BVMS PhD DipECVN MRCVS RCVS and European Specialist in Veterinary Neurology

SM MRI screening  - additional information for veterinary surgeons

 

 

What are the minimum images to obtain? 
The minimum required images are
1) Sagittal T1W from intra thalamic adhesion to as far caudal as possible – The images must include a mid sagittal section of spinal cord visible in one section from the cisterna magna to the C4/C5 intervertebral disc space.  If this cannot be achieved because the dog has scoliosis secondary to syringomyelia then a dorsal image of the spinal cord must be included in addition.
2) Sagittal T2W as above
3) T1W Transverse images though the maximum width of the syrinx if there is syringomyelia or as a block centred on C2/C3 and extending from at least mid point of the vertebral body of C2 and reaching the mid point of the vertebral body of C3


In addition transverse images though the lateral ventricles and tympanic bullae are preferred (The latter can be low quality images).


For examples of settings for ESOVATE machines click here


Example of a good quality “mini” MRI scan.

What information must be incorporated on the DICOM images?

 


 
Essential
• Microchip / tattoo number
• Kennel Club Registration number
• Sex
• Breed
• Date of birth 
 

 

 

 

******Important note for ESOVATE VET MRI ® users******


Information entered in the “Animal Name” field is NOT incorporated in the exported DICOM images. For suggestions on how to enter information so that dog can be identified see image below.

Preferred
• Microchip / tattoo number
• Kennel Club Registration number
• Sex
• Breed
• Date of birth
• Surname of owner
• Pedigree name of dog

Does quality matter?

In the UK low cost MRI screening for SM is performed in many cases on ESOVATE MRI machines. Images of excellent quality can be obtained but operators should beware of taking short cuts either for time or economic reasons. Subtle SM may be missed. The images above are taken from the same dog with a narrow syringomyelia (arrow). The image on the left is taken with a short acquisition times and the SM is not appreciable. The image on the right is a longer acquisition time. The consequence to the breeder of missing subtle disease may be devastating as his or her whole breeding program may be based on the assumption that the dog in question is unaffected.

 

How should the animal be positioned?
The dog’s head should be in extension as mild flexion can “improve” a chiari malformation. This is often easiest to achieve by having the dog in sternal recumbency (prone) with the head elevated on a small foam cushion. If the dog is positioned in either dorsal or lateral recumbency then care must be taken to ensure that the head in extension especially in brachycephalic dogs as the head tends to flop forward especially when in dorsal recumbency.

How head position affects apparent chiari malformation. The dog on the left, positioned in dorsal recumbency (supine) may have a mild chiari malformation however it is difficult to be sure.

 

It is also essential that the head and neck are straight and in line with each other.

TW1 MRI images from a dog positioned with the head slightly rotated with respect to the neck. The images on the left were obtained for assessment of the cervical spinal cord and demonstrate a cervical syrinx (midsagittal cervical spine). However the section though the bran is slightly oblique giving an impression that the dog has only a mild herniation of cerebellum through the foramen magnum. The image on the right indicates the true appearance of the cerebellar herniation (midsagittal brain).

In The images above illustrate how difficult it is to make assessments of severity of cerebellar herniation using isolated "snap shots" especially the person interpreting the MRI scan is not aware of how the dog was positioned. It also illustrates how important it is to position the dog accurately. A study on the effect of positioning on apparent severity of the chiari malformation was funded by the UK CKCS club.

How do I submit DICOM images for reporting by Clare Rusbridge?
For outside MRI reporting the following is required
1) Submission form


2) Copy of Kennel Club registration documents


3) Verification (i.e. signature by veterinary surgeon) that microchip / tatoo pertains the animal scanned


4) CD of DICOM images (radiography film of limited images is not acceptable). A copy should be submitted as the CD will not be returned.


5) The fee is £35 plus VAT for EU residents or £35 for non EU residents. Payment is in UK pounds. It is possible to use PAYPAL (for details contact CRusbridge@goodardvetgroup.co.uk ).


Address for submitting images and documents – Clare Rusbridge, Stone Lion Veterinary Centre, 41 High Street, Wimbledon, SW19 5AU

 

Are the MRI results submitted to the Animal Health Trust for the Estimated Breeding Value database?
Yes. For more information about this scheme click here

 

At what age should dogs have CM/SM MRI screening? 
The minimum screening age is 12 months. It is also recommended that breeders determine the MRI status of their breeding dogs at 2-3 years and again when 6 years of age. This will provide further information about that individual dog’s estimated breeding value (EBV) (and therefore the EBV of that individual dog’s offspring).

 
When is the proposed BVA / KC MRI screening scheme going to start?
Unfortunately the process of conception to an up-and- running scheme can be lengthy. The proposed scheme has been submitted to the BVA/KC Management Committee for their consideration and is currently in progress.

Stone Lion Veterinary Hospital, Goddard Veterinary Group, 41 High Street Wimbledon Common London SW19 5AU

Email: CRusbridge@goddardvetgroup.co.uk

Telephone: 020 8946 4228, Fax: 020 8944 0871

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