Background: Multi-tracer PET/SPECT imaging enables different modality tracers to be present simultaneously, allowing multiple physiological processes to be imaged in the same subject, within a short time-frame. Fluorine-18 and technetium-99m, two commonly used PET and SPECT radionuclides, respectively, possess different emission profiles, offering the potential for imaging one in the presence of the other. However, the impact of the presence of each radionuclide on scanning the other could be significant and lead to confounding results. Here we use combinations of 18 F and 99m Tc to explore the challenges posed by dual tracer PET/SPECT imaging, and investigate potential practical ways to overcome them. Methods:Mixed-radionuclide 18 F/ 99m Tc phantom PET and SPECT imaging experiments were carried out to determine the crossover effects of each radionuclide on the scans using Mediso nanoScan PET/CT and SPECT/CT small animal scanners.Results: PET scan image quality and quantification were adversely affected by 99m Tc activities higher than 100 MBq due to a high singles rate increasing dead-time of the detectors. Below 100 MBq 99m Tc, PET scanner quantification accuracy was preserved. SPECT scan image quality and quantification were adversely affected by the presence of 18 F due to Compton scattering of 511 keV photons leading to over-estimation of 99m Tc activity and increased noise. However, 99m Tc: 18 F activity ratios of > 70:1 were found to mitigate this effect completely on the SPECT. A method for correcting for Compton scatter was also explored. Conclusion:Suitable combinations of injection sequence and imaging sequence can be devised to meet specific experimental multi-tracer imaging needs, with only minor or insignificant effects of each radionuclide on the scan of the other.
Background: The timely diagnosis of burns depth is crucial to avoid unnecessary surgery and delays in adequate management of patients with burn injuries. Whilst it is mostly a clinical diagnosis, indocyanine green, laser Doppler imaging and infrared thermography have been used alongside clinical findings to support the diagnosis. Infrared thermography is a noninvasive technique which uses temperature differences to diagnose tissue burn depth. Our study aims to assess its use in differentiating between superficial and deep burns. Methods: We conducted a systematic literature review and meta-analysis using electronic databases. We used a mixed-effects logistic regression bivariate model to estimate summary sensitivity and specificity and developed hierarchical summary receiver operating characteristic (HSROC) curves. Results: We identified 6 studies reporting a total of 197 burns, of which 92 were proven to be deep burns. The reference standard was clinical assessment at the time of injury and burn healing time. The pooled estimates for sensitivity and specificity were 0.84 (95%CI 0.71–0.92) and 0.76 (95%CI 0.56–0.89), respectively. Conclusions: IRT is a promising burns assessment modality which may allow surgeons to correctly classify burn injuries at the time of presentation. This will allow a more efficient management of burns and timely surgical intervention.
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