Citations

Abstract Objective . This study characterized optically-stimulated luminescent dosimeter (OSLD) nanoDots for use in a therapeutic carbon beam using the Imaging and Radiation Oncology Core (IROC) framework for remote output verification. Approach . The absorbed dose correction factors for OSLD (fading, linearity, beam quality, angularity, and depletion), as defined by AAPM TG 191, were characterized for carbon beams. For the various correction factors, the effect of linear energy transfer (LET) was examined by characterizing in both a low and high LET setting. Main results . Fading was not statistically different between reference photons and carbon, nor between low and high LET beams; thus, the standard IROC-defined exponential function could be used to characterize fading. Dose linearity was characterized with a linear fit; while low and high LET carbon linearity was different, these differences were small and could be rolled into the uncertainty budget if using a single linearity correction. A linear fit between beam quality and dose-averaged LET was determined. The OSLD response at various angles of incidence was not statistically different, thus a correction factor need not be applied. There was a difference in depletion between low and high LET irradiations in a primary carbon beam, but this difference was small over the standard five readings. The largest uncertainty associated with the use of OSLDs in carbon was because of the k Q correction factor, with an uncertainty of 6.0%. The overall uncertainty budget was 6.3% for standard irradiation conditions. Significance . OSLD nanoDot response was characterized in a therapeutic carbon beam. The uncertainty was larger than for traditional photon applications. These findings enable the use of OSLDs for carbon absorbed dose measurements, but with less accuracy than conventional OSLD audit programs.

Introduction: In vitro, ST2 is a marker of myocyte stress and inflammation but in vivo, there is no trans-cardiac ST2 concentration step-up to support cardiac ST2 activation in human heart failure (HF) calling into question the source of ST2 in HF. While ST2 is predictive of adverse outcomes in HF, the relationship between ST2 and key pathophysiologic domains in HF with preserved ejection fraction (HFpEF) is not well characterized. Hypothesis: ST2 levels increase in proportion to the severity of left ventricular (LV) remodeling and dysfunction in HFpEF. Methods: At enrollment, patients (n=174) from the RELAX trial testing sildenafil in HFpEF had serum ST2 levels measured and underwent assessment of pathophysiologic domains including congestion, cardiac structure and function, exercise performance (peak oxygen consumption (VO2)) and biomarkers of neurohumoral activation (NT-proBNP, aldosterone, endothelin-1), renal dysfunction (cystatin-C), fibrosis (pro-collagen III N-terminal peptide [NTP], C-telopeptide for type I collagen [CITP]), inflammation (high-sensitivity CRP [hsCRP]) and myocardial necrosis (high-sensitivity troponin-I [hsTnI]). Analysis adjusted for sex, a covariate associated with ST2 levels in normal persons. Results: See table. ST2 was associated with greater congestion, worse right ventricular (RV) pressure overload and dysfunction, lower peak VO2 and biomarkers of neurohumoral activation, renal dysfunction, fibrosis and myocardial necrosis and tended to be associated with systemic inflammation (hsCRP). ST2 was not associated with LV structure or LV systolic or diastolic function. Conclusions: In HFpEF, ST2 was associated with measures of right sided congestion, RV overload and dysfunction, exercise intolerance and other systemic markers of more advanced HF but not with LV structure or LV systolic or diastolic function. These data suggest that mechanisms distinct from LV stress stimulate ST2 activation in HFpEF.