Mutual contribution by "track" microradioautography method (MRA) and secondary ion mass spectrometry (SIMS) microscopy: prospects in technetium dosimetry at-the cellular level.
The determination of cellular uptake sites of radioligands used for cell labelling for diagnostic purposes is an essential prerequisite for evaluating the radiation dose to the cell nucleus and cytoplasm. The distribution of 99mTc-HMPAO in labelled leukocytes was studied by two microscopic imaging techniques on the same biological material: the "track" microradioautographic method (MRA) and Secondary Ion Mass Spectrometry (SIMS) microscopy. The "track" method used internal conversion electrons of 99mTc, leading to the formation of silver grains in a thick layer nuclear emulsion deposited onto cellular smear. In order to improve the specificity of the "track" detection, a minimum of 5 consecutive silver grains was required. In SIMS Microscopy, mapping with 99Tc "daughter" nuclide of 99mTc (half-life: 2.13.10(5) years) was obtained after sputtering of superficial molecular layers on embedded specimen sections. A mass resolution of about 5,000 was needed to circumvent polyatomic ion interferences. Both methods were able to demonstrate a very heterogeneous distribution of technetium from one cell to another. The sensitivity and signal/noise ratios were excellent for both methods. The lateral resolution of SIMS microscopy (0.5 microns) was far better than that of MRA. Therefore, only SIMS is able to distinguish between nuclear and cytoplasmic localization. On the other hand, quantification was not achieved for SIMS, although semi-quantification is possible with MRA. The field of view of MRA is far larger, allowing a better statistical approach for quantification. Both methods appear to be complementary to determine the distribution of technetium at the cell level. MRA is simpler and better fitted to the study of a cell population or a tissue. The unique spatial resolution of SIMS allows to focus the study on subcellular structures.
Fourré
C
C
Equipe de Microscopie Ionique INSERM (Dr. Philippe Fragu), Institut Gustave Roussy, Villejuif, France.
Petiet
A
A
Colas-Linhart
N
N
D001345:Autoradiography / Q000191:economics / Q000379:methods*; D002451:Cell Compartmentation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007962:Leukocytes; D015609:Organotechnetium Compounds / Q000378:metabolism; D010091:Oximes / Q000378:metabolism; D011834:Radiation Monitoring / Q000191:economics / Q000379:methods*; D012680:Sensitivity and Specificity; D018629:Spectrometry, Mass, Secondary Ion; D013667:Technetium / Q000302:isolation & purification*; D019690:Technetium Tc 99m Exametazime
D015609:Organotechnetium Compounds; D010091:Oximes; D019690:Technetium Tc 99m Exametazime; D013667:Technetium