MICRO-MAGNETOCARDIOGRAPHY SYSTEM WITH SQUID MAGNETOMETER ARRAY
RENJITH . E. R
S7 AEI
College of engineering , Trivandrum
2007-11 batch

Overview
Need for MCG
Materials
Development of SQUID Sensor
Noise cancelling system and its evaluation
Object table
Magnetically Shielded box and Cryostat
Total System

Method
In Vivo Measurement
Myocardial Injury
Drug induced QT Prolongation
Correlation between ECG and MCG


Human ECG setup
Mouse ECG setup
Magneto Cardiography
Biomagnetism
SQUIDs Baule and McFee
QT Analysis David Cohen : Magnetically shielded room
Arrhythmia James Zimmerman : SQUID


Josephson junction


DC Josephson Effect : direct current crossing from the insulator in the absence of any external electromagnetic field, owing to tunneling
AC Josephson Effect : With a fixed voltage across the junctions, the phase will vary linearly with time and the current will be an AC current with amplitude Ic and frequency 2e/h * UDC




SQUID
The basic components of a SQUID System
Development of SQUID Sensor
9 channel SQUID Micro magneto meter array
6 sectorial pick up loops connected in parallel to Josephson junction in each SQUID
FLL on PCB by flip chip interconnection technology










Noise canceling System
Evaluation of the Canceling System
Cancelling method in analog within the FLL circuit
Reference sensor : 2.2mm square pick-up loop ,Signal resolution 40fTHz^(1/2)
Effect of noise cancelling : 6dB in time domain ,10 dB and 16 dB at power line frequencies
Noise floor increased 10 dB due to white noise

Effect on Time and Frequency domain
Object Table
3–axis stage to ensure the reproducibility and reliability of the measurement system

A detachable plate to fix an object and was equipped with temperature control capability to stabilize the physical condition of the object

Magnetically Shielded Box and Cryostat
500mm×300mm×400mm
2 layered magnetic shielding
Sensor at the center
Cryostat at center and FRP tube houses sensors inside the tube through a hole
Total System
In Vivo Measurement
Myocardial Injury
Drug-Induced QT Prolongation
Correlation Between ECG and MCG
Advantages & Challenges ahead

Capability of the newly developed MCG system for clear and real-time measurement of cardiac biomagnetism from small animals such as mice.

Possibility of differential diagnosis of posterior myocardial infarction from anterior myocardial infarction in rats, which is sometimes difficult to achieve by means of ECG

Magnetocardiography using a large magnetometer array would give a deep insight into current conduction in the heart of small animals

MCG measurement of the QT interval correlated well with ECG measurement.

No need to put electrodes on the tiny legs or chest of small animals when measuring MCGs


References
[1] D. Brisinda, A. M. Meloni, and R. Fenici, “Contactless magnetocardiographic study of ventricular repolarization in intactWistar rats: Evidence of gender-related differences,” Basic Res. Cardiol., vol. 99, no.3, pp. 193–203, 2004.
[2] Y. Ono and A. Ishiyama, “Non-invasive cardiac functional mapping of disease-model mice: Development of high spatial resolution SQUID system for MCG on mice,” J. Cryo. Soc. Jpn., vol. 40, no. 2, pp. 44–50,2005.
[3] R. Ackermann, F.Wiekhorst, A. Beck, D. Gutkelch, F. Ruede, A. Schnabel,U. Steinhoff, D. Drung, J. Beyer, C. Assmann, L. Trahms, H.Koch, T. Schurig, R. Fischer, M. Bader, H. Ogata, and H. Kado, “Multichannel SQUID system with integrated magnetic shielding for magnetocardiography of mice,” IEEE Trans. Appl. Supercond., vol. 17, no.2, pp. 827–830, 2007.
[4] International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use, ICH Harmonised Tripartite Guideline S7B: Nonclinical Evaluation of the Potential for Delayed Ventricular Repolarization (QT Interval Prolongation) by Human Pharmaceuticals, [Online]. Available:
http://ichcache/compo/276-254-1.html [Online]. Available:
http://fda.gov/CbER/gdlns/ichqt.htm

http://en.wikipediawiki/Magnetocardiography
http://en.wikipediawiki/Magnetometer
http://en.wikipediawiki/Biomagnetism
http://en.wikipediawiki/Josephson_effect
http://en.wikipediawiki/SQUID
http://freepatentsonline4004217.html