Introduction
In veterinary medicine, access to modern medical imaging techniques such as CT and MRI is now relatively easy. Twenty years ago, CT scans in particular, could only be found in a few universities or specialized clinics, whereas today many more referral centers and some general clinics are also equipped.
Detailed interpretation of these complex studies require specific training, and often the services of a medical imaging specialist (a graduate of the European College of Veterinary Diagnostic Imaging or the American College of Veterinary Radiology). When the veterinary facility does not have a specialist among their staff, it can request remote interpretation of the examinations, which are usually available within 24 to 48 hours.
vet-Anatomy is a digital anatomy atlas for veterinary students in training, veterinary practitioners, residents and medical imaging specialists. As such, it is not a clinical tool for interpreting images. On the other hand, it provides users with precise anatomical information, thereby contributing to the analysis of clinical images: learning normal anatomy to be able to reason about pathology.
The aim of this article is to demonstrate the use of vet-Anatomy in localizing liver and lung masses in a study.
Material and method
CT scans of two dogs (a 12-year-old male Fox Terrier and a 14-year-old male Shepherd cross), obtained after iodine injection, were provided by the imaging department of the veterinary hospital TRIOVet, Rennes (France): an examination of the abdomen and an examination of the thorax. For both exams, images were reconstructed in the three main planes.
Studies were compared with the reference examinations that can be found on vet-Anatomy: the Dog Abdomen/Pelvis CT and Dog Thorax CT modules, in which hepatic segmentation and lung lobes were identified respectively.
Results (figures 1 and 2)
Figure 1. 12-year-old, 7.7kg male Fox Terrier CT abdomen after contrast injection (A), compared with the reference vet-Anatomy examination in the Dog Abdomen/Pelvis CT module (B), in the three main slice planes.
Figure 2. 7.4kg dog chest CT scan after contrast injection, compared with the vet-Anatomy reference scan in the Dog Abdomen/Pelvis CT module, in the three main slice planes.
Discussion
vet-Anatomy is a digital anatomy atlas and is not a diagnostic tool: it is not intended to replace the professional expertise of a medical imaging specialist. On the other hand, as these examples show, vet-Anatomy can provide non-specialist clinicians with basic information for reading a CT scan.
Identification of lung and liver lobes (in domestic carnivores) is tricky on CT: in anatomical position and in the absence of effusion, these lobes can hardly be distinguished from one another. Identifying the organ's functional division involves identifying the distribution of the arterial, venous or bronchial system. This enables the organ to be divided into segments. In the dog, lung segmentation is superimposed on the pulmonary lobes described in the Nomina Anatomica Veterinaria. The same applies to liver segmentation, with the exception of the caudate lobe: the caudate process and papillary process, which are included in the same lobe, do not have a single vascularization unit: the caudate process receives blood from the right division of the portal vein, while the papillary process receives blood from the left division. They cannot therefore be included in the same hepatic segment.
In our two examples, clinical images and vet-Anatomy reference images are not completely superimposable: lesion volume and racial and individual variations alter anatomical relationships. Lobe identification, however, is easily achieved. Thus, the radiologist's reports on these lesions were for example A a "hepatic lesion with cavitary aspect in the left medial lobe compatible with a benign tumoral process" and for example B a "bronchocentric mass in the right middle lung lobe compatible with a primary tumoral process". Alongside the location of these major lesions, the reports also included a wealth of additional information, useful to clinicians but more difficult for the untrained eye to spot.
Conclusion
vet-Anatomy is an invaluable tool, particularly for non-specialist clinicians interested in anatomy and wishing to apply their knowledge to clinical indications. Our example shows that vet-Anatomy can identify liver and lung segments and locate the corresponding lobes.
Acknowledgements: the two clinical studies were provided by the Imaging Department of the AniCura TRIOVet veterinary clinic in Rennes.
