3D Volume Acquisition Research Articles

Untersuchung von Strömungsverhältnissen an künstlichen Modellen mittelgroßer stenotischer Gefäße mit der 3D-Phasenkontrast-Magnetresonanztomographie

Phase contrast MRI allows access to tri-directional encoded velocity information and therefore, measurement of flow in the human hemodynamic system. The aim of this work was to investigate whether this technology could be applied to support the grading of stenosis in mid-size arteries. Using a specially constructed flow phantom and a stenosis model with tube diameter of 5 mm and 8 mm and a stenosis of 50%, experiments at different flow rates (180–640 ml/min), slice thickness (1–4 mm), field strength (1.5 and 3.0 T), and multi-slice as well as 3D volume acquisition were performed. The observations were assessed visually and evaluated by signal-to-noise (SNR) ratios in regions before and after the stenosis. The obtained results show that examinations should be performed at high field (3.0 T) and at flow rates up to 500 ml/min without hampering the measurements by areas of signal loss. In comparison, no detectable differences in the flow patterns of the two acquisition schemes could be observed. However, the SNR was higher using the 3D volume acquisition and thick slices. In summary, 3D PC-MRI of mid-size vessels with stenosis is feasible for certain flow rates. The presented results could be seen as guidance for in vivo situations to assess if an examination of a patient is reasonable in terms of outcome.

Automated sonographic tubal patency evaluation with three‐dimensional coded contrast imaging (CCI) during hysterosalpingo‐contrast sonography (HyCoSy)

Evaluation of tubal status is one of the initial steps in the diagnostic work-up of infertile women. Hysterosalpingo- contrast sonography (HyCoSy), currently performed as part of the infertility work-up to assess tubal patency by transvaginal ultrasound (TVS) 1 , is based on the introduction of fluid into the uterine cavity and Fallopian tubes. To evaluate the Fallopian tubes, a sonographic enhancing positive-contrast medium may be used. Air, albumin with micro air bubbles, and galactose with micro air bubbles have been studied. These positive- contrast agents outline the course of the Fallopian tubes, producingahyperechoicappearance.Themostsimpleand inexpensive positive-contrast medium is saline solution mixed with air. When this solution is shaken, it generates as uspension of air bubbles that is easily identif ied sonographically when injected into the uterine cavity and Fallopian tubes 2-4 with spillage around the ovaries. However, while two-dimensional (2D) TVS HyCoSy with saline solution mixed with air appears to be an accurate and inexpensive screening tool to assess tubal patency, it is highly observer-dependent and is accurate only in the hands of experienced investigators 2-5 . In addition,

Tubal patency evaluation: feasibility of new automated three dimensional sonographic method

OBJECTIVE: To evaluate the feasibility of a new automated three dimensional contrast-enhanced ultrasound technology called “Coded Contrast Imaging” (3D CCI-GE Healthcare) in the evaluation of tubal patency and visualization of tubal course.DESIGN: Patients undergoing transvaginal hystero-salpingo-contrast-sonography (TVS HyCoSy) with automated 3D CCI were prospectively evaluated.MATERIALS AND METHODS: Sixtytwo patients of reproductive age underwent automated 3D CCI HyCoSy. The CCI allows the detection of an ultrasound contrast agent in the tube by discriminating the harmonic response of contrast bubbles from the echoes of other tissues. 3D TVS allows the visualization of tubal course. In order to evaluate the feasibility of this method we considered first the tubal patency and the 3D visualization of tubal course after two consecutive contrast agent injections. The visualization with CCI of the contrast agent around the ovaries, the need for more than one fluid injection to assess tubal patency, the detection in 2D real time of the bubbles movement around the ovaries, and the side effects and pain during and after the procedure were assessed.RESULTS: Sixtytwo patients underwent automated 3D CCI HyCoSy; 50 women showed bilateral tubal patency and 12 a tubal occlusion (4 cases bilateral, 8 unilateral). The 3D tubal course automated reconstruction was achieved in 41cases (66%) after the first contrast injection, while in other 15 cases a second injection was needed, for a total of 56(90%) 3D tubal imaging. For the 108 patent tubes, in 101 cases CCI clearly showed the contrast agent around the omolateral ovary. 2D realtime evaluation was performed in all cases to confirm tubal status and it was helpful to assess tubal patency in those 6 patients in whom 3D reconstruction wasn't good enough to achieve a diagnosis.CONCLUSIONS: Automated 3D-CCI HyCoSy allows for a reliable assessment of tubal patency in 90% of cases. Automated 3D volume acquisition allows less experienced operators to easily evaluate the tubal course. OBJECTIVE: To evaluate the feasibility of a new automated three dimensional contrast-enhanced ultrasound technology called “Coded Contrast Imaging” (3D CCI-GE Healthcare) in the evaluation of tubal patency and visualization of tubal course. DESIGN: Patients undergoing transvaginal hystero-salpingo-contrast-sonography (TVS HyCoSy) with automated 3D CCI were prospectively evaluated. MATERIALS AND METHODS: Sixtytwo patients of reproductive age underwent automated 3D CCI HyCoSy. The CCI allows the detection of an ultrasound contrast agent in the tube by discriminating the harmonic response of contrast bubbles from the echoes of other tissues. 3D TVS allows the visualization of tubal course. In order to evaluate the feasibility of this method we considered first the tubal patency and the 3D visualization of tubal course after two consecutive contrast agent injections. The visualization with CCI of the contrast agent around the ovaries, the need for more than one fluid injection to assess tubal patency, the detection in 2D real time of the bubbles movement around the ovaries, and the side effects and pain during and after the procedure were assessed. RESULTS: Sixtytwo patients underwent automated 3D CCI HyCoSy; 50 women showed bilateral tubal patency and 12 a tubal occlusion (4 cases bilateral, 8 unilateral). The 3D tubal course automated reconstruction was achieved in 41cases (66%) after the first contrast injection, while in other 15 cases a second injection was needed, for a total of 56(90%) 3D tubal imaging. For the 108 patent tubes, in 101 cases CCI clearly showed the contrast agent around the omolateral ovary. 2D realtime evaluation was performed in all cases to confirm tubal status and it was helpful to assess tubal patency in those 6 patients in whom 3D reconstruction wasn't good enough to achieve a diagnosis. CONCLUSIONS: Automated 3D-CCI HyCoSy allows for a reliable assessment of tubal patency in 90% of cases. Automated 3D volume acquisition allows less experienced operators to easily evaluate the tubal course.

Usefulness of Intraoperative Real‐Time 3D Transesophageal Echocardiography in Cardiac Surgery

Recent advances in three-dimensional (3D) echocardiography allow to obtain real-time 3D transesophageal (RT3DTEE) images intraoperatively. Preoperative transthoracic echocardiography (TTE) revealed: hypertrophic ventricular septum (TTE:19.3 mm), systolic anterior motion (SAM) not causing obstruction and malcoaptation of the anterior mitral valve leaflet (AMVL), and posterior mitral valve leaflet (PMVL) with severe mitral regurgitation. Intraoperative TEE with a x7-2t MATRIX-array transducer (Philips, Andover, MA, USA) with a transducer frequency of x7-2 t mHz, connected to a iE33 (Philips), shows us that the main mechanism and site of regurgitation was an AMVL cleft. We also measured a 24.3-mm thickness of the ventricular septum and analyzing the 3D full volume acquisition revealed that there was no SAM. Intraoperative RT3DTEE permitted comprehensive 3D viewing of the mitral valve revealing the mechanism of mitral valve regurgitation, SAM, and the exact width of the hypertrophic ventricular septum.

P26.10: The additional value of 3D ultrasound in fetuses suspected of having coarctation of the aorta

Objective: For many years, disproportion of ventricles and great arteries has been the main ultrasonographic finding to suspect and diagnose coarctation of the aorta prenatally. This is associated with low positive predictive value. We report the use of three-dimensional ultrasound (3D-US) in 2 fetuses with suspected coarctation and highlight the role of 3D-US in these cases. Materials and methods: We used the combination of twodimensional (2D-US) and 3D-US to assess the aortic isthmus in 2 fetuses with suspected coarctation of the aorta (CoA) at 23 and 32 weeks of gestation. Bidirectional high definition flow (HDF) was used to examine the aortic isthmus area directly during standard 2D imaging and 3D volume acquisition. Results: Using 2D-US, the aortic isthmus was seen well on transverse views in both cases but not on longitudinal views. 3D-US allowed good visualisation of the isthmal area in all views. Both fetuses showed a discrete isthmal narrowing prenatally (coarctation ‘‘shelf?). Both newborn babies had coarctation requiring surgical treatment. Conclusion: 3D-US improves visualisation of the isthmus part of the aorta and the presence of the shelf when it exists. We suggest that this technique is of additional value in fetuses suspected to have coarctation of the aorta. This may improve the accuracy of prenatal diagnosis of coarctation.

A three-dimensional ultrasonographic quantitative analysis of non-ulcerated carotid plaque morphology in symptomatic and asymptomatic carotid stenosis

Background and purpose Studies evaluating the association between carotid plaque composition and occurrence of ischemic cerebrovascular disease reveal inconsistent results. This study correlates the carotid echomorphology with the degree of stenosis in symptomatic and asymptomatic patients. Methods We included consecutive patients with hemispheric stroke or asymptomatic carotid artery stenosis assessed with 2D ultrasound. The echomorphology was assessed with mean gray value (MGV) of the three-dimensional (3D) volume. We used the free-hand approach for 3D image and volume acquisition. Analyses of the stored carotid plaque volumes were carried out offline using the Virtual Organ Computer-aided Analysis (VOCAL™) program. Results We studied 110 symptomatic and 104 asymptomatic atherosclerotic carotid plaques. MGV was lower in symptomatic carotid plaques causing <70% stenosis compared to plaques causing ≥70% stenosis (25.95 ± 7.40 vs. 32.16 ± 11.35, p = 0.002). There was no difference in MGV between plaques producing <60% and those with ≥60% in asymptomatic patients (32.08 ± 8.36 vs. 31.46 ± 9.25, p = 0.724). There were significant differences in MGV between symptomatic and asymptomatic plaques causing <60 or <70% stenosis; MGV was lower in symptomatic patients. Conclusions Lower plaque echogenicity is observed in symptomatic than in asymptomatic patients with moderate degree of carotid stenosis, indicating that it is a significant factor for the production of cerebral ischemia. Our method could be useful in assessing the risk of cerebral ischemia and the response of carotid artery atherosclerosis to medical therapies.

OC232: Can 3D volume acquisitions displayed with TUI be used to interpret and archive GYN scans done remotely?

OC232: Can 3D volume acquisitions displayed with TUI be used to interpret and archive GYN scans done remotely?

Assessment of the third‐trimester fetus using 3‐dimensional volumes: A pilot study

To examine whether the third-trimester fetus can be assessed sonographically using 3-dimensional (3D) volume data sets. Twenty-seven consecutive third-trimester fetuses were evaluated. Fetuses were scanned using 2-dimensional (2D) imaging followed by 5 3D volume acquisitions. The initial scan was interpreted and reported based on the 2D images. The 3D volume data sets were independently reviewed offline several weeks later by 2 sonologists. Parameters evaluated included fetal presentation, placental location, amniotic fluid volume, fetal biometry including a calculation of estimated fetal weight, and major fetal anatomic structures. The result of the interpretation via 3D reconstruction of the volume from each of the 2 sonologists was compared with the original 2D sonography report. Fetal presentation, amniotic fluid volume, and placental location with respect to the cervix were correctly identified 100% of the time by each sonologist. The estimated fetal weight was within 10% of the 2D estimate 89% (95% CI, 0.71-0.98) of the time for sonologist A and 96% (95% CI, 0.81-0.99) of the time for sonologist B. The majority of major anatomic landmarks were adequately seen by both sonologists. Offline review of 3D volume data sets is a reliable method for determining fetal presentation, amniotic fluid volume, placental location, and estimating fetal weight in the third trimester.

Rapid Assessment of Abdominal Aortic Aneurysms by 3-Dimensional Ultrasonography

The purpose of this study was to assess the application and accuracy of 3-dimensional (3D) volume acquisition ultrasonography in the measurement of abdominal aortic aneurysms (AAAs). Thirty consecutive patients undergoing surveillance ultrasonographic examinations of known AAAs were scanned according to a conventional protocol, after which 3D volume data sets were acquired with a commercially available mechanical transducer. Maximum aortic diameters were measured with multiplanar reconstructions from the 3D volume data, and these were compared with those from the conventional technique. Abdominal aortic aneurysm diameters were between 2.9 and 6.75 cm. For both anteroposterior and transverse diameters, a paired t test showed a Pearson correlation coefficient of 0.98 (significant at the P = .01 level) and a coefficient of determination of 0.96. Bland-Altman analysis showed that the mean difference between the two sets of measurements was very close to 0 (P = .05). Thus, there was no significant difference between the conventional and 3D volume measurement methods. The scan acquisition time for the 3D volume data was only 3 seconds for each set (anteroposterior and transverse). Three-dimensional ultrasonography using volume acquisition offers a new opportunity to acquire fast and reliable AAA measurements. The reduced scan times can be used to allow greater patient throughput and will help cope with the increasing workload of AAA surveillance. By archiving a complete set of data, 3D ultrasonography allows subsequent analysis and comparison of measurements. This study also suggests that the technique could be used for other applications with similar efficiency gains.

A comparison between acoustic output indices in 2D and 3D/4D ultrasound in obstetrics

Three-dimensional (3D) ultrasound is gaining popularity in prenatal diagnosis. While there are no studies regarding the safety of 3D ultrasound, it is now widely performed in non-medical facilities, for non-diagnostic purposes. The present study was aimed at comparing the acoustic output, as expressed by thermal index (TI) and mechanical index (MI), of conventional two-dimensional (2D) and 3D/4D ultrasound during pregnancy. A prospective, observational study was conducted, using three different commercially available machines (iU22, Philips Medical Systems; Prosound Alfa-10, Aloka; and Voluson 730 Expert, General Electric). Patients undergoing additional 3D/4D ultrasound examinations were recruited from those scheduled for fetal anatomy and follow-up exams. Fetuses with anomalies were excluded from the analysis. Data were collected regarding duration of the exam, and each MI and TI during 2D and 3D/4D ultrasound exams. A total of 40 ultrasound examinations were evaluated. Mean gestational age was 31.1 +/- 5.8 weeks, and mean duration of the exam was 20.1 +/- 9.9 min. Mean TIs during the 3D (0.27 +/- 0.1) and 4D examinations (0.24 +/- 0.1) were comparable with the TI during B-mode scanning (0.28 +/- 0.1, P = 0.343). The MIs during the 3D volume acquisitions were significantly lower than those in the 2D B-mode ultrasound studies (0.89 +/- 0.2 vs. 1.12 +/- 0.1, P = 0.018). The 3D volume acquisitions added 2.0 +/- 1.8 min of actual ultrasound scanning time (i.e. not including data processing and manipulation, or 3D displays, which are all post-processing steps). The 4D added 2.2 +/- 1.2 min. Acoustic exposure levels during 3D/4D ultrasound examination, as expressed by TI, are comparable with those of 2D B-mode ultrasound. However, it is very difficult to evaluate the additional scanning time needed to choose an adequate scanning plane and to acquire a diagnostic 3D volume.

Improving the Efficiency of Gynecologic Sonography With 3-Dimensional Volumes

The purpose of this study was to determine whether 3-dimensional (3D) sonography can provide a rapid, efficient, and accurate way to do a transvaginal gynecologic scan compared with traditional 2-dimensional (2D) sonography. Thirty-five consecutive patients who underwent gynecologic sonography formed the study cohort. After a standard 2D transvaginal scan was done, including measurements of the endometrium and abnormalities, 4 volume acquisitions were obtained, encompassing the uterus (2 volumes) and the ovaries. These volumes were reviewed offline without any patient information. Endometrium and other measurements were performed on the volumes. The 2D and 3D results were compared by paired t tests. The mean time needed for the standard 2D scan was 2.6 minutes compared with 1.07 minutes for the 3D volume acquisitions. The mean time for the reconstruction, measurement, and interpretation of the volumes offline was 1.19 minutes. The mean time for the entire 3D examination (both parts) was 2.26 minutes (P = .047, comparing 2D with total 3D). There was no significant difference between the measurements of the endometrium, fibroids, and ovarian cysts when comparing 2D and reconstructed 3D images. Two-dimensional and 3D sonography differed little in their ability to identify the organs and the abnormalities on the scans. This study shows that a complete transvaginal gynecologic examination can be done in 1.07 minutes of scan time and interpreted offline in an additional 1.19 minutes. The 35 cases were scanned and interpreted with the use of 3D sonography in 79.17 minutes total compared with 91.46 minutes of 2D scan time (P = .047). The accuracy of the scan was similar for both techniques.

Three-dimensional US of the Fetus: Volume Imaging

To retrospectively compare the rapidity, efficiency, and accuracy of three-dimensional (3D) and two-dimensional (2D) ultrasonography (US) for complete anatomic survey in fetuses at 17-21 weeks of gestation. Institutional review board approval was obtained, informed consent was waived, and the study was HIPAA compliant. Fifty consecutive women undergoing fetal anatomic survey at 17-21 weeks of gestation formed the study cohort. After standard 2D US was performed by one of eight sonographers, the same sonographer also obtained five 3D volumes to encompass the entire fetal anatomy. Three physicians interpreting the scans independently evaluated the completeness of the examination and time needed to read the scans, comparing the standard 2D method with the 3D volume reconstruction technique. The paired t test was used to compare biparietal diameter (BPD), femur length, and performance times between the 3D measurements and the 2D measurement. The t test was used to compare fetal anatomy according to volume angle. Differences were significant when P < .05. Mean time to perform 2D US was 19.6 minutes per examination, whereas mean time to perform complete 3D volume acquisition was 1.8 minutes. Mean times needed to interpret 3D images and measure the BPD and femur were 5.53, 4.79, and 5.34 minutes for the three interpreting physicians. Compared with complete fetal surveys performed with 2D US, individual fetal anatomic landmarks (except for fetal arms and cavum septum pellucidum) were identified more than 94% of the time by using 3D US. Grouping anatomic views by region, the heart, head, extremities, and abdominal views were completely seen in 88%, 90%, 90%, and 95% of patients, respectively. No significant difference was seen between the three physicians regarding completeness of the 3D examinations (P = .7). One fetus had multiple anomalies, with 3D volumes identified as abnormal by all three physicians. Overall, 74% of 3D BPD measurements were within 1 mm of the 2D measurements, and 64% of 3D femur measurements were within 1 mm of the 2D measurements. The standard fetal anatomic survey can be performed in less than 2 minutes with 3D volume US, and the volumes can be interpreted in 6-7 minutes, compared with a mean of 19.6 minutes to perform standard 2D US.

Three- and 4-Dimensional Ultrasound in Obstetrics and Gynecology

The American Institute of Ultrasound in Medicine convened a panel of physicians and scientists with interest and expertise in 3-dimensional (3D) ultrasound in obstetrics and gynecology to discuss the current diagnostic benefits and technical limitations in obstetrics and gynecology and consider the utility and role of this type of imaging in clinical practice now and in the future. This conference was held in Orlando, Florida, June 16 and 17, 2005. Discussions considered state-of-the-art applications of 3D ultrasound, specific clinical situations in which it has been found to be helpful, the role of 3D volume acquisition for improving diagnostic efficiency and patient throughput, and recommendations for future investigations related to the utility of volume sonography in obstetrics and gynecology.

How Sonographic Tomography Will Change the Face of Obstetric Sonography

This study was undertaken to determine whether 3-dimensional (3D) volume sonography (sonographic tomography) can yield a far quicker and equally accurate anatomic examination of the second-trimester fetus compared with traditional 2-dimensional (2D) scanning. Twenty-five consecutive second-trimester fetuses with normal structural surveys on standard 2D imaging underwent 5 standard 3D volume acquisitions each (in the regions of the head, chest, abdomen, face, and lower extremities) immediately after the 2D scan. The 2D and 3D images were subsequently compared in relation to the completeness of the fetal survey, measurements of the biparietal diameter and femur length, and time required to obtain the fetal survey. The structural surveys were complete in 20 of 25 cases using 3D reconstructed volumes. One fetus had an incomplete evaluation of the face on 3D volumes (and limited on 2D imaging because of the prone position of the fetus). The other 4 fetuses with incomplete surveys done on 3D volumes had missing images of a hand or foot. Three-dimensional reconstructions slightly overmeasured the biparietal diameter compared with the 2D reference standard (mean difference, 1.1 mm; P < .001). For femur length, the mean difference was not statistically significant. It took a mean time of 1.1 minutes to obtain the 3D volumes and 5.5 minutes to reconstruct the complete surveys by the 3D volume method. With the standard 2D technique, the structural surveys were done in a mean time of 13.9 minutes. The mean time difference between both methods was 7.3 minutes (P = 2.4 x 10(-9)). Using 3D volume acquisition, it is feasible to perform and interpret a structural survey in half the time in which a 2D survey is performed. Further research is necessary to standardize the acquisition of volumes to minimize artifacts and produce uniform images.

Ultrasound quantification in real-time using acoustic data in more than two dimensions

A system and method of ultrasound quantification acquires acoustic image data from anatomic locations distributed in more than 2 dimensions, and uses a segmentation algorithm to provide real-time volume measurements. A 2D array is used to acquire two orthogonal (bi-plane) 2D images simultaneously. The images are segmented individually to determine the volume borders using any number of acoustic algorithms. The borders from the two bi-plane images are mathematically combined to give a volume measurement. A control processor controls the system to thereby obtain instant feedback of the segmented image data and enhance the volume measurements of the image. The system and method is extended to a number of simultaneous 2D images and to a full 3D volume acquisition.

Whole-brain 3D perfusion MRI at 3.0 T using CASL with a separate labeling coil.

A variety of continuous and pulsed arterial spin labeling (ASL) perfusion MRI techniques have been demonstrated in recent years. One of the reasons these methods are still not routinely used is the limited extent of the imaging region. Of the ASL methods proposed to date, continuous ASL (CASL) with a separate labeling coil is particularly attractive for whole-brain studies at high fields. This approach can provide an increased signal-to-noise ratio (SNR) in perfusion images because there are no magnetization transfer (MT) effects, and lessen concerns regarding RF power deposition at high field because it uses a local labeling coil. In this work, we demonstrate CASL whole-brain quantitative perfusion imaging at 3.0 T using a combination of strategies: 3D volume acquisition, background tissue signal suppression, and a separate labeling coil. The results show that this approach can be used to acquire perfusion images in all brain regions with good sensitivity. Further, it is shown that the method can be performed safely on humans without exceeding the current RF power deposition limits. The current method can be extended to higher fields, and further improved by the use of multiple receiver coils and parallel imaging techniques to reduce scan time or provide increased resolution.

MR imaging of epilepsy: State of the art at 1.5 T and potential of 3 T

ABSTRACT Shortly after being introduced in the nineteen eighties, magnetic resonance imaging (MRI) became a key tool for the investigation of patients with epilepsy, due to its ability to acquire high quality images. The strength of the magnetic field of a scanner is measured in tesla (T). This review addresses the clinical and research potential in epilepsy of MR imaging at 1.5 T and 3 T. A typical clinical scanning protocol at 1.5 T for a patient with refractory epilepsy may include T1‐ and T2‐weighted imaging, fluid‐attenuated inversion recovery (FLAIR) imaging, and a 3D volume acquisition sequence. A research protocol may add quantification of structural imaging, such as volumetric assessment and T2‐relaxometry, together with functional measures, such as MR‐spectroscopy, functional MRI and diffusion weighted sequences. MR‐spectroscopy assesses the metabolites of the seizure focus and other brain areas. Functional MRI allows localisation of cognitive and sensori‐motor function and the ability to assess the spatial relationship of these functions to the seizure focus. Whereas these techniques can be performed at 1.5 T, particularly MR‐spectroscopy and functional MRI benefit from increased magnetic field‐strength. Higher magnetic field‐strength is associated with a higher signal‐to‐noise ratio (SNR). The increased SNR can allow shorter imaging times for a given resolution, higher resolution for a given imaging time, or combination of both. The use of higher magnetic field‐strengths is therefore indicated for the (fast) imaging of ill subjects, for long protocols, including structural, metabolic and functional imaging, and for novel applications, such as continuous EEG recording and functional MRI for the detection of the seizure focus. Disadvantages of MR imaging in epilepsy at a high field‐strength of 3 T and above are, apart from engineering and technical challenges, the greater energy deposition into tissue and increased susceptibility to artefacts. So far, magnets of 3 T and above have been used mainly for research applications, however the benefits of high field‐strength for MR spectroscopy and functional MRI, and the usefulness of these techniques for the investigation of epilepsy patients are obvious incentives for the use of 3 T systems in routine clinical investigations. [Published with neuroimaging sequences.]

The assessment of fetal brain morphology and circulation by transvaginal 3D sonography and power Doppler.

The objective of this article is to describe the use of transvaginal 3D ultrasound in prenatal neuroimaging and to investigate its clinical usefulness. Firstly, 18 fetuses with hydrocephalus, ventriculomegaly and/or space occupying lesion were examined by transvaginal 3D sonography, and fetal CNS abnormalities were evaluated. Multiplanar image analysis and volumetric assessment were performed off-line. Longitudinal volume changes of target structure were evaluated, and usefulness of transvaginal 3D ultrasound was evaluated. Secondly, in 56 normal cephalic fetuses of between 18 and 32 weeks, 3D Doppler volume acquisition and reconstruction of the intracranial vascular structure were performed. Longitudinal changing appearance in the same cutting section of the enlarged ventricle or cystic lesion could be demonstrated in all cases and volumetric assessment was also successful in all cases. Longitudinal objective data were useful in the brain assessment, consultation and counselling. 3D Doppler acquisition time was 5.6-26 seconds and symmetrical 3D reconstruction was successful in 51.8%. Transvaginal 3D imaging technology provides us with not only comprehensive intracranial images in exactly the right sections, but also with objective volume data. Prenatal information with objective data analyses is useful in consultation for both specialists and parents, and leads to proper management of CNS diseases.

Fast 3D T 2-weighted MRI with Hadamard encoding in the slice select direction

A fast method to obtain 3-dimensional (3D) magnetic resonance imaging with long repetition times is presented. It can be used to obtain fast 3D MRI with for example T 2 or diffusion weighted imaging. The method uses a 3D multiple thin slab sequence with radio frequency encoding, preferably Hadamard encoding, in the slice select direction. The point-spread function of the Hadamard-encoded slices is close to ideal even at low encoding numbers. This allows the acquisition of 3D data volumes with tolerable image quality up to four times faster than is possible using Fourier phase encoding. The scope of the method includes both longitudinal and transverse encoding. Longitudinal encoding provides a better point spread function than transverse encoding, at the expense of having to discard one slice per slab. The method is demonstrated experimentally for 4th order longitudinal Hadamard encoding to obtain 3D T 2-weighted images.

Double-oblique free-breathing high resolution three-dimensional coronary magnetic resonance angiography

OBJECTIVESThe goal of the present study was to develop a strategy for three-dimensional (3D) volume acquisition along the major axes of the coronary arteries.BACKGROUNDFor high-resolution 3D free-breathing coronary magnetic resonance angiography (MRA), coverage of the coronary artery tree may be limited due to excessive measurement times associated with large volume acquisitions. Planning the 3D volume along the major axis of the coronary vessels may help to overcome such limitations.METHODSFifteen healthy adult volunteers and seven patients with X-ray angiographically confirmed coronary artery disease underwent free-breathing navigator-gated and corrected 3D coronary MRA. For an accurate volume targeting of the high resolution scans, a three-point planscan software tool was applied.RESULTSThe average length of contiguously visualized left main and left anterior descending coronary artery was 81.8 ± 13.9 mm in the healthy volunteers and 76.2 ± 16.5 mm in the patients (p = NS). For the right coronary artery, a total length of 111.7 ± 27.7 mm was found in the healthy volunteers and 79.3 ± 4.6 mm in the patients (p = NS). Comparing coronary MRA and X-ray angiography, a good agreement of anatomy and pathology was found in the patients.CONCLUSIONSDouble-oblique submillimeter free-breathing coronary MRA allows depiction of extensive parts of the native coronary arteries. The results obtained in patients suggest that the method has the potential to be applied in broader prospective multicenter studies where coronary MRA is compared with X-ray angiography.