Highly efficient and sensitive patient-specific quality assurance for spot-scanned proton therapy.

The purpose of this work was to develop an end-to-end patient-specific quality assurance (QA) technique for spot-scanned proton therapy that is more sensitive and efficient than traditional approaches. The patient-specific methodology relies on independently verifying the accuracy of the delivered proton fluence and the dose calculation in the heterogeneous patient volume. A Monte Carlo dose calculation engine, which was developed in-house, recalculates a planned dose distribution on the patient CT data set to verify the dose distribution represented by the treatment planning system. The plan is then delivered in a pre-treatment setting and logs of spot position and dose monitors, which are integrated into the treatment nozzle, are recorded. A computational routine compares the delivery log to the DICOM spot map used by the Monte Carlo calculation to ensure that the delivered parameters at the machine match the calculated plan. Measurements of dose planes using independent detector arrays, which historically are the standard approach to patient-specific QA, are not performed for every patient. The nozzle-integrated detectors are rigorously validated using independent detectors in regular QA intervals. The measured data are compared to the expected delivery patterns. The dose monitor reading deviations are reported in a histogram, while the spot position discrepancies are plotted vs. spot number to facilitate independent analysis of both random and systematic deviations. Action thresholds are linked to accuracy of the commissioned delivery system. Even when plan delivery is acceptable, the Monte Carlo second check system has identified dose calculation issues which would not have been illuminated using traditional, phantom-based measurement techniques. The efficiency and sensitivity of our patient-specific QA program has been improved by implementing a procedure which independently verifies patient dose calculation accuracy and plan delivery fidelity. Such an approach to QA requires holistic integration and maintenance of patient-specific and patient-independent QA.

Axial observables in d-->p--> breakup and the three-nucleon force.

We have measured three axial polarization observables in d-->p--> breakup with a polarized 270 MeV deuteron beam on a polarized proton target. Axial observables are zero by parity conservation in elastic scattering but can be easily observed in the breakup channel at the present energy. Based on a symmetry argument, the sensitivity of these observables to the three-nucleon force might be enhanced. Calculations without three-nucleon force are in fair agreement with our measurement, indicating that the expected sensitivity of axial observables to the three-nucleon force is not confirmed. Including a three-nucleon force in the calculation does not improve the agreement with the data.

Identification and semiquantification of estrogen and progesterone receptors in pyogenic granulomas of pregnancy.

Cases of pyogenic granuloma in pregnant women, nonpregnant women, and men were evaluated for the detection of estrogen and progesterone receptor proteins by immunoperoxidase staining. Immunostaining for estrogen receptors revealed a marked immunoreactivity of the endothelium within lesional tissue and in the overlying mucosal epithelium in many cases. Progesterone receptor immunoreactivity was only present within the epithelium, where it was much less than that of estrogen receptor immunoreactivity in both quantity (proportion of positive cells) and intensity. No characteristic staining pattern or significant quantitative difference among the three study groups could be discerned. These findings suggest that the quantity of estrogen or progesterone receptors in pyogenic granuloma is not the determining factor in the pathogenesis of this lesion. Rather, such a role may be attributed to the levels of circulating hormones. The levels of estrogen and progesterone are markedly increased in pregnancy and could therefore exert a greater effect on the endothelium of the pyogenic granuloma.

Isotopic shift of the (5)F degrees (1) ? (3)F(2) transition in (91)Zr.

Laser-induced fluorescence spectra of Zr atoms sputtered by ion bombardment have been obtained for the (5)F degrees (1) ? (3)F(2) transition at 595.5 nm. The isotopic shift of (91)Zr is found to be -70 +/- 40 MHz relative to the (90)Zr peak. A discrepancy in literature values for the hyperfine constants of the (5)F degrees (1) state is also resolved.

Laser-enhanced electron-impact ionization spectroscopy.

Sequential photon-excitation, electron-impact ionization with subsequent mass analysis has been applied to a barium atomic beam. High-resolution, Doppler-free laser excitation produces the 6s6p(1)P(1) excited state, which is then ionized by electron bombardment. The excited state is selectively ionized when bombardment energies are between the excited- and ground-state ionization thresholds. Mass discrimination has permitted the recording of individual optical spectra for all the stable isotopes, including the 0.1% abundant (130)Ba and (132)Ba, in a sample with natural isotopic abundances.