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Biomedical subjects

R A Levy

Publications and source records attributed to R A Levy.

At least 19 recordsLinked to original sources
PubMed2001

Mechanisms of pregnancy loss in antiphospholipid syndrome.

Antiphospholipid antibodies are associated with intrauterine fetal growth retardation and fetal distress leading to premature birth or fetal death. These complications are caused by uteroplacental insufficiency that is the result of multiple placental thromboses, infarcts, and spiral artery vasculopathy, which are almost certainly provoked by the hypercoagulable state induced by aPL antibodies. Available data indicate that the thrombogenic function of aPL antibodies involves their general effect on platelets, endothelial cells, anticoagulant mechanisms, and fibrinolytic pathways, as well as their local effect on trophoblasts and villi cells, leading to reduction of annexin V (placental anticoagulant protein-I) production and inhibition of its anticoagulant function.

Abortion, Spontaneous↗
PubMed2001

Hydroxychloroquine (HCQ) in lupus pregnancy: double-blind and placebo-controlled study.

We conducted a randomized, controlled study to assess the need for hydroxychloroquine (HCQ) during lupus pregnancy and to assess safety. Twenty consecutive pregnant patients with similar characteristics were enrolled. The HCQ group included eight patients with systemic lupus erythematosus (SLE) and two with discoid lupus erythematosus (DLE). The placebo (PL) group included nine patients with SLE and one with DLE. The HCQ group had no flare-ups. SLEPDAI scores were similar at study entry, and at conclusion the placebo group had significantly higher scores. One patient had improvement of skin lesions and another of arthritis, allowing a decrease of prednisone dose. There were no retinal effects. Three patients in the PL group flared up, two with skin rashes, one also with arthritis and uveitis, and one (previously in remission on HCQ) with hemolytic anemia, polyserositis and anti-dsDNA antibody. Toxemia was diagnosed in only three patients in the PL group (one fetal death). Comparing prednisone dosage change, we noted a decrease in the HCQ and an increase in the PL group. Delivery age and Apgar scores were higher in the HCQ group. Neonatal examination did not reveal congenital abnormalities, nor did a neuro-ophthalmological and auditory evaluation at 1.5-3 y of age. In spite of the small number of patients studied, we noted beneficial effects of HCQ during lupus pregnancy, as measured by SLEPDAI and decrease in prednisone dose with no detriment to patients' health.

Adult↗
PubMed2000

An image-based approach for designing and manufacturing craniofacial scaffolds.

Bone tissue engineering (BTE), which combines biomaterial scaffolds with biologically active factors, holds tremendous promise for reconstructing craniofacial defects. A significant challenge in craniofacial reconstructive BTE applications is the complex patient-specific geometry that must be reconstructed. In this paper, we present an image-based approach for designing and manufacturing patient-specific craniofacial biomaterial scaffolds directly from CT or MRI data. In this approach, voxel density distribution is used to define scaffold topology. The scaffold design topology is created using image processing techniques. This voxel density distribution is then converted to data that can be used to drive a Solid Free-Form Fabrication machine to either directly build the scaffold or build a mold for the scaffold. Several preliminary applications for craniofacial surgery, including a mandibular condyle scaffold, an orbital floor scaffold, and a general mandibular defect scaffold, are illustrated. Finally, we show applications to in vivo models.

Animals↗
PubMed1998

Catastrophic antiphospholipid syndrome. Clinical and laboratory features of 50 patients.

We analyzed the clinical and laboratory characteristics of 50 patients with catastrophic antiphospholipid syndrome (APS) (5 from our clinics and 45 from a MEDLINE computer-assisted review of the literature from 1992 through 1996). Thirty-three (66%) patients were female and 17 (34%) were male. Twenty-eight (56%) patients had primary APS, 15 (30%) had defined systemic lupus erythematosus (SLE), 6 (12%) had "lupus-like" syndrome, and 1 (2%) had rheumatoid arthritis. Mean age of patients in this series was 38 +/- 14 years (range, 11-74 yr). Three (6%) patients developed the clinical picture of catastrophic APS under the age of 15 years, and 11 (22%) were 50 years old or more. In 11 (22%) patients, precipitating factors contributed to the development of catastrophic APS (infections in 3, drugs in 3, minor surgical procedures in 3, anticoagulation withdrawal in 2, and hysterectomy in 1). The presentation of the acute multi-organ failure was usually complex, involving multiple organs simultaneously or in a very short period of time. The majority of patients manifested microangiopathy--that is, occlusive vascular disease affecting predominantly small vessels of organs, particularly kidney, lungs, brain, heart, and liver--with a minority of patients experiencing only large vessel occlusions. Thrombocytopenia was reported in 34 (68%) patients, hemolytic anemia in 13 (26%), disseminated intravascular coagulation in 14 (28%), and schistocytes in 7 (14%). The following antibodies were detected: lupus anticoagulant (94%), anticardiolipin antibodies (94%), anti-dsDNA (87% of patients with SLE), antinuclear antibodies (58%), anti-Ro/SS-A (8%), anti-RNP (8%), and anti-La/SS-B (2%). Anticoagulation was used in 70% of the patients, steroids in 70%, plasmapheresis in 40%, cyclophosphamide in 34%, intravenous gammaglobulins in 16%, and splenectomy in 4%. Most patients, however, received a combination of nonsurgical therapies. Death occurred in 25 of the 50 (50%) patients. In most, cardiac problems seemed to be the major cause of death. In several of these, respiratory failure was also present, usually due to acute respiratory distress syndrome and diffuse alveolar hemorrhage. Among the 20 patients who received the combination of anticoagulation, steroids, and plasmapheresis or intravenous gammaglobulins, recovery occurred in 14 (70%) patients. The use of ancrod and defibrotide appeared to be effective in the 2 respective patients in whom they were used.

Adolescent↗
PubMed1998

Placental pathology in antiphospholipid syndrome.

One of the major targets of antiphospholipid antibodies (aPL) is the placenta, the evolution of which during pregnancy has been well documented. Histopathological findings are related to gestational age, and several physiologic and pathologic alterations that occur during its development. The major findings in placentae from aPL positive patients are thrombosis, acute atherosis, a decreased number of syncytio-vascular membranes, increased number of syncytial knots and obliterative arteriopathy. These findings are not specific to the antiphospholipid syndrome (APS) and sometimes do not correlate with the fetal outcome. Histopathological study of placentae may elucidate mechanisms of action of aPL in fetal loss and other obstetric complications. In addition, it may assist in the investigation of the differential diagnosis between APS and pregnancy-induced hypertension. Immunohistochemical studies of local placental proteins contribute to this differential diagnosis.

Abortion, Habitual↗
PubMed1998

Three-dimensional contrast-enhanced MR angiography of the extracranial carotid arteries: two techniques.

Two methods of contrast-enhanced dynamic 3-D MR angiography of the head and neck are demonstrated. In the first, arterial and arteriovenous phases are temporally resolved by timing contrast injection such that maximum arteriovenous signal intensity difference is matched to acquisition of central k-space. A second, faster sequence allows for temporal resolution of arterial, early arteriovenous, late arteriovenous, and washout arteriovenous phases without a need for precise injection timing.

Carotid Arteries↗
PubMed1997

CT-generated porous hydroxyapatite orbital floor prosthesis as a prototype bioimplant.

Hydroxyapatite bioceramic was used for the manufacture of an orbital floor prosthesis from spiral CT data acquired transaxially at 1-mm beam collimation, pitch of 1, and 0.2-mm reconstruction intervals. CT data were converted to vector file format for subsequent prosthesis manufacture on a stereo-lithography machine. The orbital floor prosthesis was engrafted onto an acrylic model of the orbit as a qualitative indication of its overall accuracy. High anatomic accuracy was achieved, as determined by visual inspection. Cross-hatching of the vector file data allowed a porous internal architecture of the prosthesis. Refinements in chemical structure of the hydroxyapatite bioceramic are expected to enhance mechanical properties.

Child↗
PubMed1996

Clinical manifestations of the aPL syndrome.

The antiphospholipid syndrome may present itself to virtually all medical specialties. It can be as non-threatening as thrombophlebitis or mild thrombocytopenia or as severe as cerebral arterial infarct or the so called "catastrophic APS". In order to diagnose it properly, it is important to be aware of its clinical manifestations and laboratory peculiarities. The primary form of APS seems to be more common than the SLE related one. Because any artery or vein may be involved, the spectrum of clinical manifestations of APS is so wide that they include virtually all medical specialties.

Antiphospholipid Syndrome↗
PubMed1996

Arterial-phase three-dimensional contrast-enhanced MR angiography of the carotid arteries.

OBJECTIVE: The purpose of this study was to evaluate IV injection of a single dose of gadopentetate dimeglumine for three-dimensional (3D) arterial phase MR angiography of the carotid arteries. SUBJECTS AND METHODS: Nine adult patients were serially imaged after IV injection of a single-dose bolus of gadopentetate dimeglumine at 1.5 T with a coronal single-slice spoiled two-dimensional (2D) gradient-echo acquisition encompassing the common carotid arteries and internal jugular veins. Region-of-interest measurements for the nine patients generated a composite arteriovenous signal versus time profile. The time interval of maximum arteriovenous signal difference was subsequently matched to the center of K-space in a 3D spoiled gradient-echo coronal MR angiography sequence (field of view, 24 or 26 cm; matrix size, 256 x 128; slice thickness, 3 mm; number of slices, 12; one excitation; bandwidth, 16 kHz; and scan time, 29 sec). This protocol allowed us to selectively enhance the arterial phase for carotid angiography. The protocol was then tested in 20 adult patients, after which we graded the degree of coincidental venous enhancement and the presence of artifacts. RESULTS: On the 2D dynamic images, we identified a 10-sec window of selective arterial enhancement that began 20 sec after the start of the injection of the bolus of gadopentetate dimeglumine. With 3D MR angiography, we saw selective enhancement during the arterial phase of carotid MR angiography in nine of 20 patients. In seven of the remaining 11 patients, we saw the signal intensity of the arterial phase exceed a threshold greater than two standard deviations from venous signal. In the final four patients, we saw arterial signal equal to venous signal. We saw no ghosting artifact (from intravascular signal changing too rapidly during phase encoding) in any patient. CONCLUSION: By precisely timing the infusion of a single dose of gadopentetate dimeglumine, we were able to selectively enhance the arterial phase on 3D MR angiograms of the carotid arteries.

Adult↗
PubMed1996

Pleomorphic xanthoastrocytoma presenting with massive intracranial hemorrhage.

A 46-year-old woman presented with massive left temporal lobe intraparenchymal and diffuse subarachnoid hemorrhage on CT. Lack of enhancement excluded intermediate and high-grade primary tumor or metastasis as likely causes. At surgery, a fibrovascular left temporal lobe mass adherent to the dura proved to be a pleomorphic xanthoastrocytoma. The unusual hemorrhagic presentation of this typically benign entity is thought to be related to the meningeal involvement, which itself is characteristic of this neoplasm.

Astrocytoma↗
PubMed1996

Predicting neuroradiologic outcome in patients referred for audiovestibular dysfunction.

PURPOSE: To relate clinical presentation and results of audiovestibular testing to neuroradiologic outcome in patients with audiovestibular dysfunction. METHODS: We retrospectively reviewed the neuroimaging studies, results of audiometric and vestibular testing, and medical records of 118 patients referred for imaging over a 2-year period for evaluation of sensorineural hearing loss, dizziness, and/or vertigo, and to rule out acoustic neuroma. Patients' presentation and results of audiometric and vestibular testing were associated with either a positive or negative neuroimaging outcome. Discriminant analysis was performed to identify variables related significantly to imaging results. Two-way cross-tabulation of these significant variables was performed to assess their sensitivity and specificity in predicting imaging outcome. RESULTS: Fifteen (13%) of 118 patients had neuroimaging findings related to presenting symptoms. Discriminant analysis identified vertigo, dizziness, and dysequilibrium as corresponding to negative radiologic outcome. Nonvestibulocochlear cranial nerve involvement correlated significantly with positive neuroimaging results. Of all audiovestibular testing, only vestibular testing results correlated significantly with neuroimaging outcome. In conjunction with the results of vestibular testing the symptoms and signs identified above yielded a sensitivity of 57% and specificity of 93% in predicting neuroradiologic results. In the absence of vestibular testing, sensitivity and specificity were 29% and 98%, respectively. CONCLUSIONS: Clinical presentation and audiovestibular testing could not sensitively predict the outcome of neuroimaging in our cohort of patients referred for audiovestibular dysfunction.

Adult↗
PubMed1996

Unusual tumours of the skull and skull base: a pictorial essay.

Six unusual tumours of the skull and skull base are illustrated in this pictorial essay; for three of the tumours, both magnetic resonance imaging and computed tomography were performed preoperatively. These two imaging modalities can provide complementary information in the preoperative evaluation of unusual tumours of the skull and skull base.

Adenoma↗
PubMed1995

A histogram-based algorithm for semiautomated three-dimensional craniofacial modeling.

RATIONALE AND OBJECTIVES: I conducted a study designed to facilitate thresholding and reduce volume averaging in three-dimensional (3D) computed tomography (CT) craniofacial modeling. METHODS: Three-dimensional CT reconstructions of orbits from two cadavers and seven clinical cases were generated from paired axial and coronal data. A histogram-based algorithm that was based on preliminary phantom and craniofacial specimen trials was applied to orbital data to identify volume averaged regions of thin bone to be used in conjunction with standard bone thresholds. Region-of-interest measurement of the orbital floors on the original two-dimensional slice data assessed algorithm performance. RESULTS: In five of the nine cases (55%), configuration of the superimposed histograms predicted regions of volume averaging. In only one case did such a region localize to the orbital floor. In the remaining four cases, the air-mucosa interface deep to the orbital floor was identified by the histogram method. CONCLUSION: Operator-dependent editing remains superior to this histogram-based algorithm in reducing volume averaging in 3D craniofacial modeling.

Adult↗
PubMed1995

Three-dimensional craniocervical helical CT: is isotropic imaging possible?

PURPOSE: To assess whether isotropic resolution is attainable in three-dimensional craniocervical helical computed tomography (CT). MATERIALS AND METHODS: Two cadaveric cervical spine and two orbital phantoms were scanned in air and water by using 180 degrees-interpolated helical CT with three-dimensional reconstruction. Scan parameters yielded nominally isotropic voxels with reconstruction of 1-mm collimated and incremental sections at 0.2-mm intervals. CT scan angle was varied with the assumption that volume-averaging artifacts should be scan angle-independent with isotropic voxels. Twelve blinded observers analyzed three-dimensional images generated from multiple CT orientations to assess changes in volume-averaging artifacts that would indicate voxel anisotropy. RESULTS: Significant observable differences in three-dimensional image representation were present in test anatomic regions in one cervical spine phantom (two-tailed P < .006) and in both orbital phantoms (P < .008 and P < .006). No statistically significant differences were present for control anatomic regions. CONCLUSION: Isotropic scanning is not possible in three-dimensional craniocervical helical CT.

Adult↗
PubMed1994

Semiautomated three-dimensional craniofacial imaging and modeling.

RATIONALE AND OBJECTIVES: The author identified clinical parameters and developed thresholding strategies that facilitate semiautomated three-dimensional craniofacial imaging and modeling. METHODS: A polyvinylchloride phantom was imaged on a computed tomography (CT) scanner using multiple scan planes, surrounding media, and two-dimensional reconstruction filters. Three-dimensional reconstructions were performed by an experienced operator on a commercial workstation. A simple mathematical thresholding algorithm derived from these trials was applied to 17 embryologic craniofacial specimens and compared with operator-selected thresholds in the generation of three-dimensional CT images. RESULTS: Utilization of the parameter alpha provides an experimental framework in which operator-selected thresholds can be used to refine simple mathematical thresholding formulae. We demonstrated significant changes in three-dimensional image accuracy based on CT scan plane. CONCLUSIONS: Experimentation with a CT phantom enables semiautomated three-dimensional craniofacial imaging and modeling. Further investigation of two-dimensional CT craniofacial datasets is justified.

Computer Simulation↗