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Biomedical subjects

L Azario

Publications and source records attributed to L Azario.

28 records · Page 2Linked to original sources
PubMed1990

[Intraoperative radiotherapy with electrons (IORT). Dosimetry problems, first experience].

In this paper, preliminary results on the IORT dosimetry performed on the two radiotherapy centers, "Regina Elena National Cancer Institute" and "S. Cuore Catholic University", are presented. The absolute dosimetry has been performed with ion chambers (ENEA chamber and Markus flat chamber) using a water phantom. The relative measurements have been performed with solid state diodes and radiographic films, calibrated on absolute dosimetry system.

Combined Modality Therapy↗
PubMed1989

[Evaluation of the absorbed dosage in Compton tomography].

Tomographic images with electronic density can be obtained by irradiation with a monoenergetic beam and detection of the scattered Compton photons. The results of a dosimetric study on the beam of an irradiating Compton unit (equipped with two 192Ir 277.5 GBq sources) are here presented. Doses along the central axis of the beam were measured using thermoluminescent LIF-100 dosimeters. Measurements were taken both in water (RFA-3 Therados) and in cork phantoms. Isodose distributions were estimated by reading the automatic photo-densitometry of radiographic films. A simple algorithm for calculating depth dose values was obtained by analyzing experimental data. The mean absorbed dose (mad) in soft tissues (up to 25 cm deep) was 2.81 mGy for a work load of 7.4 X 10(11) Bq min. The mad in standard thorax was calculated also, which amounted to 3.78 mGy.

Absorption↗
PubMedDate not supplied

A study of quality of bremsstrahlung spectra reconstructed from transmission measurements.

A numerical method for the reconstruction of bremsstrahlung spectra has been applied to the analysis of simulated data. The method is found to be reliable in reconstructing x-ray spectra of maximum energy up to 10 MeV. Measurements of aluminum transmission data carried out for five linear accelerators have also been analyzed by this method to determine the fractional energy fluence. The values of the Spencer-Attix water/air stopping power ratio, SS.A. w,air, reported as a function of the ratios TPR20 10, are in good agreement with computed results. Quality index values were correlated to mean incident energies of x-ray beams used in radiotherapy. The experimental setup has also provided information regarding the softening effect on the off-axis beam, which can be used in clinical computer dosimetry to correct conventional zero field size tissue maximum ratio.

Image Processing, Computer-Assisted↗
PubMedDate not supplied

Two quality control procedures on radiotherapy beam calibration and treatment planning system implementation.

New challenging dosimetric approaches, such as narrow beams and 3D algorithms, are being used in radiotherapy. In this paper two quality control (QC) procedures are reported. The first one concerns the QC of the dosimetry of small x-ray beams, generally carried out by using silicon detectors. The comparison of dose values obtained by a silicon diode, a diamond detector, and radiochromic films shows that for x-ray beams of high energy, the silicon diode can give an overestimation of the output factors in phantom, up to 4%. This is due to the higher than unit density silicon diode and the surrounding envelope that restore the lateral electron equilibrium. About the 3D algorithms for breast treatment planning, a quality control test has been adopted to verify the accuracy of the computed dosimetry when "loss of scatter" occurs. The results show a sensible agreement (within 1.5%) between computed and experimental data.

Humans↗
PubMedDate not supplied

Dosimetric aspects in stereotactic radiotherapy using small shielded sources.

In stereotactic irradiation by external beams there are many problems involved with dosimetry of small fields, three-dimensional representation of dose distribution, radiobiological involvement of tissue response to total dose and fractionation. Dosimetric problems arise by critical dimension of dosimetric chambers and by difficulties of films calibration. The amount of data required for a correct three-dimensional simulation of isodose curves, tumor and anatomical structures require a very speed computer system, sophisticated computer graphic techniques and calculation algorithm. By use the linear quadratic model of cell survival, maps of combined dose and biological effect (isoeffect curves) are also obtained.

Humans↗
PubMedDate not supplied

Preoperative concomitant radiochemotherapy and IORT in locally advanced rectal cancer.

34 patients with locally advanced (T4) or recurrent rectal cancer have been treated with: 1. external beam radiotherapy (45-48 Gy) + 5FU(1000 mg/m2/daily iv continuous infusion day 1-4) + MMC (10 mg/m2/daily iv, day 1); 2. surgical resection (if feasible) + IORT (10-15 Gy); 3. adjuvant chemotherapy (5FU+leucovorin, 6-8 cycles). Grade 3 acute hematological toxicity was observed in 1 case only. 23 of 34 patients underwent radical surgery. Perioperative mortality and morbidity was 0% and 17% respectively. In the 23 operated patients with a mean follow-up of 18.6 months there were 2 local recurrences, 5 blood metastases, (1 death of disease). 16 patients were shown to be NED (3-36 months).

Antibiotics, Antineoplastic↗
PubMedDate not supplied

Quality assurance in planning and implementing radiation therapy.

Quality Assurance (QA) programs in radiotherapy are based on an interdisciplinary team work with the participation of physicists and physicians in treatment decision-making and in the determination of accuracy in dosimetry. In this short article, quality control (QC) procedures for computer-assisted treatment planning and implementation, are reported. Particular attention is paid to the technological developments which could make QC programs feasible at Radiotherapy centers.

Humans↗