Tomography Attenuation Research Articles

СОВРЕМЕННЫЕ ВОЗМОЖНОСТИ МЕТОДОВ ЛУЧЕВОЙ ДИАГНОСТИКИ В ОЦЕНКЕ ТЯЖЕСТИ ЖИРОВОГО ГЕПАТОЗА ПРИ НЕАЛКОГОЛЬНОЙ ЖИРОВОЙ БОЛЕЗНИ ПЕЧЕНИ (КЛИНИЧЕСКИЙ СЛУЧАЙ)

Purpose: To estimate the potential of imaging methods in the diagnosis of non-alcoholic fatty liver disease (NAFLD) based on the example of a clinical case. Material and methods: A 42 years-old man with suspected of NAFLD, by the clinical and laboratory tests results, underwent a quantitative assessment of fatty hepatosis using radiodiagnosis imaging methods. We used US “liver protocol” with attenuation imaging technique (ATI), shear wave elastography (SWE), shear wave dispersion imaging (SWD), computed tomography (CT) with quantitative and qualitative assessment using the liver-spleen index (CTL-S); MRI with application that provides volumetric whole-liver fat fraction (FF) measurements by proton density (PDFF), on the basis of IDEAL IQ program. The morphological verification of liver biopsy was also performed. Results: All imaging method used in this clinical case showed severe degree of fatty hepathosis, that correlated with biopsy of liver. In repeated studies, on the background of treatment, the quantitative indicators of all imaging methods had a similar dynamics of reduction of the degree of fatty hepatosis. Conclusion: The clinical case of verified acute steatohepatitis shows the possibilities of its diagnostics by means of the radiation modalities. We used US with ATI, SWE и SWD, CT with CTL-S, MRI with FF that demonstrated high diagnostic efficiency for determination fatty hepatosis and the possibility of its quantification. These technologies are suitable for widespread implementation into clinical practice providing good diagnostic accuracy. CT associated with higher doses of radiation is not considered to be the basic method of choice for diagnosing NAFLD, but still may provide a physician with necessary information to determine further treatment strategy.

Resolution and trade-offs in global anelastic full-waveform inversion

Summary Improving the resolution of seismic anelastic models is critical for a better understanding of the Earth’s subsurface structure and dynamics. Seismic attenuation plays a crucial role in estimating water content, partial melting, and temperature variations in the Earth’s crust and mantle. However, compared to seismic wavespeed models, seismic attenuation tomography models tend to be less resolved. This is due to the complexity of amplitude measurements and the challenge of isolating the effect of attenuation in the data from other parameters. Physical dispersion caused by attenuation also affects seismic wavespeeds, and neglecting scattering/defocusing effects in classical anelastic models can lead to biased results. To overcome these challenges, it is essential to account for the full 3D complexity of seismic wave propagation. Although various synthetic tests have been conducted to validate anelastic Full-Waveform Inversion (FWI), there is still a lack of understanding regarding the trade-off between elastic and anelastic parameters, as well as the variable influence of different parameter classes on the data. In this context, we present a synthetic study to explore different strategies for global anelastic inversions. To assess the resolution and sensitivity for different misfit functions, we first perform mono-parameter inversions by inverting only for attenuation. Then, to study trade-offs between parameters and resolution, we test two different inversion strategies (simultaneous and sequential) to jointly constrain the elastic and anelastic parameters. We found that a sequential inversion strategy performs better for imaging attenuation than a simultaneous inversion. We also demonstrate the dominance of seismic wavespeeds over attenuation, underscoring the importance of determining a good approximation of the Hessian matrix and suitable damping factors for each parameter class.

In vivo optical coherence tomography attenuation imaging of the breast surgical cavity using a handheld probe

Approximately 20–30% of breast-conserving surgery (BCS) patients require follow-up re-excision surgery due to inadequate cancer resection. To aid cancer detection and resection, we present a handheld optical coherence tomography (OCT) probe and attenuation imaging method to enable in vivo imaging of the surgical cavity during BCS. The attenuation imaging method incorporates three-dimensional correction of system factors in the probe, namely, confocal function and sensitivity roll-off function, demonstrating accurate and repeatable attenuation imaging of phantoms, validated using the Mie scattering model. To assess the imaging performance of the probe prior to in vivo imaging, ex vivo attenuation imaging of breast specimens from eight mastectomy patients was performed and the results compared to those acquired using a benchtop imaging system, showing consistent tissue contrast in attenuation images. In vivo imaging of breast tissue in the surgical cavity of seven patients was subsequently performed during BCS. The results demonstrate the potential of attenuation imaging to delineate cancer in vivo in the surgical cavity. Attenuation imaging provides an additional tissue contrast mechanism to complement OCT imaging, potentially contributing to more complete identification and resection of cancer during BCS.

Seismic attenuation tomography of Eastern Europe from ambient seismic noise analysis

SUMMARY The Eastern-Europe region (EER), is a complex geotectonic area that captures part of the Alpine-Himalayan Orogen, the subduction of multiple NeoTethys Branches and part of the East European Craton. It is one of the most exciting geological areas in Europe due to a diversity of tectonic processes acting within it: extensional basin evolution, oceanic subduction, post-collisional volcanism, as well as active crustal deformation associated with the push of the Adria plate or the pull of the actively detaching Vrancea slab. This makes EER an excellent natural laboratory to study the behaviour of the lithosphere–asthenosphere system in a heterogeneous tectonic setting. To investigate the lateral heterogeneity and physical properties of the crust in the EER, we use ambient seismic noise data recorded by the vertical components of broad-band stations that have been operational between 1999 and 2020 in Eastern Europe and surrounding regions. We used this significant amount of data and the latest processing techniques of the ambient seismic noise field based on the continuous wavelet transform to compute cross-correlations between various station pairs, turning every available seismic station into a virtual source. The coda of the interstation cross-correlograms were used to determine coda quality factors (Qc) of Rayleigh waves in four different period ranges (3.0–5.0, 5.0–10.0, 10.0–20.0 and 20.0–30.0 s) and to invert them in the 2-D space, constructing the highest resolution attenuation tomography of the region. Our results reveal high attenuation features throughout the northeast Pannonian region, the Bohemian Massif, the East Carpathians and the Moesian Platform. Nevertheless, our findings do not emphasize a close correlation between the depth of sedimentary basins and attenuation features identified at longer periods. In addition, Qc variations are larger at short periods, indicating higher heterogeneity in the uppermost crust of Eastern Europe. Our findings demonstrate the higher efficiency of noise correlation approaches relative to earthquake data analyses investigating Qc at low frequencies.

Accuracy of attenuation coefficient measurement (ACM) for real-time ultrasound hepatic steatometry: Comparison of simulator/phantom data with magnetic resonance imaging proton density fat fraction (MRI-PDFF)

ObjectivesTo evaluate the accuracy and reproducibility of real time ultrasound (US) steatometry with the Attenuation Coefficient (AC) measurement in comparison with magnetic resonance imaging with proton density software module (MRI-PDFF). MethodsThis study was conducted between January 2021 and October 2021. The comparison of instrumental methods for assessing and grading hepatic steatosis using a multimodal phantom simulator of different fat and water ratios was performed. The study involved 3 radiological centers. The steatophantom was simultaneously investigated using three methods: magnetic resonance imaging with proton density software module (MRI-PDFF) and 128-slice multidetector computed tomography, and then by 2 different US scanner for steatosis assessment via Measurement Attenuation Imaging (ATI) ant Attenuation Coefficient Measurement (ACM). ResultsModeling of hepatic steatosis using a series of phantom simulators allows evidence-based medicine to determine the diagnostic accuracy of the latest US techniques for steatosis. The ACM and ATI of both US systems on phantoms correlated well with each other and with MRI-PDFF and, thus, can provide good diagnostic value in the assessment of hepatic steatosis. MDCT was less sensitive to mild steatosis than AC and MRI-PDFF. ConclusionMeasurement of ACs in US studies by devices from different vendors compared to other modalities of radiological imaging (MDCT and MRI-PDFF) by special phantoms is an accurate and promising method for noninvasive quantification of hepatic steatosis.

Ultrasound Shear Wave Attenuation Imaging for Grading Liver Steatosis in Volunteers and Patients With Non-alcoholic Fatty Liver Disease: A Pilot Study.

The aims of the work described here were to assess shear wave attenuation (SWA) in volunteers and patients with non-alcoholic fatty liver disease (NAFLD) and compare its diagnostic performance with that of shear wave dispersion (SWD), magnetic resonance imaging (MRI) proton density fat fraction (PDFF) and biopsy. Forty-nine participants (13 volunteers and 36 NAFLD patients) were enrolled. Ultrasound and MRI examinations were performed in all participants. Biopsy was also performed in patients. SWA was used to assess histopathology grades as potential confounders. The areas under curves (AUCs) of SWA, SWD and MRI-PDFF were assessed in different steatosis grades by biopsy. Youden's thresholds of SWA were obtained for steatosis grading while using biopsy or MRI-PDFF as the reference standard. Spearman's correlations of SWA with histopathology (steatosis, inflammation, ballooning and fibrosis) were 0.89, 0.73, 0.62 and 0.31, respectively. Multiple linear regressions of SWA confirmed the correlation with steatosis grades (adjusted R2 = 0.77, p < 0.001). The AUCs of MRI-PDFF, SWA and SWD were respectively 0.97, 0.99 and 0.94 for S0 versus ≥S1 (p > 0.05); 0.94, 0.98 and 0.78 for ≤S1 versus ≥S2 (both MRI-PDFF and SWA were higher than SWD, p < 0.05); and 0.90, 0.93 and 0.68 for ≤S2 versus S3 (both SWA and MRI-PDFF were higher than SWD, p < 0.05). SWA's Youden thresholds (Np/m/Hz) (sensitivity, specificity) for S0 versus ≥S1, ≤S1 versus ≥S2 and ≤S2 versus S3 were 1.05 (1.00, 0.92), 1.37 (0.96, 0.96) and 1.51 (0.83, 0.87), respectively. These values were 1.16 (1.00, 0.81), 1.49 (0.91, 0.82) and 1.67 (0.87, 0.92) when considering MRI-PDFF as the reference standard. In this pilot study, SWA increased with increasing steatosis grades, and its diagnostic performance was higher than that of SWD but equivalent to that of MRI-PDFF.

Dosimetry Validation of MR-Only Treatment Planning Based upon the Synthetic MRCAT Pelvis with Continuous Hounsfield Units in Prostate Cancer

MR-based radiotherapy delivery systems are increasingly encouraging treatment planning based upon an AI generated synthetic CT created from an MR image. Concerns remain concerning the dosimetric accuracy of this approach. to evaluate and compare the feasibilities and dosimetry of magnetic resonance (MR) image-based planning using pelvic synthetic computed tomography (sCT) versus conventional computed tomography (cCT) based planning. We used the new MRCAT pelvis MRI-SIM (1.5T) with continuous Hounsfield units for dose calculation. The hypothesis was that planning based upon sCT vs cCT would not lead to a difference in dose delivery. A total of 10 consecutive patients with prostate cancer representing a range of treatment regimens underwent both a conventional CT based 3d simulation and also an MR simulation from which an MRI-simulation procedure for calculating attenuation (MRCAT) image was generated. A VMAT plan was generated based upon the cCT, and then applied to the sCT without re-optimization. Delivered dose was recalculated on the sCT plan using the fixed monitor units previously optimized for the cCT. Dose volume histograms (DVHs) were calculated for targets and organs at risk (OAR) and compared with those achieved with the cCT. In addition, dose values from 10 different point-coordinates and dose distributions volumes (i.e., volume receiving 80%, 50%, 30% prescribe dose etc.) were compared. All patients were receiving definitive RT to prostate: 2 prostate and seminal vesicles and 8 prostate with lymph nodes were treated. Median prostate volume was 34.3 cc (range 29 cc-84 cc), median number of fractions was 12 (range 5 fr-26 fr), median prescription dose was 51.6 Gy (range 40 Gy-70.2 Gy). The mean dose to the prostate planning target volume and six different OAR were calculated on sCT and cCT, differed by 0.7% ± 1.3% (p = 0.02). Three dose distribution line volume between 30%-80% of prescribed dose, differed by 1.8%±3% (p = 0.02). Ten point-coordinate dose values from different tissues including bone, fat, air and muscle around the planning treatment volume differed by 0.4% ±0.7% (p = 0.03). There was a very small (∼ 1%), but clinically insignificant, difference in the dose distribution results obtained using sCT from MRCAT compared with those obtained with cCT. The Philips pelvic MRCAT, even in the absence of a cCT, is suitable for clinical treatment planning in prostate radiotherapy.

Crustal deformation in the southeastern margin of the Tibetan Plateau: insights from broad-band Pg-wave attenuation tomography

SUMMARY The deformation mechanism in southeastern Tibet since the continental collision between the Indian and Eurasian plates could be explained by several models, including two major classic end-member models, the rigid-block extrusion model and the crustal flow model. Crustal channel flow is likely an important tectonic regime for properly explaining a large number of geological and geophysical observations but remains in competition with the block extrusion model. Consequently, detecting ductile flow connectivity would play a key role in understanding the tectonic evolution of the southeastern Tibetan Plateau. Here, we established a high-resolution broad-band QPg model for the crust in SE Tibet by using a joint inversion tomography method based on both single- and two-station Pg data. We verified the stability of the QPg tomography by comparing the QPg values at 1 Hz between the joint inversion and the two-station method. Two low-QPg zones were observed, isolated by the high-QPg Emeishan large igneous province (ELIP). Strong Pg attenuation beneath the Songpan-Ganzi Block and Western Sichuan Block may indicate the presence of crustal material flow due to relatively weak rheological strength. Cooled basaltic magma remnants in the inner zone of the ELIP likely block the southeastward migration of crustal materials driven by the gravity and lateral pressure gradient, and restrict the flow to the Western Sichuan Block, resulting in surface uplift and crustal thickening. Strong Pg attenuation near the Xiaojiang Fault and the Red River Fault may result from mantle upwelling in this region. Our QPg model, combined with previous results, suggests that the tectonic deformation in the southeastern Tibetan Plateau has been mainly controlled by the effects of crustal channel flow and asthenospheric upwelling since the Late Miocene.

Quantitative ultrasound fatty liver evaluation in a pediatric population: comparison with magnetic resonance imaging of liver proton density fat fraction

BackgroundBiopsy remains the gold standard for the diagnosis of hepatic steatosis, the leading cause of pediatric chronic liver disease; however, its costs call for less invasive methods.ObjectiveThis study examined the diagnostic accuracy and reliability of quantitative ultrasound (QUS) for the assessment of liver fat content in a pediatric population, using magnetic resonance imaging proton density fat fraction (MRI-PDFF) as the reference standard.Materials and methodsWe enrolled 36 patients. MRI-PDFF involved a 3-dimensional T2*-weighted with Dixon pulse multiple-echo sequence using iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL IQ). QUS imaging relied on the ultrasound system “RS85 A” (Samsung Medison, Seoul, South Korea) and the following software: Hepato-Renal Index with automated region of interest recommendation (EzHRI), Tissue Attenuation Imaging (TAI), and Tissue Scatter Distribution Imaging (TSI). For each QUS index, receiver operating characteristic (ROC) curve analysis against MRI-PDFF was used to identify the associated cut-off value and the area under the ROC curve (AUROC). Concordance between two radiologists was assessed by intraclass correlation coefficients (ICCs) and Bland–Altman analysis.ResultsA total of 61.1% of the sample (n=22) displayed a MRI-PDFF ≥ 5.6%; QUS cut-off values were TAI=0.625 (AUROC 0.90, confidence interval [CI] 0.77–1.00), TSI=91.95 (AUROC 0.99, CI 0.98–1.00) and EzHRI=1.215 (AUROC 0.98, CI 0.94–1.00). Inter-rater reliability was good-to-excellent for EzHRI (ICC 0.91, 95% C.I. 0.82–0.95) and TAI (ICC 0.94, 95% C.I. 0.88–0.97) and moderate to good for TSI (ICC 0.73; 95% C.I. 0.53–0.85).ConclusionOur results suggest that QUS can be used to reliably assess the presence and degree of pediatric hepatic steatosis.Graphical abstract

Single-Shot Phase-Contrast Imaging with a Single Grating

In the field of X-ray phase-contrast imaging, a time-saving approach and preservation of details are crucial factors for obtaining phase-contrast images. In this manuscript, a single grating imaging system is proposed to perform the X-ray phase-contrast imaging. Instead of the time-consuming phase-stepping method, this system uses a single-shot algorithm to retrieve the distribution of samples’ attenuation and phase gradient. Unlike the single-shot Fourier transform algorithm, which truncates the high-frequency component of the image and reduces the spatial resolution, our method can retrieve the attenuation and phase information images with the same spatial resolution as the images acquired directly by the X-ray detector used. Furthermore, by using a large-size X-ray detector (29 cm × 23 cm), the imaging system can be configured as either a microscopic instrument or a normal large field-of-view imaging system. Finally, a series of experiments were performed to validate the feasibility of the proposed method.

Advanced biomedical imaging for accurate discrimination and prognostication of mediastinal masses.

To investigate the potential of radiomic features and dual-source dual-energy CT (DECT) parameters in differentiating between benign and malignant mediastinal masses and predicting patient outcomes. In this retrospective study, we analysed data from 90 patients (38 females, mean age 51 ± 25 years) with confirmed mediastinal masses who underwent contrast-enhanced DECT. Attenuation, radiomic features and DECT-derived imaging parameters were evaluated by two experienced readers. We performed analysis of variance (ANOVA) and Chi-square statistic tests for data comparison. Receiver operating characteristic curve analysis and Cox regression tests were used to differentiate between mediastinal masses. Of the 90 mediastinal masses, 49 (54%) were benign, including cases of thymic hyperplasia/thymic rebound (n = 10), mediastinitis (n = 16) and thymoma (n = 23). The remaining 41 (46%) lesions were classified as malignant, consisting of lymphoma (n = 28), mediastinal tumour (n = 4) and thymic carcinoma (n = 9). Significant differences were observed between benign and malignant mediastinal masses in all DECT-derived parameters (p ≤ .001) and 38 radiomic features (p ≤ .044) obtained from contrast-enhanced DECT. The combination of these methods achieved an area under the curve of .98 (95% CI, .893-1.000; p < .001) to differentiate between benign and malignant masses, with 100% sensitivity and 91% specificity. Throughout a follow-up of 1800 days, a multiparametric model incorporating radiomic features, DECT parameters and gender showed promising prognostic power in predicting all-cause mortality (c-index = .8 [95% CI, .702-.890], p < .001). A multiparametric approach combining radiomic features and DECT-derived imaging biomarkers allows for accurate and noninvasive differentiation between benign and malignant masses in the anterior mediastinum.

Application of noninvasive test (acoustic attenuation imaging and ultrasonic shear wave elastography) to grade nonalcoholic fatty liver disease: An observational study.

The aim of this study was to validate the diagnostic efficacy of acoustic attenuation imaging (ATI) and ultrasonic shear wave elastography (SWE) in classifying nonalcoholic fatty liver disease (NAFLD). A total of 100 patients with NAFLD were recruited from our hospital between January 2021 and December 2022. Patient demographics and clinical data were collected, and 2-dimensional ultrasound was used to screen patients based on liver echo characteristics. Patients without liver space-occupying lesions underwent routine ultrasound examinations. Imaging or serology was used to confirm the presence of fatty liver in patients or healthy individuals. Patients with alcoholic liver disease (alcohol equivalent content < 20 g/day for women, <30 g/day for men), as well as those with lenticular degeneration, total parenteral nutrition, autoimmune liver disease, drug-induced hepatitis, and viral hepatitis, were excluded from the study. Out of the 100 included patients, 24 had normal liver, 21 had mild fatty liver, 30 had moderate fatty liver, and 25 had severe fatty liver. There were age differences between the normal group and patients with mild fatty liver, and the average body mass index (BMI) varied across the 4 groups. As the severity of the disease increased, the average BMI also increased (P < .05). The ATI scores and SWE scores differed significantly among the different groups (P < .05), with both scores showing an upward trend as the fatty liver condition worsened. Correlation analysis revealed positive correlations between ATI and SWE scores and the degree of fatty liver (P < .05), positive correlations with BMI (P < .05), and negative correlations with high-density lipoprotein cholesterol expression (P < .05). The area under the curve (AUC) for the ATI score in diagnosing different degrees of fatty liver was > 0.750, and the AUC for the SWE score was also > 0.750. The AUC for SWE score in diagnosing different degrees of fatty liver ranged from 1.01 to 4.57, while the combined AUC for ATI and SWE scores was > 0.850, with respective cutoff values of 3.62, 5.72, and 7.57 based on the maximum approximate entry index. The combination of ATI and SWE has a significant impact on the grading diagnosis of NAFLD, and its application can be extended to clinical practice.

Study on the penetration capability of GPR for the steel-fibre reinforced concrete (SFRC) segment based on numerical simulations and model test

The SFRC segment is gaining attention in shield tunnels due to their better mechanical properties. However, the existence of steel fibres poses a greater difficulty when attempting to utilize ground penetrating radar (GPR) for nondestructive quality inspection compared to conventional reinforced concrete segments. This paper presented a refined numerical model of SFRC segments with gprMax software, to investigate the penetration characteristics of GPR. The numerical model incorporated four different steel fibre contents, namely 0%, 0.5%, 2.5%, and 5%. The model also included an internal void and a surface metal plate to compare and analyze the waveform characteristics of GPR with the normal sections of the segment. The orthogonal test of numerical simulation investigates the imaging characteristics, power attenuation patterns, and imaging features of three different GPR frequency gradients: 200 MHz, 500 MHz, and 1000 MHz. This analysis helps in selecting the appropriate detection frequency based on the observed energy attenuation patterns and imaging characteristics. Then, the model test was conducted at the selected frequency to study the penetration performance of GPR. The research results indicate that the numerical model established in this paper demonstrates good effectiveness in studying the waveform characteristics of steel fibre-reinforced concrete under various conditions. The numerical model established in this paper realized the study of the penetration characteristics and imaging features of different steel fibre contents, GPR frequencies, and detection targets. Analysis of waveform characteristics, power attenuation, and imaging results indicates that GPR at 500 MHz exhibits better detection performance for SFRC segments. The results of the numerical simulation were verified through model tests of real SFRC segments, demonstrating that 500 MHz has good penetration performance for SFRC segments. This paper also proposed a calculation method for equivalent relative dielectric constant (ERDC) based on the model test results and validated its rationality through the analysis of numerical simulation results and real GPR waveforms.

QOCT-Net: A Physics-Informed Neural Network for Intravascular Optical Coherence Tomography Attenuation Imaging.

Intravascular optical coherence tomography (IVOCT) provides high-resolution, depth-resolved images of coronary arterial microstructure by acquiring backscattered light. Quantitative attenuation imaging is important for accurate characterization of tissue components and identification of vulnerable plaques. In this work, we proposed a deep learning method for IVOCT attenuation imaging based on the multiple scattering model of light transport. A physics-informed deep network named Quantitative OCT Network (QOCT-Net) was designed to recover pixel-level optical attenuation coefficients directly from standard IVOCT B-scan images. The network was trained and tested on simulation and in vivo datasets. Results showed superior attenuation coefficient estimates both visually and based on quantitative image metrics. The structural similarity, energy error depth and peak signal-to-noise ratio are improved by at least 7%, 5% and 12.4%, respectively, compared with the state-of-the-art non-learning methods. This method potentially enables high-precision quantitative imaging for tissue characterization and vulnerable plaque identification.

Increased material differentiation through multi-contrast x-ray imaging: a preliminary evaluation of potential applications to the detection of threat materials

Most material discrimination in security inspections is based on dual-energy x-ray imaging, which enables the determination of a material’s effective atomic number (Zeff) as well as electron density and its consequent classification as organic or inorganic. Recently phase-based ‘dark-field’ x-ray imaging approaches have emerged that are sensitive to complementary features of a material, namely its unresolved microstructure. It can therefore be speculated that their inclusion in the security-based imaging could enhance material discrimination, for example of materials with similar electron densities and Zeff but different microstructures. In this paper, we present a preliminary evaluation of the advantages that such a combination could bear. Utilising an energy-resolved detector for a phase-based dark-field technique provides dual-energy attenuation and dark-field images simultaneously. In addition, since we use a method based on attenuating x-ray masks to generate the dark-field images, a fifth (attenuation) image at a much higher photon energy is obtained by exploiting the x-rays transmitted through the highly absorbing mask septa. In a first test, a threat material is imaged against a non-threat one, and we show how their discrimination based on maximising their relative contrast through linear combinations of two and five imaging channels leads to an improvement in the latter case. We then present a second example to show how the method can be extended to discrimination against more than one non-threat material, obtaining similar results. Albeit admittedly preliminary, these results indicate that significant margins of improvement in material discrimination are available by including additional x-ray contrasts in the scanning process.

Extracardiac findings with increased perfusion during clinical O-15-H2O PET/CT myocardial perfusion imaging: A case series

BackgroundCoincidental extracardiac findings with increased perfusion were reported during myocardial perfusion imaging (MPI) with various retention radiotracers. Clinical parametric O-15-H2O PET MPI yielding quantitative measures of myocardial blood flow (MBF) was recently implemented at our facility. We aim to explore whether similar extracardiac findings are observed using O-15-H2O. Methods and resultsAll patients (2963) were scanned with O-15-H2O PET MPI according to international guidelines and extracardiac findings were collected. In contrast to parametric O-15-H2O MBF images, extracardiac perfusion was assessed using summed images. Biopsy histopathology and other imaging modalities served as reference standards. Various malignant lesions with increased perfusion were detected, including lymphomas, large-celled neuroendocrine tumour, breast, and lung cancer plus metastases from colonic and renal cell carcinomas. Furthermore, inflammatory and hyperplastic benign conditions with increased perfusion were observed: rib fractures, gynecomastia, atelectasis, sarcoidosis, pneumonia, chronic lung inflammation and fibrosis, benign lung nodule, chronic diffuse lung infiltrates, pleural plaques and COVID-19 infiltrates. ConclusionsMalignant and benign extracardiac coincidental findings with increased perfusion are readily visible and frequently seen on O-15-H2O PET MPI. We recommend evaluating the summed O-15-H2O PET images in addition to the low-dose CT attenuation images.

Dark-field X-ray imaging for the assessment of osteoporosis in human lumbar spine specimens.

Background: Dark-field imaging is a novel imaging modality that allows for the assessment of material interfaces by exploiting the wave character of x-ray. While it has been extensively studied in chest imaging, only little is known about the modality for imaging other tissues. Therefore, the purpose of this study was to evaluate whether a clinical X-ray dark-field scanner prototype allows for the assessment of osteoporosis. Materials and methods: In this prospective study we examined human cadaveric lumbar spine specimens (vertebral segments L2 to L4). We used a clinical prototype for dark-field radiography that yields both attenuation and dark-field images. All specimens were scanned in lateral orientation in vertical and horizontal position. All specimens were additionally imaged with CT as reference. Bone mineral density (BMD) values were derived from asynchronously calibrated quantitative CT measurements. Correlations between attenuation signal, dark-field signal and BMD were assessed using Spearman's rank correlation coefficients. The capability of the dark-field signal for the detection of osteoporosis/osteopenia was evaluated with receiver operating characteristics (ROC) curve analysis. Results: A total of 58 vertebrae from 20 human cadaveric spine specimens (mean age, 73years ±13 [standard deviation]; 11 women) were studied. The dark-field signal was positively correlated with the BMD, both in vertical (r = 0.56, p < .001) and horizontal position (r = 0.43, p < .001). Also, the dark-field signal ratio was positively correlated with BMD (r = 0.30, p = .02). No correlation was found between the signal ratio of attenuation signal and BMD (r = 0.14, p = .29). For the differentiation between specimens with and without osteoporosis/osteopenia, the area under the ROC curve (AUC) was 0.80 for the dark-field signal in vertical position. Conclusion: Dark-field imaging allows for the differentiation between spine specimens with and without osteoporosis/osteopenia and may therefore be a potential biomarker for bone stability.

An Optimal Prognostic Model Based on Multiparameter Ultrasound for Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is associated with a considerably high mortality, and accurate prognosis prediction is critical to navigate intervention decisions and improve clinical outcomes. The objective of this study was to establish a better prognostic model for ACLF based on multiparameter ultrasound in combination with clinical features. A total of 149 patients with ACLF were prospectively enrolled and underwent conventional ultrasound, 2-D shear wave elastography (SWE), attenuation imaging, color Doppler sonography, superb microvascular imaging and contrast-enhanced ultrasound (CEUS). Univariate and multivariate analyses were performed to identify independent ultrasound signatures for the prognosis of ACLF, which, when integrated with clinical characteristics, were used to establish a prognostic model. Hepatic perfusion features of CEUS differed significantly between the poor and good prognosis groups, among which the time interval (TI) between peak portal vein (PV) velocity and liver parenchyma (LP) enhancement, TI(PV, LP), was independently associated with the prognosis of ACLF. A prediction model comprising TI(PV, LP) and the international normalized ratio was established, and the area under the curve (AUC) was 0.851, which is greater than those of the Model for End-stage Liver Disease (0.785), fall time of LP model (0.754), 2-D SWE nomogram (0.708) and TI(PV, LP) (0.352). Furthermore, the performance of the model was verified in an independent validation cohort (AUC=0.920). The newly developed model performs better than existing tested models; thus, it has potential as a better non-invasive model for predicting the prognosis of patients with ACLF. A future multicenter, large-sample study is required to validate the performance of this model.

Quantitative Diagnosis of Nonalcoholic Fatty Liver Disease with Ultrasound Attenuation Imaging in a Biopsy-Proven Cohort

To evaluate the performance of attenuation imaging (ATI) based on ultrasound for detection of hepatic steatosis in patients with nonalcoholic fatty liver disease (NAFLD). This prospective study was approved by our institutional review board (B2021-092R). Written informed consent was obtained from all patients. This study included 60 patients who had clinical suspicion of NAFLD and were referred for liver biopsy after ATI and controlled attenuation parameter (CAP) examinations between September 2020 and December 2021. The histologic hepatic steatosis was graded. The area under curve (AUC) analysis was performed. The success rate of the ATI examination was 100%. The intraobserver reproducibility of ATI was 0.981. The AUCs of ATI for detecting ≥S1, ≥S2, and S3 were 0.968 (cut-off value of 0.671dB/cm/MHz), 0.911 (cut-off value of 0.726dB/cm/MHz), and 0.766 (cut-off value of 0.757dB/cm/MHz), respectively. The AUCs of CAP for detecting ≥S1, ≥S2, and S3 were 0.916 (cut-off value of 258.5dB/m), 0.872 (cut-off value of 300.0dB/m), and 0.807 (cut-off value of 315.0dB/m), respectively. The diagnostic values showed no significant difference between ATI and CAP in detecting ≥S1, ≥S2, and S3 (P=.281, P=.254, and P=.330, respectively). The ATI had significant correlations with high-density lipoprotein cholesterol (P<.001), and with triglycerides (P=.015). ATI showed good feasibility and diagnostic performance in the detection of varying degrees of hepatic steatosis in NAFLD patients.

Application of attenuation imaging for the detection of fatty liver in potential liver donors

PurposeIn living donor liver transplantation (LDLT), fatty liver adversely affects the outcome in donors or in recipients. The attenuation imaging (ATI) may be valuable for detecting fatty liver in potential liver donors. We aimed to investigate the role of ATI in screening liver donors. MethodIn this prospective study, potential liver donors undergoing MR examination, including proton MR spectroscopy (1H-MRS), were enrolled between January 2020 and December 2021 (study identifier: KCT0004486). All participants underwent ATI examinations to assess fatty liver disease. The reference standard for fatty liver was the hepatic fat fraction (HFF) on 1H-MRS, with 8% defined as the threshold for significant fatty liver. The correlation between attenuation coefficient (AC) and HFF was evaluated using Spearman’s correlation coefficient. The diagnostic performance of AC for the detection of fatty liver disease was evaluated using receiver operating characteristic curve analysis. ResultsA total of 102 participants (median age, 37 [range, 20–61] years; 65 men) were enrolled. Nineteen participants (18.6%) had significant fatty liver on 1H-MRS. AC significantly correlated with HFF on 1H-MRS (ρ = 0.674, P < 0.001), and was significantly higher in patients with HFF on 1H-MRS ≥ 8% than in patients with HFF on 1H-MRS < 8% (0.76 vs. 0.59, P < 0.001). By using the cutoff value of 0.66, the area under the curve of AC for the detection of significant fatty liver on 1H-MRS was 0.923 (95% confidence interval [CI]: 0.853–0.967), with sensitivity, specificity, and negative predictive values of 89.5% (95% CI: 66.9–98.7%), 83.1% (95% CI: 73.3–90.5%), and 97.2% (95% CI: 90.3–99.2%), respectively. ConclusionsATI showed good diagnostic performance with a high negative predictive value for the detection of significant fatty liver among potential liver donors.