Biomedical subjects

A Zanardo

Publications and source records attributed to A Zanardo.

6 recordsLinked to original sources

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↗