Conventional Gating Research Articles

Whole‐heart coronary MRA with 100% respiratory gating efficiency: Self‐navigated three‐dimensional retrospective image‐based motion correction (TRIM)

To develop a three-dimensional retrospective image-based motion correction technique for whole-heart coronary MRA with self-navigation that eliminates both the need to setup a diaphragm navigator and gate the acquisition. The proposed technique uses one-dimensional self-navigation to track the superior-inferior translation of the heart, with which the acquired three-dimensional radial k-space data is segmented into different respiratory bins. Respiratory motion is then estimated in image space using an affine transform model and subsequently this information is used to perform efficient motion correction in k-space. The performance of the proposed technique on healthy volunteers is compared with the conventional navigator gating approach as well as data binning using diaphragm navigator. The proposed method is able to reduce the imaging time to 7.1±0.5 min from 13.9±2.6 min with conventional navigator gating. The scan setup time is reduced as well due to the elimination of the navigator. The proposed method yields excellent image quality comparable with either conventional navigator gating or the navigator binning approach. We have developed a new respiratory motion correction technique for coronary MRA that enables 1 mm(3) isotropic resolution and whole-heart coverage with 7 min of scan time. Further tests on patient population are needed to determine its clinical usage.

Common-Mode Cancellation in Sinusoidal Gating With Balanced InGaAs/InP Single Photon Avalanche Diodes

We demonstrate a sinusoidal-gated InGaAs/InP single photon avalanche diode (SPAD) pair with high photon detection efficiency (PDE) and low dark count rate (DCR). The photodiode pair is biased in a balanced configuration with only one of the SPADs illuminated. The advantage of balanced detectors is cancellation of the common component of the output signal, which in this case arises from sinusoidal gating. In conventional sinusoidal gating, narrow-band RF filters are used to eliminate the gating signal while imparting minimal change to the avalanche pulses. A disadvantage of this approach is that the requisite filters fix the operating frequency, whereas the balanced SPAD receiver is frequency agile. At a laser repletion rate of 1 MHz and a temperature of 240 K, the DCR and PDE are 58 kHz and 43%, respectively. The afterpulse probability is lower than a single sinusoidal-gated SPAD. Jitter of 240 ps is achieved with one photon per pulse and an excess bias of 1.6%.

Ultrasound‐guided identification of cardiac imaging windows

Currently, the use of cine magnetic resonance imaging (MRI) to identify cardiac quiescent periods relative to the electrocardiogram (ECG) signal is insufficient for producing submillimeter-resolution coronary MR angiography (MRA) images. In this work, the authors perform a time series comparison between tissue Doppler echocardiograms of the interventricular septum (IVS) and concurrent biplane x-ray angiograms. Our results indicate very close agreement between the diastasis gating windows identified by both the IVS and x-ray techniques. Seven cath lab patients undergoing diagnostic angiograms were simultaneously scanned during a breath hold by ultrasound and biplane x-ray for six to eight heartbeats. The heart rate of each patient was stable. Dye was injected into either the left or right-coronary vasculature. The IVS was imaged using color tissue Doppler in an apical four-chamber view. Diastasis was estimated on the IVS velocity curve. On the biplane angiograms, proximal, mid, and distal regions were identified on the coronary artery (CA). Frame by frame correlation was used to derive displacement, and then velocity, for each region. The quiescent periods for a CA and its subsegments were estimated based on velocity. Using Pearson's correlation coefficient and Bland-Altman analysis, the authors compared the start and end times of the diastasis windows as estimated from the IVS and CA velocities. The authors also estimated the vessel blur across the diastasis windows of multiple sequential heartbeats of each patient. In total, 17 heartbeats were analyzed. The range of heart rate observed across patients was 47-79 beats per minute (bpm) with a mean of 57 bpm. Significant correlations (R > 0.99; p < 0.01) were observed between the IVS and x-ray techniques for the identification of the start and end times of diastasis windows. The mean difference in the starting times between IVS and CA quiescent windows was -12.0 ms. The mean difference in end times between IVS and CA quiescent windows was -3.5 ms. In contrast, the correlation between RR interval and both the start and duration of the x-ray gating windows were relatively weaker: R = 0.63 (p = 0.13) and R = 0.86 (p = 0.01). For IVS gating windows, the average estimated vessel blurs during single and multiple heartbeats were 0.5 and 0.66 mm, respectively. For x-ray gating windows, the corresponding values were 0.26 and 0.44 mm, respectively. In this study, the authors showed that IVS velocity can be used to identify periods of diastasis for coronary arteries. Despite variability in mid-diastolic rest positions over multiple steady rate heartbeats, vessel blurring of 0.5-1 mm was found to be achievable using the IVS gating technique. The authors envision this leading to a new cardiac gating system that, compared with conventional ECG gating, provides better resolution and shorter scan times for coronary MRA.

Near Infrared Single Photon Detector Using an InGaAs/InP Avalanche Photodiode Operated with a Bipolar Gating Signal

We report a near infrared (NIR) single photon detector (SPD) using an InGaAs/InP avalanche photodiode (APD) operated with a bipolar rectangular gating signal. The use of the bipolar gating pulse enabled us to operate the APD well below the breakdown voltage during the gate-off time. As a result, it permits to decrease the lifetime of the trapped carriers, and then reduces the after-pulse noise of the detector. At a repetition rate of 200 MHz, the after-pulse probability is 8.2% less comparing to that of conventional gating signal SPD.

Controlling the Performance of a Three-Terminal Molecular Transistor: Conformational versus Conventional Gating

The effect of conformational changes in the gate arm of a three-terminal device is investigated. In the ground state, the gate (triphenyl) arm is nonplanar, where the middle phenyl ring is approximately 30° out-of-plane relative to other two rings. At this geometry, the calculated tunnel current (Id) as a function of external bias (Vds) across the two D−A substituted arms exhibits a typical insulator-semiconductor behavior. Similar Id−Vds characteristics is calculated when planarity of the triphenyl arm is restored. However, a significant increase, by more than an order of magnitude, and a distinct variation in the current are predicted in its operational mode (Vds > 1.5 V) when additional nonplanarity is induced in the triphenyl chain. Analysis of the results suggest that, unlike in gating, neither the HOMO−LUMO gap nor the dipole moment of the system undergo significant changes due to pure conformational gating, as observed in this study. Instead, the observed conformational gating affects the current via localization/delocalization of the electronic wave function in the conduction channel. Furthermore, the tunneling current corresponding to conformational gating in two different directions appears to exhibit oscillatory nature with a phase factor of π/2 in the presence of the gate field. The current modulation is found to reach its maximum only under exclusive effect of voltage or conformational gating and diminishes when both of them are present.

Dynamic MRI of the fetal myocardium

Background Fetal cardiovascular MRI has been hampered by the lack of a reliable cardiac gating signal. A recently proposed solution to this problem is metric optimized gating (MOG) [1-3]. Here, we demonstrate the ability of MOG to acquire images of the fetal myocardium without conventional cardiac gating. Our work is motivated by the need for high-resolution dynamic imaging in the assessment of fetal congenital heart disease [4].

4D micro-CT using fast prospective gating

Micro-CT is currently used in preclinical studies to provide anatomical information. But, there is also significant interest in using this technology to obtain functional information. We report here a new sampling strategy for 4D micro-CT for functional cardiac and pulmonary imaging. Rapid scanning of free-breathing mice is achieved with fast prospective gating (FPG) implemented on a field programmable gate array. The method entails on-the-fly computation of delays from the R peaks of the ECG signals or the peaks of the respiratory signals for the triggering pulses. Projection images are acquired for all cardiac or respiratory phases at each angle before rotating to the next angle. FPG can deliver the faster scan time of retrospective gating (RG) with the regular angular distribution of conventional prospective gating for cardiac or respiratory gating. Simultaneous cardio-respiratory gating is also possible with FPG in a hybrid retrospective/prospective approach. We have performed phantom experiments to validate the new sampling protocol and compared the results from FPG and RG in cardiac imaging of a mouse. Additionally, we have evaluated the utility of incorporating respiratory information in 4D cardiac micro-CT studies with FPG. A dual-source micro-CT system was used for image acquisition with pulsed x-ray exposures (80 kVp, 100 mA, 10 ms). The cardiac micro-CT protocol involves the use of a liposomal blood pool contrast agent containing 123 mg I ml−1 delivered via a tail vein catheter in a dose of 0.01 ml g−1 body weight. The phantom experiment demonstrates that FPG can distinguish the successive phases of phantom motion with minimal motion blur, and the animal study demonstrates that respiratory FPG can distinguish inspiration and expiration. 4D cardiac micro-CT imaging with FPG provides image quality superior to RG at an isotropic voxel size of 88 µm and 10 ms temporal resolution. The acquisition time for either sampling approach is less than 5 min. The radiation dose associated with the proposed method is in the range of a typical micro-CT dose (256 mGy for the cardiac study). Ignoring respiration does not significantly affect anatomic information in cardiac studies. FPG can deliver short scan times with low-dose 4D micro-CT imaging without sacrificing image quality. FPG can be applied in high-throughput longitudinal studies in a wide range of applications, including drug safety and cardiopulmonary phenotyping.

Quasi-breath-hold Technique Using Personalized Audio-visual Biofeedback for Respiratory Motion Management in Radiotherapy

Purpose: To introduce a respiratory motion management technique, so called quasi-breath-hold (QBH) technique and evaluate its feasibility. As a hybrid technique combining free-breathing-based gating (denoted as gating for convenience) and breath-hold (BH), the QBH is designed to overcome typical limitations existing in either one such as phase-shift, residual motion, complexity, and discomfort. Methods: The QBH is realized using an audio-visual biofeedback system (AVBFS) and a respiratory motion management program (RMMP). The AVBFS, consisting of two infra-red stereo cameras and a head mounted display, monitors respiratory motion and provides dynamic feedback to patients. The RMMP establishes a personalized respiration model based on deep free breathing. The model is further processed to generate a QBH model by inserting a short breath-hold period into the end point of the-end-of-expiration phase. Then the patient is guided to follow the QBH model through the AVBFS. A simulation study with ten volunteers was performed to evaluate the feasibility of the proposed technique. In the simulation, an in-house developed macro program automatically controlled the QBH procedure to virtually deliver an intensity modulated radiation therapy(IMRT) plan. For each volunteer subject, three QBH maneuvers with different breath-hold times of 3, 5, and 7s (denoted as QBH3s, QBH5s, and QBH7s, respectively) and a conventional gating maneuver with 30% duty cycle (for comparison purpose) were applied. External respiration motion signals obtained during the gating window were analyzed to obtain mean absolute error (MAE) between the measured and guiding curve, mean absolute deviation (MAD) of the measured curve, and an inverse uncertainty time histogram (IUTH). Results: Every volunteer successfully performed all of the four maneuvers (1 gating and 3 QBH patterns). The average treatment times were 466.8, 452.3, and 430.8 s for the QBH3s, QBH5s, and QBH7s, respectively, compared to 530.4 s for the gating technique. The mean absolute errors between measured and guiding curve during the gating window were 0.9 ± 0.7, 0.8 ± 0.6, 0.7 ± 0.6, and 0.6 ± 0.7 mm for the gating, QBH3s, QBH5s, and QBH7s, respectively. The mean absolute deviations of the measured curve during the gating window were 0.7 ± 0.7, 0.5 ± 0.5, 0.5 ± 0.4, and 0.5 ± 0.6 mm for the gating, QBH3s, QBH5s, and QBH7s, respectively. In the analysis of the IUTH during the gating window, the QBH simulations showed similar (QBH3s) or less (QBH5s and QBH7s) motion uncertainties compared to the gating simulation. Conclusions: The proposed QBH technique with personalized audio-visual biofeedback was feasible for respiratory motion management. It showed equivalent or less motion uncertainty and shorter treatment time than the conventional free-breathing-based gating technique did. The technique is expected to optimally compromise between patient comfort and treatment efficiency.

Quasi-breath-hold technique using personalized audio-visual biofeedback for respiratory motion management in radiotherapy

To introduce a respiratory motion management technique, so called quasi-breath-hold (QBH) technique and evaluate its feasibility. As a hybrid technique combining free-breathing-based gating (denoted as gating for convenience) and breath-hold (BH), the QBH is designed to overcome typical limitations existing in either one such as phase-shift, residual motion, complexity, and discomfort. The QBH is realized using an audio-visual biofeedback system (AVBFS) and a respiratory motion management program (RMMP). The AVBFS, consisting of two infra-red stereo cameras and a head mounted display, monitors respiratory motion and provides dynamic feedback to patients. The RMMP establishes a personalized respiration model based on deep free breathing. The model is further processed to generate a QBH model by inserting a short breath-hold period into the end point of the-end-of-expiration phase. Then the patient is guided to follow the QBH model through the AVBFS. A simulation study with ten volunteers was performed to evaluate the feasibility of the proposed technique. In the simulation, an in-house developed macro program automatically controlled the QBH procedure to virtually deliver an intensity modulated radiation therapy (IMRT) plan. For each volunteer subject, three QBH maneuvers with different breath-hold times of 3, 5, and 7s (denoted as QBH3s, QBH5s, and QBH7s, respectively) and a conventional gating maneuver with 30% duty cycle (for comparison purpose) were applied. External respiration motion signals obtained during the gating window were analyzed to obtain mean absolute error (MAE) between the measured and guiding curve, mean absolute deviation (MAD) of the measured curve, and an inverse uncertainty time histogram (IUTH). Every volunteer successfully performed all of the four maneuvers (1 gating and 3 QBH patterns). The average treatment times were 466.8, 452.3, and 430.8 s for the QBH3s, QBH5s, and QBH7s, respectively, compared to 530.4 s for the gating technique. The mean absolute errors between measured and guiding curve during the gating window were 0.9 +/- 0.7, 0.8 +/- 0.6, 0.7 +/- 0.6, and 0.6 +/- 0.7 mm for the gating, QBH3s, QBH5s, and QBH7s, respectively. The mean absolute deviations of the measured curve during the gating window were 0.7 +/- 0.7, 0.5 +/- 0.5, 0.5 +/- 0.4, and 0.5 +/- 0.6 mm for the gating, QBH3s, QBH5s, and QBH7s, respectively. In the analysis of the IUTH during the gating window, the QBH simulations showed similar (QBH3s) or less (QBH5s and QBH7s) motion uncertainties compared to the gating simulation. The proposed QBH technique with personalized audio-visual biofeedback was feasible for respiratory motion management. It showed equivalent or less motion uncertainty and shorter treatment time than the conventional free-breathing-based gating technique did. The technique is expected to optimally compromise between patient comfort and treatment efficiency.

Imaging the Operation of a Carbon Nanotube Charge Sensor at the Nanoscale

Carbon nanotube field effect transistors (CNTFETs) are of great interest for nanoelectronics applications such as nonvolatile memory elements (NVMEs) or charge sensors. In this work, we use a scanning-probe approach based on a local charge perturbation of CNTFET-based NVMEs and investigate their fundamental operation from combined transport, electrostatic scanning probe techniques and atomistic simulations. We experimentally demonstrate operating devices with threshold voltages shifts opposite to conventional gating and with almost unchanged hysteresis. The former effect is quantitatively understood as the emission of a delocalized image charge pattern in the nanotube environment, in response to local charge storage, while the latter effect points out the dominant dipolar nature of hysteresis in CNTFETs. We propose a simple model for charge sensing using CNTFETs, based on the redistribution of the nanotube image charges. This model could be extended to gas or biosensing, for example.

Motion management with phase-adapted 4D-optimization

Cancer treatment with ionizing radiation is often compromised by organ motion, in particular for lung cases. Motion uncertainties can significantly degrade an otherwise optimized treatment plan. We present a spatiotemporal optimization method, which takes into account all phases of breathing via the corresponding 4D-CTs and provides a 4D-optimal plan that can be delivered throughout all breathing phases. Monte Carlo dose calculations are employed to warrant for highest dosimetric accuracy, as pertinent to study motion effects in lung. We demonstrate the performance of this optimization method with clinical lung cancer cases and compare the outcomes to conventional gating techniques. We report significant improvements in target coverage and in healthy tissue sparing at a comparable computational expense. Furthermore, we show that the phase-adapted 4D-optimized plans are robust against irregular breathing, as opposed to gating. This technique has the potential to yield a higher delivery efficiency and a decisively shorter delivery time.

SU-GG-T-114: A Feasibility Study of a 4D Intensity-Modulated Arc Tracking Technique for Treatment of Moving Targets

Purpose: A major challenge of Intensity‐modulated arc therapy(IMAT) is in dealing with moving targets since the conventional gating technique may not be easily applied. The purpose of this work is to develop a 4D IMAT tracking technique for moving targets and investigate its feasibility for clinical use. Method and Materials: 4DCT images at 10 different breathing phases were acquired. The target was contoured for each phase and a 3D RapidArc plan was generated based on the 50%phase CTimages. Each control point in the RapidArc plan was then correlated to the patient's respiration phases with consideration given to changes in gantry speed and dose rate. A novel program was developed to read the RapidArc plan and target contours from all 10 phases. In order to generate a 4D RapidArc plan with the capability of DMLC tracking, the MLC modification algorithm originally developed for on‐line plan modification was used to modify the MLC leaf positions at each control point to correspond to the respiration phases. 4D RapidArc plans for phantom and lung cases were used to evaluate the proposed technique. Experimental measurements for both 4D and 3D plans in a moving phantom were performed and the results were compared with the calculated and measured results for the 3D RapidArc plans in a “static” phantom. Results: Analysis of isodose and gamma distributions indicated that the dose distribution in the moving target delivered using the proposed technique is comparable to that in a static target delivered using a 3D RapidArc plan. The results were much improved using the 4D IMAT delivery compared with the 3D plans for a moving target. Conclusion: A 4D RapidArc tracking technique can be implemented and our results indicated that it is feasible to incorporate the intra‐fraction organ motion into a 4D IMAT planning to track the moving targets.

Validation of simple and robust protocols for high‐resolution lung proton MRI in mice

One fundamental limitation of spatial resolution for in vivo MR lung imaging is related to motion in the thoracic cavity. To overcome this limitation, several methods have been proposed, including scan-synchronous ventilation and the cardiac gating approach. However, with cardiac and ventilation triggered techniques, the use of a predetermined and constant sequence repetition time is not possible, resulting in variable image contrast. In this study, the potential of two "constant repetition time" approaches based on retrospective self-gating and signal averaging were investigated for lung imaging. Image acquisitions were performed at a very short echo time for visualization of the lung structures and the parenchyma. Highly spatially resolved images acquired using retrospective self-gating, signal averaging technique and conventional cardiorespiratory gating are presented and compared.

Model‐based reconstruction for cardiac cine MRI without ECG or breath holding

This paper describes an acquisition and reconstruction strategy for cardiac cine MRI that does not require the use of electrocardiogram or breath holding. The method has similarities with self-gated techniques as information about cardiac and respiratory motion is derived from the imaging sequence itself; here, by acquiring the center k-space line at the beginning of each segment of a balanced steady-state free precession sequence. However, the reconstruction step is fundamentally different: a generalized reconstruction by inversion of coupled systems is used instead of conventional gating. By correcting for nonrigid cardiac and respiratory motion, generalized reconstruction by inversion of coupled systems (GRICS) uses all acquired data, whereas gating rejects data acquired in certain motion states. The method relies on the processing and analysis of the k-space central line data: local information from a 32-channel cardiac coil is used in order to automatically extract eigenmodes of both cardiac and respiratory motion. In the GRICS framework, these eigenmodes are used as driving signals of a motion model. The motion model is defined piecewise, so that each cardiac phase is reconstructed independently. Results from six healthy volunteers, with various slice orientations, show improved image quality compared to combined respiratory and cardiac gating.

Multihypothesis Viterbi Data Association: Algorithm Development and Assessment

Two algorithms for tracking in clutter, based on the Viterbi algorithm are presented: single-target Viterbi data association (ST-VDA) and multihypothesis VDA (MH-VDA). MH-VDA is designed specifically for multiple-target tracking (MTT), although ST-VDA still achieves good performance on MTT problems. The basic philosophy of both methods is to set up an optimisation problem for the sequence of measurement-to-target associations rather than directly seeking the target state estimates. The joint optimisation problem for the data association sequence is decomposed into a sequence of scalar optimisation problems by means of an approximate forward dynamic programming recursion to which the Viterbi algorithm is applicable. Once the data association problem is solved, the target state estimates can be retrieved by backtracking. The operation of the algorithms is easily visualised as a search on a trellis for the optimal path. For ST-VDA, nodes in the trellis correspond to measurements. For MH-VDA, nodes correspond to multitarget data association hypotheses. Conventional measurement gating is extended to work within this context. Results from simulations that compare the performance of ST-VDA and MH-VDA with four, standard, zero-scan-back tracking approaches are given. The performance assessment includes metrics for track loss and track swaps in a multiple crossing target context. The Viterbi data association (VDA) algorithms are shown to outperform the alternative algorithms. In particular the ST-VDA is found to have the best track swap performance, while MH-VDA has the lowest track loss figure. Average state estimation errors for both VDA algorithms are only about 10% larger than a Kalman filter with known data associations. While both variants of VDA are essentially batch processing approaches, the simulation results indicate that the algorithms can be implemented with a fixed processing lag of only a few scans without significant loss in performance.

Saving Dose in Triple-Rule-Out Computed Tomography Examination Using a High-Pitch Dual Spiral Technique

High radiation doses remain a drawback of current triple-rule-out computed tomography (CT) protocols. With dual source CT, a new high-pitch dual spiral technique offers the possibility to acquire an Electrocardiography (ECG)-gated-synchronized dataset of the whole chest in less than 1 second. The aim of this study was to compare the dose of such a protocol to a standard, nongated chest scan and to a conventional, retrospectively ECG-gated triple-rule-out protocol. Also, the efficacy and dose of this dual spiral protocol was to be compared in patients examined with this high-pitch technique and matched controls scanned with the conventional technique. An anthropomorphic Alderson Rando phantom was equipped with thermoluminescent detectors and scanned with the high-pitch protocol (Siemens Somatom Definition Flash; 2 x 120 kVp, 426 mAseff, 128 x 0.6 mm collimation, pitch 3.2), the nongated chest scan (same scanner; 120 kVp, 160 mAseff, 128 x 0.6 mm, pitch 1.2; equivalent Computed Tomography Dose Index (CTDI) of 7.12 mGy), and the conventional gating technique (Siemens Somatom Definition; 120 kVp, 560 mAseff with ECG pulsing interval at 30%-70% of the R-R cycle, 64 x 0.6 mm, pitch 0.3). Noise was measured in air, central and peripheral soft tissue of the phantom. Conversion factors were determined based on the measured dose and the dose-length products of the scanner. The protocol was then applied with ethics committee approval in 31 patients suffering from acute chest pain. The 120 mL of contrast material (Ultravist 370, Bayer Schering Pharma) was applied at 5 mL/s. Dose was calculated based on the dose-length products and the conversion factor. Image quality was assessed by 2 readers for aorta, pulmonary arteries, and coronary arteries. The results were compared with matched controls scanned with the conventional ECG gating technique and non-ECG gated thorax scans. The dose determined with thermoluminescent dosimeters measurements amounted to 2.65, 2.68, and 19.27 mSv, respectively, for the dual spiral technique, the standard chest scan, and the conventional retrospective technique. There was no significant difference in image noise. Respective conversion factors were 0.0186, 0.0188, and 0.0180 mSv/mGy x cm. In the patient examinations, dose was 4.08 +/- 0.81 mSv with the high-pitch protocol compared with 20.4 +/- 5.3 mSv in the matched controls with the conventional technique, and 4.40 +/- 0.83 mSv for the non-ECG gated thorax scan. Scan times were 0.7 +/- 0.1 seconds for the high-pitch scan and 15 +/- 3 seconds for the conventional chest pain scan. Aorta and pulmonary arteries were depicted in diagnostic quality in both groups. About 84.7% of coronary artery segments were rated as diagnostic in the high-pitch exams (95.4% below 65 bpm and only 72.8% in higher heart rates), whereas 92.9% were diagnostic with the conventional approach. The high-pitch dual spiral technique requires only about one-fifth of the dose of conventional ECG gated triple-rule-out protocols, thus matching that of a standard nongated chest scan. With less than 1 second, the scan time is very short. This protocol can be recommended for patients with unclear chest pain with rhythmic heart rates below 65 bpm.

Optical Demultiplexing of 320 Gb/s to 8$\,\times\,$40 Gb/s in Single Parametric Gate

In this paper, we report the experimental demonstration of 320 Gb/s demultiplexing to eight simultaneous always-on 40 Gb/s tributaries with near-zero latency. The single-channel, single-polarization 320 Gb/s optical-time-division-multiplexed signal was processed by a copy-and-sample-all architecture. 1-to-8 wavelength multicasting over more than 10 THz of bandwidth was achieved in a self-seeded two-pump parametric amplifier, and was followed by a single gate, multicolored sampling with equalized response over more than 20 THz. The single gate operation allows for truly scalable real-time processing while avoiding the complexity of parallel pipelines processing. Error-free performance was measured over all extracted 40 Gb/s tributaries with less than 4 dB power penalty compared to conventional single tributary gating.

Using Multiparametric Flow Cytometry to Analysis the Immunophenotypic Abnormalities of Bone Marrow Cells in Patients with MDS-RAEB.

Abstract 4856 ObjectiveThe multiparametric flow cytometry is becoming a very useful tool of the diagnosis and prognostication for patients with Myelodysplastic Syndrome(MDS). This study was aimed at using multiparametric flow cytometry to explore the immunophenotypic abnormalities of bone marrow cells from patients with RAEB. MethodsWe collected BM samples from 12 MDS-RAEB patients (6 male, 6 female, Median Age 67.5) and 20 non-MDS patients (11 male, 9 female, median age 32.5, 7 AA, 5 PNH, 3 IDA, 1 ALL, 2 CML, 2 MM). The multiparametric flow cytometric analysis was performed using an extensive panel of monoclonal antibodies. We used the conventional and secondary gating strategies to analysis the BM cells compartments such as the percents of blast cells and the expression of lineage and maturation-associated antigens of BM hemopoietic cells quantified. ResultsCompared with the non-MDS group, the proportion of blast cells increased significantly in the MDS-RAEB group (P=0.001), but the percentages of nucleated erythrocyte, lymphocyte, monocyte and granulocyte were no significant difference (P=0.954, P=0.893, P=0.730 and P=0.182). As the percentage of blasts cells increasing, the survival time became shorter (13 ± 6 vs 35 ± 15 months; P=0.02). The expressions of haemopoietic stem/progenitor cell surface marker CD34+ and T lymphocyte surface marker CD7+ on blast cells were much higher by secondary gating method than non-MDS group (P=0.009, P=0.002, respectively), while no significant difference of the expression of CD56 (P=0.375). The expressions of CD7+ and CD56+ on lymphocyte were no significant difference between the two groups (P=0.195, P=0.369, respectively), however the expression of CD19+ may be different (P=0.039). The expressions of CD33+ and CD13+ on granulocyte were no significant difference between the two groups (P=0.289, P=0.744, respectively). However, the expression levels of CD15+CD11b+, CD15+CD11b-, CD10+, HLA-DR, CD56+ in the MDS-RAEB group were significantly higher than those in the non-MDS group, specially, the levels of CD10+, HLA-DR and CD56+ were much higher (P=0.016, P=0.011, P=0.005, P=0.005 and P=0.005, respectively) and these patients showed a shorter median overall survival (15 ± 5 vs 36 ± 10 months; p = 0.03). ConclusionsThe percentage of blast cells increased in MDS-RAEB patients and the expressions of CD34+, CD7+ on blast cells and the expressions of CD10+, HLA-DR and CD56+ on granulocyte is higher than non-MDS group. It will be necessary to increase the number of cases (MDS-RAEB) to confirm our findings. Using multiparametric flow cytometry can find the immunophenotypic abnormalities more sensitively, accurately and objectively, and this new approach could provide much more useful information in the diagnosis and prognosis of MDS-RAEB patients. DisclosuresNo relevant conflicts of interest to declare.

Analysis of the Immunophenotypic Features of Blast Cells, Lymphocytes and Granulocytes by Multiparametric Flow Cytometry in Bone Marrow (BM) Cells of Myelodysplastic Syndromes.

Abstract 4843 BackgroundThe myelodysplastic syndromes (MDS) are a group of clonal heterogeneous bone marrow disorders characterized by peripheral cytopenias, ineffective hematopoiesis, and unilineage or multilineage dysplasia. Multiparametric flow cytometry is increasingly being used as an adjunct to the establishing of MDS. While many antigens have been described to be aberrantly expressed in MDS the findings are generally heterogeneous and there is no consistent finding that would be present in all cases with MDS. AimTo investigate the immunophenotypic features of MDS and non-MDS patients and the characteristic of subtypes of MDS. MethodsBM samples were collected from 22 MDS patients including 3 RA (2 male, 1 female, median age 57), 3 RAS (2 male, 1 female, median age 72), 12 RAEB (6 male, 6 female, median age 67.5), 4 MDS-AML (2 male, 2 female, median age 69.5) and 20 non-MDS (11 male, 9 female, median age 32.5, 7 AA, 5 PNH, 3 IDA, 1 ALL, 2 CML, 2 MM). The multiparametric flow cytometric analysis was performed using an extensive panel of monoclonal antibodies and using the conventional and secondary gating strategies to analysis the immunophenotypic features of BM cells. ResultsThis study showed that the proportion of blast cells increased significantly than non-MDS group (P=0.002). As the disease progressing, the percentage of blast cells became higher and significantly difference compared to the non-MDS group (P=0.226, P=0.464, P=0.001 and P=0.000, respectively). The expressions of CD34+ and CD7+ on blast cells were significantly difference between MDS and non-MDS groups (P=0.005, and P=0.002, respectively). Compared with the subtypes of MDS and non-MDS group, the expressions of CD34+ and CD7+ on blast cells became high gradually (P=0.534, P=0.487, P=0.009, P=0.004 and P=0.294, P=0.166, P=0.002, P=0.001) and the high percentage of blast cells and high expression levels of CD34+ and CD7+ might indicate poor prognosis. The expression of CD7+ on lymphocytes was similar with CD34+ and CD7+ on blast cells, but the expressions of CD19+ and CD56+ on lymphocytes were no significantly difference (P=0.076, P=0.252, respectively). The expressions of antigens on granulocytes showed that the expressions of CD15+CD11b+, CD10+ and HLA-DR were significantly difference between MDS and non-MDS groups(P=0.000, P=0.009 and P=0.007, respectively), meanwhile, as the disease progressing, the expression rates of CD15+CD11b+, CD10+ and HLA-DR in subtypes of MDS increased gradually and the survival time of these patients who had over-expression of these antigens was shorter than control group(P=0.002). However, the expressions of CD33+, CD13+, CD56+ and CD15+CD11b- were significantly difference between subtypes of MDS and non-MDS group (P=0.059, P=0.588, P=0.063 and P=0.207, respectively). ConclusionsOur results showed that using multiparametric flow cytometry to analyze the immunophenotypic features of BM cells could provide clinically useful information for the diagnosis, classification and prognosis of MDS patients. Particularly, the percentage of blast cells, the expression of CD34+ and CD7+ on blast cells, the expression of CD7+ on lymphocytes and the expression of CD15+CD11b+, CD10+ and HLA-DR on granulocytes may provide the much more useful information. However, further studies including larger number of patients with a longer follow-up are necessary to confirm these results. DisclosuresNo relevant conflicts of interest to declare.

WE‐C‐BRB‐05: Tracking of Thoracic Tumor Using EPID for Respiratory Gating Purposes: A Retrospective Feasibility Study

Purpose: Conventional respiratory gating relies on an external surrogate which might provide suboptimal tracking of the tumor in many cases. In the present study, an attempt has been made to exploit the density differences between the tumor and its surrounding lung tissue to gate treatments directly using electronic portal imaging device [EPID]. Material &amp; Methods: Varian Trilogy unit equipped with EPID [AS1000, resolution 1024×1024] was used. During treatment, a custom designed image acquisition template captured the portal images. The treatment plan along with the raw scan data and structures was also exported. DRRs for each field with the tumor [hereafter referred as nodule] projection overlaid on it, were also exported and were used as a shaped prior. Nodule was segmented in each portal image using a level set segmentation algorithm which includes an energy term that is minimized when the shape of the segmented region matches the shape prior. Results: The nodule segmentation algorithm was evaluated on a series of 20 portal images of a nodule located just above the diaphragm. The nodule has an average distance from the center of the portal of 5.68 mm with the standard deviation, minimum, and maximum distance of 1.79, 2.44, and 9.13 mm, respectively. The distance between the nodule and segmented region center was 1.98 mm and the standard deviation, minimum, and maximum distance being 0.96, 0.13, and 4.12 mm, respectively. The average &amp; maximum position error between the portal and nodule center could be reduced by 35% &amp; 45%, respectively, using the nodule segmentation algorithm. Present runtime of 4 seconds will be reduced to real‐time as the algorithm is being ported to graphic cards [GPUs]. Conclusion: The proposed method utilizes the tumor motion directly, thereby, eliminating an external surrogate system and its associated inaccuracies and offers promise for respiratory gating treatment delivery.