Silicone Gel Breast Implants: MRI

A lady with silicone gel breast implants(SGBI)   reported for evaluation  with no clinical abnormality.  MR shows normal SGBIs with diaphragm type valves and no complications with rest of the breast unremarkable

Teaching points by Dr MGK Murthy

·         Performed for augmentation or Reconstructions

·         Modern silicone gel breast implants date back to first use in 1963 by Dr Thomas Cronin, after paraffin, plastics, and gels have produced  unacceptable complications

·         MR mammography is considered as gold standard for evaluation including detection of complications .

·         Short  tau Inversion recovery (STIR) to null fat at inversion time of 150 m sec with frequency selective pulse train (to exploit chemical shift difference) with transverse magnetization spoiler to null water, with spin echo will leave only silicone signal to be highlighted

·         14 implant types: 1) single-lumen silicone gel-filled, 2) single-lumen gel-saline adjustable, 3) single-lumen saline-, dextran-, or polyvinyl pyrrolodone-filled, 4) standard double-lumen, 5) reverse double-lumen, 6) reverse-adjustable double-lumen, 7) gel-gel double-lumen, 8) triple-lumen, 9) Cavon “cast gel”, 10) custom, 11) solid pectus, 12) sponge (simple or compound), 13) sponge (adjustable), and 14) other.

Intact  single lumen implant appearance 

•    Smooth, low–signal-intensity silicone membrane shell

•    Low–signal-intensity radial folds in the shell, (may be complex; always abut the implant at its periphery and span the gel substance only at periphery)

•    A few internal water droplet signals (common; not a reliable indication of rupture)

•    Reactive fluid around textured implants (common; not indicative of rupture)

•    Fibrous capsule (dark, ring like structure around the implant)

Intact Double-lumen implants

·         Gradual deflation of the saline chamber leads to complex fold patterns

Valves

·         Most of the implants presently are valve less, however the older ones could be seal-seal type or retention, peripheral folds, internal tube valve, four quadrant fixation patches  or diaphragm types

Intracapsular rupture

·         Collapsed and folded elastomer shell floating in gel,  is the most reliable sign of intracapsular rupture.(Linguine sign)

·         Presence of silicone both inside and outside a radial fold is key hole or teardrop or inverted tear drop sign.

Extra capsular rupture

•       Intracapsular rupture + silicone in to surrounding parenchyma/pectorals/Lymphnodes.  Internal rupture of double lumen implants

•       Saline droplets  floating within(some tiny ones are normal variation also)

Capsular contracture

·         Asymmetrical, serrated, focal folding of the fibrous capsule that changes the normal ovoid appearance

·         Transverse diameter less than twice the AP depth= clinically felt as contracture

False Positives

·         Radial folds are normal and mimic keyhole sign(false +)(Silicone should not be present however, inside and outsideof radial folds)

·         Excessive gel bleeding looks like intracapsular rupture(however keyhole sign  is positive  and Linguine sign negative)