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The gadolinium contrast agent increases the signal from tissues where there is increased blood flow, particularly in the setting of inflammation or neoplasm. The resulting improvement in contrast between normal and pathological tissue is often much higher than can be achieved with iodinated contrast at computed tomography (CT).
This is most useful in the brain and spinal cord, where the blood–brain barrier might be disrupted by the pathology, and the signal increase is therefore particularly strong.
It is also useful in suspected inflammatory joint disease, inflammatory bowel disease, and inflammatory and neoplastic conditions of solid organs, such as the liver and kidney. It is sometimes useful in inflammatory and neoplastic conditions of bone, muscle, and connective tissue.
A second category of uses exploits the greatly increased signal from blood vessels themselves, to allow the production of MR angiograms. This works best in the arterial phase of the contrast injection, meaning the scan must be completed very quickly (2–3 minutes). This technique (‘contrast-enhanced MRA’) is used outside the head; intracranially, slower non-gadolinium techniques produce better resolved images of the intracranial circulation.
Gadolinium-based contrast injection might be contraindicated in patients with:
Hence, a history of any previous gadolinium-based contrast agent exposure, risk factors for, or known, kidney disease, and possible pregnancy, should be sought.
The RANZCR, in conjunction with the Australian and New Zealand Society of Nephrology and Kidney Health Australia, has issued guidelines on the use of gadolinium-containing MRI contrast agents in patients with renal impairment, endorsed in June 2013. Further information can be found in Diagnostic Imaging Pathways: Gadolinium based contrast medium.
Questions about renal disease should be included in safety screening.
The following minimum set of questions is suggested:
If the answer to any of these questions is “yes”, an estimated glomerular filtration rate (eGFR) that has been carried out no more than 3 months before the examination should be available when the patient presents for the MRI.
Note that patients with chronic liver function impairment might have reduced muscle mass. This can make estimation of eGFR less accurate.
Unstable or acutely deteriorating renal function is a relative contraindication to gadolinium-based contrast agent administration.
Previous or pre-existing nephrogenic systemic fibrosis (see below).
Only for the more severe adverse effects listed above.
The total number of patients in whom there is a relative or absolute contraindication to the use of gadolinium contrast agents is small.
Contrast enhancement can also be achieved in CT and ultrasound, with the use of different agents. The choice of modality will depend on the anatomy to be assessed and the nature of the clinical problem.
The nephrotoxicity of iodinated contrast used in CT has been overestimated in the past, and can be ameliorated by pre-hydration, so that contrast-enhanced CT is a potential alternative to contrast-enhanced MRI, depending on the particular indication. (see Contrast Medium: Gadolinium versus Iodine in patients with kidney problems).
In cardiac MRI, gadolinium-based contrast agents might be essential in assessing cardiac function and muscle viability. However, in ischaemic heart disease, numerous other modalities are available, such as conventional electrocardiogram stress testing, stress echo and thallium perfusion scanning, as well as transoesophageal echo. In the diagnosis of myocardial disease, such as specific types of cardiomyopathy, contrast-enhanced MRI might add to confidence in a particular diagnosis, but is rarely if ever essential for management.
In high-risk groups (eGFR<30 mL/min/1.73 m2), or individuals with acutely unstable/deteriorating renal function, the risk–benefit of contrast-enhanced MRI will need to be assessed in conjunction with the radiologist. A history of previous exposure to gadolinium-based contrast agents or of other factors thought to contribute to the risk of NSF, such as metabolic acidosis, vascular surgery and recent thrombotic events, should be taken into account (see Contrast Medium: Gadolinium versus Iodine in patients with kidney problems).
Informed and written consent should be obtained from the high-risk group (or parents/guardians) by the MRI practice.
The gadolinium dose will be limited to standard doses (or less), limiting the ability to carry out contrast-enhanced MR angiograms.
In patients already receiving haemodialysis, in whom a gadolinium injection is deemed diagnostically essential, schedule gadolinium-based contrast agent administration immediately before haemodialysis and consider an extra dialysis session afterwards. Referring doctors should ensure that they discuss appropriate timing of the MRI scan with the MRI facility.
Note: peritoneal dialysis does not remove gadolinium-based contrast agents effectively.
Page last modified on 12/10/2016.
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