um et ric ▁rather ▁than ▁radial ▁growth . ▁This ▁is ▁usually ▁followed ▁by ▁a ▁period ▁of ▁slower ▁growth ▁that ▁can ▁last ▁ 6 – 9 ▁months , ▁with ▁ 8 0 % ▁of ▁the ▁growth ▁completed ▁by ▁ 3 ▁months . ▁Finally , ▁I H s ▁invol ute ▁over ▁a ▁period ▁of ▁years . ▁The ▁exceptions ▁to ▁these ▁growth ▁characteristics ▁include ▁minim ally ▁pro l ifer ative ▁His , ▁which ▁do ▁not ▁substantial ly ▁pro l ifer ate ▁and ▁large , ▁deep ▁I H s ▁in ▁which ▁notice able ▁growth ▁starts ▁later ▁and ▁last s ▁longer . ▁ ▁If ▁the ▁diagn osis ▁is ▁not ▁clear ▁based ▁on ▁physical ▁exam ination ▁and ▁growth ▁history ▁( most ▁often ▁in ▁deep ▁hem ang iom as ▁with ▁little ▁cut aneous ▁invol vement ), ▁then ▁either ▁imag ing ▁or ▁hist op ath ology ▁can ▁help ▁confirm ▁the ▁diagn osis .< ref ▁ ▁name = N orth 2 0 0 1 ></ ref > ▁On ▁Do pp ler ▁ul tras ound , ▁an ▁I H ▁in ▁the ▁pro l ifer ative ▁phase ▁appears ▁as ▁a ▁high - flow , ▁soft - t issue ▁mass ▁usually ▁without ▁direct ▁ar ter i oven ous ▁sh un ting . ▁ ▁On ▁M RI , ▁I H s ▁show ▁a ▁well - circ ums cribed ▁les ion ▁with ▁intermediate ▁and ▁increased ▁signal ▁intensity ▁on ▁T 1 - ▁and ▁T 2 - weight ed ▁sequences , ▁respectively , ▁and ▁strong ▁enh ancement ▁after ▁g ad olin ium ▁in jections , ▁with ▁fast - flow