Magnetically-enhanced radionuclide therapy (MERiT): in vitro evaluation.
OBJECTIVE
Radionuclide therapy is a promising method for delivering radiation dose selectively to tumors. In situations where electron -emitters are used and the tumor is small relative to the maximum range of therapeutic electrons, these particles exit the tumor before delivering the maximum amounts of radiation dose. In this study, the method of magnetically constraining electrons to small tumors, known as magnetically -enhanced radionuclide therapy (MERiT), is explored using in vitro experiments.


METHODS
The potential utility of MERiT was investigated by first measuring the reduction of number of electrons exiting a small sphere containing 90Y embedded in a block of plastic scintillator. Measurements of total energy deposited in the plastic scintillator made inside and outside a 7 Tesla magnetic field were compared. Furthermore, an experiment utilizing lymphoma cells of human origin was performed. Groups of cells were added to wells containing 90Y-labeled bovine serum albumin (and control groups containing no radioactivity) were placed either inside a 7 Tesla magnet or at a position where the magnetic field was minimal (essentially zero) for 18 hr.


RESULTS
The presence of a 7 Tesla magnetic field reduced the amount of energy deposited in the scintillator by 16.63 +/- 1.05%. This demonstrates that the magnetic field constrains a large fraction of the emissions to the sphere and implies that normal tissues adjacent to radiotracer-avid tumors can be protected from radiation dose. Results from the cell culture experiment showed that the presence of a 7 Tesla magnetic field significantly (p < 0.005) reduced the number of viable cells remaining after treatment with non-specific 90Y-labeled bovine serum albumin by 11.7% compared to the appropriate control group (90Y treated, not exposed to magnetic field).


CONCLUSIONS
These initial physical and biological studies indicate that magnetically-enhanced radionuclide therapy can be effective in increasing radiation absorbed dose to small tumors, consequently reducing radiation dose to surrounding normal structures.
Raylman
R R
RR
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, USA. rraylman@wvuhsc1.hsc.wvu.edu
Clavo
A C
AC
Crawford
S C
SC
Recker
B
B
Wahl
R L
RL
D002470:Cell Survival; D006801:Humans; D008280:Magnetics / Q000627:therapeutic use*; D009010:Monte Carlo Method; D019275:Radiopharmaceuticals / Q000627:therapeutic use*; D012710:Serum Albumin, Bovine; D014407:Tumor Cells, Cultured; D015021:Yttrium Radioisotopes / Q000627:therapeutic use
D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes; D012710:Serum Albumin, Bovine