Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs42155-021-00258-y/MediaObjects/42155_2021_258_Fig1_HTML.png)
Angiography and intravascular ultrasound (IVUS) of the treatment with the fracking technique in case 1. A Control angiography for quantitative vessel analysis (QVA) showed stenosis of 94% in eccentric calcified plaque in the right common femoral artery (green arrow), and IVUS before treatment showed a minimal lumen area (MLA) of 6.2-mm2. B After dilatation with a 6.0 × 20-mm cutting balloon, QVA showed 24% stenosis (yellow arrow), and the MLA was 10.7-mm2. C After a 7.0 × 40-mm noncompliant balloon inflation and percutaneous direct needle puncture of calcified plaque (PIERCE) to modify the calcification (Ichihashi et al. 2014), the MLA was 17.1-mm2. D After the fracking was repeated at three locations at up to 8-atm, QVA showed an improvement of stenosis to 16% (blue arrow), and the MLA was significantly much greater, to 27.1-mm2