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Objective:
Ischemic stroke is a relatively uncommon cause of dizziness in the emergency department (ED) setting but is difficult to differentiate from nonischemic etiologies, presenting a diagnostic dilemma for ED clinicians. This dilemma is further hindered by the poor sensitivity of CT and CTA for posterior fossa strokes. Previous work shows that MRI provides a high sensitivity for detecting posterior fossa strokes, though conventional MRI may not be readily available in all practice setting. Alternative imaging strategies, including portable MRI (pMRI) and CT perfusion (CTP), may help fill diagnostic testing needs in many acute care settings, with higher sensitivity than CT/CTA alone. This study seeks to assess the cost effectiveness of pMRI and CTP for stroke evaluation compared to standard of care imaging with CT and CTA.

Materials and Methods:
A Markov decision-analytic model was constructed to assess cost and outcomes between cohorts of ED patients presenting with dizziness using one of five strategies with varying sensitivity (no imaging: 0%, CT: 23%, CTA: 42%, pMRI: 69%, CTP: 74%). Sensitivity for emerging techniques was estimated based on the best available literature. We modeled patients who would not be candidates for acute thrombolysis/thrombectomy in the case of underlying stroke, and outcomes vary primarily as a result of differing selection for secondary prevention. Costs were estimated using the CMS physician fee schedule for imaging examinations and previously reported costs of preventive care, recurrent stroke, and stroke disability. Health outcomes were measured in quality-adjusted life-years (QALYs). A 3% discount rate was applied to all costs and QALYs.

Results:
Use of noncontrast CT head was associated with a benefit of 0.81 QALYs for $12,377.CTA was associated with a benefit of 0.99 QALYs for $14,254. pMRI was associated with a benefit of 1.19 QALYs for $15,389. CTP(in conjunction with CT/CTA) was associated with a benefit of 1.24 QALYs for $16,073. If high-field MRI is not available, then either CTP or pMRI provides the highest utility, with incremental cost-effectiveness over CT/CTA of < $6000 per QALY.Both deterministic and probabilistic sensitivity analyses recapitulated these findings, with pMRI and CTP more cost-effective than CTA alone across a wide range of a parameters.In sensitivity analyses comparing pMRI to CTP, relative cost-effectiveness was most dependent on which of these emerging modalities was more sensitive for stroke.

Conclusion:
This model suggests a greater cost effectiveness of pMRI and CTP compared to commonly used CT/CTA evaluation of dizziness in ED settings. Where access to conventional MRI is limited, these modalities may be the preferred option to maximize long-term outcomes and cost of care. CTP and particularly pMRI are emerging technologies for use in posterior circulation stroke, and further investigation of clinical use is warranted to support our findings. Our investigation suggests potential for use in a common diagnostic scenario and provides early evidence supporting the billing and clinical integration of these techniques in acute care.