T1w Contrast Research Articles

Age-specific optimization of the T2-weighted MRI contrast in infant and toddler brain.

In 0-2-year-old brains, the T2-weighted (T2w) contrast between white matter (WM) and gray matter (GM) is weaker compared with that in adult brains and rapidly changes with age. This study aims to design variable-flip-angle (VFA) trains in 3D fast spin-echo sequence that adapt to the dynamically changing relaxation times to improve the contrast in the T2w images of the developing brains. T1 and T2 relaxation times in 0-2-year-old brains were measured, and several age groups were defined according to the age-dependent pattern of T2 values. Based on the static pseudo-steady-state theory and the extended phase graph algorithm, VFA trains were designed for each age group to maximize WM/GM contrast, constrained by the maximum specific absorption rate and overall signal intensity. The optimized VFA trains were compared with the default one used for adult brains based on the relative contrast between WM and GM. Dice coefficient was used to demonstrate the advantage of contrast-improved images as inputs for automatic tissue segmentation in infant brains. The 0-2-year-old pool was divided into groups of 0-8 months, 8-12 months, and 12-24 months. The optimal VFA trains were tested in each age group in comparison with the default sequence. Quantitative analyses demonstrated improved relative contrasts in infant and toddler brains by 1.5-2.3-fold at different ages. The Dice coefficient for contrast-optimized images was improved compared with default images (p < 0.001). An effective strategy was proposed to improve the 3D T2w contrast in 0-2-year-old brains.

MMORF—FSL’s MultiMOdal Registration Framework

Abstract We present MMORF—FSL’s MultiMOdal Registration Framework—a newly released nonlinear image registration tool designed primarily for application to magnetic resonance imaging (MRI) images of the brain. MMORF is capable of simultaneously optimising both displacement and rotational transformations within a single registration framework by leveraging rich information from multiple scalar and tensor modalities. The regularisation employed in MMORF promotes local rigidity in the deformation, and we have previously demonstrated how this effectively controls both shape and size distortion, leading to more biologically plausible warps. The performance of MMORF is benchmarked against three established nonlinear registration methods—FNIRT, ANTs, and DR-TAMAS—across four domains: FreeSurfer label overlap, diffusion tensor imaging (DTI) similarity, task-fMRI cluster mass, and distortion. The evaluation is based on 100 unrelated subjects from the Human Connectome Project (HCP) dataset registered to the Oxford-MultiModal-1 (OMM-1) multimodal template via either the T1w contrast alone or in combination with a DTI/DTI-derived contrast. Results show that MMORF is the most consistently high-performing method across all domains—both in terms of accuracy and levels of distortion. MMORF is available as part of FSL, and its inputs and outputs are fully compatible with existing workflows. We believe that MMORF will be a valuable tool for the neuroimaging community, regardless of the domain of any downstream analysis, providing state-of-the-art registration performance that integrates into the rich and widely adopted suite of analysis tools in FSL.

Diagnostic Contribution of Additional Sequences to the Evaluation of Cord Lesions in Patients with Cervical Spinal Multiple Sclerosis in Turkey: A Retrospective Study.

Multiple Sclerosis (MS) is the most common cause of non-traumatic disability in young adults. Spinal cord involvement is observed in 55-75% of patients with MS. To identify the strengths and shortcomings of sagittal phase-sensitive inversion recovery (PSIR), sagittal proton density/T2-weighted (PD/T2W), and axial turbo inversion recovery magnitude (TIRM) sequences in the detection of cervical MS plaques by comparing with routine sequences (axial and sagittal T2W, sagittal T1W, sagittal TIRM, fat-suppressed contrast T1W) and therefore determine their diagnostic contributions. A total of 48 patients in whom additional magnetic resonance imaging (MRI) sequences were obtained for the diagnosis of cervical MS were retrospectively identified and included in the study. A total of 111 MS plaques were analyzed in terms of visibility, number, size, border sharpness, and intensity ratio based on the routine and additional MRI sequences. The evaluation of the images was independently undertaken by two radiologists. The highest visibility was provided by sagittal PSIR, sagittal TIRM, and axial TIRM sequences (P < 0.05 for all additional sequences). Seven lesions in PD/T2W and four lesions in axial T2W sequences were unable to be detected. Lesions seen in sagittal and axial TIRM sequences were larger than the others. The sharpest borders were determined in the axial TIRM sequence, and the most diffuse borders in the PD/T2W sequence. In intensity ratio, the sagittal PSIR sequence revealed the most significant contrast difference. The sagittal PSIR sequence may improve the detection of cervical MS plaques due to the improved visibility and intensity ratios. The axial TIRM sequence may be more useful than routine axial T2W in the evaluation of visibility, border sharpness, and size measurement of MS plaques.

Performance and Dimensionality of Pretreatment MRI Radiomics in Rectal Carcinoma Chemoradiotherapy Prediction.

(1) Background: This study aimed to develop a machine learning model based on radiomics of pretreatment magnetic resonance imaging (MRI) 3D T2W contrast sequence scans combined with clinical parameters (CP) to predict neoadjuvant chemoradiotherapy (nCRT) response in patients with locally advanced rectal carcinoma (LARC). The study also assessed the impact of radiomics dimensionality on predictive performance. (2) Methods: Seventy-five patients were prospectively enrolled with clinicopathologically confirmed LARC and nCRT before surgery. Tumor properties were assessed by calculating 2141 radiomics features. Least absolute shrinkage selection operator (LASSO) and multivariate regression were used for feature selection. (3) Results: Two predictive models were constructed, one starting from 72 CP and 107 radiomics features, and the other from 72 CP and 1862 radiomics features. The models revealed moderately advantageous impact of increased dimensionality, with their predictive respective AUCs of 0.86 and 0.90 in the entire cohort and 0.84 within validation folds. Both models outperformed the CP-only model (AUC = 0.80) which served as the benchmark for predictive performance without radiomics. (4) Conclusions: Predictive models developed in this study combining pretreatment MRI radiomics and clinicopathological features may potentially provide a routine clinical predictor of chemoradiotherapy responders, enabling clinicians to personalize treatment strategies for rectal carcinoma.

Evaluating novel imaging-based mathematical modeling prediction of immunotherapy response by individual melanoma brain metastasis and patient prognosis.

e14013 Background: Ipilimumab/Nivolumab (Ipi/Nivo) significantly transformed outcomes for patients with melanoma brain metastases (MBM), however inter- and intra-patient responses can vary widely. The purpose of this study is to develop and calibrate an imaging-based mathematical model to predict lesion-specific immune response to Ipi/Nivo in patients with MBM to guide early local treatments such as radiotherapy and evaluate the prognostic value of identifying treatment resistant lesions. Methods: Baseline and follow-up 3D T1-W contrast MRIs of patients who solely received Ipi/Nivo after diagnosis with MBM were used to segment individual brain metastases and track serial volumetric data for each lesion to develop a mechanistic model (eq 1). After applying appropriate assumptions to our model, tumor burden ( ρ), intrinsic lesion growth rate ( α 0), Ipi/Nivo-induced kill rate ( μ) and immune response strength ( Λ) were quantified for each lesion. Growth rate shortly after the start of treatment ( α 1 ) was calculated using the short-term model solution (eq 2). dρ/dt= (α0- μ+μ.Λ).ρ - μ.Λ.ρ2 (eq 1) ρ(t)≈eα1.t (eq 2) Change in BM volume between baseline and last follow-up was used to classify each lesion as either ‘responder’ or ‘non-responder’; these were compared with the Wilcoxon-rank-sum test. The highest α1 value for any one BM within a patient tumor was evaluated for its potential to sort patient overall survival (OS). Because the median survival was not reached for this cohort, we determined the α1 threshold of 0.005 to sort patients using an optimization routine that generates the maximum AUC to separate the cohort into 2 groups on an ROC curve. Kaplan-Meier (KM) curves were compared between these 2 groups. Results: In 23 patients, we evaluated 61 lesions. At the lesion level, model parameters representing μ and Λ were significantly different between responder and non-responder lesions (p-values &lt;0.0001 and 0.0004, respectively). The highest α1value for any one BM within a patient tumor was used to sort patient overall survival (OS) into prognostically ‘favorable’ or ‘unfavorable’ groups based on patient survival to ±1,200 days. In this limited cohort, OS KM curves by most aggressive lesion for favorable (α1 &lt; 0.005) vs. unfavorable (α1 &gt; 0.005) were not significant by log-rank test (p = 0.3263). Conclusions: In this limited cohort, we demonstrate feasibility to leverage serial conventional imaging and tumor volumetric data to calibrate a mechanistic model to predict per-lesion treatment response of MBM to Ipi/Nivo. Although the p-value between groups was found to be insignificant when predicting survival using α1, this is likely because of the small number of patients included in this study (n=23). Furthermore, when taken together with the notable AUC (=0.7917) observed in the ROC curve, this promising result supports further investigation in a larger cohort.

Contrast enhancement: Cross-modal learning approach for medical images

Contrast is an imperative perceptible attribute embodying the image quality. In medical images, the poor quality specifically low contrast inhibits precise interpretation of the image. Contrast enhancement is, therefore, applied not merely to improve the visual quality of images but also enabling them to facilitate further processing tasks. We propose a contrast enhancement approach based on cross-modal learning in this paper. Cycle-GAN (Generative Adversarial Network) is used for this purpose, where UNet augmented with global features acts as a generator. Besides, individual batch normalization has been used to make generators adapt specifically to their input distributions. The proposed method accepts low contrast T2-weighted (T2-w) Magnetic Resonance images (MRI) and uses the corresponding high contrast T1-w MRI to learn the global contrast characteristics. The experiments were conducted on a publicly available IXI dataset. Comparison with recent CE methods and quantitative assessment using two prevalent metrics FSIM and BRISQUE validate the superior performance of the proposed method.

An Investigation for Large Volume, Focal Blood-Brain Barrier Disruption with High-Frequency Pulsed Electric Fields.

The treatment of CNS disorders suffers from the inability to deliver large therapeutic agents to the brain parenchyma due to protection from the blood-brain barrier (BBB). Herein, we investigated high-frequency pulsed electric field (HF-PEF) therapy of various pulse widths and interphase delays for BBB disruption while selectively minimizing cell ablation. Eighteen male Fisher rats underwent craniectomy procedures and two blunt-tipped electrodes were advanced into the brain for pulsing. BBB disruption was verified with contrast T1W MRI and pathologically with Evans blue dye. High-frequency irreversible electroporation cell death of healthy rodent astrocytes was investigated in vitro using a collagen hydrogel tissue mimic. Numerical analysis was conducted to determine the electric fields in which BBB disruption and cell ablation occur. Differences between the BBB disruption and ablation thresholds for each waveform are as follows: 2-2-2 s (1028 V/cm), 5-2-5 s (721 V/cm), 10-1-10 s (547 V/cm), 2-5-2 s (1043 V/cm), and 5-5-5 s (751 V/cm). These data suggest that HF-PEFs can be fine-tuned to modulate the extent of cell death while maximizing peri-ablative BBB disruption. Furthermore, numerical modeling elucidated the diffuse field gradients of a single-needle grounding pad configuration to favor large-volume BBB disruption, while the monopolar probe configuration is more amenable to ablation and reversible electroporation effects.

INNV-18. EFFECT OF DURATION OF TUMOR TREATING FIELDS THERAPY ON CELLULARITY DISTRIBUTIONS BEYOND T1W MRI CONTRAST ENHANCING MARGIN AT AUTOPSY IN GLIOMA PATIENTS: PRELIMINARY RESULTS

Abstract Tumor treating fields (TTFields) are thought to disrupt the cell division process in glioma. This study uses autopsy tissue samples from patients recruited for brain donation to determine whether TTFields treatment duration and usage affects cellularity distributions beyond the gadolinium contrast enhancing region on T1-weighted (T1w) magnetic resonance imaging (MRI). At autopsy, 43 tissue samples from 18 patients who had undergone TTFields treatment (inclusion criteria: &amp;gt;50% compliance and 25-day duration) were collected from brain slices sectioned in-line with slices from the patients’ final MRI prior to death. Nuclei were segmented on the digitized hematoxylin and eosin (HE) stained tissue samples, which were then used to compute cell count across the slides. Tissue was then aligned to the patient’s final MRI scan prior to death using a custom in-house software, where manually defined control points were used to compute a nonlinear transform to warp the tissue to match the MRI. Histogram features including mean, median, 90th percentile, variance, and skewness, were computed from the cellularity distributions within regions outside the traditional tumor margin defined by T1w contrast enhancement for each subject. General linear models were fit to assess the effects of TTFields usage (percent of day) and duration (in days) on each histogram feature, controlling for age, overall survival, and time between TTFields treatment and death, as well as time between MRI acquisition and death. Longer TTFields treatment duration and overall survival was associated with significantly decreased skewness in the non-enhancing cellularity distributions (p&amp;lt; 0.05) while associations with other metrics remained statistically insignificant. These preliminary results in a small patient cohort suggest that TTFields duration may reduce the presence of high cellularity tails in the non-contrast enhancing distributions. Additional research in larger patient populations is warranted to better understand these findings given the number of confounding factors.

Simultaneous T1 -weighted and T2 -weighted 3D MRI using RF phase-modulated gradient echo imaging.

T1 -weighted and T2 -weighted (T1w and T2w) imaging are essential sequences in routine clinical practice to detect and characterize a wide variety of pathologies. Many approaches have been proposed to obtain T1w and T2w contrast, although many challenges still remain, including long acquisition time and limitations that favor 2D imaging. In this study, we propose a novel method for simultaneous T1w and T2w imaging using RF phase-modulated 3D gradient-echo imaging. Configuration theory is used to derive closed-form equations for the steady state of RF phase-modulated gradient-echo signal. These equations suggest the use of small RF phase increments to provide orthogonal signal contrast with T2w and T1w in the real and imaginary components, respectively. Background phase can be removed using a two-pass acquisition with opposite RF phase increments. Simulation and phantom experiments were performed to validate our proposed method. Volunteer images of the brain and knee were acquired to demonstrate the clinical feasibility. The proposed method was compared with T1w and T2w fast spin-echo imaging. The relative signal intensity of images acquired using the proposed method agreed closely with simulations and fast spin-echo imaging in phantoms. Images from volunteer imaging showed very similar contrast compared to conventional fast spin-echo imaging. Radiofrequency phase-modulated gradient-echo with small RF phase increments is an alternative method that provides simultaneous T1w and T2w contrast in short scan times with 3D volumetric coverage.

P04.06 Can BraTS Toolkit Brain Tumor Segmentation Algorithms be relevant when dealing with post-operative MRI in clinical practice?

Abstract BACKGROUND Segmentation of brain tumors is crucial for radiotherapy plans and treatment outcome evaluation. As manual segmentation (MS) is a time-consuming task, many algorithms to automate the process were proposed over the past decades. BraTS toolkit (BTK) offers a solution for automatic brain tumor segmentation in 3 steps: a Preprocessor for image conversion and registration, a Segmentor generating segmentations from 4 deep-learning based algorithms and a Fusionator combining the results. As most algorithms published, BTK was trained on pre-operative data. Yet, as surgery is the first treatment of glioblastomas, most MRIs in clinical practice are post-operative images. This study aimed to assess whether segmentation of post-operative brain tumors could benefit from an initial automatic segmentation (AS) using BTK. MATERIAL AND METHODS MRI dataset from the multicenter, STERIMGLI clinical trial provided 92 series from 25 patients with a unifocal recurrence of glioblastoma. AS were generated using BTK Preprocessor and Segmentor. Out of the 4 algorithms output, the best AS was selected after visual appraisal. AS contained 3 labels: T1w contrast enhanced tumor (ET), flair edema (ED) and non-enhanced tumor (NET). AS were then reviewed by a radiation oncologist and a neuroradiologist to produce the MS. ET and ED were corrected; surgical cavity (SC) was also segmented, either from the NET label or de novo. Dice-score, Hausdorff Distance (HD) and Average Hausdorff Distance (AHD) were used to quantify the similarity between AS and MS for each label. RESULTS AS succeeded to label 89.3% (82/92), 100% (92/92) and 85.8% (79/92) of ET, ED and NET respectively. Among the 4 algorithms in BTK, Zyx_2019 produced 36% of AS, mic-dkfz 32%, xfeng 18%, lfb_rwth 14%. Mean Dice-scores of 75.8%, 94.8% were found for ET and ED respectively. Mean HD and AHD were 25.2mm (±39.7), 2.8mm (±10.9) for ET; 14.9mm (±25.8), 0.9mm (±5.8) for ED. Concerning SC, Dice-scores were &amp;lt;0.1 for 49% (39/79), &amp;gt;0.6 for 30% (42/79). CONCLUSION BraTS Toolkit was trained to segment necrosis as the label NET. Still, it detected the surgical cavity and saved time for the MS in 51% of post-operative cases. Even though BTK was designed to segment pre-operative brain tumors, similarity metrics show that minimal or no manual corrections are necessary most of the time when used to segment ET and ED on post-operative MRI acquired in clinical routine. The development of a unique AS tool for pre and post-operative images would be useful in clinical practice.

DIAGNOSTIC ACCURACY OF MAGNETIC RESONANCE IMAGING IN DIAGNOSING BONE TUMORS KEEPING HISTOPATHOLOGICAL CORRELATION AS GOLD STANDARD

Objective: To determine the diagnostic accuracy of magnetic resonance imaging in diagnosing bone tumorskeeping histopathological as correlation gold standard.&#x0D; Study Design: Descriptive cross-sectional study.&#x0D; Place and Duration of Study: Departments of Radiology, Orthopedics and Pathology of Pakistan Institute ofMedical Sciences, Islamabad, from Jan 2018 to Jan 2019.&#x0D; Methodology: All the patients who had complain of bone deformity or pain with high suspicion of neoplasticpathology involving bone and soft tissue on radiograph were included in study. Patients were first diagnosed on conventional radiography followed by magnetic resonance imaging. Magnetic resonance imaging with contrast was done on Phillips 1.5 tesla machine. T1W, T2W, STIR images, Fat suppressed, PD spair and post contrast T1W images were obtained. Positive magnetic resonance imaging findings which were noted were; marrow involvement, cortical break, soft tissue involvement, joint involvement, neurovascular bundle involvement and post contrast enhancement on T1W imaging. Then bone biopsy was performed. The removed bone was sent for histopathological examination in all cases. The histopathological reports were collected. The results were entered in structured proformas. Data was collected after the informed consent. All the data was entered and analyzed using SPSS version-23.&#x0D; Results: Fifty patients of both genders were recruited during our study duration. 32 (64.0%) were male while 18(36.0%) were female patients. Mean age of the patient was 54.5 ± 14.3 years with range 18 to 80 years. Among the benign tumors vertebral hemangiomas were most commonly found 5 (10.0%) followed by osteochondroma which was 4 (8.0%), while among malignant........

Marmoset Brain Mapping V3: Population multi-modal standard volumetric and surface-based templates

The standard anatomical brain template provides a common space and coordinate system for visualizing and analyzing neuroimaging data from large cohorts of subjects. Previous templates and atlases for the common marmoset brain were either based on data from a single individual or lacked essential functionalities for neuroimaging analysis. Here, we present new population-based in-vivo standard templates and tools derived from multi-modal data of 27 marmosets, including multiple types of T1w and T2w contrast images, DTI contrasts, and large field-of-view MRI and CT images. We performed multi-atlas labeling of anatomical structures on the new templates and constructed highly accurate tissue-type segmentation maps to facilitate volumetric studies. We built fully featured brain surfaces and cortical flat maps to facilitate 3D visualization and surface-based analyses, which are compatible with most surface analyzing tools, including FreeSurfer, AFNI/SUMA, and the Connectome Workbench. Analysis of the MRI and CT datasets revealed significant variations in brain shapes, sizes, and regional volumes of brain structures, highlighting substantial individual variabilities in the marmoset population. Thus, our population-based template and associated tools provide a versatile analysis platform and standard coordinate system for a wide range of MRI and connectome studies of common marmosets. These new template tools comprise version 3 of our Marmoset Brain Mapping Project and are publicly available via marmosetbrainmapping.org/v3.html.

A preclinical study of diffusion-weighted MRI contrast as an early indicator of thermal ablation.

Intraoperative T2 -weighted (T2-w) imaging unreliably captures image contrast specific to thermal ablation after transcranial MR-guided focused ultrasound surgery, impeding dynamic imaging feedback. Using a porcine thalamotomy model, we test the unproven hypothesis that intraoperative DWI can improve dynamic feedback by detecting lesioning within 30 minutes of transcranial MR-guided focused ultrasound surgery. Twenty-five thermal lesions were formed in six porcine models using a clinical transcranial MR-guided focused ultrasound surgery system. A novel diffusion-weighted pulse sequence monitored the formation of T2-w and diffusion-weighted lesion contrast after ablation. Using postoperative T2-w contrast to indicate lesioning, apparent intraoperative image contrasts and diffusion coefficients at each lesion site were computed as a function of time after ablation, observed peak temperature, and observed thermal dose. Lesion sizes segmented from imaging and thermometry were compared. Image reviewers estimated the time to emergence of lesion contrast. Intraoperative image contrasts were analyzed using receiver operator curves. On average, the apparent diffusion coefficient at lesioned sites decreased within 5 minutes after ablation relative to control sites. In-plane lesion areas on intraoperative DWI varied from postoperative T2-w MRI and MR thermometry by mm2 and mm2 , respectively. The 0.25, 0.5, and 0.75 quantiles of the earliest times of observed T2-w and diffusion-weighted lesion contrast were 10.7, 21.0, and 27.8 minutes and 3.7, 8.6, and 11.8 minutes, respectively. The T2-w and diffusion-weighted contrasts and apparent diffusion coefficient values produced areas under the receiver operator curve of 0.66, 0.80, and 0.74, respectively. Intraoperative DWI can detect MR-guided focused ultrasound surgery lesion formation in the brain within several minutes after treatment.

NIMG-04. MRI EVALUATION OF THE EFFECT OF WHOLE BRAIN RADIOTHERAPY ON BRAIN METASTASIS

Abstract Poor prognosis of breast cancer brain metastasis partially results from the inability of therapeutics to penetrate the Blood-Brain-Barrier (BBB). Whole Brain Radiotherapy (WBRT) is standard-of-care for brain metastasis, however the early effects of fractionated WBRT on brain metastases have not been evaluated. Here, we applied longitudinal MRI to study WBRT’s effect on tumor volume, BBB permeability, and tumor-cell killing using anatomic, Dynamic Contrast Enhanced (DCE), and Diffusion-weighted (DW) MRI, evaluating tumor volume, permeability, and cytotoxic effect, respectively. The BCBM mouse model was established with left ventricle MDA-MB231-Br cell injection. MRI occurred before and 24h after 3 daily fractionated 4Gy WBRT (2.4Gy/min) or sham irradiation. In addition to anatomic MRI, DW MRI measured tissue ADC to study cytotoxic effect, and DCE MRI measured BBB permeability, quantified as the permeability variable Ktrans. Before treatment, T2-weighted images revealed hyperintense multifocal lesions in brains, and many had intact BBB indicated by no T1-w contrast-enhancement. WBRT tumors were smaller than sham irradiated tumors after 3 days (p&amp;lt; 0.05), while no difference in the number of new lesions was observed. DW MRI demonstrated increased ADC in WBRT tumors (p&amp;lt; 0.05), correlating well with elevated Caspase-3 staining of apoptotic cells. T1-w contrast enhanced images of tumors after treatment revealed no differences in the population of contrast-enhanced tumors between the WBRT and sham radiation groups. However, quantitative DCE MRI showed higher Ktrans in WBRT treated tumors relative to sham treated lesions, and an increase in Ktrans of WBRT tumors (p&amp;lt; 0.05), despite high permeability heterogeneity both inter- and intra-tumorally, indicating remaining impermeable BBB. In addition to monitoring tumor volume, longitudinal MRI provided non-invasive assessments of temporal and spatial changes in cellularity and vascular permeability of brain metastasis in response to WBRT, which may prove to be useful for defining an ideal treatment window for potential combination BCBM treatments.

MRI-based radiomics to predict lipomatous soft tissue tumors malignancy: a pilot study

ObjectivesTo develop and validate a MRI-based radiomic method to predict malignancies in lipomatous soft tissue tumors.MethodsThis retrospective study searched in the database of our pathology department, data from patients with lipomatous soft tissue tumors, with histology and gadolinium-contrast enhanced T1w MR images, obtained from 56 centers with non-uniform protocols. For each tumor, 87 radiomic features were extracted by two independent observers to evaluate the inter-observer reproducibility. A reduction of learning base dimension was performed from reproducibility and relevancy criteria. A model was subsequently prototyped using a linear support vector machine to predict malignant lesions.ResultsEighty-one subjects with lipomatous soft tissue tumors including 40 lipomas and 41 atypical lipomatous tumors or well-differentiated liposarcomas with fat-suppressed T1w contrast enhanced MR images available were retrospectively enrolled. Based on a Pearson’s correlation coefficient threshold at 0.8, 55 out of 87 (63.2%) radiomic features were considered reproducible. Further introduction of relevancy finally selected 35 radiomic features to be integrated in the model. To predict malignant tumors, model diagnostic performances were as follow: AUROC = 0.96; sensitivity = 100%; specificity = 90%; positive predictive value = 90.9%; negative predictive value = 100% and overall accuracy = 95.0%.ConclusionThis work demonstrates that radiomics allows to predict malignancy in soft tissue lipomatous tumors with routinely used MR acquisition in clinical oncology. These encouraging results need to be further confirmed in an external validation population.

T2* dynamic contrast enhanced MR perfusion for cervical cord lesions; does it work?

BackgroundThe goal of this work was to assess the value of magnetic resonance (MR) perfusion in narrowing the differential diagnosis of cord lesions.Thirty eight patients with different cervical cord lesions were involved in this study. This includes 20 males and 18 females, ranging between 13 and 60 years old.Conventional MR with T2W (axial and sagittal) and pre and post contrast T1W (axial and sagittal) in addition to the T2* MR perfusion sequence were done. The final diagnosis of cervical cord tumors was achieved by biopsy and histopathological diagnosis, while inflammatory lesions were proved by clinical, laboratory data and follow-up for six months.ResultsNeoplastic lesions were found in 13 patients, while 25 patients had inflammatory lesions. Relative cord/cerebral blood volume (rCBV) was significantly higher in neoplastic lesions when compared to non-neoplastic ones (2 ± 1.13 vs 1.01 ± 0.62), respectively. A cutoff value of 1.38 or higher has high sensitivity of 78% and specificity of 83% in differentiating between these lesions.ConclusionT2* is a valuable technique in differentiating neoplastic from non-neoplastic cervical cord lesions.

RTHP-26. DOSIMETRIC FEASIBILITY STUDY USING HIPPOCAMPAL AVOIDANCE WITH SIMULTANEOUS INTEGRATED BOOST WHOLE BRAIN RADIOTHERAPY (HA-SIB-WBRT)

Abstract BACKGROUND Recently Hippocampal Avoidance (HA-) WBRT has become a recommended treatment option in patients with multiple (≥ 5) brain metastases and good prognosis. We wanted to investigate the dosimetric feasibility of dose painting technique combining HA-WBRT with a simultaneous integrated boost (SIB) to tumours. METHOD 5 patients who had a CT simulation fused with brain MRI with fine cuts, were selected for this study. Volumes were contoured on T1w contrast images. Whole brain prescription dose was 30Gy in 12 fractions. A PTV margin of 2mm was applied to lesions, except when these were ≤5mm from organs at risks (OARs). A simultaneous integrated boost (SIB) of 48Gy and 40.2Gy was prescribed to these volumes respectively. Hippocampal constraints followed RTOG 0933 protocol. For lesions ≤5mm from OARs, the acceptable D0.03cc≤42Gy was allowed. All plans were planned on EclipseTM v.13.6 TPS using 6MV photons, VMAT technique with 3 coplanar and 1 non-coplanar arcs for Varian TrueBeam machine. RESULTS Plans had between 6–24 lesions with GTV and PTV of 3.02–11.32cc and 7.05–31.74cc respectively. 3 of the plans had lesions within/adjacent to brainstem or hippocampus. The achieved PTV_40.2Gy D95% 37.42–39.05Gy with Conformity Index (CI)(95%) 0.63–1.06, PTV_48Gy D95% 44.64–47.04Gy with CI(95%) 0.75–0.97 and GTV_48Gy D95% 47.44–50.16Gy. Whole brain Dmean 31.87–33.15Gy with a Homogeneity Index (D2%-D98%/Dmean) 0.18–0.58. Hippocampal D100% 8.69–10.1Gy, D0.03cc 16.5–40.43Gy and Dmean 12.66–24.68Gy. SUMMARY: There was a steep learning curve when adopting this technique and multiple plan iterations were made to achieve target constraints. To meet acceptable OAR constraints, SIB coverage was compromised. Lesions ≤5mm from hippocampus resulted in higher Hippocampal average Dmean 22.8Gy vs. 12.8Gy. The significance of this value should be tested in clinical trials. Overall, HA-SIB-WBRT seems feasible even with ≥ 5 brain metastases and could result in better brain metastases control then HA-WBRT alone.

The diagnostic precision of apparent diffusion coefficient (ADC) in grading of malignant endometrial lesions compared with histopathological findings.

Objective:The present study aimed to extract apparent diffusion coefficient (ADC) values from the diffusion-weighted imaging (DWI) sequence of endometrial lesions and compare them with tissue specimen results in order to determine the precision of ADC values in grading of malignant endometrial lesions.Methods:The present prospective study was conducted on 22 patients complaining of abnormal vaginal bleeding or evidence for endometrial thickening or masses detected using the ultrasound. Sampling was performed for pathological examination. MRI T2W+DWI+T1W+Post Contrast T1W were performed for patients. The statistical analysis was performed in SPSS 20 and MedCalc.Results:In this study, although the mean ADC value was lower in patients with endometrial cancer than those with benign endometrial lesions, the difference was not significant (0.86 ± 0.2 mm2/sec versus 1.33 ± 0.53 mm2/sec; P = 0.13). Using the cutoff point of 0.53, the sensitivity and specificity of ADC value for differentiating benign and malignant lesions, respectively, equaled 90.91 and 9.09, with an equal positive and negative predictive value of 50%. In patients with endometrioid adenocarcinoma, mean ADC value was 0.93 ± 0.15 in FIGO Grade I, and 0.76 ± 0.165 in FIGO Grade II. Based on the statistical test, no significant difference existed between the two groups in terms of ADC values.Conclusion:Results indicate that the use of a DWI sequence (ADC values) can prevent invasive measures in the diagnosis of benign endometrial lesions and the identification of malignant lesions with a high precision in many patients having accompanying diseases or other cases for which invasive measures cannot be used. Also, there is no significant difference in the mean ADC values between G1 and G2 of endometrioid carcinoma.

Comparison of Gadolinium Based T1 Weighted and Flair Mr Sequences for the Assessment of Leptomeningeal Enhancement in Meningoencephalitis

AIM: To compare the sensitivity and specificity of post contrast T1W sequence with post contrast FLAIR sequence of MRI brain for early detection of leptomeningitis. METHODS: A prospective comparative study was conducted for a period of 4 months. MRI brain examination was performed on 55 patients with suspicion of meningitis. Out of these, 48 patients were male and 7 were female. For those patients, contrast enhanced MRI brain with post contrast T1W sequence and post contrast FLAIR sequences were acquired. Then MRI findings were compared with CSF analysis results which was taken by lumbar puncture and considered as a “reference standard”. RESULTS: On CSF analysis of 55 patients, 43 patients were diagnosed positive as having meningitis and 12 patients were negative. Out of these 43 patients, post contrast FLAIR sequence was positive in 41 patients and 33 patients were positive on post contrast T1W sequence. In the finding of meningitis, post contrast FLAIR sequence sensitivity was 95.3% and specificity was 83.3%. While, post contrast T1W sequence sensitivity was 76.7% and 75% was specificity. CONCLUSION: The sensitivity and specificity of post contrast FLAIR sequence is more as compared to post contrast T1W sequence in the diagnosis of meningitis. In suspected cases of meningitis post contrast FLAIR sequence should be used as a routine sequence for the diagnosis of meningitis.

Electrochemical investigation of the Eu3+/2+ redox couple in complexes with variable numbers of glycinamide and acetate pendant arms.

The Eu3+/2+ redox couple provides a convenient design platform for responsive pO2 sensors for magnetic resonance imaging (MRI). Specifically the Eu2+ ion provides T1w contrast enhancement under hypoxic conditions in tissues, whereas, under normoxia, the Eu3+ ion can produce contrast from chemical exchange saturation transfer in MRI. The oxidative stability of the Eu3+/2+ redox couple for a series of tetraaza macrocyclic complexes was investigated in this work using cyclic voltammetry. A series of Eu-containing cyclen-based macrocyclic complexes revealed positive shifts in the Eu3+/2+ redox potentials with each replacement of a carboxylate coordinating arm of the ligand scaffold with glycinamide pendant arms. The data obtained reveal that the complex containing four glycinamide coordinating pendant arms has the highest oxidative stability of the series investigated.