Objective: To develop and evaluate an integrated approach to intra-operative dosimetry for permanent prostate brachytherapy (PPB) by combining a fluoroscopy-based seed localization routine with a ...transrectal ultrasound (TRUS)-to-fluoroscopy fusion technique.
Materials and Methods: Three-dimensional seed coordinates are reconstructed based on the two-dimensional seed locations identified from three fluoroscopic images acquired at different angles. A seed-based registration approach was examined in both simulation and phantom studies to register the seed locations identified from the fluoroscopic images to the TRUS images. Dose parameters were then evaluated and compared to CT-based dosimetry from a patient dataset.
Results: Less than 0.2% error in the D90 value was observed using the TRUS-fluoroscopy image-fusion-based method relative to the CT-based post-implantation dosimetry. In the phantom study, an average distance of 3 mm was observed between the seeds identified from TRUS and the reconstructed seeds at registration. Isodose contours were displayed superimposed on the TRUS images.
Conclusions: Promising results were observed in this preliminary study of a TRUS-fluoroscopy fusion-based brachytherapy dosimetry analysis method, suggesting that the method is highly sensitive and calculates clinically relevant dosimetry, including the prostate D90. Further validation of the method is required for eventual clinical application.
Purpose: To measure dispersion of a clinical proton therapy beam. Methods and Materials: The proton center at our institution uses a Hitachi PROBEAT V synchrotron that delivers beams with energies ...ranging from 70 to 230 MeV to five treatment rooms, four of which have gantries and one fixed beam. For this study, the magnetic field strengths of all optics in the transport line were varied to measure the dispersion of 230 MeV beams in each of the four gantry rooms. Beam position was measured using the Spot Position Monitor (SPM), a multi-wire proportional counter (MWPC) in the nozzle approximately 0.5 meters upstream of the treatment isocenter. Measured beam positions as a function of momentum offset were fitted to a linear function to extract dispersion. In one gantry, dispersions for 70 and 140 MeV beams were also measured. Because spot position is continuously monitored during treatments and a position deviation will abort the beam delivery, the dispersion at the spot position monitor was used to set an upper limit of range uncertainty originating from momentum deviation. When dispersion was approximately zero, dose rate measurements were used to set an upper limit of momentum deviation that could reach the patient. Results: Dispersion was 0.45 m, 0.48 m and 0.30 m for 70 MeV, 140 MeV, and 230 MeV beams in a gantry, respectively, corresponding to 0.3 mm, 1.0 mm and 3.5 mm maximum range uncertainty during treatments. For 230 MeV beams, dispersion ranged from 0 to 0.73 m across the four gantries, corresponding to the upper limits of range uncertainty due to momentum deviation of 1.4 to 6.2 mm (0.4 to 1.9% in fractional range uncertainty). Conclusions: The measured dispersion was both energy- and gantry-dependent and ranged from 0 to 0.73 m.
Angular distributions of the differential cross sections and analyzing powers have been measured for the $\rm\sp3He(\vec p,\pi\sp+)\sp4He$ and $\sp4$He($\vec p,\pi\sp+)\sp5$He reactions at proton ...bombarding energies between 240 and 507 MeV providing a comprehensive set of data spanning the region of the $\Delta\sb{1232}$ resonance. For these experiments, the University of Manitoba/TRIUMF liquid $\sp3$He target was extensively refurbished and modified for provision of stable and reliable operation. A Monte Carlo study of the TRIUMF Medium Resolution Spectrometer for detecting pions was performed to investigate the acceptance, solid angle, and pion decay length of the spectrometer. Furthermore, for the $\sp5$He spectra, a final interaction calculation was carried out which uses information from the n + $\alpha$ elastic phase shifts. The results obtained are of very high quality and are compared with a recent microscopic (p,$\pi\sp+$) calculation and a phenomenological study based upon the pp $\to$ d$\pi\sp+$ amplitudes.
The influence of oceanic biological activity on sea spray aerosol composition, clouds, and climate remains poorly understood. The emission of organic material and gaseous dimethyl sulfide (DMS) from ...the ocean represents well-documented biogenic processes that influence particle chemistry in marine environments. However, the direct emission of particle-phase biogenic sulfur from the ocean remains largely unexplored. Here we present measurements of ocean-derived particles containing reduced sulfur, detected as elemental sulfur ions (e.g., 32S+, 64S2 +), in seven different marine environments using real-time, single particle mass spectrometry; these particles have not been detected outside of the marine environment. These reduced sulfur compounds were associated with primary marine particle types and wind speeds typically between 5 and 10 m/s suggesting that these particles themselves are a primary emission. In studies with measurements of seawater properties, chlorophyll-a and atmospheric DMS concentrations were typically elevated in these same locations suggesting a biogenic source for these sulfur-containing particles. Interestingly, these sulfur-containing particles only appeared at night, likely due to rapid photochemical destruction during the daytime, and comprised up to ∼67% of the aerosol number fraction, particularly in the supermicrometer size range. These sulfur-containing particles were detected along the California coast, across the Pacific Ocean, and in the southern Indian Ocean suggesting that these particles represent a globally significant biogenic contribution to the marine aerosol burden.
Oceans represent a significant natural source of gases and particles to the atmosphere. Relative to gas phase compounds, less is known regarding the influence of changes in biological activity in the ...ocean on the chemistry of sea spray aerosols produced in marine environments. To gain insight into the influence of ocean biology and chemistry on atmospheric aerosol chemistry, simultaneous real‐time measurements were made of atmospheric aerosol size and chemical mixing‐state, gas phase dimethyl sulfide (DMS), as well as seawater DMS and chlorophyll a. In three different marine environments with elevated chlorophyll a and DMS, unique Mg particles were detected containing Mg2+, Ca2+, K+, and organic carbon. These particles were segregated from sea salt particles highlighting that two subpopulations within the sea spray were being ejected from the ocean. Strong temporal correlations were observed between these unique ocean‐derived particles and freshly emitted sea salt particles (R2 = 0.86), particularly as wind speed increased to at least 10 m/s, and atmospheric DMS (R2 = 0.76). Time series correlations between ocean measurements and atmospheric aerosol chemistry suggest that chlorophyll a and DMS serve as indicators of changes in the chemistry of the ocean, most likely an increase in organic material, which is directly reflected in the single particle mixing‐state. This is the first time such real‐time correlations are shown between ocean chemistry and atmospheric aerosol mixing‐state. The reasons behind these observed changes in aerosol chemistry are critical for understanding the heterogeneous reactivity, water uptake, and cloud forming potential of sea spray aerosols.
Key Points
Enrichment of alkaline metals is occurring in sea spray aerosol
This chemical enrichment is occurring at the single particle level
These unique particles are correlated with other tracers of biological activity
Human beings have a strong fundamental need to form and maintain relationships. Social exclusion therefore evokes social pain in excluded individuals, whereas social inclusion evokes pleasure in ...those individuals who are included. The present study used near-infrared spectroscopy (NIRS) to investigate whether individual differences in personality, specifically differences in behavioral inhibition and activation system (BIS and BAS) functioning, affect the experiences of social pleasure and pain. Thirty-seven undergraduates participated in an NIRS session that involved both social rejection and inclusion during an online ball-tossing game. People with greater BIS sensitivity experienced more social pain during social exclusion, while people with greater BAS sensitivity reported more social pleasure during social inclusion. BIS sensitivity was negatively correlated with ventrolateral prefrontal cortex (VLPFC) activity during social exclusion. Finally, VLPFC activity partially mediated the relationship between BIS sensitivity and social pain experienced during social exclusion.
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