Keywords:
Dosimetry, Thrombolysis, Decision analysis, CT-High Resolution, CT-Angiography, CT, Radioprotection / Radiation dose, Neuroradiology brain, Interventional vascular, Acute, Obstruction / Occlusion, Ischaemia / Infarction
Authors:
N. J. Darcy1, S. Rienecker2, J. Blazak1; 1QLD/AU, 2Sunshine Coast/AU
DOI:
10.26044/ranzcr2019/R-0015
Conclusion
This audit revealed that stroke is common in patients selected by our stroke service for a CT based stroke protocol. A large portion of patients shown to have a stroke were suitable for either thrombolysis or ECR, both of which have good evidence for improving function outcomes with imaging guided decision making (1-9).
The dose related risk associated with these scans is low, even in younger females, as the brain is particularly radio-resistant.
When comparing the radiation risk to the potential benefit of reperfusion therapy, the benefit greatly outweighs any potential risk (Figure 2). The LAR does not come close to the potential benefit of thrombolysis in isolation, which is amplified when consideration is given to clot retrieval. The potential benefit to younger patients is compounded by the remaining years of life that would potentially be encumbered if not functionally independent.
There are several limitations to the data, particularly the time of onset was not recorded, therefore it is difficult to determine if these patient fell within the time frame of the referenced studies. However, the movement in the literature has been towards personalised image based criteria for determining suitability for reperfusion, as patient’s individual collateral blood supply has been shown to play an increasingly important role in determining those who will benefit from these treatments (16). This is in contrast to the antiquated rigid time criteria applied to all patients. It has also been shown that time of onset is difficult to estimate, particularly in wake up strokes (17, 18). The study does not take into consideration other more obvious contraindications to the above treatments, such a poor functional status, NIHSS, anti-coagulation status and significant hypertension, as this information was often not recorded. It was generally presumed that patients undergoing CTP imaging would be eligible for reperfusion, should the imaging appear favourable.
This study also used MIStar as opposed to RAPID for perfusion calculations. Both software packages use the same criteria for core estimation (CBV<30% of the contralateral side), however a slightly different metric for penumbra. Despite this, both criteria are comparable (9). Notwithstanding these limitations, this audit underscores the safety of CT based stroke imaging, even in young patients, along with the significant benefits of reperfusion therapy when guided by advance CT perfusion imaging.