Application and indications of magnetic resonance imaging and computed tomography of the equine head

Sphenoid sinus in the Holstein cow: A sectional and 3D reconstructive anatomical study

Cattle disorders affecting the sphenoid sinus are underreported, likely due to difficulties in imaging and lacking topographic knowledge. This study aimed to provide a detailed description of the normal anatomical and morphometric features of the cattle sphenoid sinus. Twelve healthy adult Holstein cow heads were used, and the sinus was examined using CT, anatomical sectioning and 3D modelling. The sinus was bilaterally detected in all animals but exhibited structural asymmetry and significant interindividual differences in morphological characteristics. Three parts of the sinus were defined, namely the rostral, median and alar parts, which conform to the morphological structure of the sphenoid bone. The rostral part was bilateral in shape and located on the orbit wall of the presphenoid bone in all animals. The median part, which pneumatized the body of the sphenoid bone, was observed bilaterally in seven animals, while the alar part, which pneumatized the wing of the sphenoid bone, was formed bilaterally in four animals. The sinus volume and surface area were 11 ± 8 cm3 and 49 ± 30 cm2 , respectively. These findings may aid in the diagnosis of cattle sphenoid sinus disorders and contribute to the knowledge of regional anatomy for radiologists and clinicians.

An application of the density standard and scaled-pixel-counting protocol to assess the radiodensity of equine incisor teeth affected by resorption and hypercementosis: preliminary advancement in dental radiography

BACKGROUND

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) syndrome is a dental disease where the radiographic signs may be quantified using radiographic texture features. This study aimed to implement the scaled-pixel-counting protocol to quantify and compare the image structure of teeth and the density standard in order to improve the identification of the radiographic signs of tooth resorption and hypercementosis using the EOTRH syndrome model.

METHODS AND RESULTS

A detailed examination of the oral cavity was performed in 80 horses and maxillary incisor teeth were evaluated radiographically, including an assessment of the density standard. On each of the radiographs, pixel brightness (PB) was extracted for each of the ten steps of the density standard (S1-S10). Then, each evaluated incisor tooth was assigned to one of 0-3 EOTRH grade-related groups and annotated using region of interest (ROI). For each ROI, the number of pixels (NP) from each range was calculated. The linear relation between an original X-ray beam attenuation and PB was confirmed for the density standard. The NP values increased with the number of steps of the density standard as well as with EOTRH degrees. Similar accuracy of the EOTRH grade differentiation was noted for data pairs EOTRH 0-3 and EOTRH 0-1, allowing for the differentiation of both late and early radiographic signs of EOTRH.

CONCLUSION

The scaled-pixel-counting protocol based on the use of density standard has been successfully implemented for the differentiation of radiographic signs of EOTRH degrees.

Trephination versus Minimally Invasive Transnasal Approaches for the Diagnosis and Treatment of Sinus Disease in Horses

This retrospective case series aims to highlight the advantages and disadvantages of different treatment options for sinus disease in horses, with a special focus on surgical approaches. The medical records of 25 horses with sinusitis which presented to the equine hospital, Vetmeduni Vienna, between August 2020 and January 2022 were analysed. In 11 cases, conservative treatment by the transnasal endoscopic lavage of the affected sinuses through the sinonasal channel or through a developed, pre-existing sinonasal fistula was performed. In the remaining 14 cases, openings into the sinus for subsequent lavage were surgically created either via classical trephination/bone flaps (8) or by transnasal endoscopically guided minimally invasive approaches (8). In some cases (2), a combination of classical extra-nasal and minimally invasive transnasal approaches was required. The minimally invasive techniques used were comprised of laser surgery (3), electrosurgery (3) and balloon sinoplasty (2). The sinusitis and underlying diseases were successfully treated in all of the horses until hospital discharge. Long-term follow-up could be obtained only from a small number of patients due to the temporal proximity (the study began two years ago) to their initial discharge from the hospital, but they showed the continuous resolution of clinical signs in all cases in which follow up data were available. The results of this case series indicate that if surgical intervention is required, minimally invasive techniques appear to be a promising and potentially cheaper alternative to classical extra-nasal approaches for the treatment of sinus disease in selected cases. In the future, the use of these techniques should be considered more commonly with the broader availability of improved endoscopes and instruments. Additionally, by using small-diameter endoscopes, the need for any surgical intervention might be significantly reduced in many cases.

Use of a novel helical fan beam imaging system for computed tomography of the head and neck in sedated standing horses: 120 cases (2019–2020)

OBJECTIVE

To evaluate the diagnostic capabilities of a novel helical fan beam CT system used for imaging of horses with clinical problems of the head and neck.

ANIMALS

120 horses.

PROCEDURES

Medical records were reviewed of horses presented for CT of the head or neck at 2 university hospitals. The following data were recorded: age, sex, breed, presenting complaint, sedation used for imaging, scanning time, procedure time, other diagnostic imaging methods performed, imaging diagnosis, clinical diagnosis, and complications during imaging.

RESULTS

Quarter Horses and Warmbloods were the most common breeds, and the most common complaint was nasal discharge. The head (101/120 [84%] horses) was scanned most frequently, and the most common diagnoses were primary dental disease and a space-occupying lesion of the paranasal sinuses. Nuchal bursitis was the most common imaging diagnosis in the neck region. Procedure time ranged from 20 to 45 minutes with a scanning time of 30 to 40 seconds. No complications with horse sedation occurred, and horses tolerated scanning well. An imaging diagnosis was more frequently achieved with CT (109/120 [91%] horses) than with planar digital radiography (23/61 [38%] horses).

CLINICAL RELEVANCE

The helical fan beam CT system had fast scanning times and could be used safely for routine imaging of the teeth and sinuses in horses. The caudal extent of scanning in the neck region was limited by the shape of the horse’s neck and thorax.

Correlation between computed tomography, magnetic resonance imaging and cross-sectional anatomy of the head of the guinea pig (Cavia porcellus, Linnaeus 1758)

The current work aimed to study the anatomical features of the guinea pig's head by two medical imaging techniques: computed tomography (CT) and magnetic resonance imaging (MRI), and their correlation with the anatomical cross-sectional images. Six adult healthy guinea pigs were used in the present study. Two heads were imaged by CT scanner and then by MRI. The examined heads were cut sagittally and transversely, and two skulls were macerated. The anatomical features were identified on the anatomical sections and compared with the tomographic and MRI images obtained. Data were presented as three-dimensional reconstructed images of the head. In addition, representative combinations of the sagittal and transverse anatomical sections and the corresponding CT scans and MRI images were also presented. Reconstruction of CT images enabled the visualization of different bony structures and airways of the guinea pig head. In addition, skull bones were easily visualized on CT scans, while different parts of the brain were identified on MRI images. Air cavities could be identified by their different contrast on the CT scans and their low intensity on MRI images. The study showed that guinea pig had poorly developed paranasal sinus system represented by rostral and caudal maxillary sinuses. On the contrary, the guinea pig had two tympanic bullae: a small dorsal and a large ventral bulla. In conclusion, this study provides one of the first investigations that uses the multislice CT scans and MRI to study the guinea pig's head and their correlation with the corresponding anatomical sections.

Use of cone-beam computed tomography for advanced imaging of the equine patient

Access to volumetric imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), has increased over the past decade and has revolutionised the way clinicians evaluate equine anatomy. More recent advancements have resulted in the development of multiple commercially available cone-beam CT (CBCT) scanners for equine use. CBCT scanners modify the traditional fan-shaped beam of ionising radiation into a three-dimensional pyramidal- or cone-shaped beam of radiation. This modification enables the scanner to acquire sufficient data to create diagnostic images of a region of interest after a single rotation of the gantry. The rapid acquisition of data and divergent X-ray beam causes some artifacts to be more prominent on CBCT images-as well as the unique cone-beam artifact-resulting in decreased contrast resolution. While the use of CT for evaluation of the equine musculoskeletal anatomy is not new, there is a paucity of literature and scientific studies on the capabilities of CBCT for equine imaging. CBCT units do not require a specialised table for imaging and in some cases are portable for imaging in the standing or anaesthetised patient. This review article summarises the basic physics of CT technology, including how CBCT imaging differs, and provides objective information about the strengths and limitations of this modality. Finally, potential future applications and techniques for imaging with CT which will need to be explored in order to fully consider the capabilities of CT imaging in the horse are discussed.

Magnetic resonance dacryocystography in the horse: A feasibility study

OBJECTIVE

To provide a comprehensive anatomical description of the normal equine nasolacrimal duct using magnetic resonance imaging, and to develop a practical protocol for performing magnetic resonance dacryocystography (MRD) in horses.

ANIMAL STUDIED

The heads of ten fresh horse cadavers with no history of sinonasal or ophthalmologic disorders were used for this study.

PROCEDURE

An MRD technique was developed in this study, which consisted of two parts. In the first part, olive oil and gadolinium were compared as contrast medium, using five horses. Two concentrations of gadolinium were used: 0.25 mmol/mL and 0.5 mmol/mL. In the second part, the influence of different head recumbencies using olive oil as the sole contrast medium was studied in the remaining five horses.

RESULTS

Injection with olive oil resulted in better distention and a complete filling of the nasolacrimal duct (ND) in all horses. Injection of 0.25 mmol/mL of gadolinium resulted in incomplete filling of the ND, whereas injection of 0.5 mmol/mL of gadolinium resulted in slightly better filling of the duct. The nondependent duct showed better distention compared to the dependent duct when scanning in lateral recumbency. No differences were observed between ducts in a dorsal recumbency. The degree of distention in dorsal recumbency was slightly less than the degree of distention observed in the nondependent ND in lateral recumbency.

CONCLUSIONS

Magnetic resonance dacryocystography is a suitable technique for evaluating the nasolacrimal duct and can be performed during a normal magnetic resonance examination.