art and medicine_columbia_2013

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Novel Applications of High Frequency Radiations:

I) THz Radiation and Art, a new tool in the inspection of cultural heritage

II) Potential Use of GHz Radiation in Medicine

Columbia-Rice Frontier CMP Lecture

November 1st, 2013

Professor Javier Tejada.Dept. Física Fonamental, Universitat de Barcelona.

Part 1: Art Inspection - Finding Goya

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The Terahertz Frequency Band

K 47meV 4m 300ps 1cm 33THz 1 -1 ≈≈≈≈≈ µ

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Terahertz Features

๏ See-through Penetrates most materials

๏ Pinpoint measurement and imaging Excellent spatial resolution (sub-mm)

๏ Molecular fingerprint Spectroscopic identification

๏ Safety Non-ionizing radiation

๏ Non-contact Standoff emission/detection

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Terahertz Time-Domain Sources and Detectors

Sources

✓ Photoconductive Antennas (PCA)

✓ Optical Rectification

✓ Four-wave Mixing (Plasma)

✓ Surface Emitter (Photo-Dember)

✓ Tilted Wavefront (Cherenkov)

✓ Free-Electron Laser

Detectors

✓ Photoconductive Antennas

✓ Electro-Optical (EO) Sampling

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Generation and Detection of THz radiation

๏ A femto-second laser pulse generates carriers on the substrate

๏ Carriers are accelerated across the electrodes with a bias, generating a time varying photo-current

๏ The derivative of the photo-current generates the THz pulse

Photo-Conductive Antenna (PCA)

Electro-Optical Sampling (EO)

๏ Linear polarized probe goes through an Electro-Optic (EO) crystal

๏ Wollaston prism separates polarization perpendicular components, which are detected by individual photo-diodes in differential configuration

๏ The components of the polarization are different resulting in a net current proportional to the electric field of the THz wave

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Operation Modes

Time-domain Frequency-domain

๏ Non-destructive evaluation✓ Cracks, voids, and other structural defects

✓ Thickness and coatings measurement

✓ Corrosion inspection

๏ Spectroscopy✓ Pharmaceutical characterization and drug discovery

✓ Chemical and biological threat assessment

✓ Explosive detection

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Examples: Spectroscopy

Material characterization and identification (fingerprint) Spectroscopic imaging

๏ Many molecules show unique resonances in the THz range (fingerprint)

๏ Imaging can be combined with spectroscopy to identify materials in an image

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Frequency Dependent Resolution

300 GHz 1 THz

๏ A broadband system has many frequencies available

๏ Resolution will depend on selected frequency to generate image

๏ Higher frequencies show better resolution (shorter wavelength)

๏ In time-domain, resolution approximately corresponds to resolution of peak peak frequency

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Tera-Art

๏ THz has been explored to inspect:✓ Papyrus

✓ Mural paintings

✓ Pottery

Labaune, J., Jackson, J. B., Pagès-Camagna, S., Duling, I. N., Menu, M., & Mourou, G. A. (2010). Papyrus imaging with Terahertz time domain spectroscopy. Applied Physics A, 100(3), 607–612.

Jackson, J. B., Mourou, M., Whitaker, J. F., Duling, I. N., Williamson, S. L., Menu, M., & Mourou, G. A. (2008). Terahertz imaging for non-destructive evaluation of mural paintings. Optics Communications, 281(4), 527–532.

Caumes, J.-P., Younus, A., Salort, S., Chassagne, B., Recur, B., Ziéglé , A., et al. (2011). Terahertz tomographic imaging of XVIIIth Dynasty Egyptian sealed pottery. Applied Optics, 50(20), 3604–3608.

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Why Terahertz for Art Inspection

X-ray Infrared Terahertz

Strengths• Highest penetration• Highest resolution• Fast (cameras available)

• Excellent resolution• Fast (cameras available)• Non-hazardous

• Can penetrate deep into the sample (~mm)

• Sensitive to molecular composition

• Layer analysis• Non-hazardous

Weaknesses• Cannot discriminate

compounds with similar atomic weight

• Hazardous

• Only penetrates few um into the sample (no depth data)

• No layer structureSlow (single pixel acquisition)

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Sample Structure

๏ Varnish✓ Protects paint and gives glossy finishing

๏ Paint✓ Contains the actual image

๏ Drawing✓ Draft of the composition of the painting

๏ Primer

✓ Interface to allow paint to stick to canvas

๏ Canvas✓ Interwoven textile structure

Complex Structure!

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Setup

๏ Single pixel system -> raster scan is necessary to generate an image.

๏ Lens diameter and focal length is 1” (NA=1), low NA provide better spatial resolution.

๏ Scanning of the sample is performed by displacing it mechanically in the XY plane.

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Analysis

๏ Time-domain contains structure and spectroscopic data

๏ Multiple image analysis mode

✓ Amplitude (time-domain and frequency-domain)

✓ Peak position

✓ Spectroscopic identification

๏ Layer analysis

✓ Roughness

✓ Curvature

✓ Tomography

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Data Acquisition Considerations

๏ Size is 33x24 cm Data file is too large to be handled by the

computer

๏ Tiling Break up sample in different sections so

data files are manageable

๏ Stitching Analyze each tile separately and stitch

final results

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Painting in X-rays

Goya, “Sacrifice to Vesta” (1771)

X-rays do not show much information about potential damage or hidden information

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Finding Goya

Seco-Martorell, C., López-Domínguez, V., Arauz-Garofalo, G., Redo-Sanchez, A., Palacios, J., & Tejada, J. (2013). Goya ’s artwork imaging with Terahertz waves. Optics Express, 21(15), 17800.

THz image show more structural information than another inspection technique.

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Goya’s signature

Appearance of feature with strong resemblance with the artist’s signature!!

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Conclusions

๏ THz image provides structural data complementary to other techniques

๏ Feature (signature) not seen in X-rays or optical was detected

๏ Spectroscopy imaging is challenging✓ Layered structure generate many reflections

✓ Multiple reflections reduce usable window for Fourier Transform

✓ Library needs to be built

๏ Need of more sophisticated data analysis methods to deal with complex layer structure

Microwave Spectrometry to Study the Ageing of Coronary Stents: Fracture, Recoil and Restenosis

Part 2 - Potential Use of GHz Radiation in Medicine

INTRODUCTION – CORONARY STENTS: PAST, PRESENT & FUTURE

Introduction Experimental method Results Discussion Conclusions

Angioplasty

Atherosclerosis

Stenting

Restenosis

In-stent restenosis


(X2) Right-handed circularly-polarized cavity-backed spiral antennas (1.0 - 20.0 GHz).Model JXTXLX-20180, Chengdu A-info.

(X1) 2-port vector network analyzer.Model HP 8510C model, Agilent Technologies.

(X1) Steeper motor (sample holder)Model ST2818M1006-B, Nanotec.

Stimulate the development of new non-invasive and non-ionizing intensive follow-up techniques able to improve the quality of life

of stented patients.

X-Ray → Microwave

Microwave Spectrometry (MWS)


MWS (Data Acquisition)

(1st) Reference measurement

(2nd) Sample positioning

(3rd) Sample measurement

(4th) Absorbance calculation


Medtronic Integrity bare-metal stent. P = 22.0 atm, ϕnom = 2.50 mm, ℓnom = 26.00 mm

MWS (Stent Characterization)

A(f) with discreteresonant fn frequencies

f1, f2, f3…

A(φ) with characteristic2n-lobular patterns

2-lobular, 4-lobular, 6-lobular…

A(φ) patterns closely resemble gain patterns of a center-feed

half-wave dipole antenna…


In terms of microwave scattering metallic stents behave akin of dipole antennas of

length L = aℓ, where a is a scaling factor that would give a hint about the folding degree of

a particular stent architecture

Drug-eluting stents of different nominal lengths and diameters, each one expanded up to its nominal inflation pressure using its corresponding delivery system.

Center-feed Half-wave Dipole Antenna Model

Fracture Tests


Medtronic Driver Sprint. P = Pnom = 9.0 atm, ϕnom = 2.75 mm, ℓnom = 24.00 mm

M. JAff, M. DAKE, J. POMPA, G. ANSEL, AND T. YODER. Catheterization and Cardiovascular Interventions (2007)Standardized evaluation and reporting of stent fractures in clinical trials of noncoronary devices.

Type I & II fractures:Downshift of f1.

● A qualitative inspection of A(f, φ) denotes signs of Type I

& II fractures.

Fracture Tests



Type III & IV fractures:Split of f1 resonance of the unaltered stent (or stent segment) in two new f1 at

higher frequencies, one for each emerging segment.

•A qualitative inspection of A(f, φ) denotes signs of Type

III & IV fractures.

• Rough quantitative assessment of the length of each emerging segment by

measuring each f1 appeared in the A(f, φ).

Fracture Tests



RECOIL TESTIntroduction Experimental method Results Discussion Conclusions

Let’s define the Recoil Degree as…

Medtronic Integrity bare-metal stent. ϕnom = 2.75 mm, ℓnom = 26.00 mm, expanded using its corresponding delivery system up to p = 14.0 atm.

Recoil process:Reduction of the stent diameter executed by stages and achieved by means of mechanical methods.

Recoil Test

( )mr

Mr

rmr

rrφφφφφ

−−=

RECOIL TESTIntroduction Experimental method Results Discussion Conclusions

Let’s define the Recoil Degree as…

Recoil Test

( )mr

Mr

rmr

rrφφφφφ

−−=

FRACTURE AND RECOIL TESTS SUMMARYIntroduction Experimental method Results Discussion Conclusions

FRACTURE TEST A simple stent fracture appears in A(f,φ) as the disappearance of the characteristic f1 and f2 modes of the unaltered stent, and the appearance of two new f1 modes of higher frequency.

A quantitative assessment of the fracture point is possible since, these two new f1 are linked to the lengths of the resulting two segments via:

Said determination would be double since an independent calculation of ℓ(fn) would be obtained from each new f1 corresponding to each segment.

RECOIL TEST An homogeneous stent recoil appears in A(f,φ) as the shift up of all fn. This is because narrowings of ϕr involves slight shortenings of ℓr.

A quantitative assessment of the recoil degree is possible with a previous knowledge of the ϕr(ℓr) dependence of the stent and:

An independent determination would be obtained from each new fn monitored.

Fracture and recoil tests summary

( )mr

Mr

rmr

rrφφφφφ

−−=

RESTENOSIS TEST (UNDER DEVELOPMENT)Introduction Experimental method Results Discussion Conclusions

Bare-metal stent (ϕ = 2.50 mm and ℓ = 8.00 mm) expanded up to p = 9.0 atm using its corresponding delivery system.

Restenosis process:Artificial cholesterol-based restenosis performed over the entire length and diameter of the stent. The amount of cholesterol applied is of tens of mg.

Restenosis test (under development)

IN VITRO & IN VIVO FREQUENCY BAND Introduction Experimental method Results Discussion Conclusions

Due to the 1/√εµ factor, the in vitro resonant frequencies of

stents will shift down with respect to the in vivo frequencies.

δ(f) is found to be of severaltens of millimeters for in vivo

operating frequencies

In-vivo and in-vitro frequency band

IN VITRO & IN VIVO FREQUENCY BAND Introduction Experimental method Results Discussion Conclusions

In-vivo and in-vitro frequency band

Water-based phantom tests


Medtronic Integrity Driver Sprint bare-metal stent. P = Pnom = 9.0 atm, ϕnom = 4.50 mm, ℓnom = 24.00 mm ℓnom = 30.00 mm

Airεr ≈ 1 - μr ≈ 1

Water(0.1 - 1.0 GHz)ε'r ≈ 78 - μ'r ≈ 1

f ’1 measured using our phantom are compatible with

theoretical f ’1 values.


A simple stent fracture is detectable by MWS. A simple stent recoil is detectable by MWS. An artificial restenosis process is detectable by MWS.

Characterization of stents within biological tissue

mimics are under development.

Metallic stents of a given nominal size exhibit characteristic fn in their open air microwave scattering spectra.

Further experiments will include ex vivo and in

vivo trials in animal models.

Conclusions

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