Time-of-flight PET time calibration using data consistency

Defrise, Michel; Rezaei, Ahmadreza

doi:10.1088/1361-6560/aabeda

Cited by 11 publications

(5 citation statements)

References 19 publications

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“…Even with our measured CTRs in the range of few hundreds of picoseconds FWHM, a range easily achieved nowadays, other sources of time offsets were important to take into account, such as the radioactive source exact position, SiPM delays and missed annihilation photon travel time when using side irradiation. There are already extensive works on time calibration in the context of TOF-PET to compensate for possible delays essentially due to SiPMs (Defrise et al 2018, Li 2019. Controlling very precisely all the possible time offsets that could impact the accuracy of the signal time-stamping process in a scanner is paramount to reach ultra-fast timing in the range of tens of picoseconds for TOF-PET.…”

Section: Discussionmentioning

confidence: 99%

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET

Loignon-Houle¹,

Toussaint²,

Lee³

et al. 2020

Phys. Med. Biol.

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Depth-of-interaction (DOI) variability of annihilation photons is known to be a source of coincidence time resolution (CTR) degradation for fast time-of-flight–positron emission tomography detectors. An analytical model was recently proposed to explicitly include the DOI time bias separately from variance-related statistical factors, such as scintillation photon emission and photosensor jitter, in the CTR evaluation. In the present work, an experimental validation of this new model is provided. An unconventional signal readout configuration was used to magnify the DOI bias with 20 mm long LYSO:Ce crystals. In a head-to-head orientation of the crystals, simulations performed using the metric with DOI bias exhibited a much better agreement (within 21 ps) with the experimentally measured CTR of 413 ± 8 ps full-width at half maximum, whereas simulations without DOI bias underestimated the CTR by 138 ps. The metric including DOI bias was shown to also be effective at predicting the CTR of the head-to-head setup (without DOI information) using data from a DOI-collimated experimental setup (with partial DOI information). With the development of new low-variance ultra-fast detectors, the DOI timing blur will become increasingly important and will need to be taken into account in analytical predictions and in some experimental measurements through the proposed metric.

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Section: Discussionmentioning

confidence: 99%

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET

Loignon-Houle¹,

Toussaint²,

Lee³

et al. 2020

Phys. Med. Biol.

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“…To finish this Section, recent work has indicated that MLAA can be sensitive to errors in the system modeling including timing calibration. Methods to compensate for this are still under development …”

Section: Past and Present Attenuation Estimation Methodsmentioning

confidence: 99%

PET/MRI attenuation estimation in the lung: A review of past, present, and potential techniques

et al. 2020

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Positron emission tomography/magnetic resonance imaging (PET/MRI) potentially offers several advantages over positron emission tomography/computed tomography (PET/CT), for example, no CT radiation dose and soft tissue images from MR acquired at the same time as the PET. However, obtaining accurate linear attenuation correction (LAC) factors for the lung remains difficult in PET/MRI. LACs depend on electron density and in the lung, these vary significantly both within an individual and from person to person. Current commercial practice is to use a single‐valued population‐based lung LAC, and better estimation is needed to improve quantification. Given the under‐appreciation of lung attenuation estimation as an issue, the inaccuracy of PET quantification due to the use of single‐valued lung LACs, the unique challenges of lung estimation, and the emerging status of PET/MRI scanners in lung disease, a review is timely. This paper highlights past and present methods, categorizing them into segmentation, atlas/mapping, and emission‐based schemes. Potential strategies for future developments are also presented.

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“…Based on linear fitting in logarithmic scales, the RMS errors with and without scatter were respectively proportional to N −0.520 and N −0.497 , with N denotes the total number of true events. The numerical method has the similar noise behavior to the method using integral equation (Defrise et al 2018).…”

Section: Timing Offsets Estimated From Noisy Datamentioning

confidence: 97%

“…Inspired by the paper (Werner and Karp 2013) and the recent works Aykac 2017, Rezaei et al 2017), we attempted to tackle the timing calibration problem using TOF data consistency. Most recently, Defrise et al (2018) presented a time calibration method using data consistency for 2-D TOF PET, and timing offsets can be computed by solving an integral equation. Since 3-D PET geometry is open along the axial direction, the method cannot be extended to 3-D (all current clinical PET scanners are operated in 3-D acquisition mode).…”

Section: Introductionmentioning

confidence: 99%

Consistency equations in native detector coordinates and timing calibration for time-of-flight PET

2019

Biomed. Phys. Eng. Express

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Fully 3-D time-of-flight (TOF) PET scanners offer the potential of previously unachievable image quality in clinical PET imaging. Timing calibration is critical to achieve the best possible timing resolution, to maximize the true counts and minimize the random counts. In this paper, we consider a data-driven timing calibration based on TOF data consistency. First, we derive two consistency equations for TOF data parameterized in the native detector coordinates where each line of response (LOR) is represented by the two azimuthal angles and axial coordinates of the two crystals detecting the LOR. By exploiting the consistency equations that must be satisfied by the time corrected TOF data, we derive the timing offset equations which only involve the zeroth and first moments with respect to the TOF variable. We also provide a numerical solution that unknown timing offsets can be directly estimated from the two moments by solving linear equations. The timing offsets can be determined up to a global constant which is immaterial for timing calibration. The data-driven timing calibration can be applied to data acquired with an arbitrary tracer distribution, which eliminates the need for a specialized data acquisition. We evaluate the timing calibration method with twodimensional numerical simulations. The results show that the timing offsets can be determined with root mean square (RMS) errors of 1 ps and 15 ps from noise-free data and from noisy data with 16 million counts, respectively. Next generation TOF PET scanners have significantly improved timing resolution using silicon photomultiplier (SiPM) based detectors, which may require frequent timing calibration and close monitoring in performance compared to photomultiplier-tube based detectors. The proposed data-driven method allows the residual timing offsets be corrected automatically using clinical data sets whenever computing resources are available.

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Time-of-flight PET time calibration using data consistency

Cited by 11 publications

References 19 publications

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET

Experimental validation of a coincidence time resolution metric including depth-of-interaction bias for TOF-PET

PET/MRI attenuation estimation in the lung: A review of past, present, and potential techniques

Consistency equations in native detector coordinates and timing calibration for time-of-flight PET

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