The Diagnostic Value of 3-Dimensional Sampling Perfection With Application Optimized Contrasts Using Different Flip Angle Evolutions (SPACE) MRI in Evaluating Lower Extremity Deep Venous Thrombus

Advanced cerebrospinal fluid flow MRI findings of aqueductal stenosis caused by web

BACKGROUND

The aqueductal web (AW) is one of the causes of aqueductus stenosis (AS). Recent advances in Magnetic resonance (MR) imaging have enabled us to better reveal the cerebrospinal fluid (CSF) flow dynamics and aqueductal anatomy.

PURPOSE

The aim of this study is to evaluate the CSF flow dynamics of patients with AW with phase contrast Magnetic resonance imaging (MRI) and compare them with the imaging findings.

MATERIALS AND METHODS

We evaluated 23 patients under 65-year-old age. On constructive interference in steady-state (T2 CISS) images, the width of prepontine cistern (PPC) and the width of Sylvian aqueduct (SA) were measured. Localization and number of webs were evaluated. The existence of flow at the aqueduct and the presence of spontaneous third ventriculostomy (STV) were evaluated on sagittal Sampling Perfection with Application optimized Contrast (SPACE) sequences.

RESULTS

Of the 23 patients included in the study, 11 were male and 12 were female. The mean age was 34.02 (0.5-64). A total of 31 AWs were detected in 23 patients. Six of 23 patients (26.1%) had STV and 17 of those not. Four of 23 patients (17.4%) had aqueductal flow on SPACE sequences. The PPC distance was significantly wider in patients with STV (median: 6.7-4.5, interquartile range (IQR): 1.35, p = 0.004). In the cases where artifact secondary to flow is observed in SPACE sequences in aqueduct, the Evan index (EI) was significantly lower (median: 0.2955-0.3900, IQR: 0.03-0.14, p < 0.001).

CONCLUSION

In patients with a low EI, there may be flow in the SA even if there is a web. In patients with a wide PPC distance, it is necessary to consider the presence of STV and evaluate the presence of flow with the SPACE sequences.

Pitfall for systemic artery aneurysms evaluation using electrocardiogram-gated subtracted three-dimensional fast spin echo sequence of magnetic resonance imaging in patients with Kawasaki disease

Kawasaki disease (KD) is described as a syndrome that causes both coronary and systemic artery aneurysms (SAAs). This report describes the pitfall for SAAs’ evaluation when using electrocardiogram (ECG)-gated subtracted three-dimensional fast spin echo (3D FSE) sequence of magnetic resonance imaging in KD patients. A 12-year-old male was diagnosed with KD at 3 months of age. We acquired ECG-gated 3D FSE images in the diastole and systole phases with coronal sections. Subtraction was then performed from diastolic phase imaging to systolic phase imaging. A 15.5 mm right axillary artery aneurysm and an 8.0 mm left axillary artery aneurysm were identified with ECG-gated 3D FSE in the diastolic phase. However, we observed signal loss in the right axillary artery aneurysm when subtraction was performed to selectively detect arteries; further, the brachial artery was poorly detected. ECG-gated subtracted 3D FSE sequence of magnetic resonance imaging can compromise the image quality of both aneurysm and peripheral artery images when detecting SAAs.

T1 mapping is useful for staging deep venous thrombosis in the lower extremities

BACKGROUND

The discrimination of acute and chronic deep venous thrombosis (DVT) is of great importance. Quantitative imaging is an urgent requirement in reflecting intrinsic characteristics of thrombosis.

PURPOSE

To investigate the feasibility of T1 mapping in staging DVT in the lower extremities.

MATERIAL AND METHODS

A total of 57 patients with DVT in the lower extremities (26 men, 31 women; mean age = 53.3 years) underwent T1-weighted imaging and T1 mapping for obtaining T1 signal intensity (SI) and T1 time of thrombus. The relative SI (rSI) of DVT was obtained by calculating the ratio of thrombus SI to muscle SI. The Mann-Whitney U test was used to compare rSI and T1 time of DVT between acute group (patients with limb edema ≤ 2 weeks) and chronic group (patients with limb edema > 2 weeks). A receiver operator characteristic (ROC) curve was constructed for further evaluation.

RESULTS

DVT rSI was significantly higher in the acute group versus the chronic group (2.8 ± 1.2 vs. 1.4 ± 0.6; P<0.05). DVT T1 time was significantly lower in the acute group versus the chronic group (819.4 ± 223.7 ms vs. 1264.8 ± 270.7 ms; P<0.05). The area under the curve (AUC) was 0.93 for T1 time and 0.75 for rSI. When using 1015 ms as the cut-off, the sensitivity and specificity of T1 time were 91% (32/35) and 86% (19/22), respectively.

CONCLUSION

T1 mapping is a potential technique in discriminating acute from chronic DVT in the lower extremities and warrants further investigation.

Comparison Between the Diagnostic Performance of 1.5 T and 3.0 T field Strengths for Detecting Deep Vein Thrombosis Using Magnetic Resonance Black-Blood Thrombus Imaging

BACKGROUND

Magnetic resonance (MR) black-blood thrombus imaging (BTI) is an accurate diagnostic technique for detecting deep vein thrombosis (DVT) but to date there have been no studies comparing the diagnostic performance and consistency of this technique at different field strengths. In this study, we evaluated and compared the diagnostic performance of BTI for detecting DVT at 1.5 T and 3.0 T field strengths.

METHODS

A total of 40 patients with DVT were enrolled in this study from November 2015 up to October 2018. All patients underwent BTI, a contrast-free T1-weighted MR imaging technique for detecting DVT, and contrast-enhanced MR venography (CE-MRV) at 1.5 T or 3.0 T field strengths. The MR data analyses used 1160 segments from the venous lumen of the 40 patients. The signal-to-noise ratio and contrast-to-noise ratio between thrombus and muscle/lumen were calculated to compare BTI at 1.5 T or 3.0 T to determine the image performance for thrombus detection at 1.5 T or 3.0 T. Two physicians blinded to the study evaluated all BTI images and calculated the overall sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV), accuracy, and diagnostic consistency at 1.5 T and 3.0 T. These images and values were compared to control CE-MRV images that had been obtained by 2 senior physicians and used as reference standards. In addition, the reliability and consistency of diagnoses between observers were also evaluated.

RESULTS

Two study-blind physicians reviewed all BTI images to diagnose thrombus and to determine SE, SP, PPV, NPV, and accuracy. There were no statistical differences in SE, SP, PPV, NPV, or accuracy between the 1.5 T and 3.0 T groups.

CONCLUSIONS

Black-blood thrombus imaging has high SE, SP, and accuracy for DVT diagnosis both at 1.5 T and 3.0 T field strengths. This noninvasive diagnostic technique, which does not require the use of contrast agents, can be widely used in the clinical screening of DVT and follow-up after treatment.

Time-efficient and contrast-free magnetic resonance imaging approach to the diagnosis of deep vein thrombosis on black-blood gradient-echo sequence: a pilot study

Background

Black-blood thrombus imaging (BTI) has shown to be advantageous for the diagnosis of deep vein thrombosis (DVT). However, previous techniques using fast spin echo have a high specific absorption rate. As DANTE (delay alternating with nutation for tailored excitation) black-blood preparation can suppress blood flows over a broad range of velocities, we hypothesized that a DANTE black-blood preparation combined with a fast low-angle shot (FLASH) gradient-echo readout-DANTE-FLASH could be used to diagnose DVT.

Methods

Eleven healthy volunteers and 30 suspected DVT patients were recruited to undergo DANTE-FLASH and magnetic resonance direct thrombus imaging (MRDTI). The suspected DVT patients were also examined by ultrasound (US). For the segment level, a total of 1,066 venous vessel segments were analyzed. Using US and MRDTI as the references, the sensitivity (SE), specificity (SP), positive and negative predictive values (PPV and NPV), and accuracy (ACC) of DANTE-FLASH were calculated. To quantitatively compare image quality between DANTE-FLASH and MRDTI, image signal-to-noise ratio (SNR), apparent contrast-to-noise ratio (CNR) between muscle and the venous lumen, and the apparent CNR between the thrombus and venous lumen were measured. Additionally, diagnostic confidence, image quality, and clot burden were also evaluated.

Results

Using the consensus results of US and MRDTI as a standard reference, the diagnostic SE, SP, PPV, NPV, and ACC of DANTE-FLASH for the 2 readers were 97.0% and 93.2%, 99.0% and 98.2%, 93.4% and 87.9%, 99.6% and 99.0%, and 98.8% and 97.6%, respectively. According to the image quantitative analysis results, DANTE-FLASH demonstrated higher image SNR and CNR than MRDTI. The image quality and diagnostic confidence scores of DANTE-FLASH were higher than MRDTI (3.66±0.44 vs. 3.52±0.52, P<0.001, and 3.84±0.36 vs. 3.76±0.41, P<0.001). There was excellent agreement between DANTE-FLASH and MRDTI on clot burden evaluation.

Conclusions

DANTE-FLASH provided better image quality than MRDTI and accurately detected thrombi. It may, therefore, serve as a safe and convenient alternative for the diagnosis of DVT.

Feeding arteries and arteriovenous shunt for discrimination of soft tissue tumors

Time resolved magnetic resonance angiography with interleaved stochastic trajectories (TWIST) allows for identification of tumor feeding arteries and arteriovenous shunt (AVS). We used TWIST to obtain number of feeding arteries (NFA) and detect AVS for 43 cases of pathology-confirmed soft tissue tumors. We compared normalized number of feeding arteries (nNFA) and AVS between malignant and benign tumors, and found nNFA was significantly greater in malignant tumors versus benign tumors (2.1 vs 1.3, P < .05). The incidence of AVS was significantly higher in malignant tumors versus benign tumors (87.5% vs 10.5%, P < .05). TWIST derived nNFA and AVS could be useful in the discrimination of benign and malignant soft tissue tumors.