Interrater Agreement and Detection Accuracy for Medium-Vessel Occlusions Using Single-Phase and Multiphase CT Angiography

Abstract

BACKGROUND AND PURPOSE: Accurate and reliable detection of medium-vessel occlusions is important to establish the diagnosis of acute ischemic stroke and initiate appropriate treatment with intravenous thrombolysis or endovascular thrombectomy. However, medium-vessel occlusions are often challenging to detect, especially for unexperienced readers. We aimed to evaluate the accuracy and interrater agreement of the detection of medium-vessel occlusions using single-phase and multiphase CTA.MATERIALS AND METHODS: Single-phase and multiphase CTA of 120 patients with acute ischemic stroke (20 with no occlusion, 44 with large-vessel occlusion, and 56 with medium-vessel occlusion in the anterior and posterior circulation) were assessed by 3 readers with varying levels of experience (session 1: single-phase CTA; session 2: multiphase CTA). Interrater agreement for occlusion type (large-vessel occlusion versus medium-vessel occlusion versus no occlusion) and for detailed occlusion sites was calculated using the Fleiss k with 95% confidence intervals. Accuracy for the detection of medium-vessel occlusions was calculated for each reader using classification tables. RESULTS:Interrater agreement for occlusion type was moderate for single-phase CTA (k ¼ 0.58; 95% CI, 0.56-0.62) and almost perfect for multiphase CTA (k ¼ 0.81; 95% CI, 0.78-0.83). Interrater agreement for detailed occlusion sites was moderate for singlephase CTA (k ¼ 0.55; 95% CI, 0.53-0.56) and substantial for multiphase CTA (k ¼ 0.71; 95% CI, 0.67-0.74). On single-phase CTA, readers 1, 2, and 3 classified 33/56 (59%), 34/56 (61%), and 32/56 (57%) correctly as medium-vessel occlusions. On multiphase CTA, 48/56 (86%), 50/56 (89%), and 50/56 (89%) medium-vessel occlusions were classified correctly. CONCLUSIONS:Interrater agreement for medium-vessel occlusions is moderate when using single-phase CTA and almost perfect with multiphase CTA. Detection accuracy is substantially higher with multiphase CTA compared with single-phase CTA, suggesting that multiphase CTA might be a valuable tool for assessment of medium-vessel occlusion stroke.ABBREVIATIONS: EVT ¼ endovascular treatment; LVO ¼ large-vessel occlusion; mCTA ¼ multiphase CTA; MeVO ¼ medium-vessel occlusion M edium-vessel occlusions (MeVOs) are defined as occlusions of the M2 and M3/4 segments of the MCA, A2 and A3/4 segments of the anterior cerebral artery, and P2 and P3/4 segments of the posterior cerebral artery. 1 MeVOs account for approximately 25%-40% of all acute ischemic strokes, and although they have traditionally been thought to cause only minor symptoms, MeVO strokes frequently result in disabling deficits. 2,3 This outcome has led to a paradigm shift in treatment: An increasing number of physicians now routinely offers endovascular treatment (EVT) as a stand-alone therapy instead of or in addition to intravenous thrombolysis for MeVO stroke. 4-6 Furthermore, 2 randomized trials, ESCAPE-MeVO and DISTAL, are being planned to generate level 1A evidence for EVT in MeVO stroke (personal communication: Ma...

Diagnostic accuracy of CT angiography and CT perfusion imaging for detecting distal medium vessel occlusions: Protocol for a systematic review and meta-analysis

“…We will include a subgroup analysis according to the technique used in CTA (single phase or multiphase) as different accuracy values have been suggested between both algorithms [ 15 , 16 ].…”

Recent developments in pre-hospital and in-hospital triage for endovascular stroke treatment

“…Multi-phase CTA has some benefits over conventional single-phase CTA, as it improves occlusion detection, particularly for MeVOs, which are increasingly treated with EVT, and allows for a more accurate evaluation of collateral blood supply in the ischemic territory. [50][51][52] Although for late time window patients (6-24 hours from last known well), current guidelines recommend using perfusion imaging for EVT patient selection; the increased accuracy of penumbra and core estimation with advanced imaging should be balanced against the additional time lost and the risk of 'decision paralysis' due to unnecessary and potentially confusing or even misleading information. More recent data from a British national registry study 53 and the CLEAR study suggest that simpler imaging paradigms using non-contrast CT (NCCT) and singleor multiphase CTA may be equally capable of selecting patients for late time window EVT [54][55][56][57] compared with CT perfusion.…”

“…CTA allows for visualization of an EVT target occlusion (LVO or MeVO) and visualizes the cervical vasculature and aortic arch, which allows for appropriate choice of EVT devices. Multi-phase CTA has some benefits over conventional single-phase CTA, as it improves occlusion detection, particularly for MeVOs, which are increasingly treated with EVT, and allows for a more accurate evaluation of collateral blood supply in the ischemic territory 50–52…”

Angiographic Systems for Classifying Distal Arterial Occlusions

“…Interrater agreement for detailed occlusion sites was moderate for single-phase CTA ( k = 0.55; 95% CI: 0.53–0.56) and substantial for multiphase CTA ( k = 0.71; 95% CI: 0.67–0.74). Diagnostic accuracy of MVO also improved with the multiphase CTA (86–89%) as compared to the single-phase CTA (57–61%) [30]. The diagnostic accuracy for detection of DAO with CT perfusion is significantly higher compared to that of CTA alone [31].…”