A system for estimating a relative substance composition, RSC, of a portion of a body of a patient in a field of view for a magnetic resonance image to be taken from the patient in a medical imaging scan, comprising: an input interface for receiving at least one piece of patient information data, PPID, and for receiving at least one piece of field-of-view information data, PFID; a computing device configured to implement a trained machine learning algorithm, MLA, wherein the trained MLA is configured and trained to receive the at least one PPID and the at least one PFID received by the input interface as its input and to generate as its output at least one output signal indicating an RSC of a portion of the body of the patient for the medical image based on the at least one PPID and the at least one PFID; and an output interface for outputting at least the at least one output signal, wherein the at least one PPID comprises at least one of the following: - at least one a piece of information indicating the sex of the patient; - at least one piece of information indicating at least one size or sizing of the patient; - at least one piece of information indicating a weight of the patient; - at least one piece of information indicating the age of the patient and/or - at least one piece of information indicating information about implants in the body of the patient, wherein the at least one PFID comprises at least one of the following: - at least one piece of information indicating a field-of-view position; - at least one piece of information indicating a field-of-view size; - at least one piece of information indicating a field-of-view rotation, characterized in that the RSC comprises, or consists of, a ratio between water, fat, and at least one substance not naturally occurring in the human body from which a prosthesis for the human body may be fabricated. an input interface for receiving at least one piece of patient information data, PPID, and for receiving at least one piece of field-of-view information data, PFID; a computing device configured to implement a trained machine learning algorithm, MLA, wherein the trained MLA is configured and trained to receive the at least one PPID and the at least one PFID received by the input interface as its input and to generate as its output at least one output signal indicating an RSC of a portion of the body of the patient for the medical image based on the at least one PPID and the at least one PFID; and an output interface for outputting at least the at least one output signal, wherein the at least one PPID comprises at least one of the following: - at least one a piece of information indicating the sex of the patient; - at least one piece of information indicating at least one size or sizing of the patient; - at least one piece of information indicating a weight of the patient; - at least one piece of information indicating the age of the patient and/or - at least one piece of information indicating information about implants in the body of the patient, - at least one a piece of information indicating the sex of the patient; - at least one piece of information indicating at least one size or sizing of the patient; - at least one piece of information indicating a weight of the patient; - at least one piece of information indicating the age of the patient and/or - at least one piece of information indicating information about implants in the body of the patient, wherein the at least one PFID comprises at least one of the following: - at least one piece of information indicating a field-of-view position; - at least one piece of information indicating a field-of-view size; - at least one piece of information indicating a field-of-view rotation, - at least one piece of information indicating a field-of-view position; - at least one piece of information indicating a field-of-view size; - at least one piece of information indicating a field-of-view rotation, characterized in that the RSC comprises, or consists of, a ratio between water, fat, and at least one substance not naturally occurring in the human body from which a prosthesis for the human body may be fabricated.