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Yes / Objectives: This study aimed to determine the impact on radiation dose and image quality of a new cardiac interventional X-ray system for trans-catheter aortic valve implantation (TAVI) patients compared to the previously-used cardiac X-ray system. Methods: Patient dose and image data were retrospectively collected from a Philips AlluraClarity (new) and Siemens Axion Artis (reference) X-ray system. Patient dose area product (DAP) and fluoroscopy duration of 41 patient cases from each X-ray system were compared using a Wilcoxon test. Ten patient aortograms from each X-ray system were scored by 32 observers on a continuous scale to assess the clinical image quality at the given phase of the TAVI procedure. Scores were dichotomised by acceptability and analysed using a Chi-squared test. Results: Significant reductions in patient dose (p<<0.001) were found for the new system with no significant change in fluoroscopy duration (p=0.052); procedure DAP reduced by 55%, fluoroscopy DAP by 48% and “cine” acquisition DAP by 61%. There was no significant difference between image quality scores of the two X-ray systems (p=0.06). Conclusions: The new cardiac X-ray system demonstrated a very significant reduction in patient dose with no loss of clinical image quality. Advances in Knowledge: The huge growth of TAVI may impact on the radiation exposure of cardiac patients and particularly on operators including anaesthetists; cumulative exposure of interventional cardiologists performing high volume TAVI over 30-40 years may be harmful. The Phillips Clarity upgrade including improved image enhancement and optimised X-ray settings significantly reduced radiation without reducing clinically acceptable image quality.

Yes / This work presents a methodology to optimize the selection of multiple parameter levels of an image acquisition, degradation, or post-processing process applied to stimuli intended to be used in a subjective image or video quality assessment (QA) study. It is known that processing parameters (e.g. compression bit-rate) or techni- cal quality measures (e.g. peak signal-to-noise ratio, PSNR) are often non-linearly related to human quality judgment, and the model of either relationship may not be known in advance. Using these approaches to select parameter levels may lead to an inaccurate estimate of the relationship between the parameter and subjective quality judgments – the system’s quality model. To overcome this, we propose a method for modeling the rela- tionship between parameter levels and perceived quality distances using a paired comparison parameter selection procedure in which subjects judge the perceived similarity in quality. Our goal is to enable the selection of evenly sampled parameter levels within the considered quality range for use in a subjective QA study. This approach is tested on two applications: (1) selection of compression levels for laparoscopic surgery video QA study, and (2) selection of dose levels for an interventional X-ray QA study. Subjective scores, obtained from the follow-up single stimulus QA experiments conducted with expert subjects who evaluated the selected bit-rates and dose levels, were roughly equidistant in the perceptual quality space - as intended. These results suggest that a similarity judgment task can help select parameter values corresponding to desired subjective quality levels. / Parts of this work were performed within the Telesurgery project (co-funded by iMinds, a digital research institute founded by the Flemish Government; project partners are Unilabs Teleradiology, SDNsquare and Barco, with project support from IWT) and the PANORAMA project (co-funded by grants from Belgium, Italy, France, the Netherlands, the United Kingdom, and the ENIAC Joint Undertaking).

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During catheterized x-ray interventions the patient and medical staff is exposed to scatter radiation, as a consequence of tissue interactions. Ionizing radiation for medical purpose is potentially dangerous and can cause malignancy, skin damage and more. Studies have suggested an increase in the prevalence of eye lens cataract, thyroid cancer and left sided brain tumors in doctors. Therefore, it is mandatory to reduce the radiation dose in medicine, a principle known as ALARA (as low as Reasonably Achievable). Lead aprons, collars and shieldings are safety precautions to protect the team in the operating room. The x-ray equipment and surgical techniques are constantly evolving and the interventions become more complex which may increase the x-ray dose. Although x-ray imaging is required in interventional procedures endeavors of reducing radiation exposure to staff is of high interest. There is a need to increase the awareness about scatter radiation and radiation protection efforts are gaining momentum. Initiative to train a dose reducing behavior by education and awareness are key documents within the European Union’s guidelines on Radiation protection. The aims of this thesis were to create a 3D model for representation of real-time exposure and accumulated scatter radiation to staff performing interventional x-ray procedures and identify parameters that affect the scatter radiation. Extensive measurements were made with real time dosimeters while irradiating an anthropomorphic phantom. For five lateral C-arm projections, 68 - 80 data points each were used to measure scatter dose distribution around the patient. In the typical operator position, the effect of craniocaudal projection angle, patient size, field size, image detector height and pulse rate on scatter radiation dose was also investigated. It was possible to create a 3D model from interpolated measurement data that can generate dose rate with promising results. Six out of eight modelled doses deviated +/- 26.6 % from the validation cases. A model that delivers relative dose is an intuitive approach in education for interventional x-ray radiation safety. The staff position in relation to the x-ray source and the patient size have a significant correlation to the dose rate. Additional measurements are needed to ensure the reliability of the model. This work completes the effect of scatter radiation distribution around the patient table, which is not yet evaluated as thoroughly by other authors.