Evaluation of neuroendocrine liver metastases: a comparison of dynamic contrast-enhanced magnetic resonance imaging and positron emission tomography/computed tomography. Invest Radiol. 2014;49:7-14. [PMID: 24002080 DOI: 10.1097/rli.0b013e3182a4eb4a]

Impact of Dynamic Contrast Enhanced and Diffusion-Weighted MR Imaging on Detection of Early Local Recurrence of Soft Tissue Sarcoma

BACKGROUND

Diagnosis of residual or recurrent tumor in soft-tissue sarcomas (STS) is a differential diagnostic challenge since post-therapeutic changes impede diagnosis.

PURPOSE

To evaluate the diagnostic accuracy of quantitative dynamic contrast enhanced (DCE)-MRI and diffusion-weighted imaging (DWI) to detect local recurrence of STS of the limb.

STUDY TYPE

Prospective.

POPULATION

A totalof 64 consecutive patients with primary STS of the limbs were prospectively included 3-6 months after surgery between January 2016 and July 2021.

FIELD STRENGTH/SEQUENCE

A 1.5 T; axial DWI echo-planar imaging sequences and DCE-MRI using a 3D T1-weighted spoiled gradient-echo sequence.

ASSESSMENT

The quantitative DCE-MRI parameters relative plasma flow (rPF) and relative mean transit time (rMTT) were calculated and ADC mapping was used to quantify diffusion restriction. Regions of interest of tumor growth and postoperative changes were drawn in consensus by two experts for diffusion and perfusion analysis. An additional morphological assessment was done by three independent and blinded radiologists.

STATISTICAL TEST

Unpaired t-test, ROC-analysis, and a logistic regression model were applied. Interobserver reliability was calculated using Fleiss kappa statistics. A P value of 0.05 was considered statistically significant.

RESULTS

A total of 11 patients turned out to have local recurrence. rPF was significantly higher in cases of local recurrence when compared to cases without local recurrence (61.1-4.5) while rMTT was slightly and significantly lower in local recurrence. ROC-analysis showed an area under the curve (AUC) of 0.95 (SEM ± 0.05) for rPF while a three-factor multivariate logistic regression model showed a high diagnostic accuracy of rPF (R²  = 0.71). Compared with morphological assessment, rPF had a distinct higher specificity and true positive value in detection of LR.

DATA CONCLUSION

DCE-MRI is a promising additional method to differentiate local recurrence from benign postoperative changes in STS of the limb. Especially specificity in detection of LR is increased compared to morphological assessment.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

A decade of multi-modality PET and MR imaging in abdominal oncology

OBJECTIVES

To investigate trends observed in a decade of published research on multimodality PET(/CT)+MR imaging in abdominal oncology, and to explore how these trends are reflected by the use of multimodality imaging performed at our institution.

METHODS

First, we performed a literature search (2009-2018) including all papers published on the multimodality combination of PET(/CT) and MRI in abdominal oncology. Retrieved papers were categorized according to a structured labelling system, including study design and outcome, cancer and lesion type under investigation and PET-tracer type. Results were analysed using descriptive statistics and evolutions over time were plotted graphically. Second, we performed a descriptive analysis of the numbers of MRI, PET/CT and multimodality PET/CT+MRI combinations (performed within a ≤14 days interval) performed during a similar time span at our institution.

RESULTS

Published research papers involving multimodality PET(/CT)+MRI combinations showed an impressive increase in numbers, both for retrospective combinations of PET/CT and MRI, as well as hybrid PET/MRI. Main areas of research included new PET-tracers, visual PET(/CT)+MRI assessment for staging, and (semi-)quantitative analysis of PET-parameters compared to or combined with MRI-parameters as predictive biomarkers. In line with literature, we also observed a vast increase in numbers of multimodality PET/CT+MRI imaging in our institutional data.

CONCLUSIONS

The tremendous increase in published literature on multimodality imaging, reflected by our institutional data, shows the continuously growing interest in comprehensive multivariable imaging evaluations to guide oncological practice.

ADVANCES IN KNOWLEDGE

The role of multimodality imaging in oncology is rapidly evolving. This paper summarizes the main applications and recent developments in multimodality imaging, with a specific focus on the combination of PET+MRI in abdominal oncology.

68Ga-DOTATATE PET/CT compared to standard imaging in metastatic neuroendocrine tumors: a more sensitive test to detect liver metastasis?

PURPOSE

68Ga-DOTATATE PET is becoming a popular imaging technique for detecting neuroendocrine tumors (NETs). The sensitivity and specificity of 68Ga-DOTATATE PET compared to standard cross-sectional imaging with triple phase CT or MRI with Eovist has not been studied extensively.

METHODS

68Ga-DOTATATE PET scans ordered at our institution between 11/2017 and 7/2018 were reviewed. Patients with evidence of liver metastases were sorted and cross-sectional imaging results were reviewed. Specifically, the number of lesions detected by standard cross-sectional imaging versus 68Ga-DOTATATE PET was compared.

RESULTS

32 patients with 68Ga-DOTATATE PET scans and a corresponding MRI or CT were identified. Primary tumors were pancreatic (43.8%), small bowel (25%), hepatic (9.4%), gastric (6.3%), appendiceal (3.1%), and not localized (12.5%). 26/32 (81%) patients had CT scans and 17/32 (53%) had MRI scans. 25/32 (78%) patients had at least equal or increased number of lesions identified on 68Ga-DOTATATE PET when compared with CT or MRI. 7/32 (21.9%) had fewer lesions on 68Ga-DOTATATE PET compared to CT or MRI. However, 3 of these cases had numerous liver lesions. The overall sensitivity and specificity of 68Ga-DOTATATE PET are 92.9% and 75% respectively.

CONCLUSION

68Ga-DOTATATE PET appears to have superior sensitivity in detecting metastatic NET to the liver. Further studies are needed to determine if it should be considered the test of choice for evaluating patients with metastatic NET to the liver. While standard cross-sectional imaging will be needed for surgical planning, 68Ga-DOTATATE PET will identify lesions that may not be seen on other imaging modalities.

Simultaneous evaluation of perfusion and morphology using GRASP MRI in hepatic fibrosis

OBJECTIVES

To determine if golden-angle radial sparse parallel (GRASP) dynamic contrast-enhanced (DCE)-MRI allows simultaneous evaluation of perfusion and morphology in liver fibrosis.

METHODS

Participants who were scheduled for liver biopsy or resection were enrolled (NCT02480972). Images were reconstructed at 12-s temporal resolution for morphologic assessment and at 3.3-s temporal resolution for quantitative evaluation. The image quality of the morphologic images was assessed on a four-point scale, and the Liver Imaging Reporting and Data System score was recorded for hepatic observations. Comparisons were made between quantitative parameters of DCE-MRI for the different fibrosis stages, and for hepatocellular carcinoma (HCCs) with different LR features.

RESULTS

DCE-MRI of 64 participants (male = 48) were analyzed. The overall image quality consistently stood at 3.5 ± 0.4 to 3.7 ± 0.4 throughout the exam. Portal blood flow significantly decreased in participants with F2-F3 (n = 18, 175 ± 110 mL/100 mL/min) and F4 (n = 12, 98 ± 47 mL/100 mL/min) compared with those in participants with F0-F1 (n = 34, 283 ± 178 mL/100 mL/min, p < 0.05 for all). In participants with F4, the arterial fraction and extracellular volume were significantly higher than those in participants with F0-F1 and F2-F3 (p < 0.05). Compared with HCCs showing non-LR-M features (n = 16), HCCs with LR-M (n = 5) had a significantly prolonged mean transit time and lower arterial blood flow (p < 0.05).

CONCLUSIONS

Liver MRI using GRASP obtains both sufficient spatial resolution for confident diagnosis and high temporal resolution for pharmacokinetic modeling. Significant differences were found between the MRI-derived portal blood flow at different hepatic fibrosis stages.

KEY POINTS

A single MRI examination is able to provide both images with sufficient spatial resolution for anatomic evaluation and those with high temporal resolution for pharmacokinetic modeling. Portal blood flow was significantly lower in clinically significant hepatic fibrosis and mean transit time and extracellular volume increased in cirrhosis, compared with those in no or mild hepatic fibrosis. HCCs with different LR features showed different quantitative parameters of DCE-MRI: longer mean transit time and lower arterial flow were observed in HCCs with LR-M features.

The impact of 18F-FDOPA-PET/MRI image fusion in detecting liver metastasis in patients with neuroendocrine tumors of the gastrointestinal tract

Background

This study assesses the value of image fusion using 18F-fluoro-L-DOPA (18F-DOPA) positron emission tomography (PET) and magnetic resonance imaging (MRI) for examining patients with neuroendocrine tumors (NETs) and a suspicion of metastasis of the liver.

Methods

Eleven patients (five women and six men aged between 20 and 81, with a mean age of 54.6 years) were included in the study. All patients underwent whole-body 18F-DOPA PET examinations and contrast-enhanced MRI with diffusion-weighted sequences (DWS). Image fusion was performed using a semiautomatic voxel-based algorithm. Images obtained using PET and MRI were assessed separately. Side-by-side evaluations of fused PET/MRI images were also performed.

Results

In total, 55 liver lesions (52 liver metastases and 3 benign lesions) were detected in the 11 patients. Sensitivity detection for liver lesions was higher when using PET/CT than when using contrast-enhanced MRI without DWSs and lower than using MRI with DWSs. The sensitivity of PET/MRI image fusion in the detection of liver metastasis was significantly higher than that of MRI with DWSs (P < 0.05).

Conclusion

Images of the liver obtained using PET and MRI in patients with NETs exhibited characteristic features. These findings suggest that an appropriate combination of available imaging modalities can optimize patient evaluations.

PET/MRI for neuroendocrine tumors: a match made in heaven or just another hype?

Purpose

To evaluate the current literature on technical feasibility and diagnostic value of PET/MRI in management of patients with neuroendocrine tumors (NETs).

Methods

A systematic literature search of the PubMed/MEDLINE database identified studies that evaluated the role of simultaneous PET/MRI for the evaluation of neuroendocrine tumors in human subjects. Exclusion criteria included studies lacking simultaneous PET/MRI, absence of other than attenuation-correction MRI pulse sequences, and case reports. No data-pooling or statistical analysis was performed due to the small number of articles and heterogeneity of the methodologies.

Results

From the 21 identified articles, five were included, which demonstrated successful technical feasibility of simultaneous PET/MRI through various imaging protocols in a total of 105 patients. All articles demonstrated equal or superior detection of liver lesions by PET/MRI over PET/CT. While one study reported superior detection of bone lesions by PET/MRI, two demonstrated favorable detection by PET/CT. Two studies demonstrated superiority of PET/CT in detection of nodal metastases; three studies reported the pitfall of PET/MRI in detection of lung lesion.

Conclusion

The current literature reports successful technical feasibility of PET/MRI for imaging of NETs. While whole-body PET/CT in conjunction with an abdominal MRI may serve as a comprehensive approach for baseline staging, follow up with PET/MRI may be preferred for those with liver-only disease. Another possible role for PET/MRI is to provide a multiparametric approach to follow up of response to treatment. With further advances in MRI imaging acquisitions and post-processing techniques, PET/MRI may become more applicable to a broader group of patients with NETs, and possibly the imaging modality of choice for this patient population.

Functional imaging in pancreatic disease

In addition to the classical morphological evaluation of pancreatic disease, the constant technological advances in imaging techniques based fundamentally on computed tomography and magnetic resonance imaging have enabled the quantitative functional and molecular evaluation of this organ. In many cases, this imaging-based information results in substantial changes to patient management and can be a fundamental tool for the development of biomarkers. The aim of this article is to review the role of emerging functional and molecular techniques based on computed tomography and magnetic resonance imaging in the evaluation of pancreatic disease.

Dynamic enhanced CT: is there a difference between liver metastases of gastroenteropancreatic neuroendocrine tumor and adenocarcinoma

This study proposed to evaluate the feasibility of dynamic enhanced CT in differentiation of liver metastases of gastroenteropancreatic well-differentiated neuroendocrine tumors (GEP NETs) from GEP adenocarcinomas based on their characteristic features. CT images of 23 well-differentiated (G1 or G2) GEP NETs and 23 GEP adenocarcinomas patients with liver metastases were retrospectively reviewed. The distribution type, shape, intra-tumoral neovascularity, enhancement on hepatic artery phase, dynamic enhancement pattern and lymphadenopathy were subjective analyzed. Meanwhile, the size, number, CT value of tumor and adjacent normal liver parenchyma were measured and the metastasis-to-liver ratios were calculated objectively. Compared with GEP adenocarcinomas, the liver metastases of GEP NETs more frequently demonstrated a hyper enhancement on hepatic artery phase, washout dynamic enhancement pattern, absence of lymphadenopathy and higher metastasis-to-liver ratios on both hepatic artery phase and portal venous phase (P=0.017, P<0.001, P =0.038, P <0.001 and P =0.008, respectively). Logistic regression analysis showed that the dynamic enhancement pattern (P=0.012), and the metastasis-to-liver ratios on hepatic artery phase (P=0.009) were independent CT predictors for liver metastases of GEP NETs. The sensitivity and specificity of combing the two predictors in differentiation of liver metastases of GEP adenocarcinomas from GEP NET were 82.6% (19 of 23) and 91.3% (21 of 23), respectively. CT features are helpful in differentiating liver metastases of well-differentiated GEP NETs from that of GEP adenocarcinomas.

Imaging of Neuroendocrine Tumors: Indications, Interpretations, Limits, and Pitfalls

Imaging is critical in the diagnosis, prognosis, and management of neuroendocrine tumors (NETs). NETs share common imaging features, but each type exhibits unique features. Computed tomography scans or MRI of the abdomen is used to assess tumor burden routinely. Functional imaging with octreotide scan or gallium-68 somatostatin analog PET is used selectively to confirm diagnosis and guide therapy. Clinicians and radiologists should be familiar with the indications and interpretations of imaging modalities. Novel functional imaging modalities likely will be developed to detect small NETs, predict prognosis, guide therapeutic choices, and design novel therapies.

Technical Note: Quantitative dynamic contrast-enhanced MRI of a 3-dimensional artificial capillary network

PURPOSE

Variability across devices, patients, and time still hinders widespread recognition of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) as quantitative biomarker. The purpose of this work was to introduce and characterize a dedicated microchannel phantom as a model for quantitative DCE-MRI measurements.

METHODS

A perfusable, MR-compatible microchannel network was constructed on the basis of sacrificial melt-spun sugar fibers embedded in a block of epoxy resin. Structural analysis was performed on the basis of light microscopy images before DCE-MRI experiments. During dynamic acquisition the capillary network was perfused with a standard contrast agent injection system. Flow-dependency, as well as inter- and intrascanner reproducibility of the computed DCE parameters were evaluated using a 3.0 T whole-body MRI.

RESULTS

Semi-quantitative and quantitative flow-related parameters exhibited the expected proportionality to the set flow rate (mean Pearson correlation coefficient: 0.991, P < 2.5e-5). The volume fraction was approximately independent from changes of the applied flow rate through the phantom. Repeatability and reproducibility experiments yielded maximum intrascanner coefficients of variation (CV) of 4.6% for quantitative parameters. All evaluated parameters were well in the range of known in vivo results for the applied flow rates.

CONCLUSION

The constructed phantom enables reproducible, flow-dependent, contrast-enhanced MR measurements with the potential to facilitate standardization and comparability of DCE-MRI examinations.

Functional imaging in liver tumours

Functional imaging encompasses techniques capable of assessing physiological parameters of tissues, and offers useful clinical information in addition to that obtained from morphological imaging. Such techniques may include magnetic resonance imaging with diffusion-weighted sequences or hepatobiliary contrast agents, perfusion imaging, or molecular imaging with radiolabelled tracers. The liver is of major importance in oncological practice; not only is hepatocellular carcinoma one of the malignancies with steadily rising incidence worldwide, but hepatic metastases are regularly observed with a range of solid neoplasms. Within the realm of hepatic oncology, different functional imaging modalities may occupy pivotal roles in lesion characterisation, treatment selection and follow-up, depending on tumour size and type. In this review, we characterise the major forms of functional imaging, discuss their current application to the management of patients with common primary and secondary liver tumours, and anticipate future developments within this field.

Progressing Toward a Cohesive Pediatric 18F-FDG PET/MR Protocol: Is Administration of Gadolinium Chelates Necessary?

With the increasing availability of integrated PET/MR scanners, the utility and need for MR contrast agents for combined scans is questioned. The purpose of our study was to evaluate whether administration of gadolinium chelates is necessary for evaluation of pediatric tumors on (18)F-FDG PET/MR images.

METHODS

First, in 119 pediatric patients with primary and secondary tumors, we used 14 diagnostic criteria to compare the accuracy of several MR sequences: unenhanced T2-weighted fast spin-echo imaging; unenhanced diffusion-weighted imaging; and-before and after gadolinium chelate contrast enhancement-T1-weighted 3-dimensional spoiled gradient echo LAVA (liver acquisition with volume acquisition) imaging. Next, in a subset of 36 patients who had undergone (18)F-FDG PET within 3 wk of MRI, we fused the PET images with the unenhanced T2-weighted MR images (unenhanced (18)F-FDG PET/MRI) and the enhanced T1-weighted MR images (enhanced (18)F-FDG PET/MRI). Using the McNemar test, we compared the accuracy of the two types of fused images using the 14 diagnostic criteria. We also evaluated the concordance between (18)F-FDG avidity and gadolinium chelate enhancement. The standard of reference was histopathologic results, surgical notes, and follow-up imaging.

RESULTS

There was no significant difference in diagnostic accuracy between the unenhanced and enhanced MR images. Accordingly, there was no significant difference in diagnostic accuracy between the unenhanced and enhanced (18)F-FDG PET/MR images. (18)F-FDG avidity and gadolinium chelate enhancement were concordant in 30 of the 36 patients and 106 of their 123 tumors.

CONCLUSION

Gadolinium chelate administration is not necessary for accurate diagnostic characterization of most solid pediatric malignancies on (18)F-FDG PET/MR images, with the possible exception of focal liver lesions.

Prognostication and response assessment in liver and pancreatic tumors: The new imaging

Diffusion-weighted imaging (DWI), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and perfusion computed tomography (CT) are technical improvements of morphologic imaging that can evaluate functional properties of hepato-bilio-pancreatic tumors during conventional MRI or CT examinations. Nevertheless, the term “functional imaging” is commonly used to describe molecular imaging techniques, as positron emission tomography (PET) CT/MRI, which still represent the most widely used methods for the evaluation of functional properties of solid neoplasms; unlike PET or single photon emission computed tomography, functional imaging techniques applied to conventional MRI/CT examinations do not require the administration of radiolabeled drugs or specific equipments. Moreover, DWI and DCE-MRI can be performed during the same session, thus providing a comprehensive “one-step” morphological and functional evaluation of hepato-bilio-pancreatic tumors. Literature data reveal that functional imaging techniques could be proposed for the evaluation of these tumors before treatment, given that they may improve staging and predict prognosis or clinical outcome. Microscopic changes within neoplastic tissues induced by treatments can be detected and quantified with functional imaging, therefore these techniques could be used also for post-treatment assessment, even at an early stage. The aim of this editorial is to describe possible applications of new functional imaging techniques apart from molecular imaging to hepatic and pancreatic tumors through a review of up-to-date literature data, with a particular emphasis on pathological correlations, prognostic stratification and post-treatment monitoring.

Perfusion imaging in liver MRI

Liver perfusion magnetic resonance (MR) imaging is currently being actively investigated as a functional imaging technique that provides physiologic information on the microcirculation and microenvironment of liver tumors and the underlying liver. It has gained importance in light of antiangiogenic therapy for hepatocellular carcinoma and colorectal liver metastases. This article explains the various model-free and model-based approaches for liver perfusion MR imaging and their relative clinical utility. Relevant published works are summarized for each approach so that the reader can understand their relative strengths and weaknesses, to make an informed choice when performing liver perfusion MR imaging studies.

MR imaging of primary hepatic neuroendocrine neoplasm and metastatic hepatic neuroendocrine neoplasm: a comparative study

PURPOSE

To investigate MR characteristics in differentiating primary hepatic neuroendocrine neoplasm (PHNEN) from metastatic hepatic neuroendocrine neoplasm (MHNEN).

MATERIALS AND METHODS

Thirty-nine patients with histopathologically proven liver neuroendocrine neoplasm were retrospectively analyzed. The morphological and MR signal features on T1, T2-weighted, dynamic-enhanced, and diffusion-weighted imaging were evaluated and compared between the PHNEN group (n = 12) and the MHNEN group (n = 27).

RESULTS

The tumor size (P = 0.0084), number (P = 0.017), distribution (P = 0.000), contour (P = 0.041), the presence of capsule-like enhancement (P = 0.034), tumor homogeneity (P = 0.018) and the apparent diffusion coefficient (ADC) values (P = 0.024) were different between PHNENs and MHNENs. Large, solitary or massive-growing nodules with lobulated or irregular contour, capsule-like enhancement, heterogeneous signals or lower ADC values supported the diagnosis of PHNEN compared with MHNEN. ROC analysis demonstrated an area under the curve of 0.746, when the optimal cutoff value of 1.049 × 10(-3) mm(2)/s was used, a sensitivity of 63.0 % (95 % CI, 44.2-79.4 %), a specitivity of 80.0 % (95 % CI, 50.1-96.4 %), a positive predictive value of 89.5 % (95 % CI, 70.9-98.2 %), and a negative predictive value of 44.4 % (95 % CI, 23.4-67.0 %) can be achieved.

CONCLUSIONS

MRI may provide valuable information for the diagnosis and differential diagnosis of PHNENs and MHNENs.

The status of neuroendocrine tumor imaging: from darkness to light?

Diagnostic imaging plays a pivotal role in the diagnosis, staging, treatment selection and follow-up for neuroendocrine tumors. The available diagnostic strategies are morphologic imaging, including computed tomography, magnetic resonance imaging (MRI) and ultrasound techniques, and molecular imaging, including scintigraphy with (111)In-pentetreotide and positron emission tomography with (68)Ga-DOTA-peptides, (18)F-DOPA and (11)C-5-HTP. A combination of anatomic and functional techniques is routinely performed to optimize sensitivity and specificity. The introduction of diffusion-weighted MRI and dynamic contrast-enhanced techniques represents a promising advance in radiologic imaging, whereas new receptor-binding peptides, including somatostatin agonists and antagonists, represent the recent most favorable innovation in molecular imaging. Future development includes the short-term validation of these techniques, but in extension also a more comprehensive multilevel integration of biologic information pertaining to a specific tumor and patient, possibly encompassing genomic considerations, currently evolving as a new entity denoted 'precision medicine'. The ideal is a diagnostic sequence that captures the global status of an individual's tumor and encompasses a multidimensional characterization of tumor location, metabolic performance and target identification. To date, advances in imagery have focused on increasing resolution, discrimination and functional characterization. In the future, the fusion of imagery with the parallel analysis of biological and genomic information has the potential to considerably amplify diagnosis.

Direct parametric reconstruction from undersampled (k, t)-space data in dynamic contrast enhanced MRI

The Magnetic Resonance Imaging (MRI) signal can be made sensitive to functional parameters that provide information about tissues. In dynamic contrast enhanced (DCE) MRI these functional parameters are related to the microvasculature environment and the concentration changes that occur rapidly after the injection of a contrast agent. Typically DCE images are reconstructed individually and kinetic parameters are estimated by fitting a pharmacokinetic model to the time-enhancement response; these methods can be denoted as "indirect". If undersampling is present to accelerate the acquisition, techniques such as kt-FOCUSS can be employed in the reconstruction step to avoid image degradation. This paper suggests a Bayesian inference framework to estimate functional parameters directly from the measurements at high temporal resolution. The current implementation estimates pharmacokinetic parameters (related to the extended Tofts model) from undersampled (k, t)-space DCE MRI. The proposed scheme is evaluated on a simulated abdominal DCE phantom and prostate DCE data, for fully sampled, 4 and 8-fold undersampled (k, t)-space data. Direct kinetic parameters demonstrate better correspondence (up to 70% higher mutual information) to the ground truth kinetic parameters (of the simulated abdominal DCE phantom) than the ones derived from the indirect methods. For the prostate DCE data, direct kinetic parameters depict the morphology of the tumour better. To examine the impact on cancer diagnosis, a peripheral zone prostate cancer diagnostic model was employed to calculate a probability map for each method.