Greater caseloads managed by the general veterinary practitioner – together with client’s increasing demands for more sophisticated treatment for their pet - have increased the number of cases referred for second opinion in recent years. Referrals can also be an important component of client management. A difficult client who is unwilling to accept that there is no appropriate treatment for their pet may be happy to accept the same answer from a recognised ‘specialist’. There are many clinical indications for referral but imaging referrals are generally made when a second opinion is required on results and findings already obtained or for further investigation using more specialised equipment not available to the general practitioner. MRI is important for investigation of central nervous system disease – the brain is hard to image accurately with any other modality. External referral should be considered an important part of everyday practice. One of the keys to successful treatment is being able to recognise your own limitations. Seeking a specialist opinion is nothing to be ashamed of. The more experienced a clinician is the more they seek advice.
Access to magnetic resonance imaging (MRI) has been available through specialist referral centres for many years. Mobile MR scanners touring the country are making the facility available to practitioners in their own town. As MR imaging remains one of the most expensive imaging modalities it is of particular importance that the most appropriate and highest quality study is performed at the first attempt. There are many indications for MR scanning, but each case must be considered individually to decide whether the study will be of value to a particular individual. If all other investigative alleys have been followed there is little point in pursuing an MR scan in the hope of a diagnosis if the client is unlikely to consider treatment. Where the information gained from the scan will not alter case management there may be little point in having a scan. If an animal is referred for MR scanning it is highly unlikely that an inappropriate study will be performed. Some centres only accept scan requests from recognised second opinion referral centres to reduce the risk of inappropriate studies. However, if you are requesting a scan yourself there are a number of additional factors to consider above whether or not the study is appropriate. The quality of the image produced is highly dependent both on machine characteristics (basically the strength of the magnet and the type of the coils), and the skill of the person acquiring the images. It may be impossible to get diagnostic images of some anatomical sites using certain machines. If the diagnosis is likely to indicate that further treatment is necessary consider if you are able to perform this treatment? An animal with a suspected brain tumour, for which the owner’s are likely to want treatment if this is appropriate, is best referred to a centre that is able to assess the case, perform the scan and then provide appropriate treatment.
• Is MRI the most appropriate study or would other imaging studies be more useful?
• Is the correct part of the body being imaged? – if the animal is collapsing have you correctly differentiated seizures from other causes.
• When you refer the animal for the scan consider if the machine is able to provide a suitable quality of image for the area to be scanned.
• Will the person who scans the animal be able to interpret the images for you – in some cases scans are performed by physicists who are trained to optimise images but will not be able to comment on the study or its results. MRI needs some degree of interpretation whilst performing the scan otherwise lesions may be missed or special sequences not performed.
• The person who reads the film should have experience in reading animal MR scans for the region presented – if you do not have this experience the scans are often meaningless.
• When sending films for interpretation elsewhere it is worth asking the radiographer to print all the images and to ensure the images are of sufficient size to assess accurately and ensure films are printed according to veterinary rather than human conventions.
• In the majority of cases contrast agents should be used.
• MRI requires general anaesthesia in animals and specialised monitoring equipment - does the MRI centre have appropriate facilities for safe anaesthesia in patients that may be have serious brain disease.
Fraser McConnell BVMS CSAM DVR DipECVDI MRCVS RCVS and European Specialist in Diagnostic Imaging
Fraser McConnell qualified from Edinburgh University in 1993, and obtained the RCVS Certificate in Veterinary Radiology from practice in 1998. He moved to The University of Cambridge where he studied at the Cambridge Veterinary School for 18 months obtaining the RCVS Certificate in Small Animal Medicine in 1999 and the RCVS Diploma in Veterinary Radiology in 2000. From 2001 to 2006 he worked as a clinical radiologist at the Animal Health Trust and gained his diploma from the ECVDI in 2003. During this time Fraser gained extensive experience in small animal MRI and neuroimaging. Fraser joined The University of Liverpool as senior lecturer in veterinary diagnostic imaging and head of the imaging service in November 2007. Fraser’s clinical and research interests include all aspects of small animal MRI and neuroimaging. He regularly lectures and publishes on small animal MRI and neuroimaging. Fraser is a RCVS & European Specialist in Veterinary Diagnostic Imaging and is director of AVDIS a veterinary teleradiology company specialising in MRI reporting.
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