Arms down cone beam CT hepatic angiography: are we focusing on the wrong target?

We read with great interest the recent article by Dr. Gonzalez-Aguirre and colleagues entitled ‘‘Arms Down Cone Beam CT Hepatic Angiography Performance Assessment: Vascular Imaging Quality and Imaging Artefacts’’ [1]. One of the most important advantages of cone beam CT (CBCT) is the possibility to evaluate the lesion’s feeders assisting their identification and catheterization [2]. In this set, the patient’s arms positioning is crucial in order not to impair CBCT imaging. Dr. Gonzalez-Aguirre et al. had elegantly demonstrated that vessels’ visualization is independent from the patient’s arms position, allowing to perform the entire procedure without patient’s movements. This minimizes the risk of contamination and reduces procedural time. However, literature shows that the major pivotal strength of CBCT, either mono-phasic or possibly bi-phasic, is the ability to depict in intra-procedurally ‘‘occult lesions’’, not visible at pre-procedural second-line non-invasive imaging (MRI, MDCT) [3]. This ability is not just for show, but yield to some major clinical implications: the visualization of an occult nodule identifies a subset of population experiencing fast tumour growth, having consequences on the number of adjunctive treatments controlling tumour growth (adjunctive RFA, or TACE procedures) and prioritization for transplantation [4]. Moreover, bi-phasic CBCT, with its unique ability to intra-procedural permit nodule characterization, could help in patients’ reclassification and real-time TACE strategy modification [5]. In this light would be a crucial interest for the audience to know whether the CBCT acquisition with arms down does not alter the diagnostic performance of the modality and ability of lesion’s characterization, especially for those lesion localized peripherally, where the beam hardening artefacts have been shown to be significant. Finally, patient’s positioning is fundamental for CBCT imaging. By acquiring the scan with patient’s arm down, liver volume would not be located within the rotation isocentre. This could be a substantial limitation for lesion located within the left liver lobe, eventually hypertrophied, and for high BMI patients

Rayleigh-wave dispersion curve: a proxy for site effect estimation?

One of the open issues on the effects of surface geology regards the estimation of site response when limited resources are available. In that restrictive context, one solution is to use soil characteristics as proxy. Despite its extensive use, the most common proxy, Vs30, is presently criticized because it cannot carry alone the main physics of site response. We propose here a statistical investigation of the capabilities of another proxy, the Rayleigh-wave dispersion curve, DC. When considered over a broad enough frequency band, it can provide deeper information missing in the single Vs30 parameter. A set of shear-wave velocity profiles measured for more than 600 Japanese KiK-net stations is used to compute theoretical dispersion curves (DC) and theoretical SH transfer functions (SH), while instrumental surface/downhole spectral ratios were calculated in a previous work (Cadet et al., 2011a). Canonical correlation techniques are applied to this large data set to analyze the relationship between DC and theoretical or empirical site responses. The results indicate very encouraging qualitative statistical relationships between DC and site amplification for numerically derived SH transfer functions, showing significant canonical couples with correlations up to 0.95. Results for instrumental surface/downhole transfer functions correspond to lower correlations (up to 0.73) but still allow the development of quantitative relationships

Polyethylene Glycol Epirubicin-Loaded Transcatheter Arterial Chemoembolization Procedures Utilizing a Combined Approach with 100 and 200 μm Microspheres: A Promising Alternative to Current Standards

PURPOSE:To report clinical effectiveness, toxicity profile, and prognostic factors of combined 100 μm ± 25 and 200 μm ± 50 epirubicin-loaded polyethylene glycol (PEG) microsphere drug-eluting embolic transcatheter arterial chemoembolization protocol in patients with hepatocellular carcinoma. MATERIALS AND METHODS: In this prospective, single-center, single-arm study with 18 months of follow-up, 36 consecutive patients (mean age 69.9 y ± 10.8; 26 men, 10 women; 54 naïve lesions) were treated. Embolization was initiated with 100 μm ± 25 microspheres, and if stasis (10 heart beats) was not achieved, 200 μm ± 50 microspheres were administered. Each syringe (2 mL) of PEG microsphere was loaded with 50 mg of epirubicin. Results were evaluated using Modified Response Evaluation Criteria In Solid Tumors with multidetector computed tomography/magnetic resonance imaging at 1, 3-6, 9-12, and 15-18 months. Toxicity profile was assessed by laboratory testing before and after the procedure. Complications were recorded. Postembolization syndrome (PES) was defined as onset of fever/nausea/pain after the procedure. Patient/lesion characteristics and treatment results were correlated with predicted outcome using regression analysis. Child-Pugh score was A in 86.1% of patients (31/36) and B in 13.9% (5/36). RESULTS: In 10 of 21 lesions, < 2 cm in diameter (47.5%) stasis was achieved with 100 μm ± 25 microspheres only, whereas all other lesions required adjunctive treatment with 200 μm ± 50 microspheres. Reported adverse events were grade 1 acute liver bile duct injury (3/39 cases, 7.7%) and PES (grade 2; 3/39 cases, 7.7%). Complete response (CR) at 1, 3-6, 9-12, and 15-18 months was 61.1%, 65.5%, 63.63%, and 62.5%. Objective response (CR + partial response) at 1, 3-6, 9-12, and 15-18 months was 83.3%, 65.85%, 63.63%, and 62.5%. No single factor (laboratory testing, etiology, patient status, hepatic status, tumor characteristics, administration protocol) predicted outcomes except for albumin level at baseline for CR (P < .05, odds ratio = 1.09). CONCLUSIONS: The combined microsphere sizing strategy was technically feasible and yielded promising results in terms of effectiveness and toxicity

Statistical estimation of earthquake site response from noise recordings

Standard spectral ratio from earthquake recordings (SSR) is considered the reference empirical method for assessing site effects as a function of frequency. However, other estimates can be easily obtained from noise measurements (i.e., Horizontal-to-Vertical Spectral Ratio, HVN), even though their reliability in terms of amplitude is controversial. In the framework of the ToK ITSAK-GR (2006-2010) EC project, Cultrera et al. (2010) analyzed recordings from 64 sites worldwide, founding that it is possible to have linear combinations of the HVN amplitudes significantly correlated to linear combinations of the SSR. In the present paper we show how to estimate the SSR spectral ratios when only noise measurements are available, using the results of the canonical correlation analysis between SSR and HVN recorded at several sites. The SSR evaluation has been tested by a cross validation procedure: the expected SSR at each validation site are in turn estimated by a weighted average of the SSR values measured at the other sites; the weights are properly set to account more for the sites with similar behavior in terms of the canonical correlation between HVN and SSR. To evaluate the goodness of the estimation, we compared all the inferred and original SSR, and we performed a critical analysis on the spectral characteristics of earthquake site response that can be easily recovered from noise measurements

Analisi statistica degli effetti di sito da dati di terremoti e di rumore ambientale.

L’ultimo ventennio ha visto lo sviluppo e l’uso di tre metodi empirici per l’analisi degli effetti di sito: Standard Spectral Ratio (SSR), Horizontal-to-Vertical Spectral Ratio da registrazioni sismiche (HVSR) e Horizontal-to-Vertical Spectral Ratio da registrazioni di rumore ambientale (HVN). SSR è considerato il metodo empirico di riferimento per rilevare le amplificazioni in funzione della frequenza. HVSR e HVN, invece, danno una stima realistica della frequenza fondamentale ma, generalmente, non riescono a fornire valori affidabili di amplificazione. Nel presente lavoro sono state utilizzate le registrazioni sismiche effettuate in 168 siti provenienti da diverse aree geografiche e per cui sono stati calcolati tutti e tre i tipi di rapporti spettrali (Haghsenas et al., 2008). Su questi dati abbiamo applicato delle analisi statistiche multivariate quali la correlazione canonica (Davis, 2002), con lo scopo di mettere in evidenza e quantificare le correlazioni tra i differenti rapporti spettrali nell’intero intervallo di frequenza compreso tra 0.2Hz e 10Hz. Questo tipo di analisi permette inoltre di associare alle correlazioni una stima della loro significatività ed è stata già utilizzata da Theodulidis et al. (2008) per studiare la relazione tra HVN e danneggiamento in aree urbane. I risultati mostrano che la correlazione tra HVN e HVSR è molto buona ad esclusione delle basse frequenze e che, per entrambe le tecniche, la presenza di un picco di amplificazione nell’intervallo 0.6-2 Hz è correlato ad un minimo per frequenze 3-10Hz. I picchi di amplificazione evidenziati da queste due tecniche sono inoltre correlabili con un più largo intervallo di frequenze nei rapporti SSR. Abbiamo quindi esteso l’analisi per correlare SSR, HVSR e HVN in bacini sedimentari (un subset dei dati utilizzati) con parametri geofisici e geometrici. La riduzione del numero dei dati deriva dall’esigenza di avere siti con una buona qualità di informazioni geofisiche e geometriche. Sono stati scelti cinque parametri indicatori delle velocità medie delle onde S e delle caratteristiche geometriche 2D della valle. Sebbene un più esteso data-set migliorerebbe l’analisi statistica, stabilendo migliori stime quantitative della correlazione tra rapporti spettrali e le caratteristiche geofisiche e geometriche dei bacini sedimentari, i nostri risultati mostrano chiaramente che le correlazioni tra SSR e HVN-HVSR esistono e si modulano in specifici intervalli di frequenza. Questo studio è stato condotto nell’ambito del progetto ToK ITSAK-GR EC (2006-2010)

Statistical investigation of site ef f ects with emphasis on sedimentary basins, using earthquake and ambient noise recordings

During the last two decades, three empirical methods for assessing site effects have been widely used: the Standard Spectral Ratio (SSR), the Horizontal-to-Vertical Spectral Ratio from earthquake recordings (HVSR) and the Horizontal-to-Vertical Spectral Ratio from ambient noise recordings (HVN). The SSR is considered the reference empirical method to detect amplification as a function of frequency, while the HVSR and the HVN realistically indicate fundamental frequency but, for the majority of the worldwide examined sites, they cannot give reliable amplification curves as a function of frequency. Given the fact that HVSR and especially HVN can be easily obtained, it is challenging to search for any correlation with SSR amplification functions. We used recordings from 168 sites worldwide, for which all three types of spectral ratios were homogeneously processed (Haghsenas et al., Bull. Earthquake Eng. 2008). On this data set we applied standard multivariate statistical analyses, namely, factor analysis and canonical correlation, to investigate and quantify -where it is possible- any correlation between spectral ratios for a certain number of the examined frequency bins. Results show that the correlation between HVN and HVSR is very good. Moreover, their correlation with broad band SSR can be statistically quantified and receive a satisfactory physical explanation. In addition, we looked for the correlation of SSR, HVSR and HVN collected in sedimentary basins (a subset of the previous database) with geometrical and geophysical parameters. T hese attempts were constrained by the limited amount of reliable in-situ data. Among many, we select 5 parameters: Vs30, Hb, Vs_average/Hb, Hb/W_valley, Hb/W_edge (where Hb is the bedrock’s depth below the station; Vs_average is the average Vs from surface to bedrock; W_valley is 2D-width of the valley; W_edge is the distance from the closest valley’s edge). T he analysis assesses that larger are the first 4 parameters, larger is the low-frequency amplification in HVSR and HVN, and lower the high-frequency contribution. Although additional data would improve our statistical investigation and better establish quantitative correlation between spectral ratios and geophysical or/and geometrical characteristics of sedimentary basins, our results clearly show that statistical correlation between SSR and HVN-HVSR is present and modulated in specific frequency domains. T his study has been performed in the framework of the T oK IT SAK-GR EC project (2006-2010)

Earthquake statistics and fractal faults

We introduce a Self-affine Asperity Model (SAM) for the seismicity that mimics the fault friction by means of two fractional Brownian profiles (fBm) that slide one over the other. An earthquake occurs when there is an overlap of the two profiles representing the two fault faces and its energy is assumed proportional to the overlap surface. The SAM exhibits the Gutenberg-Richter law with an exponent $\beta$ related to the roughness index of the profiles. Apart from being analytically treatable, the model exhibits a non-trivial clustering in the spatio-temporal distribution of epicenters that strongly resembles the experimentally observed one. A generalized and more realistic version of the model exhibits the Omori scaling for the distribution of the aftershocks. The SAM lies in a different perspective with respect to usual models for seismicity. In this case, in fact, the critical behaviour is not Self-Organized but stems from the fractal geometry of the faults, which, on its turn, is supposed to arise as a consequence of geological processes on very long time scales with respect to the seismic dynamics. The explicit introduction of the fault geometry, as an active element of this complex phenomenology, represents the real novelty of our approach.Comment: 40 pages (Tex file plus 8 postscript figures), LaTeX, submitted to Phys. Rev.

Self-affine Asperity Model for earthquakes

A model for fault dynamics consisting of two rough and rigid brownian profiles that slide one over the other is introduced. An earthquake occurs when there is an intersection between the two profiles. The energy release is proportional to the overlap interval. Our model exhibits some specific features which follow from the fractal geometry of the fault: (1) non-universality of the exponent of the Gutenberg-Richter law for the magnitude distribution; (2) presence of local stress accumulation before a large seismic event; (3) non-trivial space-time clustering of the epicenters. These properties are in good agreement with various observations and lead to specific predictions that can be experimentally tested.Comment: TeX file, 14 pages, 3 figures available from [email protected]

An update of pitfalls in prostate mpMRI: a practical approach through the lens of PI-RADS v. 2 guidelines

ObJECTIVES: The aim of the current report is to provide an update in the imaging interpretation of prostate cancer on multiparametric magnetic resonance imaging (mpMRI), with a special focus on how to discriminate pathological tissue from the most common pitfalls that may be encountered during daily clinical practice using the Prostate Imaging Reporting and Data System (PI-RADS) version 2 guidelines. METHODS: All the cases that are shown in this pictorial review comply with the European Society of Urogenital Radiology (ESUR) guidelines for technical mpMRI requirements. RESULTS: Despite the standardised manner to report mpMRI (PI-RADS v. 2), some para-physiologic appearances of the prostate can mimic cancer. As such, it is crucial to be aware of these pitfalls, in order to avoid the under/overestimation of prostate cancer. CONCLUSIONS: A detailed knowledge of normal and abnormal findings in mpMRI of the prostate is pivotal for an accurate management of the wide spectrum of clinical scenarios that radiologists may encounter during their daily practice. TEACHING POINTS: • Some para-physiologic appearances of the prostate may mimic cancer. • Knowledge of normal and abnormal findings in prostate mpMRI is pivotal. • Any radiologist involved in prostate mpMRI reporting should be aware of pitfalls

Microtremor Measurements in the City of Palermo, Italy: Analysis of the Correlation between Local Geology and Damage

This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two riverbeds masked by urbanization since the seventeenth century. HVNSRs show significant variations in the study area: when the transition stiff to soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1–2 Hz, and exceeding a factor of 3 in amplitude. Using available information on subsurface geological structure, we compute theoretical 1D and 2D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling. The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European macroseismic scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5–3 Hz) and the occurrence of the highest damage grades. This approach allows us (1) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes, which separates zones of light damage from zones of significant damage, and therefore (2) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements