Precision and Test-Retest Repeatability of Stiffness Measurement with MR Elastography: A Multicenter Phantom Study

Background MR elastography (MRE) has been shown to have excellent performance for noninvasive liver fibrosis staging. However, there is limited knowledge regarding the precision and test-retest repeatability of stiffness measurement with MRE in the multicenter setting. Purpose To determine the precision and test-retest repeatability of stiffness measurement with MRE across multiple centers using the same phantoms. Materials and Methods In this study, three cylindrical phantoms made of polyvinyl chloride gel mimicking different degrees of liver stiffness in humans (phantoms 1-3: soft, medium, and hard stiffness, respectively) were evaluated. Between January 2021 and January 2022, phantoms were circulated between five different centers and scanned with 10 MRE-equipped clinical 1.5-T and 3-T systems from three major vendors, using two-dimensional (2D) gradient-recalled echo (GRE) imaging and/or 2D spin-echo (SE) echo-planar imaging (EPI). Similar MRE acquisition parameters, hardware, and reconstruction algorithms were used at each center. Mean stiffness was measured by a single observer for each phantom and acquisition on a single section. Stiffness measurement precision and same-session test-retest repeatability were assessed using the coefficient of variation (CV) and the repeatability coefficient (RC), respectively. Results The mean precision represented by the CV was 5.8% (95% CI: 3.8, 7.7) for all phantoms and both sequences combined. For all phantoms, 2D GRE achieved a CV of 4.5% (95% CI: 3.3, 5.7) whereas 2D SE EPI achieved a CV of 7.8% (95% CI: 3.1, 12.6). The mean RC of stiffness measurement was 5.8% (95% CI: 3.7, 7.8) for all phantoms and both sequences combined, 4.9% (95% CI: 2.7, 7.0) for 2D GRE, and 7.0% (95% CI: 2.9, 11.2) for 2D SE EPI (all phantoms). Conclusion MRE had excellent in vitro precision and same-session test-retest repeatability in the multicenter setting when similar imaging protocols, hardware, and reconstruction algorithms were used. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Tang in this issue.

Magnetic resonance elastography for noninvasive detection of liver fibrosis: is there an added value of 3D acquisition?

PURPOSE

(1) Assess the diagnostic performance of liver 3D magnetic resonance elastography (MRE) parameters (including stiffness, storage/loss modulus and damping ratio) compared to liver stiffness measured with 2D MRE for noninvasive detection of advanced liver fibrosis (F3-F4) and cirrhosis (F4) in patients with chronic liver disease. (2) Assess the value of serum markers (FIB-4) in detecting advanced liver fibrosis and cirrhosis in the same patients.

METHODS

This was a single center, prospective IRB-approved cross-sectional study that included 49 patients (M/F: 23/26, mean age 50.8 y) with chronic liver disease and concomitant liver biopsy. MRE was acquired at 1.5T using a spin echo-EPI sequence. The following parameters were measured: liver stiffness using 2D MRE (LS-2D) and 3D MRE parameters (LS-3D, liver storage, loss modulus and damping ratio). The Mann-Whitney U test, ROC curve analysis, Spearman correlation and logistic regression were performed to evaluate diagnostic performance of MRE parameters and FIB-4.

RESULTS

LS-2D and LS-3D had similar diagnostic performance for diagnosis of F3-F4, with AUCs of 0.87 and 0.88, sensitivity of 0.71 and 0.81, specificity of 0.89 for both. For diagnosis of F4, LS-2D and LS-3D had similar performance with AUCs of 0.81 for both, sensitivity of 0.75 and 0.83, and specificity of 0.84 and 0.73, respectively. Additional 3D parameters (storage modulus, loss modulus, damping ratio) had variable performance, with AUC range of 0.59-0.78 for F3-F4; and 0.52-0.70 for F4. FIB-4 had lower diagnostic performance, with AUCs of 0.66 for F3-F4, and 0.68 for F4.

CONCLUSION

Our study shows no added value of 3D MRE compared to 2D MRE for detection of advanced fibrosis and cirrhosis, while FIB-4 had lower diagnostic performance.

Transcriptome and Genome Analysis Uncovers a DMD Structural Variant: A Case Report

Objective

Duchenne muscular dystrophy (DMD) is caused by pathogenic variants in the dystrophin gene (DMD). Hypermethylated CGG expansions within DIP2B 5' UTR are associated with an intellectual development disorder. Here, we demonstrate the diagnostic utility of genomic short-read sequencing (SRS) and transcriptome sequencing to identify a novel DMD structural variant (SV) and a DIP2B CGG expansion in a patient with DMD for whom conventional diagnostic testing failed to yield a genetic diagnosis.

Methods

We performed genomic SRS, skeletal muscle transcriptome sequencing, and targeted programmable long-read sequencing (LRS).

Results

The proband had a typical DMD clinical presentation, autism spectrum disorder (ASD), and dystrophinopathy on muscle biopsy. Transcriptome analysis identified 6 aberrantly expressed genes; DMD and DIP2B were the strongest underexpression and overexpression outliers, respectively. Genomic SRS identified a 216 kb paracentric inversion (NC_000023.11: g.33162217-33378800) overlapping 2 DMD promoters. ExpansionHunter indicated an expansion of 109 CGG repeats within the 5' UTR of DIP2B. Targeted genomic LRS confirmed the SV and genotyped the DIP2B repeat expansion as 270 CGG repeats.

Discussion

Here, transcriptome data heavily guided genomic analysis to resolve a complex DMD inversion and a DIP2B repeat expansion. Longitudinal follow-up will be important for clarifying the clinical significance of the DIP2B genotype.

4D flow MRI in abdominal vessels: prospective comparison of k-t accelerated free breathing acquisition to standard respiratory navigator gated acquisition

Volumetric phase-contrast magnetic resonance imaging with three-dimensional velocity encoding (4D flow MRI) has shown utility as a non-invasive tool to examine altered blood flow in chronic liver disease. Novel 4D flow MRI pulse sequences with spatio-temporal acceleration can mitigate the long acquisition times of standard 4D flow MRI, which are an impediment to clinical adoption. The purpose of our study was to demonstrate feasibility of a free-breathing, spatio-temporal (k-t) accelerated 4D flow MRI acquisition for flow quantification in abdominal vessels and to compare its image quality, flow quantification and inter-observer reproducibility with a standard respiratory navigator-gated 4D flow MRI acquisition. Ten prospectively enrolled patients (M/F: 7/3, mean age = 58y) with suspected portal hypertension underwent both 4D flow MRI acquisitions. The k-t accelerated acquisition was approximately three times faster (3:11 min ± 0:12 min/9:17 min ± 1:41 min, p < 0.001) than the standard respiratory-triggered acquisition. Vessel identification agreement was substantial between acquisitions and observers. Average flow had substantial inter-sequence agreement in the portal vein and aorta (CV < 15%) and poorer agreement in hepatic and splenic arteries (CV = 11-38%). The k-t accelerated acquisition recorded reduced velocities in small arteries and reduced splenic vein flow. Respiratory gating combined with increased acceleration and spatial resolution are needed to improve flow measurements in these vessels.

Performance of native and gadoxetate-enhanced liver and spleen T1 mapping for noninvasive diagnosis of clinically significant portal hypertension: preliminary results

PURPOSE

In this preliminary study, our aim was to assess the utility of quantitative native-T₁ (T₁-pre), iron-corrected T₁ (cT₁) of the liver/spleen and T₁ mapping of the liver obtained during hepatobiliary phase (T₁-HBP) post-gadoxetate disodium, compared to spleen size/volume and APRI (aspartate aminotransferase-to-platelet ratio index) for noninvasive diagnosis of clinically significant portal hypertension [CSPH, defined as hepatic venous pressure gradient (HVPG) ≥ 10 mm Hg].

METHODS

Forty-nine patients (M/F: 27/22, mean age 53y) with chronic liver disease, HVPG measurement and MRI were included. Breath-held T₁ and cT₁ measurements were obtained using an inversion recovery Look-Locker sequence and a T2* corrected modified Look-Locker sequence, respectively. Liver T₁-pre (n = 49), spleen T₁ (obtained pre-contrast, n = 47), liver and spleen cT₁ (both obtained pre-contrast, n = 30), liver T₁-HBP (obtained 20 min post gadoxetate disodium injection, n = 36) and liver T₁ uptake (ΔT₁, n = 36) were measured. Spleen size/volume and APRI were also obtained. Spearman correlation coefficients were used to assess the correlation between each of liver/spleen T₁/cT₁ parameters, spleen size/volume and APRI with HVPG. ROC analysis was performed to determine the performance of measured parameters for diagnosis of CSPH.

RESULTS

There were 12/49 (24%) patients with CSPH. Liver T₁-pre (r = 0.287, p = 0.045), liver T₁-HBP (r = 0.543, p = 0.001), liver ΔT₁ (r =  - 0.437, p = 0.008), spleen T₁ (r = 0.311, p = 0.033) and APRI (r = 0.394, p = 0.005) were all significantly correlated with HVPG, while liver cT₁, spleen cT₁ and spleen size/volume were not. The highest AUCs for the diagnosis of CSPH were achieved with liver T₁-HBP, liver ΔT₁ and spleen T₁: 0.881 (95%CI 0.76-1.0, p = 0.001), 0.852 (0.72-0.98, p = 0.002) and 0.781 (0.60-0.95, p = 0.004), respectively.

CONCLUSION

Our preliminary results demonstrate the potential of liver T₁ mapping obtained during HBP post gadoxetate disodium for the diagnosis of CSPH. These results require further validation.

Extra credit for disruption: trend of disruption in radiology academic journals

AIM

To identify the most disruptive publications, which are those that are cited more frequently than their own references, in academic radiology journals and their characteristics, such as the number of authors and relative time to publication.

MATERIAL AND METHODS

A comprehensive literature search was undertaken to identify the 100 most disruptive publications in the field of radiology. Subsequently, statistical analysis was applied to establish the distribution of disruptive scores of the isolated publications using a non-parametric probability density function. The relation between disruptive scores and citation counts was then determined, with the aid of a correlation coefficient. Finally, data regarding any significant connection between disruption scores and time of publication, number of authors, and study design were examined.

RESULTS

Analysing the top 100 papers in increments of 10-year periods showed no significant difference in the distribution of disruption scores over time. No correlation between an article's citation count and disruption score was established. Additionally, no significant relation between the number of authors/study design and disruption scores was identified.

CONCLUSION

The disruption score highlights significant impact elements not entirely accounted for by citation count. Its potential benefit in assessing scientific impact should be contemplated.

Experience of a systematic approach to care and prevention of fragility fractures in New Zealand

This narrative review describes efforts to improve the care and prevention of fragility fractures in New Zealand from 2012 to 2022. This includes development of clinical standards and registries to benchmark provision of care, and public awareness campaigns to promote a life-course approach to bone health.

PURPOSE

This review describes the development and implementation of a systematic approach to care and prevention for New Zealanders with fragility fractures, and those at high risk of first fracture. Progression of existing initiatives and introduction of new initiatives are proposed for the period 2022 to 2030.

METHODS

In 2012, Osteoporosis New Zealand developed and published a strategy with objectives relating to people who sustain hip and other fragility fractures, those at high risk of first fragility fracture or falls and all older people. The strategy also advocated formation of a national fragility fracture alliance to expedite change.

RESULTS

In 2017, a previously informal national alliance was formalised under the Live Stronger for Longer programme, which includes stakeholder organisations from relevant sectors, including government, healthcare professionals, charities and the health system. Outputs of this alliance include development of Australian and New Zealand clinical guidelines, clinical standards and quality indicators and a bi-national registry that underpins efforts to improve hip fracture care. All 22 hospitals in New Zealand that operate on hip fracture patients currently submit data to the registry. An analogous approach is ongoing to improve secondary fracture prevention for people who sustain fragility fractures at other sites through nationwide access to Fracture Liaison Services.

CONCLUSION

Widespread participation in national registries is enabling benchmarking against clinical standards as a means to improve the care of hip and other fragility fractures in New Zealand. An ongoing quality improvement programme is focused on eliminating unwarranted variation in delivery of secondary fracture prevention.

MR elastography outperforms shear wave elastography for the diagnosis of clinically significant portal hypertension

OBJECTIVES

Portal hypertension (PH) is associated with complications such as ascites and esophageal varices and is typically diagnosed through invasive hepatic venous pressure gradient (HVPG) measurement, which is not widely available. In this study, we aim to assess the diagnostic performance of 2D/3D MR elastography (MRE) and shear wave elastography (SWE) measures of liver and spleen stiffness (LS and SS) and spleen volume, to noninvasively diagnose clinically significant portal hypertension (CSPH) using HVPG measurement as the reference.

METHODS

In this prospective study, patients with liver disease underwent 2D/3D MRE and SWE of the liver and spleen, as well as HVPG measurement. The correlation between MRE/SWE measures of LS/SS and spleen volume with HVPG was assessed. ROC analysis was used to determine the utility of MRE, SWE, and spleen volume for diagnosing CSPH.

RESULTS

Thirty-six patients (M/F 22/14, mean age 55 ± 14 years) were included. Of the evaluated parameters, 3D MRE SS had the strongest correlation with HVPG (r = 0.686, p < 0.001), followed by 2D MRE SS (r = 0.476, p = 0.004). 3D MRE SS displayed the best performance for diagnosis of CSPH (AUC = 0.911) followed by 2D MRE SS (AUC = 0.845) and 3D MRE LS (AUC = 0.804). SWE SS showed poor performance for diagnosis of CSPH (AUC = 0.583) while spleen volume was a fair predictor (AUC = 0.738). 3D MRE SS was significantly superior to SWE LS/SS (p ≤ 0.021) for the diagnosis of CSPH.

CONCLUSION

SS measured with 3D MRE outperforms SWE for the diagnosis of CSPH. SS appears to be a useful biomarker for assessing PH severity. These results need further validation.

KEY POINTS

• Spleen stiffness measured with 2D and 3D MR elastography correlates significantly with hepatic venous pressure gradient measurement. • Spleen stiffness measured with 3D MR elastography demonstrates excellent performance for the diagnosis of clinically significant portal hypertension (AUC 0.911). • Spleen stiffness measured with 3D MR elastography outperforms liver and spleen stiffness measured with shear wave elastography for diagnosis of clinically significant portal hypertension.

Towards Image Guided Magnetic Resonance Elastography via Active Driver Positioning Robot

Magnetic Resonance Elastography (MRE) is a developing imaging technique that enables non-invasive estimation of tissue mechanical properties through the combination of induced mechanical displacements in the tissue and Magnetic Resonance Imaging (MRI). The mechanical drivers necessary to produce shear waves in the tissue have been a focus of engineering effort in the development and refinement of MRE. The potential targeting of smaller and stiffer tissues calls for increases in actuation frequency and refinement of mechanical driver positioning. Furthermore, the anisotropic nature of soft tissues results in driver position related changes in observed displacement wave patterns. These challenges motivate the investigation and development of the concept of active MRE driver positioning through visual servoing under MR imaging.

OBJECTIVE

This work demonstrates the initial prototype of an MRE driver positioning system, allowing capture of displacement wave patterns from various mechanical vibration loading angles under different vibration frequencies through MR imaging.

METHODS

Three different configurations of the MRE driver positioning robot are tested with an IVD shaped gel phantom.

RESULTS

Both the OSS-SNR and estimated stiffness show statistically significant dependence on driver configuration in each of the three phantom IVD regions.

CONCLUSION

This dependence demonstrates that driver configuration is a critical factor in MRE, and that the developed robot is capable of producing a range of configurations.

SIGNIFICANCE

This work presents the first demonstration of an active, imaging guided MRE driver positioning system, with significance for the future application of MRE to a wider range of human tissues.

Neoadjuvant cemiplimab for resectable hepatocellular carcinoma: a single-arm, open-label, phase 2 trial

BACKGROUND

Surgical resection of early stage hepatocellular carcinoma is standard clinical practice; however, most tumours recur despite surgery, and no perioperative intervention has shown a survival benefit. Neoadjuvant immunotherapy has induced pathological responses in multiple tumour types and might decrease the risk of postoperative recurrence in hepatocellular carcinoma. We aimed to evaluate the clinical activity of neoadjuvant cemiplimab (an anti-PD-1) in patients with resectable hepatocellular carcinoma.

METHODS

For this single-arm, open-label, phase 2 trial, patients with resectable hepatocellular carcinoma (stage Ib, II, and IIIb) were enrolled and received two cycles of neoadjuvant cemiplimab 350 mg intravenously every 3 weeks followed by surgical resection. Eligible patients were aged 18 years or older, had confirmed resectable hepatocellular carcinoma, an Eastern Cooperative Oncology Group performance status of 0 or 1, and adequate liver function. Patients were excluded if they had metastatic disease, if the surgery was not expected to be curative, if they had a known additional malignancy requiring active treatment, or if they required systemic steroid treatment or any other immunosuppressive therapy. After resection, patients received an additional eight cycles of cemiplimab 350 mg intravenously every 3 weeks in the adjuvant setting. The primary endpoint was significant tumour necrosis on pathological examination (defined as >70% necrosis of the resected tumour). Secondary endpoints included delay of surgery, the proportion of patients with an overall response, change in CD8+ T-cell density, and adverse events. Tumour necrosis and response were analysed in all patients who received at least one dose of cemiplimab and completed surgical resection; safety and other endpoints were analysed in the intention-to-treat population. Patients underwent pre-treatment biopsies and blood collection throughout treatment. This trial is registered with ClinicalTrials.gov (NCT03916627, Cohort B) and is ongoing.

FINDINGS

Between Aug 5, 2019, and Nov 25, 2020, 21 patients were enrolled. All patients received neoadjuvant cemiplimab, and 20 patients underwent successful resection. Of the 20 patients with resected tumours, four (20%) had significant tumour necrosis. Three (15%) of 20 patients had a partial response, and all other patients maintained stable disease. 20 (95%) patients had a treatment-emergent adverse event of any grade during the neoadjuvant treatment period. The most common adverse events of any grade were increased aspartate aminotransferase (in four patients), increased blood creatine phosphokinase (in three), constipation (in three), and fatigue (in three). Seven patients had grade 3 adverse events, including increased blood creatine phosphokinase (in two patients) and hypoalbuminaemia (in one). No grade 4 or 5 events were observed. One patient developed pneumonitis, which led to a delay in surgery by 2 weeks.

INTERPRETATION

This report is, to our knowledge, the largest clinical trial of a neoadjuvant anti-PD-1 monotherapy reported to date in hepatocellular carcinoma. The observed pathological responses to cemiplimab in this cohort support the design of larger trials to identify the optimal treatment duration and definitively establish the clinical benefit of preoperative PD-1 blockade in patients with hepatocellular carcinoma.

FUNDING

Regeneron Pharmaceuticals.

Precision of MRI radiomics features in the liver and hepatocellular carcinoma

OBJECTIVES

To assess the precision of MRI radiomics features in hepatocellular carcinoma (HCC) tumors and liver parenchyma.

METHODS

The study population consisted of 55 patients, including 16 with untreated HCCs, who underwent two repeat contrast-enhanced abdominal MRI exams within 1 month to evaluate: (1) test-retest repeatability using the same MRI system (n = 28, 10 HCCs); (2) inter-platform reproducibility between different MRI systems (n = 27, 6 HCCs); (3) inter-observer reproducibility (n = 16, 16 HCCs). Shape and 1st- and 2nd-order radiomics features were quantified on pre-contrast T1-weighted imaging (WI), T1WI portal venous phase (pvp), T2WI, and ADC (apparent diffusion coefficient), on liver regions of interest (ROIs) and HCC volumes of interest (VOIs). Precision was assessed by calculating intraclass correlation coefficient (ICC), concordance correlation coefficient (CCC), and coefficient of variation (CV).

RESULTS

There was moderate to excellent test-retest repeatability of shape and 1st- and 2nd-order features for all sequences in HCCs (ICC: 0.53-0.99; CV: 3-29%), and moderate to good test-retest repeatability of 1st- and 2nd-order features for T1WI sequences, and 2nd-order features for T2WI in the liver (ICC: 0.53-0.73; CV: 12-19%). There was poor inter-platform reproducibility for all features and sequences, except for shape and 1st-order features on T1WI in HCCs (CCC: 0.58-0.99; CV: 3-15%). Good to excellent inter-observer reproducibility was found for all features and sequences in HCCs (CCC: 0.80-0.99; CV: 4-15%) and moderate to good for liver (CCC: 0.45-0.86; CV: 6-25%).

CONCLUSIONS

MRI radiomics features have acceptable repeatability in the liver and HCC when using the same MRI system and across readers but have low reproducibility across MR systems, except for shape and 1st-order features on T1WI. Data must be interpreted with caution when performing multiplatform radiomics studies.

KEY POINTS

• MRI radiomics features have acceptable repeatability when using the same MRI system but less reproducible when using different MRI platforms. • MRI radiomics features extracted from T1 weighted-imaging show greater stability across exams than T2 weighted-imaging and ADC. • Inter-observer reproducibility of MRI radiomics features was found to be good in HCC tumors and acceptable in liver parenchyma.

Oxylipin metabolism is controlled by mitochondrial β-oxidation during bacterial inflammation

Oxylipins are potent biological mediators requiring strict control, but how they are removed en masse during infection and inflammation is unknown. Here we show that lipopolysaccharide (LPS) dynamically enhances oxylipin removal via mitochondrial β-oxidation. Specifically, genetic or pharmacological targeting of carnitine palmitoyl transferase 1 (CPT1), a mitochondrial importer of fatty acids, reveal that many oxylipins are removed by this protein during inflammation in vitro and in vivo. Using stable isotope-tracing lipidomics, we find secretion-reuptake recycling for 12-HETE and its intermediate metabolites. Meanwhile, oxylipin β-oxidation is uncoupled from oxidative phosphorylation, thus not contributing to energy generation. Testing for genetic control checkpoints, transcriptional interrogation of human neonatal sepsis finds upregulation of many genes involved in mitochondrial removal of long-chain fatty acyls, such as ACSL1,3,4, ACADVL, CPT1B, CPT2 and HADHB. Also, ACSL1/Acsl1 upregulation is consistently observed following the treatment of human/murine macrophages with LPS and IFN-γ. Last, dampening oxylipin levels by β-oxidation is suggested to impact on their regulation of leukocyte functions. In summary, we propose mitochondrial β-oxidation as a regulatory metabolic checkpoint for oxylipins during inflammation.

Brain-mimicking phantom for biomechanical validation of motion sensitive MR imaging techniques

Motion sensitive MR imaging techniques allow for the non-invasive evaluation of biological tissues by using different excitation schemes, including physiological/intrinsic motions caused by cardiac pulsation or respiration, and vibrations caused by an external actuator. The mechanical biomarkers extracted through these imaging techniques have been shown to hold diagnostic value for various neurological disorders and conditions. Amplified MRI (aMRI), a cardiac gated imaging technique, can help track and quantify low frequency intrinsic motion of the brain. As for high frequency actuation, the mechanical response of brain tissue can be measured by applying external high frequency actuation in combination with a motion sensitive MR imaging sequence called Magnetic Resonance Elastography (MRE). Due to the frequency-dependent behavior of brain mechanics, there is a need to develop brain phantom models that can mimic the broadband mechanical response of the brain in order to validate motion-sensitive MR imaging techniques. Here, we have designed a novel phantom test setup that enables both the low and high frequency responses of a brain-mimicking phantom to be captured, allowing for both aMRI and MRE imaging techniques to be applied on the same phantom model. This setup combines two different vibration sources: a pneumatic actuator, for low frequency/intrinsic motion (1 Hz) for use in aMRI, and a piezoelectric actuator for high frequency actuation (30-60 Hz) for use in MRE. Our results show that in MRE experiments performed from 30 Hz through 60 Hz, propagating shear waves attenuate faster at higher driving frequencies, consistent with results in the literature. Furthermore, actuator coupling has a substantial effect on wave amplitude, with weaker coupling causing lower amplitude wave field images, specifically shown in the top-surface shear loading configuration. For intrinsic actuation, our results indicate that aMRI linearly amplifies motion up to at least an amplification factor of 9 for instances of both visible and sub-voxel motion, validated by varying power levels of pneumatic actuation (40%-80% power) under MR, and through video analysis outside the MRI scanner room. While this investigation used a homogeneous brain-mimicking phantom, our setup can be used to study the mechanics of non-homogeneous phantom configurations with bio-interfaces in the future.

Dynamic contrast-enhanced MRI perfusion quantification in hepatocellular carcinoma: comparison of gadoxetate disodium and gadobenate dimeglumine

OBJECTIVES

(1) To assess the quality of the arterial input function (AIF) during dynamic contrast-enhanced (DCE) MRI of the liver and (2) to quantify perfusion parameters of hepatocellular carcinoma (HCC) and liver parenchyma during the first 3 min post-contrast injection with DCE-MRI using gadoxetate disodium compared to gadobenate dimeglumine (Gd-BOPTA) in different patient populations.

METHODS

In this prospective study, we evaluated 66 patients with 83 HCCs who underwent DCE-MRI, using gadoxetate disodium (group 1, n = 28) or Gd-BOPTA (group 2, n = 38). AIF qualitative and quantitative features were assessed. Perfusion parameters (based on the initial 3 min post-contrast) were extracted in tumours and liver parenchyma, including model-free parameters (time-to-peak enhancement (TTP), time-to-washout) and modelled parameters (arterial flow (F_a), portal venous flow (F_p), total flow (F_t), arterial fraction, mean transit time (MTT), distribution volume (DV)). In addition, lesion-to-liver contrast ratios (LLCRs) were measured. Fisher's exact tests and Mann-Whitney U tests were used to compare the two groups.

RESULTS

AIF quality, modelled and model-free perfusion parameters in HCC were similar between the 2 groups (p = 0.054-0.932). Liver parenchymal flow was lower and liver enhancement occurred later in group 1 vs group 2 (F_p, p = 0.002; F_t, p = 0.001; TTP, MTT, all p < 0.001), while there were no significant differences in tumour LLCR (max. positive LLCR, p = 0.230; max. negative LLCR, p = 0.317).

CONCLUSION

Gadoxetate disodium provides comparable AIF quality and HCC perfusion parameters compared to Gd-BOPTA during dynamic phases. Despite delayed and decreased liver enhancement with gadoxetate disodium, LLCRs were equivalent between contrast agents, indicating similar tumour conspicuity.

KEY POINTS

• Arterial input function quality, modelled, and model-free dynamic parameters measured in hepatocellular carcinoma are similar in patients receiving gadoxetate disodium or gadobenate dimeglumine during the first 3 min post injection. • Gadoxetate disodium and gadobenate dimeglumine show similar lesion-to-liver contrast ratios during dynamic phases in patients with HCC. • There is lower portal and lower total hepatic flow and longer hepatic mean transit time and time-to-peak with gadoxetate disodium compared to gadobenate dimeglumine.

Diminishing returns drive altruists to help extended family

Altruism between close relatives can be easily explained. However, paradoxes arise when organisms divert altruism towards more distantly related recipients. In some social insects, workers drift extensively between colonies and help raise less related foreign brood, seemingly reducing inclusive fitness. Since being highlighted by W. D. Hamilton, three hypotheses (bet hedging, indirect reciprocity and diminishing returns to cooperation) have been proposed for this surprising behaviour. Here, using inclusive fitness theory, we show that bet hedging and indirect reciprocity could only drive cooperative drifting under improbable conditions. However, diminishing returns to cooperation create a simple context in which sharing workers is adaptive. Using a longitudinal dataset comprising over a quarter of a million nest cell observations, we quantify cooperative payoffs in the Neotropical wasp Polistes canadensis, for which drifting occurs at high levels. As the worker-to-brood ratio rises in a worker's home colony, the predicted marginal benefit of a worker for expected colony productivity diminishes. Helping related colonies can allow effort to be focused on related brood that are more in need of care. Finally, we use simulations to show that cooperative drifting evolves under diminishing returns when dispersal is local, allowing altruists to focus their efforts on related recipients. Our results indicate the power of nonlinear fitness effects to shape social organization, and suggest that models of eusocial evolution should be extended to include neglected social interactions within colony networks.

Early effect of 90Y radioembolisation on hepatocellular carcinoma and liver parenchyma stiffness measured with MR elastography: initial experience

OBJECTIVES

To quantify hepatocellular carcinoma (HCC) and liver parenchyma stiffness using MR elastography (MRE) and serum alpha fetoprotein (AFP), before and 6 weeks (6w) after ⁹⁰Y radioembolisation (RE), and to assess the value of baseline tumour and liver stiffness (TS/LS) and AFP in predicting response at 6w and 6 months (6 m).

METHODS

Twenty-three patients (M/F 18/5, mean age 68.3 ± 9.3 years) scheduled to undergo RE were recruited into this prospective single-centre study. Patients underwent an MRI exam at baseline and 6w following RE (range 39-47 days) which included MRE using a prototype 2D EPI sequence. TS, peritumoural LS/LS remote from the tumour, tumour size, and AFP were measured at baseline and at 6w. Treatment response was determined using mRECIST at 6w and 6 m.

RESULTS

MRE was technically successful in 17 tumours which were classified at 6w as complete response (CR, n = 7), partial response (PR, n = 4), and stable disease (SD, n = 6). TS and peritumoural LS were significantly increased following RE (p = 0.016, p = 0.039, respectively), while LS remote from tumour was unchanged (p = 0.245). Baseline TS was significantly lower in patients who achieved CR at 6w (p = 0.014). Baseline TS, peritumoural LS (both AUC = 0.857), and AFP (AUC = 0.798) showed fair/excellent diagnostic performance in predicting CR at 6w, but were not significant predictors of OR or CR at 6 m.

CONCLUSION

Our initial results suggest that HCC TS and peritumoural LS increase early after RE. Baseline TS, peritumoural LS, and AFP were all significant predictors of CR to RE at 6w. These results should be confirmed in a larger study.

KEY POINTS

• Magnetic resonance elastography-derived tumour stiffness and peritumoural liver stiffness increase significantly at 6 weeks post radioembolisation whereas liver stiffness remote from the tumour is unchanged. • Baseline tumour stiffness and peritumoural liver stiffness are lower in patients who achieve complete response at 6 weeks post radioembolisation. • Baseline tumour size is significantly correlated with baseline tumour stiffness.

Fully automated prediction of liver fibrosis using deep learning analysis of gadoxetic acid-enhanced MRI

OBJECTIVES

To (1) develop a fully automated deep learning (DL) algorithm based on gadoxetic acid-enhanced hepatobiliary phase (HBP) MRI and (2) compare the diagnostic performance of DL vs. MR elastography (MRE) for noninvasive staging of liver fibrosis.

METHODS

This single-center retrospective study included 355 patients (M/F 238/117, mean age 60 years; training, n = 178; validation, n = 123; test, n = 54) who underwent gadoxetic acid-enhanced abdominal MRI, including HBP and MRE, and pathological evaluation of the liver within 1 year of MRI. Cropped liver HBP images from a custom-written fully automated liver segmentation were used as input for DL. A transfer learning approach based on the ImageNet VGG16 model was used. Different DL models were built for the prediction of fibrosis stages F1-4, F2-4, F3-4, and F4. ROC analysis was performed to evaluate the performance of DL in training, validation, and test sets and of MRE liver stiffness in the test set.

RESULTS

AUC values of DL were 0.99/0.70/0.77 (F1-4), 0.92/0.71/0.91 (F2-4), 0.91/0.78/0.90 (F3-4), and 0.98/0.83/0.85 (F4) for training/validation/test sets, respectively. The AUCs of MRE liver stiffness in the test set were 0.86 (F1-4), 0.87 (F2-4), 0.92 (F3-4), and 0.86 (F4). AUCs of MRE and DL were not significantly different for any of the fibrosis stages (p > 0.134).

CONCLUSIONS

The fully automated DL models based on HBP gadoxetic acid MRI showed good-to-excellent diagnostic performance for staging of liver fibrosis, with similar diagnostic performance to MRE. After validation in independent sets, the DL algorithm may allow for noninvasive liver fibrosis assessment without the need for additional MRI hardware.

KEY POINTS

• The developed deep learning algorithm, based on routine standard-of-care gadoxetic acid-enhanced MRI data, showed good-to-excellent diagnostic performance for noninvasive staging of liver fibrosis. • The diagnostic performance of the deep learning algorithm was equivalent to that of MR elastography in a separate test set.

Noninvasive imaging assessment of portal hypertension

Portal hypertension (PH) is a spectrum of complications of chronic liver disease (CLD) and cirrhosis, with manifestations including ascites, gastroesophageal varices, splenomegaly, hypersplenism, hepatic hydrothorax, hepatorenal syndrome, hepatopulmonary syndrome and portopulmonary hypertension. PH can vary in severity and is diagnosed via invasive hepatic venous pressure gradient measurement (HVPG), which is considered the reference standard. Accurate diagnosis of PH and assessment of severity are highly relevant as patients with clinically significant portal hypertension (CSPH) are at higher risk for developing acute variceal bleeding and mortality. In this review, we discuss current and upcoming noninvasive imaging methods for diagnosis and assessment of severity of PH.

Association of chain of survival factors with out of hospital cardiac arrest survival in a region with low average population-density: a retrospective population-based cohort study

Background

Out of hospital cardiac arrest (OHCA) has an average global survival rate to discharge of 8%. Chain of survival factors are heavily time-dependant and optimization can increase survival. Regions with low population density encounter challeges in providing optimal OHCA care. Nova Scotia's average population density is 17.4 persons per square kilometer in compasiron to Toronto with 4334.4 person per square kilometer. OHCAs have been described well in large urban centers globally, however the characterization of OHCA chain of survival in low density populations is sparse.

Purpose

To describe chain of survival factors and identify characteristics of survivors and non-survivors among those treated by paramedics in a low average density provincial population.

Methods

This was a retrospective cohort study of OHCAs responded to by paramedics. All OHCA responses with a cardiac etiology in Nova Scotia, Canada were included. Exclusion criteria were non-cardiac cause arrests, those with “do not resuscitate” (DNR) directives and expected deaths. The paramedic electronic patient care record was reviewed for demographic, bystander, out of hospital treatment and operational characteristics. Primary outcome was survival to hospital discharge. Descriptive statistics were calculated to describe differences between survivorship using Prism 8.0 (San Diego, CA) with alpha=0.05 applying unpaired, Mann-Whitney tests.

Results

Of 1517 OHCA, 463 were excluded leaving 1054 OHCA. Of these, 478 (45.3%) were treated by paramedics and included in this analysis. Most were men (67.2%; n=274) with a mean age 66.8 (±16.4). A total of 7.1% (n=75) survived to discharge with 76% of survivors (n=58) discharged home. Survivors were more likely to present with ventricular fibrillation than non-survivors (42.7% vs. 19.6%). Survivors compared to non-survivors had significantly shorter paramedic response time (8.1 vs. 10.7 min, P&lt;0.001), paramedic time on scene (35.7 vs. 45.4 min, P=0.002), estimated time to paramedic defibrillation (13.2 vs 19.4 min, P&lt;0.001), and estimated time to return of spontaneous circulation (ROSC) (22.9 vs 31.9min, P&lt;0.001).

Conclusion

Links in the chain of survival are associated with survival from OHCA. OHCA survival is lower in the less densely populated province of Nova Scotia compared to studies in urban Canadian centers and worldwide. Our study is limited by the retrospective nature of data collection and lack of access to neurological outcomes. Even among survivors, EMS response is delayed compared to more densely populated centers. In Nova Scotia, longer paramedic response times are associated with decreased survival.

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): Maritime Heart Center

4D flow MRI for the assessment of renal transplant dysfunction: initial results

OBJECTIVES

(1) Determine inter-observer reproducibility and test-retest repeatability of 4D flow parameters in renal allograft vessels; (2) determine if 4D flow measurements in the renal artery (RA) and renal vein (RV) can distinguish between functional and dysfunctional allografts; (3) correlate haemodynamic parameters with estimated glomerular filtration rate (eGFR), perfusion measured with dynamic contrast-enhanced MRI (DCE-MRI) and histopathology.

METHODS

Twenty-five prospectively recruited renal transplant patients (stable function/chronic renal allograft dysfunction, 12/13) underwent 4D flow MRI at 1.5 T. 4D flow coronal oblique acquisitions were performed in the transplant renal artery (RA) (velocity encoding parameter, VENC = 120 cm/s) and renal vein (RV) (VENC = 45 cm/s). Test-retest repeatability (n = 3) and inter-observer reproducibility (n = 10) were assessed by Cohen's kappa, coefficient of variation (CoV) and Bland-Altman statistics. Haemodynamic parameters were compared between patients and correlated to the estimated glomerular filtration rate, DCE-MRI parameters (n = 10) and histopathology from allograft biopsies (n = 15).

RESULTS

For inter-observer reproducibility, kappa was > 0.99 and 0.62 and CoV of flow was 12.6% and 7.8% for RA and RV, respectively. For test-retest repeatability, kappa was > 0.99 and 0.5 and CoV of flow was 27.3% and 59.4%, for RA and RV, respectively. RA (p = 0.039) and RV (p = 0.019) flow were both significantly reduced in dysfunctional allografts. Both identified chronic allograft dysfunction with good diagnostic performance (RA: AUC = 0.76, p = 0.036; RV: AUC = 0.8, p = 0.018). RA flow correlated negatively with histopathologic interstitial fibrosis score ci (ρ = - 0.6, p = 0.03).

CONCLUSIONS

4D flow parameters had better repeatability in the RA than in the RV. RA and RV flow can identify chronic renal allograft dysfunction, with RA flow correlating with histopathologic interstitial fibrosis score.

KEY POINTS

• Inter-observer reproducibility of 4D flow measurements was acceptable in both the transplant renal artery and vein, but test-retest repeatability was better in the renal artery than in the renal vein. • Blood flow measurements obtained with 4D flow MRI in the renal artery and renal vein are significantly reduced in dysfunctional renal transplants. • Renal transplant artery flow correlated negatively with histopathologic interstitial fibrosis score.

Assessment of Hepatocellular Carcinoma Response to 90Y Radioembolization Using Dynamic Contrast Material-enhanced MRI and Intravoxel Incoherent Motion Diffusion-weighted Imaging

PURPOSE

To quantify diffusion and perfusion changes in hepatocellular carcinoma (HCC) induced by yttrium 90 (⁹⁰Y) radioembolization and to assess the value of dynamic contrast material-enhanced (DCE) MRI and intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) for predicting HCC response.

MATERIALS AND METHODS

Institutional review board approval was obtained for this prospective study (clinical trial registry NCT01871545). Twenty-four participants with HCC (mean age, 69 years ± 9 [standard deviation], 18 men) underwent multiparametric MRI, including IVIM DWI and gadoxetic acid DCE MRI before (n = 24) and 6 weeks (n = 21) after radioembolization. IVIM DWI and DCE MRI histogram parameters were quantified in HCCs and liver parenchyma. HCC response was assessed by using modified Response Evaluation Criteria in Solid Tumors at 6 weeks and 6-12 months after radioembolization. Logistic regression analysis was used to evaluate the diagnostic performance of baseline MRI and clinical parameters for prediction of response.

RESULTS

Twenty-five HCCs were analyzed (mean size, 3.6 cm ± 1.9). Radioembolization resulted in significantly decreased perfusion (DCE MRI arterial flow, P = .002; IVIM pseudodiffusion coefficient [D*], P = .014). Multivariate logistic regression selected combined serum α-fetoprotein and portal flow (F _p ) skewness (area under the curve [AUC] = 0.924) and combined D* standard deviation and F _p kurtosis (AUC = 0.916) for prediction of objective and complete response at 6 weeks, respectively. Standard deviation of DCE MRI parameter arterial fraction was selected as the optimal predictor for complete response at 6-12 months (AUC = 0.857).

CONCLUSION

Diffusion and perfusion MRI can be used to evaluate the response of HCC to radioembolization. Pretreatment DCE MRI histogram parameters may be useful for radioembolization treatment stratification. Supplemental material is available for this article. © RSNA, 2020.

Collagen-targeted MRI contrast agent for liver fibrosis detection

A novel MRI gadolinium-based contrast agent designed to bind with collagen, a key component in liver fibrosis progression, provides direct quantification of collagen deposition in several preclinical liver disease models. This tool could have large implications in clinical diagnosis and in drug trials.

Magnetic resonance elastography vs. point shear wave ultrasound elastography for the assessment of renal allograft dysfunction

PURPOSE

To investigate the utility of magnetic resonance elastography (MRE) vs. ultrasound (US) point shear wave elastography (pSWE) for the assessment of chronic renal allograft dysfunction, prediction of outcome and determine the correlation with Banff pathology scores.

METHODS

In this IRB approved prospective study, 27 enrolled patients with functional (n = 15) and chronic dysfunctional (n = 12) renal allografts underwent same day 2D MRE and pSWE. Histogram parameters [including mean, median, standard deviation, kurtosis and skewness] of the magnitude of the complex shear modulus (MRE) and median Young's modulus (pSWE) were measured in the cortex (MRE and pSWE) and combined corticomedullary regions (MRE). Histopathology was available for 16 patients (4 functional, 12 dysfunctional).

RESULTS

MRE and pSWE stiffness were not significantly different between functional and dysfunctional groups (p range 0.139-0.347). The skewness of MRE corticomedullary stiffness was significantly lower (p = 0.04) in patients with chronic dysfunction and correlated significantly with Banff histopathologic scores (range r=-0.518-0.567, p = 0.035-0.040). MRE cortical and corticomedullary mean stiffness showed strong performance in predicting graft loss/relist (AUC 0.958, p = 0.011 for both). Reliable pSWE measurements were obtained in 13 patients (48 %). pSWE stiffness did not correlate with Banff scores and did not predict outcome.

CONCLUSIONS

The skewness of MRE corticomedullary stiffness is sensitive to changes in chronic allograft dysfunction, while mean/median MRE renal stiffness and median US stiffness did not differentiate patients with stable function vs those with chronic renal allograft dysfunction. MRE corticomedullary mean stiffness appears to be a predictor of graft loss/relist. pSWE was not found to be a useful method for assessing renal allografts.

Sibling quality and the haplodiploidy hypothesis

The 'haplodiploidy hypothesis' argues that haplodiploid inheritance in bees, wasps, and ants generates relatedness asymmetries that promote the evolution of altruism by females, who are less related to their offspring than to their sisters ('supersister' relatedness). However, a consensus holds that relatedness asymmetry can only drive the evolution of eusociality if workers can direct their help preferentially to sisters over brothers, either through sex-ratio biases or a pre-existing ability to discriminate sexes among the brood. We show via a kin selection model that a simple feature of insect biology can promote the origin of workers in haplodiploids without requiring either condition. In insects in which females must found and provision new nests, body quality may have a stronger influence on female fitness than on male fitness. If altruism boosts the quality of all larval siblings, sisters may, therefore, benefit more than brothers from receiving the same amount of help. Accordingly, the benefits of altruism would fall disproportionately on supersisters in haplodiploids. Haplodiploid females should be more prone to altruism than diplodiploid females or males of either ploidy when altruism elevates female fitness especially, and even when altruists are blind to sibling sex.

Splenic T1ρ as a noninvasive biomarker for portal hypertension

BACKGROUND

There is a need for noninvasive methods for the diagnosis and monitoring of portal hypertension (PH).

PURPOSE

To 1) assess the correlation of liver and spleen T₁ and T_1ρ measurements with portal pressures in patients with chronic liver disease, and 2) to compare the diagnostic performance of the relaxation parameters with radiological assessment of PH.

STUDY TYPE

Prospective.

SUBJECTS

Twenty-five patients (M/F 16/9, mean age 56 years, range 21-78 years) undergoing portal pressure (hepatic venous pressure gradient [HVPG]) measurements.

FIELD STRENGTH/SEQUENCE

1.5T abdominal MRI scan, including T_1ρ and T₁ mapping.

ASSESSMENT

Liver and spleen T_1ρ and T₁ , radiological PH score, and (normalized) spleen length were evaluated.

STATISTICAL TESTS

Spearman correlation of all MRI parameters with HVPG was assessed. The diagnostic performance of the assessed parameters for prediction of PH (HVPG ≥5 mmHg) and clinically significant PH (CSPH, HVPG ≥10 mmHg) was determined by receiver operating characteristic (ROC) analysis.

RESULTS

The mean HVPG measurement was 7.8 ± 5.3 mmHg (PH, n = 18 [72%] including CSPH, n = 9 [36%]). PH score, (normalized) spleen length and spleen T_1ρ significantly correlated with HVPG, with the strongest correlation found for spleen T_1ρ (r = 0.613, P = 0.001). Spleen T_1ρ was the only parameter that showed significant diagnostic performance for assessment of PH (area under the curve [AUC] 0.817, P = 0.015) and CSPH (AUC = 0.778, P = 0.024). Normalized spleen length also showed significant diagnostic performance for prediction of CSPH, with a slightly lower AUC (= 0.764, P = 0.031). The radiological PH score, T_1ρ and T₁ of the liver and T₁ of the spleen, did not show significant diagnostic performance for assessment of CSPH (P > 0.075).

DATA CONCLUSION

Spleen T_1ρ showed a significant correlation with portal pressure and showed improved diagnostic performance for prediction of CSPH compared to radiological assessment. These initial results need confirmation in a larger cohort.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;52:787-794.

Patient-led identification and prioritization of exercise interventions for fatigue on dialysis: a workshop report

Background

Fatigue is one of the most important symptoms among patients receiving dialysis and is nominated as a core outcome to be reported in all clinical trials in this setting. However, few trials of interventions targeting fatigue have been conducted. Patients historically have rarely been involved in the design of interventions, which can limit acceptability and uptake. When asked, they have indicated a preference for lifestyle interventions, such as exercise, to improve fatigue. While some research has focussed on intradialytic exercise for patients receiving haemodialysis, patients have also indicated a preference for a convenient method of exercising with guidance, but on their own time outside of dialysis hours. In response to this, a mobile phone application was proposed as the method of delivery for a home-based exercise intervention targeting fatigue.

Methods

We convened a workshop with five breakout group sessions in Australia, with 24 patients on dialysis (16 haemodialysis and 8 peritoneal dialysis) and 8 caregivers to identify, prioritize and discuss exercise interventions for fatigue in patients receiving dialysis and the delivery of this through a mobile application.

Results

Of the 21 types of exercise identified, the top-ranked were walking outdoors, walking on a treadmill and cardio and resistance training. Six themes were identified: (i) ‘an expectation of tangible gains from exercise’, including strengthening and protecting against bodily deterioration related to dialysis; (ii) ‘overcoming physical limitations’, meaning that comorbidities, baseline fatigue and fluctuating health needed to be addressed to engage in exercise; (iii) ‘fear of risks’, which reinforced the importance of safety and compatibility of exercise with dialysis; (iv) ‘realistic and achievable’ exercise, which would ensure initial readiness for uptake; (v) ‘enhancing motivation and interest’ , which expected to support sustained use of the exercise intervention and (vi) ‘ensuring usability of the mobile application’ , which would require simplicity, convenience and comprehensibility.

Conclusion

Exercise interventions that are expected by patients to improve health outcomes and that are safe, realistic and easy to adopt may be more acceptable to patients on dialysis.

Magnetic resonance elastography (MRE) shows significant reduction of thigh muscle stiffness in healthy older adults

Determining the effect of ageing on thigh muscle stiffness using magnetic resonance elastography (MRE) and investigate whether fat fraction and muscle cross-sectional area (CSA) are related to stiffness. Six healthy older adults in their eighth and ninth decade and eight healthy young men were recruited and underwent a 3 T MRI protocol including MRE and Dixon fat fraction imaging. Muscle stiffness, fat fraction and muscle CSA were calculated in ROIs corresponding to the four quadriceps muscles (i.e. vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)), combined quadriceps, combined hamstrings and adductors and whole thigh. Muscle stiffness was significantly reduced (p < 0.05) in the older group in all measured ROIs except the VI (p = 0.573) and RF (p = 0.081). Similarly, mean fat fraction was significantly increased (p < 0.05) in the older group over all ROIs with the exception of the VI (p = 0.059) and VL muscle groups (p = 0.142). Muscle CSA was significantly reduced in older participants in the VM (p = 0.003) and the combined quadriceps (p = 0.001), hamstrings and adductors (p = 0.008) and whole thigh (p = 0.003). Over the whole thigh, stiffness was significantly negatively correlated with fat fraction (r = − 0.560, p = 0.037) and positively correlated with CSA (r = 0.749, p = 0.002). Stepwise regression analysis revealed that age was the most significant predictor of muscle stiffness (p = 0.001). These results suggest that muscle stiffness is significantly decreased in healthy older adults. Muscle fat fraction and muscle CSA are also significantly changed in older adults; however, age is the most significant predictor of muscle stiffness.

Multiparametric magnetic resonance imaging shows promising results to assess renal transplant dysfunction with fibrosis

Here we assessed the diagnostic value of a quantitative multiparametric magnetic resonance imaging (mpMRI) protocol for evaluation of renal allograft dysfunction with fibrosis. Twenty-seven renal transplant patients, including 15 with stable functional allografts (eGFR mean 71.5 ml/min/1.73m²), and 12 with chronic dysfunction/established fibrosis (eGFR mean 30.1 ml/min/1.73m²), were enrolled in this prospective single-center study. Sixteen of the patients had renal biopsy (mean 150 days) before the MRI. All patients underwent mpMRI at 1.5T including intravoxel-incoherent motion diffusion-weighted imaging, diffusion tensor imaging, blood oxygen level dependent (BOLD R₂*) and T₁ quantification. True diffusion D, pseudodiffusion D*, perfusion fraction PF, apparent diffusion coefficient (ADC), fractional anisotropy (FA), R₂* and T₁ were calculated for cortex and medulla. ΔT₁ was calculated as (100x(T₁ Cortex-T₁ Medulla)/T₁ Cortex). Test-retest repeatability and inter-observer reproducibility were assessed in four and ten patients, respectively. mpMRI parameters had substantial test-retest and interobserver repeatability (coefficient of variation under 15%), except for medullary PF and D* (coefficient of variation over 25%). Cortical ADC, D, medullary ADC and ΔT₁ were all significantly decreased, while cortical T₁ was significantly elevated in fibrotic allografts. Cortical T₁ showed positive correlation to the Banff fibrosis and tubular atrophy scores. The combination of ΔT₁ and cortical ADC had excellent cross-validated diagnostic performance for detection of chronic dysfunction with fibrosis. Cortical ADC and T₁ had good performance for predicting eGFR decline at 18 months (4 or more ml/min/1.73m²/year). Thus, the combination of cortical ADC and T₁ measurements shows promising results for the non-invasive assessment of renal allograft histology and outcomes.

Deep Learning Techniques for Medical Image Segmentation: Achievements and Challenges

Deep learning-based image segmentation is by now firmly established as a robust tool in image segmentation. It has been widely used to separate homogeneous areas as the first and critical component of diagnosis and treatment pipeline. In this article, we present a critical appraisal of popular methods that have employed deep-learning techniques for medical image segmentation. Moreover, we summarize the most common challenges incurred and suggest possible solutions.

CD8+ T cells regulate tumor ferroptosis by targeting the system xc− during cancer immunotherapy

Cytotoxic T cells recognize specific antigens expressed on tumor cells and mediate tumor cell apoptosis mainly through perforin–granzyme-mediated and FAS-mediated pathways. Ferroptosis is a recently discovered form of cell death that differs from apoptosis and results from iron-dependent lipid peroxide accumulation. The potential contribution of CD8+ T cell-mediated cytotoxic activity and immunotherapy to tumor ferroptosis remains unknown. Here, we find that immunotherapy-activated CD8+ T cells sensitize tumor cell ferroptosis. Mechanistically, IFNγ released from CD8+ T cells downregulates expression of SLC3A2 and SLC7A11, two subunits of glutamate-cystine antiporter system xc−, restrains tumor cell cystine uptake, and as a consequence, promotes tumor cell lipid peroxidation and ferroptosis. In preclinical models, depletion of cyst(e)ine by cyst(e)inase in combination with checkpoint blockade synergistically enhances T cell-mediated anti-tumor immunity and induces tumor cell ferroptosis. Expression of glutamate-cystine antiporter system xc− is negatively associated with CD8+ T cell signature, IFNγ expression, and cancer patient outcome. Transcriptome analyses before and during nivolumab therapy reveal that clinical benefits correlate with reduced expression of SLC3A2 and increased IFNγ and CD8. Thus, T cell-promoted tumor ferroptosis is a novel anti-tumor mechanism. Targeting tumor ferroptosis pathway constitutes a therapeutic approach in combination with checkpoint blockade.

Positive airway pressure for sleep-disordered breathing in acute quadriplegia: a randomised controlled trial

RATIONALE

Highly prevalent and severe sleep-disordered breathing caused by acute cervical spinal cord injury (quadriplegia) is associated with neurocognitive dysfunction and sleepiness and is likely to impair rehabilitation.

OBJECTIVE

To determine whether 3 months of autotitrating CPAP would improve neurocognitive function, sleepiness, quality of life, anxiety and depression more than usual care in acute quadriplegia.

METHODS AND MEASUREMENTS

Multinational, randomised controlled trial (11 centres) from July 2009 to October 2015. The primary outcome was neurocognitive (attention and information processing as measure with the Paced Auditory Serial Addition Task). Daytime sleepiness (Karolinska Sleepiness Scale) was a priori identified as the most important secondary outcome.

MAIN RESULTS

1810 incident cases were screened. 332 underwent full, portable polysomnography, 273 of whom had an apnoea hypopnoea index greater than 10. 160 tolerated at least 4 hours of CPAP during a 3-day run-in and were randomised. 149 participants (134 men, age 46±34 years, 81±57 days postinjury) completed the trial. CPAP use averaged 2.9±2.3 hours per night with 21% fully 'adherent' (at least 4 hours use on 5 days per week). Intention-to-treat analyses revealed no significant differences between groups in the Paced Auditory Serial Addition Task (mean improvement of 2.28, 95% CI -7.09 to 11.6; p=0.63). Controlling for premorbid intelligence, age and obstructive sleep apnoea severity (group effect -1.15, 95% CI -10 to 7.7) did not alter this finding. Sleepiness was significantly improved by CPAP on intention-to-treat analysis (mean difference -1.26, 95% CI -2.2 to -0.32; p=0.01).

CONCLUSION

CPAP did not improve Paced Auditory Serial Addition Task scores but significantly reduced sleepiness after acute quadriplegia.

TRIAL REGISTRATION NUMBER

ACTRN12605000799651.

T1ρ mapping for assessment of renal allograft fibrosis

BACKGROUND

There is an unmet need for noninvasive methods to diagnose and stage renal allograft fibrosis.

PURPOSE

To investigate the utility of T_1ρ measured with MRI for the assessment of fibrosis in renal allografts.

STUDY TYPE

Institutional Review Board (IRB)-approved prospective.

SUBJECTS

Fifteen patients with stable functional allograft (M/F 9/6, mean age 56 years) and 12 patients with allograft dysfunction and established fibrosis (M/F 6/6, mean age 51 years).

FIELD STRENGTH/SEQUENCE

T_1ρ imaging at 1.5T using a custom-developed sequence.

ASSESSMENT

Average T_1ρ in the cortex and medulla was quantified and T_1ρ repeatability (expressed by the coefficient of variation [CV]) was measured in four patients.

STATISTICAL TESTS

Differences in T_1ρ values between the 2 groups were assessed using Mann-Whitney U-tests. Diagnostic performance of T_1ρ for differentiation between functional and fibrotic allografts was evaluated using receiver operating characteristic (ROC) analysis. Spearman correlations of T_1ρ with Masson's trichrome-stained fractions and serum estimated glomerular filtration rate (eGFR) were assessed.

RESULTS

Higher T_1ρ repeatability was found for cortex compared with medulla (mean CV T_1ρ cortex 7.4%, medulla 13.3%). T_1ρ values were significantly higher in the cortex of fibrotic vs. functional allografts (111.8 ± 17.2 msec vs. 99.0 ± 11.0 msec, P = 0.027), while there was no difference in medullary T_1ρ values (122.6 ± 20.8 msec vs. 124.3 ± 20.8 msec, P = 0.789). Cortical T_1ρ significantly correlated with Masson's trichrome-stained fractions (r = 0.515, P = 0.044) and eGFR (r = -0.546, P = 0.004), and demonstrated an area under the curve (AUC) of 0.77 for differentiating between functional and fibrotic allografts (sensitivity and specificity of 75.0% and 86.7%, using threshold of 106.9 msec).

DATA CONCLUSION

Our preliminary results suggest that T_1ρ is a potential imaging biomarker of renal allograft fibrosis. These results should be verified in a larger study.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1085-1091.

Detection of liver fibrosis using qualitative and quantitative MR elastography compared to liver surface nodularity measurement, gadoxetic acid uptake, and serum markers

BACKGROUND

Multiparametric magnetic resonance imaging (mpMRI) combining different techniques such as MR elastography (MRE) has emerged as a noninvasive approach to diagnose and stage liver fibrosis with high accuracy allowing for anatomical and functional information.

PURPOSE

To assess the diagnostic performance of mpMRI including qualitative and quantitative assessment of MRE, liver surface nodularity (LSN) measurement, hepatic enhancement ratios postgadoxetic acid, and serum markers (APRI, FIB-4) for the detection of liver fibrosis.

STUDY TYPE

IRB-approved retrospective.

SUBJECTS

Eighty-three adult patients.

FIELD STRENGTH/SEQUENCE

1.5T and 3.0T MR systems. MRE and T₁ -weighted postgadoxetic acid sequences.

ASSESSMENT

Two independent observers analyzed qualitative color-coded MRE maps on a scale of 0-3. Regions of interest were drawn to measure liver stiffness on MRE stiffness maps and on pre- and postcontrast T₁ -weighted images to measure hepatic enhancement ratios. Software was used to generate LSN measurements. Histopathology was used as the reference standard for diagnosis of liver fibrosis in all patients.

STATISTICAL TESTS

A multivariable logistic analysis was performed to identify independent predictors of liver fibrosis. Receiver operating characteristic (ROC) analysis evaluated the performance of each imaging technique for detection of fibrosis, in comparison with serum markers.

RESULTS

Liver stiffness measured with MRE provided the strongest correlation with histopathologic fibrosis stage (r = 0.74, P < 0.001), and the highest diagnostic performance for detection of stages F2-F4, F3-F4, and F4 (areas under the curve [AUCs] of 0.87, 0.91, and 0.89, respectively, P < 0.001) compared to other methods. Qualitative assessment of MRE maps showed fair to good accuracy for detection of fibrosis (AUC range 0.76-0.84). Multivariable logistic analysis identified liver stiffness and FIB-4 as independent predictors of fibrosis with AUCs of 0.90 (F2-F4), 0.93 (F3-F4) and 0.92 (F4) when combined.

DATA CONCLUSION

Liver stiffness measured with MRE showed the best performance for detection of liver fibrosis compared to LSN and gadoxetic acid uptake, with slight improvement when combined with FIB-4.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1552-1561.

Quantitative Elastography Methods in Liver Disease: Current Evidence and Future Directions

Chronic liver diseases often result in the development of liver fibrosis and ultimately, cirrhosis. Treatment strategies and prognosis differ greatly depending on the severity of liver fibrosis, thus liver fibrosis staging is clinically relevant. Traditionally, liver biopsy has been the method of choice for fibrosis evaluation. Because of liver biopsy limitations, noninvasive methods have become a key research interest in the field. Elastography enables the noninvasive measurement of tissue mechanical properties through observation of shear-wave propagation in the tissue of interest. Increasing fibrosis stage is associated with increased liver stiffness, providing a discriminatory feature that can be exploited by elastographic methods. Ultrasonographic (US) and magnetic resonance (MR) imaging elastographic methods are commercially available, each with their respective strengths and limitations. Here, the authors review the technical basis, acquisition techniques, and results and limitations of US- and MR-based elastography techniques. Diagnostic performance in the most common etiologies of chronic liver disease will be presented. Reliability, reproducibility, failure rate, and emerging advances will be discussed. ^© RSNA, 2018 Online supplemental material is available for this article.

Noninvasive prediction of portal pressure with MR elastography and DCE-MRI of the liver and spleen: Preliminary results

BACKGROUND

Portal hypertension (PH), defined by hepatic venous pressure gradient (HVPG) ≥5 mmHg and clinically significant PH, defined by HVPG ≥10 mmHg, are complications of chronic liver disease.

PURPOSE

To assess the diagnostic performance of MR elastography (MRE) and dynamic contrast-enhanced MRI (DCE-MRI) of the liver and spleen for the prediction of PH and clinically significant PH, in comparison with a qualitative PH imaging scoring system.

STUDY TYPE

IRB-approved prospective study.

POPULATION

In all, 34 patients with chronic liver disease who underwent HVPG measurement.

FIELD STRENGTH/SEQUENCE

1.5/3T examination including 2D-GRE MRE (n = 33) and DCE-MRI of the liver/spleen (n = 28).

ASSESSMENT

Liver and spleen stiffness were calculated from elastogram maps. DCE-MRI was analyzed using model-free parameters and pharmacokinetic modeling. Two observers calculated qualitative PH imaging scores based on routine images.

STATISTICAL TESTS

Imaging parameters were correlated with HVPG. Receiver operating characteristic (ROC) analysis was performed for prediction of PH and clinically significant PH.

RESULTS

There were significant correlations between DCE-MRI parameters (liver time-to-peak, r = 0.517 / P = 0.006, liver distribution volume, r = 0.494 / P = 0.009, liver upslope, r = -0.567 / P = 0.002), liver stiffness (r = 0.478 / P = 0.016), PH imaging score (r = 0.441 / P = 0.009), and HVPG. ROC analysis provided significant area under the ROC (AUROCs) for PH (liver upslope 0.765, liver stiffness 0.809, spleen volume/diameter 0.746-0.731, PH imaging score 0.756) and for clinically significant PH (liver and spleen perfusion parameters 0.733-0.776, liver stiffness 0.742, PH imaging score 0.742). The ratio of liver stiffness to liver upslope had the highest AUROC for diagnosing PH (0.903) and clinically significant PH (0.785).

DATA CONCLUSION

These preliminary results suggest that the combination of liver stiffness and perfusion metrics provide excellent accuracy for diagnosing PH, and fair accuracy for clinically significant PH. Combined MRE and DCE-MRI outperformed qualitative imaging scores for prediction of PH.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1091-1103.

Abstract P2-09-09: Polyligand profiling differentiates cancer patients according to their benefit of treatment

Introduction: Deconvolution of multi-nodal perturbations in cancer network architecture demands highly multiplexed profiling assays. We demonstrate the value of polyligand profiling of tumor systems states using libraries of single stranded oligodeoxynucleotides (ssODN) to distinguish between tumor tissue from breast cancer patients who did or did not derive benefit from treatment regimens containing trastuzumab.

Methods: This study included cases from women with invasive breast cancer who received chemotherapy+ trastuzumab (C+T) or trastuzumab monotherapy with available retrospective data on the time to next treatment (TTNT). A library of 2x1012 unique ssODN was exposed to FFPE tissues from patients who benefited (B) or not (NB) from trastuzumab-based regimens in several rounds of positive and negative selection. Two enriched libraries were screened on independent set of 42 B and 19 NB cases using a modified IHC protocol for detection of bound ssODNs. Poly-Ligand Profiles (PLP) were scored by a blinded pathologist. Two libraries, EL-NB and EL-B, showed significant p-values between groups of responders and non-responders. A Cox-PH model was fitted using either tumors' HER2 status or PLP test results as the independent variable. Median survival time was calculated from the Kaplan-Meier estimate. A separate group of 63 cases with TTNT data from chemotherapy without trastuzumab was used as a control to distinguish prognostic from predictive performance.

Results: The PLP scores of EL-NB and EL-B were assessed by receiver operating characteristic (ROC) curves and resulted in a combined AUC value of 0.81. EL-NB and EL-B were able to effectively classify B and NB patients with either HER2-negative/equivocal (AUC = 0.73) or HER2-positive cancers (AUC = 0.84). In contrast, HER2 status alone yielded an AUC value of 0.47. The combined PLP scores for the independent set of 63 patients treated with C excluding trastuzumab resulted in an AUC value of 0.53, indicating that the assay was predictive and not simply prognostic. Kaplan-Meier curves analysis shows that PLP+ cases have 429 days median TTNT, while PLP- cases have 129 days (HR = 0.38, log-rank p = 0.001). Analysis based on HER2 status showed no significant difference in TTNT between patients that were HER2+ (280 days) or HER2-negative/equivocal (336 days, HR = 1.27, log-rank p =0.45).

Summary: Performance of the PLP assay in differentiating patients who did or did not benefit from trastuzumab therapy outperforms the standard IHC assay for HER2 status. These results represent a promising step towards the development of a CDx to identify the 50-70% of HER2+ patients who will not benefit from trastuzumab. In addition, PLP also has the potential to identify the HER2-negative/equivocal patients who may benefit from trastuzumab-containing regimens.

Citation Format: Domenyuk V, Gatalica Z, Santhanam R, Wei X, Stark A, Kennedy P, Toussaint B, Levenberg S, Wang R, Xiao N, Greil R, Rinnerthaler G, Gampenrieder S, Heimberger AB, Berry DJ, Barker A, Demetri GD, Quackenbush J, Marshall JL, Poste G, Vacirca JL, Vidal GA, Schwartzberg LS, Halbert DD, Voss A, Miglarese MR, Famulok M, Mayer G, Spetzler D. Polyligand profiling differentiates cancer patients according to their benefit of treatment [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-09-09.

Finite element analysis to investigate variability of MR elastography in the human thigh

PURPOSE

To develop finite element analysis (FEA) of magnetic resonance elastography (MRE) in the human thigh and investigate inter-individual variability of measurement of muscle mechanical properties.

METHODS

Segmentation was performed on MRI datasets of the human thigh from 5 individuals and FEA models consisting of 12 muscles and surrounding tissue created. The same material properties were applied to each tissue type and a previously developed transient FEA method of simulating MRE using Abaqus was performed at 4 frequencies. Synthetic noise was applied to the simulated data at various levels before inversion was performed using the Elastography Software Pipeline. Maps of material properties were created and visually assessed to determine key features. The coefficient of variation (CoV) was used to assess the variability of measurements in each individual muscle and in the groups of muscles across the subjects. Mean measurements for the set of muscles were ranked in size order and compared with the expected ranking.

RESULTS

At noise levels of 2% the CoV in measurements of |G^*| ranged from 5.3 to 21.9% and from 7.1 to 36.1% for measurements of ϕ in the individual muscles. A positive correlation (R² value 0.80) was attained when the expected and measured |G^*| ranking were compared, whilst a negative correlation (R² value 0.43) was found for ϕ.

CONCLUSIONS

Created elastograms demonstrated good definition of muscle structure and were robust to noise. Variability of measurements across the 5 subjects was dramatically lower for |G^*| than it was for ϕ. This large variability in ϕ measurements was attributed to artefacts.

The relationship between pain and mood following spinal cord injury

OBJECTIVES

To explore the relationship between pain and mood during spinal cord injury rehabilitation, and to discuss clinical implications to optimize rehabilitation outcomes.

DESIGN

Repeated measures, retrospective cohort study.

SETTING

Tertiary care, spinal cord injury rehabilitation center.

PARTICIPANTS

Patients (N = 509) who completed both Needs Assessment Checklist (NAC) 1 and NAC2 between February 2008 and February 2015.

INTERVENTIONS

Not applicable.

OUTCOME MEASURE

Pain ratings (0-10) and mood scores (0-24) were obtained from the Needs Assessment Checklist (NAC). NAC1 is completed within 4 weeks post-mobilization and NAC2 upon the patient moving to the pre-discharge ward.

RESULTS

There were statistically significant improvements in both pain and mood from NAC1 to NAC2. There were significant correlations between pain and mood at both NAC1 and NAC2 (a decrease in pain was associated with an improvement in mood). Individuals who reported that pain interfered with their rehabilitation had higher pain scores and lower mood scores at both NAC1 and NAC2.

CONCLUSIONS

Pain and mood evidently interact following spinal cord injury, and the nature of this relationship is complex. The current study provides some support for the bidirectional causality hypothesis, suggesting that pain and mood exert an effect upon each other. It is important to address pain and psychological issues early and together in the post-injury phase to optimize rehabilitation outcomes.

A Brain-Derived Neurotrophic Factor-Based p75NTR Peptide Mimetic Ameliorates Experimental Autoimmune Neuritis Induced Axonal Pathology and Demyelination

Axonal damage and demyelination are major determinants of disability in patients with peripheral demyelinating neuropathies. The neurotrophin family of growth factors are essential for the normal development and myelination of the peripheral nervous system (PNS), and as such are potential therapeutic candidates for ameliorating axonal and myelin damage. In particular, BDNF promotes peripheral nerve myelination via p75 neurotrophin receptor (p75NTR) receptors. Here, we investigated the therapeutic efficacy of a small structural mimetic of the region of BDNF that binds to p75NTR (cyclo-dPAKKR) in experimental autoimmune neuritis (EAN), an established animal model of peripheral demyelinating neuropathy. Examination of rodents induced with EAN revealed that p75NTR is abundantly expressed in affected peripheral nerves. We found that systemic administration of cyclo-dPAKKR ameliorates EAN disease severity and accelerates recovery. Animals treated with cyclo-dPAKKR displayed significantly better motor performance compared to control animals. Histological assessment revealed that cyclo-dPAKKR administration limits the extent of inflammatory demyelination and axonal damage, and protects against the disruption of nodal architecture in affected peripheral nerves. In contrast, a structural control peptide of cyclo-dPAKKR exerted no influence. Moreover, all the beneficial effects of cyclo-dPAKKR in EAN are abrogated in p75NTR heterozygous mice, strongly suggesting a p75NTR-dependent effect. Taken together, our data demonstrate that cyclo-dPAKKR ameliorates functional and pathological defects of EAN in a p75NTR-dependant manner, suggesting that p75NTR is a therapeutic target to consider for future treatment of peripheral demyelinating diseases and targeting of p75NTR is a strategy worthy of further investigation.

MR elastography measurement of the effect of passive warmup prior to eccentric exercise on thigh muscle mechanical properties

Purpose

To investigate the effect of warmup by application of the thermal agent Deep Heat (DH) on muscle mechanical properties using magnetic resonance elastography (MRE) at 3T before and after exercise‐induced muscle damage (EIMD).

Materials and Methods

Twenty male participants performed an individualized protocol designed to induce EIMD in the quadriceps. DH was applied to the thigh in 50% of the participants before exercise. MRE, T₂‐weighted MRI, maximal voluntary contraction (MVC), creatine kinase (CK) concentration, and muscle soreness were measured before and after the protocol to assess EIMD effects. Five participants were excluded: four having not experienced EIMD and one due to incidental findings.

Results

Total workload performed during the EIMD protocol was greater in the DH group than the control group (P < 0.03), despite no significant differences in baseline MVC (P = 0.23). Shear stiffness |G*| increased in the rectus femoris (RF) muscle in both groups (P < 0.03); however, DH was not a significant between‐group factor (P =  0.15). MVC values returned to baseline faster in the DH group (5 days) than the control group (7 days). Participants who displayed hyperintensity on T₂‐weighted images had a greater stiffness increase following damage than those without: RF; 0.61 kPa vs. 0.15 kPa, P < 0.006, vastus intermedius; 0.34 kPa vs. 0.03 kPa, P = 0.06.

Conclusion

EIMD produces increased muscle stiffness as measured by MRE, with the change in |G*| significantly increased when T₂ hyperintensity was present. DH did not affect CK concentration or soreness; however, DH participants produced greater workload during the EIMD protocol and exhibited accelerated MVC recovery.

Level of Evidence: 1

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2017;46:1115–1127.

ABC chromogenic agar: a cost-effective alternative to standard enteric media for Salmonella spp. isolation from routine stool samples

Salmonellosis is the second most common cause of bacterial gastroenteritis, yet the yield from routine stool culture is low. Commonly used selective enteric media have poor specificities for salmonella identification, resulting in a high laboratory workload. A special chromogenic medium, ABC agar, is a promising alternative but its cost-effectiveness has not been evaluated in diagnostic laboratories. A collaborative study is therefore undertaken in two district general hospitals laboratories. Routine stool samples (n=866) were subcultured onto ABC agar half plates after selective enrichment in selenite broth. Similarly, 246 and 620 stool samples were subcultured onto desoxycholate lactose sucrose (DCLS) and xylose lactose desoxycholate (XLD) whole agar plates, respectively. Salmonella spp. were isolated from only 14 (1.6%) of stool samples tested. Specificity was significantly higher for ABC (98%) than DCLS (67%) or XLD (78%) agars. Welcan workload units (ABC 4.8, XLD and DCLS both 7.3) and costs per specimen (ABC 1.26 pounds sterling, DCLS 3.81 pounds sterling and XLD 1.83 pounds sterling) were similarly lower with ABC agar. The results indicate that ABC chromogenic agar offers improvements in specificity, workload and costs over conventional enteric media for Salmonella spp. isolation.