Table 1.

Relaxivities of Nine PEGylated SPIO Nanoparticles and Commercial Contrast Agent (Magnevist and Ferumoxytol) at Different Main Magnetic Fields

Sample	0.5 T			1.5 T			3.0 T
	r1 (mM−1 s−1)	r2 (mM−1 s−1)	r2/r1	r1 (mM−1 s−1)	r2 (mM−1 s−1)	r2/r1	r1 (mM−1 s−1)	r2 (mM−1 s−1)	r2/r1
4-nm SPIO@PEG550a	14.2	24.6	1.73	11.5	35.5	3.08	6.99	41.5	5.94
4-nm SPIO@PEG2ka	13.5	22.5	1.67	11.4	30.9	2.71	7.57	33.1	4.38
4-nm SPIO@PEG5ka	16.1	28.0	1.74	14.2	40.5	2.85	8.82	46.2	5.24
6-nm SPIO@PEG550a	28.1	54.9	1.95	14.2	67.5	4.76	6.84	67.9	9.92
6-nm SPIO@PEG2ka	29.1	63.1	2.17	16.9	70.6	4.17	8.36	72.2	8.63
6-nm SPIO@PEG5ka	34.2	70.1	2.05	19.8	77.8	3.93	10.2	81.4	7.96
8-nm SPIO@PEG550a	41.6	102.7	2.47	17.2	117.1	6.81	7.94	119.4	15.1
8-nm SPIO@PEG2ka	45.3	111.0	2.45	19.0	122.0	6.42	8.60	129.5	15.1
8-nm SPIO@PEG5ka	47.3	118.1	2.49	20.0	130.1	6.52	10.1	141.4	14.0
Magnevist (GdDTPA)	3.72	4.29	1.15	3.56	4.08	1.15	3.58	3.96	1.11
Ferumoxytolb	38.0	85	2.24	19.9	60.8	3.06	10.0	62.3	6.23

Notes: ^aMeasurement in this work, room temperature; ^bData from Knobloch et al³⁸ and Questions and answers in MRI (http://mriquestions.com/ferumoxytol.html).³⁹