Multiexponential T2 relaxometry of benign and malignant adipocytic tumours

Katerina Nikiforaki,Georgios H. Manikis,Kostas Marias,Apostolos Karantanas,Georgios S. Ioannidis,Eleni Lagoudaki,Eelco de Bree,Thomas G. Maris

doi:10.1186/s41747-020-00175-0

Abstract

BackgroundWe investigated a recently proposed multiexponential (Mexp) fitting method applied to T2 relaxometry magnetic resonance imaging (MRI) data of benign and malignant adipocytic tumours and healthy subcutaneous fat. We studied the T2 distributions of the different tissue types and calculated statistical metrics to differentiate benign and malignant tumours.MethodsTwenty-four patients with primary benign and malignant adipocytic tumours prospectively underwent 1.5-T MRI with a single-slice T2 relaxometry (Carr-Purcell-Meiboom-Gill sequence, 25 echoes) prior to surgical excision and histopathological assessment. The proposed method adaptively chooses a monoexponential or biexponential model on a voxel basis based on the adjusted R2 goodness of fit criterion. Linear regression was applied on the statistical metrics derived from the T2 distributions for the classification.ResultsHealthy subcutaneous fat and benign lipoma were better described by biexponential fitting with a monoexponential and biexponential prevalence of 0.0/100% and 0.2/99.8% respectively. Well-differentiated liposarcomas exhibit 17.6% monoexponential and 82.4% biexponential behaviour, while more aggressive liposarcomas show larger degree of monoexponential behaviour. The monoexponential/biexponential prevalence was 47.6/52.4% for myxoid tumours, 52.8/47.2% for poorly differentiated parts of dedifferentiated liposarcomas, and 24.9/75.1% pleomorphic liposarcomas. The percentage monoexponential or biexponential model prevalence per patient was the best classifier distinguishing between malignant and benign adipocytic tumours with a 0.81 sensitivity and a 1.00 specificity.ConclusionsHealthy adipose tissue and benign lipomas showed a pure biexponential behaviour with similar T2 distributions, while decreased adipocytic cell differentiation characterising aggressive neoplasms was associated with an increased rate of monoexponential decay curves, opening a perspective adipocytic tumour classification.

Highlights

We investigated a recently proposed multiexponential (Mexp) fitting method applied to T2 relaxometry magnetic resonance imaging (MRI) data of benign and malignant adipocytic tumours and healthy subcutaneous fat
Tumours of adipocytic origin comprise the largest group of soft tissue tumours and can be both benign or malignant
Based on the National Cancer Institute and French Federation of Cancer Centers [2] scoring system on tumour differentiation, mitotic count and percentage of tumour necrosis, each liposarcoma is characterised by a histological grade of malignancy which ranges from G1 to G3 [3]

Summary

Introduction

We investigated a recently proposed multiexponential (Mexp) fitting method applied to T2 relaxometry magnetic resonance imaging (MRI) data of benign and malignant adipocytic tumours and healthy subcutaneous fat. We studied the T2 distributions of the different tissue types and calculated statistical metrics to differentiate benign and malignant tumours. Tumours of adipocytic origin comprise the largest group of soft tissue tumours and can be both benign (lipomas) or malignant (liposarcomas). Accuracy of the preoperative diagnosis, by means of identification of the correct adipocytic tumour type, as well as the definition of its histological malignancy grade is essential for patient management, including treatment planning [4]. In the case of malignant soft tissue tumours (sarcomas), wide excision of the tumour together with a rim of adjacent healthy structures is necessary to reduce the risk of local recurrence. A precise noninvasive method for the differentiation between benign and malignant soft tissue tumours and the classification of their histological type is warranted

Objectives

Methods

Results

Conclusion