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Titolo:
THE EFFECT OF ACTIVITY OUTSIDE THE DIRECT FIELD-OF-VIEW IN A 3D-ONLY WHOLE-BODY POSITRON TOMOGRAPH
Autore:
SPINKS TJ; MILLER MP; BAILEY DL; BLOOMFIELD PM; LIVIERATOS L; JONES T;
Indirizzi:
HAMMERSMITH HOSP,MRC CYCLOTRON UNIT,DUCANE RD LONDON W12 0NN ENGLAND
Titolo Testata:
Physics in medicine and biology
fascicolo: 4, volume: 43, anno: 1998,
pagine: 895 - 904
SICI:
0031-9155(1998)43:4<895:TEOAOT>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
PHYSICAL PERFORMANCE; RETRACTABLE SEPTA; PET; SCANNER; SCATTER;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
13
Recensione:
Indirizzi per estratti:
Citazione:
T.J. Spinks et al., "THE EFFECT OF ACTIVITY OUTSIDE THE DIRECT FIELD-OF-VIEW IN A 3D-ONLY WHOLE-BODY POSITRON TOMOGRAPH", Physics in medicine and biology, 43(4), 1998, pp. 895-904

Abstract

The ECAT EXACT3D (CTI/Siemens 966) 3D-only PET tomograph has unprecedented sensitivity due to the large EGO (bismuth germanate) detector volume. However, the consequences of a large (23.4 cm) axial field-of-view (FOV) and the need for a patient port diameter to accommodate body scanning make the device more sensitive to photons arising from activity outside the direct (coincidence) FOV. This leads to relatively higher deadtime and an increased registration of random and scatter (true)coincidences. The purpose of this study is to determine the influenceDf activity outside the FOV on (i) noise-equivalent counts (NEC) and (ii) the performance of a 'model-based' scatter correction algorithm, and to investigate the effect of side shielding additional to that supplied with the tomograph. Annular shielding designed for brain scanning increased the NEC for blood flow ((H2O)-O-15) measurement (integrated over 120 s) by up to 25%. For C-11 tracer studies, the increase is less than 5% over 120 min. Purpose-built additional body shielding madeto conform to the shape of a volunteer, reduced the randoms count rate in a heart blood Bow measurement ((H2O)-O-15) by about 30%. After scatter correction the discrepancy between ROI count ratios for compartments within the 20 cm diameter 'Utah' phantom differed by less than 5%from true (sampled) activity concentration ratios. This was so with or without activity outside the FOV and with or without additional sideshielding. Count rate performance is thus improved by extra shieldingbut more improvement is seen in head than in body scanning. Measurement of heart blood flow using bolus injections of (H2O)-O-15 would benefit from the use of detectors with lower deadtime and superior timing resolution such as LSO (lutetium oxyorthosilicate).

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Documento generato il 29/11/20 alle ore 16:27:19