Search PubMed⌕ Search

Biomedical subjects

I Rosen

Publications and source records attributed to I Rosen.

At least 19 recordsLinked to original sources
PubMed1998

A comparison of measured and calculated output for highly blocked photon fields.

The present work measured the accuracy of VAX monitor unit calculations currently used for highly blocked photon fields at The University of Texas M. D. Anderson Cancer Center. The VAX program is an in-house computer program that calculates the setting for linear accelerator photons that is needed to deliver a prescribed dose to a muscle miniphantom located on the beam's central axis at a prescribed depth beneath the surface in water. Monitor unit settings were computed for the Varian 2100 with multileaf collimation using 6 MV and 18 MV photons at a depth of 10 cm with different blocking ratios. Concentric and lateral blocking methods were used. Measurements were taken with an ion chamber and then compared with the VAX calculations with off-axis factors and peak scatter factors added in that are not available in the program. The results showed less than 2% difference for the concentric fields containing no more than 80% blocking and an equivalent square of at least 3.5 cm for 6 MV and 5 cm for 18 MV X-rays. For the lateral fields with the central axis blocked, less than 2% difference was found when blocking was 80% or less and the equivalent square was no less than 3.5 cm for 6 MV X-rays. For 18 MV X-rays, the maximum blocking and minimum equivalent square were 60% and 5 cm for 2% accuracy. This confirmed that the VAX system currently in use is accurate unless a very large amount of blocking is present or the central axis is blocked in very small fields. Previous research done at dmax with similar blocking ratios produced similar results.

Humans↗
PubMed1997

Extracranial localization of intracranial interictal epileptiform activity using LORETA (low resolution electromagnetic tomography).

Besides the standard clinical methods of EEG waveshape analysis, mathematical models for reconstruction of dipolar sources from the digitized surface EEG have been introduced in epilepsy research. Although useful for localizing focal sources, these methods are inadequate for analyzing widespread epileptiform activity. A recently introduced alternative method called LORETA (low resolution electromagnetic tomography, Pascual-Marqui et al., 1994), directly computes the current distribution throughout the full brain volume, assuming that neighboring neuronal populations are simultaneously and synchronously activated. In mathematical terms the method selects the smoothest of all possible 3-dimensional current distributions, inherently introducing a certain amount of dispersion. In 7 patients, undergoing simultaneous EEG recording from 10 intracranial (subdural) and 22 extracranial electrodes, 111 subdural discharges (61 subtemporal and 50 lateral temporal) were identified. The exact time point of maximal intracranial activity was automatically identified, and the LORETA solution at that timepoint was computed from the surface EEG. Statistical comparison revealed significantly higher LORETA current density in the area corresponding to the subdurally recorded spike compared to other areas, and a more anterior and more medial LORETA location for subtemporal compared to lateral temporal spikes. This study indicates that the LORETA technique may become a useful method to localize electrical activity in the brain.

Adolescent↗
PubMed1996

Laser-evoked cerebral potentials and sensory function in patients with central pain.

Central pain syndromes (CPS) could be caused by disinhibition of spinothalamic excitability or by other central nervous system (CNS) changes caused by reduced spinothalamic function. To examine these possibilities, we studied 11 patients (ages 51-82 years) with unilateral central pain and with reproducible cerebral evoked vertex potentials in response to cutaneous stimulation of the normal side with pulses from an infra-red CO2 laser. All patients had normal tactile and kinesthetic sensation; one had slightly decreased vibratory sense bilaterally. All showed, from the unaffected (asymptomatic) side, laser evoked potentials (LEPs) with negative (N) components ranging from 208 to 280 msec peak latency (av: 240 +/- 6 SE msec) and peak amplitudes of 1-7 microV (av: 2.9 +/- 0.5 SE microV), followed, in all but 1 patient, by positive (P) potentials ranging from 288 to 370 msec peak latency (av: 319 +/- 7.7 SE msec) with peak amplitudes of 1-7 microV (2.8 +/- 0.5 SE microV). Laser stimulation of the affected (symptomatic) side in 5 patients evoked LEPs with N-P interpeak amplitudes that were within 20% of those evoked from the normal side. All but one of these patients had thresholds for warm, heat pain, and deep pain that were normal in comparison with the unaffected side. The excepted patient had the largest N-P interpeak amplitude asymmetry (18.5%) of this group. Ratings of laser pulse intensity were either symmetrical (n = 2) or increased on the affected side (n = 3) in these patients. In contrast, laser stimulation of the affected side failed to evoke either N or P potentials in 6 patients, all of whom had lateralized increased thresholds for warm, heat pain, or deep pain, or reduced ratings of laser pulse sensation. Although 1 patient had increased ratings of laser pulse sensation, the amplitude of the LEP was always reduced on the side of increased pain or heat threshold in these CPS patients (Fisher exact test: P = 0.015). These results reflect primarily a deficit in spinothalamic tract function and do not suggest excessive CNS responses to synchronous activation of cutaneous heat nociceptors in patients with CPS.

Aged↗
PubMed1991

A comparison of the results following oromandibular reconstruction using a radial forearm flap with either radial bone or a reconstruction plate.

Fifteen cases of oromandibular reconstruction using a radial osteocutaneous flap were compared with 16 in which the mandible was replaced with a reconstruction plate and a forearm flap was used for intraoral lining. All cases involved oral cancer; most had been irradiated. Nine survived in each group. Complications included one infected nonunion in addition to two bone exposures in the bone group, compared with three cases of plate exposure and two bone exposures in the plate group. Functional results were similar in both, but osteointegrated implants were possible only in the patients receiving bone. Cosmesis seemed somewhat better in the plate group. Donor-site problems were common but minor, and long-term forearm function was slightly reduced in both groups. Although the sample sizes were small, the reconstruction plate together with a radial forearm flap appeared to provide effective reconstruction following composite resection. However, we would not recommend this for the younger patient or in benign disease.

Adult↗
PubMed1991

A study of peripheral diabetic neuropathy. The application of age-related reference values.

The standardization of methodology and the provision of age-related reference values have been addressed for the design of and interpretation of data from a multicentre neuropathy trial. Age-related reference values were generated from 120 healthy volunteers. Vibration perception thresholds (VPT) deteriorated significantly with age (p less than 0.001). Patients were selected on the basis of age-related abnormal VPT and peroneal motor nerve conduction velocity. They were assessed at the beginning and end of a placebo run-in period (baseline data). The coefficients of variation (CV%) for VPT at the medial malleolus (16.81 per cent, n = 316) and great toe (19.23 per cent, n = 313) were lower compared to results in healthy volunteers (29.7 per cent and 20.8 per cent, respectively, n = 49). The CV% for expiratory:inspiratory (E:I) ratio (4.82 per cent, n = 215), Valsalva manoeuvre (10.84 per cent, n = 249) and 30:15 ratio (7.73 per cent, n = 292) from patients corresponded to those recorded in volunteers (7.6 per cent, n = 45 11.0 per cent, n = 49 9.5 per cent, n = 48, respectively). Most patient values for VPT at the great toe fell beyond the 95 centile line for volunteers. E:I ratio for volunteers showed a more variable relationship with age, although patient values appeared to be located below the 5 centile line for volunteer data.

Adult↗
PubMed1991

Self-esteem as a factor in social and domestic violence.

Psychoanalytical ideas are used to outline how poor narcissistic development can lead to poor regulation of self-esteem. This in turn often underlies domestic violence, the short-term treatment of which can be aided by psychodynamic understanding.

Adult↗
PubMed1990

Neurophysiological changes during insulin-induced hypoglycaemia and in the recovery period following glucose infusion in type 1 (insulin-dependent) diabetes mellitus and in normal man.

Hypoglycaemia (median venous blood glucose 1.8 mmol/l; range 1.6-2.3) was induced by an intravenous infusion of regular insulin in eight patients with Type 1 (insulin-dependent) diabetes mellitus (age 28.0 +/- 7.4 years; mean +/- SD, duration 15.5 +/- 5.1 years) and in 12 age-matched healthy male control subjects. Multi-channel frequency analysis of electroencephalogram (electrophysiologic brain mapping) and recording of P300 and somatosensory evoked potentials were performed before, during and immediately after the hypoglycaemic period. The hypoglycaemia produced a significant increase in low frequency electroencephalographic activity in both groups, most pronounced over anterior regions of the brain. The electroencephalographic activity was normalised immediately after the hypoglycaemic period. The patients with diabetes showed somewhat longer P300 latencies during the initial normoglycaemic examination. Hypoglycaemia caused a marked reduction of the P300 amplitude in both groups of subjects and the amplitude was not restored immediately after normalisation of blood glucose levels. The somatosensory cortical responses were not affected by hypoglycaemia. We conclude that hypoglycaemia results in impairment in cerebral function, as measured by neurophysiological techniques, which is not immediately normalised when blood glucose is restored to normal.

Adult↗
PubMed1990

The iliac crest and the radial forearm flap in vascularized oromandibular reconstruction.

Sixty cases (59 patients) of oromandibular reconstruction using vascularized iliac crests were compared with 13 in which radial osteocutaneous flaps were used. These patients were reviewed from the standpoint of cosmetic results and function as well as their operative and postoperative courses. In both groups, the results were generally good. However, revisionary surgery was more frequent in those receiving the iliac crest. This group also had a higher incidence of intraoral wound breakdown and bone exposure. Nevertheless, the sheer size of the iliac crest made it ideal for massive oromandibular defects, just as its natural curvature lent itself to precise replication of the mandible in bone-only reconstructions. Its bulk proved a major obstacle in small composite defects. The radial forearm flap carried thin, pliable, well-vascularized skin that was superior to groin skin for oral lining. Bone gaps of up to 9 cm could be handled with ease, thus making it complementary to the iliac crest over the wide spectrum of mandibular reconstruction.

Adolescent↗
PubMed1989

The development of an immunosensor for the electrochemical determination of the isoenzyme LDH5.

In this work we describe an immunoelectrochemical technique for the determination of LDH isoenzymes. The method is based on the covalent binding of monoclonal antibody against the isoenzyme LDH5 to a glassy carbon electrode, and the exploitation of the electrode surface as the solid phase for enzyme immunoassay. The resulting enzyme electrode was studied by a computerized electrochemical system. This combination formed the basis of a highly sensitive fast and convenient technique for the determination of the LDH isoenzymes in sera.

Animals↗
PubMed1989

Etiologic aspects of impotence in diabetes.

An investigation of 37 diabetics with impotence (15) or erectile difficulties (22) is presented. On average two significant abnormalities per patient were found. Ranked in order of incidence, the causes were as follows: 1) Combination of neuropathy and psychosocial factors, 2) combination of neuropathy and vascular disease, 3) peripheral neuropathy only, 4) combination of hormonal imbalance and psychosocial factors, 5) combination of three or more defects, and 6) penile vascular disease or psychosocial problems only, or hormonal imbalance combined with peripheral neuropathy.

Diabetic Angiopathies↗
PubMed1989

Preventing staff-patient sexual relationships.

Just as the awareness of incest and childhood sexual abuse has grown in recent years, so too has knowledge of sexual exploitation of patients by psychotherapists and other mental health professionals. Almost no one, however, has discussed the prevalence of this problem in the hospital setting. The authors were members of a study group that thoroughly reviewed reported incidents in their own institution, leading to the recommendation that education is the best preventive measure currently available. The authors discuss fundamental issues involved in such a study, summarize profiles of patients and staff members who may be vulnerable to sexual involvement, and describe the main components of a preventive educational approach.

Antisocial Personality Disorder↗
PubMed1986

A surface mold using iridium-192 seeds.

A radioactive mold for treating skin was constructed by embedding ribbons of iridium-192 seeds in bolus material. The mold was designed to match the treatment area outlined on the patient's skin. Computer-assisted pre-planning was performed to optimize the seed strength, number of seeds, and spacing of ribbons. An outline of the treatment area was transferred to the surface of a uniform slab of tissue-equivalent bolus material 1.3 to 1.4 cm thick and planned locations for the ribbons were marked. Seeds were loaded into the bolus material at a depth to place the sources approximately 1.0 cm from the skin. The resulting mold was flexible enough to conform to the patient's skin and the seeds were so tightly confined within the bolus that there was no possibility of loss. Isodose distributions for the mold on a flat surface agreed well with preplans. A velcro strap and neck collar were used to attach the mold to the anterior portion of the patient's neck. For situations in which radioactive surface applicators are desirable, the use of iridium-192 seeds offers uniform dose within a highly individualized treatment area.

Brachytherapy↗
PubMed1985

Sleep-waking shifts and cerebral blood flow in stable preterm infants.

Cerebral blood flow was estimated on 60 occasions in 15 well infants, 29-34 wk of gestational age, 5-17 days after birth, using 133-Xenon clearance after intravenous injection. The sleep state of the infants was determined by biparietal electroencephalography, clinical observation, and tracings of heart rate and respiration. Blood flow was 22% higher in the 11 estimations made during wakefulness, when compared to the 17 estimations made during quiet sleep. There was no difference between blood flow in active and quiet sleep. Also there was no difference between blood flow during periods of trace alternant and blood flow during periods of continuous electroencephalographic activity. It is suggested that flow-metabolism coupling is present in stable, preterm infants. The absence of an increase in cerebral blood flow during active sleep as compared with quiet sleep suggests that the neurophysiologic and neurometabolic mechanisms of rapid eye movement sleep are not yet fully developed in preterm infants.

Brain↗
PubMed1984

Pitfall in the investigation of splenic trauma.

A patient with suspected splenic trauma is reported in whom, because of an anatomic variant, both radionuclide and sonographic examinations were misleading and led to the erroneous diagnosis of splenic laceration. Confusion arose because of an overlying left lobe of liver and this was clarified by biliary scintigraphy.

False Positive Reactions↗
PubMed1982

Mucus-producing medullary cell carcinoma of the thyroid gland.

A case of medullary carcinoma of the thyroid with the presence of mucus-secreting (goblet) cells was reported. Ultrastructurally, the tumor was composed of two types of cells, one with neurosecretory granules and the other with mucus granules. The secretion of calcitonin and mucus was demonstrated by histochemical methods. The presence of two cell populations in this tumor casts doubts on the "APUD" concept, which proposes a neuroectodermal origin for parafollicular (C) cells of the thyroid gland. The significance of this tumor with regard to the histogenesis of the cells involved, is discussed.

Adult↗