1. A dynamic analysis system comprising: an imaging device which performs dynamic imaging by emitting radiation to a chest part of a human body, thereby obtaining a series of frame images showing a dynamic state of the chest part; and an analysis device including a controller which: selects a first plurality of frame images to be analyzed from the series of frame images obtained by the imaging device; calculates, based on the first plurality of frame images, a ventilation amount index value that indicates an amount of ventilation of a lung field and a perfusion amount index value that indicates an amount of perfusion of the lung field; and calculates a ratio of the ventilation amount index value to the perfusion amount index value, wherein the controller: filters, with a low-pass filter in a time direction, time change in pixel signal value of (a) a lung field region of the first plurality of frame images or (b) each of small regions into which the lung field region of the first plurality of frame images is divided; calculates, for the whole lung field region or each of the small regions of each of the first plurality of frame images, the ventilation amount index value based on the pixel signal value of the lung field region or each of the small regions of the first plurality of frame images filtered with the low-pass filter; filters, with a high-pass filter or band-pass filter in the time direction, the time change in the pixel signal value of the lung field region or each of the small regions of the first plurality of frame images; and calculates, for the whole lung field region or each of the small regions of each of the first plurality of frame images, the perfusion amount index value based on the pixel signal value of the lung field region or each of the small regions of the first plurality of frame images filtered with the high-pass filter.