The design, physical properties and clinical utility of an iris collimator for robotic radiosurgery.

Robotic radiosurgery using more than one circular collimator can improve treatment plan quality and reduce total monitor units (MU). The rationale for an iris collimator that allows the field size to be varied during treatment delivery is to enable the benefits of multiple-field-size treatments to be realized with no increase in treatment time due to collimator exchange or multiple traversals of the robotic manipulator by allowing each beam to be delivered with any desired field size during a single traversal. This paper describes the Iris variable aperture collimator (Accuray Incorporated, Sunnyvale, CA, USA), which incorporates 12 tungsten-copper alloy segments in two banks of six. The banks are rotated by 30 degrees with respect to each other, which limits the radiation leakage between the collimator segments and produces a 12-sided polygonal treatment beam. The beam is approximately circular, with a root-mean-square (rms) deviation in the 50% dose radius of <0.8% (corresponding to <0.25 mm at the 60 mm field size) and an rms variation in the 20-80% penumbra width of about 0.1 mm at the 5 mm field size increasing to about 0.5 mm at 60 mm. The maximum measured collimator leakage dose rate was 0.07%. A commissioning method is described by which the average dose profile can be obtained from four profile measurements at each depth based on the periodicity of the isodose line variations with azimuthal angle. The penumbra of averaged profiles increased with field size and was typically 0.2-0.6 mm larger than that of an equivalent fixed circular collimator. The aperture reproducibility is < or =0.1 mm at the lower bank, diverging to < or =0.2 mm at a nominal treatment distance of 800 mm from the beam focus. Output factors (OFs) and tissue-phantom-ratio data are identical to those used for fixed collimators, except the OFs for the two smallest field sizes (5 and 7.5 mm) are considerably lower for the Iris Collimator. If average collimator profiles are used, the assumption of circular symmetry results in dose calculation errors that are <1 mm or <1% for single beams across the full range of field sizes; errors for multiple non-coplanar beam treatment plans are expected to be smaller. Treatment plans were generated for 19 cases using the Iris Collimator (12 field sizes) and also using one and three fixed collimators. The results of the treatment planning study demonstrate that the use of multiple field sizes achieves multiple plan quality improvements, including reduction of total MU, increase of target volume coverage and improvements in conformality and homogeneity compared with using a single field size for a large proportion of the cases studied. The Iris Collimator offers the potential to greatly increase the clinical application of multiple field sizes for robotic radiosurgery.

Mycotic granuloma caused by Phialophora repens.

This is the first reported infection by the saprophytic fungus, Phialophora repens. The infection was a solitary granulomatous nodule in the scalp of a Zaïrian man with advanced lepromatous leprosy. The patient was being treated by long-term prednisolone therapy. In tissue sections there were nonpigmented microcolonies composed of irregularly branched septate hyphae. A darkly pigmented fungus was isolated on Sabouraud's medium. The mycologic features of the etiologic agent were typical of P. repens. The infection was treated successfully by excision of the nodule.

The CyberKnife Robotic Radiosurgery System in 2010.

This review provides a complete technical description of the CyberKnife VSI System, the latest addition to the CyberKnife product family, which was released in September 2009. This review updates the previous technical reviews of the original system version published in the late 1990s. Technical developments over the last decade have impacted virtually every aspect of the CyberKnife System. These developments have increased the geometric accuracy of the system and have enhanced the dosimetric accuracy and quality of treatment, with advanced inverse treatment planning algorithms, rapid Monte Carlo dose calculation, and post-processing tools that allow trade-offs between treatment efficiency and dosimetric quality to be explored. This review provides a system overview with detailed descriptions of key subsystems. A detailed review of studies of geometric accuracy is also included, reporting a wide range of experiments involving phantom tests and patient data. Finally, the relationship between technical developments and the greatly increased range of clinical applications they have allowed is reviewed briefly.

Metabolism by rat hepatic microsomes of fluorinated ether anesthetics following ethanol consumption.

The possibility that the metabolism of volatile inhalational anesthetics is altered following chronic ethanol consumption was investigated in male Fischer 344 rats. The hepatic microsomal defluorination rates of methoxyflurane, enflurane, and sevoflurane were determined for pair-fed rats receiving ethanol with normal caloric or with 50% of normal caloric intake. For comparison, the effects of phenobarbital treatment on anesthetic defluorination rates also were examined. Fourteen days of ad libitum consumption of 16% ethanol resulted in maximal defluorination rates of the above anesthetics. No overt signs of ethanol toxicity were observed. Ethanol-treated rats with a normal caloric intake had significantly increased microsomal defluorination rates per mg protein compared with pair-fed control rats as follows: methoxyflurane, 190% of control; enflurane, 298% of control; and sevoflurane, 301% of control. Ethanol-treated animals with 50% of normal caloric intake showed similar elevations in microsomal defluorination rates when compared with pair-fed controls. Phenobarbital treatment significantly increased the rate of methoxyflurane defluorination (673% of control), whereas the rates of sevoflurane defluorination (127% of control) and enflurane defluorination (86% of control) were not altered significantly. Phenobarbital treatment increased the microsomal content of cytochrome P-450, while ethanol treatment did not. This study demonstrated that regardless of total caloric intake, chronic ethanol consumption increases defluorination of inhalation anesthetics in Fischer 344 rats. It also illustrated that the two enzyme-inducing agents are unique with respect to the degree to which they enhance anesthetic defluorination.

Fertility, reproduction and postnatal survival in mice chronically exposed to halothane.

Reproductive studies were performed in Swiss/ICR mice chronically exposed to subanesthetic and anesthetic concentrations of halothane. Male and female mice were treated five or seven days a week for nine weeks prior to mating; exposure of females was continued daily throughout pregnancy. Halothane exposures were 0.025, 0.1, 0.4, 1.2, and 4.0 MAC hours per day. No adverse effect on reproduction was observed at the lowest two exposure levels studied. Exposures to 0.4 MAC hour per day or more were associated with decreased maternal weight gain, fetal fetal length and weight, and early postnatal weight gain. Pregnancy rate, implantation rate, and number of live fetuses per litter were significantly decreased at 1.2 MAC hours per day. The percentage of resorption or fetuses dead in utero was not increased, and postnatal survival of offspring was unaltered. Subsequent matings between untreated females and males exposed to halothane, 1.2 MAC hours per day for 17 weeks, resulted in normal reproductive performance; this suggests that the adverse reproductive changes observed when both males and females were exposed represented a primary effect on females. The least exposure at which effects were seen is approximately 40 times greater than the level of human occupational exposure is unscavenged operating rooms.

Manual sobre al fiebre amarilla y su diagnóstico diferencial histopatológico

A CONTINUACION SE REVISARA BREVEMENTE LA HISTORIANATURAL Y LAS CARACTE RISTICAS CLINICAS DE LA FIEBRE AMARILLA, PARA DESPUES HACER REFERENCIA A LA MORFOLOGIA MICROSCOPICA DE ESTA Y DE OTRAS ENFERMEDADES QUE EL PA TOLOGO PUEDE CONFUNDIR CON ELLA