3D T1w Research Articles

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 <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 < 0.005) vs. unfavorable (α1 > 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.

Scanner agnostic large-scale evaluation of MS lesion delineation tool for clinical MRI.

Patients with MS are MRI scanned continuously throughout their disease course resulting in a large manual workload for radiologists which includes lesion detection and size estimation. Though many models for automatic lesion segmentation have been published, few are used broadly in clinic today, as there is a lack of testing on clinical datasets. By collecting a large, heterogeneous training dataset directly from our MS clinic we aim to present a model which is robust to different scanner protocols and artefacts and which only uses MRI modalities present in routine clinical examinations. We retrospectively included 746 patients from routine examinations at our MS clinic. The inclusion criteria included acquisition at one of seven different scanners and an MRI protocol including 2D or 3D T2-w FLAIR, T2-w and T1-w images. Reference lesion masks on the training (n = 571) and validation (n = 70) datasets were generated using a preliminary segmentation model and subsequent manual correction. The test dataset (n = 100) was manually delineated. Our segmentation model https://github.com/CAAI/AIMS/ was based on the popular nnU-Net, which has won several biomedical segmentation challenges. We tested our model against the published segmentation models HD-MS-Lesions, which is also based on nnU-Net, trained with a more homogenous patient cohort. We furthermore tested model robustness to data from unseen scanners by performing a leave-one-scanner-out experiment. We found that our model was able to segment MS white matter lesions with a performance comparable to literature: DSC = 0.68, precision = 0.90, recall = 0.70, f1 = 0.78. Furthermore, the model outperformed HD-MS-Lesions in all metrics except precision = 0.96. In the leave-one-scanner-out experiment there was no significant change in performance (p < 0.05) between any of the models which were only trained on part of the dataset and the full segmentation model. In conclusion we have seen, that by including a large, heterogeneous dataset emulating clinical reality, we have trained a segmentation model which maintains a high segmentation performance while being robust to data from unseen scanners. This broadens the applicability of the model in clinic and paves the way for clinical implementation.

Automated subfield volumetric analysis of amygdala, hippocampus, and thalamic nuclei in mesial temporal lobe epilepsy

PurposeIdentifying relationships between clinical features and quantitative characteristics of the amygdala-hippocampal and thalamic subregions in mesial temporal lobe epilepsy (mTLE) may offer insights into pathophysiology and the basis for imaging prognostic markers of treatment outcome. Our aim was to ascertain different patterns of atrophy or hypertrophy in mesial temporal sclerosis (MTS) patients and their associations with post-surgical seizure outcomes. To assess this aim, this study is designed in 2 folds: (1) hemispheric changes within MTS group and (2) association with postsurgical seizure outcomes. Methods and materials27 mTLE subjects with mesial temporal sclerosis (MTS) were scanned for conventional 3D T1w MPRAGE images and T2w scans. With respect to 12 months post-surgical seizure outcomes, 15 subjects reported being seizure free (SF) and 12 reported continued seizures. Quantitative automated segmentation and cortical parcellation were performed using Freesurfer. Automatic labeling and volume estimation of hippocampal subfields, amygdala, and thalamic subnuclei were also performed. The volume ratio (VR) for each label was computed and compared between (1) between contralateral and ipsilateral MTS using Wilcoxon rank-sum test and (2) SF and not seizure free (NSF) groups using linear regression analysis. False Discovery rate (FDR) with significant level of 0.05 were used in both analyses to correct for multiple comparisons. ResultsAmygdala: The medial nucleus of the amygdala was the most significantly reduced in patients with continued seizures when compared to patients who remained seizure free. Hippocampus: Comparison of ipsilateral and contralateral volumes with seizure outcomes showed volume loss was most evident in the mesial hippocampal regions such as CA4 and hippocampal fissure. Volume loss was also most explicit in the presubiculum body in patients with continued seizures at the time of their follow-up. Ipsilateral MTS compared to contralateral MTS analysis showed the heads of the ipsilateral subiculum, presubiculum, parasubiculum, dentate gyrus, CA4, and CA3 were more significantly affected than their respective bodies. Volume loss was most noted in mesial hippocampal regions. Thalamus: VPL and PuL were the most significantly reduced thalamic nuclei in NSF patients. In all statistically significant areas, volume reduction was observed in the NSF group. No significant volume reductions were noted in the thalamus and amygdala when comparing ipsilateral to contralateral sides in mTLE subjects. ConclusionsVarying degrees of volume loss were demonstrated in the hippocampus, thalamus, and amygdala subregions of MTS, especially between patients who remained seizure-free and those who did not. The results obtained can be used to further understand mTLE pathophysiology. Clinical relevance/applicationIn the future, we hope these results can be used to deepen the understanding of mTLE pathophysiology, leading to improved patient outcomes and treatments.

Effect of geometric distortion correction on thickness and volume measurements of cortical parcellations in 3D T1w gradient echo sequences.

Automated brain volumetric analysis based on high-resolution T1-weighted MRI datasets is a frequently used tool in neuroimaging for early detection, diagnosis, and monitoring of various neurological diseases. However, image distortions can corrupt and bias the analysis. The aim of this study was to explore the variability of brain volumetric analysis due to gradient distortions and to investigate the effect of distortion correction methods implemented on commercial scanners. 36 healthy volunteers underwent brain imaging using a 3T magnetic resonance imaging (MRI) scanner, including a high-resolution 3D T1-weighted sequence. For all participants, each T1-weighted image was reconstructed directly on the vendor workstation with (DC) and without (nDC) distortion correction. For each participant's set of DC and nDC images, FreeSurfer was used for the determination of regional cortical thickness and volume. Overall, significant differences were found in 12 cortical ROIs comparing the volumes of the DC and nDC data and in 19 cortical ROIs comparing the thickness of the DC and nDC data. The most pronounced differences for cortical thickness were found in the precentral gyrus, the lateral occipital and postcentral ROI (2.69, -2.91% and -2.79%, respectively) while cortical volumes differed most prominently in the paracentral, the pericalcarine and lateral occipital ROI (5.52%, -5.40% and -5.11%, respectively). Correcting for gradient non-linearities can have significant influence on volumetric analysis of cortical thickness and volume. Since the distortion correction is an automatic feature of the MR scanner, it should be stated by each study that applies volumetric analysis which images were used.

Feasibility of online radial magnetic resonance imaging for adaptive radiotherapy of pancreatic tumors.

Online adaptive magnetic resonance (MR)-guided treatment planning for pancreatic tumors on 1.5T systems typically employs Cartesian 3D T 2w magnetic resonance imaging (MRI). The main disadvantage of this sequence is that respiratory motion results in substantial blurring in the abdomen, which can hamper delineation accuracy. This study investigated the use of two motion-robust radial MRI sequences as main delineation scan for pancreatic MR-guided radiotherapy. Twelve patients with pancreatic tumors were imaged with a 3D T 2w scan, a Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) scan (partially overlapping strips), and a 3D Vane scan (stack-of-stars), on a 1.5T MR-Linac under abdominal compression. The scans were assessed by three radiation oncologists for their suitability for online adaptive delineation. A quantitative comparison was made for gradient entropy and the effect of motion on apparent target position. The PROPELLER scans were selected as first preference in 56% of the cases, the 3D T 2w in 42% and the 3D Vane in 3%. PROPELLER scans sometimes contained a large interslice variation which would have compromised delineation. Gradient entropy was significantly higher in 3D T 2w patient scans. The apparent target position was more sensitive to motion amplitude in the PROPELLER scans, but substantial offsets did not occur under 10mm peak-to-peak. PROPELLER MRI may be a superior imaging sequence for pancreatic MRgRT compared to standard Cartesian sequences. The large interslice variation should be mitigated through further sequence optimization before PROPELLER can be adopted for online treatment adaptation.

Reliability of Cervical Neural Foramen Stenosis Grading Based on Axial Three-Dimensional Magnetic Resonance Images

Objective: To assess the reliability of cervical neural foramen stenosis (CNFS) grading by using three-dimensional (3D) T1W, 3D T2W, and twodimensional (2D) T2W images in axial plane. Materials and Methods: The authors enrolled 32 patients between December 2019 and February 2020 who underwent cervical spine magnetic resonance imaging (MRI) with clinical manifestations of cervical spondylosis. Two blinded radiologists interpreted the axial 3D T1W TSE, 3D T2W TSE, and 2D T2W TSE images using a 4-point visual scale for CNFS grading in all cervical levels. Intra-observer agreement of CNFS grading on the three imaging pulse sequences for each observer and inter-observer agreement between both observers were analyzed using intra-class correlation coefficient (ICC). Results: Three hundred eighty-four neural foramina were evaluated. The overall mean intra-observer agreement of CNFS grading was strong on the axial 3D T1W TSE, 3D T2W TSE, and 2D T2W TSE images for each observer with ICC values of 0.79 and 0.82. The overall mean inter-observer agreement for CNFS grading was strong on 3D T1W TSE, 3D T2W TSE, and 2D T2W TSE images with ICC values of 0.79, 0.79, and 0.86, respectively. Conclusion: Axial 3D T1W TSE, 3D T2W TSE, and 2D T2W TSE images exhibited comparable strong reliability in the grading of cervical neural foramen stenosis without the significant benefit of 3D over 2D technique. Keywords: Cervical spine; Neural foramen stenosis; MRI; Grading

Changes in the hippocampal volume in chronic migraine, episodic migraine, and medication overuse headache patients.

<p>Hippocampi are the structures located in the medial depths of both temporal lobes, mainly responsible for memory, navigation and regulation of emotions, and activated during the processing of pain and the modification of nociceptive stimuli. Chronic pain is thought to have stress-like detrimental modulatory effects on the hippocampal neurogenesis, and adults with chronic pain have been showed to have lower hippocampal volumes. The present study aims to show the relationship between headaches and hippocampal volume by comparing the right, left and total hippocampal volumes of patients with Episodic Migraine (EM), Chronic Migraine (CM) and Medication Overuse Headache (MOH) to those of the healthy control group using the Magnetic Resonance Imaging (MRI) technique, also by looking into the correlation between the number of painful days and attacks and the current hippocampal volumes.</p>. <p>A total of 30 patients (10 EM, 10 CM, 10 MOH) from 18 to 45 years of age diagnosed with migraine and also followed up by the neurology outpatient clinic from February to May 2022 and 30 healthy volunteers of similar ages and sexes to the patient group were included in the study. In addition to the routine cranial MRI protocols of all the participants, further cranial images were taken with the addition of the T1W 3D FSPGR sequence adjusted to the hippocampal body in the coronal plane and covering the whole brain. Hippocampal volumes were measured manually.</p>. <p>There were 27 females and 3 males in the patient group versus 28 females and 2 males in the control group, and no statistically significant differences in age and sex were found between the groups. The control group had higher average right, left and total hippocampal volumes than the whole patient group, but only the total hippocampal volume was significantly different between the groups. There was a negative correlation between the number of painful days and the measured right hippocampal and total hippocampal volumes; however, the measured values were not statistically significant.&nbsp;</p>. <p>It was concluded that the changes in the hippocampal volume in migraine might be associated with the pain characteristics of the disorder.&nbsp;</p>.

Improving the detection of new lesions in multiple sclerosis with a cascaded 3D fully convolutional neural network approach.

Longitudinal magnetic resonance imaging (MRI) has an important role in multiple sclerosis (MS) diagnosis and follow-up. Specifically, the presence of new lesions on brain MRI scans is considered a robust predictive biomarker for the disease progression. New lesions are a high-impact prognostic factor to predict evolution to MS or risk of disability accumulation over time. However, the detection of this disease activity is performed visually by comparing the follow-up and baseline scans. Due to the presence of small lesions, misregistration, and high inter-/intra-observer variability, this detection of new lesions is prone to errors. In this direction, one of the last Medical Image Computing and Computer Assisted Intervention (MICCAI) challenges was dealing with this automatic new lesion quantification. The MSSEG-2: MS new lesions segmentation challenge offers an evaluation framework for this new lesion segmentation task with a large database (100 patients, each with two-time points) compiled from the OFSEP (Observatoire français de la sclérose en plaques) cohort, the French MS registry, including 3D T2-w fluid-attenuated inversion recovery (T2-FLAIR) images from different centers and scanners. Apart from a change in centers, MRI scanners, and acquisition protocols, there are more challenges that hinder the automated detection process of new lesions such as the need for large annotated datasets, which may be not easily available, or the fact that new lesions are small areas producing a class imbalance problem that could bias trained models toward the non-lesion class. In this article, we present a novel automated method for new lesion detection of MS patient images. Our approach is based on a cascade of two 3D patch-wise fully convolutional neural networks (FCNNs). The first FCNN is trained to be more sensitive revealing possible candidate new lesion voxels, while the second FCNN is trained to reduce the number of misclassified voxels coming from the first network. 3D T2-FLAIR images from the two-time points were pre-processed and linearly co-registered. Afterward, a fully CNN, where its inputs were only the baseline and follow-up images, was trained to detect new MS lesions. Our approach obtained a mean segmentation dice similarity coefficient of 0.42 with a detection F1-score of 0.5. Compared to the challenge participants, we obtained one of the highest precision scores (PPVL = 0.52), the best PPVL rate (0.53), and a lesion detection sensitivity (SensL of 0.53).

ANGI-05. VASCULAR NORMALIZATION IN MURINE GLIOBLASTOMA IS CONTROLLED BY APLN-SIGNALING AND CAN BE MONITORED BY DCE-MR IMAGING IN VIVO

Abstract OBJECTIVE Glioblastoma (GBM) expansion is accompanied by aberrant tumor vascularization. We demonstrated that the peptide hormone Apelin (APLN) controls GBM neo-vascularization and that the APLN-receptor antagonist Apelin-F13A improved the efficiency and reduced the invasive side effect of established antiangiogenic therapy. Here we investigated if Apelin-F13A blunts the formation of vasogenic edema, which can be monitored by MRI in vivo. METHODS To investigate the role of APLN -signaling in regulating the tightness of the tumor vasculature we performed in vivo leakage assays using Evans-Blue dye and fluorescent dextran. By confocal immunofluorescence, we characterized the maturation of the tumor vasculature with respect to pericyte-coverage and established a dynamic contrast enhanced (DCE) MR imaging protocol to follow vascular edema formation. RESULTS We found that Evans-Blue extravasation is significantly increased by 3-fold in APLNKO tumors compared to controls. Uptake of fluorescent Dextran by CD31+ endothelia was quantified and increased massively from 200μm2 per high magnification field (HMF) in wildtype to 3500μm2 per HMF in APLNKO tumors. Interestingly, intracerebral infusion of Apelin-F13A enhanced pericyte coverage of the tumor vasculature by 50%, decreased Evans-Blue extravasation from 25 μg/ml in controls to 8 μg/ml in treated tumors significantly and efficiently reversed the APLN-dependent vasogenic edema assessed by comparison of T2w-MRI to HE tumor volumes. To follow vasogenic edema formation in vivo, T1w 3D FLASH images were acquired every second over a 360s time course after gadolinium-based MR-contrast agent injection and demonstrated a delayed washout of the contrast in APLN-deficient GBM. CONCLUSION Together, our study shows that DCE-MRI can document APLN-dependent intratumoral vascular normalization and allows inspecting vasogenic edema formation in vivo. In addition to its anti-angiogenic / anti-invasive effect, Apelin-F13A can potently reduce vasogenic edema and might thus serve as a multimodal therapy for the treatment of human GBM in the future.

PHSPP05 Presentation Time: 3:10 PM: Optimization Strategies in MR-Only Workflow for Interstitial and Intracavitary Gynecological HDR Brachytherapy

<h3>Purpose</h3> Image-guided interstitial and intracavitary gynecological brachytherapy (IGBT) is advancing towards MR-only workflows because of MR's superior soft-tissue contrast for tumor delineation and tissue segmentation. However, current treatment planning still necessitates the use of CT/MR fusion to aid in needle reconstruction and quality assurance (QA). In this work, we present strategies to visualize needles on MR and provide QA procedures for MR-only IGBT with comparisons to the conventional CT/MR approach. <h3>Materials and Methods</h3> Three 6F interstitial plastic needles and one CT/MR-compatible intrauterine tandem and ring (T&R) applicator set were examined in this study with the Flexitron afterloading system (Elekta Brachytherapy, Netherlands). To visualize the needles, they were immersed in demineralized water and scanned without markers in a 3T MRI system (Signa Premier; GE Healthcare, Milwaukee, WI). MR images were acquired with three protocols: 3D T1W (TR\TE 552\10 ms, and 1 mm voxel), 3D T2W (TR\TE 3051\104 ms, and 1 mm voxel) and silent Zero TE sequence (TR\TE 1060\20 ms, and 0.58 mm voxel). For QA, a 2D MR protocol (T1W, 7-10 mm thick slice) was utilized that allowed a projection-like image of an EBT3-film-based setup which was also imaged (with CT/x-ray markers) in CT (Philips, Netherlands) and x-ray imager (Varian Medical Systems, Palo Alto, CA). This setup consists of attaching catheters and four vitamin-D pills to EBT3 film pieces. The four corners of each film piece (5" x 4") were marked with skin markers that are visible in CT and MR images. These skin markers served as surrogates for a 4-point registration system between all images, and the vitamin-D pills were used to assess registration quality. An efficient film handling/scanning protocol was designed for this work and the source first dwell position (FDP) on the film was determined using a commissioned source localization algorithm. The FDP was compared between film, x-ray/CT markers, and applicator library models. <h3>Results</h3> For needle visualization, ZTE images generated a positive contrast for the interstitial needles as compared to conventional T1 and T2 images (See Figure). For QA, the 2D MR slice and x-ray image clearly displayed applicators, needles, vitamin-D pills, and skin markers allowing accurate registration to film images, visualization, and localization of the catheters, source positions, and markers in one fused image (See Figure). The tandem tip from MR was 1.1 mm longer than that of the x-ray and model which was not evident in the vitamin-D matching, implying a potential MR artifact at the tip (Sub-Figure B) which should be taken into account while planning. FDP reconstruction errors from the needle tip in MR with respect to film and x-ray markers were less than 1 mm (Sub-Figure D). <h3>Conclusions</h3> While further investigation is required, ZTE imaging offers a promising alternative to CT imaging for needle reconstruction supporting MR-only gynecological brachytherapy treatment planning. However, MR-only workflow requires special considerations in QA to account for possible systematic shifts that could exceed the level of accuracy achieved in x-ray-based IGBT.

A Novel Approach to Vessel-Sparing Prostate Radiotherapy Using MR-Only Simulation and Non-Contrast MR Angiography: Vessel Delineation Feasibility and SBRT Dosimetric Analysis

<h3>Purpose/Objective(s)</h3> Erectile dysfunction is a common side effect of prostate cancer treatment, including prostate radiotherapy (RT). Vessel-sparing RT with avoidance of the internal pudendal artery (IPA) has shown promising rates of erectile function in non-randomized data. Implementation of vessel-sparing RT can be complicated by factors such as difficulty of MRI registration to planning CT and clinical desires to reduce routine use of IV contrast. We optimized a non-contrast MR angiography (ncMRA) sequence and compared IPA delineation on ncMRA with contrast MRA in a cohort of patients undergoing prostate stereotactic body RT (SBRT). We further performed dosimetric analysis on the IPAs. <h3>Materials/Methods</h3> Prostate cancer patients were prospectively enrolled on an IRB-approved MR imaging protocol. Treatment was with SBRT to a dose of 37.5 – 40 Gy in 5 fractions every other day. MR-only simulation was performed including MRA (2D T1w fast field echo (FFE) time-of-flight) and ncMRA (3D T1 FFE, 12 dynamics, temporal resolution = 14 seconds) sequences. Bilateral IPAs were delineated by a single blinded observer on MRA and ncMRA sequences. Analytical comparison between IPA contours on each patient was performed using mean distance to agreement (MDA), Dice similarity coefficient (DSC), and Jaccard index (JI). DSC and JI were also performed on IPA contour expansions of 2mm and 5mm. Dosimetry evaluated D50 and D05 on raw contours and 5mm expansion, and t-test compared dose on MRA and ncMRA. <h3>Results</h3> 10 patients were enrolled; 8 received 40 Gy, and 2 received 37.5 Gy. The median (range) analytical difference between IPA contours on MRA and ncMRA for MDA, DSC, and JI were 2.21 mm (0.99 – 4.16 mm), 0.54 (0.51 – 0.65), 0.37 (0.34 – 0.48), respectively. Using 2 mm contour expansion, DSC and JI were 0.69 (0.61 – 0.77) and 0.53 (0.44 – 0.63), while 5 mm expansion produced DSC and JI of 0.77 (0.69 – 0.85) and 0.62 (0.52 – 0.73). Dosimetrically, there was no difference in left and right IPA D50 or D05 between contours on MRA and ncMRA (Table). On 5mm expansion, the median (range) of D50 and D05 to IPA contours on ncMRA were 16.2 Gy (11.2 – 22.0 Gy) and 26.7 Gy (17.5 – 31.7 Gy). <h3>Conclusion</h3> This study found that delineation of IPAs using ncMRA was feasible and produced contours similar to those delineated on contrast MRA with no dosimetric differences. We feel that this agreement between imaging modalities demonstrates that ncMRA can be used alone for IPA delineation in vessel-sparing RT. Furthermore, the dosimetric findings of this study can serve as a baseline for expected IPA dose in prostate SBRT.

Pediatric reference values of anterior visual pathway structures measured with axis-correction on high-resolution 3D T2 fast spin echo sequences

BackgroundThe size of the anterior visual pathway (AVP) structures is affected by patient age and pathology. Normative data is useful when determining whether pathology is present. AVP structures do not respect the standard planes of magnetic resonance (MR) imaging. The aim of this study was to produce normative age-related and axis-corrected data of the AVP structures using multiplanar reformation (MPR) of high-resolution 3D T2-weighted fast spin echo (3D T2w FSE) images.MethodsFor each patient 32 measurements of AVP structures were obtained in 145 children (2 months - 18 years) with normal brain MR studies on high-resolution 3D T2w FSE images adjusted to the axis of each AVP structure. Descriptive statistics were calculated for different age classes and growth models were fitted to the data and assessed for their performance to create a formal statistical model that allows inference beyond the sample.ResultsDescriptive statistics were compiled in a reference table and prediction plots in relation to age, height, and body surface area (BSA) were obtained from the best overall performing statistical model, also taking field strength (1.5 vs. 3 T) into account. Intraclass correlation coefficient values were calculated for all variables ranging from 0.474 to 0.967, the most reliable being the transverse diameter of the globe, the maximum diameter of the retrobulbar nerve sheath, the intracranial segment of the optic nerve and the transverse diameter of the chiasm. The maximum retrobulbar diameter of the optic nerve sheath and the lateral superoinferior diameter of the chiasm showed no statistically significant change with age.ConclusionDetailed charts of reference values for AVP structures as well as prediction plots in relation to age, height and BSA were established using axis-corrected measurements from the MPR of high-resolution 3D T2w FSE images. Furthermore, an Excel spreadsheet that allows users to calculate normative values for the 9 AVP structures of key interest is provided as supplementary material.

The effect of respiration-induced target motion on 3D magnetic resonance images used to guide radiotherapy

3D Magnetic Resonance Imaging (MRI) is used in radiation therapy for reference planning and, lately, for adaptive treatments on MR accelerators. This study aimed to investigate the impact of different types of respiratory motion on the apparent target position and extent in such scans. An MRI motion phantom with a 30mm diameter target was used to simulate cranial-caudal (CC) motion and imaged at an MR-Linac using a standard clinically released 3D T2w sequence. Scans were acquired for each combination of functions (sin(t), sin4(t) and sin12(t)), peak-to-peak amplitudes(5, 10, 15 and 20mm), and periods (4, 5 and 6s). Furthermore, respiration CC motion patterns fromtwo patients were used. Motion functions were shifted such that the time average target position would match a static reference scan at 0-position. The target was automatically identified in coronal and sagittal images using k-means clustering. The mean position and area of the target were calculated and compared to the reference scan. Artefacts increased with amplitude and depended on the motion type. Sin(t) and sin4(t) oscillations resulted in a blurring of the target, which led to an increased target area, while sin12(t) motion did not show significant changes in the target area. However, for the sin12(t) motion, the offset in apparent position was prominent, while that was not the case for the sin(t) and sin4(t) motion. The patient respiration motion profiles showed similar trends. In 3D MRI, target motion can change apparent tumour extent and apparent position. The changes increase with motion amplitude and depend on the motion type.

Comparison of compressed sensing-sensitivity encoding (CS-SENSE) accelerated 3D T2W TSE sequence versus conventional 3D and 2D T2W TSE sequences in rectal cancer: a prospective study

PurposeThis study aimed to evaluate the image quality and diagnostic value of compressed sensing-sensitivity encoding (CS-SENSE) accelerated 3-dimensional (3D) T2-weighted turbo spin-echo (T2W TSE) sequence in patients with rectal cancer compared with conventional 3D and 2-dimensional (2D) sequences.MethodsA total of 54 patients who underwent the above three sequences were enrolled. Two radiologists independently reviewed the image quality using an ordinal 5-point Likert scale. The quantitative measurement was performed to calculate the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The diagnostic value was assessed using TN staging, extramural vascular invasion and mesorectal fascia status. Friedman and McNemar’s tests were applied for comparative analysis.ResultsForty-two patients were successfully included. Compared with 3D and 2D sequences, the CS-SENSE 3D sequence speeded up by 39% and 23%, respectively. The edge sharpness of CS-SENSE 3D images was similar to that of 3D and 2D images. The noise of CS-SENSE 3D images was comparable to that of 3D images but higher than that of 2D images. The SNRtumor and SNRrectal wall of CS-SENSE 3D images were considerably lower than those of 3D and 2D images. The CNR of CS-SENSE 3D images was similar to that of 3D images but lower than that of 2D images. However, no considerable differences were noted in diagnostic value among the three sequences.ConclusionsCS-SENSE 3D T2 sequence provided comparable diagnostic performance, with substantially reduced imaging time and no significant sacrifices in image quality. This technique may serve as a reliable tool for evaluating rectal cancer.Graphical abstract

Change in Morphological Features of Enlarged Subarachnoid Spaces Following Treatment in Idiopathic Normal Pressure Hydrocephalus.

Focally enlarged sulci (FES) are areas of proposed extraventricular fluid entrapment that may occur within idiopathic normal pressure hydrocephalus (iNPH) with radiographic evidence of disproportionately enlarged subarachnoid-space hydrocephalus (DESH), and should be differentiated from atrophy. To evaluate for change in FES size and pituitary height after shunt placement in iNPH. Retrospective. A total of 125 iNPH patients who underwent shunt surgery and 40 age-matched controls. 1.5 T and 3T. Axial T2w FLAIR, 3D T1w MPRAGE, 2D sagittal T1w. FES were measured in three dimensions and volume was estimated by assuming an ellipsoid shape. Pituitary gland height was measured in the mid third of the gland in iNPH patients and controls. Wilcoxon signed-rank test for comparisons between MRI measurements; Wilcoxon rank sum test for comparison ofcases/controls. Significance level was P < 0.05. Fifty percent of the patients had FES. FES volume significantly decreased between the pre and first postshunt MRI by a median of 303 mm3 or 30.0%. Pituitary gland size significantly increased by 0.48 mm or 14.4%. FES decreased significantly by 190 mm3 or 23.1% and pituitary gland size increased significantly by 0.25 mm or 6% between the first and last postshunt MRI. Decrease in size of FES after shunt placement provides further evidence that these regions are due to disordered cerebrospinal fluid (CSF) dynamics and should not be misinterpreted as atrophy. A relatively smaller pituitary gland in iNPH patients that normalizes after shunt is a less-well recognized feature of altered CSF dynamics. 3 TECHNICAL EFFICACY: Stage 2.

High Fall Risk Associated With Memory Deficit and Brain Lobes Atrophy Among Elderly With Amnestic Mild Cognitive Impairment and Mild Alzheimer's Disease.

ObjectivesThis study aimed to primarily examine the association between memory deficit and increased fall risk, second, explore the underlying neuroanatomical linkage of this association in the elderly with aMCI and mild AD.MethodsIn this cross-sectional study, a total of 103 older adults were included (55 cognitively normal, CN; 48 cognitive impairment, CI, elderly with aMCI, and mild AD). Memory was assessed by the Auditory Verbal Learning Test (AVLT). Fall risk was evaluated by the Timed Up and Go (TUG) Test, heel strike angles, and stride speed, which were collected by an inertial-sensor-based wearable instrument (the JiBuEn™ gait analysis system). Brain volumes were full-automatic segmented and quantified using AccuBrain® v1.2 from three-dimensional T1-weighted (3D T1W) MR images. Multivariable regression analysis was used to examine the extent of the association between memory deficit and fall risk, the association of brain volumes with memory, and fall risk. Age, sex, education, BMI, and HAMD scores were adjusted. Sensitivity analysis was conducted.ResultsCompared to CN, participants with aMCI and mild AD had poorer cognitive performance (p < 0.001), longer TUG time (p = 0.018), and smaller hippocampus and medial temporal volumes (p = 0.037 and 0.029). In the CI group, compared to good short delayed memory (SDM) performance (AVLT > 5), the elderly with bad SDM performance (AVLT ≤ 3) had longer TUG time, smaller heel strike angles, and slower stride speed. Multivariable regression analysis showed that elderly with poor memory had higher fall risk than relative good memory performance among cognitive impairment elderly. The TUG time increased by 2.1 s, 95% CI, 0.54∼3.67; left heel strike angle reduced by 3.22°, 95% CI, −6.05 to −0.39; and stride speed reduced by 0.09 m/s, 95% CI, −0.19 to −0.00 for the poor memory elderly among the CI group, but not found the association in CN group. In addition, serious medial temporal atrophy (MTA), small volumes of the frontal lobe and occipital lobe were associated with long TUG time and small heel strike angles; small volumes of the temporal lobe, frontal lobe, and parietal lobe were associated with slow stride speed.ConclusionOur findings suggested that memory deficit was associated with increased fall risk in the elderly with aMCI and mild AD. The association might be mediated by the atrophy of medial temporal, frontal, and parietal lobes. Additionally, increased fall risk, tested by TUG time, heel stride angles, and stride speed, might be objective and convenient kinematics markers for dynamic monitoring of both memory function and fall risk.

Impact of the implementation of a Contouring Atlas on Therapeutic Radiographer Inter-observer Contour Variation in Prostate Radiotherapy

Republished from RTi3 2021 due to author omission. Purpose: The clinical implementation of MR-guided adaptive radiotherapy requires fast, accurate delineation of target volumes and organs at risk (OAR's). It is important with the introduction of new online imaging strategies to mitigate the potential for contouring inaccuracies, as they could potentially result in treatment errors. To support the introduction of radiographer-led real-time MR-guided adaptive radiotherapy on the MR-Linac (MRL), an MR contouring atlas for prostate radiotherapy delineation guidance was developed. This tool was based on the ‘Male Pelvis Normal Tissue RTOG Consensus Contouring’ recommendations and local guidelines, and its impact on inter-observer variation was subsequently determined. Methods: Multi-disciplinary consensus on the contouring of the prostate, seminal vesicles and associated OAR's was obtained by developing a contouring guide (3 MRL radiographers, 2 clinical oncologists and 1 diagnostic radiographer). Contours were defined on T2-weighted three-dimensional turbo spin echo sequences, reconstructed axially (T2w 3D Tra) acquired on the MRL. To assess the guide's utility, 9 radiographers with varying MRL experience contoured 5 MRI scans in the Monaco treatment planning system, from 5 different patients (n= 25). Each radiographer contoured the prostate, seminal vesicles, bladder, and rectum on each data set before and after the introduction of the atlas. The ‘after’ contours were generated &gt;21 days following the ‘before’ contours to minimise the effects of repetition. In addition to DICE coefficients and descriptive statistics, inter-observer contour variations, time to contour and observer contouring confidence was determined prior to and following the introduction of the atlas utilising a 5-point Likert scale (observers score confidence 1 not confident to 5 extremely confident). Results: The contouring atlas has been agreed by the multidisciplinary team incorporating locally defined gold-standard contours and RTOG guidance. Five sets of images from 5 different patients have been acquired on the MRL (T2w 3D Tra) and to date the ‘before’ contours have been completed. Mean contouring time without the atlas for all contours was 54 minutes with the rectum and prostate contouring taking the greatest amount of time, a mean time of 15 minutes each. Contour confidence levels varied between participants greatly. Minimum contour variability between the observers was for the bladder contour, with the maximum range being 22.0cm3. This corresponded with the participants scoring the bladder contour with the higher confidence level rates (majority scoring ≥ 3). Prostate and rectum structures had the greatest contour variability between observers with the maximum range being 32.6cm3 and 36.1 cm3 respectively. Confidence levels also corresponded with this large variation with majority of observers scoring ≤ 2. The same radiographers will repeat the process with the aid of the contouring atlas. Conclusion: It is anticipated that the new atlas for contouring prostate and surrounding OAR anatomy during both online and offline radiotherapy planning scenarios will reduce inter-observer variability, uncertainty and the time needed to contour. This will be of particular benefit in future adapt to shape pathways.

Spinal cord grey matter atrophy in Multiple Sclerosis clinical practice

PurposeSeveral studies have indicated the relevance of spinal cord grey matter atrophy for Multiple Sclerosis (MS) related disability. This work aimed at evaluating feasibility and clinical relevance of MRI-derived estimations of spinal cord grey matter atrophy in clinical practice. MethodsA convenience sample of MS patients (n=48) and healthy controls (HC, n=11) was scanned using brain sagittal 3D T1w (MPRAGE) and transverse T2w-FLAIR, and transverse single-slice spinal cord 2D heavily T1w (PSIR: phase-sensitive inversion recovery) sequences. An experienced technician with neuroradiological supervision used a semiautomated thresholding method implemented in JIM software on PSIR sequences to obtain cross-sectional area (CSA) of the spinal canal (CSAcanal), whole cord (CSAcord), grey (CSAgm) and white matter (CSAwm) at C2-C3. MPRAGE and T2w-FLAIR sequences were used to obtain brain parenchymal, grey and white matter fractions (BPF, GMF and WMF) using the Statistical Parametric Mapping software. Appropriate statistical tests were used before and after age and sex adjustment. ResultsCSAgm and CSAwm could be obtained in all HC, but only 18 patients (37.5%) due to presence of lesions at C2-C3. Significant univariate associations between EDSS and BPF (rho =−0.376, p=0.015), GMF (rho =−0.287, p=0.069), CSAcanal (rho =−0.310, p=0.049), CSAcord (rho =−0.533 p<0.001) and CSAgm (rho =−0.511, p=0.062) were detected. After age/sex adjustment trends were observed for CSAcanal and CSAcord. ConclusionIn a clinical practice setting, relevance of spinal cord grey matter is confirmed, but cervical cord lesions could greatly hamper its application. Clinical associations with disability have been observed and seem stronger for spinal cord than for brain atrophy measures.

Investigation of the Inter- and Intrascanner Reproducibility and Repeatability of Radiomics Features in T1-Weighted Brain MRI.

Radiomics is the high throughput analysis of medical images using computer algorithms, which specifically assess textural features. It has increasingly been proposed as a tool for the development of imaging biomarkers. However, an important acknowledged limitation of radiomics is the lack of reproducibility of features produced. To assess reproducibility and repeatability of radiomics variables in brain MRI through a multivisit, multicenter study. Retrospective. Fourteen individuals visiting three institutions twice, 10 males with the mean age of 36.3 years and age range 25-51. 3D T1W inversion recovery on three 1.5-T General Electric scanners. Radiomics analysis by a consultant radiologist performed on the T1W images of the whole brain on all visits. All possible radiomics features were generated. Concordance correlation coefficient (CCC) and dynamic range (DR) for all variables were calculated to assess the test-retest repeatability. Intraclass correlation coefficients (ICCs) were calculated to investigate the reproducibility of features across centers. Of 1596 features generated, 57 from center 1, 15 from center 2, and 22 from center 3 had a CCC > 0.9 and DR > 0.9. Eight variables had CCC > 0.9 and DR > 0.9 in all centers. Forty-one variables had an ICC of >0.9. No variables had CCC > 0.9, DR > 0.9, and ICC > 0.9. Repeatability and reproducibility of variables is a significant limitation of radiomics analysis in 3DT1W brain MRI. Careful selection of radiomic features is required. 4 TECHNICAL EFFICACY STAGE: 2.

Whole-Body Magnetic Resonance Imaging in the Large Population-Based German National Cohort Study: Predictive Capability of Automated Image Quality Assessment for Protocol Repetitions.

Reproducible image quality is of high relevance for large cohort studies and can be challenging for magnetic resonance imaging (MRI). Automated image quality assessment may contribute to conducting radiologic studies effectively. The aims of this study were to assess protocol repetition frequency in population-based whole-body MRI along with its effect on examination time and to examine the applicability of automated image quality assessment for predicting decision-making regarding repeated acquisitions. All participants enrolled in the prospective, multicenter German National Cohort (NAKO) study who underwent whole-body MRI at 1 of 5 sites from 2014 to 2016 were included in this analysis (n = 11,347). A standardized examination program of 12 protocols was used. Acquisitions were carried out by certified radiologic technologists, who were authorized to repeat protocols based on their visual perception of image quality. Eleven image quality parameters were derived fully automatically from the acquired images, and their discrimination ability regarding baseline acquisitions and repetitions was tested. At least 1 protocol was repeated in 12% (n = 1359) of participants, and more than 1 protocol in 1.6% (n = 181). The repetition frequency differed across protocols (P < 0.001), imaging sites (P < 0.001), and over the study period (P < 0.001). The mean total scan time was 62.6 minutes in participants without and 67.4 minutes in participants with protocol repetitions (mean difference, 4.8 minutes; 95% confidence interval, 4.5-5.2 minutes). Ten of the automatically derived image quality parameters were individually retrospectively predictive for the repetition of particular protocols; for instance, "signal-to-noise ratio" alone provided an area under the curve of 0.65 (P < 0.001) for repetition of the Cardio Cine SSFP SAX protocol. Combinations generally improved prediction ability, as exemplified by "image sharpness" plus "foreground ratio" yielding an area under the curve of 0.89 (P < 0.001) for repetition of the Neuro T1w 3D MPRAGE protocol, versus 0.85 (P < 0.001) and 0.68 (P < 0.001) as individual parameters. Magnetic resonance imaging protocol repetitions were necessary in approximately 12% of scans even in the highly standardized setting of a large cohort study. Automated image quality assessment shows predictive value for the technologists' decision to perform protocol repetitions and has the potential to improve imaging efficiency.