T2-weighted Turbo Spin Echo Research Articles

Application of Contrast-Enhanced 3-Dimensional T2-Weighted Volume Isotropic Turbo Spin Echo Acquisition Sequence in the Diagnosis of Prolactin-Secreting Pituitary Microadenomas

This study aimed to investigate the value of contrast-enhanced 3-dimensional (3D) T2-weighted (T2W) Volume Isotropic Turbo Spin Echo Acquisition (VISTA) sequence in prolactin-secreting pituitary adenoma diagnosis. We enrolled 158 patients with hyperprolactinemia. Coronal dynamic contrast-enhanced (DCE) T1 spin echo and T2W VISTA sequences were performed. The detection of pituitary microadenomas in 3 imaging groups (DCE magnetic resonance imaging [MRI], VISTA, and DCE MRI + VISTA) were compared using McNemar test and χ2 test. The DCE MRI + VISTA group detected 28 more pituitary microlesions than DCE MRI alone. Among these, 20 lesions were clearly observed on VISTA images but were negative on DCE MRI. The combined sequences showed higher sensitivity (85.3%) and diagnostic accuracy (89.2%) for adenoma detection than any of the sequences alone (P < 0.01). We noted that in 65.7% of the patients with adenoma (46 of 70), a "hypointense rim" was present around the lesion on the VISTA images. Of them, 11 patients underwent surgery. Histopathology confirmed that the "hypointense rim" was a pseudocapsular structure at the edge of the adenoma. For patients with hyperprolactinemia, the 3D T2W VISTA sequence is an important supplement to DCE MRI, because it could improve the detection rate of pituitary microadenomas.

Measuring HCC Tumor Size in MRI-The Sequence Matters!

Background: The aim of this paper was to assess and compare the accuracy of common magnetic resonance imaging (MRI) pulse sequences in measuring the lesion sizes of hepatocellular carcinomas (HCCs) with respect to the Milan criteria and histopathology as a standard of reference. Methods: We included 45 patients with known HCC who underwent contrast-enhanced MRI of the liver prior to liver transplantation or tumor resection. Tumor size was assessed pathologically for all patients. The MRI protocol contained axial T2-weighted images as well as T1-weighted imaging sequences before and after application of Gd-EOB-DTPA. Tumor diameters, the sharpness of lesions, and the presence of artifacts were evaluated visually on all available MRI sequences. MRI measurements and pathologically assessed tumor dimensions were correlated using Pearson’s correlation coefficient and Bland–Altman plots. The rate of misclassifications following Milan criteria was assessed. Results: The mean absolute error (in cm) of MRI size measurements in comparison to pathology was the smallest for the hepatobiliary phase T1-weighted acquisition (0.71 ± 0.70 cm, r = 0.96) and largest for the T2w turbo-spin-echo (TSE) sequence (0.85 ± 0.78 cm, r = 0.94). The misclassification rate regarding tumor size under the Milan criteria was lowest for the T2w half-Fourier acquisition single-shot turbo spin-echo sequence and the hepatobiliary phase T1w acquisition (each 8.6%). The highest rate of misclassification occurred in the portal venous phase T1w acquisition and T2w TSE sequence (each 14.3%). Conclusions: The hepatobiliary phase T1-weighted acquisition seems to be most accurate among commonly used MRI sequences for measuring HCC tumor size, resulting in low rates of misclassification with respect to the Milan criteria.

Evaluation of Visualizing the Prostatic Urinary Tract in MRI With a Super Resolution Deep Learning Model for Urethra Sparing Radiotherapy

<h3>Purpose/Objective(s)</h3> In the treatment planning for urethra-sparing radiation therapy in localized prostate cancer, it is important to visualize the prostatic urinary tract to reduce the risk of urinary symptoms linked to the urethral dose. We developed a methodology for visualizing the prostatic urinary tract by post-urination magnetic resonance imaging (PU-MRI) without using a urethral catheter for urethra-sparing radiotherapy. Several super-resolution (SR) deep learning models were proposed for improving image quality. This study investigated whether these SR deep learning models improve the visibility of the prostatic urinary tract in PU-MRI. <h3>Materials/Methods</h3> We enrolled 30 patients who had previously undergone real-time-image-gated spot scanning proton therapy (RGPT) by inserting fiducial markers at our institution from October 2019 to October 2020. PU-MRI was performed using a non-contrast high-resolution two-dimensional T2-weighted turbo spin-echo (TSE) imaging sequence. Four different SR deep learning models were constructed: the EDSR (enhanced deep SR network), WDSR (widely activated SR network), SRGAN (SR generative adversarial network), and RDN (residual dense network). All models were trained using a diverse 2K resolution high-quality image dataset. We imported PU-MRIs as low-resolution images and exported four SR images that were enlarged using one of the models each. To assess the performance of the proposed SR image compared to PU-MRI, we used the complex wavelet structural similarity index measure (CW-SSIM) as the quantitative metric. A 1-to-5 scale was used to subjectively evaluate the visibility of the prostatic urinary tract by two radiation oncologists. <h3>Results</h3> The mean (± standard deviation) of the CW-SSIM in the EDSR, WDSR, SRGAN, and RDN were 0.999 ± 0.001, 0.999 ± 0.002, 0.993 ± 0.002, and 0.997 ± 0.002, respectively. The mean prostatic urinary tract visibility scores for oncologist 1 and 2 were 3.70 ± 0.64 and 3.53 ± 0.99 for PU-MRI, 3.67 ± 0.60 and 2.70 ± 0.82 for EDSR, 3.70 ± 0.53 and 2.73 ± 0.81 for WDSR, 3.67 ± 0.65 and 2.73 ± 0.81 for SRGAN, and 4.37 ± 0.61 and 3.73 ± 0.93 for RDN, respectively. <h3>Conclusion</h3> This study investigated whether the combination of PU-MRI and SR deep learning models improves visibility of the prostatic urinary tract. The results suggest that SR images using RDN are highly similar to the original image and subjectively improve the visibility of the prostatic urinary tract.

Pulmonary Imaging of Immunocompromised Patients during Hematopoietic Stem Cell Transplantation using Non-Contrast-Enhanced Three-Dimensional Ultrashort Echo Time (3D-UTE) MRI.

To evaluate the feasibility of non-contrast-enhanced three-dimensional ultrashort echo time (3D-UTE) MRI for pulmonary imaging in immunocompromised patients during hematopoietic stem cell transplantation (HSCT). MRI was performed using a stack-of-spirals 3D-UTE sequence (slice thickness: 2.34mm; matrix: 256 × 256; acquisition time: 12.7-17.6 seconds) enabling imaging of the entire thorax within single breath-holds. Patients underwent MRI before HSCT initiation, in the case of periprocedural pneumonia, before discharge, and in the case of re-hospitalization. Two readers separately assessed the images regarding presence of pleural effusions, ground glass opacities (GGO), and consolidations on a per lung basis. A T2-weighted (T2w) multi-shot Turbo Spin Echo sequence (BLADE) was acquired in coronal orientation during breath-hold (slice thickness: 6.00mm; matrix: 320 × 320; acquisition time: 3.1-5.5 min) and read on a per lesion basis. Low-dose CT scans in inspiration were used as reference and were read on a per lung basis. Only scans performed within a maximum of three days were included in the inter-method analyses. Interrater agreement, sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of 3D-UTE MRI were calculated. 67 MRI scans of 28 patients were acquired. A reference CT examination was available for 33 scans of 23 patients. 3D-UTE MRI showed high sensitivity and specificity regarding pleural effusions (n = 6; sensitivity, 92 %; specificity, 100 %) and consolidations (n = 22; sensitivity 98 %, specificity, 86 %). Diagnostic performance was lower for GGO (n = 9; sensitivity, 63 %; specificity, 84 %). Accuracy rates were high (pleural effusions, 98 %; GGO, 79 %; consolidations 94 %). Interrater agreement was substantial for consolidations and pleural effusions (κ = 0.69-0.82) and moderate for GGO (κ = 0.54). Compared to T2w imaging, 3D-UTE MRI depicted the assessed pathologies with at least equivalent quality and was rated superior regarding consolidations and GGO in ~50 %. Non-contrast 3D-UTE MRI enables radiation-free assessment of typical pulmonary complications during HSCT procedure within a single breath-hold. Yet, CT was found to be superior regarding the identification of pure GGO changes. · 3D-UTE MRI of the thorax can be acquired within a single breath-hold.. · 3D-UTE MRI provides diagnostic imaging of pulmonary consolidations and pleural effusions.. · 3D-UTE sequences improve detection rates of ground glass opacities on pulmonary MRI.. · 3D-UTE MRI depicts pulmonary pathologies at least equivalent to T2-weighted Blade sequence.. · Metz C, Böckle D, Heidenreich JF et al. Pulmonary Imaging of Immunocompromised Patients during Hematopoietic Stem Cell Transplantation using Non-Contrast-Enhanced Three-Dimensional Ultrashort Echo Time (3D-UTE) MRI. Fortschr Röntgenstr 2022; 194: 39 - 48.

Orthotopic Versus Allotopic Implantation: Comparison of Radiological and Pathological Characteristics.

BackgroundIn experimental animal models, implantation location might influence the heterogeneity and overall development of the tumor, leading to an interpretation bias.PurposeTo investigate the effects of implantation location in experimental tumor model using magnetic resonance imaging (MRI) and pathological findings.Study TypeProspective.SubjectsForty‐five breast cancer‐bearing mice underwent orthotopic (N = 15) and heterotopic (intrahepatic [N = 15] and subcutaneous [N = 15]) implantation.Field Strength/SequenceSequences including: T1‐weighted turbo spin echo sequence, T2‐weighted blade sequence, diffusion‐weighted imaging, pre‐ and post‐contrast T1 mapping, multi‐echo T2 mapping at 3.0 T.AssessmentMRI was performed at 7, 14, and 21 days after implantation. Native T1, post‐contrast T1, T2, and apparent diffusion coefficient (ADC) of tumors, the tumor volume and necrosis volume within tumor were obtained. Lymphocyte cells from H&E staining, Ki67‐positive, and CD31‐positive cells from immunohistochemistry were determined.Statistical TestsOne‐way analysis of variance and Spearman's rank correlation were performed. P value <0.05 was considered statistically significant.ResultsThe tumor volume (intrahepatic vs. orthotopic vs. subcutaneous: 587.50 ± 77.62 mm3 vs. 814.00 ± 43.85 mm3 vs. 956.13 ± 119.22 mm3), necrosis volume within tumor (89.10 ± 26.60 mm3 vs. 292.41 ± 57.92 mm3 vs. 179.91 ± 31.73 mm3, respectively), ADC at day 21 (543.41 ± 42.28 vs. 542.92 ± 99.67 vs. 369.83 ± 42.90, respectively), and post‐contrast T1 at all timepoints (day 7: 442.00 ± 11.52 vs. 435.00 ± 22.90 vs. 394.33 ± 29.95; day 14: 459.00 ± 26.11 vs. 436.83 ± 26.01 vs. 377.00 ± 27.83; day 21: 463.50 ± 23.49 vs. 458.00 ± 34.28 vs. 375.00 ± 30.55) were significantly different between three groups. Necrosis volumes of subcutaneous and intrahepatic tumors were significantly lower than those of orthotopic tumors. The CD31‐positive rate in the intrahepatic implantation was significantly higher than in orthotopic and subcutaneous groups. Necrosis volume (r = −0.71), ADC (r = −0.85), and post‐contrast T1 (r = −0.75) were strongly correlated with vascular invasion index.Data ConclusionOrthotopic and heterotopic tumors have their unique growth kinetics, necrosis volume, and vascular invasion. Non‐invasive MR quantitative parameters, including ADC and post‐contrast T1, may reflect vascular invasion in mice.Level of Evidence1Technical EfficacyStage 3

Diagnostic value of gadolinium contrast administration for spinal cord magnetic resonance imaging in multiple sclerosis patients and correlative markers of lesion enhancement

BackgroundMagnetic resonance imaging is essential for monitoring people with multiple sclerosis, but the diagnostic value of gadolinium contrast administration in spine magnetic resonance imaging is unclear.ObjectiveTo assess the diagnostic value of gadolinium contrast administration in spine magnetic resonance imaging follow-up examinations and identify imaging markers correlating with lesion enhancement.MethodsA total of 65 multiple sclerosis patients with at least 2 spinal magnetic resonance imaging follow-up examinations were included. Spine magnetic resonance imaging was performed at 3 Tesla with a standardized protocol (sagittal and axial T2-weighted turbo spin echo and T1-weighted post-contrast sequences). T2 lesion load and enhancing lesions were assessed by two independent neuroradiologists for lesion size, localization, and T2 signal ratio (T2 signallesion/T2 signalnormal appearing spinal cord).ResultsA total of 68 new spinal T2 lesions and 20 new contrast-enhancing lesions developed during follow-up. All enhancing lesions had a discernable correlate as a new T2 lesion. Lesion enhancement correlated with a higher T2 signal ratio compared to non-enhancing lesions (T2 signal ratio: 2.0 ± 0.4 vs. 1.4 ± 0.2, ****p < 0.001). Receiver operating characteristics analysis showed an optimal cutoff value of signal ratio 1.78 to predict lesion enhancement (82% sensitivity and 97% specificity).ConclusionGadolinium contrast administration is dispensable in follow-up spine magnetic resonance imaging if no new T2 lesions are present. Probability of enhancement correlates with the T2 signal ratio.

Synthetic T2-weighted images of the lumbar spine derived from an accelerated T2 mapping sequence: Comparison to conventional T2w turbo spin echo

ObjectivesTo evaluate the diagnostic usefulness of synthetic T2-weighted images of the lumbar spine derived from ten-fold undersampled k-space data using GRAPPATINI, a combination of a model-based approach for rapid T2 and M0 quantification (MARTINI) extended by generalized autocalibrating partial parallel acquistion (GRAPPA). Materials and methodsOverall, 58 individuals (26 female, mean age 23.3 ± 8.1 years) were examined at 3 Tesla with sagittal and axial T2w turbo spin echo (TSE) sequences compared to synthetic T2−weighted contrasts derived at identical effective echo times and spatial resolutions. Two blinded readers graded disk degeneration and evaluated the lumbar intervertebral disks for present herniation or annular tear. One reader reassessed all studies after four weeks. Weighted kappa statistics were calculated to assess inter-rater and intra-rater agreement. Also, all studies were segmented manually by one reader to compute contrast ratios (CR) and contrast-to-noise ratios (CNR) of the nucleus pulposus and the annulus fibrosus. ResultsOverall, the CRT2w was 4.45 ± 1.80 and CRT2synth was 4.71 ± 2.14. Both correlated (rsp = 0.768;p < 0.001) and differed (0.26 ± 1.38;p = 0.002) significantly. The CNRT2w was 1.73 ± 0.52 and CNRT2synth was 1.63 ± 0.50. Both correlated (rsp = 0.875;p < 0.001) and differed (−0.10 ± 0.25;p < 0.001) significantly. The inter-rater agreement was substantial to almost perfect (κ = 0.808–0.925) with the intra-rater agreement also substantial to almost perfect (κ = 0.862–0.963). The area under the curve of the receiver operating characteristics assessing disk herniation or annular tear ranged from 0.787 to 0.892. ConclusionsThis study concludes that synthetic images derived by GRAPPATINI can be used for clinical routine assessment with inter-rater and intra-rater agreements comparable to conventional T2w TSE.

Pediatric MR lung imaging with 3D ultrashort-TE in free breathing: Are we past the conventional T2 sequence?

Magnetic resonance imaging (MRI) of the lungs is challenging for several reasons, mainly due to the respiratory motion, low proton density, and rapid T2* decay. Recent MR sequences with ultrashort TE (UTE) coupled with respiratory compensation promise to overcome these obstacles. So far, there are very few studies on the relevance of these sequences in children. The aim of the study was to compare the diagnostic value of a respiratory-self-gated three-dimensional UTE sequence versus a conventional respiratory-triggered T2-weighted turbo spin echo (T2-TSE) sequence in a pediatric collective. Seventy-one patients between 0 and 18 years of age, who were scheduled for a thoracic MRI based on diverse clinical indications, were examined on a 3T MRI system. The UTE and T2-TSE sequences were evaluated by two readers regarding quality features and visualization of eight common pathology patterns. The image quality of both sequences was equally high, with UTE depicting pleural and central bronchi more clearly. In pathologies, UTE was superior to T2-TSE for so-called "MR-negative pathologies", significant for air trapping, and in tendency for bullae and cysts. In all remaining pathologies, T2-TSE proved to be at least equivalent to UTE. At present, UTE cannot serve as a universal replacement for conventional T2-TSE for all pathologies. It yields, however, a substantial benefit in the context of hyperinflation, emphysema, cysts, or pathologies of the bronchial system.

3D Isotropic Super-resolution Prostate MRI Using Generative Adversarial Networks and Unpaired Multiplane Slices.

We developed a deep learning-based super-resolution model for prostate MRI. 2D T2-weighted turbo spin echo (T2w-TSE) images are the core anatomical sequences in a multiparametric MRI (mpMRI) protocol. These images have coarse through-plane resolution, are non-isotropic, and have long acquisition times (approximately 10-15min). The model we developed aims to preserve high-frequency details that are normally lost after 3D reconstruction. We propose a novel framework for generating isotropic volumes using generative adversarial networks (GAN) from anisotropic 2D T2w-TSE and single-shot fast spin echo (ssFSE) images. The CycleGAN model used in this study allows the unpaired dataset mapping to reconstruct super-resolution (SR) volumes. Fivefold cross-validation was performed. The improvements from patch-to-volume reconstruction (PVR) to SR are 80.17%, 63.77%, and 186% for perceptual index (PI), RMSE, and SSIM, respectively; the improvements from slice-to-volume reconstruction (SVR) to SR are 72.41%, 17.44%, and 7.5% for PI, RMSE, and SSIM, respectively. Five ssFSE cases were used to test for generalizability; the perceptual quality of SR images surpasses the in-plane ssFSE images by 37.5%, with 3.26% improvement in SSIM and a higher RMSE by 7.92%. SR images were quantitatively assessed with radiologist Likert scores. Our isotropic SR volumes are able to reproduce high-frequency detail, maintaining comparable image quality to in-plane TSE images in all planes without sacrificing perceptual accuracy. The SR reconstruction networks were also successfully applied to the ssFSE images, demonstrating that high-quality isotropic volume achieved from ultra-fast acquisition is feasible.

Comparison of Phase-Sensitive Inversion Recovery and Conventional Magnetic Resonance Imaging for Detection of Cortical Plaques in MS Patients

Background: Precise detection and classification of intracortical (IC) lesions in multiple sclerosis (MS) patients are very important for understanding their role in disease progression and determining their effects on the clinical presentations of the disease. Objectives: This study aimed to evaluate the efficacy of phase-sensitive inversion recovery (PSIR) in delineation of cortical lesions in MS patients. Patients and Methods: This cross-sectional, single-center study was performed among 38 patients with the mean age of 31 years, who were recruited from December 2018 to August 2020. All MS patients underwent magnetic resonance imaging (MRI), using a 1.5-Tesla scanner. Two expert neuroradiologists interpreted the fluid-attenuated inversion recovery (FLAIR), T2-weighted turbo spin echo (T2W-TSE), and PSIR images. The lesions were classified as purely IC, mixed gray/white matter (WM) [leukocortical (LC)], and juxtacortical (JC). The number of lesions in each region was compared between the FLAIR, T2W-TSE, and PSIR sequences. Results: The number of cortical lesions (IC and LC) was significantly higher in PSIR compared to T2W-TSE and Fluid attenuated inversion recovery (FLAIR) (P &lt; 0.001), while the number of JC lesions was lower; in other words, the mean number of plaques was higher in T2W-TSE and FLAIR as compared to PSIR. Conclusion: The PSIR sequence significantly improved the delineation of cortical lesions and could be useful in monitoring cortical injuries and disease progression in MS patients.

Fluid-based augmentation of magnetic resonance visualization of interventional devices.

PurposeTo evaluate the transient artifact augmentation of microtubes in magnetic resonance imaging by fluid injection.MethodsTwenty‐one fluorinated ethylene propylene catheters (inner diameter 760 μm) were filled with three different contrast media at various concentrations (Ferucarbotran, Resovist®, Bayer Schering Pharma; Manganese dichloride, MnCl2, Sigma‐Aldrich; Gadobutrol, Gadovist®, Bayer Schering Pharma). Artifact appearance was determined in an ex vivo phantom at 1.5 T using three different sequences: T1‐weighted three‐dimensional volume interpolated breath‐hold examination, T2‐weighted turbo spin echo, and T1‐weighted fast low angle shot. Catheter angulation to the main magnetic field (B0) was varied. Influence of parameters on artifact diameters was assessed with a multiple linear regression similar to an analysis of variance.ResultsArtifact diameter was significantly influenced by the contrast agent (p < 0.001), concentration of the contrast agent (p < 0.001), angulation of the phantom to B0 with the largest artifact at 90° (p < 0.001), and encoding direction with a larger diameter in phase encoding direction (PED, p < 0.001). Mean artifact diameters at 90° angulation to B0 in PED were 18.5 ± 5.4 mm in 0.5 mmol/ml Ferucarbotran, 8.7 ± 2.5 mm in 1 mmol/ml Gadobutrol, and 11.6 ± 4.6 mm in 5 mmol/ml MnCl2.ConclusionsFluid‐based contrast agents might be applied to interventional devices and thus temporarily augment the artifact ensuring both visibility and safe navigation.

Diagnostic quality assessment of compressed SENSE accelerated magnetic resonance images in standard neuroimaging protocol: Choosing the right acceleration.

To investigate the impact of compressed sensing - sensitivity encoding (CS-SENSE) acceleration factor on the diagnostic quality of magnetic resonance images within standard brain protocol. Three routine clinical neuroimaging sequences were chosen for this study due to their long acquisition time: T2-weighted turbo spin echo (TSE), fluid - attenuated inversion recovery (FLAIR), and 3D time of flight (TOF). Fully sampled reference scans and multiple prospectively 2x to 5x undersampled CS scans were acquired. Retrospectively, undersampled scans were compared to fully sampled scans and visually assessed for image quality and diagnostic quality by three independent radiologists. Images obtained with CS-SENSE accelerated acquisition were of diagnostically acceptable quality at up to 3x acceleration for T2 TSE (average qualitative score 3.53 on a 4-point scale, with the acquisition time reduction of 64%), up to 2x for FLAIR (average qualitative score 3.27, with the acquisition time reduction of 43%) and 4x acceleration for 3D TOF sequence (average qualitative score 3.13, with the acquisition time reduction of 73%). There were no substantial differences between the readers' diagnostic quality scores (p>0.05). CS-SENSE accelerated T2 TSE, FLAIR, and 3D TOF sequences of the brain show image quality similar to that of conventional acquisitions with reduced acquisition time. CS-SENSE can moderately reduce scan time, providing many benefits without losing the image quality.

Accelerated T2-Weighted TSE Imaging of the Prostate Using Deep Learning Image Reconstruction: A Prospective Comparison with Standard T2-Weighted TSE Imaging.

Simple SummaryMultiparametric magnetic resonance imaging (mpMRI) has become an important diagnostic tool in the assessment of clinically significant prostate cancer. The disadvantages of this technique are primarily related to its long examination time and limited availability. This prospective study presents a novel accelerated deep learning image reconstructed T2-weighted turbo spin echo (TSE) sequence providing an acquisition time reduction of more than 60%. The study results show that the acquisition of three imaging planes of the prostate is feasible within 3:50 min, using deep learning image reconstruction, compared to 10:21 min in standard imaging. Additionally, image quality parameters were evaluated to be superior in deep learning imaging.Multiparametric MRI (mpMRI) of the prostate has become the standard of care in prostate cancer evaluation. Recently, deep learning image reconstruction (DLR) methods have been introduced with promising results regarding scan acceleration. Therefore, the aim of this study was to investigate the impact of deep learning image reconstruction (DLR) in a shortened acquisition process of T2-weighted TSE imaging, regarding the image quality and diagnostic confidence, as well as PI-RADS and T2 scoring, as compared to standard T2 TSE imaging. Sixty patients undergoing 3T mpMRI for the evaluation of prostate cancer were prospectively enrolled in this institutional review board-approved study between October 2020 and March 2021. After the acquisition of standard T2 TSE imaging (T2S), the novel T2 TSE sequence with DLR (T2DLR) was applied in three planes. Overall, the acquisition time for T2S resulted in 10:21 min versus 3:50 min for T2DLR. The image evaluation was performed by two radiologists independently using a Likert scale ranging from 1–4 (4 best) applying the following criteria: noise levels, artifacts, overall image quality, diagnostic confidence, and lesion conspicuity. Additionally, T2 and PI-RADS scoring were performed. The mean patient age was 69 ± 9 years (range, 49–85 years). The noise levels and the extent of the artifacts were evaluated to be significantly improved in T2DLR versus T2S by both readers (p < 0.05). Overall image quality was also evaluated to be superior in T2DLR versus T2S in all three acquisition planes (p = 0.005–<0.001). Both readers evaluated the item lesion conspicuity to be superior in T2DLR with a median of 4 versus a median of 3 in T2S (p = 0.001 and <0.001, respectively). T2-weighted TSE imaging of the prostate in three planes with an acquisition time reduction of more than 60% including DLR is feasible with a significant improvement of image quality.

Impact of rescanning and repositioning on radiomic features employing a multi-object phantom in magnetic resonance imaging

Our purpose was to analyze the robustness and reproducibility of magnetic resonance imaging (MRI) radiomic features. We constructed a multi-object fruit phantom to perform MRI acquisition as scan-rescan using a 3 Tesla MRI scanner. We applied T2-weighted (T2w) half-Fourier acquisition single-shot turbo spin-echo (HASTE), T2w turbo spin-echo (TSE), T2w fluid-attenuated inversion recovery (FLAIR), T2 map and T1-weighted (T1w) TSE. Images were resampled to isotropic voxels. Fruits were segmented. The workflow was repeated by a second reader and the first reader after a pause of one month. We applied PyRadiomics to extract 107 radiomic features per fruit and sequence from seven feature classes. We calculated concordance correlation coefficients (CCC) and dynamic range (DR) to obtain measurements of feature robustness. Intraclass correlation coefficient (ICC) was calculated to assess intra- and inter-observer reproducibility. We calculated Gini scores to test the pairwise discriminative power specific for the features and MRI sequences. We depict Bland Altmann plots of features with top discriminative power (Mann–Whitney U test). Shape features were the most robust feature class. T2 map was the most robust imaging technique (robust features (rf), n = 84). HASTE sequence led to the least amount of rf (n = 20). Intra-observer ICC was excellent (≥ 0.75) for nearly all features (max–min; 99.1–97.2%). Deterioration of ICC values was seen in the inter-observer analyses (max–min; 88.7–81.1%). Complete robustness across all sequences was found for 8 features. Shape features and T2 map yielded the highest pairwise discriminative performance. Radiomics validity depends on the MRI sequence and feature class. T2 map seems to be the most promising imaging technique with the highest feature robustness, high intra-/inter-observer reproducibility and most promising discriminative power.

Comparison of metal artifact reduction techniques in magnetic resonance imaging of carbon-reinforced PEEK and titanium spinal implants.

Carbon-reinforced PEEK (C-FRP) implants are non-magnetic and have increasingly been used for the fixation of spinal instabilities. To compare the effect of different metal artifact reduction (MAR) techniques in magnetic resonance imaging (MRI) on titanium and C-FRP spinal implants. Rod-pedicle screw constructs were mounted on ovine cadaver spine specimens and instrumented with either eight titanium pedicle screws or pedicle screws made of C-FRP and marked with an ultrathin titanium shell. MR scans were performed of each configuration on a 3-T scanner. MR sequences included transaxial conventional T1-weighted turbo spin echo (TSE) sequences, T2-weighted TSE, and short-tau inversion recovery (STIR) sequences and two different MAR-techniques: high-bandwidth (HB) and view-angle-tilting (VAT) with slice encoding for metal artifact correction (SEMAC). Metal artifact degree was assessed by qualitative and quantitative measures. There was a much stronger effect on artifact reduction with using C-FRP implants compared to using specific MRI MAR-techniques (screw shank: P < 0.001; screw tulip: P < 0.001; rod: P < 0.001). VAT-SEMAC sequences were able to reduce screw-related signal loss artifacts in constructs with titanium screws to a certain degree. Constructs with C-FRP screws showed less artifact-related implant diameter amplification when compared to constructs with titanium screws (P < 0.001). Constructs with C-FRP screws are associated with significantly less artifacts compared to constructs with titanium screws including dedicated MAR techniques. Artifact-reducing sequences are able to reduce implant-related artifacts. This effect is stronger in constructs with titanium screws than in constructs with C-FRP screws.

Concentration of Gallbladder Phosphatidylcholine in Cholangiopathies: A Phosphorus-31 Magnetic Resonance Spectroscopy Pilot Study.

Biliary phosphatidylcholine (PtdC) concentration plays a role in the pathogenesis of bile duct diseases. In vivo phosphorus-31 magnetic resonance spectroscopy (31 P-MRS) at 7 T offers the possibility to assess this concentration noninvasively with high spectral resolution and signal intensity. Comparison of PtdC levels of cholangiopathic patient groups to a control group using a measured T1 relaxation time of PtdC in healthy subjects. Case control. Two patient groups with primary sclerosing cholangitis (PSC, 2f/3 m; age: 43 ± 7 years) and primary biliary cholangitis (PBC, 4f/2 m; age: 57 ± 6 years), and a healthy control group (CON, 2f/3 m; age: 38 ± 7 years). Ten healthy subjects for the assessment of the T1 relaxation time of PtdC. A 3D phase-encoded pulse-acquire 31 P-MRSI sequence for PtdC quantification and a 1D image-selected in vivo 31 P spectroscopy for T1 estimation at 7 T, and a T2-weighted half-Fourier single-shot turbo spin echo MRI sequence for volumetry at 3 T. Calculation of gallbladder volumes and PtdC concentration in groups using hepatic gamma-adenosine triphosphate signal as an internal reference and correction for insufficient relaxation of PtdC with a T1 value assessed in healthy subjects. Group comparison of PtdC content and gallbladder volumes of the PSC/PBC and CON group using Student's t-tests with a significance level of 5%. PtdC T1 value of 357 ± 85 msec in the gallbladder. Significant lower PtdC content for the PSC group, and for the female subgroup of the PBC group compared to the CON group (PSC/CON: 5.74 ± 0.73 mM vs. 9.64 ± 0.97 mM, PBC(f)/CON: 5.77 ± 1.44 mM vs. 9.64 ± 0.97 mM). Significant higher gallbladder volumes of the patient groups compared to the CON group (PSC/CON: 66.3 ± 15.8 mL vs. 20.9 ± 2.2 mL, PBC/CON: 49.8 ± 18.2 mL vs. 20.9 ± 2.2 mL). This study demonstrated the application of a 31 P-MRSI protocol for the quantification of PtdC in the human gallbladder at 7 T. Observed differences in PtdC concentration suggest that this metabolite could serve as a biomarker for specific hepatobiliary disorders. 2 TECHNICAL EFFICACY STAGE: 3.

The impact of image acquisition time on registration, delineation and image quality for magnetic resonance guided radiotherapy of prostate cancer patients.

Background and PurposeMagnetic resonance (MR) guided radiotherapy utilizes MR images for (online) plan adaptation and image guidance. The aim of this study was to investigate the impact of variation in MR acquisition time and scan resolution on image quality, interobserver variation in contouring and interobserver variation in registration.Materials and MethodsNine patients with prostate cancer were included. Four T2-weighted 3D turbo spin echo (T2w 3D TSE) sequences were acquired with different acquisition times and resolutions. Two radiologists assessed image quality, conspicuity of the capsule, peripheral zone and central gland architecture and motion artefacts on a 5 point scale. Images were delineated by two radiation oncologists and interobserver variation was assessed by the 95% Hausdorff distance. Seven observers registered the MR images on the planning CT. Registrations were compared on systematic offset and interobserver variation.ResultsAcquisition times ranged between 1.3 and 6.3 min. Overall image quality and capsule definition were significantly worse for the MR sequence with an acquisition time of 1.3 min compared to the other sequences. Median 95% Hausdorff distance showed no significant differences in interobserver variation of contouring. Systematic offset and interobserver variation in registration were small (<1 mm) and of no clinical significance.ConclusionsOur results can be used to effectively shorten overall fraction time for online adaptive MR guided radiotherapy by optimising the imaging sequence used for registration. From the sequences studied, a sequence of 3.1 min with anisotropic voxels of 1.2 × 1.2 × 2.4 mm3 provided the shortest acquisition time without compromising image quality.

Assessment of the fetal thymus gland: Comparing MRI-acquired thymus volumes with 2D ultrasound measurements

ObjectivesThe fetal thymus gland has been shown to involute in response to intrauterine infection, and therefore could be used as a non-invasive marker of fetal compartment infection. The objective of this study was to evaluate how accurately 2D ultrasound-derived measurements of the fetal thymus reflect the 3D volume of the gland derived from motion corrected MRI images. Study designA retrospective study was performed using paired ultrasound and MRI datasets from the iFIND project (http://www.ifindproject.com). To obtain 3D volumetry of the thymus gland, T2-weighted single shot turbo spin echo (ssTSE) sequences of the fetal thorax were acquired. Thymus volumes were manually segmented from deformable slice-to-volume reconstructed images. To obtain 2D ultrasound measurements, previously stored fetal cine loops were used and measurements obtained at the 3-vessel-view (3VV) and 3-vessel-trachea view (3VT): anterior-posterior diameter (APD), intrathoracic diameter (ITD), transverse diameter (TD), perimeter and 3-vessel-edge (3VE). Inter-observer and intra-observer reliability (ICC) was calculated for both MRI and ultrasound measurements. Pearson correlation coefficients (PCC) were used to compare 2D-parameters with acceptable ICC to TV. Results38 participants were identified. Adequate visualisation was possible on 37 MRI scans and 31 ultrasound scans. Of the 30 datasets where both MRI and ultrasound data were available, MRI had good interobserver reliability (ICC 0.964) and all ultrasound 3VV 2D-parameters and 3VT 3VE had acceptable ICC (>0.75). Four 2D parameters were reflective of the 3D thymus volume: 3VV TD r = 0.540 (P = 0.002); 3VV perimeter r = 0.446 (P = 0.013); 3VV APD r = 0.435 (P = 0.110) and 3VT TD r = 0.544 (P = 0.002). ConclusionsMRI appeared superior to ultrasound for visualization of the thymus gland and reproducibility of measurements. Three 2D US parameters, 3VV TD, perimeter and 3VT APD, correlated well with TV. Therefore, these represent a more accurate reflection of the true size of the gland than other 2D measurements, where MRI is not available.

Quantitative Muscle MRI in Patients with Neuromuscular Diseases-Association of Muscle Proton Density Fat Fraction with Semi-Quantitative Grading of Fatty Infiltration and Muscle Strength at the Thigh Region.

(1) Background and Purpose: The skeletal muscles of patients suffering from neuromuscular diseases (NMD) are affected by atrophy, hypertrophy, fatty infiltration, and edematous changes. Magnetic resonance imaging (MRI) is an important tool for diagnosis and monitoring. Concerning fatty infiltration, T1-weighted or T2-weighted DIXON turbo spin echo (TSE) sequences enable a qualitative assessment of muscle involvement. To achieve higher comparability, semi-quantitative grading scales, such as the four-point Mercuri scale, are commonly applied. However, the evaluation remains investigator-dependent. Therefore, effort is being invested to develop quantitative MRI techniques for determination of imaging markers such as the proton density fat fraction (PDFF). The present work aims to assess the diagnostic value of PDFF in correlation to Mercuri grading and clinically determined muscle strength in patients with myotonic dystrophy type 2 (DM2), limb girdle muscular dystrophy type 2A (LGMD2A), and adult Pompe disease. (2) Methods: T2-weighted two-dimensional (2D) DIXON TSE and chemical shift encoding-based water-fat MRI were acquired in 13 patients (DM2: n = 5; LGMD2A: n = 5; Pompe disease: n = 3). Nine different thigh muscles were rated in all patients according to the Mercuri grading and segmented to extract PDFF values. Muscle strength was assessed according to the British Medical Research Council (BMRC) scale. For correlation analyses between Mercuri grading, muscle strength, and PDFF, the Spearman correlation coefficient (rs) was computed. (3) Results: Mean PDFF values ranged from 7% to 37% in adults with Pompe disease and DM2 and up to 79% in LGMD2A patients. In all three groups, a strong correlation of the Mercuri grading and PDFF values was observed for almost all muscles (rs > 0.70, p < 0.05). PDFF values correlated significantly to muscle strength for muscle groups responsible for knee flexion (rs = −0.80, p < 0.01). (4) Conclusion: In the small, investigated patient cohort, PDFF offers similar diagnostic precision as the clinically established Mercuri grading. Based on these preliminary data, PDFF could be further considered as an MRI-based biomarker in the assessment of fatty infiltration of muscle tissue in NMD. Further studies with larger patient cohorts are needed to advance PDFF as an MRI-based biomarker in NMD, with advantages such as its greater dynamic range, enabling the assessment of subtler changes, the amplified objectivity, and the potential of direct correlation to muscle function for selected muscles.

Impact of the implementation of a Contouring Atlas on Therapeutic Radiographer inter-observer contour variation in prostate radiotherapy

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.