MRI scanner under scanner

Date:03/05/2007 URL: http://www.thehindu.com/thehindu/seta/2007/05/03/stories/2007050300371600.htm Sci Tech
— Photo: K. Pichumani


MRI scanner under scanner

MRI with a gadolinium-based contrast agent may cause a sometimes fatal condition

# Free unbound gadolinium (a paramagnetic heavy metal) is very toxic
# Dialysis a must after recieving the gadolinum based agent for moderate to end stage kidney patients



UNIQUE TOOL: Many MRI uses are unique and a few of them tend to be irreplaceable.

MAGNETIC RESONANCE imaging (MRI), a non-invasive technique used to characterise and discriminate tissues using their physical and chemical properties, finds applications in cardiology, neurology and oncology.

Many MRI uses are unique and a few of them tend to be irreplaceable. But now the scanner itself has come under the scanner.

The press release

A report by Dr T. Grobner in January 2006 and a press release, dated May 29, 2006 from the Danish Medicines Agency (DMA) described patients with renal failure who developed a rare, potentially life-threatening condition called Nephrogenic Systemic Fibrosis/Nephrogenic Fibrosing Dermopathy (NSF/NFD).

These patients had gadolinium-enhanced Magnetic Resonance Angiography (MRA) procedures a few weeks to a few months before developing NSF/NSD.

Health advisory

The US Food and Drug Administration (FDA) posted two advisories on the topic in June 2006 and December 2006. The agency warned that patients with moderate to end-stage kidney disease who receive an MRI or MRA with a gadolinium-based contrast agent may get NSF/NFD, a debilitating and sometimes fatal condition. When such a patient needs an imaging study, physicians should select methods other than MRI or MRA with a gadolinium-based contrast agent for the study whenever possible, FDA cautioned.

If these patients must receive a gadolinium-based contrast agent, the physicians must consider arranging prompt dialysis following the MRI or MRA.

The UK Commission on Human Medicines (CHM) together with the European Pharmaco-vigilance Working Party (PhVWP) of the Committee for Medicinal Products for Human Use (CHMP) and Health Canada issued appropriate health advisories on NSF during February and March this year.

Signs of the disease

FDA reported the following signs of the disease: burning, itching, swelling, hardening and tightening of the skin; red or dark patches on the skin; yellow spots on the whites of the eyes; stiffness in joints with trouble moving or straightening the arms, hands, legs or feet; pain, deep in the hip bones or ribs; and muscle weakness. NSF patients develop swelling and tightening of the skin over a period of days to several weeks (Journal of American Medical Association-JAMA- January 17, 2007). Often, the thickening of the skin inhibits joint movement. In severe cases, the patient cannot walk. Fibrosis may lead to multiple organ failure and death.

Physicians identified NSF/NFD for the first time in1997. In 2000, Dr Shawn Cowper at Yale University School of Medicine described the condition (Auntminnie.com, March 27, 2007).

NSF/NFD has no known treatment; improved renal function (spontaneous or via kidney transplant) appears to slow down or arrest its development and may even yield a gradual reversal of the condition (FDA, December 22, 2006).

Middle-aged affected

NSF appears to affect males and females nearly equally. Children and the elderly suffer from it. It tends to affect the middle-aged most commonly. Specialists identified it in patients from different ethnic backgrounds and from North America, Europe, and Asia. In 2006-2007, six papers in prestigious medical journals dealt with NSF.

The ACR Guidance Document on Safe MR Practices from the American College of Radiology (American Journal of Roentgenology, March 1, 2007) specifically addressed NSF calling "gadolinium administration a necessary factor in the development of NSF at this time". This 27-page document deals with all issues of MRI safety.

Free unbound gadolinium (a paramagnetic heavy metal) is very toxic; but in the contrast agent it is chelated with a ligand; then its safety profile improves dramatically, resulting in a 500-fold increase in renal excretion (Kramer, ACR, 2007).

Initiating the process

In patients with poor kidney function, gadolinium may disassociate from the ligand and may deposit in tissue beds and initiate the fibrotic process. Specialists have isolated gadolinium from biopsy specimens of NSF patients.

Dr Christopher M. Kramer, an MRI specialist estimated that nearly 200 million patients have received a magnetic resonance imaging examination using gadolinium-based contrast agent since 1988.

"The NSF registry currently contains over 215 worldwide cases, it is reasonable to assume that NSF is largely under-recognized", Dr Kramer said

Dr Shawn Cowper who set up a world registry of NSF patients also felt that what is recorded is only a small fraction of actual cases.

Physicians should consider the advisories from different agencies before carrying out MRI screening

K.S PARTHASARATHY

Former Secretary, AERB(ksparth@yahoo.co.uk)

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