A technique for pediatric total skin electron irradiation

<p>Abstract</p> <p>Background</p> <p>Total skin electron irradiation (TSEI) is a special radiotherapy technique which has generally been used for treating adult patients with mycosis fungoides. Recently, two infants presented with leukemia cutis isolated to the skin requiring TSEI. This work discusses the commissioning and quality assurance (QA) methods for implementing a modified Stanford technique using a rotating harness system to position sedated pediatric patients treated with electrons to the total skin.</p> <p>Methods and Results</p> <p>Commissioning of pediatric TSEI consisted of absolute calibration, measurement of dosimetric parameters, and subsequent verification in a pediatric patient sized cylindrical phantom using radiographic film and optically stimulated luminance (OSL) dosimeters. The depth of dose penetration under TSEI treatment condition was evaluated using radiographic film sandwiched in the phantom and demonstrated a 2 cm penetration depth with the maximum dose located at the phantom surface. Dosimetry measurements on the cylindrical phantom and in-vivo measurements from the patients suggested that, the factor relating the skin and calibration point doses (i.e., the <it>B</it>-factor) was larger for the pediatric TSEI treatments as compared to adult TSEI treatments. Custom made equipment, including a rotating plate and harness, was fabricated and added to a standard total body irradiation stand and tested to facilitate patient setup under sedated condition. A pediatric TSEI QA program, consisting of daily output, energy, flatness, and symmetry measurements as well as in-vivo dosimetry verification for the first cycle was developed. With a long interval between pediatric TSEI cases, absolute dosimetry was also repeated as part of the QA program. In-vivo dosimetry for the first two infants showed that a dose of ± 10% of the prescription dose can be achieved over the entire patient body.</p> <p>Conclusion</p> <p>Though pediatric leukemia cutis and the subsequent need for TSEI are rare, the ability to commission the technique on a modified TBI stand is appealing for clinical implementation and has been successfully used for the treatment of two pediatric patients at our institution.</p

Protocol Techniques for Testing Radiotherapy Accelerators

The nature of radiotherapy accelerators is briefly explained. It is argued that these complex safety-critical systems need a systematic basis for testing their software. The paper describes a novel application of protocol specification and testing methods to radiotherapy accelerators. An outline specification is given in LOTOS (Language Of Temporal Ordering Specification) of the accelerator control system. It is completely infeasible to use this directly for test generation. Instead, specification inputs are restricted using annotations in a Parameter Constraint Language. This is automatically translated into LOTOS and combined with the accelerator specification. It then becomes manageable to generate tests automatically of the actual accelerator to check that it agrees with its specification according to the relation ioconf (input-output conformance). Sample input annotations, their translation to LOTOS, and the resulting test cases are described

Solution of the kinetic equations governing trap filling. Consequences concerning dose dependence and dose-rate effects

The equations governing the traffic of charge carriers during the filling, by ionizing radiation, of traps and luminescence centers in an insulator are numerically solved. The numerical solution is that of a set of four simultaneous differential equations governing the time-dependent functions of concentrations of electrons and holes in the conduction and valence bands and in traps and centers. The results are more general and accurate than those reported previously since no assumptions concerning the proximity to equilibrium have to be made. Moreover, all previous calculations took into account the accumulated concentrations at the end of the irradiation, whereas we have considered an additional period of time after the excitation which allows for the relaxation of carriers in the bands. This simulates the experimental conditions more accurately because during this time any charge carriers which may have accumulated in the conduction and valence bands will relax into the traps and centers and, in doing so, will contribute to the final concentration of trapped charge. In our calculations we have allowed for this by letting the charge in the bands decay for a period of time T following the cessation of the irradiation (which occurs at time t). Thus, the level of trapped charge n is calculated at time t+ T and this is taken to be a better representation of the trapped charge density. Results were obtained for very high and very low dose rates (intensities) of the radiation. Experimental findings of the dose dependence of thermoluminescence (TL) are susceptible to analysis by the approach developed by us. By adding a competing trapping level and changing the set of equations appropriately, we get a set of five simultaneous differential equations. In this way we can test the previous approximative results yielding a superlinear filling of one of the traps. It is found that, under an appropriate choice of parameters, superlinearity emerges, although the results are not identical to those of the previous approximations. In addition, an important result to emerge from the analysis is the possible dependence of TL output on the dose rate for a constant total dose. Recent experimental results of such a dependence on TL in quartz are shown to be in general accord with the numerical results.Peer reviewedPhysic

Lonely or Just Distant? The Role of Interpretation in the Emotional Impact of a Metaphorical Game

When playing a metaphorical game, what is the role of the player’s interpretation in the game’s emotional impact? If players are consciously aware of the metaphor, do they experience a stronger effect of that metaphor? This dissertation extends part of the debate on deliberate metaphor (Gibbs, 2015b; Steen, 2008, 2017) into the empirical space of video games. Participants played a version of the game Loneliness (Magnuson, 2007). In the game, the player controls a square. When the player approaches other squares, the other squares move away as if rejecting the player. Since this game communicates primarily through the metaphor AFFECTION IS PROXIMITY, any change in the player’s emotions can be attributed to this metaphor. In a series of experiments, participants played the game described above, a variation on that game in which the other squares approach the player’s square, or Tetris as a baseline. Participants self-reported their emotional state before and after playing the game, and the change from before to after was the primary dependent variable. Experiment 1 established that Loneliness influences feelings of loneliness and acceptedness and piloted methods of measuring participants' perceptions of metaphor deliberateness. In Experiment 2, participants who played Loneliness were split into Aware and Unaware groups based on ratings of agreement with statements adapted from Gibbs (2015b). The Aware showed a significant change in both loneliness and acceptedness, while the Unaware and baseline groups showed little or no change. These results are interpreted based on a set of hypotheses motivated by the paradox of metaphor (Steen, 2008, 2017), responses to the paradox (Gibbs, 2015), and implicit metaphor studies (Thibodeau &amp; Boroditsky, 2011, 2013). The overall pattern of results is consistent deliberate metaphor theory, in that conscious awareness of metaphor in Loneliness seems to be critical to its emotional impact

Lonely or Just Distant? The Role of Interpretation in the Emotional Impact of a Metaphorical Game

When playing a metaphorical game, what is the role of the player’s interpretation in the game’s emotional impact? If players are consciously aware of the metaphor, do they experience a stronger effect of that metaphor? This dissertation extends part of the debate on deliberate metaphor (Gibbs, 2015b; Steen, 2008, 2017) into the empirical space of video games. Participants played a version of the game Loneliness (Magnuson, 2007). In the game, the player controls a square. When the player approaches other squares, the other squares move away as if rejecting the player. Since this game communicates primarily through the metaphor AFFECTION IS PROXIMITY, any change in the player’s emotions can be attributed to this metaphor. In a series of experiments, participants played the game described above, a variation on that game in which the other squares approach the player’s square, or Tetris as a baseline. Participants self-reported their emotional state before and after playing the game, and the change from before to after was the primary dependent variable. Experiment 1 established that Loneliness influences feelings of loneliness and acceptedness and piloted methods of measuring participants' perceptions of metaphor deliberateness. In Experiment 2, participants who played Loneliness were split into Aware and Unaware groups based on ratings of agreement with statements adapted from Gibbs (2015b). The Aware showed a significant change in both loneliness and acceptedness, while the Unaware and baseline groups showed little or no change. These results are interpreted based on a set of hypotheses motivated by the paradox of metaphor (Steen, 2008, 2017), responses to the paradox (Gibbs, 2015), and implicit metaphor studies (Thibodeau &amp; Boroditsky, 2011, 2013). The overall pattern of results is consistent deliberate metaphor theory, in that conscious awareness of metaphor in Loneliness seems to be critical to its emotional impact