Abstract
Purpose: The aim of this study was to evaluate the benefit of using quantitative diffusion-weighted
imaging (DWI) with apparent diffusion coefficient (ADC) mapping in the initial diagnosis
and post-therapeutic follow-up of extremity soft tissue masses. Patients and Methods: This study included 90 patients with extremity soft tissue masses. The DWI was obtained
with 3 b values, including 0, 400, and 800 s/mm2. Calculation of the ADC value of the lesion was done by placing the region of interest
(ROI) to include the largest area of the lesion. ADC values were compared with the
histopathology. Eighteen patients had posttherapeutic magnetic resonance imaging (MRI).
Results: Benign masses, fibromatosis, and malignant soft tissue masses had mean ADC values
of 1.18 ± 1.0191 × 10−3 mm2/s; 1.31 ± 0.245 × 10−3 mm2/sec; and 1.3 ± 0.7 × 10−3 mm2/s, respectively. Myxomatous malignant masses had an ADC value of 2.6 ± 0.55 × 10−3 mm2/s, while nonmyxomatous malignant masses had an ADC value of 1.1 ± 0.8 × 10−3 mm2/s. ADC cutoff value between benign and non-benign (including malignant and locally
aggressive masses) was 0.6 × 10−3 mm2/sec with 98.3% sensitivity and 50% specificity (P = 0.5123). The statistical difference between malignant soft tissue masses (mean
ADC 1.309 ± 0.723 × 10−3 mm2/s) and fibromatosis masses (mean ADC value 1.31 ± 0.245 × 10−3 mm2/s) using a comparative T-test proved to be of poor significance level (P value ~ 0.9757). Nine patients with soft tissue sarcomas (STSs) had pre and post-therapeutic
MRI examinations showing a mean increase of the recorded ADC values by about 0.28
× 10−3 mm2/s in the post-therapy study as compared with the recorded initial pretreatment values.
Analysis of the post-therapy follow-up studies of fibromatosis showed that lesions
with favorable response to chemotherapy or radiotherapy (8/12) exhibited significantly
lower ADC values than those showing progressive disease course. Conclusion: DWI with ADC mapping of extremity soft tissue tumors are so complicated that they
alone may not be of much value in differentiating between benign and malignant tumors;
however, it can be used as a tool for monitoring response to treatment.
Keywords
Diffusion-weighted imaging - post-therapeutic - soft tissue sarcomas
