BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CERN//INDICO//EN
BEGIN:VEVENT
SUMMARY:List-mode TOF MLEM reconstruction for the total-body J-PET with a 
 realistic system response matrix
DTSTART;VALUE=DATE-TIME:20211011T072000Z
DTEND;VALUE=DATE-TIME:20211011T074000Z
DTSTAMP;VALUE=DATE-TIME:20261008T201256Z
UID:indico-contribution-241@indico.koza.if.uj.edu.pl
DESCRIPTION:Speakers: Roman Shopa (National Centre for Nuclear Research\, 
 Poland)\nWe modify the time-of-flight maximum likelihood expectation maxim
 isation (TOF MLEM) image reconstruction algorithm by an updated model for 
 the system response matrix (SRM) of the total-body Jagiellonian PET (J-PET
 ) scanners\, which modular multi-layer geometry complicates SRM estimation
  and requires more computational power to calculate correction factors [1]
 .\nThe elongated plastic scintillators of the J-PET\, which use Compton sc
 attering for the detection of positron-electron annihilation photons\, imp
 ly the smooth dependence of SRM on the obliqueness angle $\\theta$. We thu
 s represent it as a set of functions unique for each bin and acquired by a
  log-polynomial fit of the Monte Carlo simulated emissions of $\\gamma$-ph
 otons on 2D transverse planes with different $\\theta$.\nBy utilising the 
 GATE software [2]\, a NEMA IEC phantom [3] was simulated in a 140-cm long 
 24-module J-PET\, comprised of 2 detector layers (inner radius 393 mm) and
  a layer of wavelength shifters [4]. The data collected from a 500-s long 
 scan was post-smeared according to the assessed temporal (191 ps) and axia
 l (5 mm) resolution. Only true coincidences were considered. \nThe updated
  SRM was employed for the list-mode TOF MLEM reconstruction. For the prede
 fined NEMA IEC attenuation map\, two versions of attenuation correction we
 re applied: a conventional (integration over bins) and a simplified on-the
 -fly recalculation for each measurement\, which improves performance and i
 s less sensitive to boundary effects. \nCompared to the reference list-mod
 e TOF MLEM from the CASToR framework [5]\, a substantial improvement in th
 e image quality and mean squared error with respect to ground truth were o
 bserved. The simplified attenuation correction proved to be a reliable alt
 ernative\, producing outcomes similar or better than the conventional appr
 oach.\nTo summarise\, the proposed analytical SRM model for the total-body
  J-PET proved to be superior to the reference method employed for crystal-
 based scanners. The modified TOF MLEM and attenuation correction do not re
 quire high computational power and can be extended to account for the non-
 collinearity\, positron range and other factors.\n\n[1] P. Moskal et al.\,
  “Simulating NEMA characteristics of the modular total-body J-PET scanne
 r—an economic total-body PET from plastic scintillators\,” Phys. Med. 
 Biol.\, vol. 66\, no. 17\, pp. 175015\, Sep. 2021.\n[2] S. Jan et al.\, 
 “GATE: a simulation toolkit for PET and SPECT\,” Phys. Med. Biol.\, vo
 l. 49\, no. 19\, pp. 4543-4561\, Oct. 2004. \n[3] Performance Measurements
  of Positron Emission Tomographs\, NEMA NU 2-2012\, 2013.\n[4] J. Smyrski 
 et al.\, "Measurement of gamma quantum interaction point in plastic scinti
 llator with WLS strips\," Nucl. Instrum. Methods Phys. Res. A\, vol. 851\,
  pp. 39-42\, Apr. 2017.\n[5] T. Merlin et al.\, "CASToR: a generic data or
 ganization and processing code framework for multi-modal and multi-dimensi
 onal tomographic reconstruction\," Phys. Med. Biol.\, vol. 63\, no. 18\, p
 p. 185005\, Sep. 2018.\n\nhttps://indico.koza.if.uj.edu.pl/event/4/contrib
 utions/241/
LOCATION:Theranostics Center / on-line
URL:https://indico.koza.if.uj.edu.pl/event/4/contributions/241/
END:VEVENT
END:VCALENDAR