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Biomedical subjects

M Bucciolini

Publications and source records attributed to M Bucciolini.

17 recordsLinked to original sources
PubMed2002

An investigation of the operating characteristics of two PTW diamond detectors in photon and electron beams.

The dosimetric properties of two PTW Riga diamond detectors type 60003 were studied in high-energy photon and electron therapy beam. Properties under study were current-voltage characteristic, polarization effect, time stability of response, dose response, dose-rate dependence, temperature stability, and beam quality dependence of the sensitivity factor. Differences were shown between the two detectors for most of the previous properties. Also, the observed behavior was, to some extent, different from what was reported in the PTW technical specifications. The necessity to characterize each diamond detector individually was addressed.

Calibration↗
PubMed1996

A pencil beam algorithm for proton dose calculations.

The sharp lateral penumbra and the rapid fall-off of dose at the end of range of a proton beam are among the major advantages of proton radiation therapy. These beam characteristics depend on the position and characteristics of upstream beam-modifying devices such as apertures and compensating boluses. The extent of separation, if any, between these beam-modifying devices and the patient is particularly critical in this respect. We have developed a pencil beam algorithm for proton dose calculations which takes accurate account of the effects of materials upstream of the patient and of the air gap between them and the patient. The model includes a new approach to picking the locations of the pencil beams so as to more accurately model the penumbra and to more effectively account for the multiple-scattering effects of the media around the point of interest. We also present a faster broad-beam version of the algorithm which gives a reasonably accurate penumbra. Predictions of the algorithm and results from experiments performed in a large-field proton beam are presented. In general the algorithm agrees well with the measurements.

Algorithms↗
PubMed1993

Role of portal imaging in clinical radiotherapy: Florence experience.

A portal imaging device developed at the Netherlands' Cancer Institute (NKI) in Amsterdam was provided to the Radiotherapy Section of the University of Florence as a partner of a cooperative study on quality assurance (QUIRT) granted by the EC (AIM Project). The device was used for portal imaging in 30 patients treated for tumors of different sites (5 rectum, 6 prostate, 5 Hodgkin's lymphomas, 5 head and neck tumors, 9 other sites). Portal images were obtained three times per week over the whole treatment period. An off-line quantitative analysis of discrepancies with respect to the simulation image was performed for the 5 rectum cases; a similar analysis was also done on the portal images of 4 rectal cases treated at the NKI in Amsterdam. The analysis proved capable of demonstrating the existence of some systematic errors in both centres and the different level of global accuracy between them. The on-line use of the device was also able to demonstrate some major errors of patient setup during the first session, which were immediately corrected.

Head and Neck Neoplasms↗
PubMed1991

Quantitative magnetic resonance imaging in cervical carcinoma: a report on 30 cases.

T1 and T2 relaxation times were calculated, before radiation therapy, in 30 patients with cervical carcinoma. Eight healthy young women were submitted to magnetic resonance imaging (MRI) to determine T1 and T2 times of the normal cervix. Magnetic resonance imaging was repeated, in 22 patients, during radiation therapy and at follow-up. During treatment and follow-up, patients with complete tumour response showed a significant T1 reduction compared with the pre-treatment values. With persistence of palpable or visible tumour, T1 times showed a small decrease during therapy, and a marked increase at subsequent examinations. The results suggest that the modifications of T1 times, during radiation therapy and follow-up, could be considered as a useful discriminant between patients with differing tumour response.

Adult↗
PubMed1990

Determination of dependence of spin-lattice relaxation rate in serum upon concentration of added iron by magnetic resonance imaging.

Dependence of spin-lattice relaxation rate (1/T1) in serum upon concentration of added iron was studied in the concentration range 0.0179-0.179 mmol l-1 for each of ferrous and ferric iron. In conjunction with the serum study, 1/T1 in solutions of transferrin and a mixture of albumin and gamma globulin was also studied as a function of added iron concentration. At low concentrations 1/T1 in serum increases linearly with increasing amounts of iron for each ion, and then reaches saturation for ferrous iron, whereas it shows an inflection for ferric iron. To explain the partition of added iron between various serum components, the effect of iron on 1/T1 in serum was compared with those of transferrin and the mixture. This effect can be defined as relaxivity or the incremental increase in relaxation rate per millimolar of added iron. At low concentrations the relaxivities of iron in serum, about 0.91 mmol-1 l s-1 for ferric and 0.95 mmol-1 l s-1 for ferrous ion, approximate well to the relaxivity of iron in transferrin solutions, which was measured to be about 0.92 mmol-1 l s-1. Furthermore, at high concentrations the relaxivity of ferric iron in serum, 0.44 mmol-1 l s-1, becomes similar to that of the mixture which is about 0.39 mmol-1 l s-1. These findings imply that iron added to serum first satisfies the binding requirements of transferrin, and the binding of iron to the other serum proteins occurs at high concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗
PubMed1990

Fast multiphase MR imaging of aqueductal CSF flow: 1. Study of healthy subjects.

Gradient-echo MR sequences are more sensitive to flow phenomena than spin-echo sequences are. We investigated aqueductal CSF flow by fast multiphase imaging. Fast multiphase imaging offers the opportunity to perform a dynamic study of fluid motion that is synchronous with the cardiac cycle. A section perpendicular to the cerebral aqueduct was imaged in 18 healthy volunteers. Serial, gated (every 50 msec from the ECG R wave), flow-compensated modulus images with 70 degrees-flip-angle excitation pulses were obtained with a single acquisition. The behavior vs time of CSF signal in the aqueduct was compared with that in the lateral ventricles. The former showed a peak at 0.47 +/- 0.1 fractions of a heart cycle after the R wave. No periodicity with the heart rate was observed for the ventricular CSF signal intensity. The mean CSF signal intensity in the aqueduct was found to range from about twice to three times that in the lateral ventricles over a cardiac cycle. Fast multiphase imaging is a sensitive and practical sequence for the MR investigation of aqueductal CSF flow. Its potential in patients with hydrocephalus is studied in a companion article.

Adult↗
PubMed1990

Fast multiphase MR imaging of aqueductal CSF flow: 2. Study in patients with hydrocephalus.

The signal intensity in the region corresponding to the cerebral aqueduct was evaluated in three patients with noncommunicating tension hydrocephalus (caused by aqueductal obstruction in two and type I Arnold-Chiari malformation in the other), seven patients with suspected normal-pressure hydrocephalus (three of whom subsequently underwent successful shunting), and 10 patients with ex vacuo (atrophic) hydrocephalus. A gradient-echo MR sequence, called fast multiphase imaging, was used. Serial images corresponding to different phases of the cardiac cycle were acquired. No flow-related enhancement was observed over the entire cardiac cycle in the patients with noncommunicating hydrocephalus. Patients with normal-pressure hydrocephalus showed a higher aqueductal CSF signal intensity, consistent with increased systolic flow rates, than patients with ex vacuo hydrocephalus. When comparing the above two groups of patients with a control group of healthy volunteers, significantly higher and lower values of the (mean) maximum aqueductal signal intensity were found in the normal-pressure hydrocephalus patients and the ex vacuo hydrocephalus patients, respectively. Fast multiphase MR evaluation of aqueductal CSF flow may help to differentiate patients with different types of hydrocephalus.

Adult↗
PubMed1987

Modifications of relaxation times induced by radiation therapy in cervical carcinoma: preliminary results.

Pelvic Magnetic Resonance Imaging (MRI) was performed in eight healthy women and in eight patients with carcinoma of the cervix, using a 0.5 T superconductive magnet, to evaluate relaxation times of the normal uterine cervix and carcinomas. Spin-lattice (T1) and spin-spin (T2) relaxation times for skeletal muscle, adipose tissue and bone marrow of the epiphysis of the femur were also measured in all cases. In the group of patients with carcinoma of the cervix MRI was performed before, during and after radiation therapy. The mean T1 and T2 values for the normal uterine cervix and cervical carcinoma were evaluated. Mean spin-lattice time for carcinomas were confirmed to be higher than the mean calculated value for the normal cervix, while no significant variation was observed with respect to spin-spin time. A high individual T1 and T2 variability was noted not only in the group of patients affected by cervical carcinoma, but among the healthy subjects too. After radiation therapy a mean T1 time reduction of approximately 20% was found in cervical carcinomas compared with pretreatment measurements, whereas no difference was evident for T2 time. These preliminary results confirm that reduction in spin-lattice time is demonstrated in tumours submitted to radiation therapy. More detailed biological information, such as percentages of vital and necrotic cells, tissue water content and cellular kinetics are probably necessary for a clearer understanding of this phenomenon even in an apparently homogeneous group of patients.

Adult↗
PubMed1987

Magnetic resonance imaging of blood flow in thoracic vessels of patients with impaired left ventricular function.

In order to test the ability of magnetic resonance (MR) in the detection of pathologic flow conditions in man, we imaged 10 normal volunteers and 10 patients with congestive heart failure (CHF) with ECG-gated MR. We used a single spin-echo sequence on a transverse plane through the main vessels of the upper chest. The analysis of the variation of the mean signal intensity vs time from the ascending aorta (AA), descending aorta (DA), and pulmonary artery (PA) of the ten normal volunteers on the TE = 30 ms images, showed a common pattern characterized by an end-diastolic intraluminal signal not present in other moments of the cardiac cycle. On the contrary, in patients with CHF, we did not observe the systolic disappearance of the intraluminal MR signal. The main difference between CHF patients and control subjects was found in the DA where an abnormally high signal intensity was present for the whole cardiac cycle. The MR imaging can offer blood flow information underlying the behavior of intraluminal signal intensity and could provide functional information in patients with heart failure.

Adult↗
PubMedDate not supplied

Relaxation rates of paramagnetic solutions: evaluation by nuclear magnetic resonance imaging.

Methods for accurate calculation of nuclear magnetic resonance relaxation times are presented. Data from inversion recovery sequences with different delay times were fitted to derive T1 information on water solutions of paramagnetic ions. T2 values of the same samples were obtained by fitting signals from a multiecho sequence. According to the theory, for the field strength used (0.5 T), T1's and T2's are nearly equal and the enhancement of relaxation rates is found to be directly proportional to molar concentration. Tests performed suggest the opportunity of using the same approach in studies of tissues.

Biometry↗