Forensic Radiology and the Physiology of Sinuses

Forensic medicine generally covers a heterogeneous group of various disciplines or subspecialties sharing a common interest. The application of specialized scientific and/or technical knowledge aim is to aid in civil and criminal law. Among those disciplines, forensic radiology is a specialized area of medical imaging using radiological techniques to assist physicians and pathologists in matters related to the law. The forensic application of diagnostic medical radiology can be applied in many fields where the prime target of evaluation is the skeleton (37).

Due to technological progress in radiology field, a lot of potential tools are added to forensic radiology that allows wider fields of applications in this matter (37). Forensic radiology is not just to image human remains or bullet fragments; it is the application of diagnostic imaging technology and examinations to answer questions of law. However, the definition, scope and use of forensic radiology examination results are poorly defined. Although radiography is one of the most common scientific methods used to accumulate and analyze forensic evidence, forensic radiology is not recognized formally as a branch of forensic sciences (38).

The credit of field of radiology goes back to Wilhelm Conrad Rontgen, professor of physics, director of the Physics Institute, and Rector of the University of Würzburg who observed an unusual phenomenon while experimenting with cathode ray tubes on November 1895. After intensive investigation, he determined that he had discovered a new kind of ray, which penetrate solid, opaque materials and give photographic representations about their contents. This rays are called “X-rays” as “x” was the symbol of the unknown, Roentgen's findings announced in 1896 (39). Professor Arthur William Wright, director of the Sloan Physics Lab. Yale University, is accorded primacy in the production of X-ray images in the United States on January 1896. He exposed one rabbit’s carcass to an X-ray beam for an hour, then photographic plate revealed lead shot within body. There were small, round objects inside the rabbit that appeared as dark spots on the positive film. This was the first time to establish a cause of death through radiography which was the first step in forensic radiology (39,40). Forensic radiology application in life was introduced later, one year after X-ray discovery, when lead bullets were discovered inside the head of a victim which is the first court case with the aid of forensic radiology (41).

The first civil case where a Court accepted x-ray took place in United States, which began on June 1895 when James Smith fell from a ladder. Dr. Grant found no evidence of a fracture and let him do his normal activity and requested him to return after 1 week. The diagnosis was free. On April 1896, Mr. Smith brought a $10,000 suit for malpractice against Dr. Grant, as his hip was injured and he suffered from limb shortening and disability due to a misdiagnosing the impacted fracture in the left femoral neck. Several x-rays for Mr. Smith’s hip were made, the last of which showed the outline of an impacted fracture of the proximal femur (39).

In 1935, Feet x-ray played an important role related to identification of dead bodies. On September 15, 1935, Dr. Ruxton’s wife and her nursemaid disappeared suddenly from the family home and were never again seen. After two weeks, some of human remains were found in the surrounding area and search continued for another month until most of two female bodies could be collected. Unfortunately, the faces were mutilated, the teeth were extracted, the terminal digits of the hands amputated and other distinguishing topographical features were excised from soft tissues, all to preclude identification (39).

In 1949, the Great Lakes liner Noronic caught fire and burned totally in Toronto, with many fatalities. Dr. Arthur C Singleton, a professor & head of the Radiology Department at the University of Toronto, considered as the father of mass casualty radiology as he was able to identify 24 of 119 fatalities by radiologic comparison alone (39). In 1981, Evans and Knight’s book, described applications of radiology for the purpose of identification and to confirm diagnosis of abuse, mishaps, and malpractice, as well as for identification, age determination and other anthropological issues and its relation with forensic pathology, gunshot wounds, head injuries and several types of trauma (19).

In 1994 Austin and Maples have published a study which aim to evaluate the accuracy of methods of image superimposition and they found that with two frontal and lateral view of skull antemortem radiographs and without dental data, identification can be made (42). In 1995 Andersen and Wensel have assessed the capacity of individual identification by analyzing the conventional bite-wing films and radiographic subtraction through antemortem and postmortem simulation (43). Just under 80 years later, a new technology sparked great revolution in the medical community, more than the first X-ray images had done before which is the computed tomography. Computed tomography (CT) is also based on X-ray technology, but it visualizes the inside of the body on screen, one slice at a time. In conventional X-ray images, different structures are superimposed on top of each other. In advanced systems, these slices are just 0.5 to 1 millimeter thick, allowing physicians to see even the tiniest changes in tissue (44).

It is, in general slow to implement the modern diagnostic imagining modalities, partly due to unawareness of its potentials and probably also for financial reasons. Now CT and other imagining techniques such as magnetic resonance imaging are gaining access to forensic medicine. The CT in forensic investigation is growing and other technologies once reserved primarily for diagnostic medical imaging are proving useful to forensic investigators (45). The forensic application of diagnostic medical radiology can be applied in many fields: human identification (particularly in investigations of mass disasters and decomposed bodies), evaluation and documentation of injury or cause of death (accidental or non-accidental), criminal and civil litigation (fatal or non-fatal), administrative proceedings, education, research and administration (37).

The prime target of forensic radiological evaluation is the osseous skeleton, but in many cases the soft tissues and the abdominal and thoracic viscera may offer key findings (46). Radiology role in identification and determination of individual identity may be presumptive upon demonstration of pre-existing injuries, illness, or congenital and/or developmental peculiarities but radiological identification needs direct comparison of ante-mortem and post-mortem images of the body or its parts (46). Radiology also has a great role in evaluation of injury which requires elements of detection, pattern recognition, interpretation and comparison, all based on radiologic experience with normal and abnormal findings (37,46).

Radiology role in bone fracture is to analyze the localization and the type of fracture and determine whether the injury is accidental or inflicted. Some types of fractures, dislocations and epiphyseal separations are common in the course of normal activities in certain age ranges; others are instead impossible to sustain accidentally in daily activities (40). In skull fractures, radiology imaging offers information about the impact point and direction of impact, indicate the sequence of repetitive blows and sometimes, the shape of the object or weapon used (37,40). Fractures of the hyoid bone or thyroid cornu seen by radiology usually suggest strangulation. In vehicular injuries associated with certain fracture/dislocations, radiology imaging may actually suggest the velocity of impact or deceleration (40).

Gunshot wounds, missiles and other foreign bodies in the body such as knives are the object of many forensic scenario and their radiological evaluation may provide important information (19). Other trauma can be revealed with injected contrast media such as intracranial hemorrhage from shaking (battered child syndrome), penetrating wounds…etc. (46). Identification of mass-disaster victims is one of the most important fieldworks in forensic radiology, in cases where the deceased needs to be identified. CT scanning is playing a vital role in these cases as it gives a quick overview of the body, revealing old fractures, transplants and dentition. CT scanning may be helpful in cases of terror bombings by allowing a quick evaluation of the distribution and type of shell fragments (12).

One of the advantages of CT imaging is its ability to 3D reconstruct in cases where the deceased presents in a non-standard way.(47) Reconstruction of skeletal structures using 3-D volume rendering software on a workstation allows soft tissue to be removed without mechanical intervention or maceration (48). The benefits of the CT scan in sex determination are evident and include (i) facilitation of the identification of unknown deceased individuals, (ii) avoidance of time-consuming maceration procedures, (iii) non-destructiveness of the procedure, and (iv) availability of large datasets of recent samples from various populations (49). Given the noninvasive nature of the CT technology, together with the relative speed with which it may be performed, it has generated interest from certain religious denominations. Similarly, the nondestructive nature of a radiological examination allows access to historical remains, such as Egyptian mummies, performed while still wrapped in ceremonial bindings (47). An effort to document the body by objective and noninvasive means began at the “Institute of Forensic Medicine”, “Diagnostic Radiology”, and “Neuroradiology” of the University of Bern. This effort resulted in the ‘Virtopsy’ project, which aimed to detect forensic findings in corpses using CT and MRI, as well as comparing these results with traditional autopsy findings (50).

Virtopsy is a word combining ‘virtual’ and ‘autopsy’ and employs imaging methods that are also used in clinical medicine such as computed tomography (CT), magnetic resonance imaging (MRI), etc., for the purpose of autopsy and to find the cause of the death. Virtopsy can be employed as an alternative to standard autopsies for broad and systemic examination of the whole body as it is less time consuming, aids better diagnosis and renders respect to religious sentiments. Virtopsy is quickly gaining importance in the field of medico-legal cases, but still has its own disadvantages (51). Traditional autopsy still remains the best method for post-mortem examination and is the gold standard when evaluating postmortem imaging techniques. CT may, however, contribute important new information. CT scanning was introduced as a routine procedure at every autopsy at the Institute of Forensic Medicine in united kingdom (47).

The physiology and function of the sinuses has been the subject of much research. The physiology and function of the paranasal sinuses is a subject that reflects the complexity of their anatomy. Unfortunately, we still are unsure as to all the functions of these air-filled spaces. Multiple theories of function exist. These include the functions of warming/humidification of air, assisting in regulation of intranasal pressure and serum gas pressures (and subsequently minute ventilation), contributing to immune defense, increasing mucosal surface area, lightening the skull, giving resonance to the voice, absorbing shock and contributing to facial growth (55). Because of the sinuses' copious mucous production, they contribute heavily to the immune defense/air filtration performed by the nose. The nasal and sinus mucosa are ciliated and move mucus to the choanae and the stomach beyond. The thickened superficial layer of nasal mucus serves to trap bacteria and particulate matter in a substance rich with immune cells, antibodies and antibacterial proteins. The underlying layer is much thinner and serves to provide a thinner substrate in which the cilia are able to beat their tips essentially grabbing the superficial layer and pushing it in the direction of the beat. Unless obstructed by disease or anatomical variance, the sinuses move mucous through their cavities and out of their ostia toward the choana (55). The most recent research on sinus function has focused on the molecule Nitrous Oxide (NO). Studies have shown that the production of intranasal NO is primarily in the sinuses. NO has been shown to be toxic to bacteria, fungi and viruses at levels as low as 100 ppb. Nasal concentrations of this substance can reach 30,000 ppb, which some researchers have theorized as the mechanism of sinus sterilization. NO has also been shown to increase ciliary motility (54).

From a historical perspective, the first illustration and description of the frontal sinus is dated in 1489. Also, among the first mentions of the frontal sinuses, those made by Volcher Coiter (1534-1576) and Basilius, but the citing authors offer no actual citation. The first detailed description on the anatomy and pathology of the paranasal sinuses belongs to Zuckerkandl; the “father of modern sinus anatomy”(56). Frontal sinuses are part of paranasal sinuses and are located in the frontal bone above each eye. The frontal sinuses are likely formed by the upward movement of the anterior-most ethmoid cells, begins around the 4th and 5th week of gestation and continues in intrauterine life, postnatal, puberty and early adulthood (52). Primary and secondary pneumatization continues from 2 years up to 18 years. Since the frontal bone is membranous at birth there is seldom seen more than a recess until the bone begins to ossify around age of two years old. Thus, radiographs seldom show this structure before that time (57).

The volume of the sinus is approximately 6-7 ml (28x24x20mm). Frontal sinus anatomy is highly variable, but generally there are two sinuses, which are funnel shaped and point upward. In an adult, two frontal sinuses are usually seen. Each frontal sinus cavity takes on the shape of a pyramid with a thick anterior table and a thinner posterior table (57). The volume of the sinus is approximately 6-7 ml (28x24x20mm). Frontal sinus anatomy is highly variable, but generally there are two sinuses which are funnel shaped and point upward. In an adult, two frontal sinuses are usually seen. Each frontal sinus cavity takes on the shape of a pyramid, with a thick anterior table and a thinner posterior table (57).

Both frontal sinuses have their ostia at the most dependent portion of the cavity (posteromedial). Both the anterior and posterior walls of this sinus are composed of diploe bone. However, the posterior wall (separates the frontal sinus from the anterior cranial fossa) is much thinner. The floor of the sinus also functions as a portion of the orbital roof (55).

A triangular-shaped intersinus septum separates the frontal sinuses into separately draining sinus cavities. It is the continuation, anteriorly of the fused and ossified embryologic sagittal suture line. Although the intersinus septum may vary in direction and thickness as it proceeds superiorly, the base of the intersinus septum will almost always be close to the midline at the level of the infundibulum. At this level, the intersinus septum is continuous with the crista galli posteriorly, the perpendicular plate of the ethmoid inferiorly and the nasal spine of the frontal bone anteriorly. Inferiorly, the frontal sinus cavity is limited by the supraorbital rim and wall (or roof). Laterally the cavity extends itself as far as the angular prominence of the frontal bone. The superior border of the frontal sinus is the non-pneumatized cancellous bone of the frontal bone (58).

During the fetal period, the frontal sinus and posterior ethmoidal cells are still rudimentary surrounded by cartilage. It is possible that earlier ossification of the cartilage will interfere with their further development, manifesting as a hypoplastic (59). Complete aplasia of frontal sinus is very rare but unilateral or hypoplasia was 7.2% in plain radiographies studies(60). In one study, unusual conditions include an unpartitioned central sinus (2.5% cases), unilateral absence of a sinus (14.3% of males; 7.1% females) and agenesis (5%).(61) In another study there are aplasia seen more in females (18.2%) than in males (10%) (62). Complete aplasia is found in 15% of Caucasian, 52% in Eskimos and 35% in other races. Studies by Harris et al. (1987) showed frontal sinuses were absent in 6.7% of blacks (58).

As right and left frontal sinuses develop interdentally, it is common to find one larger than the other and the larger sinus may cross the midline and overlap the other. A review by Donald et al. (1994) reported that in 4-15% of the population, one sinus may be totally absent and the absence may be attributed to an extremely deviated septum. Aplasia of the left frontal sinus occurred 3.6% in men and 2.8% in women (56). It is suggested that the frontal sinuses are generally larger in males except for the Canadian Eskimo population, In females the frontal sinuses are smaller and their upper borders are more scalloped (61). In elderly, the osseous resorption leads to an enlargement of the sinus cavity and can be responsible for orbital complications (63).

Sizes of the frontal sinuses are also highly variable, ranging from a few cubic centimeters in volume to occupying most of the frontal bone (56). Three or more frontal sinuses are rare, but incomplete septations of various lengths extending from the roof are not uncommon. These septations give the sinus its scalloped configuration, which can be appreciated in radiographs. As a rule, the frontal sinuses of both sides are asymmetric in configuration (58). Yoshino et al. (1987) proposed a system of classifying the frontal sinuses utilizing the following criteria: area size, degree of bilateral asymmetry, form of scalloping, number of septa and complete cells (61). The dimensions of frontal sinuses from 14 to 20 years are around 65 mm wide and 36 mm high; from 21 to 30 years are 65 mm wide and 38 mm high; from 31 to 40 years are 66 mm wide and 39 mm high; from 41 to 50 years are 70 mm wide and 39 high and finally above 51 years are 71 mm wide and 41 mm high. Considering all age ranges, the height was 55 to 59% smaller than the width (64) As has been showed in Barghout, et al., 2002, the size of the frontal sinuses is very variable. The frontal sinuses are generally larger in males than in females (65).