This study is a prospective gathered in house registry (PMU/085/09/2018-09/2020) consisting of all patients with acute ischemic stroke at our Comprehensive stroke center. Participants were 152 patients admitted from September 2, 2018 to September 2, 2020 with acute ischemic stroke who underwent mechanical thrombectomy treatment. Patients with a clinical diagnosis of acute stroke were evaluated using National Institutes of Health Stroke Scale (NIHSS), modified Rankin scale (mRS) and were randomized into MRI brain-based protocol or CT-based protocol consecutively.
The regional review board has approved the use of human subjects for this study. All participants had given written informed consent. This Study did not require further approval as it used existing standard imaging, such as CT scan and MRI. There was no new drug or invasive procedure used in this study outside the standard existing recommendation.
Patient inclusion and exclusion criteria
Patients aged 18–80 years with acute ischemic stroke and symptomatic anterior proximal large vessel occlusion on CTA/MRA/DSA with NIHSS of at least 2 points within 6 h of stroke onset with informed consent was included in the study. A specific exclusion criterion for intended mechanical thrombectomy is concurrent myocardial infarction or severe infection (endocarditis or sepsis), uncontrollable hypertension defined as systolic blood pressure > 185 mmHg or diastolic pressure > 110 mmHg, Life expectancy of less than 90 days before stroke onset, pregnant or lactating women, known severe allergy to radiographic contrast medium and improvement of NIHSS score > 4 in less than 1 h. CT or MRI evidence of significant mass effect with midline shift, CT or MRI showing more than 1/3 of MCA territory infarct, CT or MRI evidence of intracranial hemorrhage (ICH), Subarachnoid Hemorrhage (SAH), Aneurysm or Cerebral arteriovenous malformations (CAVMs).
Fast imaging techniques such as echo-planar imaging (EPI), Propeller (GE)/ BLADE (Siemens) and turbo spin echo has significantly reduced the timing of MRI scan without compromising the image quality. The purpose of this study was to establish the feasibility of a fast MR protocol that can be obtained in ≈13 min.
In MRI on a 1.5 T (Siemens Essenza) MR system, we followed a protocol of MRI consuming less time taken with imaging protocol including diffusion-weighted imaging (DWI), EPI fluid attenuation inversion recovery imaging (FLAIR), EPI-gradient recalled echo (GRE), MRA brain & neck (TOF). We removed the sagittal T2, coronal FLAIR and axial T1 and axial T2 sequences from the fast MR protocol for acute stroke to reduce timing as the above mentioned sequences does not affect the diagnosis of the stroke. If there is stroke mimic-like condition than we add these sequences for further additional information.
In addition to the new sequences which consume lesser amount of time, we have changed the certain parameters of the sequences. We have reduced the phase resolution from 80 to 70 in axial FLAIR and SWI sequences avoiding the 500 B value images and only acquired the 0 and 1000 B value images in DWI this further reduced the timings of the MRI scan. We have also changed the slice thickness of TOF angiography neck and brain from 0.6 to 0.8 and reduced phase FOV from 100 to 80–85 (vary according the patient) and also reduced the base resolution of angiography from 320 to 256 and phase resolution to 70 to 63 reduce the scan time dramatically and when this MR scan compared with the MR scan obtained by the sequences with normal parameters (provided by factory settings of the machine), No significant difference in the image quality was shown.
Detailed parameters of sequence timings are shifting and preparation time-2 min, localizer-20 s, DWI Axial 1 min 10 s, SWI Axial 1 min 27 s, FLAIR Axial 2 min 5 s, TOF MRA Brain 2 min 50 s, Localizer Neck 15 s and TOF MRA Neck 2 min 50 s. The time taken for the post processing of TOF angiography is negligible as after acquiring the TOF raw data we can obtain 3D image reconstruction in just 10 s each for brain and neck angiography. Total duration of the scan time is 12 min and 57 s.
The 13-min time is an estimate calculated based on all steps required to complete the image acquisition. It should be noted that acquisition time may vary on a case by case basis depending on factors, such as patient cooperation and technical difficulties.
All the CT scan head and CT angiography were performed on the 128 slice dual source CT scanner of Somatom definition by Siemens.
When, we see the only scan timing, which is less than a minute, but few additional time consuming process which are also necessary for scan. The total, calculated time of CT scanning with reconstruction is approximately 10 min which is less than the time taken for MR stroke protocol. It does not include the timing of contrast filling in the injector as it is already prepared before patient shift.
The Various details of the timing for CT scan are shifting and positioning 2 min, Topogram and planning 20 s, CT head scan time 18 s, Reconstruction time 2 min 30 s, Plain Angio scan 6 s, Contrast Bolus tracking 40 s, Angio run contrast 20 s, Angio reconstruction 3 Min, total time is 9 min 23 s (Fig. 1).
We performed Modified Rankin Scale (MRS) at admission, and at 3 months. Patients who refused to sign the informed consent, non cooperative or non fit for MRI or CT scan for the study, were excluded before randomization. To achieve the objective the hypothesis is framed which is further tested (Table 2). There is no significant difference on outcome based on CT and MRI scan after 3 months.
Statistical analysis
The CT and MRI groups were compared using the Mann–Whitney U test for quantitative variables and the χ2 test for qualitative variables. Factors with a significant (P < 0.10) association with favorable outcome in analysis—that is, age, hypertension, hyperlipidemia ischemic heart disease, National Institutes of Health Stroke Scale score, diabetes mellitus, history of previous stroke. For two groups CT-based versus MRI-based outcome prior to mechanical thrombectomy, and imaging modality (MRI versus CT)—were candidates for the model. Reported P values were two-sided, with values < 0.05 indicative of a significant difference. All tests were two-sided. The statistical analysis was performed using SPSS (Version 25.0; IBM,)