Target volume coverage and dose to organs at risk in prostate cancer patients. Dose calculation on daily cone-beam CT data sets.

PURPOSE: On the basis of correct Hounsfield unit to electron density calibration, cone-beam computed tomography (CBCT) data provide the opportunity for retrospective dose recalculation in the patient. Therefore, the consequences of translational positioning corrections and of morphological changes in the patient anatomy can be quantified for prostate cancer patients. MATERIALS AND METHODS: The organs at risk were newly contoured on the CBCT data sets of 7 patients so as to evaluate the actual applied dose. The daily dose to the planning target volume (PTV) was recalculated with and without the translation data, which result from the real patient repositioning. RESULTS: A CBCT-based dose recalculation with uncertainties less than 3 % is possible. The deviations between the planning CT and the CBCT without the translational positioning correction vector show an average dose difference of - 8 % inside the PTV. An inverse proportional relation between the mean bladder dose and the actual volume of the bladder could be established. The daily applied dose to the rectum is about 1-54 % higher than predicted by the planning CT. CONCLUSION: A dose calculation based on CBCT data is possible. The daily positioning correction of the patient is necessary to avoid an underdosage in the PTV. The new contouring of the organs at risk - the bladder and rectum - allows a better appraisal to be made of the total applied dose to these organs.

Deep l-independent potentials from supersymmetric inversion

Central potentials, independent of both the energy and the angular momentum l, are constructed from elastic phase shifts. The ambiguities of a fixed- l inversion are exploited to fit the phase shifts of other partial waves. The fitted quantities are the energy and normalization constant of forbidden bound states, and the small-distance behavior of the potential. The method is based on supersymmetric transformations of the radial Schrodinger equation. It is applied to the alpha+alpha collision in nuclear physics, and to the e(-)+Ne collision in atomic physics.

Relationships between Schill's Self-defeating Personality Scale and Coolidge's Personality Disorders Inventory.

81 men and 82 women were administered Schill's (1990) Self-defeating Personality Scale and Coolidge's (1992) Axis Two Inventory. As expected, Schill's and Coolidge's measures of self-defeating personality disorder were highly correlated (.70 for men and .74 for women). Scores on Schill's scale also had correlations > .50 with scores on six of the other personality disorder scales for men and five for women. This argues against self-defeating personality disorder as measured by Schill's scale being a distinct construct. The pattern of the correlations suggests that besides assessing a person's maladaptive self-defeating traits, Schill's measure also may assess the person's anxiety and concerns about interpersonal relationships.

Resolution of the Gross-Pitaevskii equation with the imaginary-time method on a Lagrange mesh.

The Lagrange-mesh method is an approximate variational calculation which has the simplicity of a mesh calculation. Combined with the imaginary-time method, it is applied to the iterative resolution of the Gross-Pitaevskii equation. Two variants of a fourth-order factorization of the exponential of the Hamiltonian and two types of mesh (Lagrange-Hermite and Lagrange-sinc) are employed and compared. The accuracy is checked with the help of these comparisons and of the virial theorem. The Lagrange-Hermite mesh provides very accurate results with short computing times for values of the dimensionless parameter of the nonlinear term up to 104. For higher values up to 107, the Lagrange-sinc mesh is more efficient. Examples are given for anisotropic and nonseparable trapping potentials.

Note on the glide of a bird with wings bent downwards.

This note considers the influence of the bending down of the wings of a bird on the performance of its glide. The induced drag of bent wings is compared with the induced drag of a corresponding straight wing. Numerical results are given.