Assessment of Magnetic Resonance Imaging Artefacts Caused by Equine Anaesthesia Equipment: A Cadaver Study.

Acquisition of magnetic resonance images of the equine limb is still sometimes conducted under general anaesthesia. Despite low-field systems allow the use of standard anaesthetic equipment, possible interferences of the extensive electronic componentry of advanced anaesthetic machines on image quality is unknown. This prospective, blinded, cadaver study investigated the effects of seven standardised conditions (Tafonius positioned as in clinical cases, Tafonius on the boundaries of the controlled area, anaesthetic monitoring only, Mallard anaesthetic machine, Bird ventilator, complete electronic silence in the room (negative control), source of electronic interference [positive control]) on image quality through the acquisition of 78 sequences using a 0.31T equine MRI scanner. Images were graded with a 4-point scoring system, where 1 denoted absence of artefacts and 4 major artefacts requiring repetition in a clinical setting. A lack of STIR fat suppression was commonly reported (16/26). Ordinal logistic regression showed no statistically significant differences in image quality between the negative control and either the non-Tafonius or the Tafonius groups (P = 0.535 and P = 0.881, respectively), and with the use of Tafonius compared to the other anaesthetic machines (P = 0.578). The only statistically significant differences in scores were observed between the positive control and the non-Tafonius (P = 0.006) and the Tafonius groups (P = 0.017). Our findings suggest that anaesthetic machines and monitoring do not appear to affect MRI scan quality and support the use of Tafonius during acquisition of images with a 0.31T MRI system in a clinical context.

Equine odontogenic tumors: Clinical presentation, CT findings, and outcome in 11 horses.

Odontogenic tumors present as locally invasive, slow growing, firm swellings on the face. They are rare in all species and are characterized histologically by the degree of differentiation and dental tissue of origin. Radiographic appearance is not pathognomonic for these lesions. Computed tomographic (CT) examination allows exact determination of tumor extension and aggressiveness. The objectives of this retrospective, case series study were to describe the clinical presentation, CT characteristics, and outcome in horses with histologically confirmed odontogenic tumors, and to identify imaging features suggestive of individual types of tumors. Four ameloblastomas, two ameloblastic carcinomas, three ameloblastic fibromas, and two complex odontomas were included. All but one complex odontoma presented as a single mass. All tumors were associated with maxillary or mandibular bone expansion, alveolar and cortical bone lysis, and cortical bone thinning. The majority also had cortical bone thickening and periosteal proliferation. All tumors contained some degree of mineral attenuation, although only the complex odontomas contained enamel attenuation allowing differentiation from other types of odontogenic tumors in this study. Ameloblastomas were found to have variable CT characteristics likely due to the sub-groups of ameloblastomas. Both ameloblastic carcinomas contained a mixture of mineralized and soft tissue attenuating material whereas ameloblastic fibromas were mainly composed of soft tissue attenuating material. Computed tomographic characteristics of odontogenic tumors generally indicate that they are expansile, aggressive tumors and can occur in a wide range of ages. Further investigation is needed to elucidate differences between each type of equine odontogenic tumor.

NEUROLOGIC AND COMPUTED TOMOGRAPHY FINDINGS IN SEA TURTLES WITH HISTORY OF TRAUMATIC INJURY.

Boat strikes have been widely documented as a major cause of anthropogenic trauma and mortality in sea turtles. Axial trauma in these species involves the head and/or carapace and may cause severe damage to the nervous and pulmonary systems. The aims of this study were to develop an updated protocol for neurologic examinations in sea turtles, to describe computed tomography (CT) findings in sea turtles with sustained trauma, and to associate CT findings with neurologic status in sea turtles with and without traumatic injury. Ten sea turtles were examined, six green (Chelonia mydas) and four loggerhead (Caretta caretta) turtles: seven underwent neurologic and CT examinations, two had CT examinations only, and one had a neurologic examination only. The updated neurologic examination protocol was considered useful in differentiating normal from abnormal neurologic status, however some of these tests remain unreliable in sea turtles. Sea turtles with no history of trauma were found to have normal carapace shape, vertebral column, and neurologic status. Sea turtles with history of traumatic injury (more than 10 years prior to examination) had findings dependent on trauma site. Those with head trauma had variable presentations dependent on location of injury; while those with carapace trauma had varying degrees of kyphosis, lordosis, and scoliosis of the carapace, vertebral fractures, and paraparesis. Kyphosis of the carapace was associated with vertebral fractures detected on CT; however, the severity of vertebral abnormalities was not associated with the severity of neurologic deficits. These findings suggest that a combination of neurologic and CT examination may be beneficial in determining clinical significance of carapace deformation and associated neurologic deficits in sea turtles with traumatic injury.

Use of high-field and low-field magnetic resonance imaging to describe the anatomy of the proximal portion of the tarsal region of nonlame horses.

OBJECTIVE To use high-field and low-field MRI to describe the anatomy of the proximal portion of the tarsal region (proximal tarsal region) of nonlame horses. SAMPLE 25 cadaveric equine tarsi. PROCEDURES The proximal portion of 1 tarsus from each of 25 nonlame horses with no history of tarsal lameness underwent high-field (1.5-T) and low-field (0.27-T) MRI. Resulting images were used to subjectively describe the anatomy of that region and obtain measurements of the collateral ligaments of the tarsocrural joint. RESULTS Long and short components of the lateral and medial collateral ligaments of the tarsocrural joint were identified. Various bundles of the short collateral ligaments were difficult to delineate on low-field images. Ligaments typically had low signal intensity in all sequences; however, multiple areas of increased signal intensity were identified at specific locations in most tarsi. This signal intensity was attributed to focal magic angle effect associated with orientation of collagen fibers within the ligaments at those locations. Subchondral bone of the distal aspect of the tibia was uniform in thickness, whereas that of the medial trochlear ridge of the talus was generally thicker than that of the lateral trochlear ridge. In most tarsi, subchondral bone of the talocalcaneal joint decreased in thickness from proximal to distal. CONCLUSIONS AND CLINICAL RELEVANCE Results generated in this study can be used as a reference for interpretation of MRI images of the proximal tarsal region in horses.

IMAGING DIAGNOSIS-IDIOPATHIC HYOID MALFORMATION IN AN 8-YEAR-OLD WELSH SECTION D HORSE.

An 8-year-old gelding was evaluated for intermittent dorsal displacement of the soft palate (DDSP) at exercise. Standing laterolateral radiographs demonstrated an abnormal crossed appearance of the stylohyoid bones. Computed tomography (CT) confirmed abnormal positioning of the left stylohyoid bone and articulations with both the left thyrohyoid and ceratohyoid bones. Surgical treatment consisted of combined left ceratohyoidectomy and thyrohyoidectomy. Postoperatively the patient's presenting complaint resolved completely, with the horse returning to full work. Standing laterolateral radiographs should be obtained prior to laryngeal or hyoid surgery to rule out hyoid anomalies, which could result in surgical failure or subsequent hyoid fracture.

IMAGING DIAGNOSIS - UNILATERAL TRIGEMINAL NEURITIS MIMICKING PERIPHERAL NERVE SHEATH TUMOR IN A HORSE.

A 16-year old Warmblood gelding presented with a nonhealing corneal ulcer and absent corneal sensation in the left eye. A lesion affecting the maxillary and ophthalmic branches of the left trigeminal nerve was suspected. Magnetic resonance (MR) imaging identified marked thickening of the ophthalmic and maxillary branches of the left trigeminal nerve. The nerve was iso- to hypointense on T1-weighted and T2-weighted images with heterogeneous enhancement. A peripheral nerve sheath tumor was suspected, however granulomatous neuritis was histopathologically confirmed. These inflammatory changes can result in severe nerve enlargement and should be considered with MR findings suggestive of peripheral nerve sheath tumor.

Magnetic resonance imaging characteristics of equine head disorders: 84 cases (2000-2013).

The equine head is an anatomically complex area, therefore advanced tomographic imaging techniques, such as computed tomography or magnetic resonance imaging (MRI), are often required for diagnosis and treatment planning. The purpose of this multicenter retrospective study was to describe MRI characteristics for a large sample of horses with head disorders. Horses imaged over a period of 13 years were recruited. Eighty-four horses met the inclusion criteria, having neurological (n = 65), sinonasal (n = 14), and soft tissue (n = 5) disorders. Magnetic resonance imaging accurately depicted the anatomy and allowed identification of the primary lesion and associated changes. There were good correlations between MRI findings and intraoperative or postmortem results. Magnetic resonance imaging showed the exact localization of the lesions, their size, and relation to surrounding structures. However, in the neurological group, there were 45 horses with no MRI abnormalities, 29 of which had a history of recurrent seizures, related to cryptogenic epilepsy. Magnetic resonance imaging was otherwise a valuable diagnostic tool, and can be used for studying a broad range of head disorders using either low-field or high-field magnets.

Imaging diagnosis--split cord malformation.

The features of a calf with a split cord malformation are described. Clinically, there was severe cervicothoracic kyphoscoliosis and an interscapular dermal sinus associated with cerebrospinal fluid drainage. Using magnetic resonance imaging, complete duplication of the spinal cord at the cervical intumescence was detected. There was associated syringohydromyelia, multiple cervicothoracic vertebral malformations resulting in kyphoscoliosis and rachischisis, herniation of the cerebellar vermis, meningoencephalocele, and calvarial defects.

Scintigraphic assessment of the metacarpophalangeal and metatarsophalangeal joints of horses with joint pain.

Our aims were to evaluate the pattern of radiopharmaceutical uptake in horses with lameness related to the metacarpophalangeal and/or metatarsophalangeal joint and compare the results with similar information from sound horses. It was hypothesized bthat there would be a difference in radiopharmaceutical uptake between the lame and contralateral limb in unilaterally lame horses and that there would be a difference between lame and sound horses. Nuclear scintigraphic images of 43 horses with forelimb lameness and 30 horses with hindlimb lameness were evaluated. In all horses lameness was improved by intraarticular analgesia of the joint, or by perineural analgesia of the palmar/plantar (at the junction of the proximal 3/4 and the distal 1/4 of the metacarpal/metatarsal regions) and palmar/plantar metacarpal/metatarsal nerves. All images were assessed subjectively and a quantitative image analysis was performed by drawing a vertical line profile through the center of each joint in the lateral images and using region of interest analysis in both lateral and dorsal/plantar images. Ratios of radiopharmaceutical uptake were compared for each region between lame and contralateral limbs in unilaterally lame horses and between lame and control horses. There was a significant difference in the ratio of radiopharmaceutical uptake in the proximal aspect of the proximal phalanx between lame and nonlame forelimbs in unilaterally lame horses and in both lame and contralateral limbs of lame horses compared with control horses for the regions of the distal aspect of the third metacarpal/metatarsal bone and the proximal sesamoid bones. However, the profile analysis was of limited clinical value.