Comparison of whole-body DW-MRI with 2-[18F]FDG PET for staging and treatment monitoring of children with Langerhans cell histiocytosis.

PURPOSE: To assess and compare the diagnostic accuracy of whole-body (WB) DW-MRI with 2-[18F]FDG PET for staging and treatment monitoring of children with Langerhans cell histiocytosis (LCH). METHODS: Twenty-three children with LCH underwent 2-[18F]FDG PET and WB DW-MRI at baseline. Two nuclear medicine physicians and two radiologists independently assessed presence/absence of tumors in 8 anatomical areas. Sixteen children also performed 2-[18F]FDG PET and WB DW-MRI at follow-up. One radiologist and one nuclear medicine physician revised follow-up scans and collected changes in tumor apparent diffusion (ADC) and standardized uptake values (SUV) before and after therapy in all detectable lesions. 2-[18F]FDG PET results were considered the standard of reference for tumor detection and evaluation of treatment response according to Lugano criteria. Sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of WB DW-MRI at baseline were calculated, and the 95% confidence intervals were estimated by using the Clopper-Pearson (exact) method; changes in tumor SUVs and ADC were compared using a Mann-Whitney U test. Agreement between reviewers was assessed with a Cohen's weighted kappa coefficient. Analyses were conducted using SAS software version 9.4. RESULTS: Agreement between reviewers was perfect (kappa coefficient = 1) for all analyzed regions but spine and neck (kappa coefficient = 0.89 and 0.83, respectively) for 2-[18F]FDG PET images, and abdomen and pelvis (kappa coefficient = 0.65 and 0.88, respectively) for WB DW-MRI. Sensitivity and specificity were 95.5% and 100% for WB DW-MRI compared to 2-[18F]FDG PET. Pre to post-treatment changes in SUVratio and ADCmean were inversely correlated for all lesions (r: -0.27, p = 0·06) and significantly different between responders and non-responders to chemotherapy (p = 0.0006 and p = 0·003 for SUVratio and ADCmean, respectively). CONCLUSION: Our study showed that WB DW-MRI has similar accuracy to 2-[18F]FDG PET for staging and treatment monitoring of LCH in children. While 2-[18F]FDG PET remains an approved radiological examination for assessing metabolically active disease, WB DW-MRI could be considered as an alternative approach without radiation exposure. The combination of both modalities might have advantages over either approach alone.

Detection of bone marrow metastases in children and young adults with solid cancers with diffusion-weighted MRI.

OBJECTIVE: To compare the diagnostic accuracy of diffusion-weighted (DW)-MRI with b-values of 50 s/mm2 and 800 s/mm2 for the detection of bone marrow metastases in children and young adults with solid malignancies. METHODS: In an institutional review board-approved prospective study, we performed 51 whole-body DW-MRI scans in 19 children and young adults (14 males, 5 females; age range: 1-25 years) with metastasized cancers before (n = 19 scans) and after (n = 32 scans) chemotherapy. Two readers determined the presence of focal bone marrow lesions in 10 anatomical areas. A third reader measured ADC and SNR of focal lesions and normal marrow. Simultaneously acquired 18F-FDG-PET scans served as the standard of reference. Data of b = 50 s/mm2 and 800 s/mm2 images were compared with the Wilcoxon signed-rank test. Inter-reader agreement was evaluated with weighted kappa statistics. RESULTS: The SNR of bone marrow metastases was significantly higher compared to normal bone marrow on b = 50 s/mm2 (mean ± SD: 978.436 ± 1239.436 vs. 108.881 ± 109.813, p < 0.001) and b = 800 s/mm2 DW-MRI (499.638 ± 612.721 vs. 86.280 ± 89.120; p < 0.001). On 30 out of 32 post-treatment DW-MRI scans, reconverted marrow demonstrated low signal with low ADC values (0.385 × 10-3 ± 0.168 × 10-3mm2/s). The same number of metastases (556/588; 94.6%; p > 0.99) was detected on b = 50 s/mm2 and 800 s/mm2 images. However, both normal marrow and metastases exhibited low signals on ADC maps, limiting the ability to delineate metastases. The inter-reader agreement was substantial, with a weighted kappa of 0.783 and 0.778, respectively. CONCLUSION: Bone marrow metastases in children and young adults can be equally well detected on b = 50 s/mm2 and 800 s/mm2 images, but ADC values can be misleading.

Characterization of the diffusion signal of breast tissues using multi-exponential models.

PURPOSE: Restriction spectrum imaging (RSI) decomposes the diffusion-weighted MRI signal into separate components of known apparent diffusion coefficients (ADCs). The number of diffusion components and optimal ADCs for RSI are organ-specific and determined empirically. The purpose of this work was to determine the RSI model for breast tissues. METHODS: The diffusion-weighted MRI signal was described using a linear combination of multiple exponential components. A set of ADC values was estimated to fit voxels in cancer and control ROIs. Later, the signal contributions of each diffusion component were estimated using these fixed ADC values. Relative-fitting residuals and Bayesian information criterion were assessed. Contrast-to-noise ratio between cancer and fibroglandular tissue in RSI-derived signal contribution maps was compared to DCE imaging. RESULTS: A total of 74 women with breast cancer were scanned at 3.0 Tesla MRI. The fitting residuals of conventional ADC and Bayesian information criterion suggest that a 3-component model improves the characterization of the diffusion signal over a biexponential model. Estimated ADCs of triexponential model were D1,3 = 0, D2,3 = 1.5 × 10-3 , and D3,3 = 10.8 × 10-3 mm2 /s. The RSI-derived signal contributions of the slower diffusion components were larger in tumors than in fibroglandular tissues. Further, the contrast-to-noise and specificity at 80% sensitivity of DCE and a subset of RSI-derived maps were equivalent. CONCLUSION: Breast diffusion-weighted MRI signal was best described using a triexponential model. Tumor conspicuity in breast RSI model is comparable to that of DCE without the use of exogenous contrast. These data may be used as differential features between healthy and malignant breast tissues.

Diagnostic Accuracy of 2-[18F]FDG-PET and whole-body DW-MRI for the detection of bone marrow metastases in children and young adults.

OBJECTIVES: To compare the diagnostic accuracy of 2-[18F]fluoro-2-deoxy-D-glucose-enhanced positron emission tomography (2-[18F]FDG-PET) and diffusion-weighted magnetic resonance imaging (DW-MRI) for the detection of bone marrow metastases in children and young adults with solid malignancies. METHODS: In this cross-sectional single-center institutional review board-approved study, we investigated twenty-three children and young adults (mean age, 16.8 years ± 5.1 [standard deviation]; age range, 7-25 years; 16 males, 7 females) with 925 bone marrow metastases who underwent 66 simultaneous 2-[18F]FDG-PET and DW-MRI scans including 23 baseline scans and 43 follow-up scans after chemotherapy between May 2015 and July 2020. Four reviewers evaluated all foci of bone marrow metastasis on 2-[18F]FDG-PET and DW-MRI to assess concordance and measured the tumor-to-bone marrow contrast. Results were assessed with a one-sample Wilcoxon test and generalized estimation equation. Bone marrow biopsies and follow-up imaging served as the standard of reference. RESULTS: The reviewers detected 884 (884/925, 95.5%) bone marrow metastases on 2-[18F]FDG-PET and 893 (893/925, 96.5%) bone marrow metastases on DW-MRI. We found different "blind spots" for 2-[18F]FDG-PET and MRI: 2-[18F]FDG-PET missed subcentimeter lesions while DW-MRI missed lesions in small bones. Sensitivity and specificity were 91.0% and 100% for 18F-FDG-PET, 89.1% and 100.0% for DW-MRI, and 100.0% and 100.0% for combined modalities, respectively. The diagnostic accuracy of combined 2-[18F]FDG-PET/MRI (100.0%) was significantly higher compared to either 2-[18F]FDG-PET (96.9%, p < 0.001) or DW-MRI (96.3%, p < 0.001). CONCLUSIONS: Both 2-[18F]FDG-PET and DW-MRI can miss bone marrow metastases. The combination of both imaging techniques detected significantly more lesions than either technique alone. KEY POINTS: • DW-MRI and 2-[18F]FDG-PET have different strengths and limitations for the detection of bone marrow metastases in children and young adults with solid tumors. • Both modalities can miss bone marrow metastases, although the "blind spot" of each modality is different. • A combined PET/MR imaging approach will achieve maximum sensitivity and specificity for the detection of bone marrow metastases in children with solid tumors.

Quantitative multiparametric MRI predicts response to neoadjuvant therapy in the community setting.

BACKGROUND: The purpose of this study was to determine whether advanced quantitative magnetic resonance imaging (MRI) can be deployed outside of large, research-oriented academic hospitals and into community care settings to predict eventual pathological complete response (pCR) to neoadjuvant therapy (NAT) in patients with locally advanced breast cancer. METHODS: Patients with stage II/III breast cancer (N = 28) were enrolled in a multicenter study performed in community radiology settings. Dynamic contrast-enhanced (DCE) and diffusion-weighted (DW)-MRI data were acquired at four time points during the course of NAT. Estimates of the vascular perfusion and permeability, as assessed by the volume transfer rate (Ktrans) using the Patlak model, were generated from the DCE-MRI data while estimates of cell density, as assessed by the apparent diffusion coefficient (ADC), were calculated from DW-MRI data. Tumor volume was calculated using semi-automatic segmentation and combined with Ktrans and ADC to yield bulk tumor blood flow and cellularity, respectively. The percent change in quantitative parameters at each MRI scan was calculated and compared to pathological response at the time of surgery. The predictive accuracy of each MRI parameter at different time points was quantified using receiver operating characteristic curves. RESULTS: Tumor size and quantitative MRI parameters were similar at baseline between groups that achieved pCR (n = 8) and those that did not (n = 20). Patients achieving a pCR had a larger decline in volume and cellularity than those who did not achieve pCR after one cycle of NAT (p < 0.05). At the third and fourth MRI, changes in tumor volume, Ktrans, ADC, cellularity, and bulk tumor flow from baseline (pre-treatment) were all significantly greater (p < 0.05) in the cohort who achieved pCR compared to those patients with non-pCR. CONCLUSIONS: Quantitative analysis of DCE-MRI and DW-MRI can be implemented in the community care setting to accurately predict the response of breast cancer to NAT. Dissemination of quantitative MRI into the community setting allows for the incorporation of these parameters into the standard of care and increases the number of clinical community sites able to participate in novel drug trials that require quantitative MRI.

Reduced Flow in Delayed Graft Function as Assessed by IVIM Is Associated With Time to Recovery Following Kidney Transplantation.

BACKGROUND: Delayed graft function (DGF), defined as the need for dialysis in the first week after kidney transplantation, frequently complicates posttransplantation care. The most common cause of DGF is ischemia-reperfusion injury (IRI). To date, no clinical tools can accurately estimate its severity, nor the time required for recovery of kidney function. PURPOSE: To investigate if parameters related to directed flow and diffusion of water, as determined by intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), could be used to differentiate DGF from normal graft function posttransplantation, predict time to recovery from DGF, and hence serve as a surrogate measure of IRI severity. STUDY TYPE: Prospective, cross-sectional cohort study. POPULATION: Fifty consecutive kidney transplant recipients within 3-10 days posttransplantation at our hospital. FIELD STRENGTH/SEQUENCE: 3.0T/IVIM-DWI. ASSESSMENT: The following IVIM-DWI parameters were studied: flow-fraction (f), apparent diffusion coefficient (ADC), and total-ADC (ADCT ). Mean intrarenal resistive index (R.I.) from Doppler ultrasound was also included for a comparison of IVIM-DWI with the clinical standard of care. STATISTICAL TESTS: Welch's t-test, Spearman's correlation, and linear regression. RESULTS: f was significantly reduced in DGF compared to non-DGF patients in the cortex, medulla, and whole renal parenchyma (P < 0.05). Time to recovery with respect to MRI correlated negatively with f (P < 0.05; rho = -0.52 (cortex), and -0.65 [parenchyma]), ADC (P < 0.05; rho = -0.59 [cortex], 0.59 [medulla], and -0.59 [parenchyma]) and ADCT (P < 0.05; rho = -0.54 [cortex], and -0.52 [medulla]). Whole renal parenchymal f predicted time to recovery relative to MRI (P < 0.05, adjusted r-squared = 0.36). R.I. was significantly different between the groups but did not correlate with time to recovery with respect to MRI (rho = 0.43, P = 0.096). DATA CONCLUSION: Quantification of renal flow using IVIM-DWI has the potential to serve as a surrogate measure of IRI severity to estimate the degree of and recovery from DGF. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 3.

Silent Brain Infarction After Endovascular Arch Procedures: Preliminary Results from the STEP Registry.

OBJECTIVE: Few data exist concerning the rate of silent cerebral ischaemic events following endovascular treatment of the aortic arch. The objective of this work was to quantify these lesions using the STEP registry (NCT04489277). METHODS: This multicentre retrospective cohort study included consecutive patients treated with an aortic endoprosthesis deployed in Ishimaru zone 0-3 and brain diffusion weighted magnetic resonance imaging (DW-MRI) within seven days following the procedure. DW-MRI was performed to identify the location and number of new silent brain infarctions (SBI). All endografts were carbon dioxide flushed prior to implantation. RESULTS: The study population included 91 patients (mean age, 69 years; men, 64%) from two academic centres treated between September 2018 and January 2020. The procedure was elective in 71 patients (78%). The treatment was performed for a dissection, degenerative aneurysm, or other aortic disease in 44 (49%), 34 (37%), and 13 (14%) patients, respectively. Endografts were deployed in zone 0, 1, 2 or 3 in 23 (25%), 10 (11%), 47 (52%), and 11 (12%) patients, respectively. Endografts were branched (25%), fenestrated (17%), or tubular (58%). At 30 days, there were no deaths or clinical strokes. On cerebral DW-MRI, a total of 245 SBI were identified in 45 patients (50%). Lesions were in the left hemisphere in 63% of the patients (153/245), predominantly in the middle territory (94/245). Deployment in zone 0-1 (p = .026), placement of a branched or fenestrated endograft (p = .038), a proximal endoprosthesis diameter ≥ 40 mm (p = .038), and an urgent procedure (p = .005) were significantly associated with the presence of SBI on univariable analysis, while urgent procedure was found to be an independent predictor on multivariable analysis (binary logistic regression) (p = .002). CONCLUSION: SBI following endovascular repair of the aortic arch is frequent, although there were no clinical strokes. Innovative strategies to reduce the risk of embolisation need to be developed.

Role of Various DW MRI and DCE MRI Parameters as Predictors of Malignancy in Solid Pulmonary Lesions.

PURPOSE: We aimed to evaluate various diffusion and dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) parameters in differentiating malignant from benign pulmonary lesions. METHODS: We enrolled 31 (22 males) patients who had solid pulmonary lesion(s) >2 cm in our cross sectional study. Of these, 23 (74.2%) were found to be malignant on histopathology. Dynamic contrast-enhanced MRI was performed using 36 dynamic measurements (volumetric interpolated breath-hold examination). Diffusion-weighted MRI (DW MRI) performed at b value of 800 s/mm2. We measured different diffusion and perfusion parameters, for example, diffusion-weighted imaging (DWI) SI, mean apparent diffusion coefficient (ADC), minimum ADC, lesion-to-spinal cord ratio, DWI score, T2 score, Ktrans, Kep, and Ve. We stratified values of each parameter as high if it was >median of values observed in our data set and low if it was ≤median. Normally distributed data were compared by unpaired t test, whereas non-normal continuous data were compared by Kruskal Wallis-H test. We applied Wilson score method to calculate sensitivity, specificity, and predictive values of parameters that were statistically significant by type of lesion with reference to histopathological examination as gold standard. RESULTS: Diffusion-weighted imaging SI, mean ADC, minimum ADC, DWI score and Ktrans values were found to be significantly different (P value < .05) by type of lesion. Ktrans was found to have the highest diagnostic accuracy (74.2%) among these parameters. CONCLUSION: Ktrans and mean ADC had similar sensitivity of 65.2%. However, Ktrans had highest diagnostic accuracy among various DWI and DCE MRI parameters in predicting malignancy in solid pulmonary lesions. In our study, we found a cutoff value 0.251 min-1 for Ktrans as 100% specific.

Tractography reproducibility challenge with empirical data (TraCED): The 2017 ISMRM diffusion study group challenge.

BACKGROUND: Fiber tracking with diffusion-weighted MRI has become an essential tool for estimating in vivo brain white matter architecture. Fiber tracking results are sensitive to the choice of processing method and tracking criteria. PURPOSE: To assess the variability for an algorithm in group studies reproducibility is of critical context. However, reproducibility does not assess the validity of the brain connections. Phantom studies provide concrete quantitative comparisons of methods relative to absolute ground truths, yet do no capture variabilities because of in vivo physiological factors. The ISMRM 2017 TraCED challenge was created to fulfill the gap. STUDY TYPE: A systematic review of algorithms and tract reproducibility studies. SUBJECTS: Single healthy volunteers. FIELD STRENGTH/SEQUENCE: 3.0T, two different scanners by the same manufacturer. The multishell acquisition included b-values of 1000, 2000, and 3000 s/mm2 with 20, 45, and 64 diffusion gradient directions per shell, respectively. ASSESSMENT: Nine international groups submitted 46 tractography algorithm entries each consisting 16 tracts per scan. The algorithms were assessed using intraclass correlation (ICC) and the Dice similarity measure. STATISTICAL TESTS: Containment analysis was performed to assess if the submitted algorithms had containment within tracts of larger volume submissions. This also serves the purpose to detect if spurious submissions had been made. RESULTS: The top five submissions had high ICC and Dice >0.88. Reproducibility was high within the top five submissions when assessed across sessions or across scanners: 0.87-0.97. Containment analysis shows that the top five submissions are contained within larger volume submissions. From the total of 16 tracts as an outcome relatively the number of tracts with high, moderate, and low reproducibility were 8, 4, and 4. DATA CONCLUSION: The different methods clearly result in fundamentally different tract structures at the more conservative specificity choices. Data and challenge infrastructure remain available for continued analysis and provide a platform for comparison. LEVEL OF EVIDENCE: 5 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:234-249.

Does valve in valve TAVR carry a higher risk for thromboembolic events compared to native valve TAVR?

OBJECTIVE: To evaluate the risk for brain lesions in valve in valve (VIV)-transcatheter aortic valve replacement (TAVR) compared to native valve procedures (NV-TAVR). BACKGROUND: TAVR is associated with the risk of stroke and a high incidence of brain lesions in diffusion-weighted magnetic resonance imaging (DW-MRI). The risk in VIV procedures is unknown. METHODS: Patients were included, if they received a Sapien-3 or an Evolut-R valve for an NV-TAVR or VIV-TAVR and a DW-MRI within 3-5 days after the procedure. RESULTS: Two hundred nine patients had NV-TAVR and 41 patients had VIV-TAVR. The VIV group was significantly younger (mean 82.3 vs. 74.7 years old, p < .001) but had higher mean EuroSCORE II (4.8 vs. 7.8, p < .001). Predilatation was significantly more common with native valve (39% vs. 2%, p < .01), postdilatation rate was lower in VIV but without statistical significance (17% vs. 7%, p = .110). Combined in-hospital safety outcome was comparable [13(6.6%) vs. 5(12.2%), p = .205]. Any stroke was documented in four (0.5%) patients after native valve and in one (2.4%) after VIV-TAVR. New DW-MRI brain lesions were significantly more often found in patients with native valves [153(73.2%) vs. 21(51.2%), p = .005], mean number of new lesions was also higher with native valve (2.8 ± 3.2 vs. 1.0 ± 1.4, p < .001). Forward stepwise of logistic regression found age and post dilatation significant predictors of new MRI lesions. CONCLUSIONS: Compared to native valves, VIV procedures were associated with lower incidence and number of brain lesions according to DW-MRI; these were explained by lower patients' age and lower rate of postdilatation.

Quantification of heterogeneity to classify benign parotid tumors: a feasibility study on most frequent histotypes.

Aim: To differentiate Warthin tumors (WTs) and pleomorphic adenomas (PAs) measuring heterogeneity of intravoxel incoherent motion (IVIM) and dynamic-contrast enhanced-magnetic resonance imaging biomarkers. Methods: Volumes of interest were traced on 18 WT and 18 PA in 25 patients. For each IVIM and dynamic-contrast enhanced biomarker, histogram parameters were calculated and then compared using the Wilcoxon-signed-rank test. Receiver operating characteristic curves and multivariate analysis were employed to identify the parameters and their pairs with the best accuracy. Results: Most of the biomarkers exhibited significant difference (p < 0.05) between PA and WT for histogram parameters. Time to peak median and skewness, and D* median and entropy showed the highest area under the curve. No meaningful improvement of accuracy was obtained using two features. Conclusion: IVIM and dynamic-contrast enhanced histogram descriptors may help in the classification of WT and PA.

The Microarchitecture of Pancreatic Cancer as Measured by Diffusion-Weighted Magnetic Resonance Imaging Is Altered by T Cells with a Tumor Promoting Th17 Phenotype.

Diffusion-weighted magnetic resonance imaging (DW-MRI) is a diagnostic tool that is increasingly used for the detection and characterization of focal masses in the abdomen, among these, pancreatic ductal adenocarcinoma (PDAC). DW-MRI reflects the microarchitecture of the tissue, and changes in diffusion, which are reflected by changes in the apparent diffusion coefficient (ADC), are mainly attributed to variations in cellular density, glandular formation, and fibrosis. When analyzing the T cell infiltrates, we found an association of a tumor-promoting subpopulation, characterized by the expression of interleukin (IL) 21 and IL26, with high ADC values. Moreover, the presence of IL21+ and IL26+ positive T cells was associated with poor prognosis. Pancreatic cancers-but not healthy pancreatic tissue-expressed receptors for IL21 and IL26, a finding that could be confirmed in pancreatic cell lines. The functionality of these receptors was demonstrated in pancreatic tumor cell lines, which showed phosphorylation of ERK1/2 and STAT3 pathways in response to the respective recombinant interleukins. Moreover, in vitro data showed an increased colony formation of tumor cells. In summary, our data showed an association of IL21+ and IL26+ immune cell infiltration, increased ADC, and aggressive tumor disease, most likely due to the activation of the key cancer signaling pathways ERK1/2 and STAT3 and formation of tumor colonies.

Assessment of intravoxel incoherent motion MRI with an artificial capillary network: analysis of biexponential and phase-distribution models.

PURPOSE: To systematically analyze intravoxel incoherent motion (IVIM) MRI in a perfusable capillary phantom closely matching the geometry of capillary beds in vivo and to compare the validity of the biexponential pseudo-diffusion and the recently introduced phase-distribution IVIM model. METHODS: IVIM-MRI was performed at 12 different flow rates ( 0.2⋯2.4mL/min ) in a capillary phantom using 4 different DW-MRI sequences (2 with monopolar and 2 with flow-compensated diffusion-gradient schemes, with up to 16b values between 0 and 800s/mm2 ). Resulting parameters from the assessed IVIM models were compared to results from optical microscopy. RESULTS: The acquired data were best described by a static and a flowing compartment modeled by the phase-distribution approach. The estimated signal fraction f of the flowing compartment stayed approximately constant over the applied flow rates, with an average of f=0.451±0.023 in excellent agreement with optical microscopy ( f=0.454±0.002 ). The estimated average particle flow speeds v=0.25⋯2.7mm/s showed a highly significant linear correlation to the applied flow. The estimated capillary segment length of approximately 189um agreed well with optical microscopy measurements. Using the biexponential model, the signal fraction f was substantially underestimated and displayed a strong dependence on the applied flow rate. CONCLUSION: The constructed phantom facilitated the detailed investigation of IVIM-MRI methods. The results demonstrate that the phase-distribution method is capable of accurately characterizing fluid flow inside a capillary network. Parameters estimated using the biexponential model, specifically the perfusion fraction f , showed a substantial bias because the model assumptions were not met by the underlying flow pattern.

Impact of sodium 18F-fluoride PET/CT, 18F-fluorocholine PET/CT and whole-body diffusion-weighted MRI on the management of patients with prostate cancer suspicious for metastasis: a prospective multicentre study.

PURPOSE: To compare the impact of 18F-sodium-fluoride (NaF) PET/CT, 18F-fluorocholine (FCH) PET/CT and diffusion-weighted whole-body MRI (DW-MRI) on the management of patients with prostate cancer (PCa) suspicious for distant metastasis. METHODS: Prostate cancer patients were prospectively included between December 2011 and August 2014 and benefited from these three whole-body imaging (WBI) modalities within 1 month in addition to the standard PCa workup. Management was prospectively decided by clinicians during two multidisciplinary meetings, before and after the whole-body imaging workup. Rates of induced changes of whole-body imaging modalities were compared by Cochran's Q test. RESULTS: One-hundred-one patients (27 at staging, 59 at first biochemical recurrence (BCR) and 15 at first episode of rising serum level of prostate-specific antigen during androgen-deprivation therapy) were included. The overall rate of management changes was 52%: 29% as a consequence of WBI, higher for FCH-PET/CT than for NaF-PET/CT or DW-MRI (p < 0.0001) and highest (41%) for FCH-PET/CT at BCR. Actual management was adequate in all patients but two. CONCLUSIONS: Whole-body imaging induced a change in management in approximately a third of PCa patients suspicious for metastasis. The impact rate was determined to be greatest at first BCR using FCH-PET/CT. NaF-PET/CT and DW-MRI seemed less useful in this context.

Diffusion-weighted MRI of the lung at 3T evaluated using echo-planar-based and single-shot turbo spin-echo-based acquisition techniques for radiotherapy applications.

PURPOSE: To compare single-shot echo-planar (SS-EPI)-based and turbo spin-echo (SS-TSE)-based diffusion-weighted imaging (DWI) in Non-Small Cell Lung Cancer (NSCLC) patients and to characterize the distributions of apparent diffusion coefficient (ADC) values generated by the two techniques. METHODS: Ten NSCLC patients were enrolled in a prospective IRB-approved study to compare and optimize DWI using EPI and TSE-based techniques for radiotherapy planning. The imaging protocol included axial T2w, EPI-based DWI and TSE-based DWI on a 3 T Philips scanner. Both EPI-based and TSE-based DWI sequences used three b values (0, 400, and 800 s/mm2 ). The acquisition times for EPI-based and TSE-based DWI were 5 and 8 min, respectively. DW-MR images were manually coregistered with axial T2w images, and tumor volume contoured on T2w images were mapped onto the DWI scans. A pixel-by-pixel fit of tumor ADC was calculated based on monoexponential signal behavior. Tumor ADC mean, standard deviation, kurtosis, and skewness were calculated and compared between EPI and TSE-based DWI. Image distortion and ADC values between the two techniques were also quantified using fieldmap analysis and a NIST traceable ice-water diffusion phantom, respectively. RESULTS: The mean ADC for EPI and TSE-based DWI were 1.282 ± 0.42 × 10-3 and 1.211 ± 0.31 × 10-3  mm2 /s. The average skewness and kurtosis were 0.14 ± 0.4 and 2.43 ± 0.40 for DWI-EPI and -0.06 ± 0.69 and 2.89 ± 0.62 for DWI-TSE. Fieldmap analysis showed a mean distortion of 13.72 ± 8.12 mm for GTV for DWI-EPI and 0.61 ± 0.4 mm for DWI-TSE. ADC values obtained using the diffusion phantom for the two techniques were within 0.03 × 10-3  mm2 /s with respect to each other as well as the established values. CONCLUSIONS: Diffusion-weighted turbo spin-echo shows better geometrical accuracy compared to DWI-EPI. Mean ADC values were similar with both acquisitions but the shape of the histograms was different based on the skewness and kurtosis values. The impact of differences in respiratory technique on ADC values requires further investigation.

Cerebral embolic protection in thoracic endovascular aortic repair.

BACKGROUND: Stroke occurs in 3% to 8% and silent cerebral infarction in >60% of patients undergoing thoracic endovascular aortic repair (TEVAR). We investigated the utility of a filter cerebral embolic protection device (CEPD) to reduce diffusion-weighted magnetic resonance imaging (DW-MRI) detected cerebral injury and gaseous and solid embolization during TEVAR. METHODS: Patients anatomically suitable underwent TEVAR with CEPD, together with intraoperative transcranial Doppler to detect gaseous and solid high-intensity transient signals (HITSs), pre- and postoperative DW-MRI, and clinical neurologic assessment ≤6 months after the procedure. RESULTS: Ten patients (mean age, 68 years) underwent TEVAR with a CEPD. No strokes or device-related complications developed. The CEPD added a median of 7 minutes (interquartile range [IQR], 5-16 minutes) to the procedure, increased the fluoroscopy time by 3.3 minutes (IQR, 2.4-3.9 minutes), and increased the total procedural radiation by 2.2%. The dose area product for CEPD was 1824 mGy·cm2 (IQR, 1235-3392 mGy·cm2). The average contrast volume used increased by 23 mL (IQR, 24-35 mL). New DW-MRI lesions, mostly in the hindbrain, were identified in seven of nine patients (78%). The median number was 1 (IQR, 1-3), with a median surface area of 6 mm2 (IQR, 3-16 mm2). A total of 2835 HITSs were detected in seven patients: 91% gaseous and 9% solid. The maximum number of HITSs were detected during CEPD manipulation: 142 (IQR, 59-146; 95% gaseous and 5% solid). The maximum number of HITSs during TEVAR occurred during stent deployment: 82 (IQR, 73-142; 81% gas and 11% solid). Solid HITSs were associated with an increase in surface area of new DW-MRI lesions (rs = 0.928; P = .01). Increased gaseous HITSs were associated with new DW-MRI lesions (rs = 0.912; P = .01), which were smaller (<3 mm; r = 0.88; P = .02). Embolic debris was captured in 95% of the filters. The median particle count was 937 (IQR, 146-1687), and the median surface area was 2.66 mm2 (IQR, 0.08-9.18 mm2). CONCLUSIONS: The use of a CEPD with TEVAR appeared to be safe and feasible in this first pilot study and could serve as a useful adjunct to reduce cerebral injury. The significance of gaseous embolization and its role in cerebral injury in TEVAR warrants further investigation.

Preoperative image-guided identification of response to neoadjuvant chemoradiotherapy in esophageal cancer (PRIDE): a multicenter observational study.

BACKGROUND: Nearly one third of patients undergoing neoadjuvant chemoradiotherapy (nCRT) for locally advanced esophageal cancer have a pathologic complete response (pCR) of the primary tumor upon histopathological evaluation of the resection specimen. The primary aim of this study is to develop a model that predicts the probability of pCR to nCRT in esophageal cancer, based on diffusion-weighted magnetic resonance imaging (DW-MRI), dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and 18F-fluorodeoxyglucose positron emission tomography with computed tomography (18F-FDG PET-CT). Accurate response prediction could lead to a patient-tailored approach with omission of surgery in the future in case of predicted pCR or additional neoadjuvant treatment in case of non-pCR. METHODS: The PRIDE study is a prospective, single arm, observational multicenter study designed to develop a multimodal prediction model for histopathological response to nCRT for esophageal cancer. A total of 200 patients with locally advanced esophageal cancer - of which at least 130 patients with adenocarcinoma and at least 61 patients with squamous cell carcinoma - scheduled to receive nCRT followed by esophagectomy will be included. The primary modalities to be incorporated in the prediction model are quantitative parameters derived from MRI and 18F-FDG PET-CT scans, which will be acquired at fixed intervals before, during and after nCRT. Secondary modalities include blood samples for analysis of the presence of circulating tumor DNA (ctDNA) at 3 time-points (before, during and after nCRT), and an endoscopy with (random) bite-on-bite biopsies of the primary tumor site and other suspected lesions in the esophagus as well as an endoscopic ultrasonography (EUS) with fine needle aspiration of suspected lymph nodes after finishing nCRT. The main study endpoint is the performance of the model for pCR prediction. Secondary endpoints include progression-free and overall survival. DISCUSSION: If the multimodal PRIDE concept provides high predictive performance for pCR, the results of this study will play an important role in accurate identification of esophageal cancer patients with a pCR to nCRT. These patients might benefit from a patient-tailored approach with omission of surgery in the future. Vice versa, patients with non-pCR might benefit from additional neoadjuvant treatment, or ineffective therapy could be stopped. TRIAL REGISTRATION: The article reports on a health care intervention on human participants and was prospectively registered on March 22, 2018 under ClinicalTrials.gov Identifier: NCT03474341 .

A multiparametric analysis combining DCE-MRI- and IVIM -derived parameters to improve differentiation of parotid tumors: a pilot study.

AIM: To evaluate dynamic contrast-enhanced (DCE)-MRI and diffusion weighted (DW)-MRI diagnostic value to differentiate Warthin tumors (WT) by pleomorphic adenomas (PA). MATERIALS & METHODS: Seven WT and seven PA were examined. DCE- and  DW-MRI parameters were extracted from volumes of interest; volume of interest-based averages and standard deviations were calculated. Statistical analysis included: linear discriminant analysis, receiver operating characteristic curves, sensitivity and specificity. RESULTS: No single feature was able to differentiate WT by PA (p > 0.05); linear discriminant analysis analysis showed that a combination of all features or combinations of feature pairs (namely: Ktrans(std) & f(std), Ktrans(std) & D(std), kep(std) & D(std), MRE(av) & TTP(av)) might achieve sensitivity (SENS), specificity (SPEC) = 100%, with a slight reduction after cross-validation analysis (SENS = 0.875; SPEC = 1). CONCLUSION: Although preliminary and not conclusive, our results suggest that differentiation between WT and PA is possible through a multiparametric approach based on combination of DCE- and DW-MRI parameters.

Rapid measurement of intravoxel incoherent motion (IVIM) derived perfusion fraction for clinical magnetic resonance imaging.

OBJECTIVE: This study aimed to investigate the reliability of intravoxel incoherent motion (IVIM) model derived parameters D and f and their dependence on b value distributions with a rapid three b value acquisition protocol. MATERIALS AND METHODS: Diffusion models for brain, kidney, and liver were assessed for bias, error, and reproducibility for the estimated IVIM parameters using b values 0 and 1000, and a b value between 200 and 900, at signal-to-noise ratios (SNR) 40, 55, and 80. Relative errors were used to estimate optimal b value distributions for each tissue scenario. Sixteen volunteers underwent brain DW-MRI, for which bias and coefficient of variation were determined in the grey matter. RESULTS: Bias had a large influence in the estimation of D and f for the low-perfused brain model, particularly at lower b values, with the same trends being confirmed by in vivo imaging. Significant differences were demonstrated in vivo for estimation of D (P = 0.029) and f (P < 0.001) with [300,1000] and [500,1000] distributions. The effect of bias was considerably lower for the high-perfused models. The optimal b value distributions were estimated to be brain500,1000, kidney300,1000, and liver200,1000. CONCLUSION: IVIM parameters can be estimated using a rapid DW-MRI protocol, where the optimal b value distribution depends on tissue characteristics and compromise between bias and variability.

Predictors of false negative diffusion-weighted MRI in clinically suspected central cause of vertigo.

INTRODUCTION: Vertigo is classified as peripheral and central. Differentiation of stroke mimics is the most important diagnostic challenge. There is no clinical guidance for the indications of neuroimaging in isolated vertigo patients. The primary aim of this study is to test the diagnostic value of a DWI-MRI protocol to rule-out a central cause in patients with acute isolated vertigo in the ED. METHODS: We prospectively enrolled 144 patients who were presented with isolated vertigo to the ED. A detailed neurological examination and maneuvers were performed for differential diagnosis. All patients underwent CT and/or DW-MRI either during ED visit or at the follow-up, if necessary. Out-patient follow-up exams and evaluations were repeated until all patients had a definitive diagnosis. RESULTS: In the study, 137 of the 144 patients completed the follow-up period, and 34 of 137 patients were diagnosed with central vertigo. Six of 34 central vertigo patients had normal DW-MRI findings. One was diagnosed with migraine headache and five with vertebra-basilar insufficiency during the out-patient follow-up. One of the 28 patients with a pathological MRI was diagnosed with mass and the rest was stroke. The utility of DW-MRI in vertigo patients was moderately high (sensitivity: 82%, specificity: 100%). We found that age, history of HT, history of CAD and vertigo unresponsive to ED treatment were significantly associated with a central cause of vertigo. CONCLUSION: We suggest that unresponsiveness to ED treatment, especially in patients with a history of HT and CAD, should alert physicians for central causes and warrant DW-MRI imaging.