Volumetric Calculations Research Articles

Micro-CT based quantitative evaluation of caries excavation

Objectives To optimize a microtomographic (micro-CT) technique to quantitatively evaluate the effectiveness of contemporary caries-excavation techniques. Methods A beam-hardening curve was obtained from an initial reconstruction of a wedge-shaped hydroxyapatite (HAp) block and fitted with a 5th order polynomial function, after which each micro-CT tooth slice was corrected accordingly. Calibration of the 8-bit gray values into mineral-density values was obtained by scanning, reconstructing and processing volume of interests (VOIs) of HAp phantoms with different mineral densities (0.25, 0.75, 3.14 g/cm 3). One carious tooth was scanned before and after caries removal with an experimental enzyme-based gel. After reconstruction, a 3D-median filter was applied to each micro-CT slice, and a connected threshold grower algorithm was used to blank-out undesired structures in each slice. Volume rendering with a look-up-table (LUT), based on mineral densities, was accomplished for the tooth before and after caries removal. Finally, the actual volume of excavated tissue was quantified. Results Correction for beam hardening produced tooth slices with relatively homogeneous gray values along the whole area of enamel and dentin. Accurate mineral-density values were obtained for enamel, dentin and carious regions (2.89, 1.74 and 0.27 g/cm 3, respectively). After pre-processing (3D-median filtering and connected threshold grower algorithm), acceptable segmentation of carious dentin based on gray values was accomplished (Otsu method, gray value = 75 or mineral density = 1.12 g/cm 3), from which quantitative volumetric parameters were calculated. Significance Accurate calibration, standardization of scanning and reconstruction steps and adequate pre-processing of micro-CT slices allowed detailed volumetric calculation of caries-excavation techniques.

Imaging features of invasion and preoperative and postoperative tumor burden in previously untreated glioblastoma: Correlation with survival

Background:A paucity of data exists concerning the prognostic usefulness of preoperative and postoperative imaging after resection of glioblastoma multiforme (GBM). This study aimed to connect outcome with imaging features of GBM.Methods:Retrospective computer-assisted volumetric calculations quantified central necrotic (T0), gadolinium-enhanced (T1) and increased T2-weighted signal volumes (T2) in 70 patients with untreated GBM. Clinical and treatment data, including extent of resection (EOR), were obtained through chart review. T1 volume was used as a measure of solid tumor burden; and T2 volume, as an indicator of invasive isolated tumor cell (ITC) burden. Indicators of invasiveness included T2:T1 ratios as a propensity for ITC infiltration compared to solid tumor volumes and qualitative analysis of subependymal growth and infiltration of the basal ganglia, corpus callosum or brainstem. Cox multivariate analysis (CMVA) was used to identify significant associations between imaging features and survival.Results:In the 70 patients studied, significant associations with reduced survival existed for gadolinium-enhancing tumor crossing the corpus callosum (odds ratio, 3.14) and with increased survival with gross total resection (GTR) (GTR median survival, 62 weeks versus 37 and 34 weeks for sub-total resection and biopsy, respectively). For a selected “GTR-eligible” subgroup of 52 patients, prolonged survival was associated with smaller preoperative gadolinium-enhancing volume (T1) and actual GTR.Conclusion:Some magnetic resonance (MR) imaging indicators of tumor invasiveness (gadolinium-enhancing tumor crossing the corpus callosum) and tumor burden (GTR and preoperative T1 volume in GTR-eligible subgroup) correlate with survival. However, ITC-infiltrative tumor burden (T2 volume) and “propensity” for ITC invasiveness (T2:T1 ratio) did not impact survival. These results indicate that while the ITC component is the ultimate barrier to cure for GBM, the pattern of spread and volumes of gadolinium-enhancing solid tumor are more robust indicators of prognosis.

A revised approach to water footprinting to make transparent the impacts of consumption and production on global freshwater scarcity

Through the interconnectedness of global business, the local consumption of products and services is intervening in the hydrological cycle throughout the world to an unprecedented extent. In order to address the unsustainable use of global freshwater resources, indicators are needed which make the impacts of production systems and consumption patterns transparent. In this paper, a revised water footprint calculation method, incorporating water stress characterisation factors, is presented and demonstrated for two case study products, Dolmio ® pasta sauce and Peanut M&M's ® using primary production data. The method offers a simple, yet meaningful way of making quantitative comparisons between products, production systems and services in terms of their potential to contribute to water scarcity. As such, capacity is created for change through public policy as well as corporate and individual action. This revised method represents an alternative to existing volumetric water footprint calculation methods which combine green and blue water consumption from water scarce and water abundant regions such that they give no clear indication about where the actual potential for harm exists.

Determination of Placental Weight Using Two-dimensional Sonography and Volumetric Mathematic Modeling

An abnormally decreased placental weight has been linked to increased perinatal complications, including intrauterine fetal demise (IUFD) and fetal growth restriction (IUGR). Despite its promise, determining placental weight prenatally using three-dimensional systems is time-consuming and requires expensive technology and expertise. We propose a novel method using two-dimensional sonography that provides an immediate estimation of placental volume. Placental volume was calculated in 29 third-trimester pregnancies using linear measurements of placental width, height, and thickness to calculate the convex-concave shell volume within 24 hours of birth. Data were analyzed to calculate Spearman's rho (r (s)) and significance. There was a significant correlation between estimated placental volume (EPV) and actual placental weight (r (s) = 0.80, P < 0.001). Subgroup analysis of preterm gestations ( N = 14) revealed an even more significant correlation of EPV to actual placental weight (r (s) = 0.89, P < 0.001). Placental weight can be accurately predicted by two-dimensional ultrasound with volumetric calculations. This method is simple, rapid, and accurate, making it practical for routine prenatal care, as well as for high-risk cases with decreased fetal movement and IUGR. Routine EPV surveillance may decrease the rates of perinatal complications and unexpected IUFD.

Evaluation of Placental Volume at 7–10 + 6 Weeks of Pregnancy by 3D-Sonography

The aim of the study was to establish normative data for placental volume (PV) at 7–10 + 6 weeks of gestation using three-dimensional ultrasound (3DUS). The cross-sectional study involved 70 healthy pregnancies between 7 and 11 weeks. The VOCAL (Virtual Organ Computer-aided Analysis) method with a 30° rotation angle and six planes was used for volumetric calculations. Regression models were constructed to assess the correlation between PV and crown–rump length (CRL) adjusted by the determination coefficient ( R 2). The method proposed by Royston and Wright was used to establish the 2.5th; 10th; 50th; 90th and 97.5th percentiles (percentile = mean + K × SD). The intraclass correlation coefficient (ICC), Bland–Altman graphs and Student’s paired t-tests were used to assess intra- and interobserver variability. PV ranged from 1.7 to 42.6 cm 3, with a mean of 13.6 cm 3 (±9.4 cm 3). There was a strong correlation between PV and CRL; the exponential equation was the model that best expressed the correlation between them ( R 2 = 0.76). For CRL between 9 and 40 mm, the mean PV increased 10.5 times, while CRL increased only 4.4 times. Inter- and intraobserver correlation were excellent (ICC = 0.979 and 0.971, respectively). Bland–Altman graphs indicated a good reproducibility with a mean intraobserver and interobserver difference of 0.2 cm 3 (95% CI: −0.7–1.2 cm 3) and −0.2 cm 3 (95% CI: −1.3–0.9 cm 3), respectively. Reference limits were generated for first trimester PV assessed by 3DUS using the VOCAL method. There is a strong correlation between PV and CRL. Placental volume obtained through this method was highly reproducible.

Nomogram of amniotic fluid volume at 7 to 10 + 6 weeks of pregnancy by three-dimensional ultrasonography using the rotational method (VOCAL)

To establish normative data for amniotic fluid volume (AFV) between 7 and 10+6 weeks gestation using three-dimensional ultrasonography (3DUS). A cross-sectional study involving 74 normal pregnancies was performed to assess AFV. All measurements were performed using an endocavitary volumetric transducer. The VOCAL (virtual organ computer-aided analysis) method was used for volumetric calculations, with a 30 degrees rotation angle. The AFV was obtained subtracting the embryonic volume from the amniotic sac volume. To analyze the correlation between AFV and gestational age, regression models were constructed and adjustments were made using the determination coefficient (R2). The following AFV values were obtained for each week: mean, median, standard deviation, minimum and maximum. The method proposed by Royston and Wright was used to calculate the reference intervals according to crown-rump length (CRL). Mean AFV increased from 3.97 cm3 (range 1.17-10.97 cm3) at 7 to 7+6 weeks to 23.33 cm3 (ranging from 11.93 to 32.41 cm3) at 10 to 10+6 weeks of pregnancy. There was a significant correlation between AFV and gestational age (R2=0.635) and between AFV and CRL (R2=0.756). Mean AFV increased from 7.81 cm3 (ranging from 0.18 to 15.43 cm3) to 50.28 cm3 (range 16.49-84.07 cm3) for CRL between 12 and 40 mm. Reference limits for AFV using 3DUS were generated for pregnancies between 7 and 10+6 weeks according to CRL.

Ischemic lesion volume determination on diffusion weighted images vs. apparent diffusion coefficient maps

Though diffusion weighted imaging (DWI) is frequently used for identifying the ischemic lesion in focal cerebral ischemia, the understanding of spatiotemporal evolution patterns observed with different analysis methods remains imprecise. DWI and calculated apparent diffusion coefficient (ADC) maps were serially obtained in rat stroke models (MCAO): permanent, 90 min, and 180 min temporary MCAO. Lesion volumes were analyzed in a blinded and randomized manner by 2 investigators using (i) a previously validated ADC threshold, (ii) visual determination of hypointense regions on ADC maps, and (iii) visual determination of hyperintense regions on DWI. Lesion volumes were correlated with 24 hour 2,3,5-triphenyltetrazoliumchloride (TTC)-derived infarct volumes. TTC-derived infarct volumes were not significantly different from the ADC and DWI-derived lesion volumes at the last imaging time points except for significantly smaller DWI lesions in the pMCAO model (p=0.02). Volumetric calculation based on TTC-derived infarct also correlated significantly stronger to volumetric calculation based on last imaging time point derived lesions on ADC maps than DWI (p<0.05). Following reperfusion, lesion volumes on the ADC maps significantly reduced but no change was observed on DWI. Visually determined lesion volumes on ADC maps and DWI by both investigators correlated significantly with threshold-derived lesion volumes on ADC maps with the former method demonstrating a stronger correlation. There was also a better interrater agreement for ADC map analysis than for DWI analysis. Ischemic lesion determination by ADC was more accurate in final infarct prediction, rater independent, and provided exclusive information on ischemic lesion reversibility.

The geomorphologic response of a large pristine alluvial river to tremendous deforestation in the South American tropics: The case of the Araguaia River

The geomorphic response of the Araguaia River to catastrophic deforestation of the Cerrado since 1970s is discussed. With a mean annual discharge of 6500 m 3/s and a drainage area of ~ 380,000 km 2, the Araguaia River is the main system draining the savannas of Central Brazil. Here, we demonstrate that the river is undergoing a substantive increase in bed load transport and changes in its geomorphology. A multi-approach methodology was used and involved detailed geomorphologic mapping for three decades (60, 70, and 90), a budget of erosional and deposition areas using GIS, volumetric calculations, and estimations of bed load transport. Our results show that the alluvial plain is undergoing active sedimentation and 233 Mt of sediments were stored by channel activity in a reach 570 km long of the middle Araguaia. The bed load transport has increased 31% from 6.6 Mt in the sixties to 8.8 Mt in the 1990s and the channel pattern has been metamorphosed to some extent. This is an outstanding current example of short term geomorphic response to deforestation in a large pristine tropical fluvial system without direct human interventions in the channel.

Quantifying carbon and sulphate loss in drained acid sulphate soils

SummaryApproximately 25 years before they were sampled, one of a pair of adjacent and initially similar acid sulphate soils was drained. During the ensuing 25 years, the surface of the drained soil declined approximately 1.2 m relative to its undrained neighbour. The losses of carbon (C) and sulphur (S) from the drained soil were estimated as the difference between the amounts remaining in the drained soil and its undrained neighbour. I made these comparisons in two ways. Firstly, I determined the amounts of C and S by summing their volumetric concentrations to a common depth (relative to the Australian Height Datum) where these concentrations became equal. Secondly, I made comparisons using mass‐based concentrations and a material coordinate defined by integrating the bulk density profile down from the soil surface. In this latter convention, the distance is the cumulative mass of soil solids per unit area of cross‐section, measured to any depth from the soil surface. The former approach yields estimates of C loss almost 30% greater than the latter. The S loss based on volumetric calculations was approximately 25% greater than that based on mass‐based coordinates. These overestimates of loss of C and S arise because the depth‐based method fails to take account of the vertical movement of the soil solid accompanying drainage in these soils. As a result, chemical reactions and their products, which are uniquely identified with parcels of soil solids, have no unique depth in swelling soils over time. The material calculations are therefore correct, but I identify conditions where a conventional volume‐based estimate might be used.

What's difficult about chemistry? An Irish perspective

This semi-longitudinal investigation identified the chemistry topics that the majority of Irish chemistry pupils/students find difficult, from Junior Certificate level (age 15/16 years) right the way through to University level (age 18+). Pupils/students completed a five point, Likert-type questionnaire listing the topics covered in the different chemistry courses, which asked them whether they found each topic difficult or easy. They were also asked to identify which five topics they found most difficult, ranked 1 to 5. This paper highlights the topics that Irish pupils/students find difficult in chemistry. Topics identified by Irish students are similar to results of studies carried out in the UK by Ratcliffe and in Scotland by Johnstone. This study indicates that a number of topics ranked high in terms of perceived difficulty in both the Leaving Certificate chemistry pupils and University chemistry students’ lists. These topics were Volumetric Analysis Calculations, Redox Reactions and Concentration of Solutions. The persistence of these topics being seen as difficult throughout the pupils’/students’ experience of chemistry indicates that problems associated with these topics have never truly been addressed. Other findings indicate that the mathematical ability of the pupils/students has an effect on the topics pupils/students chose as difficult or very difficult.

Measurement of embryo volume at 7–10 weeks' gestation by 3D-sonography

SummaryThe embryo volume (EV) is an important parameter for the early diagnosis of growth disorders. The objective of this study was to establish normal data for EV at 7–10 weeks' gestation with three-dimensional ultrasonography (3DUS). A cross-sectional study involving 50 pregnancies was performed. An endocavitary volumetric transducer (3D5–8EK) was used for all measurements. The VOCAL (Virtual Organ Computer-aided AnaLysis) method with a 30° rotation angle was used for volumetric calculations. To analyse the correlation between EV and gestational age (GA) and crown–rump length (CRL), regression models were constructed. The mean, standard deviation, median, minimum and maximum values were calculated for each gestational age. The intraclass correlation coefficient (ICC) was used to determine inter- and intraobserver reliability. There was a significant correlation between EV and GA and CRL (R2 = 0.951 and R2 = 0.880, respectively). The exponential equation was the model that best expressed the correlation between these variables: [EV = exp(0.9481 × GA–8.117)] and [EV = 0.0871 exp(0.1207 × CRL)]. The mean EV ranged from 0.23 cm3 (95% CI 0.03–0.42) at 7 weeks to 3.91 cm3 (95% CI 3.85–3.96) at 10 weeks. Inter- and intraobserver correlation were excellent (ICC = 0.993 and 0.999, respectively). Embryo volume assessed through 3DUS increased from 7 to 10 weeks. Reference limits were generated for first trimester EV using 3DUS.

Cranial mesohepatectomy: a challenging parenchyma-preserving operation for colorectal liver metastases

Dear Editor: The treatment of colorectal liver metastases has evolved over time. Improvements in chemotherapeutic regimens coupled with a multidisciplinary approach have resulted in a greater number of patients undergoing liver resections and major surgical challenges. Chemotherapeutic injury to the liver mandates preservation of as much parenchymal volume as possible in order to minimize the risk of liver failure. Furthermore, the potential for second and third resections for recurrent disease mandates the maintenance as much as possible of the intrahepatic anatomical relationships. Our present report describes a cranial mesohepatectomy in a case considered to be inoperable by others. A 57-year-old woman presented to our institution with a colorectal liver metastasis. Approximately 1 year ago, she had undergone a low anterior resection for a nodal negative rectal adenocarcinoma (pT3N0V0L0R0G2). Adjuvant radiochemotherapy according to the MAYO protocol had been initiated but side effects led to its discontinuation after the first cycle. A computed tomography (CT) scan at the time of presentation showed a 19 cm in diameter central solitary liver lesion infiltrating the right and middle hepatic veins. A right trisectionectomy (resection of segments 4– 8) was considered but not pursued due to the high risk of postoperative liver insufficiency (calculated remnant liver volume of 215 ml). Careful study of CT images showed a right inferior hepatic vein draining part of the lateral sector of the right liver lobe. Virtual postresection reconstruction with computer-assisted three-dimensional CT showed adequate drainage of segments 5 and 6 and partial drainage of segment 4b (379 ml) via the right inferior hepatic vein. A cranial mesohepatectomy (segments 4a, 7, and 8) was undertaken. The lesion was resected en bloc with the right and middle hepatic veins. Pathological examination of the specimen showed tumor-free margins (R0 resection). The patient tolerated the operation well, with no signs of liver insufficiency. She was discharged on postoperative day 10. Surgical resection of colorectal liver metastases requires precise anatomical study of the individual intrahepatic anatomy. Recent developments in computer-assisted imaging provide improved visualization of the hepatic vascular and segmental anatomy and allow for volumetric calculation. Image-based computer assistance and three-dimensional reconstruction are particularly useful for planning challenging liver resections, such as cranial mesohepatectomy, minimizing the risk of postoperative liver failure. Int J Colorectal Dis (2009) 24:243 DOI 10.1007/s00384-008-0610-1

Gestational sac volume by 3D-sonography at 7–10 weeks of pregnancy using the VOCAL method

Establish normative data for gestational sac volume (GSV) between 7 and 10 weeks gestation using three-dimensional ultrasonography (3DUS). A cross-sectional study involving 74 normal pregnancies was performed to assess GSV between 7 and 10 weeks gestation. All measurements were performed using an endocavitary volumetric transducer. The virtual organ computer-aided analysis (VOCAL) method was used for volumetric calculations, with a 30 degrees rotation angle. To analyze the correlation between GSV and gestational age, regression models were constructed and adjustments were made using the determination coefficient (R (2)). For each week the mean, median, standard-deviation, minimum and maximum GSV values were calculated. The method proposed by Royston and Wright was used to calculate the reference intervals according to crown-rump length (CRL). The interclass correlation coefficient (ICC) and Bland-Altman graph were used to evaluate intraobserver variability. There was a high correlation between GSV and gestational age (R (2) = 0.816). Mean GSV increased from 8.50 cm(3) at 7 weeks to 44.35 cm(3) at 10 weeks. There was also a significant correlation between GSV and CRL (R (2) = 0.693) with mean GSV increasing from 5.00 to 50.28 cm(3) for CRL between 9 and 40 mm. Intraobserver variability was excellent with an ICC = 0.9997 (95% CI, 0.9994-0.9998), with an average difference between measurements of 0.5 cm(3). There is a correlation between GSV and CRL and this is a reproducible first trimester parameter. Reference limits for GSV using 3DUS were generated for pregnancies between 7 and 10 weeks.

Cyclic eruptions and sector collapses at Monowai submarine volcano, Kermadec arc: 1998–2007

Repeated multibeam bathymetric surveys at Monowai Cone, a shallow submarine basaltic volcano and part of the Monowai Volcanic Center in the northern Kermadec arc, were conducted in 1998, 2004, and 2007. These surveys document dramatic depth changes at the volcano including negative changes up to −176 m from two sector collapses and positive changes up to +138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars. One sector collapse occurred on the SE slope between 1998 and 2004 with a volume of ∼0.09 km3, and another occurred on the SW slope between 2004 and 2007 with a volume of ∼0.04 km3. The volume of positive depth change due to addition of volcanic material by eruption is of the same order: ∼0.05 km3 between 1998 and 2004 and ∼0.06 km3 between 2004 and 2007. During these time intervals, monitoring by the Polynesian Seismic Network detected frequent T wave swarms at Monowai, indicative of explosive eruptive activity every few months. An unusual T wave swarm on 24 May 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys, but no similarly anomalous T waves were detected between 2004 and 2007, probably because the Polynesian Seismic Network stations were acoustically shadowed from the second slide event. We interpret that the sector collapses on Monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano (&gt;20°). Moreover, there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano. Volumetric rate calculations suggest that these two processes may be more or less in equilibrium. The repeated collapses at Monowai are relatively modest in volume (involving only 0.1–0.5% of the edifice volume), have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes, and may be characteristic of how persistently active shallow submarine arc volcanoes grow.

Stereolithography build time estimation based on volumetric calculations

PurposeNot all the inventors and designers have access to computer‐aided design (CAD) software to transform their design or invention into a 3D solid model. Therefore, they cannot submit an STL file to a rapid prototyping (RP) service bureau for a quotation but perhaps only a 2D sketch or drawing. This paper proposes an alternative approach to build time estimation that will enable cost quotations to be issued before 3D CAD has been used.Design/methodology/approachThe study presents a method of calculating build time estimations within a target error limit of 10 per cent of the actual build time of a prototype. This is achieved by using basic volumetric shapes, such as cylinders and cones, added together to represent the model in the 2D sketch. By using this information the build time of the product is then calculated with the aid of models created in a mathematical solving software package.FindingsThe development of the build time estimator and its application to several build platforms are described together with an analysis of its performance in comparison with the benchmark software. The estimator was found to meet its target 10 per cent error limit in 80 per cent of the stereolithography builds that were analysed.Research limitations/implicationsThe estimator method was not able to handle multi‐component complex parts builds in a timely manner. There is a trade‐off between accuracy and processing time.Practical implicationsThe output from the estimator can be fed directly into cost quotations to be sent to RP bureau customers at a very early stage in the design process.Originality/valueUnlike all the other build estimators that were encountered, this method works directly from a 2D sketch or drawing rather than a 3D CAD file.

Three-Dimensional Transesophageal Echocardiographic Imaging and Volumetry of Giant Left Atrial Myxomas

TWO CASES IN WHICH real-time 3-dimensional transesophageal echocardiography (RT-3D TEE) was able to accurately depict a giant atrial myxoma showing prolapse into the left ventricle with resultant ventricular inflow obstruction are reported. Volumetric calculation of these masses using 3D techniques was more accurate than traditional 2-dimensional approaches when compared with ex vivo volumetric measurements by water displacement. These cases show the efficacy and potential usefulness of RT-3D TEE in cardiac surgery.

SU‐GG‐J‐130: Monte Carlo Simulation of Elekta XVI Cone Beam System and Dose Distribution in CTDI Phantom

Purpose: (1) To validate a Monte Carlo model for kV cone beam CT simulations. (2) To determine whether a bow‐shaped radial dose distribution with equal weighting can be applicable for cone beam CT. Method and Materials: A BEAMnrcMP Monte Carlo package has been employed and modified to simulate the Elekta XVI system operated at 120 kVp with collimator M20 and bowtie filter F1. Percentage Depth Dose (PDD) has been measured with PTW Farmer and Roos chambers in a CNMC water tank as well as a GAMMEX Solid Water phantom at 100cm SSD with 10cm backscatter. Dose profile at depth of 1cm has been measured with a Wellhofer IC‐10 chamber in Solid Water. Sample dose calculation is performed on a standard CDTI phantom aligned at Linac isocenter. Results: The simulated PDD curve agrees very well with both Farmer and Roos chamber measurements in water, but differ slightly with the Farmer chamber measurement in solid water at large depths and build‐up region. This is due to the higher attenuation of solid water in kV range and the loss of scatter equilibrium at phantom surface. Excellent agreement has been shown between the measured dose profile and the Monte Carlo simulations along both in‐plane and cross‐plane directions. The CTDI calculations have indicated that equal weighting on both the center and the periphery can result in errors of −1.1% while unequal standard weighting (1/3 for center and 2/3 for periphery) can result in errors of up to 8.1%. Conclusion: Our Monte Carlo model has been validated by various measurements to simulate the kV cone beams from the Elekta XVI system. A bow‐shape radial profile in CDTI phantom results in equal weightings for volumetric average dose calculations using only center and peripheral CTDI measurements. Investigation on patient dose deposition due to kV CBCT is in progress.

Yolk sac volume assessed by three‐dimensional ultrasonography using the VOCAL method

Establish normative data for yolk sac volume (YSV) at 7-10 weeks of gestation assessed by transvaginal three-dimensional ultrasonography (3D-US) using the VOCAL method and analyze its correlation with gestational age (GA) and crown-rump length (CRL). A cross-sectional study involving 62 normal pregnancies was performed to assess YSV from 7 to 10 weeks of gestational age. An endocavitary volumetric transducer (3D5-8EK) was used for all measurements. The VOCAL (Virtual Organ Computer-aided AnaLysis) method with a 30 degrees rotation angle was used for volumetric calculations. Regression models were constructed to analyze the correlation between YSV and GA or CRL The mean, standard deviation, median, minimum and maximum values were calculated for each gestational age. There was a poor correlation between YSV and GA or CRL. The quadratic regression was the model that best expressed the correlation between these variables: R2=0.188 for GA and R2=0.203 for CRL. The mean YSV went from 0.063 cm(3) (95% CI: 0.047; 0.080) at 7 weeks to 0.164 cm3 (95% CI 0.095; 0.232) at 10 weeks. Reference limits were generated for first trimester YSV using 3D-US. There was a poor correlation between YSV and GA or CRL.

Cardiac MRI for determining functional left ventricular parameters

To prove the accuracy of MR methods in the determination of left ventricular (LV) functional parameters and anatomy. At 1.5 T, 20 healthy volunteers and 22 patients with aortic valvular disease (stenosis n = 15, regurgitation n = 7) were examined. Functional parameters like cardiac output, ejection fraction, end-diastolic volume, aortic flow maximum, and time interval from the R-wave to maximum flow were obtained using a velocity encoding 2D FLASH sequence (TR 24 ms, TE 5 ms, venc 250 cm/sec) and segmented breath-hold cine FLASH 2D technique (TR 100 ms, TE 4.8 ms, flip angle 25 degrees, temporal resolution 50 ms). Invasive measurements (Fick principle) served as gold standard, intra- and interobserver variability were determined. Differences of functional parameters between normal volunteers and patients were detectable at a high level of significance (p < 0.0001). For cardiac output a superior correlation with the gold standard was found using flow measurements (r = 0.66, p < 0.0007) compared to volumetric calculations from cine studies (r = 0.47, p < 0.02). Interobserver variability was 2.5 +/- 2.7%/4.5 +/- 6.9% (flow quantification/calculations from cine studies), intraobserver variability was 1.7 +/- 1.6%/3.3 +/- 2.2%. MRI is an appropriate tool for determining LV functional parameters and anatomy. Differences between normal volunteers and patients with aortic valvular disease can be detected reliably. Flow measurements turned out to be more accurate than calculations from cine images. Therefore, flow quantification techniques should be preferred for clinical use.

Volumetric Imaging of the Malar Fat Pad and Implications for Facial Plastic Surgery

Volumetric Imaging of the Malar Fat Pad and Implications for Facial Plastic Surgery