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Radiographic Testing

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Radiograpic Clinical Procedures

About Radiology
Radiological services cover an enormous breadth of medical knowledge. Very routine to more difficult radiological determinations are undertaken to attempt to establish differential diagnoses in subjects with diverse disease processes common in cardiology, thoracic surgery, oncology, neurology, orthopedics, obstetrics, accident and emergency, and general medicine.

Radiologic Subspecialties:

Interventional radiologists intervene with the body more aggressively than is done by taking x-rays or injecting dyes. They dilate arteries with balloons and put in stents that keep arteries dilated, put filters into veins, and drain abscesses deep within body cavities. Interventional radiologists function as radiologists diagnostically and as surgeons therapeutically.

Neuroradiologists provide diagnostic and therapeutic services for vertebral destructive processes (vertebroplasty).

Radiation oncologists oversee the care of cancer patients undergoing radiation treatment. They develop, prescribe and monitor the treatment plan.

Radiation Physicists and Dosimetrists work directly with the MD in the treatment plan and delivery. The physicists oversee the dosimetrist calculations to make sure treatments are precisely tailored to a patient. Physicists take precise measurements of the radiation beam characteristics and do other safety tests on a regular basis. Not necessarily medical doctors, they are certified by the American Board of Radiology.

TECHNIQUES AND PROCEDURES

What do radiologists do?

A school of thought is that the role of radiologists is to creep about in the basements or other dark areas of hospitals doing tests on the unsuspecting or unconscious. And why can’t the films or computer data just be sent to the clinicians? That way the clinician could simply hold the films up to the nearest light and murmur, "Hmmm, looks a bit patchy and fluffy round there." Because radiologists have undergone intensive training they read/interpret (and sometimes dictate) results better and faster. They attach a film to the back lighted area, look at it, compare it to others, relate precisely what the problem is, then convey it as simply and quickly as possible to the clinician. If it is a computerized image, they also interpret the data.

Radiologists are diagnosticians who use various imaging modalities to reach conclusions. Originally these modalities all involved the use of ionising radiation, but since the advent of ultrasound and magnetic resonance imaging (MRI) this is no longer the case. The evolution of interventional radiology and the continued improvements in imaging resolution has led to increased diagnostic and therapeutic possibilities.

Imaging now impacts on almost all medical specialties from general practice, through medicine, surgery, obstetrics, and orthopedics, even to psychiatry.

Radiologists use words as they appear in the next few reports. Most of them are relatively standard medical terms. A comment at the end of each will discuss their radiologic relativity.

Lytic lesion in the anteromedial aspect of the proximal tibial metadiaphysis, probably representing a solitary bone cyst. However, correlation with bone scan or MRI exam is advised given that the appearance of the lesion is not the one most typical for a solitary bone cyst and not one lending itself to the exclusion of a more aggressive lesion.

So what are the radiology words in that report? Well, pretty much all of them. The articular osteophytosis is a pathologic condition in the joint space of the first metatarsophalangeal joint. There are calcium deposits (calcific densities) in the femur and tibial joint space that describe a condition termed osteochondromatosis. A lytic lesion is also seen in the tibia. That leaves us with small, round, calcific densities, lytic lesions, and sclerotic borders.

Let us do another.

AP CHEST: Portable chest films taken in both inspiration and expiration show no cardiac abnormalities. No active pulmonic infiltrate is seen.
That report is not particularly remarkable for specialty-related vocabulary except for the “pulmonic infiltrate.” Obviously, pulmonic is commonly heard in other specialities, so “infiltrate” is about the only radiology word.

Here is a Magnetic Resonance Image (MRI) report:

At least partial disruption of the transverse atlantal ligament at its attachment to the left side of the atlas.
Mild subluxation of C7 on T1. If there is pain referable to this region, consider posterior ligamentous injury. No acute fracture injury.

On the MRI, we finally have a few more: weighted, images, axial, defect, alignment, and signal. Those are all pretty easy.

And a computerized tomogram of the neck:

Enlarged thyroid with minimal displacement of the trachea.
No tracheal compression.

On this MRI, we have contiguous, AP dimension, transverse, superior and inferior, deviation, soft tissue masses. Against those are pretty simple.

The point is that radiology as a new vocabulary is a little difficult to pin down since it uses lots of medical words, anatomical sites, obviously pathologic conditions, directions, and many English words. The technological aspects of the radiology vocabulary are unique to that practice.

Words common to radiology are:

azygous lobe

aphtha

bone/boney

brachytherapy

bulla

bursa

cardiac, cardiothymic silhouette

congestive heart failure CHF

cyclotron

density, densitometry

echo

flat plate

fluoroscope

fractionation

gadolinium

gamma

gantry

hysterogram, hysterosalpingography, hysterosonography

image-guided

intraosseous

intravenous pyelography (IVP)

ionizing

irradiation

isotope

lateral view

linear accelerator
LINAC

localization

low dose rate (LDR)

lucent, lucency

lumen, lumina

lung

lymphoscinigraphy

magnetic field gradient

magnetic resonance angiography
cholangiopancreatography

mediastinum

milliroentgens

MR Spectroscopy

myelogram
myelography

myocardial perfusion scan

osteoporosis/osteopenia

pancreatography

parathyroid imaging

particle beam therapy

patency

perfusion

pericardial effusion

pulmonary edema

rad

radiation

radioactive iodine I-131
radioactive iodine uptake test (RAIU)
radioisotope

radiofrequency ablation

radiograph/ic

radionuclide

radiopaque

radiopharmaceutical, radiotracer

roentgen (R, r)

scintigraphy

simulation

sonogram, sonography

spectral Doppler

splenoportography

spot film

staging

stenosis

stent

stereotactic

synchrotron

shadows

Technetium-99m

thyroid scan
thyroid uptake

tomography

transducer

urethrocystometry

urography

vasography

venography

vesicoureteral

X-ray

X-ray therapy

PROCEDURE DESCRIPTIONS

X-rays:

When a conventional x-ray is taken, there is an interaction between the radiation source and the various structures in the body. In an x-ray, that information is displayed in high-resolution analog form (increasingly, digital forms are being used). The problem is that all soft tissue looks about the same, because all soft tissue interacts in basically the same way with x-radiation. So the liver, gallbladder, and the important bile ducts, for example, are all hidden in the same large soft tissue shadow. Soft tissue is not seen well. Bone is seen very well, so fractures, dislocations, are apparent.

Computerized Axial Tomography (CAT, CT) Scan - [Learn More...]

A CT is a computerized imaging test. The story with CT is quite different than standard x-rays. The physics allow for greater discrimination between the various structures that make up the soft tissue.

The typical CT scanner is composed of three main sections. First, there is the table that resembles a bed or stretcher, which slides into a gantry. The gantry is the second main section, and this contains the detector array. The array sweeps around the body sending and receiving a fine beam of x-rays. These x-rays pass through your body and into a detector at the other side, at many different points on the circle, so each individual detector will see the beam coming through an individual part of the body.

That process produces a ton of information, so the detectors need to convene and come to a consensus about what they have seen. That is the purpose of the third main section, the computer. The computer takes all the information from the detectors and makes a picture of the particular slice. Remember, a typical CT study may use anywhere from 12 to 40 slices. The table slides you in or out of the scanner (depending on what part of the body is being scanned), the array spins around your body getting information about that slice and then moves on to the next slice where the same process is repeated. So it is, take a picture, stop, slide, stop, and take another picture, stop, and slide.

Spiral/helical CT:

The arrival of the spiral or helical CT has greatly improved the CT by sliding and taking pictures continuously. The test takes much less time and slices can be obtained more quickly. The cough and breath-holding problem of the conventional CT scanner doesn't exist with helical CT, since the entire chest is scanned in one short breath hold. There is much less chance of overlooking an entire section. Numerous slices are done in a very short period of time.

So what can you do with all these images? The computer helps, but the radiologist interprets. First, the radiologist sits down in front of a computer monitor and flies through the images. Say he wanted to see if there was a stone in the lower ureter. He could start at the top of that tube, focus on it, and fly through the rest of it, almost like being in it. The radiologist could focus on all sorts of other structures: the liver, the pancreas, the bile ducts, the aorta, to mention a few. If anything odd is seen, a return to the rough data is done, the individual slices. Images can be reformatted from a different perspective. Observation can be made of only the structures with dye or a dynamic virtual reality is created where the observer may "travel" through the body seeing everything.

Intravenous Pyelogram (IVP)

This test could be more accurately called "IVU," or intravenous urogram, but most have accepted the old-fashioned term, IVP. IVPs are basically x-rays of the urinary tract. Because the kidneys, ureters (the tubes that connect the kidneys with the bladder), and the bladder blend in with other soft tissues in the abdomen, they are not easily visible on regular x-rays. To see them better, dye (contrast material) must be injected into a vein. After the dye is excreted through the kidneys, excellent pictures of the various components of the kidneys, ureters, and bladder can be obtained. Before the advent of CT scan and ultrasound, IVP was essentially the only study that allowed radiologists to evaluate the upper urinary tract. Now, because of the newer technologies, there are fewer conditions that require intravenous urography. These include flank pain and hematuria, which may suggest the passage of a stone through the ureter, and other circumstances that require an overall look at the entire urinary tract from the kidneys to the bladder.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging revolutionized medical imaging. Basically, the patient is placed in a tube where various magnetic fields are applied to the body. The way the body responds to those fields and how it relaxes when the magnetic field is removed is noted and sent to a computer along with information about where the interactions occurred. Myriads of these points are sampled and fed into a computer that processes the information and creates an image.

MRI was developed in the 1980s. Its technology has been developed for use in magnetic resonance angiography (MRA), magnetic resonance spectroscopy (MRS), and, more recently, magnetic resonance cholangiopancreatography (MRCP). MRA was developed to study blood flow, whereas MRS can identify the chemical composition of diseased tissue and produce color images of brain function. MRCP is evolving into a non-invasive potential alternative for the diagnostic procedure endoscopic retrograde cholangiopancreatography (ERCP).

An interesting feature of magnetic resonance imaging is that flowing things have a distinctive appearance on MRI scans (similar to Doppler ultrasound). Flowing structures cause "flow voids," which appear as black holes on the scans. There are computers powerful enough to extract information about a given flow void, such as in the carotid arteries in the neck. The computer does this for each and every slice and puts together images of the vessel causing the flow void. The images look just like someone had injected dye, as in an angiogram. This type of magnetic resonance angiography (MRA), offers another way of looking at vascular structures in the body. For example, in cases where the aorta is injured by arteriosclerosis, aging, or trauma, MRA can provide exquisite images. Resolution can be somewhat of a problem, however, for small structures, such as the carotid arteries. In those cases, angiograms remain the method of choice to delineate the specific pathology.

MRI creates precise images of the body based on the varying proportions of magnetic elements in different tissues. Very minor fluctuations in chemical composition can be determined. MRI images have greater natural contrast than standard x rays, computed tomography scan (CT scan), or ultrasound, all of which depend on the differing physical properties of tissues. This sensitivity allows MRI to distinguish fine variations in tissues deep within the body. It is also particularly useful for spotting and distinguishing diseased tissues (tumors and other lesions) early in their development. Often, doctors require an MRI scan to investigate more fully earlier findings of other imaging techniques.

The entire body can be scanned, from head to toe and from the skin to the deepest recesses of the brain. Moreover, MRI scans are not obstructed by bone, gas, or body waste, which can hinder other imaging techniques. (Although the scans can be degraded by motion such as breathing, heartbeat, and bowel activity.) The MRI process produces cross-sectional images of the body that are as sharp in the middle as on the edges, even of the brain through the skull. A close series of these two dimensional images can provide a three-dimensional view of the targeted area. Along with images from the cross-sectional plane, the MRI can also provide images sagitally (from one side of the body to the other, from left to right for example), allowing for a better three-dimensional interpretation, which is sometimes very important for planning a surgical approach.

What MRI can do that other imaging techniques don’t do as well:

Brain: One of the few imaging tools that can see through bone (the skull) and deliver high-quality pictures of the brain's delicate soft tissue structures.
Spine: Identifying and evaluating degenerated or herniated spinal discs. It can also be used to determine the condition of nerve tissue within the spinal cord.
Joints: Diagnose and assess joint problems providing clear images of the bone, cartilage, ligament, and tendon that comprise a joint.
Skeleton: The properties of MRI that allow it to see through the skull also allow it to view the inside of bones. Accordingly, it can be used to detect bone cancer, inspect the marrow for leukemia and other diseases, assess bone loss (osteoporosis), and examine complex fractures.
Heart and circulatory system: MRI evaluates the heart and blood flow and provides a good natural contrast medium that allows structures of the heart to be clearly distinguished.

Mammography

Mammography is a test that uses x-rays to create images of breast tissue. The test is performed to detect and evaluate abnormalities such as tumors and cysts. There are two basic forms of mammography: screening and diagnostic.

Screening

A screening mammogram is used to look for cancer in women with no symptoms and no history of breast surgery. Mammograms are used for comparative study, that is, the left breast is compared to the right breast, and current films are compared to older films. The goal of regular screening is to detect small cancers in breast tissue because they are easier to treat and present a better prognosis for the patient.

Standard Studies

The breast is positioned between two panels and compressed. Two images of each breast are obtained for evaluation: a side (mediolateral oblique) view and a view from above (craniocaudal). X-rays penetrate the breast and record the images on film.

Different tissues in the breast absorb different amounts of x-rays, producing different shades of black, gray, and white on the film:

Fatty tissue absorbs a small amount of x-rays and appears black or dark gray.
Normal fibrous and glandular tissues (milk glands, lymph nodes) contain water fluid and absorb a moderate amount of x-rays, and appear light gray.
Fibrous and glandular tissues may contain calcium and appear nearly white or white.

Cancerous tissue contains watery fluid and sometimes calcium, making small cancers difficult to distinguish from normal breast tissue. As the cancer grows, it appears whiter than breast tissue on film.

Comparison with prior mammograms helps the radiologist recognize changes in the patterns of lights and darks on the film that may indicate the presence of small breast cancers. Women are encouraged to have a mammogram at age 35 to provide a baseline study for comparison with mammograms taken when they are 40 and older.

Findings

Because small cancers are difficult to distinguish from normal breast tissue on a mammogram and may not be palpable during a breast exam, some go undetected. Cases that elude diagnosis are referred to as false negatives. These cancers are usually found after they have grown to a size that can be seen or felt.

Other conditions in the breasts may look similar to cancer, such as calcifications or cysts. Usually, the radiologist will ask for additional studies that focus on the area of the breast where the suspicious lesion is located. If additional studies are inconclusive, a biopsy is recommended. If the biopsy proves to be noncancerous, the finding is called a false positive.

Calcifications commonly develop in women's breasts because the breasts produce milk, which contains calcium. Because many breast cancers contain calcifications, it is important to determine whether or not they are within cancerous tissue. Most calcifications can be evaluated a mammogram. Those that are difficult to evaluate require additional studies.

A mass, or lump, found on a mammogram may be a lymph node, cyst, or fibroadenoma (fibrous milk gland). These types of masses usually are easy to identify and do not require additional studies. A new mass or a mass that has grown since the last mammogram was taken is usually evaluated with ultrasound.

Several masses can be seen in women who have fibrocystic disease. If there has been a change in the size or the shape of the edges of a mass, or if a suspicious calcification within a mass is seen, the radiologist may order additional studies.

An area in one breast that has a distinctly different appearance than the same area in the other breast is referred to as asymmetric density. This finding usually requires additional studies with mammography or ultrasound.

Dense breast tissue can make mammogram evaluation difficult because the tissue can obscure small cancers.

Ultrasound (A-mode and B-mode, Gray scale)

Ultrasound works with sound waves. The ultrasound technologist places a handheld transducer up against the part of the body to be examined. Mineral oil or acoustic gel are spread on the body surface to provide a good seal between the transducer and the skin surface. The transducer sends a sound signal into the body that is transformed by whatever it comes into contact with. The reflected signal is processed and made into something that looks like a picture.

The sound pulse is sent into the body and the reflected beam is a line with three distinct peaks that form where the sound encounters something hard. For instance, in the skull adjacent to where the beam starts, the other side of the skull; and in the middle, a midline structure in the brain, called the falx. The falx is a fibrous septum that separates the right and left sides of the brain. The falx is not as hard as bone, but it is hard enough to deflect sound, so the falx can be seen between the two sides of the skull. That is, unless, of course, something in the brain is causing the midline septum to shift, like blood or a tumor. This test, called an echoencephalogram, was the mainstay for figuring what was going on in the skull as late as the 1960s. Ultrasound sampling of a single line across the brain is known as A-mode testing.

Suppose a device allowed drawing multiple lines across the body. Doing an ultrasound of multiple lines is almost like putting a piece of paper over the face of a coin and drawing lines over it with a soft pencil. The picture develops line by line. If it's done right, an outline of some of the organs that aren't visible with conventional x-ray, such as the gallbladder appears. A gallstone may also be visible. The stone, which is solid, completely reflects the sound bouncing and has a characteristic appearance. Sampling multiple lines is known as B-mode testing.

The first B-mode images were simple black or white pictures, with no shades of gray. There was either a line or no line, making them very hard to interpret. Gray-scale images were then developed, a huge step forward in the quality of ultrasound pictures. Instead of setting a threshold that determines where a dot or line is stuck onto a blank screen, each intensity of the reflected sound is assigned a gray-scale value. A very strong reflector looks white, while a very poor reflector looks almost black, and all the others are various shades of gray.

Another very important improvement was the development of real time ultrasound. Originally, the technologist had to move the B-mode transducer all over the body to get images of internal structures. Moving a transducer with the hand often produced a jerky, unreliable scan. Why not put a bunch of transducers together that fire at different times to get different pieces of information? This is ultrasound in motion, in real time. This is the technology that enables us to watch the truly astounding image of a fetus sucking his or her thumb in utero.

It may seem surprising when there is so little color used in radiology. It has been said that color is distracting, and instead of improving information, it actually degrades it. There is one place that color has become invaluable, ultrasound. Technicians are able to not only locate a structure in the body with sound waves, but also determine how fast and in which direction that structure is moving. When the sound hits a moving object, it is deflected differently, and by analyzing that difference the computer calculates all sorts of things about the motion of that structure. In ultrasound, movement is color coded. Flow toward the transducer is red and flow away, blue.

For most organs in the body that are relatively motionless, flow information is not such a big deal. But for other structures (e.g., red cells in the blood flowing through arteries and veins), color-coded flow information is a big plus. In the neck, for example, blood can be seen flowing through the carotid arteries, and information may be obtained about that flow, such as how fast it flowing and how turbulent it is, providing a remarkably accurate view of what is happening. Such flow information can be important in many places, including the head, neck, heart, liver, abdomen, pelvis, legs, and arms.

Upper GI

Once the mainstay of radiology, the upper GI (UGI) series has lost considerable ground in the past few decades to other imaging tests, such as ultrasound and CT scan. The upper GI series provides the single best way to study the upper gastrointestinal tract. The test is noninvasive, easy to tolerate, and sensitive enough to detect important pathology. Using a UGI, the radiologist can evaluate the swallowing mechanism, check the rest of the esophageal tube for inflammation or obstruction, and study that very sensitive gastroesophageal junction. The radiologist also studies the stomach and duodenum, while looking for ulcers, tumors, and signs of inflammation. Sometimes the upper GI series is extended to include the entire small bowel, in what is known as a small bowel series.

Often the UGI series can be abbreviated to focus on the esophagus and the gastro-esophageal junction. This shortened study is called a barium swallow or esophagram.

You may view a list of pretty standard (and some are even outdated having been replaced by better technology) on this resource and tool page at:

http://www.proedge2000.com/radiology.html

Page Last Revised: Tuesday, 04-Mar-2008 15:46:02 GMT