Vesical Imaging-Reporting and Data System (VI-RADS) as a grouping imaging biomarker combined with a decision-tree mode to preoperatively predict the pathological grade of bladder cancer

AIM

To investigate whether the Vesical Imaging-Reporting and Data System (VI-RADS) could be used to develop a new non-invasive preoperative grade-prediction system to partially predict high-grade bladder cancer (HG-BC).

MATERIALS AND METHODS

The present study enrolled 89 primary BC patients prospectively from March 2022 to June 2023. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of VI-RADS for predicting HG-BC and muscle-invasive bladder cancer (MIBC) in the entire group. In the low VI-RADS (≤2) group, the decision tree-based method was used to obtain significant predictors and construct the decision-tree model (DT model). The performance of the DT model and low VI-RADS scores for predicting HG-BC was determined using ROC, calibration, and decision curve analyses.

RESULTS

At a cut-off of ≥3, the specificity and positive predictive value of VI-RADS for predicting HG-BC in the entire group was 100%, and the area under the ROC curve (AUC) was 0.697. Among 65 patients with low VI-RADS scores, the DT model showed an AUC of 0.884 in predicting HG-BC compared to 0.506 for low VI-RADS scores. Calibration and decision curve analyses showed that the DT model performed better than the low VI-RADS scores.

CONCLUSION

Most VI-RADS scores ≥3 correspond to HG-BCs. VI-RADS could be used as a grouping imaging biomarker for a pathological grade-prediction procedure, which in combination with the DT model for low VI-RADS (≤2) populations, would provide a potential preoperative non-invasive method of predicting HG-BC.

Transient Respiratory-motion Artifact and Scan Timing during the Arterial Phase of Gadoxetate Disodium-enhanced MR Imaging: The Benefit of Shortened Acquisition and Multiple Arterial Phase Acquisition

Purpose:

To investigate whether shortened acquisition or multiple arterial phase acquisition improves image quality of the arterial phase compared with conventional protocol.

Methods:

This retrospective study was approved by the relevant Institutional Review Board. A total of 615 consecutive patients who underwent gadoxetate disodium-enhanced MRI including one of the following three sequences in three different periods were included: (i) conventional liver acquisition with volume acceleration (LAVA) (between October 2014 and January 2015, n = 149), (ii) Turbo-LAVA (between March and August 2016, n = 216), and (iii) differential sub-sampling with Cartesian ordering (DISCO) (between January and September 2015, n = 250). We monitored the respiratory bellows waveform during breath holding for each patient and recorded breath-hold fidelity of the patients. Two radiologists independently evaluated the degree of respiratory artifact and scan timing on the arterial phase and compared them between the three protocols (i.e., conventional LAVA, Turbo-LAVA, and DISCO), with conventional LAVA as control.

Results:

The ratio of patients with breath-hold failure was not significantly different among the three protocols (P = 0.6340 and 0.1085). Respiratory artifact was significantly lower in DISCO than in conventional LAVA (P = 0.0424), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.2593). The ratio of adequate scan timing and diagnosable image defined as no or mild artifact and adequate scan timing were higher in DISCO than in conventional LAVA (P = 0.0025 and 0.0019), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.0780 and 0.0657).

Conclusion:

Compared with conventional protocol, multiple arterial phase acquisition (DISCO) obtained a higher number of diagnosable images by reducing respiratory motion artifact and optimizing the scan timing of arterial phase.

Preliminary Exploration of the Application of Vesical Imaging-Reporting and Data System (VI-RADS) in Post-treatment Patients With Bladder Cancer: A Prospective Single-Center Study

BACKGROUND

Vesical Imaging-Reporting and Data System (VI-RADS) has been shown to be effective in diagnosing muscle invasion of bladder cancer (BC) in primary patients.

PURPOSE

To evaluate the diagnostic efficacy of VI-RADS in a BC target population which included post-treatment patients, and to determine the repeatability.

STUDY TYPE

Prospective.

POPULATION

Seventy-three patients (42 with primary BC, 31 with post-treatment BC).

FIELD STRENGTH/SEQUENCE

3.0 T MRI with propeller fast spin-echo T₂ WI, echo planer imaging diffusion-weighted imaging (DWI), and dynamic contrast-enhanced imaging (DCEI).

ASSESSMENT

VI-RADS scores were independently assessed by five radiologists with different levels of experience. The diagnostic efficiency in each group (primary and post-treatment) and of each radiologist was assessed.

STATISTICAL TESTS

Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), and area under the curve (AUC) in receiver operating characteristic curve analysis were calculated to evaluate VI-RADS diagnostic performance. Interobserver agreement was assessed using weighted Kappa statistics. A P value <0.05 was considered statistically significant.

RESULTS

At the corresponding cut-off, AUC values of three groups range from 0.936 to 0.947 and AUC values of five observers range from 0.901 to 0.963. There was no significant difference between the AUCs in the primary and post-treatment groups (P = 0.870). The cut-off of the whole group and the post-treatment group was ≥4, and the cut-off of the primary group was ≥3. The Kappa values of interobserver agreements range from 0.709 to 0.923.

CONCLUSIONS

After expanding the target population to include post-treatment patients, VI-RADS still has good diagnostic efficacy and repeatability. VI-RADS could potentially be a preoperative staging tool for post-treatment patients.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 2.

Alternative approach of hepatocellular carcinoma surveillance: abbreviated MRI

This review focuses on emerging abbreviated magnetic resonance imaging (AMRI) surveillance of patients with chronic liver disease for hepatocellular carcinoma (HCC). This surveillance strategy has been proposed as a high-sensitivity alternative to ultrasound for identification of patients with early-stage HCC, particularly in patients with cirrhosis or obesity, in whom sonographic visualization of small tumors may be compromised. Three general AMRI approaches have been developed and studied in the literature - non-contrast AMRI, dynamic contrast-enhanced AMRI, and hepatobiliary phase contrast-enhanced AMRI - each comprising a small number of selected sequences specifically tailored for HCC detection. The rationale, general technique, advantages and disadvantages, and diagnostic performance of each AMRI approach is explained. Additionally, current gaps in knowledge and future directions are discussed. Based on emerging evidence, we cautiously recommend the use of AMRI for HCC surveillance in situations where ultrasound is compromised.

Effects of gadoxetic acid on image quality of arterial multiphase magnetic resonance imaging of liver: comparison study with gadoteric acid-enhanced MRI

PURPOSE

To compare the effects of gadoxetic acid and gadoteric acid on the image quality of single-breath-hold, triple (first, second, and third) arterial hepatic magnetic resonance imaging (MRI).

METHODS

Two hundred and eleven patients were divided into two groups according to the contrast materials used (gadoxetic acid, 108 patients and gadoteric acid, 103 patients). All 3.0-T MR examinations included triple arterial phase acquisition using the 4D enhanced T1-weighted high-resolution isotropic volume examination (eTHRIVE) keyhole technique. The image qualities of the pre-contrast and triple arterial phases were assessed in terms of image artifacts, sharpness of the intrahepatic vessel and liver edge, and overall image quality with a 5-point scale for qualitative analysis.

RESULTS

The image quality of gadoxetic acid-enhanced liver MRI in the triple arterial phases was significantly degraded compared with that of gadoteric acid-enhanced liver MRI, although better image scores were observed in the pre-contrast images in the gadoxetic acid group (P < 0.001). The overall image quality gradually improved from the first to the third arterial phases in both groups (P < 0.003).

CONCLUSIONS

Intravenous gadoxetic acid could have a detrimental effect on image quality of triple arterial phase MRI with the 4D eTHRIVE Keyhole technique. The third arterial phase images had the best image qualities; thus, they could be used as key scans.

Respiratory Motion-Resolved Compressed Sensing Reconstruction of Free-Breathing Radial Acquisition for Dynamic Liver Magnetic Resonance Imaging

OBJECTIVE

This study aimed to demonstrate feasibility of free-breathing radial acquisition with respiratory motion-resolved compressed sensing reconstruction [extra-dimensional golden-angle radial sparse parallel imaging (XD-GRASP)] for multiphase dynamic gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced liver imaging, and to compare image quality to compressed sensing reconstruction with respiratory motion-averaging (GRASP) and prior conventional breath-held Cartesian-sampled data sets [BH volume interpolated breath-hold examination (VIBE)] in same patients.

SUBJECTS AND METHODS

In this Health Insurance Portability and Accountability Act-compliant prospective study, 16 subjects underwent free-breathing continuous radial acquisition during Gd-EOB-DTPA injection and had prior BH-VIBE available. Acquired data were reconstructed using motion-averaging GRASP approach in which consecutive 84 spokes were grouped in each contrast-enhanced phase for a temporal resolution of approximately 14 seconds. Additionally, respiratory motion-resolved reconstruction was performed from the same k-space data by sorting each contrast-enhanced phase into multiple respiratory motion states using compressed sensing algorithm named XD-GRASP, which exploits sparsity along both the contrast-enhancement and respiratory-state dimensions.Contrast-enhanced dynamic multiphase XD-GRASP, GRASP, and BH-VIBE images were anonymized, pooled together in a random order, and presented to 2 board-certified radiologists for independent evaluation of image quality, with higher score indicating more optimal examination.

RESULTS

The XD-GRASP reconstructions had significantly (all P < 0.05) higher overall image quality scores compared to GRASP for early arterial (reader 1: 4.3 ± 0.6 vs 3.31 ± 0.6; reader 2: 3.81 ± 0.8 vs 3.38 ± 0.9) and late arterial (reader 1: 4.5 ± 0.6 vs 3.63 ± 0.6; reader 2: 3.56 ± 0.5 vs 2.88 ± 0.7) phases of enhancement for both readers. The XD-GRASP also had higher overall image quality score in portal venous phase, which was significant for reader 1 (4.44 ± 0.5 vs 3.75 ± 0.8; P = 0.002). In addition, the XD-GRASP had higher overall image quality score compared to BH-VIBE for early (reader 1: 4.3 ± 0.6 vs 3.88 ± 0.6; reader 2: 3.81 ± 0.8 vs 3.50 ± 1.0) and late (reader 1: 4.5 ± 0.6 vs 3.44 ± 0.6; reader 2: 3.56 ± 0.5 vs 2.94 ± 0.9) arterial phases.

CONCLUSION

Free-breathing motion-resolved XD-GRASP reconstructions provide diagnostic high-quality multiphase images in patients undergoing Gd-EOB-DTPA-enhanced liver examination.

Optimal visualization of focal nodular hyperplasia: quantitative and qualitative evaluation of single and multiphasic arterial phase acquisition at 1.5 T MR imaging

PURPOSE

To evaluate the qualitative and quantitative benefit of multiple arterial phase acquisitions for the depiction of hypervascularity in FNH explored MR imaging using an extracellular contrast agent.

METHODS

Between 2007 and 2014, all patients who underwent MR imaging for the exploration of FNH were included. The protocol included a single or a triple arterial phase ("single" and "triple" group, respectively). Arterial phases were visually divided into four types: (1) angiographic, (2) early, (3) late, and (4) portal. Signal intensity on arterial phase images was visually recorded as intense, moderate, or low for each lesion. Lesion-to-liver contrast (LLC) and relative lesion enhancement (RE) were calculated and compared between the two groups using the Mann-Whitney test.

RESULTS

Thirty-five women were included (mean 45-year old, range 20-66), with 50 FNH (mean size 30 mm). Single and triple groups included 20 patients (30 FNH) and 15 patients (20 FNH), respectively. Signal intensity was intense in all lesions in the triple group and in 22/30 (73%) in the single group (p = 0.041). Intense signals were more frequently found in the early arterial phase (p < 0.001). RE was not significantly different (1.78 ± 0.84 vs. 1.98 ± 1.81 p = 0.430, in the single and triple groups, respectively) but LLC was significantly higher in the triple group (0.32 ± 0.10 vs. 0.22 ± 0.10, p = 0.005). LLC was significantly higher in the first two arterial phases in the triple group (p < 0.001).

CONCLUSION

Acquisition of three arterial phases improves the visualization of hypervascularity of FNH, as lesions show high visual signal intensity and contrast. Optimal visualization is obtained in the early arterial phase.

Body MR angiography in children: how we do it

Vascular pathology is ubiquitous in children. Common indications for angiographic imaging in the body include congenital anomalies, portal hypertension, assessing resectability of neoplasms, renovascular hypertension, vascular malformations, vasculitis, systemic vein thrombosis, and trauma. MR angiography, with or without the use of intravenous contrast agents, is therefore a mainstay in the repertoire of MR imaging in children. Pediatric contrast-enhanced MR angiography has benefited from several innovations in recent years, including improved hardware options like high-field-strength scanners and integrated high-density coil arrays, new sequences that combine parallel imaging, innovative k-space sampling and Dixon fat suppression with time-resolved imaging, new contrast agents with longer blood-pool residence time, and advanced post-processing solutions like image fusion. This article focuses on the principles of contrast-enhanced MR angiography of the body as it pertains to the physiologies and pathologies encountered in children. It also discusses tools to adapt the MR angiographic technique to the clinical indication, as well as pitfalls of post-processing and interpretation in commonly encountered vascular imaging scenarios in the pediatric body.

Single-breath-hold thin-slice gadoxetic acid-enhanced hepatobiliary MR imaging using a newly developed three-dimensional fast spoiled gradient-echo sequence

PURPOSE

To prospectively evaluate the efficacy of a new three-dimensional gradient-echo sequence (Turbo LAVA) that uses undersampled k-space acquisition combined with a two-dimensional parallel imaging technique for hepatobiliary MRI.

MATERIALS AND METHODS

Sixty patients underwent T1-weighted gadoxetic acid-enhanced hepatobiliary axial MRI during a single breath-hold using both Turbo LAVA (thickness/interval=1.6/0.8mm) and conventional three-dimensional gradient-echo (4/2mm; LAVA) sequences at 3T. Axial 4-mm-thick reformation was performed from Turbo LAVA images. Portal vein-to-liver contrast (PLC), bile duct-to-liver contrast (BLC), and lesion-to-liver contrast (LLC) were compared. Two radiologists independently assessed image quality using a five-point scale. Sagittal 4-mm-thick multiplanar reconstructions (MPR) were performed from both sequences and assessed together with directly obtained 4-mm-thick sagittal LAVA images in terms of sharpness. The paired t-test was used to compare PLC, BLC, and LLC. The Wilcoxon signed rank test was used to compare five-point scales.

RESULTS

The mean PLC (P<0.001), BLC (P<0.001), and LLC (P<0.005) were significantly higher for Turbo LAVA than for LAVA; the scores for image noise and sharpness were inferior (P=0.000 and 0.005) and superior (0.005 and 0.157) for Turbo LAVA. There were no significant differences in the scores for bile duct visualization, artifacts, fat suppression quality, overall quality, and focal lesion conspicuity. For sagittal images, MPR Turbo LAVA showed significantly better sharpness than MPR LAVA but showed significantly worse sharpness compared with directly obtained LAVA.

CONCLUSION

High-spatial-resolution single-breath-hold hepatobiliary MRI using Turbo LAVA was feasible. Diagnostic-quality MPR images can be obtained using this sequence.

[Evaluation of Image Quality in Three-dimensional Fat-suppressed T1-weighted Images with Fast Acquisition Mode for Upper Abdomen]

We compared the uniformity of fat-suppression and image quality using three-dimensional fat-suppressed T₁-weighted gradient-echo sequences that are liver acquisition with volume acceleration (LAVA) and Turbo-LAVA at 3.0T-MRI. The subjects were seven patients with liver disease (mean age, 66.7±8.2 years). The axial slices of two LAVA sequences were used for the comparison of the uniformity of fat-suppression and image quality at a region-of-interest (ROI) of the liver dome, the porta, and the renal hilum. To yield a quantitative measurement of the uniformity of fat suppression, the percentage standard deviation (%SD) was calculated by comparing two sequences. For image signal to noise ratio (SNR), the contrast between the liver and fat (C_liver-fat), and the liver and muscle (C_liver-muscle), the other ROIs were placed in the superficial fat, liver, spleen, pancreas, and muscle. The %SD in Turbo-LAVA (28.1±16.8%) was lower than that in LAVA (41.5±13.4%). The SNRs in Turbo-LAVA (17.8±4.1 [liver], 12.5±3.0 [pancreas], 14.7±1.6 [spleen], 8.2±3.5 [fat]) were lower than those in LAVA (20.9±6.1 [liver], 16.8±4.1 [pancreas], 17.4±2.4 [spleen], 12.0±4.5 [fat]). While, the C_liver-fat in the Turbo-LAVA (0.72±0.06) was significantly higher than that in LAVA (0.59±0.07). Turbo-LAVA sequence offers superior and more homogenous fat-suppression in comparison to LAVA sequence.

Optimizing Liver Magnetic Resonance Imaging: Does Intuitive Protocol Management Software Save Time and Produce Better Scans than Manually Optimized Protocols?

PURPOSE

The purpose of this study is to determine if a software package (Abdomen DOT; Siemens Medical Systems, Erlangen Germany) designed to automate magnetic resonance imaging (MRI) scans of the liver results in faster and higher quality examinations compared to optimized protocols performed by appropriately trained technologists.

MATERIALS AND METHODS

One hundred eight liver MRIs obtained using Abdomen DOT and 94 liver MRIs obtained without Abdomen DOT were retrospectively reviewed. Total scan time and the number of repeated sequences were objectively measured. Timing of the arterial phase, motion artifact, and quality of subtraction images were subjectively evaluated.

RESULTS

The examinations scanned using Abdomen DOT averaged 2 minutes and 2 seconds shorter than the examinations scanned without Abdomen DOT (P = 0.004) and on average, fewer sequences were repeated. The arterial phase was timed correctly 67% (63/94) of the time without using Abdomen DOT and 81% (87/108) of the time when using Abdomen DOT (P = 0.019). There was no difference in the amount of respiratory artifact. The subtraction images obtained using Abdomen DOT were considered slightly better (P < 0.005 for arterial, portal venous, and equilibrium phase images).

CONCLUSIONS

The Abdomen DOT software helped our technologists scan slightly faster and obtain correctly timed arterial phase images more often.

Patch based reconstruction of undersampled data (PROUD) for high signal-to-noise ratio and high frame rate contrast enhanced liver imaging

PURPOSE

High spatial-temporal four-dimensional imaging with large volume coverage is necessary to accurately capture and characterize liver lesions. Traditionally, parallel imaging and adapted sampling are used toward this goal, but they typically result in a loss of signal to noise. Furthermore, residual under-sampling artifacts can be temporally varying and complicate the quantitative analysis of contrast enhancement curves needed for pharmacokinetic modeling. We propose to overcome these problems using a novel patch-based regularization approach called Patch-based Reconstruction Of Under-sampled Data (PROUD).

THEORY AND METHODS

PROUD produces high frame rate image reconstructions by exploiting the strong similarities in spatial patches between successive time frames to overcome the severe k-space under-sampling. To validate PROUD, a numerical liver perfusion phantom was developed to characterize contrast-to-noise ratio (CNR) performance compared with a previously proposed method, TRACER. A second numerical phantom was constructed to evaluate the temporal footprint and lag of PROUD and TRACER reconstructions. Finally, PROUD and TRACER were evaluated in a cohort of five liver donors.

RESULTS

In the CNR phantom, PROUD, compared with TRACER, improved peak CNR by 3.66 times while maintaining or improving temporal fidelity. In vivo, PROUD demonstrated an average increase in CNR of 60% compared with TRACER.

CONCLUSION

The results presented in this work demonstrate the feasibility of using a combination of patch based image constraints with temporal regularization to provide high SNR, high temporal frame rate and spatial resolution four dimensional imaging.

Response stratification and survival analysis of hepatocellular carcinoma patients treated with intra-arterial therapy using MR imaging-based arterial enhancement fraction

PURPOSE

To investigate the feasibility that arterial enhancement fraction (AEF) is associated with response of hepatocellular carcinoma (HCC) following intra-arterial therapy (IAT) and to compare AEF response with currently used tumor response metrics.

MATERIALS AND METHODS

The AEF, Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST (mRECIST), and European Association for the Study of the Liver (EASL) of the largest treated index lesion and AEF of the tumor-free hepatic parenchyma was measured on representative axial images in 131 patients (108 male; mean age, 61.9 years). Clinical measures and patient survival were assessed. Statistical analysis included Wilcoxon signed-rank test and the COX proportional hazards model.

RESULTS

After IAT, the mean AEF of the tumor decreased by 22% (66.7-44.8%, P < 0.0001), while the mean AEF of the tumor-free parenchyma remained unchanged (27.2-26.5%, P = 0.50). Median survival of all 131 patients with liver cancer was 17 months. Patients were stratified into AEF-responders if they had an AEF-decrease ≥35% (AEF-responders: n = 67; AEF-nonresponders: n = 64). AEF-responders survived longer than nonresponders (34.8 months versus 10.8 months, hazard ratio = 0.39; P < 0.0001). Responders according to RECIST, mRECIST, or EASL did not survive significantly longer compared with nonresponders.

CONCLUSION

Evaluating the AEF values based on tri-phasic MRI is associated with tumor response in patients with unresectable HCC treated with IAT.

DIfferential Subsampling with Cartesian Ordering (DISCO): a high spatio-temporal resolution Dixon imaging sequence for multiphasic contrast enhanced abdominal imaging

PURPOSE

To develop and evaluate a multiphasic contrast-enhanced MRI method called DIfferential Sub-sampling with Cartesian Ordering (DISCO) for abdominal imaging.

MATERIALS AND METHODS

A three-dimensional, variable density pseudo-random k-space segmentation scheme was developed and combined with a Dixon-based fat-water separation algorithm to generate high temporal resolution images with robust fat suppression and without compromise in spatial resolution or coverage. With institutional review board approval and informed consent, 11 consecutive patients referred for abdominal MRI at 3 Tesla (T) were imaged with both DISCO and a routine clinical three-dimensional SPGR-Dixon (LAVA FLEX) sequence. All images were graded by two radiologists using quality of fat suppression, severity of artifacts, and overall image quality as scoring criteria. For assessment of arterial phase capture efficiency, the number of temporal phases with angiographic phase and hepatic arterial phase was recorded.

RESULTS

There were no significant differences in quality of fat suppression, artifact severity or overall image quality between DISCO and LAVA FLEX images (P > 0.05, Wilcoxon signed rank test). The angiographic and arterial phases were captured in all 11 patients scanned using the DISCO acquisition (mean number of phases were two and three, respectively).

CONCLUSION

DISCO effectively captures the fast dynamics of abdominal pathology such as hyperenhancing hepatic lesions with a high spatio-temporal resolution. Typically, 1.1 × 1.5 × 3 mm spatial resolution over 60 slices was achieved with a temporal resolution of 4-5 s.

MRCP and 3D LAVA imaging of extrahepatic cholangiocarcinoma at 3 T MRI

Extrahepatic cholangiocarcinoma (CCA) is a primary bile duct malignant tumour with poor prognosis. Familiarity with their varied imaging characteristics can be helpful in developing a correct diagnosis and in optimal treatment planning, and thus contribute to a better prognosis. The purpose of this article is to illustrate the typical appearances of extrahepatic CCA on magnetic resonance cholangiopancreatography (MRCP) and three-dimensional (3D) LAVA (liver acquisition with volume acceleration) sequences at 3 T magnetic resonance imaging (MRI), and to discuss the superiority of the two techniques in the diagnosis of CCA.