303. Image registration – precise quality assessment of radiotherapy without necessity of showing corresponding points in simulation and portal images

PurposeEnabling the quality assessment of radiotherapy to be made in daily practice, using the new software tool to analyze the simulation and portal images.MethodIn the registration of the anatomical structures as well as the irradiation fields, the features used as landmarks are the edges. The significant edge fragments must be chosen manually, but without showing any specific corresponding points. Field edges marked with wires in the simulation image are found fully automatically with the original combination of a dedicated line edge detector and a version of hierarchical, combined Hough transform. The registration is guided by the robust accuracy criterion using the modified Hausdorff distance measure. The only parameter of the measure – quantile rank, or share of data used in comparison – is not fixed, but evolves from 1 to 0 during the optimization of the accuracy. This has two advantages. 1: The user can choose the result found for the share corresponding to the actual share of erroneous data in the images, which can be seen only after the results for all the possible ranks are known. 2: The algorithm can avoid the local minima. The registration takes few seconds on a typical PC. The method has been implemented in a software tool which supports the complete process of measurement, and has been tested in clinical triais with positive result.ConclusionsThe modified Hausdorff distance measure with evolving rank is a good and efficient registration accuracy measure for quality assessment of radiotherapy based on the comparison of portal and simulation images

3/Evaluation of set-up deviations during the irradiation of patients suffering from breast cancer treated with two different techniques

PurposeTo present results of patient positioning during routine radiotherapy for patients treated after mastectomy and to compare the inaccuracies in patient set-up for this group of patients and for the patients treated after breast conserving therapy with tangential fields.Methods and materialsIn total, the analysis comprised 56 pairs of portal and simulator films for 14 consecutive patients treated following breast conserving therapy and 98 pairs of portal and simulator films for 20 consecutive patients treated after mastectomy. For the first group the tangential field technique (TF technique) was used, for the second the inverse hockey stick technique (IHS technique). The comparison of the treatment reproducibility obtained for both groups of patients was performed in terms of systematic and random error calculated for the whole groups and by the comparison of cumulative distribution of the length of the displacement vector.ResultsIn the IHS and TF techniques for medial and lateral fields, displacement larger than 5 mm occurred in 28.3%, 15.8% and 25.4% respectively. For the IHS technique, the systematic errors for lateral and cranial-caudal direction were 1.9 and 1.7 mm respectively (1 standard deviation – SD), the random errors for lateral and cranial-caudal direction were 2.0 and 2.5 mm. For the TF technique, the systematic errors for lateral and cranial-caudal direction were 2.6 and 1.3 mm for medial field and 3.7 and 0.7 mm for lateral fields respectively, the random errors for lateral and cranial-caudal direction were 2.2 and 1.0 mm for medial field and 2.9 and 1.1 for lateral field respectively. Rotations were negligible in the HIS technique. For the TF technique the systematic component and random component amounted to about 2.0 degrees (1 SD).ConclusionsBoth the inverse hockey stick and standard tangential techniques showed good reproducibility of patients set-up with respect to cranial-caudal direction. For the TF technique, the accuracy should be improved for the medial field with respect to the ventral-dorsal direction

A Bose-Einstein Approach to the Random Partitioning of an Integer

Consider N equally-spaced points on a circle of circumference N. Choose at random n points out of $N$ on this circle and append clockwise an arc of integral length k to each such point. The resulting random set is made of a random number of connected components. Questions such as the evaluation of the probability of random covering and parking configurations, number and length of the gaps are addressed. They are the discrete versions of similar problems raised in the continuum. For each value of k, asymptotic results are presented when n,N both go to infinity according to two different regimes. This model may equivalently be viewed as a random partitioning problem of N items into n recipients. A grand-canonical balls in boxes approach is also supplied, giving some insight into the multiplicities of the box filling amounts or spacings. The latter model is a k-nearest neighbor random graph with N vertices and kn edges. We shall also briefly consider the covering problem in the context of a random graph model with N vertices and n (out-degree 1) edges whose endpoints are no more bound to be neighbors

The formation of medical workers subjectity in the patient care institution environment from a position of the eco-psychological approach

The process of the medical worker's subjectity development as the realization of the ability to be a subject of the optional activity in the shape of professional performance in the patient care institution environment is analyse

25. Assessment of the accuracy of radiotherapy by digital superposition of portal and rference images

Teleradiotherapy imposes the requirement of high accuracy in reference to its medical as well as technical aspects. Close adherence to the geometrical parameters set up in therapy planning is vital. The current location of the irradiation field and anatomical structures can be recorded in the portal image acquired during the therapy course. Assessment of the treatment accuracy consists in registration (overlaying) of the reference and the portal image to compare the layout of anatomical structures and the irradiation field. Edges of the compared features are difficult to find in the portal image, which is inherently of low contrast. Hence, not all the edges present in the reference image can be found in the portal one, and the comparison of geometries in these images is difficult and time-consuming. There exists a need for a tool that could support and objectify this process.At present the accuracy assessment is done manually by an experienced observer. As a rule, this tedious procedure is not performed routinely. The wide literature on image registration refers to portal images made with beams generated in accelerators rather than with the cobalt apparata. In Poland more than a half of patients are treated with cobalt. There are numerous references to image registration methods tailored for finding the fitting and non-fitting fragments of the compared edges. The majority of these methods lack generality.The methodology to be presented is general and requires little user intervention.•Features to be matched: edges of selected anatomical structures, irradiation field and shields, as seen in scanned images.•Edge detector: zero-second-derivative with scale fitted to noise and scale of edges, separately in portal and reference images.•Geometrical transformation: affine (2 translations, rotation, 2 scalings – along two coordinate axes).•Measure of fitting accuracy: modified Hausdorff distance measure – robust method based on voting. Parts of the contours that do not fit the general tendency are rejected. This is vital if portal images made with cobalt apparata are analysed.•Optimisation method for finding the best transformation: maximum gradient (chamfer matching).•Final fit can be calculated with le least squares method for only those pixels which were classified as fitting.•Speed-ups: hierarchical method (pyramid of resolutions); in some cases: pre-calculated virtual transformations.•Automatic classification of edges as belonging to anatomic structures, irradiation field or shields is possible.•Experiments with enhancing the contrast of portal images using the optical system transfer function concept.The software tool will be presented which makes it possible to correct the therapeutic system geometry or the location of the patient. Full control of the physician over the measurement process will be maintained, according to the requirement of human decision-making in the therapeutical process. The registration (overlaying) of a portal and a reference image is visualised for verification. Manual corrections of the result will be possible in the final version of the program.Acknowledgement The work is supported by the Committee for Scientific Research within the grant no. KBN 4 P05B 064 18

Searching for planar signatures in WMAP

We search for planar deviations of statistical isotropy in the Wilkinson Microwave Anisotropy Probe (WMAP) data by applying a recently introduced angular-planar statistics both to full-sky and to masked temperature maps, including in our analysis the effect of the residual foreground contamination and systematics in the foreground removing process as sources of error. We confirm earlier findings that full-sky maps exhibit anomalies at the planar ($l$) and angular ($\ell$) scales $(l,\ell)=(2,5),(4,7),$ and $(6,8)$, which seem to be due to unremoved foregrounds since this features are present in the full-sky map but not in the masked maps. On the other hand, our test detects slightly anomalous results at the scales $(l,\ell)=(10,8)$ and $(2,9)$ in the masked maps but not in the full-sky one, indicating that the foreground cleaning procedure (used to generate the full-sky map) could not only be creating false anomalies but also hiding existing ones. We also find a significant trace of an anomaly in the full-sky map at the scale $(l,\ell)=(10,5)$, which is still present when we consider galactic cuts of 18.3% and 28.4%. As regards the quadrupole ($\ell=2$), we find a coherent over-modulation over the whole celestial sphere, for all full-sky and cut-sky maps. Overall, our results seem to indicate that current CMB maps derived from WMAP data do not show significant signs of anisotropies, as measured by our angular-planar estimator. However, we have detected a curious coherence of planar modulations at angular scales of the order of the galaxy's plane, which may be an indication of residual contaminations in the full- and cut-sky maps.Comment: 15 pages with pdf figure

Anatomy of F_D-Term Hybrid Inflation

We analyze the cosmological implications of F-term hybrid inflation with a subdominant Fayet--Iliopoulos D-term whose presence explicitly breaks a D-parity in the inflaton-waterfall sector. This scenario of inflation, which is called F_D-term hybrid model for brevity, can naturally predict lepton number violation at the electroweak scale, by tying the mu-parameter of the MSSM to an SO(3)-symmetric Majorana mass m_N, via the vacuum expectation value of the inflaton field. We show how a negative Hubble-induced mass term in a next-to-minimal extension of supergravity helps to accommodate the present CMB data and considerably weaken the strict constraints on the theoretical parameters, resulting from cosmic string effects on the power spectrum P_R. The usual gravitino overabundance constraint may be significantly relaxed in this model, once the enormous entropy release from the late decays of the ultraheavy waterfall gauge particles is properly considered. As the Universe enters a second thermalization phase involving a very low reheat temperature, which might be as low as about 0.3 TeV, thermal electroweak-scale resonant leptogenesis provides a viable mechanism for successful baryogenesis, while thermal right-handed sneutrinos emerge as new possible candidates for solving the cold dark matter problem. In addition, we discuss grand unified theory realizations of F_D-term hybrid inflation devoid of cosmic strings and monopoles, based on the complete breaking of an SU(2) subgroup. The F_D-term hybrid model offers rich particle-physics phenomenology, which could be probed at high-energy colliders, as well as in low-energy experiments of lepton flavour or number violation.Comment: 73 pages, LaTeX, minor rewordings, references added, to appear in JHE

Technology and performances of silicon oxynitride waveguides for optomechanical sensors fabricated by plasma-enhanced chemical vapour deposition

The technology and performances of a micromachined channel waveguides, based on PECVD deposition of silicon oxynitride (SiOxNy) thin films, is presented. The deposition parameters of the PECVD process are studied in connection with their optical, mechanical and chemical properties. Waveguide deign is optimized allowing single mode, low loss propagation and high efficiency of coupling with single mode optical fiber. The proposed technology is applied to fabricate the pigtailed Mach-Zehnder interferometers, where the coupling from optical fiber to waveguide is based on the etch of U-grooves, supporting fibers in the same substrate as the waveguide substrate