Imaging findings of acute intravascular thrombus on non-enhanced computed tomography

The accuracy of the Hounsfield unit in pulmonary embolism diagnostics

OBJECTIVE

Pulmonary embolism (PE) is a vascular disease that is most frequently diagnosed using the radiological imaging technique computed tomography pulmonary angiography (CTPA). In this study, we aimed to demonstrate the diagnostic accuracy of the Hounsfield unit (HU) for PE based on the hypothesis that acute thrombosis causes an increase in HU value on CT.

METHODS

This research was a single-center, retrospective study. Patients presenting to the emergency department diagnosed with PE on CTPA were enrolled as the study group. Patients admitted to the same emergency department who were not diagnosed with PE and had noncontrast CT scans were included as the control group. A receiver operating curve was produced to determine the diagnostic accuracy of HU values in predicting PE.

RESULTS

The study population (n=74) consisted of a study group (n=46) and a control group (n=28). The sensitivity and specificity of the HU value for predicting PE on thoracic CT were as follows: for the right main pulmonary artery, 61.5% and 96.4% at a value of 54.8 (area under the curve [AUC], 0.690); for the left main pulmonary artery, 65.0% and 96.4% at a value of 55.9 (AUC, 0.736); for the right interlobar artery, 44.4% and 96.4% at a value of 62.7 (AUC, 0.615); and for the left interlobar artery, 60.0% and 92.9% at a value of 56.7 (AUC, 0.736).

CONCLUSION

HU may exhibit high diagnostic specificity on CT for thrombi up to the interlobar level. An HU value exceeding 54.8 up to the interlobar level may raise suspicion of the presence of PE.

Safety and efficacy of intravenous thrombolysis before mechanical thrombectomy in patients with atrial fibrillation

BACKGROUND

Intravenous thrombolysis (IVT) before endovascular thrombectomy (EVT) is the standard treatment for patients with acute ischemic stroke caused by large vessel occlusion (AIS-LVO). However, the efficacy and safety of IVT before EVT in AIS-LVO patients with atrial fibrillation (AF) remains controversial. Thus, this study aims to assess the benefit of IVT plus EVT and direct EVT alone in AIS-LVO patients with AF.

METHOD

Relevant studies that evaluated the outcomes of IVT plus EVT versus direct EVT alone in AIS-LVO patients with AF were systematically searched in PubMed, Embase, and Cochrane Library from inception to August 10, 2023. The outcomes included successful reperfusion (score of 2b to 3 for thrombolysis in cerebral infarction), symptomatic intracerebral hemorrhage (sICH), good clinical outcome (modified Rankin scale score ≤ 2) at 3 months, and 3-month mortality.

RESULT

Eight eligible observational studies involving 6998 (3827 in the IVT plus EVT group and 3171 in the direct EVT group) patients with AIS-LVO complicated by AF were included. Compared with direct EVT, IVT plus EVT resulted in better 3-month clinical outcomes (odds ratio [OR] 1.27, 95% confidence interval [CI] 1.05-1.54) and lower 3-month mortality (OR 0.78, 95% CI 0.68-0.88). However, the incidence of sICH (OR 1.26, 95% CI 0.91-1.75) and the rate of successful reperfusion (OR 0.98, 95% CI 0.83-1.17) were not significantly different between treatment modalities.

CONCLUSION

IVT plus EVT leads to better functional outcomes and lower mortality in AIS-LVO patients with AF. Withholding IVT plus EVT from patients with AF alone may not be justified.

Multimodality Characterization of the Clot in Acute Stroke

Aim: Current treatment of occluded cerebral vessels can be done by a variety of endovascular techniques. Sometimes, the clot responds in varying degrees to the treatment chosen. The Ex vivo characterization of the clot occluding the arteries in acute ischemic stroke can help in understanding the underlying imaging features obtained from pre-treatment brain scans. For this reason, we explored the potential of microCT when combined with electron microscopy for clot characterization. Results were compared to the clinical CT findings.

Methods: 16 patients (9 males, 8 females, age range 54–93 years) who were referred to our institution for acute stroke underwent dual-source CT.

Results: Clinical CT clots were seen as either iso or hyperdense. This was corroborated with micro-CT, and electron microscopy can show the detailed composition.

Conclusion: MicroCT values can be used as an indicator for red blood cells-rich composition of clots. Meaningful information regarding the clot composition and modalities of embedding along the stent retrievers can be obtained through a combination of microCT and electron microscopy.

Evolution of Nonmalignant Portal Vein Thrombosis in Liver Cirrhosis: A Pictorial Review

Portal vein thrombosis (PVT) is a common complication in liver cirrhosis, especially in advanced cirrhosis. It may be related to a higher risk of liver-related events and liver function deterioration. Imaging examinations can not only provide an accurate diagnosis of PVT, such as the extent of thrombus involvement and the degree of lumen occupied, but also identify the nature of thrombus (i.e., benign/malignant and acute/chronic). Evolution of PVT, mainly including development, recanalization, progression, stability, and recurrence, could also be assessed based on the imaging examinations. This article briefly reviews the pathophysiology, diagnosis, classification, and evolution of PVT with an emphasis on their computed tomography imaging features.

Effect of intravenous contrast for CT abdomen and pelvis on detection of urgent and non-urgent pathology: can repeat CT within 72 hours be avoided?

PURPOSE

To determine if administering IV contrast for CT abdomen and pelvis improves detection of urgent and clinically important non-urgent pathology in patients with urgent clinical symptoms compared to patients not receiving IV contrast, and in turn to determine whether repeat CT exams on the same patient within 72 h were of low diagnostic benefit if the first CT was performed with IV contrast.

METHODS

We evaluated 400 consecutive patients who had CT abdomen and pelvis (CT AP) examinations repeated within 72 h. For each patient, demographic data, reason for examination, examination time stamps, and examination technique were documented. CT AP radiology reports were reviewed and both urgent and non-urgent pathology was extracted.

RESULTS

Of 400 patients, 63% had their initial CT AP without contrast. Administration of IV contrast for the first CT AP was associated with increased detection of urgent findings compared with non-contrast CT (p = 0.004) and a contrast-enhanced CT AP following an initial non-contrast CT AP examination better characterized both urgent (p = 0.002) and non-urgent findings (p < 0.001). Adherence to ACR appropriateness criteria for IV contrast administration was associated with increased detection of urgent pathology on the first CT (p = 0.02), and the second CT was more likely to be performed with IV contrast if recommended by the radiologist reading the first CT (p = 0.0006).

CONCLUSION

In the absence of contraindications, encouraging urgent care physicians to preferentially order IV contrast-enhanced CT AP examinations in adherence with ACR appropriateness criteria may increase detection of urgent pathology and avoid short-term repeat CT AP.

Can clot density predict recanalization in acute ischemic stroke treated with intravenous tPA?

Stroke has become an absolute emergency that is treated by additional endovascular means or by replacing pharmacological options. Modern neuroradiological techniques such as computed tomography (CT) allow us to examine multiple parameters of the diseased brain. These focused on the parenchyma and hemodynamics for pretherapeutic decisions. However, it has become evident that the clot is the current target for interventional measures. Clot length is established as a marker for recanalization. The dense artery sign is known as an acute CT sign of stroke that is readily visible on acute nonenhanced CT. The rationale behind our study was to study if clot density might represent clot vulnerability or resistance to treatment. We conducted a prospective study of all consecutive stroke patients admitted to our hospital over 1 year, who presented with signs of acute middle cerebral artery stroke within the therapeutic window, and who underwent either intravenous or combined intravenous and intra-arterial thrombolysis. All patients were evaluated with a complete stroke CT protocol, transcranial color-coded duplex sonography monitoring, and clinical evaluation with the National Institutes of Health Stroke Scale (NIHSS) score. We measured clot length using planimetry on unenhanced CT and measured Hounsfield units in the clots on the same images. A total of 31 patients were included in the study (19 men, 12 women, aged 35–90 years). We found that patients with a longer clot on the unenhanced CT had a higher NIHSS score, confirming previous literature. However, we found that patients with a lower clot density recanalized to a more marked degree and had a better clinical outcome. Patients who did not recanalize had a higher clot density (49 Hounsfield units) than those who did recanalize (23 Hounsfield units). Overall, measuring the clot seems to be an important additional parameter to be taken into account. In our study, CT clot density seems to correlate with clinical outcome and recanalization. The higher density seems to represent a higher red blood cell content. This is evidence that clot composition could play a much more important role in acute stroke than thought until now and characterizing it with imaging may help in choosing the adequate treatment modality. Higher density seems to reflect erythrocyte content. Therefore, patients with a longer and denser clot may necessitate direct thrombectomy.