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