Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals

González-Montoro, Andrea; Sánchez, F.; Bruyndonckx, Peter; Cañizares, Gabriel; Benlloch, J.; González, Antonio J.

doi:10.1016/j.nima.2018.12.056

Cited by 24 publications

(23 citation statements)

References 39 publications

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“…Moreover, the whole assembly was placed inside a light tight box. A 22 Na source (1 mm in diameter, 475 kBq) was used for all experiments. All results mentioned below, have been obtained after applying about 30% (350-650 keV) energy window around the 511 keV photopeak.…”

Section: Detector Set-upsmentioning

confidence: 99%

“…In monolithic blocks the scintillation photons are isotropically emitted travelling straight in all directions, differently from the pixelated crystal case in which the optical photons are trapped inside bouncing on the walls until they reach one photosensor. The light spread in the monolithic block permits an accurate position decoding of the gamma ray impact, being a convenient choice for a high intrinsic detector spatial resolution [22]. In addition to the position, a monolithic scintillator could ideally show a better timing performance compared to a pixelated one, due to the fact that the generated optical photons are not suffering from the aforementioned internal reflections inside the crystal pixel introducing time delays.…”

Section: Introductionmentioning

confidence: 99%

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Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs

et al. 2020

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A B S T R A C TMonolithic scintillators are more frequently used in PET instrumentation due to their advantages in terms of accurate position estimation of the impinging gamma rays both planar and depth of interaction, their increased efficiency, and expected timing capabilities. Such timing performance has been studied when those blocks are coupled to digital photosensors showing an excellent timing resolution.In this work we study the timing behaviour of detectors composed by monolithic crystals and analog SiPMs read out by an ASIC. The scintillation light spreads across the crystal towards the photosensors, resulting in a high number of SiPMs and ASIC channels fired. This has been studied in relation with the Coincidence Timing Resolution (CTR). We have used LYSO monolithic blocks with dimensions of 50 × 50 × 15 mm 3 coupled to SiPM arrays (8 × 8 elements with 6 × 6 mm 2 area) which compose detectors suitable for clinical applications.While a CTR as good as 186 ps FWHM was achieved for a pair of 3 × 3 × 5 mm 3 LYSO crystals, when using the monolithic block and the SiPM arrays, a raw CTR over 1 ns was observed. An optimal timestamp assignment was studied as well as compensation methods for the time-skew and time-walk errors. This work describes all steps followed to improve the CTR. Eventually, an average detector time resolution of 497 ps FWHM was measured for the whole thick monolithic block. This improves to 380 ps FWHM for a central volume of interest near the photosensors. The timing dependency with the photon depth of interaction and planar position are also included.

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Section: Detector Set-upsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs

et al. 2020

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“…3D images were generated in a binary raw file with a matrix size of 416 × 416 × 50 voxels with 1 × 1 × 1 mm 3 voxel size. Since monolithic crystals allow one to define the pixel size, somehow based on the measured detector resolution [24], we have selected virtual detector pixels of 1 × 1 mm 2 , which is also a compromise between statistics and computational cost.…”

Section: Castor Reconstruction Platformmentioning

confidence: 99%

“…It was placed at the scanner center FOV. The phantom has a drilled hole of 3.2 mm in diameter and at 13 mm off-radial direction [24]. Through this hole, a silicone tube (170 mm Fig.…”

Section: Count Rate Performancementioning

confidence: 99%

Pilot performance of a dedicated prostate PET suitable for diagnosis and biopsy guidance

et al. 2020

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Background: Prostate cancer (PCa) represents one of the most common types of cancers facing the male population. Nowadays, to confirm PCa, systematic or multiparametric MRI-targeted transrectal or transperineal biopsies of the prostate are required. However, due to the lack of an accurate imaging technique capable to precisely locate cancerous cells in the prostate, ultrasound biopsies sample random parts of the prostate and, therefore, it is possible to miss regions where those cancerous cells are present. In spite of the improvement with multiparametric MRI, the low reproducibility of its reading undermines the specificity of the method. Recent development of prostatespecific radiotracers has grown the interest on using positron emission tomography (PET) scanners for this purpose, but technological improvements are still required (current scanners have resolutions in the range of 4-5 mm). Results: The main goal of this work is to improve state-of-the-art PCa imaging and diagnosis. We have focused our efforts on the design of a novel prostate-dedicated PET scanner, named ProsPET. This system has small scanner dimensions defined by a ring of just 41 cm inner diameter. In this work, we report the design, implementation, and evaluation (both through simulations and real data) of the ProsPET scanner. We have been able to achieve < 2 mm resolution in reconstructed images and high sensitivity. In addition, we have included a comparison with the Philips Gemini-TF scanner, which is used for routine imaging of PCa patients. The ProsPET exhibits better contrast, especially for rod sizes as small as 4.5 mm in diameter. Finally, we also show the first reconstructed image of a PCa patient acquired with the ProsPET. Conclusions: We have designed and built a prostate specific PET system, with a small footprint and improved spatial resolution when compared to conventional whole-body PET scanners. The gamma ray impact within each detector block includes accurate DOI determination, correcting for the parallax error. The potential role of combined organdedicated prostate-specific membrane antigen (PSMA) PET and ultrasound devices, as a prebiopsy diagnostic tool, could be used to guide sampling of the most aggressive sites in the prostate.

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“…Advantages of the monolithic system include reduced manufacturing costs of designs compared to pixelated crystals with decreasing cross section, a maximized detection efficiency due to reduced dead space, and also direct application of an inherent correction for depth of interaction, the effects of which can be important for PET systems with a small ring diameter such as preclinical or organ-specific systems. Current commercial and research systems have employed monolithic crystals for imaging purposes up to sizes of 50 mm × 50 mm × 20 mm [42,43]. Potential issues with monolithic crystal imaging include lower signal-to-noise (SNR) due to a wider spread of scintillation light compared to one-to-one coupling.…”

Section: Study Limitations and Future Improvementsmentioning

confidence: 99%

Simulation study of a coincidence detection system for non-invasive determination of arterial blood time-activity curve measurements

et al. 2020

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Background: Arterial sampling in PET studies for the purposes of kinetic modeling remains an invasive, time-intensive, and expensive procedure. Alternatives to derive the blood time-activity curve (BTAC) non-invasively are either reliant on large vessels in the field of view or are laborious to implement and analyze as well as being prone to many processing errors. An alternative method is proposed in this work by the simulation of a non-invasive coincidence detection unit. Results: We utilized GATE simulations of a human forearm phantom with a blood flow model, as well as a model for dynamic radioactive bolus activity concentration based on clinical measurements. A fixed configuration of 14 and, also separately, 8 detectors were employed around the phantom, and simulations were performed to investigate signal detection parameters. Bismuth germanate (BGO) crystals proved to show the highest count rate capability and sensitivity to a simulated BTAC with a maximum coincidence rate of 575 cps. Repeatable location of the blood vessels in the forearm allowed a half-ring design with only 8 detectors. Using this configuration, maximum coincident rates of 250 cps and 42 cps were achieved with simulation of activity concentration determined from 15 O and 18 F arterial blood sampling. NECR simulated in a water phantom at 3 different vertical positions inside the 8-detector system (Y = − 1 cm, Y = − 2 cm, and Y = −3 cm) was 8360 cps, 13,041 cps, and 20,476 cps at an activity of 3.5 MBq. Addition of extra axial detection rings to the half-ring configuration provided increases in system sensitivity by a factor of approximately 10. Conclusions: Initial simulations demonstrated that the configuration of a single halfring 8 detector of monolithic BGO crystals could describe the simulated BTAC in a clinically relevant forearm phantom with good signal properties, and an increased number of axial detection rings can provide increased sensitivity of the system. The system would find use in the derivation of the BTAC for use in the application of kinetic models without physical arterial sampling or reliance on image-based techniques.

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Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals

Cited by 24 publications

References 39 publications

Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs

Exploring TOF capabilities of PET detector blocks based on large monolithic crystals and analog SiPMs

Pilot performance of a dedicated prostate PET suitable for diagnosis and biopsy guidance

Simulation study of a coincidence detection system for non-invasive determination of arterial blood time-activity curve measurements

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