Forensic Radiology Essay

INTRODUCTION Forensic radiology has a long tradition in the forensic sciences. Its history started in 1895 when the first radiograph was made by Conrad roentgen. Three years later, in 1898 postmortem radiographic examination was introduced. Forensic radiology so far as depended almost exclusively on the X-ray and the static image captured on the roetgenogram.
Uses and utilization of Radiology in Forensic Dentistry 1, 2, 3 Radiographs have helped to solve difficult cases in the forensic science.
1. Identification of victims:
Radiographs are helpful to determine age of an individual by assessing the stage of eruption of teeth. Skull Radiographs can be used in identification by superimposing on antemortem radiograph or photograph. Since
frontal sinuses are known for greatest normal variations among individuals they are used for this purpose. Yoshino et al have classified frontal sinuses based on size, bilateral asymmetry, superiority of side, outline of upper borders, presence of partial septa and supra orbital cells and reported a criminal case in which frontal sinus was used to identify a person.
Sassouni has suggested use of measurements in postero-anterior and lateral radiographs of the skull to match the ante and postmortem radiographs, which includes
1. Bigonial width
2. Cranial height (from mastoid to vertex)
3. Bimaxillary breadth
4. Height from bigonial width to temporal crest
5. Maximum cranial breadth
6. Frontal sinus breadth
7. Incisor height
8. Facial height
2. Evidence in the Identification of suspect:
Cases have been reported where suspects were identified because of fractured tooth parts of victims in the body of the suspects or fractured tooth of suspect in the victim as in the bite mark cases. Deliberate alteration in the shape of the teeth in suspects can be identified with radiographs in bite mark cases.
3. To determine the cause of death:
Radiographs may provide evidence of bullets or foreign bodies in the soft tissues following firearm incidence and explosion. After air crash accidents the cause of crash may be elucidated by the presence of radio opaque objects in the soft tissues. This is due to contamination with molten aircraft metal producing irregular shaped radio opacity.
4. To find faulty charting of teeth:
Sometimes while charting postmortem data teeth may be wrongly numbered especially in cases where adjacent tooth migrate in to the extraction space. This can be connected using radiographs. 5. Legal matters:
Following injury or assault radiological imaging is commonly obtained by medical expert interpretation of these images may provide useful evidence in criminal and civil jurisdiction.
6. Body identification:
Along with dental and DNA analysis radiographic images be used in the unknown victims. This requires the securing of pre-mortem examination eg: CT scan or radiograph of the suspect individual and the matching of specific anatomical details with similar postmortem studies. 7. Post mortem examination:
Nortje (1986) stated “radiographic appearance of teeth and of bone of face is a permanent record of these tissues even when teeth and sections of bone are removed for histopathologic examination”.
8. Non-accidental injuries of children:
Radiology places an important role in diagnosing child abuse. Accidental cranial fractures in infants are usually simple, linear and unilateral, affect the parietal bone and do not branch or cross sutures. Forensic radiologists suggest different techniques for specific head injury. CT is recommended for detection of subarachnoid hemorrhages while MRI is superior in revealing subdural hematomas, concussive injuries and shear injuries. CT and MRI are equally efficient for demonstrative epidural haematoma and CT advocated for detection of fractures.
9. Forensic anthropology:
Establishing biological age and identification of human remains are issues addressed by forensic anthropologists. The most common radiograph used for establishing age up to 16 year old are dental radiographs and hand radiographs. Post-cranial radiographs of specific ossification centers depending on the reputed age of the individual are useful estimating older individual. Panoramic radiographs which visualize most structures of the jaws and related areas on a single radiograph, have been advocated for mass
screening.

10. Record keeping:
Careful record keeping in medical facilities and private practices for as long as feasible is extremely important. In most countries, radiographs pertaining to inactive patient’s files are stored for at least five years. Radiographs are generally regarded as the property of the hospital or office in which they were produced although the law guarantees patient access to them
11. Expert testimony: It is important to remember to present the biological data both in scientific and in layman terms. Before submitting the data circumstances the radiographs were produced. The expert should know if the radiograph is original or a copy and the whereabouts of the radiographs at all times.
Basic principle used for post mortem radiograph 1, 4
When a radiograph of post mortem remains is performed to compare with ante mortem radiograph “Identical projection” must be achieved with similar magnification, exposure factors and angulations so as to reproduce the ante mortem radiograph like image. This is carried out by using various angles of projection and by varying technical factors.
General Considerations: Radiograph should be taken before and after head and neck autopsy. When ever possible radiograph should be made at the scene of accident or crime. They should be properly labeled with identification number, site and date of examination for future reference.
All intra and extra oral projections including panoramic radiographs have to be taken as and when it is needed depending on the case and type of remains.

Intra oral radiographs: Intra oral radiographs are difficult to perform particularly when there is restricted mouth opening. It may be necessary to remove soft tissues from the floor of the mouth or cheeks to insert the film. A miniature intra oral x-ray source may be used.
Resected maxilla may be split through the midpalatal suture. The posterior mandible and maxilla are placed on occlusal film to produce an “enlarged bite-wing film”.
Whenever fragmented remains consisting of teeth, restorations, bone pieces, appliances are recovered they have to be separated by the method proposed by Johanson.
Johanson’s method:
Place the debris on the plastic grid.
Place the film on a wire grid identical to the plastic grid.
From the resultant radiograph type of remain can be identified.
RADIOGRAPHIC TECHNIQUES USED IN FORENSIC DENTISTRY4
Extra oral radiography With the oblique –lateral technique it is necessary to increase the anode –object distance in order to enlarge field of irradiation. The minimum distance is 40 cm which will project onto the film a 10 cm diameter beam of X-rays .The exposure factors using high definition intensifying screens will be 55-60 KVp and 20mAs. When using faster screens the milliampere seconds is reduced.

View kVp mAs Time (S)
PA TOWNES 65 30 0.3
LATERAL 55 30 0.3
OM 65-75 60 0.3
Panoramic radiographs
The X-ray tube and film rotate around a stationery patient; specimens must be elevated in position, articulated, and oriented with the occlusal line or Frankfort plane parallel to the ground. A setting of 8 mA at 80 KVp is a good starting exposure, a previously exposed black film can be placed in the cassette against the unexposed film to reduce the effect of intensifying screen.
INVESTIGATORY METHODS IN FORENSIC DENTISTRY BY MEANS OF VARIOUS RADIOGRAPHIC INTERVENTIONS
BITE MARKS:
Radiographs may be used to assist in identification by bite marks. The impressions are made with dental modelling wax and cut to size of an occlusal film. The resultant impression is then filled with radiopaque dental alloy and placed with occlusal surface downwards on film. The X-ray beam is directed centrally at right angles to the object and film. An anode –film distance of atleast 40 cm is recommended to give more parallel beam.
Comparisons of Antemortem and Postmortem Radiographs
Antemortem and postmortem radiographs are compared noting similarities and differences .The most current films are examined first because they will show the greatest similarity to the postmortem status of the teeth and jaws. Comparison is done on
1. Number and arrangement of teeth(missing teeth, rotated teeth, spacing, extra teeth, impacted teeth)
2. Caries and periodontal bone loss
3. Coronal restorations
4. Hidden restorations (posts, implants, root canal fillings)
5. Bony pathology
6. Dental anatomy
7. Trabecular bone pattern
8. Anatomic bony landmarks
9. Maxillary sinus and nasal aperture
10. Frontal sinus

(a) Antemortem bitewing radiographs. (b) Postmortem lower bitewing radiographs.
Age estimation of adults from dental radiograph 5,6,7,8,9
With the advancing age the size of the dental pulp cavity is reduced as a result of secondary dentine deposit, so that the measurements of this reduction can be used as an indicator of age.
Secondary dentine as also been measured indirectly on radiograph of extracted teeth. Such measurements were suggested use in non-destructive method to predict age. The ratio between pulp and the root have also been used in age estimation, as the size of the pulp is reduced with age. Radiographs of the middle phalanx of the third finger (MP3) are taken to know the skeletal maturation status of the child.
Diversity of dental patterns in the orthopantomography for human identification 11
The comparison and antemortem and postmortem dental characteristics is a commonly applied method to perform personal identification. Orthopantomography is broadly applied standard method in dentistry. It provides the complete view of the teeth and both jaws and one image. Gustafson was the first to use orthopantomography in forensic practice for the purpose of identification, according to the theory proposed by Paatero, Rocca et al considered orthopantomograms to be the most important antemortem source of information outside the written treatment records.The use of orthopantomography is practically applicable for the identification of victims of mass disasters as well as wars.
Personal Identification on the basis of antemortem and postmortem radiographs 12,13
There are many parts of the human skeleton, which because of their anatomical variability are very applicable to the identification process. The first authority to point this out was Schuller who found that X-rays of the frontal sinuses are very good tool for identification.
Currently there are three main comparison methods of personal identification used in Hungarian forensic practice
a. Examination of dental records
b. Superimposition of photographs
c. Comparison of radiographs
New Horizons in forensic radiology – Multislice Computed Tomography (MSCT) 14, 15, 16
Alternatives to classic autopsy to collect forensically relevant data the potential of MSCT can be used. With this modern method the scan time for a full body examination with a gunshot wound to the head is approximately 60 Seconds. This method is more rapid, based on non-destructive documentation process and in some respects is more precise than the standard forensic autopsy.
DENTAL CT SCREENING TOOL FOR DENTAL PROFILING 17 The newer CT imaging based software called DENTASCAN used for identification purpose. Using the Dentascan software, reformatted panoramic images could be reconstructed for each cases that were compared to the antemortem dental periapical radigraphs , bite wing films, and panoramic radiograph.
A reformated panoramic overview created by Dentascan delivers in a non invasive way to overview jaws showing basic components of teeth, (enamel, dentin, pulp) anatomic structures of alveolar bone (mandibular nerve canal or floor of nasal cavity and maxillary sinus), pathology (caries, radiolucencies, radioopacities, or position of third molars)and restorations .
The most important advantage of Dentascan in contrast to classical methods is that documentation can be made non invasive and digital way without jaw resection, which is often performed to facilitate classical radiological documentation on decomposed, charred, and mutilated corpses.
Identification of skull by its suture patterns 18
The examination of 320 skulls collected at random revealed ectocranial suture patterns in them are highly individualistic and that no two skulls can ever have an identical pattern. The possibility of the suture patterns being recorded incidentally in routine diagnostic skull radiograph was verified by examining the skull skiagrams preserved in radiology department and can be more effectively used in personal identification problems. A positive method of identification of the skull is suggested by the comparison of radiographic with visible skull suture pattern. The added advantage in process of identification through suture pattern is that they cannot be altered or destroyed in case of finger ridges.
Individual identification by means of conventional bite-wing film and subtraction radiography 19, 20
The digital subtraction technique used in clinical trials for the evaluation of small tissue changes. It may however, also be able to determine hard tissue similarities for use in forensic dentistry. Principle of digital subtraction included features for correction of variations in exposure geometry and density. Subtractions were performed between identical images (Images of same individual) and between non-identical images (images of two different individuals).
Bite-wing radiography is considered as a good candidate for potential victim identification. A quantitative analysis of subtraction images based on bite-wing radiographs as recently been reported. The subtraction images derived from identical photographs significantly more homogenous than those derived from non-identical radiographs originating in individuals with and without simple dental restorations.
Sex determination by lateral radiographic cephalometry 21
In general male skulls are identifiable by being more robust. Female skull is characterized by weaker development of its super-structures. All bony ridges, crests and processes are smaller and smoother in the female skull than in the male skull, especially true for the temporal line, mastoid processes, nuchal lines, external occipital protuberance and superciliary arches. Sella to nasion, Frankfort horizontal place and basion to nasion as reference lines or planes are commonly used in lateral radiographic cephalometric analysis. .Thus morphometric traits of the skull superstructures and intra cranial structures are easily assessed. This enables us to use them as morphometric variables.
X-Ray Screening System at a Mass Disaster 22 A security scanning system known as Linescan unit were used which allows screening where space may be limited. They operate on 105 to 125 VAC and the X-Ray voltage is 160 KVp.

SUMMARY AND CONCLUSION The radiological identification of individual human remains depends entirely on matching specific and unique visual findings or features on both ante mortem and post mortem radiological images of that person. Post mortem findings confirming sex, age, stature, or race may be either confirmatory or exclusionary. Dental identification is also scientific, relying on the patterns of missing, filled, and decayed teeth as well as anatomic variation of the teeth, jawbones, and sinuses. Teeth and bones are also durable, surviving decompositional and destructive forces. The decedents teeth are compared to ante mortem written records although the most accurate and reliable method is by comparison of ante mortem and post mortem records. Unlike subjective records, which lack detail and can include errors, radiographs supply objective data through precise recording of unique morphology of dental restorations and dento –osseous anatomy.

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