Combined gadoxetic acid and gadofosveset enhanced liver MRI for detection and characterization of liver metastases

Apparent Variation in Measurement Size of Colorectal Cancer Metastases to the Liver on Dual Contrast MRI

PURPOSE

The aim of this study was to formally investigate the apparent variation in lesion size of hepatic metastatic lesions from colorectal cancer on hepatobiliary phase (HBP) and dual contrast images of magnetic resonance imaging performed with both hepatobiliary and extracellular contrast agents.

METHODS

Patients with known colorectal carcinoma who had undergone dual contrast liver magnetic resonance imaging were identified in our institutional database. Metastatic lesions were measured semiautomatically on both HBP and dual contrast images with a custom software tool that automatically identifies the lesion edge and thereby the lesion diameter. Lesion measurements from both sets of images were compared with a Student t test and Bland-Altman analysis. Lesions were also measured on both HBP and dual contrast images by 2 fellowship-trained abdominal radiologists. Measurements from the software and radiologists were compared with a Student t test and Bland-Altman analysis; interreader agreement was evaluated with the intraclass correlation coefficient.

RESULTS

A total of 70 liver lesions in 39 patients was identified. Software-based measurements were significantly larger on HBP than dual contrast images ( P < 0.001), with a mean lesion size of 10.9 ± 4.2 mm for HBP and 10.5 ± 4.2 mm for dual contrast measurements. Radiologist-based measurements showed a similar trend, with HBP measurements being significantly larger than dual contrast measurements ( P < 0.001). Bland-Altman analysis indicated a mean bias ± 2 SD of +0.4 ± 1.6 mm for software-based measurements and +0.9 ± 2.9 mm and +0.7 ± 2.1 mm for readers 1 and 2, respectively. The intraclass correlation coefficient for interreader agreement was 0.9.

CONCLUSIONS

Both software-based and radiologist-based measurements of colorectal cancer liver metastases are significantly larger on HBP than dual contrast images. Based on these findings, we recommend that longitudinal assessment be performed consistently on either HBP or dual contrast phases to avoid introduction of avoidable variability.

Utility of combined gadoxetic acid and ferumoxytol-enhanced liver MRI for preoperative detection of colorectal cancer liver metastases: a pilot study

Background

Colorectal cancer (CRC) is the second-leading cause of cancer-related death worldwide and resection of CRC metastases confined to the liver is the treatment of choice when feasible. Ferumoxytol is an off-label contrast agent that opacifies vasculature and may be helpful in distinguishing metastases from small hemangiomas and blood vessels on gadoxetic acid-enhanced magnetic resonance imaging (MRI).

Purpose

To compare the diagnostic accuracy of MRI using a standard gadoxetic acid protocol and a combined gadoxetic acid/ferumoxytol protocol in patients with suspected colorectal hepatic metastases.

Material and Methods

In this institutional review board-approved, single-institution, retrospective study, eight patients underwent gadoxetic acid-enhanced liver MRI, supplemented with additional T1-weighted ferumoxytol enhanced sequences. Two radiologists in consensus identified all metastases using all available sequences, which served as the reference standard. Two different radiologists reviewed each exam twice, once using the standard protocol and once with additional ferumoxytol sequences. The detection rate was estimated as the predicted probability of a metastasis along with the 95% confidence interval (CI) using hierarchical logistic regression models.

Results

A total of 49 metastases were identified. The mean diameter was 10 mm, measured in greatest axial dimension (median=7 mm; range=2–70 mm). Readers 1 and 2 had detection rates of 69.6% (95% CI = 48.2–85.0) and 53.1% (95% CI = 35.2–70.3) for gadoxetic acid alone and 98.0% (95% CI = 86.3–99.7) and 83.5% (95% CI = 59.3–94.7) for combined protocol.

Conclusion

In this preliminary investigation, adding ferumoxytol-enhanced sequences to gadoxetic acid liver MRI protocol increased the detection rate of CRC hepatic metastases and may aid in preoperative decision making.

Deciphering albumin-directed drug delivery by imaging

Albumin is the most abundant plasma protein, exhibits extended circulating half-life, and its properties have long been exploited for diagnostics and therapies. Many drugs intrinsically bind albumin or have been designed to do so, yet questions remain about true rate limiting factors that govern albumin-based transport and their pharmacological impacts, particularly in advanced solid cancers. Imaging techniques have been central to quantifying - at a molecular and single-cell level - the impact of mechanisms such as phagocytic immune cell signaling, FcRn-mediated recycling, oncogene-driven macropinocytosis, and albumin-drug interactions on spatial albumin deposition and related pharmacology. Macroscopic imaging of albumin-binding probes quantifies vessel structure, permeability, and supports efficiently targeted molecular imaging. Albumin-based imaging in patients and animal disease models thus offers a strategy to understand mechanisms, guide drug development and personalize treatments.

Overcoming differential tumor penetration of BRAF inhibitors using computationally guided combination therapy

BRAF-targeted kinase inhibitors (KIs) are used to treat malignancies including BRAF-mutant non-small cell lung cancer, colorectal cancer, anaplastic thyroid cancer, and, most prominently, melanoma. However, KI selection criteria in patients remain unclear, as are pharmacokinetic/pharmacodynamic (PK/PD) mechanisms that may limit context-dependent efficacy and differentiate related drugs. To address this issue, we imaged mouse models of BRAF-mutant cancers, fluorescent KI tracers, and unlabeled drug to calibrate in silico spatial PK/PD models. Results indicated that drug lipophilicity, plasma clearance, faster target dissociation, and, in particular, high albumin binding could limit dabrafenib action in visceral metastases compared to other KIs. This correlated with retrospective clinical observations. Computational modeling identified a timed strategy for combining dabrafenib and encorafenib to better sustain BRAF inhibition, which showed enhanced efficacy in mice. This study thus offers principles of spatial drug action that may help guide drug development, KI selection, and combination.

Dual contrast liver MRI: a pictorial illustration

Liver magnetic resonance imaging (MRI) is a commonly performed imaging technique with multiple indications and applications. There are two general groups of contrast agents used when imaging the liver, extracellular contrast agents (ECA) and hepatobiliary agents (HBA), each of which has its own advantages and limitations. Liver MRI with ECA provides excellent information on abdominal vasculature and better quality multi-phasic studies for characterization of focal liver lesions. HBA improves lesion detection, provides information regarding liver function and can be helpful for evaluating biliary tree anatomy, excretion, anastomotic stenoses, or leaks. Most liver MRI studies are usually performed with one agent, however in some cases, a second study is performed with another agent to obtain additional information or confirm the findings in the first study. Administering both agents in a single exam can potentially eliminate the need for additional imaging in certain situations. In this pictorial review, the techniques and indications for dual contrast MRI will be detailed with multiple demonstrative examples.

Abdominal Applications of 4D Flow MRI

BACKGROUND

 Four-dimensional flow magnetic resonance imaging (4D flow MRI) provides volumetric and time-resolved visualization and quantification of blood flow. This review presents an overview of possible applications of 4D flow MRI for non-invasive assessment of abdominal hemodynamics.

METHOD

 This review is based on the authors' experience and the current literature. A PubMed database literature research was performed in December 2019 focusing on abdominal applications of 4D flow MRI. We illustrated the review with exemplary figures and movies of clinical cases from our institution.

RESULTS AND CONCLUSION

 4D flow MRI offers the possibility of comprehensive assessment of abdominal blood flows in different vascular territories and organ systems. Results of recent studies indicate that 4D flow MRI improves understanding of altered hemodynamics in patients with abdominal disease and may be useful for monitoring therapeutic response. Future studies with larger cohorts aiming to integrate 4D flow MRI in the clinical routine setting are needed.

KEY POINTS

  · 4D flow MRI enables comprehensive visualization of the complex abdominal vasculature. · 4D flow MRI enables quantification of abdominal blood flow velocities and flow rates. · 4D flow MRI may enable deeper understanding of altered hemodynamics in abdominal disease. · Further validation studies are needed prior to broad distribution of abdominal 4D flow MRI.

CITATION FORMAT

· Riedel C, Lenz A, Fischer L et al. Abdominal Applications of 4D Flow MRI. Fortschr Röntgenstr 2021; 193: 388 - 398.

Combined gadoxetic acid and gadobenate dimeglumine enhanced liver MRI: a parameter optimization study

PURPOSE

To demonstrate the feasibility of combined delayed-phase gadoxetic acid (GA) and gadobenate dimeglumine (GD) enhanced liver MRI for improved detection of liver metastases, and to optimize contrast agent dose, timing, and flip angle (FA).

METHODS

Fourteen healthy volunteers underwent liver MRI at 3.0T at two visits during which they received two consecutive injections: 1. GA (Visit 1 = 0.025 mmol/kg; Visit 2 = 0.05 mmol/kg) and 2. GD (both visits = 0.1 mmol/kg) 20 min after GA administration. Two sub-studies were performed: Experiment-1 Eight subjects underwent multi-phase breath-held 3D-fat-saturated T1-weighted spoiled gradient echo (SGRE) imaging to determine the optimal imaging window for the combined GA + GD protocol to create a homogeneously hyperintense liver and vasculature ("plain-white-liver") with maximum contrast to muscle which served as a surrogate for metastatic lesions in both experiments. Experiment-2 Six subjects underwent breath-held 3D-fat-saturated T1-weighted SGRE imaging at three different FA to determine the optimal FA for best image contrast. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated.

RESULTS

Experiment-1 The combined GA + GD protocol created a homogeneously hyperintense liver and vasculature with maximum CNR liver/muscle at approximately 60-120 s after automatic GD-bolus detection. Experiment-2 Flip angles between 25° and 35° at a dose of 0.025 mmol/kg GA provided the best combination that minimized liver/vasculature CNR, while maximizing liver/muscle CNR. CNR performance to achieve a "plain-white-liver" was superior with 0.025 mmol/kg GA compared to 0.05 mmol/kg.

CONCLUSION

Combined GA + GD enhanced T1-weighted MRI is feasible to achieve a homogeneously "plain-white-liver". Future studies need to confirm that this protocol can improve sensitivity of liver lesion detection in patients with metastatic liver disease.

Late Gadolinium Hyperintensity of Suspected Colorectal Liver Metastases on Gadofosveset-Enhanced Magnetic Resonance Imaging: A Predictor of Benignity and a Potential Problem-Solving Tool

PURPOSE

Late gadolinium hyperintensity (LGH) is sometimes seen in colorectal liver metastasis (CRLM) and represents a significant diagnostic pitfall due to overlap with LGH in benign hemangiomas; therefore, the objective of this study was to determine the prevalence of LGH and the ability of LGH to differentiate between CRLM and benign lesions with intravascular (gadofosveset) vs extracellular contrast agents (gadobutrol).

METHODS

Patients with known colorectal cancer and suspected liver lesions were prospectively recruited into this institutional review board-approved, single institution study and received magnetic resonance imaging of the liver with gadofosveset and gadobutrol. The prevalence of LGH for CRLMs and solid benign lesions was determined. Receiver operating characteristics curves were determined for the presence of LGH as a predictor of benignity. The utility of LGH to differentiate between CRLM and solid benign lesions using gadofosveset vs gadobutrol was compared using the generalized estimating equation.

RESULTS

Twenty-five patients with 131 solid focal liver lesions were recruited. The prevalence of LGH of CRLMs was 11.2% (95% confidence interval [CI]: 0.5%-21.8%) with gadofosveset vs 63.7% (95% CI: 45.7%-81.7%) with gadobutrol. The area under the receiver operating characteristic curve for the presence of LGH as a predictor of benignity was 0.86 using gadofosveset vs 0.75 using gadobutrol. Both LGH (P = .003) and the interaction of contrast agent and LGH (P = .003) statistically significantly differentiated CRLM from benign lesions.

CONCLUSION

LGH is more common with extracellular than with intravascular contrast agents and is statistically significantly associated with benign lesions rather than metastases.

Non-contrast MR angiography at 1.5 Tesla for aortic monitoring in Marfan patients after aortic root surgery

BACKGROUND

Contrast-enhanced cardiovascular magnetic resonance angiography (CE-CMRA) is the established imaging modality for patients with Marfan syndrome requiring life-long annual aortic imaging before and after aortic root replacement. Contrast-free CMRA techniques avoiding side-effects of contrast media are highly desirable for serial imaging but have not been evaluated in the postoperative setup of Marfan patients. The purpose of this study was to assess the feasibility of non-contrast balanced steady-state free precession (bSSFP) magnetic resonance imaging for aortic monitoring of postoperative patients with Marfan syndrome.

METHODS

Sixty-four adult Marfan patients after aortic root replacement were prospectively included. Fourteen patients (22%) had a residual aortic dissection after surgical treatment of type A dissection. bSSFP imaging and CE-CMRA were performed at 1.5 Tesla. Two radiologists evaluated the images regarding image quality (1 = poor, 4 = excellent), artifacts (1 = severe, 4 = none) and aortic pathologies. Readers measured the aortic diameters at defined levels in both techniques. Statistics included observer agreement for image scoring and diameter measurements and ROC analyses for comparison of the diagnostic performance of bSSFP and CE-CMRA.

RESULTS

Both readers observed no significant differences in image quality between bSSFP and CE-CMRA and found a median image quality score of 4 for both techniques (all p > .05). No significant differences were found regarding the frequency of image artifacts in both sequences (all p > .05). Sensitivity and specificity for detection of aortic dissections was 100% for both readers and techniques. Compared to bSSFP imaging, CE-CMRA resulted in higher diameters (mean bias, 0.9 mm; p < .05). The inter-observer biases of diameter measurements were not significantly different (all p > .05), except for the distal graft anastomosis (p = .001). Using both techniques, the readers correctly identified a graft suture dehiscence with aneurysm formation requiring surgery.

CONCLUSION

Unenhanced bSSFP CMR imaging allows for riskless aortic monitoring with high diagnostic accuracy in Marfan patients after aortic root surgery.