Physica Medica: European Journal of Medical Physics - Volume 32 - Supplement 1

Developments in Nuclear Medicine

C.329

IN VIVO SMALL ANIMALS BETA DETECTION: A MONTE CARLO FEASIBILITY

STUDY FROM BETA TO CERENKOV LUMINESCENCE IMAGING

L. Altabella

, C.R. Gigliotti, A.E. Spinelli.

Ospedale San Raffaele, Milano, Italy

Introduction:

In this work we investigate using Monte Carlo simulations

(MCs) the feasibility of beta imaging of small animals considering pros

and cons of different approaches for beta emitter imaging. In particular

the different approaches we considered are: Cerenkov luminescence imaging

(CLI), bremsstrahlung (BREM) and direct (DB) and indirect beta (IB) de-

tection. The use of Cerenkov radiator (RAD) to enhance the CLI detected

signal has been also studied. DB and IB detection are based on direct

interaction with the detector or on conversion into light by means of a

scintillator.

Materials and Methods:

MCs were implemented using GAMOS, a plug-

in for GEANT4 validated for Cerenkov and optical processes. We considered

a slab of mouse muscle and a radioactive source (32P or 90Y) at 0.5 mm

depth. For IB a 0.2 mm CsI(Tl) scintillator was superimposed to slab. For

RAD several materials have been simulated to find the optimal one.

Results:

BREM has the worst efficiency and spatial resolution. CLI guar-

anteed an efficiency 8–9 times greater than DB with the same spatial

resolution (FWHM

0.79 mm for both radionuclides). 1 mm of RAD with

high refractive index and low density does not allow to obtain an improve-

ment in efficiency and causes a degradation in spatial resolution

(FWHM

1.74 mm for 32P, 2.36 mm for 90Y). With SCINT we obtain the

best efficiency (10^4 times greater than beta) with a loss in spatial reso-

lution (FWHM

1.70 mm for 32P, 1.81 mm for 90Y).

Conclusions:

BREM and RAD do not represent the best choice in small

animal imaging. The use of thin SCINT increases signal without strongly

affecting spatial resolution. DB presents a good spatial resolution but the

total number of collected particles is small. CLI is a good alternative to DB

and SCINT and it allows larger FOV using standard optical imaging systems

with respect to beta detection. Finally CLI is a flexible approach for in vivo

beta emitter imaging.

http://dx.doi.org/10.1016/j.ejmp.2016.01.335

C.330

RADIOBIOLOGICAL ALPHA PARAMETER ESTIMATE FOR A PERSONALIZED

90Y MICROSPHERE TREATMENT OF HEPATO- AND CHOLANGIO-

CARCINOMA

C. Avigo

* , a ,

M. Piccinno

b ,

A. Traino

c .

Scuola di Specializzazione in Fisica

Medica, Università di Pisa, Pisa, Italy;

Dipartimento di Fisica E. Fermi,

Università di Pisa, Pisa, Italy;

U.O. Fisica Sanitaria, Azienda Ospedaliero-

Universitaria Pisana, Pisa, Italy

Introduction:

Several recent works on radionuclide therapy optimiza-

tion are focused on the personalized calculation of the activity to be

injected into the patient. Hepatic radioembolization is a procedure for

the treatment of hepatic lesions that involves an activity administration,

through an intra-arterial injection of biocompatible microspheres 90Y

loaded. In order to increase the treatment efficacy, the optimization of

the activity calculation is crucial. For this reason the radiobiological α

parameter of the linear-quadratic (LQ) model, that is the radiobiological

reference model, has been estimated for hepato-carcinoma (HCC) and

cholangio-carcinoma (CCC).

Material and Methods:

In order to estimate α, a group of 16 patients (2

CCC and 14 HCC) was followed after the treatment for a period of time up

to 9 months. The mass of the tumor was measured every 3 months and

introduced, together with the 3D target absorbed dose, in a macroscopi-

cal formulation of the LQ model. The 3D voxel-based target absorbed dose

was calculated based on the activity distribution in the CT-SPECT pre-

therapeutic images, obtained injecting the patient with 99mTc albumin

aggregated in the same site where microspheres will be injected.

Results:

The estimated values for α are 0.23

0.26 Gy

−

and 0.20

0.22 Gy

−

for HCC and CCC patients respectively and agree with the order of mag-

nitude of the same parameter proposed by AAPM REPORT NO. 166.

Conclusions:

The estimate of the radiobiological α parameter is crucial for

the personalized calculation of the activity to be injected for the hepatic

radioembolization. Future works will be conducted by using the results ob-

tained in order to verify the improvement of the treatment effectiveness.

http://dx.doi.org/10.1016/j.ejmp.2016.01.336

C.331

APPLICATION OF STANDARDIZED PROCEDURE ENHANCES RELIABILITY

OF SUV DATA IN PET/CT STUDIES

F. Bergesio

, a , b ,

A. Terulla

a ,

E. Berton

e a ,

S. Chauvi

e a .

Medical Physics Unit,

ASO S. Croce e Carle, Cuneo, Italy;

School of Medical Physics, University of

Torino, Torino, Italy

Introduction:

Standardized Uptake Value (SUV) and derived metrics are

frequently used in clinical practice and in clinical trials as a marker of tumor

avidity. Although SUV value is affected by several well-known factors. The

aim of this work was to endeavor whether using standardized procedure

for Positron Emission Tomography/Computed Tomography (PET/CT) could

reduce the error in its measurement.

Materials and Methods:

Several strategies for errors reduction were carried

out: scanner and activity-meter calibration, measurement of residual in the

syringe used for injection, clock synchronization, acquisition and recon-

struction parameters optimization, standardization of uptake time, correct

patient’s weight and height measurements. Two patient populations were

compared, with and without the application of these strategies.

Results:

Two populations of 100 PET/CT scans performed in 5 different sites

(P1) and in the same site using standardized procedures (P2) were com-

pared. Mean uptake times were (79

21) min (range 42–144) for P1 and

(62

7) min (range 45–75) for P2. The ratios between injected activity and

body weight were (4.07

1.11) MBq/kg (range 7.43–2.57) for P1 and

(5.24

0.56) MBq/kg (range 7.38–3.92) for P2. Mean liver SUVs were

(1.92

0.59) for P1 and (2.03

0.39) for P2. The Fisher test rejected the hy-

pothesis that the variances are equal (F

2.22, p-value

9.35e

−

5).

Conclusion:

In conclusion this preliminary work showed that using stan-

dardized procedure reduces the variability of the SUV of the liver.

http://dx.doi.org/10.1016/j.ejmp.2016.01.337

C.332

IMPACT OF UPTAKE TIME IN PHYSIOLOGICAL COMPARTMENTS FOR

PET/CT EXAMINATION

F. Bergesio

* , a , b ,

A. Terull

a a ,

D. Guerr

a b ,

E. Bertone

a ,

S. Chauvi

e a .

Medical

Physics Unit, ASO S. Croce e Carle, Cuneo, Italy;

University of Torino, Torino,

Italy

Introduction:

Positron Emission Tomography (PET) imaging at more than

1 h after 2-deoxy-2-[18F]fluoro-D-glucose (FDG) administration may result

in possibly decreased normal FDG uptake in tissues as liver. The purpose

Physica Medica 32 (2016) e97–e115

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