Category Archives: Imaging

How Much Radiation is the Trauma Team Really Exposed To?

October 23, 2019 The Trauma Pro Leave a comment

Previously, I posted about “other people” wearing perfectly good lead aprons lifting them up to their chin during portable xrays in the trauma bay. Is that really necessary, or is it just an urban legend?

After hitting the medical radiation physics books (really light reading, I must say), I’ve finally got an answer. Let’s say that the xray is taken in the “usual fashion”:

Portable technique in your trauma bay
Tube is approximately 5 feet above the xray plate
Typical chest settings of 85kVp, 2mAs, 3mm Al filtration
Xray plate is 35x43cm

The calculated exposure to the patient is 52 microGrays. Most of the radiation goes through the patient onto the plate. A very small amount reflects off their bones and the table itself. This is the scatter we worry about.

So let’s assume that the closest person to the patient is 3 feet away (1 meter). Remember that radiation intensity diminishes as the square of the distance. So if the distance doubles, the intensity decreases to one fourth. By calculating the intensity of the small amount of scatter at 3 feet from the patient, we come up with a whopping 0.2 microGrays. Since most people are even further away, the dose is much, much less for them.

Let’s put it perspective now. The background radiation we are exposed to every day (from cosmic rays, brick buildings, etc) amounts to about 2400 microGrays per year. So 0.2 microGrays from chest xray scatter is less than the radiation we are exposed to naturally in about 44 minutes!

The bottom line: unless you need to work out you shoulders and pecs, don’t bother to lift your lead apron every time the portable xray unit beeps. It’s a waste of time and effort, unless you are dealing with xray imaging on a very regular basis! And that 52 microGrays the patient absorbed? That’s 8 days worth of background radiation.

Imaging

Wear The Damn Lead Gown!

October 22, 2019 The Trauma Pro Leave a comment

Pet peeve time. All trauma team members must wear personal protective equipment (PPE) when they attend a trauma activation. It’s for their own protection as well as our patients’. When I am the primary faculty at any trauma activation, I quickly scan all the other team members to ensure they are wearing it. If not, I give them a “gentle reminder” that they need to go get dressed properly.

This is all well and good. But recently I’ve noticed a trend when it comes time to shoot the basic x-rays needed for assessment (chest and/or pelvic images). When the radiology tech calls out to clear the torso and make sure someone else’s head or hands are not over the patient, half the team goes running out of the room. They are missing one key component of their gear:

Yes, their lead gown! Now granted, the amount of radiation exposure is not huge as I’ve documented in previous posts. But it is cumulative and for safety reasons, x-ray exposure must be limited.

But is running out of room the best way to decrease exposure? I think not! This is very disruptive to the way the team should function and interrupts patient care. Ideally, everyone in the room within 2-3 meters of the x-ray tube should be shielded in some way. And the most effective way to do this is to wear the damn lead gown!

Bottom line: I’ve adjusted my scan when the trauma team assembles. I now look for a lead gown underneath the usual PPEs. And if I don’t see it, I remind the offenders that, if they leave the room when the x-rays are taken, I’m not letting them back in. It’s been very effective at reversing this troubling trend.

In my next two posts, I’ll detail how much radiation the team is exposed to, and how much our patients receive from the studies we order.

Imaging

Do You Really Need To Repeat That Trauma Bay Xray?

October 4, 2019 The Trauma Pro Leave a comment

It happens all the time. You get that initial chest and/or pelvic xray in the resuscitation room while evaluating a blunt trauma patient. A few minutes later the tech returns with another armful of xray plates to repeat them. Why? The patient was not centered properly and part of the image is clipped.

Where is the left side of the chest, and do we care?

Do you really need to go through the process of setting up again, moving the xray unit in, watching people run out of the room (if they are not wearing lead, and see my post below about how much radiation they are really exposed to), and shooting another image? The answer to the question lies in what you are looking for. Let’s address the two most common (and really the only necessary) images needed during early resuscitation of blunt trauma.

First, the chest xray. You are really looking for 3 things:

Big air (pneumothorax)
Big blood (hemothorax)
Big mediastinum (hinting at aortic injury)

Look at the clipped xray above. A portion of the left chest wall is off the image. If there were a large pneumothorax on the left, would you be able to see it? What about a large hemothorax? And the mediastinum is fully included, so no problem there. So in this case, no need to repeat immediately.

The same thing goes for the pelvis. You are looking for gross disruption of the pelvic ring, especially posteriorly because this will cause you to intervene in the ED (order blood, consider wrapping the pelvis). So if parts of the edges or top and bottom are clipped, no big deal.

Bottom line: Don’t let the xray tech disrupt the team again by reflexively repeating images that are not technically perfect. See if you can use what you already have. And how do you decide if you need to repeat it later, if at all? Consider the mechanism of injury and the physical exam. Then ask yourself if there is anything you could possibly see that was not imaged the first time that would change your management in any way. If not, you don’t need it. But it certainly will irritate the radiologists!

Imaging

The Lead Gown Pull-Up: Part 3!

July 22, 2019 The Trauma Pro Leave a comment

Okay, I’ve written about the lead gown pull-up several times. Here’s how it goes:

I wrote in some detail about when this is necessary for thyroid and thymus protection and how much radiation exposure the trauma team actually gets.

But recently I’ve noticed some members of my own trauma team failing to wear the lead aprons, AND leaving the room when x-rays are taken!

Here’s the thing. Yes, it is important to shield yourself when working in proximity to the x-ray machine when in use. But no, leaving the room is not an acceptable way of accomplishing this! The patient is relatively less attended, and by definition less gets done while several of the team members are outside the room waiting for x-the ray tech to shoot.

Here’s my solution: I make a special announcement as part of the team pre-briefing (before patient arrival) that the lead gown is part of their personal protective equipment (PPE). It is also expected that everybody wears appropriate shielding. We already have a rule that every member of the trauma team MUST wear PPEs or they can’t enter the resuscitation room. And I follow it up by announcing my new rule: if anyone leaves the room because they don’t have proper PPEs, they will not be allowed back in the room.

Works like a charm!

Related post:

The lead gown pull-up: part 2

Imaging

Management Of Penetrating Neck Trauma: The Future?

June 3, 2019 The Trauma Pro Leave a comment

In my last post, I described the evolution of the classic approach to penetrating neck injury. Today, I’ll propose a new way of managing it based on a combination of physical exam and CT scan.

This proposal is based on the high degree of accuracy that CT angiography of the neck provides. It is very sensitive for identifying even small injuries to the aerodigestive tract and vascular system. This study is based on work done at LA County – USC Hospital several years ago.

The trauma group at LAC+USC organized a prospective, multicenter study using a multidetector CT angiography of the neck for initial screening of penetrating neck injury. This allows evaluation the neck as a single unit, not as three zones. It also solves the problem of trying to apply zones to injuries that cross several of them.

The new algorithm that was tested utilized an initial physical exam, first looking specifically for “hard signs” of injury. The following were considered the hard signs:

Active hemorrhage
Expanding or pulsatile hematoma
Bruit or thrill over the injured area
Unresponsive shock
Hemoptysis or hematemesis
Air bubbling from the wound

These patients were immediately taken to the OR and explored through an appropriate incision.

Patients with no signs or symptoms were admitted and observed for at least 24 hours. All other patients were considered to have “soft signs.” They underwent multidetector CT angiography of the neck, with a scanner having at least 40 slices. Further evaluation of these patients was based on the exam and CT scan.

Here are the factoids:

453 patients with penetrating neck injury were identified during the 31 month study period
9% had hard signs and were taken to OR; 50% had soft signs are underwent CT; 41% had no signs and were observed
For soft sign patients, 86% of scans were negative and all were true negatives after observation
12% of soft sign patients had a positive scan, and of those 81% were true positives
4 patients (2%) with soft signs had too much artifact for an accurate CT and other tests were performed; 1 of the 4 had an injury
Sensitivity of CTA was 100% and specificity was 97.5% in the soft sign patients
The authors concluded that CTA is very reliable for identifying injuries in patient with soft signs, and that patients with no signs do not require scanning, only observation

Bottom line: This is an intriguing paper that takes advantage of both physical examination at CT angiography. The results are impressive, but the numbers are still relatively small. It lends support to the argument that CTA is not required in all stable patients. But I can’t recommend completely changing our practice yet based on this one study. Additional numbers are certainly needed, but I suspect that this will become the norm in the future. I would also recommend that we all carefully look at our diagnostic algorithms to see other areas where we might identify and eliminate unneeded imaging, labs, etc.

Reference: Evaluation of multidetector computed tomography for
penetrating neck injury: A prospective multicenter study. J Trauma 72(3):576-584, 2012.

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