Table 2. K-distribution and OCT parameters in human in vivo tissues^a.

Depth (µm)	Skin (finger)					Fingernail
	αF	αV	Neff		SNR	αF	αV	Neff	SNR
	(mean ± SD)			(mean)	(mean)	(mean ± SD)		(mean)	(mean)
90	4.0 ± 1.6	5.1 ± 1.4	2.3		19.3	19.3 ± 5.2	13.1 ± 2.6	8.1	12.8
180	3.3 ± 0.5	2.8 ± 0.5	1.5		13.7	8.7 ± 0.5	9.3 ± 1.8	4.5	11.4
270	4.3 ± 0.9	2.7 ± 0.8	1.8		11.6	3.3 ± 0.9	2.8 ± 0.9	1.5	14.6

^aK-distribution shape parameter α, effective number of scatterers in coherence volume N_eff, and SNR of OCT measurements in human skin (finger) and fingernail. For each sample, three measurements were repeated at laterally different sample positions. The shape parameters α_F and α_V generally agree well, and the SNR > 10 dB, suggesting the suitability of the K-distribution PDF formalism. As seen, the derived effective number of scatterers N_eff ( = α_ave/2) in the OCT coherence volume ranges from ~2 to ~8. The higher SNR at 270 µm for fingernail compared to other depths is indicative of higher reflectance from the deeper bright ventral nail plate as observed in Fig. 6(b); this is not a system-related SNR anomaly, since the measured sensitivity had a monotonic roll-off (~10dB/mm), without singularities over the whole depth range.