Purpose: This paper introduces a new external beam radiotherapy device named GammaPod that is dedicated for stereotactic radiotherapy of breast cancer.
Methods:The design goal of the GammaPod as a dedicated system for treating breast cancer is the ability to deliver ablative doses with sharp gradients under stereotactic image guidance. Stereotactic localization of the breast is achieved by a vacuum-assisted breast immobilization cup with built-in stereotactic frame. Highly focused radiation is achieved at the isocenter due to the cross-firing from 36 radiation arcs generated by rotating 36 individual Cobalt-60 beams. The dedicated treatment planning system optimizes an optimal path of the focal spot using an optimization algorithm borrowed from computational geometry such that the target can be covered by 90%-95% of the prescription dose and the doses to surrounding tissues are minimized. The treatment plan is intended to be delivered with continuous motion of the treatment couch. In this paper the authors described in detail the gamma radiation unit, stereotactic localization of the breast, and the treatment planning system of the GammaPod system. Results: A prototype GammaPod system was installed at University of Maryland Medical Center and has gone through a thorough functional, geometric, and dosimetric testing. The mechanical and functional performances of the system all meet the functional specifications. Conclusions: An image-guided breast stereotactic radiotherapy device, named GammaPod, has been developed to deliver highly focused and localized doses to a target in the breast under stereotactic image guidance. It is envisioned that the GammaPod technology has the potential to significantly shorten radiation treatments and even eliminate surgery by ablating the tumor and sterilizing the tumor bed simultaneously.
To explore the associations of SNPs within hsa-miR-605 (rs2043556) and hsa-miR-149 (rs2292832) and lifestyle-related factors with gastrointestinal cancer, a case-control study including 762 cases and 757 controls was conducted. Marginally significant associations were found both for hsa-miR-149 rs2292832 with gastric cancer risk (TC + CC vs. TT, OR = 0.68, 95% CI: 0.44-1.04) and for hsa-miR-605 rs2043556 with colorectal cancer risk (AG + GG vs. AA, OR = 0.70, 95% CI: 0.48-1.02) in males. Tea drinking showed a protective effect on gastric cancer risk (OR = 0.28, 95% CI: 0.13-0.60), while smoke inhalation increased the risk of gastric cancer (OR = 1.94, 95% CI: 1.08-3.47). Irritability was found to be a risk factor for both colorectal cancer (OR = 1.61, 95% CI: 1.02-2.53) and gastric cancer (OR = 1.96, 95% CI: 1.17-3.29). Among those that engaged in smoke inhalation, miR-149 CT/CC and miR-605 AG/GG genotype carriers had increased susceptibilities to colorectal cancer (OR = 1.90, 95% CI: 1.11-3.25) and gastric cancer (OR = 1.87, 95% CI: 1.03-3.42), respectively. Among the tea drinkers, there exists a marginally protective effect of miR-605 AG/GG genotypes on colorectal cancer incidence (OR = 0.71, 95% CI: 0.47-1.06) and a significantly protective effect of miR-149 CT/CC on gastric cancer incidence (OR = 0.47, 95% CI: 0.29-0.77). The SNPs of rs2292832 and rs2043556 might be able to modify the susceptibility to male gastric and colorectal cancers, respectively. Tea drinking is a protective factor, while smoke inhalation is a risk factor for gastric cancer, and they might have the potential to modify the associations between miR-149 and miR-605 polymorphisms with gastrointestinal cancer risk. In addition, irritability was shown to be a risk factor for both gastric and colorectal cancers.
A theoretical model is described for a magnetic resonance imaging (MRI) radio-frequency resonator (an MRI "coil") that is useful at ultrahigh frequencies. The device is a "TEM resonator," which is based on a concept originally proposed by Röschmann (1988). The coil comprises a circular cavity-like structure containing several coaxial transmission lines operating in a transverse electromagnetic (TEM) mode. The model developed herein treats the empty coil and is based on multiconductor transmission line theory. This work generalizes and extends similar analyses of the device by Röschmann (1995) and Chingas and Zhang (1996). The model employs explicit calculation of per-unit-length parameters for TEM lines having arbitrary geometries. Calculations of the resonator's frequency response are found to compare well with measurements. Fields produced by linear (single-point) and quadrature drive are also computed and compared to images of low-permittivity phantoms.
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