Generation Of Scanners Research Articles

Consensus approach for 3D joint space width of metacarpophalangeal joints of rheumatoid arthritis patients using high-resolution peripheral quantitative computed tomography.

Joint space assessment for rheumatoid arthritis (RA) by ordinal conventional radiographic scales is susceptible to floor and ceiling effects. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides superior resolution, and may detect earlier changes. The goal of this work was to compare existing 3D methods to calculate joint space width (JSW) metrics in human metacarpophalangeal (MCP) joints with HR-pQCT and reach consensus for future studies. Using the consensus method, we established reproducibility with repositioning as well as feasibility for use in second-generation HR-pQCT scanners. Three published JSW methods were compared using datasets from individuals with RA from three research centers. A SPECTRA consensus method was developed to take advantage of strengths of the individual methods. Using the SPECTRA method, reproducibility after repositioning was tested and agreement between scanner generations was also established. When comparing existing JSW methods, excellent agreement was shown for JSW minimum and mean (ICC 0.987-0.996) but not maximum and volume (ICC 0.000-0.897). Differences were identified as variations in volume definitions and algorithmic differences that generated high sensitivity to boundary conditions. The SPECTRA consensus method reduced this sensitivity, demonstrating good scan-rescan reliability (ICC >0.911) except for minimum JSW (ICC 0.656). There was strong agreement between results from first- and second-generation HR-pQCT (ICC >0.833). The SPECTRA consensus method combines unique strengths of three independently-developed algorithms and leverages underlying software updates to provide a mature analysis to measure 3D JSW. This method is robust with respect to repositioning and scanner generations, suggesting its suitability for detecting change.

Diagnostic value of CT contrast extravasation for major arterial injury after pelvic fracture: A meta-analysis

PurposeWe conducted a meta-analysis to determine diagnostic performance of CT intravenous contrast extravasation (CE) as a sign of angiographic bleeding and need for angioembolization after pelvic fractures. Materials and methodsA systematic literature search combining the concepts of contrast extravasation, pelvic trauma, and CT yielded 206 potentially eligible studies. 23 studies provided accuracy data or sufficient descriptive data to allow 2x2 contingency table construction and provided 3855 patients for meta-analysis. Methodologic quality was assessed using the QUADAS-2 tool. Sensitivity and specificity were synthesized using bivariate mixed-effects logistic regression. Heterogeneity was assessed using the I2-statistic. Sources of heterogeneity explored included generation of scanner (64 row CT versus lower detector row) and use of multiphasic versus single phase scanning protocols. ResultsOverall sensitivity and specificity were 80% (95% CI: 66–90%, I2 = 92.65%) and 93% (CI: 90–96, I2 = 89.34%), respectively. Subgroup analysis showed pooled sensitivity and specificity of 94% and 89% for 64- row CT compared to 69% and 95% with older generation scanners. CE had pooled sensitivity and specificity of 95% and 92% with the use of multiphasic protocols, compared to 74% and 94% with single-phase protocols. ConclusionThe pooled sensitivity and specificity of 64-row CT was 94 and 89%. 64 row CT improves sensitivity of CE, which was 69% using lower detector row scanners. High specificity (92%) can be maintained by incorporating multiphasic scan protocols.

The effect different substrates have on the trueness and precision of eight different intraoral scanners.

This in vitro study compares the newest generation of intraoral scanners to their older counterparts, and tests whether material substrates affect the trueness and precision of intraoral scanners (IOS). A custom model, used as the reference standard, was fabricated with teeth composed of different dental materials. The reference standard scan was obtained using a three-dimensional (3D) optical scanner, the ATOS III. Experimental scans were obtained using eight different IOS, operated by experienced clinicians, using the manufacturer's recommended scanning strategy. A comprehensive metrology program, Geomagic Control X, was used to compare the reference standard scan with the experimental scans. For all scanners tested, except Trios3, the substrate does influence the trueness and precision of the scan. Furthermore, differences exist when comparing the same substrate across different scanners with some of the latest generation scanners clearly leaping ahead of the older generation regarding both trueness and precision. Substrate type affects the trueness and precision of a scan. Active Triangulation scanners are more sensitive to substrate differences than their parallel confocal counterparts. Some scanners scan certain substrates better, but in general the new generation of scanners outperforms the old, across all substrates. The substrates being scanned play an import role in the trueness and precision of the 3D model. The new generation of scanners is remarkably accurate across all substrates and for complete-arch scanning.

Multi-slice Energy Resolving CT system using a THCOBRA detector operating in NeCH4

Abstract A 2D-Thick-COBRA based detector with 10 × 10 cm2 active area operating in Ne/CH 4 (95/5) flow mode, was applied to X-ray Computed Tomography (CT). The CT system is based on a third generation scanner with the object motion provided by a stepper motor. Multi-slice acquisitions of a Poly(methyl methacrylate) phantom and of a sea snail were done and the cross-sectional images were used to perform tri-dimensional (3D) visualization of the objects. Both kind of images (cross-sectional and 3D) are presented. Cross-sectional images using energy intervals of the spectrum are shown. Also, a simulation study of the influence of discharges (intrinsic to the MicroPatterned Gaseous Detector operation) in the resulting cross-sectional image was done and presented, showing no significant influence on the final image.

Interpretability of coronary CT angiography performed with a novel whole-heart coverage high-definition CT scanner in 300 consecutive patients with coronary artery bypass grafts

AimsCoronary CT angiography (CCTA) is an accurate non-invasive tool for the evaluation of coronary artery bypass graft (CABG). However, inability to sustain a long breath-hold, high heart rate (HR) and atrial fibrillation may affect image quality. Moreover, radiation exposure is still a matter of some concern. A scanner combining 0.23-mm spatial resolution, new iterative reconstruction and fast gantry rotation time has been recently introduced in the clinical field. The aims of our study were to evaluate interpretability, radiation exposure and diagnostic accuracy of CCTA performed with the latest generation of cardiac-CT scanners compared to invasive coronary angiography (ICA) in the assessment of bypass grafts, and non-grafted and post-anastomotic native coronary arteries. Methods and resultsWe prospectively enrolled 300 patients undergoing clinically indicated CCTA with a 16-cm z-axis coverage, 256-detector rows, and 0.28-sec gantry rotation time scanner. Coronary artery and graft interpretability, image quality and effective dose (ED) were assessed in all patients and diagnostic accuracy was evaluated in a subgroup of 100 patients who underwent ICA.Mean HR during the scan was 69.6 ± 10.8. Sinus rhythm was present in 118 patients with HR < 75 bpm and in 112 patients with HR ≥ 75 bpm, while 70 patients had atrial fibrillation. CABG interpretability was 100%. Compared to ICA, CCTA was able to correctly detecting occlusions or significant stenoses of all CABG segments. Overall interpretability of native coronary segments was 95.6%. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of coronary arteries were 98.3%, 97.4%, 93.1%, 99.3% and 96.5%, respectively. The diagnostic accuracy in a patient based analysis was 95.2%. Mean ED was 3.14 ± 1.7 mSv. ConclusionsThe novel whole-heart coverage CT scanner allows to evaluating CABG and native coronary arteries with excellent interpretability and low radiation exposure even in the presence of unfavorable heart rhythm.

A QR Code Secret Hiding Scheme against Contrast Analysis Attack for the Internet of Things

Due to the advantages of larger content and error correction capability, quick response (QR) code is commonly used as a tagging technology for the Internet of Things (IoT) recently. However, the cover message of QR code can be easily decoded by a QR code reader, which causes the security and privacy of the cover message to raise the important issues. In this paper we present a new secret hiding scheme based on QR code. The proposed scheme has low computational complexity and is suitable for low-power devices in IoT systems because of utilizing the error correction property of QR code to hide secret information. The proposed scheme hides the secret information without changing the cover message of QR code and the user can get the cover message by using a general scanner, which contributes to reducing attacker’s curiosity. The hidden secret information can be read by a special scanner with the help of the user key. One thing which is better than other known schemes is that the proposed scheme can resist contrast analysis attack. In addition, experimental results show the proposed scheme has feasibility, low computational complexity, and high hiding payload.

Plaque quantification by coronary computed tomography angiography using intravascular ultrasound as a reference standard: a comparison between standard and last generation computed tomography scanners.

The emerging role of coronary computed tomography angiography (CCTA) as a non-invasive tool for atherosclerosis evaluation is supported by data reporting a good correlation between CCTA and intravascular ultrasound (IVUS) for plaque volume quantification. Aim of the present study was to evaluate whether a last generation CT-scanner may improve coronary plaque volume assessment using IVUS as standard-of-reference. From a registry of 1915 consecutive, all-comers, patients who underwent a clinically indicated IVUS evaluation we enrolled 59 patients who underwent CCTA with a 64-slice CT (Group 1) and 59 patients who underwent CCTA with whole-heart coverage CT scanner (Group 2). Patients who underwent CCTA with unfavourable heart rhythm were not excluded from the analysis. Image quality (4-point Likert scale) focused on plaque analysis was evaluated. Plaque volume quantification by CCTA was compared to IVUS. No difference in clinical characteristics was found between Group 1 and Group 2. Plaque volume quantification by CCTA was considered not feasible in 11 plaques of Group 1 and in 4 plaques of Group 2 (P = 0.09). Higher correlation for plaque volume quantification by CCTA vs. IVUS was demonstrated in Group 2 when compared with Group 1 (r = 0.9888 vs. 0.9499; P < 0.0001). The Bland-Altman analysis showed plaque volume overestimation by CCTA of 11.9 mm3 in Group 1 and 4 mm2 in Group 2 (P < 0.001). Effective radiation dose of CCTA was significantly lower in Group 2 vs. Group 1 (2.7 ± 0.9 vs. 8.1 ± 3.6 mSv, respectively; P < 0.001). CCTA using a new scanner generation showed to be an accurate non-invasive tool to assess and quantify coronary plaque volume.

TLS FOR DETECTING SMALL DAMAGES ON A BUILDING FAÇADE

Abstract. Weathering, aging, infiltration, solar radiation and several other factors cause the deterioration of buildings and infrastructures and hence the need for periodical maintenance and restoration. The need for maintenance has been traditionally determined based on visual inspections of qualified operators. Since this process is obviously time consuming and quite expensive, especially when the considered building is quite large and high, then a number of recent studies have been recently published proposing remote sensing tools in order to ease the monitoring process. Among the possible spatial data acquisition sensors, terrestrial laser scanning has been considered in several of the existing studies, mostly because of its high reliability, to cope with cracks and defect detection up to the millimeter level of resolution, which is the typical accuracy of the current generation of professional laser scanners. This paper considers the problem of detecting small defects on the façade of a University building. Similar to other previous studies, in this work defect detection is accomplished by considering distances with respect to a planar surface locally fitted on the building façade. Then, statistical filtering and machine learning tools have been implemented in order to cope with damage detection of the brick surfaces at sub-millimeter level.

PET detectors with 127 ps CTR for the Tachyon-II time-of-flight PET scanner.

The signal-to-noise ratio (SNR) of the reconstructed image of Positron Emission Tomography (PET) can be improved by the timing measurement. In this article, we designed, fabricated and tested 32 time-of-flight (TOF) detectors for the second generation of Tachyon TOF-PET scanners. The detector module consists of two arrays of 2 × 12 lutetium-yttrium oxyorthosilicate (LYSO) crystal cubes of 6 ×6× 6 mm3. The discrete crystals were coupled to the 6 mm silicon photomultipliers (SiPMs) with optical glue. All the SiPM were tested for dark current. To correct the errors in the timing measurements caused by time-walk, two compensation methods (log-correction and linear-correction) based on the relationship between energy and timing information were purposed. As a comparison, the SiPM arrays coupled to 4 mm and 6 mm side crystal cube without optical glue were tested for coincidence timing resolution (CTR). The mean and standard deviations (SD) of dark current for the 1536 tested SiPMs were 12.72 +/- 1.70 μA at the bias voltage of 31.5 V and the temperature of 20 °C (±1 °C). CTR performance has increased by ~5% within a narrow energy window, and ~10% in a wide energy window by log-correction. The mean and SD of the CTR of 6 mm side crystal cube glue coupled was 126.9 +/- 3.6 ps for the 768 pairs of tested SiPMs. The detector is expected to provide a technical reference for the next generation of ultra-fast CTR commercial PET scanner using multilayer detectors.

UNSUPERVISED DOMAIN ADAPTION WITH ADVERSARIAL LEARNING (UDAA) FOR EMPHYSEMA SUBTYPING ON CARDIAC CT SCANS: THE MESA STUDY.

Emphysema quantification and sub-typing is actively studied on cohorts of full-lung high-resolution CT (HRCT) scans, with promising results. Transfer of quantification and classification tools to cardiac CT scans, which involve 70% of the lungs, is challenging due to lower image resolution and degradation of textural patterns. In this study, we propose an original deep-learning domain-adaptation framework to use a pre-existing dictionary of lung texture patterns (LTP), learned on gold-standard full-lung HRCT scans, to label emphysema regions on cardiac CT scans. The method exploits convolutional neural networks (CNNs) trained for: 1) supervised lung texture classification on synthetic cardiac images, and 2) adversarial learning to discriminate between real and synthetic cardiac images. Combination of the classification and adversarial tasks enables to label real cardiac CT scans, and is evaluated on the MESA cohort (N = 15,357 scans). Our results show that image features derived from the adversarial training preserve the labeling accuracy on synthetic scans. LTP histogram signatures generated on 4,315 longitudinal pairs of cardiac CT scans, show high level of consistency over time and scanner generations. The ability to robustly label emphysema texture patterns on cardiac CT scans will enable large-scale longitudinal studies over 10 years of follow-up, for better understanding of the disease progression.

DESIGN AND IMPLEMENTATION OF A LANGUAGE SCANNER GENERATOR (KnitAutoGen)

The need for fast, efficient and simple scanner generator that has the primary responsibility to perform efficiently gave rise to this paper. This is due to the fact that, on daily basis new technologies arise which brings a great improvement on the design of computer architecture. However, attention was given to speed, run time and resource availability of the design machine to be used since lexical analysis has an impact on how the compiler works. This paper seeks to develop a lexical analyzer (scanner generator) automatically by specifying the lexemes patterns to a lexical analyzer generator and compiling those patterns into a code that functions as a lexical analyzer. The scanner accepts characters as input and breaks them down to produce tokens by grouping the characters and not deviating from specifications. The project employs one of the different methods of lexical analyzer generator to perform pattern-matching on text using regular expression over a global character set. The paper shows how input is matched and specifies what to do when a pattern is matched. This was achieved with the use of regular expressions (RE) which were converted to non-deterministic finite automata (NFA) or deterministic finite automata (DFA). The regular expression and the regular grammar were thus joined together mathematically. Various results are presented and further work on micro compilers was proposed. Keyword: Scanner generator, Regular expression, KnitAutoGen, DFA, NFA. DOI : 10.7176/CTI/8-02

A new low-cost method of virtual cardiac dissection of computed tomographic datasets.

Computed tomography has an established role in the evaluation of a variety of cardiac disorders, including congenital heart diseases. The current generation of high-speed scanners produces volumetric data at low doses of radiation. The interpretation of cardiac anatomy, however, is generally limited to multiplanar assessment of two-dimensional images. The volume rendering technique provides an excellent three-dimensional demonstration of external morphology but offers little information about the intracardiac anatomy. The alternative approach of virtual cardiac dissection, which is a modification of volume rendering, on the other hand, provides crucial insights regarding the intracardiac anatomy. At present, virtual cardiac dissection requires expensive software packages. These software packages are not available in all countries, thus limiting its use in routine clinical care. We present here the details of a newly developed technique that permits virtual cardiac dissection using a personal computer and open-source software. Our technique involves no additional cost and can be achieved in the comfort of the office or operating room of the cardiologist, radiologist, or cardiac surgeon. This enhanced three-dimensional visualization of intracardiac anatomy will surely improve the understanding of the morphological details of both normal and malformed hearts. In addition, by permitting assessment in projections with which modern-day cardiologists and cardiac surgeons are conversant, it is likely to improve clinical decision-making. We illustrate here its potential utility in the morphologic assessment of the atrial septum and its deficiencies, along with malformations of the ventricular outflow tracts, including common arterial trunk.

Diagnostic accuracy of coronary CT angiography performed in 100 consecutive patients with coronary stents using a whole-organ high-definition CT scanner

AimsTo evaluate image quality, interpretability, diagnostic accuracy and radiation exposure of coronary CT angiography (CCTA) performed with a new scanner equipped with 0.23-mm spatial resolution, new generation iterative reconstruction, 0.28-second gantry rotation time and intra-cycle motion-correction algorithm in consecutive patients with coronary stents, including those with high heart rate (HR) and atrial fibrillation (AF). Materials and methodsWe enrolled 100 consecutive patients (85 males, mean age 65 ± 10 years) with previous coronary stent implantation scheduled for clinically indicated non-emergent invasive coronary angiography (ICA). Image quality, coronary interpretability and diagnostic accuracy vs. ICA were evaluated and the effective dose (ED) was recorded. ResultsMean HR during the scan was 67 ± 13 bpm. Twenty-six patients had >65 bpm HR during scanning and 13 patients had AF. Overall, image quality was high (Likert = 3.2 ± 0.9). Stent interpretability was 95.8% (184/192 stents). Among 192 stented segments, CCTA correctly identified 22 out of 24 with >50% in-stent restenosis (ISR) (sensitivity 92%). In a stent-based analysis, specificity, positive and negative predictive values and diagnostic accuracy for ISR detection were 91%, 99%, 60% and 91%, respectively. In a patient-based analysis, CCTA diagnostic accuracy was 85%. Overall, mean ED of CCTA was 2.4 ± 1.2 mSv. ConclusionsA whole-organ CT scanner was able to evaluate coronary stents with good diagnostic performance and low radiation exposure, also in presence of unfavorable HR and heart rhythm. Translational aspectThe present study is the first to evaluate the CCTA capability of detecting in-stent restenosis in consecutive patients, including those with high HR and AF, using a recent scanner generation that combines improved spatial and temporal resolution with wide coverage. Using the whole-organ high-definition CT scanner we obtained high quality images of coronary stents with good interpretability and diagnostic accuracy combined with low radiation exposure, even in patients with unfavorable HR or heart rhythm for CCTA evaluation.

TCT-458 Additional Diagnostic Value of CT Perfusion over Coronary CT Angiography in Stented Patients with Suspected In-stent Restenosis or Coronary Artery Disease Progression: ADVANTAGE study. Preliminary Results

Aim of the study is to assess the diagnostic performance of CCTA alone, CTP alone and CCTA plus CTP performed with the latest scanner generation that combine a whole-heart coverage with high spatial and temporal resolution, by using invasive coronary angiography (ICA) as standard of reference. A

Harmonizing finite element modelling for non-invasive strength estimation by high-resolution peripheral quantitative computed tomography

The finite element (FE) method based on high-resolution peripheral quantitative computed tomography (HR-pQCT) use a variety of tissue constitutive properties and boundary conditions at different laboratories making comparison of mechanical properties difficult. Furthermore, the advent of a second-generation HR-pQCT poses challenges due to improved resolution and a larger region of interest (ROI). This study addresses the need to harmonize results across FE models. The aims are to establish the relationship between FE results as a function of boundary conditions and a range of tissue properties for the first-generation HR-pQCT system, and to determine appropriate model parameters for the second-generation HR-pQCT system. We implemented common boundary conditions and tissue properties on a large cohort (N = 1371), and showed the relationships were highly linear (R2 > 0.99) for yield strength and reaction force between FE models. Cadaver radii measured on both generation HR-pQCT with matched ROIs were used to back-calculate a tissue modulus that accounts for the increased resolution (61 µm versus 82 µm), resulting in a modulus of 8748 MPa for second-generation HR-pQCT to produce bone yield strength and reaction force equivalent to using 6829 MPa for first-generation HR-pQCT. Finally, in vivo scans (N = 61) conducted on both generations demonstrated that the larger ROI in the second-generation system results in stronger bone outcome measures, suggesting it is not advisable to convert FE results across HR-pQCT generations without matching ROIs. Together, these findings harmonize FE results by providing a means to compare findings with different boundary conditions and tissue properties, and across scanner generations.

Low-Dose Coronary CT Angiography in Patients with Atrial Fibrillation: Comparison of Image Quality and Radiation Exposure with Two Different Approaches

To evaluate image quality, coronary interpretability and radiation exposure of coronary CT angiography (CCTA) performed in patients with atrial fibrillation (AF) with the latest scanner generation, comparing two different technical approaches. A new scanner that combines a 0.23mm spatial resolution, a new generation of iterative reconstruction, fast gantry rotation time and the intracycle motion-correction algorithm to improve the temporal resolution was recently introduced in the clinical field. We enrolled 105 consecutive patients with chronic AF who performed CCTA with a whole-heart coverage high-definition CT scanner (16-cm z-axis coverage with 256 detector rows, 0.28s gantry rotation time). Five of them were excluded for impaired renal function. Patients were randomized between a double acquisition protocol (50 patients, group 1) or a single acquisition protocol (50 patients, group 2). The image quality, coronary segment interpretability and effective dose (ED) of CCTA were assessed. The mean HR during the scan was 85.6±21bpm in group 1vs. 83.7±23bpm in Group 2, respectively (p<ns). In group 2, overall image quality was high and comparable with that of group 1 (Likert scale=3.2±1.4vs. 3.3±1.2, p=ns, in group 1 and 2, respectively). Coronary interpretability was high and similar between the two groups (97.5% and 97.1% in group 1 and 2, p =ns, respectively). Mean ED was significantly higher in group 1 than in group 2 (5.3±1.8mSv vs. 2.7±0.7mSv, p<0.001). The novel whole-heart coverage CT scanner allows to perform CCTA with a single-acquisition protocol with high image quality and low radiation exposure in AF patients.

Rationale and design of advantage (additional diagnostic value of CT perfusion over coronary CT angiography in stented patients with suspected in-stent restenosis or coronary artery disease progression) prospective study

BackgroundRecent studies demonstrated a significant improvement in the diagnostic performance of coronary CT angiography (CCTA) for the evaluation of in-stent restenosis (ISR). However, coronary stent assessment is still challenging, especially because of beam-hardening artifacts due to metallic stent struts and high atherosclerotic burden of non-stented segments. Adenosine-stress myocardial perfusion assessed by CT (CTP) recently demonstrated to be a feasible and accurate tool for evaluating the functional significance of coronary stenoses in patients with suspected coronary artery disease (CAD). Yet, scarce data are available on the performance of CTP in patients with previous stent implantation. Aim of the studyWe aim to assess the diagnostic performance of CCTA alone, CTP alone and CCTA plus CTP performed with a new scanner generation using quantitative invasive coronary angiography (ICA) and invasive fractional flow reserve (FFR) as standard of reference. MethodsWe will enroll 300 consecutive patients with previous stent implantation, referred for non-emergent and clinically indicated invasive coronary angiography (ICA) due to suspected ISR or progression of CAD in native coronary segments. All patients will be subjected to stress myocardial CTP and a rest CCTA. The first 150 subjects will undergo static CTP scan, while the following 150 patients will undergo dynamic CTP scan. Measurement of invasive FFR will be performed during ICA when clinically indicated. ResultsThe primary study end points will be: 1) assessment of the diagnostic performance (diagnostic rate, sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy) of CCTA, CTP, combined CCTA-CTP and concordant CCTA-CTP vs. ICA as standard of reference in a territory-based and patient-based analysis; 2) assessment of sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CCTA, CTP, combined CCTA-CTP and concordant CCTA-CTP vs. invasive FFR as standard of reference in a territory-based analysis. ConclusionsThe ADVANTAGE study aims to provide an answer to the intriguing question whether the combined anatomical and functional assessment with CCTA plus CTP may have higher diagnostic performance as compared to CCTA alone in identifying stented patients with significant ISR or CAD progression.

Quantitative transmission ultrasound tomography: Imaging and performance characteristics.

PurposeQuantitative Transmission (QT) ultrasound has shown promise as a breast imaging modality. This study characterizes the performance of the latest generation of QT ultrasound scanners: QT Scanner 2000.MethodsThe scanner consists of a 2048‐element ultrasound receiver array for transmission imaging and three transceivers for reflection imaging. Custom fabricated phantoms were used to quantify the imaging performance parameters. The specific performance parameters that have been characterized are spatial resolution (as point spread function), linear measurement accuracy, contrast to noise ratio, and image uniformity, in both transmission and reflection imaging modalities.ResultsThe intrinsic in‐plane resolution was measured to be better than 1.5 mm and 1.0 mm for transmission and reflection modalities respectively. The linear measurement accuracy was measured to be, on average, approximately 1% for both the modalities. Speed of sound image uniformity and measurement accuracy were calculated to be 99.5% and <0.2% respectively. Contrast to noise ratio (CNR) measurements vary as a function of object size.ConclusionsThe results show an improvement in the imaging performance of the system in comparison to earlier ultrasound tomography systems, which are applicable to clinical applications of the system, such as breast imaging.

Development of a congenital cardiovascular computed tomography imaging registry: Rationale and implementation

BackgroundThe cumulative exposure and risk of anesthesia, vascular access, contrast agents and radiation is emerging as a significant lifelong burden in patients with congenital heart disease (CHD). Latest generation computerized tomographic (CT) scanners are increasingly used for high resolution cardiovascular imaging and have both hardware and post processing radiation dose reduction strategies that can be implemented. Currently, these dose reduction strategies are not uniformly applied and there is a large variability in radiation dose used for the performance of CT in CHD. MethodsWe propose the development and implementation of a prospective, multi-center and multi-specialty consortium to measure the variability of use, risk and image quality of CT scans in patients of all ages with CHD. The primary goals of this collaboration are 1) define variability of use, diagnostic quality, and risk of cardiac CT 2) establish best practice guidelines designed to optimize diagnostic image quality with appropriate use of radiation and anesthesia exposure 3) provide institution specific feedback compared with the group norm across participating centers 4) improve the level of evidence for the use of CT in CHD through the collection of prospective and multi-institutional data. ConclusionsProspective multi-institutional data is needed to inform risk estimates of CT in CHD using current generation scanners and aggressive dose optimization techniques. This registry will provide a platform for future collaboration establishing a multi-modality risk assessment tool specific to patients with CHD.

Impact of event positioning algorithm on performance of a whole-body PET scanner using one-to-one coupled detectors

The advent of silicon photomultipliers (SiPMs) has introduced the possibility of increased detector performance in commercial whole-body PET scanners. The primary advantage of these photodetectors is the ability to couple a single SiPM channel directly to a single pixel of PET scintillator that is typically 4 mm wide (one-to-one coupled detector design). We performed simulation studies to evaluate the impact of three different event positioning algorithms in such detectors: (i) a weighted energy centroid positioning (Anger logic), (ii) identifying the crystal with maximum energy deposition (1st max crystal), and (iii) identifying the crystal with the second highest energy deposition (2nd max crystal). Detector simulations performed with LSO crystals indicate reduced positioning errors when using the 2nd max crystal positioning algorithm. These studies are performed over a range of crystal cross-sections varying from 1 × 1 mm2 to 4 × 4 mm2 as well as crystal thickness of 1 cm to 3 cm. System simulations were performed for a whole-body PET scanner (85 cm ring diameter) with a long axial FOV (70 cm long) and show an improvement in reconstructed spatial resolution for a point source when using the 2nd max crystal positioning algorithm. Finally, we observe a 30–40% gain in contrast recovery coefficient values for 1 and 0.5 cm diameter spheres when using the 2nd max crystal positioning algorithm compared to the 1st max crystal positioning algorithm. These results show that there is an advantage to implementing the 2nd max crystal positioning algorithm in a new generation of PET scanners using one-to-one coupled detector design with lutetium based crystals, including LSO, LYSO or scintillators that have similar density and effective atomic number as LSO.