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
Methods and materials
This was a five-month audit, including all patients who underwent a complete stroke protocol over the period between the 3rd November 2018 and the 3rd April 2019. A complete stroke protocol was defined as a Non-Contrast CT Brain (NCCTB), CT Carotid Angiogram (CTCA) and a CT Neuroperfusion (CTP) scan.
Dose data was recorded for all patients, including DLP and CTDIvol. The average dose was calculated across all patients for all three scans. The average effective dose was calculated (mSv) using the DLP and CT Expo simulation methodology (14). The average effective dose of the complete protocol was calculated. The effective dose was converted to a Lifetime Attributable Cancer Risk (LAR) using the BEIR VII modeling (15) and decade of patient age.
The CTP, NCCTB and CTCA data was used exclusively to determine eligibility for thrombolysis and ECR. CTP data was calculated using MIStar software and the final radiology report was used to verify the result was not artifactual. The interpretation of the NCCTB and CTCA was based on the finalised radiology report. Based on the above parameters patients were determined to be eligible for thrombolysis or clot retrieval. The criteria for reperfusion was based on the recently published EXTEND (1) (Thrombolysis) and DEFUSE-3 (3) (ECR) trials. Thrombolysis criteria was defined as a mismatch ratio greater than 1.2 between the volume of hypoperfusion and the volume of the ischemic core, an absolute difference in volume greater than 10 ml, an ischemic-core volume of less than 70 ml and a perfusion lesion with a minimum volume of 20 ml. ECR criteria was defined as a proximal middle-cerebral-artery (M1) or internal-carotid-artery occlusion (ICA), an ischemic-core volume of less than 70 ml, mismatch ratio greater than 1.8 between the volume of hypoperfusion and the volume of the ischemic core, and a perfusion lesion with a minimum volume of 15 ml.
The number of definitive strokes were recorded, with the diagnosis of stroke being made on initial imaging report if consistent with clinic syndrome and stroke team assessment, or on follow up CT or MRI.
Benefit was defined by the number of patients that were eligible for the two major reperfusion techniques (prevalence) and the absolute increase in functional independence (mRs 0-2) of the modality at 90 days as quoted in EXTEND and DEFUSE-3 trials (% prevalence x % absolute benefit of treatment = total benefit to imaged population). The sum of these two values was used to determine cumulative benefit to the population that was imaged.