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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Deep Learning Models for PET Scatter Estimations
摘要： Projection data acquired from a positron emission tomography (PET) scanner consist of true, scattered and random events. Scattered events can cause severe artifacts and quantitation errors in reconstructed PET images unless corrected for properly. A scatter correction algorithm is required to predict scattered events from the measurement. Scatter correction requires estimation of both single scatter and multiple scatter profiles. Usually, single scatter profiles are calculated by model-based simulation and multiple scatter profiles are estimated by a kernel-based convolution method. However, design of the convolution kernels for multiple scatter estimation is sophisticated and requires fine parameter tuning. In this work, we adopt deep learning techniques for scatter estimation. We propose two convolutional neural networks. The first network estimates multiple scatter profiles from single scatter profiles, replacing the kernel-based convolution method. The second network is designed to predict the total scatter profiles (including single and multiple scatters) directly from the input of emission and attenuation sinograms. Initial results from both networks show a promise with the potential for more accurate and faster scatter correction for PET.
关键词： Monte Carlo Simulation,Deep Learning,Scatter Estimation,Convolutional Neural Networks,PET
更新于2025-09-09 09:28:46
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Effect of PET-MR Inconsistency in the Kernel Image Reconstruction Method
摘要： Anatomically-driven image reconstruction algorithms have become very popular in positron emission tomography (PET) where they have demonstrated improved image resolution and quantification. This work, consider the effect of spatial inconsistency between MR and PET images in hot and cold regions of the PET image. We investigate these effects on the kernel method from machine learning, in particular, the hybrid kernelized expectation maximization (HKEM). These were applied to Jaszczak phantom and patient data acquired with the Biograph Siemens mMR. The results show that even a small shift can cause a significant change in activity concentration. In general, the PET-MR inconsistencies can induce the partial volume effect, more specifically the 'spill-in' of the affected cold regions and the 'spill-out' from the hot regions. The maximum change was about 100% for the cold region and 10% for the hot lesion using KEM, against the 37% and 8% obtained with HKEM. The findings of this work suggest that including PET information in the kernel enhances the flexibility of the reconstruction in case of spatial inconsistency. Nevertheless, accurate registration and choice of the appropriate MR image for the creation of the kernel is essential to avoid artifacts, blurring, and bias.
关键词： hybrid kernel,image prior,expectation maximization (EM),kernel method,positron emission tomography (PET),iterative reconstruction,anatomically-driven
更新于2025-09-09 09:28:46
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Utility of first positron emission tomography-computed tomography scan as a prognostic tool following treatment of sinonasal and skull base malignancies
摘要： Background: The prognostic value of the first posttreatment whole body integrated positron emission tomography-computed tomography (PET/CT) scanning in patients with sinonasal/skull base malignancies is undetermined. Methods: We retrospectively reviewed the data of all patients that underwent surgery for sinonasal/skull base malignancies in 2000-2015. The results of the pretreatment and posttreatment PET/CT findings and the clinical course were retrieved. Results: Thirty-eight patients (average age 60.6 years, 20 males) were included. Sensitivity and specificity, positive predictive value, and negative predictive value of the first PET/CT scan for predicting persistent/recurrent disease were 85.7%, 87.5%, 80%, and 91.3%, respectively. Overall 5-year survival was significantly lower in the first posttreatment PET/CT-positive group (35%) compared to the PET/CT-negative group (93%) (P = .0008). Conclusion: Posttreatment PET/CT findings are highly prognostic in patients with sinonasal/skull base malignancies. Negative findings on the first posttreatment PET/CT scan predict a significantly better overall survival.
关键词： sinonasal malignancy,skull base,prognosis,PET/CT,survival
更新于2025-09-09 09:28:46
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Photoplethysmography in dogs and cats: a selection of alternative measurement sites for pet monitor
摘要： Objective: Photoplethysmography (PPG) is an increasingly popular health and well-being tool for monitoring heart rate and oxygen saturation. Due to pigmentation and hairiness of dogs and cats, a pulse oximeter is routinely placed solely on the tongue. As this approach is feasible only for the pet monitor use during surgical procedures, we investigate PPG signal quality on several other measurement sites that would be better tolerated by conscious animals. Approach: Acquired PPG signals are analyzed by four signal quality indices (SQI): mean baseline, signal power, kurtosis, and tolerance score. Main Results: In dogs, the metacarpus and tail can substitute for oral pulse oximeter placement since both measurement sites exhibited high PPG signal kurtosis and were considered well-tolerated. In cats, the digit could be used with some limitations. Significance: Pet monitors with pulse oximeter probes adjusted to promising measurement sites, could enable veterinarians and owners to monitor animals when fully awake.
关键词： pet monitor,motion artifact,veterinary medicine,oxygen saturation,heart rate,pulse oximeter,signal quality index,photoplethysmography
更新于2025-09-09 09:28:46
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The use of F-FDG PET/CT in testicular cancer
摘要： Testicular germ cell tumors are one of the most common neoplasms in young men. After inguinal orchiectomy is performed, treatment options range from active surveillance to chemotherapy, radiation therapy or retroperitoneal lymphadenectomy. For the accurate use of the different treatment options, precise imaging techniques are necessary to reduce side effects of the aggressive therapies but also to avoid undertreatment exposing the patient to the risk of recurrence. F-FDG PET/CT is already recommended in the European guidelines for the follow up of seminomas under certain conditions but conventional primary staging or restaging is still performed with CT or MRI. Recently, the importance of F-FDG PET/CT in this context has become an interesting topic of academic discussion and subject of various clinical trials which are reviewed in the following.
关键词： unclear scrotal mass,F-FDG PET/CT,testicular cancer,testicular germ cell tumor
更新于2025-09-09 09:28:46
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Molecular Imaging of Neuroinflammation in HIV
摘要： The development of combined antiretroviral therapy (cART) has increased the lifespan of persons living with HIV (PLWH), with most PLWH having a normal life expectancy. While significant progress has occurred, PLWH continue to have multiple health complications, including HIVassociated neurocognitive disorders (HAND). While the exact cause of HAND is not known, persistent neuroinflammation is hypothesized to be an important potential contributor. Molecular imaging using positron emission tomography (PET) can non-invasively evaluate neuroinflammation. PET radiotracers specific for increased expression of the translocator protein18kDa (TSPO) on activated microglia can detect the presence of neuroinflammation in PLWH. However, results from these studies have been inconsistent and inconclusive. Future studies are needed to address key limitations that continue to persist with these techniques before accurate conclusions can be drawn regarding the role of persistent neuroinflammation in PLWH.
关键词： Neuroinflammation,Human immunodeficiency virus (HIV),Positron emission tomography (PET),Translocator protein 18 kDa (TSPO),HIV-associated neurocognitive impairment (HAND)
更新于2025-09-09 09:28:46
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Development of 2-(2-(3-(4-([18F]Fluoromethoxy-d2)phenyl)-7-methyl- 4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione for Positron Emission Tomography Imaging of Phosphodiesterase 10A (PDE10A) in Brain
摘要： Phosphodiesterase 10A (PDE10A) is a newly identified therapeutic target for central nervous system disorders. 2-(2-(3-(4-([18F]Fluoroethoxy)phenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]MNI-659, [18F]5) is a useful positron emission tomography (PET) ligand for imaging of PDE10A in the human brain. However, the radiolabeled metabolite of [18F]5 can accumulate in the brain. In this study, using [18F]5 as a lead compound, we designed four new 18F-labeled ligands ([18F]6–9) to find one more suitable than [18F]5. Of these, 2-(2-(3-(4-([18F]fluoromethoxy-d2)phenyl)-4-oxo-3,4-dihydroquinazolin-2-yl)ethyl)-4-isopropoxyisoindoline-1,3-dione ([18F]9) exhibited high in vitro binding affinity (Ki = 2.9 nM) to PDE10A and suitable lipophilicity (LogD = 2.2). In PET studies, the binding potential (BPND) of [18F]9 (5.8) to PDE10A in rat brains was significantly higher than that of [18F]5 (4.6). Furthermore, metabolite analysis showed much lower levels of contamination with radiolabeled metabolites of [18F]9 in the brain than those of [18F]5. In conclusion, [18F]9 is a useful PET ligand for PDE10A imaging in brain.
关键词： [18F]MNI-659,PDE10A,PET imaging,[18F]fluoromethoxy-d2,brain,Phosphodiesterase 10A,radioligand
更新于2025-09-09 09:28:46
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Prototype time-of-flight PET utilizing capacitive multiplexing readout method
摘要： Positron emission tomography (PET) is an imaging technique that provides the spatial distribution of radiopharmaceuticals labeled with positron emitting radioisotopes by detecting the gamma rays produced from positron-electron annihilation. Recently, a time-of-flight (TOF) PET has drawn an increasing attention because it is capable of reducing the scan time or injected dose with improved the signal-to-noise ratio (SNR) in reconstructed PET images by precisely localizing the emission point along the line-of-response using TOF information. This study presents a multiplexing method that can effectively reduce the number of readout channels of a silicon photomultiplier (SiPM) based TOF PET while achieving excellent timing resolution. A capacitive multiplexing method was employed that could improve the degradation of the timing performance occurring in a conventional resistive multiplexing method. In addition, a high-speed signal processing method is also presented for the TOF PET. A TOF PET prototype was developed to demonstrate the imaging capability of the TOF PET system. A flood histogram of a PET detector module, composed of an 8×8 array of 3.01×3.01×20.00 mm3 lutetium fine silicate (LFS) scintillators and an 8×8 array of 3.16×3.16 mm2 SiPMs, was acquired using the proposed method. All 64 scintillators were successfully resolved in the flood histogram. The average energy resolution and coincidence resolving time (CRT) were 14.2±1.1% and 431±41 ps full width at half maximum (FWHM), respectively. A tomographic image of the hot-rod phantom was successfully acquired using the TOF PET prototype, and rods with a size of 2.4 mm in diameter were clearly resolved in the reconstructed image.
关键词： PET imaging,silicon photomultiplier,Time-of-flight PET,capacitive multiplexing,timing resolution
更新于2025-09-04 15:30:14
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Visual and Quantitative Assessment of a New Anisotropic Diffusion Filter (Statistical Transfer with Optimizing Noise and Edge Sensing) for Positron Emission Tomography
摘要： Post-filtering with a Gaussian filter is commonly used to reduce noise in positron emission tomography (PET) images. However, its non-selective smoothing obscures the edges of lesions or organs. We compared the performance of a newly developed anisotropic diffusion filter called “Statistical Transfer with Optimizing Noise and Edge Sensing” (STONES) with that of the Gaussian filter for small lesions on PET images. We selected seven PET/computed tomography (CT) image slices of the lungs from three patients with multiple lung metastases. For each slice, the lesion detection rates by two physicians (A and B) were compared for Gaussian- and STONES-filtered PET images. The maximum standardized uptake (SUVmax) values of the detected lesions were also compared for non-, Gaussian-, and STONES-filtered images. Physician A detected 19 lesions in the Gaussian-filtered images and 23 lesions in the STONES-filtered images, while Physician B detected 14 lesions in the Gaussian-filtered images and 19 lesions in the STONES-filtered images. SUVmax for the STONES-filtered images was significantly higher and closer to that of the non-filtered images compared to those for the Gaussian-filtered images. STONES improved the detection rate and increased SUVmax in comparison with Gaussian filter. Thus, it should be more advantageous for the detection of small lesions with PET.
关键词： Anisotropic diffusion filter,Lung,Edge preservation,Gaussian filter,STONES,FDG-PET
更新于2025-09-04 15:30:14
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Multimodal Imaging in Lung Cancer: It Is Time to Change
摘要： The imaging techniques can be classified into two main groups: Structural/morphological imaging (SMI), which includes X rays (XR), computed tomography (CT), ultrasounds (US) as well as some varieties of magnetic resonance (MRI), and shows anatomic-morphological aspects, and molecular imaging (MI), which includes nuclear medicine (SPECT, PET), fMRI, optical and nanosystems techniques, and provides information about biochemistry/biological activity, often before structural changes. According to Society of Nuclear Medicine and Molecular Imaging, MI “is the visualization, characterization, and measurement of biological processes at the molecular and cellular levels in humans and other living systems”. MI procedures are noninvasive, safe and painless. Its sensitivity is greater than SMI, but it lacks anatomical detail, which has led to the development of multimodal imaging, combining structural and molecular techniques, widely used at present in daily practice. The pillars of MI are biochemistry/biology, instrumentation and software, and its cycle is the following: study of biology/biochemistry of a process, establishment/definition of specific targets, and development of tracers, preclinical imaging, histological validation and finally clinical imaging. This new concept led to the individualized diagnostic and treatment, being the patient the center of the medical activity. “As opposed to the doctor-centric, curative model of the past, the future is going to be patient-centric and proactive” said Dr. Zerhouni (NIH Medline Plus Winter 2007). The doctor must adapt to the needs of the own patient and this fact requires a true change of heart, because MI is intimately tied to the biology of the disease to analyzing. A new and strong interrelationship came into being: a bidirectional system biology-imaging that will allow to be much more effective in the daily practice, not only in relation to diagnosis (specific and early), but also with therapy (guide cancer treatment selection and evaluate early treatment response). There is an absolute necessity to lock the two together. Likewise, in the future the biology of a disease will indicate us what is the most adequate imaging technique and vice versa. In this regard, we know that in non-small cell lung cancer (NSCLC), ALK+ status is associated with distinct characteristics at CT imaging (CT radiogenomic characterization) [1], and that in lung adenocarcinomas 18F-FDG uptake values are related with expression levels of cellular Glucose Transporters and EGFR mutations. For this reason, different EGFR mutations correlate with different FDG uptake values.
关键词： Small Cell Lung Cancer,PET,Biomarkers,CT,MRI,Lung Cancer,Molecular Imaging,Multimodal Imaging,Non-Small Cell Lung Cancer,Structural/Morphological Imaging
更新于2025-09-04 15:30:14