External validation of a pharmacokinetic model for target-controlled infusion of cefazolin as a prophylactic antibiotic.

AIMS: This study aimed to evaluate the predictive performance of previously constructed cefazolin pharmacokinetic models and determine whether cefazolin administration via the target-controlled infusion (TCI) method may be possible in clinical practice. METHODS: Twenty-five gastrectomy patients receiving cefazolin as a prophylactic antibiotic were enrolled. Two grams of cefazolin was dissolved in 50 mL of normal saline to give a concentration of 40 mg mL-1 . Before skin incision, cefazolin was administered using a TCI syringe pump, and its administration continued until the end of surgery. The target total plasma concentration was set to 100 µg mL-1 . Total and unbound plasma concentrations of cefazolin were measured in three arterial blood samples collected at 30, 60 and 120 min after the start of cefazolin administration. The predictive performance of the TCI system was evaluated using four measures: inaccuracy, divergence, bias and wobble. RESULTS: Total (n = 75) and unbound (n = 75) plasma concentration measurements from 25 patients were included in the analysis. The pooled median (95% confidence interval) biases and inaccuracies were 6.3 (4.0-8.5) and 10.5 (8.6-12.4) for the total concentration model and -10.3 (-16.8 to -3.7) and 22.4 (18.2-26.7) for the unbound concentration model, respectively. All unbound concentrations were above 10 µg mL-1 . CONCLUSION: Administration of cefazolin by the TCI method showed a clinically acceptable performance. Applying the TCI method by setting the total concentration as the target concentration rather than the unbound concentration is effective in maintaining a constant target concentration of cefazolin.

Time-resolved dynamics of stable open- and closed-shell neutral radical and oxidized tripyrrindione complexes.

Stable open- and closed-shell Pd(II) and Cu(II) complexes of hexaethyl tripyrrin-1,14-dione (TD1) produce triplet, doublet or singlet states depending on the metal center and the redox state of the ligand. Pd(II) and Cu(II) form neutral TD1 complexes featuring ligand-based radicals, thus resulting in doublet and triplet states, respectively. The reversible one-electron oxidation of the complexes removes an unpaired electron from the ligand, generating singlet and doublet states. The optical properties and time-resolved dynamics of these systems are studied here using steady-state and ultrafast transient absorption (pump-probe) measurements. Fast relaxation with recovery of the ground state in tens of picoseconds is observed for the copper neutral radical and oxidized complexes as well as for the palladium neutral radical complex. Significantly longer timescales are observed for the oxidized palladium complex. The ability to tune the overall spin state of the complexes through their stable open-shell configurations as well as the reversible redox activity of the tripyrrolic systems makes them particularly interesting for catalytic applications as well as exploring magnetism and conductivity properties.

Geometric parameters on MRA source images to differentiate small Proximal Posterior communicating artery aneurysms from Infundibular dilation.

BACKGROUND AND PURPOSE: We aimed to assess the accuracy of magnetic resonance angiography (MRA) in the differentiation of small aneurysms versus infundibular dilations (IDs) at the internal carotid artery-posterior communicating artery (ICA-PComA) junction, emphasizing the role of MRA axial source images. METHODS: This retrospective study consisted of 83 focal arterial protrusions at ICA-PComA junction in 76 patients who underwent both MRA and digital subtraction angiography (DSA)/3-dimensional rotational angiography (3DRA). The diagnostic performance of MRA for differential diagnosis of aneurysm from ID was calculated using DSA/3DRA interpretation as the standard of reference. In addition, long-axis diameter, short-axis diameter, long-axis diameter/short-axis diameter (L/S) ratio, and angle of lesion (angle of the long-axis of lesion with respect to the x-axis) measured on MRA source images were compared between aneurysms and IDs. RESULTS: Sensitivity, specificity, and accuracy of MRA for distinguishing aneurysms from IDs were 74.4% (57.9-87.0%) to 76.9% (60.7-88.9%), 93.2% (81.3-98.6%) to 95.5% (84.5-99.4%), and 85.5% (76.1-92.3%), respectively. Significant differences were found for the long-axis diameter (P < .001), short-axis diameter (P < .001), L/S ratio (P < .05), and angle of the lesion (P < .001) on MRA axial source images between aneurysms and IDs. The angle of the lesion had the highest discriminatory ability (area under the curve = .966 [.902-.994]) to differentiate aneurysms from IDs. An angle of lesion >60° was 89.7% (75.8-97.1%) sensitive and 100% (92.0-100.0%) specific for diagnosis of aneurysm. CONCLUSIONS: MRA is a useful imaging modality for distinguishing between aneurysm and ID at the ICA-PComA junction. Furthermore, geometric parameters on MRA axial source images can provide added value in their differentiation.

256-row multislice CT angiography in the postoperative evaluation of cerebral aneurysms treated with titanium clips: using three-dimensional rotational angiography as the standard of reference.

OBJECTIVE: To assess the diagnostic accuracy of 256-row multislice computed tomographic angiography (CTA) compared with three-dimensional rotational angiography (3DRA) in the postoperative evaluation of cerebral aneurysms treated with titanium clips. METHODS: A total of 128 patients (42 men, 86 women; mean age, 57.6 years) with 143 cerebral aneurysms treated using titanium clips underwent both CTA and 3DRA. Two reviewers retrospectively evaluated the following parameters on CTA and 3DRA: (1) residual/recurrent aneurysm (absent or present), (2) patency of parent artery (patent or occluded/severe stenotic (> 70%)), and (3) patency of adjacent branch (patent or occluded/absent). RESULTS: A total of 24 residual/recurrent aneurysms were detected by 3DRA. The sensitivity, specificity, and accuracy of CTA for the detection of residual/recurrent aneurysms were 83.3%, 100%, and 97.2% for reviewer 1 and 79.2%, 100%, and 96.5% for reviewer 2, respectively. The sensitivity, specificity, and accuracy of CTA for the evaluation of patency of parent artery were 100%, 100%, and 100%, respectively, for both reviewers. The sensitivity, specificity, and accuracy of CTA for evaluation of the patency of adjacent branch were 85.1%, 100%, and 92.3% for reviewer 1 and 82.4%, 100%, and 90.9% for reviewer 2, respectively. CONCLUSION: A 256-row multislice CTA is a valuable non-invasive tool for assessment of cerebral aneurysms treated with titanium clips. KEY POINTS: • A 256-row multislice CTA is an accurate imaging technique for the postoperative assessment of cerebral aneurysms treated with titanium clips. • Sensitivity of CTA for the detection of residual/recurrent aneurysms was 79-83% compared with 3DRA. • CTA is still limited in detecting residual/recurrent aneurysms of < 2 mm and small adjacent branches.

Ultrafast Dynamics of Tripyrrindiones in Solution Mediated by Hydrogen-Bonding Interactions.

The optical properties and ultrafast dynamics of hexaethyl tripyrrin-1,14-dione (H3TD1) are tuned by hydrogen-bonding interactions between the solute and the solvent. In solvents with low hydrogen-bonding affinity, H3TD1 preferentially forms hydrogen-bonded dimers, whereas in solvents that can either donate or accept hydrogen bonds H3TD1 is present as a monomer. The distinction between dimer and monomer determines the dynamics of the system, with faster internal conversion observed in the dimer form. The ultrafast dynamics were characterized using time-correlated single photon counting, fluorescence upconversion, and transient absorption measurements. The time-resolved dynamics of both the monomer and dimer in solution were modeled using a Pauli master equation treatment for a three level system. The solvent-dependent optical properties were measured using steady-state absorption and fluorescence. This data was then used to calculate the quantum yield and extinction coefficients.

A hybrid operating room for combined surgical and endovascular procedures for cerebrovascular diseases: a clinical experience at a single centre.

Purpose: To describe our experiences with a fully equipped high-end digital subtraction angiography (DSA) system within a hybrid operating room (OR). Material and methods: A single-plane DSA system with 3-dimensional rotational angiography (3DRA), cone-beam computed tomography, and real-time navigation software was used in our hybrid OR. Between April 2014 and January 2018, 191 sessions of neurovascular procedures were performed in our hybrid OR. After the retrospective review of all cases, the procedures were categorised into five subcategorical procedures according to the dominance of surgical and/or endovascular procedures: intraoperative angiographic evaluation, combined endovascular and surgical procedure, complementary rescue procedure during intervention and surgery, surgical approach for interventional procedure, and frameless stereotaxic operation. Results: Intraoperative angiography revealed unsatisfactory clipping of intracranial aneurysms in 6 (13.6%) patients and remnant AVMs in 1 (16.7%) patient, which were determined as complete surgical outcome via indocyanine green videoangiography. Four cases of blood blister aneurysms and a ruptured posterior inferior cerebellar artery aneurysm were treated using bypass surgery and endovascular trapping. Eight cases of ruptured aneurysm with intracranial haemorrhage (ICH) were treated by partial embolisation and surgical clipping. Two (5.4%) of the 37 cases of pre-mature rupture during clipping were secured by endovascular coil embolisation. In 1 (0.8%) complicated case of 103 intra-arterial (IA) thrombectomy procedures, emergency surgical embolectomy with bypass surgery was performed. Direct puncture of the common carotid artery or vertebral artery was performed to achieve interventional access to treat aneurysm or recanalise vessel occlusions in 7 cases. In 27 cases of ICH, frameless stereotaxic haematoma aspiration was performed using XperGuide® system. All procedures were performed in single sessions without any procedural complications. Conclusion: Hybrid OR with a fully equipped DSA system could provide safe and precise treatment for neurovascular diseases. Hybrid procedures for neurovascular diseases in hybrid OR are a promising new trend.

Four-Year Experience Using an Advanced Interdisciplinary Hybrid Operating Room : Potentials in Treatment of Cerebrovascular Disease.

OBJECTIVE: To describe our experiences with a fully equipped high-end digital subtraction angiography (DSA) system within a hybrid operating room (OR). METHODS: A single-plane DSA system with 3-dimensional rotational angiography, cone-beam computed tomography (CBCT), and real-time navigation software was used in our hybrid OR. Between April 2014 and January 2018, 191 sessions of cerebrovascular procedures were performed in our hybrid OR. After the retrospective review of all cases, the procedures were categorized into three subcategorical procedures : combined endovascular and surgical procedure, complementary rescue procedure during intervention and surgery, and frameless stereotaxic operation. RESULTS: Forty-nine of 191 procedures were performed using hybrid techniques. Four cases of blood blister aneurysms and a ruptured posterior inferior cerebellar artery aneurysm were treated using bypass surgery and endovascular trapping. Eight cases of ruptured aneurysm with intracranial hemorrhage (ICH) were treated by partial embolization and surgical clipping. Six cases of ruptured arteriovenous malformation with ICH were treated by Onyx embolization of nidus and subsequent surgical removal of nidus and ICH. Two (5.4%) of the 37 cases of pre-mature rupture during clipping were secured by endovascular coil embolization. In one (0.8%) complicated case of 103 intra-arterial thrombectomy procedures, emergency surgical embolectomy with bypass surgery was performed. In 27 cases of ICH, frameless stereotaxic hematoma aspiration was performed using XperGuide® system (Philips Medical Systems, Best, the Netherlands). All procedures were performed in single sessions without any procedural complications. CONCLUSION: Hybrid OR with a fully equipped DSA system could provide precise and safe treatment strategies for cerebrovascular diseases. Especially, we could suggest a strategy to cope flexibly in complex lesions or unexpected situations in hybrid OR. CBCT with real-time navigation software could augment the usefulness of hybrid OR.

The most mentioned neurointervention articles in online media: a bibliometric analysis of the top 101 articles with the highest altmetric attention scores.

BACKGROUND AND PURPOSE: Alternative metrics (altmetrics), based on mentions in online media, is a new tool that can help to identify the most influential articles to diverse public audiences. This article aimed to determine the 100 most mentioned articles in the field of neurointervention and to analyze their characteristics. MATERIALS AND METHODS: We selected the 808 journals that were considered journals potentially publishing articles on neurointervention. We also selected articles using keywords. Using the Altmetric.com search tool, we identified the 101 most mentioned neurointervention articles based on the highest altmetric attention scores (AASs) within selected journals and articles. Each article was evaluated for several characteristics including AAS, number of citations, journal title, journal category, impact factor of the journal, year of publication, authorship, country, type of document, and topic. RESULTS: The AASs for the top 101 articles ranged from 1586 to 39. Stroke published the largest number of articles (19.8%) followed by the New England Journal of Medicine (17.8%). The majority of articles were published in multidisciplinary journals (38.6%), were published in 2017-2018 (43.6%), originated from the USA (54.5%), were original articles (66.3%), and dealt with intra-arterial thrombolysis or thrombectomy for acute ischemic stroke (58.4%). Tudor G Jovin was the most prolific author, authoring 18 of the most mentioned neurointervention articles CONCLUSIONS: This study presents a detailed list of the 101 most mentioned neurointervention articles in online media, thus providing useful information on the dissemination of neurointervention research to the general public.

Endovascular Coiling for a Wide-neck Bifurcated Aneurysm with Anterograde Horizontal Stenting via Microcatheter Looping: A Technical Case Report.

Technical advances with devices such as catheters, balloons, and stents have widened the indications for endovascular coiling for unfavorable aneurysms. The authors report two cases of coil embolization for a wide-neck bifurcated aneurysm with anterograde horizontal stenting via microcatheter looping. Two women, aged 56 and 38 years, respectively, had an undertall- and overwide-neck aneurysm with bifurcated branches at the basilar bifurcation and middle cerebral bifurcation, respectively. The delivery microcatheter was steamed so that it could be looped deliberately to the opposite vessel. The enterprise stent was first anchored to the vessel of the posterior cerebral artery on one side. The remaining portion was spanned into a looped microcatheter to the opposite branch while pushing the stent. The Neuroform Atlas stent was passed directly through the looped segment of the microcatheter at the M2 branch and spanned horizontally by unsheathing. Under horizontal stenting, complete coil embolization was achieved without immediate or delayed complications in both cases. This novel technique presents a viable option for stent-assisted coiling within an optimal anatomy.

Dual-Frequency Comb Transient Absorption: Broad Dynamic Range Measurement of Femtosecond to Nanosecond Relaxation Processes.

We experimentally demonstrate a dual-frequency comb-based transient absorption (DFC-TA) technique, which has a 12 fs time resolution and an ultrafast scan rate. Here, the fast scan rate is achieved by employing asynchronous optical sampling (ASOPS), which utilizes two independent mode-locked lasers with a slightly detuned repetition rates. The ASOPS approach is advantageous because photodegradation damage of optical sample during TA measurements can be minimized by a gated sampling. We show that the vibrational and electronic population relaxations of near-IR dye molecules in solution that occur in the time range from femtoseconds to nanoseconds can be resolved even with a single time scan measurement. The phase coherent nature of our dual-frequency comb lasers is shown to be the key for successful coherent averaging with femtosecond time resolution preserved over many data acquisitions. We anticipate that the present DFC-TA method without using any pump-probe time delay devices could be of use in developing ultrafast TA-based microscopy and time-resolved coherent multidimensional spectroscopy.

Sample exchange by beam scanning with applications to noncollinear pump-probe spectroscopy at kilohertz repetition rates.

In laser spectroscopy, high photon flux can perturb the sample away from thermal equilibrium, altering its spectroscopic properties. Here, we describe an optical beam scanning apparatus that minimizes repetitive sample excitation while providing shot-to-shot sample exchange for samples such as cryostats, films, and air-tight cuvettes. In this apparatus, the beam crossing point is moved within the focal plane inside the sample by scanning both tilt angles of a flat mirror. A space-filling spiral scan pattern was designed that efficiently utilizes the sample area and mirror scanning bandwidth. Scanning beams along a spiral path is shown to increase the average number of laser shots that can be sampled before a spot on the sample cell is resampled by the laser to ∼1700 (out of the maximum possible 2500 for the sample area and laser spot size) while ensuring minimal shot-to-shot spatial overlap. Both an all-refractive version and an all-reflective version of the apparatus are demonstrated. The beam scanning apparatus does not measurably alter the time delay (less than the 0.4 fs measurement uncertainty), the laser focal spot size (less than the 2 µm measurement uncertainty), or the beam overlap (less than the 3.3% measurement uncertainty), leading to pump-probe and autocorrelation signal transients that accurately characterize the equilibrium sample.

Intraobserver and interobserver variability in CT angiography and MR angiography measurements of the size of cerebral aneurysms.

PURPOSE: Accurate and reliable measurement of aneurysm size is important for treatment planning. The purpose of this study was to determine intraobserver and interobserver variability of CTA and MRA for measurement of the size of cerebral aneurysms. METHODS: Thirty patients with 33 unruptured cerebral aneurysms (saccular, >3 mm in their maximal dimension, with no daughter sacs or lobulations) who underwent 256-row multislice CTA, 3-D TOF MRA at 3.0T, and 3D rotational angiography (3DRA) were retrospectively analyzed. Three independent observers measured the neck, height, and width of the aneurysms using the CTA and MRA images. Intraobserver and interobserver variability of CTA and MRA measurements was evaluated using the standardized difference and intraclass correlation coefficient, with 3DRA measurements as the reference standard. In addition, the mean values of the measurements using CTA and MRA were compared with those using 3DRA. RESULTS: The overall intraobserver and interobserver standardized differences in CTA/MRA were 12.83-15.92%/13.48-17.45% and 14.08-17.00%/12.08-17.67%, respectively. The overall intraobserver and interobserver intraclass correlation coefficients of CTA/MRA were 0.88-0.98/0.84-0.96 and 0.86-0.98/0.85-0.95, respectively. Compared to the height and width measurements, measurements of the neck dimensions showed higher intraobserver and interobserver variability. The sizes of the cerebral aneurysms measured by CTA and MRA were 1.13-9.26 and 5.20-9.67% larger than those measured by 3DRA, respectively; however, these differences were not statistically significant. CONCLUSION: There were no noticeable differences between intraobserver and interobserver variability for both CTA- and MRA-based measurements of the size of cerebral aneurysms.

Bandgap Inhomogeneity of a PbSe Quantum Dot Ensemble from Two-Dimensional Spectroscopy and Comparison to Size Inhomogeneity from Electron Microscopy.

Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. The absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.

Citation classics in neurointerventional research: a bibliometric analysis of the 100 most cited articles.

BACKGROUND AND PURPOSE: The number of citations that an article has received can be used to evaluate its impact on the scientific community. This study aimed to identify the 100 most cited articles in the field of neurointervention and to analyze their characteristics. MATERIALS AND METHODS: We selected the 669 journals that were considered potentially to publish neurointervention articles based on the database of Journal Citation Reports. Using the Web of Science citation search tool, we identified the 100 most cited articles relevant to neurointervention within the selected journals. Each article was evaluated for several characteristics including publication year, journal, journal category, impact factor, number of citations, number of citations per year, authorship, department, institution, country, type of article, and topic. RESULTS: The number of citations for the top 100 articles ranged from 1912 to 170 (mean 363.4) and citations per year ranged from 271.0 to 4.1 (mean 40.0). The majority of articles were published in clinical neurology journals (63%), were published in 2000-2009 (39%), originated in the USA (45%), were original articles (95%), and dealt with endovascular treatment of cerebral aneurysm (42%). The Department of Radiology, University of California School of Medicine (n=12) was the leading institution and Viñuela F (n=11) was the most prolific author. CONCLUSIONS: Our study presents a detailed list and analysis of the 100 most cited articles in the field of neurointervention and provides a historical perspective on the scientific progress in this field.

Delayed improvement after endoscopic carpal tunnel release.

OBJECTIVE: In most patients with carpal tunnel syndrome (CTS), pain and/or paresthesia disappeared or decreased in a month after endoscopic carpal tunnel release (ECTR). However, subpopulation of patients showed delayed improvement following ECTR. We analyzed the delayed improvement hands to investigate the characteristics of those patients and to determine the predictable factors of delayed improvement. METHODS: Single-portal ECTRs were performed in 1194 hands of 793 CTS patients from 2002 to 2011. Five-hundred seventy hands with minimal 1-year postoperative follow-up were included. We divided the 545 satisfied hands into early (group A) and delayed (group B) groups according to improvement period of 1 month. Demographic data, clinical severity and electrodiagnostic abnormality were compared between groups. RESULTS: Group A included 510 hands and group B included 35 hands. In group B, 11 hands improved in 2 months, 15 hands in 3 months and 9 hands in 6 months, respectively. In group A/B, according to clinical severity, 60/1 hands were graded to I, 345/24 hands to II, 105/10 hands to III. In group A/B, based on electrodiagnostic abnormality, 57/3 hands were classified to mild, 221/11 hands to moderate and 222/21 hands to severe group. Statistical analysis between groups did not reach significance but electrodiagnostic or clinical severity had a tendency to affect the delayed response. CONCLUSION: It is difficult to predict the factors contributing to postoperatively-delayed response in subpopulation of CTS patients. However, we recommend that postoperative observation for at least 6 months is necessary in patients without symptomatic improvement.

Infundibular dilation and aneurysm at the origin of the posterior communicating artery: differential diagnosis by CT angiography.

INTRODUCTION: Infundibular dilation (ID) and aneurysm at the internal carotid artery (ICA)-posterior communicating artery (PComA) junction can be difficult to distinguish but may differ in clinical significance. The aim of this study was to evaluate the utility of CT angiography (CTA) in differentially diagnosing IDs and small unruptured aneurysms at the ICA-PComA junction. METHODS: This retrospective study comprised 88 patients diagnosed with 107 protrusions (70 IDs and 37 aneurysms <5 mm; 19 bilateral lesions) at the ICA-PComA junction who underwent both CTA and digital subtraction angiography (DSA). Two neuroradiologists independently reviewed CTA and DSA images according to these criteria: (a) size (maximum dimension <3 or ≥3 mm), (b) shape (triangular or round/oval/irregular), (c) aneurysmal neck (absent or present), (d) horizontal direction (posteriomedial or posteriolateral), and (e) PComA origin (apex, no PComA, or base). The intermodality (between CTA and DSA) and interobserver (between the two readers) agreement were determined for each finding. We also evaluated the sensitivity and specificity of CTA for distinguishing ID and aneurysm, using DSA as the reference standard. RESULTS: The mean κ values of intermodality agreement for the size, shape, aneurysmal neck, horizontal direction, and PComA origin were 0.88, 0.87, 0.84, 0.71, and 0.56, respectively. All interobserver agreements of CTA and DSA were excellent. The sensitivity, specificity, and accuracy of CTA for differentiating aneurysms from IDs were 94.6, 100, and 98.0 %, respectively. CONCLUSION: CTA may be a useful noninvasive modality for differential diagnosis of ID and aneurysm at the ICA-PComA junction.

Enhanced interferometric detection in two-dimensional spectroscopy with a Sagnac interferometer.

An intrinsically phase-stable Sagnac interferometer is introduced for optimized interferometric detection in partially collinear two-dimensional (2D) spectroscopy. With a pump-pulse pair from an actively stabilized Mach-Zehnder interferometer, the Sagnac scheme is demonstrated in broadband, short-wave IR (1-2 µm), 2D electronic spectroscopy of IR-26 dye.

Clinical and radiological spectrum of posterior reversible encephalopathy syndrome.

OBJECTIVE: Symptoms of posterior reversible encephalopathy syndrome (PRES) include headache, altered mental status, visual disturbances, and seizures. Typical radiological features include edema of the parieto-occipital lobes. The purpose of this study is to review the clinical and radiological findings in patients diagnosed with PRES. METHODS: All patients diagnosed with PRES between January 2006 and December 2012 were retrospectively included in this study. We reviewed demographic and clinical characteristics, and radiological findings. RESULTS: We identified 16 patients with PRES. The most common clinical presentation was seizure (n = 12, 75%). Clinical recovery occurred in all patients within days (mean, 5.7 ± 4.6 days). Comorbid conditions included hypertension (n = 4, 25%), cytotoxic medications (n = 3, 18.8%), sepsis (n = 4, 25%), malignancy (n = 4, 25%), subarachnoid hemorrhage (n = 1, 6.3%), autoimmune disorders (n = 1, 6.3%) and eclampsia (n = 1, 6.3%). The most commonly involved location was the parieto-occipital lobe (n = 13, 81.3%). Atypical radiological findings included significant basal ganglia involvement in 4 episodes; brainstem in 3, cerebellum in 2, and thalamus in 3. Eleven patients (68.8%) underwent diffusion-weighted imaging and apparent diffusion coefficient mapping. Of those, 9 patients (81.8%) had hypo- or isointensity on diffusion-weighted imaging. On the apparent diffusion coefficient map, 10 patients (90.9%) had hyperintensity, and the other had normal values. CONCLUSION: We suggest that PRES may occur in patients with complex systemic conditions. The prognosis of PRES is usually benign. Physicians should be aware of certain atypical radiological findings to avoid a delayed diagnosis of PRES, as delayed diagnosis and treatment can result in permanent neurological sequlae.

Simultaneous all-optical determination of molecular concentration and extinction coefficient.

Absolute molecular number concentration and extinction coefficient are simultaneously determined from linear and nonlinear spectroscopic measurements. This method is based on measurements of absolute femtosecond pump-probe signals. Accounting for pulse propagation, we present a closed form expression for molecular number concentration in terms of absorbance, fluorescence, absolute pump-probe signal, and laser pulse parameters (pulse energy, spectrum, and spatial intensity profile); all quantities are measured optically. As in gravimetric and coulometric determinations of concentration, no standard samples are needed for calibration. The extinction coefficient can then be determined from the absorbance spectrum and the concentration. For fluorescein in basic methanol, the optically determined molar concentrations and extinction coefficients match gravimetric determinations to within 10% for concentrations from 0.032 to 0.540 mM, corresponding to absorbance from 0.06 to 1. In principle, this photonumeric method is extensible to transient chemical species for which other methods are not available.

Absolute measurement of femtosecond pump-probe signal strength.

The absolute femtosecond pump-probe signal strength of deprotonated fluorescein in basic methanol is measured. Calculations of the absolute pump-probe signal based on the steady-state absorption and emission spectrum that use only independently measured experimental parameters are carried out. The calculation of the pump-probe signal strength assumes the pump and probe fields are both weak and includes the following factors: the transverse spatial profile of the laser beams; the pulse spectra; attenuation of the propagating pulses with depth in the sample; the anisotropic transition probability for polarized light; and time-dependent electronic population relaxation. After vibrational and solvent relaxation are complete, the calculation matches the measurement to within 10% error without any adjustable parameters. This demonstrates quantitative measurement of absolute excited state population.