Keywords:
Tissue characterisation, Metastases, Cancer, Complications, Ablation procedures, Percutaneous, MR, CT, Musculoskeletal soft tissue, Musculoskeletal bone, Interventional non-vascular
Authors:
F. Bing1, J. Garnon1, G. Tsoumakidou1, I. Enescu1, N. Ramamurthy2, A. Gangi1; 1Strasbourg/FR, 2Manchester/UK
DOI:
10.1594/ecr2013/C-2177
Methods and Materials
- Between January 2010 and October 2012,
we retrospectively analysed 24 bone tumoral lesions (16 in the pelvis,
3 in the shoulder and 5 paravartebral lesions) in 21 patients (mean age 53.8 years;11 females) treated by image-guided percutaneous cryoablation and followed-up with MRI.
- MRI was performed 28.5 ± 15 days after the cryotherapy.
- Muscular T2 STIR hyperintensity was taken to represent an inflammatory myositis,
and graded as follows:
–Grade 0: no myositis
–Grade 1: local myositis (figure 1)
–Grade 2: less than the half volume of the muscle (figure 2)
–Grade 3: more than the half the volume of the muscle (figure 3 and 4)
- The presence of a T2 STIR hyperintensity in the muscles surrounding the cryoablation site was then correlated to the intra-muscular ice-ball volume measured on the scanner performed at the end of the cryotherapy.
- The ice-ball volume was determined as follow:
–Most of the time,
the intramuscular ice-ball was corresponding to a spherical cap (section of a sphere cut off by a plane).
The volume of a spherical cap is: V= πh/6(3a²+h²) (figure 5).
–The intramuscular ice-ball can also correspond to a triaxial ellipsoid: in that case,
the intramuscular ice-ball is calculated as belove:
If V corresponds to the total volume of the ice-ball and Vt to the intratumoral ice-ball,
then the intramuscular ice-ball Vim is:
Vim= V – Vit =4/3*π*(a*b*c-ait*bit*cit) where a,
b and c are the three axes of the ice-ball (c corresponding to the height,
not shown on the figure 6)