RPS 1411c - New and advanced neuroimaging

Purpose:

To assess the diagnostic accuracy of T1- and T2-weighted contrasts generated by the MR data post-processing software SyMRI for neonatal brain imaging.

Methods and materials:

A total of 32 neonates were included in this retrospective study. 4 independent rating neuroradiologists assessed the neonatal brain on the basis of conventional and SyMRI generated T1- and T2-weighted contrasts. The sensitivity and specificity of both methods were calculated and compared with each other.

Results:

Compared to conventionally acquired T1- and T2-weighted images, SyMRI-generated contrasts showed a lower sensitivity but a higher specificity [SyMRI: sensitivity: 0.88, confidence interval (CI): 0.72-0.95; specificity: 1, CI: 0.89-1/conventional MRI: sensitivity: 0.94, CI: 0.80-0.98; specificity: 0.94, CI: 0.80-0.98].

Conclusion:

T1- and T2-weighted images, generated by SyMRI showed a comparable diagnostic accuracy to conventionally acquired contrasts. In addition to semi-quantitative imaging data, SyMRI provides diagnostic images and leads to more efficient use of available imaging time in neonatal brain MRI.

Limitations:

The small sample size.

Ethics committee approval

The protocol of this study was approved by the local ethics commission and performed in accordance with the declaration of Helsinki.

Funding:

No funding was received for this work.

Purpose:

To assess the intraoperative neuroimaging findings in patients treated with transcranial MR-guided focused ultrasound (tcMRgFUS) thalamotomy using 1.5T equipment in comparison with the 48-hours follow-up.

Methods and materials:

50 prospectively-enrolled patients undergoing unilateral tcMRgFUS thalamotomy for either medication-refractory essential tremor (n=39) or Parkinson tremor (n=11) were included. Two radiologists evaluated the presence and size of concentric lesional zones (i.e. zone I, zone II, and zone III) and the presence of oedema extending to the internal capsule on 2D T2-weighted sequences acquired intraoperatively after the last high-energy sonication and at 48-hours follow-up. Sonication parameters including the number of sonications, delivered energy, and treatment temperatures were also recorded. Differences in the lesion pattern and size were assessed using the McNemar test and paired t-test, respectively.

Results:

All three concentric zones were visualised intraoperatively in 26 (52%) patients after the last high-energy sonication. Zone I was visible in 29 (58%) cases at intraoperative imaging but was significantly more commonly visualised at 48-hours (96%, p<0.001). The diameter of zone I and II and the thickness of zone III significantly increased at 48-hours (p<0.001). Diameters of zone I and zone II measured intraoperatively demonstrated a significant correlation with thermal maps temperatures (p≤0.006). The maximum average temperature significantly correlated with zone II diameter at 48-hours (p=0.038). A threshold of 56.5° had a sensitivity of 71.4% and a specificity of 60.5% for zone II >10 mm at 48-hours.

Conclusion:

Intraoperative imaging may accurately detect typical lesional findings before completing the treatment. These imaging characteristics significantly correlate with sonications parameters and 48-hours follow-up.

Limitations:

The different tremor aetiologies, lack of long-term imaging appearance or clinical outcome evaluation, and tcMRgFUS software updates over time.

Ethics committee approval

An IRB-approved study. Informed consent was waived.

Funding:

No funding was received for this work.

Purpose:

Magnetic resonance imaging has great relevance in CNS pathology, mainly thanks to the multiple, excellent contrasts between tissues. Among its limitations stand long scan times and sensitivity to patients’ motion. The present work compared conventional MR sequences with three-dimensional SSFP MR-fingerprinting (MRF) with spiral projection k-space trajectories. Through such technique, acquisition of quantitative data of T1, T2, and proton density allows for the post-hoc synthesis of conventional qualitative contrasts with reduced motion sensitivity. The aim of this study was to compare MRF with conventional MRI in examining normal and pathological brain structures.

Methods and materials:

The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated on one phantom and two healthy volunteers. Assessment of absolute and relative contrast between grey and white matter, and qualitative evaluation of both normal encephalic structures and pathological findings representation, was conducted in 10 patients with different diseases, part of a protocol including 250 patients.

Results:

SNR and CNR were comparable between MRF and conventional imaging (p>0.05 for all comparisons, except higher SNR of conventional FLAIR sequences in white matter, p=0.016). In MRF, absolute contrast was higher in T1-weighted (p=0.01) but lower in T2-weighted and FLAIR images. Relative contrast was higher in T1-weighted (p=0.0003) and comparable in T2-weighted and FLAIR images. Although not superior to conventional imaging in anatomical detail, MRF alone provided sequences with high diagnostic confidence in 7/10 patients, while the others needed further MR scans to reach conclusive diagnoses.

Conclusion:

MRF is a promising tool for MRI in that it may preserve a good diagnostic accuracy while reducing the detriment of a long scan time.

Limitations:

The small sample size.

Ethics committee approval

Approved by the local ethics committee.

Funding:

Italian Ministry of Health, Health Service of Tuscany (research project GR-2016-02361693).

Purpose:

To evaluate the utility of synthetic imaging in refractory epilepsy imaging.

Methods and materials:

40 patients with refractory seizures aged 12-54 years (Mean age 33+6, M:F ratio 3:2) underwent MR exams on a 3T Pioneer scanner (GE Healthcare, Milwaukee) using an epilepsy protocol+MAGIC sequence.

The conventional epilepsy protocol was supplemented with the synthetic MAGIC sequence, which is one scan yielding 6 contrasts: T1, PD T2FLAIR, STIR DIR, PSIR with quantitative T1 and T2 maps (4 minutes).

The images were randomised and independently assessed for diagnostic quality, morphologic legibility, and diagnostic radiologic findings by two independent neuroradiologists compared to the conventional protocol.

The interobserver variability was recorded using Kappa statistics.

Results:

The overall diagnostic quality of synthetic MR images was superior to conventional MR imaging for epilepsy on a 5-level Likert scale (P<0.001; mean synthetic-conventional, -0.344±0.312; Δ=0.5; lower limit of the 95% CI, -0.398).

The legibility of synthetic and conventional morphology agreed in >95%, except in the basifrontal cortex and insulo opercular region in T1 and T1 FLAIR (all, >80%). Synthetic T2 FLAIR had more obvious artefacts, including +19.4% of cases with flow artefacts and +12.5% cases with white noise artefacts.

Interobserver variability was in acceptable limits (Cohen’s kappa 0.9).

Conclusion:

Synthetic MR imaging (MAGIC) with multiple contrasts is an useful adjunct tool in the comprehensive epilepsy protocol for reducing time penalties.

Limitations:

iSyntheic image datasets are still 2D datasets. 3D synthetic imaging data is emerging and high-resolution 3D FLAIR T1 and T2 are still needed for a comprehensive evaluation.

Ethics committee approval

Waiver of informed consent by ERB.

Funding:

No funding was received for this work.

Purpose:

To evaluate the role of multi b-value synthetic diffusion-weighted imaging in the evaluation of stroke.

Methods and materials:

52 patients who presented with symptoms suggestive of stroke with ages of 39-81 years (mean age 49.5+/-10 years; M: F ratio 2:3) were evaluated by a dedicated stroke protocol and supplemented by an additional 2-minute synthetic magic DWI multi b-value protocol after a waiver from IRB.

The parameters of synthetic DWI sequence are as follows: multi b-value DWI acquisition with b-values of 0-1,000 and synthesis of b-values of 1,500 and 2,000, with the maximum b-value not exceeding 2,500.

The sensitivity of the detection of infarcts on conventional DWI was compared to MAGIC DWI.

Results:

Of 52 patients, 31 had multiple acute lacunar infarcts in the MCA territory and MCA and PCA watershed zones, 21 in the infratentorial region including the brain stem and cerebellum, and 6 with a sensitivity of 92% and specificity of 97% with conventional DWI.

Using the MAGIC DWI with the synthesis of multiple b-values between 1,000 to 2,500, the sensitivity and specificity significantly improved to 97% and 99%, with an NPV of 99%.

Conclusion:

Multi B-value ultra-fast synthetic MAGIC DWI, which is a synthetic diffusion technique, is a powerful adjunct tool to the conventional stroke protocol offering the user a retrospective synthetic slider to generate multi b-value data from 100-2,500, increasing the sensitivity of stroke detection with no time or SNR penalties.

Limitations:

B-values above 2,500 are not feasible. The ADC value can be calculated until 1,000.

Ethics committee approval

Ethics committee approval and informed consent obtained.

Funding:

No funding was received for this work.

Purpose:

To explore the potential of superb microvascular imaging (SMI) technology in visualising brain microvessels in preterm neonates of different gestational ages (GA).

Methods and materials:

A retrospective, observational, single-centre study including 15 newborns (8 females) was conducted. Preterm patients were equally divided into GA groups according to the WHO sub-categories: extremely (GA< 28 weeks, EP), very (28-31 weeks and 6 days, VP), and moderate to late preterm (32-37 weeks, MLP). All patients underwent transcranial ultrasound (US) using a Toshiba Aplio500 scanner (Canon Medical Systems Corporation) and a linear 14 MHz transducer. Exams were performed during the first day of life via the anterior fontanel including superficial and deep scans (each on coronal and parasagittal planes). Based on their SMI morphology and location, microvessels were classified as extrastriatal (subdivided into cortical and medullary), striatal, or thalamic. Two examiners independently classified the vessels as visible (echogenic linear structures) or invisible. To assess the association between vessel visibility and GA, a binomial logistic regression analysis (separate for each microvessel group) was performed, taking visibility as a dependent variable and both examiners and GA as predictor variables.

Results:

A statistically significant difference among GA groups was found in sex (p=0.030), GA by definition (p=0.002), weight at birth (p=0.007), and the Apgar score within 1 minute (p=0.024). GA significantly contributed to the visibility of superficial vessels (p<0.05 for both cortical and medullary ones) but not striatal and thalamic vessels.

Conclusion:

SMI-US is a feasible tool for visualising and assessing intraparenchymal brain microvasculature in pre-term neonates. The morphology and distribution of the brain microvessels seen in the current study are consistent with those described in previous anatomical and radiological research.

Limitations:

The retrospective analysis of images.

Ethics committee approval

Written informed consent was obtained.

Funding:

No funding was received for this work.