PubMed · 9775543
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B J Roth, J P Wikswo. 1998. Comments on "Hall effect imaging".. https://doi.org/10.1109/10.720207
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Gold electrodes of thickness-shear mode acoustic wave sensors were modified with poly[(mercaptopropyl)methylsiloxane]. The flow-through adsorption of three major plasma proteins (human serum albumin, fibrinogen, and immunoglobulin G) was detected by acoustic network analysis. The elution of fibrinogen and albumin from coated and unmodified gold surfaces by sodium dodecyl sulfate was studied with respect to different adsorption times and protein concentrations. Both sequential and competitive adsorptions of the three proteins on polymer-modified surfaces of sensors were examined as were simultaneous adsorptions from binary and ternary mixtures. The experimental results confirm that the competitive behaviors of proteins in terms of adsorptive processes are explained by factors other than displacement phenomena.
PURPOSE: To examine the optimal ultrasound frequency and the treatable domain determined by the tumor size and tumor depth when an external ultrasound heating system is employed for the brain tumor hyperthermia. METHODS AND MATERIALS: This work employs a simplified model of a scanned ultrasound transducer power deposition (a cone with convergent/divergent shape) and a search algorithm to investigate the optimal frequency and the treatable domain. The distributions of temperature and SAR (specific absorption rate) ratio are used to determine the appropriateness of the acoustic window size and the input power level for a yielded set of tumor conditions. The factors considered are the acoustic window size, tumor size and depth, ultrasound frequency, and the acoustic absorption of the post-target bone behind the tumor. RESULTS: Simulation results demonstrate that the optimal frequency depends on the tumor depth and the acoustic absorption of the post-target bone. However, it is almost independent of the acoustic window size. The optimal frequency shifts to a higher level for a deeper tumor heating to reduce the effect of the high acoustic absorption of post-target bone. Moreover, the treatable domain is proportional to the acoustic window size and related to the ultrasound frequency. CONCLUSION: It may not be possible to deliver appropriate ultrasonic energy to heat a brain tumor without overheating the normal brain tissue and/or the post-target bone under the constraints of the available acoustic window size for the ultrasonic beam, ultrasonic attenuation of brain tissue, high absorption of post-target bone, and high blood perfusion rate. The results of this study can be a guideline for designing an optimal ultrasound heating system, arranging the transducers, and implementing further treatment planning for the brain tumor hyperthermia.
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