After gadolinium, the transition metal manganese (25Mn) possesses the second highest paramagnetic moment of any element. This property derives from the Mn+2 ion having 5 unpaired electrons in its 3d shell. Thus the potential of using manganese at the center of a paramagnetic contrast agent has always excited considerable interest.
After injection Teslascan® is taken up by hepatocytes and eventually excreted into the bowel. Accumulation of manganese produces a prominent T1 shortening effect, rendering normal liver bright on T1-weighted images, while non-hepatocyte-containing masses remain dark.
Although initial clinical trials of Teslascan® demonstrated a low incidence of mild and expected adverse effects (headache, nausea, etc.), concern about the dangers of the free Mn+2 ion arose. In industrial workers Mn+2 is known to accumulate in the brain with long-term exposure producing a Parkinson-like syndrome. This risk is increased in patients with liver failure. Reports of myocardial depression also arose resulting from Mn+2 entering heart cells through Ca+2 channels.
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Silva AC, Lee JH, Aoki I, Koretsky AP. Manganese-enhanced magnetic resonance imaging (MEMRI): methodological and practical considerations. NMR Biomed 2004; 17:532-543.
Youk JH, Lee JM, Kim CS. MRI for detection of hepatocellular carcinoma: comparison of mangafodipir trisodium and gadopenetate dimeglumine contrast agents. AJR Am J Roentgenol 2004; 183:1049-1054.
How does gadolinium cause relaxation?