Tag Archives: radiation

Repeat Imaging: What Good Is It?

I’ve written previously about how often imaging gets repeated once a trauma patient gets transferred to a trauma center (click here). There are many reasons, including clinical indications, need for advanced imaging (reconstructions), or lack of contrast. But at least 20% have to be repeated because the media is incompatible or not sent with the patient. Sounds like a problem, but is it a significant one?

A recent retrospective analysis of about 2,000 transfers to a Level I center looked at the reasons for repeat imaging and changes in outcome due to it. The paper found several interesting things:

  • Repeat imaging was more likely in more severely injured patients
  • Hospitals that transferred more patients to the trauma center tended to do more scans before transfer
  • Patients who had repeat imaging stayed in the ED longer waiting for definitive disposition
  • Repeat images did not improve outcomes (LOS, DC home, mortality)
  • A rough estimate of $354 more in charges was attributed to repeat imaging

Bottom line: Repeat imaging is wasteful, expensive and increases time in the ED. And don’t forget about the radiation exposure. With all the emphasis on pushing hospitals to use an electronic medical record, there needs to be a similar push to standardize methods for transferring radiographic images between hospitals to address the problem of repeat imaging.

Related posts:

Reference: Repeat imaging in trauma transfers: A retrospective analysis of computed tomography scans repeated upon arrival to a Level I trauma center. J Trauma 72(5):1255-1262, 2012.

How Much Radiation is the Trauma Team Really Exposed To?

Okay, so you’ve seen “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”:

  • 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. 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 every hour!

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!

Repeat Imaging: What Good Is It?

I’ve written previously about how often imaging gets repeated once a trauma patient gets transferred to a trauma center (click here). There are many reasons, including clinical indications, need for advanced imaging (reconstructions), or lack of contrast. But at least 20% have to be repeated because the media is incompatible or not sent with the patient. Sounds like a problem, but is it a significant one?

A recent retrospective analysis of about 2,000 transfers to a Level I center looked at the reasons for repeat imaging and changes in outcome due to it. The paper found several interesting things:

  • Repeat imaging was more likely in more severely injured patients
  • Hospitals that transferred more patients to the trauma center tended to do more scans before transfer
  • Patients who had repeat imaging stayed in the ED longer waiting for definitive disposition
  • Repeat images did not improve outcomes (LOS, DC home, mortality)
  • A rough estimate of $354 more in charges was attributed to repeat imaging

Bottom line: Repeat imaging is wasteful, expensive and increases time in the ED. And don’t forget about the radiation exposure. With all the emphasis on pushing hospitals to use an electronic medical record, there needs to be a similar push to standardize methods for transferring radiographic images between hospitals to address the problem of repeat imaging.

Related posts:

Reference: Repeat imaging in trauma transfers: A retrospective analysis of computed tomography scans repeated upon arrival to a Level I trauma center. J Trauma 72(5):1255-1262, 2012.

Papers To Change Our Practice 2: Radiation Exposure

The second paper I’ll be discussing at the Penn Trauma reunion tomorrow deals with radiation exposure in trauma. Specifically, I’ll be talking about the amount of radiation the patient is exposed to during their initial evaluation. A lot of work is being published on this topic, but the paper I selected took a different and more accurate approach.

The trauma group at Sunnybrook in Toronto measured surface radiation exposure in a group of 172 major trauma patients. Dosimiters were placed on the neck, chest and groin, and were ideally kept there during the entire hospital stay. A software algorithm was used to calculate organ dose based on the surface measurements. This differs from the more commonly used method of counting studies and calculating dose based on published averages of radiation delivery.

The study was weakened by the number of patients that were excluded or who decided to remove their dosimeter at some point. But a number of interesting facts were revealed:

  • Patients received an average of 5 CT scans and 14 plain xrays during their stay
  • The average total effective dose was 23mSv, about 10 times the normal background exposure for an entire year
  • A surprisingly high dose was delivered to the thyroid, which is more sensitive to radiation exposure
  • A total of 190 extra cancer mortalities would be expected per 100,000 patients, given these exposure numbers
  • Radiation was underestimated using non-dosimeter techniques

Bottom line: We know radiation exposure occurs in our patients, and we know that it’s increasing. It won’t be that long until we start to see the after-effects of these imaging studies, especially in younger patients. What you can’t see does hurt your patients! We need to quickly strike a balance between avoiding missed injuries and irradiating the patient. Specific guidelines to direct ordering of radiographic studies must be developed, and our radiology colleagues need to continue to strive for techniques that adhere to the ALARA (as low as reasonably achievable) philosophy.

Related posts:

Reference: Radiation exposure from diagnostic imaging in severely injured trauma patients. J Trauma 62(1):151-156, 2007.

Pediatric CT Scans Before Transfer to a Pediatric Trauma Center

CT scan is essential in diagnosing injury, although concerns for unnecessary radiation exposure are growing. These concerns are even greater in children, who may be more likely to have long-term effects from it. This makes avoiding duplication of CT scanning extremely important.

Unfortunately, there are only about 50 pediatric trauma centers in the US, so the majority of seriously injured children are seen at another hospital before transfer. Does CT evaluation at the first hospital increase the likelihood that a repeat scan will be needed at the trauma center, increasing radiation exposure and risk?

Rainbow Babies and Children’s Hospital in Cincinnati looked at 3 years of transfers of injured children from community hospitals. They then looked at how many of those children had an initial head and/or abdomen scan at the outside hospital, and whether a repeat scan of those areas was performed within 4 hours or arrival at Rainbow.

Numbers were small, but here are the results:

  • 33 had an outside CT scan, 28 (90%) were repeated
  • 6 had an outside abdominal scan, 2 (33%) were repeated
  • 55 did not have outside scans, none were repeated at Rainbow. (This is a weird thing to look at. I would hope that the trauma center didn’t have to repeat any of their own scans within 4 hours!)

Bottom line: It is critically important for referring hospitals to use radiation wisely! First, if the patient has obvious injuries that require transfer, don’t scan, just send. If you need to scan to decide whether you can keep the patient, use the best ALARA* technique you can. And trauma centers, please send a copy of your CT protocols to your referring hospitals so they can get the best images possible.

*ALARA = As low as reasonably achievable (applied to radiation exposure). Also known as ALARP outside of North America (as low as reasonably practicable). Click here for more info.

Related posts:

Reference: Computed tomography before transfer to a level I pediatric trauma center risks duplication with associated radiation exposure. J Pediatric Surg 43(12): 2268-2272, 2008.