Systems and methods are described for determining a minimum radiation dose for a computed tomography (CT) scanning device. The method includes receiving a first input indicative of a selected minimum detectable contrast and a second input indicative of an estimate of a size of a subject to be exposed to the radiation dose. A minimum radiation dose to be applied via a radiation source is determined. The minimum radiation dose is determined at least in part by a power law model relating the size of the subject, a lesion size, and a minimum detectable contrast. The power law model is defined as MDC=A(L) dB(L) DoseC(L), wherein (i) MDC is the selected minimum detectable contrast, (ii) d is lesion size, (iii) Dose is radiation dose, (iv) A(L), B(L), and C(L) are pre-determined fitted parameters, and (v) L is the estimate of the size of the subject.