Comparison of 2-dimensional and 3-dimensional cardiac 82Rb PET studies.
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Most new PET scanners have the capability to collect data in 3-dimensional (3D) (septa removed) mode. This allows many more detected events at the cost of increased random events and scatter. In the case of 82Rb imaging, the injected dose might have to be limited to avoid saturating the scanner. We present a comparison of 2-dimensional (2D) and 3D data collection for 82Rb cardiac studies using the ECAT EXACT scanner. METHODS: Resting 82Rb cardiac studies were collected in 2D and 3D modes for 33 consecutive patients. Four experienced physicians rated the images to determine if the different acquisition methods would lead to different patient care. A separate quantitative analysis was performed on data from multiple scans of a thoracic phantom filled to simulate cardiac and background radioactivity corresponding to 82Rb injections between 37 and 1740 MBQ: RESULTS: The 2D and 3D studies were significantly different, with the image quality being poorer in the 3D studies. The scanner collected data at near its maximal counting rate for either 1480-MBq 2D or 37-MBq 3D acquisitions. Because the data collection was counting rate limited in either mode, and there are more random and scatter events in 3D mode, the 2D acquisitions resulted in more detected true events and a better signal-to-noise ratio. CONCLUSION: Cardiac 82Rb studies should be performed in 2D mode when using the ECAT EXACT scanner. (+info)
Absolute changes in regional cerebral blood flow in association with upright posture in humans: an orthostatic PET study.
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To determine whether hemodynamic parameters are changed by upright posture in healthy middle-aged humans, absolute values of regional cerebral blood flow (rCBF) were investigated for three different orthostatic conditions. METHODS: PET with [15O]H2O and arterial blood sampling were performed on eight middle-aged healthy volunteers while they were sitting passively or standing actively. Absolute rCBF values estimated by the autoradiographic method in regions of interest were compared using ANOVA, and relative changes in rCBF were also analyzed voxel by voxel using statistical parametric mapping (SPM). RESULTS: Physiologic data remained unchanged for different conditions. ANOVA and SPM showed that absolute and relative rCBF levels were significantly elevated in the cerebellar vermis in the standing position compared with those in the supine and sitting positions. In contrast, ANOVA showed that rCBF in the frontal and parietal cortices tended to be lower in the sitting and standing positions than in the supine position. Regression analysis showed that the frontal rCBF measured during standing tended to be inversely correlated with age. CONCLUSION: The results showed that cerebellar vermis activation was more marked in the standing position than in the sitting or supine positions, indicating that the vermis is a neural substrate for controlling voluntary upright posture. Brain perfusion in the distal internal carotid artery region may be subject to orthostatic postural changes in healthy middle-aged humans. (+info)
Preoperative and early postoperative three-dimensional changes of the rib cage after posterior instrumentation in adolescent idiopathic scoliosis.
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Rib cage deformity is an important component of scoliosis, but few authors have reported the three-dimensional (3-D) effect of surgical procedures with posterior instrumentation systems on the shape of the rib cage. The objective of this prospective clinical study was to measure the short-term 3-D changes in the shape of the rib cage at the apex of the curve after corrective surgery of adolescent idiopathic scoliosis by a posterior approach using a multi rod, hook and screw system. The 3-D shape of the spine and rib cage was modelled pre- and postoperatively using a 3-D reconstruction technique based on multi-planar radiography in a group of 29 adolescents with idiopathic scoliosis. Geometrical indices describing the scoliotic deformity of the rib cage were computed from these models and were compared pre- and postoperatively using Student's t-tests. The frontal spinal curve correction averaged 53% in the frontal plane, while no significant change was noted in the sagittal plane. Significant changes were noted in the shape of the rib cage: rib hump at the apex and at the adjacent lower level were improved (36% and 38%), and small but significant differences were detected in rib frontal orientation in the concavity of the curves at the apex and adjacent lower rib levels. Multi rod, hook and screw instrumentation systems, such as Cotrel-Dubousset instrumentation, are effective in producing significant improvements in the 3-D shape of the rib cage, but these changes are less important than those observed at the spine level. (+info)
Three-dimensional contrastless varicography by spiral computed tomography.
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OBJECTIVE: to report and discuss preliminary results obtained in varicose limbs by means of a volume rendering (VR)-computed tomography (CT) technique without contrast medium injection. MATERIALS AND METHODS: VR-CT and duplex sonography (US) were performed to visualise the superficial veins of the lower extremity in eight healthy and 12 varicose limbs. RESULTS: VR-CT clearly demonstrated the 3D arrangement of the superficial veins and visualised small sized veins which were not visible at US examination. CONCLUSIONS: VR-CT is not suitable for routine evaluation of varicose limbs. VR-CT 3D reconstructions may be useful in the evaluation of atypical varicosis. Further studies are needed to define the role of VR-CT in deep venous disease. (+info)
Anomalous subaortic position of the brachiocephalic vein associated with Tetralogy of Fallot.
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The left brachiocephalic vein is found in an anomalous position less frequently than the superior vena cava or azygous channels in thoracic venous systems. We experienced a rare case of anomalous left brachiocephalic vein which was clearly demonstrated by spiral computed tomography (3D-CT). Although the malformation in itself seems to be of no functional importance, we assessed its importance in terms of associated conditions and its relevance to subsequent operations. (+info)
Quantitative analysis of three-dimensional-resolved fiber architecture in heterogeneous skeletal muscle tissue using nmr and optical imaging methods.
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The determination of principal fiber directions in structurally heterogeneous biological tissue substantially contributes to an understanding of its mechanical function in vivo. In this study we have depicted structural heterogeneity through the model of the mammalian tongue, a tissue comprised of a network of highly interwoven fibers responsible for producing numerous variations of shape and position. In order to characterize the three-dimensional-resolved microscopic myoarchitecture of the intrinsic musculature of the tongue, we viewed its fiber orientation at microscopic and macroscopic length scales using NMR (diffusion tensor MRI) and optical (two-photon microscopy) imaging methods. Diffusion tensor imaging (DTI) of the excised core region of the porcine tongue resulted in an array of 3D diffusion tensors, in which the leading eigenvector corresponded to the principal fiber orientation at each location in the tissue. Excised axially oriented lingual core tissues (fresh or paraffin-embedded) were also imaged with a mode-locked Ti-Sapphire laser, (76 MHz repetition rate, 150 femtosecond pulse width), allowing for the visualization of individual myofibers at in situ orientation. Fiber orientation was assessed by computing the 3D autocorrelation of discrete image volumes, and deriving the minimal eigenvector of the center voxel Hessian matrix. DTI of the fibers, comprising the intrinsic core of the tongue, demonstrated directional heterogeneity, with two distinct populations of fibers oriented orthogonal to each other and in-plane to the axial perspective. Microscopic analysis defined this structural heterogeneity as discrete regions of in-plane parallel fibers, with an angular separation of ~80 degrees, thereby recapitulating the macroscopic angular relationship. This analysis, conceived at two different length scales, demonstrates that the lingual core is a spatially complex tissue, composed of repeating orthogonally oriented and in-plane fiber patches, which are capable of jointly producing hydrostatic elongation and displacement. (+info)
The assessment of contact stress in the hip joint after operative treatment for severe slipped capital femoral epiphysis.
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We determined contact stress on the articular surface of the hip joint in a group of patients who underwent operative treatment for severe slipped capital femoral epiphysis. Two different procedures were considered: the modified osteotomy of Dunn-Fish and the osteotomy of Imhauser. In order to determine the stress distribution, a three-dimensional mathematical model was used taking into account the geometrical parameters of the pelvis and hip, which were measured from standard antero-posterior radiographs. We found that the Dunn-Fish procedure produced lower peak stress than the Imhauser procedure. (+info)
Three-dimensional ultrasound: a novel technique for investigating the urethral sphincter in the third trimester of pregnancy.
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OBJECTIVES: To measure urethral sphincter volume by three-dimensional (3D) ultrasound. To assess the reproducibility of this measurement technique and to compare volumes obtained using 3D ultrasound with volumes calculated from a formula based on 2D ultrasound measurements. METHODS: Women were recruited as part of an ongoing study of changes to the pelvis resulting from pregnancy and childbirth. One hundred and eleven women in the third trimester of pregnancy (between 32 and 41 completed weeks' gestation) underwent a 3D transvaginal ultrasound scan of the urethra. In 10 cases the scan was analyzed twice by different observers to assess the reproducibility of the measurements from the scans and the results were analyzed using limits of agreement. RESULTS: The interobserver error was consistent between all the linear, 2D and 3D measurements obtained from the area scanned. There was a significant difference between volumes calculated directly by 3D ultrasound and the approximated volumes from conventional 2D measurements. CONCLUSIONS: Three-dimensional ultrasound appears to be a useful tool in measuring urethral sphincter volume. The error is consistent with that of linear and 2D imaging. However, the increase in normal range generated by biological variation in all three planes makes 3D ultrasound a more sensitive method of evaluating change to the urethral sphincter. (+info)