Limited benefit of systematic head CT for mild traumatic brain injury in patients under antithrombotic therapy.

BACKGROUND AND PURPOSE: Mild traumatic brain injury (mTBI) in patients on antiplatelet (AP), anticoagulant (AC) or direct oral anticoagulant (DOAC) medication has become a systematic indication for head CT. However, the over-risk and impact of the intracranial hemorrhages (IH) detected with CT in this population remain unclear and need to be assessed. MATERIALS AND METHODS: We prospectively assessed head CTs performed in adults taking AP/AC/DOAC referred after a mTBI to our Emergency Departments between September 2016 and January 2018. Frequency, type and severity of IH were described and frequency was analyzed as a function of treatment. RESULTS: 840 patients were prospectively included. 58.9% were treated with AP, 23.7% with AC, 11.7% with DOAC and 5.7% with a combination of antithrombotic agents. The rate of IH detected with head CT was 5.8% (n...=...49), of which 81.6% (n...=...40) and 18.4% (n...=...9) with minor and intermediate severity respectively. No patient required surgical care and no death occurred. No statistically significant difference was found in treatment distribution between patients with or without IH (p...=...0.98). Among the patients who discontinued their antithrombotic treatment after mTBI, three experienced thrombotic events during the hospitalization. CONCLUSIONS: Our results showed a low frequency and severity of IH in mTBI patients indifferently treated with AP, AC or DOAC, without secondary neurological deterioration, death or need of surgical care. Our study suggests the limited benefit of systematic CT head scan as a standard practice for the management of mTBI patients under antithrombotic therapy.

Synthetic T2 mapping is correlated with time from stroke onset: a future tool in wake-up stroke management?

OBJECTIVES: FLAIR-DWI mismatch is an effective method to select eligible wake-up stroke (WUS) patients for intravenous thrombolysis, but shows limitations in the case of subtle FLAIR hyperintensities. T2 mapping is a quantitative method, directly generated from synthetic MRI, which provides T2 relaxation times. We aimed to assess the correlation between T2 values and onset time in acute stroke patients. METHODS: We prospectively included stroke patients in the 4.5-h window undergoing brain MRI including MAGnetic resonance Image Compilation (MAGiC) from March to October 2017. T2 relaxation times and FLAIR signal intensities were measured in ischemic and contralateral nonischemic regions to calculate FLAIR signal intensity ratio (rSI), difference, and ratio of T2 values. Correlation analysis with time from the onset was achieved using Pearson or Spearman correlation coefficient (ρ) test. RESULTS: Forty-two patients were included. The strongest correlation with the time from onset was the difference in T2 relaxation times (ρ = 0.71; CI95% = [0.48; 0.85]), followed by the ratio (ρ = 0.65; CI95% = [0.37; 0.82]) and the absolute T2 relaxation time (ρ = 0.4; CI95% = [0.06; 0.66]), whereas the FLAIR rSI showed the weakest correlation (ρ = 0.18; CI95% = [- 0.16-0.51]). CONCLUSIONS: The difference and ratio in T2 relaxation times were correlated with the onset time in stroke patients in the 4.5-h window. T2 mapping generated from synthetic MRI may become a relevant tool to select WUS patients with subtle FLAIR hyperintensities. Given that no definitive statement can be made about its usefulness in the 4.5-h windows, further study including patients with an onset time > 4.5 h is required. KEY POINTS: • The difference and ratio in T2 relaxation times are each individually correlated with the time from stroke onset in the 4.5-h window. • FLAIR rSI showed a poor correlation with the time from stroke onset. • T2 mapping, directly generated from synthetic MRI, may be a suitable quantitative marker to select safely WUS patients with subtle FLAIR hyperintensities for intravenous thrombolysis.

ASL and susceptibility-weighted imaging contribution to the management of acute ischaemic stroke.

Magnetic resonance imaging (MRI) plays a central role in the early diagnosis of cerebral vascular events. Today, MRI is used not only for the detection of acute ischaemic lesions, but also to fine tune the diagnosis and improve patient selection for early therapeutic decision-making. In this perspective, new tools such as arterial spin labelling (ASL) and susceptibility-weighted imaging (SWI) sequences have been developed. These MRI sequences enable noninvasive assessment of brain damage, providing important diagnostic and prognostic information: evaluation of cerebral parenchymal perfusion; detection and aetiological assessment of thrombi; ruling out differential diagnoses. After a brief recall of the fundamental basis of these sequences, this article proposes an update on their current contribution to the early management of stroke victims. TEACHING POINTS: • These noninvasive sequences provide essential information for early management of acute stroke. • They can detect zones of parenchymal hypoperfusion. • Susceptibility-weighted sequences provide information on thrombus localisation and composition. • ASL can identify certain aetiologies of stroke mimics. • Post-therapeutic ASL perfusion status predicts outcome.

Radiation dose levels in pediatric chest CT: experience in 499 children evaluated with dual-source single-energy CT.

BACKGROUND: The availability of dual-source technology has introduced the possibility of scanning children at lower kVp with a high-pitch mode, combining high-speed data acquisition and high temporal resolution. OBJECTIVE: To establish the radiation dose levels of dual-source, single-energy chest CT examinations in children. MATERIALS AND METHODS: We retrospectively recorded the dose-length product (DLP) of 499 consecutive examinations obtained in children <50 kg, divided into five weight groups: group 1 (<10 kg, n = 129); group 2 (10-20 kg, n = 176); group 3 (20-30 kg, n = 99), group 4 (30-40 kg, n = 58) and group 5 (40-49 kg, n = 37). All CT examinations were performed with high temporal resolution (75 ms), a high-pitch mode and a weight-adapted selection of the milliamperage. RESULTS: CT examinations were obtained at 80 kVp with a milliamperage ranging between 40 mAs and 90 mAs, and a pitch of 2.0 (n = 162; 32.5%) or 3.0 (n = 337; 67.5%). The mean duration of data acquisition was 522.8 ± 192.0 ms (interquartile range 390 to 610; median 490). In the study population, the mean CT dose index volume (CTDIvol32) was 0.83 mGy (standard deviation [SD] 0.20 mGy; interquartile range 0.72 to 0.94; median 0.78); the mean DLP32 was 21.4 mGy.cm (SD 9.1 mGy.cm; interquartile range 15 to 25; median 19.0); and the mean size-specific dose estimate (SSDE) was 1.7 mGy (SD 0.4 mGy; interquartile range 1.5 to 1.9; median 1.7). The DLP32, CTDIvol32 and SSDE were found to be statistically significant in the five weight categories (P < 0.0001). CONCLUSION: This study establishes the radiation dose levels for dual-source, single-kVp chest CT from a single center. In the five weight categories, the median values varied 15-37 mGy.cm for the DLP32, 0.78-1.25 mGy for the CTDIvol32 and 1.6-2.1 mGy for the SSDE.

Skull Vault Lesions: A Review.

OBJECTIVE: The aim of this article is to describe the imaging features of the most common benign or malignant skull vault lesions, which may be focal, multifocal, or diffuse. CONCLUSION: Imaging features, in association with the age, history, and clinical symptoms of the patient, make it possible to propose a course of action: simple survey, pathologic confirmation, or complete surgical resection.

Estimated risk of radiation-induced cancer from paediatric chest CT: two-year cohort study.

BACKGROUND: The increasing absolute number of paediatric CT scans raises concern about the safety and efficacy and the effects of consecutive diagnostic ionising radiation. OBJECTIVE: To demonstrate a method to evaluate the lifetime attributable risk of cancer incidence/mortality due to a single low-dose helical chest CT in a two-year patient cohort. MATERIALS AND METHODS: A two-year cohort of 522 paediatric helical chest CT scans acquired using a dedicated low-dose protocol were analysed retrospectively. Patient-specific estimations of radiation doses were modelled using three different mathematical phantoms. Per-organ attributable cancer risk was then estimated using epidemiological models. Additional comparison was provided for naturally occurring risks. RESULTS: Total lifetime attributable risk of cancer incidence remains low for all age and sex categories, being highest in female neonates (0.34%). Summation of all cancer sites analysed raised the relative lifetime attributable risk of organ cancer incidence up to 3.6% in female neonates and 2.1% in male neonates. CONCLUSION: Using dedicated scan protocols, total lifetime attributable risk of cancer incidence and mortality for chest CT is estimated low for paediatric chest CT, being highest for female neonates.

Pediatric chest CT at 70 kVp: a feasibility study in 129 children.

BACKGROUND: Before introducing 70-kVp settings in the low-kilovoltage strategies for pediatric examinations, it was mandatory to demonstrate, at similar dose levels, an equivalence of image quality at 70 kVp and 80 kVp. OBJECTIVE: To assess image quality of chest CT examinations acquired at 70 kVp in comparison with standard scanning at 80 kVp. MATERIALS AND METHODS: We prospectively evaluated 129 children with a 70-kVp scanning protocol (group 1). All scanning parameters were kept similar to those usually selected for pediatric standard 80-kVp protocols, except the milliamperage increased by a factor of 1.6 to maintain comparable radiation dose. Image quality of group 1 examinations was compared to that of a paired population scanned at 80 kVp (group 2). The noninferiority hypothesis was fixed at 10% of the mean level of image noise. RESULTS: There was no significant difference in the mean dose length product (DLP) and the volume computed tomography dose index (CTDIvol) between the groups (DLP: 20.5 ± 5.8 mGy.cm [group 1] vs. 19.7 ± 7.6 mGy.cm [group 2]; P = 0.06) (CTDIvol: 0.8 ± 0.1 mGy [group 1] vs. 0.8 ± 0.18 mGy [group 2]; P = 0.94). The mean of differences in image noise between group 1 and group 2 examinations was -1.38 (-2.59; -0.18), verifying the noninferiority hypothesis. Subjective image quality did not significantly differ between group 1 and group 2 examinations (P = 0.18). CONCLUSION: At equivalent radiation dose levels, 70-kVp protocols provide similar image quality to that achievable at 80 kVp.

Assignment of relative configuration of desoxypropionates by 1H NMR spectroscopy: method development, proof of principle by asymmetric total synthesis of xylarinic acid A and applications.

The determination of the relative configuration of 1,3-dimethyl-substituted alkyl chains is possible by interpretation of (1)H NMR shift differences. Additionally, assignments are feasible in a variety of deuterated solvents, because the corresponding shift differences are not significantly influenced by the solvent. The trends for Δδ values depending on functional groups adjacent to the stereogenic centers are shown. Based on a thorough comparison with literature data, the relative configuration of natural products can be predicted. For this purpose, we derived an empirical rule for the ranges in which Δδ values usually occur. Furthermore, we were able to proof the validity of our method by the successful prediction of the relative configuration for the polyketide natural product xylarinic acid A, which was confirmed by the asymmetric total synthesis of its enantiomer. Based on the proposed simple analysis of published (1)H NMR data and the determination of the relevant chemical-shift differences, we predicted the relative configurations of several previously unassigned natural products.