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Optimising Radiation Dose of CT Pulmonary Angiogram for Imaging Pulmonary Embolism and Alternative Acute Respiratory Diseases

Date

2021

Authors

Hashi, Ahmed

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Abstract

Abstract CT pulmonary angiogram (CTPA) is utilised to diagnose pulmonary embolus in various clinical settings. CT imaging has considerable advantages over other imaging modalities. Whilst considering its widespread application and advantages, it tends to have high radiation exposure. Additionally, there are high rates of suboptimal and non-diagnostic examinations that result in unnecessary radiation dose. Therefore appropriate radiation dose reduction techniques are required without compromising imaging quality; unfortunately, efforts to reduce radiation dose can also diminish image quality and lead to missed pulmonary emboli and other lung pathologies. Several studies have investigated 80kV CTPA protocols and found a considerable upsurge in image noise and reduced imaging quality. The purpose of this research project was to develop an 80kV CTPA protocol with reduced imaging noise, decreased radiation dose and simultaneously reducing suboptimal examinations in patients with suspected pulmonary embolism. Both qualitative and quantitative approaches were conducted to achieve this purpose. This study has demonstrated that the new 80kV CTPA protocol can significantly (t (60) = -17.8, p < 0.05) reduce patient mean effective radiation dose by 66% with a mean radiation dose 1.005mSv compared to 3.03mSv with current 100kV protocols. The study has also demonstrated a reduced rate of suboptimal examinations and a significant increase (t (75) =9.1, p<0.05) in contrast enhancement of the pulmonary arterial tree at the 80kV exposures. It has also been found that a gentle breath-hold open mouth technique with an 80kV scanning protocol also improves imaging quality. In terms of imaging quality assessment, the improved 80kV CTPA yielded acceptable image quality comparable to the standard protocol as per the radiologist assessment. This study's original contribution to knowledge is introducing a new, improved 80kV CTPA that allows the imaging departments to achieve an excellent contrast enhancement and lower suboptimal examinations. This study's overall significance is a demonstrable reduction in radiation dose without affecting the CTPA image quality in the majority of the patients.

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Thesis (PhD)

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DOI

10.25911/F9R2-CN74

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