1. A medical screening method for examining a patient comprising the steps of: providing an NMR apparatus having a scanning volume region into which a part of a person to be examined is positioned and having NMR imaging means operable to produce a collection of spatially encoded NMR image data for a set of volume elements from said part of said person positioned in said scanning volume region, said NMR imaging means being operable to produce said collection of spatially encoded NMR image data relative to said scanning volume region during the course of a single scanning operation and said collection of spatially encoded NMR image data including spatial information and NMR signal information for said set of volume elements; positioning a patient within said NMR apparatus so that said scanning volume region defines a first volume portion of said patient having a first set of volume elements; operating said NMR imaging means to conduct a scanning operation to produce said collection of NMR image data for said first set of volume elements; storing said collection of NMR image data for said first set of volume elements; moving said patient so that said scanning volume region defines at least one additional volume portion of said patient having at least one additional set of volume elements, said at least one additional set of volume elements being different from said first set of volume elements; repeating said operating and storing steps for said at least one additional volume portion of said patient defined by said scanning volume region so as to produce and store said collection of NMR image data for said at least one additional set of volume of elements; selecting an array of selected region elements from said volume elements of said sets of volume elements so that said array of selected region elements is representative of a selected region of said patient contained within parts of said first and said at least one additional volume portions of said patient, said array of selected region elements including volume elements contained in said first set of volume elements and volume elements contained in said at least one additional set of volume elements, but consisting of less than all of said volume elements of said sets of volume elements; and producing from said stored collections of NMR image data a composite image of said patient in said selected region of said patient by utilizing said spatially encoded NMR image data which corresponds to said array of selected region elements.