IMAGING DIAGNOSIS—LEFT RETROCAVAL URETER AND TRANSPOSITION OF THE CAUDAL VENA CAVA IN A DOG

Retrocaval ureter and transposition of the caudal vena cava are each, rare developmental anomalies. We describe the usefulness of static fluid magnetic resonance urography and dynamic contrast-enhanced magnetic resonance urography in the diagnosis of these anomalies. Basic techniques, benefits, and drawbacks of magnetic resonance urography are presented.     

DYNAMIC CONTRAST‐ENHANCED MAGNETIC RESONANCE IMAGING OF CANINE BRAIN TUMORS

We evaluated dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) in canine brain tumors. Magnetic resonance data sets were collected on seven canine intracranial tumors with a 3 T magnet using a T1‐weighted fast spin echo fluid attenuated inversion recovery sequence after an IV bolus injection (0.2 mmol/kg) of Gd‐DTPA. The tumors were confirmed histopathologically as adenocarcinoma (n=1), ependymoma (n=1), meningioma (n=3), oligodendroglioma (n=1), and pituitary macroadenoma (n=1) The data were analyzed using a two‐compartment pharmacokinetic model for estimation of three enhancement parameters, E_R (rate of enhancement), K_el (rate of elimination), and K_ep (rate constant), and a model‐free phenomenologic parameter initial area under the Gd concentration curve (IAUGC) defined over the first 90 s postenhancement. Pearson's correlations were calculated between parameters of the two methods. The IAUGC has a relatively strong association with the rate of enhancement E_R, with r ranges from 0.4 to 0.9, but it was weakly associated with K_ep and K_el. To determine whether any two tumors differed significantly, the Kolmogorov–Smirnov test was used. The results showed that there were statistical differences (P<0.05) between distributions of the enhancement pattern of each tumor. These kinetic parameters may characterize the perfusion and vascular permeability of the tumors and the IAUGC may reflect blood flow, vascular permeability, and the fraction of interstitial space. The kinetic parameters and the IAUGC derived from DCE‐MRI present complementary information and they may be appropriate to noninvasively differentiate canine brain tumors although a larger prospective study is necessary.     

Radiological interpretation of the navicular bone

Accurate radiological interpretation of a navicular bone requires at least a true lateromedial (LM) image, dorsoproximal‐palmarodistal oblique (DPr‐PaDiO) and palmaroproximal‐palmarodistal oblique (PaPr‐PaDIO) images. Additional information is sometimes acquired from a weightbearing dorsopalmar (DPa) image. The LM image is used to assess thickness of the palmar cortex, proximal or distal extension of the palmar cortex, demarcation between the cortex and spongiosa and the presence of periarticular osteophytes. The number, size, shape and position of radiolucent zones along the distal borders of the navicular bone are assessed in a PaPr‐PaDiO image, together with the presence of central or acentric radiolucent osseous cyst‐like lesions in the spongiosa, proximal or distal border entheseophytes, distal or proximal border fragments and a fracture. The PaPr‐PaDiO image is used to identify radiolucent lesions in the palmar cortex and to confirm the thickness of the palmar cortex and the presence of a fracture, and to assess the trabecular architecture of the spongiosa. The presence of a bipartite or tripartite navicular bone is determined from DPr‐PaDiO, PaPr‐PaDiO and DPa images.     

Anatomical, magnetic resonance imaging and histological findings in the accessory ligament of the deep digital flexor tendon of forelimbs in nonlame horses

Reasons for performing the study: Detailed magnetic resonance imaging (MRI) and histological appearances of the accessory ligament of the deep digital flexor tendon (AL‐DDFT) have not been documented previously in detail. Objectives: To: 1) describe anatomical connections between the AL‐DDFT and adjacent structures; 2) describe high‐field and low‐field MRI and histological appearances of the AL‐DDFT in the forelimb of horses with no carpal or proximal metacarpal pain; and 3) assess the relationship between age, breed, gender, height, weight and MRI findings. Methods: Ten forelimbs were dissected to determine anatomical relationships among the AL‐DDFT and adjacent structures. High‐ and low‐field MR images of the AL‐DDFT and related structures from 29 cadaver limbs of nonlame horses were analysed subjectively and objectively. The relationship between age, breed, gender, height, weight and MRI findings was assessed using a Chi‐squared test. Twelve ALs‐DDFT were examined histologically. Histological and MRI findings were compared subjectively. Results: Fibrous bundles were seen between the AL‐DDFT and the lateral aspect of the superficial digital flexor tendon (n = 9) and the DDFT (n = 2). The AL‐DDFT had low to intermediate signal intensity in most limbs in most high‐field and low‐field MRI sequences. In 69% of limbs, oblique bands of higher signal intensity than the rest of the ligament were identified in high‐field images of the AL‐DDFT. The cross‐sectional area of the AL‐DDFT in the proximal 7 cm of the metacarpal region ranged from 68.1–299 mm². There was no significant relationship between age, gender, weight or height and either the cross‐sectional area of the AL‐DDFT or the presence of oblique higher signal intensity bands. Histological examination revealed that the AL‐DDFT had thick collagen bundles arranged in large crimps and sometimes crossing in oblique directions. The cellularity was greater than in the deep digital flexor tendon in all limbs. Conclusion and potential relevance: The large variability in the MRI appearance and size of the AL‐DDFT in nonlame horses should be borne in mind when interpreting MR images of lame horses.     

Surgical treatment of a second metacarpal bone exostosis with associated desmitis of the body of the suspensory ligament in a horse

This report outlines the diagnosis, surgical treatment and successful outcome following treatment of second metacarpal bone exostosis with concurrent suspensory ligament desmitis, and lameness in a horse. Magnetic resonance imaging was useful in determining the extent of pathology within the suspensory ligament and site of proposed surgical resection. MRI was also utilised as a post-operative tool in determining the timescale for satisfactory healing to enable the horse to return to athletic work.     

Accuracy of selected neurological clinical tests in diagnosing MRI-detectable forebrain lesion in dogs

This retrospective case study aims to evaluate the accuracy of menace response, response to nasal stimulation and proprioceptive placing in diagnosing forebrain lesion in dogs. A total of 145 client-owned dogs investigated by magnetic resonance imaging study of the brain between December 2017 and June 2019 were evaluated. Seventy-one dogs with no magnetic resonance imaging-detectable intracranial and significant cerebrospinal fluid abnormality or recent history of seizure (<48 h) served as controls. Binary regression analysis was performed to determine the sensitivity, specificity and likelihood ratios of each selected test. Older age at presentation was a significant risk factor for the presence of a forebrain lesion. Menace (62.5%) and proprioceptive deficits (40.5%) were common findings in all dogs. They were also significantly associated with the presence of forebrain abnormality. Moreover, they were more sensitive (77.3% and 82.2%, respectively) and specific (50.0% and 62.5%, respectively) when applied to dogs aged 6 years or older. Nonetheless, all of these tests' likelihood ratios, and thus reliability are poor. These neurological tests are commonly employed for diagnosing forebrain disease in dogs, yet are not highly accurate in diagnosing forebrain abnormality. Clinicians should interpret these clinical test results along with the patient history when designing a diagnostic plan.     

Magnetic resonance imaging and analyses of tempering processes in rice kernels

This research involved a magnetic resonance imaging (MRI) technique that was applied to examine water distribution and migration in single rice kernels during the tempering process. The imaging experiments were performed in a Bruker 9.4T MRI system. Three-dimensional spin-echo (SE) imaging sequences were optimized by adjusting the scanning parameters of echo time (TE) and repetition time (TR) to obtain images with maximum contrast. The MR images showed that the moisture distribution in the rice kernel is non-uniform and compartmental. The embryo region exhibited much higher MR signal intensity than the starchy endosperm portion. The tempering process was analyzed with spatial-temporal signal intensities of the endosperm following the drying process of the rice kernel. The transient change of the signal intensities in the endosperm was well fitted with a double exponential function suggesting that both convection and diffusion contributed to the reduction of the moisture gradient within the rice kernel during tempering. This hypothesis was further supported by the experimental data of the insulated rice kernel whose convective mass transfer was excluded. The experimental results revealed that MR imaging of rice kernels could be used as an efficient tool to examine the mechanisms of moisture migration within cereal grains.