Friday, May 18, 2007

Strange Effects of 7T

My very first MRI was in the 7 Tesla scanner here at the center, and I have to say it was a pretty scary experience. I've gotten used to it now, but the opening is very very small, and there are subjective effects of the high field - specifially I felt like I was curving around a bend when I was being put straight into the magnet. There's also some evidence for mild cognitive effects of the 7T field (see here) - I, for one, can attest to dizziness if I wave my head around in front of the magnet too much.

A decade-old study that I came across today finds evidence for another strange effect of the 7T field. Here is the entire abstract (click on title for link to PubMed):

1: Bioelectromagnetics. 1996;17(5):358-63. Links

Exposure to strong static magnetic field slows the growth of human cancer cells in vitro.

University of Michigan Medical Center, Department of Internal Medicine, Ann Arbor, USA.

Proposals to enhance the amount of radiation dose delivered to small tumors with radioimmunotherapy by constraining emitted electrons with very strong homogeneous static magnetic fields has renewed interest in the cellular effects of prolonged exposures to such fields. Past investigations have not studied the effects on tumor cell growth of lengthy exposures to very high magnetic fields. Three malignant human cell lines, HTB 63 (melanoma), HTB 77 IP3 (ovarian carcinoma), and CCL 86 (lymphoma: Raji cells), were exposed to a 7 Tesla uniform static magnetic field for 64 hours. Following exposure, the number of viable cells in each group was determined. In addition, multicycle flow cytometry was performed on all cell lines, and pulsed-field electrophoresis was performed solely on Raji cells to investigate changes in cell cycle patterns and the possibility of DNA fragmentation induced by the magnetic field. A 64 h exposure to the magnetic field produced a reduction in viable cell number in each of the three cell lines. Reductions of 19.04 +/- 7.32%, 22.06 +/- 6.19%, and 40.68 +/- 8.31% were measured for the melanoma, ovarian carcinoma, and lymphoma cell lines, respectively, vs. control groups not exposed to the magnetic field. Multicycle flow cytometry revealed that the cell cycle was largely unaltered. Pulsed-field electrophoresis analysis revealed no increase in DNA breaks related to magnetic field exposure. In conclusion, prolonged exposure to a very strong magnetic field appeared to inhibit the growth of three human tumor cell lines in vitro. The mechanism underlying this effect has not, as yet, been identified, although alteration of cell growth cycle and gross fragmentation of DNA have been excluded as possible contributory factors. Future investigations of this phenomenon may have a significant impact on the future understanding and treatment of cancer.

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