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Biomedical subjects

G Horev

Publications and source records attributed to G Horev.

71 records · Page 4Linked to original sources

AIDS awareness in the conduct of radiologic procedures: guidelines to safe practice.

The epidemic of the acquired immunodeficiency syndrome (AIDS) has affected all geographic regions of the United States. Indeed, it is likely that a majority of U.S. hospitals have cared for patients who are infected with the human immunodeficiency virus (HIV), the virus that causes AIDS. More than 46,000 individuals with HIV infection have fulfilled the strict diagnostic criteria for AIDS (1). All of these patients with AIDS have been seriously ill and have been hospitalized, often multiple times and for prolonged periods. Another, larger group patients with HIV infection has had another form of the disease, the so-called AIDS-related complex. Many of these patients have also spent time in hospitals. An even larger group of individuals has been infected with HIV but has remained asymptomatic to date. Some of these persons have been admitted to hospitals or have received outpatient diagnostic procedures for intercurrent medical or dental complaints that were unrelated to their asymptomatic HIV infection. At the time of their medical evaluation, some of these asymptomatic individuals were known to have a positive HIV antibody test. It is likely, however, that the serologic status of the majority of asymptomatically infected patients was unknown. Thus, by now a very large number of health-care personnel in the United States, including diagnostic radiology staff, have assisted in the care of HIV-infected patients.

Acquired Immunodeficiency Syndrome↗

Anesthesia-induced pulmonary macroatelectasis: a cause of false-positive computerized tomography.

In three pediatric patients having CT of the chest done under general anesthesia, we encountered multiple areas of macroatelectasis in the lung. All patients had malignant disease, and the chest findings could have been interpreted as metastatic spread to the lung. To prevent this critical false-positive diagnosis, we believe general anesthesia for CT of the chest should be given with controlled rather than spontaneous ventilation.

Adolescent↗

Current perspectives on medical imaging.

Advances in biomedical technology have expanded the potential of medical imaging. Selected aspects of developments in sonography, nuclear medicine, nuclear magnetic resonance and digital imaging are addressed, stressing the wide scope permitted by these newer modalities.

Angiography↗

Work in progress: ultrasonic texture of normal rat liver tissue using a standardized in vivo measurement.

A prototype computer-augmented diagnostic ultrasound system was used in an investigation of the range of echo amplitudes obtained from measurements of normal exteriorized rat livers. A secondary goal was to develop a method for minimizing variations in measurement techniques and instrument stability. The average echo amplitude was obtained from a user-selected homogeneous region of the liver on a B-mode scan image. A similar B-mode scan of a commercially available liver tissue equivalent phantom was also obtained immediately after each rat liver measurement and was used as a calibration scan. A normalization factor developed from the calibration scan was used to correct all in vivo measurements for system variation. The average echo amplitude from the livers of a group of normal rats, when corrected by the calibration scan, exhibited a narrow range of values with a coefficient of variation of only 5%. The development of a technique that yields a narrow range of values for normal tissues should encourage further investigation of tissue characterization methods.

Animals↗

Aphakic ultrasonographic refraction in adults. Comparison with retinoscopy and subjective refraction.

A simple method of aphakic refraction using ultrasonographic axial length measurement and keratometry was tried on 97 eyes of adult aphakic patients. The refractive errors determined by this method and by retinoscopy were compared to the subjective refraction of the same eyes. The ultrasonographically determined refractive errors were significantly nearer the subjective refraction than were the retinoscopically determined refractive errors.

Aged↗

Pediatric brain stem gliomas: an update.

It has become evident that pediatric brain stem gliomas are a heterogeneous pathology and should be classified according to clinical and radiological criteria. This classification has contributed to better treatment and greatly improved prognosis. Based on a review of the literature, we describe the different types of brain stem astrocytomas reported, which are: cervicomedullary, exophytic, cystic, focal and diffuse. Particular attention is paid to therapeutic modalities. For the first three lesions named the treatment is surgical and oncological therapy should be evaluated only for regrowth of the mass. Focal tumors of the medulla and pons are still treated empirically (surgically and/or with radiotherapy), because a definitive therapeutic protocol has not yet been elaborated; on the other hand it is well established that if the focal mass is in the midbrain this should merely be monitored by means of serial MRI, while radiotherapy should be applied in the event of the tumor's growth. Diffuse gliomas are treated with oncological therapy, and surgery (for biopsy or tumor excision) is not indicated. Five illustrative cases from our department are presented.

Adolescent↗

The right-left symmetry axis of the brain on CT.

The location of the brain's symmetry axis on computerized tomography (CT) images was mathematically formulated. A series of computer programs were written to "peel off" the skull and artifacts external to the skull. Image lines were then tested for right-left symmetry and in each line a pixel was selected which best represented the center of symmetry of the skull contents. The resultant calculated symmetry line of images with and without pathology was comparable to the visually determined symmetry axis. This method permits computed screening for right-left asymmetry.

Brain↗

Prevalence and new phenotypic and radiologic findings in congenital onychodysplasia of the index finger.

Congenital onychodysplasia of the index finger (COIF) is a rare condition characterized by dysplastic changes in the nail with variable phenotypic manifestations. Its prevalence is unknown. We describe three newborn patients with various clinical and radiologic expressions of this entity. The first, born to a mother treated with multiple antidepressant drugs, had bilateral nail dysplasia of the index finger without bony involvement. The second presented with bilateral hypoplastic nail of the index finger and bilateral symphalangism of the fifth finger; aplastic distal phalanges of the second finger was also noted radiologically. The third baby (born to a diabetic mother treated with insulin), had micronychia and brachydactyly of the right index finger and syndactyly of the second and third fingers; the radiologic finding was bilateral brachymesophalangia of the index finger. It would seem that, besides the nail dysplasia of the index finger, COIF may also be associated with bone dysplasia of the same finger.

Female↗

Effect of P-glycoprotein expression on outcome in the Ewing family of tumors.

This study was designed to determine the prognostic significance of multidrug resistance, mediated by P-glycoprotein (Pgp) expression, in Ewing sarcoma. The clinical and laboratory features, treatment protocol, and outcome of 75 patients with Ewing sarcoma or peripheral neuroectodermal tumor treated between 1972 and 1997 were reviewed. Pgp expression was tested with the monoclonal antibody JSB-1. Thirty-four (64%) of the 53 tissue samples from untreated patients stained positive for Pgp. Progression-free and overall survival were 44 and 59%, respectively, in patients with negative findings, and 28 and 41% in those with positive findings; neither difference was significant. Of the 12 relapsed patients, 6 (50%) expressed more Pgp after chemotherapy than at diagnosis and 4 (33%) expressed less. Within these subgroups, 5 out of 6 and 3 out of 4 died from the disease. No correlation was found between Pgp and known prognostic factors of Ewing tumors. Pgp expression is probably an intrinsic factor of Ewing tumors but has no correlation to prognosis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Visual pathway tumor: a heterogeneous tumor with a variable clinical course.

The aim of the study was to delineate the clinical characteristics of visual pathway tumor in children without neurofibromatosis-I. The authors reviewed the charts of all patients meeting these criteria (n = 12) who were followed in their center over a 13-year period. In 8 patients the disease was relentlessly progressive, and imaging showed a chiasmatic/hypothalamic, exophytic globular lesion. The remainder had a benign course with long periods of tumor stability; one showed some spontaneous visual improvement. The lesions of the latter subgroup were multilobular, with elongated posterior extension into the optic tract. This differentiation, according to the imaging findings, may have significant therapeutic implications. In the first type, every effort should be made to arrest the disease and decrease the size of the lesion, whereas in the second, despite decreased visual ability, careful observation in the appropriate approach. There are as yet no known biological markers to better delineate these two types of tumor behavior.

Cranial Nerve Neoplasms↗

Magnetic resonance imaging in the diagnosis of childhood discitis.

Diagnosis of disc space infection in childhood is often delayed and is usually made on the basis of multiple roentgenographic, laboratory, and nuclear imaging studies. Four cases of septic discitis in children are described. Special emphasis is placed on the diagnostic findings with magnetic resonance imaging. Magnetic resonance sensitivity for this entity and its role in comparison with other imaging modalities are discussed.

Child, Preschool↗

Successful chemotherapeutic treatment of diencephalic syndrome with continued tumor presence.

A 7-month-old infant with typical features of diencephalic syndrome (DES) associated with a hypothalamic mass, most probably a glioma, was treated with chemotherapy. The tumor showed clear shrinkage, but after more than 2 years regrowth was noted. During the treatment period the child regained normal growth and became free of symptoms. As radiation therapy, especially at a young age, has significant adverse effects and a neurosurgical approach to the diencephalic region also has the potential to cause significant sequelae, a chemotherapeutic option, when it exists, is preferred. Thus, in an infant in whom a glioma is suspected to be the cause of the DES, based on the clinical picture and the neuroimaging appearance, chemotherapy should be considered the primary therapeutic modality. Even if its effect is temporary, its use is well justified. The most appropriate treatment protocol still needs to be determined.

Abducens Nerve Diseases↗

Optic pathway glioma: correlation of imaging findings with the presence of neurofibromatosis.

BACKGROUND AND PURPOSE: Despite the benign histology of optic pathway glioma (OPG) (low-grade astrocytoma), its biological behavior is unpredictable, and it is unclear whether specific morphologic or anatomic patterns may be predictive of prognosis. It is also unclear whether OPG associated with neurofibromatosis (NF) is a distinct entity from non-NF-OPG. Our purpose was to describe the MR imaging features of OPG, compare the findings between patients with and those without NF, and identify prognostic imaging signs. METHODS: MR examinations of 91 patients with OPG (47 with NF and 44 without) were reviewed at presentation and during follow-up. The images were evaluated for size and extension of tumor, and imaging parameters. Statistical bivariate analysis was used to compare the patients with and those without NF, and Pearson correlation was used to evaluate the correlation between the different imaging parameters and prognosis. Kappa values were calculated to determine intraobserver and interobserver variability. RESULTS: The most common site of involvement in the NF group was the orbital nerve (66%), followed by the chiasm (62%). In the non-NF group, the chiasm was the most common site of involvement (91%); the orbital nerves were involved in only 32%. Extension beyond the optic pathway at diagnosis was uncommon in the NF group (2%) but frequent in the non-NF group (68%). In the NF group, the tumor was smaller and the original shape of the optic pathways was preserved (91% vs. 27% in the non-NF group). The presence of cystic components was significantly more common in the non-NF patients (66% vs. 9% in the NF group). During follow-up, half the NF patients remained stable, in contrast to 5% of the non-NF group. No statistical correlation was found between imaging features and biological behavior of the tumor. CONCLUSION: NF-OPG is a separate entity from non-NF-OPG, with different imaging features and prognosis, thereby warranting a specific diagnostic, clinical, and therapeutic approach.

Adolescent↗

CT and MR evaluation of the brain in patients with anorexia nervosa.

Thirteen adolescent girls with anorexia nervosa had MR imaging of the brain; 11 were also examined by CT. Fifteen children, ages 10-12 years, served as a control group. The CT and MR studies were evaluated qualitatively for cortical and central atrophic changes. CT detected sulcal and ventricular enlargement in 5/11 patients. On the MR images, enlarged sulci were seen in 10/13 and dilated ventricles in 5/13. In the anorectic patients, the range of the width of the third ventricle was 1-5 mm (mean, 3.2 mm) and the maximal distance between the anterior horns was 22.5-39.0 mm (mean, 30.0 mm). Anterior horns at their minimal width measured 11-30 mm (mean, 16.5 mm). The corresponding measurements in the control group were 1.5-3.5 mm (mean, 2.3 mm) for the third ventricle, 21-35 mm (mean, 28.5 mm) for the distance between the anterior horns, and 10-16 mm (mean, 12.8 mm) for their minimal width. Overall, the patient group had larger ventricles than the control group; however, the difference between the two groups was not significant. Measurement of the number of visible cortical sulci at one cut below the vertex yielded 2-11 sulci in the anorectic girls (mean, 6.6) versus 0-6 sulci (mean, 3.3) in the controls. These results are statistically significant (p = .0009), indicating peripheral volume loss in the anorectic patients. The MR examination did not reveal any additional structural or parenchymal changes when compared with the results of the CT studies. However, the pituitary glands of these patients did not have the expected normal pubertal hypertrophy on the MR examinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Early experience with balloon catheter angioplasty.

Percutaneous transluminal angioplasty with the Gruntzig balloon catheter was undertaken in 12 patients with chronic lower limb ischemia. As judged by postdilatation angiography, the procedure was successful in 11 patients (91.6%). Nine patients were either free of symptoms or very significantly improved at follow-up, one to five months after angioplasty. Indications for angioplasty and the technique are described and discussed.

Adult↗

Primary bone tumor resectability: the value of serial MRI studies in the determination of the feasibility, timing, and extent of tumor resection.

We report the prospective analysis of 119 magnetic resonance imaging (MRI) studies in 41 patients with primary bone tumors performed from January 1984 to December 1990 to evaluate the contribution of serial MRI studies in the determination of feasibility, timing, and extent of tumor resection. Long repetition time (TR)-long echo time (TE) T2-weighted (T2, second echo) imaging was the most useful in assessing soft-tissue involvement, and short TR-short TE T1-weighted (T1) imaging for documenting the bone marrow changes. The feasibility, timing, and extent of resection was determined with the help of MRI in 20 cases with only two local recurrences. One study falsely suggested active tumor. In four other cases, a treatment decision was made based on the MRI. The MRI added significantly to the evaluation by computed tomography, radiographs, and bone scans.

Adolescent↗