Impact de l'IRM multimodale dans la prise en charge des AVC ischémiques à la phase aigüe

Cerebral imaging plays a crucial role in stroke patients. The advent of mechanical thrombectomy has transformed the management of acute ischemic stroke (AIS) patients, and consequently the role of MRI in the acute phase. Here, we propose to study the contribution of multimodal MRI to the management of AIS. To this end, we have coupled the analysis of admission MRI from the HIBISCUS-STROKE (CoHort of Patients to Identify Biological and Imaging markerS of CardiovascUlar Outcomes in Stroke) cohort with functional outcome, final infarct volume and the dynamics of serum markers of inflammation. In the first part of our work, we examined the contribution of MRI to the selection of patients eligible for mechanical thrombectomy. We observed that MRI angiography techniques were inferior to cerebral arteriography in localizing intracranial occlusion, despite taking into account the migratory nature of the thrombus. We showed that the estimation of the volume of the ischemic penumbra varied substantially according to the post-processing software used, and that these differences could have an impact on the selection of patients eligible for mechanical thrombectomy. In a pilot study, we observed that the optimal parameters defining the volumes of perfusion defect varied according to the software used. In the second part of our work, we assessed the prognostic contribution of MRI in patients who had achieved successful recanalization after mechanical thrombectomy. We observed that “brush sign” was associated with >11.6mL growth in infarct volume, and that mild vascular FLAIR hypersignals were associated with poorer functional outcome at 3 months. In the third part of our work, we examined the relationships between blood-brain barrier permeability on admission MRI and neuroinflammatory response. In the total population, we showed that increased blood-brain barrier permeability was associated with greater infarct volume. In patients within 6 hours of the onset of symptoms, we observed that increased permeability was associated with larger infarct volume and higher serum levels of matrix metalloprotease 9. The HIBISCUS-STROKE cohort gave us the opportunity to assess the contribution of MRI to patient selection and prognosis, and to identify factors associated with increased blood-brain barrier permeability in the acute phase.L'imagerie cérébrale joue un rôle crucial chez les patients victimes d'un accident vasculaire cérébral (AVC). L'avènement de la thrombectomie mécanique a bouleversé la prise en charge des patients atteints d'AVC ischémique et par conséquent la place de l'IRM à la phase aigüe. Notre travail de thèse se propose d'étudier l'apport de l'IRM multimodale dans la prise en charge de l'AVC ischémique à la phase aigüe. Dans cette perspective, nous avons couplé l'analyse des IRM d'admission de la cohorte HIBISCUS-STROKE (CoHort of Patients to Identify Biological and Imaging markerS of CardiovascUlar Outcomes in Stroke) au devenir fonctionnel, au volume final de l'infarctus et à la dynamique des marqueurs sériques de l'inflammation. Dans la première partie de notre travail, nous avons examiné l'apport de l'IRM dans la sélection des patients éligibles à une thrombectomie mécanique. Nous avons observé que les techniques d'angio-IRM étaient inférieures à l'artériographie cérébrale dans la localisation de l'occlusion intracrânienne malgré la prise en compte du caractère migratoire du thrombus. Nous avons montré que l'estimation du volume de la pénombre ischémique variait substantiellement selon le logiciel de post-traitement utilisé et que ces différences pouvaient impacter la sélection des patients éligibles à une thrombectomie mécanique. Dans une étude pilote, nous avons observé que les paramètres optimaux définissant le trouble de perfusion variaient selon le logiciel utilisé. Dans la deuxième partie de notre travail, nous avons évalué l'apport pronostic de l'IRM chez les patients ayant bénéficié d'une recanalisation efficace après thrombectomie mécanique. Nous avons observé que le « brush sign » était associé à une croissance >11.6mL du volume de l'infarctus et que des hypersignaux FLAIR vasculaires peu étendus étaient associés à un moins bon résultat fonctionnel à 3 mois. Dans la troisième partie de notre travail, nous avons examiné les relations entre la perméabilité de la barrière hémato-encéphalique sur l'IRM d'admission et la réponse neuroinflammatoire. Sur la population totale, nous avons montré qu'une perméabilité accrue de la barrière hémato-encéphalique était associée à un volume plus important de l'infarctus sur la population totale. Chez les patients à moins de 6h du début des symptômes, nous avons observé qu'une perméabilité accrue était associée à un volume plus important de l'infarctus et à des taux sériques plus importants de métalloprotéase matricielle 9. La cohorte HIBISCUS-STROKE nous a donc permis de préciser l'apport de l'IRM dans la sélection et le pronostic des patients et d'identifier les facteurs associés à une augmentation de la perméabilité de la barrière hémato-encéphalique à la phase aigüe

Isolated atlas-duplication as a manifestation of persistent proatlas: a case report

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In vivo gadolinium nanoparticle quantification with SPECT/CT

International audienceBackground: Gadolinium nanoparticles (Gd-NP) combined with radiotherapy are investigated for radiation dose enhancement in radiotherapy treatment. Indeed, NPs concentrated in a tumor could enhance its radiosensitization. The noninvasive quantification of the NP concentration is a crucial task for radiotherapy treatment planning and post-treatment monitoring as it will determine the absorbed dose. In this work, we evaluate the achievable accuracy of in vivo SPECT-based Gd-NP organ concentration on rats. Methods: Gd-NPs were labeled with 111 In radionuclide. SPECT images have been acquired on phantom and rats, with various Gd-NP injections. Images have been calibrated and corrected for attenuation, scatter, and partial volume effect. Image-based estimations were compared to both inductively coupled plasma mass spectrometer (ICP-MS) for Gd concentration and ex vivo organ activity measured by gamma counter. Results: The accuracy for the Gd mass measurements in organ was within 10% for activity above 2 MBq or concentrations above ∼ 3-4 MBq/mL. The Gd mass calculation is based on In-Gd coefficient which defines the Gd detection limit. It was found to be in a range from 2 mg/MBq to 2 μg/MBq depending on the proportions of initial injection preparations. Measurement was also impaired by free Gd and 111 In formed during metabolic processes. Conclusions: Even if SPECT image quantification remains challenging mostly due to partial volume effect, this study shows that it has potential for the Gd mass measurements in organ. The main limitation of the method is its indirectness, and a special care should be taken if the organ of interest could be influenced by different clearance rate of free Gd and 111 In formed by metabolic processes. We also discuss the practical aspects, potential, and limitations of Gd-NP in vivo image quantification with a SPECT

Conventional MRI radiomics in patients with suspected early- or pseudo-progression

International audienceAbstract Background After radiochemotherapy, 30% of patients with early worsening MRI experience pseudoprogression (Psp) which is not distinguishable from early progression (EP). We aimed to assess the diagnostic value of radiomics in patients with suspected EP or Psp. Methods Radiomics features (RF) of 76 patients (53 EP and 23 Psp) retrospectively identified were extracted from conventional MRI based on four volumes-of-interest. Subjects were randomly assigned into training and validation groups. Classification model (EP versus Psp) consisted of a random forest algorithm after univariate filtering. Overall (OS) and progression-free survivals (PFS) were predicted using a semi-supervised principal component analysis, and forecasts were evaluated using C-index and integrated Brier scores (IBS). Results Using 11 RFs, radiomics classified patients with 75.0% and 76.0% accuracy, 81.6% and 94.1% sensitivity, 50.0% and 37.5% specificity, respectively, in training and validation phases. Addition of MGMT promoter status improved accuracy to 83% and 79.2%, and specificity to 63.6% and 75%. OS model included 14 RFs and stratified low- and high-risk patients both in the training (hazard ratio [HR], 3.63; P = .002) and the validation (HR, 3.76; P = .001) phases. Similarly, PFS model stratified patients during training (HR, 2.58; P = .005) and validation (HR, 3.58; P = .004) phases using 5 RF. OS and PFS forecasts had C-index of 0.65 and 0.69, and IBS of 0.122 and 0.147, respectively. Conclusions Conventional MRI radiomics has promising diagnostic value, especially when combined with MGMT promoter status, but with moderate specificity. In addition, our results suggest a potential for predicting OS and PFS

Assessment of three MR perfusion software packages in predicting final infarct volume after mechanical thrombectomy

International audienceAims To evaluate the performance of three MR perfusion software packages (A: RAPID; B: OleaSphere; and C: Philips) in predicting final infarct volume (FIV). Methods This cohort study included patients treated with mechanical thrombectomy following an admission MRI and undergoing a follow-up MRI. Admission MRIs were post-processed by three packages to quantify ischemic core and perfusion deficit volume (PDV). Automatic package outputs (uncorrected volumes) were collected and corrected by an expert. Successful revascularization was defined as a modified Thrombolysis in Cerebral Infarction (mTICI) score ≥2B. Uncorrected and corrected volumes were compared between each package and with FIV according to mTICI score. Results Ninety-four patients were included, of whom 67 (71.28%) had a mTICI score ≥2B. In patients with successful revascularization, ischemic core volumes did not differ significantly from FIV regardless of the package used for uncorrected and corrected volumes (p>0.15). Conversely, assessment of PDV showed significant differences for uncorrected volumes. In patients with unsuccessful revascularization, the uncorrected PDV of packages A (median absolute difference −40.9 mL) and B (median absolute difference −67.0 mL) overestimated FIV to a lesser degree than package C (median absolute difference −118.7 mL; p=0.03 and p=0.12, respectively). After correction, PDV did not differ significantly from FIV for all three packages (p≥0.99). Conclusions Automated MRI perfusion software packages estimate FIV with high variability in measurement despite using the same dataset. This highlights the need for routine expert evaluation and correction of automated package output data for appropriate patient management

Quantification of Gd-Nanoparticles Concentration with SPECT and Spectral Photon Counting CT

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Does the Brush-Sign Reflect Collateral Status and DWI-ASPECTS in Large Vessel Occlusion?

International audienceIntroduction The relevance of the brush-sign remained poorly documented in large vessel occlusion (LVO). We aimed to assess the relationship between the brush-sign and collateral status and its potential impact on baseline diffusion-weighted imaging–Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) in acute ischemic stroke (AIS) patients eligible to mechanical thrombectomy (MT). Methods Consecutive patients admitted in the Lyon Stroke Center with anterior circulation AIS due to intracranial internal carotid artery (ICA) and/or M1 or M2 segment of the middle cerebral artery (MCA) occlusion eligible for MT were included. The brush-sign was assessed on T2-gradient-echo MRI. Collateral status was assessed on digital subtraction angiography according to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) score. Results In this study, 504 patients were included, among which 171 (33.9%) patients had a brush-sign. Patients with a brush-sign more frequently had a poor collateral status [72 (42.1%) vs. 103 (30.9%); p = 0.017]. In univariable analysis, a DWI-ASPECTS < 7 was associated with a brush sign. Following multivariable analysis, the brush-sign no longer affected DWI-ASPECTS < 7 while the latter remained associated with younger age [odds ratio (OR) 0.97, 95% CI.96–0.99], male sex (OR 1.79, 95% CI 1.08–2.99), a higher National Institutes of Health Stroke Scale (NIHSS) score (OR 1.16, 95% CI 1.1–1.21), a poor collateral status (OR 9.35, 95% CI 5.59-16.02), MCA segment (OR 2.54, 95% CI 1.25–5.38), and intracranial ICA (OR 3.01, 95% CI 1.16–8) occlusion. Conclusions and Relevance The brush-sign may be a marker of poor collateral status but did not independently predict a lower DWI-ASPECTS. Clinical Trial Registration ClinicalTrials.gov , identifier: NCT04620642

Simultaneous assessment of microcalcifications and morphological criteria of vulnerability in carotid artery plaque using hybrid 18F-NaF PET/MRI

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