On the Feasibility of Ultrasound Imaging Enrichment by Medium-Temperature Changes.

We describe the concept of a new imaging modality based on the tracking and dynamic modeling of local intensity changes (ICs) observed in conventional ultrasound images collected during a medium-temperature change. We computed the pixel-by-pixel IC from averaged B-mode images that exhibited different behaviors with varying temperature resulting from changes in the speed of sound, which consequently induce changes in the backscattered energy. Moreover, for each pixel, a first-order polynomial model was adjusted to the different temperature-dependent ICs. The representation of the polynomial angular parameter in 2D pixel space was used to obtain a parametric image. The results obtained by simulations and with real B-mode images indicated that this new ultrasound imaging modality was able to enhance the contrast and highlight structures that were poorly visible or even undetected in conventional images. A temperature change of 3°C was found to be sufficient to generate appropriate images with the proposed method. In addition, if a temperature change of 6°C was considered, the thermal dose, measured as the cumulative number of equivalent minutes at 43°C (CEM43°C), was 2.4 CEM43°C, which is a value that is considered safe according to the literature. We provide a proof-of-concept of a new imaging modality that opens new opportunities for the enhancement of ultrasound images and consequently contributes to improvements in ultrasound-based diagnoses. Our approach is based on images returned by commercial ultrasound scanners. Therefore, it can be implemented in any ultrasound system and is independent of specific ultrasound hardware and software data acquisition characteristics.

Computerized lesion segmentation of breast ultrasound based on marker-controlled watershed transformation.

PURPOSE: This paper presents a computerized segmentation method for breast lesions on ultrasound (US) images. METHODS: It consists of first applying a contrast-enhanced approach, i.e., a contrast-limited adaptive histogram equalization. Then, aiming at removing speckle and enhancing the lesion boundary, an anisotropic diffusion filter, guided by texture descriptors derived from a set of Gabor filters, is applied. To eliminate the distant pixels that do not belong to the tumor, the resulting filtered image is multiplied by a constraint Gaussian function. By doing so, both the segmentation and the marker functions are generated and could be used in the marker-controlled watershed transformation algorithm to create potential lesion boundaries. Finally, to determine the lesion contour, the average radial derivative function is evaluated. The proposed method was tested with 50 breast US images and 60 simulated "ultrasound-like" images. Accuracy and precision of the segmentation method were then assessed. For the accuracy, three parameters were used: Overlap ratio (OR), normalized residual value (nrv), and proportional distance (PD) between contours. RESULTS: The average results for US images were OR = 0.86 +/- 0.05, nrv = 0.16 +/- 0.06, and PD = 6.58 +/- 2.52%. For simulated ultrasound-like images, a better performance (OR = 0.92 +/- 0.01, nrv = 0.08 +/- 0.01, and PD = 3.20 +/- 0.53%) was achieved. CONCLUSIONS: The segmentation method proposed was capable of delineating the lesion contours with high accuracy in comparison to both the radiologists' delineations and the true delineations of simulated images. Moreover, this method was also found to be robust to human-dependent parameters variations.

Study of cutaneous cell carcinomas ex vivo using ultrasound biomicroscopic images.

BACKGROUND: The ultrasound biomicroscopy (UBM) technique generates high-resolution echographic images using acoustic frequencies between 20 and 200 MHz. In dermatology, it enables non-invasive visualization of cutaneous structures. In this sense, several studies are being conducted for the measurement of cutaneous tumor sizes and for the evaluation of their response to therapeutic procedures. The present work was conducted to analyze the ability of UBM to identify diverse histological structures associated with cutaneous carcinomas ex vivo regarding the evaluation of the technique as a diagnostic tool that could, eventually, improve the patient's healthcare protocol. METHODS: Ex vivo human tissue samples, corresponding to basal cell carcinoma and squamous cell carcinoma cases, were studied. The ultrasonic system operated with a center frequency of 45MHz and the histological structures were identified by comparison with the light microscopy images. RESULTS: The histological components present in the tumors were identified by variations in the echogenicity level for several of the studied cases and particular characteristics were observed for the different tumor types. CONCLUSION: The possibility of differentiating the histological components associated with cutaneous carcinomas indicates the potential use of UBM for diagnostic applications. However, a larger number of specimens must be studied.

Computed Tomography Scanner Productivity and Entry-Level Models in the Global Market.

Objective: This study evaluated the productivity of computed tomography (CT) models and characterized their simplest (entry-level) models' supply in the world market. Methods: CT exam times were measured in eight health facilities in the state of Rio de Janeiro, Brazil. Exams were divided into six stages: (1) arrival of patient records to the examination room; (2) patient arrival; (3) patient positioning; (4) data input prior to exam; (5) image acquisition; and (6) patient departure. CT exam productivity was calculated by dividing the total weekly working time by the total exam time for each model. Additionally, an internet search identified full-body CT manufacturers and their offered entry-level models. Results: The time durations of 111 CT exams were obtained. Differences among average exam times were not large, and they were mainly due to stages not directly related to data acquisition or image reconstruction. The survey identified that most manufacturers offer 2- to 4-slice models for Asia, South America, and Africa, and one offers single-slice models (Asia). In the USA, two manufacturers offer models below 16-slice. Conclusion: Productivity gains are not linearly related to "slice" number. It is suggested that the use of "shareable platforms" could make CTs cheaper, increasing their availability.

Non-invasive temperature prediction of in vitro therapeutic ultrasound signals using neural networks.

In this paper, a novel black-box modelling scheme applied to non-invasive temperature prediction in a homogeneous medium subjected to therapeutic ultrasound is presented. It is assumed that the temperature in a point of the medium is non-linearly related to some spectral features and one temporal feature, extracted from the collected RF-lines. The black-box models used are radial basis functions neural networks (RBFNNs), where the best-fitted models were selected from the space of model structures using a genetic multi-objective strategy. The best-fitted predictive model presents a maximum absolute error less than 0.4 degrees C in a prediction horizon of approximately 2 h, in an unseen data sequence. This work demonstrates that this type of black-box model is well-suited for punctual and non-invasive temperature estimation, achieving, for a single point estimation, better results than the ones presented in the literature, encouraging research on multi-point non-invasive temperature estimation.

In vitro chronic hepatic disease characterization with a multiparametric ultrasonic approach.

Although, high resolution, real-time ultrasonic (US) imaging is routinely available, image interpretation is based on grey-level and texture and quantitative evaluation is limited. Other potentially useful diagnostic information from US echoes may include modifications in tissue acoustic parameters (speed, attenuation and backscattering) resulting from disease development. Changes in acoustical parameters can be detected using time-of-flight and spectral analysis techniques. The objective of this study is to explore the potential of three parameters together (attenuation coefficient, US speed and integrated backscatter coefficient-IBC) to discriminate healthy and fibrosis subgroups in liver tissue. Echoes from 21 fresh in vitro samples of human liver and from a plane reflector were obtained using a 20-MHz central frequency transducer (6-30 MHz bandpass). The scan plane was parallel to the reflector placed beneath the liver. A 30 x 20 matrix of A-scans was obtained, with a 200-microm step. The samples were classified according to the Metavir scale in five different degrees of fibrosis. US speed, attenuation and IBC were estimated from standard methods described in the literature. Statistical tests were applied to the results of each parameter individually and indicated that it was not possible to identify all the fibrosis groups. Then a discriminant analysis was performed for the three parameters together resulting in a reasonable separation of fibrotic groups. Although the number of tissue samples is limited, this study opens the possibility of enhancing the discriminant capability of ultrasonic parameters of liver tissue disease when they are combined together.

Breast tumor classification in ultrasound images using neural networks with improved generalization methods.

Mammography, scintimammography and ultrasound images have been used to increase the specificity of breast cancer image diagnosis. Concerning breast cancer image diagnosis with ultrasound, some results found in the literature show better performance of morphological features in breast cancer lesion differentiation and that a reduced set of features shows a better performance than a large set of features. In this study we evaluated the performance of neural network classifiers, with different training stop criteria: mean square error, early stop and regularization. The last two criteria were developed to improve neural network generalization. Different sets of morphological features were used as neural network inputs. Training sets comprised of 22, 8, 7, 6, 5 and 4 features were employed. To select reduced sets of features, a scalar selection technique with correlation was used. The best results obtained for accuracy and area under the ROC curve were 96.98% and 0.98, respectively. The performance obtained with all 22 features is slightly better than the one obtained with a reduced set of features.

Performance of ultrasound echo decomposition using singular spectrum analysis.

Diagnostic ultrasonography has its well-established role in medicine. Nevertheless, the quantitative characterisation of biological tissues by ultrasound (US) is still a main topic of research. Several parameters have been explored with this purpose, (e.g. attenuation, backscatter coefficient, US speed). More recently, mean scatterer space (MSS) has been proposed as a characterisation parameter. The objective of this work was to investigate the potential of the singular spectrum analysis (SSA) to estimate MSS. This method proposes the reconstruction of the periodic part of the original US signal from where the MSS of the medium can be estimated. SSA is applied to simulated and real backscattered echoes from a phantom and a bovine liver sample. Consistent results were obtained from both Monte-Carlo simulation and real data. They were compared with literature. Presently, precision, accuracy and sensibility of SSA are being investigated.

A computerised information system for the analysis of hospital admission flow and characteristics.

This paper presents a computerised information system for the characterisation and analysis of the hospital admission flow of patients. Based on administrative data made available by the Ministry of Health of Brazil (DATASUS-MS), the system allows the representation of patients' flow from residence to hospital, as well as information on performed medical procedures, diagnoses and other patient and hospital characteristics. Residences are represented in terms of their postal codes and admission diagnosis according to the ICD-10 classification. The system has a flexible and simple geographic coordinates input module, and can be used even when no standard coordinates system (e.g., Mercator) are available. It provides two types of graphical representation: 'static' (concerning characteristics of a hospital or geographical area) and 'dynamic' (residence to hospital flow). Its use is exemplified with a geographical representation of access to ultra-sound exams in selected hospitals in the city of Rio de Janeiro, Brazil, July 1998. In conclusion, the system seems a powerful instrument for health needs identification and planning, as well as for quality assessment and for the generation of information useful for epidemiological research.

Ultrasonic wave speed measurement using the time-delay profile of rf-backscattered signals.

Conventional methods determine the ultrasonic wave speed by measuring the medium path length propagated by a pulsed wave and the corresponding time-of-flight. In this study, the wave speed is determined without the need of the path length. A transmitting transducer sends a pulsed wave into the medium (constant wave speed along the beam axis) and the backscattered signal is collected by a hydrophone placed at two distinct positions near the transmitted beam. The time-delay profile, between gated windows of the two rf-signals received by the hydrophone, is determined using a cross-correlation method. Also, a theoretical time-delay profile is determined considering the wave speed as a parameter. The measured wave speed is obtained upon minimization of the RMS error between theoretical and experimental time-delay profiles. A PZT conically focused transmitting transducer with center frequency of 3.3 MHz, focal depth of 20 mm and beam width (-6 dB) of 2 mm at the focus was used together with a PZT hydrophone, 0.8 mm in aperture. The method was applied to three phantoms (wave speed of 1220, 1501 and 1715 m/s) and, in vitro, to fresh bovine liver sample, immersed in a temperature-controlled water bath. The results vary within 3% of those obtained with a conventional method.

[Bifrontal decompressive craniotomy as the treatment for severe cerebral edema]. / Craniotomia descompressive bifrontal no tratamento do edema cerebral grave

The authors present the results observed with large bifrontal decompressive craniotomy performed on 12 patients with severe cerebral edema, 10 of them related to cerebral contusion, which did not respond to conventional methods of therapy. All patients had before surgery very bad prognosis, with severe neurological signs of higher brain stem compression. Bilateral carotid angiography was sistematically performed before and after surgery, constituting as a matter of fact the decisive element indicating cerebral decompression. Six patients (50 per cent) survived and 5 of them (41.6 per cent) had an excellent neurological and mental improvement. Considering these results, we think that a large bifrontal decompressive craniotomy is the best method of treatment in such cases, specially when performed precociously. These patients, however, need very special care after surgery, if possible in units of intensive therapy, owing to the large incidence of complications.

Anterior floor meningoencephaloceles surgical treatment. Experience based on eleven cases.

The authors relate their experience in the anterior floor meningoencephaloceles surgical treatment, excised by the intracranial pathway and extradural approach. They compare their results on five cases operated according to this technique, with other six cases treated in the same Department using other surgical procedures and with those in the literature.

[Megadolichobasilar anomaly: apropos of 5 cases diagnosed angiographically]. / Anomalia megadolicobasilar; a propósito de 5 casos diagnosticados angiograficamente.

After brief considerations on the symptomatology and ethiopathogeny of megadolichobasilar, five cases of this vascular anomaly are presented. Agreeing with the majority of the papers on the subject, the age of the patients was between the fourth and the sixth decades, all of them presenting arterial hypertension of long duration and advanced atherosclerosis; the neurological findings were varied, having in common the fact of an abrupt (ictal) beggining. The angiographic study of the vertebrobasilar system was basic in the diagnosis in every case.

[Lesion of the Lissauer tract and of the posterior horn of the gray substance of the spinal cord and the electrical stimulation of the central nervous system for the treatment of brachial plexus avulsion pain]. / A lesão do trato de Lissauer e do corno posterior da substância cinzenta da medula espinal e a estimulação elétrica do sistema nervoso central para o tratamento da dor por avulsão de raízes do plexo braquial.

We analyze the effectiveness of the treatment of 10 patients of brachial plexus avulsion pain. Seven underwent dorsal root entry zone lesions (DREZ), 3, dorsal column stimulation (DCS) and, 2 thalamic stimulation (TS). DCS resulted in immediate improvement of pain in 50% of the patients. After a long term follow up period, just 25% of the patients were still better. TS resulted the in temporary improvement of 2 patients. Both had full recurrence few months after the operation. Immediate improvement of the symptoms occurred in all patients treated by DREZ. After a long term follow up period, excellent results were observed in 71.4% of the patients and good results in the remainder. The complication rate was higher among DREZ patients. It is concluded that DREZ is a better procedure for treatment of brachial plexus avulsion pain than DCS and TS (p = 0.0046); however, DCS and TS are safer.

Feasibility of non-invasive temperature estimation by the assessment of the average gray-level content of B-mode images.

This paper assesses the potential of the average gray-level (AVGL) from ultrasonographic (B-mode) images to estimate temperature changes in time and space in a non-invasive way. Experiments were conducted involving a homogeneous bovine muscle sample, and temperature variations were induced by an automatic temperature regulated water bath, and by therapeutic ultrasound. B-mode images and temperatures were recorded simultaneously. After data collection, regions of interest (ROIs) were defined, and the average gray-level variation computed. For the selected ROIs, the AVGL-Temperature relation were determined and studied. Based on uniformly distributed image partitions, two-dimensional temperature maps were developed for homogeneous regions. The color-coded temperature estimates were first obtained from an AVGL-Temperature relation extracted from a specific partition (where temperature was independently measured by a thermocouple), and then extended to the other partitions. This procedure aimed to analyze the AVGL sensitivity to changes not only in time but also in space. Linear and quadratic relations were obtained depending on the heating modality. We found that the AVGL-Temperature relation is reproducible over successive heating and cooling cycles. One important result was that the AVGL-Temperature relations extracted from one region might be used to estimate temperature in other regions (errors inferior to 0.5 °C) when therapeutic ultrasound was applied as a heating source. Based on this result, two-dimensional temperature maps were developed when the samples were heated in the water bath and also by therapeutic ultrasound. The maps were obtained based on a linear relation for the water bath heating, and based on a quadratic model for the therapeutic ultrasound heating. The maps for the water bath experiment reproduce an acceptable heating/cooling pattern, and for the therapeutic ultrasound heating experiment, the maps seem to reproduce temperature profiles consistent with the pressure field of the transducer, and in agreement with temperature maps developed by COMSOL®MultiPhysics simulations.

Ultrasound method applied to characterize healthy femoral diaphysis of Wistar rats in vivo.

A simple experimental protocol applying a quantitative ultrasound (QUS) pulse-echo technique was used to measure the acoustic parameters of healthy femoral diaphyses of Wistar rats in vivo. Five quantitative parameters [apparent integrated backscatter (AIB), frequency slope of apparent backscatter (FSAB), time slope of apparent backscatter (TSAB), integrated reflection coefficient (IRC), and frequency slope of integrated reflection (FSIR)] were calculated using the echoes from cortical and trabecular bone in the femurs of 14 Wistar rats. Signal acquisition was performed three times in each rat, with the ultrasound signal acquired along the femur's central region from three positions 1 mm apart from each other. The parameters estimated for the three positions were averaged to represent the femur diaphysis. The results showed that AIB, FSAB, TSAB, and IRC values were statistically similar, but the FSIR values from Experiments 1 and 3 were different. Furthermore, Pearson's correlation coefficient showed, in general, strong correlations among the parameters. The proposed protocol and calculated parameters demonstrated the potential to characterize the femur diaphysis of rats in vivo. The results are relevant because rats have a bone structure very similar to humans, and thus are an important step toward preclinical trials and subsequent application of QUS in humans.

A comparative study of automatic thresholding approaches for 3D x-ray microtomography of trabecular bone.

PURPOSE: This paper presents a comparative study of automatic thresholding algorithms for segmenting trabecular bone volume in x-ray microtomography (µCT). METHODS: First, a preprocessing stage was established, which considered noise reduction by applying anisotropic diffusion filtering and contrast enhancement by using morphological top-hats. Next, four automatic thresholding algorithms were implemented: clustering, maximum entropy, moment preservation, and concavity-based. These approaches analyze the preprocessed 3D µCT image histogram to optimize some parameters to find the best gray-level threshold. Thirty-eight vertebra bone samples were acquired from 19 normal Wistar rats, specifically the L3 and L4 vertebrae. The µCT images were acquired with a microfocus x-ray device at 100 slices/sample. Next, three human operators segmented the entire 3D µCT images manually to establish ground-truth segmentations so as to associate the segmentation problem with perceptual grouping. The normalized probabilistic Rand index (NPRI) was used to quantify the agreement between each computerized segmentation and the corresponding set of three ground-truth segmentations. Hence, the NPRI value should tend toward unity for an acceptable performance. Finally, a statistical analysis was done to determine which thresholding approach achieved the best performance. Besides, 3D morphometric indices were also measured. RESULTS: The Games-Howell test (α = 0.05) was used to compare the equality of means from the NPRI results considering the four thresholding algorithms (multiple comparisons). This statistical analysis indicated that the clustering and moment preservation techniques performed similarly, with NPRI values of 0.594 ± 0.126 and 0.607 ± 0.127, respectively. CONCLUSIONS: The main advantage of computerized segmentation is that it is fully automatic; that is, no interaction with the user is required. Thus, the method could be considered objective. Besides, the proposed preprocessing stage plays an important role in enhancing the µCT image quality to achieve better separation between the background volume and the trabecular bone volume.

Analysis of co-occurrence texture statistics as a function of gray-level quantization for classifying breast ultrasound.

In this paper, we investigated the behavior of 22 co-occurrence statistics combined to six gray-scale quantization levels to classify breast lesions on ultrasound (BUS) images. The database of 436 BUS images used in this investigation was formed by 217 carcinoma and 219 benign lesions images. The region delimited by a minimum bounding rectangle around the lesion was employed to calculate the gray-level co-occurrence matrix (GLCM). Next, 22 co-occurrence statistics were computed regarding six quantization levels (8, 16, 32, 64, 128, and 256), four orientations (0° , 45° , 90° , and 135°), and ten distances (1, 2,...,10 pixels). Also, to reduce feature space dimensionality, texture descriptors of the same distance were averaged over all orientations, which is a common practice in the literature. Thereafter, the feature space was ranked using mutual information technique with minimal-redundancy-maximal-relevance (mRMR) criterion. Fisher linear discriminant analysis (FLDA) was applied to assess the discrimination power of texture features, by adding the first m-ranked features to the classification procedure iteratively until all of them were considered. The area under ROC curve (AUC) was used as figure of merit to measure the performance of the classifier. It was observed that averaging texture descriptors of a same distance impacts negatively the classification performance, since the best AUC of 0.81 was achieved with 32 gray levels and 109 features. On the other hand, regarding the single texture features (i.e., without averaging procedure), the quantization level does not impact the discrimination power, since AUC = 0.87 was obtained for the six quantization levels. Moreover, the number of features was reduced (between 17 and 24 features). The texture descriptors that contributed notably to distinguish breast lesions were contrast and correlation computed from GLCMs with orientation of 90° and distance more than five pixels.

Bone quality analysis using X-ray microtomography and microfluorescence.

Bone quality is an evaluation index often applied in order to interpret clinical observations made upon bone health, such as bone mineral density, micro and macro architecture, and mineral content. Conventional inspection techniques do not provide full information on trabecular bone quality. This study shows the high resolution potential and the non-destructive character of X-ray microtomography and microfluorescence upon the application of such techniques for evaluating bone quality. The mineral content assessment was performed by two-dimensional concentration mappings of calcium, zinc, and strontium. The results showed significant changes in bone morphology.

Discrete-event computer simulation methods in the optimisation of a physiotherapy clinic.

OBJECTIVE: To develop a computer model to analyse the performance of a standard physiotherapy clinic in the city of Rio de Janeiro, Brazil. DESIGN AND SETTING: The clinic receives an average of 80 patients/day and offers 10 treatment modalities. Details of patient procedures and treatment routines were obtained from direct interviews with clinic staff. Additional data (e.g. arrival time, treatment duration, length of stay) were obtained for 2000 patients from the clinic's computerised records from November 2005 to February 2006. METHODS AND MAIN OUTCOME MEASURES: A discrete-event model was used to simulate the clinic's operational routine. The initial model was built to reproduce the actual configuration of the clinic, and five simulation strategies were subsequently implemented, representing changes in the number of patients, human resources of the clinic and the scheduling of patient arrivals. RESULTS: Findings indicated that the actual clinic configuration could accept up to 89 patients/day, with an average length of stay of 119minutes and an average patient waiting time of 3minutes. When the scheduling of patient arrivals was increased to an interval of 6.5minutes, maximum attendance increased to 114 patients/day. For the actual clinic configuration, optimal staffing consisted of three physiotherapists and 12 students. According to the simulation, the same 89 patients could be attended when the infrastructure was decreased to five kinesiotherapy rooms, two cardiotherapy rooms and three global postural reeducation rooms. CONCLUSIONS: The model was able to evaluate the capacity of the actual clinic configuration, and additional simulation strategies indicated how the operation of the clinic depended on the main study variables.