Testicular Dosimetry Custom Essay
Project aim and achievement
The main objective of the project is to improve the dosimetry of testes during RNT through enhancements and use of small-scale dosimetry techniques that take into consideration the localization and distribution of radionuclide in testes tissues. This is in order to correlate dose or dose distributions to testes tissues with the testicular toxicity. To test these hypotheses,
1- A small-scale dosimetry model has been developed (see the reference Erik_Suaad among the refrences I uplowded ). The Monte Carlo code(MCNP5 1.4) together with the testes geometry was used to generate S-values for different source target regions in the Seminiferous tubules within the testes. The S-values were calculated for electron, photons and some radionuclides.
The results shows that the absorbed dose to spermatogonia (loops 3 in Figure 1) is highly dependent on the bio distribution and emission characteristics of the radionuclide within the testis and comparing to the traditionally used mean absorbed dose to the testes, the absorbed dose to Spermatogonia can be either underestimated or overestimated depending on the radionuclides used
On going and future work.
2- The absorbed dose per administered activity (mGy/MBq) of 111In/90Y- zevalin to the highly radiosensitive spermatogonia cells (layer 3 in Figure 1) in the testes of the non hodgkin’s lymphoma patient underwent RIT. We are using the testicular dosimetry model and assuming that the different fractions of the activity (1 (or 100% of the activity in the testis ) , 2/3 and 1/3) fraction of the activity are located in different sources layer in the seminiferous tubules.
In this work we also developed our testicular model more in a way we could get an estimation of the uncertainty of the model and this work could then acts as a template as how to use these small-scale dosimetry models.
3- The thired work we are doing ( I have preliminary results) to assess localized doses of 111In-chlorid and 111In-Rituximab in the testes tissue using mice specimens. A digital (Bio-Molex 700) and film (phosphor plate and nuclear emulsion film) autoradiography system as well as nSPECT used to defining the activity distributions in testes tissues. This system will be used to assess the fractional activity distribution in human testes models. Finally, the true absorbed dose to different layer in the seminiferous tubules in the human testes will be calculated (this will be only manuscript in my dissertation book)
4- Radiopharmaceuticals are generally distributed non uniformly in tissue. At the microscopic level, only a fraction of the cells in tissue are labeled. Consequently, the labeled cells receive an absorbed dose from radioactivity within the cell (self-dose) as well as an absorbed dose from radioactivity in surrounding cells (cross-dose). On the other hand, unlabeled cells only receive a cross-dose. This work uses a novel approach to examine the lethal effects of microscopic nonuniformities of 111In-chloriode distribution in the testes tissue on the cells. We used ɣ-H2AX antibodies to define the site of damages. Where DSB creation in cells is generally acompanied by the formation of hundreds of histone ɣ-H2AX molecules in the chromatin flanking the DSB site. Antibodies to ɣ-H2AX allow the visualization of a �?œfocus�? or Fuci at the DSB site. We are working now on quantification of the immunoreacted cells in the seminiferious tubule and will do quantification of fuci in these cells finaly will relate it to the radiobiological consequences
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