Improved visualization of the lumbar spine nerve roots in dogs using water excitation (ProSet) as opposed to short tau inversion recovery: A retrospective study of two fat suppression MRI sequences.

Magnetic resonance imaging fat suppression techniques are commonly used for diagnosis of canine spinal disease, however, studies comparing different techniques are currently lacking. This retrospective, methods comparison study aimed to evaluate water excitation and STIR MRI pulse sequences for visualization of canine lumbar spinal nerve roots. For inclusion, all dogs had to have dorsal planar MRI studies of the lumbar spine using both sequences. Visual grading analysis was used for scoring the following five criteria: degree of fat suppression; nerve root visualization; subjective tissue contrast; presence of noise; and overall better image quality. Scores were independently recorded by three board-certified veterinary radiologists on two separate occasions, 3-6 weeks apart. A total of 90 dogs were sampled. A two-tailed t-test showed that there were significant differences in all scored parameters (P < 0.00001), with the exception of noise (P = 0.47343), and that the water excitation sequence scored higher in all cases excluding noise. A Gwets AC kappa for intraobserver and interobserver reliability showed "almost perfect" agreement for the nerve roots in both tests (intra: k = 0.88; inter: k = 0.90). Intraobserver agreement was "substantial" for the degree of fat suppression (k = 0.68), subjective tissue contrast (k = 0.75), and overall better image quality (k = 0.76) and it was "fair" for the noise (k = 0.46). Interobserver agreement was "moderate" for the degree of fat suppression (k = 0.53), subjective tissue contrast (k = 0.63), and overall better image quality (k = 0.66) and "slight" for noise (k = 0.25). These findings supported using the water excitation pulse sequence for fat-suppressed MRI of canine lumbar spinal nerve roots.

Comparison of T1wFLAIR and T1wTSE sequences in imaging the brain of small animals using high-field MRI.

BACKGROUND: T1w turbo spin echo (TSE) represents a fundamental sequence in magnetic resonance imaging (MRI) protocols investigating the brain. Recent human literature has reported T1w Fluid Attenuated Inversion Recovery's (FLAIR's), superiority to T1wTSE in relation to tissue contrast for grey-to-white matter (GM-WM) and lesion-to-WM, although conflicting results are reported concerning lesion detection.To the author's knowledge, T1wFLAIR has not been investigated in veterinary medicine. The aim of this prospective study was to determine quantitatively and qualitatively which sequence provides better overall better image quality both pre- and post-gadolinium. RESULTS: Twenty-eight animals underwent MRI of the brain with T1wTSE and T1wFLAIR sequences performed with equivalent mean acquisition times. Quantitative assessment of the sequences was undertaken using contrast-to-noise (CNR) and signal-to-noise (SNR) ratios from predefined locations. T1wFLAIR provided a better CNR compared to T1wTSE, while T1wTSE provided better SNR due to the higher noise levels of T1wFLAIR images. Qualitative assessment of the sequences was performed using Visual Grading Analysis Scoring (VGAS) for a number of criteria by three observers on two separate occasions. T1wFLAIR performed better for cerebrospinal fluid (CSF) suppression, white-to-grey matter (WM-GM) and white matter-to-CSF (WM-to-CSF) definition in both pre- and post-contrast images whereas the T1wTSE sequence was less affected by noise levels. The individual parameter for overall image quality found no significant difference between the two sequences. However, the composite VGAS favored T1wFLAIR as the preferred sequence. Although case numbers were insufficient for statistical analysis, comparison of the sequences indicates that lesion definition and margination was better in T1wFLAIR pre-contrast images, however post-contrast lesion detection was almost equivalent between sequences with slightly better margination in the T1wTSE sequence. CONCLUSIONS: T1wFLAIR provides better CNR with better WM-GM and WM-CSF definition both pre- and post-contrast compared to T1wTSE albeit with a higher degree of noise; this was confirmed both quantitatively and qualitatively. Our results also suggest that T1wFLAIR is better for lesion detection and margination pre-contrast administration and sequences are relatively equivocal post-gadolinium administration although further research is required to determine the benefit that inversion recovery sequences make when investigating brain lesions in small animal MRI.

DEVELOPING A TECHNIQUE FOR ULTRASOUND-GUIDED INJECTION OF THE ADULT CANINE HIP.

An accurate method for guiding injections into the canine hip would facilitate diagnostic localization of lameness and targeted treatments. Ultrasound-guided hip injections are commonly used in humans and large animals. Aims of this prospective study were to describe ultrasound (US) anatomy of the adult canine hip and determine the feasibility and accuracy of intra-articular placement of injectate using US-guidance. Seven adult dogs were used to describe US anatomy, five dog cadavers were used to assess the feasibility of the injection technique and 11 dog cadavers were used to assess accuracy of injections. For the accuracy test, 22 joints were injected with iodinated contrast medium by three operators with different experience. With dogs in lateral recumbency, the hyperechoic femoral head surface was identified by following the femoral neck from the greater trochanter or the acetabular rim was localized by following caudally the ilium from the iliac wing. An anechoic gap between the femoral head and acetabular surface represented the joint. The capsule was visible as a triangular echoic structure and the femoral head articular cartilage appeared as an anechoic band. The needle was inserted axial to the greater trochanter and directed in a dorsolateral-ventromedial direction toward the joint space and then pushed through the capsule. Based on postinjection radiography, accuracy was 81.8% at first attempt and 100% at second attempt. This study indicated that US-guided injection is a feasible and accurate technique for injecting the adult canine hip. Future studies in live dogs are needed to assess safety and efficacy.

Hypertensive nonobstructive hydrocephalus as main magnetic resonance imaging feature in a dog with disseminated choroid plexus carcinomatosis.

Obstructive or nonobstructive hypertensive hydrocephalus is reported in choroid plexus tumors. Choroid plexus tumors typically present as T2-weighted hyperintense intraventricular masses with occasional cerebrospinal fluid-drop metastasis. Acquired neoplastic nonobstructive hydrocephalus without visible mass lesion in magnetic resonance imaging is not reported in dogs. A 4.5-year-old Rhodesian Ridgeback presented with reduced mental status, unilaterally absent pupillary light reflex, and neck pain. Magnetic resonance imaging revealed a nonobstructive hydrocephalus and widened lumbar subarachnoid space with no evidence of a primary mass lesion. Postmortem examination confirmed a disseminated choroid plexus tumor affecting the ependyma and choroid plexi of all ventricles and the cerebral and lumbar subarachnoid space. Disseminated choroid plexus carcinomatosis should be considered as a possible cause of hypertensive hydrocephalus even in absence of a primary mass.

Sonoelastographic Features of the Patellar Ligament in Clinically Normal Dogs.

OBJECTIVE: This article describes the sonoelastographic features of the patellar ligament of sound dogs and tests feasibility, reproducibility and repeatability. METHODS: Clinically healthy medium-to-large breed dogs were enrolled. Sonoelastographic images of the patellar ligaments were obtained in lateral recumbency with the stifle flexed by an experienced operator and by a senior veterinary student. The elasticity colour map included red (soft), green (intermediate) and blue (hard). Tissue elasticity was measured by calculating the percentage of softness with dedicated software. Categorical, qualitative data analysis was performed using a weighted kappa statistic for repeatability and reproducibility. A categorical qualitative assessment was performed based on a grading scale of 1 to 5 (soft, mostly soft, intermediate, mostly hard and hard). RESULTS: Fourteen clinically normal dogs were considered. A total of 28 patellar ligaments were examined. Overall, 25 of the patellar ligaments were graded as soft or mostly soft and the remaining 3 as intermediate. Repeatability was 86.2%, with a weighted kappa of 0.64 (good), for the well-trained sonographer and 83.3%, with a weighted kappa of 0.53 (moderate), for the senior student. Reproducibility was 86.2%, with a weighed kappa of 0.65 (good). CLINICAL SIGNIFICANCE: Sonoelastography of the canine patellar ligament is a feasible and reproducible technique. Patellar ligaments in clinically normal dogs showed highly elastic biomechanical properties.

Periaortic lymphoma in a cat.

CASE SUMMARY: A 14-year-old neutered male Siamese cat was presented with a 3 month history of lethargy, inappetence, dehydration, hindlimb ataxia and intermittent proprioceptive deficits in the hindlimbs. Physical examination revealed low body condition score (1.75/5), pallor and bilateral basilar grade II/VI systolic heart murmur. Neurological examination revealed hindlimb ataxia, severe atrophy of the hindlimb musculature, intermittent hindlimb proprioceptive deficits and normoreflexia. Clinicopathological investigations revealed non-regenerative anaemia (haematocrit 0.17 l/l; reference interval [RI] 0.24-0.45 l/l) and increased feline pancreatic lipase concentration (Spec fPL test [IDEXX] 8.3 µg/l; RI 0.1-3.5 µg/l). Feline leukaemia virus antigen and feline immunodeficiency virus antibody tests were negative. Thoracic and abdominal imaging revealed a soft tissue structure in the area of the thoracoabdominal aorta. CT confirmed a periaortic contrast-enhancing mass extending from the level of T9-L2, with associated intervertebral infiltration at the level of T11-T12. Post-mortem examination confirmed the presence of a solid, white, multinodular, well-demarcated mass encircling the aorta extending from T9-L2. Based on histopathology and immunohistochemistry, a diagnosis of B-cell lymphoma was made. Lymphoma was also identified histopathologically within the kidneys and spleen. Evidence of mild Wallerian degeneration was present within the spinal cord, indicating compression at the level of the periaortic mass. RELEVANCE AND NOVEL INFORMATION: To our knowledge, this is the first report of periaortic lymphoma in the cat. Although periaortic tumours are exceptionally rare in veterinary medicine, lymphoma should be considered as a differential in cats.

Comparison of two ultrasound-guided injection techniques targeting the sacroiliac joint region in equine cadavers.

OBJECTIVES: To compare the accuracy and distribution of injectate for cranial (CR) and caudomedial (CM) ultrasound-guided injections of equine sacroiliac joints. METHODS: Both sacroiliac joints from 10 lumbosacropelvic specimens were injected using cranial parasagittal (CR; curved 18 gauge, 25 cm spinal needles) and caudomedial (CM; straight 18 gauge, 15 cm spinal needles) ultrasound-guided approaches. Injectate consisted of 4 ml iodinated contrast and 2 ml methylene blue. Computed tomographical (CT) scans were performed before and after injections. Time for needle guidance and repositioning attempts were recorded. The CT sequences were analysed for accuracy and distribution of contrast. RESULTS: Intra-articular contrast was detected in sacroiliac joints following 15/40 injections. The CR and CM approaches deposited injectate ≤2 cm from sacroiliac joint margins following 17/20 and 20/20 injections, respectively. Median distance of closest contrast to the sacroiliac joint was 0.4 cm (interquartile range [IQR]: 1.5 cm) for CR approaches and 0.6 cm (IQR: 0.95 cm) for CM approaches. Cranial injections resulted in injectate contacting lumbosacral intertransverse joints 15/20 times. Caudomedial injections were perivascular 16/20 times. LIMITATIONS: Safety and efficacy could not be established. CLINICAL RELEVANCE: Cranial and CM ultrasound-guided injections targeting sacroiliac joints were very accurate for periarticular injection, but accuracy was poor for intra-articular injection. Injectate was frequently found in contact with interosseous sacroiliac ligaments, as well as neurovascular and synovial structures in close vicinity of sacroiliac joints.