High-resolution susceptibility-weighted imaging for detecting cerebral venous thrombosis across various venous segments and disease stages

Abstract

Purpose

We aimed to compare the performance of susceptibility-weighted imaging and standard magnetic resonance imaging sequences for cerebral venous thrombosis in diverse venous segments and disease stages.

Materials and methods

We compared the sensitivity of susceptibility-weighted imaging, T1-weighted imaging, T2-weighted imaging, and fluid-attenuated inversion recovery in detecting cerebral venous thrombosis across various venous segments and disease stages. Additionally, the sensitivity of susceptibility-weighted imaging was compared with that of magnetic resonance venography for identifying cerebral venous thrombosis in different venous segments.

Results

The study cohort comprised 33 lesions in the acute stage, 37 in the subacute stage, and 17 in the chronic stage. Susceptibility-weighted imaging demonstrated superior sensitivity, with values reaching 94% in the acute stage and 88% in the chronic stage, significantly outperforming the other three magnetic resonance imaging sequences (p < 0.001 and p = 0.04, respectively). For the superior sagittal sinus, deep venous system, and cortical veins, susceptibility-weighted imaging achieved detection rates of 81% (17/21), 100% (5/5), and 100% (7/7), respectively, exceeding the values obtained using T1-weighted imaging, T2-weighted imaging, and fluid-attenuated inversion recovery (p = 0.02, p = 0.01, and p < 0.001, respectively). However, in the subacute stage, T1-weighted imaging exhibited higher sensitivity than susceptibility-weighted imaging (p = 0.02). Notably, susceptibility-weighted imaging showed better sensitivity than magnetic resonance venography in the evaluation of cortical veins (p = 0.02).

Conclusions

Susceptibility-weighted imaging may offer heightened sensitivity in detecting cortical vein thrombosis during acute and chronic stages.

Keywords

Cerebral venous thrombosis susceptibility-weighted imaging magnetic resonance imaging sensitivity

Introduction

Cerebral venous thrombosis (CVT), a relatively rare condition, accounts for <1% of all strokes.¹ The diverse modes of onset and broad spectrum of symptoms associated with CVT present a significant diagnostic challenge for clinicians. Unlike arterial thrombotic occlusions, venous thrombi have the potential for complete resolution without causing permanent neurological deficits.² Therefore, timely and accurate diagnosis followed by prompt treatment is crucial for optimal patient outcomes. CVT often manifests as nonspecific brain parenchymal lesions, such as hemorrhage, infarction, or edema, which may occur independently or in combination. The definitive diagnosis of CVT relies on the identification of thrombosis within the cerebral veins and/or sinuses.

Currently, magnetic resonance imaging (MRI) in conjunction with magnetic resonance venography (MRV) serves as the primary imaging modality for diagnosing CVT.³ However, standard MRI sequences exhibit limitations in sensitivity and specificity, particularly during the acute phase. During this phase, thrombi frequently appear hypointense on T2-weighted imaging (T2WI), a feature that can be easily mistaken for a normal void.⁴ Moreover, MRV, similar to other angiographic techniques, often fails to differentiate between thrombosis and hypoplasia, especially in the lateral sinuses. Consequently, these methods are often unable to diagnose cortical venous thrombosis, necessitating the use of standard angiography despite its invasive nature and high cost.

T2*-weighted gradient recalled echo (GRE) sequences have gained widespread clinical application.^5–8 Susceptibility-weighted imaging (SWI), a more advanced magnetic resonance (MR) sequence than T2*-weighted GRE, has been in clinical use for over a decade. SWI demonstrates superior sensitivity to cerebral microbleeds compared with T2*-weighted GRE sequences.^9,10 In recent years, the scope of SWI’s application has expanded beyond vascular diseases to encompass brain trauma, brain tumors, and degenerative diseases.^11–14 For the diagnosis of cortical vein (CV) thrombosis, contrast-enhanced sequences and SWI have emerged as the most effective techniques.¹⁴

Despite these advancements, a thorough review of the literature revealed a notable gap: the absence of a dedicated study assessing the diagnostic value of SWI in patients with CVT across different venous segments and disease stages. Therefore, we believe that there is an urgent need for such a study to elucidate the strengths and limitations of SWI, providing radiologists with the essential guidance to enhance diagnostic accuracy.

Materials and methods

Patients

All procedures in our study were performed in accordance with the ethical standards of our committee on human experimentation and the Helsinki Declaration of 1975, as revised in 2024. This study was approved by the Regional Ethics Committee of our hospital, and all patients provided written informed consent. All patient identifiers were removed prior to analysis to ensure complete de-identification. The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.¹⁵

Twenty-five patients with confirmed CVT who underwent MRI examinations, including the SWI sequence, from January 2018 to June 2024 were enrolled in this retrospective study. For all patients, the diagnosis of CVT was based on the following criteria proposed by Idbaih et al.¹⁶ in 2006: (a) patient’s history and clinical manifestations compatible with or suggestive of CVT; (b) presence of partial or complete venous occlusion on MRV, computed tomography angiography, or standard angiography; and (c) typical signal changes highly suggestive of the intraluminal thrombosis in sinuses or veins on T1-weighted imaging (T1WI) or T2WI. A case was considered acute if the symptom duration was 0–7 days, subacute if it was 8–30 days, and chronic if it was >30 days.

Imaging parameters

All examinations with standard MRI and SWI sequences were performed on a 3.0 T scanner (Achieva3.0 T, Philips Healthcare, Best, Netherlands) equipped with a standard eight-channel head coil. Standard MRI was performed with the following parameters: (a) Axial T1WI. repetition time (TR)/ echo time (TE)/number of excitations (NEX), 480–500 ms/15 ms/1.00; field of view (FOV), 230 × 183 mm; section thickness, 5 mm with a 1-mm gap; and matrix size, 256 × 204; (b) Axial T2WI. TR/TE/NEX, 4100 ms/110 ms/3.00; FOV, 220 × 210 mm; section thickness, 6 mm with a 1-mm gap; and matrix size, 368 × 286; and (c) Fluid-attenuated inversion recovery (FLAIR). TR/TE/inversion time (TI)/NEX, 6000 ms/120 ms/2000 ms/2.00; FOV, 230 ×200 mm; section thickness, 6 mm with a 1-mm gap; and matrix size, 352 × 184. The SWI parameters were as follows: TR, 25 ms; TE, 35 ms; flip angle, 10°; FOV, 220 ×180 mm; section thickness, 2 mm with no gap; and matrix size, 220 × 180. Directional phase contrast (PC) MRV parameters were as follows: TR, 16 ms; TE, 6.7 ms; interleaved section, 1.8 mm slice thickness and 150 slices; matrix size, 256 × 138; field of view, 230 × 160 mm; flip angle, 20°; bandwidth, 1.263 pix; acquisition time, 7.02 min; and NEX, 1.

Image analysis

All SWI images were post-processed on the workstation using Functool software (PRIDE DWI Tool, version 1.5, Philips Healthcare, Netherlands). Subsequently, high-pass filtered phase and magnitude images as well as images with the minimal intensity projection (MinIP) algorithm were automatically presented. Two neuroradiologists, with a combined experience of approximately 20 years, independently reviewed the SWI images on the Picture Archiving and Communication System. The investigators were blinded to the clinical information, diagnoses, radiology reports, MRV findings, and all other MRI sequences. Evaluation of SWI sequence involved independent analysis of magnitude images (Mags), processed Mags (pMag), and minimum intensity pixel images to prevent recall bias. One MRI vendor refers to pMag images as SWI. To distinguish between the sequence name and one of the three components used in the sequence, we chose the term pMag for SWI.¹⁷

The segments of venous occlusion were assessed systematically on each MRI examination at the following locations: superior sagittal sinus (SSS), inferior sagittal sinus (ISS), left transverse sinus (LTS), right transverse sinus (RTS), left sigmoid sinus (LSS), right sigmoid sinus (RSS), deep venous system (DVS; vein of Galen, internal cerebral veins, or straight sinus), and right CVs (RCVs) or left CVs (LCVs). At each site of thrombosis, the presence of a normal flow void, isointense signal, or hyperintense signal on T1WI, T2WI, FLAIR, and SWI were recorded.

Positive thrombosis was defined as a hyperintense signal on T1WI, T2WI, or FLAIR or as an obvious hypointense signal on SWI. The recognizability of CVT was graded as noticeable, sufficient for diagnosis (2); partially noticeable, but insufficient for diagnosis (1); and unnoticeable (0).

Slow flow and turbulence can lead to false-positive findings; therefore, the following protocol is recommended. perform repeat scanning in multiple planes; combine with PC-MRV or contrast-enhanced MRV to confirm absent flow; and, if necessary, alter the patient’s position or use black-blood thrombus imaging techniques.

Statistical analyses

Statistical analyses were performed using the Statistical Package for Social Sciences (SPSS, version 19.0; SPSS Inc., Chicago, IL, USA). To compare the sensitivity of different MRI sequences for diagnosing CVT across various venous segments and disease stages, the chi-square test was applied for categorical data. A p value of <0.05 was considered statistically significant.

Observer performance in the analysis of MR images was evaluated using a kappa statistic. Interobserver agreement was considered to be slight when the kappa coefficient was <0.21, fair when it was 0.21–0.40, moderate when it was 0.41–0.60, substantial when it was 0.61–0.80, and almost perfect when it was 0.81–1.00.

Results

Patients

Twenty-five patients were included in our study, comprising 15 females and 10 males, with a mean age of 30.18 ± 5.35 (19–68) years. All patients underwent MRV examination and 15 underwent digital subtraction angiography simultaneously. The clinical onset was acute in 9 cases, subacute in 11, and chronic in 5. The clinical symptoms were nonspecific, including varying degrees of headache, vomiting, blurred vision, memory hypomnesis, limb weakness, and disturbance in consciousness. Following treatment, 24 patients achieved complete clinical recovery, and only one patient experienced focal neurological sequelae with recurrent epileptic seizures.

Interobserver agreement

Substantial agreement was observed in the evaluation of lesion distribution (κ = 0.72) and lesion signal (κ = 0.78).

Distribution of venous thrombosis

Among 25 patients, 87 thrombosed venous segments were identified. Of these, 33 segments were in the acute stage, 37 in the subacute stage, and 17 in the chronic stage. Thrombosed segments included the SSS (n = 21), ISS (n = 9), LTS (n = 12), RTS (n = 13), LSS (n = 9), RSS (n = 11), DVS (n = 5), RCV (n = 4), and LCV (n = 3). A single venous site was involved in 4 patients, 2 segments were involved in 5 patients, and ≥3 segments were involved in 16 patients with extensive cerebral venous sinus thrombosis.

Sensitivity of different MRI sequences for various venous segments in different disease stages

The sensitivity of different MRI sequences at varied stages is presented in Figure 1(a). In the acute stage (Figures 2 and 3), the thrombus appeared hypointense on SWI in 94% (31/33) of the segments, hyperintense on T1WI in 39% (13/33), hyperintense on T2WI in 24% (8/33), and hyperintense on FLAIR in 21% (7/33). The results indicate that the sensitivity of SWI was significantly higher than that of T1WI, T2WI, and FLAIR (p < 0.001). In the subacute stage, the thrombosis appeared hypointense on SWI in 54% (20/37) of the segments, hyperintense on T1WI in 78% (29/37), hyperintense on T2WI in 46% (17/37), and hyperintense on FLAIR in 49% (18/37). Statistically significant differences were observed between the four sequences (p = 0.02). The sensitivity of SWI was higher than that of T2WI but lower than that of T1WI. In the chronic stage (Figure 4), the thrombosis appeared hypointense on SWI in 88% (15/17) of the segments, hyperintense on T1WI in 41% (7/17), hyperintense on T2WI in 53% (9/17), and hyperintense on FLAIR in 65% (11/17). The sensitivity of SWI was significantly higher than that of the other sequences (p = 0.04).

Figure 1.

(a) Sensitivity of different MRI sequences at different stages and (b) sensitivity of different MRI sequences at various venous segments. MRI: magnetic resonance imaging.

Figure 2.

A 26-year-old male presented with recurrent headaches for 5 days and convulsions for 2 days. (a) SWI revealed multiple thrombosis in the bilateral CVs (straight black arrows) and hypointensity in the SSS, with bilateral frontal lobe hemorrhages (bent arrows); however, no definite thrombosis was visible on (b) T1WI, (c) T2WI, or (d) FLAIR and (e) MRV confirmed the presence of thrombi in the SSS; however, thrombi in the CVs are difficult to visualize. SWI: susceptibility-weighted imaging; CVs: cortical veins; SSS: superior sagittal sinus; T1WI: T1-weighted imaging; T2WI: T2-weighted imaging; FLAIR: fluid-attenuated inversion recovery; MRV: magnetic resonance venography.

Figure 3.

A 53-year-old male presented with dizziness, headache, and weakness on the right side of the body for 7 days. (a) SWI showed thrombosis in the right CVs (arrow). (b) MinIP SWI showed multiple dilated medullary veins (arrows). The thrombosis in the right CV could not be recognized on other sequences. The SSS thrombosis showed (c) hyperintensity on FLAIR (arrow), (d) slight hyperintensity on T2WI (arrow), and (e) hyperintensity on T1WI (arrow). (f) MRV confirmed thrombosis in the SSS; however, it remained unclear whether there was thrombosis in the right CVs. SWI: susceptibility-weighted imaging; CVs: cortical veins; MinIP: minimal intensity projection; SSS: superior sagittal sinus; FLAIR: fluid-attenuated inversion recovery; T2WI: T2-weighted imaging; T1WI: T1-weighted imaging; MRV: magnetic resonance venography.

Figure 4.

A 61-year-old male presented with a 30-day history of memory decline, with worsening of symptoms over the past 5 days. (a) The thrombosis in the DVS (straight arrow) appeared markedly hypointense on SWI, with symmetrical hemorrhage in the bilateral basal ganglia (curved arrow). (b) MinIP SWI showed multiple dilated medullary veins (arrows). Symmetrical infarctions were visible in the bilateral thalami on (c) T1WI (curved arrows), (d) T2WI (curved arrows), and (e) FLAIR (curved arrows). However, thrombosis was difficult to visualize because it appeared as a hypointense region on (c) T1WI (straight arrow), (d) T2WI (straight arrow), and (e) FLAIR (straight arrow). (f) MRV confirmed the presence of thrombosis in the DVS. DVS: deep venous system; SWI: susceptibility-weighted imaging; MinIP: minimal intensity projection; T1WI: T1-weighted imaging; T2WI: T2-weighted imaging; FLAIR: fluid-attenuated inversion recovery; MRV: magnetic resonance venography.

A comparison of the sensitivity of different MRI sequences at various venous segments is shown in Figure 1(b). In the SSS (Figures 2 and 3), DVS (Figure 4), and CVs (Figures 2 and 3), thrombosis was detected in 81% (17/21), 100% (5/5), and 100% (7/7) of the segments, respectively, on SWI. These values were significantly higher than those obtained using T1WI, T2WI, and FLAIR, with all p values <0.05 (p = 0.02, p = 0.01, and p < 0.001, respectively). However, in the ISS, transverse sinuses (TS), and sigmoid sinus (SS), thrombosis was detected in 44% (4/9), 72% (18/25), and 72% (15/20) of the segments, respectively, on SWI. These results were not significantly different from those obtained using the other three MRI sequences (T1WI, p = 0.44; T2WI, 0.25; and FLAIR, 0.14).

A comparison of the sensitivity of SWI and MRV in detecting CVT across various venous segments is shown in Table 1. MRV demonstrated significantly higher sensitivity than SWI for venous segments in the ISS, TS, and SS, (p = 0.03, p = 0.04, and p = 0.04, respectively); however, SWI showed significantly higher sensitivity in detecting venous segments in the CVs (p = 0.02).

Table 1.

Sensitivity of SWI and MRV across different venous segments.

	SWI	MRV	p value
SSS	81% (17/21)	100% (21/21)	0.1
ISS	44% (4/9)	100% (9/9)	0.03
TS	72% (18/25)	96% (24/25)	0.04
SS	75% (15/20)	100% (20/20)	0.04
DVS	100% (5/5)	80% (4/5)	1
CV	100% (7/7)	23% (3/7)	0.02

SWI: susceptibility-weighted imaging; MRV: magnetic resonance venography; SSS: superior sagittal sinus; ISS: inferior sagittal sinus; TS: transverse sinus; SS: sigmoid sinus; DVS: deep venous system; CV: cortical vein.

Of these patients, 13 had brain parenchymal abnormalities related to the thrombosed venous segments. In total, 34 parenchymal hemorrhage lesions were manifested on SWI, 24 on T1WI, and 22 on T2WI and FLAIR. SWI MinIP revealed expansion of the medullary vein in 10 patients, whereas, only one patient exhibited expansion of the medullary vein on T2WI and FLAIR and none on T1WI.

Discussion

In this study, we comprehensively evaluated the sensitivity of various MRI sequences in detecting CVT across different venous segments and disease stages. Our findings highlight the significant diagnostic value of SWI in acute and chronic stages of CVT. Specifically, SWI demonstrated superior sensitivity in detecting thrombosis in the SSS (p = 0.02), DVS (p = 0.01), and CVs (p < 0.001), achieving 100% sensitivity in the latter two segments. Furthermore, SWI outperformed MRV in evaluating CV thrombosis.^18–20

SWI is based on high–spatial resolution, three-dimensional, fully flow-compensated gradient echo sequences that utilize magnitude and phase information. Similar to T2*-weighted GRE sequences, paramagnetic compounds such as deoxyhemoglobin, intracellular methemoglobin, and hemosiderin act as intrinsic contrast agents to create contrast in SWI.^21–23 However, SWI is more sensitive to susceptibility effects than T2*-weighted GRE sequences and can be displayed using the MinIP algorithm to enhance the visualization of smaller veins.⁷

Our data suggest that SWI is highly sensitive in diagnosing CVT in the early (94%) and chronic (88%) phases. This sensitivity is likely due to the presence of deoxyhemoglobin in the acute phase and hemosiderin in the chronic phase, both of which are strong paramagnetic materials.^24,25 In contrast, during the subacute stage, SWI often shows isointensity or hyperintensity, which may be related to the presence of methemoglobin and diamagnetic methemoglobin, which exhibit very weak susceptibility effects.²⁶ In the subacute stage, T1WI typically shows hyperintensity because of the presence of methemoglobin, providing the highest diagnostic value (78%); however, the signal intensity on T2WI varies, presenting as hypointense in the early subacute stage and hyperintense in the late subacute stage, depending on the state of methemoglobin.

Studies investigating the efficacy of SWI in evaluating venous sinus thrombosis across different stages remain limited. Studies have reported that T2*-weighted GRE sequences have high diagnostic value in acute CVT.^6–8 However, Altinkaya et al. demonstrated that T2*-weighted GRE has no diagnostic value in chronic CVT.⁶ Consistent with these previous reports, in our study, SWI demonstrated the highest sensitivity and accuracy for detecting early-stage CV clots.²⁷

In this study, SWI demonstrated higher sensitivity than the other three sequences in detecting thrombosis in the SSS, DVS, and CVs, reaching 100% in DVS and CVs. Furthermore, SWI remained significantly more sensitive than MRV in evaluating CV thrombosis. These findings suggest that SWI is the most sensitive sequence for detecting CV thrombosis. CV thrombi appear as hypointense signals on SWI, and the venous diameter is usually enlarged and contorted, facilitating diagnosis. In contrast, MRV has difficulty in visualizing small blood vessels due to limitations associated with blood flow rate and orientation. T2*-weighted GRE sequences have been reported to be more valuable than other standard sequences in detecting CV thrombosis.^6–7 However, susceptibility artifacts from the skull base may hinder the assessment of thrombosis in the TS and SSs, resulting in lower sensitivity of SWI compared with that of MRV in the ISS. This limitation may be due to the inability to reconstruct SWI images in a three-dimensional space structure, leading to poor visualization of the ISS.

Additionally, SWI can detect cerebral hemorrhages and enlarged medullary veins. Detecting cerebral hemorrhages is crucial for the treatment and prognosis of CVT, consistent with a recent systematic review reporting that 58.3% of intracranial hemorrhages are fatal.²³ Our study revealed that SWI detected more cerebral hemorrhages than other sequences. It visualized not only deep medullary veins but also small veins with less than 1 pixel.²⁸ We observed dilated medullary veins in 10 of the 25 cases using SWI, demonstrating higher sensitivity than that with other sequences. In some cases, medullary vein expansion is the primary clue for detecting occult CVT.

There are certain limitations in this study. First, the sample size was relatively small, which may limit the generalizability of our findings. Second, the stage of CVT may have been inaccurately determined due to the lack of correspondence between the time of thrombosis occurrence and the onset of clinical symptoms. Moreover, the same patient may present thrombosis at different stages, complicating the analysis. In this study, cases were stratified solely based on symptom onset; a more refined classification method remains to be developed and warrants future investigation. Third, follow-up MRI was not performed; thus, signal changes of thrombosis over time could not be observed.

In conclusion, SWI provides valuable additional diagnostic information for CVT when combined with standard MRI sequences. This study highlights the superior sensitivity of SWI compared with that of other routine MRI sequences in acute and chronic thrombosis, particularly in the SSS, DVS, and CV thrombosis. For patients in the subacute stage, careful evaluation of the T1WI sequence is recommended. Future studies with larger sample sizes and longitudinal follow-up are needed to further validate these findings and explore the full potential of SWI in CVT diagnosis.

Footnotes

Acknowledgments

We express our deepest gratitude to our colleagues from the Department of Radiology at the Guangdong Provincial People’s Hospital for their invaluable assistance in managing the patients.

Author contributions

LZY: conception and design; acquisition, analysis, and interpretation of data; and manuscript drafting. CKY and CXZ: acquisition, analysis, and interpretation of data and manuscript drafting. LHJ: analysis and interpretation of data. YLF: critical revision of the manuscript for important intellectual content. All authors were involved in patient management and manuscript revision and have approved the submitted version of the manuscript.

Data availability statement

The data that support the findings of this study are available from the corresponding author.

Declaration of conflicting interest

The authors declare that there are no conflicts of interest.

Ethics statement

Ethics approval for this case report was not required because of the retrospective nature of the study. Written informed consent was obtained from the patient for the publication of this report.

Funding

This work was supported by the National Natural Scientific Foundation of China (No. 82202095).

ORCID iD

Zhouyang Lian

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