Standardization of 3-D CT measurements for length and angles by matrix transformation in the 3-D coordinate system

OBJECTIVE

We attempted to establish a new 3-D cephalometry with helical computed tomography (CT) by introducing the matrix transformation of the 3-D coordinate system.

SUBJECTS AND METHODS

Three-dimensional cephalometric landmarks on the craniofacial bones were expressed as 3-D vectors originating from the center of the sella. These vectors were standardized by the matrix transformation so that the midsagittal plane and cranial base line coincided with the XZ plane and X axis of the 3-D coordinate system, respectively. We also applied this new method to trace the normal growth of the craniofacial bones in 44 patients with head and neck cancer (age range, 5 to 26 years; 19 women and 25 men).

RESULTS

The accuracy for length measurements was less than 3% of standard error of means with a slice thickness of 1 or 3 mm for 28 out of the 29 length measurements recorded. The precision errors by repeated measurements were 0.8% to 1.0% coefficients of variation for intra- and interobserver variability. Standardization of 3-D vectors representing the cephalometric landmarks allowed us to assess successfully the age-related transition of these landmarks of the patients' craniofacial bones.

CONCLUSION

A new assessment method for 3-D CT cephalometry has been developed by standardizing cephalometric landmarks using a matrix transformation of the 3-D coordinate system. This new assessment method may offer potential in planning plastic and reconstructive surgery.

[Microsurgical anatomy of sellar region in cadavers using a photographic technique with fluorescein]

The microsurgical anatomy of sellar regions in 20 cadavers with a 12 hours maximum post mortem was studied. Fluorescein was used as contrast for vascular anatomy examination. The use of fresh specimen and fluorescein had the objective of avoiding any distortion of normal anatomy. The drug was diluted with water or, in order to have more consistency, in gel for ultrasonography. Contrast injection was made into the internal carotid artery and photographs were taken with three different kinds of lighting: 1) only with Wood's lamp; 2) Wood's lamp and normal white light; 3) only with white light. Lighting only with Wood's lamp showed more contrast. After measurement, data often showed discrepancies with other authors' data. The photographic technique with fluorescein is simple and accessible; the drug showed high quality as a vascular contrast for neuroanatomic research.

Extradural neural axis compartment

The lengthy, continuous, slender extradural neural axis compartment (EDNAC), which extends from the coccyx to the orbit, has been not so much discovered as recognized. Through this compartment run arteries, myelinated and unmyelinated nerves, and valveless veins. Adipose tissue is abundant in the orbital and spinal segments, possibly due to movement requirements, although it is very sparse in the skull base segment, the last segment to be recognized as a continuation of the EDNAC, which connects Breschet's veins to the orbit. The lateral sellar compartment (in older terminology, the cavernous sinus) is an enlarged segment of this EDNAC along the skull base connecting the orbit with the extradural space through the superior orbital fissure and down the dorsum to Breschet's veins of the basilar process of the occipital bone. Understanding the continuity of the EDNAC should help the student understand any segment, particularly the skull base. As Batson noted, "Living anatomy is slowly editing and replacing the anatomy of the dead room."

An investigation of mandibular morphology in subjects with different vertical facial growth patterns

In the present study, mandibular morphology was investigated on lateral cephalometric head films and dental casts of 60 subjects (30 females and 30 males) who had different vertical facial growth patterns. The sample had a mean age of 13.5 years, with a range of 11 to 15.5 years. The subjects were divided into three groups with regard to vertical facial growth by using the SN/GoGn angle to define low-angle, normal, and high-angle groups. In addition, each group was divided into two subgroups according to sex. The effects of the SN/GoGn angle and gender on mandibular morphology were investigated by means of analysis of variances. Tan Go, IMPA, SL, and EL measurements were found to be related to SN/GoGn, and the measurements of Go-Gn, Symphysis depth, and Intermolar width to be related to sex.

The reliability and variability of SN and PFH reference planes in cephalometric diagnosis and therapeutic planning of dentomaxillofacial malformations

Various interpretations of clinical and cephalometric data lead to different diagnostic and surgical planning in the study of dentoskeletal malformations. Many authors have identified this discrepancy as an incorrect positioning between the skeletal structures and the Frankfurt plane (PFH)--a plane that is used routinely for the sagittal measurement of the upper and lower jaw. The aim of this study was to establish a control method to verify the correct positioning of the sella-nasion point plane (SN) and the PFH. To find a reference plane, the authors concentrated their attention on measuring the intersecting angles between these two planes and the vertical posterior maxillary (PM) plane. Fifty patients (33 women and 17 men), all of whom were aesthetically and structurally harmonious class I dentoskeletal types, were analyzed using this method. Student's t-test, the Kolmogorov-Smirnov test, and Fisher's F-test were used for statistical analysis. The results were compared with those proposed by the University of Michigan. To achieve a correct diagnosis and to obtain good functional and cosmetic results in the treatment of these kinds of malformations, it is necessary to make use of the PM vertical plane during cephalometric analysis.

A cephalometric study of the stability of the base of the pharyngeal flap following a modified 'unified velopharyngoplasty procedure'

A cephalometric study was conducted on 12 patients with repaired cleft palate to evaluate the stability in level and length of the base attachment of the velopharyngeal complex following pharyngeal flap surgery by a modified velopharyngoplasty. Complete velopharyngeal closure and normal articulation with a speech appliance were confirmed in all patients prior to pharyngeal flap surgery, which was performed on patients 10 years of age and above. Cephalometric radiographs were taken immediately, 1 year, 2 years and 3 years postoperatively. Cephalometric analysis revealed that although the level and length of the base of the velopharyngeal complex showed changes during the first postoperative year, they remained stable when compared with the palatal plane during the last two years. This indicated therefore that the base of a velopharyngoplasty should be attached at the same level of the palatal plane, namely the level of velopharyngeal closure, and that the procedure appeared useful in producing a stable velopharyngeal complex.

Fifteen-year reproducibility of natural head posture: A longitudinal study

Natural head posture continues to be widely used as the logical reference position for the evaluation of craniofacial morphology. The basic underlying premise is that the long-term clinical reproducibility (variability) of natural head posture is significantly less than the variability of conventional reference planes with respect to the vertical. This study reports the 15-year longitudinal reproducibility of natural head posture. Twenty Chinese adults in Hong Kong, who had initial natural head posture radiographs at age 12 years, were followed up and had repeated cephalograms after 15 years. The method error (reproducibility) after 15 years was 2.2 degrees, which compared favorably with the 5-year reproducibility (method error = 3.0 degrees ) and the 5 to 10 minutes reproducibility (method error = 1.9 degrees ). The individual variability of natural head posture reproducibility increased slightly over time. After 15 years the variance of natural head posture (4.8 degrees [= 2.2(2)]) remains significantly less than the variance of intracranial reference planes to the vertical (25 degrees to 36 degrees ). Cephalometric analyses based on natural head posture therefore remain valid over time.

Approaches to the sellar and parasellar region: anatomic comparison of the microscope versus endoscope

OBJECTIVE

Traditionally, surgical approaches to the sellar region require the use of the operating microscope. Over the past decade endoscopic surgery has gained much popularity because of advances in optics and illumination. Endoscopic surgery of the sellar region has been performed successfully. The goal of the present study was to quantify the amount of exposure to the sellar and suprasellar region that the endoscope provides versus the microscope, with three different anterior approaches to the sellar region.

METHODS

The transethmoidal, endonasal-transsphenoidal, and sublabial-transsphenoidal approaches were performed on 14 formalin-fixed cadaver heads with a 0 degrees endoscope and repeated with the operative microscope. The distances of relevant surgical landmarks and the amount of exposure superior and anterior to the dorsum sella, as well as the lateral exposure, were measured. The mean distances were then used to calculate the volume of exposure for each of the approaches.

RESULTS

It was found that the endoscope provided greater view than the operating microscope in all three approaches. The difference was statistically significant using a paired Student t test and a signed-rank test (P<.001).

CONCLUSION

The authors believe that endoscopic surgery of the sellar region can be performed safely and effectively, while providing the surgeon with a view that is superior to that afforded by the operating microscope.

Differences in cephalometric reference values between five centres: relevance to the Eurocleft Study

Cephalometric data from five different geographical areas (Oslo, Manchester, London, Nijmegen, and Michigan) were compared. The angles SNA, SNB, and ANB were taken from published tables in the form of mean, standard deviation (SD) and number in the sample, divided up by age and sex. Angles SNA and SNB were significantly different among centres on univariate analysis. The Oslo data showed 23 instances in which they differed significantly from the other data, London 16, Manchester 11, Nijmegen 11, and Michigan 7. Multivariate analysis using Penrose distances were Oslo (2.04), Manchester (1.39), London (0.93), Nijmegen (0.80), and Michigan (0.66). The sums of the Mahalanobis distances were Nijmegen (3.60), Oslo (3.10), London (2.80), Manchester (2.25), and Michigan (1.49). As these results probably reflect racial and genetic differences, these must be taken into account when international comparisons are being made, as in the Eurocleft study.

Comparison of cephalometric analysis using a non-radiographic sonic digitizer (DigiGraph Workstation) with conventional radiography

Cephalometric analysis conventionally requires radiographic exposure which may not be compatible with the growing concern over radiation hazards. Recently, the Dolphin Workstation Imaging System introduced to the dental profession a non-radiographic system, called the DigiGraph Workstation which may be an alternative to cephalometric radiography. The aims of this study were to compare the validity and reproducibility of cephalometric measurements obtained from the DigiGraph Workstation with conventional cephalometric radiographs. The sample consisted of 30 human dry skulls. Two replicated sets of lateral cephalograms were obtained with steel ball markers placed at the majority of the cephalometric landmarks. Duplicate tracings prepared from each radiograph were digitized to obtain cephalometric measurements using the computer software, Dentofacial Planner. For the DigiGraph Workstation, double sonic digitizations were repeated twice for each skull, on two occasions. Fifteen angular and one linear measurements were obtained from both methods and these findings compared using ANOVA, paired t-tests and F-tests. All, except one, cephalometric measurement showed significant differences between the two methods (P < 0.0001). The DigiGraph Workstation consistently produced higher values in 11 measurements (mean differences +0.5 to +15.7 degrees or mm) and lower values in four measurements (mean differences -0.2 to -3.5 degrees). The standard deviations of the differences between readings of both methods were large (0.4-5.8 degrees or mm). The reproducibility of the DigiGraph Workstation measurements was lower than that of the radiographic measurements. The method error of the DigiGraph Workstation ranged from 7 to 70 per cent, while that of radiographic tracings was less than 2 per cent. It was concluded that measurements obtained with the DigiGraph Workstation should be interpreted with caution.

Imaging of sellar and parasellar pathology

This article reviews the complex anatomic relationships between structures in the sellar and parasellar regions. Normal anatomy and the normal imaging spectrum are reviewed, with emphasis on the diversity of pathology that originates from this region. Both CT and MR imaging may be used to evaluate the sellar and parasellar regions. This article discusses how modern imaging techniques enable characterization of the many lesions that alter the structure and function of normal sellar and parasellar anatomy.

Is there a dural wall between the cavernous sinus and the pituitary fossa? Anatomical and MRI findings

We compared MRI studies of the sellar area and embryological and adult histological studies of the cavernous sinuses and pituitary fossa. MRI studies were performed in 50 normal subjects with coronal sections using a fast inversion-recovery sequence to demonstrate the dural walls of the cavernous sinus and pituitary fossa. With this sequence, dura mater appears as a high-signal linear structure. The lateral and superior walls of the cavernous sinus was easily identified on all studies, but demonstration of a dural wall separating the cavernous sinus from the pituitary fossa was not possible. These results correlated well with embryological and adult histological studies obtained from 14 specimens. The absence of a strong separation between the pituitary fossa and the cavernous sinus explains the high incidence of extension of pituitary tumours to the cavernous sinuses and vice versa.

Surgical anatomy of the juxta-dural ring area

OBJECT

The authors report on the surgical anatomy of the juxta-dural ring area of the internal carotid artery to add to the information available about this important structure.

METHODS

Twenty sides of cadaver specimens were used in this study. The plane of the dural ring was found to incline in the posteromedial direction. Medial inclination was measured at 21.8 degrees on average against the horizontal line in the anteroposterior view on radiographic studies. Posterior inclination was measured at 20.3 degrees against the planum sphenoidale in the lateral projection, and the medial edge of the dural ring was located 0.4 mm above the tuberculum sellae in the same projection. The lateral edge of the dural ring was located 1.4 mm below the superior border of the anterior clinoid process. The carotid cave was situated at the medial or posteromedial aspect of the dural ring; however, two of the 20 specimens showed no cave formation. The carotid cave contained the subarachnoid space in 13 sides, the arachnoid membrane only in three sides, and the extraarachnoid space in two sides. The authors propose that the marker of the medial side of the dural ring, which is more proximal than the lateral, is the tuberculum sellae in the lateral view on radiographic studies. In the medial aspect of the dural ring the intradural space can be situated below the level of the tuberculum sellae because of the existence of the carotid cave.

CONCLUSIONS

An aneurysm arising from the medial side of the juxta-dural ring area even below the tuberculum sellae is a potential cause of subarachnoid hemorrhage.

Microanatomy of the hypophyseal fossa boundaries

OBJECT

The authors studied the heads of 17 adult cadavers and one fetus to clarify the anatomy of the sellar region, particularly the lateral boundaries of the hypophyseal fossa.

METHODS

Vascular injections and microdissection or histological techniques were used in this study. The roof of the cavernous sinuses and diaphragma sellae were part of a single horizontal dural layer that joined the two anterior petroclinoid folds. Laterally, the direction of this layer changed; it became the lateral wall of the cavernous sinus and joined the dura mater of the middle cerebral fossa. On the midline, this layer ballooned toward the sella through the diaphragmatic foramina, created a dural bag containing the hypophysis, and attached to the inferior aspect of the diaphragma sellae. As a consequence, no straight sagittal dural wall existed between the pituitary gland and cavernous sinus; the lateral border of the hypophyseal fossa was part of this anteroposterior and superoinferior convex bag. The authors stress the importance of the venous elements of the region and discuss the structure of the cavernous and coronary sinuses.

CONCLUSIONS

Invasion of the cavernous sinus makes surgery more risky and difficult and may necessitate modification of the surgical treatment plan. The preoperative diagnosis of cavernous sinus invasion is thus of great interest, but the possibility of normal lateral expansions of the pituitary gland must be kept in mind. A lateral expansion of this gland into the cavernous sinus was encountered in 29% of the specimens, and an adenoma that developed in such an expansion could easily mimic cavernous sinus invasion.

Anatomy of the cerebral veins, dural sinuses, sella, meninges, and CSF spaces

This article discusses the composition, pathways, and mechanisms of some of the intricate systems within the head and neck. The anatomy of several regions are demonstrated on computed tomography scans and T1-weighted and T2-weighted magnetic resonance images. Major emphasis is given to the consonance of this system.

Cephalometry needs innovation, not renovation

Units of length, degree, and area are used when measuring cephalograms. In particular, the measurement of angles is a conventional method of quantifying shape. Because angles do not provide information about direction, there is no way to tell how and where one part of the facial structure has moved with respect to the rest. A new landmark data system using x- and y-coordinates is proposed, and some of its advantages over conventional methods are explained.

The association between prenatal sella turcica morphology and notochordal remnants in the dorsum sellae

The purpose of this study was to describe the location and morphology of notochordal remnants in the cranial base in normal and pathological conditions and to relate these findings to the morphological appearance of the sella turcica. Serially cut sagittal sections of paraffin-embedded sella turcica tissue blocks from 88 normal and pathological fetuses, 13 to 24 weeks of gestation, were examined. Twenty-seven specimens out of 88 had visible notochordal remnants in the cranial base, and these constituted the material available for this study. A straight notochordal course is always seen in normal sella turcica morphology, and a non-straight notochordal course is always seen in malformed sella turcica. Among the fetuses diagnosed at autopsy as "normal fetuses," both normal and pathological findings in the sella turcica regions were observed. The pathological findings were always found in the spontaneously aborted fetuses (five cases). Among the fetuses diagnosed at autopsy as "pathological fetuses," both normal and pathological findings were also observed in the sella region. Our conclusion is that the morphological appearance of the notochordal remnants in the dorsum sellae is associated with the morphology of the sella turcica. These structures ought to be analyzed on larger materials of both normal and pathological fetuses. One of the more obvious perspectives opened up by the present study is the probable disclosure of malformations in spontaneously aborted fetuses without external malformations.

Skeletal and dental changes after orthognathic surgical treatment of mandibular prognathism

Ten patients with skeletal and dental Class III malocclusion with mandibular prognathism were treated orthodontically and surgically and the effects of the ramus sagittal split osteotomy technique on facial morphology and the dentofacial complex were investigated.

Anatomy and embryology of the trigeminal nerve and its branches in the parasellar area

The cavum trigeminale (Meckel's cave) anatomy is still poorly understood. Many different descriptions are found in the literature. In order to clarify the relationship of trigeminal ganglion and its branches with dura and arachnoid, we underwent an embryological and adult microanatomical and histological study. Serial sections of human embryos and fetuses were used. For adult study, microdissections and histological serial sections were performed. We found that dura and arachnoid stop at the trigeminal ganglion and do not extend the three branches of the trigeminal nerve. These three branches are embedded into separate peripheral sheaths. These results are important for clear understanding of the anatomy of the parasellar lodge (cavernous sinus) lateral wall.

Association between facial height development and mandibular growth rotation in low and high MP-SN angle faces: a longitudinal study

Two groups of children with low (n = 29) and high (n = 29) MP-SN angles were followed longitudinally from 6 to 15 years of age. The purpose was to thoroughly examine associations between vertical craniofacial growth and mandibular growth rotation. Correlations between dimensional and rotational variables occurred in different variable pairs in the two groups and changed with age. Increase in posterior lower facial height distinguished itself by being consistently positively correlated with forward matrix rotation irrespective of mandibular plane angle or age. The same applied to increase in ramus height. Increase in lower anterior facial height was, surprisingly, weakly correlated with mandibular rotation, but strongly and positively correlated with increase in corpus length. Overdevelopment of lower anterior facial height in high angle cases occurred because the steep mandibular plane directed corpus growth more downward than normal, not because the mandible rotated backward.

Vertical facial growth and statural growth in girls: a longitudinal comparison

Individual and average growth patterns of the facial dimensions Nasion-Gnathion and Sella-Gonion, as related to statural growth were studied. The sample consisted of 134 girls aged 7-14 years. Data were analysed using a multivariate extension of the multilevel model for longitudinal data. The results confirmed that the mean growth curves of Nasion-Gnathion, Sella-Gonion and body height parallel each other to a large extent. At an individual level it appeared that the pubertal growth spurt of body height and the growth spurts of both facial dimensions are coincident. The major results of the present study pertain to the dynamic (age-dependent) relationship between statural growth and the growth of the face. It appears that there exists a stronger relationship between the growth velocities of standing height, Sella-Gonion and Nasion-Gnathion than between the actual lengths of the three variables themselves. The strongest relation was found between the growth velocity of body height and that of Sella-Gonion. These findings may be a contribution for diagnosis and treatment planning of individual cases.

Incidental finding of an enlarged sella turcica on a lateral cephalogram

The lateral cephalogram is a film that is routinely used in orthodontics. Orthodontists should therefore be familiar with the normal radiographic appearance of the skull as seen on the lateral cephalogram. We present a case of an enlarged sella turcica that was discovered during routine orthodontic workup. Referral and further investigation led to a diagnosis of a prolactinoma.

Identification of condylar anatomy affects the evaluation of mandibular growth: guidelines for accurate reporting and research

Mandibular length is measured on cephalographs to depict changes during growth and after orthodontic treatment, and is often defined between condylion (Co, most posterior superior point on the condylar outline) and pogonion (Pog, most anterior point on the chin). The aim of this study was to assess the accuracy of identifying condylar anatomy, thus the validity of using Co-Pog to evaluate mandibular growth. The sample included 34 children from a prospective study on the early treatment of distoclusions. Two lateral head films were taken of each child, the first with the mouth closed (MC), the second with the mouth open (MO). Three examiners, two orthodontists (U.H. and K.H.) and a dental radiologist (R.B.), rated the condyle as identifiable, nonidentifiable, and interpreted. The rating was applied to the left (L) and right (R) condyles, or to only one outline (O) when the R and L structures appeared superimposed and were not distinguished separately. Besides Co-Pog, the orthodontists traced sella-nasion (SN) and incisor tip-menton (I-Me) to evaluate variability in measurements that do not include Co. One operator (J.G.) measured all distances. Agreement among the three examiners was best in rating the MO radiographs (50%): 4.1% identifiable, 5.9% nonidentifiable or interpreted; in the MC films, they agreed in 32.3% of the cases, but only one of the ratings was identifiable (2.9%). The highest agreement was in identifying the left condyle on the MO film (35.3%). Intraclass correlation coefficients for CO-Pog ranged from r = 0.73 (L side) to r = 0.92 (O) for one orthodontist, and for the other from r = 0.76 (O) to r = 0.85 (L). Both orthodontists had high correlations for SN and I-Me between MC and MO (0.94 < r < 0.98). The variability between examiners in recognizing condylar anatomy, particularly on radiographs taken with the mouth closed, suggests that the identification of condylar anatomy must be rated in studies of mandibular growth. Researchers measuring mandibular length in investigations of mandibular growth after orthodontic therapy should differentiate between cases where the condyle is readily identified, and those where condylar anatomy is interpreted.

Sella-Nasion line revisited

The anterior cranial base or the Sella-Nasion (SN) line is often used by orthodontists as a reference line for assessment of dentofacial deformities. Its most important value is its relative stability, practicality and the ease of location of both points Sella and Nasion. Reliability of the SN line as a suitable assessor for exact facial measurements has been discussed before. The intent of this study was to identify unusual SN rotations for subjects acquiring normal and abnormal skeletal profiles and hence correct values associated with SN line, both in vertical and horizontal planes. A random sample of 150 British white school children aged 9-12 years old was selected. Lateral head films of the children were traced and digitized. Point Nasion was joined to posterior nasal spine and also to point Sella, thus producing a Z angle when the posterior nasal spine is extended to anterior nasal spine. Means and standard deviations were calculated. The mean angle S-N-PNS was 38 degrees +/- 5 while the mean of angle N-PNS-ANS was 47 degrees +/- 3. Comparison of these angles for patients of the same age group with the mean Z angle can identify rotation of the palatal and Sella-Nasion planes. Hence corrections of angular measurements involving Sella point can be performed.

Sphenoid and sellar tumors

The management of tumors of the sphenoid sinus and sellar-parasellar region has experienced dramatic conceptual and technical advances over the past two decades. Malignant lesions and benign invasive lesions, once carrying a dismal outlook and deemed inoperable, are now being adequately circumscribed and resected with good results. The formation of skull base teams throughout the world and the widespread concept of a multidisciplinary approach to skull base tumors has led to advancements in the treatment of sphenoid and sellar-parasellar tumors.