Radiographic Alternative for Opening Joint Spaces

We all know the basics of opening joint spaces on our radiographs.  Keep the joint space opening perpendicular to the image receptor while aligning the central ray directly to the joint.  No problem... x-ray 101 right?  But what about those joint spaces like wrists and ankles?  You know, the ones where some of the radiologists say "you should have gotten more of the tibia (or forearm)!"  Sometimes it's good to include a little extra - especially if your radiologists prefer it when there is obvious deformity.

The problem lies within x-ray beam geometry.  I was going to make a video to demonstrate a basic principle in beam geometry, but Peter Gleeson did an exceptional job on his YouTube channel... watch his short video before we move on to some possible solutions.

Now that we know a tube angle does not change the distortion of an object because the x-ray source does not change position, we can evaluate our options... below, we have a traditional positioning setup for an AP ankle.

Sometimes we need a bit more of the distal tib-fib.  One proposed solution I have seen is to simply move the joint to the bottom of the image receptor, while placing the central ray a few inches above the joint space.  This accomplishes our goal of including more of the distal tibia, but can also close the ankle joint because it no longer lies directly in the central ray.  The beam is divergent at the point of intersection with the joint.

I have seen the following method used in another state that does not have very strict guidelines on radiation protection.  The tech would center to the joint space, but open the collimated field beyond the edge of the image receptor.  I do NOT recommend this for ALARA purposes, but I thought I would throw this example in there because I have seen it before.

I propose we can take the best of both worlds with the following solution.  Start out with the central ray over the joint space as in the previous example.  Without moving the x-ray tube (longitudinal, transverse, or vertical) from its current location, angle it cephalic so the crosshair is a few inches proximal to the joint space.  Collimate vertically so the field size does not go beyond the image receptor.

If you watched the video, you understand that the actual source of photons does not change with the tube angle.  There is still a perpendicular path of x-ray photons opening the joint space, while we include more of the proximal tib-fib.  The only disadvantage is there will be some elongation of the tibia near the periphery of the field of view.  But also take note that the same amount of elongation would occur in the prior method due to the same beam divergence.

Don't believe me?  Take any 3-dimensional object and place it directly under your perpendicular central ray.  Open the collimation and angle the tube in either direction.  You will notice (just as in the video) that the object's shadow does not move.  As long as you do NOT move the tube from its current location prior to tube angulation, the beam divergence will be exactly the same with the tube angle as if you simply opened the collimation.

I should mention that the BEST way to avoid this whole scenario would be to have the physician order a tib-fib (or correct corresponding body part).  But since we as technologists cannot order the exams, sometimes we have to make the best out of imperfect situations.

UGI Image Evaluation

One of the things I used to do multiple times per day as a radiologic technologist was upper GI's.  Though they're still being done quite a lot these days, I often forget how much effort we spent in x-ray school to learn how to properly tell them apart for hanging protocols.  We can distinguish our views by evaluating three things:

1. Location of barium within the stomach
2. Location of air within stomach
3. The spatial relationship between the stomach and spine

If you take the first image below, it's easy to look at the radiograph and think it was performed supine, when in fact, it was exposed with the patient prone.  The original x-ray may have been flipped horizontally upon first glance, but we are required to hang images in the anatomical position so it has been flipped.  The fundus of the stomach is full of air, while the body contains barium.  It is also superimposed over a non-rotated spine.  This tells me the patient was prone.

On a double-contrast study, we need to remember how the anatomy lies in relationship to other structures to tell the difference.  The fundus is superior to the body and also rests more posterior.  I can tell it is prone because the air will rise to the most posterior anatomy when prone.  I know this is not an upright exposure because while it would also demonstrate the barium in the body of the stomach, there would be more of a horizontal line separating the air/fluid level.

The lateral stomach view below demonstrates how the fundus is posterior to the body.  I know different hospitals can have different hanging protocols for lateral views.  So if I'm going to evaluate the image below to tell which lateral was performed, I could also reference the picture above knowing that the fundus lies to the patient's left side while the body and pylorus are more midline.  If we remember that the air will rise while barium settles, it should be easy to differentiate between a right and left lateral.  Since the barium is exiting the body and collecting in the pylorus and duodenum, we know that the patient's right side is down and a right lateral was performed.

Now, lets talk about oblique views.  Still referencing the first image, we can tell that if an RPO is performed, the stomach should superimpose the spine, which is typically undesirable for UGI studies.  The same would hold true for the opposite LAO.  We almost always perform RAO or LPO views of the stomach to free the pylorus, body and duodenum from superimposition of the spine.  That being said, look at the next image.  We can tell it is LPO because the stomach is free of the spine, and the body is full of air.  This is actually one of the radiologist's spot views.  After the stomach drains some of the contrast, the barium coats and we can rotate the patient to allow air to accumulate at the juncton.  Unfortunately, we cannot visualize the fundus, which is most likely full of barium, which would support our claim that this is an LPO.

*Tip: although the textbooks say "rotate 45 degrees," we should be mindful as technologists of the reasons for the rotation.  In this case, the radiologist needs to visualize gastric emptying function in profile while not being superimposed by the spine.  Some times we need to rotate more or less depending on patient body habitus, so keep an eye on the fluoro monitor when assisting the patient while rotating.  If you rotate 45 degrees, it may not be enough to adequately allow for an optimum view.  When contrast is involved, we need to be efficient, so we don't want to stand there waiting for the radiologist to tell us to turn the patient more while we're missing a good opportunity to image the stomach emptying.

Compared to the image above, the next set of images differs in that the barium is in the body, while air is in the fundus.  This tells us the fundus is superior to the body, but we also know it's an oblique due to several give-aways.  The fundus and body are free of superimposition of the spine, and you can also notice rotation of the spine itself.  For these reasons, we know these are RAO views.  They were taken in the position of the bottom left image below (where the fundus is closer to the x-ray tube/superior to the rest of the stomach).  The images were then flipped horizontally to represent anatomical position like in the bottom right image.

Evaluating UGI images can be somewhat confusing at first, but once you get it, it's like riding a bike.  If you can visualize how the stomach lies within the abdominal cavity, it's not so difficult.  Acquiring that knowledge early on in your studies will make a huge difference later when you're in the middle of a procedure.

*if you like the virtual images I posted, check out the interactive anatomy site, https://www.biodigitalhuman.com/.  There is an interactive anatomy skeleton with all body tissues which gives you the opportunity to isolate tissues of interest, rotate, zoom, and a few other helpful tools.

Radiographic Sitzmarker Study

Unless you work in a hospital that routinely treats pediatrics or you have been around the world of radiography for a while, you may not have seen a Sitzmarker test.  This exam is done for patients who have experienced chronic constipation, and may be used to support a number of gastrointestinal disorders.  

Procedure:  A capsule is swallowed containing several metal rings encased in plastic.  Once the capsule dissolves, the rings disperse and can be followed through the GI tract.

I have seen varying routines depending upon radiologists' preference at different imaging departments.  The patient could return every day (approximately the same time of day) for a follow-up KUB, and I have seen them spaced out as far as 5 days.  The dictation should note the difference in location of the rings, as well as the amount of time for motility to allow the rings to pass.

The normal GI tract should evacuate the rings within 2-3 days.  Other disease processes could make the rings take more or less time, but most frequent findings are with constipation where it delays passage for more than 5 days.