May 18, 2017
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Room-temperature susceptometer noninvasively verifies liver iron

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Room-temperature susceptometer offers a noninvasive method to assess liver iron and may result in increased cost efficacy compared with methods that require helium cooling, according to a recently published study.

“[Room-temperature susceptometer] is a new non-invasive bedside method to assess liver iron, mainly hepatocellular iron. Since no helium cooling is required, it could result in a cost efficient and more widespread technology to monitor liver iron also in comparison with MRI,” Johannes Mueller, MD, from the University of Heidelberg, Germany, and colleagues wrote. “Future studies are urgently wanted to better understand distribution, mechanisms, chemical nature and consequences of hepatic iron overload in large populations with various iron related disorders.”

To verify room-temperature susceptometer’s ability to measure different paramagnetic susceptibilities, the researchers enrolled 264 patients between June 2013 and March 2017 to undergo a series of measurements on different ferric iron solutions with increasing concentrations in 10 mm distance to the susceptometer probe.

Thirty-five patients required medically indicated liver biopsies. Of these patients, 33 had liver iron concentration quantified by atomic absorption spectroscopy and 15 had hepatic iron quantified by MRI.

Etiologies included alcoholic liver disease (n = 171), nonalcoholic fatty liver disease (n = 9), hereditary hemochromatosis (n = 18), transfusional iron overload due to thalassemia, sickle cell disease (n = 13) or other non-iron homeostasis dependent diseases with or without increased serum ferritin values (n = 45).

The researchers found a highly linear (r2 = 0.99) association between room-temperature susceptometer signal and iron with a detection limit of 0.3 mM. Regarding spatial sensitivity, the signal of a large plane object (eg, 250 x 250 x 100 mm) against air decreased exponentially from 10 mm to 35 mm by a factor of 7.5. However, room-temperature susceptometer was still able to sufficiently measure magnetic susceptibility at a distance of 35 mm.

Compared with the 33 biopsies with quantified liver iron concentration, the magnetic susceptibility of room-temperature susceptometer correlated significantly with liver iron content-atomic absorption spectroscopy (r = 0.74; 95% CI, 0.53-0.86) and MRI (r = 0.64; 95% CI, 0.19-0.87).

Among the 35 patients with biopsies, atomic absorption spectroscopy-measure liver iron concentration correlated significantly with macrophage (r = 0.47; P < .01) and hepatocyte iron (r = 0.67; P < .01). Room-temperature susceptometer correlated significantly with hepatocyte iron (r = 0.47; P < .01) but not with macrophage. The susceptometer method remained significantly correlated with hepatocyte iron when excluding patients with hemochromatosis (r = 0.38; P < .05).

“We here demonstrate that [room-temperature susceptometer] allows the rapid, noninvasive and sensitive detection of liver iron in a large and heterogeneous patient cohort. Notably, [room-temperature susceptometer] correlated primarily with hepatocellular iron and was superior to all serum iron markers such as ferritin and [transferrin saturation],” the researchers wrote. “Further studies are necessary to better understand all the factors affecting the technical assessment of iron such as degree of steatosis, inflammation and cirrhosis.” – by Talitha Bennett

Disclosures: The researchers report no relevant financial disclosures.