Quantification of superparamagnetic iron oxide (SPIO)-labeled cells using MRI.
OBJECTIVE
To show the feasibility of using magnetic resonance imaging (MRI) to quantify superparamagnetic iron oxide (SPIO)-labeled cells.


METHODS
Lymphocytes and 9L rat gliosarcoma cells were labeled with ferumoxides-protamine sulfate complex (FE-PRO). The cells were labeled efficiently (more than 95%) and the iron concentration inside each cell was measured by spectrophotometry (4.77-30.21 pg). Phantom tubes containing different numbers of labeled or unlabeled cells, as well as different concentrations of FE-PRO, were made. In addition, labeled and unlabeled cells were injected into fresh and fixed rat brains.


RESULTS
Cellular viability and proliferation of labeled and unlabeled cells were shown to be similar. T2-weighted images were acquired using 7T and 3T MRI systems, and R2 maps of the tubes containing cells, free FE-PRO, and brains were made. There was a strong linear correlation between R2 values and labeled cell numbers, but the regression lines were different for the lymphocytes and gliosarcoma cells. Similarly, there was strong correlation between R2 values and free iron. However, free iron had higher R2 values than the labeled cells for the same concentration of iron.


CONCLUSIONS
Our data indicate that in vivo quantification of labeled cells can be done by careful consideration of different factors and specific control groups.
Rad
Ali M
AM
Department of Radiology, Henry Ford Health System, Detroit, Michigan 48202, USA.
Arbab
Ali S
AS
Iskander
A S M
AS
Jiang
Quan
Q
Soltanian-Zadeh
Hamid
H
D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D003287:Contrast Media / Q000494:pharmacology; D003911:Dextrans; D005290:Ferric Compounds / Q000378:metabolism / Q000494:pharmacology*; D052203:Ferrosoferric Oxide; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000494:pharmacology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D010087:Oxides / Q000494:pharmacology; D019047:Phantoms, Imaging; D011479:Protamines / Q000494:pharmacology; D051381:Rats; D013053:Spectrophotometry
D003287:Contrast Media; D003911:Dextrans; D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; D010087:Oxides; D011479:Protamines; C000499:ferric oxide; D007501:Iron; C065507:ferumoxides; D052203:Ferrosoferric Oxide