PubMed Health⌕ Search

Biomedical subjects

A Piermattei

Publications and source records attributed to A Piermattei.

At least 55 records · Page 3Linked to original sources
PubMed1985

[Evaluation of the dose in permanent implants of I-125].

The Anderson's nomograph is currently used in 125I implants planning. For a given treatment volume, this method provides the activity and the seeds number and spacing. In order to obtain indications of the dose delivered in that 125I volume implants, we computed the average peripheral dose (APD), the average tumor dose (ATD) and the "matched peripheral dose" (MPD), for spherical, ellypsoidal and cylindrical volumes. By using the 125I source dosimetric data, we found that both the APD and the ATD are independent of sources randomizing in both position and orientation. Therefore the 125I seeds can be considered as point sources, provided that the dose values are scaled down by a factor which accounts for the spatial distribution anisotrophy. Since the computed parameters are only dependent on the implanted activity, the L. L. Anderson method can be applied even if brachytherapy treatments are associated with external beam radiotherapy ("boost"-therapy).

Brachytherapy↗
PubMed1984

Intracavitary dosimetry of a high-activity remote loading device with oscillating source.

Dosimetric experiments have been carried out in order to obtain the dose distribution in water around a Fletcher applicator loaded by a Buchler system containing two 137Cs 148 GBq (4 Ci) sources and one 192Ir 740 GBq (20 Ci) source. The mechanical system which controls the movement of the 192Ir source and the resulting motion of the source are described. The dose distribution around the sources was measured photographically and by a PWT Normal 0.22 cm3 ionisation chamber. The absolute dose rate was measured along the lateral axes of the sources. The measurements of exposure in water near the sources were corrected for the effect due to the finite volume of the chamber. The "quantisation method" described by Cassell (1983) was utilised to calculate the variation of the dose rate along the lateral axes of the sources. The dose distribution around both 192Ir and 137Cs sources was found to be spherical for angles greater than 40 degrees from the longitudinal axes of the sources. A simple algorithm fitting the data for the moving 192Ir source is proposed. A program written in FORTRAN IV and run on a Univac 1100/80 computer has been used to plot dose distributions on anatomical data obtained from CT images. The uncertainties of the measurements and calculations have been examined and the greatest error has been found to be 5.5%. The clinical significance of the treatment method is discussed.

Brachytherapy↗
PubMedDate not supplied

Dose measurements and calculations of small radiation fields for 9-MV x rays.

Measurements of dose distribution for square fields with sizes ranging from 1 X 1 to 30 X 30 cm for a 9-MV x-ray beam from a Neptune 10 linear accelerator, manufactured by CGR, are reported. Special attention was paid to field sizes smaller than 4 X 4 cm, used in radiosurgery techniques. To express the dose-monitor units relationship, total, collimator, and phantom scatter correction factors were obtained by experimental measurements. A strong dependence of these factors on the smallest field sizes (less than 4 X 4 cm) was shown. Measurements of the maximum depth dose dmax, plotted as a function of field size, showed a maximum at about 5 X 5 cm, in good agreement with previous results. dmax was also measured for the smallest fields, demonstrating that the contaminating electron component of the x-ray beam was not responsible for the dmax shift. Analysis of the penumbra width of cross dose distributions, as a function of field sizes, allowed us to postulate that the dmax shift could be due to the phantom scattered photons, which in turn were generated by the collimator scattered photons. Newly derived tissue-maximum ratio and scatter-maximum ratio data were used for dose profile calculations of 2 X 2, 4 X 4, and 10 X 10 cm field sizes. The agreement between experimental and calculated data was found to be +/- 2% within the geometrical edges of the fields and +/- 6% outside of them. A dose profile from the isocenter of a 2 X 2 cm square field moving through a 360 degree rotation arc was obtained and compared with that from the center of a 125I shielded source, as measured by Ling. Advantages and problems relating to the use of x-ray beams from linear accelerators in radiosurgery are discussed.

Humans↗
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

Quality handbook in radiotherapy: personal experience.

The Quality Handbook includes the description of the activities carried out in Radiotherapy and the methodology used to ensure the Quality Assurance according to the principles indicated in national and international documents of reference and the recommendations of accreditation agencies. The structure of the Quality Handbook, the main aspects of single chapters, the selected quality indicators undergoing inspections are analysed and procedures to be followed for changes and updating of the Quality Handbook are described. The Quality Assurance program is illustrated in another article of this issue.

Humans↗
PubMedDate not supplied

Quality assurance in radiotherapy: personal experience.

The approach to the implementation of a Quality Assurance Program applied from 1 October 2000 at the Radiotherapy Service of the "Università Cattolica del S. Cuore, Policlinico "A. Gemelli" of Rome, is described. Some major aspects of this program are analyzed.

Humans↗
PubMedDate not supplied

Quality handbook in radiotherapy. Brachytherapy: personal experience.

Brachytherapy is a conventional method of radiation therapy characterized by peculiar technical, clinical, operational and radioprotection problems. Therefore, the management of a service or department of brachytherapy requires a specific organization aimed at Quality Assurance. In this report, the personal experience with the drawing up of a Quality Handbook of brachytherapy with reference to the method used and the structure of the document, is described.

Brachytherapy↗
PubMedDate not supplied

[Conservative treatment of splenic trauma].

Authors present a series of 19 patients accepted for a splenic trauma. Four cases underwent TNO and 15 splenectomy, associated in 9 of them to autotransplant in omental pouch. Authors stress the importance of the conservative management of spleen injuries, to preserve its hematologic and immunologic functions.

Adolescent↗
PubMedDate not supplied

[Bilateral retroperitoneal lymphadenectomy in tumors of the testis: anatomo-clinical considerations].

Bilateral retroperitoneal lymphadenectomy is usually indicated for non-seminomatous testis tumour at stage IIA and IIB. For seminoma is generally used radiotherapy, although some Authors prefer the surgical approach. Radical retroperitoneal lymphadenectomy must be bilateral, because metastatic cell can often spread to the contralateral lymph nodes. Lymphadenectomy is used not only for therapy, but also for staging: thus clinical evaluation and other diagnostic techniques are not always correct (30% of understaging). Permanent sexual disfunction can follow radical surgery, due to extensive retroperitoneal dissection and exeresis of lumbar sympathetic nerves; so it is proposed, for stage I tumors, a monolateral or limited retroperitoneal lymphadenectomy. Eight patients with non-seminomatous testicular tumours are reported by the authors; 2 (stage I) were treated with monolateral, 4 (stage IIA and IIB) with bilateral retroperitoneal lymphadenectomy; in 2 patients (stage IIC and IID) chemotherapy was followed by debulking surgery. Relapses were observed between 3 and 19 months. Sexual dysfunctions after surgery were present in 5 patients (69%); in all of these a bilateral retroperitoneal lymphadenectomy was performed.

Adolescent↗
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↗