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.
Reference: Radiation exposure from diagnostic imaging in severely injured trauma patients. J Trauma 62(1):151-156, 2007.
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.
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.
In my previous post (click here to view) I discussed an imaging protocol that we developed and implemented last year. Today, I’ll detail what it has accomplished in our patients.
We looked at 229 patients who had their imaging performed according to the new protocol during a 3 month period and compared them to 215 patients who were imaged the previous year. Each scan administered to each body area (head, chest, abdomen/pelvis, c-spine, t-spine, l-spine, face, neck angio) were tabulated separately.
We found that the overall number of scans performed decreased significantly. We looked at our data and generated numbers per 100 patients. During the control period, we did 298 CT scans per 100 patients. This decreased to 271 during the study period. The number of head scans remained the same (82 per 100 patients during control, 85 per 100 during the study), as did the cervical spine scans (84 vs 86).
The biggest declines were seen in chest CT (53 per 100 control vs 33 per 100 study) and abdominal CT (57 vs 43).
We did see an increase in conventional xrays of the thoracic and lumbar spines to offset the absence of reformatted spine images that would have been generated from the chest and abdominal CT scans. We also noted small increases in CT of the head, cervical spine, and neck angio. This was likely due to better adherence to specific guidelines.
Bottom line: we believe that our work shows that careful adoption of well thought out guidelines can make a difference in practice and significantly decreases radiation exposure in our blunt trauma patients.
To read the post on this protocol, or to download it, click here.
Click here to download the Blunt Trauma Radiographic Imaging Protocol Worksheet
Last year, we developed an evidence-based protocol for deciding what radiographic images to order in our blunt trauma patients. For some body regions, there is fairly good literature available for guidance (i.e. Canadian head and cervical spine rules). For other areas, there is not nearly as much.
We convened a small group of people, including trauma surgeons, emergency physicians, radiologists and a radiation physicist to combine the information into a practical tool.
You can view or download the worksheet we use by clicking the link at the bottom of this post. The protocol has been in use for about 9 months, and has significantly decreased the use of higher radiation dose imaging (CT). As a result, there has been a small increase in the use of lower dose conventional imaging (plain spine studies), but no missed injuries.
Tomorrow, I’ll write about the specifics of how this protocol has changed our ordering habits. Click here to view it.
Click here to download the Blunt Trauma Radiographic Imaging Protocol Worksheet
Click here to download a bibliography of the literature used to develop the protocol
Trauma professionals worry about radiation exposure in our patients. A lot. There are a growing number of papers dealing with this topic in the journals every month. The risk of dying from cancer due to CT scanning is negligible compared to the risk from acute injuries in severely injured patients. However, it gets a bit fuzzier when you are looking at risk vs benefit in patients with less severe injuries. Is it possible to quantify this risk to help guide our use of CT scanning in trauma?
A nice paper from the Mayo clinic looked at their scan practices in 642 adult patients (age > 14) over a one year period. They developed dose estimates using a detailed algorithm, and combined them with data from the Biological Effects of Ionizing Radiation VII data. The risk level for injury was estimated using their trauma team activation criteria. High risk patients met their highest level activation criteria, and intermediate risk patients met their intermediate level activation criteria.
Key points in this article were:
- Average radiation dose was fairly consistent across all age groups (~25mSv)
- High ISS patients had a significantly higher dose
- Cumulative risk of cancer death from CT radiation averaged 0.1%
- This risk decreased with age. It was highest in young patients (< 20 yrs) at 0.2%, and decreased to 0.05% in the elderly (> 60 yrs)
Bottom line: Appropriate CT scan use in trauma evaluation is challenging. It’s use is widespread, and although it changes management it has not decreased trauma mortality. This paper shows that the risk of death from trauma in the elderly outweighs the risk of death from CT scan radiation. However, this gap narrows in younger patients with less serious injuries because of their very low mortality rates. Therefore, we need to focus our efforts to reduce radiation exposure on our young patients with minor injuries.
- Comparison of trauma mortality and estimated cancer mortality from computed tomography during initial evaluation of intermediate-risk trauma patients. J Trauma 70(6):1362-1365, 2011.
- Health risks from low levels of ionizing Radiation: BEIR VII, Phase 2. Washington DC: The National Academies Press, 2006.