Biomedical subjects
Publications and source records attributed to Chris Brooks.
We investigate the fabrication tolerance of novel slanted-angle silicon-on-insulator polarization rotators with asymmetric external waveguiding regions. We also minimize the input and output coupling loss between the polarization rotator and the rib waveguides through a lateral shift in the relative waveguide positions.
OBJECTIVE: Three phase 1 clinical trials of a superpotent melanotropic peptide, melanotan-1 (MT-1, or [Nle(4)-D-Phe(7)]alpha-melanocyte-stimulating hormone) were performed to demonstrate safety for MT-1 therapy combined with UV-B light or sunlight. DESIGN: Open-label studies at 2 dose levels of MT-1 combined with small doses of UV-B to the neck or buttock or full sunlight to half of the back. SETTING: Dermatology clinics at the Arizona Health Sciences Center, Tucson. INTERVENTIONS: The first study randomized 4 subjects to MT-1 (0.08 mg/kg per day subcutaneously) and 4 subjects to injections of isotonic sodium chloride (9%) solution for 10 days, followed by neck irradiation with 3 times the minimal erythema dose (MED) of UV-B light. In the next study (n = 12), the MT-1 dosage was increased to 0.16 mg/kg per day for 10 days, with UV-B radiation (0.25-0.75 MED) given to a buttock site for 5 days during (n = 7) or after (n = 5) MT-1 administration. A final study randomized 8 subjects to 3 to 5 days of sunlight to half of the back or to sunlight plus 0.16 mg/kg of MT-1 for 5 days per week for 4 weeks. RESULTS: Tanning in the first study was achieved in 3 of 4 subjects receiving MT-1, and these subjects also had 47% fewer sunburn cells at the irradiated neck site. More skin sites darkened with the higher dose of MT-1 in the second study. In the third study, there was significantly enhanced tanning of the back in the MT-1 group, and this was maintained at least 3 weeks longer than the tanning in the sunlight-only controls, who required 50% more sun-exposure time for equivalent tanning. MAIN OUTCOME MEASURE: There were no pathologic findings at any UV-B or sun-exposed sites in any subject. Toxic effects due to MT-1 were minor, consisting of nausea and transient facial flushing. CONCLUSION: Melanotan-1 can be safely combined with UV-B light or sunlight and appears to act synergistically in the tanning response to light.
Clinical trials often require homogeneous treatment plans. Many institutions, however, have begun using heterogeneous plans. Is it possible to satisfy the requirements of such a protocol while achieving the superior accuracy of heterogeneous treatment planning? At the University of Texas M. D. Anderson Cancer Center, we currently use conformal treatment planning with heterogeneities for thoracic cancers. This paper describes a procedure that has been developed to satisfy the requirements of a homogeneous protocol, such as RTOG 98-01 (A Phase III Study of Amifostine mucosal protection), while maintaining accuracy in treatment planning.
PURPOSE: To quantify the differences in doses to target volumes and critical thoracic structures calculated by traditional homogeneous point-dose prescription and heterogeneity-corrected volume-dose prescription. METHODS AND MATERIALS: Between 1998 and 2001, 30 patients with inoperable Stage I/II non-small-cell lung cancer underwent radiation treatment planning at our institution. A commercially available convolution/superposition- based algorithm was used. Three treatment plans were calculated for each patient using identical beam geometries: one plan was generated by traditional homogeneous point-dose prescription, a second by the traditional method with heterogeneity correction, and a third by heterogeneity-corrected volume-dose prescription that would cover 95% of the planned target volume (PTV). Target volume coverage, isocenter dose, and dose uniformity in the second and third plans were compared. RESULTS: The PTV, clinical target volume (CTV), and isocenter calculated by the heterogeneity-corrected volume-dose method were equivalent to those calculated by the traditional homogeneous point-dose method with heterogeneity correction. The fraction of the PTV covered by heterogeneity-corrected volume-dose prescription was significantly greater than the fraction covered by traditional homogeneous point-dose prescription with heterogeneity correction (p = 0.05). The dose prescribed using the traditional method would have been delivered to less than 90% of the PTV in 14 of 30 patients. There was no significant difference in the maximum and minimum doses to the PTV, the CTV, or the isocenter calculated by the traditional homogeneous method with heterogeneity correction and the heterogeneity-corrected volume-dose method. There was also no significant difference in the planned volume of lung receiving greater than 20 Gy as calculated by these two methods. CONCLUSION: When compared with traditional homogeneous radiation treatment planning, heterogeneity-corrected methods produce equivalent PTV, CTV, and isocenter doses while providing superior PTV coverage.
This study sought to determine whether fitting a more aggressive seat belt reminder system to new vehicles would be cost-beneficial for Australia. While seat belt wearing rates have been observed around 95% in the front seat, non-wearing rates in casualty crashes are as high as 33% among persons killed and 19% among seriously injured occupants. Benefits were computed for three device options (simple, simple-2 and complex) and three introduction scenarios (driver-only, front seat occupants and all occupants). Four levels of effectiveness were assumed, from 10% to 40%, depending on the type of device fitted. Unit benefits were computed assuming a 5% discount rate and a 15yr fleet life. Various industry experts provided the costs. The findings showed that Benefit-Cost-Ratios ranged from 4.0:1 at best (simple device for the driver only) to 0.9:1 for all seating positions. These figures are conservative, given the assumptions made and the discounted human capital methods used.