Tag Archives: radiation

Imaging

Arms Up or Arms Down In Torso CT Scans?

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CT scan is a valuable tool for initial screening and diagnosis of trauma patients. However, more attention is being paid to radiation exposure and dosing. Besides selecting patients carefully and striving for ALARA radiation dosing (as low as reasonably achievable) by adjusting technique, what else can be done? Obviously, shielding parts of the body that do not need imaging is simple and effective. But what about simply changing body position?

One simple item to consider is arm positioning in torso scanning. There are no consistent recommendations for use in trauma scanning. Patients with arm and shoulder injuries generally keep the affected upper extremity at their side. Radiologists prefer to have the arms up if possible to reduce scatter and provide clearer imaging.

Radiation physics research has examined arm positioning and its effect on radiation dose. A retrospective review of 690 patients used dose information computed by the CT software and displayed on the console. Radiation exposure was estimated using this data and was stratified by arm positioning. Even though there are some issues with study design, the results were impressive.

The dose results were as follows:

  • Both arms up: 19.2 mSv (p<0.0000001)
  • Left arm up: 22.5 mSv
  • Right arm up: 23.5 mSv
  • Arms down: 24.7 mSv

Bottom line: Do everything you can to reduce radiation exposure:

  1. Be selective with your imaging. Do you really need it?
  2. Work with your radiologists and physicists to use techniques that reduce dose yet retain image quality
  3. Shield everything that’s not being imaged.
  4. Think hard about getting CT scans in children
  5. Raise both arms up during torso scanning unless injuries preclude it.

Reference: Influence of arm positioning on radiation dose for whole body computed tomography in trauma patients. J Trauma 70(4):900-905, 2011.

Imaging

The Cost Of Duplicate Radiographic Studies

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Speaking of radiation, here’s another tidbit. Duplicate radiographic studies are a continuing issue for trauma professionals, particularly after transfer from a smaller hospital to a trauma center. The incidence has been estimated anywhere from 25% to 60% of patients. A lot has been written about the radiation dangers, but what about cost?

A Level II trauma center reviewed their experience with duplicate studies in orthopedic transfer patients retrospectively over a one year period. They looked at the usual demographics, but also included payor, cost information, and reason for repeat imaging. Radiation dose information was also collected.

Here are the factoids:

  • 513 patients were accepted from 36 referring hospitals
  • 48% had at least one study repeated, 256 CT scans and 161 conventional imaging studies
  • Older patients and patients with low GCS were much more likely to receive repeat studies
  • There were no association with the size of the referring hospital or the ability of the patient to pay
  • Most transfers had commercial insurance; only 11% had Medicaid and 17% were uninsured
  • Additional radiation from repeat scans was 8 mSv. The average radiation dose from both hospitals was 38 mSv. This is 13 years of background radiation exposure!
  • The cost of all the repeat studies was over $96,000

Bottom line: This is an eye-opening study, particularly regarding how often repeat imaging is needed, how much additional radiation is delivered, and now, the cost. And remember that these are orthopedic patients, many of whom had isolated bony injuries. I would expect that patients with multiple and multi-system injuries would require more repeat imaging and waste even more money. It is imperative that all centers that receive transfers look at adopting some kind of electronic data transfer for imaging, be it a VPN or some cloud-based service. With the implementation of the Orange Book by the American College of Surgeons, Level I and II centers will receive a deficiency if they do not have some reliable mechanism for this.

“Level I and II facilities must have a mechanism in place to view radiographic imaging from referring hospitals within their catchment area (CD 11–42).”

Reference: Clinical and Economic Impact of Duplicated Radiographic Studies in Trauma Patients Transferred to a Regional Trauma Center. J Ortho Trauma 29(7):e214-e218, 2015.

Imaging

How Much Radiation is the Trauma Team Really Exposed To?

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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?

Lead apron fly

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!

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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

The Lead Gown Pull-Up: Part 3!

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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!

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