TABLE 1

Biologic Parameters of Fractional Distribution Function, α_h(t) (α_h(t) = α_h1exp(−λ_h1t) + α_h2exp(−λ_h2t)), for Intravenous Administration of ²⁰¹Tl as Thallous Chloride

Source organ*	α_h1^†	λ_h1 (h⁻¹)^‡	α_h2^†	λ_h2 (h⁻¹)^‡	τ_h (h)^§
Brain	0.0176	0			1.85
Lower large intestine	0.036	0.00363			2.74
Small intestine	0.144	0.00363			10.96
Stomach	0.028	0.00338			2.17
Upper large intestine	0.047	0.00363			3.58
Heart wall	0.034	0.00387			2.54
Kidneys	0.045	0.00267	0.0097	0.0257	3.97
Liver	0.046	0.00318			3.63
Spleen	0.0074	0.00108	0.0028	0.0187	0.798
Testes^‖	0.00568	0.00445	−0.00614	0.298	0.255
Thyroid	0.0029	0.00198	0.0024	0.00417	0.428
Urinary bladder^¶	0.062	0.00475	0.138	0.00138	0.0913
Remainder					52.2

↵* For organs other than testes, data used were from Table 1 in Krahwinkel et al. (17), which gives mean and SD of kinetic data for their 15 patients. Following the revision of Castronovo (18), these pooled data were reanalyzed in this report.
↵^† α_hj values are fractional distribution functions for source organ, h.
↵^‡ λ_hj values are biologic rate constants for source organ, h.
↵^§ Residence time τ_h (h) includes physical decay and, with exception of urinary bladder (see ¶ below), is calculated using the relationship: τ_h = Σ α_hj/(λ + λ_hj), where λ is physical decay constant given in reciprocal hours (for ²⁰¹Tl, λ = 0.009482 h⁻¹).
↵^‖ For testes, the results were derived from quantitative scintigraphy of 28 patients (56 studies) (25). Values shown for testes parameters are averages of individual results obtained for each patient. As testes residence time shown is average of individual patient τ values, it differs from value that would be derived from average α and λ values given in table. Residence time for testes: range = 0.095–0.46 h; SD = 0.087 h.
↵^¶ For urinary bladder, residence time was determined using model of Cloutier et al. (33) with a 4.8-h voiding interval.