1,721,036 research outputs found
Investigation of a possibility of ECG and PPG common measurement
No full textElectrocardiography and Photoplethysmography are basic investigative methods used in healthcare. As the ECG and the PPG are non-invasive methods. The principle consists in ECG recording of electrical activity of the heart and the result of this sensing is a graph plotting—electrocardiogram. PPG is one of the main methods of measurement plethysmography when the result is a graphic record of pulse wave. The main function of PPG is the volumetric flow measurement of blood (e.g. in atherosclerosis, which is possible by vascular permeability derive their rigidity). Both of these methods are used for monitoring of cardiovascular system. It would be advantageous to have possibility to measure ECG and PPG from one place on human body. It would be also advantageous to have only one device and reduce number or size of sensors or electrodes. In this paper we describe developing such system and also investigation the ideal place for placing of sensors for satisfactory measurement
Analysis of kinematic parameters relationships in normal and dysgraphic children
No full textKinematic analysis of handwriting, using digital tablet together with appropriate tests and processing software, allows evaluation of subject graphomotor abilities. Several studies focused on the kinematic parameters extracted from the writing of both normal subjects and subjects with specific disorder, such as dysgraphia, recorded during simple tasks. However, relationships between these parameters have not yet been analyzed. The aim of this study was to examine and identify possible links between kinematic parameters like Amplitude (SA), Duration (SD) and Peak Velocity (PkVS) of Strokes extracted from handwriting and their changes between normal and dysgraphic children. Fifty normal and eighteen dysgraphic children, attending classes from 2nd to 5th grade of primary school, were involved in the study; three cursive tests were administered and analyzed. Results showed a linear relation between SA and PkVS parameters with a similar slope in both groups and reduced peak velocities in some dysgraphic children. A linear relationship was also present between SA and SD parameters in all tests for normal children while an unclear relation was found for dysgraphic children. The latter showed longer durations and slightly lower amplitudes than in normal subjects, in all tasks, as expected in case of poor fluency
Influence of dysgraphia on kinematic characteristics of handwriting in Italian primary school children
No full textHandwriting is a complex skill that improves with
schooling and it is accomplished after the child has
achieved and integrated underlying perceptual-motor
performance components. Even though nowadays children
are expected to acquire a level of handwriting
proficiency, even on the first day of school, at least 27%
of the school population has difficulty with handwriting
and needs to be screened for (with) an intervention
program. In this paper, we examined the influence of
dysgraphia on kinematic characteristics of normal and
dysgraphic Italian children from 2nd to 5th grade of
primary school. Three cursive tasks (sequence of lelele
and Accurate and Fast copy of a sentence) were proposed
and several kinematic parameters were evaluated. Since
differences were present among grades both in normal
and dysgraphic children, each parameter was compared
between children coming from corresponding grades by
means of the Wilcoxon rank sum test. The main results
showed significant differences between the two groups
within each grade for curvilinear velocity, total length and
number of letters per second. Pen-lift durations were
significantly different only in the Accurate and Fast tasks
while number of strokes per second as well as stroke
duration and length showed significant differences
depending on the task and grade. These differences
support the hypothesis of a lower fluency and automation
as well as a different motor planning in dysgraphic
subjects. Finally, many kinematic parameters could be
useful for an early identification of dysgraphia in order to
activate an immediate rehabilitative treatment
Linac leakage dose received by patients treated using non-coplanar radiotherapy beams
No full textAs non-coplanar beams are increasingly used to deliver cranial and extra-cranial stereotactic radiotherapy treatments, radiation leakage from the accelerating waveguide, bending magnet and other components of the medical linear accelerator (linac) that are not conventionally brought into proximity to the patient becomes increasingly concerning. In this study, the leakage dose in the patient plane was measured using optically stimulated luminescence dosimeters placed along the treatment couch, at 10, cm intervals. A Varian iX linac was operated in 6 and 10, MV photon mode, with all jaws and multi-leaf collimators closed. Dose measurements were made (a) using a “standard” setup, with couch and gantry at zero degrees and (b) using a worst-case non-coplanar setup, with the couch at 90° and the gantry at 30° (rotated over the couch). Results indicated that the leakage dose in the patient plane was uniformly low (less than 2, cGy/10,000MU) at all measurement positions for both energies, using the standard setup. However, when the gantry and couch were rotated, there was a systematic increase in dose to 4.2, cGy/10,000MU at a point 80, cm from isocentre (below the bending magnet). While these doses are within recommended out-of-field dose limits for static beam treatments, if IMRT/VMAT factors are applied then the leakage dose to the patient from non-coplanar treatments may become unacceptable. Specific checks of out-of-field dose from non-coplanar beam directions are advisable prior to acceptance of new or modified linacs
Optically stimulated luminescence dosimeters as an alternative to radiographic film for performing “Head-Wrap” linac leakage measurements
No full textThe linac “head-wrap”, where a new or modified linac is covered with radiographic film as a means to identify regions of increased radiation leakage, is an important part of the linac acceptance/commissioning process. However, as radiographic film and developing equipment decrease in availability and increase in cost, a simple, reusable, non-chemical solution becomes increasingly desirable. This study investigated whether discrete dose points measured using optically stimulated luminescence dosimeters (OSLDs) could be used to detect regions of increased radiation, as a substitute for radiographic film. After establishing the ability of the OSLDs to detect leakage and differentiate between high and low leakage doses, via a set of proof-of-concept measurements made in known high and low leakage regions on a Varian iX linac, a systematic evaluation of leakage at the surface of the linac head was undertaken. 60 OSLDs were positioned at regular intervals over the linac head by a member of the research team who was unfamiliar with the expected patterns of linac leakage. The OSLD measurements were able to detect linac head leakage and quantify high and low doses (from 0.6 to 44.7, cGy per 10,000 MU) with sufficient geometric precision to guide the use of an ionisation chamber to measure leakage doses in the patient plane. Reusable point dosimeters such as OSLDs are a promising solution to the problem of diminishing availability of film stock for linac head-wrap tests
Calibration seed sampling for iodine-125 prostate brachytherapy
No full textUse of iodine-125 seeds for intraoperative planning and delivery of low dose rate brachytherapy treatments for prostate cancer requires that the air kerma strength of the seeds be checked against the vendor-supplied calibration certificate at the beginning of the surgical procedure. In practise, activity checks of multiple sources are difficult to achieve in surgery. This study therefore investigated the reliability of a calibration method that sampled only one seed, or a small number of seeds, by evaluating the consistency the air kerma strengths of all seeds in three small batches of 10, 20 and 30 iodine-125 seeds and calculating the probability of achieving results representative of each batch, within different levels of uncertainty. For the cartridges containing 10, 20 and 30 seeds, the mean differences between the source strengths identified by physical measurement and their decay-corrected calibration certificate values were respectively 5.0% ± 4.4%, ± 2.7% ± 3.7%, and 0.4% ± 2:8%.. Assays of 5 randomly sampled seeds were shown to produce results within 3% of the mean air kerma strength of each batch, with larger assays producing less uncertainty. For these seeds, there was a greater than 30% chance that a randomly selected seed would have an activity that differed by more than 3% from the mean activity of all seeds in the cartridge. Although attractive as an efficiency measure, the testing of just one seed from a cartridge of iodine-125 seeds has a significant probability of producing an activity measurement that is not representative of the activity of the other seeds in the cartridge, potentially leading to substantial inaccuracies in implant dosimetry
Long-term reliability of optically stimulated luminescence dosimeters
No full textOptically stimulated luminescence dosimeters (OSLDs) can be used as accurate and re-usable dosimeters for radiotherapy applications. OSLDs have been observed to decline in sensitivity with repeated use and it is important to determine whether this decline in sensitivity is associated with a decline in reliability. This study used three batches of OSLDs (purchased in 2012, 2014 and 2016) that had been repeatedly re-used in a mature in vivo dosimetry programme over a period of up to five years and evaluated the consistency of their response over repeated irradiation-readout-bleaching cycles. Each irradiation delivered 105, cGy to all OSLDs, using a 12, meV electron beam from a Varian iX linear accelerator. The five- and three-year-old OSLDs respectively displayed 86% and 89% of the sensitivity of the one year old OSLDs, but when a correction factor for each OSLD was derived based on the first measurement result and applied to each subsequent reading, all OSLDs were able to measure the 105, cGy test dose accurately, within standard deviations of 2.0% for the OSLDs from 2012 and 1.3% for the OSLDs from 2014 and 2016. If a mean calibration value was applied to the readings from each batch of OSLDs, instead of applying a measurement-derived sensitivity correction factor to each individual OSLD reading, the standard deviations increased to an unacceptable 6.1, 5.6 and 2.9%. Well-used three- and five-year-old OSLDs were shown to be capable of providing measurements with similar accuracy to a more recently-purchased batch of OSLDs, when measurement-derived sensitivity correction factors were applied to each result. If this extra step is included in the OSLD measurement process, then the same OSLDs may be reliably used for years without needing to be retired and replaced
Radiotherapy quality assurance using statistical process control
No full textStatistical process control (SPC) is an analytical decision-making tool that employs statistics to measure and monitor a system process. The fundamental concept of SPC is to compare current statistics in a process with its previous corresponding statistic for a given period. Using SPC, a control chart is obtained to identify random and systematic variations based on the mean of the process and trends are observed to see how data can vary in each evaluated period. An upper and lower control limit in an SPC derived control chart indicate the range of the process calculated based on the standard deviations from the mean, thereby points that are outside these limits indicate the process to be out of control. Metrics such as: process capability and acceptability ratios were employed to assess whether an applied tolerance is applicable to the existing process. SPC has been applied in this study to assess and recommend quality assurance tolerances in the radiotherapy practice for helical tomotherapy. Various machine parameters such as beam output, energy, couch travel as well as treatment planning parameters such as minimum percentage of open multileaf collimators (MLC) during treatment, planned pitch (couch travel per gantry rotation) and modulation factor (beam intensity) were verified against their delivery quality assurance tolerances to produce SPC based tolerances. Results obtained were an indication of the current processes and mechanical capabilities in the department rather than a vendor recommended or a prescriptive approach based on machine technicalities. In this study, we have provided a simple yet effective method and analysis results to recommend tolerances for a radiotherapy practice. This can help improve treatment efficiency and reduce inaccuracies in dose delivery using an assessment tool that can identify systematic and random variations in a process and hence avoid potential hazardous outcomes
Retrospective audit of patient specific quality assurance results obtained using helical diode arrays
No full textA retrospective audit was performed for existing patient specific quality assurance (PSQA) results measured on two ArcCheck helical diode arrays (Sun Nuclear Corporation). Twenty-five volumetric modulated arc therapy (VMAT) and thirty-two helical tomotherapy (HT) treatment plans were re-analysed using SNC patient software (version 6.2) and in-house gamma analysis code (developed in Python). Global gamma analyses were performed on the measured and calculated data (2%/2 mm) to identify the registration shift which provided the greatest gamma agreement index (GAI). Audit results indicated that when the ArcCheck devices were used for VMAT and HT, 1 mm longitudinal (Y) registration shifts frequently provided better GAI results than no shift. Specifically, the SNC and Python codes both identified a significant trend for longitudinal shifts for both ArcCheck devices. No significant trend was observed for roll (X) registration shifts. Measurements performed with physical shifts of the ArcCheck device improved the GAI results with no shift applied, suggesting that unless there is a co-incidental offset in the position of the radiation isocentre on both the TomoTherapy unit and the linac, there may be an actual displacement of the centre of the diode array and the marking lines on the two ArcCheck devices. This behaviour is dependent on gamma evaluation criteria used. The results of this study confirm the necessity of undertaking regular audits of QA results, as well as the need to consider sources of geometric uncertainty when selecting gamma evaluation criteria and when applying automatic geometric shifts to measured data
- …
