A method for selecting a medical device for use in the performance of a medical procedure involving the left atrial appendage, LAA, of a patient's heart, comprising: acquiring image data relating to an anatomical region of interest of a patient's body; generating a multi-dimensional depiction of the anatomical region of interest using the acquired image data; defining a plurality of points relative to the multi-dimensional depiction, wherein the plurality of points defined in the defining step comprises two or more of the following individual points: a point within a plane that contains a true ostium of the LAA ("true ostium plane"), wherein the point corresponds to the centroid of the true ostium of the LAA, this true ostium being the portion of the LAA having the greatest circumference, and the plane that contains the true ostium being spaced from the conventional ostium of the LAA, namely the opening of the LAA immediately adjacent the left atrium; a point within a plane that is a duplicate of and offset from the true ostium plane in a direction that is perpendicular to the true ostium plane ("offset true ostium plane"), wherein the point corresponds to an origin of the offset true ostium plane, which corresponds to the centroid of the true ostium of the LAA offset in a direction perpendicular to the true ostium plane; a point within a plane that contains the fossa ovalis of the patient's heart ("fossa ovalis plane"), wherein the point corresponds to the centroid of the fossa ovalis; or a point within a plane that contains the inferior vena cava ("IVC") ostium of the patient's heart ("IVC ostium plane"), wherein the point corresponds to the centroid of the IVC ostium; determining one or more measurements based on the defined plurality of points; and selecting a medical device to be used based on the determined measurements, wherein the medical device is a catheter used to deliver an LAA occlusion device to the LAA of the patient's heart. acquiring image data relating to an anatomical region of interest of a patient's body; generating a multi-dimensional depiction of the anatomical region of interest using the acquired image data; defining a plurality of points relative to the multi-dimensional depiction, wherein the plurality of points defined in the defining step comprises two or more of the following individual points: a point within a plane that contains a true ostium of the LAA ("true ostium plane"), wherein the point corresponds to the centroid of the true ostium of the LAA, this true ostium being the portion of the LAA having the greatest circumference, and the plane that contains the true ostium being spaced from the conventional ostium of the LAA, namely the opening of the LAA immediately adjacent the left atrium; a point within a plane that is a duplicate of and offset from the true ostium plane in a direction that is perpendicular to the true ostium plane ("offset true ostium plane"), wherein the point corresponds to an origin of the offset true ostium plane, which corresponds to the centroid of the true ostium of the LAA offset in a direction perpendicular to the true ostium plane; a point within a plane that contains the fossa ovalis of the patient's heart ("fossa ovalis plane"), wherein the point corresponds to the centroid of the fossa ovalis; or a point within a plane that contains the inferior vena cava ("IVC") ostium of the patient's heart ("IVC ostium plane"), wherein the point corresponds to the centroid of the IVC ostium; a point within a plane that contains a true ostium of the LAA ("true ostium plane"), wherein the point corresponds to the centroid of the true ostium of the LAA, this true ostium being the portion of the LAA having the greatest circumference, and the plane that contains the true ostium being spaced from the conventional ostium of the LAA, namely the opening of the LAA immediately adjacent the left atrium; a point within a plane that is a duplicate of and offset from the true ostium plane in a direction that is perpendicular to the true ostium plane ("offset true ostium plane"), wherein the point corresponds to an origin of the offset true ostium plane, which corresponds to the centroid of the true ostium of the LAA offset in a direction perpendicular to the true ostium plane; a point within a plane that contains the fossa ovalis of the patient's heart ("fossa ovalis plane"), wherein the point corresponds to the centroid of the fossa ovalis; or a point within a plane that contains the inferior vena cava ("IVC") ostium of the patient's heart ("IVC ostium plane"), wherein the point corresponds to the centroid of the IVC ostium; determining one or more measurements based on the defined plurality of points; and selecting a medical device to be used based on the determined measurements, wherein the medical device is a catheter used to deliver an LAA occlusion device to the LAA of the patient's heart.