Search results for "frequency [modulation]"
showing 10 items of 569 documents
Evaluation of posttreatment response of hepatocellular carcinoma: comparison of ultrasonography with second-generation ultrasound contrast agent and …
2010
We evaluated the ability of one-month follow-up contrast-enhanced ultrasound (CEUS) with second-generation contrast agent in monitoring radio frequency ablation (RFA) and transcatheter arterial chemoembolization (TACE) treatments of hepatocellular carcinoma (HCC). One-hundred forty-eight HCCs were studied using CEUS: 110 nodules were treated with RFA [41/110 RFA were performed using a pretreatment and an immediate postablation evaluation using CEUS (group 1); 69/110 using only US guidance (group 2)] and 38 nodules treated with TACE. For statistical analysis, McNemar test was used. Overall complete response was observed in 107/148 nodules (92/110 treated with RFA and 15/38 with TACE). A bett…
Radiofrequency ablation as first-line treatment in patients with early colorectal liver metastases amenable to surgery.
2010
Aiming at avoidance of futile surgery, we have tested whether radiofrequency ablation (RFA) may be used as first-line treatment in patients with colorectal metastases (CRLM) occurring within the first year after colorectal surgery.Surgical resection is the standard treatment in patients with CRLM. Major retrospective analyses have identified the interval between colorectal surgery and the occurrence of CRLM to be of prognostic importance. So far, it is unknown whether survival of the respective patients is hampered if RFA is used as first-line treatment.According to a clinical pathway, we have treated patients with CRLM detected within the first year after colorectal surgery preferentially …
Combined treatment of hidradenitis suppurativa with intense pulsed light (IPL) and radiofrequency (RF)
2019
BACKGROUND Hidradenitis suppurativa is a chronic inflammatory disease with high burden. Treatment options are often unsatisfactory. We assessed the effect of a combination therapy of intense pulsed light (IPL) and radiofrequency (RF). METHODS The explorative study included 47 patients and was performed as a prospective, monocentric, randomized, three-arm parallel-group design trial with a prior 12 weeks observation period. Treatment arms were IPL and RF monotherapies or IPL + RF combination therapy. After 12 weeks, all patients received IPL + RF for additional 12 weeks (cross-over). Primary endpoint was the change in active lesion numbers, secondary endpoint the change in Dermatology Qualit…
Symptom dimensions in obsessive-compulsive disorder: differences in distress, interference, appraisals and neutralizing strategies.
2012
Abstract Background and objectives Cognitive proposals about the mediating role of misinterpretations, emotional reactions, and control strategies in the escalation of obsessional intrusive thoughts (OIT) to clinical obsessions have received only partial support. This study aims to examine these variables, taking into account the obsession/OIT contents and the severity of the Obsessive-Compulsive Disorder (OCD). Methods After identifying their most upsetting OIT/obsession, 61 OCD patients and 61 non-clinical individuals assessed the associated distress, interference and appraisals, and the strategies used to control the obsession/OIT. Results Compared with the nonclinical subjects, OCD indi…
Measuring postural-related changes of spontaneous baroreflex sensitivity after repeated long-duration diving: Frequency domain approaches
2012
Sustained water immersion is thought to modulate orthostatic tolerance to an extent dependent on the duration and repetition over consecutive days of the diving sessions. We tested this hypothesis investigating in ten healthy subjects the potential changes in the cardiovascular response to head-up tilt induced by single and multiple resting air dives. Parametric cross-spectral analysis of spontaneous RR interval and systolic arterial pressure variability was performed in three experimental sessions: before diving (BD), after single 6-hour dive (ASD), and after multiple 6-hour dives (AMD, 5 consecutive days with 18-hour surface interval). From this analysis, baroreflex sensitivity (BRS) was …
Clinical observations and risk factors for tinnitus in a Sicilian cohort.
2014
The aims of this study were to determine the distribution of risk factors associated with tinnitus analysing their role in the development of tinnitus and the effects of their interaction; to evidence the importance of a suitable and adequate clinical and audiologic assessment to avoid those modifiable risk factors responsible for cochlear dysfunction and tinnitus onset. 46 subjects with tinnitus and 74 controls were studied according to: age, sex, Body Mass Index (BMI), neck circumference, tobacco smoking, feeling fatigue or headache, self reporting snoring, hypertension, diabetes, coronary heart disease, and/or hyperlipidemia, and laboratory finding as lipid profile and levels of reactive…
Surrogate data approaches to assess the significance of directed coherence: Application to EEG activity propagation
2009
This paper addresses the topic of evaluating the significance of frequency domain measures of causal coupling in multivariate time series through generation of surrogate data. The considered approaches are the traditional Fourier Transform (FT) algorithm and a new causal FT (CFT) algorithm for surrogate data generation. Both algorithms preserve the FT modulus of the original series; differences are in the phase relationships, that are completely destroyed for FT surrogates and imposed after switching off the link over the considered causal direction for CFT surrogates. The ability of the algorithms to assess causality in the frequency domain was tested using the directed coherence as discri…
Testing Frequency-Domain Causality in Multivariate Time Series
2010
We introduce a new hypothesis-testing framework, based on surrogate data generation, to assess in the frequency domain, the concept of causality among multivariate (MV) time series. The approach extends the traditional Fourier transform (FT) method for generating surrogate data in a MV process and adapts it to the specific issue of causality. It generates causal FT (CFT) surrogates with FT modulus taken from the original series, and FT phase taken from a set of series with causal interactions set to zero over the direction of interest and preserved over all other directions. Two different zero-setting procedures, acting on the parameters of a MV autoregressive (MVAR) model fitted on the ori…
Phase information of time-frequency transforms as a key feature for classification of atrial fibrillation episodes
2015
[EN] Patients suffering from atrial fibrillation can be classified into different subtypes, according to the temporal pattern of the arrhythmia and its recurrence. Nowadays, clinicians cannot differentiate a priori between the different subtypes, and patient classification is done afterwards, when its clinical course is available. In this paper we present a comparison of classification performances when differentiating paroxysmal and persistent atrial fibrillation episodes by means of support vector machines. We analyze short surface electrocardiogram recordings by extracting modulus and phase features from several time-frequency transforms: short-time Fourier transform, Wigner-Ville, Choi-…
An automatic test for frequency discrimination
1987
Békésy audiometry has been applied to the determination of the frequency discrimination threshold. The automatic test for frequency discrimination is performed by means of a modified automatic audiometer at fixed frequencies, each administered for a duration of 60 s. The test involves the stimulus of a series of pairs of tone bursts of 500 ms duration: the frequency of one of the tone bursts (f0) is constant, while the other (f0 + delta f) gradually increases and decreases according to the subject's response. The tracings obtained facilitate the evaluation of the discrimination capability of the subject. The pattern obtained from a sample of normally hearing people was analysed in order to …