Post-contrast 3D T1-weighted TSE MR sequences (SPACE, CUBE, VISTA/BRAINVIEW, isoFSE, 3D MVOX): Technical aspects and clinical applications

Pearls and Pitfalls of T1-Weighted Neuroimaging: A Primer for the Clinical Radiologist

All T1-weighted images are built upon one of two fundamental pulse sequences, spin-echo and gradient echo, each of which has distinct signal characteristics and clinical applications. Moreover, within each broadly defined category of T1-weighting, acquisition parameters can be modified to affect image quality, contrast, and scan duration; each tailored sequence has unique advantages, drawbacks, clinical indications, and potential artifacts. In this review, we describe key features that distinguish different types of T1-weighted sequences and discuss the utility of each sequence for specific clinical settings, including neuro-oncology, vasculopathy, and pediatric neuroradiology. In addition, we provide case examples from our institution that illustrate common artifacts and pitfalls associated with image interpretation. The findings described herein provide a framework to individualize the imaging protocol based on patient presentation and clinical indication.

Efficacy of 3D-TSE sequence-based radiosurgery in prolonging time to distant intracranial failure: A session-wise analysis in a histology-diverse patient cohort

BACKGROUND

Stereotactic radiosurgery (SRS) for patients with brain metastases (BM) is associated with a risk of distant intracranial failure (DIF). This study evaluates the impact of integrating dedicated 3D fast/turbo spin echo (3D-TSE) sequences to MPRAGE in BM detection and DIF prolongation in a histology-agnostic patient cohort.

METHODS

The study population included adults treated with SRS from February 2019 to January 2024 who underwent MPRAGE alone or dual sequence with the addition of 3D-TSE starting from February 2020. Median times to DIF were estimated using the Kaplan-Meier method.

RESULTS

The 216 study patients who underwent 332 SRS courses for 1456 BM imaged with MPRAGE and 3D-TSE (primary cohort) were compared to a control cohort (92 patients, 135 SRS courses, 462 BM). In the session-wise analysis, the median time to DIF between the cohorts was significantly prolonged in the primary vs. control cohorts (11.4 vs. 6.8 months, P = .029), more pronounced in the subgroups with 1-4 metastases (14.7 vs. 8.1 months, P = .008) and with solitary BM (36.4 vs. 10.9 months, P = .001). While patients relapsing on immunotherapy or targeted therapy did not significantly benefit from 3D-TSE (7.2 vs. 5.7 months, P = .280), those who relapsed on chemotherapy or who were off systemic therapy (including synchronous metastases) exhibited a trend toward longer time to DIF with 3D-TSE integration (14.7 vs. 7.9 months, P = .057).

CONCLUSIONS

Implementing 3D-TSE sequences into SRS practice increases BM detection across all patients and translates into clinical relevance by prolonging time to DIF, particularly in those with limited intracranial disease and those not receiving central nervous system-active agents.

Technical note: Enhanced radiosurgical planning for cavernous sinus tumors using T1 SPACE sequences with Motion-Sensitized Driven Equilibrium (MSDE)

BACKGROUND AND OBJECTIVE

Radiosurgery can serve as a primary, adjuvant, or salvage treatment modality for cavernous sinus tumors (CST), providing high tumor control. However, particularly with cavernous sinus expansion, there may be insufficient distance from the optic apparatus to perform radiosurgery safely. The internal carotid artery adjacent to the distal dural ring (ICAddr), when enhancing similarly to the CST, can be difficult to delineate, and can lead to over-contouring of target volume near the optic nerve and therefore increasing the risk of radiation-induced optic toxicity. To evaluate the efficacy and safety of 3D T1-weighted Turbo Spin-Echo (TSE) MR sequence with the Motion-Sensitized Driven Equilibrium (MSDE) technique in accurately delineating the internal carotid artery adjacent to the distal dural ring (ICAddr) to minimize the risk of radiation-induced optic toxicity during radiosurgery for cavernous sinus tumors (CST).

METHODS

Nine patients were treated for CST with Gamma Knife radiosurgery from 2021 to 2023, utilizing a 3D T1-weighted Turbo Spin-Echo (TSE) MR sequence with the Motion-Sensitized Driven Equilibrium (MSDE) technique. Improved delineation of the ICAddr from the lesion facilitated precise dosimetry near the optic nerve.

RESULTS

At a median follow-up of 15 months, all patients demonstrated stable disease with no reported tumor progression. The use of the T1-weighted TSE MR sequence with MSDE significantly improved the delineation of the ICAddr from the cavernous sinus tumors. Only one patient experienced a transient episode of diplopia. No additional visual deficits were reported.

CONCLUSION

The use of T1 SPACE sequence has enhanced the radiosurgical planning process for CST, allowing for more precise contouring of the lesion near the ICAddr and optic nerve and reducing radiation dose to the ipsilateral optic nerve. Integration of these techniques into standard practice may offer significant benefits for the radiosurgical management of CST.

High-resolution magnetic resonance vessel wall imaging in extracranial cervical artery dissection

Extracranial cervical artery dissection (eCAD) is the second leading cause of stroke in young and middle-aged adults. Clinical management strategies for eCAD are continuously being explored and optimized, as revealed by the recently published CADISS and TREAT-CAD studies. The type of drug, dosage, and timing of administration can affect the regression of carotid artery dissection and the risk of recurrence of stroke. Based on imaging evidence, it is important to develop individualized treatment strategies for different risk groups. Currently, High-resolution magnetic resonance vessel wall imaging (MR-VWI) technology has made significant progress in the qualitative diagnosis of eCAD, vascular lesion progression, and the assessment of recurring ischemic stroke risk. To better understand the pathogenesis and progression of eCAD using MR-VWI, a comprehensive review is presented here.

Deep Learning-Based Signal Amplification of T1-Weighted Single-Dose Images Improves Metastasis Detection in Brain MRI

OBJECTIVES

Double-dose contrast-enhanced brain imaging improves tumor delineation and detection of occult metastases but is limited by concerns about gadolinium-based contrast agents' effects on patients and the environment. The purpose of this study was to test the benefit of a deep learning-based contrast signal amplification in true single-dose T1-weighted (T-SD) images creating artificial double-dose (A-DD) images for metastasis detection in brain magnetic resonance imaging.

MATERIALS AND METHODS

In this prospective, multicenter study, a deep learning-based method originally trained on noncontrast, low-dose, and T-SD brain images was applied to T-SD images of 30 participants (mean age ± SD, 58.5 ± 11.8 years; 23 women) acquired externally between November 2022 and June 2023. Four readers with different levels of experience independently reviewed T-SD and A-DD images for metastases with 4 weeks between readings. A reference reader reviewed additionally acquired true double-dose images to determine any metastases present. Performances were compared using Mid-p McNemar tests for sensitivity and Wilcoxon signed rank tests for false-positive findings.

RESULTS

All readers found more metastases using A-DD images. The 2 experienced neuroradiologists achieved the same level of sensitivity using T-SD images (62 of 91 metastases, 68.1%). While the increase in sensitivity using A-DD images was only descriptive for 1 of them (A-DD: 65 of 91 metastases, +3.3%, P = 0.424), the second neuroradiologist benefited significantly with a sensitivity increase of 12.1% (73 of 91 metastases, P = 0.008). The 2 less experienced readers (1 resident and 1 fellow) both found significantly more metastases on A-DD images (resident, T-SD: 61.5%, A-DD: 68.1%, P = 0.039; fellow, T-SD: 58.2%, A-DD: 70.3%, P = 0.008). They were therefore able to use A-DD images to increase their sensitivity to the neuroradiologists' initial level on regular T-SD images. False-positive findings did not differ significantly between sequences. However, readers showed descriptively more false-positive findings on A-DD images. The benefit in sensitivity particularly applied to metastases ≤5 mm (5.7%-17.3% increase in sensitivity).

CONCLUSIONS

A-DD images can improve the detectability of brain metastases without a significant loss of precision and could therefore represent a potentially valuable addition to regular single-dose brain imaging.

Stereotactic radiosurgery for 1-10 brain metastases to avoid whole-brain radiotherapy: Results of the CYBER-SPACE randomized phase 2 trial

BACKGROUND

Stereotactic radiosurgery (SRS) is an emerging alternative to whole-brain radiotherapy (WBRT) for treating multiple brain metastases (BM), reducing toxicity, and improving tumor control. The CYBER-SPACE trial compared SRS based on either SPACE or MPRAGE MRI sequence for avoiding or delaying WBRT in patients with 1-10 BM.

METHODS

Patients with 1-10 untreated BM were randomized 1:1 to receive SRS of all lesions based on either SPACE or MPRAGE MRI sequences. If subsequently new BM occurred, SRS was repeated. WBRT was indicated upon occurrence of >10 new BM, leptomeningeal disease, or exhausted SRS-radiotolerance. The primary outcome was freedom from WBRT indication (WBRTi). Secondary outcomes included overall survival (OS), safety, and quality of life.

RESULTS

A total of 202 patients were randomized; SPACE n = 99, MPRAGE n = 103. Twelve-month WBRTi-free survival was 77.1% (95% CI: 69.5%-83.1%) overall, 78.5% (95% CI: 66.7%-86.5%) for SPACE, and 76.0% (95% CI: 65.2%-83.9%) for MPRAGE (hazard ratio [HR] = 0.84, 95% CI: 0.43-1.63, P = .590). Patients with 5-10 BM had shorter WBRTi-free survival (HR = 3.13, 95% CI: 1.53-6.40, P = .002). Median OS was 13.1 months overall, 10.5 months for SPACE, and 15.2 months for MPRAGE (HR = 1.10, 95% CI: 0.78-1.56, P = .585). Neurologic death rate was 10.1%. Predictors for longer OS included Karnofsky Performance Status >80% (HR = 0.51, 95% CI: 0.33-0.77, P = .002) and concurrent immunotherapy (HR = 0.34, 95% CI: 0.23-0.52, P < .001).

CONCLUSIONS

The more sensitive SPACE sequence did not improve outcomes over MPRAGE. SRS with thorough monitoring and immediate re-treatment for new lesions decreases the need for WBRT and achieves low neurologic death rates. SRS should be considered a favorable alternative to WBRT for patients with 1-10 BM.

Enhancing deep learning methods for brain metastasis detection through cross-technique annotations on SPACE MRI

BACKGROUND

Gadolinium-enhanced "sampling perfection with application-optimized contrasts using different flip angle evolution" (SPACE) sequence allows better visualization of brain metastases (BMs) compared to "magnetization-prepared rapid acquisition gradient echo" (MPRAGE). We hypothesize that this better conspicuity leads to high-quality annotation (HAQ), enhancing deep learning (DL) algorithm detection of BMs on MPRAGE images.

METHODS

Retrospective contrast-enhanced (gadobutrol 0.1 mmol/kg) SPACE and MPRAGE data of 157 patients with BM were used, either annotated on MPRAGE resulting in normal annotation quality (NAQ) or on coregistered SPACE resulting in HAQ. Multiple DL methods were developed with NAQ or HAQ using either SPACE or MRPAGE images and evaluated on their detection performance using positive predictive value (PPV), sensitivity, and F1 score and on their delineation performance using volumetric Dice similarity coefficient, PPV, and sensitivity on one internal and four additional test datasets (660 patients).

RESULTS

The SPACE-HAQ model reached 0.978 PPV, 0.882 sensitivity, and 0.916 F1-score. The MPRAGE-HAQ reached 0.867, 0.839, and 0.840, the MPRAGE NAQ 0.964, 0.667, and 0.798, respectively (p ≥ 0.157). Relative to MPRAGE-NAQ, the MPRAGE-HAQ F1-score detection increased on all additional test datasets by 2.5-9.6 points (p < 0.016) and sensitivity improved on three datasets by 4.6-8.5 points (p < 0.001). Moreover, volumetric instance sensitivity improved by 3.6-7.6 points (p < 0.001).

CONCLUSION

HAQ improves DL methods without specialized imaging during application time. HAQ alone achieves about 40% of the performance improvements seen with SPACE images as input, allowing for fast and accurate, fully automated detection of small (< 1 cm) BMs.

RELEVANCE STATEMENT

Training with higher-quality annotations, created using the SPACE sequence, improves the detection and delineation sensitivity of DL methods for the detection of brain metastases (BMs)on MPRAGE images. This MRI cross-technique transfer learning is a promising way to increase diagnostic performance.

KEY POINTS

Delineating small BMs on SPACE MRI sequence results in higher quality annotations than on MPRAGE sequence due to enhanced conspicuity. Leveraging cross-technique ground truth annotations during training improved the accuracy of DL models in detecting and segmenting BMs. Cross-technique annotation may enhance DL models by integrating benefits from specialized, time-intensive MRI sequences while not relying on them. Further validation in prospective studies is needed.

Improved detection of brain metastases using contrast-enhanced 3D black-blood TSE sequences compared to post-contrast 3D T1 GRE: a comparative study on 1.5-T MRI

OBJECTIVES

Brain metastases are the most common intracranial malignancy in adults, and their detection is crucial for treatment planning. Post-contrast 3D T1 gradient-recalled echo (GRE) sequences are commonly used for this purpose, but contrast-enhanced 3D T1 turbo spin-echo (TSE) sequences with motion-sensitized driven-equilibrium (MSDE) technique ("black blood") may offer improved detection. This study aimed to compare the effectiveness of contrast-enhanced 3D black blood sequences to standard 3D T1 GRE sequences in detecting brain metastases on a 1.5-T MRI.

MATERIALS AND METHODS

A retrospective analysis of 183 patients with suspected or follow-up brain metastases between May 2022 and September 2023 was conducted. Among these patients, 107 were included in the final analysis. Both post-contrast 3D T1 GRE and 3D black blood sequences were acquired on the same scanner with similar acquisition times. Two neuroradiologists independently evaluated the images for the number, size, and location of metastases. Interobserver variability and statistical analysis were performed.

RESULTS

Among the 107 patients (mean age 60.8 years ± 13.2 years; 55 males, 52 females), 3D black blood sequences detected a significantly higher number of brain metastases, particularly small lesions (< 5 mm), compared to 3D T1 GRE sequences (p < 0.05). There was no significant difference in detecting large metastases (≥ 5 mm) between the sequences. In addition, the black blood sequences provided better conspicuity of metastases in the majority of patients (85%).

CONCLUSION

Contrast-enhanced 3D T1 TSE with MSDE ("black blood") sequences offer improved detection of brain metastases, especially small lesions, on 1.5-T MRI compared to standard 3D T1 GRE sequences.

KEY POINTS

Question Accurate identification of the number and location of brain metastases using MRI is essential for planning and managing effective treatment. Findings Contrast-enhanced 3D T1 TSE black blood sequences detected significantly more small brain metastases than standard 3D T1 GRE sequences on 1.5-T MRI. Clinical relevance The use of 3D black blood sequences on 1.5-T MRI may have the potential to improve the accuracy of detection of brain metastases, leading to better treatment planning and potentially improved patient outcomes.

Comparison between contrast-enhanced fat-suppressed 3D FLAIR brain MR images and T2-weighted orbital MR images at 3 Tesla for the diagnosis of acute optic neuritis

PURPOSE

The purpose of this study was to compare the capabilities of contrast-enhanced fat-suppressed (CE FS) three-dimensional fluid-attenuated inversion recovery (3D FLAIR) brain magnetic resonance imaging (MRI) with those of coronal T2-weighted orbital MRI obtained at 3 Tesla for the diagnosis of optic neuritis (ON).

MATERIALS AND METHODS

Patients who presented to our center with acute visual loss and underwent MRI examination of the orbits and the brain between November 2014 and February 2020 were retrospectively included. Three radiologists independently and blindly analyzed CE FS 3D FLAIR and coronal T2-weighted images. Disagreements in image interpretation were resolved by consensus with an independent neuroradiologist who was not involved in the initial reading sessions. The primary adjudication criterion for the diagnosis of ON was the presence of an optic nerve hypersignal. Sensitivity, specificity, and accuracy of CE 3D FLAIR brain images were compared with those of coronal T2-weighted orbital images using McNemar test. Artifacts were classified into three categories and compared between the two image sets.

RESULTS

A total of 1023 patients were included. There were 638 women and 385 men with a mean age of 42 ± 18.3 (standard deviation) years (age range: 6-92 years). Optic nerve hyperintensities were identified in 375/400 (94%) patients with ON using both 3D FLAIR and coronal T2-weighted images. Sensitivity, specificity, and accuracy of both sequences were 94% (95% CI: 91.3-96.1), 79% (95% CI: 75.5-82.2), and 89% (95% CI: 86.8-90.7), respectively. Optic disc hypersignal was detected in 120/400 patients (30%) using 3D FLAIR compared to 3/400 (0.75%) using coronal T2-weighted images (P < 0.001). Optic radiation hypersignal was observed in 2/400 (0.5%) patients using 3D FLAIR images. Significantly more artifacts (moderate or severe) were observed on coronal T2-weighted images (801/1023; 78%) by comparison with 3D FLAIR images (448/1023; 44%) (P < 0.001).

CONCLUSION

The performance of 3D FLAIR brain MRI for the diagnosis of ON is not different from that of coronal T2-weighted orbital MRI and its use for optic nerve analysis may be beneficial.

Contrast-enhanced 3D black-blood magnetic resonance imaging for diagnosis of cerebral venous thrombosis

PURPOSE

Cerebral venous thrombosis (CVT) is often under-recognized on routine magnetic resonance imaging (MRI) examinations without concomitant magnetic resonance venography (MRV). Contrast-enhanced black-blood MRI (BBMRI) based on a three-dimensional T1-weighted variable-flip-angle turbo spin echo sequence, one of the sequences used routinely in our practice, has the potential for detection of thrombi in patients with CVT. The aim of this study is to evaluate the diagnostic performance and enhancement patterns of contrast-enhanced three-dimensional BBMRI for the diagnosis of CVT.

MATERIALS AND METHODS

Contrast-enhanced BBMRI and contrast-enhanced MRV sequences of 64 patients, acquired from June 2018 to January 2021, were retrospectively reviewed by neuroradiologists for detection of CVT in each venous sinus segment. Diagnostic performance values were calculated for contrast-enhanced BBMRI based on enhancement patterns.

RESULTS

Of 749 venous segments from 64 patients analyzed, CVT was demonstrated in 41 venous segments from 12 patients on contrast-enhanced MRV (CE MRV). Thick wall enhancement and total enhancement patterns were dominantly demonstrated in thrombosed segments. Compared with contrast-enhanced MRV, contrast-enhanced BBMRI had a patient-based sensitivity and specificity of 100% and 98.1%, respectively, and a segment-based sensitivity and specificity of 87.8% and 96.2%, respectively. The positive predictive value of contrast-enhanced BBMRI in detecting CVT was 92.3% (patient-based) and 57.1% (segment-based), and the negative predictive value was 100% (patient-based) and 99.3% (segment-based).

CONCLUSION

Contrast-enhanced BBMRI has high diagnostic performance in detection and diagnosis of CVT. This sequence may be useful to recognize CVT when dedicated CE MRV was not performed in patients with nonspecific neurological symptoms.

Design of calibration-free RF pulses for T 2 $$ {}_2 $$ -weighted single-slab 3D turbo-spin-echo sequences at 7T utilizing parallel transmission

PURPOSE

T  2 $$ {}_2 $$ -weighted turbo-spin-echo (TSE) sequences are a fundamental technique in brain imaging but suffer from field inhomogeneities at ultra-high fields. Several methods have been proposed to mitigate the problem, but were limited so far to nonselective three-dimensional (3D) measurements, making short acquisitions difficult to achieve when targeting very high resolution images, or needed additional calibration procedures, thus complicating their application.

METHODS

Slab-selective excitation pulses were designed for flexible placement utilizing the concept of k  T $$ {}_T $$ -spokes. Phase-coherent refocusing universal pulses were subsequently optimized with the Gradient Ascent Pulse Engineering algorithm and tested in vivo for improved signal homogeneity.

RESULTS

Implemented within a 3D variable flip angle TSE sequence, these pulses led to a signal-to-noise ratio (SNR) improvement ranging from 10% to 30% compared to a two-dimensional (2D) T2w TSE sequence employingB 1 + $$ {\mathrm{B}}_1^{+} $$ -shimmed pulses.B 1 + $$ {\mathrm{B}}_1^{+} $$ field inhomogeneities could be mitigated and artifacts fromB 0 $$ {\mathrm{B}}_0 $$ deviations reduced. The concept of universal pulses was successfully applied.

CONCLUSION

We present a pulse design method which provides a set of calibration-free universal pulses (UPs) for slab-selective excitation and phase-coherent refocusing in slab-selective TSE sequences.

Quantitative brain T1 maps derived from T1-weighted MRI acquisitions: a proof-of-concept study

BACKGROUND

Longitudinal T1 relaxation time is a key imaging biomarker. In addition, T1 values are modulated by the administration of T1 contrast agents used in patients with tumors and metastases. However, in clinical practice, dedicated T1 mapping sequences are often not included in brain MRI protocols. The aim of this study is to address the absence of dedicated T1 mapping sequences in imaging protocol by deriving T1 maps from standard T1-weighted sequences.

METHODS

A phantom, composed of 144 solutions of paramagnetic agents at different concentrations, was imaged with a three-dimensional (3D) T1-weighed turbo spin-echo (TSE) sequence designed for brain imaging. The relationship between the T1 values and the signal intensities was established using this phantom acquisition. T1 mapping derived from 3D T1-weighted TSE acquisitions in four healthy volunteers and one patient with brain metastases were established and compared to reference T1 mapping technique. The concentration of Gd-based contrast agents in brain metastases were assessed from the derived T1 maps.

RESULTS

Based on the phantom acquisition, the relationship between T1 values and signal intensity (SI) was found equal to T1 = 0.35 × SI-1.11 (R2 = 0.97). TSE-derived T1 values measured in white matter and gray matter in healthy volunteers were equal to 0.997 ± 0.096 s and 1.358 ± 0.056 s (mean ± standard deviation), respectively. Mean Gd3+ concentration value in brain metastases was 94.7 ± 30.0 μM.

CONCLUSION

The in vivo results support the relevance of the phantom-based approach: brain T1 maps can be derived from T1-weighted acquisitions.

RELEVANCE STATEMENT

High-resolution brain T1 maps can be generated, and contrast agent concentration can be quantified and imaged in brain metastases using routine 3D T1-weighted TSE acquisitions.

KEY POINTS

Quantitative T1 mapping adds significant value to MRI diagnostics. T1 measurement sequences are rarely included in routine protocols. T1 mapping and concentration of contrast agents can be derived from routine standard scans. The diagnostic value of MRI can be improved without additional scan time.

Pushing MP2RAGE boundaries: Ultimate time-efficient parameterization combined with exhaustive T1 synthetic contrasts

PURPOSE

MP2RAGE parameter optimization is redefined to allow more time-efficient MR acquisitions, whereas the T1 -based synthetic imaging framework is used to obtain on-demand T1 -weighted contrasts. Our aim was to validate this concept on healthy volunteers and patients with multiple sclerosis, using plug-and-play parallel-transmission brain imaging at 7 T.

METHODS

A "time-efficient" MP2RAGE sequence was designed with optimized parameters including TI and TR set as small as possible. Extended phase graph formalism was used to set flip-angle values to maximize the gray-to-white-matter contrast-to-noise ratio (CNR). Several synthetic contrasts (UNI, EDGE, FGATIR, FLAWSMIN , FLAWSHCO ) were generated online based on the acquired T1 maps. Experimental validation was performed on 4 healthy volunteers at various spatial resolutions. Clinical applicability was evaluated on 6 patients with multiple sclerosis, scanned with both time-efficient and conventional MP2RAGE parameterizations.

RESULTS

The proposed time-efficient MP2RAGE protocols reduced acquisition time by 40%, 30%, and 19% for brain imaging at (1 mm)3 , (0.80 mm)3 and (0.65 mm)3 , respectively, when compared with conventional parameterizations. They also provided all synthetic contrasts and comparable contrast-to-noise ratio on UNI images. The flexibility in parameter selection allowed us to obtain a whole-brain (0.45 mm)3 acquisition in 19 min 56 s. On patients with multiple sclerosis, a (0.67 mm)3 time-efficient acquisition enhanced cortical lesion visualization compared with a conventional (0.80 mm)3 protocol, while decreasing the scan time by 15%.

CONCLUSION

The proposed optimization, associated with T1 -based synthetic contrasts, enabled substantial decrease of the acquisition time or higher spatial resolution scans for a given time budget, while generating all typical brain contrasts derived from MP2RAGE.

Use of gadolinium-based contrast agents in multiple sclerosis: a review by the ESMRMB-GREC and ESNR Multiple Sclerosis Working Group

Magnetic resonance imaging (MRI) is the most sensitive technique for detecting inflammatory demyelinating lesions in multiple sclerosis (MS) and plays a crucial role in diagnosis and monitoring treatment effectiveness, and for predicting the disease course. In clinical practice, detection of MS lesions is mainly based on T2-weighted and contrast-enhanced T1-weighted sequences. Contrast-enhancing lesions (CEL) on T1-weighted sequences are related to (sub)acute inflammation, while new or enlarging T2 lesions reflect the permanent footprint from a previous acute inflammatory demyelinating event. These two types of MRI features provide redundant information, at least in regular monitoring of the disease. Due to the concern of gadolinium deposition after repetitive injections of gadolinium-based contrast agents (GBCAs), scientific organizations and regulatory agencies in Europe and North America have proposed that these contrast agents should be administered only if clinically necessary. In this article, we provide data on the mode of action of GBCAs in MS, the indications of the use of these agents in clinical practice, their value in MS for diagnostic, prognostic, and monitoring purposes, and their use in specific populations (children, pregnant women, and breast-feeders). We discuss imaging strategies that achieve the highest sensitivity for detecting CELs in compliance with the safety regulations established by different regulatory agencies. Finally, we will briefly discuss some alternatives to the use of GBCA for detecting blood-brain barrier disruption in MS lesions. CLINICAL RELEVANCE STATEMENT: Although use of GBCA at diagnostic workup of suspected MS is highly valuable for diagnostic and prognostic purposes, their use in routine monitoring is not mandatory and must be reduced, as detection of disease activity can be based on the identification of new or enlarging lesions on T2-weighted images. KEY POINTS: • Both the EMA and the FDA state that the use of GBCA in medicine should be restricted to clinical scenarios in which the additional information offered by the contrast agent is required. • The use of GBCA is generally recommended in the diagnostic workup in subjects with suspected MS and is generally not necessary for routine monitoring in clinical practice. • Alternative MRI-based approaches for detecting acute focal inflammatory MS lesions are not yet ready to be used in clinical practice.

Review of strategies to reduce the contamination of the water environment by gadolinium-based contrast agents

Gadolinium-based contrast agents (GBCA) are essential for diagnostic MRI examinations. GBCA are only used in small quantities on a per-patient basis; however, the acquisition of contrast-enhanced MRI examinations worldwide results in the use of many thousands of litres of GBCA per year. Data shows that these GBCA are present in sewage water, surface water, and drinking water in many regions of the world. Therefore, there is growing concern regarding the environmental impact of GBCA because of their ubiquitous presence in the aquatic environment. To address the problem of GBCA in the water system as a whole, collaboration is necessary between all stakeholders, including the producers of GBCA, medical professionals and importantly, the consumers of drinking water, i.e. the patients. This paper aims to make healthcare professionals aware of the opportunity to take the lead in making informed decisions about the use of GBCA and provides an overview of the different options for action.In this paper, we first provide a summary on the metabolism and clinical use of GBCA, then the environmental fate and observations of GBCA, followed by measures to reduce the use of GBCA. The environmental impact of GBCA can be reduced by (1) measures focusing on the application of GBCA by means of weight-based contrast volume reduction, GBCA with higher relaxivity per mmol of Gd, contrast-enhancing sequences, and post-processing; and (2) measures that reduce the waste of GBCA, including the use of bulk packaging and collecting residues of GBCA at the point of application.Critical relevance statement This review aims to make healthcare professionals aware of the environmental impact of GBCA and the opportunity for them to take the lead in making informed decisions about GBCA use and the different options to reduce its environmental burden.Key points• Gadolinium-based contrast agents are found in sources of drinking water and constitute an environmental risk.• Radiologists have a wide spectrum of options to reduce GBCA use without compromising diagnostic quality.• Radiology can become more sustainable by adopting such measures in clinical practice.

Noninvasive investigations of human glymphatic dynamics in a diseased model

OBJECTIVES

To explore human glymphatic dynamics in a diseased model via a noninvasive technique.

METHODS

Patients with reversible vasoconstriction syndrome (RCVS) presenting with blood-brain barrier disruption, i.e., para-arterial gadolinium leakage on 3-T 3-dimensional isotropic contrast-enhanced T2-fluid-attenuated inversion recovery (CE-T2-FLAIR) magnetic resonance imaging (MRI), were prospectively enrolled. Consecutive 9-min-CE-T2-FLAIR for 5-6 times (early panel) after intravenous gadolinium-based contrast agent (GBCA) administration and one time-varying deferred scan of noncontrast T2-FLAIR (delayed panel) were performed. In Bundle 1, we measured the calibrated signal intensities (cSIs) of 10 different anatomical locations. In Bundle 2, brain-wide measurements of para-arterial glymphatic volumes, means, and medians of the signal intensities were conducted. We defined mean (mCoIs) or median (mnCoIs) concentration indices as products of volumes and signal intensities.

RESULTS

Eleven subjects were analyzed. The cSIs demonstrated early increase (9 min) in perineural spaces: (cranial nerve [CN] V, p = 0.008; CN VII + VII, p = 0.003), choroid plexus (p = 0.003), white matter (p = 0.004) and parasagittal dura (p = 0.004). The volumes, mCoIs, and mnCoIs demonstrated increasing rates of enhancement after 9 to 18 min and decreasing rates after 45 to 54 min. The GBCA was transported centrifugally and completely removed within 961-1086 min after administration.

CONCLUSIONS

The exogenous GBCA leaked into the para-arterial glymphatics could be completely cleared around 961 to 1086 min after administration in a human model of BBB disruption. The tracer enhancement started variously in different intracranial regions but was eventually cleared centrifugally to brain convexity, probably towards glymphatic-meningeal lymphatics exits.

CLINICAL RELEVANCE STATEMENT

Glymphatic clearance time intervals and the centrifugal directions assessed by a noninvasive approach may have implications for clinical glymphatic evaluation in the near future.

KEY POINTS

• This study aimed to investigate the human glymphatic dynamics in a noninvasive diseased model. • The intracranial MR-detectable gadolinium-based contrast agents were removed centrifugally within 961 to 1086 min. • The glymphatic dynamics was demonstrable by enhancing MRI in an in vivo diseased model noninvasively.

Association of intravascular enhancement sign on 3D-T1W TSE with collateral status in middle cerebral artery occlusion stroke

OBJECTIVE

The significance of the intravascular enhancement sign (IVES) on high-resolution magnetic resonance vascular wall imaging (HR-VWI) remains unclear. This study aimed to investigate the correlation between the IVES and collateral assessment derived from digital subtraction angiography (DSA).

METHOD

A total of 75 patients with occlusion of the first segment of the middle cerebral artery (MCA) who underwent HR-VWI and DSA examinations at our research institution between November 2016 and February 2023 were included. The number of vessels with IVES, IVES-Alberta Stroke Program Early Computed Tomography Score (ASPECTS), American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) collateral grade, and DSA collateral blood flow grade were retrospectively evaluated. Correlations between these indicators were assessed using Spearman's correlation.

RESULTS

Interrater agreement was good for the assessment of HR-VWI and DSA indicators. After adjustments for age, degree of wall enhancement, and hypertension, a multivariable ordinal logistic regression model identified both the number of IVES vessels (OR = 1.37; 95%CI [1.06-1.78]; P = 0.017) and IVES-ASPECTS (OR = 2.00; 95%CI [1.03-3.87]; P = 0.041) as independent predictors of ischemic stroke. In the patient group with acute ischemic stroke, we found weak correlations between the number of IVES vessels and the ASITN/SIR collateral grade (rho = -0.35; P = 0.002) and between the IVES-ASPECTS and ASITN/SIR collateral grade (rho = -0.27; P = 0.02). Moreover, there were strong correlations between the number of IVES vessels and the DSA collateral blood flow grade (rho = -0.74; P < 0.001) and between the IVES-ASPECTS and the DSA collateral blood flow grade (rho = -0.65; P < 0.001). The number of IVES vessels correlated strongly with the IVES-ASPECTS (rho = 0.92, P < 0.001).

CONCLUSION

We find that the IVES is closely associated with sluggish collateral blood flow, which further confirms the hemodynamic mechanism underlying the IVES in MCA occlusion.

Multiple sclerosis imaging in clinical practice: a European-wide survey of 428 centers and conclusions by the ESNR Working Group

OBJECTIVES

To evaluate compliance with the available recommendations, we assessed the current clinical practice of imaging in the evaluation of multiple sclerosis (MS).

METHODS

An online questionnaire was emailed to all members and affiliates. Information was gathered on applied MR imaging protocols, gadolinium-based contrast agents (GBCA) use and image analysis. We compared the survey results with the Magnetic Resonance Imaging in MS (MAGNIMS) recommendations considered as the reference standard.

RESULTS

A total of 428 entries were received from 44 countries. Of these, 82% of responders were neuroradiologists. 55% performed more than ten scans per week for MS imaging. The systematic use of 3 T is rare (18%). Over 90% follow specific protocol recommendations with 3D FLAIR, T2-weighted and DWI being the most frequently used sequences. Over 50% use SWI at initial diagnosis and 3D gradient-echo T1-weighted imaging is the most used MRI sequence for pre- and post-contrast imaging. Mismatches with recommendations were identified including the use of only one sagittal T2-weighted sequence for spinal cord imaging, the systematic use of GBCA at follow-up (over 30% of institutions), a delay time shorter than 5 min after GBCA administration (25%) and an inadequate follow-up duration in pediatric acute disseminated encephalomyelitis (80%). There is scarce use of automated software to compare images or to assess atrophy (13% and 7%). The proportions do not differ significantly between academic and non-academic institutions.

CONCLUSIONS

While current practice in MS imaging is rather homogeneous across Europe, our survey suggests that recommendations are only partially followed.

CLINICAL RELEVANCE STATEMENT

Hurdles were identified, mainly in the areas of GBCA use, spinal cord imaging, underuse of specific MRI sequences and monitoring strategies. This work will help radiologists to identify the mismatches between their own practices and the recommendations and act upon them.

KEY POINTS

• While current practice in MS imaging is rather homogeneous across Europe, our survey suggests that available recommendations are only partially followed. • Several hurdles have been identified through the survey that mainly lies in the areas of GBCA use, spinal cord imaging, underuse of specific MRI sequences and monitoring strategies.

Deep learning based on dynamic susceptibility contrast MR imaging for prediction of local progression in adult-type diffuse glioma (grade 4)

Adult-type diffuse glioma (grade 4) has infiltrating nature, and therefore local progression is likely to occur within surrounding non-enhancing T2 hyperintense areas even after gross total resection of contrast-enhancing lesions. Cerebral blood volume (CBV) obtained from dynamic susceptibility contrast perfusion-weighted imaging (DSC-PWI) is a parameter that is well-known to be a surrogate marker of both histologic and angiographic vascularity in tumors. We built two nnU-Net deep learning models for prediction of early local progression in adult-type diffuse glioma (grade 4), one using conventional MRI alone and one using multiparametric MRI, including conventional MRI and DSC-PWI. Local progression areas were annotated in a non-enhancing T2 hyperintense lesion on preoperative T2 FLAIR images, using the follow-up contrast-enhanced (CE) T1-weighted (T1W) images as the reference standard. The sensitivity was doubled with the addition of nCBV (80% vs. 40%, P = 0.02) while the specificity was decreased nonsignificantly (29% vs. 48%, P = 0.39), suggesting that fewer cases of early local progression would be missed with the addition of nCBV. While the diagnostic performance of CBV model is still poor and needs improving, the multiparametric deep learning model, which presumably learned from the subtle difference in vascularity between early local progression and non-progression voxels within perilesional T2 hyperintensity, may facilitate risk-adapted radiotherapy planning in adult-type diffuse glioma (grade 4) patients.

Signal-to-noise ratio penalties from a loss of stimulated echoes when using slab-selective excitation in three-dimensional fast spin echo imaging with long echo trains

Three-dimensional fast spin echo imaging with long echo trains combines high resolution with reasonable acquisition times and reduced specific absorption rate due to low refocusing flip angles. Typically, an entire volume is encoded (nonselective excitation) or localization can be performed with slab select excitation, which uses a long 90° pulse for precise localization, followed by a preliminary nonselective 180° pulse bounded by spoiler gradients to destroy signal outside of the volume of interest. Subsequent flip angles in the train are nonselective and identical between the two methods. The inclusion of the initial selective pulse and spoiler gradients results in a signal-to-noise ratio (SNR) penalty for slab selection, beyond the slice-averaging dependence, arising from a loss of stimulated echoes. SNR differences are explored using Bloch equation simulations of a T2-weighted 96 echo train sequence with varying parameters including T2, T1, and B1⁺ and compared with phantom and in vivo brain, neck, and knee experiments. In vivo SNR measurements in the three regions showed a maximum decrease of selective SNR by 29% (gastrocnemius muscle), 25% (pons), and 22% (globus pallidus), despite similar experimental parameters to nonselective experiments. Decreased SNR was compounded by B1⁺ variation affecting prescribed flip angles with further smaller reductions with T2 and T1 times. In conclusion, the elimination of coherences via the preliminary nominal 180° pulse and spoiler gradients in addition to the extended echo timing from the long excitation pulse resulted in a reduction in SNR compared with the nonselective case. Consideration of the required SNR and chosen anatomy as well as sequence restrictions should be weighed before choosing slab-selective excitation.

Contrast-Enhanced 3D Spin Echo T1-Weighted Sequence Outperforms 3D Gradient Echo T1-Weighted Sequence for the Detection of Multiple Sclerosis Lesions on 3.0 T Brain MRI

BACKGROUND

Using reliable contrast-enhanced T1 sequences is crucial to detect enhancing brain lesions for multiple sclerosis (MS) at the time of diagnosis and over follow-up. Contrast-enhanced 3D gradient-recalled echo (GRE) T1-weighted imaging (WI) and 3D turbo spin echo (TSE) T1-WI are both available for clinical practice and have never been compared within the context of this diagnosis.

PURPOSE

The aim of this study was to compare contrast-enhanced 3D GRE T1-WI and 3D TSE T1-WI for the detection of enhancing lesions in the brains of MS patients.

METHODS

This single-center prospective study enrolled patients with MS who underwent a 3.0 T brain MRI from August 2017 to April 2021 for follow-up. Contrast-enhanced 3D GRE T1-WI and 3D TSE T1-WI were acquired in randomized order. Two independent radiologists blinded to all data reported all contrast-enhanced lesions in each sequence. Their readings were compared with a reference standard established by a third expert neuroradiologist. Interobserver agreement, contrast ratio, and contrast-to-noise ratio were calculated for both sequences.

RESULTS

A total of 158 MS patients were included (mean age, 40 ± 11 years; 95 women). Significantly more patients had at least 1 contrast-enhanced lesion on 3D TSE T1-WI than on 3D GRE T1-WI for both readers (61/158 [38.6%] vs 48/158 [30.4%] and 60/158 [38.6%] vs 47/158 [29.7%], P < 0.001). Significantly more contrast-enhanced lesions per patient were detected on 3D TSE T1-WI (mean 2.47 vs 1.56 and 2.56 vs 1.39, respectively, P < 0.001). Interobserver agreement was excellent for both sequences, κ = 0.96 (confidence interval [CI], 0.91-1.00) for 3D TSE T1-WI and 0.92 (CI, 0.86-0.99) for 3D GRE T1-WI. Contrast ratio and contrast-to-noise ratio were significantly higher on 3D TSE T1-WI (0.84 vs 0.53, P < 0.001, and 87.9 vs 57.8, P = 0.03, respectively).

CONCLUSIONS

At 3.0 T, contrast-enhanced 3D TSE-T1-WI supports the detection of significantly more enhancing lesions than 3D GRE T1-WI and should therefore be used for MS patients requiring contrast-enhanced examination.

Clinical application of three-dimensional T1-weighted BrainVIEW in magnetic resonance imaging of cerebral venous thrombosis: a case report and literature review

To date, there is no clinical scoring system or laboratory indicator that can rule out cerebral venous thrombosis (CVT) or provide diagnostic proof for evaluating post-treatment thrombosis recanalization during follow-up. We therefore explored an imaging method for quantitative assessment of CVT and assessed thrombotic changes during follow-up. A patient presented with severe posterior occipital distension extending to the top of the forehead and an elevated plasma D-dimer (DD2) level. Computed tomography and pre-contrast-enhanced magnetic resonance imaging revealed only a small amount of cerebral hemorrhage. Three-dimensional (3D) T1-weighted (T1W) BrainVIEW pre-contrast-enhanced magnetic resonance scanning showed subacute thrombosis in the venous sinus, and the post-contrast-enhanced scan combined with volume rendering reconstruction showed cerebral thrombosis of the venous sinus and allowed for measurement of the thrombus volume. On days 30 and 60 of post-treatment follow-up, post-contrast-enhanced scans showed progressive reduction of the thrombus volume as well as recanalization and fibrotic flow voids in the chronic thrombosis. 3D T1W BrainVIEW was helpful to observe the size of the thrombi and the situation of venous sinus recanalization during the follow-up after clinical treatment of CVT. This technique can reflect the imaging manifestations of CVT throughout the whole process to guide clinical treatment decisions.

Optimization of workflow for detection of brain metastases at 3T: is a black-blood MTC prepared 3D T1 used alone robust enough to replace the combination of conventional 3D T1 and the black-blood 3D T1 MTC?

PURPOSE

Sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE) is a black-blood 3D T1-weighted (T1w) magnetic resonance imaging (MRI) sequence that has shown robust performance for brain metastases detection. However, this could generate false positive results due to suboptimal blood signal suppression. For that reason, SPACE is used in our institution alongside a non-black-blood T1w sequence: volumetric interpolated breath-hold examination (VIBE). Our study aims to (i) evaluate the diagnostic accuracy of SPACE compared to its use in combination with VIBE, (ii) investigate the effect of radiologist's experience in the sequence's performance, and (iii) analyze causes of discordants results.

METHODS

Four hundred seventy-three 3T MRI scans were retrospectively analyzed following a monocentric study design. Two studies were formed: one including SPACE alone and one combining both sequences (SPACE + VIBE, the reference). An experienced neuroradiologist and a radiology trainee independently reviewed the images of each study and reported the number of brain metastases. The sensitivity (Se) and specificity (Sp) of SPACE compared to SPACE + VIBE in metastases detection were reported. Diagnostic accuracy of SPACE compared to SPACE + VIBE was assessed by using McNemar's test. Significance was set at p < 0.05. Cohen's kappa was used for inter-method and inter-observer variability.

RESULTS

No significant difference was found between the two methods, with SPACE having a Se > 93% and a Sp > 87%. No effect of readers' experience was disclosed.

CONCLUSION

Independently of radiologist's experience, SPACE alone is robust enough to replace SPACE + VIBE for brain metastases detection.

Altered spontaneous brain activity during dobutamine challenge in healthy young adults: A resting-state functional magnetic resonance imaging study

Introduction

There is a growing interest in exploring brain-heart interactions. However, few studies have investigated the brain-heart interactions in healthy populations, especially in healthy young adults. The aim of this study was to explore the association between cardiovascular and spontaneous brain activities during dobutamine infusion in healthy young adults.

Methods

Forty-eight right-handed healthy participants (43 males and 5 females, range: 22-34 years) underwent vital signs monitoring, cognitive function assessment and brain MRI scans. Cardiovascular function was evaluated using blood pressure and heart rate, while two resting-state functional magnetic resonance imaging (rs-fMRI) methods-regional homogeneity (ReHo) and amplitude of low-frequency fluctuation (ALFF)-were used together to reflect the local neural activity of the brain. Logistic regression was used to model the association between brain and heart.

Results

Results showed that blood pressure and heart rate significantly increased after dobutamine infusion, and the performance in brain functional activity was the decrease in ReHo in the left gyrus rectus and in ALFF in the left frontal superior orbital. The results of logistic regression showed that the difference of diastolic blood pressure (DBP) had significant positive relationship with the degree of change of ReHo, while the difference of systolic blood pressure (SBP) had significant negative impact on the degree of change in ALFF.

Discussion

These findings suggest that the brain-heart interactions exist in healthy young adults under acute cardiovascular alterations, and more attention should be paid to blood pressure changes in young adults and assessment of frontal lobe function to provide them with more effective health protection management.

Phantom Study on the Robustness of MR Radiomics Features: Comparing the Applicability of 3D Printed and Biological Phantoms

The objectives of our study were to (a) evaluate the feasibility of using 3D printed phantoms in magnetic resonance imaging (MR) in assessing the robustness and repeatability of radiomic parameters and (b) to compare the results obtained from the 3D printed phantoms to metrics obtained in biological phantoms. To this end, three different 3D phantoms were printed: a Hilbert cube (5 × 5 × 5 cm³) and two cubic quick response (QR) code phantoms (a large phantom (large QR) (5 × 5 × 4 cm³) and a small phantom (small QR) (4 × 4 × 3 cm³)). All 3D printed and biological phantoms (kiwis, tomatoes, and onions) were scanned thrice on clinical 1.5 T and 3 T MR with 1 mm and 2 mm isotropic resolution. Subsequent analyses included analyses of several radiomics indices (RI), their repeatability and reliability were calculated using the coefficient of variation (CV), the relative percentage difference (RPD), and the interclass coefficient (ICC) parameters. Additionally, the readability of QR codes obtained from the MR images was examined with several mobile phones and algorithms. The best repeatability (CV ≤ 10%) is reported for the acquisition protocols with the highest spatial resolution. In general, the repeatability and reliability of RI were better in data obtained at 1.5 T (CV = 1.9) than at 3 T (CV = 2.11). Furthermore, we report good agreements between results obtained for the 3D phantoms and biological phantoms. Finally, analyses of the read-out rate of the QR code revealed better texture analyses for images with a spatial resolution of 1 mm than 2 mm. In conclusion, 3D printing techniques offer a unique solution to create textures for analyzing the reliability of radiomic data from MR scans.

Automated Brain Volumetry in Patients With Memory Impairment: Comparison of Conventional and Ultrafast 3D T1-Weighted MRI Sequences Using Two Software Packages

BACKGROUND. Isotropic 3D T1-weighted imaging has long acquisition times, potentially leading to motion artifact and altered brain volume measurements. Acquisition times may be greatly shortened using an isotropic ultrafast 3D echo-planar imaging (EPI) T1-weighted sequence. OBJECTIVE. The purpose of this article was to compare automated brain volume measurements between conventional 3D T1-weighted imaging and ultrafast 3D EPI T1-weighted imaging. METHODS. This retrospective study included 36 patients (25 women, 11 men; mean age, 68.4 years) with memory impairment who underwent 3-T brain MRI. Examinations included both conventional 3D T1-weighted imaging using inversion recovery gradient-recalled echo sequence (section thickness, 1.0 mm; acquisition time, 3 minutes 4 seconds) and, in patients exhibiting motion, an isotropic ultrafast 3D EPI T1-weighted sequence (section thickness, 1.2 mm; acquisition time, 30 seconds). The 36-patient sample excluded five patients in whom severe motion artifact rendered the conventional sequence of insufficient quality for volume measurements. Automated brain volumetry was performed using NeuroQuant (version 3.0, CorTechs Laboratories) and FreeSurfer (version 7.1.1, Harvard University) software. Volume measurements were compared between sequences for nine regions in each hemisphere. RESULTS. Volumes showed substantial to almost perfect agreement between the two sequences for most regions bilaterally. However, most regions showed significant mean differences between sequences, and Bland-Altman analyses showed consistent systematic biases and wide limits of agreement (LOA). For example, for the left hemisphere using NeuroQuant, volume was significantly greater for the ultrafast sequence in four regions and significantly greater for the conventional sequence in three regions, whereas standardized effect size between sequences was moderate for four regions and large for one region. Using NeuroQuant, mean bias (ultrafast minus conventional) and 95% LOA were greatest in cortical gray matter bilaterally (-50.61 cm3 [-56.27 cm3, -44.94 cm3] for the left hemisphere; -50.02 cm3 [-54.88 cm3, -45.16 cm3] for the right hemisphere). The variation between the two sequences was observed in subset analyses of 16 patients with and 20 patients without Alzheimer disease. CONCLUSION. Brain volume measurements show significant differences and systematic biases between the conventional and ultrafast sequences. CLINICAL IMPACT. In patients in whom severe motion artifact precludes use of the conventional sequence, the ultrafast sequence may be useful to enable brain volume-try. However, the current conventional 3D T1-weighted sequence remains preferred in patients who can tolerate the standard examination.

From Dose Reduction to Contrast Maximization: Can Deep Learning Amplify the Impact of Contrast Media on Brain Magnetic Resonance Image Quality? A Reader Study

OBJECTIVES

The aim of this study was to evaluate a deep learning method designed to increase the contrast-to-noise ratio in contrast-enhanced gradient echo T1-weighted brain magnetic resonance imaging (MRI) acquisitions. The processed images are quantitatively evaluated in terms of lesion detection performance.

MATERIALS AND METHODS

A total of 250 multiparametric brain MRIs, acquired between November 2019 and March 2021 at Gustave Roussy Cancer Campus (Villejuif, France), were considered for inclusion in this retrospective monocentric study. Independent training (107 cases; age, 55 ± 14 years; 58 women) and test (79 cases; age, 59 ± 14 years; 41 women) samples were defined. Patients had glioma, brain metastasis, meningioma, or no enhancing lesion. Gradient echo and turbo spin echo with variable flip angles postcontrast T1 sequences were acquired in all cases. For the cases that formed the training sample, "low-dose" postcontrast gradient echo T1 images using 0.025 mmol/kg injections of contrast agent were also acquired. A deep neural network was trained to synthetically enhance the low-dose T1 acquisitions, taking standard-dose T1 MRI as reference. Once trained, the contrast enhancement network was used to process the test gradient echo T1 images. A read was then performed by 2 experienced neuroradiologists to evaluate the original and processed T1 MRI sequences in terms of contrast enhancement and lesion detection performance, taking the turbo spin echo sequences as reference.

RESULTS

The processed images were superior to the original gradient echo and reference turbo spin echo T1 sequences in terms of contrast-to-noise ratio (44.5 vs 9.1 and 16.8; P < 0.001), lesion-to-brain ratio (1.66 vs 1.31 and 1.44; P < 0.001), and contrast enhancement percentage (112.4% vs 85.6% and 92.2%; P < 0.001) for cases with enhancing lesions. The overall image quality of processed T1 was preferred by both readers (graded 3.4/4 on average vs 2.7/4; P < 0.001). Finally, the proposed processing improved the average sensitivity of gradient echo T1 MRI from 88% to 96% for lesions larger than 10 mm (P = 0.008), whereas no difference was found in terms of the false detection rate (0.02 per case in both cases; P > 0.99). The same effect was observed when considering all lesions larger than 5 mm: sensitivity increased from 70% to 85% (P < 0.001), whereas false detection rates remained similar (0.04 vs 0.06 per case; P = 0.48). With all lesions included regardless of their size, sensitivities were 59% and 75% for original and processed T1 images, respectively (P < 0.001), and the corresponding false detection rates were 0.05 and 0.14 per case, respectively (P = 0.06).

CONCLUSION

The proposed deep learning method successfully amplified the beneficial effects of contrast agent injection on gradient echo T1 image quality, contrast level, and lesion detection performance. In particular, the sensitivity of the MRI sequence was improved by up to 16%, whereas the false detection rate remained similar.

Incidence of Developmental Venous Anomalies in Patients With Multiple Sclerosis: A 3 Tesla MRI Study

Objectives

There is evidence of involvement of the venous system in multiple sclerosis (MS). If this bears also an association with the frequency and extent of developmental venous anomalies (DVA) still has to be determined. We therefore investigated this in patients with different phenotypes of MS and in comparison, to a control population.

Methods

We analyzed the contrast-enhanced T1-weighted MR scans of 431 patients (clinically isolated syndrome—CIS, n = 108; MS, n = 323) and of 162 control individuals for the presence of a DVA. We also measured the size of the DVA and draining vein and compared the DVA frequency between MS phenotypes.

Results

A DVA was found in 38 (8.8 %) of patients with CIS or MS and in 11 (6.8%) controls (p = 0.4). DVA frequency was highest in CIS (14.8%) and lowest in progressive MS (4.0%). The mean cranio-caudal and axial extension of the DVA was significantly lower in MS patients than controls (p < 0.05).

Conclusions

The frequency of DVA in MS patients is comparable to that in controls. Whether DVA size and appearance may change over time will have to be investigated in a longitudinal manner and with larger sample size.

T2 quantification in brain using 3D fast spin-echo imaging with long echo trains

Purpose

Three‐dimensional fast spin‐echo (FSE) sequences commonly use very long echo trains (>64 echoes) and severely reduced refocusing angles. They are increasingly used in brain exams due to high, isotropic resolution and reasonable scan time when using long trains and short interecho spacing. In this study, T₂ quantification in 3D FSE is investigated to achieve increased resolution when comparing with established 2D (proton‐density dual‐echo and multi‐echo spin‐echo) methods.

Methods

The FSE sequence design was explored to use long echo trains while minimizing T₂ fitting error and maintaining typical proton density and T₂‐weighted contrasts. Constant and variable flip angle trains were investigated using extended phase graph and Bloch equation simulations. Optimized parameters were analyzed in phantom experiments and validated in vivo in comparison to 2D methods for eight regions of interest in brain, including deep gray‐matter structures and white‐matter tracts.

Results

Phantom and healthy in vivo brain T₂ measurements showed that optimized variable echo‐train 3D FSE performs similarly to previous 2D methods, while achieving three‐fold‐higher slice resolution, evident visually in the 3D T₂ maps. Optimization resulted in better T₂ fitting and compared well with standard multi‐echo spin echo (within the 8‐ms confidence limits defined based on Bland‐Altman analysis).

Conclusion

T₂ mapping using 3D FSE with long echo trains and variable refocusing angles provides T₂ accuracy in agreement with 2D methods with additional high‐resolution benefits, allowing isotropic views while avoiding incidental magnetization transfer effects. Consequently, optimized 3D sequences should be considered when choosing T₂ mapping methods for high anatomic detail.

3D MRI: Technical Considerations and Practical Integration

One of the main advantages of three-dimensional (3D) magnetic resonance imaging (MRI) is the possibility of isotropic voxels and reconstructed planar cuts through the volumetric data set in any orientation with multiplanar reformation software through real-time evaluation. For example, reformats by the radiologist during reporting allows exploitation of the full potential of isotropic 3D volumetric acquisition or through standardized retrospective reformats of thicker predefined slices of an isotropic volumetric data set by technologists. The main challenges for integrating 3D fast spin echo (FSE) and turbo spin-echo (TSE) MRI in clinical practice are a long acquisition time and some artifacts, whereas for integrating 3D gradient-recalled echo protocols, the main challenges are lower signal-to-noise ratios (SNRs) and the inability to produce intermediate, and T2-weighted contrast. The implementation of bidirectional parallel imaging acquisition and random undersampling acceleration strategies of 3D TSE pulse sequences substantially shortens the examination time with only minor SNR reductions. This article provides an overview of general technical considerations of 3D FSE and TSE sequences in musculoskeletal MRI. It also describes how these sequences achieve efficient data acquisition and reviews the main advantages and challenges for their introduction to clinical practice.

Non-contrast-enhanced magnetic resonance imaging technique diagnoses DVT and classifies thrombus

The accuracy of non-contrast MRI in diagnosing acute deep vein thrombosis (DVT) of the lower extremities is different. To explore the application of high-resolution non-contrast 3D CUBE T1-weighted MRI in the lower extremities DVT. We recruited 26 patients suspected DVT of the lower extremities from Hebei General Hospital in China. All patients underwent high-resolution non-contrast 3D CUBE T1-weighted MRI. We evaluated the sensitivity, specificity, positive predictive value, and negative predictive value of diagnosing thrombosis. And we divided thrombi into two parts: filling thrombus (FT) and non-filling thrombus (NFT), compared the agreement between MRI and Ultrasound (US) and analysed the locations of thrombi. Compared with US, MRI yielded a sensitivity of 79%, a specificity of 94.2% in mean value, a sensitivity of 85.7%, 97.4%, and 51.7% in iliac, femoral-popliteal, and calf segments respectively, a specificity of 97.6%, 88.3%, and 98.2% in iliac, femoral-popliteal, and in calf segments respectively. The accuracy of MRI in the diagnosis of lower extremity DVT was in very good agreement (κ = 0.711, 95% CI 0.627, 0.795). The FT was the most part in US and CUBE (68/56), CUBE can detect more NFT in femoral vein than US (22/4). 3D CUBE T1-weighted MRI can be used to accurately diagnose acute DVT and detect more NFT. It has the potential of follow-up at the end of treatment to establish a new baseline to stop anticoagulant drug.

European Society for Paediatric Oncology (SIOPE) MRI guidelines for imaging patients with central nervous system tumours

INTRODUCTION

Standardisation of imaging acquisition is essential in facilitating multicentre studies related to childhood CNS tumours. It is important to ensure that the imaging protocol can be adopted by centres with varying imaging capabilities without compromising image quality.

MATERIALS AND METHOD

An imaging protocol has been developed by the Brain Tumour Imaging Working Group of the European Society for Paediatric Oncology (SIOPE) based on consensus among its members, which consists of neuroradiologists, imaging scientists and paediatric neuro-oncologists. This protocol has been developed to facilitate SIOPE led studies and regularly reviewed by the imaging working group.

RESULTS

The protocol consists of essential MRI sequences with imaging parameters for 1.5 and 3 Tesla MRI scanners and a set of optional sequences that can be used in appropriate clinical settings. The protocol also provides guidelines for early post-operative imaging and surveillance imaging. The complementary use of multimodal advanced MRI including diffusion tensor imaging (DTI), MR spectroscopy and perfusion imaging is encouraged, and optional guidance is provided in this publication.

CONCLUSION

The SIOPE brain tumour imaging protocol will enable consistent imaging across multiple centres involved in paediatric CNS tumour studies.

MRI Highly Accelerated Wave-CAIPI T1-SPACE versus Standard T1-SPACE to detect brain gadolinium-enhancing lesions at 3T

BACKGROUND AND PURPOSE

High-resolution three-dimensional (3D) post-contrast imaging of the brain is essential for comprehensive evaluation of inflammatory, neoplastic, and neurovascular diseases of the brain. 3D T1-weighted spin-echo-based sequences offer increased sensitivity for the detection of enhancing lesions but are relatively prolonged examinations. We evaluated whether a highly accelerated Wave-controlled aliasing in parallel imaging (Wave-CAIPI) post-contrast 3D T1-sampling perfection with application-optimized contrasts using different flip angle evolutions (T1-SPACE) sequence (Wave-T1-SPACE) was noninferior to the standard high-resolution 3D T1-SPACE sequence for visualizing enhancing lesions with comparable diagnostic quality.

METHODS

One hundred and three consecutive patients were prospectively evaluated with a standard post-contrast 3D T1-SPACE sequence (acquisition time [TA] = 4 min 19 s) and an optimized Wave-CAIPI 3D T1-SPACE sequence (TA = 1 min 40 s) that was nearly three times faster than the standard sequence. Two blinded neuroradiologists performed a head-to-head comparison to evaluate the visualization of enhancing pathology, perception of artifacts, and overall diagnostic quality. A 15% margin was used to test whether post-contrast Wave-T1-SPACE was noninferior to standard T1-SPACE.

RESULTS

Wave-T1-SPACE was noninferior to standard T1-SPACE for delineating parenchymal and meningeal enhancing pathology (p < 0.01). Wave-T1-SPACE showed marginally higher background noise compared to the standard sequence and was noninferior in the overall diagnostic quality (p = 0.03).

CONCLUSIONS

Our findings show that Wave-T1-SPACE was noninferior to standard T1-SPACE for visualization of enhancing pathology and overall diagnostic quality with a three-fold reduction in acquisition time compared to the standard sequence. Wave-T1-SPACE may be used to accelerate 3D post-contrast T1-weighted spin-echo imaging without loss of clinically important information.

Deep learning-based automatic delineation of the hippocampus by MRI: geometric and dosimetric evaluation

BACKGROUND

Whole brain radiotherapy (WBRT) can impair patients' cognitive function. Hippocampal avoidance during WBRT can potentially prevent this side effect. However, manually delineating the target area is time-consuming and difficult. Here, we proposed a credible approach of automatic hippocampal delineation based on convolutional neural networks.

METHODS

Referring to the hippocampus contouring atlas proposed by RTOG 0933, we manually delineated (MD) the hippocampus on the MRI data sets (3-dimensional T1-weighted with slice thickness of 1 mm, n = 175), which were used to construct a three-dimensional convolutional neural network aiming for the hippocampus automatic delineation (AD). The performance of this AD tool was tested on three cohorts: (a) 3D T1 MRI with 1-mm slice thickness (n = 30); (b) non-3D T1-weighted MRI with 3-mm slice thickness (n = 19); (c) non-3D T1-weighted MRI with 1-mm slice thickness (n = 11). All MRIs confirmed with normal hippocampus has not been violated by any disease. Virtual radiation plans were created for AD and MD hippocampi in cohort c to evaluate the clinical feasibility of the artificial intelligence approach. Statistical analyses were performed using SPSS version 23. P < 0.05 was considered significant.

RESULTS

The Dice similarity coefficient (DSC) and Average Hausdorff Distance (AVD) between the AD and MD hippocampi are 0.86 ± 0.028 and 0.18 ± 0.050 cm in cohort a, 0.76 ± 0.035 and 0.31 ± 0.064 cm in cohort b, 0.80 ± 0.015 and 0.24 ± 0.021 cm in cohort c, respectively. The DSC and AVD in cohort a were better than those in cohorts b and c (P < 0.01). There is no significant difference between the radiotherapy plans generated using the AD and MD hippocampi.

CONCLUSION

The AD of the hippocampus based on a deep learning algorithm showed satisfying results, which could have a positive impact on improving delineation accuracy and reducing work load.

Twofold improved tumor-to-brain contrast using a novel T1 relaxation-enhanced steady-state (T1RESS) MRI technique

A technique that provides more accurate cancer detection would be of great value. Toward this end, we developed T1 relaxation-enhanced steady-state (T₁RESS), a novel magnetic resonance imaging (MRI) pulse sequence that enables the flexible modulation of T1 weighting and provides the unique feature that intravascular signals can be toggled on and off in contrast-enhanced scans. T₁RESS makes it possible to effectively use an MRI technique with improved signal-to-noise ratio efficiency for cancer imaging. In a proof-of-concept study, "dark blood" unbalanced T₁RESS provided a twofold improvement in tumor-to-brain contrast compared with standard techniques, whereas balanced T₁RESS greatly enhanced vascular detail. In conclusion, T₁RESS represents a new MRI technique with substantial potential value for cancer imaging, along with a broad range of other clinical applications.