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Biomedical subjects

A Zanardo

Publications and source records attributed to A Zanardo.

10 recordsLinked to original sources
PubMed2004

Homocysteine in Alzheimer disease and vascular dementia.

Hyperhomocysteinemia is an important risk factor for atherosclerosis and it has recently been suggested as a diagnostic marker for Alzheimer disease (AD). The present studies compared homocysteinemia in patients with AD and with vascular dementia (VD),as well as in controls. Homocysteinemia was measured in 137 probable AD patients,diagnosed by the NINCDS-ADRDA criteria, in 40 probably VD patients diagnosed by the NINDS-AIREN criteria, and in 42 control subjects. Homocysteine levels were significantly higher in AD and VD groups, than in controls, however, VD patients were significantly older than the controls. The proportion of females was higher in the AD group, while serum folate and B12 vitamin levels tended to be lower in both the AD and VD groups, compared to the controls. In order to adjust the results for these potentially interfering factors, a multivariate ANCOVA calculation was performed, where homocysteine levels were analyzed considering 2 grouping factors (gender and neurological type) and 4 covariates (age, albumin,serum folate and vitamin B12 ). This analysis confirmed that even after adjusting for the covariates, the difference between AD and VD groups and controls remain highly significant,while neither the gender itself, nor the interaction of gender and the neurological type had any significant influence on the homocysteine levels. The main finding, therefore, is a significant increase of homocysteine levels in the 2 disease groups, compared to controls.

Aged↗
PubMed1990

Linear accelerator radiosurgery of three-dimensional irregular targets.

Current radiosurgical techniques allow concentration of radiation from external sources into spherical targets. Nonspherical target volumes require a modification of the irradiation technique. Moreover, isodose shaping is sometimes necessary to spare nearby important radiosensitive structures. To meet these prerequisites we have introduced some technical refinements: (1) computer-controlled rectilinear translations of the target in combination with different angular positions of the source and (2) computer-controlled rotations of the target around a vertical axis in combination with different angular positions of the source. The first solution has proven efficient for treating irregular targets, while the second one was employed for focusing the radiation dose inside volumes obtained by rotation of ellipses.

Brain Neoplasms↗
PubMed1987

New technique for three-dimensional linear accelerator radiosurgery.

A new method for external stereotactic focal irradiation of three-dimensional irregular target volumes is proposed. In this method the target is irradiated by a linear accelerator set in various angular positions around the isocenter. During the irradiation the target is translated in a direction perpendicular to the beam. By controlling the velocity of the translation it is possible to modify the configuration of therapeutic isodoses so as to make them follow the borders of the target.

Brain Diseases↗
PubMed1986

Axiomatization of genetics 2. Formal development.

When certain assumptions are claimed to "found" a scientific theory, two kinds of controls are needed: it must be proved that every assertion of the theory is derived from the assumptions and that no assumption depends on (that is, derives from) the other ones. The formal approach (when possible) is the best method of achieving these results. In this paper the axiomatization of the elementary laws of genetics considered in Rizzotti & Zanardo (1986) is translated into a formal language and an axiomatic theory is defined in which the (translated) laws are deducible. Independence results are also considered.

Chromosomes↗
PubMed1986

Axiomatization of genetics. 1. Biological meaning.

Axiomatization is a trend in science to settle and reduce fundamental assertions, from which all the others are deducible. Classical genetics has been extensively axiomatized and formalized by Woodger (1952), who resorted to 53 axioms and 12 theorems. The molecular settlement of modern genetics provides the basis for a different axiomatic theory. In this paper 3 axioms and 14 theorems are informally expressed. They cover a few elementary laws of "chromosome genetics" in Eukaryotes. The biological problems connected with the further development of this first attempt are discussed.

Cells↗
PubMed1985

Stereotactic radiosurgery utilizing a linear accelerator.

The authors have developed a radiosurgical technique based on multiple arc irradiations. The target is fixed to the rotational isocenter of a Varian 4 MV linear accelerator. The first irradiation is carried out while the radiating source is rotating on a 100-140 degrees arc. The patient is then rotated around a vertical axis passing through the target, and arc irradiations are repeated in different angular positions. By this technique it is possible to obtain very steep dose gradients at the borders of the target volume. High doses are usually delivered in two shots. 47 patients have been treated so far in a clinical trial that started in November 1982. The paper deals with the preliminary results (more than 6 months' follow-up) obtained in patients affected by nonresectable brain tumors and AVMs.

Adolescent↗
PubMed1985

External stereotactic irradiation by linear accelerator.

Stereotactic radiotherapy has two advantages: (a) the possibility of giving high radiation doses to small but spatially well-defined target volumes and (b) the presence of a stepped dose gradient between the target volume and the surrounding healthy tissues. To utilize these advantages, the authors built a new stereotactic head frame by which the intracranial target is fixed to the rotational isocenter of a 4-MV linear accelerator. The collimator openings are selected according to the volume and the three-dimensional configuration of the target, and the radiation dose is based on the radiosensitivity of the lesion. After the patient is fixed to the frame, the radiation source and the patient are rotated so that the target is irradiated through infinite portals distributed over the convexity of the skull. It is thereby possible to obtain very high radiation doses centered into the target with a stepped dose gradient. The preliminary radiodosimetric tests and the operative technique are described. The advantages of this technique compared to interstitial radiotherapy and Leksell's radiosurgery are emphasized. This noninvasive procedure has been used to treat a series of intracranial tumors.

Adolescent↗
PubMed1984

[Stereotaxic irradiation with a linear accelerator].

At least two fundamental requirements must subsist for every stereotaxic radiotherapy treatment: 1) a capacity to administer extremely high doses of radiation to small areas which have been precisely defined in three dimensions; 2) the presence of a steep gradient between adjacent isodose curves so that damage to the tissues close to the target may be reduced to the minimum. The authors have built a special stereotaxic device for the fixing of the head of the patient (together with the chosen intracranial target), once the indispensable neuroradiological evaluations and bioptic controls have been effected, at the isocenter of a linear accelerator (Varian Clinac 4). Once the dimensions of the collimator have been chosen in accordance with the volume and the three dimensional conformation of the target and the dose to be administered has been decided upon in accordance with the histological nature of the lesion, both the linear accelerator and the patient are rotated about the isocenter of the therapy unit. It this way it is possible to reach extremely high dosages with very steep isodose gradients, centered exclusively upon the target ("gamma knife"). The procedure employed is described in full. The dosimetric evaluations which preceded the use of the set-up in clinical practice are illustrated as well. The advantages that this technique offers when compared with interstitial brachytherapy and/or Leksell's radiosurgical procedures are stressed. The described procedure, which is entirely bloodless and thus applicable also to high vascularized lesions, has so far been used in a limited series of cases.

Brain Diseases↗
PubMed1981

A new method for utilizing CT data in stereotactic surgery: measurement and transformation technique.

The proposed system is essentially based on the definition of a coordinate system, rigidly connected with the skull, by the introduction of three reference X-ray opaque points, secured into the bone of the skull. Target and reference points CT coordinates are given by the image display console. The three reference points are also identified on stereoradiographs, and their actual stereotactic coordinates are calculated by a geometrical approach which takes into account radiological distortion. A programmed computer links the target, identified on tomograms, to the three points system and calculates its stereotactic coordinates.

Humans↗