FP7 FMTXCT ProjectUMCE-HGUGM first year activity report

Partner FIHGM

Laboratorio de Imagen Médica. Medicina ExperimentalHospital Universitario Gregorio Marañón, Madrid

Workpackage 2: XCT development

Workpackage 8: FMT-XCT imaging accuracy versus PET-XCT

Workpackage 2: XCT development

Use of X-ray contrast agents

Double exposure techniques

Dual energy X-ray source

CT System OutlineMechanical Design

Multi-Energy data acquisition/processingNew Tube Features

Voltage setting range 40 to 110 kV

Current setting range 10 to 800 μA

Output window Beryllium (thickness 500 μm)

Focal spot size 15 μm (6 W) – 80 μm (50 W)

Emission angle 62 deg (max)

Power 50 W

Detector Dynamic Range Expansion

Dual-Exposure technique

Main features

• Two datasets acquired

• First

• Low SNR for dense materials

• Detector not saturated for soft materials

• Second

• High SNR for dense materials

• Detector saturated for soft materials

• Same X-ray beam spectral properties

• Different photon flux

Detector Dynamic Range Expansion

Dual-Exposure technique

Dataset #1 Dataset #2

Detector Dynamic Range Expansion

Dual-Exposure technique (work in progress)

Dual exposure

CNR (PTFE/Air) = 22.11

Single exposure

CNR (PTFE/Air) = 13.91

0 50 100 1500

1

2

3

4

5

6

7x 10

4

keV

Pho

ton

Out

put

Predicted Spectrum with and without added filtration

100kVp with 0.5mm Be Inherent filtration

Added Filtration: 2mm Al, 0.75mmCu

0 50 100 1500

1

2

3

4

5

6

7x 10

4

keV

Pho

ton

Out

put

Predicted Spectrum with and without added filtration

100kVp with 0.5mm Be Inherent filtration

Added Filtration: 2mm Al, 0.1mmCu

Mean Energy = 55.6 kV Mean Energy = 66.1 kV

Multi-Energy data acquisition/processingSimulated Spectra for the new tube

• Changing filter setting

Spectral simulations carried out using SPEKTR software librariesSiewerdsen, et.al., “Spektr: A computational tool for x-ray spectral analysis and imaging system optimization”, Med. Phys.31(9), 2004

0 50 100 1500

1

2

3

4

5

6

7x 10

4

keV

Pho

ton

Out

put

Predicted Spectrum with and without added filtration

100kVp with 0.5mm Be Inherent filtration

Added Filtration: 2mm Al, 0.1mmCu

Mean Energy = 34.9 kV Mean Energy = 66.1 kV

Multi-Energy data acquisition/processingSimulated Spectra for the new tube

• Changing X-ray tube setting

0 50 100 1500

0.5

1

1.5

2

2.5

3x 10

4

keV

Pho

ton

Out

put

Predicted Spectrum with and without added filtration

60kVp with 0.5mm Be Inherent filtration

Added Filtration: 2mm Al, 0.1mmCu

Fenestra Iopamiro

Use of X-ray contrast agents

Mouse

200 µA, voltage 50 kV

200 µm

Fenestra LC

Mouse

200 µA, voltage 50 kV

200 µm

Iopamiro

Mouse

200 µA, voltage 50 kV

200 µm

Iopamiro

Dynamic study

Workpackage 8: FMT-XCT imaging accuracy versus PET-XCT

Materials selection for the optical phantom construction

Water

Gelatin

Silicon Ti02 Pro Jet

Polyester resin India ink

Lipid emulsions

(Intralipid)

Polymer microspheres

Bulk materials Scatterers Absorbers

+ +

Things to have in mind when designing a FMT phantom.

Resolution is depth dependent

Diffusion approximation: One photon mean free path ≈ 1mm

SourceDetector

Source

Things to have in mind when designing a FMT phantom.

Heterogeneities, surface

Phantom design

Heterogeneities

4 mm

Fluorescent spheres, 2 mm

(Should their size vary?)

FMT-XCT

How to insert the fluorophore in the phantom?

Resin vs Silicon

- Mix the fluorophore with the bulk material*

- Capillaries (diffusive-non diffusive interfaces)

- Pellets

* John Baeten et al “Development of fluorescent materials for Diffuse Fluorescence Tomography standars and phantoms” Optics express vol 15 2007

What to measure

Resolution. FWHM of point-like source?

Quantification accuracy

Sensitivity: In-vivo specific application

PET phantom remarks

Will the imaging performance hold in the “many body imaging situation”?

PET phantom

PET phantom

PET phantom

Detector Dynamic Range Expansion

Dual-Exposure techniqueMain features

• X-ray tube current calculation for the second scan

• Based on Histogran processing

• Shift the histogram to place 75% of the total value into the High-Gain region

• Dataset combination

• Detector Model

• Image combination based on a Maximum-Likelihood calculation assuming Independent Gaussian distribution.

( ) j

iij ijx

AY N

e

- i : Acquisition number

- j : Pixel number

- A: Current value

- N: Noise value

FMT system

Resultados preliminares, maniquíes:

Agar based, TiO2 (scatter), Blank ink (absorption)

coronal Z=0.25 cm

Planar imaging