The Virtopsy Approach: Bridging Necroscopic and Radiological Data for Death Investigation of Stranded Cetaceans in the Hong Kong Waters
Veterinary clinical and diagnostic sciences have experienced revolutionary changes in different fields, in contrast, death investigation still utilizes the century-old scalpel-based necropsy of a carcass. Although conventional x-rays have been used in the investigation of some dead cetaceans,3,4 multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) seem to lag behind in their postmortem application1,2. 'Virtual autopsies' using various radiological techniques like MDCT and MRI, named virtopsy, joining conventional dissection methods, are being introduced to the field of forensic medicine worldwide in human medicine.5,9 Virtopsy has the advantages of being observer-independent, non-subjective, non-invasive, digitally storable and transferable in facilitating a second-opinion by another forensic expert or institute placed anywhere in the world. Veterinary virtual necropsy has been previously performed in fox,6 dog,7 red kangaroo8 and lynx10. To the best of our knowledge, the formal literature is devoid of any reference to the routine applicability of virtopsy in stranded cetaceans. This study aimed to evaluate the practicality of virtopsy techniques in stranded cetaceans and compared the findings obtained by conventional necropsy.
Between March 2014 and January 2016, a total of 82 cetacean deaths were confirmed in the Hong Kong waters. Whole body virtopsy of 34 carcasses were performed and analyzed for pathologic findings. Two cetacean species, Sousa chinensis and Neophocaena phocaenoides (12 males, 17 females, 5 unknown sex; calf to adult; 50–259 cm in length), were included, with the carcass code ranging from 1–4. MDCT was performed on a 16-slice multi-detector row Toshiba AlexionTM CT system (Toshiba Medical Systems, Tochigi, Japan). The MRI examination of brain, thorax and spine was performed on a 0.25 Tesla Esaote Vet MRI Grande scanner (Esaote Biomedica, Genova, Italy). Post processing was performed with the built-in software and/or TeraRecon Aquarius workstation (San Mateo, California). Radiological findings were compared with subsequent necropsy findings.
Most of the radiological findings, pertaining to head and neck, heart and vascular, thorax, abdomen, vertebral column and pectoral limbs, corresponded to necroscopic findings. MDCT was useful in diagnosing fatal hemorrhage, organ herniation, and pathological gas collection, as well as determining the number, shapes and characteristics of the fractures sites and the direction of external force. MRI was effective in evaluating soft tissue lesions, musculoskeletal injuries, integrity of spinal cord and brain herniation. Radiological assessment of the degree of epiphyseal fusion/ossification at postcranial skeleton allowed individual age-at-death estimation, supplementing the data obtained by dental growth layer group pattern. Gradual increment of postmortem gas accumulation in the brain, pleural cavity, mediastinum, esophagus, cardiac chambers, subcutaneous tissue, gastrointestinal tract, liver, spleen, kidney, blood vessels and musculatures could be quantified with MDCT, which might gain invaluable insight to the individual death interval.
This study demonstrated virtopsy is a potentially powerful tool, providing non-invasive and objective measurements to supplement the necroscopic findings for cetacean death and life history investigation. Virtopsy could also facilitate veterinary personnel to perform image-guided target specimen necropsy and sampling for histology and toxicology. The calibrated 3-D documentation and analysis of virtopsy findings would lead to qualitative improvements in conventional necropsy.
This project was financially supported by the Hong Kong Research Grants Council [Grant number: UGC/FDS17/M07/14]. The authors would like to thank the Agriculture, Fisheries and Conservation Department of the Hong Kong SAR Government for the continuous support in this project. Sincere appreciation is also extended to veterinarians, staff and volunteers from Ocean Park Hong Kong, Ocean Park Conservation Foundation Hong Kong, and Tung Wah College for paying great effort on the stranding response and necropsy in this project. Special gratitude is owed to technicians from Hong Kong Veterinary Imaging Center for operating the CT and MRI for this research.
* Presenting author
1. Alonso-Farré JM, Gonzalo-Orden M, Barreiro-Vázquez JD, Ajenjo JM, Barreiro-Lois A, Llarena-Reino M, Degollada E. Cross-sectional anatomy, computed tomography and magnetic resonance imaging of the thoracic region of common dolphin (Delphinus delphis) and striped dolphin (Stenella coeruleoalba). Anat Histol Embryol. 2014;43:221–229.
2. Alonso-Farré JM, Gonzalo-Orden M, Barreiro-Vázquez JD, Barreiro-Lois A, André M, Morell M, Llarena-Reino M, Monreal-Pawlowsky T, Degollada E. Cross-sectional anatomy, computed tomography and magnetic resonance imaging of the head of common dolphin (Delphinus delphis) and striped dolphin (Stenella coeruleoalba). Anat Histol Embryol. 2015;44:13–21.
3. Brook F. Ultrasound diagnosis of anencephaly in the fetus of a bottlenose dolphin (Tursiops aduncas). J Zoo Wildl Med. 1994;25:569–574.
4. Butti C, Corain L, Cozzi B, Podestà M, Pirone A, Affronte M, Zotti A. Age estimation in the Mediterranean bottlenose dolphin Tursiops truncatus (Montagu 1821) by bone density of the thoracic limb. J Anat. 2007;211:639–646.
5. Dirnhofer R, Jackowski C, Vock P, Potter K, Thali MJ. VIRTOPSY: minimally invasive, imaging-guided virtual autopsy. Radiographics. 2006;26:1305–1333.
6. Franckenberg S, Kern F, Vogt M, Thali MJ, Flach PM. Fatal gunshot to a fox: the virtopsy approach in a forensic veterinary case. JOFRI. 2015;3:72–75.
7. Heng HG, Selvarajah GT, Lim HT, Ong JS, Lim J, Ooi JT. Serial postmortem thoracic radiographic findings in canine cadavers. Forensic Sci Int. 2008;188:119–124.
8. Lee KJ, Sasaki M, Miyauchi A, Kishimoto M, Shimizu J, Iwasaki T, Miyake Y, Yamada K. Virtopsy in a red kangaroo with oral osteomyelitis. J Zoo Wildl Med. 2011;42:128–130.
9. Thali MJ, Yen K, Schweitzer W, Vock P, Boesch C, Ozdoba C, Schroth G, Ith M, Sonnenschein M, Doernhoefer T, Scheurer E, Plattner T, Dirnhofer R. Virtopsy, a new imaging horizon in forensic pathology: virtual autopsy by postmortem multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) - a feasibility study. J Forensic Sci. 2003;48:386–403.
10. Thali MJ, Kneubuehl BP, Bolliger SA, Christe A, Koenigsdorfer U, Ozdoba C, Spielvogel E, Dirnhofer R. Forensic veterinary radiology: ballistic-radiological 3D computer tomographic reconstruction of an illegal lynx shooting in Switzerland. Forensic Sci Int. 2007;171:63–66.