Evaluation of stroke services in Anglia Stroke Clinical Network to examine the variation in acute services and stroke outcomes

Background

Stroke is the third leading cause of death in developed countries and the leading cause of long-term disability worldwide. A series of national stroke audits in the UK highlighted the differences in stroke care between hospitals. The study aims to describe variation in outcomes following stroke and to identify the characteristics of services that are associated with better outcomes, after accounting for case mix differences and individual prognostic factors.

Methods/Design

We will conduct a cohort study in eight acute NHS trusts within East of England, with at least one year of follow-up after stroke. The study population will be a systematically selected representative sample of patients admitted with stroke during the study period, recruited within each hospital. We will collect individual patient data on prognostic characteristics, health care received, outcomes and costs of care and we will also record relevant characteristics of each provider organisation. The determinants of one year outcome including patient reported outcome will be assessed statistically with proportional hazards regression models. Self (or proxy) completed EuroQol (EQ-5D) questionnaires will measure quality of life at baseline and follow-up for cost utility analyses.

Discussion

This study will provide observational data about health service factors associated with variations in patient outcomes and health care costs following hospital admission for acute stroke. This will form the basis for future RCTs by identifying promising health service interventions, assessing the feasibility of recruiting and following up trial patients, and provide evidence about frequency and variances in outcomes, and intra-cluster correlation of outcomes, for sample size calculations. The results will inform clinicians, public, service providers, commissioners and policy makers to drive further improvement in health services which will bring direct benefit to the patients.

Serotonin syndrome: an unusual cause of acute confusion and fever in the elderly

Delirium is a common cause for hospital admission among elderly patients. Although infection is the most common explanation, there is a large number of other potential causes. We present a case of acute delirium due to serotonin syndrome, precipitated by concomitant prescription of clarithromycin and fluoxetine. The symptoms improved following treatment with a benzodiazepine and discontinuation of the fluoxetine. The diagnosis and management of serotonin syndrome is discussed.

Improved search for a Higgs boson produced in association with Z → l+ l- in pp collisions sqrt[s] = 1.96 TeV

We search for the standard model Higgs boson produced with a Z boson in 4.1 fb(-1) of integrated luminosity collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section multiplied by the H → bb branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches. At a Higgs boson mass of 115 GeV/c2 we set a limit of 5.9 times the standard model cross section.

Three-Dimensional Contrast-Enhanced Multidetector CT for Anatomic, Dynamic, and Perfusion Characterization of Abnormal Myocardium To Guide Ventricular Tachycardia Ablations

Background—

Advances in contrast-enhanced multidetector CT enable detailed characterization of the left ventricular myocardium. Myocardial scar and border zone (BZ), as the target of ventricular tachycardia ablations, displays abnormal anatomic, dynamic, and perfusion characteristics during first-pass CT. This study assessed how contrast-enhanced CT can predict voltage-defined scar and BZ and integrate its scar reconstructions into clinical mapping systems to guide ventricular tachycardia ablations.

Methods and Results—

Eleven patients with ischemic cardiomyopathy underwent contrast-enhanced CT before ventricular tachycardia ablation. Segmental anatomic (end-systolic and end-diastolic wall thickness), dynamic (wall thickening, wall motion), and perfusion (hypoenhancement) characteristics were evaluated. Receiver operating characteristic curves assessed the ability of CT to determine voltage-defined scar and BZ segments. Three-dimensional epi- and endocardial surfaces and scar borders were reconstructed, coregistered, and compared to voltages using a 17-segment model. Abnormal anatomic, dynamic, and perfusion data correlated well with abnormal (<1.5 mV) endocardial voltages ( r =0.77). Three-dimensional reconstruction integrated into the clinical mapping system (registration accuracy, 3.31±0.52 mm) allowed prediction of homogenous abnormal voltage (<1.5 mV) in 81.7% of analyzed segments and correctly displayed transmural extent and intramural scar location. CT hypoperfusion correlated best with scar and BZ areas and encompassed curative ablations in 82% cases.

Conclusions—

Anatomic, dynamic, and perfusion imaging using contrast-enhanced CT allows characterization of left ventricular anatomy and 3D scar and BZ substrate. Integration of reconstructed 3D data sets into clinical mapping systems supplements information of voltage mapping and may enable new image approaches for substrate-guided ventricular tachycardia ablation.

Real-time tracking of liver motion and deformation using a flexible needle

PURPOSE

A real-time 3D image guidance system is needed to facilitate treatment of liver masses using radiofrequency ablation, for example. This study investigates the feasibility and accuracy of using an electromagnetically tracked flexible needle inserted into the liver to track liver motion and deformation.

METHODS

This proof-of-principle study was conducted both ex vivo and in vivo with a CT scanner taking the place of an electromagnetic tracking system as the spatial tracker. Deformations of excised livers were artificially created by altering the shape of the stage on which the excised livers rested. Free breathing or controlled ventilation created deformations of live swine livers. The positions of the needle and test targets were determined through CT scans. The shape of the needle was reconstructed using data simulating multiple embedded electromagnetic sensors. Displacement of liver tissues in the vicinity of the needle was derived from the change in the reconstructed shape of the needle.

RESULTS

The needle shape was successfully reconstructed with tracking information of two on-needle points. Within 30 mm of the needle, the registration error of implanted test targets was 2.4 ± 1.0 mm ex vivo and 2.8 ± 1.5 mm in vivo.

CONCLUSION

A practical approach was developed to measure the motion and deformation of the liver in real time within a region of interest. The approach relies on redesigning the often-used seeker needle to include embedded electromagnetic tracking sensors. With the nonrigid motion and deformation information of the tracked needle, a single- or multimodality 3D image of the intraprocedural liver, now clinically obtained with some delay, can be updated continuously to monitor intraprocedural changes in hepatic anatomy. This capability may be useful in radiofrequency ablation and other percutaneous ablative procedures.

Laparoscopic inguinal hernia repair in the pediatric age group--experience with 437 children

BACKGROUND/PURPOSE

A retrospective analysis of prospectively collected data of pediatric patients that underwent laparoscopic inguinal hernia repair.

MATERIAL AND METHODS

A retrospective review was performed of the prospectively collected data of 576 laparoscopic internal ring closures in 437 children (age, 30 days-11 years; median, 1.9 years) from June 1999 to February 2009. The internal ring was closed with a 3-0 nonabsorbable suture. Both extracorporeal and intracorporeal methods of knotting were used. All patients were asked to return at 1 week and 6 weeks postoperatively for routine follow-up.

RESULTS

A contralateral patent processus vaginalis was present in 13% (45/352) of boys and 15% (12/83) of girls on the right side, and 7% (25/352) of boys and 6% (5/83) of girls on the left side. Follow-up range was from 1 week postoperatively to 108 months. There were 14 recurrences (2.4 % [14/576], 11 in boys and on the right side and 3 in girls) and 2 hydroceles 0.35% (2/576). Mean operating time was 23 minutes for unilateral and 29 minutes for bilateral inguinal hernia. There was neither metachronus hernia nor testicular atrophy observed during follow-up.

CONCLUSION

Laparoscopic inguinal hernia repair is technically easier, as there is no need to dissect the vas deferens and vessels. The risk of metachronous hernia is reduced, and we believe the cosmetic result is better. Although recurrences were more common early in the series, currently they are much less frequent. Laparoscopic inguinal hernia repair appears to have less morbidity than open herniotomy and can be used as routine procedure in the pediatric age group.

Incorporation of preprocedural PET into CT-guided radiofrequency ablation of hepatic metastases: a nonrigid image registration validation study

This study evaluates the accuracy of augmenting initial intraprocedural computed tomography (CT) during radiofrequency ablation (RFA) of hepatic metastases with preprocedural positron emission tomography (PET) through a hardware-accelerated implementation of an automatic nonrigid PET-CT registration algorithm. The feasibility of augmenting intraprocedural CT with preprocedural PET to improve localization of CT-invisible but PET-positive tumors with images from actual RFA was explored. Preprocedural PET and intraprocedural CT images from 18 cases of hepatic RFA were included. All PET images in the study originated from a hybrid PET/CT scanner, and PET-CT registration was performed in two ways: (1) direct registration of preprocedural PET with intraprocedural CT and (2) indirect registration of preprocedural CT (i.e., the CT of hybrid PET/CT scan) with intraprocedural CT. A hardware-accelerated registration took approximately 2 min. Calculated registration errors were 7.0 and 8.4 mm for the direct and indirect methods, respectively. Overall, the direct registration was found to be statistically not distinct from that performed by a group of clinical experts. The accuracy, execution speed, and compactness of our implementation of nonrigid image registration suggest that existing PET can be overlaid on intraprocedural CT, promising a novel, technically feasible, and clinically viable approach for PET augmentation of CT guidance of RFA.

Measurement of the top-quark mass with dilepton events selected using neuroevolution at CDF

We report a measurement of the top-quark mass M_{t} in the dilepton decay channel tt[over ] --> bl;{'+} nu_{l};{'}b[over ]l;{-}nu[over ]_{l}. Events are selected with a neural network which has been directly optimized for statistical precision in top-quark mass using neuroevolution, a technique modeled on biological evolution. The top-quark mass is extracted from per-event probability densities that are formed by the convolution of leading order matrix elements and detector resolution functions. The joint probability is the product of the probability densities from 344 candidate events in 2.0 fb;{-1} of pp[over ] collisions collected with the CDF II detector, yielding a measurement of M_{t} = 171.2 +/- 2.7(stat) +/- 2.9(syst) GeV / c;{2}.

Transient global amnesia--a review

Transient global amnesia (TGA) is an isolated amnesic syndrome with normal neurological examination where patients remain alert and communicative with no loss of personal identity; however, they experience striking loss of memory for recent events and an impaired ability to retain new information. TGA could be triggered by venous congestion and there is evidence of association between younger patients and history of migraine. Most episodes last 2-12 h and the recurrence rate of future amnesic events is very low.

Automated 3D elastic registration for improving tumor localization in whole-body PET-CT from combined scanner

Combined PET/CT scanners provide the ability to produce matching metabolic (from PET) and anatomic (from CT) information in a single examination. However, misalignments continue to exist in tumor localization in PET and CT images acquired using these scanners, due to their inability to compensate for nonrigid misalignment resulting from patient breathing and involuntary movement. We demonstrate that our automatic image subdivision-based elastic registration algorithm can correct this misalignment. In a quantitative validation involving 13 expert-identified tumor nodules in six PET-CT image pairs, the algorithm demonstrated statistically significant improvement over the scanner-defined localization. The accuracy of algorithm-determined localization was evaluated to be comparable to average manually defined localization. The results indicate the potential of using our registration algorithm for applications like radiotherapy treatment planning and treatment-monitoring involving combined PET/CT scanners.

Effect of ultrasound probe on dose delivery during real-time ultrasound-guided tumor tracking

Ultrasound is a noninvasive and less costly modality for real-time imaging of soft tissues. It has the capability of tracking soft tissue at levels of submillimeter precision even in the presence of radiation beams. The effect of a transducer on radiation dose is not fully known. The best imaging location for an ultrasound transducer happens to coincide with the path of an anterior-posterior beam in intensity modulated radiation therapy (IMRT). This study indicates a significant change in dose when this juxtaposition occurs. If the anterior-posterior beam is avoided in IMRT planning, however, the effect of the transducer on radiotherapy is found to be negligible.

Automated detection of a blood pool in ultrasound images of abdominal trauma

Ultrasound imaging is commonly used for emergency diagnosis of blunt trauma. Portable scanners are able to provide adequate imaging in remote and dangerous areas; however, medical expertise may not be available in the immediate local area to interpret the acquired images. The presence of pooled blood in the abdomen is a critical clinical symptom after trauma. This article describes an automated algorithm to detect blood pools in ultrasound images of abdominal trauma. The algorithm creates and uses a feature space consisting of local intensities, averaged local gradient magnitudes and second-order central rotation invariant moments. Successful tests were performed with a set of clinical images of a liver-kidney interface covering the Morrison's pouch, which is the most likely space for blood from an abdominal injury to gather. When implemented in a portable scanner, the reported algorithm will provide rapid, on-the-spot detection of trauma-induced blood pooling and advance notice of a significant blunt traumatic injury.

Automatic segmentation of phase-correlated CT scans through nonrigid image registration using geometrically regularized free-form deformation

Conventional radiotherapy is planned using free-breathing computed tomography (CT), ignoring the motion and deformation of the anatomy from respiration. New breath-hold-synchronized, gated, and four-dimensional (4D) CT acquisition strategies are enabling radiotherapy planning utilizing a set of CT scans belonging to different phases of the breathing cycle. Such 4D treatment planning relies on the availability of tumor and organ contours in all phases. The current practice of manual segmentation is impractical for 4D CT, because it is time consuming and tedious. A viable solution is registration-based segmentation, through which contours provided by an expert for a particular phase are propagated to all other phases while accounting for phase-to-phase motion and anatomical deformation. Deformable image registration is central to this task, and a free-form deformation-based nonrigid image registration algorithm will be presented. Compared with the original algorithm, this version uses novel, computationally simpler geometric constraints to preserve the topology of the dense control-point grid used to represent free-form deformation and prevent tissue fold-over. Using mean squared difference as an image similarity criterion, the inhale phase is registered to the exhale phase of lung CT scans of five patients and of characteristically low-contrast abdominal CT scans of four patients. In addition, using expert contours for the inhale phase, the corresponding contours were automatically generated for the exhale phase. The accuracy of the segmentation (and hence deformable image registration) was judged by comparing automatically segmented contours with expert contours traced directly in the exhale phase scan using three metrics: volume overlap index, root mean square distance, and Hausdorff distance. The accuracy of the segmentation (in terms of radial distance mismatch) was approximately 2 mm in the thorax and 3 mm in the abdomen, which compares favorably to the accuracies reported elsewhere. Unlike most prior work, segmentation of the tumor is also presented. The clinical implementation of 4D treatment planning is critically dependent on automatic segmentation, for which is offered one of the most accurate algorithms yet presented.

A Longitudinal Study of LASIK Flap and Stromal Thickness with High-speed Optical Coherence Tomography

OBJECTIVE

To assess corneal anatomic changes after LASIK with a high-speed corneal and anterior segment optical coherence tomography (CAS-OCT) system.

DESIGN

Cross-sectional observational study.

PARTICIPANTS

Fifty-one eyes of 26 healthy persons undergoing LASIK.

METHODS

The CAS-OCT prototype operated at a 1.3-mum wavelength and 2000 axial scans/second. The corneas were scanned with a flap profile pattern (horizontal line, 512 axial scans) and a flap map pattern (4 radials, 256 axial scans each). Both patterns are 8 mm long and are centered on the corneal vertex. LASIK flaps were created using either a mechanical microkeratome (Hansatome; Bausch & Lomb, Inc., Rochester, NY) or a femtosecond laser (Pulsion; IntraLase Corp., Irvine, CA). Intraoperative pachymetry was performed using a 50-MHz ultrasound probe. Three OCT scans were obtained on preoperative and post-LASIK visits up to 6 months. An automated algorithm was developed to process the OCT images and to calculate corneal, flap, and stromal bed thickness profiles and maps. The profiles and maps were divided into central (diameter, <2 mm), pericentral (2-5 mm), and transitional (5-7 mm) zones for analysis.

MAIN OUTCOME MEASURES

Corneal, flap, and stromal bed thicknesses as determined by OCT and ultrasound pachymetry.

RESULTS

The flap interface was best detected in the pericentral zone. One week after surgery, the repeatability of OCT flap and stromal bed thickness measurement was 2 to 7 microm by pooled standard deviation for zones inside a 5-mm diameter. The central flap thickness in 24 Hansatome eyes with a 180-microm setting was 143+/-14 microm by OCT and 131+/-17 microm by ultrasound. In the 8 IntraLase cases with a 120-microm setting, it was 156+/-11 microm by OCT and 160+/-19 microm by ultrasound. Eyes with other settings also were analyzed. There were small systematic changes in flap thickness up to 1 week and bed thickness up to 3 months.

CONCLUSIONS

We have developed a method for using high-speed OCT to measure LASIK flap thickness after surgery. The measurement is noncontact, rapid, and repeatable. Profile and map measurements provide more information than point measurements previously demonstrated. This could be valuable for planning LASIK enhancement and characterizing microkeratome performance.

FPGA-Accelerated Deformable Image Registration for Improved Target-Delineation During CT-Guided Interventions

Minimally invasive image-guided interventions (IGIs) are time and cost efficient, minimize unintended damage to healthy tissue, and lead to faster patient recovery. With the advent of multislice computed tomography (CT), many IGIs are now being performed under volumetric CT guidance. Registering pre-and intraprocedural images for improved intraprocedural target delineation is a fundamental need in the IGI workflow. Earlier approaches to meet this need primarily employed rigid body approximation, which may not be valid because of nonrigid tissue misalignment between these images. Intensity-based automatic deformable registration is a promising option to correct for this misalignment; however, the long execution times of these algorithms have prevented their use in clinical workflow. This article presents a field-programmable gate array-based architecture for accelerated implementation of mutual information (Ml)-based deformable registration. The reported implementation reduces the execution time of MI-based deformable registration from hours to a few minutes. This work also demonstrates successful registration of abdominal intraprocedural noncontrast CT (iCT) images with preprocedural contrast-enhanced CT (preCT) and positron emission tomography (PET) images using the reported solution. The registration accuracy for this application was evaluated using 5 iCT-preCT and 5 iCT-PET image pairs. The registration accuracy of the hardware implementation is comparable with that achieved using a software implementation and is on the order of a few millimeters. This registration accuracy, coupled with the execution speed and compact implementation of the reported solution, makes it suitable for integration in the IGI-workflow.

Physically correct mesh manipulation in multi-level free-form deformation-based nonrigid registration

We present a new solution to prevent mesh folding artifacts common in free-form deformation-based nonrigid registration. Our algorithm imposes linear bounds on the search space of control point locations, thereby enabling the use of constrained optimization algorithms. We also introduce a new method for controlling the mesh rigidity, based on maximum voxel displacement. Our method allows local control of the deformation, based on a priori knowledge of the magnitude of possible local deformations.

Quantitative Real-time 3-Dimensional Stress Echocardiography: A Preliminary Investigation of Feasibility and Effectiveness

BACKGROUND

Use of rapidly emerging real-time 3-dimensional (3D) echocardiography promises to improve the diagnostic accuracy of stress echocardiography (SE). However, widespread acceptance of 3D-SE, based on real-time 3D echocardiography, is hampered in part by lack of efficient, accurate, and objective analysis tools.

METHODS

We propose novel algorithms for interactive visualization, registration (alignment), and quantitative analysis of prestress and poststress real-time 3D echocardiography to facilitate an objective diagnosis. In a preliminary evaluation, two experts independently performed wall-motion analysis in 15 patients with known/suspected coronary artery disease, using the novel quantitative 3D-SE methods.

RESULTS

Compared with previously reported values for conventional 2-dimensional SE, improved interexpert agreement (kappa = 0.85) was observed for segment-wise classification of normal/abnormal wall motion using the novel 3D-SE methods. Overall, 6 of 6 patients with abnormal myocardial segments were correctly identified by both experts with 3D-SE, compared with 4 of 6 with conventional 2-dimensional SE.

CONCLUSION

Initial results are promising and indicate the feasibility and potential of our proposed quantitative 3D-SE methodologies for improving diagnosis of wall-motion abnormalities.

Automatic elastic image registration by interpolation of 3D rotations and translations from discrete rigid-body transformations

We present an algorithm for automatic elastic registration of three-dimensional (3D) medical images. Our algorithm initially recovers the global spatial mismatch between the reference and floating images, followed by hierarchical octree-based subdivision of the reference image and independent registration of the floating image with the individual subvolumes of the reference image at each hierarchical level. Global as well as local registrations use the six-parameter full rigid-body transformation model and are based on maximization of normalized mutual information (NMI). To ensure robustness of the subvolume registration with low voxel counts, we calculate NMI using a combination of current and prior mutual histograms. To generate a smooth deformation field, we perform direct interpolation of six-parameter rigid-body subvolume transformations obtained at the last subdivision level. Our interpolation scheme involves scalar interpolation of the 3D translations and quaternion interpolation of the 3D rotational pose. We analyzed the performance of our algorithm through experiments involving registration of synthetically deformed computed tomography (CT) images. Our algorithm is general and can be applied to image pairs of any two modalities of most organs. We have demonstrated successful registration of clinical whole-body CT and positron emission tomography (PET) images using this algorithm. The registration accuracy for this application was evaluated, based on validation using expert-identified anatomical landmarks in 15 CT-PET image pairs. The algorithm's performance was comparable to the average accuracy observed for three expert-determined registrations in the same 15 image pairs.