Antioxidant capacity and protein oxidation in cerebrospinal fluid of amyotrophic lateral sclerosis.

BACKGROUND: The causes of Amyotrophic Lateral Sclerosis (ALS) are unknown. A bulk of evidence supports the hypothesis that oxidative stress and mitochondrial dysfunction can be implicated in ALS pathogenesis. METHODS =: We assessed, in cerebrospinal fluid (CSF) and in plasma of 49 ALS patients and 8 controls, the amount of oxidized proteins (AOPP, advanced oxidation protein products), the total antioxidant capacity (FRA, the ferric reducing ability), and, in CSF, two oxidation products, the 4-hydroxynonenal and the sum of nitrites plus nitrates. RESULTS: The FRA was decreased (p = 0.003) in CSF, and AOPP were increased in both CSF (p = 0.0039) and plasma (p = 0.001) of ALS patients. The content of AOPP was differently represented in CSF of ALS clinical subsets, resulting in increase in the common and pseudopolyneuropathic forms (p < 0.001) and nearly undetectable in the bulbar form, as in controls. The sum of nitrites plus nitrates and 4-hydroxynonenal were unchanged in ALS patients compared with controls. CONCLUSION: Our results, while confirming the occurrence of oxidative stress in ALS, indicate how its effects can be stratified and therefore implicated differently in the pathogenesis of different clinical forms of ALS.

[A method for optimizing the estimation of the dose to the patient in traditional radiology]. / Un metodo per l'ottimizzazione della stima della dose al paziente nella radiologia tradizionale.

INTRODUCTION: The method recommended by Report no. 34 (1982) of the International Commission on Radiological Protection (ICRP) for patient dose computation in diagnostic radiology is based on tabulated dosimetric data obtained from Monte Carlo simulations on anthropomorphic phantoms described by simple mathematical functions. When computing the dose absorbed by an adult patient, this method suffers from two main limitations: first, the geometrical parameters--and in particular focus-to-film distance and film size--are fixed, which makes the dosimetric data of limited use when the examination geometry differs from the ICRP standard. In addition, when patient size and mass differ considerably from the corresponding quantities of the mathematically described phantom (the so-called reference man, with a height of 174 cm and a mass of 70.9 kg) the ICRP method may lead to great errors in dose estimate. The aim of the present paper is to indicate a method to overcome the above limitations. MATERIAL AND METHODS: The algorithm proposed in this work is based on the method suggested by Huda and Gkanatsios in order to compute the effective dose through a linear first of the energy imparted per unit dose-area product as a function of the half value thickness and by using fit coefficients depending on both phantom thickness and peak voltage. We devised a procedure to normalize the dose computed with this methods with respect to the equivalent effective dose obtained with the ICRP method. We therefore determined the dependence of the absorbed dose on focus-to-film distance, film size and patient anatomy. RESULT AND DISCUSSION: We found that--for each value of patient mass--the dose dependence on film size can be approximated by a polynomial function, while the dose dependence on focus-to-film distance can be approximated by a power law. If the above parameters vary in a limited range close to the ICRP standard, a linear fit can be performed without introducing a considerable error. The linear fit coefficients, on the other hand, were found to depend on the average body surface, a parameter which takes into account both patient height and mass. Thus, determining the normalization factor for each projection and each view allows to estimate the absorbed dose under different geometrical conditions. The method has been verified by considering four of the most common X-ray procedures (chest AP, cervical spine LAT, lumbar spine AP and head LAT). CONCLUSIONS: The average error on dose estimation is about 13%. In the very next future the method will be extended to all the projections and views of ICRP Report no. 34, and we plan to integrate the described algorithm in a computer program devoted to the automatic computation of patient dose.

[A method for quantitative evaluation of the physical quality of radiologic devices]. / Un metodo per la valutazione quantitativa della qualità fisica delle apparecchiature radiologiche.

INTRODUCTION: The evaluation of the quality of a radiological device depends on both clinical judgement about diagnostic imaging and physical judgement about technical performance. The latter is the final result of a set of measurements of several physical quantities. The aim of the present paper is to make a synthesis of such measurements through a parameter whose comparison with a threshold value would allow to establish whether a given radiological machine is acceptable from the point of view of physical quality. MATERIAL AND METHODS: The parameter, which we called quality index, was obtained by considering, for each operating condition, the values of physical quantities which exceed their limits and by giving them a different weight, depending on their influence on image quality, patient dose, or both. Further analysis led to assign a gravity index to such quantities as a function of the extent of the discrepancies with respect to their limits. RESULTS AND DISCUSSION: The method was illustrated through the example of a simple radiological equipment with two separate hypothetical cases corresponding to different degrees of fault gravity. The method gave very different values of quality index, according to the extent of discrepancies found in the two cases. We gave suggestions about the way to follow in order to determine a proper threshold value for each kind of equipment. The invariance of the method with respect to the choice of the physical quantities and their limits was also shown. CONCLUSIONS: The proposed method appears to be useful because it makes a synthesis, through a single parameter, of a series of measurements of several physical quantities and allows to discriminate, through direct comparison with a threshold value, about the physical quality of a radiological device; in addition, it may be easily implemented into programs for the automated analysis of quality controls. The quality index may contribute, together with some other parameters to be defined in a forthcoming paper, in establishing a quantitative criterion in order to define equipment replacement priorities within the context of the technological improvement requested by the laws currently in force.

[Assessment of potential exposure risk for radiotherapy staff working with lineal accelerators]. / Valutazione del rischio da esposizioni potenziali per il personale operante con acceleratori lineari per radioterapia.

INTRODUCTION: Radiation exposure to the radiotherapy staff operating with linear accelerators comes from both normal exposure, which can be easily quantified by direct measurement, and potential exposure, whose evaluation is made difficult by its stochastic character. International guidelines recommend that risk be of the same order of magnitude for both types of exposure. We evaluated the health risk associated with potential exposure following the fault-tree approach suggested by the International Commission on Radiological Protection (IRCP) in its Publication 76. MATERIAL AND METHODS: Considering a typical radiotherapy installation we identified four possible staff irradiation scenarios, namely: 1) entry into the treatment room after a high-energy photon beam treatment, when induced radioactivity from photonuclear reactions has not decayed; 2) unintentional entry into the treatment room when the radiation beam is on; 3) beam failing to turn off at the end of treatment, and subsequent entry into the treatment room; 4) treatment room door inadvertently left ajar, and subsequent entry when the radiation beam is on. Each scenario depends on a particular set of parameters which are related to failure probabilities and workload. Average absorbed dose, exposure probability and related risk have been evaluated for each scenario. RESULTS: Under standard parameter set-up, the overall risk did not exceed the IRCP threshold (i.e., .0002) by more than four orders of magnitude. Two main sources of potential exposure have been identified, that is early entry into the treatment room before safe decay of activation products and unintentional entry during treatment. By varying the parameters within reasonable ranges, risk has been shown to correlate with personnel training, workload, installation characteristics and operational procedures. To optimize protection, quantitative limitations have been set for human error probability, daily workload, number and quality of safety devices and waiting time before entry after a treatment with high-energy radiations. CONCLUSIONS: Although the potential exposure risk for a typical radiotherapy department with standard safety devices is well below international recommended values, our results indicate that risk can be further decreased by improving personnel training, in particular relative to minimum time to entry after a high-energy treatment, to respecting warning signs and being skilled in emergency procedures. In addition, failing to install some safety devices or removing them after a failure may result in rapidly exceeding IRCP thresholds.

[Automated procedures for radiation protection and quality controls in conventional diagnostic radiology]. / Automatizzazione delle procedure per i controlli di qualità e radioprotezionistici nella radiodiagnostica tradizionale.

To comply with regulations on radiation protection and quality controls is a difficult task when operating in large hospitals. This leads to the need of defining more efficient protocols and of making procedures as automated as possible. The procedure described in this paper is based on a multimeter controlled by a portable PC, and on a spreadsheet program for data processing. Multimeter data are automatically imported and processed, in order to assess the compliance of measured parameters with the reference regulations (IEC recommendations, radiation safety rules, etc.). The spreadsheet is permanently linked to a data base. It is therefore possible to perform the controls and to store the corresponding results in a shorter time (one hour per machine, approximately). By using a properly chosen quality index, monitoring the efficiency of the diagnostic equipment is also possible, which allows to prevent the onset of severe failures.