Environmental Lead-210 gamma-ray measurements in brain tumors

Abstract

In 2006 Mom\v{c}ilovi\'c et al. measured radioactvity levels of 210Po and 210Bi by alpha- and beta-measurements resp. to determine the natural distribuion of environmental radon daughters in the different brain areas of an Alzheimer Disease victim. We show that gamma-ray spectrometry of the mother nucleus 210Pb can be used. It is a direct measurement without tampering with the sample. However, because this technique is far less sensitive than alpha- and beta-spectrometry, activity values previously published were out-of-reach for gamma-ray spectrometry. This is no longer the case with our ultra-low background high purity Ge detectors which have been developed in the frame of the neutrino experiments. To ascertain this possibility, ten brain samples from Alzheimer patients and blanks as well as 10 samples of brain tumors have been investigated and results were cross-checked with two different spectrometers. Localization of the samples in the brain was not known to avoid biased interpretation of the results. Data taking lasted between 1 and 4 weeks for each sample. All ten Alzheimer/blank samples were below the limit of detection (LOD), 3 out of the 10 tumors lead to positive results (3.8 to 4.9 mBq/g of 210Pb) with a statistical significance of at least 3 standard deviations. Potential followup of this method is to enhance the detector sensitivity, having the spectrometer installed in an underground laboratory such as the one in Modane under the Alps where the background noise is 30- fold less than at the present location in Bordeaux. The final aim is to map a brain in collaboration with Alzheimer/Parkinson experts.