Absolute Signal Intensity Research Articles

Duplex Vertical-Flow Rapid Tests for Point-of-Care Detection of Anti-dsDNA and Anti-Nuclear Autoantibodies.

The goal of this study is to develop a rapid diagnostic test for rheumatic disease and systemic lupus erythematosus (SLE) screening. A novel rapid vertical flow assay (VFA) was engineered and used to assay anti-nuclear (ANA) and anti-dsDNA (αDNA) autoantibodies from systemic lupus erythematosus (SLE) patients and healthy controls (HCs). Observer scores and absolute signal intensities from the VFA were validated via ELISA. The rapid point-of-care VFA test that was engineered demonstrated a limit of detection of 0.5 IU/mL for ANA and αDNA autoantibodies in human plasma with an inter-operator CV of 19% for ANA and 12% for αDNA. Storage stability was verified over a three-month period. When testing anti-dsDNA and ANA levels in SLE and HC serum samples, the duplex VFA revealed 95% sensitivity, 72% specificity and an 84% ROC AUC value in discriminating disease groups, comparable to the gold standard, ELISA. The rapid αDNA/ANA duplex VFA can potentially be used in primary care clinics for evaluating patients or at-risk subjects for rheumatic diseases and for planning follow-up testing. Given its low cost, ease, and rapid turnaround, it can also be used to assess SLE prevalence estimates.

Pitch Angle Distributions of Energetic Particles Near Callisto

AbstractThe Galileo spacecraft performed close flybys of the moon Callisto between 1996 and 2001. We reanalyzed particle data of the energetic particles detector onboard Galileo and derived pitch angle distributions in the energy range of several keV to MeV during Callisto flybys C3, C9, C10, and C30. We establish that field‐aligned beams observed during the flyby periods are more likely to originate from Callisto's magnetospheric interaction rather than by independent magnetospheric processes. These beams are prominent only during flyby C3, they come mainly from the North, and connect the moon and the ionosphere of Jupiter. For short intervals they have also been observed propagating from the South. The beams are regularly unidirectional and typically extend to 300 keV in energy, occasionally reaching above 600 keV. Energetic particle depletions in Callisto's wake during the downstream flybys are not at all obvious, even at low altitudes and in the wake center. The signature of the wake becomes more apparent when energetic particle observations are organized in pitch angle. In that case, pitch angle distribution minima at 90 deg can be discerned in some flybys, however, not always associated with a profound drop in the absolute signal intensity. They instead indicate that field‐aligned particle flux within the wake is higher. Outside the wake these minima continue in an energy‐dependent disturbed region toward Jupiter which seems to be at least partially collocated with Alfvén‐wing structures as predicted from magnetohydrodynamic simulation results or simple flyby geometry considerations.

Effect and imaging analysis of cetuximab combined with radiotherapy in patients with rectal carcinoma

ABSTRACT Objective. To analyze the effect of cetuximab combined with radiotherapy in patients with rectal carcinoma (RC) by imaging analysis. Methods. The clinical data of 104 RC patients at our hospital from February 2021 to February 2022 were retrospectively analyzed. They were separated into control group (n = 52) and experimental group (n = 52) according to the order of admission, with the former treated with radiotherapy alone and the latter receiving cetuximab and radiotherapy. The clinical efficacy, tumor marker levels and imaging parameters of different treatment regimens were compared, and Quality of Life questionnaire (QLQ-C30) was used to evaluate the quality of life. Results. The incidence of tumor regression grade (TRG) downgrade, T stage downgrade and N stage downgrade was remarkably higher in the experimental group than in the control group (P < 0.05). The experimental group had remarkably lower tumor marker levels (P < 0.001) and higher mean score of EORTC Core QLQ-C30 (P < 0.001) than those in the control group. The relative signal intensity of tumor (SIT/M), relative signal intensity reduction rate of tumor (SIT/MRR) and apparent diffusion coefficient (ADC) values were remarkably higher (P < 0.001) and the absolute signal intensity of tumor (SIT) value was remarkably lower (P < 0.001) in the experimental group than the control group. Conclusion. Treatment with cetuximab and radiotherapy can greatly reduce serum tumor marker levels in RC patients and bring them health benefits, and further studies will help establish a better solution for such patients.

Ratiometric optical probes for biosensing.

Biosensing by optical probes is bringing about a revolution in our understanding of physiological and pathological states. Conventional optical probes for biosensing are prone to inaccurate detection results due to various analyte-independent factors that can lead to fluctuations in the absolute signal intensity. Ratiometric optical probes provide built-in self-calibration signal correction for more sensitive and reliable detection. Probes specifically developed for ratiometric optical detection have been shown to significantly improve the sensitivity and accuracy of biosensing. In this review, we focus on the advancements and sensing mechanism of ratiometric optical probes including photoacoustic (PA) probes, fluorescence (FL) probes, bioluminescence (BL) probes, chemiluminescence (CL) probes and afterglow probes. The versatile design strategies of these ratiometric optical probes are discussed along with a broad range of applications for biosensing such as sensing of pH, enzymes, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), metal ions, gas molecules and hypoxia factors, as well as the fluorescence resonance energy transfer (FRET)-based ratiometric probes for immunoassay biosensing. Finally, challenges and perspectives are discussed.

Quantitative NMR Interpretation without Reference

As has been documented numerous times over the years, nuclear magnetic resonance (NMR) experiments are intrinsically quantitative. Still, quantitative NMR methods have not been widely adopted or largely introduced into pharmacopoeias. Here, we describe the quantitative interpretation of the 1D proton NMR experiment using only absolute signal intensities with the variation of common experimental parameters and their application.

Research on detection performance improvement of polarization GM-APD LiDAR with adaptive adjustment of aperture diameter and spatial correlation method

The triggering probability of GM-APD (Geiger-mode avalanche photodiode) is affected by the absolute signal intensity and the SNR (Signal-to-Noise Ratio). Through investigation, the polarization detection can effectively enhance the signal’s triggering probability by increasing the signal’s SNR; however, the triggering probability cannot reach the highest value at a certain SNR. In this paper, the polarization detection with the adaptive adjustment of aperture diameter (AAAD) and spatial correlation method was proposed to enhance the detection results, which could help to get the highest triggering probability, and the signal detection performance was obviously improved. Firstly, the theoretical model of the polarization detection with AAAD was built. Secondly, the effects of factors such as noise intensity, range, SNR, etc. on the triggering probabilities of the non-polarization detection, the polarization detection and the polarization detection with AAAD were analyzed; the theoretical analysis showed that the polarization detection with AAAD could effectively increase the triggering probability and the detection probability; besides, by introducing the spatial correlation method, the detection probability could be improved in a further step. Finally, the experimental verifications were carried out in the low SNR surroundings, the results showed that the combination of the polarization detection with AAAD and spatial correlation could enhance the signal detection probability by 80.8% of the initial detection probability, and the target restoration ratio could reach 96.9%. The research in this paper improves the daytime detection performance to a large extent, and it is very useful for the actual application of GM-APD LiDAR.

Radiometric and design model for the tunable light-guide image processing snapshot spectrometer (TuLIPSS)

The tunable light-guide image processing snapshot spectrometer (TuLIPSS) is a novel remote sensing instrument that can capture a spectral image cube in a single snapshot. The optical modelling application for the absolute signal intensity on a single pixel of the sensor in TuLIPSS has been developed through a numerical simulation of the integral performance of each optical element in the TuLIPSS system. The absolute spectral intensity of TuLIPSS can be determined either from the absolute irradiance of the observed surface or from the tabulated spectral reflectance of various land covers and by the application of a global irradiance approach. The model is validated through direct comparison of the simulated results with observations. Based on tabulated spectral reflectance, the deviation between the simulated results and the measured observations is less than 5% of the spectral light flux across most of the detection bandwidth for a Lambertian-like surface such as concrete. Additionally, the deviation between the simulated results and the measured observations using global irradiance information is less than 10% of the spectral light flux across most of the detection bandwidth for all surfaces tested. This optical modelling application of TuLIPSS can be used to assist the optimal design of the instrument and explore potential applications. The influence of the optical components on the light throughput is discussed with the optimal design being a compromise among the light throughput, spectral resolution, and cube size required by the specific application under consideration. The TuLIPSS modelling predicts that, for the current optimal low-cost configuration, the signal to noise ratio can exceed 10 at 10 ms exposure time, even for land covers with weak reflectance such as asphalt and water. Overall, this paper describes the process by which the optimal design is achieved for particular applications and directly connects the parameters of the optical components to the TuLIPSS performance.

Exploring the Influence of Different Albumin Binders on Molecular Imaging Probe Distribution.

The biodistribution of molecular imaging probes or tracers mainly depends on the chemical nature of the probe and the preferred metabolization and excretion routes. Small molecules have rather short half-lives while antibodies reside inside the organism for a longer period of time. An excretion via kidneys and bladder is faster than a mainly hepatobiliary elimination. To manipulate the biodistribution behavior of probes, different strategies have been pursued, including utilizing serum albumin as an inherent transport mechanism for small molecules. Here, we modified an existing small molecular fluorescent probe targeted to the endothelin-A receptor (ETAR) with three different albumin-binding moieties to search for an optimal modification strategy. A diphenylcyclohexyl (DPCH) group, a p-iodophenyl butyric acid (IPBA), and a fatty acid (FA) group were attached via amino acid linkers. All three modifications result in transient albumin binding of the developed compounds, as concluded from gel electrophoresis investigations. Spectrophotometric measurements applying variable amounts of bovine, murine, and human serum albumin (BSA, MSA, and HSA) reveal distinct variations of absorption and emission intensities and shifts of their maximum wavelengths. Binding to MSA results in the weakest effects, while binding to HSA leads to the strongest. Cell-based in vitro investigations utilizing ETAR-positive HT-1080 fibrosarcoma and ETAR-negative BT-20 breast adenocarcinoma cells support a retained specific target-binding capacity of the modified compounds and different degrees of unspecific binding. In vivo analysis of a HT-1080 xenograft model in nude mice over the course of 1 week by fluorescence reflectance imaging illustrates noticeable differences between the four examined probes. While the IPBA-modified probe shows the highest absolute signal intensity values, the FA-modified probe exhibits the most favorable tumor-to-organ ratios. In summary, reversible binding to albumin enhances the biological half-life of the designed probes substantially and enables near infrared optical imaging of subcutaneous tumors for several days in vivo. Because the unmodified probe already exhibits reasonable results, the attachment of albumin-binding moieties does not lead to a substantially improved imaging outcome in terms of target-to-background ratios. On the other hand, because the implemented transient albumin binding results in an overall higher amount of probe inside tumor lesions, this strategy might be adaptable for theranostic or therapeutic approaches in a future clinical routine.

Numerical simulation of the interaction of wave phase conjugation with bubble clouds

The interaction of the Wave Phase Conjugation (WPC) process with bubble cloud dynamics is investigated via numerical modeling in application to bubble size measurements. The WPC simulator by Modarreszadeh and Timofeev (Computers and Fluids 197, 104353) is used as a starting point. In the simulator, a modified version of the high-order Nodal Discontinuous Galerkin method is used for modeling of acoustic wave propagation in the active WPC conjugator and the surrounding linear or non-linear fluid in 2D/axisymmetric domains. The effects of bubble dynamics are incorporated with the help of induced volume fractions. The modified Keller–Miksis model is employed to simulate vibrations of bubbles subjected to acoustic waves. After thorough verification and validation of the numerical scheme and the physical model, the interaction of various bubble clouds, including poly-disperse ones, with the WPC process is examined with the help of some existing and newly suggested descriptive indicators, e.g., the amplification factor and the absolute and relative signal intensities. The results show that signals scattered from bubble-plane clouds, in which the bubbles are non-physically synced, are strong enough to affect the modulation process if the stimulation frequency is close to the natural frequency of bubbles. For more realistic bubble clouds, the modulation process is almost intact. However, conjugate waves do carry some signatures of bubble-cloud dynamics, e.g., signals with frequencies higher than the natural frequency of bubbles are significantly diminished. The study demonstrates that WPC-based techniques have a promising potential to be used for measuring bubble dimensions.

High spatiotemporal resolution dynamic contrast-enhanced MRI improves the image-based discrimination of histopathology risk groups of peripheral zone prostate cancer: a supervised machine learning approach.

To assess if adding perfusion information from dynamic contrast-enhanced (DCE MRI) acquisition schemes with high spatiotemporal resolution to T2w/DWI sequences as input features for a gradient boosting machine (GBM) machine learning (ML) classifier could better classify prostate cancer (PCa) risk groups than T2w/DWI sequences alone. One hundred ninety patients (68 ± 9years) were retrospectively evaluated at 3T MRI for clinical suspicion of PCa. Included were 201 peripheral zone (PZ) PCa lesions. Histopathological confirmation on fusion biopsy was matched with normal prostate parenchyma contralaterally. Biopsy results were grouped into benign tissue and low-, intermediate-, and high-risk groups (Gleason sum score 6, 7, and > 7, respectively). DCE MRI was performed using golden-angle radial sparse MRI. Perfusion maps (Ktrans, Kep, Ve), apparent diffusion coefficient (ADC), and absolute T2w signal intensity were determined and used as input features for building two ML models: GBM with/without perfusion maps. Areas under the receiver operating characteristic curve (AUC) values for correlated models were compared. For the classification of benign vs. malignant and intermediate- vs. high-grade PCa, perfusion information added relevant information (AUC values 1 vs. 0.953 and 0.909 vs. 0.700, p < 0.001 and p = 0.038), while no statistically significant effect was found for low- vs. intermediate- and high-grade PCa. Perfusion information from DCE MRI acquisition schemes with high spatiotemporal resolution to ML classifiers enables a superior risk stratification between benign and malignant and intermediate- and high-risk PCa in the PZ compared with classifiers based on T2w/DWI information alone. • In the recent guidelines, the role of DCE MRI has changed from a mandatory to recommended sequence. • DCE MRI acquisition schemes with high spatiotemporal resolution (e.g., GRASP) have been shown to improve the diagnostic performance compared with conventional DCE MRI sequences. • Using perfusion information acquired with GRASP in combination with ML classifiers significantly improved the prediction of benign vs. malignant and intermediate- vs. high-grade peripheral zone prostate cancer compared with non-contrast sequences.

Protein precipitation coupled to paper spray with a tube for one-step analysis of blood.

Accurate measurement of trace compounds in blood samples is important in clinical diagnosis and life science. Ambient ionization mass spectrometry, however, suffers from the matrix effect when dealing with complex samples such as blood. Therefore, it is important to reduce the matrix effects in blood samples. A low-cost and disposable Teflon tube was used as a platform to precipitate the protein in blood. The analytes are extracted into organic solvent, and the precipitated protein can be adsorbed by the chromatography paper inserted. Therefore, the Teflon tube after precipitation can be directly subjected to paper spray ionization mass spectrometry, achieving one-step analysis of blood. High sensitivity and satisfactory stability were achieved for pharmaceuticals, acids, and endogenic metabolites in blood. The absolute signal intensities of characteristic product ions of the tested analytes were 8-20 times higher after protein precipitation than those obtained using paper spray. Detection limits and quantitative performance were evaluated for three drugs: carbamazepine, metformin, and tioconazole. In addition, the limits of detection and quantitation were improved 9-14- and 8-12-fold, respectively. Protein precipitation coupled to paper spray with a tube and then to mass spectrometry was successfully achieved and applied in the one-step analysis of trace compounds in blood samples. The experimental results showed that this method was sensitive, stable, convenient, and economic for the direct analysis of blood.

Correlation between fat signal ratio on T1-weighted MRI in the lower vertebral bodies and age, comparing 1.5-T and 3-T scanners.

BackgroundThe hypothesis was that the fat-dependent T1 signal intensity in vertebral bodies increases with age due to red-yellow marrow conversion.PurposeTo analyze the increasing fatty conversion of red bone marrow with age.Material and MethodsA continuous sample of 524 patients (age range 2–96 years) with normal lumbar spine MRIs (T11–L5) was retrospectively selected in order to get a representative sample from our 1.5-T and 3-T MRI units (Siemens, Erlangen, Germany). Four radiologists read the images independently. Absolute T1 signal intensities were measured in the lower vertebral bodies and standardized by dividing their value by the signal of the subcutaneous fat on lumbar and sacral level.ResultsThe standardized T1 signal correlated significantly with patients’ age at the 1.5-T unit, with the best correlation demonstrated by thoracic vertebra T11, followed by lumbar vertebra L1, with correlation coefficients (R) of 0.64 (95% CI 0.53–0.72, P < 0.0001) and 0.49 (95% CI 0.38–0.59, P < 0.0001), respectively. For women and men, the R values were similar in thoracic vertebra T11 at 0.62 (95% CI 0.49–0.72) and 0.64 (95% CI 0.44–0.77), respectively. The vertebral signal correlated significantly better with age in the 1.5-T compared to the 3-T unit on all vertebral levels: the best R value of the 3-T unit was only 0.20 (95% CI 0.09–0.30, P < 0.0001). Our study showed an average increase of the relative T1 signal in T11 of 10% per decade.ConclusionT1 fat signal ratio increases with age in the vertebral bodies, which could help estimating the age of a person. Best age correlation was found when measuring T1 signal in T11, standardized by the sacral subcutaneous fat signal and using a 1.5-T MRI.

Differentiation of malignant liver tumors by software-based perfusion quantification with dynamic contrast-enhanced ultrasound (DCEUS).

Assessing the diagnostic value of dynamic contrast-enhanced ultrasound (DCEUS) for the discrimination of different malignant liver lesions. 148 malignant focal liver lesions were assessed prospectively with DCEUS (hepatocellular carcinoma = HCC; cholangiocellular carcinoma = CCC; pancreatic adenocarcinoma = PCA; breast cancer = BC; colorectal cancer = CRC; melanoma = MM). Focal-nodular-hyperplasias (FNH) served as a reference for benign lesions. DCEUS-clips were recorded continuously over three minutes. DCEUS-values were compared between the tumor entities. For better inter-individual comparability, perfusion kinetics were analyzed considering the perfusion characteristics of the surrounding liver parenchyma (Relative Signal Intensity = RSI: lesion-liver tissue/liver tissue) at different points in time. Absolute signal intensity in FNH showed a tendency towards higher values compared with malignant liver lesions [Peak Enhancement(a.u.): FNH 7111.4; HCC 549.9; CCC -6654.3; PCA -7307.9; BC -4562.4; CRC -10672.9; MM -3034.1]. Washout was significantly less in FNH versus PCA and CRC, and more pronounced and earlier in PCA and CRC versus HCC [RSI 30 seconds after PE-lesion(%): FNH +52; PCA -65; CRC -76; HCC -26]. Rise Time, Fall Time and mean-Transit-Time did not differ significantly. DCEUS-values reflect significant differences between malignant liver lesions, especially at peak enhancement and during the washout phases.

Antiferromagnetic ordering based on intermolecular London dispersion interactions in amphiphilic TEMPO ammonium salts.

Antiferromagnetic coupling in TEMPO-based radicals can be enhanced via self-assembly through London dispersion interactions in amphiphilic solids. The synthesis, magnetic characterization, and three crystal structures of the solid radical ion salts (R-DMAT-n)X with various counterions X and alkyl chain lengths n are reported. Magnetic susceptibility and absolute EPR signal intensity measurements show singlet-triplet transitions in a number of cases, which is discussed in relation to the crystal structures. Antiferromagnetic ordering effects are sensitive to both the length of the alkyl chain and the counter anion.

Comparison of 3- and 20-Gradient Direction Diffusion-Weighted Imaging in a Clinical Subacute Cohort of Patients with Transient Ischemic Attack: Application of Standard Vendor Protocols for Lesion Detection and Final Infarct Size Projection.

Diffusion tensor imaging may aid brain ischemia assessment but is more time consuming than conventional diffusion-weighted imaging (DWI). We compared 3-gradient direction DWI (3DWI) and 20-gradient direction DWI (20DWI) standard vendor protocols in a hospital-based prospective cohort of patients with transient ischemic attack (TIA) for lesion detection, lesion brightness, predictability of persisting infarction, and final infarct size. We performed 3T-magnetic resonance imaging including diffusion and T2-fluid attenuated inversion recovery (FLAIR) within 72 h and 8 weeks after ictus. Qualitative lesion brightness was assessed by visual inspection. We measured lesion area and brightness with manual regions of interest and compared with homologous normal tissue. 117 patients with clinical TIA showed 78 DWI lesions. 2 lesions showed only on 3DWI. No lesions were uniquely 20DWI positive. 3DWI was visually brightest for 34 lesions. 12 lesions were brightest on 20DWI. The median 3DWI lesion area was larger for lesions equally bright, or brightest on 20DWI [median (IQR) 39 (18-95) versus 18 (10-34) mm2, P = 0.007]. 3DWI showed highest measured relative lesion signal intensity [median (IQR) 0.77 (0.48-1.17) versus 0.58 (0.34-0.81), P = 0.0006]. 3DWI relative lesion signal intensity was not correlated to absolute signal intensity, but 20DWI performed less well for low-contrast lesions. 3DWI lesion size was an independent predictor of persistent infarction. 3-gradient direction apparent diffusion coefficient areas were closest to 8-week FLAIR infarct size. 3DWI detected more lesions and had higher relative lesion SI than 20DWI. 20DWI appeared blurred and did not add information. http://www.clinicaltrials.gov. Unique Identifier NCT01531946.

Evaluation of sample preparation protocols for spider venom profiling by MALDI-TOF MS

Spider venoms are highly complex mixtures containing biologically active substances with potential for use in biotechnology or pharmacology. Fingerprinting of venoms by Matrix-Assisted Laser Desorption-Ionization – Time of Flight Mass Spectrometry (MALDI-TOF MS) is a thriving technology, enabling the rapid detection of peptide/protein components that can provide comparative information. In this study, we evaluated the effects of sample preparation procedures on MALDI-TOF mass spectral quality to establish a protocol providing the most reliable analytical outputs. We adopted initial sample preparation conditions from studies already published in this field. Three different MALDI matrixes, three matrix solvents, two sample deposition methods, and different acid concentrations were tested. As a model sample, venom from Brachypelma albopilosa was used. The mass spectra were evaluated on the basis of absolute and relative signal intensities, and signal resolution. By conducting three series of analyses at three weekly intervals, the reproducibility of the mass spectra were assessed as a crucial factor in the selection for optimum conditions. A sample preparation protocol based on the use of an HCCA matrix dissolved in 50% acetonitrile with 2.5% TFA deposited onto the target by the dried-droplet method was found to provide the best results in terms of information yield and repeatability. We propose that this protocol should be followed as a standard procedure, enabling the comparative assessment of MALDI-TOF MS spider venom fingerprints.

SyMRI of the Brain: Rapid Quantification of Relaxation Rates and Proton Density, With Synthetic MRI, Automatic Brain Segmentation, and Myelin Measurement.

Conventional magnetic resonance images are usually evaluated using the image signal contrast between tissues and not based on their absolute signal intensities. Quantification of tissue parameters, such as relaxation rates and proton density, would provide an absolute scale; however, these methods have mainly been performed in a research setting. The development of rapid quantification, with scan times in the order of 6 minutes for full head coverage, has provided the prerequisites for clinical use. The aim of this review article was to introduce a specific quantification method and synthesis of contrast-weighted images based on the acquired absolute values, and to present automatic segmentation of brain tissues and measurement of myelin based on the quantitative values, along with application of these techniques to various brain diseases. The entire technique is referred to as “SyMRI” in this review. SyMRI has shown promising results in previous studies when used for multiple sclerosis, brain metastases, Sturge-Weber syndrome, idiopathic normal pressure hydrocephalus, meningitis, and postmortem imaging.

Simplifying the Preparation of Pollen Grains for MALDI-TOF MS Classification.

Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) is a well-implemented analytical technique for the investigation of complex biological samples. In MS, the sample preparation strategy is decisive for the success of the measurements. Here, sample preparation processes and target materials for the investigation of different pollen grains are compared. A reduced and optimized sample preparation process prior to MALDI-TOF measurement is presented using conductive carbon tape as target. The application of conductive tape yields in enhanced absolute signal intensities and mass spectral pattern information, which leads to a clear separation in subsequent pattern analysis. The results will be used to improve the taxonomic differentiation and identification, and might be useful for the development of a simple routine method to identify pollen based on mass spectrometry.

Diffusion weighted MRI of osteoid osteomas: Higher ADC values after radiofrequency ablation

PurposeFeasibility of diffusion weighted MRI (DWI) pre- and post-radiofrequency ablation (RFA) in patients with osteoid osteoma (OO). Material and methodsTen patients (1 female, 24±9years) received RFA of OO (mean size 8.7±3.2mm). Two OO recurred, in one of these a second RFA was performed. A 1.5T DWI (b=50, 400, and 800s/mm2) and a fat saturated DCE MRI were obtained the day before and after RFA. In DWI, the mean apparent diffusion coefficient (ADC) was recorded. With DCE MRI, signal-to-noise ratio, contrast-to-noise ratio, absolute signal intensity (SI), relative SI, and SI ratio were documented. All parameters were compared pre- and post-RFA using paired Wilcoxon rank test. ResultsADC values were significantly higher post-ablation, 1.6±0.5μm2/ms versus 1.3±0.6μm2/ms (p<0.05). Perfusion was significantly reduced after ablation [SNR, CNR, SI, %SI, and SI OO/SI muscle]; post-RFA: 55±13, 27±20, 757±534, 102±16, and 1.6±0.2; pre-RFA: 88±37, 65±22, 1038±755, 226±51, and 2.0±0.5 (p<0.05). DiscussionDWI is feasible in OO. ADC values increased and contrast enhancement decreased after RFA of OO. This may be explained by RFA-induced necrosis and devascularization.

Bone assessment via thermal photo-acoustic measurements.

The feasibility of an innovative biomedical diagnostic technique, thermal photo-acoustic (TPA) measurement, for non-ionizing and non-invasive assessment of bone health is investigated. Unlike conventional photo-acoustic PA methods that are mostly focused on the measurement of absolute signal intensity, TPA targets the change in PA signal intensity as a function of the sample temperature, i.e., the temperature-dependent Grueneisen parameter that is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique are less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non-organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well-established rat models of bone loss and preservation, PA measurements of rat tibia bones were conducted over a temperature range from 37°C to 44°C. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis.