The inappropriateness of conventional cephalometrics

1. Cephalometric conventions today may have little basis in either biology or biometrics. 2. There is no theory of cephalometrics, only conventions which involve landmarks and straight lines only. These fail to capture the curving of form and its changes, exclude proper measures of size for bent structures, and misrepresent growth, portraying it as vector displacement rather than a generalized distortion. 3. Conventional cephalometric procedures misinform by fabrication of misleading geometric quantities, by camouflage, particularly of remodeling, by confusion about what is happening (analysis of rotations, treating shape separately from size, and registering angles on landmarks as vertices), and by subtraction as a representation of growth. 4. We suggest that the present systems offer little real hope of improvement sufficient to meet our needs in craniofacial growth research. We call attention to three possible techniques to be included in future cephalometric conventions: (1) tangents and curvatures, (2) Blum's medial axis ("skeleton"), and (3) biorthogonal grids.

Digital three-dimensional photogrammetry: evaluation of anthropometric precision and accuracy using a Genex 3D camera system

OBJECTIVE

To determine the precision and accuracy of facial anthropometric measurements obtained through digital three-dimensional (3D) photogrammetry.

DESIGN

Nineteen standard craniofacial measurements were repeatedly obtained on 20 subjects by two independent observers, using calipers and 3D photos (obtained with a Genex 3D camera system), both with and without facial landmarks labeled. Four different precision estimates were then calculated and compared statistically across techniques. In addition, mean measurements from 3D photos were compared statistically with those from direct anthropometry.

RESULTS

In terms of measurement precision, the 3D photos were clearly better than direct anthropometry. In almost all cases, the 3D photo with landmarks labeled had the highest overall precision. In addition, labeling landmarks prior to taking measurements improved precision, regardless of method. Good congruence was observed between means derived from the 3D photos and direct anthropometry. Statistically significant differences were noted for seven measurements; however, the magnitude of these differences was often clinically insignificant (< 2 mm).

CONCLUSIONS

Digital 3D photogrammetry with the Genex camera system is sufficiently precise and accurate for the anthropometric needs of most medical and craniofacial research designs.

Reliability and validity of MRI measurement of the amygdala and hippocampus in children with fragile X syndrome

Evidence from numerous structural magnetic resonance imaging (MRI) studies has converged to implicate mesial temporal lobe structures in the pathophysiology of several developmental and psychiatric disorders. Efforts to integrate the results of these studies are challenged, however, by the lack of consistency, detail and precision in published protocols for the manual measurement of the amygdala and hippocampus. In this study, we describe a highly detailed, standardized protocol for measuring the amygdala and the hippocampus. Within the context of this protocol, we tested the inter- and intra-rater reliability of two frequently cited methods for normalizing the anatomical position of the amygdala and hippocampus prior to measurement. One method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the long axis of the hippocampus. The second method consisted of creating a coronal data set in which images are rotated in a plane perpendicular to the axis connecting the anterior and posterior commissures. Inter- and intra-rater reliability coefficients (using the intraclass correlation) ranged from 0.80 to 0.98, indicating that both methods for positional normalization are highly reliable. In addition, we tested the validity of each method by comparing the temporal lobe anatomy of children with fragile X syndrome to a group of unaffected children matched by age and gender. We found that hippocampal volumes in children with fragile X were significantly increased when either rotational method was used. These results replicated previous findings, suggesting that either method can be validly applied to neuronanatomic studies of pediatric populations.

The relationship between obesity and craniofacial structure in obstructive sleep apnea

STUDY OBJECTIVE

To evaluate the interaction between craniofacial structure and obesity in male patients with obstructive sleep apnea (OSA).

DESIGN

Retrospective analysis of a cohort of OSA patients. The relationships between neck circumference (NC), body mass index, apnea severity, and craniofacial and upper airway soft-tissue measurements from upright lateral cephalometry were examined. Patients were divided into groups; small to normal NC (group A), intermediate NC (group B), or large NC (group C).

SETTING

A university teaching hospital and tertiary sleep referral center.

PATIENTS

A consecutive series of patients with OSA who underwent polysomnography and lateral cephalometry.

MEASUREMENTS AND RESULTS

Group A patients were less obese and had more craniofacial abnormalities such as a smaller mandible and maxilla and a more retrognathic mandible. Group B patients had both upper airway soft-tissue and craniofacial abnormalities. Group C patients were more obese with larger tongues and soft palates, and an inferiorly placed hyoid. Group C patients also had fewer craniofacial abnormalities than group A or B patients. There was no difference in airway size among the three groups.

CONCLUSIONS

We conclude that there is a spectrum of upper airway soft-tissue and craniofacial abnormalities among OSA patients: obese patients with increased upper airway soft-tissue structures, nonobese patients with abnormal craniofacial structure, and an intermediate group of patients with abnormalities in both craniofacial structure and upper airway soft-tissue structures.

The reproducibility of natural head posture: a methodological study

Current clinical interest in natural head posture (NHP) derives from studies correlating NHP to craniofacial morphology, future growth trends, and to respiratory needs. It has also been argued that NHP is the logical reference and orientation position for craniofacial analysis and the publication of illustrations. The individual or group is presented as they naturally appear in life. Hence, lateral cephalometric radiographs recorded routinely in NHP would be more meaningful for the clinician. Underpinning all these potential clinical benefits is the incompletely answered question of the clinical reproducibility of NHP. In this study a natural head posture, the orthoposition, was defined and standardized for clinical use. The effects of ear posts, an external source of eye reference (a wall mirror), sex and time were evaluated in relation to the reproducibility of recording lateral cephalometric radiographs in this natural head posture. The sample comprised 217 randomly selected 12-year-old Chinese children in Hong Kong. Boys looked up more when changing from the self-balance position to the mirror eye reference position (mean change 2 degrees, P less than or equal to 0.001). No other significant male-versus-female differences were detected. NHP reproducibility was better with a mirror (with mirror, method error = 1.9 degrees, without mirror, method error = 2.7 degrees). No significant differences in reproducibility were detected between NHP recordings taken with and without ear posts. However, without ear posts the radiographs tended to be of poor quality. The reproducibility of same-day repeat radiographs recorded with ear posts and with a mirror (after 4 to 10 minutes and 1 to 2 hours) was 1.9 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional surface acquisition systems for the study of facial morphology and their application to maxillofacial surgery

BACKGROUND

There has been a growing interest in three-dimensional (3D) surface imaging devices over the last few years.

METHODS

This comprehensive review discusses the various emerging technologies in this field of 3D imaging and applies the use of technology to oral and maxillofacial imaging.

RESULTS

The paper shows that there is increased awareness and application of technology to the field.

CONCLUSION

3D surface acquisition technology is improving at a rapid pace and has a place in oral and maxillofacial surgery.

Reliability of measuring facial morphology with a 3-dimensional laser scanning system

INTRODUCTION

The purpose of this prospective clinical trial was to evaluate the reliability of a 3-dimensional facial scanning technique for the measurement of facial morphology.

METHODS

A field study was conducted in 2 comprehensive schools in the South Wales region of the United Kingdom. Forty subjects, mean age 11 years 3 months, were analyzed for soft tissue changes at baseline (T1), within 3 minutes (T2), and 3 days later (T3) by using 2 commercially available Minolta Vivid 900 (Osaka, Japan) laser-scanning devices assembled as a stereo pair. Left and right images were merged to form the whole face, and these images were superimposed to assess the errors at T1 and T2, and T1 and T3.

RESULTS

The results showed that premerged left and right mean shell deviations were 0.38 +/- 0.14 mm for scans at T1, 0.31 +/- 0.09 mm at T2, and 0.34 +/- 0.12 mm at T3. The mean differences of the merged composite face were 0.31 +/- 0.08 mm between T1 and T2, and 0.40 +/- 0.11 mm between T1 and T3. Paired t tests showed no significant difference between these groups (P > .05). Shell deviation facial maps of the merged scans showed that 90% of the created composite facial scans were within an error of 0.85 mm.

CONCLUSIONS

Capturing the soft tissue morphology of the face with this technique is clinically reproducible within 3 minutes and 3 days of the initial records.

Comparative localized linear accuracy of small-field cone-beam CT and multislice CT for alveolar bone measurements

OBJECTIVES

To compare the accuracy of cone-beam computerized tomography (CBCT) and multislice CT (MSCT) for linear jaw bone measurements.

STUDY DESIGN

An ex vivo formalin-fixed human maxilla was imaged with both CBCT (Accuitomo 3D; Morita, Kyoto, Japan) and MSCT (4-slice Somatom VolumeZoom and 16-slice Somatom Sensation 16; Siemens, Erlangen, Germany). The MSCT images were reconstructed using different reconstruction filters to optimize bone visualization (U70u and U90u for VolumeZoom, H30s and H60s for Sensation 16). Before scanning, triplets of small gutta-percha markers were glued onto the soft tissues overlying the maxillary bone on the top and on both sides of the alveolar ridge to define a set of reproducible linear measurements in 11 planes. Image measurements were performed by 2 observers. The gold standard was determined by means of physical measurements with a caliper by 3 observers.

RESULTS

The accuracy of the linear measurements was 0.35 +/- 1.31 mm (U70u) and 0.06 +/- 1.23 mm (U90u) for the Somatom VolumeZoom, 0.24 +/- 1.20 mm (H60s) and 0.54 +/- 1.14 mm (H30s) for the Sensation 16, and -0.09 +/- 1.64 mm for the Accuitomo 3D. Statistical analysis with 2-way analysis of variance showed no significant inter- or intraobserver disagreement for the physical or the radiologic measurements. There was also no significant difference for the measurements on the different reconstruction filters.

CONCLUSION

Both CBCT and MSCT yield submillimeter accuracy for linear measurements on an ex vivo specimen.

Accuracy of linear measurements from imaging plate and lateral cephalometric images derived from cone-beam computed tomography

INTRODUCTION

As orthodontic practice moves toward 3-dimensional cephalometric analyses, a solution is required to ensure sustained availability of well-established projected treatment outcomes based on 2-dimensional analyses. This ex-vivo study was conducted to compare the accuracy of linear measurements made on photostimulable phosphor cephalograms with 3 methods for simulating lateral cephalograms with cone-beam computed tomography (CBCT).

METHODS

The linear distances between anatomical landmarks on dentate dry human skulls were measured by observers using digital calipers for S-N, Ba-N, M-N, ANS-N, ANS-PNS, Pog-Go, Go-M, Po-Or, and Go-Co. The skulls were imaged with CBCT with a single 360 degrees rotation, producing 306 basis images and achieving 0.4 mm isotrophic voxel resolution on volumetric reconstruction for making ray-sum reconstructed cephalograms. Two other cephalogram approaches were used with the CBCT system--a single transmission image generated as a scout image designed to check patient positioning before CBCT, and a single-frame lateral basis image. Conventional digital lateral cephalograms (LCs) were acquired with the photostimulable phosphor system. Images were imported into a cephalometric analysis program (Dolphin Imaging Cephalometric and Tracing Software, Chatsworth, Calif) to compute the included linear measurements. Analyses were repeated 3 times and statistically compared with measured anatomic truth with ANOVA (P < or =.05). The intraclass correlation coefficient was determined as an index of intra- and interobserver reliability.

RESULTS

The intraclass correlation coefficient for the LCs was significantly less than for the measured anatomic truth and for all CBCT-derived images. CBCT images either produced with individual frames or reconstructed from the volumetric data set were accurate for all measurements except Pog-Go and Go-M. CBCT scout images had the second highest accuracy for all measurements except Pog-Go, Go-M, and Go-Co. Conventional LCs had the least accuracy; they were accurate only for Po-Or and ANS-N.

CONCLUSIONS

CBCT-derived 2-dimensional LCs proved to be more accurate than LCs for most linear measurements calculated in the sagittal plane. No advantage was found over single-frame basis images in using ray-sum generated cephalograms from the CBCT volumetric data set.

Reliability of a 3D surface laser scanner for orthodontic applications

A device for recreating three-dimensional (3D) objects on a computer is the surface laser scanner. By triangulating distances between the reflecting laser beam and the scanned surface, the surface laser scanner can detect not only an object's length and width but also its depth. The scanner's ease of use has opened various possibilities in laboratory research and clinical investigation. We assessed the reliability of generating 3D object reconstructions using the Minolta Vivid700 3D surface laser scanner (Minolta USA, Ramsey, NJ). Accuracy and reproducibility were tested on a geometrical calibrated cylinder, a dental study model, and a plaster facial model. Tests were conducted at varying distances between the object and the scanner. It was found that (1) in the calibrated cylinder tests, spatial distance measurement was accurate to 0.5 mm (+/- 0.1 mm) in the vertical dimension and 0.3 mm (+/- 0.3 mm) in the horizontal dimension; (2) in the study model test, molar width was accurate to 0.2 mm (+/- 0.1 mm, P >.05), and palatal vault depth could be measured to 0.7 mm (+/- 0.2 mm, P > 0.05); and (3) for the facial model, an accuracy of 1.9 +/- 0.8 mm was obtained. The findings suggest that the surface laser scanner has great research potential because of its accuracy and ease of use. Treatment changes, growth, surgical simulations, and many other orthodontic applications can be approached 3-dimensionally with this device.

Comparison between traditional 2-dimensional cephalometry and a 3-dimensional approach on human dry skulls

The cephalogram is the standard used by orthodontists to assess skeletal, dental, and soft tissue relationships. This approach, however, is based on 2-dimensional (2D) views used to analyze 3-dimensional (3D) objects. The purpose of this project was to evaluate and compare a 3D imaging system and traditional 2D cephalometry for accuracy in recording the anatomical truth as defined by physical measurements with a calibrated caliper. Thirteen skeletal landmarks were located by both radiographic methods on 9 dry human skulls. Intraclass correlation (0.995), variance (0.054 mm(2)), and standard deviation (SD) (0.237 mm) were averaged over 76 measurements and derived from precision calipers to establish these physical measurements as a reliable gold standard to make comparisons of the 2D and 3D radiographic methods. The results showed great variability of the 2D from the gold standard, with the range varying from -17.68 mm (underestimation of Gn-Zyg R) to +15.52 mm (overestimation of Zyg L-Zyg R). In contrast, the 3D method (Sculptor, Glendora, Calif) indicated a range of the SD from -3.99 (underestimation) mm to +2.96 mm (overestimation). The 3D evaluation was much more precise, within approximately 1 mm of the gold standard. These results indicate that, when the actual distance is measured on a human skull in its true dimensions of 3D space, the Sculptor program, by using a 3D method, is more precise and 4 to 5 times more accurate than the 2D approach. Evaluating distances in 3D space with a 2D image grossly exaggerates the true measure and offers a distorted view of craniofacial growth. There is an inherent problem of representing a linear measure occupying a 3D space with a 2D image.

Preliminary experience with medical applications of rapid prototyping by selective laser sintering

Rapid prototyping techniques, originally developed for building components from computer aided designs in the motor industry, are now being applied in medicine to build models of human anatomy from high resolution multiplanar imaging data such a computed tomography (CT). The established technique of stereolithography and the more recent selective laser sintering (SLS), both build up an object layer by layer. Models have applications in surgical planning, for the design of customised implants and for training. Preliminary experience of using the SLS technique for medical applications is described, addressing questions regarding image processing, data transfer and manufacture. Pilot models, built from nylon, included two skills (a child with craniosynoslosis and an adult with hypertetorism) and a normal femur which was modelled for use in a bioengineering test of an artificial hip. The dimensions of the models were found to be in good agreement with the CT data from which they were built-for the child's skull the difference between the model and the CT data was less than 1.0 +/- 0.5 mm in each direction. Our experience showed that, with care, a combination of existing software packages may be used for data conversion. Ideally, image data of high spatial resolution should be used. The pilot models generated sufficient clinical interest for the technique to be pursued in the orthopaedic field.

Accuracy of measurements and reliability of landmark identification with computed tomography (CT) techniques in the maxillofacial area: a systematic review

OBJECTIVE

The objective of this study was to evaluate the available published information on the reliability and accuracy of skeletal CT landmark identification and associated measurement accuracy through CT in the maxillofacial region.

STUDY DESIGN

Electronic databases were searched with the help of a senior health sciences librarian. Abstracts that appeared to fulfill the initial selection criteria were selected by consensus. The original articles were then retrieved and their references hand-searched for possible missing articles.

RESULTS

A total of 8 articles met the selection criteria. Differences between the magnitudes of errors of landmarks and their associated measurements were discussed.

CONCLUSIONS

It was concluded that each landmark exhibited a characteristic pattern of error that contributed to measurement inaccuracy, and with repeated practice of landmark identifications, the error can be reduced to within 0.5 mm for 2-D CT. Considerations have to be given to some of the 3-D CT reliability values because they can have diagnosis implications.

Measurement of anterior loop length for the mandibular canal and diameter of the mandibular incisive canal to avoid nerve damage when installing endosseous implants in the interforaminal region: a second attempt introducing cone beam computed tomography

PURPOSE

To measure and compare the anterior loop length (ALL) for the mandibular canal and the mandibular incisive canal diameter (ICD) at its origin in cadavers using anatomy and cone beam computed tomography (CBCT) to safely install endosseous implants in the most distal area of the interforaminal region.

MATERIALS AND METHODS

The ALL and ICD were measured using CBCT in 4 cadavers, and using anatomy in 71 cadavers.

RESULTS

The ranges and mean +/- SD for the anatomic measurements were: ALL, 0.0 to 9.0 mm and 1.9 +/- 1.7 mm; ICD, 1.0 to 6.6 mm and 2.8 +/- 1.0 mm. The average discrepancies between CBCT and anatomic measurements were 0.06 mm or less for both the ALL and the ICD, which were less than the resolution of CBCT.

CONCLUSIONS

Because large variations in measurements were observed, both for ALL and ICD, no fixed distance mesially from the mental foramen should be considered safe. The ALL and the ICD can be estimated from the CBCT measurement. The preoperative CBCT measurement yields important information for each case.

Development of imaging selection criteria and procedures should precede cephalometric assessment with cone-beam computed tomography

Cone-beam computed tomography (CBCT) systems for craniofacial imaging are now available from several manufacturers. CBCT potentially provides opportunities for 3-dimensional cephalometrics in orthodontic assessment of bony landmarks and air-bounded surfaces such as the facial skin. Two-dimensional cephalogram simulation could facilitate the transfer of growth projections from existing data sets as a starting point for use of a new 3-dimensional paradigm. Three methods are described to simulate conventional 2-dimensional cephalograms from CBCT images and volumetric data sets. However, certain precautions are required to assure that selection criteria and imaging parameters guarantee a radiation dose that is as low as reasonably achievable.

Cortical bone thickness of the alveolar process measured with cone-beam computed tomography in patients with different facial types

INTRODUCTION

The purpose of this study was to determine the cortical bone thickness of the alveolar process in the maxilla and the mandible on cone-beam computed tomographs of adults with low, normal, and increased facial heights.

METHODS

This study was conducted on 155 images of adult patients (20-45 years old) who were assigned to the low-angle, normal, and high-angle groups. The thickness of the buccal cortical plates of the maxilla and the mandible, and the palatal cortical plates of the maxilla, were measured.

RESULTS

There was no statistically significant difference between the groups regarding mean ages, sex, and sagittal facial types. High-angle patients had significantly lower values than did low-angle patients in all mini-implant insertion sites in both the maxillary and mandibular alveolar bones. The mandibular and maxillary buccal measurements showed a similar pattern; the lowest values were for the high-angle group, followed by the normal group; the highest values were measured in the low-angle patients.

CONCLUSIONS

Clinicians should be aware of the probability of thin cortical bone plates and the risk of mini-implant failures at maxillary buccal alveolar mini-implant sites in high-angle patients, and at mandibular buccal alveolar mini-implant sites between the canine and the first premolar in normal and high-angle patients.

A comparison of the nasal cross-sectional areas and volumes obtained with acoustic rhinometry and magnetic resonance imaging

Acoustic rhinometry (AR) evaluates the geometry of the nasal cavity with acoustic reflections and provides information about nasal cross-sectional areas (CSA) and nasal volume within a given distance. The accuracy of the information obtained by AR was compared with that of magnetic resonance imaging (MRI) of the nasal cavity. Five healthy subjects were evaluated with AR and the MRI before and after the application of a long-acting nasal decongestant spray, to eliminate possible interference of the nasal cycle with both measurement techniques. The MRI images of 2 mm coronal sections of the nasal cavity were traced by three independent observers and the CSAs were calculated by computer-aided imaging digitization, to be compared with the calculated CSAs obtained with the AR at the corresponding distance from the nasal tip. Digitized data from the MRI images were also used to calculate the nasal volume within the first 6 cm from the nasal tip and compared with the AR volume measurements. The interobserver variation of digitized MRI data predecongestant and postdecongestant was not significant. The correlations of CSA and volume measurements between the AR and MRI were high (0.969) after the application of the decongestant. The correlation between the AR and MRI measurements before the decongestant was low (0.345). This may have been the result of interference of the nasal cycle during the long MRI measurements (1 hour) or other unknown factors. We conclude that AR measurements of nasal CSAs and volumes provide accurate information when compared with the MRI of the decongested nasal airway.

Comparison of Infant Head Shape Changes in Deformational Plagiocephaly Following Treatment With a Cranial Remolding Orthosis Using a Noninvasive Laser Shape Digitizer

Deformational Plagiocephaly (DP) is a multi-planar deformity of the cranium occurring either pre-or postnatally in infants. In the last decade, the incidence of DP has increased substantially due to a number of factors, including supine sleeping positioning to reduce Sudden Infant Death Syndrome and the use of child carriers that increase supine positioning. Clinical questions persist about which children should be treated for DP and how to intervene, questions that are difficult to answer without accurate documentation of three-dimensional (3-D) head shape. This study explored a method for quantifying head shape and used that method to evaluate the success of orthotic treatment. Two hundred twenty-four infants who were diagnosed with DP received either a cranial remolding orthosis or a repositioning program with no orthotic intervention. Data from 25 head shape variables were collected using a noninvasive laser shape digitizer. Only variables attributable to growth showed significant differences in the control population, while the treatment population showed significant differences in pre-and post-treatment values for all variables. The study identified four variables as particularly important in assessing the head shape of infants with plagiocephaly: the cranial vault asymmetry index, radial symmetry index, posterior symmetry ratio, and overall symmetry ratio. Ninety-six percent or more of subjects in the treatment group showed improvement in each variable. These data document the utility of a 3-D scanning device and the effectiveness of treatment with a cranial remolding orthosis.

Validation of a three-dimensional facial scanning system based on structured light techniques

The aim of this study was to validate a newly developed three-dimensional (3D) structured light scanning system in recording the facial morphology. The validation was performed in three aspects including accuracy, precision and reliability. The accuracy and precision were investigated using a plaster model with 19 marked landmarks. The accuracy was determined by comparing the coordinates from the 3D images and from the coordinates measure machine (CMM). The precision was quantified through the repeated landmarks location on 3D images. The reliability was investigated in 10 adult volunteers. Each was scanned five times in 3 weeks. The 3D images acquired at different times were compared with each other to measure the reliability. We found that the accuracy was 0.93 mm, the precision was 0.79 mm, the reliability was 0.2mm. These findings suggested that the structured light scanning system was accurate, precise and reliable to record the facial morphology for both clinic and research purposes.

A three-dimensional soft tissue analysis of fifteen patients with Class II, Division 1 malocclusions after bimaxillary surgery

A three-dimensional soft tissue study of the results of surgery in a group of 15 women with Class II, Division I malocclusions after orthognathic surgery was performed with laser scans. A group of 30 women with Class I malocclusions ages between 19 and 25 years were used as controls. Laser scans were taken before surgery, 3 months after surgery, and at least 1 year after retention. The skeletal 2 patients were shown to have a narrowing of the face over the maxillary complex, checks, the nose, as well as around the alar bases, the so called "adenoid facies." There was also the expected mandibular deficiency. The effects of the bimaxillary surgery were not simply confined to the maxilla and the mandible, with soft tissue changes extending as far as the outer canthi of the eyes. There was very little relapse in the group as a whole from the third month to 1 year after surgery. This technique has proved to be a simple noninvasive method of measuring three dimensionally. It has proven to be a very useful tool in auditing surgical outcome and measuring surgical relapse.

Secondary post-traumatic enophthalmos: high-resolution magnetic resonance imaging compared with multislice computed tomography in postoperative orbital volume measurement

PURPOSE

Multislice computed tomography (MSCT) was the modality of choice for orbital volume measurement. This first prospective study compares MSCT with high-resolution magnetic resonance imaging (MRI) combined with micro (MRImc) and headcoil (MRIhc) in volumetric evaluation of the postsurgical enophthalmic orbit.

PATIENTS AND METHODS

Morphologic and dimensional changes of the orbit, eyebulb, and fat content were investigated 3 to 4 months after reconstruction of complex orbital fractures in 36 patients. Image analysis and volumetric assessment from 2-dimensional and 3-dimensional-MRImc and MRIhc were compared with MSCT. The volume segmentation algorithm operated on multispectral, 3-dimensional MR data acquired at isotropic proton density weighted acquisitions.

RESULTS

CT and MRI volume data correlated significantly (P < .01). Enlargement of the posterior segment often resulted in orbital geometry change from conical to convex. Even cases of correct orbital reconstruction presented significant volume enlargement compared to the contralateral side (P < .01). The retro bulbar fat showed itself fragmented and was dislocated in the medial posterior region mostly. We found reduced sagittal eye projection, increased width of the orbital rim, and dislocation of the posteromedial orbital floor (P < .01). High correlation was detected between orbital volume increment and degree of enophthalmos (0.93 mm per 1 cm3 orbital volume enlargement diameter) (P < .01).

CONCLUSIONS

As MRI orbital volume measurement permitted prediction of postsurgical enophthalmos, which is related to possible failure in orbital volume correction and reduction of the posterior medial bulge and not to fat content changes, it is suited for planning secondary correction.