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Biomedical subjects

G Loi

Publications and source records attributed to G Loi.

At least 19 recordsLinked to original sources
PubMed2006

HCV infection and chronic arthritis: Does viral replication matter?

BACKGROUND: HCV infection beside chronic hepatitis can induce immunological disorders with different clinical expressions such as chronic arthritis. AIM: To study the prevalence of arthritis in HCV-Ab positive patients and verify possible correlation with viral replication, hepatic damage and autoimmunity imbalance. STUDY DESIGN: Three hundred and eighty patients (196 M and 184 F) affected by HCV infection were examined and 38 (10%) were selected according to the presence of arthritis. Eight of them were excluded because arthritis raised before HCV infection. Each patient, once undergone liver biopsy, was evaluated for: clinical examination (articular evolution), Rx examination, serum expression of hepatic damage (mainly ALT), viral replication, and involvement of autoimmunity (ANA, RF, crioglobulins, AKA, CCP). RESULTS: Data from patients [Lamprecht P, Gause A, Gross WL. Cryoglobulinemic vasculitis. Arthritis Rheum 1999; 42:2507-16.] with AKA and CCP positivity were not considered for statistical examination because the clear correlation between rheumatoid arthritis and these parameters. The remaining 20 patients showed hepatic damage 47%, viral replication in 74%, RF 42%, ANA 16%, crioglobulins 42% (RF positive). No correlation was evident between ANA serum concentrations and viral replication; furthermore a significant negative correlation between RF positivity and viral replication only in a subgroup of patients with serologic expression of hepatic damage was found. CONCLUSIONS: These data support hypothesis that the onset of arthritis and presence of autoimmunity parameters ANA, RF are not related to the viral replication but others mechanism immunological induced by HCV might be considered.

Journal Article↗
PubMed2006

Neutron production from a mobile linear accelerator operating in electron mode for intraoperative radiation therapy.

Intraoperative electron beam radiotherapy is increasingly performed using mobile linac delivering therapeutic radiation doses in unshielded operating rooms. While no special neutron-shielding problem should arise for operation at 10 MeV or less, it is not clear whether this holds true for operation at higher energies. This paper reports the measured neutron production from a Mobetron mobile electron linac, operated at 12 MeV, and compares the results with those from a conventional linac, also operated at 12 MeV in electron mode. Neutron leakage measurements were performed by means of passive bubble detectors in the scattering foil, patient and floor planes. Neutron dose equivalent rates per unit of electron dose delivered by the Mobetron at its normal treatment distance (50 cm SSD) were 0.33 microSv Gy(-1) at the accelerator head, 0.18 microSv Gy(-1) in the patient plane at 15 cm from the beam axis and 0.31 microSv Gy(-1) at the floor plane, on the beam axis and under the beam stopper. For a weekly workload of 250 Gy, the weekly neutron dose equivalents at 12 MeV for the Mobetron at a distance of 300 cm from the scattering foil were 14.3 and 1.7 microSv/week for floor below and adjoining areas on the same floor, respectively. Neutron dose equivalent rates generated from Mobetron are at least one order of magnitude lower than ones produced by a conventional linac operated at the same energy in electron mode. Mobetron can be used at 12 MeV in an unshielded operating room for a weekly workload of up to 250 Gy if the bremsstrahlung x-rays are shielded to negligible levels.

Combined Modality Therapy↗
PubMed2004

Frontal cortical perfusion abnormalities related to gluten intake and associated autoimmune disease in adult coeliac disease: 99mTc-ECD brain SPECT study.

OBJECTIVE: Since brain perfusion abnormalities have been described by single-photon emission computed tomography in some autoimmune diseases, the aim of the present study was to evaluate the incidence of perfusion abnormalities by brain single-photon emission computed tomography in a group of coeliac disease patients, and to investigate whether gluten intake and associated autoimmune diseases may be considered risk factors in causing cerebral impairment. METHODS: Thirty-four adult coeliac patients (16 on a gluten-free diet and 18 on a gluten-containing diet, 18 (53%) with autoimmune diseases) underwent 99mTc-ethyl cysteinate dimer brain single-photon emission computed tomography and qualitative evaluation of brain perfusion was performed together with a semiquantitative estimation using the asymmetry index. Ten subjects on our database, matched for sex, age and ethnic group, who were proved normal by histology ofjejunal mucosa (four males and six females; median age 39 years, range 27-55 years), were included as control group. RESULTS: Twenty-four out of 34 patients (71%) showed brain single-photon emission computed tomography abnormalities confirmed by abnormal regional asymmetry index (>5%; range 5.8-18.5%). Topographic comparison of the brain areas showed that the more significant abnormalities were localised in frontal regions, and were significantly different from controls only in coeliac disease patients on unrestricted diet. The prevalence of single-photon emission computed tomography abnormalities was similar in coeliac disease patients with (74%) and without (69%) associated autoimmune disease. CONCLUSIONS: Abnormalities of brain perfusion seem common in coeliac disease. This phenomenon is similar to that previously described in other autoimmune diseases, but does not appear to be related to associated autoimmunity and, at least in the frontal region, may be improved by a gluten-free diet.

Adult↗
PubMed2001

Frequency decomposition and compounding of ultrasound medical images with wavelet packets.

Ultrasound beams propagating in biological tissues undergo distortions due to local inhomogeneities of the acoustic parameters and the nonlinearity of the medium. The spectral analysis of the radio-frequency (RF) backscattered signals may yield important clinical information in the field of tissue characterization, as well as enhancing the detectability of tissue parenchymal diseases. In this paper, we propose a new tissue spectral imaging technique based on the wavelet packets (WP) decomposition. In a conventional ultrasound imaging system, the received echo-signals are generally decimated to generate a medical image, with a loss of information. With the proposed approach, all the RF data are processed to generate a set of frequency subband images. The ultrasound echo signals are simultaneously frequency decomposed and decimated, by using two quadrature mirror filters, followed by a dyadic subsampling. In addition, to enhance the lesion detectability and the image quality, we apply a nonlinear filter to reduce noise in each subband image. The proposed method requires simple additional signal processing and it can be implemented on any real-time imaging system. The frequency subband images, which are available simultaneously, can be either used in a multispectral display or summed up together to reduce speckle noise. To localize the different frequency response in the tissues, we propose a multifrequency display method where three different subband images, chosen among those available, are encoded as red, green, and blue intensities (RGB) to create a false-colored RGB image. According to the clinical application, different choices can evidence different spectral proprieties in the biological tissue under investigation. To enhance the lesion contrast in a grey-level image, one of the possible methods is the summation of the images obtained from narrow frequency subbands, according to the frequency compounding technique. We show that by adding the denoised subband images created with the WP decomposition, the contrast-to-noise ratio in two phantom images is largely increased.

Image Processing, Computer-Assisted↗
PubMed1999

Accuracy evaluation of fusion of CT, MR, and spect images using commercially available software packages (SRS PLATO and IFS).

PURPOSE: A problem for clinicians is to mentally integrate information from multiple diagnostic sources, such as computed tomography (CT), magnetic resonance (MR), and single photon emission computed tomography (SPECT), whose images give anatomic and metabolic information. METHODS AND MATERIALS: To combine this different imaging procedure information, and to overlay correspondent slices, we used commercially available software packages (SRS PLATO and IFS). The algorithms utilize a fiducial-based coordinate system (or frame) with 3 N-shaped markers, which allows coordinate transformation of a clinical examination data set (9 spots for each transaxial section) to a stereotactic coordinate system. The N-shaped markers were filled with fluids visible in each modality (gadolinium for MR, calcium chloride for CT, and 99mTc for SPECT). The frame is relocatable, in the different acquisition modalities, by means of a head holder to which a face mask is fixed so as to immobilize the patient. Position errors due to the algorithms were obtained by evaluating the stereotactic coordinates of five sources detectable in each modality. RESULTS: SPECT and MR position errors due to the algorithms were evaluated with respect to CT: deltax was < or = 0.9 mm for MR and < or = 1.4 mm for SPECT, deltay was < or = 1 mm and < or = 3 mm for MR and SPECT, respectively. Maximal differences in distance between estimated and actual fiducial centers (geometric mismatch) were in the order of the pixel size (0.8 mm for CT, 1.4 mm for MR, and 1.8 mm for SPECT). In an attempt to distinguish necrosis from residual disease, the image fusion protocol was studied in 35 primary or metastatic brain tumor patients. CONCLUSIONS: The image fusion technique has a good degree of accuracy as well as the potential to improve the specificity of tissue identification and the precision of the subsequent treatment planning.

Algorithms↗
PubMed1999

Dosimetry of Gamma Knife and linac-based radiosurgery using radiochromic and diode detectors.

In stereotactic radiosurgery the choice of appropriate detectors, whether for absolute or relative dosimetry, is very important due to the steep dose gradient and the incomplete lateral electronic equilibrium. For both linac-based and Leksell Gamma Knife radiosurgery units, we tested the use of calibrated radiochromic film to measure absolute doses and relative dose distributions. In addition a small diode was used to estimate the relative output factors. The data obtained using radiochromic and diode detectors were compared with measurements performed with other conventional methods of dosimetry, with calculated values by treatment planning systems and with data prestored in the treatment planning system supplied by the Leksell Gamma Knife (LGK) vendor. Two stereotactic radiosurgery techniques were considered: Leksell Gamma Knife (using gamma-rays from 60Co) and linac-based radiosurgery (LR) (6 MV x-rays). Different detectors were used for both relative and absolute dosimetry: relative output factors (OFs) were estimated by using radiochromic and radiographic films and a small diode; relative dose distributions in the axial and coronal planes of a spherical polystyrene phantom were measured using radiochromic film and calculated by two different treatment planning systems (TPSs). The absolute dose at the sphere centre was measured by radiochromic film and a small ionization chamber. An accurate selection of radiochromic film was made: samples of unexposed film showing a percentage standard deviation of less than 3% were used for relative dose profiles, and for absolute dose and OF evaluations this value was reduced to 1.5%. Moreover a proper calibration curve was made for each set of measurements. With regard to absolute doses, the results obtained with the ionization chamber are in good correlation with radiochromic film-generated data, for both LGK and LR, showing a dose difference of less than 1%. The output factor evaluations, performed using different methods, are in good agreement with a maximum difference of 1.5% for all field sizes considered (LGK and LR) except the 4 mm helmet used in the LGK unit. In this case, differences exist between diode and radiochromic film measurements and both detectors show data values larger than the prestored OF value of 0.80. Dose profiles measured by radiochromic film and calculated are in excellent agreement for both LGK and LR with a maximum deviation of less than 1.0 mm, when full widths of the dose profiles at 20%, 50%, 80% levels are considered. When external photon beams are used in stereotactic radiosurgery, the 'well selected' radiochromic films are very accurate detectors both for relative and absolute dosimetry. The experimental results, obtained using both radiochromic and diode detectors, show that the 4 mm helmet relative output factor could be underestimated.

Film Dosimetry↗
PubMed1998

Design and characterization of a dynamic multileaf collimator.

The characteristics of a prototype computer-assisted dynamic multileaf collimator (DMLC), specifically designed for small-field conformal radiotherapy, were evaluated at the Istituto Nazionale Tumori of Milan. The collimating device consists of two opposing banks of 16 pairs of 8 cm thick, 3.6 mm wide tungsten leaves and allows shaping of a radiation field up to a size of 10 x 10 cm2 at the isocentre. The screening thickness of each leaf is 6.25 mm at the accelerator gantry isocentre. The leaves have a trapezoidal cross section and move along an arched path, thus providing a 'double focused' collimation system. The DMLC was installed on the head of a Varian Clinac 2100C linear accelerator. Mechanical and dosimetric evaluations were performed to test the stability of the mechanical isocentre and to determine leaf leakage, penumbra width, accuracy of leaf positions and uniformity of leaf speed. Displacement of the mechanical isocentre was less than 1 mm at all gantry angles. Standard radiographic films exposed to 6 MV x-ray radiation were used for dosimetric evaluations. Leakage between leaves was less than 2.5%, and leakage through abutted leaves was less than 5.5%. The penumbra width between 20% and 80% isodose at different positions of leaf banks was 2.7 mm in the direction of the leaf motion and 3.1 mm along the side of the leaf with a standard deviation of 0.2 mm in both directions. Accuracy in the positioning of the leaf was 0.3 mm, whereas the maximum repositioning error was less than 0.2 mm. Finally, during movement of the leaves at the maximum speed of 0.5 mm s(-1), the standard deviation of the leaf positioning error was 0.2 mm, proving an accurate uniformity of leaf speed.

Neoplasms↗
PubMed1996

Double phase parathyroid technetium-99m-MIBI scintigraphy to identify functional autonomy in secondary hyperparathyroidism.

UNLABELLED: Double-phase 99mTc-methoxyisobutylisonitrile (MIBI) parathyroid scintigraphy has been proposed to detect hyperplastic parathyroid tissue, but the clinical usefulness of this technique in secondary hyperparathyroidism is still debated. METHODS: Technetium-99m-MIBI parathyroid scintigraphy associated with parathyroid echography and [99mTc]pertechnetate thyroid scans were performed on 38 patients with chronic renal failure (CRF) and secondary hyperparathyroidism. In all patients, serum calcium, phosphorus, FT3, FT4, TSH, calcitonin and intact PTH (iPTH) were determined. Nine patients eventually underwent neck exploration and 28 parathyroid glands were removed. RESULTS: Thyroid diseases were excluded in all patients. Echography revealed parathyroid enlargement in 22/38 (58%) patients, while MIBI scintigraphy was positive in 28/38 (74%), including 5 ectopic glands. Mean serum iPTH concentration was significantly higher in MIBI-positive glands compared to MIBI-negative glands, but several discrepancies were observed in single patients. A significant positive correlation between serum iPTH and gland size was observed when MIBI-positive, but not MIBI-negative, parathyroids were considered. A paradoxical positive correlation between serum calcium and iPTH concentrations was found in MIBI-positive patients. CONCLUSION: Double-phase 99mTc-MIBI scintigraphy is positive in the majority of patients with uremic hyperparathyroidism. Comparison of scintigraphic data with morphological and functional data strongly suggests that 99mTc-MIBI scans do not reveal simple parathyroid enlargement but rather, identify the presence of hyperfunctioning (autonomous) parathyroid tissue suggestive of tertiary hyperparathyroidism.

Adult↗
PubMed1995

[Design, development, and dosage control of individual compensatory filters for 6 MV X-ray radiotherapy].

An automated system for the design and manufacturing of individual compensators has been implemented. The system based on computed tomography enables 3D compensation of missing tissue and tissue heterogeneities. The relationship between Hounsfield numbers and electron densities was obtained empirically. Compensator design is based on the calculation of the water equivalent thicknesses between the compensation plane and the patient surface. After calculation a styrofoam mould is cut by a computer driven machine and filled with bee's wax or tin granules. Compensator thickness is calculated by means of the conversion ratio tau, which is defined as t/x, where t is the compensator thickness equivalent to the missing tissue in the treatment geometry. Relations between tau and field size, depth of compensation plane and focus-compensation plane distance were assessed. The conversion ratio is a linear function of the missing tissue and depends markedly on field size; for a 10-cm-deep compensation plane at 1 m from the accelerator target the tau value, calculated for bee's wax, decreases by 25% from 7 x 7 cm2 to 23 x 23 cm2 field size. Conversion ratio rises by approximately 10% for a 3-cm increase in compensation plane depth and reduces by about 5% when increasing the focus-compensation plane distance from 100 cm to 140 cm. It must be stressed that a 10% variation of tau, for bee's wax, involves only a 2% dose variation in the compensation plane. Therefore, for compensator design it is enough to consider tau as depending on field size only. Compensation effectiveness has been tested by a film-densitometric technique using phantoms with tilted incident surfaces and heterogeneities. The results show that the compensators reduce the flatness of the beam profile below 4% and increase the relative dose uniformity on the compensation plane from 18% to 60%.

Filtration↗
PubMed1993

Microbial purification technique of mineral dressing plants reject waters.

Earlier investigations on laboratory and pilot plant scale have shown the resort to microorganisms to be a practicable approach to the problem of purifying mineral dressing plant reject waters from residual flotation reagents and/or metal ions. In spite of the proven effectiveness of this method, one major drawback, namely the pathogenicity of some microorganisms, has so far hampered its application on a commercial scale. A research programme, aimed at developing a microbial reject water purification technique utilizing non-pathogenic strains was thus drawn up and is currently being implemented. Strains such as Bacillus subtilis, Saccharomyces cerevisiae, Bifidobacterium bifidum, Lactobacillus acidophilus and Acinetobacter calcoaceticus, which are not harmful to human health, some of them being commonly found in the human intestine, have been successfully tested for removing alkylsulphates, alkylamines and fatty acids from solutions simulating flotation plant tailings waters. Removals as high as 90% in less than 48 h can be easily achieved with no nutrient requirements, since in most cases the flotation reagent residue to be removed is metabolized by the microorganisms themselves.

Acinetobacter calcoaceticus↗
PubMed1990

[Diagnosis of hepatic hemangioma with simplified double 99mTc labelling].

The authors report on their experience with liver hemangioma (LH) diagnosis by means of a simplified method--that is, the simultaneous, in vivo, double labelling of liver reticuloendothelial system (RES) and of red blood cells (RBC) by 99mTc. Twenty-eight patients with US diagnosis of suspected LH and 15 controls were examined after sequential iv injection of SnCl2, of 99mTc-mucolloid albumin and, after liver scintigraphy, of 99mTc-pertechnetate to conclude in vivo RBC labelling. All patients underwent CT and, if necessary, CT-guided biopsy. Focal colloid defects filled after RBC labelling were shown in 20/22 patients with unquestionable LH. No colloid defects were shown in 6/28 cases (expansive process). 15/15 controls showed unchanged non-filling defects after double labelling. Finally, the authors point out that, in the diagnosis of LH, sequential double labelling of liver RES and RBC appears to be a quicker scintigraphic technique than conventional ones. Moreover, this technique has the same high specificity and sensitivity as more time-consuming ones.

Adult↗