Multislice CT transforms trauma patient management

November 1, 2005

The ability of multislice CT to detect trauma more accurately than alternative methods is profoundly affecting the management of trauma patients. Its speed and accuracy strengthen the case for radiologists to become team leaders in the emergency setting, according to Dr. Otto Chan, a consultant radiologist at the Royal London Hospital.

The ability of multislice CT to detect trauma more accurately than alternative methods is profoundly affecting the management of trauma patients. Its speed and accuracy strengthen the case for radiologists to become team leaders in the emergency setting, according to Dr. Otto Chan, a consultant radiologist at the Royal London Hospital.

Traditionally, surgeons have directed the care of trauma patients, but their diagnostic knowledge and awareness of interventional radiology may not be up to date, Chan said at the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) meeting in Florence. In cases of blunt major trauma, patients may be under the influence of alcohol or require intubation, making clinical examinations unreliable and of limited value.

Some surgeons initially referred to a CT scanner as the "doughnut of death," but it saves lives and enables many patients to avoid surgery, Chan said.

In particular, MSCT is transforming bowel trauma. Images can be obtained within one minute of the patient's arrival in the accident and emergency unit. Sixteen-slice CT with 0.4-second scans produces about 2400 slices per minute, while new 64-slice scanners yield 9600 slices a minute. Whole-body CT can thus be performed in less than 30 seconds with 2 to 3-mm sections.

"You should really be looking at all these images in the coronal plane because you can see the whole image three to four times faster and get a better overview of what the surgeon is looking at," Chan said. "With so many slices, you're going to have to look a lot more carefully. I suspect that the more experienced the radiologist, the greater the number of injuries will be detected."

Findings on MSCT can be subtle and therefore challenging, and the emphasis on speed often leaves insufficient time to administer contrast agents. The best approach may be to delay contrast administration and, if necessary, repeat the scan with contrast, he said.

Patients transported to the Royal London by rescue helicopter undergo mobile ultrasound scans administered en route by paramedics and are taken directly to the CT suite on arrival. Chan recommends that patients be resuscitated in the CT scanning suite to save time and resources. A 64-slice system was installed at the Royal London in June, and another will be operational by the end of the year.

Ultrasound continues to play an important role in primary survey imaging, as it can detect free intraperitoneal fluid, check the pleural space, and exclude a pericardial tamponade. It is not organ-specific, however, and its role is limited if it is not high definition, Chan said.

Trauma care is a dynamic process that frequently requires repeated imaging of patients. Teamwork, good communication, and availability of data are essential, said Prof. Robert F. Dondelinger of the department of medical imaging at the University Hospital of Liege, Belgium, and president of ESGAR.

"Speed is of paramount importance in trauma; a patient often must be diagnosed and treated within an hour. The emergency room is not the place where internal conflicts of the hospital should be fought. It has to be a peaceful place," Dondelinger said.

Ergonomics are important in the trauma setting. The ER should be at least 60 square meters in size and provide adequate viewing stations for orthopedic surgeons, neurosurgeons, and other personnel.

On arrival at University Hospital, trauma patients are classified into three categories: unstable, marginally stabilized, and stable or fully stabilized.

Patients frequently become unstable during a scan, Dondelinger said. Clinical signs of decompensation are unpredictable, especially in children, and compensation of normal blood pressure before sudden shock may occur. The cumulative effect of associated injuries can influence a patient's survival.

Radiologists should be watchful for hypothermia in trauma patients, which can lead to metabolic acidosis and washout coagulopathy that may complicate hemostatic embolization.

"Be prepared to interrupt imaging in patients who become decompensated. Don't rely too much on imaging. The clinical aspects are also quite important," he said. "Hypothermia is always a threat."

Dondelinger urged radiologists to remember two golden rules: Finding internal bleeding is the essential task, and patients can be "diagnosed to death." He recommended minimizing the time spent transporting patients.

Ultrasound units should have color Doppler capability and probes for small body parts. The modality's sensitivity varies greatly, depending on the specific organ that is injured. It may be 35% sensitive for the gastrointestinal tract and 70% sensitive for duodenopancreatic injuries. Sensitivity is even lower for unstable patients, which limits its usefulness, he said.

MRI is beneficial in orthopedic cases and should be available around the clock, Dondelinger said. It can confirm the stability of fractures by demonstrating injuries of the spinal ligaments, and it identifies cord injuries and compression.

CT makes a valuable contribution to the immediate assessment of multitrauma cases (Figures 1 and 2). It guides and orients angiography, and the two modalities combined can reveal occult internal bleeding and its source.

According to researchers at the University of Bern in Switzerland, 16-slice CT shortens ER examination times and provides superior image quality. In a study published in the July issue of the American Journal of Roentgenology, Dr. Jan Gralla and colleagues enrolled 503 consecutive ER patients who underwent 16-slice CT scanning. The investigators measured time intervals and image quality and tried an innovative "feet-first" setting to scan multitrauma patients. Their dedicated 16-slice unit reduced examination times, while maintaining high-level image resolution.

Patient positioning averaged eight minutes, depending on the body region examined. In multitrauma patients, initial positioning and repositioning took a mean of six minutes and eight minutes, respectively. Fifty-six patients also underwent CT angiography, requiring a mean room time of 21 minutes. Gralla and colleagues compared results with existing data from a similar clinical setting using a four-slice CT scanner. In the earlier study, room time for scanning single body regions ranged from 11 to 22 minutes.

ER scanning protocols for 16-slice CT were standardized by body regions, including head, cervical spine, abdomen, pelvis, extremities, and thorax. Protocols for CT were sequential/ helical mode, 0.5 to 1.5-sec rotation time, 0.75 to 1.5-mm collimation, five to 30-sec approximate scanning time (depending on region size), pitch of 1, 1.3, or 2, and 6 to 30-mm table speed rotation.

Most ERs scan multitrauma patients in a head-first position, which allows fast scanning but at the expense of imaging artifacts from arm positioning and clinical hardware attached to the body. The Bern team used a head-first approach only for head and cervical spine cases. Although the feet-first position was time-consuming, the procedure showed potential to significantly reduce artifacts and improve image quality.

The investigators faced several problems: CTA studies proved particularly lengthy; some patients became too restless and uncooperative for scanning because of the nature of their injuries; and malfunctioning equipment occasionally caused examination delays, although this was rare.

The results might reflect a learning curve, as the evaluation of time intervals for scanning in the ER began shortly after installation of the 16-slice scanner. Future studies should compare different types of MSCT scanners in similar settings, the researchers said. Further advances should focus on transportation and positioning equipment to take advantage of the quality and speed of the newest generation of 16-slice CT scanners.