Radiation dose optimisation in interventional cardiology.
Creators: name: Badawy, Mohamed
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 320101
subject: Cardiology (incl. cardiovascular diseases)
classificationCode: 510502
subject: Medical physics

description: The focus of this project has been to explore practical applications of radiation dose optimisation in the clinical setting of the cardiac catheterisation laboratory. The relevance of interventional procedures and hence fluoroscopy, to modern cardiology practice, is illustrated, and the clinical significance of radiation dose management outlined. Current radiation dose management techniques, as well as the proposals for further dose optimisation, are detailed in this thesis.<br><br>The first experiment in this project aims to establish an automated method of data collection for the monitoring of radiation dose optimisation techniques. A combination of open source programming languages and database management software has been used to create software that receives information directly from the fluoroscopic systems following patient procedures in the form of Radiation Dose Structured reports. All information about radiation exposure as well as study type, length and patient demographics are collected and stored. A further application of the software is to calculate the patient skin dose to monitor the likelihood of adverse tissue reactions following any high dose procedures. This information is then analysed and disseminated to operators to drive radiation dose optimisation.<br><br>The second experiment in this project assessed the accuracy of the reported radiation dose metrics for different manufacturers collected in the above experiment. Fluoroscopic units used for cardiac catheterisation procedures are tested routinely for compliance. However, under Australian regulations, it is not required to validate certain metrics that impact on patient dose management. This study aimed to assess the accuracy of standard DICOM values used in patient dose calculations through direct measurement. The results indicate that the accuracy of the table height was dependent on the age of the unit, with older units varying by up to 4 cm. The reference air kerma and DAP were all within 10%. The FOV showed the greatest discrepancy from the directly measured value with up to 20% inaccuracy. The results of this experiment show that table height, and FOV should be directly measured and accounted for when calculating patient skin dose. This chapter also presents recommendations regarding the frequency and tolerance of testing.<br><br>The third experiment in this thesis addresses the feasibility of using a novel ‘ultralow’ fluoroscopic pulse rate during routine diagnostic coronary angiograms. Fluoroscopic pulse rate, one of the factors that influence patient dose in a coronary angiogram, is also under control of the operator and can thus be adjusted accordingly. Literature relating to reduction in fluoroscopic pulse rate as a means of radiation dose optimisation shows positive results. However, the resulting loss of diagnostic clarity has been a limiting factor. This study aimed to evaluate the effects of using an ultra low fluoroscopic pulse rate of 3 pulses per second on procedure duration, diagnostic clarity and radiation dose in an analysis of 50 coronary angiograms performed at a large metropolitan centre. The results showed a statistically significant reduction in DAP (58%) with no reduction in diagnostic clarity or increase in procedure length.<br><br>The fourth experiment uses the above results in conjunction with educational talks to practically apply radiation dose optimisation techniques at a large teaching hospital. Dose optimisation is particularly pertinent in teaching hospitals, where longer procedure times may be necessary to accommodate the teaching needs of junior staff, and thus impart a greater dose. The aim of this study is to analyse the effects of varying optimisation protocols in conventional coronary angiograms, from the perspective of a large tertiary centre implementing a rapid dose reduction program. Routine coronary angiograms were chosen to compare baseline levels of radiation, and the dose imparted before and after dose optimisation techniques was measured. Such techniques included lowering dose per pulse, pulse rate, frame rate and encouraging larger field of views and collimation. The results showed up to 54% dose reduction from a lowering of both frame rate and dose per pulse, without any adverse impact on clinical outcomes or teaching of junior staff.<br><br>The fifth experiment focuses on the radiation exposure received by the operators in the cardiac catheterisation laboratory. Established research indicates potential long-term harm from low dose protracted radiation exposure to operators of cardiac angiography, with increasing exposure imparting greater risk. This experiment used a phantom model and thermoluminescent dosimeters to measure radiation dose to operators in a conventional coronary angiogram procedure, specifically looking at radiation dose to target regions of the operator to better examine clinical effects. Correspondingly, the results allow for a deduction of a comprehensive list of factors that allow the conversion from readily available patient dose metrics to operator dose. The study also found that basic monitoring using only a single under apron dosimeter underestimates the radiation dose by up to 68%. Finally, the study provides recommendations to best mitigate the risk of radiation-induced disease through the use of radiation protection tools in high exposure regions of the body.<br><br>The sixth and final experiment in this thesis outlines the production and evaluation of a real-time radiation dose detector for the purpose of educational simulation and furthering understanding of radiation safety, and eventually clinical applications. Current conventional dose measurement methods, while clinically useful, are usually limited to retrospective analysis of dose only. In the cases where a real-time dose can be measured and displayed, the onus to continually assess the radiation dose visually adds cognitive load to the operator. This project examines the creation of a real-time dose detector that can provide visual, audible and tactile feedback to the interventional cardiologist. The aim of such a device is to provide ongoing feedback to the operator which can result in dose savings to the patient in real time via procedural modifications. A prototype was created and tested, with calibration results showing that detector performance was comparable to available products and comfortable to wear for the operator. The vibration module providing tactile feedback can be programmed to either activate during increased dose rates (thus allowing procedural modifications) or following a set dose threshold, serving as a reminder that the procedure is resulting in a high patient and operator radiation exposure.