Multiparametric MR Imaging of Benign and Malignant Bone Lesions

The role of imaging in extremity sarcoma surgery

The surgical management of extremity bone and soft tissue sarcomas has evolved significantly over the last 50 years. The introduction and refinement of high-resolution cross-sectional imaging has allowed accurate assessment of anatomy and tumor extent, and in the current era more than 90% of patients can successfully undergo limb-salvage surgery. Advances in imaging have also revolutionized the clinician's ability to assess treatment response, detect metastatic disease, and perform intraoperative surgical navigation. This review summarizes the broad and essential role radiology plays in caring for sarcoma patients from diagnosis to post-treatment surveillance. Present evidence-based imaging paradigms are highlighted along with key future directions.

Society of skeletal radiology position paper - recommendations for contrast use in musculoskeletal MRI: when is non-contrast imaging enough?

The following White Paper will discuss the appropriateness of gadolinium administration in MRI for musculoskeletal indications. Musculoskeletal radiologists should consider the potential risks involved and practice the judicious use of intravenous contrast, restricting administration to cases where there is demonstrable added value. Specific nuances of when contrast is or is not recommended are discussed in detail and listed in table format. Briefly, contrast is recommended for bone and soft tissue lesions. For infection, contrast is reserved for chronic or complex cases. In rheumatology, contrast is recommended for early detection but not for advanced arthritis. Contrast is not recommended for sports injuries, routine MRI neurography, implants/hardware, or spine imaging, but is helpful in complex and post-operative cases.

Zero Echo Time vs. T1-Weighted MRI for Assessment of Cortical and Medullary Bone Morphology Abnormalities Using CT as the Reference Standard

BACKGROUND

Conventional MR pulse sequences result in poor signal from low T2 cortical bone because the minimum achievable echo time is limited. A sequence resulting in improved bone contrast is desirable.

PURPOSE

To evaluate the image quality and diagnostic performance of grayscale inversion zero echo time imaging (GI-ZTE) and grayscale inversion T1-weighted imaging (GI-T1WI) compared with computed tomography (CT).

STUDY TYPE

Prospective.

SUBJECTS

A total of 50 patients with musculoskeletal tumors or tumor-like diseases of the lower extremities having MRI and CT studies.

FIELD STRENGTH/SEQUENCE

GI-T1WI and GI-ZTE sequences at 1.5 T.

ASSESSMENT

Assessed cortical and medullary bone morphology abnormalities using CT as the reference standard. Three radiologists scored the images quality and recorded nine metrics to assess the diagnostic performance.

STATISTICAL TESTS

Differences in image quality were calculated using the Wilcoxon signed-rank test. The intraclass correlation coefficient (ICC) was used to analyze the agreement of quantitative lesion parameters between CT and MR sequences, as well as the interobserver reliability. A P value <0.05 was considered statistically significant.

RESULTS

Image quality score was significantly higher for CT images than GI-TIWI images. Except for radiologist 3 [4(0) vs 4 (1)], there was no significant difference in scores between CT and GI-ZTE [radiologist 1: 4 (0) vs 4 (0), P = 0.133; radiologist 2: 4 (0) vs 4 (0), P = 0.085]. There was good-excellent agreement between both MR sequences and CT for size, lesion number, location, sclerotic rim, expanded shell, destruction pattern, and matrix mineralization for all radiologists (ICC: 0.636-1.000). The consistency of periosteal reaction and penetration of the cortex was fair to good (0.481-0.729) between GI-T1WI and CT and good to excellent between GI-ZTE and CT (0.682-0.852).

DATA CONCLUSIONS

GI-ZTE images had superior intermodality agreement with CT images and allowed visualization of more cortical bone detail than GI-T1WI images.

EVIDENCE LEVEL

1.

TECHNICAL EFFICACY

Stage 2.

Differentiation between spinal multiple myeloma and metastases originated from lung using multi-view attention-guided network

Purpose

Multiple myeloma (MM) and metastasis originated are the two common malignancy diseases in the spine. They usually show similar imaging patterns and are highly demanded to differentiate for precision diagnosis and treatment planning. The objective of this study is therefore to construct a novel deep-learning-based method for effective differentiation of two diseases, with the comparative study of traditional radiomics analysis.

Methods

We retrospectively enrolled a total of 217 patients with 269 lesions, who were diagnosed with spinal MM (79 cases, 81 lesions) or spinal metastases originated from lung cancer (138 cases, 188 lesions) confirmed by postoperative pathology. Magnetic resonance imaging (MRI) sequences of all patients were collected and reviewed. A novel deep learning model of the Multi-view Attention-Guided Network (MAGN) was constructed based on contrast-enhanced T1WI (CET1) sequences. The constructed model extracts features from three views (sagittal, coronal and axial) and fused them for a more comprehensive differentiation analysis, and the attention guidance strategy is adopted for improving the classification performance, and increasing the interpretability of the method. The diagnostic efficiency among MAGN, radiomics model and the radiologist assessment were compared by the area under the receiver operating characteristic curve (AUC).

Results

Ablation studies were conducted to demonstrate the validity of multi-view fusion and attention guidance strategies: It has shown that the diagnostic model using multi-view fusion achieved higher diagnostic performance [ACC (0.79), AUC (0.77) and F1-score (0.67)] than those using single-view (sagittal, axial and coronal) images. Besides, MAGN incorporating attention guidance strategy further boosted performance as the ACC, AUC and F1-scores reached 0.81, 0.78 and 0.71, respectively. In addition, the MAGN outperforms the radiomics methods and radiologist assessment. The highest ACC, AUC and F1-score for the latter two methods were 0.71, 0.76 & 0.54, and 0.69, 0.71, & 0.65, respectively.

Conclusions

The proposed MAGN can achieve satisfactory performance in differentiating spinal MM between metastases originating from lung cancer, which also outperforms the radiomics method and radiologist assessment.

Evaluation of risk classifications for gastrointestinal stromal tumor using multi-parameter Magnetic Resonance analysis

BACKGROUND

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal malignancy of the gastrointestinal tract. At present, it is generally believed that the prognosis of GIST is closely related to its risk classification. It may add value to correctly diagnose and evaluate the risk of invasion using a noninvasive imaging examination prior to surgery. MRI has the advantages of multiple parameters and high soft tissue resolution, which may be the potential method to preoperatively evaluate the risk of GIST.

PURPOSE

To retrospectively evaluate the diagnostic accuracy of multi-parameter MR analysis for preoperative risk classification of GIST.

MATERIALS AND METHODS

In this 6-year retrospective study, full MRI examination was performed on all 60 GIST cases confirmed classified by pathology, including 35 cases of very low-to-low-risk GIST and 25 cases of intermediate-to-high-risk GIST. Dynamic contrast-enhanced T1- and T2-weighted images, and apparent diffusion coefficient (ADC) maps were reviewed independently by two radiologists blinded to pathologic results. Volume, ADC ratio, three wash-in indexes (WII) were calculated and compared using t-test or Kruskal-Wallis nonparametric test. Sensitivity and specificity analyses were performed to calculate diagnostic accuracy using ROC analyses. Differences were considered significant at p < 0.05.

RESULTS

All GISTs were resected. Patient age, sex, tumor location and tumor shape did not differ significantly across the two groups (p = 0.798, 0.767, 0.822 and 0.096, respectively). GIST in the intermediate-to-high-risk group presented significantly greater volume (p = 0.0045), lower ADC ratio (p = 0.0125) and faster enhancement (for WII2, p < 0.0001; for WII3, p = 0.0358) than that of GIST in the very low-to-low-risk group. This combination of the volume, ADC ratio and WII2 provided sensitivity of 88%, specificity of 94.29%, and accuracy of 91.7% for the risk classification of GIST.

CONCLUSION

Multi-parameter MR analysis provides a preoperative imaging standard for accurately distinguishing very low-to-low-risk GIST from intermediate-to-high-risk GIST.

Bone Metastases: Mechanisms of the Metastatic Process, Imaging and Therapy

The mechanisms by which tumors metastasize to bone are complex. Upon the successful establishment of metastatic deposits in the skeleton, detection of the disease becomes essential for therapeutic planning. The roles of CT, skeletal scintigraphy, SPECT/CT, MRI, PET/CT and PET/MRI will be reviewed. Therapeutic response criteria specifically designed to evaluate bone metastases (MD Anderson/MDA criteria) can guide image interpretation. Knowledge of therapeutic strategies such as systemic therapy with bisphosphonates or radiopharmaceuticals, radiation therapy, surgery, and percutaneous interventions such as vertebroplasty and radiofrequency ablation can help the radiologist produce reports that will provide maximum benefit to clinicians and patients.