Role of diffusion weighted MR-imaging in the evaluation of malignant mediastinal lesions

Role of diffusion-weighted MRI in differentiation between benign and malignant anterior mediastinal masses

Diffusion-weighted imaging (DWI) is considered to be a useful biomarker to characterize the cellularity of lesions, yet its application in the thorax to evaluate anterior mediastinal lesions has not been well investigated. The aims of our study were to describe the magnetic resonance (MR) characteristics of anterior mediastinal masses and to assess the role of apparent diffusion coefficient (ADC) value in distinguishing benign from malignant lesions of the anterior mediastinum. We conducted a retrospective cross-sectional study including 55 patients with anterior mediastinal masses who underwent preinterventional MR scanning with the following sequences: T1 VIBE DIXON pre and post-contrast, T2 HASTE, T2 TIRM, DWI-ADC map (b values of 0 and 2000 sec/mm2). The ADC measurements were obtained by two approaches: hot-spot ROI and whole-tumor histogram analysis. The lesions were grouped by three distinct ways: benign versus malignant, group A (benign lesions and type A, AB, B1 thymoma) versus group B (type B2, B3 thymoma and other malignant lesions), lymphoma versus other malignancies. The study was composed of 55 patients, with 5 benign lesions and 50 malignant lesions. The ADCmean, ADCmedian, ADC10, ADC90 in the histogram-based approach and the hot-spot-ROI-based mean ADC of the malignant lesions were significantly lower than those of benign lesions (P values< 0.05). The hot-spot-ROI-based mean ADC had the highest value in differentiation between benign and malignant mediastinal lesions, as well as between group A and group B; the ADC cutoffs (with sensitivity, specificity) to differentiate malignant from benign lesions and group A from group B were 1.17 x 10-3 mm2/sec (80%, 80%) and 0.99 x 10-3 mm2/sec (78.4%, 88.9%), respectively. The ADC values obtained by using the hot-spot-ROI-based and the histogram-based approaches are helpful in differentiating benign and malignant anterior mediastinal masses.

Role of diffusion MRI in diagnosis of mediastinal lymphoma: initial assessment and response to therapy

Background

Malignant lymphoma accounts for nearly 20% of all mediastinal neoplasms in adults and 50% in children. Hodgkin’s disease is the most common primary mediastinal lymphoma. In non-Hodgkin’s lymphoma, the two most common forms of primary mediastinal lymphoma are lymphoblastic lymphoma and diffuse large B-cell lymphoma. The aim of this study is to implement diffusion MRI in the algorithm of diagnosis of mediastinal lymphoma, differentiating Hodgkin's from non-Hodgkin's lymphoma and assessment of post therapeutic response.

Results

Using Diffusion weighted magnetic resonance imaging DWI-MRI, there were statistic significant difference between ADC values in lymph nodes and mediastinal masses in Hodgkin and non-Hodgkin lymphomas. ADC range in non-treated Hodgkin lymphoma cases was 0.774 to 1.4, while ADC range in in non-treated non-Hodgkin lymphoma was 0.476 to 0.668. In this study, there was statistically significant difference of ADC values in lymphoma cases presented by mediastinal masses with and without chemotherapy.

Conclusions

Diffusion weighted magnetic resonance imaging DWI-MRI is a promising functional technique in diagnosis of Hodgkin's and non-Hodgkin's lymphoma and assessment of response to treatment with no need for special preparation, contrast injection or radiation exposure.

Lymph nodes in the head and neck cancer: would diffusion-weighted magnetic resonance imaging solve the diagnostic dilemma?

Background

Head and neck cancer has been labeled as the fifth most common cancer. Lymph node (LN) metastases were reported as the most important predatory factor for diagnosis and selection of suitable treatment. Diffusion-weighted (DW) magnetic resonance (MR) imaging is a very important tool that gives quantitative data in several compartments. This work aims to evaluate the diagnostic value of diffusion-weighted as a part of the magnetic resonance imaging in patients with head and neck cancer to allow differentiation of lymph nodes, cancer staging, assessment of recurrence, and evaluation of the effects of oncologic therapy.

Results

The size of pathologically proven benign LNs ranged from 1 to 3 cm (1.71 ± 0.724) and malignant LNs ranged from 1.1 to 5.6 cm (2.54 ± 0.92) (P = 0.0103). The ADC value for benign LNs ranged from 1.26 × 10−3 to 2.49 × 10−3 (mean 1.98 × 10−3 ± 0.32 × 10−3), and malignant LNs from 0.608 × 10−3 to 2.1 × 10−3 (mean 0.971 × 10−3 ± 0.305 × 10−3) (P < 0.001) with sensitivity and a specificity of 94% and 100% respectively. The ADC value for metastatic LNs ranged from 0.70 × 10−3 to 2.10 × 10−3 (1.08 × 10−3 ± 0.31 × 10−3) while lymphomatous nodes ranged 0.608 × 10−3 to 1.16 × 10−3 (0.78 × 10−3 ± 0.17 × 10−3). In this study, a significant statistical difference was also observed between the ADC value of the SCC and lymphomatous LN (P = 0.0034) with sensitivity and a specificity of 90% and 75% respectively.

Conclusion

Diffusion-weighted MR imaging is an effective assist in differentiating benign and malignant lymph nodes. It acts as an indicator for recovery or recurrence after chemotherapy and radiotherapy.

Whole body diffusion-weighted MRI in detection of metastasis and lymphoma: a prospective longitudinal clinical study

Background

Whole-body diffusion-weighted magnetic resonance imaging (WB-DWI-MRI) is an emerging tool that has an increasing role in the diagnosis of metastasis and lymphoma. This is a longitudinal study in actual clinical settings designed to assess WB-DWI-MRI in detection of tumor spread. The study included all patients who were referred to Radiology Department, during the period from June 2016 till May 2018, with either a known primary tumor (either laboratory, radiologically, or histologically proven, of any type, affecting any organ) or with biopsy-proven lymphoma of any subtype, affecting any organ. All patients underwent WB coronal T1-weighted, STIR, axial T2-weighted, and DWI-MRI examinations before commencing any treatment with curative intent. The body was divided into lymph nodes (LNs), skeletal system, and organs (brain, lung, and liver). Patients were followed up till the nature of the lesion(s) was confirmed (clinically, radiologically, or histologically).

Results

The study included 46 patients; 27 patients had metastases and 19 had lymphomas. Sensitivities, specificities, and accuracies for LN detection were 77%, 85%, and 83%; for skeletal metastasis were 88%, 94%, and 92%; for brain lesions were 78%, 95%, and 91%; and for lung lesion were 64%, 88%, and 76%, respectively. As for the liver, all lesions were correctly identified and did not miss any lesion with accuracy of 100%. Overall, 1739 lesions were discovered in 1271 regions out of 3818 examined regions with overall sensitivity, specificity, and accuracy of 86%, 92%, and 90% respectively.

Conclusion

The diagnostic performance of WB-DWI-MRI is variable among different anatomical sites. It has good performance in diagnosis of some organs as liver, bone marrow, and some LNs regions as porta-hepatis. It has a less diagnostic performance in the lung, and LNs located in cervical, mediastinum, supraclavicular, and mesenteric regions.