Fast Energy Dependent Scatter Correction for List-Mode PET Data

Alvarez-Gomez, Juan M.; Santos, Joaquín; Martínez, Laura Moliner; Rodríguez-Álvarez, M. J.

doi:10.3390/jimaging7100199

Cited by 5 publications

(4 citation statements)

References 42 publications

(45 reference statements)

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“…Once calculated, the scatter contribution may be subtracted from the data or added to the forward projection model. A few authors implemented experimental approaches based on multiple energy windows (spectral approaches) [116][117][118]. The basic hypothesis is that the whole energy spectrum of the scattered counts or at least the integral of that spectrum -from the lower energy discriminator to the upper one of the photopeak window -could be estimated given a big enough number of events below and above the photopeak.…”

Section: Scatter Correctionmentioning

confidence: 99%

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Galve,

Rodriguez-Vila,

Herraiz

et al. 2024

J. Inst.

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Hybrid imaging modalities combine two or more medical imaging techniques offering exciting new possibilities to image the structure, function and biochemistry of the human body in far greater detail than has previously been possible to improve patient diagnosis. In this context, simultaneous Positron Emission Tomography and Magnetic Resonance (PET/MR) imaging offers great complementary information, but it also poses challenges from the point of view of hardware and software compatibility. The PET signal may interfere with the MR magnetic field and vice-versa, posing several challenges and constrains in the PET instrumentation for PET/MR systems. Additionally, anatomical maps are needed to properly apply attenuation and scatter corrections to the resulting reconstructed PET images, as well motion estimates to minimize the effects of movement throughout the acquisition. In this review, we summarize the instrumentation implemented in modern PET scanners to overcome these limitations, describing the historical development of hybrid PET/MR scanners. We pay special attention to the methods used in PET to achieve attenuation, scatter and motion correction when it is combined with MR, and how both imaging modalities may be combined in PET image reconstruction algorithms.

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Section: Scatter Correctionmentioning

confidence: 99%

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Galve,

Rodriguez-Vila,

Herraiz

et al. 2024

J. Inst.

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“…A common method in PET/MRI to correct for attenuated and scattered events and enable quantitative PET imaging is the generation of AC maps. There are several approaches such as joint emission and attenuation reconstruction or energy‐based attenuation and scatter estimation, which could be used to correct PET images based on the emission data without the generation of AC maps 8–13 . Nevertheless, among other approaches, four main techniques for AC in PET/MRI have been established in the last decade: segment‐based AC, atlas/template‐based AC, PET‐based AC and more recently deep‐learning‐based AC 14.…”

Section: Introductionmentioning

confidence: 99%

“…There are several approaches such as joint emission and attenuation reconstruction or energy-based attenuation and scatter estimation, which could be used to correct PET images based on the emission data without the generation of AC maps. [8][9][10][11][12][13] Nevertheless, among other approaches, four main techniques for AC in PET/MRI have been established in the last decade: segmentbased AC, atlas/template-based AC, PET-based AC and more recently deep-learning-based AC.14 Independent of the vendor, the current clinical standard MR-based AC in whole-body PET/MRI is still the segment-based approach. 15-18 MR images, for example, based on a Dixon-VIBE MR sequence, are segmented into three or four tissue classes with predefined single LAC per tissue class.…”

Section: Introductionmentioning

confidence: 99%

Systematic evaluation of human soft tissue attenuation correction in whole‐body PET/MR: Implications from PET/CT for optimization of MR‐based AC in patients with normal lung tissue

Lindemann,

Gratz,

Grafe

et al. 2023

Medical Physics

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BackgroundAttenuation correction (AC) is an important methodical step in positron emission tomography/magnetic resonance imaging (PET/MRI) to correct for attenuated and scattered PET photons.PurposeThe overall quality of magnetic resonance (MR)‐based AC in whole‐body PET/MRI was evaluated in direct comparison to computed tomography (CT)‐based AC serving as reference. The quantitative impact of isolated tissue classes in the MR‐AC was systematically investigated to identify potential optimization needs and strategies.MethodsData of n = 60 whole‐body PET/CT patients with normal lung tissue and without metal implants/prostheses were used to generate six different AC‐models based on the CT data for each patient, simulating variations of MR‐AC. The original continuous CT‐AC (CT‐org) is referred to as reference. A pseudo MR‐AC (CT‐mrac), generated from CT data, with four tissue classes and a bone atlas represents the MR‐AC. Relative difference in linear attenuation coefficients (LAC) and standardized uptake values were calculated. From the results two improvements regarding soft tissue AC and lung AC were proposed and evaluated.ResultsThe overall performance of MR‐AC is in good agreement compared to CT‐AC. Lungs, heart, and bone tissue were identified as the regions with most deviation to the CT‐AC (myocardium −15%, bone tissue −14%, and lungs ±20%). Using single‐valued LACs for AC in the lung only provides limited accuracy. For improved soft tissue AC, splitting the combined soft tissue class into muscles and organs each with adapted LAC could reduce the deviations to the CT‐AC to < ±1%. For improved lung AC, applying a gradient LAC in the lungs could remarkably reduce over‐ or undercorrections in PET signal compared to CT‐AC (±5%).ConclusionsThe AC is important to ensure best PET image quality and accurate PET quantification for diagnostics and radiotherapy planning. The optimized segment‐based AC proposed in this study, which was evaluated on PET/CT data, inherently reduces quantification bias in normal lung tissue and soft tissue compared to the CT‐AC reference.

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“…However, there have been some recent advances (Guérin et al 2010, Berker et al 2017, 2019, Brusaferri et al 2020, Álvarez-Gómez et al 2021 in successfully utilizing scattered data in finding the attenuation map. For instance, an algorithm has been proposed by Brusaferri et al (2020) for the simultaneous estimation of both activity and attenuation images, incorporating the scatter component of the measured PET data with multiple energy windows.…”

Section: Introductionmentioning

confidence: 99%

Improvement of CNR in low-count PET scans using tissue-scattered data as initial estimate in non-TOF MLEM reconstruction

Ghosh¹,

Das²

2023

Biomed. Phys. Eng. Express

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We have proposed a method to improve contrast-to-noise ratios (CNRs) of lesions in low-count PET scans using the rejected single scattered (inside tissue) data. Indeed, with the advent of high-quality detectors regarding their energy and time resolution, and list mode data acquisition, adding single scattered events by estimating their original line of response has become more and more feasible. The low-count PET scan data were simulated using GATE software considering Jaszczak type object, and images were reconstructed using STIR. A deconvolution based method to create images from rejected single scatter data has been proposed. These scatter images were, in turn, used as an initial estimate in non-TOF MLEM reconstruction. Three types of human-sized PET scanners – ideal, state-of-art, and future generation – with different timing and energy resolutions were considered. We found a significant improvement in trade-off between the contrast recovery coefficient (CRC) and coefficient of variation (CoV) for the non-TOF MLEM reconstructed images while comparing with other less computational ways of creating initial estimates. CNR improvements were found for all lesions. The present work demonstrated the beneficial use of tissue-scattered TOF PET events which constitutes a high percentage of data in PET imaging, and rejected in general. Our approach has a potential and scope for further study.

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Fast Energy Dependent Scatter Correction for List-Mode PET Data

Cited by 5 publications

References 42 publications

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Systematic evaluation of human soft tissue attenuation correction in whole‐body PET/MR: Implications from PET/CT for optimization of MR‐based AC in patients with normal lung tissue

Improvement of CNR in low-count PET scans using tissue-scattered data as initial estimate in non-TOF MLEM reconstruction

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