Production of ¹⁵³Sm-labelled microparticles and dosimetric studies for potiental application in liver radioembolization / Nurul Hashikin Ab. Aziz
Yttrium-90 (90Y)-microspheres have been increasingly used for transarterial radioembolization (TARE) of hepatocellular carcinoma (HCC). 90Y (a pure beta emitter) does not show sufficient post-procedural imaging capability. Samarium-153 (153Sm) may serve as a better alternative, due to its promisi...
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| Format: | Thesis |
| Published: |
2017
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| Online Access: | http://studentsrepo.um.edu.my/7584/ http://studentsrepo.um.edu.my/7584/7/hashikin.pdf |
| Summary: | Yttrium-90 (90Y)-microspheres have been increasingly used for transarterial
radioembolization (TARE) of hepatocellular carcinoma (HCC). 90Y (a pure beta emitter)
does not show sufficient post-procedural imaging capability. Samarium-153 (153Sm) may
serve as a better alternative, due to its promising theranostic (therapy and diagnostic)
characteristics. This thesis explored the production of 153Sm-microparticles and
dosimetric studies for its application in TARE of HCC. A pilot study was performed to
determine the suitable microparticle (diameter: 20-40µm) to be labelled with 153Sm. Two
commercially available ion-exchange resins; Fractogel® EMD SO3
-
and Amberlite® IR-
120H+
, each was labelled with 1g of samarium chloride (
152SmCl3) in six different
formulations and sent for neutron activation in the TRIGA PUSPATI research reactor.
Radionuclide purity of these microparticles were tested via gamma spectrometry, and the
optimum formulation for each microparticle was determined following a 48h
radiolabelling efficiency study in distilled water and human blood plasma. Amberlite®
IR-120H+ was chosen, as it possesses excellent (99.9%) radiolabelling efficiency and did
not produced any radionuclide impurity following neutron activation. Physicochemical
properties of the chosen microparticle before and after neutron activation was further
investigated. Fourier transform infrared (FTIR) spectroscopy showed its unaffected
functional group throughout the preparation processes. Energy dispersive x-ray (EDX)
spectroscopy confirmed the absence of radionuclide impurity. The microparticles possess
irregular surface with increased fragments (<10µm) following neutron activation, as seen
via a field emission scanning electron microscope (FESEM). The measured particle
density was 2.5g.cm-3 with specific radioactivity of 54Bq per microparticle, and settling
velocity of 0.03cm.s-1
. Monte Carlo (MC) simulations were done using the Geometry and
Tracking 4 (Geant4) software toolkit, to study the dosimetric accuracy of the routinely
iv
used Medical Internal Radiation Dose (MIRD) based partition model (PM) for TARE
with 90Y-microspheres. It was found that PM markedly underestimated the normal liver
dose by up to -78%, due to exclusion of cross-fire irradiation between the tumour and
normal liver tissue. The model also overestimated both tumour and lung dose by up to 8
and 12%, respectively. These data can be used to recognise the cases with large dosimetric
inaccuracy when PM is being used. Also, a corrected formula for lung dose was suggested
for future used. Dosimetric assessment for TARE with 153Sm-microparticles was
performed using similar MC method. Various treatment scenarios were simulated by
targeting 120Gy to the tumour. The 153Sm-microparticles were able to deliver comparable
tumour dose with normal liver and lung dose close to that of 90Y-microspheres, and other
organ doses far below 1Gy. Finally, the simulations were repeated with other potential
radionuclides; holmium-166 (
166Ho), lutetium-177 (177Lu) and rhenium-188 (188Re), and
the doses were compared with 90Y and 153Sm. 153Sm-microparticles showed great
potential as alternative to 90Y with advantage of post-procedure imaging. It possesses
ideal characteristics including; stable for neutron activation, excellent radiolabelling
efficiency, absence of radionuclide impurities, stable in suspension, low production cost,
and ability to deliver comparable tumour dose, without exceeding the organ dose limit.
However, improvements should be made to its physical structure for better intraarterial
delivery to the tumour. |
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