This code system http://hl7.org/fhir/imagingselection-3dgraphictype defines the following codes:

CodeDisplayDefinition
point POINTA single location denoted by a single (x,y,z) triplet.
multipoint MULTIPOINTmultiple locations each denoted by an (x,y,z) triplet; the points need not be coplanar.
polyline POLYLINEa series of connected line segments with ordered vertices denoted by (x,y,z) triplets; the points need not be coplanar.
polygon POLYGONa series of connected line segments with ordered vertices denoted by (x,y,z) triplets, where the first and last vertices shall be the same forming a polygon; the points shall be coplanar.
ellipse ELLIPSEan ellipse defined by four (x,y,z) triplets, the first two triplets specifying the endpoints of the major axis and the second two triplets specifying the endpoints of the minor axis.
ellipsoid ELLIPSOIDa three-dimensional geometric surface whose plane sections are either ellipses or circles and contains three intersecting orthogonal axes, "a", "b", and "c"; the ellipsoid is defined by six (x,y,z) triplets, the first and second triplets specifying the endpoints of axis "a", the third and fourth triplets specifying the endpoints of axis "b", and the fifth and sixth triplets specifying the endpoints of axis "c".
<status value="active"/><experimental value="false"/><date value="2021-01-05T10:01:24+11:00"/><publisher value="HL7 (FHIR Project)"/><contact><telecom><system value="url"/><value value="http://hl7.org/fhir"/></telecom><telecom><system value="email"/><value value="fhir@lists.hl7.org"/></telecom></contact><description value="The type of coordinates describing an image region."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/imagingselection-3dgraphictype"/><content value="complete"/><concept><code value="point"/><display value="POINT"/><definition value="A single location denoted by a single (x,y,z) triplet."/></concept><concept><code value="multipoint"/><display value="MULTIPOINT"/><definition value="multiple locations each denoted by an (x,y,z) triplet; the points need not be coplanar."/></concept><concept><code value="polyline"/><display value="POLYLINE"/><definition value="a series of connected line segments with ordered vertices denoted by (x,y,z) triplets; the points need not be coplanar."/></concept><concept><code value="polygon"/><display value="POLYGON"/><definition value="a series of connected line segments with ordered vertices denoted by (x,y,z) triplets, where the first and last vertices shall be the same forming a polygon; the points shall be coplanar."/></concept><concept><code value="ellipse"/><display value="ELLIPSE"/><definition value="an ellipse defined by four (x,y,z) triplets, the first two triplets specifying the endpoints of the major axis and the second two triplets specifying the endpoints of the minor axis."/></concept><concept><code value="ellipsoid"/><display value="ELLIPSOID"/><definition value="a three-dimensional geometric surface whose plane sections are either ellipses or circles and contains three intersecting orthogonal axes, "a", "b", and "c"; the ellipsoid is defined by six (x,y,z) triplets, the first and second triplets specifying the endpoints of axis "a", the third and fourth triplets specifying the endpoints of axis "b", and the fifth and sixth triplets specifying the endpoints of axis "c"."/></concept></CodeSystem>