Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen

The dominant powder scintillator in most medical imaging modalities for decades is Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Except for Gd2O2S:Tb there are alternative powder phosphor scintillators like Lu2SiO5:Ce and Gd2O2S:Eu that has been suggested for use in var...

Πλήρης περιγραφή

Λεπτομέρειες βιβλιογραφικής εγγραφής
Κύριος συγγραφέας: Σεφέρης, Ιωάννης
Άλλοι συγγραφείς: Παναγιωτάκης, Γεώργιος
Μορφή: Thesis
Γλώσσα:English
Έκδοση: 2013
Θέματα:
Διαθέσιμο Online:http://hdl.handle.net/10889/6242
id nemertes-10889-6242
record_format dspace
institution UPatras
collection Nemertes
language English
topic Medical imaging
Mammography
Digital radiography
CMOS
Gd2O2S:Eu
Ποιότητα εικόνας
Μαστογραφία
Ακτινοδιαγνωστική
621.367
spellingShingle Medical imaging
Mammography
Digital radiography
CMOS
Gd2O2S:Eu
Ποιότητα εικόνας
Μαστογραφία
Ακτινοδιαγνωστική
621.367
Σεφέρης, Ιωάννης
Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
description The dominant powder scintillator in most medical imaging modalities for decades is Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Except for Gd2O2S:Tb there are alternative powder phosphor scintillators like Lu2SiO5:Ce and Gd2O2S:Eu that has been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital imaging devices like CCDs and CMOS based detectors. The purposes of the present thesis, is to investigate the fundamental imaging performance of a high resolution CMOS based imaging sensor combined with custom made Europium (Eu3+) activated Gd2O2S screens in terms of Modulation Transfer Function (MTF), Normalized Noise Power Spectrum (NNPS), Detective Quantum Efficiency (DQE), Noise Equivalent Quanta (NEQ) and Information Capacity (IC) covering the mammography and general radiography energy ranges. The CMOS sensor was coupled to two Gd2O2S:Eu scintillator screens with coating thicknesses of 33.3 and 65.1 mg/cm2, respectively, which were placed in direct contact with the photodiode array. The CMOS photodiode array, featuring 1200x1600 pixels with a pixel pitch of 22.5 m , was used as an optical photon detector. In addition to frequency dependent parameters (MTF, NPS, DQE) characterizing image quality, image information content was assessed through the application of information capacity (IC). The MTF was measured using the slanted-edge method to avoid aliasing while the Normalized NPS (NNPS) was determined by two-dimensional (2D) Fourier transforming of uniformly exposed images. Both parameters were assessed by irradiation under the RQA-5 protocol (70kVp digital-radiography) recommended by the International Electrotechnical Commission Reports 62220-1 and the W/Rh, W/Ag beam qualities (28kVp digital-mammography). The DQE was assessed from the measured MTF, NNPS and the direct entrance surface air-Kerma (ESAK) obtained from X-ray spectra measurement with a portable cadmium telluride (CdTe) detector. The spectral matching factor between the optical spectra emitted by the Gd2O2S:Eu and the Gd2O2S:Tb screens and the CMOS optical sensor, evaluated in the present study, was 1 and 0.95 respectively. The ESAK values ranged between 11.2-87.5 Gy , for RQA-5, and between 65.8-334 Gy , for W/Rh, W/Ag beam qualities. It was found that the detector response function was linear for the exposure ranges under investigation. Under radiographic conditions the MTF of the present system was found higher than previously published MTF data for a 48 m CMOS sensor, in the low up to medium frequency ranges. DQE was found comparable, while the NNPS appeared to be higher in the frequency range under investigation (0–10 cycles/mm). NEQ reached a maximum (73563 mm-2) in the low frequency range (1.8 cycles/mm), under the RQA 5 (ESAK: 11.2 Gy ) conditions. IC values were found to range between 1730-1851 bits/mm2. Under mammographic conditions MTF, NNPS and NEQ were found comparable to data previously published for the 48 m CMOS sensor while the DQE was found lower. The corresponding IC values were found ranging between 2475 and 2821 bits/mm2. The imaging performance of europium (Eu3+) activated Gd2O2S screens in combination to the CMOS sensor, investigated in the present study, was found comparable to those of Terbium (Tb) activated Gd2O2S screens (combined with the CMOS sensor). It can be thus claimed that red emitting phosphors could be suitably used in digital imaging systems, where the Silicon (Si) based photodetectors are more sensitive to longer wavelength ranges, and particularly in the red wavelength range.
author2 Παναγιωτάκης, Γεώργιος
author_facet Παναγιωτάκης, Γεώργιος
Σεφέρης, Ιωάννης
format Thesis
author Σεφέρης, Ιωάννης
author_sort Σεφέρης, Ιωάννης
title Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
title_short Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
title_full Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
title_fullStr Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
title_full_unstemmed Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen
title_sort investigatoin and imaging characteristics of a cmos sensor based digital detector coupled to a red emitting fluorescent screen
publishDate 2013
url http://hdl.handle.net/10889/6242
work_keys_str_mv AT sepherēsiōannēs investigatoinandimagingcharacteristicsofacmossensorbaseddigitaldetectorcoupledtoaredemittingfluorescentscreen
AT sepherēsiōannēs diereunēsētōnapeikonistikōncharaktēristikōnpsēphiakouanichneutēbasismenouseaisthētēracmossesyzeuxēmephthorizousaothonēerythrasekpompēs
_version_ 1771297147521597440
spelling nemertes-10889-62422022-09-05T05:37:44Z Investigatoin and imaging characteristics of a CMOS sensor based digital detector coupled to a red emitting fluorescent screen Διερεύνηση των απεικονιστικών χαρακτηριστικών ψηφιακού ανιχνευτή βασισμένου σε αισθητήρα CMOS σε σύζευξη με φθορίζουσα οθόνη ερυθράς εκπομπής Σεφέρης, Ιωάννης Παναγιωτάκης, Γεώργιος Παναγιωτάκης, Γεώργιος Κανδαράκης, Ιωάννης Κωσταρίδου, Ελένη Seferis, Ioannis Medical imaging Mammography Digital radiography CMOS Gd2O2S:Eu Ποιότητα εικόνας Μαστογραφία Ακτινοδιαγνωστική 621.367 The dominant powder scintillator in most medical imaging modalities for decades is Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Except for Gd2O2S:Tb there are alternative powder phosphor scintillators like Lu2SiO5:Ce and Gd2O2S:Eu that has been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital imaging devices like CCDs and CMOS based detectors. The purposes of the present thesis, is to investigate the fundamental imaging performance of a high resolution CMOS based imaging sensor combined with custom made Europium (Eu3+) activated Gd2O2S screens in terms of Modulation Transfer Function (MTF), Normalized Noise Power Spectrum (NNPS), Detective Quantum Efficiency (DQE), Noise Equivalent Quanta (NEQ) and Information Capacity (IC) covering the mammography and general radiography energy ranges. The CMOS sensor was coupled to two Gd2O2S:Eu scintillator screens with coating thicknesses of 33.3 and 65.1 mg/cm2, respectively, which were placed in direct contact with the photodiode array. The CMOS photodiode array, featuring 1200x1600 pixels with a pixel pitch of 22.5 m , was used as an optical photon detector. In addition to frequency dependent parameters (MTF, NPS, DQE) characterizing image quality, image information content was assessed through the application of information capacity (IC). The MTF was measured using the slanted-edge method to avoid aliasing while the Normalized NPS (NNPS) was determined by two-dimensional (2D) Fourier transforming of uniformly exposed images. Both parameters were assessed by irradiation under the RQA-5 protocol (70kVp digital-radiography) recommended by the International Electrotechnical Commission Reports 62220-1 and the W/Rh, W/Ag beam qualities (28kVp digital-mammography). The DQE was assessed from the measured MTF, NNPS and the direct entrance surface air-Kerma (ESAK) obtained from X-ray spectra measurement with a portable cadmium telluride (CdTe) detector. The spectral matching factor between the optical spectra emitted by the Gd2O2S:Eu and the Gd2O2S:Tb screens and the CMOS optical sensor, evaluated in the present study, was 1 and 0.95 respectively. The ESAK values ranged between 11.2-87.5 Gy , for RQA-5, and between 65.8-334 Gy , for W/Rh, W/Ag beam qualities. It was found that the detector response function was linear for the exposure ranges under investigation. Under radiographic conditions the MTF of the present system was found higher than previously published MTF data for a 48 m CMOS sensor, in the low up to medium frequency ranges. DQE was found comparable, while the NNPS appeared to be higher in the frequency range under investigation (0–10 cycles/mm). NEQ reached a maximum (73563 mm-2) in the low frequency range (1.8 cycles/mm), under the RQA 5 (ESAK: 11.2 Gy ) conditions. IC values were found to range between 1730-1851 bits/mm2. Under mammographic conditions MTF, NNPS and NEQ were found comparable to data previously published for the 48 m CMOS sensor while the DQE was found lower. The corresponding IC values were found ranging between 2475 and 2821 bits/mm2. The imaging performance of europium (Eu3+) activated Gd2O2S screens in combination to the CMOS sensor, investigated in the present study, was found comparable to those of Terbium (Tb) activated Gd2O2S screens (combined with the CMOS sensor). It can be thus claimed that red emitting phosphors could be suitably used in digital imaging systems, where the Silicon (Si) based photodetectors are more sensitive to longer wavelength ranges, and particularly in the red wavelength range. - 2013-07-26T09:12:56Z 2013-07-26T09:12:56Z 2013-04-16 2013-07-26 Thesis http://hdl.handle.net/10889/6242 en Η ΒΚΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της. 0 application/pdf