, ▁this ▁velocity ▁field ▁in ▁not ▁limited ▁to ▁the ▁beam ▁direction . ▁St rain ▁rate ▁and ▁stra in ▁are ▁then ▁calculated ▁from ▁the ▁veloc ities . ▁Spe ck le ▁tracking ▁has ▁been ▁shown ▁to ▁be ▁compar able ▁to ▁t issue ▁Do pp ler ▁derived ▁stra in , ▁and ▁has ▁been ▁valid ated ▁against ▁MR ▁ ▁St rain ▁ ▁St rain ▁is ▁defined ▁as ▁the ▁fraction al ▁or ▁percentage ▁change ▁in ▁an ▁objects ▁dimension ▁in ▁comparison ▁to ▁the ▁object ’ s ▁original ▁dimension . ▁Similarly , ▁stra in ▁rate ▁can ▁be ▁defined ▁as ▁the ▁speed ▁at ▁which ▁de formation ▁occurs . ▁Mathemat ically , ▁three ▁components ▁of ▁normal ▁stra in ▁( ε x , ▁ ε y , ▁and ▁ ε z ) ▁and ▁three ▁components ▁of ▁she ar ▁stra in ▁( ε xy , ▁ ε x z , ▁and ▁ ε yz ) ▁are ▁recognized . ▁Cong ru ently , ▁when ▁applied ▁to ▁the ▁left ▁vent ric le , ▁left ▁vent ric ular ▁de formation ▁is ▁defined ▁by ▁the ▁three ▁normal ▁stra ins ▁( long itud inal , ▁circum fer ential , ▁and ▁radial ) ▁and ▁three ▁she ar ▁stra ins ▁( circ um fer ential - long itud inal , ▁circum fer ential - rad ial , ▁and ▁longitud inal - rad ial ). ▁The ▁principal ▁benefit ▁of ▁L V ▁she ar ▁stra ins ▁is ▁ampl ification ▁of ▁the ▁ 1 5 % ▁short ening ▁of ▁my ocy tes ▁into ▁ 4 0 % ▁radial ▁L V ▁wall ▁thick ening ,