A real time programmable digital filter for biomedical signal enhancement incorporating a high-level design interface

A simple but highly integrated digital signal processing system is described for real time filtering of biomedical signals. It includes the necessary processing and communications hardware, the processing code itself and a high-level software interface that enables the user to design and download arbitrary finite impulse response filters to the run-time system. The filter coefficients are calculated using the frequency sampling method. Since the filters are realized using a finite impulse response, no phase distortion is introduced into the processed signals. A unique feature of the design is the manner in which the software and hardware components have been organized as an intelligent system, obviating on the part of the user a detailed knowledge of filter design theory or any abilities in processor architecture and assembly code programming.     

Method of transmission filters to measure emission spectra in strongly scattering media

We describe a method based on a pair of transmission filters placed in the emission path of a microscope to resolve the emission wavelength of every point in an image. The method can be applied to any type of imaging device that provides the light in the wavelength transmission range of the filters. Unique characteristics of the filter approach are that the light does not need to be collimated and the wavelength response does not depend on the scattering of the sample or tissue. The pair of filters are used to produce the spectral phasor of the transmitted light, which is sufficient to perform spectral deconvolution over a broad wavelength range. The method is sensitive enough to distinguish free and protein-bound NADH and can be used in metabolic studies.     

Apheresis techniques and cellular immunomodulation.

Significant advances have been made in the capabilities to remove white blood cells (WBCs) from blood by both centrifugal and filtration techniques. New techniques have applications for both donor products (and their effects upon the recipients) and for selected disease therapeutics. The immunomodulatory effects of donor WBCs may be therapeutic, e.g., granulocytes harvested by apheresis may be used for the treatment of sepsis, or mononuclear cells collected by apheresis for peripheral blood progenitor (stem) cell transplantation or graft versus leukemia effect. In contrast, WBCs are removed from many transfusable components to decrease the immune effects in recipients. This has been accomplished primarily by the use of leukoreduction filters although newer adaptations of centrifugal equipment allow for the reduction of WBCs to target range of <1 x 10(6) WBCs/product. Therapeutic WBC removal by centrifuge has been used for treatment of the effects due to elevated levels of WBCs or platelets. More specific cellular immunotherapy has included lymphocytapheresis for the treatment of autoimmune diseases such as systemic lupus erythematosis (SLE). Various mononuclear cell fractions collected by apheresis have been used for lymphokine activated killer cells (LAK) and tumor infiltrating lymphocytes (TIL) cell therapy or autologous stem cell transplantation. The development of WBC adsorbent filters for therapeutic use has evolved as nonspecific filter materials have been demonstrated to show selective WBC removal, and filter columns permit therapeutic reductions in WBCs using online filtration therapy. Specific adsorption techniques, e.g., CD-34 selection, are in use in vitro and indicate directions for further developments in cellular immunotherapy.     

下腔静脉滤器置入预防肺栓塞

背景:下腔静脉滤器置入预防肺栓塞是有效的,也为手术取栓提供了安全保障。目的:探讨下腔静脉滤器临床应用的研究进展。方法:由第一作者检索1985/2010FMJS数据库及万方数据库有关下腔静脉滤器材料学的发展,置入的适应证、禁忌证,置入技术,并发症及置入后抗凝问题方面的文献。结果与结论:下腔静脉滤器材料学发展迅速,其置入技术显著提高,但对其临床应用指针还没有统一的认识。对于置入后抗凝问题认识也存在差异,而滤网位置偏移、游走、成角及腔静脉穿孔和对周围脏器的损伤报道随着下腔静脉滤器应用的增多而相应增多。下腔静脉滤器置入预防肺栓塞的临床疗效是值得肯定的,但应该高度重视置入后的并发症及其严重性,相信随着下腔静脉滤器材料学的进一步发展及生物相容性的提高,其临床应用前景会越来越广阔。     

From Research to Clinic and Beyond—NRC Experience in Commercialization/Technology Transfer

Medical imaging technologists operate some of the most advanced health care equipment on the market and understand the constant evolution of new hardware, new techniques, and new applications that various manufacturers introduce each year. Before appearing as a new product offering, there is usually a long history beginning with identifying a clinical need, coming up with an idea to solve the clinical problem, preliminary studies, applications for grant funding, scientific review, research ethics board reviews, years of research, intellectual property protection, journal publications, beta testing, regulatory approvals, small-scale trials, larger clinical trials, negotiations with manufacturers, and finally the push to develop a product.This article explores the path from idea to product, providing an appreciation for the amount of work behind a product that appears in the newest software/hardware release seen by a technologist.     

Modeling and optimization of galvanometric point-scanning temporal dynamics

Galvanometers are ubiquitous in point-scanning applications in optical imaging, display, ranging, manufacturing, and therapeutic technologies. However, galvanometer performance is constrained by finite response times related to mirror size and material properties. We present a model-driven approach for optimizing galvanometer response characteristics by tuning the parameters of the closed-loop galvanometer controller and demonstrate settling time reduction by over 50%. As an imaging proof-of-concept, we implement scan waveforms that take advantage of the optimized galvanometer frequency response to increase linear field-of-view, signal-to-noise ratio, contrast-to-noise ratio, and speed. The hardware methods presented may be directly implemented on galvanometer controllers without the need for specialized equipment and used in conjunction with customized scan waveforms to further optimize scanning performance.     

Bilateral linear SURE-based SAR interferogram filter

This article proposes a new filter for interferometric synthetic aperture radar (InSAR) phase denoising. Traditional phase filters generally face two major challenges: to preserve texture details while reducing noise and to perform well in less time. The local linear model-based guided filter and Stein’s unbiased risk estimate (SURE)-based filter, in contrast, have a high quality of edge-preserving performance and high efficiency owing to the feature of SURE formula and simplicity. Nevertheless, as these filters are designed for general digital images, they are not suitable for periodic and high-noise-level interferometric phase images. In this article, we modified the original filters by considering the coherence coefficient and features of the interferometric phase image, creating a new patch-based filter adapted to areas characterized by different coherences. Moreover, after obtaining the solution of a patch, considering the geometric closeness and the phasic similarity, we used a bilateral filter combining the pixels in the patch to obtain the estimate. Experimental results based on the simulated and real data confirmed the effectiveness of the proposed algorithm.     

Adaptive clutter filtering for ultrasound color flow imaging

In this article, we present an adaptive clutter rejection method for selecting different clutter filters in ultrasound color flow imaging. A single clutter filter is typically used to reject the clutter. Because the clutter characteristics vary in both space and time, the single clutter filter approach has difficulty in providing optimum clutter rejection in ultrasound images. To achieve more accurate velocity estimation, we have developed a method to select a clutter filter adaptively at each location in an image from a set of predefined filters. Selection criteria have been developed based on the underlying clutter characteristics and the properties of various filters (e.g., minimum-phase finite impulse response, projection-initialized infinite impulse response and polynomial regression). We have incorporated our adaptive clutter rejection method in an ultrasound system. We have found that our adaptive method can reduce the mean absolute error between the estimated and true flow velocities significantly compared with the conventional methods, in which a single clutter filter is used throughout the entire image. With in vivo abdominal data, we obtained an average gain of 5.0 dB in signal-to-clutter ratio (SCR), compared with the conventional method. These preliminary results indicate that the proposed adaptive method could improve the accuracy of flow velocity estimation in ultrasound color flow imaging through the improvement in SCR and the reduction in bias.     

Performance of bacteria filters.

Several kinds and brands of bacteria filters are commercially available for use in anesthesia and respiratory therapy applications. Clinical experience of high airflow resistance, ruptured media, failure to retain visible dust particles, and lack of consistent performance statements or warranties by manufacturers about their bacteria filters prompted a study of the performance of 13 different filters. The filters were challenged by mineral oil droplets, Serratia marcescens and Excherichia coli bacteriophages T4 and T7, tobacco smoke, nebulized india ink, dioctylphthalate smoke (DOP), and water. Results showed that viable bacterial passed through some filters, many filters were unable to retain visible ink or tobacco smoke particles, and resistance to airflow was increased two-fold or more in many filters when the filters were laden with 10 ml of water. Conflicting data resulted from two different types of DOP testing machines. There was a wide variation in performance among the different brands of filters; variable results also were seen within a given brand. Five brands of filters met the federal DOP standards for HEPA filters, but the wide variation in DOP testing results with two different kinds of DOP machines indicates a need for better standards. The DOP 0.3-micron bubble test is the most readily available nontoxic test to rate filtration efficiency; however, the DOP efficiency rating cannot be used to equate equivalent performance against infectious organisms.     

Laboratory study of the effectiveness of filters used by heroin injectors

Aims: (a) To compare in the laboratory the effectiveness of various filters at removing particles from heroin injections; (b) To measure the amount of heroin retained by the filters; and (c) To describe the relevance of these preliminary findings to future research.

Design: A laboratory‐based investigation. Injections were prepared with street heroin obtained from the police, copying the methods of injectors. Pieces of cigarette filter, hand‐rolling cigarette filter, cotton wool from buds and commercially produced syringe filters were tested. The Coulter Multisizer (IIe) was used to count and size particles; Capillary Zone Electrophoresis was used to measure the amount of heroin retained in the filters.

Findings: All methods of filtration reduced the amount of particles, with the commercially produced syringe filter producing the largest reduction. The syringe filter retained the most heroin after use; however, less drug material was evident on the spoon, suggesting further work is needed with a range of quantities. The cigarette, hand‐rolling and cotton bud filters all retained some drug with no significant difference detected between the different filters.

Conclusions: This preliminary study suggests all the filters tested may convey health benefits. Further work is needed with varying quantities of drug, acid and water and to establish safety in use. Then future studies can establish the health consequences for injecting drug users from the use of such filters.     

A Comparative Analysis of Signal Processing Methods for Motion-Based Rate Responsive Pacing

Pacemakers that augment heart rate (HR) by sensing body motion have been the most frequently prescribed rate responsive pacemakers. Many comparisons between motion-based rate responsive pacemaker models have been published. However, conclusions regarding specific signal processing methods used for rate response (e.g., filters and algorithms) can be affected by device-specific features. To objectively compare commonly used motion sensing filters and algorithms, acceleration and ECG signals were recorded from 16 normal subjects performing exercise and daily living activities. Acceleration signals were filtered (1–4 or 15-Hz band-pass), then processed using threshold crossing (TC) or integration (IN) algorithms creating four filter/algorithm combinations. Data were converted to an acceleration indicated rate and compared to intrinsic HR using root mean square difference (RMSd) and signed RMSd. Overall, the filters and algorithms performed similarly for most activities. The only differences between filters were for walking at an increasing grade (1–4 Hz superior to 15-Hz) and for rocking in a chair (15-Hz superior to 1–4 Hz). The only differences between algorithms were for bicycling (TC superior to IN), walking at an increasing grade (IN superior to TC), and holding a drill (IN superior to TC). Performance of the four filter/algorithm combinations was also similar over most activities. The 1–4/IN (filter [Hz]/algorithm) combination performed best for walking at a grade, while the 15/TC combination was best for bicycling. However, the 15/TC combination tended to be most sensitive to higher frequency artifact, such as automobile driving, downstairs walking, and hand drilling. Chair rocking artifact was highest for 1–4/IN. The RMSd for bicycling and upstairs walking were large for all combinations, reflecting the nonphysiological nature of the sensor. The 1–4/TC combination demonstrated the least intersubject variability, was the only filter/algorithm combination insensitive to changes in footwear, and gave similar RMSd over a large range of amplitude thresholds for most activities. In conclusion, based on overall error performance, the preferred filter/algorithm combination depended upon the type of activity.     

Preparation of white cell-depleted blood. Comparison of two bedside filter systems

Numerous techniques have been established for preparing white cell-poor blood, such as centrifugation, sedimentation, freezing, and filtration. All of these methods have disadvantages that restrict their practical use: they are time-consuming, they require the facilities of a blood bank, and the white cell-poor units cannot be stored. Therefore tests have been performed on two filter systems that make possible the depletion of white cells directly at the bedside. Both filters have a high white cell-removal rate. The number of residual white cells in 1 unit of packed red cells was calculated as 1.08 +/- 0.53 x 10(7) in one system and 1.54 +/- 0.71 x 10(7) in the other. The filters do not affect the filtered red cells. Pressure filtration is performed without significant loss of efficiency. One of the systems can filter 2 units via one filter; however, handling the filters is tedious, and both filters are characterized by a low red cell recovery. Despite these disadvantages, the tested filter systems provide an effective device for preparing white cell-poor blood at the bedside. They are a suitable alternative to the conventional methods.     

Studies on the characterisation of the cause of leucoreduction failures, with particular reference to extra gatal events.

The causes of leucodepletion failure are multifactoral and can be related to haematological variability in blood donors or donation, defective filters, poor specimen handling or ageing, and/or the presence of non-adhering leucocyte/platelets. Since refiltering removes all types of leucocytes, including the populations appearing as extra gated events, we have developed a practical method for refiltering the failed leucodepleted components on standard filters and back-flushing the second filter to assess the nature of the WBC sub-population. In practice, recovered leucocytes from red cell filters and whole blood mainly consist of neutrophils. Those from platelet and plasma filters were mainly lymphocyte with considerable differences depending on the type of leucodepletion process. Atypical leucocytes are often seen in some pre-/post-cellular leucofiltered components. These appear characteristically as small WBC with a lower affinity for filter matrix, or as cell fragment, pinched leucocyte or apoptotic cells. Different reagents in use show variable sensitivity in identifying these extra gatal events. Storage of leucodepleted samples also induces different types of abnormality in leucocyte dot plot. A useful practical approach for characterisation of the nature of leucocyte sub-populations causing failure in leucodepleted components is provided.     

Hygiene and room climate in the operating room

The ventilation system is not the most important source to cause surgical site infections via the air. More important is the skin of both staff and patients. The literature did not reveal any reduction of the risk of surgical site infections resulting from the employment of ultra‐clean air‐systems during surgical procedures, the one exception being high risk operations such as orthopaedic implant surgery. Both ultra‐clean air and antimicrobial prophylaxis can reduce the incidence of surgical site infections. If HEPA filters are used, they are only necessary directly in the operating rooms. Other rooms such as the washroom, the anaesthesia preparation room or corridors which are connected to the OR do not have to be treated with HEPA filters. If a laminar air‐flow system is installed, there are some factors which have to be considered. The number of operating lamps and the heads of the operating team affect the function of the air ceiling as they form thermic and air‐flow resistance and create turbulences. Also, forced air‐warming systems, which are used to maintain normal body temperatures for patients during surgery, disturb the ultra‐clean field through the air emitted from the blankets used. Moreover, any medical equipment which is cooled by integrated cooling blowers can influence an ultra‐clean air system. Existing ventilation systems are not able to create good room conditions for all persons inside the OR. Therefore new ways have to be found to create a room climate taking into account the level of activity.     

Digital radiograph (DR) guided bedside IVC filter placements in patients with intracranial pressure monitors

PurposeThe purpose of this study is to report a single center experience with portable digital radiographically (DR) guided bedside IVC filters placed in intensive care unit (ICU) patients with high ICP and elevated head of bed (HOB).Materials and methodsA retrospective chart review was conducted on all bedside IVC filters placed from January 1, 2010 to September 16, 2020. Patients with high ICP and elevated head of bed requirements were included. Charts were reviewed for filter type, common femoral vein (CFV) access, filter location, pre procedure imaging, pre and post filter ICPs, glascow coma scale, number of radiographs taken, and filter removal. ICPs were obtained 1 ​h prior to procedure and 2 ​h post procedure and analyzed with a paired T test.Filters were placed by reviewing prior CT scan for IVC size, caval variants, renal and iliac veins and vertebral body landmarks. Then, CFV access was obtained and a Bentson wire was advanced 30–40 ​cm. A radiograph was used to confirm adequate position of the of the wire. The filter sheath was advanced and serial radiographs were used to position the filter sheath at the final predetermined position below the renal veins and above the iliac bifurcation. The filter was deployed, and a radiograph was obtained to confirm filter positioning.ResultsA total of 9 DR guided bedside IVC filters were placed (4 Denali, 3 Option Elite, 2 Celect). Indications included prophylactic placement (n ​= ​8) and acute DVT (n ​= ​1). The average patient age was 35.8 years (range: 18–56 years) CT abdomen and pelvis was used to assess for the level of renal veins in all patients (n ​= ​9). No caval variants were encountered on pre-procedural planning. The average pre, intraprocedural, and post procedure intracranial pressure was 16 ​mmHg, 13 ​mmHg, and 16 ​mmHg, respectively. Confirmation of placement after final placement was available in 7 patients (4 DR, 2 CT and one fluoroscopic examination). Two non-procedural related deaths occurred.Technical success, defined as successful placement of IVC filter at the predetermined level, was achieved in 100% of patients (n ​= ​9). The right CFV was used in most patients (n ​= ​7). The left CFV was used for access in two patients due to right CFV thrombus (n ​= ​1) and existing right femoral venous central line (n ​= ​1). The average number of radiographs taken was 5.8 (range 4–9). In all cases, filters were placed below the level of the lowest renal vein (n ​= ​9). A comparison of pre, during and post intervention ICP pressures is shown in table, 2. No differences between pre and post filter ICP was noted (p ​= ​0.77). Three filters were later removed. One minor complication was reported, which was filter tilt (23%) in an Option filter.ConclusionBedside IVC filters can be safely placed in patients with head trauma and high ICP who are unable to lay supine using portable DR guidance with a high rate of technical success and minimal complications.     

Cascade filtration with reverse rinse of the secondary filter

With cascade filtration (CF) secondary filter plugging may render some procedures difficult, particularly with cryoglobulinemia or macroglobulinemia patients, when filters are subjected to the most consistent burden. To prevent plugging, in the initial management of seven patients with cryoglobulinemia or macroglobulinemia we employed polymethylmethacrylate secondary filters produced by Toray Industries Inc., Tokyo, with pores calculated at 0.1 micron (QS-12-70). In the subsequent sessions, when circulating macroproteins were reduced to more acceptable levels, secondary filters with pores of 0.06 micron were used (QS-12-50). The filtration efficiency of both filters was maintained throughout the procedures with reverse rinses carried out when the transmembrane pressure from the values of 80-130 mm Hg reached the values of 250 mm Hg. With this improved technique, 2.6-3.31 liters of plasma could be treated, producing adequate clinical benefits. From a laboratory point of view, the differential sieving for albumin and macroglobulins was 61% for the QS-12-50 filters and 56% for the QS-12-70 models.     

Review article: Do inferior vena cava filters prevent pulmonary embolism in critically ill trauma patients and does the benefit outweigh the risk of insertion? A narrative review article

Venous thromboembolic disease (VTE) increases the risk of mortality in trauma patients. To decrease the occurrence of VTE, low dose anticoagulants are commonly prescribed. This may be unacceptable in trauma patients who have a high risk of bleeding. Inferior vena cava (IVC) filters can be employed as an alternative strategy to decrease the risk of pulmonary embolism (PE). Insertion of an IVC filter is an invasive procedure that has a range of complications. The benefits of IVC filter insertion must be compared to its risk of complications in each individual patient. A search of the literature since 2005 was conducted on MEDLINE, Evidence-Based Medicine Reviews, Cochrane Central Register of Controlled Trials and Embase. The clinical question posed was does prophylactic IVC filter insertion decrease the risk of PE in trauma patients? The available evidence was low level and unable to definitively answer this question. The majority of articles infer that IVC filter insertion is safe and may decrease the risk of PE. However, there is a need for well-designed randomised controlled trials to be conducted in this area.     

A single-ensemble clutter rejection method based on the analytic geometry for ultrasound color flow imaging

In ultrasound color flow imaging (CFI), the single-ensemble eigen-based filters can reject clutter components using each slow-time ensemble individually. They have shown excellent spatial adaptability. This article proposes a novel clutter rejection method called the single-ensemble geometry filter (SGF), which is derived from an analytic geometry perspective. If the transmitted pulse number M equals two, the clutter component distribution on a two-dimensional (2-D) plane will be similar to a tilted ellipse. Therefore, the direction of the major axis of the ellipse can be used as the first principal component of the autocorrelation matrix estimated from multiple ensembles. Then the algorithm is generalized from 2-D to a higher dimensional space by using linear algebra representations of the ellipse. Comparisons have been made with the high-pass filter (HPF), the Hankel-singular value decomposition (SVD) filter and the recursive eigen-decomposition (RED) method using both simulated and human carotid data. Results show that compared with HPF and Hankel-SVD, the proposed filter causes less bias on the velocity estimation when the clutter velocity is close to that of the blood flow. On the other hand, the proposed filter does not need to update the autocorrelation matrix and can achieve better spatial adaptability than the RED.     

Comparison of physiological motion filters for in vivo cardiac ARFI

Acoustic radiation force impulse (ARFI) imaging is being utilized to investigate mechanical properties ofcardiac tissue. The underlying physiological motion, however, presents a major challenge. This paper aims to investigate the effectiveness of various physiological motion filters using in vivo canine data with a simulated ARFI push pulse. Ideally, the motion filter will exactly model the physiological motion and, when subtracted from the total displacement, leave only the simulated ARFI displacement profile. We investigated three temporal quadratic motion filters: (1)interpolation, (2) extrapolation and (3) a weighted technique. Additionally, the various motion filters were compared when using 1-D versus 2-D autocorrelation methods to estimate motion. It was found that 2D-autocorrelation always produced better physiological motion estimates regardless of the type of filter used. The extrapolation filter gives the most accurate estimate of the physiological motion at times immediately after the ARFI push (0.1 ms) while a close-time interpolation filter using displacement estimates at times before full tissue recovery gives the most accurate estimates at later times after the ARFI push (0.7 ms). While improvements to the motion filter during atrial systole and the onset of ventricular systole are needed, the weighted, close-time interpolation and extrapolation motion filters all offer promising results for estimating cardiac physiological motion more accurately, while allowing faster ARFI frame rates than previous motion filters. This study demonstrates the ability to eliminate physiological motion in a clinically-feasible manner, opening the door for more extensive clinical experimentation.