Diffusion Weighted Imaging Can Distinguish Benign from Malignant Mediastinal Tumors and Mass Lesions: Comparison with Positron Emission Tomography

Evaluation of the effect of PET/CT Fluorodeoxyglucose inclusion on mortality and survival in operated thymoma patients

PURPOSE

In recent years, the use of fluorodeoxyglucose PET-computed tomography (PET-CT) has become widespread to evaluate the diagnosis, metabolism, stage and distant metastases of thymoma. In this study, it was aimed to investigate the connection of malignancy potential, survival and maximum standardized uptake value (SUV max ) measured by PET-CT before surgery according to the histological classification of the WHO in patients operated for thymoma. In addition, the predictive value of the Glasgow prognostic score (GPS) generated by C-reactive protein (CRP) and albumin values on recurrence and survival was investigated and its potential as a prognostic biomarker was evaluated.

METHODS

Forty-five patients who underwent surgical resection for thymoma and were examined with PET-CT in the preoperative period between January 2010 and January 2022 were included in the study. The relationship between WHO histological classification, tumor size and SUV max values on PET-CT according to TNM classification of retrospectively analyzed corticoafferents were evaluated. Preoperative albumin and CRP values were used to determine GPS.

RESULTS

The cutoff value for SUV max was found to be 5.65 in the patients and the overall survival rate of low-risk (<5.65) and high-risk (>5.65) patients was compared according to the SUV max threshold value (5.65) and found to be statistically significant. In addition, the power of PET/CT SUV max value to predict mortality (according to receiver operating characteristics analysis) was statistically significant ( P  = 0.048). Survival expectancy was 127.6 months in patients with mild GPS (O points), 96.7 months in patients with moderate GPS (1 point), and 25.9 months in patients with severe GPS (2 points).

CONCLUSION

PET/CT SUV max values can be used to predict histological sub-type in thymoma patients, and preoperative SUV max and GPS are parameters that can provide information about survival times and mortality in thymoma patients.

Positron emission tomography/computed tomography differentiates resectable thymoma from anterior mediastinal lymphoma

OBJECTIVE

Discrete anterior mediastinal masses most often represent thymoma or lymphoma. Lymphoma treatment is nonsurgical and requires biopsy. Noninvasive thymoma is ideally resected without biopsy, which may potentiate pleural metastases. This study sought to determine if clinical criteria or positron emission tomography/computed tomography could accurately differentiate the 2, guiding a direct surgery versus biopsy decision.

METHODS

A total of 48 subjects with resectable thymoma and 29 subjects with anterior mediastinal lymphoma treated from 2006 to 2019 were retrospectively examined. All had pretreatment positron emission tomography/computed tomography and appeared resectable (solitary, without clear invasion or metastasis). Reliability of clinical criteria (age and B symptoms) and positron emission tomography/computed tomography maximum standardized uptake value were assessed in differentiating thymoma and lymphoma using Wilcoxon rank-sum test, chi-square test, and logistic regression. Receiver operating characteristic analysis identified the maximum standardized uptake value threshold most associated with thymoma.

RESULTS

There was no association between tumor type and age group (P = .183) between those with thymoma versus anterior mediastinal lymphoma. Patients with thymoma were less likely to report B symptoms (P < .001). The median maximum standardized uptake value of thymoma and lymphoma differed dramatically: 4.35 versus 18.00 (P < .001). Maximum standardized uptake value was independently associated with tumor type on multivariable regression. On receiver operating characteristic analysis, lower maximum standardized uptake value was associated with thymoma. Maximum standardized uptake value less than 12.85 was associated with thymoma with 100.00% sensitivity and 88.89% positive predictive value. Maximum standardized uptake value less than 7.50 demonstrated 100.00% positive predictive value for thymoma.

CONCLUSIONS

Positron emission tomography/computed tomography maximum standardized uptake value of resectable anterior mediastinal masses may help guide a direct surgery versus biopsy decision. Tumors with maximum standardized uptake value less than 7.50 are likely thymoma and thus perhaps appropriately resected without biopsy. Tumors with maximum standardized uptake value greater than 7.50 should be biopsied to rule out lymphoma. Lymphoma is likely with maximum standardized uptake value greater than 12.85.

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&lt; 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.

Diagnostic value of apparent diffusion coefficient in predicting pathological T stage in patients with thymic epithelial tumor

Purposes

This study aimed to evaluate the diagnostic capacity of apparent diffusion coefficient (ADC) in predicting pathological Masaoka and T stages in patients with thymic epithelial tumors (TETs).

Methods

Medical records of 62 patients who were diagnosed with TET and underwent diffusion-weighted imaging (DWI) prior to surgery between August 2017 and July 2021 were retrospectively analyzed. ADC values were calculated from DWI images using b values of 0, 400, and 800 s/mm². Pathological stages were determined by histological examination of surgical specimens. Cut-off points of ADC values were calculated via receiver operating characteristic (ROC) analysis.

Results

Patients had a mean age of 56.3 years. Mean ADC values were negatively correlated with pathological Masaoka and T stages. Higher values of the area under the ROC curve suggested that mean ADC values more accurately predicated pathological T stages than pathological Masaoka stages. The optimal cut-off points of mean ADC were 1.62, 1.31, and 1.48 × 10^–3 mm²/sec for distinguishing pathological T2-T4 from pathological T1, pathological T4 from pathological T1-T3, and pathological T3-T4 from pathological T2, respectively.

Conclusion

ADC seems to more precisely predict pathological T stages, compared to pathological Masaoka stage. The cut-off values of ADC identified may be used to preoperatively predict pathological T stages of TETs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40644-022-00495-x.

Multifocal Cholesterol Granulomas of the Thymus: A Case Report of Positron Emission Tomography- Positive Benign Tumor of the Anterior Mediastinum

Cholesterol granulomas of the thymus are extremely rare benign entities. Herein, we describe a case of cholesterol granuloma in a 45-year-old man who presented with multifocal anterior mediastinal lesions on computed tomography (CT). Positron emission tomography (PET)-CT revealed increased fluorodeoxyglucose uptake, with a maximum standardized uptake value of 8.3. Diffusion-weighted magnetic resonance imaging (MRI) revealed extreme hypointensity. He underwent total thymectomy by median sternotomy for presumed multiple thymoma. On histopathological analysis, cholesterol granuloma of the thymus was confirmed, and the patient had an uneventful postoperative course without recurrence for 28 months. Cholesterol granuloma of the thymus is a PET-CT-positive benign tumor with unique histological findings. The MRI findings were indicative of hypocellularity associated with a benign entity, whereas the PET-CT findings corresponded to granulomatous inflammation. Therefore, concurrent use of PET-CT and MRI can be helpful in distinguishing between benign cholesterol granulomas and malignant anterior mediastinal tumors.

Extracellular volume fraction measurement correlates with lymphocyte abundance in thymic epithelial tumors

Background

Recent advance in tissue characterization with parametric mapping imaging has the potential to be a novel biomarker for histopathologic correlation with thymic epithelial tumors (TETs). The purpose of our study is to evaluate MRI T1 mapping with the calculation of extracellular volume (ECV) fraction for histologic correlation with thymic epithelial tumor based on lymphocyte abundance.

Methods

A retrospective study including 31 consecutive patients (14 men and 17 women, median age, 56 years; interquartile range, 12 years) with TETs was performed. The T1 values and ECV were assessed by using quantitative MRI mapping techniques. Mann-Whitney U test, Kruskal-Wallis H test, and receiver operating characteristic curve analyses were used to assess discrimination between different types of TETs based on lymphocyte abundance.

Results

Extracellular volume was significantly higher in TETs with sparse lymphocyte, including type A, type B3, and thymic carcinoma, compared with those with abundant lymphocyte, including type B1, B2, and AB thymomas (42.5% vs 26.9%, respectively; p < 0.001). Extracellular volume was significantly higher in thymic carcinoma compared with low grade and high grade thymomas (48.6% vs 31.1% vs 27.6%, respectively; p = 0.002).

Conclusions

T1 mapping with the calculation of extracellular volume (ECV) fraction correlate with the WHO histologic classification of thymic epithelial tumor based on lymphocyte abundance.

Dual-energy CT perfusion imaging for differentiating WHO subtypes of thymic epithelial tumors

To evaluate the role of conventional contrast-enhanced CT (CECT) imaging and dual-energy spectral CT (DECT) perfusion imaging in differentiating the WHO histological subtypes of thymic epithelial tumours (TETs). Eighty-eight patients with TETs who underwent DECT perfusion scans (n = 51) and conventional CT enhancement scans (n = 37) using a GE Discovery CT750 HD scanner were enrolled in this study. The mean maximal contrast-enhanced range (mean CEmax) and the perfusion and spectral parameters of the lesions were analysed. Among the six WHO subtypes (Type A, AB, B1, B2, and B3 thymoma and thymic carcinoma), the mean CEmax values and most of the perfusion and spectral parameter values of Type A and Type AB were significantly higher than those of the other subtypes (all P < 0.05), and there was no difference among Type B1, B2 and B3 (all P > 0.05). The mean CEmax value was not different between Type B (including Type B1, B2, and B3) and thymic carcinoma (P = 1.000). The PS, IC, NIC and λHU values in the optimal venous phase of thymic carcinoma were higher than those of Type B (all P < 0.05). The parameters of conventional CECT imaging and DECT perfusion imaging can help identify the subtype of TETs, especially those of DECT perfusion imaging in type B thymomas and thymic carcinomas.

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

Background

Conducted studies showed that the ADC (apparent diffusion coefficient) values of malignant mediastinal lesions are significantly lower than those of benign lesions. Investigators determined cut-off ADC values to differentiate the two; concluding that ADC value is a promising noninvasive, imaging parameter that helps assess and characterize mediastinal tumors.

Taking this a step forward, the primary objective of our prospective study was to investigate the potential of DW-MRI (diffusion-weighted magnetic resonance imaging) to characterize malignant mediastinal lesions using their ADC values.

Thirty-three patients that underwent MRI of the chest with DWI and latter pathologically diagnosed with a malignant mediastinal lesion were included in this study. Lesions’ ADC values were measured and correlated with the histopathological results. The statistical significance of differences between measurements was tested using the one-way ANOVA (analysis of variance) test; p values equal to or less than 0.05 were considered significant.

Results

There was no statistically significant difference between the ADCmean values of the histopathological groups of lesions assessed with the overlap of their ADCmean values. The average ADCmean value of NHL (non-Hodgkin lymphoma) was evidently lower than that of HD (Hodgkin disease) with no overlap between their ADCmean values. DWI failed at characterizing one lesion in this study as a malignant tumor, namely an immature teratoma (germ-cell tumor). Again DWI could not be used to evaluate a mass, latter pathologically diagnosed as an angiosarcoma, because of its overall hemorrhagic nature showing no definite non-hemorrhagic soft tissue components. The aforementioned results did not differ considerably when minimum ADC was used instead of mean ADC.

Conclusion

There was no statistically significant difference between the ADC values of the malignant mediastinal lesions evaluated. However, regarding lymphoma subtypes, our limited sample study of lymphoma suggested a considerable difference between the ADC values of Hodgkin disease and non-Hodgkin lymphoma.

Quantitative analysis of metabolic parameters at 18F-fluorodeoxyglucose positron emission tomography in predicting malignant potential of anterior mediastinal tumors

To evaluate the utility of ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) for predicting the malignancy of anterior mediastinal tumors, the present study retrospectively examined a total of 105 consecutive patients who underwent surgical resection of anterior mediastinal tumors at Gunma University Hospital after undergoing a preoperative FDG-PET scan. Patients were divided into benign and malignant groups in accordance with the following three classification systems: i) Clinical classification, benign or malignant (thymoma and carcinoma); ii) recurrence-based classification, low-risk recurrence (benign and low-risk thymoma) or high-risk recurrence (high-risk thymoma and carcinoma); and iii) pathological classification, benign (benign and thymoma) or malignant (carcinoma). The present study analyzed the differences between the benign and malignant groups in terms of FDG-PET parameters, including maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The malignant group exhibited a significantly greater SUVmax than the benign group according to all classification systems. By contrast, there was only a slight difference between groups in volume-based metabolic parameters (MTV and TLG) using the clinical classification, and no intergroup differences using the recurrence-based and pathological classifications. The area under the curve in receiver-operating characteristic curve analysis for predicting malignancy was significantly greater for SUVmax than for volume-based metabolic parameters using all classification methods. The respective optimal cut-off value, sensitivity and specificity of SUVmax to predict malignancy were 1.77, 92.0 and 87.0% for the clinical classification, 2.54, 93.6 and 60.3% for the recurrence-based classification, and 5.15, 78.9 and 90.7% for the pathological classification. SUVmax was the most useful parameter for predicting the malignancy of anterior mediastinal tumors.

The Value of CT and MRI for Determining Thymoma in Patients With Myasthenia Gravis

The aim of the study was to evaluate the usefulness of computed tomography (CT) and magnetic resonance imaging (MRI) for differentiating thymoma from nonthymoma abnormalities in patients with myasthenia gravis (MG). A cross-sectional study of 53 patients with MG, who had undergone surgical thymectomy, was conducted at 103 Hospital (Hanoi, Vietnam) and Cho Ray Hospital (Ho Chi Minh City, Vietnam) during August 2014 and January 2017. The CT and MRI images of patients with MG were qualitatively and quantitatively (radiodensity and chemical shift ratio [CSR]) analyzed to determine and compare their ability to distinguish thymoma from nonthymoma abnormalities. Logistic regression was used to identify the association between imaging parameters (eg, CSR) and the thymoma status. The receiver operating curve (ROC) analysis was used to determine the differentiating ability of CSR and radiodensity. As results, of the 53 patients with MG, 33 were with thymoma and 20 were with nonthymoma abnormalities. At qualitative assessment, MRI had significantly higher accuracy than did CT in differentiating thymoma from nonthymoma abnormalities (94.3% vs 83%). At quantitative assessment, both the radiodensity and CSR were significantly higher for thymoma compared with nonthymoma groups (P < .001). The ROC analysis showed that CSR had significantly higher sensitivity (Se) and specificity (Sp) than radiodensity in discriminating between the 2 groups (CSR: Se 100%, Sp 95% vs radiodensity: Se 90.9%, Sp 70%). When combining both qualitative and quantitative parameters, MRI had even higher accuracy than did CT in thymoma diagnosis (P = .031). In conclusion, chemical shift MRI was more accurate than CT for differentiating thymoma from nonthymoma in patients with MG.

Comparison between CT and MRI in the Diagnostic Accuracy of Thymic Masses

Purpose: The aim of this study was to compare diagnostic accuracy between CT and MRI for thymic masses.

Methods: We searched literature and collected information on first author, publication year, cases of different types of thymic lesions, correct diagnostic cases of CT and MRI and results of quantitative analysis of CT and MRI. The ROC curve was applied to compare the diagnostic performance of different imaging modalities.

Results: Eight literatures were finally included and analyzed in this study. There were 253 cases examined by CT and 340 cases by MRI in total. We showed outcomes of quantitative analysis of each study in this article. The sensitivity of CT and MRI was both 100%, while the specificity was 75% and 80%, respectively. AUC of CT was 0.875 [95%CI: 0.473, 0.997] and that of MRI was 0.880 [95%CI: 0.531, 0.995].

Conclusion: The diagnostic accuracy of MRI is superior to CT in detecting thymomas, thymic cysts or thymic hyperplasia but that of CT and MRI is still unclear in differentiating thymic carcinomas and lymphomas/germ cell tumors.

Application of the apparent diffusion coefficient in magnetic resonance imaging in an assessment of the early response to treatment in Hodgkin's and non-Hodgkin's lymphoma - pilot study

Purpose

Lymphoproliferative neoplasms are the largest and most frequently diagnosed entities in the group of haematological malignancies. The aim of the study was to assess whether apparent diffusion coefficient (ADC) measured on the first day of the second cycle of chemotherapy could be a predictor of prognosis and of the final treatment’s outcome.

Material and methods

The study included 27 patients with diagnosed Hodgkin’s and non-Hodgkin’s lymphoma, who had magnetic resonance (MR) performed with diffusion weighted imaging/apparent diffusion coefficient (DWI/ADC) before and on the first day of the second cycle of chemotherapy. Imaging was performed using a 1.5 T MR scanner. ADC was measured in lymphoma infiltration in the area of the lowest signal in the ADC map and the highest signal on β 800 images in post-treatment study. After that, the corresponding area was determined in a pre-treatment study and an ADC value was measured.

Results

The difference between ADC values in pre-treatment (ADC = 720 mm²/s) and post-treatment (ADC = 1059 mm²/s) studies was statistically significant (p < 0.001). Cutoff values for estimating response to treatment were established at the level of ADC 1080 mm²/s, and ADC to muscle ratio at 0.82 in post-treatment study. Patients with ADC > 752 mm²/s before treatment manifested lower probability of progression than patients with ADC < 752 mm²/s.

Conclusions

ADC measurement’s before treatment and on the first day of the second cycle of chemotherapy can be used as a prognostic marker in lymphoma therapy. ADC values lower than 1080 mm²/s and an increase of the ratio after the treatment can be considered as a marker of disease progression.

A Thymic Hyperplasia Case without Suppressing on Chemical Shift Magnetic Resonance Imaging

A 22-year-old woman with myasthenia gravis (MG) presented with ptosis and mild muscle weakness symptoms for one year. Computed tomography (CT) presented a diffuse bilobulate enlargement gland with a high density of soft tissue. Magnetic resonance imaging (MRI) showed the gland with no suppression on the opposed-phase chemical shift. After the thymic tumor diagnosis, she underwent thoracoscopic surgery for tumor resection. The postoperative histopathological finding was thymic lymphoid hyperplasia. This case suggests chemical shift MRI is not enough in distinguishing, and supplementary examination is essential to avoid unnecessary thymic biopsy and surgery.

Economic Benefits and Diagnostic Quality of Diffusion-Weighted Magnetic Resonance Imaging for Primary Lung Cancer

This paper focuses on the latest research of diffusion-weighted magnetic resonance imaging (DWI), and deals with economic benefits, diagnostic benefits, and prospects of DWI for lung cancer. The medical cost of a magnetic resonance imaging (MRI) is 81%-84% cheaper than that of 18-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (FDG-PET/CT). DWI is reported to be useful for differential diagnosis of malignancy or benignity for neoplasm in various organs. Diagnostic efficacy by DWI for pulmonary nodules and masses and the evaluation of N factor and M factor in lung cancer are equivalent to or more than that of FDG-PET/CT. The diagnostic capability of whole-body DWI (WB-DWI) for the staging of clinically operable lung cancers is equivalent to that of FDG-PET/CT and brain MRI, and WB-DWI is now becoming a more main stream procedure. Although the diagnostic performance of DWI for lung cancer may be equivalent to that of FDG-PET/CT, prospective randomized controlled trial for comparison of diagnostic efficacy between FDG-PET/CT and DWI for lung cancer is necessary for an accurate comparison. DWI may have an advantage in the aspect of the cost and diagnostic efficacy in lung cancer management.