Biomagnetic measurements of iron stores in human organs

IOANNIS PAPADOPOULOS, PHOTIOS ANNINOS, ATHANASIA KOTINI, ADAM ADAMOPOULOS, NIKOLAOS TSAGAS*

Lab of Medical Physics, Medical School, Democritus Univ. of Thrace,

University Campus Alex/polis, 68100,

* Nuclear Technology,Univ. of Thrace, Xanthi

GREECE

Abstract: - The standard quantitative measurement of iron stores method was required a surgical or needle biopsy which is very discomfort and in some cases with significant risk to the subject. An alternative method is proposed using the biomagnetometer SQUID. With the use of the SQUID is providing an accurate and without risk quantitative method of iron measurement in liver, spleen and heart for adults and children suffering from Thalassemia.

The above non-invasive biomagnetic method exploits the effects of magnetism and superconductivity.

Thus, when an organ, such as the liver or the spleen is placed in a magnetic field, it will slightly distort the applied field. If the liver is normal or anemic, the applied magnetic field will be reduced slightly. On the other hand if the liver is iron overloaded, as is in the case of patients suffering from Thalassemia, the local applied magnetic field will be enhanced. Hence, the change in the detected magnetic field measured with the SQUID will be directly related to the iron concentration of the organ under investigation.

Running title: SQUID, MEG, Thalassemia, Liver, Spleen, Heart.

1. Introduction

Time varying electric currents, in wires or brain cells, all produce time varying magnetic fields (1).

The detection and isolation of neuromagnetic signals was a challenging problem. Thus, these magnetic fields, which are very weak in order to be detected we need very sensitive and sophisticated devices. Such sophisticated devices are the ones which are based on the Josephson effect of superconductivity (2) and are called SQUID from the initials of the words (Supercoductive Quantum Interference Device).

The SQUID’s becomes superconducting when their sensors are immersed in liquid helium contained in a large dewar. The liquid helium cools the SQUID’s sensor to 40 Kelvin (-2690 C).The SQUID has the ability to detect magnetic fields of the order of 10-15 T (fT).The signal measured by the SQUID is a time varying voltage waveform that reflects local changes in the magnetic flux as a function of time. The higher the concentration of living cells in the area under study, the higher the biomagnetic fields produced and recorded from it (3).

As a result the magnetic field measured with the SQUID is very useful technique for clinical use for

diagnostic purposes in epilepsy, Parkinson, Thalassemia and so on.(4).

2. Material and Methods

Magnetic recordings will be obtained from the liver or the spleen of the patients suffering from Thalassemia. On the first visit, the patient information including name, age, height and weight is taken. The depth and shape of the liver or spleen is measured by ultrasound and will be stored into the patient data base. The patient is positioned on a special wooden bed directly beneath to the SQUID detector and a weak magnetic field of the order of 0-20mT will be generated within the body tissue by an external magnet. When the under investigation organ is placed in the applied external magnetic field it will slightly distort the applied field measured by the SQUID. If the organ is normal or anemic, the field with the SQUID will be reduced slightly. If on the other hand the organ is iron overloaded, the measured field with the SQUID will be enhanced. Hence, the change in the detected magnetic field measured with the SQUID will be directly related to the iron concentration of the organ under investigation.

To minimize the body’s contribution to the distortion in the magnetic field a small bag of water is placed between the SQUID detector and the skin above the organ.

3. Results and Discussion

Since the susceptibility of the organ under investigation is close to that of the water in the bag, the resultant SQUID measurement will be essentially that of the magnetized organ, which is within a uniform diamagnetic environment, and the only change detected by the SQUID will be due to the organ itself.

For higher accuracy, our computer software removes any contribution from the tissues next to the organ under investigation (skin, bone, muscle, fat, etc.). This consideration gives the iron concentration of the organ alone for all kind of subjects.

All the above results are preliminary and need further investigations.

References:

(1) Anninos PA, Raman s. Derivation of a mathematical equation for the EEG and the general solution within the brain and in space. Int. J. of Theor.Phys.12,1-9(1975).

(2) Josepshon, B.D. Possible effects in superconductive tunneling. Physics Letters,1,252-256(1962).

(3) Anastasiadis P, Anninos Ph, Sivridis E. Biomagnetic activity in breast lesions. The Breast 3,177(1994).

(4) Anninos PA, Anogianakis G, Lehnertz G, Pantev CH, Hoke M.Biomagnetic measurements using SQUID. Int. J. of Neurosci. 37, 149 (1987).