Diagnostic imaging lets doctors seek answers about a medical condition within the body. There are a number of devices and techniques that can produce representations of the structures and activities inside your body. Your doctor’s use of the imaging form depends on the symptoms and the part of the body being investigated.
Many imaging tests are quick and painless. Some require that you sit inside a computer for a long time. That can be awkward. Some experiments require a small amount of radiation exposure.
Below is a list of the most common diagnostic imaging procedures.
What are X-rays?
X-rays use invisible electromagnetic energy beams to create images on a film or digital media of the internal tissues, bones, and organs. For various purposes, regular X-rays are done for the detection of tumours or bone fractures. X-rays are produced for medical purposes through the use of external radiation to produce images of the body, its organs and other internal structures. X-rays move through body structures onto specially-treated plates (similar to camera film), or digital media and a “negative” style image is formed (the more solid a structure is, the whiter it appears on the film).
As the body undergoes X-rays, various parts of the body cause the X-ray beams to pass through differing quantities. The body’s soft tissues (such as blood, skin, fat, and muscle) cause much of the X-ray to move through the film or digital camera and appear dark grey. A bone or tumour that is denser than soft tissue enables the passage of several X-rays and appears white on the X-ray. When a bone break occurs, the X-ray beam travels through the fractured region and appears in the white bone as a dark line.
Other types of diagnostic procedures such as arteriograms, computed tomography ( CT) scans, and fluoroscopy also use X-ray technology.
Radiation can cause birth defects during pregnancy. If you think you might be pregnant, always tell your radiologist or doctor.
How are X-rays performed?
X-rays may be done on an outpatient basis or as part of hospital treatment.
Although each facility may have complex procedures in place, this method usually follows an X-ray procedure:
- The patient may be asked to remove any clothing or jewellery that should conflict with the area of the body to be examined. If clothes must be removed, the patient will be given a gown to wear.
- The patient is placed on an X-ray table carefully placing the portion of the body to be X-rayed between the X-ray machine and a cassette containing the X-ray film or specialized picture disk. Some exams can be carried out in a seated or standing position with the patient.
- Body parts which are not imaged can be covered with a lead apron (shield) to prevent X-ray exposure.
- The X-ray beam targets the area to be imaged.
- The patient needs to be very quiet or the picture gets blurred.
- The tech will step behind a protective window, and the picture will be taken.
- Different X-rays can be taken at various angles, such as the front and side view of an X-ray in the abdomen, depending on the body part under examination.
Computerized tomography (CT)
What is a CT or CAT scan?
A CT or CAT scan is a diagnostic imaging technique which uses a combination of X-rays and computer technology to produce horizontal, or axial, images of the body (often called slices). A CT scan provides clear photographs of every body part, including the bones, muscles, fat, lungs, and blood vessels. More comprehensive CT scans than normal X-ray scans.
In normal X-rays, the body part being examined is exposed to a beam of energy. A plate behind the portion of the body catches energy beam variations as it passes through skin, bone, muscle and other tissue. While much knowledge can be obtained from a standard X-ray, there is not much data available on internal organs and other structures.
The X-ray beam travels across the body in a circle, in computed tomography. This facilitates many different views of the same organ or structure, and offers much more detail. The X-ray information is sent to a computer which interprets and displays the X-ray data on a monitor in two-dimensional form. New technology and computer software allow for three-dimensional ( 3-D) images.
CT scans may be performed with contrast or without. “Contrast” refers to a drug that is taken by mouth or inserted into an intravenous ( IV) line, which makes the actual organ or tissue under examination more clearly visible. Contrast exams can require that you speed for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.
CT scans can help diagnose tumours, investigate internal bleeding or search for other internal injuries or injury.
You may want to ask your doctor about the amount of radiation used during the CT procedure as well as the risks associated with your case. It is a good idea to keep track of your prior records of exposure to radiation, such as previous CT scans and other forms of X-rays, so you can educate your doctor. Risks associated with radiation exposure can be linked over a long period of time to the total number of X-ray exams and/or treatments. If you are pregnant or think you might be pregnant, tell your doctor.
Advances in computed tomography technology include the following:
- High-resolution computed tomography. This form of CT scan uses very thin slices (less than one-tenth of an inch), which in some cases, such as lung disease, are useful in offering more detail.
- Helical or spiral computed tomography. Both the patient and the X-ray beam constantly shift during this form of CT scan, with the X-ray beam rotating around the patient. The images are collected much quicker than with normal CT scans. The resulting images have higher resolution and contrast and thus provide more accurate information. Multidetector row helical CT scanners can be used to provide details on calcium build-up inside the heart’s coronary arteries.
- Ultrafast computed tomography (also called electron beam computed tomography). This type of CT scan creates images very quickly, thereby producing a form of “movie” of moving body parts, such as the heart chambers and valves. This scan can also be used to obtain calcium build-up information within the heart’s coronary arteries, but the helical scanners are far more popular.
- Computed tomographic angiography (CTA). Angiography (or arteriography) is an image of the blood vessels by x-ray. A CT angiogram uses CT technology to acquire images of blood vessels, for example, the heart’s coronary arteries, rather than traditional X-rays or fluoroscopy.
- Combined tomography measured with positron emission tomography ( PET / CT). PET / CT is the integration of computed tomography and positron emission tomography technologies into one integrated unit. PET / CT combines CT’s ability to provide comprehensive anatomy with PET’s ability to demonstrate cell function and metabolism to provide greater precision in the diagnosis and treatment of some forms of diseases, especially cancer. PET / CT can also be used to determine epilepsy, Alzheimer’s and coronary artery disease.
Studies suggest that 85 percent of the population will not experience an iodinated contrast adverse reaction; however, if you have ever had a reaction to any contrast dye and/or kidney problems, you will need to let your doctor know. A reported allergy to seafood is not considered a contraindication to the iodinated comparison. If you have any medical problems or recent illnesses, notify your doctor. Over the past decade, the effects of kidney disease and contrast agents have gained greater interest, as patients with kidney disease are more vulnerable to kidney damage following exposure to contrast.
You should contact your health care provider if you are pregnant, or think you might be pregnant. If you are claustrophobic or appear to get nervous quickly, inform your doctor ahead of time, as he or she can prescribe a mild sedative to make you more relaxed before the operation. During the operation, which can take 10 to 20 minutes, you will need to stay still and quiet.
How is a CT or CAT scan performed?
CT scans may be done on an outpatient basis unless they are part of inpatient treatment for a patient. Whilst each facility can have unique protocols in place, CT scans typically follow this method:
- Upon arrival for the CT scan, the patient may be asked to remove any clothes, jewellery or other items that could interfere with the scan.
- If the patient is taking a contrast treatment, an intravenous ( IV) line may be initiated in the hand or arm for the contrast drug to be administered. The patient shall be given the contrast substance to swallow for oral comparison.
- The patient will lie on a scan table, which slides into the scanning machine’s wide, circular opening.
- The CT team will be in another room where the controls to the scanner are mounted. The patient would also be through a window in constant sight of the workers. Speakers inside the scanner enable the staff to communicate with the patient and listen to him. The patient will have a call bell to let the staff know if he or she is having any difficulties during the process.
- As the scanner rotates around the patient, X-rays can continue for a brief period of time travel through the body. The motion is concealed within the gantry, the machine’s doughnut-shaped portion. As the X-ray tube rotates, the patient can hear ringing, whirling and clicking.
- The scanner will identify the X-rays absorbed by the body’s tissues and pass them on to the device.
- The computer will convert the information into a picture which the radiologist can interpret.
- During the process, it is very important for the patient to stay very still. During the procedure, you may be asked to hold your breath at different times.
- The technologist will always observe the patient and will be in continuous contact.
- The patient may be asked to wait a short time while the radiologist looks at the scans to make sure they are clear. If the scans are not sufficiently clear to obtain adequate details, additional scans will need to be performed.
Positron Emission Tomography (PET)
What is PET?
Positron emission tomography ( PET) is a sophisticated radiology technique that has been used to analyze different body tissues to distinguish diseases. PET can also be used to monitor the progress of such diseases in treating. While PET is most widely used in the fields of neurology, oncology and cardiology, applications are currently being studied in other areas.
PET is a type of procedure in nuclear medicine. This indicates that during the treatment, a small amount of a radioactive material, called a radionuclide (radiopharmaceutical or radioactive tracer), is used to aid in the examination of the tissue being studied. In particular, PET studies examine the metabolism of a specific organ or tissue, so that knowledge on the organ or tissue’s physiology (functionality) and anatomy (structure) and its biochemical properties are evaluated. PET can thus detect biochemical changes in an organ or tissue that can define the initiation of a disease process before other imaging methods such as computed tomography (CT) or magnetic resonance imaging (MRI) can show anatomical changes related to the disease.
PET is most widely used by oncologists (doctors specializing in cancer care), neurologists and neurochirurgians (doctors specializing in brain and nervous system care and surgery), and cardiologists (doctors specializing in cardiac treatment). However, this technique is starting to be used more commonly in other areas as developments in PET technology continue.
Along with other diagnostic tests such as computed tomography (CT), PET is often used to provide more reliable knowledge about malignant (cancerous) tumours and other lesions. The combination of PET and CT demonstrates a particular promise in the diagnosis and treatment of several cancers.
PET procedures were performed in dedicated PET centres. The equipment is very expensive. However, a new technology called gamma camera systems (devices used to scan patients that have been treated with small quantities of radionuclides and are currently in use for other procedures in nuclear medicine) is now being modified for use in PET scanning. The gamma camera system can complete a scan faster than a conventional PET scan, and at less expense.
How does PET work?
PET acts to detect positrons (subatomic particles) released by a radionuclide in the organ or tissue being investigated by using a scanning system (a computer with a large hole at its centre).
The radionuclides used in PET scans are created by adding a radioactive atom to chemical substances which the individual organ or tissue use naturally during its metabolic process. For instance, a radioactive atom is added to glucose (blood sugar) to produce a radionuclide called fluorodeoxyglucose (FDG) in brain PET scans, since the brain uses glucose for its metabolism. FDG is used extensively in PET scans.
Depending on the intent of the scan, other substances can be used for PET scanning. Where blood flow and perfusion are of concern to an organ or tissue, the radionuclide may be a form of radioactive oxygen, carbon, nitrogen or gallium.
The radionuclide is administered via intravenous ( IV ) line into a vein. The PET scanner then travels slowly across the part of the body that is being investigated. The radionuclide breakdown emits positrons. Gamma rays are produced during positron emission, and the gamma rays are then detected by the scanner. A computer analyzes the gamma rays and makes use of the knowledge to create a picture map of the studied organ or tissue. The amount of radionuclide contained in the tissue determines how brightly the tissue appears on the picture, and shows the degree of function of the organ or tissue.
Other potential associated procedures include computed tomography (CT scan) and magnetic resonance imaging ( MRI). For more details, please see these procedures.
Reasons for the procedure
In general, PET scans can be used to determine the existence of the disease or other diseases in organs and/or tissues. PET can also be used to measure the function of such organs like the heart or brain. Another use of PET scans is in evaluating cancer care.
More precise explanations for PET scans include the following but are not limited to:
- To diagnose dementias such as Alzheimer’s disease, as well as other neurological disorders such as Parkinson’s disease (a progressive nervous system disorder in which fine tremor, muscle weakness, and an unusual form of gait are observed), Huntington’s disease (an inherited nervous system disease that induces increased dementia, strange involuntary movements, and irregular posture);
- The relevant surgical site to be found before brain surgery
- To examine the brain after trauma to identify the hematoma (blood clot), bleeding, and/or perfusion (blood and oxygen flow)
- To detect cancer spread from the original cancer site into other parts of the body
- Assessing the success of cancer therapy
- To measure myocardial perfusion (heart muscle) as an aid in assessing the effectiveness of a therapeutic procedure to enhance myocardial blood flow
- To classify more lung lesions or masses found on X-ray torso and/or chest CT
- Helps control and treat lung cancer by staging lesions and monitoring the development of lesions during treatment
- To detect tumour recurrence earlier than with other methods of diagnosis
Your doctor might come up with other reasons to prescribe a PET scan.
Risks of the procedure
For the operation, the amount of radionuclide inserted into your vein is minimal enough to not require precautions against radioactive radiation. The radionuclide injection may cause some mild discomfort. Allergic radionuclide reactions are uncommon, but they can occur.
For certain patients, it can cause certain discomfort or pain to have to lie still on the scanning table for the duration of the operation.
Patients resistant to or vulnerable to drugs, contrast dyes, iodine, or latex should inform their doctor.
If you are pregnant or think you might be pregnant, you should alert your health care provider from a PET scan, because of the possibility of damage to the foetus. If you are lactating, or breastfeeding, your health care provider should be aware of the possibility of radionuclide contamination of breast milk.
Depending on your particular medical condition, there may be other dangers. Be sure to speak with your doctor about any questions prior to the operation.
The accuracy of a PET scan can be compromised by certain variables or conditions. These considerations include the following but are not limited to:
- High levels of blood glucose among diabetics
- Ingested caffeine, alcohol or nicotine within 24 hours of the treatment
- Medicines, such as morphine, sedatives and tranquilizers
If any of the above circumstances can apply to you, inform your doctor.
Before the procedure
- Your doctor will describe the procedure and will give you the opportunity to ask any questions you might have about the procedure.
- You will be asked to sign a consent form allowing you to do the procedure. Carefully read the document, and ask questions if there is anything ambiguous.
- If you are allergic to latex and/or sensitive to medicine, contrast colouring, or iodine, notify the radiologist or technologist.
- Fasting is usually needed for a specified period of time before the operation. Your doctor will send you specific instructions in advance as to how many hours you will deprive of food and drink. You will also be told by your doctor about the use of drugs before the PET Scan.
- Notify your health care provider of all drugs (prescribed and over-the-counter) and herbal supplements you take.
- You should not drink any alcohol or caffeine, or use tobacco for at least 24 hours before the treatment.
- If you are a diabetic who uses insulin, you might be advised to take the insulin dose several hours before the treatment, with a meal. Your doctor will give you detailed instructions depending on the condition you are in. A fasting blood sugar test can also be obtained before the operation. If the blood sugar is high, insulin may be given to lower the blood sugar.
- Your doctor may order a further detailed preparation based on your medical condition.
During the procedure
PET scans can be conducted on an outpatient basis or as part of your hospital stay. Procedures can differ according to your condition and the practices of your doctor.
A PET scan normally follows the process:
- You will be asked to remove any clothes, jewellery, or other items that could interfere with the scan.
- If you are asked to remove your pants, you will get to wear a robe.
- Before beginning the procedure, you will be asked to clear your bladder.
- For radionuclide injection one or two intravenous ( IV) lines will be initiated in the hand or arm.
- Some forms of abdominal or pelvic scans can involve the insertion of a urinary catheter into the bladder to drain urine throughout the procedure.
- In certain cases, an initial scan can be done before the radionuclide is injected, depending on the type of research being conducted. Within the scanner, you will be put on a padded table
- They will inject the radionuclide into your vein. The radionuclide would be able to accumulate for about 30 to 60 minutes in the organ or tissue. At that time you can stay in the room. You would not be harmful to anyone because the radionuclide releases less radiation than a normal X-ray.
- The scan will begin after the radionuclide has been absorbed for the corresponding period of time. The scanner travels slowly across the section of the body being examined.
- Upon completion of the scan, the IV line will be removed. If a catheter is used, it will be removed.
Although the PET scan itself does not cause pain, having to lie still for the duration of the procedure can cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure, such as operation. The technologist will use every possible measure of comfort and complete the operation as soon as possible to reduce any discomfort or pain.
After the procedure
When you get up from the scanner table, you can step slowly to prevent any dizziness or light headedness from lying flat for the duration of the operation.
After the test, you will be advised to drink plenty of water and periodically empty your bladder to help flush the excess radionuclide out of your body for 24 to 48 hours.
Any symptoms of redness or swelling will be tested at the IV Site. If you experience any discomfort, redness, and/or swelling at the IV site after returning home after your treatment, you should alert your doctor as this may suggest an infection or some kind of reaction.
After the procedure, your doctor can give you additional or alternative instructions, depending on your particular situation.
Fluoroscopy is a study of moving body structures – similar to a “film” X-ray. A continuous X-ray beam is transmitted through the inspecting body component. The beam is transmitted to a TV-like display, enabling precise visualization of the body part and its motion. As an imaging instrument, fluoroscopy helps doctors to look at multiple body structures, including the skeletal, digestive, urinary, cardiovascular, and reproductive systems. Fluoroscopy can be used to examine particular parts of the body, including bones, muscles, and joints, as well as strong organs such as the heart, lung, or kidneys. Other related techniques which may be used to diagnose bone, muscle or joint disorders include X-rays, myelography (myelogram), computed tomography (CT scan), magnetic resonance imaging ( MRI), and arthrography. For more details, please see these procedures.
Reasons for the procedure
Fluoroscopy is used in many types of tests and procedures, including barium X-rays, cardiac catheterization, arthrography (visualization of a bone or organ), lumbar puncture, insertion of intravenous ( IV) catheters (hollow tubes inserted into veins or arteries), intravenous pyelogram, hysterosalpingogram, and biopsies.
Fluoroscopy may be used as a diagnostic technique on its own or may be used in conjunction with other diagnostic or therapeutic means or procedures.
Fluoroscopy used on its own in barium X-rays allows the doctor to see the movement of the intestines as the barium passes through them and helps the doctor to position the patient for spot imaging. Fluoroscopy is used as an aid in cardiac catheterization to allow the doctor to see the flow of blood through the coronary arteries to determine the presence of arterial blockages. For the placement of intravenous catheters, fluoroscopy lets the doctor direct the catheter to a particular position within the body.
Such fluoroscopic applications include, but are not limited to:
- Locating foreign bodies
- Image-guided anaesthetic injections into joints or the spine
- Percutaneous vertebroplasty. A minimally invasive procedure used to treat compression fractures of the vertebrae of the spine
There may be other reasons for your doctor to recommend fluoroscopy.
Risks of the procedure
You may want to ask your doctor about the amount of radiation used during the operation as well as the risks associated with your unique case. It is a good idea to keep a record of your past radiation exposure records, such as previous scans and other forms of X-rays, so you can keep your doctor updated. Risks associated with radiation exposure can be linked over a long period of time to the total number of X-ray exams and/or treatments.
If you are pregnant or think you may be pregnant, contact your doctor. Exposure to radiation during pregnancy may cause birth defects.
If contrast dye is used, the possibility of an allergic reaction to the dye occurs. Patients allergic to or vulnerable to drugs, contrast media, iodine, or latex should alert their physician. Patients suffering from kidney failure or other kidney disorders should also contact their doctor.
Depending on your particular medical condition, there may be other dangers. Be sure to speak with your doctor about any questions prior to the operation.
Any factors or conditions can interfere with the correctness of a fluoroscopy procedure. A recent X-ray procedure with barium can interfere with abdominal or lower back region exposure.
Before the procedure
Your doctor will describe the procedure to you and will give you the opportunity to ask any questions you might have about the procedure.
You will be asked to sign a consent form allowing you to do the procedure. Carefully read the document, and ask questions if there is anything ambiguous.
The particular type of procedure or test that is being performed can decide whether any planning is needed prior to the procedure. Your doctor will inform you of any recommendations about the pre-procedure.
If you have ever had a reaction to some contrast dye, or if you are allergic to iodine, contact your doctor.
If you are pregnant or think you may be pregnant, contact your doctor.
Dependent on your prescription.
Your doctor may recommend a more detailed preparation based on your medical condition.
During the procedure
Fluoroscopy can be conducted on an outpatient or as part of a hospital stay. Procedures can differ according to your condition and the practices of your doctor.
Usually, fluoroscopy follows this process:
- You will be required to remove any clothing or jewelry that may conflict with body area exposure to be inspected.
- If you are asked to remove your pants, you will be given a robe to wear.
- A contrast substance may be administered by swallowing, enema, or an intravenous ( IV) line in your hand or arm, depending on the type of procedure being performed.
- You are going to be sitting on the X-ray table. You may be required to assume various roles depending on the type of operation, shift a certain part of the body or hold your breath at intervals while the fluoroscopy is being performed.
- For procedures that involve the insertion of the catheter, such as cardiac catheterization or placement of the catheter into a joint or other body part, an additional line insertion site can be used in the groin, elbow, or elsewhere.
- The fluoroscopic images of the body structure being examined or treated are created using a special X-ray machine.
- To help visualize the organs or structures being examined a dye or contrast material can be injected into the IV line.
- In the case of arthrography (visualization of a joint), any fluid inside the joint may be aspirated (withdrawn with a needle) before the contrast material is inserted. You may be required to rotate the joint for a few minutes after the contrast is applied, in order to spread the contrast material equally across the joint.
- The type of treatment done and the section of the body being investigated and/or handled will decide the duration of the treatment.
- Upon completion of the procedure, the IV line will be removed.
While fluoroscopy itself is not painful, the actual procedure being done may be painful, such as the angiography injection into a joint or the connection to an artery or vein. The radiologist would take all necessary comfort steps in these situations, which may include local anesthesia, conscious sedation or general anesthesia depending on the specific procedure.
After the procedure
The type of treatment needed after the procedure will depend on the type of fluoroscopy done. Many procedures, such as cardiac catheterization, would likely involve a multiple-hour recovery period of the leg or arm immobilization where the cardiac catheter was placed. Other procedures may take less recovery time.
If you experience any discomfort, redness and/or swelling at the IV site after returning home after your treatment, you should contact your doctor as this may suggest an infection or some form of reaction.
After the test or treatment, the doctor will give you more detailed guidance on the care.
Magnetic Resonance Imaging (MRI)
How does an MRI scan work?
The MRI is a large, cylindrical (tube-shaped) system that generates a powerful magnetic field around the patient and sends radio wave pulses from a scanner. The intense magnetic field allows the body’s hydrogen atoms to align themselves around the same axis. Out of this balanced location the radio waves knock the nuclei of the atoms in your body. They send out radio signals as the nuclei realign back into proper position. A device that analyzes and translates these signals into an picture of the part of the body being studied receives those signals. This picture will appear on a display for viewing. You can get cross-sectional views to show additional information. Some MRI machines look like narrow tunnels, and others are more widespread.
In cases where organs or soft tissue are being examined, magnetic resonance imaging ( MRI) can be used instead of computed tomography ( CT), since MRI is better at telling the difference between different types of soft tissue and the difference between normal and abnormal soft tissue.
There is no chance of exposure to ionizing radiation during an MRI operation since ionizing radiation is not used.
MRI can not be done on most patients with implanted pacemakers, older intracranial aneurysm films, cochlear implants, some prosthetic devices, implanted drug infusion pumps, neurostimulators, bone growth stimulators, some intrauterine contraceptive devices, or any other type of iron-based metal implants, due to the usage of the powerful magnet. Also, MRI is not approved for people who have internal metal items such as bullets or shrapnel and certain surgical sticks, pins, plates, screws, metal sutures or wire mesh in their bodies. Colouring used in tattoos may contain iron and can heat up during an MRI, but this is an uncommon occurrence.
Newer MRI uses, and signs have helped improve new magnetic resonance technology. Magnetic resonance angiography (MRA) is a non-invasive (the skin is not pierced) technique used to measure blood flow across arteries. MRI can also be used to diagnose brain aneurysms and vascular malformations (blood vessel defects within the brain, spinal cord, or other parts of the body).
Magnetic resonance spectroscopy (MRS) is another non-invasive technique used in the assessment of chemical anomalies in body tissues, including the brain. MRS may be used to evaluate disorders such as brain HIV infection, stroke, headache, coma, Alzheimer’s disease, tumours, and multiple sclerosis.
Functional brain magnetic resonance imaging (fMRI) is used to determine the specific place within the brain where there is a specific function, such as speech or memory. The general areas of the brain where such functions occur are known, but the exact location can vary from individual to individual. You may be asked to perform a particular task during functional resonance imaging of the brain, such as reciting the Pledge of Allegiance while the scan is being performed. Doctors may prepare surgery or other therapies for a particular brain condition by determining the precise position of the functional core within the brain.
The “accessible” MRI is yet another development in MRI technology. Standard MRI units are equipped with a closed cylinder-shaped tunnel into which the patient is put. Open MRI units do not cover the patient entirely, and certain units may be open on all sides. Open MRI units are especially useful for procedures which involve:
- Children. Parents or other caregivers may stay with a child during the procedure to provide comfort and security.
- Claustrophobia. Before the development of open MRI units, persons with severe claustrophobia often required a sedative medication prior to the procedure.
- Very large or obese persons. Almost anyone can be accommodated in most open MRI units.
How is an MRI performed?
An MRI can be done on an outpatient basis, or as part of hospital treatment. Although each facility may have unique protocols in place, this method usually follows an MRI procedure:
The patient has to remove all jewelry and metal items, such as hairpins or barrettes, hearing aids, eyeglasses, and dental bits, because of the strong magnetic field.
If an intravenous line (IV) is to deliver a contrast drug and/or sedative, an IV line is initiated in the hand or arm. If the contrast is to be taken by mouth, then the contrast to swallow is offered to the patient.
The patient will be lying on a table in the scanner, which slides into a tunnel.
The MRI team will be in another room where the controls of the scanner are stored. The patient would also be through a window in constant sight of the workers. Speakers inside the scanner enable the staff to communicate with the patient and listen to him. The patient will have a call bell to let the staff know if he or she is having any concerns during the operation.
A clicking noise can sound during the scanning process, as the magnetic field is generated and radio wave signals are transmitted from the scanner. To help block the sounds from the MRI scanner and hear any signals or orders from the technologist, the patient may be given headphones to wear.
During the examination, it is necessary for the patient to remain very still.
At intervals, depending on the part of the body being examined, the patient may be advised to hold his or her breath, or not breathe, for a few seconds. When he or she can breathe the patient will then be told. The patient should have no more than a few seconds to catch his or her breath, so this should not be painful.
The technologist will always observe the patient and will be in continuous contact.
What is an ultrasound?
An ultrasound technique is a non-invasive diagnostic technique (the skin is not pierced) that is used to determine structures of soft tissue such as muscles, blood vessels and organs. Ultrasound uses a transducer, which sends out ultrasonic sound waves at too high a frequency to be heard. The ultrasonic sound waves pass through the skin and other body tissues to the organs and structures inside when the transducer is positioned at certain positions and angles. The sound waves bounce like an echo off the organ and return to the transducer. The transducer absorbs the reflected waves, which are then transformed into an electronic representation of the organs or tissues under analysis by a computer.
Various forms of body tissue influence the rate at which sound waves fly. Sound passes through bone tissue the fastest and moves through the air the most slowly. The transducer describes the speed at which the sound waves are transmitted to the transducer, as well as how much of the sound wave returns, as various types of tissues. A clear conductive gel is placed between the transducer and the skin to enable the transducer to pass smoothly over the skin and to remove air between the skin and the transducer for better conduction of sound. Blood flow can be measured by using an alternative mode of ultrasound technology during an ultrasonic procedure. An ultrasonic transducer able to assess blood flow contains a Doppler probe.
Inside the transducer, the Doppler probe measures the vessel’s velocity and direction of blood flow and makes the sound waves audible. Ultrasounds are used to view internal organs as they function (like a live TV broadcast in “real-time”), and to measure blood flow into different vessels. Ultrasound tests are also used to test various areas of the body, including the heart, breasts, female pelvis, prostate, scrotum, thyroid and parathyroid glands and the vascular system. Ultrasounds are conducted during pregnancy to determine fetal growth. Ultrasound technological advances now provide images that can be viewed in a three-dimensional (3-D) and/or four-dimensional (4-D) perspective. The added 4-D dimension is motion, so it is a moving 3-D view.
What are the different types of ultrasound procedures?
Different ultrasound techniques exist for different conditions. Examples of some of the more common types of ultrasound examinations include the following:
- Doppler ultrasound. Used to see structures inside the body, while evaluating blood flow at the same time. Doppler ultrasound can determine if there are any problems within the veins and arteries.
- Vascular ultrasound. Used to see the vascular system and its function, including the detection of blood clots.
- Echocardiogram. Used to see the heart and its valves, and to evaluate the effectiveness of the heart’s pumping ability.
- Abdominal ultrasound. Used to detect any abnormalities of the abdominal organs (i.e., kidneys, liver, pancreas, gallbladder), such as gallstones or tumours.
- Renal ultrasound. Used to examine the kidneys and urinary tract.
- Obstetrical ultrasound. Used to monitor the development of the foetus.
- Pelvic ultrasound. Used to find the cause of pelvic pain, such as an ectopic pregnancy in women, or to detect tumours or masses.
- Breast ultrasound. Used to examine a mass in the breast tissue.
- Thyroid ultrasound. Used to see the thyroid and to detect any abnormalities.
- Scrotal ultrasound. Used to further investigate pain in the testicles.
- Prostate ultrasound. Used to examine any nodules felt during a physical examination.
- Musculoskeletal ultrasound. Used to examine any joint or muscle pain for conditions, such as a tear.
- Intraoperative ultrasound. Used to help the surgeon during a minimally invasive operation or biopsy.
- Interventional ultrasound. Used by an interventional radiologist to guide a minimally invasive procedure.
- Intravascular ultrasound (IVUS). Used to provide direct visualization and measurement of the inside of blood vessels.
- Endoscopic ultrasound. Used to obtain direct ultrasound examination of the inside of a body cavity or organ, using an ultrasound transducer inside an endoscope (a small, flexible tube with a light and a lens at the end).
How are ultrasounds performed?
An ultrasound procedure may be done on an outpatient basis, or as part of inpatient care. Although each facility may have specific protocols in place, generally, an ultrasound procedure follows this process:
- A gel-like substance will be smeared on the area of the body to undergo the ultrasound (the gel acts as a conductor).
- Using a transducer, a tool that sends ultrasound waves, the ultrasound will be sent through the patient’s body.
- The sound from the transducer will be reflected off structures inside the body, and the information from the sound waves will be analyzed by a computer.
- The computer will create an image of these structures on a television screen. The moving pictures can be recorded.
- There are no confirmed adverse biological effects on patients or instrument operators caused by exposures to ultrasound.