Medical Imaging and Radiotherapy Journal (MIRTJ) 39 (Suppl. 1) 23
Medical Imaging and Radiotherapy Journal (MIRTJ) 39 (Suppl. 1)
OPTIMIZACIJA SPECT/CT IN PET/CT PROTOKOLOV
OPTIMIZATION OF SPECT/CT AND PET/CT PROTOCOLS 
Sebastijan Rep , Slodnjak Ivan 
Univerzitetni klinični center Ljubljana, Klinika za nuklearno medicino, Zaloška cesta 7, 1000 Ljubljana, Slovenija / 
University medical centre Ljubljana, Clinic of nuclear medicine, Zaloška cesta 7, 1000 Ljubljana, Slovenia
Korespondenca / Corresponding author: sebastijan.rep@guest.arnes.si
Prejeto/Recived: 14. 11. 2019
Sprejeto/Accepted: 3. 3. 2022
IZVLEČEK 
Uvod: Tomografski metodi slikanja v nuklearni medicini sta 
enofotonska emisijska računalniška tomografi ja (SPECT) 
in pozitronska emisijska tomografi ja (PET). Obe metodi 
prikažeta razporeditev radiofarmaka (RF) v telesu v treh 
ravninah. Pri prehodu fotonov skozi homogeno telo se 
prikaže neenakomerna razporeditev RF zaradi atenuacije. 
Računalniška tomografi ja (CT) v kombinaciji s funkcionalnimi 
metodami slikanja (SPECT/CT in PET/CT) korigira problem 
atenuacije fotonov. Slika, dobljena pri SPECT/CT in PET/CT, se 
lahko optimizira z uporabo CT za korekcijo atenuacije in fuzijo 
ter z rekonstrukcijskimi algoritmi, ki vključujejo korekcijo 
ločljivosti.
Namen: Namen opravljene raziskave je kvalitativno in 
kvantitativno oceniti in analizirati PET/CT in SPECT/CT slike z 
namenom optimizacije protokolov. 
Metode: Uporabili smo NEMA body fantom in ga napolnili 
z 99mTc in 18F FDG v različnih razmerjih. Analizirali smo 
kontrastnost za SPECT/CT pri različnih rekonstrukcijskih 
algoritmih. Na PET/CT smo analizirali CNR (razmerje kontrast/
šum) in CRC (koefi cient vrnitve kontrasta) pri različnih 
matrikah. Primerjali smo tudi CNR med PET/CT in SPECT/CT. 
Za analizo smo uporabili programsko orodje SPSS 21.
Rezultati: Analiza kontrastnosti je pokazala statistično 
pomembno razliko med različnimi rekonstrukcijskimi 
algoritmi pri SPECT/CT (p < 0,001). Pri uporabi manjših 
matričnih elementov se CNR in CRC pri PET/CT povišata pri 
lezijah s premerom ≤ 1,21 cm do 11 %. Primerjava CNR za PET/
CT in SPECT/CT je pokazala signifi kantno razliko med obema 
metodama (p = 0,002). Pri obeh metodah se vrednost SNR viša 
glede na višino razmerja in kaže dobro korelacijo (r = 0,85 in 
p < 0,001).
Zaključek: Rezultati analize so potrdili, da se z optimizacijo 
slikovnih in obdelovalnih parametrov lahko vpliva na SPECT/
CT in PET/CT slike.
Ključne besede: kontrastnost, SNR, CNR, SPECT/CT, PET/CT
ABSTRACT
Introduction: Tomographic imaging methods in nuclear 
medicine are single-photon emission computed tomography 
(SPECT) and positron emission tomography (PET). Both methods 
show the distribution of radiopharmaceuticals (RF) in the body in 
three planes. In the transition of photons through a homogeneous 
body, uneven distribution of RF due to attenuation appears. 
Computed tomography (CT) combined with functional imaging 
methods (SPECT/CT and PET/CT) corrects the problem of photon 
attenuation. The image obtained with SPECT/CT and PET/CT can 
be optimized by using CT for attenuation and fusion correction 
and reconstruction algorithms involving resolution correction.
Purpose: The purpose of the study is to qualitatively and 
quantitatively evaluate and analyze PET/CT and SPECT/CT 
images in order to optimize protocols.
Methods: We used a NEMA body phantom and fi lled it with 
99mTc and 18F-FDG in diff erent ratio. Contrast for SPECT/CT was 
analyzed for diff erent reconstruction algorithms. CNR (contrast/
noise ratio) and CRC (contrast return coeffi  cient) for diff erent 
matrices were analyzed on PET/CT. We also compared CNR 
between PET/CT and SPECT/CT. The SPSS 21 software tool was 
used for analysis.
Results: Analysis of contrastness showed a statistically signifi cant 
diff erence between the diff erent reconstructive algorithms in 
SPECT/CT (p <0.001). When smaller matrix elements are used, 
CNR and CRC for PET/CT are increased for lesions ≤ 1.21 cm to 
11% in diameter. The CNR comparison for PET/CT and SPECT/CT 
showed a signifi cant diff erence between the two methods (p = 
0.002). In both methods, the SNR value increases with respect to 
ratio height and shows a good correlation (r = 0.85 and p <0.001).
Conclusion: The results of the analysis confi rmed that SPECT/CT 
and PET/CT images can be aff ected by the optimization of the 
imaging and processing parameters.
Keywords: contrast, SNR, CNR, SPECT/CT, PET/CT
24 Medical Imaging and Radiotherapy Journal (MIRTJ) 39 (Suppl. 1)
Medical Imaging and Radiotherapy Journal (MIRTJ) 39 (Suppl. 1)
LITERATURA / REFERENCES
Frelih N, Ležaič L, Žibert: J, Rep S. The eff ect of attenuation 
correction on image quality in single photon emission 
computed tomography: The eff ect of attenuation 
correction on image quality. Med Sci Discov. 2021 
Feb;8(2):73-8. c
Kupitz D, Wissel H, Wuestemann J, Bluemel S, Pech M, Amthauer 
H, Kreissl MC, Grosser OS. Optimization of SPECT/CT 
imaging protocols for quantitative and qualitative 99mTc 
SPECT. EJNMMI Phys. 2021 Jul 30;8(1):57. 
Adler S, Seidel J, Choyke P, Knopp MV, Binzel K, Zhang J, et al. 
Minimum lesion detectability as a measure of PET system 
performance. EJNMMI Phys. 2017 Dec;4(1):13.