Stereotactic radiotherapy treatments use high doses of radiation delivered in relatively few fractions compared with conventional radiotherapy. Specialist planning, immobilization and image guidance techniques are needed to achieve accurate treatment. Because doses are high and fractions few, the consequences of treatment errors are more severe than for conventional therapy. A credentialing program for staff and equipment is one strategy that can be used to reduce risk. The Icon Group runs a network of 20 radiotherapy centres in Australia. There has been a rapid growth of stereotactic treatments at Icon. In order to reduce the risks of introducing stereotactic therapy, an in-house credentialing and endorsement program was developed. A multi-disciplinary working group comprising medical physicists, radiation oncologists and radiation therapists was established to develop endorsement policies and procedures. Elements considered included the purchase, commissioning and quality assurance of equipment, the establishment and documentation of safe work practices and staff competency assessment. The endorsement program is in the process of being implemented across the Icon network.
A difference of 12% has been observed in the output of an 80 kV, 2.2 mm A1 HVL x-ray beam when comparing measurements made according to the TRS 398 medium energy protocol with measurements made according to the TRS 277 low energy protocol. Absorbed dose to water chamber calibration factors used for the TRS 398 measurements were derived from standards of air kerma with the use of the TRS 277 medium energy protocol, and given this fact the discrepancy observed can be considered in terms of a difference between the TRS 277 low and medium energy protocols for this beam. Repeat measurements using the TRS 277 low and medium energy protocols have been made to confirm this. The most likely origins for the discrepancy observed are the chamber perturbation correction, p(u), obtained from TRS 277, and the value of the measured percentage depth dose at a depth of 2 g.cm(-2) for this beam. Given these findings, reference dosimetry for this beam will be performed according to the TRS 398 low energy protocol.
In this work, a methodology for using a smartphone camera, in conjunction with a light-tight box operating in reflective transmission mode, is investigated as a proof of concept for use as a film dosimetry system. An imaging system was designed to allow the camera of a smartphone to be used as a pseudo densitometer. Ten pieces of Gafchromic EBT3 film were irradiated to doses up to 16.89 Gy and used to evaluate the effects of reproducibility and orientation, as well as the ability to create an accurate dose response curve for the smartphone based dosimetry system, using all three colour channels. Results were compared to a flatbed scanner system. Overall uncertainty was found to be best for the red channel with an uncertainty of 2.4% identified for film irradiated to 2.5 Gy and digitised using the smartphone system. This proof of concept exercise showed that although uncertainties still exceed a flatbed scanner system, the smartphone system may be useful for providing point dose measurements in situations where conventional flatbed scanners (or other dosimetry systems) are unavailable or unaffordable.
We have measured the autofluorescence from suspensions of Pseudomonas aeruginosa in the growth medium and after one, two, and three washes. The bacterium was grown in two different media, nutrient broth and King's B broth. The bacterium was harvested after 12, 24, and 48 h of growth. The fluorescence was measured with excitation every 10 nm from 200 nm to 600 nm. The fluorescence profiles were analyzed using principal component analysis. We found that most of the information is in the first three principal components. Stark differences in the value of the first principal component were noted between the samples in broth and those with one, two, or three washings. The second and third principal components noted differences between the samples washed once and those washed two or three times. There was no significant difference between samples washed two and three times. There are small differences noted between the samples grown in the two different broths, and no differences were noted among the samples harvested at different times.
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