Diffusion Of Tracer Research Articles

Superdiffusion and heterogeneous dynamics in liquid crystals by microrheology

Microrheology (MR) has emerged as a powerful tool for unraveling the intricate local viscoelastic properties of various soft materials. By tracking the free (passive MR) or forced (active MR) diffusion of a tracer, valuable insights into the mechanical characteristics of the host system can be obtained. In this study, we investigate the forced diffusion of a spherical tracer within isotropic and smectic liquid crystal phases of hard rod-like particles. Our findings reveal superdiffusive behaviour induced by external forces, particularly pronounced when these are aligned parallel to the nematic director. Analysis of the dynamical susceptibility unveils heterogeneities strongly correlated with the magnitude and orientation of applied forces, highlighting the system's critical dependence on structural ordering. Intriguingly, we observe that tracer superdiffusion, driven by external forces and evident across all relevant system directions, does not demonstrate a strong correlation with resulting dynamical heterogeneities.

Clinical use of [18F]fluoro-ethyl-L-tyrosine PET co-registered with MRI for localizing prolactinoma remnants

PurposeTo assess the utility of [18F]fluoroethyl-L-tyrosine PET co-registered with magnetic resonance imaging ([18F]FET-PET/MRICR) in patients with difficult-to-localize prolactinoma to inform clinical decision-making and (surgical) treatment planning.MethodsRetrospective cohort study of 17 consecutive patients with prolactinoma undergoing [18F]FET-PET/MRICR between October 2020 and September 2022 for either (1) additional information in case of difficult-to-visualize remnants after prior transsphenoidal surgery (TSS), or pharmacological treatment, or (2) radiological diagnosis in absence of a (clear) adenoma on diagnostic/post-treatment conventional MRI.Results[18F]FET-PET/MRICR identified a lesion in 14/17 patients, yet failed to identify active lesions in 2 patients with negative conventional MRI despite prolactin > 7.5 times upper limit of normal. [18F]FET-PET/MRICR results were inconclusive in 1 patient due to diffuse tracer uptake 10 weeks post-surgery. [18F]FET-PET/MRICR was completely concordant with a suspected lesion on conventional MRI in 10/17 patients, and partially concordant in 3/17 patients. New foci were identified in 4/17 patients. The [18F]FET-PET/MRICR conclusions influenced clinical shared decision-making in 15/17 patients, of whom 7 patients underwent TSS and 8 refrained from TSS. One patient underwent TSS despite negative [18F]FET-PET/MRICR, and one patient underwent additional imaging. Intraoperative findings corresponded with [18F]FET-PET/MRICR in 5/8 patients, and immunohistochemistry was positive in 5/8 patients. The treatment goal was achieved in 7/8 patients, and remission was achieved in 5/7 patients in whom total resection was considered feasible.Conclusion[18F]FET-PET/MRICR can be of added value in the preoperative decision-making process for selected patients with difficult-to-localize prolactinoma (remnants), or patients lacking a substrate on conventional MRI.

Osteochondral fluid transport in an ex vivo system

ObjectiveAlterations to fluid transport from bone-to-cartilage may contribute to the development of osteoarthritis. Larger biological molecules found in bone may transport from bone-to-cartilage (e.g., insulin, 5kDa). However, many questions remain about fluid transport between these tissues. The objectives of this study were to (1) test for diffusion of 3kDa molecular tracers from bone-to-cartilage and (2) assess potential differences in bone-to-cartilage fluid transport between different loading conditions. DesignOsteochondral cores extracted from bovine femurs (N=10 femurs, 10 cores/femur) were subjected to either no-load (i.e., pure diffusion), pre-load only, or cyclic compression (5±2% or 10±2% strain) in a two-chamber transport system. The bone was placed into the bone compartment followed by a 3kDa dextran tracer, and tracer concentrations in the cartilage compartment were measured every 5 minutes for 120 minutes. Tracer concentrations were analyzed for differences in beginning, peak and equilibrium concentrations, loading effects, and time-to-peak tracer concentration. ResultsPeak tracer concentration in the cartilage compartment was significantly higher compared to beginning and equilibrium tracer concentrations indicating fluid transport from bone-to-cartilage. Cartilage-compartment tracer concentration, and maximum fluorescent intensity was influenced by strain magnitude. No time-to-peak relationship was found when comparing strain magnitudes impact on cartilage-compartment tracer concentration. ConclusionThis study shows that osteochondral fluid transport occurs from bone-to-cartilage with 3kDa dextran molecules. These are much larger molecules to move between bone and cartilage than previously reported. Further, these results demonstrate the potential for cyclic compression to impact osteochondral fluid transport. Determining the baseline osteochondral fluid transport in healthy tissues is crucial to elucidating the potential mechanisms of progression and onset of osteoarthritis.

Archie's cementation factors for natural rocks: Measurements and insights from diagenetic perspectives

Archie's cementation factor, m, is a critical parameter for petrophysical studies, and the value is influenced by several factors such as the shape, type, and size of grains, degrees of diagenesis, and associated pore structure. Using integrated experimental and theoretical approaches, the goal of this study is to obtain the cementation factor of rocks (both reservoir rock and caprock) and assess the impact of diagenetic processes on the values of the cementation factor. Thirteen samples of geologically diverse rocks (six mudstones, four fossiliferous limestones, two marbles, and one sandstone) were selected to achieve these research objectives. Two approaches, the diffusion of gas tracers and the Bosanquet formula calculation using pore-throat sizes from mercury intrusion porosimetry analyses, were used to derive the cementation factors of these rock samples. These rocks were categorized into two groups based on the correlation between average pore-throat diameter and diffusivity, and an exponential-law relationship between the cementation factor and porosity was determined for these sample groups. In addition, thin-section petrography and field emission-scanning electron microscopy observations were utilized to investigate diagenetic processes, with four diagenetic patterns being established: (1) strong compaction, strong cementation, and weak dissolution-diagenesis pattern; (2) weak compaction, medium cementation, and weak dissolution-diagenesis pattern; (3) weak compaction, medium cementation, and strong dissolution-diagenesis pattern; and (4) fracture-matrix pattern. The results indicated that diagenetic processes and microfractures contribute to the variability in the cementation factors of these rock samples.

SAT569 Papillary Thyroid Carcinoma With Renal Metastasis Treated With Radioactive Iodine: A Case Report

Abstract Disclosure: A.A. Apa-ap: None. M.B. Sedurante: None. J. Lacuata: None. J. Gacula: None. V. Lee: None. M.L. Hernandez: None. INTRODUCTION. Papillary thyroid cancer (PTC) is one of the most treatable cancers in comparison to undifferentiated thyroid malignancies. It advances slowly, and there is only 1-4 percent of cases of distant metastases. Renal involvement from PTC is very rare with an incidence of 0.47 percent. CASE DESCRIPTION. This paper describes a 34-year-old Filipino female presenting with an 8-year history of hoarseness and a gradually enlarging anterior neck mass. Metastatic workup revealed innumerable bilateral pulmonary nodules bilateral cervical lymphadenopathy, and bilateral renal mass on CT scan. The right pole of the kidney shows a solid heterogeneously enhancing partially-exophytic focus measuring 4.9 x 4.2 x 4.3cm likely a primary renal cell carcinoma versus metastasis. The left renal mass shows a hypodense non-enhancing partially-exophytic focus measuring 3.9 x 3.6 x 3.6cm probably a renal cyst. Clinically, the patient did not show any urinary symptoms and creatine clearance was normal. The patient underwent total thyroidectomy and neck dissection and histopathology revealed PTC. The patient underwent simultaneous ultrasound right renal mass biopsy which revealed few fragments of thyroid tissues with atypia most likely representative of metastasis of PTC. Since the radiographic finding was suggestive of a renal cyst, the left renal mass was not biopsied. Patient refused nephrectomy and underwent 1 cycle of Radioactive Iodine (RAI) Therapy. Post therapy whole body scan showed mildly increased and diffuse tracer uptake activity in bilateral lungs and large avid focus, approximately 5.0 x 4.4 cm, seen in the inferior pole of the right kidney. Surveillance showed increased thyroglobulin. To date, the patient still refused surgery and is contemplating undergoing another cycle of RAI therapy. DISCUSSION. Due to the rarity of the metastatic site, the ideal course of treatment for this illness is unknown. To our knowledge, there are only approximate of 30 case reports on WDTC with renal metastasis in the literature. Presentation: Saturday, June 17, 2023

Elevated prostate-specific antigen in Paget’s disease

ABSTRACT A 70-year-old man diagnosed with acinar adenocarcinoma prostate (Gleason score 4 + 4 = 8) underwent bone scintigraphy due to high serum prostate-specific antigen level (224 ng/mL; normal <4 ng/mL). Bone scan revealed moderately increased diffuse tracer uptake in the right hemipelvis, while the rest of the scan appeared normal, leading to suspicion of Paget’s disease. Gallium-68-prostate-specific membrane antigen (PSMA) positron emission tomography–computed tomography scan (CT) showed a PSMA-avid lesion in the left lobe of the prostate, with no PSMA uptake in the areas of diffuse sclerosis in the right hemipelvis, as seen on CT. This confirmed the diagnosis of Paget’s disease.

Analyzing the Role of Arterial Spin Labelling in Patients Undergoing Endovascular Thrombectomy for Large Vessel Occlusion—a Prospective Single Center Study

Acute stroke is one of the leading causes of death globally. Imaging remains the most common modality to diagnose and predict outcomes in patients with stroke. Conventionally, computed tomography (CT) was the preferred choice; however, imaging has expanded to include newer modalities such as Dynamic Susceptibility Contrast (DSC), Dynamic Contrast-Enhanced MRI (DCE), and Arterial Spin Labelling MRI. An alternative method of assessing perfusion, ASL uses the spins of endogenous water protons as a tracer rather than administering a contrast agent. In this manner, endogenous water in the arterial blood is labelled electromagnetically and employed as a freely diffusible tracer. ASL, as opposed to CT, DSC or DCE, allows estimation of cerebral blood flow without exposure to radiation or the administration of contrast material, which is advantageous for patients with impaired renal function or repetitive perfusion imaging. Thus a prospective study was conducted to explore the use of Arterial Spin Labelling MRI in the setting of acute ischemic stroke in both pre and post-thrombectomy patients. Our study is significant as there are no existing prospective studies comparing the cerebral perfusion measured using ASL with neurological outcomes.

ACE2 PET in healthy and diseased conditions

AbstractAngiotensin converting enzyme 2 (ACE2) played a critical role in regulating renin‐angiotensin‐aldosterone system (RAAS). In this research, 68Ga‐cyc‐DX600 was synthesized as PET tracer of ACE2 imaging. ACE2 positron emission tomography/magnetic resonance (PET/MR) was preliminary administered on twelve healthy volunteers, and the images were normalized and registered to establish the standard model of ACE2 PET. In diseased conditions, 68Ga‐cyc‐DX600 PET and 18F‐FDG PET were compared for COVID‐19 (one in acute phase and three in post‐COVID), anemia (n = 1) and malignancies (n = 2) to evaluate the diagnostic efficiency. 68Ga‐cyc‐DX600 PET was of a definite ACE2 dependence. For the tracer uptake of ACE2 PET/MR of female and male, differences existed in salivary glands, upper respiratory tract and kidneys, meanwhile, age, and body mass index (BMI) were also the confounding factors. RAAS‐related tissue and organs were of the relatively higher tracer uptake, such as SUVmean of cardiac chamber (3.786 ± 1.495), liver (5.342 ± 2.267), spleen (4.465 ± 2.508), and kidney (4.906 ± 1.619 for female and 8.431 ± 5.179 for male). For COVID‐19, ACE2 PET revealed ACE2 fluctuations, particularly in the susceptible organs, including liver, spleen and testis. In the case of anemia, the activated local RAS in the bone marrow was of diffuse high tracer uptake. ACE2 PET of malignancies added supplementary information to FDG PET. 68Ga‐cyc‐DX600‐based ACE2 PET models were established for visually monitoring of whole‐body ACE2 expression. The feasibility of ACE2 PET in supervising disease was primarily proved in COVID‐19, anemia and malignancies as providing a comprehensive view on the disease process and functional recovery.

Experimental Observations of Bedload Tracer Movement: Effects of Mixed Particle Sizes and Bedforms

AbstractPredicting the transport of bedload tracer particles is a problem of significant theoretical and practical interest. Yet, little understanding exists for transport in rivers in the presence of bedforms, which may trap grains and thereby influence travel distance. In a series of flume experiments with a sandy gravel bed in a large experimental flume, bed elevation and tracer travel distances were measured at high resolution for a range of discharges. As discharge increased, bedform height increased and bedform length decreased, increasing bedform steepness. For all tracer sizes and flow conditions, bedforms act as primary controls on the tracer travel distances. Bedform trapping increases linearly with the ratio of bedform height to tracer grain size, with 50% trapping efficiency for a ratio of two and 90% trapping efficiency for a ratio of four. A theoretical model based on the extended active layer formulation for sediment transport is able to capture much of the distribution of measured travel distances for all tracer sizes and discharges, providing a first connection between tracer transport theory and bedform trapping and indicating normal diffusion of tracers at relatively small timescales. Variable bedform geometry can influence trap efficiency for individual bedforms and the theoretical model can help identify “preferential trapping” conditions. The distribution of tracer travel distances for a mixture of grain sizes and variable discharge, as expected in natural rivers, displays heavy tail characteristics.

Investigating physical states of molecular gas in the overlapping region of interacting galaxies NGC 4567/4568 using ALMA

Abstract We present ALMA observations of a diffuse gas tracer, CO(J = 1–0), and a warmer and denser gas tracer, CO(J = 3–2), in the overlapping region of interacting galaxies NGC 4567/4568, which are in the early stage of interaction. To understand the impact of galaxy interactions on molecular gas properties, we focus on interacting galaxies during the early stage and study their molecular gas properties. We investigate the physical states of a filamentary molecular structure at the overlapping region, which was previously reported. Utilizing new higher-resolution CO(J = 1–0) data, we identify molecular clouds within overlapping and disk regions. Although the molecular clouds in the filament have a factor of two higher average virial parameter (0.56 ± 0.14) than that in the overlapping region (0.28 ± 0.12) and in the disk region (0.26 ± 0.16), all the identified molecular clouds are gravitationally bound. These clouds in the filament also have a larger velocity dispersion than that in the overlapping region, suggesting that molecular gas and/or atomic gas with different velocities collide there. We calculate the ratio of the integrated intensity of CO(J = 3–2) and CO(J = 1–0) (= R3−2/1−0) on the molecular cloud scale. The maximum R3−2/1−0 is 0.17 ± 0.04 for all identified clouds. R3−2/1−0 for the molecular clouds in the filament is lower than that of the surrounding area. This result contradicts the predictions of previous numerical simulations, which suggested that the molecular gas on the collision front of galaxies is compressed and becomes denser. Our results imply that NGC 4567/4568 is in a very early stage of interaction; otherwise, the molecular clouds in the filament would not yet fulfill the conditions necessary to trigger star formation.

Quantifying stream-loss recovery in a spring using dual-tracer injections in the Snake Creek drainage, Great Basin National Park, Nevada, USA

Simultaneous short-pulse injections of two tracers (sodium bromide [Br–] and fluorescein dye) were made in a losing reach of Snake Creek in Great Basin National Park, Nevada, USA, to evaluate the quantity of stream loss through permeable carbonates that resurfaces at a spring approximately 10 km down drainage. A revised hydrogeologic cross section for a possible flow path of the infiltrated Snake Creek water is presented, and the results may inform water management in the region. First arrival and peak concentration of the two tracers occurred at 9.5 and 12.7 days after injection, respectively. Fracture transport simulations indicate that Br– preferentially diffuses into immobile regions of the aquifer, and this diffusive flux is likely responsible for the major differences in the breakthrough curves. When considering the diffusive tracer flux, total apparent Br– and fluorescein dye recoveries were 16.9–22.1% and 21.7–24.3%, respectively. These findings imply that consideration of diffusive flux and long-term monitoring in fracture-dominated flow may support accurate quantification of tracer recovery. In addition, the apparent power law slopes of the breakthrough tails for both tracers were steeper at early times than have been attributed to heterogeneous advection or channeling in meter-scale tests, but the late-time Br– power law slope becomes less steep than has been attributed to diffusive exchange. These deviations may reflect fracture transport patterns that occur at larger scales.

Diagnostic edge of SPECT/CT scintigraphy over planar bone imaging for detection of bone metastases in prostate cancer patients

Background: Bone scintigraphy with 99mTc-labelled diphosphonates can identify prostate cancer (PCa) bone metastases with high sensitivity but relatively low specificity. Single photon emission computed tomography /computed tomography (SPECT/CT) can add value to the planar bone scintigraphy in the detection of bone metastases. Case presentation: We present a diagnosed case of Prostatic Adenocarcinoma of a 62 year old male patient who underwent 99mTc-Methyldiphosphonate (MDP) planar bone scintigraphy followed by SPECT/CT as a part of staging algorithm. Planar bone imaging showed homogeneous and symmetrical tracer uptake throughout the visualized skeleton. As the patient had complaints of urinary obstruction and severe backache: so, the sacrum could not be adequately assessed on planar bone imaging; therefore SPECT/CT of lumbar spine and pelvic region was performed. His regional SPECT-CT study of the lumbar and pelvic region, revealed widespread diffuse tracer avid osteoblastic lesions throughout the visualized lower lumbar spine, sacrum, pelvis and proximal femori, suggestive of skeletal metastases. Conclusion: We conclude that SPECT/CT scintigraphy has a diagnostic edge over planar bone imaging in detecting bone metastases in prostate cancer patients.

Arterial Spin Labeling: Techniques, Clinical Applications, and Interpretation.

Arterial spin labeling (ASL) is an emerging noninvasive MRI technique for assessing cerebral perfusion. An important advantage of ASL perfusion is the lack of a requirement for an exogenous tracer. ASL uses magnetically labeled water protons from arterial blood as an endogenous diffusible tracer. For this reason, ASL is an attractive perfusion imaging modality for children and for patients with contraindications or adverse reactions to gadolinium, patients with renal failure, and those who need repeated follow-up imaging. Another advantage of ASL is the possibility of quantifying cerebral blood flow, which provides an opportunity for comparative analysis among multiple longitudinal studies, unlike other MR perfusion techniques, which are semiquantitative and yield relative perfusion parameters. Advances in MRI technology and pulse sequence design have translated ASL beyond the research arena to successful clinical implementation. However, ASL is still underused in routine clinical practice. Some disadvantages of ASL include a lower signal-to-noise ratio and a longer acquisition time than those with dynamic susceptibility contrast-enhanced MRI. Additional factors limiting the use of ASL include variations in existing techniques and pulse sequence design, the complexity of implementation and postprocessing, insufficient experience with and/or knowledge of the potential clinical applications, and the absence of interpretation guidelines. The authors review the technical and physiologic basis of ASL perfusion, as well as artifacts, pitfalls, and its current clinical applications. A practical approach for interpreting ASL findings is also suggested.

Diffusion of a tracer in a dense mixture of soft particles connected to different thermostats.

We study the dynamics of a tracer in a dense mixture of particles connected to different thermostats. Starting from the overdamped Langevin equationsthat describe the evolution of the system, we derive the expression of the self-diffusion coefficient of a tagged particle in the suspension, in the limit of soft interactions between the particles. Our derivation, which relies on the linearization of the Dean-Kawasaki equationsobeyed by the density fields and on a path-integral representation of the dynamics of the tracer, extends previous derivations that held for tracers in contact with a single bath. Our analytical result is confronted to results from Brownian dynamics simulations. The agreement with numerical simulations is very good even for high densities. We show how the diffusivity of tracers can be affected by the activity of a dense environment of soft particles that may represent polymer coils-a result that could be of relevance in the interpretation of measurements of diffusivity in biological media. Finally, our analytical result is general and can be applied to the diffusion of tracers coupled to different types of fluctuating environments, provided that their evolution equationsare linear and that the coupling between the tracer and the bath is weak.

The Fokker-Planck equation of the superstatistical fractional Brownian motion with application to passive tracers inside cytoplasm.

By collecting from literature data experimental evidence of anomalous diffusion of passive tracers inside cytoplasm, and in particular of subdiffusion of mRNA molecules inside live Escherichia coli cells, we obtain the probability density function of molecules' displacement and we derive the corresponding Fokker-Planck equation. Molecules' distribution emerges to be related to the Krätzel function and its Fokker-Planck equation to be a fractional diffusion equation in the Erdélyi-Kober sense. The irreducibility of the derived Fokker-Planck equation to those of other literature models is also discussed.

CONSIDERING PLEURAL FLUID GLUCOSE LEVELS COULD PREVENT UNNECESSARY PROCEDURES

CONSIDERING PLEURAL FLUID GLUCOSE LEVELS COULD PREVENT UNNECESSARY PROCEDURES

Sodium diffusion in heterogeneous porous media: Connecting laboratory experiments and simulations

Sodium has been suggested as a tracer for brine in reservoir formations where a significant amount of sodium ion is found mainly in the aqueous phase. Fortunately, the most abundant sodium isotope, 23Na, is Nuclear Magnetic Resonance (NMR) active, making it possible to study the structure and dynamical properties of both bulk and pore confined fluid systems. We investigated the diffusion of key dissolved sodium species in bulk solution and porous media as a function of composition, ionic strength, and permeability of the carbonate samples using NMR relaxometry and pulsed-field gradient (PFG) NMR techniques. We use Indiana limestone as an example of natural porous media and water as a freely diffusible tracer and carrier. We demonstrate apparent diffusion measurement of sodium based on changes in spin–spin relaxation time (T2) signal in pore confinement. The diffusion rate of sodium decreases with increasing counter-ion size. This effect is greater at higher ionic strengths and lower chemical potentials in porous media. The reactive transport code, CrunchFlow, was used to complement the NMR experiments to simulate diffusion behavior in porous media. Combining these two methods provides a powerful approach to estimating effective diffusion coefficients in heterogeneous matrices. The modeling considers the influence of physical properties (porosity and tortuosity) and chemical properties (geochemical composition and chemical gradients). The results presented in this work highlight the advantage of measuring apparent diffusivity using NMR T2 relaxometry in conjunction with numerical simulation to derive effective diffusivity and the corresponding matrix properties (i.e., tortuosity) of the system.

Diapycnal displacement, diffusion, and distortion of tracers in the ocean

Abstract Small-scale mixing drives the diabatic upwelling that closes the abyssal ocean overturning circulation. Indirect microstructure measurements of in-situ turbulence suggest that mixing is bottom-enhanced over rough topography, implying downwelling in the interior and stronger upwelling in a sloping bottom boundary layer. Tracer Release Experiments (TREs), in which inert tracers are purposefully released and their dispersion is surveyed over time, have been used to independently infer turbulent diffusivities—but typically provide estimates in excess of microstructure ones. In an attempt to reconcile these differences, Ruan and Ferrari (2021) derived exact tracer-weighted buoyancy moment diagnostics, which we here apply to quasi-realistic simulations. A tracer’s diapycnal displacement rate is exactly twice the tracer-averaged buoyancy velocity, itself a convolution of an asymmetric upwelling/downwelling dipole. The tracer’s diapycnal spreading rate, however, involves both the expected positive contribution from the tracer-averaged in-situ diffusion as well as an additional non-linear diapycnal distortion term, which is caused by correlations between buoyancy and the buoyancy velocity, and can be of either sign. Distortion is generally positive (stretching) due to bottom-enhanced mixing in the stratified interior but negative (contraction) near the bottom. Our simulations suggest that these two effects coincidentally cancel for the Brazil Basin Tracer Release Experiment, resulting in negligible net distortion. By contrast, near-bottom tracers experience leading-order distortion that varies in time. Errors in tracer moments due to realistically sparse sampling are generally small (< 20%), especially compared to the O(1) structural errors due to the omission of distortion effects in inverse models. These results suggest that TREs, although indispensable, should not be treated as “unambiguous” constraints on diapycnal mixing.

Active Diffusion of Self-Propelled Particles in Flexible Polymer Networks

Biopolymer networks having a meshwork topology, e.g., extracellular matrix and mucus gels, are ubiquitous. It is an open question to understand how self-propelled agents such as Janus colloidal particles diffuse through such a biopolymer network. Here, we computationally explore this issue in-depth by explicitly modeling three-dimensional biopolymer networks and performing Langevin dynamics simulations of active diffusion of the self-propelled tracers therein. We show that the active tracer performs distinct diffusion dynamics depending on the mesh-to-particle size and P\'eclet number (Pe). When the particle is smaller than the mesh size, it moves as if in free space with a decreased mobility depending on the polymer occupation density and Pe. However, when the particle size is increased to be comparable to the mesh size, the active particles explore the polymer network using the trapped-and-hopping mechanism. We study the trapped time distribution, flight length distribution, the mean-squared displacement, and the long-time diffusivity at varying Pe. If the particle is larger than the mesh, it captures the collective viscoelastic dynamics from the polymer network at short times and the simple diffusion of the total system at large times. Finally, we discuss the scaling behavior of the long-time diffusivity with Pe, where we find a range of Pe that yields a nontrivial power law. The latter turns out to arise from a large fluctuation of trapped, activated tracers in conjugation with responsive polymer networks.

Physiological tracer distribution and benign lesion incidental uptake of Al18F-NOTA-FAPI-04 on PET/CT imaging.

To systematically investigate the physiological distribution and benign lesion incidental uptake of Al18F-NOTA-FAPI-04 (18F-FAPI) in cancer patients to establish the normal uptake range in relevant organs and lesions. Twenty patients who underwent 18F-FAPI PET/CT imaging were retrospectively assessed. Organ and benign lesion tracer uptake was quantified based on standardized uptake values (SUVmax and SUVmean). We compared the variation in tracer uptake in certain organs between men and women, analyzed the possible reasons for diffuse uptake in the thyroid, and assessed tracer uptake variations in the uterus in different menstrual cycle phases. Incidental tracer uptake in benign lesions was also assessed. Physiological 18F-FAPI uptake was observed in the urinary tract, biliary tract system, submandibular glands, pancreas, thyroid, uterus, intestine, prostate gland, parotid gland, myocardium, kidney cortex, and muscles, but not the brain, lungs, liver, spleen, colon, and breasts. The SUVmean for each organ was similar for women and men (all P > 0.05). Diffuse tracer uptake in the thyroid was caused by normal thyroid or thyroiditis; there were no statistically significant differences between them (SUVmax: t = -1.3, P = 0.25; SUVmean: t = -1.1, P = 0.31). There was a significant difference for uterus uptake among different menstrual cycle phases (SUVmax: F = 5.08, P = 0.04; SUVmean: F = 5.19, P = 0.04). Incidental benign lesion tracer uptake was observed in patients with esophagitis, thyroiditis, arthritis, fractures, and uterine fibroids. This study provides a reference range for 18F-FAPI uptake in relevant organs and benign lesions. Benign lesion 18F-FAPI uptake may reduce 18F-FAPI PET/CT specificity.