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Robert Jeraj - One of the best experts on this subject based on the ideXlab platform.

  • on the sensitivity of imrt dose optimization to the Mathematical Form of a biological imaging based prescription function
    Physics in Medicine and Biology, 2009
    Co-Authors: Stephen R Bowen, Ryan T Flynn, Soren M Bentzen, Robert Jeraj
    Abstract:

    Voxel-based prescriptions of deliberately non-uniForm dose distributions based on molecular imaging, so-called dose painting or theragnostic radiation therapy, require specification of a transFormation that maps the image data intensities to prescribed doses. However, the functional Form of this transFormation is currently unknown. An investigation into the sensitivity of optimized dose distributions resulting from several possible prescription functions was conducted. TransFormations between the radiotracer activity concentrations from Cu-ATSM PET images, as a surrogate of tumour hypoxia, and dose prescriptions were implemented to yield weighted distributions of prescribed dose boosts in high uptake regions. Dose escalation was constrained to reflect clinically realistic whole tumour doses and constant normal tissue doses. Optimized heterogeneous dose distributions were found by minimizing a voxel-by-voxel quadratic objective function in which all tumour voxels were given equal weight. Prescriptions based on a polynomial mapping function were found to be least constraining on their optimized plans, while prescriptions based on a sigmoid mapping function were the most demanding to deliver. A prescription Formalism that fixed integral dose was less sensitive to errors in the choice of the mapping function than one that boosted integral dose. Integral doses to normal tissue and critical structures were insensitive to the shape of the prescription function. Planned target dose conFormity improved with smaller beamlet dimensions until the inherent spatial resolution of the functional image was matched. Clinical implementation of dose painting depends on advances in absolute quantification of functional images and improvements in delivery techniques over smaller spatial scales.

Angus John Clarke - One of the best experts on this subject based on the ideXlab platform.

  • Genetic risk: women's understanding of carrier risks in Duchenne muscular dystrophy.
    Journal of medical genetics, 1993
    Co-Authors: Evelyn Patricia Parsons, Angus John Clarke
    Abstract:

    This paper reports a study of 48 women (16 mothers and 32 daughters representing 28 families) who had lived with Duchenne muscular dystrophy (DMD) in their family. It looks at the way the women talked about their carrier risks during the course of an unstructured interview. It points to a significant difference between lay and health professionals' perspectives, in particular the thresholds they used to distinguish between high and low risk. A number of women, when quoting their risk in a Mathematical Form, confused their reproductive risks with their carrier risk, another indication of differential perceptions between the women and health professionals. There was evidence that several of the women did not retain their risk in a Mathematical Form but had translated it into a descriptive category which resolved their risk into greater certainty.

Brian Wesley Williams - One of the best experts on this subject based on the ideXlab platform.

Richard G. Forbes - One of the best experts on this subject based on the ideXlab platform.

  • Call for experimental test of a revised Mathematical Form for empirical field emission current-voltage characteristics
    Applied Physics Letters, 2008
    Co-Authors: Richard G. Forbes
    Abstract:

    There are now good theoretical reasons to believe that experimental current-voltage (i-V) relationships for cold field electron emission (CFE) should approximately obey the empirical law i=CVκexp(−B∕V), where B, C, and κ are effectively constant, and κ≠2. Since −dlni∕d(1∕V)=(V2∕i)di∕dV=B+κV, κ for a given emission situation could be experimentally established from an appropriate data plot if sufficiently accurate current-voltage measurements were available. Knowledge of experimental κ values could lead to greater physical understanding of CFE and variations as between materials. It is strongly urged that the feasibility of measurements of this kind be carefully explored.

Tae-young Choi - One of the best experts on this subject based on the ideXlab platform.

  • A unified Mathematical Form of the Walsh-Hadamard transForm for lossless image data compression
    Signal Processing, 1997
    Co-Authors: Ho-youl Jung, Rémy Prost, Tae-young Choi
    Abstract:

    Abstract A unified Mathematical Form of the integer Walsh-Hadamard transForm (WHT) has been introduced for lossless image data compression, which is called the unified lossless WHT (ULWHT). The ULWHT extends the previous schemes that have been defined for only 2 × 2 WHT. This allows a larger size WHT to be applied to the lossless pyramid structured coding. We show that, due to its ability to process large block sizes, the ULWHT always reduces the entropy when each transForm coefficient is encoded separately. However, in the case of encoding all transForm coefficients at the same time, the total entropy will first decrease and then increase for a sufficiently large block size. In the latter case, computer simulation results show that the ULWHT has the lowest entropy of all the test images when using the 2 3 × 2 3 block size. In the application of the ULWHT to lossless pyramid structured coding, the use of the smallest size ULWHT (i.e., S-TransForm) perForms better than that of the other sizes.