Saudi Cultural Missions Theses & Dissertations
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Item Restricted The utility of computed tomography in evaluating rib fractures in live children investigated for suspected physical abuse(The University of Sheffield, 2024) Alzahrani, Nasser; Offiah, Amaka; Jeanes, AnnmarieRib fractures are strongly associated with physical abuse in infants and young children. Computed tomography (CT) may be an accurate diagnostic tool when compared to chest radiography, the current imaging standard, for detecting rib fractures in children with suspected physical abuse (SPA). A systematic review showed that CT has better diagnostic accuracy than initial chest radiographs (CXR) for detecting rib fractures in children with SPA. A multicentre retrospective observational study was conducted to assess the diagnostic accuracy of chest CT for detecting rib fractures in children under 2 years investigated for SPA, using initial and follow-up CXRs as the reference standard. An analysis of 64 of these cases showed overall accuracy of CT as 83.72%, 93.46% and 96.47%, per-patient, rib and location, respectively. A sub-study of the multicentre study, conducted to assess the feasibility of dating rib fractures using CT, showed substantial agreement between chest radiography and CT in estimating broad timeframes for rib fracture dating (acute vs. healing) (kappa (k)=0.76). Callus formation features on CT scans showed a discriminative pattern for estimating the specific age range of rib fractures. Concerns regarding higher radiation exposure of CT compared to chest radiography have made CT less desirable in routine clinical practice when evaluating children with SPA. A study using post-mortem animal models at two paediatric centres to optimise chest CT scanning parameters gave these sets with the lowest radiation dose and acceptable diagnostic image quality (≥3 out of 5): Centre 1: 80 kV/30 mA, effective dose 0.32 millisieverts (mSv), 93.5% sensitivity; Centre 2: 80 kV/40 mA, effective dose 0.2 mSv, 84.3% sensitivity. Compared to the current clinical standard (initial and follow-up CXRs), chest CT shows high diagnostic accuracy. Furthermore, dating rib fractures from chest CT and optimising its radiation dose seems to be possible.37 0Item Restricted The Role of Non-enhanced CT Characteristics for Differentiating Reversible and Irreversible Brain Tissue Injury and Estimating the Tissue Fate in Acute Ischaemic Stroke(University of Edinburgh, 2024) Alzahrani, Awad; Grant, Mair; Joanna, WardlawTreatment approach for patients with delayed presentation or an unknown time of onset following an ischaemic stroke has largely been based on advanced imaging techniques such as CT perfusion and MRI. However, the universal availability of these techniques is limited. Non-enhanced computed tomography (NECT) is the most widely accessible imaging technique and mainly used to exclude contraindications to treatment, such as haemorrhagic stroke or other conditions mimicking stroke. NECT also provides features on the area of the brain injured by ischaemic stroke. However, there remains uncertainty over what these features actually mean, and if we should use them to decide which patients might benefit, or possibly be harmed, by treatment. In addition, it might be possible to use the baseline NECT scan to determine how much of the brain injured by the ischaemic stroke can be reversible or not, especially when quick treatment decisions are needed, and advanced scans are not available. This thesis aims to better understand how particular features of the NECT scan can be used to distinguish between areas of salvageable tissue at risk (Penumbra), and irreversibly damaged tissue (infarct core) in patients with ischaemic stroke. It also seeks to predict the outcome of brain tissue fate - whether it will develop into infarct or show signs of recovery - within 24-48 hours after the stroke. I summarised the main aspects of stroke, covering techniques for stroke imaging and NECT ischaemic features, and the use of imaging for predicting tissue outcomes. I conducted a systematic review and meta-analysis to determine the diagnostic accuracy of NECT brain scans for 1) differentiating penumbra from infarct core, and 2) detecting any ischaemic brain injury. I used data from Saudi Arabia, King Abdulaziz University Hospital (KAUH) involving consecutive patients with acute ischaemic stroke. These patients underwent NECT and concurrent CT perfusion imaging upon admission. I used these data to visually correlate early ischaemic features observed on NECT with concurrent CTP changes indicating penumbra or core. Additionally, I sought to identify a specific NECT brain attenuation threshold that distinguishes reversible (penumbra) from irreversible (core) ischaemic brain tissue injury, as defined by CTP. Furthermore, I used a subgroup of IST-3 and EuroHype-1 trials patients, which used baseline NECT scans and subsequent 24-48 hours NECT follow-ups. I used these data to assess whether the CT attenuation of ischaemic lesions measured on baseline NECT can predict brain tissue fate at follow-up after stroke, and to develop and validate a novel nomogram model to predict tissue fate in acute ischaemic stroke. In my systematic review and meta-analysis, I included eighteen studies, with a total of 975 participants. Five studies contributed to the assessment of brain swelling and hypoattenuation on NECT to predict different subtypes of ischaemic brain injury, and thirteen studies to the assessment of NECT for detecting any ischaemic brain injury. I found that for predicting penumbra, swelling on NECT had a pooled sensitivity of 35% and specificity of 98%. For predicting infarct core, parenchymal hypoattenuation on NECT had a pooled sensitivity of 68% and specificity of 98%. For detecting any ischaemic brain injury, combined ischaemic features on NECT had a pooled sensitivity of 61% and specificity of 97%. In 142 patients from KAUH, I measured 206 ischaemic lesions (124 penumbra, 82 core). Optimal CT attenuation ratio for identifying penumbra was >0.87, with 86% sensitivity 91% specificity (area under the receiver operating characteristic curve, 0.95. In 122 patients from KAUH, I qualitatively assessed 976 cerebral regions (72 isolated swelling, 254 hypoattenuation). On NECT, isolated swelling usually corresponded to CTP penumbra (70/72, 97%), whereas visible NECT hypoattenuation was found with core (141/254, 56%) and penumbra (109/254, 43%). In 255 patients from IST-3, I demonstrated that CT attenuation measurements at baseline NECT enable the detection of brain tissue fate after acute ischaemic stroke, as defined using 24-48 NECT follow-up imaging. In addition to that, I developed and externally validated a practical nomogram model based on a few readily available variables for all patients to predict brain tissue fate outcomes after acute ischaemic stroke. The suggested nomogram demonstrated excellent discriminative ability, yielding a high C- index of 0.89 in the development cohort comprising 255 patients from IST-3. During external validation, this capability remained robust, resulting in an excellent C-index of 0.91 in the validation cohort consisting of 59 patients from EuroHype-1. Overall, these findings highlight the potential for assessing brain tissue viability after ischaemic stroke using NECT. My work holds promise for empowering frontline clinicians with a deeper comprehension of these methods, potentially enhancing patient selection for stroke treatment, especially where imaging resources are limited though this requires prospective validation. Moreover, further investigation is essential to fully grasp the impact of these methods on the long-term functional outcomes of individuals with ischaemic stroke. Furthermore, these results showed that early parenchymal hypoattenuation lesion in baseline NECT indicating ischaemic injury may not progress and can even be reversible on follow-up. Therefore, a critical reassessment of the conventional concept of core or infarct core on NECT, as applied in clinical practice, appears essential.101 0