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

Magnetic resonance urography: a practical approach to preparation, protocol and interpretation

Magnetic resonance urography (MRU) is an important MRI application that provides noninvasive comprehensive morphological and functional evaluation of the kidneys and urinary tract. It can be used to assess congenital anomalies of the kidney and urinary tract, which often present as urinary tract dilation. In children, MRU allows for high tissue contrast and high spatial resolution without requiring ionizing radiation. Magnetic resonance urography requires patient preparation in the form of pre-examination intravenous hydration, placement of a urinary catheter, and the administration of diuretics at the time of the exam. The imaging protocol is based on T2-weighted images for anatomical assessment and dynamic post-contrast images for functional evaluation. These images are then used to generate quantitative and graphic results including contrast transit and excretion time as well as to calculate differential renal function. This review focuses on a simple approach to pediatric MRU acquisition and interpretation based on clinical cases and the authors' experience.

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.

Comparing compressed sensing breath-hold 3D MR cholangiopancreatography with two parallel imaging MRCP strategies in main pancreatic duct and common bile duct

PURPOSE

To evaluate the image quality and image consistency between 3D Breath-hold (BH)-MRCP with parallel imaging (3D-BH-PI-MRCP) and 3D-BH compressed sensing (CS)-MRCP (3D-BH-CS-MRCP) in patients with suspected pancreaticobiliary diseases, compared with 3D navigator-triggered (NT)-MRCP.

MATERIALS AND METHODS

The A total number of 109 patients who underwent 3D-NT-MRCP, 3D-BH-PI-MRCP and 3D-BH-CS-MRCP were prospectively enrolled in this study. The Friedman test was performed to compare quantitative values, image acquisition time, the presence of artifacts, overall image quality, and duct visualization among the three protocols. Additionally, we compared 3D-BH-PI-MRCP and 3D-BH-CS-MRCP with 3D-NT-MRCP in morphological consistency of main pancreatic duct and common bile duct (CBD) based on overall image quality score of = 4.

RESULTS

Three MRCP methods were successfully performed in all the patients. The contrast ratio, SNR and CNR of the CBD were significantly higher for 3D-BH-CS-MRCP than those for 3D-NT-MRCP and 3D-BH-PI-MRCP images. Overall image quality did differ significantly across the three sequences. Visualization of the CBD, RHD, LHD, anterior branch, posterior branch and cystic duct was similar with the 3D-BH-CS-MRCP and 3D-BH-PI-MRCP sequences. In contrast, segment 2 or 3 branch and main pancreatic duct visualization were significantly better with 3D-BH-PI-MRCP than with 3D-BH-CS-MRCP and 3D-NT-MRCP (p < 0.001).

CONCLUSIONS

Both the two breath-hold approaches were considering the time-saving advantages without deterioration of image quality. Compared with 3D-BH-CS-MRCP, 3D-BH-PI-MRCP yielded significantly better visualization of the segment 2 and 3 branch of the intrahepatic duct and performed better consistency in main pancreatic duct and common bile duct morphology.

Comparisons between image quality and diagnostic performance of 2D- and breath-hold 3D magnetic resonance cholangiopancreatography at 3T

OBJECTIVES

To compare the image quality and diagnostic performance of 2D MRCP to those of breath-hold 3D MRCP using compressed sensing (CS-MRCP) and gradient and spin-echo (GRASE-MRCP) at 3T.

METHODS

From January to November 2018, patients who underwent pancreatobiliary MRI including 2D MRCP and two breath-hold 3D MRCP using CS and GRASE at 3T were included. Three radiologists independently evaluated image quality, motion artifact, and pancreatic cyst conspicuity. Diagnostic performance was assessed for bile duct anatomic variation, bile duct, and pancreatic diseases using a composite algorithm as reference standards. Pancreatic lesion detectability and conspicuity were evaluated using JAFROC and generalized estimating equation analysis.

RESULTS

One hundred patients (male = 50) were included. Bile duct anatomic variation, bile duct and pancreatic diseases were present in respectively 31, 15, and 79 patients. Breath-hold 3D MRCP provided better image quality than 2D MRCP (3.5 ± 0.6 in 2D MRCP; 4.0 ± 0.7 in GRASE-MRCP and 3.9 ± 0.8 in CS-MRCP, p < 0.001 for both). There was no difference in motion artifact between 2D and breath-hold 3D MRCP (p = 0.1). Breath-hold 3D CS-MRCP provided better pancreatic cyst conspicuity than 2D MRCP (2.7 [95% CI: 2.5-3.0] vs. 2.3 [95% CI: 2.1-2.5], p = 0.001). There were no significant differences between the diagnostic performance of the three sequences in the detection of bile duct anatomic variation or pancreatic lesions (p > 0.05).

CONCLUSION

Breath-hold 3D MRCP with GRASE or CS can provide better image quality than 2D MRCP in a comparable scan time.

KEY POINTS

• Breath-hold 3D MRCP using compressed sensing (CS) or gradient and spin-echo (GRASE) provided a better image quality with less image blurring than 2D MRCP. • There were no significant differences between 2D MRCP and breath-hold 3D MRCP in either motion artifact or the number of non-diagnostic exams. • There were no significant differences between 2D MRCP and either type of breath-hold 3D MRCP in the diagnosis of bile duct anatomic variation or detection of pancreatic lesions.

Comparison of Compressed Sensing and Gradient and Spin-Echo in Breath-Hold 3D MR Cholangiopancreatography: Qualitative and Quantitative Analysis

While magnetic resonance cholangiopancreatography (MRCP) is routinely used, compressed sensing MRCP (CS-MRCP) and gradient and spin-echo MRCP (GRASE-MRCP) with breath-holding (BH) may allow sufficient image quality with shorter acquisition times. This study qualitatively and quantitatively compared BH-CS-MRCP and BH-GRASE-MRCP and evaluated their clinical effectiveness. Data from 59 consecutive patients who underwent both BH-CS-MRCP and BH-GRASE-MRCP were qualitatively analyzed using a five-point Likert-type scale. The signal-to-noise ratio (SNR) of the common bile duct (CBD), contrast-to-noise ratio (CNR) of the CBD and liver, and contrast ratio between periductal tissue and the CBD were measured. Paired t-test, Wilcoxon signed-rank test, and McNemar’s test were used for statistical analysis. No significant differences were found in overall image quality or duct visualization of the CBD, right and left 1st level intrahepatic duct (IHD), cystic duct, and proximal pancreatic duct (PD). BH-CS-MRCP demonstrated higher background suppression and better visualization of right (p = 0.004) and left 2nd level IHD (p < 0.001), mid PD (p = 0.003), and distal PD (p = 0.041). Image quality degradation was less with BH-GRASE-MRCP than BH-CS-MRCP (p = 0.025). Of 24 patients with communication between a cyst and the PD, 21 (87.5%) and 15 patients (62.5%) demonstrated such communication on BH-CS-MRCP and BH-GRASE-MRCP, respectively. SNR, contrast ratio, and CNR of BH-CS-MRCP were higher than BH-GRASE-MRCP (p < 0.001). Both BH-CS-MRCP and BH-GRASE-MRCP are useful imaging methods with sufficient image quality. Each method has advantages, such as better visualization of small ducts with BH-CS-MRCP and greater time saving with BH-GRASE-MRCP. These differences allow diverse choices for visualization of the pancreaticobiliary tree in clinical practice.

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.

Navigator-triggered and breath-hold 3D MRCP using compressed sensing: image quality and method selection factor assessment

PURPOSE

To examine whether MRCP using a combination of compressed sensing and sensitivity encoding with navigator-triggered and breath-hold techniques (NT C-SENSE and BH C-SENSE, respectively) have comparable image quality to that of navigator-triggered MRCP using only sensitivity encoding (NT SENSE) at 1.5-T.

METHODS

Fifty-one participants were enrolled in this prospective study between July and October 2018 and underwent the three 3D MRCP sequences each. The acquisition time and relative duct-to-periductal contrast ratios (RC values) of each bile duct segment were obtained. Visualization of the bile and main pancreatic ducts, background suppression, artifacts, and overall image quality were scored on 5-point scales. Mean and median differences in RC values and qualitative scores of NT C-SENSE and BH C-SENSE relative to NT SENSE were calculated with 95% confidence intervals (CIs).

RESULTS

Acquisition time of NT SENSE, NT C-SENSE, and BH C-SENSE were 348, 143 (mean for both), and 18 s (for all participants), respectively. The RC value of each bile duct segment was inferior, but the lower limits of the 95% CIs of the mean differences were ≥ - 0.10, for both NT C-SENSE and BH C-SENSE. The visualization score of the intrahepatic duct in BH C-SENSE was inferior to that in NT SENSE (lower 95% CI limit, - 1.5). In both NT C-SENSE and BH C-SENSE, the 95% CIs of the median differences in the other qualitative scores were from - 1.0 to 0.0.

CONCLUSION

NT C-SENSE and BH C-SENSE have comparable image quality to NT SENSE at 1.5-T.

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.

Rapid 3D navigator-triggered MR cholangiopancreatography with SPACE sequence at 3T: only one-third acquisition time of conventional 3D SPACE navigator-triggered MRCP

PURPOSE

The purpose of this study was to compare the proposed rapid NT-MRCP protocol and the conventional NT-MRCP protocol with respect to image quality as well as the acquisition time.

MATERIALS AND METHODS

Between January 2019 and May 2019, a total number of 67 consecutive patients with suspected pancreaticobiliary diseases were included in this prospective study and underwent 3D rapid MRCP and 3D conventional MRCP sequences. Both acquisition protocols were set from the same navigator-triggered 3D SPACE sequence. The acquisition time was recorded. Two blinded radiologists performed qualitative analyses with respect to overall image quality, motion artifacts, and CBD visibility using a four-point scale. Quantitative evaluation included the contrast, signal-noise ratio (SNR), and contrast-noise ratio (CNR) between the common bile duct (CBD) and periductal tissues. A paired t test was used to assess differences in the qualitative and quantitative evaluations between the two acquisition methods.

RESULTS

All MRCP studies were completed successfully. The mean acquisition time of rapid NT-MRCP (96.64 ± 30.55 s) was significantly lower than that of the conventional NT-MRCP (271.42 ± 61.63 s; p < 0.001).The contrast ratio, SNR, and CNR of the CBD were significantly higher for conventional NT-MRCP than with rapid NT-MRCP images (0.95 ± 0.02 vs. 0.93 ± 0.03, p < 0.001; 10.36 ± 4.63 vs. 8.90 ± 4.71, p = 0.011; 14.01 ± 6.02 vs. 12.22 ± 6.36, p = 0.020, respectively). The rapid MRCP depicted the overall image quality, artifacts, CBD visibility, right and left hepatic duct, segment 2 branch, main pancreatic duct, and cystic duct significantly better compared with conventional MRCP (p < 0.05). There were no statistically significant differences between the two methods regarding visibility of anterior, posterior, and segment 3 branches (p > 0.05).

CONCLUSIONS

In conclusion, the proposed rapid MRCP protocol yielded significantly higher overall image quality and better visualization of the pancreaticobiliary tree with a significantly reduced imaging time without deterioration of image quality compared with the conventional MRCP at 3T.

Comparison and evaluation of the efficacy of compressed SENSE (CS) and gradient- and spin-echo (GRASE) in breath-hold (BH) magnetic resonance cholangiopancreatography (MRCP)

CONTRACT GRANT SPONSOR

Chinese Academy of Medical Sciences (CAMS) Initiative for Innovative Medicine; Contract grant number: 2017-I2M-1-001; Contract grant sponsor: Outstanding Youth Fund of Peking Union Medical College Hospital; Contract grant number: JQ201704; Contract grant sponsor: National Natural Science Foundation of China; Contract grant number: 81871512; Contract grant sponsor: National Public Welfare Basic Scientific Research Program of Chinese Academy of Medical Sciences; Contract grant numbers: 2018PT32003 and 2017PT32004.

BACKGROUND

Both compressed-sensing (CS) and gradient- and spin-echo (GRASE) sequences can achieve 3D magnetic resonance cholangiopancreatography (MRCP) with a single breath-hold (BH). This work hypothesized that compared with conventional navigator-triggered (NT)-MRCP, the two BH-MRCP protocols, GRASE and CS, may provide better imaging quality, especially for patients with irregular breathing.

PURPOSE

To evaluate and compare the image quality and diagnostic performance of three MRCP protocols.

STUDY TYPE

Prospective.

SUBJECTS

Seventy-four patients suspected to have duct-related pathologies were enrolled.

FIELD STRENGTH

3.0T.

SEQUENCES

NT-MRCP, BH-CS-MRCP, and BH-GRASE-MRCP.

ASSESSMENT

Breath regularity was evaluated subjectively according to the respiratory waves. The acquisition time was compared. The pancreaticobiliary system was divided into 12 segments and evaluated on a 5-point scale. The diagnostic performance of the three MRCPs was evaluated and compared.

STATISTICAL TESTS

The Friedman test with a post-hoc test, receiver operating characteristic (ROC) curve analysis, McNemar test, and Kendall's W test were used.

RESULTS

The BH-MRCP decreased the scan time significantly (P < 0.05). The overall imaging scores of GRASE-MRCP and CS-MRCP were significantly higher than that of NT-MRCP for patients with irregular breathing (4.283 and 4.283 vs. 3.000, both P < 0.05). Compared with NT-MRCP, the diagnostic performance of BH-CS and BH-GRASE MRCP was significantly improved for patients with irregular breathing (AUC = 0.860 and 0.863 vs. 0.572, both P < 0.001).

DATA CONCLUSION

Compared with conventional NT-MRCP, the overall imaging quality and diagnostic performance of BH-CS and BH-GRASE MRCP were not significantly different for patients with regular breathing and significantly superior for patients with irregular breathing.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:824-832.

Usefulness of 3D balanced turbo-field-echo MR sequence evaluating the branching pattern of the intrahepatic bile ducts: comparison with drip infusion CT cholangiography

PURPOSE

For liver surgery, it is crucial to preoperatively examine the course of the right posterior bile duct. While MR cholangiopancreatography (MRCP) can only visualize the bile ducts, 3D balanced turbo-field-echo (BTFE) sequence clearly depicts the bile ducts and portal veins as well as drip infusion CT cholangiography (DIC-CT), without contrast media. We evaluated whether BTFE could substitute for DIC-CT.

MATERIALS AND METHODS

Thirty patients undergoing MRCP and BTFE on 1.5-T MR and DIC-CT were evaluated. Two readers retrospectively evaluated the branching pattern (supra-type: A-C or infra-type: D-E) and scored the degree of confidence and motion artifacts using a 3-point scale for the three 2-mm-thick reconstructed images.

RESULTS

The bile duct diameter did not differ between DIC-CT and MRCP (p = 0.07). Five patients (17%) had intrahepatic biliary dilatation (>3 mm). The A, B, C, D, and E types were diagnosed in 21, 6, 1, 1, and 1 patient, respectively (28 supra-types and 2 infra-types) on DIC-CT. For DIC-CT, MRCP, and BTFE, the mean motion artifact scores were 3.0/3.0, 2.7/2.6, and 2.9/2.8, respectively. The mean diagnostic confidence scores were 2.9/2.9, 2.4/2.4, and 2.9/2.8, respectively, with no difference between DIC-CT and BTFE. The concordance between DIC-CT and BTFE was high (infra- or supra-type: κ = 1.00/1.00, A-E: κ = 0.86/0.66), but it was poor between DIC-CT and MRCP (infra- or supra-type: κ = 0.35/-0.05, A-E: κ = 0.33/0.41) for both readers.

CONCLUSIONS

Similar to DIC-CT, the BTFE MR sequence had high diagnostic accuracy regarding the branching pattern of the intrahepatic bile duct, especially for the supra/infraportal type.

Improved diagnosis of common bile duct stone with single-shot balanced turbo field-echo sequence in MRCP

PURPOSE

To evaluate the value of adding single-shot balanced turbo field-echo (b-TFE) sequence to conventional magnetic resonance cholangiopancreatography (MRCP) for the detection of common bile duct (CBD) stone.

METHODS

One hundred thirty-seven consecutive patients with suspected CBD stone underwent MRCP including single-shot b-TFE sequence. Twenty-five patients were confirmed with CBD stone by endoscopic retrograde cholangiopancreatography or ultrasonography. Two radiologists reviewed two image protocols: protocol A (conventional MRCP protocol: unenhanced T1-, T2-, and respiratory-triggered three-dimensional fat-suppressed single-shot turbo spin-echo MRCP sequence) and protocol B (protocol A plus single-shot b-TFE sequence). The sensitivity, specificity, positive (PPV) and negative predictive value (NPV), and area under the receiver-operating-characteristic (ROC) curve (AUC) for the detection of CBD stone were compared.

RESULTS

The sensitivity (72%) and NPV (94%) were the same between the two protocols. However, protocol B was greater in the specificity (99%) and PPV (94%) than protocol A (92% and 67%, respectively) (P = 0.0078 and 0.031, respectively). The AUC was significantly greater for protocol B (0.93) than for protocol A (0.86) (P = 0.026).

CONCLUSIONS

Inclusion of single-shot b-TFE sequence to conventional MRCP significantly improved the specificity and PPV for the detection of CBD stone.

Clinical application of navigator-gated three-dimensional balanced turbo-field-echo magnetic resonance cholangiopancreatography at 3 T: prospective intraindividual comparison with 1.5 T

OBJECTIVE

To evaluate and compare the clinical utility of balanced turbo-field-echo (BTFE) magnetic resonance cholangiopancreatography (MRCP) sequences obtained at 3 and 1.5 T.

METHODS

We acquired three-dimensional (3D) BTFE MRCP scans with a navigator-gated technique at 3 T on a different day after 1.5 T in 39 consecutive patients. Two radiologists independently rated the image quality and visibility of anatomical structures (right and left hepatic duct, cystic duct, gallbladder, common bile duct, and main pancreatic duct) using a four-point scale. For quantitative analysis, the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and acquisition time were evaluated.

RESULTS

All visual scores tended to be higher for 1.5 T than 3 T images. There was a significant difference in the image quality and the depiction of the main pancreatic duct (p < 0.01). The image acquisition time was significantly shorter for 3 T than 1.5 T (199.3 ± 40.1 vs. 264.0 ± 86.5 s, p < 0.01). There was no significant difference in SNR and CNR.

CONCLUSIONS

3D-BTFE MRCP scans acquired at 3 T were of sufficient image quality with respect to the biliary tree. SNR and CNR were comparable on 3 and 1.5 T scans, although the acquisition time was significantly shorter with the 3 T scanner.

Usefulness of 3D hybrid profile order technique with 3T magnetic resonance cholangiography: Comparison of image quality and acquisition time

PURPOSE

To evaluate the image quality and acquisition time of magnetic resonance cholangiopancreatography (MRCP) with and without the 3D hybrid profile order technique.

MATERIALS AND METHODS

We studied 32 consecutive patients at 3T. They underwent MRCP with and without the 3D hybrid profile order imaging technique during free breathing and MRCP with the 3D hybrid profile order technique during a single breath-hold. The image acquisition time was 82% shorter with the 3D hybrid profile order technique than without it. The contrast, signal-to-noise-ratio (SNR), and contrast-noise-ratio (CNR) between the common bile duct (CBD) and periductal tissues on 3D-MRCP were evaluated quantitatively.

RESULTS

The contrast, SNR, and CNR of the CBD under free breathing was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). The contrast, SNR, and CNR of the CBD under a single breath-hold was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). There were no significant differences in the contrast, SNR, and CNR of the CBD between the 3D hybrid profile order with a single breath-hold and with free breathing (P = 0.12, 0.28, 0.28, respectively).

CONCLUSION

Using 3T MRI for MRCP with the 3D hybrid profile order sequence yielded significantly improved contrast and CNR with a shorter image acquisition time without sacrificing image quality when compared to imaging without the 3D hybrid profile order sequence. J. Magn. Reson. Imaging 2016;44:1346-1353.

The diagnostic value of magnetic resonance urography using a balanced turbo field echo sequence

OBJECTIVES

The aim of the study was to compare the inter-observer variability and the accuracy of magnetic resonance urography (MRU) using a thin sectional balanced-turbo field echo (B-TFE) sequence for detecting ureteral calculi and to determine the effect of additional factors (size, density and location of the calculus) on the sensitivity and specificity of the MRU.

MATERIALS & METHODS

MRU and CT images were evaluated independently by two radiologists according to presence, density and localization of calculi. The degrees of inter-rater agreement for categorical items were evaluated by the Kappa coefficient.

RESULTS

According to the 1st and 2nd observers, the sensitivity of MRU was 65.9 %, 71.8 % and the specificity of MRU was 95.9 %, 100 %, respectively. Inter-observer agreement was 84.6 % for stone detection. The larger size had a better effect on detectability (p < 0.05). Also, the higher density had a better impact on detectability (p < 0.05).

CONCLUSION

Our study has shown that B-TFE MRU was useful to detect ureteral calculi. However, B-TFE MRU has low sensitivity and high specificity in comparison with CT images. MRU is a reasonable alternative imaging technique for follow-up periods of selective groups like patients with large urinary stones, children or pregnant patients when ionizing radiation is undesirable.

KEY POINTS

• According to 1st and 2nd observers, sensitivity of MRU was 65.9 %, 71.8 %, respectively. • According to 1st and 2nd observers, MRU specificity was 95.9 %, 100 %, respectively. • Interobserver agreement was found to be over 84 % for stone detection. • B-TFE sequence provides calculus follow-up without radiation. • Larger calculi and more dense calculi individually have the better effect on detectability.

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.