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Papers by Chang Chang

1999 IEEE LEOS Annual Meeting Conference Proceedings. LEOS'99. 12th Annual Meeting. IEEE Lasers and Electro-Optics Society 1999 Annual Meeting (Cat. No.99CH37009)

Summary form only given. Coherent radiation is readily available at EUV wavelengths due to the ad... more Summary form only given. Coherent radiation is readily available at EUV wavelengths due to the advent of undulator beamlines at synchrotron radiation facilities such as the advanced light source (ALS) at Berkeley. Here we present the results of the coherence characterization of an undulator beamline as measured at the image plane of the Kirkpatrick-Baez system used to re-image the undulator

Emerging Lithographic Technologies III, 1999

Recent experiments with four 10× EUV imaging systems provide the first direct comparisons of visi... more Recent experiments with four 10× EUV imaging systems provide the first direct comparisons of visible-light and at-wavelength EUV interferometries performed using the state-of-the-art measurement tools that will be used to assemble and align the next generation of EUV imaging systems. Measurements from four individual multilayer-coated Schwarzschild objectives are discussed. Favorable agreement has been achieved between EUV and visible-light system wavefront measurements in all four optical systems. Measurements made in the presence of surface contamination and multilayer thickness variation, however, do show expected localized differences between the two measurements.

Emerging Lithographic Technologies II, 1998

The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed and impl... more The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing extreme ultraviolet (EUV) projection lithography systems. Here progress on the characterization of the PS/PDI accuracy is presented. Two major classes of errors affect the accuracy of the interferometer: the first being systematic effects arising from the measurement geometry, and the second being random and systematic errors caused by an imperfect reference wave. In order to characterize these contributions and calibrate the interferometer, a null test is required. This null test also serves as a measure of the absolute accuracy of the interferometer. Experimental results demonstrating a systematic-error-limited accuracy of 0.004 waves (λ/250 or 0.05 nm at λ = 13.4 nm) is reported.

Toxins, Aug 1, 2010

Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler's di... more Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler's diarrhea by binding to and activating the intestinal receptor guanylyl cyclase C (GC-C). Advances in understanding the biology of GC-C have extended ST from a diarrheagenic peptide to a novel therapeutic agent. Here, we summarize the physiological and pathophysiological role of GC-C in fluid-electrolyte regulation and intestinal crypt-villus homeostasis, as well as describe translational opportunities offered by STs, reflecting the unique characteristics of GC-C, in treating irritable bowel syndrome and chronic constipation, and in preventing and treating colorectal cancer.

Drug News & Perspectives, 2009

Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones... more Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin that coordinate mucosal homeostasis and its silencing contributes to intestinal transformation. It orchestrates proliferative and metabolic circuits by limiting the cell cycle and programming metabolic transitions central to regeneration along the crypt-villus axis. Mice deficient in GCC are more susceptible to colon cancer induced by germline mutations or carcinogens. Moreover, guanylin and uroguanylin are the most commonly lost gene products in colon cancer. The role of GCC as a tumor suppressor and the universal loss of its hormones in transformation suggest a paradigm in which colorectal cancer is a disease of paracrine hormone insufficiency. Indeed, GCC signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism. These data suggest a pathophysiological hypothesis in which GCC is a tumor suppressor coordinating proliferative homeostasis whose silencing through hormone loss initiates transformation. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral hormone replacement therapy employing GCC ligands.

AIP Conference Proceedings, 2000

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was develo... more The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing EUV projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996. This unique and flexible tool is applicable to any imaging system with real conjugate points, including Schwarschild objectives, Fresnel zone plates, and Kirkpatrick-Baez systems. Here we describe recent improvements made to the-interferometer, and we summarize metrology results from state-of-the-art lOx-reduction EUV Schwarschild objective.

Coherence Techniques at Extreme Ultraviolet Wavelengths

AIP Conference Proceedings, 2000

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was develo... more The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing EUV projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996. Here we describe recent improvements made to the interferometer, and we summarize metrology results from state-of-the-art 1 Ox-reduction EUV projection optics.

Partially coherent image formation theory for a full-field imaging microscope is introduced. Prop... more Partially coherent image formation theory for a full-field imaging microscope is introduced. Propagation of mutual coherence is presented following Huygens-Fresnel principle. The concept of mutual intensity, together with the quasimonochromatic condition under which it is valid, is also introduced. Detailed analysis of a microscope illuminated by a partially coherent source is presented. Mutual intensity distributions at each stage of the image formation process, i.e. at the condenser, object, objective lens and image planes, are examined thoroughly. The overall imaging process is summarized using amplitude spread function and illumination mutual intensity. The resultant image intensity distribution is obtained analytically. Furthermore, Fourier domain techniques such as modulation transfer function and pupil function are also introduced, together with the associated space invariance conditions. These techniques greatly simplify the analysis and provide valuable insight into the ima...

Cureus, 2018

This study aimed to evaluate the effectiveness of four-dimensional (4D) robust optimization for p... more This study aimed to evaluate the effectiveness of four-dimensional (4D) robust optimization for proton pencil-beam scanning (PBS) treatment of lung tumors. Patients and methods In seven patients with lung cancer, proton beam therapy was planned using 4D robust optimization over 4D computed tomography (CT) data sets. The gross target volume (GTV) was contoured based on individual breathing phases, and a 5-mm expansion was used to generate the clinical target volume (CTV) for each phase. The 4D optimization was conducted directly on the 4D CT data set. The robust optimization settings included a CT Hounsfield unit (HU) uncertainty of 4% and a setup uncertainty of 5 mm to obtain the CTV. Additional target dose objectives such as those for the internal target volume (ITV) as well as the organ-atrisk (OAR) dose requirements were placed on the average CT. For comparison, three-dimensional (3D) robust optimization was also performed on the average CT. An additional verification 4D CT was performed to verify plan robustness against inter-fractional variations. Results Target coverages were generally higher for 4D optimized plans. The difference was most pronounced for ITV V70Gy when evaluating individual breathing phases. The 4D optimized plans were shown to be able to maintain the ITV coverage at full prescription, while 3D optimized plans could not. More importantly, this difference in ITV V70Gy between the 4D and 3D optimized plans was also consistently observed when evaluating the verification 4D CT, indicating that the 4D optimized plans were more robust against interfractional variations. Less difference was seen between the 4D and 3D optimized plans in the lungs criteria: V5Gy and V20Gy. Conclusion The proton PBS treatment plans optimized directly on the 4D CT were shown to be more robust when compared to those optimized on a regular 3D CT. Robust 4D optimization can improve the target coverage for the proton PBS lung treatments.

International Journal of Particle Therapy, 2016

Purpose: To report the dosimetric advantages of a comparison between pencil beam scanning (PBS) p... more Purpose: To report the dosimetric advantages of a comparison between pencil beam scanning (PBS) proton therapy versus intensity-modulated radiation therapy (IMRT) for parotid gland cancers. Patients and Methods: This was a retrospective, dosimetric comparison of 8 patients who received external beam radiation therapy at our institution between 2009 and 2011. Two separate plans were generated for each patient: 1 IMRT and 1 PBS plan. The prescription dose for each plan was 60 Gy for IMRT and 60 Gy (RBE) for PBS. We measured dose-volume relationships for target volumes and organs at risk with each treatment technique. Dosimetric comparisons for each organ at risk were made by using the Wilcoxon signed rank test. All tests were 2-tailed, with P values , .05 considered statistically significant. Results: The mean patient planning target volume was 160.9 cm 3 (SD 74.6). Pencil beam scanning, compared to IMRT, significantly reduced the mean dose to the following structures: ipsilateral temporal lobe (2.86 versus 9.59 Gy (RBE), P ¼ .01), oral cavity (0.58 versus 13.48 Gy (RBE), P ¼ .01), mandible (V 50 : 7.4% versus 12.8%, P ¼ .01), contralateral parotid gland (0.003 versus 4.64 Gy (RBE), P ¼ .01), ipsilateral submandibular gland (16.59 versus 38.94 Gy (RBE), P ¼ .03), and contralateral submandibular gland (0.02 versus 5.34 Gy (RBE), P ¼ .01). Pencil beam scanning also significantly reduced the maximum dose delivered to the brainstem (7.1 versus 30.9 Gy (RBE), P ¼ .01). Conclusion: Pencil beam scanning allows for superior normal tissue sparing while still maintaining excellent target coverage in patients with resected parotid gland cancers. These findings suggest that PBS may allow for an improved therapeutic index for these patients. Clinical outcomes with PBS should be evaluated prospectively, with a focus on disease outcomes as well as treatment-related toxicities and patient quality of life.

The 1998 international conference on characterization and metrology for ULSI technology, 1998

A phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to evaluat... more A phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to evaluate optics for extreme ultraviolet (EUV) projection lithography systems. The interferometer has been implemented at the Advanced Light Source at Lawrence Berkeley National Laboratory and is currently being used to test experimental EUV Schwarzschild objectives. Recent PS/PDI measurements indicate these experimental objectives to have wavefront errors on the order

Optics Letters, 2006

High-resolution soft x-ray differential interference contrast (DIC) imaging was demonstrated thro... more High-resolution soft x-ray differential interference contrast (DIC) imaging was demonstrated through the use of a single-element objective, the XOR pattern, in a full-field soft x-ray microscope. DIC images of the magnetic domains in a 59 nm thick amorphous Gd 25 Fe 75 layer were obtained and magnetic phase contributions were directly imaged. With its elemental, chemical, and magnetic specificity, compatibility with various sample environments, and ease of implementation, we expect this soft x-ray DIC technique to become one of the standard modes of operation for existing full-field soft x-ray microscopes.

Optics Communications, 2000

The coherence properties of undulator radiation at extreme ultraviolet EUV wavelengths are measur... more The coherence properties of undulator radiation at extreme ultraviolet EUV wavelengths are measured using the Thompson-Wolf two-pinhole method. The effects of asymmetric source size and beamline apertures are observed. High spatial coherence EUV radiation is demonstrated. Projection of these same capabilities to the x-ray region is straightforward.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001

The Thompson-Wolf two-pinhole technique was used to characterize the spatial coherence properties... more The Thompson-Wolf two-pinhole technique was used to characterize the spatial coherence properties of undulator radiation. Both vertical and horizontal coherence properties are measured with various pinhole separations. High spatial coherence of extreme ultraviolet undulator radiation is demonstrated.

IEEE Journal of Quantum Electronics, 1999

Undulator radiation, generated by relativistic electrons traversing a periodic magnet structure, ... more Undulator radiation, generated by relativistic electrons traversing a periodic magnet structure, can provide a continuously tunable source of very bright and partially coherent radiation in the extreme ultraviolet (EUV), soft X-ray (SXR), and X-ray regions of the electromagnetic spectrum. Typically, 1-10 W are radiated within a 1=N relative spectral bandwidth, where N is of order 100. Monochromators are frequently used to narrow the spectral bandwidth and increase the longitudinal coherence length, albeit with a more than proportionate loss of power. Pinhole spatial filtering is employed to provide spatially coherent radiation at a power level determined by the wavelength, electron beam, and undulator parameters. In this paper, experiments are described in which broadly tunable, spatially coherent power is generated at EUV and soft X-ray wavelengths extending from about 3 to 16 nm (80-430-eV photon energies). Spatially coherent power of order 10 W is achieved in a relative spectral bandwidth of 9 2 10 04 , with 1.90-GeV electrons traversing an 8-cm period undulator of 55 periods. This radiation has been used in 13.4nm interferometric tests that achieve an rms wavefront error (departure from sphericity) of euv =330. These techniques scale in a straightforward manner to shorter soft X-ray wavelengths using 4-5-cm period undulators at 1.90 GeV and to X-ray wavelengths of order 0.1 nm using higher energy (6-8 GeV) electron beams at other facilities.

International Journal of Particle Therapy, 2021

Purpose A multi-field optimization (MFO) technique that uses beam-specific spot placement volumes... more Purpose A multi-field optimization (MFO) technique that uses beam-specific spot placement volumes (SPVs) and spot avoidance volumes (SAVs) is introduced for bilateral head and neck (H&N) cancers. These beam-specific volumes are used to guide the optimizer to consistently achieve optimal organ-at-risk (OAR) sparing with target coverage and plan robustness. Materials and Methods Implementation of this technique using a 4-beam, 5-beam, and variant 5-beam arrangement is discussed. The generation of beam-specific SPVs and SAVs derived from target and OARs are shown. The SPVs for select fields are further partitioned into optimization volumes for uniform dose distributions that resemble those of single-field optimization (SFO). A conventional MFO plan that does not use beam-specific spot placement guidance (MFOcon) and an MFO plan that uses only beam-specific SPV (MFOspv) are compared with current technique (MFOspv/sav), using both simulated scenarios and forward-calculated plans on weekl...

Physics in Medicine & Biology, 2021

Proton radiotherapy treatment planning systems use a constant relative biological effectiveness (... more Proton radiotherapy treatment planning systems use a constant relative biological effectiveness (RBE) = 1.1 to convert proton absorbed dose into biologically equivalent high-energy photon dose. This method ignores linear energy transfer (LET) distributions, and RBE is known to change as a function of LET. Variable RBE approaches have been proposed for proton planning optimization. Experimental validation of models underlying these approaches is a pre-requisite for their clinical implementation. This validation has to probe every level in the evolution of radiation-induced biological damage leading to cell death, starting from DNA double-strand breaks (DSB). Using a novel FIESTA-DNA probe, we measured the probability of double-strand break (P DSB) along a 160 MeV proton Bragg curve at two dose levels (30 and 60 Gy (RBE)) and compared it to measurements in a 6 MV photon beam. A machined setup that held an Advanced Markus parallel plate chamber for proton dose verification alongside th...

Cureus, 2017

Tang et al. This is an open access article distributed under the terms of the Creative Commons At... more Tang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 3.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

1999 IEEE LEOS Annual Meeting Conference Proceedings. LEOS'99. 12th Annual Meeting. IEEE Lasers and Electro-Optics Society 1999 Annual Meeting (Cat. No.99CH37009)

Summary form only given. Coherent radiation is readily available at EUV wavelengths due to the ad... more Summary form only given. Coherent radiation is readily available at EUV wavelengths due to the advent of undulator beamlines at synchrotron radiation facilities such as the advanced light source (ALS) at Berkeley. Here we present the results of the coherence characterization of an undulator beamline as measured at the image plane of the Kirkpatrick-Baez system used to re-image the undulator

Emerging Lithographic Technologies III, 1999

Recent experiments with four 10× EUV imaging systems provide the first direct comparisons of visi... more Recent experiments with four 10× EUV imaging systems provide the first direct comparisons of visible-light and at-wavelength EUV interferometries performed using the state-of-the-art measurement tools that will be used to assemble and align the next generation of EUV imaging systems. Measurements from four individual multilayer-coated Schwarzschild objectives are discussed. Favorable agreement has been achieved between EUV and visible-light system wavefront measurements in all four optical systems. Measurements made in the presence of surface contamination and multilayer thickness variation, however, do show expected localized differences between the two measurements.

Emerging Lithographic Technologies II, 1998

The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed and impl... more The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing extreme ultraviolet (EUV) projection lithography systems. Here progress on the characterization of the PS/PDI accuracy is presented. Two major classes of errors affect the accuracy of the interferometer: the first being systematic effects arising from the measurement geometry, and the second being random and systematic errors caused by an imperfect reference wave. In order to characterize these contributions and calibrate the interferometer, a null test is required. This null test also serves as a measure of the absolute accuracy of the interferometer. Experimental results demonstrating a systematic-error-limited accuracy of 0.004 waves (λ/250 or 0.05 nm at λ = 13.4 nm) is reported.

Toxins, Aug 1, 2010

Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler's di... more Heat-stable toxins (STs) produced by enterotoxigenic bacteria cause endemic and traveler's diarrhea by binding to and activating the intestinal receptor guanylyl cyclase C (GC-C). Advances in understanding the biology of GC-C have extended ST from a diarrheagenic peptide to a novel therapeutic agent. Here, we summarize the physiological and pathophysiological role of GC-C in fluid-electrolyte regulation and intestinal crypt-villus homeostasis, as well as describe translational opportunities offered by STs, reflecting the unique characteristics of GC-C, in treating irritable bowel syndrome and chronic constipation, and in preventing and treating colorectal cancer.

Drug News & Perspectives, 2009

Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones... more Guanylyl cyclase C (GCC) is the receptor expressed by intestinal cells for the paracrine hormones guanylin and uroguanylin that coordinate mucosal homeostasis and its silencing contributes to intestinal transformation. It orchestrates proliferative and metabolic circuits by limiting the cell cycle and programming metabolic transitions central to regeneration along the crypt-villus axis. Mice deficient in GCC are more susceptible to colon cancer induced by germline mutations or carcinogens. Moreover, guanylin and uroguanylin are the most commonly lost gene products in colon cancer. The role of GCC as a tumor suppressor and the universal loss of its hormones in transformation suggest a paradigm in which colorectal cancer is a disease of paracrine hormone insufficiency. Indeed, GCC signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism. These data suggest a pathophysiological hypothesis in which GCC is a tumor suppressor coordinating proliferative homeostasis whose silencing through hormone loss initiates transformation. The correlative therapeutic hypothesis suggests that colorectal cancer is a disease of hormone insufficiency that can be prevented or treated by oral hormone replacement therapy employing GCC ligands.

AIP Conference Proceedings, 2000

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was develo... more The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing EUV projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996. This unique and flexible tool is applicable to any imaging system with real conjugate points, including Schwarschild objectives, Fresnel zone plates, and Kirkpatrick-Baez systems. Here we describe recent improvements made to the-interferometer, and we summarize metrology results from state-of-the-art lOx-reduction EUV Schwarschild objective.

Coherence Techniques at Extreme Ultraviolet Wavelengths

AIP Conference Proceedings, 2000

The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was develo... more The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) was developed and implemented at Lawrence Berkeley National Laboratory to meet the significant measurement challenge of characterizing EUV projection lithography optics. The PS/PDI has been in continuous use and under ongoing development since 1996. Here we describe recent improvements made to the interferometer, and we summarize metrology results from state-of-the-art 1 Ox-reduction EUV projection optics.

Partially coherent image formation theory for a full-field imaging microscope is introduced. Prop... more Partially coherent image formation theory for a full-field imaging microscope is introduced. Propagation of mutual coherence is presented following Huygens-Fresnel principle. The concept of mutual intensity, together with the quasimonochromatic condition under which it is valid, is also introduced. Detailed analysis of a microscope illuminated by a partially coherent source is presented. Mutual intensity distributions at each stage of the image formation process, i.e. at the condenser, object, objective lens and image planes, are examined thoroughly. The overall imaging process is summarized using amplitude spread function and illumination mutual intensity. The resultant image intensity distribution is obtained analytically. Furthermore, Fourier domain techniques such as modulation transfer function and pupil function are also introduced, together with the associated space invariance conditions. These techniques greatly simplify the analysis and provide valuable insight into the ima...

Cureus, 2018

This study aimed to evaluate the effectiveness of four-dimensional (4D) robust optimization for p... more This study aimed to evaluate the effectiveness of four-dimensional (4D) robust optimization for proton pencil-beam scanning (PBS) treatment of lung tumors. Patients and methods In seven patients with lung cancer, proton beam therapy was planned using 4D robust optimization over 4D computed tomography (CT) data sets. The gross target volume (GTV) was contoured based on individual breathing phases, and a 5-mm expansion was used to generate the clinical target volume (CTV) for each phase. The 4D optimization was conducted directly on the 4D CT data set. The robust optimization settings included a CT Hounsfield unit (HU) uncertainty of 4% and a setup uncertainty of 5 mm to obtain the CTV. Additional target dose objectives such as those for the internal target volume (ITV) as well as the organ-atrisk (OAR) dose requirements were placed on the average CT. For comparison, three-dimensional (3D) robust optimization was also performed on the average CT. An additional verification 4D CT was performed to verify plan robustness against inter-fractional variations. Results Target coverages were generally higher for 4D optimized plans. The difference was most pronounced for ITV V70Gy when evaluating individual breathing phases. The 4D optimized plans were shown to be able to maintain the ITV coverage at full prescription, while 3D optimized plans could not. More importantly, this difference in ITV V70Gy between the 4D and 3D optimized plans was also consistently observed when evaluating the verification 4D CT, indicating that the 4D optimized plans were more robust against interfractional variations. Less difference was seen between the 4D and 3D optimized plans in the lungs criteria: V5Gy and V20Gy. Conclusion The proton PBS treatment plans optimized directly on the 4D CT were shown to be more robust when compared to those optimized on a regular 3D CT. Robust 4D optimization can improve the target coverage for the proton PBS lung treatments.

International Journal of Particle Therapy, 2016

Purpose: To report the dosimetric advantages of a comparison between pencil beam scanning (PBS) p... more Purpose: To report the dosimetric advantages of a comparison between pencil beam scanning (PBS) proton therapy versus intensity-modulated radiation therapy (IMRT) for parotid gland cancers. Patients and Methods: This was a retrospective, dosimetric comparison of 8 patients who received external beam radiation therapy at our institution between 2009 and 2011. Two separate plans were generated for each patient: 1 IMRT and 1 PBS plan. The prescription dose for each plan was 60 Gy for IMRT and 60 Gy (RBE) for PBS. We measured dose-volume relationships for target volumes and organs at risk with each treatment technique. Dosimetric comparisons for each organ at risk were made by using the Wilcoxon signed rank test. All tests were 2-tailed, with P values , .05 considered statistically significant. Results: The mean patient planning target volume was 160.9 cm 3 (SD 74.6). Pencil beam scanning, compared to IMRT, significantly reduced the mean dose to the following structures: ipsilateral temporal lobe (2.86 versus 9.59 Gy (RBE), P ¼ .01), oral cavity (0.58 versus 13.48 Gy (RBE), P ¼ .01), mandible (V 50 : 7.4% versus 12.8%, P ¼ .01), contralateral parotid gland (0.003 versus 4.64 Gy (RBE), P ¼ .01), ipsilateral submandibular gland (16.59 versus 38.94 Gy (RBE), P ¼ .03), and contralateral submandibular gland (0.02 versus 5.34 Gy (RBE), P ¼ .01). Pencil beam scanning also significantly reduced the maximum dose delivered to the brainstem (7.1 versus 30.9 Gy (RBE), P ¼ .01). Conclusion: Pencil beam scanning allows for superior normal tissue sparing while still maintaining excellent target coverage in patients with resected parotid gland cancers. These findings suggest that PBS may allow for an improved therapeutic index for these patients. Clinical outcomes with PBS should be evaluated prospectively, with a focus on disease outcomes as well as treatment-related toxicities and patient quality of life.

The 1998 international conference on characterization and metrology for ULSI technology, 1998

A phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to evaluat... more A phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to evaluate optics for extreme ultraviolet (EUV) projection lithography systems. The interferometer has been implemented at the Advanced Light Source at Lawrence Berkeley National Laboratory and is currently being used to test experimental EUV Schwarzschild objectives. Recent PS/PDI measurements indicate these experimental objectives to have wavefront errors on the order

Optics Letters, 2006

High-resolution soft x-ray differential interference contrast (DIC) imaging was demonstrated thro... more High-resolution soft x-ray differential interference contrast (DIC) imaging was demonstrated through the use of a single-element objective, the XOR pattern, in a full-field soft x-ray microscope. DIC images of the magnetic domains in a 59 nm thick amorphous Gd 25 Fe 75 layer were obtained and magnetic phase contributions were directly imaged. With its elemental, chemical, and magnetic specificity, compatibility with various sample environments, and ease of implementation, we expect this soft x-ray DIC technique to become one of the standard modes of operation for existing full-field soft x-ray microscopes.

Optics Communications, 2000

The coherence properties of undulator radiation at extreme ultraviolet EUV wavelengths are measur... more The coherence properties of undulator radiation at extreme ultraviolet EUV wavelengths are measured using the Thompson-Wolf two-pinhole method. The effects of asymmetric source size and beamline apertures are observed. High spatial coherence EUV radiation is demonstrated. Projection of these same capabilities to the x-ray region is straightforward.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001

The Thompson-Wolf two-pinhole technique was used to characterize the spatial coherence properties... more The Thompson-Wolf two-pinhole technique was used to characterize the spatial coherence properties of undulator radiation. Both vertical and horizontal coherence properties are measured with various pinhole separations. High spatial coherence of extreme ultraviolet undulator radiation is demonstrated.

IEEE Journal of Quantum Electronics, 1999

Undulator radiation, generated by relativistic electrons traversing a periodic magnet structure, ... more Undulator radiation, generated by relativistic electrons traversing a periodic magnet structure, can provide a continuously tunable source of very bright and partially coherent radiation in the extreme ultraviolet (EUV), soft X-ray (SXR), and X-ray regions of the electromagnetic spectrum. Typically, 1-10 W are radiated within a 1=N relative spectral bandwidth, where N is of order 100. Monochromators are frequently used to narrow the spectral bandwidth and increase the longitudinal coherence length, albeit with a more than proportionate loss of power. Pinhole spatial filtering is employed to provide spatially coherent radiation at a power level determined by the wavelength, electron beam, and undulator parameters. In this paper, experiments are described in which broadly tunable, spatially coherent power is generated at EUV and soft X-ray wavelengths extending from about 3 to 16 nm (80-430-eV photon energies). Spatially coherent power of order 10 W is achieved in a relative spectral bandwidth of 9 2 10 04 , with 1.90-GeV electrons traversing an 8-cm period undulator of 55 periods. This radiation has been used in 13.4nm interferometric tests that achieve an rms wavefront error (departure from sphericity) of euv =330. These techniques scale in a straightforward manner to shorter soft X-ray wavelengths using 4-5-cm period undulators at 1.90 GeV and to X-ray wavelengths of order 0.1 nm using higher energy (6-8 GeV) electron beams at other facilities.

International Journal of Particle Therapy, 2021

Purpose A multi-field optimization (MFO) technique that uses beam-specific spot placement volumes... more Purpose A multi-field optimization (MFO) technique that uses beam-specific spot placement volumes (SPVs) and spot avoidance volumes (SAVs) is introduced for bilateral head and neck (H&N) cancers. These beam-specific volumes are used to guide the optimizer to consistently achieve optimal organ-at-risk (OAR) sparing with target coverage and plan robustness. Materials and Methods Implementation of this technique using a 4-beam, 5-beam, and variant 5-beam arrangement is discussed. The generation of beam-specific SPVs and SAVs derived from target and OARs are shown. The SPVs for select fields are further partitioned into optimization volumes for uniform dose distributions that resemble those of single-field optimization (SFO). A conventional MFO plan that does not use beam-specific spot placement guidance (MFOcon) and an MFO plan that uses only beam-specific SPV (MFOspv) are compared with current technique (MFOspv/sav), using both simulated scenarios and forward-calculated plans on weekl...

Physics in Medicine & Biology, 2021

Proton radiotherapy treatment planning systems use a constant relative biological effectiveness (... more Proton radiotherapy treatment planning systems use a constant relative biological effectiveness (RBE) = 1.1 to convert proton absorbed dose into biologically equivalent high-energy photon dose. This method ignores linear energy transfer (LET) distributions, and RBE is known to change as a function of LET. Variable RBE approaches have been proposed for proton planning optimization. Experimental validation of models underlying these approaches is a pre-requisite for their clinical implementation. This validation has to probe every level in the evolution of radiation-induced biological damage leading to cell death, starting from DNA double-strand breaks (DSB). Using a novel FIESTA-DNA probe, we measured the probability of double-strand break (P DSB) along a 160 MeV proton Bragg curve at two dose levels (30 and 60 Gy (RBE)) and compared it to measurements in a 6 MV photon beam. A machined setup that held an Advanced Markus parallel plate chamber for proton dose verification alongside th...

Cureus, 2017

Tang et al. This is an open access article distributed under the terms of the Creative Commons At... more Tang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 3.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.