A novel high-resolution magnetic resonance imaging microscopy coil as an alternative to the multislice computed tomography in postoperative imaging of orbital fractures and computer-based volume measurement.

Background: Multislice computed tomography (MSCT) has been the modality of choice for postoperative detailed imaging of orbital trauma. Unfortunately, it involves extensive exposition of the lens to radiation, especially when taking multiple readings. Also, it holds beam hardening effects and limited imaging (delineation) of the reconstruction material. Alternative conventional magnetic resonance imaging (MRI) head coils (MRIhc) present reduced differentiation of anatomic structures caused by low signal and artifact appearance. A substantially improved depiction is made possible by a newly introduced MRI microscopy coil (MRImc), used for the first time in this field.

Patients And Methods: In this prospective study, 32 patients with extended orbital wall fractures (n = 36) were treated surgically using a polydioxanonsulfate (PDS) foil after reconstruction. Postoperatively, imaging was performed using MRImc, conventional MRI, and MSCT to evaluate the different imaging techniques.

Results: The position of the PDS foil could precisely be depicted in 29 of 36 fractures by MRImc, whereas by conventional MRI and MSCT the reconstruction material could only be detected in 25 and 24 of 36 fractures, respectively. In contrast to MRIhc, the new microscopy coil allows fast and high resolution imaging and therefore a clear differentiation of eventual postoperative complications (eg, dislocation of the PDS foil with secondary soft tissue entrapment resulting in limitation of ocular movements or enophthalmos). In 13 long lasting symptomatic cases, revision surgery could be avoided because of regular MRImc findings, apart from muscle swelling and hematoma. In 11 cases of inadequate PDS foil position resulting in revision, the mean volume of displaced tissue (VDT) of 0.62 cm3 correlated significantly to an enophthalmos of more than 2 mm.

Conclusion: In this pilot study, MRImc proved to be highly superior to MRIhc and MSCT in postsurgical orbital imaging, especially for decision making regarding revision surgery.