Which imaging before reperfusion strategy?

Safety of the effective radiation dose received during stroke hospitalization

Background

Neuroimaging is widely used for diagnosis and treatment of stroke. However, little is known about whether the radiation doses received by patients comply with international safety guidelines.

Objectives

The aim of this study was to evaluate the effective radiation dose received while in hospital for stroke and analyze its safety according to current guidelines.

Methods

This cross-sectional study included 109 patients who were hospitalized and diagnosed with ischemic stroke. The National Institutes of Health Stroke Scale was used to evaluate stroke severity, the Bamford clinical classification was used for topography, and the TOAST classification was used for etiology. The computed tomography dose index and size-specific dose estimates were used to calculate the effective radiation dose (ERD) received while in hospital. A Mann-Whitney test was used to compare the ERD received by thrombolysed and non-thrombolysed patients. Non-parametric statistics were used to analyze the data with a 95% confidence interval.

Results

During the study period, the median ERD received was 10.9 mSv. Length of stay was not associated with radiation exposure. No differences were demonstrated in ERD according to stroke etiology or Bamford clinical classification. Patients who had CT perfusion (only or in addition to CT or angiotomography) received the highest ERD (46.5 mSv) and the difference compared to those who did not (10.8 mSv) was statistically significant (p<0.001). No differences were found in the ERD between thrombolysed and non-thrombolysed patients. There was no correlation between ERD while in hospital and stroke severity.

Conclusions

According to the current national guidelines, the protocol for examining images at our stroke unit is safe in terms of the ERD received by the patient while in hospital. There was no difference in the ERD received by patients stratified by thrombolytic treatment or stroke severity.

Relationships between brain perfusion and early recanalization after intravenous thrombolysis for acute stroke with large vessel occlusion

In large vessel occlusion (LVO) stroke, it is unclear whether severity of ischemia is involved in early post-thrombolysis recanalization over and above thrombus site and length. Here we assessed the relationships between perfusion parameters and early recanalization following intravenous thrombolysis administration in LVO patients. From a multicenter registry, we identified 218 thrombolysed LVO patients referred for thrombectomy with both (i) pre-thrombolysis MRI, including diffusion-weighted imaging (DWI), T2*-imaging, MR-angiography and dynamic susceptibility-contrast perfusion-weighted imaging (PWI); and (ii) evaluation of recanalization on first angiographic run or non-invasive imaging ≤ 3 h from thrombolysis start. Infarct core volume on DWI, PWI-DWI mismatch volume and hypoperfusion intensity ratio (HIR; defined as Tmax ≥ 10 s volume/ Tmax ≥ 6 s volume, low HIR indicating milder hypoperfusion) were determined using a commercially available software. Early recanalization occurred in 34 (16%) patients, and multivariable analysis was associated with lower HIR (P = 0.006), shorter thrombus on T2*-imaging (P < 0.001) and more distal occlusion (P = 0.006). However, the relationship between HIR and early recanalization was robust only for thrombus length <14 mm. In summary, the present study disclosed an association between lower HIR and early post-thrombolysis recanalization. Early post-thrombolysis recanalization is therefore determined not only by thrombus site and length but also by severity of ischemia.

Cerebral ischaemia with unknown onset: Outcome after recanalization procedure

BACKGROUND

Stroke of unknown time of onset (UTOS) accounts for one-third of contra-indications for revascularization procedures. With modern neuroimaging techniques it is possible to differentiate the core infarcts and the presence of penumbra.

OBJECTIVE

To evaluate outcomes in patients with UTOS, treated with intravenous (i.v.) recombinant tissue-plasminogen activator (rt-PA), mechanical thrombectomy (MT), or both.

METHOD

We conducted this observational study in patients treated by i.v. rt-PA, MT, or both, selected by a diffusion-weighted image/fluid-attenuated inversion recovery mismatch. We evaluated outcomes with the modified Rankin scale (mRS) at 3 months.

RESULTS

Of 992 consecutive patients (522 women, 52.6%; median age 76 years; median baseline national institutes of health stroke scale [NIHSS] 10), 153 (15.4%) had UTOS, including 101 with wake-up strokes. Compared to other patients, they were more likely to have pre-existing mRS scores >2 (P=0.022), multiple infarcts (P<0.001), middle cerebral artery occlusions (P=0.023), and to undergo MT (P=0.003), and less likely to receive i.v. rt-PA (P<0.001). They had higher NIHSS scores (P<0.001) and longer discovery to treatment initiation times (P<0.001). They were more likely to develop pulmonary (P=0.001) and urinary (P=0.006) infections, and pulmonary embolism (P=0.019), and tended to have a higher mortality rate (P=0.052) within 7 days. After adjustment, there was no association of UTOS with any of these outcome measures anymore.

CONCLUSION

Patients with UTOS have more severe strokes and more comorbidities, but after adjustment, their outcomes did not differ from those of other patients.

Dual-phase 16 slice CT angiography in stroke imaging: a poor man's multiphase study?

Multiphase CT angiography (CTA) in collateral assessment provides time-resolved cerebral angiograms of the intracranial vasculature, requiring a high-speed multidetector CT (MDCT) scanner with ≥ 64 slices. Unfortunately, many hospitals are equipped with lower speed MDCT scanners. Herein, we present our experience performing dual-phase CTA (d-CTA) on a 16 slice MDCT with a biphasic rate injection to grade intracranial collaterals as predictor of clinical outcome. 42 patients were evaluated with both dual-phase CTA (d-CTA) and single-phase CTA (s-CTA) for occluded anterior intracranial circulation and collaterals. They were treated with endovascular reperfusion. Univariate and multivariate analyses were performed to define the independent predictors for favorable outcome at 3 months. Good collateral circulation status on d-CTA was associated with a lower median 24-h (5 vs. 7.5, p = 0.03) and discharge (2 vs. 4.6, p = 0.04) NIHSS. A logistic regression model showed that only age (OR 0.95, 95% CI 0.91-0.98, p = 0.03) and good collateral circulation status at d-CTA (OR 4.3, 95% CI 1.87-11.3, p < 0.01) were independent predictors of favorable functional outcome at 3 months, but that s-CTA was not. The collateral status on d-CTA can be a useful predictor for clinical outcome in acute stroke patients. The proposed protocol adapted to a low-speed MDCT scanner could be of particular interest in hospitals without access to the more up-to-date technology.