Are liver contour and bone fusion comparable to fiducials for IGRT in liver SBRT?

Introduction: Liver stereotactic body radiotherapy (SBRT) is increasingly being used to treat tumours. The purpose of this study was to compare the differences in patient positioning when using implanted fiducials as surrogates compared to alternative methods based on liver contour or bone registration. Material and methods: Eighteen patients treated with SBRT who underwent a fiducial placement procedure were included. Fiducial guidance was our gold standard to guide treatment in this study. After recording the displacements, when fusing the planning CT and CBCT performed in the treatment unit using fiducials, liver contour and bone reference, the differences between fiducials and liver contour and bone reference were calculated. Data from 88 CBCT were analyzed. The correlation between the displacements found with fiducials and those performed based on the liver contour and the nearest bone structure as references was determined. The mean, median, variance, range and standard deviation of the displacements with each of the fusion methods were obtained. µ, Æ©, and σ values and margins were obtained. Results: Lateral displacements of less than 3 mm with respect to the gold standard in 92% vs. 62.5% of cases using liver contour and bone references, respectively, with 93.2% vs. 65.9% in the AP axis and SI movement in 69.3% vs. 51.1%. The errors µ, σ and Æ© of the fusions with hepatic contour and bone reference in SI were 0.26 mm, 4 mm and 3 mm, and 0.8 mm, 5 mm and 3 mm respectively. Conclusion: Our study showed that displacements were smaller with the use of hepatic contour compared to bone reference and comparable to those obtained with the use of fiducials in the lateral, AP and SI motion axes. This would justify that hepatic contouring can be a guide in the treatment of patients in the absence of fiducials.

Magnetically confined electron beam system for high resolution electron transmission-beam experiments.

A novel experimental setup has been implemented to provide accurate electron scattering cross sections from molecules at low and intermediate impact energies (1-300 eV) by measuring the attenuation of a magnetically confined linear electron beam from a molecular target. High-resolution electron energy is achieved through confinement in a magnetic gas trap where electrons are cooled by successive collisions with N2. Additionally, we developed and present a method to correct systematic errors arising from energy and angular resolution limitations. The accuracy of the entire measurement procedure is validated by comparing the N2 total scattering cross section in the considered energy range with benchmark values available in the literature.

A process to describe radiation damage at the molecular level. Application to the 125I seeds in water.

The correlation between the absorbed energy and the induced biological damage still has unclear aspects, especially in the low energy and low dose rate irradiation regimes. From the knowledge of the molecular-induced effects (dissociations), it would be possible to better understand the side effects of radiation, such as induced cancers or damage to healthy tissue. With this in view, this paper presents results of a simulation of a 125I-seed treatment with an event-by-event MC code (LEPTS) specifically designed to account for the low energy secondary particle interactions, such as electron attachment, vibro-rotational and neutral dissociation interactions. This calculation allowed us to analyze the potential radiation damage not only in connection with the energy deposition, but also in terms of induced molecular dissociations by taking into account ionizing and non-ionizing dissociative processes. We propose that this description of the molecular level damage be the basis for nanodosimetric evaluations.

Stopping power for electrons in pyrimidine in the energy range 20-3000 eV.

In this work, we present new experimental electron energy loss distribution functions for pyrimidine (C4H4N2) measured for the incident energy range 30-2000 eV. Theoretical total and elastic cross sections for electron scattering from pyrimidine were calculated using the screening-corrected additivity rule (IAM-SCAR) method. Based on the mean energy loss observed in the experiment and the theoretical integral inelastic cross section, the stopping power for electrons in pyrimidine is calculated in the energy range 20-3000 eV.

Estimation of neutron-equivalent dose in organs of patients undergoing radiotherapy by the use of a novel online digital detector.

Neutron peripheral contamination in patients undergoing high-energy photon radiotherapy is considered as a risk factor for secondary cancer induction. Organ-specific neutron-equivalent dose estimation is therefore essential for a reasonable assessment of these associated risks. This work aimed to develop a method to estimate neutron-equivalent doses in multiple organs of radiotherapy patients. The method involved the convolution, at 16 reference points in an anthropomorphic phantom, of the normalized Monte Carlo neutron fluence energy spectra with the kerma and energy-dependent radiation weighting factor. This was then scaled with the total neutron fluence measured with passive detectors, at the same reference points, in order to obtain the equivalent doses in organs. The latter were correlated with the readings of a neutron digital detector located inside the treatment room during phantom irradiation. This digital detector, designed and developed by our group, integrates the thermal neutron fluence. The correlation model, applied to the digital detector readings during patient irradiation, enables the online estimation of neutron-equivalent doses in organs. The model takes into account the specific irradiation site, the field parameters (energy, field size, angle incidence, etc) and the installation (linac and bunker geometry). This method, which is suitable for routine clinical use, will help to systematically generate the dosimetric data essential for the improvement of current risk-estimation models.

High-dose-rate (HDR) plesiotherapy with custom-made moulds for the treatment of non-melanoma skin cancer

BACKGROUND: Non-melanoma skin tumours (NMSC) are one of the most frequent types of cancer, accounting for nearly one third of newly diagnosed tumours. NMSC are frequently diagnosed in elderly patients and while mortality rates are low, NMSC can be associated with significant morbidity in terms of cosmetic and functional impairment. OBJECTIVE: Surgical excision is nowadays considered the standard treatment for NMSC, although this approach might not be suitable for all the patients. Good rates of local control and cosmetic outcome are achieved by using high-dose-rate (HDR) plesiotherapy. METHODS: Nine consecutive patients with 11 NMSC were treated with custom-made moulds and HDR plesiotherapy reaching a fi nal dose of 44-48 Gy in 11-12 fractions of 4 Gy over 4 weeks. RESULTS: No local or distant relapses have been observed after a mean follow-up of 15 months (range 4-36 months). Acute toxicity was acceptable and cosmetic result was considered as excellent/good in 7 patients. CONCLUSIONS: This modality of treatment offers an alternative for those patients not candidates for surgical procedures because of medical contraindications or risk of disfigurement or functional impairment (AU)

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[Experimental study on usefulness of silicone-fluorsilicone copolymer oil (SiFO) in vitreoretinal surgery]. / Estudio experimental sobre la utilidad del aceite de copolímero de silicona-fluorsilicona (SiFO) en la cirugía vitreorretiniana.

PURPOSE: To evaluate the usefulness of silicone-fluorsilicone copolymer oil (SiFO) as an intraoperative tool and a vitreous substitute in vitreoretinal surgery. METHODS: Handling properties of SiFO were tested and compared with those of perfluorooctane (PFO). The transparency of both substances was measured by spectrophotometry and subjectively assessed. Their tendency to dispersion was observed during injection in balanced saline solution (BSS) and after mechanized and manual shaking. Ease of injection and aspiration through small-gauge instruments was evaluated. Ocular tolerance to SiFO and PFO was studied after intravitreal injection in rabbit eyes: intraocular pressure, anterior segment inflammatory response and dispersion were evaluated, and a histopathological study was performed. RESULTS: Injection and aspiration of SiFO were more difficult than those of PFO because of its higher viscosity. PFO dispersed progressively into small droplets as early as two days after intravitreal injection, whereas SiFO remained as a single bubble for 14 days. Histopathologically both substances induced an inflammatory response over the inferior retina, with microvacuolated macrophages and foreign body giant cells, which were larger in eyes wearing SiFO. CONCLUSIONS: SiFO may be useful as an intraoperative tool, although its main drawback is a more difficult injection and aspiration compared to PFO. It has been well tolerated as a short-term vitreous substitute, but further clinical studies are needed.

Bases físicas y diferencias de la planificación en RT conformacional, radiocirugía, radioterapia estereotáxica y RTD. Implicaciones terapéuticas

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Estudio comparativo sobre la eficacia y tolerancia del policosanol y la simvastatina en pacientes con hipercolesterolemia tipo II / Study comparative on the effectiveness and tolerance of the policosanol and the simvastatin in patient with hipercholesterolemia type II

Cuarenta y nueve (49) pacientes con hipercolesterolemia tipo II fueron enrolados en estudio prospectivo y comparativo a fin de evaluar el efecto terapéutico y la tolerabilidad de 10 mg de Policosanol y Simvastatina sobre el colesterol total, el LDL-Colesterol, HDL-Colesterol, Triglicéridos y los índices Colesterol total/HDL-Colesterol y LDL-Colesterol/HDL-Colesterol. Previo al tratamiento, los pacientes siguieron una dieta estándar para reducción de colesterol durante 4 semanas. Ambos productos redujeron los niveles de colesterol total (Simvastatina 20 por ciento y Policosanol 21 por ciento), el LDL-Colesterol (Simvastatina 24 por ciento y Policosanol 30 por ciento). Los niveles de triglicéridos se redujeron en 24 por ciento en el grupo que recibió Simvastatina y 10 por ciento en el grupo que recibió Policosanol. En ambos grupos se observó una evaluación de los niveles de HDL-Colesterol sin alcanzar éste significación estadística. Los índices colesterol total/HDL-Colesterol y LDL-Colesterol/HDL-Colesterol descendieron de manera importante con ambos tratamientos. Ambas drogas fueron bien toleradas, ningún paciente salió del estudio a causa de efectos adversos, se observó una tendencia en el grupo que recibió Policosanol a mejorar los niveles de Aspartalo-aminotransferasa previamente alterados

Electrocardiographic abnormalities and left ventricular systolic function in Chagas' heart disease.

In chagasic patients, the electrocardiogram becomes abnormal very late in the course of the disease. Most clinical studies concerning cardiac autonomic function of chagasic patients have been carried out in this very late stage of the disease. The purpose of this study was to assess accurately the left ventricular systolic function of chagasic patients with abnormal electrocardiograms. We performed left ventricular contrast cineangiography in 44 patients with positive complement fixation test for Chagas' disease and abnormal electrocardiograms. On the basis of the electrocardiographic abnormalities found in the electrocardiogram taken the night before the hemodynamic procedure, we divided our patients into three subgroups; those with rhythm disturbances, those with ventricular conduction abnormalities, and those with rhythm disturbances plus ventricular conduction abnormalities. The chagasic patients with only cardiac rhythm disturbances, had left ventricular volumes and ejection fractions which were similar to those of controls. On the other hand, the left ventricular volumes of the chagasic patients with ventricular conduction defects, although slightly larger, were still not different from those of controls. Finally, the chagasic patients, with cardiac rhythm disturbances and left ventricular conduction defects, had the largest left ventricular volumes (P less than 0.05), and the lowest ejection fractions (P less than 0.001) of all three subgroups. These findings clearly indicate that chagasic patients, in this very late stage of the disease, have a very variable degree of left ventricular systolic dysfunction. Furthermore, our results show a distinct tendency for the left ventricular volumes to increase, and for the ejection fraction to decrease; when the electrocardiogram becomes progressively more abnormal, and "mixed" electrocardiographic abnormalities appear.(ABSTRACT TRUNCATED AT 250 WORDS)