noninvasive in vivo measurement of pb with a portable xrf device
Post on 24-Feb-2016
67 Views
Preview:
DESCRIPTION
TRANSCRIPT
Noninvasive In Vivo Measurement of Pb with a Portable XRF
DeviceLinda Nie, Assistant Professor
School of Health SciencesPurdue University
Why portable x-ray fluorescence technology
Approach Results and discussion More work in progress Acknowledgements
Outline
Portable Multi-metals Fast More sensitive in some cases
Accessible, suitable for large population human studies
Why Portable XRF?
Soft tissue attenuationIt is difficult to detect signals
through tissue over 5 mm Soft tissue attenuation correction
◦Spectrum to determine the soft tissue thickness
Bone surface/volumn? (mfp in bone: 0.5 mm vs. 25 mm)
Bone Pb Quantification with Portable XRF- Disadvantage
Schematic plot
Overall: develop a portable XRF technology to quantify multiple metals in bone and skin
Hardware designselection of tube target, filter combination, and geometry design; selection of parameters
Methodology and algorithm development Consider in vivo situation Radiation risk assessment
Objectives
Monte Carlo simulations (MCNP) X-ray tube voltage, current, filter combinations;
x-ray tube target, geometry design etc.
Calculate minimum detection limit (MDL)
Approach - Hardware
2 bnMDL ct
( )m
t b
C ppmc
n n
Approach – calibration
2-A(2)( ) = A(1) exp(- ) (4) exp( (5) )A(3)xy x A A x
222
1 ( )i ii
X y y x
Once the hardware design is determined ……
Method #1: peak fitting and traditional cal.
Method #2: background subtraction
Calibration – Cont.
21 1 1( ) = K bkg A c B c C
22 2 2(100 ) = K ppm A c B c C
21 1 1( ) = ( ) ( )K net K total A c B c C
= ( ) 100 / (100 )Concentration K net K ppm
K ( ) ( )2 concentrationlive time =
( )
total K bkg
K net
Soft Tissue Thickness Determination
MC simulation
Experiments
Dosimetry
Phantom, goat bone, and cadaver bone experiments◦ICP-MS, KXRF
Human studies
Validation of the Technology
Lucite Thickness (mm)
Detection Limit (ppm)
0 2.31 4.12.04 7.13.08 11.84.08 18.64.92 25.9
Detection limit
Phantom Concentration
(ppm)
Portable XRF (ppm) KXRF (ppm) ICPMS (ppm)
0mm Lucite 1mm Lucite 2.72mm Lucite
0 -1.05±1.73 0.72±2.30 0.62±7.26 -.068±1.96 0.63±0.20
10 11.3±1.83 12.8±3.07 9.81±7.09 8.97±1.81 11.2±0.71
20 17.2±1.90 17.3±3.15 20.2±7.16 19.6±1.91 16.7±1.89
30 31.3±2.09 29.3±3.30 26.6±7.34 30.6±1.84 36.0±0.89
50 45.4±2.24 45.0±3.49 40.0±7.59 51.8±1.77 72.5±11.7
100 99.9±2.72 96.0±3.96 100±8.16 106±2.16 127±16.0
Bone lead concentration of phantoms using portable XRF, conventional XRF, and ICPMS
Goat Bone # Portable XRF (ppm) KXRF (ppm)0mm Lucite 1mm Lucite 2mm Lucite
1 19.7±1.95 15.4±3.05 22.2±5.31 23.5±1.649 2.73±2.23 0.84±2.72 6.33±5.30 4.5±1.4012 29.9±2.00 32.3±3.17 30.5±5.32 31.5±1.7513 13.6±1.79 15.6±2.91 19.1±5.06 12.3±1.49
Comparison of portable XRF and KXRF bone lead measurements for goat bones
(adjusted for Compton peak counts)
LXRF vs. KXRF for goat bones
0 5 10 15 20 25 30 35-5
0
5
10
15
20
25
30
35
40
KXRFBare LXRF2mm LXRF
Concentration From KXRF (ppm)
Mea
sure
d Co
ncen
trat
ion
from
por
tabl
e XR
F (p
pm)
Bone KXRF LXRF (0mm) ICPMS ICPMS ICPMS
7202 21.37 1.51E+01
6895 13.17 1.03E+01
6900 22.63 1.30E+01 1.16E+01 9.87E+00 1.13E+01
6918 18.78 1.16E+01
7002 16.56 9.93E+00
7031 20.33 1.10E+01
7131 20.59 1.41E+01 1.23E+01 1.81E+01 1.40E+01
7142 15.72 7.39E+00 9.73E+00 8.03E+00 5.74E+00
7162 18.30 8.45E+00 8.47E+00 8.45E+00 6.82E+00
7168 6.90 3.04E+00 2.28E+00 1.50E+00 2.88E+00
Cadaver bone results
Overestimate backgroundSolution: a. ‘real’ bone phantoms; b. adjustment using MC simulation results;Surface bone? Pb distribution in bone.
Validation: KXRF vs. Portable XRF
Radiation Risk Skin dose of ~13 mSv and total body
effective dose of 1.5µSv compared with
Exposure limit of 500 mSv per year to extremities for occupational workers (no limit set for general public) and a typical whole body effective dose of 100 µSv for chest x-ray
System optimization – customized device Standardize the calibration process (true
bone equivalent phantoms, or MC simulations to adjust for differences)
Validation of the technology with a large human population
Apply the technology for metal epi and metal toxicology study
Bone Sr measurement
More work in progress
X-ray tube output simulation
In vivo simulation
Steven Sanchez, Graduate Student, School of Health Sciences, Purdue University
Aaron Specht, Graduate Student, School of Health Sciences, Purdue University
Dr. Lee Grodzins, ThermoFisher Niton
Dr. Marc Weisskopf, HSPH
Acknowledgement
Thank you!Questions??
Cadaver Bone Spectrum
Portable XRF Cadaver Measurement,Pb concentration ~20ppm
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
500
1000
1500
2000
2500
3000
Goat BonePlaster
Lucite thickness (mm)
Com
pton
pea
k co
unrs
(/s)
Pilot studies – Methodology and Feasibility
ThermoFisher Niton: XL3t-GOLDD
1. 100 lbs vs. 3 lbs2. 30 mins vs. 2 min3. Multi-metals
Bone Pb Measurement Quantification with Portable XRF - Advantages
top related