Preliminary Study on Facial Soft Tissue Thickness by Magnetic Resonance Imaging in Northwest Indians. Sahni, Daisy (Forensic Science Communications, January 2002)
January 2002 - Volume 4 - Number 1
Research and Technology
Preliminary Study on Facial Soft Tissue Thickness by Magnetic Resonance Imaging in Northwest Indians
Associate Professor of Anatomy
Emeritus Professor of Anatomy and Forensic Medicine
Professor and Department Head of Anatomy
Assistant Professor of Radiodiagnosis and Imaging
Professor and Department Head of Radiodiagnosis and Imaging
Postgraduate Institute of Medical Education and Research
Department Head of Biology
Central Forensic Science Laboratory
Department of Anthropology
Paper presented at the 9th Biennial Meeting of the International Association for Craniofacial Identification, FBI, Washington, DC, July 2000.
Facial soft tissue thickness was measured in 60 northwest Indian adults (30 women and 30 men) between the ages of 18 and 40 years by magnetic resonance imaging (MRI). Seven MRI sections were taken to measure thickness at standard anatomical landmarks--one sagittal section, one parasagittal section at the level of midorbit, two coronal sections, and three transverse (axial) sections. Measurements of facial soft tissues of northwest Indian men were higher than northwest Indian women except beneath the chin, infraorbital margin, and lower lip margin. Statistically, sexual differences in most of the measurements were highly significant. The end of the nasal opisthocranion and supra M2, however, were insignificant. Slight asymmetry in two sides was present at the frontal eminence, porion, gonion, zygion, and Whitnall's tubercle (outer canthus), where left measurements were slightly greater than were those of the right. Racial differences were seen in the measurements of facial soft tissue thickness.
In forensic work it is not uncommon to attempt to identify the deceased from a skull. To date in India, only the approximate age and sex of the skull (Jit 1979) and sometimes the cause of death (Jit 1993) can be determined by examining the skull. If data on facial soft tissue thickness were available, it would be possible to reconstruct the face. This type of work has been done on the skulls of Japanese (Suzuki 1948), African Americans (Rhine and Campbell 1980), American Caucasians (Rhine et al. 1982), and South Africans of mixed race (Phillips and Smuts 1996). The data generated from one population, however, cannot be applied to another population. Lack of data on the Indian population results in the inability to accurately reconstruct the facial features from skeletal remains, and thus, many cases of identity and murder go unsolved. It is, therefore, important to determine the facial soft tissue thickness in various populations in India.
In Japan and western countries, the following methods have been used for measuring facial soft tissue thickness:
- Needle-depth probe and double-edged knife (His 1895; Kollmann and Buchly 1898)
- Ultrasonography (Lebedinskaya et al. 1993)
- Radiography including computerized tomography (CT) scan (Aulsebrook et al. 1996; George 1987; Phillips and Smuts 1996)
Magnetic resonance imaging (MRI) offers the following advantages over the methods just listed:
- MRI allows multiple planes for study, enabling researchers to take accurate measurements of soft tissues on various anatomical points of the cranium and face.
- A greater number of anatomical landmarks can be studied accurately on MRI compared to CT, where only axial sections are measured.
In this study, an attempt was made to measure the facial soft tissue thickness at various standard anatomical points by MRI on the northwest Indian population.
Materials and Methods
Facial soft tissue thickness was measured in 60 adults (30 men and 30 women) ranging in age from 18 to 40 years who visited the Department of Radiodiagnosis and Imaging at the Postgraduate Institute of Medical Education and Research, Chandigarh, India, for brain MRIs. Patients with head and neck trauma or other pathology that could distort the normal facial structures were excluded from the study. Subjects' age, sex, height, and weight were recorded before taking the tissue measurements. On the basis of Indian insurance charts that give weight against height, body mass index (BMI) was calculated. The subjects below or equal to the 15th percentile of BMI were considered underweight, whereas the 85th percentile or above BMI were overweight. The subjects between the 16th and 84th percentile were considered normal weight (Sanjeev et al. 1991). Underweight and overweight subjects were excluded from the study.
MRI measured the following sections for facial soft tissue thickness at various standard anatomical points:
- Midsagittal section (Figures 1 and 2): from above downwards and forwards -- vertex, supraglabella, glabella, nasion, end of nasal, midphiltrum, upper lip margin, lower lip margin, chin-lip fold, mental eminence, beneath chin; from above backwards and downwards-opisthocranion, inion.
- Parasagittal section at the level of midorbit (Figure 3): right frontal eminence, left frontal eminence, right supraorbital, left supraorbital, right infraorbital, left infraorbital.
- Two coronal sections: right porion, left porion (Figure 4) right gonion, left gonion (Figure 5).
- Three transverse sections: right outer canthus, left outer canthus (Figure 6), right zygion, left zygion (Figure 7), right supra M2, and left supra M2 (Figure 8).
|Figure 2 Another midsagittal section of the head indicating (1) lower lip margin, (2) chin-lip fold, (3) mental eminence, (4) beneath chin, (5) inion, and (6) opisthocranion. Click here to view enlarged image.|
|Figure 1 MRI in midsagittal section of the head. Outer thick white line shows the soft tissue thickness. Landmarks indicated: (1) vertex, (2) supraglabella, (3) glabella, (4) nasion, (5) end of nasal, (6) midphiltrum, and (7) upper lip margin. Click here to view enlarged image.|
|Figure 3 A parasagittal section at the level of midorbit that indicates (1) supraorbital margin, (2) infraorbital margin, and (3) frontal eminence. Click here to view enlarged image.|
|Figure 4 Coronal section of the head at the level of internal auditory canal indicating porion on both sides. Click here to view enlarged image.|
|Figure 5 Coronal section of the head at the angle of the jaw indicating gonion on both the sides. Click here to view enlarged image.|
|Figure 6 Transverse section of the head at the level of Whitnall's tubercle on both sides. Click here to view enlarged image.|
|Figure 8 Transverse section of the head at the level of upper second molar tooth indicating the thickness of the cheek on both sides. Click here to view enlarged image.|
|Figure 7 Transverse section of the head at the level of most protruding part of zygomatic bone on both sides. Click here to view enlarged image.|
Table 1 illustrates that all measurements are greater in men than in women except beneath the chin, infraorbital, and lower lip margin. Means of the measurements were the same in the two sexes at the end of the nasal. Sexual differences in the mean values of all the measurements were highly significant (p < 0.001) or significant (p < 0.01). The end of the nasal, opisthocranion, left gonion, and supra M2 were insignificant (p > 05). Slight asymmetry in two sides was present at the frontal eminence, porion, gonion, zygion, and Whitnall's tubercle (outer canthus), where left measurements were slightly greater than right measurements.
Determining soft tissue thickness in cadavers may not give correct measurements because of cadaver dehydration. To overcome this problem, Rhine and Campbell (1980) determined the soft tissue thickness in cadavers less than 12 hours after death or after 12 hours in refrigeration. No data is available as to how much variation occurs during this period. It is possible that soft tissue thickness changes on an hourly basis. It is also possible that keeping the bodies in refrigeration may result in rehydration. Measuring soft tissue thickness is not easy from a plane radiograph because superimposition of various structures causes problems in taking measurements. A CT scan cannot take all measurements because only axial sections are measured. Radiography and CT scans use X-ray radiation that is harmful to biological tissues and thus is a major limiting factor. Ultrasonography does not involve ionizing radiation and allows real-time adjustment of planes of study. Bone may not show well on ultrasonography, however, and the technique is operator-dependent and does not allow adequate reliability or reproducibility. The technique of measuring soft tissue thickness by MRI has been used by Helmer et al. (1986) and by Lam et al. (1989). For the purpose of this study, MRI measurements were taken.
Comparison of soft tissue thickness in the northwest Indians with those given by Phillips and Smuts (1996) in other populations is illustrated in Table 2. In addition to the anatomical points evaluated in other studies, this study evaluated additional points, vertex, opisthocranion, inion, porion, and Whitnall's tubercle (outer canthus), which will help in three-dimensional facial reconstruction.
Table 2 shows that the facial soft tissue thickness at various anatomical landmarks is greater in African American men and women than those at corresponding points in northwest Indians except at the supraorbital, which is 4.75 mm in African American men and 5.80 mm in northwest Indian men. Soft tissue thickness in Japanese men and women at various anatomical points is smaller than in present material except two measurements--the end of the nasal and the chin-lip fold. A comparison with observations by Phillips and Smuts (1996) on the South African mixed population indicates that most of their measurements are more than the northwest Indians. Measurements at the nasion, lower lip margin, supraorbital, and supra M2, however, are higher in Indian men. Two measurements, lower lip margin and supra M2, are higher in Indian women. Most of the measurements in the American Caucasians are higher compared to Indians except the midphiltrum, lower lip margin, and frontal eminence.
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