A recent paper in Medicine and Science in Sport and Exercise gave very good detail regarding the ultrasound settings as well as the calculations they performed including pennation angle.
Timmins, RG, Ruddy, JD, Presland, J, Maniar, N, Shield, AJ, Williams, MD, Opar, DA (2016) Architectural changes of the biceps femoris long head after concentric or eccentric training. Med Sci Sport Exer, 48(3): 499 - 508.
Also some recent papers from Kellis and colleagues may help? (e.g. biceps femoris and semitendinosus tendon aponeurosis strain during passive and active (isometric) conditions).