Imaging orofacial tissues by magnetic resonance

A dynamic ultrasonographic in vivo study of the musculoaponeurotic architecture of the human masseter muscle

OBJECTIVE

In the present study, we sought to investigate the in vivo musculoaponeurotic architecture of the masseter muscle (MM) volumetrically with ultrasound in asymptomatic participants. It was hypothesized that the mean fiber bundle length (FBL) and mean aponeurotic height of laminae of the MM differ significantly between the relaxed state and maximally contracted state upon elevation of the mandible.

STUDY DESIGN

The MM was investigated volumetrically in 12 male and 12 female asymptomatic participants (mean age, 25.8 ± 4.1 years) using ultrasound. The mean FBL and mean height of aponeuroses in the relaxed and maximally contracted states were compared using paired t tests, with significance established at P ≤ .05. Intrarater reliability was assessed using the intraclass correlation coefficient (ICC).

RESULTS

The MM consisted of the superficial head (SH) and deep head, each arranged in multiple laminae. Fiber bundles extended between superior and inferior aponeuroses and/or bone. Statistically significant differences (P ≤ .05) were observed in mean FBL and in mean height of aponeuroses between the relaxed and contracted states only in superficial laminae of the SH.

CONCLUSIONS

These results suggest there is differential contraction of the laminae of the MM in the transition from relaxed to contracted states. Future comparison with pathologic patients can be made on the basis of an established normative database.

Design of an Intraoral Dipole Antenna for Dental Applications

OBJECTIVE

In dental MRI, intraoral coils provide higher signal-to-noise ratio (SNR) than coils placed outside the mouth. This study aims to design an intraoral dipole antenna and demonstrates the feasibility of combining it with an extraoral coil.

METHODS

Dipole antenna design was chosen over loop design, as it is open toward the distal; therefore, it does not restrain tongue movement. The dipole design offers also an increased depth-of-sensitivity that allows for MRI of dental roots. Different dipole antenna designs were simulated using a finite-difference-time-domain approach. Ribbon, wire, and multi-wire arms were compared. The best design was improved further by covering the ends of the dipole arms with a high-permittivity material. Phantom and in vivo measurements were conducted on a 3T clinical MRI system.

RESULTS

The best transmit efficiency and homogeneity was achieved with a multi-wire curved dipole antenna with 7 wires for each arm. With an additional high-permittivity cap the transmit field inhomogeneity was further reduced from 20% to 5% along the dipole arm. When combined with extraoral flexible surface-coil, the coupling between the coils was less than -32dB and SNR was increased.

CONCLUSION

Using intraoral dipole design instead of loop improves patient comfort. We demonstrated feasibility of the intraoral dipole combined with an extraoral flexible coil-array for dental MRI. Dipole antenna enabled decreasing imaging field-of-view, and reduced the prevalent signal from tongue.

SIGNIFICANCE

This study highlights the advantages and the main challenges of the intraoral RF coils and describes a novel RF coil that addresses those challenges.

A Prospective, Randomized, Double-Blind, Placebo-Controlled Clinical Trial Comparing the Efficacy of Anti-edema Drugs for Edema Control in Orthognathic Surgery Using Digitizer 3-D to Measure Facial Swelling

INTRODUCTION

Orthognathic surgery involves making several osteotomies. Any osteotomies leads to varying degrees of post-operative swelling. The aim of this study was to evaluate the effectiveness of anti-edema drugs for the control of edema, using Digitizer 3D™ for measuring soft-tissue thickness, in patients who underwent bimaxillaryorthognathic surgery.

MATERIALS AND METHODS

In this double-blinded, randomized, control trial, 24 patients (study group: 12 patients, control group: 12 patients) in whom bimaxillary orthognathic surgery was indicated, were included in this study. All swelling measurements were expressed as total 3-D area of the landmarks (cm(2)) in T0 pre-operative, T1 first day after surgery, T2 fourth day after surgery, T3 4 months after surgery. For each patient we compared, by adding left and right area, the increase of swelling between T1-T0, T2-T0 and T1-T3.

RESULTS

The differences T0-T1 are highly significant (p < 0.01) between group 1 or study group (treated with Venoplant(®)) and group 2 (control group); the differences T0-T2 are significant (p < 0.05) between group 1 (treated with Venoplant(®)) and group 2 (control group). The differences T1-T3 are significant (p < 0.05) between group 1 (treated with Venoplant(®)) and group 2 (control group).

DISCUSSION

The present study suggests that Venoplant(®) significantly decreases postoperative edema in orthognathic surgery, thus precluding long-term corticosteroid use.

Influence of sex and body mass index on facial soft tissue thickness measurements of the northern Chinese adult population

Forensic facial reconstruction is a mixture of science and art, as it attempts to reestablish the contours of the soft tissues over the skull. From a forensic point of view, identification of an unknown body relies heavily on this visual aspect of recognition. To obtain acceptable results in forensic facial reconstruction, accurate facial soft tissue thickness data are essential. Until now, despite numerous works related to soft tissue thickness, there is little information in this area for the Chinese population. To this end, this study developed soft tissue thickness data for the Chinese adult population. Spiral computed tomography (CT) data and the body mass index (BMI) of 200 northern Chinese aged 18-32 years were collected. Soft tissue thickness measurements at 20 anthropological landmarks on the skull were taken, based on the three-dimensional models of the skull and face reconstructed from the spiral CT data of each subject. Considering the sex and BMI of the individuals, general descriptive analyses of soft tissue thickness were determined. Statistical analyses were performed between males and females in each BMI group, as well as between each of the BMI categories for males and females, respectively. The results revealed that males have thicker soft tissues than females at most of the anthropological landmarks in the Chinese population, similar to other populations. However, only one-third of these differences were statistically significant between males and females. Taking into consideration the nutritional status, the soft tissue thickness measurements increased with increased BMI levels for both sexes at each landmark, and the statistically significant differences were depicted between the different BMI categories at most of the landmarks. In conclusion, this study has provided useful reference points of the adult northern Chinese population for forensic facial reconstruction, and recommends that the nutritional status of the subject be considered during skull reconstruction procedures.

Human tooth pulp anatomy visualization by 3D magnetic resonance microscopy

Background

Precise assessment of dental pulp anatomy is of an extreme importance for a successful endodontic treatment. As standard radiographs of teeth provide very limited information on dental pulp anatomy, more capable methods are highly appreciated. One of these is 3D magnetic resonance (MR) microscopy of which diagnostic capabilities in terms of a better dental pulp anatomy assessment were evaluated in the study.

Materials and methods

Twenty extracted human teeth were scanned on a 2.35 T MRI system for MR microscopy using the 3D spin-echo method that enabled image acquisition with isotropic resolution of 100 μm. The 3D images were then post processed by ImageJ program (NIH) to obtain advanced volume rendered views of dental pulps.

Results

MR microscopy at 2.35 T provided accurate data on dental pulp anatomy in vitro. The data were presented as a sequence of thin 2D slices through the pulp in various orientations or as volume rendered 3D images reconstructed form arbitrary view-points. Sequential 2D images enabled only an approximate assessment of the pulp, while volume rendered 3D images were more precise in visualization of pulp anatomy and clearly showed pulp diverticles, number of pulp canals and root canal anastomosis.

Conclusions

This in vitro study demonstrated that MR microscopy could provide very accurate 3D visualization of dental pulp anatomy. A possible future application of the method in vivo may be of a great importance for the endodontic treatment.

Facial soft tissue thickness in individuals with different occlusion patterns in adult Turkish subjects

Knowledge of variation in facial soft tissue thickness is important for forensic anthropologists, dentists, and plastic surgeons. Forensic anthropologists use such information as a guide in facial reconstruction and superimposition methods. The purpose of this study was to measure facial tissue thicknesses of adult males and females of Turkish origin across different types of occlusion, and to compare the results with each other and with values obtained for other populations. The study was conducted on 200 healthy individuals. The analysis of facial tissue thickness included 20 landmarks (10 dentoskeletal and 10 soft tissue) and 10 linear variables. Sex-based variation in facial tissue thickness was noted. The highest soft tissue thickness values were observed in the group with Class III occlusion type at Sn-A point for both the females (16.9, SD=2.4) and the males (17.8, SD=3.3). In the Class I group, the highest tissue depth was observed at Sn-A point (15.3, SD=2.1) in females, and at Li-Id point (17.1, SD=1.9) in males. In the Class II group, contrary to the findings for Class I, the highest soft tissue depth was at Li-Id point (16.0, SD=1.4) in females, and at Sn-A point (18.1, SD=2.6) in males. In conclusion, facial tissue thickness varied in adults depending on the sex and on the type of occlusion.

Age and sex related measurement of craniofacial soft tissue thickness and nasal profile in the Chinese population

The purpose of this study was to acquire accurate data of craniofacial soft tissue thickness (CFSTT) and nasal profile in Chinese people of Han population. A total of 31 anatomical landmarks and 4 nasal profile parameters were determined using magnetic resonance imaging (MRI) in 425 subjects (233 males and 192 females). In the present study, the mean CFSTT values of male subjects exceeded those of female subjects at most anatomical landmarks except at seven (22.58%) and 6 out of the 7 landmarks were bilateral anatomical landmark points. The age-related and sex × age interactions were found to be statistically significant at all landmarks. Significant differences were found in the nasal profile data of males and females, and 15 out of 20 different groups had significant differences between sexes, and the mean values of nasal length, nasal height, nasal depth and nasal breadth in males were all greater than those in females. Furthermore, both CFSTT and nasal profile showed good correlation with age. The thickest CFSTT of male and female were found at the respective ages of 45-59 and 35-44, and the nasal profile becomes more constant after 24 years of age. CFSTT of the lower part of the face shows greater variation compared to the upper part, so special care needs to be applied when reconstructing the lower portion of the face. Our data on CFSTT and nasal profile for the Chinese Xi'an Han population is important in understanding craniofacial characteristics of the Chinese population and might be potentially helpful in forensic identification.

Three-dimensional localization of impacted teeth using magnetic resonance imaging

Impacted teeth remain embedded in the jawbone beyond the normal eruption time with completed root growth. They can often get infected or damage neighboring teeth. Information about the three-dimensional position of impacted teeth is invaluable in orthodontic diagnosis and treatment planning. The purpose of this prospective study was to assess the feasibility of using magnetic resonance imaging (MRI) for the three-dimensional localization of impacted teeth in children and adults. The study included 39 patients from the pediatric age group with different tooth impactions and seven adults with impacted wisdom teeth. MRI yielded a clear separation between impacted teeth and the surrounding tissue, and the position and angulation of impacted teeth in all three spatial dimensions could be assessed. Compared to conventional radiography, dental MRI provides the advantage of full volumetric morphology accompanied by complete elimination of ionizing radiation, which is particularly relevant for repeated examinations of the pediatric group.

Facial soft tissue thickness in northwest Indian adults

In order to reconstruct the face from a bare skull, the facial soft tissue thickness (FSTT) was determined at 29 standard anthropological landmarks by magnetic resonance imaging (MRI) in 173 male and 127 female adult subjects of northwest Indian origin. Repeatability and accuracy of the measurements was assessed by paired t-test and 95% confidence intervals. A stepwise discriminant function analysis selected nine landmarks for better sex classification in FSTT measurements. The thickness of soft tissue was different from that described in the literature and reported for samples from other countries. A correlation between skinfold thickness and body mass index (BMI) with that of FSTT was observed. The data of facial soft tissue thickness will help forensic experts in reconstructing the face from a skull for identification purposes.

Accuracy of facial soft tissue thickness measurements in personal computer-based multiplanar reconstructed computed tomographic images

The purpose of this study was to determine the precision and accuracy of facial soft tissue measurement using personal computer (PC)-based multiplanar reconstructed (MPR) computed tomography (CT) images and to evaluate the effect of the various CT scanning protocols on the facial soft tissue thickness measurement. Thirteen different CT imaging protocols were used to image a cadaver head. MPR reformations and three-dimensional (3D) reconstructions viewed on a laptop PC were used to make measurements at six specific sites on each set of images. These measurements were compared to physical measurements at the same sites. Increasing the slice thickness resulted in decreased image quality. Within the same slice thickness, increasing the pitch ratio in the spiral mode, resulted in decreasing image quality. The image quality of conventional CT scanning was relatively poorer than that of the spiral CT scanning. However, the mean deviation from the physical measurement was within 0.43 mm in every instance. This mean deviation was quite small and clinically acceptable for measuring the soft tissue thickness of the facial area. PC-based MPR CT images of the face using routine scanning CT protocols can be used to accurately measure soft tissue thickness in the facial region. However, for more fine and accurate data collection, scanning protocols with slice thicknesses less than 5mm, and a spiral/helical mode pitch less than 2:1 are recommended.

A Comparative Study of Computed Tomography and Magnetic Resonance Imaging for the Detection of Mandibular Canals and Cross-Sectional Areas in Diagnosis prior to Dental Implant Treatment

BACKGROUND

Computed tomography (CT) is effective in the diagnosis of dental implants. However, it has the disadvantage of exposing patients to high doses of x-rays, and the mandibular canals cannot be detected by CT in some clinical cases.

PURPOSE

The purpose of this study was to examine the detectability of the anatomic morphology of the molar region in the lower jaw (where implantation is common) by CT and magnetic resonance imaging (MRI), to compare the data, and to determine the usefulness of MRI in diagnosis prior to dental implant treatments.

MATERIALS AND METHODS

Eleven female subjects (average age, 59 years) who had partially edentulous mandibles (total of 19 sites) were included in the study. CT and MRI were performed with the same subjects, and the degrees of identification of the mandibular canal in the first and second molar regions were compared. Dimensional accuracy in the second molar region was also compared.

RESULTS

With CT, the canals of the first molar regions were not identified in 11 of 19 sites; however, MRI identified the canals in all 19 sites. Using the kappa index, we found that the inter- and intraobserver identification reliabilities (0.84 and 0.87, respectively) were excellent, especially for MRI. Dimensional positioning of the canal in the second molar region was almost the same with MRI as with CT.

CONCLUSIONS

MRI is an alternative method in diagnosis prior to dental implant treatment in the mandibular molar region.

Ultrasonic assessment of facial soft tissue thicknesses in adult Egyptians

The production of a three-dimensional plastic face on an unknown human skull has been practiced sporadically since the latter part of the last century. In recent years, the technique has been revived and applied to forensic science cases. The morphometric method of forensic facial reconstruction rests heavily on the use of facial soft tissue depth measurements. Moreover, it has been established that measurements made on the living are of more value than those made on the dead. In view of the well-known genetic complexities of the Egyptians, and the lack of knowledge of average facial soft tissue depths of the Egyptians that makes facial reconstruction questionable, it was decided to set up a table of norms for facial tissue thicknesses in 204 adult Egyptians aged 20-35 years. Tissue depths at 17 established landmarks (according to Aulsebrook et al. [Forensic Sci. Int. 79 (1996) 83]) were obtained using ultrasonic probing. The study revealed a unique spectrum of measurements for the Egyptians that might be useful for facial reconstruction purposes with obvious sexual dimorphism in facial soft tissue thickness. Additionally, the study provided evidence for the presence of interpopulation differences in average facial soft tissue thicknesses as evidenced from the comparison of the present data of Egyptians with those previously reported for some other populations.

Factors in the pathogenesis of tumors of the sphenoid and maxillary sinuses: a comparative study

OBJECTIVES/HYPOTHESIS

To explain the processes that lead to the development of tumors in the maxillary and sphenoid sinuses.

STUDY DESIGN

A 32-year review of the world's literature on neoplasms of these two sinuses and a randomized case-controlled study comparing the normal mucosal architecture of the maxillary to the sphenoid sinus.

METHODS

Analysis of a 32-year world literature review reporting series of cases of maxillary and sphenoid sinus tumors. Tumors were classified by histological type and separated into subgroups if an individual incidence rate was reported. Histomorphometry of normal maxillary and sphenoid sinus mucosa was performed in 14 randomly selected patients (10 sphenoid and 4 maxillary specimens). Specimens were fixed in 10% formalin, embedded in paraffin, and stained with periodic acid-Schiff (PAS) and hematoxylin. Histomorphometric analysis was performed with a Zeiss Axioscope light microscope (Carl Zeiss Inc., Thornwood, NY) mounted with a Hamamatsu (Hamamatsu Photonics, Tokyo, Japan) color-chilled 3 charge coupled device digital camera. The images were captured on a 17-inch Sony (Sony Corp., Tokyo, Japan) multiscan monitor and analyzed with a Samba 4000 Image Analysis Program (Samba Corp., Los Angeles, CA). Five random areas were selected from strips of epithelium removed from each sinus, and goblet and basal cell measurements were made at magnifications x 100 and x 400.

RESULTS

The literature review revealed that the number and variety of tumors in the maxillary sinus are much greater than those in the sphenoid. The incidence of metastatic lesions to each sinus is approximately equal. No recognized pattern of spread from any particular organ system could be determined. On histomorphometric study there were no statistically significant differences between the sinuses in the concentration of goblet cells, basal cells, or seromucinous glands.

CONCLUSIONS

Factors involved in the pathogenesis of tumors of the maxillary and sphenoid sinuses include differences in nasal physiology, embryology, morphology, and topography. There are no significant histological differences in the epithelium and submucous glands between the two sinuses to explain the dissimilar formation of neoplasms.

Facial soft-tissue thicknesses in the adult male Zulu

The morphometric method of forensic facial reconstruction rests heavily on the use of facial soft tissue depth measurements. In reconstructing the Negroid face, much use has been made of the tables of soft tissue thickness of American Negroid cadavers. However, the genetic complexities of American blacks are well known. In addition it is felt that measurements made on the living are of more value than those made on the dead. In view of this it was decided to set up a table of norms for facial soft tissue depths of the living Zulu, an African Negroid who has remained relatively free from genetic admixture with other populations. The tightly controlled sample consisted of 55 healthy male Zulus, aged 20 to 35. Tissue depths at established landmarks were measured from lateral and oblique cephalometric radiographs. These were then combined with ultrasonic readings at other landmarks on the subject's face to yield a comprehensive set of tissue depth data. This paper presents a set of average facial soft tissue depth measurements from the Zulu face that results in the development of a new profile. It also provides a method for linking two systems of measurement.

Superimposition and reconstruction in forensic facial identification: a survey

Forensic facial reconstruction, is the reproduction of the lost or unknown facial features of an individual, for the purposes of recognition and identification. It is generally accepted that facial reconstruction can be divided into four categories: (1) replacing and repositioning damaged or distorted soft tissues onto a skull; (2) the use of photographic transparencies and drawings in an identikit-type system; (3) the technique of graphic, photographic or video superimposition; (4) plastic or three-dimensional reconstruction of a face over a skull, using modelling clay. This paper sets out to review work done on both superimposition and plastic reconstruction, however, the authors believe that only the latter category can correctly be termed facial reconstruction. The survey is divided according to work done through anthropological evaluation of the skull, clinical examination and dissection of the soft tissues, as well as methods of measuring soft tissue thicknesses using tissue puncture, ultrasound, cephalometric radiography and magnetic resonance imaging. In addition, a method of the combined use of ultrasound and radiography to collect a wider range of facial soft tissue depths and a method of producing skull and face profiles are outlined.

Internal organization in the human jaw muscles

The human jaw muscles are essential to mastication and play an important part in craniofacial growth. They contribute to dental and articular forces, deform the mandible, and, like other tissues, are subject to disorders, often manifested as pain. The literature describes how their contraction is controlled by the nervous system, and how their general structure and function contribute to craniofacial biology, but there has been little appraisal of their internal organization. Most of these muscles are not simple; they are multipennate, complexly layered, and divided by aponeuroses. This arrangement provides substantial means for differential contraction. In many ways, jaw muscle fibers are intrinsically dissimilar from those found in other skeletal muscles, because they are arranged in homogeneous clusters and generally reveal type I or type II histochemical profiles. Most are type I and are distributed preferentially in the anterior and deeper parts of the jaw closers. Additionally, most motor unit (MU) territories are smaller than those in the limbs. There is circumstantial evidence for intramuscular partitioning based in part on innervation by primary muscle nerve branches. During normal function. MU recruitment and the rate coding of MU firing in human jaw muscles follow the general principles established for the limbs, but even here they differ in important respects. Jaw muscle MUs do not have stable force recruitment thresholds and seem to rely more on rate coding than on sequential unit recruitment to grade the amplitude of muscle contraction. Unlike those in the limbs, their twitch tensions correlate weakly with MU fatiguability and contraction speed, probably because there are so few slow, fatigue-resistant MUs in the jaw muscles. Moreover, the type I fibers that are present in such large numbers do not contract as slowly as normally expected. To complicate matters, estimation of jaw MU twitch tensions is extremely difficult, because it is affected by the location used to measure the twitch, the background firing rate, muscle coactivation, and regional, intramuscular mechanics. Finally, there have been very few systematic studies of jaw MU reflex behavior. The most recent have concentrated on exteroceptive suppression and suggest that MU inhibition following intra- and perioral stimulation depends on the location of the MU, its background firing rate, the timing of the stimulus, and the task used to drive the unit. Task dependency is a common feature of human jaw MU behavior, reflecting interaction between peripheral sensory information from orofacial and muscle afferents and corticobulbar drive.(ABSTRACT TRUNCATED AT 400 WORDS)

Magnetic resonance imaging of human teeth

There is a need in clinical dentistry for improved diagnostic methods for an accurate evaluation of pulp tissue pathosis. The purpose of this investigation was to attempt to image extracted human teeth with the aim of establishing the possible future application of magnetic resonance imaging in the diagnosis of pulpal pathosis. The results of this pilot study demonstrate that, in the in vitro setting, the outline of the tooth and pulp chamber can be imaged with a high degree of accuracy, and detailed images of the periodontal membrane and gross pulpal anatomy can be obtained. There were obvious differences in the signals given off by different locations within these teeth, and the images of the dental pulp tissue were detailed enough to suggest the possible correlation with histology. The high (9.4 T) field strengths used in this study demonstrate the in vitro application of this technology and the future possibilities for diagnosis of periodontal and odontogenic problems are significant.

Estimation of tendon-plane orientation within human masseter muscle from reconstructed magnetic resonance images

The human masseter is a powerful multipennate jaw elevator with complex internal architecture. The three-dimensional disposition of tendon planes within the muscle is thought to be an important determinant of function. We selected five adult subjects and used cephalometric radiography, magnetic resonance imaging and graphical, three-dimensional reconstruction to describe the organization of these planes within the muscle. Putative tendon planes were fitted to the surfaces of the three-dimensional reconstructions, and these were related to the mid-sagittal plane in the coronal and transverse views. To confirm whether putative planes disclosed by magnetic resonance represented true anatomical entities, a fresh human cadaver head was imaged and the magnetic resonance slices were compared with cryosections obtained in the same planes. Tendon-plane angulation appeared to be related to ramal length and lower face height measured cephalometrically. In the transverse view, the tendon planes appeared roughly to follow the angulations of the zygomatic arch and the lateral face of the mandibular ramus. These findings suggest that the angulation of tendon planes, and possibly pennation angles, are different depending on the viewing angle. Rather than reporting pennation angle as a single angle, alpha, which has been the convention, it may be more appropriate to express it as a three-dimensional angle relative to the normal of a particular tendon plane. The inference is that muscle fibres inserting on either side of a central tendon may need to develop different tensile forces if translation is to occur directly along the tendon axis.

Location of needle electrode recording sites in the human masseter muscle by magnetic resonance imaging

A stereotactic method was developed for locating needle electrode recording sites within the human masseter muscle. The method combines a single motor unit (SMU) electromyographic (EMG) technique, magnetic resonance imaging, the 3-dimensional reconstruction of orofacial tissues, and a common reference systems. SMU EMG activity can be recorded from different sites in the masseter muscle, and the location of these sites displayed graphically in 3 dimensions. The technique should be a useful adjunct in future studies of the internal architecture and electrophysiological properties of the human masseter muscle.