How helical CT helps the surgeon in oculo-orbital trauma

Retrospective Cohort Study of Frequency and Patterns of Orbital Injuries on Whole-Body CT with Maxillofacial Multi-Slice CT

Background: High-impact trauma frequently leads to injuries of the orbit, but literature focusing on the viscerocranium rather than the neurocranium is underrepresented. Methods: Retrospective cohort study (2006–2014) at an urban level 1 trauma center assessing the frequency and typical patterns of orbital injuries on whole-body computed tomography (WBCT) with maxillofacial multi-slice CT (MSCT) after severe trauma. (1) Screening of consecutive WBCT cases for dedicated maxillofacial MSCT. (2) Examination by two independent experts’ radiologists for (peri-/)orbital injuries. (3) Case review for trauma mechanisms. Results: 1061 WBCT were included revealing 250 (23.6%) patients with orbital injuries. Less than one-quarter (23.3%) of patients showed osseous and 9.5% showed soft tissue injuries. Combined osseous and soft tissue lesions were present in 39.2% of orbital injuries, isolated soft tissue injuries were rare. Single- or two-wall fractures of the orbit were prevalent, and the orbital floor was affected in 67% of fractures. Dislocated extraocular muscles (44.6%), deformation of the ocular globe (23.8%), and elongation of the optic nerve (12.9%) were the most frequently soft tissue findings. Vascular trauma was suspected in 15.8% of patients. Conclusions: Orbital trauma was confirmed in 23.6% of cases with suspected facial injuries after severe trauma. Concomitant soft tissue injuries should be excluded explicitly in cases with orbital fractures to prevent loss of vision or ocular motility.

Quality of CT Imaging of Periocular Metallic Foreign Bodies Using Artifact Reduction Software

PURPOSE

CT is the standard of care for assessment of ocular and orbital trauma; however, artifacts from metallic foreign bodies can limit the utility of CT. The authors hypothesize that implementation of metal artifact reduction techniques can improve image quality and diagnostic confidence for a diverse group of interpreters.

METHODS

A case series of ten subjects with retained periocular metallic foreign bodies imaged with CT were identified retrospectively from a large urban trauma center. Postacquisition images were processed with an iterative-based metal streak artifact reduction software. The severity of the metal streak artifact was assessed by clinicians including radiologists (4), ophthalmologists (4), and oculoplastic specialists (3) using a numeric scale to grade images on seven clinically relevant criteria. Each image was also analyzed to measure the size of the artifact and degree of streaking.

RESULTS

Overall confidence in diagnosis and severity of metallic streak was improved with metallic artifact reduction (p < 0.001, Wilcoxon signed-rank test). Similarly, confidence in assessing specific features-including extra-ocular muscle, optic nerve, globe rupture, orbital fracture and identification of foreign bodies-was improved after metallic artifact reduction (p < 0.001, Wilcoxon signed-rank test). The standard deviation of pixel intensity for a path surrounding the foreign body as well as the area of the streak artifact decreased in the metallic artifact reduction-processed images (p < 0.001, paired t test).

CONCLUSIONS

Metal artifact reduction in CT has potential benefits in improving image quality and reader confidence for periocular trauma cases in real-world settings.

Diagnostic performance of isolated orbital CT scan for assessment of globe rupture in acute blunt facial trauma

OBJECTIVES

We determine the diagnostic performance of emergent orbital computed tomography (CT) scans for assessing globe rupture in patients with blunt facial trauma.

METHODS

We performed a retrospective cohort study based on prospectively collected trauma registry and acute care surveillance data in a tertiary-care hospital. Patients aged at least 18 years who underwent isolated orbital CT scanning for assessing potential ocular trauma were examined. Analyses were performed to evaluate the magnitude of agreement between diagnosis by CT scanning and ophthalmic assessment, including globe rupture.

RESULTS

Our study cohort comprised 136 patients, 30% of whom (41 patients) sustained orbital wall fractures. Concordance for orbital CT diagnosis and the ophthalmic assessment of globe rupture was substantial (k=0.708). The relative risk of globe rupture was 0.692 (95% confidence interval (CI): 0.054-8.849) for superior wall fractures, 0.459 (95% CI: 0.152-1.389) for inferior wall fractures, 2.286 (95% CI: 1.062-4.919) for lateral wall fractures, and 0.637 (95% CI: 0.215-1.886) for medial wall fractures. According to multivariate analysis, lateral wall fractures were an independent risk factor for globe ruptures (adjusted odds ratio (OR)=12.01, P=0.011), and medial or inferior wall fracture was a protective factor (adjusted OR=0.14, P=0.012). In the stratified analysis of diagnostic performance of CT scan, specificity was highest among patients with orbital wall fractures (97.2%), followed by negative predictive volume (NPV, 97%), and accuracy (95.1%).

CONCLUSION

Among patients with blunt facial trauma who underwent isolated orbital CT scanning as part of ocular trauma assessment, the diagnostic performance of CT in detecting globe rupture is more accurate in patients with orbital wall fractures. Nevertheless, isolated orbital CT alone does not have a sufficiently high diagnostic performance to be reliable to rule out all globe ruptures. Lateral orbital wall fractures in blunt facial trauma patients, in particular, should prompt thorough evaluation by an ophthalmologist.

Abnormalities of the globe

Although much has been published in the radiology literature on the multitudinous conditions affecting the bony orbit, there has been relatively little on diseases confined to the globe itself. As current cross-sectional imaging techniques evolve, the globes can be visualized in ever greater detail, facilitating the recognition of even fairly subtle disease entities in this region. Indeed, the fact that high-resolution detailed images of this area are achievable without significant time or radiation penalty when evaluating surrounding structures means that incidental disease is not infrequently encountered. As such, common disease entities in this region are of interest to the general radiologist and the diagnosis of globe disease need not be the remit of experienced observers in specialist centres. At our institutions we have recently encountered a number of cases covering a broad spectrum of diagnoses including traumatic, neoplastic, iatrogenic, inflammatory, and infective aetiologies. The purpose of this review is to briefly revise the pertinent anatomical and physiological properties of the globe and to familiarize the reader with the computed tomography (CT) and magnetic resonance imaging (MRI) appearances of a number of these disease states. The collection of abnormalities included is not intended to be exhaustive, merely representative, with the emphasis towards those more commonly encountered.