Navigator-triggered prospective acquisition correction (PACE) technique vs. conventional respiratory-triggered technique for free-breathing 3D MRCP: An initial prospective comparative study using healthy volunteers

The effect on gastrointestinal peristalsis for magnetic resonance cholangiopancreatography during breath-holding methods

The breath-hold (BH) 3D magnetic resonance cholangiopancreatography method has been reported to suppress "respiratory artifacts"; however, the influence of gastrointestinal peristalsis around the target organs has not been discussed. In contrast, the autonomic nervous system has been reported to affect gastrointestinal peristalsis and BH imaging has been reported to influence venous blood flow signal (BFS) through its involvement with the autonomic nervous system. We examined the impact of BH imaging on gastrointestinal peristalsis. Seven healthy volunteers participated. Three respiratory patterns-free breathing (FB), BH at maximum inspiration (Insp-BH), and BH at maximum expiration (Exp-BH)-were used. Gastrointestinal peristalsis was measured using cine MRI. Cine MRI data were analyzed using the normalized interframe difference method, focusing on the duodenum and gastric body. Hemodynamic changes resulting from BH methods were evaluated using 2D phase contrast, targeting the inferior vena cava (IVC). The BFS was examined for all phases of each respiratory pattern. Peristalsis variation in the duodenum showed no significant differences among FB, Exp-BH, and Insp-BH. In the gastric body, no significant differences were observed between FB and Exp-BH or between Exp-BH and Insp-BH. However, a significant difference emerged between FB and Insp-BH. Regarding BFS, in the IVC, significant differences were observed between Exp-BH and Insp-BH and between FB and Insp-BH (both, p < 0.01), with no significant difference between FB and Exp-BH. Insp-BH reduces venous blood flow and suppresses the influence of peristalsis variation.

Deep learning-based reconstruction and 3D hybrid profile order technique for MRCP at 3T: evaluation of image quality and acquisition time

OBJECTIVES

To evaluate the image quality of the 3D hybrid profile order technique and deep-learning-based reconstruction (DLR) for 3D magnetic resonance cholangiopancreatography (MRCP) within a single breath-hold (BH) at 3 T magnetic resonance imaging (MRI).

METHODS

This retrospective study included 32 patients with biliary and pancreatic disorders. BH images were reconstructed with and without DLR. The signal-to-noise ratio (SNR), contrast, contrast-to-noise ratio (CNR) between the common bile duct (CBD) and periductal tissues, and full width at half maximum (FWHM) of CBD on 3D-MRCP were evaluated quantitatively. Two radiologists scored image noise, contrast, artifacts, blur, and overall image quality of the three image types using a 4-point scale. Quantitative and qualitative scores were compared using the Friedman test and post hoc Nemenyi test.

RESULTS

The SNR and CNR were not significantly different when under respiratory gating- and BH-MRCP without DLR. However, they were significantly higher under BH with DLR than under respiratory gating (SNR, p = 0.013; CNR, p = 0.027). The contrast and FWHM of MRCP under BH with and without DLR were lower than those under respiratory gating (contrast, p < 0.001; FWHM, p = 0.015). Qualitative scores for noise, blur, and overall image quality were higher under BH with DLR than those under respiratory gating (blur, p = 0.003; overall, p = 0.008).

CONCLUSIONS

The combination of the 3D hybrid profile order technique and DLR is useful for MRCP within a single BH and does not lead to the deterioration of image quality and space resolution at 3 T MRI.

CLINICAL RELEVANCE STATEMENT

Considering its advantages, this sequence might become the standard protocol for MRCP in clinical practice, at least at 3.0 T.

KEY POINTS

• The 3D hybrid profile order can achieve MRCP within a single breath-hold without a decrease in spatial resolution. • The DLR significantly improved the CNR and SNR of BH-MRCP. • The 3D hybrid profile order technique with DLR reduces the deterioration of image quality in MRCP within a single breath-hold.

Chest magnetic resonance imaging in cystic fibrosis: technique and clinical benefits

Cystic fibrosis (CF) is one of the most common inherited and life-shortening pulmonary diseases in the Caucasian population. With the widespread introduction of newborn screening and the development of modulator therapy, tremendous advances have been made in recent years both in diagnosis and therapy. Since paediatric CF patients tend to be younger and have lower morbidity, the type of imaging modality that should be used to monitor the disease is often debated. Computed tomography (CT) is sensitive to many pulmonary pathologies, but radiation exposure limits its use, especially in children and adolescents. Conventional pulmonary magnetic resonance imaging (MRI) is a valid alternative to CT and, in most cases, provides sufficient information to guide treatment. Given the expected widespread availability of sequences with ultra-short echo times, there will be even fewer reasons to perform CT for follow-up of patients with CF. This review aims to provide an overview of the process and results of monitoring CF with MRI, particularly for centres not specialising in the disease.

Pancreatic imaging using diffusivity mapping - Influence of sequence technique on qualitative and quantitative analysis

PURPOSE

To compare image quality of an optimized diffusion weighted imaging (DWI) sequence with advanced post-processing and motion correction (advanced-EPI) to a standard DWI protocol (standard-EPI) in pancreatic imaging.

MATERIALS AND METHODS

62 consecutive patients underwent abdominal MRI at 1.5 T were included in this retrospective analysis of data collected as part of an IRB approved study. All patients received a standard-EPI and an advanced-EPI DWI with advanced post-processing and motion correction. Two blinded radiologists evaluated the parameters image quality, detail of parenchyma, sharpness of boundaries and discernibility from adjacent structures on b = 900 s/mm² images using a Likert-like scale. Segmentation of pancreatic head, body and tail were obtained and apparent diffusion coefficient (ADC) was calculated separately for each region. Apparent tissue-to-background ratio (TBR) was calculated at b = 50 s/mm² and at b = 900 s/mm².

RESULTS

The advanced-EPI yielded significantly higher scores for pancreatic parameters of image quality, detail level of parenchyma, sharpness of boundaries and discernibility from adjacent structures in comparison to standard-EPI (p < 0.001 for all, kappa = [0.46,0.71]) and was preferred in 96% of the cases when directly compared. ADC of the pancreas was 7% lower in advanced-EPI (1.236 ± 0.152 vs. 1.146 ± 0.126 μm²/ms, p < 0.001). ADC in the pancreatic tail was significantly lower for both sequences compared to head and body (all p < 0.001). There was comparable TBR for both sequences at b = 50 s/mm² (standard-EPI: 19.0 ± 5.9 vs. advanced-EPI: 19.0 ± 6.4, p = 0.96), whereas at b = 900 s/mm², TBR was 51% higher for advanced-EPI (standard-EPI: 7.1 ± 2.5 vs. advanced-EPI: 10.8 ± 5.1, p < 0.001).

CONCLUSION

An advanced DWI sequence might increase image quality for focused imaging of the pancreas and providing improved parenchymal detail levels compared to a standard DWI.

Three-Dimensional (3D) Breath-Hold Zoomed MR Cholangiopancreatography (MRCP): Evaluation of Additive Value to Conventional 3D Navigator Triggering MRCP in Patients With Branch Duct Intraductal Papillary Mucinous Neoplasms

BACKGROUND

To resolve drawbacks of navigator triggering (NT) three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP), several approaches were proposed to obtain 3D MRCP within a single breath-hold (BH). However, reduced field-of-view technique in the phase-encoding direction combined with two-dimensional spatially selective radiofrequency excitation pulses has not yet been applied to 3D BH MRCP.

PURPOSE

To investigate the feasibility and the complementary value of 3D BH zoomed MRCP to conventional 3D NT MRCP in patients with branch duct intraductal papillary mucinous neoplasms (BD-IPMNs) of the pancreas.

STUDY TYPE

Retrospective.

POPULATION

A total of 221 patients (116 male and 105 female, median age 73 years) with BD-IPMNs.

FIELD STRENGTH/SEQUENCE

3.0 T/3D turbo spin echo ASSESSMENT: MR images were analyzed by three radiologists (R.M., H.O., M.T., with 1, 13, and 17 years of experience) to compare blurring and motion artifacts, background suppression, visualization of main pancreatic duct (MPD), conspicuity of BD-IPMN, and overall image quality.

STATISTICAL TESTS

Wilcoxon-signed rank, Mann-Whitney U, chi-squared or Fisher's exact tests (P < 0.05).

RESULTS

Image quality was significantly higher on 3D NT MRCP images than on 3D BH zoomed MRCP (median (interquartile range); background suppression, 4 (4-4) vs. 3 (3-4); visualization of MPD, 4 (3-4) vs. 4 (3-4), conspicuity of BD-IPMN, 4 (3-4) vs. 3 (3-4); and overall image quality, 3 (3-4) vs. 3 (3-3)). However, in 32 (14%) patients, 3D NT MRCP showed a score of 1 or 2 in overall image quality. Regarding the conspicuity of BD-IPMN, a conspicuity score of 1 or 2 was rendered in 31 (14%) patients in 3D NT MRCP group. Conversely, 3D BH zoomed MRCP showed a score of 3 or 4 in 29 (94%) of these 31 patients.

DATA CONCLUSION

3D BH zoomed MRCP plays a complementary role to 3D NT MRCP, and may improve the conspicuity of BD-IPMNs in patients with irregular breathing pattern.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY: Stage 2.

Comparison of respiratory-triggered 3D MR cholangiopancreatography and breath-hold compressed-sensing 3D MR cholangiopancreatography at 1.5 T and 3 T and impact of individual factors on image quality

PURPOSE

To evaluate the image quality of an accelerated compressed-sensing single-breath-hold 3D magnetic resonance cholangiopancreatography (BH-CS-MRCP) prototype sequence compared to the standard 3D sequence with respiratory triggering (STD-MRCP) at 1.5 T and 3 T. To assess the individual factors that can affect image quality.

METHOD

This is a retrospective analysis. Both sequences (BH-CS-MRCP and STD-MRCP) were performed in 200 patients at 1.5 T and 200 patients at 3 T. Overall image quality and the visualization of the bilio-pancreatic ducts were rated on a 5-point scale. Image sharpness and background suppression were rated on a 4-point scale. A double reading was performed in 50 patients to assess the inter-observer reproducibility. Individual characteristics studied were gender, age, BMI, ascites, abdominal surface and breath-hold quality.

RESULTS

At 1.5 T, BH-CS-MRCP was inferior to STD-MRCP in terms of overall quality (p = 0.0046), background suppression (p < 0.0001), visualization of the cystic duct (p < 0.0001), the right bile duct (p = 0.0008), the left bile duct (p = 0.0152), and the main pancreatic duct (p < 0.0001). However, BH-CS-MRCP was sharper than STD-MRCP (p = 0.028). At 3 T, BH-CS-MRCP was superior to STD-MRCP for overall quality (p < 0.0001), sharpness (p < 0.0001), and visualization of the bilio-pancreatic ducts (p < 0.0001). Background signal was conversely better suppressed in STD-MRCP (p < 0.0001). At 1.5 T, the volume of ascites was inversely correlated with image quality for BH-CS-MRCP while BMI was inversely correlated with image quality for STD-MRCP. Breath-hold quality was correlated with image quality for BH-CS-MRCP at 1.5 T and 3 T.

CONCLUSION

BH-CS-MRCP is feasible in clinical routine at 1.5 and 3 T, yielding significantly better perceived image quality at 3 T but not at 1.5 T. BH-CS-MRCP appears to be influenced by ascites whereas STD-MRCP is influenced by BMI at 1.5 T. This study was approved by the Ethics Review Board for Research in Medical Imaging (IRB: CRM-2003-065).

Spectral diffusion analysis of kidney intravoxel incoherent motion MRI in healthy volunteers and patients with renal pathologies

PURPOSE

To assess the feasibility of measuring tubular and vascular signal fractions in the human kidney using nonnegative least-square (NNLS) analysis of intravoxel incoherent motion data collected in healthy volunteers and patients with renal pathologies.

METHODS

MR imaging was performed at 3 Tesla in 12 healthy subjects and 3 patients with various kidney pathologies (fibrotic kidney disease, failed renal graft, and renal masses). Relative signal fractions f and mean diffusivities of the diffusion components in the cortex, medulla, and renal lesions were obtained using the regularized NNLS fitting of the intravoxel incoherent motion data. Test-retest repeatability of the NNLS approach was tested in 5 volunteers scanned twice.

RESULTS

In the healthy kidneys, the NNLS method yielded diffusion spectra with 3 distinguishable components that may be linked to the slow tissue water diffusion, intermediate tubular and vascular flow, and fast blood flow in larger vessels with the relative signal fractions, f_slow , f_interm and f_fast , respectively. In the pathological kidneys, the diffusion spectra varied substantially from those acquired in the healthy kidneys. Overall, the renal cyst showed substantially higher f_interm and lower f_slow , whereas the fibrotic kidney, failed renal graft, and renal cell carcinoma demonstrated the opposite trend.

CONCLUSION

NNLS-based intravoxel incoherent motion could potentially become a valuable tool in assessing changes in tubular and vascular volume fractions under pathophysiological conditions.

Balanced steady-state free precession MRCP is a robust alternative to respiration-navigated 3D turbo-spin-echo MRCP

Background

Despite synchronization to respiration, respiration-navigated (RN) 3D turbo-spin-echo MRCP is limited by susceptibility to motion artifacts. The aim of this study was to assess the quality of pancreaticobiliary duct visualization of a non-RN MRCP alternative based on balanced steady-state free precession imaging (BSSFP) with overlapping slices compared with RN-MRCP.

Methods

This is a retrospective study on 50 patients without pancreaticobiliary duct disease receiving MRCP at 1.5 T. We performed an intraindividual comparison of coronal RN-MRCP with combined coronal and transverse BSSFP-MRCP. Image quality was scored by 3 readers for 6 pancreaticobiliary duct segments (3 pancreatic, 3 biliary) using a 6-point scale. A segment score of 3 or lower as assessed by at least 2 of 3 readers was defined as insufficient segment visualization. Nonparametric tests and interrater reliability testing were used for statistical analysis.

Results

Overall duct visualization averaged over all readers was scored with 4.5 ± 1.1 for RN-MRCP (pancreatic, 4.1 ± 0.5; biliary, 5.0 ± 0.4) and 4.9 ± 0.9 for combined coronal and transverse BSSFP-MRCP (pancreatic, 4.6 ± 0.6; biliary, 5.1 ± 0.6), respectively (p < 0.001). The number of segments visualized insufficiently was 81/300 for RN-MRCP and 43/300 for BSSFP-MRCP (p < 0.001). Segments visualized insufficiently only in RN-MRCP had a mean score of 4.4 ± 0.8 in BSSFP-MRCP. Overall interrater agreement on superiority of BSSFP-MRCP segment scores over corresponding RN-MRCP was 0.70. Mean acquisition time was 98% longer for RN-MRCP (198.0 ± 98.7 s) than for combined coronal and transverse BSSFP-MRCP (100.2 ± 0.4 s).

Conclusions

Non-RN BSSFP-MRCP with overlapping slices is a fast alternative to RN-MRCP, frequently providing sufficient duct visualization when RN-MRCP fails.

Optimized Breath-Hold Compressed-Sensing 3D MR Cholangiopancreatography at 3T: Image Quality Analysis and Clinical Feasibility Assessment

Magnetic resonance cholangiopancreatography (MRCP) has been widely used in clinical practice, and recently developed compressed-sensing accelerated MRCP (CS-MRCP) has shown great potential in shortening the acquisition time. The purpose of this prospective study was to evaluate the clinical feasibility and image quality of optimized breath-hold CS-MRCP (BH-CS-MRCP) and conventional navigator-triggered MRCP. Data from 124 consecutive patients with suspected pancreaticobiliary diseases were analyzed by two radiologists using a five-point Likert-type scale. Communication between a cyst and the pancreatic duct (PD) was analyzed. Signal-to-noise ratio (SNR) of the common bile duct (CBD), contrast ratio between the CBD and periductal tissue, and contrast-to-noise ratio (CNR) of the CBD and liver were measured. Optimized BH-CS-MRCP showed significantly fewer artifacts with better background suppression and overall image quality. Optimized BH-CS-MRCP demonstrated communication between a cyst and the PD better than conventional MRCP (96.7% vs. 76.7%, p = 0.048). SNR, contrast ratio, and CNR were significantly higher with optimized BH-CS-MRCP (p < 0.001). Optimized BH-CS-MRCP showed comparable or even better image quality than conventional MRCP, with improved visualization of communication between a cyst and the PD.

Advances in MR Imaging of the Biliary Tract

Imaging of the biliary system has improved and has allowed MR to become a key noninvasive tool for evaluation of the biliary system. A variety of magnetic resonance cholangiopancreatography techniques have been developed, with improved visualization of the biliary system and biliary pathology. Key avenues of advancement include increasing the speed of acquisition, improving spatial resolution, and reducing artifacts. T1-weighted imaging using gadolinium-based hepatobiliary contrast agents allows for evaluation in additional indications, such as liver donor evaluation, biliary leak identification, and choledochal cyst confirmation. There is potential for further increased utility of MR in the evaluation of the biliary system.

Magnetic resonance cholangiopancreatography at 3T in a single breath-hold: comparative effectiveness between three-dimensional (3D) gradient- and spin-echo and two-dimensional (2D) thick-slab fast spin-echo acquisitions

Background

To compare the depiction conspicuity of three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) based on gradient- and spin-echo (GRASE) and two-dimensional (2D) thick-slab MRCP using fast spin-echo (FSE) in different segments of hepatic and pancreatic ducts at 3T.

Methods

Both 3D GRASE and 2D thick-slab FSE MRCP, with parameters adjusted under the constraints of specific absorption rate and scan time within single breath-hold, were performed for 95 subjects (M/F =49:46; age range, 25-75) at 3T. Conspicuity of eight ductal segments was graded by two experienced raters using a 4-point score. Situations where one technique is superior or inferior to the other were recorded.

Results

3D GRASE MRCP outperformed 2D thick-slab FSE MRCP in the common bile duct and common hepatic ducts (both with P<0.001), but compared inferiorly in the right hepatic ducts (P<0.001), right posterior hepatic ducts (P<0.005) and pancreatic duct distal (P<0.05). Performing both 3D and 2D MRCP would reduce the number of non-diagnostic readings in the left hepatic duct to 10 remaining (5.3%), compared with 31 (16.3%) or 21 (11.1%) out of 190 readings if using 3D GRASE or 2D thick-slab FSE alone, respectively.

Conclusions

Although 3D GRASE MRCP is preferential to visualize the common bile duct and common hepatic duct within one single breath-hold, the complementary role of 2D thick-slab FSE MRCP in smaller hepatic and pancreatic ducts makes it a useful adjunct if performed additionally.

Improved Liver Diffusion-Weighted Imaging at 3 T Using Respiratory Triggering in Combination With Simultaneous Multislice Acceleration

OBJECTIVES

The aim of this study was to retrospectively compare optimized respiratory-triggered diffusion-weighted imaging with simultaneous multislice acceleration (SMS-RT-DWI) of the liver with a standard free-breathing echo-planar DWI (s-DWI) protocol at 3 T with respect to the imaging artifacts inherent to DWI.

MATERIALS AND METHODS

Fifty-two patients who underwent a magnetic resonance imaging study of the liver were included in this retrospective study. Examinations were performed on a 3 T whole-body magnetic resonance system (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany). In all patients, both s-DWI and SMS-RT-DWI of the liver were obtained. Images were qualitatively evaluated by 2 independent radiologists with regard to overall image quality, liver edge sharpness, sequence-related artifacts, and overall scan preference. For quantitative evaluation, signal-to-noise ratio was measured from signal-to-noise ratio maps. The mean apparent diffusion coefficient (ADC) was measured in each liver quadrant. The Wilcoxon rank-sum test was used for analysis of the qualitative parameters and the paired Student t test for quantitative parameters.

RESULTS

Overall image quality, liver edge sharpness, and sequence-related artifacts of SMS-RT-DWI received significantly better ratings compared with s-DWI (P < 0.05 for all). For 90.4% of the examinations, both readers overall preferred SMS-RT-DWI to s-DWI. Acquisition time for SMS-RT-DWI was 34% faster than s-DWI. Signal-to-noise ratio values were significantly higher for s-DWI at b50 but did not statistically differ at b800, and they were more homogenous for SMS-RT-DWI, with a significantly lower standard deviation at b50. Mean ADC values decreased from the left to right hepatic lobe as well as from cranial to caudal for s-DWI. With SMS-RT-DWI, mean ADC values were homogeneous throughout the liver.

CONCLUSIONS

Optimized, multislice, respiratory-triggered DWI of the liver at 3 T substantially improves image quality with a reduced scan acquisition time compared with s-DWI.

Comparison of Navigator Triggering Reduced Field of View and Large Field of View Diffusion-Weighted Imaging of the Pancreas

RATIONALE AND OBJECTIVES

The purpose of this study is to compare image quality, presence and grade of artifacts, signal-to-noise ratio, and apparent diffusion coefficient (ADC) values in pancreatic tissue between high-resolution navigator-triggered (NT) restricted field of view (rFOV) FOCUS single-shot (SS) echo-planar imaging (EPI) diffusion-weighted imaging (DWI) and NT large FOV SS-EPI DWI.

MATERIALS AND METHODS

Magnetic resonance imaging examinations were performed with GE 3-T systems using a 32-channel body array coil. Seventeen consecutive patients were imaged. A 5-point scale semiquantitative grading system was used to evaluate image quality and general artifacts. Signal-to-noise ratio and ADC were measured in the head, body, and tail of the pancreas. Statistical analysis was performed using Student t test and Wilcoxon signed rank test, with differences considered significant for P value less than 0.05.

RESULTS

More artifacts were present on large FOV compared with rFOV FOCUS SS-EPI DW images (P < 0.01). Restricted field of view image quality was subjectively better (P < 0.01). No difference in the signal-to-noise ratio was demonstrated between the 2 image datasets. Apparent diffusion coefficient values were significantly lower (P < 0.01) when calculated from rFOV images than large FOV images.

CONCLUSIONS

Our results demonstrate better image quality and reduced artifacts in rFOV images compared with large FOV DWI. Measurements from ADC maps derived from rFOV DWI show significantly lower ADC values when compared with ADC maps derived from large FOV DWI.

The Performance of Noncontrast Magnetic Resonance Angiography in Detecting Renal Artery Stenosis as Compared With Contrast Enhanced Magnetic Resonance Angiography Using Conventional Angiography as a Reference

OBJECTIVE

The aims of this study were to evaluate the performance of noncontrast magnetic resonance angiography (NC MRA) for detecting renal artery stenosis (RAS) as compared with contrast-enhanced magnetic resonance angiography (CE MRA) and to evaluate the clinical feasibility, technical success rate, and performance of NC MRA for detecting RAS as compared with CE MRA.

METHODS

Thirty-six subjects who underwent NC MRA and/or CE MRA were enrolled. Feasibility, technical success rate, and image quality scores were compared. Diagnostic ability was calculated using conventional angiography as a reference.

RESULTS

Noncontrast MRA had higher feasibility and technical success rates than CE MRA did (100% and 97.2% vs 83.3% and 90%, respectively). Noncontrast MRA yielded significantly better image quality in motion artifact (P = 0.016). The diagnostic ability for detecting RAS is without significant difference between NC MRA and CE MRA.

CONCLUSION

Although NC MRA and CE MRA demonstrated comparable ability in diagnosing RAS, NC MRA achieved better technical success rates, feasibility, and image quality in motion artifacts than CE MRA did.

Radial Ultrashort TE Imaging Removes the Need for Breath-Holding in Hepatic Iron Overload Quantification by R2* MRI

OBJECTIVE

The objective of this study is to evaluate radial free-breathing (FB) multiecho ultrashort TE (UTE) imaging as an alternative to Cartesian FB multiecho gradient-recalled echo (GRE) imaging for quantitative assessment of hepatic iron content (HIC) in sedated patients and subjects unable to perform breath-hold (BH) maneuvers.

MATERIALS AND METHODS

FB multiecho GRE imaging and FB multiecho UTE imaging were conducted for 46 test group patients with iron overload who could not complete BH maneuvers (38 patients were sedated, and eight were not sedated) and 16 control patients who could complete BH maneuvers. Control patients also underwent standard BH multiecho GRE imaging. Quantitative R2* maps were calculated, and mean liver R2* values and coefficients of variation (CVs) for different acquisitions and patient groups were compared using statistical analysis.

RESULTS

FB multiecho GRE images displayed motion artifacts and significantly lower R2* values, compared with standard BH multiecho GRE images and FB multiecho UTE images in the control cohort and FB multiecho UTE images in the test cohort. In contrast, FB multiecho UTE images produced artifact-free R2* maps, and mean R2* values were not significantly different from those measured by BH multiecho GRE imaging. Motion artifacts on FB multiecho GRE images resulted in an R2* CV that was approximately twofold higher than the R2* CV from BH multiecho GRE imaging and FB multiecho UTE imaging. The R2* CV was relatively constant over the range of R2* values for FB multiecho UTE, but it increased with increases in R2* for FB multiecho GRE imaging, reflecting that motion artifacts had a stronger impact on R2* estimation with increasing iron burden.

CONCLUSION

FB multiecho UTE imaging was less motion sensitive because of radial sampling, produced excellent image quality, and yielded accurate R2* estimates within the same acquisition time used for multiaveraged FB multiecho GRE imaging. Thus, FB multiecho UTE imaging is a viable alternative for accurate HIC assessment in sedated children and patients who cannot complete BH maneuvers.

Usefulness of three-dimensional magnetic resonance cholangiopancreatography with partial maximum intensity projection for diagnosing autoimmune pancreatitis

PURPOSE

To compare three-dimensional magnetic resonance cholangiopancreatography (MRCP) with/without partial maximum intensity projection (MIP) and endoscopic retrograde cholangiopancreatography (ERCP) in patients with autoimmune pancreatitis (AIP).

MATERIALS AND METHODS

Three-dimensional MRCP and ERCP images were retrospectively analyzed in 24 patients with AIP. We evaluated the narrowing length of the main pancreatic duct (NR-MPD), multiple skipped MPD narrowing (SK-MPD), and side branches arising from the narrowed portion of the MPD (SB-MPD) using four MRCP datasets: 5 original images (MIP₅), 10 original images (MIP₁₀), all original images (full-MIP), and a combination of these three datasets (a-MIP). The images were scored using a 3- or 5-point scale. The scores of the four MRCP datasets were statistically analyzed, and the positive rate of each finding was compared between MRCP and ERCP.

RESULTS

The median scores for SB-MPD on MIP₅ and a-MIP were significantly higher than those on MIP₁₀ and full-MIP. In other words, partial MIP is superior to full-MIP for visualization of detailed structures. The positive rate for SB-MPD on full-MIP was significantly lower than that on ERCP, whereas the positive rate on MIP₅, MIP₁₀, and a-MIP was not significantly different from that on ERCP. Moreover, the positive rate for NR-MPD and SK-MPD on the MRCP images was significantly higher than that on the ERCP images.

CONCLUSION

Partial MIP is useful for evaluating the MPD and is comparable with ERCP for diagnosing AIP.

Three-dimensional MR Cholangiopancreatography in a Breath Hold with Sparsity-based Reconstruction of Highly Undersampled Data

Purpose To develop a three-dimensional breath-hold (BH) magnetic resonance (MR) cholangiopancreatographic protocol with sampling perfection with application-optimized contrast using different flip-angle evolutions (SPACE) acquisition and sparsity-based iterative reconstruction (SPARSE) of prospectively sampled 5% k-space data and to compare the results with conventional respiratory-triggered (RT) acquisition. Materials and Methods This HIPAA-compliant prospective study was institutional review board approved. Twenty-nine patients underwent conventional RT SPACE and BH-accelerated SPACE acquisition with 5% k-space sampling at 3 T. Spatial resolution and other parameters were matched when possible. BH SPACE images were reconstructed by enforcing joint multicoil sparsity in the wavelet domain (SPARSE-SPACE). Two board-certified radiologists independently evaluated BH SPARSE-SPACE and RT SPACE images for image quality parameters in the pancreatic duct and common bile duct by using a five-point scale. The Wilcoxon signed-rank test was used to compare BH SPARSE-SPACE and RT SPACE images. Results Acquisition time for BH SPARSE-SPACE was 20 seconds, which was significantly (P < .001) shorter than that for RT SPACE (mean ± standard deviation, 338.8 sec ± 69.1). Overall image quality scores were higher for BH SPARSE-SPACE than for RT SPACE images for both readers for the proximal, middle, and distal pancreatic duct, but the difference was not statistically significant (P > .05). For reader 1, distal common bile duct scores were significantly higher with BH SPARSE-SPACE acquisition (P = .036). More patients had acceptable or better overall image quality (scores ≥ 3) with BH SPARSE-SPACE than with RT SPACE acquisition, respectively, for the proximal (23 of 29 [79%] vs 22 of 29 [76%]), middle (22 of 29 [76%] vs 18 of 29 [62%]), and distal (20 of 29 [69%] vs 13 of 29 [45%]) pancreatic duct and the proximal (25 of 28 [89%] vs 22 of 28 [79%]) and distal (25 of 28 [89%] vs 24 of 28 [86%]) common bile duct. Conclusion BH SPARSE-SPACE showed similar or superior image quality for the pancreatic and common duct compared with that of RT SPACE despite 17-fold shorter acquisition time. (©) RSNA, 2016.

Magnetic resonance cholangiopancreatography: Comparison of two- and three-dimensional sequences for the assessment of pancreatic cystic lesions

The present study aimed to compare two-dimensional (2D) and three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) for the assessment of pancreatic cystic lesions. Between February 2009 and December 2011, 35 patients that had been diagnosed with pancreatic cystic lesions, which was confirmed by surgery and pathology, underwent pre-operative 2D or 3D MRCP for pre-operative evaluation. In the present study, the quality of these 2D and 3D MRCP images, the visualization of the features of the cystic lesions, visualization of the pancreatic main duct and prediction of ductal communication with the cystic lesions were evaluated and compared using statistical software. The 3D MRCP images were determined to be of higher quality compared with the 2D MRCP images. The features of the cystic lesions were visualized better on 3D MRCP compared with 2D MRCP. The same capability for the visualization of the segment of the pancreatic main duct was exhibited by 3D and 2D MRCP. There was no significant difference between the area under the receiver operating characteristic curve values of 2D and 3D MRCP, which assessed the prediction of communication between cystic lesions and the pancreatic main duct. It was concluded that, compared with 2D MRCP, 3D MRCP provides an improved assessment of pancreatic cystic lesions, but does not exhibit an improved capability for the visualization of the pancreatic main duct or for the prediction of communication between cystic lesions and the pancreatic main duct.

Post-contrast T1-weighted sequences in pediatric abdominal imaging: comparative analysis of three different sequences and imaging approach

BACKGROUND

Post-contrast T1-weighted imaging is an essential component of a comprehensive pediatric abdominopelvic MR examination. However, consistent good image quality is challenging, as respiratory motion in sedated children can substantially degrade the image quality.

OBJECTIVE

To compare the image quality of three different post-contrast T1-weighted imaging techniques-standard three-dimensional gradient-echo (3-D-GRE), magnetization-prepared gradient-recall echo (MP-GRE) and 3-D-GRE with radial data sampling (radial 3-D-GRE)-acquired in pediatric patients younger than 5 years of age.

MATERIALS AND METHODS

Sixty consecutive exams performed in 51 patients (23 females, 28 males; mean age 2.5 ± 1.4 years) constituted the final study population. Thirty-nine scans were performed at 3 T and 21 scans were performed at 1.5 T. Two different reviewers independently and blindly qualitatively evaluated all sequences to determine image quality and extent of artifacts.

RESULTS

MP-GRE and radial 3-D-GRE sequences had the least respiratory motion (P < 0.0001). Standard 3-D-GRE sequences displayed the lowest average score ratings in hepatic and pancreatic edge definition, hepatic vessel clarity and overall image quality. Radial 3-D-GRE sequences showed the highest scores ratings in overall image quality.

CONCLUSIONS

Our preliminary results support the preference of fat-suppressed radial 3-D-GRE as the best post-contrast T1-weighted imaging approach for patients under the age of 5 years, when dynamic imaging is not essential.

Breath-held MR cholangiopancreatography (MRCP) using a 3D Dixon fat-water separated balanced steady state free precession sequence

A novel 3D breath-held Dixon fat-water separated balanced steady state free precession (b-SSFP) sequence for MR cholangiopancreatography (MRCP) is described and its potential clinical utility assessed in a series of patients. The main motivation is to develop a robust breath-held alternative to the respiratory gated 3D Fast Spin Echo (FSE) sequence, the current clinical sequence of choice for MRCP. Respiratory gated acquisitions are susceptible to motion artifacts and blurring in patients with significant diaphragmatic drift, erratic respiratory rhythms or sleep apnea. A two point Dixon fat-water separation scheme was developed which eliminates signal loss arising from B0 inhomogeneity effects and minimizes artifacts from perturbation of the b-SSFP steady state. Preliminary results from qualitative analysis of 49 patients demonstrate robust performance of the 3D Dixon b-SSFP sequence with diagnostic image quality acquired in a 20-24s breath-hold.

Papel da ranitidina como meio de aprimorar a qualidade do exame de colangiopancreatografia por ressonância magnética

OBJETIVO: Avaliar o impacto da ranitidina por via oral na qualidade do exame de colangiopancreatografia por ressonância magnética (CPRM). MATERIAIS E MÉTODOS: Trinta e dois pacientes realizaram CPRM com aquisições 3D e 2D, com três estratégias de supressão do sinal líquido gastrintestinal: a) apenas em jejum; b) 12 horas após ingerir 300 mg de ranitidina; c) após a ingestão de solução de gadolínio. Três observadores avaliaram os estudos, atentos para o grau de visualização da árvore biliopancreática. Foi medida a concordância interobservador com o teste kappa. A diferença entre técnicas e formas de aquisição foi avaliada pela média da soma dos escores de graduação. RESULTADOS: As três estratégias de supressão do sinal líquido gastrintestinal apresentaram elevada reprodutibilidade. A supressão do sinal líquido gastrintestinal com a ranitidina foi semelhante ao jejum e ambas foram piores do que a solução de gadolínio. As aquisições 3D superaram a 2D apenas na visualização do ducto cístico e da vesícula biliar, sendo inferior ou equivalente nos demais segmentos ductais biliopancreáticos. CONCLUSÃO: O uso da ranitidina não parece justificado para aprimorar a avaliação da árvore biliopancreática em exames de CPRM. A CPRM 2D apenas em jejum permite a visualização ductal com elevada qualidade e reprodutibilidade na maioria dos casos.

Preoperative evaluation of the cystic duct for laparoscopic cholecystectomy: comparison of navigator-gated prospective acquisition correction- and conventional respiratory-triggered techniques at free-breathing 3D MR cholangiopancreatography

OBJECTIVE

To evaluate the quality of magnetic resonance cholangiopancreatography (MRCP) images obtained with a three-dimensional navigator-gated (NG) technique and compare findings with conventional respiratory-triggered (RT) images in pre-laparoscopic cholecystectomy patients.

METHODS

Turbo-spin-echo (TSE) RT-MRCP (average 242 s) and balanced turbo-field-echo (bTFE) NG-MRCP (average 263 s) were acquired at 1.5-T MRI for 49 pre-laparoscopic cholecystectomy patients. Two radiologists independently assessed image quality, visibility of anatomical structures, common bile duct (CBD) stones, and signal-to-noise ratios (SNRs). Interobserver agreement was also evaluated.

RESULTS

The anatomical details of the cystic duct were clearly demonstrated in 33 (67.3 %, reader A) and 35 (71.4 %, reader B) patients on RT-MRCP, and in 45 (91.8 %) and 44 (89.7 %) patients on NG-MRCP. On NG-MRCP, visualisation of the cystic duct (3.22/3.12), its origin (3.57/3.55), and the gallbladder(3.61/3.59) was statistically better than on RT-MRCP (2.90/2.78, 3.29/3.12, 2.98/2.88, respectively). The overall image quality was statistically better on NG-MRCP than RT-MRCP. Each technique identified the presence of CBD stones in all affected patients. The SNR was significantly higher on NG-MRCP (CHD 22.40, gallbladder 17.13) than RT-MRCP (CHD 17.05, gallbladder 9.30). Interobserver agreement was fair to perfect.

CONCLUSION

Navigator-gated MRCP is more useful than respiratory-triggered MRCP for evaluating the gallbladder and cystic duct in patients scheduled for laparoscopic cholecystectomy.

KEY POINTS

• Magnetic resonance cholangiopancreatography (MRCP) provides important cystic duct information before laparoscopic cholecystectomy. • Navigator-gated (NG) MRCP images were better than conventional respiratory-triggered (RT) MRCP. • The signal-to-noise ratio was significantly higher for NG-MRCP than for conventional RT-MRCP. • Balanced turbo-field-echo NG-MRCP is useful for evaluating the gallbladder and cystic duct.

Diffusion-weighted MRI in the assessment of split renal function: comparison of navigator-triggered prospective acquisition correction and breath-hold acquisition

OBJECTIVE

The purpose of this study was to ascertain whether prospective acquisition correction (PACE) diffusion-weighted MRI (DWI) is superior to conventional breath-hold DWI in assessment of split renal function.

SUBJECTS AND METHODS

Fifty-four subjects underwent coronal breath-hold DWI and PACE DWI with the b value set at 0 and 800 s/mm(2). Isotope renographic glomerular filtration rate (GFR) was used as the reference standard for assessing split renal function. A GFR of 40 mL/min or greater indicated normal and a GFR less than 40 mL/min indicated reduced split renal function. Reduced split renal function was further divided into a mild reduction group (GFR ≥ 20 mL/min) and a moderate-to-severe reduction group (GFR < 20 mL/min). Various comparisons between the imaging methods were conducted.

RESULTS

The signal-to-noise and contrast-to-noise ratios of the PACE DW images were greater than those of the breath-hold DW images (p < 0.001). The correlation between the apparent diffusion coefficient (ADC) value and GFR was stronger when the ADC was measured with PACE DWI than with breath-hold DWI (p = 0.033). Area under the receiver operator curve (AUC) analysis revealed that PACE DWI (AUC, 0.790 ± 0.045; p < 0.001) but not breath-hold DWI (AUC, 0.616 ± 0.060; p = 0.053) had diagnostic value in predicting a reduction in split renal function. ADC value assessed with PACE DWI was lower in the groups with mild and moderate-to-severe reduction in split renal function than in the group with normal function (p < 0.01).

CONCLUSION

Preliminary results imply that PACE DWI is superior to breath-hold DWI in the assessment of split renal function.

Usefulness of the navigator-echo triggering technique for free-breathing three-dimensional magnetic resonance cholangiopancreatography

PURPOSE

To prospectively compare the navigator-echo triggering technique (navigator technique) and the conventional respiratory triggering technique using bellows (bellows technique) for free-breathing three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) under clinical conditions.

MATERIALS AND METHODS

Forty patients referred for evaluation of biliary or pancreatic diseases underwent 3D MRCP examination using both navigator and bellows techniques. Two independent radiologists visually evaluated the image quality of 12 segments of the pancreaticobiliary tree in a blinded manner. In addition, the clarity of the lesion was compared between the two techniques in a side-by-side manner.

RESULT

MRCP images were successfully acquired using both techniques in all patients. No significant difference in acquisition time was found between the two techniques. The image quality was significantly better using the navigator technique than using the bellows technique for the following seven segments: the head, body, and tail of the pancreatic duct; right hepatic duct; anterior and posterior segments of the right hepatic duct; and cystic duct. The other segments (common hepatic and bile duct, left hepatic duct, medial and lateral segments of left hepatic duct, gallbladder) showed no significant difference. The clarity of lesion depiction was significantly better using the navigator technique than using the bellows technique.

CONCLUSION

Respiratory-triggered 3D MRCP using the navigator technique was shown to be feasible in routine clinical practice. The navigator technique improved the image quality of free-breathing 3D MRCP compared with the bellows technique. The clarity of lesion visualization was also better using the navigator technique than using the bellows technique.

Free-breathing 3D T1-weighted gradient-echo sequence with radial data sampling in abdominal MRI: preliminary observations

OBJECTIVE

The purposes of this study were to evaluate the feasibility of a free-breathing 3D gradient-recalled echo sequence with radial data sampling (radial 3D GRE) in abdominal MRI compared with a standard 3D GRE volumetric interpolated breath-hold examination (VIBE) sequence for imaging of cooperative patients and to perform a preliminary assessment in imaging of noncooperative patients.

MATERIALS AND METHODS

Fifty-five consecutively registered patients who underwent unenhanced and contrast-enhanced abdominal MRI with the free-breathing radial 3D GRE technique constituted the study population. Two readers independently and blindly evaluated the images.

RESULTS

Overall image quality with the contrast-enhanced radial 3D GRE sequence was lower than but rated at least nearly as good as that with the 3D GRE VIBE sequence (p < 0.0001). Higher scores were recorded for 3D GRE VIBE images with respect to pixel graininess, streaking artifact, and sharpness (p = 0.0009 to p < 0.0001). Except for sharpness of vessels on unenhanced images, results for the radial 3D GRE sequence did not differ significantly in the comparison of cooperative and noncooperative patients (p = 0.004). For imaging of noncooperative patients, radial 3D GRE images of children had higher ratings for shading (unenhanced, p = 0.0004; contrast-enhanced, p < 0.0001) and streaking artifacts on contrast-enhanced images (p = 0.0017) than did those of adults. Overall image quality was higher for pediatric patients. In lesion analysis, use of the 3D GRE VIBE sequence was associated with significantly greater detectability, confidence, and conspicuity than was use of the radial 3D GRE sequence (p = 0.00026-0.011).

CONCLUSION

A free-breathing radial 3D GRE sequence is feasible for abdominal MRI and may find application in imaging of patients who are unable to suspend respiration, especially children.

Comparison of a single shot T1-weighted in- and out-of-phase magnetization prepared gradient recalled echo with a standard two-dimensional gradient recalled echo: preliminary findings

PURPOSE

To compare in-phase (IP)/out-of-phase (OP) single shot magnetization-prepared gradient-recalled-echo (MP-GRE) with a standard two-dimensional gradient-recalled-echo (2D-GRE), and to compare image quality of MP-GRE in cooperative and noncooperative subjects.

MATERIALS AND METHODS

Ninety-six consecutive subjects (52 males, 44 females; mean age, 53.2 ± 16.7 years), both cooperative (n = 73) and noncooperative (n = 23) subjects who had MRI examinations including precontrast T1-weighted IP/OP MP-GRE with or without IP/OP 2D-GRE were included in the study. The sequences were independently qualitatively evaluated by two radiologists. Quantitative analysis of liver fat index, signal-to-noise ratio (SNR) and liver-lesion contrast-to-noise ratio (CNR) was also performed. Data were subjected to statistical analysis.

RESULTS

The visual detection of the presence or absence of liver steatosis showed no differences between 2D-GRE and MP-GRE imaging (k = 1). Minor differences were observed on image quality between MP-GRE and 2D-GRE in cooperative subjects, and between MP-GRE sequences performed in cooperative and noncooperative subjects. Liver fat index results were strongly positively correlated (r = .98; 95% confidence interval [CI] 0.97 to 0.98; P < .0001). Intercept (.14; 95% CI .13 to .15; P < .0001) and slope (.83; 95% CI .79 to .86; P < .0001) were statistically significant.

CONCLUSION

IP/OP MP-GRE and 2D-GRE comparably demonstrate the presence or absence of hepatic steatosis. Image quality of MP-GRE was also comparable to 2D-GRE, and was not substantially adversely affected if subjects were unable to cooperate with breathholding instructions.

Noncontrast MR angiography for comprehensive assessment of abdominopelvic arteries using quadruple inversion-recovery preconditioning and 3D balanced steady-state free precession imaging

PURPOSE

To develop a noncontrast magnetic resonance angiography (MRA) method for comprehensive evaluation of abdominopelvic arteries in a single 3D acquisition.

MATERIALS AND METHODS

A noncontrast MRA (NC MRA) pulse sequence was developed using four inversion-recovery (IR) pulses and 3D balanced steady-state free precession (b-SSFP) readout to provide arterial imaging from renal to external iliac arteries. Respiratory triggered, high spatial resolution (1.3 × 1.3 × 1.7 mm(3)) noncontrast angiograms were obtained in seven volunteers and ten patients referred for gadolinium-enhanced MRA (CE MRA). Images were assessed for diagnostic quality by two radiologists. Quantitative measurements of arterial signal contrast were also performed.

RESULTS

NC MRA imaging was successfully completed in all subjects in 7.0 ± 2.3 minutes. In controls, image quality of NC MRA averaged 2.79 ± 0.39 on a scale of 0-3, where 3 is maximum. Image quality of NC MRA (2.65 ± 0.41) was comparable to that of CE MRA (2.9 ± 0.32) in all patients. Contrast ratio measurements in patients demonstrated that NC MRA provides arterial contrast comparable to source CE MRA images with adequate venous and excellent background tissue suppression.

CONCLUSION

The proposed noncontrast MRA pulse sequence provides high-quality visualization of abdominopelvic arteries within clinically feasible scan times.

Clinical usefulness of free-breathing navigator-triggered 3D MRCP in non-cooperative patients: comparison with conventional breath-hold 2D MRCP

PURPOSE

To assess the clinical usefulness of free-breathing 3D MRCP in non-cooperative patients compared conventional breath-hold 2D MRCP.

MATERIALS AND METHODS

We performed FB navigator-triggered 3D MRCP using prospective acquisition correction and BH 2D MRCP in 48 consecutive, non-cooperative patients among 772 patients. Thirteen patients had malignant obstruction. Two radiologists independently graded the likelihood of a malignant obstruction, the overall image quality, and the visibility of ten, individual anatomic segments of both the biliary and pancreatic duct in each sequence. The area under the ROC curve and the repeated measures analyses of variance with multiple comparisons were used for the comparison. The κ statistics were used for interobserver agreement.

RESULT

The diagnostic performance for detecting malignancy was significantly higher on FB MRCP (A(z)=0.962) than on either BH SS-RARE (A(z)=0.820, P<0.0185) or MS-HASTE MRCP (A(z)=0.816, P<0.0067). Interobserver agreement was excellent for FB MRCP (κ=0.889) and fair for both BH SS-RARE (κ=0.578) and MS-HASTE MRCP (κ=0.49). FB MRCP had a significantly higher technical quality than BH MRCP (P<0.001). FB MRCP was seen to have statistically better visibility of peripheral IHD, right main IHD, CHD, cystic duct, and CBD than BH MRCP (P<0.001). FB MRCP and BH SS-RARE MRCP had statistically better visibility of both the left main IHD and pancreatic duct than did BH MS-HASTE MRCP (P<0.001).

CONCLUSION

FB 3D MRCP is useful for non-cooperative patients in whom conventional BH 2D methods cannot be used successfully.

Respiratory motion compensated MR cholangiopancreatography at 3.0 Tesla

PURPOSE

To reduce irregular respiratory motion-induced artifacts in free-breathing prospective navigator-triggered three-dimensional (3D) MR cholangiopancreatography (MRCP).

MATERIALS AND METHODS

A reference respiration model was estimated from the first-five respiration periods during the initial navigator scan. With the navigator information acquired before and after triggering, the un-acquired diaphragm position during the actual imaging was interpolated using the amplitude-scaled reference model. Craniocaudal translational motion during imaging was retrospectively corrected using the estimated diaphragm position. T2-weighted 3D MRCP data were acquired from 17 healthy volunteers. For quantitative analysis, contrast-to-noise ratio (CNR) and relative contrast (RC) of the biliary tree and gallbladder were compared using the paired t-test.

RESULTS

The CNR and RC of the biliary tree and gallbladder were significantly higher (P < 0.05) in the maximum intensity projection images after motion compensation.

CONCLUSION

The proposed algorithm can be an effective tool to reduce the irregular respiratory motion-induced artifacts in 3D MRCP imaging.

MR imaging of cystic lesions of the pancreas

Pancreatic cystic lesions are relatively common imaging findings and may be secondary to both benign and malignant disease processes. Accurate characterization of the internal features of a cyst--including fluid, hemorrhage, septa, and enhancing soft-tissue components--is important to guide the differential diagnosis, and cross-sectional magnetic resonance (MR) imaging is the optimal modality for depicting these features. Cystic lesions of the pancreas may be divided into two categories: (a) primary cystic lesions, which include pseudocysts, serous cystadenomas, various mucin-containing cysts (mucinous nonneoplastic cysts, mucinous cystadenomas, mucinous cystadenocarcinomas, intraductal papillary mucinous neoplasms), and lymphoepithelial cysts, and (b) various solid neoplasms undergoing cystic changes (ductal adenocarcinoma with cystic features, pseudopapillary tumors of the pancreas, and cystic neuroendocrine tumors). Primary cystic lesions are more common than solid neoplasms with cystic changes. Knowledge of the varied MR imaging appearances of pancreatic cystic lesions may help radiologists achieve greater specificity in diagnostic reporting.

Morphine- and glucagon-augmented magnetic resonance cholangiopancreatography to evaluate living liver donors

The purpose of this study was to investigate the effectiveness of the combined use of intravenous morphine and intramuscular glucagon in improving magnetic resonance cholangiopancreatography (MRCP) image quality in donors for living-related liver transplantation. Sixteen healthy donor candidates underwent an MRCP study. Coronal, single-shot, fast spin-echo, heavily T2-weighted dynamic MRCP images were obtained before and 3 minutes after the intravenous administration of morphine HCl with a dose of 0.04 mg/kg. Thirty minutes after the injection of morphine, intramuscular glucagon was used. Another MRCP image of the same pulse sequence was generated 15 minutes after the injection of glucagon with a dose of 1 mg. The diameter, signal intensity, and number of branches of bile ducts in MRCP images taken immediately before and after the injection of morphine and after the injection of glucagon (plus delayed morphine effects) were compared and analyzed. In all 16 donor candidates, the diameters of the right and left hepatic ducts, common bile duct, and main pancreatic duct were significantly increased (P < 0.05) in the MRCP images taken 3 minutes after the injection of morphine and 15 minutes after the injection of glucagon (plus delayed morphine effects) in comparison with MRCP images taken before any drug administration. The qualitative grading scores of the signal intensity and order of branches of bile ducts revealed improvements in the MRCP images after the injection of glucagon (plus delayed morphine effects; P < 0.05). In conclusion, combining the intravenous administration of low-dose morphine and the intramuscular use of glucagon before MRCP examination improves the visualization of the nondilated biliary ductal anatomy, which is important for the preoperative biliary evaluation of donor candidates for living-related liver transplantation.

Prospective ECG-gated mouse cardiac imaging with a 34-MHz annular array transducer

Prospective imaging with electrocardiogram (ECG) and respiratory gating presents an imaging application that leverages the improved image quality of high-frequency (>20 MHz) annular arrays without the need for rapid mechanical motion. The limitation of prospective imaging is that the object being imaged must have a periodically stable motion. The present study investigated the implementation of prospective imaging with a 34 MHz annular-array scan system to image the mouse heart at high effective frame rates, >200 frames/s (fps). M-mode data for all transmit-to-receive pairs were acquired at a series of spatial locations using ECG and respiratory gating, and the data were then synthetically focused in postprocessing. The pulse-repetition frequency of the M-mode data determined the effective frame rate of the final B-mode image sequence. The hearts of adult mice were prospectively imaged and compared with retrospective data acquired with a commercial ultrasonic biomicroscope (UBM). The annular array data were acquired at an effective frame rate of 500 fps spanning 0.5 s, and the UBM data were acquired at 1000 fps spanning 0.15 s. The resulting images showed that multiple heart cycles could be clearly resolved using prospective imaging and that synthetic focusing improved image resolution and SNR of the right ventricle, interventricular septum, posterior edge of the left ventricle (LV), and papillary muscles of the LV versus fixed-focused imaging and the retrospective imaging of the UBM machine.