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Biomedical subjects

Y Itzchak

Publications and source records attributed to Y Itzchak.

At least 19 recordsLinked to original sources
PubMed2003

Complications of tracheal and thoracic surgery: the role of multisection helical CT and computerized reformations.

Helical computed tomography (CT) has an important role in the evaluation of a wide range of congenital and acquired thoracic abnormalities. The development of advanced computerized reformations enables the generation of bronchographic and bronchoscopic images of the tracheobronchial tree, as well as angiographic images of pulmonary arteries and veins. Additionally, it provides coronal and sagittal reconstruction imaging of parenchymal abnormalities. This information is obtained by a 20-30s procedure on a typical single channel system, which makes helical CT an optimal technique for the evaluation of patients undergoing major upper airways and thoracic interventions. The recent introduction of multisection CT scanners allows faster imaging of patients with thinner collimation, thus improving spatial resolution along the longitudinal (z) axis of the patient along with reduction of motion artefacts. This article demonstrates the use of dual and quad-section helical CT in the postoperative evaluation of patients undergoing laryngo-tracheal and thoracic interventions, including laryngoplasty, tracheal endoscopic laser ablation, lobectomy, pneumonectomy, lung transplantation, sleeve resection, pulmonary angioplasty, and pulmonary artery thromboendarterectomy. Emphasis is given to the additive value of using computerized reformations over axial images, especially for delineation of complex postoperative anatomical details in the tracheobronchial tree and pulmonary vasculature.

Adolescent↗
PubMed2002

Analysis of muscular fatigue and foot stability during high-heeled gait.

Plantar pressure measurements and surface electromyography (EMG) were used to determine the effects of muscular fatigue induced by high-heeled gait. The medio-lateral (M/L) stability of the foot was characterized by measuring the M/L deviations of the center of pressure (COP) and correlating these data with fatigue of lower-limb muscles seen on EMG. EMG measurements from habitual high-heeled shoe wearers demonstrated an imbalance of gastrocnemius lateralis versus gastrocnemius medialis activity in fatigue conditions, which correlated with abnormal lateral shifts in the foot-ground or shoe-ground COP of these women.

Adult↗
PubMed2001

In vivo molecular imaging of met tyrosine kinase growth factor receptor activity in normal organs and breast tumors.

Molecular imaging techniques allow visualization of specific gene products and their physiological processes in living tissues. In this study, we present a new approach for molecular imaging of endogenous tyrosine kinase receptor activity. Met and its ligand hepatocyte growth factor scatter factor (HGF/SF), which mediate mitogenicity, tumorigenicity, and angiogenesis, were used as a model. HGF/SF and Met play a significant role in the pathogenesis and biology of a wide variety of human epithelial cancers and, therefore, may serve as potential targets for cancer prognosis and therapy. We have shown previously that in vitro activation of Met by HGF/SF increases oxygen consumption. In this study, we demonstrate that Met activation in vivo by HGF/SF alters the hemodynamics of normal and malignant Met-expressing tissues. Tumor-bearing BALB/C mice were i.v. injected with HGF/SF and imaged using magnetic resonance imaging (MRI) and Doppler ultrasound. Organs and tumors expressing high levels of Met showed the most substantial alteration in blood oxygenation levels as measured by blood oxygenation level depended (BOLD)-MRI. No significant alteration was observed in tumors or organs that does not express Met. In the liver, which expresses high levels of Met, MRI signal alteration of about 60% was observed. In the kidneys, signal alteration was approximately 30%, and no change was observed in muscles. The extent of MRI signal alteration was also in correlation with HGF/SF doses. Injection of 7 and 170 ng/g body weight resulted in signal alteration of 5% and 30%, respectively, in tumors. Doppler ultrasound measurements demonstrated that these MRI changes are at least partially attributable to altered blood flow. These hemodynamic alterations, measured by MRI and Doppler ultrasound, were used in this study for the molecular imaging of Met activity in vivo. This novel molecular imaging technique may be used for in vivo diagnosis, prognosis, and therapy of Met-expressing tumors.

Adenocarcinoma↗
PubMed2001

Usefulness of spiral computed tomography (dual-slice mode) for the detection of coronary artery calcium in patients with chronic atypical chest pain, in typical angina pectoris, and in asymptomatic subjects with prominent atherosclerotic risk factors.

The prevalence and extent of coronary calcium were retrospectively assessed by spiral computed tomography in 541 patients (mean age 62 +/- 9 years), of whom 101 had typical angina pectoris, 307 had atypical chest pain, and 133 were asymptomatic subjects with prominent atherosclerotic risk factors. The highest prevalence of coronary calcium was in men with angina pectoris (89%), whereas it was not detected in 48% of men and 56% of women with atypical chest pain.

Aged↗
PubMed2001

In vivo biomechanical behavior of the human heel pad during the stance phase of gait.

A technique is introduced for simultaneous measurements of the heel pad tissue deformation and the heel-ground contact stresses developing during the stance phase of gait. Subjects walked upon a gait platform integrating the contact pressure display optical method for plantar pressure measurements and a digital radiographic fluoroscopy system for skeletal and soft tissue motion recording. Clear images of the posterior-plantar aspect of the calcaneus and enveloping soft tissues were obtained simultaneously with the pressure distribution under the heel region throughout the stance phase of gait. The heel pad was shown to undergo a rapid compression during initial contact and heel strike, reaching a strain of 0.39 +/- 0.05 in about 150 ms. The stress-strain relation of the heel pad was shown to be highly non-linear, with a compression modulus of 105 +/- 11 kPa initially and 306 +/- 16 kPa at 30% strain. The energy dissipation during heel strike was evaluated to be 17.8+/-0.8%. The present technique is useful for biomechanical as well as clinical evaluation of the stress-strain and energy absorption characteristics of the heel pad in vivo, during natural gait.

Adult↗
PubMed2001

Integration of plantar soft tissue stiffness measurements in routine MRI of the diabetic foot.

OBJECTIVE: A method of measuring mechanical properties of plantar soft tissues in vivo by integrating a photoelastic technique into an MRI system is presented. BACKGROUND: Plantar tissue stiffening in the diabetic foot is associated with development of ulcers at the highest-pressure sites. MRI is used as an effective means of demonstrating tissue damage caused by diabetic ulceration. DESIGN: The new measurement method uses the indentation of a sphere into the plantar tissue, which is simultaneously scanned by MRI. The indentation force is obtained using the photoelastic technique while tissue deflection is measured on the MRI scans, to yield a characteristic load-displacement curve. METHODS: Applicability of the proposed method in characterizing the plantar tissue stiffness and indentation patterns of two young normal subjects and two older diabetic patients was tested. RESULTS: Significantly higher effective shear and elastic moduli were measured for the diabetic plantar tissue compared with that of normal. For the diabetic patients, local stiffness in proximity of the 1st metatarsal head was substantially larger than in other sites, and this could be associated with initial tissue ulceration at this location. RELEVANCE: The present method seems applicable as a practical means of identifying regions in the diabetic plantar tissue that are vulnerable to ulceration, and can be easily integrated into routine MRI scans for assessing tissue damage in these patients.

Case-Control Studies↗
PubMed2001

CT findings in congenital anomalies of the spleen.

There is a wide range of congenital anomalies of the spleen. Some are common, such as splenic lobulation and accessory spleen. Other less common conditions, such as wandering spleen and polysplenia, have particular clinical significance. Radiologists need to be aware of the various congenital variants of the spleen in order to recognize clinically important anomalies and to avoid mistaking less significant ones for an abnormality. In this pictorial review, the embryology of congenital anomalies of the spleen as well as their appearance on CT are described, diagnostic pitfalls are identified and complications of the anomalies are discussed.

Choristoma↗
PubMed2001

Prevalence of the juxtaphrenic peak after upper lobectomy.

OBJECTIVE: The purpose of this study was to determine the prevalence of the juxtaphrenic peak after upper lobectomy in a large number of consecutive patients. MATERIALS AND METHODS: Available chest radiographs of 172 of 199 sequential patients who had undergone upper lobectomy in a university hospital were evaluated for the presence of a juxtaphrenic peak. The study included 98 cases with right upper lobectomy and 74 with left upper lobectomy. Radiographs were grouped in three postoperative periods: period I, within 7 days after lobectomy (n = 142); period II, between 8 and 30 days (n = 113); and period III, 31 days or more after lobectomy (n = 101). Four experienced radiologists in consensus determined the prevalence of the "juxtaphrenic peak sign," in relation to age, sex, side of lobectomy, positioning (erect or supine), presence of juxtadiaphragmatic abnormalities, and time interval since surgery. RESULTS: The prevalence of the juxtaphrenic peak sign gradually increased from 40.6% in period I to 71.9% in period III after right upper lobectomy (p < 0.01), and from 19% to 47.7%, respectively, after left upper lobectomy (p < 0.01). Its overall prevalence was significantly higher after right upper lobectomy (58.2%) than after left upper lobectomy (40.5%) (p = 0.02), and on erect chest films (51.4%) than on supine ones (28.9%). CONCLUSION: The prevalence of the juxtaphrenic peak sign increases gradually during the weeks following lobectomy. It is more frequent on erect films and after right upper lobectomy. The juxtaphrenic peak may serve as an additional useful radiologic sign suggesting upper lobectomy.

Adolescent↗
PubMed2000

Biomechanical analysis of the three-dimensional foot structure during gait: a basic tool for clinical applications.

A novel three-dimensional numerical model of the foot, incorporating, for the first time in the literature, realistic geometric and material properties of both skeletal and soft tissue components of the foot, was developed for biomechanical analysis of its structural behavior during gait. A system of experimental methods, integrating the optical Contact Pressure Display (CPD) method for plantar pressure measurements and a Digital Radiographic Fluoroscopy (DRF) instrument for acquisition of skeletal motion during gait, was also developed in this study and subsequently used to build the foot model and validate its predictions. Using a Finite Element solver, the stress distribution within the foot structure was obtained and regions of elevated stresses for six subphases of the stance (initial-contact, heel-strike, midstance, forefoot-contact, push-off, and toe-off) were located. For each of these subphases, the model was adapted according to the corresponding fluoroscopic data, skeletal dynamics, and active muscle force loading. Validation of the stress state was achieved by comparing model predictions of contact stress distribution with respective CPD measurements. The presently developed measurement and numerical analysis tools open new approaches for clinical applications, from simulation of the development mechanisms of common foot disorders to pre- and post-interventional evaluation of their treatment.

Biomechanical Phenomena↗
PubMed2000

Tracking coronary calcification by using dual-section spiral CT: a 3-year follow-up.

PURPOSE: To investigate the accuracy of dual-section spiral computed tomography (CT) in tracking the progression of coronary calcification, as measured during a 3-year follow-up. MATERIALS AND METHODS: Two hundred forty-six patients with hypertension (mean age, 66 years +/- 6 [SD]) were preselected in accordance with the International Nifedipine Study Intervention as a Goal for Hypertension Therapy protocol. Subjects had no clinical coronary arterial disease prior to the study and no cardiovascular events during follow-up. All participants underwent baseline CT (3.2-mm section thickness; reconstruction increment, 1.5 mm) and follow-up CT after 3 years. Calcification progression was defined as any increase in total calcification score (TCS) and analyzed in accordance with five baseline TCS categories: 1-9, 10-35, 36-100, 101-250, and greater than 250. RESULTS: At baseline CT, 152 patients had a TCS greater than 0, and 106 (70%) showed progression after 3 years, while 94 had a baseline TCS of 0; of these, 26 (28%) showed progression (P: <.01 between groups). The mean TCS was significantly higher in each baseline TCS category after 3 years. The percentage increase was negatively correlated with baseline TCS (P: <.01) and ranged from 466% in the lowest category to 38% in the highest. CONCLUSION: Dual-section spiral CT depicts significant change in TCS over time and is useful in tracking calcified coronary atherosclerosis.

Aged↗
PubMed2000

CT diagnosis of malpositioned chest tubes.

Insertion of a chest tube into the pleural space is standard management for various pleural disorders. Malpositioning of chest tubes in extrathoracic, intraparenchymal and mediastinal locations and in the fissures is common. Malpositioning results not only in inadequate drainage of air and fluid but may also result in increased morbidity and mortality. Diagnosis of a malpositioned tube is sometimes difficult to establish on a chest radiograph. CT, however, has proven to be extremely accurate in evaluating the position of a chest tube and has often provided additional valuable information with significant therapeutic impact.

Adult↗
PubMed2000

Spiral computerized tomography (dual helical mode) as a detector of aortic atheromas in patients with stroke and systemic emboli: additional benefit of the contrast-enhanced technique.

BACKGROUND: Protruding aortic atheromas are a potential source of stroke and systemic emboli. The single modality currently available for their detection has been transesophageal echocardiography. However, TEE does not allow full visualization of the upper part of the ascending aorta and proximal aortic arch. OBJECTIVES: To investigate whether double helical computerized tomography--both with and without contrast injection--may represent a useful technique for noninvasive detection of PAA in stroke patients. METHODS: Forty consecutive patients > or = 50 years of age who sustained a recent ischemic stroke and/or systemic emboli (within 15 days after the onset of the event) were enrolled in the study and underwent TEE and DHCT without contrast injection using thin slice acquisition (3.2 mm thickness and 1.5 mm reconstruction increment). In addition, the last eight consecutive patients, after obtaining an unenhanced scan, underwent a contrast-enhanced DHCT following peripheral intravenous injection of a small amount of contrast material (15 ml of diatrizoate). RESULTS: PAAs were demonstrated by TEE in 18 patients (45%); in 16 of them (89%) the atheromas were recognized by DHCT. Of the 22 patients without PAA on TEE, DHCT confirmed their absence in 18 (82%). DHCT yielded a sensitivity of 89%, a specificity of 82%, and an overall accuracy of 85%. The total number of protruding plaques detected by TEE was 43, of which 41 (95%) were correctly identified by DHCT. The mean thickness of the plaques was 5.6 +/- 2.4 mm on TEE, and 5.4 +/- 2.3 on DHCT (P = NS), with a good correlation between the modalities (r = 0.84). Contrast-enhanced DHCT scans demonstrated absolute equivalence to TEE in aortic areas defined as "clearly visualized by TEE." DHCT detected PAA between the distal ascending aorta and the proximal arch in seven patients; these atheromas were not included in the comparative analysis. In these "occult" areas, DHCT may be superior to TEE. CONCLUSIONS: DHCT without contrast injection using thin slice acquisition may become a useful modality for rapid noninvasive detection of PAA. Contrast-enhanced DHCT scans significantly improve imaging quality and may be superior to TEE in the upper ascending aorta and the proximal arch (areas not well visualized by TEE).

Aged↗
PubMed1999

Differential processing of objects under various viewing conditions in the human lateral occipital complex.

The invariant properties of human cortical neurons cannot be studied directly by fMRI due to its limited spatial resolution. Here, we circumvented this limitation by using fMR adaptation, namely, reduction of the fMR signal due to repeated presentation of identical images. Object-selective regions (lateral occipital complex [LOC]) showed a monotonic signal decrease as repetition frequency increased. The invariant properties of fMR adaptation were studied by presenting the same object in different viewing conditions. LOC exhibited stronger fMR adaptation to changes in size and position (more invariance) compared to illumination and viewpoint. The effect revealed two putative subdivisions within LOC: caudal-dorsal (LO), which exhibited substantial recovery from adaptation under all transformations, and posterior fusiform (PF/LOa), which displayed stronger adaptation. This study demonstrates the utility of fMR adaptation for revealing functional characteristics of neurons in fMRI studies.

Adaptation, Physiological↗
PubMed1999

Double-helical CT as a new tool for tracking of allograft atherosclerosis in heart transplant recipients.

RATIONALE AND OBJECTIVES: Tracking the progression of allograft atherosclerosis in heart transplant recipients is currently accomplished using invasive techniques. If its monitoring feasibility is demonstrated, spiral CT could be a non-invasive alternative for this objective. METHODS: Twenty-four consecutive heart transplant patients (21 men, 3 women, mean age 55 +/- 11 years) were scanned using double-helical CT. The first scan was performed 1.9 +/- 1.3 years after transplantation. After 2 years of follow-up, 4 patients died and the remaining 20 underwent a second scan. All scans were performed according to a previously reported double-helical CT protocol. RESULTS: The incidence of coronary calcification at the first scan was 4.2% (1/24); it increased to 40% (8/20) at the second scan (P < 0.001). Spiral CT identified new but very mild calcific deposits in seven patients with a mean total calcium score of 6.7 +/- 4.0. CONCLUSIONS: Double-helical CT is a viable tool to diagnose and track newly developed allograft atherosclerosis.

Adult↗
PubMed1999

Risk factors associated with postpartum ovarian vein thrombosis.

Thrombosis of the ovarian vein is a remarkable process occuring within a few days of labor in 1:500-1:2000 women. Its presentation is characterized by fever, abdominal pain and occasionally by a palpable abdominal mass that in earlier years sometimes lead to explorative laparotomy. With the advent of modern imaging techniques the diagnosis can be made relatively easily. The pathogenesis has been attributed to an infectious process expanding from the uterus to the right ovarian vein and stasis. A predisposition towards thrombosis has not been so far explored. In this study we retrospectively analysed the clinical features, diagnosis and treatment of 22 patients with objective documentation of post partum ovarian vein thrombosis (POVT) and assessed potential risk factors. In 11 of the 22 patients (50%) inherited prothrombotic risk factors were detected as follows: 4 were heterozygous for factor V G1691A, 2 had protein S deficiency, one had protein S deficiency and was heterozygous for factor V G1691A, and 4 were homozygous for MTHFR C677T. Eight of the 11 patients who bore a prothrombotic predisposition underwent cesarean section. Taken together, the data suggest that POVT may result from the combined effect of an infection, cesarean section and a prothrombotic tendency.

Adult↗
PubMed1998

Cue-invariant activation in object-related areas of the human occipital lobe.

The extent to which primary visual cues such as motion or luminance are segregated in different cortical areas is a subject of controversy. To address this issue, we examined cortical activation in the human occipital lobe using functional magnetic resonance imaging (fMRI) while subjects performed a fixed visual task, object recognition, using three different primary visual cues: motion, texture, or luminance contrast. In the first experiment, a region located on the lateral aspect of the occipital lobe (LO complex) was preferentially activated in all 11 subjects both by luminance and motion-defined object silhouettes compared to full-field moving and stationary noise (ratios, 2.00+/-0.19 and 1.86+/-0.65, respectively). In the second experiment, all subjects showed enhanced activation in the LO complex to objects defined both by luminance and texture contrast compared to full-field texture patterns (ratios, 1.43+/-0.08 and 1.32+/-0.08, respectively). An additional smaller dorsal focus that exhibited convergence of object-related cues appeared to correspond to area V3a or a region slightly anterior to it. These results show convergence of visual cues in LO and provide strong evidence for its role in object processing.

Adult↗
PubMed1998

Dual-helical CT for detecting aortic atheromas as a source of stroke: comparison with transesophageal echocardiography.

PURPOSE: To investigate whether unenhanced dual-helical computed tomography (CT) is useful in the rapid, noninvasive detection of protruding aortic atheromas. MATERIALS AND METHODS: Thirty-two consecutive patients at least 50 years of age who had recent ischemic stroke, systemic emboli, or both, underwent transesophageal echocardiography (TEE) and unenhanced dual-helical CT with thin sections (section thickness, 3.2 mm; reconstruction increment, 1.5 mm). RESULTS: TEE demonstrated protruding aortic atheromas 15 patients (47%); dual-helical CT depicted protruding aortic atheromas in 13 of those 15 patients (87%). Of the 17 patients without a protruding aortic atheroma at TEE, dual-helical CT helped confirm the absence in 14 (82%). Dual-helical CT yielded a sensitivity of 87%, a specificity of 82%, and an overall accuracy of 84%. Thirty-six protruding plaques were detected with TEE, of which 34 (94%) were correctly identified with dual-helical CT. Of those 34 plaques, 27 (79%) contained variable amounts of calcium and seven (21%) showed hypoattenuation suggestive of soft plaques and thrombi. In six patients, dual-helical CT depicted a protruding aortic atheroma between the distal ascending aorta and the proximal arch; these plaques were not included in the comparative statistics and were analyzed separately. CONCLUSION: Unenhanced dual-helical CT with thin sections appears to be useful for the rapid, noninvasive detection of a protruding aortic atheroma, especially in areas not clearly visualized with TEE.

Aorta↗