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F Gómez

Publications and source records attributed to F Gómez.

At least 19 recordsLinked to original sources
PubMed2006

Verification of intensity modulated profiles using a pixel segmented liquid-filled linear array.

A liquid isooctane (C8H18) filled ionization chamber linear array developed for radiotherapy quality assurance, consisting of 128 pixels (each of them with a 1.7 mm pitch), has been used to acquire profiles of several intensity modulated fields. The results were compared with film measurements using the gamma test. The comparisons show a very good matching, even in high gradient dose regions. The volume-averaging effect of the pixels is negligible and the spatial resolution is enough to verify these regions. However, some mismatches between the detectors have been found in regions where low-energy scattered photons significantly contribute to the total dose. These differences are not very important (in fact, the measurements of both detectors are in agreement using the gamma test with tolerances of 3% and 3 mm in most of those regions), and may be associated with the film energy dependence. In addition, the linear array repeatability (0.27% one standard deviation) is much better than the film one ( approximately 3%). The good repeatability, small pixel size and high spatial resolution make the detector ideal for the real time profile verification of high gradient beam profiles like those present in intensity modulated radiation therapy and radiosurgery.

Computer Graphics↗
PubMed2006

Monte Carlo correction factors for a Farmer 0.6 cm3 ion chamber dose measurement in the build-up region of the 6 MV clinical beam.

Reference dosimetry of photon fields is a well-established subject and currently available protocols (such as the IAEA TRS-398 and AAPM TG-51) provide methods for converting the ionization chamber (IC) reading into dose to water, provided reference conditions of charged particle equilibrium (CPE) are fulfilled. But these protocols cannot deal with the build-up region, where the lack of CPE limits the applicability of the cavity theorems and so the chamber correction factors become depth dependent. By explicitly including the IC geometry in the Monte Carlo simulations, depth-dependent dose correction factors are calculated for a PTW 30001 0.6 cm(3) ion chamber in the build-up region of the 6 MV photon beam. The corrected percentage depth dose (PDD) agrees within 2% with that measured using the NACP 02 plane-parallel ion chamber in the build-up region at depths greater than 0.4 cm, where the Farmer chamber wall reaches the phantom surface.

Calibration↗
PubMed2006

Solid mesenchymal hamartoma in an adult: a case report.

Mesenchymal hamartoma of the liver (MHL) is an uncommon tumour composed of architecturally abnormal bile ducts in an uncommitted myxoid stroma. Most MHL are diagnosed in childhood and few cases have been reported in adults. This report describes a case of a well defined solid mass in the right lobe of the liver in a 51 year old man. Preoperative radiological examination revealed a large completely solid mass. Biopsy showed a dense fibrous stroma with hyalinisation and some bile ducts. A provisional diagnosis of MHL was made. Surgical excision was impossible and liver transplantation was undertaken. Definitive pathology confirmed the diagnosis. Review of published reports shows this to be the fourth case of MHL treated by liver transplantation.

Hamartoma↗
PubMed2005

Monte Carlo study of Siemens PRIMUS photoneutron production.

Neutron production in radiotherapy facilities has been studied from the early days of modern linacs. Detailed studies are now possible using photoneutron capabilities of general-purpose Monte Carlo codes at energies of interest in medical physics. The present work studies the effects of modelling different accelerator head and room geometries on the neutron fluence and spectra predicted via Monte Carlo. The results from the simulation of a 15 MV Siemens PRIMUS linac show an 80% increase in the fluence scored at the isocentre when, besides modelling the components necessary for electron/photon simulations, other massive accelerator head components are included. Neutron fluence dependence on inner treatment room volume is analysed showing that thermal neutrons have a 'gaseous' behaviour and then a 1/V dependence. Neutron fluence maps for three energy ranges, fast (E > 0.1 MeV), epithermal (1 eV < E < 0.1 MeV) and thermal (E < 1 eV), are also presented and the influence of the head components on them is discussed.

Monte Carlo Method↗
PubMed2005

Study and culture of haematopoietic progenitor cells from peripheral blood in rats, hamsters and mice.

The aim of this work was to isolate and cultivate a subpopulation of pluripotent stem cells present in peripheral blood of different animal species, frequently used in laboratory studies (mice, rats and hamsters). Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker, specific for haematopoietic stem cells. Commonly used human commercial media were investigated for culturing animal PSCs. These findings suggest that this simple and standardized methodology may be applicable in several fields such as the study of the pharmacological effects of drugs on the haematopoietic line and the study of new strategies in cellular therapy for some human diseases.

Animals↗
PubMed2005

Development and operation of a pixel segmented liquid-filled linear array for radiotherapy quality assurance.

A liquid isooctane (C(8)H(18)) filled ionization linear array for radiotherapy quality assurance has been designed, built and tested. The detector consists of 128 pixels, each of them with an area of 1.7 mm x 1.7 mm and a gap of 0.5 mm. The small pixel size makes the detector ideal for high gradient beam profiles such as those present in intensity modulated radiation therapy (IMRT) and radiosurgery. As the read-out electronics we use the X-ray Data Acquisition System with the Xchip developed by the CCLRC. Studies concerning the collection efficiency dependence on the polarization voltage and on the dose rate have been made in order to optimize the device operation. In the first tests, we have studied dose rate and energy dependences. Dose rate dependence was found to be lower than 2.1% up to 5 Gy min(-1), and energy dependence lower than 2.5% up to 20 cm depth in solid water. Output factors and penumbras for several rectangular fields have been measured with the linear array and were compared with the results obtained with a 0.125 cm(3) air ionization chamber and radiographic film, respectively. Finally, we have acquired profiles for an IMRT field and for a virtual wedge. These profiles have also been compared with radiographic film measurements. All the comparisons show a good correspondence. The device has proved its capability to verify on-line therapy beams with good spatial resolution and signal-to-noise ratio.

Dose-Response Relationship, Radiation↗
PubMed2005

Liver transplantation at the Cuban Center for Medical and Surgical Research.

From July 4, 1999, when a liver transplantation program was started in Cuba, to October 2003, 66 procedures had been performed in 60 patients. The most frequent reason was cirrhosis caused by hepatitis C virus (29%), and alcoholic cirrhosis (22%). Two patients received simultaneous liver-kidney transplants. Half of the patients were men. Patient ages ranged from 12 to 62 years; the average surgical time was 6 hours; and cold ischemia time was 4 to 14 hours. The average blood consumption was 2033 mL; 2900 mL of plasma and 8 units of platelets were used in 7 cases. Immunosuppression was mainly cyclosporine (Neoral), mycophenolate mofetil or azathioprine, and prednisone. Acute cellular rejections were treated in almost all cases with 3 doses of methylprednisolone. The most frequent complications were biliary (24%), hepatic arterial thrombosis (12%), post-surgical bleeding (10%), acute cellular rejection (24%), and ductopenic rejection (2%). The overall 1-year survival rate was 73.7%.

Cuba↗
PubMed2004

Commissioning of a medical accelerator photon beam Monte Carlo simulation using wide-field profiles.

A method for commissioning an EGSnrc Monte Carlo simulation of medical linac photon beams through wide-field lateral profiles at moderate depth in a water phantom is presented. Although depth-dose profiles are commonly used for nominal energy determination, our study shows that they are quite insensitive to energy changes below 0.3 MeV (0.6 MeV) for a 6 MV (15 MV) photon beam. Also, the depth-dose profile dependence on beam radius adds an additional uncertainty in their use for tuning nominal energy. Simulated 40 cm x 40 cm lateral profiles at 5 cm depth in a water phantom show greater sensitivity to both nominal energy and radius. Beam parameters could be determined by comparing only these curves with measured data.

Algorithms↗
PubMed2004

Laparoscopic drainage of pancreatic pseudocysts.

BACKGROUND: Laparoscopic drainage of pancreatic pseudocysts (PPs) has been used in selected cases. The aim of this study is to analyze our results with the laparoscopic technique and to compare them with those of a cohort of patients treated by open surgery during the same time period. PATIENTS AND METHODS: Ten patients underwent laparoscopic drainage of PPs during a 7-year period [laparoscopic group (LG)]. The type of drainage was chosen according to the size and location of the PP. Demography, surgical details, results, and complications were analyzed and contrasted with those of 6 patients who underwent open drainage [open group (OG)]. RESULTS: All patients presented with mature PPs developed after a documented episode of acute pancreatitis. Mean age of the LG was 42 years (six males and four females). In the OG, mean age was 36 years (five males and one female). Etiology of the pancreatitis was alcoholic in eight patients, biliary in five, toxic in two, and associated with systemic lupus erythematous in one. Laparoscopic procedures included Roux-en-Y cystojejunostomy in four patients, extraluminal cystogastrostomy in four, and intraluminal cystogastrostomy in two. There were no conversions. In the OG, cystogastrostomy was performed in three patients and Roux-en-Y cystojejunostomy in three. One patient in the LG developed upper gastrointestinal bleeding the day after surgery that resolved uneventfully, one patient presented a postoperative abscess that required open drainage, and one patient presented a residual pseudocyst that was treated by endoscopy. Morbidity in the OG included a small bowel obstruction secondary to an internal hernia that required reoperation, pneumonia, and a residual pseudocyst that was treated conservatively in one patient each. At a median follow-up of 22 months (range, 1-72) all patients were asymptomatic with no evidence of recurrent disease by computed tomography scan. CONCLUSION: Laparoscopic drainage of PPs is feasible, safe, and effective. Results are similar to those obtained using the open technique.

Adolescent↗
PubMed2004

Free ion yield observed in liquid isooctane irradiated by gamma rays. Comparison with the Onsager theory.

We have analysed data on the free ion yield observed in liquid isooctane irradiated by 60Co gamma rays within the framework of the Onsager theory about initial recombination. Several distribution functions describing the electron thermalization distance have been used and compared with the experimental results: a delta function, a Gaussian-type function and an exponential function. A linear dependence between the free ion yield and the external electric field has been found at low-electric-field values (E < or = 1.2 x 10(3) V mm(-1)) in excellent agreement with the Onsager theory. At higher electric field values, we obtain a solution in power series of the external field using the Onsager theory.

Cobalt Radioisotopes↗
PubMed2003

Transcranial Doppler sonography in fulminant hepatic failure.

UNLABELLED: The clinical course of patients with fulminant hepatic failure (FHF) is often worsened by the presence of cerebral edema and endocranial hypertension. In spite of the multiple studies using Transcranial Doppler Sonography (TCDS), few have shown the cerebral blood flow (CBF) pattern among patients with encephalopathy resulting from FHF. OBJECTIVE: Our objective was to characterize the CBF pattern in these patients through the use of TCDS to provide therapeutic strategies. METHOD: The TCDS pattern was assessed in five patients diagnosed with FHF and compared with a control group who displayed critical neurologic conditions not associated with FHF. Pulsatile index, systolic, diastolic, and mean velocity of the middle cerebral artery were measured. RESULTS: The mean age of patients with FHF was 45.4 years. One hundred percent were women, with viral hepatitis as the predominant etiology. A cerebral hypoperfusion pattern was found in 80% of the FHF group and 40% of the control group. In the former group there was no evidence of hyperemia, as there was among 20% of the control group. The mean values of velocity and pulsatile index were 36.6 cm/sec and 2.4, respectively, in the FHF group and 47.8 cm/s and 1.8 in the control group (P=0.268, P=0.402). CONCLUSIONS: FHF patients show a predominance of cerebral hypoperfusion pattern with mean velocities lower than normal values and an increased pulsatile index. We recommend that clinicians take appropriate measures to improve cerebral perfusion and avoid hypoxia. Hyperventilation as a first level measure is contraindicated.

Adult↗
PubMed2003

[Value of C-reactive protein level in the detection of necrosis in acute pancreatitis].

OBJECTIVES: To evaluate the utility of C-reactive protein (CRP) in the detection of necrosis in acute pancreatitis and to determine the best cut-off point for CRP used for this purpose. MATERIAL AND METHODS: We performed a retrospective study of 157 patients with acute pancreatitis who underwent computed tomography (CT) with intravenous contrast material between 72 h and 8 days after the onset of symptoms and whose serum CRP values were determined by nephelometry 24 h or later after the onset of pain. RESULTS: Ninety-four patients were men and 63 were women, with a mean age of 61 years (range, 15-96 years). The cause of pancreatitis was biliary lithiasis in 53.5%, alcohol in 20.4%, and idiopathic in 10.8%. Other causes were found in 15.3%. The mean (standard deviation) time elapsed between symptom onset and extraction to evaluate CRP was 3.21 (1.7) days. The patients were divided into two groups according to the results of CT: 132 patients with acute intersitial edematous pancreatitis and 25 patients with acute necrotizing pancreatitis. The mean CRP concentrations were: 322 mg/l (range, 10.7-538) in patients with acute necrotizing pancreatitis and 133 mg/l (range, 3-442) in those with acute interstitial pancreatitis; this difference was statistically significant (p < 0.001). The area under the ROC curve of CRP vs. the occurrence of necrosis was 0.862 (95% CI, 0.778, 0.946). To evaluate the presence of pancreatic necrosis a cut-off level of 200 mg/l showed a sensitivity of 88% and a specificity of 75% while a cut-off level of 279 mg/l presented a sensitivity of 72% and a specificity of 88%. CONCLUSIONS: In acute pancreatitis, a CRP value of less than or equal to 200 mg/l obtained at 72 h of symptom onset is useful for ruling out, with a high degree of probability, the presence of necrosis. With higher values, additional investigations should be performed to determine the presence of pancreatic necrosis; nevertheless, with values higher than 279 mg/l the risk of necrosis markedly increases.

Acute Disease↗
PubMed2003

Ki-67 immunolabeling in pre-malignant lesions and carcinoma of the prostate. Histological correlation and prognostic evaluation.

The antigen Ki-67, which is associated with cell proliferation, has been demonstrated to be useful in predicting the development of human tumors. The objective of this study was to evaluate the prognostic utility of this biomarker in pre-malignant and malignant lesions of the prostate. A total of 162 prostate biopsies taken from patients diagnosed for benign prostatic hyperplasia (BPH, n=49), low grade prostatic intraepithelial neoplasia (LGPIN, n=53), high grade prostatic intraepithelial neoplasia (HGPIN, n=25) and carcinoma (CAR, n=35), were studied. Immunohistochemistry for Ki-67 was carried out on all the samples and the number of labeled cells was semi-quantitatively evaluated (weak, moderate or intense). In the non-invasive lesions, the presence of Ki-67-positive cells in the luminal layer of the epithelium was evaluated qualitatively as positive or negative. The correlation between the immunolabeling for Ki-67 and the histological diagnosis showed highly significant differences between BPH and CAR, LGPIN and CAR and HGPIN and CAR, with no significant differences being found among the other groups. Analysis of the immunolabeling in luminal cells of non-invasive lesions showed an increase in accordance with the increase in the degree of histological lesion, the greatest percentage being obtained in the HGPIN lesions (88.0%), with significant differences among all the groups. Bearing in mind that Ki-67 is a prognostic biomarker for cell proliferation, our results demonstrating the immunolabeling of Ki-67 in the luminal compartment of non-invasive lesions having the potential to evolve to malignancy, may have prognostic implications.

Biomarkers, Tumor↗
PubMed2002

Efficacy and safety of oral sildenafil citrate (Viagra) in the treatment of male erectile dysfunction in Colombia, Ecuador, and Venezuela: a double-blind, multicenter, placebo-controlled study.

The objective of this work was to assess the efficacy and safety of sildenafil in patients with erectile dysfunction (ED) from Colombia, Ecuador, and Venezuela. One hundred and fifty-eight outpatients with ED participated in a double-blind, flexible-dose, randomized-controlled trial. Efficacy measures included question 3 (achieving an erection) and question 4 (maintaining an erection) from the International Index of Erectile Function (IIEF), the five functional domains of the IIEF, a global efficacy question, and patient event log. Sildenafil increased patients' ability to achieve/maintain erections (P<0.01). Seventy-seven per cent of sildenafil- vs 46% of placebo-treated patients reported improved erections (P<0.001). Sixty-five percent and 35% of intercourse attempts were successful among sildenafil and placebo patients, respectively (P<0.05). Sildenafil patients showed significant improvements in three of the five IIEF functional domains (P<0.05). Adverse events were reported for 51% and 33% of sildenafil and placebo patients, respectively. It can be concluded that sildenafil is an effective, well-tolerated treatment for ED in patients from Latin America.

Administration, Oral↗
PubMed2002

The EMECAM project: a multicentre study on air pollution and mortality in Spain: combined results for particulates and for sulfur dioxide.

OBJECTIVE: The EMECAM study is a collaborative effort to evaluate the impact of air pollution on mortality in Spain. In this paper the combined results are presented for the short term effects of particulates and sulfur dioxide on both daily mortality for all and for specific causes. METHODS: The relation between daily mortality for all causes, cardiovascular diseases, and respiratory diseases, and air pollution for particulates (daily concentrations) and SO(2) (24 and 1 hour concentrations) was assessed in 13 Spanish cities for the period 1990-6. With a standardised method, magnitude of association in each city was estimated by Poisson regression in a generalised additive model. Local estimates were obtained from both single and two pollutant analyses. Lastly, combined estimates for each cause and pollutant were obtained. RESULTS: For combined results, in single pollutant models a 10 microg/m(3) increase in the concentration of the mean of the concurrent and one day lag for black smoke was associated with a 0.8% (95% confidence interval (95% CI) 0.4 to 1.1%) increase in total mortality. The estimates for total suspended particles (TSPs) and particulate matter of aerodynamic diameter <10 microm (PM(10)) and total mortality were slightly lower. The same increase in concentrations of SO(2) was associated with a 0.5% increase in daily deaths. For groups of specific causes, higher estimations were found, specially for respiratory conditions. Peak concentrations of SO(2) showed significant associations with the three groups of mortality. When two pollutant analyses were performed, estimates for particulates, specially for black smoke, did not substantially change. The estimates for daily concentrations of SO(2) were greatly reduced, but, on the contrary, the association with peak concentrations of SO(2) did not show any change. CONCLUSIONS: There is an association between mortality and pollution through particulates among city populations in Spain. Peak rather than daily concentrations of SO(2) were related to mortality. Results suggest that populations in Spanish cities are exposed to health risks derived from air pollution.

Air Pollutants↗
PubMed2001

[Lymphadenomegaly in patients with chronic liver disease].

Abdominal lymphadenomegaly is a frequent ultrasonographic finding in patients with chronic liver disease. Its clinical significance is not well understood. The aim of this study was to determine the relationship between this finding and several characteristics of liver disease in 44 patients with chronic liver disease (79.5% due to hepatitis C virus). To do this, all patients underwent simultaneous liver biopsy and abdominal ultrasonography, in which the number and localization of the enlarged abdominal lymph nodes were confirmed. Viral load in patients with chronic hepatitis C virus infection was determined. No significant differences were found in serum hepatitis C RNA concentrations between patients who presented lymphadenomegaly and those who did not. However, the presence of lymphadenomegaly was associated with greater histological activity. If this finding were confirmed in studies with larger samples, the presence of ultrasonographically-detected enlarged abdominal lymph nodes in patients with chronic liver disease due to hepatitis C virus infection would indicate more severe histological lesions.

Abdomen↗
PubMed2001

Living morphogenesis of the ventricles and congenital pathology of their component parts.

Living morphogenetic studies show that each definitive ventricle is constructed from different primitive cardiac segments, and each has its specific anatomical features. These ventricular segments are the atrioventricular junction; the primitive inlet segment, part of the primary heart tube, which initially provides the inlets of each ventricle; the primitive outlet segment, which gives rise to both ventricular outlets; and the apical trabeculated regions of the right and left ventricles which grow from the primary heart tube, respectively. In this review, we describe regional pathology based on the relationship of these primitive ventricular components. We propose that the abnormal morphogenesis of one of these segments gives origin to regional ventricular pathology. For example, abnormal embryogenesis of the atrioventricular canal produces malformations of the atrioventricular junctions, such as double inlet ventricle, absence of one atrioventricular connection, and straddling and overriding atrioventricular valves. Similarly, abnormal morphogenesis of the primitive outlet segment gives rise to malformations of the subarterial region of each ventricle, along with the valves guarding these vessels. The principal anatomical features of these malformations of the ventricular inlets and outlets are described, and their possible morphogenesis is discussed. Due to the fact that the apical trabeculated region of each ventricle arises from a separate primitive segment, each ventricle can be identified according to the pattern of its apical trabeculations. This feature is crucial in the elucidation of complex congenital pathology, such as discordant atrioventricular connections.

Animals↗