Splitting test experimental dataset of hollow concrete blocks.

Masonry structures are widely used nowadays for their advantages like low-cost workmanship, efficiency and fast construction techniques. The compressive strength of the materials that compose masonry (block and mortar) is very important to the behavior of the system, but the tensile strength is even more significant for the standards and building codes. In this work, a dataset for indirect tensile tests of hollow concrete blocks is obtained. Splitting tests as described in ASTM C-1006-13 are applied. Two sets of blocks were tested, one with medium compressive strength and the other with high compressive strength. The first set was tested in three directions named A, B, and C; the second one was tested in two directions, A and B. The data was collected with a servo-hydraulic machine. The data is presented in tables and can be used by material researchers, as well as in numerical modeling.

Dynamics of SARS-CoV-2 Variants of Concern in Brazil, Early 2021.

Brazil is the country with the second-largest number of deaths due to the coronavirus disease-2019 (COVID-19). Two variants of concern (VOCs), Alpha (B.1.1.7) and Gamma (P.1), were first detected in December 2020. While Alpha expanded within an expected rate in January and February 2021, its prevalence among new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cases started to decrease in March, which coincided with the explosion of Gamma variant incidence all over the country, being responsible for more than 95% of the new cases over the following months. A significantly higher viral load [i.e., mean cycle threshold (Ct) values] for Gamma in comparison to non-VOC samples was verified by the analysis of a large data set of routine reverse transcription-PCR (RT-PCR) exams. Moreover, the rate of reinfections greatly increased from March 2021 onward, reinforcing the enhanced ability of Gamma to escape the immune response. It is difficult to predict the outcomes of competition between variants since local factors like frequency of introduction and vaccine coverage play a key role. Genomic surveillance is of uttermost importance for the mitigation of the pandemic.

Point Organ Radiation Dose in Abdominal CT: Effect of Patient Off-Centering in an Experimental Human Cadaver Study.

To determine the effect of patient off-centering on point organ radiation dose measurements in a human cadaver scanned with routine abdominal CT protocol. A human cadaver (88 years, body-mass-index 20 kg/m2) was scanned with routine abdominal CT protocol on 128-slice dual source MDCT (Definition Flash, Siemens). A total of 18 scans were performed using two scan protocols (a) 120 kV-200 mAs fixed-mA (CTDIvol 14 mGy) (b) 120 kV-125 ref mAs (7 mGy) with automatic exposure control (AEC, CareDose 4D) at three different positions (a) gantry isocenter, (b) upward off-centering and (c) downward off-centering. Scanning was repeated three times at each position. Six thimble (in liver, stomach, kidney, pancreas, colon and urinary bladder) and four MOSFET dosimeters (on cornea, thyroid, testicle and breast) were placed for calculation of measured point organ doses. Organ dose estimations were retrieved from dose-tracking software (eXposure, Radimetrics). Statistical analysis was performed using analysis of variance. There was a significant difference between the trends of point organ doses with AEC and fixed-mA at all three positions (p < 0.01). Variation in point doses between fixed-mA and AEC protocols were statistically significant across all organs at all Table positions (p < 0.001). There was up to 5-6% decrease in point doses with upward off-centering and in downward off-centering. There were statistical significant differences in point doses from dosimeters and dose-tracking software (mean difference for internal organs, 5-36% for fixed-mA & 7-48% for AEC protocols; p < 0.001; mean difference for surface organs, >92% for both protocols; p < 0.0001). For both protocols, the highest mean difference in point doses was found for stomach and lowest for colon. Measured absorbed point doses in abdominal CT vary with patient-centering in the gantry isocenter. Due to lack of consideration of patient positioning in the dose estimation on automatic software-over estimation of the doses up to 92% was reported.

Assessment of sub-milli-sievert abdominal computed tomography with iterative reconstruction techniques of different vendors.

AIM: To assess diagnostic image quality of reduced dose (RD) abdominal computed tomography (CT) with 9 iterative reconstruction techniques (IRTs) from 4 different vendors to the standard of care (SD) CT. METHODS: In an Institutional Review Board approved study, 66 patients (mean age 60 ± 13 years, 44 men, and 22 women) undergoing routine abdomen CT on multi-detector CT (MDCT) scanners from vendors A, B, and C (≥ 64 row CT scanners) (22 patients each) gave written informed consent for acquisition of an additional RD CT series. Sinogram data of RD CT was reconstructed with two vendor-specific and a vendor-neutral IRTs (A-1, A-2, A-3; B-1, B-2, B-3; and C-1, C-2, C-3) and SD CT series with filtered back projection. Subjective image evaluation was performed by two radiologists for each SD and RD CT series blinded and independently. All RD CT series (198) were assessed first followed by SD CT series (66). Objective image noise was measured for SD and RD CT series. Data were analyzed by Wilcoxon signed rank, kappa, and analysis of variance tests. RESULTS: There were 13/50, 18/57 and 9/40 missed lesions (size 2-7 mm) on RD CT for vendor A, B, and C, respectively. Missed lesions includes liver cysts, kidney cysts and stone, gall stone, fatty liver, and pancreatitis. There were also 5, 4, and 4 pseudo lesions (size 2-3 mm) on RD CT for vendor A, B, and C, respectively. Lesions conspicuity was sufficient for clinical diagnostic performance for 6/24 (RD-A-1), 10/24 (RD-A-2), and 7/24 (RD-A-3) lesions for vendor A; 5/26 (RD-B-1), 6/26 (RD-B-2), and 7/26 (RD-B-3) lesions for vendor B; and 4/20 (RD-C-1) 6/20 (RD-C-2), and 10/20 (RD-C-3) lesions for vendor C (P = 0.9). Mean objective image noise in liver was significantly lower for RD A-1 compared to both RD A-2 and RD A-3 images (P < 0.001). Similarly, mean objective image noise lower for RD B-2 (compared to RD B-1, RD B-3) and RD C-3 (compared to RD C-1 and C-2) (P = 0.016). CONCLUSION: Regardless of IRTs and MDCT vendors, abdominal CT acquired at mean CT dose index volume 1.3 mGy is not sufficient to retain clinical diagnostic performance.

Quantification of interstitial fluid on whole body CT: comparison with whole body autopsy.

PURPOSE: Interstitial fluid accumulation can occur in pleural, pericardial, and peritoneal spaces, and subcutaneous tissue planes. The purpose of the study was to assess if whole body CT examination in a postmortem setting could help determine the presence and severity of third space fluid accumulation in the body. MATERIALS AND METHODS: Our study included 41 human cadavers (mean age 61 years, 25 males and 16 females) who had whole-body postmortem CT prior to autopsy. All bodies were maintained in the morgue in the time interval between death and autopsy. Two radiologists reviewed the whole-body CT examinations independently to grade third space fluid in the pleura, pericardium, peritoneum, and subcutaneous space using a 5-point grading system. Qualitative CT grading for third space fluid was correlated with the amount of fluid found on autopsy and the quantitative CT fluid volume, estimated using a dedicated software program (Volume, Syngo Explorer, Siemens Healthcare). RESULTS: Moderate and severe peripheral edema was seen in 16/41 and 7/41 cadavers respectively. It is not possible to quantify anasarca at autopsy. Correlation between imaging data for third space fluid and the quantity of fluid found during autopsy was 0.83 for pleural effusion, 0.4 for pericardial effusion and 0.9 for ascites. The degree of anasarca was significantly correlated with the severity of ascites (p < 0.0001) but not with pleural or pericardial effusion. There was strong correlation between volumetric estimation and qualitative grading for anasarca (p < 0.0001) and pleural effusion (p < 0.0001). CONCLUSION: Postmortem CT can help in accurate detection and quantification of third space fluid accumulation. The quantity of ascitic fluid on postmortem CT can predict the extent of anasarca.

Assessment of Filtered Back Projection, Adaptive Statistical, and Model-Based Iterative Reconstruction for Reduced Dose Abdominal Computed Tomography.

PURPOSE: To compare standard of care and reduced dose (RD) abdominal computed tomography (CT) images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), model-based iterative reconstruction (MBIR) techniques. MATERIALS AND METHODS: In an Institutional Review Board-approved, prospective clinical study, 28 patients (mean age 59 ± 13 years ), undergoing clinically indicated routine abdominal CT on a 64-channel multi-detector CT scanner, gave written informed consent for acquisition of an additional RD (<1 milli-Sievert) abdomen CT series. Sinogram data of RD series were reconstructed with FBP, ASIR, and MBIR and compared with FBP images of standard dose abdomen CT. Two radiologists performed randomized, independent, and blinded comparison for lesion detection, lesion margin, visibility of normal structures, and diagnostic confidence. RESULTS: Mean CT dose index volume was 10 ± 3.4 mGy and 1.3 ± 0.3 mGy for standard and RD CT, respectively. There were 73 "true positive" lesions detected on standard of care CT. Nine lesions (<8 mm in size) were missed on RD abdominal CT images which included liver lesions, liver cysts, kidney cysts, and paracolonic abscess. These lesions were missed regardless of patient size and types of iterative reconstruction techniques used for reconstruction of RD data sets. The visibility of lesion margin was suboptimal in (23/28) patients with RD FBP, (15/28) patients with RD ASIR, and (14/28) patients with RD MBIR compared to standard of care FBP images (P < 0.001). Diagnostic confidence for the assessment of lesions on RD images was suboptimal in most patients regardless of iterative reconstruction techniques. CONCLUSIONS: Clinically significant lesions (< 8 mm) can be missed on abdominal CT examinations acquired at a CT dose index volume of 1.3 mGy regardless of patients' size and reconstruction techniques (FBP, ASIR, and MBIR).

Tube potential and CT radiation dose optimization.

OBJECTIVE: This article describes tube potential and its effect on image quality and radiation dose for CT in different body regions and clinical indications. CONCLUSION: Tube potential is an important scanning parameter for radiation dose optimization. Reduction of tube potential results in increased image contrast of iodine-enhanced CT as well as increased image noise.

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans.

PURPOSE: To present a study of radiation dose measurements with a human cadaver scanned on a clinical CT scanner. METHODS: Multiple point dose measurements were obtained with high-accuracy Thimble ionization chambers placed inside the stomach, liver, paravertebral gutter, ascending colon, left kidney, and urinary bladder of a human cadaver (183 cm in height and 67.5 kg in weight) whose abdomen/pelvis region was scanned repeatedly with a multidetector row CT. The flat energy response and precision of the dosimeters were verified, and the slight differences in each dosimeter's response were evaluated and corrected to attain high accuracy. In addition, skin doses were measured for radiosensitive organs outside the scanned region with OSL dosimeters: the right eye, thyroid, both nipples, and the right testicle. Three scan protocols were used, which shared most scan parameters but had different kVp and mA settings: 120-kVp automA, 120-kVp 300 mA, and 100-kVp 300 mA. For each protocol three repeated scans were performed. RESULTS: The tube starting angle (TSA) was found to randomly vary around two major conditions, which caused large fluctuations in the repeated point dose measurements: for the 120-kVp 300 mA protocol this angle changed from approximately 110° to 290°, and caused 8%-25% difference in the point dose measured at the stomach, liver, colon, and urinary bladder. When the fluctuations of the TSA were small (within 5°), the maximum coefficient of variance was approximately 3.3%. The soft tissue absorbed doses averaged from four locations near the center of the scanned region were 27.2±3.3 and 16.5±2.7 mGy for the 120 and 100-kVp fixed-mA scans, respectively. These values were consistent with the corresponding size specific dose estimates within 4%. The comparison of the per-100-mAs tissue doses from the three protocols revealed that: (1) dose levels at nonsuperficial locations in the TCM scans could not be accurately deduced by simply scaling the fix-mA doses with local mA values; (2) the general power law relationship between dose and kVp varied from location to location, with the power index ranged between 2.7 and 3.5. The averaged dose measurements at both nipples, which were about 0.6 cm outside the prescribed scan region, ranged from 23 to 27 mGy at the left nipple, and varied from 3 to 20 mGy at the right nipple over the three scan protocols. Large fluctuations over repeated scans were also observed, as a combined result of helical scans of large pitch (1.375) and small active areas of the skin dosimeters. In addition, the averaged skin dose fell off drastically with the distance to the nearest boundary of the scanned region. CONCLUSIONS: This study revealed the complexity of CT dose fluctuation and variation with a human cadaver.

What is the minimal radiation dose that can be used for detecting pleural effusion?

OBJECTIVE: The objective of our study was to assess the effect of radiation dose reduction on the detection of pleural effusions, thickening, and calcifications. MATERIALS AND METHODS: Forty-five human cadavers (mean age at death, 60 ± 17 [SD] years; male-female ratio, 29:16; mean body mass index, 29 ± 5.7 [SD] kg/m(2)) were scanned at seven different dose levels (CT Dose Index volume [CTDIvol] = 20, 12, 10, 6, 4, 2, and 0.8 mGy) on a 128-MDCT unit (Definition FLASH). Images were reconstructed at a 3-mm slice thickness and 2-mm increment with filtered back projection (FBP) technique. Two chest radiologists independently reviewed all image series for the detection of pleural effusion, pleural calcification, and adjacent parenchymal opacification from atelectasis or consolidation. Objective image noise was measured at each dose level on the pleural effusion using ImageJ software. Data analysis was performed with the Student t test and kappa test. RESULTS: Pleural effusions were seen in 39 of 45 cadavers on image series acquired at 2-20 mGy. Only 14 of 39 pleural effusions were identified at 0.8 mGy. Pleural effusions were not detected in 25 of 39 cadavers at 0.8 mGy because of photon starvation and increased image noise. Patient size was significantly larger in subjects with undetected pleural effusion than in those with detectable pleural effusion at 0.8 mGy (p < 0.01). Pleural calcifications and thickening (seen at 2-10 mGy images in three of three cadavers) were not identified on 0.8-mGy FBP images. On the other hand, adjacent parenchymal opacification could be assessed at all dose levels. The mean CT numbers of the pleural effusion were significantly lower on 0.8-mGy images than on images obtained at all other dose levels (-21 ± 55 [SD] vs 17.6 ± 19 HU, respectively) (p < 0.001). CONCLUSION: Pleural effusions, thickening, and calcifications can be seen on FBP images reconstructed at a CTDIvol as low as 2 mGy (32-cm body phantom). CT at 0.8 mGy may provide suboptimal information on very small pleural effusions, pleural thickening, and calcifications.

Role of compressive sensing technique in dose reduction for chest computed tomography: a prospective blinded clinical study.

PURPOSE: The purpose of this study was to assess pulmonary lesion detection, diagnostic confidence, and noise reduction in sparse-sampled (SpS) computed tomographic (CT) data of submillisievert (SubmSv) chest CT reconstructed with iterative reconstruction technique (IRT). MATERIALS AND METHODS: This Human Insurance Portability and Accountability-compliant, institutional review board-approved prospective study was performed using SpS-SubmSv IRT chest CT in 10 non-obese patients (body-mass index, 21-35 kg/m; age range, 26-90 years). Written informed consent was obtained. The patients were scanned at standard-dose CT (mean [SD] volumetric CT dose index, 6 [0.9] mGy; mean [SD] dose-length product, 208 ± 44 mGy·cm; and mean [SD] effective dose, 3 [0.6] mSv) and at SubmSv dose (1.8 [0.2] mGy, 67 [2] mGy·cm, 0.9 [0.03] mSv, respectively) on a Philips 128-slice CT scanner with double z-sampling. Sparse angular sampling data were reconstructed using 25% of the angular projections from the SubmSv sinogram to reduce the number of views and radiation dose by approximately 4-fold. Hence, the patients were scanned and then, simulation-based sparse sampling was performed with a resultant dose hypothetical SpS scan estimated mathematically (0.2 mSv). From each patient data, 3 digital imaging and communications in medicine series were generated: SpS-SubmSv with IRT, fully sampled SubmSv filtered back projection (FBP), and fully sampled standard-dose FBP (SD-FBP). Two radiologists independently assessed these image series for detection of lung lesions, visibility of small structures, and diagnostic acceptability. Objective noise was measured in the thoracic aorta, and noise spectral density was obtained for SpS-SubmSv IRT, SubmSv-FBP, and SD-FBP. RESULTS: The SpS-SubmSv IRT resulted in 75% (0.2/0.9 mSv) and 92% (0.2/2.9 mSv) dose reduction, when compared with the fully sampled SubmSv-FBP and SD-FBP, respectively. Images of SpS-SubmSv displayed all 46 lesions (most <1 cm, 30 lung nodules, 7 ground glass opacities, 9 emphysema) seen on the SubmSv-FBP and SD-FBP data sets. Lesion margins with sparse-sampled data were deemed acceptable compared with both SubmSv-FBP and SD-FBP. Overall diagnostic confidence was maintained with SpS-SubmSv IRT despite the presence of minor pixilation artifacts in 3 of 10 cases. The SpS-SubmSv IRT showed 63% and 38% noise reduction when compared with SubmSv-FBP (P < 0.0001) and SD-FBP (P < 0.01), respectively, with no significant change in Hounsfield unit values (P > 0.05). Noise-spectral density showed that SpS-SubmSv IRT gives a linear decrease over frequency in the semilog plot and an exponential decrease of noise power over frequency compared with SubmSv-FBP and SD-FBP. CONCLUSIONS: More than 90% dose reduction could be achieved with one-fourth sparse-sampled and SubmSv chest CT examination when reconstructed with IRT. Chest CT dose at one fourth of a millisievert with SpS is possible with optimal lesion detection and diagnostic confidence for the evaluation of pulmonary findings.

Computed tomography (CT) of the chest at less than 1 mSv: an ongoing prospective clinical trial of chest CT at submillisievert radiation doses with iterative model image reconstruction and iDose4 technique.

PURPOSE: To assess lesion detection and diagnostic confidence of computed tomography (CT) of the chest performed at less than 1 mSv with 2 iterative reconstruction (IR) techniques. MATERIALS AND METHODS: Ten patients gave written informed consent for the acquisitions of images at submillisievert dose (0.9 mSv), in addition to clinical standard-dose (SD) chest CT (2.9 mSv). Submillisievert images were reconstructed with iDose and iterative model reconstruction (IMR). Two radiologists assessed lesion detection, margins, diagnostic confidence, and visibility of small structures. Objective noise and noise spectral density were measured. RESULTS: Lesion detection was identical for standard-dose filtered back projection (FBP), submSv iDose, and submSv IMR. Lesion margins were better seen for 30% of detected lung lesions with submSv IMR compared to standard-dose FBP and submSv iDose (P < 0.05). Visibility of abdominal structures, and diagnostic confidence with submSv iDose and submSv IMR were similar to standard-dose FBP. There was 21% to 64% noise reduction with submSv IMR and 1% to 15% higher noise with iDose compared to standard-dose FBP (P < 0.0001). CONCLUSIONS: Submillisievert IMR improves delineation of lesion margins compared to standard-dose FBP and submSv iDose.

Radiation dose optimization and thoracic computed tomography.

In the past 3 decades, radiation dose from computed tomography (CT) has contributed to an increase in overall radiation exposure to the population. This increase has caused concerns over harmful effects of radiation dose associated with CT in scientific publications as well as in the lay press. To address these concerns, and reduce radiation dose, several strategies to optimize radiation dose have been developed and assessed, including manual or automatic adjustment of scan parameters. This article describes conventional and contemporary techniques to reduce radiation dose associated with chest CT.

Iterative image reconstruction and its role in cardiothoracic computed tomography.

Revolutionary developments in multidetector-row computed tomography (CT) scanner technology offer several advantages for imaging of cardiothoracic disorders. As a result, expanding applications of CT now account for >85 million CT examinations annually in the United States alone. Given the large number of CT examinations performed, concerns over increase in population-based risk for radiation-induced carcinogenesis have made CT radiation dose a top safety concern in health care. In response to this concern, several technologies have been developed to reduce the dose with more efficient use of scan parameters and the use of "newer" image reconstruction techniques. Although iterative image reconstruction algorithms were first introduced in the 1970s, filtered back projection was chosen as the conventional image reconstruction technique because of its simplicity and faster reconstruction times. With subsequent advances in computational speed and power, iterative reconstruction techniques have reemerged and have shown the potential of radiation dose optimization without adversely influencing diagnostic image quality. In this article, we review the basic principles of different iterative reconstruction algorithms and their implementation for various clinical applications in cardiothoracic CT examinations for reducing radiation dose.

Miastenia gravis: presentación de tres casos / Myasthenia gravis: report of 3 cases

Se informan de tres casos de pacientes con miastenia gravis y embarazo. Todas las pacientes recibieron un régimen de medicación anticolineasterásica con buena respuesta terapéutica. En cada paciente se efectuaron estudios ecosonográficos y cardiotocográficos seriados. La prueba sin estrés (PSS) fue normal en todos los casos. El estudio ultrasonográfico mostró un feto con retraso en el crecimiento intrauterino (RCIU) que desarrolló miastenia gravis neonatal (MGN). Dos pacientes requirieron operación cesárea. La paciente restante inició trabajo de parto espontáneo que finalizó en parto eutócico. Dos fetos nacieron con buenas puntuaciones de Apgar y no desarrollaron MGN. En todas las pacientes se efectuó bloqueo epidural (BED) como método de analgesia-anestesia

Estenosis del cordón umbilical e hydrops fetalis no inmunológico: presentación de un caso / Stenosis of the umbilical cord and non-immunologic hydrops fetalis: a case report

Se presenta un caso de hydrops fetalis no inmunológico (HFNI) asociado a constricción del cordón umbilical. La presencia de edema fetal generalizado y acumulación de líquido en los compartimientos serosos del feto sin evidencia de isoinmunización, especialmente isoinmunización al factor Rh, fue el criterio empleado para el diagnóstico de HFNI. El cordón umbilical mostró constricción y oclusión vascular con anormalidad de la gelatina de Wharton. Se sugiere la estenosis del cordón umbilical como la causa subyacente del HFNI y muerte fetal