Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?

PURPOSE: To determine whether a 3-mm isotropic target margin adequately covers the prostate and seminal vesicles (SVs) during administration of an intensity-modulated radiation therapy (IMRT) treatment fraction, assuming that daily image-guided setup is performed just before each fraction. MATERIALS AND METHODS: In-room computed tomographic (CT) scans were acquired immediately before and after a daily treatment fraction in 46 patients with prostate cancer. An eight-field IMRT plan was designed using the pre-fraction CT with a 3-mm margin and subsequently recalculated on the post-fraction CT. For convenience of comparison, dose plans were scaled to full course of treatment (75.6 Gy). Dose coverage was assessed on the post-treatment CT image set. RESULTS: During one treatment fraction (21.4+/-5.5 min), there were reductions in the volumes of the prostate and SVs receiving the prescribed dose (median reduction 0.1% and 1.0%, respectively, p\u3c0.001) and in the minimum dose to 0.1 cm(3) of their volumes (median reduction 0.5 and 1.5 Gy, p\u3c0.001). Of the 46 patients, three patients\u27 prostates and eight patients\u27 SVs did not maintain dose coverage above 70 Gy. Rectal filling correlated with decreased percentage-volume of SV receiving 75.6, 70, and 60 Gy (p\u3c0.02). CONCLUSIONS: The 3-mm intrafractional margin was adequate for prostate dose coverage. However, a significant subset of patients lost SV dose coverage. The rectal volume change significantly affected SV dose coverage. For advanced-stage prostate cancers, we recommend to use larger margins or improve organ immobilization (such as with a rectal balloon) to ensure SV coverage

19th Annual Conference on Legal Issues For Financial Institutions

Materials from the 19th Annual Conference on Legal Issues For Financial Institutions held by UK/CLE in May 1999

Internal Wavelength Locking Of Grating-Coupled Semiconductor Lasers Using Integrated On-Chip Littrow Grating

We have conceived, fabricated, and tested a semiconductor laser with an integrated wavelength locking mechanism using an out-coupling grating combined with a total internal reflection (TIR) Littrow grating. © 2005 OSA/IPRA 2005

Internal Wavelength Locking Of Broad Stripe Gratingcoupled Semiconductor Lasers

This paper investigates wavelength locking of broad stripe grating coupled surface emitting lasers. This approach introduces an innovative TIR-type Littrow grating for locking with comparisons it to a conventional DBR. © 2005 Optical Society of America

Compact High Peak Power Mopa Assembly Based On Grating Coupled Laser Diodes

A hybrid MOPA was assembled by stacking laser diodes incorporating grating couplers. Applying subnanosecond driving pulses for both MO and flared PA, optical pulses with 130W peak power and 98psec pulsewidth were achieved. © 2006 IEEE

Multi-Bounce Dual Grating Reflector For Internal Wavelength Locking Of Laser Diodes

This paper introduces a multi-bounce scheme based on a Dual Grating Reflector concept for integrated wavelength locking of broad stripe laser diodes. Theoretical and experimental results are shown to have a line-width of less than 50 pm for a broad stripe device. © 2007 Optical Society of America

Micro And Nano-Optics In Surface Emitting Lasers

This paper investigates surface emitting lasers using nano and micro-optics integration for spatial and spectral beam control. Specific results will be presented for beam shaping, anti-reflection coatings, and integrated wavelength locking schemes for high power devices. © 2006 Optical Society of America

Auc-Based Resolution In Optical Coherence Tomography

Optical coherence tomography (OCT) is an interferometric technique using the low coherence property of light to axially image at high resolution in biological tissue samples. Transverse imaging is obtained with two-dimensional scanning and transverse resolution is limited by the size of the scanning beam at the imaging point. The most common metrics used for determining the axial resolution of an OCT system are the full-width-at-half-maximum (FWHM), the absolute square integral (ASI), and the root-mean-square (RMS) width of the axial PSF of the system, where the PSF of an OCT system is defined as the envelope of the interference fringes when the sample has been replaced by a simple mirror. Such metrics do not take into account the types of biological tissue samples being imaged. In this paper we define resolution in terms of the instrument and the biological sample combined by defining a resolution task and computing the associated detectability index and area under the receiver operating characteristic curve (AUC). The detectability index was computed using the Hotelling observer or best linear observer. Results of simulations demonstrate that resolution is best quantified as a probability of resolving two layers, and the impact on resolution of variations in the index of refraction between the layers is clearly demonstrated

Process-based ecological river restoration: Visualizing three-dimensional connectivity and dynamic vectors to recover lost linkages

Human impacts to aquatic ecosystems often involve changes in hydrologic connectivity and flow regime. Drawing upon examples in the literature and from our experience, we developed conceptual models and used simple bivariate plots to visualize human impacts and restoration efforts in terms of connectivity and flow dynamics. Human-induced changes in longitudinal, lateral, and vertical connectivity are often accompanied by changes in flow dynamics, but in our experience restoration efforts to date have more often restored connectivity than flow dynamics. Restoration actions have included removing dams to restore fish passage, reconnecting flow through artificially cut-off side channels, setting back or breaching levees, and removing fine sediment deposits that block vertical exchange with the bed, thereby partially restoring hydrologic connectivity, i.e., longitudinal, lateral, or vertical. Restorations have less commonly affected flow dynamics, presumably because of the social and economic importance of water diversions or flood control. Thus, as illustrated in these bivariate plots, the trajectories of ecological restoration are rarely parallel with degradation trajectories because restoration is politically and economically easier along some axes more than others