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A Van de Graaff proton accelerator was tested for its application to the study of CR-39 SSNTD response to accelerated protons. The energies of the proton beams ranged from 0.2 to 2.3 MeV. Two different beam angles of incidence were taken into consideration for each proton energy (i.e. normal incidence and 45°). The complete procedure for the irradiation of a CR-39 sample required relatively little time and the results obtained — in agreement with others as reported in the literature — demonstrated that the Van de Graaff proton accelerator can find a useful application to the problem of neutron dosimetry using SSNTDs.

Background The routine follow-up of cardioverter defibrillators (CD) is a time-consuming procedure. Aim of the Study and Methods The present study was a prospective randomized cross-over evaluation on the clinical usefulness of a specific semi-automatic software algorithm (Quick Check) for CD follow-up, available in CPI Guidant systems (CD and programmer). Time-saving, while ensuring all the required data and patient safety, was evaluated in a large group of patients (105), recruited in different centers. In the same session and under a physician's supervision all patients underwent a follow-up with the aid of Quick Check or a standard follow-up, in a randomized sequence. Each patient served as his own control. Results In the overall population of 105 patients, the time spent for follow-up was reduced by Quick Check from 186±105 sec to 106±67 sec (pConclusions Use of a specific software algorithm for routine follow-up of implanted CDs allows a significant shortening of the time spent on routine follow-up, thus reducing costs. The supervision of a physician is a guarantee of patient safety.

Monte Carlo simulation for a silicon microstrip detector used for digital radiography.

Description of a hardare and software tool for simulation of the response of a silicon detectors to photons in the diagnostic energy range.

The management of patients with isolated congenital complete heart block is controversial, and indications for cardiac pacing are not clearly defined. In the present study we report our long-term experience in the management of patients with this disease.Thirty-eight consecutive patients aged 2 days to 28 years (mean age 10 years) were studied and followed up for 130 +/- 57 months (range 18 to 274). They underwent an extensive evaluation including history, physical examination, electrocardiography and echocardiography; thirty-seven patients had Holter monitoring and exercise test. Electrophysiologic study was performed in 24 patients.Twenty-two patients were asymptomatic, sixteen had symptoms as syncope or presyncope (7 patients), marked exercise intolerance (1 patient), presyncope and marked exercise intolerance (1 patient), heart failure (1 patient), mild dyspnea on exertion (6 patients). Electrocardiograms showed a narrow QRS in all patients. Holter monitoring showed a marked bradycardia (awake heart rateor = 55 beats/min in infants,or = 40 beats/min in children and adults) in 15 patients and junctional pauses of3 seconds in 9 of them. The exercise test showed a markedly reduced exercise tolerance in 2 patients and exercise-induced complex ventricular arrhythmias in 3 patients. Echocardiography showed a structurally normal heart and a normal left ventricular function in all patients. The electrophysiologic study always showed a suprahisian site of block. Twenty patients (53%) underwent cardiac pacing at a median age of 14 +/- 10 years and were followed up for 110 +/- 59 months (range 18 to 253) after pacing; prophylactic pacing was performed in 10 patients. Indications for cardiac pacing were: syncope or presyncope (7 patients), presyncope and marked exercise intolerance (1 patient), neonatal heart failure (1 patient), marked exercise intolerance (1 patient), neonatal marked bradycardia (2 patients), marked bradycardia with junctional pauses of3 seconds and/or complex ventricular arrhythmias (7 patients), complex ventricular arrhythmias (1 patient). No death occurred during the follow-up. In 9 of 20 patients who had cardiac pacing, indication for this procedure appeared during the follow-up (development of symptoms, marked bradycardia and/or complex ventricular arrhythmias). Complications of pacing were infrequent (9 complications in 7 patients) and mainly occurred in the first years of our experience. At present 12 patients have an atrioventricular sequential pacing and 8 have a rate-responsive ventricular one. All patients who had pacing showed an improvement of exercise tolerance; 11 of them underwent exercise test after pacing which showed a significant increase in exercise duration (from 11.1 +/- 1.9 to 15.3 +/- 1.1 min, p0.01). In the 3 patients with complex ventricular arrhythmias we observed their suppression after atrioventricular sequential pacing. At present 35 patients are asymptomatic and 3 have mild dyspnea on exertion.Our results confirm that patients with isolated congenital complete heart block often have symptoms and/or signs of electric instability without symptoms. Cardiac pacing relieves symptoms and improves working capacity. Although in this study we are not able to draw conclusions on the therapeutic value of prophylactic pacing, our favourable follow-up results suggest that this therapeutic approach may prevent complications.

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 relaxation times, during radiation therapy and follow-up, could be considered as a useful discriminant between patients with differing tumour response.

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)

The author starting from the electron beams production describes their interaction with matter in terms of stopping and diffusion. The "dose" and its spatial distribution is considered the physical parameter more suitable to describe the electron beams characteristics. Particularly, it is outlined that the experimental depth penetration curve of dose in water, can provide the parameter evaluation useful to characterize the electron beams both qualitatively and quantitatively, i.e.: beam dimensions at the entrance surface; mean energy Eo; maximum dose (Dmax) depth, R100; surface dose, Ds (% Dmax); depth of 50% of Dmax, R50; practical range, Rp; therapeutic range, R85. The operative steps are described as referred to the National Protocol of Standardization (basic dosimetry).

Methods for accurate calculation of nuclear magnetic resonancerelaxation times are presented. Data from inversion recovery sequences with different delay times were fitted to derive T 1 information on water solutions of paramagnetic ions. T 2 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), T 1’s and T 2’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.

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 carinoma, 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.

An unexpected clinical presentation of an unusual pacing failure has been observed in two patients who had had recent implantation of a pacemaker model whose electrodes were made of an nonnoble metal alloy. An intermittent current leakage from the output capacitor and possibly from the output transistor accounted for electrolytic corrosion at the anode, premature depletion of the battery, heart muscle damage and for massive gas generation around electrodes, leading to right ventricular perforation, pneumopericardium and subcutaneous thoracic emphysema. The occurrence of this syndrome shows that, if nonnoble metals are used for electrodes, more attention should be addressed to those conditions which add to polarization problems, as is current leakage from the output circuit components.

The proton spin-lattice relaxation time T1 in iron-doped serum was measured with a magnetic resonance imager operating at 0.5 T. The T1 in aqueous solutions of iron and iron-doped solutions of albumin and gamma globulin was also measured in order to analyse the paramagnetic contribution in iron-doped serum. The enhancement in serum is not linearly dependent on concentration of iron added. It is known that Fe(III) added to serum is mainly complexed with transferrin, albumin, gamma globulin and water. With serum pH (7.9) Fe(III) in the protein solution results in enhancement. Fe(III) in water does not cause any enhancement. As a result, the 1/T1 enhancement in serum should be caused solely by iron-binding serum proteins.

The reverse transcriptase of avian myeloblastosis virus (AMV) exists either as a dimer of two polypeptides or as a single polypeptide, designated αβ and α, respectively. Both the α and αβ forms of the enzyme possess DNA polymerase and RNase H activities (EC 3.1.4.34). Antisera raised in rabbits against the α and αβ forms inhibit the DNA polymerase activity of both forms but only the RNase H activity of the enzyme form used as immunogen. Antibody specifically inhibitory for αβ RNase H activity can be absorbed by purified α, and antibody specifically inhibitory for α RNase H activity can be absorbed by purified αβ. These data indicate that antibodies against α and αβ forms of AMV reverse transcriptase recognize distinct antigenic determinants present on α and that the α and αβ forms differ in the steric relationship of these determinants to the RNase H active site. These results are consistent with possible functional differences between the RNase H activity of the α and αβ forms of AMV reverse transcriptase.

According to a recent national survey, 387 patients were treated by permanent pacing in 10 Italian centers, between 1961 and 1966. Of these patients 205 have died; 131 (77 males and 54 females) are still alive and no informations could be obtained for the remaining 51 (13%). The overall survival of patients treated during this period of time is therefore not less than 34% which is comparable to that of general population of the same age group. The 131 patients still alive have totaled 1,486 years of pacing and have used up to 784 pacers. Comparing the incidence of the most common causes for replacement during the periods 1961-66 and 1973-77, electrode failures dropped from 21 to 0.9%; circuitry malfunctions occurred in 10.5 and 7.8%; battery depletion rose from 36.8 to 69% of the cases. According to their clinical conditions, the 131 patients on long-term follow-up can be grouped as follows: 62% are in class 1 or 2 of NYHA; 26.7% are in class 3, and 3.8% in class 4. Moreover, 53.4% of patients are living an active life, having some sort of occupation and 29% are holding a driving license.