Image-based dosimetry for 225Ac-PSMA-I&T therapy using quantitative SPECT

Purpose!#!After a decade of PET/MR, the case of attenuation correction (AC) remains open. The initial four-compartment (air, water, fat, soft tissue) Dixon-based AC scheme has since been expanded with several features, the latest being MR field-of-view extension and a bone atlas. As this potentially changes quantification, we evaluated the impact of these features in PET AC in prostate cancer patients.!##!Methods!#!Two hundred prostate cancer patients were examined with either !##!Results!#!High correlation and no visually perceivable differences between all evaluated methods (r > 0.996) were found. The mean relative difference in lesion uptake of !##!Conclusions!#!Based on these results and the encountered bone atlas registration inaccuracy, we deduce that including bones and extending the MR field-of-view did not introduce clinically significant differences in PSMA diagnostic accuracy and tracer uptake quantification in prostate cancer pelvic lesions, facilitating the analysis of serial studies respectively. However, in the absence of ground truth data, we advise against atlas-based methods when comparing serial scans for bone lesions

A Comparison of Wood Density between Classical Cremonese and Modern Violins

Classical violins created by Cremonese masters, such as Antonio Stradivari and Giuseppe Guarneri Del Gesu, have become the benchmark to which the sound of all violins are compared in terms of their abilities of expressiveness and projection. By general consensus, no luthier since that time has been able to replicate the sound quality of these classical instruments. The vibration and sound radiation characteristics of a violin are determined by an instrument's geometry and the material properties of the wood. New test methods allow the non-destructive examination of one of the key material properties, the wood density, at the growth ring level of detail. The densities of five classical and eight modern violins were compared, using computed tomography and specially developed image-processing software. No significant differences were found between the median densities of the modern and the antique violins, however the density difference between wood grains of early and late growth was significantly smaller in the classical Cremonese violins compared with modern violins, in both the top (Spruce) and back (Maple) plates (p = 0.028 and 0.008, respectively). The mean density differential (SE) of the top plates of the modern and classical violins was 274 (26.6) and 183 (11.7) gram/liter. For the back plates, the values were 128 (2.6) and 115 (2.0) gram/liter. These differences in density differentials may reflect similar changes in stiffness distributions, which could directly impact vibrational efficacy or indirectly modify sound radiation via altered damping characteristics. Either of these mechanisms may help explain the acoustical differences between the classical and modern violins

Psychophysics of reading: I. Normal vision

Legge, G. E., Pelli, D. G., Rubin, G. S., & Schleske, M. M. (1985). Psychophysics of reading--I. Normal vision. Vision Res, 25(2), 239-252.\ud http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=4013091 \ud http://www.psych.nyu.edu/pelli/pubs/legge1985reading.pdf\ud http://www.psych.nyu.edu/pelli/pubs/legge1985reading1reprint.pdf\ud Abstract-This paper is about the visual requirements for reading with normal vision. It is the first in a series devoted to the psychophysics of reading with normal and low vision. We have measured reading rates for text scanned across the face of a TV monitor while varying parameters that are important in current theories of pattern vision. Our results provide estimates of the stimulus parameters required for optimal reading of scanned text. We have found that maximum reading rates are achieved for characters subtending 0.3 degree to 2 degrees. Contrast polarity (black-on-white vs white-on-black text) has no effect. Reading rate increases with field size, but only up to 4 characters, independent of character size. When text is low-pass spatial-frequency filtered, reading rate increases with bandwidth, but only up to two cycles/character, independent of character size. When text is matrix sampled, reading rate increases with sample density, but only up to a critical sample density which depends on character size. The critical sample density increases from about 4 X 4 samples/character for 0.1 degree characters to more than 20 X 20 samples/character for 24 degrees characters. We suggest that one spatial-frequency channel suffices for reading.\ud \u

Parametric Experimental Modal Analysis of a Modern Violin Based on a Guarneri del Gesù Model

Mechanical effects and dynamic behaviour of a modern violin, built on a Guarneri del Gesù model, were examined via parametric experimental modal analysis. Among the few mobile components of a violin, the soundpost has a particular relevance for the final acoustic performance, even if its dimensions are extremely small. Therefore, the aim of this first research is to understand the violin sensitivity to the soundpost position considering its influence on the overall structural-vibrational behaviour. Experimental modal analysis was performed in six different configurations, related to different positions of the soundpost inside the violin, including both the outer possible locations and optimal position, generally defined by the violinist according only to the perceived best acoustic performance. Six “Signature” modes were identified and tracked in all configurations, comparing mode shapes, damping and natural frequencies of involved modes, in order to find a correlation between mechanical vibrations and acoustic performance of the instrument. The effects of the soundpost position on the modal properties of the “Signature” mode shapes are highlighted and discussed. Finally, the potential role of soundpost as a practical engineering tool to improve the signature and sound quality is discussed