Modern Scanners Research Articles

Experimental assessment of clinical MRI-induced global SAR distributions in head phantoms

ObjectiveAccurate estimation of SAR is critical to safeguarding vulnerable patients who require an MRI procedure. The increased static field strength and RF duty cycle capabilities in modern MRI scanners mean that systems can easily exceed safe SAR levels for patients. Advisory protocols routinely used to establish quality assurance protocols are not required to advise on the testing of MRI SAR levels and is not routinely measured in annual medical physics quality assurance checks. This study aims to develop a head phantom and protocol that can independently verify global SAR for MRI clinical scanners. MethodsA four-channel birdcage head coil was used for RF transmission and signal reception. Proton resonance shift thermometry was used to estimate SAR. The SAR estimates were verified by comparing results against two other independent measures, then applied to a further four scanners at field strengths of 1.5 T and 3 T. ResultsScanner output SAR values ranged from 0.42 to 1.52 W/kg. Percentage SAR differences between independently estimated values and those calculated by the scanners differed by 0–2.3%. ConclusionWe have developed a quality assurance protocol to independently verify the SAR output of MRI scanners.

Image quality evaluation in a modern PET system: impact of new reconstructions methods and a radiomics approach

The present work investigates the influence of different biological and physical parameters on image quality (IQ) perception of the abdominal area in a modern PET scanner, using new reconstruction algorithms and testing the utility of a radiomics approach. Scans of 112 patients were retrospectively included. Images were reconstructed using both OSEM + PSF and BSRM methods, and IQ of the abdominal region was subjectively evaluated. First, 22 IQ related parameters were obtained (including count rate and biological or mixed parameters) and compared to the subjective IQ scores by means of correlations and logistic regression. Second, an additional set of radiomics features was extracted, and a model was constructed by means of an elastic-net regression. For the OSEM + PSF and especially for the BSRM reconstructions, IQ parameters presented only at best moderated correlations with the subjective IQ. None of the studied parameters presented a good predictive power for IQ, while a simple radiomics model increased the performance of the IQ prediction. These results suggest the necessity of changing the standard parameters to evaluate IQ, particularly when a BSRM algorithm is involved. Furthermore, it seems that a simple radiomics model can outperform the use of any single parameter to assess IQ.

Robust Beam Hardening Artifacts Reduction for Computed Tomography Using Spectrum Modeling

The aim of this paper is to develop a fast and accurate beam hardening correction method by modeling physical interactions between X-ray photons and materials for computed tomography (CT) imaging. The nonlinear attenuation process of the X-ray projection is modeled by reprojecting a template image with the estimated polychromatic spectrum. By adding the scaled difference of the monochromatic reprojection data and the polychromatic reprojection to the raw projection data, the raw projection data is mapped into the corresponding monochromatic projection data, which is to reconstruct the beam hardening artifacts corrected images. The algorithm can also be implemented in image-domain which takes the uncorrected image volume as input when there is an adequate model of the spectrum. In this case, the scaled difference is reconstructed to yield a set of artifacts images that can be added directly to the uncorrected images. Numerical simulations, experimental phantom data, and animal data which are acquired on a modern diagnostic CT scanner (Discovery CT750 HD, GE Healthcare, WI, USA), and a modern C-Arm CT scanner (Artis Zee, Siemens Healthcare, Forchheim, Germany), respectively, are used to evaluate the proposed method. The results show the proposed method significantly reduced both cupping and streak artifacts, and successfully recovered the Housfield units accuracy. Extensive studies suggest the proposed model-based method successfully corrects the beam hardening artifacts. This paper is practically useful and is promising to be applied to commercial products.

Quality assurance measurements of geometric accuracy for magnetic resonance imaging-based radiotherapy treatment planning

BackgroundUsing magnetic resonance imaging (MRI) as the only imaging method for radiotherapy treatment planning (RTP) is becoming more common as MRI-only RTP solutions have evolved. The geometric accuracy of MR images is an essential factor of image quality when determining the suitability of MRI for RTP. The need is therefore clear for clinically feasible quality assurance (QA) methods for the geometric accuracy measurement. Materials and methodsThis work evaluates long-term stability of geometric accuracy and the validity of a 2D geometric accuracy QA method compared to a prototype 3D method and analysis software in routine QA. The long-term follow-up measurements were conducted on one of the 1.5 T scanners over a period of 19 months using both methods. Inter-scanner variability of geometric distortions was also evaluated in three 1.5 T and three 3 T MRI scanners from a single vendor by using the prototype 3D QA method. ResultsThe geometric accuracy of the magnetic resonance for radiotherapy (MR-RT) platform remained stable within 2 mm at distances of <250 mm from isocenter. All scanners achieved good geometric accuracy with mean geometric distortions of <1 mm at <150 mm and <2 mm at <250 mm from the isocenter. Both measurement methods provided relevant information about geometric distortions. ConclusionsGeometric distortions are often considered a limitation of MRI-only RTP. Results indicate that geometric accuracy of modern scanners remain within acceptable limits by default even after many years of clinical use based on the 3D QA evaluation.

Methodological consensus on clinical proton MRS of the brain: Review and recommendations.

Proton MRS (1 H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good-quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi-adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0 ) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.

The futility of continued surveillance of epididymal cysts - A study of the prevalence and clinico-demographics in pre- vs. post-pubertal boys.

The first description of epididymal cysts in children appears from a 1976 case study. Since then, there have been a total of 24 indexed publications relating to pediatric epididymal cysts. Risk factors that may exist for children presenting with epididymal cyst remain unknown, as has the best method of management. And there have not been any studies looking at the cost implications of this diagnosis. The aim of this study was to assess the incidence, clinico-demographics, outcomes, and costs of epididymal cysts in pre-pubertal boys compared with a post-pubertal epididymal cyst cohort, and to assess whether this cohort requires continued surveillance METHODS:: Our institutional ultrasound (US) database was searched for all scrotal US. From these, a filtered, institution review board-approved search was performed for any reports containing the word "cyst." These were then cross-referenced with a retrospective chart review (October 2006 to September 2017). Clinico-demographics, cyst characteristics, and outcomes were analysed for both pre- and post-pubertal boys using descriptive and non- parametric statistical methods RESULTS:: Of 4508 boys undergoing scrotal US during the study period, 191 were indicated to contain cysts. This was manually reduced to 109 scans (2.4%) that met inclusion criteria (85 pre-pubertal; 24 post-pubertal). Thirty-one scans were ordered by urology, including all those with abnormal testicular echotexture (n=5). The average age of the post-pubertal cohort was 15.8 years, compared with 3.8 years in the pre-pubertal cohort. Most (70.5%) epididymal cysts were incidental. There was no difference between the pre- and post-pubertal cohorts in terms of presence of hydrocoeles (p=0.9), symptoms (p=0.9), ordering service (p=0.61), rate of resolution (4.2% vs. 8.2%; p=0.68), or length of followup (4 vs. 4.5 years; p=0.44). Pre- pubertal cysts were significantly smaller in size (3.35 vs. 14.52 mm; p=0.025) and more likely to trigger repeat scanning (67 vs. 10; p=0.008). There were no operative interventions and no subsequent clinical deterioration occurred with observation. At a cost of $71.10 CAD per US, $15 002.10 CAD was expended on epididymal cyst surveillance in direct cost to the healthcare system. Epididymal cysts are comparable in both pre- and post-pubertal boys and can be safely managed non-operatively without the use of continued US surveillance or urological referral. The higher than expected rate of detection may be a result of the improved ultra-resolution of modern scanners. These children should not require continued followup with repeat surveillance imaging solely for epididymal cysts and could be managed in the primary care setting as part of routine clinical examination.

In vivo positron emission tomographic blood pool imaging in an immunodeficient mouse model using 18F-fluorodeoxyglucose labeled human erythrocytes.

99m-Technetium-labeled (99mTc) erythrocyte imaging with planar scintigraphy is widely used for evaluating both patients with occult gastrointestinal bleeding and patients at risk for chemotherapy-induced cardiotoxicity. While a number of alternative radionuclide-based blood pool imaging agents have been proposed, none have yet to achieve widespread clinical use. Here, we present both in vitro and small animal in vivo imaging evidence that the high physiological expression of the glucose transporter GLUT1 on human erythrocytes allows uptake of the widely available radiotracer 2-deoxy-2-(18F)fluoro-D-glucose (FDG), at a rate and magnitude sufficient for clinical blood pool positron emission tomographic (PET) imaging. This imaging technique is likely to be amenable to rapid clinical translation, as it can be achieved using a simple FDG labeling protocol, requires a relatively small volume of phlebotomized blood, and can be completed within a relatively short time period. As modern PET scanners typically have much greater count detection sensitivities than that of commonly used clinical gamma scintigraphic cameras, FDG-labeled human erythrocyte PET imaging may not only have significant advantages over 99mTc-labeled erythrocyte imaging, but may have other novel blood pool imaging applications.

Correlation of acute pulmonal embolism with D-dimer levels and the diameter of the pulmonary trunk in thoracic multislice computed tomography. A single-centre retrospective analysis of 100 patients

PurposeThe aim of this retrospective study was to evaluate the correlation between D-dimer levels in positive thromboembolic thoracic computed tomography (CT) with the diameter of the pulmonary trunk and to study the relation between the D-dimer and the uni- or bilateralism of the lesions and the presence of pulmonal trunk involvement. We also analysed gender-specific differences in patients with and without dilatation of the pulmonal trunk.Material and methodsA total of 100 acute care patients (50 men and 50 women) with positive thromboembolic multiple detector computed tomography of the thorax, performed on two modern CT scanners, were retrospectively studied. All thoracic CTs were evaluated by two expert radiologists, with attention paid to the diameter of the pulmonary trunk and the correlation of D-dimer level with the uni-or bilateralism of the lesions. We also analysed sex-specific correlations. All patients underwent multislice computed tomography-examination after applying 70 ml iodinated non-ionic contrast media. Graphpad Prism 8.1.1 software was used for statistical data.ResultsThe “strongest” weak correlation resulted between D-dimer levels and the axial diameter of the pulmonal trunk. Considering the correlation between the axial diameter of the pulmonal trunk and gender-related distributions, we found that female patients had higher axial diameters than men. Another weak relationship, almost zero, was found between the D-dimer level and gender. Regarding the correlation between the uni- or bilateralism of thromboembolism and the D-dimer levels, we also found a weak correlation.ConclusionsThis retrospective study showed that D-dimer levels, the diameter of the pulmonal trunk, the location, and gender-related distributions have almost no correlation and are not significantly predictive in imaging.

Offset compensated baseline restoration and computationally efficient hybrid interpolation for the brain PET

Abstract The acquisition of positron emission tomography (PET) pulses introduces artifacts and limits the performance of the scanner. To minimize these inadequacies, this work focuses on the design of an offset compensated digital baseline restorer (BLR) along with a two-stage hybrid interpolator. They respectively treat the incoming pulse offsets and limited temporal resolution and improve the scanner performance in terms of calculating depth of interactions and line of responses. The offset of incoming PET pulses is compensated by the BLR and then their interesting parts are selected. The selected signal portion is up-sampled with a hybrid interpolator. It is composed of an optimized weighted least-squares interpolator (WLSI) and a simplified linear interpolator. The processes of calibrating the WLSI coefficients and characterizing the BLR and the interpolator modules are described. The functionality of the proposed modules is verified with an experimental setup. Results have shown that the devised BLR effectively compensates a dynamic range of bipolar offsets. The signal selection process allows focusing only on the relevant signal part and avoids the unnecessary operations during the post-interpolation process. Additionally, the hybrid nature allows improving the signal temporal resolution with an appropriate precession at a reduced computational complexity compared to the mono-interpolation-based arithmetically complex counterparts. The component-level architectures of the BLR and the interpolator modules are also described. It promises an efficient integration of these modules in modern PET scanners while using standard and economical analog-to-digital converters and field-programmable gate arrays. It avoids the development of high-performance and expensive application-specific integrated circuits and results in a cost-effective realization.

Denoising of MR images using Kolmogorov-Smirnov distance in a Non Local framework

Data coming from any acquisition system, such as Magnetic Resonance Imaging ones, are affected by noise. Although modern high field scanners can reach high Signal to Noise Ratios, in some circumstances, for example in case of very weak signals due to a specific acquisition sequence, noise becomes a critical issue that has to be properly handled. In the last years methods based on the so called Non Local Mean have proven to be very effective in denoising tasks. The idea of these filters is to find similar patches across the image and to jointly exploit them to obtain the restored image. A critical point is the distance metric adopted for measuring similarity. Within this manuscript, we propose a filtering technique based on the Kolmogorov-Smirnov distance. The main innovative aspect of the proposed method consists of the criteria adopted for finding similar pixels across the image: it is based on the statistics of the points rather than the widely adopted weighted Euclidean distance. More in details, the Cumulative Distribution Functions of different pixels are evaluated and compared in order to measure their similarities, exploiting a stack of images of the same slice acquired with different acquisition parameters. To quantitatively and qualitatively assess the performances of the approach, a comparison with other widely adopted denoising filters in case of both simulated and real datasets has been carried out. The obtained results confirm the validity of the proposed solution.

Diagnosis of diaphragm injuries using modern 256-slice CT scanners: too early to abandon operative exploration

BackgroundMissed injury of the diaphragm may result in hernia formation, enteric strangulation, and death. Compounding the problem, diaphragmatic injuries are rare and difficult to diagnose with standard imaging. As such,...

Dermatoglyphic pattern in the men with essential hypertension, who are carriers of the polymorphic genes of angiotensin II type 1 receptors

Essential hypertension and its common complication - chronic heart failure, is one of the most significant medical, economic and social problems in the XXI century. At the same time, this pathology is 30-40% genetically predisposed. One of significant pathogenic factors is the inheritance of definite variants of genes, coding the receptors to angiotensin II type 1. For this reason, the effective and inexpensive researches for screening of the mentioned genetic phenomenon are being carried out. Objective: to improve the screening diagnostic methods for carriers of polymorphic genes of angiotensin II type 1 receptors with essential hypertension and essential hypertension complicated by chronic heart failure. There were studied dermatoglyphic prints of men 40-60 years, who are carriers of polymorphic gene variants of angiotensin II type 1 receptor with no cardiovascular diseases (n=79), male patients with essential hypertension and hypertrophy of the myocardium (stage II), II-III stages (n=62) and essential hypertension (n=50) complicated by chronic heart failure, residents of Podillya region of Ukraine. Genotyping of the gene of angiotensin II type 1 receptor was performed using polymerase chain reaction. All patients included in the control group and those with essential hypertension underwent dermatoglyphic examination of fingers on both hands using modern portable rolling scanner Futronic FS50 (Korea). Interpretation and decoding of dermatoglyphic prints was conducted by T. D. Gladkova’s method. Statistical analysis was done on personal computer using standard statistical package “STATISTICA 10.0”. The found ulnar loop was dominant dermatoglyphic print regardless of the presence or absence of essential hypertension and chronic heart failure in 40-60 year old men. Besides, positive correlation relationship was revealed between the inheritance gene of angiotensin II type 1 receptors and fingerprint patterns: the third finger on the left hand in males with no cardiovascular pathology (weak strength) and the second finger on the right hand in patients with essential hypertension (medium strength). In individuals with no cardiovascular diseases, carriers of genotype A1166A, prevalence of ulnar loop on the third finger of left hand is higher than in carriers of C allele gene of angiotensin II type 1 receptors. In males with essential hypertension, carriers of C allele, degree of incidence of the whorl on the second finger of right hand is significantly higher than in carriers of genotype А1166А, offering the possibility to determine the carriership of a particular gene of angiotensin II type 1 receptors. Carrying out dermatoglyphic examination in patients with an increase in blood pressure and determining the variant of carrier of the gene of the receptor to angiotensin II type 1 will make it possible to facilitate the selection of those individuals who in the future need to spend all the necessary amount of research to confirm the diagnosis of essential hypertension and the possible development of complications of the course of this cardiovascular disease.

POSSIBILITIES AND LIMITATIONS OF COMBINED SCANNERS

The technique of optical scanning is continuously developing in the direction of creating new and improving existing types of scanners (deflectors), radiation sources, methods of reading, converting and reproducing information. However, the absence of universal scanner, able to satisfy different applications leads to necessity of application of combined scanning, finding the most effective combination of deflectors with complementary characteristics taking into account their limit values. The purpose of this work is an overview of a typical combined of the scanners used in the systems of wide application, analysis of existing experience in the use of combined deflectors. The article discusses the optical schemes of modern combined scanners, which include scanners of different operating principles and design. The analysis of combined devices for various applications is given, which included optical-mechanical, electronic, acoustic-optical, electro-optical scanners, as well as micro-electromechanical (MEMS) systems, expanding the sphere of scanning tools. The consideration was conducted with a wide set of parameters and characteristics, such as speed, resolution, accuracy of the control of the optical beam, the size of the scanned space, etc. Identified features and benefits of the combined scanning for dynamic, precision, spectral, and structural characteristics and functionality, and also are noted difficulty in implementing a combined scanning. Among them are optical harmonization, dynamic, algorithmic and precision matching of scanners integrated into the device.

Radiation burden and associated cancer risk for a typical population to be screened for lung cancer with low-dose CT: A phantom study.

To estimate (a) organ doses and organ-specific radiation-induced cancer risk from a single low-dose CT (LDCT) for lung cancer screening (LCS) and (b) the theoretical cumulative risk of radiation-induced cancer for a typical cohort to be subjected to repeated annual LCS LDCT. Sex- and body size-specific organ dose data from scan projection radiography (SPR) and helical CT exposures involved in LCS 256-slice LDCT were determined using Monte Carlo methods. Theoretical life attributable risk (LAR) of radiogenic cancer from a single 256-slice chest LDCT at age 55-80 years and the cumulative LAR of cancer from repeated annual LDCT studies up to age 80 years were estimated and compared to corresponding nominal lifetime intrinsic risks (LIRs) of being diagnosed with cancer. The effective dose from LCS 256-slice LDCT was estimated to be 0.71 mSv. SPR was found to contribute 6-12 % to the total effective dose from chest LDCT. The radiation-cancer LAR from a single LDCT study was found to increase the nominal LIR of cancer in average-size 55-year-old males and females by 0.008 % and 0.018 %, respectively. Cumulative radiogenic risk of cancer from repeated annual scans from the age of 55-80 years was found to increase the nominal LIR of cancer by 0.13 % in males and 0.30 % in females. Modern scanners may offer sub-millisievert LCS LDCT. Cumulative radiation risk from repeated annual 256-slice LDCT LCS examinations was found to minimally aggravate the lifetime intrinsic cancer risk of a typical screening population. • Effective dose from lung cancer screening low-dose CT may be <1 mSv. • Screening with modern low-dose CT minimally aggravates lifetime cancer induction intrinsic risk. • Dosimetry of lung cancer screening low-dose CT should encounter the radiation burden from the localizing scan projection radiography. • DLP method may underestimate effective dose from low-dose chest CT by 27 %.

Feasibility of 15O-water PET studies of auditory system activation during general anesthesia in children

Background15O-Water positron emission tomography (PET) enables functional imaging of the auditory system during stimulation via a promontory electrode or cochlear implant, which is not possible using functional magnetic resonance imaging (fMRI). Although PET has been introduced in this context decades ago, its feasibility when performed during general anesthesia has not yet been explored. However, due to a shift to earlier (and bilateral) auditory implantation, the need to study children during general anesthesia appeared, since they are not able to cooperate during scanning. Therefore, we evaluated retrospectively results of individual SPM (statistical parametric mapping) analysis of 15O-water PET in 17 children studied during general anesthesia and compared them to those in 9 adults studied while awake. Specifically, the influence of scan duration, smoothing filter kernel employed during preprocessing, and cut-off value used for statistical inferences were evaluated. Frequencies, peak heights, and extents of activations in auditory and extra-auditory brain regions (AR and eAR) were registered.ResultsIt was possible to demonstrate activations in auditory brain regions during general anesthesia; however, the frequency and markedness of positive findings were dependent on some of the abovementioned influence factors. Scan duration (60 vs. 90 s) had no significant influence on peak height of auditory cortex activations. To achieve a similar frequency and extent of AR activations during general anesthesia compared to waking state, a lower cut-off for statistical inferences (p < 0.05 or p < 0.01 vs. p < 0.001) had to be applied. However, this lower cut-off was frequently associated with unexpected, “artificial” activations in eAR. These activations in eAR could be slightly reduced by the use of a stronger smoothing filter kernel during preprocessing of the data (e.g., [30 mm]3).ConclusionsOur data indicate that it is feasible to detect auditory cortex activations in 15O-water PET during general anesthesia. Combined with the improved signal to noise ratios of modern PET scanners, this suggests reasonable prospects for further evaluation of the method for clinical use in auditory implant users. Adapted parameters for data analysis seem to be helpful to improve the proportion of signals in AR versus eAR.

ЗАСТОСУВАННЯ ТРИВИМІРНОГО МОДЕЛЮВАННЯ ЯК СПОСОБУ ІНФОРМАЦІЙНО-ТЕХНІЧНОГО ЗАБЕЗПЕЧЕННЯ КРИМІНАЛІСТИЧНОЇ РЕЄСТРАЦІЇ

The article is devoted to the issues of using three-dimensional modeling as a way of information and technical support of forensic registration. It is stated that none of the modern researches focuses on the use of three- dimensional modeling technology of information and technical support of forensic registration. An assessment of the technological capabilities of modern three-dimensional scanners (3D-scanners), which are used (or can be used) in the information and technical support of forensic registration. The technological possibilities of three-dimensional modeling are analyzed, in particular in the construction of three-dimensional models of the scene, the creation of virtual rooms for educational purposes, forensic examinations, etc. Emphasis is placed on the fact that in criminology, three-dimensional (3D) modeling is carried out according to the rules of solid modeling (in which the key is to reproduce the physical properties of three-dimensional modeling objects). It is the physical properties of forensic registration objects, as a rule, that are the key information, the fixation of which is carried out within the framework of forensic registration. It is determined that the prospects of using three-dimensional (3D) modeling during forensic registration are to ensure the possibility of creating objects of accounting using additive technologies (ie three-dimensional printing (3D- printing)). The position is expressed that the technologies of three-dimensional (3D) modeling can be applied, first of all, in: trasological accounting; ballistic accounting; cold steel accounting; registration of persons on the basis of appearance; accounting of materials, substances and products. Therefore, with 3D modeling, it is possible to reproduce a certain three-dimensional object if it has been properly scanned. The described technologies create opportunities not only to quickly create exact copies or duplicates of evidence or other objects that are placed in forensic accounting, and use them for other research or for use as objects of orientation during operational or investigative actions.

The connection the dermatoglyphic of fingers and human`s growth

The identification of an unknown person remains one of the most important areas of forensic medicine. The use of simple and materially nonburdensome research methods can accelerate the process of identifying common anthroposcopic and anthropometric parameters of a person. Dermatoglifical parameters of distal, middle and proximal phalanges of fingers are stable phenotypic features of a person, which correlate with other parameters of it. Obtained using modern scanners dermatoglific parameters are already digitized and are subject to rapid processing of modern computer programs. The conducted research allowed to establish the correlation between the dermatological signs of fingers and the height of the female population of Hutsul, Lemko and Boyko ethno-territorial groups. Correlation ties between dermatoglyphic parameters of distal, middle and proximal phalanges of hands andanthropometric parameters were sufficiently informative, which allowed them to be used in the prediction of foreign-recognizable features of a person.

Quantitative imaging of peripheral trabecular bone microarchitecture using MDCT.

Osteoporosis associated with reduced bone mineral density (BMD) and microarchitectural changes puts patients at an elevated risk of fracture. Modern multidetector row CT (MDCT) technology, producing high spatial resolution at increasingly lower dose radiation, is emerging as a viable modality for trabecular bone (Tb) imaging. Wide variation in CT scanners raises concerns of data uniformity in multisite and longitudinal studies. A comprehensive cadaveric study was performed to evaluate MDCT-derived Tb microarchitectural measures. A human pilot study was performed comparing continuity of Tb measures estimated from two MDCT scanners with significantly different image resolution features. Micro-CT imaging of cadaveric ankle specimens (n=25) was used to examine the validity of MDCT-derived Tb microarchitectural measures. Repeat scan reproducibility of MDCT-based Tb measures and their ability to predict mechanical properties were examined. To assess multiscanner data continuity of Tb measures, the distal tibias of 20 volunteers (age:26.2±4.5Y,10F) were scanned using the Siemens SOMATOM Definition Flash and the higher resolution Siemens SOMATOM Force scanners with an average 45-day time gap between scans. The correlation of Tb measures derived from the two scanners over 30% and 60% peel regions at the 4% to 8% of distal tibia was analyzed. MDCT-based Tb measures characterizing bone network area density, plate-rod microarchitecture, and transverse trabeculae showed good correlations (r∈0.85,0.92) with the gold standard micro-CT-derived values of matching Tb measures. However, other MDCT-derived Tb measures characterizing trabecular thickness and separation, erosion index, and structure model index produced weak correlation (r<0.8) with their micro-CT-derived values. Most MDCT Tb measures were found repeatable (ICC∈0.94,0.98). The Tb plate-width measure showed a strong correlation (r = 0.89) with experimental yield stress, while the transverse trabecular measure produced the highest correlation (r = 0.81) with Young's modulus. The data continuity experiment showed that, despite significant differences in image resolution between two scanners (10% MTF along xy-plane and z-direction - Flash: 16.2 and 17.9 lp/cm; Force: 24.8 and 21.0 lp/cm), most Tb measures had high Pearson correlations (r > 0.95) between values estimated from the two scanners. Relatively lower correlation coefficients were observed for the bone network area density (r = 0.91) and Tb separation (r = 0.93) measures. Most MDCT-derived Tb microarchitectural measures are reproducible and their values derived from two scanners strongly correlate with each other as well as with bone strength. This study has highlighted those MDCT-derived measures which show the greatest promise for characterization of bone network area density, plate-rod and transverse trabecular distributions with a good correlation (r ≥ 0.85) compared with their micro-CT-derived values. At the same time, other measures representing trabecular thickness and separation, erosion index, and structure model index produced weak correlations (r < 0.8) with their micro-CT-derived values, failing to accurately portray the projected trabecular microarchitectural features. Strong correlations of Tb measures estimated from two scanners suggest that image data from different scanners can be used successfully in multisite and longitudinal studies with linear calibration required for some measures. In summary, modern MDCT scanners are suitable for effective quantitative imaging of peripheral Tb microarchitecture if care is taken to focus on appropriate quantitative metrics.

Measurement properties and usability of non-contact scanners for measuring transtibial residual limb volume.

Non-contact scanners may have potential for measurement of residual limb volume. Different non-contact scanners have been introduced during the last decades. Reliability and usability (practicality and user friendliness) should be assessed before introducing these systems in clinical practice. The aim of this study was to analyze the measurement properties and usability of four non-contact scanners (TT Design, Omega Scanner, BioSculptor Bioscanner, and Rodin4D Scanner). Quasi experimental. Nine (geometric and residual limb) models were measured on two occasions, each consisting of two sessions, thus in total 4 sessions. In each session, four observers used the four systems for volume measurement. Mean for each model, repeatability coefficients for each system, variance components, and their two-way interactions of measurement conditions were calculated. User satisfaction was evaluated with the Post-Study System Usability Questionnaire. Systematic differences between the systems were found in volume measurements. Most of the variances were explained by the model (97%), while error variance was 3%. Measurement system and the interaction between system and model explained 44% of the error variance. Repeatability coefficient of the systems ranged from 0.101 (Omega Scanner) to 0.131 L (Rodin4D). Differences in Post-Study System Usability Questionnaire scores between the systems were small and not significant. The systems were reliable in determining residual limb volume. Measurement systems and the interaction between system and residual limb model explained most of the error variances. The differences in repeatability coefficient and usability between the four CAD/CAM systems were small. Clinical relevance If accurate measurements of residual limb volume are required (in case of research), modern non-contact scanners should be taken in consideration nowadays.

FPGA implementation of real-time SENSE reconstruction using pre-scan and Emaps sensitivities

Sensitivity Encoding (SENSE) is a widely used technique in Parallel Magnetic Resonance Imaging (MRI) to reduce scan time. Reconfigurable hardware based architecture for SENSE can potentially provide image reconstruction with much less computation time. Application specific hardware platform for SENSE may dramatically increase the power efficiency of the system and can decrease the execution time to obtain MR images. A new implementation of SENSE on Field Programmable Gate Array (FPGA) is presented in this study, which provides real-time SENSE reconstruction right on the receiver coil data acquisition system with no need to transfer the raw data to the MRI server, thereby minimizing the transmission noise and memory usage. The proposed SENSE architecture can reconstruct MR images using receiver coil sensitivity maps obtained using pre-scan and eigenvector (E-maps) methods. The results show that the proposed system consumes remarkably less computation time for SENSE reconstruction, i.e., 0.164ms @ 200MHz, while maintaining the quality of the reconstructed images with good mean SNR (29+ dB), less RMSE (<5×10−2) and comparable artefact power (<9×10−4) to conventional SENSE reconstruction. A comparison of the center line profiles of the reconstructed and reference images also indicates a good quality of the reconstructed images. Furthermore, the results indicate that the proposed architectural design can prove to be a significant tool for SENSE reconstruction in modern MRI scanners and its low power consumption feature can be remarkable for portable MRI scanners.