Two-stage Correction Research Articles

Two-stage ionoacoustic range verification leveraging Monte Carlo and acoustic simulations to stably account for tissue inhomogeneity and accelerator-specific time structure - A simulation study.

Range errors constrain treatment planning by limiting choice of ion beam angles and requiring large margins. Ionoacoustic range verification requires recovering the location of an acoustic source from low frequency signals. A priori information is applied to stably overcome resolution limits of inverse acoustic source imaging in this simulation study. In particular, the accuracy and robustness of ionoacoustic range verification for lateral and oblique delivery of high-energy protons to the prostate is examined. Dose maps were computed using GEANT4 Monte Carlo simulations via the TOPAS user interface. Thermoacoustic pulses were propagated using k-Wave software, with initial pressures corresponding to instantaneous dose deposition and piecewise constant maps of tissue properties derived from the planning CT. A database of dose maps with corresponding thermoacoustic emissions and Bragg peak locations, referred to as "control points," were precomputed. Corresponding thermoacoustic emissions were also precomputed. Pulses were recorded at four coplanar locations corresponding to the outer surface of a virtual transrectal array. To model experimental beam delivery, k-Wave results were convolved in time with a Gaussian envelope to account for noninstantaneous proton delivery by a synchrocyclotron. Thermoacoustic pulses were bandlimited below 150 kHz, and amplitudes were directly proportional to charge delivered. To test robustness of our method, white noise was added. Range was estimated in a two-step process. The first step obtained a preliminary range estimate by one-way beamforming. The second step was taken using data corresponding to the "control point" nearest to the preliminary range estimate. For each receiver, the time of flight difference, ∆t, between the measured and control thermoacoustic signals were accurately estimated by applying the Fourier shift theorem. Receiver-Bragg peak distance was then estimated by adding vs ∆t to the known distance of the control point, where vs is soundspeed. A linear system of equations based upon all receiver locations and distances was solved to recover the Bragg peak location. All simulations were performed relative to the planning CT. Because ultrasound (US) images were not available, results were overlaid onto the planning CT. Beamformed estimates from noise-free data tracked all beam locations within 1 cm. Final estimates for oblique and lateral beams were accurate to within 1.0 and 1.6 mm respectively. Average errors of final range estimates for oblique beams from data with SNR = 0 dB were no greater than 2.0 mm. Ionoacoustic range verification may improve current practice. Ionoacoustic range estimates can be inherently co-registered to ultrasound images of underlying anatomy. To ensure estimates are robust in clinical practice, dose maps based upon the planning CT should be overlaid onto ultrasound volumes acquired at time of treatment and acoustic simulations re-computed to provide a database of control points and corresponding thermoacoustic emissions. Computation times for beamformed estimates are already fast enough for online range verification, but are not accurate enough for a measurement aperture limited to the surface of a transrectal ultrasound probe. Accelerated acoustic simulations will be required to enable online two-stage correction, but offline calculation is already suitable for adaptive planning.

Two-stage correction of type IV total anomalous pulmonary venous connection

BackgroundThe small size of the pulmonary veins in infants increases the risk of pulmonary vein obstruction (PVO) after surgical repair of type IV total anomalous pulmonary venous connection (TAPVC). Here, we described the outcomes of our strategy, which delayed total correction after initial partial correction.MethodsWe reviewed the data of patients who underwent total correction for type IV TAPVC. In total, 11 out of 103 patients with TAPVC had type IV TAPVC with biventricular physiology. Of these 11 patients, we retrospectively reviewed the data of 7 patients who underwent two-stage correction. Major pulmonary venous confluent chambers, with the exception of the left superior pulmonary vein (LSPV), were initially anastomosed to the left atrium (LA), followed by anastomosis between the LSPV and the LA auricle.ResultsThe median weight, age, and LSPV size were 4.3 kg (range, 3.5–5.4 kg), 40 days (range, 20–103 days), and 4.5 mm (range, 3.0–5.4 mm), respectively, during the first operation and 12.2 kg (range, 8.5–31.5 kg), 1,165 days (range, 280–3,250 days), and 9.8 mm (range, 8.0–12.3 mm), respectively, during the second operation. The median Qp/Qs was 1.61 (range, 1.22–1.65) and the median cardiothoracic ratio was 0.52 (range, 0.49–0.57) at second operation. The median interval between the operations was 1,094 days (range, 196–3,226 days). The median follow-up period was 22 month (range, 7–59 month). No mortality or major morbidities occurred after either operation. The median Vmax at the LSPV anastomosis site was 1.0 m/s (range, 0.8–1.3 m/s) on predischarge echocardiography. This patency was maintained at the last follow-up, showing an identical median Vmax of 1.0 m/s (range, 0.8–1.3 m/s). All 7 patients who underwent two-stage correction were in good condition, without any clinical symptoms of PVO.ConclusionsOur results suggest that leaving the isolated LSPV uncorrected during infancy and performing a second operation when the LSPV has grown adequately is a viable treatment option for patients with type IV TAPVC.

Evaluation of the efficiency of one-stage and two-stage correction of the full form of atrioventricular communication complicated by pulmonary hypertension

Evaluation of the efficiency of one-stage and two-stage correction of the full form of atrioventricular communication complicated by pulmonary hypertension

飞机共形窗口像差的二级静态校正

飞机共形窗口像差的二级静态校正

Occurrence of radial club hand in children with different syndromes

Aim. Clinical analysis of congenital radial club hand as part of some genetic syndromes as well as the optimization of methods of non-surgical and surgical treatment of patients with this pathology. Material and Methods. From 2007 to 2014, we conducted a survey of 170 children with congenital radial club hand. Among them, 32 patients were diagnosed (18.8%) with different syndromes. We assessed the degree to which the radius was underdeveloped among this group of patients as well as the management features of patients according to various comorbidities. Results. The assessment identified Holt-Oram syndrome in 17 children (nine boys and eight girls; 53.1%) and TAR-syndrome in nine children (four boys and five girls; 28.1%). VACTERL syndrome was detected in four male patients (12.5%) and Nagera syndrome was observed in two children (one boy and one girl; 6.25%). Surgical treatment of radial club hand in patients with genetic syndromes is the same as that of the patients with isolated congenital radial club hand: a single- or two-stage correction of the hand relative to the ulna with subsequent reconstruction of the rays of the hand. The duration of treatment of such patients did not significantly differ compared to the patients with isolated congenital radial club hand. Conclusion. Congenital radial club hand, identified as part of genetic syndromes, requires a comprehensive examination to diagnose comorbidities, observation, and treatment by specialists to determine the optimal age for surgical correction of the existing strain of the upper limb.

Two-stage posterior correction in the treatment of severe rigid neuromuscular scoliosis: Case report

Background: Treatment of severe rigid scoliosis is challenging. Traditional methods such as combined anterior and posterior surgery with or without perioperative halo-gravity traction, or more aggressive one-stage posterior correction methods carry many drawbacks and potential risks. To overcome this, a staged posterior approach was raised. We report a patient successfully treated with this new method. Case Report: A 15-year-old boy was diagnosed to have neuromuscular scoliosis of unknown origin. The Cobb angle was 110 degrees at T9- L4, and 77 degrees at T2- T9. The preoperative pelvic tilt was 16 degrees. Bending views showed the flexibility about 10%. Two-stage correction was performed. The major curve magnitude reduced 40 degrees or 36.3% after the first-stage surgery, and 25 degrees or 35.7% after the second-stage surgery. The final correction rate was 59.1%. The postoperative pelvic tilt reduced to 6 degrees. No complication such as infection, neurological injury or respiratory compromise was found. Discussion: This two-stage approach has many advantages, including preventing pulmonary function deterioration, no need of halo traction, avoiding too much manipulation of the spinal cord during each surgery, and facilitating curve correction. However, we should also take into consideration of its large blood loss, nutritional demand and potential risk of infection. Conclusion: Two-stage posterior correction is a reasonable and suitable alternative correction strategy in the treatment of severe rigid scoliosis. However, further study is needed to verify its validity and safety.

TWO-STAGE TREATMENT APPROACH TO SEVERE CASES OF HIP INSTABILITY IN PATIENTS WITH INFANTILE CEREBRAL PALSY

Hip instability is a common condition in patients with cerebral palsy. Its development leads to severe degenerative changes in the joint, accompanied with rapidly progressive contractures, pain, deformities of the adjacent segments and decreased limb support ability. One of the characteristic features of this disease is the development of osteochondral defect in the external part of the femoral head epiphysis. We report two clinical cases of successful two-stage surgical correction of joint elements aimed at moving the defect in the joint area, which is not loaded by the arch socket.

Accounting principle choice by ADR firms and auditors' fees

This paper examines whether ADR issuers, selecting US GAAP, IFRS, or home-country accounting principles for the preparation of financial statements accompanying the Form 20-F filing, are paying different auditors’ fees. We employ the Heckman Probit decision choice model and two-stage OLS correction to estimate the impact of selection of Form 20-F accounting standards upon ADR firms periodic auditors’ fees. We find that firms choosing to present US GAAP financial statements incur the highest auditors’ fees, while firms choosing to present IFRS financial statements accompanying the Form 20-F filing incur the second largest auditors’ fees. They also find that ADR firms incur significantly greater costs (associated with Form 20-F filings) than non-US firms opting not to list on the major US stock exchanges in order to improve comparability with other firms listed on the major US exchanges.

Which Continuous-Time Model is Most Appropriate for Exchange Rates?

This paper determines the most appropriate ways to model diffusion and jump features of exchange rates. Simulations show that intraday periodicity in volatility prevents conventional tests from accurately identifying the frequency and location of jumps. We propose a two-stage correction for this periodicity that improves the properties of the test statistics. The most plausible model for 1-minute exchange rate data features Brownian motion and Poisson jumps but not infinite activity jumps. We also show that microstructure noise biases but does not unduly impair the statistical tests for jumps and diffusion behavior in finite samples.

Two-Stage Correction of Blepharophimosis Syndrome: Analysis of Surgical Outcome-Author Reply.

Two-Stage Correction of Blepharophimosis Syndrome: Analysis of Surgical Outcome-Author Reply.

Two-Stage Correction of Blepharophimosis Syndrome: Analysis of Surgical Outcome.

To evaluate the outcome of surgical correction of blepharophimosis syndrome. A retrospective, non-randomized, interventional case series. Ten patients undergoing surgical correction of blepharophimosis syndrome in 2 stages were reviewed. In the first stage, correction of epicanthic fold and telecanthus was done by either Y-V plasty or Roveda procedure with or without medial canthal tendon shortening. In the second stage, ptosis correction was done by bilateral frontalis sling. The preoperative and postoperative ratio of intercanthal distance (ICD) to horizontal palpebral fissure length (HPFL) was compared to assess the outcome of surgical correction of blepharophimosis. The ratio was graded as good (ratio < 1.3), suboptimal (ratio between 1.3 and 1.5), and poor (ratio > 1.5). The outcome of ptosis correction was graded as good, moderate, and poor. Of 10 patients, 5 (50%) underwent Y-V plasty, and 5 (50%) underwent Roveda procedure. Medial canthal tendon shortening was done in 5 patients (50%) having a preoperative ICD of 35 mm or more. After surgical correction, mean reduction in ICD was 4.8 mm (P < 0.0001), and mean improvement in HPFL was 5.45 mm (P < 0.0001). The mean ICD to HPFL ratio changed from 2.02 to 1.31 after surgery, which was statistically significant (P < 0.0001). Two patients (20%) had a ratio greater than 1.5. Nine patients (90%) had either good or moderate ptosis correction after bilateral frontalis sling with silicone rod. Functionally and cosmetically acceptable outcome can be achieved after surgical correction of blepharophimosis syndrome in 2 stages.

Delayed papillary muscle rupture following repair of post-infarction ventricular septal defect

Ventricular septal defect (VSD) and papillary muscle rupture are severe complications of myocardial infarction which are usually observed individually although their simultaneous occurrence has been observed in pathological studies. An 82-year-old female underwent repair of a post-infarction VSD and 13 days later required mitral valve replacement due to delayed papillary muscle rupture. Mechanical complications of myocardial infarction can occur in the same patient even in delayed fashion and a two-stage correction may be successfully accomplished.

Successful Two-Stage Correction of Ventricular Septal Defect and Patent Ductus Arteriosus in a Patient with Fixed Pulmonary Hypertension

We report a case of a 6-year-old boy with fixed severe pulmonary artery hypertension secondary to a ventricular septal defect (VSD) together with a patent ductus arteriosus (PDA). As a preliminary step, PDA embolization was performed following therapy with inhaled prostacyclin over a period of 6 months. Further, the patient underwent successful surgical VSD closure. We postulate that a staged procedure with long-term prostaglandin therapy might be capable of reducing pulmonary artery resistance and permitting total correction in a patient once considered to have inoperable pulmonary arteriopathy.

Adaptive two-stage FEC scheme for scalable video transmission over wireless networks

In this paper, we present a two-stage forward error correction (FEC) scheme with an enhanced link-layer protocol especially for multimedia data transmission over wireless LANs. At the application layer, packet-level FEC (stage-one) is added across packets to correct packet losses due to congestion and route disruption. Bit-level FEC (stage-two) is then added to both application packets and stage-one FEC packets to recover bit errors from the link layer. Then at the link layer, header-CRC/FEC is used to enhance protection and to cooperate with the two-stage FEC scheme. The proposed scheme thus provides joint protection across the protocol stack. We explore both its bandwidth efficiency and video performance for the highly efficient and scalable MC-EZBC video codec using the network simulator ns-2. Our results show that the proposed scheme can effectively increase application-layer throughput, reduce both end-to-end transmission delay and application bandwidth fluctuation, and significantly improve video performance.

Delayed-onset neurological deficit following correction of severe thoracic kyphotic deformity

There are many potential risks associated with spinal deformity correction procedures including transient and/or permanent neurological deficits. Typically, neurological deficits caused by the surgical correction of spinal kyphosis occur acutely during surgery or immediately after surgery. Delayed postoperative neurological deficits are extremely rare. The authors report a case of delayed neurological deficit that occurred 48 hours after surgical correction of thoracic hyperkyphosis. An 18-year-old man with myotonic dystrophy presented with a 110 degrees T7-L1 kyphosis. The patient underwent an uneventful two-stage correction procedure of the hyperkyphotic deformity. First, anterior discectomies and fusion were performed from T-7 to L-1 using rib autograft, and all segmental vessels were preserved. Subsequently, on the same day, the patient underwent posterior Smith-Petersen osteotomies and T7-L2 pedicle screw fixation. Intact somatosensory and motor evoked potentials were maintained throughout both operations. Postoperatively, he remained neurologically intact without sequelae for nearly 48 hours. On postoperative Day 2, the patient developed delayed monoplegia of the left leg and sensory level loss below T-10. Medical management enabled complete reversal of the patient's monoplegia and sensory loss. At 2-year follow-up, the patient had no adverse neurological sequelae. In this case, a delayed postoperative neurological deficit occurred following spinal hyperkyphosis correction. The authors discuss the possible etiological mechanisms behind this complication and suggest strategies for its management.

Expansion tissulaire et seins tubéreux : à propos de dix cas

Introduction Tuberous breast is a deficiency of mammary development, principally in the lower lateral and medial quadrants. In types II and III of the Grolleau classification, we perform a two-stage correction by tissue expansion associated with an implant in order to avoid the double bubble deformity and the difficulty of medial infra-mammary fold reconstruction. Materiels and methods Between February 2003 and February 2006, ten patients have been treated by implantation of an anatomical expander associated with a vertical and horizontal Puckett plasty. The second operation consisted in the replacement of the expander by an anatomical prosthesis associated, if necessary, with a second Puckett plasty and lipofilling. Results There was no double bubble deformity. Three patients required a complementary lipofilling to improve the result of the lower medial fold. One prosthesis had to be repositioned and one expander infection was responsible of a three-month delay in the reconstruction procedure. Conclusion Tuberous breast correction is a therapeutic challenge in quite psychologically distressed patients. In types II and III, tissue expansion associated with a Puckett plasty increase the volume of the lower pole and reduces the risk of the double bubble deformity. The implantation of an anatomical prosthesis gives more natural effect to the contour of the glandular lower pole. This therapeutic attitude gives the chance of achieving a completely satisfactory result.

Model-Based Optical Proximity Correction for Resist Reflow Process

For the patterning of sub-100 nm contact holes, thermal reflow is suggested as a good method of resolving the cost problems of resolution-enhancement technology and the new lithography technology. However, it is difficult to use this process in lithography process because the optical proximity effect of thermal reflow is quite severe. In this study, the optical proximity effects before and after thermal reflow are described. Resist reflow is modeled and simulated for a top-view image. For repeated contacts and random contacts, thermal reflow biases are modeled and compensated for pattern arrays. Simulation results agree well with the experiment results in a small error range according to baking temperature, time, and pitch size. For the optical proximity correction of thermal reflow, two-stage corrections, and model-based optical proximity corrections before and after thermal reflow, are described. The model-based optical proximity correction before thermal reflow can be required using pull-simulated images rather than an aerial image as pattern critical dimension shrinks down to sub-100 nm. The possibility of thermal reflow for the formation of a sub-100 nm pattern is shown by simulating a model-based optical proximity correction of a 45 nm contact hole.

Do Students Benefit From Supplemental Instruction?

Peer assisted study sessions (PASS) are a type of supplemental instruction (SI) that provide students with out-of-class study review sessions with a group of peers. A student, who has successfully completed the subject and acts as a mentor, facilitates the voluntary sessions. Results of the PASS program at the University of Wollongong have been quite positive in that students, on average, who attend more PASS, achieve higher marks. However, a simple comparison does not control for self-selection bias. We control for self-selection in two ways. Firstly, we use Heckman's two-stage correction technique to analyze the 2002 cohort. Secondly, students in the 2003 cohort were randomly allocated into three groups of equal size: - A control group that was allocated to normal tutorials with standard class sizes and ineligible to attend PASS - A group that was eligible to attend PASS and had normal tutorials of standard sizes - A group that was ineligible to attend PASS but allocated to normal tutorials with smaller class sizes. The results of both methods are consistent and indicate the PASS program has a positive impact on the academic performance of students after correcting for selection bias.

Lower limb deformities in children: two-stage correction using the Taylor spatial frame

Lower limb deformities in children: two-stage correction using the Taylor spatial frame

Lower limb deformities in children: two-stage correction using the Taylor spatial frame

Lower limb deformities in children: two-stage correction using the Taylor spatial frame