Contrast-enhanced MR imaging of metastatic brain tumor at 3 tesla: utility of T(1)-weighted SPACE compared with 2D spin echo and 3D gradient echo sequence

Where Does Auto-Segmentation for Brain Metastases Radiosurgery Stand Today?

Detection and segmentation of brain metastases (BMs) play a pivotal role in diagnosis, treatment planning, and follow-up evaluations for effective BM management. Given the rising prevalence of BM cases and its predominantly multiple onsets, automated segmentation is becoming necessary in stereotactic radiosurgery. It not only alleviates the clinician's manual workload and improves clinical workflow efficiency but also ensures treatment safety, ultimately improving patient care. Recent strides in machine learning, particularly in deep learning (DL), have revolutionized medical image segmentation, achieving state-of-the-art results. This review aims to analyze auto-segmentation strategies, characterize the utilized data, and assess the performance of cutting-edge BM segmentation methodologies. Additionally, we delve into the challenges confronting BM segmentation and share insights gleaned from our algorithmic and clinical implementation experiences.

Reducing false positives in deep learning-based brain metastasis detection by using both gradient-echo and spin-echo contrast-enhanced MRI: validation in a multi-center diagnostic cohort

OBJECTIVES

To develop a deep learning (DL) for detection of brain metastasis (BM) that incorporates both gradient- and turbo spin-echo contrast-enhanced MRI (dual-enhanced DL) and evaluate it in a clinical cohort in comparison with human readers and DL using gradient-echo-based imaging only (GRE DL).

MATERIALS AND METHODS

DL detection was developed using data from 200 patients with BM (training set) and tested in 62 (internal) and 48 (external) consecutive patients who underwent stereotactic radiosurgery and diagnostic dual-enhanced imaging (dual-enhanced DL) and later guide GRE imaging (GRE DL). The detection sensitivity and positive predictive value (PPV) were compared between two DLs. Two neuroradiologists independently analyzed BM and reference standards for BM were separately drawn by another neuroradiologist. The relative differences (RDs) from the reference standard BM numbers were compared between the DLs and neuroradiologists.

RESULTS

Sensitivity was similar between GRE DL (93%, 95% confidence interval [CI]: 90-96%) and dual-enhanced DL (92% [89-94%]). The PPV of the dual-enhanced DL was higher (89% [86-92%], p < .001) than that of GRE DL (76%, [72-80%]). GRE DL significantly overestimated the number of metastases (false positives; RD: 0.05, 95% CI: 0.00-0.58) compared with neuroradiologists (RD: 0.00, 95% CI: - 0.28, 0.15, p < .001), whereas dual-enhanced DL (RD: 0.00, 95% CI: 0.00-0.15) did not show a statistically significant difference from neuroradiologists (RD: 0.00, 95% CI: - 0.20-0.10, p = .913).

CONCLUSION

The dual-enhanced DL showed improved detection of BM and reduced overestimation compared with GRE DL, achieving similar performance to neuroradiologists.

CLINICAL RELEVANCE STATEMENT

The use of deep learning-based brain metastasis detection with turbo spin-echo imaging reduces false positive detections, aiding in the guidance of stereotactic radiosurgery when gradient-echo imaging alone is employed.

KEY POINTS

•Deep learning for brain metastasis detection improved by using both gradient- and turbo spin-echo contrast-enhanced MRI (dual-enhanced deep learning). •Dual-enhanced deep learning increased true positive detections and reduced overestimation. •Dual-enhanced deep learning achieved similar performance to neuroradiologists for brain metastasis counts.

Comparison between postcontrast thin-slice T1-weighted 2D spin echo and 3D T1-weighted SPACE sequences in the detection of brain metastases at 1.5 and 3 T

OBJECTIVES

Accurate detection of metastatic brain lesions (MBL) is critical due to advances in radiosurgery. We compared the results of three readers in detecting MBL using T1-weighted 2D spin echo (SE) and sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) sequences with whole-brain coverage at both 1.5 T and 3 T.

METHODS

Fifty-six patients evaluated for MBL were included and underwent a standard protocol (1.5 T, n = 37; 3 T, n = 19), including postcontrast T1-weighted SE and SPACE. The rating was performed by three raters in two sessions > six weeks apart. The true number of MBL was determined using all available imaging including follow-up. Intraclass correlations for intra-rater and inter-rater agreement were calculated. Signal intensity ratios (SIR; enhancing lesion, white matter) were determined on a subset of 46 MBL > 4 mm. A paired t-test was used to evaluate postcontrast sequence order and SIR. Reader accuracy was evaluated by the coefficient of determination.

RESULTS

A total of 135 MBL were identified (mean/subject 2.41, SD 6.4). The intra-rater agreement was excellent for all 3 raters (ICC = 0.97-0.992), as was the inter-rater agreement (ICC = 0.995 SE, 0.99 SPACE). Subjective qualitative ratings were lower for SE images; however, signal intensity ratios were higher in SE sequences. Accuracy was high in all readers for both SE (R2 0.95-0.96) and SPACE (R2 0.91-0.96) sequences.

CONCLUSIONS

Although SE sequences are superior to gradient echo sequences in the detection of small MBL, they have long acquisition times and frequent artifacts. We show that T1-weighted SPACE is not inferior to standard thin-slice SE sequences in the detection of MBL at both imaging fields.

CRITICAL RELEVANCE STATEMENT

Our results show the suitability of 3D T1-weighted turbo spin echo (TSE) sequences (SPACE, CUBE, VISTA) in the detection of brain metastases at both 1.5 T and 3 T.

KEY POINTS

• Accurate detection of brain metastases is critical due to advances in radiosurgery. • T1-weighted SE sequences are superior to gradient echo in detecting small metastases. • T1-weighted 3D-TSE sequences may achieve high resolution and relative insensitivity to artifacts. • T1-weighted 3D-TSE sequences have been recommended in imaging brain metastases at 3 T. • We found T1-weighted 3D-TSE equivalent to thin-slice SE at 1.5 T and 3 T.

Deep learning-based detection and quantification of brain metastases on black-blood imaging can provide treatment suggestions: a clinical cohort study

OBJECTIVES

We aimed to evaluate whether deep learning-based detection and quantification of brain metastasis (BM) may suggest treatment options for patients with BMs.

METHODS

The deep learning system (DLS) for detection and quantification of BM was developed in 193 patients and applied to 112 patients that were newly detected on black-blood contrast-enhanced T1-weighted imaging. Patients were assigned to one of 3 treatment suggestion groups according to the European Association of Neuro-Oncology (EANO)-European Society for Medical Oncology (ESMO) recommendations using number and volume of the BMs detected by the DLS: short-term imaging follow-up without treatment (group A), surgery or stereotactic radiosurgery (limited BM, group B), or whole-brain radiotherapy or systemic chemotherapy (extensive BM, group C). The concordance between the DLS-based groups and clinical decisions was analyzed with or without consideration of targeted agents. The performance of distinguishing high-risk (B + C) was calculated.

RESULTS

Among 112 patients (mean age 64.3 years, 63 men), group C had the largest number and volume of BM, followed by group B (4.4 and 851.6 mm3) and A (1.5 and 15.5 mm3). The DLS-based groups were concordant with the actual clinical decisions, with an accuracy of 76.8% (86 of 112). Modified accuracy considering targeted agents was 81.3% (91 of 112). The DLS showed 95% (82/86) sensitivity and 81% (21/26) specificity for distinguishing the high risk.

CONCLUSION

DLS-based detection and quantification of BM have the potential to be helpful in the determination of treatment options for both low- and high-risk groups of limited and extensive BMs.

CLINICAL RELEVANCE STATEMENT

For patients with newly diagnosed brain metastasis, deep learning-based detection and quantification may be used in clinical settings where prompt and accurate treatment decisions are required, which can lead to better patient outcomes.

KEY POINTS

• Deep learning-based brain metastasis detection and quantification showed excellent agreement with ground-truth classifications. • By setting an algorithm to suggest treatment based on the number and volume of brain metastases detected by the deep learning system, the concordance was 81.3%. • When dividing patients into low- and high-risk groups, the sensitivity for detecting the latter was 95%.

Comparison of Contrast-Enhanced 3D Imaging with 2D Imaging in the Evaluation of Perianal Fistula at 3T: A Prospective Observational Study

Introduction  Perianal fistula and its recurrence is a challenging entity for surgeons. It is a well-establi1shed fact that magnetic resonance imaging (MRI) findings influence surgical procedures and reduce the rate of recurrence. In this study, we assessed the contrast-enhanced (CE) three dimensional T1 sequences [sampling perfection with application optimized contrast using different flip angle evolution (SPACE) and volumetric interpolated breath-hold examination (VIBE)] in a 3T MRI system to evaluate perianal fistulas and compared them with two-dimensional (2D) sequences. Materials and Methods  Forty-four patients (mean age, 38.8 ± 15.3 [standard deviation]; 32 males, 12 females) with perianal fistula were included in this prospective study. The patients underwent conventional noncontrast, 2D sequences, diffusion-weighted imaging, followed by postcontrast, 2D T1 images in both axial and coronal planes, and 3D sequences at 3T. Acquisition times were recorded for each sequence. Each postcontrast sequence was evaluated in terms of image quality, presence of artifacts, fistula type, presence of an abscess, visibility, and number of internal orifices. The surgical findings were considered the gold standard. The imaging findings were compared with the surgical findings. Results  In all three sequences, the fistula type and abscess were identified correctly in all patients. The sensitivity value for identification of ramifications utilizing CE 3D T1 VIBE sequence, CE 3D T1 SPACE, and CE 2D T1 images was 100, 86, and 36%, respectively. The number of internal orifices was identified by the CE 3D T1 VIBE and CE 3D T1 SPACE sequences in 100 and 92% of patients, respectively. CE 2D T1 images correctly identified internal orifices in 80% of patients. The overall scan time for each 3D sequence was shorter than for the combined postcontrast 2D sequences. Conclusion  CE 3D T1 SPACE and CE 3D T1 VIBE sequences outperformed conventional CE 2D sequences in the evaluation of perianal fistulas in terms of visibility and the number of internal orifices with a shorter scanning time. Among the 3D sequences, CE 3D T1 VIBE is slightly superior to CE 3D T1 SPACE sequence.

Association between the Putative Meningeal Lymphatics at the Posterior Wall of the Sigmoid Sinus and Delayed Contrast-agent Elimination from the Cerebrospinal Fluid

PURPOSE

To investigate the characteristics of the putative meningeal lymphatics located at the posterior wall of the sigmoid sinus (PML-PSS) in human subjects imaged before and after intravenous administration (IV) of a gadolinium-based contrast agent (GBCA). The appearance of the PML-PSS and the enhancement of the perivascular space of the basal ganglia (PVS-BG) were analyzed for an association with gender, age, and clearance of the GBCA from the cerebrospinal fluid (CSF).

METHODS

Forty-two patients with suspected endolymphatic hydrops were included. Heavily T2-weighted 3D-fluid attenuated inversion recovery (hT2w-3D-FLAIR) and 3D-real inversion recovery (IR) images were obtained at pre-administration, immediately post-administration, and at 4 and 24 hours after IV-GBCA. The appearance of the PML-PSS and the presence of enhancement in the PVS-BG were analyzed for a relationship with age, gender, contrast enhancement of the CSF at 4 hours after IV-GBCA, and the washout ratio of the GBCA in the CSF from 4 to 24 hours after IV-GBCA.

RESULTS

The PML-PSS and PVS-BG were seen in 23 of 42 and 21 of 42 cases, respectively, at 4 hours after IV-GBCA. In all PML-PSS positive cases, hT2w-3D-FLAIR signal enhancement was highest at 4 hours after IV-GBCA. A multivariate analysis between gender, age, CSF signal elevation at 4 hours, and washout ratio indicated that only the washout ratio was independently associated with the enhancement of the PML-PSS or PVS-BG. The odds ratios (95% CIs; P value) were 4.09 × 10-5 (2.39 × 10-8 - 0.07; 0.0078) for the PML-PSS and 1.7 × 10-4 (1.66 × 10-7 - 0.174; 0.014) for the PVS-BG.

CONCLUSION

The PML-PSS had the highest signal enhancement at 4 hours after IV-GBCA. When the PML-PSS was seen, there was also often enhancement of the PVS-BG at 4 hours after IV-GBCA. Both observed enhancements were associated with delayed GBCA excretion from the CSF.

Quality requirements for MRI simulation in cranial stereotactic radiotherapy: a guideline from the German Taskforce "Imaging in Stereotactic Radiotherapy"

Accurate Magnetic Resonance Imaging (MRI) simulation is fundamental for high-precision stereotactic radiosurgery and fractionated stereotactic radiotherapy, collectively referred to as stereotactic radiotherapy (SRT), to deliver doses of high biological effectiveness to well-defined cranial targets. Multiple MRI hardware related factors as well as scanner configuration and sequence protocol parameters can affect the imaging accuracy and need to be optimized for the special purpose of radiotherapy treatment planning. MRI simulation for SRT is possible for different organizational environments including patient referral for imaging as well as dedicated MRI simulation in the radiotherapy department but require radiotherapy-optimized MRI protocols and defined quality standards to ensure geometrically accurate images that form an impeccable foundation for treatment planning. For this guideline, an interdisciplinary panel including experts from the working group for radiosurgery and stereotactic radiotherapy of the German Society for Radiation Oncology (DEGRO), the working group for physics and technology in stereotactic radiotherapy of the German Society for Medical Physics (DGMP), the German Society of Neurosurgery (DGNC), the German Society of Neuroradiology (DGNR) and the German Chapter of the International Society for Magnetic Resonance in Medicine (DS-ISMRM) have defined minimum MRI quality requirements as well as advanced MRI simulation options for cranial SRT.

Comparison of post contrast fluid attenuated inversion recovery, 3D T1-SPACE, and T1W MRI sequences with fat suppression in the diagnosis of infectious meningitis

OBJECTIVE

To assess the usefulness of post contrast Fluid attenuated inversion recovery (FLAIR), 3D T1-SPACE, and T1W magnetic resonance imaging (MRI) sequences with fat suppression in diagnosis of infectious meningitis.

METHODS

75 patients with clinical suspicion of meningitis were evaluated with post contrast FLAIR (PC-FLAIR), post contrast T1-SPACE (PC-T1-SPACE), and post contrast T1WI (PC-T1WI). Sensitivity, specificity, positive predictive value, and negative predictive value of individual sequences were assessed.

RESULTS

The sensitivity of PC-FLAIR (88.4%) was greater than PC-T1-SPACE (85.5%) and PC-T1WI (82.6%), considering cerebrospinal fluid (CSF) analysis as gold standard (p < 0.05). Kappa inter-rater agreement between two radiologists was 0.921 for PC-T1-SPACE, 0.921 for PC-T1WI, and 1.0 for PC-FLAIR with a p value <0.05. Both PC-T1-SPACE and PC-FLAIR performed equally in sulcal space enhancement. PC-T1-SPACE and PC-T1WI performed better in evaluation of pachymeningeal enhancement, ependymal enhancement in cases of ventriculitis, whereas PC-FLAIR was more sensitive in assessment of basal cistern enhancement and enhancement along the cerebellar folia.

CONCLUSION

Meningeal enhancement could be better appreciated in PC-FLAIR image than PC-T1WI and PC-T1-SPACE. Enhancement in PC-T1-SPACE was comparable to that of PC-T1WI. Being a T1 based spin echo sequence, PC-T1-SPACE has all the advantages of PC-T1WI in addition to its ability to differentiate meningeal enhancement from leptomeningeal vessels. Hence, PC-T1WI can be replaced by PC-T1-SPACE and PC-FLAIR can be added to routine MRI protocol in suspected case of meningitis.

Multi-parametric MRI for radiotherapy simulation

Magnetic resonance imaging (MRI) has become an important imaging modality in the field of radiotherapy (RT) in the past decade, especially with the development of various novel MRI and image-guidance techniques. In this review article, we will describe recent developments and discuss the applications of multi-parametric MRI (mpMRI) in RT simulation. In this review, mpMRI refers to a general and loose definition which includes various multi-contrast MRI techniques. Specifically, we will focus on the implementation, challenges, and future directions of mpMRI techniques for RT simulation.

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.

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.

Modulation transfer function measurement of three-dimensional T1-weighted turbo spin echo sequence with low refocusing flip angles using single-plate method

This study aimed to demonstrate the usefulness of modulation transfer function (MTF) measurements using the single-plate method to evaluate changes in resolution properties that are dependent on three parameters: echo train length (ETL), low refocusing flip angle (RFA), and start-up echo in three-dimensional T₁-weighted turbo spin echoes (TSE) with a low RFA and to optimize these parameters. Although the MTFs were slightly degraded with an RFA of 120°, they were considerably degraded with an RFA of ≤ 90°. On the other hand, the MTF of low RFA was greatly improved by setting the start-up echo, allowing setting a long ETL. The single-plate method provided a clear and easy evaluation of the resolution properties of low RFA TSE. Furthermore, this method allows us to visualize changes in the signal intensity of each echo in k-space, depending on the sequence variation. These results suggest that the MTF measurement using the single-plate method is useful for evaluating the resolution properties of TSE sequences and optimizing the measured parameters.

Usefulness of 3D T1-Turbo Spin Echo Imaging for the Evaluation of Intracranial Stent Placement

Objective

Evaluation of intracranial stent placement by MRI suffers the problems of signal artifacts during time-of-flight MRA (TOF-MRA). Therefore, angiographic examination is required for detailed intravascular assessment of the stent placement site. Recently, 3D T1-turbo spin echo (3D-TSE) has been developed for evaluation of carotid artery stent placement. We investigated the use of the 3D-TSE imaging method for the evaluation of intracranial vascular stent placement.

Methods

The subjects consisted of nine patients who underwent intracranial vascular stent placement between April 2015 and December 2019. Postoperatively, the lumens of the placed stents were measured by TOF-MRA, DSA, and 3D-TSE imaging. Analysis was performed by type of stent and placement site.

Results

The stents used were Neuroform Atlas (3 patients), LVIS (3 patients), LVIS Jr (2 patients), and Integrity (1 patient). TOF-MRA of the stent placement site showed defects in the image or poor visualization in all nine patients, whereas 3D-TSE imaging visualized the lumen at the stent indwelling site in all patients. The blood vessel diameter measured by the DSA and 3D-TSE imaging exhibited positive correlations regardless of the stent type and placement site.

Conclusion

3D-TSE imaging allows visualization of the lumen of the site of an intracranial vascular stent, regardless of the type of stent or the vessel. Thus, this method may be useful for evaluating the vascular lumen of a lesion.

Brain metastases: A Society for Neuro-Oncology (SNO) consensus review on current management and future directions

Brain metastases occur commonly in patients with advanced solid malignancies. Yet, less is known about brain metastases than cancer-related entities of similar incidence. Advances in oncologic care have heightened the importance of intracranial management. Here, in this consensus review supported by the Society for Neuro-Oncology (SNO), we review the landscape of brain metastases with particular attention to management approaches and ongoing efforts with potential to shape future paradigms of care. Each coauthor carried an area of expertise within the field of brain metastases and initially composed, edited, or reviewed their specific subsection of interest. After each subsection was accordingly written, multiple drafts of the manuscript were circulated to the entire list of authors for group discussion and feedback. The hope is that the these consensus guidelines will accelerate progress in the understanding and management of patients with brain metastases, and highlight key areas in need of further exploration that will lead to dedicated trials and other research investigations designed to advance the field.

Stereotactic radiotherapy of brain metastases: clinical impact of three-dimensional SPACE imaging for 3T-MRI-based treatment planning

Purpose

For planning CyberKnife stereotactic radiosurgery (CK SRS) of brain metastases (BM), it is essential to precisely determine the exact number and location of BM in MRI. Recent MR studies suggest the superiority of contrast-enhanced 3D fast spin echo SPACE (sampling perfection with application-optimized contrast by using different flip angle evolutions) images over 3D gradient echo (GE) T1-weighted MPRAGE (magnetization-prepared rapid gradient echo) images for detecting small BM. The aim of this study is to test the usability of the SPACE sequence for MRI-based radiation treatment planning and its impact on changing treatment.

Methods

For MRI-based radiation treatment planning using 3T MRI in 199 patients with cerebral oligometastases, we compared the detectability of BM in post-gadolinium SPACE images, post-gadolinium MPRAGE images, and post-gadolinium late-phase MPRAGE images.

Results

When SPACE images were used for MRI-based radiation treatment planning, 29.8% and 16.9% more BM, respectively, were detected and included in treatment planning than in the post-gadolinium MPRAGE images and the post-gadolinium late-phase MPRAGE images (post-gadolinium MPRAGE imaging: n_total = 681, mean ± SD 3.4 ± 4.2; post-gadolinium SPACE imaging: n_total = 884, mean ± SD 4.4 ± 6.0; post-gadolinium late-phase MPRAGE imaging: n_total = 796, mean ± SD 4.0 ± 5.3; P_{post-gadolinium SPACE imaging versus post-gadolinium MPRAGE imaging} < 0.0001, P_{post-gadolinium SPACE imaging versus post-gadolinium late-phase MPRAGE imaging}< 0.0001).

Conclusion

For 3T MRI-based treatment planning of stereotactic radiosurgery of BM, we recommend the use of post-gadolinium SPACE imaging rather than post-gadolinium MPRAGE imaging.

Dedicated isotropic 3-D T1 SPACE sequence imaging for radiosurgery planning improves brain metastases detection and reduces the risk of intracranial relapse

BACKGROUND

Stereotactic radiosurgery (SRS) is increasingly used for brain metastases (BM) patients, but distant intracranial failure (DIF) remains the principal disadvantage of this focal therapeutic approach. The objective of this study was to determine if dedicated SRS imaging would improve lesion detection and reduce DIF.

METHODS

Between 02/2020 and 01/2021, SRS patients at a tertiary care institution underwent dedicated treatment planning MRIs of the brain including MPRAGE and SPACE post-contrast sequences. DIF was calculated using the Kaplan-Meier method; comparisons were made to a historical consecutive cohort treated using MPRAGE alone (02/2019-01/2020).

RESULTS

134 patients underwent 171 SRS courses for 821 BM imaged with both MPRAGE and SPACE (primary cohort). MPRAGE sequence evaluation alone detected 679 lesions. With neuroradiologists evaluating SPACE and MPRAGE, an additional 108 lesions were identified (p<0.001). Upon multidisciplinary review, 34 additional lesions were identified. Compared to the historical cohort (103 patients, 135 SRS courses, 479 BM), the primary cohort had improved median time to DIF (13.5 vs. 5.1 months, p=0.004). The benefit was even more pronounced for patients treated for their first SRS course (18.4 vs. 6.3 months, p=0.001). SRS using MPRAGE and SPACE was associated with a 60% reduction in risk of DIF compared to the historical cohort (HR: 0.40; 95%CI: 0.28-0.57, p<0.001).

CONCLUSIONS

Among BM patients treated with SRS, a treatment planning SPACE sequence in addition to MPRAGE substantially improved lesion detection and was associated with a statistically significant and clinically meaningful prolongation in time to DIF, especially for patients undergoing their first SRS course.

A deep convolutional neural network-based automatic detection of brain metastases with and without blood vessel suppression

OBJECTIVES

To develop an automated model to detect brain metastases using a convolutional neural network (CNN) and volume isotropic simultaneous interleaved bright-blood and black-blood examination (VISIBLE) and to compare its diagnostic performance with the observer test.

METHODS

This retrospective study included patients with clinical suspicion of brain metastases imaged with VISIBLE from March 2016 to July 2019 to create a model. Images with and without blood vessel suppression were used for training an existing CNN (DeepMedic). Diagnostic performance was evaluated using sensitivity and false-positive results per case (FPs/case). We compared the diagnostic performance of the CNN model with that of the twelve radiologists.

RESULTS

Fifty patients (30 males and 20 females; age range 29-86 years; mean 63.3 ± 12.8 years; a total of 165 metastases) who were clinically diagnosed with brain metastasis on follow-up were used for the training. The sensitivity of our model was 91.7%, which was higher than that of the observer test (mean ± standard deviation; 88.7 ± 3.7%). The number of FPs/case in our model was 1.5, which was greater than that by the observer test (0.17 ± 0.09).

CONCLUSIONS

Compared to radiologists, our model created by VISIBLE and CNN to diagnose brain metastases showed higher sensitivity. The number of FPs/case by our model was greater than that by the observer test of radiologists; however, it was less than that in most of the previous studies with deep learning.

KEY POINTS

• Our convolutional neural network based on bright-blood and black-blood examination to diagnose brain metastases showed a higher sensitivity than that by the observer test. • The number of false-positives/case by our model was greater than that by the previous observer test; however, it was less than those from most previous studies. • In our model, false-positives were found in the vessels, choroid plexus, and image noise or unknown causes.

Clinical Feasibility of Ultrafast Contrast-Enhanced T1-Weighted 3D-EPI for Evaluating Intracranial Enhancing Lesions in Oncology Patients: Comparison with Standard 3D MPRAGE Sequence

BACKGROUND AND PURPOSE

Contrast-enhanced 3D T1WI is a preferred sequence for brain tumor imaging despite the long scan time. This study investigated the clinical feasibility of ultrafast contrast-enhanced T1WI by 3D echo-planar imaging compared with a standard contrast-enhanced 3D MPRAGE sequence for evaluating intracranial enhancing lesions in oncology patients.

MATERIALS AND METHODS

Sixty-one patients in oncology underwent brain MR imaging including both contrast-enhanced T1WI, 3D-EPI and 3D MPRAGE, in a single examination session for evaluating intracranial tumors. Two neuroradiologists evaluated image quality, lesion conspicuity, diagnostic confidence, number and size of the lesions, and contrast-to-noise ratio measurements from the 2 different sequences.

RESULTS

Ultrafast 3D-EPI T1WI did not reveal significant differences in diagnostic confidence, contrast-to-noise ratio_{lesion/parenchyma}, and the number of enhancing lesions compared with MPRAGE (P > .05). However, ultrafast 3D-EPI T1WI revealed inferior image quality, inferior anatomic delineation and greater susceptibility artifacts with fewer motion artifacts than images obtained with MPRAGE. The mean contrast-to-noise ratio_WM/GM and visual conspicuity of the lesion on ultrafast 3D-EPI T1WI were lower than those of MPRAGE (P < .001).

CONCLUSIONS

Ultrafast 3D-EPI T1WI showed comparable diagnostic performance with sufficient image quality and a 7-fold reduction in scan time for evaluating intracranial enhancing lesions compared with standard MPRAGE, even though it was limited by an inferior image quality and frequent susceptibility artifacts. Therefore, we believe that ultrafast 3D-EPI T1WI may be a viable option in oncology patients prone to movement during imaging studies.

Brain metastases: An update on the multi-disciplinary approach of clinical management

IMPORTANCE

Brain metastasis (BM) is the most common malignant intracranial neoplasm in adults with over 100,000 new cases annually in the United States and outnumbering primary brain tumors 10:1.

OBSERVATIONS

The incidence of BM in adult cancer patients ranges from 10-40%, and is increasing with improved surveillance, effective systemic therapy, and an aging population. The overall prognosis of cancer patients is largely dependent on the presence or absence of brain metastasis, and therefore, a timely and accurate diagnosis is crucial for improving long-term outcomes, especially in the current era of significantly improved systemic therapy for many common cancers. BM should be suspected in any cancer patient who develops new neurological deficits or behavioral abnormalities. Gadolinium enhanced MRI is the preferred imaging technique and BM must be distinguished from other pathologies. Large, symptomatic lesion(s) in patients with good functional status are best treated with surgery and stereotactic radiosurgery (SRS). Due to neurocognitive side effects and improved overall survival of cancer patients, whole brain radiotherapy (WBRT) is reserved as salvage therapy for patients with multiple lesions or as palliation. Newer approaches including multi-lesion stereotactic surgery, targeted therapy, and immunotherapy are also being investigated to improve outcomes while preserving quality of life.

CONCLUSION

With the significant advancements in the systemic treatment for cancer patients, addressing BM effectively is critical for overall survival. In addition to patient's performance status, therapeutic approach should be based on the type of primary tumor and associated molecular profile as well as the size, number, and location of metastatic lesion(s).

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.

Consensus recommendations for a standardized brain tumor imaging protocol for clinical trials in brain metastases

A recent meeting was held on March 22, 2019, among the FDA, clinical scientists, pharmaceutical and biotech companies, clinical trials cooperative groups, and patient advocacy groups to discuss challenges and potential solutions for increasing development of therapeutics for central nervous system metastases. A key issue identified at this meeting was the need for consistent tumor measurement for reliable tumor response assessment, including the first step of standardized image acquisition with an MRI protocol that could be implemented in multicenter studies aimed at testing new therapeutics. This document builds upon previous consensus recommendations for a standardized brain tumor imaging protocol (BTIP) in high-grade gliomas and defines a protocol for brain metastases (BTIP-BM) that addresses unique challenges associated with assessment of CNS metastases. The "minimum standard" recommended pulse sequences include: (i) parameter matched pre- and post-contrast inversion recovery (IR)-prepared, isotropic 3D T1-weighted gradient echo (IR-GRE); (ii) axial 2D T2-weighted turbo spin echo acquired after injection of gadolinium-based contrast agent and before post-contrast 3D T1-weighted images; (iii) axial 2D or 3D T2-weighted fluid attenuated inversion recovery; (iv) axial 2D, 3-directional diffusion-weighted images; and (v) post-contrast 2D T1-weighted spin echo images for increased lesion conspicuity. Recommended sequence parameters are provided for both 1.5T and 3T MR systems. An "ideal" protocol is also provided, which replaces IR-GRE with 3D TSE T1-weighted imaging pre- and post-gadolinium, and is best performed at 3T, for which dynamic susceptibility contrast perfusion is included. Recommended perfusion parameters are given.

Implementation of a dedicated 1.5 T MR scanner for radiotherapy treatment planning featuring a novel high-channel coil setup for brain imaging in treatment position

Purpose

To share our experiences in implementing a dedicated magnetic resonance (MR) scanner for radiotherapy (RT) treatment planning using a novel coil setup for brain imaging in treatment position as well as to present developed core protocols with sequences specifically tuned for brain and prostate RT treatment planning.

Materials and methods

Our novel setup consists of two large 18-channel flexible coils and a specifically designed wooden mask holder mounted on a flat tabletop overlay, which allows patients to be measured in treatment position with mask immobilization. The signal-to-noise ratio (SNR) of this setup was compared to the vendor-provided flexible coil RT setup and the standard setup for diagnostic radiology. The occurrence of motion artifacts was quantified. To develop magnetic resonance imaging (MRI) protocols, we formulated site- and disease-specific clinical objectives.

Results

Our novel setup showed mean SNR of 163 ± 28 anteriorly, 104 ± 23 centrally, and 78 ± 14 posteriorly compared to 84 ± 8 and 102 ± 22 anteriorly, 68 ± 6 and 95 ± 20 centrally, and 56 ± 7 and 119 ± 23 posteriorly for the vendor-provided and diagnostic setup, respectively. All differences were significant (p > 0.05). Image quality of our novel setup was judged suitable for contouring by expert-based assessment. Motion artifacts were found in 8/60 patients in the diagnostic setup, whereas none were found for patients in the RT setup. Site-specific core protocols were designed to minimize distortions while optimizing tissue contrast and 3D resolution according to indication-specific objectives.

Conclusion

We present a novel setup for high-quality imaging in treatment position that allows use of several immobilization systems enabling MR-only workflows, which could reduce unnecessary dose and registration inaccuracies.

Electronic supplementary material

The online version of this article (10.1007/s00066-020-01703-y) contains supplementary material, which is available to authorized users.

Detection of brain metastases using alternative magnetic resonance imaging sequences: a comparison between SPACE and VIBE sequences

Background

Accurate identification of brain metastases is crucial for cancer treatment.

Objectives

To compare the ability to detect brain metastases of two alternative types of contrast-enhanced three-dimensional (3D) T1-weighted sequences called SPACE (Sampling Perfection with Application optimized Contrasts using different flip angle Evolutions) and VIBE (Volumetric Interpolated Brain Sequence) on magnetic resonance imaging (MRI) at 3 tesla.

Methods

Between April 2017 and February 2018, 27 consecutive adult Thai patients with a total number of 424 brain metastases were retrospectively included. The patients underwent both contrast-enhanced 3D T1-weighted SPACE and 3D T1-weighted VIBE MRI sequences at 3 tesla. Two neuroradiology experts independently reviewed the images to determine the number of enhancing lesions on each sequence. Wilcoxon signed rank test was used to compare the difference between the numbers of detectable parenchymal enhancing lesions. Interobserver reliability was calculated using intraclass correlation.

Results

3D T1-weighted SPACE detected more parenchymal enhancing lesions than 3D T1-weighted VIBE (424 vs. 378 lesions, median 6 vs. 5, P = 0.008). Fifteen patients (55.6%) had equal number of parenchymal enhancing lesions between two sequences. 3D T1-weighted SPACE detected more parenchymal enhancing lesions (up to 9 more lesions) in 10 patients (37%), while 3D T1-weighted VIBE detected more enhancing lesions (up to 2 more lesions) in 2 patients (7.4%). Interobserver reliability between the readers was excellent.

Conclusion

Contrast-enhanced 3D T1-weighted SPACE sequence demonstrates a higher ability to detect brain metastases than contrast-enhanced 3D T1-weighted VIBE sequence at 3 tesla.

Perianal fistula mapping at 3 T: volumetric versus conventional MRI sequences

AIM

To evaluate volumetric contrast-enhanced three-dimensional T1-weighted (CE 3D T1) turbo spin-echo (TSE) with variable flip angle (SPACE), CE 3D T1 volumetric interpolated breath-hold examination (VIBE) sequences with conventional CE-two-dimensional (2D)-T1 and 2D-T2-weighted imaging (WI) sequences in assessing perianal fistulas.

METHODS AND MATERIALS

Twenty-three patients with perianal fistula were included in this prospective study and underwent pelvic magnetic resonance imaging (MRI) at 3 T including fat-supressed CE 3D T1 SPACE, CE 3D T1 VIBE, axial and coronal 2D-T1WI together with 2D-T2WI sequences in the axial and coronal planes. Acquisition times were recorded. Performance of each sequence was evaluated in terms of image quality, presence of artefacts, lesion conspicuity, fistula type, presence of abscess, visibility of internal orifice, and number of internal orifices. Results were compared with post-surgical findings defined as the reference standard.

RESULTS

Both CE 3D T1 VIBE and CE 3D T1 SPACE were the best sequences to determine fistula type and in terms of image quality, artefacts, and determining locations of internal orifices. The number of internal orifices was detected correctly in 23 (100%) patients for CE 3D T1 SPACE and CE 3D T1 VIBE sequences, in 17 (73.9%) patients on CE-T1WI, and in seven (30.4%) patients on 2D-T2WI. Lesion conspicuity was higher for CE 3D T1 SPACE and CE 3D T1 VIBE sequences compared to the 2D sequences (p<0.05). The overall acquisition time for each 3D sequence was shorter compared to the 2D sequences combined.

CONCLUSION

CE 3D T1 SPACE and CE 3D T1 VIBE sequences may outperform conventional 2D sequences in the evaluation of perianal fistulas in terms of visibility and number of internal orifices with a shorter scanning time.

Magnetic resonance imaging for brain stereotactic radiotherapy : A review of requirements and pitfalls

Due to its superior soft tissue contrast, magnetic resonance imaging (MRI) is essential for many radiotherapy treatment indications. This is especially true for treatment planning in intracranial tumors, where MRI has a long-standing history for target delineation in clinical practice. Despite its routine use, care has to be taken when selecting and acquiring MRI studies for the purpose of radiotherapy treatment planning. Requirements on MRI are particularly demanding for intracranial stereotactic radiotherapy, where accurate imaging has a critical role in treatment success. However, MR images acquired for routine radiological assessment are frequently unsuitable for high-precision stereotactic radiotherapy as the requirements for imaging are significantly different for radiotherapy planning and diagnostic radiology. To assure that optimal imaging is used for treatment planning, the radiation oncologist needs proper knowledge of the most important requirements concerning the use of MRI in brain stereotactic radiotherapy. In the present review, we summarize and discuss the most relevant issues when using MR images for target volume delineation in intracranial stereotactic radiotherapy.

Deep-Learning Detection of Cancer Metastases to the Brain on MRI

BACKGROUND

Approximately one-fourth of all cancer metastases are found in the brain. MRI is the primary technique for detection of brain metastasis, planning of radiotherapy, and the monitoring of treatment response. Progress in tumor treatment now requires detection of new or growing metastases at the small subcentimeter size, when these therapies are most effective.

PURPOSE

To develop a deep-learning-based approach for finding brain metastasis on MRI.

STUDY TYPE

Retrospective.

SEQUENCE

Axial postcontrast 3D T₁ -weighted imaging.

FIELD STRENGTH

1.5T and 3T.

POPULATION

A total of 361 scans of 121 patients were used to train and test the Faster region-based convolutional neural network (Faster R-CNN): 1565 lesions in 270 scans of 73 patients for training; 488 lesions in 91 scans of 48 patients for testing. From the 48 outputs of Faster R-CNN, 212 lesions in 46 scans of 18 patients were used for training the RUSBoost algorithm (MatLab) and 276 lesions in 45 scans of 30 patients for testing.

ASSESSMENT

Two radiologists diagnosed and supervised annotation of metastases on brain MRI as ground truth. This data were used to produce a 2-step pipeline consisting of a Faster R-CNN for detecting abnormal hyperintensity that may represent brain metastasis and a RUSBoost classifier to reduce the number of false-positive foci detected.

STATISTICAL TESTS

The performance of the algorithm was evaluated by using sensitivity, false-positive rate, and receiver's operating characteristic (ROC) curves. The detection performance was assessed both per-metastases and per-slice.

RESULTS

Testing on held-out brain MRI data demonstrated 96% sensitivity and 20 false-positive metastases per scan. The results showed an 87.1% sensitivity and 0.24 false-positive metastases per slice. The area under the ROC curve was 0.79.

CONCLUSION

Our results showed that deep-learning-based computer-aided detection (CAD) had the potential of detecting brain metastases with high sensitivity and reasonable specificity.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:1227-1236.

Usefulness of the Delay Alternating with Nutation for Tailored Excitation Pulse with T1-Weighted Sampling Perfection with Application-Optimized Contrasts Using Different Flip Angle Evolution in the Detection of Cerebral Metastases: Comparison with MPRAGE Imaging

BACKGROUND AND PURPOSE

Contrast-enhanced T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolution (SPACE) with the delay alternating with nutation for tailored excitation (DANTE) pulse could suppress the blood flow signal and provide a higher contrast-to-noise ratio of enhancing lesion-to-brain parenchyma than the MPRAGE sequence. The purpose of our study was to evaluate the usefulness of SPACE with DANTE compared with MPRAGE for detecting brain metastases.

MATERIALS AND METHODS

Seventy-one patients who underwent contrast-enhanced SPACE with DANTE and MPRAGE sequences and who were suspected of having metastatic lesions were included. Two neuroradiologists determined the number of enhancing lesions, and diagnostic performance was evaluated using figure of merit, sensitivity, positive predictive value, interobserver agreement, and reading time. Contrast-to-noise ratio_{lesion/parenchyma} and contrast-to-noise ratio_{white matter/gray matter} were also assessed.

RESULTS

SPACE with DANTE (observer one, 328; observer two, 324) revealed significantly more small (<5 mm) enhancing lesions than MPRAGE (observer one, 175; observer two, 150) (P < 0.001 for observer 1, P ≤ .0001 for observer 2). Furthermore, SPACE with DANTE showed significantly higher figure of merit and sensitivity and shorter reading time than MPRAGE for both observers. The mean contrast-to-noise ratio_{lesion/parenchyma} of SPACE with DANTE (52.3 ± 43.1) was significantly higher than that of MPRAGE (17.5 ± 19.3) (P ≤ .0001), but the mean contrast-to-noise ratio_{white matter/gray matter} of SPACE with DANTE (-0.65 ± 1.39) was significantly lower than that of MPRAGE (3.08 ± 1.39) (P ≤ .0001).

CONCLUSIONS

Compared with MPRAGE, SPACE with DANTE significantly improves the detection of brain metastases.

Brain Tumor-Enhancement Visualization and Morphometric Assessment: A Comparison of MPRAGE, SPACE, and VIBE MRI Techniques

BACKGROUND AND PURPOSE

Postgadolinium MR imaging is crucial for brain tumor diagnosis and morphometric assessment. We compared brain tumor enhancement visualization and the "target" object morphometry obtained with the most commonly used 3D MR imaging technique, MPRAGE, with 2 other routinely available techniques: sampling perfection with application-optimized contrasts by using different flip angle evolutions (SPACE) and volumetric interpolated brain examination (VIBE).

MATERIALS AND METHODS

Fifty-four contrast-enhancing tumors (38 gliomas and 16 metastases) were assessed using MPRAGE, VIBE, and SPACE techniques randomly acquired after gadolinium-based contrast agent administration on a 3T scanner. Enhancement conspicuity was assessed quantitatively by calculating the contrast rate and contrast-to-noise ratio, and qualitatively, by consensus visual comparative ratings. The total enhancing tumor volume and between-sequence discrepancy in the margin delineation were assessed on the corresponding 3D target objects contoured with a computer-assisted software for neuronavigation. The Wilcoxon signed rank and Pearson χ² nonparametric tests were used to investigate between-sequence discrepancies in the contrast rate, contrast-to-noise ratio, visual conspicuity ratings, tumor volume, and margin delineation estimates. Differences were also tested for 1D (Response Evaluation Criteria in Solid Tumors) and 2D (Response Assessment in Neuro-Oncology) measurements.

RESULTS

Compared with MPRAGE, both SPACE and VIBE obtained higher contrast rate, contrast-to-noise ratio, and visual conspicuity ratings in both gliomas and metastases (P range, <.001-.001). The between-sequence 3D target object margin discrepancy ranged between 3% and 19.9% of lesion tumor volume. Larger tumor volumes, 1D and 2D measurements were obtained with SPACE (P range, <.01-.007).

CONCLUSIONS

Superior conspicuity for brain tumor enhancement can be achieved using SPACE and VIBE techniques, compared with MPRAGE. Discrepancies were also detected when assessing target object size and morphology, with SPACE providing more accurate estimates.

Three-dimensional T1-weighted gradient echo is a suitable alternative to two-dimensional T1-weighted spin echo for imaging the canine brain

Volumetric imaging (VOL), a three‐dimensional magnetic resonance imaging (MRI) technique, has been described in the literature for evaluation of the human brain. It offers several advantages over conventional two‐dimensional (2D) spin echo (SE), allowing rapid, whole‐brain, isotropic imaging with submillimeter voxels. This retrospective, observational study compares the use of 2D T1‐weighted SE (T1W SE), with T1W VOL, for the evaluation of dogs with clinical signs of intracranial disease. Brain MRI images from 160 dogs who had T1W SE and T1W VOL sequences acquired pre‐ and postcontrast, were reviewed for presence and characteristics of intracranial lesions. Twenty‐nine of 160 patients were found to have intracranial lesions, all visible on both sequences. Significantly better grey‐white matter (GWM) differentiation was identified with T1W VOL (P < .001), with fair agreement between the two sequences (weighted κ = 0.35). Excluding a mild reduction in lesion intensity in three dogs precontrast on the T1W VOL images compared to T1W SE, and meningeal enhancement noted on the T1W VOL images in one dog, not identified on T1W SE, there was otherwise complete agreement between the two sequences. The T1W VOL sequence provided equivalent lesion evaluation and significantly improved GWM differentiation. Images acquired were of comparable diagnostic quality to those produced using a conventional T1W SE technique, for assessment of lesion appearance, number, location, mass effect, and postcontrast enhancement. T1W VOL, therefore, provides a suitable alternative T1W sequence for canine brain evaluation and can facilitate a reduction in total image acquisition time.

To Compare Diagnostic Ability of Contrast-Enhanced Three-Dimensional T1-SPACE with Three-Dimensional Fluid-Attenuated Inversion Recovery and Three-Dimensional T1-Magnetization Prepared Rapid Gradient Echo Magnetic Resonance Sequences in Patients of Meningitis

Aims:

The aim of this study is to compare postcontrast three-dimensional (3D) T1-Sampling perfection with application-optimized contrasts by using different flip angle evolutions, 3D fluid-attenuated inversion recovery (FLAIR), and 3D T1-magnetization prepared rapid gradient echo (MPRAGE) sequences in patients of meningitis.

Settings and Design:

A hospital-based cross-sectional study done in the Department of Radiodiagnosis, IGMC Shimla for a period of 1 year from June 1, 2016, to May 30, 2017.

Subjects and Methods:

A total of 30 patients suspected of meningitis underwent magnetic resonance imaging evaluation with postcontrast 3D T1-MPRAGE, 3D T1-SPACE, and 3D FLAIR sequences. The abnormal leptomeningeal enhancement was noted by two radiologists together on these sequences and scores were given to the abnormal leptomeningeal enhancement.

Statistical Analysis Used:

The sensitivity of 3D T1-SPACE, 3D T1-MPRAGE, and 3D FLAIR was calculated and compared. The level of agreement between these sequences was assessed by kappa coefficient. P < 0.05 was taken as statistically significant.

Results:

3D T1-SPACE shows superiority in meningeal enhancement along basal cisterns, Sylvian fissure and along cerebral convexities. It is also found to be better in delineating parenchymal lesions. 3D FLAIR failed to demonstrate enhancement along cerebral convexities however found to be better than 3D T1-MPRAGE in delineating enhancement along basal cisterns and Sylvian fissures. 3D T1-MPRAGE has shown subtle enhancement in basal cisterns, Sylvian fissure and along cerebral convexities. 3D T1-SPACE, 3D FLAIR, and 3D T1-MPRAGE has sensitivity of 91.67%, 66.67%, and 54.17%, respectively.

Conclusion:

Postcontrast 3D T1-SPACE sequence is an excellent tool than postcontrast 3D T1-MPRAGE and 3D FLAIR sequences in the evaluation of meningeal enhancement and depiction of additional lesions in brain parenchyma.

Pseudo-Leptomeningeal Contrast Enhancement at 3T in Pediatric Patients Sedated by Propofol

BACKGROUND AND PURPOSE

Propofol is a cerebral vasoconstrictor that modulates cerebral perfusion by decreasing the metabolic rate of oxygen. Because younger children often undergo intravenous sedation for MR imaging, this study set out to evaluate the degree of leptomeningeal contrast enhancement on 3T postcontrast brain MR imaging and to determine whether this phenomenon relates to sequence, sedation dosage, or patient age or weight.

MATERIALS AND METHODS

During a 2-year period, of 152 children 1-5 years of age who underwent MR imaging, 43 were included for MRI review. Of these, 37 underwent postcontrast imaging with either solely gradient-echo T1WI (n = 20) or spin-echo T1WI (n = 17); notably, 6 patients underwent both sequences. Three neuroradiologists separately graded the degree of leptomeningeal contrast enhancement (grades 0-3) that was correlated with various factors and calculated the interobserver reliability.

RESULTS

For the 43 patients, the mean patient age was 3.1 ± 1.4 years. The leptomeningeal contrast-enhancement grade was significantly greater (P < .0001) on spin-echo T1WI (1.9-2.1) versus gradient-echo TIWI (1.2-1.4). Patient weight (r = -0.366 to -.418, P = .003-.01) and age (r = -0.315 to -0.418, P = .004-.032) moderately and inversely correlated with the leptomeningeal contrast-enhancement grade, while the propofol dosage, sedation duration, and time to T1WI post-contrast administration did not (each, P > .05). The interobserver κ was strong regarding the leptomeningeal contrast-enhancement grade on both spin-echo T1WI (κ = 0.609-0.693, P < .0001) and gradient-echo TIWI (κ = 0.567-0.698, P < .0001).

CONCLUSIONS

Leptomeningeal contrast enhancement (or "pseudo"-leptomeningeal contrast enhancement) occurs with a greater frequency and degree on 3T postcontrast spin-echo T1WI relative to gradient-echo TIWI in younger children sedated with propofol and should not be mistaken for disease. This phenomenon may be more prominent with lower age or size and may arise from propofol-induced vascular smooth-muscle dilation.

Evaluation of Thick-Slab Overlapping MIP Images of Contrast-Enhanced 3D T1-Weighted CUBE for Detection of Intracranial Metastases: A Pilot Study for Comparison of Lesion Detection, Interpretation Time, and Sensitivity with Nonoverlapping CUBE MIP, CUBE, and Inversion-Recovery-Prepared Fast-Spoiled Gradient Recalled Brain Volume

BACKGROUND AND PURPOSE

Early and accurate identification of cerebral metastases is important for prognostication and treatment planning although this process is often time consuming and labor intensive, especially with the hundreds of images associated with 3D volumetric imaging. This study aimed to evaluate the benefits of thick-slab overlapping MIPs constructed from contrast-enhanced T1-weighted CUBE (overlapping CUBE MIP) for the detection of brain metastases in comparison with traditional CUBE and inversion-recovery prepared fast-spoiled gradient recalled brain volume (IR-FSPGR-BRAVO) and nonoverlapping CUBE MIP.

MATERIALS AND METHODS

A retrospective review of 48 patients with cerebral metastases was performed at our institution from June 2016 to October 2017. Brain MRIs, which were acquired on multiple 3T scanners, included gadolinium-enhanced T1-weighted IR-FSPGR-BRAVO and CUBE, with subsequent generation of nonoverlapping CUBE MIP and overlapping CUBE MIP. Two blinded radiologists identified the total number and location of metastases on each image type. The Cohen κ was used to determine interrater agreement. Sensitivity, interpretation time, and lesion contrast-to-noise ratio were assessed.

RESULTS

Interrater agreement for identification of metastases was fair-to-moderate for all image types (κ = 0.222-0.598). The total number of metastases identified was not significantly different across the image types. Interpretation time for CUBE MIPs was significantly shorter than for CUBE and IR-FSPGR-BRAVO, saving at least 50 seconds per case on average (P < .001). The mean lesion contrast-to-noise ratio for both CUBE MIPs was higher than for IR-FSPGR-BRAVO. The mean contrast-to-noise ratio for small lesions (<4 mm) was lower for nonoverlapping CUBE MIP (1.55) than for overlapping CUBE MIP (2.35). For both readers, the sensitivity for lesion detection was high for all image types but highest for overlapping CUBE MIP and CUBE (0.93-0.97).

CONCLUSIONS

This study suggests that the use of overlapping CUBE MIP or nonoverlapping CUBE MIP for the detection of brain metastases can reduce interpretation time without sacrificing sensitivity, though the contrast-to-noise ratio of lesions is highest for overlapping CUBE MIP.

Deep-learned 3D black-blood imaging using automatic labelling technique and 3D convolutional neural networks for detecting metastatic brain tumors

Black-blood (BB) imaging is used to complement contrast-enhanced 3D gradient-echo (CE 3D-GRE) imaging for detecting brain metastases, requiring additional scan time. In this study, we proposed deep-learned 3D BB imaging with an auto-labelling technique and 3D convolutional neural networks for brain metastases detection without additional BB scan. Patients were randomly selected for training (29 sets) and testing (36 sets). Two neuroradiologists independently evaluated deep-learned and original BB images, assessing the degree of blood vessel suppression and lesion conspicuity. Vessel signals were effectively suppressed in all patients. The figure of merits, which indicate the diagnostic performance of radiologists, were 0.9708 with deep-learned BB and 0.9437 with original BB imaging, suggesting that the deep-learned BB imaging is highly comparable to the original BB imaging (difference was not significant; p = 0.2142). In per patient analysis, sensitivities were 100% for both deep-learned and original BB imaging; however, the original BB imaging indicated false positive results for two patients. In per lesion analysis, sensitivities were 90.3% for deep-learned and 100% for original BB images. There were eight false positive lesions on the original BB imaging but only one on the deep-learned BB imaging. Deep-learned 3D BB imaging can be effective for brain metastases detection.

Sensitivity of different MRI sequences in the early detection of melanoma brain metastases

BACKGROUND

After the emergence of new MRI techniques such as susceptibility- and diffusion-weighted imaging (SWI and DWI) and because of specific imaging characteristics of melanoma brain metastases (MBM), it is unclear which MRI sequences are most beneficial for detection of MBM. This study was performed to investigate the sensitivity of six clinical MRI sequences in the early detection of MBM.

METHODS

Medical records of all melanoma patients referred to our center between November 2005 and December 2016 were reviewed for presence of MBM. Analysis encompassed six MRI sequences at the time of initial diagnosis of first or new MBM, including non-enhanced T1-weighted (T1w), contrast-enhanced T1w (ceT1w), T2-weighted (T2w), T2w-FLAIR, susceptibility-weighted (SWI) and diffusion-weighted (DWI) MRI. Each lesion was rated with respect to its conspicuity (score from 0-not detectable to 3-clearly visible).

RESULTS

Of 1210 patients, 217 with MBM were included in the analysis and up to 5 lesions per patient were evaluated. A total of 720 metastases were assessed and all six sequences were available for 425 MBM. Sensitivity (conspicuity ≥2) was 99.7% for ceT1w, 77.0% for FLAIR, 64.7% for SWI, 61.0% for T2w, 56.7% for T1w, and 48.4% for DWI. Thirty-one (7.3%) of 425 lesions were only detectable by ceT1w but no other sequence.

CONCLUSIONS

Contrast-enhanced T1-weighting is more sensitive than all other sequences for detection of MBM. Disruption of the blood-brain-barrier is consistently an earlier sign in MBM than perifocal edema, signal loss on SWI or diffusion restriction.

Consensus recommendations on standardized magnetic resonance imaging protocols for multicenter canine brain tumor clinical trials

The National Cancer Institute Comparative Brain Tumor Consortium, Patient Outcomes Working Group, propose a consensus document in support of standardized magnetic resonance imaging protocols for canine brain tumor clinical trials. The intent of this manuscript is to address the widely acknowledged need to ensure canine brain tumor imaging protocols are relevant and have sufficient equivalency to translate to human studies such that: (1) multi-institutional studies can be performed with minimal inter-institutional variation, and (2) imaging protocols are consistent with human consensus recommendations to permit reliable translation of imaging data to human clinical trials. Consensus recommendations include pre- and postcontrast three-dimensional T1-weighted images, T2-weighted turbo spin echo in all three planes, T2*-weighted gradient recalled echo, T2-weighted fluid attenuated inversion recovery, and diffusion weighted imaging/diffusion tensor imaging in transverse plane; field of view of ≤150 mm; slice thickness of ≤2 mm, matrix ≥ 256 for two-dimensional images, and 150 or 256 for three-dimensional images.

Comparison of lesion enhancement between BB Cube and 3D-SPGR images for brain tumors with 1.5-T magnetic resonance imaging

PURPOSE

This study aimed to compare the detectability of neoplastic lesion enhancement after gadolinium-based contrast media injection in three-dimensional T1-weighted black blood Cube (3D-T1W BB Cube) and three-dimensional T1-weighted fast spoiled gradient-echo (3D-T1W fast SPGR) images obtained with 1.5-T magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Phantom and clinical studies were performed to compare the lesion detectability and contrast ratio (CR) between 3D-T1W BB Cube and 3D-T1W fast SPGR pulse sequences.

RESULTS

In the phantom study, the CRs for 3D-T1W BB Cube and 3D-T1W fast SPGR were equivalent at low gadolinium concentrations (0.125-1.25 mmol/l). In the clinical study, the detectability in the two modalities was similar for enhanced lesions ≥5 mm, but was significantly better in 3D-T1W BB Cube for lesions <5 mm (p = 0.011). Similarly, the CRs in both modalities were similar for lesions ≥5 mm (0.66 ± 0.36 vs. 0.56 ± 0.30, p = 0.153), but significantly lower in 3D-T1W BB Cube images for lesions <5 mm (0.29 ± 0.19 vs. 0.39 ± 0.21, p = 0.006).

CONCLUSIONS

Contrast 3D-T1W BB Cube imaging appears more sensitive than 3D-T1W fast SPGR imaging for detecting neoplastic lesion enhancement in the clinical setting using a 1.5-T MRI scanner, particularly for lesions <5 mm in diameter.

Efficacy of Maximum Intensity Projection of Contrast-Enhanced 3D Turbo-Spin Echo Imaging with Improved Motion-Sensitized Driven-Equilibrium Preparation in the Detection of Brain Metastases

Objective

To evaluate the diagnostic benefits of 5-mm maximum intensity projection of improved motion-sensitized driven-equilibrium prepared contrast-enhanced 3D T1-weighted turbo-spin echo imaging (MIP iMSDE-TSE) in the detection of brain metastases. The imaging technique was compared with 1-mm images of iMSDE-TSE (non-MIP iMSDE-TSE), 1-mm contrast-enhanced 3D T1-weighted gradient-echo imaging (non-MIP 3D-GRE), and 5-mm MIP 3D-GRE.

Materials and Methods

From October 2014 to July 2015, 30 patients with 460 enhancing brain metastases (size > 3 mm, n = 150; size ≤ 3 mm, n = 310) were scanned with non-MIP iMSDE-TSE and non-MIP 3D-GRE. We then performed 5-mm MIP reconstruction of these images. Two independent neuroradiologists reviewed these four sequences. Their diagnostic performance was compared using the following parameters: sensitivity, reading time, and figure of merit (FOM) derived by jackknife alternative free-response receiver operating characteristic analysis. Interobserver agreement was also tested.

Results

The mean FOM (all lesions, 0.984; lesions ≤ 3 mm, 0.980) and sensitivity ([reader 1: all lesions, 97.3%; lesions ≤ 3 mm, 96.2%], [reader 2: all lesions, 97.0%; lesions ≤ 3 mm, 95.8%]) of MIP iMSDE-TSE was comparable to the mean FOM (0.985, 0.977) and sensitivity ([reader 1: 96.7, 99.0%], [reader 2: 97, 95.3%]) of non-MIP iMSDE-TSE, but they were superior to those of non-MIP and MIP 3D-GREs (all, p < 0.001). The reading time of MIP iMSDE-TSE (reader 1: 47.7 ± 35.9 seconds; reader 2: 44.7 ± 23.6 seconds) was significantly shorter than that of non-MIP iMSDE-TSE (reader 1: 78.8 ± 43.7 seconds, p = 0.01; reader 2: 82.9 ± 39.9 seconds, p < 0.001). Interobserver agreement was excellent (κ > 0.75) for all lesions in both sequences.

Conclusion

MIP iMSDE-TSE showed high detectability of brain metastases. Its detectability was comparable to that of non-MIP iMSDE-TSE, but it was superior to the detectability of non-MIP/MIP 3D-GREs. With a shorter reading time, the false-positive results of MIP iMSDE-TSE were greater. We suggest that MIP iMSDE-TSE can provide high diagnostic performance and low false-positive rates when combined with 1-mm sequences.

Comparison of post-contrast 3D-T1-MPRAGE, 3D-T1-SPACE and 3D-T2-FLAIR MR images in evaluation of meningeal abnormalities at 3-T MRI

OBJECTIVE

This study was to assess the usefulness of newer three-dimensional (3D)-T₁ sampling perfection with application optimized contrast using different flip-angle evolutions (SPACE) and 3D-T₂ fluid-attenuated inversion recovery (FLAIR) sequences in evaluation of meningeal abnormalities.

METHODS

78 patients who presented with high suspicion of meningeal abnormalities were evaluated using post-contrast 3D-T₂-FLAIR, 3D-T₁ magnetization-prepared rapid gradient-echo (MPRAGE) and 3D-T₁-SPACE sequences. The images were evaluated independently by two radiologists for cortical gyral, sulcal space, basal cisterns and dural enhancement. The diagnoses were confirmed by further investigations including histopathology.

RESULTS

Post-contrast 3D-T₁-SPACE and 3D-T₂-FLAIR images yielded significantly more information than MPRAGE images (p < 0.05 for both SPACE and FLAIR images) in detection of meningeal abnormalities. SPACE images best demonstrated abnormalities in dural and sulcal spaces, whereas FLAIR was useful for basal cisterns enhancement. Both SPACE and FLAIR performed equally well in detection of gyral enhancement. In all 10 patients, where both SPACE and T₂-FLAIR images failed to demonstrate any abnormality, further analysis was also negative.

CONCLUSION

The 3D-T₁-SPACE sequence best demonstrated abnormalities in dural and sulcal spaces, whereas FLAIR was useful for abnormalities in basal cisterns. Both SPACE and FLAIR performed holds good for detection of gyral enhancement. Post-contrast SPACE and FLAIR sequences are superior to the MPRAGE sequence for evaluation of meningeal abnormalities and when used in combination have the maximum sensitivity for leptomeningeal abnormalities. The negative-predictive value is nearly 100%, where no leptomeningeal abnormality was detected on these sequences. Advances in knowledge: Post-contrast 3D-T₁-SPACE and 3D-T₂-FLAIR images are more useful than 3D-T₁-MPRAGE images in evaluation of meningeal abnormalities.

MIP Improves Detection of Brain Metastases

PURPOSE

This study aimed to compare the sensitivity for detection of brain metastases using postcontrast 3-dimensional, T1W-gradient echo sequence (3DT1W) and maximum intensity projections (MIPs) obtained from the same data set.

MATERIALS AND METHODS

A prospective analysis of patients with known brain metastases was performed. We compared 1-mm postcontrast 3DT1W with 6-mm MIP reconstructions obtained from the same images (MIP-3DT1) in 95 patients using 1.5 (42 patients) and 3 T (53 patient). Two independent readers analyzed all studies and the examinations were presented in anonymized and random fashion for a total of 190 interpretations per observer. One reader had more than 20 years of experience and the second reader had 1 year of experience.

RESULTS

The least experienced observer found 542 brain metastases on postcontrast non-MIP 3DT1W and 605 with the MIP-3DT1 technique. For this observer, use of MIP resulted in increased number of detected metastases in 36% of patients regardless of field strength. The more experienced observer found 589 brain metastases on non-MIP 3DT1W and 621 with the MIP-3DT1 technique and the use of the latter also resulted in increased detection of metastases in 33% of patients regardless of field strength.

CONCLUSIONS

In our study, we found that using MIP-3DT1 reconstructions of previously obtained postcontrast 3DT1W improved detection of brain metastases. This improvement was experienced by both the junior and experienced neuroradiologists and was also better at 3.0 T than at 1.5 T.

[Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse]

Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T₁-weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T₁ contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T₁ contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T₁ contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T₁ value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T₁ value is long (>600 ms), at a TR of 600 ms, improvement in T₁ contrast by applying spoiled equilibrium pulse cannot be expected.

Detection of Leptomeningeal Metastasis by Contrast-Enhanced 3D T1-SPACE: Comparison with 2D FLAIR and Contrast-Enhanced 2D T1-Weighted Images

Introduction

To compare the diagnostic accuracy of contrast-enhanced 3D(dimensional) T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolutions (T1-SPACE), 2D fluid attenuated inversion recovery (FLAIR) images and 2D contrast-enhanced T1-weighted image in detection of leptomeningeal metastasis except for invasive procedures such as a CSF tapping.

Materials and Methods

Three groups of patients were included retrospectively for 9 months (from 2013-04-01 to 2013-12-31). Group 1 patients with positive malignant cells in CSF cytology (n = 22); group 2, stroke patients with steno-occlusion in ICA or MCA (n = 16); and group 3, patients with negative results on MRI, whose symptom were dizziness or headache (n = 25). A total of 63 sets of MR images are separately collected and randomly arranged: (1) CE 3D T1-SPACE; (2) 2D FLAIR; and (3) CE T1-GRE using a 3-Tesla MR system. A faculty neuroradiologist with 8-year-experience and another 2^nd grade trainee in radiology reviewed each MR image- blinded by the results of CSF cytology and coded their observations as positives or negatives of leptomeningeal metastasis. The CSF cytology result was considered as a gold standard. Sensitivity and specificity of each MR images were calculated. Diagnostic accuracy was compared using a McNemar’s test. A Cohen's kappa analysis was performed to assess inter-observer agreements.

Results

Diagnostic accuracy was not different between 3D T1-SPACE and CSF cytology by both raters. However, the accuracy test of 2D FLAIR and 2D contrast-enhanced T1-weighted GRE was inconsistent by the two raters. The Kappa statistic results were 0.657 (3D T1-SPACE), 0.420 (2D FLAIR), and 0.160 (2D contrast-enhanced T1-weighted GRE). The 3D T1-SPACE images showed the highest inter-observer agreements between the raters.

Conclusions

Compared to 2D FLAIR and 2D contrast-enhanced T1-weighted GRE, contrast-enhanced 3D T1 SPACE showed a better detection rate of leptomeningeal metastasis.

T1-weighted MR imaging of glioma at 3T: a comparative study of 3D MPRAGE vs. conventional 2D spin-echo imaging

PURPOSE

This study aims to investigate difference between magnetization-prepared rapid gradient-echo imaging (MPRAGE) and spin-echo (SE) imaging for evaluating glioma on pre-contrast-enhanced (CE) and post-CE T1-weighted images at 3 T.

MATERIALS AND METHODS

We retrospectively assessed pre-CE and post-CE T1-weighted images for tumor contrast in 64 consecutive glioma patients.

RESULTS

In the nonenhancing tumors, the contrast was significantly clearer in MPRAGE than SE. In the enhancing tumors, post-CE contrast ratio was significantly higher in SE than MPRAGE, but when subtraction images are evaluated, the difference got smaller.

CONCLUSION

MPRAGE can be a good substitute of SE for T1-weighted imaging of glioma.

The detectability of brain metastases using contrast-enhanced spin-echo or gradient-echo images: a systematic review and meta-analysis

This study aimed to compare the detectability of brain metastases using contrast-enhanced spin-echo (SE) and gradient-echo (GRE) T1-weighted images. The Ovid-MEDLINE and EMBASE databases were searched for studies on the detectability of brain metastases using contrast-enhanced SE or GRE images. The pooled proportions for the detectability of brain metastases were assessed using random-effects modeling. Heterogeneity among studies was determined using χ (2) statistics for the pooled estimates and the inconsistency index, I (2) . To overcome heterogeneity, subgroup analyses according to slice thickness and lesion size were performed. A total of eight eligible studies, which included a sample size of 252 patients and 1413 brain metastases, were included. The detectability of brain metastases using SE images (89.2 %) was higher than using GRE images (81.6 %; adjusted 84.0 %), but this difference was not statistically significant (p = 0.2385). In subgroup analysis of studies with 1-mm-thick slices and small metastases (<5 mm in diameter), 3-dimensional (3D) SE images demonstrated a higher detectability in comparison to 3D GRE images (93.7 % vs 73.1 % in 1-mm-thick slices; 89.5 % vs 59.4 % for small metastases) (p < 0.0001). Although both SE or GRE images are acceptable for detecting brain metastases, contrast-enhanced 3D SE images using 1-mm-thick slices are preferred for detecting brain metastases, especially small lesions (<5 mm in diameter).

Comparison of contrast-enhanced modified T1-weighted 3D TSE black-blood and 3D MP-RAGE sequences for the detection of cerebral metastases and brain tumours

OBJECTIVES

To compare a modified T1-weighted 3D TSE black-blood sequence with sub-millimetre resolution (T1-mVISTA) with a magnetization-prepared rapid gradient echo (MP-RAGE) sequence for the diagnosis of cerebral malignomas.

METHODS

Forty-six patients with known or suspected intracranial tumours and 15 control patients were included in this retrospective study. All patients underwent T1-mVISTA (0.75-mm isotropic resolution, 4:43 min) and MP-RAGE (0.8-mm isotropic resolution, 4:46 minutes) at 3-Tesla in random order after application of contrast agent. Two experienced radiologists determined the number of lesions. Maximum diameter, diagnostic confidence (DC), visual assessment of contrast enhancement (VCE) and CNRlesion/parenchyma were assessed for each lesion.

RESULTS

Significantly more lesions were detected with T1-mVISTA compared to the MP-RAGE (61 vs. 36; p < 0.05). Further, DC and VCE was rated significantly higher in the T1-mVISTA (p < 0.05 and p < 0.001). Mean CNRlesion/parenchyma was twofold higher for T1-mVISTA (24.2 ± 17.5 vs. 12.7 ± 11.5, p < 0.001). The 25 lesions detected only in T1-mVISTA were significantly smaller than those detected in both sequences (4.3 ± 3.7 mm vs. 11.3 ± 10.7 mm; p < 0.01).

CONCLUSIONS

T1-mVISTA increases the contrast of lesions significantly compared to MP-RAGE and might therefore improve detection rates of small lesions in early stages of disease.

KEY POINTS

• T1-mVISTA leads to significantly higher contrast-to-noise ratios of cerebral malignomas. • T1-mVISTA detects significantly more metastatic lesions compared to 3D-MPRAGE. • Lesions detected only by T1-mVISTA are smaller than those detected in both sequences. • Diagnostic confidence is significantly higher for lesions detected by T1-mVISTA. • Application of T1-mVISTA might be of high relevance in early stages of disease.

Comparison of Brain Tumor Contrast-enhancement on T1-CUBE and 3D-SPGR Images

PURPOSE

T1-Cube (GE HealthCare) is a relatively new 3-dimensional (3D) fast spin-echo (FSE)-based magnetic resonance (MR) imaging sequence that uses a variable flip angle to acquire gap-free volume scans. We compared the gadolinium enhancement characteristics of a heterogeneous population of brain tumors imaged by T1-Cube and then 3D fast spoiled gradient recall acquisition in steady state (3D FSPGR) 3-tesla MR imaging to identify the superior modality for specific diagnostic purposes.

METHODS

We examined 61 lesions from 32 patients using the 2 sequences after administration of gadopentetic acid (Gd-DTPA; 0.1 mmol/kg). Two neuroradiologists independently measured each lesion twice using a region-of-interest (ROI) method. We measured the contrast-to-noise ratio (CNR), the difference in signal intensity (SI) between the tumor and normal white matter relative to the standard deviation (SD) of the SI within the lesion, for both post-contrast 3D FSPGR and post-contrast T1-Cube images of the same tumor and compared modality-specific CNRs for all tumors and in subgroups defined by tumor size, enhancement ratio, and histopathology.

RESULTS

The mean CNR was significantly higher on T1-Cube images than 3D FSPGR images for the total tumor population (1.85 ± 0.97 versus 1.12 ± 1.05, P < 0.01) and the histologic types, i.e., metastasis (P < 0.01) and lymphoma (P < 0.05). The difference in CNR was even larger for smaller tumors in the metastatic group (4.95 to 23.5 mm(2)) (P < 0.01). In contrast, mean CNRs did not differ between modalities for high grade glioma and meningioma.

CONCLUSIONS

Gadolinium enhancement of brain tumors was generally higher when imaged by T1-Cube than 3D FSPGR, and T1-Cube with Gd enhancement may be superior to 3D FSPGR for detecting smaller metastatic tumors.

Contrast enhancement of intracranial lesions at 1.5 T: comparison among 2D spin echo, black-blood (BB) Cube, and BB Cube-FLAIR sequences

OBJECTIVES

The purpose of this study was to investigate the usefulness of T1W black-blood Cube (BB Cube) and T1W BB Cube fluid-attenuated inversion recovery (BB Cube-FLAIR) sequences for contrast-enhanced brain imaging, by evaluating flow-related artefacts, detectability, and contrast ratio (CR) of intracranial lesions among these sequences and T1W-SE.

METHODS

Phantom studies were performed to determine the optimal parameters of BB Cube and BB Cube-FLAIR. A clinical study in 23 patients with intracranial lesions was performed to evaluate the usefulness of these two sequences for the diagnosis of intracranial lesions compared with the conventional 2D T1W-SE sequence.

RESULTS

The phantom study revealed that the optimal parameters for contrast-enhanced T1W imaging were TR/TE = 500 ms/minimum in BB Cube and TR/TE/TI = 600 ms/minimum/300 ms in BB Cube-FLAIR imaging. In the clinical study, the degree of flow-related artefacts was significantly lower in BB Cube and BB Cube-FLAIR than in T1W-SE. Regarding tumour detection, BB Cube showed the best detectability; however, there were no significant differences in CR among the sequences.

CONCLUSIONS

At 1.5 T, contrast-enhanced BB Cube was a better imaging sequence for detecting brain lesions than T1W-SE or BB Cube-FLAIR.

KEY POINTS

• Cube is a single-slab 3D FSE imaging sequence. • We applied a black-blood (BB) imaging technique to T1W Cube. • At 1.5 T, contrast-enhanced T1W BB Cube was valuable for detecting brain lesions.

Comparison of contrast-enhanced isotropic 3D-GRE-T1WI sequence versus conventional non-isotropic sequence on preoperative staging of cervical cancer

Purpose

To compare contrast-enhanced isotropic 3D-GRE-T1WI sequence vs. conventional non-isotropic sequence in terms of image quality, estimated signal-to-noise ratio (eSNR), relative tumor contrast and performance of cervical cancer staging.

Methods

This retrospective study was approved by the institutional review board, and informed consent was waived. Seventy-one patients (47 ± 9.4 years), with pathologically-confirmed cervical cancer underwent axial contrast-enhanced 1mm³ isotropic 3D-GRE-T1WI sequence (herein referred to Isotropy), and 3-mm-thick non-isotropic sagittal and coronal sequences. Image quality score, eSNR and relative contrast between tumor to myometrium, gluteal muscle, and fat respectively, were compared between 3-mm-thick reconstructed images from Isotropy and directly scanned non-isotropic images by paired t-test. Difference in tumor staging obtained from Isotropy and combined Three-planes including reconstructed axial images, directly scanned sagittal and coronal sequence were compared by McNemar test.

Results

Both sequences showed similar image quality. Reconstructed images demonstrated higher eSNR, equal or lower relative tumor contrast compared with non-isotropic images. Compared with performing diagnosis on Three-planes, both reviewers showed higher accuracy when diagnosing vaginal invasion on Isotropy (p = 0.039 and 0.003, respectively).

Conclusion

Compared with non-isotropic sequence, 3.0T MR isotropic 3D-GRE-T1WI sequence exhibited better eSNR, providing more reliable clinical information for preoperative staging of cervical cancer.

Detection of small brain metastases at 3 T: comparing the diagnostic performances of contrast-enhanced T1-weighted SPACE, MPRAGE, and 2D FLASH imaging

The aim of this study was to compare the diagnostic performance of contrast-enhanced T1-weighted sampling perfection with application-optimized contrasts using different flip angle evolutions (SPACE), magnetization-prepared rapid gradient-echo (MPRAGE), and two-dimensional (2D) fast low angle shot (FLASH) for the detection of small brain metastases. Twelve patients who had brain metastases less than 10 mm in diameter were enrolled. The diagnostic performance was evaluated using alternative free-response receiver operating characteristic analysis. Sensitivity and positive predictive value were also calculated. The mean Az and sensitivities of SPACE for all observers were significantly higher than those of MPRAGE and 2D FLASH.