Most commonly used sequences and clinical protocols for brain and spine magnetic resonance imaging allowing better identification of pathological changes in dogs

Evaluation of the Canine Intervertebral Disc Structure in Turbo Spin Echo-T2 and Fast Field Echo-T1 Sequences in Magnetic Resonance Imaging

In the current study the hypothesis should be proven that T1 weighted Fast Field Echo (FFE) sequence is a useful method to visualize intervertebral disc degeneration, respectively changes of the expected disc appearance. Medical records of 208 dogs were reviewed and images of 781 intervertebral discs were evaluated by two blinded examiners using a modified Pfirrmann classification system in two MRI sequences: FFE and Turbo-Spin-Echo T2-weighted sequence (T2W). The patients were allocated to three categories based on body conformation: (1) brachycephalic and chondrodystrophic breeds, (2) non-chondrodystrophic and non-brachycephalic breeds with a body weight of < 25 kg, and (3) non-chondrodystrophic and non-brachycephalic breeds with a body weight greater or equal 25 kg. In brachycephalic and chondrodystrophic dogs 340 intervertebral discs were evaluated, the majority of them presented a mild change of the normal disc structure, 53% in the FFE sequence and 41% in T2W images. High discrepancies were observed between mild and moderate degeneration: in the FFE-sequence 15% (n = 50) of the discs had signs of mild degeneration, whereas in T2W the same discs were graded as moderately degenerated. In non-chondrodystrophic and non-brachycephalic breeds under 25 kg body weight 320 intervertebral discs were assessed. In the FFE-sequence 52% (n = 166) of the intervertebral discs were judged as having a mild degeneration. In contrast, these same discs were graded as healthy discs (22%), mildly degenerated (33%), moderately degenerated (37%), and severely degenerated (8%) in T2W. In non-chondrodystrophic and non-brachycephalic breeds greater or equal 25 kg 121 intervertebral discs were assessed. The grading was equal in 43%, but differed in one grade (47%) and in two grades (10%) between the two sequences. In both sequences intervertebral disc herniations were equally well-diagnosed. The Kappa coefficient revealed a high discrepancy between the two MRI-sequences. In conclusion, FFE cannot replace the well-established T2W sequence for grading disc degeneration.

Evaluation of T2-weighted versus short-tau inversion recovery sagittal sequences in the identification and localization of canine intervertebral disc extrusion with low-field magnetic resonance imaging

Sagittal T2-weighted sequences (T2-SAG) are the foundation of spinal protocols when screening for the presence of intervertebral disc extrusion. We often utilize sagittal short-tau inversion recovery sequences (STIR-SAG) as an adjunctive screening series, and experience suggests that this combined approach provides superior detection rates. We hypothesized that STIR-SAG would provide higher sensitivity than T2-SAG in the identification and localization of intervertebral disc extrusion. We further hypothesized that the parallel evaluation of paired T2-SAG and STIR-SAG series would provide a higher sensitivity than could be achieved with either independent sagittal series when viewed in isolation. This retrospective diagnostic accuracy study blindly reviewed T2-SAG and STIR-SAG sequences from dogs (n = 110) with surgically confirmed intervertebral disc extrusion. A consensus between two radiologists found no significant difference in sensitivity between T2-SAG and STIR-SAG during the identification of intervertebral disc extrusion (T2-SAG: 92.7%, STIR-SAG: 94.5%, P = 0.752). Nevertheless, STIR-SAG accurately identified intervertebral disc extrusion in 66.7% of cases where the evaluation of T2-SAG in isolation had provided a false negative diagnosis. Additionally, one radiologist found that the parallel evaluation of paired T2-SAG and STIR-SAG series provided a significantly higher sensitivity than T2-SAG in isolation, during the identification of intervertebral disc extrusion (T2-SAG: 78.2%, paired T2-SAG, and STIR-SAG: 90.9%, P = 0.017). A similar nonsignificant trend was observed when the consensus of both radiologists was taken into consideration (T2-SAG: 92.7%, paired T2-SAG, and STIR-SAG = 97.3%, P = 0.392). We therefore conclude that STIR-SAG is capable of identifying intervertebral disc extrusion that is inconspicuous in T2-SAG, and that STIR-SAG should be considered a useful adjunctive sequence during preliminary sagittal screening for intervertebral disc extrusion in low-field magnetic resonance.

Comparison of Feline Brain Anatomy in 0.25 and 3 Tesla Magnetic Resonance Images

The intention of the comparison of both low and high field was to examine which anatomical brain structures of cats were visible on low field images, as in clinical veterinary practice, 3 Tesla (T) magnets were of limited availability. The research was performed on 20 European short-haired male and female cats, aged 1-3 years, with body weight of 2-4 kg. 0.25 T magnetic resonance images of neurocranium were acquired in all using T2-weighted fast spin echo sequences with repetition time (TR) of 4010 ms and echo time (TE) of 90 ms in dorsal and transverse plane, and T2-weighted fast spine echo sequences with TR of 4290 ms and TE of 120 ms in sagittal plane. Based on a detailed catalogue of feline brain structures visible at 3 T in previously published studies, it was examined which structures were visible on low field images. Anatomic structures were identified and compared to assess the reliability of diagnoses made based on low-field magnetic resonance imaging. In low-field scans, 92 structures were identified. Elements of auditory, visual, motor pathways, hippocampus and cerebral ventricular system were distinguished. Low-field as well as high-field magnetic resonance imaging support the identification of local tissue lesions, metastasis, focal ischaemia and haemorrhage, disorders associated with ventricular system dilation and hydrocephalus. It also produced accurate images of the hippocampus, which contributes to reliable diagnoses of various forms of epilepsy in cats. Due to technical limitations, a low-field scanner is unlikely to visualize microtraumas, local inflammations, small haematomas or metastatic tumours.

Magnetic resonance imaging assisted with fine needle aspiration biopsy in the diagnosis of fibrosarcomas of the skull in dogs

Five canine patients were directed to low-field magnetic resonance imaging due to different neurological defects. In each case there were heterogeneous extraaxial masses covering left or right dorsal parietal and occipital lobes that were isointense to the brain on T1-weighted Spin Echo images, isointense to hypointense to the brain on T2-weighted Fast Spin Echo sequences and hypointense to the brain on Flair sequence. After MRI study fine needle aspiration biopsy of the tumors was performed. On the basis of the cytological examination fibrosarcomas with of moderate malignancy were diagnosed.