SciFi detector and associated method for real-time determination of profile and output factor for small fields in stereotactic radiotherapy.

PURPOSE: For determining small-field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) detector with output image acquisition and processing to allow real-time monitoring of profile and output factor. MATERIALS AND METHODS: The employed detector is a SciFi detector made of tissue-equivalent scintillating plastic fibers arranged in 6-layer fiber ribbons with a fiber pitch of 275 µm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal-oxide-semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water-equivalent phantom and irradiated by a 6 MV photon beam. RESULTS: The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real-time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro-cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes. CONCLUSIONS: We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS-483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI-LINAC.

Design and testing of a phantom and instrumented gynecological applicator based on GaN dosimeter for use in high dose rate brachytherapy quality assurance.

PURPOSE: High dose rate brachytherapy (HDR-BT) is widely used to treat gynecologic, anal, prostate, head, neck, and breast cancers. These treatments are typically administered in large dose per fraction (>5 Gy) and with high-gradient-dose-distributions, with serious consequences in case of a treatment delivery error (e.g., on dwell position and dwell time). Thus, quality assurance (QA) or quality control (QC) should be systematically and independently implemented. This paper describes the design and testing of a phantom and an instrumented gynecological applicator for pretreatment QA and in vivo QC, respectively. METHODS: The authors have designed a HDR-BT phantom equipped with four GaN-based dosimeters. The authors have also instrumented a commercial multichannel HDR-BT gynecological applicator by rigid incorporation of four GaN-based dosimeters in four channels. Specific methods based on the four GaN dosimeter responses are proposed for accurate determination of dwell time and dwell position inside phantom or applicator. The phantom and the applicator have been tested for HDR-BT QA in routine over two different periods: 29 and 15 days, respectively. Measurements in dwell position and time are compared to the treatment plan. A modified position-time gamma index is used to monitor the quality of treatment delivery. RESULTS: The HDR-BT phantom and the instrumented applicator have been used to determine more than 900 dwell positions over the different testing periods. The errors between the planned and measured dwell positions are 0.11 ± 0.70 mm (1σ) and 0.01 ± 0.42 mm (1σ), with the phantom and the applicator, respectively. The dwell time errors for these positions do not exhibit significant bias, with a standard deviation of less than 100 ms for both systems. The modified position-time gamma index sets a threshold, determining whether the treatment run passes or fails. The error detectability of their systems has been evaluated through tests on intentionally introduced error protocols. With a detection threshold of 0.7 mm, the error detection rate on dwell position is 22% at 0.5 mm, 96% at 1 mm, and 100% at and beyond 1.5 mm. On dwell time with a dwell time threshold of 0.1 s, it is 90% at 0.2 s and 100% at and beyond 0.3 s. CONCLUSIONS: The proposed HDR-BT phantom and instrumented applicator have been tested and their main characteristics have been evaluated. These systems perform unsupervised measurements and analysis without prior treatment plan information. They allow independent verification of dwell position and time with accuracy of measurements comparable with other similar systems reported in the literature.

Protocols for massive blood transfusion: when and why, and potential complications.

PURPOSE: An update paper on massive bleeding after major trauma. A review of protocols to address massive bleeding, and its possible complications, including coagulation abnormalities, complications related to blood storage, immunosuppression and infection, lung injury associated with transfusion, and hypothermia is carried out. METHODS: Literature review and discussion with authors' experience. RESULTS: Massive bleeding is an acute life-threatening complication of major trauma, and consequently its prompt diagnosis and treatment is of overwhelming importance. Treatment requires rapid surgical management together with the massive infusion of colloid and blood. CONCLUSIONS: Since massive transfusion provokes further problems in patients who are already severely traumatized and anaemic, once this course of action has been decided upon, a profound knowledge of its potential complications, careful monitoring and proper follow-up are all essential. To diagnose this bleeding, most authors favour, as the main first choice tool, a full-body CT scan (head to pelvis), in non-critical severe trauma cases. In addition, focused abdominal sonography for trauma (FAST, an acronym that highlights the necessity of rapid performance) is a very important diagnostic test for abdominal and thoracic bleeding. Furthermore, urgent surgical intervention should be undertaken for patients with significant free intraabdominal fluid and haemodynamic instability. Although the clinical situation and the blood haemoglobin concentration are the key factors considered in this rapid decision-making context, laboratory markers should not be based on a single haematocrit value, as its sensitivity to significant bleeding may be very low. Serum lactate and base deficit are very sensitive markers for detecting and monitoring the extent of bleeding and shock, in conjunction with repeated combined measurements of prothrombin time, activated partial thromboplastin time, fibrinogen and platelets.

Fiber background rejection and crystal over-response compensation for GaN based in vivo dosimetry.

For dosimetric measurements using an implantable optical fiber probe with GaN (Gallium Nitride) scintillator as radioluminescence (RL) transducer, a bi-channel method is proposed to reject the background contribution of the irradiated fiber segment. It is based on spectral differences between the narrow-band light emission from GaN and the large-band background from the irradiated optical fiber. Experimental validation of this method using 6 MV photon beam has shown that the remaining background contribution after subtraction is below 1.2% for square field sizes ranging from 3 cm to 20 cm. Furthermore, a compensation method for the over-response of GaN is also proposed, since GaN is not tissue equivalent. The over-response factor of GaN exhibits a linear increase with square field aperture and depends on depth from phantom surface. This behaviour is modelled to allow compensation in specific conditions. The proposed method has been evaluated and has shown a maximum deviation of 3% for a 6 MV photon beam and 1% for an 18 MV photon beam at a depth beyond the build-up region.

Radiotherapy quality assurance by individualized in vivo dosimetry: state of the art.

The quality insurance in radiotherapy in the frame of highly complex technical process as Intensity modulated radiotherapy (IMRT) needs independent control of the delivered dose to the patient. Actually, up to now, most of the radiotherapy treatments rely only on computed dosimetry through a rather complicated series of linked simulation tool. This dosimetry approach requires also qualified treatment means based on cautious quality insurance procedures. However, erroneous parameters could be difficult to detect and systematical errors could happen leading to radiotherapy accidents. In this context, in vivo dosimetry has a critical role of final control of the delivered dose. As many beam incidences and ports are used for any photontherapy treatment, external control could be very tedious and time consuming. Therefore, innovations are needed for in vivo dosimetry to provide ergonomic and efficient tools for these controls. This paper presents a review of technologies and products that can be used for in vivo dosimetry. It proposes also a reflection on the concepts to develop future devices suitable for this purpose. The technical means with their physical principles are reviewed, the clinical experiences demonstrating the feasibility of new techniques are then summarized and finally, the early clinical use and its impact on clinical practice is review.

Taquicardia ventricular tipo torsades de pointes en un paciente con intoxicación digitálica en tratamiento crónico con sulfato de quinina / Torsades de pointes type ventriculartachycardia in a patient with digitalisintoxication under chronic treatmentwith quinine sulfate

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[Cysticercosis. Scientific productivity measured with with a review of the literature published from 1965 to 1995]. / Cisticercosis. Productividad científica medida por medio de un análisis de la literatura publicada entre 1965 y 1995.

There have been 2521 articles published on cysticercosis between 1965 and 1995. An analysis of these articles is presented in this paper and includes the subjects, grouped in 61 descriptors and the frequency of each one, the number of articles published each year, which has increased, the journals used, in total 663, 7% of which include 42% of the articles, the parameters used to measure the quality and importance of the main journals used for cysticercosis, for example, 56% have impact factor, the authors and co-authors which add 4848, of these, 59 have published between 9 and 79 articles each one, the analysis of their frequency of publication indicates that once they start publishing on cysticercosis they follow on in this area. Of the most productive authors 58% are Latinoamerican, 22 of which are Mexican.