Detection of Early CT Signs of >1/3 Middle Cerebral Artery Infarctions

Abstract

Background and Purpose —This study had 2 goals: (1) to assess interrater reliability of academic neuroradiologists when classifying acute infarction by CT scan as >1/3 middle cerebral artery (MCA) involvement, <1/3 MCA involvement, or no infarction and (2) to determine the sensitivity of physicians potentially involved in acute stroke treatment in detecting >1/3 MCA acute infarctions. Studies of tissue plasminogen activator show an association between early signs of major infarction and poor outcome. The American Academy of Neurology and the American Heart Association recommend avoiding thrombolysis if early signs of major infarction are present. Methods —We presented 25 scans (normals, acute infarctions, and old infarctions) to 3 academic neuroradiologists. A scoring sheet based on Alteplase Thrombolysis for Acute Noninterventional Therapy in Ischemic Stroke (ATLANTIS)/CT Summit criteria was used to determine >1/3 MCA territory involvement. Nine of the 25 scans were presented again to assess intrarater reliability. We recalculated results of our previous study in which physicians interpreted infarction scans, now designating the scans as >1/3 MCA, <1/3 MCA, or normal, as determined by the neuroradiologists. Results —All 3 neuroradiologists agreed on no infarction, <1/3 MCA, and >1/3 MCA on 64% of the scans. Neuroradiologist test-retest agreement was 96% for >1/3 MCA territory. Overall sensitivity for emergency physicians, neurologists, and general radiologists for detecting the presence of infarction in scans rated as >1/3 MCA was 78%. Conclusions —Neuroradiologists can achieve moderate agreement in detecting >1/3 MCA infarction. The emergency physicians, neurologists, and general radiologists tested were reasonably skilled at detecting >1/3 MCA acute infarction. However, their performance did not reliably identify all patients who have early CT infarct signs that place them at increased risk for cerebral hemorrhage after thrombolytic therapy.

CT for Acute Ischaemic Stroke

“…However, the trial suffered from a high number of 'protocol violators' -52 of 620 patients randomised had CT abnormalities that should have resulted in exclusion from the trial. Defi ning what constituted 1/3 or more of the MCA territory proved to be diffi cult, as it has in many other studies (Wardlaw et al 1999;Kalafut et al 2000;Grotta et al 1999). In fact, there is no defi nition.…”

“…However, at present, clinicians must assess their own scans (particularly at unsociable hours), and may need to base treatment decisions on the CT scan. Unfortunately, the reliability amongst general radiologists, stroke clinicians and emergency physicians so far for detecting early signs of infarction is poor, barely better than would be achieved by chance alone (Wardlaw et al 1999;Kalafut et al 2000;Barber et al 2000;Grotta et al 1999). …”

“…Even amongst neuroradiologists with an interest in stroke, agreement of early signs is moderate at best (Marks et al 1999;Kalafut et al 2000). There are not -and will probably never be -enough neuroradiologists to provide timely reports to clinicians (Brillman et al 1997) (although in the future, use of image link technology may allow Parenchymal hypodensity Hypodensity in < 50%, 50-90%, > 90% of the middle cerebral artery territory Hypodensity in < 33%, > 33% of the middle cerebral artery territory Early infarct oedema (does this mean swelling or low density?)…”

Computer-Aided Diagnosis for Acute Stroke in CT Images

“…Patients showing large ischemic lesions (parenchymal hypoattenuation or brain swelling) on CT images have a high risk of fatal hemorrhagic complications after thrombolytic therapy (Kummer et al, 1997;Barber et al, 2000;Kalafut et al, 2000). Therefore, quantification of the extent of areas of ischemic lesions appeared on CT images is mandatory to avoid the risk.…”

What is the best imaging strategy for acute stroke?

“…The six studies (948 scans) that documented observer agreement as either proportions in agreement or percentage accuracy, tended to mirror more closely real clinical situations 223,[286][287][288][289][290] ( interpretation of scans by emergency physicians noted 87-98% accuracy for all pathological lesions. 286,287 Accuracy fell to 67% when emergency physicians were asked to identify lesions pertinent to the interpretation of ischaemia and haemorrhage only.…”