Reconstruction Time Research Articles

In-line imaging and recognition of flip chip fabrication defects by real-time photoacoustic remote sensing system

Microscopic defects in flip chips, originating from manufacturing, significantly affect performance and longevity. Post-fabrication sampling methods ensure product functionality but lack in-line defect monitoring to enhance chip yield and lifespan in real-time. This study introduces a photoacoustic remote sensing (PARS) system for in-line imaging and defect recognition during flip-chip fabrication. We first propose a real-time PARS imaging method based on continuous acquisition combined with parallel processing image reconstruction to achieve real-time imaging during the scanning of flip-chip samples, reducing reconstruction time from an average of approximately 1134 ms to 38 ms. Subsequently, we propose improved YOLOv7 with space-to-depth block (IYOLOv7-SPD), an enhanced deep learning defect recognition method, for accurate in-line recognition and localization of microscopic defects during the PARS real-time imaging process. The experimental results validate the viability of the proposed system for enhancing the lifespan and yield of flip-chip products in chip manufacturing facilities.

Time of the Day Variability in Pit-Building Behavior of Antlion Larvae

Pit-building behavior in antlion larvae is a unique trait that ensures survival, growth, and metamorphosis. In the present study, we examined the 24-hour rhythm in the pit-building behavior of 16 antlion larvae collected from the PRSU campus, Raipur. We kept each larva individually in a plastic drinking cup in the laboratory. We observed the pit-building behavior of antlion larvae by monitoring two variables, i.e., the time lag for the initiation of pit reconstruction (TLIPR) and total time for pit construction (TTPC) after its demolition over three consecutive days, at four time points each day. We employed single Cosinor Rhythmometry to compute the characteristics of 24-hour rhythm in TLIPR and TTPC. We found a statistically significant 24-hour rhythm in both variables. We found the peaks of TLIPR between 14.32 h and 17.15 h, irrespective of days. Further, the factor 'time of the day' produced a statistically significant effect on the TLIPR and the maximum and minimum values were found at 14.00 h and 02.00 h, respectively. This implies that antlion larvae took time during the afternoon to initiate pit construction. This phenomenon was reversed during nighttime. TTPC exhibited a statistically significant 24-hour rhythm on day 3 and at the group level. We concluded that antlion larvae exhibit a 24-hour rhythm in pit-building behavior and are nocturnal as they initiate pit construction quickly at night.

Prefabricated Fibula Flap vs Bone-Driven and Delayed Implant Installation for Jaw Reconstruction

Restoration of dental occlusion and oral rehabilitation is the ultimate goal of functional jaw reconstruction. To evaluate the prefabricated fibula flap (PFF) technique in occlusion-driven jaw reconstruction for benign or previously treated malignant disease. This cohort study was conducted from January 2000 to December 2019 at the University of Alberta Hospital and Institute of Reconstructive Sciences in Medicine in Edmonton, Alberta, Canada, among patients who underwent PFF or bone-driven and delayed osseointegrated implant installation (BDD). Patients were followed up for a minimum of 1 year after occlusal rehabilitation. Data were analyzed from July 2021 to June 2022. Patients underwent BDD or PFF, which consists of osseointegrated dental implant installation and skin grafting of the fibular bone 3 to 6 months before jaw tumor resection or defect reconstruction. The implant osseointegration is completed at the time of jaw reconstruction, allowing for full reconstruction, loading, and restoration of the dental occlusion in the immediate postoperative period. Safety, effectiveness, accuracy, timeliness of occlusal reconstruction, and aesthetic appeal were compared between PFF and BDD. Groups were compared for the following variables: postoperative complications, number of bony segments used, number of procedures needed, total operative time, time to occlusal rehabilitation, and number of implants installed, exposed, lost, and used (ie, exposed implants - lost implants). Aesthetic appeal was assessed using standardized full-face and profile digital photographs taken before and 6 to 12 months after the operation and analyzed by 3 naive raters. Among 9 patients receiving PFF (mean [SD] age, 43.3 [13.0] years; 7 men [77.8%]) and 12 patients receiving BDD (mean [SD] age, 41.9 [18.0] years; 8 men [66.7%]), the overall complication rate was similar (4 patients [44.4%] vs 3 patients [25.0%], respectively; relative risk, 1.78 [95% CI, 0.52 to 6.04]). The number of patients with implant loss was similar between PFF and BDD groups (0 patients vs 3 patients [25.0%], respectively; difference, -25.0 percentage points [95% CI, -48.4 to 9.7 percentage points]). PFF had a clinically meaningful faster mean (SD) occlusal rehabilitation compared with BDD (12.1 [1.9] months vs 60.4 [23.1] months; difference, -48.3 months [95% CI, -64.5 to -32.0 months]). The mean (SD) difference in preoperative to postoperative aesthetic score was similar between PFF and BDD groups (-0.8 [1.5] vs -0.2 [0.8]; difference, -0.6 [95% CI, -1.6 to 0.4]). This study found that PFF compared with BDD was a safe, effective, and aesthetic reconstructive option for patients with benign or previously treated jaw malignant tumors. This technique may provide rapid occlusal reconstruction and oral rehabilitation.

Histologic Examination of Mastectomy Scars during Breast Reconstruction: A Systematic Review.

Breast reconstruction is a standard procedure in postmastectomy plastic surgery. The necessity of routine histological examinations for mastectomy scars during delayed reconstruction remains a topic of debate. We evaluated the need for histological examination of scars during delayed breast reconstruction. We conducted a systematic review using PubMed, TDnet, and Cochrane Central in August 2023. Inclusion criteria involved delayed breast reconstruction with histological scar analysis and malignancy reporting. Exclusion criteria encompassed noncancerous breast diseases, prophylactic mastectomies, articles lacking relevant information, case reports, technique descriptions, and reviews. We independently assessed articles. Differences in recurrence rates were determined using a Z-test for proportions. A linear regression model explored the relationship between reconstruction timing and pathological results. The number needed to treat was calculated based on the literature. The Wilcoxon test was used to compare mean reconstruction times and postreconstruction follow-up between groups. Our analysis covered 11 retrospective observational studies published between 2003 and 2018, including 3754 mastectomy scars. The malignancy recurrence rate was 0.19%, consistent with previous reports, with a number needed to treat of 144.93-188.68 patients. The timing of breast reconstruction postmastectomy averaged 19.9 months, without statistically significant association between reconstruction timing and recurrence rates. Postreconstruction follow-up periods ranged from 60 to 87 months. The postreconstruction adverse outcomes ratio was 2.21%. Assessing the necessity of histological examination in breast reconstruction is complex. Based on the literature and this study, we do not recommend routine histological examination of mastectomy scars during delayed reconstruction. A selective approach based on risk factors may be beneficial, warranting further research.

Image fast reconstruction for sparse view computed tomography with reduced sampling integration time

Industrial computed tomography (CT) can detect the internal structure of objects nondestructively. Its scanning and image reconstruction are time-consuming, which limits its application in the fast detection field. In this work, we reduce the sampling integration time in sparse view CT to achieve ultra-fast scanning in only 5 s. However, this ultra-fast scanning method produces more noise and streak artifacts in the reconstructed CT images. The existing reconstruction methods cannot effectively reconstruct high quality CT images under this ultra-fast scanning. To solve this issue, a faster and higher quality CT image reconstruction method is proposed in this paper. We construct a novel objective function using multi-directional TV and adaptive non-local means (ANLM), and design a solution algorithm to solve the objective function. The multi-directional TV-norm takes into account the differences in horizontal, vertical, and 45° directional gradients to obtain more image detail information, while the ANLM-norm focuses on noise suppression. Simulation and practical experiments show that the proposed method can reconstruct higher quality CT images under faster CT scanning strategy, and the peak signal to noise ratio (PSNR) is 1.3 dB higher than the optimal baseline algorithm. On the other hand, our method converges faster and achieves a shorter CT image reconstruction time, which is 47 s shorter than the current popular iterative reconstruction methods. This reconstruction method provides a reliable scheme for faster CT scanning and image reconstruction.

Do Age and Timing Influence the Outcomes of Single-stage Reconstruction of Multiple Ligament Knee Injuries? 5-10 Years Follow Up.

Multiple ligament knee injuries (MLKIs) are disruptive injuries, however, there are controversies in the results of acute and delayed reconstruction. Also, clinical outcomes between patients older or younger than 40 have not been compared in MLKIs. This study was designed to investigate the influence of age and timing of reconstruction on the outcomes of single-stage reconstruction of MLKIs. The patients who underwent reconstruction of multiple injured ligaments because of MLKIs between May 2013 and July 2019 were added to the cohort. The postoperative complications, knee range of motion (ROM), Lysholm score, International Knee Documentation Committee (IKDC) 2000 score, Tegner activity level, patient satisfaction, and SF-36 score were compared between young (≤ 40 years old, n = 41) and old patients (n = 61); acute (≤ 3 weeks after injury, n = 75) and delayed reconstruction (n = 27), using Mann-Whitney U test or χ2 test. A total of 102 MLKI patients managed by single-stage multi-ligament reconstruction were retrospectively reviewed. Patients were followed up after surgery for a mean of 7.3 years (5.2-10.7 years). At the last follow-up, no significant difference was found in knee ROM, functional scores, and patient-reported outcomes between patients older or younger than 40; acute and delayed reconstruction (p > 0.05). The rate of complications in the delayed reconstruction group was higher than that of the acute reconstruction group (22.2% vs 5.3%, p < 0.05). The IKDC objective scores reached grade A in 63.7%-80.4% of patients, and grade B in 11.8%-23.5% patients. The single-stage reconstruction of MLKIs can obtain comparative long-term functional and objective outcomes regardless of patients older or younger than 40; acute and delayed reconstruction, however, delayed reconstruction is related to a high rate of postoperative complications.

Complete Neuron Reconstruction Based on Branch Confidence.

In the past few years, significant advancements in microscopic imaging technology have led to the production of numerous high-resolution images capturing brain neurons at the micrometer scale. The reconstructed structure of neurons from neuronal images can serve as a valuable reference for research in brain diseases and neuroscience. Currently, there lacks an accurate and efficient method for neuron reconstruction. Manual reconstruction remains the primary approach, offering high accuracy but requiring significant time investment. While some automatic reconstruction methods are faster, they often sacrifice accuracy and cannot be directly relied upon. Therefore, the primary goal of this paper is to develop a neuron reconstruction tool that is both efficient and accurate. The tool aids users in reconstructing complete neurons by calculating the confidence of branches during the reconstruction process. The method models the neuron reconstruction as multiple Markov chains, and calculates the confidence of the connections between branches by simulating the reconstruction artifacts in the results. Users iteratively modify low-confidence branches to ensure precise and efficient neuron reconstruction. Experiments on both the publicly accessible BigNeuron dataset and a self-created Whole-Brain dataset demonstrate that the tool achieves high accuracy similar to manual reconstruction, while significantly reducing reconstruction time.

Iterative image reconstruction algorithm analysis for optical CT radiochromic gel dosimetry

Background. Modern radiation therapy technologies aim to enhance radiation dose precision to the tumor and utilize hypofractionated treatment regimens. Verifying the dose distributions associated with these advanced radiation therapy treatments remains an active research area due to the complexity of delivery systems and the lack of suitable three-dimensional dosimetry tools. Gel dosimeters are a potential tool for measuring these complex dose distributions. A prototype tabletop solid-tank fan-beam optical CT scanner for readout of gel dosimeters was recently developed. This scanner does not have a straight raypath from source to detector, thus images cannot be reconstructed using filtered backprojection (FBP) and iterative techniques are required. Purpose. To compare a subset of the top performing algorithms in terms of image quality and quantitatively determine the optimal algorithm while accounting for refraction within the optical CT system. The following algorithms were compared: Landweber, superiorized Landweber with the fast gradient projection perturbation routine (S-LAND-FGP), the fast iterative shrinkage/thresholding algorithm with total variation penalty term (FISTA-TV), a monotone version of FISTA-TV (MFISTA-TV), superiorized conjugate gradient with the nonascending perturbation routine (S-CG-NA), superiorized conjugate gradient with the fast gradient projection perturbation routine (S-CG-FGP), superiorized conjugate gradient with with two iterations of CG performed on the current iterate and the nonascending perturbation routine (S-CG-2-NA). Methods. A ray tracing simulator was developed to track the path of light rays as they traverse the different mediums of the optical CT scanner. Two clinical phantoms and several synthetic phantoms were produced and used to evaluate the reconstruction techniques under known conditions. Reconstructed images were analyzed in terms of spatial resolution, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), signal non-uniformity (SNU), mean relative difference (MRD) and reconstruction time. We developed an image quality based method to find the optimal stopping iteration window for each algorithm. Imaging data from the prototype optical CT scanner was reconstructed and analysed to determine the optimal algorithm for this application. Results. The optimal algorithms found through the quantitative scoring metric were FISTA-TV and S-CG-2-NA. MFISTA-TV was found to behave almost identically to FISTA-TV however MFISTA-TV was unable to resolve some of the synthetic phantoms. S-CG-NA showed extreme fluctuations in the SNR and CNR values. S-CG-FGP had large fluctuations in the SNR and CNR values and the algorithm has less noise reduction than FISTA-TV and worse spatial resolution than S-CG-2-NA. S-LAND-FGP had many of the same characteristics as FISTA-TV; high noise reduction and stability from over iterating. However, S-LAND-FGP has worse SNR, CNR and SNU values as well as longer reconstruction time. S-CG-2-NA has superior spatial resolution to all algorithms while still maintaining good noise reduction and is uniquely stable from over iterating. Conclusions. Both optimal algorithms (FISTA-TV and S-CG-2-NA) are stable from over iterating and have excellent edge detection with ESF MTF 50% values of 1.266 mm−1 and 0.992 mm−1. FISTA-TV had the greatest noise reduction with SNR, CNR and SNU values of 424, 434 and 0.91 × 10−4, respectively. However, low spatial resolution makes FISTA-TV only viable for large field dosimetry. S-CG-2-NA has better spatial resolution than FISTA-TV with PSF and LSF MTF 50% values of 1.581 mm−1 and 0.738 mm−1, but less noise reduction. S-CG-2-NA still maintains good SNR, CNR, and SNU values of 168, 158 and 1.13 × 10−4, respectively. Thus, S-CG-2-NA is a well rounded reconstruction algorithm that would be the preferable choice for small field dosimetry.

Tracking Fat Grafts by Magnetic Resonance Imaging: A Comparative Study of Adolescent and Adult Patients with Stable Localized Scleroderma.

The optimal timing of reconstruction for patients with facial localized scleroderma is uncertain. The purpose of this study was to compare the outcomes of autologous fat transplantation in adolescent and adult patients with stable localized scleroderma. Adolescent (age 10-19 years) and adult (age >19 years) patients with no previous surgery were enrolled (n = 10, each group). Preoperative magnetic resonance imaging (MRI), blood tests and dermatological assessments were used for disease activity assessment. All patients underwent autologous fat transplantation for anatomic facial fat restoration with preoperative MRI planning. Preoperative, immediate and one-year postoperative 3D Dixon MRI scans with image registration and fusion techniques were used for fat graft tracking. Patient satisfaction was assessed with a 5-point Likert scale. There was no significant difference in sex, body mass index, disease severity, or volume of injected fat between the two groups (p > 0.05), except for age (p < 0.05). The one-year postoperative fat graft retention rate was not significantly different, with 36.6 ± 2.4% (ranging from 25.3 to 49.3%) in the adolescent group and 32.9 ± 1.7% (ranging from 27.3 to 40.1%) in the adult group (p > 0.05). Surgical outcomes were favorable in all patients, with satisfaction scores of 3.8 ± 0.2 points in the adolescent group and 3.6 ± 0.2 points in the adult group (p > 0.05). In stable localized scleroderma, the initial autologous fat transplantation was equally effective for facial contour deformity improvement, with no significant difference in fat graft retention or satisfaction.

Letter to the editor: Dynamic insights into infection risk over time in two-stage implant-based breast reconstruction: a retrospective cohort study.

Letter to the editor: Dynamic insights into infection risk over time in two-stage implant-based breast reconstruction: a retrospective cohort study.

Lightweight super-resolution multimode fiber imaging with regularized linear regression

Super-resolution multimode fiber imaging provides the means to image samples quickly with compact and flexible setups finding many applications from biology and medicine to material science and nanolithography. Typically, fiber-based imaging systems suffer from low spatial resolution and long measurement times. State-of-the-art computational approaches can achieve fast super-resolution imaging through a multimode fiber probe but currently rely on either per-sample optimised priors or large data sets with subsequent long training and image reconstruction times. This unfortunately hinders any real-time imaging applications. Here we present an ultimately fast non-iterative algorithm for compressive image reconstruction through a multimode fiber. The proposed approach helps to avoid many constraints by determining the prior of the target distribution from a simulated set and solving the under-determined inverse matrix problem with a mathematical closed-form solution. We have demonstrated theoretical and experimental evidence for enhanced image quality and sub-diffraction spatial resolution of the multimode fiber optical system.

457 Timing of Surgery as an Outcome Predictor in Brachial Plexus Injury: A Systematic Review and Meta-Analysis

INTRODUCTION: Injuries that affect the brachial plexus are considered to have a high impact on the quality of life of patients. Brachial plexus injuries in adults require reconstruction using microsurgical techniques. At least, there is still controversy about the impact of the timing of surgical reconstruction and its effect on outcome. METHODS: We searched PubMed, EMBASE, Cochrane Library, SCOPUS, and MEDLINE, up to March 2023, for published studies on evidence of timing of surgery in Brachial plexus injury and neurological outcome. Primary outcome Good motor functional Recovery (MRC). RESULTS: In this meta-analysis, it was found that early surgical treatment before 6 months post-injury increases motor recovery (MRC) three times more than late intervention (after 6 months) with adequate statistical significance and good homogeneity (OR 3,115 [95% CI 2,248–4,317] p = &lt;0.0001; I2 = &lt;0.00001%). CONCLUSIONS: The available evidence suggests that performing brachial plexus surgery in less than 6 months can be associated with a better outcome. Further research is needed to characterize various subgroups of BPI patients. It is necessary to improve the quality of the evidence, so we suggest the creation of a multicenter database in the United States that allows us to obtain better conclusions.

188 Timing of Nerve Reconstruction Surgery to Optimize Long-Term Recovery at the Elbow and Forearm in Neonatal Brachial Plexus Palsy

INTRODUCTION: Restoration of elbow flexion is highly prioritized in nerve reconstruction for neonatal brachial plexus palsy (NBPP). Elbow extension and forearm supination are also frequently impacted in NBPP. Timing of surgical reconstruction for optimal outcomes at the elbow and forearm remains unknown. METHODS: We interrogated a prospectively collected database of all children with NBPP who underwent nerve reconstruction at a single center between 2005-2020. AROM was collected for elbow flexion and extension and forearm supination at every clinic visit and normalized between 0 and 1. The cohort was divided into those with surgery =6 months old, 6-9 months old, and &gt;9 months old. We compared elbow and forearm AROM in local age windows between the groups using a regression model expressing the expected AROM as a linear function. Significant differences between the groups were identified using a Wald test. RESULTS: Of 99 included children 28 had surgery =6 months old, 46 had surgery between 6-9 months, and 25 had surgery &gt;9 months. At ∼13 years follow up, there was no difference in recovery of AROM for elbow flexion between the groups. For elbow extension, mean normalized AROM was significantly worse when comparing the &gt;9 month and =6 month group (0.41 vs 0.84, p &lt; 0.001). For forearm supination, the =6 month group had significantly better AROM than the 6-9 month (0.57 vs 0.77, p = 0.02) and &gt;9 month (0.46 vs 0.77, p &lt; 0.001) groups. Children who presented earlier had surgery at a younger age. CONCLUSIONS: Earlier surgery may result in better long-term recovery of elbow extension and surgery =6 months of age may yield the best outcomes for forearm supination. Early referral may help optimize timing of nerve surgery.

In-and-out Technique: An In-house Efficient Predictive Hole Fabrication Workflow

Summary: Virtual surgical planning (VSP) and three-dimensional (3D) printing can increase precision and reduce surgical time in craniofacial reconstruction. However, the elevated cost and manufacturing time of outsourced workflows is increasing the development of in-house solutions. One of the main challenges in in-house workflows is to create cutting guides that hold plate position information. This is due to the fact that hospitals usually lack the infrastructure required to design and 3D print custom-made plates. Including plate-positioning information in resection guides is especially relevant in complex reconstructions and when tumor extension limits plate placement before resection. Current in-house workflows revolve around the idea of 3D scanning the bent plate’s shape and to fuse it with the VSP. The goal of this article is to share our technique to transfer plate position information to resection guides. Our protocol uses a 3D model of the reconstruction as an intermediate step to transfer the plate position of a bent stock reconstruction plate to cutting guides. Two patients who required mandibular reconstruction with fibula flap are presented to illustrate the technique. This workflow requires a 3D-printed model of the desired outcome, cutting guides, and a stock plate. Results were satisfactory in terms of cutting location and angulation, plate adaptation and condylar position. This technique allows for a simple, safe, cheap, and quick alternative to add reconstruction plate information to cutting guides.

Three-dimensional particle image velocimetry measurement through three-dimensional U-Net neural network

This paper proposes a light field (LF) three-dimensional (3D) particle image velocimetry (PIV) method based on a digital refocused algorithm and 3D U-Net neural network for 3D three-component (3D-3C) velocity measurement. A digital refocused algorithm is used to generate a stack of LF-refocused images of tracer particles for establishing the 3D U-Net. The 3D U-Net is then used for the 3D particle field reconstruction. Based on a pair of 3D particle fields, the 3D-3C velocity field is obtained through a 3D cross correlation algorithm. Numerical simulations and experiments are conducted to analyze the accuracy and efficiency of the proposed method. The simulation results show that the elongation along the depth direction and the efficiency of the 3D particle field reconstruction are improved by the 3D U-Net. The 3D U-Net also provides a better correlation coefficient. The experimental results show that the reconstruction time of the proposed method is ∼220 s which is 10 times faster than the LF tomographic PIV. This further demonstrates that the proposed method improves the reconstruction efficiency without affecting the accuracy of velocity measurement.

The seismic resilience-based methodology of regional building function recovery assessment

Regional assessment of the functional recovery time of urban buildings is critical for decision-making after an earthquake, both as a key indicator of seismic disaster risk and for evaluating urban resilience. However, existing studies are insufficient for assessing the functional recovery time of buildings at the city scale. To address this issue, this study proposes a new methodology for predicting the functional recovery time of an area. This approach comprehensively considers performance-based repair objectives, various damage states, and the affected building area. It offers two improvements over traditional methods based on the assumption of unlimited restoration resources within the disaster area. First, the method establishes a standard for categorizing damaged buildings into repairable and reconstructive buildings using the building damage level parameter. The existing moderate damage states are considered rough and are further divided into three detailed damage states. The distribution functions of the three new states relative to the existing moderate damage are derived from actual earthquake cases. Second, a new parameter, the reconstruction rate, which characterizes the rate of reconstruction time per unit area of a building, is proposed. The repair time per unit area of a house in a repairable state, i.e., the repair rate, is discounted based on this new parameter using the damage state as an indicator. To illustrate the methodology in more detail, we constructed an earthquake scenario for the northeastern margin of the Tibetan Plateau and then provided a detailed assessment of the postearthquake recovery time of Zhangye under the earthquake scenario. This study aims to provide valuable insights for the government to formulate appropriate predisaster prevention policies and rational postdisaster recovery and reconstruction.

Development and Validation of a Deep-Learning-Based Algorithm for Detecting and Classifying Metallic Implants in Abdominal and Spinal CT Topograms.

To develop and validate a deep-learning-based algorithm (DLA) that is designed to segment and classify metallic objects in topograms of abdominal and spinal CT. DLA training for implant segmentation and classification was based on a U-net-like architecture with 263 annotated hip implant topograms and 2127 annotated spine implant topograms. The trained DLA was validated with internal and external datasets. Two radiologists independently reviewed the external dataset consisting of 2178 abdomen anteroposterior (AP) topograms and 515 spine AP and lateral topograms, all collected in a consecutive manner. Sensitivity and specificity were calculated per pixel row and per patient. Pairwise intersection over union (IoU) was also calculated between the DLA and the two radiologists. The performance parameters of the DLA were consistently >95% in internal validation per pixel row and per patient. DLA can save 27.4% of reconstruction time on average in patients with metallic implants compared to the existing iMAR. The sensitivity and specificity of the DLA during external validation were greater than 90% for the detection of spine implants on three different topograms and for the detection of hip implants on abdominal AP and spinal AP topograms. The IoU was greater than 0.9 between the DLA and the radiologists. However, the DLA training could not be performed for hip implants on spine lateral topograms. A prototype DLA to detect metallic implants of the spine and hip on abdominal and spinal CT topograms improves the scan workflow with good performance for both spine and hip implants.

Reducing femoral flow artefacts in radial magnetic resonance fingerprinting of the prostate using region-optimised virtual coils.

High acceleration factors in radial magnetic resonance fingerprinting (MRF) of the prostate lead to strong streak-like artefacts from flow in the femoral blood vessels, possibly concealing important anatomical information. Region-optimised virtual (ROVir) coils is a beamforming-based framework to create virtual coils that maximise signal in a region of interest while minimising signal in a region of interference. In this study, the potential of removing femoral flow streak artefacts in prostate MRF using ROVir coils is demonstrated in silico and in vivo. The ROVir framework was applied to radial MRF k-space data in an automated pipeline designed to maximise prostate signal while minimising signal from the femoral vessels. The method was tested in 15 asymptomatic volunteers at 3 T. The presence of streaks was visually assessed and measurements of whole prostate T1, T2 and signal-to-noise ratio (SNR) with and without streak correction were examined. In addition, a purpose-built simulation framework in which blood flow through the femoral vessels can be turned on and off was used to quantitatively evaluate ROVir's ability to suppress streaks in radial prostate MRF. In vivo it was shown that removing selected ROVir coils visibly reduces streak-like artefacts from the femoral blood flow, without increasing the reconstruction time. On average, 80% of the prostate SNR was retained. A similar reduction of streaks was also observed in silico, while the quantitative accuracy of T1 and T2 mapping was retained. In conclusion, ROVir coils efficiently suppress streaking artefacts from blood flow in radial MRF of the prostate, thereby improving the visual clarity of the images, without significant sacrifices to acquisition time, reconstruction time and accuracy of quantitative values. This is expected to help enable T1 and T2 mapping of prostate cancer in clinically viable times, aiding differentiation between prostate cancer from noncancer and healthy prostate tissue.

Assessment of the axial resolution of a compact gamma camera with coded aperture collimator

PurposeHandheld gamma cameras with coded aperture collimators are under investigation for intraoperative imaging in nuclear medicine. Coded apertures are a promising collimation technique for applications such as lymph node localization due to their high sensitivity and the possibility of 3D imaging. We evaluated the axial resolution and computational performance of two reconstruction methods.MethodsAn experimental gamma camera was set up consisting of the pixelated semiconductor detector Timepix3 and MURA mask of rank 31 with round holes of 0.08 mm in diameter in a 0.11 mm thick Tungsten sheet. A set of measurements was taken where a point-like gamma source was placed centrally at 21 different positions within the range of 12–100 mm. For each source position, the detector image was reconstructed in 0.5 mm steps around the true source position, resulting in an image stack. The axial resolution was assessed by the full width at half maximum (FWHM) of the contrast-to-noise ratio (CNR) profile along the z-axis of the stack. Two reconstruction methods were compared: MURA Decoding and a 3D maximum likelihood expectation maximization algorithm (3D-MLEM).ResultsWhile taking 4400 times longer in computation, 3D-MLEM yielded a smaller axial FWHM and a higher CNR. The axial resolution degraded from 5.3 mm and 1.8 mm at 12 mm to 42.2 mm and 13.5 mm at 100 mm for MURA Decoding and 3D-MLEM respectively.ConclusionOur results show that the coded aperture enables the depth estimation of single point-like sources in the near field. Here, 3D-MLEM offered a better axial resolution but was computationally much slower than MURA Decoding, whose reconstruction time is compatible with real-time imaging.

Seismic Resilience Scenario of Algerian Buildings’ Context: Blida City Case Study

Several studies have been carried out to assess the building’s seismic vulnerability, to mitigate the seismic risk in urban areas, which is one of the most devastating natural hazards causing considerable economic and human losses. These studies must be incorporated to improve the planning of urban areas to have resistant and resilient cities in case of disasters. The seismic feedback has shown that the build-back-better concept has a direct impact on the city’s economic growth. In this paper, the existing buildings’ resilience is assessed, in order to highlight the capacity of these last to keep the functionality when an earthquake occurs. This building’s resilience has been determined for three types of structures: masonry, reinforced concrete and steel, according to the reconstruction time, the reconstruction cost and the damage state. This last has been assessed from empirical fragility curves developed using the log normal distribution for five structures typologies (Unreinforced masonry; reinforced masonry; RC frame; RC shear walls/Mixed RC frame-RC shear walls and steel structures). A seismic resilience scenario was performed using a geographic information system (GIS) and applied for the Blida city (Algeria) classified as a high seismic zone according to Algerian seismic regulations. According to the results found, the old districts of the Blida city, built mainly during the so-called pre-code period, will not be resilient in case of disaster. The other districts built later in the low-code and high-code periods will have, respectively, medium and good functionality.