Study of TOF PET using Cherenkov light

Korpar, S.; Dolenec, R.; Križan, P.; Pestotnik, R.; Stanovnik, A.

doi:10.1016/j.nima.2011.06.035

Cited by 77 publications

(41 citation statements)

References 13 publications

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“…A strategy for energy discrimination based on the refractive index of the material was proposed and investigated by Ooba et al (2004) and Korpar et al (2011). Bilevych et al suggested Holl et al (1988).…”

Section: Cherenkov Effect For Tof-petmentioning

confidence: 99%

BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET

2017

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Due to detector developments in the last decade, the time-of-flight (TOF) method is now commonly used to improve the quality of positron emission tomography (PET) images. Clinical TOF-PET systems based on L(Y)SO:Ce crystals and silicon photomultipliers (SiPMs) with coincidence resolving times (CRT) between 325 ps and 400 ps FWHM have recently been developed. Before the introduction of L(Y)SO:Ce, BGO was used in many PET systems. In addition to a lower price, BGO offers a superior attenuation coefficient and a higher photoelectric fraction than L(Y)SO:Ce. However, BGO is generally considered an inferior TOF-PET scintillator. In recent years, TOF-PET detectors based on the Cherenkov effect have been proposed. However, the low Cherenkov photon yield in the order of ∼10 photons per event complicates energy discrimination-a severe disadvantage in clinical PET. The optical characteristics of BGO, in particular its high transparency down to 310 nm and its high refractive index of ∼2.15, are expected to make it a good Cherenkov radiator. Here, we study the feasibility of combining event timing based on Cherenkov emission with energy discrimination based on scintillation in BGO, as a potential approach towards a cost-effective TOF-PET detector. Rise time measurements were performed using a timecorrelated single photon counting (TCSPC) setup implemented on a digital photon counter (DPC) array, revealing a prompt luminescent component likely to be due to Cherenkov emission. Coincidence timing measurements were performed using BGO crystals with a cross-section of 3 mm × 3 mm and five different lengths between 3 mm and 20 mm, coupled to DPC arrays. NonGaussian coincidence spectra with a FWHM of 200 ps were obtained with the 27 mm 3 BGO cubes, while FWHM values as good as 330 ps were achieved Institute of Physics and Engineering in MedicineOriginal content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. with the 20 mm long crystals. The FWHM value was found to improve with decreasing temperature, while the FWTM value showed the opposite trend.

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Section: Cherenkov Effect For Tof-petmentioning

confidence: 99%

BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET

2017

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“…The selections of these detectors are thus very crucial to the system resolution and performance. Other nonconventional detectors that have shown ToF's capabilities include gaseous detectors, such as resistive-plate chambers (RPC) [46], and concepts based on detection of prompt Cerenkov light are also being investigated [47].…”

Section: Choice Of Detectors For Tof-petmentioning

confidence: 99%

Instrumentation for Time-of-Flight Positron Emission Tomography

Ullah

Pratiwi

Cheon

et al. 2016

Nucl Med Mol Imaging

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Positron emission tomography (PET) is a molecular imaging modality that provides information at the molecular level. This system is composed of radiation detectors to detect incoming coincident annihilation gamma photons emitted from the radiopharmaceutical injected into a patient's body and uses these data to reconstruct images. A major trend in PET instrumentation is the development of time-of-flight positron emission tomography (ToF-PET). In ToF-PET, the time information (the instant the radiation is detected) is incorporated for image reconstruction. Therefore, precise and accurate timing recording is crucial in ToF-PET. ToF-PET leads to better localization of the annihilation event and thus results in overall improvement in the signal-to-noise ratio (SNR) of the reconstructed image. Several factors affect the timing performance of ToF-PET. In this article, the background, early research and recent advances in ToF-PET instrumentation are presented. Emphasis is placed on the various types of scintillators, photodetectors and electronic circuitry for use in ToF-PET, and their impact on timing resolution is discussed.

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“…Consequently, we hypothesized that the coincidence timing resolution of BGO can be much improved by efficiently detecting these Cerenkov photons, while scintillation photons are still used for determining energy information. However, the number of Cerenkov photons is very small compared to the scintillation photons (Williams et al 2001, Lecoq et al 2010, Korpar et al 2011, Brunner et al 2014). For BGO, the energy threshold for an energetic electron to emit Cerenkov photons is about 66 keV given the refractive index of 2.15.…”

Section: Introductionmentioning

confidence: 99%

Bismuth germanate coupled to near ultraviolet silicon photomultipliers for time-of-flight PET

Kwon¹,

Gola²,

Ferri³

et al. 2016

Phys. Med. Biol.

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Bismuth germanate (BGO) was a very attractive scintillator in early-generation positron emission tomography (PET) scanners. However, the major disadvantages of BGO are lower light yield and longer rise and decay time compared to currently popular scintillators such as LSO and LYSO. This results in poorer coincidence timing resolution and it has generally been assumed that BGO is not a suitable scintillator for time-of-flight (TOF) PET applications. However, when a 511-keV photon interacts in a scintillator, a number of Cerenkov photons are produced promptly by energetic electrons released by photoelectric or Compton interactions. If these prompt photons can be captured, they could provide a better timing trigger for PET. Since BGO has a high refractive index (increasing the Cerenkov light yield) and excellent optical transparency down to 320 nm (Cerenkov light yield is higher at shorter wavelengths), we hypothesized that the coincidence timing resolution of BGO can be significantly improved by efficient detection of the Cerenkov photons. However, since the number of Cerenkov photons is far less than the number of scintillation photons, and they are more abundant in the UV and blue part of the spectrum, photosensors need to have high UV/blue sensitivity, fast temporal response, and very low noise in order to trigger on the faint Cerenkov signal. In this respect, NUV-HD silicon photomultipliers (SiPMs) (FBK, Trento, Italy) are an excellent fit for our approach. In this study, coincidence events were measured using BGO crystals coupled with NUV-HD SiPMs. The existence and influence of Cerenkov photons on the timing measurements were studied using different configurations to exploit the directionality of the Cerenkov emissions. Coincidence resolving time values (FWHM) of ~270 ps from 2 × 3 × 2 mm3 BGO crystals and ~560 ps from 3 × 3 × 20 mm3 BGO crystals were obtained. To our knowledge, these are the best coincidence resolving time values reported for BGO to date. With these values, BGO can be considered as a relevant scintillator for TOF PET scanners, especially if photodetectors with even better near UV/blue response can be developed to further improve the efficiency of Cerenkov light detection.

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Study of TOF PET using Cherenkov light

Cited by 77 publications

References 13 publications

BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET

BGO as a hybrid scintillator / Cherenkov radiator for cost-effective time-of-flight PET

Instrumentation for Time-of-Flight Positron Emission Tomography

Bismuth germanate coupled to near ultraviolet silicon photomultipliers for time-of-flight PET

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