Measured Defect Size Research Articles

Mohs Micrographic Surgery for Invasive Melanoma Allows for Tissue Preservation Compared With Wide Local Excision: A Retrospective Cohort Study.

While increasing evidence supports the safety and effectiveness of immunohistochemistry-assisted Mohs micrographic surgery (MMS) for superficially invasive melanoma, there is a paucity of the literature investigating its effect on final defect size. To evaluate the tissue sparing effect of MMS for melanoma. Three hundred and twenty-eight patients with early-stage (T1a/T1b) cutaneous melanomas treated with MMS from January 2008 to December 2018 were evaluated. Measured defect sizes after Mohs tumor extirpation were compared with anticipated defect size that would result from standard-margin wide local excision (WLE). Average actual versus anticipated defect areas were compared using a paired t-test (95% confidence intervals). The following groups demonstrated a significantly smaller defect area for MMS-treated tumors when compared with anticipated standard-margin WLE defect: All tumors combined (13.8 cm2 vs 10.4 cm2, p < .001), tumors requiring 1 stage (13.6 cm2 vs 10.1 cm2,p < .001), and tumors requiring 2 stages (13.2 cm2 vs 10.5 cm2, p = .004). The majority of patients (83.5%, n = 274) achieved clear margins with 1 stage. Immunohistochemistry-assisted MMS for early-stage invasive melanoma is associated with smaller final defect size and overall tissue sparing effect compared with standard WLE margins.

Fatigue behavior of low-temperature hot isostatic pressed electron beam powder bed fusion manufactured Ti-6Al-4 V

Ti-6Al-4 V finds application in the fan and compressor modules of gas turbine engines due to its high specific strength. Ti-6Al-4 V components manufactured using one of the additive manufacturing (AM) techniques, the electron beam powder bed fusion (PBF-EB) process, has been an active area of research in the past decade. The fatigue life of such PBF-EB built Ti-6Al-4 V components is improved by hot isostatic pressing (HIP) treatment typically performed at about 920 ˚C. The HIP treatment at 920 ˚C results in coarsening of α laths and reduced static strength and therefore a low-temperature HIP treatment is performed at about 800 ˚C to limit the impact on static mechanical properties. In the present work, the low cycle fatigue and fatigue crack growth behavior of such a modified HIP (low-temperature HIP) treated material is assessed and compared with the respective data for the standard HIP-treated material. The modified HIP-treated material has fatigue performance comparable to the standard HIP-treated material. This work suggests that the modified HIP treatment improves the static mechanical properties without significantly impacting the fatigue performance. Also, fatigue life predictions were made from the measured defect size at the crack initiation site using a linear elastic fracture mechanics tool. The life predictions show good agreement with the experimental values for defects greater than the intrinsic crack length, where life is well predicted by large-crack growth methodology.

Defect-based fatigue model for additive manufacturing

A novel defect-based fatigue model for the prediction of S–N (stress versus number of cycles) data points and curves is proposed in this paper. The model is capable of predicting the material fatigue performance based on defect size and location from the surface. A defect factor was introduced and obtained based on notch theory, which considers the notch sensitivity of the material as well as the stress concentration obtained using the finite element method. A newly developed equation was applied to represent the relationship between the defect factor, defect size and defect location from the surface. AlSi10Mg samples were manufactured using laser powder bed fusion, and then machined. The samples were tested under rotational bending cyclic loading until failure. The failed samples were analysed using scanning electron microscopy and it was found that cracks initiated from defects located at the surface. The measured defect size and location were used to predict the number of cycles for an applied stress using the proposed defect-based fatigue model. This model was validated by comparing the predicted and experimentally obtained S–N data. The proposed model has the potential to be applied to component-level fatigue assessment and integrated into industrial quality assurance workflows. For instance, defects can be measured for each produced industrial component and directly assessed against fatigue performance using the developed defect-based fatigue model. This could enable the rapid approval and certification of future additively manufactured industrial components, which can unleash the commercial potential of additive manufacturing for light-weight multi-functional component designs.

Arthroscopic Hip Labral Reconstruction: Treatment of Irreparable Labral Tears With Segmental Allograft Reconstruction

Background: At the time of hip arthroscopy, some patients are found to have irreparable labral tears that are not amenable to primary repair. For these patients, treatment with segmental reconstruction is a surgical option to restore labral tissue and biomechanics. Indications: Patients with segmental irreparable hip labral tears that are technically not amenable for primary labral repair should be considered for labral reconstruction with allograft. Technique Description: Standard hip arthroscopic portals are established. An interportal capsulotomy is performed, and acetabular rim trimming is performed to remove the pincer deformity. Visualized segmental labral defects are measured using a piece of suture to allow for measurement of a curved surface and 1.4-mm polyether ether ketone (PEEK) anchors are placed in anticipation of labral fixation. On the back table, the tibialis anterior allograft is prepared for labral reconstruction. We mark a central portion of the graft tissue based on the measured defect size. A 3-0 vicryl suture is used to place a running stitch from one end to the other of the marked portion of the allograft and the marked, prepared graft is sharply divided from the rest of the tissue. Stitches from the anterior and posterior anchors are passed through the graft using a free needle. The graft is then placed through the distal accessory anterolateral portal and positioned into place. The posterolateral and then medial-most anchors are secured and tied using arthroscopic knots, followed by sequential tying of the middle anchors. Any additional arthroscopic procedures, such as cam resection, are performed, and capsular/skin closure is performed using standard methods. Results: Published outcomes support reconstruction of the labrum using allograft, with 2 series consisting of a total of 141 segmental/circumferential reconstructions demonstrating similar outcome scores at 2 years of follow-up as compared to matched cases of primary labral repairs. Discussion/Conclusion: Hip segmental labral reconstruction with tibialis anterior allograft provides a viable surgical option for patients with labral defects precluding primary labral repair. The presented material demonstrates a readily employable technique as well as clear, step-by-step postoperative rehabilitation protocols, and satisfactory published short- and mid-term outcomes literature.

Breaking the power law: Multiscale simulations of self-ion irradiated tungsten

The initial stage of radiation defect creation has often been shown to follow a power law distribution at short time scales, recently so with tungsten, following many self-organizing patterns found in nature. The evolution of this damage, however, is dominated by interactions between defect clusters, as the coalescence of smaller defects into clusters depends on the balance between transport, absorption, and emission to/from existing clusters. The long-time evolution of radiation-induced defects in tungsten is studied with cluster dynamics parameterized with lower length scale simulations, and is shown to deviate from a power law size distribution. The effects of parameters such as dose rate and total dose, as parameters affecting the strength of the driving force for defect evolution, are also analyzed. Excellent agreement is achieved with regards to an experimentally measured defect size distribution at 30 K. This study provides another satisfactory explanation for experimental observations in addition to that of primary radiation damage, which should be reconciled with additional validation data.

Factors Affecting Early Single Heel Raise after Repair of Achilles Tendon Rupture

Category: Sports Introduction/Purpose: No physical exam or clinical test can clearly predict a final course of acute Achilles tendon rupture after surgical treatment. But, in recent studies, ability to perform single-heel-raise during the early postoperative period was considered as a significant prognostic factor. Therefore, analysis of the relationship between preoperative factors and timing of the single heel raise might help to predict the prognosis and aid to establish an individualized rehabilitation plan. The purpose of this study was to analyze the factors affecting early single heel raise after surgical treatment of acute Achilles tendon rupture. Methods: From January 2012 to August 2015, a retrospective analysis was performed for 68 patients who met the inclusion criteria among 98 cases of surgically treated acute Achilles tendon rupture. Operative technique and rehabilitation protocol were same in all cases. The patients who were able to perform a single heel raise within 3 months postoperatively were classified into the study group and the rest was determined as the control group. During periodic outpatient observation, we evaluated Achilles tendon total rupture score (ATRS), Visual Analog Scale (VAS), and timing capable of a single heel raise. We also preoperatively measured defect size and distance between calcaneal osteotendinous junction and rupture site by ultrasound image in all cases. Results: No difference was found in demographic factors between the study group (23 cases) and the control group (45 cases) who performed a single heel raise later than 3 months postoperatively. There were no significant difference in defect size and distance between calcaneal osteotendinous junction to the rupture site (P=0.38, P=0.63). However, when the rupture site was divided into hyporvascular zone (from calcaneal osteotendinous junction to the rupture site: 4~7 cm) and hypervascular zone, the study group showed a significantly low hyporvascular zone rupture rate. (14/23, 41/45, P=0.003). Also, in the logistic regression analysis that included age, BMI, smoking, hyporvascular zone rupture, defect size, and operation delay, patients with hypervascular region rupture showed odds ratio of 5.3 (P=0.017) in performing a single heel raise within postoperative 3 month. ATRS score at postoperative 3 months and last f/u were significantly higher in the study group. (p&lt;0.01) Conclusion: Achilles tendon rupture at hypovascular zone is a poor prognostic factor for the early single heel raise and might significantly affect the prognosis after acute Achilles tendon rupture operation.

Three-Dimensional Magnetic Resonance Imaging Quantification of Glenoid Bone Loss Is Equivalent to 3-Dimensional Computed Tomography Quantification: Cadaveric Study

To assess the ability of 3-dimensional (3D) magnetic resonance imaging (MRI, 1.5 and 3tesla [T]) to quantify glenoid bone loss in a cadaveric model compared with the current gold standard, 3D computed tomography (CT). Six cadaveric shoulders were used to create a bone loss model, leaving the surrounding soft tissues intact. The anteroposterior (AP) dimension of the glenoid was measured at the glenoid equator and after soft tissue layer closure the specimen underwent scanning (CT, 1.5-T MRI, and 3-T MRI) with the following methods (0%, 10%, and 25% defect by area). Raw axial data from the scans were segmented using manual mask manipulation for bone and reconstructed using Mimics software to obtain a 3D en face glenoid view. Using calibrated Digital Imaging and Communications in Medicine images, the diameter of the glenoid at the equator and the area of the glenoid defect was measured on all imaging modalities. In specimens with 10% or 25% defects, no difference was detected between imaging modalities when comparing the measured defect size (10% defect P= .27, 25% defect P= .73). All 3 modalities demonstrated astrong correlation with the actual defect size (CT, ρ= .97; 1.5-T MRI, ρ= .93; 3-T MRI, ρ= .92, P < .0001). When looking at the absolute difference between the actual and measured defect area, no significance was noted between imaging modalities (10% defect P= .34, 25% defect P= .47). The error of 3-T 3D MRI increased with increasing defect size (P=.02). Both 1.5- and 3-T-based 3D MRI reconstructions of glenoid bone loss correlate with measurements from 3D CT scan data and actual defect size in a cadaveric model. Regardless of imaging modality, the error in bone loss measurement tends to increase with increased defect size. Use of 3D MRI in the setting of shoulder instability could obviate the need for CT scans. The goal of our work was to develop a reproducible method of determining glenoid bone loss from 3D MRI data and hence eliminate the need for CT scans in this setting. This will lead to decreased cost of care as well as decreased radiation exposure to patients. The long-term goal is a fully automated system that is as approachable for clinicians as current 3D CT technology.

Impact of injection dose, post-reconstruction filtering, and collimator choice on image quality of myocardial perfusion SPECT using cadmium-zinc telluride detectors in the rat.

BackgroundThe aims of this study were (1) to evaluate the impact of injection dose, post-reconstruction filtering, and collimator choice on image quality of myocardial perfusion single-photon emission computed tomography (SPECT) using cadmium-zinc telluride (CZT) detectors and (2) to determine how these factors affect measured infarct size in the in vivo rat.MethodsTwenty-four healthy and eight myocardial infarct (MI) rats underwent myocardial perfusion SPECT imaging after injection of various doses (25 to 200 MBq) of 99mTc-tetrofosmin using a standard (STD) five-pinhole collimator and high-sensitivity (HS) five-pinhole collimator. Image quality score, contrast-to-noise ratio, sharpness index, coefficient of variation (CV), and measured defect size were assessed as measures of image quality.ResultsThe image quality score increased and CV decreased as a function of injection dose. The contrast-to-noise ratio increased and sharpness index decreased as a function of Gaussian kernel size. When STD and HS were compared, HS tended to show higher image quality score and lower CV than STD. The use of post-reconstruction filter significantly improved image quality score and lessened CV. The reproducibility of defect size measurements, as assessed by intraclass correlation coefficients (ICC), between the collimators was poor-to-moderate (ICC = −0.31~0.57) with low (25 MBq) injection dose and with no or light (1.5-mm kernel size) filtering, whereas it was good-to-excellent (ICC = 0.75~0.97) with high (200 MBq) dose or low dose with heavy (2.5-mm kernel size) filtering. The filtering-related reproducibility was poor (ICC = −0.18~0.17) for STD with low injection dose, whereas it was good-to-excellent (ICC = 0.79~0.89) for HS. Furthermore, there was a filtering-related underestimation of defect size particularly with the use of heavy smoothing.ConclusionsAppropriate imaging setting is important to obtain high quality images and thereby reliable measurements using a preclinical myocardial SPECT in the rat. When only a low injection dose (25 MBq) is allowed, we would recommend to use HS with light (1.5-mm kernel size) filtering.

Titanium cranioplasty and the prediction of complications

Objectives. Titanium cranioplasty (TC), the operative repair of a skull defect with an ergonomically manufactured plate to restore cosmesis, cranial function and reduce complications is a common neurosurgical procedure. It is technically simple but has high complication rates. This study aimed to determine the incidence and predictors of complications following TC. Design. Retrospective review. Subjects. All patients undergoing TC over a 42-month period in our institution. Methods. Data was collected from the hospital database and case-notes. 3D CT reconstructions accurately measured defect size and location. Statistical analysis included correlation, independent variable analysis and descriptive methods. Results. A total of 95 TCs were analysed in 92 patients (3 cases of bifrontal cranioplasty). The commonest indications for TC were bony defect following removal of infected bone flap (n = 20), acute subdural haematoma (n = 18) and post-malignant infarction (n = 11). The commonest site was frontotemporoparietal (n = 61) and the overall complication rate was 30.4%. The commonest complication was infection and the overall removal rate was 8.4%. The mean cranioplasty area was 73.26 cm2 (range 12.78–178.26 cm2). There was a significant relationship between area and length of post-operative hospital stay (p = 0.008, Pearson Rank). There was no significant relationship between area and complications, removal rates or infections. There was no relationship between age and total complications, post-operative hospital stay and infections. There was a non-significant trend for older patients to have their cranioplasty removed. Conclusions. TC size is predictive of postoperative length of stay. However, the TC size is not predictive of complications or removal rate. Also, there was no association between interval since primary operation and complications. There was a non-significant trend for greater rates of TC removal in the elderly. There were no predictors of complications identified but they are common and patients should be consented accordingly.

Evaluation of Fatigue Limit Characteristics of Lamellar Pearlitic Steel in Consideration of Microstructure

In this study, tensile and fatigue tests were performed to evaluate the fatigue limit of lamellar pearlitic steel used for manufacturing railroad rail. The fatigue ratio of lamellar pearlitic steel was lower than that of general steels, the reason for which is unknown. Fatigue cracks initiated in pearlitic steel at a very early stage of the fatigue test. Then, it was speculated that the steel should be treated as that with initial defects. In order to determine the initial defect size in the ultra-low cycle fatigue test, tensile tests were performed. The tensile test results clarified that the crack initiation size depends on the crystal structure. In order to predict the fatigue limit of the pearlitic steel, the prediction method proposed by Murakami was applied to the steel. The measured defect sizes were applied to the prediction method, and fatigue tests were performed. The predicted fatigue limit and the test results were in good agreement. In addition, in order to evaluate the crystal structure at the location of the fatigue crack initiation, electron backscatter diffraction pattern (EBSD) analyses were performed. The analysis results revealed that the crack initiation depends on the pearlite block. Then, we concluded that the fatigue limit of pearlitic steel can be predicted by Murakami's method and the defect size is pearlite block size. Then, decreasing the pearlite block size would cause an improvement in the fatigue limit of the pearlitic steel.

Fatigue limit evaluation considering crack initiation for lamellar pearlitic steel

In order to evaluate the fatigue limit of lamellar pearlitic steel used for railroad rails, tensile tests and fatigue tests are performed. Although the fatigue ratio of the lamellar pearlitic steel is lower than that of general steels, the reason for this has not been clarified. The fatigue cracks of the pearlitic steel initiate at a very early stage during the fatigue test. It is speculated that the steel should be treated as a steel with initial defects. In order to determine the initial defect size of the ultra-low cycle fatigue test, tensile tests are performed. Based on the test results, it was clarified that the crack initiation size depends on the crystal structure. In order to predict the fatigue limit of the pearlitic steel, Murakami's prediction method is applied to the steel. The measured defect sizes are applied to the method, and the fatigue tests are performed. The predicted fatigue limits and the test results have good agreement. In addition, from the SEM observations, the initial crack causing the fatigue failure was found to be a pearlite block. We then concluded that the fatigue limit of the pearlitic steel can be predicted by Murakami's method and the defect size is the pearlite block size. If the pearlite block sizes then become small, the fatigue limit of the pearlitic steel will increase.

Myocardial Perfusion Imaging is Feasible for Infarct Size Quantification in Mice Using a Clinical Single-photon Emission Computed Tomography System Equipped with Pinhole Collimators

The aim of this study is to evaluate a non-invasive method for measuring myocardial perfusion defect size in mice using a clinical single-photon emission computed tomography system equipped with pinhole collimators (pinhole SPECT). Thirty days after ligation of the left anterior descending coronary artery, 13 mice (C57BL/6J) were imaged following intravenous injection of 370 MBq [99mTc]sestamibi. Eight control mice without myocardial infarction were likewise investigated. Image quality optimization had been achieved by repeated scanning of a multiple point phantom, with varying zoom factors, number of projection angles, and pinhole diameter. Volumetric sampling was used to generate polar maps, in which intensity was normalized to that of a standard septal region of interest (ROI), which was set at 100%. Receiver operating characteristic analyses were performed to define an optimal threshold as compared to histologically measured defect sizes, which were considered as gold standard. A spatial resolution of 1.9 mm was achieved using a pinhole diameter of 0.5 mm, a zoom factor of 2, and 6 degrees projection angles. Histological results were best reproduced by a 60% threshold relative to the septal reference ROI. By applying this threshold, SPECT perfusion defect sizes revealed very high correlation to the histological results (R(2) = 0.867) with excellent intra- and interobserver reproducibility (intraclass correlation coefficients of 0.84 and 0.82). We achieved a spatial resolution of 1.9 mm in myocardial perfusion imaging in mice using a clinical SPECT system mounted with pinhole collimators. Compared to a histological gold standard, the infarct sizes were accurately estimated, indicating that this method shows promise to monitor experimental cardiac interventions in mice.

Accuracy of cardiac PET imaging using post-injection transmission scan

The purpose of this study was to investigate the accuracy of cardiac PET with post-injection transmission scans. We performed a phantom study using 18F solution as well as 13N-ammonia PET study of ten patients. The average activities of no myocardial defect phantom model were estimated, and myocardial defect sizes of 12 phantom models were measured by pre- and post-injection transmission methods at various 18F activities. In 13N-ammonia PET at rest and during adenosine triphosphate (ATP) stress studies, measured defect sizes were compared between both methods. The ratios of average activity estimated by both methods (post/pre value) were almost 1.00 at each 18F activity and segment. Measured defect sizes by both methods showed an excellent correlation with true defect sizes (r = 0.98, p < 0.01 for pre vs. true value: r = 0.98, p < 0.01 for post vs. true value). The mean absolute errors of measurements were minimal up to 3.5% LV, and were similar between both methods. In 13N-ammonia PET, measured defect sizes by both methods also showed a good correlation (r = 0.97, p < 0.01). The results indicate that cardiac PET imaging with post-injection transmission scan provides information on myocardial tracer activity as well as myocardial defect size as does conventional pre-injection transmission method.

Adaptive prognostics for rolling element bearing condition

Rolling element bearing failure is one of the foremost causes of breakdown in rotating machinery. This paper proposes a remaining life adaptation methodology based on mechanistic modeling and parameter tuning. Vibration measurement is used to estimate defect severity by monitoring the signals generated from rotating bearings. Through a defect propagation model and defect diagnostic model, an adaptive algorithm is developed to fine tune the parameters involved in the propagation model by comparing predicted and measured defect sizes. In this manner, the instantaneous rate of defect propagation can be captured despite defect growth behavior variation. Therefore, a precise estimation of the remaining life can be determined. Simulations and experimental results are presented to illustrate the implementation principles and to verify the applicability of the adaptive prognostic methodology.

Effect of scatter correction on measured defect size from clinical cardiac SPECT studies

Effect of scatter correction on measured defect size from clinical cardiac SPECT studies

Evaluation of a multicrystal gamma camera and rotating chair for tomographic studies of the heart

Background. This study evaluates the feasibility of performing tomographic studies with a multicrystal gamma camera combined with a rotating chair. Methods and Results. Tomographic acquisitions were performed with a cardiac phantom containing eight defects of different sizes. Defect size was determined from the fraction of counts in the short-axis slices that fell below a fixed threshold value. Image contrast was determined from the ratio of minimum/maximum counts. Images of an American College of Nuclear Physicians cardiac single-photon emission computed tomographic phantom were acquired and the results were compared with those obtained from 194 centers in the United States. For cardiac studies with 201T1 and 99mTc, threshold values of 65% to 70% gave the best correlation ( R 2 > 0.94) between true and measured defect sizes, although the slope of the regression line was less than 0.95 for both isotopes. Small inferior defects demonstrated poor image contrast, particularly for 99mTc. Of the three defects in the American College of Nuclear Physicians phantom, the two largest were identified in the tomographic images. Conclusions. A multicrystal gamma camera system coupled with a rotating chair can be used for tomographic studies of the heart. Image quality is poorer than that seen on conventional single-photon emission computed tomographic systems, particularly for 99mTc.