Linac calibration is done in water, but patients are comprised primarily of soft tissue. Conceptually, and specified in NRG/RTOG trials, dose should be reported as dose-to-muscle to describe the dose to the patient. Historically, the dose-to-water of the linac calibration was often converted to dose-to-muscle for patient calculations through manual application of a 0.99 dose-to-water to dose-to-muscle correction factor, applied during the linac clinical reference calibration. However, many current treatment planning system (TPS) dose calculation algorithms approximately provide dose-to-muscle (tissue), making application of a manual scaling unnecessary. There is little guidance on when application of a scaling factor is appropriate, resulting in highly inconsistent application of this scaling by the community. In this report we provide guidance on the steps necessary to go from the linac absorbed dose-to-water calibration to dose-to-muscle in patient, for various commercial TPS algorithms. If the TPS does not account for the difference between dose-to-water and dose-to-muscle, then TPS reference dose scaling is warranted. We have tabulated the major vendors' TPS in terms of whether they approximate dose-to-muscle or calculate dose-to-water and recommend the correction factor required to report dose-to-muscle directly from the TPS algorithm. Physicists should use this report to determine the applicable correction required for specifying the reference dose in their TPS to achieve this goal and should remain attentive to possible changes to their dose calculation algorithm in the future.

In this dosimetric study, the outdated techniques used in postoperative radiation protocols included in the postoperative radiotherapy meta-analysis provided inadequate target coverage with excessive radiation doses to organs at risk. We provide quantitative evidence for one of the explanations behind the detrimental effect noticed in the meta-analysis, invalidating its finding in the modern era of radiation planning and delivery. Background: A previous meta-analysis (MA) found postoperative radiotherapy (PORT) in lung cancer patients to be detrimental in N0/N1 patients and equivocal in the N2 setting. We hypothesized that treatment plans generated using MA protocols had worse dosimetric outcomes compared to modern plans. Patients and Methods: We retrieved plans for 13 patients who received PORT with modern planning. A plan was recreated for each patient using the 8 protocols included in MA. Dosimetric values were then compared between the modern and simulated MA plans. Results: A total of 104 MA plans were generated. Median prescribed dose was 50.4 (range, 50-60) Gy in the modern plans and 53.2 (30-60) Gy in the MA protocols. Median planning volume coverage was 96% (93%-100%) in the modern plans, versus 58% (0%-100%) in the MA plans (P < .001). Internal target volume coverage was 100% (99%-100%) versus 65% (0%-100%), respectively (P < .001). Organs at risk received the following doses: spinal cord maximum dose, 36.8 (4.6-50.4) Gy versus 46.8 (2.9-74.0) Gy (P < .001); esophageal mean dose, 22.9 (5.5-35) Gy versus 30.5 (11.1-52.5) Gy (P = .003); heart V30 (percentage of volume of an organ receiving at least a dose of 30 Gy), 16% (0%-45%) versus 35% (0%-79%) (P = .047); mean lung dose, 12.4 (3.4-24.3) Gy versus 14.8 (4.1-27.4) Gy (P = .008); and lung V20, 18% (4%-34%) versus 25% (8%-67%) (P = .023). Conclusion: We quantitatively confirm the inferiority of the techniques used in the PORT MA. Our analysis showed a lower therapeutic ratio in the MA plans, which may explain the poor outcomes in the MA. The findings of the MA are not relevant in the era of modern treatment planning.

The MA showed detrimental effect of radiation therapy in N1 lung cancer patients and no significant improvement in outcome for N2 disease, but was criticized for the crude radiation therapy techniques in the included trials. We hypothesized that MA treatment plans would demonstrate poor tumor coverage with excessive dose to the organs at risk (OARs) when compared to modern treatment plans. We retrieved images and plans for 13 patients who received PORT at our center (2007–2012). Patients were chosen to represent a variety of prior left and right lobectomies and/or pneumonectomies, but otherwise at random. All patients underwent 4D simulation. Modern treatment plans utilized 3D conformal radiation or IMRT, with heterogeneity corrections (collapsed cone convolution (CCC)). The IGTV to ITV expansion was 8mm (edited according to anatomy), with 3-7mm PTV expansion. Treatment details for the 9 trials included in the MA were gathered and the local planning CT scans were used to simulate MA plans according to the 8 distinct protocols used. The MA plans were then re-planned with CCC and heterogeneity corrections, using the same MUs as the water-equivalent simulated MA plans. Tumor coverage and achieved OAR dosimetric values were then compared between the modern and simulated MA plans, with statistical significance of the differences ascertained by the Mann-Whitney U test. A total of 104 MA plans were generated on 13 patients. Eight patients (62%) had right lung disease. Two (15%) patients underwent pneumonectomy and 11 (85%) underwent lobectomy. Median prescribed dose was 50.4 Gy (range 50-60 Gy) in the modern plans, and 53.2 Gy (30-60) in the MA protocols. Median PTV coverage by the prescription dose was 96% (93-100%) in the modern plans and 58% (0-100%) across the MA plans (P<0.001). ITV coverage was 100% (99-100%) versus 65% (0-100%), respectively (P<0.001). The OARs received significantly less dose in the modern plans: spinal cord max dose: 36.8 Gy (4.6-50.4) vs. 46.8 Gy (2.9-74.0) in the MA plans (P<0.001); esophageal mean dose: 22.9 Gy (5.5-35) vs. 30.5 Gy (11.1-52.5) (P=0.003); heart V30: 16% (0%-45%) vs 35% (0%-79%) (P=0.047); mean lung dose: 12.4 Gy (3.4-24.3) vs. 14.8 Gy (4.1-27.4) (P=0.008); lung V20: 18% (4%-34%) vs. 25% (8%-67%) (P=0.023). We quantitatively confirm inferiority of the MA techniques with significantly reduced ITV/PTV coverage and increased doses to OARs. This leads to a lower therapeutic ratio in the MA plans, which likely explains the poor MA outcomes. The MA conclusions are therefore not relevant to modern patients. The pending results of the randomized LungART study may elucidate whether modern adjuvant radiation would benefit appropriately selected patients.

PURPOSE:The authors designed data, methods, and metrics that can serve as a standard, independent of any software package, to evaluate dose-volume histogram (DVH) calculation accuracy and detect limitations. The authors use simple geometrical objects at different orientations combined with dose grids of varying spatial resolution with linear 1D dose gradients; when combined, ground truth DVH curves can be calculated analytically in closed form to serve as the absolute standards.METHODS:dicom RT structure sets containing a small sphere, cylinder, and cone were created programmatically with axial plane spacing varying from 0.2 to 3 mm. Cylinders and cones were modeled in two different orientations with respect to the IEC 1217 Y axis. The contours were designed to stringently but methodically test voxelation methods required for DVH. Synthetic RT dose files were generated with 1D linear dose gradient and with grid resolution varying from 0.4 to 3 mm. Two commercial DVH algorithms-pinnacle (Philips Radiation Oncology Systems) and PlanIQ (Sun Nuclear Corp.)-were tested against analytical values using custom, noncommercial analysis software. In Test 1, axial contour spacing was constant at 0.2 mm while dose grid resolution varied. In Tests 2 and 3, the dose grid resolution was matched to varying subsampled axial contours with spacing of 1, 2, and 3 mm, and difference analysis and metrics were employed: (1) histograms of the accuracy of various DVH parameters (total volume, Dmax, Dmin, and doses to % volume: D99, D95, D5, D1, D0.03 cm(3)) and (2) volume errors extracted along the DVH curves were generated and summarized in tabular and graphical forms.RESULTS:In Test 1, pinnacle produced 52 deviations (15%) while PlanIQ produced 5 (1.5%). In Test 2, pinnacle and PlanIQ differed from analytical by >3% in 93 (36%) and 18 (7%) times, respectively. Excluding Dmin and Dmax as least clinically relevant would result in 32 (15%) vs 5 (2%) scored deviations for pinnacle vs PlanIQ in Test 1, while Test 2 would yield 53 (25%) vs 17 (8%). In Test 3, statistical analyses of volume errors extracted continuously along the curves show pinnacle to have more errors and higher variability (relative to PlanIQ), primarily due to pinnacle's lack of sufficient 3D grid supersampling. Another major driver for pinnacle errors is an inconsistency in implementation of the "end-capping"; the additional volume resulting from expanding superior and inferior contours halfway to the next slice is included in the total volume calculation, but dose voxels in this expanded volume are excluded from the DVH. PlanIQ had fewer deviations, and most were associated with a rotated cylinder modeled by rectangular axial contours; for coarser axial spacing, the limited number of cross-sectional rectangles hinders the ability to render the true structure volume.CONCLUSIONS:The method is applicable to any DVH-calculating software capable of importing dicom RT structure set and dose objects (the authors' examples are available for download). It includes a collection of tests that probe the design of the DVH algorithm, measure its accuracy, and identify failure modes. Merits and applicability of each test are discussed.

PURPOSE:To evaluate a method for in-vivo determination of proton range and post-Bragg peak straggling by detection of proton induced x-ray fluorescence of markers placed at known locations.METHODS:Therapeutic beams from the UF Proton Therapy Institute were used to excite proton-induced x-ray fluorescence emission (PIXE) from cylindrical pure gold fiducial markers. The markers were embedded in a homogeneous water phantom and PIXE was measured using NaI photodetectors with energy dispersive spectral analysis. The geometry of the phantom and marker placement was chosen to model parallel-opposed beam treatment of prostate cancer by proton therapy. The fluorescence yield from these markers was further modeled using the GEANT4 Monte-Carlo package with low-energy corrections. Gold K and L shell fluorescence yield as determined by the GEANT4 simulations was verified quantitatively by comparison to measured Au yield at energies from 1 MeV to 68 MeV, and to semiempirical model calculations covering the energy range from 1 MeV to 15 MeV.RESULTS:The Au K-shell fluorescence cross section is significantly smaller thanthat of the L-shell, but the higher yield of the L-shell fluorescence isoffset by the larger absorption as the x-ray exits the phantom. The overallrelative detection efficiency of K and L shell fluorescence depends on thedetails of the shape of the phantom and location of the marker. Acharacteristic shape of fluorescence yield as it depends on proton range isfound, which can be used to extract an in-vivo PDD profile of a spread-outBragg peak (SOBP).CONCLUSIONS:A combination of a specific protocol for delivering a SOBP, geometriclocation of fiducial markers from CT, and simultaneous detection of protoninduced x-ray fluorescence, can determine the depth range of a primary protonbeam in-vivo. The fluorescence yield as measured at the Proton Therapy Institute is easily distinguished from background radiation.

Purpose: To evaluate the potential clinical uses of gamma‐ray beams generated by the process of laser‐Compton backscattering from relativistic electron beams. Methods: Inverse‐Compton backscattering has been demonstrated to produce short pulse‐length, high brightness, gamma‐ray beams with energy in the neighborhood of 1 MV (F. Albert et al., Phys. Rev. ST 13, 070704 (2010)). The reported experimental parameters for inverse‐ Compton beams in the high orthovoltage energy range are used to estimate potential future performance of >1 MV sources, with realistically achievable parameters for spectral bandwidth and beam emittance. A model source based on these parameters is implemented in a commercial treatment planning system (Pinnacle 8.0) and used to deliver small‐field treatments to phantoms, and to compare to retrospective stereotactic radiosurgery plans. Results: The emittance of current and future laser‐gamma sources are compared to the requirements of SRS and SBRT. These features have a measurable effect on the beam penumbra that can be beneficially exploited in radiotherapy. Not unexpectedly, the principle limitation of such sources would appear to be the peak flux that can be obtained, since these sources are high brightness, but not necessarily high flux producers, leading to long treatment times that would not be clinically useful. Relaxation of some beam parameters, such as larger source size, would not significantly affect the use of such a source in SRS. Conclusions: The generation of highly collimated gamma‐rays of energy 1 MV and above is possible using the Thompson‐Compton scattering of laser photons from linac accelerated electron beams. The flux produced by these beams has been increasing steadily with each new construction project, and theoretical estimates of the achievable flux indicate that they may reach clinically relevant levels of output in the future. Certain characteristics of these beams, specifically the angular divergence and small source size, can be beneficially employed in radiotherapy.

We present examples of the application of synchrotron-based spectroscopies and microscopies to environmentally relevant samples. The experiments were performed at the molecular environmental science beamline (11.0.2) at the Advanced Light Source, Lawrence Berkeley National Laboratory. Examples range from the study of water monolayers on Pt(1 1 1) single crystal surfaces using X-ray emission spectroscopy and the examination of alkali halide solution/water vapor interfaces using ambient pressure photoemission spectroscopy, to the investigation of actinides, river water biofilms, Al-containing colloids and mineral–bacteria suspensions using scanning transmission X-ray spectromicroscopy. The results of our experiments show that spectroscopy and microscopy in the soft X-ray energy range are excellent tools for the investigation of environmentally relevant samples under realistic conditions, i.e., with water or water vapor present at ambient temperature.

The need for increased sensitivity in the detection of metallic contamination, in microelectronics fabrication, led to the development of heavy ion backscattering spectrometry (HIBS). This technique, based on principles similar to those of Rutherford backscattering spectrometry, permits one to quantitatively detect heavy impurities, at a level below 1×1010 atoms/cm2, on the surface of an otherwise clean silicon substrate. The approach was developed at Sandia National Laboratories, in collaboration with SEMATECH member companies, and Vanderbilt University. Recently, the HIBS instrument was transferred to the Department of Physics of the University of Central Florida, with the purpose of continuing the development of this unique resource, and making it available to industrial and academic investigators. The instrument has been successfully returned to operation, and preliminary tests showed sensitivity levels similar to those obtained at Sandia. A program is being developed to further increase the sensitivity of the instrument, as well as to explore potential new applications. A progress report of these efforts is presented.

We have applied Scanning Transmission Soft X-ray Microscopy (STXM) to investigate the charge state distribution of Mn in two kinds of Mn-biominerals, Mn nodules collected from Lake Michigan sediments and Mn precipitates formed by spores of a marine bacillus SG-1 under transport limited reaction conditions. A data analysis technique was developed, which allows for extraction of spatially resolved 2-d charge state maps of manganese on a submicron level. We find that the charge state of Mn dominates the spectral shape of L-edge spectra of environmentally important single oxidation state Mn minerals and that spectra of mixed oxidation state oxides can be modelled by a combination of appropriate single oxidation state reference spectra. Two-dimensional maps of charge state distributions clearly reveal domains of different oxidation states within single particles of Mn-micronodules. Spots of preferred accumulation of Mn(II) were found, which indicates biogenic precipitation of Mn(II)-species as a first step of nodule formation. The presence of Mn(III) in the studied sediment samples suggests the involvement of one-electron oxidation processes and reaction conditions which inhibit or slow down the disproportionation of Mn(III)-products. Under transport limited conditions, Mn oxidation products formed by spores of the marine bacillus SG-1 can vary from cell to cell. The presence of significant amounts of Mn(III) containing species points to the involvement of one-electron oxidation reactions as in the case of the micro-nodules. Our technique and the results obtained form a new basis for the mechanistic understanding of the formation of Mn biominerals in the environment.

We investigate the initial oxidation and interface formation of cubic silicon carbide for the silicon rich β-SiC(100) 3×2 surface reconstruction by high resolution synchrotron radiation-based soft x-ray photoemission spectroscopy. The surface is exposed to low doses of molecular oxygen ranging from 1 up to 10 000 L, at surface temperatures from 25 to 500 °C. Significant formation of SiO2 is found for the surface at room temperature, with the rate of oxidation increasing with temperature. Valence band data and Si 2p core level spectra show that even at low exposures, significant oxidation is taking place, with a surface reactivity to oxygen much larger than for silicon surfaces. The oxidation products, which are grown at very low temperatures (⩽500 °C) include SiO2 as a dominant feature but also substoichiometric oxides Si+1, Si+2, Si+3, and significant amounts of mixed oxide products involving C atoms (Si–O–C).

The structure of the Si-rich 3C-SiC(001)-(3x2) surface reconstruction has been determined using x-ray photoelectron diffraction. The experimental results are only compatible with a modified version of the two-adlayer asymmetric dimer model. Other possible models can be discarded on the basis of our results.

We propose differential holography as a method to overcome the long-standing forward-scattering problem in photoelectron holography and related techniques for the three-dimensional imaging of atoms. Atomic images reconstructed from experimental and theoretical Cu 3p holograms from Cu(001) demonstrate that this method suppresses strong forward-scattering effects so as to yield more accurate three-dimensional images of side- and backscattering atoms.

We have applied a new differential method of photoelectron holography to both experimental and theoretical multiple-energy photoelectron diffraction data for Cu 3p bulk emission from Cu(001). Dominant forward-scattering effects contained in a normalized hologram χk have been eliminated by taking the k-difference δχk along each direction k̂. Two data sets that are different in k-space sampling ranges and densities have been analyzed to compare atomic images reconstructed from χ and δχ. In both cases, the original scheme has yielded only very weak images of back-scattering atoms and spurious features in the forward-scattering directions. On the other hand, the differential scheme has been found to be successful in suppressing the forward-scattering effects to image not only side-scattering and back-scattering atoms in either case, but also forward-scattering atoms in one of the two cases.

The interfaces between solid mineral particles and water play a crucial role in partitioning and chemical transformation of many inorganic as well as organic pollutants in environmental systems. Among environmentally significant minerals, mixed-valent oxides and hydroxides of iron (e.g. magnetite, green rusts) and manganese (hausmanite, birnessite) have been recognized as particularly strong sorbents for metal ions. In addition, minerals containing Fe(II) have recently been proven to be powerful reductants for a wide range of pollutants. Chemical properties of these minerals strongly depend on the distribution and availability of reactive sites and little is known quantitatively about the nature of these sites. We have investigated the bulk distribution of charge states of manganese (Mn (II, III, IV)) and iron (Fe(II, III)) in single particles of natural manganese nodules and synthetic green rusts using Scanning Transmission X-ray SpectroMicroscopy (STXM). Pixel resolved spectra (XANES) extracted from stacks of images taken at different wave lengths across the metal absorption edge were fitted to total electron yield (TEY) spectra of single valent reference compounds. Two dimensional maps of bulk charge state distributions clearly reveal domains of different oxidation states within single particles of Mn-nodules and green rust precipitates. Changes of oxidation states of iron were followed as a result of reductive transformation of an environmental contaminant (CCl4) using green rust as the only reductant.

We performed feasibility tests of photoelectron emission spectromicroscopy of wet samples in the water window (285–532 eV) soft x-ray spectral region. Water was successfully confined in an ultrahigh vacuum compatible compartment with x-ray transparent sides. This water cell was placed in the MEPHISTO spectromicroscope in a transmission geometry, and complete x-ray absorption spectra of the water window region were acquired. We also show micrographs of test samples, mounted outside of the compartment, and imaged through the water. This technique can be used to study liquid chemistry and, at least to the micron level, the microstructure of wet samples. Possibilities include cells in water or buffer, proteins in solution, oils of tribological interest, liquid crystals, and other samples not presently accessible to the powerful x-ray photoelectron emission spectromicroscopy technique.