Decrease Scan Time Research Articles

Assessment of third ventriculostomy patency with the 3D-SPACE technique: a preliminary multicenter research study.

The goal of this study was to determine the value of the 3D sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE) technique in the evaluation of endoscopic third ventriculostomy (ETV) patency. Twenty-six patients with ETV were examined using 3-T MRI units. Sagittal-plane 3D-SPACE with variant flip-angle mode, 3D T1-weighted (T1W), and 3D heavily T2-weighted (T2W) images were obtained with isotropic voxel sizes. Also, sagittal-axial plane phase-contrast cine (PC)-MR images were obtained. The following findings were evaluated: diameters of stoma and third ventricle, flow-void sign on 3D-SPACE and PC-MR images, integrity of the third ventricle on heavily T2W images, and quantitative PC-MRI parameters of the stoma. Obtained sequences were evaluated singly, in combination with one another, and all together. The mean area, flow, and velocity values measured at the level of stoma in patients with patent stoma were significantly higher than those measured in patients with closed stoma (p < 0.05). There was significant correlation among PC-MRI, 3D-SPACE, and 3D heavily T2W techniques regarding assessment of ETV patency (p < 0.001). The 3D-SPACE technique provided the lowest rate of ambiguous results. The 3D-SPACE technique seems to be the most efficient one for determination of ETV patency. The authors suggest the use of 3D-SPACE as a stand-alone first-line sequence in addition to routine brain MRI protocols in assessing patients with ETV, thereby decreasing scan time and reserving the use of a combination of additional sequences such as PC-MRI and 3D heavily T2W images in suspicious or complex cases.

Clinical applications of dual-channel transmit MRI: A review.

This article reviews the principle of dual-channel transmit MRI and highlights current clinical applications which are performed primarily at 3 Tesla. The main benefits of dual-channel transmit compared with single-transmit systems are the increased image contrast homogeneity and the decreased scanning time due to the more accurate local specific absorption ratio estimation, meaning that less conservative safety limits are needed. The dual-transmit approach has been particularly beneficial in body imaging applications, and is also promising in terms of cardiac, spine, and fetal imaging. Future advances in transmit SENSE, the combination of dual-channel transmit with high permittivity pads, as well as the potential increase in the number of transmit channels are also discussed.

Improving efficiency and decreasing scanning time of sonographic examination of the shoulder by using a poster illustrating proper shoulder positioning to the patient.

Patients often have difficulty performing the various movements required for ideal positioning to enable accurate sonographic (US) assessment of the shoulder; this may result from pain and or unclear oral instructions. We performed this study to ascertain whether the use of a poster depicting the positions required during the examination would decrease scanning time and hence improve the overall efficiency of shoulder US. We retrospectively compared results from 50 consecutive patients who underwent US examination without (group 1) and 50 with (group 2) the use of an illustrative poster produced by the European Society of Musculoskeletal Radiology. The difference in mean scanning time between the two groups was analyzed with Student's two-tailed t test. There was a statistically significant difference in scanning time between the two groups (group 1: 3 minutes and 5 seconds versus group 2: 2 minutes and 9 seconds; p < 0.0001). The patients in group 2, especially those who had hearing difficulty, found the poster useful. The use of a poster illustrating positioning of the shoulder during an US examination is an effective way to improve patient compliance and significantly decreases scanning time.

Acute Spinal Cord Compression: CQI Framework Increases Resource Efficiency While Promoting Delivery of High-Quality Care

PurposeLiterature reports indicate that advanced imaging is overutilized, especially in the emergency setting. At our institution, stat spinal MRI for suspected acute spinal cord compression (ASCC) was perceived to be excessively utilized. A continuous quality improvement process was employed to investigate this trend and improve the efficiency of this diagnosis. MethodsSpine imaging in patients with suspected ASCC was retrospectively evaluated for appropriateness of indications and quality of imaging. Based on the results, a new institutional policy for ordering MR for suspected ASCC was implemented, concurrent with development of a new screening spine MRI protocol. Subsequently, indications, efficacy, and imaging utilization of the new strategy were analyzed for improved operational effectiveness. ResultsThe initial retrospective study demonstrated only a 1.4% positive rate of ASCC as well as image-quality degradation due to patient motion resulting from prolonged scan times. Based on these results, a new institutional policy for ordering stat ASCC spine MRI was instituted with an updated screening MRI protocol. This policy resulted in a positive rate of ASCC of 4.4%, and decreased scan time by 50%-70%, while preserving diagnostic image quality and decreasing resource utilization. ConclusionsAs suspected, stat spinal MRI for ASCC was excessively utilized at our institution. The study demonstrated that systemic improvements regarding this issue can be achieved by using a multidisciplinary approach and following a continuous quality improvement methodology. A new MRI protocol for identification of ASCC was found to preserve image quality and diagnostic confidence, while simultaneously decreasing scan time and use of valuable health care resources.

MRI of the Brachial Plexus: Modified Imaging Technique Leading to a Better Characterization of Its Anatomy and Pathology

Magnetic resonance imaging (MRI) is the imaging modality of choice for the evaluation of the brachial plexus due to its superior soft tissue resolution and multiplanar capabilities. The evaluation of the brachial plexus however represents a diagnostic challenge for the clinician and the radiologist. The imaging assessment of the brachial plexus, in particular, has been traditionally challenging due to the complexity of its anatomy, its distribution in space and due to technical factors. Herein, we describe a modified technique used in our institution for the evaluation of the brachial plexus which led to a substantial decrease in scanning time and to better visualization of all the segments of the brachial plexus from the roots to the branches, in only one or two images, facilitating therefore the understanding of the anatomy and the interpretation of the study. To our knowledge, we are the first group to describe this technique of imaging the brachial plexus. We illustrate the benefit of this modified technique with an example of a patient with a lesion in the proximal branches of the left brachial plexus that was clinically suspected but missed on conventional brachial plexus imaging for six consecutive years. In addition, we review the common and infrequent benign and malignant pathology that can affect the brachial plexus.

Comparison of Area–Length Method by Echocardiography Versus Full-Volume Quantification by Cardiac Magnetic Resonance Imaging for the Assessment of Left Atrial Volumes in Children, Adolescents, and Young Adults

Left atrial (LA) size is a known predictor of adverse cardiovascular events. Echocardiography is the modality of choice for the evaluation of atrial size; however, cardiac magnetic resonance imaging (cMRI) remains the "gold standard." We sought to calculate atrial volumes using the area-length method by both echocardiography and cMRI and compare them with area-volume quantification by cMRI. Thiry-eight patients (mean age 20 ± 12 years, 71% male) who underwent cMRI and echocardiography between September 2010 and June 2012 were retrospectively identified. The time interval between the two studies was ≤ 6 months. LA volumes by echocardiogram were estimated using the area-length method: LA volume = (0.85 × area(4ch) × area(2ch))/(shortest atrial length). The atrial length and area were measured in standard apical two-chamber and four-chamber planes. Measured values were indexed to body surface area (BSA). CMRI measurements were obtained from prospectively gated steady-state free precession cine stack images obtained in a standard four-chamber plane. LA volumes were calculated using Simpson's method: LA volume = LA area × (slice thickness + gap) per slice. Slice thickness ranged from 5 to 7 mm with contiguous slices of 5 to 7 mm. The values were indexed to BSA. Statistics were summarized using measures of central tendency. LA volumes by echocardiography were significantly less than those by full-volume cMRI quantification. The mean LA volume by echocardiography and full-volume cMRI were 35 ± 14.5 and 42.4 ± 17.2, respectively (p = 0.05). The mean difference between LA volumes obtained by the two methods was 7.4 ± 10.6. LA volume measured by cMRI using the area-length method closely approximated full-volume assessment by cMRI with mean values of 42.9 ± 17.4 versus 42.4 ± 17.2, respectively (p = 0.91). There were no significant differences in the patient characteristics between the two study modalities. LA volumes as measured by echocardiography using the area-length method consistently underestimated the true volume when compared with cMRI. LA volumes measured using the area-length method by cMRI is an alternative technique for accurately quantifying chamber size and can be useful in decreasing scan time or when full-volume data sets are incomplete.

Rapid imaging protocol in trauma: a whole-body dual-source CT scan

The purpose of this study is to determine whether a single acquisition whole-body trauma multi-detector CT scan is able to reduce resuscitation time, scan time, and effective radiation dose without compromising diagnostic quality in the setting of polytrauma. Retrospective analysis of 33 trauma patients undergoing single acquisition whole-body CT with injury severity scores of ≥ 16 was compared to 34 patients imaged with a segmented whole-body CT protocol. Time spent in the emergency department, effective radiation dose, image quality, and mortality rates were compared. The single acquisition group spent 53.7 % less time in the emergency department prior to imaging (p=0.0044) and decreased scanning time by 25 %. The protocol yielded a 24.5 % reduction in mean effective radiation dose (24.66 mSv vs. 32.67 mSv, p<0.0001). The image noise was similar in both groups. Standardized mortality ratios were comparable. The single acquisition protocol significantly reduces time spent in the emergency department by allowing faster imaging at a lower radiation dose while maintaining image quality. Other contributors to reduction in radiation dose include use of dual-source CT technology, removal of delayed CT intravenous pyelogram, and arm positioning.

WE-E-144-01: The Management of Imaging Procedure Dose 3: Computed Tomography

WE-E-144-01: The Management of Imaging Procedure Dose 3: Computed Tomography

MO‐F‐WAB‐10: Evaluation of Scan Time Required for Motion Tracking in Four‐Dimensional Cone Beam CT Using Patient Data Sets

Purpose: Applying four‐dimensional cone beam CT in a radiation treatment setting requires a tradeoff between image quality and scan time. The aim of this study is to assess the minimum scan time required to determine the motion of tumors immediately prior to radiation treatment. Methods: Long CBCT scans of approximately 10 minutes were taken from 11 patients with lung lesions. Shorter scan times (down to about 1 minute) for these patients were simulated by removing projections. Four dimensional images were created from each full and simulated scan time using a ROI based FDK reconstruction algorithm with 8 breathing phases. Tumor motion for each phase relative to the first phase was determined through deformable image registration in a region of interest. The ability to track motion was assessed by comparing the results of the image registration of the simulated scans to the results for the full data scan. Results: For each comparison between the full data set and a reduced data set, a root‐mean‐square error was calculated comparing the two motions on a phase by phase basis, with the summation being over the phases. As anticipated, the RMS error as well as the spread in the RMS error increased with decreasing scan time. Good tumor tracking was observed down to 2 minute scan times (RMS error = 1.9 ± 0.6 mm), while 1 minute scan times demonstrated a large spread in the error (RMS error = 2.4 ± 1.8 mm). Conclusion: This study suggests scan times down to two minutes are sufficient for the extraction of tumor motion trajectories from 4D CBCT images. Additionally, this study sets up the ability to compare other reconstruction methods to the traditional FDK method.

Quality of Extracranial Carotid Evaluation with 256-Section CT

To date, no systematic evaluation of image quality has been performed on the 256-section multidetector CT scanner for extracranial carotid evaluations. We evaluated image quality, patient dose, and examination time and compared these parameters with a 64-section multidetector CT. We reviewed extracranial CTA scans obtained on a 256-detector CT scanner in 50 consecutive patients. Image quality was analyzed for artifacts and vessel contrast opacification from the aortic arch to the skull base, dose to patient, and scan time. Results were compared with a control group of 50 patients imaged on a 64-section CT scanner. A Fisher exact test was used to analyze both groups with respect to vessel contrast opacification and presence of artifacts, and a Student t test was used to assess differences in patient dose between the 2 groups. Quantitative and qualitative evaluations revealed >95% acceptable vessel opacification at all levels measured on the 256-section scanner. Scan time was improved (4 seconds on 256-channel). There were fewer artifacts related to metallic streak on the 256-channel CTA study, and DLP was lower on the 256-channel CTA (113.9 versus 159.8 mGy). The 256-channel CTA imaging protocol for carotid arteries yielded similar vessel contrast opacification compared with the 64-channel CTA but with fewer metallic artifacts, a modest decrease in scan time, similar image quality, and a statistically significant reduction in radiation dose of 10%.

뇌기능 활성화 검사 시 적정한 자극 횟수에 관한 연구

BOLD기법은 자극 횟수가 늘어날수록 시간의 증가 및 검사 실패율이 높아지므로 본 연구를 통해 가장 적절한 자극 횟수를 도출하여 제시함을 목적으로 하였다. 연구대상은 정상인 10명을 대상으로 손 운동 기능검사의 paradigm을, 1회에서 7회까지 자극 횟수로 나누어 피검자에게 시행하였다. 실험장비는 Philips Intera Archieva 3.0T MRI System 및 Invivo사의 Eloquene를 사용하였으며, BOLD-EPI 기법을 이용하여 10번의 휴지기와 10번의 활성기의 block design을 이용하였다. 관심영역인 primary hand motor area의 활성화 여부와 활성화 cluster 수, 활성화도, 비관심영역의 활성화 cluster 수를 비교하였다. 관심영역의 활성화 cluster 수는 2회 자극이 가장 낮았고, 3회부터는 일정하였으며, 활성화도는 자극 횟수가 늘어날수록 증가하지만, 비례하지는 않았다. 비관심 영역의 활성화 cluster 수는 3회부터 일정하였고, 6회부터 다시 증가하였다. 결론적으로 관심영역과 비관심영역의 활성화를 감안하고, 시간 감소에 따른 환자의 피로를 감소시키면서 정확성에 영향을 주지 않는 자극 횟수로 3회가 적정하리라 사료된다. BOLD technique in functional MRI has to apply multiple stimulations. However as the stimulation time increases failure rates rise. In this study we are proposing proper number of stimulations through our experiments. Ten normal people underwent functional MRI hand motor sanning and the paradigms were designed from first to seventh stimulation. Under Philips Intera Achieva 3.0T MR system and Invivo cop's Eloquence equipment, activation periods and rest periods were repeated ten times each, using BOLD EPI technique. Primary hand motor area stimulation and number of clusters, activation rates and number of activated clusters in and outside the region of interest were compared to each other. Number of clusters in region of interest was lower than others at second stimulation and became static from third stimulation. The stimulated ratios were elevated as the number of stimulations were increased but it was not proportional. Number of clusters outside the ROI became static from the third stimulation and started increasing from sixth stimulation. As results, given the activation ratios of ROI and out side the ROI, three times stimulation was the most appropriate because it does not affect accuracy, also decreasing the fatigue of patients by with the decreased scanning time.

Role of Limited Whole-Body PET/CT in Pediatric Lymphoma

Performing true whole-body FDG PET/CT is standard practice in pediatric lymphoma staging and follow-up. In adults, imaging is typically limited whole-body PET/CT, which has advantages over true whole-body PET/CT, primarily decreased scanning time and decreased radiation. We hypothesize that in pediatric lymphoma, limited whole-body PET/CT is sufficient for routine follow-up when disease on the true whole-body staging study is confined to the limited whole-body field of view (FOV). True whole-body PET/CT studies performed for staging and follow-up of pediatric lymphoma patients between November 2004 and July 2009 at two tertiary pediatric referral hospitals were retrospectively reviewed. Abnormalities on the limited whole-body and additional true whole-body FOV were documented. One hundred seventy patients met the inclusion criteria (752 examinations). At staging, disease involved the limited whole-body FOV without involving the additional true whole-body FOV in 150. Of the 150, 145 had routine follow-up (508 examinations). In these patients, no new (18)F-FDG-avid disease was identified outside of the limited whole-body FOV on routine follow-up (positive predictive value, 0%, 95% CI, 0-0.02). The limited whole-body PET/CT for routine follow-up when disease is confined to the limited whole-body FOV at staging is appropriate. Given its definite advantages over true whole-body PET/CT, it is preferred.

Reproducibility of subregional trabecular bone micro-architectural measures derived from 7-Tesla magnetic resonance images

High-resolution magnetic resonance imaging (MRI) of trabecular bone combined with quantitative image analysis represents a powerful technique to gain insight into trabecular bone micro-architectural derangements in osteoporosis and osteoarthritis. The increased signal-to-noise ratio of ultra high-field MR (≥7 Tesla) permits images to be obtained with higher resolution and/or decreased scan time compared to scanning at 1.5/3T. In this small feasibility study, we show high measurement precision for subregional trabecular bone micro-architectural analysis performed on 7T knee MR images. The results provide further support for the use of trabecular bone measures as biomarkers in clinical studies of bone disorders.

Application of 3-Dimensional Ultrasonography in Assessing Carpal Tunnel Syndrome

The aim of study was to assess the usefulness of 3D ultrasonography (3DUS) in the diagnosis of carpal tunnel syndrome. Fifty patients with carpal tunnel syndrome confirmed by electromyography and 37 healthy control participants underwent 3DUS of the wrists. The mean times per participant for the 3DUS examination and review of the 3D volume set were recorded. The cross-sectional area at the proximal carpal tunnel and the maximum swelling point were measured. Data from patients and controls were compared for determination of statistical significance. The accuracy of the 3DUS diagnostic criteria for carpal tunnel syndrome was evaluated using receiver operating characteristic analysis, and changes in the median nerve shape, including the maximum swelling point, were assessed by review of the 3D volume data. The mean times for examination of a participant and review in each wrist were 56 seconds and 5.7 minutes, respectively. Significant differences were observed in the mean cross-sectional areas of the median nerve between patients and controls. The mean cross-sectional areas ± SD were 16.7 ± 6.7 mm(2) in patients and 8.3 ± 1.9 mm(2) in controls. Using the receiver operating characteristic curve, a cutoff value of greater than 10.5 mm(2) provided diagnostic sensitivity of 84% and specificity of 86%. In 42 of 73 wrists with carpal tunnel syndrome, the median nerve showed fusiform morphologic abnormalities and maximum swelling points. Our results show that 3DUS could markedly decrease scanning time, and measurement of the median nerve cross-sectional area combined with morphologic analysis using 3DUS is a promising supplementary method for the diagnosis of carpal tunnel syndrome.

Cardiac magnetic resonance whole-heart two-dimensional single-breathhold and navigator-guided three-dimensional free-breathing quantification of infarct size are accurate alternative techniques to standard two-dimensional late gadolinium enhancement imaging

Introduction Although infarct size by late gadolinium enhancement (LGE) CMR imaging is a robust prognostic marker in patients with recent MI, long scan times and repeated breathholds associated with the current standard, singleslice 2D multiple-breathhold (SS2D), limit clinical use of this technique. Two new techniques, whole-heart 2D single-breathhold (WHOLE) and navigator-guided 3D freebreathing (3DNAV), offer the advantages of decreased scan time and higher spatial resolution without breathholding, respectively.

Applications of cardiac multidetector CT beyond coronary angiography

Noninvasive imaging of the coronary arteries using multidetector CT (MDCT) represents one of the most promising diagnostic imaging advances in contemporary cardiology. This challenging application has driven a rapid and impressive advancement in CT technology over the past 10 years; leading to increased spatial and temporal resolution, decreased scan times and substantial reductions in radiation dose. Recent technological improvements have not only improved the status of CT coronary angiography but have also enabled new functional myocardial applications that are gaining a foothold in clinical practice as adjuncts or replacements for conventional coronary angiographic studies. Wide-detector CT designs along with prospective ECG-triggered protocols have opened the possibility of performing multiple complementary myocardial measurements during a coronary CT exam with acceptable radiation and contrast exposure. In this Review, we discuss recent technical developments in cardiac MDCT and outline newly enabled noncoronary cardiac applications including viability assessment, myocardial perfusion and molecular imaging.

Novel 320-slice multislice CT angiography as a gatekeeper for invasive coronary angiography

“While diagnostic accuracy of 320‑slice CTA will most likely be similar to 64‑slice systems, the main advantages of this technique are decreased scan time, contrast administration and radiation dose. Furthermore, volumetric scanning allows for CTA in conjunction with myocardial perfusion imaging in a single examination and heart beat.”

Dynamic Automatic Ultrasound Optimization

The aims of this study were to evaluate if a dynamic automatic image optimization technique decreases examination time and number of keystrokes while maintaining or improving image quality and to determine if these variables vary with sonographer experience. Five sonographers of varying experience performed a randomized standard abdominal ultrasonography using manual and automatic techniques on 5 healthy volunteers. The time to perform the examinations and the number of images obtained were recorded, and a keystroke log was maintained for all examinations. Images were stored digitally for review and image analysis. The sonographers graded their pain during the examinations on a 10-point sliding scale. The mean scanning time for the manual examination was 9 minutes 43 seconds, whereas the mean time for the Native Tissue Equalization examination was 8 minutes 47 seconds (P = 0.005). The mean number of images per manual examination was 46.1, whereas the mean number of images per Native Tissue Equalization examination was 45.2 (P > 0.05). The individual increases in scanning time of the sonographers were 0.0%, 5.6%, 10.5%, 14.9%, and 15% from the most experienced to the least experienced. The mean number of keystrokes for the manual examination was 975.1, whereas the mean number of keystrokes for the Native Tissue Equalization examination was 767.3 (P = 0.0022). This resulted in a mean decrease of 208 keystrokes per examination. Sonographers rated their pain as less severe with the Native Tissue Equalization. Native Tissue Equalization provided a mean decrease in image scan time of 9.6% and a decrease in keystrokes of 21.3%. The decrease in scanning time is correlated to the scanning experience. There was less pain experienced by the sonographer in the Native Tissue Equalization examinations.

3T Magnetic Resonance Imaging of Ankle and Hindfoot Tendon Pathology

Ankle tendon pathology is relatively common in the active adult population. Magnetic resonance imaging is often the preferred advanced imaging option for the evaluation of tendon pathology of the hindfoot and ankle. The almost linear increase in signal-to-noise ratio provided by higher field strength imaging allows for improved image resolution and decreased scan times. Newer systems with faster gradients allow for optimal fast spin-echo imaging with lower echo spacing for longer echo train lengths and minimal image blurring. The ability to comfortably scan the ankle within the magnet isocenter using high-field strength-compatible extremity coils further maximizes the image resolution. It is imperative for the radiologist to be aware of necessary protocol adjustments and potential imaging artifacts unique to high-field strength imaging of the ankle. Our review outlines high-field strength magnetic resonance imaging technique and artifacts and also details the specifics of our own methods of ankle imaging.

Using the GRAPPA operator and the generalized sampling theorem to reconstruct undersampled non‐Cartesian data

As expected from the generalized sampling theorem of Papoulis, the use of a bunched sampling acquisition scheme in conjunction with a conjugate gradient (CG) reconstruction algorithm can decrease scan time by reducing the number of phase-encoding lines needed to generate an unaliased image at a given resolution. However, the acquisition of such bunched data requires both modified pulse sequences and high gradient performance. A novel method of generating the "bunched" data using self-calibrating GRAPPA operator gridding (GROG), a parallel imaging method that shifts data points by small distances in k-space (with Deltak usually less than 1.0, depending on the receiver coil) using the GRAPPA operator, is presented here. With the CG reconstruction method, these additional "bunched" points can then be used to reconstruct an image with reduced artifacts from undersampled data. This method is referred to as GROG-facilitated bunched phase encoding (BPE), or GROG-BPE. To better understand how the patterns of bunched points, maximal blip size, and number of bunched points affect the reconstruction quality, a number of simulations were performed using the GROG-BPE approach. Finally, to demonstrate that this method can be combined with a variety of trajectories, examples of images with reduced artifacts reconstructed from undersampled in vivo radial, spiral, and rosette data are shown.