Impact of the dead-time correction method on quantitative 177Lu-SPECT (QSPECT) and dosimetry during radiopharmaceutical therapy

EJNMMI Physics

Table 2 Patients quantitative SPECT data

Patient	Injected activity (GBq)	Time per projection on Day-1 (s)^a	Estimated activity in FOV Day-1 (GBq)	Averaged R_Wo Day-1 (cps)	Averaged DTCF Day-1	Estimated activity in FOV Day-3 (GBq)	Averaged R_Wo Day-3 (cps)	Averaged DTCF Day-3
1	5.92	20	0.43	14,026	1.0077	0.25	7927	1.0044
2	8.10	15	1.82	55,938	1.0324	1.19	37,063	1.0211
3	7.81	15	2.31	62,364	1.0364	1.55	41,518	1.0234
4	17.76	15	3.73	104,385	1.0630	2.48	65,789	1.0381
5	23.46	15	7.38	200,111	1.1330	3.82	113,748	1.0694
6	8.84	15	6.22	169,030	1.1083	4.22	117,650	1.0718
7	28.05	15	9.81	212,717	1.1430	5.22	118,999	1.0729
8	24.83	15	7.09	174,099	1.1126	4.94	121,948	1.0747
9	22.16	20	10.69	211,140	1.1417	6.49	125,913	1.0777
10	21.83	15	11.02	257,596	1.1826	6.19	161,778	1.1029
11	14.65	15	9.24	225,779	1.1544	6.36	167,101	1.1071
12	22.13	15	11.99	293,284	1.2170	8.32	221,955	1.1506
13	28.86	15	16.85^b	363,755^b	1.2957^b	12.22	278,233	1.2017
14	25.53	20	16.12^b	364,852^b	1.2971^b	12.11	297,712	1.2216

DTCF dead-time correction factor, FOV field of view. R_Wo, observed wide-spectrum count rate
^aTime per projection on Day-3 was always 20 s
^bAcquisitions were saturated. Quantification and DTCFs were thus underestimated