Eliminate Motion Artifacts Research Articles

Artifacts in spiral CT protocols: The importance of the spatial reconstruction

Purpose This study recorded and analysed streak and motion artifacts in spiral CT examinations and evaluated the elimination and minimization of them by the use of segmental reconstruction with and without alterations of the initial examination protocol. Materials and methods One hundred CT scans of the chest and 300 CT scans of the brain have been included in this study. All studies were performed by a helical CT scanner (Philips 5000 SR) with the standard protocol and were randomly selected due to the presence of either streak or motion artifacts. Segmental reconstruction was applied in all cases by the same experienced radiographer. Image evaluation was performed by two experienced radiologists using a scoring system for each artifact and a grading system for classifying post-processing images. Results Among series of images that were evaluated after the application of segmental reconstruction, brain examinations demonstrated the following results: 10.9% of the cases showed no artifact improvement, 19.6% showed slight artifact improvement 31.5% showed moderate improvement and 38% showed significant improvement. The results of chest examinations were as follows: 27% of the cases showed no artifact improvement, 23% showed slight artifact improvement, 26% showed moderate improvement and 24% of showed significant improvement. Spatial reconstruction was useless in brain CT images when a patient moved during the entire scan and in chest CT images when streak and motion artifacts co-existed. Conclusions Spatial reconstruction may improve the image quality in brain and chest CT examinations and thus may contribute to more diagnostic images. Elimination of motion artifacts is also suggested due to the limitation of intravenous contrast medium that can be administered per patient per day and in cases of non-cooperative patients.

Preoperative Evaluation of Donor Kidney With 16-Section Computed Tomography Angiography: A Pilot Study

kidney disease. 1 Preoperative imaging of donor renal vasculature and functional evaluation is necessary to select a suitable donor and to plan surgery. The ability to view the vascular imaging in three-dimensional (3D) space should be undoubtedly helpful. An increase of detector rows in helical computed tomography (CT) from 4 to 16 has improved the speed of scanning, thereby eliminating motion artifacts and enhancing temporal resolution. 2 These benefits resulted in enhanced quality of both 2- and 3-dimensional (3D) images of renal anatomy. In this study we retrospectively evaluated the sensitivity and specificity of 16-section CT to evaluate renal vessels in living kidney donors by comparing 3D imaging data from 16-section CT with surgical findings.

Systematic Contact-Free 3D Topometry of the Soft Tissue Profile in Cleft Lips

To evaluate the clinical application of three-dimensional (3D) imaging for the analysis of a broad variety of cleft lips and to conduct a systematic analysis. This was a prospective study using a noncontact 3D laser scanner to acquire the preoperative 3D facial profiles. The data sets were analyzed qualitatively and quantitatively. The data were expressed by ratios and scores. Forty nonsedated patients (1 to 39 years, average age 2.7 years) with unilateral cleft lip, cleft lip and alveolus, or complete unilateral cleft in Cambodia. The acquired 3D data sets (mean acquisition time: 2.5 seconds) from facial surfaces were of diagnostic quality in 27 of 40 patients (average age, 14.2 years). In these cases all anatomical structures could be mapped precisely by means of landmark positioning in the range of millimeters. A new method of systematic analysis could be elaborated, allowing for data set expression independent of size and growth factors. In children under age 3, the measuring procedure was of limited value because of motion artifacts and was successful in only 6% (1 of 15) of these patients. The system offers a solid and precise tool for 3D imaging of the complex cleft lip anatomy in compliant patients and is useful for preoperative cleft assessment and follow-up. However, the application is limited in moving infants or uncooperative adults because of scanning time and acquisition method. The development of motion tracking and faster devices could eliminate motion artifacts.

SU‐GG‐I‐17: A Technique for Removing Motion Related Image Artifacts in KV Cone‐Beam CT From On‐Board Imager: 4D‐CBCT Implications

Purpose: To correct motion related image artifacts in kV cone‐beam CT (CBCT) by tracking a seed marker in cone‐beam projections obtained from an on‐board imager (OBI). Method and Materials: The motion of metal markers attached to the CATPHAN phantom mounted on a moving platform was measured by tracking the marker positions in kV cone‐beam projections. The motion tracking algorithm is based on a normalized cross‐correlation algorithm that determines the position of the marker in each projection. The position of the marker was determined from 650 projections (0°–360°) acquired for about a minute in a single CBCT scan. The motion cycle of the moving platform was set at 15cycles/min, with 1.75 cm amplitude, in order to mimic respiratory motion. The marker motion track was used to map cone‐beam projections to eliminate motion shifts. Pre‐processed projections were used to reconstruct CBCT using Feldkamp back‐projection. The CATPHAN was used to evaluate image quality parameters such as contrast, position resolution, uniformity and linearity of CBCT reconstructed before and after motion correction. Results: A new technique was developed and tested to track the motion of seed markers in cone‐beam projections acquired in a kV CBCT scan with no additional dose other than that for imaging. We were able to successfully remove motion related image artifacts such as blurring, spatial distortion and improve contrast and position resolution from CBCT reconstructed from motion‐corrected projections. Besides motion correction, this technique also allows to extract information about seed marker motion that can be used to correlate internal and external marker motion providing possible usage for beam gating implications. Conclusion: This technique eliminates motion artifacts in CBCT. Combining 3D volumetric CBCT with motion tracks of one or more markers may provide a method to perform four‐dimensional CBCT where anatomical information and dynamic positioning of the tumor can be utilized.

Multiwavelength Pulse Oximetry: Theory for the Future

As the use of pulse oximeters increases, the needs for higher performance and wider applicability of pulse oximetry have increased. To realize the full potential of pulse oximetry, it is indispensable to increase the number of optical wavelengths. To develop a multiwavelength oximetry system, a physical theory of pulse oximetry must be constructed. In addition, a theory for quantitative measurement of optical absorption in an optical scatterer, such as in living tissue, remains a difficult theoretical and practical aspect of this problem. We adopted Schuster's theory of radiation through a foggy atmosphere for a basis of theory of pulse oximetry. We considered three factors affecting pulse oximetry: the optics, the tissue, and the venous blood. We derived a physical theoretical formula of pulse oximetry. The theory was confirmed with a full SO2 range experiment. Based on the theory, the three-wavelength method eliminated the effect of tissue and improved the accuracy of Spo2. The five-wavelength method eliminated the effect of venous blood and improved motion artifact elimination. Our theory of multiwavelength pulse oximetry can be expected to be useful for solving almost all problems in pulse oximetry such as accuracy, motion artifact, low-pulse amplitude, response delay, and errors using reflection oximetry which will expand the application of pulse oximetry. Our theory is probably a rare case of success in solving the difficult problem of quantifying optical density of a substance embedded in an optically scattering medium.

Spectral domain OCT at 850 nm and OFDI at 1050 nm for retinal imaging in glaucoma and AMD patients

Abstract Purpose: We have realized a 150 fold improvement of the sensitivity over conventional time domain OCT technology allowing video rate in vivo retinal imagingwithout compromising image quality. Methods: Two different but similar technologies (SD‐OCT and OFDI) provide high speed imaging at a wavelength of 850 nm and 1050 nm, respectively. An overview of the latest system developments will be presented. Data processing techniques to extract and quantify features such as retinal nerve fiber layer thickness, drusen volume, CNV size and volume, and subretinal fluid volume will be presented for a number of glaucoma and AMD patients. Results: Ultra‐high‐resolution video rate SD‐OCT at 850 nm and OFDI at 1050 nm offers many advantages in retinal imaging, maintaining high signal to noise while operating at a safe ocular exposure level. Conclusions: The unprecedented speed eliminates motion artifacts and the need to re‐align A‐lines, enabling accurate 3‐D mapping of the retinal topography, and provides a shift from two‐dimensional imaging to three‐dimensional screening of large retinal volumes.

Snapshot hyperspectral imaging in ophthalmology

Retinal imaging spectroscopy can provide functional maps using chromophore spectra. For example, oxygen saturation maps show ischemic areas from diabetes and venous occlusions. Obtaining retinal spatial-spectral data has been difficult due to saccades and long data acquisition times (>5 s). We present a snapshot imaging spectrometer with far-reaching applicability that acquires a complete spatial-spectral image cube in approximately 3 ms from 450 to 700 nm with 50 bands, eliminating motion artifacts and pixel misregistration. Current retinal spectral imaging approaches are incapable of true snapshot operation over a wide spectral range with a large number of spectral bands. Coupled to a fundus camera, the instrument returns true color retinal images for comparison to standard fundus images and for image validation while the patient is still dilated. Oxygen saturation maps were obtained with a three-wavelength algorithm: for healthy subjects arteries were approximately 95% and veins 30 to 35% less. The instrument is now undergoing clinical trials.

Retrospective ECG-gated left ventriculography using multislice CT following left ventricular bolus injection and evaluation of its utility and motion artifact at every cardiac phase

Following left ventricular bolus injection of contrast material, multislice CT scanning was performed. With retrospective ECG-gated reconstruction, we could acquire volume data for the heart at any cardiac phase and selectively depict only the left ventricle and aorta with maximum intensity projection. Temporal resolution of multislice CT was not sufficient to eliminate motion artifact except just before atrial contraction periods.

Developments in megavoltage cone beam CT with an amorphous silicon EPID: Reduction of exposure and synchronization with respiratory gating

We have studied the feasibility of a low-dose megavoltage cone beam computed tomography (MV CBCT) system for visualizing the gross tumor volume in respiratory gated radiation treatments of nonsmall-cell lung cancer. The system consists of a commercially available linear accelerator (LINAC), an amorphous silicon electronic portal imaging device, and a respiratory gating system. The gantry movement and beam delivery are controlled using dynamic beam delivery toolbox, a commercial software package for executing scripts to control the LINAC. A specially designed interface box synchronizes the LINAC, image acquisition electronics, and the respiratory gating system. Images are preprocessed to remove artifacts due to detector sag and LINAC output fluctuations. We report on the output, flatness, and symmetry of the images acquired using different imaging parameters. We also examine the quality of three-dimensional (3D) tomographic reconstruction with projection images of anthropomorphic thorax, contrast detail, and motion phantoms. The results show that, with the proper choice of imaging parameters, the flatness and symmetry are reasonably good with as low as three beam pulses per projection image. Resolution of 5% electron density differences is possible in a contrast detail phantom using 100 projections and 30 MU. Synchronization of image acquisition with simulated respiration also eliminated motion artifacts in a moving phantom, demonstrating the system's capability for imaging patients undergoing gated radiation therapy. The acquisition time is limited by the patient's respiration (only one image per breathing cycle) and is under 10 min for a scan of 100 projections. In conclusion, we have developed a MV CBCT system using commercially available components to produce 3D reconstructions, with sufficient contrast resolution for localizing a simulated lung tumor, using a dose comparable to portal imaging.

体幹部領域における深吸気時停止SPECT法の有用性に関する研究 : 分解能の向上に関する検討

Because SPECT images are acquired under normal respiration, the respiratory motion induces artifacts and decreases resolution. In this study we developed a novel method of acquiring SPECT data during deep inhalation breath-hold (BrST) and assessed its efficacy in reducing motion artifacts and improving resolution. Reproducibility studies found that variations in SPECT image homogeneity were reduced using the BrST method to within a clinically non-problematic range. An experiment using a custom-built respiration phantom showed almost complete elimination of motion artifacts and significant improvement in resolution using the BrST method. Clinical assessment confirmed a significant reduction in motion artifacts along with the improvement in resolution. The BrST method enabled visualization of lesions that previously had been impossible to detect by standard acquisition under normal respiration. The BrST method is expected to both significantly reduce motion artifacts and improve resolution.

46.4: Improved Technology for Motion Artifact Elimination in LCD Monitors: Advanced DCC

This paper presents a new technology, Advanced Dynamic Capacitance Compensation (A-DCC), for improved dynamic performance of LCD monitors. Conventional LCD monitors suffer from certain specific artifacts, such as wire-frame flicker and line dimming, which are not an issue for the simpler motion images found in television content. A-DCC addresses these more challenging monitor cases through an advanced architecture which analyzes multi-frame data and applies more comprehensive lookup table corrections according to the specific frame sequence.

RatCAP: miniaturized head-mounted PET for conscious rodent brain imaging

Anesthesia is currently required for positron emission tomography (PET) studies of the animal brain in order to eliminate motion artifacts. However, anesthesia profoundly affects the neurological state of the animal, complicating the interpretation of PET data. Furthermore, it precludes the use of PET to study the brain during normal behavior. The rat conscious animal PET tomograph (RatCAP) is designed to eliminate the need for anesthesia in rat brain studies. It is a miniaturized full-ring PET scanner that is attached directly to the head, imaging nearly the entire brain. RatCAP utilizes arrays of 2 mm /spl times/ 2 mm LSO crystals coupled to matching avalanche photodiode arrays, which are in turn read out by full custom integrated circuits. Principal challenges have been addressed considering the physical constraints on size, weight, and heat generation in addition to the usual requirements of small-animal PET, such as high spatial resolution in the presence of parallax error. A partial prototype has been constructed and preliminary measurements and optimization completed. Realistic Monte Carlo simulations have also been carried out to optimize system performance, which is predicted to be competitive with existing microPET systems.

Volume Visualization of the Cervical Spine: Principles, Techniques, and Clinical Applications

Multidetector computed tomography (CT) offers important advantages over conventional imaging modalities in the evaluation of the cervical spine. It allows for faster scanning times by a factor of 4 to 16 over conventional CT scanning, which is critical for triaging patients after trauma. Faster scanning times help to eliminate motion artifacts, and the newest multidetector scanners allow for thinner collimation and the ability to achieve an isotropic data set that can be reformatted in any plane without loss of spatial resolution. In addition, three-dimensional volume-rendered reconstructions of images obtained using multidetector scanners can provide additional information in defining the extent of injury or neoplasm, allowing neurosurgeons to see fractures or tumors in any plane, simulating intraoperative views. Three-dimensional volume-rendered images also can significantly reduce streak artifact and beam-hardening artifact that can occur with two-dimensional images in the presence of metal surgical hardware. Three-dimensional volume-rendered multidetector CT represents an advance in CT technology and can help to ensure rapid, accurate evaluation of cervical spine pathology. In this article, the authors demonstrate the utility of three-dimensional volume-rendered images in evaluating cervical spine trauma, neoplasm, and postoperative conditions, with the majority of images presented being obtained with multidetector CT scanners.

Cervical spine trauma: evaluation by multidetector CT and three-dimensional volume rendering.

Multidetector-row computed tomography (CT) offers important advantages over conventional imaging modalities in the evaluation of the post-trauma cervical spine. It allows for faster scanning times, critical for triaging post-trauma patients as well as for eliminating motion artifacts, and allows for thinner collimation and the ability to achieve an isotropic data set which can be reformatted in any plane without loss of spatial resolution. In addition, three-dimensional volume-rendered reconstructions of images obtained using multidetector scanners can provide additional information in defining extent of injury, allowing neurosurgeons to see the fractures in any plane, simulating intraoperative views. 3D multidetector-row CT represents an advance in CT technology and can help ensure rapid, accurate evaluation of cervical spine injuries.

Telesurgical presence and consultation for open surgery.

When telemedicine emerged in the late 1950s, the innovative and sophisticated technology used at the time was quite expensive. Historically, the use of telemedicine applications was limited to institutions that either had funding through government-sponsored grants or could afford the cost of the technologic tools. This hindered the broad use and expansion of telemedicine. Today, the use of this technologic method is still cost-dependent; however, the advent of the Internet as well as a broader expansion of telecommunication to remote areas make the concept of globalization more feasible. In recent years, several groups have experimented with less expensive telecommunication resources that are capable of handling less bandwidth, while nonetheless establishing safe and effective telemedicine applications. Access to specialized medical attention by those in remote areas has traditionally limited adequate patient care. The feasibility and effectiveness of mobile health care delivery to remote areas has been demonstrated. However, the sense of remoteness and isolation in certain medical scenarios could limit the potential of this service. Laparoscopic tools make it possible to share the surgical visual field with the rest of the surgical team, with the benefit of superior optics. Endoscopic visualization techniques recently applied to open surgery facilitate surgical performance and add a new tool to the armamentarium of today’s surgeon. Transmission of such visualization techniques, especially with current compression software, may be severely limited by motion artifacts resulting from both intentional and inadvertent human manipulation. While small movements within the visual field may have no adverse effects, moving the entire field causes severe pixelation of the transmitted images. Stabilization of the camera to eliminate motion artifacts allows compression of laparoscopic images with the H.323 protocol for Internet transmission, with

Mesenteric venous thrombosis: diagnosis and noninvasive imaging.

Mesenteric venous thrombosis is an uncommon but potentially lethal cause of bowel ischemia. Several imaging methods are available for diagnosis, each of which has advantages and disadvantages. Doppler ultrasonography allows direct evaluation of the mesenteric and portal veins, provides semiquantitative flow information, and allows Doppler waveform analysis of the visceral vessels; however, it is operator dependent and is often limited by overlying bowel gas. Conventional contrast material-enhanced computed tomography (CT) allows sensitive detection of venous thrombosis within the central large vessels of the portomesenteric circulation and any associated secondary findings; however, it is limited by respiratory misregistration, motion artifact, and substantially decreased longitudinal spatial resolution. Helical CT and CT angiography, especially when performed with multi-detector row scanners, and magnetic resonance (MR) imaging, particularly gadolinium-enhanced MR angiography, enable volumetric acquisitions in a single breath hold, eliminating motion artifact and suppressing respiratory misregistration. Helical CT angiography and three-dimensional gadolinium-enhanced MR angiography should be considered the primary diagnostic modalities for patients with a high clinical suspicion of mesenteric ischemia. Conventional angiography is reserved for equivocal cases at noninvasive imaging and is also used in conjunction with transcatheter therapeutic techniques in management of symptomatic portal and mesenteric venous thrombosis.

Detection and elimination of motion artifacts by regeneration of k-space.

A method has been developed using techniques from partially parallel imaging (PPI) to detect localized inconsistencies in k-space that are caused by certain types of motion. The inconsistent data are discarded and consistent data regenerated from the remaining data using PPI techniques. The price is a small decrease in signal-to-noise ratio (SNR) and additional postprocessing. An iterative scheme is presented which does not require separately acquired coil sensitivity information for the PPI reconstructions. This method has been found to reduce artifact levels in phantom and in vivo test studies.

Optimal Electrocardiographically Triggered Phase for Reducing Motion Artifact at Electron-Beam CT in the Coronary Artery

Rationale and Objectives The authors performed this study to ( a) investigate coronary movement with electron-beam computed tomography (CT) and ( b) find the optimal electrocardiographic (ECG) triggering phase for eliminating motion artifact. Materials and Methods One hundred fifty-one patients without arrhythmia were examined with electron-beam CT. First, movie scans were obtained to create displacement and velocity graphs of coronary artery movement. Then, a volume scan with an exposure time of 100 msec was obtained with various ECG trigger settings. Results Movement patterns of coronary arteries varied with heart rate. Optimal triggering phase was before atrial systole (near 71% of the R-R interval) when heart rate was slower than 68 beats per minute and at ventricular end systole when heart rate was fast. Rate of severe motion artifacts decreased from 43% to 0% when triggering was altered from 80% of the R-R interval to the individual optimal value. Experimental values of the optimal phase at different heart rates were derived, and severe motion artifact was only 3.0% with these values. Conclusion ECG triggering set according to the heart rate enables a great reduction in motion artifacts at electron-beam CT with a 100-msec exposure time. The results may have implications for magnetic resonance imaging of the coronary artery.

MYOCARDIAL CONTRAST ENHANCEMENT AFTER IV OPTISON[trade mark sign] FOR INTRAOPERATIVE ECHOCARDIOGRAPHY DURING CARDIAC SURGERY

Introduction. Since 1998, Optison[trade mark sign], a venous ultrasound contrast agent of albumin micro-spheres filled with octafluoropropane, has been available to improve left ventricular (LV) endocardial border delineation. Optison[trade mark sign] was used to show myocardial perfusion in dogs. Contrast agents injected arterially have been used in humans to show myocardial perfusion. The noninvasive demonstration of myocardial perfusion during cardiac surgery with transesophageal echocardiography (TEE) would be helpful in distinguishing stunned but perfused from ischemic myocardium. Methods. 23 patients (pts) undergoing valvular surgery with normal coronary anatomy were studied. Two different echo systems equipped for on-line measurement of reflected ultrasound energy in a user defined region of interest (ROI) [Acuson Aspen[trade mark sign] (AA) and Hewlett Packard Sono 5500[trade mark sign] (HP)] were used to measure contrast intensity. In a transgastric shortaxis view of the LV, the ROI was placed in the inferior wall, and a bolus of 0.3 ml of Optison[trade mark sign] was injected into a central vein while contrast intensity was measured and recorded. Imaging was triggered by electrocardiography and ventilation interrupted to eliminate motion artifacts during image acquisition. Results. In 2 of 30 injections in 11 pts imaged with the AA system, increases in myocardial contrast intensity were seen in 2 pts. In 12 of 42 injections in 12 pts imaged with the HP system, increases in myocardial contrast intensity were seen in 5 pts, with the most dramatic response shown (Figure 1). In 3 of these pts, effects were repeatable in multiple injections, while one patient showed increased myocardial contrast intensity only during a dobutamine infusion. 16 pts (9 imaged with AA, 5 with HP) showed no contrast effect on multiple contrast injections.Figure 1Discussion. We inconsistently detected increased myocardial contrast intensity in the LV inferior wall after IV injection of Optison[trade mark sign]. This effect was not repeatable in all pts and was never seen in others. Some of the differences seen might be due to the methods used by the echo systems to measure and process reflected ultrasound energy into data. Also, in 6 of 11 pts imaged with the AA system we triggered at every heart beat, which might have caused accelerated destruction of microspheres, thereby unabling us to measure contrast effect. All other studies were triggered at every 4th heart beat. More study and technical advances are needed to make myocardial contrast echocardiography a reliable, reproducible technique for the intraoperative setting.

A Fungal Metabolite That Eliminates Motion Artifacts

A Fungal Metabolite That Eliminates Motion Artifacts