CTP Protocol Research Articles

Impact of Implementing an Elaborated CT Perfusion Protocol for Aneurysmal SAH on Functional Outcome: CTP Protocol for SAH.

The acute phase of aneurysmal SAH is characterized by a plethora of impending complications with the potential to worsen patients' outcomes. The aim of this study was to evaluate whether an elaborated CTP-based imaging protocol during the acute aneurysmal SAH phase is able to prevent delayed infarctions and contribute to a better outcome. In 2012, an elaborated CTP-based protocol was implemented for the management of patients with aneurysmal SAH. Retrospective analysis of patients with aneurysmal SAH treated from 2010 to 2013 was performed, comparing the patients treated before (group one, 2010-2011) with those treated after the protocol implementation (group two, 2012-2013) with regard to delayed infarctions and outcome according to the mRS at 3-months' follow-up. A total of 133 patients were enrolled, of whom 57 were included in group 1, and 76, in group 2. There were no significant differences between the groups concerning baseline characteristics. In the multivariate analysis, independent predictors of a good outcome (mRS ≤ 2) were younger age (P < .001), lower World Federation of Neurosurgical Societies grade (P < .001), absence of delayed infarction (P = .01), and management according to the CTP protocol (P = .01). Larger or multiple infarctions occurred significantly more often in group 1 compared with group 2 (88% versus 33% of all delayed infarctions, P = .03). The outcome in group 2 was significantly better compared with group 1 (P = .005). The findings suggest that implementation of an elaborated CTP protocol is associated with a better outcome. An earlier initiation of further diagnostics and treatment with prevention of large territorial and/or multiple infarctions might have led to this finding.

Data Privacy Protection Algorithm Based on Redundant Slice Technology in Wireless Sensor Networks

In order to solve the problem that the privacy preserving algorithm based on slicing technology is incapable of dealing with packet loss, this paper presents the redundancy algorithm for privacy preserving. The algorithm guarantees privacy by combining disturbance data and ensures redundancy via carrying hidden data. It also selects the routing tree that is generated by the CTP protocol as the routing path for data transmission. Through division at the source node, the method adds hidden information and disturbance data. This algorithm uses hidden data and adds perturbation data to improve the privacy preserving. Nonetheless, it can restore the original data when data are partly lost. According to the simulation via TOSSIM (TinyOS simulator), in the case of partial packet loss, the algorithm can completely restore the original data. Furthermore, the authors compared accuracy of proposed algorithm, probability of data reduction, data fitting degree, communication overhead, and PLR. As a result, it improves the reliability and privacy of data transmission while ensuring data redundancy.

CT-Perfusion In Diagnostic Of Pancreatic Cancer

Introduction: High rates of morbidity and mortality create the need to improve methods of radiological diagnosis of pancreatic cancer. Method: The results of a survey of 67 patients aged from 27 to 94 years with pancreatic cancer were analyzed. All patients underwent SCT according to a standard protocol using a three-phase scanning technique and PCT on GE 64 Optima 660 CT. Data verification is based on the results of biopsy and surgery in 40 (59%) patients, sectional data in 8 (12%). Result: In the standard CT protocol, pancreatic cancer had a hypovascular contrast pattern in 47 (70%) patients, Tumors were isovascular pancreatic parenchyma in 20 (30%) patients. Indirect signs of biliary and pancreatic hypertension were present in 18 (90%) of 20 patients. In PCT, the tumor on the perfusion parametric maps was visualized in 66 of 67 (98.5%) cases. In one case, against the background of retention pancreatitis with pancreatic hypertension, it was not possible to identify the tumor site. PCT allowed us to estimate the local distribution of the process and determine the indications for performing a radical surgical intervention in 20 patients. The sensitivity of the standard CTP protocol in detecting tumors was 95.8%, specificity was 95.2%, diagnostic accuracy was 95.6%, PCT rates were 97.9%, 100% and 98.6%, respectively. Conclusion: The use of PCT in the detection of pancreatic cancer in comparison with the standard CT protocol increased sensitivity to 97.9%, specificity to 100%, diagnostic accuracy to 98.6%.

TDRHN: A Threshold Sensitive Dynamic Responsive Hybrid Network Protocol based on CTP

The protocols of Wireless Sensor Networks (WSNs) can be categorized into two classes: proactive network protocol like CTP and reactive network protocol like TEEN. The former periodically collects data, working well in the applications of collecting data persistently. However, it can’t dynamically alter the transmission frequency and the routing selecting strategy. The latter can react to the environment change, so it is widely used in the applications requiring nodes to be reactive to some emergencies. But it only works in reactive networks without collecting data under normal circumstance. We find that dynamically altering the transmission frequency and the routing selecting strategy according to the environment change is very effective and significant. For the reasons above, this paper presents TDRHN protocol. It periodically collects data in normal situation and can not only take faster transmission frequency but also alter the routing selecting strategy when it detects some emergencies. So TDRHN can effectively work in hybrid networks combining proactive networks and reactive networks. Finally, we evaluate TDRHN on the testbed with TelosB motes in real deployment. The concluded results of the experiments demonstrate that TDRHN has some particular advantages.

The Simulation Platform in City Traffic Environment Based on TinyOS for Wireless Sensor Networks

Currently, the algorithms for wireless sensor networks which are applied in the field of intelligent transportation use NS2, Matlab software to simulate. The theoretical research results remain a certain distance from their applications in practical system. In order to solve the problem, the simulation platform in city traffic environment based on TinyOS for wireless sensor networks is researched. The structural framework of simulation platform in city traffic environment which is composed of vehicle nodes, relay nodes and sink nodes is proposed. Four design steps of application program and five simulation steps which are composed of simulation compile, network configuration, python simulation, data statistics and simulation result analysis are proposed. CTP protocol and three different movement scenes are used to test and verify the platform. Experimental results show that the algorithm performances with different parameters are obtained, and the simulation platform can verify the algorithms of wireless sensor networks in city traffic environment. The simulation platform combines theory simulation and practical application. It provides a simulation platform for the research on intelligent traffic algorithms, and shortens the algorithm development time.

Whole-brain adaptive 70-kVp perfusion imaging with variable and extended sampling improves quality and consistency while reducing dose.

Despite common use of CTP to assess cerebral hemodynamics in the setting of ischemia, concerns over radiation exposure remain. Our aim was to evaluate the efficacy of an adaptive 70-kVp (peak) whole-brain CTP protocol with variable sampling intervals and extended duration against an established fixed-sampling, limited-period protocol at 80 kVp. A retrospective analysis of 37 patients with stroke scanned with conventional (n = 17) and variant-protocol (n = 20) whole-brain CTP was performed. We compared radiation dose, parametric map quality, and consistency of full-contrast circulation capture between a modified 70-kVp protocol, with 20 whole-brain passes at variable sampling intervals over an extended sampling period, and a conventional 80-kVp CTP examination with 24 passes at fixed-sampling intervals and a more limited scanning window. Mann-Whitney U test analysis was used to compare both protocols. The 70-kVp CTP scan provided superior image quality at a 45% lower CT dose index volume and 13% lower dose-length product/effective dose compared with the conventional 80-kVp scan. With respect to the consistency of contrast-passage capture, 95% of the adaptive, extended protocol continued through the venous return to baseline, compared with only 47% by using the conventional limited-length protocol. Rapid sampling during the critical arterial arrival and washout period was accomplished in nearly 95% with both the variable and fixed-sampling-interval protocols. Seventy-kilovolt (peak) CTP with variable and extended sampling produces improved image quality at lower radiation doses with greater consistency of full contrast passage capture.

CT Brain Perfusion Protocol to Eliminate the Need for Selecting a Venous Output Function

In CTP, an arterial input function is used for cerebral blood volume measurement. AIFs are often influenced by partial volume effects resulting in overestimated CBV. A venous output function is manually selected to correct for partial volume. This can introduce variability. Our goal was to develop a CTP protocol that enables AIF selection unaffected by partial volume. First, the effects of partial volume on artery sizes/types including the MCA were estimated by using a CTP phantom with 9 protocols (section thicknesses of 1, 1.8, and 5 mm and image resolutions of 0.5, 1, and 1.5 mm). Next, these protocols were applied to clinical CTP studies from 6 patients. The influence of the partial volume effect was measured by comparison of the time-attenuation curves from different artery locations with reference veins. AIFs from MCAs were unaffected by partial volume effects when using high image resolution (1 mm) and medium section thickness (1.8 mm). For the clinical data, a total of 104 arteries and 60 veins was selected. The data confirmed that high image resolution and thin section thickness enable selection of MCAs for AIFs free of partial volume influences. In addition, we found that large veins were not insusceptible to partial volume effects relative to large arteries, questioning the use of veins for partial volume correction. A CTP protocol with 1.8-mm section thickness and 1-mm image resolution allows AIF selection unaffected by partial volume effects in MCAs.

Optimal timing for first-pass stress CT myocardial perfusion imaging

CT-based myocardial perfusion imaging (CTP) has been shown to accurately detect myocardial perfusion defects when compared to SPECT. When performing single-phase first-pass stress CTP, timing is of major importance. The aim of this study was to provide guidance for optimal timing of single-phase first-pass stress CTP acquisitions. 16 patients (12 male, age, 69 ± 8 years) with known or suspected coronary artery disease underwent invasive coronary angiography with fractional flow reserve (FFR) measurements using a pressure wire as well as a time-resolved CTP protocol under adenosine stress, performed on a dual-Source CT scanner over a period of 30 s. From the CTP data, time-attenuation curves have been determined both in known ischemic myocardium with a corresponding coronary artery stenosis as proven by a FFR below 0.75 in invasive coronary angiography, as well as in non-ischemic reference myocardium during pharmacological stress. Furthermore, contrast enhancement in the ascending aorta was determined. The time point for an optimal contrast (i.e., difference in Hounsfield Units, HU) between ischemic and normal myocardium was determined. Under pharmacological stress using adenosine, a maximum mean HU difference between ischemic and non-ischemic myocardium (17.7-22.5 HU) was observed 24-32 s after injection of contrast medium. The maximal attenuation difference between normal and ischemic myocardium ranged from 15 to 77 HU in the analyzed patient cohort. When applying a bolus-tracking technique with an automatic contrast detection in the proximal ascending aorta, the optimal time frame for stress CTP was between 8 and 16 s after contrast enhancement in the aorta exceeds 100 HU, or between 7 and 15 s using a threshold of 150 HU. For first-pass CT myocardial perfusion imaging there is a time frame of approximately 8 s for optimal differentiation of ischemic and non-ischemic myocardium, which will be helpful to optimize single-phase CTP scans.

Cerebral CT Perfusion Using an Interventional C-Arm Imaging System: Cerebral Blood Flow Measurements

CTP imaging in the interventional suite could reduce delays to the start of image-guided interventions and help determine the treatment progress and end point. However, C-arms rotate slower than clinical CT scanners, making CTP challenging. We developed a cerebral CTP protocol for C-arm CBCT and evaluated it in an animal study. Five anesthetized swine were imaged by using C-arm CBCT and conventional CT. The C-arm rotates in 4.3 seconds plus a 1.25-second turnaround, compared with 0.5 seconds for clinical CT. Each C-arm scan had 6 continuous bidirectional sweeps. Multiple scans each with a different delay to the start of an aortic arch iodinated contrast injection and a novel image reconstruction algorithm were used to increase temporal resolution. Three different scan sets (consisting of 6, 3, or 2 scans) and 3 injection protocols (3-mL/s 100%, 3-mL/s 67%, and 6-mL/s 50% contrast concentration) were studied. CBF maps for each scan set and injection were generated. The concordance and Pearson correlation coefficients (ρ and r) were calculated to determine the injection providing the best match between the following: the left and right hemispheres, and CT and C-arm CBCT. The highest ρ and r values (both 0.92) for the left and right hemispheres were obtained by using the 6-mL 50% iodinated contrast concentration injection. The same injection gave the best match for CT and C-arm CBCT for the 6-scan set (ρ = 0.77, r = 0.89). Some of the 3-scan and 2-scan protocols provided matches similar to those in CT. This study demonstrated that C-arm CBCT can produce CBF maps that correlate well with those from CTP.

Visual field loss following vitrectomy for stage 2 and 3 macular holes.

To describe the phenomenon of peripheral field loss following routine pars plana vitrectomy for stage 2 and 3 full thickness macular hole and to investigate the underlying mechanism. Five patients, who reported peripheral field defects after apparently uncomplicated vitrectomy, posterior cortical vitreous peeling, and perfluoropropane (C3F8) gas tamponade, were studied retrospectively with slit-lamp biomicroscopy, automated and kinetic perimetry, fundal fluorescein angiography, focal electroretinography (ERG), and colour contrast sensitivity (CCS) testing. All five patients, who were between 50 and 73 years of age, reported an inferotemporal field defect following resolution of the intraocular gas bubble. In all eyes, the scotomata encroached to within 20 degrees to 30 degrees of fixation and to within 5 degrees to 15 degrees of the blind spot. In one eye, a partial altitudinal component was evident. All scotomata subsequently remained stable and three eyes developed subtle segmental nasal disc pallor and nerve fibre loss corresponding to the field defect. CCS testing revealed absent colour contrast in the scotomatous area, in the presence of a preserved focal quadrantic flash ERG, compared with normal CCS protan thresholds and focal ERGs in unaffected quadrants, indicating preserved outer retinal function in the area of the scotoma. These observations support the hypothesis that field defects occur as a result of retinal nerve fibre layer damage. It is proposed, on the basis of intraoperative observations and other evidence, that the most likely site of nerve fibre damage is at the nasal portion of the optic nerve rim or peripapillary retina, probably due to traction during cortical vitreous peeling.