Utility of diffusion weighted Magnetic Resonance Imagining to detect non-palpable undescended testis.

Objective: To assess the effectiveness of diffusion-weighted magnetic resonance imaging (DW-MRI) in the detection of non-palpable undescended testis (NPUT) and to compare DW-MRI results with surgical findings. Methods: This descriptive, cross-sectional study was carried out at Dow Institute of Radiology, Dow University of Health Sciences. Karachi on a cohort of patients who underwent DW-MRI for suspected NPUT between 15th September, 2022 to 16th March, 2023. The study included 175 boys below the age of 16 years with history of clinically non-palpable testes. MRI scans were acquired using additional DWI sequence. Two radiology faculty of more than five years of experience independently evaluated the DW-MRI images for the presence or absence of testes in its normal anatomical position, abnormal location, side and size of testes. Results: Out of the 175 patients, DW-MRI successfully detected 128 (73.1%) non-palpable undescended testes. Statistical analysis in clinically detected cases of showed sensitivity of NPTU 0.8%, specificity of 92.5%, diagnostic accuracy 94.29%, positive predictive value 97.7%, and negative predictive value 84.1% for localizing undescended testes with Diffusion Weighted DW-MRI taking surgical findings as gold standard. Conclusion: DWI sequences complement the conventional MRI, increasing its sensitivity and diagnostic accuracy. By facilitating early and accurate diagnosis, DW-MRI has the potential to streamline patient management, reduce unnecessary surgical exploration, and ultimately improve the long-term reproductive health and quality of life for individuals with undescended testes.

Light-weight neural network for intra-voxel structure analysis.

We present a novel neural network-based method for analyzing intra-voxel structures, addressing critical challenges in diffusion-weighted MRI analysis for brain connectivity and development studies. The network architecture, called the Local Neighborhood Neural Network, is designed to use the spatial correlations of neighboring voxels for an enhanced inference while reducing parameter overhead. Our model exploits these relationships to improve the analysis of complex structures and noisy data environments. We adopt a self-supervised approach to address the lack of ground truth data, generating signals of voxel neighborhoods to integrate the training set. This eliminates the need for manual annotations and facilitates training under realistic conditions. Comparative analyses show that our method outperforms the constrained spherical deconvolution (CSD) method in quantitative and qualitative validations. Using phantom images that mimic in vivo data, our approach improves angular error, volume fraction estimation accuracy, and success rate. Furthermore, a qualitative comparison of the results in actual data shows a better spatial consistency of the proposed method in areas of real brain images. This approach demonstrates enhanced intra-voxel structure analysis capabilities and holds promise for broader application in various imaging scenarios.

Staging peritoneal metastases in colorectal cancer: The correlation between MRI, surgical and histopathological peritoneal cancer index.

INTRODUCTION: DW-MRI is a non-invasive way to determine the peritoneal cancer index (PCI) in colorectal cancer (CRC) patients with peritoneal metastases (PM). However, like surgeons during surgery, radiologists struggle to differentiate between PM and fibrosis. This study aimed to investigate the agreement between the PCI as determined by MRI (mriPCI), during surgery (sPCI) and histopathology examination (pPCI) in CRC patients undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC). MATERIALS AND METHODS: This was a single-centre, retrospective study of CRC patients with PM who were staged with DW-MRI and underwent subsequent CRS-HIPEC. All initial patients' radiological, surgical and histopathology reports were reviewed for the PCI. Histopathology was the reference standard. Primary outcome was the correlation and agreement between mriPCI and pPCI. RESULTS: Eighty-seven patients were included. All patients had a complete macroscopic resection. Median (interquartile range) PCI for MRI, surgery, and histopathology were respectively 6.0 (2.5-9.0), 6.0 (4.0-11.0) and 6.0 (2.5-9.5). The intraclass correlation coefficient between the sPCI and pPCI was excellent 0.87 (p <0.001), and good between mriPCI and pPCI 0.77 (p <0.001) and between sPCI and mriPCI 0.70 (p <0.001). CONCLUSION: MRI is a promising non-invasive tool to assess the PCI rather accurately.

Addressing intra- and inter-institution variability of a radiomic framework based on Apparent Diffusion Coefficient in prostate cancer.

BACKGROUND: Prostate cancer (PCa) is a highly heterogeneous disease, making tailored treatment approaches challenging. Magnetic resonance imaging (MRI), notably diffusion-weighted imaging (DWI) and the derived Apparent Diffusion Coefficient (ADC) maps, plays a crucial role in PCa characterization. In this context, radiomics is a very promising approach able to disclose insights from MRI data. However, the sensitivity of radiomic features to MRI settings, encompassing DWI protocols and multicenter variations, requires the development of robust and generalizable models. PURPOSE: To develop a comprehensive radiomics framework for noninvasive PCa characterization using ADC maps, focusing on identifying reliable imaging biomarkers against intra- and inter-institution variations. MATERIALS AND METHODS: Two patient cohorts, including an internal cohort (118 PCa patients) used for both training (75%) and hold-out testing (25%), and an external cohort (50 PCa patients) for independent testing, were employed in the study. DWI images were acquired with three different DWI protocols on two different MRI scanners: two DWI protocols acquired on a 1.5-T scanner for the internal cohort, and one DWI protocol acquired on a 3-T scanner for the external cohort. One hundred and seven radiomics features (i.e., shape, first order, texture) were extracted from ADC maps of the whole prostate gland. To address variations in DWI protocols and multicenter variability, a dedicated pipeline, including two-way ANOVA, sequential-feature-selection (SFS), and ComBat features harmonization was implemented. Mann-Whitney U-tests (α = 0.05) were performed to find statistically significant features dividing patients with different tumor characteristics in terms of Gleason score (GS) and T-stage. Support-Vector-Machine models were then developed to predict GS and T-stage, and the performance was assessed through the area under the curve (AUC) of receiver-operating-characteristic curves. RESULTS: Downstream of ANOVA, two subsets of 38 and 41 features stable against DWI protocol were identified for GS and T-stage, respectively. Among these, SFS revealed the most predictive features, yielding an AUC of 0.75 (GS) and 0.70 (T-stage) in the hold-out test. Employing ComBat harmonization improved the external-test performance of the GS model, raising AUC from 0.72 to 0.78. CONCLUSION: By incorporating stable features with a harmonization procedure and validating the model on an external dataset, model robustness, and generalizability were assessed, highlighting the potential of ADC and radiomics for PCa characterization.

Is the rabbit a natural model of fetal growth restriction? Morphological and functional characterization study using diffusion-weighted MRI and stereology.

INTRODUCTION: Rabbits are routinely used as a natural model of fetal growth restriction (FGR); however, no studies have confirmed that rabbits have FGR. This study aimed to characterize the fetoplacental unit (FPU) in healthy pregnant rabbits using diffusion-weighted MRI and stereology. A secondary objective of the study was to describe the associations among findings from diffusion-weighted MRI (DW-MRI), fetal weight measurement and histological analysis of the placenta. METHODS: Pregnant rabbits underwent DW-MRI under general anesthesia on embryonic day 28 of pregnancy. MR imaging was performed at 3.0 T. The apparent diffusion coefficient (ADC) values were calculated for the fetal brain, liver, and placenta. The placenta was analyzed by stereology (volume density of trophoblasts, the maternal blood space and fetal vessels). Each fetus and placenta were weighed. Two groups of fetuses were defined according to the position in the uterine horn (Cervix group versus Ovary group). RESULTS: We analyzed 20 FPUs from 5 pregnant rabbits. Fetuses and placentas were significantly lighter in the Cervix group than in the Ovary group (34.7 ± 3.7 g vs. 40.2 ± 5.4 g; p = 0.02). Volume density analysis revealed that the percentage of fetal vessels, the maternal blood space and trophoblasts was not significantly affected by the position of the fetus in the uterine horn. There was no difference in ADC values according to the position of the fetus in the uterine horn, and there was no correlation between ADC values and fetal weight. DISCUSSION: The findings of a multimodal evaluation of the placenta in a rabbit model of FGR suggested is not a natural model of fetal growth restriction.

Investigating locations of recurrences with MRI after CRS-HIPEC for colorectal peritoneal metastases.

PURPOSE: Patients with colorectal peritoneal metastases (PM) treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are at high risk of recurrent disease. Understanding where and why recurrences occur is the first step in finding solutions to reduce recurrence rates. Although diffusion-weighted (DW) MRI is not routinely used in the follow-up of CRC patients, it has a clear advantage over CT in detecting the location and spread of (recurrent) PM. This study aimed to identify common locations of recurrence in CRC patients after CRS-HIPEC with MRI. METHOD: This was a single-centre retrospective study of patients with recurrent PM after CRS-HIPEC performed between January 2016 and August 2020. Patients were eligible for inclusion if they had both an MRI preoperatively (MRI1) and at the time of recurrent disease (MRI2). Two abdominal radiologists reviewed in consensus and categorized recurrences according to their location on MRI2 and in correlation with previous disease location on prior imaging (MRI1) and the surgical report of the CRS-HIPEC. RESULTS: Thirty patients were included, with a median surgical PCI of 7 (range 3-21) at the time of primary CRS-HIPEC. In total, 68 recurrent metastases were detected on MRI2, of which 14 were extra-peritoneal. Of the remaining 54 PM, 42 (78%) occurred where the peritoneum was damaged due to earlier resections or other surgical procedures (e.g. inserted surgical abdominal drains). Most recurrent metastases were found in the mesentery, lower abdomen/pelvis and abdominal wall (87%). CONCLUSIONS: Most recurrent PMs appeared in the mesentery, lower abdomen/pelvis and abdominal wall, especially where the peritoneum was previously damaged.

Does Bladder Cancer Subtype Influence Pathologic Complete Response (pCR) and Pelvic Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) Response Evaluation After Neoadjuvant Chemotherapy? Pathological Perspective.

INTRODUCTION: We aimed to provide a pathological perspective on the management of muscle-invasive bladder cancer (MIBC) by correlating the prechemotherapy transurethral resection of bladder tumor findings and postchemotherapy radiologic evaluation with final radical cystectomy (RC) findings. MATERIALS AND METHODS: This retrospective study included 79 MIBC patients treated with neoadjuvant chemotherapy (NAC) and RC. Pelvic diffusion-weighted magnetic resonance imaging (DW-MRI) and pathologic reports were retrieved from our institutional database. All pathology slides were reviewed based on diagnostic criteria with high interobserver reproducibility. RESULTS: Pathologic complete response (pCR) was confirmed in 32 patients (40.5%). The concordance and discordance between MRI and RC findings occurred in 68.3% and 31.7% of cases, respectively. The 21.5% of cases that were clinical CR (cCR) on MRI actually achieved pCR on RC specimens and 46.8% of cases that were non-cCR on MRI were actually non-pCR on RC specimens. In 19.0% of cases, RC findings were pCR, but MRI demonstrated residual tumor and the opposite was 12.7%. The greatest discrepancy between the 2 methods (75%, 3/4) was for the plasmacytoid subtype. Plasmacytoid histology was the most common histological subtype identified in RC specimens after NAC, followed by micropapillary and squamous histologies. CONCLUSIONS: We found that all cases with plasmacytoid and micropapillary subtypes, and squamous differentiation did not show pCR. In particular, the largest discrepancy between MRI findings and RC pathology after NAC was seen in the plasmacytoid subtype. An accurate pathologic diagnosis based on strict criteria to identify histological subtypes of MIBC is necessary for proper treatment.

Performance of Non-EPI DW MRI for Pediatric Cholesteatoma Follow-Up.

OBJECTIVE: To evaluate the accuracy, sensitivity, and specificity of nonecho planar (non-EPI) diffusion-weighted (DW) magnetic resonance imaging (MRI) to detect residual cholesteatoma in children. STUDY DESIGN: Retrospective study. SETTING: Tertiary comprehensive hospital. METHODS: Children operated on for a first-stage cholesteatoma procedure from 2010 to 2019 were included. MRIs were performed with non-EPI DW sequences. Initial reports were collected, indicating the presence or absence of hyperintensity suggestive of cholesteatoma. Three hundred twenty-three MRIs were correlated with the subsequent surgery (66%) or year-later MRI (21%), or were considered accurate if performed 5 years or more after the last surgery (13%). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each imaging procedure for the detection of cholesteatoma were calculated. RESULTS: Two hundred twenty-four children with mean age of 9 ± 4 years old presented with cholesteatoma. MRIs were performed 27 ± 24 months after surgery. Residual cholesteatoma was diagnosed in 35%. The sensitivity, specificity, PPV, and NPV of MRI were 62%, 86%, 74%, and 78%, respectively. Accuracy, sensitivity, and specificity increased significantly over time (multivariate analysis). The mean delay after last surgery was of 30 ± 2.0 months for accurate MRI (true positive or negative) versus 17 ± 2.0 months for nonaccurate (false positive or negative) MRIs (p < .001). CONCLUSION: However, long the delay after the last surgery, the sensitivity of non-EPI diffusion sequence MRI in children has limitations for the detection of residual cholesteatoma. Surveillance for residual cholesteatoma should incorporate findings at primary surgery, surgeon experience, a low threshold for second-look procedures, and routine imaging.

Unraveling the Enigma: A Report of a Rare Case of Acute Cord Syndrome Caused by Spinal Meningioma.

Spinal meningiomas (SMs) are a prevalent subtype of central nervous system tumors, with the majority adhering to the dura mater. In this case, we present the case of a 72-year-old female who initially reported numbness in her legs and the gradual onset of gait disturbances. Over a three-week period, these symptoms progressively worsened until she experienced a sudden onset of weakness and neurological deficits, leading to the diagnosis of acute cord syndrome (ACS). Magnetic resonance imaging revealed an anomaly within the extramedullary space, precisely located at the T8-T9 level. This anomaly exhibited peripheral gadolinium enhancement and demonstrated a dural tail sign, indicating the presence of an abnormal mass. Furthermore, a dorsal spine CT scan confirmed these findings by revealing a hyperdense lesion localized within the T8-T9 region. The lesion was situated posterior to the spinal cord, and conspicuous alterations in the coloration of the dura mater at the corresponding level were evident. A complete surgical resection was performed successfully, and the patient's surgical intervention proceeded without complications. Following the surgery, we observed significant improvements in both sensory and motor functions compared to the patient's preoperative state.

Microstructural Changes in the Spinothalamic Tract of CPSS Patients: Preliminary Results from a Single-Center Diffusion-Weighted Magnetic Resonance Imaging Study.

INTRODUCTION: Chronic pain after spinal surgery (CPSS), formerly known as failed back surgery syndrome, encompasses a variety of highly incapacitating chronic pain syndromes emerging after spinal surgery. The intractability of CPSS makes objective parameters that could aid classification and treatment essential. In this study, we investigated the use of cerebral diffusion-weighted magnetic resonance imaging. METHODS: Cerebral 3T diffusion-weighted (DW-) MRI data from adult CPSS patients were assessed and compared with those of healthy controls matched by age and gender. Only imaging data without relevant artefacts or significant pathologies were included. Apparent diffusion coefficient (ADC) maps were calculated from the b0 and b1000 values using nonlinear regression. After skull stripping and affine registration of all imaging data, ADC values for fifteen anatomical regions were calculated and analyzed with independent samples T-tests. RESULTS: A total of 32 subjects were included (sixteen CPSS patients and sixteen controls). The mean ADC value of the spinothalamic tract was found to be significantly higher in CPSS patients compared with in healthy controls (p = 0.013). The other anatomical regions did not show statistically different ADC values between the two groups. CONCLUSION: Our results suggest that patients suffering from CPSS are subject to microstructural changes, predominantly within the cerebral spinothalamic tract. Additional research could possibly lead to imaging biomarkers derived from ADC values in CPSS patients.

Assessment of Apparent Diffusion Coefficient Parameters and Coefficient of Variance in Discrimination of Receptor Status and Molecular Subtypes of Breast Cancer.

OBJECTIVE: The objective of this study was to investigate the diagnostic power of apparent diffusion coefficient/coefficient of variance (ADCcV) as well as ADC parameters formed based on magnetic resonance images (MRI) in the distinction of molecular breast cancer subtypes. METHODS: The study involved 205 patients who had breast cancer at stages 1-3. Estrogen receptor (EsR), progesterone receptor (PrR), human epidermal growth factor receptor 2 (Her2), and proliferation index (Ki-67) were histologically analyzed in the tumor. The correlations between the immunohistochemistry and intrinsic subtypes were analyzed using ADC and ADCcV. RESULTS: The maximum whole tumor (WTu) ADC (p=0.004), minimum WTu ADC (p<0.001), and mean WTu ADC (p<0.001) values were significantly smaller in the EsR-positive tumors than those in the EsR-negative tumors. Compared to the PrR-negative tumors, the PrR-positive tumors showed significantly smaller maximum, minimum, and mean WTu ADC values (p=0.005, p=0.001, and p<0.001, respectively). In the comparisons of the molecular subtypes in terms of ADCcV, the p-values indicated statistically significant differences between the luminal A (lumA) group and the triple negative (TN) group, between the luminal B (lumB) group and the TN group, and between the Her2-enriched and TN groups (p<0.001, p=0.011, and p=0.004, respectively). Considering the luminal and non-luminal groups, while a significant difference was observed between the groups considering their minimum, maximum, and mean WTu ADC values, their ADCcV values were similar (p<0.001, p=0.004, and p<0.001, respectively). CONCLUSION: Using ADCcV in addition to ADC parameters increased the diagnostic power of diffusion weighted-MRI (DW-MRI) in the distinction of molecular subtypes of breast cancer.

Optimal time for early therapeutic response prediction in nasopharyngeal carcinoma with functional magnetic resonance imaging.

Background and Purpose: Physiological changes in tumour occur much earlier than morphological changes. They can potentially be used as biomarkers for therapeutic response prediction. This study aimed to investigate the optimal time for early therapeutic response prediction with multi-parametric magnetic resonance imaging (MRI) in patients with nasopharyngeal carcinoma (NPC) receiving concurrent chemo-radiotherapy (CCRT). Material and Methods: Twenty-seven NPC patients were divided into the responder (N = 23) and the poor-responder (N = 4) groups by their primary tumour post-treatment shrinkages. Single-voxel proton MR spectroscopy (1H-MRS), diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) MRI were scanned at baseline, weekly during CCRT and post-CCRT. The median choline peak in 1H-MRS, the median apparent diffusion coefficient (ADC) in DW-MRI, the median influx rate constant (Ktrans), reflux rate constant (Kep), volume of extravascular-extracellular space per unit volume (Ve), and initial area under the time-intensity curve for the first 60 s (iAUC60) in DCE-MRI were compared between the two groups with the Mann-Whitney tests for any significant difference at different time points. Results: In DW-MRI, the percentage increase in ADC from baseline to week-1 for the responders (median = 11.39%, IQR = 18.13%) was higher than the poor-responders (median = 4.91%, IQR = 7.86%) (p = 0.027). In DCE-MRI, the iAUC60 on week-2 was found significantly higher in the poor-responders (median = 0.398, IQR = 0.051) than the responders (median = 0.192, IQR = 0.111) (p = 0.012). No significant difference was found in median choline peaks in 1H-MRS at all time points. Conclusion: Early perfusion and diffusion changes occurred in primary tumours of NPC patients treated with CCRT. The DW-MRI on week-1 and the DCE-MRI on week-2 were the optimal time points for early therapeutic response prediction.

Deep Constrained Spherical Deconvolution for Robust Harmonization.

Diffusion weighted magnetic resonance imaging (DW-MRI) captures tissue microarchitecture at millimeter scale. With recent advantages in data sharing, large-scale multi-site DW-MRI datasets are being made available for multi-site studies. However, DW-MRI suffers from measurement variability (e.g., inter- and intra-site variability, hardware performance, and sequence design), which consequently yields inferior performance on multi-site and/or longitudinal diffusion studies. In this study, we propose a novel, deep learning-based method to harmonize DW-MRI signals for a more reproducible and robust estimation of microstructure. Our method introduces a data-driven scanner-invariant regularization scheme to model a more robust fiber orientation distribution function (FODF) estimation. We study the Human Connectome Project (HCP) young adults test-retest group as well as the MASiVar dataset (with inter- and intra-site scan/rescan data). The 8th order spherical harmonics coefficients are employed as data representation. The results show that the proposed harmonization approach maintains higher angular correlation coefficients (ACC) with the ground truth signals (0.954 versus 0.942), while achieves higher consistency of FODF signals for intra-scanner data (0.891 versus 0.826), as compared with the baseline supervised deep learning scheme. Furthermore, the proposed data-driven framework is flexible and potentially applicable to a wider range of data harmonization problems in neuroimaging.

intravoxel incoherent motion diffusion-weighted MRI assessing the effect of the vascular disrupting agent CA4P on VX2 liver tumors in rabbits.

OBJECTIVE: This study aimed to assess the response of combretastatin-A4-phosphate (CA4P) in rabbit VX2 liver tumors using intravoxel incoherent motion diffusion-weighted MRI (IVIM DW-MRI). METHODS: Forty rabbits with implanted VX2 liver tumors underwent baseline MRI and were then given 10 mg/kg CA4P (n=20) or saline (n=20). After 4 h, 10 rabbits from each group underwent an MRI examination and were then sacrificed. The remaining rabbits underwent MRI after 1, 3, and 7 days and were then sacrificed. Liver samples were processed for H&E and immunohistochemical staining. IVIM parameters (D, f, D*) were compared in the treatment and control groups, and the correlations of IVIM parameters with microvascular density (MVD) were determined. RESULTS: At 4 h, the two treatment groups had significantly different f and D* values (p<0.001), and these values were at their minimum in the treatment group. The treatment group had moderate correlations between MVD and f at 4 h (r=0.676, p=0.032) and 7 days (r=0.656, p=0.039) and with D* at 4 h (r=0.732, p=0.016) and 7 days (r=0.748, p=0.013), but no correlation was reported between MVD and f or D* in the control group (all P>0.05). CONCLUSION: IVIM DW-MRI is a sensitive imaging technique. It successfully evaluated the effect of CA4P on VX2 liver tumors in rabbits. The f and D* values correlated with MVD at 4 h and 7 days after using CA4P, indicating that these parameters have the potential to be used as indicators of tumor angiogenesis after treatment.

The impact of fusion imaging technique on middle ear cholesteatoma surgery: a prospective comparative study.

BACKGROUND: The fusion of computed tomography images with non-echo planner diffusion-weighted magnetic resonance images may overcome the limitations of each individual modality. OBJECTIVES: This study aimed to assess the ability of the 'fusion' technique to predict the location of middle ear cholesteatoma by evaluating Its impact on preoperative surgical planning and postoperative results. METHODOLOGY: Eighty-three adults with cholesteatoma underwent preoperative CT scans and non-EPI-DW-MRI with or without the 'fusion' technique. We evaluated cholesteatoma localization in both groups, selecting the most appropriate surgical technique, and correlating it with the intraoperative findings. Both groups were compared in terms of residual/recurrent cholesteatoma at one, six and twelve months after surgery. RESULTS: The 'fusion' technique's sensitivity, specificity, and accuracy in predicting the location of cholesteatoma were 97.5. 97.4, and 97.5%, respectively, versus 97.59, 57.69, and 73.21% of CT alone. There was a total operators agreement after the evaluation of the 'fusion' images with the adopted surgical technique. A statistically significant decrease in residual and recurrence cholesteatoma rates was found in group A. CONCLUSIONS: The 'fusion' technique provides the surgeon with the precise cholesteatoma location, guiding him in making the correct surgical decision, contributing to the decrease in postoperative residual and recurrence rates.

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.

Microstructural parameters from DW-MRI for tumour characterization and local recurrence prediction in particle therapy of skull-base chordoma.

BACKGROUND: Quantitative imaging such as Diffusion-Weighted MRI (DW-MRI) can be exploited to non-invasively derive patient-specific tumor microstructure information for tumor characterization and local recurrence risk prediction in radiotherapy. PURPOSE: To characterize tumor microstructure according to proliferative capacity and predict local recurrence through microstructural markers derived from pre-treatment conventional DW-MRI, in skull-base chordoma (SBC) patients treated with proton (PT) and carbon ion (CIRT) radiotherapy. METHODS: Forty-eight patients affected by SBC, who underwent conventional DW-MRI before treatment and were enrolled for CIRT (n = 25) or PT (n = 23), were retrospectively selected. Clinically verified local recurrence information (LR) and histological information (Ki-67, proliferation index) were collected. Apparent diffusion coefficient (ADC) maps were calculated from pre-treatment DW-MRI and, from these, a set of microstructural parameters (cellular radius R, volume fraction vf, diffusion D) were derived by applying a fine-tuning procedure to a framework employing Monte Carlo simulations on synthetic cell substrates. In addition, apparent cellularity (ρapp ) was estimated from vf and R for an easier clinical interpretation. Histogram-based metrics (mean, median, variance, entropy) from estimated parameters were considered to investigate differences (Mann-Whitney U-test, α = 0.05) in estimated tumor microstructure in SBCs characterized by low or high cell proliferation (Ki-67). Recurrence-free survival analyses were also performed to assess the ability of the microstructural parameters to stratify patients according to the risk of local recurrence (Kaplan-Meier curves, log-rank test α = 0.05). RESULTS: Refined microstructural markers revealed optimal capabilities in discriminating patients according to cell proliferation, achieving best results with mean values (p-values were 0.0383, 0.0284, 0.0284, 0.0468, and 0.0088 for ADC, R, vf, D, and ρapp, respectively). Recurrence-free survival analyses showed significant differences between populations at high and low risk of local recurrence as stratified by entropy values of estimated microstructural parameters (p = 0.0110). CONCLUSION: Patient-specific microstructural information was non-invasively derived providing potentially useful tools for SBC treatment personalization and optimization in particle therapy.

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.

Utility of Mid-treatment DWI in Selecting Pathological Responders to Neoadjuvant Chemoradiotherapy in Locally Advanced Esophageal Cancer.

PURPOSE: Pathological complete response correlates with better clinical outcomes in locally advanced esophageal cancer (LA-EC). However, there is lack of prognostic markers to identify patients in the current setting of neoadjuvant chemoradiotherapy (NACRT) followed by surgery. This study evaluates the utility of mid-treatment diffusion-weighted imaging (DWI) in identifying pathological responders of NACRT. METHODS: Twenty-four patients with LA-EC on NACRT were prospectively recruited and underwent three MRI (baseline, mid-treatment, end-of-RT) scans. DWI-derived apparent diffusion coefficient (ADC) mean and minimum were used as a surrogate to evaluate the treatment response, and its correlation to pathological response was assessed. RESULTS: Mid-treatment ADC mean was significantly higher among patients with pathological response compared to non-responders (p = 0.011). ADC difference (ΔADC) between baseline and mid-treatment correlated with tumor response (p = 0.007). ADC at other time points did not correlate to pathological response. CONCLUSION: In this study, mid-treatment ADC values show potential to be a surrogate for tumor response in NACRT. However, larger trials are required to establish DW-MRI as a definite biomarker for tumor response.

Assessment of pulmonary morphometry using hyperpolarized 129 Xe diffusion-weighted MRI with variable-sampling-ratio compressed sensing patterns.

BACKGROUND: Hyperpolarized (HP) 129 Xe multiple b-values diffusion-weighted magnetic resonance imaging (DW-MRI) has been widely used for quantifying pulmonary microstructural morphometry. However, the technique requires long acquisition times, making it hard to apply in patients with severe pulmonary diseases, who cannot sustain long breath holds. PURPOSE: To develop and evaluate the technique of variable-sampling-ratio compressed sensing (VCS) patterns for accelerating HP 129 Xe multiple b-values DW-MRI in humans. METHODS: Optimal variable sampling ratios and corresponding k-space undersampling patterns for each b-value were obtained by retrospective simulations based on the fully sampled (FS) DW-MRI dataset acquired from six young healthy volunteers. Then, the FS datasets were retrospectively undersampled using both VCS patterns and conventional compressed sensing (CS) pattern with a similar average acceleration factor. The quality of reconstructed images with retrospective VCS (rVCS) and CS (rCS) datasets were quantified using mean absolute error (MAE) and structural similarity (SSIM). Pulmonary morphometric parameters were also evaluated between rVCS and FS datasets. In addition, prospective VCS multiple b-values 129 Xe DW-MRI datasets were acquired from 14 cigarette smokers and 13 age-matched healthy volunteers. The differences of lung morphological parameters obtained with the proposed method were compared between the groups using independent samples t-test. Pearson correlation coefficient was also utilized for evaluating the correlation of the pulmonary physiological parameters obtained with VCS DW-MRI and pulmonary function tests. RESULTS: Lower MAE and higher SSIM values were found in the reconstructed images with rVCS measurement when compared to those using conventional rCS measurement. The details and quality of the images obtained with rVCS and FS measurements were found to be comparable. The mean values of the morphological parameters derived from rVCS and FS datasets showed no significant differences (p > 0.05), and the mean differences of measured acinar duct radius, mean linear intercept, surface-to-volume ratio, and apparent diffusion coefficient with cylinder model were -0.87%, -2.42%, 2.04%, and -0.50%, respectively. By using the VCS technique, significant differences were delineated between the pulmonary morphometric parameters of healthy volunteers and cigarette smokers (p < 0.001), while the acquisition time was reduced by four times. CONCLUSION: A fourfold reduction in acquisition time was achieved using the proposed VCS method while preserving good image quality. Our preliminary results demonstrated that the proposed method can be used for evaluating pulmonary injuries caused by cigarette smoking and may prove to be helpful in diagnosing lung diseases in clinical practice.