Three-dimensional morphometry in ultrasound

Estimation of Three-dimensional Blood Flow with Ultrasound - Continuity Equation on Multiplane Dual-angle Doppler Imaging

Atherosclerosis plays the major role in myocardial infarction and stroke and its pathophysiology is closely related to blood flow. Among clinical imaging modalities, ultrasound has the highest temporal resolution. Doppler ultrasound has been clinically applied for blood flow measurement and several parameters obtained with Doppler have been considered as essential for diagnosis. However, conventional Doppler method merely measures one-dimensional component of the blood flow along the ultrasonic beam. Based on previous approaches with multi-angle Doppler measurement for two-dimensional (2D) blood flow, this study aims to expand 2D flow measurement into three-dimensional (3D) flow estimation by applying continuity equation on multiplane 2D velocity mapping. The algorithm was validated by numerical simulation based on computational fluid dynamics and comparison with particle image velocimetry of carotid artery model. The method visualized 3D spiral flow in the carotid artery bifurcation model where 2D blood flow showed Iaminar flow. Clinical application of 3D blood flow visualization will provide important information on pathophysiology in common sites of atherosclerosis.

Estimation of uterine volume: A comparison between Viewpoint and 3D ultrasound estimation in women undergoing laparoscopic hysterectomy

Objectives: To assess the three‐dimensional (3D) tool, Virtual Organ Computed‐aided AnaLysis™ (VOCAL) in the calculation of pre‐operative uterine volume and to correlate the measurements with those obtained with Viewpoint, using uterine dry weight (UDW) as the gold standard.

Methods: Prospective observational study of women consented for a laparoscopic hysterectomy (LH) at Nepean Hospital between October 2008 and November 2011. All women underwent detailed transvaginal scan (TVS) at the pre‐operative assessment. Two‐dimensional (D) images of the uterus were obtained both in the mid‐sagittal and transverse planes. 3D volumetric acquisitions were also obtained for each uterus in the mid‐sagittal plane. 2D measurements of the uterus in millimetres (Anterio‐Posterior, longitudinal and transverse) were recorded in Viewpoint software package (GE Healthcare ViewPoint, Germany); which then generated an estimated uterine volume (ml) using the ellipsoid formula. The 3D uterine volumetric datasets were reviewed using SonoView Pro and uterine volumes were estimated with off‐line processing using VOCAL™. The gold standard for comparison was UDW in grams (g), measured by the histopathologist at the time of analysis of the LH specimens. The relationship between the estimated uterine volumes and actual UDW was evaluated using correlation analysis. P‐values were calculated to ascertain the significance of these findings; P values &< 0.05 represented statistical significance.

Results: 76 women underwent LH during the study period. Complete data were available in 96% (74/76) of cases. The mean age of the women was 43.7 years and 92% were multiparous. The mean Viewpoint uterine volume was 283 ml, the mean VOCAL™ uterine volume was 249 ml and the mean UDW was 295 g. There was a significant correlation between UDW and estimated uterine volumes both for Viewpoint (R = 0.83, P < 0.001) and VOCAL™ (R = 0.97, P < 0.001), respectively. Viewpoint systematically overestimated weight by 43.1 g, whereas VOCAL™ underestimated by an average of 42.4 g, and this difference was statistically significant (P < 0.001). In terms of absolute values, the mean prediction error for VOCAL™ was −18.0 g and for Viewpoint it was 27.6 g (P &< 0.0001). Conclusion: VOCAL™ was found to be significantly more accurate than Viewpoint in the estimation of uterine volumes, and it was better correlated with UDW.

Estimation of gastrocnemius muscle volume using ultrasonography in children with spastic cerebral palsy

PURPOSE

This study aimed to investigate useful parameters for estimating gastrocnemius (GCM) muscle volume (MV) using ultrasonography (US) and anthropometry in children with spastic cerebral palsy (CP).

MATERIALS AND METHODS

Eighteen legs from nine children with spastic CP aged 2 to 6 years were investigated in this study. Tibial length (TL) of each leg was measured and muscle thickness (MT) and anatomical cross-sectional area (aCSA) of GCM muscles were assessed using US. The volume of the GCM was measured by magnetic resonance imaging (MRI) scans. The relationship of TL, MT, and aCSA with MV measured by MRI was investigated. Simple and multiple regression analyses were performed to establish muscle volume prediction equations.

RESULTS

Resting MT, aCSA, and TL were highly related to MV of both medial and lateral head of GCM determined by MRI. The MV prediction equation based on simple regression analysis resulted in r² values ranging from 0.591 to 0.832 (p<0.05). The r² values were higher using aCSA as independent variable than using MT. The MV prediction equation based on multiple regression analysis resulted in r² values ranging from 0.779 to 0.903 (p<0.05). However, the relatively high standard error of the estimate values ranged from 18.0-33.6% on simple regression and 15.5-25.6% on multiple regression. The contribution of aCSA was higher than that of MT for predicting MV of GCM.

CONCLUSION

Our study demonstrated the suitability of US assessment of aCSA and MT combined with TL for estimating MV of GCM in children with spastic CP and showed that aCSA is more useful parameter than MT.

Usefulness of fetal three-dimensional ultrasonography for detecting of congenital heart defects and associated syndromes

Congenital heart defects (CHDs) occur in 1% of live-born infants and frequently are associated with extracardiac malformations. This study aimed to assess the feasibility and accuracy of three-dimensional ultrasonography (3DUS) in fetuses with CHD and to investigate whether 3DUS can add information about the heart and general fetal morphology that shows other congenital malformations or suggests syndromes. For 30 fetuses affected by CHD, 3DUS was performed using a Sonos 7500 ultrasound machine with a cardiac 3D transducer. In 44% of the exams, 3DUS was completely diagnostic for the CHD, providing additional information in 28% of the exams. Furthermore, 3DUS showed 82% of associated malformations, providing the complete diagnosis in 57% of the cases and helping with recognition of syndromes in others. The diagnostic accuracy of 3DUS was superior, with a higher number of acquisitions per exam. Performance was better in fetuses younger than 24 weeks for general morphologic details and in fetuses older than 24 weeks for the heart morphology.

Micro-computed tomography-based phenotypic approaches in embryology: procedural artifacts on assessments of embryonic craniofacial growth and development

Background

Growing demand for three dimensional (3D) digital images of embryos for purposes of phenotypic assessment drives implementation of new histological and imaging techniques. Among these micro-computed tomography (μCT) has recently been utilized as an effective and practical method for generating images at resolutions permitting 3D quantitative analysis of gross morphological attributes of developing tissues and organs in embryonic mice. However, histological processing in preparation for μCT scanning induces changes in organ size and shape. Establishing normative expectations for experimentally induced changes in size and shape will be an important feature of 3D μCT-based phenotypic assessments, especially if quantifying differences in the values of those parameters between comparison sets of developing embryos is a primary aim. Toward that end, we assessed the nature and degree of morphological artifacts attending μCT scanning following use of common fixatives, using a two dimensional (2D) landmark geometric morphometric approach to track the accumulation of distortions affecting the embryonic head from the native, uterine state through to fixation and subsequent scanning.

Results

Bouin's fixation reduced average centroid sizes of embryonic mouse crania by approximately 30% and substantially altered the morphometric shape, as measured by the shift in Procrustes distance, from the unfixed state, after the data were normalized for naturally occurring shape variation. Subsequent μCT scanning produced negligible changes in size but did appear to reduce or even reverse fixation-induced random shape changes. Mixtures of paraformaldehyde + glutaraldehyde reduced average centroid sizes by 2-3%. Changes in craniofacial shape progressively increased post-fixation.

Conclusions

The degree to which artifacts are introduced in the generation of random craniofacial shape variation relates to the degree of specimen dehydration during the initial fixation. Fixation methods that better maintain original craniofacial dimensions at reduced levels of dehydration and tissue shrinkage lead to the progressive accumulation of random shape variation during handling and data acquisition. In general, to the degree that embryonic organ size and shape factor into μCT-based phenotypic assessments, procedurally induced artifacts associated with fixation and scanning will influence results. Experimental designs will need to address these significant effects, either by employing alternative methods that minimize artifacts in the region of focus or in the interpretation of statistical patterns.

Three-dimensional and four-dimensional fetal echocardiography: a new frontier

PURPOSE OF REVIEW

One of the difficulties of conventional two-dimensional cardiac imaging is the inability to examine fetal cardiac anatomy from multiple angle planes. Three-dimensional and four-dimensional ultrasound allows the fetal examiner to more accurately accomplish this task. Currently, multiple disciplines may be involved in the examination of the fetal heart (pediatric cardiologists, obstetricians, maternal-fetal medicine specialists, and radiologists). The three-dimensional and four-dimensional imaging equipment used by these specialty physicians varies greatly. The purpose of this communication is to review techniques using three-dimensional and four-dimensional imaging that the pediatric cardiologist may not be exposed to in the clinical environment, however, in consulting with colleagues needs to have an understanding of these imaging modalities.

RECENT FINDINGS

The reconstruction of cardiac structures using this technology allows the examiner to view cardiac anatomy in a manner that was limited by previous two-dimensional imaging. Volume datasets are obtained in the three-dimensional static mode (no cardiac motion) or using four-dimensional - the three-dimensional heart is observed contracting during one or multiple cardiac cycles. Therefore, the fourth dimension is time. Using either three-dimensional or four-dimensional technology datasets are acquired, followed by image reconstruction. The image reconstruction enables the examiner to evaluate a two-dimensional image using multiple views, evaluate intracardiac anatomy at different depth planes, and recreate casts of blood flow of the chambers and great vessels.

SUMMARY

This new technology has enhanced the ability of the examiner to identify normal and complex fetal heart anatomy during the early second to the late third trimesters of pregnancy.

Clarifying the role of three-dimensional transvaginal sonography in reproductive medicine: an evidenced-based appraisal

This overview describes and illustrates the clinical applications of three-dimensional transvaginal sonography in reproductive medicine. Its main applications include assessment of uterine anomalies, intrauterine pathology, tubal patency, polycystic ovaries, ovarian follicular monitoring and endometrial receptivity. It is also useful for detailed evaluation of failed and/or ectopic pregnancy. Three-dimensional color Doppler sonography provides enhanced depiction of uterine, endometrial, and ovarian vascularity.

Three-Dimensional Ultrasound in Small Parts

For longer than 40 years, ultrasound (US) has been a widely used imaging tool in medical practice, which has proved helpful for the diagnosis and staging of diseases. Although three-dimensional ultrasound (3D) US has been available for more than 10 years, it was only through the development of the most recent computer technologies and its adaptation to ultrasound systems, that 3D US has become able to achieve the high level of sensitivity and performance necessary to be considered seriously in clinical practice. 3D US is rapidly turning into a technology with an ever-increasing range of applications in numerous fields because, among other reasons, it helps overcome some of the key limitations related to two-dimensional imaging. 3D US can be used in ultrasonography for small parts, among other medical areas. The assessment of the testicle, parotid, thyroid and parathyroid glands is properly achieved. The multiplanar presentation and niche mode are quite useful to determine the extension--inside or outside the organs-, of nodules, cysts or tumors. The volume measurement is better assessed with 3D US and given this, we can perform studies that follow growth in order to decide medical or surgical treatment. The VOCAL makes it possible to obtain a proper after-treatment follow-up of focal disorders in these small organs. Neovascularization is clearly viewed with 3D US and probably can suggest malignant origin of a neoplasm. 3D US offers a more comprehensive image of anatomical structures and pathological conditions and also permits to observe the exact spatial relationships. We are aware more studies are needed to demonstrate specificity and sensibility of 3D US in particular clinical conditions, not only in small parts but also is some other non-Ob/Gyn applications.

The interobserver reliability and validity of volume calculation from three-dimensional ultrasound datasets in the in vitro setting

OBJECTIVES

The primary aim of this validation study was to determine the interobserver reliability and validity of measurements of phantom objects of known volume using conventional and rotational techniques of volume calculation according to measurement technique.

METHODS

Two observers each acquired a single three-dimensional ultrasound dataset of three water-filled objects of different size and shape. The same two observers measured all six datasets using both the conventional technique and the newer rotational technique (Virtual Organ Computer-aided AnaLysis, VOCAL( trade mark )) of volume calculation. Reliability was assessed by calculating intraclass correlation coefficients (ICC) and validity by examining the percentage difference from the 'true' volume, as determined by a water displacement technique, by the limits of agreement method.

RESULTS

All of the techniques were highly reliable (ICC: 0.9962-0.9997) and valid to within 4% of the 'true' volumes. There were no significant differences in reliability according to measurement plane or between observers. Measurements made with the 6 degrees rotation step were significantly more reliable than those made by all other techniques with the exception of the 9 degrees rotation step (P < 0.05) and significantly more valid than those made with the 30 degrees rotation step or conventional technique (P < 0.05).

CONCLUSIONS

Volume calculation in the in vitro setting is both reliable and valid but is dependent upon the technique applied, with rotational measurements of volume proving superior to conventional techniques.

Limb deformities and three-dimensional ultrasound

AIM

To assess the ability of three-dimensional (3D) ultrasonography for improvement of antenatal detection of limb deformities.

METHODS

347 patients were selected from a routine outpatient clinic or sent for supervision from other units because of suspected anomalies of fetal extremities. 3D ultrasound devices used in the study were Combison 530D and Voluson 530D MT (Kretztechnik, Zipf, Austria) with a 3-5 MHz annular array transducer for three-dimensional volume scanning.

RESULTS

In 41 of 347 patients the initial diagnosis was suspected by two-dimensional sonography (gestational age 18-32 weeks). In 28 of 41 suspected cases the diagnosis of abnormalities was determined after examination by 3D sonography: 17/28 clubfoot, 3/28 hand-polydactily, 2/28 upper limb contractures, 1/28 lower limb contractures, 4/28 micromelia within the syndrome of skeletal dysplasia. In 13 of 41 suspected cases, normal anatomy was confirmed using 3D sonography.

CONCLUSION

Three-dimensional sonography is the "method of choice" for the detection of an isolated defect of a single limb, developmental or positional deformations and minor defects of hands and feet. Surface-mode reconstruction of the complete limb and transparent-view reconstruction of the entire skeletal structure are effective technical advantages enabling a completely new visual perception of the unborn baby.

Dynamic three-dimensional color Doppler ultrasound of human fetal intracardiac flow

OBJECTIVES

To develop dynamic three-dimensional ultrasound techniques for prenatal imaging of the intracardiovascular flow as well as the cardiovascular structure to address difficulties in assessing the spatially complex hemodynamics and morphology of the fetal heart.

METHODS

Gray-scale and color (velocity) Doppler echocardiography were performed on 12 fetuses to provide serial anatomical and rheological tomograms which were spatially registered in three dimensions. Using a second ultrasound machine simultaneously, spectral Doppler ultrasound was performed to record umbilical arterial waveforms, thus providing the temporal (fourth) dimension in terms of the cardiac cycle and facilitating removal of motion artifacts.

RESULTS

Acquisitions were successful in eight of 15 attempts. Imaging of the flow of blood in four dimensions was achieved in six of the eight datasets. In one case with complex cardiac malformations, three-dimensional reconstructions at systole and diastole offered dynamic diagnostic views not appreciated on the cross-sectional images.

CONCLUSIONS

Our novel technique has made possible the prenatal visualization of the spatial distribution and true direction of intracardiac flow of blood in four dimensions in the absence of motion artifacts. The technique suggests that diagnosis of cardiac malformations can be made on the basis of morphological and hemodynamic changes throughout the entire cardiac cycle, offering unique and significant information complementary to conventional techniques. Further work to integrate the several non-purpose-built machines into a single system will improve the rate of acquisition of data, and may provide a new means of imaging and modeling structure and hemodynamics, not only for the fetal heart but for many other moving body parts.

Three-dimensional sonography in prenatal diagnosis: a luxury or a necessity?

Three-dimensional sonography revolutionized ultrasound imaging with its capacity to depict an unlimited number of planes in which the object of interest can be displayed. The addition of numerous modalities of image rendering promotes three-dimensional sonography to the top of the spectrum of diagnostic imaging in obstetrics and gynecology. The aim of this article is to present our experience in 3-D sonography during the second and third trimester of pregnancy and to give a comparative review of literature. 247 patients in gestational age ranging from 12 to 40 weeks of gestation were examined over a three year period. The majority of patients entered the study because fetal anomaly was suspected at two-dimensional sonography. Some patients were sent on to three-dimensional sonography because it was not possible to depict clearly normal fetal anatomy by two dimensional sonography. Out of 170 fetal anomalies three-dimensional sonographic analysis failed in only three cases. In all three anomaly was accompanied with severe oligohydramnios. Main advantages of three-dimensional ultrasound in perinatal medicine and antenatal diagnosis include scanning in the coronal plane, improved assessment of complex anatomic structures, surface analysis of minor defects, volumetric measuring of organs, "plastic" transparent imaging of fetal skeleton, spatial presentation of blood flow arborization and, finally, storage of scanned volumes and images. It is our decided opinion that three-dimensional sonography has gained a valuable place in prenatal diagnosis, becoming a necessity for every modern perinatal unit.