MRI of the Prostate
Dr Stefan Heinze Dr John Faulder What is an MRI scan of the prostate? A magnetic resonance imaging (MRI) scanner…Read more
The treating multidisciplinary team, including at least the operating surgeon and a radiologist, should decide timing and method of localisation. The operating surgeon should make requests for hookwire localisation to the radiologist. All previous imaging should be assessed by the treating team prior to localisation to ensure that it is complete. A diagnostic study performed with the chosen modality for guidance should be available prior to the localisation procedure. In general, if a lesion is seen by one modality only, that modality will be used to guide the localisation procedure. For mammographic hookwire procedures, the patient should be capable of sitting in a chair and understanding simple instructions. MRI contraindications and renal function status (for IV contrast administration) will have been assessed at the time of diagnostic MRI scanning but these should be reassessed prior to localisation. It is useful to be aware of anticoagulation (this would be standard information required prior to any radiological interventional or surgical procedure).
Absolute contraindications for hookwire localisation are rare. Perhaps the only absolute contraindication would occur in the setting of MRI if a patient had a non-MRI compatible device (e.g. pacemaker) placed between the time of the diagnostic MRI scan and the time of localisation, making it unsafe to localise the lesion with MRI even though it was clearly demonstrated on an earlier MRI (before the patient had the pacemaker placed, for example), when it was still safe for the patient to have MRI.
Relative contraindications are also rare since these would usually have been encountered in the diagnostic phase of work-up and would inform the choice of subsequent localisation procedure.
Vasovagal reactions occur in approximately 7%, ranging from light-headedness to severe bradycardia hypotension and loss of consciousness. The risk of a vasovagal attack is increased by patient anxiety. The radiology practice should employ anxiety reducing strategies, including the provision of a relaxed and friendly atmosphere and fast, efficient procedures so that most vasovagal reactions are avoided or minimised. Occasionally atropine is required to reverse severe bradycardia.
Adverse events related to MRI in general include the small risk of allergic reactions to gadolinium, the risk of nephrogenic systemic fibrosis in women with kidney failure who receive gadolinium during the localisation procedure, and the general risks of entering the MRI environment, such as pacemaker malfunction or metallic foreign body migration. See items on MRI and gadolinium contrast medium.
Wire misplacement or migration can affect the accuracy of excision and occasionally small wire fragments are retained in the breast. These rarely cause harm.
Alternatives to hookwire localisation include injection of medical carbon as a track to the lesion, injection of radionuclide tracer into the lesion, and deposition of various clips and markers at the time of diagnostic needle biopsy. The latter methods usually then involve intra-operative localisation by the surgeon with an ultrasound probe or a gamma probe, in the case of radionuclide injection, without need for a preoperative radiological localisation method. The choice of timing and method is made by the treating multidisciplinary team and will vary according to the available facilities and expertise. All methods have excellent track records when success is measured on the basis of correct identification and removal of the lesion.
Page last modified on 29/3/2017.
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