Single Radiograph Research Articles

Ultrasensitive and stable X-ray detection using zero-dimensional lead-free perovskites

Abstract Sensitive and reliable X-ray detectors are essential for medical radiography, industrial inspection and security screening. Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence. Three-dimensional (3D) organic–inorganic hybrid lead halide perovskites are promising for direct X-ray detection – they show improved sensitivity compared to conventional X-ray detectors. However, their high and unstable dark current, caused by ion migration and high dark carrier concentration in the 3D hybrid perovskites, limits their performance and long-term operation stability. Here we report ultrasensitive, stable X-ray detectors made using zero-dimensional (0D) methylammonium bismuth iodide perovskite (MA3Bi2I9) single crystals. The 0D crystal structure leads to a high activation energy (Ea) for ion migration (0.46 eV) and is also accompanied by a low dark carrier concentration (~ 106 cm−3). The X-ray detectors exhibit sensitivity of 10,620 µC Gyair−1 cm−2, a limit of detection (LoD) of 0.62 nGyair s−1, and stable operation even under high applied biases; no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of ~23,800 mGyair, equivalent to > 200,000 times the dose required for a single commercial X-ray chest radiograph. Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.

Reliability and discriminative accuracy of 5 measures for craniocaudal humeral position: an assessment on conventional radiographs

HypothesisThis study aimed to examine the reliability and diagnostic discriminative accuracy of 5 different methods that quantity the craniocaudal humeral position with respect to the scapula on conventional radiographs.MethodsIn this retrospective, cross-sectional diagnostic study, 2 observers randomly assessed the conventional anteroposterior shoulder radiographs of 280 subjects with rotator cuff imaging for the (1) acromiohumeral (AH) interval, (2) upward migration index (UMI), (3) glenohumeral center-to-center measurement (GHCC), (4) glenohumeral arc measurement (GHa), and (5) scapular spine–humeral head center method (SHC). Reliability was assessed by means of relative consistency (intraclass correlation coefficient) and absolute consistency. Discriminative accuracy for detecting a rotator cuff tear was calculated.ResultsRelative consistency (intraclass correlation coefficient) for the AH interval, UMI, GHCC, GHa, and SHC was 0.961, 0.913, 0.806, 0.924, and 0.726, respectively. The AH interval had the highest absolute consistency with a random residual measurement error of 0.58 mm compared with 1.0-3.2 mm for the other measurements. The discriminative accuracy of the AH interval did not significantly differ from that of the UMI (−0.010; 95% confidence interval [CI], −0.042 to 0.022; P = .545) but was significantly better than that of the GHCC (0.112; 95% CI, 0.043-0.181; P = .001), GHa (0.074; 95% CI, 0.009-0.139; P = .027), and SHC (0.178; 95% CI, 0.100-0.256; P < .001).ConclusionAssessment of the craniocaudal humeral position is performed with good to excellent intraobserver and interobserver reliability. The discriminative accuracy for detecting a rotator cuff tear on a single radiograph was highest for the AH interval and UMI. We recommend using the AH interval or UMI as an indirect measure of the presence of a rotator cuff tear on conventional radiographs.

Radiographic assessment of the cup orientation after total hip arthroplasty: a literature review.

Optimal acetabular cup orientation is of substantial importance to good long-term function and low complication rates after total hip arthroplasty (THA). The radiographic anteversion (RA) and inclination (RI) angles of the cup are typically studied due to the practicability, simplicity, and ease of interpretation of their measurements. A great number of methods have been developed to date, most of which have been performed on pelvic or hip anteroposterior radiographs. However, there are primarily two influencing factors for these methods: X-ray offset and pelvic rotation. In addition, there are three types of pelvic rotations about the transverse, longitudinal, and anteroposterior axes of the body. Their effects on the RA and RI angles of the cup are interactively correlated with the position and true orientation of the cup. To date, various fitted or analytical models have been established to disclose the correlations between the X-ray offset and pelvic rotation and the RA and RI angles of the cup. Most of these models do not incorporate all the potential influencing parameters. Advanced methods for performing X-ray offset and pelvic rotation corrections are mainly performed on a single pelvic AP radiograph, two synchronized radiographs, or a two-dimensional/three-dimensional (2D-3D) registration system. Some measurement systems, originally developed for evaluating implant migration or wear, could also be used for correcting the X-ray offset and pelvic rotation simultaneously, but some drawbacks still exist with these systems. Above all, the 2D-3D registration technique might be an alternative and powerful tool for accurately measuring cup orientation. In addition to the current methods used for postoperative assessment, navigation systems and augmented reality are also used for the preoperative planning and intraoperative guidance of cup placement. With the continuing development of artificial intelligence and machine learning, these techniques could be incorporated into robot-assisted orthopaedic surgery in the future.

Trends in Estimated Thyroid, Salivary Gland, Brain, and Eye Lens Doses From Intraoral Dental Radiography Over Seven Decades (1940 TO 2009).

The purpose of this study is to support retrospective dose estimation for epidemiological studies by providing estimates of historical absorbed organ doses to the brain, lens of the eye, salivary glands, and thyroid from intraoral dental radiographic examinations performed from 1940 to 2009. We simulated organ doses to an adult over 10 y time periods from 1940 to 2009, based on commonly used sets of x-ray machine settings collected from the literature. Simulations to estimate organ dose were performed using personal computer x-ray Monte Carlo software. Overall, organ doses were less than 1 mGy for a single intraoral radiograph for all decades. From 1940 to 2009, doses to the brain, eye lens, salivary glands, and thyroid decreased by 86, 96, 95, and 89%, respectively. Of these four organs, the salivary glands received the highest doses, with values decreasing from about 0.23 mGy in the 1940s to 0.025 mGy in the 2000s for a single intraoral radiograph. Based on simulations using collected historical data on x-ray technical parameters, improvements in technology and optimization of the technical settings used to perform intraoral dental radiography have resulted in a decrease in absorbed dose to the brain, eye lens, salivary glands, and thyroid over the period from 1940 to 2009.

Effects of Single-Foot Centered and Double-Foot Centered X-ray Projection on Hallux Valgus Measurement.

ObjectiveTo investigate whether use of single‐foot centered and double‐foot centered weight‐bearing X‐rays has an impact on the relevant indicators of hallux valgus.MethodsA total of 55 female patients from the Department of Ankle Surgery of Beijing Tongren Hospital with hallux valgus (110 feet) were collected from September to December 2015. The age of these patients ranged from 18 to 43 years, with an average age of 47.9 ± 8.5 years. All selected patients fit the diagnostic criteria of hallux valgus and had weight‐bearing single foot centered and double foot centered radiographs taken. During the projection, all patients were instructed to stand on the X‐ray box, with the knee joint straightened and legs perpendicular to the floor. The projection center of the single foot was directed at the lateral part of the scaphoid bone of the foot, while the projection center was directed at the position between the scaphoid bones of both feet for the double‐foot shooting. The hallux valgus angle (HAV), the intermetatarsal angle between the first and second metatarsals (IMA), the intermetatarsal angle between the first and fifth metatarsals (IM1‐5), and the metatarsal adduction angle (MAA) were measured and examined. The difference between these two shooting conditions was compared and analyzed.ResultsThe differences in X‐ray measurement results (IMA, HAV, IM1‐5, and MMA) between different measures for the same patient were not statistically significant. The values of HAV, IMA, IM1‐5, and MAA are common indexes for evaluating hallux valgus. The average IMA was 15.9° for single‐foot centered and 14.1° for double‐foot centered X‐rays. The average HAV was 30.2° for single‐foot centered and 29.7° for double‐foot centered X‐rays. The average IM1‐5 was 31.1° for single‐foot centered and 29.7° for double‐foot centered X‐rays. The average of metatarsal adduction angle was 13.8° for single‐foot centered and 14.1° for double‐foot centered X‐rays. The differences between single‐foot centered and double‐foot centered X‐rays were statistically significant in terms of the measurement index (P < 0.05). In addition, compared with double‐foot centered weight‐bearing X‐rays, the focus of single‐foot centered X‐rays was located on the lateral part of the scaphoid bone of the foot, and the ray was closer to the vertical foot in the single‐foot centered weight‐bearing X‐ray.ConclusionWhen the weight‐bearing position and projection distance are the same, the single‐foot centered weight‐bearing X‐ray is more effective in evaluating the severity of hallux valgus compared with the double‐foot centered weight‐bearing X‐ray.

Preoperative coil localization for spinal surgery: technical note.

Intraoperative localization in spinal surgery is essential to facilitate the best surgical outcome and to avoid wrong-site surgery. Intraoperative fluoroscopy is generally adequate, but anatomical variation, body habitus, and the inherent difficulties of fluoroscopy at certain levels may lead the surgeon astray. Here, the authors present their technique for preoperative localization that relies solely on fixed anatomical landmarks using CT-guided, percutaneously placed radiopaque markers. In the outpatient setting, low-dose CT scanning of the neuraxis is performed to identify fixed landmarks and, under local anesthesia and CT guidance, a pushable microcoil is inserted through a Chiba needle into the periosteum of the pedicle at the level of interest. The patient returns home with no precautions while the coil is in situ, and then the patient returns sometime later for surgery. Intraoperatively, typically a single lateral radiograph is required to visualize the coil and the level. Preoperative placement of radiopaque markers at the level of interest is an effective tool for avoiding wrong-site surgery, especially in circumstances in which fluoroscopy may be troublesome. The authors' method is accurate, effective, and expeditious and can be performed easily in the outpatient setting.

An Updated Algorithm for Radiographic Screening of Upper Cervical Instability in Patients With Down Syndrome

Study DesignRetrospective evaluation of cervical spine images from 2006–2012 for the purposes of “screening” children with Down syndrome for instability. ObjectiveTo determine whether a full series of cervical spine images including flexion/extension lateral (FEL) radiographs was needed to avoid missing upper cervical instability. Summary of Background DataThe best algorithm, measurements, and criteria for screening children with Down syndrome for upper cervical instability are controversial. Many authors have recommended obtaining flexion and extension views. We noted that patients who require surgical stabilization due to myelopathy or cord compression typically have grossly abnormal radiographic measurements on the neutral upright lateral (NUL) cervical spine radiograph. MethodsThe atlanto-dental interval, space available for cord, and basion axial interval were measured on all films. The Weisel-Rothman measurement was made in the FEL series. Clinical outcome of those with abnormal measurements were reviewed. Sensitivity, specificity, and positive and negative predictive values of NUL and FEL radiographs for identifying clinically significant cervical spine instability were calculated. ResultsA total of 240 cervical spine series in 213 patients with Down syndrome between the ages of 4 months and 25 years were reviewed. One hundred seventy-two children had an NUL view, and 88 of these patients also had FEL views. Only one of 88 patients was found to have an abnormal atlanto-dental interval (≥6 mm), space available for cord at C1 (≤14 mm), or basion axial interval (>12 mm) on an FEL series that did not have an abnormal measurement on the NUL radiograph. This patient had no evidence of cord compression or myelopathy. ConclusionsObtaining a single NUL radiograph is an efficient method for radiographic screening of cervical spine instability. Further evaluation may be required if abnormal measurements are identified on the NUL radiograph. We also propose new “normal” values for the common radiographic measurements used in assessing risk of cervical spine instability in patients with Down syndrome. Level of EvidenceLevel IV.

Deep Learning to Assess Long-term Mortality From Chest Radiographs

Chest radiography is the most common diagnostic imaging test in medicine and may also provide information about longevity and prognosis. To develop and test a convolutional neural network (CNN) (named CXR-risk) to predict long-term mortality, including noncancer death, from chest radiographs. In this prognostic study, CXR-risk CNN development (n = 41 856) and testing (n = 10 464) used data from the screening radiography arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) (n = 52 320), a community cohort of asymptomatic nonsmokers and smokers (aged 55-74 years) enrolled at 10 US sites from November 8, 1993, through July 2, 2001. External testing used data from the screening radiography arm of the National Lung Screening Trial (NLST) (n = 5493), a community cohort of heavy smokers (aged 55-74 years) enrolled at 21 US sites from August 2002, through April 2004. Data analysis was performed from January 1, 2018, to May 23, 2019. Deep learning CXR-risk score (very low, low, moderate, high, and very high) based on CNN analysis of the enrollment radiograph. All-cause mortality. Prognostic value was assessed in the context of radiologists' diagnostic findings (eg, lung nodule) and standard risk factors (eg, age, sex, and diabetes) and for cause-specific mortality. Among 10 464 PLCO participants (mean [SD] age, 62.4 [5.4] years; 5405 men [51.6%]; median follow-up, 12.2 years [interquartile range, 10.5-12.9 years]) and 5493 NLST test participants (mean [SD] age, 61.7 [5.0] years; 3037 men [55.3%]; median follow-up, 6.3 years [interquartile range, 6.0-6.7 years]), there was a graded association between CXR-risk score and mortality. The very high-risk group had mortality of 53.0% (PLCO) and 33.9% (NLST), which was higher compared with the very low-risk group (PLCO: unadjusted hazard ratio [HR], 18.3 [95% CI, 14.5-23.2]; NLST: unadjusted HR, 15.2 [95% CI, 9.2-25.3]; both P < .001). This association was robust to adjustment for radiologists' findings and risk factors (PLCO: adjusted HR [aHR], 4.8 [95% CI, 3.6-6.4]; NLST: aHR, 7.0 [95% CI, 4.0-12.1]; both P < .001). Comparable results were seen for lung cancer death (PLCO: aHR, 11.1 [95% CI, 4.4-27.8]; NLST: aHR, 8.4 [95% CI, 2.5-28.0]; both P ≤ .001) and for noncancer cardiovascular death (PLCO: aHR, 3.6 [95% CI, 2.1-6.2]; NLST: aHR, 47.8 [95% CI, 6.1-374.9]; both P < .001) and respiratory death (PLCO: aHR, 27.5 [95% CI, 7.7-97.8]; NLST: aHR, 31.9 [95% CI, 3.9-263.5]; both P ≤ .001). In this study, the deep learning CXR-risk score stratified the risk of long-term mortality based on a single chest radiograph. Individuals at high risk of mortality may benefit from prevention, screening, and lifestyle interventions.

Assessing a Novel Method of Calculation of the Cobb Angle for Scoliosis: Interexaminer Reliability and Student Satisfaction

ObjectiveThe objectives of this pilot study were to compare the interexaminer reliability of 2 different methods of Cobb angle measurement and to determine whether the participants considered 1 of the 2 methods easier to learn, understand, and apply. MethodsEntry-level anatomy students who have familiarity with vertebral column anatomy but have not had previous radiology training were instructed on how to measure a Cobb angle. Each student measured 2 curves (thoracic and lumbar) on a single radiograph, first with the traditional method of Cobb angle measurement and second with a novel method of Cobb angle measurement using a digital level. ResultsThe variance of measurements decreased by using the novel method from thoracic to lumbar measurements and for the moderate and severe scoliosis films. All decreases in variance were statistically significant except for the lumbar measurement variance for the severe scoliosis film. The novel method of Cobb angle measurement with these same participants showed interexaminer reliability. More than 78% of naive participants considered the proposed method easier to learn, understand, and apply when compared with the traditional method. ConclusionIn this group of naive students, there was improved interrater reliability, greater satisfaction, and reduced measurement variances in some cases, with a novel method using a digital level to measure the Cobb angle compared with the traditional method of measurement.

Single-Energy Material Decomposition in Radiography Using a Three-Dimensional Laser Scanner

We investigated an efficient method for material decomposition in radiography, which can separate soft tissues and bones from a single radiograph with the aid of a surface image obtained using a three-dimensional laser scanner through which the attenuation length within an object is estimated. This approach does not require double radiation exposures; thus, it can eliminate the technical difficulties associated with the conventional dual-energy material decomposition (DEMD) method, such as increased patient doses, increased execution time, and misregistration errors between two scans. We implemented the proposed algorithm and performed a computational simulation and an experiment to demonstrate its viability for single-energy material decomposition in radiography (80 kVp was used). The image characteristics of the proposed method were investigated and compared with those obtained using the DEMD method (50 kVp and 80 kVp were used). Our results indicate that the estimate of the attenuation length by using the surface image of the examined object may substitute for one of the two dual-energy measurements in conventional DEMD. Accordingly, the proposed method yielded material decomposition results similar to the results elicited by the DEMD method in radiography.

Soft Tissue/Bone Decomposition of Conventional Chest Radiographs Using Nonparametric Image Priors

Background and Objective When radiologists diagnose lung diseases in chest radiography, they can miss some lung nodules overlapped with ribs or clavicles. Dual-energy subtraction (DES) imaging performs well because it can produce soft tissue images, in which the bone components in chest radiography were almost suppressed but the visibility of nodules and lung vessels was still maintained. However, most routinely available X-ray machines do not possess the DES function. Thus, we presented a data-driven decomposition model to perform virtual DES function for decomposing a single conventional chest radiograph into soft tissue and bone images. Methods For a given chest radiograph, similar chest radiographs with corresponding DES soft tissue and bone images are selected from the training database as exemplars for decomposition. The corresponding fields between the observed chest radiograph and the exemplars are solved by a hierarchically dense matching algorithm. Then, nonparametric priors of soft tissue and bone components are constructed by sampling image patches from the selected soft tissue and bone images according to the corresponding fields. Finally, these nonparametric priors are integrated into our decomposition model, the energy function of which is efficiently optimized by an iteratively reweighted least-squares scheme (IRLS). Results The decomposition method is evaluated on a data set of posterior-anterior DES radiography (503 cases), as well as on the JSRT data set. The proposed method can produce soft tissue and bone images similar to those produced by the actual DES system. Conclusions The proposed method can markedly reduce the visibility of bony structures in chest radiographs and shows potential to enhance diagnosis.

Correlation of Short Knee Radiographs and Full-length Radiographs in Patients Undergoing Total Knee Arthroplasty.

The clinical success and longevity of a primary total knee arthroplasty (TKA) in large part depend on our ability to control coronal alignment. However, controversy exists regarding which radiographs to use for the most accurate interpretation. The study assesses the accuracy of coronal alignment measurements using a single short knee radiograph (SKR) in comparison with full-length radiographs (FLRs). Using our institutional database, we retrieved radiographs of all patients who have had pre- and postoperative FLRs for their primary TKA in 2014. The following measurements were obtained on both short and long radiographs: femoral-tibial angle (FTA), anatomic lateral distal femoral angle, medial proximal tibial angle, condylar-plateau angle, and condylar-plateau distance. A reliability analysis was conducted between the pre- and postoperative SKRs and FLRs using the intraclass correlation coefficient (ICC). Radiographs of 236 limbs were included in the analysis. The FTA showed an ICC of 0.84 and 0.69 on the pre- and postoperative radiographs, respectively. Good ICC was seen in the lateral distal femoral angle in both the pre- and postoperative radiographs; these were 0.70 and 0.67, respectively. Also, the medial proximal tibial angle showed good to excellent correlation, with an ICC of 0.83 on the preoperative and 0.66 on the postoperative radiographs. This study illustrates that SKRs could be an appropriate substitute for FLRs for the evaluation of primary TKA coronal alignment, especially in the postoperative assessment of these patients. Level III.

Placement of Provisional External Fixation of Pediatric Femoral Shaft Fractures Using Radiopaque Markers in the Setting of Severe Polytrauma: A Technical Report

Background: In polytraumatic pediatric patients, life-saving or stabilizing measures must often be prioritized over permanent orthopedic solutions to a fractured extremity. The standard application of external fixation to femur fractures can be difficult in the pediatric intensive care unit setting due to the limited mobility of the patient and adaptability of C-arm radiography. We propose a technique utilizing radiopaque markers and digital radiographs in lieu of C-arm imaging to accurately plan the pin placement in a reproducible manner that eases application and reduces errant placement that may result in physeal injury. Methods: Two patients are reported, aged 7 and 11, involved in motor vehicle accidents who sustained multiple injuries including femur fractures which were addressed with this method. Beekley Medical 7″×7.5″ Guidelines calibrated radiopaque markers were placed on the involved thigh and a single digital radiograph was performed. On the basis of preoperative templating from the radiographic markers, the fracture site and proposed pin sites were marked and the pins were placed. Results: Both patients eventually had the external fixators removed and underwent definitive fixation with internal fixation. They both healed with successful union of the femoral fracture. Conclusions: The use of radiopaque markers reproducibly aids radiologically guided placement of threaded Shanz pins during external fixation of femur fractures in polytraumatized pediatric patients undergoing damage control orthopaedics. The technique also minimizes radiation exposure, uses equipment readily available in the hospital setting, and alleviates the need to have a radiolucent bed in the pediatric intensive care unit. Level of Evidence: Case report.

Heterotopic Ossification: A Challenging Complication of Total Hip Arthroplasty: Risk Factors, Diagnosis, Prophylaxis, and Treatment.

Background This review is intended to summarize the risk factors, classification, diagnosis, and treatment of heterotopic ossification (HO) of previously published studies. Results Heterotopic ossification is a common complication of total hip arthroplasty. Its prevalence is not the same in all of the patient groups. Frequency of HO varies from 15 to 90%. Hip ankylosis, male gender, and previous history of HO are said to be risk factors with a significant level. Diagnosis is based on a single AP radiograph: the Brooker classification that divides HO into four grades is the most commonly used. The confirmation test that can be used is a bone scan. A great amount of bone metabolic turnover markers have been tested, but none of them seems to be relevant in case of prevention or diagnosis of HO. The most effective prophylactic treatment is radiotherapy or administration of nonsteroidal anti-inflammatory drugs. Over the years a lot of different RT protocols have been tested. Nowadays the most often used regimen is 7 Gy given postoperatively in a single dose. The most commonly prescribed drug in prophylaxis of HO is indomethacin. Also, the efficacy of ibuprofen and diclofenac was proven. Recently researchers focused on selective COX-2 inhibitors. They appear to be as effective as nonselective NSAIDs having less side effects. The one and only treatment of HO is a revision arthroplasty.

Automatic Hand Skeletal Shape Estimation From Radiographs

Rheumatoid arthritis (RA) is an autoimmune disease whose common manifestation involves the slow destruction of joint tissue, a damage that is visible in a radiograph. Over time, this damage causes pain and loss of functioning, which depends, to some extent, on the spatial deformation induced by the joint damage. Building an accurate model of the current deformation and predicting potential future deformations are the important components of treatment planning. Unfortunately, this is currently a time-consuming and labor-intensive manual process. To address this problem, we propose a fully automated approach for fitting a shape model to the long bones of the hand from a single radiograph. Critically, our shape model allows sufficient flexibility to be useful for patients in various stages of RA. Our approach uses a deep convolutional neural network to extract low-level features and a conditional random field (CRF) to support shape inference. Our approach is significantly more accurate than previous work that used hand-engineered features. We provide a comprehensive evaluation for various choices of network hyperparameters, as current best practices lack significantly in this domain. We evaluate the accuracy of our pipeline on two large datasets of hand radiographs and highlight the importance of the low-level features, the relative contribution of different potential functions in the CRF, and the accuracy of the final shape estimates. Our approach is nearly as accurate as a trained radiologist and, because it only requires a few seconds per radiograph, can be applied to large datasets to enable better modeling of disease progression.

Augmented Reality in Transsphenoidal Surgery

We investigated how augmented reality (AR) can be applied to support transsphenoidal surgery. AR was established using the head-up displays integrated into operating microscopes. Navigation registration was performed with either fiducial-based or automatic registration using intraoperative computed tomography (iCT). Correct microscope calibration was ensured by checking the geometric overlap between the AR representation of the reference array and the 3-dimensional reality while focusing on the reference array. From a consecutive single-surgeon series of 288 transsphenoidal procedures, 47 patients (16.3%) had undergone microscope-based AR to visualize the target and risk structures. AR was smoothly integrated into the surgical workflow. AR accuracy depended on navigation accuracy and microscope calibration. The target registration error in patients with fiducial-based registration was 2.33 ± 1.30 mm. Automatic, user-independent iCT-based registration significantly (P < 0.001) increased AR accuracy (target registration error, 0.83 ± 0.44 mm). Applying low-dose iCT protocols reduced the effective dose caused by iCT registration scanning to within the range of a single chest radiograph (0.041 mSv). No vascular injuries and no aggravation of neurological deficits occurred in the present series. AR greatly facilitated orientation in the reoperations and the patients with anatomical variants, thereby increasing surgeon comfort. Enhanced AR visualizations improved the 3-dimensional perception compared with the standard display of dashed lines by the head-up display of the operating microscope. Microscope-based AR is a reliable tool to increase patient safety in complicated transsphenoidal procedures. Intraoperative imaging-based automatic patient registration is recommended.

A methodological approach to standardize and control the quality of the position and alignment of lamina implants on two-dimensional radiographs.

We sought to validate a new method to detect the degree of correlation between simulated and real tilted blade implants as they appear on a single two-dimensional radiograph. The angular correction factor (CF^) was defined as the coupling of two subsequent angle transformations, a set of five angular values describing the theoretical radiographic appearance of the blade implant: (1) three consecutive rotations about the axes of the blade ([Formula: see text], θ, and ψ, standing for pitch, roll, and yaw, respectively) to represent the polarization directions; (2) a two-dimensional projection defined by two angles (λ and [Formula: see text], respectively, longitude and latitude) to represent the vector of the X-ray beam intersecting the detector plate. Data of patients who received fixed prostheses supported by blade-form implants were employed to calculate a dimensional correction factor (CF°), a specific length through the major axis. The simulation of a distorted radiograph of a blade positioned in space was compared with the real radiograph. Differences in the angular measurements served as an initial test to assess the effectiveness of the method. In the acquired sets of periapical radiographs, mean misalignments of + 3.58° in longitude and - 0.04° in latitude were registered. The following variations were detected during the accuracy testing: the absolute error was 0.1 ± 7.5° for angle [Formula: see text]; 2.4 ± 6.7° for angle θ; - 1.0 ± 3.7° for angle ψ; 4.5 ± 8.6° for angle λ; and 2.0 ± 9.3° for angle [Formula: see text]. The linear dependence between CF° and CF^ was estimated by a robust linear regression: slope + 0.991, intercept + 0.007, and adjusted R2 0.992. This a posteriori analysis introduces the explicit trigonometric equations of the theoretical standard (CF^) used to describe the blade implant radiographic position and misalignment on two-dimensional radiographs.

Reproducibility of pelvic sagittal inclination while acquiring radiographs in supine and standing postures.

Pelvic position on the sagittal plane is usually evaluated with the pelvic sagittal inclination (PSI) angle from a single radiograph. However, the reproducibility of pelvic positioning has not been investigated, and thus, the validity of measuring the PSI from a single film/time point is not understood. Herein, the reproducibility of a patient's pelvic positions in supine and standing postures was analyzed. A total of 34 patients who underwent either a pelvic osteotomy or total hip arthroplasty were enrolled in this study. Preoperative radiographs in both supine and standing postures were acquired twice (first X-ray and second X-ray) within 6 months; preoperative computed tomography (CT) images of the full pelvis were also acquired in a supine posture (preop-CT). To eliminate measurement variability, each PSI was automatically measured from radiographs and CT images through the use of CT segmentation and landmark localization followed by intensity-based 2D-3D registration. The absolute difference of PSI among each image was calculated and the intra-class correlation coefficient (ICC) in each posture was also analyzed. The median absolute differences of PSI in the supine posture were 1.3° between the first and second X-rays, 1.2° between the first X-ray and preop-CT, and 1.3° between the second X-ray and preop-CT. The median absolute difference of PSI in the standing posture was 1.5°. The ICC was 0.965 (95% CI: 0.939-0.981) in supine and 0.977 (95% CI: 0.954-0.988) during standing. Pelvic positions in supine and standing postures are reproducible. Thus, measuring the PSI from a single radiograph is reliable.

Fast four-dimensional tensile test monitored via X-ray computed tomography: Elastoplastic identification from radiographs

A projection-based digital volume correlation method (presented in a companion paper) is extended to an integrated approach for the calibration of an elastoplastic law based on a single radiograph per loading step. Instead of following a two-step sequential procedure (i.e. first, measurement of the displacement field; second, identification), the integrated method aims at identifying few model parameters directly from the gray-level projections. The analysis of an in situ tensile test composed of 127 loading steps performed in 6 min is presented. An isotropic elastoplastic constitutive law with free-form hardening behavior (i.e. controlled by only eight parameters) is identified and shows a ductile behavior (up to 6.3% strain before failure). A large improvement on the residual quality is shown and validates the proposed model and procedure. The obtained displacement fields are similar to those measured with no mechanical integration. A different parameterization of the constitutive law provides a very close result, thereby assessing the robustness of the procedure.

Predictive value of colonic transit time indices for differentiating nonnormal from normal sensation in children with chronic functional constipation identified by anorectal manometry.

Background:Constipation is a common disorder in pediatrics, although the underlying pathogenesis is not fully understood. The current study aimed at evaluating the efficacy of different colonic transit time (CTT) indices for differentiating normal from nonnormal sensation in children with chronic functional constipation identified by anorectal manometry (ARM).Materials and Methods:In this cross-sectional study, 47 children with chronic idiopathic constipation, aged 5–15 years, were studied. The total and segmental CTTs were estimated by administering multiple radiopaque markers for 6 days and performing a single abdominal radiograph on day 7. Anorectal function was evaluated using manometry with an Arhan probe. The predictive value of CTT indices was evaluated by receiver operating characteristic curve analysis. Area under the curve (AUC) along with 95% confidence interval (CI) as well as sensitivity and specificity was calculated.Results:The mean age of the participants was 8.30 ± 2.99 years, with a mean constipation duration of 2.90 ± 0.46; 28 children were identified with nonnormal sensation. The mean values of CTT indices were statistically significantly longer in the nonnormal sensation patients than that in the normal group (P < 0.001). In addition, the mean values of manometry parameters were statistically significantly higher in nonnormal sensation patients than that in normal group (P < 0.01). Among CTT indices, rectosigmoid CTT (AUC [95% CI] =0.999 [0.99–1]; P < 0.001) with sensitivity = 100% and specificity = 94.7% and total CTT (AUC [95% CI] =0.972 [0.93–1] P < 0.001) with sensitivity = 82.3% and specificity = 100% had the highest predictive values for differentiating nonnormal from normal sensation patients.Conclusion:CTT is a simple and noninvasive technique for classifying patients with constipation. It can be used for identifying children suffering from chronic constipation with nonnormal sensation reliably, instead of ARM. Colonic inertia may be a manifestation of global motility dysfunction. Children with delayed distal colonic transits are more likely to have abnormal defecation dynamics.