Concordance Between Ultra-low Dose (ULD) and Standard Dose CT Scans in the Search for Traumatic Brain Injury

Concordance Between Ultra-low Dose (ULD) and Conventional Standard Dose CT Scans in the Search for Traumatic Brain Injury at the Emergency Department

The aim of this research is to evaluate the diagnostic concordance of ultra low-dose and standard dose reconstructed computed tomography acquisitions using the ADMIRE algorithm to search for intracranial lesions - both hemorrhagic and bone lesions - in trauma patients at the emergency department. The study will also evaluate the diagnostic performance of the two protocols, as well as the speed of image reading. For the first time, acquisitions ≤ 10 mGy (lower value than reported in the literature) will be performed with top-of-the-range scanners available in the emergency room to search for intracranial lesions. These scanners are equipped with the latest generation of ADMIRE iterative algorithms.

Head trauma is a common reason for consultation at the casualty department. The CT computed tomography scan is the standard examination leading to rapid patient management (admission to intensive care or neurosurgical management). The prevalence of traumatic lesions, intracranial bleeding or fractures, is estimated at 90% in moderate or severe head trauma patients, justifying the systematic use of a CT scan.

X-ray exposure from CT scanners is among the highest (order of May 23, 2019 for the Diagnostic Reference Levels, DRL). Radiation protection principles therefore require continuous optimization of acquisition procedures to ensure the lowest possible dose to the patient whilst maintaining satisfactory image quality for diagnosis. In recent years, technological innovations have been developed to optimize the dose delivered to the scanner, such as iterative reconstructions. Numerous studies on image quality and anthropomorphic phantoms and on cadavers have been performed at the imaging department of Nîmes University Hospital. Subsequently, feasibility studies have been conducted on patients, highlighting the use of the ultra low-dose scanner to detect common pathologies. These studies have made it possible to set up "ultra-low dose" acquisitions for several pathologies with an effective dose level close to a standard radiographic examination. These ultra low-dose acquisitions are now routinely used in our clinical practice for thoracic, spine, pelvis and proximal femurs, extremities and abdomino-pelvic explorations.

In the literature, some studies have explored the feasibility of ultra low-dose acquisitions for ear, nose and throat or skull explorations. Our study is in the context of evaluating ULD acquisitions for skull CT for traumatic intracranial lesions. The study by Corcuera-Solano et al. (2014) showed the feasibility of ULD acquisitions (Scanographic Dose Index in Volume, mean SDVI = 15.5 mGy) compared to standard acquisition (mean SDVI = 48.38 mGy) in the follow-up of a heterogeneous group of patients admitted to the neurosurgical intensive care unit, without evaluating the diagnostic performance of the two acquisitions. In this study, the Siemens scanner used was equipped with a 2nd generation iterative reconstruction algorithm (SAFIRE).

A 3rd generation algorithm has since been developed (ADMIRE) allowing an improvement in image texture, thus favoring the use of ultra low-dose acquisition for structures with lower spontaneous contrast such as the encephalon. We believe it would therefore be possible to search for intracranial lesions in trauma patients using ultra low-dose protocols, which should make it possible to reduce the doses delivered to the patient whilst maintaining sufficient image quality for diagnosis.

Inclusion Criteria:

• All patients in an emergency situation with a head trauma requiring a scan, i.e. moderate or severe skull trauma, Group 1 or 2 according to the Brain Trauma Task Force classification (Guidelines for management of severe head injury. J Neurotrauma 2000 ; 17 : 507-11) as described by P. Schoettker et al. 2001).
• Patient with an isolated skull trauma or polytraumatized patient including skull trauma.
• Patient capable of giving informed consent or for whom a person of confidence or legal representative / family member has given informed consent and signed the consent form on the patient's behalf if the patient has been included in an emergency.
• Patients affiliated to or beneficiary of a health insurance scheme.
• All adult patients aged 18 or over.

Exclusion Criteria:

• Patients already taking part in another study for which it is not allowed to participate in other clinical studies.
• Patients in an exclusion period determined by another study.
• Patients who are pregnant, breastfeeding or about to give birth.