How It Works - CT Scanners

The next installment of my ongoing series called “How It Works” has to do with Computed Tomography, frequently referred to as CT imaging. Like conventional x-ray imaging, CT imaging uses x-rays to make images of the human body. However, CT imaging uses computers and a moving x-ray tube to obtain 3-dimenional, high-resolution, high-detail images of anatomical structures.

History

The CT scanner was developed and demonstrated by Godfrey Hounsfield, a British physicist working for EMI, Ltd. Originally developing the idea in 1967, the first working prototype was unveiled in 1972. Atkinson Morley's Hospital in Wimbledon, England was the first institution to use a CT scanner to scan a patient. The first CT scanner sold in the US was to Massachusetts General Hospital and George Washington University for $390,000.

CT Technology

The first CT scanners were very limited in their applications compared to those used today. Primarily used to scan the brain, the earliest scanners could only form axial (horizontal) images of the human body; that is, a slice from side-to-side, similar to a slice of bread (see picture below). Thus the name Computed Axial Tomography, or CAT scan, was used to describe a scan from this machine. However, this name is no longer accurate, as today’s versions make it possible to see almost every structure in the body in a coronal, sagittal or axial plane, often in a clear 3-D view. Therefore, the term Computed Tomography, or CT imaging, has been adopted.

Axial, Coronal and Sagittal planes of the body

CT - Axial View

CT - Coronal View

CT - Sagittal View

The CT scanner is a complex machine that relies on electronic/digital as well as mechanical equipment to make an image. The patient is placed on a movable platform that is raised and “inserted” into a short tube that looks something like a large donut. Within this tube is a revolving x-ray tube and image receptor (IR), or sensor. As the scan begins the x-ray tube begins to spiral around the patient emitting a thin curtain of x-rays as it moves. Directly across from the tube (on the other side of the patient) is a sensor that picks up the x-rays after they have passed through the patient, collects the data and transfers it to a computer. The computer then uses complex algorithms to form a visual image from the data and projects it onto a computer screen.

View of inner workings of a CT scanner; tube revolves around patient.

With conventional x-ray, different anatomical structures are superimposed on top of each other and often cannot be clearly seen on the x-ray image. However, with CT, because the x-ray tube and IR rotate around the patient’s body scanning it from all angles, it is able to combine all the data it receives from the scan into a comprehensible image for the doctor to evaluate. This is one of the reasons CT imaging is often considered “superior” to conventional x-ray imaging. However, there are some considerations to keep in mind.

A patient generally receives a higher dose of radiation when receiving a CT scan than a conventional x-ray. This is because the patient is being exposed to radiation during the entire time the CT is making its scan, which can last up to several minutes. However, with conventional x-ray the patient is exposed to just a brief emission of x-rays, often measured in just fractions of a second. This is why conventional x-ray is still used for simple imaging procedures such as a broken arm or finger or chest x-rays. Also, CT machines are not portable, so the patient must come to the machine, where as mobile x-ray units allow the machine to come to the patient’s room to make the image.

Conclusion

Overall, the computed tomography has proved to be an invaluable asset to medical imaging and has saved countless lives, whether from helping a doctor diagnose a brain tumor or allowing a surgeon to identify a brain bleed in a car accident victim. As technology advances it is likely that CT scanners will become faster, more precise and more compact, and will continue to allow medical professionals to save lives.

Grossness

A quote from my positioning book in the Paranasal Sinuses chapter:

"Exudate contained in the [paranasal] sinuses is not fluid in the usual sense of the word but is commonly a heavy, semigelatinous material. The exudate, rather than flowing freely, clings to the walls of the cavity and takes several minutes, depending on its viscosity, to shift position".

Eewwwwwwww!

Patient Obesity Is Obscuring Medical Scans

An article from Forbes online magazine. Here's the direct link to the article.

07.25.06, 12:00 AM ET

TUESDAY, July 25 (HealthDay News) -- In yet another example of how obesity is playing havoc with Americans' health, a new study finds that the number of inconclusive diagnostic imaging exams has doubled in the last 15 years -- a phenomenon experts attribute to all those extra pounds.

"Obesity is affecting the ability to image these people. We're having trouble finding out what's wrong," explained Dr. Raul N. Uppot, lead author of the study, and an assistant radiologist at Massachusetts General Hospital and an instructor in radiology at Harvard Medical School, both in Boston.

"When they come to the hospital, people are so concerned about the disease they have that they don't realize that being obese could hinder the ability to deliver health care," he said.

In fact, it could hinder it considerably, given medicine's ever-growing reliance on imaging technology such as X-rays and ultrasound.

"In the past 10 years or so, medicine has become so dependent on imaging," Uppot said. "Instead of doing very meticulous clinical examinations, a lot of doctors now rely on CT scans, ultrasounds, etcetera, to tell them what's happening inside the body. What happens when you're too big to fit on a table? Or you can fit on a table but the image is poor quality?"

The new study is published in the August issue of the journal Radiology.

The findings did not come as a surprise to outside experts. "The study shows more systemically what all of us felt was true anyway," said Dr. Levon Nazarian, professor of radiology and vice chairman for education at Thomas Jefferson University Hospital, in Philadelphia.

"Patients may not realize that there are two aspects to being overweight, one of which is the increased risk of a number of different diseases," Nazarian added. "They may not realize that once they actually get sick, their size is going to limit the ability to even tell them what's wrong."

According to official estimates, about two-thirds of adult Americans are overweight or obese, and the effect on individual health and the health-care system is considerable. Obese people are more likely to develop illnesses such as cancer, diabetes and heart disease. Hospitals have also had to "super-size" their wheelchairs and beds to accommodate the new generation of sick and overweight Americans.

To assess the effect of obesity on the quality of imaging exams, the researchers reviewed all radiology records from tests performed at Massachusetts General Hospital between 1989 and 2003. Specifically, they were looking at incomplete exams due to patient size.

"We looked at people who were able to fit on the imaging equipment and get the scan," Uppot said. "When radiologists read the film, they had trouble interpreting the film because the quality of the image was not very good because of [the patient's] size."

In 1989, 0.10 percent of inconclusive exams were due to patient size. By 2003, that number had almost doubled to 0.19 percent.

"What was most alarming was the increase," Uppot said. "The number itself was small."

Difficulties varied according to the type of imaging. By 2003, abdominal ultrasounds exhibited the most difficulty in giving a proper diagnosis (1.9 percent), followed by chest X-rays (0.18 percent), abdominal computed tomography (CT), abdominal X-rays, chest CT and magnetic resonance imaging (MRI).

Ultrasound sends high-frequency sound waves through the patient, where they bounce off internal organs and come back, like a submarine's sonar. But the thicker the fat, the less able the waves are to penetrate. A similar phenomenon is at work with X-rays, the study authors said.

CT scans and MRI have a different problem -- weight limitations of the table that holds the patient and the size of the opening on the imager.

"Many manufacturers have started to address the issue by increasing table weights," Uppot said.

The weight limit for CT scans has been increased from 450 pounds to 550 pounds. For MRI, the weight limit went from 350 to 550 pounds, he said.

But that doesn't solve the bigger problem. "We are now able to fit people on the machine. Then the issue is, what do you do?" Uppot said.

The imaging power can be increased on standard X-ray and CT machines, but this leads to an increase in radiation dose as well, he said.

"What we're realizing is that not only do obese people have increased health problems but our ability to deliver quality diagnostic imaging to them is limited," Uppot said. "A large patient can no longer walk into a hospital and say, 'I want the best quality care, let me get imaged and operated on.' If you're that big, there will be issues."

The problems don't stop with diagnosis. "It puts stress on personnel," said Dr. Jorge Guerra, professor of radiology at the University of Miami Miller School of Medicine. "X-ray personnel will be more prone to injury. We receive patients who are 400, 500, 600 pounds. It paralyzes our ability to provide care for other patients. We need special equipment, special beds, the imaging is lower quality so it takes longer to complete." Size also affects interventional radiology, or procedures meant to treat a patient, which is Guerra's specialty.

And as the University of Miami builds a new hospital, it is having to take into account that more than one-third of the patient population will be more than 350 pounds, he said.

Seasons

Summer in Phoenix reminds me of winters growing up in Minnesota. "What!" you say "How can July in the sun-baked desert of Phoenix, Arizona remind you of the frozen, wind-blown tundra-like environment of Minnesota in January?" Well believe it or not it does.

There are actually several similarities.

1. The weather is extreme: e.g. Minnesota in January = - 30 degress F, Arizona in July = 115 deg. F.

2. Everyone stays inside because it's either too hot or too cold to be outside for any length of time.

3. Energy usage hits an all time high for heating your homes in Minnesota and cooling them in Arizona.

4. Touching metal objects is a no-no and can result in either a nasty burn or painful frostbite.

5. Both cause me to question why anyone decided to settle here in the first place.

6. Nobody from out of state visits you.

7. You make trips to places with the opposite temperature: e.g. Mexico in the winter and Canada in the summer.

8. Plants and animals are doment and/or clinging to life.

9. Golf courses are suddenly empty.

10. You will refuse to go anywhere if the climate control is not working in your car.

So there you have it. Surprisingly there are several similarities between Minnesota winters and Arizona summers. Once you've experienced either one of them you are truely a survivor.

The poke heard 'round the world.......or at least in my apartment

This weekend my wife was gracious enough to be my guinea pig for my very first attempt at venipuncture. What a doll!!

I had called her early last week, and requested that she permanently "borrow" a butterfly needle or two from work, so I could practice venipuncture on her over the weekend. She obliged and on Sunday night at approximately 5:32 pm I inserted a metal needle into a person's vein for the very first time.

It wasn't without problems though. As a nurse, she has had plenty of experience putting in IVs and the like, so she walked me through the steps involved and before I knew it, it was my turn to try. I did all the prep, applied the tourniquet, cleaned the area with alcohol, located the vein and then dove in. He shoots and........he misses! Damn! Just as I slide the tip of the needle under the skin the bugger of a vein decides to do a little shimmy to the left, my right! With some soft cursing and the draining of what little confidence I had, I withdraw the needle and take a breath.

"It's OK," she tells me, "That happens a lot, just try to hold the skin tighter with your other hand so the vein can't move around." Infinite patience, this woman has. So I reprep, pick a different vein in the same hand and gear up again for insertion.

Holding the skin tighter so the vein has no where to go, I slip the needle under the skin in as smooth a motion as I can. It feels the same as before and I am just about ready to begin with the soft curses again, when I feel a light "pop" and a flash of blood appears in the clear tubing attached to the needle. I'm in!! Success!! I ask her how she's doing and she says "fine", although her face looks a little whiter than normal. I secure the butterfly portion of the needle with some tape, like we have to do for the comp test, and sit back and admire my work.

"Great job," she tells me, "now can you take it out, I'm not feeling so good." I glance up at her and her face is completely ashen. I quickly get to work removing the tape and then the needle. I tell her to put her head down between her knees, of which she is already in the process. She is a nurse after all. I have the needle out and am holding the gauze tightly against her hand when she sits back up and I can see some color returning to her face. "It's a lot easier when you are on the other end of the needle," she says, "now I know how my patients feel."

She's a little embarrassed about getting woozy, so I try to distract her with all my stupid stories about passing out at the doctors office when I was 16 after getting my first Hepatitis shot, and about going completely white and scaring the phlebotomists the first COUPLE of times I gave plasma. Within a few minutes she looks and feels better and tells me that her hand doesn't even hurt where I put in the needle. I take this as good news and explain to her that it's probably because of my unmatched, inherent skill at doing IV injections. She doesn't buy this for a second, but lets me believe it at least for a while.

A few hours later she suggests I try it one more time before I head back to Phoenix, just to make sure I have the process down. Once again I do all the prep. I take her other hand this time and insert the needle and get flashback right away. Success again. This time she doesn't watch or talk during it and just lets me do it all myself. I think this helps, because this time she doesn't get woozy at all and says that she only felt a slight pinch right when I put in the needle, but after that no pain. I guess my practice is paying off.

What a sweetheart letting me practice venipuncture on her. However, she has already told me that when it comes time to test off on administering Barium enemas, I will have to find myself someone else to practice on. Can you blame her?

Favorite Photos

Check out some of my favorite photos that my wife and I have taken. What do you think? Maybe a new hobby?!

Radiologic Technologist, X-ray Tech, Rad Tech, Radiographer, Medical Imaging

If you are considering a career as a Radiologic Technologist (aka X-ray Tech), have I got a page for you. Please check out Desert Imaging II: A Blog for Prospective X-ray Technologist Students. It provides some basic and not so basic information about the job of Radiologic Technologist.

In the blog, I talk about the educational background you will need as well as things to expect when you start the job. Also, there are many useful links to webpages with additional information on medical imaging.

Please take a moment to check it out if you are interested in becoming a Radiologic Technologist.

T is for Technologist

TECHNOLOGIST v. TECHNICIAN. What's the difference, you ask? In radiography circles, the difference is huge!

For many years the term X-ray Technician, or radiology technician, was used to describe the healthcare worker who was in charge of creating x-ray images of sick or hurt patients. They had little, or no, formal education, were trained on the job and were not licensed or credentialed in any way.

That has all changed. Although still misused by the lay-person, and even some people within the healthcare field, x-ray technician is no longer an accurate title for the personnel who are involved in creating medical images.

Currently, we are in a period of transition. Although the term technician is no longer used, a solid, universally-accepted title has not yet been estabished. I guess the most commonly used title in the US, and one endorsed by our major certifying organization the ARRT, is Radiologic Technologist. The title is right there in their name (American Registry of Radiologic Technologists). After taking a nationally recognized exam administered by the ARRT, a student becomes certified as a Technologist, is registered with the ARRT, and can later take another exam to be licensed in the state in which the tech works.

However, that's not to say other names are not used in everyday conversation. X-ray Technologist is still common, as is Rad Tech and RT. Radiographer is commonly used in Great Britain and is likely derived from our common use of the word photographer (a person who make pictures with light rather than x-ray radition). Imaging Tech is more general, including techs who work in CT, MR and ultrasound, and more accurate in that these modalities all produce images of the human body, but they do not all use x-ray radiation to do it.

Presently, radiology departments are employing a level of imaging worker that is similar to the antiquated X-ray Technician, called a Practical Technologist or X-ray Tech of limited scope. This position requires less education than an Radiologic Technologist and is much more limited in their scope of practice, as the name would imply. They are certified to image parts of the distal extremeties, the shoulder girdle, the chest, skull and spine. They are NOT able to image the GI tract, the pelvis, the reproductive tract, the urinary tract or work in Specials. Also, they can NOT use fluoroscopy, CT, MR or bone densitometry. And because of their limited capacity this position is being phased out in many of the hospitals around the United States.

Still a little confused? One way to look at it is comparing a Radiologic Technologist to a Technician is like comparing an RN with an LPN or a physician with a physician's assistant. While all positions in healthcare are important and worthy of respect (right down to the guy who mops the floors), there are often vast differences in education, experience and scope of practice between the different branches in the healthcare hierarchy.

Another way to look at it (and I can't take credit for this, since it's something my instructor told us) is that:

A Technician is TRAINED
A Technologist is EDUCATED

or

A Technician can push the button
and a Technologist knows why.

I hope this information has helped clear up the difference between a technician and a technologist. Keep in mind terminology and practices differ from region to region and between institutions, so this information may not be entirely accurate in all instances. But in a general way it should help you to realize that a difference exists between the two terms and it is important to use the correct one when referring to a Radiologic Technologist.

Factoid #1548

If properly motivated, I can eat an entire box of Krispy Kreame donuts and still resect myself in the morning.

3-D gaming tech used to train Radiographers

Here's a link to a BBC News article on how 3-D gaming technology is being employeed to train student radiographers on patient positioning and other aspects of radiography. Check it out!

Update

Re: the "Hardest Test EVER" test

Well, I guess it wasn't so hard after all since I apparently got 99%. Don't ask me how though. :-)

Hardest test.....EVER!!!

OK, maybe not the hardest test EVER, but pretty hard anyway. It was one of the most difficult tests so far in my radiography program. It was in Radiographic Techniques, and although I think I did pretty well, I left the classroom brain-fried.

It was one of those tests with questions like:

"If you increase focal spot size how does it affect image detail?", "If kVP is increased by 15% what will happen to image density?", "When you increase OID what happens to radiographic contrast?" "If the patient is larger than average how will the increase in patient thickness affect image density and detail?" yada, yada, yada, blah, blah, blah, etc., etc., etc.......

A lot of if-then statements.........YUCK!! There seem to be endless variables you can change when making an image of a patient, and we have to know what will happen to the image if one or more of those variables are changed. It's a lot to keep straight in your head without having any experience in making x-ray images to use as a reference.

Our instructors said it will come together during clinicals (we shall see!), but for now we essentially had to memorize a + and - chart which tells us how one variable is affected if another variable is increased or decreased. For example, if you increase the mAs (which stands for milliamperes per second) you are basically increasing the amount of radiation leaving the x-ray tube. This increase in radiation means that more radiation will penetrate the patient and pass through to the other side, which in turn exposes more of the x-ray film making it appear more dark or have a higher visual density (degree of blackness).

Here's the chart, in case you're curious.

+ = increase, - = decrease, O = no change

Fun stuff, huh!?