Imaging Molecolare con radionuclidi: un potente mezzo di indagine di processi biologici in vivoF. Garibaldi - Fisica e tecnologie Nucleari per la Salute - Dipartimento TESA

Roma 08/06/06

- perche’ imaging molecolare con radionuclidi

- come

- SPECT/PET/Compton camera

- tecniche di collimazione

- qualche esempio- applicazioni cliniche

- cancro della mammella

- cancro della prostata

- piccoli animali- rivelazione di placche aterosclerotiche vulnerabili

- monintoring della diffusione di cellule staminali

X-ray mammography,the most sensitive method

but

- it shows lesions, not cancers

-15-30% positive predictive value

biopsy

- invasiveness (proportional to the risk of missing the cancer) - expensive - ansiety - false positive (problems in successive mammographyc controls) - false negative (medical problem great, delay in operation)

Diagnosi del cancro della mammella

γ Imaging: Single Photon Detector Module

Patient injected with radioactive drug. Drug localizes according to its metabolic properties.Gamma rays, emitted by radioactive decay, that exit the patient are imaged.

1.CollimatorOnly gammas that are perpendicular to imaging plane reach the detector

2.ScintillatorConvert gammas to visible light

3.Photomultiplier Convert light to electrical signal

4.Readout ElectronicsAmplify electrical signal and interface to computer

5.Computer decoding procedureElaborate signal and gives image output

Le tecniche

Single

Photon

Emission

Computed

Tomography

Positron

Emission

Tomography

140 keV

ris. sp. ed efficienza “tipiche” (vedi)

Ris. Sp

Eff.

Ris. Sp

Eff.

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Complementary non invasive Complementary non invasive “specific”“specific” technique technique is neededis needed

Nuclear medicine:

- uptake of single radiotracer

- when the uptake due to a specific function of the tumor

or to a function specifically enhanced in the

cancer, specific tumor imaging can take place

Emission (Computed Tomography) (SPECT)

Positron Emission Tomography (PET)

10 -15 cmObject – collimator distance

ANGER CAMERA

OCD (cm )

Spatial resolution in PSMFrom: J.A.Sorenson and m:e:Phelps “Physics in Nuclesr Medicine” Grune & Strattom

Necessita’ di compressione

Molecular imaging: high resolution detectors for early diagnosis and therapy monitoring of breast cancer (ISS, University of Rome2 and Napoli) (Project funded by Ministry of Health)

Preparation of clinical trials at Dipartimento di Diagnostica per Immagini. University of Tor Vergata

dual head detector 100 x 100

mm2

150 x 200 mm2

foto Tor Vergata con “spot compression”

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Dual detector configurationS. Majewski et al.

Combining the images taken by two detectors, an increase of lesion contrast is obtainedLesions are not seen by the detector on the other side of the lesion. Combining the images both lesions are visible

Lesions in the middle of the breast are seen barely seen by both detectors.

Fusion: contrast increased

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NaI(Tl) 1.2 pitch

H9500 (3x3 mm2)

tum 8 mm

tumors: (5, 6, 7, 8,9,10,12)

uptake 1:10; breast 6 cm

NaI(Tl) 1.5 pitch; H8500 (6x6 mm2)

NaI(Tl) 1.3 pitch; H8500(6x6 mm2)

6 mm

7 mm

8 mm

SNR vs tumor dimension(10:1-breast 6cm-NaI 1.0-H8500(6x6mm2)

0

2

4

6

8

10

12

14

16

18

20

4 5 6 7 8 9 10 11 12 13

t(mm)

SNR HX (H9500)

measurements confirm simulation

smaller scintillator pixel, higher SNR

anode pixel has to be small

measurements

but

6 mm tumors visible

First Preliminary Clinical Trials

Case 1: Positive Case 3: Positive

Small Head (top) Large Head (bottom)

Case 2: Negative

Small Head (top)

Small Head (top)

Improvements: “dual head” software implemented, better anode sampling (NaI(Tl) 1.2 mm pitch + H9500 (3 x 3 mm2 anode) + coded aperture collimation