| 總結: | X-ray guided interventional procedure is a common diagnostic and/or treatment
modality for various vascular and cardiac diseases. Advanced technology has enabled
interventional radiologists in performing more complex neuro-radiology procedures,
resulting in concomitant increase in radiation dose to the patients.
The main contributions of this thesis were firstly, characterisation of the MOSkin
detector in kilovoltage photon beams and testing its suitability for in-vivo patient’s dose
measurements during interventional radiology procedures. Secondly, a comprehensive
evaluation of the exposure parameters contributions on patient’s dose during neurointerventional
procedures was performed. It was found that the lateral x-ray tube
contributed considerably high radiation dose to patient’s eye lens. This led to the design
and fabrication of a novel type of eye lens protector for those procedures that patient’s
eye is repeatedly positioned within the lateral tube exposure field, where the applying of
collimation on lateral beam is not possible. The eye lens protector was designed to be
placed within the x-ray field of view, attenuating the direct beam from the lateral x-ray
tube while being sufficiently radiolucent not to perturb the radiological image and the
interventional procedure.
Finally, a new type of an anthropomorphic head phantom was fabricated with more
options for dosimeter placement and more similar tissue substitute materials to actual
human eye, in order to evaluate the dose delivered to the patient’s eye lens during a
clinical neuro-interventional procedure.
The MOSkin detector has been proven to be a reliable and suitable dosimetry system
for the measurement of the radiation dose in kilovoltage photon beams and has been
successfully utilised during 35 clinical neuro-interventional procedures to evaluate the
radiation dose received by the patients’ eye lenses. This study revealed that among the
35 patients, the left outer canthus regions of 8 patients and left eyelid region of one
iv
patient were found to receive higher dose than the recommended threshold dose for
cataract formation (500 mGy).
Based on the study of the contribution of exposure parameters on patient’s dose, it is
recommended that the judicial use of acquisition imaging techniques and the use of the
lateral x-ray tube particularly in the anterior-oblique orientation, in order to reduce the
patient’s eye lens dose during neuro-interventional procedures. In the situation where
the application of physical collimation on lateral tube beam is not possible, the novel
eye protector layer may be used to attenuate the direct radiation beam to the patient’s
eye lens.
This work showed that for a simulated aneurysm procedure this protector reduced the
maximum radiation dose received by the eye lens and eyelid up to 62.1% and 23.3%,
respectively. The eye protector also had negligible effects on the exposure parameters
(by a maximum of 8% for the tube current-time product of the DSA (2 frame per
second) imaging mode) and image quality (increases the fluoroscopy image pixel value
up to 4.7% ± 0.6%). Lastly, the fabricated anthropomorphic phantom has been proved
to be a suitable tissue-mimicking medium for the evaluation of the radiation dose
received by the patient’s eye lens during clinical diagnostic procedures.
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