Chin-Cheng Chen - Academia.edu (original) (raw)
Papers by Chin-Cheng Chen
EPJ Web of Conferences, 2017
The dose distributions from proton pencil beam scanning were calculated by FLUKA, GEANT4, MCNP, a... more The dose distributions from proton pencil beam scanning were calculated by FLUKA, GEANT4, MCNP, and PHITS, in order to investigate their applicability in proton radiotherapy. The first studied case was the integrated depth dose curves (IDDCs), respectively from a 100 and a 226-MeV proton pencil beam impinging a water phantom. The calculated IDDCs agree with each other as long as each code employs 75 eV for the ionization potential of water. The second case considered a similar condition of the first case but with proton energies in a Gaussian distribution. The comparison to the measurement indicates the inter-code differences might not only due to different stopping power but also the nuclear physics models. How the physics parameter setting affect the computation time was also discussed. In the third case, the applicability of each code for pencil beam scanning was confirmed by delivering a uniform volumetric dose distribution based on the treatment plan, and the results showed general agreement between each codes, the treatment plan, and the measurement, except that some deviations were found in the penumbra region. This study has demonstrated that the selected codes are all capable of performing dose calculations for therapeutic scanning proton beams with proper physics settings.
International Journal of Radiation Oncology*Biology*Physics, 2010
Symptomatic vertebral hemangiomas (SVHs) are rare benign tumors that when symptomatic require pro... more Symptomatic vertebral hemangiomas (SVHs) are rare benign tumors that when symptomatic require procedural intervention or radiotherapy (RT). Although conventionally-fractionated RT has been an alternative to surgical resection, there is very little data on stereotactic body radiotherapy (SBRT) for SVHs. Six consecutively treated patients with SVHs underwent definitive single-fraction SBRT from 2010 to 2018 at our institution. The RT planning parameters, treatment, outcome, and toxicities are reported for 6 patients with 6 total SVHs treated with single-fraction SBRT. Each patient presented with back pain and received single-fraction SBRT to a thoracic vertebral body hemangioma. One patient had received radiofrequency ablation prior to SBRT. The median SBRT dose was 18 Gy (range, 13-20). Following SBRT, 4 (67%) patients reported improvement in presenting symptoms and 2 patients (33%) were refractory. There were no acute or chronic toxicities associated with SBRT including esophagitis, vertebral compression fractures, or myelopathy. To date, this is the largest series of single-fraction SBRT for SVHs. Single fraction SBRT appears to be a feasible option for SVHs. Further studies are needed to confirm our preliminary findings and optimize dose fractionation.
International Journal of Radiation Oncology*Biology*Physics, 2009
International Journal of Radiation Oncology*Biology*Physics, 2009
To report our clinical experiences with on-board imager (OBI) kV image verification for cranial s... more To report our clinical experiences with on-board imager (OBI) kV image verification for cranial stereotactic radiosurgery (SRS) and radiotherapy (SRT) treatments. Between January 2007 and May 2008, 42 patients (57 lesions) were treated with SRS with head frame immobilization and 13 patients (14 lesions) were treated with SRT with face mask immobilization at our institution. No margin was added to the gross tumor for SRS patients, and a 3-mm three-dimensional margin was added to the gross tumor to create the planning target volume for SRT patients. After localizing the patient with stereotactic target positioner (TaPo), orthogonal kV images using OBI were taken and fused to planning digital reconstructed radiographs. Suggested couch shifts in vertical, longitudinal, and lateral directions were recorded. kV images were also taken immediately after treatment for 21 SRS patients and on a weekly basis for 6 SRT patients to assess any intrafraction changes. For SRS patients, 57 pretreatment kV images were evaluated and the suggested shifts were all within 1 mm in any direction (i.e., within the accuracy of image fusion). For SRT patients, the suggested shifts were out of the 3-mm tolerance for 31 of 309 setups. Intrafraction motions were detected in 3 SRT patients. kV imaging provided a useful tool for SRS or SRT setups. For SRS setup with head frame, it provides radiographic confirmation of localization using the stereotactic target positioner. For SRT with mask, a 3-mm margin is adequate and feasible for routine setup when TaPo is combined with kV imaging.
Medical Physics, 2009
Purpose: Due to the lifetime dose limit for these critical structures such as brainstem and spina... more Purpose: Due to the lifetime dose limit for these critical structures such as brainstem and spinal cord, achieving an additional dose of 60 Gy to patients with recurrent head and neck cancer is challenging for who received a previous dose of ∼60 Gy. Specifically, previously irradiated head and neck patients may be near tolerance dose to their brainstem and spinal cord. In this study, a reproducible IMRTtreatment design is presented to spare the doses to brainstem and spinal cord with no compromise of prescribed dose delivery. Method and Materials: Seven patients with previously irradiated, recurrent head‐and‐neck cancers were treated with DMLC IMRT. The jaws of each field were set fixed with the goal of shielding the brainstem and spinal cord at the sacrifice of partial coverage of the planning target volume (PTV) from any particular beam orientation. Beam geometry was arranged to have sufficient coverage of the PTV and ensure that the constraints of spinal cord <10 Gy and brainstem < 15 Gy were met. Results: The mean maximum dose to the brainstem was 12.1 Gy (range: 6.1–17.3 Gy), and the mean maximum dose to spinal cord was 10.4 Gy (range: 8.2–14.1 Gy). For most cases, 97% of the PTV volume was fully covered by the 95% isodose volume. We found empirically that if the angle of cervical spine curvature (Cobb's angle) was less than ∼30 degrees, patients could be treated by 18 fields. Six patients met these criteria and were treated in 25 minutes per fraction. One patient exceeded a 30 degree Cobb's angle and was treated by 31 fields in 45 minutes per fraction. Conclusion: We have demonstrated a new technique for re‐treatment of head and neck cancers. The angle of cervical spine curvature plays an important role in the efficiency and effectiveness of our approach.
PLoS ONE, 2009
Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melan... more Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. Methodology/Principal Findings: We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or L-DOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14?10 18 , 7.09?10 18 , and 9.05?10 17 spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy (137 Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. Conclusions/Significance: We propose that due to melanin's numerous aromatic oligomers containing multiple p-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species.
A 2×2 phased-array transmitter designed for V-band communications has been implemented by using C... more A 2×2 phased-array transmitter designed for V-band communications has been implemented by using CMOS 0.18 μm process. The circuit is based on a 30-GHz injection-locked oscillator (ILO) without using power amplifier. Combing a frequency doubler (FD) with the differential signal injection can generate a 60-GHz signal and perform a 360° phase shift with a harmonic suppression of 15 dBc. The power consumption of each channel in the transmitter is 65 mW from a 1.8 V supply. The measured output signal exhibits a self-oscillation frequency ranging from about 63.7 GHz to 65.9 GHz with an output power of -11 dBm. The transmitter demonstrates the maximum locking range up to 350 MHz under a fundamental injection. Due to the injection locking technique used in the circuit, the phase noise can be improved to -116 dBc/Hz at 1-MHz offset.
2009 Asia Pacific Microwave Conference, 2009
A frequency tripler designed for V-band signal generation has been implemented by using CMOS 0.18... more A frequency tripler designed for V-band signal generation has been implemented by using CMOS 0.18 ¿m process. Based on the circuit topology of differential binary phase shift keying (BPSK) modulator, a function of frequency triplication can be performed under the operation modes of class-AB and class-C when choosing the proper biases on the NMOS devices. For achieving a large 60
2012 IEEE International Conference on Automation Science and Engineering (CASE), 2012
Seminars in Nuclear Medicine, 2008
Radiation therapy has evolved from 2-dimensional (2D) to 3-dimensional (3D) treatments and, more ... more Radiation therapy has evolved from 2-dimensional (2D) to 3-dimensional (3D) treatments and, more recently, to intensity-modulated radiation therapy and image-guided radiation therapy. Improvements in imaging have enabled improvements in targeting and treatment. As computer-processing power has improved during the past few decades, it has facilitated developments in both imaging and treatment. The historical role of imaging from 2D to image-guided radiation therapy is reviewed here. Examples of imaging technologies such as positron emission tomography and magnetic resonance imaging are provided. The role of these imaging technologies, organ motion management approaches and their potential impacts on radiation therapy are described.
PLoS ONE, 2009
Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melan... more Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown.
Physics in Medicine and Biology, 1981
Dynamic computer-assisted tomographic (CT) measurements using non-radioactive xenon gas have rece... more Dynamic computer-assisted tomographic (CT) measurements using non-radioactive xenon gas have recently been employed along with a simple model of pulmonary transport to derive ventilation rate constants (K) in small tissue volumes. Inherent in the model description is the assumption that instantaneous diffusion equilibrium occurs between inhaled Xe gas and lung tissue. The validity of this assumption as it relates to the accuracy of the derived values of K has been considered for both normal and oedematous tissue, the latter characterised by a severe widening of the interstitial fluid space. It was found that only a small error in the predicted values for K results, when the simple model is applied to the dynamic cT measurements of xenon enhancement.
Medical Physics, 2011
Sharp dose fall off outside a tumor is essential for high dose single fraction stereotactic radio... more Sharp dose fall off outside a tumor is essential for high dose single fraction stereotactic radiosurgery (SRS) plans. This study explores the relationship among tumor dose inhomogeneity, conformity, and dose fall off in normal tissues for micromultileaf collimator (mMLC) linear accelerator (LINAC) based cranial SRS plans. Between January 2007 and July 2009, 65 patients with single cranial lesions were treated with LINAC-based SRS. Among them, tumors had maximum diameters &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm: 31; between 20 and 30 mm: 21; and &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30 mm: 13. All patients were treated with 6 MV photons on a Trilogy linear accelerator (Varian Medical Systems, Palo Alto, CA) with a tertiary m3 high-resolution mMLC (Brainlab, Feldkirchen, Germany), using either noncoplanar conformal fixed fields or dynamic conformal arcs. The authors also created retrospective study plans with identical beam arrangement as the treated plan but with different tumor dose inhomogeneity by varying the beam margins around the planning target volume (PTV). All retrospective study plans were normalized so that the minimum PTV dose was the prescription dose (PD). Isocenter dose, mean PTV dose, RTOG conformity index (CI), RTOG homogeneity index (HI), dose gradient index R50-R100 (defined as the difference between equivalent sphere radius of 50% isodose volume and prescription isodose volume), and normal tissue volume (as a ratio to PTV volume) receiving 50% prescription dose (NTV50) were calculated. HI was inversely related to the beam margins around the PTV. CI had a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;V&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; shaped relationship with HI, reaching a minimum when HI was approximately 1.3. Isocenter dose and mean PTV dose (as percentage of PD) increased linearly with HI. R50-R100 and NTV50 initially declined with HI and then reached a plateau when HI was approximately 1.3. These trends also held when tumors were grouped according to their maximum diameters. The smallest tumor group (maximum diameters &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm) had the most HI dependence for dose fall off. For treated plans, CI averaged 2.55 +/- 0.79 with HI 1.23 +/- 0.06; the average R50-R100 was 0.41 +/- 0.08, 0.55 +/- 0.10, and 0.65 +/- 0.09 cm, respectively, for tumors &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm, between 20 and 30 mm, and &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30 mm. Tumor dose inhomogeneity can be used as an important and convenient parameter to evaluate mMLC LINAC-based SRS plans. Sharp dose fall off in the normal tissue is achieved with sufficiently high tumor dose inhomogeneity. By adjusting beam margins, a homogeneity index of approximately 1.3 would provide best conformity for the authors&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; SRS system.
Medical Dosimetry, 2011
Because of the dose limit for critical structures such as brainstem and spinal cord, administerin... more Because of the dose limit for critical structures such as brainstem and spinal cord, administering a dose of 60 Gy to patients with recurrent head and neck cancer is challenging for those who received a previous dose of 60؊70 Gy. Specifically, previously irradiated head and neck patients may have received doses close to the tolerance limit to their brainstem and spinal cord. In this study, a reproducible intensity-modulated radiation therapy (IMRT) treatment design is presented to spare the doses to brainstem and spinal cord, with no compromise of prescribed dose delivery. Between July and November 2008, 7 patients with previously irradiated, recurrent head and neck cancers were treated with IMRT. The jaws of each field were set fixed with the goal of shielding the brainstem and spinal cord at the sacrifice of partial coverage of the planning target volume (PTV) from any particular beam orientation. Beam geometry was arranged to have sufficient coverage of the PTV and ensure that the constraints of spinal cord <10 Gy and brainstem <15 Gy were met. The mean maximum dose to the brainstem was 12.1 Gy (range 6.1؊17.3 Gy), and the corresponding mean maximum dose to spinal cord was 10.4 Gy (range 8.2؊14.1 Gy). For most cases, 97% of the PTV volume was fully covered by the 95% isodose volume. We found empirically that if the angle of cervical spine curvature (Cobb's angle) was less than ϳ30°, patients could be treated by 18 fields. Six patients met these criteria and were treated in 25 minutes per fraction. One patient exceeded a 30°Cobb's angle and was treated by 31 fields in 45 minutes per fraction. We have demonstrated a new technique for retreatment of head and neck cancers. The angle of cervical spine curvature plays an important role in the efficiency and effectiveness of our approach.
Journal of Circuits, Systems and Computers, 2011
ABSTRACT Light-weight network gateways often employ a cost-effective embedded network processor a... more ABSTRACT Light-weight network gateways often employ a cost-effective embedded network processor and have received a strong demand for empowering content filtering services. In this regard, we were motivated to propose a specialized cache, fuzzy-updated cache automata matching (FCAM) circuit for accelerating the embedded network processors. Although automata matching algorithms are robust with deterministic matching time, there is still plenty of room for improving its average-case performance. The proposed FCAM employs cache to accelerate the root state and nonroot state with the multiple characters matching, and applies the fuzzy decision to improve the cache performance. In our experiment, the FPGA implementation of FCAM can perform at the rate of 10.5 Giga bits per second with the patterns of 25,642 bytes. This performance is superior to previous matching hardware in terms of throughput and pattern set.
International Journal of Radiation Oncology*Biology*Physics, 2013
EPJ Web of Conferences, 2017
The dose distributions from proton pencil beam scanning were calculated by FLUKA, GEANT4, MCNP, a... more The dose distributions from proton pencil beam scanning were calculated by FLUKA, GEANT4, MCNP, and PHITS, in order to investigate their applicability in proton radiotherapy. The first studied case was the integrated depth dose curves (IDDCs), respectively from a 100 and a 226-MeV proton pencil beam impinging a water phantom. The calculated IDDCs agree with each other as long as each code employs 75 eV for the ionization potential of water. The second case considered a similar condition of the first case but with proton energies in a Gaussian distribution. The comparison to the measurement indicates the inter-code differences might not only due to different stopping power but also the nuclear physics models. How the physics parameter setting affect the computation time was also discussed. In the third case, the applicability of each code for pencil beam scanning was confirmed by delivering a uniform volumetric dose distribution based on the treatment plan, and the results showed general agreement between each codes, the treatment plan, and the measurement, except that some deviations were found in the penumbra region. This study has demonstrated that the selected codes are all capable of performing dose calculations for therapeutic scanning proton beams with proper physics settings.
International Journal of Radiation Oncology*Biology*Physics, 2010
Symptomatic vertebral hemangiomas (SVHs) are rare benign tumors that when symptomatic require pro... more Symptomatic vertebral hemangiomas (SVHs) are rare benign tumors that when symptomatic require procedural intervention or radiotherapy (RT). Although conventionally-fractionated RT has been an alternative to surgical resection, there is very little data on stereotactic body radiotherapy (SBRT) for SVHs. Six consecutively treated patients with SVHs underwent definitive single-fraction SBRT from 2010 to 2018 at our institution. The RT planning parameters, treatment, outcome, and toxicities are reported for 6 patients with 6 total SVHs treated with single-fraction SBRT. Each patient presented with back pain and received single-fraction SBRT to a thoracic vertebral body hemangioma. One patient had received radiofrequency ablation prior to SBRT. The median SBRT dose was 18 Gy (range, 13-20). Following SBRT, 4 (67%) patients reported improvement in presenting symptoms and 2 patients (33%) were refractory. There were no acute or chronic toxicities associated with SBRT including esophagitis, vertebral compression fractures, or myelopathy. To date, this is the largest series of single-fraction SBRT for SVHs. Single fraction SBRT appears to be a feasible option for SVHs. Further studies are needed to confirm our preliminary findings and optimize dose fractionation.
International Journal of Radiation Oncology*Biology*Physics, 2009
International Journal of Radiation Oncology*Biology*Physics, 2009
To report our clinical experiences with on-board imager (OBI) kV image verification for cranial s... more To report our clinical experiences with on-board imager (OBI) kV image verification for cranial stereotactic radiosurgery (SRS) and radiotherapy (SRT) treatments. Between January 2007 and May 2008, 42 patients (57 lesions) were treated with SRS with head frame immobilization and 13 patients (14 lesions) were treated with SRT with face mask immobilization at our institution. No margin was added to the gross tumor for SRS patients, and a 3-mm three-dimensional margin was added to the gross tumor to create the planning target volume for SRT patients. After localizing the patient with stereotactic target positioner (TaPo), orthogonal kV images using OBI were taken and fused to planning digital reconstructed radiographs. Suggested couch shifts in vertical, longitudinal, and lateral directions were recorded. kV images were also taken immediately after treatment for 21 SRS patients and on a weekly basis for 6 SRT patients to assess any intrafraction changes. For SRS patients, 57 pretreatment kV images were evaluated and the suggested shifts were all within 1 mm in any direction (i.e., within the accuracy of image fusion). For SRT patients, the suggested shifts were out of the 3-mm tolerance for 31 of 309 setups. Intrafraction motions were detected in 3 SRT patients. kV imaging provided a useful tool for SRS or SRT setups. For SRS setup with head frame, it provides radiographic confirmation of localization using the stereotactic target positioner. For SRT with mask, a 3-mm margin is adequate and feasible for routine setup when TaPo is combined with kV imaging.
Medical Physics, 2009
Purpose: Due to the lifetime dose limit for these critical structures such as brainstem and spina... more Purpose: Due to the lifetime dose limit for these critical structures such as brainstem and spinal cord, achieving an additional dose of 60 Gy to patients with recurrent head and neck cancer is challenging for who received a previous dose of ∼60 Gy. Specifically, previously irradiated head and neck patients may be near tolerance dose to their brainstem and spinal cord. In this study, a reproducible IMRTtreatment design is presented to spare the doses to brainstem and spinal cord with no compromise of prescribed dose delivery. Method and Materials: Seven patients with previously irradiated, recurrent head‐and‐neck cancers were treated with DMLC IMRT. The jaws of each field were set fixed with the goal of shielding the brainstem and spinal cord at the sacrifice of partial coverage of the planning target volume (PTV) from any particular beam orientation. Beam geometry was arranged to have sufficient coverage of the PTV and ensure that the constraints of spinal cord <10 Gy and brainstem < 15 Gy were met. Results: The mean maximum dose to the brainstem was 12.1 Gy (range: 6.1–17.3 Gy), and the mean maximum dose to spinal cord was 10.4 Gy (range: 8.2–14.1 Gy). For most cases, 97% of the PTV volume was fully covered by the 95% isodose volume. We found empirically that if the angle of cervical spine curvature (Cobb's angle) was less than ∼30 degrees, patients could be treated by 18 fields. Six patients met these criteria and were treated in 25 minutes per fraction. One patient exceeded a 30 degree Cobb's angle and was treated by 31 fields in 45 minutes per fraction. Conclusion: We have demonstrated a new technique for re‐treatment of head and neck cancers. The angle of cervical spine curvature plays an important role in the efficiency and effectiveness of our approach.
PLoS ONE, 2009
Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melan... more Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown. Methodology/Principal Findings: We rationally designed melanins from either 5-S-cysteinyl-DOPA, L-cysteine/L-DOPA, or L-DOPA with diverse structures as shown by elemental analysis and HPLC. Sulfur-containing melanins had higher predicted attenuation coefficients than non-sulfur-containing melanins. All synthetic melanins displayed strong electron paramagnetic resonance (2.14?10 18 , 7.09?10 18 , and 9.05?10 17 spins/g, respectively), with sulfur-containing melanins demonstrating more complex spectra and higher numbers of stable free radicals. There was no change in the quality or quantity of the stable free radicals after high-dose (30,000 cGy), high-energy (137 Cs, 661.6 keV) irradiation, indicating a high degree of radical stability as well as a robust resistance to the ionizing effects of gamma irradiation. The rationally designed melanins protected mammalian cells against ionizing radiation of different energies. Conclusions/Significance: We propose that due to melanin's numerous aromatic oligomers containing multiple p-electron system, a generated Compton recoil electron gradually loses energy while passing through the pigment, until its energy is sufficiently low that it can be trapped by stable free radicals present in the pigment. Controlled dissipation of high-energy recoil electrons by melanin prevents secondary ionizations and the generation of damaging free radical species.
A 2×2 phased-array transmitter designed for V-band communications has been implemented by using C... more A 2×2 phased-array transmitter designed for V-band communications has been implemented by using CMOS 0.18 μm process. The circuit is based on a 30-GHz injection-locked oscillator (ILO) without using power amplifier. Combing a frequency doubler (FD) with the differential signal injection can generate a 60-GHz signal and perform a 360° phase shift with a harmonic suppression of 15 dBc. The power consumption of each channel in the transmitter is 65 mW from a 1.8 V supply. The measured output signal exhibits a self-oscillation frequency ranging from about 63.7 GHz to 65.9 GHz with an output power of -11 dBm. The transmitter demonstrates the maximum locking range up to 350 MHz under a fundamental injection. Due to the injection locking technique used in the circuit, the phase noise can be improved to -116 dBc/Hz at 1-MHz offset.
2009 Asia Pacific Microwave Conference, 2009
A frequency tripler designed for V-band signal generation has been implemented by using CMOS 0.18... more A frequency tripler designed for V-band signal generation has been implemented by using CMOS 0.18 ¿m process. Based on the circuit topology of differential binary phase shift keying (BPSK) modulator, a function of frequency triplication can be performed under the operation modes of class-AB and class-C when choosing the proper biases on the NMOS devices. For achieving a large 60
2012 IEEE International Conference on Automation Science and Engineering (CASE), 2012
Seminars in Nuclear Medicine, 2008
Radiation therapy has evolved from 2-dimensional (2D) to 3-dimensional (3D) treatments and, more ... more Radiation therapy has evolved from 2-dimensional (2D) to 3-dimensional (3D) treatments and, more recently, to intensity-modulated radiation therapy and image-guided radiation therapy. Improvements in imaging have enabled improvements in targeting and treatment. As computer-processing power has improved during the past few decades, it has facilitated developments in both imaging and treatment. The historical role of imaging from 2D to image-guided radiation therapy is reviewed here. Examples of imaging technologies such as positron emission tomography and magnetic resonance imaging are provided. The role of these imaging technologies, organ motion management approaches and their potential impacts on radiation therapy are described.
PLoS ONE, 2009
Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melan... more Background: Melanin, a high-molecular weight pigment that is ubiquitous in nature, protects melanized microorganisms against high doses of ionizing radiation. However, the physics of melanin interaction with ionizing radiation is unknown.
Physics in Medicine and Biology, 1981
Dynamic computer-assisted tomographic (CT) measurements using non-radioactive xenon gas have rece... more Dynamic computer-assisted tomographic (CT) measurements using non-radioactive xenon gas have recently been employed along with a simple model of pulmonary transport to derive ventilation rate constants (K) in small tissue volumes. Inherent in the model description is the assumption that instantaneous diffusion equilibrium occurs between inhaled Xe gas and lung tissue. The validity of this assumption as it relates to the accuracy of the derived values of K has been considered for both normal and oedematous tissue, the latter characterised by a severe widening of the interstitial fluid space. It was found that only a small error in the predicted values for K results, when the simple model is applied to the dynamic cT measurements of xenon enhancement.
Medical Physics, 2011
Sharp dose fall off outside a tumor is essential for high dose single fraction stereotactic radio... more Sharp dose fall off outside a tumor is essential for high dose single fraction stereotactic radiosurgery (SRS) plans. This study explores the relationship among tumor dose inhomogeneity, conformity, and dose fall off in normal tissues for micromultileaf collimator (mMLC) linear accelerator (LINAC) based cranial SRS plans. Between January 2007 and July 2009, 65 patients with single cranial lesions were treated with LINAC-based SRS. Among them, tumors had maximum diameters &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm: 31; between 20 and 30 mm: 21; and &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30 mm: 13. All patients were treated with 6 MV photons on a Trilogy linear accelerator (Varian Medical Systems, Palo Alto, CA) with a tertiary m3 high-resolution mMLC (Brainlab, Feldkirchen, Germany), using either noncoplanar conformal fixed fields or dynamic conformal arcs. The authors also created retrospective study plans with identical beam arrangement as the treated plan but with different tumor dose inhomogeneity by varying the beam margins around the planning target volume (PTV). All retrospective study plans were normalized so that the minimum PTV dose was the prescription dose (PD). Isocenter dose, mean PTV dose, RTOG conformity index (CI), RTOG homogeneity index (HI), dose gradient index R50-R100 (defined as the difference between equivalent sphere radius of 50% isodose volume and prescription isodose volume), and normal tissue volume (as a ratio to PTV volume) receiving 50% prescription dose (NTV50) were calculated. HI was inversely related to the beam margins around the PTV. CI had a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;V&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; shaped relationship with HI, reaching a minimum when HI was approximately 1.3. Isocenter dose and mean PTV dose (as percentage of PD) increased linearly with HI. R50-R100 and NTV50 initially declined with HI and then reached a plateau when HI was approximately 1.3. These trends also held when tumors were grouped according to their maximum diameters. The smallest tumor group (maximum diameters &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm) had the most HI dependence for dose fall off. For treated plans, CI averaged 2.55 +/- 0.79 with HI 1.23 +/- 0.06; the average R50-R100 was 0.41 +/- 0.08, 0.55 +/- 0.10, and 0.65 +/- 0.09 cm, respectively, for tumors &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; or = 20 mm, between 20 and 30 mm, and &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 30 mm. Tumor dose inhomogeneity can be used as an important and convenient parameter to evaluate mMLC LINAC-based SRS plans. Sharp dose fall off in the normal tissue is achieved with sufficiently high tumor dose inhomogeneity. By adjusting beam margins, a homogeneity index of approximately 1.3 would provide best conformity for the authors&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; SRS system.
Medical Dosimetry, 2011
Because of the dose limit for critical structures such as brainstem and spinal cord, administerin... more Because of the dose limit for critical structures such as brainstem and spinal cord, administering a dose of 60 Gy to patients with recurrent head and neck cancer is challenging for those who received a previous dose of 60؊70 Gy. Specifically, previously irradiated head and neck patients may have received doses close to the tolerance limit to their brainstem and spinal cord. In this study, a reproducible intensity-modulated radiation therapy (IMRT) treatment design is presented to spare the doses to brainstem and spinal cord, with no compromise of prescribed dose delivery. Between July and November 2008, 7 patients with previously irradiated, recurrent head and neck cancers were treated with IMRT. The jaws of each field were set fixed with the goal of shielding the brainstem and spinal cord at the sacrifice of partial coverage of the planning target volume (PTV) from any particular beam orientation. Beam geometry was arranged to have sufficient coverage of the PTV and ensure that the constraints of spinal cord <10 Gy and brainstem <15 Gy were met. The mean maximum dose to the brainstem was 12.1 Gy (range 6.1؊17.3 Gy), and the corresponding mean maximum dose to spinal cord was 10.4 Gy (range 8.2؊14.1 Gy). For most cases, 97% of the PTV volume was fully covered by the 95% isodose volume. We found empirically that if the angle of cervical spine curvature (Cobb's angle) was less than ϳ30°, patients could be treated by 18 fields. Six patients met these criteria and were treated in 25 minutes per fraction. One patient exceeded a 30°Cobb's angle and was treated by 31 fields in 45 minutes per fraction. We have demonstrated a new technique for retreatment of head and neck cancers. The angle of cervical spine curvature plays an important role in the efficiency and effectiveness of our approach.
Journal of Circuits, Systems and Computers, 2011
ABSTRACT Light-weight network gateways often employ a cost-effective embedded network processor a... more ABSTRACT Light-weight network gateways often employ a cost-effective embedded network processor and have received a strong demand for empowering content filtering services. In this regard, we were motivated to propose a specialized cache, fuzzy-updated cache automata matching (FCAM) circuit for accelerating the embedded network processors. Although automata matching algorithms are robust with deterministic matching time, there is still plenty of room for improving its average-case performance. The proposed FCAM employs cache to accelerate the root state and nonroot state with the multiple characters matching, and applies the fuzzy decision to improve the cache performance. In our experiment, the FPGA implementation of FCAM can perform at the rate of 10.5 Giga bits per second with the patterns of 25,642 bytes. This performance is superior to previous matching hardware in terms of throughput and pattern set.
International Journal of Radiation Oncology*Biology*Physics, 2013