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PubMedDate not supplied

Management of metastatic spinal cord compression.

Metastatic spinal cord compression, diagnosed in 3-7% of cancer patients, is one of the most dreaded complications of metastatic cancer. It is an oncologic emergency, which must be diagnosed early and treated promptly to achieve the best results and avoid progressive pain, paralysis, sensory loss and sphincter incontinence. Patients who are ambulatory at the time of the diagnosis have a higher probability of obtaining good response to treatment and a longer survival. In clinical practice, back pain accompanies metastatic spinal cord compression in most cases, even in patients with no neurologic deficits. Magnetic resonance imaging is the best tool for diagnosing metastatic spinal cord compression and is able to identify spinal cord compression in 32-35% patients with back pain, bone metastases and normal neurologic examination. Moreover, magnetic resonance imaging gives the extension of the lesion, can diagnose other unsuspected clinical metastatic spinal cord compression sites, and is useful for the radiation oncologist in defining the target volume. Radiotherapy is the treatment of choice in most cases, whereas surgery is advised only in selected patients (ie, if stabilization is necessary, if radiotherapy has already been given in the same area, when vertebral body collapse causes bone impingement on the cord or nerve roots, when there are diagnostic doubts, or when computed tomography-guided percutaneous vertebral biopsy cannot be performed). Laminectomy should be abandoned in favor of more aggressive surgery (ie, posterior, anterior, and/or lateral approach, tumor mass resection, and stabilization of the spine). Generally, radiotherapy must be administered 7-10 days after surgery. The optimal radiation schedule has not been defined. However, as recently suggested by some clinical trials, even the hypofractionated radiotherapy regimens are effective and can be used without increasing radiation-induced myelopathy. Moderate doses of dexamethasone should be used in the early phases of therapy. After radiotherapy, spinal recurrence is generally found in sites different from the first compression area. A close post-treatment follow-up is suggested using clinical parameters (pain, motor and sphincter function), and magnetic resonance imaging should be performed only when a second metastatic spinal cord compression and/or myelopathy are clinically suspected.

Algorithms↗

PubMed1998

ECG compression: evaluation of FFT, DCT, and WT performance.

This work investigates a set of ECG data compression schemes to compare their performances in compressing and preparing ECG signals for automatic cardiac arrhythmia classification. These schemes are based on transform methods such as fast Fourier transform (FFT), discrete cosine transform (DCT), wavelet transform (WT), and their combinations. Each specific transform is applied to a pre-selected data segment from the MIT-BIH database and then compression is performed in the new domain. These transformation methods are known as an important class of ECG compression techniques. The WT has been shown as the most efficient method for further improvement. A compression ratio of 7.98 to 1 has been achieved with a percent of root mean square difference (PRD) of 0.25%, indicating that the wavelet compression technique offers the best performance over the other evaluated methods.

Algorithms↗

PubMed1999

Controlling the pain of venous leg ulceration.

Compression therapy can often exacerbate the pain of venous leg ulceration. A pain management programme using a team approach to care can promote compliance with compression therapy. Nurses need to be sensitive and responsive to an individual's pain.

Aged↗

PubMed1988

Heteronuclear NMR studies of cobalamins. 31P NMR observations of cobalamins bound to a haptocorrin from chicken serum.

A vitamin B12-binding protein (haptocorrin) from chicken serum has been purified to homogeneity by photodissociative affinity chromatography and characterized by gel electrophoresis and UV-visible spectrophotometry of its aquocobalamin, hydroxocobalamin, and cyanocobalamin complexes. The haptocorrin is a glycoprotein with a molecular mass of about 70 kDa and a protein moiety of about 40 kDa. 31P NMR resonances of the haptocorrin-cobalamin complexes are relatively broad singlets (with or without proton decoupling) shifted downfield by 0.7-1.0 ppm from the position of the free cobalamin resonances. From the line width data, the relaxation of the phosphorus nucleus is found to be dominated by chemical shift anisotropy with a very minor (13%) component from dipolar interaction with the two nearest neighbor protons. The rotational correlation time of the haptocorrin at 25 degrees C is estimated to be 85 ns and the activation energy for rotational correlation 3.9 +/- 0.3 kcal mol-1. The downfield shift of the 31P resonances of cobalamins upon binding to the haptocorrin cannot be due to hydrogen bonding phosphodiester moiety or displacement of the axial base by a group on the protein. Calculations also show that the downfield shift is very unlikely to be due to dipolar deshielding of the phosphorus nucleus by the ring current of an aromatic residue of the protein. It is concluded that the downfield shift of the 31P resonance must be due to sterically induced changes in phosphodiester conformation which may, or may not, involve steric compression of the axial Co-N bond.

Algorithms↗

PubMed1997

Initial rate of healing predicts complete healing of venous ulcers.

BACKGROUND: Venous ulcers represent a clinical problem with considerable morbidity, especially in the elderly population. Standard treatment is the use of leg compression bandages to improve the underlying venous hypertension, but not every ulcer heals in a timely fashion with this treatment modality. Methods are needed to predict the outcome of standard treatment as soon as possible to institute alternative therapy. OBJECTIVE: To prospectively study the rate of healing in a group of elderly patients with venous ulcers, based on a previously described equation that takes into account the size and perimeter of the ulcer. METHODS: We studied by computerized planimetry 15 elderly patients with venous ulcers treated with leg compression bandages for up to 24 weeks or until complete healing. We determined weekly healing rate by comparing ulcer size at each visit to initial baseline size (baseline-adjusted healing rate). Also, we used a novel way to calculate the healing rate at a given week by taking the mean of all previous healing rates between each visit (mean-adjusted healing rate). RESULTS: When using the baseline-adjusted healing rate, we noted what we describe as a healing rate instability from week to week, which decreases the ability to predict complete healing. However, the mean-adjusted healing rate allowed us to predict complete healing as early as 3 weeks from starting therapy (P<.001). CONCLUSION: In this prospective study of elderly patients with venous ulcers, we describe a novel and more powerful method for predicting complete healing of venous ulcers with compression therapy alone.

Administration, Cutaneous↗

PubMed1994

Evaluation of a combined two- and three-dimensional compression method using human visual characteristics to yield high-quality 10:1 compression of cranial computed tomography scans.

RATIONALE AND OBJECTIVES: The compression of cranial computed tomography scans was improved by using independent intra- and interframe compression techniques. METHODS: For intraframe compression, an image was decomposed into four subimages, one subimage was chosen as a reference subimage, and three of the subimages were predicted from the reference subimage. The prediction error was encoded with a classified vector quantizer (CVQ) based on human visual perception characteristics. Interframe redundancy is exploited by a displacement estimated interslice (DEI) algorithm that encodes the differences between reference subimages from adjacent slices. This combined DEI/CVQ method was subjectively evaluated by 13 radiologists under a blinded protocol, and was compared to the CVQ method alone, the DEI method alone, the original images, and to a standard intraframe discrete cosine transform (DCT) compression method. RESULTS: Only the combined DEI/CVQ method at 10:1 compression was not scored significantly different from the original images. At 15:1 compression, the DEI/CVQ method was scored significantly better than the 10:1 DCT and any other 15:1 compression methods. CONCLUSIONS: Compressed image quality is enhanced by exploiting inter- and intraframe redundancy, and by modeling some characteristics of human visual perception. The DEI/CVQ method is well-suited for progressive transmission, and thus, holds potential in teleradiology as well as picture archiving and communications systems.

Analysis of Variance↗

PubMed1995

Thyroid diagnosis by thermogram sequence analysis.

A computerised thermal imaging system for thyroid diagnosis was developed by the authors and it was discovered that the rate of changes of temperature, rather than the absolute values, associated with a sequence of thermograms could help the medical doctors to identify clinical disorders. In order to further enhance the diagnostic capabilities and speed, a new method for medical thermogram analysis has been developed that compresses a sequence of thermograms into one thermogram while retaining the important information such as the geometrical patterns of the objects and the rate of temperature changes of each pixel within the images. As motion artifacts are unavoidable when a patient undergoes minutes of thermogram recording, direct comparison between images is deemed impossible. A high speed image matching algorithm has been developed to provide an absolute geometrical foundation for pixel-to-pixel comparison. The rate of change of temperature of a particular pixel along the sequence is represented by one single parameter after a process of temperature integration which can then be converted into a corresponding gray level for display. The resultant compressed thermogram can give a clear distinction between problem areas and normal ones. Although our emphasis is on thyroid diagnosis, it is anticipated that this new technique can be applicable to other areas of a human body.

Algorithms↗

PubMed2005

Quantitative shear wave magnetic resonance elastography: comparison to a dynamic shear material test.

Magnetic resonance elastography (MRE), a phase contrast MRI technique, images the propagation of applied mechanical waves in tissue, allowing shear stiffness to be quantified in vivo. This MRE technique has been validated with static mechanical compression tests. Dynamic mechanical analysis (DMA) may be a more appropriate comparison to MRE because it directly measures the shear modulus dynamically, while compression tests convert the measured elastic modulus to shear modulus with an assumed Poisson ratio. This study compared the shear stiffness estimated with various MRE inversion algorithms (i.e., manual calculation, local frequency estimate, phase gradient, direct inversion, and matched filter) to the dynamic mechanical test. The shear stiffness of five agarose gels with concentrations ranging from 1.5 to 3.5% were measured using MRE and DMA. The phase gradient inversion algorithm overestimated the shear modulus at higher concentrations (i.e., 3-3.5% agar), while the results from the other techniques correlated well with the dynamic mechanical test.

Agar↗

PubMed2003

Velocity estimation in ultrasound images: a block matching approach.

In this paper, we focus on velocity estimation in ultrasound images sequences. Ultrasound images present many difficulties in image processing because of the typically high level of noise found in them. Recently, Cohen and Dinstein have derived a new similarity measure, according to a simplified image formation model of ultrasound images, optimal in the maximum likelihood sense. This similarity measure is better for ultrasound images than others such as the sum-of-square differences or normalised cross-correlation because it takes into account the fact that the noise in an ultrasound image is multiplicative Rayleigh noise, and that displayed ultrasound images are log-compressed. In this work we investigate the use of this similarity measure in a block matching method. The underlying framework of the method is Singh's algorithm. New improvements are made both on the similarity measure and the Singh algorithm to provide better velocity estimates. A global optimisation scheme for algorithm parameter estimation is also proposed. We show that this optimisation makes an improvement of approximately 35% in comparison to the result obtained with the worst parameter set. Results on clinically acquired cardiac and breast ultrasound sequences, demonstrate the robustness of the method.

Algorithms↗

PubMed1995

A dot-matrix program with dynamic threshold control suited for genomic DNA and protein sequence analysis.

Graphical dot-matrix plots can provide the most complete and detailed comparison of two sequences. Presented here is DOTTER2, a dot-plot program for X-windows which can compare DNA or protein sequences, and also DNA versus protein. The main novel feature of DOTTER is that the user can vary the stringency cutoffs interactively, so that the dot-matrix only needs to be calculated once. This is possible thanks to a 'Greyramp tool' that was developed to change the displayed stringency of the matrix by dynamically changing the greyscale rendering of the dots. The Greyramp tool allows the user to interactively change the lower and upper score limit for the greyscale rendering. This allows exploration of the separation between signal and noise, and fine-grained visualisation of different score levels in the dot-matrix. Other useful features are dot-matrix compression, mouse-controlled zooming, sequence alignment display and saving/loading of dot-matrices. Since the matrix only has to be calculated once and since the algorithm is fast and linear in space, DOTTER is practical to use even for sequences as long as cosmids. DOTTER was integrated in the gene-modelling module of the genomic database system ACEDB3. This was done via the homology viewer BLIXEM in a way that also allows segments from the BLAST suite of searching programs to be superimposed on top of the full dot-matrix. This feature can also be used for very quick finding of the strongest matches. As examples, we analyse a Caenorhabditis elegans cosmid with several tandem repeat families, and illustrate how DOTTER can improve gene modelling.

Amino Acid Sequence↗

PubMed2002

MR imaging in cervical spine trauma.

Continual improvements in MR imaging, technology and MR imaging-compatible monitoring and fixation devices have allowed the incorporation of this relatively new imaging modality into standard algorithms for cervical spine trauma assessment. The ability of MR imaging to define the type of spinal cord injury, the cause and severity of spinal cord compression, and the stability of the spinal column is unmatched. The heavy reliance of the spinal surgeon on MR imaging for decisions regarding the type of therapy, the timing, the approach of surgical intervention, and for predicting patient outcome attests to the usefulness of this modality.

Athletic Injuries↗

PubMed2000

Hydronephrosis and renal deterioration in the elderly due to abnormalities of the lower urinary tract and ureterovesical junction.

The geriatric population presents a unique challenge to the health care provider. The incidence of common lower urinary tract disorders, such as benign prostatic hypertrophy (BPH), prostate cancer and incontinence increase dramatically with aging. In their more severe forms, these disorders may predispose to hydronephrosis and ultimately to renal deterioration. This review of lower urinary tract and ureterovesical junction (UVJ) physiology and pathophysiology, will focus on: (1) anatomic UVJ obstruction from prostate cancer, or severe bladder hypertrophy, (2) functional obstruction from compression or stretching of the UVJ during bladder distention from urinary retention, and (3) bladder decompensation in the female. We will present a diagnostic and treatment algorithm and discuss future trends in the geriatric population. Clearly, the geriatric health care provider always must consider the lower urinary tract when confronted with acute renal deterioration, because prompt diagnosis and treatment of significant, lower-urinary-tract disease can maximize recovery of renal function.

Age Factors↗

PubMed2002

Automatic image matching for breast cancer diagnostics by a 3D deformation model of the mamma.

X-ray mammograms and MR volumes provide complementary information for early breast cancer diagnosis. The breast is deformed during mammography, therefore the images can not be compared directly. A registration algorithm is investigated to fuse the images automatically. A finite element simulation was applied to a MR image of an underformed breast and compared to a compressed breast using different tissue models and boundary conditions. Based on the results a set of patient data was registered. To archive the requested accuracy distinguishing between the different tissue types of the breast was not necessary. A linear elastic model was sufficient. It was possible to simulate the deformation with an average deviation of approximately of the size of a voxel in the MRI data and retrieve the position of a lesion with an error of 3.8 mm in the patient data.

Breast↗

PubMed2002

A fundus camera dedicated to the screening of diabetic retinopathy in the primary-care physician's office.

PURPOSE: To increase the number of diabetic patients being screened for retinopathy, an instrument, the DigiScope, was specifically designed to operate in primary-care physicians' offices. The DigiScope is described and its automated functions are evaluated. METHODS: The DigiScope consists of a semiautomated optical head to acquire fundus images, evaluate visual acuity, and transmit the data to a remote reading center through telephone lines. Normal volunteers and 17 consecutive diabetic patients visiting their primary-care physician were recruited, and nonophthalmic staff performed the acquisition session. RESULTS: The pupil center and working distance were set automatically. Centering was achieved within 750 microm in less than 500 ms. The fundus was successfully focused by an automated algorithm, and an imaging session covering 71 degrees of the posterior pole of both eyes lasted 5.6 +/- 2.4 minutes. It was found that a file-compression ratio of 12 did not degrade the clinical information and allowed data transfer in less than 6 minutes. A pilot study in normal eyes showed that the DigiScope images yielded the same amount of details as conventional color fundus photographs obtained by an expert photographer. CONCLUSIONS: The DigiScope fulfills the instrumental requirements for a practical and cost-effective tool to acquire data needed to identify diabetic patients who must be referred to an eye-care specialist. Widespread screening with the DigiScope may help reduce the risk of vision loss in an estimated 4 million individuals in the United States alone, who currently do not undergo an annual eye examination.

Diabetic Retinopathy↗

PubMed2006

Reversible gastroparesis: functional documentation of celiac axis compression syndrome and postoperative improvement.

Celiac axis compression syndrome has generated much controversy since its original description in 1963. The main symptoms are postprandial epigastric abdominal pain, regurgitation of undigested food, and weight loss, all of which are caused by gastric ischemia from impingement of the celiac axis by the median arcuate ligament of the diaphragm. These symptoms are seen in other common disorders such as chronic mesenteric ischemia and gastroparesis. This makes the diagnosis of celiac axis compression syndrome a true challenge for the clinician. We present data on three patients successfully treated. The pre- and postoperative studies clearly demonstrate a resolution of the condition. The duplex ultrasound images clearly show variable compression on the celiac axis. The angiogram presented shows a classic image of the disease. A review of the data has enabled us to develop an algorithm for the diagnosis of this disease.

Adult↗

PubMed2004

[Three-dimensional computed tomography in acquired pediatric airway diseases].

To investigate the role of three-dimensional computed tomography (CT) in pediatric tracheobronchial diseases. Eleven male, six female patients aged from two weeks to 12 years (mean age, 3.3 years) were referred to spiral CT with a preliminary diagnosis of foreign body aspiration, extrinsic airway compression, acquired tracheoesophageal fistula, post-intubation stenosis, and bronchial erosion by a cavitary lung lesion. Tracheobronchial tree was scanned with 3 mm collimation, 1.5/1 pitch, 1.5 mm reconstruction interval, and standard reconstruction algorithm. Surface-rendered three-dimensional images and virtual bronchoscopic images were created from the axial raw data. Three-dimensional and virtual bronchoscopy findings were compared with findings of bronchoscopy. Virtual bronchoscopy revealed the level of obstruction in five patients with foreign body aspiration, but failed to disclose the nature of the aspirated foreign body and distinguish between a foreign body and mucoid obstruction. Virtual bronchoscopy correctly ruled out foreign body aspiration in four patients. Axial CT images also showed extraluminal findings including atelectasis, air trapping, peribronchial thickening, and infiltrations. In a patient with tracheitis virtual bronchoscopy failed to identify necrotic plaques observed in bronchoscopy. In patients with extrinsic compression, three-dimensional images showed the site and degrees of stenosis, whereas axial images revealed the cause of compression. In one patient, an anomalous tracheal bronchus was demonstrated on three-dimensional and virtual bronchoscopy images. Three-dimensional CT can localize tracheobronchial obstructions accurately. Virtual images may eliminate the need for invasive bronchoscopy in patients with questionable foreign body aspiration. Inability to evaluate the mucosal changes remains an important disadvantage of this technique.

Bronchial Diseases↗

PubMed2005

An adaptive multirate algorithm for acquisition of fluorescence microscopy data sets.

We propose an algorithm for adaptive efficient acquisition of fluorescence microscopy data sets using a multirate (MR) approach. We simulate acquisition as part of a larger system for protein classification based on their subcellular location patterns and, thus, strive to maintain the achieved level of classification accuracy as much as possible. This problem is similar to image compression but unique due to additional restrictions, namely causality; we have access only to the information scanned up to that point. While we do want to acquire fewer samples with as low distortion as possible to achieve compression, our goal is to do so while affecting the overall classification accuracy as little as possible. We achieve this by using an adaptive MR scanning scheme which samples the regions of the image area that hold the most pertinent information. Our results show that we can achieve significant compression which we can then use to aquire faster or to increase space resolution of our data set, all while minimally affecting the classification accuracy of the entire system.

Algorithms↗

PubMed2003

Prediction of osteoporotic spinal deformity.

STUDY DESIGN: A biomechanical model was developed from full-spine lateral radiographs to predict osteoporotic spinal deformity in elderly subjects. OBJECTIVE: To investigate the biomechanics of age-related spinal deformity and concomitant height loss associated with vertebral osteoporosis. SUMMARY OF BACKGROUND DATA: Vertebral bone loss and disc degeneration associated with aging causes bone and disc structures to weaken and deform as a result of gravity and postural stresses. METHODS: An anatomically accurate sagittal-plane, upright-posture biomechanical model of the anterior spinal column (C2-S1) was created by digitizing lateral full-spine radiographs of 20 human subjects with a mean height of 176.8 cm and a mean body weight of 76.6 kg. Body weight loads were applied to the model, after which intervertebral disc and vertebral body forces and deformation were computed and the new spine geometry was calculated. The strength and stiffness of the vertebral bodies were reduced according to an osteopenic aging model and modulus reduction algorithm, respectively. RESULTS: The most osteopenic model (L3 F(ult) = 750 N) produced gross deformities of the spine, including anterior wedge-like fracture deformities at T7 and T8. In this model, increases in thoracic kyphosis and decreases in vertebral body height resulted in a 25.2% decrease in spinal height (C2-S1), an 8.6% decrease in total body height, and a 15.1-cm anterior translation of the C2 spine segment centroid. The resulting deformity qualitatively resembled deformities observed in elderly individuals with osteoporotic compression fractures. CONCLUSIONS: These predictions suggest that postural forces are responsible for initiation of osteoporotic spinal deformity in elderly subjects. Vertebral deformities are exacerbated by anterior translation of the upper spinal column, which increases compressive loads in the thoracolumbar region of the spine.

Age Factors↗