Magnetic Resonance Imaging: An Accurate, Radiation-Free, Alternative to Computed Tomography for the Primary Imaging and Three-Dimensional Reconstruction of the Bony Orbit

doi:10.1016/j.joms.2013.08.030

Journal of Oral and Maxillofacial Surgery

Volume 72, Issue 3, March 2014, Pages 611-618

https://doi.org/10.1016/j.joms.2013.08.030 Get rights and content

Purpose

To determine the extent to which the accuracy of magnetic resonance imaging (MRI) based virtual 3-dimensional (3D) models of the intact orbit can approach that of the gold standard, computed tomography (CT) based models. The goal was to determine whether MRI is a viable alternative to CT scans in patients with isolated orbital fractures and penetrating eye injuries, pediatric patients, and patients requiring multiple scans in whom radiation exposure is ideally limited.

Materials and Methods

Patients who presented with unilateral orbital fractures to the Royal Brisbane and Women's Hospital from March 2011 to March 2012 were recruited to participate in this cross-sectional study. The primary predictor variable was the imaging technique (MRI vs CT). The outcome measurements were orbital volume (primary outcome) and geometric intraorbital surface deviations (secondary outcome) between the MRI- and CT-based 3D models.

Results

Eleven subjects (9 male) were enrolled. The patients' mean age was 30 years. On average, the MRI models underestimated the orbital volume of the CT models by 0.50 ± 0.19 cm³. The average intraorbital surface deviation between the MRI and CT models was 0.34 ± 0.32 mm, with 78 ± 2.7% of the surface within a tolerance of ±0.5 mm.

Conclusions

The volumetric differences of the MRI models are comparable to reported results from CT models. The intraorbital MRI surface deviations are smaller than the accepted tolerance for orbital surgical reconstructions. Therefore, the authors believe that MRI is an accurate radiation-free alternative to CT for the primary imaging and 3D reconstruction of the bony orbit.

Section snippets

Study Design/Sample

To address the research purpose, the authors designed and implemented a cross-sectional study. The study population was composed of selected patients presenting to the maxillofacial outpatient clinic at the Royal Brisbane and Women's Hospital (Brisbane, QLD, Australia) for the evaluation and management of fractures involving the bony orbit from March 2011 through March 2012. To be included in the study sample, patients were required to have had a clinical CT scan that included the bony orbit as

Results

Eleven patients (9 male, 2 female; mean age, 30 ± 7.1 yr) were recruited for this study. The main outcome measurements (orbital volume, intraorbital surface deviations) of this study are presented in Table 1.

On average, the volume of the MRI-based models deviated by 0.50 ± 0.19 cm³ from the CT-based models. The volumetric differences ranged from 0.23 to 0.85 cm³. All MRI models underestimated the volume of the CT models. Statistically, there was a significant difference (P < .05) between the

Discussion

The purpose of the present study was to investigate the feasibility of using MRI as an alternative to CT for the acquisition of morphologic data for subsequent virtual 3D reconstructions of the orbit. It was hypothesized that with a suitable scanning protocol the accuracy of MRI-based 3D reconstructions of the orbit could approach that of standard CT models. The specific goals of this study were to measure and compare differences in orbital volume and intraorbital surface geometry between MRI-

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Magnetic resonance imaging in paediatric ocular and orbital lesions: A pictorial review
2024, Current Problems in Diagnostic Radiology
Paediatric orbital lesions encompass a wide spectrum of benign and malignant entities that can arise from different components of the orbit. Clinical symptoms and signs are often nonspecific, and imaging plays a crucial role in the diagnosis and management. Ultrasonography has a limited role and radiation is a major concern with CT especially in the paediatric population. MRI is the modality of choice that avoids the radiation hazard and provides superior soft tissue contrast. The lesions can be localized using the ‘compartment’ approach which helps to narrow the list of differentials. MRI also provides critical information for management such as presence of perineural spread and intracranial extension. This article depicts the spectrum of Magnetic Resonance imaging findings encountered in paediatric ocular and orbital lesions.
Are Magnetic Resonance Imaging-Generated 3Dimensional Models Comparable to Computed Tomography-Generated 3Dimensional Models for Orbital Fracture Reconstruction? An In-Vitro Volumetric Analysis
2023, Journal of Oral and Maxillofacial Surgery
Magnetic resonance imaging (MRI) is being increasingly considered as an alternative for the evaluation and reconstruction of orbital fractures. No previous research has compared the orbital volume of an MRI-imaged, three-dimensional (3D), reconstructed, and virtually restored bony orbit to the gold standard of computed tomography (CT).
To measure the orbital volumes generated from MRI-based 3D models of fractured bony orbits with virtually positioned prebent fan plates in situ and compare them to the volumes of CT-based virtually reconstructed orbital models.
This retrospective in-vitro study used CT and MRI data from adult patients with orbital trauma assessed at the Royal Brisbane and Women's Hospital Outpatient Maxillofacial Clinic from 2011 to 2012. Only those with orbital blowout fractures were included in the study.
The primary predictor variable was imaging modality, with CT- and MRI-based 3D models used for plate bending and placement.
The primary outcome variable was the orbital volume of the enclosed 3D models.
Additional data collected was age, sex, and side of fractured orbit. The effect of operator variability on plate contouring and orbital volume was quantified.
The Wilcoxon signed rank test was used to assess differences between orbital volumes with a significance level P < .05.
Of 11 eligible participants, six patients (four male and two female; mean age 31 ± 8.6 years) were enrolled. Two sets of six CT-based virtually restored orbits were smaller than the intact contralateral CT models by an average of 1.02 cm³ (95% CI −0.07 to 2.11 cm³; P = .028) and 0.99 cm³ (95% CI 0.07 to 1.91 cm³; P = .028), respectively. The average volume difference between the MRI-based virtually restored orbit and the intact contralateral MRI model was 0.97 cm³ (95% CI −1.08 to 1.94 cm³; P = .75). Imaging modality did affect orbital volume difference for 1 set of CT and MRI models (0.63 cm³; 95% CI −0.11 to 1.29 cm³; P = .046) but not the other (0.69 cm³; 95% CI −0.11 to 1.23 cm³; P = .075). Single operator variability in plate bending did not result in significant (P = .75) volume differences.
MRI can be used to reconstruct orbital volume with a clinically acceptable level of accuracy.
Automatic Segmentation of Bone Selective MR Images for Visualization and Craniometry of the Cranial Vault
2022, Academic Radiology
Solid-state MRI has been shown to provide a radiation-free alternative imaging strategy to CT. However, manual image segmentation to produce bone-selective MR-based 3D renderings is time and labor intensive, thereby acting as a bottleneck in clinical practice. The objective of this study was to evaluate an automatic multi-atlas segmentation pipeline for use on cranial vault images entirely circumventing prior manual intervention, and to assess concordance of craniometric measurements between pipeline produced MRI and CT-based 3D skull renderings.
Dual-RF, dual-echo, 3D UTE pulse sequence MR data were obtained at 3T on 30 healthy subjects along with low-dose CT images between December 2018 to January 2020 for this prospective study. The four-point MRI datasets (two RF pulse widths and two echo times) were combined to produce bone-specific images. CT images were thresholded and manually corrected to segment the cranial vault. CT images were then rigidly registered to MRI using mutual information. The corresponding cranial vault segmentations were then transformed to MRI. The “ground truth” segmentations served as reference for the MR images. Subsequently, an automated multi-atlas pipeline was used to segment the bone-selective images. To compare manually and automatically segmented MR images, the Dice similarity coefficient (DSC) and Hausdorff distance (HD) were computed, and craniometric measurements between CT and automated-pipeline MRI-based segmentations were examined via Lin's concordance coefficient (LCC).
Automated segmentation reduced the need for an expert to obtain segmentation. Average DSC was 90.86 ± 1.94%, and average 95th percentile HD was 1.65 ± 0.44 mm between ground truth and automated segmentations. MR-based measurements differed from CT-based measurements by 0.73–1.2 mm on key craniometric measurements. LCC for distances between CT and MR-based landmarks were vertex-basion: 0.906, left-right frontozygomatic suture: 0.780, and glabella-opisthocranium: 0.956 for the three measurements.
Good agreement between CT and automated MR-based 3D cranial vault renderings has been achieved, thereby eliminating the laborious manual segmentation process. Target applications comprise craniofacial surgery as well as imaging of traumatic injuries and masses involving both bone and soft tissue.
Dynamic three-dimensional finite element analysis of orbital trauma
2021, British Journal of Oral and Maxillofacial Surgery
Citation Excerpt :
Orbital fractures represent more than 40% of midface fractures.1,2
This study comprises a dynamic finite element (FE) analysis of the mechanisms of orbital trauma, specifically buckling and hydraulic theories. A digital model of the orbital cavity - including the eyeball, fatty tissue, extraocular muscles, and the bone orbit – was created from magnetic resonance imaging and computed tomographic data from a real patient. An impactor hit the FE model following two scenarios: one was a hydraulic mechanism for direct impact to the eyeball and the other a buckling mechanism for direct impact over the infraorbital rim. The first principal stress was calculated to determine the stress distribution over the orbital walls. The FE model presented more than 900,000 elements and time of simulation was 4.8 milliseconds (ms) and 0.6 ms, for the hydraulic and buckling mechanisms, respectively. The stress distribution in the hydraulic mechanism affected mainly the medial wall with a high stress area of 99.08 mm², while the buckling mechanism showed a high stress area of 378.70 mm² in the orbital floor. The presence of soft tissue absorbed the energy, especially in the hydraulic mechanism. In conclusion, the applied method of segmentation allowed the construction of a complete orbital model. Both mechanisms presented results that were similar to classic experiments. However, the soft tissue in the hydraulic mechanism absorbed the impact, demonstrating its role in orbital pathophysiology.
Semi-automatic magnetic resonance imaging based orbital fat volumetry: reliability and correlation with computed tomography
2021, International Journal of Oral and Maxillofacial Surgery
Citation Excerpt :
A strong positive correlation has been shown between fat volume measurements on MRI and CT scan. A tendency for underestimation of fat volume in MRI is observed, which corresponds with findings by Schmutz et al. who compared the orbital volume on CT and MRI 14. The mean difference (1.3 cm3) in fat volume between MRI and CT is in agreement with earlier reports comparing the intact orbital cavity volume on CT and MRI (differences of up to 1.5 cm3), although the orbital cavity is probably easier to delineate than the fat tissue14,24.
Post-processing analysis can provide valuable information for diagnosis and planning of orbital disorders. This cross-sectional study aims to evaluate the reliability of semi-automatic, orbital fat volumetry using magnetic resonance imaging (MRI). Two observers assessed the orbital fat volume using a standard MRI protocol (3T, T1w sequence) in 12 orbits diagnosed with Graves’ orbitopathy (GO) and 10 healthy control orbits. MRI and computed tomography (CT) based analysis were compared. Intra-observer variability was good (intraclass correlation coefficient (ICC) 0.88; 95% confidence interval (CI) [0.70, 0.95]) and interobserver agreement was moderate (ICC 0.55; 95% CI [−0.09, 0.81]), which corresponds to a mean percentage difference of 1.3% and 17.9% of the total orbital fat volume. Mean differences between MRI and CT measurements were, respectively, 1.1 cm³ (P= 0.064, 95% CI [−0.20, 2.43]) and 1.4 cm³ (P=0.016, 95% CI [0.21, 2.56]) for the control and the GO group. MRI volumetry was strongly correlated with CT (Pearson’s r= 0.7, P<0.001). We conclude that orbital fat volumetry is feasible with a semi-automatic segmentation procedure and standard MRI protocol. Correlation with CT volumetry is good, but considerable bias may derive from observer variability and these errors should be taken into account for the purpose of volumetric analysis. Better definition of error sources may increase measurement accuracy.
Magnetic resonance imaging for three-dimensional printing of the bony orbit: is clinical use imminent?
2020, International Journal of Oral and Maxillofacial Surgery
Citation Excerpt :
A retrospective design was used, with MRI and CT data made available from a previous study6.
The aim of this study was to examine the accuracy of three dimensionally (3D) printed models of the bony orbit derived from magnetic resonance imaging (MRI) for the purpose of preoperative plate bending in the setting of orbital blowout fracture. Retrospective computed tomography (CT) and MRI data from patients with suspected orbital fractures were used. Virtual models were manually generated and analysed for spatial accuracy of the fracture margins. 3D-printed models were produced and orbital fan plates bent by a single operator. The plates were then digitized and analysed for spatial discrepancy using reverse engineering software. Seven orbital blowout fractures were evident in six orbits. Analysis of the virtual models revealed high congruence between blowout fracture margins on CT and MRI (n = 7, average deviation 0.85 mm). Three zygomaticomaxillary complex fractures were seen, for which MRI did not demonstrate the same accuracy. For plates bent to the 3D-printed models of blowout fractures (n = 6), no significant difference was found between those bent to CT versus those bent to MRI when compared for average surface and average border deviation (Wilcoxon signed rank test). Orbital blowout fractures can be defined on MRI with clinically acceptable accuracy. 3D printing of orbital biomodels from MRI for bending reconstructive plates is an acceptable and accurate technique.

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: This project (C-09-03S) was supported by Craniomaxillofacial Specialty of the AO Foundation. Dr Schmutz received an industrial scholarship from Synthes GmbH.

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Surgical oncology and reconstructionMagnetic Resonance Imaging: An Accurate, Radiation-Free, Alternative to Computed Tomography for the Primary Imaging and Three-Dimensional Reconstruction of the Bony Orbit

Purpose

Materials and Methods

Results

Conclusions

Section snippets

Study Design/Sample

Results

Discussion

Oral Surg Oral Med Oral Pathol Oral Radiol Endod

Comput Assist Radiol Surg

Int J Oral Maxillofac Surg

Injury

Int J Oral Maxillofac Surg

Int J Radiat Oncol Biol Phys

J Oral Maxillofac Surg

J Oral Maxillofac Surg

J Biomech

Med Eng Physics

Orbital reconstruction with individually copy milled ceramic implants

Plast Reconstr Surg

Surgical oncology and reconstruction
Magnetic Resonance Imaging: An Accurate, Radiation-Free, Alternative to Computed Tomography for the Primary Imaging and Three-Dimensional Reconstruction of the Bony Orbit