Development of the normalization method for the Jagiellonian PET scanner Aurélien Coussat 12 Wojciech Krzemien 32

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Development of the normalization method for the

Jagiellonian PET scanner

Aurélien Coussat (1,2,*), Wojciech Krzemien (3,2),

Jakub Baran (1,2), Szymon Parzych (1,2)

(1) Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian

University, 30-348 Kraków, Poland,

(2) Centre for Theranostics, Jagiellonian University, 31-501 Kraków, Poland,

(3) High Energy Physics Division, National Centre for Nuclear Research, Otwock,

Swierk, PL-05-400, Poland

(*) Corresponding author: Aurélien Coussat, aurelien.coussat@uj.edu.pl

For the J-PET collaboration

Received September 4, 2024

This work aims at applying the theory of the component-based normal-

ization for the Jagiellonian PET scanner, currently under development at

the Jagiellonian University. In any Positron Emission Tomography acqui-

sition, eﬃciency along a line-of-response can vary due to several physical

and geometrical eﬀects, leading to severe artifacts in the reconstructed im-

age. To mitigate these eﬀects, a normalization coeﬃcient is applied to each

line-of-response, deﬁned as the product of several components. Speciﬁcity

of the Jagiellonian PET scanner geometry is taken into account. Results

obtained from GATE simulations are compared with preliminary results

obtained from experimental data.

Keywords— Positron Emission Tomography, Jagiellonian PET, Normaliza-

tion

1. Introduction

The Jagiellonian PET (J-PET) scanner is a high acceptance multi-purpose

Positron Emission Tomography (PET) detector optimized for the detection of pho-

tons from positron-electron annihilation, currently under development at the Jagiel-

lonian University [1–4]. The current prototype, named the Modular J-PET [5], is

composed of 24 individual modules arranged cylindrically. Each module is com-

posed of 13 plastic scintillator strips with a size of 24×6×500 mm3. The scintillators

are readout on both sides by a matrix of Sillicon PhotoMultipliers [1].

Several eﬀects impact the eﬃciency of detector strips, such as geometric eﬀects

or variation in detector intrinsic eﬃciencies. To counterbalance the non-uniformity

(1)

arXiv:2210.03396v2 [physics.med-ph] 31 Aug 2024

2main printed on September 4, 2024

in eﬃciency, normalization factors can be incorporated into the image reconstruc-

tion procedure. This contribution is a ﬁrst step towards proper normalization of

the Modular J-PET scanner. Section 2 describes the normalization factors and

how they are computed, Section 3 shows preliminary results and Section 4 brieﬂy

concludes.

2. Materials and Methods

2.1. Normalization coeﬃcients

The proper determination of the normalization coeﬃcient for a given line of

response (LOR) permits to compensate for the detector eﬃciency variation, and

for the geometrical eﬀects not included in the projection model. The lack of those

corrections leads to artifacts generation and the degradation of the ﬁnal image

quality [6]. The so called component-based normalization method [7] relies on

factorization of the normalization coeﬃcients into sub-components that can be

estimated separately, and on usage of the fan-sums strategy to lower the variance

of the estimations. This work adapts the deﬁnitions of Pépin et al. [8].

Unlike conventional PET scanners, whose detectors are divided into several

crystals, the J-PET scintillator strips are continuous in the axial direction. We

nevertheless deﬁne Mvirtual bins in the axial direction. We also denote as Lthe

number of strips (312 in the case of the Modular J-PET scanner). The LOR that

joins portion uof strip iwith portion vof strip jis denoted “LOR uivj". These

deﬁnitions are illustrated in Fig. 1.

(u, v)∈[1, M]2

(i, j)∈[1, L]2

LOR uivj

Fig. 1: LORs deﬁnition.

The normalization coeﬃcient for a given LOR is given by the product of several

normalization factors. Each of these factors accounts for a diﬀerent eﬀect. The

normalization coeﬃcient for the LOR uivj is given as [8]

ηuivj =bax

u·bax

v·gax

uv ·gtr

ij ·ftr

ij ·ϵui ·ϵvj (1)

where bax represents the axial block proﬁle factors, gax the axial geometric factors,

gtr the transverse geometric factors, ftr the transverse interference function and ϵ

the intrinsic detector eﬃciencies. Note that transverse interference functions are

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DevelopmentofthenormalizationmethodfortheJagiellonianPETscannerAurélienCoussat(1,2,*),WojciechKrzemien(3,2),JakubBaran(1,2),SzymonParzych(1,2)(1)FacultyofPhysics,AstronomyandAppliedComputerScience,JagiellonianUniversity,30-348Kraków,Poland,(2)CentreforTheranostics,JagiellonianUniversity,31-501Kraków...

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Development of the normalization method for the Jagiellonian PET scanner Aurélien Coussat 12 Wojciech Krzemien 32

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