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The rules say that plans must pay for a medical service or item if regular Medicare would pay for it in this case. 
You can find this rule at 42 Code of Federal Regulations (CFR) Section 422.101. 
 
The rules state cerebral perfusion analysis using computed tomography with contrast administration, including 
post-processing of parametric maps with determination of cerebral blood flow, cerebral blood volume, and 
mean transit time 
Computed Tomographic Perfusion (CTP) (using automated post-processing software algorithmic analysis) is 
medically reasonable and necessary in patients with acute ischemic stroke (AIS) caused by unilateral large 
vessel occlusion (LVO) in the proximal anterior circulation evaluated at stroke centers, to aid in selection for 
endovascular mechanical thrombectomy (EVT) if all of the following conditions are fulfilled: 
1. Intracranial internal carotid artery (ICA) OR middle cerebral artery (MCA) occlusion 
2. The medical record documents the patient is being considered for endovascular mechanical 
thrombectomy (EVT) and does not have contraindications to the EVT (based on DAWN or DEFUSE3 
trial criteria) 
3. Treatment (femoral puncture) can be started within 6-24 hours of the last time known to be at 
neurologic baseline 
Computed Tomographic Perfusion (CTP) accuracy: A 2020 systematic review aimed to evaluate the diagnostic 
accuracy of CTP in the prediction of hemorrhagic transformation and patient outcome in AIS reported CTP 
sensitivity as 85.9%, specificity of 73.9%, positive predictive value 60.3% and negative predictive value of 
92.9%.
 
A 2017 systematic review identified 27 studies with a total of 2168 patients. The pooled sensitivity of 
CTP for acute ischemic stroke was 82% (95% CI 7588%), and the specificity was 96% (95% CI 8999%). 
They determined CTP was more sensitive than Non-contrast Computerized Tomography (NCCT) and had a 
similar accuracy with Computed tomography angiography (CTA), but also that the evidence was not strong, 
and there is a need for high-quality evidence to confirm results.
 
Older systematic reviews report mixed results 
with a wide range in sensitivity and specificity of CTP for detection of acute ischemic stroke (AIS). A 2019 
systematic review and meta-analysis comparing imaging modalities for evaluation of AIS concludes that while CTP was more accurate than NCCT for detection of AIS, it was less accurate than diffusion-weighted imaging 
(DWI) magnetic resonance imaging (MRI) (sensitivity 82%, specificity 96% vs. sensitivity 15-86%, specificity 
100%, respectively).
 
DWI is considered the gold standard for imaging diagnosis of acute ischemia and more 
accurate than NCCT, CTA, and CTP to estimate or infer the size of core and penumbra. However, NCCT is 
considered the current standard for stoke evaluation as MRI use in emergency settings may be limited, as well 
as several contradictions for MRI. Most studies evaluated in these systematic reviews were retrospective with 
variability in inclusion and exclusion criteria, outcomes reported, and sampling procedures, which introduces a 
high risk for bias, heterogenicity, and overall reduced quality of evidence. The evidence for routine use of CTP 
for evaluation for AIS is low quality and there is a need for high-quality evidence to determine the role it may 
play in AIS evaluation. 
You can find this rule at the Medicare Local Coverage Determination (LCD) L35490: Category III Codes. 
 
If you want to read these Medicare rules, you can go to this website www.medicareappeal.com. 
 
The Plan contract says that the Plan covers items and services in accordance with Medicare rules.