Category Archives: Imaging

Best Of: Finding Rib Fractures On Chest X-Ray

A lot of people have been viewing and requesting this post recently.

Here’s a neat trick for finding hard to see rib fractures on standard chest xrays.

First, this is not for use with CT scans. Although chest CT is the “gold standard” for finding every possible rib fracture present, it should never be used for this. Rib fractures are generally diagnosed clinically, and they are managed clinically. There is little difference in the management principles of 1 vs 7 rib fractures. Pain management and pulmonary toilet are the mainstays, and having an exact count doesn’t matter. That’s why we don’t get rib detail xrays any more. We really don’t care. Would you deny these treatments in someone with focal chest wall pain and tenderness with no fractures seen on imaging studies? No. It’s still a fracture, even if you can’t see it.

So most rib fractures are identified using plain old chest xray. Sometimes they are obvious, as in the image of a flail chest below.

But sometimes, there are only a few and they are hard to distinguish, especially if the are located laterally. Have a look at this image:

There are rib fractures on the left side side on the posterolateral aspects of the 4th and 5th ribs. Unfortunately, these can get lost with all the other ribs, scapula, lung markings, etc.

Here’s the trick. Our eyes follow arches (think McDonald’s) better than all these crazy lines and curves on the standard chest xray. So tip the xray on its side and make those curves into nice arches, then let your eyes follow them naturally:

Much more obvious! In the old days, we could just manually flip the film to either side. Now you have to use the rotate buttons to properly position the digital image.

Final exam: click here to view a large digital image of a nearly normal chest xray. There is one subtle rib fracture. See if you can pick it out with this trick. You’ll have to save it so you can manipulate it with your own jpg viewer. 

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Part 2: Metal Splints – Can You CT Scan Through Them?

In my last post, I debunked the myth that using a pre-formed aluminum splint significantly degrades the quality of standard x-rays. But what about a study that provides much more detail, such as CT scan?

CT scan techs have told me that there would be too much artifact using any kind of metal splint. And typically, when imaging an extremity with CT, we are looking at vascular runoff. The vessels are small, and high image quality is extremely important. If the images are bad, then we risk having to give the patient another dose of both radiation and contrast.

As you know, my mantra is question everything! So i scouted around and found some images to share using one of these splints. Look closely for the intimal flap in the image below:

Can’t see it? That’s because it isn’t there! But you certainly could if it were!

Bottom line: A perforated aluminum splint causes absolutely no artifact or image degradation. Do not cause additional injury by removing it prior to imaging, either CT or conventional x-ray. Although your friendly techs, radiologists, and orthopedic surgeons may moan, it won’t hurt their ability to make decisions on the images.

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Part 1: Metal Splints – Can You X-ray Through Them?

Splinting is an important part of the trauma resuscitation process. No patient should leave your trauma resuscitation room without splinting of all major fractures. It reduces pain, bleeding, and soft tissue injury, and can keep a closed fracture from becoming an open one.

But what about imaging? Can’t the splint degrade x-rays and hamper interpretation of the fracture images? Especially those pre-formed aluminum ones with the holes in them? It’s metal, after all.

Some of my orthopedic colleagues insist that the splint be removed in the x-ray department before obtaining images. And who ends up doing it? The poor radiographic tech, who has no training in fracture immobilization and can’t provide additional pain control on their own.

But does it really make a difference? Judge for yourself. Here are some knee images with one of these splints on:

Amazingly, this thin aluminum shows up only faintly. There is minimal impact on interpretation of the tibial plateau. And on the lateral view, the splint is well posterior to bones.

On the tib-fib above, the holes are a little distracting on the AP view, but still allow for good images to be obtained.

Bottom line: In general, splints should not be removed during the imaging process for acute trauma. For most fractures, the images obtained are more than adequate to define the injury and formulate a treatment plan. If the fracture pattern is complex, it may be helpful to temporarily remove it, but this should only be done by a physician who can ensure the fracture site is handled properly. In some cases, CT scan may be more helpful and does not require splint removal. And in all cases, the splint should also be replaced immediately at the end of the study.

In my next post, I’ll look at the use of CT scans when this type of splint is in use.


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How Much Radiation Exposure In Imaging Studies?

Everyone knows that CT scans deliver more radiation than conventional x-ray. But how much does each test really deliver? And how significant is that?

Let me try to put it all into perspective. First, how much radiation are we exposed to just living outside the hospital? Background radiation is everywhere. It consists of radioactive gases (argon) in the air we breathe, radiation from the rocks and other things around us, and cosmic rays blasting through us from space.

In the United States, the average background radiation each of us is exposed to is about 3.1 milliSieverts (mSv). I’ve compiled a table to show the approximate dose delivered by some of the common radiographic studies ordered by trauma professionals. And to keep it real, I’ve calculated how much extra background radiation we would have to absorb, in units of time, to have an equivalent exposure.

Read and enjoy! Remember, doses may vary by scanner, settings, and dose reduction measures used.

Test Dose (mSv) Equivalent background
Chest x-ray 0.1 10 days
Pelvis x-ray 0.1 10 days
CT head 2 8 months
CT cervical spine 3 1 year
Plain c-spine 0.2 3 weeks
CT chest 7 2 years
CT abdomen/pelvis 10 3 years
CT T&L spine 7 2 years
Plain T&L spine 3 1 year
Millimeter wave
scanner (that hands
in the air TSA thing at
the airport)
0.0001 15 minutes
Scatter from a chest
x-ray in trauma bay
when standing one 
meter from the
0.0002 45 minutes
Scatter from a chest
x-ray in trauma bay
when standing three 
meters from the
0.000022 6 minutes
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