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Abstract Organic thin film transistors (OTFT) were investigated as a novel radiation detector. The OTFTs were fabricated on a flexible PET substrate with a PMMA dielectric layer and a pentacene semiconductor. OTFTs were irradiated up to 400 Gy using kilovoltage (100 and 180 kVp) and megavoltage (6 and 18 MV) photon beams. One OTFT was irradiated to 1000 Gy using 6 MV to observe the longevity of the device. Irradiating the devices caused a positive threshold voltage shift in each device. The magnitude of the threshold voltage shift per unit dose decreased with accumulated dose until it stabilized after approximately 200 Gy. The sensitivity ranged from 2 to 10 mV/Gy at low accumulated dose and decreased to 0.5–1.5 mV/Gy after 200 Gy of accumulated dose across the various OTFTs. After 400 Gy all of the devices were still functional with a loss in mobility of about 15, 14, 12 and 9% for beam qualities of 100 kV, 180 kV, 6 MV, and 18 MV, respectively. After 1000 Gy using 6 MV the OTFT was still functional with a sensitivity of 0.8 ± 0.1 mV/Gy after 300 Gy. This study showed that an OTFT on a flexible substrate shows a measureable response to photon irradiation of various qualities. Highlights • An organic thin film transistor (OTFT) was designed and tested as a radiation detector. • Following an initial irradiation period, the sensitivity of the OTFTs was similar across a wide photon energy range. • The mobility of the devices decreased with accumulated dose. • A longevity test demonstrated device functionality after 1000 Gy. [ABSTRACT FROM AUTHOR]

Background: Voltage criteria for ventricular mapping have been obtained from small series of patients and prioritizing high specificity.Objective: The purpose of this study was to analyse the potential influence of contact force (CF) on voltage mapping and to define voltage cutoff values for right ventricular (RV) scar using the tetralogy of Fallot as a model of transmural RV scar and magnetic resonance imaging (MRI) as reference.Methods: Fourteen patients (age 32.6 ± 14.3 years; 5 female) with repaired tetralogy of Fallot underwent high-resolution cardiac MRI (1.25 × 1.25 × 2.5 mm). Scar, defined as pixels with intensity >50% maximum, was mapped over the RV geometry and merged within the CARTO system to RV endocardial voltage maps acquired using a 3.5-mm ablation catheter with CF technology (SmartTouch, Biosense Webster).Results: In total, 2446 points were analyzed, 915 within scars and 1531 in healthy tissue according to MRI. CF correlated to unipolar (ρ = 0.186; P <.001) and bipolar voltage in healthy tissue (ρ = 0.245; P <.001) and in scar tissue. Receiver operating characteristic curve analysis excluding points with very low CF (<5g) identified optimal voltage cutoffs of 5.19 mV for unipolar voltage and 1.76 mV for bipolar voltage, yielding sensitivity/specificity of 0.89/0.85 and 0.9/0.9, respectively.Conclusion: CF is an important factor to be taken into account for voltage mapping. If good CF is applied, unipolar and bipolar voltage cutoffs of 5.19 mV and 1.76 mV are optimal for identifying RV scar on endocardial mapping with the SmartTouch catheter. Data on the diagnostic accuracy of different voltage cutoff values are provided. [ABSTRACT FROM AUTHOR]

Background: Studies analyzing optimal voltage thresholds for scar detection with electroanatomic mapping frequently lack a gold standard for comparison.Objective: The purpose of this study was to use a porcine infarct model with ex vivo magnetic resonance imaging (MRI) integration to characterize the relationship between interelectrode spacing and bipolar voltage thresholds and examine the influence of 3-dimensional scar on unipolar voltages.Methods: Thirty-two combined endocardial-epicardial electroanatomic maps were created in 8 postinfarct porcine subjects (bipolar 2-mm, 5-mm, and 8-mm interelectrode spacing and unipolar) for comparison with ex vivo MRI. Two thresholds were compared: (1) 95% normal distribution and (2) best fit to MRI. Direct electrogram analysis was performed in regions across from MRI-defined scar and adjacent to scar border zone.Results: A linear increase in optimal thresholds was observed with wider bipole spacing. The 95% thresholds for scar were lower than MRI-matched thresholds with moderate sensitivity for nontransmural scar (54% endo, 63% epi). Unipolar endocardial scar area exceeded MRI-defined scar, resulting in mismatched false scar in 5 of 8 (63%). Endocardial and epicardial unipolar voltages were lower than normal in regions adjacent and across from scar.Conclusion: Variations in interelectrode spacing necessitate tailored bipolar voltage thresholds to optimize scar detection. Statistical 95% thresholds appear to be conservative and not fully sensitive for the detection of scar defined by high-resolution ex vivo MRI. In the presence of endocardial scar, unipolar mapping to quantitatively characterize epicardial scar may be overly sensitive due to 3-dimensional spatial averaging. [ABSTRACT FROM AUTHOR]