Table 3. Blood half lives of radiolabeled V_HH.

		Fast t½			Slow t½
VHH	genotype	(min)	(95% C.I.)	%	(min)	%	(95% C.I.)
99mTc-ni3A	APP/PS1	14.71	(8.65–49.13)	89.7	580	10.3	(101.8–∞)
	Wildtype	ND		ND	ND	ND
99mTc-pa2H	APP/PS1	21.89	(14.24–39.38)	79.8	2562	20.2	(975.0–∞)
	Wildtype	10.78	(7.27–20.76)	87.1	5861	12.9	(969.3–∞)
DTPA(111In)-pa2H	APP/PS1	19.69	12.63–44.60	100	-	-
	Wildtype	15.83	9.30–53.37	100	-	-

Half lives were determined by fitting a one or a two phase exponential decay model based on blood obtained from both tail vein and cardiac puncture at several time points after intravenous bolus injection of 2 µg radiolabeled V_HH in 12–14 month old APP/PS1 mice and wildtype littermates, as depicted in Figure 2. Please note that DTPA(¹¹¹In)-pa2H was produced without any additional peptide tags.