GW Imaging Center
The GW Imaging Center uses X-rays, radioactive tracers and ultrasonic waves to detect, diagnose and guide the treatment of a number of diseases and injuries. Radiologists can then interpret imaging studies, act as consultants to other specialists and perform interventional procedures.
Radiological imaging started with the discovery of the X-ray and has advanced as continuing developments in technology; computers and science increase our aboility to look inside a patient's body at his or her skeletal structure, tissues and organs, providing essential images that help physicians detect and diagnose within the patient's body without the need for surgery.
The GW Imaging Center provides several types of radiological procedures, including:
Mammography is a type of imaging that uses a low-powered X-ray to provide pictures of breast tissue. In general, normal functioning tissue and abnormal cancerous tissue differ only slightly in their attenuation, or x-ray stopping power. However, cancerous tissues can be separated from normal tissue if the breast contains an abundance of fat. Cancerous cells, and some benign tumors, contain very small areas of calcium deposits that also may be detected. Radiologists tend to look for these visually, but may use computer-assisted software to detect these deposits (see computer aided detection). Mammography is usually used in breast cancer screenings and is able to detect 85-90% of breast cancers in women over the age of 50.
For more about mammography and breast cancer, visit the GW Breast Care Center.
Ultrasound, or sonography, uses high frequency sound waves to see inside the body. A device that acts like a microphone and speaker is placed in contact with the body using ultrasound gel to transmit the sound. As the sound waves pass through the body, echoes are produced, and bounce back to the transducer. These echoes can help doctors determine the location of a structure or abnormality, as well as information about its make up. Ultrasound is a painless way to examine internal organs such as the heart, liver, blood vessels, breast, kidney or gall bladder, and is most commonly known for its ability to examine a fetus in the mother’s womb. Ultrasound scanning currently is considered to be a safe, noninvasive, accurate and cost-effective investigation of the fetus. It has progressively become a crucial obstetric tool and plays an important role in the care of many pregnant women.
Magnetic Resonance Imaging (MRI)
MRI uses radio waves and a strong magnetic field to create clear and detailed pictures of internal organs and tissues. Since MRI does not use X-rays, no radiation exposure is involved. In MRI, radio waves are directed at the body’s protons within the magnetic field. The protons become “excited”, and as they “relax” and emit radio signals, they are then processed by a computer to create an image. MRI is very useful in diagnosing diseases in all parts of the body including cancer, vascular and heart disease, liver and bile duct abnormalities, stroke, other neurological diseases and joint and musculoskeletal disorders. An MRI exam usually will take anywhere from 30-50 minutes and consists of several imaging series. Most studies will require a small intravenous injection of an MRI contrast agent that usually contains the metal Gadolinium. MRI contrast does not contain iodine, an element that is used in other contrast agents for X-rays or CT scans. Thousands of MRI’s are conducted each year, and technology has improved this system so vastly that a doctor can image abnormalities in a matter of seconds.
Not everyone can be scanned using this process. Very large people, those who wear pacemakers, those who may have metal fragments in their eyes from prior injury, those with recent metal implants or some surgical clips and those who are claustrophobic often cannot be safely scanned.
Angiography is an imaging procedure that takes images of blood vessels in various parts of the body, including the brain, heart and kidneys. This imaging helps doctors to determine whether the vessels are diseased, narrowed, enlarged or fully blocked. There are three major forms of angiography: catheter angiography, computed tomography angiography (CTA) and magnetic resonance angiography (MRA).
Catheter angiography is a process in which a catheter usually is inserted into an artery in the groin and advanced to the area of the body being examined. Imaging is performed using X-rays. Contrast material is sent through the catheter to highlight the vessels while the X-rays are being taken. Catheter angiography is used widely as a preoperative procedure for patients who will be undergoing surgery. Also, it is used as a guide to perform angioplasty or stent placement. These are procedures performed by a radiologist, cardiologist or surgeon in order to treat abnormal or blocked vessels. Catheter angiography also may be used to intentionally embolize or block vessels that are supplying areas of bleeding or tumors. An example of this is uterine artery embolization, where vessels linked to uterine fibroids are blocked in order to shrink these benign tumors.
A specific kind of catheter angiography is performed to diagnose abnormalities of the vessels supplying the brain. Diseases of these vessels or cerebrovascular disease are best seen on devices that show the vessels from two directions at once. These machines are called biplane angiography units. The George Washington University Hospital has the technologically advanced Integris Biplane Neurovascular imaging system, manufactured by Philips Medical Systems. This biplane system dramatically improves GW’s ability to visualize vessels and conduct complex neuro-interventional procedures dealing with aneurysms, head and neck tumors and strokes. Since this machine uses biplane technology, it will allow studies to be completed with lower contrast doses, fewer potential complications and significantly reduced procedure time.
Computed Tomography Angiography (CTA)
CTA uses a CT scanner to noninvasively image vessels. Iodine is a contrast material that may be injected into a vein using a small intravenous needle, creating no need for invasive catheter placement. This type of exam has been used to screen numerous patients for arterial diseases such as aortic dissection, carotid stenosis, aneurysms and vascular disease of the kidney. Most patients can receive this exam without being admitted into the hospital. This method of detection displays the anatomical detail of blood vessels more precisely than an ultrasound, and while comparable to MRI, is faster and can be performed on patients with pacemakers and other metal implants. A prior serious allergic reaction to iodine contrast is a contraindication to CTA.
Magnetic Resonance Angiography (MRA)
MRA is another noninvasive angiography procedure that uses MRI to visualize vessels as two-dimensional and three-dimensional images that can be viewed on a computer monitor. The indications are similar to that of CTA. This noninvasive procedure requires no X-rays, invasive catheter placement or iodinated contrast material, but does involve an intravenous injection of Gadolinium. MRA is a painless, shorter exam than a catheter angiography. The results of MRA may be used to determine whether surgery or treatment such as angioplasty is needed, and to plan that treatment.
Helical (Spiral) CT Scan
CT scans use special X-ray systems that image the body from different angles, and then use computer processing to show a cross-section of the various tissues and organs pictured. With very little radiation exposure to patients, CT scans have proven very helpful in diagnosing cancer, cardiovascular disease, infectious disease, trauma and musculoskeletal disorders.
Helical (Spiral) CT is a vast improvement over conventional CT scans. The patient lies on an exam table that passes through a doughnut-shaped scanner, while an X-ray tube rotates around the table. This movement results in a spiral shaped continuous data set without any gaps. With the helical CT, there is less likelihood to miss small tumors or abnormalities, and spiral CT is about 8 to 10 times faster than a traditional CT. This procedure is especially beneficial to the elderly, very young patients and acutely injured patients who are sensitive to longer exam times.
The multi-slice CT allows doctors to simultaneously capture multiple images of a patient’s anatomy from the helical data. The GE Light Speed is an example of this technology, and is up to six times faster than traditional single slice helical CT scanners, which helps reduce the scan time from a few minutes or more to 20-30 seconds. This is especially useful in trauma situations where the faster scan can allow emergency physicians to begin treating the patient more quickly. Also, it is very helpful for patients who cannot hold their breath.
In addition, the CT scanner technology has the potential to significantly reduce diagnostic time and increase image clarity for the diagnosis of multiple chest, abdominal and pelvic conditions, including detection and staging of cancer. Life-threatening blood clots and cardiovascular conditions also can be detected faster and more reliably using a CTA performed with the LightSpeed scanner.
Cardiac Catheterization Lab
Cardiac catheterization is a type of invasive angiography that involves a catheter being advanced from an artery in the groin to the heart. Contrast material is injected to help view the heart and coronary arteries. A cardiologist usually performs these procedures. The Allura angiography unit, introduced by Philips Medical Systems, is an advanced interventional system that provides very high quality digital imaging. It is a large, field-of-view cardiac catheterization laboratory that offers 3D imaging. This superior technology provides faster and more precise cardiovascular exams, potentially decreasing time spent in the catheterization lab and operating room, and may even eliminate the need for surgery in some patients who are candidates for angioplasty or coronary stent placement.
Scintamammography is used primarily in breast cancer screenings to detect abnormal tracer uptake in areas that may be tumors. It is most useful in women with dense breast tissue and little fat, or for those whose mammogram was not diagnostic. Following injection of a radioactive tracer into the blood stream, the tracer is absorbed by any cancerous cells in the breast tissue or surrounding lymph nodes. A gamma camera, called the Dilon Camera (developed by Dilon Technologies, Inc.), is used to detect the tracer localized in abnormal cancer cells. Because the machine is designed for dedicated breast imaging, it is more comfortable and allows better uptake measurements than general nuclear medicine gamma cameras.
Computer Aided Detection (CAD)
Computer Aided Detection (CAD), a supplementary procedure in the field of mammography, is used in conjunction with conventional mammography to substantially improve diagnostic accuracy. GW Hospital was one of the first sites in the nation to use Second Look™ software developed by CADX Inc. The radiologist first reviews the whole mammogram as before, and then the Second Look™ software analyzes the digitized mammogram. Any irregularities noted by the computer are then re-evaluated by the radiologist.
The application of CAD helps to decrease the risk of observational error in the interpretation of mammograms, while also increasing the chances of detecting subtle malignancies at the earliest possible stage.
Radiation therapy is a relatively common form of treatment for cancer and is becoming more successful each year. Radiation therapy machines can more tightly control the radiation beam, directing it at the abnormal tumor and limiting the exposure to surrounding normal tissues. This type of therapy has been refined further through the usage of 3D imaging technology and computerized treatment planning to better identify and target the cancerous tissue.
Radiation therapy destroys the cancer cells’ ability to reproduce, allowing the body to naturally rid itself of these cells. Radiation therapy can be performed in two different ways. External beam radiation therapy uses radiation generated through a machine outside of the patient’s body and targeted at the abnormal tissue. Brachytherapy delivers radiation to the patient through radioactive sources that are placed into the body with a catheter or as implanted seeds.
For some cancers, radiation therapy may be the sole approach taken to fight the disease. In other cases, chemotherapy and/or surgery often accompany the radiation therapy.