7 T Lumbosacral Plexus Neurography: Feasibility and Comparison of Spinal Nerve Visualization With 3 T MRI.

7 T magnetic resonance (MR) imaging can offer superior spatial resolution compared with lower field strengths. However, its use for imaging of the lumbosacral plexus has been constrained by technical challenges and therefore remained relatively unexplored. Therefore, this study investigated the feasibility of 7 T MR neurography by means of comparing the visibility of the spinal nerves and image quality to 3 T MR neurography. In this monocentric, institutional review board-approved, prospective study, 30 healthy subjects underwent acquisition time-matched 7 T MR neurography and 3 T MR neurography of the lumbar spine using a 3-dimensional dual-echo steady-state sequence. Visibility of the nerve root, dorsal root ganglia, and spinal nerve fascicles of L1-S1, along with image artifacts and overall image quality, were compared between the different field strengths by 2 radiologists using 4-point Likert scales (1 = poor, 4 = excellent). Comparisons between field strengths were made using the Wilcoxon signed rank test, and interobserver agreement was assessed. 7 T MR neurography enabled significantly improved visualization of the lumbar nerve roots, dorsal root ganglia, and spinal nerve fascicles (P ≤ 0.002). Compared with 3 T MR neurography, no difference in overall image quality was observed (P = 0.211), although 7 T MR imaging exhibited significantly increased image artifacts (P < 0.001). Interobserver agreement (κ) for qualitative measures ranged from 0.71 to 0.88 for 7 T, and from 0.75 to 0.91 for 3 T. 7 T MR neurography allowed for improved visualization of lumbar spinal nerves, whereas overall image quality was comparable to 3 T MR neurography. This supports the feasibility of 7 T MR neurography of the lumbosacral plexus, even though image artifacts at 7 T were significantly increased.

Marth AA ，Feuerriegel GC ，Wanivenhaus F ，Nanz D ，Sutter R ... -  《-》

Comparison of Two Modern Survival Prediction Tools, SORG-MLA and METSSS, in Patients With Symptomatic Long-bone Metastases Who Underwent Local Treatment With Surgery Followed by Radiotherapy and With Radiotherapy Alone.

Survival estimation for patients with symptomatic skeletal metastases ideally should be made before a type of local treatment has already been determined. Currently available survival prediction tools, however, were generated using data from patients treated either operatively or with local radiation alone, raising concerns about whether they would generalize well to all patients presenting for assessment. The Skeletal Oncology Research Group machine-learning algorithm (SORG-MLA), trained with institution-based data of surgically treated patients, and the Metastases location, Elderly, Tumor primary, Sex, Sickness/comorbidity, and Site of radiotherapy model (METSSS), trained with registry-based data of patients treated with radiotherapy alone, are two of the most recently developed survival prediction models, but they have not been tested on patients whose local treatment strategy is not yet decided. (1) Which of these two survival prediction models performed better in a mixed cohort made up both of patients who received local treatment with surgery followed by radiotherapy and who had radiation alone for symptomatic bone metastases? (2) Which model performed better among patients whose local treatment consisted of only palliative radiotherapy? (3) Are laboratory values used by SORG-MLA, which are not included in METSSS, independently associated with survival after controlling for predictions made by METSSS? Between 2010 and 2018, we provided local treatment for 2113 adult patients with skeletal metastases in the extremities at an urban tertiary referral academic medical center using one of two strategies: (1) surgery followed by postoperative radiotherapy or (2) palliative radiotherapy alone. Every patient's survivorship status was ascertained either by their medical records or the national death registry from the Taiwanese National Health Insurance Administration. After applying a priori designated exclusion criteria, 91% (1920) were analyzed here. Among them, 48% (920) of the patients were female, and the median (IQR) age was 62 years (53 to 70 years). Lung was the most common primary tumor site (41% [782]), and 59% (1128) of patients had other skeletal metastases in addition to the treated lesion(s). In general, the indications for surgery were the presence of a complete pathologic fracture or an impending pathologic fracture, defined as having a Mirels score of ≥ 9, in patients with an American Society of Anesthesiologists (ASA) classification of less than or equal to IV and who were considered fit for surgery. The indications for radiotherapy were relief of pain, local tumor control, prevention of skeletal-related events, and any combination of the above. In all, 84% (1610) of the patients received palliative radiotherapy alone as local treatment for the target lesion(s), and 16% (310) underwent surgery followed by postoperative radiotherapy. Neither METSSS nor SORG-MLA was used at the point of care to aid clinical decision-making during the treatment period. Survival was retrospectively estimated by these two models to test their potential for providing survival probabilities. We first compared SORG to METSSS in the entire population. Then, we repeated the comparison in patients who received local treatment with palliative radiation alone. We assessed model performance by area under the receiver operating characteristic curve (AUROC), calibration analysis, Brier score, and decision curve analysis (DCA). The AUROC measures discrimination, which is the ability to distinguish patients with the event of interest (such as death at a particular time point) from those without. AUROC typically ranges from 0.5 to 1.0, with 0.5 indicating random guessing and 1.0 a perfect prediction, and in general, an AUROC of ≥ 0.7 indicates adequate discrimination for clinical use. Calibration refers to the agreement between the predicted outcomes (in this case, survival probabilities) and the actual outcomes, with a perfect calibration curve having an intercept of 0 and a slope of 1. A positive intercept indicates that the actual survival is generally underestimated by the prediction model, and a negative intercept suggests the opposite (overestimation). When comparing models, an intercept closer to 0 typically indicates better calibration. Calibration can also be summarized as log(O:E), the logarithm scale of the ratio of observed (O) to expected (E) survivors. A log(O:E) > 0 signals an underestimation (the observed survival is greater than the predicted survival); and a log(O:E) < 0 indicates the opposite (the observed survival is lower than the predicted survival). A model with a log(O:E) closer to 0 is generally considered better calibrated. The Brier score is the mean squared difference between the model predictions and the observed outcomes, and it ranges from 0 (best prediction) to 1 (worst prediction). The Brier score captures both discrimination and calibration, and it is considered a measure of overall model performance. In Brier score analysis, the "null model" assigns a predicted probability equal to the prevalence of the outcome and represents a model that adds no new information. A prediction model should achieve a Brier score at least lower than the null-model Brier score to be considered as useful. The DCA was developed as a method to determine whether using a model to inform treatment decisions would do more good than harm. It plots the net benefit of making decisions based on the model's predictions across all possible risk thresholds (or cost-to-benefit ratios) in relation to the two default strategies of treating all or no patients. The care provider can decide on an acceptable risk threshold for the proposed treatment in an individual and assess the corresponding net benefit to determine whether consulting with the model is superior to adopting the default strategies. Finally, we examined whether laboratory data, which were not included in the METSSS model, would have been independently associated with survival after controlling for the METSSS model's predictions by using the multivariable logistic and Cox proportional hazards regression analyses. Between the two models, only SORG-MLA achieved adequate discrimination (an AUROC of > 0.7) in the entire cohort (of patients treated operatively or with radiation alone) and in the subgroup of patients treated with palliative radiotherapy alone. SORG-MLA outperformed METSSS by a wide margin on discrimination, calibration, and Brier score analyses in not only the entire cohort but also the subgroup of patients whose local treatment consisted of radiotherapy alone. In both the entire cohort and the subgroup, DCA demonstrated that SORG-MLA provided more net benefit compared with the two default strategies (of treating all or no patients) and compared with METSSS when risk thresholds ranged from 0.2 to 0.9 at both 90 days and 1 year, indicating that using SORG-MLA as a decision-making aid was beneficial when a patient's individualized risk threshold for opting for treatment was 0.2 to 0.9. Higher albumin, lower alkaline phosphatase, lower calcium, higher hemoglobin, lower international normalized ratio, higher lymphocytes, lower neutrophils, lower neutrophil-to-lymphocyte ratio, lower platelet-to-lymphocyte ratio, higher sodium, and lower white blood cells were independently associated with better 1-year and overall survival after adjusting for the predictions made by METSSS. Based on these discoveries, clinicians might choose to consult SORG-MLA instead of METSSS for survival estimation in patients with long-bone metastases presenting for evaluation of local treatment. Basing a treatment decision on the predictions of SORG-MLA could be beneficial when a patient's individualized risk threshold for opting to undergo a particular treatment strategy ranged from 0.2 to 0.9. Future studies might investigate relevant laboratory items when constructing or refining a survival estimation model because these data demonstrated prognostic value independent of the predictions of the METSSS model, and future studies might also seek to keep these models up to date using data from diverse, contemporary patients undergoing both modern operative and nonoperative treatments. Level III, diagnostic study.

Lee CC ，Chen CW ，Yen HK ，Lin YP ，Lai CY ，Wang JL ，Groot OQ ，Janssen SJ ，Schwab JH ，Hsu FM ，Lin WH ... -  《-》

Magnetic resonance cholangiopancreatography at 5.0 T: quantitative and qualitative comparison with 3.0 T.

This study aimed to assess the feasibility and performance of 5.0 T MRI in MR Cholangiopancreatography (MRCP) imaging compared to 3.0 T, focusing on detail visualization, signal-to-noise ratio (SNR), and image artifacts. A prospective study from May to October 2023 involved 20 healthy subjects and 19 with biliary dilation. Both groups underwent MRCP using 3.0 T and 5.0 T scanners. The detail visualization capability of the biliary tree and the SNR of the images were quantitatively evaluated. Two experienced MRI diagnostic physicians assessed the image artifacts qualitatively on a scale of 1 to 5. The t-test or Wilcoxon signed-rank test compared the quantitative results of biliary visualization and SNR between 3.0 T and 5.0 T scanners, while the Wilcoxon signed-rank test was used for comparing the level of image artifacts between the two scanners. The inter reader consistency was tested using Kappa test. In both healthy subjects and those with biliary dilation, the 5.0 T group exhibited significantly higher numbers of biliary tree branches, along with greater total and maximum branch lengths, compared to the 3.0 T group (P<0.05). Although the maximum branch length was higher in the 5.0 T group among healthy subjects, this difference was not statistically significant (P = 0.053). No notable differences were observed in SNR and image artifact levels between the two groups across both field strengths (P>0.05). MRCP at 5.0 T offers superior biliary tree visualization compared to 3.0 T. The performance regarding SNR and image artifacts between the two is relatively comparable.

Yin L ，Li Z ，Shang M ，Li Z ，Tang B ，Yu D ，Gan J ... -  《-》

Magnetisation transfer ratio combined with magnetic resonance neurography is feasible in the proximal lumbar plexus using healthy volunteers at 3T.

Yiannakas MC ，Schneider T ，Yoneyama M ，Aforlabi-Logoh I ，Prados F ，Ciccarelli O ，Wheeler-Kingshott CAM ... -  《-》

Intravoxel incoherent motion diffusion-weighted imaging in nasopharyngeal carcinoma: comparison of the turbo spin-echo and echo-planar imaging techniques.

Traditional echo-planar imaging with intravoxel incoherent motion (EPI-IVIM) exhibits significant magnetic susceptibility artifacts and geometric distortions, which limits its application in nasopharyngeal carcinoma (NPC). This study aimed to compare the qualitative and quantitative indicators between turbo spin echo with intravoxel incoherent motion (TSE-IVIM) and EPI-IVIM in patients with NPC and to provide optimal scanning strategies based on the relationships among these indicators. A cross-sectional study was conducted between March 2022 and August 2022. Patients with pathologically confirmed NPC underwent pretreatment staging magnetic resonance (MR) examinations with both TSE-IVIM and EPI-IVIM. IVIM images were subjectively and objectively assessed for anatomical structures including nasopharyngeal lesions, nasal concha, the spinal cord, and the temporal pole. Subjective evaluation indicators (including susceptibility artifacts, geometric distortion, lesion conspicuity, and overall image quality on a five-point scale) were compared using the Wilcoxon signed rank test. Quantitative indicators, including signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), apparent diffusion coefficient (ADC), and IVIM-derived parameters (true diffusion coefficients, perfusion fraction, pseudodiffusion coefficient), were compared using the Wilcoxon signed rank test. Bland-Altman plots and coefficient of variation (CV) were used to compare the reproducibility and robustness of the ADC and IVIM-derived parameters between TSE-IVIM and EPI-IVIM. A total of 30 patients (24 males and 6 females) aged between 29 and 71 years (mean age 47.6±12.3 years) were included in the study. TSE-IVIM demonstrated significantly better subjective evaluation indicators for nasopharyngeal lesions, nasal concha, and temporal poles as compared to EPI-IVIM (all P values <0.001), with no significant difference observed in the spinal cord. The SNR of TSE-IVIM was significantly lower than that of EPI-IVIM in the spinal cord and temporal pole (SNR: P=0.027 and P=0.026, respectively). For nasopharyngeal lesions and nasal concha, TSE-IVIM showed no significant difference in SNR (P=0.926 and P=0.428, respectively) but had a significantly higher CNR compared to EPI-IVIM (P=0.003 and P=0.01, respectively). The perfusion fraction (f) value for TSE-IVIM in nasopharyngeal lesions was significantly lower than that for EPI-IVIM (P=0.004), while no statistically significant differences were found in the diffusion coefficient (D) or pseudodiffusion coefficient (D*) values (P=0.914 and P=0.644, respectively). The 95% limits of agreement (LoAs) in nasopharyngeal lesions and nasal concha were wider and had a larger CV compared to those in the spinal cord and temporal pole. TSE-IVIM provided better subjective image quality scores and a significantly higher CNR, with no significant reduction in SNR. It demonstrated superior image quality and more stable quantitative indicators for nasopharyngeal lesions and nasal concha although magnetic sensitivity artifacts were more noticeable. Due to the different f values and wide LoAs observed between the two sequences in nasopharyngeal lesions, TSE-IVIM is recommended for follow-up in patients with NPC.

Liu Y ，Hu L ，Qian L ，Chen M ，Xu S ，Sun P ，Huang J ，Lei Z ... -  《-》