Gadolinium (Gd) is commonly used in contrast agents (GBCAs) to improve magnetic resonance imaging. GBCAs improve tumor imaging and were
thought to be stable and clear from the body through excretion after administration. However, they have been found to dissociate and remain in organs
such as the liver and kidneys. In these studies, a non-invasive Cd-109 based
K x-ray fluorescence (K-XRF) “Clover-Leaf” detection system to study liver
and kidney Gd levels was investigated to improve the minimum detection
limit (MDL). Two Cd-109 sources, one with a relatively low activity of 0.78
GBq and a second high activity source of 5 GBq irradiated a human torso
water phantom containing liver and kidney phantoms with Gd concentrations ranging from 0-100 ppm. The MDL was calculated from two different
time measurements 5 hours (weak source) and 30 minutes (strong source).
In addition, liver and kidney phantom measurements with overlaying tissue
thicknesses from 6-26 mm were investigated. At present, the K-XRF detection system is able to detect the Gd in each phantom with both sources.
The MDL for the liver and kidney with the weaker source is 2.95 ppm and
3.60 ppm, respectively. The MDL for the stronger source is 3.61 ppm and
3.87 ppm, respectively. The overlaying tissue thickness MDLs decreased exponentially since the thickness increased which increases the scattering and
attenuation. Simulations with MCNP successfully modelled the experiments.
MCNP simulations of the kidney with varying Gd concentrations in the cortex and medulla suggest that the XRF measurement is not sensitive to the
Gd distribution in the phantom. To conclude, this detection system can
measure Gd in liver and kidney phantoms and has low MDLs. Future work
should focus on varying the detection capabilities, measuring the effects to
the organs at risk, possible clinical trials, and improving the MCNP model
and peak extraction. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25894 |
| Date | January 2020 |
| Creators | Cyr, Mélodie |
| Contributors | Chettle, Dr. David, McNeill, Dr. Fiona, Radiation Sciences (Medical Physics/Radiation Biology) |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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