ABSTRACT
PURPOSE: Percutaneous muscle biopsy is the gold standard for tissue assessment in clinical practice and scientific studies. The aim of this study was to assess and quantify the ensuing tissue damage by in vivo magnetic resonance imaging (MRI). METHODS: In this prospective study, we enrolled 22 healthy participants who underwent MRI of the thigh musculature about 1 wk after a percutaneous muscle biopsy of the vastus lateralis muscle. A total of 17 participants also volunteered for a second MR examination 2 wk after biopsy. Volumes of susceptibility-weighted imaging (SWI) lesions and muscle edema were assessed by SWI and T2-weighted MRI, respectively, after manual segmentation by two independent readers. For quantitative in vivo hematoma volume assessment, we additionally determined signal changes induced by experimental hematoma in an ex vivo model. RESULTS: Mean overall volume of SWI lesions 1 wk after biopsy was 26.5 ± 21.7 µL, accompanied by a mean perifocal edema volume of 790.1 ± 591.4 µL. In participants who underwent two examinations, mean volume of SWI lesions slightly decreased from 29.8 ± 23.6 to 23.9 ± 16.8 µL within 1 wk (P = 0.13). Muscle edema volume decreased from 820.2 ± 632.4 to 359.6 ± 207.3 µL at the same time (P = 0.006). By calibration with the ex vivo findings, signal alterations on SWI corresponded to a blood volume of approximately 10-50 µL. CONCLUSIONS: Intramuscular hematoma and accompanying muscle edema after percutaneous biopsy are small and decrease rapidly within the first 2 wk. These in vivo findings underline the limited invasiveness of the procedure.
