PubMed · 5037120
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G R Barer, R Barer, K Robinson. 1972. A solid-state 50 Hz electromagnetic flowmeter.. https://pubmed.ncbi.nlm.nih.gov/5037120/
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The delivery efficiency of step and shoot intensity modulated radiotherapy (IMRT) has been improved by the installation of fast-tuning magnetrons into three travelling wave linear accelerators. The IMRT delivery efficiency and the beam start-up performance have been compared before and after installation. Start-up and inter sub-field times were reduced by an average of 3.0 s. A typical start-up time from depression of the start button to beam on is now around 4 s. Delivery efficiency for a variety of clinical and quality control prescriptions was improved by an average of 30.7% (range 7.4-60.9%), depending on a complex combination of the number of sub-fields, distance moved by leaves and dose rate. For the oldest accelerator (7 years old), dosimetric accuracy was significantly improved for low dose sub-fields. The dose output was within 2% for a 1 monitor unit (MU) sub-field and 1% for a 2 MU sub-field. The two newer accelerators displayed similar or better dose characteristics even before fast-tuning magnetron installation. Beam symmetries and flatnesses were acceptable at all energies and dose rates, and showed no obvious degradation in low dose sub-fields. It is recommended that fast-tuning magnetrons are adopted for accelerators of this design performing step and shoot IMRT.
Given complete information about the normal component of a magnetic field in a plane, it is possible to directly calculate all aspects of the field at any point in a source-free, homogeneous volume above that plane. The magnetic scalar potential, the magnetic field, and its gradient have direct representations as integrals of the boundary data. This paper provides a Green function method for this problem, as well as examples of such calculations.
Advantages of the continuous magnetic flow sorting for biomedical applications over current, batch-wise magnetic separations include high throughput and a potential for scale-up operations. A continuous magnetic sorting process has been developed based on the quadrupole magnetic field centered on an annular flow channel. The performance of the sorter has been described using the conceptual framework of split-flow thin (SPLITT) fractionation, a derivative of field-flow fractionation (FFF). To eliminate the variability inherent in working with a heterogenous cell population, we developed a set of monodisperse magnetic microspheres of a characteristic magnetization, and a magnetophoretic mobility, similar to those of the cells labeled with a magnetic colloid. The theory of the magnetic sorting process has been tested by injecting a suspension of the magnetic beads into the carrier fluid flowing through the sorter and by comparing the theoretical and experimental recovery versus total flow-rate profiles. The position of the recovery maxima along the total flow-rate axis was a function of the average bead magnetophoretic mobility and the magnetic field intensity. The theory has correctly predicted the position of the peak maxima on the total flow-rate axis and the dependence on the bead mobility and the field intensity, but has not correctly predicted the peak heights. The differences between the calculated and the measured peak heights were a function of the total flow-rate through the system, indicating a fluid-mechanical origin of the deviations from the theory (such as expected of the lift force effects in the system). The well-controlled elution studies using the monodisperse magnetic beads, and the SPLITT theory, provided us with a firm basis for the future sorter evaluation using cell mixtures.