Normal cross-sectional anatomy of the feline thorax and abdomen: comparison of computed tomography and cadaver anatomy

Thoracic cavity of the Shirazi cats: New insights using computed tomography and magnetic resonance imaging

Our study provided a comprehensive characterization of the thorax of Shirazi cats by comparing the relevant soft and bone windows of computed tomography (CT) and magnetic resonance imaging (MRI) with cross, sagittal and coronal sectional anatomy. We outlined the mediastinum and its anatomic relationships with the trachea, oesophagus, lungs, heart, cranial and caudal vena cavae, and other thoracic structures using the data series gathered from adult normal Shirazi cats. The cranial mediastinum extended from the thoracic inlet to the 4th intercostal space, the middle mediastinum extended from the 5th and 7th intercostal spaces and was occupied by the heart and large blood vessels and the caudal mediastinum extended as a short and narrow portion from the 8th intercostal space to the diaphragm. The contents of the mediastinum and its relationship with the lungs and diaphragm were clearly presented in coronal-sectional anatomy and CT slices. The diaphragm was clearly observed in the lung windows of the ventral thorax. Sagittal-sectional anatomy and CT clarified the thorax's architecture and its contents, with higher density in the soft windows. The distribution of thoracic vessels on cross- and coronal-contrast CT scans was clearly visible. In addition, MRI scans provided an excellent anatomic reference of the thorax with the help of cross, coronal and sagittal scans, especially in the heart and blood vessels. Our study provides a valuable atlas for the diagnosis of malformations of the thoracic structures and offers better assessments for helping veterinary radiologists and clinicians in diagnostic processes.

Cross-sectional and skeletal anatomy of long-tailed gorals (Naemorhedus caudatus) using imaging evaluations

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.

Creation of Three-Dimensional Anatomical Vascular and Biliary Models for the Study of the Feline Liver (Felis silvestris catus L.): A Comparative CT, Volume Rendering (Vr), Cast and 3D Printing Study

In this study, six adult feline cadavers were examined using CTA, 3D printing, and casts injected with epoxy. The aorta, the portal vein, and the gallbladder of 3 feline cadavers were separately injected with a 50% mixture of colored vulcanized latex and hydrated barium sulfate as contrast medium to analyze by CT the arterial, venous and biliary systems. The other three cadavers were injected with a mixture of epoxy resin in the aorta, gallbladder and hepatic veins, separately. After the corrosion and washing process, hepatic vascular and biliary casts were obtained. The images obtained by CT showed the vascular and biliary system using a soft tissue window. For the identification of vascular and biliary structures, the 3D prints together with the 3D reconstructions were analyzed, and the results were compared with the casts obtained with epoxy resin. Each of the arterial, venous and biliary branches associated with each of the liver lobes were identified with the help of the printings. In conclusion, the creation of 3D prototypes of nonpathological feline hepatic parenchyma can be used in the veterinary clinic as a basis for the detection of pathological problems in addition to obtaining future pathological hepatic 3D models.

Imaging and endoscopic diagnosis of lung diseases in small animals. A review

Diagnostic imaging plays a fundamental role in the diagnosis of pulmonary diseases. Radiography, ultrasound, computed tomography, and endoscopy are important tools for achieving a diagnosis. The choice of diagnostic procedure varies according to the patient, the suspected diagnosis and the risk/benefit ratio. Culture, cytology and histology are nearly always necessary to obtain a definitive diagnosis. Several biopsy sampling techniques are described. Surgical biopsies are the gold standard for the diagnosis of bronchiolitis or interstitial lung diseases but often not performed due to the high risk. In humans, the introduction of transbronchial cryobiopsies has led to excellent results in the study of interstitial lung diseases.

Computer Tomography (CT) Scans as a Diagnostic Tool for Interpretation of S10 Plastinated Slides from Dog Cadaver

Computed tomography (CT) is a routine method for the diagnosis of pathological structures in the body and has been widely used in veterinary medicine as an advanced diagnostic imagining tool in veterinary clinics. However, interpretation of CT scans requires detailed knowledge of topographical animal anatomy and usually has limited scan resolution due to the ambiguous relationship between signal intensity and tissue composition. The aim of the study was to assess the morphometric similarities between S10 plastinated slides and computer tomography (CT) scans and their usability as compatible paired diagnostic methods. A 3-year-old euthanized dog cadaver was scanned on SHIMADZU SCT/6800TXL scanner immediately post-mortem, then frozen at -80 °C to preserve the correct anatomical position, and plastinated with a standardized procedure. Semi-transparent transversal slices (5 mm) were obtained from the head, thoracic, and lumbar sections of the body. The S10 plastinated slides and CT scans contained fine and small anatomical structures with high similarity. The spatial relationships of all anatomical structures on the serial S10 platinates were in the correct anatomical position. In conclusion, S10 transversal slices showed high similarity with the CT scans and allowed identification of the corresponding morphological structures. The S10 thin plastinated transversal slices could be used for additional interpretation of CT transversal scans at veterinary clinics and as a didactical tool for veterinary students.

Morphological investigation of canine epigastric organs and adjacent structures via computed tomography, ultrasound and anatomical prosection

The canine epigastric organs, their locations and visualization of these components are essential for veterinary practice and anatomical research. Despite their importance, conflicts and discrepancies in the published material, to date, still exist, even in a species that has been studied extensively. The aim of this research was to undertake computed tomography, and anatomical sections from differing views and levels in addition to the ultrasound appearance of the main organs of the epigastria region. The epigastric organs, and associated anatomical features and landmarks that affected by stomach fullness were described in relation to their relative positions, visual appearance and general anatomy for both empty and filled stomachs. These features were not only described, but also compared against the published literature.

Cross-sectional anatomy, computed tomography, and magnetic resonance imaging of the banded houndshark (Triakis scyllium)

Due to their important phylogenetic position among extant vertebrates, sharks are an invaluable group in evolutionary developmental biology studies. A thorough understanding of shark anatomy is essential to facilitate these studies and documentation of this iconic taxon. With the increasing availability of cross-sectional imaging techniques, the complicated anatomy of both cartilaginous and soft tissues can be analyzed non-invasively, quickly, and accurately. The aim of this study is to provide a detailed anatomical description of the normal banded houndshark (Triakis scyllium) using computed tomography (CT) and magnetic resonance imaging (MRI) along with cryosection images. Three banded houndsharks were scanned using a 64-detector row spiral CT scanner and a 3 T MRI scanner. All images were digitally stored and assessed using open-source Digital Imaging and Communications in Medicine viewer software in the transverse, sagittal, and dorsal dimensions. The banded houndshark cadavers were then cryosectioned at approximately 1-cm intervals. Corresponding transverse cryosection images were chosen to identify the best anatomical correlations for transverse CT and MRI images. The resulting images provided excellent detail of the major anatomical structures of the banded houndshark. The illustrations in the present study could be considered as a useful reference for interpretation of normal and pathological imaging studies of sharks.

Sample strategies for quantification of hepatic fat fraction mean MRI in healthy cats during body weight gain

Hepatic fat fraction (HFF) can be non-invasively estimated with magnetic resonance imaging (MRI) multiple echo gradient recalled echo (GRE) sequence. The aim of this study was to test different methods of sampling strategies to quantify the HFF in healthy cats during body weight gain. Twelve healthy adult male cats were examined in a 3 Tesla MRI unit. Sequences included morphological images, and multiple echo GRE sequence. Cats were scanned at the beginning of the study and twice, each 20 weeks apart during body weight gain. HFF was calculated with 5 different methods of sampling on the multiple echo GRE sequence with different number, size and position of regions of interest (ROIs) and by 2 operators. Results indicated that HFF increased with increasing body weight, and the increase was appreciated with all the 5 methods. There was overall excellent agreement (interclass correlation coefficient = 0.820 (95% confidence interval:0.775–0.856)) between the 2 operators. HFF in the left lateral hepatic lobe was lower than in the other analyzed lobes. HFF measured on large free-hand drawn ROIs was higher than HFF measured with smaller ROIs size. This study proves that different sampling methods for quantification of HFF on multiple echo GRE sequence have overall excellent repeatability and ability to appreciate increased HFF.

Morphology, ultrasonographic and computed tomography configuration of the dog pelvis and perineum

The current study used topographic anatomy, distribution of arteries and nerves, sectional anatomy of the pelvis, computed tomography (CT) and ultrasonography examination to describe the canine pelvis and its organs. This study was conducted on twenty male and female baladi dogs, weighing 30-35 kg and aged between 1.5 and 2 years. The pelvis dorsal boundary appeared long and reached to the level of the third caudal vertebra. The vesicogenital pouch in the female extended further caudally than the rectogenital pouch while in the male the two pouches were at the same level and extended to the level of the first sacral vertebra. The plexus lumbosacralis formed from the ventral branches of the last three lumbar nerves and the first three sacral nerves. The obturator nerve arose from the ventral branches of the fifth and sixth lumbar nerves. We developed an anatomical atlas of the pelvis of both sexes of the dog using CT scans compared to anatomical sections. Our study is the first research on the pelvis in both sexes of the dog to compare sagittal CT scan data to sagittal anatomical sections. In the CT slices, the prostate appeared homogenous, relatively hypodense presenting with a soft tissue density. It appeared oval in the longitudinal sections and elliptical to round at the cross sections. It was situated on the floor of the pelvic cavity or the pelvic brim depending on its size. The present study is also the first to describe the fascia diaphragmatic pelvis.

Anatomical Assessment of the Thorax in the Neonatal Foal Using Computed Tomography Angiography, Sectional Anatomy, and Gross Dissections

The purpose of this study was to correlate the anatomic features of the normal thorax of neonatal foals identified by CTA, with anatomical sections and gross dissections. Contrast-enhanced transverse CTA images were obtained in three neonatal foals using a helical CT scanner. All sections were imaged with a bone, mediastinal, and lung windows setting. Moreover, cardiac volume-rendered reconstructed images were obtained. After CT imaging, the cadaver foals were sectioned and dissected to facilitate the interpretation of the intrathoracic cardiovascular structures to the corresponding CTA images. Anatomic details of the thorax of neonatal foals were identified according to the characteristics of CT density of the different organic tissues and compared with the corresponding anatomical sections and gross dissections. The information obtained provided a valid anatomic pattern of the thorax of foals, and useful information for CTA studies of this region.

Normal anatomic reference of pastern and coffin joints in Egyptian buffalo (Bubalus bubalis): A compared atlas of cross-sectional anatomy, magnetic resonance imaging and computed tomography

The purpose of this study was to describe normal magnetic resonance imaging and computed tomographic anatomy of pastern and coffin joints in Egyptian buffalo using cadaveric distal limbs. This study was achieved using twelve fresh cadaveric distal limbs from adult healthy buffaloes of both sexes. These cadaveric limbs were scanned using a 1 Tesla MRI scanner and CT scanner, injected with red latex, frozen at -20°C for 1 week, and then sectioned into sagittal, dorsal and transverse slices. The obtained MR and CT images were selected to be matched with their corresponding anatomical cross-sections for identification and evaluation of the clinically correlated anatomical structures of the pastern and coffin joints. The difference in signal intensities on CT and MRI scans amongst the tissues allowed clear differentiation of major bone and soft tissue structures of the pastern and coffin joints. CT provided a high spatial resolution of bone and soft tissue structures, however, MRI allowed a better and higher resolution and definition between soft tissues. The current study provided a normal CT and MRI anatomic reference which could help veterinary clinicians for interpretation and diagnosis of the clinically affected pastern and coffin joints in buffalo.

64-multidetector CT anatomical assessment of the feline bronchial and pulmonary vascular structures

OBJECTIVES

The aim of the study was to provide a detailed anatomical study of the feline bronchial and vascular structures by using CT angiography (CTA).

METHODS

Adult cats with no respiratory clinical signs were enrolled in a CTA protocol to provide an anatomical study of the thorax. The dimensions, number of branches and branching pattern (monopodial vs dichotomic) of both bronchial and pulmonary vascular structures were evaluated under positive inspiration apnoea. A linear generalised estimating equations analysis (Spearman's rho) was used to identify statistical correlation between tracheal diameter, age and body weight of the cats.

RESULTS

Fourteen cats met the inclusion criteria. The pulmonary arteries had larger diameters than the pulmonary veins, and the pulmonary veins had larger diameters than the bronchial structures. A higher number of segmental bronchial and pulmonary vascular branches was observed in the left caudal lung lobe than in the other lobes. The monopodial branching pattern of both bronchial and pulmonary vascular structures was predominant in all cats of our study (100%) in cranial, caudal and right middle lung lobes, while a dichotomic branching pattern of the bronchial and pulmonary vascular structures of the accessory lung lobe was seen in 13 cats (93%). Thirteen cats (93%) had three pulmonary vein ostia, and one cat (7%) also presented with an additional left intermediate pulmonary vein ostium. Variation in the number of segmental pulmonary vein branches was noted in the right caudal lung lobe. There was no statistical correlation between tracheal diameter, age and weight.

CONCLUSIONS AND RELEVANCE

Architecture of the feline bronchovascularr structures belongs to a mixed type of monopodial and dichotomic branching pattern. In cats, the pulmonary venous drainage system predominately presents three pulmonary vein ostia. Variations in the type of formation and the number of branches of the pulmonary venous drainage system were noted.

Advances in the anatomic study of the interscapular region of the cat

Background

New clinical oriented approaches are supported by the integration of advanced imaging techniques, e.g. computed tomography and magnetic resonance, with gross anatomy imaging. The interscapular region of the cat is a typical site of a highly invasive infiltrative pathology, i.e. Feline Injection-Site Sarcoma. Even if chemotherapy and radiotherapy have been considered as pre-surgical therapies, extensive surgery is still the recommended treatment. Evidence suggested that the relationships between muscles, infiltrative mass and adjacent musculoskeletal structures could change according to the forelimb positions: a fact to be duly considered while planning the surgical approach.

Anatomic and tomographic atlases provide only images of the interscapular region from cats positioned with their forelimbs extended cranially, which means that, they do not record musculoskeletal modifications due to the forelimb movements.

Aim of this study was to provide detailed images of the changes occurring in the musculoskeletal structures of the interscapular region of cats according to their forelimb position by comparing cross-sectional gross anatomy, computed tomography and magnetic resonance imaging.

Results

We provide an atlas of normal cross-sectional anatomy, computed tomography and magnetic resonance imaging of the interscapular region of the cat, from the fifth cervical vertebra to the fifth thoracic vertebra. We compare and couple the slices obtained both in flexed and extended forelimb positioning with the animal maintained in sternal recumbency.

Conclusion

This study shows a new and dynamic way to investigate the interscapular region of the cat and provides anatomical references for in vivo computed tomography and magnetic resonance imaging, considering changes in the muscular form according to the forelimb positioning. We believe that an in-depth anatomical knowledge of the interscapular region may be helpful to approach the study of any pathology located there and, in particular, to set up an appropriate therapy for the feline injection-site sarcoma.

Computed tomography and cross-sectional anatomy of the thorax of the live bottlenose dolphin (Tursiops truncatus)

Pulmonary disease is one of the leading causes of cetacean morbidity and mortality in the wild and in managed collections. The purpose of this study was to present the computed tomographic (CT) appearance of the thorax of the live bottlenose dolphin (Tursiops truncatus) out-of-water and to describe the technical and logistical parameters involved in CT image acquisition in this species. Six thoracic CT evaluations of four conscious adult bottlenose dolphins were performed between April 2007 and May 2012. Animals were trained to slide out of the water onto foam pads and were transported in covered trucks to a human CT facility. Under light sedation, animals were secured in sternal recumbency for acquisition of CT data. Non-contrast helical images were obtained during an end-inspiratory breath hold. Diagnostic, high quality images were obtained in all cases. Respiratory motion was largely insignificant due to the species' apneustic respiratory pattern. CT findings characteristic of this species include the presence of a bronchus trachealis, absence of lung lobation, cranial cervical extension of the lung, lack of conspicuity of intrathoracic lymph nodes, and presence of retia mirabilia. Dorsoventral narrowing of the heart relative to the thorax was seen in all animals and is suspected to be an artifact of gravity loading. Diagnostic thoracic computed tomography of live cetaceans is feasible and likely to prove clinically valuable. A detailed series of cross-sectional reference images is provided.

Cross-sectional anatomy, computed tomography and magnetic resonance imaging of the thoracic region of common dolphin (Delphinus delphis) and striped dolphin (Stenella coeruleoalba)

The aim of this study was to provide a detailed anatomical description of the thoracic region features in normal common (Delphinus delphis) and striped dolphins (Stenella coeruleoalba) and to compare anatomical cross-sections with computed tomography (CT) and magnetic resonance imaging (MRI) scans. CT and MRI were used to scan 7 very fresh by-caught dolphin cadavers: four common and three striped dolphins. Diagnostic images were obtained from dolphins in ventral recumbency, and after the examinations, six dolphins were frozen (-20°C) and sliced in the same position. As well as CT and MRI scans, cross-sections were obtained in the three body planes: transverse (slices of 1 cm thickness), sagittal (5 cm thickness) and dorsal (5 cm thickness). Relevant anatomical features of the thoracic region were identified and labelled on each section, obtaining a complete bi-dimensional atlas. Furthermore, we compared CT and MRI scans with anatomical cross-sections, and results provided a complete reference guide for the interpretation of imaging studies of common and striped dolphin's thoracic structures.

High-resolution computed tomography bronchial lumen to pulmonary artery diameter ratio in anesthetized ventilated cats with normal lungs

High-resolution computed tomography (CT) is the preferred noninvasive tool for diagnosing bronchiectasis in people. A criterion for evaluating dilation of the bronchus is the bronchial lumen to pulmonary artery diameter (bronchoarterial ratio [BA ratio]). A ratio of > 1.0 in humans or > 2.0 in dogs has been suggested as a threshold for identifying bronchiectasis. The purpose of this study was to establish the BA ratio in normal cats. Fourteen specific pathogen-free cats were selected for analysis of thoracic CT images. The BA ratios of the lobar bronchi of the left cranial (cranial and caudal parts), right cranial, right middle, left caudal, and right caudal lung lobes were measured. The mean of the mean BA ratio of all lung lobes was 0.71 +/- 0.05. Individual BA ratios ranged from 0.5 to 1.11. Comparing individual lobes for each cat, there was no significant difference (P = 0.145) in mean BA ratio between lung lobes. A mean BA ratio for these normal cats was 0.71 +/- 0.1, which suggests an upper cut-off normal value > 0.91 (mean +/- 2 standard deviations) between normal and abnormal cats.

Evaluation of radiographic, computed tomographic, and cadaveric anatomy of the head of boa constrictors

OBJECTIVE

To evaluate the radiographic, computed tomographic (CT), and cadaveric anatomy of the head of boa constrictors.

ANIMALS

4 Boa constrictor imperator cadavers.

PROCEDURES

Cadavers weighed 3.4 to 5.6 kg and had a body length ranging from 189 to 221 cm. Radiographic and CT images were obtained with a high-detail screen-film combination, and conventional CT was performed with a slice thickness of 1.5 mm. Radiographic images were obtained in ventrodorsal, dorsoventral, and left and right laterolateral recumbency; CT images were obtained with the animals positioned in ventral recumbency directly laying on a plastic support. At the end of the radiographic and CT imaging session, 2 heads were sectioned following a stratigraphic approach; the other 2, carefully maintained in the same position on the plastic support, were moved into a freezer (-20°C) until completely frozen and then sectioned into 3-mm slices, respecting the imaging protocol. The frozen sections were cleaned and then photographed on each side. Anatomic structures were identified and labeled on gross anatomic images and on the corresponding CT or radiographic image with the aid of available literature.

RESULTS

Radiographic and CT images provided high detail for visualization of bony structures; soft tissues were not easily identified on radiographic and CT images.

CONCLUSIONS AND CLINICAL RELEVANCE

Results provide an atlas of stratigraphic and cross-sectional gross anatomy and radiographic and CT anatomy of the heads of boa constrictors that might be useful in the interpretation of any imaging modality in this species.

Inside out: modern imaging techniques to reveal animal anatomy

Animal anatomy has traditionally relied on detailed dissections to produce anatomical illustrations, but modern imaging modalities, such as MRI and CT, now represent an enormous resource that allows for fast non-invasive visualizations of animal anatomy in living animals. These modalities also allow for creation of three-dimensional representations that can be of considerable value in the dissemination of anatomical studies. In this methodological review, we present our experiences using MRI, CT and μCT to create advanced representation of animal anatomy, including bones, inner organs and blood vessels in a variety of animals, including fish, amphibians, reptiles, mammals, and spiders. The images have a similar quality to most traditional anatomical drawings and are presented together with interactive movies of the anatomical structures, where the object can be viewed from different angles. Given that clinical scanners found in the majority of larger hospitals are fully suitable for these purposes, we encourage biologists to take advantage of these imaging techniques in creation of three-dimensional graphical representations of internal structures.

Cross-sectional anatomy of the rabbit neck and trunk: comparison of computed tomography and cadaver anatomy

Computed tomographic images of the neck, thorax and abdomen in four healthy adult rabbits were obtained with a conventional CT using a slice-thickness of 5mm. CT images were obtained with the animals positioned in sternal recumbency on a removable plastic support directly laying on the CT-table. At the end of the CT session, each rabbit was euthanized and, while carefully maintaining the same position on the plastic support, the animal was moved into a -20 degrees C freezer until completely frozen. Each cadaver was then sectioned at 10mm slices, with the first section starting at the tip of the nose, respecting the imaging protocol. The frozen sections were cleaned and then photographed on each side. Anatomic structures were identified and labeled first on each side of the frozen section and then on the corresponding CT image with the aid of the available literature. Results from our study provide an atlas of normal cross-sectional gross and CT anatomy of the rabbit neck, thorax and abdomen, useful in the interpretation of any cross-sectional imaging modality in this species.

Normal cross-sectional anatomy of the bovine digit: comparison of computed tomography and limb anatomy

The purpose of this study was to define the structures of the digits and hoof in Holstein dairy cattle by using computed tomography scan (CT scan). Transverse, sagittal and dorsoplantar CT images of two isolated cattle cadaver digits were obtained using a Siemens ARTX2 Somatom. The CT images were compared to corresponding frozen cross-sections. Relevant anatomical structures were identified and labelled at each level. The CT images provided anatomical detail of the digits and hoof in Holstein dairy cattle. Transversal images provided excellent depiction of anatomical structures when compared to corresponding frozen cross-sections. The information presented in this paper would serve as an initial reference to the evaluation of CT images of the digits and hoof in Holstein dairy cattle.

Ultrasonographic, computed tomographic and magnetic resonance imaging anatomy of the normal canine stifle joint

Ultrasonographic (US), magnetic resonance (MR) and computed tomographic (CT) images of normal canine stifle joints were obtained and compared with plastinated cross-sectional slices of cadaver specimens from the same dogs. The bony and articular structures were identified and correlated with the three diagnostic imaging modalities. These results provide an atlas of normal cross-sectional US, MR and CT anatomy of the canine stifle, which can be used for the interpretation of stifle images from any of these imaging modalities.

Helical computed tomographic anatomy of the canine abdomen

The purpose of this study was to provide an atlas of the normal anatomy of the canine abdomen using helical computed tomographic (CT) images of the abdomen in four mature cross-breed dogs. The dogs were supported in sternal recumbency under general anaesthesia and scans were performed with 5 mm collimation and a pitch of 1. All sections were imaged with soft-tissue window settings and the cranial abdomen was also imaged with mediastinum-vascular window settings. CT scans were performed immediately after iodinated contrast medium was injected into the cephalic vein at 2 mL/kg. Iodinated contrast medium (10 mL/kg) was administered orally 2 h before the scan with a further 3 mL/kg administered immediately prior to scanning. A cross-sectional anatomy atlas was used to identify the structures of the abdominal cavity. Clinically relevant anatomical structures were identified and labelled in the CT images.

Computed tomography in small animals – Basic principles and state of the art applications

Since its clinical introduction, computed tomography (CT) has revolutionized veterinary medicine and is considered to be one of the most valuable tools for the imaging work-up of neurological, oncological and orthopaedic canine and feline patients. In small animals with acute trauma, particularly those involving complex anatomic areas such as the head, spine or pelvis, CT has been established as a standard imaging method. With the increasing availability of radiation therapy in veterinary medicine, CT has also become the principal tool to stage a tumour, assess response, and guide radiation therapy. The increasing availability of helical CT in veterinary medicine has allowed novel techniques such as spiral CT angiography and high-resolution CT. This review provides a brief overview of the historical and technical development of CT and literature reviews of the major clinical CT applications in small animals such as intracranial and extracranial lesions, the spine, the appendicular skeleton, and abdominal and thoracic diseases.

Computed tomography of the vertebral column and coelomic structures in the normal loggerhead sea turtle (Caretta caretta)

The aim of this study was to determine the normal computed tomography (CT) appearance of the vertebral column and coelomic structures of the loggerhead sea turtle (Caretta caretta) and to use three-dimensional (3D) and multiplanar reconstructions to indicate the position of each organ in relation to the vertebrae and carapace. Transverse sections of 1mm thickness were performed in seven clinically healthy and in five dead loggerhead sea turtles using multi-detector CT equipment. A computer workstation was used for multiplanar and 3D reconstructions. Dead turtles were frozen and sectioned in the transverse, dorsal and sagittal planes to compare the anatomical structures' appearance with CT images. Clinically relevant organs including the oesophagus, stomach, trachea, bronchi, lungs, liver, gallbladder, heart, spleen, kidneys and vertebral canal were identified in CT images. Computed tomography provides detailed information on the respiratory system and skeleton; the location of the coelomic structures with respect to the carapace and the vertebrae that is provided in this work will facilitate the use of other ancillary diagnostic techniques such as ultrasound, radiography and biopsy, thereby improving safety of access in surgical procedures.

Normal Anatomical Imaging of the Thorax in Three Dogs: Computed Tomography and Macroscopic Cross Sections with Vascular Injection

The purpose of this study was to provide a new reference for interpretation of the normal anatomy of the canine thorax as imaged using computed tomography (CT). Three mature dogs, all mixed breed males, were used for this study. The dogs were sedated, anaesthetized and maintained in sternal recumbency. CT study from the first to the thirteen thoracic vertebra was performed with a TOSHIBA 600 HQ scanner (third generation equipment). Dogs were killed and vascular-injection technique was performed: red latex and blue latex filled vascular system. Injected dogs were frozen and sectioned with an electric bandsaw, the cuts matched as closely as possible to the CT images. The CT images from this study are intended as a reference for clinical CT imaging studies of the thoracic cavity of the dog and for interpreting lesions of the thorax and associated structures.

Computed tomography and cross-sectional anatomy of the thorax in clinically normal dogs

OBJECTIVE

To provide a detailed anatomic description of the thorax in clinically normal dogs by means of computed tomography.

ANIMALS

4 clinically normal adult German Shepherd Dogs weighing 28 to 37 kg.

PROCEDURE

Dogs were anesthetized and positioned in ventral recumbency for computed tomographic (CT) examination of the thorax. A CT image from the thoracic inlet to the diaphragm was made by use of a third-generation scanner with a slice thickness of 5 mm. Individual images were reviewed by use of soft tissue (window width, 250 Hounsfield units; window level, 35 Hounsfield units) and lung (window width, 1,000 Hounsfield units; window level, -690 Hounsfield units) settings. One dog, weighing 28 kg, was euthanatized, bound on a wooden frame in the same position as used for CT examination, and frozen at -14 degrees C until solid. By use of an electric band saw, the frozen thorax was sectioned at 10-mm-thick intervals. Slab sections were immediately cleaned, photographed, and compared with corresponding CT images.

RESULTS

Anatomic sections were studied, and identified anatomic structures were matched with structures on corresponding CT images. Except for some blood vessels and details of the heart, most of the bony and soft tissue structures of the thorax discerned on anatomic slices could be found on matched CT images.

CONCLUSIONS AND CLINICAL RELEVANCE

Because CT images provide detailed information on most structures of the canine thorax, results of our study could be used as a guide for evaluation of CT images of the thorax of dogs with thoracic diseases.

USE OF RADIOGRAPHY IN COMBINATION WITH COMPUTED TOMOGRAPHY FOR THE ASSESSMENT OF NONCARDIAC THORACIC DISEASE IN THE DOG AND CAT

Computed tomography (CT) of the thorax was performed in 28 dogs and five cats and findings were compared with previous thoracic radiographs. The sample population included all animals that had thoracic radiographs and a CT study within 5 days of each other, where the complete imaging studies were available for review. Thoracic radiographs were considered indeterminate in 31 patients and CT examinations were done to acquire additional information. The presence of additional information from CT relating to presence of pathology, location of pathology, extent of pathology, and involvement of mediastinal structures was recorded. Whether there was a change in diagnosis based on the CT findings was also recorded. In only 4/33 animals (all dogs) did CT fail to provide any new information for the parameters evaluated when compared with survey thoracic radiographs. Additional information about the pathology that was present was gained by CT in 5/5 cats and 21/ 28 dogs. New information on compartmental location of pathology was seen in 4/5 cats and 19/28 dogs. New information on pathology extent was noted in 5/5 cats and 20/28 dogs. Additional information regarding involvement of mediastinal structures was obtained in 2/5 cats and 10/28 dogs. A change in diagnosis was made in 3/5 cats and 13/28 dogs. In conclusion, CT is a valuable tool for evaluating intrathoracic disease. CT provides additional cross-sectional anatomic information that can aid in anatomic localization and evaluation of the extent of the pathology in question.

FAT IS RESPONSIBLE FOR AN INTRAMURAL RADIOLUCENT BAND IN THE FELINE STOMACH WALL

An intramural radiolucent band in the stomach wall can be seen on abdominal radiographs of cats without concurrent clinical gastrointestinal signs. A retrospective study of cats with normal abdominal radiographs and computed tomography (CT) was performed to determine the prevalence of this finding. This gastric radiolucent band was seen in 13 of 37 (35%) radiographs. There was no relationship between age, weight and relative obesity and the presence of this radiolucent band. Using CT, an intramural hypoattenuating layer was detected in the stomach wall of four of 15 (27%) cats. The intramural radiolucent band was visible on the radiographs in all four of those cats. This radiographic and CT finding was histologically determined to be normal fat in the gastric submucosa in one cat cadaver.

Correlation of computed tomographic images with anatomic features of the abdomen of ringed seals (Phoca hispida)

OBJECTIVE

To correlate anatomic features of the abdomen of the ringed seal (Phoca hispida) identified in plastinated cross-sections with images obtained via computed tomography (CT) and thereby establish reference standards for normal abdominal organ size and position in this species.

SAMPLE POPULATION

2 adult male ringed seal cadavers.

PROCEDURE

With the seal in sternal recumbency, CT images of the abdomen were acquired by use of a 4th-generation CT scanner. Image slice thickness was 1 cm, with no interslice gap. After imaging, the abdominal region was sectioned transversely into 4-cm slices, which were plastinated and photographed. Plastinated slices were matched to their corresponding CT images in preparation for anatomic descriptions.

RESULTS

Relevant anatomic features were identified and labeled on both the plastinated tissue slice and corresponding CT image. Normal abdominal organ size and position were assessed, and topographic relationships among organs were ascertained.

CONCLUSIONS AND CLINICAL RELEVANCE

The data obtained provide some reference standards for normal abdominal organ size and position in ringed seals. This information may aid researchers of future physiologic and clinical studies in this species.

Thoracic high-resolution computed tomography in the diagnosis of metastatic carcinoma

Three dogs were presented for investigation of recurrent pyrexia of unknown origin, chronic vomiting and respiratory distress, respectively. One dog was markedly underweight and the other two were cachexic. Physical examination and initial diagnostic tests failed to establish the underlying cause of the presenting signs. Thoracic radiographs were within normal limits for the age of the dog. In each case there was a high index of suspicion for an occult neoplastic process in view of the profound unexplained weight loss present. High-resolution computed tomography (HRCT) of the thorax was performed. The lung fields were divided into three zones for analysis and a novel classification scheme was used to describe the HRCT findings in each zone. Postmortem examination and histopathology confirmed the presence of an infiltrating metastatic carcinoma in all three cases. The HRCT changes correlated closely with the pathological findings. The authors conclude that HRCT of the lung should be considered for pulmonary metastatic screening in the dog and introduce a classification system for HRCT findings, based on terminology used in human medicine.

Evaluation of the feline pancreas using computed tomography and radiolabeled leukocytes

This study was designed to test the feasibility and utility of computed tomography and radiolabeled granulocytes in evaluating the feline pancreas in six normal cats. Autologous granulocytes were labeled with 99mTc-hexamethylpropyleneamine oxime (HMPAO) and injected into each cat. Whole body scintigraphic images were acquired at 1, 5, 15, and 30 minutes, and 1, 2, and 4 hours following injection. The following day, each cat was anesthetized and computed tomographic images of the abdomen were acquired both pre- and post-contrast. Following CT, a surgical pancreatic biopsy was collected. Feline granulocytes were successfully labeled with 99mTc-HMPAO with a labeling efficiency of 15-42% (average of 27%). An average of 5.42 x 10(7) cells in a 2 mL volume were injected into each cat. Less than 1 minute was required to acquire 500,000 count images. Granulocytes distributed predominantly to the lung, spleen and liver in order of decreasing activity. Only background activity was identified in the region of the pancreas. The pancreas was easily identified on CT images of the abdomen. The pancreas was hypoattenuating relative to both the spleen and liver. The pancreas enhanced with the administration of contrast medium, peaking immediately, then gradually clearing over the 30-minute test period. Following contrast medium administration the pancreas remained hypoattenuating relative to the spleen. All biopsies confirmed the absence of pancreatic inflammation in the study cats and no adverse effects were recognized as a result of pancreatic biopsy. Both computed tomography and radiolabeled granulocytes appear to hold promise as imaging procedures for the detection of feline pancreatitis. We predict that these described normal parameters may be altered in the face of inflammation, facilitating detection of feline pancreatitis. Data from cases of suspect feline pancreatitis are needed to evaluate these methods for clinical utility.

Use of computed tomography in the diseased feline thorax

Computed tomography (CT) scanning of the thorax is gaining more attention in veterinary medicine as therapeutic possibilities increase. Plain and contrast-enhanced CT images of the thorax of five referred cats with signs of respiratory disease were evaluated using soft tissue (pleural) and lung windows. The common CT pattern in all cats was involvement of the lung lobes, either as a homogeneous or heterogeneous single lobe hyperdensity. It involved the main bronchus, invaded the cranial or caudal mediastinum, and crossed the border to the opposite lung. Right lung atelectasis and mediastinal shift caused left lung overinflation. Bronchial lymph node enlargement was found unilaterally or bilaterally. CT-guided percutaneous fine needle aspiration biopsy of the lobar lung lesion was performed in four cats; in three cases it revealed carcinoma and in one inflammation, although the cat with suspected inflammation was subsequently found to have a carcinoma on lung lobectomy. Histopathology confirmed lung metastasis in one case and bronchial adenocarcinoma in four cases. A protocol for systematic examination of thoracic CT images is proposed.

The influence of stomach volume on the liver topography in cats

The aim of this study has been to describe the effect of varying degrees of fullness of the stomach on liver topography in cats by means of the sectional anatomy of the abdominal cavity. Twenty-four adult healthy cats of both sexes and of different ages were used. The cats were divided into two groups. The first group had empty stomachs and the second group had filled stomachs. Eight cats were dissected. The remaining cats were frozen at - 20 degrees C, eight of these were then sectioned paramedially and the other eight were sectioned transversely. In the dissection and sections, it was observed that the liver shifted considerably to the right and craniodorsally in cats with full stomachs. In this article, the topographical anatomy of the liver according to varying stomach volumes is described in a manner that is useful to veterinary surgeons and clinicians. The sectional findings obtained from the paramedial and transverse sections provide information for computed tomography and magnetic resonance imaging.

Analysis of the anatomic changes in the thoracic cage after a lung resection using magnetic resonance imaging

The thoracic cage after a lung resection is filled by the remaining lobes, the elevated diaphragm, the diminished thoracic cage, and by mediastinal shifting. The changes in the thorax after a lung resection were quantified using magnetic resonance imaging. The study group consisted of 39 patients who had undergone a lobectomy, four who had undergone a pneumonectomy, and 14 controls. The left ventricular angle, ascending aortic angle, mediastinal shift, longitudinal length of the thoracic cage, the distance between the thoracic apex and the level of the aortic valve, and diaphragmatic elevation were all measured. After a right lower lobectomy, the mediastinum shifted more rightward than after a right upper lobectomy. The diaphragm became more greatly elevated after a right upper lobectomy than after a right lower lobectomy. When a chest wall resection was added to a right upper lobectomy, the mediastinal anatomical changes decreased. After a left upper lobectomy, the degree of mediastinal shifting was greater than after a left lower lobectomy. A left upper lobectomy shifted the mediastinum at the level of the right atrium. This method is easily reproducible and was found to be effective for quantifying the changes in the thorax after a lung resection.

The effect of stomach volume on the colon topography in cats

The aim of this study has been to describe the effect of varying degrees of fullness of the stomach on the topography of colon in cats by means of the sectional anatomy of the abdominal cavity. Twenty-four adult healthy cats of both sexes and of different ages were used. The cats were divided into two groups, of which group one had empty stomachs and the second filled stomachs. Eight cats were dissected. The remaining cats were frozen at -20 degrees C, the eight of which were sectioned paramedially and the other eight transversely. The ascending colon started at the level of the fifth lumbar vertebra, and the cranial boundary of the transverse colon was at the level of the second lumbar vertebra in cats with empty stomachs. The ascending colon started at the level of the sixth lumbar vertebra in cats with full stomachs, while the cranial boundary of the transverse colon was at the level of the fourth lumbar vertebra and had lost relationship to the right kidney resting directly on the vertebral column. In both groups, the descending colon was located in the left abdominal cavity up to the level of the sixth lumbar vertebra, at which point it curved medially and ran cranial to the seventh lumbar vertebra in the median plane. Results from this study are to throw light on computed tomography and magnetic resonance imaging.

Magnetic resonance imaging of the normal feline abdomen: an anatomic reference

Magnetic resonance images of two adult domestic short-haired cats were obtained with a whole body scanner. Images of the abdomen were compared with cross-sectional anatomy cadaver specimens from the same two cats. Anatomic structures were first identified on the cadaver specimens with the aid of anatomy texts and references and were then identified and labeled on the magnetic resonance images. Results from this project provide an atlas of normal cross-sectional MRI anatomy of the feline abdomen.