Category Archives: Imaging

Abstracts, Imaging

Best Of EAST 2023 #8: Use Of AI To Detect Rib Fractures On CT

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Artificial intelligence systems (AI) are increasingly finding their way into medical practice. They have been used to assist pathologists in screening microscope specimens for years. Although still amazingly complicated, one of the most obvious applications for trauma is in reading x-rays. Counting rib fractures may be helpful for care planning, and characterizing fracture patterns may assist our orthopedic colleagues in evaluating and planning rib plating procedures.

The trauma group at Stanford developed a computer vision system to assist in identifying fractures and their percent displacement.  They used a variation on a neural network deep learning system and trained it on a publicly available CT scan dataset.  They used an index of radiographic similarity (DICE score) to test how well their model matched up against the reading of an actual radiologist.

Here are the factoids:

  • The AI network was trained on a dataset of 5,000 images in 660 chest CT scans that had been annotated by radiologists
  • The model achieved a DICE score of 0.88 after training
  • With a little jiggering of the model (reweighting), the receiver operating characteristic curve improved to 0.99, which is nearly perfect

The left side shows a CT scan rotated 90 degrees; the right side shows the processed data after a fracture was detected.

Bottom line: This paper describes what lies ahead for healthcare in general. The increasing sophistication and accuracy of AI applications will assist trauma professionals in doing their jobs better. But rest easy, they will not take our jobs anytime soon. What we do (for the most part) takes very complex processing and decision making. It will be quite some time before these systems can do anything more that augment what we do.

Expect to see these AI products integrated with PACS viewing systems at some point in the not so distant future. The radiologist will interpret images in conjunction with the AI, which will highlight suspicious areas on the images as an assist. The radiologist can then make sure they have reported on all regions that both they and the AI have flagged.

Here are my questions and comments for the presenter/authors:

  • How can you be sure that your model isn’t only good for analyzing your training and test datasets? If neural networks are overtrained, they get very good at the original datasets but are not so good analyzing novel datasets. Have you tried the on your own data yet?
  • Explain what “class reweighting” is and how it improved your model. I presume you used this technique to compensate for the potential issue mentioned above. But be sure to explain this in simple terms to the audience.
  • Don’t lose the audience with the net details. You will need to give a basic description of how deep learning nets are developed and how they work, but not get too fancy.

This is an interesting glimpse into what is coming to a theater near you, so to speak. Expect to see applications appearing in the next few years.

Reference: AUTOMATED RIB FRACTURE DETECTION AND CHARACTERIZATION ON COMPUTED TOMOGRAPHY SCANS USING COMPUTER VISION. EAST 2023 Podium paper #16.

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Abstracts, Imaging

Best Of EAST 2023 #7: The CT Autopsy

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Back in the day, autopsy after trauma death was fairly commonplace. Nowadays, it is typically reserved for fatalities that involve a potential crime. And it can be challenging to get the medical examiner to release copies for trauma performance improvement.

One potential remedy for this began to surface in the literature about twenty years ago: the virtual (or CT) autopsy. This entails sending the postmortem patient to the scanner for head, cervical, chest, and pelvic scans. Although it seems like an exciting idea, there are several logistical issues that I will discuss later.

The trauma group at Indiana University performed a retrospective study to determine the common injury patterns in patients who died at or up to one hour after ED arrival. Their goal was to identify injury patterns that might improve the focus and quality of resuscitative efforts in living patients. They reviewed their experience with doing postmortem CT over a nine-year period. The primary goal was to identify sources of hemorrhage, TBI, and cervical spine injury. They also wanted to identify significant pneumothorax and misplaced airway devices.

Here are the factoids:

  • There were 80 decedents in the study, and they were severely injured, with an average ISS of 42
  • About three quarters arrested prior to arrival, and the remainder arrived with a pulse
  • The most common major injuries were severe TBI (41%), long bone fractures (25%), hemoperitoneum (23%), and cervical spine injury (19%)
  • A moderate pneumothorax was present in 19% of cases
  • Misplaced airway was identified in 5%
  • There was no difference in injury or device mishap patterns between pre-hospital and in-hospital arrest patients (although the number of patients was probably too small to detect one)

The authors concluded that the injury patterns between those who died prior to arrival vs. after were the same. They also noted that patients in arrest should automatically have their chest decompressed and the airway position checked.

Bottom line: This is an intriguing study of a concept I’ve been thinking about for years. The quality improvement benefits could be amazing! Imagine getting immediate feedback on the cause of death and how it might influence future resuscitations. The authors pointed out the power of this with their discovery of missed pneumothorax and malpositioned airways.

But, as mentioned above, there are a host of logistical problems to work out first. Here is a partial list:

  • Who accompanies the patient to scan? A nurse? The team?
  • Covered or uncovered? It might be creepy for people in the hallways to see a covered person being wheeled around. That’s why hospitals always have those white, wheeled boxes. But it’s equally creepy to see a person who is not moving or breathing being transported.
  • Be prepared for your radiologists to gripe about doing free reads
  • Where does the report go? It shouldn’t go to the medical record. Or should it?
  • What about liability issues? If the team misses something big and the report goes to the chart, it’s fair game for a lawsuit.
  • And many more!

Here are my questions and comments for the presenter/authors:

  • How did you come to do this study? It appears that your group has been performing CT autopsies for almost a decade. Was there a protocol? Was it done on every eligible patient? If not, could this have skewed your results?
  • Do you have the statistical power to detect any differences between the various groups? A few of your results did approach significance. Perhaps more subjects would have helped.
  • Tell us how you have addressed the logistical problems above.

This is great work; perhaps it will stimulate a move toward embracing this concept!

Reference: CHARACTERIZATION OF FATAL BLUNT INJURIES USING POST-MORTEM COMPUTED TOMOGRAPHY. EAST 2023 Podium paper #14.

 

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Abstracts, Guidelines, Imaging

Best Of EAST 2023 #5: Imaging The Elderly

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Several papers have been published over the years regarding underdiagnosis when applying the usual imaging guidelines to elderly trauma patients. Unfortunately, our elders are more fragile than the younger patients those guidelines were based on, leading to injury from lesser mechanisms. They also do not experience pain the same way and may sustain serious injuries that produce no discomfort on physical exam. Yet many trauma professionals continue to apply standard imaging guidelines that may not apply to older patients.

EAST sponsored a multicenter trial on the use of CT scans to minimize missed injuries. Eighteen Level I and Level II trauma centers prospectively enrolled elderly (age 65+) trauma patients in the study over one year. Besides the usual demographic information, data on physical exams, imaging studies, and injuries identified were also collected. The study sought to determine the incidence of delayed injury diagnosis, defined as any identified injury that was not initially imaged with a CT scan.

Here are the factoids:

  • Over 5,000 patients were enrolled, with a median age of 79
  • Falls were common, with 65% of patients presenting after one
  • Nearly 80% of patients actually sustained an injury (!)
  • Head and cervical spine were imaged in about 90% of patients, making them the most common initial studies
  • The most commonly missed injuries involved BCVI (blunt carotid and vertebral injury) or thoracic/lumbar spine fractures
  • 38% of BCVI injuries and 60% of T/L spine fractures were not identified during initial imaging
  • Patients who were transferred in, did not speak English, or suffered from dementia were significantly more likely to experience delayed diagnosis

The authors concluded that about one in ten elderly blunt trauma patients sustained injuries in body regions not imaged initially. They recommended the use of imaging guidelines to minimize this risk.

Bottom line: Finally! It has taken this long to perform a study that promotes standardizing how we perform initial patient imaging after blunt trauma. Granted, this study only applies to older patients, but the concept can also be used for younger ones. The elderly version must mandate certain studies, such as head and the entire spine. Physical exams can  still be incorporated in the guidelines for younger patients but not the elderly.

The overall incidence of BCVI was low, only 0.7%. But its presence was missed in 38% of patients, setting them up for a potential  stroke. Some way to incorporate CT angiography of the neck will need to be developed. The risk / benefit ratio of the contrast load vs. stroke risk will also have to be determined.

Here are my questions and comments for the presenter/authors:

  • Did you capture all of the geriatric patients presenting to the study hospitals? By my calculation, 5468 patients divided by 18 trauma centers divided by 14 months of study equals 22 patients enrolled per center per month. Hmm, my center sees more than that number of elderly injured patients in the ED per day! Why are there so few patients in your study? Were there some selection criteria not mentioned in the abstract?
  • Why should we believe these study numbers if you only included a subset of the total patients that were imaged?

My own reading of the literature leads me to believe that your conclusions are correct. I believe that all centers should develop or revise their elderly imaging guidelines to include certain mandatory scans regardless of how benign the physical exam appears. Our elders don’t manifest symptoms as reliably as the young. But the audience needs a little more information to help them understand some of the study numbers.

Reference: SCANNING THE AGED TO MINIMIZE MISSED INJURY, AN EAST MULTICENTER TRIAL. EAST 2023 podium abstract #12.

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Abstracts, Imaging

Best of AAST 2022 #4: The “Hybrid ER” – Again?

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Two years ago, an abstract was presented at this meeting describing the concept of the “hybrid ER.” Check it out using this link. This concept was pioneered in Japan, and consists of a special trauma resuscitation room in the ED with everything but an operating room built into it. It’s possible to perform whole-body CT scan, interventional procedures, and REBOA without moving the patient. Here’s a picture from that abstract:

A = CT scanner   B = CT exam table   C = movable C-arm   D = monitor screen   E = ultrasound   F = ventilator

In that abstract, about a thousand patients were compared with two thirds in the hybrid ER group and one third undergoing conventional evaluation. The authors concluded that mortality was significantly improved in the hybrid ER group, and even more so in high ISS patients.

I had a lot of questions for that abstract that were answered in the subsequently published manuscript (reference 2). The authors have updated their experience using new data from the last five years. They created a new approach to resuscitation that is different than the usual ATLS sequence for select patients. Here’s the algorithm they used:

The primary survey is completed, then the patient undergoes a quick whole body CT scan. After that, the secondary survey progresses and any necessary emergency procedures are performed.

In this abstract, the authors compared a group of 46 patients who underwent standard ATLS evaluation with 49 who received the expedited process, which they termed CT First Resuscitation (CTFR). All patients had presumptive hemorrhagic shock based on prehospital vital signs. The authors analyzed injury patterns, interventions performed, timing, adverse events, and outcome. Demographics and injury severity were similar in the two groups.

Here are the factoids:

  • Time to CT in the CTFR group was significantly shorter (1.5 min vs 15 min)
  • The expedited scan settings for CTFR resulted in blindingly fast scan times (median 56 seconds)
  • None of the CTFR patients decompensated during the scan process
  • There was no difference in mortality between CTFR and standard evaluation (14% vs 4%, p=.1)
  • There was no difference in time to hemostatic intervention (56 vs 59 minutes)
  • There was no difference in red cell transfusions (no units in either group)

The authors concluded that CTFR expedited trauma management without adverse effects, and there was no increase in mortality. They, or course, recommended further study.

Bottom line: Several trauma surgeons from a variety of centers wrote an invited commentary last year (reference 3) expressing their excitement about this concept. Reducing time to definitive control of hemorrhage has been repeatedly shown to improve survival. The hybrid ER is one way of reducing those times by eliminating most of the time needed to move the patient about and providing everything but an operating room in the emergency department.

But they also recognized the limitations of this concept. The changes to the ED physical plant are extreme and involve the installation of very expensive equipment that must be heavily shielded from the rest of the emergency department. There are also significant differences in physician training and hospital reimbursement between Japan and the US. This will probably severely limit the adoption of this technology in the States.

I believe that this is an important study showing the feasibility of this method of evaluation. Unfortunately, it does not allow us to draw any real conclusions about safety and efficacy due to the low numbers of patients enrolled. I agree with the authors that a larger study should be performed so we can truly determine whether this concept can possibly be applied outside of Japan.

Here are my questions for the authors / presenter:

  1. Did you perform a power analysis? I doubt that the sample size reported would allow for any findings of statistical significance with the exception of huge differences like time to CT.
  2. How do you protect the trauma team from radiation exposure? Since these patients are in shock when they arrive, I assume that the team cannot leave the room. CT scan radiation exposure of the team is significantly higher than a chest and pelvis x-ray. Repeated team exposure may pose risks.
  3. Does the trend toward higher mortality in the CTFR group trouble you? Sure, it is not statistically significant. But it is approaching significance with a small sample group.
  4. Why didn’t the CTFR group have more rapid hemostatic intervention? One would think these early results could help move the patient to an OR more quickly. And why did it take an hour? Isn’t that a long time?
  5. Why didn’t your patients receive any blood? Weren’t they supposed to be at risk for hemorrhagic shock? How did you treat it without blood? Perhaps your selection criteria need to be tweaked.

This is a nice follow on study from the previous presentation two years ago. It could be an exciting advance in resuscitation, but we need much more info to pass judgement. I’m looking forward to the presentation.

References:

  1. COMPUTED TOMOGRAPHY FIRST RESUSCITATION WITH HYBRID EMERGENCY ROOM FOR SEVERELY INJURED PATIENTS. Plenary paper #25, AAST 2022.
  2. Hybrid emergency room shows maximum effect on trauma resuscitation when used in patients with higher severity. J Trauma Acute Care Surg. 2021 Feb 1;90(2):232-239.
  3. Time to Hemorrhage Control in a Hybrid ER System: Is It Time to Change? Shock. 2021 Dec 1;56(1S):16-21.
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Imaging

MRI And External Fixators

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MRI is an indispensable tool for evaluation of spine and soft tissue trauma. However, a great deal of effort was be made to ensure that any patient scheduled for this test is “MRI compatible.” The fear is that any retained metallic fragments may move or heat up once the magnets are activated.

But what about trauma patients with external fixators? That is one big hunk of metal that is inserted deep into your patient. There are three major concerns:

  • Is the material ferromagnetic? If so, it will move when the magnets are activated and may cause internal injury. These days, there are many fixator sets that are not ferromagnetic, avoiding this problem.
  • Can currents be induced in the material, causing heating? This is not much of a problem for small, isolated objects. However, external fixators are configured in such a way that loops are created. The fluctuating magnetic fields can induce currents that in turn will heat the surrounding tissue. And thinner materials (narrow pins) result in more current and more heating.
  • Will the metal degrade image quality?

The biggest challenge is that there is no standard ex-fix configuration. Our orthopaedic colleagues get to unleash their creativity trying to devise the appropriate architecture to hold bones together so they can heal properly. This makes it difficult to develop standardized guidelines regarding what can and can’t go into the scanner.

However, there is a growing body of literature showing that the heating effects are relatively small, and get smaller as the distance from the magnet increases. And non-ferromagnetic materials move very little, if at all, and do not interfere with the image. So as long as nonferromagnetic materials are used, the patients are probably safe as long as basic principles are adhered to:

  • Other diagnostic options should be exhausted prior to using MRI.
  • Informed consent must be obtained, explaining that the potential risks are not completely understood.
  • The fixator must be tested with a handheld magnet so that all ferromagnetic components can be identified and removed.
  • All traction bows must be removed.
  • Ice bags are placed at all skin-pin interfaces.
  • The external fixator must remain at least 7cm outside the bore at all times.

Bottom line: MRI of patients with external fixators can be safely accomplished. Consult your radiologists and physicists to develop a policy that is specific to the scanners used at your hospital. 

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