Influence of Depth of Interaction upon the Performance of Scintillator Detectors

Brown, Mark S.; Gundacker, S.; Taylor, Alaric; Tummeltshammer, Clemens; Auffray, E.; Lecoq, P.; Papakonstantinou, Ioannis

doi:10.1371/journal.pone.0098177

Cited by 8 publications

(7 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Even though the DOI time offset issue has been studied in the past through Monte Carlo simulations (Brunner et al 2013) and experimental measurements (Brown et al 2014), the limitation of an analytical approach such as the MergedPTS model to study this time offset impact on CTR was not highlighted previously in the literature. This is likely due to the relatively limited influence of the PTS on CTR when compared to the combination of emission rate and SPTR for the typical detectors available today.…”

Section: Mergedpts Model For Typical Detectorsmentioning

confidence: 99%

Analytical model of DOI-induced time bias in ultra-fast scintillation detectors for TOF-PET

2019

View full text Add to dashboard Cite

In positron emission tomography (PET), long crystals (20 mm) are used to enhance detection efficiency and increase scanner sensitivity. However, for fast time-of-flight (TOF) scanners, this may affect the achievable coincidence time resolution (CTR) due to depth-of-interaction (DOI) induced blur on timing. Currently, the effect of DOI on CTR evaluation with analytical modeling is incorporated using the probability density function (PDF) for attenuation of the annihilation photons with the PDFs of the other scintillation processes. However, we show that the resulting PDF would not describe accurately the variation in timestamps distribution at different DOIs. We propose a new analytical model for the CTR evaluation, which consists of computing a DOI dependent CTR weighted by the DOI probability in coincidence. The CTR was thus defined as the weighted root-mean-square error (RMSE) of the DOI-wise variance and bias in order to explicitly describe the positioning bias induced by coincident annihilation photons at different DOIs. The effect of DOI bias on CTR was investigated by using four classic estimators found in the literature, each applied on contemporary scintillation detectors and nearly ideal detectors. A limited difference in the calculated CTR was found for typical scintillation detectors when assessing RMSE with and without DOI time offset correction. This was expected since the DOI bias remains negligible against other phenomena in such case. However, the difference becomes significant for nearly ideal scintillation detectors, where optimal CTR would only be attainable with DOI correction. For these nearly ideal cases, the revised model has better predictive power since the DOI time offset correction is included. Investigation with analytical approaches for realistically achievable ultra-fast CTR in TOF-PET detectors should be performed with a model that genuinely takes into account the DOI effect. We show that the proposed model is a valid candidate for such a task.

show abstract

Section: Mergedpts Model For Typical Detectorsmentioning

confidence: 99%

Analytical model of DOI-induced time bias in ultra-fast scintillation detectors for TOF-PET

2019

View full text Add to dashboard Cite

show abstract

“…A possible way to compensate the effect of the PTS would be double-sided readout of the crystal with correction for depth of interaction (DOI). However, CTR measurements of Brown et al (2014) showed that from standard scintillation no improvements were observed if the scintillation is confined to a fixed DOI. Nevertheless, double-sided readout of 20 mm long crystals would still have the advantage of reducing parallax-errors in PET because of the DOI information, and would furthermore allow better CTRs due to higher light collection comparable to that of 10 mm long, single-sided readout, crystals (Gundacker 2014).…”

Section: Discussionmentioning

confidence: 96%

Measurement of intrinsic rise times for various L(Y)SO and LuAG scintillators with a general study of prompt photons to achieve 10 ps in TOF-PET

Gundacker

Auffray²,

Pauwels³

et al. 2016

Phys. Med. Biol.

150

144

View full text Add to dashboard Cite

The coincidence time resolution (CTR) of scintillator based detectors commonly used in positron emission tomography is well known to be dependent on the scintillation decay time (τd) and the number of photons detected (n'), i.e. CTR proportional variant √τd/n'. However, it is still an open question to what extent the scintillation rise time (τr) and other fast or prompt photons, e.g. Cherenkov photons, at the beginning of the scintillation process influence the CTR. This paper presents measurements of the scintillation emission rate for different LSO type crystals, i.e. LSO:Ce, LYSO:Ce, LSO:Ce codoped Ca and LGSO:Ce. For the various LSO-type samples measured we find an average value of 70 ps for the scintillation rise time, although some crystals like LSO:Ce codoped Ca seem to have a much faster rise time in the order of 20 ps. Additional measurements for LuAG:Ce and LuAG:Pr show a rise time of 535 ps and 251 ps, respectively. For these crystals, prompt photons (Cherenkov) can be observed at the beginning of the scintillation event. Furthermore a significantly lower rise time value is observed when codoping with calcium. To quantitatively investigate the influence of the rise time to the time resolution we measured the CTR with the same L(Y)SO samples and compared the values to Monte Carlo simulations. Using the measured relative light yields, rise- and decay times of the scintillators we are able to quantitatively understand the measured CTRs in our simulations. Although the rise time is important to fully explain the CTR variation for the different samples tested we determined its influence on the CTR to be in the order of a few percent only. This result is surprising because, if only photonstatistics of the scintillation process is considered, the CTR would be proportional to the square root of the rise time. The unexpected small rise time influence on the CTR can be explained by the convolution of the scintillation rate with the single photon time resolution (SPTR) of the photodetector and the photon travel spread (PTS) in the crystal. The timing benefits of prompt photons at the beginning of the scintillation process (Cherenkov etc) are further studied, which leads to the conclusion that the scintillation rise time, SPTR and PTS have to be lowered simultaneously to fully profit from these fast photons in order to improve the CTR significantly.

show abstract

“…An accurate measure of scale is of interest as this can be used to find depth of interaction within the scintillator and therefore to improve energy resolution [55]. Also of interest is the predicted total blob intensity -the sum of all blob pixels excluding background -which indicates accurate reconstruction of deposited energy.…”

Section: Prediction Of Scale and Energymentioning

confidence: 99%

Automatic detection of scintillation light splashes using conventional and deep learning methods

Jiang¹,

Bugby²,

Cosma³

2022

J. Inst.

View full text Add to dashboard Cite

Six methods for the automatic detection of scintillation light splashes in a portable gamma camera are compared. Each imaging frame might contain any number of light splashes (including none), and the location and size of each light splash must be identified. For real-time imaging, splashes must be identified and characterised quickly and with minimal processing overhead. The techniques are compared on their ability to accurately determine the number, position, and size of light splashes, and to reconstruct the deposited energy within each splash for a simulated data set with known ground-truths. The speed of each technique and the ease of implementation are also discussed. For accuracy in blob (light splash) localisation, a Laplacian of Gaussian approach was found to provide the most accurate estimation. However, its performance greatly relies on the appropriate tuning of preprocessing parameters prior to image analysis and the number of blobs in each frame. Deep learning approaches (Faster-RCNNs) performed significantly better than traditional algorithms in terms of predicting the size of each light splash, did not require image preprocessing and were also more stable over a range of frame occupancies. Moreover, the paper fine-tuned a VGG16 based Faster-RCNN model with the simulated data set for the scintillation light splash detection, called DeepSplashSpotter (DSS).

show abstract

Influence of Depth of Interaction upon the Performance of Scintillator Detectors

Cited by 8 publications

References 19 publications

Analytical model of DOI-induced time bias in ultra-fast scintillation detectors for TOF-PET

Analytical model of DOI-induced time bias in ultra-fast scintillation detectors for TOF-PET

Measurement of intrinsic rise times for various L(Y)SO and LuAG scintillators with a general study of prompt photons to achieve 10 ps in TOF-PET

Automatic detection of scintillation light splashes using conventional and deep learning methods

Contact Info

Product

Resources

About