CT and MRI Scans in Neurological Practice: A Quick Overview
Before computed tomographic (CT) scans became available in the 1970s, there was no good method for imaging the brain. The available methods and technologies struck around the target without quite hitting the bull's-eye.
We had skull x-rays which imaged the bony brain-case, but not the brain itself. We had arteriograms which imaged the insides of blood-vessels supplying the brain. We had nuclear brain scans which imaged chunks of brain that were recently damaged. We had a particularly nasty test called a pneumoencephalogram (PEG) in which the doctor squirted air through a spinal tap needle and encouraged it to bubble around and inside the brain by turning the patient every which-a-way-including upside-down-while x-ray pictures showed where the air could and couldn't go. Finally, the most accurate method was not a physical picture at all, but a mind's-eye picture within the brain of an examining neurologist. Yet diagnoses still got made and patients did get treated.
CT scans revolutionized the practice of neurology. It's not that the other methods disappeared (well, yes, PEGs thankfully did disappear) but that CT scans vastly improved the accuracy of diagnosis and treatment. Even when CT scans didn't show the disease itself (e.g. multiple sclerosis or a fresh stroke) they assisted the diagnostic process by proving the absence of a brain tumor, abscess or hemorrhage that were also on the list of diagnostic possibilities.
CT scans did (and still do) this by sending x-ray beams through the head at various angles and collecting the x-ray beams on the opposite side that were not absorbed by the head. Then magic occurs. A series of images appear on a computer monitor or on x-ray film as if the head had been run through a giant salami-cutter and the slices were laid out flat and in sequence.
On CT pictures the different parts of the head are displayed in various shades of gray according to how much they absorb x-rays. The skull-bone absorbs x-rays the most and shows as the whitest component. At the other end of the gray-scale, the watery spaces in and around the brain absorb x-rays the least and show as the blackest components. The brain itself is somewhere in between, showing up in the mid-gray range. Abnormal components, like brain tumors and blood-collections, are identified not just by appearing in their own shades of gray, but also by their locations and shapes. Creating a second set of slices after the patient receives an infusion of intravenous dye provides an additional dimension to imaging not unlike that provided by the older, nuclear scans.
Then in the 1980s magnetic resonance imaging (MRI) scans burst upon the scene and astonished the medical community by not just imaging the brain itself, but by doing so in a brand-new way. Instead of imaging the extent to which the head's different components absorb x-rays, MRIs instead focus on water-molecules. To be more precise, MRIs image the rate at which spinning hydrogen-atoms of water molecules within different parts of the brain either line-up or fall out or alignment with a strong magnetic field. These differing rates of magnetization or de-magnetization are fed into a computer. Then magic occurs yet again. A series of slice-like images is created and displayed on a computer-screen or x-ray-type film in shades of gray. Abnormal structures, like brain-tumors or the plaques of multiple sclerosis, are displayed in their own shades of gray and are also recognizable by their shapes and locations. Obtaining another set of images after intravenous administration of gadolinium-the MRI equivalent of x-ray dye-also adds diagnostic information.
One of the virtues of MRI pictures is that they are based on physical principles totally different from those responsible for creating CT pictures. Thus, the MRI is good (or not so good) at showing different things than CTs. Another virtue is that MRIs can slice and dice the brain at different angles, while CTs slices are limited to just the horizontal plane. Yet another virtue of MRIs is that they are much better than CTs at imaging most diseases of the spine. Finally, MRIs are much more flexible than CTs: new bells, whistles and capabilities are being added all the time.
To the patient, the experiences of having a CT and of having an MRI greatly resemble each other. In both cases the patient lies horizontally on a flat table that moves into and out of an opening in the scanner that resembles a giant doughnut-hole. The doughnut-hole in the MRI machine is narrower, so claustrophobic patients need to inform their doctors if this might be a problem. The MRI machine is also noisier: a loud sound is created each time its radio-frequency coils turn on and off. For each kind of scan the technologist might stick a needle in the patient's vein to administer contrast-material.
Both tests are otherwise painless and are very safe with certain exceptions. Pregnant women who need a scan might have to do without one for fear of exposing the fetus to excessive x-rays in the case of the CT scan or to an excessive magnetic field in the case of the MRI. If push comes to shove, the woman is more likely to receive a CT scan because her abdomen can be draped with a lead shield that blocks passage of most x-rays, while there is no good method for blocking the magnetic field produced by an MRI machine.
A circumstance in which MRIs are simply not done is when the patient has a cardiac pacemaker. This is because the MRI machine's magnet might disrupt the pacemaker and stop the heart. No image is so necessary and valuable that this risk would be worth taking. Another circumstance in which an MRI is avoided is when the patient is critically ill. An unstable patient can be adequately monitored and supported while receiving a CT scan, but not while receiving an MRI.
Depending on the nature of the patient's problem, the doctor will usually order just one of the two types of scans and not the other, but in selected cases the magic of both kinds of scan might be needed.
(C) 2005 by Gary Cordingley
Gary Cordingley, MD, PhD, is a clinical neurologist, teacher and researcher who works in Athens, Ohio. For more health-related articles see his website at: http://www.cordingleyneurology.com
Stevens Johnson Syndrome (SJS) is a severe and deadly allergic reaction to certain drugs, some proscription and some over the counter, which causes the severe burning of skin and mucosal membranes from the inside out. 15% of people who develop Stevens Johnson Syndrome will die as a direct result. Many drugs which have been known to cause SJS do not have warning labels notifying users about the very real danger of Stevens Johnson Syndrome. If you or a loved one has SJS, a Stevens Johnson Syndrome lawyer can help you receive financial compensation.
Bextra and Vioxx -- Tips for Arthritis Relief Without Them
The recent withdrawal of Vioxx and Bextra from the marketplace, due to concerns over unwanted side effects, has many arthritis sufferers concerned. These drugs, which belong to a powerful class of non-steroidal anti-inflammatory drugs known as COX-2 inhibitors, are quite effective at fighting the pain and inflammation of arthritis. Unfortunately, they have been linked to increased risk of strokes and heart attacks. Their manufacturers have voluntarily withdrawn them from the market.
Orthotics and Your Feet
Orthotics are devices which fit into the shoe to aid the foot. "Functional orthotics" are rigid and designed to control motion and correct the function of the foot. Individuals with flatfeet, tendonitis, plantar fasciitis, certain foot deformities, knee, hip and back problems may benefit from functional orthotics. "Accommodative orthotics" are soft and designed to reduce pressure and prevent excess friction. Diabetics and those with a loss of sensation or circulation in their feet will benefit from accommodative orthotics. Both types of orthotics are custom made by taking a mold of the foot.
What Not to Tell Your Doctor?
For many years since medicine has been established as an ethical profession and gained widespread credence people have believed that they could and should tell their doctor everything even remotely pertinent to their health and that it was held in the strictest confidence. Furthermore, how can the physician make accurate judgments when important or significant information is missing? This system worked very well until relatively recently but there now exists a breach of this confidence that people should know about and this breach has developed from the advent of third party investigations into people's backgrounds. Your medical records are no longer confidential because you are forced to reveal them. Let us look at some scenarios.
Antibiotics 101- What You Absolutely Need to Know
What is R.I.C.E. and why do you need it? One of the most recommended icing techniques for reducing inflammation and treating minor injuries is R.I.C.E., an acronym for rest, ice, compression and elevation. It is best used for pulled muscles, sprained ligaments, soft tissue injury, and joint aches. Applying R.I.C.E. treatments will decrease pain, inflammation, muscle spasms, swelling and tissue damage. It achieves this by reducing blood flow from local vessels near the injury and decreasing fluid hemorrhaging as a result of cell damage.
Seroquel Side Effects: Effects of Seroquel Worth the Risk?
Seroquel is an atypical antipsychotic drug that is used to treat hallucinations, delusions and confusion caused by psychotic conditions such as bipolar disorder and schizophrenia. Atypical antipsychotics are not SSRIs (selective serotonin reuptake inhibitors) or benzodiazepines. Atypical antipsychotics like Seroquel affect only certain parts of the brain, blocking the input of serotonin, dopamine, norepinephrine, histamine, and muscarine. The benefit to atypical antipsychotics is that they are non-habit forming and are not as frequently abused as normal antipsychotics.
4 Reasons to Feel Safe Submitting an Electronic Medical Claim
Electronic Medical Claim
Web Therapy: Enhancing Patient Communication with Web Access
According to Jennifer Lyons' chart, she's just a bad slip and fall who's lucky enough to be on her way to a full recovery.
Low Blood Pressure ? Why is Your Blood Pressure Low?
Why is your blood pressure low?
Toenail Fungus: Treatment and Prevention
A thick, yellowish nail with splotchy white areas is a classic presentation for a fungal toenail. In the early stages the toenail is only slightly discolored, or slightly thickened. In the late stages the nail can become very thick and has a tendency to "grow up" more than in grows out. The nail will be very discolored, typically dark yellow-brown and will start to change shape and crumble. In some cases the nail becomes very loose and many will lose the nail, only for it to regrow with the fungus.
Vioxx is a prescription medication that has been used primarily in the treatment of signs and symptoms of arthritis, but has also been prescribed to treat acute pain in adults and menstrual pain in women. It is a Cox-2 selective nonsteroidal anti-inflammatory drug or NSAID. Other Cox -2 selective NSAIDs on the market are Celebrex and Bextra. Vioxx is also related to nonselective NSAIDs such as ibuprofen and naproxen.
Utah Drug Rehab: Searching For A Therapist
Finding the right treatment for any person suffering with a drug abuse problem can be a difficult task - where do you start, how do you know what to look for, how do I find a good therapist or treatment center in my area? Thankfully, there are many resources to help you find the help that you or a loved one need - here are some tips to help you locate Utah drug rehab help.
Orphan Drugs: Hope Where There Is Little or No Hope
NEW YORK, N.Y., February 18, 2004 ? On a visit to his doctor, Gary Jacob received distressing news ? not about himself, but a friend of the doctor's.
The Arthritis Pain Reliever... A New Program That Just Might Make You Younger!
For years, it's been known that regular daily exercise is one of the most important activities that people can engage in to promote good health.
Parasites In Your Colon
Your colon is a place for other parasites and organisms to breed and live. Many are harmful to your health and enter the body in various ways ? foods we eat, through the bottom of your feet, air you breathe, the water you drink, and through sexual activity.
Substance Abuse Attitude Testing by a Standardized Survey
This is a short overview of a questionnaire used for substance abuse attitude testing in testing a CREATE (Curriculum Renewal and Evaluation of Addiction Training and Education) effects on Medical Students. My afterthoughts on substance abuse attitude testing are in the end of the article.
Generating Pharmaceutical Sales before Marketing Authorization
When a patient has a serious illness and there is no approved drug available, the physician may want to try one which has not been authorized for marketing by national health authorities but has shown promise in clinical trials. European Named Patient Programs, like US compassionate use programs, offer physicians access to pharmaceuticals which have not yet been licensed. However, there is one important difference: in Europe an unlicensed drug can be reimbursed. This presents drug-makers with an opportunity to generate revenues while development is still in-progress.
Buy with confidence at Online Mexican Pharmacy
The foremost benefit of buying prescription medicines and other medical supplies from a Mexican pharmacy is the secure buying procedure and easy on the pocket rates. The health and medical care laws in Mexico are not that strict infact completely different and relaxed as compared to the US laws. Most of the medicines can be bought and sold without an authentic prescription except narcotic agents and some of the other restricted and controlled prescription items in Mexico therefore purchase of prescription drugs in Mexico is considered a unproblematic, easy procedure. The easy purchase method and easily accessible medicines in Mexico may put you to some degree of risk but what about internet frauds and counterfeit pharmaceutical preparations? The world of internet is not much reliable either, but you can save your time when you shop online and in order to secure the money you spend on online buying you should keep you up to date and alert. The text that follows provides you a easy and simple but technical guide line for online shopping of your medications and getting the optimum advantage from online ordering and buying.
Buy Electric Wheelchairs Online
Electric wheelchairs mobility for virtually any type of disability.
|home | site map|