Description and validation of a magnetic resonance imaging-guided stereotactic brain biopsy device in the dog.

A stereotactic brain biopsy system that is magnetic resonance (MR) imaging-guided has not been validated in dogs. Our purpose was to determine the mean needle placement error in the caudate nucleus, thalamus, and midbrain of a canine cadaver brain using the modified Brainsight stereotactic system. Relocatable reference markers (fiducial markers) were attached to the cadaver head using a dental bite block. A T1-weighted gradient echo three-dimensional (3D) sequence was acquired using set parameters. Fiducial markers were used to register the head to the acquired MR images in reference to a 3D position sensor. This allowed the planning of trajectory path to brain targets in real time. Coordinates (X, Y, Z) were established for each target and 0.5 microl of diluted gadolinium was injected at each target using a 26-gauge needle to create a lesion. The center of the gadolinium deposition was identified on the postoperative MR images and coordinates (X', Y', Z') were established. The precision of this system in bringing the needle to target (needle placement error) was calculated. Seventeen sites were targeted in the brain. The mean needle placement error for all target sites was 1.79 +/- 0.87 mm. The upper bound of error for this stereotactic system was 3.31 mm. There was no statistically significant relationship between needle placement error and target depth (P = 0.23). The ease of use and precision of this stereotactic system support its development for clinical use in dogs with brain lesions > 3.31 mm.

El conejo como modelo de experimentación. Inducción de lesión vascular: técnica e incidencias / The rabbit as an experimental model: technique for the induction of vascular lesions and incidents

Objetivo: Describir el proceso para conseguir la lesión aterogénica en el conejo, mostrar el daño vascular producido por 2 catéteres de balón de diferente calibre y el valor de la ecografía para su cuantificación. Material y métodos: Se emplearon 36 conejos. Se estudiaron los valores de triglicéridos y colesterol, y se realizó una ecografía de aorta e ilíacas. Se realizó una arteriografía y se indujo la lesión vascular denudando la arteria ilíaca izquierda con catéter de balón: grupo A, catéter-balón 2,5mm, y grupo B catéter-balón 3mm de diámetro. Tras 8 semanas con dieta hiperlipídica se realizaron nuevas mediciones bioquímicas y ecográficas. Resultados Colesterol antes de la dieta 37,96±19,3mg/dl, y tras la dieta 1.761±296,91mg/dl. Los hallazgos ecográficos mostraron un diámetro de la aorta de 4,1±0,7mm, de la arteria ilíaca derecha de 3±0,3mm, de la arteria ilíaca izquierda de 3±0,4mm. Tras el daño vascular y 8 semanas de dieta, en el grupo A la luz de la aorta era de 2,78±1,21mm, la arteria ilíaca derecha medía 2,18±0,81mm y la arteria ilíaca izquierda 1,16±0,63mm; en el grupo B la luz de la aorta fue de 3,07±1,06mm, la arteria ilíaca derecha 2,53 ± 0,9mm y la arteria ilíaca izquierda 1,39±1,1mm. Resultados: Murieron 4 conejos y de los 32 restantes hubo más morbimortalidad con el catéter de balón de 3 mm. Conclusión Tras la denudación con catéter de balón y dieta los conejos desarrollan estenosis de la arteria. El daño con catéter de 2,5 mm de diámetro disminuye las complicaciones (AU)

Objective: To describe the process for inducing atherogenic lesions in rabbits, to show the damage to vessels caused by two different caliber balloon catheters, and to show the usefulness of ultrasonography in the quantification of vascular damage. Material and methods: We used 36 rabbits. We studied the levels of triglycerides and cholesterol and examined the aorta and iliac arteries by ultrasonography. We performed arteriography and induced a vascular lesion by denuding the left iliac artery with a balloon catheter: group A 2.5mm diameter balloon catheter, group B 3mm diameter balloon catheter. After 8 weeks on a hyperlipidic diet, biochemical and ultrasonographic measurements were repeated. Results: Cholesterol before the diet: 37.96±19.3mg/dL and after the diet: 1761±296.91mg/dL. The baseline ultrasonographic measurements of vessel diameter were: aorta 4.1±0.7mm, right iliac artery 3±0.3mm, left iliac artery 3±0.4mm. After vascular damage and 8 weeks hyperlipidic diet, in group A the ultrasonographic measurements of vessel diameter were: aortic lumen 2.78±1.21mm, right iliac artery 2.18±0.81mm, and the left iliac artery 1.16±0.63mm; in group B, the aortic lumen measured 3.07±1.06mm, the right iliac artery 2.53±0.9mm, and the left iliac artery 1.39±1.1mm. Results: Four rabbits died; in the 32 remaining rabbits, morbidity was higher with a 3mm balloon catheter. Conclusion: After denudation with a balloon catheter and a hyperlipidic diet, the rabbits developed arterial stenosis. The damage with a 2.5mm diameter catheter reduces complications (AU)

Growth hormone excess and the effect of octreotide in cats with diabetes mellitus.

In this prospective study 16 cats with diabetes mellitus were examined for concurrent acromegaly by measuring plasma growth hormone (GH) and insulin-like growth factor-I concentrations, and magnetic resonance imaging (MRI) of the pituitary fossa. Additionally, the effects of octreotide administration on the plasma concentrations of glucose, GH, alpha-melanocyte-stimulating hormone (alpha-MSH), adrenocorticotrophic hormone (ACTH), and cortisol were measured. Five cats were diagnosed with hypersomatotropism. The pituitary was enlarged in these 5 cats and in 2 other cats. Six cats that required a maximum lente insulin dosage >or=1.5 IU/kg body weight per injection had pituitary enlargement and 5 of these cats had acromegaly. Plasma concentrations of GH, ACTH, and cortisol decreased significantly after single intravenous administration of the somatostatin analogue octreotide in the acromegalic cats. The effect on GH concentrations was more pronounced in some of the acromegalic cats than in others. In the non-acromegalic cats only ACTH concentrations decreased significantly. In both groups plasma glucose concentrations increased slightly but significantly, whereas alpha-MSH concentrations were not significantly affected. In conclusion, the incidence of hypersomatotropism with concomitant pituitary enlargement appears to be high among diabetic cats with severe insulin resistance. Some of these cats responded to octreotide administration with a pronounced decrease in the plasma GH concentration, which suggests that octreotide administration could be used as a pre-entry test for treatment with somatostatin analogues.