Three-dimensional fetal cephalometry: an evaluation of the reliability of cephalometric measurements based on three-dimensional CT reconstructions and on dry skulls of sheep fetuses

Nasal cavity and maxillary sinuses form variation among modern humans of Asian descent

OBJECTIVES

This study explores variation, covariation, and ecogeographic pattern of the nasal cavity, maxillary sinuses, and external midfacial skeleton across 15 populations of east Asian origin inhabiting the Far East, Siberia, Alaska and Greenland.

MATERIALS AND METHODS

We have collected linear measurements of the internal nasal cavity, maxillary sinus and external midfacial skeleton as well as volumes and surface areas of three-dimensional models of the cavity. A set of seven climatic variables, mtDNA and Y-chromosome genetic matrices and a matrix of geographic distances were also utilized.

RESULTS

A strong association between form of the nasal cavity and climate was found, whereby all north Asian groups display increased volumes, areas and lengths of the cavity, and surface area to volume ratios (SA/V). Most of Siberian groups exhibit not only large and long, but also wide and tall nasal cavity. The Eskimo-Aleutian speaking groups possess cavities that are vertically short and narrow but of a high SA/V ratio. The sinuses exhibit an exceptionally high level of within- and between-group variation which supports the views on the sinus as an architectural byproduct. Both volume and area of the nasal cavity can be reliably estimated based on a set of simple and repeatable linear measurements.

DISCUSSION

While the nasal cavity and maxillary sinus are both larger in a larger facial skeleton, there is a strong inverse relationship between them at a given facial size. Our results do not support the notion that the shape of the internal nasal cavity is more strongly associated with climate compared to the external midfacial morphology.

3D cephalometric analysis using Magnetic Resonance Imaging: validation of accuracy and reproducibility

The aim of this study was to validate geometric accuracy and in vivo reproducibility of landmark-based cephalometric measurements using high-resolution 3D Magnetic Resonance Imaging (MRI) at 3 Tesla. For accuracy validation, 96 angular and 96 linear measurements were taken on a phantom in 3 different positions. In vivo MRI scans were performed on 3 volunteers in five head positions. For each in vivo scan, 27 landmarks were determined from which 19 angles and 26 distances were calculated. Statistical analysis was performed using Bland-Altman analysis, the two one-sided tests procedure and repeated measures one-way analysis of variance. In comparison to ground truth, all MRI-based phantom measurements showed statistical equivalence (p < 0.001) and an excellent agreement in Bland-Altman analysis (bias ranges: -0.090-0.044°, -0.220-0.241 mm). In vivo cephalometric analysis was highly reproducible among the five different head positions in all study participants, without statistical differences for all angles and distances (p > 0.05). Ranges between maximum and minimum in vivo values were consistently smaller than 2° and 2 mm, respectively (average ranges: 0.88°/0.87 mm). In conclusion, this study demonstrates that accurate and reproducible 3D cephalometric analysis can be performed without exposure to ionizing radiation using MRI.

Midfacial growth patterns in males from newborn to 5 years old based on computed tomography

OBJECTIVES

Growth patterns of the human facial skeleton have been of great interest and importance for biological anthropologists, forensic scientists, craniofacial surgeons, and orthopedists. Nevertheless, growth trends of the facial skeleton in infancy and early childhood are still poorly known and clinical CT data have been insufficiently used for studying craniofacial ontogeny. The purpose of this study was to provide a comprehensive quantitative description of human midfacial ontogeny in infancy and early childhood, and to contribute to debates regarding the role of modularity vs. integration in shaping the human face.

METHODS

Our dataset includes 146 high resolution clinical CT datasets of males from the 2nd to 6th years of life and 101 dataset of infants (males) in the 1st year of life. Forty landmarks were collected from each 3D reconstructed skull, then 25 linear measurements describing the morphological features of the facial skeleton were calculated. The integration/modularity issue was addressed via comparison of intragroup correlation matrices at different ages.

RESULTS

Growth trends for all the measurements are presented in charts and tables of statistical parameters that can be used as normative data. The midfacial variables display a great diversity of growth patterns. The correlation structure of the measurements is different at different ages.

CONCLUSIONS

Variables commonly assigned to the same unit of the facial skeleton can exhibit rather different growth trends, but some measurements display seemingly coordinated patterns of growth change. The level of interindividual variation of most measurements is stable after the second half of the first year of life.

Lower face cephalometry based on quadrilateral analysis with cone-beam computed tomography: a clinical pilot study

OBJECTIVE

As most orthognathic surgeries focus on the lower face, the aim of this study was to transfer previously developed two-dimensional cephalometry-which is useful for surgeons in the orthognathic surgery of the lower face-to three-dimensional (3D) cephalometry by using cone-beam computed tomography (CBCT). We selected the quadrilateral lower face analysis developed by the surgeon Di Paolo, who focused only for the lower face and mentioned that data in millimeters are more easy to use than angles for surgeons. Additionally, we wanted to create a 3D lower face analysis approach based on quadrilateral analysis and establish a reference table for surgical planning.

STUDY DESIGN

Three investigators assigned 16 landmarks on CBCT images from 30 patients with normocclusion. Intra-class correlation coefficients (ICCs) and standard deviations (SDs) were calculated according to each landmark. The maxillary and mandibular lengths and widths and the anterior and posterior lower facial heights (ALFH and PLFH) are presented as means and SDs. The asymmetry of the face was calculated with paired t test, and the coherence of the lower face was assessed with correlation coefficients (r) and regression models.

RESULTS

The ICCs were ≥0.90, and the SDs of the landmarks were lower than 1.00 mm, except for the J-point, which was located at the junction of the anterior border of the ramus and the corpus of the mandible. The SDs of linear measurements were 3.06-5.20 mm, and there was no significant facial asymmetry. The r among the structures was greater than 0.3 in 13 of 15 assessments. Based on these values, we could establish a floating norm of the lower face using the following five regressions: one linear regression for the mandibular length, two quadratic models for the ALFH and PLFH, and two multivariate regressions for the posterior widths of the maxillae and mandible.

CONCLUSION

The adaptation of quadrilateral analysis can provide accurate 3D characterization of the morphology of the lower face and the floating norm based on millimeter values, which is practical for surgeons. As the 3D extension of quadrilateral analysis could provide references of the lower face, which might be an accurate 3D approach for presurgical planning, the further investigation in bigger sample would be relevant in the practice.

Comparison of measurements of mandible growth using cone beam computed tomography and its synthesized cephalograms

BACKGROUND

The current study aimed to compare the measurements of the mandible morphology using 3D cone beam computed tomography (CBCT) images with those using 2D CBCT-synthesized cephalograms; to quantify errors in measurements based on 2D synthesized cephalograms; and to clarify the effects such errors have on the description of the mandibular growth.

METHODS

Mandibles of six miniature pigs were scanned monthly using CBCT over 12 months and the data were used to reconstruct the 3D bone models. Five anatomical landmarks were identified on each bone model, and the inter-marker distances and monthly distance changes were calculated and taken as the gold standard. Synthetic 2D cephalograms were also generated for each bone model using a digitally reconstructed radiography (DRR)-generation method. Errors in cephalogram measurements were determined as the differences between the calculated variables in cephalograms and the gold standard. The variations between cephalograms and the gold standard were also compared using paired t-tests.

RESULTS

While the inter-marker distance increases varied among the marker pairs, all marker pairs increased their inter-marker distances gradually every month, reaching 50% of the total annual increases during the fourth and fifth months, and then slowing down in the subsequent months. The 2D measurements significantly underestimated most of the inter-marker distances throughout the monitoring period, in most of the monthly inter-marker distance changes during the first four months, and in the total growth (p < 0.05).

CONCLUSIONS

Significant errors exist in the measurements using 2D synthesized cephalogram, underestimating the mandibular dimensions and their monthly changes in the early stages of growth, as well as the total annual growth. These results should be considered in dental treatment planning at the beginning of the treatment in order to control more precisely the treatment process and outcome.

Evaluation of precision and accuracy assessment of different 3-D surface imaging systems for biomedical purposes

Three-dimensional (3-D) surface imaging has gained clinical acceptance, especially in the field of cranio-maxillo-facial and plastic, reconstructive, and aesthetic surgery. Six scanners based on different scanning principles (Minolta Vivid 910®, Polhemus FastSCAN™, GFM PRIMOS®, GFM TopoCAM®, Steinbichler Comet® Vario Zoom 250, 3dMD DSP 400®) were used to measure five sheep skulls of different sizes. In three areas with varying anatomical complexity (areas, 1 = high; 2 = moderate; 3 = low), 56 distances between 20 landmarks are defined on each skull. Manual measurement (MM), coordinate machine measurements (CMM) and computer tomography (CT) measurements were used to define a reference method for further precision and accuracy evaluation of different 3-D scanning systems. MM showed high correlation to CMM and CT measurements (both r = 0.987; p < 0.001) and served as the reference method. TopoCAM®, Comet® and Vivid 910® showed highest measurement precision over all areas of complexity; Vivid 910®, the Comet® and the DSP 400® demonstrated highest accuracy over all areas with Vivid 910® being most accurate in areas 1 and 3, and the DSP 400® most accurate in area 2. In accordance to the measured distance length, most 3-D devices present higher measurement precision and accuracy for large distances and lower degrees of precision and accuracy for short distances. In general, higher degrees of complexity are associated with lower 3-D assessment accuracy, suggesting that for optimal results, different types of scanners should be applied to specific clinical applications and medical problems according to their special construction designs and characteristics.

"Black Bone" MRI: a potential non-ionizing method for three-dimensional cephalometric analysis--a preliminary feasibility study

OBJECTIVES

CT offers a three-dimensional solution to the inaccuracies associated with lateral cephalogram-based cephalometric analysis. However, it is associated with significant concerns regarding ionizing radiation exposure. MRI offers a non-ionizing alternative, but this has been less well investigated. We present a novel gradient echo MRI sequence ("Black Bone") and highlight the potential of this sequence in cephalometric analysis.

METHODS

After regional ethics approval, "Black Bone" imaging was obtained in eight patients in whom lateral cephalograms were available. "Black Bone", T1 and T2 weighted spin echo imaging were obtained in the mid-sagittal plane, and measurements were compared with those obtained on the lateral cephalogram using both the Advantage Windows Workstation (GE Medical Systems, Buckinghamshire, UK) and the Dolphin(®) cephalometric software (v. 11.5.04.23, Premium; Dolphin Imaging, Chatsworth, CA) by one assessor. Further assessment was made by scoring the ease of landmark identification on a ten-point scale.

RESULTS

"Black Bone" imaging surpassed T1 and T2 weighted imaging in terms of cephalometric landmark identification. A number of mid-sagittal cephalometric landmarks could not be clearly identified on T2 weighted imaging, making analysis impossible. Measurements on "Black Bone" demonstrated the smallest discrepancy when compared with those obtained on the lateral cephalogram. The discrepancy seen between measurements completed on mid-sagittal MRI and the lateral cephalogram was compounded by inherent inaccuracies of the lateral cephalogram. The overall mean discrepancy between distance measurements on "Black Bone" imaging and those on the lateral cephalogram was 1-2 mm.

CONCLUSIONS

Overall, "Black Bone" MRI offered an improved method of cephalometric landmark identification over routine MRI sequences, and provides a potential non-ionizing alternative to CT for three-dimensional cephalometrics.

Comparison of linear and angular measurements using two-dimensional conventional methods and three-dimensional cone beam CT images reconstructed from a volumetric rendering program in vivo

OBJECTIVE

The aim of this study was to compare the linear and angular measurements made on two-dimensional (2D) conventional cephalometric images and three-dimensional (3D) cone beam CT (CBCT) generated cephalograms derived from a 3D volumetric rendering program.

METHODS

Pre-treatment cephalometric digital radiographs of 11 patients and their corresponding CBCT images were randomly selected. The digital cephalometric radiographs were traced using Vista Dent OC (GAC International, Inc Bohemia, NY) and by hand. CBCT and Maxilim® (Medicim, Sint-Niklass, Belgium) software were used to generate cephalograms from the CBCT data set that were then linked to the 3D hard-tissue surface representations. In total, 16 cephalometric landmarks were identified and 18 widely used measurements (11 linear and 7 angular) were performed by 2 independent observers. Intraobserver reliability was assessed by calculating intraclass correlation coefficients (ICC), interobserver reliability was assessed with Student t-test and analysis of variance (ANOVA). Mann-Whitney U-tests and Kruskal-Wallis H tests were also used to compare the three methods (P < 0.05).

RESULTS

The results demonstrated no statistically significant difference between interobserver analyses for CBCT-generated cephalograms (P < 0.05), except for Gonion-Menton (Go-Me) and Condylion-Gnathion (Co-Gn). Intraobserver examinations showed low ICCs, which was an indication of poor reproducibility for Go-Me and Sella-Nasion (S-N) in CBCT-generated cephalograms and poor reproducibility for Articulare-Gonion (Ar-Go) in the 2D hand tracing method (P < 0.05). No statistical significance was found for Vista Dent OC measurements (P > 0.05).

CONCLUSIONS

Measurements from in vivo CBCT-generated cephalograms from Maxilim® software were found to be similar to conventional images. Thus, owing to higher radiation exposure, CBCT examinations should only be used when the inherent 3D information could improve the outcome of treatment.

3D CT based rating of unilateral impacted canines

OBJECTIVE

The aim of this study was to develop a reference system for multislice computed tomography (MSCT) images to determine of the location of impacted teeth in metric terms.

STUDY DESIGN

The CT data of 17 patients with unilateral impacted maxillary canines were selected retrospectively from existing MSCT data sets. In a reference coordinate system, defined by anterior nasal spine (ANS), posterior nasal spine (PNS), and A-point, the axis length and the inclination of the canines were determined and impacted and non-impacted canines were compared.

RESULTS

There were significant differences between the impacted and non-impacted canines (p ≤ 0.0003) for all inclinations and the lengths in the x- and z-axes. The measurement of the inclination and sections of the impacted and non-impacted canine tooth axes showed sufficient repeatability and reproducibility.

CONCLUSION

The coordinate system proved to be suitable for the exact metric localization of impacted teeth.

Morphological evaluation of cranial and maxillary shape differences of the brachymorphic mouse with spontaneous malocclusion using three-dimensional micro-computed tomography

OBJECTIVES

The aim of this study was to determine whether significant cranial and maxillary deformity exists in BALB/c-bm/bm (brachymorphism) mouse with spontaneous malocclusion using three-dimensional (3D) images.

MATERIALS AND METHODS

Thirty female mice were divided into the following three groups: control group (BALB/c mice, n = 10), Norm group (BALB/c-bm/bm mice with normal occlusion, n = 10), and Mal group (BALB/c-bm/bm mice with malocclusion, n = 10). Nine points in the skull were selected, and transverse and antero-posterior distances were measured using three-dimensional images of micro-computed tomography (CT). Moreover, 3D images were superimposed at the median plane to visualize the skull shape asymmetry.

RESULTS

The transverse distances at the posterior cranial and maxillary region and the antero-posterior distances in the Norm and Mal groups were significantly shorter than those in the control group. The nasal septum of the Mal group was significantly shorter than that of the Norm group. Morphological measurements and superimposed 3D images showed that lateral deviation occurred at the anterior cranial and maxillary region in the Mal group.

CONCLUSION

The 3D micro-CT images revealed that the antero-posterior length and posterior transverse width at the cranium and maxilla in BALB/c-bm/bm mice were significantly smaller than those in BALB/c mice. It was quantitatively and morphologically clear that BALB/c-bm/bm mice show a spontaneous transverse crossbite owing to lateral deviation of the maxilla and nasal bone.

Three-dimensional craniomaxillary characteristics of the mouse with spontaneous malocclusion using micro-computed tomography

The aim of this study was to clarify the morphological characteristics of craniomaxillary deviations in BALB/c-bm/bm mice with a spontaneous malocclusion (incisal transverse crossbite) using three-dimensional (3D) morphological measurements. Sixty female mice aged 13 and 25 weeks were divided into the following groups: control (BALB/c-+/+ mice, n = 20), norm (BALB/c-bm/bm mice with a normal occlusion, n = 20), and mal (BALB/c-bm/bm mice with a malocclusion, n = 20). Various points in the skull were selected and the distances between two points were measured using 3D micro-computed tomography (CT) images. Statistically significant differences in measurement values among the three groups were evaluated by one-way analysis of variance with a probability level of P < 0.05 considered statistically significant. At both ages, the lengths of almost all measurements in the norm and mal groups were significantly shorter than those in the control group. Comparison between the shifted and non-shifted sides in the mal group showed that significant lateral deviation at the maxilla and nasal bone had occurred. Using 3D micro-CT images, the results of this study quantitatively showed that the craniomaxillary complex of BALB/c-bm/bm mice was significantly smaller than that of BALB/c-+/+ mice and that BALB/c-bm/bm mice have a spontaneous transverse crossbite due to lateral deviation of the maxilla and nasal bone.

A comparison of two-dimensional radiography and three-dimensional computed tomography in angular cephalometric measurements

OBJECTIVES

The objective of this study was to assess the reliability of three-dimensional (3D) cephalometric approaches by comparing this method with authenticated traditional two-dimensional (2D) cephalometry in angular cephalometric measurements.

METHODS

CT images and lateral cephalometric radiographs of ten patients (five women, five men) were used in this study. Raw CT data of the patients were converted to 3D images with a 3D simulation program (Mimics 9.0, Leuven, Belgium). Lateral cephalometric radiographs were used manually for 2D measurements. The comparisons of the two methods were made using 14 cephalometric angular measurements. The Wilcoxon matched-pairs signed-ranks test (alpha = 0.05) was used to determine the difference between the two methods. To assess the intra- and interobserver reproducibility, two sets of recordings made by each observer, in each modality were used. Dahlberg's formula was used to determine the intraobserver reproducibility, and the Wilcoxon matched-pairs signed-rank test (alpha = 0.05) was used to assess the interobserver reproducibility.

RESULTS

The method errors of both observers ranged from 0.35 degrees to 0.65 degrees. In addition, there were no significant differences between the measurements of the two observers (P > 0.05). However, comparison of 2D and 3D parameters showed significant differences in U1-NA and U1-SN measurements (P < 0.05).

CONCLUSIONS

The 3D angular cephalometric analysis is a fairly reliable method, like the traditional 2D cephalometric analysis. Currently, the 3D system is likely to be more suitable for the diagnosis of cases with complex orthodontic anomalies. However, with the decrease in radiation exposure and costs in the future, 3D cephalometrics can be a suitable alternative method to 2D cephalometry.

Maxillary distraction osteogenesis in the adolescent cleft patient: three-dimensional computed tomography analysis of linear and volumetric changes over five years

OBJECTIVE

To assess the results of maxillary distraction osteogenesis with the Rigid External Distraction System using three-dimensional computed tomography scan volume-rendered images with respect to stability and facial growth at three time frames: preoperative (T0), 1-year postoperative (T1), and 5-years postoperative (T2).

DESIGN

Retrospective analysis.

SETTING

Tertiary.

PATIENTS

A total of 12 patients with severe cleft maxillary hypoplasia were treated between June 30, 1997, and July 15, 1998. The mean age at surgery was 11 years 1 month.

INTERVENTIONS

Le Fort I maxillary distraction osteogenesis. Distraction was started 2 to 5 days postsurgery at a rate of 1 mm per day. The consolidation period was 3 months. No face mask was used. A paired t test was used for statistical analysis.

MAIN OUTCOME MEASURES

Overjet, ANB, and SNA and maxillary, pterygoid, and mandibular volumes.

RESULTS

From T0 to T1, there were statistically significant increments of overjet, ANB, and SNA and maxillary, pterygoid, and mandibular volumes. The T1 to T2 period demonstrated a reduction of overjet (30.07%) and ANB (54.42%). The maxilla showed a stable SNA and a small but statistically significant advancement of the ANS point. There was a significant increase in the mandibular volume. However, there was no significant change in the maxillary and pterygoid volumes.

CONCLUSIONS

Maxillary distraction osteogenesis demonstrated linear and volumetric maxillary growth during the distraction phase without clinically significant continued growth thereafter. Overcorrection is required to take into account recurrence of midface retrusion over the long term.

Precision of cephalometric landmark identification: cone-beam computed tomography vs conventional cephalometric views

INTRODUCTION

In this study, we compared the precision of landmark identification using displays of multi-planar cone-beam computed tomographic (CBCT) volumes and conventional lateral cephalograms (Ceph).

METHODS

Twenty presurgical orthodontic patients were radiographed with conventional Ceph and CBCT techniques. Five observers plotted 24 landmarks using computer displays of multi-planer reconstruction (MPR) CBCT and Ceph views during separate sessions. Absolute differences between each observer's plot and the mean of all observers were averaged as 1 measure of variability (ODM). The absolute difference of each observer from any other observer was averaged as a second measure of variability (DEO). ANOVA and paired t tests were used to analyze variability differences.

RESULTS

Radiographic modality and landmark were significant at P <0.0001 for DEO and ODM calculations. DEO calculations of observer variability were consistently greater than ODM. The overall correlation of 1920 paired ODM and DEO measurements was excellent at 0.972. All bilateral landmarks had increased precision when identified in the MPR views. Mediolateral variability was statistically greater than anteroposterior or caudal-cranial variability for 5 landmarks in the MPR views.

CONCLUSIONS

The MPR displays of CBCT volume images provide generally more precise identification of traditional cephalometric landmarks. More precise location of condylion, gonion, and orbitale overcomes the problem of superimposition of these bilateral landmarks seen in Ceph. Greater variability of certain landmarks in the mediolateral direction is probably related to inadequate definition of the landmarks in the third dimension.

Method selection in craniofacial measurements: advantages and disadvantages of 3D digitization method

AIM

Treatment of the craniofacial malformations is a primary goal of cranio-maxillo-facial surgeons. Surgical treatment of these malformations requires accurate data. Accuracy of measurement should be a priority of scientists to prevent statistical errors and therefore to promote the comparison of the results obtained from various research groups. In the present study, we aimed to compare three different measurement techniques, which were used frequently in craniofacial measurements.

METHODS

A total number of 35 female and 35 male volunteer adults were included to the study. Two-dimensional (2D) photogrammetry, three-dimensional (3D) digitization and manual anthropometry methods were used for the present study. Measurements were obtained from the ear, eye, nose and face.

RESULTS

By comparing three methods, our findings revealed that 3D digitization method is an easy, robust, and sensitive method to obtain the data.

CONCLUSIONS

We think that 3D digitization method is accurate, and it can be applied to both clinical practice and research. Advantages and disadvantages of three methods are discussed with the relevant literature.

A case report comparing 3-D evaluation in the diagnosis and treatment planning of hemimandibular hyperplasia with conventional radiography

INTRODUCTION

Cephalometric radiography is the main investigation used in the diagnosis of maxillofacial deformities. Three-dimensional (3-D) computed tomography (3-D CT) imaging has recently been used in the diagnosis and treatment planning of craniofacial morphology. The purpose of this report was to present the diagnosis and treatment planning of a hemimandibular hyperplasia case by using conventional radiographs and 3-D cephalometric analysis.

METHODS

A 24-year-old girl presented with hemimandibular hyperplasia and the main complaint was her facial appearance. Conventional cephalometric analysis including lateral and frontal cephalograms were traced by hand and evaluated by the same clinician. Twenty-one measurements on the lateral cephalograms and 13 measurements on the frontal cephalograms were performed. In addition, axial images were reconstructed into a 3-D model by using medical image processing software. Linear and angular measurements were presented in coronal and sagittal planes.

RESULTS

The 3-D CT analysis has a superior image quality when compared with conventional cephalograms.

CONCLUSIONS

The 3-D CT analysis provides more advanced diagnostic image information in evaluating craniofacial morphology. We conclude that 3-D CT images can facilitate the diagnosis, treatment planning, and outcome evaluation of severe asymmetry cases.

Surgical cephalometrics: applications and developments

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Describe the historical origins of modern cephalometry. 2. Identify common landmark points on the lateral cephalogram. 3. Describe multiple common clinical uses for cephalometry. 4. Exhibit knowledge of developments in imaging and analysis alternatives.

BACKGROUND

Interest in the dimensions of the human head has been present since antiquity. Proportional analysis and measures from cadaveric specimens led to the development of radiologic image capture and analysis on living subjects. These techniques were originally applied to establishing normative values, documenting growth, and diagnosing dentofacial disharmonies. This article reviews the origins of cephalometric methodology and current developments and applications.

METHODS

The authors conducted a MEDLINE search and review of all English language articles using the keywords "cephalometric" and "cephalometrics."

RESULTS

Cephalometrics have undergone substantial use and development since the introduction of radiologic imaging on living human subjects in 1931. Although frequently associated with orthognathic surgery, cephalometrics have been applied to a number of conditions involving altered craniofacial morphology. Advances in imaging and computing have led to increased interest in three-dimensional and non-x-ray-based assessment of the human head. Mathematical models have been applied to standard cephalometric information to increase the descriptive accuracy of the complex shapes involved.

CONCLUSIONS

Cephalometric techniques and analyses are versatile tools that can be applied to a wide variety of clinical scenarios involving the craniofacial region. New technologies and expanded applications promise to continue the development and use of this well-established methodology.

Contribution of three-dimensional computed tomography in the assessment of fetal skeletal dysplasia

OBJECTIVE

To compare the diagnostic accuracy of two-dimensional (2D) ultrasound and three-dimensional (3D) computed tomography (CT) for the diagnosis of fetal skeletal anomalies.

METHODS

Eleven pregnant women underwent 2D ultrasound and 3D-CT. Ten fetuses presented skeletal anomalies on 2D ultrasound and one fetus had a normal ultrasound exam but a familial history of osteopetrosis. We compared retrospectively the diagnoses established on 2D ultrasound and 3D-CT with the neonatal and/or postmortem work-up, which were used as the gold standard.

RESULTS

2D ultrasound provided the correct diagnosis in only two of the 11 cases. CT yielded the correct diagnosis in eight; in six of these, 2D ultrasound had been inconclusive. 3D-CT was more accurate than was 2D ultrasound in visualizing vertebral anomalies (abnormal shape of the vertebral bodies, abnormal interpedicular distance), pelvic bone malformations (delayed ossification of the pubic bones, abnormal acetabular shape) and enlarged metaphysis or synostoses in long bones. In three cases, neither 2D ultrasound nor CT provided the correct diagnosis.

CONCLUSION

In this series, which included a variety of skeletal dysplasias, 3D-CT had a better diagnostic yield than did 2D ultrasound. Both imaging techniques are useful in the management of fetal dysplasia; 2D ultrasound is a useful screening test and 3D-CT is a valuable complementary diagnostic tool.