Abstract
Background
Accurate diagnosis of diseases in animals is crucial for their treatment, and imaging evaluations such as radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) are important tools for this purpose. However, a cross-sectional anatomical atlas of normal skeletal and internal organs of long-tailed gorals (Naemorhedus caudatus) has not yet been prepared for diagnosing their diseases.
Objectives
The objective of this study was to create an anatomical atlas of gorals using CT and MRI, which are imaging techniques that have not been extensively studied in this type of wild animal in Korea.
Methods
The researchers used CT and MRI to create an anatomical atlas of gorals, and selected 37 cross-sections from the head, thoracic, lumbar, and sacrum parts of gorals to produce an average cross-sectional anatomy atlas.
Results
This study successfully created an anatomical atlas of gorals using CT and MRI.
Conclusions
The atlas provides valuable information for the diagnosis of diseases in gorals, which can improve their treatment and welfare. The study highlights the importance of developing cross-sectional anatomical atlases of gorals to diagnose and treat their diseases effectively.
Keywords: Cross-sectional anatomy, veterinary anatomy, wild animal, CT scan, magnetic resonance imaging
INTRODUCTION
Diagnosis of disease in animals is generally performed using various tools, including history taking and physical and imaging examinations. Thus, imaging tests, including radiographs, computed tomography (CT), and magnetic resonance imaging (MRI), are essential for the accurate diagnosis of animals before treatment [1,2,3].
CT and MRI imaging techniques provide accurate visualization of the normal skeletal and soft tissues of animals without invasive procedures [4,5]. These imaging techniques also allow for the reconstruction of an animal’s entire body in various planes with high levels of soft tissue contrast resolution [6,7,8,9]. As a result, CT and MRI are increasingly used for diagnostic and research purposes in various animals [10,11,12,13,14,15,16,17,18]. However, there have been few CT and MRI studies conducted on wild animals in Korea, and no studies have reported on the anatomy and imaging diagnostics of long-tailed gorals (Naemorhedus caudatus, gorals), a type of wild animal. To address this gap, researchers aimed to produce a comprehensive anatomical atlas of gorals by using CT and MRI scans of the head and thoracic, abdominal, and sacral cross-sections. This atlas accurately identifies normal skeletal, thoracic, and abdominal structures and serves as a reference for evaluating the normal and pathological conditions of gorals.
The purpose of this study is to provide basic data for restoring endangered gorals through systematic health management and improved medical care for injured gorals. To achieve this goal, the researchers used various image evaluations including radiographs, CT, and MRI to identify the normal body structure of gorals. This information is essential for accurate diagnosis and treatment of injured gorals and for improving the overall health management of the goral population.
MATERIALS AND METHODS
This study included ten adult gorals (seven males and three females, older than three years, average body height 67.40 cm, length 53.60 cm, and weight 35.490 kg) that had been rescued and were healthy after treatment at the Gangwon Wildlife Medical Rescue Center (WMRC), as well as two healthy adult gorals raised at the Yanggu Long-tailed Gorals and Muskdeer Center (YLMC). To establish the normal head skeletal form, vertebral formula, and dental formula, ten gorals were sedated with 1.5 mg/kg xylazine HCL (Rompun; Bayer AG, Germany) and maintained under anesthesia with isoflurane. In addition, two adult male gorals were sedated using an anesthetic gun to administer the combination of 1.5 mg/kg xylazine HCL and 4.5 mg/kg ketamine (Ketamine Inj.; Yuhan, Korea) to obtain cross-sectional anatomy data. The anesthesia was maintained with isoflurane and supplementary fluids were provided.
Clinical examinations, radiographic diagnostics, and complete blood analysis were performed on all gorals to confirm that they were clinically healthy. The gorals were placed in sternal recumbency for radiographs, CT, and MRI examinations. All radiographs were obtained using a VXR-9M digital radiography system (DRGEM, Korea). CT scans were performed using a Somatom Emotion 6 system (Siemens, Germany). A 1.5-T MRI (Vantage Elan; Toshiba, Japan) equipped with 16-channel flexible (16-channel Flex SPEEDER Large; Toshiba), and spine (Octave SPEEDER Spine; Toshiba) coils to scan one clinically healthy goral. After the examination, 0.125 mg/kg of yohimbine HCL (Zyverse; KBNP Inc., Korea) was used to minimize the side effects of anesthesia. The digital radiography system (VXR-9M ViewRex; TechHeim, Korea) was used to compare and analyze the radiographs, CT, and MRI scans. This study was approved by the Institutional Animal Care and Use Committee of Kangwon National University (KW-220314-4).
RESULTS
The results of this study are summarized in Figs. 1 and 2, and Supplementary Figs. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. Fig. 1 shows the results of the skeleton analysis for the 10 gorals, including the parts of the skull. The dental formula showed a total of 32 teeth, including incision (I) 0/4 (maxilla/mandible), canine (C) 0/0, premolar (P) 3/3, and molar (M) 3/3. The vertebral formula was identified as seven cervical vertebrae (CV), 13 thoracic vertebrae (TV), six lumbar vertebrae (LV), four sacrum (S), and 11–16 caudal vertebrae (CDV). Furthermore, the four sacral vertebrae of the gorals form the sacrum, and the anticlinal vertebra was located at TV 11.
Fig. 1. Computed tomographic anatomy atlas of the bones of the goral. (A) The cranium of goral 1. Nasal bone, 2. Supraorbital groove, 3. Frontal bone, 4. Horn, 5. Orbit, 6. Incisive bone, 6'. Labiel surface, 7. Maxilla, 7'. Facial crest, 7". Infraorbital foramen, 8. Zygomatic bone, 9. Zygomatic process of maxilla, 10. Temporal process, 11. Zygomatic process of frontal bone, 12. Zygomatic process of temporal bone, 13. Coronoid process of mandible, 14. Head of mandible, 15. Parietal bone, 16. Temporal bone, 17. External acoustic meatus, 18. Mastoid process, 19. Occipital bone, 20. Paracondylar process, 21. Palatine bone, 22. mandible, 23. Mental foramen, 24. Lacrimal bone, 25. Tympanic bulla, (B) Dental formula of goral (I 0/4, C 0/0, P 3/3, M 3/3), (C) Vertebral formula of goral (CV 7, TV 13, LV 6, S 4, CDV 11–16).
I, incision; C, canine; P, premolar; M, molar; CV, cervical vertebrae; TV, thoracic vertebrae; LV, lumbar vertebrae; S, sacrum; CDV, caudal vertebrae.
Fig. 2. Three-dimensional surface reconstructions of goral in the sternal recumbent position. Numbered lines indicate the approximate level of each CT and MRI scan shown in supplementary figures (Supplementary Fig. 1, lines 1 to 3; Supplementary Fig. 2, lines 4 to 7; Supplementary Fig. 3, lines 8 to 11; Supplementary Fig. 4, lines 12 to 14; Supplementary Fig. 5, lines 15 to 18; Supplementary Fig. 6, lines 19 to 21; Supplementary Fig. 7, lines 22 to 24; Supplementary Fig. 8, lines 25 to 27; Supplementary Fig. 9, lines 28 to 30; Supplementary Fig. 10, lines 31 to 33; Supplementary Fig. 11, lines 34 to 37).
CT, computed tomography; MRI, magnetic resonance imaging.
Fig. 2 is a diagram of the goral in the sternal recumbent state showing the approximate levels of each CT and MRI image. All CT and magnetic resonance (MR) images were printed for viewing from the cranial to the caudal direction. Supplementary Figs. 1 and 2 show the head of the goral in the order of (A) CT scan, (B) MRI T1w, and (C) MRI T2w. In the MRI scans in Supplementary Fig. 2, footnotes are attached to each part of the goral brain. In Supplementary Figs. 3, 4, 5, 6, 7, 8, 9, 10, 11, CT images of the neck, thorax, and abdomen are presented in the order of (A) bone, (B) lung, and (C) soft tissue windows according to each vertebra. The locations of the major organs identified by CT are; lung TV 1–13, heart TV 4–9, rumen TV 11–S 3, reticulum TV 9–13, omasum TV 12–LV 1, abomasum TV 12–13, liver TV 9–LV 2, spleen TV 9–LV 3, right kidney TV 13–LV 1, and left kidney LV 3–5.
DISCUSSION
Cross-sectional and skeletal anatomy is usually accurate between CT and MR images in cryosectioned cadavers. However, it is not feasible to euthanize a normal individual as gorals are an endangered species and a natural monument. Therefore, compared to the cross-sectional anatomy literature of goats and sheep, the present study aimed to establish the goral anatomy [10,19,20]. A study of the radiographs and CT scans of 10 gorals showed that the normal goral vertebral formula was CV 7, TV 13, LV 6, S 4, and CDV 11–16, which differed from sheep, goats, and cattle (Table 1) [21]. There was a difference in the anticlinal vertebra of gorals between the sheep (TV 10, 11) and the cattle (TV 11–13), with the gorals having it located at TV 11 (Table 2) [22,23]. The vertebral formula of gorals is most similar to that of the genetically closest sheep (CV 7, TV 13, LV 6–7, S 4, CDV 16–18) compared to goats and cattle. In addition, while Jo et al. [24] reported the dental formula of gorals of I 0/3, C 0/1, P 3/3, and M 3/3, the present study determined a canine to be an incisor, resulting in a dental formula of I 0/4, C 0/0, P 3/3, and M 3/3. A unique feature of small ruminant teeth is the lack of incisors and canines in the upper jaw. The canine of the lower jaw is assimilated into the incisor, eventually forming the fourth incisor [21]. This is because the first premolar of the upper and lower jaws does not develop; thus, the premolars of small ruminants begin with the second premolar. Therefore, this study confirmed that gorals have the same dental formula as sheep, goats, and cattle (Table 3).
Table 1. Comparison of vertebral formulas of gorals and three types of ruminants.
| Variables | Long-tailed goral (Naemorhedus caudatus) | Sheep (Ovis aries) | Goat (Capra hircus) | Cow (Bos indicus) |
|---|---|---|---|---|
| Study | Present study | Dyce et al., 2009 [21] | ||
| Cervical vertebrae | 7 | 7 | 7 | 7 |
| Thoracic vertebrae | 13 | 13 | 13 | 13 |
| Lumbar vertebrae | 6 | 6–7 | 6–7 | 6 |
| Sacral vertebrae (Sacrum) | 4 | 4 | 5 | 5 |
| Caudal vertebrae | 11–16 | 16–18 | 16–18 | 18–20 |
Table 2. Comparison of the anticlinal vertebra of gorals and three types of ruminants.
Table 3. Comparison of dental formulas of gorals and three types of ruminants.
| Variables | Long-tailed goral (Naemorhedus caudatus) | Sheep (Ovis aries) | Goat (Capra hircus) | Cow (Bos indicus) |
|---|---|---|---|---|
| Study | Present study | Dyce et al., 2009 [21] | ||
| Incisor | 0 / 4 | 0 / 4 | 0 / 4 | 0 / 4 |
| Canine | 0 / 0 | 0 / 0 | 0 / 0 | 0 / 0 |
| Premolar | 3 / 3 | 3 / 3 | 3 / 3 | 3 / 3 |
| Molar | 3 / 3 | 3 / 3 | 3 / 3 | 3 / 3 |
In addition, this study aimed to create a guidebook of the cross-sectional anatomy through CT scans of each vertebral body of gorals to aid in the interpretation of all cross-sectional image studies of goral. CT and MRI provide significant advantages in identifying the anatomical structure of gorals by eliminating the superposition of overlapped structures that may interfere with interpretation over conventional radiographic approaches [25]. In addition, spatial relations can be viewed in detail through a three-dimensional reconstruction of anatomical structures [26]. The detailed structures from CT scans and cross-sections of gorals were mainly organized by reference to the literature on sheep and goats with similar anatomical structures, and compared to cross-sectional and anatomical texts in the literature on various other animals [10,14,21,27,28,29,30,31].
The findings of the present study do not apply to all gorals in Korea. This study targeted ten gorals that were restored to health after being rescued by the WMRC and two healthy adult male gorals proliferating in the YLMC. However, the results of this study are clinically important because it is challenging to prepare criteria for evaluating clinical diagnosis in endangered gorals. In addition, this study is the first normal anatomical and imaging reference for gorals and is useful as a general source for veterinarians as CT and MRI are further established as diagnostic tools in veterinary medicine. In conclusion, to improve the treatment of gorals, more gorals should be added based on the reference values obtained in this study, and continuous research is needed on various disease diagnosis methodologies on thoracic radiography, CT, and MRI.
ACKNOWLEDGEMENTS
The authors would like to express their deepest gratitude to Yanggu Long-tailed Goral and Muskdeer Center for their valuable support for the rescue of goral and medical assistance. This manuscript represents a portion of the Ph.D. dissertation by Sangjin Ahn.
Footnotes
Conflict of Interest: The authors declare no conflicts of interest.
- Conceptualization: Ahn S, Kim JT.
- Data curation: Ahn S, Shin W, Han Y, Bae S, Cho C, Kim JT.
- Formal analysis: Ahn S, Shin W, Han Y, Bae S, Choi S, Kim JT.
- Investigation: Ahn S, Shin W, Han Y, Bae S, Cho C, Choi S, Kim JT.
- Methodology: Ahn S, Shin W, Han Y, Bae S, Cho C, Choi S, Kim JT.
- Project administration: Kim JT.
- Software: Choi S.
- Supervision: Ahn S, Choi S, Kim JT.
- Validation: Ahn S, Shin W, Han Y, Bae S, Choi S, Kim JT.
- Visualization: Ahn S, Choi S.
- Writing - original draft: Ahn S.
- Writing - review & editing: Ahn S, Choi S, Kim JT.
SUPPLEMENTARY MATERIALS
Transverse (A) CT, (B) MR T1w, (C) MR T2w images of goral at lines 1 to 3 of Fig. 2.
Transverse (A) CT, (B) MR T1w, (C) MR T2w images of goral at lines 4 to 7 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 8 to 11 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 12 to 14 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 15 to 18 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 19 to 21 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 22 to 24 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 25 to 27 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 28 to 30 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 31 to 33 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 34 to 37 of Fig. 2.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Transverse (A) CT, (B) MR T1w, (C) MR T2w images of goral at lines 1 to 3 of Fig. 2.
Transverse (A) CT, (B) MR T1w, (C) MR T2w images of goral at lines 4 to 7 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 8 to 11 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 12 to 14 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 15 to 18 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 19 to 21 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 22 to 24 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 25 to 27 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 28 to 30 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 31 to 33 of Fig. 2.
Transverse CT (A) bone window, (B) lung window, (C) soft tissue window images of goral at lines 34 to 37 of Fig. 2.