Arterial spin labeling demonstrates early recanalization after stroke

CT imaging selection in acute stroke

Acute stroke has become an increasingly treatable cause of acute neurological deficits. Indeed, over the last two decades, the introduction of first thrombolysis, and now thrombectomy has improved patient outcomes and extended the therapeutic window. Computed tomography has been established as the most simple and readily available technique for the diagnosis and management of patients with acute stroke. Indeed, CT allows easy confirmation or exclusion of acute hemorrhage on the one hand, and on the other hand the early signs are quite reliable in the detection of ischemia. In the early phase the clot can be seen as well as exchanges related to early changes in water concentration in ischemia and the surrounding penumbra. Additional techniques such as angio-CT show the location of the clot and perfusion techniques reveal local hemodynamics as well as potential tissue viability. Newer techniques such as double energy CT and late phase CT should provide information on collateral flow as well as on the presence of early hemorrhagic transformation. All these techniques should thus make available new information on tissue viability,that is indispensable in the choice of revascularization technique. Thus CT techniques allow a quick and reliable triage as well as a finer characterization of the ischemic process. The use of all these CT techniques in an optimal way should help improve patient triage and selection of the most adequate treatment with further improvements in clinical outcomes as a result.

Diagnostic neuroradiology: Ready for the neuro-interventional age?

Acute cerebral ischemia or stroke is currently considered an emergency for which therapeutic options are available if the therapeutic window of 4.5 h is respected. Imaging modalities have progressed greatly over the last few decades, rendering ischemia detectable in the first hours after the event. However, in order for treatment to be efficacious it is necessary to speed up all the processes before the start of therapy. Thus, one must decrease the time to arrival at the hospital and to the radiological method that is to be employed (be it computed tomography or magnetic resonance imaging); only then will the medical or interventional techniques available fulfill their potential.

Comparison of arterial spin labeling and bolus perfusion-weighted imaging for detecting mismatch in acute stroke

BACKGROUND AND PURPOSE

The perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch paradigm is widely used in stroke imaging studies. Arterial spin labeling (ASL) is an alternative perfusion method that does not require contrast. This study compares the agreement of ASL-DWI and PWI-DWI mismatch classification in patients with stroke.

METHODS

This was a retrospective study drawn from all 1.5-T MRI studies performed in 2010 at a single institution. Inclusion criteria were: symptom onset<5 days, DWI lesion>10 mL, and acquisition of both PWI and ASL. DWI and PWI time to maximum>6 seconds lesion volumes were determined using automated software. Patients were classified into reperfused, matched, or mismatch groups. Two radiologists classified ASL-DWI qualitatively into the same categories blinded to DWI-PWI. Agreement between both individual readers and methods was assessed.

RESULTS

Fifty-one studies met the inclusion criteria. Seven cases were excluded (1 due to PWI susceptibility artifact, 2 due to motion, and 4 due to severe ASL border zone sign), resulting in 44 studies for comparison. Interrater agreement for ASL-DWI mismatch status was high (κ=0.92; 95% CI, 0.80-1.00). ASL-DWI and PWI-DWI mismatch categories agreed in 25 of 44 cases (57%). In the 16 of 19 discrepant cases (84%), ASL overestimated the PWI lesion size. In 34 of 44 cases (77%), they agreed regarding the presence of mismatch versus no mismatch.

CONCLUSIONS

Mismatch classification based on ASL and PWI agrees frequently but not perfectly. ASL tends to overestimate the PWI time to maximum lesion volume. Improved ASL methodologies and/or higher field strength are necessary before ASL can be recommended for routine use in acute stroke.