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Wu, L

Publications and source records attributed to Wu, L.

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

SU-F-J-101: Stereotactic Body Radiation Therapy Planning for Primary Prostate Cancer with Selective Intraprostatic Boost Determined by 18F-Choline PET/CT

Purpose: To investigate the utility of {sup 18}F-choline positron emission tomography (PET) scans guidance for SBRT dose painting in patients with prostate cancer and its impact on tumor control probability (TCP) and normal tissue complication probability (NTCP). Methods: Twenty seven patients with localized prostate cancer who had {sup 18}F-choline PET/CT scan prior to treatment were included. A pair of nested intraprostatic dominant lesion (IDL) contours (IDL{sub suv60%} and IDL{sub suv70%}) were generated for each patient based on 60% and 70% of maximum prostate uptake on the {sup 18}F-choline PET images. GTV{sub reg} was delineated on prostate according to the gland boundary seen on CT images. The PTVs (PTV{sub suv60%} and PTV{sub suv70%}) were defined as respective IDLs with a 3-mm margin posteriorly and 5 mm in all other dimensions. Two 5-fraction SBRT plans using VMAT technique along with 10 MV FFF beams, plan{sub 36Gy} and plan{sub 50–55Gy}, were generated for each patient. All plans included a dose of 36.25 Gy prescribed to PTV{sub reg}. The Plan{sub 50–55Gy} also included a simultaneous boost dose of 50 Gy and 55 Gy prescribed to the PTV{sub suv60%} and PTV{sub suv70%}, respectively. The utility of {sup 18}F-Choline PET-guided SBRT dose escalation was evaluated by its ability to achieve the prescription dose objectives while adhering to organ-at-risk (OAR) dose constraints. The TCP and NTCP calculated by radiological models were also compared between two plans for each patient. Results: In all 54 SBRT plans generated, the planning objectives and dose constraints were met without exception. Plan{sub 50–55Gy} had a significantly higher dose in PTV{sub suv60%} and PTV{sub suv70%} than those in Plan{sub 36Gy} (p < 0.05), respectively, while still maintaining a safe OAR sparing profile. In addition, plan{sub 50–55Gy} had significantly higher TCP than plan{sub 36Gy}. Conclusion: Using VMAT with FFF beams to incorporate a simultaneous {sup 18}F-choline PET-guided radiation boost dose up to 55 Gy into a SBRT plan is technically feasible. This work was supported in part by Congressionally Directed Medical Research Programs Prostate Cancer Research Program grant PC04130, National Institutes of Health/National Cancer Institute grant R41CA110121, and the UNLV Lincy Endowed Assistant Professorship.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Structural Defects of Silver Hollandite, Ag x Mn 8 O y , Nanorods: Dramatic Impact on Electrochemistry

Hollandites (OMS-2) are an enticing class of sorbents, catalysts, and energy storage materials with a tunnel structure permitting one-dimensional insertion and deinsertion of ions and small molecules along the c direction. A 7-fold increase in delivered capacity for Li/Ag x Mn 8 O 16 electrochemical cells (160 versus 23 mAh/g) observed upon a seemingly small change in silver content ( x ~1.1 (L-Ag-OMS-2) and 1.6 (H-Ag-OMS-2)) led us to characterize the structure and defects of the silver hollandite material. In this work, Ag hollandite nanorods are studied through the combined use of local (atomic imaging, electron diffraction, electron energy-loss spectroscopy) and bulk (synchrotron based X-ray diffraction, thermogravimetric analysis) techniques. Selected area diffraction and high resolution transmission electron microscopy show a structure consistent with that refined by XRD; however, the Ag occupancy varies significantly even within neighboring channels. Both local and bulk measurements indicate a greater quantity of oxygen vacancies in L-Ag-OMS-2, resulting in lower average Mn valence relative to H-Ag-OMS-2. Electron energy loss spectroscopy shows a lower Mn oxidation state on the surface relative to the interior of the nanorods, where the average Mn valence is approximately Mn 3.7+ for H-Ag-OMS-2 and Mn 3.5+ for L-Ag-OMS-2 nanorods, respectively. The higher delivered capacity of L-Ag-OMS-2 may be related to more oxygen vacancies compared to H-Ag-OMS-2. Thus, the oxygen vacancies and MnO 6 octahedra distortion are assumed to open the MnO 6 octahedra walls, facilitating Li diffusion in the ab plane. These results indicate crystallite size and surface defects are significant factors affecting battery performance.

25 ENERGY STORAGE↗
DOE OSTI2015

SU-C-BRA-01: 18F-NaF PET/CT-Directed Dose Escalation in Stereotactic Body Radiotherapy for Spine Oligometastases From Prostate Cancer

Purpose: To investigate the technical feasibility of SBRT dose painting using {sup 18}F-NaF positron emission tomography (PET) scans guidance in patients with spine oligometastases from prostate cancer. Methods: As a proof of concept, six patients with 14 spine oligometastatic lesions from prostate cancer who had {sup 18}F-NaF PET/CT scan prior to treatment were retrospectively included. GTV{sub reg} was delineated according to the regular tumor boundary shown on PET and/or CT images; and GTV{sub MATV} was contoured based on a net metabolically active tumor volume (MATV) defined by 60% of the SUV{sub max} values on {sup 18}F-NaF PET images. The PTVs (PTV{sub reg} and PTV{sub MATV}) were defined as respective GTVs (plus involved entire vertebral body for PTV{sub reg}) with a 3-mm isotropic expansion margin. Three 1-fraction SBRT plans using VMAT technique along with 10 MV FFF beams (Plan{sub 24Gy}, Plan{sub 24–27Gy}, and Plan{sub 24–30Gy}) were generated for each patient. All plans included a dose of 24 Gy prescribed to PTV{sub reg}. The Plan{sub 24–27Gy} and Plan{sub 24–30Gy} also included a simultaneous boost dose of 27 Gy or 30 Gy prescribed to the PTV{sub MATV}, respectively. The feasibility of 18F-NaF PET-guided SBRT dose escalation was evaluated by its ability to achieve the prescription dose objectives while adhering to organ-at-risk (OAR) dose constraints. The normal tissue complication probabilities (NTCP) calculated by radiological models were also compared between the plans. Results: In all 33 SBRT plans generated, the planning objectives and dose constraints were met without exception. Plan{sub 24–27Gy} and Plan{sub 24–30Gy} had a significantly higher dose in PTV{sub MATV} than Plan{sub 24Gy} (p < 0.05), respectively, while maintaining a similar OAR sparing profile and NTCP values. Conclusion: Using VMAT with FFF beams to incorporate a simultaneous {sup 18}F-NaF PET-guided radiation boost dose up to 30 Gy into a SBRT plan is technically feasible. The relationship between local control and normal tissue toxicity in SBRT dose painting should be validated in clinical trials.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-P-56: Dosimetric Comparison of Three Post Modified Radical Mastectomy Radiotherapy Techniques for Locally Advanced Left-Sided Breast Cancer and Beyond

Purpose: To compare the dosimetry of post modified radical mastectomy radiotherapy (PMRMRT) for left-sided breast cancer using 3-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). Methods: We created ten sets of PMRMRT plans for ten consecutive patients and utilized two tangential and one or two supraclavicular beams in 3DCRT, a total of 5 beams in IMRT and two optimized partial arcs in VMAT. The difference in results between any two of the three new plans, between new and previous 3DCRT plans were compared and analyzed by ANOVA (α =0.05) and paired-sample t-test respectively. P values less than 0.05 were considered statistically significant. Results: Both IMRT and VMAT plans had similar PTV coverage, hotspot area and conformity (all p>0.05), and significantly higher PTV coverage compared with new 3DCRT (both p<0.001). IMRT plans had significantly less heart and left lung radiation exposure compared with VMAT (all p<0.05). The 3DCRT plans with larger estimated CTV displacement had better target coverage but worse OARs sparing compared to those with smaller one. Conclusion: IMRT has dosimetrical advantages over the other two techniques in PMRMRT for left-sided breast cancer. Individually quantifying and minimizing CTV displacement can significantly improve dosage distribution. This work was supported by the Medical Scientific Research Foundation of Guangdong Procvince (A2014455 to Changchun Ma)

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

SU-E-T-811: Volumetric Modulated Arc Therapy Vs. C-IMRT for the Treatment of Upper Thoracic Esophageal Cancer

Purpose: To compare plans using volumetric-modulated arc therapy (VMAT) with conventional sliding window intensity-modulated radiation therapy (c-IMRT) to treat upper thoracic esophageal cancer (EC). Methods: CT datasets of 11 patients with upper thoracic EC were identified. Four plans were generated for each patient: c-IMRT with 5 fields (5F) and VMAT with a single arc (1A), two arcs (2A), or three arcs (3A). The prescribed doses were 64 Gy/32 F for the primary tumor (planning target volume 64, PTV64). The dose-volume histogram data, the number of monitoring units (MUs) and the treatment time (TT) for the different plans were compared. Results: All of the plans generated similar dose distributions for PTVs and organs at risk (OARs), except that the 2A- and 3A-VMAT plans yielded a significantly higher conformity index (CI) than the c-IMRT plan. The CI of the PTV64 was improved by increasing the number of arcs in the VMAT plans. The maximum spinal cord dose and the planning risk volume of the spinal cord dose for the two techniques were similar. The 2A- and 3A-VMAT plans yielded lower mean lung doses and heart V50 than the c-IMRT. The V20 and V30 for the lungs in all of the VMAT plans were lower than those in the c-IMRT plan, at the expense of increasing V5, V10 and V13. The VMAT plan resulted in significant reductions in MUs and TT. Conclusion: The 2A-VMAT plan appeared to spare the lungs from moderate-dose irradiation most effectively of all plans, at the expense of increasing the low-dose irradiation volume, and also significantly reduced the number of required MUs and the TT. The CI of the PTVs and the OARs was improved by increasing the arc-number from 1 to 2. however, no significant improvement was observed using the 3A-VMAT, except for an increase in the TT. This work was sponsored by Shantou University Medical College Clinical Research Enhancement Initiative(NO.201424)

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Intrinsic Nanostructure in Zr 2-x Fe 4 Si 16-y (x=0.81, y=6.06)

We present a study of the crystal structure and physical properties of single crystals of a new Fe-based ternary compound, Zr 2-x Fe 4 Si 16-y (x=0.81,y=6.06). Zr 1.19 Fe 4 Si 9.94 is a layered compound, where stoichiometric β-FeSi 2 -derived slabs are separated by Zr-Si planes with substantial numbers of vacancies. High resolution transmission electron microscopy (HRTEM) experiments show that these Zr-Si layers consist of 3.5nm domains where the Zrand Si vacancies are ordered within a supercell sixteen times the volume of the stoichiometric cell. Within these domains, the occupancies of the Zr and Si sites obey symmetry rules that permit only certain compositions, none of which by themselves reproduce the average composition found in x-ray diffraction experiments. Magnetic susceptibility and magnetization measurements reveal a small but appreciable number of magnetic moments that remain freely fluctuating to 1.8K, while neutron diffraction confirms the absence of bulk magnetic order with a moment of 0.2μB or larger down to 1.5K. Electrical resistivity measurements find that Zr 1.19 Fe 4 Si 9.94 is metallic, and the modest value of the Sommerfeld coefficient of the specific heat γ = C/T suggests that quasi-particle masses are not particularly strongly enhanced. The onset of superconductivity at T c ≃ 6K results in a partial resistive transition and a small Meissner signal, although a bulk-like transition is found in the specific heat. Sharp peaks in the ac susceptibility signal the interplay of the normal skin depth and the London penetration depth, typical of a system in which nano-sized superconducting grains are separated by a on-superconducting host. Ultra low field differential magnetic susceptibility measurements reveal the presence of a surprisingly large number of trace magnetic and superconducting phases, suggesting that the Zr-Fe-Si ternary system could be a potentially rich source of new bulk superconductor.

36 MATERIALS SCIENCE↗
DOE OSTI2014

TH-E-BRE-05: Analysis of Dosimetric Characteristics in Two Leaf Motion Calculator Algorithms for Sliding Window IMRT

Purpose: The Smart leaf motion calculator (SLMC) in Eclipse treatment planning system is an advanced fluence delivery modeling algorithm as it takes into account fine MLC features including inter-leaf leakage, rounded leaf tips, non-uniform leaf thickness, and the spindle cavity etc. In this study, SLMC and traditional Varian LMC (VLMC) algorithms were investigated, for the first time, in dosimetric characteristics and delivery accuracy of sliding window (SW) IMRT. Methods: The SW IMRT plans of 51 cancer cases were included to evaluate dosimetric characteristics and dose delivery accuracy from leaf motion calculated by SLMC and VLMC, respectively. All plans were delivered using a Varian TrueBeam Linac. The DVH and MUs of the plans were analyzed. Three patient specific QA tools - independent dose calculation software IMSure, Delta4 phantom, and EPID portal dosimetry were also used to measure the delivered dose distribution. Results: Significant differences in the MUs were observed between the two LMCs (p≤0.001).Gamma analysis shows an excellent agreement between the planned dose distribution calculated by both LMC algorithms and delivered dose distribution measured by three QA tools in all plans at 3%/3 mm, leading to a mean pass rate exceeding 97%. The mean fraction of pixels with gamma < 1 of SLMC is slightly lower than that of VLMC in the IMSure and Delta4 results, but higher in portal dosimetry (the highest spatial resolution), especially in complex cases such as nasopharynx. Conclusion: The study suggests that the two LMCs generates the similar target coverage and sparing patterns of critical structures. However, SLMC is modestly more accurate than VLMC in modeling advanced MLC features, which may lead to a more accurate dose delivery in SW IMRT. Current clinical QA tools might not be specific enough to differentiate the dosimetric discrepancies at the millimeter level calculated by these two LMC algorithms. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant Professorship.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Factors governing Yb magnetism in Yb{sub 0.95}PtIn{sub 2} and other MgCuAl{sub 2}-type structures

The ternary compound 'YbPtIn{sub 2}' has been synthesized and its crystal structure determined using single crystal X-ray diffraction techniques. The compound crystallizes in the MgCuAl{sub 2} structure, a ternary structure type often formed when rare earth metals, Group 10 transition metals, and indium are present in a 1:1:2 ratio. The unit cell is C-centered orthorhombic, space group Cmcm (no. 63) with lattice parameters of a=4.3410(1) A, b=10.3230(2) A, and c=7.8510(2) A. Evidence is found for a substantial non-stoichiometry on the Yb site, in contrast to the Pt and In sites which behave as expected, and it is believed that the stoichiometry of this compound is more properly described as Yb{sub 0.95}PtIn{sub 2}. Magnetic and resistivity measurements reveal that 'YbPtIn{sub 2}' is a weakly interacting, non-magnetic metal exclusively containing Yb{sup 2+}, and with a resistivity ({rho}) varying from 34 {mu}{Omega} cm at room temperature to a residual resistivity {rho}{sub 0} of 23 {mu}{Omega} cm at 1.8 K. Density functional theory calculations suggest that the observed diamagnetic Yb behavior is expected for this compound, but that certain substitutions on the Pt or In site could help stabilize magnetic Yb{sup 3+} and potentially induce heavy fermion behavior. - Graphical abstract: The crystal structure, magnetic behavior, and temperature-dependent resistivity of the new ternary compound Yb{sub 0.95}PtIn{sub 2.} Highlights: Black-Right-Pointing-Pointer Flux growth method used to produce Yb{sub 0.95}PtIn{sub 2} single crystals. Black-Right-Pointing-Pointer Found rare example of non-stoichiometry in a MgCuAl{sub 2}-type structure. Black-Right-Pointing-Pointer The resistivity and diamagnetic response of Yb{sub 0.95}PtIn{sub 2} were modeled. Black-Right-Pointing-Pointer DFT correctly predicts presence of Yb{sup 2+} in Yb{sub 0.95}PtIn{sub 2}. Black-Right-Pointing-Pointer COHP results suggest other MgCuAl{sub 2}-type indides that may contain paramagnetic Yb{sup 3+}.

36 MATERIALS SCIENCE↗