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Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstructions: Living and dead subjects
Accepted Manuscript Title: Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstruction: living and dead subjects Authors: C. Villa, K.B. Olsen, S.H. Hansen PII: DOI: Reference:
S0379-0738(17)30240-2 http://dx.doi.org/doi:10.1016/j.forsciint.2017.06.033 FSI 8896
To appear in:
FSI
Received date: Revised date: Accepted date:
3-2-2017 28-6-2017 29-6-2017
Please cite this article as: C.Villa, K.B.Olsen, S.H.Hansen, Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstruction: living and dead subjects, Forensic Science Internationalhttp://dx.doi.org/10.1016/j.forsciint.2017.06.033 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstruction: living and dead subjects
Villa, C.1, Olsen, K.B.1, Hansen, S.H.1 1
Section of Forensic Pathology, Department of Forensic Medicine, University of Copenhagen, Frederik d. 5.´s Vej 11, DK-2100 Copenhagen, Denmark
Corresponding author: Chiara Villa [email protected]
Highlights
Virtual animation of ante-mortem posture helps to understand dynamic of the crime Animated victim-specific 3D can be created both for dead and living victims 3D visualizations are very important visual tool for presenting medical findings.
Abstract Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutions many years ago and has proved to be a useful tool. 3D models of bones, skin, internal organs and bullet paths can rapidly be generated using post-processing software. These 3D models reflect the individual physiognomics and can be used to create whole-body 3D virtual animations. In such way, virtual reconstructions of the probable ante-mortem postures of victims can be constructed and contribute to understand the sequence of events. This procedure is demonstrated in two victims of gunshot injuries. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. Wholebody PMCT was performed and 3D reconstruction of bones, relevant internal organs and bullet paths were generated. Using 3ds Max software and a human anatomy 3D model, a virtual animated body was built and probable ante-mortem postures visualized. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident: one in the left arm and two in the thorax. Only CT scans of the thorax, abdomen and the injured arm were provided by the hospital. Therefore, a whole-body model reflecting the anatomical proportions of the patient was made combining the actual bones of the victim with those obtained from the human anatomy 3D model.
The resulted 3D model was used for the animation process. Several probable postures were also visualized in this case. It has be shown that in Case #1 the lesions and the bullet path were not consistent with an upright standing position; instead, the victim must have been bent slightly forwards, i.e. he was sitting or running when he was shot. In Case #2, one of the bullets could have passed through the arm and continued into the thorax. In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem postures based on both PMCT and clinical CT.
1. Introduction Accurate and precise forensic pathological reconstructions are fundamental for clarifying the course of events that occurred during a crime or an accident. Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutes around the world [1-6] and has proved to be a very useful tool, complementary to the traditional autopsy [7, 8]. PMCT is more sensitive in detecting
skeletal injuries, in particular, in areas not routinely dissected, such as face and
extremities [9]. In gunshot cases, bullet paths, especially in the head, can easily be reconstructed and bullet fragments can rapidly be localized [10-12]. In case of stab wounds, CT imaging also helps in detecting the presence of gas in the injured tissues and organs, and in evaluating wound depth, especially in case of deep stab injuries [13]. 3D visualizations of bones, internal organs and bullet paths can be generated from CT data using imaging post processing software such as Osirix [14], Mimics [15], and Myrian [16]. In such way, medical findings are accurately documented and reported in a more intuitive manner [17]. In addition, it is possible to create victim-specific 3D model, i.e. 3D model with actual victim proportion and exact location of the injuries, that can be animated and used for reconstructing probably ante-mortem postures. However, the dynamic of the events or possible scenarios are often simulated using dummies, artist’s rendering [17, 18] or play-acted by persons resembling the proportion of victim (s) [19]. Recently, virtual scenarios have also been reconstructed using humanoids [17, 20-22]. To our knowledge, reconstruction of the events combining 3D models of the crime scene with animated 3D models of actual victims have been only performed by the Institute of Forensic Medicine of the University of Zurich and Bern (Switzerland) in collaboration with the local police [17, 23-25]. 3D models of actual victims were generated from whole-body CT scanning and the animation process was performed using a human model, i.e. a biped [23, 24].
Actual victim 3D models have been used for explaining the dynamic of the events in case of gunshot injuries [24] and traffic incident [23-25]. All the presented cases involved dead subjects. Actual 3D data reconstruction could also be performed for living victims, since CT scanning is often performed in cases of gunshot or sharp force injuries before surgery, but no tests have been carried out. The aim of this paper was to reconstruct ante-mortem postures of both dead and living victims, using a more advanced animation process based on a complete human anatomy 3D model. This procedure is demonstrated in two victims of gunshot injuries.
2. Materials and Methods 2.1 Cases Two victims of gunshot injuries were selected for this study. A rifle caused the lesions on both cases. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. CT scanning was performed before the autopsy using a Siemens Somatom Definition. The whole-body scans were performed in three parts: head, trunk and legs. The following scan settings were used: 120 kV, 300 mAs, soft reconstruction algorithm, variable slice thickness, and variable slice increment (head: 2 mm slice thickness and 1.5 mm slice increment; thorax and leg: 3 mm slice thickness and 2 mm slice increment). The soft reconstruction algorithm was selected to minimize the noise in 3D models. The information from CT scanning and from the autopsy report was used to describe the lesions and to determine the bullet paths. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident. CT scanning was performed at the hospital before an emergency surgery. Only the thorax and the left arm were CT scanned with 1 mm slice thickness, 0.8 mm slice increment and smooth reconstruction algorithm.
Other information was not available because the CT data were
anonymized. An external examination of the victim and interpretations of the CT scanning were carried out after the surgery by forensic pathologists. Description of the lesions and determination of the bullet paths are based on CT information and the report written by the forensic pathologists.
2.2. Creation of victim-specific 3D models and animation process Case #1
3D models of the skin, skeleton, relevant internal organs and bullet paths were created from CT scans using Mimics software [26]. 3D models of the skin were generated using automatic segmentation applying a Hounsfield unit (HU) range from -260 to 3071, while the bones applying a HU range from 150 to 3071. A manual segmentation was carried to obtain 3D models of heart and liver, using a starting HU range from -59 to 3071. The bullet paths were drawn using cylinders: the entry and the exit wounds were used to determining the direction of the cylinder or the axis, while a diameter of 5 mm was arbitrarily defined. In case of deflected bullet path, several cylinders were drawn, one for each linear path. The 3D models (bones, skin, internal organs and bullet paths) were exported as “.stl” files. The “stl” files were imported in Mesh Lab [27], where the combination of the single body parts was performed using the function “Flatten visible layers” (Fig. 1). No alignment process was necessary; the 3D models had a unique 3D coordinate system corresponded to the CT table. The body did not move during the scanning and thus the 3D body parts kept the same 3D coordinate system, even though separately scanned. The resulted models were exported as “.obj” files and imported in 3Ds Max [28]. The animation process was performed using a human anatomy 3D model designed by MotionCow [29]. The human anatomy 3D model was fully rigged, i.e. fully animated. The original anatomy model consists of complete skeleton as well cardiac, digestive, respiratory systems. We used only the skeleton for the animation; the other structures were removed (Fig. 2a). CT scanning models and human anatomy model were roughly aligned (Fig. 2b). Then each bone of the skeleton of the human anatomy 3D model (called “skeletal deformation“) was sized and rotated thus to fit as closer as possible the skeletal structure of the actual victims. The pelvis bone was the first bone to be adjusted. When the pelvis is modified, the rest of the skeleton of the human anatomy model is proportionally adjusted. After the pelvis was adjusted, we proceeded with the legs, then the vertebra column and the upper body. We did not pay particular attention to patellae and ribs, since not directly involved in the animation process. Metacarpals, metatarsals and phalanges were not adjusted since detailed movements of hands and feet were not necessary and the process would have been very time-consuming. The process of matching the bones of the human anatomy model with those of the actual person was performed to allow an easy and rapid transfer of the movements. However, manual adjusts were carried out during the “skin process” if the bones did not perfectly superimposed. Figure 2c shows the final alignment of the two skeletons. Movements of the rigged human anatomy 3D model were then transferred to the actual skeleton of the victims using the modifier called “Skin Wrap” (with the following settings: deformation engine: vertex; fall off: 2; distance Infl.: 2; threshold: 10 mm). Any
required adjustment of the movement was then performed using the “Skin” (with the following settings: edit envelopes, option “vertex”). The result of this process was a completely animated skeleton of the victim, including internal organs and bullet paths (Fig. 3 Movie).
Case #2 Similar procedure was followed in case #2. 3D models of the skin, skeleton and bullet paths were created from CT scans using automatic segmentation. This time, only the 3D models of the trunk and the injured left arm were created (Fig. 4). We performed manual separation of the humerus from the scapula and clavicle, as well separation of the broken bones (ulna and radius) for enabling post-processing. No smoothing was applied. The 3D models were then imported in 3Ds max [27] where animation process was also performed using a human anatomy 3D model. Before the animation process, some modifications were necessary: 1) actual length of the left forearm before the accident was calculated aligning the fractured bones in the normal position (Fig. 5); 2) the right arm was created mirroring the left “non-injured” arm (Fig. 6); 3) the missing bones were obtained from the human anatomy 3D model adjusted to the body structure of the victim (Fig. 7). The animation process was then performed as in Case #1.
3. RESULTS
3.1. Case #1 The victim showed three perforating gunshot injuries (A, B, C) as can be seen in the 3D reconstruction obtained from CT scanning (Fig. 1). All the lesions had the character of distance shots. No bullet was found inside the body. Autopsy report described the following lesions: - Lesion A (in yellow): entry wound on the left side of the back, 120 cm above the right heel and 18 cm left from the midline with bullet path through internal organs of the thorax and the abdomen without hitting bones. The bullet entered between the 8th and 9th left ribs, penetrated the left pulmonary cavity, left side of the diaphragm, stomach, liver, again through the diaphragm, heart, right pulmonary cavity and exiting between the 3rd and 4th right ribs, 130 cm above the right heel and 3 cm right from the midline. The bullet path was slightly forward, slightly upwards and to the right. - Lesion B (in blue): entry wound on the lower left side of the abdomen, 98 cm above the right heel and 15 cm left from the midline, with bullet path through the mesentery and the small
intestine, entering the right side of the diaphragm, right pulmonary cavity, fracturing the 9th right rib, here deflecting in upward direction and exiting on the right side of the chest between the 9 th and the 10th ribs, 117 cm above the right heel. The bullet path was slightly backwards, slightly upwards and to the right. - Lesion C (in green): entry wound on the lower right side of the abdomen, 98 cm above the right heel, with bullet path through the lumbar muscle on the right side, the caecum, through the 5th lumbar vertebra and the spinal cord, deflecting towards the left ilium and exiting on the left side of the lower back, 94 cm above the right heel. The first part of the bullet path was slightly backwards, slightly downwardly and to the left. After hitting, the 5th lumbar vertebra the bullet path changed slightly upwards. . The path of the lesion C was not consistent with an upright standing position as can be seen from 3D reconstruction of the pelvis area (Fig. 8a); the arch of the 5th lumbar vertebra was intact. It was hypothesized that the victim was slightly bent forwards and rotated to the right during the shooting. 3D animation was performed and the resulted animation can be seen in figure 8b: the path of the bullet from the body of the vertebra towards the iliac crest can be now better explained and visualized. Finally, two possible postures with the body in this position were re-created: the victim was running (Fig. 9a) or sitting (Fig. 9b) when he was shot.
3.2. Case #2 The victim showed three perforating gunshot wounds (A, B, C) as can be seen in figure 4. From interpretation of the CT scanning and the external wounds, the following lesions were identified: - Lesion A (in blue): entry wound on left posterior axillary fold with bullet path going forwards and slightly downwards to the 4th left rib, fracturing it, and deviating slightly upwards, exiting on the left side of the chest at the level of the 3rd left rib. The bullet path was forward, slightly downward and to the right. - Lesion B (in green): entry wound on the dorsal side of left forearm, c. 13 cm from the elbow, with bullet path passing through the forearm, fracturing both radius and ulna, and exiting on the palmar side, c. 8 cm from the elbow. The bullet path was forward and to the left. - Lesion C (in red): entry wound on the lower left side of the chest, 2 cm from the sternum at the height of the 5th left rib, with bullet path through the peritoneal cavity hitting the liver and
exiting on the right side of the chest below the 10th rib. The bullet path was backward, slightly downward and to the right. It was hypothesized that the lesions B and C were caused from the same bullet, precisely that the bullet passed through the left forearm (lesion B) and continuing through the abdomen (lesion C). Animation was performed and alignment of lesions B and C could easily be reconstructed: figure 10a shows the position of the man when the two lesions perfectly aligned; and figure 10b visualized a different posture when the two lesions did not align and thus they could not be caused by the same bullet. At the time of our 3D reconstructions, we knew that the victim was rising, holding his hand(s) on a table, that separated the two men.
4. Discussion In this paper, we demonstrated the benefits of using animated victim-specific 3D models to reconstruct the most probably ante-mortem postures, both in dead and, for the first time, in living subjects. In addition, the utility of using a human anatomy 3D model has been shown. CT scanning and the resulted 3D models are very important because they allow a permanent documentation of the victims, including injuries. 3D data can be stored and are always available for a re-analysis, even years later if needed [17]. Moreover, the medical findings can be accurately documented and reported in a more intuitive manner in a courtroom using 3D visualizations, enabling better understanding of the lesions by people with no medical knowledge [17]. A whole-body 3D model can be easily generated for dead victims, both from whole-body CT scanning or combining body parts CT scanned with different protocols, as showed in this study. In case of living victims, whole-body 3D models can be obtained combing 3D models from CT scans, very often performed for planning surgery, with those created using humanoid models. The latter have been already used in crime scene reconstruction [17, 20-22]. The resulted model (3D CT model combined with 3D humanoid) will have detailed and accurate information of the lesions of the person as well as general body proportion of the actual victim. The dimension of damaged areas can be extrapolated for example aligning fractures bones, as we showed in case #2. Head, feet and hands are the most difficult area to be correctly modelled. In case #2 we combined the actual bones of the victim with those obtained from the human anatomy model used for the animation process. No particular attention was given to the dimension of the head and feet, because not really necessary for understanding the dynamic of the events. The important information, such as actual length of the arm and dimension of the trunk, was obtained from CT scanning. 3D models of the
missing areas in case of living subject can be obtained using different techniques, such as surface scanning or photogrammetry [30, 31]. Animation process is important for the reconstruction of the ante-mortem postures, for example posing the victim standing or sitting. A simplified skeletal model (biped) has been used up to now [23-25]. It works very well and it is easy to fit into the actual skeleton of a person. However, the biped has a simplified skeletal structure, for instance the vertebral column is composed of only five blocks. This simplified structure was not adequate for case #1. For this reason, we opted for a more advanced model that could account for more precise movements. However, both models (biped and human anatomy 3D model) have some limitations. First, the joint movements are not limited, such as for example a 360 degree rotation of the head is possible. The knowledge of the operator regarding the anatomical joints avoids such artifacts. Furthermore, in biped the length of the different segments, i.e. bones, can be abnormally stretched causing anomalies in the simulated postures. This does not occur using the human anatomy 3D model, but the animation process is more time-consuming. We decided to limit the animation to the skeleton and not considering the skin, because skin model is more complicated to control and the aim of the paper was to simulate ante-mortem postures in case of lesions that involved bones. Future development should be focused on the combination of the internal information from CT- or MRI- scanning with external information that can be obtained from surface scanner [25] or photogrammetry [32, 33]. Indeed, the 3D models from CT scanning are not accurate enough for documentation of the skin injuries, such as bruises or superficial wounds. This may result very important for matching a wound with a 3D model of the injury-causing tool [25, 34, 35]. Alternative solutions should be consider for creating of 3D model of living individuals when CT data are not available. It is not enough to create 3D model of the external aspect using for example multi-camera system [30]; information regarding joint centers are indispensable for the animation process. Not only victim, but also perpetrator model may be created in such way. Finally, the contextualization of the human models in the crime scene can definitively help in better understating the chain of event, as already shown by Buck and colleagues [23, 24]. For example, a 3D model of the actual table in the case #2 would have improved the reliability of the reconstructions.
5. Conclusion
In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem posture both in dead and living subjects based on PMCT and clinical CT. Medical findings can be more accurately documented and reported in a more intuitive manner using such individualized human models. 3D models of the victims including lesions are permanent data sets that can be reviewed at any time if needed.
Funding: This work was supported by the Danish Council for independent Research | Technology and Production Sciences [grant number DFF–4005-00102];
Acknowledges We would like to thank of all the forensic pathologists and the technicians of the Section of Forensic Pathology of the Department of Forensic Medicine, University of Copenhagen, for their help to perform this study. We are also grateful to the anonymous reviewers for their helpful suggestions and comments.
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Captations:
Fig. 1: whole-body 3D model of case #1 created from CT scanning.
Fig 2: animation process: a) the human anatomy 3D model; 2) roungh aligment of human anatomy 3D model and the skeleton of case #1 roughly aligned; 3) final aligment of the human anatomy 3D model and the skeleton of case #1.
Fig. 3: animated skeleton of case #1 including heart, liver and bullet paths (video)
Fig. 4: 3D model of case #2 created from CT scanning
Fig. 5: 3D models of the ulna and radius as visualized in CT imaging (a) and after aligment (b).
Fig. 6: 3D models created with the actual bones of the victim. The re-aligned bones of the left arm are indicated in green. The right arm was created mirroring the left “non-injured” arm and is marked in orange.
Fig. 7: whole-body 3D model of case #2 created combining 3D bones from CT model (light grey, green and orange) and those obtained from the human anatomy 3D model (dark grey).
Fig. 8: the path of the lesion C of case #1 :a) when the victim was in standing position; b) when the victim was slightly bent forwards and rotated to the right.
Fig. 9: two possible postures of case #1 at the time of the incident
Fig. 10: two possible postures of case #2: a) position in which lesions B and C are aligned and could be casuased by the same bullet; b) position in which lesions B and C are not aligned and could not be casuased by the same bullet.
S0379-0738(17)30240-2 http://dx.doi.org/doi:10.1016/j.forsciint.2017.06.033 FSI 8896
To appear in:
FSI
Received date: Revised date: Accepted date:
3-2-2017 28-6-2017 29-6-2017
Please cite this article as: C.Villa, K.B.Olsen, S.H.Hansen, Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstruction: living and dead subjects, Forensic Science Internationalhttp://dx.doi.org/10.1016/j.forsciint.2017.06.033 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Virtual animation of victim-specific 3D models obtained from CT scans for forensic reconstruction: living and dead subjects
Villa, C.1, Olsen, K.B.1, Hansen, S.H.1 1
Section of Forensic Pathology, Department of Forensic Medicine, University of Copenhagen, Frederik d. 5.´s Vej 11, DK-2100 Copenhagen, Denmark
Corresponding author: Chiara Villa [email protected]
Highlights
Virtual animation of ante-mortem posture helps to understand dynamic of the crime Animated victim-specific 3D can be created both for dead and living victims 3D visualizations are very important visual tool for presenting medical findings.
Abstract Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutions many years ago and has proved to be a useful tool. 3D models of bones, skin, internal organs and bullet paths can rapidly be generated using post-processing software. These 3D models reflect the individual physiognomics and can be used to create whole-body 3D virtual animations. In such way, virtual reconstructions of the probable ante-mortem postures of victims can be constructed and contribute to understand the sequence of events. This procedure is demonstrated in two victims of gunshot injuries. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. Wholebody PMCT was performed and 3D reconstruction of bones, relevant internal organs and bullet paths were generated. Using 3ds Max software and a human anatomy 3D model, a virtual animated body was built and probable ante-mortem postures visualized. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident: one in the left arm and two in the thorax. Only CT scans of the thorax, abdomen and the injured arm were provided by the hospital. Therefore, a whole-body model reflecting the anatomical proportions of the patient was made combining the actual bones of the victim with those obtained from the human anatomy 3D model.
The resulted 3D model was used for the animation process. Several probable postures were also visualized in this case. It has be shown that in Case #1 the lesions and the bullet path were not consistent with an upright standing position; instead, the victim must have been bent slightly forwards, i.e. he was sitting or running when he was shot. In Case #2, one of the bullets could have passed through the arm and continued into the thorax. In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem postures based on both PMCT and clinical CT.
1. Introduction Accurate and precise forensic pathological reconstructions are fundamental for clarifying the course of events that occurred during a crime or an accident. Post-mortem CT scanning (PMCT) has been introduced at several forensic medical institutes around the world [1-6] and has proved to be a very useful tool, complementary to the traditional autopsy [7, 8]. PMCT is more sensitive in detecting
skeletal injuries, in particular, in areas not routinely dissected, such as face and
extremities [9]. In gunshot cases, bullet paths, especially in the head, can easily be reconstructed and bullet fragments can rapidly be localized [10-12]. In case of stab wounds, CT imaging also helps in detecting the presence of gas in the injured tissues and organs, and in evaluating wound depth, especially in case of deep stab injuries [13]. 3D visualizations of bones, internal organs and bullet paths can be generated from CT data using imaging post processing software such as Osirix [14], Mimics [15], and Myrian [16]. In such way, medical findings are accurately documented and reported in a more intuitive manner [17]. In addition, it is possible to create victim-specific 3D model, i.e. 3D model with actual victim proportion and exact location of the injuries, that can be animated and used for reconstructing probably ante-mortem postures. However, the dynamic of the events or possible scenarios are often simulated using dummies, artist’s rendering [17, 18] or play-acted by persons resembling the proportion of victim (s) [19]. Recently, virtual scenarios have also been reconstructed using humanoids [17, 20-22]. To our knowledge, reconstruction of the events combining 3D models of the crime scene with animated 3D models of actual victims have been only performed by the Institute of Forensic Medicine of the University of Zurich and Bern (Switzerland) in collaboration with the local police [17, 23-25]. 3D models of actual victims were generated from whole-body CT scanning and the animation process was performed using a human model, i.e. a biped [23, 24].
Actual victim 3D models have been used for explaining the dynamic of the events in case of gunshot injuries [24] and traffic incident [23-25]. All the presented cases involved dead subjects. Actual 3D data reconstruction could also be performed for living victims, since CT scanning is often performed in cases of gunshot or sharp force injuries before surgery, but no tests have been carried out. The aim of this paper was to reconstruct ante-mortem postures of both dead and living victims, using a more advanced animation process based on a complete human anatomy 3D model. This procedure is demonstrated in two victims of gunshot injuries.
2. Materials and Methods 2.1 Cases Two victims of gunshot injuries were selected for this study. A rifle caused the lesions on both cases. Case #1 was a man showing three perforating gunshot wounds, who died due to the injuries of the incident. CT scanning was performed before the autopsy using a Siemens Somatom Definition. The whole-body scans were performed in three parts: head, trunk and legs. The following scan settings were used: 120 kV, 300 mAs, soft reconstruction algorithm, variable slice thickness, and variable slice increment (head: 2 mm slice thickness and 1.5 mm slice increment; thorax and leg: 3 mm slice thickness and 2 mm slice increment). The soft reconstruction algorithm was selected to minimize the noise in 3D models. The information from CT scanning and from the autopsy report was used to describe the lesions and to determine the bullet paths. Case #2 was a man presenting three perforating gunshot wounds, who survived the incident. CT scanning was performed at the hospital before an emergency surgery. Only the thorax and the left arm were CT scanned with 1 mm slice thickness, 0.8 mm slice increment and smooth reconstruction algorithm.
Other information was not available because the CT data were
anonymized. An external examination of the victim and interpretations of the CT scanning were carried out after the surgery by forensic pathologists. Description of the lesions and determination of the bullet paths are based on CT information and the report written by the forensic pathologists.
2.2. Creation of victim-specific 3D models and animation process Case #1
3D models of the skin, skeleton, relevant internal organs and bullet paths were created from CT scans using Mimics software [26]. 3D models of the skin were generated using automatic segmentation applying a Hounsfield unit (HU) range from -260 to 3071, while the bones applying a HU range from 150 to 3071. A manual segmentation was carried to obtain 3D models of heart and liver, using a starting HU range from -59 to 3071. The bullet paths were drawn using cylinders: the entry and the exit wounds were used to determining the direction of the cylinder or the axis, while a diameter of 5 mm was arbitrarily defined. In case of deflected bullet path, several cylinders were drawn, one for each linear path. The 3D models (bones, skin, internal organs and bullet paths) were exported as “.stl” files. The “stl” files were imported in Mesh Lab [27], where the combination of the single body parts was performed using the function “Flatten visible layers” (Fig. 1). No alignment process was necessary; the 3D models had a unique 3D coordinate system corresponded to the CT table. The body did not move during the scanning and thus the 3D body parts kept the same 3D coordinate system, even though separately scanned. The resulted models were exported as “.obj” files and imported in 3Ds Max [28]. The animation process was performed using a human anatomy 3D model designed by MotionCow [29]. The human anatomy 3D model was fully rigged, i.e. fully animated. The original anatomy model consists of complete skeleton as well cardiac, digestive, respiratory systems. We used only the skeleton for the animation; the other structures were removed (Fig. 2a). CT scanning models and human anatomy model were roughly aligned (Fig. 2b). Then each bone of the skeleton of the human anatomy 3D model (called “skeletal deformation“) was sized and rotated thus to fit as closer as possible the skeletal structure of the actual victims. The pelvis bone was the first bone to be adjusted. When the pelvis is modified, the rest of the skeleton of the human anatomy model is proportionally adjusted. After the pelvis was adjusted, we proceeded with the legs, then the vertebra column and the upper body. We did not pay particular attention to patellae and ribs, since not directly involved in the animation process. Metacarpals, metatarsals and phalanges were not adjusted since detailed movements of hands and feet were not necessary and the process would have been very time-consuming. The process of matching the bones of the human anatomy model with those of the actual person was performed to allow an easy and rapid transfer of the movements. However, manual adjusts were carried out during the “skin process” if the bones did not perfectly superimposed. Figure 2c shows the final alignment of the two skeletons. Movements of the rigged human anatomy 3D model were then transferred to the actual skeleton of the victims using the modifier called “Skin Wrap” (with the following settings: deformation engine: vertex; fall off: 2; distance Infl.: 2; threshold: 10 mm). Any
required adjustment of the movement was then performed using the “Skin” (with the following settings: edit envelopes, option “vertex”). The result of this process was a completely animated skeleton of the victim, including internal organs and bullet paths (Fig. 3 Movie).
Case #2 Similar procedure was followed in case #2. 3D models of the skin, skeleton and bullet paths were created from CT scans using automatic segmentation. This time, only the 3D models of the trunk and the injured left arm were created (Fig. 4). We performed manual separation of the humerus from the scapula and clavicle, as well separation of the broken bones (ulna and radius) for enabling post-processing. No smoothing was applied. The 3D models were then imported in 3Ds max [27] where animation process was also performed using a human anatomy 3D model. Before the animation process, some modifications were necessary: 1) actual length of the left forearm before the accident was calculated aligning the fractured bones in the normal position (Fig. 5); 2) the right arm was created mirroring the left “non-injured” arm (Fig. 6); 3) the missing bones were obtained from the human anatomy 3D model adjusted to the body structure of the victim (Fig. 7). The animation process was then performed as in Case #1.
3. RESULTS
3.1. Case #1 The victim showed three perforating gunshot injuries (A, B, C) as can be seen in the 3D reconstruction obtained from CT scanning (Fig. 1). All the lesions had the character of distance shots. No bullet was found inside the body. Autopsy report described the following lesions: - Lesion A (in yellow): entry wound on the left side of the back, 120 cm above the right heel and 18 cm left from the midline with bullet path through internal organs of the thorax and the abdomen without hitting bones. The bullet entered between the 8th and 9th left ribs, penetrated the left pulmonary cavity, left side of the diaphragm, stomach, liver, again through the diaphragm, heart, right pulmonary cavity and exiting between the 3rd and 4th right ribs, 130 cm above the right heel and 3 cm right from the midline. The bullet path was slightly forward, slightly upwards and to the right. - Lesion B (in blue): entry wound on the lower left side of the abdomen, 98 cm above the right heel and 15 cm left from the midline, with bullet path through the mesentery and the small
intestine, entering the right side of the diaphragm, right pulmonary cavity, fracturing the 9th right rib, here deflecting in upward direction and exiting on the right side of the chest between the 9 th and the 10th ribs, 117 cm above the right heel. The bullet path was slightly backwards, slightly upwards and to the right. - Lesion C (in green): entry wound on the lower right side of the abdomen, 98 cm above the right heel, with bullet path through the lumbar muscle on the right side, the caecum, through the 5th lumbar vertebra and the spinal cord, deflecting towards the left ilium and exiting on the left side of the lower back, 94 cm above the right heel. The first part of the bullet path was slightly backwards, slightly downwardly and to the left. After hitting, the 5th lumbar vertebra the bullet path changed slightly upwards. . The path of the lesion C was not consistent with an upright standing position as can be seen from 3D reconstruction of the pelvis area (Fig. 8a); the arch of the 5th lumbar vertebra was intact. It was hypothesized that the victim was slightly bent forwards and rotated to the right during the shooting. 3D animation was performed and the resulted animation can be seen in figure 8b: the path of the bullet from the body of the vertebra towards the iliac crest can be now better explained and visualized. Finally, two possible postures with the body in this position were re-created: the victim was running (Fig. 9a) or sitting (Fig. 9b) when he was shot.
3.2. Case #2 The victim showed three perforating gunshot wounds (A, B, C) as can be seen in figure 4. From interpretation of the CT scanning and the external wounds, the following lesions were identified: - Lesion A (in blue): entry wound on left posterior axillary fold with bullet path going forwards and slightly downwards to the 4th left rib, fracturing it, and deviating slightly upwards, exiting on the left side of the chest at the level of the 3rd left rib. The bullet path was forward, slightly downward and to the right. - Lesion B (in green): entry wound on the dorsal side of left forearm, c. 13 cm from the elbow, with bullet path passing through the forearm, fracturing both radius and ulna, and exiting on the palmar side, c. 8 cm from the elbow. The bullet path was forward and to the left. - Lesion C (in red): entry wound on the lower left side of the chest, 2 cm from the sternum at the height of the 5th left rib, with bullet path through the peritoneal cavity hitting the liver and
exiting on the right side of the chest below the 10th rib. The bullet path was backward, slightly downward and to the right. It was hypothesized that the lesions B and C were caused from the same bullet, precisely that the bullet passed through the left forearm (lesion B) and continuing through the abdomen (lesion C). Animation was performed and alignment of lesions B and C could easily be reconstructed: figure 10a shows the position of the man when the two lesions perfectly aligned; and figure 10b visualized a different posture when the two lesions did not align and thus they could not be caused by the same bullet. At the time of our 3D reconstructions, we knew that the victim was rising, holding his hand(s) on a table, that separated the two men.
4. Discussion In this paper, we demonstrated the benefits of using animated victim-specific 3D models to reconstruct the most probably ante-mortem postures, both in dead and, for the first time, in living subjects. In addition, the utility of using a human anatomy 3D model has been shown. CT scanning and the resulted 3D models are very important because they allow a permanent documentation of the victims, including injuries. 3D data can be stored and are always available for a re-analysis, even years later if needed [17]. Moreover, the medical findings can be accurately documented and reported in a more intuitive manner in a courtroom using 3D visualizations, enabling better understanding of the lesions by people with no medical knowledge [17]. A whole-body 3D model can be easily generated for dead victims, both from whole-body CT scanning or combining body parts CT scanned with different protocols, as showed in this study. In case of living victims, whole-body 3D models can be obtained combing 3D models from CT scans, very often performed for planning surgery, with those created using humanoid models. The latter have been already used in crime scene reconstruction [17, 20-22]. The resulted model (3D CT model combined with 3D humanoid) will have detailed and accurate information of the lesions of the person as well as general body proportion of the actual victim. The dimension of damaged areas can be extrapolated for example aligning fractures bones, as we showed in case #2. Head, feet and hands are the most difficult area to be correctly modelled. In case #2 we combined the actual bones of the victim with those obtained from the human anatomy model used for the animation process. No particular attention was given to the dimension of the head and feet, because not really necessary for understanding the dynamic of the events. The important information, such as actual length of the arm and dimension of the trunk, was obtained from CT scanning. 3D models of the
missing areas in case of living subject can be obtained using different techniques, such as surface scanning or photogrammetry [30, 31]. Animation process is important for the reconstruction of the ante-mortem postures, for example posing the victim standing or sitting. A simplified skeletal model (biped) has been used up to now [23-25]. It works very well and it is easy to fit into the actual skeleton of a person. However, the biped has a simplified skeletal structure, for instance the vertebral column is composed of only five blocks. This simplified structure was not adequate for case #1. For this reason, we opted for a more advanced model that could account for more precise movements. However, both models (biped and human anatomy 3D model) have some limitations. First, the joint movements are not limited, such as for example a 360 degree rotation of the head is possible. The knowledge of the operator regarding the anatomical joints avoids such artifacts. Furthermore, in biped the length of the different segments, i.e. bones, can be abnormally stretched causing anomalies in the simulated postures. This does not occur using the human anatomy 3D model, but the animation process is more time-consuming. We decided to limit the animation to the skeleton and not considering the skin, because skin model is more complicated to control and the aim of the paper was to simulate ante-mortem postures in case of lesions that involved bones. Future development should be focused on the combination of the internal information from CT- or MRI- scanning with external information that can be obtained from surface scanner [25] or photogrammetry [32, 33]. Indeed, the 3D models from CT scanning are not accurate enough for documentation of the skin injuries, such as bruises or superficial wounds. This may result very important for matching a wound with a 3D model of the injury-causing tool [25, 34, 35]. Alternative solutions should be consider for creating of 3D model of living individuals when CT data are not available. It is not enough to create 3D model of the external aspect using for example multi-camera system [30]; information regarding joint centers are indispensable for the animation process. Not only victim, but also perpetrator model may be created in such way. Finally, the contextualization of the human models in the crime scene can definitively help in better understating the chain of event, as already shown by Buck and colleagues [23, 24]. For example, a 3D model of the actual table in the case #2 would have improved the reliability of the reconstructions.
5. Conclusion
In conclusion, specialized 3D modelling and animation techniques allow for the reconstruction of ante-mortem posture both in dead and living subjects based on PMCT and clinical CT. Medical findings can be more accurately documented and reported in a more intuitive manner using such individualized human models. 3D models of the victims including lesions are permanent data sets that can be reviewed at any time if needed.
Funding: This work was supported by the Danish Council for independent Research | Technology and Production Sciences [grant number DFF–4005-00102];
Acknowledges We would like to thank of all the forensic pathologists and the technicians of the Section of Forensic Pathology of the Department of Forensic Medicine, University of Copenhagen, for their help to perform this study. We are also grateful to the anonymous reviewers for their helpful suggestions and comments.
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Captations:
Fig. 1: whole-body 3D model of case #1 created from CT scanning.
Fig 2: animation process: a) the human anatomy 3D model; 2) roungh aligment of human anatomy 3D model and the skeleton of case #1 roughly aligned; 3) final aligment of the human anatomy 3D model and the skeleton of case #1.
Fig. 3: animated skeleton of case #1 including heart, liver and bullet paths (video)
Fig. 4: 3D model of case #2 created from CT scanning
Fig. 5: 3D models of the ulna and radius as visualized in CT imaging (a) and after aligment (b).
Fig. 6: 3D models created with the actual bones of the victim. The re-aligned bones of the left arm are indicated in green. The right arm was created mirroring the left “non-injured” arm and is marked in orange.
Fig. 7: whole-body 3D model of case #2 created combining 3D bones from CT model (light grey, green and orange) and those obtained from the human anatomy 3D model (dark grey).
Fig. 8: the path of the lesion C of case #1 :a) when the victim was in standing position; b) when the victim was slightly bent forwards and rotated to the right.
Fig. 9: two possible postures of case #1 at the time of the incident
Fig. 10: two possible postures of case #2: a) position in which lesions B and C are aligned and could be casuased by the same bullet; b) position in which lesions B and C are not aligned and could not be casuased by the same bullet.