RESUMO
BACKGROUND: Internationally, the typical allowed difference between the measured radiation dose and dose reported by a computed tomography (CT) scanner is ±20 %. The objective is to describe a method in order to analyse this difference in a CT scanner in the Emergency Department of Kanta-Häme Central Hospital, and to calculate a correction factor for more comparable radiation dose values in further studies. METHODS: Ten intra-day radiation dose measurements were performed with undisturbed setting. Measurement reports on differences between measured and displayed dose were gathered from the vendor maintenance and supervising authority over a 12-year period. Additionally, two in-house measurements were made. A total of 18 datapoints were collected, with some differences in measurement settings. Data were also analysed against imaging parameters, ambient air pressure and time to identify trends or associations in the variation of the discrepancy. RESULTS: Measured doses were generally lower than displayed doses. Differences between displayed and measured doses varied between -3.46 and -0.10 %, with a mean of -1.26 % in the intra-day measurements, and between +4.65 and -17.3 %, with a mean of -7.53 % in the long-term data. There were no trends nor connections in the variations. CONCLUSION: Since the acceptable difference between the radiation dose display and the measured dose is relevant, the average difference for every CT scanner should be determined before radiation dose studies, especially when comparing multiple scanners.
RESUMO
At present, it is not possible to reliably identify patients who will benefit from oncolytic virus treatments. Conventional modalities such as computed tomography (CT), which measure tumor size, are unreliable owing to inflammation-induced tumor swelling. We hypothesized that magnetic resonance imaging (MRI) and spectroscopy (MRS) might be useful in this regard. However, little previous data exist and neither oncolytic adenovirus nor immunocompetent models have been assessed by MRS. Here, we provide evidence that in T2-weighted MRI a hypointense core area, consistent with coagulative necrosis, develops in immunocompetent Syrian hamster carcinomas that respond to oncolytic adenovirus treatment. The same phenomenon was observed in a neuroblastoma patient while he responded to the treatment. With relapse at a later stage, however, the tumor of this patient became moderately hyperintense. We found that MRS of taurine, choline and unsaturated fatty acids can be useful early indicators of response and provide detailed information about tumor growth and degeneration. In hamsters, calprotectin-positive inflammatory cells (heterophils and macrophages) were found in abundance; particularly surrounding necrotic areas in carcinomas and T cells were significantly increased in sarcomas, when these had been treated with a granulocyte-macrophage colony-stimulating factor-producing virus, suggesting a possible link between oncolysis, necrosis (seen as a hypointense core in MRI) and/or immune response. Our study indicates that both MRI and MRS could be useful in the estimation of oncolytic adenovirus efficacy at early time points after treatment.