Quantification of thrombus hounsfield units on noncontrast CT predicts stroke subtype and early recanalization after intravenous recombinant tissue plasminogen activator

Abstract

Background and purpose: Little is known about the factors that determine recanalization after intravenous thrombolysis. We assessed the value of thrombus Hounsfield unit quantification as a predictive marker of stroke subtype and MCA recanalization after intravenous rtPA treatment.

Materials and methods: NCCT scans and CTA were performed on patients with MCA acute stroke within 4.5 hours of symptom onset. Demographics, stroke severity, vessel hyperattenuation, occlusion site, thrombus length, and time to thrombolysis were recorded. Stroke origin was categorized as LAA, cardioembolic, or indeterminate according to TOAST criteria. Two blinded neuroradiologists calculated the Hounsfield unit values for the thrombus and contralateral MCA segment. We used ROC curves to determine the rHU cutoff point to discriminate patients with successful recanalization from those without. We assessed the accuracy (sensitivity, specificity, and positive and negative predictive values) of rHU in the prediction of recanalization.

Results: Of 87 consecutive patients, 45 received intravenous rtPA and only 15 (33.3%) patients had acute recanalization. rHU values and stroke mechanism were the highest predictive factors of recanalization. The Matthews correlation coefficient was highest for rHU (0.901). The sensitivity, specificity, and positive and negative predictive values for lack of recanalization after intravenous rtPA for rHU ≤ 1.382 were 100%, 86.67%, 93.75%, and 100%, respectively. LAA thrombi had lower rHU than cardioembolic and indeterminate stroke thrombi (P = .004).

Conclusions: The Hounsfield unit thrombus measurement ratio can predict recanalization with intravenous rtPA and may have clinical utility for endovascular treatment decision making.

Fig 1.

A 78-year-old woman with severe right-sided hemiparesis and aphasia 70 minutes after symptom onset. NCCT demonstrates left HMCAS involving the proximal segment (M1) of the MCA. The rHU of the thrombus was 1.14 (ROI values at bottom row on magnified zoom ×3). Intravenous rtPA failed to achieve recanalization.

Fig 2.

A 64-year-old man with aphasia 180 minutes after symptom onset. NCCT demonstrates a hyperattenuated thrombus in the left M2 segment, corroborated on CTA axial MIP (arrow). The rHU of the thrombus was 1.48. Treatment succeeded, and the vascular hyperattenuation disappeared (bottom row).

Fig 3.

ROC curve for Hounsfield unit ratios in the prediction of vascular recanalization. The area under the ROC curve is equal to 0.96.

Fig 4.

Distribution of thrombi according to the effectiveness of intravenous rtPA and stroke etiology. The cutoff value is set at 1.382 to cover all thrombi that failed to recanalize after intravenous rtPA (top). Values above this cutoff point can reliably discriminate thrombi from LAA (above). CE indicates cardioembolic.