The Froedtert & The Medical College of Wisconsin Radiology Department is committed to offering leading-edge technology to provide the highest quality of diagnostic care for patients. Froedtert & The Medical College are at the forefront in testing and using state-of-the-art imaging equipment.
Magnetic Resonance ImagingMagnetic resonance imaging (MRI) uses radiofrequency waves and a strong magnetic field to generate images of the body. Electromagnetic energy is released from a person when he or she is exposed to radiofrequency waves in the magnetic field of the MRI machine. This energy is measured and analyzed by a computer, which creates two- or three-dimensional cross section (slices) images of tissue.
MRI is valuable in providing clear pictures of soft-tissue structures of the body, such as the heart, lungs, liver and other organs. It is used to diagnose a broad range of diseases including cancer, heart and vascular disease, stroke, and joint and musculoskeletal disorders. MRI is most often used to detect cancer in the brain and spinal cord, head, neck and musculoskeletal system. MRI is also becoming important in imaging gynecologic and breast cancer.
Specialized MRI Scans
- Magnetic resonance angiography (MRA) — an MRI study of blood vessels to detect heart disorders, stroke and blood vessel diseases. MRA is used to evaluate arteries for stenosis (narrowing) or aneurysms (a bulge in a blood vessel wall) and to evaluate the arteries of the neck, brain, aorta, kidneys and legs. A contrast material (dye) may be given to the patient to improve the quality of the images.
- Functional MRI (fMRI) — provides detailed images of moment-to-moment changes in brain activity. fMRI measures brain function to determine where vital areas, such as movement or speech, are located in relation to a tumor, epilepsy activity or other diseased part of the brain. fMRI takes detailed pictures of the brain very quickly, identifying areas where nerves become active in response to different tasks. For example, a patient may be asked to perform a task that activates his or her memory. At the same time, an MRI image of his or her brain is taken to provide a detailed picture of the exact brain activation during this memory task.
- Magnetic resonance spectroscopy (MRS) — a type of MRI that aids in determining a tumor’s cellular density and rate of growth. MRS measures chemicals within the body and brain without removing tissue or blood samples and without using radioactive tracers. MRS relies on the fact that different chemicals produce energy at different frequencies when stimulated in a magnetic field.
- Diffusion MRI assesses how easily water moves across minute distances — a process called diffusion. Healthy cells have unbroken outer membranes that slow the movement of water. The membranes around dying or dead cells break down, allowing water to move or diffuse freely. In diffusion MRI, an MRI machine is programmed to be sensitive to water movement in tissue. For example, in diagnosing a stroke, diffusion MRI can rapidly view regions in the brain where blood flow is cut off by a hemorrhage or clot.
- Regional Cerebral Blood Volume (RCBV) uses MRI to assess blood flow in the brain to detect tumors, blood vessel disease, central nervous system problems and other disorders. RCBV is also performed to check blood volume in the brain before and after various treatments.
Ultrasound is used to assess soft tissue structures such as muscles, blood vessels and organs. Nearly every organ in the body can be examined by ultrasound. Ultrasound uses high-frequency sound waves to create real-time images within the body. (Radiation is not used.) Ultrasound images show the structure and movement of the body’s internal organs as well as blood flow.
For an ultrasound test, gel is applied to the skin to help transmit the sound waves. A small, handheld instrument (a transducer) is passed back and forth over the area of the body being examined. The transducer sends high-pitched sound waves into the body. The sound waves reflect off body structures and are reflected back to the transducer. A computer analyzes the sound waves and converts them into a picture (sonogram) that is displayed on a monitor. Ultrasound may be used along with other forms of imaging, such as MRI.
There are different ultrasound techniques for different conditions. Some of the more common types of ultrasound exams include:
- Obstetrics — because ultrasound does not use radiation, it’s a very useful tool to use with pregnant women. An ultrasound scan provides a safe, non-invasive and accurate view of a fetus. In the Radiology Department, ultrasound is often used to quickly diagnose problems in pregnant women who come to the Emergency Department. The Maternal Fetal Care Center at Froedtert & The Medical College also uses ultrasound, including 3-D ultrasound and 4-D ultrasound, which allows viewing a moving fetus in real time.
- Gynecologic disorders — ultrasound is useful for diagnosing a variety of gynecologic disorders of the uterus, ovaries, Fallopian tubes and pelvis. It can detect tumors, cysts, fibroids and other disorders — often well before symptoms arise.
- Abdomen — initial evaluation of abdominal pain often begins with an ultrasound exam. Ultrasound is effective in investigating the gallbladder (e.g., for gall stones), obstructions of the bile ducts, and liver and kidney disease. It can detect the difference between a cyst and a tumor.
- Transplants — organ transplants involve many vein and artery connections. Doppler ultrasound is used to check blood flow in people who have received a transplant.
- Guidance for procedures — ultrasound is used to guide many procedures to diagnose and treat disease. For example, it can show the precise location to inject a drug into a joint, show where to inject Botox® to control significant drooling, locate abnormal growths to perform a biopsy, and guide the drainage of a pseudocyst (an abnormal, fluid-filled sac) in the pancreas. Ultrasound can also detect difficult-to-locate tumors to help in planning treatment. Ultrasound is also used for guiding many interventional radiology procedures.
- Musculoskeletal — ultrasound provides images of muscles, tendons, ligaments, joints and soft tissue throughout the body. It can detect problems such as a tear in the rotator cuff, the tendons that stabilize the shoulder joint, muscle tears and many other disorders.
- Emergency Department — ultrasound is used to diagnose a wide range of problems in the Emergency Department, from abdominal and pelvic pain to blockages in blood vessels.
- Surgery — ultrasound has many uses in surgery, such as finding tumors and locating stones in the kidneys, pancreas or bile ducts, and evaluating the spread of cancer.
Specialized Types of Ultrasound
- Doppler ultrasound uses a handheld device to view blood flow in arteries and veins throughout the body. It can show problems such as blocked or reduced blood flow in the major arteries of the neck that could cause a stroke, or blood clots in leg veins that could break loose and block blood flow to the lungs. For people who have received an organ transplant, Doppler ultrasound is used to check blood flow to the transplanted organ.
- Endoscopic ultrasound (EUS) involves the use of an endoscope, a thin, flexible tube that is passed through the mouth or anus to the area being examined. A small transducer in the endoscope produces sound waves to create images of the area. EUS is used to examine the lining and walls of the upper and lower gastrointestinal tract and nearby organs such as the pancreas, liver and gallbladder. It is also used to locate tissue for biopsy.
Computed tomography (CT) uses X-rays to create numerous cross-sectional pictures of the body (tomography is imaging by sections or “slices” of tissue). The CT scanner sends X-ray pulses through the body area being studied. Each pulse takes a picture of a thin slice of the organ or area. Pictures, which can be taken from different positions, are saved on a computer. The scanner can generate multiple two- and three-dimensional cross-sections of tissue. Certain CT examinations require patients to receive an injection of contrast (“dye”) or drink a fluid prior to the scan.
CT is used to diagnose disease and injury in many areas of the body. It is used in:
- Trauma care to quickly assess the severity of illness and injuries
- Oncology to evaluate the extent of cancer (staging) and a patient’s response to cancer therapy
- Gastrointestinal (GI) care to detect inflammatory bowel disease and other disorders of the GI tract
- Postoperative evaluation to look for leaks or obstructions following surgery
- Chest disorders to detect a pulmonary embolism (blocked artery in the lung), emphysema, lung cancer, fibrotic lung tissue and other diseases
- Orthopaedics to exam bones for fractures and tumors and to aid in planning for surgery.
Types of CT Imaging
- CT neuro-angiography (CTA) — a neuro-imaging technique that combines CT with X-rays and the injection of a contrast material to examine blood vessels in the brain. X-rays are passed through the area of interest from several different angles to create cross-sectional images, which are then assembled by into a 3-D picture by a computer.
- 64-Slice Lightspeed Volume Computed Tomography (VCT) — in 2004, Froedtert & The Medical College became the first in the world to use the VCT scanner, the latest CT system developed by GE Healthcare Technologies and the most powerful medical CT scanner in the world.
The LightSpeed VCT scanner provides doctors with high-resolution images in a fraction of the time previously needed, allowing more accurate diagnoses of a wider variety of conditions. In a single rotation, the LightSpeed VCT creates 64 high-resolution images that are combined to form a three-dimensional view of the anatomy.
With VCT imaging, physicians are able to capture images of the full heart in six seconds, the chest in three seconds, the abdomen and pelvic area in three and one-half seconds and the entire body in 10 seconds.
With its precise and rapid imaging of the body, the 64-slice VCT scanner provides a noninvasive approach to diagnosing and treating disease in many areas of the body. VCT combines rapid X-ray scanning with multiple computed tomography (CT) to produce extremely detailed images of the heart, lungs, brain and other organs. A computer assembles the X-ray “slices” into an image of the organ that reveals its complete structure. Depending on the organ or area being scanned, a patient may receive an injection of contrast dye to obtain a better image.
For patients, the benefits of VCT include:
The advanced VCT imaging system can be used to diagnose common and hard-to-detect conditions in areas such as the head (stroke assessment), neck, chest, heart and blood vessels, abdomen, lungs, colon and legs.
- Precise, high-resolution 3D images that help physicians better diagnose conditions
- Faster diagnosis (VCT requires less time for breath-holds)
- Quicker, more comfortable scans
- Less radiation exposure
In heart and vascular disease, the unprecedented speed of VCT captures superior pictures of a patient’s beating heart without the need for an angiogram (a longer procedure used to determine blood flow in arteries or veins that involves inserting a catheter and sedating the patient). VCT scans the heart in just six seconds and the chest in three seconds. A single scan that can be used to assess the three most life-threatening critical conditions in chest pain: clogged arteries, a torn aorta and pulmonary embolism (a blocked artery in the lung).
- CT angiography — angiography uses a special form of X-ray and a “dye” that is injected into the bloodstream to see the detailed anatomy of the blood vessels in the body. At Froedtert & The Medical College of Wisconsin, diagnostic angiography is performed almost exclusively with the 64-slice VCT scanner. This includes studies of the carotid artery/brain circulation, thoracic and abdominal aorta, abdominal imaging of the liver, pancreas, spleen, kidneys, and intestine, and upper and lower extremity angiography. Compared to the previous technique that involves using an invasive catheter, CT angiography is less invasive (intravenous injection), faster, more convenient for patients, and provide a high-resolution image. The VCT scanner enables angiograms to be performed at acceptable radiation dose with relative low volumes of contrast medium.
Major national and international clinical trials are demonstrating that CT angiography of the coronary arteries performed with an intravenous injection of “dye” provides comparable images to invasive, catheter-based coronary angiography in patients at low to intermediate risk of heart disease. In addition, cardiac CT can demonstrate the structure and function of cardiac valves and chambers in a manor comparable to echocardiography and MRI.
Radiography (X-Ray Imaging)Radiography uses ionizing radiation to provide images of tissues, organs, bones and vessels in the body. These images are displayed on a video monitor. Radiography is the oldest and most frequently used form of medical imaging and is used in many ways to diagnose disease and injuries. (In the past, X-ray images were recorded on film.)
Types of Radiography
- Myelography — an X-ray of the spinal cord and the space surrounding it. The X-ray film, or myelogram, is taken after injecting a contrast material through a needle placed in this space. A myelogram provides a detailed picture of the spinal cord and spinal column and any abnormalities that may be present, such as spinal lesions, or distortions of the spinal cord, spinal canal and spinal nerve roots.
- Fluoroscopy — an imaging tool that makes a moving X-ray picture of internal organs. Barium, a contrast substance, may be given to a patient in advance of the test to better visualize the structure. An X-ray beam is pulsed through the patient, and the X-rays then strike a fluorescent plate. The radiologist can view the images live on a TV monitor. A continuous image is transmitted to the monitor to view the body part and its motion. Fluoroscopy is used to look at many body systems (e.g., the skeletal, digestive, urinary, respiratory and reproductive systems) and to evaluate specific areas of the body.
- Single Photon Emission Computed Tomography (SPECT) — Single photon emission computed tomography (SPECT) uses a radioactive material (tracer) and a gamma camera to scan the body. The type of radioactive tracer used depends on the part of the body being examined. The gamma camera rotates around the patient and takes pictures from many angles. A small amount of a radioactive tracer is injected into a patient’s vein and the scanner detects areas inside the body where the tracer is taken up by the cells. A computer uses data collected by the camera to construct two- or three-dimensional images.
SPECT provides information metabolism in the body. It can help detect cancer and heart disease, confirm a diagnosis of dementia and locate an infection in the body. In the brain, SPECT can provide information on blood flow to show how regions of the brain are functioning, and identify brain abnormalities in people who have seizures. In the heart, SPECT can help detect regions receiving insufficient blood flow when under stress. In the skeleton, SPECT can help identify areas contributing to patients’ complaints of pain. In addition, some forms of bone cancer can be detected.
- Positron Emission Tomography/Computed Tomography (PET/CT) — Positron emission tomography (PET) is a nuclear medicine test that detects changes in cell function and metabolism. This requires injecting a patient with a small amount of a radioactive material (tracer) that will accumulate in a certain organ. A PET scan is more sensitive than CT in detecting many types of cancer.
A computed tomography (CT) scan uses X-rays to create more detailed, cross-sectional pictures of the body. A PET/CT exam combines these two imaging methods. By combining PET with CT, better localization of disease is possible than using PET alone. The PET scanner shows metabolism and function of cells, while the CT scanner shows detailed anatomy.
For example, a PET scan can give information about the metabolic function of cancer cells, while the CT scan shows the exact location, size and shape of the cancerous growths. Using computers, PET and CT scans are fused to produce a single scan. When the results of PET and CT scans are “fused” together, the combined image provides complete information on disease location and metabolism.
PET/CT is used to evaluate many diseases, especially cancer and the effects of cancer therapy. PET/CT is also used to diagnose heart disease and brain disorders.
- Bone density scan — A test to assess the strength of the bones and the probability of fracture in people at risk for osteoporosis. Bone density scanning is also effective in tracking the effectiveness of treatment for osteoporosis and other conditions that cause bone loss.
The test, called “dual-energy X-ray absorptiometry” (DEXA), is an enhanced form of X-ray. DEXA scanning, the most accurate test for bone density, measures bone mineral density and compares it to normal levels. While standard X-rays show changes in bone density after about 40 percent of bone loss, a DEXA scan can detect changes after about 1 percent change. DEXA is most often performed on the lower spine and hips. Portable bone density devices, including some that use ultrasound rather than X-rays, measure bones in the wrist, fingers and heel.
Author: Marla Fraunfelder
Last Review Date: Aug. 10, 2007