutting a flap in your cornea like LASIK and similar surgeries do. If you are highly active, you could accidentally dislodge a corneal flap, causing problems.
Some people who have certain lenses put in their eyes during cataract surgery may have PRK to fine-tune their vision.
To have PRK, you need to meet certain requirements:
You should be 18 years or older (ideally, over 21 years old, when vision is more likely to have stopped changing).
Your eye prescription should not have changed in the last year.
Your refractive error must be one that can be treated with PRK.
Your corneas need to be healthy, and your overall eye health must be generally good.
You need to have realistic expectations about what PRK can and cannot do for you.
Some people are not candidates for PRK. They include people with:
an unstable (changing) refractive error
skin or other disease that can affect healing
a history of a lot of scarring
cornea abrasions or disease
a cataract affecting vision
pregnant or nursing women
history of certain eye infections
Your ophthalmologist can talk with you about other conditions that may keep you from having PRK.
To determine whether you are a candidate for PRK, your ophthalmologist will examine your eyes. Here’s what will be done:
The overall health of your eyes will be checked.
Measurements of your cornea will be taken.
Your pupil size will be checked.
Your refractive error will be measured.
What Happens During Photorefractive Keratectomy (PRK)
ophthalmologist will discuss your vision needs based on your lifestyle. For example, if you play sports, you may be seeking clear distance vision from surgery.
Also, you and your ophthalmologist should discuss your expectations for PRK. People who have PRK to achieve perfect vision without glasses or contacts run the risk of being disappointed. PRK allows people to do most of their everyday tasks without corrective lenses. However, you might need to wear glasses for certain activities, such as reading or driving at night.
Your ophthalmologist will thoroughly examine your eyes and make sure you are a candidate
for PRK. Here is what he or she will do:
Test your vision. This is to make sure that your vision has not changed. It also shows how high your refractive error is and whether PRK can be used to correct your vision.
Check for other eye problems. Your ophthalmologist will make sure that you do not have eye problems. This is because other problems could affect your surgery, or PRK could make those other problems worse.
Measure and map the surface of your cornea. Your ophthalmologist will check the thickness of your cornea and make precise measurements of the cornea’s surface. Your eye surgeon uses these measurements to program the computer-based laser used during surgery.
Measure your pupil size. He or she will also measure the size of your pupil.
During Photorefractive Keratectomy (PRK)
PRK is usually done in an outpatient surgery center. The procedure usually takes about 15 minutes. Here is what to expect:
Your eye will be numbed with eye drops.
Your eye surgeon will place an eyelid holder on your eye to keep you from blinking.
Then your ophthalmologist will remove the outer layer of cells on your cornea, called the epithelium. To do this, he or she may use a special brush, blade, laser or alcohol solution.
You will be asked to stare at a target light so that your eyes will not move. The ophthalmologist then reshapes your cornea using a laser. The laser is a special instrument that has been programmed with measurements for your eye. While your ophthalmologist is using the laser, you will hear a clicking sound.
What Is PRK Surgery Recovery Like?
Right after surgery, your ophthalmologist will place a “bandage” contact lens over your eye to help it heal.
You will need to have someone drive you home after surgery. You should plan to go home and take a nap or just relax after the surgery.
Your surgeon may suggest that you take a few days off from work. Also, you should avoid strenuous activity for up to a week after surgery, as this could slow the healing process.
For two to three days after PRK, you may have some eye pain. Over-the-counter medicine usually controls the pain. Occasionally, some people may need eye drop pain relievers or other prescription medicine to relieve pain. Be sure to call your ophthalmologist if your pain is not helped by over-the-counter medicines.
You will need to use eye drop medicine for up to a month or as prescribed by your ophthalmologist. Be sure to follow your doctor’s instructions for using this medicine to help healing.
After PRK, you will need to wear sunglasses outside for as long as your doctor tells you. This is because sun exposure can lead to corneal scarring after surgery, causing vision problems.
At first, your vision will be blurry after PRK. Over 3–5 days, as you heal, your vision will gradually improve. Keep in mind it may take a month or longer to achieve your best vision.
What Are the Risks of PRK Surgery?
Like any surgery, PRK carries risks of problems or complications you should consider. These include:
glare and halos around lights, particularly at night
scarring of the cornea
cloudiness of the cornea (called corneal haze)
Also, with PRK, your vision may end up being undercorrected or overcorrected. These problems often can be improved with glasses, contact lenses, or additional laser surgery.
Most complications can be treated without any loss of vision. However, very rare problems may include:
having worse vision than before PRK, even with glasses or contacts (called loss of best-corrected vision)
If you are happy wearing contacts or glasses, you may not want to have refractive surgery. Together, you and your ophthalmologist can weigh the risks and rewards of PRK.