Evaluation of diffusion measurements reveals radial diffusivity indicative of microstructural damage following acute, mild traumatic brain injury.

PURPOSE: Mild TBI, characterized by microstructural damage, often undetectable on conventional imaging techniques, is a pervasive condition that disturbs brain function and can potentially result in long-term deficits. Deciphering the underlying microstructural damage in mild TBI is crucial for establishing a reliable diagnosis and enabling effective therapeutics. Efforts to capture this damage have been extensive, but results have been inconsistent and incomplete. METHODS: To that effect, we set out to examine the shape of the diffusion tensor in mild TBI during the acute phase of injury. We inspected diffusivity and geometric measurements describing the diffusion tensor's shape and compared mild TBI (N = 34, 20.4-66.6 yo) measurements with those from healthy control (N = 42, 20.7-67.2 yo) participants using voxelwise tract-based spatial statistics. Subsequently, to explore associations between the diffusion measurements in mild TBI, we performed nonparametric statistics and machine learning techniques. RESULTS: Overall, mild TBI displayed a diffuse increase in Dλ2, Dλ3, Dradial, Dmean, and Cspherical, with a diffuse decrease in Afractional, Amode, and Clinear, in addition to no change in Daxial or Cplanar. Most notably, our results provide evidence for Dradial as a potential biomarker for microstructural damage, specifically its main component Dλ2, based on their performance in discriminating between mild TBI and control groups. Afractional was also found to be important for discriminating between groups. CONCLUSION: Our results revealed the importance of a diffusion measurement often overlooked, Dradial, in assessing TBI and suggest differentiating diffusion measurements has the potential utility to detect variations in the underlying pathophysiology after injury.

Intraoperative MRI for newly diagnosed supratentorial glioblastoma: a multicenter-registry comparative study to conventional surgery.

OBJECTIVE: Intraoperative MRI (iMRI) is used in the surgical treatment of glioblastoma, with uncertain effects on outcomes. The authors evaluated the impact of iMRI on extent of resection (EOR) and overall survival (OS) while controlling for other known and suspected predictors. METHODS: A multicenter retrospective cohort of 640 adult patients with newly diagnosed supratentorial glioblastoma who underwent resection was evaluated. iMRI was performed in 332/640 cases (51.9%). Reviews of MRI features and tumor volumetric analysis were performed on a subsample of cases (n = 286; 110 non-iMRI, 176 iMRI) from a single institution. RESULTS: The median age was 60.0 years (mean 58.5 years, range 20.5-86.3 years). The median OS was 17.0 months (95% CI 15.6-18.4 months). Gross-total resection (GTR) was achieved in 403/640 cases (63.0%). Kaplan-Meier analysis of 286 cases with volumetric analysis for EOR (grouped into 100%, 95%-99%, 80%-94%, and 50%-79%) showed longer OS for 100% EOR compared to all other groups (p < 0.01). Additional resection after iMRI was performed in 104/122 cases (85.2%) with initial subtotal resection (STR), leading to a 6.3% mean increase in EOR and a 2.2-cm3 mean decrease in tumor volume. For iMRI cases with volumetric analysis, the GTR rate increased from 54/176 (30.7%) on iMRI to 126/176 (71.5%) postoperatively. The EOR was significantly higher in the iMRI group for intended GTR and STR groups (p = 0.02 and p < 0.01, respectively). Predictors of GTR on multivariate logistic regression included iMRI use and intended GTR. Predictors of shorter OS on multivariate Cox regression included older age, STR, isocitrate dehydrogenase 1 (IDH1) wild type, no O6-methylguanine DNA methyltransferase (MGMT) methylation, and no Stupp therapy. iMRI was a significant predictor of OS on univariate (HR 0.82, 95% CI 0.69-0.98; p = 0.03) but not multivariate analyses. Use of iMRI was not associated with an increased rate of new permanent neurological deficits. CONCLUSIONS: GTR increased OS for patients with newly diagnosed glioblastoma after adjusting for other prognostic factors. iMRI increased EOR and GTR rate and was a significant predictor of GTR on multivariate analysis; however, iMRI was not an independent predictor of OS. Additional supporting evidence is needed to determine the clinical benefit of iMRI in the management of glioblastoma.

Using Histopathology to Assess the Reliability of Intraoperative Magnetic Resonance Imaging in Guiding Additional Brain Tumor Resection: A Multicenter Study.

BACKGROUND: Intraoperative magnetic resonance imaging (iMRI) is a powerful tool for guiding brain tumor resections, provided that it accurately discerns residual tumor. OBJECTIVE: To use histopathology to assess how reliably iMRI may discern additional tumor for a variety of tumor types, independent of the indications for iMRI. METHODS: A multicenter database was used to calculate the odds of additional resection during the same surgical session for grade I to IV gliomas and pituitary adenomas. The reliability of iMRI for identifying residual tumor was assessed using histopathology of tissue resected after iMRI. RESULTS: Gliomas (904/1517 cases, 59.6%) were more likely than pituitary adenomas (176/515, 34.2%) to receive additional resection after iMRI (P < .001), but these tumors were equally likely to have additional tissue sent for histopathology (398/904, 44.4% vs 66/176, 37.5%; P = .11). Tissue samples were available for resections after iMRI for 464 cases, with 415 (89.4%) positive for tumor. Additional resections after iMRI for gliomas (361/398, 90.7%) were more likely to yield additional tumor compared to pituitary adenomas (54/66, 81.8%) (P = .03). There were no significant differences in resection after iMRI yielding histopathologically positive tumor between grade I (58/65 cases, 89.2%; referent), grade II (82/92, 89.1%) (P = .98), grade III (72/81, 88.9%) (P = .95), or grade IV gliomas (149/160, 93.1%) (P = .33). Additional resection for previously resected tumors (122/135 cases, 90.4%) was equally likely to yield histopathologically confirmed tumor compared to newly-diagnosed tumors (293/329, 89.0%) (P = .83). CONCLUSION: Histopathological analysis of tissue resected after use of iMRI for grade I to IV gliomas and pituitary adenomas demonstrates that iMRI is highly reliable for identifying residual tumor.

tbiExtractor: A framework for extracting traumatic brain injury common data elements from radiology reports.

BACKGROUND: The manual extraction of valuable data from electronic medical records is cumbersome, error-prone, and inconsistent. By automating extraction in conjunction with standardized terminology, the quality and consistency of data utilized for research and clinical purposes would be substantially improved. Here, we set out to develop and validate a framework to extract pertinent clinical conditions for traumatic brain injury (TBI) from computed tomography (CT) reports. METHODS: We developed tbiExtractor, which extends pyConTextNLP, a regular expression algorithm using negation detection and contextual features, to create a framework for extracting TBI common data elements from radiology reports. The algorithm inputs radiology reports and outputs a structured summary containing 27 clinical findings with their respective annotations. Development and validation of the algorithm was completed using two physician annotators as the gold standard. RESULTS: tbiExtractor displayed high sensitivity (0.92-0.94) and specificity (0.99) when compared to the gold standard. The algorithm also demonstrated a high equivalence (94.6%) with the annotators. A majority of clinical findings (85%) had minimal errors (F1 Score ≥ 0.80). When compared to annotators, tbiExtractor extracted information in significantly less time (0.3 sec vs 1.7 min per report). CONCLUSION: tbiExtractor is a validated algorithm for extraction of TBI common data elements from radiology reports. This automation reduces the time spent to extract structured data and improves the consistency of data extracted. Lastly, tbiExtractor can be used to stratify subjects into groups based on visible damage by partitioning the annotations of the pertinent clinical conditions on a radiology report.

Interobserver Variability in the Recognition of Hypoxic-Ischemic Brain Injury on Computed Tomography Soon After Out-of-Hospital Cardiac Arrest.

BACKGROUND: Cerebral edema and loss of gray-white matter differentiation on head computed tomography (CT) after cardiac arrest generally portend a poor prognosis. The interobserver variability in physician recognition of hypoxic-ischemic brain injury (HIBI) on early CT after out-of-hospital cardiac arrest has not been studied. METHODS: In this survey study, participating physicians and a neuroradiologist reviewed 20 randomly selected head CTs obtained within 2 h of out-of-hospital cardiac arrest and decided if HIBI was present. All participants were blinded to clinical details. Interobserver agreement on the presence of HIBI (primary outcome) and pairwise agreement between participants and the neuroradiologist (secondary outcome) were determined using multi- and dual-rater kappa statistics with 95% confidence intervals (CIs). RESULTS: Agreement among physicians regarding the presence of HIBI on head CT was fair (kappa 0.34; 95% CI 0.19-0.49). Individual physician agreement with the neuroradiologist varied from poor to moderate (kappa 0.0-0.48), with 8 of 10 physicians having no more than fair agreement. Regarding the perceived severity of HIBI on head CT, physician agreement was moderate (ICC = 0.56; 95% CI 0.38-0.77). CONCLUSION: Physicians, including radiologists, demonstrated substantial interobserver variability when identifying HIBI on head CT soon after out-of-hospital cardiac arrest.

"CHOICES": An acronym to aid in delineating potential causes of non-metabolic, non-infectious acute toxic leukoencephalopathy.

PURPOSE: To describe non-metabolic, non-infectious etiologies of acute toxic leukoencephalopathy (ATL) on DWI MRI, and provide a useful acronym to remember them. MATERIAL AND METHODS: Our PACS archive was reviewed, yielding 185 patients with suspected ATL per MRI reports and clinical follow up; infectious or metabolic causes were excluded. RESULT/DISCUSSION: The 87 included non-infectious, non-metabolic ATL patients' etiologies are represented by the acronym 'CHOICES': chemotherapy ('C',n = 34); heroin-induced ('H',n = 6), opioid analogues ('O',n = 14); immunosuppressant ('I',n = 11) or imidazole (n = 2); cocaine ('C',n = 1); environmental or ethanol abuse ('E',n = 5), splenial lesions ('S',n = 9), and 'other' (n = 5). CONCLUSION: The "CHOICES" acronym delineates various toxic etiologies of ATL.

The Effects of DWI-Infarct Lesion Volume on DWI-FLAIR Mismatch: Is There a Need for Size Stratification?

BACKGROUND: The lack of fluid-attenuated inversion-recovery (FLAIR) hyperintensity in areas of diffusion-weighted imaging (DWI) high signal, or DWI-FLAIR mismatch, is a potential imaging biomarker for timing of stroke onset. We aimed to determine the effects of DWI infarct lesion volume on DWI-FLAIR mismatch and its accuracy for identification of strokes within intravenous (IV) the thrombolytic therapy window. METHODS: Acute ischemic stroke patients with magnetic resonance imaging scan within 12 hours of witnessed stroke were included. Two neuroradiologists independently reviewed DWI and FLAIR sequences for DWI-FLAIR mismatch in areas of restricted diffusion compared to the contralateral normal side. RESULTS: DWI-FLAIR mismatch was identified in 21/82 (26%) patients. Infarct lesions with DWI-FLAIR mismatch were scanned earlier (3.8 ± .3 vs. 7.5 ± .3 hours from onset, P < .001) and were smaller in size (8.9±2.3 vs. 43.1±11.9 mL, P = .007) compared to lesions without mismatch. Multivariate regression analysis showed a significant interaction between lesion volume and time-from-onset in relationship with the presence of DWI-FLAIR mismatch (P = .045). The presence of DWI-FLAIR mismatch had 56% sensitivity, 83% specificity, 48% positive predictive value (PPV), and 87% negative predictive value (NPV) for identification of infarction within 4.5 hours of symptom onset; while for infarct lesions >15 mL, the DWI-FLAIR mismatch had 100% specificity and PPV for acute infarcts within 4.5 hours of onset. CONCLUSION: The effects of stroke onset-to-scan time gap on DWI-FLAIR mismatch are not the same for different DWI lesion volumes. At DWI lesion volumes >15 mL, the DWI-FLAIR mismatch is highly specific for acute infarcts within IV thrombolytic therapy time, and can identify wake-up stroke patients eligible for treatment.

Susceptibility-diffusion mismatch in middle cerebral artery territory acute ischemic stroke: clinical and imaging implications.

Background Recent studies have suggested a correlation between susceptibility-diffusion mismatch and perfusion-diffusion mismatch in acute ischemic stroke patients. Purpose To determine the clinical and imaging associations of susceptibility-diffusion mismatch in patients with acute ischemic stroke in the middle cerebral artery (MCA) territory. Material and Methods Consecutive patients with MCA territory acute ischemic stroke, who had magnetic resonance imaging (MRI) performed with susceptibility-weighted imaging (SWI) and diffusion-weighted imaging (DWI) within 24 h of symptom onset or time last-seen-well, were included. Two neuroradiologists reviewed SWI scans for SWI-DWI mismatch defined by regionally increased vessel number or diameter on SWI extending beyond the DWI hyperintensity territory in the affected hemisphere. The stroke severity at admission was evaluated using the National Institutes of Health Stroke Scale (NIHSS) score. Poor clinical outcome was defined by a 3-month modified Rankin Scale (mRS) score >2. Results The SWI-DWI mismatch was identified in 44 (29.3%) of 150 patients included in this study. Patients with SWI-DWI mismatch had smaller admission infarct volumes (31.2 ± 44.7 versus 55.9 ± 117.7 mL, P = 0.045) and were younger (60.4 ± 18.9 versus 67.1 ± 15.5, P = 0.026). After correction for age, admission NIHSS score, and infarct volume, the SWI-DWI mismatch was associated with a 22.6% lower rate of poor clinical outcome using propensity score matching ( P = 0.032). In our cohort, thrombolytic therapy showed no significant effect on outcome. Conclusion The presence of SWI-DWI mismatch in acute MCA territory ischemic infarct is associated with smaller infarct volume. Moreover, SWI-DWI mismatch was associated with better outcome after correction for infarct size, severity of admission symptoms, and age.

Prominent cortical and medullary veins on susceptibility-weighted images of acute ischaemic stroke.

OBJECTIVE: To determine the clinical and imaging implications of prominent cortical and medullary veins on susceptibility-weighted images (SWI) of patients with acute stroke. METHODS: Consecutive patients with acute ischaemic stroke who had SWI scan within 24 h of symptom onset or time last-seen-well were included. The SWI series were reviewed for the presence of prominent cortical and medullary veins and were graded independently by two neuroradiologists. The correlations between prominent vein grades with different imaging and clinical variables were determined. RESULTS: Among 213 patients, prominent SWI cortical and medullary veins were identified in 35 (16.4%) patients and 20 (9.4%) patients, respectively. There was fair interobserver agreement (k = 0.314-0.338, p ≤ 0.001) for grading, and moderate agreement (k = 0.406-0.413, p ≤ 0.001) for the presence of prominent veins. Both prominent cortical and medullary veins were associated with the presence of arterial occlusion (rho = 0.232, p = 0.001; rho = 0.180, p = 0.008; respectively) and larger infarct volume (rho = 0.445, p < 0.001; rho = 0.167, p = 0.015; respectively). However, neither cortical nor medullary cortical veins were associated with the severity of symptoms at admission or clinical outcome. Prominent cortical veins were independent predictors of arterial occlusion (p = 0.018), whereas prominent medullary veins were more strongly associated with larger infarct volumes (p < 0.001). CONCLUSION: There were small but significant correlations between cortical and medullary veins on SWI with arterial occlusion and large infarct volume in acute ischaemic stroke. Advances in knowledge: In consecutive patients with acute ischaemic stroke within anterior and posterior circulation territories, prominent cortical and medullary veins on SWI series are associated with imaging biomarkers of poor clinical outcome (i.e. large infarct volume and major arterial occlusion).

Diffusion-weighted MR imaging in the preoperative assessment of brain abscesses.

BACKGROUND: Diffusion-weighted MR imaging (DWI) has recently shown promise in differentiating ring-enhancing lesions such as brain abscess and malignant neoplasm. The ability of DWI to strongly suggest brain abscess enables a neurosurgeon to alter stereotactic planning to optimize diagnosis. We report our experience with DWI in 5 patients with lesions on MR imaging and review the literature to assess the usefulness of this technique in the preoperative evaluation of cerebral abscess. METHODS: The MR images of 5 patients presenting with ring-enhancing lesions that ultimately proved to be brain abscesses were retrospectively reviewed. In addition to standard MR sequences, trace DWI and apparent diffusion coefficient (ADC) calculations were performed on all patients. Additionally, 15 recently published articles or references in press concerning DWI in cerebral abscesses were reviewed. RESULTS: All lesions were markedly hyperintense on DWI and had diminished ADC. Thirty-eight of 39 previously reported abscesses were hyperintense on DWI with reduced ADC. Of 165 nonpyogenic lesions with DWI findings, 87 were hypointense or isointense, 78 lesions had variable hyperintensities, and few manifested the degree of hyperintensity observed with abscesses. Most of these included chordomas and epidermoids, which are not likely to be confused with abscesses. CONCLUSIONS: Restricted water diffusion, as indicated by hyperintensity on DWI and low ADC, in ring-enhancing lesions assists in differentiating brain abscess from necrotic tumor. This information facilitates stereotactic surgical planning: abscesses should be preferentially centrally aspirated, whereas necrotic brain tumors should have diagnostic tissue biopsied from cavity walls. Although not definitive for brain abscess, restricted water diffusion is an important MR imaging sign and is useful in neurosurgical treatment strategies for ring-enhancing lesions.