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Biomedical subjects

A Piermattei

Publications and source records attributed to A Piermattei.

At least 37 records · Page 2Linked to original sources
PubMed1997

[Simultaneous carotid and vertebral revascularization in the aged].

Five patients of a mean age of 76, have been submitted to combined vertebral and carotid artery revascularization for a severe vertebro-basilar insufficiency. Vertebral artery revascularization consisted of a transposition to the common carotid artery in one case and of a carotid-distal vertebral artery saphenous bypass graft. The associated carotid artery revascularization consisted of a carotid endarterectomy with patch in 4 cases and without patch in one case. There were no postoperative mortality and no postoperative stroke. Postoperative morbidity included a transitory revascularization syndrome, a myocardial ischemia and a Horner's syndrome. Complete relief of vertebrobasilar symptoms was obtained in 4 patients whereas in one patient only a mild positional vertigo persisted. All vascular reconstructions have been assessed with postoperative arteriography and duplex-scan every six months. At 11 months mean follow-up, all revascularizations are patent. Combined carotid and vertebral artery surgery is effective in well selected cases, and it does not enhance the risk of the two operations performed separately. It also eliminate the possibility of failure of isolated carotid revascularization for vertebrobasilar symptoms.

Aged↗
PubMed1996

Ion-recombination correction factor ksat for spherical ion chambers irradiated by continuous photon beams.

The large range of reference air kerma rates of brachytherapy sources involves the use of large-volume ionization chambers. When such ionization chambers are used the ion-recombination correction factor ksat has to be determined. In this paper three spherical ion chambers with volumes ranging from 30 to 10(4) cm3 have been irradiated by photons of a 192Ir source to determine the ksat factors. The ionization currents of the ion chambers as a function of the applied voltage and the air kerma rate have been analysed to determine the contribution of the initial and general ion recombination. The ksat values for large-volume ionization chambers obtained by considering the general ion recombination as predominant (Almond's approach) are in disagreement with the results obtained using methods that consider both initial and general ion-recombination contributions (Niatel's approach). Such disagreement can reach 0.7% when high currents are measured for a high-activity source calibration in terms of reference air kerma rate. In this study a new 'two-voltage' method, independent of the voltage ratio given by a dosimetry system, is proposed for practical dosimetry of continuous x- and gamma-radiation beams. In the case where the Almond approach is utilized, the voltage ratio V1/V2 should be less than 2 instead of Almond's limit of V1/V2 < 5.

Biometry↗
PubMed1995

Dosimetry of 169 Yb seed model X1267.

Unlike previous brachytherapy sources a number of published studies have been addressed to the dosimetry of 169 Yb seeds, manufactured in several prototypes, before widespread clinical use has been made. Discrepancies seen in the dosimetry obtained for ytterbium seed prototypes appear to be related to inconsistency and non-reproducibility in the vendor's calibration procedure to determine contained activity. Av. The comparison of 169 Yb seed dosimetries demonstrates a need for more accurate implementation of calibration procedures to determine the air kerma rate for the definitive 169 Yb seed design. This paper reports an experimental procedure to determine the reference air kerma rate, Kr (mu Gy h-1), defined as the kerma rate at 1 m along the source transverse axis in free space for the new 169 Yb seed, model X1267. A mean value of the ratio Kr/Av = 1.53 mu Gy h-1 mCi-1 was obtained from determining the Kr value of eleven seeds. Since this ratio is only 3% less than the air kerma rate constant for the 169 Yb point source, (gamma delta)k = 1.58 mu Gy h-1 m2 mCi-1, this means that the Av is closer to an apparent activity than a contained activity, Ac. A Monte Carlo simulation to determine the ratio between reference air kerma rate and the contained activity gave Kr/Ac = 1.33 mu Gy h-1 mCi-1. For the dose rate constant in water we obtained DKr (1, pi/2) = 1.20 +/- 0.05 cGy h-1 (mu Gy h-1)-1, using calibrated thermoluminescent dosimeters (TLDs) and DKr (1, pi/2) = 1.21 +/- 0.03 cGy h-1 (mu Gy h-1)-1 by Monte Carlo simulation. TLDs were used both to determine the radial dose distribution along the seed transverse axis and to calibrate GAFChromic films to obtain the two-dimensional dose distribution around the seed.

Biophysical Phenomena↗
PubMed1995

Implantation guidelines for 169 Yb seed interstitial treatments.

The adequacy of an interstitial implant carried out with a new radioactive source, the 169 Yb seed model X1267, has been examined by computing volumetric indices based on dose-volume histograms. The comparison of these indices with the ones computed for 125I seed implantations shows that the use of ytterbium seeds presents an improvement of the dose homogeneity in interstitial implants. This is due to the significant build-up associated with 169 Yb photons that reduces the rapid dose fall-off with the distance from the source. Moreover, relative to 192Ir, the lower photon energy gives 169 Yb the advantage in clinical use of reduced radiation exposure (i) to health care workers, (ii) to relatives of treated patients and (iii) to healthy neighbouring tissues of the patients if appropriate thin shielding is used.

Biophysical Phenomena↗
PubMed1995

p-type silicon detector for brachytherapy dosimetry.

The sensitivity of a cylindrical p-type silicon detector was studied by means of air and water measurements using different photon beams. A lead filter cap around the diode was used to minimize the dependence of the detector response as a function of the brachytherapy photon energy. The radial dose distribution of a high-activity 192Ir source in a brachytherapy phantom was measured by means of the shielded diode and the agreement of these data with theoretical evaluations confirms the method used to compensate diode response in the intermediate energy range. The diode sensitivity was constant over a wide range of dose rates of clinical interest; this allowed one to have a small detector calibrated in terms of absorbed dose in a medium. Theoretical evaluations showed that a single shielding filter around the p-type diode is sufficient to obtain accurate dosimetry for 192Ir, 137Cs, and 60Co brachytherapy sources.

Brachytherapy↗
PubMed1993

[The guaiac test and colorectal pathology. Clinical evaluation].

The paper reports the results of a study carried out in 187 out-patients who were examined for various reasons. A guaiac test was performed in all patients and those with positive results were further examined using more complex methods. The results obtained showed that, due to its high levels of sensitivity and specificity, as well as its low cost, the "Hemoccult test" still represents the most suitable means for the mass-screening of non-selected populations.

Adult↗
PubMed1992

Use of the fiberoptic bronchoscopy in the elderly.

The authors emphasize the primary role fiberoptic bronchoscopy has for diagnostic and therapeutic purposes in the elderly affected by pulmonary disease. Safety, efficacy and tolerability of the method in the elderly are obtained through a preliminary and careful evaluation of the patients, either clinical or instrumental.

Aged↗
PubMed1991

[Injury of the popliteal artery].

Injuries to the lower limbs are now commonplace, in particular due to the increased number of car accidents, work accidents, injuries from knives or fire arms, or sporting injuries. The popliteal artery is involved in 6% of all these injuries. A clinical case is described of a subject who was injured, causing laceration to the popliteal artery, and brought to our attention six months after the event.

Adult↗
PubMed1990

[Total parenteral nutrition in patients undergoing total gastrectomy in cancer of the stomach. A clinical study].

Total gastrectomy is the elective therapy for gastric cancer, but anastomotic dehiscences often improve the results of this surgery, performed in patients with malnutrition due to the neoplasy. The authors present a group of 27 patients treated with total gastrectomy and a routine postoperative TPN; the incidence of dehiscences and postoperative complications is very low. The preoperative evaluation of surgical risk and the choice of pre- and/or postoperative, parenteral and/or enteral nutritional therapy, are discussed.

Aged↗
PubMed1990

[Optimization of a dosimetric procedure in total body irradiation].

The experimental dosimetry of 2 radiotherapy beams produced by a 60Co Picker unit and by a Siemens 4 MV unit, respectively, was analyzed to verify the use of tissue air ratio (TAR) and tissue maximum ratio (TMR) in the computerized planning of total body irradiation (TBI). The use of a small ionization chamber PRO5P Capintec in anthropometric phantoms allowed us to test a computed calculation procedure adopted to reduce both experimental uncertainties and time consumption. The experimental test on the computed procedure was also useful to identify the equivalent fields the patient's body had to be divided into for dosimetric planning. Such dosimetric specifications as average dose to the patient and degree of dose inhomogeneity are calculated when the thickness of compensator filters in perspex is optimized. Following the guidelines reported in ICRU 29, a dosimetric record is presented. In page 1 the target volume is described, in page 2 the provisional treatment planning, and in page 3 the actual treatment planning, checked with in vivo TLD measurements, and the dose specifications for TBI.

Humans↗
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

[Anastomotic dehiscence in colorectal surgery and the total parenteral nutrition. A clinical study].

After analysing previous investigations into the incidence of anastomotic dehiscence in colorectal surgery, the paper reports experience with a group of 27 patients treated by a "routine"-TPN after major surgery. In addition, a second group of 67 patients, treated by TPN alone after a postoperative complication, was included in this study. The results show the utility of TPN in the prevention or faster healing of anastomotic dehiscences.

Anastomosis, Surgical↗
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↗
PubMed1985

[Rigid phantom dosimetry of brachytherapy sources, with special reference to 125-I].

At present, the brachytherapy dosimetry requires the highest level of accuracy in determining the physical parameters of many different radiation sources. Brachytherapy sources differ not only in the nucleus (widely ranging between 30 keV and 1 MeV), but also in the strength and geometrical and filtration characteristics. This work reports the brachytherapy dosimetry carried out in a rigid perspex phantom which allows measurements by means of solid state dosimeters (TLD, semiconductor), ionization chamber and film. Film densities were measured by means of a computerized Perkin-Elmer 1010G microdensitometer, with a spatial resolution of 50 microns. The isodensity lines were dose calibrated by TLD measurements. The dosimetry of the 125I, 192Ir and 198Au sources is reported. The dose distributions of the low energy 125I source, in two different tissues (muscle and adipose) were studied, by means of laboratory built tissue-equivalent sections of the phantoms. The experimental data suggest that this dosimetric procedure is suitable for intercomparison measurements between different radiotherapy centers using the same nuclides in different sources.

Adipose Tissue↗