Odontoid trouble?

One of the most difficult projections for a lot of radiographers continues to be the open-mouth odontoid view. Here are some alternate ways to image the odontoid:

Most technologists can acquire an open-mouth and at least get some of the C2 vertebral body, but commonly clip the dens. In this case, you could do a Fuchs (not to be confused with Scottish profanity) by aligning the CR perpendicular to the MML and centering 1" below the mental point.


You could simply adjust the elevation of the patient's chin or you could angle your tube cephalic/caudal depending on the need. Review the anatomy on the preceding image, remembering that you need to align the tips of the incisors with the base of the skull (or as I like to use, the mastoid tips which are easily palpable from the patient's side). And simply for review (not to insult anyone's intelligence), the labeled image at the beginning of the post could be improved upon by lowering the chin because the incisors are above the occipital bone. You would have to raise the chin if the incisors were below. All of these are common practices, and should probably be attempted before proceding to the next reccommendations.

How would you obtain an odontoid view on someone with a mandibular fracture, or with their jaw wired shut? Well, there are three ways:

1) You could blast right through the mandible. This would be the easiest, increasing your kVp to about 85 should do the trick. You can lower the SID to about 30" and this will minimize the detail of the mandible/teeth superimposing the dens.

The following two options will work if there is a lot of dental work or wiring in the jaw.

2) You could oblique the head and do unilateral views of the lateral masses. For the right side, you should attempt to keep your normal alignment of the incisors and mastoids while rotating the head to the patient's left. Do it just enough so that the mandibular rami (side up) crosses over the patient's midline over the neck, freeing the jaw from superimposition over the dens. Take your film with a perpendicular beam, and you will see the right lateral mass and most of the dens. Be cautious not to over-rotate the patient's head, or you will close the joint space between the dens and lateral mass on the side you're trying to image. You can do the same thing for the opposite side rotating the head in the opposite direction.

*I had trouble finding radiographs for this one, but I'll post one if I have the opportunity to perform this method in the near future.

3) You could perform tomograms. Just like for your IVP, lay the patient supine. With calipers, measure the distance from the table to the EAM, then add one cm. This should create a focal point right through the dens. You may have to take additional slices through the vertebral bodies. I would suggest 1/2 cm incriments posterior to the initial dens image. For example, if your initial measurement from table to EAM was 10 cm, then you add one, your first slice would be at 11 cm. I might try 10 1/2 cm next, then 10 cm and show the radiologist to see if any additional films are required.



And last, and probably least, another method for obtaining the dens can be performed, but not reccommended unless nothing else works. In my experience with radiograpy on patients from some Asian countries (the skull takes a less oblong shape), you may align the incisors and the base of the skull perfectly, but still will not see the dens free of superimposition. You can align the patient like you normally would, but lower the SID as close to the patient's open mouth as possible. This allows for a more dramatized beam divergence, eliminating the incisors and mandible from being able to superimpose the dens. I would not reccommend this be practiced under most circumstances due to radiation protection purposes. The only reason I would use this is if the patient's insurance didn't cover a CT scan, and all other options had failed or were unable to be performed.

Hopefully, we can become better as we practice more of these and have the ability to assess which methods would probably work best on the initial exposure. I hope this adds to your bag-of-tricks!

Intermission

I just wanted to let those of you who read this blog know that I have not disappeared... rather, I am taking a small break from blogging to manage a few personal things going on right now. I have lots of good material in mind for the blog that I will be working on soon. Thank you for your patience.

Dual C-arm Setup

If you've ever worked with a surgeon who has required 2 c-arms during a procedure, it can be quite intimidating the first time you are asked to set one up. Here's a simple method for doing so... and depending on the procedure, remember you can alter positions of each c-arm to achieve the same result.

Bring your first c-arm in like you were doing a simple AP:





Angle the c-arm 30-34 degrees and lock it in place. Then orbit the c-arm into a lateral projection.



Drive c-arm #2 into place from the head of the table. I would suggest extending the arm as far out as it will go when aligning so that if the surgeon needs it moved to work, all you have to do is retract the arm while leaving the base locked. If you collide with the arm of the first c-arm, feel free to angle it more to provide a clearance.



After the initial setup is complete, make sure to orientate both images to appear how the surgeon wants them on the monitors.

*Note: try to avoid fluoro on both c-arms at the same time during the procedure unless the surgeon actually needs it. The image intensifiers will receive scatter from either c-arm if both operate simultaneously, degrading the quality of your images. You should be able to off-set the timing by a split second if the surgeon requires a single shot of each.

You are now ready to provide the surgeon with AP and lateral projections without any c-arm manipulation!

Fat Pad Sign

Occasionally, a pediatric patient, or even the rare adult patient will have pain from a fall or traumatic injury, and there is no visible evidence of a fracture to the technologist or the radiologist. There is a tell tale sign that there is in fact a fracture without ever seeing the fracture itself... the fat pad sign.

It is usually seen on children, but can sometimes be seen on adults. The patient has decreased ROM or extreme pain when being positioned for their radiographs. The films show joint effusion marked by increased optical density surrounding the bone or joint. The provided film displays this increased radiographic density on the anterior and posterior borders of the humerus in the lateral projection.

Most radiologists (from my personal experience only) are comfortable calling a fracture when a fat pad sign exists. If I could paraphrase the reason for this as stated by a radiologist I used to work with: The other possible causes of this type of effusion can only occur with a ligament or tendon tear around a joint. If it is not directly involving the joint, it is reasonable to conclude that a fracture is what caused the effusion. It is not an injury that will require surgery, and whether the injury is actually a ligament/tendon tear or a fracture, the treatment will be the same; splint or soft cast and no surgery. A potentially incorrect diagnosis of "normal" would minimize the amount of time for immobilization and could potentially risk further injury if not allowed to heal fully.

Pediatric Chest X-ray

The most basic exam can prove to be the most difficult of challenges in your day if you've ever had an uncooperative child. Depending on the age of your patient, different approaches can be made.

Before the patient and/or parent arrives in the room, you should have all equipment set up in advance. Make sure to have an extra lead apron for a parent if they wish to remain in the room with the child. I always like to encourage this except when the physical presence of the parent seems to make the child more combative.

You should always attempt the exam without immobilization first. This doesn't mean you need to make a bad exposure. Use your judgement about the quality of your radiograph before you commit to the attempt. Better to try unsuccessfully without a radiation dose than to settle on a sub-par quality film and end up repeating anyways. Be sure to communicate with the parent about immobilization techniques and requirements of the procedure. This may encourage better parent participation because they just want to get it over with to minimize any emotionally traumatic experience the child may have to endure (i.e. the pigg-o-stat). Don't forget to ask the mother if there's a possibility she could be pregnant before letting her assist.

The table-top attempt:

Place an 8x10 or 10x12 cassette in a grid holder at one end of the table. At the other end, align the x-ray tube horizontally to the cassette. Consider placing a sheet over the cassette so the patient will not be startled because of its ice-cold tempurature. Have mom or dad put the lead on and have a small lead apron for the patient (a thyriod shield will work on small patients). You should already have a preliminary technique set up for the AP chest. Place the patient's back against the cassette and the shield over their lap. Mom or dad can hold the arms to the side, grasping mid-humerus, and making sure to keep the child's back flat against the cassette.



For the lateral, simply rotate the patient's legs to their left 90 degrees. Have a parent stand in front of the patient and grasp the arms at the elbows bringing them together to touch in front of the face, also ensuring proper elevation above the thorax. I typically like to increase the kV by 10% and double my mAs from the AP to the lateral, but everyone has a different rule of thumb.

At three years old, the pediatric patient may be too large for the pig-o-stat. If they are somewhat cooperative, you may be able to provide a foot-stool and stand them at the upright bucky. Most will not be able to perform a PA projection because they are trying to see all of the equipment and may be a little frightened to turn their back. I worked at a facility where we put a rather large "Shrek" sticker on the bottom of the x-ray tube to give them something familiar to look at for the AP projection. Another sticker was placed on the wall directly in front of them when they were in the left lateral position. All we said was "look at Shrek" and they cooperated, but you better be on the rotor because it didn't last more than a few seconds.



The pigg-o-stat:

If you have an absolutely uncooperative patient that requires immobilization, the pigg-o-stat is the method of choice for radiographers. Most come with different sized adjustable flanks and you may want to sneak a peak at your patient before bringing them into the room to estimate the appropriate size.

If you've never used one or seen one, they look like some sort of dark-age torture device, which they could easily turn into if you let the patient sit in them too long. You simply place them into the seat with arms above their head and close the flanks. Make sure to lock them in place. If you have all of this set up in advance, the patient should be in and out in just a few seconds.

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What's new in Diagnostic Radiography

If you're like me, you might have learned the practice of radiography on plain film with chemical processors and that oh-so-familiar darkroom smell. Manual techniques actually used to appear differently when you doubled your mAs or altered your kVp to adjust scale of contrast. You may currently miss the ability to create a soft-tissue technique for an extremity without post-processing manipulation or to use extremity film at 50 kVp and obtain the best recorded detail imaginable. You may feel that the skill that you were once good at has become obsolete. Well, let's face it, a lot of that knowledge gained only from experience is becoming unneeded.

I remember my earlier days of radiography in the late 1990's when our facility received the first CR system in the local area. All of the hospital administrators from competing hospitals toured our facility in amazement when they saw how you could manipulate the image in PACS. I remember the technical conversion from our regular 400 speed film to CR... we were told to begin by trippling our mAs on every exposure. Of course, this seemed like an outstanding increase in radiation to the patient, but we were told that it made up for the amount of repeats required on conventional film due to improper technical factor formation. All you had to do was perform post-process manipulation and you could turn it in. We were the test site... there was no S number or exposure index. We were to create technique charts and give them to the engineers from the company that provided us the equipment.

Well, some time has gone by, and the amount of radiation required for a CR image has gone down quite a bit. We have more accurate ways of optimizing our exposure factors and we're more strict with quality control. But DR equipment has been making some incredible changes lately. Sure, DR technology has been around for some time, but for many facilities, it has not yet been cost-effective to switch the whole department over to DR. The advantage of CR is the hospital may utilize old x-ray equipment (tables and tubes) without paying for a room overhaul. Most administrators are probably holding out for the benefits of the new technology are great enough... or until the competing hospitals make the switch.

In the former scenario, I don't think it will be long before those benefits will be top priority. Some of the new software applications that are being utilized are amazingly successful at performing tasks previously unseen on CR or plain film. Take for instance a typical lateral c-spine projection: You only see C-6 on your film and you have to shoot a swimmer's. As displayed on GE healthcare's website, there is a new feature called "tissue equalization" that provides the same radiographic density throughout the entire image regardless of differences in anatomical thickness.



There is also another feature called "dual energy subtraction" which allows different anatomy to be better visualized all with the same exposure. As GE states, "Dual energy imaging is a subtraction technique based on the different attenuation characteristics of soft tissue and bone. The two images during the PA chest exam use different energy spectra. Information from the low-energy image (60-80kVp) is combined with information from the high-energy image (110-150kVp; the same image as a standard PA exam) to generate bone and soft-tissue images. The dual energy algorithm has been optimized for thorough removal of bone from the soft-tissue image, while minimizing image noise."







Expect to see more integration of different modalities into the general diagnostic realm in the near future as well. The "Arcadis Orbic 3D" from Siemens Medical is a newer c-arm that can perform 3D images, or basic axial CT slices on extremities in the OR.



Here is an image from their website:



You can view an entire study here (it may take about 30 seconds to load with a cable connection).

In a way, I'm saddened by the inevitable loss of a skillset learned in plain-film imaging. I will miss being able to take a really nice sternum image at 55 kVp or some ribs at 60 kVp and see a noticable difference. However, one of the exciting aspects about this field is the constant lunge of technology into the previously unheard of. It is a great time in our field and we are on the brink of new imaging capabilities every year. We have to keep changing with the technology, and continue to strive for imaging excellence.