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

(3.3

1.3 mSv for CT and 4.5

0.3 mSv for PET contribution) and 7.3

1.5 mSv

for women (3.2

1.4 mSv for CT and 4.1

0.2 mSv for PET contribution).

The mean Effective Dose was 7.5

1.5 mSv for all patients (3.2

1.3 mSv for

CT and 4.3

0.3 mSv for PET contribution). These values were then com-

pared with the published literature (Tonkopi, AJR 2013).

Conclusions:

Our results were in good agreement with the published

literature and were presented to physicians and technicians of the Nuclear

Medicine Dept. We have recently installed a new PET-CT (GE Discovery-

IQ) and we will evaluate the effective dose obtained with the new

scanner.

http://dx.doi.org/10.1016/j.ejmp.2016.01.392

C.387

EVALUATION OF COMMERCIAL SOFTWARE PERFORMANCE IN

RETRIEVING INFORMATION FROM MERGED SPECT AND CT IMAGES: A

PHANTOM STUDY

C. Gilibert

i a ,

S. Stroli

n b ,

S. Ungania

b ,

A. Cacciator

e b ,

A. Soriani

b ,

G. Iaccarin

o b ,

M. D’Andrea

b ,

L. Strigari

* , b .

INAIL Dipartimento Innovazioni Tecnologiche

e Sicurezza degli Impianti, Prodotti e Insediamenti Antropici, Rome, Italy;

Laboratory of Medical Physics and Expert Systems, Regina Elena National

Cancer Institute, Rome, Italy

Introduction:

Tumor displacement in patients with liver metastasis may

be registered by multimodal imaging. The aim of this study was to inves-

tigate the performance of commercial image fusion software in measuring

the activity and the volumes of inserts simulating liver lesions at differ-

ent positions in a phantom.

Materials and Methods:

A novel experimental setup has been designed

using Jaszczak phantom and fillable plastic balloons. A solution with a con-

trast agent at 1% and a concentration of 0.42 MBq/mL were prepared. Two

balloons were filled with the solution and fixed to the phantom in order

to simulate liver lesions of equal size at different phantom position. All ac-

quisitions were performed using a three-head 3/8’’ (9.5 mm) NaI crystal

Philips IRIX gamma-camera. Two iterative algorithms were used to recon-

struct SPECT images: the maximum likelihood expectation maximization

(MLEM) and the ordered subsets expectation maximization (OSEM). The

number of iterations was 10, 20, 50 and 4, 10, 20 for MLEM and OSEM re-

spectively. Using the MIMvista

software, several regions of interest (ROIs)

were generated on both SPECT and CT images with a threshold method at

different percentages of maximum activity values. Image based recov-

ered data have been compared with the expected activity to find the most

appropriate threshold to recover the activity values under controlled ex-

perimental conditions.

Results:

MLEM algorithm with 20 iterations was the most accurate recon-

struction method with a 1% of difference between expected and recovered

activity. A 30% threshold gave the smallest volume difference between the

two ROIs and a measured value closest to the true volume measured on

the CT.

Conclusion:

This experimental setup can be used to identify appropriate

thresholds for hepatic lesions when considering internal lesion move-

ments using multimodal imaging.

http://dx.doi.org/10.1016/j.ejmp.2016.01.393

C.388

ABSOLUTE GAMMA CAMERA CALIBRATION FOR QUANTITATIVE SPECT

IMAGING WITH 177LU

M. D’Arienzo

a , b ,

M.L. Cozzella

a ,

A. Fazio

a ,

S. Ungania

, c , d ,

M. Cazzato

c ,

G. Iaccarino

c ,

M. D’Andrea

c ,

L. Strigari

c ,

A. Fenwick

e ,

M. Cox

e ,

L. Johansson

e ,

P. De Felice

a .

ENEA, National Institute of Ionizing Radiation Metrology, Rome,

Italy;

Department of Anatomical, Histological, Forensic Medicine and

Orthopedic Sciences, La Sapienza University, Rome, Italy;

Laboratory of Medical

Physics and Expert Systems, Regina Elena National Cancer Institute, Rome, Italy;

Medical Physics Specialization School, Faculty of Medicine, Tor Vergata

University, Rome, Italy;

National Physical Laboratory (NPL), Teddington, UK

Introduction:

Gamma camera calibration in molecular radiotherapy is cur-

rently performed either in-air or in-water using a source with a known

amount of activity. However, at present there are no standard protocols or

any established methods for calibration and verification of system perfor-

mance. The aim of this work was to develop an approach to gamma camera

calibration for absolute quantification of 177Lu.

Materials and Methods:

Calibration studies were performed on a Philips

IRIX and AXIS gamma camera using four reference geometries: a point source

in air, a 16 mL Jaszczak sphere surrounded by non-radioactive water, a 16 mL

Jaszczak sphere in air and a 20 cm diameter cylinder filled with 177LuCl.

Acquisitions were corrected both for scatter and attenuation. We vali-

dated our method using an anthropomorphic phantom provided with liver

cavity filled with 177LuCl.

Results:

Acquisitions performed with the IRIX gamma camera provided

better results, with agreements within 5% for all geometries for acquisi-

tions at 208 keV. The Jaszczak sphere in water provided sensitivity values

capable of recovering the activity in anthropomorphic geometry within 1%

for the 208 keV peak, for both gamma cameras. The point source provid-

ed the poorest results, most likely because scatter and attenuation correction

are not incorporated in the calibration factor. For both systems the activ-

ity in anthropomorphic geometry was recovered with an agreement in the

range

−

11.6%/

7.3% at 208 keV.

Conclusions:

Scatter and attenuation play a major role at 113 keV and

are likely to hinder an accurate quantification. Acquisitions at 208 keV are

therefore recommended in the clinical practice. Preliminary results suggest

that the gamma camera calibration factor can be determined with a stan-

dard uncertainty below 3% if activity measurements are performed with

equipment traceable to primary standards, accurate volume measure-

ments are made, and a favourable chemistry is used during the experimental

activity.

http://dx.doi.org/10.1016/j.ejmp.2016.01.394

C.389

IMPACT OF ATTENUATION AND SCATTER CORRECTION IN PREVISIONAL

DOSIMETRY BASED ON SPECT-CT IMAGES FOR RADIOEMBOLIZATION OF

LIVER LESIONS WITH 90Y MICROSPHERES

S. Valzano

* , a ,

C. Cutai

a a ,

E. Richett

a a ,

M. Pasquin

o a ,

R.E. Pellerito

b ,

M. Stas

i a .

Medical Physics Unit, AO Ordine Mauriziano, Turin, Italy;

Nuclear Medicine

Unit, AO Ordine Mauriziano, Turin, Italy

Introduction:

Previsional dosimetry of hepatic radioembolization with 90Y

microsphere is performed with 99mTc-MAA acquisitions in order to avoid

shunts and to estimate dose to lesions and normal liver. The accuracy of

the dose calculation depends both on the dosimetric method and on the

image reconstruction algorithms. The aim of this study was to compare doses

calculated with MIRD and voxel methods based on SPECT-CT images with

or without attenuation and scatter corrections.

Materials and Methods:

10 HCC patients were treated with 90Y-resin

spheres (1.4

0.4 GBq). For previsional dosimetry 99mTc-MAA SPECT-CT

(SIEMENS Symbia Intevo, LEHR, 128

128, 60 views, 18 s/view) acquisi-

tions were performed. Images were reconstructed with iterative (IT)

algorithm (Flash3D, 8i8s) with attenuation and scatter corrections and with

FBP algorithmwithout any correction. Lesion (T) and normal liver (NL) doses

were estimated from SPECT-CT images with MIRD compartmental method

(VOI counts, isocontour) and with a homemade voxel dosimetry MatLab

code. T and NL volumes were obtained on IT and FBP reconstructions and

employed for the two dosimetric approaches. MIRD and voxel mean doses

to T and NL were calculated on IT and FBP reconstructed images: abso-

lute and percentage comparisons were performed.

Results:

MIRD compartmental T mean doses were 205 Gy for IT and 224 Gy

for FBP; NL mean doses were 57 Gy (IT) and 67 Gy (FBP). Mean T doses,

obtained with voxel method, were 167 Gy (IT) and 170 Gy (FBP); NL mean

doses were 48 Gy (IT) and 54 Gy (FBP). Using MIRD compartmental method,

the mean percent dose differences (

sd), estimated on IT and FBP images,

were 11% (

35%) for T and 13% (

34%) for NL. For voxel dosimetry method,

the mean percent dose differences (

sd), estimated on reconstructed images,

were 2% (

22%) and 7% (

27%) for T and NL respectively.

Conclusions:

SPECT-CT reconstruction algorithms and attenuation and

scatter corrections could significantly affect dose calculation and must be

considered in different dosimetric approaches.

http://dx.doi.org/10.1016/j.ejmp.2016.01.395

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Abstracts/Physica Medica 32 (2016) e97–e115