Scan Delay Research Articles

Concurrent Scanning for High Quality Hand Over Support in Mobile WiMAX Networks

Mobile WiMAX is IEEE 802.16e standard established for mobile broadband wireless access (BWA). Mobility in WiMAX system is an important issue when the mobile station (MS) moves and be handover between base stations (BSs). This issue causes an unnecessary neighboring BS scanning and association, handover delay, and MAC overhead which may affect real-time applications.
 The MS movement direction prediction (MMDP) based MS scanning is used to reduce the number of scanning’s required in mobile WiMAX handover process. In this paper with reduction in number of scanning’s we propose to reduce the scanning delay required for evaluated two best target BSs by using concurrent scanning process. Network issues like ideal sectors in WiMAX 2 (IEEE 802.16m), network congestion and fast change in RSS are important parameters which can affect the QoS. With this proposed model we are able to provide the high quality hand over support in mobile WiMAX wherein we are able to solve the above stated network problems. Here on using the concurrent scanning process the authors are able to reduce the scanning delay by 40%. As a part of this paper, network layer parameters called routing protocols are analyzed for hand over support. This analysis shows an efficient routing protocol for real time application and the best effort service. This reviles that fisheye protocol is better to use for smaller network and LANMAR for the larger networks in real time application and IERP protocol is good for best effort services.

Time dependency of bone density estimation from computed tomography with intravenous contrast agent administration

Our study has demonstrated that in contrast-enhanced multi-detector computed tomography (MDCT)-based bone density measurements, the scan delay time after contrast agent administration is a statistically significant variable for the derivation of quantitative computed tomography (QCT)-equivalent bone mineral density (BMD) values. Earlier investigators have proposed to derive QCT-equivalent BMD values from contrast-enhanced MDCT scans by using a merely density-based conversion equation. The purpose of this study was to investigate whether the scan delay after intravenous (IV) contrast agent administration might affect BMD values derived in this way. A retrospective data analysis was performed on 198 subjects who underwent standardized biphasic MDCT. Average densities values (in Hounsfield units) of lumbar vertebral bodies 1 to 3 (L1-L3) were compared between phases I and II of the biphasic MDCT scan. Furthermore, QCT-equivalent BMD (BMDQCT) values were calculated using a previously published conversion equation. Paired t-test analysis revealed that IV contrast agent administration leads to a statistically significant increase (8.6 %; p < 0.0001) in overall density of L1-L3 from phases I to II. Moreover, comparison of BMDQCT values between phases I and II reveals a change from osteoporotic to osteopenic in 4.5 % of the study population and from osteopenic to normal for 11.1 % of the subjects. Furthermore, it was revealed that the density increase from phases I to II shows a weak, yet statistically significant (p < 0.001) age dependency. Our study demonstrates that the use of a mere density-based conversion equation for deriving BMDQCT from MDCT scans ignores time dependency as an important variable. Furthermore, our results indicate that the actual age-dependent BMD itself might be another relevant variable that needs to be included in a MDCT-to-QCT conversion equation.

RFID-based localization with Non-Blocking tag scanning

The simple and cheap passive RFID tag systems have recently been used for efficient localization of indoor mobile robots, where each RFID tag stores its own absolute position and the mobile robot carrying an RFID reader scans the RFID tags to localize itself. The available localization schemes using passive RFID systems do not consider the scanning delay which may cause location estimation error, especially when the robot moves at a high speed. In this paper, a new Non-Blocking scanning (reading) scheme is proposed to avoid collisions so that the scanning delay, and consequently the localization error, can be reduced. This scheme avoids collisions among tag replies by assigning tag IDs based on the FCA coloring scheme. Theoretical and simulation studies indicate that the new Non-Blocking scheme combined with the new tag arrangement pattern can achieve a good RFID localization performance in terms of both estimation error and scanning delay with reduction of tag/reader required complexities.

Mobile Station Movement Direction Prediction (MMDP) Based Handover Scanning for Mobile WiMAX System

Mobile WiMAX is a broadband technology that is capable of delivering triple play services (voice, data, and video). However, mobility in mobile WiMAX system is still an issue when the mobile station (MS) moves and its connection is handed over between base stations (BSs). In the handover process, scanning is one of the required phases to find the target BS. During the handover scanning process, the MS must synchronize with all the advertised neighbour BSs (nBSs) to select the best BS candidate for the incoming handover action. Without terminating the connection between the SBS and MS, the SBS will schedule the scanning intervals and sleep-intervals (also called interleaving interval) to MS for the handover scanning. However, during the scanning interval period, all the coming transmissions will be paused. Therefore, the redundant or unnecessary scanning of neighbouring BS cause delay and MAC overhead which may affect real-time applications. In this paper, the MS movement direction prediction (MMDP) based handover scanning scheme is introduced to overcome the mobile WiMAX handover scanning issue. It based on dividing the BS coverage area is into zones and sectors. According to the signal quality; there are three zones, no handover (No-HO), low handover (Low-HO) and high handover (High-HO) zones respectively and six sectors. In this scheme, only two BSs can become candidates; the two that the MS moves toward them will be chosen as the candidate for the handover scanning purpose. Hence, the handover scanning process repetition will be reduced with these two shortlisted BS candidates instead of scanning all nBSs. Thus, MMDP will reduce scanning delay and the number of exchange messages during the handover scanning comparing to the conventional scanning scheme. Although, the MMDP may need an extra computational time, the prediction and scanning process will be finished before the MS reach the High-HO zone, which mean the end-user's running application will be affected. Simulation results show that the proposed MMDP scheme reduces the total handover scanning delay and scanning interval duration by 25 and 50 % respectively. Also, the size of scanning message is reduced, which leads to reduced signalling overhead.

Reduction in Observation Unit Length of Stay With Coronary Computed Tomography Angiography Depends on Time of Emergency Department Presentation

Prior studies demonstrating shorter length of stay (LOS) from coronary computed tomography angiography (CCTA) relative to stress testing in emergency department (ED) patients have not considered time of patient presentation. The objectives of this study were to determine whether low-risk chest pain patients receiving stress testing or CCTA have differences in ED plus observation unit (OU) LOS and if there are disparities in testing modality use, based on the time of patient presentation to the ED. The authors examined a cohort of low-risk chest pain patients evaluated in an ED-based OU using prospective and retrospective OU registry data. During the study period, stress testing and CCTA were both available from 08:00 to 17:00 hours. CCTA was not available on weekends, and therefore only subjects presenting on weekdays were included. Cox regression analysis was used to model the effect of testing modality (stress testing vs. CCTA) on OU LOS. Separate models were fit based on time of patient presentation to the ED using 4-hour blocks beginning at midnight. The primary independent variable was testing modality: stress testing or CCTA. Age, sex, and race were included as covariates. Logistic regression was used to model testing modality choice by time period adjusted for age, sex, and race. Over the study period, 841 subjects presented Monday through Friday. Median LOS was 18.0 hours (interquartile range [IQR] = 11.7 to 22.9 hours). Objective cardiac testing was completed in 788 of 841 (94%) patients, with 496 (63%) receiving stress testing and 292 (37%) receiving CCTA. After age, race, and sex were adjusted for, patients presenting between 08:00 and 11:59 hours not only had a shorter LOS associated with CCTA (p < 0.0001), but also had a greater likelihood of being tested by CCTA (p = 0.001). None of the other time periods had significant differences in LOS or testing modality choice for CCTA relative to stress testing. In an OU setting with weekday and standard business hours CCTA availability, CCTA testing was associated with shorter LOS among low-risk chest pain patients only in patients presenting to the ED between 08:00 and 11:59 hours. That time period was also associated with a greater likelihood of being tested by CCTA, suggesting that ED providers may have intuited the inability of CCTA to shorten LOS during other times.

MDCT in the Differentiation of Adrenal Masses: Comparison between Different Scan Delays for the Evaluation of Intralesional Washout

Purpose. To evaluate the accuracy of the washout in the differential diagnosis between adenomas and nonadenomas and to compare the obtained results in delayed CT scans at 5, 10 and 15 minutes. Methods. Fifty patients with adrenal masses were prospectively evaluated. CT scans were performed by using a 320-row MDCT device, before and after injection of contrast material. In 25 cases, delayed scans were performed at 5′ and 10′ (group 1), while in the remaining 25, at 5′ and 15′ (group 2). Absolute and relative wash-out percentage values (APW and RPW) were calculated. Results. Differential diagnosis between adenomas and nonadenomas was obtained in 48/50 (96%) cases, with sensitivity, specificity, and accuracy values of 96%, 95%, and 96%, respectively. In group 1, APW and RPW values were, respectively, 69.8% and 67.2% at 5′ and 75.9% and 73.5% at 10′ for adenomas and 25.1% and 15.8% at 5′ and 33.5% and 20.5% at 10′ for nonadenomas. In group 2, APW and RPW values were 63% and 54.6% at 5′ and 73.8% and 65.5% at 15′ for adenomas and 22% and 12.5% at 5′ and 35.5% and 19.9% at 15′ for nonadenomas. Conclusions. The evaluation of the wash-out values in CT scans performed at 5′, 10′, and 15′ provides comparable diagnostic results. CT scans performed at 5′ are, therefore, to be preferred, since they reduce the examination time and patient discomfort.

Portal Venous-Phase CT of the Liver in Patients without Chronic Liver Damage: Does Portal-Inflow Tracking Improve Enhancement and Image Quality?

Purpose: This study was undertaken to determine if portal-inflow bolus tracking outperforms aortic bolus tracking with respect to the image quality of contrast-enhanced portal venous-phase CT of the liver in patients without chronic liver damage. Materials and Methods: Contrast-enhanced CT of the liver was performed in 132 consecutive patients without chronic liver damage. Patients were prospectively assigned to three protocols: Protocol A—a portal venous-phase scan delay of 6 seconds after superior mesenteric venous (SMV) enhancement increased by 70 HU or 14 seconds after SMV enhancement was visually confirmed, and Protocols B and C—40 and 50 seconds, respectively, after abdominal aortic enhancement increased by 100 HU. Enhancement (ΔHU) of abdominal aorta, portal trunk, and liver parenchyma and diagnostic acceptability were assessed. Results: ΔHU of aorta was higher for protocol A than for protocols B and C (P P < 0.05). ΔHUs of liver were similar in three protocols. No difference was found between diagnostic a ptabilities of three protocols. Conclusion: Portal-inflow bolus tracking did not outperform aortic tracking in terms of optimization of portal venous-phase CT in patients without chronic liver damage.

Two-Phase Computed Tomography Study of Warthin Tumor of Parotid Gland

The objective of this study was to define the radiological characteristics of 2-phase computed tomography (CT) of parotid gland Warthin tumors (WTs) with a pathologic basis for these findings. We prospectively enrolled 116 patients with parotid gland tumor who underwent preoperative 2-phase CT scans(scanning delays of 30 and 120 seconds). The attenuation changes and enhancement patterns were analyzed according to pathology. We also evaluated size-matched samples of WTs and pleomorphic adenoma by staining CD31, vascular endothelial growth factor-receptor 2, collagen IV, and smooth muscle actin. Computed tomography numbers in WTs were significantly higher than those in other tumors in early-phase scans and lower in delayed scans. Pathologically, CD31(+) blood vessel area was significantly higher in WTs than in pleomorphic adenomas. In addition, WTs had an extensive capillary network and many leaky blood vessels. The enhancement pattern of early fill-in and early washout is the typical finding of WTs on 2-phase CT scans, which may be attributed pathologically to abundant blood vessel and extensive capillary network.

Fast Multiband Spectrum Scanning for Cognitive Radio Systems

This paper considers the problem of how to quickly and accurately determine the availability of each spectrum band for a multi-band primary system using one or few sensors. Such problem is referred to as spectrum scanning. Two cases of practical interest are studied: 1) a single sensor case in which only one spectrum band is observed at one time; and 2) a multiple sensor case in which multiple spectrum bands are observed simultaneously. For each case, scenarios with and without a scanning delay constraint are investigated. Using mathematical tools from optimal stopping theory, optimal spectrum scanning algorithms are developed to minimize a cost function that strikes a desirable trade-off between detection performance and sensing delay. In the non delay-constrained case, it is shown that the optimal scanning algorithm is a concatenated sequential probability ratio test (C-SPRT). In the delay-constrained case, the optimal scanning algorithm has a high implementation complexity and truncation algorithms are developed as alternative low complexity options. Numerical examples are provided to illustrate the effectiveness of the proposed algorithms.

Comparison of pancreatic acinar cell carcinoma and adenocarcinoma using multidetector-row computed tomography

To distinguish acinar cell carcinoma (ACC) from pancreatic adenocarcinoma (AC) by comparing their computed tomography findings. Patients with ACC and AC were identified on the basis of results obtained using surgically resected pancreatectomy specimens. The preoperative computer tomographic images of 6 acinar cell carcinoma patients and 67 pancreatic adenocarcinoma patients in 4 phases (non-contrast, arterial, portal venous, and delayed phase) were compared. The scan delay times were 40, 70, and 120 s for each contrast-enhanced phase. The visual pattern, tomographic attenuation value, and time attenuation curve were assessed and compared between AC and ACC cases using the χ² test, Wilcoxon signed-rank test, and Mann Whitney U test. The adenocarcinomas tended to be hypodense in all 4 phases. The acinar cell carcinomas also tended to be hypodense in the 3 contrast-enhanced phases, although their computed tomographic attenuation values were higher. Further, 5 of the 6 acinar cell carcinomas (83%) were isodense in the non-contrast phase. The time attenuation curve of the adenocarcinomas showed a gradual increase through the 4 phases, and all adenocarcinomas showed peak enhancement during the delayed phase. The time attenuation curve of the acinar cell carcinomas showed peak enhancement during the portal venous phase in 4 cases and during the arterial phase in 2 cases. None of the 6 acinar cell carcinomas showed peak enhancement during the delayed phase. The tumor density in the non-contrast phase and time attenuation curve pattern clearly differ between acinar cell carcinomas and adenocarcinomas, and multidetector-row computed tomography can thus distinguish these tumors.

The Proper Scan Delay of the Hepatobiliary Phase of Gadoxetic Acid-Enhanced Magnetic Resonance Imaging to Evaluate Small-Sized (≤ 3 cm) Hepatocellular Carcinoma in Cirrhotic Liver

The Proper Scan Delay of the Hepatobiliary Phase of Gadoxetic Acid-Enhanced Magnetic Resonance Imaging to Evaluate Small-Sized (≤ 3 cm) Hepatocellular Carcinoma in Cirrhotic Liver

Carbon Dioxide-Contrasted Computed Tomography Angiography: High Pitch Protocols and Adapted Injection Parameters Improve Imaging Quality

To systematically investigate the impact of image acquisition and contrast injection parameters for CO2-enhanced CT angiography (CTA) of the aorto-iliac and peripheral arteries in a pig model using commercially available equipment. The aim was to establish an imaging protocol that is ready for use in human subjects. Three domestic swine underwent CO2-CTA with varying injection parameters: pitch (1.0, 3.0), injection pressure (0.7 bar, 1.0 bar, 1.3 bar) and scan delay (2 s, 4 s, 6 s). Objective (vessel diameter) and subjective (image quality) parameters and applied radiation doses were systematically evaluated. To ensure clinical applicability of the setting, only approved catheters/injectors and standard injection parameters were evaluated. The image quality scores were superior and the vessel diameter was larger with high pitch in comparison to standard pitch (diameters: 4.7 ± 2.0 mm vs. 3.6 ± 2.1 mm, p = 0.0040, scores: 2.6 ± 1.1 vs. 2.0 ± 1.1, p = 0.0038). High injection pressure (1.3 bar) improved the image quality as assessed by subjective and objective ratings (diameters: 3.6 ± 2.0 mm, 4.0 ± 2.1 mm and 4.6 ± 2.1 mm, for 0.7, 1.0 and 1.3 bar, p-values ≤ 0.0052, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.2, p-values ≤ 0.0017), the same was observed for a shorter injection delay (diameters: 3.5 ± 2.0 mm, 4.2 ± 2.1 mm and 4.8 ± 2.1 mm, for 6 s, 4 s, and 2 s, p ≤ 0.0022, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.1, p-values ≤ 0.0013). The dose length products were 239 ± 47 mGycm (high pitch) and 565 ± 63 mGycm (standard pitch, p-values < 0.0001). A higher pitch, shorter delay and higher injection pressure improve image quality in CO2-enhanced CTA. Since commercially available, clinically approved equipment was used. The protocol is now ready for use in human subjects.

Improved edge delineation using a low-flow and delayed-phase contrast-enhanced protocol for computed tomography imaging of oral cavity and oropharyngeal malignancies

To determine whether contrast-enhanced computed tomography (CT) performed with a high flow rate and short delay protocol or a lower flow rate and longer delay protocol resulted in better enhancement of the oral cavity and oropharyngeal tumour and tumour edge delineation. Patients with squamous cell carcinomas of the upper aerodigestive tract (UAT) who underwent contrast-enhanced CT using 100 ml contrast material with 300 mg iodine/ml were selected for this comparison study. The protocols studied used a high flow rate and short scan delay (2 ml/s and 50 s) and a lower flow rate and longer delay (1 ml/s and 100 s). Contrast enhancement by radiodensity in Hounsfield units of the tumour site, poorest and clearest tumour boundaries and contralateral lateral pterygoid muscle were measured using a region of interest tool. A t-test statistical analysis was used to compare both protocols. The lower flow and longer delay protocol maximized contrast differences at both the poorest and clearest definition boundaries of the tumour (p ≤ 0.01 and p ≤ 0.05, respectively) and the pterygoid muscle (p ≤ 0.01). There was no significant difference in contrast enhancement within the central homogeneous tumour site. A lower flow and longer delay protocol (1 ml/s and 100 s) provided better enhancement of the delineation of the tumour edge and surrounding musculature than a high flow rate and short delay protocol (2 ml/s and 50 s). Both protocols achieved similar central tumour enhancement.

Optimization of scan protocol in pulmonary angiography of second generation dual source computed tomography

To explore the scan protocol of second generation dual source computed tomography (CT) for CT pulmonary angiogram (CTPA) in patients with suspected pulmonary embolism and determine the proper volume of contrast medium. A total of 120 patients undergoing CTPA were recruited. All examinations were performed on a second generation dual source CT. The scan delay was determined with the test bolus technique. Four contrast volume protocols were designed, namely groups A, B, C and D respectively (n = 30 each). For CTPA scan of groups A, B, C and D, 35, 40, 45 and 50 ml contrast medium were injected at an injection rate of 4 ml/s, followed by a saline chaser of 55, 50, 45 and 40 ml respectively. Attenuation profiles of different vascular segments (subclavian vein, vena cava, left atrium, pulmonary trunk, S1 artery, S10 artery) were measured to evaluate the timing techniques. The image quality and artifact of iodine map were analyzed by two radiologists for comparisons. The percentage of pulmonary arteries exceeding optimal attenuation (> 200 HU) showed that groups of B, C and D were higher than group A (93% - 100% vs 80% - 90%). The image quality of group A was lower than the others (P < 0.05) while the other groups showed no significant difference. The artifacts of iodine map of group A were much fewer than the others (P < 0.05) and group D was much more than the other groups (P < 0.05). Groups B and C had a score of 4.13 and 3.67 respectively without significant difference (P = 0.091). With the aids of test bolus technique and proper injection protocol (40 ml contrast medium followed by 50 ml saline), the high quality image and low volume of iodine can be realized with second generation dual source CT for CTPA.

Unsuspected cystic left upper quadrant mass

A 27-year-old African American female with no significant medical history presented with left upper quadrant pain radiating to the back, which had been worsening over several months. She had an inability to tolerate oral intake, progressive nausea and vomiting. A review of her symptoms revealed palpitations, mild shortness of breath and two episodes of recent bilious vomiting without haematemesis. Physical examination showed diffuse abdominal tenderness on palpation and mild tachycardia. Laboratory evaluation showed no significant abnormalities, including normal pancreatic and liver enzymes. The chest radiograph was normal. A contrast-enhanced CT of the abdomen was performed with a 64-MDCT scanner (Aquilion 64; Toshiba Medical Systems, Nasu, Japan) with the following scanning parameters: rotation time, 0.5 s; beam collimation, 3261.0 mm; section thickness and interval, 5 mm; helical pitch, 27; 120 kV and tube current in the automatic milliampere exposure setting. Coronal reconstructions were obtained at 4 mm thickness and 4 mm intervals. The patient received 100 ml of intravenous (iv) iohexol (Omnipaque 300, Nycomed, Amersham, UK) administered via a mechanical injector at 3.0 ml s with a scanning delay determined by real-time contrast tracking, starting at 70 HU added to unenhanced liver. What are the CT findings? What is the most likely diagnosis?

Hepatic contrast medium enhancement at computed tomography and its correlation with various body size measures

When the same dose of iodine is given to all patients when performing abdominal computed tomography (CT) there may be a wide inter-individual variation in contrast medium (CM) enhancement of the liver. To evaluate if any of the measures body height (BH), body mass index (BMI), lean body mass (LBM), ideal body weight (IBW), and body surface area (BSA) correlated better than body weight (BW) with hepatic enhancement, and to compare the enhancement when using iodixanol and iomeprol. One hundred patients referred for standard three-phase CT examination of abdomen were enrolled. Body weight and height were measured at the time of the CT examination. Forty grams of iodine (iodixanol 320 mg I/mL or iomeprol 400 mg I/mL) was injected at a rate of 1.6 g-I/s, followed by a 50 mL saline flush. The late arterial phase was determined by using a semi-automatic smart prep technique with a scan delay of 20 s. The hepatic parenchymal phase started automatically 25 s after the late arterial phase. CM concentration was estimated by placement of regions of interest in aorta (native and late arterial phase) and in liver (native and parenchymal phase). BW (r = -0.51 and -0.64), LBM (r = -0.54 and -0.59), and BSA (r = -0.54 and -0.65) showed the best correlation coefficients with aortic and hepatic parenchymal enhancement, respectively, without any significant differences between the measures. Comparing iodixanol and iomeprol there was no significant difference in aortic enhancement. The liver enhancement was significantly higher (P < 0.05) using iodixanol than iomeprol. To achieve a consistent hepatic enhancement, CM dose may simply be adjusted to body weight instead of using more complicated calculated parameters based on both weight and height.

Feasibility of a fixed scan delay technique using a previous bolus tracking technique data for dynamic hepatic CT

ObjectiveTo compare the quality of contrast enhancement and hepatic CT images acquired using bolus tracking technique at two different time points and those acquired with fixed scan delay technique using a previous bolus tracking data. Materials and methodsFifty patients who underwent 3 different hepatic CT exams (25-s fixed injection of 600mg iodine (I)/kg or 100mL of 370mg I/mL nonionic contrast medium) were enrolled. The first and second exams were performed with a bolus tracking technique. The third exam was performed with a fixed scan delay technique using the first exam data. Differences in attenuation values in the abdominal organs were examined and evaluated visually on hepatic arterial phase images. ResultsThere was no significant difference in the mean 50-HU threshold times between the first and second bolus tracking exams with intra-patient differences between them (1.3±0.9s). No significant intra-patient differences were noted in organ attenuation and visual evaluation on hepatic arterial phase images between the 3 exams. ConclusionThe fixed scan delay technique using a previous bolus tracking data is feasible for hepatic CT exams to follow up hepatocellular carcinoma.

Comparison of a 1.5T Standard vs. 3T Optimized Protocols in Multiple Sclerosis Patients (P03.053)

Objective: To investigate the superiority of the 3T optimized vs. the 1.5T standardized protocols in detecting gadolinium enhancing (GD-E) lesions in patients with multiple sclerosis (MS). Background Use of post-contrast T1-weighted imaging (WI) is an important tool in diagnosing and predicting the course of MS. Application of optimized imaging strategies has the potential to increase detection of MRI disease activity. Design/Methods: A standard protocol was defined as a 1.5T scan with a single-dose of Gd and a 5-minute scanning delay after injection. An optimized protocol was defined as a 3T MRI scan, using a triple dose of Gd, 20 min scan delay, and using an off-resonance saturated magnetization transfer pulse to reduce the background signal. Fourteen relapsing-remitting MS patients and 3 healthy controls (HC) were scanned with 1.5T standardized and a 3T optimized protocols in random order over 72 hours. Results: There were 47 Gd-E lesions in the MS patients on 3T optimized and 34 on 1.5T standard protocols, a 38.2% increase. There was a significant increase in Gd-enhanced lesion volume (LV) detected with the optimized protocol (179.6%, p Conclusions: The 3T optimized protocol is a useful technique for increasing sensitivity of MRI to detect Gd-E lesions. Disclosure: Dr. Livshits has nothing to disclose. Dr. Hussein has nothing to disclose. Dr. Kennedy has nothing to disclose. Dr. Weinstock-Guttman has received personal compensation for activities with Acorda Therapeutics, Biogen Idec, Serono, Inc., Novartis, Pfizer Inc, Teva Neuroscience as a speaker and/or participant on an advisory board. Dr. Weinstock-Guttman has received research support from Acorda Therapeutics, Biogen Idec, Serono Inc., Novartis, Pfizer Inc, Teva Neuroscience, National Multiple Sclerosis Society, the National Institutes of Health, ITN, Teva Neuroscience, Aspreva-Roche, Acorda Therapeutics and Shire Pharmaceuticals. Dr. Hojnacki has received personal compensation for activities with Biogen Idec, Serono, Inc., Pfizer Inc, and Teva Neuroscience as a speaker and/or participant on scientific advisory boards. Dr. Zivadinov has received personal compensation for activities with Teva Neuroscience, Biogen Idec, EMD Serono, and Questcor Pharmaceuticals as a speaker and/or consultant. Dr. Zivadinov has received research support from Biogen Idec, Teva Neuroscience, Genzyme Corporation, Bracco, Questcor Pharmaceuticals and EMD Serono.

Scanning and Address Allocation Delays in Vehicular Communications

WLAN-based roadside-to-vehicle communications is an increasingly popular research trend. This paper examines the applicability of WLANs in the Intelligent Transportation Systems with focus on reducing the scanning phase delay and the address allocation delay. The handover delays become intolerable when the indoor WLAN Access Poins are accessed from by the outdoor mobile nodes at vehicular speeds. In this work, we propose a baseline scheme which calls for passively scanning only the orthogonal channels to reduce the scanning phase delay in the overall handover latency. We argue that the interference free orthogonal channels are ideal for conveying time critical information in vehicular environments. Secondly, this paper evaluates the delays incurred by the Dynamic Host Configuration Protocol (DHCP) in the handover process. The focus on establishing the amount of delay contributed by each DHCP phase and make some meaningful comments at the end. The conclusions made in this paper are based on real-world experiments and tests.

Cerebral CT angiography using a small volume of concentrated contrast material with a test injection method: optimal scan delay for quantitative and qualitative performance

The objective of this study was to determine the optimal scan delay quantitatively and qualitatively in cerebral CT angiography (CTA) with a test injection method at the circle of Willis (cW). 66 consecutive patients suspected of having unruptured intracranial aneurysms underwent CTA using 40 ml of 370 mg iodine ml(-1) contrast material (CM). After the time until CM arrival at the cW (T(cW)) was calculated, scan delay was divided into three groups according to T(cW) and scan duration (SD) between the second cervical vertebra and cW as follows: [(T(cW)+6)-SD] in 21 patients (Group A); [(T(cW)+8)-SD] in 23 patients (Group B); and [(T(cW)+10)-SD] in 22 patients (Group C). Arterial and venous attenuation in the intracranial vessels was measured. Mean attenuation values were compared quantitatively. The arterial enhancement and venous overlap at the cW and above the cW were qualitatively compared among the three groups. Mean arterial attenuation in Groups B and C was significantly higher than that in Group A. Mean venous attenuation in Group C was significantly higher than those in Groups A and B. Arterial enhancement above the cW showed a significant difference between Groups A and C, and at the cW between Groups A and B, and Groups A and C. There was a significant difference in venous overlap among the three groups, except for that at the cW between Groups B and C. Setting scan delay as [(T(cW)+8)-SD] s can produce the best performance both quantitatively and qualitatively.