MR Imaging Research Articles

A new technique of percutaneous minimally invasive surgery assisted by magnetic resonance neurography.

In order to release the contracture band completely without damaging normal tissues (such as the sciatic nerve) in the surgical treatment of gluteal muscle contracture (GMC), we tried to display the relationship between normal tissue and contracture bands by magnetic resonance neurography (MRN) images, and to predesign a minimally invasive surgery based on the MRN images in advance. A total of 30 patients (60 hips) were included in this study. MRN scans of the pelvis were performed before surgery. The contracture band shape and external rotation angle (ERA) of the proximal femur were also analyzed. Then, the minimally invasive GMC releasing surgery was performed based on the images and measurements, and during the operation, incision lengths, surgery duration, intraoperative bleeding, and complications were recorded; the time of the first postoperative off-bed activity was also recorded. Furthermore, the patients' clinical functions were evaluated by means of Hip Outcome Score (HOS) and Ye et al's objective assessments, respectively. The contracture bands exhibited three typical types of shape - feather-like, striped, and mixed shapes - in MR images. Guided by MRN images, we designed minimally invasive approaches directed to each hip. These approaches resulted in a shortened incision length in each hip (0.3 cm (SD 0.1)), shorter surgery duration (25.3 minutes (SD 5.8)), less intraoperative bleeding (8.0 ml (SD 3.6)), and shorter time between the end of the operation and the patient's first off-bed activity (17.2 hours (SD 2.0)) in each patient. Meanwhile, no serious postoperative complications occurred in all patients. The mean HOS-Sports subscale of patients increased from 71.0 (SD 5.3) to 94.83 (SD 4.24) at six months postoperatively (p < 0.001). The follow-up outcomes from all patients were "good" and "excellent", based on objective assessments. Preoperative MRN analysis can be used to facilitate the determination of the relationship between contracture band and normal tissues. The minimally invasive surgical design via MRN can avoid nerve damage and improve the release effect.

Clinical and Radiological Profile of Nine Patients with Metachromatic Leukodystrophy

Introduction: Metachromatic leukodystrophy (MLD) is a rare, demyelinating, autosomal recessive lysosomal storage disease caused by a deficiency in the arylsulfatase A enzyme (ASA), which is encoded by ARSA gene. A lack of ASA activity results in an accumulation of sulfatides in the myelin sheaths of both the central and peripheral nervous systems, leading to developmental and neurocognitive progressive deterioration that can be observed in all age groups. Methods: We present a total of 9 patients with MLD with an average age of 61 months, whose clinical, laboratory and cranial magnetic resonance imaging findings were evaluated, and who underwent an ARSA gene molecular analysis. Results: Of the 9 patients, 7 had the late infantile form of the condition, 2 had the juvenile form, and 3 were identified through family screening. The median age at diagnosis was 30 months (min 3–max 73 months), the mean ASA activity value was 2 nmol/h/mgprt and the median cranial MR imaging severity score was 10 (min 5–max 18). The grey and white matter volumes of all patients, evaluated using volBrain software, were within the normal range. At an average age of 48 months, the late-infantile MLD patients were unable to control any body part. Conclusions: Hematopoietic stem cell transplantation (HSCT), a treatment option for both the juvenile and adult forms of MLD in asymptomatic or early symptomatic patients, was performed on two of the asymptomatic and early symptomatic patients, and post-HSCT ASA activity settled within the normal range and their developmental milestones stabilized. It is important to diagnose MLD in the asymptomatic period and newborn screening can support early diagnosis.

SeqSeg: Learning Local Segments for Automatic Vascular Model Construction.

Computational modeling of cardiovascular function has become a critical part of diagnosing, treating and understanding cardiovascular disease. Most strategies involve constructing anatomically accurate computer models of cardiovascular structures, which is a multistep, time-consuming process. To improve the model generation process, we herein present SeqSeg (sequential segmentation): a novel deep learning-based automatic tracing and segmentation algorithm for constructing image-based vascular models. SeqSeg leverages local U-Net-based inference to sequentially segment vascular structures from medical image volumes. We tested SeqSeg on CT and MR images of aortic and aortofemoral models and compared the predictions to those of benchmark 2D and 3D global nnU-Net models, which have previously shown excellent accuracy for medical image segmentation. We demonstrate that SeqSeg is able to segment more complete vasculature and is able to generalize to vascular structures not annotated in the training data.

Simplified arthroscopic anterior talofibular ligament repair with inferior extensor retinaculum reinforcement: technical notes and preliminary results

PurposeCompared with open surgery, arthroscopic anterior talofibular ligament (ATFL) repair has many advantages and good clinical outcome. Inferior extensor retinaculum (IER) reinforcement is a supplement procedure that increase the strength of the ATFL. There is still no gold standard for arthroscopic ATFL repair. The purposes of this study were to describe a simplified technique for arthroscopic ATFL repair with IER reinforcement and to analyze its preliminary clinical results.MethodsTwenty-seven patients with chronic lateral ankle instability (CLAI) who underwent this simplified surgery were analyzed in this retrospective study. The patients’ characteristics and operative times were evaluated. Intraoperative photos, radiographs from the anterior drawer test and talar tilt test and postoperative MR images were recorded. The American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and visual analog scale (VAS) score were also recorded. With the assistance of a needle, we performed ATFL repair and IER reinforcement with one Pushlock anchor and nonabsorbable sutures.ResultsNo complications namely skin necrosis, superficial fibular nerve injury or wound infection, were reported. The AOFAS score and VAS score improved from 64.74 ± 9.47 and 6.00 ± 1.56 to 90.74 ± 6.46 and 1.07 ± 1.09, respectively. The talar advancement and talar tilt angle were improved after surgery. One year after the operation, the ATFL appeared to be continuous on MR images.ConclusionIn this study, we proposed a simple and effective arthroscopic ATFL repair with IER reinforcement technique. The short-term follow-up examination revealed satisfactory clinical outcomes. Our technique might be a new surgical option for the treatment of CLAI.

Synthesis of targeted doxorubicin-loaded gold nanorod −mesoporous manganese dioxide core–shell nanostructure for ferroptosis, chemo-photothermal therapy in vitro and in vivo

In the current study, a core–shell inorganic nanostructure comprising a gold nanorod core and −mesoporous manganese dioxide shell was synthesized. Then, the mesoporous manganese dioxide shell was loaded with doxorubicin (DOX) and then coated with pluronic F127 and pluronic F127-folic acid conjugate (1.5:1 wt ratio of pluronic F127: pluronic F127-folic acid conjugate) to prepare targeted final platform. In this design, mesoporous manganese dioxide acted as a reservoir for DOX loading, anti-hypoxia, and MRI contrast agent, while the gold nanorod core acted as a photothermal and CT scan imaging agent. DOX was encapsulated in the mesoporous manganese dioxide shell with a loading capacity and loading efficiency of 19.8 % ± 0.2 and 99.0 % ± 0.9, respectively. The in vitro release experiment showed the impact of glutathione (GSH), mildly acidic pH, and laser irradiating toward accelerated stimuli-responsive DOX release. The ·OH production of the prepared platform was verified by methylene blue (MB) decomposition reaction. Furthermore, thermal imaging exhibited the ability of the prepared platform to convert the NIR irradiation to heat. In vitro cytotoxicity tests on the folate receptor-positive 4 T1 cell line revealed the remarkable cytotoxicity of the targeted formulation compared to the nontargeted formulation (statistically significant). The MTT experiment demonstrated that exposure to laser 808 irradiation enhanced cytotoxicity of the targeted formulation (p < 0.0001). The production of ROS in 4 T1 cells following treatment with the targeted formulation was demonstrated by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. Furthermore, in vivo investigations by implementing subcutaneous 4 T1 tumorized female BABL/c mice indicated that the prepared platform was an effective system in suppressing tumor growth by combining chemotherapy with PTT (photothermal therapy). Additionally, simultanous PTT and anti-hypoxic activity of this system showed potent tumor growth suppression impact. The percent of tumor size reduction in mice treated with FA-F127-DOX@Au-MnO2 + 808 nm laser compared to the control group was 99.7 %. The results of the biodistribution investigation showed tumor accumulation and modified pharmacokinetics of the targeted system. Lastly, 6 and 24 h post-intravenous injection, CT-scan and MR imagings capability of the prepared platform was verified in preclinical stage. The prepared multipurpose system introduces great opportunity to provide multiple treatment strategy along with multimodal imaging capability in a single platform for breast cancer treatment.

Imaging findings of gastric glomus tumors.

Sparse literature describes the imaging findings of gastric glomus tumors (GGT), focusing on benign tumors. We are not aware of prior radiology reports on malignant GGT. The aim of the study was to determine whether it is possible to differentiate between benign and malignant GGT on CT or MR. Institutional radiology and pathology databases were queried for the diagnosis of GGT between January 2010 to December 2023. Of 22 identified subjects, five were excluded due to non-availability of preoperative CT or MR images and three due to lack of pathological confirmation in our institution. The study cohort comprised of 14 patients (males = 6) with median age of 65 years (range 31 to 79 years). Two abdominal radiologists in consensus reviewed all relevant CT and MR images. There were 10 benign and 4 malignant GGT. Benign tumors were smaller than malignant GGT (median size of 2.0cm vs. 5.3cm, p = 0.03), more likely to exhibit homogeneous hyperenhancement (9/10 vs. 0/4, p < 0.01), and demonstrated intramural rather than exophytic growth. There was no substantial difference in T2 signal or diffusion restriction between benign and malignant GGT. On follow up, benign GGT were essentially stable in size, while malignant GGT grew. A biopsy proven GGT larger than 5cm or showing necrosis is likely to be malignant. This is important since preoperative endoscopic ultrasound-guided fine needle aspiration may be indeterminate for malignancy.

Online MR-guided proton and ion beam radiotherapy: investigation of image quality

Objective.Magnetic resonance (MR) images free of artefacts are of pivotal importance for MR-guided ion radiotherapy. This study investigates MR image quality for simultaneous irradiation in an experimental setup using phantom imaging as well asin-vivoimaging. Observed artefacts are described within the study and their cause is investigated with the goal to find conclusions and solutions for potential future hybrid devices.Approach.An open MR scanner with a field strength of 0.25 T has been installed in front of an ion beamline. Simultaneous magnetic resonance imaging and irradiation using raster scanning were performed to analyze image quality in dedicated phantoms. Magnetic field measurements were performed to assist the explanation of observed artifacts. In addition,in-vivoimages were acquired by operating the magnets for beam scanning without transporting a beam.Main Results.The additional frequency component within the isocenter caused by the fringe field of the horizontal beam scanning magnet correlates with the amplitude and frequency of the scanning magnet steering and can cause ghosting artifacts in the images. These are amplified with high currents and fast operating of the scanning magnet. Applying a real-time capable pulse sequencein-vivorevealed no ghosting artifacts despite a continuously changing current pattern and a clinical treatment plan activation scheme, suggesting that the use of fast imaging is beneficial for the aim of creating high quality in-beam MR images. This result suggests, that the influence of the scanning magnets on the MR acquisition might be of negligible importance and does not need further measures like extensive magnetic shielding of the scanning magnets.Significance.Our study delimited artefacts observed in MR images acquired during simultaneous raster scanning ion beam irradiation. The application of a fast pulse sequence showed no image artefacts and holds the potential that online MR imaging in future hybrid devices might be feasible.

Added Advantages of DWI MR Imaging and ADC Mapping in the Diagnosis of Active Sacroiliitis of Axial Seronegative SpA

Aim: To evaluate the effectiveness of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping in diagnosing active sacroiliitis in patients with axial seronegative spondyloarthropathy (SpA). Material and Methods: This prospective study comprised 26 patients with MR imaging detected active sacroiliitis categorised as a case group, and compared them with healthy controls. ADC value measurements were obtained from the sacral and iliac sides of the bilateral S.I. joints in each case and control group. Independent samples t-test, Chi-square test, and ROC curve analysis were used. Result: Twenty-six patients had active sacroiliitis in 45 S.I. joints, unilateral active sacroiliitis was observed in seven patients (26.9%), bilateral symmetrical in three patients (11.5%) and bilateral asymmetrical in 16 patients (61.5%). The mean ADC value was 1.447 ± 0.528 [SD] × 10–3 mm 2 /s in the right S.I. joint and 1.630 ± 0.441 [SD] × 10–3 mm 2 /s in the left S.I. joint in active sacroiliitis (case group). The mean ADC value of the right S.I. joint was 0.965 ± 0.123 [SD] × 10–3 mm 2 /s and the left S.I. joint was 0.967 ± 0.96 [SD] × 10–3 mm 2 /s in inactive sacroiliitis (control group). A significant difference was observed statistically between the active sacroiliitis and the inactive sacroiliitis with a P &lt; .0005. A cut-off mean ADC value of 1.034 ×10–3 mm 2 /s was obtained for differentiating active sacroiliitis from inactive sacroiliitis with a sensitivity of 84.6% and specificity of 84.6% from the ROC curve analysis. Conclusion: Diffusion-weighted MRI imaging with ADC value mapping acts as a sensitive diagnostic technique in the detection of active sacroiliitis in axial seronegative spondyloarthropathies and also helps in assessing the treatment response.

Focally Enlarged Perivascular Spaces in Pediatric and Adolescent Patients with Polymicrogyria-an MRI Study.

Polymicrogyria (PMG) is acortical malformation frequently associated with epilepsy. Our aim was to investigate the frequency and conspicuity of enlarged perivascular spaces (EPVS) underneath dysplastic cortex as apotentially underrecognized feature of PMG in pediatric and adolescent patients undergoing clinical magnetic resonance imaging (MRI). We analyzed data from 28pediatric and adolescent patients with PMG and amatched control group, ranging in age from 2days to 21years, who underwent MRI at 1.5T or 3T. T2-weighted MR images were examined for the presence of EPVS underneath the dysplastic cortex. The quantity of EPVS was graded from 0to 4(0: none, 1: < 10, 2: 11-20, 3: 21-40, 4: > 40 EPVS). We then compared the presence and quantity of EPVS to the matched controls in terms of total EPVS scores, and EPVS scores underneath the dysplastsic cortex depending on the age groups, the localization of PMG, and the MRI field strength. In 23/28 (82%) PMG patients, EPVS spatially related to the dysplastic cortex were identified. EPVS scores were significantly higher in PMG patients compared to controls, independent from age or PMG location. No significant differences were observed in EPVS scores in patients examined at 1.5T compared to those examined at 3T. EPVS underneath the dysplastic cortex were identified in 82% of patients. EPVS may serve as an important clue for PMG and amarker for cortical malformation.

Focal cortical dysplasia lesion segmentation using multiscale transformer

ObjectivesAccurate segmentation of focal cortical dysplasia (FCD) lesions from MR images plays an important role in surgical planning and decision but is still challenging for radiologists and clinicians. In this study, we introduce a novel transformer-based model, designed for the end-to-end segmentation of FCD lesions from multi-channel MR images.MethodsThe core innovation of our proposed model is the integration of a convolutional neural network-based encoder-decoder structure with a multiscale transformer to augment the feature representation of lesions in the global field of view. Transformer pathways, composed of memory- and computation-efficient dual-self-attention modules, leverage feature maps from varying depths of the encoder to discern long-range interdependencies among feature positions and channels, thereby emphasizing areas and channels relevant to lesions. The proposed model was trained and evaluated on a public-open dataset including MR images of 85 patients using both subject-level and voxel-level metrics.ResultsExperimental results indicate that our model offers superior performance both quantitatively and qualitatively. It successfully identified lesions in 82.4% of patients, with a low false-positive lesion cluster rate of 0.176 ± 0.381 per patient. Furthermore, the model achieved an average Dice coefficient of 0.410 ± 0.288, outperforming five established methods.ConclusionIntegration of the transformer could enhance the feature presentation and segmentation performance of FCD lesions. The proposed model has the potential to serve as a valuable assistive tool for physicians, enabling rapid and accurate identification of FCD lesions. The source code and pre-trained model weights are available at https://github.com/zhangxd0530/MS-DSA-NET.Critical relevance statementThis multiscale transformer-based model performs segmentation of focal cortical dysplasia lesions, aiming to help radiologists and clinicians make accurate and efficient preoperative evaluations of focal cortical dysplasia patients from MR images.Key PointsThe first transformer-based model was built to explore focal cortical dysplasia lesion segmentation.Integration of global and local features enhances the segmentation performance of lesions.A valuable benchmark for model development and comparative analyses was provided.Graphical

Comprehensive commissioning of a cone beam CT imaging ring for treatment of HDR GYN patients

PurposeA new mobile cone beam computed tomography (CBCT) imaging ring (IRm, Elekta, v2.10.6, Veenendaal, Netherlands) has recently been proposed for brachytherapy to improve procedure efficiency. We describe the commissioning process and end-to-end tests for GYN HDR brachytherapy employing IRm CBCT imaging. Materials and MethodsCommissioning included imaging isocenter test, 3D image quality, 2D imaging quality, image dose, and tube characteristics. CIRS HDR GYN phantom and Venezia CT/MR gynecological applicator were used to perform end-to-end (E2E) tests and optimize workflow. Venezia applicator and four interstitial needles were inserted into the phantom and IRm CBCT images were acquired. Phantom and applicator were scanned with CT scanner (Siemens SOMATOM go.Open Pro) using department's pelvis imaging protocol. MR imaging was performed using 0.35T MR Linac TRUFI pulse sequence. CBCT images were registered to CT and MR using rigid registration to assess image quality and applicator geometry fidelity. ResultsAll physics tests passed within acceptance tolerances. Registration of CBCT images to MR and CT scans was acceptable for applicator placement. Applicator registration of CBCT images to CT demonstrated excellent agreement of most distal source dwell position (<1 mm). Slice thickness was also measured to be 1.25 mm, within 0.5 mm of its nominal value. ConclusionBased on E2E and commissioning results, IRm is an appropriate tool for brachytherapy treatment planning. This study demonstrated good image quality in GYN phantom and Venezia applicator using the IRm. Distal source dwell position agreement between CBCT and CT was acceptable for clinical use.

The role of humerus cortical thickness in predicting osteoporosis in MR imaging

The role of humerus cortical thickness in predicting osteoporosis in MR imaging

CT and MR imaging characteristics of primary hepatic lymphoma

BackgroundPrimary hepatic lymphoma (PHL) is a rare primary liver tumor. The purpose of this study was to investigate the crucial imaging characteristics of PHL.MethodsCT/MR data and clinical features of 16 patients with pathologically proven PHL were retrospectively reviewed. The assessed imaging characteristics included lesion distribution, growth appearance, density or signal characteristics, and typical signs during the dynamic enhancement.ResultsA total of sixteen patients were included in this study, ranging in age from 27 to 86 years (nine men and seven women; mean age, 62 years). Right upper abdominal pain, malaise, or first detection during physical examination were the chief complaint. Dynamic contrast-enhanced CT and MRI demonstrated focal masses in thirteen patients (13/16, 81%), and multiple nodules in three patients (3/16, 19%). The lesions showed vascular floating sign in 10 patients (10/16, 63%) and biliary pass-through sign in 6 patients (6/16, 37%). Necrosis in PHLs were observed in 10 patients (10/16, 63%) and presented target sign on T2WI in 5 out of 11 patients (5/11, 45%) undergoing MRI. After enhancement, PHLs had multinodular sign in the arterial phase in 10 patients (10/16, 63%), and presented washout of contrast medium in the portal-venous or delayed phase in 12 patients (12/16, 75%), pseudocapsule in the delayed phase in 15 patients (15/16, 94%), and double-ring sign in the delayed phase in 8 patients (8/16, 50%).ConclusionPHL is generally seen in elderly patients with elevated beta-2-microglobulin levels. Its distinctive imaging features including obviously low ADC value, biliary/vascular floating sign, multinodular sign and double-ring sign in the delayed phase, may help to diagnose and differentiate PHL.

A deep learning model for differentiating paediatric intracranial germ cell tumour subtypes and predicting survival with MRI: a multicentre prospective study

BackgroundThe pretherapeutic differentiation of subtypes of primary intracranial germ cell tumours (iGCTs), including germinomas (GEs) and nongerminomatous germ cell tumours (NGGCTs), is essential for clinical practice because of distinct treatment strategies and prognostic profiles of these diseases. This study aimed to develop a deep learning model, iGNet, to assist in the differentiation and prognostication of iGCT subtypes by employing pretherapeutic MR T2-weighted imaging.MethodsThe iGNet model, which is based on the nnUNet architecture, was developed using a retrospective dataset of 280 pathologically confirmed iGCT patients. The training dataset included 83 GEs and 117 NGGCTs, while the retrospective internal test dataset included 31 GEs and 49 NGGCTs. The model’s diagnostic performance was then assessed with the area under the receiver operating characteristic curve (AUC) in a prospective internal dataset (n = 22) and two external datasets (n = 22 and 20). Next, we compared the diagnostic performance of six neuroradiologists with or without the assistance of iGNet. Finally, the predictive ability of the output of iGNet for progression-free and overall survival was assessed and compared to that of the pathological diagnosis.ResultsiGNet achieved high diagnostic performance, with AUCs between 0.869 and 0.950 across the four test datasets. With the assistance of iGNet, the six neuroradiologists’ diagnostic AUCs (averages of the four test datasets) increased by 9.22% to 17.90%. There was no significant difference between the output of iGNet and the results of pathological diagnosis in predicting progression-free and overall survival (P = .889).ConclusionsBy leveraging pretherapeutic MR imaging data, iGNet accurately differentiates iGCT subtypes, facilitating prognostic evaluation and increasing the potential for tailored treatment.Graphical

Research on multi-sequence MR image synthesis CT algorithm based on unsupervised method

BackgroundUsing multi-sequence MRI to synthesize CT, combining different MRI sequences, and processing synthetic CT (sCT) based on unsupervised algorithms, to conduct more in-depth and comprehensive research on MR-based radiotherapy planning. MethodsFirst, we compare and analyze the effects of single-sequence MRI synthesis to CT to determine the quality of the synthesis and find a set of optimal sequence combinations. In addition, the study introduces a Staged Multi-Sequence Fusion Network (SMSF-Net) that employs an unsupervised approach to effectively fuse information from multiple MRI sequences. The staged sequence fusion module can efficiently extract information from different sequences and combine complementary information from different sequences. Finally, image encoding is processed using a multi-layer convolutional network to generate synthetic CT images. ResultsIn this study, the mean absolute error (MAE), root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and structural similarity (SSIM) of the SMSF-Net are 18.85, 84.62, 34.31, and 0.962, which are superior to other single-sequence models and multi-sequence models. Experiments show that the improvement of SMSF-Net is statistically significant. In the qualitative comparison experiment, sCT synthesized by SMSF-Net is superior to other models in detail in the synthesis of complex areas of bones and nasal cavities. ConclusionThis study proposes a Staged SMSF-Net. As a multi-sequence MRI synthesis sCT algorithm based on unsupervised learning, SMSF-Net can use the complementary information between multiple sequences to improve the quality of synthetic sCT. This study has reference value for MRI-only radiotherapy planning.

Diffusion lacunae: a novel MR imaging finding on diffusion-weighted imaging for diagnosing placenta accreta spectrum.

To evaluate the usefulness of novel diffusion-weighted imaging (DWI) findings for diagnosing placenta accreta spectrum (PAS). This retrospective study included 49 pregnant women with suspected PAS who underwent 1.5T placental MRI. Diffusion lacunae were defined as intraplacental areas showing hypointensity on DWI and hyperintensity on the apparent diffusion coefficient map. Two radiologists evaluated the number and size of placental lacunae on DWI, and flow void in the diffusion lacunae on T2-weighted imaging. The radiologists also evaluated established MRI features of PAS described in the SAR-ESUR consensus statement. Pearson's chi-square test or Mann-Whitney U test was used to compare findings between patients with and without PAS. Interobserver reliability for DWI and established MRI features was also assessed. Optimal thresholds for the number and maximum size of diffusion lacunae for differentiating PAS from the no-PAS group were determined using receiver operating characteristic curve analyses. Eighteen patients were diagnosed with PAS, and 31 patients with placental previa without PAS. The number and maximum size of diffusion lacunae were significantly larger in patients with than in patients without PAS (p < 0.0001). Combining assessment of the number of diffusion lacunae with assessment of their maximum size yielded a diagnostic performance with sensitivity, specificity and accuracy of 83%, 94% and 90%, respectively. Flow voids within the diffusion lacunae had sensitivity, specificity and accuracy of 88%, 84% and 86%, respectively. The number and size of diffusion lacunae, and T2 flow void in diffusion lacunae may be useful findings for diagnosing PAS.

PETcoil: first results from a second-generation RF-penetrable TOF-PET brain insert for simultaneous PET/MRI

Simultaneous positron emission tomography (PET)/magnetic resonance imaging provides concurrent information about anatomic, functional, and molecular changes in disease. We are developing a second generation MR-compatible RF-penetrable TOF-PET insert. The insert has a smaller scintillation crystal size and ring diameter compared to clinical whole-body PET scanners, resulting in higher spatial resolution and sensitivity. This paper reports the initial system performance of this full-ring PET insert. The global photopeak energy resolution and global coincidence time resolution, 11.74 ± 0.03 % FWHM and 238.1 ± 0.5 ps FWHM, respectively, are preserved as we scaled up the system to a full ring comprising 12, 288 LYSO-SiPM channels (crystal size: 3.2 × 3.2 × 20 mm3). Throughout a ten-hour experiment, the system performance remained stable, exhibiting a less than 1% change in all measured parameters. In a resolution phantom study, the system successfully resolved all 2.8 mm diameter rods, achieving an average VPR of 0.28 ± 0.08 without TOF and 0.24 ± 0.07 with TOF applied. Moreover, the implementation of TOF in the Hoffman phantom study also enhanced image quality. Initial MR compatibility studies of the full PET ring were performed with it unpowered as a milestone to focus on looking for material and geometry-related artifacts. During all MR studies, the MR body coil functioned as both the transmit and receive coil, and no observable artifacts were detected. As expected, using the body coil also as the RF receiver, MR image signal-to-noise ratio exhibited degradation (∼30%), so we are developing a high quality receive-only coil that resides inside the PET ring.

Shape matters: unsupervised exploration of IDH-wildtype glioma imaging survival predictors

Abstract Objectives This study examines clustering based on shape radiomic features and tumor volume to identify IDH-wildtype glioma phenotypes and assess their impact on overall survival (OS). Materials and methods This retrospective study included 436 consecutive patients diagnosed with IDH-wt glioma who underwent preoperative MR imaging. Alongside the total tumor volume, nine distinct shape radiomic features were extracted using the PyRadiomics framework. Different imaging phenotypes were identified using partition around medoids (PAM) clustering on the training dataset (348/436). The prognostic efficacy of these phenotypes in predicting OS was evaluated on the test dataset (88/436). External validation was performed using the public UCSF glioma dataset (n = 397). A decision-tree algorithm was employed to determine the relevance of features associated with cluster affiliation. Results PAM clustering identified two clusters in the training dataset: Cluster 1 (n = 233) had a higher proportion of patients with higher sphericity and elongation, while Cluster 2 (n = 115) had a higher proportion of patients with higher maximum 3D diameter, surface area, axis lengths, and tumor volume (p &lt; 0.001 for each). OS differed significantly between clusters: Cluster 1 showed a median OS of 23.8 compared to 11.4 months of Cluster 2 in the holdout test dataset (p = 0.002). Multivariate Cox regression showed improved performance with cluster affiliation over clinical data alone (C index 0.67 vs 0.59, p = 0.003). Cluster-based models outperformed the models with tumor volume alone (evidence ratio: 5.16–5.37). Conclusion Data-driven clustering reveals imaging phenotypes, highlighting the improved prognostic power of combining shape-radiomics with tumor volume, thereby outperforming predictions based on tumor volume alone in high-grade glioma survival outcomes. Clinical relevance statement Shape-radiomics and volume-based cluster analyses of preoperative MRI scans can reveal imaging phenotypes that improve the prediction of OS in patients with IDH-wild type gliomas, outperforming currently known models based on tumor size alone or clinical parameters. Key Points Shape radiomics and tumor volume clustering in IDH-wildtype gliomas are investigated for enhanced prognostic accuracy. Two distinct phenotypic clusters were identified with different median OSs. Integrating shape radiomics and volume-based clustering enhances OS prediction in IDH-wildtype glioma patients.

Training robust T1-weighted magnetic resonance imaging liver segmentation models using ensembles of datasets with different contrast protocols and liver disease etiologies

Image segmentation of the liver is an important step in treatment planning for liver cancer. However, manual segmentation at a large scale is not practical, leading to increasing reliance on deep learning models to automatically segment the liver. This manuscript develops a generalizable deep learning model to segment the liver on T1-weighted MR images. In particular, three distinct deep learning architectures (nnUNet, PocketNet, Swin UNETR) were considered using data gathered from six geographically different institutions. A total of 819 T1-weighted MR images were gathered from both public and internal sources. Our experiments compared each architecture’s testing performance when trained both intra-institutionally and inter-institutionally. Models trained using nnUNet and its PocketNet variant achieved mean Dice-Sorensen similarity coefficients>0.9 on both intra- and inter-institutional test set data. The performance of these models suggests that nnUNet and PocketNet liver segmentation models trained on a large and diverse collection of T1-weighted MR images would on average achieve good intra-institutional segmentation performance.

A novel residual fourier convolution model for brain tumor segmentation of mr images

A novel residual fourier convolution model for brain tumor segmentation of mr images