"Code-Stroke" CT Perfusion; Challenges and Pitfalls

Potential Approach to Quantifying the Volume of the Ischemic Core in Truncated Computed Tomography Perfusion Scans: A Preliminary Study

OBJECTIVE

This study aimed to provide an alternative approach for quantifying the volume of the ischemic core (IC) if truncation of computed tomography perfusion (CTP) occurs in clinical practice.

METHODS

Baseline CTP and follow-up diffusion-weighted imaging (DWI) data from 88 patients with stroke were retrospectively collected. CTP source images (CTPSI) from the unenhanced phase to the peak arterial phase (CTPSI-A) or the peak venous phase (CTPSI-V) were collected to simulate the truncation of CTP in the arterial or venous phases, respectively. The volume of IC on CTPSI-A (V CTPSI-A ) or CTPSI-V (V CTPSI-V ) was defined as the volume of the brain tissue with >65% reduction in attenuation compared with that of the normal tissue. The volume of IC on the baseline CTP (V CTP ) was defined as a relative cerebral blood flow of <30% of that in the normal tissue. The volume of the posttreatment infarct on the follow-up DWI (V DWI ) image was manually delineated and calculated. One-way analysis of variance, Bland-Altman plots, and Spearman correlation analyses were used for the statistical analysis.

RESULTS

V CTPSI-A was significantly higher than V DWI ( P < 0.001); however, no significant difference was observed between V CTP and V DWI ( P = 0.073) or between V CTPSI-V and V DWI ( P > 0.999). The mean differences between V DWI and V CTPSI-V , V DWI and V CTP , and V DWI and V CTPSI-A were 1.70 mL (limits of agreement [LoA], -56.40 to 59.70), 8.30 mL (LoA, -40.70 to 57.30), and -68.10 mL (LoA, -180.90 to 44.70), respectively. Significant correlations were observed between V DWI and V CTP ( r = 0.68, P < 0.001) and between V DWI and V CTPSI-V ( r = 0.39, P < 0.001); however, no significant correlation was observed between V DWI and V CTPSI-A ( r = 0.20, P = 0.068).

CONCLUSIONS

V CTPSI-V may be a promising method for quantifying the volume of the IC if truncation of CTP occurs.

CT perfusion - an up-to-date element of the contemporary multimodal diagnostic approach to acute ischemic stroke

Acute ischemic stroke is of great clinical and societal importance due to its high incidence and mortality rates, as well as the fact that those who are affected suffer from permanent acquired disability. Modern trends explicitly state that the disease's diagnostic plan should use a multidisciplinary approach. The therapeutic steps that ultimately determine the clinical outcome are defined by an accurate diagnosis of acute ischemic stroke. Highly specialized facilities for the diagnosis and treatment of acute ischemic stroke (Stroke Units) are in operation in countries that make significant investments in healthcare. Imaging the brain parenchyma at risk, or the so-called ischemic penumbra, in acute ischemic stroke is one of the main tasks of the multimodal computed tomography approach. The most rapid method for imaging the ischemic penumbra is computed tomography perfusion (CTP). This modality provides information about the anatomy and the physiologic state of the brain parenchyma.

Use of CTA Test Dose to Trigger a Low Cardiac Output Protocol Improves Acute Stroke CTP Data Analyzed with RAPID Software

BACKGROUND AND PURPOSE

Contrast curve truncation in CTP protocols may introduce errors. We sought to identify risk factors and design a protocol to avoid truncation while limiting radiation.

MATERIALS AND METHODS

In an initial fixed-timing cohort, patients underwent a 65-second CTP with 2-second delay postcontrast injection. Multivariable analysis identified factors associated with truncation. A later case-specific cohort underwent either the original protocol or a low cardiac output protocol with a 7-second delay and 75-second scanning window, with selection determined by CTA test-dose enhancement upswing delay. Time-density curves were assessed for truncation and compared between the 2 groups, and the radiation dose was evaluated.

RESULTS

From September 2017 through May 2018, one hundred fifty-three patients underwent the standard fixed-timing protocol. Age (OR, 1.82/10-year increase; P = .019), reduced left ventricle ejection fraction (OR, 9.23; P = .001), and hypertension (OR, 0.32; P = .06) were independently associated with truncation in an exploratory multivariable model. From May 2018 through April 2019, one hundred fifty-seven patients underwent either the standard (72 patients) or low cardiac output protocol (85 patients). The fixed-timing cohort had 15 truncations (9.8%) versus 4 in the case-specific cohort (2.5%; P = .009). If the low cardiac output protocol were applied to those with >10.6% predicted risk of truncation based on age, left ventricle ejection fraction, and hypertension, the number of truncations would have decreased from 15 to 4 in the fixed-timing cohort.

CONCLUSIONS

Older age, left ventricle ejection fraction, and the absence of hypertension increase the risk of time-density curve truncation. However, a CTA test-dose-directed case-specific protocol can reduce truncation to ensure accurate data while mitigating radiation dose increases.

Automated Brain Perfusion Imaging in Acute Ischemic Stroke: Interpretation Pearls and Pitfalls

Recent advancements in computed tomography technology, including improved brain coverage and automated processing of the perfusion data, have reinforced the use of perfusion computed tomography imaging in the routine evaluation of patients with acute ischemic stroke. The DAWN (Diffusion Weighted Imaging or Computerized Tomography Perfusion Assessment With Clinical Mismatch in the Triage of Wake Up and Late Presenting Strokes Undergoing Neurointervention) and DEFUSE 3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3) trials have established the benefit of endovascular thrombectomy in patients with acute ischemic stroke with anterior circulation large vessel occlusion up to 24 hours of last seen normal, using perfusion imaging-based patient selection. The compelling data has prompted stroke centers to increasingly introduce automated perfusion computed tomography imaging in the routine evaluation of patients with acute ischemic stroke. We present a comprehensive overview of the acquisition and interpretation of automated perfusion imaging in patients with acute ischemic stroke with a special emphasis on the interpretation pearls, pitfalls, and stroke mimicking conditions.

State of the Art Stroke Imaging: A Current Perspective

Acute stroke is a widespread, debilitating disease. Fortunately, it also has one of the most effective therapeutic options available in medicine, endovascular treatment. Imaging plays a major role in the diagnosis of stroke and aids in appropriate therapy selection. Given the rapid accumulation of evidence for patient subgroups and concurrent broadening of therapeutic options and indications, it is important to recognize the benefits of certain imaging technologies for specific situations. An effective imaging protocol should: 1) be fast, 2) easily implementable, 3) produce reliable results, 4) have few contraindications, and 5) be safe, all with the goal of providing the patient the best chance of achieving a favorable outcome. In the following, we provide a review of the currently available imaging technologies, their advantages and disadvantages, as well as an overview of the future of stroke imaging. Finally, we offer a perspective.

Automated Processing of Head CT Perfusion Imaging for Ischemic Stroke Triage: A Practical Guide to Quality Assurance and Interpretation

Recent successful trials of thrombectomy launched a shift to imaging-based patient selection for stroke intervention. Many centers have adopted CT perfusion imaging (CTP) as a routine part of stroke workflow, and the demand for emergent CTP interpretation is growing. Fully automated CTP postprocessing software that rapidly generates standardized color-coded CTP summary maps with minimal user input and with easy accessibility of the software output is increasingly being adopted. Such automated postprocessing greatly streamlines clinical workflow and CTP interpretation for radiologists and other frontline physicians. However, the straightforward interface overshadows the computational complexity of the underlying postprocessing workflow, which, if not carefully examined, predisposes the interpreting physician to diagnostic errors. Using case examples, this article aims to familiarize the general radiologist with interpreting automated CTP software data output in the context of contemporary stroke management, providing a discussion of CTP acquisition and postprocessing, a stepwise guide for CTP quality assurance and troubleshooting, and a framework for avoiding clinically significant CTP interpretative pitfalls in commonly encountered clinical scenarios. Interpreting radiologists should apply the outlined approach for quality assurance and develop a comprehensive search pattern for the identified pitfalls, to ensure accurate CTP interpretation and optimize patient selection for reperfusion.

Aortic dissection diagnosed on stroke computed tomography protocol: a case report

Background

Aortic dissection is one of the causes of stroke. Because cerebral infarction with aortic dissection is a contraindication to intravenous recombinant tissue plasminogen activator (rt-PA) therapy, exclusion of aortic dissection is necessary prior to its administration. However, imaging takes time to provide a diagnosis, possibly causing delays in surgical treatment.

Case presentation

A 65-year-old Japanese female patient was transported to the hospital for a suspected stroke, with back pain and left upper and lower extremity palsy which occurred while eating. Upon arrival at the hospital, the left lower limb paralysis had improved, but the left upper limb paralysis remained. Right back pain had also developed. A plain head computed tomography (CT) scan performed 110 minutes after onset showed no acute bleeding or infarction. Subsequent CT perfusion (CTP) showed acute perfusion disturbance in the right hemisphere without infarction, known as ischemic penumbra. The four-dimensional maximum-intensity projection image reconstructed from CTP showed a delayed enhancement at the right internal carotid and right middle cerebral arteries compared to the contralateral side, suggesting a proximal vascular lesion. Contrast helical CT from the neck to abdomen revealed an acute aortic dissection of Stanford type A with false lumen patency. The dissection extended to the proximal right common carotid artery. The patient underwent an emergency total arch replacement and open stent graft. After recovering well, the patient was ambulatory upon discharge from the hospital. The combination of plain head CT, CTP, and helical CT scan from the neck to abdomen enabled us to evaluate for stroke and aortic dissection within a short amount of time, allowing for early therapeutic intervention.

Conclusions

When acute stroke is suspected due to neurological deficits, plain head CT is the first choice for imaging diagnosis. The addition of cervical CT angiography can reliably exclude stroke due to aortic dissection. CTP can identify ischemic penumbra, which cannot be diagnosed by plain head CT or diffusion-weighted magnetic resonance imaging. These combined stroke CT protocols helped us avoid missing an aortic dissection.

Clinical considerations and assessment of risk factors when choosing endovascular thrombectomy for acute stroke

INTRODUCTION

The advent of endovascular thrombectomy (EVT) has been a game changer for the management of acute ischemic stroke due to large vessel occlusion. However, the selection of suitable candidates for EVT remains a significant challenge.

AREAS COVERED

This review focuses on the clinical, radiological, and procedural considerations for EVT in acute stroke that assist in optimal patient selection.

EXPERT OPINION

All patients presenting with significant clinical deficits with treatable occlusions, who have salvageable brain tissue at presentation might benefit from treatment up to twenty-four hours from symptom onset. Neuroimaging tools form the backbone for this decision making.

CT Imaging of Acute Ischemic Stroke [Formula: see text]

Although acute ischemic stroke remains one of the most common causes of death and disability worldwide, it is a potentially treatable condition if appropriately managed in a timely manner. The goals of acute stroke imaging include establishing a diagnosis as fast as possible with (1) accurate infarct quantification, (2) intracranial and cervical vasculature assessment, and (3) brain perfusion analysis for detection of infarct core and potentially salvageable penumbra allowing optimal patient selection for appropriate therapy. Given the extensive number of images generated from acute stroke imaging studies and as "time is brain," this article aims to highlight a logical approach for the radiologist in acute stroke computed tomography imaging in order to accurately interpret and communicate results in a timely manner.